CA1059683A

CA1059683A - Photopolymerizable resin composition for original plate

Info

Publication number: CA1059683A
Application number: CA227,841A
Authority: CA
Inventors: Takezo Sano; Tadanori Inoue; Yukikazu Uemura
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 1974-06-06
Filing date: 1975-05-27
Publication date: 1979-07-31
Also published as: JPS50155303A; FR2273827A1; SU917712A3; FR2273827B1; NL7506773A; JPS5242084B2; IT1036182B; DE2525297A1; GB1500607A

Abstract

PHOTOPOLYMERIZABLE RESIN COMPOSITION
FOR ORIGINAL PLATE
Abstract of the Disclosure A photopolymerizable resin composition is described for preparing an original relief plate useful for preparing duplicate plates from a thermoplastic matrix by pressing at a high temperature.
The novel resin comprises 80 to 40% by weight of an unsaturated polyester containing acid components of A:

and B: wherein A and B are contained in the molar ratio of 0?(B)/(A)?1, and a glycol component of the formula:

Description

1~596~3 The pre5ent inyetion relates to a phatopolymerizable resin composition for an original plate used in printing, which has good heat resistance and pressure resistance.
In recent times, printing plates made from photopolymer-izable resins have increasingly been used, because they have great -advantagesl such as safety, improvement of the working atmosphere and weight saving in comparison with the metallic printing plate.
Such photopolymerized resin printing plates have been used in various fields ranging from early small scale printings to recent use for printing newspapers. Moreover, the photopolymerized resin has been used for various other purposes, such as a resist material for etching a relief-forming resin for letterpresses. ;`
In printing of newspapers, it is very important that the printing plate has a good printability and that the duplicating thereof can be carried out speedily from the viewpoint of the large circulation of newspapers. In the newspaper industry, there has already been employed a direct printing method by using a photopolymerized resin letterpress for a small number o printing materials. However, such a method requires a long -~
time for the light exposure, development and drying steps, and therefore, the method is not necessarily suitable for printing in a large scale and at a high speed. Moreover, costs are extremely high in comparison with the conventional stereotype -method.
Accordingly, for printing by using a photopolymerizable resin at a high speed and at a low cost, it is necessary to prepare a large number of duplicate plates from a single original relief plate.
At the same time, it has been highly desirable to use a photopolymerized resin as an original plate, because it is necessary for computer type setting and because of environmental ~ 59683 pollutlon by the conventional metallic original plate.
There have, hitherto, been known varlous methods for preparing duplicate plates, such as by using a paper mold .
or by pressing a matrix material to the original plate at a ` .
high temperature (Japanese Patent Publication No. 26530/1971).
The latter method i.s par.ticularly excellent, because it can give the desired duplicate plates having a good reproducibility in a short time and at a low cost. On the other hand, for carrying out effectively the latter method, an original plate musL have a good resistance to the press at a high temperature and at a high pressure, and therefore, it has been desired to develop a photopolymerizable resin having such an excellent property. There have already been sold various photopolymerizable - -.
resins, such as a nylon, cellulose acetate, polyvinyl alcohol, .~:
polyurethane or unsaturated polyester product, which are in the .
form of liquid or solid. However, the conventional photopolymerized .
- resins are not necessarily suitable for the matrix press at a high temperature.
It is, therefore, an object of the present invention to provide a photopolymerizable resin.for an original relief 20 plate, which can be used for the preparation of duplicate plates }
by pressing a matrix at high pressures and temperatures.
The photopolymerizable resin composition of the present invention comprises 80 to 40% by weight of an unsaturated poly-ester containing acid componets of A: -~C-CH=CH-&- and B~
- ~-C6H4-~- wherein ~ and B are contained in the molar ratio `
of O~(B)/(A) ~ 1, and one or more glycol components of the i formula: t OCH2CH2~- wherein n is 2, 3 or 4, and having an acid value o 15 to 30; 20 to 60% by weight of a crosslink.ing monomer containing as an essential component ~-hydroxyethyl methacrylate;
a photopolymerization initiator in an amount of 0.1 to 10% by 30 weight on the basis of the whole weight of the composition;

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and a heat polymerl~ation inllibitor in an amount of 0.01 to 1 by weight on the basis of the whole weight of the composition.

