JP7812354B2 - Photosensitive resin composition - Google Patents

Description

The present invention relates to a photosensitive resin composition, and more specifically to a photosensitive resin composition that can be cured at low temperatures and has excellent sensitivity, film retention, and residue characteristics.

Display devices are currently widely used and come in a variety of types, including liquid crystal displays (LCDs) and organic light-emitting displays (OLEDs). Recently, curved displays have been gaining attention, as they enhance the user's sense of immersion.

In the process of forming such display devices, a photo process is used to pattern the film, and a photoresist material is used for this. Alternatively, the film can be formed directly by exposing and developing the photoresist material.

Such photoresists are used to form insulating films, column spacers, overcoat layers, and color filter layers, but the component composition of the photosensitive resin composition used to form the photoresist affects resolution, adhesive strength, film retention, and other factors.

Japanese Patent Application Laid-Open No. 2018-127621

The object of the present invention is to provide a photosensitive resin composition that can be cured at low temperatures and has excellent sensitivity, film retention, and residue characteristics, as well as a pattern formation method using the same.

A photosensitive resin composition according to one embodiment of the present invention contains, per 100 parts by weight of an acrylic copolymer, 0.1 to 20 parts by weight of a radical photoinitiator, 0.1 to 10 parts by weight of an ionic photoinitiator, 1 to 50 parts by weight of a multifunctional acrylate oligomer, 1 to 50 parts by weight of a multifunctional monomer having an ethylenically unsaturated bond, and a solvent.

The photosensitive resin composition can be cured at temperatures of 90°C or less.

The radical photoinitiator may be 2-(O-benzoyloxime)-1-[4-(phenylthio)phenyl]-1,2-octanedione or 2-(O-acetyloxime)-1-[4-(phenylthio)phenyl]-1,2-octanedione.

The ionic photoinitiator may be one or more selected from the group consisting of phenyl(4-methoxyphenyl)iodonium phosphorus hexafluoride, N,N-dimethyl-N-benzyltrifluoromethanesulfonate, 4-methylphenyl(4-(2-methylpropylphenyl))iodonium phosphorus hexafluoride, and phenyl(4-methoxyphenyl)iodonium arsenic hexafluoride.

The content ratio of the radical photoinitiator to the ionic photoinitiator may be 2:1 to 1:2.

The solids content of the photosensitive resin composition may be 10% by weight to 50% by weight.

The photosensitive resin composition may further contain a melamine crosslinker.

The photosensitive resin composition may further contain a silane coupling agent.

The acrylic copolymer is formed by copolymerizing an unsaturated carboxy compound and an unsaturated olefin compound.

The solvent may have a boiling point of less than 150°C.

A pattern formation method according to one embodiment of the present invention includes the steps of coating a photosensitive resin composition on a substrate, primarily heating the coated photosensitive resin composition to a temperature of 75°C to 85°C, exposing and developing the coated photosensitive resin composition, and secondarily heating the developed photosensitive resin composition to a temperature of 80°C to 90°C. The photosensitive resin composition includes, relative to 100 parts by weight of an acrylic copolymer, 0.1 to 20 parts by weight of a radical photoinitiator, 0.1 to 10 parts by weight of an ionic photoinitiator, 1 to 50 parts by weight of a multifunctional acrylate oligomer, 1 to 50 parts by weight of a multifunctional monomer having an ethylenically unsaturated bond, and a solvent.

The primary heating removes gas from within the photosensitive resin composition, and the secondary heating allows the photosensitive resin composition to harden.

The primary heating is carried out for 1 to 5 minutes.

The secondary heating is carried out for 30 to 240 minutes.

The radical photoinitiator may be 2-(O-benzoyloxime)-1-[4-(phenylthio)phenyl]-1,2-octanedione or 2-(O-acetyloxime)-1-[4-(phenylthio)phenyl]-1,2-octanedione.

The ionic photoinitiator may be one or more selected from the group consisting of phenyl(4-methoxyphenyl)iodonium phosphorus hexafluoride, N,N-dimethyl-N-benzyltrifluoromethanesulfonate, 4-methylphenyl(4-(2-methylpropylphenyl))iodonium phosphorus hexafluoride, and phenyl(4-methoxyphenyl)iodonium arsenic hexafluoride.

The content ratio of the radical photoinitiator to the ionic photoinitiator may be 2:1 to 1:2.

The solids content of the photosensitive resin composition may be 10% by weight to 50% by weight.

The photosensitive resin composition may further contain a melamine crosslinker.

The photosensitive resin composition may further contain a silane coupling agent.

The photosensitive resin composition of this example and the pattern formation method using it have excellent sensitivity and film retention, improved residue characteristics, and excellent adhesion and chemical resistance in low-temperature processes.

1 is a process flowchart showing a pattern formation method according to an embodiment of the present invention. 1 is a process flowchart showing a pattern formation method according to an embodiment of the present invention. 1 is a process flowchart showing a pattern formation method according to an embodiment of the present invention. 1 is a process flowchart showing a pattern formation method according to an embodiment of the present invention.

Various embodiments of the present invention will now be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention. The present invention can be realized in various different forms and is not limited to the embodiments described herein.

In order to clearly explain the present invention, parts unnecessary for the explanation will be omitted, and the same reference symbols will be used throughout the specification to refer to the same or similar components.

