JPH04202286A - Manufacture of pigment-coated phosphor - Google Patents

Abstract

PURPOSE:To obtain the title phosphor having a pigment firmly attached thereto with a small amount of a binder by sticking specified pigment particles to phosphor particles in the method of preparing the title phosphor wherein pigment particles are stuck to the surfaces of phosphor particles with a binder. CONSTITUTION:In the method of preparing the title phosphor wherein particles of a pigment(e.g. cobalt blue)are stuck to the surfaces of particles of a phosphor(e.g. ZnS:Ag,Al)with a binder, a binder comprising a hot-melt binder(e.g. acrylic resin)is applied to pigment particles to cover them or stick to them in advance, and the obtained particles are stuck to phosphor particles.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for producing pigmented phosphors used in color televisions.

[Conventional technology]

A pigment that is generally used as a phosphor for color televisions and has a pigment attached to the surface of the phosphor that transmits the preferred color of emitted light from the phosphor and absorbs other visible light for the purpose of improving the contrast of the color television screen. It is known to use attached phosphors. Usually, such pigments are the same as the emission color of the attached phosphor, such as a red pigment for a red-emitting phosphor and a blue pigment for a blue-emitting phosphor. Pigmented phosphors have conventionally been manufactured as follows. First, a pigment is dispersed in an aqueous medium to form a pigment dispersion. The pigment may be ground using a suitable milling device such as a ball mill. On the other hand, the phosphor is similarly dispersed in an aqueous medium to form a phosphor dispersion, into which the pigment dispersion described above is mixed. A binder is further added to the dispersion in which the pigment and the phosphor are mixed while stirring. The binder is added in the form of a water-soluble emulsion, latex or monomer;
Further, by adding an acid, an alkali, an aggregating agent for the binder, a curing agent, a polymerization initiator, etc., the binder is agglomerated or hardened, and at the same time, the pigment is attached to the surface of the phosphor. The phosphor with the pigment attached quickly settles and is separated.
A pigmented phosphor is obtained by drying. Pigmented phosphors are manufactured by using various binders and various methods to attach pigments to the phosphor, but in most of these methods, the phosphor and pigment are mixed in an aqueous medium. A binder is added in the form of an emulsion or a monomer, and by adding some curing agent or polymerization initiator for the binder, the binder is agglomerated, hardened, or polymerized to transform the pigment into a phosphor. It was attached. By the way, the phosphor screens of industrially produced color cathode ray tubes are made by continuously pumping and transporting a phosphor slurry in which phosphors are dispersed in an aqueous solution containing mainly PVA and ADC (ammonium dichromate). is applied to. However, in the pigmented phosphor obtained by the conventional method, the pigment is gradually peeled off in the phosphor slurry due to the pressure from the pump, and the peeled off pigment becomes phosphor dots and strips of other luminescent colors forming the phosphor screen. There were disadvantages in that it overlapped with the live image, causing a decrease in brightness, a decrease in color purity, and unevenness on the coated surface.

[Problem to be solved by the invention]

Therefore, the present invention provides a novel method for producing a pigmented phosphor with almost no peeling of the pigment in the coating slurry, in order to obtain a coated surface free from contamination of other luminescent colors caused by the pigment. It is.

[Means to solve the problem]

