Laminar thermal imaging medium containing photohardenable adhesive layer and polymeric elastic and non-brittle barrier layer

Claim 2

A laminar thermal imaging medium comprising an image-forming substance confined between a pair of sheets, said laminar medium comprising in order: a first sheet transparent to said image-forming radiation and having at least a surface zone or layer of polymeric material heat-activatable upon subjection of said thermal imaging medium to brief and intense radiation; a layer of porous or particulate image-forming substance having cohesivity in excess of its adhesivity for said polymeric heat-activatable layer; a release layer to facilitate separation of the thermal imaging medium into first and second images, each in said porous or particulate image-forming substance, upon subjection of the thermal imaging medium to brief and intense radiation and separation of the respective sheets of the medium; a polymeric elastic and non-brittle layer; a photohardenable adhesive layer comprising a macromolecular organic binder and a photopolymerizable ethylenically unsaturated monomer, said layer being hardenable to a layer of sufficient hardness to provide a durable base for an image thereon in said porous or particulate image-forming substance; and a second sheet adhesively bonded to said laminar thermal imaging medium by said photohardenable adhesive layer; said polymeric elastic and non-brittle layer having resistance to diffusion therethrough to said release layer of said photopolymerizable ethylenically unsaturated monomer of said photohardenable adhesive layer; said imaging medium being imageable upon subjection to said brief and intense radiation and being capable of absorbing said radiation and of converting said radiation to heat sufficient in intensity to activate said heat-activatable polymeric material for attachment of said porous or particulate image-forming substance firmly to said first sheet in areas of exposure to said radiation, said polymeric material upon being heated and subsequently cooled being effective to attach said porous or particulate image-forming substance in said areas to or through an intermediate layer to said first sheet.

Claim 3

The laminar thermal imaging medium of claim 1 wherein said photohardenable adhesive layer comprises a macromolecular organic binder; a photopolymerizable ethylenically unsaturated monomer having at least one terminal ethylenic group capable of forming a high molecular weight polymer by free radical-initiated, chain-propagated addition polymerization; and a free radical-generating, addition polymerization-initiating system activatable by actinic radiation.

Claim 4

The laminar thermal imaging medium of claim 2 wherein said polymeric elastic and non-brittle layer is contiguous with each of said release layer and said photohardenable adhesive layer.

Claim 5

The laminar thermal imaging medium of claim 3 wherein said polymeric elastic and non-brittle layer is a barrier layer having resistance to the diffusion therethrough to said release layer of mobile or fugitive species present in said photohardenable adhesive layer.

Claim 6

The laminar thermal imaging medium of claim 4 wherein said polymeric elastic and non-brittle barrier layer comprises polymerized repeating vinylidene chloride units.

Claim 7

The laminar thermal imaging medium of claim 5 wherein said polymeric elastic and non-brittle barrier layer includes copolymerized repeating units from an ethylenically unsaturated monomer copolymerizable with vinylidene chloride.

Claim 8

The laminar thermal imaging medium of claim 6 wherein said polymeric elastic and non-brittle barrier layer has a thickness of from about 1.5 to about 3 microns.

Claim 9

The laminar thermal imaging medium of claim 7 wherein said layer of porous or particulate image-forming substance comprises a layer of carbon black pigment uniformly distributed through a binder of polyvinylalcohol.

Claim 10

The laminar thermal imaging medium of claim 8 wherein said release layer is adapted to facilitate said separation by cohesive failure of said layer on separation of the respective sheets of said medium.

Claim 11

The laminar thermal imaging medium of claim 9 wherein said release layer comprises silica in a binder of polyvinylalcohol.

Claim 12

The laminar thermal imaging medium of claim 10 wherein said surface zone or layer of heat-activatable polymeric material comprises a thin layer of polymeric material having a softening temperature lower than that of said first sheet.

Claim 13

The laminar thermal imaging medium of claim 11 wherein said thin layer of polymeric material comprises poly(styrene-co-acrylonitrile).

Claim 14

The laminar thermal imaging medium of claim 12 wherein said photohardenable adhesive layer is photohardenable to a durable layer by ultraviolet irradiation.

Claim 15

The laminar thermal imaging medium of claim 13 wherein each of said first and second sheets comprises polyethylene terephthalate.