Furthermore, the size and thickness of each component shown in the drawings have been arbitrarily shown for the convenience of explanation, and the present invention is not necessarily limited to the illustrations. In the drawings, thicknesses have been exaggerated to clearly depict various layers and regions. Also, in the drawings, the thicknesses of some layers and regions have been exaggerated for the convenience of explanation.

Furthermore, when a layer, film, region, plate, or other part is said to be "on" another part, this includes not only the case where it is "directly on" that other part, but also the case where there is another part in between. Conversely, when a part is said to be "directly on" another part, it means that there is no other part in between. Furthermore, being "on" a reference part means being located above or below the reference part, and does not necessarily mean being located "on" in the opposite direction of gravity.

Also, throughout the specification, when a part "comprises" a certain element, this does not mean that it can further include other elements, but does not exclude other elements, unless specifically stated to the contrary.

First, a photosensitive resin composition according to one embodiment of the present invention will be described. The photosensitive resin composition according to one embodiment of the present invention contains, per 100 parts by weight of an acrylic copolymer, 0.1 to 20 parts by weight of a radical photoinitiator, 0.1 to 10 parts by weight of an ionic photoinitiator, 1 to 50 parts by weight of a multifunctional acrylate oligomer, 1 to 50 parts by weight of a multifunctional monomer having an ethylenically unsaturated bond, and a solvent.

In other words, the photosensitive resin composition according to one embodiment of the present invention contains both a radical photoinitiator and an ionic photoinitiator. Therefore, it can be cured at low temperatures of 90°C or less, and even when cured at temperatures of 90°C or less, it exhibits excellent adhesive strength and chemical resistance. The photosensitive resin composition according to this embodiment is a negative photosensitive resin composition in which the exposed portions remain cured and the unexposed portions are removed.

Typically, photosensitive resin compositions require temperatures of 200°C or higher to cure. However, when a photosensitive resin composition is used for applications such as the insulating film of a touch panel integrated with a display device, the high temperatures of 200°C or higher required to cure the photosensitive resin composition can change the properties of the light-emitting layer included in the display device. Therefore, photosensitive resin compositions that cure at high temperatures of 200°C or higher cannot be used for insulating films formed in a continuous process with the light-emitting layer; instead, a separate process is required to manufacture the insulating film and then laminate it.

However, the photosensitive resin composition of this example contains both a radical photoinitiator and an ionic photoinitiator, allowing it to cure at temperatures as low as 90°C or less. Therefore, it can be used as an insulating film manufactured in a continuous process with the light-emitting layer. This reduces the number of masks required in the manufacturing process.

In addition, since the insulating film manufactured using the photosensitive composition of this embodiment is an organic film, it is more suitable for application to flexible display devices than existing insulating films containing inorganic materials. Furthermore, it is possible to eliminate processes such as chemical vapor deposition (CVD), dry etching, and stripping, which are required in the manufacturing process of existing insulating films containing inorganic materials.

The photosensitive resin composition of the present invention can be cured at temperatures below 90°C because it contains both a radical photoinitiator and an ionic photoinitiator. In other words, for the curing reaction to occur, the bonds in the benzene ring must be broken, opening the benzene ring structure. Both the radical photoinitiator and the ionic photoinitiator function to break the benzene ring, increasing the number of reactive sites and allowing the reaction to proceed actively even at lower temperatures.

In this case, the content ratio of the radical photoinitiator to the ionic photoinitiator may be approximately 2:1 to 1:2. This is a numerical range that can maximize the adhesive strength and chemical resistance of the cured photosensitive resin composition when cured at low temperatures.

In the photosensitive resin composition according to one embodiment of the present invention, the acrylic copolymer prevents residue from being generated during development, making it easy to form patterns.

The acrylic copolymer is formed by copolymerizing an unsaturated carboxy compound and an unsaturated olefin compound. Specifically, the acrylic copolymer is
i) an unsaturated carboxylic acid, an unsaturated carboxylic acid anhydride, or a mixture thereof;
ii) The olefin-based unsaturated compound is converted into a monomer, and the resulting monomer is subjected to a radical reaction in the presence of a solvent and a polymerization initiator, followed by precipitation, filtration, and vacuum drying to remove unreacted monomers.

The unsaturated carboxylic acids, unsaturated carboxylic acid anhydrides, or mixtures thereof used in the present invention include unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid, unsaturated dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, methaconic acid, and itaconic acid, or anhydrides of these unsaturated dicarboxylic acids, used alone or in combination of two or more. Acrylic acid, methacrylic acid, and maleic acid are particularly preferred due to their excellent copolymerization reactivity and solubility in the alkaline aqueous developer solution.

The unsaturated carboxylic acid, unsaturated carboxylic anhydride, or mixture thereof is preferably contained in an amount of 5 to 40 parts by weight per 100 parts by weight of the total monomers. If the content is less than 5 parts by weight, the polymer may be poorly soluble in an alkaline aqueous solution, while if it exceeds 40 parts by weight, the polymer may be excessively soluble in an alkaline aqueous solution.