The present invention provides a method for producing a pigmented phosphor in which pigment particles are attached to the surface of the phosphor particles via a binder.
Rather than attaching the pigment and phosphor by curing or polymerizing a binder that is an emulsion or a monomer, it is possible to attach pigment particles coated or attached with a hot-melt binder as a binder to the phosphor particles. This is a characteristic method for producing a pigmented phosphor. More specifically, the present invention is a manufacturing method in which the binder attached to the pigment is heated and melted to develop fluidity, the pigment is attached to the target phosphor, and the attachment is completed by cooling and solidifying. In the present invention, the hot melt binder attached to the pigment particles usually refers to a thermoplastic resin, but more precisely it also includes a thermosetting resin, and includes ethylene-vinyl acetate copolymer (E
VA), ethylene-ethyl acrylate copolymer (EE
A), ethylene-acrylic acid coheavy metal (EAA), EV
A saponified product, acrylic-vinyl acetate copolymer (AVA)
, ionomer, nylon, polyester, thermoplastic acrylic, etc. can be preferably used. Among them, emulsion binders such as EVA, AVA, and thermoplastic acrylic are more preferably used because they can impart hydrophilicity to the phosphor. The amount of binder to be attached to or coated on the pigment is usually adjusted to 0.1 to 20 parts by weight, preferably 1 to 5 parts by weight, per 100 parts by weight of the pigment. If the amount is less than 0.1 part by weight, the adhesion to the phosphor will be insufficient;
This is because if the amount is more than 1 part by weight, the pigment and the phosphor tend to aggregate with each other due to the binder. The manufacturing method of the present invention will be explained in detail below. First, as a method for attaching a binder to a pigment, for example, a molten hot melt, a solid hot melt, or a solution in which a hot melt is dissolved or dispersed is added as a binder to a dry pigment, and the mixture is heated while stirring vigorously in a mixer. do. Continuing heating, after the hot melt is sufficiently mixed with the pigment and melted, the heating is stopped and the binder-coated pigment can be obtained by cooling while continuing stirring. It is preferable to cool the pigment as rapidly as possible rather than to cool it gradually because the pigment is less likely to aggregate. If the pigment is agglomerated depending on the cooling conditions or the type of binder, the binder-coated pigment is milled using a ball mill, Raikai machine, etc. Alternatively, a method may be used in which a dispersion or solution of a binder is sprayed onto the dried pigment while stirring it with a mixer, followed by heating and cooling. Next, in order to attach the binder-attached pigment thus obtained to the phosphor, the plasticity of the attached binder due to heat is used in the same manner, and the pigment and the phosphor are attached by reheating. For example, a phosphor and a pigment with a binder are dry-mixed or wet-mixed, and the mixture is heated and stirred in a mixer to soften the binder again to adhere the pigment to the phosphor, and then cooled. The rotation speed of the mixer is 50
The speed is preferably 0 rpm or less. This is because, if stirred at a speed of 500 rpm or more, the phosphor particles will collide with each other and be crushed, resulting in a decrease in the brightness of the phosphor. As another method, the binder-attached pigment may be attached to the phosphor using the cohesive force of silica and metal ions in an aqueous solvent, and then the binder may be plasticized by drying, and the pigment and the phosphor may be attached. However, the method of dry mixing the pigment, phosphor, and binder and attaching the pigment to the phosphor by heating and melting is
This is not preferable because the pigment does not adhere to the phosphor and the phosphors tend to aggregate with each other, and in order to prevent aggregation, the phosphor must be stirred at a very high speed.

[Effect]

Conventionally, a pigmented phosphor was obtained by attaching a binder to a phosphor and a pigment, whereas the production method of the present invention uses the plasticity of a binder attached to a pigment to attach a pigment to a phosphor. Since this is a method of attaching pigments to the phosphor, it is possible to attach the pigment to the phosphor using less binder than in the past, and a pigmented phosphor with an adhesion strength higher than that of conventional phosphors can be obtained.

[Example 1] After dry mixing 1 kg of cobalt blue as a blue pigment and 30 g of thermoplastic acrylic resin powder, 1 kg of cobalt blue as a blue pigment was mixed in a mixer.
After stirring at high speed at 200 rpm while heating to 40° C., the mixture was cooled to obtain a binder-coated pigment coated with 3.0% by weight of acrylic resin based on cobalt blue. 5 kg of blue light-emitting phosphor (ZnS:Ag, AI) and 270 g of the binder-attached pigment were dry mixed, and the binder was melted by heating to 140'C in a flash dryer to adhere the pigment to the phosphor, and then cooled. Then, a pigmented phosphor was obtained by passing it through a 300 mesh sieve. The pigment peeling rate of the pigmented phosphor thus obtained was measured as follows. First, the weight ratio of water:PVA:ADC:pigmented phosphor=2
．． A phosphor coating slurry is formed by mixing at a ratio of l:0.06:0.04:I. Next, put 100ml of this coating slurry into a beaker, put the suction side and discharge side hoses of a bead pump (NFL type, Iwaki Co., Ltd.!) into the same beaker, and operate the pump for a certain period of time at a flow rate of 1.01/m to apply the slurry. Circulate the slurry.During pump operation, the coating slurry is separated, transferred to a sedimentation tube, and the phosphor is allowed to settle.After the precipitated phosphor is separated, washed with water, and dried, the pigment attached to the phosphor surface is chemically removed. Analyze and compare with the amount of pigment before peeling.For example, in the case of the blue pigment Cobalt Blue (Coo-n 1203), CO
By analyzing the red pigment Bengara (Fe20
In the case of 3), the peeling rate of the pigment can be determined by analyzing Fe. Note that the bead pump is also called a snake pump, and has a similar structure to a pump used for transporting phosphor coating slurry in the actual cathode ray tube manufacturing process. (Comparative Example 1) 5 kg of phosphor similar to Example 1 and 270 kg of blue pigment
g was dispersed in water, a thermosetting acrylic emulsion solution (containing 30 g as solid content) was added, and the pH was adjusted to 6.0 with dilute hydrochloric acid to adhere the pigment to the phosphor, followed by washing with water,
Separation and over-drying at 110°C for 5 hours yielded a pigmented phosphor. The pigment peeling rate of this pigmented phosphor was also measured in the same manner as in Example 1, and the results are shown in FIG. As shown in Figure 1, the pigmented phosphor manufactured by the manufacturing method of the present invention only showed a pigment peeling rate of about 3% in 5 minutes and 8% in 10 minutes, whereas the pigmented phosphor of Comparative Example 1 Approximately 7% of the pigment in the phosphor was removed in 5 minutes, and 15% in 1 minute, indicating that the pigmented phosphor of the present invention is superior.

