Dispersing liquid for black partition wall material

Abstract

This invention provides a dispersion for a black spacer material, which can increase the cone angle of the black spacer material and reduce reflectivity, enabling the fabrication of high-resolution displays. The dispersion for the black spacer material contains lactam black, an acrylic dispersant, a resin, and a solvent; wherein the lactam black has a volumetric particle size D50 value of 20-60 nm and a volumetric particle size D90 value of 40-110 nm, and the acrylic dispersant contains a block copolymer.

Description

Dispersion for black spacer material This invention relates to a dispersion for a black spacer material. More specifically, this invention relates to a dispersion for a black spacer material that can increase the cone angle of the black spacer material and reduce reflectivity, for use in the manufacture of high-resolution displays. Traditionally, the black spacer material used in displays requires high electrical insulation to prevent malfunctions. Carbon black, used as a black colorant, is coated with an insulating material to achieve high electrical insulation. However, in cases of incomplete coating, no electrical insulation is observed, and sufficient reliability cannot be obtained. Furthermore, flexible displays have eliminated the circular polarizer used to prevent reflections, instead using color filters. The black spacer material used in color filters requires a lower reflectivity than conventional methods. Among the black colorants of interest in these applications is lactam black (as shown in Japanese Patent Document 1). [Patent Documents] Patent Document 1: Japanese Patent Application Publication No. 2021-86157 However, the resin composition containing dispersed lactam black described in Japanese Patent Document 1 cannot achieve a sufficient cone angle when used as a black spacer material, and is not suitable for the high precision of displays. The present invention was made in view of the above-mentioned prior art problems, and its object is to provide a dispersion for a black spacer material that can increase the cone angle of the black spacer material and reduce the reflectivity, thereby enabling the manufacture of a high-resolution display. In order to solve the above-mentioned problems, the inventors conducted intensive research and discovered that by simultaneously using micronized lactam black and an acrylic dispersant as a block copolymer, the above-mentioned problems could be solved simultaneously, thus completing the present invention. The present invention, which solves the above problems, mainly includes the following structure. (1) A dispersion for a black spacer material, comprising lactam black, an acrylic dispersant, a resin, and a solvent; wherein the lactam black has a volume-based particle size D50 value of 20-60 nm and a volume-based particle size D90 value of 40-110 nm, and the acrylic dispersant comprises a block copolymer. Based on this structure, a dispersion of black spacer material can be provided, which can increase the cone angle of the obtained black spacer material and reduce the reflectivity, thereby enabling the fabrication of high-resolution displays. According to the present invention, a dispersion for a black spacer material can be provided, which can increase the cone angle of the black spacer material and reduce the reflectivity, thereby enabling the fabrication of a high-resolution display. <Dispersion for Black Spacer Material> One embodiment of the present invention provides a dispersion for a black spacer material (hereinafter also referred to as a dispersion), comprising lactam black, an acrylic dispersant, a resin, and a solvent. The lactam black has a volumetric particle size D50 of 20–60 nm and a volumetric particle size D90 of 40–110 nm. The acrylic dispersant comprises a block copolymer. These will be described separately below. (Lactam Black) Lactam Black is a known type of lactam black having the following structure. Specifically, lactam black is Irgaphor Black S 0100 CF (manufactured by BASF), etc. [Chemical Formula 1] The lactam black of this embodiment is a micronized form of conventional lactam black. The micronization method is not particularly limited. For example, micronization is a method of pretreating conventional lactam black using a water-soluble inorganic salt and a wetting agent. Specifically, the pretreatment can be performed by mixing lactam black with a