JPS5929849B2 - Photosensitive resin composition - Google Patents

Description

Detailed Description of the Invention The present invention is a photosensitive resin that is easily three-dimensionally crosslinked by exposure to ultraviolet light, the unexposed area quickly dissolves in a dilute alkaline aqueous solution, and the exposed area has excellent water resistance and rubber elasticity. A printing plate having excellent properties such as rubber elasticity, ink resistance, and ink transferability useful as a resin letterpress plate for flexographic printing consisting of a composition, more specifically, an exposed area and a support supporting the exposed area. It is related to materials.

In recent years, letterpress printing, which has been the mainstream of original printing plates, has changed (
1) Pollution problems caused by metals such as lead, (2) Work environment during the manufacture of type made from lead, etc., (3) Back pain problems for workers due to transporting heavy objects, and (4) Difficulty in securing personnel due to inadequate work environments. Due to various problems, photopolymer letterpress printing is gradually being replaced.

In addition, the manufacturing process of conventional metal letterpress is complicated and requires skill, including (1) polishing of the zinc plate, (2) application of photosensitive liquid such as PVA-chromate, (3) drying, and (4) negative film. baking, (5) development, (6) hardening, (7) surface exposure, (8
) acid corrosion, (9) washing with water, and finishing with regular drying. On the other hand, since the photosensitive resin plate used as a printing plate material has a simple plate-making process and does not require skill, a resin letterpress plate of constant quality can be obtained no matter who makes the plate.

That is, (1) Coating a photosensitive resin composition on a metal plate such as an aluminum plate or iron plate or a transparent support (in the case of a solid plate photosensitive resin, a photosensitive resin layer is already coated on the support). ), (2) Apply negative film and expose to ultraviolet light, (3
) development, and (4) dry finishing, and resin letterpress printing can be produced by much simpler operations than metal letterpress printing. Another major reason for the development of photosensitive resin letterpress printing is that recent advances in electronics have made it possible to easily and quickly produce negative films using computer phototypesetting machines. Photosensitive resin letterpress materials have been researched and developed by companies around the world, and now more than 20 companies around the world manufacture and sell photosensitive resin letterpress materials. Looking at the recent progress in photosensitive resin letterpress printing, many products have been put on the market that are considered to be able to fully achieve their original purpose as photosensitive resin letterpress plates that can replace lead plates and metal letterpress plates for newspaper printing. In recent years, food, beverages,
The field of rubber letterpress printing, or flexographic printing, has gradually expanded, including package printing due to the rapid growth of packaging such as wrapping paper, form printing for printing business forms with the advent of computerization, and carton printing for printing on cardboard. Ta.

In conventional flexographic printing, the process of producing rubber letterpress plates is very complicated and requires skill, so photosensitive material manufacturers around the world are competing with each other to replace this with photosensitive resin plates. That is, the process of producing a rubber letterpress is that after producing the metal letterpress mentioned above, (1) making a mold using paper impregnated with phenol resin to make a matrix, and (2) using natural rubber, synthetic rubber, etc. Put the rubber into a matrix and heat-press and vulcanize it. (3) Remove unevenness to ensure the accuracy of the thickness of the rubber letterpress. If a rubber letterpress with an accurate thickness cannot be obtained, the unevenness removal operation must be repeated. No. This is because if the thickness of the rubber letterpress is not accurate, halftone objects cannot be printed with good reproduction. Rubber letterpress for printing luxury products does not rely on the above methods, but is made by hand carving by craftsmen.
It takes several days to make one rubber plate, and the number of craftsmen has been decreasing in recent years. In flexographic printing, the contact pressure between the plate cylinder and the impression cylinder is so small that it is called scratch impression, and printing is performed with light printing pressure and high speed. Therefore, flexographic printing plates have high ink receptivity and a high degree of flexibility, i.e., rubber elasticity. It must have excellent printing durability. Therefore, in order to produce a photosensitive resin letterpress plate that can replace a rubber plate for flexographic printing, the above requirements (
1) Ease of plate making and simplification of process, (2) Film thickness accuracy, (
3) It must satisfy the same rubber elasticity as rubber letterpress. With the advancement of packaging, the quality of printed matter required is also becoming higher, and for this reason, one of the characteristics that must be achieved is the ability to perform mesh printing, which was previously considered difficult with rubber letterpress. It is being counted. To meet this demand, it was thought that it would be impossible to achieve a sufficient number of screen lines using the thermocompression vulcanization method, and this problem became one of the reasons why photosensitive resins attracted attention. . Recently, regulations on pollution such as air pollution and water pollution have become stricter, but when producing a flexographic printing plate using a photosensitive resin, it is preferable that the developer is water or a dilute alkali aqueous solution.

