OPTICALLY FUNCTIONAL FILM

- NITTO DENKO CORPORATION

Provided is an optically functional film that can contribute to the widening of the color gamut of an image display apparatus, the optically functional film being suppressed in brightness reduction and being excellent in durability. The optically functional film of the present invention includes an optically functional layer having a moisture permeability of 100 g/m2 or less, wherein the optically functional layer has an absorption peak in a wavelength band in a range of from 580 nm to 610 nm, and wherein the optically functional layer contains a compound X represented by the general formula (I) or the general formula (II).

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Description
TECHNICAL FIELD

The present invention relates to an optically functional film.

BACKGROUND ART

In recent years, an image display apparatus has been required to achieve lightness and vividness (i.e., color gamut widening), and hence an organic EL display apparatus (OLED) has been attracting attention. However, a liquid crystal display apparatus has also been required to achieve color gamut widening. For example, as a method of widening the color gamut of an image display apparatus, such as a liquid crystal display apparatus, a method including arranging a color correction filter showing an absorption maximum wavelength in a specific wavelength range on the viewer side of the image display apparatus has been proposed (Patent Literature 1). In the related art method, however, a problem of a reduction in brightness caused by the absorption of light by the color correction filter, a problem with durability in which the color of the color correction filter containing a coloring matter deteriorates over time, and the like occur.

CITATION LIST Patent Literature

[PTL 1] JP 2009-251511 A

SUMMARY OF INVENTION Technical Problem

The present invention has been made to solve the conventional problems, and a primary object of the present invention is to provide an optically functional film that can contribute to the widening of the color gamut of an image display apparatus, the optically functional film being suppressed in brightness reduction and being excellent in durability.

Solution to Problem

According to one embodiment of the present invention, there is provided an optically functional film, including an optically functional layer having a moisture permeability of 100 g/m2 or less, wherein the optically functional layer has an absorption peak in a wavelength band in a range of from 580 nm to 610 nm, and wherein the optically functional layer contains a compound X represented by the following general formula (I) or general formula (II):

in the formula (I),

R1, R2, R3, R4, R5, R6, R7, and R8 each independently represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R1 and R2 form a saturated cyclic skeleton including 5 or 6 carbon atoms, and R3, R4, R5, R6, R7, and R8 each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R2 and R3 form a saturated cyclic skeleton including 5 to 7 carbon atoms, and R1, R4, R5, R6, R7, and R8 each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R5 and R6 form a saturated cyclic skeleton including 5 or 6 carbon atoms, and R1, R2, R3, R4, R7, and R8 each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R6 and R7 form a saturated cyclic skeleton including 5 to 7 carbon atoms, and R1, R2, R3, R4, R5, and R8 each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R1 and R2 form a saturated cyclic skeleton including 5 or 6 carbon atoms, R5 and R6 form a saturated cyclic skeleton including 5 or 6 carbon atoms, and R3, R4, R7, and R8 each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b), or

R2 and R3 form a saturated cyclic skeleton including 5 to 7 carbon atoms, R6 and R7 form a saturated cyclic skeleton including 5 to 7 carbon atoms, and R1, R4, R5, and R8 each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b); and

in the formula (II), R4 and R8 each independently represent a hydrogen atom, or a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms.

In one embodiment, the optically functional film further includes a pressure-sensitive adhesive layer arranged on at least one side of the optically functional layer.

In one embodiment, the optically functional film further includes a substrate arranged on at least one side of the optically functional layer.

According to another embodiment of the present invention, there is provided an image display apparatus. The image display apparatus includes the optically functional film.

Advantageous Effects of Invention

According to the present invention, the optically functional film that can contribute to the widening of the color gamut of the image display apparatus, which is suppressed in brightness reduction and is excellent in durability, can be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1(a) to FIG. 1(c) are each a schematic sectional view of an optically functional film according to one embodiment of the present invention.

 DESCRIPTION OF EMBODIMENTS

Now, preferred embodiments of the present invention are described. However, the present invention is not limited to these embodiments.

A. Optically Functional Film

FIG. 1(a) is a schematic sectional view of an optically functional film according to one embodiment of the present invention. An optically functional film 100 of this embodiment includes an optically functional layer 10. The optically functional layer 10 has a moisture permeability of 100 g/m2 or less. The optically functional layer 10 has an absorption peak in a wavelength band in the range of from 580 nm to 610 nm. Such optically functional layer may be obtained by incorporating a predetermined coloring matter into the optically functional layer. The optically functional film may include any appropriate member in addition to the optically functional layer. For example, the optically functional film may include a pressure-sensitive adhesive layer or a substrate as described later.

FIG. 1(b) is a schematic sectional view of an optically functional film according to another embodiment of the present invention. An optically functional film 100′ of this embodiment further includes a pressure-sensitive adhesive layer 20 on at least one side of the optically functional layer 10. FIG. 1(c) is a schematic sectional view of an optically functional film according to still another embodiment of the present invention. An optically functional film 100″ of this embodiment further includes a substrate 30 on at least one side of the optically functional layer 10. The optically functional layer 10 and the substrate 30 are typically laminated via the pressure-sensitive adhesive layer 20.