The olefinic unsaturated compounds used in the present invention include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, methyl acrylate, isopropyl acrylate, cyclohexyl methacrylate, 2-methylcyclohexyl methacrylate, dicyclopentenyl acrylate, dicyclopentanyl acrylate, dicyclopentenyl methacrylate, dicyclopentanyl methacrylate, 1-adamantyl acrylate, 1-adamantyl methacrylate, dicyclopentanyloxyethyl methacrylate, isobornyl methacrylate, cyclohexyl acrylate, 2-methylcyclohexyl acrylate, dicyclopentanyloxyethyl acrylate, isobornyl acrylate, phenyl methacrylate, phenyl acrylate, benzyl acrylate, 2-hydroxyethyl methacrylate, styrene, σ-methylstyrene, m-methylstyrene, p-methyl Styrene, vinyltoluene, p-methoxystyrene, 1,3-butadiene, isoprene, or 2,3-dimethyl-1,3-butadiene, glycidyl acrylate, glycidyl methacrylate, α-ethyl glycidyl acrylate, α-n-propyl glycidyl acrylate, α-n-butyl glycidyl acrylate, β-methyl glycidyl acrylate, β-methyl glycidyl methacrylate, β-ethyl glycidyl acrylate, β-ethyl glycidyl methacrylate, 3,4 acrylate One or more compounds selected from the group consisting of butyl acrylate, 3,4-epoxybutyl methacrylate, 6,7-epoxyheptyl acrylate, 6,7-epoxyheptyl methacrylate, 6,7-epoxyheptyl α-ethylacrylate, o-vinylbenzyl glycidyl ether, m-vinylbenzyl glycidyl ether, and p-vinylbenzyl glycidyl ether, and 3,4-epoxycyclohexyl methacrylate are used, and these compounds are used alone or in combination.

The olefin-based unsaturated compound is preferably contained in an amount of 60 to 95 parts by weight per 100 parts by weight of the total monomers. If the content is less than 60 parts by weight, problems arise in terms of reduced resolution and heat resistance, while if it exceeds 95 parts by weight, problems arise in terms of the acrylic copolymer being difficult to dissolve in the alkaline aqueous solution of the developer.

The olefinic unsaturated compound used is a monomer containing an epoxy group. These monomers undergo a crosslinking reaction with an ionic photoinitiator during the low-temperature curing process, forming a dense structure, further improving heat resistance, chemical resistance, and physical properties.

Solvents used for solution polymerization of such monomers include methanol, tetrahydroxyfuran, toluene, and dioxane.

The polymerization initiator used to solution polymerize such monomers is a radical polymerization initiator, specifically 2,2-azobisisobutyronitrile, 2,2-azobis(2,4-dimethylvaleronitrile), 2,2-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1-azobis(cyclohexane-1-carbonitrile), or dimethyl 2,2'-azobisisobutyrate.

These monomers are subjected to a radical reaction in the presence of a solvent and a polymerization initiator, and unreacted monomers are removed through precipitation, filtration, and vacuum drying processes to produce an acrylic copolymer. This acrylic copolymer may have a weight-average molecular weight (Mw) of 3,000 to 30,000 in terms of polystyrene. If the weight-average molecular weight (Mw) is less than 3,000 in terms of polystyrene, the developability, film retention rate, pattern development, and heat resistance may be reduced. If it exceeds 30,000, pattern development may be poor.

The photoinitiator used in the photosensitive resin composition of the present invention includes one or more radical photoinitiators and one or more ionic photoinitiators.

The radical photoinitiator may be 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, diethoxyacetophenone, p-dimethylaminoacetophenone, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-(dimethylamino)-2-[(4-methylphenyl) acetophenone compounds such as [4-(4-morpholinyl)methyl]-1-butanone, benzoin compounds such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether and benzil dimethyl ketal, benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzo benzophenone compounds such as phenone, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, 2,4-diethylthioxanthone and other thioxanthone compounds, 2,4,6-trichloro-s-triazine, 2-phenyl-4,6-bis(trichloromethyl)-s-triazine, 2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, 2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine, 2-piperonyl-4 triazine compounds such as 2-(O-benzoyloxime)-1-[4-(phenylthio)phenyl]-1,2-dichloromethyl-4,6-bis(trichloromethyl)-s-triazine, 2-(naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxy-naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2,4-trichloromethyl-(piperonyl)-6-triazine, and 2,4-trichloromethyl(4'-methoxystyryl)-6-triazine; -octanedione, 1-(O-acetyloxime)-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-ethanone, O-ethoxycarbonyl-α-oxyamino-1-phenylpropan-1-one, 1,2-octanedione, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one, 1-(4-phenylsulfanylphenyl)-butane-1,2-dione-2-oxime-O-benzoate, 1-(4-phenylsulfanylphenyl)-octane-1,2- dione-2-oxime-O-benzoate, 1-(4-phenylsulfanylphenyl)-octan-1-one oxime-O-acetate, 1-(4-phenylsulfanylphenyl)-butan-1-one oxime-O-acetate, 2-(O-benzoyloxime)-1-[4-(phenylthio)p-methylphenyl]-1,2-octanedione, 2-(O-benzoyloxime)-1-[4-(phenylthio)phenyl]-1,2-phenyldione, 2-(O-acetyloxime)-1-[4-(phenylthio)phenyl]-1,2-octanedione, 2- Oxime ester compounds such as (O-acetyloxime)-1-[4-(phenylthio)phenyl]-1,2-phenyldione, 2-(O-acetyloxime)-1-[4-(phenylthio)phenyl]-1,2-methyldione, and O-(acetyl)-N-(1-phenyl-2-oxo-2-(4'-methoxy-naphthyl)ethylidene)hydroxylamine; phosphine compounds such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide; 2,2'-bis(o-chloro)phenylphosphine oxide; Imidazole compounds such as 2,2'-bis(o-methoxyphenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, 2,2'-bis(o-methoxyphenyl)-4,4',5,5'-tetraphenylbiimidazole, and 2,2'-bis(o-methoxyphenyl)-4,4',5,5'-tetra(p-methylphenyl)biimidazole; quinone compounds such as 9,10-phenanthrenequinone, camphorquinone, and ethylanthraquinone; borate compounds; carbazole compounds; and titanocene compounds, which can be used alone or in combination of two or more.

