CA1271870A

CA1271870A - Photosensitive resin composition

Info

Publication number: CA1271870A
Application number: CA000501675A
Authority: CA
Inventors: Seio Mamoru; Hidefumi Kusuda; Masami Kawabata
Original assignee: Napp Systems USA Inc
Current assignee: Nippon Paint Co Ltd
Priority date: 1985-02-12
Filing date: 1986-02-12
Publication date: 1990-07-17
Also published as: GB8603366D0; DE3604402A1; JPH06100828B2; AU582628B2; GB2171107A; NZ215095A; AU5337786A; DE3604402C2; GB2171107B; JPS61246742A

Abstract

Abstract The invention provides a photosensitive resin composition suitable for a relief printing plate having good resistance to a water based ink, for which water or a water like solvent can be employed as a developing solution. The resin composition comprises (i) a poly-mer having a molecular weight of 5,000 to 500,000 which contains an amino group and a polymerizable double bond moiety: (ii) a monomer having an .alpha.,.beta.-ethylenically unsaturated bond and a free acid group which can qua-ternize the nitrogen atom of the polymer (i); (iii) a photopolymerizable unsaturated compound, and (iv) a photopolymerization initiator.

Description

1~7~L~'7V

Photosensitive resin composition The present invention relates to a photosensitive resin composition and, more particularly, to a photosen-sitive resin composition suitable for use in preparing a relief printing plate having goo~ resistance to water-based and oil-based inks, for which water or an aqueous solvent can be employed as a developing solution.
The photosensitive resin composition of the pre-sent invention is suitable not only for preparing a relief printing plate, but also for preparing an offset printing plate, a screen and a resist.
Various photosensitive compositions are known which can be used for producing relief printing plates, for example various types of base resins such as liquid un-saturated polyesters, polyvinyl alcohols, water soluble polyamides, alcohol-soluble polyamides, styrene copoly-mers, 1,2-polybutadienes and the like. Compositions based on liquid unsaturated polyesters are inconvenient to handle and use because of their liquid form. In addition, there is the problem that the compositions require the use of alkali solutions or particular air-knives for development.
Compositions based on polyvinyl alcohols or water-soluble polyamides have the merit that water can be employed for their development, but they have the disadvantage that water base inks cannot be employed .,. . - . ,, . "

2~7 for printing because of the poor water-resistance of the compositions. The compositions based on cellulose ace-tate succinate require the use of an alkali solution and they do not have resistance to aqueous inks. When the 5 base resin is an alcohol-soluble polyamide, an inflam-mable alcohol has to be used for dev~lopment, which is a significant drawback to environmental safety. The use of a styrene-isoprene-styrene block copolymer as the base resin requires the use of a halogenic organic solvent as a development agent, which is also a drawback ~rom the point of view of environmental safety for workers.
The object of the present invention is to provide a photosensitive resin composition, especially one suitable for forming a relief printing plate, having good resist-ance to water based ink, whereby water or an aqueoussolvent can be employed as a developing solution.
According to the invention there is provided a photosensitive resin composition for relief printing ~lates, which is water developable and, upon curing, is resistant to water and is capable of use with water based inks, compeising: (i) a polymer (A) having a molecular weight of 5,000 to 500,000 which contains an amino group and a polymerizable double bond moiety, said polymer being prepared by copolymerizing (a) 3 to 50 mole % of an , ~-ethylenically unsaturated monomer having an amino group, ~b) 5 to 95 mole ~ of a polymerizable unsaturated monomer, and (c) 20 to 60 mole % of a conjugated diene monomer, ~ii) a monomer (B) having an a,~-ethylenically unsaturated bond and a free acid group which can quaternize the nitrogen atom Oe said polymer ~A) and render said polymer wa~er soluble or water dispersible, (iii) a nongaseous ethylenically unsaturated compound ~C) which is compatible to said polymer (A) and ~iv) a photopolymerization initiator ~D).

