JP2000104055A - Phosphor paste composition for plasma display panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phosphor paste composition for a plasma display panel, excellent in the dispersedness of a phosphor, capable of being fired at a temperature lower than the conventional and small in a decrease in luminance by using a specified methacrylic ester polymer as the binder. SOLUTION: This composition essentially consists of 100 pts.wt. (A) methacrylic ester polymer essentially consisting of 60-100 wt.% isobutyl methacrylate and 0-40 wt.% alkyl methacrylate having hydroxyl group in the position β or ω, 50-50,000 pts.wt. (B) phosphor for a PDP, and 100-2,000 pts.wt. (C) normally liquid organic compound having at least one ring structure in the molecule and having a boiling point of 170 deg.C or above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a phosphor paste composition for a plasma display panel (hereinafter referred to as PDP). More specifically, the present invention includes a methacrylic binder resin which is excellent in uniformity and handleability after complexing with a phosphor, can be thermally decomposed at a low temperature, and does not cause a decrease in luminance of the phosphor itself. The present invention relates to a phosphor paste composition for PDP.

[0002]

2. Description of the Related Art In recent years, large screen cathode ray tubes (CRT = Cathode Ray Tube) exceeding 30 inches have been adopted as television receivers and have been widely used in homes, but the larger the screen, the longer the distance between the electron gun and the screen becomes. Therefore, the product form is such that the depth of the image receiver is long and the curvature of the screen is large. As a result, there have been problems in that the installation location is limited and the screen is distorted around the periphery. In addition, TFT (Thin Fi
Liquid crystal display panels, such as lm transistors, do not emit electrons and emit light compared to CRTs.
It has an extremely thin structure and is widely used in notebook computers in recent years. However, a liquid crystal display panel such as a TFT generally has a problem that a viewing angle is narrow and it is difficult to see even if the viewing angle is slightly shifted even if it is well viewed from the front.

On the other hand, PDP (Plasma Display Panel)
Displays the image by the luminescence phenomenon of the phosphor due to the ultraviolet light generated by the discharge of the rare gas. Therefore, it has a structure with a thin and flat screen without the need for a depth like a CRT. The viewing angle is wider than that. Moreover, there is an industrial advantage that a large screen can be easily obtained. PD
In P, the phosphor is located on the wall surface and bottom surface of the cell which is partitioned one by one, and the phosphor at both ends absorbs the ultraviolet light generated by the discharge of the gas and emits light. In manufacturing a PDP, such a phosphor is generally applied to the inner surface of a cell by first producing a paste in which the phosphor is dispersed with a binder, and then applying the paste to a predetermined position in the cell by a screen printing method. . Then, when finally emitting light, if traces of organic substances are present in the phosphor in the cell, clear display will be hindered, so that the organic substances may be completely eliminated in the paste baking step before gas filling. is important.

[0004]

In the case of a CRT, a phosphor is applied to a face plate using a binder, dried and baked to eliminate the binder, and a red, green, blue and black pattern is formed on the face plate. I do. Also in the case of PDP, the binder is burned at a temperature of 400 to 550 ° C. after applying and filling a phosphor containing a binder at a predetermined position in the cell. However, when firing in the presence of oxygen at a high temperature, the binder may be oxidized or a structural change may occur in some cases, and the effect may extend to the phosphor, which may reduce the luminance of the phosphor or shift the color tone. .

The phosphor for PDP is essentially different in type and structure from the phosphor for CRT, and has a wavelength of 147 nm,
Since it is necessary to emit light with 72 nm ultraviolet light,
As the blue light-emitting phosphor, an aluminate phosphor such as divalent europium-activated barium / magnesium aluminate which is completely different from the CRT is used. When this phosphor is treated at a high temperature under an atmosphere of oxygen, the luminance is significantly reduced, and particularly when used together with a binder which has been used for a conventional CRT, the luminance is reduced. As a result, the brightness of the entire panel is reduced, and particularly the blue is drastically deteriorated, so that the display becomes reddish or yellowish, and a situation in which color reproducibility and fineness are lacking occurs. Therefore, polyvinyl alcohol, ethyl cellulose, and the like are used as binders for applying the phosphor for PDP, but their thermal degradability is hardly good.

