JP2007133032A - Photosensitive resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photosensitive resin composition having good alkali developability and giving a cured object having excellent elastic recovery characteristics, and photo-spacers. <P>SOLUTION: The alkali developable photosensitive resin composition contains a hydrophilic polymer having a carboxyl group and a (meth)acryloyl group, a polyfunctional (meth)acrylate monomer and a photopolymerization initiator, wherein the hydrophilic polymer satisfies all of the following conditions (1)-(4); (1) the polymer is a polymer obtained by reacting a copolymer having an unsaturated polybasic acid anhydride as an essential constituent monomer with a compound having a (meth)acryloyl group and at least one functional group selected from a hydroxyl group, a primary amino group and a secondary amino group in one molecule, (2) the polymer has a low acid value of 100-500 mgKOH/g, (3) the polymer has a (meth)acryloyl group concentration of 2-9 mmol/g, (4) the difference in solubility parameter between the polymer and the polyfunctional (meth)acrylate monomer is -1 to 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a photosensitive resin composition that is cured by irradiation with actinic rays and is capable of alkali development, and a photospacer provided for maintaining a gap in a liquid crystal cell formed using the composition.

In recent years, liquid crystal display devices have attracted attention, and photosensitive resins are frequently used in the manufacturing process. For example, the portion corresponding to the pixel on the color filter is a color pigment dispersion resist, and the resist is also used for the black matrix. As a resist used for such a portion, a so-called negative resist is often used in which only a portion irradiated with light is hardened when exposed through a mask and an unexposed portion is peeled off by development.

  Now, in the liquid crystal display device technology, in order to maintain the thickness of the liquid crystal layer between both the color filter side substrate and the thin film transistor (TFT) side substrate, glass or resin transparent spherical particles (beads) called spacers are used. Sprayed inside the cell. Since these spacers are transparent particles, if there is a liquid crystal and a spacer in the pixel, light leaks through the spacer particles during black display, and both substrates in which the liquid crystal is sealed The presence of the spacer particles between them disturbs the orientation of the liquid crystal molecules in the vicinity of the spacer particles, causing light leakage at this portion, resulting in a decrease in the contrast of the liquid crystal display device and adversely affecting the display quality. Yes. Also, for example, in a liquid crystal display device in which the distance between the two substrates (the thickness of the liquid crystal layer) is narrow, such as a ferroelectric liquid crystal, the distance between the two substrates can be maintained uniformly and accurately using this spacer particle. It is difficult.

As a technique for solving such a problem, for example, a photosensitive resin is used and a photolithography method such as partial pattern exposure and development is performed on a black matrix in a lattice pattern located at a desired position, for example, between pixels. A method of forming a columnar resin spacer has been proposed. Such a spacer is hereinafter referred to as a photo spacer. Since the photo spacer can be formed at a position avoiding the pixels, it does not adversely affect the display quality as described above, and the display quality can be improved.

  On the other hand, in recent years, a drop method (ODF: One Drop Fill) has been proposed instead of the conventional liquid crystal inflow method (vacuum suction method) as the mother glass for LCD (Liquid Crystal Display) manufacture becomes larger. In ODF, liquid crystal is injected by dropping a predetermined amount of liquid crystal and then sandwiching it with a substrate. Therefore, the number of processes and process time can be reduced as compared with the conventional vacuum suction method. However, in the ODF system, a predetermined amount of liquid crystal calculated from the cell gap is dropped and held, so that it has an elastic characteristic that does not affect the subtle pressure difference applied in the process. Is desired for photo spacers.

That is, a photo spacer having excellent elastic recovery characteristics is required.
Photo spacers that do not have such characteristics may cause bubbles in the liquid crystal when the panel is produced, and the cell gap is not uniform, and the display quality of the liquid crystal display device deteriorates. For example, color unevenness is noticeable. Inconveniences, such as becoming something, occur.
As a proposal for solving these problems, for example, a photosensitive resin composition for photospacers having an alkali developability (Patent Document 1) has been proposed. This proposal proposes a photospacer with excellent mechanical strength by using a photopolymerizable monomer, a photopolymerization initiator, and an epoxy resin having alkali developability and reactivity in combination. However, in a composition in which such an epoxy resin and a carboxylic acid component necessary for alkali development coexist, a crosslinking reaction proceeds between the epoxy group and the carboxylic acid. As a result, there is a problem that the elastic recovery characteristic is deteriorated due to brittleness.
In recent years, a further new proposal (Patent Document 2) has been made as a material for forming a photospacer having such a characteristic as to solve such a problem. In this proposal, the amount of polyfunctional monomer in the total solid content is improved by 50 to 70%. However, when a large amount of polyfunctional monomer is used, there is a problem that alkali developability deteriorates.
JP 2001-226449 A JP 2002-174812 A

  The present invention has been made in order to solve the above problems, and provides a photosensitive resin composition having good alkali developability and having a cured product with excellent elastic recovery properties, and further excellent. An object is to provide a photo spacer having elastic recovery characteristics.

The inventors of the present invention have arrived at the present invention as a result of intensive studies to solve the above problems.
That is, the present invention is a photosensitive resin composition containing a hydrophilic polymer (A) having a carboxyl group and a (meth) acryloyl group, a polyfunctional (meth) acrylate monomer (B), and a photopolymerization initiator (C). The alkali-developable photosensitive resin composition (Q), wherein the hydrophilic polymer (A) is a polymer satisfying all of the following (1) to (4).
(1) Copolymer (D) having an unsaturated polybasic acid anhydride as an essential constituent monomer and at least one functional group selected from a hydroxyl group, a primary amino group and a secondary amino group in one molecule And a polymer obtained by reacting the compound (e) having a (meth) acryloyl group.
(2) It has a weak acid value of 100 to 500 mgKOH / g.
(3) It has a (meth) acryloyl group concentration of 2 to 9 mmol / g.
(4) The difference in solubility parameter from the polyfunctional (meth) acrylate monomer (B) is −1 to 1.
Moreover, this invention is the photo spacer formed by hardening | curing the said photosensitive resin composition.

