JPH04255631A - Blackening method for electronic part of color cathode-ray tube - Google Patents

Abstract

PURPOSE:To improve a radiation rate, and stabilize the emissivity of manufactured parts throughout the year by controlling temperature as well as atmosphere in the oxidizing thermal treatment of the parts. CONSTITUTION:Parts are subjected to oxidizing treatment in oxidizing gas atmosphere mixed with the air and, then, further subjected to another oxidizing treatment in oxidizing gas atmosphere free from the air at a temperature equivalent to the oxidizing thermal treatment or lower. In this case, DX gas of the prescribed composition normally available from the combustion of natural gas in the air is used as the oxidizing gas. The mixing ratio of the air to the oxidizing gas is between 16 and 24vol%, and more preferably approximately 20vol%. Also, treatment temperature in the oxidizing thermal treatment is between 630 and 680 deg.C, and more preferably approximately 650 deg.C. According to this process, reaction heat is generated on the surface of treated parts and in the atmosphere, thereby facilitating oxidization and enabling the manufacture of parts having a stable emissivity throughout the year.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for blackening electronic parts for color cathode ray tubes based on Fe or an alloy containing Fe and Ni as main components.

0002

2. Description of the Related Art A shadow mask will be explained as an example of an electronic component for a color cathode ray tube.

In recent years, color cathode ray tubes are required to have more phosphor picture elements per unit area for reproducing images and to have higher brightness. Therefore, efforts are being made to increase the kinetic energy of the electron beam. However, as a result, the high-energy electron beam that impinges on the shadow mask, which is the color selection electrode, during operation of the color cathode ray tube raises the temperature of the shadow mask to 40 to 80 degrees Celsius.
A problem has arisen in which the temperature rises and thermal distortion occurs. For this reason, instead of using the conventional material (iron material) whose main component is Fe as a shadow mask material, the thermal expansion is 1/2 of the iron material.
/10, which is 36% by weight of Ni and Fe, has come to be used as an INVAR material.

On the other hand, during the manufacturing process of color cathode ray tubes,
There is a process in which the shadow mask is exposed to an atmosphere of approximately 400° C. several times in the air, and a process in which light is used to create a phosphor screen, but these processes pose the following problems regarding the shadow mouse. In the former process, red rust (Fe2O3) is generated on the surface of the shadow mask, and in the latter process, light is scattered and the boundaries of the shape of the phosphor picture elements that make up the phosphor screen are not defined (indistinct).

To solve these problems, it is practically effective to form black rust (Fe3O4) on the surface of the shadow mask, as it is stable against heat treatment and has a high emissivity. Publication No. 46-767, JP-A-61-11
(See Publication No. 6734).

[0006] The black rust (Fe3O4) is usually formed using DX gas containing CO2 that contributes to oxidation, and the emissivity of the shadow mask is 0.6 to 0 for iron materials.
．． 7. Invar material has a level of 0.4 to 0.6. However, the emissivity and doming of invar material
), the higher the emissivity, the greater the effect of suppressing doming, so even higher emissivity is required for both iron and invar materials. .

The reason why the effect of suppressing doming occurs when the emissivity of the shadow mask increases is explained by the relationship between the emissivity and the heat flow velocity shown in FIG. 3.

The heat flow rate q between two opposing surfaces is expressed by the following formula.

[0009]

[Equation 1] σ: Blackbody radiation constant T1: Shadow mask surface temperature (80+273)K
T2: Surface temperature of the panel ε1: Surface emissivity of the shadow mask on the panel side ε2: Surface emissivity of the mask side of the panel Now, the temperature of the shadow mask is 8 when the color cathode ray tube is operating.
Assuming that the value is 0°C, the temperature of the panel facing the shadow mask is 5°C or 15°C, and the emissivity of the inner surface of the panel is 0.
4, curve 11 (panel temperature 5° C.) or curve 12 (panel temperature 15° C.) is obtained, and the emissivity of the shadow mask affects the heat flow rate.

[0010] As described above, by setting the emissivity of the shadow mask to a higher value, the heat flow rate increases, heat transfer from the shadow mask to the panel occurs, and therefore the temperature of the shadow mask increases in accordance with the heat flow rate. gone,
The amount of doming will be reduced.