[Example 2] 500 g of cobalt blue, the same as in Example 1, as a blue pigment
While stirring the mixture in a mixer, a thermoplastic acrylic emulsion (containing 25 g as solid content) was sprayed onto the mixture. Thereafter, the mixture was heated and melted at 140° C. while stirring, and then cooled to obtain a binder-attached pigment. Next, 5 kg of a blue-emitting phosphor (ZnS:Ag, CI) was dispersed in 51 water to form a phosphor suspension, and 200 g of the binder-attached pigment was added thereto and similarly dispersed. Furthermore, 25 g of colloidal silica with a 5i02 equivalent content of 20% and 20 g of a 2% zinc sulfate aqueous solution were added to this mixed dispersion.
0 ml was added, the pH was adjusted to 7.4 with aqueous ammonia, and the pigment with binder was attached to the phosphor. After waiting for the phosphor to settle and washing it twice with water, heat it at 140°C.
After heating and melting for 1 hour, the mixture was cooled and passed through a 300-mesh sieve to obtain a pigmented phosphor. The pigment peeling rate of this phosphor is also 3% in 5 minutes and 7% in 10 minutes.
% and showed excellent characteristics.

[Example 3] 1 kg of Bengara (F e203) as a red pigment and 50 g of polyethylene resin powder were dry mixed, then stirred at high speed at 200 rpm while heating to 120° C. in a mixer, and then cooled. Thereafter, the pigment was dispersed in water, pulverized in a ball mill for 2 hours, and then dried at 80° C. for 5 hours to obtain a binder-coated pigment coated with 5.0% by weight of polyethylene resin. After that, replace the phosphor with a red-emitting phosphor (Y2O2S: E u
) 5 kg and the melting temperature was 110°C.
A pigmented phosphor was obtained in the same manner as above. The pigment peeling rate of this phosphor is also 4% in 5 minutes and 1% in 10 minutes.
0%, which showed excellent characteristics.

[Example 4] 1 kg of Bengara (Fe20B) as a red pigment was stirred in a mixer, and then an EVA emulsion (solid content of 25
g) was sprayed, and the rest was carried out in the same manner as in Example 2 to obtain a binder-coated pigment. 5 kg of red light-emitting phosphor and 150 kg of the binder-attached pigment
After heating and melting the binder at 150° C. in a mixer, the binder was cooled and passed through a 300-mesh sieve to obtain a pigmented phosphor. The pigment peeling rate of this phosphor is also 2% in 5 minutes and 6% in 10 minutes.
% and showed excellent characteristics.

【Effect of the invention】

As described above, according to the manufacturing method of the present invention, it is possible to firmly bond the phosphor and the pigment, thereby preventing contamination of other colors on the phosphor screen.
There is less residue and a uniform phosphor screen can be obtained. In addition, since the binder can be attached to the phosphor with a smaller amount than before, aggregation of the phosphor is reduced even in the coating slurry. Furthermore, hot-melt binders require a much shorter adhesion time than solvent-based or water-based adhesives, allowing for smooth transition to the next process and improved productivity.

[Brief explanation of the drawing]

FIG. 1 is a graph showing a comparison of the pigment removal rate of a pigmented phosphor produced by the production method of the present invention and a pigmented phosphor produced by a conventional production method.

Claims (1)

[Claims] (1) In a method for producing a pigmented phosphor in which pigment particles are attached to the surface of phosphor particles via a binder, pigment particles coated with or attached to a hot-melt binder as a binder in advance are attached to the phosphor particles. A method for producing a pigmented phosphor characterized by: