Photosensitive resin composition

Abstract

Disclosed is a photosensitive resin composition which can provide a cured product having good curability to active energy rays and rapid developability, and excellent elastic recovery rate to external force. The resin composition is formed by containing a polymerizable (meth)acrylic polymer (A), a multifunctional (meth)acrylate monomer (B), and a photopolymerization initiator (C), the polymerizable (meth)acrylic polymer (A) being formed by containing, as constituent elements, a monomer unit (1) having a side chain with 2 to 3 branches each having a terminal end terminated with a radically polymerizable substituent, and a monomer unit (2) having a side chain with 2 branches each having a terminal end terminated with a carboxyl group and a terminal end terminated with a radically polymerizable substituent, or further containing a monomer unit (3) having a side chain with 1 branch having a terminal end terminated with a radically polymerizable substituent.

Description

[0001] This application is a divisional application of the Chinese patent application entitled "Photosensitive Resin Composition" with national application number 201880018048.1, which was filed after the international application PCT international application with international application number PCT / JP2018 / 010400 and international application date of March 16, 2018, entered the Chinese phase. Technical Field

[0002] This invention relates to (meth)acrylic acid resin compositions, and more specifically, to photosensitive resin compositions, particularly to photosensitive resin compositions for use as light spacers and the like. Background Technology

[0003] In display devices such as liquid crystal displays (LCDs), curable resin compositions containing a polymer having structural units containing multiple (meth)acryloyloxy groups and structural units containing carboxyl groups, as curable films used to maintain a certain thickness of insulating films, protective films, and liquid crystal layers, are known (Patent Document 1).

[0004] In the manufacturing of liquid crystal displays (LCDs), controlling the thickness of the liquid crystal layer (the spacing between the front and rear alignment films) to a certain level is crucial, directly impacting image quality. Therefore, spacers are used, and in recent years, there has been a trend towards forming columnar optical spacers (PS) on color filters. Because optical spacers are formed using photolithography, a photoresist with good photosensitivity is required as their manufacturing material. Simultaneously, from the perspective of manufacturing efficiency, rapid developability is essential; that is, after exposure to the photoresist, unwanted portions can be quickly removed with a developer. Furthermore, when external force is applied to the display screen using fingers or similar objects, this force is particularly concentrated on the columnar optical spacers. Even after repeated compression, the optical spacers should substantially recover their elasticity after the pressure is removed; therefore, it is important that the photoresist used provides a curing agent with such excellent elastic recovery.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2016-16393 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] The object of the present invention is to provide an active energy ray curable resin composition, which provides a cured product having good photosensitivity (curability) to active energy rays, rapid development after photosensitivity, and excellent elastic recovery rate to deformation caused by external load.

[0010] Technical solutions adopted to solve technical problems

[0011] As a result of research conducted to achieve the aforementioned objectives, the inventors discovered that a polymeric resin composition comprising a polymeric resin and a polyfunctional (meth)acrylate monomer exhibits excellent photosensitivity upon photocuring, rapid developability in alkaline solutions after photoexposedness, and the resulting cured product demonstrates excellent elastic recovery. This polymeric resin is formed by comprising the following monomers as constituent units: monomers with branched side chains formed by having multiple terminal free radical polymerizable substituents; and monomers with branched side chains formed by having multiple terminal carboxyl groups and free radical polymerizable substituents. This invention was completed based on further research following this discovery. Specifically, this invention provides the following technical content.

[0012] 1. A photosensitive resin composition formed by comprising a polymeric (meth)acrylate polymer (A), a polyfunctional (meth)acrylate monomer (B), and a photopolymerization initiator (C), wherein the polymeric (meth)acrylate polymer (A) is formed by comprising monomer units as constituent elements: a monomer unit (1) having side chains having branches at 2 to 3 ends respectively terminated by a free radical polymerizable substituent; and a monomer unit (2) having side chains having two branches at ends terminated by a carboxyl group and at ends terminated by a free radical polymerizable substituent; or further comprising a monomer unit (3) having a side chain having a single end terminated by a free radical polymerizable substituent.

