JPH0676571B2 - Color phosphor paste composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention is a phosphor paste for printing capable of forming a uniform and high-resolution phosphor film surface necessary for forming a phosphor surface of a cathode ray tube (hereinafter abbreviated as CRT). Regarding

<Conventional technology and problems> CRTs, which are typified by cathode ray tubes in televisions, are display devices that emit light when electron beams emitted from an electron gun collide with the phosphor film surface to excite phosphor particles. Accompanying this, various visual devices using CRTs have been diversified, and various types of products such as color CRTs, monochrome CRTs, large CRTs, and ultra-compact CRTs have been produced. The most important part of the CRT used in such visual devices is that it has no pinholes and exhibits good emission characteristics.The method for producing the phosphor film includes the slurry method and the sedimentation method. Methods, electrodeposition methods, vapor deposition methods, photoetching methods and the like are known. The phosphor screen used in a color CRT is generally composed of phosphor particles of three colors of red, green and blue arranged in dots or stripes. This phosphor has been conventionally produced by a photo-curing method using a shadow mask. Is made. However, it is essential to use a shadow mask with a fine pattern in order to form a phosphor film with excellent emission characteristics by this method, and the smaller the CRT, the more highly precise the screen is required. The more the shadow mask is required, the more accurate the shadow mask becomes, and the technical difficulty in the operation of the shadow mask and the difficulty in developing a material that can be used for this shadow mask and the productivity are reduced. Further, in the method of creating a fluorescent screen by a photo-curing method using a shadow mask, the facility cost is high, and since the phosphor paste is a photo-curing type, the paste of the excess coating portion is easy to harden,
It also has the drawback that it takes a lot of time and effort to collect the fluorescent substance and causes a large loss.

Therefore, recently, a printing method has been used as a method for forming a phosphor film for a high-resolution CRT having a uniform phosphor film thickness and less unevenness on the phosphor film surface. This printing method is characterized in that the phosphor paste is printed directly or indirectly on the CRT panel (front glass), and then the binder resin component in the paste is baked and removed to form the phosphor surface. This method is an industrially advantageous method because the equipment cost is lower than the conventional method, the recovery loss of the phosphor particles is small, the material cost can be reduced, and the productivity is high. A method for producing a CRT using this method is proposed in Japanese Examined Patent Publication No. 61-23231 and Japanese Unexamined Patent Publication No. 59-213778.

However, the average volume particle diameter of the phosphor particles contained in the phosphor paste conventionally used in the phosphor film forming method by the printing method is 10 μm, and the minimum particle diameter is 5 μm or more. Since the phosphor film formed in 2) has a large phosphor particle size, high resolution could not be obtained when it was used for a high resolution CRT because the surface irregularities were conspicuous.

Further, in order to increase the resolution of the CRT phosphor film, a method of making a phosphor paste by using phosphor particles obtained by crushing phosphor particles having a large particle size as described above is also proposed, but the crushed phosphor particles Due to its shape, when it was made into a paste, it tended to agglomerate and there was a strong tendency for poor dispersibility. That is, an aggregated phosphor portion is formed in a fluorescent film formed by a printing method using a paste containing an aggregate of phosphor particles, and when used as a CRT, the aggregate becomes an abnormal light emitting portion on the surface. However, as a result, the resolution is lowered and the CRT becomes defective.

Further, the phosphor particles are usually coated with an activator on the surface, and a product obtained by simply crushing such a phosphor has many parts where the activator is not coated on the surface of the phosphor particles. , The emission characteristics inevitably deteriorate as compared with the uncrushed phosphor, so if you try to increase the brightness of the CRT made with the paste containing such a phosphor to the practical range, the electron gun used It is necessary to increase the accelerating voltage, the operating current, etc., and not only a great load is applied to the electronic circuit, but also an unfavorable result such as an increase in cost is brought about.

<Means for Solving the Problems> The present invention is most important in manufacturing a high-resolution CRT.
The present invention relates to a phosphor paste for providing a phosphor film having few irregularities and high emission efficiency. That is, the gist of the present invention is that in a cathode ray tube fluorescent screen printing paste comprising a phosphor, a binder resin and a solvent, the phosphor particles are substantially coated with an activator, and the average volume particle diameter is CRT having high resolution and high luminous efficiency in a phosphor paste composition in which particles having a particle size of 2 to 7 μm and a particle diameter of 1 to 9 μm are contained in phosphor particles in an amount of 60% or more.
It is a phosphor paste that can be manufactured.

The phosphor used in the present invention is substantially coated on the surface with an activator, and particles having an average volume particle diameter of 2 to 7 μm and a particle diameter of 1 to 9 μm are contained in the phosphor particles in an amount of 60% or more. It was done.

