JP2017185737A - Flexographic printing plate and method for manufacturing the same, and method for manufacturing liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexographic printing plate that less likely causes deposition of a foreign substance on a plate surface or sticking of the plate surface to a print object surface such as a surface where an electrode is to be formed, a method for manufacturing the flexographic printing plate, and a method for manufacturing a liquid crystal display element by which productivity of a liquid crystal display element can be improved compared to the current situation by forming a liquid crystal alignment film using the above flexographic printing plate.SOLUTION: The flexographic printing plate has an ink transfer layer made of a cured product of a photocurable resin composition and having one surface to be used as a plate surface, in which a cohesive force of the plate surface is set to 1.4 N or less and a hardness by a type-A durometer of the ink transfer layer is set to A58 or lower. The method for manufacturing the flexographic printing plate comprises: forming a layer of a resin composition the composition of which is controlled to satisfy the above characteristics by bringing the resin composition into contact with a roughened mold surface; curing the resin composition in a layer state by irradiation with active rays; and then peeling the layer from the mold surface. The method for manufacturing a liquid crystal display element includes a step of forming a liquid crystal alignment film by flexographic printing using the above flexographic printing plate.SELECTED DRAWING: None

Description

  The present invention relates to a flexographic printing plate and a method for producing the same, and a method for producing a liquid crystal display element including a step of forming a liquid crystal alignment film of the liquid crystal display element by flexographic printing using the flexographic printing plate.

Flexographic printing is used to form a liquid crystal alignment film that is required to have a high film quality that is as uniform as possible and free from pinholes and the like on the electrode forming surface of the substrate constituting the liquid crystal display element. .
Flexographic printing is made of a flexible resin sheet whose surface is in contact with the surface to be printed such as the electrode forming surface in a state where the surface of the liquid crystal alignment film is supported. A flexographic printing plate having a plate-shaped ink transfer layer that is a plate surface for transfer onto a printing surface is used.

The plate surface is a rough surface having a predetermined surface roughness in order to improve the wettability with respect to the ink and hold the ink well and to transfer the held ink onto the printing surface. It is common.
The ink transfer layer having a roughened plate surface is produced through the following steps using, for example, a photocurable resin that undergoes a curing reaction upon irradiation with actinic rays (Patent Document 1, etc.).

In other words, the photo-curing resin is subjected to a curing reaction by irradiation with actinic rays such as ultraviolet rays in a state where the photo-curing resin is spread in layers on a roughened sheet whose surface is roughened, and then roughened. When the sheet is peeled off, an ink transfer layer is formed, and the surface of the ink transfer layer that is in contact with the mold surface of the roughened sheet is transferred to the roughened plate. The surface.
After that, the corresponding part of the formed ink transfer layer is thermally or mechanically cut to form a gripping part or a chuck hole for mounting on the printing press, or the plate surface as necessary. The flexographic printing plate is manufactured by removing the area corresponding to the non-printing area of the printing pattern thermally or mechanically.

Also, when a photocurable resin is cured and reacted with a reinforcing sheet such as a polyester sheet superimposed on the opposite surface of the layer of the photocurable resin, flexographic printing in which the reinforcing sheet is integrally laminated on the opposite surface. Can produce plates.
Examples of the photo-curable resin that is the basis of the ink transfer layer include a prepolymer having a 1,2-polybutadiene structure and having an ethylenic double bond at the terminal, one as a reactive diluent in one molecule, or A mixture of an ethylenically unsaturated monomer having two ethylenic double bonds and a photopolymerization initiator is suitably used (Patent Document 2 etc.).

JP2013-119179A JP 2012-242683 A

According to the photocurable resin described in Patent Document 2, it is possible to form an ink transfer layer having appropriate rubber elasticity and flexibility and excellent solvent resistance.
However, since the ink transfer layer made of a cured product of a conventional photocurable resin such as that described in Patent Document 2 generally has high adhesiveness (tackiness), the manufactured flexographic printing plate can be used for flexographic printing. There is a problem in that dried and solidified ink fragments, dust and other foreign matters are likely to adhere to the plate surface, which is the exposed surface of the ink transfer layer, during use and during storage.

If the flexographic printing plate with foreign matter attached to the plate surface is used as it is for the formation of the liquid crystal alignment film, the film is not formed at the place where the foreign matter is attached, or even if a film is formed. As a result of frequent occurrence of defects such as uneven thickness, the productivity of the liquid crystal display element may be greatly reduced.
For this reason, the flexographic printing plate is usually removed from the printing plate cylinder, washed with a solvent, dried, and reattached to the printing cylinder, for example, frequently at the start and end of printing, or at a predetermined number of times. It is necessary to repeat the work.