[0013] 2. The resin composition as described in 1 above, wherein, in the polymerizable (meth)acrylic polymer (A), the free radical polymerizable substituent in the monomer unit (1) is substituted on a hydrocarbon chain (L) comprising 3 to 5 carbons that forms part of the side chain; the free radical polymerizable substituent in the monomer unit (2) is substituted on a hydrocarbon chain (M) comprising 3 to 5 carbons that forms part of the side chain, and the carboxyl group is attached to the hydrocarbon chain (M) by a group -OC(O)-Z-, wherein the group -Z- constituting part of the group is a group comprising a saturated or unsaturated chain or cyclic hydrocarbon skeleton or benzene ring comprising 2 to 7 carbons; and the free radical polymerizable substituent in the monomer unit (3) is substituted on a hydrocarbon chain comprising 3 to 5 carbons that forms part of the side chain.

[0014] 3. The resin composition as described in 1 or 2 above, wherein the two bonding positions of the group -Z- in the monomer unit (2) are located on two adjacent carbon atoms of the carbon atom constituting the group.

[0015] 4. The resin composition of any one of 1 to 3 above, wherein the free radical polymerizable substituents are independently (meth)acryloyloxy.

[0016] 5. The resin composition of any one of 1 to 4 above, wherein the monomer unit (1) is composed of a monomer unit (1a) having an acryloyloxy group as a free radical polymerizable substituent and a monomer unit (1b) having a methacryloyloxy group as a free radical polymerizable substituent.

[0017] 6. The resin composition of any one of 1 to 5 above, wherein the molar ratio between the monomer units constituting the polymeric (meth)acrylic polymer (A) is monomer unit (1): monomer unit (2): monomer unit (3) = 20 to 80: 5 to 50: 0 to 30.

[0018] 7. The resin composition of any one of 1 to 5 above, wherein the polymeric (meth)acrylic acid polymer (A) is represented by the following general formula:

[0019] [Chemistry 1]

[0020]

[0021] In the formula, each R1 independently represents a hydrogen atom or a methyl group, and X1, X2, X3, and X4 independently represent substituents represented by the following general formula (1).

[0022] [Chemistry 2]

[0023]

[0024] In the formula, R2 represents a hydrogen atom or a methyl group, and "*-" represents a single bond.

[0025] R3 represents any of the substituents represented by the following structural formulas.

[0026] [Chemistry 3]

[0027]

[0028] l, m, and n represent the molar ratio between individual monomer units in the form of l:m:n.

[0029] 8. The resin composition as described in 7 above, wherein in the polymeric (meth)acrylic polymer (A) described above, l:m:n = 20-80:5-50:0-30.

[0030] 9. The resin composition of 7 or 8 above, wherein, in the general formula of the polymeric (meth)acrylic acid polymer (A) above, the monomer unit (1) represented by the following formula comprises:

[0031] [Chemistry 4]

[0032]

[0033] X1 and X2 are both monomer units of acryloyloxy (1a), and X1 and X2 are both monomer units of methacryloyloxy (1b).

[0034] 10. The composition of any one of 7 to 9 above, wherein the polymeric (meth)acrylic acid polymer (A) is a polymer represented by any one of the following formulas:

[0035] [Chemistry 5]

[0036]

[0037] [Chemistry 6]

[0038]

[0039] [Chemistry 7]

[0040]

[0041] 11. The resin composition of any one of 1 to 10 above, wherein the polyfunctional (meth)acrylate monomer (B) is selected from dipentaerythritol hexaacrylate, dipentaerythritol polyacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, bis(trimethylolpropane) tetraacrylate, trimethylolpropane triacrylate, ethoxylated isocyanurate triacrylate, and ε-caprolactone-modified tri(2-acryloyloxyethyl) isocyanurate.

[0042] 12. The resin composition of any one of 1 to 5 above, wherein the polymeric (meth)acrylic polymer (A) further comprises a monomer unit (4) that is different from any one of the monomer units (1), (2) and (3) above.