The content of the radical photoinitiator is preferably 0.1 to 20 parts by weight per 100 parts by weight of the acrylic copolymer. If the content of the radical photoinitiator is less than 0.1 part by weight, the residual film rate will be poor due to low sensitivity, and if it exceeds 20 parts by weight, there will be problems such as poor developability and reduced resolution.

The ionic photoinitiator includes cationic photoinitiators and anionic photoinitiators. Cationic photoinitiators include onium salts, such as sulfonium salts, iodonium salts, phosphonium salts, diazonium salts, pyridinium salts, benzothiazolium salts, sulfoxonium salts, and ferrocene compounds. Other examples include, but are not limited to, nitrobenzyl sulfonates, alkyl or aryl N-sulfonyloxyimides, halogenated alkyl sulfonate esters, and oxime sulfonates.

Examples of cationic photoinitiators include tetrabutylammonium tetrafluoroborate, tetrabutylammonium hexafluorophosphate, tetrabutylammonium hydrogen sulfate, tetraethylammonium tetrafluoroborate, tetraethylammonium, p-toluenesulfonate, N,N-dimethyl-N-benzylanilinium antimony hexafluoride, N,N-dimethyl-N-benzylanilinium boron tetrafluoride, and N,N-dimethyl-N-benzylpyridinium hexafluoride. Antimony, N,N-dimethyl-N-benzyltrifluoromethanesulfonate, N,N-dimethyl-N-(4-methoxybenzyl)pyridinium antimony hexafluoride, N,N-dimethyl-N-(4-methoxybenzyl)toluidinium antimony hexafluoride, ethyltriphenylphosphonium antimony hexafluoride, tetrabutylphosphonium antimony hexafluoride, triphenylsulfonium boron tetrafluoride, triphenylsulfonium antimony hexafluoride, triphenylsulfonium arsenic hexafluoride, tri(4- phenyl(4-methoxyphenyl)sulfonium arsenic hexafluoride, diphenyl(4-phenylthiophenyl)sulfonium arsenic hexafluoride, diphenyliodonium arsenic hexafluoride, di-4-chlorophenyliodonium arsenic hexafluoride, di-4-bromophenyliodonium arsenic hexafluoride, phenyl(4-methoxyphenyl)iodonium arsenic hexafluoride, diphenyliodonium phosphorus hexafluoride, di-4-chlorophenyliodonium phosphorus hexafluoride, di-4-bromophenyliodonium phosphorus hexafluoride, phenyl(4-methoxyphenyl)iodonium arsenic hexafluoride The fluorine-containing compound may be one or more selected from the group consisting of 4-methylphenyl(4-(2-methylpropylphenyl))iodonium hexafluoride, 4-methylphenyl(4-(2-methylpropylphenyl))iodonium hexafluoride, di-4-tetraphenyliodonium hexafluoride, diphenyliodonium hexafluoride, di-4-tetraphenyliodonium hexafluoride, diphenyliodonium hexafluoride, antimony hexafluoride, and 4-methylphenyl(4-(2-methylpropylphenyl))iodonium tetrafluoride, but is not limited to this.

The anionic photoinitiator may be one or more selected from the group consisting of, but is not limited to, benzoin carbamate, dimethylbenzyloxycarbamoylamine, o-acyloxime, o-nitrobenzoin carbamate, formanilide derivatives, and α-ammonium acetophenone.

The content of the ionic photoinitiator may be 0.1 to 10 parts by weight per 100 parts by weight of the acrylic copolymer. If the content of the ionic photoinitiator is less than 0.1 part by weight, the degree of cure may be low, resulting in poor chemical resistance. If the content of the ionic photoinitiator is more than 10 parts by weight, the degree of cure may be excessive, resulting in residue and reduced resolution.

The polyfunctional acrylate oligomer contained in the photosensitive resin composition according to this embodiment has 2 to 20 functional groups. Examples include aliphatic urethane acrylate oligomer, aromatic urethane acrylate oligomer, epoxy acrylate oligomer, epoxy methacrylate oligomer, polyester acrylate oligomer, silicone acrylate oligomer, melamine acrylate oligomer, and dendritic acrylate oligomer, which may be used alone or in combination of two or more.

The content of the polyfunctional acrylate oligomer is preferably 1 to 50 parts by weight per 100 parts by weight of the acrylic copolymer. If the content of the polyfunctional acrylate oligomer is less than 1 part by weight, there is a problem of poor film retention due to low sensitivity, while if it exceeds 50 parts by weight, poor developability and reduced resolution may occur.

In addition, examples of the polyfunctional monomer having an ethylenically unsaturated bond contained in the photosensitive resin composition according to one embodiment of the present invention include 1,4-butanediol diacrylate, 1,3-butylene glycol diacrylate, ethylene glycol diacrylate, trimethylolpropane diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, dipentaerythritol hexadiacrylate, dipentaerythritol tridiacrylate, dipentaerythritol diacrylate, sorbitol triacrylate, bisphenol A diacrylate derivatives, dipentaerythritol polyacrylate, and methacrylates thereof, which may be used alone or in combination of two or more.

