DE3401443A1 - COATING COMPOSITION FOR PHOTO IMAGE PURPOSES - Google Patents

Description

The present invention relates to the production of photographs, photocopies or other fixed images. More specifically, it is an imaging system that uses a coated substrate containing a chromogenic material and a photosensitive composition encapsulated in microcapsules. In the most preferred embodiment of the invention, the chromogenic material and the photosensitive composition are housed in the same microcapsules. ^;

Use various known imaging systems photosensitive inclusions. Such an imaging system which has remarkable advantages over any previously known is commonly referred to as the Sanders process. This process uses a coating composition

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Settlement normally applied to a substrate is. The coating contains a photosensitive composition, which is encapsulated and a chromogenic material which can be inside the microcapsules 5 or not. ("Encapsulated" is used here to refer to both 'open-phase systems, in which the photosensitive Composition as drops in a dispersion medium --- 'is distributed, and systems in which a discrete capsule wall is intended to "comprise") The microcapsules generally have an average diameter of 1μ - 25μ. Images are formed by imagewise exposing the coating composition to actinic radiation. ("Actinic radiation" is used to refer to the entire spectrum of electromagnetic radiation.).

"Image-wise" exposure means that radiation is supplied in a pattern so that areas that are to be dark absorb most of the radiation, while areas that should remain bright absorb little or no radiation, or vice versa. This can be achieved, for example, by placing a template between the radiation source and the Coating. The exposure can be carried out either by direct irradiation or by reflective imaging.

After exposure, the microcapsules, or at least those in the image field, can be broken open by calendering or other suitable means. In the case of a photo-curable

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Photosensitive composition is the viscosity of the photosensitive composition when exposed to it actinic radiation is significantly increased by mechanisms such as crosslinking or simple polymerization. That's why the photosensitive composition, which has been exposed to strong exposure, flows very little, if at all, when the capsules are broken while the unexposed or weakly exposed photosensitive composition is relatively can flow freely. As a direct consequence, the chromogenic material reacts image-wise with the developer accordingly the degree of exposure to form a color in the shape of the desired image. This can take place in several different ways Wise men happen.

In one embodiment, the chromogenic material is encapsulated with the photosensitive composition. Outside of of the capsules, the developer is contained in the coating, which is applied to a substrate. If the If capsules are broken, the chromogenic material can flow but its movement from the exposed capsules is through hinders the increased viscosity of the photosensitive composition in these capsules. As a result, the Ability of the chromogenic material to get to the developer depends on the locally received exposure. The developer and the chromogenic material reacts according to the exposure to form the desired image. When this embodiment of a coating composition is applied to a substrate, the result is a self-contained imaging

foil. -

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In another embodiment it is photosensitive The composition is encapsulated and the chromogenic material is inside or outside of the coating Capsules. A developer can be arranged in the coating as a layer which is separate from the chromogenic material can be on a completely separate substrate. In the former case, the capsule break gives the photosensitive according to the image Composition free. The chromogenic material now reacts with the developer to essentially give a color form in the shape of an image. In the latter case, the two substrates are placed on top of each other while the capsule is broken, so that the released chromogenic material flows onto the developer layer and there according to the image reacted. - '

In an alternative embodiment, the photosensitive Composition be a highly viscous substance which depolymerizes when exposed to actinic radiation, In this case, the chromogenic material in or near the exposed capsules, instead of the unexposed ones, can go to the developer access. This changes the imaging system from positive to negative.

The photosensitive composition contains a photoinitiator and a substance that acts upon exposure to light undergoes a change in viscosity in the presence of the photoinitiator. This substance can be a monomer, or dimer

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Be an oligomer which is polymerized to form a compound higher molecular weight, or can be a polymer which is crosslinked. Alternatively, they can connect which is depolymerized or otherwise dissolved upon exposure. Radiation-curable materials, which are often used are materials that are hardenable

one
advancing in chains triggered by / by free radicals

Addition polymerization or ionic polymerization.