[0043] Invention Effects

[0044] According to the present invention, a resin composition exhibiting good reactivity to active energy rays (hereinafter referred to as "photosensitivity") and curing, and possessing rapid developability to alkaline developing solutions after photosensitization, can be obtained. Furthermore, the resin composition of the present invention can provide a cured product exhibiting excellent elastic recovery rate to deformation caused by external force loading. Detailed Implementation

[0045] In this invention, "active energy rays" refers to ionizing radiation such as ultraviolet rays, electron rays, alpha rays, beta rays, and gamma rays. Among these, ultraviolet rays are convenient to operate, and irradiation can be easily performed using high-pressure mercury lamps or ultra-high-pressure mercury lamps.

[0046] In this invention, the term "(meth)acrylic acid" is used broadly to refer to compounds based on acrylic acid and methacrylic acid, without distinguishing between the two. The term "(meth)acrylate" is used in the same way.

[0047] In this invention, the polymeric (meth)acrylic acid polymer (A) comprises monomer units (1) and (2), or further comprises monomer unit (3), which are (meth)acrylic acid monomer units. In this invention, when referring to the structure of each monomer unit, "side chain" refers to the portion that constitutes the side chain opposite to the main chain formed by the addition polymerization of the (meth)acrylic acid ester moiety common to them.

[0048] The monomer unit (1) has side chains with 2 to 3 terminal branches, each terminated by a free radical polymerizable substituent. These free radical polymerizable substituents are preferably substituted on the hydrocarbon chain (L), which is preferably bonded to the polymer backbone via the -COO- group. The number of carbon atoms constituting the hydrocarbon chain (L) is preferably 3 to 5, more preferably 3 or 4, and particularly preferably 3.

[0049] The monomer unit (2) has a side chain with two branches, one terminated by a carboxyl group and the other terminated by a free radical polymerizable substituent. Here, the free radical polymerizable substituent is preferably substituted on a hydrocarbon chain (M), which is preferably bonded to the polymer backbone via a group -COO-. The number of carbon atoms constituting the hydrocarbon chain (M) is preferably 3 to 5, more preferably 3 or 4, and particularly preferably 3. On the other hand, the carboxyl group is substituted on the hydrocarbon chain (M) via a group -OC(O)-Z-. Here, the group -Z-, which forms part of this group, comprises a saturated or unsaturated chain-like or cyclic hydrocarbon backbone or benzene ring consisting of 2 to 7 carbon atoms. Furthermore, the two bonding positions of the group -Z- are preferably located on two adjacent carbon atoms constituting the group. Furthermore, the monomer unit (2) preferably has a molecular weight of less than 1000.

[0050] The monomer unit (3) has a side chain with a terminal end attached to a radical polymerizable substituent. This radical polymerizable substituent is preferably substituted on a hydrocarbon chain (N), which is preferably attached to the polymer backbone via a -COO- group. The number of carbon atoms constituting the hydrocarbon chain (N) is preferably 3 to 5, more preferably 3 or 4, and particularly preferably 3.

[0051] In monomer units (1) to (3), the "radical polymerizable substituent" is preferably (meth)acryloyloxy. The monomer unit (1) may be composed of a monomer unit (1a) having acryloyloxy as the radical polymerizable substituent and a monomer unit (1b) having methacryloyloxy as the radical polymerizable substituent.

[0052] The polymeric (meth)acrylic acid polymer (A) may not contain the aforementioned monomer unit (3) and may be composed of monomer units (1) and (2). In this case, there is no specific limit to the molar ratio of monomer unit (1) and monomer unit (2) in the polymer, but it is generally preferred that monomer unit (1): monomer unit (2) = 20 to 80: 5 to 50, more preferably 50 to 70: 10 to 30.

[0053] When the polymeric (meth)acrylic acid polymer (A) is composed of monomer units (3), there is no clear limit to the molar ratio between monomer units (1) to (3), but it is generally preferred that monomer unit (1): monomer unit (2): monomer unit (3) = 20 to 80: 5 to 50: 0 to 30, more preferably 50 to 70: 10 to 30: 0 to 10.

[0054] Furthermore, from the perspective of improving the elastic recovery rate of the optical spacer, the double bond equivalent of the polymeric (meth)acrylic acid polymer (A) is preferably 100 to 270. Here, "double bond equivalent" refers to the number of grams of the resin composition relative to 1 mole of acryloyloxy group. In addition, "number of grams of resin composition" refers to the total mass of the resin composition (excluding the solvent).

