JP2003041149A - Carbon black for black matrix and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon black which has a high light-shielding property and blackness and is suitable for forming a black matrix having extremely low conductivity, and a method for producing the same. A nitrogen adsorption specific surface area (N ₂ SA) of 50 m ² / g or more, and DBP absorption amount by oxidizing the following carbon black 140cm ^3/100 g, total carbon atoms per measured by X-ray photoelectron spectroscopy The value of the atomic ratio (intensity of oxygen binding energy / intensity of carbon binding energy) of all the oxygen atoms of the above is set to 0.
A functional group on the surface of carbon black that has been oxidized to at least one is converted into an azo group to form a backbone, and a vinyl polymer formed by radical graft polymerization of a monomer containing a vinyl group is chemically bonded to the backbone. Carbon black for black matrix and its manufacturing method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a black matrix pigment having a high light-shielding property and a high degree of blackness and an extremely low conductivity, as a pigment for a black matrix used in color filters for liquid crystal display devices, plasma displays and the like. And a method for producing the same.

[0002]

2. Description of the Related Art A liquid crystal display controls a transmission of incident light by sandwiching a crystal material to be a liquid crystal between transparent electrodes and applying a voltage between the electrodes to change the molecular arrangement of the liquid crystal. Image and characters are displayed by combining and because it consumes less power,
It is widely used as a display device for mobile phones, watches, cameras, and various electric devices.

A color liquid crystal display in which this liquid crystal display is colorized is one in which red, blue, and green color filters are attached to each pixel to create the three primary colors of light, and the brightness of each pixel is controlled to express a color change. Is. That is,
The color filter creates pixels of three primary colors of red, blue, and green on a transparent substrate, controls the amount of light that passes through each pixel, and performs color display by coloring by adding the three primary colors. A blocking layer (black matrix) for blocking light between each pixel is formed in order to prevent deterioration of contrast and color purity.

Naturally, the black matrix is required to have excellent light-shielding properties, but in addition, the surface is smooth, the layer thickness is thin, and the conductivity is small.
Are needed. That is, when the surface smoothness is poor and the layer thickness is large, unevenness occurs when forming the color patterns of the three primary colors, and when the conductivity is high, the semiconductor element may malfunction due to the applied voltage. is there.

As the black matrix, a black matrix made of a metal thin film of Cr, Ni, Al or the like by a photolithography method, a black matrix made of a black organic resin film in which a black pigment is dispersed, is used.
Has been used. Among them, the black matrix formed by the metal thin film has high light-shielding rate and optical density and excellent resolution, but has high conductivity and high light reflectance, so that reflection due to reflected light is likely to occur and display quality is improved. There is a drawback that is damaged.

On the other hand, the black matrix composed of the black organic resin film has few problems as described above, and in particular,
Carbon black is suitable as a black pigment for a black matrix because it has excellent blackness as a black pigment. Therefore, a method of applying a photopolymerizable resin composition in which carbon black is dispersed to a transparent substrate to form a black matrix, a method of printing an ink containing carbon black on a transparent substrate to form a black matrix, etc. have been developed. ing. The following techniques, for example, have been developed and proposed as the ones that regulate the characteristics of the carbon black for the black matrix or the carbon black of the black matrix using the carbon black.

In an ink containing at least carbon black in a resin, the carbon black has an oil absorption of 40 to 130 ml per 100 g of carbon black and has a volatilization loss of 3% by weight when heated at 950 ° C. for 7 minutes. The above is 10 with respect to 100 parts by weight of the resin.
In the liquid crystal color filter light-shielding layer ink (Japanese Patent Laid-Open No. 8-262223), a resin black matrix in which a light-shielding agent is dispersed in a resin, As below (A)
A resin black matrix comprising carbon black satisfying at least one of (D).
However, (A) PH value is 6.5 or less, (B) surface carboxyl group concentration [COOH] is 0.001 <[COOH] in terms of molar ratio per total carbon atom, (C) surface hydroxyl group concentration. [OH] is a molar ratio per total carbon atom of 0.00
1 <[OH], (D) surface sulfo group concentration [SO
₃ H] is 0.001 <in molar ratio per total carbon atom
[SO ₃ H], (JP-A-9-15403).

