JP5320652B2 - Method for producing resin-coated carbon black - Google Patents

Description

  The present invention relates to a resin-coated carbon black and a color filter. The high-resistance carbon black of the present invention is suitable as an insulating black matrix for optical color filters or a carbon black for spacers used in, for example, color televisions, liquid crystal color televisions, cameras, and the like.

  The liquid crystal display device encloses a liquid crystal substance in a gap of about 1 to 10 μm formed of a transparent substrate such as glass provided with a transparent electrode, aligns the liquid crystal in a certain direction by a voltage applied between the electrodes, An image is displayed by forming a transparent part and an opaque part. A color liquid crystal display device is provided with a color filter of three colors of red (R), green (G), and blue (B) corresponding to the three primary colors of light on any transparent substrate, and a voltage applied to the transparent electrode. Is adjusted to control the light transmission of the liquid crystal, the amount of light transmitted through the filters of the three colors R, G, and B is controlled, and color display is performed by color development by adding the three primary colors.

  As a method for forming the colored layers of R, G, and B, a method of forming on a substrate provided with a black matrix film that partitions each color in advance, or a black matrix film after forming R, G, and B There are various methods of providing the black matrix, but the role of the black matrix is that each of the three primary colors of R, G, and B and a transistor such as a TFT (thin film transistor) for driving a liquid crystal provided on a substrate facing the color filter The point is to shield the light.

  One of the black matrixes of the color filter used for the above-mentioned purposes is one obtained by patterning a resist (photopolymerizable composition) film in which carbon black is dispersed as a black material.

  By the way, in the photopolymerization of a resist in which carbon black is dispersed, there is a problem that the polymerization is inhibited by a quinone group, a phenolic hydroxyl group or the like present on the surface of the carbon black. Therefore, various carbon blacks (hereinafter abbreviated as “graft carbon black”) subjected to graft reaction treatment with a compound capable of reacting with the polymerization-inhibiting functional group as described above have been proposed (JP-A-6-214385, 8-337736, 9-3356, 11-24269, 11-52564, etc.). According to such graft carbon black, the radical scavenging property is suppressed, and a black resist with improved photocurability can be obtained.

  Carbon black is essentially a conductive material, and a resist film in which carbon black is dispersed also has a problem of showing conductivity or semiconductivity. Therefore, conventionally, carbon black having a high resistance (insulating property) while maintaining its light shielding property has been desired. In the case of graft carbon black, only the polymerization-inhibiting functional group on the surface is graft-reacted, and the surface is substantially exposed.

  Therefore, the present applicants have conventionally proposed a number of proposals for carbon black coated with a multifunctional epoxy resin or the like for a black matrix of a color filter and a method for producing the same (Japanese Patent Laid-Open No. 9-26571). JP-A-9-71733, JP-A-9-95625, JP-A-9-124969, JP-A-9-304760, JP-A-10-60169, JP-A-10-330643, (Kaihei 10-60988, JP-A-10-60989, JP-A-11-80583, JP-A-11-80584, etc.). In addition, proposals have been made on high-resistance carbon black obtained by subjecting the surface to specific oxidation treatment (Japanese Patent Laid-Open Nos. 11-181324 and 11-181326). However, the volume specific resistance value of carbon black according to the prior art as described above remains at most in the range of about 5 to 50 Ω · cm.

Problems to be solved by the invention

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a black resist having improved photocurability, thereby providing a black matrix having a high light-shielding rate and a low surface reflectance, and a thin film. An object of the present invention is to provide a resin-coated carbon black. Another object of the present invention is to provide a color filter using the above carbon black as a black matrix.

Means for solving the problem

[Means for Solving the Problems]
That is, the gist of the present invention is that the surface of carbon black is subjected to a graft reaction treatment with a compound capable of reacting with a functional group present on the surface, and then coated with a resin emulsion, followed by a heating treatment, whereby a volume resistivity is obtained. The present invention resides in a method of producing a resin-coated carbon black having a value of 100 Ω · cm or more .

  First, the resin-coated carbon black of the present invention will be described. The resin-coated carbon black of the present invention has a surface subjected to a graft reaction treatment with a compound capable of reacting with a functional group present on the surface and is coated with a resin, and is usually coated with a resin after the graft reaction treatment. Therefore, the resin-coated carbon black of the present invention is correctly a resin-coated graft carbon black.