[0055] Furthermore, the polymeric (meth)acrylic acid polymer (A) may also contain additional monomer units other than the monomer units (1) to (3) mentioned above, provided that the purpose of the invention is not violated. Such additional monomer units may be used, for example, to adjust the physical properties of the photosensitive resin composition of the invention, such as the glass transition temperature (Tg) and hydrophobicity, as required. When the additional monomer unit "monomer unit (4)" is included, there is no specific limitation on the molar ratio of each monomer unit constituting the polymeric (meth)acrylic acid polymer (A). Generally, it is preferred that monomer unit (1): monomer unit (2): monomer unit (3): monomer unit (4) = 20 to 80: 5 to 50: 0 to 30: 0 to 40, and more preferably 50 to 70: 10 to 30: 0 to 10: 0 to 30.

[0056] Examples of the additional monomer units mentioned above include polymerizable (meth)acrylic acid monomers, but are not limited to these. Specific examples of polymerizable (meth)acrylic acid monomers include dicyclopentenyl acrylate, dicyclopentenoxyethyl acrylate, dicyclopentyl acrylate, benzyl acrylate, nonylphenoxy polyethylene glycol acrylate, nonylphenoxy polyethylene glycol acrylate, nonyl glycol diacrylate, polypropylene glycol acrylate, 1,4-butanediol dimethacrylate, dicyclopentenoxyethyl methacrylate, dicyclopentyl methacrylate, pentamethylpiperidine methacrylate, tetramethylpiperidine methacrylate, methoxy polyethylene glycol methacrylate, benzyl methacrylate, neopentyl glycol dimethacrylate, polyethylene glycol dimethacrylate, etc., but are not limited to these.

[0057] The above-mentioned polymeric (meth)acrylic acid polymer (A) is particularly preferably represented by the following general formula:

[0058] [Chemistry 8]

[0059]

[0060] In the formula, each R1 independently represents a hydrogen atom or a methyl group, and X1, X2, X3, and X4 independently represent substituents represented by the following general formula (1).

[0061] [Chemistry 9]

[0062]

[0063] In the formula, R2 represents a hydrogen atom or a methyl group, and "*-" represents a single bond.

[0064] R3 represents any of the substituents represented by the following structural formulas.

[0065] [Chemistry 10]

[0066]

[0067] l, m, and n represent the molar ratio between individual monomer units in the form of l:m:n.

[0068] In the above, in the general formula of the polymeric (meth)acrylic acid polymer (A), the monomer unit (1) represented by the following formula may include:

[0069] [Chemistry 11]

[0070]

[0071] X1 and X2 are both monomer units of acryloyloxy (1a), and X1 and X2 are both monomer units of methacryloyloxy (1b).

[0072] In the above, l:m:n = 20~80:5~50:0~30 is preferred, and 50~70:10~30:0~10 is even more preferred.

[0073] Examples of polyfunctional (meth)acrylate monomers (B) that are one of the constituent elements of the active energy ray-curable resin composition of the present invention include dipentaerythritol hexaacrylate, dipentaerythritol polyacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, bis(trimethylolpropane)tetraacrylate, trimethylolpropane triacrylate, ethoxylated isocyanurate triacrylate, and ε-caprolactone-modified tri(2-acryloyloxyethyl)isocyanurate, but are not limited thereto. Among these, dipentaerythritol hexaacrylate is one of the particularly preferred monomers. In the resin composition of the present invention, the content of polyfunctional (meth)acrylate monomer (B) relative to 100 parts by weight of the solid content of the polymerizable (meth)acrylate polymer (A) is preferably 50 to 350 parts by weight, more preferably 80 to 300 parts by weight, and even more preferably 100 to 250 parts by weight.

[0074] In this invention, conventionally used free radical polymerization initiators can be appropriately used as free radical polymerization initiators. Examples of photopolymerization initiators include IRGACURE 907, IRGACURE 379, IRGACURE 819, IRGACUREOXE-01, and IRGACURE OXE-02, but the invention is not limited to these.

[0075] Example

[0076] The present invention will now be described in more detail with reference to embodiments, but it is not intended to limit the invention to these embodiments.