Further, in a black matrix containing carbon black as a black pigment, the average particle size of the carbon black is 40 to 300 nm, and a black matrix for a color filter (JP-A-9-15419), In a black matrix containing carbon black as a black pigment, the carbon black contains CO and C in the volatile matter at 950 ° C.
A black matrix for a color filter, characterized in that the total oxygen amount calculated from O ₂ is 7 mg or more per 100 m ² of surface area of carbon black (JP-A-9-2265).
No. 3), average particle size 50-200 nm, DBP oil absorption 1
Color filter resist for black matrix, characterized by containing carbon black in the range of 0 to 40 ml / 100 g (JP-A-9-80220), average primary particle diameter 35 to 150 nm, aggregate diameter 60 to 300 nm, Carbon black for forming a black resist pattern, characterized in that carbon black having a dibutyl phthalate oil absorption of 30 to 90 ml / 100 g is coated with a resin (JP-A-11-80).
No. 583), etc. have also been proposed.

Further, carbon black for an insulating black matrix obtained by coating a carbon black having a total oxygen content of 15 mg / g or more and a total oxygen content / specific surface area of 0.10 mg / m ² or more (Japanese Patent Application Laid-Open No. Hei 10 (1999) -96). 9-95625), at least one of the surface carboxyl group concentration [COOH], the surface hydroxyl group concentration [OH], and the surface sulfonic acid group concentration [SO ₃ H] is 0 in terms of molar ratio per total carbon atom. .0
A resin black matrix comprising a resin containing a carbon black larger than 05 as a light-shielding agent and having a specific resistance of 7 × 10 ⁴ Ω · cm or more (Japanese Patent Laid-Open No. 9-265006). ) Etc. have been proposed.

Generally, the black matrix has a high degree of blackness and a light-shielding property, has a high light-shielding rate even when the film thickness of the light-shielding layer is thin, the surface of the light-shielding layer is smooth, and the conductivity of the light-shielding layer is small. , Etc. are needed. Therefore, the present inventor conducted research from a different point of view on the improvement of various performances required for these black matrices, and by chemically bonding a vinyl polymer to the surface of carbon black particles, the conductivity was remarkably lowered and It was found that the dispersibility in the black matrix forming resin liquid can also be improved.

[0011] Based on this finding, the present inventor has a nitrogen adsorption specific surface area ^{_{(N 2 SA) 50m 2 /}} g or more, DBP absorption amount 140cm ^3/100 g
The following carbon black was wet-oxidized to have an atomic ratio of all oxygen atoms per total carbon atom (intensity of oxygen bond energy / intensity of carbon bond energy) measured by X-ray photoelectron spectroscopy of 0.1 or more. A carbon black pigment for a black matrix, characterized in that the vinyl polymer is chemically bonded by cationic polymerization by reacting a vinyl monomer with a functional group on the surface of the oxidized carbon black as a backbone (Japanese Patent Application No. 2000-257473). Developed and proposed.

[0012]

In the course of conducting subsequent research, the present inventor converts a functional group oxidized and formed on the surface of carbon black into an azo group to form a backbone, and graft-polymerizes a vinyl monomer to chemically bond the same. It was confirmed that the dispersibility in the resin liquid is excellent and the conductivity can be remarkably lowered. That is, the present invention was developed as a pigment for a black matrix with the purpose of providing a carbon black suitable for forming a black matrix having a high light-shielding property and blackness and having an extremely low conductivity, and a method for producing the same. is there.

[0013]

The carbon black for a black matrix according to the present invention for achieving the above object has a nitrogen adsorption specific surface area (N ₂ SA) of 50 m ² / g or more, a DBP
The absorption 140cm ^3/100 g or less of carbon black by oxidizing the value of the atomic ratio of the total oxygen atoms per total carbon atoms measured by X-ray photoelectron spectroscopy (intensity of the intensity / carbon bond energy of the oxygen binding energy) A functional group on the surface of carbon black that has been oxidized to 0.1 or more is converted to an azo group as a backbone, and a vinyl polymer produced by radical graft polymerization of a monomer containing a vinyl group is chemically bonded to the backbone. Is a structural feature.