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1(~59683 The no~el photopolymerizable resin compo9ition is suitable ~or the preparation of an original relie~ plate useful for preparing duplicate plates by pressing a matrix to the original relief plate at a pressure of 5 to 200 kg/cm2 and a temperature of 20 to 250C.
The original plate obtained is suitable for ma~ing duplicate plates used in the printlng of newspapers and for various other printing purposes. It can also be used as an original plate for various patterns and designs or for precision embossing.
The unsaturated polyester used in the present invention is obtained by condensing the acid components comprising an unsaturated dicarboxylic acid and ortho-,iso-~or tere-phthalic acid and the glycol component comprising a pol~ethylene glycol A':
Ce.g- diethylene glycol, triethylene glycol or tetraethylene glycol~ until the acid value of the product becomes from 15 to 30. The acid value of an unsaturated polyester is defi~ed as ~`
.~
a milligram number of potassium hydroxide which is required for neutralizing the carboxy group contained in one gram of the resin. It has been noted that when the acid value is too high, the ;
original plate made from the resin composition has a inferior mechanical strength when used as a press plate at high tempera-tures and is easily destroyed, and on the other hand, when the acid value is too low, the resin composition tends to gel, having a high viscosity and is very difficult to handle. This results in an excessive amount of time being required for the preparation of the original plate.
Also, when the ratio of the phthalic group ~B component) in the unsaturated polyester is too high, the rigidity of the unsaturated polyester increases, but the hardening rate lowers owing to the decrease o~ the cross-linking point and further the resin has a inferior resistance when used in a press at high temperatures. ;~

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~,~596133 The un~aturated dicarhoxylic acid includes maleic anhydride or fumaric anh~dride. The content o~ the unsaturated group (A component) has a closed relation with the hardening speed and the heat resistance of the resin, and must be one or more times the molar content oE phthalic group (B component), preferably two or more times by mol of the content of the phthalic group.
That is, the molar ratio of the A component to B component is O~ B)/(A) ~1, preferably O'~(B)/(A)~=~0.5. When the content of the unsaturated group is larger, the photosensitivity increases and the crosslinking density becomes higher, by which the heat resistance of the resin at a high te~perature increases. In an .~ . . .
extreme case, i.e. even when the unsaturated polyester has no phthalic group (B component) it still has enough heat resistance and pressure resistance, and by adding the crosslinking monomer in an amount corresponding to the molar number of the unsaturated group, the obtained resin composition has an extremely lo~ viscosi~y and is easily handled.
When the glycol component to be esterified with the acid components has a shorter glycol chain, the o~tained harden- -ing photopolymerized resin hàs a higher elasticity and the original plate produced therefrom is very brittle. For example, when ethylene glycol is used as the glycol component, the photo~
polymerized resin thus obtained is not suitable for ~he prepara~
tion of the desired original plate. On the other hand, when the glycol component has a longer glycol chain, the photopoly merized resin thus obtained has a larger hydrophilic nature and the development thereof is easier, but when the number of n is 5 or more, the development is not good. Thus, when the development is carried out by using such a photopolymerized resin, the hardening part thereof significantly swells and thereby the printing area becomes unclear, and further, the '',: ' . ~, .,. ~ : .

~9683 heat resistance and the p~essure resistance of the ~esin lower.
When a mixture of the glycols having various values of n ~i.e.
n = 2, 3 and 4~ is used as th~e glycol component for the unsatu rated polyester, the physical properties of the photopolymerized resin can be variously modified.
The crosslinking monomer used in the present invention contains as the essential component ~-hydroxyethyl methacrylate ;
~hereinafter, referred to as "HEMA"). HEMA reacts with the unsaturated group in the polyester chain by the lrradiation of light to form a crosslinked structure, and as the resul~, the area exposed to light becomes insoluble in the solvent.
~hen HEMA is added in a higher ratio to the resin composition, the elastlcity of the photopolymerized resin at room tempera-ture becomes higher and the reactivity of the photopolymerizable resin becomes higher and further the viscosity of the composî-tion lowers. On the other hand, the ratio of the homopoly-merized HEMA which does not pertain to the crosslinking reaction - increases, and as the result, at high temperatures a fluidization phenomenon occurs in the uncrosslinked area. When the ratio o~ HEMA is over 60% by weight, the heat resistance and the pressure resistance of the photopolymerized resin decrease.
On the other hand, when the ratio of HEMA is less than 20%
by weight, the hardened resin has an extremely low elastic modulus at room temperature is not practically used. ~c-cordingly, in the case of HEMA alone, the addition amount of HEMA is preferably in a range of 20 to 60%, preferably 25 to 40% by weight. In such a composition, even if the amount of un- -;
saturated polyester used is the same, the mere variation of the amount of HEMA from 20 to 60% by weight can give composi-tions having various properties ranged from a rubber-like, soft composition to a rigid composition. Furthermore, the addition ~ . - . ,, . ,, ,~