Representative radiation curable materials are ethylenically unsaturated organic compounds. These Compounds contain at least one terminal ethylene group per molecule. Typically they are at room temperature liquid and can also serve in two functions as a carrier oil for the chromogenic material in the internal Phase. A preferred group of radiation-curable materials are ethylenically unsaturated compounds, the two or more terminal ethylenic groups per molecule to have. Representative examples of these compounds include ethylenically unsaturated acidic esters of polyvalent ones Alcohols such as trimethylol propane acrylate or trimethacrylate, acrylate prepolymers derived from the Partial reaction of pentaerythritol with acrylic or methacrylic Acid or acrylic or methacrylic acid esters; isocyanate modified acrylates, methacrylic and itaconic acid esters of polyhydric alcohols, etc.

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Some typical examples of photo softeners Materials useful in other embodiments are photo-soluble compounds such as certain diazonium compounds, 3-oximino-2-butanone methacrylate, which undergoes a main chain cleavage when exposed to UV radiation and poly-4'-alkylakylophenones.

Different photo initiators are used. These compounds absorb the exposure radiation and generate a free radical alone or in combination with a sensitizer. Suitable photoinitiators contain oC alkoxyphenyl ketones, Michler's ketone, O-acylated oC-oximinoketones, polycyclic quinones, .Benzophenones and substituted benzophenones, xanthones, thioxanthones, halogenated compounds such as chlorosulfonyl and chloromethyl polynuclear aromatic compounds, chlorosulfonyl and chloromethyl heterocyclic compounds Compounds, chlorosulfonyl and chloromethylbenzophenones and fluorones, haloalkanes, o6-halo - (? C-phenylazetophenones; photo-reducible dye-reducing agent redox couples, halogenated paraffins (e.g. brominated or chlorinated paraffin) benzoin alkyl ethers etc. - "-.-.

The embodiments described above are just a few of the possible variations on the Sanders process. The devices and methods of each embodiment

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exhibit has an imaging system ', the significant practical, commercial and functional advantages over the conventional Äbbildungssystemen. Various aspects of this process are disclosed in the following co-pending applications, which are incorporated herein by reference: Serial No. 302,356, filed 11/12/1981, now U.S. Patent 4,399,209; . Serial No. 320,643, filed on 12.11.1981, - and Serial No. 339,917, einge- ^ presented on 18/01/1982..

After exposure and the capsule breakage, the oil phase (i.e. the photosensitive composition and the chromogenic material) to the developer layer, which at the self-contained imaging film on the same ■ The substrate is like the microcapsules and in the case of a transfer film on a separate substrate.

Some of the formed color is shown in the photo * sensitive oil phase retained in a mobile solution, after the image is formed. This is especially true when large quantities of heavier photosensitive materials are used Oil form the internal phase. When the photosensitive composition does not respond quickly to visible light After the capsule has been broken and the image has been formed, the image can in individual cases go down into and over the imaging film bleed, which blurs and reduces the intensity of the image. This effect will sometimes

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"Feathering" called. '

The present invention solves the problem of image diffusion in the imaging system according to the Sanders method by including an agent in the coating composition, that with the photosensitive composition released from the microcapsules after exposure reacts (especially from a photo-curable

or photo-softenable type) and cures them or hardens them in some other way. This means (hereinafter referred to as a "curing agent") is typically a free radical generating species, such as a thermal one Initiator. Even though one might expect the photosensitive composition to be present in the image areas. emerges from the microcapsules, could be cured by a subsequent exposure to actinic radiation, this has been found to be ineffective. In cases where image diffusion occurs, it has been found to be it is desirable to include a curing agent in the composition for subsequent reaction with the released photosensitive composition.

The curing agent is preferably encapsulated. It can be in the same capsules as' the photosensitive one Composition or housed in "separate photo-inert capsules. The latter is preferable. If it is housed in the same photoactive capsules

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the effect is the same at the beginning, but a pre-hardening of the capsule contents can occur in individual cases and the entire photosensitivity can be lost in a few days. An inert oil carrier can be contained in the capsules containing the hardening agent; hold to flow and harden in case of breakage ·; facilitate. . ^:

The hardening agent is preferably selected according to criteria such as durability, reactivity with the photographic ^:

. sensitive composition, lack of water solubility, Solubility in an inert oil carrier, low hydrolysis rate in the presence of water phases with a pH between about 3.5 to 9.5, ability to encapsulate; and other characteristics associated with known encapsulation,

techniques are consistent. ,;

By exposing a coating of the composition to light, breaking the capsules alone (in the case of a self-contained system) or in contact with a developer film, and preferably heating the image to activate the hardener or accelerate hardening, stable images can be obtained be formed. The chromogenic material reacts with the wrapper to form a colored image, and the hardening agent hardens the photosensitive composition which oozes from the capsules to prevent image diffusion.

