Black resist composition and method for forming a black pattern by near-infrared photolithography

Abstract

To propose a novel technique relating to photolithography for forming a black pattern such as a black matrix and to provide a black resist composition suitable for this process, having an excellent light blocking effect.SOLUTION: When forming a black pattern by photolithography, ultraviolet radiation is conventionally used as exposure light. In contrast to this conventional method, the present invention is a novel photolithography process of a black pattern, which applies near infrared radiation. And a black resist composition suitable for this process comprises as main components: a black pigment (A) which transmits near infrared radiation; a sensitizing dye (B) having an absorption in a near infrared region; a radical polymerization initiator or an acid generator (C); and a binder resin (D). As the black pigment (A), preferably used are a lactam-based pigment, a perylene-based pigment, and an azomethine-based pigment. Together with this black pigment, a cyanine dye, a squarylium dye, or a phthalocyanine dye is included as a suitable sensitizing dye.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a novel method for forming a black pattern such as a black matrix by photolithography. And the present invention relates to a resist composition containing a black pigment suitable for the above method, which is a black resist composition having near-infrared sensitivity.

Background Art

[0002] Color flat panels are used in all electronic devices with screens such as liquid crystal TVs, liquid crystal monitors, and smartphone screens. Many of these flat panels include a color filter in which pixels of each color of red, green, blue, or cyan, yellow, magenta are formed. The color filter has a black matrix with grid-shaped or stripe-shaped openings formed on the surface of a transparent substrate such as glass, and pixels of dyes showing each color are formed in these openings. The black matrix is a light-shielding material that suppresses color mixing and light leakage from each pixel to improve contrast and color visibility, and obtains a clearer image. This black matrix was formerly formed by vapor-depositing and patterning a Cr thin film in a grid pattern, but currently it is formed exclusively by a photolithography method using a photosensitive resin composition (resist composition) containing a black pigment. The photolithography method is relatively simpler in process than patterning of a Cr thin film or the like and is excellent in production cost. In particular, in recent years, direct exposure technology using a semiconductor laser or the like has attracted attention, and it has become possible to produce a high-definition black matrix with high efficiency.

[0003] As a resist composition for manufacturing a black pattern such as a black matrix by photolithography, a black resist composition mainly containing carbon black as a black pigment is used. And as a light source for exposing the resist, ultraviolet light, particularly g-line (wavelength 436 nm), h-line (wavelength 405 nm), i-line (wavelength 365 nm) is applied.

[0004] As described above, the black matrix is ​​formed to improve the contrast of adjacent pixels of each color, and therefore high light-shielding properties are required. However, this required characteristic creates a technical contradiction with the pattern formation mechanism of photolithography. Specifically, carbon black, a black pigment included in conventional black resist compositions, is a suitable material for meeting the above-mentioned requirements due to its high light-shielding properties. However, carbon black has a wide absorption wavelength range and can absorb not only visible light but also ultraviolet light (g-line, h-line, i-line). Therefore, in the exposure process of photolithography, the ultraviolet light, which is the exposure light, can contribute to the photoreaction in the upper layer of the resist film, but it cannot reach the lower layer of the resist film. In the case of negative-type resists, this results in the problem that the upper layer of the resist film hardens, but the lower layer remains unhardened.

[0005] To address problems arising from such technical inconsistencies, the countermeasures taken so far have mainly involved changing the composition of black pigments. For example, measures such as using a mixture of carbon black and an extender pigment as the black pigment (Patent Document 1), using a black pigment with a reduced carbon black ratio by using a mixture of different colored pigments as an auxiliary (Patent Documents 2 and 3), and improving the physical properties of carbon black to create a black pigment (Patent Documents 4 and 5) have been reported. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 11-149153 [Patent Document 2] International Publication No. 2013 / 115268 [Patent Document 3] Japanese Patent Application Publication No. 2000-227654 [Patent Document 4] International Publication No. 2008 / 066100 [Patent Document 5] Japanese Patent Publication No. 2006-257110 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the conventional methods described above cannot be said to fundamentally solve the problem, and differences in photoreaction between the upper and lower layers of the resist film can still occur. This is because the black pigments used in these methods still contain carbon black and therefore absorb ultraviolet light. Furthermore, recently there has been a demand for specific pattern shapes such as black matrices, and a rectangular cross-section with sharp edges and verticality is often required. Conventional technologies have difficulty adequately meeting this requirement.

[0008] Furthermore, in recent years, the development of display devices using a new technology that combines micro-LEDs and quantum dots is being established. In these display devices, a height of approximately 10 μm is required for the formation of the quantum dot layer, and therefore, a grid-like partition with a height of 10 μm or more is necessary. Attempts have been made to apply a black pattern to this grid-like partition to improve contrast and other aspects.