However, large-sized flexographic printing plates corresponding to recent large-sized liquid crystal display elements include large ones having a side exceeding, for example, 1500 mm, and minute foreign matters are spread over the entire plate surface of such large-sized flexographic printing plates. In order not to leave it, it is not easy to clean thoroughly every corner, and it is difficult to completely eliminate the problems such as film removal described above.
In addition, it is difficult to handle when removing the flexographic printing plate from the plate cylinder for cleaning, or attaching it to the plate cylinder after cleaning, resulting in defects such as folds and scratches due to work mistakes, and the quality of the flexographic printing plate deteriorates. As a result, the productivity of the liquid crystal display element may be reduced.

In addition, the ink supply is delayed due to some trouble during printing, so that the adhesion of the ink to the plate surface is partially reduced, and the flexographic printing plate is in direct contact with the electrode forming surface of the substrate constituting the liquid crystal display element. As a result, the flexographic printing plate may stick to the electrode forming surface as it is.
When the flexographic printing plate is attached, the substrate is lifted together when the plate cylinder is moved, and it breaks or breaks, or the anilox roll for supplying ink to the flexographic printing plate is lifted or broken. There is a risk of causing problems such as contact with a damaged substrate and damage.

When these problems occur, it is necessary to remove the damaged substrate, replace the anilox roll, etc., which causes a major trouble that the printing process must be stopped for a long time, and the liquid crystal display. There is also a risk that the productivity of the element is greatly reduced.
An object of the present invention is to provide a flexographic printing plate that is less likely to cause adhesion of foreign matters to the plate surface or sticking of the plate surface to a printing surface such as an electrode forming surface, a method for producing the same, and the flexographic printing plate. An object of the present invention is to provide a method of manufacturing a liquid crystal display element that can improve the productivity of the liquid crystal display element from the current state by forming a liquid crystal alignment film using the above.

The present invention is composed of a cured product of a photocurable resin composition, and includes a flat plate-like ink transfer layer having one surface as a plate surface, and the plate surface has an adhesive strength required by a probe tack test of 1. While being 4N or less, the ink transfer layer is a flexographic printing plate having a type A durometer hardness of A58 or less.
The present invention is also a method for producing the flexographic printing plate of the present invention,
The step of adjusting the composition of the resin composition that is the basis of the ink transfer layer according to the adhesive strength of the plate surface and the rubber hardness of the ink transfer layer,
A step of forming the ink transfer layer by curing reaction by irradiation of actinic rays in a layered state while the resin composition is in contact with a roughened mold surface; and And a step of making the surface of the ink transfer layer in contact with the mold surface into a roughened plate surface.

  Furthermore, this invention is a manufacturing method of the liquid crystal display element including the process of forming a liquid crystal aligning film by flexographic printing using the flexographic printing plate of the said invention.

  According to the present invention, a flexographic printing plate that is less likely to cause adhesion of foreign matter to the plate surface or sticking to the printing surface of the plate surface, a method for producing the same, and a liquid crystal alignment film using the flexographic printing plate By forming the liquid crystal display element, it is possible to provide a method for manufacturing a liquid crystal display element that can improve the productivity of the liquid crystal display element from the current level.

《Flexographic printing plate》
As described above, the flexographic printing plate of the present invention is composed of a cured product of a photocurable resin composition, and includes a plate-like ink transfer layer having one surface as a plate surface, and the plate surface is subjected to a probe tack test. The ink transfer layer is characterized by having a type A durometer hardness of A58 or less.

According to the present invention, by setting the adhesive force of the plate surface within the above range, it is possible to suppress foreign matter from adhering to the plate surface, and even at the corners of the plate surface of a large flexographic printing plate. The attached foreign matter can be easily removed by cleaning, and it is possible to suppress the occurrence of film loss or uneven thickness due to the attachment of the foreign matter.
In addition, since the number of times of cleaning can be reduced as compared with the current situation, the chances of occurrence of defects such as folds and scratches due to operational mistakes can be reduced and deterioration of the quality of the flexographic printing plate can be suppressed.

Further, it is possible to prevent the flexographic printing plate from sticking as it is even if the flexographic printing plate is in direct contact with the surface to be printed such as the electrode forming surface of the substrate, thereby preventing the substrate and the anilox roll from being damaged.
Therefore, according to the flexographic printing plate of the present invention, combined with these effects, the productivity of the liquid crystal display element can be improved from the current level.

In consideration of further improving such an effect, the adhesive strength of the plate surface is preferably as small as possible within the above range, and is ideally 0 N from the viewpoint of the above effect.
However, according to the inventor's study, the plate surface has adhesiveness due to the low molecular weight component contained in the ink transfer layer made of a cured product of the resin composition, and the low molecular weight component is reduced. Although the adhesive strength of the plate surface can be reduced as much as possible, the rubber hardness of the ink transfer layer is increased at the same time, resulting in a new problem that the flexibility is lowered and the printing characteristics of the flexographic printing plate are lowered.