Conventional photosensitive resins that use ordinary organic solvents have the drawback of not only being subject to pollution regulations, but also having to take into account unexpected accidents such as fires, in addition to being harmful to the human body. In addition, the use of heatset inks in offset rotary printing, which has rapidly increased with the advancement of modern printing technology, and the use of solvent-based inks based on alcohol and low-boiling aliphatic hydrocarbons in flexographic printing, which require drying through a dryer after printing. Solvents that evaporate during the process cause significant air pollution. In order to prevent this, each printing company takes measures such as (1) incineration of solvent in an afterburner, (2) adsorption with activated carbon and recovery with steam distillation, but all of these measures are expensive and cannot be completely resolved. The current situation is that this is not the case. Water-based inks have been developed in an attempt to solve this air pollution issue, and recently they have begun to be used particularly in flexo printing, and the amount of such inks has been increasing. Therefore, there is a need for a resin letterpress plate that can be printed without any problems even when using water-based ink. The flexographic printing plates of various companies that are now on the market do not necessarily satisfy this requirement. As a result of extensive research, the present inventors have completed a photosensitive resin composition suitable as a flexographic printing plate material with good rubber elasticity, alkali developability, water resistance, and ink receptivity.

That is, the present invention provides (0 conjugated diolefin hydrocarbon (4)
and α/β monoethylenically unsaturated carboxylic acid B) as essential components, and monoolefinic unsaturated compound wax C) A: 10 to 95 mol%, B: 5 to 90 mol%, C: 0～
This is a photosensitive resin composition comprising a copolymer containing 85 mol% of harmful substances, (6) a copolymerizable unsaturated monomer, and (e) a photosensitizer. The copolymer consisting of a conjugated diolefin hydrocarbon, an α/β monoethylenically unsaturated carboxylic acid, and a monoolefin unsaturated compound that can be used in the present invention includes a conjugated diolefin hydrocarbon? (5) and α/β-ethylenically unsaturated carboxylic acid (g)) as essential components, and a monoolefin-based unsaturated compound (Bokugen) as essential components A: 10~
95 mol%, B: 5 to 90 mol%, C: 0 to 85 mol%
A copolymer containing the following proportions is suitable.

The conjugated diolefin hydrocarbon of the copolymer is 1
- 3-Butadiene, isoprene, chloroprene, dimethylbutadiene, etc. are preferably used. Conjugated diolefin hydrocarbons may be used alone or in a total amount of 10 to 9
Two or more types may be used in combination as long as the amount is within the range of 5 mol %. When these conjugated diolefin hydrocarbons are polymerized and incorporated into a copolymer, double bonds remain in the main chain or side chain of the copolymer. Monomer radicals are added to the double bonds, and the composition after photoreaction not only forms a strong three-dimensional network structure, but also has enhanced water resistance and solvent resistance. Further, the conjugated diolefin hydrocarbon contained in the copolymer can impart flexibility, that is, rubber elasticity, which is necessary for a flexographic printing plate. The proportion of the conjugated diolefin hydrocarbon in the copolymer is 10 mol%
If it is less than that, the above-mentioned three-dimensional crosslinking property and the flexibility necessary for a flexographic printing plate will be lacking, and the intended resin letterpress plate will not be able to be produced.

