JPH03176939A - Manufacture of cathode-ray tube - Google Patents

Abstract

PURPOSE:To suppress the breakage of a glass envelope without extending the production time by controlling the temperature difference between the inside and outside of the glass envelope during the production process to 100 deg.C or below at maximum in the low-temperature region with strong breaking strength. CONSTITUTION:An in-line type color picture tube device is heated to 350-450 deg.C at maximum during the sealing process in which a panel 10 and a funnel 11 are melted and connected at a high temperature and the exhausting process in which the interior of a glass envelope is exhausted to high vacuum at a high temperature after the neck section 4 of an electron gun structure 15 is sealed. The temperature rise speed for 5 min from the start is set to about 25 deg.C/min, the temperature rise speed for 30min thereafter is reduced to about 7.5 deg.C/min, and the temperature difference between the inside and outside of the glass envelope can be made 100 deg.C or below at the internal temperature 100 deg.C or below. The breakage of the glass envelope caused during heat treat ment can be reduced without extending the work time.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a cathode ray tube, and in particular, a method for manufacturing a cathode ray tube, which can prevent destruction of a glass envelope during the manufacturing process. This relates to a manufacturing method.

(Prior Art) Generally, a color picture tube, which is a typical cathode ray tube, has a glass envelope consisting of a panel and a funnel. A phosphor screen made of three-color phosphor layers that emit light in blue, green, and red is formed on the inner surface. Further, an electron gun assembly for emitting three electron beams is disposed in the neck of the funnel, and a deflection device attached to the outside of the boundary between the funnel cone and the neck deflects the three electron beams emitted from each electron gun. The structure is such that a color image is displayed by deflecting the light horizontally and vertically and scanning the fluorescent screen.

Normally, in the manufacturing process of color picture tubes as described above,
The glass envelope undergoes several high temperature steps. Particularly, in the sealing step in which the panel and funnel are fused and bonded through low-melting glass, and in the exhaust step in which the electron gun assembly is sealed and then evacuated to a high vacuum, the electron gun assembly is heated to a high temperature of 300 to 500°C. During this high-temperature process, particularly during the temperature rising and cooling processes, various stresses are exerted on the inside of the glass depending on the temperature distribution inside the glass. Furthermore, during the evacuation process, stress is applied due to the difference in air pressure between the inside and outside of the glass envelope, and these stresses may mechanically rupture the glass envelope.

This will be explained using FIGS. 5(a) to 5(e).

First, in the temperature raising process of the above-mentioned high-temperature step, as shown in Fig. 5 (a
) as shown in panel (50) and funnel (5
1) There is a temperature difference between the outer and inner walls depending on the thickness of the glass,
Tensile stress (Fl) acts on the inner wall of the funnel, which has a low temperature. Compressive stress (F2) acts on the outer surface. On the other hand, in the temperature decreasing process of the high temperature step, as shown in FIG. 5(b), tensile stress (Fl) acts on the outer surface and compressive stress (F2) acts on the inner surface. Furthermore, in the exhaust furnace, as shown in Fig. 5(e),
Compressive and tensile stresses are complexly applied due to the deformation caused by the pressure difference between the inside and outside of the envelope.

As mentioned above, the stress that occurs during high-temperature processes, especially tensile stress, distorts the glass surface and causes microcracks to occur.If microcracks exist, stress concentration can cause the glass envelope to break. . Among the stresses mentioned above, the stress caused by the temperature difference between the inside and outside of the glass envelope becomes smaller as the temperature difference between the inside and outside is smaller when the glass wall thickness is the same.

The temperature difference between the inside and outside of the glass is determined by the temperature increase rate of the furnace and the heat transfer rate inside the glass.If the temperature increase rate is decreased, the temperature difference between the inside and outside can be reduced, but this is not preferable because the manufacturing process becomes long. Therefore, in a normal manufacturing process, the temperature is raised and lowered at a substantially constant rate of 10'C/min when the temperature is raised and about -5'C/min when the temperature is lowered. When the temperature is raised under such temperature conditions, as shown in FIG. 6, the temperature difference (5
2) becomes maximum when the inner surface temperature (54) is around 200°C, reaching about 30'C.