The carbon black used in the present invention is not particularly limited, but a carbon black having a value obtained by dividing the volatile component by the specific surface area (the amount of volatile component per unit specific surface area) is preferably 0.01 (% · g / m 2) or more. The amount of volatile matter per unit specific surface area is preferably 0.02 (% · g / m ² ) or more, more preferably 0.03 (% · g / m ² ) or more. Here, the attribute of the amount of volatile matter per unit specific surface area indicates that carbon black with a larger specific surface area gives more volatile matter, but the volume resistivity described later is not the absolute amount of volatile matter but the unit surface. This is because it correlates with the amount of volatile matter imparted to the.

The volatile matter of carbon black can be raised by oxidation treatment of carbon black with ozone and / or hydrogen peroxide. In general, as the oxidizing agent for carbon black, there are nitric acid, NO gas, NO ₂ gas, air, SO ₃ gas, fluorine gas, etc. in addition to the above, but the volume of volatile matter per unit specific surface area is relatively small. The resistance is improved when ozone and / or hydrogen peroxide is used as an essential oxidizing agent in combination with the above oxidizing agents such as nitric acid and NO ₂ gas.

  The measurement of the volatile content is obtained by a method of calculating as a weight loss percentage when carbon black is heated at 950 ° C. for 7 minutes in accordance with JISK 6221. The specific surface area is determined by a nitrogen adsorption method using the BET equation. That is, the nitrogen adsorption amount of carbon black was measured by a low temperature nitrogen adsorption method using a low temperature nitrogen adsorption device (Italy, “Carrot Elba” “Soptomatic 1800”), and then by a multipoint method using the BET equation. Can be calculated.

  Carbon black having an ash content of 1.0% by weight or less, particularly 0.5% by weight or less is preferred. The main components of ash are alkali metals such as Na, K, and Ca, alkaline earth metals, and the like, and carbon black having a high content is difficult to improve the volume resistivity. Such reduction of the ionic conductive material is achieved by selecting the raw material oil, gas, and additive used for the production of carbon black. It can also be achieved by rinsing or pickling the carbon black produced from the production furnace. The ash content can be calculated from the amount of ash remaining when carbon black is baked in air at 750 ° C. for 5 to 6 hours.

  The compound used for the carbon black graft reaction treatment is not limited as long as it is a compound that can react with a polymerization-inhibiting functional group, for example, photopolymerization having an ethylenically unsaturated double bond and other functional groups. Compound. Examples of the functional group other than the ethylenically unsaturated double bond include an epoxy group, a thioepoxy group, an aziridine group, an oxazoline, an N-hydroxyalkylamide group, an isocyanate group, and an amino group. Specific examples of the compound include glycidyl (meth) acrylate, allyl glycidyl ether, 2,3-epithiopropyl (meth) acrylate, N- (meth) acryloylaziridine, 2- (1-aziridinyl) ethyl (meth) acrylate, 2- Examples thereof include isopropenyl-2-oxazoline, N-hydroxyethyl (meth) acrylamide, isocyanate ethyl (meth) acrylate, and allylamine (Japanese Patent Laid-Open No. 8-33777).

  Further, a compound having at least one reactive group selected from the group consisting of an aziridine group, an oxazoline group, an N-hydroxyalkylamide group, an epoxy group and a thioepoxy group in the molecule (JP-A-6-214385, 11-24269, 11-52564) Unsaturated epoxy ester resin having an epoxy group and an ethylenically unsaturated double bond in one molecule (Japanese Patent Laid-Open No. 9-3356) can also be used.

  The carbon black grafting treatment varies depending on the compound used, and can be determined with reference to the descriptions in the publications. For example, when a compound described in JP-A-8-337736 is used, the following procedure is followed according to the description in the same publication.