In the present invention, when the optically functional layer selectively absorbs light in a specific wavelength range (from 580 nm to 610 nm) and is suppressed in unneeded absorption in a wavelength range except the specific wavelength range through the use of a specific coloring matter to be described later (coloring matter represented by the general formula (I) or (II)), an optically functional film that can contribute to the widening of the color gamut of an image display apparatus and to an improvement in brightness thereof can be obtained. When the optically functional film of the present invention is used, the color gamut of the image display apparatus can be significantly widened without use of a high-cost technology (an organic EL technology or a quantum dot technology). In addition, when the moisture permeability of the optically functional layer is set to 100 g/m2 or less, the optically functional layer is excellent in durability. Further, even when a coloring matter is used with a view to forming an optically functional layer having a light absorption characteristic as described above, the color deterioration (decomposition) of the coloring matter can be suppressed, and hence the color gamut widening can be stably maintained over time. The fact that the coloring matter having low durability is made usable in the optically functional film is one achievement of the present invention. When the optically functional film includes any other layer, such as a pressure-sensitive adhesive layer, the effect of the present invention can be obtained by incorporating the coloring matter not into the other layer but into the optically functional layer having a low moisture permeability.

A-1. Optically Functional Layer

As described above, the optically functional layer has an absorption peak in the wavelength band in the range of from 580 nm to 610 nm. The formation of such optically functional layer can provide an optically functional film that can contribute to the widening of the color gamut of an image display apparatus and to an improvement in brightness thereof. The absorption spectrum of the film may be measured with a spectrophotometer (manufactured by Hitachi High-Technologies Corporation, product name: “U-4100”).

The ratio (A545/Amax) of the absorbance A545 of the peak of the optically functional layer at a wavelength of 545 nm to the absorbance Amax of the highest absorption peak of the optically functional layer at a wavelength of from 580 nm to 610 nm is preferably 0.13 or less, more preferably 0.12 or less, still more preferably 0.11 or less, particularly preferably 0.1 or less. When an optically functional layer having a small absorbance at a wavelength of 545 nm as described above is formed, an optically functional film that can contribute to the widening of the color gamut of an image display apparatus by absorbing light that is not needed for color representation can be obtained. In addition, the film hardly absorbs light emitted from a light source whose wavelength is around 545 nm at which a visibility is high, and hence can be suppressed in brightness reduction.

In the optically functional layer, the half width of the absorption peak in the wavelength range of from 580 nm to 610 nm is preferably 35 nm or less, more preferably 30 nm or less, still more preferably 25 nm or less, particularly preferably 20 nm or less. When the half width falls within such ranges, an optically functional film that can contribute to the widening of the color gamut of an image display apparatus can be obtained.

In one embodiment, the optically functional layer is free of an absorption peak in the range of from 530 nm to 570 nm. More specifically, the optically functional layer is free of an absorption peak having an absorbance of 0.1 or more in the range of from 530 nm to 570 nm. The formation of such optically functional layer can provide an optically functional film that can contribute to the widening of the color gamut of an image display apparatus.

In one embodiment, the optically functional layer further has an absorption peak in a wavelength band in the range of from 440 nm to 510 nm. That is, in this embodiment, the optically functional layer has absorption peaks in the wavelength bands in the ranges of from 440 nm to 510 nm and from 580 nm to 610 nm. With such configuration, the color mixing of red light and green light, and that of green light and blue light can be satisfactorily prevented. When the optically functional film configured as described above is applied to an image display apparatus, the color gamut of the image display apparatus can be widened, and hence bright and vivid image quality can be obtained. An optically functional layer having two or more absorption peaks as described above may be obtained by using a plurality of kinds of coloring matters.

The transmittance of the optically functional layer at an absorption peak is preferably from 0% to 80%, more preferably from 0% to 70%. When the transmittance falls within such ranges, the above-mentioned effect of the present invention becomes more significant.

The visible light transmittance of the optically functional layer is preferably from 30% to 90%, more preferably from 30% to 80%. When the visible light transmittance falls within such ranges, an optically functional film that can widen the color gamut of an image display apparatus while being suppressed in brightness reduction can be obtained.

As described above, the moisture permeability of the optically functional layer is 100 g/m2 or less. The moisture permeability of the optically functional layer is preferably 90 g/m2 or less, more preferably 80 g/m2 or less, still more preferably 70 g/m2 or less. Although the moisture permeability of the optically functional layer is preferably as low as possible, its lower limit is, for example, 0.5 g/m2. The term “moisture permeability” as used herein refers to a value obtained by measuring the amount (g) of water vapor, which passes a sample having an area of 1 m2 in 24 hours in an atmosphere having a temperature of 40° C. and a humidity of 92% RH, in conformity with the moisture permeability test (cup method) of JIS Z 0208.

The thickness of the optically functional layer is typically from 0.1 μm to 100 μm, preferably from 1 μm to 100 μm, more preferably from 2 μm to 50 μm, still more preferably from 5 μm to 35 μm.

The optically functional layer may be formed from a resin composition containing a resin and a coloring matter.

Resin

Any appropriate resin is used as the resin for forming the optically functional layer as long as an optically functional layer having a moisture permeability of 100 g/m2 or less can be formed. As the resin for forming the optically functional layer, there may be used, for example: a (meth)acrylic resin; a cycloolefin-based resin, such as a norbornene-based resin; an olefin-based resin, such as polyethylene or polypropylene; or a polyester-based resin, such as polyethylene terephthalate (PET) because any such resin can satisfy the above-mentioned moisture permeability. Of those, a (meth)acrylic resin or a cycloolefin-based resin is preferably used. The “(meth)acrylic resin” refers to an acrylic resin and/or a methacrylic resin.