On the other hand, according to the present invention, by setting the type A durometer hardness of the ink transfer layer in the above-described range, the flexibility of the ink transfer layer can be suppressed from being lowered, and the flexographic printing plate can be improved. Printing characteristics can be maintained.
In the present invention, the adhesive strength of the plate surface by the probe tack test is a value obtained by the following method using a tackiness checker HTC-1 manufactured by Toyo Seiki Seisakusho Co., Ltd. based on the probe tack test method. Let's represent.

  That is, a flexographic printing plate for measuring adhesive strength is fixed to a plate cylinder of 50 mm in a state where the plate surface is outside and fixed at the temperature of 23 ° C. and relative humidity of 50% on the plate surface. After contacting the contact with a load of 4.9 N for 10 seconds, the maximum load when peeling at a peeling speed of 30 mm / min was measured at 10 locations on the plate surface, and the average value of the results was obtained. Let it be the adhesive strength of the plate surface.

The type A durometer hardness of the ink transfer layer is determined by the measurement method described in Japanese Industrial Standard JIS K6253-3 _{: 2012} "Vulcanized rubber and thermoplastic rubber-Determination of hardness-Part 3: Durometer hardness". Therefore, in a temperature 23 ° C. and relative humidity 50% environment, the pressure plate is brought into contact with the test piece and expressed with a value displayed 15 seconds later.
<Resin composition>
As the resin composition having photocurability, which is the basis of the ink transfer layer, for example, a photocurable resin and a polyfunctional component having three or more functionalities having reactivity with the photocurable resin are included. Etc.

According to such a resin composition, at the time of the curing reaction of the photocurable resin by irradiation with actinic rays, the photocurable resin is subjected to a crosslinking reaction with a polyfunctional component, so that the low molecular weight component that causes the above-described adhesion can be obtained. By reducing the ratio, the tackiness of the plate surface can be reduced.
The blending ratio of the multifunctional component is preferably 1 part by mass or more and preferably 4 parts by mass or less per 100 parts by mass of the photocurable resin.

  If the blending ratio of the multifunctional component is less than this range, the effect of reducing the adhesiveness of the plate surface by crosslinking the photocurable resin by blending the multifunctional component cannot be sufficiently obtained. If the adhesive strength of the plate surface exceeds the above-mentioned range of 1.4 N or less, various problems that occur during the adhering of foreign matter and cleaning to remove it, or various problems due to sticking to the printing surface are likely to occur. There is a risk.

  On the other hand, when the blending ratio of the polyfunctional component exceeds the above range, the photocurable resin is excessively cross-linked and the rubber hardness of the ink transfer layer exceeds the above-mentioned range of A58 or less, and the flexographic printing plate There is a risk that the printing characteristics of the printer may deteriorate. In particular, when the reinforcing sheet is laminated on the opposite surface of the ink transfer layer as described above, the flexographic printing plate may be greatly warped due to the shrinkage of the ink transfer layer during the curing reaction.

On the other hand, by setting the blending ratio of the multifunctional component within the range described above, the surface of the plate is maintained while maintaining the rubber hardness and flexibility of the ink transfer layer in a favorable range and suppressing warping of the flexographic printing plate. It is possible to reduce the stickiness of the ink and to prevent the occurrence of adhesion of foreign matter and sticking to the printing surface and various problems associated therewith.
In consideration of further improving this effect, the blending ratio of the polyfunctional component is more preferably set to 3 parts by mass or less per 100 parts by mass of the photocurable resin even in the above range.

Incidentally, when the photocurable resin contains a solvent that does not participate in the curing reaction and is removed by drying from the film, the blending ratio of the polyfunctional component is the solid content obtained by removing the solvent amount from the total amount of the photocurable resin. What is necessary is just to set to the said range on the basis of the quantity (photocuring resin itself) (100 mass parts).
<Photocurable resin>
As the photocurable resin, any of various conventionally known photocurable resins used for forming the ink transfer layer can be used.

  Considering the formation of an ink transfer layer having particularly suitable rubber elasticity and flexibility and excellent solvent resistance, the photocurable resin has a 1,2-polybutadiene structure as described above. Together with a prepolymer having an ethylenic double bond at the terminal, an ethylenically unsaturated monomer having one or two ethylenic double bonds in one molecule as a reactive diluent, and a photopolymerization initiator, It is preferable to use those blended at a predetermined ratio.

(Prepolymer)
As the prepolymer constituting the photocurable resin, any of various prepolymers having a 1,2-polybutadiene structure and having a polymerizable ethylenic double bond at the terminal can be used.
The prepolymer is, for example,
(a) a hydrogenated 1,2-polybutadiene compound having a terminal hydroxyl group, and
(b) a compound obtained by chain-extending the hydrogenated 1,2-polybutadiene compound of the above (a) with diisocyanate,
The compound is synthesized by introducing at least one polymerizable ethylenic double bond at the terminal of at least one of the compounds.