water-soluble inorganic salt and a wetting agent, and then filtering and washing the resulting pigment. The mixing can be carried out at a temperature of 40–100°C. Filtration and washing can be performed by washing with an inorganic brine solution such as water, followed by filtration. The water-soluble inorganic salt is sodium chloride, potassium chloride, etc. In this embodiment, the volumetric particle size (D50) of the micronized lactam black only needs to be greater than or equal to 20 nm, preferably greater than or equal to 30 nm. Furthermore, a D50 value of less than or equal to 60 nm is acceptable, preferably less than or equal to 50 nm. When the D50 value is less than 20 nm, the dispersion stability of the dispersion deteriorates. On the other hand, when the D50 value is greater than 60 nm, the cone angle of the black spacer material obtained from the dispersion will become smaller, and the reflectivity will increase. In this embodiment, the volumetric particle size (D90) of the micronized lactam black only needs to be greater than or equal to 40 nm, preferably greater than or equal to 50 nm. Furthermore, a D90 value of less than or equal to 110 nm is acceptable, preferably less than or equal to 100 nm. When the D90 value is less than 40 nm, the dispersion stability of the dispersion deteriorates. On the other hand, when the D90 value is greater than 110 nm, the cone angle of the black spacer material obtained from the dispersion will decrease, and the reflectivity will increase. In this embodiment, the volumetric particle size D10 value of the micronized lactam black is preferably greater than or equal to 5 nm, and more preferably greater than or equal to 15 nm. Furthermore, a D10 value is preferably less than or equal to 40 nm, and more preferably less than or equal to 30 nm. In this embodiment, Nanotrack (UPA-EX150, manufactured by Nikkiso Corporation) can be used, and the volume reference particle size can be measured using laser diffraction particle size analysis. The dispersion of this embodiment is characterized by having volumetric particle sizes, particularly D50 and D90, within a predetermined range. That is, when D50 and D90 are within this range, the cone angle of the resulting black spacer material increases, and the reflectivity decreases. In other words, the smaller the pigment particle size, the easier it is for light to pass through, thus reducing reflected light. Furthermore, if the pigment particle size is small, UV light can easily diffract to the inside of the pigment, making it easier to harden overall and thus reducing heat flow. Moreover, when the pigment particle size decreases, the surface area of ​​the pigment interacting with the resin and dispersant increases. As a result, the adhesion of the coating film within the film increases, making heat flow less likely. There is no particular limitation on the content of lactam black. For example, the preferred content of lactam black in the dispersion is ≥5% by mass, and more preferably ≥10% by mass. Additionally, the preferred content of lactam black in the dispersion is ≤30% by mass, and more preferably ≤25% by mass. When the content of lactam black is within the above range, the dispersion stability of the dispersion will be good. (Acrylic Dispersants) Acrylic dispersants include block copolymers (acrylic block copolymers). There is no particular limitation on the type of acrylic block copolymer. For example, an acrylic block copolymer is an acrylic block copolymer containing an amine compound as a monomer. The acrylic block copolymer containing monomers that are amine compounds can have two or more types of blocks. One or more of these blocks are blocks containing monomers that are amine compounds and have unsaturated bonds with free radical polymerizability. The monomers constituting the block are acyclic amine compounds, heterocyclic amine compounds, or quaternary ammonium cation compounds. Preferably, they are acyclic amine compounds, such as dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, and dimethylaminobutyl (meth)acrylate; heterocyclic amine compounds, such as vinylpyridine and pentamethylpiperidinyl (meth)acrylate; and quaternary ammonium cation compounds, such as compounds obtained by quaternizing and cationizing dimethylaminopropyl (meth)acrylate with benzyl chloride. The block can be composed of one of these monomers, or it can be a block formed by random polymerization of two or more monomers, or a block formed