Any appropriate (meth)acrylic resin is used as the (meth)acrylic resin. Examples thereof include a poly(meth)acrylic acid ester, such as polymethyl methacrylate, a methyl methacrylate-(meth)acrylic acid copolymer, a methyl methacrylate-(meth)acrylic acid ester copolymer, a methyl methacrylate-acrylic acid ester-(meth)acrylic acid copolymer, a methyl (meth)acrylate-styrene copolymer (e.g., an MS resin), and a polymer having an alicyclic hydrocarbon group (e.g., a methyl methacrylate-cyclohexyl methacrylate copolymer or a methyl methacrylate-norbornyl (meth)acrylate copolymer). A preferred example thereof is a poly(C1-C6)alkyl (meth)acrylate, such as polymethyl (meth)acrylate. Amore preferred example thereof is a methyl methacrylate-based resin including methyl methacrylate as a main component (at from 50 wt % to 100 wt %, preferably from 70 wt % to 100 wt %).

Specific examples of the (meth)acrylic resin include: ACRYPET VH and ACRYPET VRL20A manufactured by Mitsubishi Rayon Co., Ltd.; and a high-Tg (meth)acrylic resin obtained through intramolecular cross-linking or an intramolecular cyclization reaction.

In one embodiment, a (meth)acrylic resin having a glutaric anhydride structure, a (meth)acrylic resin having a lactone ring structure, or a (meth)acrylic resin having a glutarimide structure is preferred as the (meth)acrylic resin because any such resin has high heat resistance, high transparency, and high mechanical strength.

Examples of the (meth)acrylic resin having a glutaric anhydride structure include (meth)acrylic resins each having a glutaric anhydride structure described in, for example, JP 2006-283013 A, JP 2006-335902 A, and JP 2006-274118 A.

Examples of the (meth)acrylic resin having a lactone ring structure include (meth)acrylic resins each having a lactone ring structure described in, for example, JP 2000-230016 A, JP 2001-151814 A, JP 2002-120326 A, JP 2002-254544 A, and JP 2005-146084 A.

Examples of the (meth)acrylic resin having a glutarimide structure include (meth)acrylic resins each having a glutarimide structure described in, for example, JP 2006-309033A, JP 2006-317560 A, JP 2006-328329 A, JP 2006-328334 A, JP 2006-337491 A, JP 2006-337492A, JP 2006-337493 A, JP 2006-337569A, and JP 2007-009182 A.

The cycloolefin-based resin is, for example, a norbornene-based resin. The norbornene-based resin refers to a (co)polymer obtained by using a norbornene-based monomer having a norbornene ring as part or the entirety of starting materials (monomers). Examples of the norbornene-based monomer include: norbornene, alkyl and/or alkylidene substituted products thereof, such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, and 5-ethylidene-2-norbornene, and polar group (e.g., halogen) substituted products thereof; dicyclopentadiene and 2,3-dihydrodicyclopentadiene; dimethanooctahydronaphthalene, alkyl and/or alkylidene substituted products thereof, and polar group (e.g., halogen) substituted products thereof, such as

  • 6-methyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene,
  • 6-ethyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene,
  • 6-ethylidene-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene,
  • 6-chloro-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene,
  • 6-cyano-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene,
  • 6-pyridyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, and
  • 6-methoxycarbonyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene; and trimers or tetramers of cyclopentadiene, such as
  • 4,9:5,8-dimethano-3a,4,4a,5,8,8a,9,9a-octahydro-1H-benzoindene and
  • 4,11:5,10:6,9-trimethano-3a,4,4a,5,5a,6,9,9a,10,10a,11,11a-dodecahydro-1H-cyclopentaanthracene.

Various products are commercially available as the norbornene-based resin. Specific examples thereof include: products available under the product names “ZEONEX” and “ZEONOR” from Zeon Corporation; a product available under the product name “Arton” from JSR Corporation; a product available under the product name “TOPAS” from TICONA; and a product available under the product name “APEL” from Mitsui Chemicals, Inc.

The optically functional layer may contain an additive. Examples of the additive include: antioxidants, such as hindered phenol-based, phosphorus-based, and sulfur-based antioxidants; stabilizers, such as a light stabilizer, a weathering stabilizer, and a heat stabilizer; reinforcing materials, such as glass fibers and carbon fibers; a near-infrared ray absorber; flame retardants, such as tris(dibromopropyl) phosphate, triallyl phosphate, and antimony oxide; antistatic agents, such as anionic, cationic, and nonionic surfactants; colorants, such as an inorganic pigment, an organic pigment, and a dye; an organic filler and an inorganic filler; a resin modifier; an organic filler and an inorganic filler; a plasticizer; a lubricant; an antistatic agent; a flame retardant; and a retardation-reducing agent.

Although a method of producing the optically functional layer is not particularly limited, for example, the following may be adopted: the resin and any other polymer, additive, or the like are sufficiently mixed with each other by any appropriate mixing method to provide a thermoplastic resin composition in advance, and then the composition is formed into a film. Alternatively, the following maybe adopted: the resin and the other polymer, additive, or the like are turned into solutions separate from each other, and then the solutions are mixed to provide a uniform mixed liquid, followed by the forming of the mixed liquid into a film.

To produce the thermoplastic resin composition, for example, the above-mentioned film raw materials are pre-blended with any appropriate mixer, such as an omni mixer, and then the resultant mixture is extruded and kneaded. In this case, a mixer to be used in the extrusion and the kneading is not particularly limited, and any appropriate mixers including an extruder, such as a uniaxial extruder or a biaxial extruder, and a pressure kneader may each be used.

