JP2003064279A - Carbon black pigment for black matrix and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon black pigment suitable for forming a black matrix having a high light-shielding property, a low conductivity and a high film hardness, 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 is wet oxidation of the following carbon black 140cm ^3/100 g, total carbon atoms per measured by X-ray photoelectron spectroscopy The carboxyl group (COOH) on the surface of carbon black oxidized to an atomic ratio of all oxygen atoms of 0.1 or more is replaced with a potassium salt (COOK) to form a base, and the base contains an epoxide and a cyclic acid anhydride. Carbon black pigment for black matrix grafted with polyester formed by anionic ring-opening alternating copolymerization of the above and a production 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 the transmission of incident light by sandwiching a crystalline material that becomes liquid crystal between transparent electrodes and applying a voltage between the electrodes to change the molecular arrangement of the liquid crystal.
It is used to display images and characters by combining a reflector and a polarizing plate and consumes less power. Therefore, 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.
The black matrix is a liquid crystal driving electrode or TFT provided on the substrate facing the color filter.
It also has a function of shielding a transistor such as a (thin film transistor) from light.

Therefore, in the black matrix,
Naturally, it is required to have excellent light-shielding properties, but in addition, it is required to have a smooth surface, a thin layer, and low conductivity. 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,
Since carbon black has excellent blackness as a black pigment, it is suitable as a black pigment for a black matrix. 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 continuing research, the present inventor has recognized that the film strength of the black matrix is somewhat insufficient and it is necessary to increase the film strength. That is, it is an object of the present invention to provide a carbon black pigment suitable for forming a black matrix having a high light-shielding property and a blackness, a low conductivity and a high film strength, and a method for producing the same.

[0013]

To achieve the above object, a carbon black pigment for a black matrix according to the present invention has a nitrogen adsorption specific surface area (N ₂ SA) of 50 m ² / g or more, D
The BP absorption 140cm ^3/100 g or less of carbon black to wet oxidation, 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) The carboxyl group (COOH) on the surface of carbon black oxidized to a value of 0.1 or more is substituted with potassium salt (COOK) to form a backbone, and the backbone is formed by anionic ring-opening alternating copolymerization of an epoxide and a cyclic acid anhydride. The structural feature is that the produced polyester is graft-bonded.

Further, the manufacturing method is based on the nitrogen adsorption specific surface area.
^{_{(N 2 SA) 50m 2 /}} g or more, was separated and purified After stirring and mixing the following carbon black DBP absorption 140cm ^3/100 g in an oxidizing agent aqueous solution, the functional groups of the carbon black surface by X-ray photoelectron spectroscopy The measured atomic ratio of all oxygen atoms per total carbon atom (the strength of oxygen bond energy / the strength of carbon bond energy) was oxidized to 0.1 or more, and the resulting oxidized carbon black was treated with an aqueous potassium hydroxide solution. Neutralize to convert carboxyl group (COOH) to potassium salt (COOH)
After the substitution with OK), an epoxide and a cyclic acid anhydride are added, and after the reaction, the ungrafted polymer and the unreacted monomer are removed.

[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 carbon black pigment for black matrix of the present invention has a nitrogen adsorption specific surface area (N ₂ SA) of 50 m ² described above.
/ g or more, as a target of carbon black having the following properties DBP absorption 140cm ^3/100 g, by performing a wet oxidation to produce functional groups on the carbon black particle surface, carboxyl group of the resulting functional group (COOH) A polyester obtained by substituting potassium salt (COOK) for a backbone and graft-bonding a polyester produced by anionic ring-opening alternating copolymerization of an epoxide and a cyclic acid anhydride on the backbone is surface-modified.

The carbon black pigment for black matrix of the present invention is produced by the following method. Functional groups such as a carboxyl group (—COOH) and a hydroxyl group (—OH) are formed on the surface of the oxidized carbon black particles. In the present invention, the atomic ratio of total oxygen atoms per total carbon atom measured by X-ray photoelectron spectroscopy as the amount of these functional groups (strength of oxygen bond energy /
Oxidation treatment is performed so that the value of (carbon bond energy intensity) becomes 0.1 or more.