-The photosensitive resin composition of this invention is excellent in alkali developability.
-The hardened | cured material of the photosensitive resin composition of this invention has the outstanding elastic recovery characteristic.
The cured product of the photosensitive resin composition of the present invention has excellent elastic recovery characteristics as a photo spacer.

  The hydrophilic polymer (A) in the present invention (hereinafter sometimes simply referred to as (A)) is hydrophilic and has an average of at least 1 (meth) acryloyl group and at least 1 in the molecule. It has 1 carboxyl group.

The hydrophilic index of (A) is defined by HLB, and generally, the larger this value, the higher the hydrophilicity.
Although the preferable range of the HLB value of (A) varies depending on the resin skeleton of (A), it is preferably 4 to 19, more preferably 5 to 18, and particularly preferably 6 to 17. When it is 4 or more, developability of the photo solder resist is further improved, and when it is 19 or less, the water resistance of the cured product is further improved. In addition, HLB in this invention is an HLB value by the Oda method, is a hydrophilicity-hydrophobicity balance value, and can be calculated from the ratio of the organic value and inorganic value of an organic compound.
HLB≈10 × Inorganic / Organic In addition, the inorganic value and the organic value are described in the document “Surfactant Synthesis and Applications” (published by Tsuji Shoten, Oda, Teramura), page 501; It is described in detail on page 198 of “Introduction to New Surfactants” (Takehiko Fujimoto, published by Sanyo Chemical Industries, Ltd.).

  (A) has a weak acid value because it contains a carboxyl group. The weak acid value of (A) is usually 100 to 500 mgKOH / g, preferably 120 to 400 mgKOH / g, more preferably 150 to 300 mgKOH / g from the viewpoint of developability.

  When the weak acid value of (A) is less than 100 mgKOH / g, the developability cannot be exhibited, and when it exceeds 500 mgKOH / g, the water resistance of the cured product is deteriorated.

The weak acid value in the present invention can be measured by an indicator titration method using an alkaline titration solution.
The method is as follows.
(I) About 1 g of a sample is precisely weighed and placed in an Erlenmeyer flask, and then a neutral methanol / acetone solution (a mixture of acetone and methanol at 1: 1 (volume ratio)) is added and dissolved.
(Ii) Add several drops of phenolphthalein indicator and titrate with 0.1 mol / L potassium hydroxide titration solution. The end point of neutralization is defined as the time when the indicator is slightly red for 30 seconds.
(Iii) Determine using the following equation.
Weak acid value (mgKOH / g) = (A × f × 5.61) / S
However, A: The number of mL of 0.1 mol / L potassium hydroxide titration solution.
f: Potency of 0.1 mol / L potassium hydroxide titration solution
S: Sampling (g)

In (A), the concentration of the (meth) acryloyl group based on the weight of (A) is usually 2 to 9 mmol / g, preferably 2.5 to 8 mmol / g, more preferably 3 from the viewpoint of the hardness of the cured product. ~ 7 mmol / g. When the acryloyl group concentration is less than 2 mmol / g, the effect of improving the hardness cannot be exhibited. On the other hand, if it exceeds 9 mmol / g, developability deteriorates.

The concentration of the (meth) acryloyl group in the present invention can be measured by a titration method using an amine addition reaction (Michael addition) to a double bond. The method is as follows.
(I) About 1 g of a sample is precisely weighed and placed in an Erlenmeyer flask, and then about 10 ml of acetone is added and dissolved.
(ii) 10 ml of morpholine standard solution [mixed morpholine and methanol at 1: 4 (volume ratio)] was added, and 50% acetic acid standard solution [acetic acid and ion-exchanged water was mixed at 1: 1 (volume ratio). Things] Add 1.5 ml and shake well, then leave at room temperature for 15 minutes.
(iii) Add 15 ml of acetonitrile and 10 ml of acetic anhydride to the above Erlenmeyer flask and shake well.
(iv) Titrate with a 0.5 mol / L hydrochloric acid / methanol titration solution using a recording type automatic titrator.
(v) Conduct a blank test at the same time, and determine with the following formula.
Double bond concentration (mmol / g) = f * (AB) / 2S
However, A: mL number of 0.5 mol / L hydrochloric acid / methanol titration solution required for the titration of the sample.
B: Number of mL of 0.5 mol / L hydrochloric acid / methanol titration solution required for the blank test.
f: The titer of 0.5 mol / L hydrochloric acid / methanol titration solution.
S: Sampling amount (g)

Moreover, the SP value of (A) is the polyfunctional (meth) acrylate monomer (B) described below from the SP value of (A) from the viewpoint of developability (hereinafter sometimes simply referred to as (B)). The difference obtained by subtracting the SP value is usually −1 to 1, preferably −0.8 to 0.8, more preferably −0.6 to 0.6, and particularly preferably −0.3 to 0.3. If the difference in SP value is out of the range of −1 to 1, the developability deteriorates.
Those with close SP values are likely to be mixed with each other (high dispersibility), and the difference in SP value is an index that indicates that those with different numerical values are difficult to mix.
If the difference in SP value between (A) and (B) is −1 to 1, separation between (A) and (B) in the development process is unlikely to occur, so uniform development can be performed (development). It is presumed that the effect that the solubility in the liquid is uniform) can be exhibited.

  The SP value of (A) is preferably 7 to 14, more preferably 8 to 13, and particularly preferably 11 to 13. When it is 7 or more, the developability can be further improved, and when it is 14 or less, the water resistance of the cured product is further improved.