Among these, the hydrogenated 1,2-polybutadiene compound (a) has a number of terminal hydroxyl groups per molecule of 1.2 or more, particularly preferably 1.5 or more, and 2.0 or less. Is preferred.
If the number of terminal hydroxyl groups is less than this range, there is a possibility that sufficient mechanical strength cannot be imparted to the flexographic printing plate.

The hydrogenated 1,2-polybutadiene compound is preferably a compound in which 50% or more of the side chain vinyl groups of the 1,2-polybutadiene structure are hydrogenated.
If the hydrogenation rate is less than 50%, the rubber elasticity of the flexographic printing plate may be lowered or hardened, and the printing characteristics may be lowered.
Examples of the hydrogenated 1,2-polybutadiene compound include at least one of hydrogenated poly-1-butene and hydrogenated 1,2-polybutadiene.

Among these, 1,2-polybutadiene may contain cis-1,4 and trans-1,4 as a fine structure, but the content is preferably 50% or less.
The hydrogenated 1,2-polybutadiene compound (a) can be synthesized, for example, by any of the following methods.
A method in which butadiene is living anionic polymerized, ethylene oxide is added thereto, a hydroxyl group is introduced at the terminal, and then a vinyl group in the side chain is hydrogenated.
A method of polymerizing butadiene using a metal salt such as NaPdCl ₄ , KPdCl ₄ , NH ₄ PdCl ₄ , or PdBr ₂ as a polymerization initiator, introducing a hydroxyl group at the terminal, and then hydrogenating a vinyl group in the side chain.
1-butene with a peroxide or azo compound having a hydroxyl group in the molecule, such as t-butyl-β-hydroxyethyl peroxide, 4,4′-azobis-4-cyano-n-amyl alcohol, as a polymerization initiator A method of radical polymerization of

Further, the compound (b) obtained by chain extension of the hydrogenated 1,2-polybutadiene compound (a) with diisocyanate preferably has two or more urethane bonds per molecule, The number is preferably 20 or less.
This is because as the number of urethane bonds increases, the rubber elasticity of the flexographic printing plate improves, but the solvent resistance tends to decrease.

On the other hand, if the number of urethane bonds is within the above range, a flexographic printing plate having an excellent balance between rubber elasticity and solvent resistance can be obtained.
An ethylenic double bond at the end of the hydrogenated 1,2-polybutadiene compound (a) and / or the compound (b) (hereinafter (a) (b) may be collectively referred to as “prepolymer precursor”) As a method for synthesizing a prepolymer by introducing, any of the following methods can be employed, for example.
-A diisocyanate is previously reacted with the hydroxyl group of the prepolymer precursor to introduce a terminal diisocyanate group, and a compound containing an ethylenic double bond and a group having active hydrogen is reacted therewith.
A carboxyl group is introduced at the end of the prepolymer precursor, and an epoxy compound having an ethylenic double bond is reacted therewith.

In particular, when the compound (b) is used as a prepolymer precursor, by using an excess of diisocyanate with respect to the terminal hydroxyl group of the hydrogenated 1,2-polybutadiene compound (a) as the base, Simultaneously with chain extension, a terminal diisocyanate group can also be introduced at the terminal.
The chain extension reaction can be carried out in the presence of a urethanization catalyst such as a tertiary amine or a tin compound. However, the chain extension reaction can also be carried out under conditions in which no urethanization catalyst is present.

Although reaction temperature is not specifically limited, It is preferable that it is 40 degreeC or more, and it is preferable that it is 100 degrees C or less.
A reaction for synthesizing a prepolymer by introducing an ethylenic double bond into the prepolymer precursor by using a urethanization reaction between a terminal diisocyanate group and a group having active hydrogen can be carried out under the same conditions. In that case, it is preferable that a suitable polymerization inhibitor is present.

Examples of the compound containing an ethylenic double bond and a group having active hydrogen used for the urethanization reaction include hydroxyalkylene (meth) acrylate, polyalkylene glycol mono (meth) acrylate, secondary aminoalkylene (meth) acrylate, 1 type, or 2 or more types, such as N-mono substituted acrylamide and unsaturated carboxylic acid, is mentioned.
Specific examples of such compounds include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polybutylene glycol mono ( (Meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolethane di (meth) acrylate, tetramethylolmethane tri (meth) acrylate, dibromoneopentyl glycol mono (meth) acrylate, glycerin di (meth) acrylate, hydroxy Cyclohexyl (meth) acrylate, monomethylaminoethyl (meth) acrylate, monomethylaminoethyl (meth) acrylate, N-methyl (meth) acrylami , N- octyl (meth) acrylamide, acrylic acid, methacrylic acid, itaconic acid monoester, fumaric acid monoester, maleic acid mono-esters, one or more of such glycidyl (meth) acrylate.

