JPH11181326A - Carbon black and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a carbon black having high insulating properties by subjecting a carbon black obtained by a furnace method to an oxidation treatment with an oxidizing agent containing ozone and/or hydrogen peroxide. SOLUTION: This carbon black has a powder resistance of 5 Ω.cm or more, preferably 10 Ω.cm or more, a DBP absorption amount of 40-120 ml/100 g which is substantially the same value as that of a carbon black used as a raw material, a structural parameter of 40-250 and a total oxygen content/specific surface area ratio of 0.4 mg/m<2> or more. An oxidation treatment is carried out by, for example, putting carbon black in a stainless kiln and bringing it into contact with ozone. This treatment results in the introduction of an oxygen- containing functional group into a surface of the carbon black. The temperature of the atmosphere for the contact with ozone contact is 50-150 deg.C. A preferable oxidative other than ozone is hydrogen peroxide. The amount of an ash of the carbon black used for the oxidation treatment is preferably 1% or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-resistance carbon black, and more particularly to a resist and spacer for forming a black matrix of an optical color filter.
The present invention relates to a carbon black suitable for a liquid toner used in a wet electronic printer.

[0002]

2. Description of the Related Art Utilizing its excellent blackness, carbon black is used as a black pigment for a resist for forming a black matrix of an optical color filter or a liquid toner used in a wet electronic printer. The liquid crystal display device includes a transparent substrate such as glass provided with a transparent electrode, which is formed of one to one.
It is provided at an interval of about 0 μm, and a liquid crystal substance is sealed between them.
The liquid crystal is oriented in a certain direction by a voltage applied between the electrodes to form a transparent portion and an opaque portion, thereby displaying an image. The color liquid crystal display device is provided with three color filters of red (R), green (G), and blue (B) corresponding to the three primary colors of light on any transparent substrate, and applies a voltage applied to the transparent electrode. The transmission of liquid crystal is controlled by adjusting
The color display is performed by controlling the amount of light transmitted through the G and B three-color filters and by developing the three primary colors. There are various methods of forming the R, G, and B colored layers on a substrate provided with a black matrix film for partitioning between colors in advance, and a method of forming a black matrix film after forming R, G, and B. The role of the black matrix is to partition the three primary colors of R, G, and B, and to act as a light shielding electrode for driving a liquid crystal or a transistor such as a TFT (thin film transistor) provided on a substrate facing the color filter. I have.

There are several methods for producing a black matrix of a color filter used for such a purpose. One of them is a method using a black resist. This method forms a black matrix by applying a photopolymerizable composition in which a black pigment such as carbon black is dispersed on a transparent substrate, and then performing patterning by photolithography, printing, photoetching, or the like. This method is black, and the reflectance of visible light is as low as several percent or less because it is black. The reduction in contrast of the displayed image due to the reflection of external light and the reflection of bright objects around are significantly reduced compared to the metal film black matrix. Image quality is improved. However, on the other hand, there is a drawback that the light blocking ratio is low. In addition, when a black matrix made of a resist in which a black pigment such as carbon black is dispersed is used as a light shielding film for the purpose of preventing a semiconductor element installed on a TFT element from malfunctioning due to light, an insulating black matrix is indispensable. is there.

However, conventional carbon black is a conductive material, and a pigment-dispersed resist using the same also exhibits conductivity or semi-conductivity. Therefore, the thin film exhibits high light-shielding properties and has a low surface reflectance. Carbon black for an insulating black matrix, that is, carbon black with high resistance has been desired. On the other hand, also for liquid toners, high resistance carbon black has been desired. That is,
The wet electrophotographic printing method has a lower printing speed than an offset rotary press, but does not require plate replacement and has a lower printing unit price. Further, the printing speed is much faster than that of a general dry-type copying machine, and a printed matter having excellent image quality can be obtained. Liquid toner is used for this type of development. Liquid toner consists of an electrically insulating liquid and pigment fine particles such as carbon black dispersed in it.If the zeta potential is low, insufficient print density or irregular dot shape will result, resulting in high image quality. Therefore, there has been a demand for a high-resistance (that is, high powder resistance) carbon black that increases the zeta potential.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a carbon black having a significantly higher resistance than conventional carbon blacks based on such a viewpoint.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventor has succeeded in obtaining carbon black having high powder resistance by oxidizing the furnace-process carbon black. . That is, the gist of the present invention resides in a furnace method carbon black characterized by having a powder resistance of 5 Ω · cm or more. The present invention also relates to a method for producing such high resistance carbon black.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The carbon black according to the present invention is a carbon black produced by a furnace method. The powder resistance of the furnace method carbon black obtained conventionally is about 0.1 to 2 Ω · cm. For example, the oxidation resistance of the high resistance carbon black of the present invention can be improved by oxidizing under specific conditions according to the present invention. Can be obtained.