In addition to greatly reducing image diffusion, it also improves dirt and solvent resistance improved and the images become more abrasion-resistant.

The present invention is an improvement to an imaging system that includes a coating of a microencapsulated Photosensitive composition, a chromogenic material contained within the capsules may or may not be, and uses a developer that may be included in the coating or on one separate substrate can be provided, images being generated by imagewise exposure of the coated Substrate with actinic radiation and subsequent breaking of the capsules. If the developer is on a separate Is substrate, the two substrates are placed on top of one another while the capsule is being broken open. In these systems After the image develops, some color remains dissolved in the photosensitive phase emerging from the capsules leaks and can flow through and over the substrate, reducing the image sharpness and intensity until the photosensitive phase has responded.

The preferred embodiment of this invention contains a chemical (essentially non-photosensitive) Hardening agent for the photosensitive composition in the coating composition. The function of the hardener is to change the photosensitive composition

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to harden after developing. After the color is up. Once formed, the rapid curing of the photosensitive composition prevents one Overdevelopment and diffusion. The chemically hardened photosensitive composition is made in this way "frozen" and the color stays in place and does not diffuse. The hardening agent is more suitable Way with an inert carrier enclosed in capsules separate from those that are photosensitive Composition included. Maintaining, separate Encapsulation prevents pre-hardening, which could disrupt the photosensitivity of the imaging system within days. .

The selection of the curing agent and inert carrier oil for encapsulation requires consideration the capsule wall material, the conditions prevailing in the anhydrous phase outside the • capsules and the storage temperatures. Further criteria for the selection of the curing agent are lack of water solubility, solubility in inert carrier oil (which in turn should be compatible with the oil phase in the capsules of the photosensitive) Composition), relatively low hydrolysis rate in water phases with a pH value between 3.5 and 9.5 for up to i

for two hours at 40-50 ⁰ C, capability of encapsulation, and other considerations with respect to the encapsulation. It's I

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It is important that the encapsulated curing agent has a suitable shelf life. ■

Preferred curing agents are free radical generators, such as thermal initiators, which are used in the Reaction with the photosensitive composition will cause it to polymerize or crosslink. By loading

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exposing the coating composition to actinic radiation and rupturing the capsules in the presence of one Developer material, the chromogenic material and developer reacts to produce color in the form of an image, and the hardening agent reacts with and hardens the photosensitive composition, thereby causing image diffusion is prevented. In the case of certain hardeners, it may be desirable to heat the image in order to harden it

to accelerate. A hardening agent is preferably selected, which is relatively inactive at room temperature (for good storability) and which is due to heating can be easily activated at temperatures above room temperature.

A particularly useful class of thermal initiators, which are reactive with ethylenically unsaturated compounds are organic peroxides. Suitable peroxides contain e.g. diacyl peroxide, ketone peroxide, peroxydicarbonate, alkyl peroxide, alkyl hydroperoxide and sulfonyl peroxide. Useful Bisazides, perborates and diazo compounds are also used as thermal initiators.

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Carrier oils conventionally used in forming pressure sensitive Microcapsules used can be used in the present invention provided: that they are essentially inert to the curing agent.

Examples are deodorized kerosene, alkylated, Biphenyls and alkylated phthalates. j

The encapsulation process chosen must provide a high yield of thermal initiators that are over.!

j's. j

■ ν "an extended storage time, be it in water dispersion! or after being applied to a substrate, j

The temperature must also be maintained during manufacture and storage

be kept below a level that allows rapid decomposition

setting of the thermal initiator would trigger. That's why ;

initiators are preferably used which are below about;

25 ⁰ C cannot be activated.