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;i9683 of UEMA can giYe another cha~acteristic to the present composi- ;
tion that the w-ashing with a water-containing developer can be easily carried out because HEMA is a water-soluble monomer.
Besides, the crosslinking monomer used in the present invention ~`
has very low toxicity and little smell in comparison with the conventional crosslinking monomer for an unsaturated poly-ester, such as styrene. The crosslinking monomer used in the present invention contains 50% by weight or more oE HEMA as the essential component, and may contain other monomers. For instance, it may be mixed with 50% by weight or less of a difunc- ~
tional monomer, such as a polyethyleneglycol dimethacrylate or , diacrylate (e.g. diethyleneglycol dimethacrylate or triethylene-glycol dimethacrylate). Thus, by adding HEMA as the crosslink-ing agent, the photopolymerized resin composition of the pre-sent invention has excellent properties, such as excellent heat resist.ance, pressure resistance at the matrix press, and excel-lent flexibility, and further excellent development properties and compatibility, with low toxicity and smell. "~
The photopolymerizable resin composition of the present `
invention contains a photopolymerization initiator in addition to the unsaturated polyester and the crosslinking monomer. The :~
photopolymerization initiator includes the conventional ones, such as a-carbonyl alcohols (e.g. ben~oin, a-methylbenzoin or -~-phenylbenzoin), ~-carbonyl ethers (e.g. benzoin methyl ether or benzoin isopropyl ether)~ anthraquinones (e.g. sodium anthra-quinone-~-sulfonate, l-chloroanthraquinone, 2-methylanthra-quinone or l,4-naphthoquinone), thiols ~e.g. thiophenol, p-thiocresol or p-methoxythiophenol). The photopolymerization initiator i~ added in an amount of 0.1 to 10% by weight on ;;
the basis of the whole weight of the composition.
Moreover, the prese~t composition contains a heat j~ 1~5~6 !3~

polymerization inhihitor, such as hydro~uinone, methylhydro-quinone, t-but~lcatechol, pyrogallol, 2,6-di-t-but~l-p-cresol, or the like, which may be added in an amount of 0.01 to 1% :
~y weight on the basis of the whole weight of the composition.
The h.eat polymerization inhibitor can inhibit the polymeriza-tion by.heat. . . . . . .
The desired original plate can be prepared from the present photopolymerizable resin composition in the following manner. Thus, the components mentioned above are mixed to give a photopolymerizable resin composition and the composi- -tion thus obtained is applied to a support plate in the desired thickness corresponding to the depth of the desired relief.
~he resultant is irradiated with a light, for instance, .
with an ultraviolet fluorescent lamp or a high pressure mercury .
lamp which radiates a chemical light through a film having the original pattern,and thereby the area exposed to the light is hardened, and then the resultant is washed with a weakly alkaline aqueous solution to remove the unexposed area and dried to ~.
give the desired original plate. ~`.
The original plate produced from the photopolymerizable resin composition of the present invention has an excellent :~
flexibility at room temperature and an adequately crosslinked structure, and the hardened area thereof does not fluidize even ;.
at a high temperature such as 200C. The elasticity thereof i9 generally not lowered and is maintained at 10 kglcm or more, and .
therefore, it can be subjected to the matrix pres~ with a heat resistant thermoplastic resin such as a molten polycarbonate ~.
at such a temperature. Moreover, the present photopolymerized resin composition has a strong resistance to a heat shock since ~.
the elasticity thereof little changes by the change of the .
temperature. And further, although a strain caused by the ~ i . ~

1~596l~3 di~ference between the thermal expansion o~ the resin layer and that o~ the support occurs when the matrix is released from the o~iginal plate~ such a strain is a~sorbed by the resin ~-plate slnce the resin has a high flexibility, and therefore, the original plate is not destroyed and can be repeatedly used for the heat press.
The photopolymerizable resin composition of the pre~
sent invention has such excellent cha:racteristics that it can be used for the preparation of the original relief plate suitable for preparing duplicate plates at high temperatures for newspaper la printing and for other various printings, and further can be used for the original plate suitable for various pattern and designs or for precise embossing.
The present invention is illustrated by the follow~
ing ~xamples but not limited thereto.

..
To a 2 liter separation flask are added maleic anhydride (392.2 g), isophthalic acid (332.2 g), triethylene glycol (946.3 g) and hydroquinone monomethyl ether t450 mg), ana the mixture is reacted at 200C or higher for 8 hours under "`?
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nitrogen gas to give an unstaruated polyester (1527 g) having an acid value of 22.0 (measured by the provision of JIS K 6901). `
To the unsaturated Polyester (210 g) are added H~MA
(90 g), benzoin methyl ether (3 g) and hydroquinone (0.3 g) and ~
the mixture is stirred and then allowed to stand to give a photo- 3~ :
polymerizable resin composition having a viscosity of 7000 cp (25~C).
The composition thus obtained is applied in a thick-ness of 0.6 mm to an iron plate (thickness: 0.3 mm, size: 200 X 100 mm~ with a halation preventing layer, and thereon are laminated a negative film closely held between a polyethylene terephthalate film and a transparent glass plate (thickness--- 9 ~
' ' 10591~3