On the other hand, it is known that the breaking strength of glass generally tends to decrease as the temperature rises, and if the temperature difference between the inside and outside of the glass envelope is the same, the temperature on the inside of the glass envelope is The higher the value, the higher the probability that the glass envelope will be destroyed.

(Problem to be solved by the invention) The influence of such stress has not been a problem in conventional small tubes, but in recent years it has become impossible to ignore in large picture tubes and high-definition picture tubes, and it has become a problem during the manufacturing process. The probability that the glass envelope will break is high. on the other hand,
In the manufacturing process, index increase has become a problem due to the increase in the number of products produced, and it has become difficult to lengthen the manufacturing process time.

The present invention has been made in view of the above-mentioned conflicting demands, and provides a method for manufacturing a cathode ray tube that has the effect of suppressing damage to the glass envelope without increasing the manufacturing process time. is intended to provide.

[Structure of the Invention] (Means for Solving the Problems) The present invention is characterized in that the temperature difference between the inside and outside of the glass envelope during the high-temperature process that goes through in the manufacturing process of cathode ray tubes is maximum in the low-temperature region where the breaking strength of the glass is strong. This is a method for manufacturing a cathode ray tube that can suppress destruction of the glass envelope without increasing the manufacturing time.

(Function) The function of the present invention will be explained with reference to FIGS. 1 to 7, using a color picture tube manufactured by the above manufacturing method as an example.

During the temperature increase process of about 2 degrees, the glass envelope made of funnels and panels has a certain wall thickness, as shown in Figure 2, so that the heat applied to the outer wall surface (31) is transferred to the inner wall surface. It takes a certain amount of time for conduction to (32). Therefore, the glass outer wall surface (31) and inner wall surface (32)
A temperature difference occurs, and tensile stress (41) acts on the low-temperature inner wall surface (32) as shown in Figure 2 due to the difference in the amount of expansion due to the temperature difference.On the contrary, during the cooling process, the amount of contraction As shown in Figure 3, from the difference in the tensile stress (4
3) works. The tensile stress (34) acting at this time is applied to the glass surface (38), which is not completely uniform, as shown in Figure 4.
A small crack (39) is generated in a part of the area. Tensile stress is concentrated in the micro cracks (39) generated on this surface (
40) L. Eventually, a force greater than the bonding force between atoms acts and mechanically breaks the glass. It is generally said that the breaking strength of glass decreases as the temperature increases, and if the temperature difference between the inside and outside is the same, the higher the temperature of the inner surface of the glass envelope, the greater the possibility of breaking. In order to suppress destruction without prolonging the working time, the temperature at which the temperature difference between the inside and outside of the glass envelope is the maximum must be set at 10, for example, as shown in Figure 7.
This can be achieved by keeping the temperature below 0°C. The glass is strengthened by generating the maximum stress in a low temperature region where the glass strength is relatively strong and preventing strong stress from occurring in the subsequent high temperature region (Example) Hereinafter, this invention will be explained based on an example with reference to the drawings. I will explain. An embodiment of the manufacturing method of the present invention will be described based on the in-line color picture tube device shown in FIG. In an in-line color picture tube device, the panel (lO) and funnel (11) are manufactured separately at the initial stage. Panel (10)
The inner surface has a fluorescent screen (12) that emits light when an electron beam hits it.
A shadow mask (13) serving as a color selection electrode for selecting electron beams incident on the phosphor screen is attached. On the other hand, an internal conductive coating (33) containing graphite as a main component is formed on the funnel (11). The panel (10) and the funnel (11), which were manufactured separately in this way, are fused and bonded at high temperature via the low melting point glass (23). This is the so-called sealing process, and is usually at a maximum temperature of 400 to 450°C.
After heating at a substantially constant temperature increase rate of about 10° C./min, the temperature is maintained at a constant temperature for a certain period of time. Its economy is cooled at a rate of -5'C/min.