As a method for the film forming, there is given, for example, any appropriate film forming method, such as a solution casting method, a melt extrusion method, a calender method, or a compression molding method. Of those film forming methods, a solution casting method and a melt extrusion method are preferred.

As a solvent to be used in the solution casting method, there are given, for example: aromatic hydrocarbons, such as benzene, toluene, and xylene; aliphatic hydrocarbons, such as cyclohexane and decalin; esters, such as ethyl acetate and butyl acetate; ketones, such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; alcohols, such as methanol, ethanol, isopropanol, butanol, isobutanol, methyl cellosolve, ethyl cellosolve, and butyl cellosolve; ethers, such as tetrahydrofuran and dioxane; halogenated hydrocarbons, such as dichloromethane, chloroform, and carbon tetrachloride; dimethylformamide; and dimethylsulfoxide. Those solvents may be used alone or in combination thereof.

As an apparatus for performing the solution casting method, there are given, for example, a drum-type casting machine, a band-type casting machine, and a spin coater.

Examples of the melt extrusion method include a T-die method and an inflation method. A forming temperature is preferably from 150° C. to 350° C., more preferably from 200° C. to 300° C.

When the film forming is performed by the T-die method, a roll-shaped film may be obtained by: attaching a T-die to the tip portion of a known uniaxial extruder or biaxial extruder; and winding a film extruded into a film shape. At this time, uniaxial stretching may be performed by appropriately adjusting the temperature of a winding roll and stretching the film in its extrusion direction. In addition, simultaneous biaxial stretching, sequential biaxial stretching, or the like may be performed by stretching the film in a direction perpendicular to the extrusion direction.

Coloring Matter

The optically functional layer contains one or more kinds of coloring matters.

The optically functional layer contains, as a coloring matter, a compound X represented by the following general formula (I) or general formula (II). The compound X is a compound having an absorption peak in the wavelength band in the range of from 580 nm to 610 nm.

in the formula (I),

R1, R2, R3, R4, R5, R6, R7, and R8 each independently represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R1 and R2 form a saturated cyclic skeleton including 5 or 6 carbon atoms, and R3, R4, R5, R6, R7, and R8 each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R2 and R3 form a saturated cyclic skeleton including 5 to 7 carbon atoms, and R1, R4, R5, R6, R7, and R8 each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R5 and R6 form a saturated cyclic skeleton including 5 or 6 carbon atoms, and R1, R2, R3, R4, R7, and R8 each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R6 and R7 form a saturated cyclic skeleton including 5 to 7 carbon atoms, and R1, R2, R3, R4, R5, and R8 each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),

R1 and R2 form a saturated cyclic skeleton including 5 or 6 carbon atoms, R5 and R6 form a saturated cyclic skeleton including 5 or 6 carbon atoms, and R3, R4, R7, and R8 each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b), or

R2 and R3 form a saturated cyclic skeleton including 5 to 7 carbon atoms, R6 and R7 form a saturated cyclic skeleton including 5 to 7 carbon atoms, and R1, R4, R5, and R8 each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b); and

in the formula (II), R4 and R8 each independently represent a hydrogen atom, or a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms.

The saturated cyclic skeleton (number of carbon atoms: 5 or 6) formed so as to include R1 and R2, and the saturated cyclic skeleton (number of carbon atoms: 5 or 6) formed so as to include R5 and R6 may each have a substituent. The substituent is, for example, an alkyl group having 1 to 4 carbon atoms. In addition, the saturated cyclic skeleton (number of carbon atoms: 5 to 7) formed so as to include R2 and R3, and the saturated cyclic skeleton (number of carbon atoms: 5 to 7) formed so as to include R6 and R7 may each have a substituent. The substituent is, for example, an alkyl group having 1 to 4 carbon atoms.

In one embodiment, R4 and/or R8 has a benzene ring or a naphthalene ring as a substituent.

Specific examples of the compound X represented by the formula (I) or (II) include compounds represented by the following general formulae (I-1) to (I-27) and (II-1). The absorption peak of the compound X is shown in each of the following tables. With regard to each of the formulae (I-1) to (I-23), an absorption peak obtained by measuring the absorbance of a film formed of a resin composition prepared by mixing aliphatic polycarbonate with the compound X is shown, and with regard to each of the formulae (I-24) to (I-27) and (II-1), an absorption peak obtained by measuring the absorbance of a film formed of a resin composition prepared by mixing a polymethyl methacrylate resin with the compound X is shown.

Absorption peak NO. Compound X (nm) I-1 596 nm (APC) I-2 595 nm (APC) I-3 582 nm (APC) I-4 585 nm (APC) I-5 585 nm (APC) I-6 575 nm (APC) I-7 585 nm (APC) I-8 587 nm (APC) I-9 587 nm (APC) I-10 588 nm (APC) I-11 588 nm (APC) I-12 589 nm (APC) I-13 592 nm (APC) I-14 591 nm (APC) I-15 595 nm (APC) I-16 595 nm (APC) I-17 596 nm (APC) I-18 614 nm (APC) I-19 581 nm (APC) I-20 591 nm (APC) I-21 593 nm (APC) I-22 594 nm (APC) I-23 594 nm (APC) I-24 592 nm I-25 593 nm I-26 594 nm I-27 594 nm II-1 597 nm

The content of the compound X is preferably from 0.01 part by weight to 50 parts by weight, more preferably from 0.05 part by weight to 10 parts by weight, still more preferably from 0.1 part by weight to 5 parts by weight, particularly preferably from 0.1 part by weight to 1 part by weight with respect to 100 parts by weight of the resin.