In addition, if it exceeds 95 mol%, α・
The amount of β-ethylenically unsaturated carboxylic acid becomes relatively small, and the affinity of the photosensitive resin layer containing the copolymer as a component for a dilute alkali aqueous solution decreases, making it difficult to use the desired development method. become unable. Examples of α/β monoethylenically unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid, maleic anhydride, crotonic acid, itaconic acid, itaconic anhydride, monoethyl maleate,
Huma? Examples include monoesters such as monoethyl ruate and monoethyl itaconate, citracones, and mesaconic acid.

These α/β monoethylenically unsaturated carboxylic acids must be contained in the copolymer in an amount of 5 to 90 mol%, and
If it is less than mol %, the proportion of hydrophilic groups in the copolymer decreases, making it impossible to satisfy the alkali developability which is the object of the present invention.

In addition, copolymers containing more than 90 mol% of α/β monoethylenically unsaturated carboxylic acid have decreased rubber elasticity, and when exposed and developed from a photosensitive resin layer containing the copolymer as one component, This has the disadvantage that the water resistance of the resulting printing plate is reduced. α・
The β-ethylenically unsaturated carboxylic acids may be used alone or in combination of several types as long as the total amount is within the range of 5 to 90 mol%. The monoolefinic unsaturated compound does not need to be contained in the copolymer of the present invention, but it is added to improve the mechanical properties such as the rubber elasticity, strength, and elongation of the printing plate made of the copolymer as one component. This is because the purpose is to improve the printing characteristics of the printing plate, and to improve the printing surface such as the ink receptivity and ink transferability of the printing plate.

Styrene, α-
Methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene chloride, acrylamide, methacrylamide, vinyl acetate, general formula (wherein R1 is hydrogen or methyl group, R2 represents an alkyl group having 1 to 18 carbon atoms), such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, Tert-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate,
Examples include acrylates or methacrylates such as n-octyl acrylate, n-decyl acrylate, lauryl acrylate, and n-octadecyl acrylate.

Also dimethyl maleate, diethyl maleate, dibutyl maleate, dioctyl maleate, dimethyl fumarate, diethyl fumarate, dibutyl fumarate, dioctyl fumarate, dimethyl itaconate, diethyl itaconate,
Diesters such as dibutyl itaconate and dioctyl itaconate, and esters of hydroxyalkyl alcohols such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate or methacrylate are also preferably used. These may be used as a mixture of two or more types as long as the total amount does not exceed 85 mol%. When the content of the monoolefinic unsaturated compound in the copolymer exceeds 85 mol%, conjugated diolefinic hydrocarbons, α
- Since the bonding amount of β-ethylenically unsaturated carboxylic acid decreases, it becomes impossible to satisfy the three-dimensional crosslinkability, rubber elasticity, alkali developability, etc. which are the objectives of the present invention. Preferable copolymers used in the present invention are A: 30 to
70 mol%, B: 10 to 60 mol%, and C: 0 to 60 mol%. The copolymer of the present invention is one in which residual double bonds originating from a conjugated diolefin hydrocarbon are three-dimensionally crosslinked by the action of actinic rays such as ultraviolet rays and become insolubilized in a solvent. When a photopolymerizable unsaturated monomer containing a sexually unsaturated group is added,
It was found that the crosslinking reaction was promoted and the mechanical strength of the printing plate obtained after the crosslinking reaction was greatly improved. The photopolymerizable unsaturated monomers used in the present invention include styrene, α
-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene,
Unsaturated aromatic compounds such as diisopropenylbenzene and divinylbenzene; unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile; methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, Acrylates or methacrylates of alkyl alcohols such as n-pentyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, n-decyl acrylate, lauryl acrylate, n-octadecyl acrylate; 2-hydroxyethyl acrylate, 2-
Acrylates or methacrylates of hydroxyalkyl alcohols such as hydroxypropyl acrylate or methacrylate; acrylates or methacrylates of alkoxyalkylene glycols such as methoxyethylene glycol acrylate, methoxypropylene glycol acrylate; maleic acid, fumaric acid, maleic anhydride, crotonic acid, itacon α/β-ethylenically unsaturated carboxylic acids such as acid, itaconic anhydride, citraconic acid, and mesaconic acid; monoesters of unsaturated polyhydric carboxylic acids such as monoethyl maleate, monoethyl fumarate, and monoethyl itaconate; maleic acid; Diesters such as dimethyl acid, diethyl maleate, dibutyl maleate, dioctyl maleate, dimethyl fumarate, diethyl fumarate, dibutyl fumarate, dioctyl fumarate, dimethyl itaconate, diethyl itaconate, dibutyl itaconate, dioctyl itaconate, etc. ; Acrylamide, methacrylamide, N-N'-methylenebisacrylamide, N
-N''-Acrylamides or methacrylamides such as hexamethylenebisacrylamide; ethylene glycol diacrylate or dimethacrylate, diacrylates or dimethacrylates of polyalkylene glycol (2 to 23 single alkylene glycols); glycerin, pentaerythritol, Diacrylate, triacrylate, tetraacrylate, dimethacrylate, trimethacrylate or tetramethacrylate of polyhydric alcohols such as methylolalkane, tetramethylolalkane (methane, ethane, propane as alkanes); Aronix type manufactured by Toagosei Chemical Industry Co., Ltd. Monomer M-5500, M-5700,.M-6100
, M63OO,. A series of oligoacrylates M-8030 and M-8060; diarylidene pentaerythrite and its modified products, 2,25-bis(4-methacryloxydiethoxyphenyl)propane, 2,2'-bis(4 −
Acryloxydiethoxyphenyl)propane, 2.2'
-bis(4-acryloxypropoxyphenyl)propane and the like.