Acrylic polymers are known to have good thermal decomposability. For example, Japanese Patent Publication No. 7-96679 discloses that a paste made of a specific acrylic polymer, a phosphor and an organic solvent is excellent for CRT. It is described. However, there is no description about the effect of this paste on the luminance of the phosphor itself, and a copolymer from a monomer mixture containing methacrylic acid is shown as a specific acrylic polymer. When a polymer containing an unsaturated carboxylic acid such as acrylic acid or methacrylic acid as a constituent component is used, the calcination property is remarkably reduced and carbon residue is liable to occur, and as a result, there is a problem that the phosphor is easily contaminated. As described above, the phosphor for PDP, which emits light when the phosphor is excited by ultraviolet light in the vacuum ultraviolet region, has a different structure and composition from the phosphor used for the CRT. It is difficult to know the effect of combining the acrylic polymer and the phosphor for PDP from this patent even if the acrylic polymer has relatively good thermal decomposability.

[0007]

The present inventors have proposed such a P
As a result of intensive studies to solve the specific problems between the phosphor for DP and the binder resin, the main components were isobutyl methacrylate and an alkyl methacrylate having a hydroxyl group at the β or ω position as an optional component. PDPs such as methacrylate polymers and aluminate phosphors
A combination of a fluorescent substance for use and an organic compound having a boiling point of 170 ° C. or higher and having at least one benzene ring skeleton in a molecule of liquid at ordinary temperature (normal temperature means 20 ° C. under atmospheric pressure in the present specification). The paste composition used was found to be excellent in dispersibility with the phosphor, excellent in printability on the rib surface, baked at a lower temperature than in the past, and also extremely low in luminance, and reached the present invention.

That is, the gist of the present invention resides in a PD comprising at least the following (A), (B) and (C):
In the phosphor paste composition for P. (A) at least isobutyl methacrylate 60 to 100
(B) PDP phosphor: 50 parts by weight or more and 5000 parts by weight or less by weight, and 100 parts by weight of a methacrylate ester-based polymer composed of 0 to 40% by weight of a methacrylic acid alkyl ester having a hydroxyl group at the β-position or the ω-position. And (C) an organic compound having a boiling point of 170 ° C. or more and having at least one benzene ring in the molecule of a liquid at ordinary temperature: 100 parts by weight or more and 2000 parts by weight or less.

One preferred embodiment of the composition of the present invention is
The alkyl methacrylate having a hydroxyl group at the β-position or the ω-position of (A) is 2-hydroxyethyl methacrylate, and the phosphor for PDP of (B) is an aluminate. The organic compound of (C) is an aliphatic alcohol or ester having a phenoxy group.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The methacrylate ester-based polymer as the component (A) contained in the phosphor paste composition of the present invention contains 60% of isobutyl methacrylate as a main component.
The methacrylic acid alkyl ester having a hydroxyl group at the β-position or the ω-position as an optional component is composed of 0 to 40% by weight. Here, the weight% means a ratio (%) to the total weight of the polymerizable monomer. If the content of isobutyl methacrylate is less than 60% by weight, the resulting methacrylic acid-based polymer has poor thermal decomposability. Therefore, from the viewpoint of the thermal decomposability of the polymer, 60% by weight or more, preferably 63% by weight or more,
Suitably, it is used at less than 9% by weight.

The alkyl methacrylate having a hydroxyl group at the β-position as an optional component includes methacrylic acid 2
-Hydroxypropyl, 2-hydroxybutyl methacrylate, and the like. Examples of the alkyl methacrylate having a hydroxyl group at the ω-position include 2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, and 4-hydroxybutyl methacrylate. . When a polymer obtained by copolymerizing these optional components with isobutyl methacrylate is used as a binder, there is an advantage that the dispersibility and water resistance of the paste are improved. In this case, from the viewpoint of compatibility with the organic solvent as the binder and dispersibility of the phosphor, the ratio of the optional alkyl methacrylate ester is 40% by weight or less, preferably 1 to 37% by weight of all monomers. It is appropriate to use in the range. When 2-hydroxyethyl methacrylate is used as the alkyl methacrylate having a hydroxyl group at the β-position or the ω-position, the resulting copolymer hardly reduces the thermal decomposability of the homopolymer of isobutyl methacrylate. preferable.

As the component A, the methacrylic acid ester-based polymer may be used by copolymerizing another copolymerizable monomer, if necessary. Other copolymerizable monomer components include methyl acrylate, alkyl acrylates such as ethyl acrylate, methyl methacrylate, ethyl methacrylate, normal butyl methacrylate, t-amyl methacrylate, cyclohexylmethyl methacrylate, and the like. Methacrylate, styrene, α-methylstyrene, and the like. Two or more of these can be used in combination, if necessary. Among these copolymerizable monomer components, methacrylic acid esters and α-methylstyrene are suitable from the viewpoint of thermal decomposability and slurry stability, and in consideration of the polymerizability with isobutyl methacrylate as the main component and the thermal decomposability, the alcohol moiety is used. Are more preferably branched methacrylic acid alkyl esters having an alkyl group at the β-position. These copolymer component monomers are used within a range that does not impair the thermal decomposability and dispersion stability of the methacrylic acid ester-based polymer, and it is usually preferable to use up to 20% by weight based on the total amount of the monomers.

