JP2002047423A - Black paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a membrane of a black pigment-containing resin, and a paste having a high degree of blackness and insulating properties as the paste capable of forming the membrane. SOLUTION: The paste comprises a black pigment and a binder resin, the black pigment containing cobalt oxides.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a black pigment dispersion for forming a black insulating layer of a thin display element such as a liquid crystal display element, an organic EL display element and an FED by applying a pattern on a glass substrate and performing pattern processing. It is about paste.

[0002]

2. Description of the Related Art With the development of mobile communication devices and portable information terminals, small, thin, and lightweight display elements are required as information display portions. At present, monochrome liquid crystal display elements are mainly used as display elements of mobile communication devices, but it is considered that higher definition and full color display will be advanced in order to improve the quality of information display. As thin and lightweight full-color display elements, there are a liquid crystal display element and an organic EL display element. Each of these display elements performs color display by using three primary color pixels of red, green, and blue as a set of pixels to form a picture element.However, in the color display, the pixel is used to improve color reproducibility and display contrast. It is desirable to form a light shielding portion called a black matrix between the pixel and the pixel. In the case of a liquid crystal display element, a chromium film and a black resin in which carbon black is dispersed are used as the material of the black matrix.
One is already in practical use.

[0003]

In recent years, there has been a case where a black matrix is required to have insulating properties as a new driving method for a liquid crystal display. Also, in the case of an organic EL display element, an insulating layer is required between pixels, and if a black matrix is formed between pixels, the insulating layer must be used. However, both the chromium film and the carbon black-dispersed resin are conductors and cannot be used for these purposes.

As a method for forming an insulating light-shielding layer, a method using a resin in which an insulating black metal oxide or the like is dispersed has been proposed. For example, Japanese Patent Application Laid-Open No. Hei 9-124972 proposes a black matrix composition containing a composite oxide having a spinel type or inverted spinel type crystal structure containing two or more metals and a binder resin. It is said that copper-chromium, copper-manganese, or copper-iron-manganese-based materials are preferable. Japanese Patent Application Laid-Open No. 9-160243 proposes a photosensitive composition containing a metal oxide in a light-shielding material as a material for forming a light-shielding film. It is considered to be an oxide. As described above, as the most typical black pigment excluding carbon black, complex oxides represented by copper-iron-manganese have been known. In order to improve the reliability of the display element, it is preferable to use a heat-resistant resin, for example, polyimide or the like as a resin binder of a light-shielding layer material containing a black pigment. However, due to the heat treatment at the time of forming the heat-resistant resin, the copper-iron-manganese-based oxide sometimes faded, and a good light-shielding layer could not be obtained.

An object of the present invention is to provide a black matrix forming material for a display element having a high insulating property and a high light shielding property.

[0006]

That is, the present invention provides a paste containing a black pigment and a binder resin.
A paste wherein the black pigment is a cobalt oxide.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. In view of the conventional situation described above, the present inventors,
As a result of repeated studies on the fading properties of black pigments to heat treatment in heat-resistant resins, cobalt oxide-based black pigments
Copper, which was typical as a conventional metal oxide black pigment,
The inventors have found that fading is extremely small as compared with iron-manganese-based oxides, and have completed the present invention. The present invention is a paste containing a black pigment and a binder resin, wherein the black pigment is a cobalt oxide.

In the present invention, the black pigment is cobalt oxide.
Things. Generally, carbon black is used as a black pigment.
, Titanium black, and copper-iron-manganese composite
Oxides are known. But carbon black, titanium
Black is a conductor and a copper-iron-manganese composite
Oxides are highly reactive at high temperatures and can react with binders at high temperatures.
Because it is easy to react and fade, it is difficult to
It is not suitable when the temperature is high in the process. Cobalt oxide
Classes include CoO: cobalt (II) oxide, Co _TwoO_Three(H
_TwoO): Cobalt (III) oxide and Co_ThreeO_Four： Nicoba oxide
And (II) cobalt (II).
It is not limited to them. These are all black
As a substance, cobalt (II) oxide is 390 to 9 in air.
By heating to 00 ° C, cobalt (III) oxide
By heating to 150 ° C in the air, all of them are nicotine oxide.
It is known to change to
For the purpose of not fading by the heat treatment of the invention,
Baltic (III) cobalt (II) is most preferred. Also acid
Cobalt (II) shows various colors depending on the particle size,
Cobalt (III) is brownish black, whereas
Dicobalt (III) cobalt (II) oxide is gray-black to black
Indicates color and is achromatic black. Display device black mat
Is the achromatic color of Rix a point of display quality?
Baltic oxide (III) oxide
(II) is preferred.