C I , ,.,, ,. ' 12~18~
- 2a -In the composition of the present invention, the polymer (A) is quaternized by the monomer (B) to become water-soluble or water-dispersible. This composition can be formed into a sheet which can be adhered onto a S suitable substrate, such as steel, aluminum or plastics.
The photosensitive layer is then exposed to ultra-violet light through a negative film in order to cause copolymerization of the polymer (A), the monomer (B) and the photopolymerizable unsaturated compound (C) within 1~ the exposed areas which then become water-insoluble. The unexposed areas do not become copolymerized and can be ~i~7 1 ~3 dissolved and removed easily with water to bring about aevelopment of the relief plate.
The polymer (A) of the present invention contains the amino group atom in such an amount that the polymer becomes water-soluble or water-dispersible when the polymer is quaternized by the monomer (B). Also, the polymer (A) contains the polymerizable double-bond moiety in such an amount that it can be copolymerized with the photopolymerizable unsaturated compound (C) to form a water-insoluble polymer, and, in addition, the polymer (A) has a sufficiently high molecular weight to form a water-insoluble material. The double-bond moiety is not necessarily present in the polymer (A) in such an amount that the double-bond forms all of the water-insoluble materials. This insolubilization is mainly accomplished by the monomer ~B) and the photopolymerizable unsaturated compound (C).
The polymer (A) used in the present invention can be prepared, for example, by copolymerizing the following components:
(a) 3 to 50 mole %, and preferably lO to 30 mole %, of an a,B-ethylenically unsaturated monomer having an amino group, (b) 5 to 95 mole %, and preferably 20 to 60 mole %, of a polymerizable unsaturated monomer, and (c) 0 to 90 mole %, and preferably 20 to 60 mole %, of a conjugated diene monomer.
The weight average molecular weight of the polymer (A) is preferably within the range of 5,000 to 500,000, and more preferably lO,000 to 250,000.
The a,B-ethylenically unsaturated monomer (a) hav-ing the amino group used in the polymer (A) preferably has the following formula:
IRl / R4 CH2 (CH2)n-N
\

I

~ '7iL~7~3 or CH = I -CONH- ( CH 2 ) -N /

wherein Rl represents a hydrogen atom or a methyl group, (CH2)n represents an ethylene, trimethylene, or butylene moiety, and R4 represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an hydroxyalkyl group having l to 4 carbon atoms, or an alkoxyalkyl having l to 4 carbon atoms. Preferred examples are dimethylaminoethyl (meth)-acrylate, diethylaminoethyl (meth)acrylate, dimethylamino-ethyl (meth)acrylamide, dimethylaminopropyl (meth)acryl-amide and the like.
Examples of the polymerizable unsaturated monomers (b) used in the polymer (A) are styrene, a-methylstyrene, vinyltoluene, acrylonitrile, vinyl chloride, vinylidene chlorlde, a (meth)acrylic acid ester, (meth)acrylamide, dlcyclopentenyl (meth)acrylate, dicyclopentenoxyethyl (meth)acrylate, dicyclopentenoxypropyl (meth)acrylate, a (meth)acrylic ester of diethylene glycol dicyclopentenyl mQnoether and mixtures thereof. Examples of the ~meth)-acrylic esters are methyl (meth)acrylate, ethyl (meth)-acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)-acrylate and the like.
Examples of the conjugated diene monomers (C) are con~ugated diene hydrocarbons such as butadiene, isoprene, dimethylbutadiene, chloroprene and the like.
The monomer (B) having the a,~-ethyleniaally unsatu-f30 rated bond contains a free acid group which can quaternize the polymer (A) to make itself water-soluble and a poly-merizable unsaturated bond which can be photopolymerized along with the photopolymerizable unsaturated compound (C) to make itself water-insoluble.
Examples of the free acid groups are a carboxylic acid group, a phosphoric acid group, a sulfonic acid group .~

1271~70 and the like. Preferred monomers have the following formulas:

1l CH 2=C-COOH;

CH2=C-COO-R2-OOC-R3-cOoH;

CH2=C-COO-R2-O-P-OH;
OH

Rl CH2=c-co~H-R2-o-p-oH;
OH

CH2=C-COO-R2-S-OH;

R O

CEi2=C-CONH-R2-S--OH;
o wherein Rl represents a hydrogen atom or a methyl group, R2 repre8ents ~CH2)n wherein n is an integer of 1 to 6, and R3 represents an alkylene group having 1 to 6 carbon atom~ or a phenylene group.