Examples of the diisocyanate include one or more of an aliphatic diisocyanate, a diisocyanate of an alicyclic compound, and an aromatic diisocyanate.
Specific examples of such diisocyanates include hexamethylene diisocyanate (HMDI), ω, ω′-diisocyanate-1,3-dimethylbenzole, 2,6- and / or 2,4-trimethyl. Range isocyanate (TDI), paraphenylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate (MDI), hydrogenated 2,6- and / or hydrogenated 2,4-TDI, hydrogenated MDI, dicyclohexyldimethylmethane 1 type, or 2 or more types, such as a diisocyanate and a lysine isocyanate, are mentioned.

The average molecular weight of the prepolymer is preferably 1000 or more and preferably 30000 or less in terms of number average molecular weight Mn.
If the number average molecular weight Mn is less than this range, the rubber elasticity of the flexographic printing plate may be insufficient. In addition, when the above range is exceeded, the viscosity of the resin composition containing a photocurable resin as a main component is increased, and the fluidity, followability to the mold surface, and reproducibility of the rough surface may be reduced. There is.

(Ethylenically unsaturated monomer)
The ethylenically unsaturated monomer has one or two ethylenic double bonds in one molecule, and functions as a reactive diluent as described above. Specific examples of such as vinyl pyridine, N-vinyl carbazole, (meth) acrylic acid or its ester, (meth) acrylamide or its derivative, styrene, vinyl toluene, divinylbenzene, diallyl phthalate, vinyl acetate, acrylonitrile, itaconic acid , Fumaric acid, maleic anhydride, maleic acid, and mono- or dialkyl esters of these acids.

  Examples of the esters of (meth) acrylic acid include alkyl, cycloalkyl, tetrahydrofurfuryl, allyl, glycidyl, and hydroxyalkyl mono (meth) acrylates, alkylene glycol, polyoxyalkylene glycol mono or di ( Examples thereof include one or more of (meth) acrylate (for example, polypropylene glycol dimethacrylate), monomethyl or di (meth) acrylate of trimethylolpropane, and mono or di (meth) acrylate of pentaerythritol.

Further, examples of (meth) acrylamide derivatives include one or more of N-methylol (meth) acrylamide, N, N′-alkylenebis (meth) acrylamide, diacetone (meth) acrylamide, and the like.
Further, mono (meth) acrylates of monohydric alcohols having 8 to 30 carbon atoms such as octyl, capryl, nonyl, decyl, lauryl, ceryl, etc. (for example, lauryl methacrylate), 1,3-butanediol, 1,8-octanediol, Mono- or di (meth) acrylates of dihydric alcohols having 4 to 30 carbon atoms such as 1,9-nonanediol, 1,10-decanediol, 1,18-stearlanediol (for example, 1,3-butanediol diester) Methacrylate) is particularly effective in improving the solvent resistance of flexographic printing plates.

It is preferable to use two or more ethylenically unsaturated monomers in combination according to the properties required for the flexographic printing plate.
An ethylenically unsaturated monomer can be mix | blended in the ratio of 5 to 100 mass parts with respect to 100 mass parts of prepolymers.
In particular, the viscosity of a resin composition mainly composed of a photocurable resin is reduced to improve its fluidity, followability to the mold surface, and reproducibility of rough surfaces, and to improve the printing characteristics of flexographic printing plates. In consideration of what to do, it is preferable to blend at a ratio of 40 parts by mass or more and 60 parts by mass or less. This blending ratio is the ratio of the total amount to 100 parts by mass of the prepolymer when two or more ethylenically unsaturated monomers are used in combination.

(Photopolymerization initiator)
As the photopolymerization initiator, for example, benzoin alkyl ether or the like is used.
Examples of the benzoin alkyl ether include one or more of benzoin ethyl ether, benzoin-n-propyl ether, benzoin isobutyl ether, and the like.

A photoinitiator can be mix | blended in the ratio of 0.001 mass% or more and 10 mass% or less of the total amount of a prepolymer and an ethylenically unsaturated monomer. In particular, in order to obtain an optimum photosensitivity for forming an ink transfer layer by irradiation with actinic rays, it is preferable to blend at a ratio of 0.01% by mass or more and 5% by mass or less even in the above range.
<Multifunctional component>
As the polyfunctional component constituting the resin composition together with the photocurable resin, any of trifunctional or higher functional compounds having three or more groups having reactivity with the photocurable resin can be used.