The photopolymerizable unsaturated monomer is used in an amount of 5 to 200 parts by weight, preferably 10 parts by weight, based on 100 parts by weight of the copolymer.
It is used in a range of 100 parts by weight. Within this range, two or more types can be used in combination. If it is less than 5 parts by weight, sufficient curing of the photosensitive resin layer and improvement in the mechanical strength of the printing plate cannot be expected, and if it exceeds 200 parts by weight, the rubber elasticity of the copolymer will be significantly impaired, and the solvent resistance It has disadvantages such as decreased sexual performance.

Examples of the photosensitizer used in the present invention include α-
Examples include diketone compounds, acyloins such as benzoin and pivaloin, acyloin ethers such as benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether, and polynuclear quinones such as anthraquinone and 1,4-naphthoquinone. The amount of the photosensitizer added is 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of the copolymer. If it is less than 0.1 part by weight, sufficient curing cannot be given to the photosensitive resin layer, and if it exceeds 10 parts by weight, all of the added photosensitizer does not participate in the reaction, which is uneconomical. However, sometimes they have poor compatibility with the copolymer or photopolymerizable unsaturated monomer and may be unevenly dispersed.

Among the commercially available photopolymerizable unsaturated monomers mentioned above, p
- A small amount of thermal polymerization inhibitor such as methoxyphenol is added, but this has no effect at all when exposing the photosensitive resin layer, but rather acts as a storage stabilizer for the photosensitive resin composition, so the composition is During production, the thermal polymerization inhibitor can be added as is without being removed from the photopolymerizable unsaturated monomer.