[0009] In conventional color filters for liquid crystal flat panels, the black matrix film thickness is at most about 5 μm. Therefore, although the above-mentioned problems exist, it was possible to address them with conventional solutions. However, forming a black pattern with a film thickness of 10 μm or more, suitable for the novel display device described above, while maintaining perpendicularity in the cross-section, becomes extremely difficult with conventional technology.

[0010] This invention was made against the background described above, and proposes a novel process for manufacturing black patterns such as black matrices by photolithography. Furthermore, it provides a novel black resist composition that exhibits light-shielding properties equivalent to those of a carbon black-containing resist composition in the visible light region, while allowing exposure light to pass through without being affected by the film thickness during the exposure process. [Means for solving the problem]

[0011] The inventors considered that in order to solve the problems of the conventional photolithography method using the above-described black resist composition, it is necessary to apply a new process that changes the exposure light in the exposure step. Black is inherently a color with a wide absorption wavelength range, and it is difficult to allow conventional exposure light to pass through a black pigment while also exhibiting light-shielding properties.

[0012] Specifically, the inventors investigated a photolithography method that applies near-infrared light as the exposure light. Furthermore, the inventors diligently investigated a black resist composition that is compatible with a photolithography method that applies near-infrared light, containing a predetermined black pigment, and having near-infrared photosensitivity as well as light-shielding properties equivalent to or better than conventional compositions. As a result, they arrived at the present invention.

[0013] In other words, the present invention is a black resist composition containing the following components (A) to (D) as essential components. Component (A): Black pigment that transmits near-infrared light Component (B): Sensitizing dye that absorbs in the near-infrared region Component (C): Radical polymerization initiator or acid generator Ingredient (D): Binder resin

[0014] The present invention relates to a black resist composition compatible with photolithography using near-infrared light as the exposure light source. Its features include a combination of a black pigment that transmits near-infrared light (component (A)) and a sensitizing dye that absorbs in the near-infrared region (component (B)), thereby achieving both suitable photosensitivity and light-shielding properties. The composition of the black resist composition and the photolithography method according to the present invention will be described below. In this invention, the near-infrared light used as the exposure light source is defined as light with a wavelength range of 700 nm to 1000 nm.

[0015] (I) Composition of the black resist composition according to the present invention • Ingredient (A): Black pigment The black pigment applied in the present invention absorbs light from ultraviolet rays to visible light to the same extent as carbon black and shields light, while having permeability to near-infrared rays.

[0016] As the black pigment having permeability to near-infrared rays as described above, those containing at least any one of lactam pigments, perylene pigments, and azomethine pigments are preferable.

[0017] Specifically, as the lactam pigment, Irgaphor Black S 0100 CF of BASF can be mentioned. As the perylene pigment, Perylene black31 (PB31) can be mentioned, and as the azomethine pigment, Chromofine Black A1103 of Dainichi Seika Co., Ltd. etc. can be mentioned. Also, in the market, black pastes obtained by adding a dispersant, a surfactant, etc. to the above-mentioned black pigment and dispersing it in an organic solvent are available, and such black pastes can also be used. Note that carbon black is not included as the black pigment of the present invention.

[0018] Note that the permeability of the near-infrared rays of the black resist composition according to the present invention, when formed into a resist film with a thickness of 10 μm based on a resist composition containing 15% by weight of the above-mentioned black pigment in the total solid content of the resist, can transmit 50% or more of the near-infrared rays with a wavelength of 700 nm or more and 1000 nm or less.

[0019] ·Component (B): Sensitizing dye Certain dyes become excited by absorbing near-infrared rays, and the energy thereof moves to a polymerization initiator or an acid generator. Such dyes are known to be able to cause radical generation or acid generation as a result, and are called sensitizing dyes. In the present invention, a sensitizing dye that absorbs near-infrared rays with a wavelength of 700 nm or more and 1000 nm or less is preferable.

[0020] In the present invention, as the sensitizing dye as described above, those containing at least any one of cyanine dyes, squarium dyes, and phthalocyanine dyes are preferable.

[0021] Specifically, examples of the cyanine dye include IR-797 and IR-820 manufactured by Sigma Aldrich, and IRT manufactured by Showa Denko. Examples of the squarylium dye include 2,4-di-3-guaiaculenyl-1,3-dihydroxycyclobutenediylidium dihydroxide bis(inner salt), 2,4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl] squarylium, and the like. Further, examples of the phthalocyanine dye include copper(II) 5,9,14,18,23,27,32,36-octabutoxy-2,3-naphthalocyanine. Incidentally, many dyes applicable to the present invention are listed on pages 106 to 109 of the "Catalog of Reagents for Materials Science Research (2004 Edition)" of Sigma Aldrich, and on the page of "Near Infrared Absorbing Dyes" in the website of Tokyo Chemical Industry Co., Ltd., and they are easily available on the market.