The compound X is a compound that is typically difficult to use as an additive for an optical member because the compound has the following feature: the compound is liable to alter (its color is liable to deteriorate) under the influence of moisture, oxygen, or the like. According to the present invention, however, even when an optically functional layer containing the compound X is formed, the deterioration of the optically functional layer over time can be prevented.

The optically functional layer may further contain a compound having an absorption peak in the wavelength band in the range of from 440 nm to 510 nm. For example, an anthraquinone-based, oxime-based, naphthoquinone-based, quinizarin-based, oxonol-based, azo-based, xanthene-based, or phthalocyanine-based compound (dye) is used as such compound.

The content of the compound having an absorption peak in the wavelength band in the range of from 440 nm to 510 nm is preferably from 0.01 part by weight to 50 parts by weight, more preferably from 0.01 part by weight to 25 parts by weight with respect to 100 parts by weight of the resin.

A-2. Pressure-sensitive Adhesive Layer

The pressure-sensitive adhesive layer includes any appropriate pressure-sensitive adhesive. The pressure-sensitive adhesive preferably has transparency and optical isotropy. Specific examples of the pressure-sensitive adhesive include a rubber-based pressure-sensitive adhesive, an acrylic pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, an epoxy-based pressure-sensitive adhesive, and a cellulose-based pressure-sensitive adhesive. Of those, a rubber-based pressure-sensitive adhesive or an acrylic pressure-sensitive adhesive is preferred.

A rubber-based polymer serving as the rubber-based pressure-sensitive adhesive is a polymer showing rubber elasticity in a temperature region around room temperature. Preferred examples of the rubber-based polymer (A) include a styrene-based thermoplastic elastomer (A1), an isobutylene-based polymer (A2), and a combination thereof.

Examples of the styrene-based thermoplastic elastomer (A1) may include styrene-based block copolymers, such as a styrene-ethylene-butylene-styrene block copolymer (SEBS), a styrene-isoprene-styrene block copolymer (SIS), a styrene-butadiene-styrene block copolymer (SBS), a styrene-ethylene-propylene-styrene block copolymer (SEPS, a hydrogenated product of SIS), a styrene-ethylene-propylene block copolymer (SEP, a hydrogenated product of a styrene-isoprene block copolymer), a styrene-isobutylene-styrene block copolymer (SIBS), and a styrene-butadiene rubber (SBR). Of those, a styrene-ethylene-propylene-styrene block copolymer (SEPS, a hydrogenated product of SIS), a styrene-ethylene-butylene-styrene block copolymer (SEBS), and a styrene-isobutylene-styrene block copolymer (SIBS) are preferred because the copolymers each have polystyrene blocks at both ends of a molecule thereof and have a high cohesive force as a polymer. A commercial product maybe used as the styrene-based thermoplastic elastomer (A1). Specific examples of the commercial product include SEPTON and HYBRAR manufactured by Kuraray Co., Ltd., Tuftec manufactured by Asahi Kasei Chemicals Corporation, and SIBSTAR manufactured by Kaneka Corporation.

The weight-average molecular weight of the styrene-based thermoplastic elastomer (A1) is preferably from about 50,000 to about 500,000, more preferably from about 50,000 to about 300,000, still more preferably from about 50,000 to about 250,000. The weight-average molecular weight of the styrene-based thermoplastic elastomer (A1) preferably falls within such ranges because both of the cohesive force and viscoelasticity of the polymer can be achieved.

A styrene content in the styrene-based thermoplastic elastomer (A1) is preferably from about 5 wt % to about 70 wt %, more preferably from about 5 wt % to about 40 wt %, still more preferably from about 10 wt % to about 20 wt %. The styrene content in the styrene-based thermoplastic elastomer (A1) preferably falls within such ranges because viscoelasticity based on a soft segment can be secured while a cohesive force based on a styrene moiety is maintained.

Examples of the isobutylene-based polymer (A2) may include polymers each including isobutylene as a constituent monomer and having a weight-average molecular weight (Mw) of preferably 500,000 or more. The isobutylene-based polymer (A2) may be a homopolymer of isobutylene (polyisobutylene, PIB) or may be a copolymer including isobutylene as a main monomer (i.e., a copolymer obtained by copolymerizing isobutylene at a ratio of more than 50 mol %). Examples of such copolymer may include a copolymer of isobutylene and normal butylene, a copolymer of isobutylene and isoprene (e.g., a butyl rubber, such as a regular butyl rubber, a chlorinated butyl rubber, a brominated butyl rubber, or a partially cross-linked butyl rubber), and vulcanized products and modified products thereof (e.g., a product modified with a functional group, such as a hydroxyl group, a carboxyl group, an amino group, or an epoxy group). Of those, polyisobutylene (PIB) is preferred because the polyisobutylene is free of a double bond in its main chain, and is excellent in weatherability. A commercial product may be used as the isobutylene-based polymer (A2). The commercial product is specifically, for example, OPPANOL manufactured by BASF.

The weight-average molecular weight (Mw) of the isobutylene-based polymer (A2) is preferably 500,000 or more, more preferably 600,000 or more, still more preferably 700,000 or more. In addition, the upper limit of the weight-average molecular weight (Mw) is preferably 5,000,000 or less, more preferably 3,000,000 or less, still more preferably 2,000,000 or less. When the weight-average molecular weight of the isobutylene-based polymer (A2) is set to 500,000 or more, a pressure-sensitive adhesive that is more excellent in durability at the time of its high-temperature storage can be obtained.

