JPS6159448A - Photosensitive image forming material using capsulization radio-sensitive composition having improved tone quality - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

BACKGROUND OF THE INVENTION The present invention relates to imaging materials of the type in which a layer of photosensitive microcapsules is provided on a photographic support, and more particularly the microcapsules contain a crystalline organic material in the internal phase. Imaging materials with improved tonal properties containing compounds.

U.S. Pat. The specification describes a transfer image forming system in which the image forming sheet comprises a support carrying a layer of photosensitive microcapsules, and a self-contained (5elf-contained) image forming system.
ained) Describe the image forming system.

Microcapsules are exposed to actinic radiation (aatlnl).

ra old atlon) contains an internal phase containing a photosensitive composition that undergoes a viscosity change upon exposure. The photosensitive composition is typically a photocurable composition, such as a composition that undergoes radical addition polymerization. Imaging materials can be used to form dye images or light scattering images, but imaging agents are typically substantially colorless compounds that generate colored dyes upon reaction with a color developer. is encapsulated with a photosensitive composition in the internal phase of the microcapsule. In self-contained imaging systems, co-reactive developer materials are provided on the surface of the imaging sheet along with photosensitive microcapsules. In transfer imaging systems, the developer is provided on a separate sheet.

To form an image, the imaging sheet is image-wise exposed to actinic radiation and subjected to a uniform destructive force, during which the microcapsules rupture and the internal phase is image-wise released. In the case of microcapsules containing photocurable compositions, the internal phase is released in areas that are not exposed or underexposed to actinic radiation. In these regions, the microcapsules remain fluid enough to rupture and the internal phase to be released from the microcapsules. How, in these regions, the imaging agent associated with the microcapsules can react with the developer material and form a color image. In sufficiently exposed areas, the microcapsules either cannot be broken or, even if they are, the internal phase is too viscous to be released from the capsule. Detailed descriptions of these imaging materials and methods of forming images can be found in both of the aforementioned patent specifications.

SUMMARY OF THE INVENTION It is a principal object of the present invention to provide an imaging material of the above type having a low gamma value and a wide (4t) range that is useful in forming images with improved tonal characteristics. The imaging materials of this invention are particularly useful in applications requiring continuous tone quality.

According to the invention, crystalline organic compounds are added to the internal phase of the photosensitive microcapsules characterizing said imaging system. The crystalline organic compound has the effect of increasing shoulder velocity while decreasing foot velocity, thus extending the dynamic range of the imaging material by 5 Kt. Although not wishing to be limiting, in the microcapsules of the present invention, the photosensitive composition is trapped within the crystalline matrix within the microcapsule, where it is protected from oxygen and remains free from oxygen inhibition. I can believe it if you don't accept it. It is believed that this can respond to the increased shoulder velocity obtained with these imaging materials. The reduced foot speed is likely a result of requiring more photosensitive composition to react to immobilize the imaging agent when non-polymerizable crystalline organic compounds are present. It appears that the halftone speed of the imaging material of the present invention M→Zenbon is not affected by crystalline organic compounds. In this way, the addition of crystalline organic compounds to the internal phase of photosensitive microcapsules can transform an imaging material that would otherwise have a relatively high gamma into an imaging material that has a lower gamma, without sacrificing film speed. can be used to convert These materials are useful in applications requiring better tonal quality.

Thus, one specific example of the present invention is an image forming material comprising a support having a photosensitive microcapsule layer on its surface9, wherein the microcapsules contain a photocurable composition and a crystalline organic compound. Including internal phase containing.

According to a preferred embodiment of the invention, disjoint (dls
microcapsules having a capsule wall and an internal phase may additionally contain an imaging agent, e.g. a substantially colorless electron-donating compound, which forms a color upon reaction with an electron-accepting compound, e.g. acid clay or a salicylic acid derivative. include.

According to a still further preferred embodiment of the invention, the radiation-sensitive composition is a photocurable composition, more particularly a composition that undergoes radical addition polymerization, such as a composition comprising an ethylenically unsaturated compound and a photoinitiator. It is a thing.

Definitions The term "microcapsule" as used herein encompasses both microcapsules with discrete capsule walls and so-called open phase microcapsules formed by dispersing the internal phase in a binder.

The term "actinic radiation" as used herein encompasses the entire electromagnetic spectrum, such as visible, ultraviolet and infrared radiation, and particle radiation, such as X-rays and ion beam radiation. Preferred forms of actinic radiation include ultraviolet and visible light (wavelength/
O-♂00nrn, more preferably 310-4'J'
(17 nm).