[0022] In the present invention, it has been confirmed that the above-described cyanine dyes, squarylium dyes, and phthalocyanine dyes function effectively. In particular, the cyanine dyes (IR-797, IR-820, IRT) have absorption maximum wavelengths (λmax) of 813 nm, 820 nm, and 817 nm, respectively. In the present invention, an LED can be used as a light source for near infrared exposure, and the LED light source widely available on the market is an 850 nm LED. Since the absorption maximum wavelengths of the above-described cyanine dyes are close to the wavelength of this LED light source, they can be said to be suitable sensitizing dyes.

[0023] Incidentally, in conventional black resist compositions, benzophenone-based compounds (for example, 4,4'-bis(diethylamino)benzophenone), acridine-based compounds (for example, 9-phenylacridine), anthracene-based compounds (for example, 9,10-dibutoxyanthracene), etc. have been used as sensitizing dyes for a long time. These sensitizing dyes are widely used as sensitizers on the long wavelength side of ultraviolet rays, but they do not have absorption in the near infrared region and do not function as the sensitizing dye of the present invention.

[0024] · Component (C): polymerization initiator or acid generator These generate radicals or acids from the energy excited by light irradiation, forming a resist film. However, with respect to the combination with the sensitizing dye having absorption in the near-infrared region of the present invention described above, energy transfer does not necessarily proceed effectively with all polymerization initiators and acid generators. In the present invention, iodnium salts, triazine compounds, and boron ion complexes are effective as preferred polymerization initiators and acid generators.

[0025] Specifically, suitable and preferred iodine salts include diaryliodonium phosphate (e.g., IK-1 from Sanapro), triazine compounds include bischloromethyl-S-triazine compounds (e.g., TFE-triazine, TME-triazine, MP-triazine, dimethoxytriazine from Sanwa Chemical), and boron ion complexes include tetrabutylammonium butyltriphenyl borate (P3B from Showa Denko) and tetrabutylammonium butyltrinaphthyl borate (N3B from Showa Denko).

[0026] • Ingredients (D): Binder resin The binder resin is added to a substrate when applying a prepared photosensitive resin composition to form a uniform coating. It also acts as a resin that dissolves unwanted parts of the pattern in the developing step of photolithography using the developer solution for an appropriate amount of time. Basically, any binder resin used in conventional resist resin compositions can be applied; there are no particular limitations on the type of resin as long as it can perform the aforementioned role.

[0027] Typical binder resins are alkali-soluble resins. Specifically, acrylic resins are a good example. To achieve alkali solubility, copolymers of ethylenically unsaturated monomers containing carboxyl groups or hydroxyl groups with other copolymerizable ethylenically unsaturated monomers are preferred. Novolac resins and polyhydroxystyrene resins (PHS resins) also exhibit excellent film-forming properties and alkali solubility, making them suitable for the present invention. Many of these products are on the market, and their manufacturing methods have been extensively documented in prior art (e.g., Japanese Patent Application Publication No. 2006-58385, Japanese Patent No. 6226104, etc.).

[0028] A negative-type resist composition is obtained by mixing the above-mentioned binder resin with either a radically polymerizable monomer or a crosslinking agent. On the other hand, for positive-type resist compositions, a novolac resin with a protective group or a PHS resin with a protective group can be used as the binder resin. The manufacturing methods for these resins with protective groups are also known (for example, a detailed explanation can be found in Japanese Patent Application Publication No. 2019-204036).

[0029] • Ingredient (E): Radical polymerizable monomer or crosslinking agent (selective additive) Components (A) to (D) described above are essential components of the black resist composition according to the present invention. As described above, by mixing these with either a radical polymerizable monomer or a crosslinking agent, a negative-type resist composition can be obtained.

[0030] The radical polymerizable monomers used in the present invention are preferably polyfunctional monomers. Examples include diacrylates or dimethacrylates of alkylene glycols such as ethylene glycol and propylene glycol; diacrylates or dimethacrylates of polyalkylene glycols such as polyethylene glycol and polypropylene glycol; and polyacrylates or polymethacrylates of polyhydric alcohols of trivalent or higher hydration, such as glycerin, trimethylolpropane, pentaerythritol, and dipentaerythritol.

[0031] Of these, polyacrylates or polymethacrylates of trivalent or higher polyhydric alcohols are preferred, specifically trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, dipentaerythritol tetraacrylate, dipentaerythritol tetramethacrylate, dipentaerythritol hexaacrylate, and dipentaerythritol hexamethacrylate are preferred, with trimethylolpropane triacrylate, pentaerythritol triacrylate, and dipentaerythritol hexaacrylate (DPHA) being particularly preferred due to their high reactivity. These polyfunctional monomers can be used individually or in combination of two or more.

[0032] In the present invention, alkoxymethylated melamine is preferred as a crosslinking agent. Alkoxymethylated melamine has a structure in which the hydrogen atoms of the amino group of melamine are all or partially replaced by alkoxymethyl groups. Specific examples of alkoxymethylated melamine include methoxymethylated melamine, ethoxymethylated melamine, propoxymethylated melamine, and butoxymethylated melamine.