If too much carboxylic acid, such as acrylic acid or methacrylic acid, is added too much, the thermal decomposability deteriorates. Therefore, the content is preferably 2% by weight or less based on 100% by weight of other monomer components. Further, a polyfunctional monomer such as dimethacrylate may be added. However, if too much is added, it gels and loses fluidity, so that it is preferably 3% by weight or less based on 100% by weight of other monomer components. As the dimethacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate and the like are preferable.

[0014] The molecular weight of the methacrylic acid ester-based polymer of the component (A) can be used in the range of 10,000 to 1.5 million in terms of weight average molecular weight (MW). A lower molecular weight is more appropriate when reduction is important, while a higher molecular weight is more appropriate when the sedimentation of the phosphor proceeds slowly. Therefore, the weight average molecular weight (MW) is preferably in the range of 30,000 to 500,000, and more preferably in the range of 50,000 to 300,000. In addition, the ratio (MW / MN) of the weight average molecular weight (MW) to the number average molecular weight (MN) of the methacrylate polymer is preferably 1.1 to 7.0, more preferably 1.3 to 4.0. . If it is smaller than this, the phosphor composition is applied to the cell, and the phosphor sediments during drying, and the brightness is reduced without remaining on the cell walls. It is not preferable because bubbles are apt to be left and the luminance is similarly lowered. The polymer having the above-mentioned properties such as molecular weight can be produced by a known method using a chain transfer agent. As the chain transfer agent, known compounds can be used, and specific examples thereof include unsaturated hydrocarbon compounds such as terpinolene and thiol compounds such as dodecanethiol, which are preferable.

The method for polymerizing the methacrylic acid ester polymer of the present invention is not particularly limited, and any conventional polymerization technique of this kind of vinyl compound can be appropriately employed. The reaction may be carried out at a specific temperature and for a specific time by a polymerization method such as solution polymerization, emulsion polymerization, suspension polymerization, and melt polymerization using a radical initiator such as azo compound or azo compound as a catalyst.

The phosphor for PDP which is the component (B) of the present invention is not particularly limited as long as it can emit light with high efficiency under the excitation of vacuum ultraviolet rays having a wavelength of 200 nm or less, and any known phosphor can be used. Specifically, red is trivalent europium-activated yttrium oxide, trivalent europium-activated yttrium borate, etc., and green is manganese-activated zinc silicate, manganese-activated barium magnesium aluminate, and the like. For blue, divalent europium activated barium magnesium aluminate and others are used.

These phosphors are usually kneaded with the component (A) of the organic binder resin and the component (C) as a solvent to obtain a paste composition, which is applied to a predetermined position of a cell by a printing method. The phosphor layer is formed by completely removing the organic substances by drying and firing, but the decomposition of the organic substances in this firing step chemically damages the structure of the phosphor, and consequently the luminance is significantly reduced. Many occur. Particularly, this phenomenon is remarkable in the case of aluminates, especially in the case of barium / magnesium aluminate phosphors activated with divalent europium and / or manganese, which are blue or green light emitting phosphors. In the presence of oxygen, the luminance deteriorates, and in the presence of the organic binder used for forming the paste, the luminance further decreases significantly, and the luminance of the entire PDP decreases.

In the present invention, by using a specific methacrylic acid ester polymer as the organic binder resin, a structural change of the phosphor due to decomposition of an organic substance in a firing step can be suppressed, and a decrease in luminance can be prevented. The phosphor for PDP, which is a component of the paste composition of the present invention, is particularly effective for aluminate, which is liable to deteriorate in luminance. As such an aluminate, BaMg
A phosphor in which aluminate is activated by divalent europium or manganese, which can be represented by Al _a O _b : Eu ²⁺ , BaMgAl _a O _b : Mn, is particularly preferable. As representative phosphors, KX-501A (BaMgAl ₁₀ O ₁₇ : Eu ²⁺ manufactured by Kasei Optonics), KX-503A ((Ba, S
_{r, Mg) O · aAl 2} O 3: Mn Chemical Co., Ltd. Optonix Co., Ltd.) is known.