The average particle diameter of the cobalt oxide black pigment is preferably 10 nm or more and less than 200 nm. Powders of less than 10 nm are unsuitable because they are difficult to manufacture and handle, tend to aggregate and have poor dispersibility. When the particle diameter is 200 nm or more, the scattering of visible light increases and the degree of blackness decreases.

As the binder resin, a resin excellent in heat resistance is desirable from the viewpoint of being exposed to a high-temperature step in the display element manufacturing process and the durability in using the display element.
Examples of the resin used as the electronic material include polyimide, polyamide imide, polyamide, acryl, and epoxy. Among them, polyimide is most preferable because of its excellent heat resistance and chemical resistance. As a polyimide coating agent contains a polyimide precursor such as polyamic acid, and after coating on a substrate, a polyimide is generally formed by heat treatment to form a polyimide by ring closure of the imide, and also has excellent film performance. In the paste of the present invention, a binder resin containing a polyimide precursor and forming a black polyimide film by heat treatment after coating is the most preferable configuration.

As the polyimide precursor, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride Tetracarboxylic dianhydride such as a compound and 4,4′-diaminodiphenyl ether,
3,3′-diaminodiphenylsulfone, bis (3-
Aminopropyl) polyamic acid obtained by reacting a diamine such as tetramethyldisiloxane, metaphenylenediamine or paraphenylenediamine in an aprotic polar solvent such as N-methyl-2-pyrrolidone or N, N'-dimethylacetamide And esters thereof, but are not limited thereto.

The amount of the black pigment to be added is preferably 50% by weight or more and less than 95% by weight based on the total solid content of the paste. If the addition amount is less than 50 wt%, sufficient blackness cannot be obtained, and if it is 95 wt% or more, the film quality is poor and sufficient adhesion to the substrate cannot be obtained. In the present invention, the total solid content weight of the paste is defined as the weight remaining after the paste is applied and dried. As a measurement method, take a small amount of paste,
There is a method of performing the same heating step as the case where the paste is heated and dried in the black matrix production step, and measuring the residual weight. Alternatively, the same result can be obtained simply by measuring the residue after heating for 1 hour to 2 hours at the same constant temperature as the maximum temperature in the heating step. The amount of the black pigment means that the organic component is completely decomposed and volatilized by treating the paste at a high temperature of 800 ° C. to 1000 ° C. for 1 to 2 hours, and the weight of the black pigment is obtained by measuring the residual weight.

In the present invention, the binder resin may contain an inorganic component other than the black pigment. In this case, the weight of all inorganic components is 50 wt% or more of the total solids of the paste.
It is preferably less than 5 wt%, and in order to obtain a high degree of blackness, it is preferable that 80 wt% or more of all the inorganic components is a black pigment.

Next, a method for producing a paste according to the present invention and a method for forming a film from the obtained paste will be described with reference to an example in which the binder resin is a polyimide precursor, but the present invention is not limited to this. Absent.

A solution of the polyimide precursor and a black pigment are mixed in a predetermined amount. At this time, a dispersant may be added as needed to improve the dispersibility of the powder. Further, a leveling agent may be added for the purpose of improving the smoothness of the coating film. This mixture is stirred until it becomes a slurry. The paste is obtained by applying the obtained slurry to an apparatus such as a three-roll mill, a ball mill, a homogenizer, and a sand mill.

The obtained paste is uniformly applied on a substrate such as a glass substrate by a screen printer or a spin coater. Thereafter, by heating and drying using a hot plate or a hot air oven, a coating film containing a black pigment in the polyimide precursor is obtained. Drying temperature is 80 ℃ ～ 16
At 0 ° C., heat and dry for 1 minute to 10 minutes for a hot plate and 10 minutes to 60 minutes for a hot air oven.

On the coating film of the obtained polyimide precursor,
A photoresist is applied by a spin coater or the like, and is exposed and developed through a photomask having a desired pattern to form a black matrix pattern. At this time, if the photoresist is an alkali developing type, the polyimide precursor can be etched simultaneously with the development of the photoresist. After pattern formation, the photoresist is stripped.

Further, by using a polyimide precursor solution having photosensitivity, it is also possible to form a black matrix pattern by directly exposing and developing a polyimide precursor film by using a mask without using a photoresist.