  That is, carbon black and a compound (photopolymerizable compound having an ethylenically unsaturated double bond and other functional group) used for the graft reaction treatment are heat-treated in the presence of a solvent as necessary. Solvents include hydrocarbons such as toluene and xylene, cellosolves such as cellosolve and butylcellosolve, carbitols such as carbitol and butylcarbitol, esters such as cellosolve acetate and carbitol acetate; ketones such as methylethylketone, And ethers such as diethylene glycol dimethyl ether. The use ratio of the above compound is usually 1 to 500 parts by weight with respect to 100 parts by weight of carbon black, and the reaction temperature is usually 50 to 250 ° C., preferably 100 to 200 ° C.

  The resin used for coating the carbon black is not particularly limited, but is preferably an epoxy resin, particularly a polyfunctional epoxy resin. Specific examples of the polyfunctional epoxy resin include glycidylamine epoxy resin, triphenylglycidylmethane epoxy resin, tetraphenylglycidylmethane epoxy resin, aminophenol epoxy resin, diaminodiphenylmethane epoxy resin, phenol novolac epoxy resin, Orthocresol type epoxy resin bisphenol A novolac type epoxy resin and the like can be mentioned.

  For example, in the case of an epoxy resin, it is possible to use a curing agent or a curing accelerator as a means for controlling the volume resistivity or surface property of the resin-coated carbon black. By using these, it is possible to impart excellent properties such as insulation and heat resistance to the coated resin.

  Although it does not restrict | limit especially as a hardening | curing agent, From a viewpoint of giving the characteristic to insulation, an acid anhydride, an imidazole compound, or BF3 complex is preferable. Furthermore, in view of the efficiency in the reaction process, an imidazole compound having a relatively low curing time and a short curing time is preferable.

  Typical imidazole compounds include 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1-benzyl-2-methylimidazole, 1 -Cyanoethyl-2-methylimidazole, 2,4diamino-6- [2-methylimidazolyl- (1)]-ethyl S-triazine and the like. The amount of the curing agent used is usually 1 to 30% by weight, preferably 5 to 25% by weight, and more preferably 10 to 20% by weight, as a ratio to the total amount of the resin and the curing agent. The kind and amount of the curing accelerator can be selected according to the kind of the curing agent to be used according to a conventional method.

  The carbon black resin coating is preferably carried out by adding a resin emulsion to the carbon black dispersion. A resin solution can also be used in place of the resin emulsion.

  For the preparation of the above resin emulsion, a surfactant, alcohol or the like can be used. The surfactant is not particularly limited as long as a resin emulsion can be formed, but a surfactant that is nonionic or amphoteric and does not contain a metal is preferable. Moreover, the surfactant of HLB8-18 suitable for O / W emulsion is preferable. The diameter of the resin emulsion is preferably 10 microns or less, particularly 5 microns or less. By using the resin emulsion, the uniformity of the resin coated on the carbon black aggregate is stabilized, and the surface coating state becomes uniform.

  After the resin emulsion is added to the carbon black dispersion, the resin in the dispersion is cured by heating treatment. The heating treatment conditions in this case differ depending on the volume specific resistance value of the target resin-coated carbon black, the type of resin, and the presence or absence of the use of a curing accelerator, but 3,000 Ω · cm or more using a curing agent. In order to prepare a high resistance carbon black, it is necessary to perform a heating treatment at 70 ° C. for 4 hours or more after the evaporation of the solvent.

  The coating amount of the resin on the carbon black is preferably 5 to 40% by weight, particularly 7 to 20% by weight, based on the total amount of the carbon black and the resin. When the coating amount is less than 5% by weight, only dispersibility, dispersion stability, and volume resistivity value similar to those of untreated carbon black may be obtained. On the other hand, when the coating amount exceeds 40% by weight, the resin for fusing the agglomerates becomes excessive, and the dispersibility may be lowered.

  The volume resistivity of carbon black (powder) coated with resin is about 2g of sample in a 2cm inner diameter Teflon container with a brass electrode attached to the bottom, and a Teflon rod with a brass electrode at the tip. Then, the load is applied at a rate of 0.2 mm / min with Tensilon, and the resistance at 50 kg / cm 2 is measured with a high sensitivity tester. Then, the volume resistivity is calculated from the bulk of the powder under this load and the resistance value by the following equation.