by block polymerization of two or more monomers. Furthermore, a particularly preferred material has a structure consisting of blocks of pentamethylpiperidinyl methacrylate and / or dimethylaminopropyl acrylate and blocks formed from other polymerizable vinyl unsaturated monomers. Other polymerizable blocks copolymerized with block copolymers derived from monomers that are amine compounds can be blocks composed of a single monomer or blocks formed by random polymerization of two or more monomers. Preferably, they do not contain units derived from monomers containing amino or pyridine rings. Furthermore, more preferably, they do not contain carboxylic acid groups, hydroxyl groups, mercapto groups, thiol groups, or phosphorus-containing groups. Additionally, blocks formed from other polymerizable vinyl unsaturated monomers can be one or two types. Other polymerizable vinyl unsaturated monomers can be alkyl methacrylates, such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, etc.; glyceryl methacrylates, such as styrene, 2-hydroxyethyl methacrylate, allyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, glyceryl monoacrylate, etc.; monomers, such as N-phenylmaleimide, polystyrene macromonomer, polymethyl methacrylate macromonomer, epoxy diacrylate, etc.; and copolymers with at least one vinyl unsaturated monomer selected from oligomers. However, the use of N-vinylpyrrolidone and sulfur-containing monomers is undesirable. Block copolymers can be block resins synthesized using living radical polymerization or anionic polymerization. There is no particular limitation on the content of acrylic dispersants. For example, the content of acrylic dispersants in the dispersion is preferably greater than or equal to 0.5% by mass, more preferably greater than or equal to 1.0% by mass. Additionally, the content of acrylic dispersants in the dispersion is preferably less than or equal to 30.0% by mass, more preferably less than or equal to 25.0% by mass. When the content of acrylic dispersants is within the above ranges, the dispersion can be easily prepared to have a particle size within the desired particle size distribution range, and the dispersion stability is improved. (Resin) There are no particular limitations on the type of resin. For example, alkali-soluble resins are preferred, and acrylic copolymer resins, maleic acid copolymer resins, polyester resins obtained through polycondensation reactions, and polyurethane resins are even more preferred. Among these, acrylic copolymer resins are preferred in terms of developability, range of molecular design, and cost. Using alkali-soluble resins, the dispersion can be developed with alkaline developers, allowing the creation of patterns such as spacing. There are no particular limitations on alkali-soluble resins. For example, alkali-soluble resins contain anionic groups such as carboxyl groups, sulfonic acid groups, and phosphonic acid groups (-P(=O)(OH). 2)) resin. From the perspective of alkaline developability, the optimal acid value for alkali-soluble resins is greater than or equal to 10 mg KOH / g, and even better is greater than or equal to 20 mg KOH / g. Furthermore, the optimal acid value is less than or equal to 300 mg KOH / g, and even better is less than or equal to 200 mg KOH / g. From the perspective of photoresist film formation, the preferred weight-average molecular weight (MAM) of alkali-soluble resins is ≥5,000, and more preferably ≥10,000. Furthermore, from the perspective of improving solubility, the preferred MAM of alkali-soluble resins is ≤100,000, and more preferably ≤50,000. The MAM can be measured using gel permeation chromatography (GPC). For example, using a Water2690 (manufactured by Waters) as the GPC apparatus, a PLgel, 5μm, MIXED-D (manufactured by Polymer Laboratories) column, tetrahydrofuran as the developing solvent, and chromatographic analysis under the following conditions—column temperature 25°C, flow rate 1 mL / min, RI detector, sample injection concentration 10 mg / mL, and injection volume 100 μL—the MAM converted from polystyrene can be determined. Alkali-soluble resins include acrylic copolymer resins, maleic acid copolymer resins, polyester resins obtained through polycondensation reactions, and polyurethane resins. Among these, acrylic copolymer resins are considered superior in terms of developability, molecular design range, and cost. There is no particular limitation on the content of alkali-soluble resin. For