JPS6318085A - Production of shadow mask - Google Patents

Abstract

PURPOSE:To produce a shadow mask capable of improving the quality of an image by spraying a mixed liq. prepd. by mixing ultrafine particles contg. a heavy metal or the oxide thereof with a solvent on the surface of a shadow mask under the action of ultrasonic waves. CONSTITUTION:A mixed liq. 2 prepd. by mixing ultrafine particles contg. a heavy metal or the oxide thereof with a solvent is filled into a tank 1 and circulated between a spray gun 3 and the tank 1 through pipes 7, 5, 6. High pressure air is fed to the gun 3 through an air pipe 8 to spray the circulating liq. 2 on the surface of a shadow mask 13. At this time, the liq. 2 is heated to about 60 deg.C with a heater 9 placed at the lower part of the tank 1 and ultrasonic waves are applied to the liq. 2 from an ultrasonic generator 10 placed under the tank 1. Thus, the ultrafine particles are homogeneously dissolved in the liq. 2 and a layer of the heavy metal is uniformly formed on the surface of the shadow mask 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a shadow mask built into a color cathode ray tube, and particularly to surface treatment thereof.

[Prior art] The manufacturing process of the shadow mask, which is a component of color cathode ray tubes, that is, the color selection electrode, is described in "Electronic Science".
(Published by Sanpo Co., Ltd.) 1964.

VOL, 14 (No. 9), pages 36, 39, and 40.

FIG. 9 is a schematic exploded perspective view of a color cathode ray tube, in which a shadow mask (130) includes a panel (loo) that is a dish-shaped glass container, and an electron gun (11) that emits an electron beam.
It is located between the funnel-shaped funnel (120) containing the panel (
100).

This shadow mask (130) has a plate thickness of 0.15-0.
30mm thin iron plate, or in recent years 36% Ni-Fe
It is manufactured using a low-expansion material of In order to obtain a curved surface close to a spherical shape on the inner surface of the panel (toe), it is heat treated at 600 to 900°C in a hydrogen stream, press-formed into a predetermined shape, and then the surface is coated with black rust. Surface treatment is performed to obtain (Fe304). The process of obtaining this black rust is called surface blackening.

The surface treatment mentioned above can be done by first completely removing the oil that adhered to the surface during pressing, then immersing it in molten alkali salt and heating it to obtain black rust, or blackening with water vapor or carbon dioxide gas. The resulting black rust film is exposed to air for approximately 40 minutes during the process of manufacturing color cathode ray tubes.
A shadow mask (130
) is oxidized and rusts red (Fe203).
Its role is to prevent this from occurring.

In addition, when a color cathode ray tube is in operation, about 80% of the electron beam emitted from the electron gun passes through the shadow mask (13
0). Therefore, the kinetic energy of this electron beam is converted into thermal energy, and the shadow mask (130
) increases in temperature by approximately 40 to 80° C. and causes thermal expansion, resulting in distortion of the shadow mask (130). However, the above-mentioned black rust treatment is performed using a shadow mask (130
) emissivity from 0°15 to 0.38 to 0.75,
It also has the role of improving heat dissipation and reducing distortion caused by heat.

However, this black rust has an emissivity of about 0.75, and it is difficult to obtain anything higher than that from the material of the shadow mask. By the way, from the perspective of faithful image reproduction, recent color cathode ray tubes are required to have a flat panel surface, increase the amount of information per unit area, and make the image brighter and clearer. .

In order to meet these demands, it is necessary to reduce the diameter and pitch of the electron beam passing holes that determine the amount of information per unit area.

The minimum value of the hole diameter based on processing technology is determined by the thickness of the shadow mask base, and the hole diameter is set to 0.150 mm.
If so, the plate thickness will be as thin as approximately 0.150 mm. The rate at which the kinetic energy of the electron beam is converted to natural energy depends on the plate thickness, so when the plate thickness becomes thinner, the above-mentioned black rust treatment alone is insufficient as a measure to prevent distortion of the shadow mask. It is.