[0077] [Manufacturing Example 1] Manufacturing of acrylic resin (A-1) (X:Y = 80:20)

[0078] [Chemistry 12]

[0079]

[0080] In a glass flask equipped with heating, cooling, and stirring devices, a reflux condenser, and a nitrogen inlet tube, 100 g of glycidyl methacrylate and 150 g of propylene glycol monomethyl ether acetate were added. After purging the gaseous phase of the system with nitrogen, 8.7 g of 2,2'-azobis(2,4-dimethylpentanonitrile) was added, and the mixture was heated to 80°C and allowed to react at the same temperature for 8 hours.

[0081] To the resulting solution, 15g of acrylic anhydride, 2g of acrylic acid, 0.3g of tetrabutylammonium chloride, 173g of hydroquinone, and 173g of propylene glycol monomethyl ether acetate were added, and the mixture was reacted at 70°C for 12 hours. Then, 14g of succinic anhydride was added to the reacted solution, and the mixture was reacted at 70°C for 6 hours to obtain a 40% solution of the target polymer (A-1).

[0082] The acrylic resin has an acid value of 37.4 based on its solids content. Its weight-average molecular weight (Mw) based on GPC is 24,000.

[0083] [Manufacturing Example 2] Manufacturing of acrylic resin (A-2) (X:Y = 80:20)

[0084] [Chemistry 13]

[0085]

[0086] In a glass flask equipped with heating, cooling, and stirring devices, a reflux condenser, and a nitrogen inlet tube, 100 g of glycidyl methacrylate and 150 g of propylene glycol monomethyl ether acetate were added. After purging the gaseous phase of the system with nitrogen, 8.7 g of 2,2'-azobis(2,4-dimethylpentanonitrile) was added, and the mixture was heated to 80°C and allowed to react at the same temperature for 8 hours.

[0087] To the resulting solution, 87 g of methacrylic anhydride, 15 g of acrylic acid, 2 g of tetrabutylammonium chloride, 0.3 g of hydroquinone, and 190 g of propylene glycol monomethyl ether acetate were further added, and the mixture was reacted at 70 °C for 12 hours. Then, 14 g of succinic anhydride was further added to the solution, and the mixture was reacted at 70 °C for 6 hours to obtain a 40% solution of the target polymer (A-2).

[0088] The acrylic resin has an acid value of 34.8 based on its solids content. Its weight-average molecular weight (Mw) based on GPC is 21,000.

[0089] [Manufacturing Example 3] Manufacturing of acrylic resin (A-3) (X:Y:Z = 40:40:20)

[0090] [Chemistry 14]

[0091]

[0092] In a glass flask equipped with heating, cooling, and stirring devices, a reflux condenser, and a nitrogen inlet tube, 100 g of glycidyl methacrylate and 150 g of propylene glycol monomethyl ether acetate were added. After purging the gaseous phase of the system with nitrogen, 8.7 g of 2,2'-azobis(2,4-dimethylpentanonitrile) was added, and the mixture was heated to 80°C and allowed to react at the same temperature for 8 hours.

[0093] To the obtained solution, 35 g of acrylic anhydride, 43 g of methacrylic anhydride, 15 g of acrylic acid, 2 g of tetrabutylammonium chloride, 0.3 g of hydroquinone, and 180 g of propylene glycol monomethyl ether acetate were further added, and the mixture was reacted at 70 °C for 12 hours. Then, 14 g of succinic anhydride was further added to the solution, and the mixture was reacted at 70 °C for 6 hours to obtain a 40% solution of the target polymer (A-3).

[0094] The acrylic resin has an acid value of 36.2 based on its solids content. Its weight-average molecular weight (Mw) based on GPC is 22,000.

[0095] [Manufacturing Example 4] Manufacturing of acrylic resin (A-4) (X:Y = 80:20)

[0096] [Chemistry 15]

[0097]

[0098] In a glass flask equipped with heating, cooling, and stirring devices, a reflux condenser, and a nitrogen inlet tube, 100 g of glycidyl methacrylate and 150 g of propylene glycol monomethyl ether acetate were added. After purging the gaseous phase of the system with nitrogen, 8.7 g of 2,2'-azobis(2,4-dimethylpentanonitrile) was added, and the mixture was heated to 80°C and allowed to react at the same temperature for 8 hours.