example, relative to 100 parts by weight of lactam black, the preferred content of alkali-soluble resin is greater than or equal to 5 parts by weight, and more preferably greater than or equal to 10 parts by weight. Furthermore, the preferred content of alkali-soluble resin relative to 100 parts by weight of lactam black is less than or equal to 90 parts by weight, and more preferably less than or equal to 80 parts by weight. (Solvents) There are no particular restrictions on solvents. For example, from the viewpoint of being able to stably disperse lactam black and fully dissolve resins, better solvents are ester solvents, ether solvents, ether ester solvents, ketone solvents, aromatic hydrocarbon solvents, nitrogen-containing solvents, etc. Ester solvents can be: methyl 2-hydroxypropionate, ethyl 2-hydroxypropionate, ethyl 2-hydroxy-2-methylpropionate, 3-methyl-3-methoxybutylpropionate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, ethyl ethoxypropionate, glycolic acid ester, n-pentyl formate, etc. Ether solvents can be: ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, etc. Ether ester solvents can be: ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, etc. Ketone solvents can include: methyl isobutyl ketone, cyclohexanone, 2-heptanone, δ-butyrolactone, etc. Aromatic hydrocarbon solvents can include toluene, xylene, and alkylnaphthalene. Nitrogen-containing solvents include N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide. There is no particular limitation on the solvent content. For example, the solvent content in the dispersion is preferably 40% or more by mass, and more preferably 50% or more by mass. Alternatively, the solvent content in the dispersion is preferably 90% or less by mass, and more preferably 80% or less by mass. Because the solvent content is within the above range, the dispersion stability of lactam black in the dispersant is excellent. Returning to the overall description of the dispersion, the method for manufacturing the dispersion in this embodiment is not particularly limited. For example, the dispersion can be manufactured by mixing various materials and grinding them for 24 hours using a bead mill or similar equipment. The dispersion in this embodiment can increase the cone angle of the black spacer material and reduce the reflectivity, enabling the production of high-resolution displays. <Black Spacer Material> The black spacer material is formed by curing the aforementioned dispersion. Specifically, firstly, the dispersion of this embodiment is coated onto a substrate to form a resin layer (coating). Then, the resin layer is exposed using a mask with a predetermined pattern to photocur the exposed portions. Next, the unexposed and partially exposed portions are developed using an alkaline developer to form the black spacer material. Finally, the black spacer material is post-baked as needed. There are no particular limitations on the substrate. For example, the substrate can be a glass substrate, a silicon substrate, a polycarbonate substrate, a polyester substrate, a polyamide substrate, a polyamide-imide substrate, a polyimide substrate, an aluminum substrate, a printed wiring substrate, an array substrate, etc. There are no particular restrictions on the coating method for the dispersion. For example, coating methods can include screen printing, roller coating, curtain coating, spraying, and spin coating. Additionally, after coating, heating devices such as circulating ovens, infrared heaters, and heating plates can be used as needed to evaporate the solvent in the resin layer. The heating conditions should be appropriately set according to the composition of the dispersion used; generally, heating conditions are at a temperature of 50℃ to 120℃ for 30 seconds to 30 minutes. There are no particular limitations on the exposure method for the resin layer. For example, exposure methods can include ultraviolet irradiation, excimer laser irradiation, or irradiation with active energy lines. The energy level can be appropriately set according to the composition of the dispersion. For example, the energy level for dyes can be 30–2000 mJ / cm². 2 There are no particular limitations on the light source used for exposure. For example, the light source can be a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, a xenon lamp, a metal halide lamp, etc. There are no particular limitations on the alkaline developers used for development. Examples of developers