In order to solve the above-mentioned problems and further reduce the distortion caused by the heat caused by the impact of the electron beam, ultrafine particles containing heavy metals such as Bi2O3 or their oxides are mixed with the solvent. It has been proposed to spray a liquid onto the surface of a shadow mask to form a layer of heavy metal or its oxide (hereinafter simply referred to as "heavy metal layer") on the surface.

According to this, the heavy metal layer has a high emissivity and is also excellent in terms of elastic scattering of electron beams, so it promotes thermal radiation and elastic scattering of electron beams, and as a result, the shadow mask due to the impact of the electron beams is The occurrence of thermal strain due to temperature rise can be suppressed.

[Problems to be solved by the invention] However, in the initial stage, ultrafine particles containing heavy metals or their oxides are individually crushed into fine particles, but due to load applied during transportation, absorption of moisture, etc. Tends to cause agglomeration.

In this way, when agglomerated ultrafine particles are mixed with a solvent and sprayed, the ultrafine particles are not homogeneously dissolved in the mixture, so a heavy metal layer is not uniformly formed on the surface of the shadow mask, and electrons are Ultrafine particles may adhere to the inner wall of the beam passage hole, causing a so-called clogging condition.
There was a problem in that the image quality of the color cathode ray tube was significantly impaired.

An object of the present invention is to solve the above-mentioned problems and provide a method for manufacturing a shadow mask that can uniformly form a heavy metal layer on the surface of the shadow mask and improve image quality.

[Means for Solving the Problems] This invention mixes ultrafine particles containing heavy metals or their oxides with a solvent, and sprays this mixture onto the surface of a shadow mask to form a heavy metal layer on the surface. The method for manufacturing a shadow mask is characterized in that the liquid mixture is sprayed while being subjected to ultrasonic waves.

[Function] In the shadow mask manufacturing method of the present invention, ultrasonic waves are applied to the liquid mixture, and the coagulated ultrafine particles are separated and dispersed by the energy of the ultrasonic waves, and when this is sprayed, , a heavy metal layer is uniformly formed on the surface of the shadow mask.

[Example] Embodiments of the present invention will be described below based on the drawings.

(First Embodiment) FIG. 1 is a schematic diagram showing a first embodiment of the method for manufacturing a shadow mask according to the present invention. In the figure, (1) is a tank containing a liquid (2) in which ultrafine particles of Bi2O3, an oxide of heavy metals, are mixed with an aqueous solution of water glass; (3)
The mixed liquid (2) is atomized and the shadow mask (13
), and (4) is a pump that sucks the mixed liquid (2) in the tank (1).

(5) is a polyethylene pipe installed between the spray gun (3) and the pump (4), and (6) is the spray gun (
3) is a polyethylene pipe installed between the pump (4) and the tank (1), (7) is a polyethylene pipe installed between the pump (4) and the tank (1), and these pipes and the spray gun (3) and the pump (4) pumps the mixed liquid (
2) circulatory system is constructed.

The circulating liquid mixture (2) is supplied to the spray gun (3) only when the spray gun (3) sprays the mixture.

(8) is a spray gun (3) with high pressure air (0.3Kg/
cm') supply air pipe, (8) is tank (1)
A heater (1o) is an ultrasonic oscillator installed at the bottom of the heater. The bottom material of the tank (1) is made of high quality glass, and the tank (1) is equipped with an ultrasonic oscillator (
10).

In the above configuration, Bi203 (average particle size 0°5 gm)
When forming a film by spraying on the shadow mask (13), first, the heater (8) provided in the tank (1) is energized to heat the liquid mixture (2).

The temperature of the mixed liquid (2) at this time is optimally about 60°C, as will be described later.

When the liquid temperature is heated to about 60° C., the ultrasonic oscillator (10) is then operated. The oscillation frequency of the ultrasonic oscillator (10) is 20KHz±2KHz, and a 300W B-sonic vibrator is used. Note that the ultrasonic oscillator (10) may be operated in parallel with the heating of the heater (9).

After that, operate the pump (4) to pump the mixed liquid (2) from the tank (1) to the pipes (7), (5),
(6) and supplying high pressure air from the air pipe (8), the mixed liquid (2) is atomized from the spray gun (3) and sprayed onto the shadow mask (13).