[0099] To the resulting solution, 51 g of acrylic acid, 2 g of tetrabutylammonium chloride, 0.3 g of hydroquinone, and 110 g of propylene glycol monomethyl ether acetate were further added, and the mixture was reacted at 100 °C for 12 hours. Then, 14 g of succinic anhydride was further added to the solution, and the mixture was reacted at 70 °C for 6 hours to obtain a 40% solution of the target polymer (A-4).

[0100] The acrylic resin has an acid value of 46.2 based on its solids content. Its weight-average molecular weight (Mw) based on GPC is 17,000.

[0101] [Manufacturing Example 5] Manufacturing of acrylic resin (A-5) (X:Y = 80:20)

[0102] [Chemistry 16]

[0103]

[0104] In a glass flask equipped with heating, cooling, and stirring devices, a reflux condenser, and a nitrogen inlet tube, 100 g of glycidyl methacrylate and 150 g of propylene glycol monomethyl ether acetate were added. After purging the gaseous phase of the system with nitrogen, 8.7 g of 2,2'-azobis(2,4-dimethylpentanonitrile) was added, and the mixture was heated to 80°C and allowed to react at the same temperature for 8 hours.

[0105] To the resulting solution, 51 g of acrylic acid, 2 g of tetrabutylammonium chloride, 0.3 g of hydroquinone, and 240 g of propylene glycol monomethyl ether acetate were further added, and the mixture was reacted at 100 °C for 12 hours. After the reaction, 87 g of Karenz MOI was added, and the mixture was reacted at 70 °C for 10 hours. Then, 14 g of succinic anhydride was further added to the solution, and the mixture was reacted at 70 °C for 6 hours to obtain a 40% solution of the target polymer (A-5).

[0106] The acrylic resin has an acid value of 30.0 based on its solids content. Its weight-average molecular weight (Mw) based on GPC is 28,000.

[0107] [Manufacturing Example 6] Manufacturing of acrylic resin (A-6) (W:X:Y:Z = 20:56:16:8)

[0108] [Chemistry 17]

[0109]

[0110] In a glass flask equipped with heating, cooling, and stirring devices, a reflux condenser, and a nitrogen inlet, 100 g of glycidyl methacrylate, 39 g of dicyclopentyl methacrylate, and 208 g of propylene glycol monomethyl ether acetate were added. After purging the gaseous phase of the system with nitrogen, 7.2 g of 2,2'-azobis(2,4-dimethylpentanonitrile) was added, and the mixture was heated to 80°C and allowed to react at the same temperature for 8 hours.

[0111] To the resulting solution, 76 g of methacrylic anhydride, 15 g of acrylic acid, 2 g of tetrabutylammonium chloride, 0.3 g of hydroquinone, and 160 g of propylene glycol monomethyl ether acetate were further added, and the mixture was reacted at 70 °C for 12 hours. Then, 14 g of succinic anhydride was added to the resulting solution, and the mixture was reacted at 70 °C for 6 hours to obtain a 40% solution of the target polymer (A-6).

[0112] The acrylic resin has an acid value of 32.3 based on its solids content. Its weight-average molecular weight (Mw) based on GPC is 25,000.

[0113] [Examples 1-14, Comparative Examples 1-8]

[0114] (1) Preparation of photoresist for optical spacers

[0115] According to the composition shown in Table 1, a photoresist for photoresist of Example 1 was prepared by mixing 35.7 g of polymer (A-1), 14.3 g of dipentaerythritol hexaacrylate (KAYARAD DPHA) (B-1) as a polyfunctional acrylate monomer (B), 1.5 g of photopolymerization initiator IRGACURE 907 (C-1), and 48.5 g of propylene glycol monomethyl ether acetate under light-shielding conditions. Examples 2-14 and Comparative Examples 1-8 in the table were prepared in the same manner. Additionally, B-2 in the table is pentaerythritol triacrylate (manufactured by Osaka Organic Chemicals Co., Ltd., product name: PET3A).

[0116] [Table 1]

[0117] Table 1.