The content of the polyfunctional monomer having an ethylenically unsaturated bond may be 1 to 50 parts by weight relative to 100 parts by weight of the acrylic copolymer. If the content is less than 1 part by weight, the residual film rate will be poor due to low sensitivity, and if it exceeds 50 parts by weight, the developability will be poor and the resolution may decrease.

The solvent used in the photosensitive resin composition according to one embodiment of the present invention is not limited, but may have a boiling point of less than 150°C, for example. When a solvent with a boiling point of less than 150°C is used, residual solvent can be minimized during low-temperature processes, ensuring chemical resistance.

As an example, it is preferable to select one or more solvents from the group consisting of esters such as methyl-2-hydroxyisobutyrate, ethylene glycol methyl ether acetate, 2-methoxy-1-methylethyl ester, propylene acetate, ethyl propionate, and ethyl pyruvate; ethers such as 1-methoxy-2-propanol, dibutyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycol dimethyl ether, and tetrahydrofuran; and alcohols such as methanol, ethanol, and isopropyl alcohol, taking into consideration solubility, reactivity with each component, and ease of forming a coating film.

The solvent is preferably included in the overall photosensitive resin composition so that the solids content is 10 to 50% by weight. Compositions with solids content within this range are used after filtration using a 0.1 to 0.2 μm Millipore filter or similar. As an example, the solvent content in the photosensitive resin composition may be in a range that results in a solids content of 15 to 40% by weight.

If the solids content of the photosensitive resin composition is less than 10% by weight, the coating thickness will be thin and the coating flatness will decrease. If it exceeds 50% by weight, the coating thickness will be thick, which may put strain on the coating equipment during coating and may increase the amount of residual solvent.

The photosensitive composition according to this embodiment may further contain a melamine crosslinker. The melamine crosslinker improves the heat resistance, chemical resistance, and adhesive strength of the photosensitive composition.

The melamine crosslinking agent used may be a condensation product of urea and formaldehyde, a condensation product of melamine and formaldehyde, or a methylol urea alkyl ether or methylol melamine alkyl ether obtained from alcohol.

Specifically, monomethylol urea, dimethylol urea, etc. are used as the condensation product of urea and formaldehyde. Hexamethylol melamine is used as the condensation product of melamine and formaldehyde, and partial condensation products of melamine and formaldehyde can also be used.

The methylol urea alkyl ethers are obtained by reacting alcohols with some or all of the methylol groups on a condensation product of urea and formaldehyde. Specific examples include monomethyl urea methyl ether and dimethyl urea methyl ether. The methylol melamine alkyl ethers are obtained by reacting alcohols with some or all of the methylol groups on a condensation product of melamine and formaldehyde. Specific examples include hexamethylol melamine hexamethyl ether and hexamethylol melamine hexabutyl ether. Furthermore, compounds in which the hydrogen atoms of the amino groups of melamine are substituted with hydroxymethyl and methoxymethyl groups, and compounds in which the hydrogen atoms of the amino groups of melamine are substituted with butoxymethyl and methoxymethyl groups can also be used. Methylol melamine alkyl ethers are particularly preferred.

The content of the melamine crosslinking agent may be 0.1 to 20 parts by weight per 100 parts by weight of the acrylic copolymer.

The photosensitive composition according to this embodiment may further contain a silane coupling agent. The silane coupling agent improves the adhesive strength of the photosensitive composition to the underlying substrate. Examples of the silane coupling agent include (3-glycidoxypropyl)trimethoxysilane, (3-glycidoxypropyl)triethoxysilane, (3-glycidoxypropyl)methyldimethoxysilane, (3-glycidoxypropyl)methyldiethoxysilane, (3-glycidoxypropyl)dimethylethoxysilane, 3,4-epoxybutyltrimethoxysilane, 3,4-epoxybutyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. Ethoxysilane, aminopropyltrimethoxysilane, aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3 dimethyl-butylidene)propylamine, N-2(aminoethyl)3-aminopropyltrimethoxysilane, N-2(aminoethyl)3-aminopropyltriethoxysilane, N-2(aminoethyl)3-aminopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, or (3-isocyanatepropyl)triethoxysilane can be used alone or in combination of two or more.

The silane coupling agent is contained in an amount of 0.1 to 20 parts by weight per 100 parts by weight of the acrylic copolymer.

The photosensitive resin composition according to one embodiment of the present invention may further contain a surfactant. Such surfactants improve the coatability and developability of the photosensitive resin composition. Examples of such surfactants include silicone-based and fluorine-based surfactants. The surfactant is included in an amount of 0.0001 to 2 parts by weight per 100 parts by weight of the solid content in the photosensitive resin composition.

A method for forming a pattern using a photosensitive resin composition according to one embodiment of the present invention will now be described. The photosensitive resin composition according to one embodiment of the present invention includes the steps of coating the photosensitive resin composition on a substrate, primarily heating the photosensitive resin composition to a temperature of 75°C to 85°C, exposing and developing the photosensitive resin composition, and secondarily heating the developed photosensitive resin composition to a temperature of 80°C to 90°C. The photosensitive resin composition used here is the same as the photosensitive resin composition described above. Duplicate descriptions of the same components will be omitted.

Figures 1 to 4 are process flowcharts illustrating a pattern formation method according to one embodiment of the present invention.

Referring to FIG. 1, first, a photosensitive resin composition 400 is coated on a substrate 110 to form a coating layer of the photosensitive resin composition 400. At this time, the coating is performed by a spray method, a roll coater method, a spin coating method, etc.