That is, the value of the 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 such as XPS or ESCA is equal to that of carboxyl group or Related to the amount of hydroxyl groups produced, when this value is less than 0.1, the amount of carboxyl groups produced is small, so the amount of COOK substituted is also small, and anion ring-opening alternation between epoxide and cyclic acid anhydride is performed. This is because the amount of polyester produced by copolymerization and graft-bonded is small, and it tends to be nonuniform. As a result, the electric resistance of the carbon black itself becomes small, and the dispersion performance in the resin decreases when the resin composition for forming the black matrix is produced. The value of this atomic ratio (strength ratio) is about 0.003 to 0.02 in ordinary furnace black, and in the case of vapor phase oxidation of ozone, etc., this value should be efficiently oxidized to 0.1 or more. However, a wet oxidation treatment is performed.

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 oxidant. 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.

After the oxidation treatment, the carbon black is filtered off, and the obtained oxidized carbon black is put into an aqueous potassium hydroxide solution for neutralization. After neutralization, electrodialysis or a separation membrane (reverse osmosis membrane, ultrafiltration membrane) is conducted. , Loose RO, etc.) to separate and purify the remaining salt, concentrate, and then dry by vacuum drying, etc., and grind to obtain carbon black in which the carboxyl group (COOH) is replaced with potassium salt (COOK). .

This carbon black was placed in a container, epoxide and cyclic acid anhydride were added and stirred, and the reaction was carried out by controlling the reaction temperature, reaction time, etc., and the anion ring-opening was carried out according to the reaction formula shown in the following formula (1). Alternate copolymerization reaction is performed. As the epoxide, for example, styrene oxide,
Glycidyl phenyl ether, epichlorohydrin, glycidyl methacrylate, etc. are used, and as the cyclic acid anhydride, for example, succinic anhydride, maleic anhydride, phthalic anhydride, etc. are used.

[0022]

[Chemical 1]

After the completion of the anionic ring-opening alternating copolymerization reaction, the reaction solution is poured into a large amount of methanol or ethanol and stirred, and the ungrafted polymer and unreacted monomer are phase-shifted to methanol or ethanol and carbon black is precipitated. The ungrafted polymer and the unreacted monomer are removed by filtration separation. Thus, the carbon black pigment of the present invention in which the polyester produced by the anionic ring-opening alternating copolymerization is graft-bonded to (COOK) on the surface of carbon black is produced.

In the carbon black pigment for black matrix of the present invention, the carboxyl group (COOH) among the functional groups thus formed on the surface of the carbon black by the oxidation treatment is replaced with a potassium salt (COOK) to form a backbone. The polyester having a structure in which an epoxide and a cyclic acid anhydride are copolymerized by anionic ring-opening alternating copolymerization and graft-bonded to the backbone. In this case, it is desirable that the proportion of grafted monomers (grafting rate) is 10% by weight or more. The grafting ratio is a value calculated from the weight of the grafted monomer (g) / the weight of carbon black (g) × 100.

This carbon black pigment 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,
The reason is that if it exceeds 20% by weight, the viscosity increases and it becomes difficult to control the film thickness.

The examples of the present invention will be specifically described below 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
Oxidation treatment was carried out under conditions of time and rotation speed of 0.12 (1 / s) and then filtered to obtain oxidized carbon black. About this oxidized carbon black sample, Surface Scienc
The intensity of oxygen binding energy and the intensity of carbon binding energy were measured by using S-Probe ESCA 2803 manufactured by e Instruments, and the atomic ratio of total oxygen atoms per total carbon atom was determined.