The SP value in the present invention is calculated by the method described in the following document proposed by Fedors et al.
“POLYMER ENGINEERING AND SCIENCE, FEBRUARY, 1974, Vol. 14, No. 2, ROBERT F. FEDORS. (Pages 151-153)”

In the photosensitive resin composition of the present invention, the hydrophilic polymer (A) has a weak acid value in the above range, a (meth) acryloyl group concentration in the above range, and has an SP value of (A) and (B). The difference is −1 to 1.
Here, in order to make the difference in SP value between (A) and (B) be −1 to 1, first, the composition of (B) is set and the SP value is determined. The composition of (A) may be selected so that the difference in the above is within the above range. Conversely, the SP value is determined by first setting the composition in (A), and the difference from the SP value is within the above range. (B) may be selected.
In (B), the composition is easy to select from the viewpoint of the elastic recovery characteristics of the cured product, so that the SP value is easy to set, and (A) is preferable from the viewpoint that there are many combinations of compositions.
In addition to the setting of the SP value, it is necessary to set the weak acid value (A) and the (meth) acryloyl group concentration. The order of these settings is first the SP value, then the weak acid value, and finally (meth). A method of setting the composition (A) in consideration of the acryloyl group concentration is preferable.

  The number average molecular weight (hereinafter abbreviated as Mn, measured by gel permeation chromatography) of (A) is preferably 500 to 100,000 from the viewpoint of elastic recovery characteristics and developability when it becomes a photospacer. More preferably, it is 1,000 to 30,000, particularly preferably 5,000 to 20,000.

The hydrophilic polymer (A) is a copolymer of an unsaturated polybasic acid anhydride as essential constituent monomer (A ₀₎ and an acid anhydride group (hereinafter, simply there if referred to as A ₀₎ in In the compound (e) having at least one functional group selected from a hydroxyl group, a primary amino group and a secondary amino group and a (meth) acryloyl group (hereinafter sometimes simply referred to as (e)) A polymer obtained by reacting a functional group, which is obtained by reacting a part or all of the acid anhydride group in (A ₀ ) with a functional group such as a hydroxyl group in (e). It has a carboxyl group and an acid anhydride group or a carboxyl group. .

(A ₀ ) is obtained by copolymerizing an unsaturated polybasic acid anhydride and one or more other radical polymerizable monomers copolymerizable with the unsaturated polybasic acid anhydride using a radical polymerization initiator. The polymer obtained is mentioned.

  Examples of unsaturated polybasic acid anhydrides include divalent and trivalent polybasic acid anhydrides having radically polymerizable unsaturated groups. Examples of unsaturated dibasic acid anhydrides include maleic anhydride and itaconic anhydride. And unsaturated tribasic acid anhydrides include aconitic anhydride. Of these, maleic anhydride is preferred from the viewpoint of copolymerization.

  The other radical polymerizable monomer copolymerizable with the unsaturated polybasic acid anhydride is not particularly limited as long as it is a monomer that does not react with the acid anhydride group under the polymerization reaction conditions. For example, olefinic hydrocarbons having 2 to 12 carbon atoms such as ethylene, propylene and butene; aromatic monomers such as styrene, α-methylstyrene, chloromethylstyrene and vinylphenol; methyl (meth) acrylate, ethyl (meth) acrylate And (meth) acrylic acid alkyl ester monomers having 1 to 12 carbon atoms of alkyl groups such as butyl (meth) acrylate; acrylamide monomers such as (meth) acrylamide and alkyl-substituted (meth) acrylamide; alkyl groups such as methyl vinyl ether A C 1-8 alkyl vinyl ether monomer; a C 2-12 carboxylic acid vinyl ester monomer of a carboxylic acid such as vinyl acetate. These can be used alone or in combination of two or more. Of these, aromatic monomers are preferable from the viewpoint of heat resistance, and styrene is more preferable from the viewpoint of copolymerization.

  From the viewpoint of developability, the ratio of the unsaturated polybasic acid anhydride and the other radical polymerizable monomer copolymerized therewith is preferably another radical polymerizable monomer relative to 1 mol of the unsaturated polybasic acid anhydride. Is a ratio of 0.3 to 3 mol, more preferably 0.5 to 1.5 mol.

The production of (A ₀ ) can be achieved by diluting the unsaturated polybasic acid anhydride and other copolymerizable monomer that can be copolymerized with a solvent, if necessary, and then performing polymerization with a radical polymerization initiator.
Examples of the solvent include glycol diethers (such as ethylene glycol dialkyl ether and propylene glycol dialkyl ether), ketones (such as acetone, methyl ethyl ketone, and methyl isobutyl ketone), and halogenated hydrocarbons (such as dichloroethane). Of the solvents, ketones are preferred.
When a solvent is used, the amount used is not particularly limited, but is usually 400% by weight or less, preferably 5 to 300% based on the total weight of monomers (in the following,% represents weight% unless otherwise specified). Especially preferably, it is 10 to 200%.
Examples of the radical polymerization initiator include normal peroxides and azo compounds, and preferred are azo compounds. The amount of the polymerization initiator used is usually preferably 0.0001 to 20%, more preferably 0.001 to 15%, and particularly preferably 0.005 to 10% based on the total weight of the monomers. The reaction temperature is appropriately determined depending on the type of radical polymerization initiator, but is preferably 40 to 150 ° C.

The hydrophilic polymer (A) can be obtained by adding (e) to (A ₀ ) and heating and stirring in the presence of a solvent and / or a catalyst as necessary.
This reaction is a reaction in which an acid anhydride group in (A ₀ ) and a hydroxyl group, primary amino group and / or secondary amino group in (e) react to form a half ester and / or a half amide. It is.

  Examples of (e) include compounds having one, two, or three (meth) acryloyl groups in one molecule, and the following (e1) to (e4) and mixtures thereof are exemplified.

As a compound (e1) having one functional group selected from a hydroxyl group, a primary amino group or a secondary amino group, and one (meth) acryloyl group in one molecule:
C2-C20 hydroxyalkyl (meth) acrylate of alkyl group [2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate and 1-hydroxybutyl (meth) Acrylates, etc.]; polyalkylene glycol mono (meth) acrylate (2 to 8 carbon atoms of alkylene group, weight average molecular weight 100 to 10,000) [polyethylene glycol mono (meth) acrylate, polyethylene / polypropylene glycol (oxyethylene content) 10 to 90% by weight) mono (meth) acrylate and polypropylene glycol mono (meth) acrylate, etc.]; aminoalkyl (meth) acrylate having 2 to 20 carbon atoms in the alkyl group [aminoethyl (meth) acrylate , Aminoisopropyl (meth) acrylate, aminobutyl (meth) acrylate, aminohexyl (meth) acrylate, etc.] and N-alkylaminoalkyl (meth) acrylate having 3 to 24 carbon atoms in total of the alkyl group [N-methylaminoethyl (Meth) acrylate, N-ethylaminoethyl (meth) acrylate, N-methylaminoisopropyl (meth) acrylate, N-methylaminobutyl (meth) acrylate, N-methylaminohexyl (meth) acrylate, etc.]. .