[0118]

[0119] (2) Preparation of optical spacers

[0120] On a 10cm × 10cm square glass substrate, the photoresists of the examples and comparative examples were applied using a spin coater and dried to form a coating film with a dry film thickness of 3μm. This coating film was then heated on a hot plate at 90°C for 2 minutes. The resulting coating film was then subjected to a light-sensitive material formed using a mask with multiple openings at 100mJ / cm². 2 The illuminance of the ultra-high pressure mercury lamp (calculated as i-rays) is 20 mW / cm². 2 Additionally, exposure was performed with a mask and substrate spacing (exposure interval) of 100 μm. Then, alkaline development was performed using a 0.3% K₂CO₃ aqueous solution. After washing with water, the material was baked at 230°C for 30 minutes to produce an optical spacer with a film thickness of 3 μm. Furthermore, by adjusting the mask aperture, an optical spacer with a bottom diameter of 7 μm was fabricated.

[0121] (3) Determination of developing speed

[0122] A 3 μm thick coating was formed on a 10 cm × 10 cm square glass substrate using a spin coater and dried. The coating was then heated at 90 °C for 2 minutes on a hot plate. The coating obtained using a 0.3% K₂CO₃ aqueous solution was subjected to alkaline development, and the development time until resist residue disappeared from the substrate was measured. The results are shown in Table 2.

[0123] (4) Determination of elastic recovery rate

[0124] The elastic recovery characteristics of the optical spacer can be evaluated by the "elastic recovery rate" defined by the following equation (1) when a certain pressure is applied. The higher the value of the elastic recovery rate (%), the better the elastic recovery characteristics.

[0125] For any one optical spacer selected from those formed on the glass substrate, the deformation during loading and recovery was measured using a microhardness tester (FISCHERSCOPE H-100, manufactured by FISCHERSCOPE) and a square indenter (50 μm × 50 μm). First, a load of 20 mN was applied over 10 seconds at a loading rate of 2 mN / s, and held for 5 seconds. The deformation of the optical spacer from its initial position under load was measured. This change was recorded as the total deformation T0 (μm). Next, the load was removed over 10 seconds at a deloading rate of 2 mN / s until it reached 0, and held for 5 seconds. This deformation was recorded as the plastic deformation T1 (μm).

[0126] Based on the measured T0 and T1, the elastic recovery rate was calculated using the following equation (1). The results are shown in Table 2.

[0127] • Elastic recovery rate (%) = [(T0-T1) / T0] × 100……(1)

[0128] [Table 2]

[0129] Table 2.

[0130] Developing speed (seconds) Elastic recovery rate (%) Example 1 10 80.3 Example 2 13 84.5 Example 3 8 78.2 Example 4 12 81.0 Example 5 10 74.2 Example 6 13 83.9 Example 7 9 71.9 Example 8 13 74.9 Example 9 10 77.2 Example 10 13 84.0 Example 11 10 75.3 Example 12 13 78.5 Comparative Example 1 20 67.0 Comparative Example 2 50 74.8 Comparative Example 3 20 63.4 Comparative Example 4 15 68.1 Comparative Example 5 25 69.1 Comparative Example 6 60 77.2 Comparative Example 7 25 65.2 Comparative Example 8 20 70.6

[0131] As can be seen from Table 2, the photoresist of the Examples developed in 8-13 seconds, which is significantly faster than the 15-60 seconds of the Comparative Examples. Furthermore, among the photoresists of the Examples, 5 cases (42% of the total) had an elastic recovery rate of 80% or higher, 4 cases (33% of the total) had an elastic recovery rate of 75% to less than 80%, and 3 cases (25% of the total) had an elastic recovery rate of 70% to less than 75%. In contrast, among the photoresists of the Comparative Examples, none had an elastic recovery rate of 80% or higher (0% of the total), 1 case (13% of the total) had an elastic recovery rate of 75% to less than 80%, 2 cases (25% of the total) had an elastic recovery rate of 70% to less than 75%, 4 cases (50% of the total) had an elastic recovery rate of 65% to less than 70%, and 1 case (13% of the total) had an elastic recovery rate of 60% to less than 65%. Overall, the photoresists of the Examples are significantly superior to those of the Comparative Examples. Furthermore, among the resists in the comparative examples, those with an elastic recovery rate of 70 or higher required development speeds of 50 seconds (Comparative Example 2), 60 seconds (Comparative Example 6), and 20 seconds (Comparative Example 8), indicating particularly long development times. These results demonstrate that the resists used in the examples can simultaneously achieve rapid development and excellent elastic recovery rate.