In the above case, since a pressure of 1 at (= 1 Kg/cm') (7) of the outside air is normally acting on the mixed liquid (2), the ultrasonic oscillator (10) is operated to e.g. 2. If a sound wave that produces a pressure of 0 Kg/cm' is propagated, the pressure will be 3.0 Kg/crri' when compressed.
, when it is thin, a tensile force of 1.0 K g/cm' acts on it.

Usually, there are bubbles with at least a minute diameter in the liquid mixture (2), and when these bubbles burst due to the action of the ultrasonic waves, the energy generated at this time causes the coagulated ultrafine particles to Separate and disperse.

FIG. 2 is a graph showing the relationship between the liquid temperature of the mixed liquid and the bubble bursting frequency. As can be seen from this, in order to most effectively destroy the bubbles, the temperature of the mixed liquid (2) is optimally about 60°C.

- As mentioned above, when ultrasonic waves are applied to the mixed liquid (2), the fine air bubbles contained in the liquid are attracted to each other and bonded together by the tensile force caused by the ultrasonic waves, so that large air bubbles form and floats to the surface of the liquid.

This causes convection in the liquid and stirs the liquid, thereby further promoting separation and dispersion of the aggregated ultrafine particles.

In addition, since air bubbles come out more easily than in the liquid, the air in the liquid is effectively degassed, and when the bubbles burst, thermal energy is generated, which also contributes to an increase in the liquid temperature. Can be done.

Furthermore, Bi2O3 has a specific gravity of nearly 9 and tends to settle, but applying ultrasonic waves from the bottom of the tank (1) as described above is also effective in preventing settling of Bi2O3. .

As described above, by applying ultrasonic waves to the mixed liquid (2), the ultrafine particles coagulated in the mixed liquid (2) were separated and dispersed, and were homogeneously dissolved in the mixed liquid (2). When this is sprayed onto the surface of the shadow mask (13), a uniform and dense layer 1203 is formed on the surface of the shadow mask (13). In addition, the shadow mask (
13), the surface of which has been subjected to a blackening treatment in advance to form black rust, which is an oxide film, as in the conventional case.

In the shadow mask (13) processed as described above, Bi2O3 has a density of 8.64 and an emissivity of 0.8.
5. The electron beam has an elastic scattering coefficient of 0.5, and has excellent characteristics in terms of thermal distortion caused by temperature rise, so the shadow mask (13) can reduce thermal distortion caused by temperature rise compared to conventional ones. In comparison, the amount can be reduced by about 30%, making it possible to reproduce bright and clear color images.

Furthermore, since the Bi2O3 layer is uniformly formed on the surface of the shadow mask (13), the a-particles do not excessively adhere to the inner wall of the electron beam passage hole and cause clogging, thereby improving image quality. It can be measured.

As for the material for the bottom of the tank (+) that receives ultrasonic waves, a material with low acoustic impedance for longitudinal waves and transverse waves, that is, a material with low density and low velocity of longitudinal waves and transverse waves, will attenuate the energy of ultrasonic waves. For example, as shown in FIG. 3, crown glass or the like is preferably used.

In addition, in order to make the convection effect by ultrasonic waves more effective,
It is better for the ultrasonic transducer to be located in the center of the bottom of the tank (1) than for the entire bottom of the tank (1) to be the ultrasonic transducer surface.

(Second Embodiment) FIG. 4 is a schematic diagram showing a second embodiment of the method for manufacturing a shadow mask according to the present invention. In the figure, (1) is a tank, and (2) is a tank containing Bi2O3, which is a heavy metal oxide.
(3) is a mixture of ultrafine particles of gm or less mixed with an aqueous solution of water glass with a few percent surfactant added. (3) is a shadow mask (13) in which this mixture (2) is atomized.
The spray gun (4) is a pump that sucks the mixed liquid (2) in the tank (1). (5) , (
8) , (?) are pipes that make up the circulatory system, (8)
Insert high pressure air (0.6Kg/Cm') into the spray gun (3).
) is an air pipe that supplies air. (13) is a shadow mask, and (14) is a pipe for supplying the required amount of the mixed liquid (2) from the circulation system to the spray gun (3).