(2) Neutralization treatment: An oxidized carbon black sample was put into an aqueous potassium hydroxide solution, stirred and neutralized, and then subjected to an ultrafiltration membrane (AHP-1010, manufactured by Asahi Kasei, molecular weight cutoff of 500).
00) to separate the remaining salt, then concentrate and purify, then dry with a vacuum dryer, pulverize with a mixer and replace the carboxyl group (COOH) with potassium salt (COOK) to replace carbon black (K-substituted oxidized carbon black). ) A sample of 85 g was obtained.

(3) Anionic ring-opening alternating copolymerization; 2000 cm
Into a separable flask of No. ³ , 45 g of K-substituted oxidized carbon black sample was put, 200 g of glycidyl methacrylate as an epoxide and 2 phthalic anhydride as a cyclic acid anhydride.
10 g was added, and the mixture was reacted at a temperature of 120 ° C. for 5 hours while stirring in a nitrogen atmosphere at a rotation speed of 0.2 (1 / s).
Next, this reaction slurry was put into about 10 times the amount of methanol, decanted and centrifuged, and vacuum dried to produce a carbon black pigment grafted with polyester.

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 anionic ring-opening alternating copolymerization was not carried out. ) Oxidation treatment and (2) neutralization treatment were carried out to produce a carbon black pigment.

Comparative Examples 4 to 6 Examples 1 to 3 except that carbon black having a nitrogen adsorption specific surface area (N ₂ SA) and a DBP absorption amount outside the requirements of the present invention was used.
Under the same conditions as above, (1) oxidation treatment, (2) neutralization treatment, and (3) anionic ring-opening alternating copolymerization were performed to produce a carbon black pigment.

Comparative Examples 7 to 9 In the above Examples 1 to 3, (1) Oxidation was carried out by the following method to oxidize ozone, and the atomic ratio of all oxygen atoms per total carbon atom (strength of oxygen bond energy / The value of (the strength of carbon bond energy) was less than 0.1, and the same carbon black as in Examples 1 to 3 was used, and under the same conditions, (2) neutralization treatment and (3) alternating anion ring-opening Copolymerization was performed to prepare a carbon black pigment. Ozone oxidation treatment: 150 g of carbon black was put into an ozone treatment device, and was kept for 5 hours under the conditions of a generation voltage of 200 V and an ozone generation amount of 5 mg / s by an ozone generator (Japan Ozone Co., Ltd. IOT-4A6). .

Regarding these carbon black pigments,
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 6 × 10 ⁻³ (1 / s) 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

[0037]

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

[Preparation of Resin Composition] 10 g of carbon black pigment, 70 g of cyclohexanone and 20 g of methacrylic acid resin were lightly mixed, and then 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.

From Table 2, it is recognized that the resin compositions of Comparative Examples 1 to 3 and Comparative Examples 7 to 9 have high viscosities and the particle size of the carbon black particle aggregates in the resin compositions is large.

[0041]

[Table 2]

[Formation of Black Matrix] The resin composition thus prepared was spin-coated on a transparent glass plate washed with trichloroethylene at a rotation speed of 0.06 (1 / s).
After applying and holding at room temperature for 30 minutes, 120 ~ 25
It processed on the hotplate of 0 degreeC for 120 second. Then, using a 500 W ultra-high pressure mercury lamp, 100 mJ / c was passed through a photomask on which a black matrix pattern was drawn.
Energy of m ² was applied from above the coating film. Then 0.0
A developer (25 ° C.) containing 5% sodium carbonate and 0.4% Emulgen A-60 (manufactured by Kao Corporation) was used, and the flow rate was 8.33.
60 cm ³ / s, discharge pressure 0.098 MPa, shower shower 60
Went for a second. 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) Film hardness: Measured according to the method of JIS K5400 “pencil scratch test”.