In the present invention, the phosphor particle surface needs to be substantially coated with an activator, and the phosphor particle surface is obtained by simply crushing a large particle size luminescent material to reduce the particle size. The number of phosphor particles not coated with the activator increases, and the phosphor film formed by using the paste containing such phosphor particles has poor emission characteristics, which is not preferable.

The average volume particle diameter of the phosphor particles used for the phosphor surface for a color cathode ray tube is preferably 2 to 7 μm. It is difficult to manufacture phosphor particles having an average volume particle diameter of less than 2 μm,
Further, in a paste containing such phosphor particles, agglomerates of phosphor particles are generated in the formed phosphor film, and the light emission efficiency of the phosphor film is likely to decrease, so that the light emitting property of this phosphor film is increased. In addition, it is necessary to increase the acceleration current of the electron gun used, which shortens the life of the phosphor film. Further, since the emission efficiency of each of the red, green, and blue phosphors differs depending on the particle size, the smaller the particle size, the greater the difference in the emission efficiency of each phosphor particle, and the unfavorable result that the color emission becomes unbalanced. Bring

Further, if a stripe or the like is formed by a printing method using a paste containing a phosphor having an average volume particle diameter of more than 7 μm, the pattern accuracy becomes poor and the phosphor film surface also becomes a phosphor film with many irregularities, which is not preferable. . Further, it is preferable that the phosphor particles contain 60 or more, preferably 80% or more of particles having a particle size of 1 to 9 μm, and a phosphor formed of a paste containing phosphor particles having a wider particle size distribution than this. The film is not preferable because pinholes are generated, smoothness is insufficient, or phosphor particles are agglomerated.

The phosphor particles and the activator used in the present invention are not particularly limited and may be arbitrarily selected from generally known ones such as monochrome and color according to the purpose. Also,
RNA numbers based on JEDEC are used for the description of the phosphor particles and the activator.

The binder resin used in the present invention is not particularly limited as long as it has good baking properties and can uniformly disperse the phosphor particles, and may be arbitrarily selected according to the purpose.

Specific examples of the binder resin include known resins such as cellulose-based resins, vinyl alcohol-based resins and acrylic resins.

The solvent used in the present invention may be any solvent as long as it can prevent the paste composition from changing over time, and may be arbitrarily selected according to the type and purpose of the binder resin.
Diethylene glycol monoethyl ether acetate,
Diethylene glycol monobutyl ether acetate,
2,2,4-trimethyl 1,3-pentadiol monoisobutyrate, isophorone, 3-methoxybutyl acetate and the like can be mentioned.

In the present invention, the mixing ratio of the phosphor particles and the binder resin is not particularly limited and can be arbitrarily selected according to the purpose, but usually phosphor particles / binder resin = 100 g
/ 5g to 100 / 50g, preferably 100g / 10g to 100g / 40g.

Further, the solvent is used for adjusting the viscosity of the paste composition, and the compounding amount may be arbitrarily compounded so as to obtain the desired viscosity of the paste composition. Usually, the viscosity of the paste composition is about 5,000 to 200,000 centipoise and may be set according to the purpose.

In the present invention, various additives such as commonly known plasticizers, dispersion stabilizers, leveling agents, and thixotropy imparting agents can be added depending on the purpose, as long as the objects of the present invention are not impaired. .

The present invention will be described in detail below with reference to examples. In the examples, parts and% represent parts by weight and% by weight, respectively.

Example 1 Isobutyl methacrylate 99.5 parts Methacrylic acid 0.5 part and benzoyl peroxide 2.0 parts were added to 2,2,4-trimethyl 1,
The reaction was carried out in 3-pentadiol monoisobutyrate at 80 ° C for 10 hours. The obtained acrylic resin has a weight average molecular weight.
It showed a characteristic value of 150,000. P-22 color phosphor particles were added to a resin solution containing 100 parts of the obtained acrylic resin as a binder resin (red is yttrium oxysulfide (Y ₂ O ₂ S) coated with europium as an activator, and green is activated). Zinc sulfide coated with copper and aluminum (Zn
S), blue is zinc sulfide coated with silver as activator (ZnS)
Then, 400 parts of phosphor particles having an average volume particle diameter of 4.5 μm and 9 μm (9%) are dispersed and kneaded to obtain 2,2,4-trimethyl 1,3
-Pentadiol monoisobutyrate viscosity of 50,000 cps
The temperature was adjusted to (25 ° C.) to obtain three types of phosphor paste compositions. The three types of phosphor paste compositions obtained were screen-printed on a glass plate with a pattern width of 150 μm and a thickness of 2 μm.
It was applied in a stripe shape of 0 μm, dried and baked to form a phosphor film surface, and the phosphor film surface was evaluated for pattern accuracy and surface condition by an optical microscope of 50 to 400 times. as a result,
The pattern accuracy of the obtained phosphor film surface is ± 10 μm,
The surface of the phosphor film had a smooth surface without irregularities.