Examples of the ,~-ethylenically unsaturated mono-mers (B) containing the carboxylic acid group are (meth)-acrylic acid, maleic acid, fumaric acid, citraconic acid and the like. Examples of the monomers (B) containing the sulfonic acid group are 2-acrylamido-2-methylpropanesul-fonic acid and the like. Also examples of the monomers (B) containing the phosphoric acid group are 2-hydroxy-'70 ethyl acryloyl phosphate, 2-hydroxypropyl acryloyl phos-phate, 2-hydroxy-~-chloropropyl acryloyl phosphate and the like. The above monomers can be used individ~ally or can be mixed together.

The photopolymerizable unsaturated compound (c) of the present invention may be one of the conventional types which are non-gaseous ethylenically unsaturated compounds that preferably contain at least one ethylene group in the terminal and can also be dissolved with the above polymer ~A). Examples of the compounds (C) are unsaturated car-boxylic esters such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)-acrylate, 1,4-cyclohexanediol di(meth)acrylate, propylene-diol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol tetra(meth)acrylate; unsaturated amides such as ~,N'-methylene bisacrylamide, N,N'-ethylene bis-acrylamide, N,N'-hexamethylenebisacrylamide, N,N'-xyl-lenebisacrylamide, N-(~-hydroxyethyl)methacrylamide, N,N'-bis(B-hydroxyethyl)acrylamide; urethanized (meth)acrylates derived from 2-hydroxyethyl (meth)acrylate and an iso-cyanate compound; mono- or di-(meth)acrylates of diepoxy polyethers modified by aromatic polyhydric alcohols such as bisphenol, a noborac compound and the like; and mixtures thereof. Compounds having poor hydrophilic characteristics are preferred.
Examples of the photopolymerization initiators (D) are benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether;
benzophenones such as benzophenone, o-benzoylmethyl ben-zoate and the like; xanthones such as xanthone, thioxan-thone, 2-chlorothioxanthone, 2-isopropylthioxanthone and the like; acetophenones such as acetophenone, trichloro-3s acetophenone, 2,2-diethoxyacetophenone, 2,2-dimethoxyace-tophenone, 2,2-dimethoxy-2-phenyl acetophenone and the ~/

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like; benzyl-2-ethyl-anthraquinone; methylbenzoyl formate;
2-hydroxy-2-methyl-propiophenone; 2-hydroxy-4-isopropyl-2-methylpropiophenone; l-hydroxycyclohexyl phenyl ketone;
and mixtures thereof.
The photosensitive resin composition of the present invention preferably contains:
(i) 30 to 9o%~ and more preferably 40 to 80% by weight, of the above polymer (A);
(ii) a sufficient amount of ~,~-ethylenically unsaturated monomer (B) having an acid group to quaternize 20 to 250 mole % of the amino group in the polymer (A), generally l to 60%
by weight;
(iii) 5 to 70%, and more preferably lO to 55% by weight, of the photopolymerizable unsaturated compound (C); and (iv) 0.01 to 20%, and more preferably 0.05 to 10% by weight, of the photopolymerization initiator (D).
The present composition may optionally contain a polymerization inhibitor such as hydroquinone, p-methoxy-phenol, 2,6-di-t-butylcatechol, benzoquinone, naphthoqui-none, 2,6-diphenyl-p-benzoquinone, phenothiazine, and the like; a dye such as eosine Y, rose bengal, malachite green, methylene blue and the like; and a plasticizer such as a dialkyl phthalate, a dialkyl fumarate, a dialkyl sebacate, a dialkyl itaconate, an alkyl phosphate, (poly)ethylene glycol, a (poly)ethylene glycol ester, a (poly)ethylene glycol ether.
The photosensitive resin composition of the present invention is generally molded to form a uniform sheet size of 0.01 to lO.OOmm by a molding method such as extrusion molding, calendar molding and the like and the sheet is then bonded to a substrate through an adhesive layer. The photosensitive layer is exposed with ultraviolet light so that the com~osition is polymerized in the exposed part ~, i ~' 1~'71~70 to form a polymerized latent image which is insoluble in water, an alkali solution, or an organic solvent. The unexposed part is removed with water to form a relie~
printing plate which has good resistance to aqueous inks.
The photosensitive resin composition of the present invention is essentially water-soluble, but the plate formed from the composition is easily polymerized to form a water-insoluble polymer. Therefore, when the plate is exposed to ultraviolet light through a negative film and the plate is washed with water, a printing plate having an image faithful to the film. Accordingly, development can be carried out with water, and the resulting plate is water-insoluble so that printing can be carried out with a water based ink. The photosensitive resin composition of the present invention is suitable not only for relief printing plates, but also for offset printing plates, screens and resists.
The present invention is illustrated by the follow-! ing Examples, which are not to be construed as limiting the invention to their details. All parts and percentagesin the Examples are by weight unless otherwise specified.
Example 1 A photosensitive resin composition was prepared by mixing the following ingredients;
Inqredients Parts by weiqht Copolymer resin 1) 40 VISCOAT*-2,000 2) 14 Hydroxypropyl acrylate 17 1,6-hexandiol diacrylate 16.6 2,2-dimethoxy-2-phenyl acetophenone 2.16 2,6-di-t-butylcatechol 0.24 1) The copolymer resin (MW=100,000) was prepared from 15 parts of butadiene, 20 parts of ethyl acrylate, 25 parts of acrylonitrile, and 40 parts of dimethylaminoethyl acrylate.