In using the phosphor of the component (B), a phosphor having a pigment component adhered to and adhered to the surface of the phosphor may be used in order to increase the contrast of the panel. In this case, the method of attaching and applying the pigment is not limited.
Generally, an acrylic emulsion, polyvinyl alcohol, or the like is used. The amount of component (B) added is (A) component 1
50 parts by weight or more and 5000 parts by weight or less with respect to 00 parts by weight. If the amount is less than 50 parts by weight, a sufficient amount cannot be deposited on the partition walls of the cell, and the luminance is reduced. Also,
If the amount exceeds 5,000 parts by weight, the phosphor is excessively deposited on the partition walls, so that even if the phosphor on the surface emits light, the underlying phosphor does not emit light, and the luminous efficiency is reduced.

When the boiling point of the component (C) is 170 ° C. or higher,
An organic compound having at least one benzene ring skeleton in a molecule that is liquid at normal temperature is important to completely fill an independent cell when the paste composition is applied to the back panel. It controls the viscosity of the paste and the filling amount of the phosphor. Basically, any solvent that is liquid at ordinary temperature and does not separate from the component (A) may be used. Examples of the type include alcohols having at least one benzene ring skeleton in the molecule,
Ethers and esters are preferable, and among them, those having a boiling point of 200 ° C to 350 ° C are particularly preferable. As a specific solvent, 2-phenoxyethanol (boiling point 2
37 ° C.); 1-phenoxy-2-propanol (boiling point 2
43 ° C.), 3-phenoxy-1,2-propanediol (boiling point 315 ° C.) and 2-phenoxyethyl acetate (boiling point 257 ° C.), and aliphatic alcohols or esters having a phenoxy group are preferred. In the composition of the present invention, a stable paste is generated by using a relatively high boiling organic solvent having a benzene ring skeleton in a molecule in combination with a binder resin, and a phosphor layer is uniformly formed on the cell inner wall by printing. At the same time, by lowering the firing temperature in the firing step, it is possible to suppress a decrease in the luminance of the phosphor due to the decomposition of organic substances.

The amount of component (C) added is determined in consideration of the desired viscosity of the paste composition, and is usually preferably in the range of 100 to 2,000 parts by weight per 100 parts by weight of component (A). If the amount is less than 100 parts by weight, the viscosity of the paste is too high to be applied sufficiently and the workability is reduced.
On the other hand, when the amount exceeds 2,000 parts by weight, drying takes a long time, and the advantage of the production is reduced. Therefore, it is preferable to use the additive in the range of 150 to 1500 parts by weight per 100 parts by weight of the component (A). When the constituent monomer (A) is polymerized in the component (C) and produced, the amount to be added is determined with respect to the charged monomer amount. Also, the viscosity of the polymer solution is
Usually 300 to 100,000 centipoise, preferably 5
It is adjusted to 00 to 30,000 centipoise. Organic solvents having a boiling point of less than 170 ° C. other than the component (C) and a boiling point of 1
A liquid having no at least one benzene ring in the molecule at 70 ° C. or higher can be used in combination. However, if the amount used is too large, the paste will dry and thicken before application,
Since the yarn is drawn and the workability is reduced, the amount of addition is preferably 30 parts by weight or less based on 100 parts by weight of the component (C).

The method for producing the paste composition from the components (A), (B) and (C) of the present invention is not particularly limited. For example, the component (A) may be previously dissolved and dispersed in the component (C), Alternatively, after preparing a solution (C) containing the component (A) by polymerizing the component (A) to produce the component (A), the component (B) is added to the solution, and the solution is then ball milled or sand milled. It can be obtained by dispersing and stirring with a three-roll mill, a homomixer or the like.

The paste composition thus prepared can be applied to a predetermined position by screen printing on a glass substrate (back surface) on which a transparent electrode is printed.
In the case of DP, a screen is placed on a glass partition wall, and a paste composition in which a phosphor of a specific color is dispersed is applied only to a necessary part, followed by a drying and baking process, followed by sealing a gas and filling a glass substrate. (Surface) can be joined to form a PDP.

[0024]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto without departing from the scope of the invention.

Embodiment 1 Production Examples Production of Methacrylic Ester Polymers Production Examples 1 to 3 (Examples) and Production Example 4 (Comparative Examples) 0.5 L Separa equipped with a stirrer, thermometer, cooling pipe, nitrogen inlet pipe, and dropping funnel 100 parts by weight (66 g) of the monomers shown in Table 1 and 170 parts by weight of a solvent are placed in a bull flask, and nitrogen is blown into the flask to replace the inside of the flask with nitrogen. On the other hand, a solution prepared by dissolving 1.5 parts by weight of a polymerization initiator perbutyl I (trade name: tertiary butyl peroxyisopropyl carbonate manufactured by NOF Corporation) in 10 parts by weight of the solvent shown in Table 1 is charged into the dropping funnel. Then, the temperature of the flask is raised to 110 ° C., and the polymerization initiator solution is dropped from the dropping funnel over 5 minutes. Four hours after the start of the dropping, the same amount of the polymerization initiator solution was dropped in the same manner over a period of 5 minutes. The temperature was further raised to 120 ° C. for one hour, and the mixture was stirred and reacted for two hours.
After the completion of the reaction, polymer solutions of Production Examples 1 to 4 described in Table 1 were obtained.