In this case, the photosensitive resin composition contains 0.1 to 20 parts by weight of a radical photoinitiator, 0.1 to 10 parts by weight of an ionic photoinitiator, 1 to 50 parts by weight of a polyfunctional acrylate oligomer, 1 to 50 parts by weight of a polyfunctional monomer having an ethylenically unsaturated bond, and a solvent, relative to 100 parts by weight of the acrylic copolymer. Because this photosensitive resin composition simultaneously contains both a radical photoinitiator and an ionic photoinitiator, it can be cured at temperatures as low as 90°C or less, and even when cured at temperatures as low as 90°C or less, it exhibits excellent adhesive strength and chemical resistance. This photosensitive resin composition is a negative photosensitive resin composition in which the exposed portions remain cured.

Next, referring to FIG. 2, the coated photosensitive resin composition 400 is first heated to a temperature of 75°C to 85°C. This is a pre-bake process, which removes gases contained within the coated photosensitive resin composition 400. The first heating is performed for approximately 1 minute to 5 minutes. Since the photosensitive resin composition of the present invention uses a solvent with a low boiling point of less than 150°C, gases contained within the solvent can be more effectively removed.

Next, referring to FIG. 3, the coated photosensitive resin composition is exposed and developed to form a photosensitive resin composition layer 410. The photosensitive resin composition according to one embodiment of the present invention is a negative photosensitive resin composition, and the portions corresponding to the openings of the mask 700, i.e., the exposed portions, are cured and remain, while the unexposed portions are removed. Here, exposure is performed using visible light, ultraviolet light, far ultraviolet light, electron beams, X-rays, etc. Development is performed using a developer to remove the unexposed portions.

The developer preferably uses an aqueous alkaline solution, specifically inorganic alkalis such as sodium hydroxide, potassium hydroxide, and sodium carbonate; primary amines such as n-propylamine; secondary amines such as diethylamine and n-propylamine; tertiary amines such as trimethylamine, methyldiethylamine, dimethylethylamine, and triethylamine; alcohol amines such as dimethylethanolamine, methyldiethanolamine, and triethanolamine; or aqueous solutions of quaternary ammonium salts such as tetramethylammonium hydroxide and tetraethylammonium hydroxide. In this case, the developer is prepared by dissolving the alkaline compound at a concentration of 0.1 to 10% by weight, and an appropriate amount of a water-soluble organic solvent such as methanol or ethanol and a surfactant may be added.

Next, referring to FIG. 4, the photosensitive resin composition layer 410 is subjected to a second heating at a temperature of approximately 80°C to 90°C. This second heating is a process for curing the photosensitive resin composition layer 410. This second heating is performed for approximately 30 to 240 minutes. Since the photosensitive resin composition 400 according to one embodiment of the present invention can be cured at temperatures below 90°C, an insulating film can be manufactured without damaging the light-emitting layer, even if a light-emitting layer is located underneath the photosensitive resin composition.

In other words, the photosensitive resin composition of the present invention and the pattern formation method using the same can be used as a passivation insulating film, gate insulating film, planarizing film, column spacer, overcoat, or color resist contained inside display elements such as TFT-LCDs, TSPs (Touch Screen Panels), or OLEDs. Because the photosensitive resin composition cures at a low temperature, it can be manufactured in a single process on top of structures including light-emitting layers, simplifying the process.

In addition, the structure of the manufactured display device can be simplified. As an example, a display device with a structure in which a touch panel is built onto an organic light-emitting element can be manufactured using the pattern formation method using the photosensitive resin composition of this example. That is, touch sensing electrodes can be formed directly on the thin film encapsulation layer on the organic light-emitting element, and the photosensitive resin composition of this example can be used as the insulating film located between the touch sensing electrodes. In this structure, temperatures exceeding 100°C during the insulating film manufacturing process are undesirable because they can damage the light-emitting layer of the organic light-emitting element. However, the photosensitive resin composition of this example and the pattern formation method using the same cure at temperatures of 90°C or less, allowing the insulating film to be manufactured without damaging the lower light-emitting layer.

Hereinafter, the effects of the photosensitive resin composition according to an embodiment of the present invention and the pattern forming method using the same will be described through specific experimental examples.
Synthesis Example 1: (Production of Acrylic Copolymer)
A mixed solution of 400 parts by weight of tetrahydrofuran, 30 parts by weight of methacrylic acid, 30 parts by weight of styrene, and 40 parts by weight of glycidyl methacrylate was placed in a flask equipped with a condenser and a stirrer. The liquid composition was thoroughly mixed in a mixing vessel at 600 rpm, and then 15 parts by weight of 2,2'-azobis(2,4-dimethylvaleronitrile) was added. The polymerization mixture was slowly heated to 55°C and maintained at this temperature for 24 hours. Then, it was cooled to room temperature, and 500 ppm of hydrobenzophenone was added as a polymerization inhibitor to obtain a polymer solution with a solids concentration of 30% by weight.

To remove unreacted monomers from the polymer solution, 100 parts by weight of the polymer solution was precipitated in 1,000 parts by weight of n-hexane. After precipitation, the solvent containing the unreacted materials (poor solvent) was removed by filtering using a mesh. After that, to remove any remaining solvent containing unreacted monomers after the filtering process, the solution was vacuum dried at 30°C or below to completely remove the solvent containing unreacted monomers, producing an acrylic copolymer.

