Abstract: An toy set having at least one section which bears a color memory dye of an electron-supplying organic coloring compound, an electron accepting compound and an ester. The color memory dye assumes a first color below t1 (.degree.C.) and a second color above t2 (.degree.C.), wherein t2>t1, 0.ltoreq.t1, t2.ltoreq.50.degree. C. and 5.ltoreq.t2-t1.ltoreq.35. Both the first and second colors can be displayed between t1 and t2. For the purpose of determining the proper temperature range for a color characteristic, temperature-sensitive visual indicators are provided.

Abstract: An artificial plant having at least one section which bears a color memory dye of an electron-supplying organic coloring compound, an electron accepting compound an an ester. The color memory dye assumes a first color below t1 (.degree. C.) and a second color above t2 (.degree. C.), wherein t2>t1, 0.ltoreq.t1, t2.ltoreq.50.degree. C. and 5.ltoreq.t2-t1.ltoreq.35. Both the first and second colors can be displayed between t1 and t2.

Abstract: A color memory toy set has a color memory toy with surface, at least one portion of the surface being provided with a color memory temperature-sensitive color changing layer colored with a coloring material including a color memory temperature-sensitive dye exhibiting hysteresis characteristics in response to temperature change between a colored state and a colorless state or between a color (I) state and a color (II) state. The toy set also includes a writing pen for either causing an image to appear or disappear on the color memory temperature-sensitive layer by drawing the image on the layer to change the color state of the drawn portion into a first state, or for causing an image to appear or disappear on the color memory temperature-sensitive layer by drawing the image on the layer to change the color state of the drawn portion to a second state.

Abstract: A new reversible heat sensitive recording composition for erasable recording is disclosed which is used as a recording or marking material that is capable of erasure at a specific temperature so that coloring or decoloring can be controlled to occur at desired temperature ranges. This range or the hysteresis value of the composition is determined by the .DELTA.T value of the contained ester compound. In addition, the compostion can provide a wide variety of hues and can readily be prepared. The marking or recording drawn in this composition can be maintained at room temperature or less.

Abstract: A new reversible temperature indicating composition for use in temperature indicating instruments is diclosed which is capable of accurate temperature indication in a variety of colors and characterized by a minimum range of hysteresis so that the marking drawn in this composition can decolor at or close the temperature at which its coloring takes place. In addition, the composition can provide a wide variety of hues and can be readily prepared. These and other advantages are provided by the inclusion as a main ingredient of an ester compound having .DELTA.T value, defined .DELTA.T=melting point--clouding point, in the range under 3.degree. C., the value that determines a desirably small range of hysteresis.

Abstract: A new reversible heat sensitive recording composition for erasable recording is disclosed which is used as a recording or marking material that is capable of erasure at a specific temperature so that coloring or decoloring can be controlled to occur at desired temperature ranges. This range or the hysteresis value of the composition is determined by the .DELTA.T value of the contained ester compound. In addition, the composition can provide a wide variety of hues and can readily be prepared. The marking or recording drawn in this composition can be maintained at room temperature or less.

Abstract: A thermochromic material is described which comprises (a) an electron-donating, chromatic organic compound, (b) a compound capable of reversibly accepting an electron or electrons from the electron-donating, chromatic organic compound, (c) a compound controlling the temperature and sensitivity of coloration/decoloration of the thermochromic material and (d) a N-radical, P-radical, O-radical or S-radical cationic compound having an aromatic ring or rings which improves by light-fastness.