include: aqueous solutions of sodium carbonate, potassium carbonate, calcium carbonate, sodium hydroxide, potassium hydroxide, etc.; aqueous solutions of amine compounds, such as ethylamine, diethylamine, and dimethylethanolamine; and aqueous solutions of p-phenylenediamine compounds, such as tetramethylammonium, 3-methyl-4-amino-N,N-diethylaniline, 3-methyl-4-amino-N-ethyl-N-β-hydroxyethylaniline, 3-methyl-4-amino-N-ethyl-N-β-methanesulfonylaminoethylaniline, 3-methyl-4-amino-N-ethyl-N-β-methoxyethylaniline, and their sulfates, hydrochlorides, or p-toluenesulfonates. Additionally, defoamers and surfactants may be added to the alkaline developer as needed. The black spacer material formed by alkaline development can be post-baked to promote resin curing. There are no particular restrictions on the post-baking conditions. For example, post-baking conditions can be a temperature of 80°C to 250°C and a time of 10 minutes to 4 hours. The resulting black spacer material has a large cone angle and low reflectivity, making it suitable for manufacturing high-resolution displays. <Image Display Device> The image display device (display) of this embodiment includes the aforementioned black spacer material. Specific examples of image display devices include liquid crystal display devices and organic EL display devices. The image display device can be manufactured using conventional methods, except for forming the aforementioned black spacer material. [Examples] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In addition, unless otherwise specified, "%" means "mass %" and "parts" means "parts by mass". The raw materials used are as follows. <Lactam Black> Lactam Black: Irgaphor S100CF (manufactured by BASF) • Preparation of Finely Blended Lactam Black: In a Trimix TX-15 container (manufactured by Inoue Manufacturing Co., Ltd., Japan), 800 parts by weight of the above-mentioned lactam black, 8000 parts by weight of sodium chloride with a particle size of 20 μm, and 1920 parts by weight of diethylene glycol were added. The mixture was kneaded at 45°C for 3 hours within 70% of the rated current of 9.3A, and then salt-milled. 1300 parts by weight of the resulting mixture were added to 3 liters of warm water and stirred for 1 hour while heating to 70°C to form a slurry. After repeated filtration and washing with water to remove sodium chloride and diethylene glycol, the mixture was dried at 40°C for 24 hours to obtain 95 parts by weight of finely blended lactam black. • Preparation of Finely Blended Lactam Black (SOLTRIM-Fortified): In the above-described method for manufacturing finely blended lactam black, except that 400 parts by mass of lactam black were kneaded for 6 hours, the same process was performed to obtain 40 parts by mass of finely blended lactam black (salt-milled fortified). <Dispersant> • Preparation of Acrylic Dispersant (ABA Triblock): 17 g of methyl methacrylate (MMA), 24 g of butyl methacrylate (BMA), 1 L of tetrahydrofuran (THF), and 4.5 mmol of a hexane solution of n-butyllithium were added to a degassed glass container, and a random copolymer moiety was synthesized from MMA and BMA. The mixture was then cooled to -78°C and stirred for 2 hours. Then, 33 g of pentamethylpiperidinium methacrylate (PMPMA) was added and stirred for 2 hours to synthesize the PMPMA block moiety bonded to the random copolymer moiety of MMA and BMA. Add 17g of MMA and 24g of BMA to synthesize an ABA-type triblock copolymer. Stir for 2 hours and then stop the reaction. The synthesized solution is added dropwise to a large amount of methanol to precipitate the copolymer. Collect the dispersant on filter paper, wash several times with methanol, and dry under reduced pressure at 60°C to obtain an acrylic dispersant. The obtained acrylic dispersant is an ABA triblock copolymer with the following composition: BMA / MMA / / b-PMPMA / / b-BMA / MMA = (24 / 17) / / 18 / / (24 / 17). Monomers separated by " / " are randomly polymerized, and monomers separated by " / / b-" form a block structure.Acrylic dispersant (grafted): BYKJET-9151 (manufactured by BYK Chemical Co., Ltd., Japan) Polyurethane dispersant (grafted): DISPERBYK-167 (manufactured by BYK Chemical Co., Ltd., Japan) <Photopolymerizable compound> DPEHA: Dipentaerythritol hexaacrylate <Photoinitiator> Irgacure OXE02 (manufactured by BASF) <Solvent> PGME: Propylene glycol monomethyl ether PGMEA: Propylene glycol methyl ether acetate <Resin> Follett ZAH-110 (alkali-soluble