  For example, as described in the previous section, a prepolymer having a 1,2-polybutadiene structure and having an ethylenic double bond at the terminal, ethylene having one or two ethylenic double bonds in one molecule as a reactive diluent As a polyfunctional component having reactivity with a photocurable resin containing a photopolymerizable unsaturated monomer and a photopolymerization initiator, a trifunctional or higher functional group having three or more ethylenic double bonds in one molecule is used. At least one selected from the group consisting of a monomer, an oligomer, and a prepolymer is preferred.

  Examples of such polyfunctional components include pentaerythritol triacrylate, trimethylolpropane triacrylate (A-TMPT), ditrimethylolpropane tetraacrylate, ethoxylated pentaerythritol tetraacrylate, pentaerythritol tetraacrylate, dipentaerythritol polyacrylate, dipentaerythritol. Examples thereof include one or more of 3 to 6 functional compounds such as pentaerythritol hexaacrylate and trimethylolpropane trimethacrylate (TMPT).

Among them, A-TMPT and / or TMPT excellent in reactivity with the photocurable resin is preferable, and TMPT is particularly preferable.
The blending ratio of the polyfunctional component is preferably 1 part by mass or more per 100 parts by mass of the total amount of the photocurable resin, preferably 4 parts by mass or less, and particularly preferably 3 parts by mass or less. The reason for this is as described above.

<Other ingredients>
The resin composition containing the photocurable resin and the multifunctional component further includes various additives for adjusting the viscosity, rubber elasticity and strength of the flexographic printing plate, solvent resistance, weather resistance, and the like. May be blended.
Examples of such additives include softeners such as dioctyl phthalate, process oil, and liquid paraffin, liquid rubbers (butyl rubber, butadiene rubber, styrene butadiene rubber, nitrile rubber, etc.), antioxidants, thermal polymerization inhibitors, and the like. .

<Flexographic printing plate and manufacturing method thereof>
The flexographic printing plate of the present invention includes, for example, an ink transfer layer made of a cured product of the above resin composition. As described above, the adhesive force required by the probe tack test is 1.4 N or less, and the ink transfer layer type A The durometer hardness is set to A58 or less.
For this reason, the flexibility of the ink transfer layer is maintained in a favorable range, and the adhesiveness of the plate surface is reduced well while suppressing the flexure of the flexographic printing plate, so that foreign matter adheres to the printing surface. And various problems associated therewith can be made less likely to occur than in the current situation.

In consideration of further improving this effect, the adhesive strength of the plate surface is preferably 0.7 N or less, particularly 0.4 N or less even in the above range. The type A durometer hardness of the ink transfer layer is preferably A53 or less, particularly A50 or less, even in the above range.
The lower limit of the adhesive strength is 0N as described above. In other words, the plate surface does not have adhesiveness, which is ideal for preventing the occurrence of film loss or uneven thickness due to adhesion of foreign matter.

Further, the type A durometer hardness of the ink transfer layer is A20 or higher even in the above range, considering that the durability of the ink transfer layer is improved or that the rubber elasticity is improved to make it difficult to cause settling or the like. Preferably there is.
The flexographic printing plate of the present invention is produced by the production method of the present invention using the resin composition described above.

Specifically, first, a resin composition is prepared while adjusting the blending ratio of the multifunctional component in the above-described range according to the adhesive force required for the plate surface and the rubber hardness required for the transfer layer. .
The resin composition may be prepared by blending a multifunctional component at the same time as the photocurable resin is prepared, or by adding a multifunctional component to the ready-made photocurable resin as described above. May be.

In the latter case in particular, there is an advantage that it is possible to provide a flexographic printing plate in which the adhesive strength and rubber hardness are controlled according to the customer's request, etc., without significantly changing the current flexographic printing plate manufacturing process. .
Next, for example, a flexible roughened sheet having a mold surface corresponding to the rough surface shape of the plate surface is set on a solid surface plate such as a glass plate, on which a photocurable resin and a multifunctional component are placed. And irradiating actinic rays such as ultraviolet rays in a state where the resin composition is in a layered state with a certain thickness, for example, by superimposing a reinforcing sheet thereon as necessary. After the curing reaction and the crosslinking reaction, the roughened sheet is peeled off.

Then, the rough surface shape is transferred to the surface of the roughened sheet that has been in contact with the mold surface, and an ink transfer layer having the roughened plate surface is formed. When the reinforcing sheets are stacked, the reinforcing sheet and the ink transfer layer are integrated.
After that, the corresponding part of the formed ink transfer layer is thermally or mechanically cut to form a gripping part or a chuck hole for mounting on the printing press, or the plate surface as necessary. The flexographic printing plate of the present invention is manufactured by removing the area corresponding to the non-printing area of the printing pattern thermally or mechanically.