[0044]

[Table 3]

From the results of Tables 1 to 3, the black matrices of Examples 1 to 3 formed by using the carbon black pigment of the present invention have optical density, film thickness, surface roughness, volume resistivity and film hardness. It is recognized that all are at a good level. On the other hand, in the black matrixes of Comparative Examples 1 to 3, which are formed by using carbon black pigments in which polyesters produced by anionic ring-opening alternating copolymerization of epoxide and cyclic acid anhydride with K-substituted oxidized carbon black are not graft-bonded, The dispersion performance of carbon black in a resin is low, and since the particle aggregate of carbon black in the resin composition is large, the viscosity of the resin composition is high,
It becomes difficult to form a uniform and thin film, and the film thickness is large, and the film thickness is 1μ.
It is recognized that the optical density and volume resistivity per m 2 are low, and the surface roughness and hardness of the film surface are also poor.

Comparative Examples 4 to 4 formed using carbon black pigments whose carbon black characteristics deviate from the requirements of the present invention
It can be seen that the black matrix of No. 6 has lower optical density and surface smoothness than the black matrices of Examples 1 to 3. Further, the black matrixes of Comparative Examples 7 to 9 using the carbon black pigments in which the value of the atomic ratio of all oxygen atoms to all carbon atoms due to the oxidation treatment is less than 0.1
It is recognized that all of the optical density, film thickness, surface roughness, volume resistivity and film hardness are significantly inferior to those of the black matrices of Examples 1 to 3.

[0047]

As described above, the carbon black pigment for black matrix of the present invention has a nitrogen adsorption specific surface area (N
₂ SA) and carbon black having a DBP absorption amount within a specific range are subjected to a wet oxidation treatment to generate a carboxyl group (C
OOH) is replaced by a potassium salt (COOK) to form a backbone, and a polyester produced by anionic ring-opening alternating copolymerization of an epoxide and a cyclic acid anhydride is graft-bonded to the backbone. The black matrix formed as a light-shielding agent has excellent light-shielding properties, exhibits a high light-shielding rate even when the thickness of the black matrix is thin, the surface of the light-shielding layer is smooth, the light-shielding layer has low conductivity, and the film hardness is high. Excellent light shielding performance is provided. Further, according to the production method of the present invention, it is possible to produce a carbon black pigment capable of forming a black matrix having such excellent light-shielding performance.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02F 1/1335 G02F 1/1335 5C094 G09F 9/30 349 G09F 9/30 349C F term (reference) 2H042 AA09 AA15 AA26 2H048 BA11 BA47 2H091 FA35Y FB06 LA07 LA18 4J029 AA01 AB07 AC05 AE01 AE18 CA04 CB04A GA03 HB06 JA022 JB242 JB282 JB292 JB302 4J037 AA02 CA10 CC24 DD07 DD17 DD20 EE11 EE12 FF15EE4 EE12 EE43 EE19 EE19 EE43 EE19 EE19 EE43 EE19 EE19 FF19EE43

Claims (2)

[Claims] 1. 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 to wet oxidation, 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) The carboxyl group (COOH) on the surface of carbon black oxidized to a value of 0.1 or more is substituted with potassium salt (COOK) to form a backbone, and the backbone is formed by anionic ring-opening alternating copolymerization of epoxide and cyclic acid anhydride. A carbon black pigment for a black matrix, wherein the produced polyester is graft-bonded. 2. 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 separated and purified After stirring mixed in the oxidizing agent aqueous solution, the functional groups of the carbon black surface of the total oxygen atoms per total carbon atoms measured by X-ray photoelectron spectroscopy The value of atomic ratio (the strength of oxygen bond energy / the strength of carbon bond energy) is oxidized to 0.1 or more, and the resulting oxidized carbon black is neutralized with an aqueous solution of potassium hydroxide to change the carboxyl group (COOH) to potassium. 2. The production of a carbon black pigment for a black matrix according to claim 1, wherein after substitution with a salt (COOK), an epoxide and a cyclic acid anhydride are added and after the reaction, ungrafted polymer and unreacted monomer are removed. Method.