Further, the manufacturing method is based on the nitrogen adsorption specific surface area.
^{_{(N 2 SA) 50m 2 /}} g or more, put less carbon black DBP absorption 140cm ^3/100 g in an oxidizing agent aqueous solution, was separated and purified After stirring and mixing, X-rays light functional groups of the carbon black surface electron spectroscopy Oxidation treatment is performed so that the value of the atomic ratio of all oxygen atoms per total carbon atom (oxygen bond energy strength / carbon bond energy strength) measured by the method is 0.1 or more, and the oxidized carbon black is dispersed in a solvent. After the reaction by adding a diazotizing agent, the solvent and unreacted substances are removed to convert the functional group into an azo group, and then the monomer is added to a solvent containing a vinyl group-containing group for radical graft polymerization reaction, The structural feature is that the ungrafted polymer and the unreacted monomer are extracted and removed in a solvent.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Carbon black has a nitrogen adsorption specific surface area (N ₂ SA) of 50 m ² / g or more and a DBP absorption amount of 140 cm.
Those with the characteristics of ³ / 100g or less are used. When the nitrogen adsorption specific surface area (N ₂ SA) is less than 50 m ² / g, when dispersed in a solvent, the average particle size of carbon black in the dispersion becomes large, so that the blackness of the black matrix and the light-shielding power decrease. As a result, the light-shielding layer becomes thicker. Also if the DBP absorption amount is mixed with the resin exceeds 140cm ³ / 100g, is because so that the smoothness of the light-shielding layer increases viscosity is impaired.

The black matrix for carbon black of the present invention, the nitrogen adsorption specific surface area ^{_{(N 2 SA) 50m 2 /}} g or more, the oxidation treatment by setting a carbon black having a DBP absorption 140cm ^3/100 g or less of properties Then, a functional group is generated on the surface of the carbon black particles, the generated functional group is converted into an azo group to form a backbone, and a vinyl polymer produced by radical graft polymerization of a monomer containing a vinyl group is chemically bonded to the backbone. Surface modified.

Generally, when carbon black is dispersed in a dispersion medium, the functional groups present on the surface of the carbon black are the main factors affecting the wettability with the dispersion medium, and the contact electric resistance at the interface between the carbon black particles is also increased. Affect. That is, the functional group becomes a factor that determines the dispersion performance in the dispersion medium and the electrical resistance of the formed black matrix when the carbon black dispersion resin composition for forming the black matrix is prepared.

Functional groups such as a carboxyl group (-COOH) and a hydroxyl group (-OH) are formed on the surface of the oxidized carbon black particles. The carbon black for a black matrix of the present invention has a value of atomic ratio of total oxygen atoms per total carbon atom (intensity of oxygen bond energy / intensity of carbon bond energy) measured by X-ray photoelectron spectroscopy as the amount of these functional groups. Is oxidized to 0.1 or more.

That is, the value of the atomic ratio of all oxygen atoms per total carbon atom (the strength of oxygen bond energy / the strength of carbon bond energy) measured by X-ray photoelectron spectroscopy such as XPS or ESCA is Related to the amount of hydroxyl groups produced, when this value is less than 0.1, the amount of carboxyl groups and hydroxyl groups produced is small, so the amount of converted azo groups also becomes small, and monomers containing vinyl groups are radical-grafted. When polymerized, the amount of vinyl polymer formed and chemically bonded is small, and it tends to be non-uniform. As a result, the electric resistance of the carbon black itself becomes small, and the dispersion performance in the resin is lowered when the resin composition for forming the black matrix is prepared. The value of the intensity ratio (atomic ratio) is about 0.003 to 0.02 in ordinary furnace black, and the value of the intensity ratio (atomic ratio) is 0.1 or more in vapor phase oxidation such as ozone. Because it is difficult to oxidize efficiently,
Wet oxidation treatment is preferred.

In the wet oxidation treatment of carbon black, for example, a peroxo acid salt such as persulfate, perborate, percarbonate, perphosphate or the like, or a peroxo acid is preferably used as an oxidizing agent. Is preferably an alkali metal salt or ammonium salt. The wet oxidation treatment is carried out by adding carbon black to these oxidant aqueous solutions and stirring and mixing them to obtain the concentration of the oxidant aqueous solution,
By appropriately controlling the amount of carbon black added, the reaction temperature, the reaction time, etc., the value of the atomic ratio of all oxygen atoms per total carbon atom (the strength of oxygen bond energy / the strength of carbon bond energy) is 0.1. Oxidation is performed as described above.