By heating the obtained pattern in the air or in nitrogen, the polyamide acid is imide-ring-closed to obtain a polyimide film containing a black pigment. The heating temperature profile at this time is, for example, from room temperature to 120 ° C. to 180 °.
° C in 30 minutes, and after holding for 30 minutes, the temperature is raised again to 300 ° C to 400 ° C in 1 hour and held for 1 hour,
Then cool. By this heating step, the residual solvent in the coating film is completely removed, and the polyimide precursor is imidized through a dehydration ring-closing reaction to form a polyimide film. The black pigment-dispersed polyimide film obtained from the paste according to the present invention has the original high insulation and mechanical strength of polyimide, and also has an excellent blackness, so it is very suitable for a black matrix material of a display element requiring insulation. It is suitable.

[0020]

EXAMPLES The present invention will be described in detail with reference to the following examples, but the present invention is not limited by these examples.

A. Black pigment (1) Cobalt oxide black pigment (Co ₃ O ₄ ) Average particle diameter 70 nm (2) Carbon black (3) Copper-iron-manganese composite oxide Average particle diameter 50 nm (4) Cobalt oxide black pigment (Co ₃ O ₄ ) Average particle size 200 nm (5) Cobalt oxide black pigment (CoO) Average particle size 70 nm.

B. Polyimide precursor Abbreviations of tetracarboxylic dianhydride and diamine used are as follows. PMDA: pyromellitic dianhydride BTDA: 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride DAE: 4,4'-diaminodiphenyl ether SiDA: bis (3-aminopropyl) tetramethyldisiloxane.

(1) Polyimide precursor solution Copolymer composition: PMDA / BTDA / DAE / SiDA =
50/50/95/5 Solution concentration: Solid content 14 wt% N-methyl-2-pyrrolidone solution.

C. A. Acrylic resin Styrene acrylic copolymer “Joncryl SCX-281” (manufactured by Johnson Polymer Co., Ltd.) Polyfunctional monomer “KAYACURE DPHA” (manufactured by Nippon Kayaku Co., Ltd.) Photopolymerization initiator “Irgacure 369” (manufactured by Ciba Specialty Chemicals Co., Ltd.) Solvent N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) Ethyl lactate γ-butyrolactone (hereinafter abbreviated as γBL).

Preparation of Paste (1) A polymer solution was prepared by mixing other than the black pigment in the table. (2) Each polymer solution and black pigment powder were mixed and stirred until a slurry was obtained. (3) The obtained slurry was rolled into three rolls (EXACT m
odel 50) to obtain a paste.

The viscosity was measured using a Brookfield viscometer DV-II +. The measurement conditions were as follows: measurement temperature 25 ° C, rotation speed 10 rpm
(Shear speed 4 s ^-1 ).

Forming a coating film (when the binder resin is a polyimide precursor) (1) The paste is applied on a glass substrate (blue soda glass 1.3 mm, manufactured by Matsunami Glass) using a spin coater at 1500 rpm × 30 seconds. Then, it was dried at 140 ° C. for 2 minutes using a hot plate. The thickness after drying is 1.4
μm. (2) A photoresist was spin-coated on the coating film and dried on a hot plate at 100 ° C. × 2 minutes to obtain a film having a thickness of 1 μm. (3) Exposure was performed at 100 mJ / cm ² (i-line measurement value) by full-wave exposure using a high-pressure mercury lamp through a predetermined photomask. (4) Dip development was performed with a 2.38% TMAH developer for 50 seconds, followed by washing with water. (5) The resist was stripped with butyl acetate. (6) The obtained black polyimide precursor pattern was subjected to heat treatment in the atmosphere under the following conditions to obtain a polyimide film. Heating conditions: temperature rise from room temperature to 140 ° C. in 30 minutes, 140
The temperature was kept at 30 ° C. for 30 minutes, the temperature was raised from 140 ° C. to 350 ° C. for 1 hour, the temperature was kept at 350 ° C. for 1 hour, and the cooling was performed in this order. The thickness of each sample after curing was about 1 μm.

(1) Paste paste on glass substrate (blue plate soda glass: 1.3 mm, manufactured by Matsunami Glass Co., Ltd.) using a spin coater at 1500 rpm × 30 seconds. And dried at 80 ° C. for 2 minutes using a hot plate. After drying, the thickness was 1.3 μm. (2) Exposure was performed at 100 mJ / cm ² (i-line measured value) by full-wave exposure using a high-pressure mercury lamp through a predetermined photomask. (3) Dip development was performed with 0.2% TMAH developer for 60 seconds, followed by washing with water. (4) The obtained black acrylic resin pattern was subjected to a heat treatment in the atmosphere under the following conditions to obtain a polyimide film. Heating conditions: temperature rise from room temperature to 220 ° C. in 40 minutes, 220
Hold at 30 ° C for 30 minutes and cool. The film thickness after curing was about 1 μm for the sample.