The carbon black of the present invention has a dibutyl phthalate absorption (DBP absorption) of 40 to 120.
It is obtained by oxidizing carbon black having a product of the DBP absorption amount per 1 g and the specific surface area (referred to as “structural index”) of 40 to 250 in the range of ml / 100 g with ozone or / and hydrogen peroxide. . DBP absorption amount is 120
When the amount exceeds ml / 100 g, the powder resistance does not increase even if the oxidation treatment is performed. In addition, DBP absorption amount 40ml / 10
Carbon black of less than 0 g has high powder resistance, but is extremely poorly dispersed in resins and solvents, and is not suitable for practical use.

The structural index means that an optimum specific surface area is present depending on the level of each DBP absorption amount. In a region where this value is smaller than 40, high blackness printing and coating film density can be obtained. I can't. Further, when it exceeds 250, the number of carbon blacks per unit weight increases, so that not only a desired powder resistance cannot be obtained, but also a carbon black having a high specific surface area, that is, a small particle diameter, resulting in dispersibility. Poor, high blackness product cannot be obtained.

The carbon black of the present invention has a powder resistance of 5 Ω · cm or more, preferably 10 Ω · cm or more.
When the powder resistance is smaller than 5 Ω · cm, for example, when used for a black matrix of a pigment-dispersed resist in which carbon black is dispersed, a desired insulating property (1 in surface resistance)
0 ¹⁰ Ω · cm or more, preferably 10 ¹¹ Ω · cm) cannot be obtained. Also, when used for liquid toner, the zeta potential does not improve and high quality printed matter cannot be obtained.

The DBP absorption amount of carbon black,
The specific surface area does not change significantly by the oxidation treatment of the present invention. Accordingly, the DBP of the carbon black of the present invention
The absorption amount is 40 to 120 ml / g, which is substantially the same as that of the carbon black used as the raw material, and the structural index is 40 to 250. Further, the carbon black of the present invention has a value obtained by dividing the total oxygen content determined by the volatile component composition at 1500 ° C. by the specific surface area, that is, the total oxygen content / specific surface area is 0,4.
mg / m ² or more. This attribute has the following properties:

That is, on the surface of the carbon black particles,
Oxygen functional groups such as a hydroxyl group, a carbonyl group, and a carboxyl group are present, and the powder resistance is greatly changed depending on the amount thereof. Generally, when carbon black is oxidized by various methods, the larger the specific surface area, the more oxygen functional groups are provided. However, the powder resistance and the physical properties when blended with various materials are correlated not with the absolute amount of oxygen functional groups but with the number of oxygen functional groups provided on the unit surface. When the total oxygen content / specific surface area is 0.4 mg / m ² or less, carbon black having a powder resistance of 5 Ω · cm or more is not obtained.

Incidentally, the oxygen functional group is usually measured by the volatile composition, the hydroxyl group and the carbonyl group can be quantified as CO, the amount of the carboxyl group can be quantified as CO ₂ , and the total oxygen amount can be measured as C 2.
It is the amount converted from O and CO ₂ . The volatile component composition was measured by placing a certain amount of dried carbon black in a heat-resistant sample tube and reducing the pressure to 10-2 mmHg.
After charging into an electric furnace heated to 0 ° C. and collecting and mixing all the volatile components desorbed in 30 minutes in a tank, the composition and amount of the gas were measured by gas chromatography, and the total oxygen amount /
Calculate the specific surface area.

