Abstract: A resist film comprises a dimensionally stable base (B), which is transparent to actinic light in the wavelength range from 300 to 420 nm, and a mask-forming layer (ML) which is sensitive to heat radiation and contains a thermochromic system which, when irradiated with an IR laser having a wavelength greater than 1.00 .mu.m, undergoes an irreversible change in its absorption spectrum in the wavelength range from 300 to 420 nm so that the optical density of the mask-forming layer (ML) in this wavelength range changes by not less than 1.3 units. The base of the resist film can also be applied onto the photosensitive relief-forming layer (RL) of a recording material to give a multilayer image-recording material. Imagewise irradiation with heat, for example using an IR laser, produces, in the mask-forming layer (ML) of the resist film, a UV photomask which is very useful for exposing photosensitive recording materials.

Abstract: A resist film comprises a dimensionally stable base (B), which is transparent to actinic light in the wavelength range from 300 to 420 nm, and a mask-forming layer (ML) which is sensitive to heat radiation and contains a thermochromic system which, when irradiated with an IR laser having a wavelength greater than 1.00 .mu.m, undergoes an irreversible change in its absorption spectrum in the wavelength range from 300 to 420 nm so that the optical density of the mask-forming layer (ML) in this wavelength range changes by not less than 1.3 units. The base of the resist film can also be applied onto the photosensitive relief-forming layer (RL) of a recording material to give a multilayer image-recording material. Imagewise irradiation with heat, for example using an IR laser, produces, in the mask-forming layer (ML) of the resist film, a UV photomask which is very useful for exposing photosensitive recording materials.

Abstract: Acylphosphine oxides of the general formula ##STR1## where R.sup.1 is methyl or ethyl, R.sup.2 is a branched or straight-chain alkyl radical or chlorine, alkoxy or hydrogen, R.sup.3 and R.sup.4 are identical or different, and are each alkyl, alkoxy, alkylthio or chlorine and R.sup.5 is hydrogen, chlorine, alkoxy, alkylthio or alkyl, may be used as photoinitiators in photopolymerizable materials.