Claim 16

A laminar thermal imaging medium comprising an image-forming substance confined between a pair of sheets, said laminar medium comprising in order: a first sheet transparent to said image-forming radiation and having at least a surface zone or layer of polymeric material heat-activatable upon subjection of said thermal imaging medium to brief and intense radiation; a layer of porous or particulate image-forming substance having cohesivity in excess of its adhesivity for said polymeric heat-activatable layer; a release layer to facilitate separation of the thermal imaging medium into first and second images, each in said porous or particulate image-forming substance, upon subjection of the thermal imaging medium to brief and intense radiation and separation of the respective sheets of the medium; a polymeric elastic and non-brittle layer; a photohardened adhesive layer obtained by photohardening a photohardenable layer comprising a macromolecular organic binder and a photopolymerizable ethylenically unsaturated monomer, said photohardened adhesive layer being of sufficient hardness to provide a durable base for an image thereon in said porous or particulate image-forming substance; and a second sheet adhesively bonded to said laminar thermal imaging medium by said photohardenable adhesive layer; said polymeric elastic and non-brittle layer having resistance, prior to said photohardening, to diffusion therethrough to said release layer of said photopolymerizable ethylenically unsaturated monomer of said polyhardenable layer; said imaging medium being imageable upon subjection to said brief and intense radiation and being capable of absorbing said radiation and of converting said radiation to heat sufficient in intensity to activate said heat-activatable polymeric material for attachment of said porous or particulate image-forming substance firmly to said first sheet in areas of exposure to said radiation, said polymeric material upon being heated and subsequently cooled being effective to attach said porous or particulate image-forming substance in said areas to or through an intermediate layer to said first sheet.

Claim 17

A laminar thermal imaging medium comprising an image-forming substance confined between a pair of sheets, said laminar medium comprising in order: a first sheet transparent to said image-forming radiation and having at least a surface zone or layer of polymeric material heat-activatable upon subjection of said thermal imaging medium to brief and intense radiation; a layer of porous or particulate image-forming substance having cohesivity in excess of its adhesivity for said polymeric heat-activatable layer; a release layer to facilitate separation of the thermal imaging medium into first and second images, each in said porous or particulate image-forming substance, upon subjection of the thermal imaging medium to brief and intense radiation and separation of the respective sheets of the medium; a polymeric elastic and non-brittle layer; a photohardened adhesive layer obtained by photohardening a photohardenable layer comprising a macromolecular organic binder and a photopolymerizable ethylenically unsaturated monomer, said photohardened adhesive layer being of sufficient hardness to provide a durable base for an image thereon in said porous or particulate image-forming substance; and a second sheet adhesively bonded to said laminar thermal imaging medium by said photohardenable adhesive layer; said polymeric elastic and non-brittle layer having resistance, prior to said photohardening, to diffusion therethrough to said release layer of said photopolymerizable ethylenically unsaturated monomer of said polyhardenable layer; said imaging medium being imageable upon subjection to said brief and intense radiation and being capable of absorbing said radiation and of converting said radiation to heat sufficient in intensity to activate said heat-activatable polymeric material for attachment of said porous or particulate image-forming substance firmly to said first sheet in areas of exposure to said radiation, said polymeric material upon being heated and subsequently cooled being effective to attach said porous or particulate image-forming substance in said areas to or through an intermediate layer to said first sheet.

Claim 18

The laminar thermal imaging medium of claim 15 wherein said photohardenable adhesive layer comprises a macromolecular organic binder, a photopolymerizable ethylenically unsaturated monomer having at least one terminal ethylenic group capable of forming a high molecular weight polymer by free radical-initiated, chain-propagated addition polymerization; and a free radical-generating, addition polymerization-initiating system activatable by actinic radiation.

Claim 19

The laminar thermal imaging medium of claim 16 wherein said polymeric elastic and non-brittle layer is contiguous with each of said release layer and said photohardened adhesive layer and has resistance to the diffusion therethrough to said release layer of mobile or fugitive species present in said photohardenable adhesive layer.

Claim 20

The laminar thermal imaging medium of claim 17 wherein said polymeric elastic and non-brittle barrier layer comprises polymerized repeating vinylidene chloride units.

Claim 21

The laminar thermal imaging medium of claim 17 wherein said release layer comprises silica in a binder of polyvinylalcohol.

Claim 22

The laminar thermal imaging medium of claim 15 wherein said photohardened adhesive layer is photohardened to said durable layer by ultraviolet irradiation.