* Trade Mark ~t71~7~) 2) This is a half-ester of 2-hydroxyethyl acrylate with phthalic acid, and is commercially available from OSAKA YUKI KAGAKU Co. LTD.
The resultant composition was calender-molded on a steel plate 0.18mm in thickness, providing a total thick-ness of about 0.5mm at about 80C.
A negative film was contacted with the photosensi-tive plate under a vacuum on the composition side. Then the composition was exposed with a 350 W chemical lamp at a distance of 6 cm for one minute followed by removal of the negative film and washing with a nylon blush in water at 40C for 2 minutes to form a relief image faithful to the negative film having a Shore A hardness of 95.
When this was used for printing on a kraft paper in a Stack type flexographic press using a water based ink, a sharp image was maintained for more than 2 hours at 50 m/min. In addition, when a 2.5 cm X 5.0 cm sample of this plate was dipped for 2 hours at 40C in a water solution containing 1 wt% of Na2C03 and 5 wt% of butyl cellosolve, the surface of the sample was swelled by 6.4X of the thickness of the sample. This showed that the composition had excellent water-resistance.
ComParative Example 1 A photo~ensitive resin composition was prepared from 25 the following ingredients;
Ingredients Parts by weight ,~
Water-soluble polyamide resin~ 80 Tetraethylene glycol 10 Acrylamide 6 N,N'-methylene bisacrylamide 2 Benzoin isobutyl ether 2.5 2,6-di-t-butylcatechol 0.4 p-methoxyphenol 0.1

3) This was a water-soluble polyamide resin hav-ing hydrogen atoms at the a-position of polyE-capramide ~, substituted for the dimethylamino group in the amount of 52 mole%.
The above ingredients were mixed at room temperature by a press kneader, and then the mixture was extruded into a rod shape with an extruder. The extruded stock was calender-molded on a color galvanized plate of 0.3mm thickness to form a photosensitive composition sheet having a total thickness of 0.96mm.
The composition sheet was made up as generally described in Example 1 to form a relief image faithful to the negative having a thickness of 0.66mm and a Shore A hardness of 96. When a 2.5 cm X 5.0 cm sample of this plate was dipped for 2 hours at 40C in a solution con-taining 1 wt% of Na2CO3 and 5 wt~ of butyl cellosolve, the surface of the sample was swelled by more than 20%
of the thickness of the sample.
Example 2 A photosensitive resin composition was prepared by mixing the following ingredients;
Ingredients Parts by weight Copolymer resin of Example 1 50 2-hydroxyethyl acryloyl phosphate 4.8 Phenoxyethyl acrylate 23.9 1,6-hexandiol acrylate 23.9 2,2-dimethoxy-2-phenyl acetophenone 2.16 2,6-di-t-butylcatechol 0.24 The resultant composition was calender-molded on a steel panel 0.18mm in thickness, providing a total thickness of about O.Smm at about 80C.
The resultant resin composition was exposed as generally described in Example 1 followed by washing with a nylon brush in water at 40C for 50 seconds to form a relief image faithful to the negative film having Shore A hardness of 84. When a 2.5 cm X 5.0 cm sample of this plate was dipped for 2 hours at 40C in a water solution f ~, ~,~.