Here, a part of the pipe (5) is formed of a glass tube. As shown in FIG. 5, an ultrasonic transducer (12) is disposed outside the glass tube (11). This ultrasonic vibrator (12) has an annular shape and is arranged so that its vibration focal point (15) coincides with the center of the glass tube (11). Furthermore, the oscillation frequency of the ultrasonic wave is 20KH.
z±2KHz, 300 as ultrasonic transducer (12)
I am using W.

In the above configuration, when the pump (4) is operated, the mixed liquid (2) in the tank (1) flows through the pipe (5).

(8), (7), a part of which is supplied with high pressure air from the air pipe (8).
Spray from the spray gun (3) via the pipe (14).

Mixed liquid (2) is transferred to pipes (5), (8), (
7) while the ultrasonic transducer (12
), the mixed liquid (
Ultrasonic waves act on 2).

Part of the mixed liquid (2) is sprayed from the pipe (14), but most of it is sprayed from the pipes (5), (8), (
? ) and returns to the tank (1), so by applying ultrasonic waves to the mixed liquid (2) passing through the pipe (5) as described above, the liquid mixture is purified according to the same principle as in the first embodiment. The ultrafine particles coagulated in the liquid mixture (2) are separated and dispersed, and become homogeneously dissolved in the liquid mixture (2). Therefore, when this is sprayed from the spray gun (3) onto the surface of the shadow mask (13),
), a uniform and dense layer of ultrafine particles is formed on the surface. In addition, the ultrafine particles are crushed by the action of the ultrasonic waves, and the formation of atomized particles is promoted.

In this way, also in this second embodiment, the Bi2O3 layer is uniformly formed on the surface of the shadow mask (13), so that the image quality can be improved.

The reason why glass material was selected for the tube (11) is the same as that in the first embodiment.

(Third Embodiment) FIG. 6 is a schematic diagram showing a third embodiment of the method for manufacturing a shadow mask according to the present invention. In the figure, (1) is a tank containing a liquid (2) in which ultrafine particles of Bi2O3, an oxide of heavy metals, are mixed with an aqueous solution of water glass; (3)
The mixed liquid (2) is atomized and the shadow mask (13
), and (4) is a pump that sucks the mixed liquid (2) in the tank (1).

(5) is a polyethylene pipe installed between the spray gun (3) and the pump (4), and (8) is the spray gun (
3) is a polyethylene pipe installed between the pump (4) and the tank (1), (7) is a polyethylene pipe installed between the pump (4) and the tank (1), and these pipes and the spray gun (3) and the pump (4) pumps the mixed liquid (
2) circulatory system is constructed.

The circulating liquid mixture (2) is supplied to the spray gun (3) only when the spray gun (3) sprays the mixture.

(8) is an air pipe for supplying high pressure air to the spray gun (3) to atomize the liquid mixture (2), and (9) is a heater disposed at the bottom of the tank (1).

Here, as shown in FIG. 7, an ultrasonic vibrator (18) is disposed at the tip of the spray gun (3). This ultrasonic vibrator (18) is divided into four sections into an annular shape, and is arranged so that the focal point of the vibration coincides with the center of the spray gun (3). Note that the oscillation frequency of ultrasonic waves is 2
The frequency is 0 KHz±2 KHz, and a 300 W ultrasonic transducer (18) is used.

In the above configuration, when the pump (4) is operated, the mixed liquid (2) in the tank (1) flows through the pipe (5).

(6), (7), a part of which is atomized from the spray gun (3) by supplying high pressure air from the air pipe (8). At this time, the ultrasonic transducer (
16), the glass spray gun (3)
The ultrasonic waves act on the atomized Bi2O3 ultrafine particles, separating and dispersing the agglomerated ultrafine particles, and the ultrafine particles atomized by high-pressure air are further pulverized by the action of the ultrasonic waves. This makes it possible to achieve several percent atomization.

When the thus atomized Bi2O3 is sprayed from the spray gun (3) onto the surface of the shadow mask (13), the surface of the shadow mask (13) becomes uniform and dense.
Since 203 layers are formed, the image quality can be improved in the same manner as in the above embodiment.