In individual cases, peroxides can be flammable. This problem can be avoided by limiting the amount used. Preferably, the amount of peroxide used should be about 0.1 to 1% by weight of the photosensitive composition used. Thus, if 3 lbs. Of photosensitive composition ^{capsules are used for 3.3-feet 2} of substrate paper, only 0.03 lbs. Of peroxide will be present at a 1% usage level. This amount corresponds to about 0.6 lbs. Of peroxide oil solution, which is non-explosive and can be safely burned off.

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The following examples illustrate the preparation according to the present invention and its effectiveness when braking image diffusion.

The microcapsules containing the peroxide used in the following examples were as is made as follows:

A batch of peroxide-containing capsules was prepared by incorporating 5 g of commercial peroxide into a 'diocthyl phthalate oil phase made from Lupersol PDO (made by Lucidol, Pennwalt). The total solution was about 50g. After heating to 60 ⁰ C, the oil phase a Waring blender Wurd added which contained a water phase of about 6O ⁰ C which was stirred already at full power. The water phase contained 26.9 g of a 17.1% isobam solution, the pH of which was adjusted to 4.0, 38.3 g of distilled water, 25 g of a 10% aqueous gum arabic solution, 6.6 g of dissolved urea and 0.8 g Resorcinol. After the oil phase had been dispersed with an average of about 5μ, the tension was reduced to. about 40 ν and 17 ml of 37% formaldehyde solution was added. The combined solutions were mixed at 40 V and 60 ⁰ C for more than two hours. A solution of 0.6 g ammonium sulfate and 12.1 g water was then added and mixed for an additional 15 minutes. The mixture was transferred to a beaker and further mixed for one hour at 60 ⁰ C. The pH was adjusted to 7.0 by the dropwise feeding of a 10% sodium hydroxide solution, and the

Capsules were retained for further use.

The photosensitive microcapsules used in the following Examples used were prepared as follows.

A batch of photosensitive capsules was treated in the same manner under darkroom conditions like the batch of peroxide capsules, with two exceptions. The ingredients were doubled in amount and contained the oil phase 100g trimethylolpropene triacrylate, 6g Kopikem IV (a product of the Hilton-Davis Co.), 5g benzoin methyl ether and 2g of Michler's ketone. The final pH was adjusted to 9.0 and 5.6 g of sodium bisulfate was added and dissolved. The capsules were in foil-wrapped bottles housed to prevent premature exposure.

Comparative example · . .

Part of the photosensitive capsule batch 2 was mixed with j the same amount of 10% solution of gum arabic I. dissolved and then mixed well. Then the mixture was under. Darkroom conditions over the coated side of a j

Cast sheet of Mead Transrite Impact paper. The damp Mixing was through a No. 10 Mayer rod in machine;

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direction deducted. The coating was dried in a circulating hot air oven for 2 minutes at 9O ⁰ C.

Two strips of the dried coated surface were cooled, aged for one hour under darkroom conditions, and then imagewise exposed with a Stouffer transparent sensitivity guide, which is a stepped gray scale. The two strips were then developed with Gilclear and covered by passing through a laboratory super calendar, the measured value was set at 20 lbs., Which is approximately 600 Pfd./Linear-Inch contact surface .. One of the films was developed for 5 minutes in the 90 ⁰ C oven placed. This created a gray scale on each sample. The samples were placed in a heavy gray envelope for aging. The effect of aging on image density (the final gray level step) is shown in Table 1 below.

example 1

The coating composition was prepared by mixing 10 g of peroxide capsules with 90 g of photosensitive capsules Capsules and 100g of a 10% solution of gum arabic. The pH was adjusted to 7.0.

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This composition was used to make paper coat and produce exposed and developed samples as in the comparative example. The two resulting Samples were placed in the same envelope as the control. The aging effect on the Image density is shown in Table 1.