As a compound (e2) having one functional group selected from a hydroxyl group, a primary amino group or a secondary amino group, and two (meth) acryloyl groups in one molecule: ) Acrylates [glycerin di (meth) acrylate and trimethylolpropane di (meth) acrylate etc.] and N, N-di (meth) acryloylethylalkylenediamine [N, N-di (meth) acryloylethylethylenediamine etc.]. .

As a compound (e3) having one functional group selected from a hydroxyl group, a primary amino group or a secondary amino group, and 3 or more (preferably 3 to 5) (meth) acryloyl groups in one molecule Is: tri (meth) acrylate of tetrahydric alcohol [pentaerythritol tri (meth) acrylate, diglycerin tri (meth) acrylate, sorbitan tri (meth) acrylate, etc.]; tetrahydric alcohol tetra (meth) acrylate [triglycerin tetra (Meth) acrylates and the like]; and penta (meth) acrylates of hexavalent alcohols [dipentaerythritol penta (meth) acrylates and the like].

One molecule has 2 or more (preferably 2 to 3) one or more functional groups selected from a hydroxyl group, a primary amino group or a secondary amino group, and one or more (meth) acryloyl groups. Compound (e4): trivalent alcohol mono (meth) acrylate [glycerin mono (meth) acrylate and trimethylolpropane mono (meth) acrylate, etc.]; tetravalent alcohol mono or di (meth) acrylate [pentaerythritol mono (Meth) acrylate, pentaerythritol di (meth) acrylate and diglycerin di (meth) acrylate, etc.]; monovalent, di- or tri (meth) acrylate of pentavalent alcohol [triglycerin tri (meth) acrylate etc.]; and hexavalent alcohol Mono, di, tri or tetra (meta) acrylate [Dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate], and.

Of the hydroxyl group, primary amino group and secondary amino group contained in (e) above, a hydroxyl group is preferred from the viewpoint of ease of production of (e).
(E) may be a mixture of (e1) to (e4), and the mixing ratio in the case of the mixture is not particularly limited, but from the viewpoint of elastic recovery properties, the functional group is preferably contained in one molecule. One (meth) acrylate [(e1) to (e3)] having only one is 50% or more, more preferably 70% or more, particularly 80% or more.
Among (meth) acrylates [(e1) to (e3)] having only one of the above functional groups in one molecule, (e2) or (e) is more preferable from the viewpoint that the (meth) acryloyl group can be highly concentrated. e3), particularly (e3), and among (e3), tri (meth) acrylates of tetrahydric alcohols, particularly pentaerythritol tri (meth) acrylate, from the viewpoint that the cured product is not too hard.

The charged amount of (e) in the reaction of (A ₀ ) and (e) is appropriately selected depending on the target weak acid value of (A), (meth) acryloyl group concentration and SP value, but (A ₀ ) Preferably it is 5-60 mol% with respect to the number-of-moles of unsaturated polybasic acid anhydride at the time of manufacture, More preferably, it is 10-50 mol%. Within this range, the weak acid value, (meth) acryloyl group concentration, and SP value of (A) are likely to fall within the above-mentioned ranges.

Examples of the solvent are the same as those in the production of (A ₀ ).
Examples of the catalyst include basic catalysts such as pyridine, triethylamine, and 2-methylimidazole. The catalyst is added in an amount of preferably 0.05 to 1%, more preferably 0.1 to 0.6%, based on the weight of (A ₀ ).
The reaction temperature is usually 50 to 120 ° C., preferably 95 to 100 ° C., and the reaction time is usually 0.5 to 10 hours, preferably 1 to 5 hours.

As a specific example of (A),
Reaction product of 100 parts of maleic anhydride / styrene (46.5 / 53.5 molar ratio) copolymer and 110.3 parts of pentaerythritol triacrylate (weak acid value = 128 mg KOH / g, acryloyl group concentration = 6.0 mmol / g, SP value = 11.3, Mn = 25,000);
Reaction product of 100 parts of maleic anhydride / styrene (46.5 / 53.5 molar ratio) copolymer and 59.7 parts of 2-hydroxyethyl methacrylate (weak acid value = 177 mgKOH / g, acryloyl group concentration = 3. 15 mmol / g, SP value = 10.24, Mn = 22,000);

The photosensitive resin composition of the present invention contains (A) preferably 3 to 50%, more preferably 3 to 35%, and particularly preferably 3 to 29% based on the solid content of the photosensitive resin composition. .
If it is 3% or more, the developability can be further improved, and if it is 50% or less, the water resistance of the cured product is further improved.
In the present specification, the “solid content” means a component obtained by removing the solvent from the composition.

  In the present invention, the polyfunctional (meth) acrylate monomer (B) (hereinafter sometimes simply referred to as (B)) used as one component in the photosensitive resin composition is a known polyfunctional (meta) The acrylate monomer is not particularly limited, and examples thereof include bifunctional (meth) acrylate (B1), trifunctional (meth) acrylate (B2), and 4-6 functional (meth) acrylate (B3).

Examples of the bifunctional (meth) acrylate (B1) include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, and polyethylene glycol di (meth). Acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, glycerin di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate ( SP value of methacrylate = 12.5, SP value of acrylate = 10.3), 1,9-nonanediol di (meth) acrylate, 1,10-decandiol di (meth) acrylate, 3-methyl-1, -Pentanediol di (meth) acrylate, 2-butyl-2-ethyl-1,3-propanediol di (meth) acrylate, dimethylol-tricyclodecane di (meth) acrylate, di (ethylene oxide adduct of bisphenol A ( Examples include (meth) acrylate, di (meth) acrylate of propylene oxide adduct of bisphenol A, and neopentyl glycol di (meth) acrylate of hydroxypivalate.