The weight-average molecular weight of the acrylic copolymer was 6,000. The weight-average molecular weight was measured using GPC and converted into polystyrene equivalent.

Example 1: Preparation of Negative Photosensitive Resin Composition 100 parts by weight of the acrylic copolymer solution prepared in Synthesis Example 1, 10 parts by weight of 2-(O-benzoyloxime)-1-[4-(phenylthio)phenyl]-1,2-octanedione as a radical photoinitiator, 10 parts by weight of phenyl(4-methoxyphenyl)iodonium hexafluoride as an ionic photoinitiator, 10 parts by weight of a decafunctional urethane acrylate oligomer, 20 parts by weight of dipentaerythritol hexaacrylate as a polyfunctional monomer having an ethylenically unsaturated bond, 3 parts by weight of hexamethylolmelamine hexamethyl ether as a melamine crosslinker, and 2 parts by weight of (3-glycidoxypropyl)methyldiethoxysilane as a silane coupling agent were mixed together. Propylene glycol monoethyl acetate was added to the mixture to a solids concentration of 20% by weight, and the mixture was then filtered through a 0.2 μm Millipore filter to prepare a negative photosensitive resin composition coating solution.

Example 2: Preparation of negative photosensitive resin composition A photosensitive resin composition coating solution was prepared in the same manner as in Example 1, except that ethylene glycol methyl ether acetate was used as the solvent.

Example 3: Preparation of negative photosensitive resin composition A photosensitive resin composition coating solution was prepared in the same manner as in Example 1, except that N,N-dimethyl-N-benzyltrifluoromethanesulfonic acid was used as the ionic photoinitiator.

Example 4: Preparation of negative photosensitive resin composition A photosensitive resin composition coating solution was prepared in the same manner as in Example 1, except that 4-methylphenyl(4-(2-methylpropylphenyl))iodonium hexafluoride was used as the ionic photoinitiator.

Example 5: Preparation of negative photosensitive resin composition A photosensitive resin composition coating solution was prepared in the same manner as in Example 1, except that phenyl(4-methoxyphenyl)iodonium arsenic hexafluoride was used as the ionic photoinitiator.

Comparative Example 1: Preparation of negative photosensitive resin composition A photosensitive resin composition coating solution was prepared in the same manner as in Example 1, except that 0.05 parts by weight of the ionic photoinitiator was used.

Comparative Example 2: Preparation of negative photosensitive resin composition A photosensitive resin composition coating solution was prepared in the same manner as in Example 1, except that 25 parts by weight of the ionic photoinitiator was used.

Comparative Example 3: Preparation of negative photosensitive resin composition A photosensitive resin composition coating solution was prepared in the same manner as in Example 1, except that the ionic photoinitiator in Example 1 was completely removed.

Comparative Example 4: Preparation of negative photosensitive resin composition A photosensitive resin composition coating solution was prepared in the same manner as in Comparative Example 3, except that 2-(O-acetyloxime)-1-[4-(phenylthio)phenyl]-1,2-octanedione was used as the radical photoinitiator.

Comparative Example 5: Preparation of negative photosensitive resin composition A photosensitive resin composition coating solution was prepared in the same manner as in Example 1, except that ethyl lactate was used as the solvent.

Comparative Example 6: Preparation of negative photosensitive resin composition A photosensitive resin composition coating solution was prepared in the same manner as in Example 1, except that propylene glycol monomethyl propionate was used as the solvent.

The physical properties of the negative photosensitive resin composition coating solutions prepared in Examples 1 to 5 and Comparative Examples 1 to 6 were evaluated using the methods described below in Experimental Examples 1 to 5, and the results are shown in Table 1 below.

Experimental Example 1: Measurement of Sensitivity and Film Retention Ratio A negative photosensitive composition solution prepared in Examples 1 to 5 and Comparative Examples 1 to 6 was applied to a glass substrate on which _SiNx had been deposited using a spin coater, and then prebaked on a hot plate at 80°C for 2 minutes to form a 2.0 μm film. Using a pattern mask, the resulting film was irradiated with ultraviolet light at 365 nm with an intensity of 10 mW/ ^cm2 using a broadband exposure device for 1 to 5 seconds at 0.2 second intervals. The film was then developed in a 2.38 wt% aqueous solution of tetramethylammonium hydroxide at 23°C for 60 seconds and then washed with ultrapure water for 60 seconds.

For final curing, the patterned film was obtained by heating in an oven at 85°C for 60 minutes. Using an SEM, sensitivity was measured based on the exposure dose at which the residual film rate reached saturation on a 20 μm line and space CD basis.

Experimental Example 2: Film Remaining Rate The film remaining rate at which the film remaining rate reached saturation was determined during the sensitivity measurement in Experimental Example 1. If the film remaining rate was 80% or higher, it was marked as O, if it was 80% to 75%, it was marked as △, and if it was 75% or lower, it was marked as X.

Experimental Example 3: Residue Residue was inspected based on the contact hole of the pattern film formed during the sensitivity measurement in Experimental Example 1. In this case, the absence of residue was represented by ◯, and the presence of residue was represented by X.

Experimental Example 4: Adhesion Strength When the pattern film formed during the sensitivity measurement in Experimental Example 1 did not peel off, it was indicated by ◯, and when peel off occurred, it was indicated by X.

Experimental Example 5: Chemical Resistance The pattern film formed during the sensitivity measurement in Experimental Example 1 was placed in a stripper and left there, and the change in thickness was measured. When the change in thickness was 0.5 μm or less, it was marked with ○, when it was 0.5 μm to 1.0 μm, it was marked with △, and when it was 1.0 μm or more, it was marked with X.