[0033] It is also possible to use commercially available alkoxymethylated melamines. Examples include Cymel 300 (methoxymethylated melamine) and Cymel 303 (methoxymethylated melamine) from Ornex, and Nikalac MW-30HM (methoxymethylated melamine) and Nikalac MW-40 (methoxy and butoxy mixed methylated melamine) from Sanwa Chemical. These melamines can be used individually or in combination in the compositions according to the present invention.

[0034] Furthermore, polyfunctional epoxy compounds can also be used as crosslinking agents. For example, polyfunctional epoxy compounds having alkylene glycol skeletons such as ethylene glycol and propylene glycol, diphenylmethane skeletons, dinaphthylmethane skeletons, triazine skeletons, biphenyl skeletons, phenol novolac skeletons, tetraphenylethane skeletons, bisphenol skeletons, etc., can be used.

[0035] These compounds are widely available on the market. For example, Epolite 40E and Epolite 70P from Kyoeisha Chemical Co., Ltd., TEPIC-S from Nissan Chemical Corporation, Epiclon 830 from DIC Corporation, and JER-YX-4000 and JER-604 from Mitsubishi Chemical Corporation can be used. These polyfunctional epoxy compounds can be used individually or in combination in the compositions according to the present invention.

[0036] Furthermore, it is also possible to use a combination of the melamine compound and the polyfunctional epoxy compound mentioned above as a crosslinking agent.

[0037] The mixing ratios of each component (A) to (E) described above are preferably as follows, when the total solid content of the resist composition is 100 parts by weight. (a) Black pigment: 3 parts by weight or more and 50 parts by weight or less, more preferably 10 parts by weight or more and 30 parts by weight or less. If the amount of black pigment falls below the above range, there is a concern that the light-shielding properties will decrease. On the other hand, if it exceeds the above range, it will absorb near-infrared light, affecting the uniformity of the photoreaction in the film thickness direction. (b) Sensitizing dye: 0.5 parts by weight or more and 10 parts by weight or less, more preferably 1 part by weight or more and 5 parts by weight or less. If the sensitizing dye falls below the above range, insufficient excitation by infrared light may occur, leading to concerns about decreased sensitivity. Conversely, if it exceeds the above range, the sensitizing dye itself may absorb too much infrared energy, resulting in decreased sensitivity. (c) Polymerization initiator or acid generator: 0.5 parts by weight or more and 10 parts by weight or less, more preferably 1 part by weight or more and 7 parts by weight or less. If these values ​​fall below the above range, a decrease in sensitivity is a concern. On the other hand, if they exceed the above range, the sensitivity becomes extremely high, and the reaction extends to the unexposed areas near the exposed areas, resulting in a deterioration of resolution and contrast. (d) Binder resin: 30 parts by weight or more and 80 parts by weight or less, more preferably 40 parts by weight or more and 75 parts by weight or less. If the binder resin falls below the above range, the coating film formation ability decreases, making it difficult to obtain a uniform film. Conversely, if it exceeds the above range, the image formation function deteriorates. (e) Radical polymerizable monomer or crosslinking agent: 10 parts by weight or more and 50 parts by weight or less, more preferably 15 parts by weight or more and 45 parts by weight or less. If these values ​​fall below the above range, radical polymerization reactivity or crosslinking reactivity decreases, and if they exceed the above range, excessive reaction reduces workability.

[0038] Other additives In addition to the above components, surfactants can be added as appropriate to improve film formation uniformity during spin coating and prevent the occurrence of radial streaks called striations, as well as dispersants and dispersing aids to improve the dispersibility of pigments, and second and third solvents can be added in addition to the main solvent to improve the solubility of each solid component and to adjust the solvent evaporation speed during spin coating and the solvent evaporation speed during baking.

[0039] (II) Method for forming a black pattern according to the present invention Next, a method for forming a black pattern, such as a black matrix, according to the present invention will be described. The method for forming a black pattern according to the present invention basically follows a conventional pattern formation method using photolithography. The pan formation method using photolithography consists of the following steps: a film formation step in which a resist composition is applied to a substrate and dried to form a resist film; an exposure step in which the resist film is exposed to light to cause a photoreaction in the resist film; and a development step in which the exposed resist film is treated with a developer to remove excess resist film and obtain a desired pattern. The present invention is characterized by applying the black resist composition according to the present invention described above as the resist composition for forming the resist film, and by applying near-infrared light with a wavelength of 700 nm to 1000 nm as the light source in the exposure step. The following describes each step of the method for forming a black pattern according to the present invention.

[0040] (film formation process) As a substrate for forming a resist film, considering the original purpose of a black pattern such as a black matrix, which is to shield key areas on a transparent substrate, a transparent substrate, such as a transparent glass substrate or a transparent film, is suitable, but it is not limited to these. A silicon wafer, ceramic substrate, aluminum substrate, SiC wafer, GaN wafer, metal substrate such as copper, or a metal film deposition substrate such as copper can be used as appropriate. The substrate may be an unprocessed substrate or a substrate with electrodes or elements formed on its surface.