As trifunctional (meth) acrylate (B2), glycerin tri (meth) acrylate, trimethylolpropane tri (meth) acrylate (SP value of methacrylate = 12.5, SP value of acrylate = 10.3), pentaerythritol tri Examples include (meth) acrylate (SP value of methacrylate = 12.5, SP value of acrylate = 10.3), tri (meth) acrylate of ethylene oxide adduct of trimethylolpropane, and the like.

As the 4- to 6-functional (meth) acrylate (B3), pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate (methacrylate SP value = 12.5, acrylate SP value = 10.3), Examples include dipentaerythritol hexa (meth) acrylate (SP value of methacrylate = 12.5, SP value of acrylate = 10.3).

(B) is required to have a difference in SP value from the hydrophilic polymer (A) of −1 to 1, and from these viewpoints and from the viewpoint of the elastic recovery properties of the cured product, preferred are among these , (B2) and (B3), most preferred is dipentaerythritol hexa (meth) acrylate. Examples of (B) that can be easily obtained from the market include Aronix M-101, M-208, M-240, M-305, and M-400 (manufactured by Toagosei Co., Ltd.).

Moreover, (B) in this invention may contain the photosensitive (meth) acryl oligomer (B4) in the one part. As (B4), Mn is 1,000 or less, does not contain a carboxyl group, and has two or more (meth) acryloyl groups in one molecule, urethane (meth) acrylate, polyester (meth) acrylate, and Examples include polyether (meth) acrylate.
The content of (B4) in (B) is preferably 50% or less, more preferably 30% or less.

  The content of (B) based on the weight of the solid content of the photosensitive resin composition is preferably 10 to 95%, more preferably 50 to 95%, and particularly preferably 70 to 95%. If it is 10% or more, the elastic recovery property is preferable, if it is 70% or more, the elastic recovery property is more preferable, and if it is 95% or less, the developability is further improved.

  As the photopolymerization initiator (C) (hereinafter sometimes simply referred to as (C)) used as one component in the photosensitive resin composition, a photoradical polymerization initiator is used. For example, benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzophenone, methyl benzoyl formate, isopropyl thioxanthone, 4,4-bis (dimethylamino) benzophenone 3,3-dimethyl-4-methoxy-benzophenone, anthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, tert-butylanthraquinone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, acetophenone, 2,2- Dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, 2-hydroxy-2-methylpropiophenone, 4-isopropyl-2-hydride Xyl-2-methylpropiophenone, 2-methyl-1- (4- (methylthio) phenyl) -2-morpholino-1-propanone, 2-chlorothioxanthone, diethylthioxanthone, isopropylthioxanthone, diisopropylthioxanthone, Michler's ketone, benzyl- 2,4,6- (trihalomethyl) triazine, 2- (o-chlorophenyl) -4,5-diphenylimidazolyl dimer, 9-phenylacridine, 1,7-bis (9-acridinyl) heptane, 1,5- Bis (9-acridinyl) pentane, 1,3-bis (9-acridinyl) propane, dimethylbenzyl ketal, trimethylbenzoyldiphenylphosphine oxide, tribromomethylphenylsulfone and 2-benzyl-2-dimethylamino-1- (4 Morpholinophenyl) - butan-1-one, and the like.

  As (C), a commercially available product can be easily obtained. Examples thereof include Irgacure 907 and Irgacure 369 (manufactured by Ciba Specialty Chemicals).

  The content of (C) based on the weight of the solid content of the photosensitive resin composition is preferably 0.0001 to 20%, more preferably 0.001 to 15%, and particularly preferably 0.005 to 10%. . If it is 0.0001% or more, the elastic recovery property can be exhibited more satisfactorily, and if it is 20% or less, the developability can be exhibited more satisfactorily.

The photosensitive resin composition may further contain other components (F) as necessary.
As (F), inorganic fine particles (F1), sensitizers (F2), polymerization inhibitors (F3), solvents (F4), and other additives (F5) (for example, inorganic pigments, silane coupling agents, Dyes, fluorescent brighteners, yellowing inhibitors, antioxidants, antifoaming agents, deodorants, fragrances, bactericides, antibacterial agents and fungicides, and the like.

As the inorganic fine particles (F1), metal oxide (F11) and metal salt (F12) can be used.
Examples of (F11) include known materials such as titanium oxide, silicon oxide, and aluminum oxide.
Examples of (F12) include known ones such as calcium carbonate and barium sulfate.
Among these, from the viewpoint of heat resistance and chemical resistance, (F11) is preferable, and silicon oxide and titanium oxide, particularly silicon oxide is more preferable.
(F1) is preferably 1 to 150 nm, more preferably 1 to 120 nm, and particularly preferably 5 to 20 nm from the viewpoint of transparency and elastic resilience when the volume average primary particle diameter is 1 to 200 nm and a photo spacer is used. belongs to.

 The content of (F1) based on the weight of the solid content of the photosensitive resin composition is usually 0 to 50%, preferably 1 to 45%, particularly preferably 2 to 40%. If it is 50% or less, the flexibility can be further improved, and if it is 2 to 40%, the elastic recovery property is particularly excellent.

 As the sensitizer (F2), nitro compounds (for example, anthraquinone, 1,2-naphthoquinone, 1,4-naphthoquinone, benzanthrone, p, p'-tetramethyldiaminobenzophenone, carbonyl compounds such as chloranil, nitrobenzene, p -Dinitrobenzene and 2-nitrofluorene), aromatic hydrocarbons (eg anthracene and chrysene), sulfur compounds (eg diphenyl disulfide etc.) and nitrogen compounds (eg nitroaniline, 2-chloro-4-nitroaniline) , 5-nitro-2-aminotoluene, tetracyanoethylene and the like).