Volume resistivity (Ω · cm) = Cross sectional area of carbon black powder (cm ² ) × resistance value (Ω) / bulk height of carbon black powder (cm)

  Further, the carbon black coated with the resin preferably has a pH measured in the state of a water slurry of 5 or more, particularly 7 or more. And the upper limit of pH is 10 normally. These pH values mean values for a water slurry after adding 10 g of carbon black coated with resin to 100 ml of water and thoroughly stirring for 5 minutes.

  The high-resistance carbon black of the present invention as described above is suitably used as a black material in a color filter having a black matrix obtained by patterning a resist film in which a black material is dispersed. The volume resistivity value of the high resistance carbon black of the present invention is 100 Ω · cm or more, preferably 3,000 Ω · cm or more, more preferably 5,000 to 5,000,000 Ω · cm. .

  Next, the color filter of the present invention will be described. The color filter of the present invention is characterized in that, in a color filter having a black matrix obtained by patterning a resist film in which a black material is dispersed, the above-described carbon black is used as the black material. That is, the color filter of the present invention is basically the same as a conventionally known one, and the surface of the transparent substrate provided with the above black matrix has a hue of three colors of R, G, and B, and 10 to 150 μm. It is manufactured by forming a color pattern such as a stripe shape or a mosaic shape with a width of several μm.

  The black matrix can be formed by applying a resist (photopolymerizable composition) in which carbon black is dispersed on a transparent substrate, and then performing heat drying, image exposure, development, and heat curing. . In the above color filter, each photopolymerizable composition in which R, G, and B are dispersed is applied to the black matrix forming surface, and each process of heat drying, image exposure, development, and thermosetting is performed. It can be manufactured by sequentially forming pixel images of respective colors. A counter electrode (transparent electrode) for driving the color filter is formed in a thin film shape on the pixel image surface from ITO or the like.

  The above-mentioned photopolymerizable composition for black matrix or each color includes carbon black or each color, a photopolymerization initiation system that generates radicals by absorbing light, and addition-polymerizable ethylene in which polymerization is induced by the radicals. And a compound having at least one polymerizable unsaturated double bond (ethylenic compound). Moreover, said composition contains a dispersing agent etc. as needed with an organic polymer substance (binder resin). And said composition is used as a coating liquid prepared with the suitable solvent. The photopolymerization initiation system, ethylenic compound, organic polymer substance and solvent are appropriately selected according to the purpose of the resist pattern.

  As the coating device, a spinner, a wire bar, a flow coater, a die coater, a roll coater, a spray, or the like is used. Image exposure is performed by introducing a negative matrix pattern mask onto the photopolymerizable layer and irradiating an ultraviolet or visible light source through the pattern mask. As the alkali developer, for example, an inorganic alkali agent such as sodium carbonate, potassium carbonate, sodium silicate, potassium silicate, sodium hydroxide, potassium hydroxide, or the like is used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded.

Examples 1-2 and Comparative Example 1
Carbon black was produced by a normal oil furnace method except that raw material oil with less Na · Ca · S was used and water treated with an ion exchange resin was used as reaction stop water. Then, 100 g of the obtained carbon black was put into a cylindrical kiln having an inner diameter of 10 cm and a length of 10 cm, and contacted with a mixed gas of air and ozone (ozone 6,000 ppm) at room temperature for 4 hours while rotating at 9 rpm. Table 1 shows the physical properties of carbon black.

  First, according to Example 1 of JP-A-8-337736, a separable flask equipped with a stirring blade and a reflux condenser was charged with 30 g of glycidyl methacrylate, 90 g of each of the above carbon blacks, and 480 g of ethyl carbitol acetate, and a 3 mm diameter stainless steel. 6000 g of beads were added and stirred at 160 ° C. for 30 minutes to obtain a mixture of graft carbon black and ethyl carbitol acetate (concentration of graft carbon black of 20% by weight).

  Next, after the grafted carbon black was recovered by a centrifugal separator, unreacted glycidyl methacrylate adhered to the carbon black was removed by vacuum drying (100 ° C., 0.1 torr, 10 hrs). Thereafter, the surface oxidation treatment (additional oxidation) was performed again for the half amount of the graft carbon black under the same conditions as described above.

  Next, 30 g of each of the above graft carbon blacks with or without additional oxidation was dispersed in 650 cc of pure water. At this time, ethanol was used as a dispersant, and a sand mill containing zirconia beads having a diameter of 1 mm was used as a disperser, and carbon black of 5 microns or less was selected by filtration.