The content of the rubber-based polymer (A) in the pressure-sensitive adhesive is preferably 30 wt % or more, more preferably 40 wt % or more, still more preferably 50 wt % or more, particularly preferably 60 wt % or more in the total solid content of the pressure-sensitive adhesive. The upper limit of the content of the rubber-based polymer is preferably 95 wt % or less, more preferably 90 wt % or less.

In the rubber-based pressure-sensitive adhesive, the rubber-based polymer (A) and any other rubber-based polymer may be used in combination. Specific examples of the other rubber-based polymer include: a butyl rubber (IIR), a butadiene rubber (BR), an acrylonitrile-butadiene rubber (NBR), EPR (binary ethylene-propylene rubber), EPT (ternary ethylene-propylene rubber), an acrylic rubber, a urethane rubber, and a polyurethane-based thermoplastic elastomer; a polyester-based thermoplastic elastomer; and a blend-based thermoplastic elastomer, such as a polymer blend of polypropylene and EPT (ternary ethylene-propylene rubber). The compounding amount of the other rubber-based polymer is preferably about 10 parts by weight or less with respect to 100 parts by weight of the rubber-based polymer (A).

The acrylic polymer of the acrylic pressure-sensitive adhesive typically contains an alkyl (meth)acrylate as a main component, and may contain an aromatic ring-containing (meth)acrylate, an amide group-containing monomer, a carboxyl group-containing monomer, and/or a hydroxyl group-containing monomer as a copolymerization component in accordance with a purpose. The term “(meth)acrylate” as used herein means an acrylate and/or a methacrylate. The alkyl (meth)acrylate may be, for example, an alkyl (meth)acrylate having a linear or branched alkyl group having 1 to 18 carbon atoms. The aromatic ring-containing (meth)acrylate is a compound containing an aromatic ring structure in its structure and containing a (meth)acryloyl group. The aromatic ring is, for example, a benzene ring, a naphthalene ring, or a biphenyl ring. The aromatic ring-containing (meth)acrylate satisfies durability and can alleviate display unevenness due to a white void of the peripheral portion of an image display apparatus. The amide group-containing monomer is a compound containing an amide group in its structure and containing a polymerizable unsaturated double bond, such as a (meth)acryloyl group or a vinyl group. The carboxyl group-containing monomer is a compound containing a carboxyl group in its structure and containing a polymerizable unsaturated double bond, such as a (meth)acryloyl group or a vinyl group. The hydroxyl group-containing monomer is a compound containing a hydroxyl group in its structure and containing a polymerizable unsaturated double bond, such as a (meth)acryloyl group or a vinyl group. Details about the acrylic pressure-sensitive adhesive are described in, for example, JP 2015-199942 A, the description of which is incorporated herein by reference.

A-3. Substrate

Examples of the substrate include: a separator to be arranged for protecting the pressure-sensitive adhesive layer until the optically functional film is used; a glass film; and an optical film, such as a retardation film or a polarizing plate.

In one embodiment, a glass film is used as the substrate.

Any appropriate glass film may be adopted as the glass film. According to classification based on composition, examples of the glass film include soda-lime glass, borate glass, aluminosilicate glass and quartz glass films. In addition, according to classification based on an alkali component, examples of the glass film include alkali-free glass and low-alkali glass films. The content of an alkali metal component (e.g., Na2O, K2O, Li2O) in the glass is preferably 15 wt % or less, more preferably 10 wt % or less.

The glass film has a thickness of 100 μm or less, preferably 80 μm or less, more preferably 50 μm or less, still more preferably 40 μm or less, particularly preferably 35 μm or less. The lower limit of the thickness of the glass film is preferably 5 μm or more.

The glass film preferably has a light transmittance at a wavelength of 550 nm of 85% or more. The glass film preferably has a refractive index at a wavelength of 550 nm of from 1.4 to 1.65.

The glass film has a density of preferably from 2.3 g/cm3 to 3.0 g/cm3, more preferably from 2.3 g/cm3 to 2.7 g/cm3. When the glass film has a density falling within the range, an optically functional film can be obtained.

Any appropriate method may be adopted as a forming method for the glass film. The glass film is typically produced by melting a mixture containing a main raw material, such as silica or alumina, a fining agent, such as salt cake or antimony oxide, and a reducing agent, such as carbon, at a temperature of from 1,400° C. to 1,600° C., and forming the molten mixture into a thin sheet shape, followed by cooling. Examples of the forming method for the glass film include a slot down-draw method, a fusion method, and a float method. The glass film formed in a sheet shape by any one of those methods may be chemically polished with a solvent, such as hydrofluoric acid, as required, in order to reduce its thickness or enhance its smoothness.

A commercial glass film may be used as it is as the glass film, or the commercial glass film may be polished into a desired thickness before use. Examples of the commercial glass film include: “7059”, “1737”, or “EAGLE 2000” manufactured by Corning; “AN100” manufactured by Asahi Glass Co., Ltd.; “NA-35” manufactured by NH Techno Glass; “OA-10” manufactured by Nippon Electric Glass Co., Ltd.; and “D263” or “AF45” manufactured by Schott AG.