 The content of the sensitizer (F2) based on the weight of the photopolymerization initiator (C) is usually 0.1 to 100%, preferably 0.5 to 80%, particularly preferably 1 to 70%.

 There is no limitation in particular as a polymerization inhibitor (F3), What is used for normal reaction is used. Specifically, diphenylhydrazyl, tri-p-nitrophenylmethyl, N- (3-N-oxyanilino-1,3-dimethylbutylidene) aniline oxide, p-benzoquinone, p-tert-butylcatechol, nitrobenzene, Examples include picric acid, dithiobenzoyl disulfide, and copper (II) chloride.

 The content of the polymerization inhibitor (F3) based on the weight of the solid content of the photosensitive resin composition is preferably 0 to 1.0%, more preferably 0.01 to 0.5%, particularly preferably 0.02. ~ 0.1%.

 As the solvent, the same solvent as the solvent (F4) used in the production of the above (A) can be used. When the solvent is used, the amount of the solvent is not particularly limited, but is preferably 50 to 1,000%, more preferably 70 to 900%, particularly based on the weight of the solid content of the photosensitive resin composition. Preferably it is 80 to 800%. In addition, the solvent used for manufacture of above-mentioned (A) is also contained in the compounding quantity of a solvent.

 The total content of (F) is usually 1,000% or less, preferably 80 to 800%, based on the weight of the photosensitive resin composition.

In the photosensitive resin composition, the concentration of the (meth) acryloyl group based on the weight of the photosensitive resin composition is preferably 2 mmol / g or more, more preferably 6 to 12 mmol / g, from the viewpoint of the elastic recovery property of the cured product. Particularly preferably, it is 7.5 to 10 mmol / g. If the (meth) acryloyl group concentration is 6 mmol / g or more, the elastic recovery property can be exhibited more satisfactorily, and if it is 12 mmol / g or less, the alkali developability can be exhibited more satisfactorily.
The (meth) acryloyl group in the photosensitive resin composition is derived from (A) and (B).

The photosensitive resin composition of the present invention can be obtained, for example, by mixing the above-described components with a known mixing device such as a planetary mixer.
The photosensitive resin composition is usually liquid at room temperature and has a viscosity of 0.1 mPa · s to 10,000 mPa · s at 25 ° C., preferably 1 mPa · s to 8,000 mPa · s.

Since the photosensitive resin composition of the present invention is excellent in the elastic recovery property of the cured product, it is particularly suitable as a photosensitive resin composition for a photospacer provided for maintaining a gap in a liquid crystal cell.

The photo spacer of the present invention will be described below.
The photospacer of the present invention is a photospacer provided for maintaining a gap in a liquid crystal cell formed by curing the photosensitive resin composition (Q).
The photo spacer determines the gap of the liquid crystal cell when the color filter substrate and the TFT substrate are bonded together, and plays an important role for display quality. The photo spacer has a constant height in the range of about 2 to 5 μm, and its uniformity is required. In addition to the height, the shape, size, density, and the like required for the photo spacer are appropriately determined depending on the design of the liquid crystal display device.

Description will be made based on a method of forming a photo spacer by a photolithography method using the photosensitive resin composition (Q) of the present invention.
(Q) of this invention is uniformly apply | coated by a well-known method, such as a roll coat, a spin coat, a spray coat, a slit coat, on a board | substrate, It is made to dry and the photosensitive resin composition layer is formed. As the coating apparatus, a known coating apparatus can be used, and examples thereof include a spin coater, an air knife coater, a roll coater, a bar coater, a curtain coater, a gravure coater, and a comma coater.

Here, an example of forming on a transparent common electrode further provided on the colored layer will be described.
The photosensitive resin composition layer is dried by applying heat as necessary (pre-baking).
The drying temperature is preferably 10 ° C or higher, more preferably 12 ° C or higher, particularly preferably 15 ° C or higher, most preferably 20 ° C or higher, and preferably lower than 100 ° C, more preferably 90 ° C or lower, particularly preferably. Is 60 ° C. or lower, most preferably 50 ° C. or lower. The drying time is preferably 30 seconds or more, more preferably 1 minute or more, particularly preferably 2 minutes or more, and preferably 10 minutes or less, more preferably 8 minutes or less, particularly preferably 5 minutes or less. Drying may be performed under reduced pressure or normal pressure, but reduced pressure is preferred. Moreover, although it may carry out in air or in an inert gas, it is preferably in an inert gas.

Next, the photosensitive resin composition layer is exposed with actinic rays through a predetermined photomask.
In the case of the photosensitive resin composition of the present invention, even a mask opening having a diameter of about 5 to 10 μm (area of about ²⁰ to 100 μm ² ) has high accuracy, that is, a diameter of 6 to 12 μm (area of 30 to 120 μm ² ). A pattern can be formed in a range.

Examples of the active light used for exposure include visible light, ultraviolet light, and laser light. Examples of the light source include sunlight, a high-pressure mercury lamp, a low-pressure mercury lamp, a metal halide lamp, and a semiconductor laser.
Although it does not specifically limit as an exposure amount, Preferably it is 20-300 mJ / cm < ² >.

Subsequently, the unexposed portion is removed with a developer, and development is performed.
Here, as the developer used for development, an alkaline aqueous solution is usually used. Examples of the alkaline aqueous solution that can be used as the developer include aqueous solutions of inorganic substances such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and sodium bicarbonate; aqueous solutions of organic substances such as hydroxytetramethylammonium and hydroxytetraethylammonium. Is mentioned. These can be used alone or in combination of two or more kinds, and a surfactant such as an anionic surfactant, a cationic surfactant, an amphoteric surfactant and a nonionic surfactant can be added and used.
As a developing method, there are a dip method and a shower method, but the shower method is preferable. The temperature of the developer is preferably 25 to 40 ° C. The development time is appropriately determined according to the film thickness and the solubility of the photosensitive resin composition.