[0041] The resist composition to be applied to the substrate is the black pigment-containing resist according to the present invention, as described above. The method of applying the resist composition is not particularly limited. Rotary coating using a spin coater is common, but spray coating using a spray coater, slit coating, roll coating, inkjet method, etc., may also be used.

[0042] The drying (pre-baking) of the resist composition applied to the substrate is typically performed by heat treatment using a hot plate or a hot air oven. The heating temperature is preferably 80°C to 140°C, and more preferably 90°C to 120°C. The heating time varies depending on the heating device, but when using a hot plate, it is preferably 30 seconds to 300 seconds, and more preferably 60 seconds to 180 seconds. When using a hot air oven, it is preferably 5 minutes to 60 minutes, and more preferably 10 minutes to 30 minutes.

[0043] The thickness of the resist film is not particularly limited and can be adjusted as appropriate depending on the application and the required pattern. For example, when forming a black matrix for a color filter, a thickness of 1 μm to 5 μm is preferred, and more preferably 2 μm to 3 μm. In the case of black patterns for device applications using the above-mentioned quantum dots, a thick film of 10 μm to 15 μm may be required for the partition wall application that fills the quantum dots.

[0044] (Exposure process) Unlike conventional photolithography methods that use ultraviolet light (wavelengths of approximately 200-500 nm), the exposure process of the present invention uses near-infrared light with a wavelength of 700 nm to 1000 nm for exposure. A laser or LED is preferred as the light source emitting near-infrared light, and an exposure apparatus designed to produce parallel light is preferred. However, light sources that emit a broad wavelength band including near-infrared light, such as xenon lamps, can also be used. In this case, light in the wavelength range of 700 nm to 1000 nm can be extracted using a bandpass filter or the like to serve as the light source. In the exposure process, the resist film is exposed through a photomask designed with the desired pattern. Furthermore, with the recent advancements in information technology and image processing technology, a technique has been developed in photolithography that does not use a photomask, but instead directly exposes the desired pattern with a beam of light (direct drawing exposure or maskless exposure). The black resist composition and photolithography method of the present invention can also perform such maskless exposure.

[0045] After the exposure process, a step of heating the resist film before the development process may be added as needed. This heating is sometimes called post-exposure baking (PEB). The heating temperature for PEB is, for example, 70°C to 150°C, preferably 70°C to 120°C, and the heating time, when using a hot plate, can be 30 seconds to 300 seconds, preferably 60 seconds to 180 seconds. PEB is preferably applied to resist compositions called three-component chemically amplified negative resists or positive resists utilizing a deprotection reaction.

[0046] (Development process) A desired pattern can be obtained by developing an exposed resist film with a developer solution. Development can be carried out using methods such as immersion, paddle, or spray. In the development process, in negative-type resist films, the exposed areas are crosslinked and solidified by a photoreaction, remaining as a pattern, while the unexposed areas are eluted and removed. In the case of positive-type resist films, the exposed areas are eluted and removed, and the unexposed areas remain as a pattern.

[0047] As the developer, an alkaline aqueous solution is preferred. Specific examples of alkaline aqueous solutions include (i) inorganic alkaline aqueous solutions such as sodium hydroxide, sodium carbonate, sodium silicate, and ammonia; (ii) organic amine aqueous solutions such as ethylamine, diethylamine, triethylamine, and triethanolamine; and (iii) aqueous solutions of quaternary ammonium salts such as tetramethylammonium hydroxide and tetrabutylammonium hydroxide. A more preferred developer is an aqueous solution of tetramethylammonium hydroxide. In this developer, the concentration of tetramethylammonium hydroxide is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.4% by mass or more and 2.5% by mass or less. Furthermore, a surfactant may be added to the developer as appropriate to enhance its permeability.

[0048] (Other processes) After the developing process, it is preferable to clean the pattern and substrate with a rinsing solution. Ultrapure water is preferred as the rinsing solution.

[0049] Furthermore, after pattern formation, a post-bake process can be performed to firmly fix the pattern to the substrate and to enhance the physical and chemical resistance of the pattern itself. The post-bake conditions can be determined as appropriate, but it is generally common to set the temperature 10°C to 30°C higher than the heating temperature during pre-bake.