Next, after the electron gun assembly (15) that emits three electron beams is sealed in the neck part (4), the inside of the glass envelope is evacuated to high vacuum at high temperature. This is the so-called exhaust process. In the exhaust process, the temperature is heated at a nearly constant rate of 10°C/min to a maximum temperature of 350 to 4000°C, and then heated to -5°C.
It is cooled at a rate of around C/min. Under such normal temperature conditions, as mentioned above, the temperature difference between the inside and outside of the glass envelope becomes maximum when the temperature rises when the temperature of the inner surface of the glass, where tensile stress acts, is 150°C or higher. This increases the burden on the strength.

On the other hand, in this example, as shown in FIG. 7, the temperature increase rate for the first 5 minutes of the initial heat treatment was approximately 25°C/min, and the temperature increase rate for the subsequent 30 minutes was approximately 7.5°C/min. By reducing the temperature difference between the inside and outside of the glass envelope (56)
The temperature at which the inner surface temperature (59) becomes 100 degrees Celsius or lower and the stress generated on the inner surface of the glass reaches its maximum is 10.
We were able to reduce the temperature to below 0°C.

Under the temperature conditions of the embodiment of the present invention shown in FIG. 7, compared to the case of heat treatment under the normal temperature conditions shown in FIG.
The inner temperature (58) when the inner and outer temperature difference (56) is maximum
> has clearly decreased, and the temperature difference between inside and outside at 200°C or higher has also decreased. Furthermore, the heat treatment time also hardly changed. By heat-treating under such temperature conditions, the tensile stress acting on the inner surface of the glass (32) at high temperatures where the glass strength is weak can be reduced without increasing the working time, and the tensile stress that occurs during heat treatment can be reduced. Destruction can be reduced.

In the above example, the desired temperature conditions were obtained by controlling the temperature increase rate, but the method is not limited to this, and there is a method of controlling the temperature by replacing the inside with hot air during the sealing process. or other methods may be used, as long as temperature conditions are obtained such that the temperature difference between the inside and outside becomes maximum when the inner surface temperature is 100° C. or less.

Further, in the above embodiment, the temperature raising process was described, but the same applies to the temperature lowering process, and the lower the temperature at which the inside and outside temperature difference is maximum, the better, but usually the cooling rate is smaller than the temperature rising rate. During the process, the difference in temperature between the inside and outside of the tube does not become large, so there is no particular problem.

In the following, the embodiments of the present invention have been described using a color picture tube as an example, but it goes without saying that the present invention is not limited to this and is widely applicable to cathode ray tubes having glass envelopes.

[Effects of the Invention] The present invention reduces mechanical breakage of the glass envelope during heat treatment in the manufacturing process, which has become a problem with the recent increase in size of color picture tubes, without particularly prolonging the working time. can be done.

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[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the configuration of a color picture tube device, which does not provide a detailed explanation of the present invention, and FIGS. 2 to 4 are partial cross-sectional views for explaining the problems to be solved by the present invention. , Figure 2 shows the stress that acts during the temperature rising process in the high-temperature process, Figure 3 shows the stress that acts during the temperature cooling process in the high-temperature process, and Figure 4 shows the microcracks and stress concentration that occur on the glass surface. Figure 5(b) shows the temperature increasing process in the process shown in Fig. 5(b).
C) is a schematic cross-sectional view of the envelope in the exhaust furnace, FIG. 6 is a diagram showing the change in temperature inside and outside the glass envelope over time when heat treatment is performed under normal temperature conditions, and FIG. FIG. 3 is a diagram showing temporal changes in temperature inside and outside a glass envelope for explaining the invention in detail.

Claims (1)

[Claims] It is equipped with a vacuum envelope made of glass, a phosphor screen formed inside the envelope, and an electron gun that emits electrons at a position opposite to the phosphor screen to cause the phosphor screen to emit light, and is evacuated at at least a high temperature. In a method for manufacturing a cathode ray tube, the method includes the steps of:
A method for manufacturing a cathode ray tube, characterized in that the temperature of the inner surface of the glass envelope when the temperature difference between the outer surface and the inner surface is maximum is 100° C. or less.