In addition, in this embodiment, since ultrasonic waves are applied at the tip of the spray gun (3), the ultrafine particles stacked at the tip of the spray gun (3) will not solidify and the spray gun (3) will not be clogged. In addition, it is possible to eliminate the risk of the solidified material peeling off during spraying and adhering to the shadow mask (13).

Furthermore, as shown in Fig. 8, an ultrasonic vibrator (18a) is attached to the glass conduit (17) that draws out the mixed liquid (2), and the mixed liquid is heated by high-pressure air blowing out from the outlet (18). If the ultrasonic vibrator (18b) is arranged to focus on the atmosphere in which (2) is atomized, atomization by ultrasonic waves can be further promoted.

As described in the first embodiment, the material for the portion receiving ultrasonic waves is preferably a material with low acoustic impedance to longitudinal waves and transverse waves.

[Effects of the Invention] As described above, according to the present invention, a heavy metal layer with excellent emissivity etc. is formed on the surface of the shadow mask, so the occurrence of thermal distortion due to temperature rise of the shadow mask is suppressed. ,
In addition to providing bright and clear images, by applying ultrasonic energy to the mixed liquid during spraying,
Because it can disperse coagulated ultrafine particles,
After spraying, a uniform heavy metal layer is formed on the surface of the shadow mask, making it possible to improve image quality.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a first embodiment of the method for manufacturing a shadow mask according to the present invention, FIG. 2 is a graph showing the relationship between the liquid temperature of the mixed liquid and the bubble bursting frequency, and FIG. A diagram showing the distribution of materials when the vertical axis is the acoustic impedance for transverse waves and the horizontal axis is the acoustic impedance for transverse waves.
FIG. 4 is a schematic diagram showing a second embodiment of the method for manufacturing a shadow mask according to the present invention, FIG. 5 is a diagram showing the arrangement relationship between a glass tube and an ultrasonic transducer, and FIG. A schematic diagram showing the third embodiment of the method for manufacturing a mask, FIG. 7 is a diagram showing the arrangement relationship between the spray gun and the ultrasonic transducer, FIG. 8 is a diagram showing a modification of the arrangement of the ultrasonic transducer, and FIG. 9
The figure is a schematic exploded perspective view of a color cathode ray tube. (2)...Mixed liquid, (10)...Ultrasonic oscillator,
(12)...Ultrasonic transducer, (13)...Shadow mask, (16)...Super 11-wave transducer. In addition, in the figures, the same reference numerals refer to the same or equivalent parts.

Claims (9)

[Claims] (1) In the method for manufacturing a shadow mask, which comprises mixing ultrafine particles containing heavy metals or their oxides in a solvent, and spraying this mixture onto the surface of the shadow mask to form a layer of the heavy metals or its oxides on the surface, A method for producing a shadow mask, which comprises spraying a liquid mixture while applying ultrasonic waves. (2) The method for manufacturing a shadow mask according to claim 1, in which ultrasonic waves are applied from the bottom of a tank containing the mixed liquid. (3) The method for manufacturing a shadow mask according to claim 2, wherein the mixed liquid is heated with a heater disposed at the bottom of the tank and subjected to ultrasonic waves. (4) The method for manufacturing a shadow mask according to claim 1, wherein ultrasonic waves are applied to a part of a pipe installed between a tank containing the mixed liquid and a spray gun that sprays the mixed liquid. (5) The method for manufacturing a shadow mask according to claim 4, wherein ultrasonic waves are applied by an annular ultrasonic vibrator arranged so that the focal point of vibration coincides with the center of the pipe. (6) The method for manufacturing a shadow mask according to claim 4 or 5, wherein a part of the pipe on which the ultrasonic waves act is made of glass. (7) The method for manufacturing a shadow mask according to claim 1, wherein ultrasonic waves are applied at the tip of a spray gun that sprays the liquid mixture. (8) A method for manufacturing a shadow mask according to claim 7, in which ultrasonic waves are applied by an annular ultrasonic vibrator disposed so that the focus of vibration coincides with the center of the tip of the spray gun. . (9) The method for manufacturing a shadow mask according to claim 7 or 8, wherein the tip of the spray gun is made of glass.