[0050] The photolithography method according to the present invention, as described above, can form a black pattern such as a black matrix on a substrate. The black resist composition according to the present invention can form a suitable black pattern without differences in photoreaction across film thickness and also exhibits excellent light-shielding properties in the visible light region. The black pattern formed by the present invention, which includes the black pigment described above, has sharp pattern edges and maintains a good rectangular cross-sectional shape. [Effects of the Invention]

[0051] As described above, the present invention solves the problems of the past by applying near-infrared light as the exposure light source in a photolithography process for forming black patterns such as black matrices. According to the black resist composition of the present invention, black patterns of a desired pattern can be efficiently manufactured by applying near-infrared light. At this time, the photoreaction can proceed uniformly and with high sensitivity without being affected by the thickness of the resist film. The black resist composition of the present invention has light-shielding ability equivalent to carbon black in the visible light region and can form rectangular pixel patterns. [Modes for carrying out the invention]

[0052] Embodiments of the present invention will be described below. In this embodiment, three types of binder resins (alkaline solution resins) were synthesized (referred to as resin F-1, resin F-2, and resin F-3), and various black pigments and additives were added to them to produce black resist compositions that will serve as examples and comparative examples. Then, black matrices were produced by photolithography using the various resist compositions produced.

[0053] Synthesis of [binder resin (alkaline-soluble resin)] Synthesis of resin F-1 Isopropyl alcohol was charged into a four-necked flask, maintained at 80°C in an oil bath, and nitrogen-sealed. Methyl methacrylate / methacrylic acid / styrene was then added in a weight ratio of 30 / 40 / 30 while stirring to synthesize a copolymer. Furthermore, 40 parts by weight of glycidyl methacrylate were added, and the mixture was re-precipitated with pure water, filtered, and dried to obtain a methyl methacrylate / methacrylic acid / styrene copolymer partially added by glycidyl methacrylate. The resulting copolymer had an average molecular weight (Mw) of 17100 and an acid value of 113 (mgKOH / g). This acrylic polymer is designated as "F-1".

[0054] Synthesis of resin F-2 In a separable flask equipped with a thermometer, stirrer, and reflux condenser, 100 parts of o-cresol, 32.5 parts of 92% paraformaldehyde, and 1.0 part of oxalic acid were charged and reacted under reflux for 4 hours. Then, 50.0 parts of propylene glycol monomethyl ether acetate were added, and the temperature was raised to 120°C while removing the distilled water. After further reaction at 120°C for 5 hours, the mixture was heated to 180°C and the propylene glycol monomethyl ether acetate was removed under reduced pressure. The molten resin was extracted at 180°C and cooled to obtain a solid o-cresol novolac resin. The weight-average molecular weight of this resin was 6000 by gel permission chromatography (polystyrene equivalent). This novolac resin is designated as F-2.

[0055] Synthesis of resin F-3 A novolac resin was synthesized in which phenolic hydroxyl groups were protected by alkoxyalkyl groups. The novolac resin F-2 obtained above was dissolved in cyclopentanone to a resin content of 15%, and 3.6 mg of p-toluenesulfonic acid monohydrate was charged into 130 g of this resin solution. 7.8 g of ethyl vinyl ether was added dropwise to this resin solution, and the mixture was reacted at room temperature for 3 hours. Then, in order to remove the acid catalyst, deionized water was added to the reaction solution and stirred, and after standing, the organic layer was separated by liquid-liquid extraction. This washing process was repeated 5 times. The finally extracted organic layer was concentrated to remove water. A resin solution with a resin concentration of 59% was obtained. 1 Analysis by 1H-NMR revealed that 45% of the phenolic hydroxyl groups in the novolac resin were protected by 1-ethoxyethyl groups. This protected novolac resin is designated as "F-3".

[0056] [Manufacturing of Black Resist Composition] Example 1 A negative-type resist composition was obtained by dissolving F-1 as an alkali-soluble resin, dipentaerythritol hexaacrylate (DPHA) as a radical polymerizable monomer, and tetrabutylammonium butyltriphenyl borate (P3B) as a polymerization initiator in propylene glycol monomethyl ether acetate (PGMEA) as a solvent. Then, lactam black was mixed with this resist composition as a black pigment component and cyanine dye (IRT) as a sensitizing dye to obtain a black resist composition. The weight ratio of the solid content of each component is as shown in Table 1 below. Surfactants, dispersants, and dispersion aids were added as appropriate to improve film-forming properties and pigment dispersibility.

[0057] Example 2 A black resist composition was prepared by changing the polymerization initiator and sensitizing dye of Example 1. In this example, triazine (TME-triazine, Sanwa Chemical Co., Ltd.) was used as the polymerization initiator and IR-797 as the sensitizing dye, and the black resist composition was obtained in the same manner as in Example 1. The composition is shown in Table 1.

[0058] Example 3 In this example, an iodine salt (diaryliodonium phosphate triazine: IK-1) was used as a polymerization initiator, and IR-820 was used as a sensitizing dye. Otherwise, a black resist composition was obtained in the same manner as in Example 1. The composition is shown in Table 1.