Example 2

■ A coating composition was prepared by mixing 20 g of peroxide capsules with 80 g of photosensitive capsules and 100 g of a 10% solution of gum arabic. The pH was adjusted to 10.0. Otherwise the procedure was the same as in Example 1 ... The results are shown in Table 1. \

Table 1 shows the results of these tests carried out by;

the last grayscale step of the sample images was measured

before the change in visibility of the gray scale.

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Tabel-Ie Ί

Example illustration aging

Last gray scale level 15 min. After 60 days after development Development

comparison 26 ° C. 26 ° C 9 comparison 26 ° C. 5 minutes at 90 ° C
then chilled
to 26 ° C 8th 1 26 ° C. 26 ° C 9 26 ° C. 5 minutes at 90 ° C
then chilled
to 26 ° C . 9 2 "26 ° C. 26 ⁰ C 9 2 26 ° C. 5 minutes at 90 ° C
then chilled
to 26 ° C 9

7 7

9 9

9 9

These results clearly show that the embedding of peroxide capsules in the coating provides a precise and stable image over a long period of time. Even if no tests were done, it is believed that there will also be improved soil and solvent resistance and abrasion resistance occurs as a result. An additional check confirmed that the organic, peroxide remained active and that a very large fraction remained at least for several months, both in the case of the water-suspended. Encapsulation as well as on the dried paper.

The foregoing description is for illustrative purposes only. You should not determine the scope of the invention, the only is intended to be limited by the following claims. .

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Claims (16)

Claims 10 1. ^l '. Coating composition for photographic purposes which contains a chromogenic material, breakable microcapsules containing a photosensitive composition and a hardening agent, characterized in that images are formed by imagewise exposing the coating composition to actinic radiation and by breaking the microcapsules in the image field, so that the chromogenic material can react with an associated coreactive developer material to form a color image, and after the capsule is broken, the hardening agent reacts with and cures the photosensitive composition to provide image stability as it ages. '"' ^: 340H43 -ι- 2. Composition according to claim 1, characterized in that the curing agent is a free one Free radical generating compound is. 3. Composition according to claim 2, characterized in that that the curing agent is a thermal initiator. ". ■■ * ' " .ν ■ 4. Composition according to claim 3, characterized in that the thermal initiator is an organic peroxide. 5. Composition according to claim 4, characterized in that the amount of the organic Peroxide is less than 1% by weight of the amount of the photosensitive composition. 6. Composition according to claim 5, characterized in that - j. 15 indicates that the organic peroxide is selected from the group of diacyl peroxide, ketone peroxide, peroxydicarbonate, alkyl peroxide, alkyl hydroperoxide and sulfonyl peroxide. 7. Composition according to claim 1, characterized in that - indicates that the photosensitive composition is a photopolymerizable ethylenically unsaturated one Connection contains. 8. An imaging film comprising a substrate and a coating composition on a surface of the substrate, the composition being a chromogenic material, breakable microcapsules that are photosensitive Composition containing, and containing a hardening agent, characterized in that Images are generated by image-wise exposure of the sub- ^. strats with an actinic radiation, and by breaking it open of the microcapsules in the image field, so that the chromogenic material with an associated Korean developer material reacts to form a color image, and the hardener reacts with the one that has leaked from the microcapsules photosensitive composition reacts to improve image stability with aging. 9. Film according to claim 8, characterized in that the curing agent is a generator from free radicals. 10. Film according to claim 9, characterized in that the curing agent is a thermal Is the initiator. 11. Film according to claim 10, characterized in that the thermal initiator is an organic Is peroxide. - ■ -3 - O _Opv * 12. Film according to claim 11, characterized in that the amount of the organic peroxide is less than 1% by weight of the amount of the photosensitive composition. 13. Film according to claim 1-2 / characterized in that the organic peroxide is selected . «- ■" from the group of diacyl peroxide, ketone peroxide, peroxydicarbonate, Alkyl peroxide, alkyl hydroperoxide and sulfonyl peroxide. 14. Film according to claim 8, characterized in that the photosensitive composition is a photopolymerizable ethylenically unsaturated compound. 15. Foil according to claim 8, characterized in that g e k e η η, that the developer material is on the same surface of the substrate as the coating composition is provided. 16. Film according to claim 8, characterized in that the developer is on a separate Foil is provided.