[0132] Industrial applications

[0133] This invention can be used to provide cured products that have good photosensitivity to active energy rays, rapid developability to alkaline developing solutions after photosensitization, and excellent elastic recovery rate in the face of deformation caused by external force loads.

Claims

1. A polymeric (meth)acrylic acid polymer (A), characterized in that, The polymeric (meth)acrylic acid polymer (A) is formed by comprising the following monomer units as constituent elements: a monomer unit (1) having side chains with branches having 2 to 3 ends respectively terminated by free radical polymerizable substituents; and a monomer unit (2) having side chains with 2 branches having ends terminated by carboxyl groups and ends terminated by free radical polymerizable substituents; or further comprising a monomer unit (3) having a side chain having 1 end terminated by a free radical polymerizable substituent. The free radical polymerizable substituents are independently (meth)acryloyloxy groups. In the polymeric (meth)acrylic acid polymer (A), the radical polymerizable substituent in the monomer unit (1) is substituted on a hydrocarbon chain (L) containing 3 to 5 carbons that forms part of the side chain; the radical polymerizable substituent in the monomer unit (2) is substituted on a hydrocarbon chain (M) containing 3 to 5 carbons that forms part of the side chain, and a carboxyl group is attached to the hydrocarbon chain (M) by a group -OC(O)-Z-, wherein the group -Z-, which constitutes part of the group, is a group consisting of a saturated or unsaturated chain or cyclic hydrocarbon skeleton or benzene ring containing 2 to 7 carbons; and the radical polymerizable substituent in the monomer unit (3) is substituted on a hydrocarbon chain containing 3 to 5 carbons that forms part of the side chain. The molar ratio between the monomer units constituting the polymeric (meth)acrylic acid polymer (A) is monomer unit (1): monomer unit (2): monomer unit (3) = 20-80: 5-50: 0-30.

2. The polymeric (meth)acrylic acid polymer (A) as described in claim 1, characterized in that, The two bonding positions of the group -Z- in the monomer unit (2) are located on two adjacent carbon atoms of the carbon atoms constituting the group.

3. The polymeric (meth)acrylic acid polymer (A) as described in claim 1, characterized in that, The monomer unit (1) is composed of a monomer unit (1a) having an acryloyloxy group as the free radical polymerizable substituent and a monomer unit (1b) having a methacryloyloxy group as the free radical polymerizable substituent.

4. The polymeric (meth)acrylic acid polymer (A) as described in claim 1, characterized in that, The polymeric (meth)acrylic acid polymer (A) is represented by the following general formula: [Chemistry 1] In the formula, each R1 independently represents a hydrogen atom or a methyl group, and X1, X2, X3, and X4 independently represent substituents represented by the following general formula (1). [Chemistry 2] In the formula, R2 represents a hydrogen atom or a methyl group, and "*-" represents a single bond. R3 represents any of the substituents represented by the following structural formulas. [Chemistry 3] l, m, and n represent the molar ratio between individual monomer units in the form of l:m:n.

5. The polymeric (meth)acrylic acid polymer (A) as described in claim 4, characterized in that, In the polymeric (meth)acrylic acid polymer (A), l:m:n = 20-80:5-50:0-30.

6. The polymeric (meth)acrylic acid polymer (A) as described in claim 4, characterized in that, In the general formula of the polymeric (meth)acrylic acid polymer (A), the monomer unit (1) represented by the following formula comprises a monomer unit (1a) in which X1 and X2 are both acryloyloxy groups, and a monomer unit (1b) in which X1 and X2 are both methacryloxy groups. [Chemistry 4] 7. The polymeric (meth)acrylic acid polymer (A) as described in claim 1, characterized in that, The polymeric (meth)acrylic polymer (A) also contains a monomer unit (4) that is different from any of the monomer units (1), (2) and (3).

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