The oxygen permeability of the substrate is preferably 1 [cm3/(m2·24 h·atm)] or less, more preferably 0.8 [cm3/(m2·24 h·atm)] or less, still more preferably 0.6 [cm3/(m2·24 h·atm)] or less, particularly preferably 0.5 [cm3/(m2·24 h·atm)] or less. When the oxygen permeability falls within such ranges, an optically functional film whose optically functional layer is excellent in durability can be obtained. The oxygen permeability maybe adjusted by, for example, a material forming the substrate or the thickness of the substrate. The oxygen permeability may be measured under the conditions of 23° C. and 0% RH in conformity with JIS K 7126-2.

G. Image Display Apparatus

An image display apparatus of the present invention includes an image display panel and the optically functional film. Examples of the image display panel include a liquid crystal display panel and an organic EL panel. The optically functional film may be arranged on the viewer side of the image display panel.

EXAMPLES

Now, the present invention is specifically described byway of Examples. However, the present invention is by no means limited by these Examples. Methods of measuring the respective characteristics are as described below.

(1) Moisture Permeability

The moisture permeability of a layer containing a coloring matter was measured in conformity with JIS Z 0208 (cup method).

(2) Transmittance and Transmittance Change

The transmittance of an optically functional film was measured with a haze meter (manufactured by Murakami Color Research Laboratory Co., Ltd., product name: “HM-150”) by a method defined in JIS 7136.

A heating treatment in which the optically functional film was left to stand under an environment at 80° C. for 144 hours was performed, and a transmittance change was determined from the transmittance of the optically functional film after the heating treatment and the initial transmittance of the optically functional film immediately after its production by using the expression “{(transmittance after heating treatment-initial transmittance)/initial transmittance}×100”.

Example 1

A product available under the product name “DELPET” from Asahi Kasei Chemicals Corporation was dissolved in methylene chloride to produce an acrylic resin solution having a solid content concentration of 25%. 100 Parts by weight of the acrylic resin was mixed with a resin composition containing 0.1 part by weight of the squaraine compound represented by the general formula (I-20) to prepare a liquid. The liquid was applied to a triacetylcellulose substrate having a thickness of 80 μm to provide an optically functional layer having a thickness of 7 μm (absorption maximum wavelength: 588 nm).

Next, a monomer mixture containing 100 parts by weight of butyl acrylate, 0.01 part by weight of 2-hydroxyethyl acrylate, and 5 parts by weight of acrylic acid was loaded into a reaction vessel including a condenser, a nitrogen-introducing tube, a temperature gauge, and a stirring apparatus. Further, 0.1 part by weight of 2,2′-azobisisobutyronitrile serving as a polymerization initiator was loaded into 100 parts by weight of the monomer mixture together with 100 parts by weight of ethyl acetate. While the mixture was gently stirred, a nitrogen gas was introduced into the vessel to purge air in the vessel with nitrogen. After that, the temperature of the liquid in the reaction vessel was kept at around 55° C., and a polymerization reaction was performed for 8 hours to prepare a solution (solid content concentration: 30 wt %) of an acrylic polymer having a weight-average molecular weight (Mw) of 1,800,000 and an Mw/Mn of 4.1.

A pressure-sensitive adhesive composition containing 0.23 part by weight of a radical generator (benzoyl peroxide, available under the product name “NYPER BMT” from Nippon Oil & Fats Co., Ltd.) and 1 part by weight of an isocyanate-based cross-linking agent (available under the product name “CORONATE L” from Tosoh Corporation) with respect to 100 parts by weight of the solid content of the acrylic polymer solution produced in the foregoing was prepared. The pressure-sensitive adhesive composition was applied to a separator to form a pressure-sensitive adhesive layer having a thickness of 20 μm, and the layer was bonded to the optical functional layer. Finally, the triacetylcellulose substrate was peeled. Thus, an optically functional film was obtained.

The squaraine compound represented by the general formula (I-20) was synthesized by the following method.

Synthesis of Squaraine Compound

1-Phenyl-1,4,5,6-tetrahydrocyclopenta[b]pyrrole was synthesized by a method described in “M. Beller et. al., J. Am. Chem. Soc., 2013, 135(30), 11384-11388”.

300 Milligrams of 1-phenyl-1,4,5,6-tetrahydrocyclopenta[b]pyrrole and 80 mg of squaric acid were mixed in 5 mL of ethanol, and the mixture was stirred at 80° C. for 2 hours. After that, the mixture was cooled to room temperature, and the product was filtered out. The product that had been filtered out was washed with ethanol, and was dried under reduced pressure at 70° C. to provide 197 mg of a squaraine compound. Further, the compound was purified by silica gel chromatography to provide 120 mg of a squaraine compound.

The optically functional film (optically functional layer/pressure-sensitive adhesive layer) obtained as described above was subjected to the above-mentioned evaluation. The result is shown in Table 1.

Example 2

A cycloolefin-based resin (manufactured by JSR Corporation, product name: “ARTON F4520”) was dissolved in toluene to provide a solution having a solid content of 25%. A resin composition containing 0.2 part by weight of the squaraine compound represented by the general formula (I-20) with respect to 100 parts by weight of the resin solid content of the solution was prepared. A film was produced in the same manner as in Example 1 except that its optically functional layer was formed by using the resin composition.

The optically functional film (optically functional layer/pressure-sensitive adhesive layer) obtained as described above was subjected to the above-mentioned evaluation. The result is shown in Table 1.