The specific surface area is measured by a BET method. That is, the low-temperature nitrogen adsorption device “Soapmatic 1”
800 "(Italy, manufactured by Carlo Elba), the nitrogen adsorption amount of carbon black was measured by a low-temperature nitrogen adsorption method, and the calculated amount was calculated by the multipoint method using the BET equation. Powder resistance, about 2 g of carbon black was placed in a 2 cm inner diameter Teflon container with a brass electrode attached to the lower part, and the tip was covered with a Teflon rod with a brass electrode at the tip. A load is applied at a speed of 2 mm / min, and the resistance at 50 kg / cm ² is measured with a high-sensitivity tester. The powder resistance is calculated from the bulk of the powder under this load and the resistance value using the following equation.

[0015]

## EQU1 ## Powder resistance (Ω · cm) = [Cross-sectional area of carbon black powder (cm ² )] × [resistance value (Ω) / bulk height of carbon black powder (cm)]

On the other hand, the DBP absorption and the volatile content were measured according to JIS-K6221-82. Such carbon black of the present invention has a DBP absorption of 4 produced by the furnace method.
It is obtained by oxidizing carbon black having a structure index of 0 to 120 ml / 100 g and a structure index of 40 to 250. The oxidation treatment is performed, for example, by putting carbon black into a stainless steel kiln and bringing it into contact with ozone. This treatment gives an oxygen functional group to the carbon black surface.

The temperature of the atmosphere brought into contact with ozone is not particularly limited. However, in the vicinity of room temperature, physical adsorption of ozone increases and the reaction rate becomes slow.
It is good to process at ° C. Oxidants other than ozone include:
Hydrogen peroxide is preferred, but ozone or hydrogen peroxide may be used in combination with an oxidizing agent such as nitric acid, NO gas, NO ₂ gas, SO ₃ gas, fluorine gas and the like.

The ash of carbon black used for oxidation is
1% or less, preferably 0 or 5% or less. The main components of the ash are alkali metals such as Na, K, and Ca, alkaline earth metals, and the like, and carbon black containing a large amount of these hardly has high powder resistance. In order to reduce this ionic conductive substance, examination of the raw material oil during carbon black production,
Achieved by examining spray water used during quenching and examining additives. The ash can also be reduced by washing or pickling carbon black produced from the production furnace. It can also be reduced by appropriately combining these. The ash content is calculated from the amount of ash remaining when the carbon black is calcined in air at 750 ° C. for 5 to 6 hours.

The high-resistance carbon black according to the present invention is particularly suitable for use in a photopolymerizable composition for a black resist or a liquid toner. The photopolymerizable composition for black resist, in addition to the carbon black of the present invention that is a black pigment, a photopolymerization initiation system that absorbs light to generate a radical, and an addition polymerizable polymerizable by the radical-induced polymerization. It contains a compound having at least one ethylenically unsaturated double bond, a binder resin, and the like, and is used after being prepared in a coating solution using a suitable solvent. Further, if necessary, various additives such as a dispersant can be added.
(See, for example, JP-A-9-22653).

The liquid toner is obtained by dispersing the carbon black of the present invention as a black pigment in an electrically insulating liquid such as a liquid aliphatic hydrocarbon, and is preferably a resin for improving the dispersion and fixing of carbon black particles. It is prepared by adding If necessary, a charge adjusting agent and a fixing agent may be added with an acrylic resin or the like soluble in an electrically insulating liquid, and a dispersing agent may be added with various surfactants and the like. (See, for example, JP-A-6-19220).

[0021]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which, however, are not intended to limit the scope of the present invention. The carbon blacks obtained in Examples and Comparative Examples were prepared as black matrix resists and liquid toners according to the following formulations, and evaluated for performance.

[Preparation and evaluation of resist] In a sand mill containing 300 g of zirconia beads having a diameter of 1 mm, 32 g of carbon black and 18 g of an organic polymer substance having the following structure were prepared.
And propylene glycol monomethyl ether acetate (hereinafter abbreviated as PGMEA) 150 as a solvent.
g was added and mixed and dispersed at 2000 rpm for 10 hours to obtain a dispersion.