photosensitive resin, solid content 35% by mass, manufactured by Soken Chemical Co., Ltd., Japan) ZCR-1569H (alkali-soluble photosensitive resin, solid content 70% by mass, manufactured by Nippon Kayaku Co., Ltd.) <Leveling agent> Megafac F-554 (manufactured by DIC). <Examples 1-4, Comparative Examples 1-6> (Preparation of Pigment Dispersions for Black Spacer Materials) Various materials were mixed according to the compositions shown in Table 1 (unit: mass %) and kneaded overnight in a bead mill to prepare pigment dispersions for black spacer materials as in Examples 1-4 and Comparative Examples 1-6. The particle sizes of the dispersed compositions in the obtained dispersions were measured using a Nanotrac (manufactured by Nikkiso Co., Ltd., UPA-EX150) and laser diffraction method, specifically D10, D50, and D90 particle sizes. The results are shown in Table 1. (Preparation of a pigment dispersion photoresist composition for black spacer materials) Using a high-speed mixer, 40.00 parts by weight of the above-mentioned pigment dispersion with a concentration of 15% by weight, 10.60 parts by weight of alkali-soluble photosensitive resin ZCR-1569H, 3.00 parts by weight of PEHA, 0.80 parts by weight of Irgacure OXE02, MegaFac F-554, and 45.55 parts by weight of PGMEA were uniformly mixed and then filtered through a filter with a pore size of 3 μm to obtain a pigment dispersion photoresist composition for black spacer materials. The obtained photoresist composition was used, and the viscosity stability, cone angle, and reflectivity were measured using the following methods. The results are shown in Table 1. (Viscosity Stability) The black spacer materials of the above examples and comparative examples were stored at 40°C for one week using pigment dispersion photoresist compositions. The viscosity changes before and after storage were measured and evaluated according to the following evaluation criteria: ○: Viscosity change is less than or equal to 10%. △: Viscosity change exceeds 10% but is less than or equal to 20%. ×: Viscosity change exceeds 20%. (Conical Angle) The black spacer material of the above-described examples and comparative examples, along with the pigment dispersion photoresist composition, was coated onto a glass substrate (Corning 1737) using a spin coater to achieve a film thickness of 1 μm. The substrate was then pre-baked at 100°C for 2 minutes. Afterward, the gap between the patterned photomask and the substrate was set to 20 μm, and a high-pressure mercury lamp was used at a UV cumulative light intensity of 40 mJ / cm². 2 Exposure was performed at 23°C. Development was carried out using a 2.4% (w / w) aqueous solution of TMAH (tetramethylammonium hydroxide) at a spray pressure of 0.07 MPa, followed by rinsing with water at a spray pressure of 0.07 MPa. Afterward, post-baking was performed at 250°C for 30 minutes. The resulting substrate was divided along the pattern width using a glass cutter. The division surfaces of the 6μm pattern were observed using an electron microscope, and the cone angle was measured using image analysis. The results are shown in Table 1. A larger cone angle is better. (Reflectivity) Perform the same operation as described above for the cone angle, but without post-exposure development. Bake at 100°C for 30 minutes to obtain a coating formed only in the β region. The average reflectivity (in %) of the obtained β-region coating surface at wavelengths of 360–740 nm was measured using a reflectometer (photoal MC-7300:SC, ​​manufactured by Otsuka Electronics Co., Ltd., Japan). The results are shown in Table 1. A lower average reflectivity is better. [Table 1] As shown in Table 1, the dispersion for the black spacer material of the present invention is prepared with small viscosity variation and volume-based particle size (especially D50 and D90 values) within a predetermined range. Therefore, when used as a black spacer material, the dispersion for the black spacer material of the present invention can increase the cone angle and obtain a low-reflectivity coating, making it suitable as a display material. none none

Claims

1. A dispersion for a black spacer material, comprising lactam black, an acrylic dispersant, a resin, and a solvent; wherein the lactam black has a volumetric particle size D10 value of 5–40 nm, a volumetric particle size D50 value of 20–60 nm, and a volumetric particle size D90 value of 40–110 nm, and the acrylic dispersant contains a block type copolymer.