The carbon black dispersion liquid subjected to the wet oxidation treatment is subjected to electrodialysis or a separation membrane (reverse osmosis membrane, ultrafiltration membrane, loose RO, etc.) to separate and purify carbon black. In this case, if the residual salt concentration in the carbon black dispersion is high, for example, the reaction between the carboxyl group and the vinyl monomer will be hindered. Therefore, the residual salt concentration in the carbon black dispersion should be the same as the carbon black content concentration. 20
It is preferable to purify so as to have a conductivity of less than 0.2 s / m 2 as wt%. Then, by vacuum drying or the like 11
It is heated to about 0 ° C., dried, and pulverized to obtain an oxidation-treated carbon black.

The functional groups such as carboxyl groups and hydroxyl groups formed on the surface of the carbon black particles by the oxidation treatment as described above are then converted into azo groups.
Conversion to an azo group can be accomplished by 2,2'-azobis (2-cyano-n-propanol) (ACP), 4,4'-azobis (4-cyanovaleric acid) (ACV), or 4,4 '-(4 -Azobis chemicals such as cyanovalerin chloride) (ACV-COCl) are used, but not limited to this.

The carbon black for a black matrix of the present invention is converted to a azo group by converting functional groups such as carboxyl groups and hydroxyl groups produced on the surface of the carbon black by the oxidization treatment as described above into a skeleton, The vinyl group-containing monomer has a structure in which a vinyl polymer produced by radical graft polymerization is chemically bonded. In this case, it is desirable that the rate of radical graft polymerization of the monomer (grafting rate) is 10% by weight or more. When the grafting ratio is less than 10% by weight, the amount of vinyl polymer chemically bonded is small, so that the dispersibility in the resin liquid for forming the black matrix is not sufficiently improved, and the electrical resistance of the black matrix is insufficient. This is because it becomes difficult to lower the level. However, the grafting ratio is the weight of the grafted monomer (g)
/ It is a value calculated from carbon black weight (g) x 100.

Vinyl monomers include N-vinyl-2-pyrrolidone (pyrrolidinone), N-vinylacetamide and N-
Vinyl formamide, α-methyl styrene, N-vinyl carbazole, isobutyl vinyl ether, N-butyl vinyl ether, ethyl vinyl ether, 4-vinyl pyridine, methyl methacrylate, glycidyl methacrylate,
Methyl acrylate, acrylonitrile, etc. are used,
Put carbon black in a predetermined solvent containing a vinyl group-containing monomer, stir at a predetermined temperature for a predetermined time,
After the reaction, the vinyl polymer is chemically bonded by radical graft polymerization according to the reaction formula shown in the following formula (1). In addition, ungrafted polymer (homopolymer)
And unreacted monomer is extracted and removed in a solvent such as methanol or ethanol.

[0025]

[Chemical 1]

This carbon black is mixed with a solvent and a resin to prepare a resin composition for forming a black matrix, and the resin composition is applied to a substrate and formed by a photoresist method. The resin composition is applied to a transparent substrate. The black matrix is formed by a printing method, a spin coating method, or the like, which is applied to a transparent substrate.

As the solvent, for example, water, methanol,
Ethanol, N-methyl-2-pyrrolidone, N, N'-dimethylformamide, N, N'-dimethylacetamide, N,
Various solvents such as N'-dimethyl sulfoxide, cyclohexanone, tetrahydrofuran, ethyl lactate, pyridine, methyl isobutyl ketone, methyl ethyl ketone, xylene, toluene, and benzene can be used as long as they do not affect the solubility of the resin and the dispersibility of carbon black. Can be used.

As the resin, for example, phenol resin, melamine resin, xylene resin, diallyl phthalate resin, glyptal resin, epoxy resin, alkylbenzene resin, polyimide resin, acrylic acid resin, methacrylic acid resin, polyvinyl alcohol, polyester resin, etc. Various resins are used as long as they do not affect heat resistance, fluidity and dispersibility of carbon black.

The resin composition for forming the black matrix is prepared by mixing carbon black, a solvent and a resin in a proportion of 2 to 20% by weight of carbon black, 60 to 96% by weight of solvent and 2 to 20% by weight of resin. Is prepared. When the amount of carbon black is less than 2% by weight, the light-shielding property is low. When the amount of carbon black is more than 20% by weight, the film thickness becomes thick, and when the amount of solvent is less than 60% by weight, the fluidity is lowered. However, when it exceeds 96% by weight, the light-shielding property is deteriorated,
If the resin content is less than 2% by weight, the film strength will decrease,
This is because if it exceeds 20% by weight, the viscosity tends to increase, making it difficult to control the film thickness.