DETAILED DESCRIPTION OF THE INVENTION The imaging material of the present invention further comprises that the internal phase of the microcapsules includes a crystalline organic compound. Virtually any crystalline organic compound that does not inhibit the reaction of the radiation-sensitive composition and that substantially absorbs the exposing radiation can be used in the present invention. The internal phase of the microcapsule containing the radiation-sensitive composition is lipophilic, and as such, water-soluble organic-inorganic compounds cannot be incorporated into the internal phase and cannot be encapsulated using conventional encapsulation techniques. , crystalline compounds are described herein as "organic."

Thus, the term "organic" simply means that the crystalline compound is compatible with the internal phase of the microcapsule.

The crystalline organic compounds used in the present invention preferably have a melting point of less than 100°C, even more preferably less than 5'0°C. At the same time, the compound must be crystalline at room temperature (,2J'C). Preferably, the crystalline organic compound is miscible with the radiation-sensitive composition,9 and more particularly the crystalline organic compound is miscible with the monomer, such as trimethylolpropane triacrylate,9 and is therefore crystalline. Upon melting the organic compound and mixing with the monomer/radiation-sensitive composition, a homogeneous phase is formed which upon cooling provides a crystalline matrix with microvoids containing the radiation-sensitive composition. Preferably, the crystalline organic compound is substantially insoluble in water so that it can be dispersed in the subsequent aqueous phase for encapsulation without being removed from the internal phase by extraction.

Representative examples of useful crystalline organic compounds include /, 2-diphenoxyethane, cyclododecanol, /-docosanol, l-octadecanol, p-jethoxybenzene, octacosane, pentamethylbenzene, bibenzyl, and piphenyl. Including.

Crystalline organic compounds are typically used in amounts of about 0.1 to 7 parts by weight per part by weight of the radiation sensitive composition.

Crystalline organic compounds can be synthesized by melting the crystalline organic compound, mixing it with a photosensitive composition, and forming a wall around it using conventional encapsulation techniques, such as coacervation or interfacial polymerization. , 2 or 9 can be encapsulated in the internal phase of microcapsules by dispersing the internal phase in a suitable binder.

As mentioned above, it is particularly desirable that the crystalline organic compound be miscible with the radiation-sensitive composition so as to provide a crystalline arrangement with photosensitive regions or microvoids. Preferred microcapsules are urea-formaldehyde or urea-formaldehyde.
It has a discrete capsule wall formed from a resorcinol-formaldehyde copolymer.

The radiation-sensitive compositions of the present invention are photocurable compositions that undergo an increase in viscosity upon exposure to actinic radiation.5 The photocurable compositions described in the aforementioned US patents may be used in the present invention. Preferred compositions contain an ethylenically unsaturated compound and a photoinitiator system. Typically, the ethylenically unsaturated compound contains one or more terminal tf containing pendant vinyl or allyl groups. What compounds are well known in the art?9
It also includes acrylic esters and methacrylic esters of polyhydric alcohols such as trimethylolpro-kun and pentaerythritol nato. Typical examples are ethylene glycol diacrylate, ethylene glycol dimethacrylate, trimethylolpropane triacrylate (
TMPTA), )limethylolpropane trimethacrylate (TMPTMA), pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, hexanediol-/, &-dimethacrylate, diethylene glycol dimethacrylate and dipentaerythritol hydroxypentaacrylate. Commercially available photopolymers such as acrylate and methacrylate terminated polyesters and polyethers are also useful in the present invention.

The radiation-sensitive compositions used in the present invention typically include a photoinitiator system. The photoinitiator system can include a sensitizer. Absorbers can also be used in conjunction with the system to adjust the sensitivity of the photosensitive composition. A photoinitiator that generates free radicals upon photochemical cleavage (
Homolytic initiators), such as benzoin ethers, and initiators that act by hydrogen abstraction are useful.

Diaryl ketone derivatives and benzoin alkyl ethers are particularly useful. Specific examples of useful initiator systems are benzophenone, Michler's ketone, benzoin methyl ether, and λ2,2'-dimethoxy λ-phenyl-acetophenone, isopropylxanthone, isopropylthioxanthone, (ethyl p-dimethylaminobenzoate), and U.S. Pat. It includes ketocoumarin compounds such as those described in the specification of No. g/4'ZtJ-λ.

The photoinitiator is present in the photosensitive composition in an amount effective to initiate polymerization or crosslinking. For example, isopropylthioxanthone is typically present in an amount up to about 10% by weight, based on the weight (l/) amount of photocrosslinkable or photopolymerizable material present in the photosensitive composition. The exact amount of photoinitiator used will vary depending on the nature of the photosensitive composition. It is also possible to shorten the exposure time by incorporating a scattering agent, such as magnesium oxide, into the capsule layer. Scattering agents increase the mean free path, thereby enhancing exposure.