Comparative Example 1

A product available under the product name “DELPET” from Asahi Kasei Chemicals Corporation was loaded into a uniaxial extruder. The product was melted and kneaded, and was passed through a T-die to be formed into a film. The resultant extruded film was subjected to simultaneous biaxial stretching at a stretching temperature of 240° C. in its lengthwise direction and widthwise direction twice each (area stretch ratio: 4.0) to provide an acrylic resin film having a thickness of 40 μm.

Next, a monomer mixture containing 100 parts by weight of butyl acrylate, 0.01 part by weight of 2-hydroxyethyl acrylate, and 5 parts by weight of acrylic acid was loaded into a reaction vessel including a condenser, a nitrogen-introducing tube, a temperature gauge, and a stirring apparatus. Further, 0.1 part by weight of 2,2′-azobisisobutyronitrile serving as a polymerization initiator was loaded into 100 parts by weight of the monomer mixture together with 100 parts by weight of ethyl acetate. While the mixture was gently stirred, a nitrogen gas was introduced into the vessel to purge air in the vessel with nitrogen. After that, the temperature of the liquid in the reaction vessel was kept at around 55° C., and a polymerization reaction was performed for 8 hours to prepare a solution (solid content concentration: 30 wt %) of an acrylic polymer having a weight-average molecular weight (Mw) of 1,800,000 and an Mw/Mn of 4.1.

A pressure-sensitive adhesive composition containing 0.1 part by weight of a squaraine compound represented by the general formula (I-20), 0.23 part by weight of a radical generator (benzoyl peroxide, available under the product name “NYPER BMT” from Nippon Oil & Fats Co., Ltd.), and 1 part by weight of an isocyanate-based cross-linking agent (available under the product name “CORONATE L” from Tosoh Corporation) with respect to 100 parts by weight of the solid content of the acrylic polymer solution produced in the foregoing was prepared. The pressure-sensitive adhesive composition was applied to a separator to form a pressure-sensitive adhesive layer having a thickness of 20 μm, and the layer was bonded to the acrylic resin film to provide an optically functional film.

The optically functional film (resin layer/pressure-sensitive adhesive layer containing a coloring matter) obtained as described above was subjected to the above-mentioned evaluation. The result is shown in Table 1.

TABLE 1 Coloring Transmittance matter-containing layer Coloring matter change Example 1 Optically functional Squaraine 25.4 layer (moisture compound permeability: 64 g/m2) Example 2 Optically functional Squaraine 9.6 layer (moisture compound permeability: 7 g/m2) Comparative Pressure-sensitive Squaraine 44.1 Example 1 adhesive layer (moisture compound permeability: 7,144 g/m2)

INDUSTRIAL APPLICABILITY

The optically functional film of the present invention is suitably used in an image display apparatus, such as a liquid crystal display apparatus.

REFERENCE SIGNS LIST

  • 10 optically functional layer
  • 20 pressure-sensitive adhesive layer
  • 30 substrate
  • 100, 100′, 100″ optically functional film

Claims

1. An optically functional film, comprising an optically functional layer having a moisture permeability of 100 g/m2 or less, in the formula (I),

wherein the optically functional layer has an absorption peak in a wavelength band in a range of from 580 nm to 610 nm, and
wherein the optically functional layer contains a compound X represented by the following general formula (I) or general formula (II):
R1, R2, R3, R4, R5, R6, R7, and R8 each independently represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),
R1 and R2 form a saturated cyclic skeleton including 5 or 6 carbon atoms, and R3, R4, R5, R6, R7, and R8 each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),
R2 and R3 form a saturated cyclic skeleton including 5 to 7 carbon atoms, and R1, R4, R5, R6, R7, and R8 each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),
R5 and R6 form a saturated cyclic skeleton including 5 or 6 carbon atoms, and R1, R2, R3, R4, R7, and R8 each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),
R6 and R7 form a saturated cyclic skeleton including 5 to 7 carbon atoms, and R1, R2, R3, R4, R5, and R8 each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b),
R1 and R2 form a saturated cyclic skeleton including 5 or 6 carbon atoms, R5 and R6 form a saturated cyclic skeleton including 5 or 6 carbon atoms, and R3, R4, R7, and R8 each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b), or
R2 and R3 form a saturated cyclic skeleton including 5 to 7 carbon atoms, R6 and R7 form a saturated cyclic skeleton including 5 to 7 carbon atoms, and R1, R4, R5, and R8 each independently represent a hydrogen atom, a halogen atom, which is preferably Cl, a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms, a substituent represented by the formula (a), or a substituent represented by the formula (b); and
in the formula (II), R4 and R8 each independently represent a hydrogen atom, or a substituted or unsubstituted alkyl group having 1 or more and 20 or less carbon atoms.

2. The optically functional film according to claim 1, further comprising a pressure-sensitive adhesive layer arranged on at least one side of the optically functional layer.

3. The optically functional film according to claim 1, further comprising a substrate arranged on at least one side of the optically functional layer.

4. An image display apparatus, comprising the optically functional film of claim 1.

Patent History
Publication number: 20210181394
Type: Application
Filed: Nov 29, 2018
Publication Date: Jun 17, 2021
Applicant: NITTO DENKO CORPORATION (Ibaraki-shi, Osaka)
Inventors: Kozo Nakamura (Ibaraki-shi), Peng Wang (San Diego, CA), Michael Welch (San Diego, CA), Shijun Zheng (San Diego, CA)
Application Number: 16/767,728
Classifications
International Classification: G02B 5/22 (20060101); C09J 7/20 (20060101); C09B 57/00 (20060101); G02F 1/1333 (20060101); G02F 1/1335 (20060101); G02B 1/10 (20060101);