[0023]

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Next, 45 g of the above dispersion, 1.35 g of dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku Co., Ltd.) as an ethylenic compound, and bisphenol A were mixed with 140 g of mayonnaise containing 90 g of zirconia beads having a diameter of 1 mm. 1.13 g of co-condensation monomer with chlorohydrin ([SP-1509], manufactured by Showa Polymer Co., Ltd.)
And 0.37 g of ethyl p-diethylaminobenzoate as a photopolymerization initiator composition and 39 g of PGME were added,
The mixture was dispersed for 30 minutes with a paint conditioner.

The obtained composition was subjected to high-pressure washing, ultraviolet irradiation and ozone treatment on a glass substrate (Corning N.
o. 7059, 1.1 mm thick) by spin coating, and heat-treated under three levels of temperature conditions between 220 ° C. and 260 ° C. to form a resist layer having a thickness of 1.0 μm. Measurement of OD value: Macbeth reflection densitometer "RD-914"
(Sakata Inx). Measurement of surface resistance: A high resistance measuring device “Hiresta MCP-HT210” manufactured by Yuka Electronics Co., Ltd. was used.

[Preparation and Evaluation of Liquid Toner] Supermixer having a capacity of 20 liters (“SMV-20” manufactured by Kawata Co., Ltd.)
Mold)) and partially saponified ethylene-vinyl acetate copolymer “Dumilan C-2280” (manufactured by Takeda Pharmaceutical Co., Ltd.) 2400
g, carbon black 600 g, and nigrosine ("Bontron N-09" manufactured by Orient Chemical Co., Ltd.) 30 g,
Add 300 g of "MRB-8" (Daiichi Kogyo Seiyaku Co., Ltd.)
Mix for 5 minutes at 2000 rpm. This mixture was set at a maximum temperature of 150 ° C. with a twin-screw extruder (“TE
M-35B ") and then knead with a strand cutter to about 1-2
It was cut to a diameter of mm to obtain a kneaded pellet. The pellet was immersed in liquid nitrogen and cooled sufficiently, and then pulverized using a jet mill (“STJ-200” manufactured by Seishin Enterprise Co., Ltd.). The ground product was dried in a vacuum dryer set at 70 ° C. for 10 hours. The average particle size of the pulverized product was 120 μm.

Next, a mixed solvent 2550 composed of 48% of Isopar G (manufactured by Esso Oil), 32% of toluene (manufactured by Katayama Chemical), and 20% of ethanol (manufactured by Katayama Chemical).
g and the above crushed product 450 g in a stainless steel container,
The temperature was gradually increased while stirring at 100 rpm,
The mixture was dissolved for 30 minutes while keeping it at 0 ° C. This melted product was mixed in a kneading unit volume of 1.4 liters “Dynomill”.
(KDL-Pilot type, sold by Shinmaru Enterprises Co., Ltd.) at a rate of 3.5 liter / min and dispersed for 3 hours. A part of the dispersion was thinly applied to a glass plate, and the dispersibility was observed with an optical microscope at 400 times.

Next, 2 parts of the dispersion and 150 parts of the mixed solvent were placed in a vessel equipped with a stirrer, thermometer, and reflux condenser.
"MRB-8" 0.24 copy, "Dumilan C-228"
0 ”and stirred at 70 ° C. for 30 minutes to completely dissolve“ Dumilan C-2280 ”.
The mixture was allowed to cool to 0 ° C. to precipitate pigment resin particles. The mixed solvent of the pigment resin particle dispersion was replaced with “Isopar G”, and zirconium naphthenate was added as a charge control agent to obtain a positively charged liquid toner. Measurement of zeta potential: Laser zeta potentiometer "LEZA-600" of Otsuka Electronics Co., Ltd.
It was used.

Example 1 Carbon black was produced by a conventional oil furnace method using an ethylene bottom oil having a small content of Na, Ca and S as a raw material oil and using a coke oven gas for combustion. Further, pure water treated with an ion exchange resin was used as the reaction stopping water. The powder resistance of the obtained carbon black was 0.49 Ω · cm.