  Next, 0.7 g of a curing agent was added to a resin solution dissolved in toluene (phenol novolac-type epoxy resin: 3.4 g, toluene: 30 cc) and sufficiently dissolved, and then 300 cc of water and 60 cc of ethanol were added, and 9000 by a homogenizer. A resin emulsion was prepared by stirring for 30 minutes by rotation. The curing agent used here is 2-ethyl-4-methylimidazole (“EMI24” manufactured by Yuka Shell Epoxy). The diameter of the obtained resin emulsion was 5 microns.

  Next, the carbon black surface was coated with a resin. Specifically, after gradually adding the above resin emulsion while stirring the carbon black dispersion with a screw, the mixture was heated while maintaining stirring, and cured at 70 ° C. for 4 hours after toluene evaporated. It was.

  Subsequently, after draining by filtration, it put into the vacuum dryer, it was made to dry at 62 degreeC for 10 hours, the water | moisture content and the solvent were removed, and resin coating carbon black was obtained. The resulting resin-coated carbon black had a residual solvent amount of about 50 ppm and a residual water content of about 500 ppm. Table 1 shows the results of measuring physical properties of the resin-coated carbon black.

  Next, a resist composition for a black matrix was prepared by the following method using the above carbon black. That is, 32 g of carbon black and 150 g of propylene glycol monomethyl ether acetate (hereinafter abbreviated as “PGMEA”) as a solvent were added to a sand mill containing 300 g of 1 mm zirconia beads, and a dispersion was obtained by mixing and dispersing at 2000 rpm for 10 hours. It was. In a 140 cc mayonnaise bottle containing 90 g of 1 mm zirconia beads, 45 g of the above dispersion, 1.13 g of dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku Co., Ltd.) as an ethylene compound, bisphenol A and epichlorohydrin 1.13 g of a monomer to be polymerized (“SP-1509” manufactured by Showa Polymer Co., Ltd.), 0.37 g of ethyl P-diethylaminobenzoate and 39 g of PGMEA as a photopolymerization initiator composition were added and dispersed for 30 minutes with a paint conditioner. Thus, a black matrix resist composition was obtained.

  Next, the above resist composition was applied on a 1.1 mm thick glass substrate (Corning “No. 7059”) subjected to high pressure water washing, ultraviolet irradiation and ozone treatment, and a metal substrate by spin coating. And a heat treatment under a temperature condition of 220 ° C. to form a resist thin film having a thickness of 1.0 μm. The thin film on the glass substrate was used for OD (optical density) measurement, and the thin film on the metal substrate was used for volume resistivity measurement. Table 2 shows the physical properties of the resist thin film. The OD (optical density) values in Table 3 were measured using a Macbeth reflection densitometer (“RD-914” manufactured by Sakata Inx Corporation). Further, the volume resistivity was measured in the thickness direction of the resist thin film using a high resistance measuring machine (“HIRESTA MCP-HT210” manufactured by Yuka Electronics Co., Ltd.).

The resist composition was applied by spin coating so that the dry film thickness on the glass substrate was 1 μm, and the coating film was dried at 100 ° C. for 10 seconds. A 10 μm line / space photomask was used for the resulting film, and the film was exposed at 100 mJ for 30 seconds with an ultrahigh pressure mercury lamp, and then immersed in a 1 wt% Na ₂ CO ₃ aqueous solution to observe the pattern formation. And when the pattern omission is slightly observed, it is photocuring (Δ), when the pattern omission is very slightly observed, it is photocurable (O), and when no pattern omission is observed, it is cured. It was set as the property (◎) The results are shown in Table 1.

Effect of the invention

  According to the present invention described above, a black resist with improved photocurability is provided, thereby providing a resin-coated carbon black capable of providing a thin black matrix with a high light shielding rate and low surface reflectance. The industrial value of the present invention is remarkable.

Claims (1)

  After the surface of carbon black is subjected to a graft reaction treatment with a compound capable of reacting with a functional group present on the surface, it is further coated with a resin emulsion and heated to have a volume resistivity of 100 Ω · cm or more. A method for producing a resin-coated carbon black, comprising obtaining a resin-coated carbon black.