UV-sensitive microcapsules are generally preferred because they can be handled in room light for a short time.

UV sensitive microcapsules are also useful for copying from CRT screens. However, one disadvantage of UV-sensitive systems is that many prints are on paper that contains optical brighteners that absorb UV radiation. For copying printed matter, front-window color light systems are therefore advantageous.

According to certain embodiments of the invention, particularly those in which the photosensitive composition contains a photopolymerizable monomer, such as TMPTA, the photosensitive composition contains an oligomer and / or may include polymeric materials. Typically, these materials have average molecular weights in the range of about 100 to 3,000 for oligomers and 1.0 to 3,000 for polymers. to, oo
It is up to o. The oligomer or polymer can be reactive, ie, capable of being cured or polymerized by radically initiated polymerization, or it is not reactive. In both cases, the oligomer or polymer increases film speed by increasing the rate at which the viscosity of the composition reaches a level where it can selectively destroy the microcapsules.

Representative of some commercially available oligomers useful in the present invention are Ebeoryl, 2110
゜Ebecryl, 270, Ebecryl 110 (Virginia Chemicals, Inc.); DE
RJJ, 2, DERJ3U, DERJ4GU (Dow Chemica/l/-Kanpashi); Cargll
l ) /! 70 (Kargil); Uvlth
ans) Iri3 (Morton Thiokol Inc.); 0-diallyl phthalate prepolymer (
Polysciences); polyvinylpyrrolidone (GAF
).

In some cases it is advantageous to incorporate polythiols into photosensitive compositions to improve sensitivity (film speed). Useful polythiols contain two or more terminal or bendane)-8H groups.

Examples of desirable polythiols for use in the present invention are:
They are esters of thioglycolic acid and β-mercaptopropionic acid. Representative examples of preferred polythiols include ethylene glycol bis(thioglyconaute) and ethylene glycol bis(β-mercaptopropionate).
, trimethylolpropane tris (thiocricholate)
, pentaerythritol tetrakis (thioglycolate) and most preferred pentaerythritol tetrakis (β-mercaptopropionate), dipentaerythritol hexa (β-mercaptopropionate) and trimethylolpropane tris (β-mercaptopropionate), and mixtures thereof. These compounds are commercially available. Polypropylene ether glycol bis(β-mercaptopropionate), produced by varnish (/II) chilling, may also be useful.

One example of an imaging agent useful in the present invention is a colorless electron donating compound. Typical examples of such color formers include substantially colorless compounds having a lactone, lactam, sultone, spiropyran, ester or amide structure in their partial skeleton, such as triarylmethane compounds, bisphenylmethane compounds, xanthine compounds, Includes fluorans, thiazine compounds, spiropyran compounds, etc. Crystal Violet Lactone and Copichem (Cop
ikam)

Typical examples of color developers used in conjunction with electron-donating color precursors are clay minerals, such as acid clay, activated clay, attapulgite, etc.; organic acids, such as tan(/,5) nic acid, gallic acid, propyl gallate. etc; acid type combination,
For example, phenol-formaldehyde resins, phenolacetylene condensation resins, condensates of formaldehyde and organic carboxylic acids having at least one hydroxy group; metal salts of aromatic carboxylic acids, such as zinc salicylate, tin salicylate.

Zinc co-hydroxynaphthoate, 3.3-di-tart
-Zinc butylsalicylate (U.S. Patent No. 3, IAIA/
μ in the specification and 3. 345,070), 3. Zinc t-di(methylbenzyl)salicylate,
Oil-soluble metal salts of phenol-formaldehyde novolac resins (e.g., U.S. Pat. No. J, A 7.1?, Li 3)
J, 732.720 and J, 73 Z Hiroshi 70). For example, U.S. Patent No. J, 7 J, 2. /20, zinc-modified oil-soluble phenol-formaldehyde resins, zinc carbonate, etc., and mixtures thereof.

Images can also be formed using chelating agents as imaging agents that react with metal salts as color developers to generate color images upon release from the microcapsules. Some typical examples of useful imaging pairs of this type are nickel nitrate/
N,N'-bis(2-octanoyloxyethyl)dithioxamide, and Fe(m)miWuban/yellow salt.

Virtually any color former that can be encapsulated and will react with the developer material to form an image can be used in the present invention. Additionally, either a color former or developer can be associated with the microcapsules.