~ ~'71~
.

containing 1 wt% of Na2CO3 and 5 wt% of butyl cellosolve, the surface of the sample was swelled by 7.9% of the thickness of the sample. In addition, when printing was conducted at a speed of 150 m/min on kraft paper with the press described in Example 1 using the relief plate ob-tained in the above method, a sharp image was maintained for more than 2 hours.
Example 3 A photosensitive resin composition was prepared by mixing the following ingredients;
Ingredients Parts by weight Copolymer resin of Example 1 50 2-acrylamide-2-methylpropane- 4.8 sulfonic acid Urethane compound of 2-hydroxyethyl 23.9 acrylate and butylisocyanate 1,6-hexandiol acrylate 23.9 2,2-dimethoxy-2-phenyl acetophenone 2.16 2~6-di-t-butylcatechol 0.24 The resultant composition was calender-molded onto a steel panel of 0.18mm in thickness, providing a total thickness of about 1.9mm at about 80C.
The resultant resin composition was exposed as generally described in Example 1 followed by washing with a nylon brush in water at 40C for 1 minute to form a relief image faithful to the negative film having a Shore A hardness of 76. When a 2.5 cm X 5.0 cm sample of this plate was dipped for 2 hours at 40C in a water solution of 1 wt% of Na2CO3 and 5 wt% of butyl cellosolve, the surface of the sample was swelled by 9.6% of the thickness of the sample. In addition when printing was conducted for 1 hour as generally described in Example 2, a sharp image was maintained.

Claims

Claims:

1. A photosensitive resin composition for relief printing plates, which is water developable and, upon curing, is resistant to water and is capable of use with water based inks, comprising:
(i) a polymer (A) having a molecular weight of 5,000 to 500,000 which contains an amino group and a poly-merizable double bond moiety, said polymer being prepared by copolymerizing (a) 3 to 50 mole % of an .alpha.,.beta.-ethylenically unsaturated monomer having an amino group, (b) 5 to 95 mole % of a polymerizable unsaturated monomer,and (c) 20 to 60 mole % of a conjugated diene monomer, (ii) a monomer (B) having an .alpha.,.beta.-ethylenically unsaturated bond and a free acid group which can quaternize the nitrogen atom of said polymer (A) and render said polymer water soluble or water dispersible, (iii) a nongaseous ethylenically unsaturated compound (C) which is compatible to said polymer (A) and (iv) a photopolymerization initiator (D).

2. A composition according to claim 1 in which the .alpha.,.beta.-ethylenically unsaturated monomer (a) having the amine group is a (meth)acrylate or (meth)acrylamide having the amino group.

3. A composition according to claim 1 in which the polymerizable unsaturated monomer (b) is a (meth)-acrylate or a (meth)acrylamide.

4. A composition according to claim 1 in which the monomer (B) having an .alpha.,.beta.-ethylenically unsaturated bond is selected from the group consisting of monomers having the following formulas:
wherein R1 represents a hydrogen atom or a methyl group, R2 represents (CH2)n wherein n is an integer of one to 6, and R3 represents an alkylene group having 1 to 6 carbon atoms or a phenylene group.

5. A composition according to claim 1 in which the photopolymerizable compound (C) is a compound having an ethylene bond in the terminal.

6. A composition of claim 1 in which the photo-polymerization initiator is selected from a benzoin ether, acetophenone, benzophenone and a ketal derivative.

7. A photosensitive resin composition according to claim 1 which contains:
(i) polymer (A) in an amount of 30 to 90% by weight (ii) a monomer (B) in an amount of 1 to 60% by weight (iii) a photopolymerizable unsaturated compound (C) in an amount of 5 to 70% by weight, and (iv) a photopolymerization initiator (D) in an amount of 0.01 to 20% by weight.

8. A photopolymer printing plate developable with water, comprising a support and a coating thereon of the water-developable photosensitive composition according to any one of claims 1 to 3.