In order to make the curing more reliable, heating (baking) may be performed as necessary.
When baking is performed, the baking temperature is preferably 100 to 250 ° C, more preferably 150 to 240 ° C, and particularly preferably 180 to 230 ° C. The baking time is 5 minutes to 6 hours, preferably 15 minutes to 4 hours, particularly preferably 30 minutes to 3 hours.
The baking may be performed under reduced pressure or normal pressure, but reduced pressure is preferred. Moreover, although it may carry out in air or in an inert gas, it is preferably in an inert gas.

The photospacer of the present invention obtained as described above is a photospacer excellent in elastic recovery characteristics.
The elastic recovery characteristic of the photospacer can be evaluated by “total deformation amount” and “plastic deformation amount” when pressure is applied. The larger the total deformation amount and the smaller the plastic deformation amount, the better the elastic recovery characteristics.

In the present invention, the elastic recovery characteristic can be evaluated by measuring the following “elastic recovery rate in a pressure range of 0.2 to 0.8 mN / μm ² ”.

“Elastic recovery rate (%)”;
At 25 ° C., a predetermined pressure is applied at a constant speed, held for 1 second, and then the total deformation amount T ₀ from the hysteresis curve (FIG. 1) between the load and the deformation amount when the pressure is unloaded at a constant speed, The amount of plastic deformation T ₁ is obtained, and the elastic recovery rate at a predetermined pressure is calculated by the following equation.
Elastic recovery rate (%) = (T ₀ −T ₁ / T ₀ ) × 100
As ^{pressure, 0.2mN / μm 2, 0.4mN /} μm 2, the hysteresis curve measured at four different pressures of 0.6mN / μm ² and 0.8mN / μm ^2, the elastic recovery rate in each Ask.

Elastic recovery photo spacer of the present invention may be any pressure conditions of ^{0.2mN / μm 2 ~0.8mN / μm 2} , preferably 70% or more, more preferably 75% or more, particularly preferably Is 80% or more. If the elastic recovery rate is 70% or more, particularly 75% or more, there is a high possibility that it can be used practically as a spacer for holding the liquid crystal cell gap.

The photosensitive resin composition (Q) of the present invention can be suitably used for a photospacer as described above, but various other resist materials such as a photosensitive resist film, a photoresist, a photosensitive resin relief plate, It is suitable as a photosensitive layer for screen plates, photoadhesives, or hard coat agents.
Furthermore, coating agents for various materials such as metals (for example, iron, aluminum, titanium, copper, etc.), plastics (for example, polycarbonate, polyethylene terephthalate, poly (meth) acrylate), paper, glass, rubber and wood, paints, It can be used as printing ink and adhesive, and can also be applied as a molding material.

[Example]
EXAMPLES Hereinafter, although an Example and a manufacture example demonstrate this invention concretely, this invention is not limited to these. Hereinafter, the part means part by weight.
[Production of hydrophilic polymer (A)]

<Production Example 1>
Into a glass Kolben equipped with a heating / cooling / stirring device, a reflux condenser, a dropping funnel and a nitrogen introduction tube, 150 parts of maleic anhydride was charged and heated to 80 ° C. After replacing the gas phase part in the system with nitrogen, 150 parts of styrene prepared in advance, 5 parts of azobisisobutyronitrile (V-60: Wako Pure Chemical Industries, Ltd., hereinafter referred to as AIBN), and cyclohexanone 50 205 parts of the mixed solution was dropped into Kolben at 80 ° C. over 60 minutes, and further reacted at the same temperature for 6 hours. Thereafter, the resin was diluted with cyclohexanone so that the resin concentration was 25% by weight, and the temperature was adjusted to 60 ° C. to obtain a cyclohexanone solution of a maleic anhydride / styrene copolymer (A0). To this polymer solution, 361 parts of “NK Ester A-TMM-3L” (manufactured by Shin-Nakamura Chemical Co., Ltd .: main component pentaerythritol triacrylate), 1,099 parts of cyclohexanone, and 5 parts of trimethylamine were charged at 60 ° C. By reacting for a period of time, a cyclohexanone solution of the desired hydrophilic polymer (A1) was obtained (solid content: 25%).

<Production Example 2>
A cyclohexanone solution of maleic anhydride / styrene copolymer (A0) obtained in the same manner as Kolben as in Production Example 1 was charged with 177 parts of 2-hydroxyethyl methacrylate, 546 parts of cyclohexanone, and 5 parts of trimethylamine. The mixture was reacted at 0 ° C. for 2 hours to obtain a cyclohexanone solution of the desired hydrophilic polymer (A2) (solid content: 25%).

<Comparative Production Example 1>
In the same Kolben as in Production Example 1, methyl methacrylate 40 parts (0.40 mole part), 2-hydroxyethyl methacrylate 40 parts (0.31 mole part), methacrylic acid 20 parts (0.23 mole part), and cyclohexanone 150 parts were charged and heated to 80 ° C. After substituting the gas phase part in the system with nitrogen, 55 parts of a solution prepared by dissolving 5 parts of AIBN prepared in advance in 50 parts of cyclohexanone was dropped into Kolben at 80 ° C. over 10 minutes, and further 3 at the same temperature. Reacted for hours. Furthermore, 35 parts (0.31 mole part) of glycidyl methacrylate, 364 parts of cyclohexanone and 1.1 part of hydroquinone were charged and reacted at 60 ° C. for 5 hours to obtain a cyclohexanone solution of the desired hydrophilic polymer (X1) (resin The content is 25%).

<Comparative Production Example 2>
A cyclohexanone solution of maleic anhydride / styrene copolymer (A0) obtained in the same manner as Kolben as in Production Example 1 was charged with 40 parts of 2-hydroxyethyl methacrylate and 5 parts of trimethylamine and reacted at 60 ° C. for 2 hours. To obtain a cyclohexanone solution of the target hydrophilic polymer (X2) (solid content: 25%).

The values obtained by measuring the (meth) acryloyl group concentration, acid value, and Mn of the hydrophilic polymers (A1), (A2), (X1), and (X2), respectively, as well as the SP value and the HLB value described above. The values calculated by the calculation method are shown in Table 1.