Hereinafter, examples of the present invention will be specifically described in comparison with comparative examples.

Examples 1 to 3 (1) Oxidation treatment: Using carbon black having different nitrogen adsorption specific surface area (N ₂ SA) and DBP absorption amount, 100 g of carbon black was added with sodium persulfate having a concentration of 1.0 mol / dm ^3. Add to ³ dm ³ of aqueous solution, reaction temperature 60 ℃, reaction time 10
The treatment was carried out at a stirring speed of 500 rpm for an hour. The salt remaining in the reaction solution was separated from this oxidation reaction solution by an ultrafiltration membrane (AHP-1010, manufactured by Asahi Kasei, molecular weight cutoff: 50,000), and then concentrated and purified. Then, it is dried at 110 ° C. in a vacuum dryer and pulverized with a mixer to obtain a carbon black sample 85.
got g.

For these oxidized carbon black samples, S-Pro manufactured by Surface Science Ins-truments
The intensity of oxygen binding energy and the intensity of carbon binding energy were measured using be ESCA 2803 type, and the atomic ratio of all oxygen atoms per total carbon atom was determined.

(2) Azo group conversion treatment; 2000 cm ³ separable flask was charged with dimethyl sulfoxide as a solvent.
(DMSO) 500 cm ³ , Tolylene diisocyanate (TDI)
5.0 cm ³ and a small amount of α-picoline were added, 30 g of carbon black sample was put in this solution, and the mixture was stirred at a stirring speed of 300 rpm in a nitrogen atmosphere at 60 ° C.
It was made to react at the temperature of 4 hours. After the reaction, cool to room temperature,
20 g of 4,4′-azobis (4-cyanovaleric acid ACV) was added, and the reaction was carried out at 30 ° C. for 8 hours in a nitrogen atmosphere. After the reaction, the reaction slurry was put into a large amount of methanol to remove unreacted ACV and solvent, and carbon black was precipitated by decantation and centrifugation. The precipitated carbon black was vacuum dried at 30 ° C. to prepare a carbon black sample in which the surface functional group was converted into an azo group, and the sample was stored in a cool dark place.

(3) Radical graft polymerization; Next, 200
In a 0 cm ³ separable flask, 25 g of these carbon black samples and 500 cm ³ of a methacrylic acid monomer as a monomer containing a vinyl group were placed, and the mixture was placed in a nitrogen atmosphere.
The reaction was carried out at a temperature of 70 ° C. for 8 hours while stirring at a stirring speed of 300 rpm. After the reaction, the product was put in a large amount of methanol to precipitate a polymer containing carbon black. The precipitated carbon black was vacuum dried at 40 ° C. to prepare a carbon black sample for black matrix of the present invention in which a vinyl polymer produced by radical graft polymerization was chemically bonded to the surface of the carbon black.

Comparative Examples 1 to 3 In the above Examples 1 to 3, the same carbon black as in Examples 1 to 3 was used, except that (3) the radical graft polymerization reaction was not carried out. A carbon black sample was prepared by treating and (2) converting the azo group.

Comparative Examples 4 to 6 Examples 1 to 3 except that carbon black whose nitrogen adsorption specific surface area (N ₂ SA) and DBP absorption amount are outside the requirements of the present invention was used.
Under the same conditions as (1) Oxidation treatment, (2) Azo group conversion treatment,
(3) A carbon black sample was prepared by performing a radical graft polymerization reaction.

Comparative Examples 7 to 9 In the above Examples 1 to 3, (1) Oxidation was carried out by the following method to reduce the atomic ratio of total oxygen atoms / total carbon atoms to less than 0.1. Examples 1-3 except oxidation
Using the same carbon black as above, under the same conditions, (2) azo group conversion treatment and (3) radical graft polymerization reaction were performed to prepare a carbon black sample. Ozone oxidation treatment;
Put 150g of carbon black in the ozonator,
5 with an ozone generator (IOT-4A6 manufactured by Nippon Ozone Co., Ltd.) under conditions of a generation voltage of 200 V and an ozone generation amount of 5 mg / s.
Hold for time.