<< Method for manufacturing liquid crystal display element >>
This invention is a manufacturing method of the liquid crystal display element including the process of forming a liquid crystal aligning film by flexographic printing using the flexographic printing plate of the said invention.
According to the present invention, by using the flexographic printing plate of the present invention in which the adhesiveness of the plate surface is reduced as compared with the present situation, various problems that occur at the time of adhering foreign matter or cleaning to remove it, or the printing surface The liquid crystal alignment film can be formed without causing various problems due to sticking to the substrate, and the productivity of the liquid crystal display element can be improved.

Other steps of the production method of the present invention can be carried out in the same manner as in the prior art.
That is, a transparent electrode layer corresponding to a predetermined matrix pattern or the like is formed on the surface of a transparent substrate such as a glass substrate, and a liquid crystal alignment film is formed by flexographic printing using the flexographic printing plate. If necessary, the surface is oriented by rubbing or the like to produce a substrate.

Next, two substrates are prepared, and in a state where the respective transparent electrode layers are aligned, a liquid crystal material is sandwiched between them and fixed together to form a laminated body. A liquid crystal display element is manufactured by disposing a polarizing plate on the outside.
The configuration of the present invention is not limited to the examples described above, and various modifications can be made without departing from the scope of the present invention.

<Example 1>
(Resin composition)
-Preparation of photocurable resin Both ends hydroxyl group polybutadiene (number average molecular weight Mn = 3000), TDI (mixture of 2,4 and 2,6), and 2-hydroxypropyl (meth) acrylate were reacted to give 1 A prepolymer having a number average molecular weight Mn = 15000 having a 1,2-polybutadiene structure and having an ethylenic double bond at the terminal was synthesized.

Subsequently, 100 parts by mass of the prepolymer, 50 parts by mass in total of lauryl methacrylate, 1,3-butanediol dimethacrylate and polypropylene glycol dimethacrylate as ethylenically unsaturated monomers, and benzoin isobutyl ether 2 as a photopolymerization initiator .3 parts by mass was blended to prepare a photocurable resin.
-Preparation of resin composition A resin composition having photocurability was prepared by blending 100 parts by mass of the photocurable resin with 1 part by mass of TMPT as a multifunctional component.

(Flexographic printing plate)
-Roughening sheet As the roughening sheet, a urethane thermoplastic elastomer sheet (Silklon (registered trademark) SNESS80-100 μm manufactured by Okura Kogyo Co., Ltd.) with a PET film bonded to the back surface as a reinforcing film was exposed. The surface was embossed using an embossing roll to obtain a roughened mold surface.
-Production of flexographic printing plate In the state where the roughened sheet is fixed on a smooth and transparent glass plate with the mold surface facing up, the resin composition prepared above is supplied onto the mold surface, While a PET sheet as a reinforcing sheet is stacked on top of the resin composition, the resin composition is spread in a layered form with a certain thickness and then irradiated with ultraviolet rays to cure and crosslink to form an ink transfer layer, followed by roughening. The sheet was peeled off to produce a flexographic printing plate using the surface of the ink transfer layer that was in contact with the mold surface as the roughened plate surface.

<Comparative example 1>
A resin composition was prepared in the same manner as in Example 1 except that TMPT as a multifunctional component was not blended to produce a flexographic printing plate.
<Examples 2 to 4, Comparative Example 2>
The blending ratio of TMPT as a polyfunctional component is 2 parts by mass (Example 2), 3 parts by mass (Example 3), 4 parts by mass (Example 4), and 5 parts by mass per 100 parts by mass of the photocurable resin. A resin composition was prepared in the same manner as in Example 1 except that the parts (Comparative Example 2) were used, and a flexographic printing plate was produced.

<Examples 5 to 8, Comparative Example 3>
While using A-TMPT instead of TMPT as a polyfunctional component, the blending ratio of the A-TMPT is 1 part by mass (Example 5) and 2 parts by mass (Examples) per 100 parts by mass of the photocurable resin. 6) A resin composition was prepared in the same manner as in Example 1 except that 3 parts by mass (Example 7), 4 parts by mass (Example 8), and 5 parts by mass (Comparative Example 3) were obtained. A printing plate was produced.

<Adhesion measurement>
Using the tackiness checker HTC-1 manufactured by Toyo Seiki Seisakusho Co., Ltd. based on the probe tack test method as described above, the adhesive strength of the plate surface of the flexographic printing plate produced in each example and comparative example, It calculated | required with the following method.
That is, a flexographic printing plate (width: 10 mm) produced in each of the above examples and comparative examples was fixed to a plate cylinder of φ50 mm with double-sided tape with the plate surface outside and a temperature of 23 ° C. and a relative humidity of 50 % Of the tackiness checker contact with the surface of the plate at a load of 4.9 N for 10 seconds, and then the maximum load when peeling at a peeling speed of 30 mm / min is applied to the plate surface. The measurement was performed at 10 locations, and the average value of the results was obtained and used as the adhesive strength of the plate surface.