[0059] Example 4 A base resist composition was prepared by dissolving F-2 as an alkali-soluble resin, melamine (Sanwa Chemical Co., Ltd. Nikalac MW-30HM) as a crosslinking agent, and triazine (Sanwa Chemical Co., Ltd. TFE-triazine) as an acid generator in PGMEA (this solution is referred to as Solution A). Solution A is a negative-type resist that undergoes photocrosslinking when exposed to ultraviolet light containing g, h, and i rays. IR-797 dissolved in γ-butyrolactone was mixed with Solution A, and then perylene black (PB31) was added as a black pigment component to obtain a black resist composition. This composition is shown in Table 1.

[0060] Example 5 A base resist composition was prepared by dissolving F-3 as an alkali-soluble resin and triazine (TME-triazine, Sanwa Chemical Co., Ltd.) as an acid generator in PGMEA (this solution is referred to as Solution B). Solution B functions as a photo-dissociative positive resist when exposed to ultraviolet light containing g, h, and i rays. IR-797 dissolved in γ-butyrolactone was mixed with Solution B, and an azomethine-based pigment (A1103) was added as a black pigment to obtain a black resist composition. This composition is shown in Table 1 below.

[0061] Comparative Example 1 In Example 1, a black resist composition was prepared in the same manner as in Example 1, but without adding the sensitizing dye IRT.

[0062] Comparative Example 2 A black resist composition was prepared in the same manner as in Example 1, except that the sensitizing dye was replaced from IRT to 9-phenylacridine (9PA), which is a well-known sensitizer for the long wavelength side of ultraviolet light.

[0063] Comparative Example 3 A black resist composition was prepared in the same manner as in Example 1, except that the black pigment component was replaced from a lactam-based pigment to carbon black.

[0064] Comparative Example 4 In Example 4, a black resist composition was prepared in the same manner as in Example 4, but without adding the sensitizing dye IRT.

[0065] Comparative Example 5 In Example 4, a solution with a composition that did not include the sensitizing dye (IR-797) and the black pigment (Perylene Black), i.e., Solution A, was used as the resist composition of Comparative Example 5.

[0066] The composition of the resist compositions of Examples 1 to 5 and Comparative Examples 1 to 5 manufactured in this embodiment is shown in Table 1 below.

[0067] [Table 1]

[0068] [Pattern formation test using photolithography] The patterns formed by Example 1 to Example 5 and Comparative Example 1 to Comparative Example 5, which were manufactured as described above, were evaluated by photolithography. In this pattern formation test, the following two processes were carried out, taking into consideration the components of the resist composition. Process A: Coating → Pre-baking → Exposure → Development Process B: Coating → Pre-baking → Exposure → PEB → Development

[0069] A glass slide substrate was used as the substrate. In the coating process, the resist composition was dropped onto the center of the glass slide substrate set in a spin coater and rotated at 1000 rpm for 10 seconds to form a uniform coating film. Then, the coated glass slide substrate was pre-baked on a hot plate at 120°C for 1 minute to dry and obtain the resist film. The thickness of the resist film was measured using a stylus-type film thickness gauge and was found to be 10 μm in all cases.

[0070] In the exposure process, the substrate was exposed by passing it through an exposure mask with a Cr pattern. As the light source, an LED chip (emission wavelength: either 850nm or 940nm) was set in a near-infrared lamp unit (UniqueFire UF-120). This lamp unit can approximately emit parallel light by setting the focal point to a long distance using a lens. In Comparative Example 5 only, exposure was performed using ultraviolet light with a mask aligner (g, h, i-line mixed wavelength) as the light source. The exposure time was 3 minutes. For pattern B, post-exposure heat treatment (PEB) was performed after exposure. In this heat treatment, the substrate was heated at 130°C for 1 minute using a direct hot plate.

[0071] In the development process, paddle development was performed using a 1.19% tetramethylammonium hydroxide solution (TMAH solution) as the developer. Afterwards, the substrate was washed with water and air-blown dry.

[0072] The black patterned glass slides obtained through the above process were evaluated. This evaluation involved confirming the presence or absence of a black film (pattern) formation on the substrate, as well as observing the pattern edges with an optical microscope and the cross-sectional shape with an electron microscope. The light-shielding rate of the formed black pattern was also measured using an OD meter (X-rite). The results of this photolithography pattern formation test are shown in Table 2.

[0073] [Table 2]

[0074] For the black resist compositions (negative type) of Examples 1 to 4, the areas shielded by the exposure mask completely dissolved in 15 seconds during the development process, leaving only the desired black pattern. For the black resist composition (positive type) of Example 5, the areas shielded by the exposure mask remained during the development process, while the exposed areas completely dissolved in 15 seconds, resulting in the desired black pattern. Optical microscopy observation of the black patterns confirmed that the pattern edges were very sharp and had excellent edge roughness. Furthermore, electron microscopy observation of the pattern cross-section revealed that it was a rectangle with excellent perpendicularity. In addition, light shielding rate measurements confirmed that the black patterns produced by the black resist compositions of Examples 1 to 5 had good light shielding properties with OD values ​​of 4.8 to 5.3. From the above, it can be said that the black resist compositions of each example can form black patterns of good thickness and shape using near-infrared photolithography. Furthermore, it was confirmed that even with three-component chemically amplified negative resists like those in Examples 4 and 5, or positive resists utilizing deprotection reactions, good results can be obtained by applying suitable black pigments and sensitizing dyes.