<Example 2> 90 parts of isobutyl methacrylate (IBMA), 10 parts of 2-hydroxyethyl methacrylate (HEMA) and 3.0 parts of azobisisobutyronitrile were reacted in 180 parts of diethylene glycol monoethyl ether acetate at 80 ° C for 10 hours. It was The obtained acrylic resin had a weight average molecular weight of 200,000. 400 parts of the same color phosphor particles (P-22) as in Example 1 were dispersed and kneaded in a resin solution containing 100 parts of this acrylic resin as a binder resin, and the resulting mixture was mixed with diethylene glycol monoethyl ether acetate to obtain a viscosity (25 ° C., EHD type viscosity). (Measured by Tokyo Keiki Co., Ltd.) Adjusted to 30000cps 3
A seed phosphor paste composition was obtained.

The composition obtained as described above is applied on a glass plate by a screen printing method in a stripe shape having a pattern width of 150 μm and a thickness of 20 μm, dried and baked to obtain a phosphor film surface of 50 to 400 times. The pattern accuracy and the surface condition were evaluated by the optical microscope of No. As a result, the pattern accuracy of the phosphor film surface was ± 10 μm, and the phosphor film surface had a smooth surface with no irregularities.

<Examples 3 to 6 and Comparative Examples 1 to 3> 7 kinds of phosphor pastes are used in the same manner as in Example 1 except that 7 kinds of phosphor particles having phosphor particles having the characteristics shown in Table 1 are used. And using these phosphor pastes,
A phosphor film surface was formed in the same manner as in Example 1 and its characteristics were evaluated. The obtained results are shown in Table 1.

<Comparative Examples 4 to 7> Similar to Example 1 except that the color phosphor particles having an average volume particle diameter of 7.6 μm are simply pulverized into phosphor particles having an average volume particle diameter as shown in Table 2. Then, four kinds of phosphor pastes were prepared, a phosphor film surface was prepared in the same manner as in Example 1, and the characteristics thereof were evaluated. The obtained results are shown in Table 2.

As is clear from the results of Table-2, when the phosphor particles that are simply crushed are used, even if the phosphor particles having the characteristics within the range specified by the present invention are obtained, the phosphor film obtained can be obtained. Was inferior in light emission property, and the state of the phosphor film was almost the same as in the case of unpowdered particle size.

<Examples 7 to 10> Four kinds of phosphor pastes were prepared in the same manner as in Example 1 except that the phosphor particles having the average volume particle size and the viscosity distribution shown in Table 3 were used. Using this, a phosphor film surface was formed in the same manner as in Example 1 and its characteristics were evaluated. The obtained results are shown in Table-3.

-Phosphor film pinhole: The phosphor paste composition was printed on a glass plate, dried and baked, and the phosphor film surface was examined for the presence of pinholes using transmitted light with an optical microscope of 50 to 400 times. .

⊚: No pinholes were observed ○: Pinholes were hardly observed Δ: Some pinholes were observed ×: Pinholes were observed considerably ・ Smoothness: The phosphor paste composition was printed on a glass plate, dried and baked. The surface of the phosphor film was visually evaluated using reflected light with an optical microscope of 50 to 400 times.

◎: Very small irregularities, no screen mesh traces ○: Small irregularities, no screen mesh traces Δ: Large irregularities ×: Very large irregularities, screen mesh traces ・ Agglomerates: phosphor paste composition It was printed on a glass plate, dried and baked, and the phosphor film surface was evaluated with a 50 × optical microscope.

◯: No phosphor aggregate of 30 μm or more △: 〃 〃 Slightly present ×; 〃 〃 Very large ・ Emission characteristics: CRT using phosphor particles not crushed was evaluated as a standard.

○: Equivalent to non-crushed phosphor particles ×; Inferior to 〃 〃 ・ 150μm pattern accuracy: Print fine line 150μm stripe pattern on 300 mesh screen and evaluate the fluorescent film width with an optical microscope of 50 to 400 times did.

◯: Within ± 10 μm Δ: Within ± 20 μm ×: Within ± 25 μm <Effect of the Invention> As described in detail above, the phosphor paste composition of the present invention uses phosphor particles having a specific particle size and a specific particle size distribution. Therefore, the CRT obtained using this is very large as a phosphor paste composition for high-resolution CRT because it has few irregularities on the phosphor surface, no pinholes occur, and has excellent emission characteristics. It is effective.

Claims (1)

[Claims] 1. A cathode ray tube phosphor screen printing paste comprising phosphor particles, a binder resin and a solvent, wherein the phosphor particles are substantially coated with an activator and have an average volume particle diameter of 2 to 7 μm. And 60% or more of particles having a particle diameter of 1 to 9 μm are contained in the phosphor particles.