<Examples 1-3 and Comparative Examples 1-4>
[Production of photosensitive resin composition]
According to the formulation example of Table 2, the cyclohexanone solution of each hydrophilic polymer is charged into a glass container, and the following (B-1) or (B-2) and (C-1) are further charged and stirred until uniform. Further, an additional solvent (propylene glycol monomethyl ether acetate) was added to obtain the photosensitive resin compositions (Q1) to (Q3) of Examples and the photosensitive resin compositions (Y1) to (Y4) of Comparative Examples. Manufactured.
(Meth) acryloyl group concentration based on weight of solid content of photosensitive resin composition, content of (B) based on weight of solid content of photosensitive resin composition, and SP value of (A) and (B) Table 3 shows the difference.

B-1 (Polyfunctional (meth) acrylate)
: "Neomer DA-600" (mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate: manufactured by Sanyo Chemical Industries, Ltd.)
B-2 (Polyfunctional (meth) acrylate)
: "NK ester A-TMM-3L" (mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate: manufactured by Shin-Nakamura Chemical Co., Ltd.)
C-1 (photopolymerization initiator)
: “Irgacure 907” (2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one: manufactured by Ciba Specialty Chemicals Co., Ltd.)

Evaluation Examples 1-3, Comparative Evaluation Examples 1-4
[Measurement of developability]
The photosensitive resin compositions (Q1) to (Q3) and (Y1) to (Y4) were each spin-coated on a glass substrate so that the finished film thickness was 5 μm, dried at 25 ° C. for 5 minutes, and then Development was performed for 30 seconds using a 1% aqueous sodium carbonate solution to evaluate the developability. The results are shown in Table 3. The evaluation criteria are as follows.
A: There is no residue visually.
○: There is a slight residue visually.
Δ: There are many residues by visual inspection.
X: Development is not possible.

Examples 4 to 6, Comparative Examples 5 and 6
[Production of photo spacer]
The photosensitive resin compositions (Q1) to (Q3), (Y3), and (Y4) were each spin-coated on a glass substrate so as to have a finished film thickness of 5 μm, and dried at 25 ° C. for 5 minutes. The light of a high pressure mercury lamp was 100 mJ / cm ² irradiation through a photomask for forming photo spacers. The exposure was performed with a gap (exposure gap) between the photomask and the substrate of 100 μm. Thereafter, development was performed using a 1% aqueous sodium carbonate solution. After washing with water, post-baking was performed at 230 ° C. for 60 minutes to form a photo spacer on the color filter. The upper base area of the photo spacer was 150 μm ² and the lower base area was 400 μm ² .

[Measurement of elastic recovery characteristics]
The elastic characteristics of the photospacer obtained as described above were measured using a Fischerscope H-100 (Fischer Instruments) apparatus according to the above-described elastic recovery rate measurement method.
A flat indenter (50 μm × 50 μm) having a square cross section was used. The results are shown in Table 4.

In the photospacer of Comparative Example 5, the hydrophilic polymer (X2) in the used photosensitive resin composition (Y3) does not have a sufficient amount of (meth) acryloyl groups, so the reactivity is low and is required. The crosslinking reaction does not proceed sufficiently. In such a case, since the “shear” between molecules increases, the elastic recovery rate decreases. When a liquid crystal panel is produced using such a photo spacer, the cell gap is not uniform and the display quality is deteriorated.
In the photospacer of Comparative Example 6, the hydrophilic polymer (X1) in the used photosensitive resin composition (Y5) does not have a sufficient amount of acid value, and thus developability is poor.
In the photosensitive resin composition of Comparative Example 4 and the photo spacer of Comparative Example 6, the content of the hydrophilic polymer (X1) in the used photosensitive resin composition (Y4) was increased to ensure developability. However, it is estimated that the (meth) acryloyl group density | concentration based on the solid content weight of the photosensitive resin composition fell, and the elastic recovery characteristic deteriorated.

The photosensitive resin composition of the present invention can be suitably used for photo spacers, but in addition to various resist materials such as photosensitive resist films, photoresists, photosensitive resin relief plates, screen plates, photoadhesives, Or it is suitable as a photosensitive layer of a hard coat agent.
Furthermore, coating agents for various materials such as metals (for example, iron, aluminum, titanium, copper, etc.), plastics (for example, polycarbonate, polyethylene terephthalate, poly (meth) acrylate), paper, glass, rubber and wood, paints, It can be used as printing ink and adhesive, and can also be applied as a molding material.

Hysteresis curve of load and deformation

Explanation of symbols

T ₀ : Total deformation amount T ₁ : Plastic deformation amount T ₂ : Elastic deformation amount

Claims (4)

A photosensitive resin composition comprising a hydrophilic polymer (A) having a carboxyl group and a (meth) acryloyl group, a polyfunctional (meth) acrylate monomer (B), and a photopolymerization initiator (C), which is hydrophilic A photosensitive resin composition (Q) capable of alkali development, wherein the polymer (A) is a polymer satisfying all of the following (1) to (4).
(1) Copolymer (D) having an unsaturated polybasic acid anhydride as an essential constituent monomer and at least one functional group selected from a hydroxyl group, a primary amino group and a secondary amino group in one molecule And a polymer obtained by reacting the compound (e) having a (meth) acryloyl group.
(2) It has a weak acid value of 100 to 500 mgKOH / g.
(3) It has a (meth) acryloyl group concentration of 2 to 9 mmol / g.
(4) The difference in solubility parameter from the polyfunctional (meth) acrylate monomer (B) is −1 to 1.   The photosensitive resin composition according to claim 1, wherein the content of the polyfunctional (meth) acrylate monomer (B) based on the weight of the solid content of the photosensitive resin composition (Q) is 70 to 95% by weight.   The photosensitive resin composition according to claim 1, wherein the (meth) acryloyl group concentration based on the weight of the solid content of the photosensitive resin composition (Q) is 6 to 12 mmol / g.   A photospacer provided for maintaining a gap in a liquid crystal cell formed by curing the photosensitive resin composition according to claim 1.

Images