As is common practice, encapsulating the color former is
Not necessarily necessary.

As yet another alternative, the capsules can contain visible dyes or pigments. Virtually any mildly colored dye, ie, a dye that does not deleteriously attenuate the exposing radiation, may be used in this embodiment. A few examples are Sudan Blue and Rhodamine B dyes. Pigments or toners can also be used.

The imaging agent can be associated with the microcapsules in a variety of ways that upon release of the internal phase, the imaging agent can react and/or migrate to form an image. Imaging agents are typically encapsulated with the photosensitive composition in microcapsules, but can also be incorporated into the walls of the microcapsules. Those skilled in the art will recognize that a variety of arrangements can be used, provided that activation or migration of an imaging agent is controlled by rupturing the microcapsules and releasing the internal phase.

The internal phase can additionally include diluent oil. The oil composition is
It will often improve the 7-tone gradation in the visual image. Preferred diluent oils are weakly polar solvents with a boiling point greater than 170°C, preferably between /rθ and 3θ0°C. Examples of carrier oils include alkylated biphenyls (e.g.
monoisopropyl biphenyls), polychlorinated biphenyls, castor oil.

Mineral oils, deodorized solvent oils, naphthenic mineral oils, dibutyl fumarate, dibutyl fumarate, brominated paraffins and mixtures thereof. Alkylated biphenyls and soluble oils are generally used as well! 7. It's not good, but it's preferable. The amount of diluent oil incorporated into the microcapsules will depend on the photographic properties desired for the light-sensitive material.

Typically, the diluent oil is about 10% by weight of the internal phase.
g] to J weight range.

Photosensitive microcapsules of the present invention can be easily formed using known encapsulation techniques. The photosensitive composition and related agents may contain hydrophilic wall-forming materials, such as gelatin-type materials (
U.S. Patent No. 6730,1ljA and Citr.
1. For example, gum arabic, polyvinyl alcohol, carboxymethyl cellulose; resorcinol-formaldehyde wall-forming agents (see U.S. Pat. No. 3.7J/90); isocyanate wall-forming agents (U.S. Pat. (See Patent No. 3/41,311); isocyanate-polyol wall forming agent (
Urea-formaldehyde wall-forming agents, especially urea-resorcinol whose lipophilicity is increased by the addition of resorcinol
Formaldehyde (U.S. Patent No. 4007./IAO
No. Specification, No. 1 AOIZ37 to No. Specification and No. 'AO
and melami/formaldehyde) (see US Pat. No. 11.02/RS);

The average size of the microcapsules of the present invention is generally in the range of about /-gμ. In general, resolution improves as the capsule size decreases, except that if the capsule size is too small, the capsule may disappear into some of the substrate pores or fibrous structures.

The imaging agent is used in an amount sufficient to form a visible image of the desired density upon reaction with the developer or upon transfer. Generally, the imaging agent is about 0.0% based on the weight of the photopolymerizable or photocrosslinkable species. It is present in an amount of j − j j weight. A preferred range is about 2 to io weight.

The most common substrate for image-receiving sheets is paper. The paper can be a commercial impact base paper or a special grade paper such as cast foot paper or chrome rolled paper. Transparent substrates, such as polyethylene terephthalate and translucent substrates, can also be used in the present invention.

The teachings of the present invention can be used with both transfer imaging systems and self-contained imaging systems such as those described in U.S. Pat. obtain.

Further, the teachings of the present invention are disclosed in U.S. Pat. It can be used with full color imaging systems such as those described in the Tata patent.

The invention is illustrated in more detail by the following non-limiting examples. Unless otherwise specified9, all complaints are based on weight.

Example/ As Home Secretary, Fanticure BMS (Ward Blenkinsop Limited), Fanticure E
PD (Ward Blenkinsop Limited), 2
and crystal violet lactone/g and microcapsules containing trimethylolpropane triacrylate (TMPTA) and/or 2-diphenoxyethane in a total amount of 5 Og as shown in the table below. Prepared by encapsulation method.

Capsule preparation/100 m water in a stainless steel beaker
μg and isobutylene-maleic anhydride copolymer (2
Insert 0,6chi), 22,jll.

λ, clamp the beaker in place on a hot plate under an overhead mixer. 4tJ” with 2 blades
Pitch turbine impellers are used on the mixer.

3. After mixing thoroughly, slowly pour 3.1g of pectin into the beaker. The mixture was stirred for 20 minutes (Q2) (Quadrol) (2-hydroxypropylethylenediamine with propylene oxide from BASF) 0. ．． Add 2g.