500 g of the above carbon black was put into a cylindrical kiln having an inner diameter of 30 cm and a length of 60 cm, and this was placed in an electrothermal high-temperature bath capable of heating up to 200 ° C.
While rotating at 0 rpm, 10,000 ppm ozone generated by a model OR-4Z manufactured by Wako System Control Co., Ltd. was flowed at a flow rate of 5 L / min to cause a contact reaction with carbon black. The temperature of the contact portion between ozone and carbon black was 50 ° C., and the treatment was performed for 4.0 hours. Three batches were processed under the same conditions, and the obtained carbon blacks were mixed uniformly to obtain carbon blacks for evaluation.
The performance as a black matrix resist and a liquid toner was evaluated. The results are shown in Table 1. In addition, according to the dispersibility observation during the production of the liquid toner, most of the aggregates were 0.5%.
１1 μm.

Examples 2 and 3 The treatment time of carbon black with ozone was measured in Example 2.
In Example 3, high resistance carbon black was obtained in the same manner as in Example 1 except that the time was changed to 5, 4 hours, and that in Example 3 was changed to 6, 0 hours. Table 1 shows the physical properties and evaluation results of the obtained carbon black. Example 4 Specific surface area 200 m ² / g, DBP absorption amount 115 ml / 1
Using 100 g of carbon black, the ozone treatment time was 2
A high-resistance carbon black was obtained in the same manner as in Example 1 except that the time was 0 hour. Table 1 shows the physical properties and evaluation results of the obtained carbon black.

Example 5 100 g of the same carbon black used in Example 1
Was placed in a 10-liter SUS kiln, and 31% high-purity hydrogen peroxide was passed through at a flow rate of 7.3 g / min for 3.2 hours in an atmosphere at a rotation speed of 20 rpm and a temperature of 120 ° C. The carbon black was oxidized. The physical properties and evaluation of the obtained high-resistance carbon black were performed in the same manner as in Example 1, and the results are shown in Table 1.

[0033]

[Table 1]

Comparative Example 1 Specific surface area 120 m ² / g, DBP absorption 45 ml / 10
0 g of carbon black (500 g) is placed in a cylindrical kiln having an inner diameter of 50 cm and a length of 100 cm, and while rotating at 25 rpm, a mixed gas of air and NO ₂ gas (NO ₂ concentration 25
000 ppm) and treated for 8, 5 hours. Next, the carbon black was placed in another externally heated kiln and heated at 200 ° C. for 30 minutes while flowing air, and was taken out after completely cooled to obtain a sample for evaluation. Table 2 shows the physical properties and evaluation results of the obtained carbon black.

Comparative Example 2 Specific surface area 210 m ² / g, DBP absorption 132 ml / 1
The mixture was treated with a mixed gas of air and NO ₂ gas for 12 hours using 00 g of carbon black. Next, a sample for evaluation was prepared in the same manner as in Comparative Example 1. Table 2 shows the physical properties and evaluation results of the obtained carbon black.

[0036]

[Table 2]

[0037]

The carbon black of the present invention has a high powder resistance. The photopolymerizable composition using the carbon black of the present invention can form a black matrix having high insulating properties and high optical density. Further, the liquid toner using the carbon black of the present invention has a high zeta potential, and can record high quality images.

Claims (5)

[Claims] 1. A furnace method carbon black having a powder resistance of 5 Ω · cm or more. 2. The carbon black according to claim 1, wherein the powder resistance is 10 Ω · cm or more. 3. A DBP absorption amount of 40 to 120 ml / 10.
The carbon black according to claim 1 or 2, wherein the carbon black is 0 g. 4. The product of the amount of DBP absorption per 1 g of carbon black and the specific surface area is 40 to 250, and more preferably 150 to 250.
The carbon black according to any one of claims 1 to 3, wherein a value obtained by dividing a total oxygen content obtained by a volatile component composition at 0 ° C by a specific surface area is 0 or 4 mg / m ² or more. 5. The method for producing carbon black according to claim 1, wherein the furnace method carbon black is oxidized with an oxidizing agent containing ozone and / or hydrogen peroxide.