And the adhesiveness of the plate surface was evaluated according to the following criteria.
A: Adhesive strength was 0.4 N or less. Very good.
(Circle): Adhesive force exceeded 0.4N and was 0.7N or less. Good.
(Triangle | delta): The adhesive force exceeded 0.7N and was 1.4N or less. Normal level.
X: The adhesive strength exceeded 1.4N. Bad.

<Rubber hardness measurement>
The type A durometer hardness of the ink transfer layer of the flexographic printing plate produced in each of Examples and Comparative Examples was determined by using Japanese Industrial Standard JIS K6253-3 _{: 2012} "Vulcanized rubber and thermoplastic rubber-Determination of hardness-No. 1 In accordance with the measurement method described in “Part 3: Durometer Hardness”, the pressure plate was brought into contact with the test piece in an environment of a temperature of 23 ° C. and a relative humidity of 50%, and reading was performed after 15 seconds.

The rubber hardness of the ink transfer layer was evaluated according to the following criteria.
A: Type A durometer hardness was A50 or less. Very good.
○: The type A durometer hardness exceeded A50 and was A53 or less. Good.
Δ: Type A durometer hardness exceeded A53 and was A58 or less. Normal level.
X: The type A durometer hardness exceeded A58. Bad.

<Curve evaluation>
The warping immediately after production of the flexographic printing plate produced in each example and comparative example was evaluated according to the following criteria.
A: No warpage was observed. Very good.
○: Slight warping was observed, but it was resolved after standing for a while on a flat plate. Good.

(Triangle | delta): Warpage was seen and it was not able to be completely eliminated even if it left still for a while on a flat plate, but it could be used for flexographic printing. Normal level.
X: Warp was large and could not be used for flexographic printing. Bad.
<Comprehensive evaluation>
The score of each of the above evaluations is ◎, 5 points, ◯ 3 points, △ 1 point, × 0 point, and the adhesive strength and rubber hardness are important items, and the above scores are squared. The product of scores was obtained and comprehensive evaluation was performed according to the following criteria.

A: The score was 1000 points or more. Very good.
A: The score was 100 points or more and less than 1000 points. Good.
Δ: The score was 1 point or more and less than 100 points. Normal level.
X: The score was less than 1 point. Bad.
The above results are shown in Tables 1 and 2.

  From the results of Examples 1 to 8 and Comparative Examples 1 to 3 in Tables 1 and 2, a prepolymer having an 1,2-polybutadiene structure and having an ethylenic double bond at the terminal, an ethylenically unsaturated monomer In a combination of a photocurable resin containing a photopolymerization initiator and a polyfunctional component having an ethylenic double bond, 1 mass part or more of the polyfunctional component per 100 mass parts of the photocurable resin, It was found that by blending at a ratio of 4 parts by mass or less, a flexographic printing plate having a plate surface adhesive strength of 1.4 N or less and a type A durometer hardness of the ink transfer layer of A58 or less can be formed.

  Moreover, considering that the effects are further improved from the results of Examples 1 to 8, the blending ratio of the multifunctional component is preferably 3 parts by mass or less even in the above range, the multifunctional component. As for A-TMPT and / or TMPT, it turned out that TMPT is especially preferable.

Claims (5)

  A plate-shaped ink transfer layer comprising a cured product of a photocurable resin composition, one side of which is a plate surface, and the plate surface has an adhesive strength of 1.4 N or less determined by a probe tack test. The ink transfer layer is a flexographic printing plate having a type A durometer hardness of A58 or less. The resin composition forming the ink transfer layer is
1 to 4 parts by mass of a photocurable resin and a trifunctional or higher polyfunctional component having a reactivity with the photocurable resin per 100 parts by mass of the photocurable resin. Item 3. A flexographic printing plate according to item 1.   The photocurable resin is a prepolymer having a 1,2-polybutadiene structure and having an ethylenic double bond at the terminal, and an ethylenically unsaturated monomer having one or two ethylenic double bonds in one molecule. And the polyfunctional component is at least one selected from the group consisting of a monomer having three or more ethylenic double bonds in one molecule, an oligomer, and a prepolymer. Item 3. A flexographic printing plate according to item 2. A method for producing a flexographic printing plate according to any one of claims 1 to 3,
The step of adjusting the composition of the resin composition that is the basis of the ink transfer layer according to the adhesive strength of the plate surface and the rubber hardness of the ink transfer layer,
A step of forming the ink transfer layer by curing reaction by irradiation of actinic rays in a layered state while the resin composition is in contact with a roughened mold surface; and The manufacturing method of the flexographic printing plate including the process which peels from 2 and makes the surface which was contacting the said mold surface of the said ink transfer layer into the roughened plate surface.   The manufacturing method of a liquid crystal display element including the process of forming a liquid crystal aligning film by flexographic printing using the flexographic printing plate of any one of the said Claim 1 thru | or 3.