5. Accelerate mixer to 3000 rpm and add internal phase over 10-13 seconds. Continue emulsification for 70 minutes.

B. At the start of emulsification, raise the temperature of the hot plate to 5 so that heating continues during emulsification.

7. After 70 minutes, reduce the mixing speed to 100 Orpm and add urea solution (, tO% w/w) #;, 1 11, water 1
Add resorcinol o, rg in 01/, formaldehyde (37%) u/, 5, 9 and ammonium sulphate o, tg in water lo ml at λ minute intervals.

8. Cover the beaker with foil and use a heating gun to bring the temperature of the product to 6S°C. When 63° C. is reached, adjust the hot plate to maintain the temperature for 2-3 hours of curing time. At this time, the capsule wall is formed.

(,2,?) 9. After curing, stop heating and adjust pH to 2.0 using JO% NaOH solution.

10. Add dry sodium bisulfite (.2, lrg) and cool the capsule product to room temperature.

Imaging Sheet Preparation The capsule product obtained in step 5 above was treated with water containing o,rs Triton X-100 surfactant (Haas Company, Rohm-End):
/ diluted and Nn12, go bond with wire wound rod (
Approximately Jt#kl) black and white paper (The Mead Co., Ltd.) was coated.

After drying, roll the sheet into 7 7! ; a light source consisting of T r/B L and one 13Tr/D fluorescent tube was exposed for V seconds at a distance of 6 inches from the light source through a step wedge. 90chi, left Ochi, and IO clerk D
The stair floors and γ values corresponding to m-rainbows are shown in the table below.

Table/ TMPTA (jOg) 3. / 1
0.11/ 9.07 7. Hiro TMP
TA(JQ) TMPTA , 2jg As Table 1 shows, the addition of /,2-diphenoxyethane reduces the γ value of the imaging material from 3.0 to /,θ. Similarly, the dynamic range (RI0%Dmax and IO%Dmax
The number of stairs 11h) between the two steps increases from about 3 steps to about 7 steps. Thus, the addition of crystalline organic compounds such as /,2-diphenoxyethane represents a viable means of reducing gamma while simultaneously providing a high speed photographic system.

Example λ Fanticure EMS (Ward Blenkinsopp Limited) 4J5, Fanticure EPD (Ward Blenkinsopp Limited), 2g, Crystal Violet Lactone/y,) Limethylolpropane Triacrylate 8g and Crystalline Organic Microcapsules containing cyclododecanol Sg as the compound were prepared according to the same method as described in Example/5. Imaging sheets were prepared as in Example 5 and imagewise exposed. The imaging materials exhibited gamma values and dynamic ranges shown in Table 1 below.

Table Cocyclododecanol (27g) Although the present invention has been described in detail and with reference to specific embodiments thereof, it does not fall within the scope of the invention as defined in the claims. It will be obvious that many modifications and variations are possible without departing from the invention.

Claims (1)

[Scope of Claims] 1. An image-forming material comprising a support having a layer of an image-forming agent and photosensitive microcapsules on its surface,
An image forming material characterized in that the microcapsules contain an internal phase containing a photocurable composition and a crystalline organic compound. 2. The image forming material according to claim 1, wherein the microcapsules have discrete capsule walls. 3. The image forming material according to claim 1, wherein the image forming agent is present in the internal phase of the microcapsules. 4. The image forming material according to claim 3, wherein the image forming agent is a substantially colorless electron-donating compound. 5. The imaging material according to claim 4, wherein the photocurable composition includes an ethylenically unsaturated compound and a photoinitiator system. 6. The imaging material of claim 5, wherein the crystalline organic compound has a melting point of less than about 100°C. 7. The image forming material according to claim 6, wherein the crystalline organic compound does not substantially inhibit the reaction of the photocurable composition. 8. Claim 7, wherein the crystalline organic compound is miscible with the ethylenically unsaturated compound as a melt.
Imaging materials as described in Section. 9. The image forming material according to claim 5, further comprising a color developer substance on the same support surface as the photosensitive microcapsules. 10. The imaging material according to claim 5, wherein the image-forming material additionally includes a color developer material provided on a support separate and different from the support carrying the photosensitive microcapsules. Imaging materials. 11. The image forming material according to claim 1, wherein the crystalline organic compound is 1,2-diphenoxyethane or cyclododecanol. 12. The image forming material according to claim 9, wherein the color developer substance is an electron-accepting compound. 13. The image forming material according to claim 1, wherein the radiation-sensitive composition is present in micropores within the crystalline organic compound. 14. The image forming material according to claim 8, wherein the crystalline organic compound is substantially insoluble in water.