Furthermore, if necessary, storage stabilizers may be added, such as hydroxy aromatic compounds such as hydroquinone, p-methoxyphenol, p-tert-butylcatechol, 2,6-di-tert-butyl-p-cresol, pyrogallol, benzoquinone, Quinones such as -torquinone and p-xyloquinone, and amines such as phenyl-α-naphthylamine can be added in an amount of 0.01 to 2 parts by weight per 100 parts by weight of the copolymer. Conjugated diolefin hydrocarbon of the present invention/
A method for producing a photosensitive resin composition containing a copolymer of α/β ethylenically unsaturated carboxylic acid/monoolefinic unsaturated compound, a photopolymerizable unsaturated monomer, and a photosensitizer includes: A photopolymerizable unsaturated monomer,
After adding an appropriate amount of photosensitizer and stirring thoroughly to make a homogeneous solution, remove the solvent under reduced pressure while heating, or remove the solvent in advance under reduced pressure and make the copolymer into a highly viscous or solid state before heating. However, it is possible to rely on a method of adding and mixing a photopolymerizable unsaturated monomer and a photosensitizer.

The photosensitive resin composition obtained in this way becomes a liquid photosensitive resin composition or a rubber-like solid photosensitive resin composition. It can be coated onto a support using a roll coater or the like, or it can be formed into a photosensitive resin layer of a constant thickness by compression molding, extrusion molding, etc., exposed to light with a negative film, and developed to form a photosensitive resin relief plate. The photosensitive resin composition has high rubber elasticity and is therefore ideal for flexographic printing plates, and a support having the same degree of rubber elasticity as the photosensitive resin composition can be used as a support for supporting the resin layer. Examples include natural rubber, styrene-butadiene rubber, butadiene rubber, acrylonitrile-butadiene rubber, isoprene rubber, ethylene-propylene rubber (crystalline 1,2-butadiene resin,
A sheet made of soft vinyl chloride resin or the like, and films made of polyester, polypropylene, polystyrene, nylon, vinylidene chloride, polyethylene, etc. can also be used in fields where a support with low rubber elasticity can be used. In addition, grained aluminum plates, iron plates,
Zinc plates, magnesium plates, etc. can also be used. One of the features of the present invention is the developability with a dilute aqueous alkali solution, but the alkali used may be any ordinary alkali, such as sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia, sodium carbonate, potassium carbonate. A low concentration aqueous solution of about 0.1 to 1.0%, such as lithium carbonate, is used as the developer.

Furthermore, the photosensitive resin composition of the present invention can of course be developed not only with an alkaline aqueous solution but also with an organic solvent such as an alcohol, a ketone, or an aromatic hydrocarbon. Since the photosensitive resin composition of the present invention has high photosensitivity, exposure time can be shortened, and its solubility in dilute aqueous alkaline solutions is extremely good and it can be developed in 1 to 2 minutes.

Since printing can be performed immediately after drying, the complicated manufacturing process and manufacturing time of conventional rubber letterpress plates for flexographic printing can be greatly improved. In addition, it is possible to print with solvent-based flexo ink, but since it has good water resistance despite being soluble in alkali, it is now possible to print with water-based flexo ink, which is replacing solvent-based flexo ink due to air pollution concerns. Summer. The photosensitive resin composition of the present invention can be used not only as a resin plate for flexographic printing, but also as a photosensitive material for newspapers, resin letterpress plates for general commercial printing, name plates, printed wiring, displays, and optical adhesives. is also widely available.

Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to the following examples in any way unless it exceeds the gist thereof.

Example 1 1 Preparation of photosensitive resin composition Butadiene/styrene/methyl methacrylate/methacrylic acid obtained by polymerization using methanol as a solvent -45/10
/30/15 (mole ratio) 62.8% by weight solution of copolymer 159.27% nonaethylene glycol dimethacrylate as photopolymerizable unsaturated monomer 40.0y1 benzoin isopropyl ether as photosensitizer 2.07% , and 500 ml each of hydroquinone 0.17 as a storage stabilizer.
The mixture was placed in a Mitsuro separable flask and thoroughly stirred until a homogeneous solution was obtained.

The separable flask containing the contents was immersed in a water bath controlled at about 40°C, and the solvent methanol was removed under reduced pressure while stirring to produce a viscous photosensitive resin composition.

2 The photosensitive resin composition 5.07 prepared in plate making 1 was placed on a styrene-butadiene rubber sheet (64 cd 1 thickness 1.0 mm), and 1.
．． 0m7ftf) A photosensitive resin layer was produced.