The viscosity of each of the obtained polymer solutions was measured with an E-type viscometer (manufactured by Tokyo Keiki Co., Ltd .: 25 ° C.), and the results are shown in Table 1. The spinnability and plate cleanability of the obtained solution were evaluated. The results are shown in Table 1. For spinnability, a metal spatula was immersed in a solution at a depth of 2 mm, the spatula was raised at a speed of 10 cm / min, and the maximum length of a thread formed between the liquid surface and the spatula at that time was measured. The shorter this is, the lower the spinnability is, which is suitable for printing. For plate cleanliness, 1 cc of the polymer solution was dropped on the plate, spread quickly with a urethane rubber squeegee, spread 30 minutes later and wiped with a paper wiper (trade name: Bemcott; manufactured by Asahi Kasei Kogyo Co., Ltd.) to evaluate the tackiness of the surface. did. Here, the tackiness is a tactile sensation with a finger. If there is a feeling of sticking to the finger, it is determined that there is a tackiness. The less tackiness, the better the plate cleanliness.

[0027]

[Table 1]

2. Preparation of paste composition Examples 1 to 3 and Comparative Example 1 Each of the polymer solutions described in Table 1 and produced in the above Production Example 1
300 parts by weight of blue phosphor KX-501A for plasma display (manufactured by Kasei Optonics) was added to 00 parts by weight (20 g), mixed and dispersed to prepare a phosphor paste composition. This paste composition was applied to a glass substrate so that the dry film thickness became 30 μm. Apply fluorescent film at 120 ° C for 15
After drying for 10 minutes, raise the temperature to 450 ° C at 10 ° C
For 60 minutes. The baked fluorescent film was excited by vacuum ultraviolet light (147 nm), and the luminance at that time was measured. The value with respect to the luminance of the phosphor powder (standard: 100) is shown in Table 2. Further, the pastes of Examples 1 to 3 were stably stored at room temperature for one week or more and had good storage stability, whereas the pastes of Comparative Example 1 were separated into layers and had poor storage stability. . In Comparative Example 1, the phosphor was separated from the glass substrate after drying in the drying step.

[0029]

[Table 2]

[0030]

Industrial Applicability The phosphor paste composition for PDP according to the present invention has low spinnability during printing, excellent paste stability, excellent drying and firing properties, and the obtained phosphor has high brightness. It greatly contributes to the improvement of the brightness of the plasma display.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akio Umemoto 1060 Narita, Odawara City, Kanagawa Prefecture Inside the Odawara Plant of Kasei Optonics Co., Ltd. (72) Inventor Norio Miura 1060 Narita, Odawara-shi, Kanagawa Prefecture F-term in Odawara Plant, Kasei Optonics Co., Ltd.

Claims (5)

[Claims] At least the following (A), (B) and (C)
A phosphor paste composition for a plasma display panel, comprising: (A) at least isobutyl methacrylate 60 to 100
Methacrylic acid ester-based polymer composed of 0 to 40% by weight of a methacrylic acid alkyl ester having a hydroxyl group at the β-position or the ω-position: 100 parts by weight; (B) a phosphor for a plasma display panel: 50 to 5,000 parts by weight Or less, and (C) an organic compound having a boiling point of 170 ° C. or more and at least one benzene ring in the molecule of a liquid at ordinary temperature: 100 parts by weight or more and 2000 parts by weight or less. 2. The phosphor paste composition for a plasma display panel according to claim 1, wherein the alkyl methacrylate having a hydroxyl group at the β-position or the ω-position is 2-hydroxyethyl methacrylate. 3. The phosphor paste composition for a plasma display panel according to claim 1, wherein the phosphor for a plasma display panel (B) is an aluminate. 4. The method according to claim 1, wherein the aluminate is divalent europium and / or
4. The phosphor paste composition for a plasma display panel according to claim 3, wherein the phosphor is a phosphor activated with manganese. 5. The phosphor paste composition for a plasma display panel according to claim 1, wherein the organic compound (C) is an aliphatic alcohol or ester having a phenoxy group. .