For these carbon black samples,
The characteristics of carbon black, the atomic ratio of all oxygen atoms per total carbon atom after the oxidation treatment, and the grafting ratio were measured by the following methods, and the results are shown in Table 1. In addition,
Comparative Examples 7 to 9 are examples in which the oxidation treatment is insufficient, the grafting ratio is low, and the carbon black powder resistance is small. Measurement of grafting ratio: A carbon black sample is dispersed in cyclohexanone and centrifuged at 1 × 10 ⁴ rpm to completely settle the carbon black. The precipitated carbon black was transferred to a cylindrical filter paper, subjected to Soxhlet extraction to completely remove the remaining non-grafted polymer, and the grafting ratio (% by weight) was calculated from the following formula. Grafted monomer weight (g) / carbon black weight (g) x 100

[0039]

[Table 1] Note * 1 Measured according to JIS K1469

[Preparation of Resin Composition] Carbon Black 1
0 g, cyclohexanone 70 g, methacrylic acid resin 20
After lightly mixing g, carbon black was finely dispersed by a homogenizer to prepare a resin composition for forming a black matrix. The viscosity, surface tension and particle size of carbon black in the resin composition were measured by the following methods, and the results are shown in Table 2.

Viscosity: The viscosity at a temperature of 25 ° C. was measured using a rotational vibration type viscometer (VM-100A-L manufactured by Yamaichi Denki Co., Ltd.). Surface tension: Measured using a surface tension measuring device manufactured by Kyowa Interface Science Co., Ltd. Particle size: Measured using a heterodyne laser Doppler type particle size distribution measuring device (UPA model 9340 manufactured by Microtrac). From the cumulative frequency distribution curve of the particle size distribution in the resin composition, the value of 50% cumulative frequency was taken as the average particle size, and the value of 99% cumulative frequency was taken as the maximum particle size.

It can be seen from Table 2 that the resin compositions of Comparative Examples 1 to 3 and Comparative Examples 7 to 9 have high viscosities and the carbon black particle aggregates in the resin compositions are also large.

[0043]

[Table 2]

[Formation of Black Matrix] The prepared resin composition was applied onto a transparent glass plate washed with trichloroethylene at a rotation speed of 16.7 / s by using a spin coater and kept at room temperature for 30 minutes, and then 120 ~ 250 ° C
On a hot plate for 120 seconds. Then 5
The coating film was irradiated with energy of 100 mJ / cm ² through a photomask on which a black matrix pattern was drawn using a 00 W ultra-high pressure mercury lamp. After that, 0.05% sodium carbonate, 0.4% Emulgen A-60 (manufactured by Kao)
Flow rate of 8.33 cm ³ / s using the developing solution (25 ℃)
The shower cleaning was performed for 60 seconds at a discharge pressure of 0.098 MPa. After washing with water, post-baking was performed on a hot plate having a surface temperature of 250 ° C. to form a black matrix.

The black matrix thus formed was measured and evaluated by the following methods, and the results are shown in Table 3. Optical density (OD value): It was measured using a Macbeth densitometer (RD-927, manufactured by Kolmogen), and the optical density per 1 μm of film thickness was determined. Film thickness; SEM (electron microscope, Hitachi S-2
100B) and the film thickness was measured. Surface roughness: SPM (scanning probe microscope, AFM mode)
The surface was observed by SII SPI-3100) to measure the surface roughness. Volume resistivity: A coating film was formed in the same manner as the black matrix except that the glass plate was changed to a chromium vapor deposition substrate, and a circular electrode having an area of 0.28 cm ² (S) was formed on the cured coating film by silver paste. A constant voltage generator (made by Kenwood) between this electrode and the chromium vapor deposition surface which is the counter electrode.
A constant voltage (100 V) was applied using a PA36-2A regulated DC power supply, and the current (I) flowing through the membrane was measured with an ammeter (R644C digital multimeter manufactured by Advantest). Next, the film thickness (d) cm of the black film was measured, the volume resistivity R was calculated from the following formula, and the logarithmic value (log ₁₀ R) was calculated. R (Ω · cm) = (V · S) / (I · d) Pencil hardness: Measured by JIS K5400 “pencil scratch test”.