As can be seen from Table 1, Examples 1 to 5, which contain an ionic photoinitiator and a low-boiling-point solvent according to one embodiment of the present invention, were found to have superior sensitivity, film retention rate, residue, adhesion strength, and chemical resistance compared to Comparative Examples 3 to 6.

Furthermore, when comparing Comparative Examples 1 and 2, in which the ionic photoinitiator content range was outside the 0.1-10 parts by weight range, with Example 1, it was confirmed that consistent performance in terms of film retention rate, residue, and adhesive strength was only achieved when the ionic photoinitiator content range was within the 0.1-10 parts by weight range. In other words, Comparative Example 1, in which the ionic photoinitiator content was 0.05 parts by weight, had poor film retention rate and adhesive strength, while Comparative Example 2, in which the ionic photoinitiator content was 25 parts by weight, had poor residue.

In other words, the photosensitive resin composition according to one embodiment of the present invention, which contains both a radical photoinitiator and an ionic photoinitiator, has excellent sensitivity, film retention rate, and residue, and is particularly excellent in adhesion strength and chemical resistance in low-temperature processes at temperatures below 90°C, making it suitable for use in flexible displays.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited to these examples, and various modifications and improvements made by those skilled in the art that utilize the basic concepts of the present invention defined in the claims also fall within the scope of the present invention.

110: Substrate 400: Photosensitive resin composition 410: Photosensitive resin composition layer 700: Mask

Claims (5)

For 100 parts by weight of the acrylic copolymer,
10 to 20 parts by weight of a radical photoinitiator,
0.1 to 10 parts by weight of an ionic photoinitiator,
The content ratio of the radical photoinitiator to the ionic photoinitiator is 2:1 to 1:2;
1 to 50 parts by weight of a multifunctional acrylate oligomer,
a polyfunctional monomer having an ethylenically unsaturated bond, and a solvent;
the acrylic copolymer is a copolymer of an unsaturated carboxy compound and an olefin compound having a glycidyl group,
the radical photoinitiator is 2-(O-benzoyloxime)-1-[4-(phenylthio)phenyl]-1,2-octanedione or 2-(O-acetyloxime)-1-[4-(phenylthio)phenyl]-1,2-octanedione;
the ionic photoinitiator is phenyl(4-methoxyphenyl)iodonium phosphorus hexafluoride , 4 -methylphenyl(4-(2-methylpropylphenyl))iodonium phosphorus hexafluoride, or phenyl(4-methoxyphenyl)iodonium arsenic hexafluoride;
the polyfunctional acrylate oligomer is an aliphatic urethane acrylate oligomer, an aromatic urethane acrylate oligomer, an epoxy acrylate oligomer, an epoxy methacrylate oligomer, a polyester acrylate oligomer, a silicon acrylate oligomer, a melamine acrylate oligomer, and a dendritic acrylate oligomer, either alone or in a mixture of two or more thereof;
The olefin compound having a glycidyl group is selected from the group consisting of glycidyl acrylate, glycidyl methacrylate, α-ethyl glycidyl acrylate, α-n-propyl glycidyl acrylate, α-n-butyl glycidyl acrylate, β-methyl glycidyl acrylate, β-methyl glycidyl methacrylate, β-ethyl glycidyl acrylate, β-ethyl glycidyl methacrylate, 3,4-epoxybutyl acrylate, 3,4-epoxybutyl methacrylate, 6,7-epoxyheptyl acrylate, 6,7-epoxyheptyl methacrylate, α-ethyl acrylate, and 3,4-epoxycyclohexyl methacrylate, either alone or in a mixture of two or more thereof;
The photosensitive resin composition, wherein the solvent is propylene glycol monoethyl acetate or ethylene glycol methyl ether acetate, each of which has a boiling point of less than 150°C. The photosensitive resin composition according to claim 1, characterized in that the photosensitive resin composition cures at a temperature of 90°C or less. The photosensitive resin composition according to claim 1, characterized in that the solids content of the photosensitive resin composition is 10% by weight to 50% by weight. The photosensitive resin composition according to claim 1, further comprising a melamine crosslinking agent, wherein the melamine crosslinking agent is one or more selected from the group consisting of monomethylol urea, dimethylol urea, hexamethylol melamine, monomethyl urea methyl ether, dimethyl urea methyl ether, hexamethylol melamine hexamethyl ether, and hexamethylol melamine hexabutyl ether. The composition further contains a silane coupling agent, which may be (3-glycidoxypropyl)trimethoxysilane, (3-glycidoxypropyl)triethoxysilane, (3-glycidoxypropyl)methyldimethoxysilane, (3-glycidoxypropyl)methyldiethoxysilane, (3-glycidoxypropyl)dimethylethoxysilane, 3,4-epoxybutyltrimethoxysilane, 3,4-epoxybutyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, or 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane. The photosensitive resin composition according to claim 1, characterized in that the silane is at least one selected from the group consisting of silane, aminopropyltrimethoxysilane, aminopropyltriethoxysilane, 3-triethoxysily-N-(1,3 dimethyl-butylidene)propylamine, N-2(aminoethyl)3-aminopropyltrimethoxysilane, N-2(aminoethyl)3-aminopropyltriethoxysilane, N-2(aminoethyl)3-aminopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and (3-isocyanatopropyl)triethoxysilane.