A negative film with an optical density of 3.5 is applied while maintaining a distance of 0.3 mm from the resin layer, and the upper surface 60 of the resin layer is
Ultraviolet light was exposed for 60 seconds using a 250W ultra-high pressure mercury lamp from CTn. By spraying a 0.5% aqueous sodium hydroxide solution onto the exposed resin layer for 2 minutes and developing it, a resin letterpress faithful to the original image in which the unexposed areas were completely dissolved and removed was produced.

Resin letterpress has rubber elasticity, and the rubber hardness (Shore A
The hardness (measured at 20°C) was 60. In addition, the entire surface was exposed for 60 seconds without using a negative film, and the resin layer was 3.5mm in diameter.
The degree of swelling was measured after 24 hours by punching out a disk shape and soaking it in hot water controlled at 40℃, which was 0.2.
%, and it was found that almost no water was absorbed. 3 Printing When the resin relief plate was printed with black letterpress ink, printed matter with very good ink transfer properties was obtained.

Examples 2 to 4 The copolymers shown in Table 1 were obtained by polymerization using methanol as a solvent in the same manner as in Example 1, and resin relief plates were produced by the same plate-making method as in Example 1.

All were printing plates with low rubber hardness in which the unexposed areas were completely removed, and when printed, printed materials with good ink transfer properties were obtained. Although the affinity for water increases as the amount of methacrylic acid increases, the water resistance was not found to be that large. Examples 5 to 8 Photosensitive resin relief plates were produced in exactly the same manner except that the photopolymerizable unsaturated monomers shown in Table 2 were used in the copolymer synthesized in Example 1.

All of them gave good printing plates, low rubber hardness, good water resistance, and printed matter with excellent ink transfer properties. Example
9-18 The copolymers shown in Table 3 were obtained using ethanol as a solvent.

When these copolymer solutions were heated at 40°C under reduced pressure to remove the solvent ethanol, all of them became rubber-like small lumps. A mixed monomer of 2,2'-bis(4-methacryloxydiethoxyphenyl)propane/lauryl methacrylate-75/25 (weight ratio) was added to the above copolymer 1.
807 added to 007, similarly benzoin isopropyl ether 2.07, p-methoxyphenol 0.17
By adding and continuing stirring, transparent viscous photosensitive resin compositions were produced in each case.

When the plate was made in exactly the same manner as in Example 1, an excellent printing plate having the rubber elasticity shown in Table 3 and good water resistance was obtained, and the printed matter was also good. Comparative Example 1 Butadiene/styrene/methyl methacrylate/methacrylic acid-5/10/70/1 was prepared in exactly the same manner as in Example 9.
A viscous photosensitive resin composition containing a copolymer having the composition No. 5 as one component was prepared, and a printing plate was obtained by plate making in the same manner as in Example 1. Although the water resistance was good, It was found that the shore-A hardness was 98, showing almost no rubber elasticity, and that it could not be used as a flexo plate.

Comparative Example 2 Butadiene/styrene/methyl methacrylate/methacrylic acid-45/10/43/2 was prepared in exactly the same manner as in Example 9.
A viscous photosensitive resin composition containing a copolymer having the same composition as one component was prepared, exposed to light using a negative film in the same manner as in Example 1, and sprayed with a 0.5% aqueous sodium hydroxide solution. Although it was developed, the unexposed areas were not dissolved and it was not possible to obtain a printing plate with good alkali developability, which is the object of the present invention.

Claims (1)

[Claims] 1 (I) Conjugated diolefin hydrocarbon (A) and α・
A β-ethylenically unsaturated carboxylic acid (B) is an essential component, and a monoolefinically unsaturated compound (C) is added to this as an essential component.
: 10-95 mol%, B: 5-90 mol%, C: 0-8
A photosensitive resin composition comprising a copolymer in a proportion of 5 mol %, (II) a photopolymerizable unsaturated monomer, and (III) a photosensitizer.