[0046]

[Table 3]

From the results shown in Tables 1 to 3, the black matrices of Examples 1 to 3 formed using the carbon black of the present invention have optical density, film thickness, surface roughness, volume resistivity, pencil hardness, etc. It is recognized that all are at a good level. On the other hand, in the black matrices of Comparative Examples 1 to 3 formed by using carbon black in which vinyl polymer is not chemically bonded to the carbon black surface functional group, the dispersion performance of the carbon black in the resin is low, and in the resin composition Since the carbon black particle agglomerates are large, the viscosity of the resin composition is high, making it difficult to form a uniform and thin film. The film thickness is large, and the optical density and volume resistivity per 1 μm of film thickness are low. It can be seen that the surface roughness of the surface also increases.

In the black matrices of Comparative Examples 4 to 6 formed by using carbon black whose carbon black characteristics are out of the requirements of the present invention, the optical density and surface smoothness are lower than those of the black matrices of Examples 1 to 3. I know there is. Further, the black matrixes of Comparative Examples 7 to 9 using carbon black having an atomic ratio of total oxygen atoms and total carbon atoms of less than 0.1 by oxidation treatment have optical density, film thickness, surface roughness, and volume. It is recognized that both the specific resistance and the pencil hardness are significantly inferior to those of the black matrices of Examples 1 to 3.

[0049]

As described above, the carbon black for a black matrix of the present invention has a nitrogen adsorption specific surface area (N ₂ SA)
And a carbon polymer having a DBP absorption amount within a specific range is oxidized to convert the generated surface functional group into an azo group, and a vinyl polymer produced by radical graft polymerization of a monomer containing a vinyl group on the azo group is chemically produced. The black matrix formed by using carbon black as a light-shielding agent shows a high light-shielding rate even when the thickness of the light-shielding layer is small, and the surface of the light-shielding layer is smooth. The conductivity of the light-shielding layer is also small, and it becomes possible to impart excellent light-shielding performance. Further, according to the production method of the present invention, it is possible to easily produce these carbon blacks for the black matrix.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02B 5/20 101 G02B 5/20 101 4J100 G03F 7/004 505 G03F 7/004 505 5C094 G09F 9/30 349 G09F 9/30 349C F term (reference) 2H025 AA19 AA20 AB13 AB14 AB17 CC12 2H042 AA09 AA15 AA26 2H048 BA11 BA47 BB42 4J026 AC00 BA05 BA16 BA27 BA30 BA31 DD40EE03 DD20EE17 DD201718 DD02DD1718A02 DD1818 DD02DD1718A02 DD1818 EE43 FF02 FF05 FF11 FF15 4J100 GB01 GC01 GC07 JA43 5C094 AA43 BA43 CA19 CA24 ED15 FB15

Claims (3)

[Claims] 1. A nitrogen adsorption specific surface area (N ₂ SA) of 50 m ² / g or more,
By oxidizing a DBP absorption 140cm ^3/100 g or less of carbon black, the atomic ratio of the total oxygen atoms per total carbon atoms measured by X-ray photoelectron spectroscopy (intensity of the intensity / carbon bond energy of the oxygen binding energy) A functional group on the surface of carbon black that has been oxidized to a value of 0.1 or more is converted into an azo group to form a backbone, and a vinyl polymer produced by radical graft polymerization of a monomer containing a vinyl group is chemically bonded to the backbone. Carbon black for black matrix, which is characterized. 2. The carbon black for a black matrix according to claim 1, wherein the grafting ratio calculated by the following formula is 10% by weight or more. Grafted monomer weight (g) / carbon black weight (g) x 100 3. A nitrogen adsorption specific surface area (N ₂ SA) of 50 m ² / g or more,
The DBP absorption 140cm ^3/100 g or less of carbon black was placed in an oxidizing agent aqueous solution, was separated and purified After stirring and mixing, the total oxygen per total carbon atoms of the measurement of the functional groups of the carbon black surface by X-ray photoelectron spectroscopy The atomic ratio of atoms (strength of oxygen bond energy / strength of carbon bond energy) is oxidized to a value of 0.1 or more, the oxidized carbon black is dispersed in a solvent, a diazotizing agent is added, and the reaction is conducted. After removing the unreacted material and converting the functional group into an azo group, and then introducing the monomer into the solvent containing a vinyl group for radical graft polymerization reaction, the ungrafted polymer and the unreacted monomer are added to the solvent. The method for producing carbon black for a black matrix according to claim 1, wherein the carbon black is extracted and removed.