[0075] On the other hand, in the case of the black resist compositions of Comparative Example 1 and Comparative Example 2, the entire resist film dissolved and washed away during development in both cases. It is thought that polymerization did not occur because a photoreaction with near-infrared light did not take place. In the case of Comparative Example 1, this is because it does not contain a sensitizing dye, and in the case of Comparative Example 2, although 9-phenylacridine is commonly used as a photosensitizer, it is thought that this also does not produce a photoreaction with near-infrared light.

[0076] In Comparative Example 3, the same pattern as the mask pattern was briefly observed during development, but the entire resist film quickly dissolved and washed away. In this comparative example, it is thought that a slight reaction occurred on the surface layer under near-infrared light, but because the carbon black absorbed and blocked the near-infrared light, the light did not reach the lower layers and polymerization was insufficient.

[0077] In Comparative Example 4, the entire black film dissolved and washed away during development. This was because, although the black resist composition of Comparative Example 4 contained a suitable black pigment, it lacked a photosensitizing dye, and therefore no photoreaction occurred under near-infrared light.

[0078] Comparative Example 5 is a resist composition that does not contain black pigment (Solution A). When this resist film is exposed to ultraviolet light, the pattern edges are sharp and the cross-section is perpendicular. However, because it does not contain black pigment, the OD value is below the lower limit of the measurement limit, and only a nearly transparent film can be obtained. [Industrial applicability]

[0079] The black resist composition and near-infrared photolithography method using the same described above can form a suitable black pattern with excellent light-shielding properties and a rectangular cross-section without edge roughness. The present invention is suitable for manufacturing black matrices for color flat panels such as LCD TVs and smartphone screens, as well as black patterns that form grid-like partitions in display devices combining micro-LEDs and quantum dots, which have been developed in recent years.

Claims

1. A method for forming a black pattern by photolithography, comprising a film formation step of applying and drying a resist composition onto a substrate to form a resist film, an exposure step of exposing the resist film to light, and a development step of developing the exposed resist film, As the resist composition, a black resist composition is applied, which contains components (A) to (D) as essential components as described in (1) below, and components (A) to (C) in the blending ratio described in (2) below. A method for forming a black pattern, characterized in that the resist film is exposed in the exposure step using only near-infrared light with a wavelength of 700 nm to 1000 nm. (1) Components (A) to Components (D) Component (A): Black pigment component consisting solely of black pigment that transmits near-infrared light. Component (B): Sensitizing dye that absorbs in the near-infrared region Component (C): A radical polymerization initiator or acid generator that, when present with the sensitizing dye of component (B), can generate radicals or acids upon near-infrared irradiation. Ingredient (D): Binder resin (2) Mixing ratio of ingredients (A) to (C) Component (A): 3 to 50 parts by weight when the total solid content of the resist composition is 100 parts by weight. Component (B): 0.5 parts by weight or more and 10 parts by weight or less, when the total solid content of the resist composition is 100 parts by weight. Component (C): 0.5 parts by weight or more and 10 parts by weight or less, when the total solid content of the resist composition is 100 parts by weight.

2. The method for forming a black pattern according to claim 1, wherein the near-infrared light-transmitting black pigment of component (A) is a pigment that transmits 50% or more of near-infrared light with a wavelength of 700 nm or more and 1000 nm or less.

3. The method for forming a black pattern according to claim 1, wherein the near-infrared transparent black pigment of component (A) is at least one of a lactam-based pigment, a perylene-based pigment, or an azomethine-based pigment.

4. The method for forming a black pattern according to claim 1, wherein the sensitizing dye of component (B) having absorption in the near-infrared region is a dye having absorption in near-infrared light with a wavelength of 700 nm to 1000 nm.

5. The method for forming a black pattern according to claim 1, wherein the sensitizing dye having absorption in the near-infrared region of component (B) is at least one of a cyanine dye, a squalium dye, and a phthalocyanine dye.

6. The method for forming a black pattern according to claim 1, wherein the radical polymerization initiator or acid generator capable of generating radicals or acids by near-infrared irradiation of component (C) is an iodnium salt, a triazine compound, or a boron ion complex.

7. A method for forming a black pattern according to claim 1, wherein the negative-type photoresist comprises an alkali-soluble resin as the binder resin of component (D), and further comprises either a radical polymerizable monomer or a crosslinking agent as component (E).

8. The method for forming a black pattern according to claim 1, wherein the binder resin of component (D) is a positive-type photoresist containing an alkali-soluble resin protected by an acid-degradable group.

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