Measurement of Coating Adhesive Strength (1) A 100 mm square was formed by making a cut of 10 × 10 with a width of 1 mm in the coating film, and a peeling test was performed with a cellophane tape. Was evaluated (based on JIS-K5400). (2) It was placed in a PCT (pressure cooker tester) at 120 ° C. and 2 atm, and the adhesive strength after 100 hours was similarly evaluated.

Measurement of Film Thickness The film thickness was measured with a surface shape measuring device "Surfcom 1500A" (manufactured by Tokyo Seimitsu Co., Ltd.). Blackness Measurement The lightness L ^* value was measured by a specular reflection removal mode of a colorimeter CM2002 (manufactured by Minolta Co., Ltd.). The smaller the value, the higher the blackness.

Specific resistance measurement Surface high resistance meter MCP TESTER Hiresta mo
The surface resistance R of the cured film was measured using del HT-201 (manufactured by Mitsubishi Yuka Corporation), and the specific resistance ρ of the film was measured using the following equation.

Specific resistance (ρ: unit μΩ · cm) = surface resistance (R: unit Ω) × film thickness (t: unit μm) × 100.

Transmittance measurement UV-visible spectrophotometer UV-260 (Shimadzu Corporation)
And the transmittance at a wavelength of 550 nm was measured.

The results are summarized in Table 1.

[0035]

[Table 1]

In Example 1, cobalt oxide Co ₃ O ₄ was used as a black pigment, and in Comparative Examples 1 and 2, carbon black and a copper-iron-manganese composite oxide were used as black pigments. In Example 1, the blackness was high and the insulation was good. Comparative Example 1
When carbon black was used, the blackness was very high, but the electric resistance was low and sufficient insulating properties could not be obtained. The copper-iron-manganese composite oxide of Comparative Example 2 had good insulation but low blackness. This is due to the fading of the black pigment due to the heat treatment.

In Example 2, a cobalt oxide Co ₃ O ₄ having an average particle diameter larger than that of Example 1 was used. In this case, however, good results were obtained.

Examples 3 and 4 are different from Example 1 in the content of cobalt oxide Co ₃ O ₄ . In each case, a black insulating film was obtained. However, Example 3 was slightly lower in blackness than Example 1, and Example 4 was slightly inferior in substrate adhesion as compared to Example 1.

In Example 5, CoO was used as the cobalt oxide.
Was used. As in Example 1, high blackness and insulation were obtained, but the color was slightly brown.

In Example 6, an acrylic resin was used as the binder resin, but also in this case, good blackness and insulation were obtained.

[0041]

According to the present invention, a black pigment-containing polyimide precursor paste capable of forming a black polyimide film having a high degree of blackness and having good electrical insulation can be obtained by having the above-described structure.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03F 7/038 504 G03F 7/038 504 F term (Reference) 2H025 AB13 AB20 AC01 AD01 BC13 BC42 CB25 CC11 2H091 FA35Y FB06 FB13 FC12 FC22 FC26 FD04 LA03 LA15 4J002 CM041 DE096 FD096 GQ01 HA08

Claims (8)

[Claims] 1. A paste containing a black pigment and a binder resin, wherein the paste contains cobalt oxides as a black pigment. 2. The paste according to claim 1, wherein the paste contains at least dicobalt (III) oxide and cobalt (II) as cobalt oxides. 3. The paste according to claim 1, wherein the content of the black pigment is 50% by weight or more and less than 90% by weight based on the total solid content of the paste. 4. The black pigment has an average particle diameter of 10 nm or more and 20 nm or more.
2. The paste according to claim 1, wherein the thickness is less than 0 nm. 5. The paste according to claim 1, wherein the binder resin is a polyimide precursor. 6. The paste according to claim 1, wherein the specific resistance of the thin film obtained by applying the paste on a substrate and heat-treating the paste is 5 × 10 6 Ω · cm or more. 7. The paste according to claim 1, wherein the blackness of the thin film obtained by applying the paste on a substrate and heat-treating it is 15 or less in terms of reflection lightness L ^* at a film thickness of 1 μm. 8. The paste according to claim 1, wherein the transmittance of the thin film obtained by applying the paste on a substrate and heat-treating the paste is 2% or less at a thickness of 1 μm.