2 mm~. The laminated product is îrradiated with ultraviolet ;
fluorescent lamps (2Q ~. bIack light; 15 lamps~ at a distance of 5 cm for 5 minutes. After the light exposure, the resultant is washed with 0.1% aqueous sodium hydroxide and then dried.
Onto the letterpress (the original plate) thus obtained is put a polycarbonate sheet (size: 200 X 10~ mm), and the resultant is subjected to a heat press at 200C to give a good matrix plate of polycarbonate without any destruction of the original plate.
EXAMPLE 2 ~`
Maleic anhydride (147.1 g), ~riethylene glycol (236.6 g) and hydroquinone monomethyl ether (150 mg) are reacted in thesame manner as described in Exmaple 1 to give an unsaturated polyester having an acid value of 16 . 5 .
The unsaturated Po'yester thus obtained (165 g) is ;
mixed with HEMA (135 g), benzoin (3 g) and hydroquinone (0.3 g) to give a photo-resin composition having a viscosity of 1500 cp (25C~.
In the same manner as described in Example 1, an original plate is prepared from the composition and is sub-jected to the heat press to give a good matrix of polycarbonate without any destruction of the original plate.

Example 1 is repeated except that a mixture of HEMA
(45 g) and triethyleneglycol dimethacrylate (45 g) is used instead of HEMA (90 g) to give an original plate. The origi-nal plate is sub;ect to the heat press to give a good matrix of polycarbonate without any destruction of the original plate.

Example 1 is repeated except that heptaethylene glycol is used as the glycol component to give a resin composi-tion which is very soft and brittle. When an original plateis prepared from the resin composition9 the original plate is - 10 - ' ,, ~O~i9683 destroyed at the heat press at 200QC.
REFEREN:CE EXA~PLE 2 By using the same unsaturated polyester as in Example 1~ an original plate is prepared in the same manner as described in Example 1 except that the amount of HEMA is 70% by weight. :: :
When the original plate thus obtained is subjected to the heat press to result in an occurrence of dulling on the original plate.
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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A photopolymerizable resin composition useful for making an original relief plate, which comprises 80 to 40% by weight of an unsaturated polyester containing acid components of A: and B: wherein A and B are contained in the molar ratio of O?(B)/(A)?1, and a glycol component of the formula: wherein n is 2, 3 or 4, and having an acid value of 15 to 30; 20 to 60% by weight of a crosslinking monomer containing as an essential component .beta.-hydroxyethyl methacrylate; a photopolymerization initiator in an amount of 0.1 to 10% by weight on the basis of the whole weight of the composition; and a heat polymerization inhibitor in an amount of 0.01 to 1% by weight on the basis of the whole weight of the composition.

2. The photopolymerizable resin composition according to claim 1, wherein the unsaturated polyester is a conden-sation product of the acid components comprising an unsaturated dicarboxylic acid and ortho-, iso- or tere-phthalic acid and the glycol component comprising a polyethylene glycol wherein the condensation reaction is carried out until the acid value of the product becomes from 15 to 30.

3. The photopolymerizable resin composition accord-ing to claim 2, wherein the unsaturated dicarboxylic acid is maleic anhydride or fumaric anhydride.

4. The photopolymerizable resin composition according to claim 2, wherein the glycol component is a member selected from the group consisting of diethylene glycol, triethylene glycol, tetraethylene glycol and mixtures thereof.

5. The photopolymerizable resin composition according to claim 1, wherein the molar ratio of the component A and the component B in the unsaturated polyester is in a range of O?(B)/(A)?5.

6. The photopolymerizable resin composition accord-ing to claim 1, wherein the crosslinking monomer is .beta.-hydroxy-ethyl methacrylate or a mixture of 50% by weight or more of .beta.-hydroxyethyl methacrylate with 50% by weight or less of a difunctional monomer selected from the group consisting of di-ethyleneglycol dimethacrylate and triethyleneglycol dimetha-crylate.

7. The photopolymerizable resin composition accord-ing to claim 1, wherein the photopolymerization initiator is a member selected from the group consisting of benzoin, .alpha.-methylbenzoin, .alpha.-phenylbenzoin, benzoin methyl ether, benzoin isopropyl ether, sodium anthraquinone-.alpha.-sulfonate, 1-chloro-anthraquinone, 2-methylanthraquinone, 1,4-napthoquinone, thio-phenol, p-thiocresol and p-methoxythiophenol.

8. The photopolymerizable resin composition according to claim 1, wherein the heat polymerization inhibitor is a member selected from the group consisting of hydroquinone, methylhydroquinone, t-butylcatechol, pyrogallol and 2,6-di-t-butyl-p-cresol.