[0011] A method of forming black rust on Invar material to obtain an emissivity of 0.6 or more is disclosed in Japanese Patent Application No. 2-183755.
As shown in the specification of the issue, the atmosphere inside the furnace was
DX gas (composition (volume %): CO2 10~
13%, CO 1-2%, H2 0.5-1.5%,
H2O 0.5-1.5%, balance N2) at 105 N
There is a method in which air is introduced at a rate of 15 Nm3/hour and DX gas is introduced at a rate of 350 Nm3/hour after the treatment, and the Invar material is thermally oxidized in such an atmosphere. Furthermore, JP-A-1-195630 describes a method of heating Invar material in the atmosphere, then heating it in a mixed gas of hydrogen and nitrogen, and further heating it in the atmosphere after pressing. .

0012

[Problems to be Solved by the Invention] However, when such a blackened shadow mask is exposed to a hot atmosphere of about 420°C in the air for about 15 minutes during the CRT manufacturing process, the emissivity changes depending on the season. It was found that a phenomenon of deterioration of around 10% occurred. It was found that this is because the humidity in the air changes throughout the year, which changes the degree of deterioration of the oxide film and changes the emissivity.

[0013]

[Means for Solving the Problems] The present invention provides Fe or F
A method for blackening electronic components for color cathode ray tubes based on alloys mainly composed of e and Ni, in which oxidation heat treatment is performed in an oxidizing gas atmosphere mixed with air, followed by oxidation without mixing air. The present invention relates to a method for blackening electronic components for color cathode ray tubes, characterized in that oxidation treatment is carried out in an oxidation gas atmosphere at a temperature equal to or lower than the temperature of the oxidation heat treatment.

[0014]

[Function and Examples] In the present invention, the emissivity can be increased by controlling the temperature as well as the atmosphere in the oxidation heat treatment of electronic components for color cathode ray tubes such as shadow masks, and furthermore, the emissivity can be increased. It is possible to stabilize the radiation rate throughout the year. Although the details of the reason for this are not clear, the present inventor assumes that this is because black rust is formed thick and densely by the method of the present invention.

F blackened by the method of the present invention
Electronic components for color cathode ray tubes based on alloys mainly composed of Fe or Ni include iron materials (Fe99
Contains 36% by weight or more), Invar material (36% by weight Ni, Fe
Examples include shadow masks, mask frames, internal magnetic shields, etc. that are based on materials such as

In the method of the present invention, first, oxidation heat treatment (hereinafter referred to as oxidation heat treatment 1) is performed in an atmosphere containing an oxidizing gas atmosphere mixed with air in a high temperature section of a furnace.

As the oxidizing gas, DX gas having the composition shown in Table 1, which is usually obtained by burning natural gas in air, is used. Further, propane gas may be used instead of natural gas.

[0018]

[Table 1] The dew point of the DX gas is preferably about 55±10°C. A high dew point is preferable; however, if it is too high, dew condensation may occur during cooling, and water droplets may drip onto the processed product from the furnace wall.

The mixing ratio of air to oxidizing gas is 1
6 to 24% by volume, more preferably about 20% by volume. When the ratio is less than 16 volume%, the emissivity tends to be low (0.5 or less), and when it exceeds 24 volume%, black rust (Fe3
O4) tends to peel off. The composition of the air is shown in Table 1.

[0020] The treatment temperature in oxidation heat treatment 1 was 630°C.
~680°C, more preferably about 650°C. If the temperature is less than 630°C, the emissivity tends to be low (0.5 or less), and if it exceeds 680°C, the treated product tends to be deformed. For example, the treatment time is 15
~20 minutes is preferred. If the treatment time is too short, the emissivity tends to be low (0.5 or less), and if the treatment time is too long, the treated product tends to be deformed.

In the oxidation heat treatment 1, the following reactions occur on the surface of the parts to be treated and in the atmosphere, and the oxidation is promoted by utilizing the reaction heat.

2(H2) + (O2) = 2(H2O)
(I)2(CO) + (O2) = 2(CO2)
(II) H2O-based oxidation: <Fe> + (H2O) = <FeO> + (
H2) (III)3<FeO>
+ (H2O) = <Fe3O4> + (H2)
(IV)2<Fe3O4> + (H
2O) = 3<Fe2O3> + (H2)
(V) CO2-based oxidation: <Fe> + (CO2) = <FeO> + (C
O) (VI)3<FeO> + (CO2) = <
Fe3O4> + (CO) (VII
)2<Fe3O4> + (CO2) = 3<Fe2
O3> + (CO) (VIII) O2-based oxidation: 2<Fe> + (O2) = 2<FeO>
(IX)6<FeO> + (O2) = 2
<Fe3O4>(X)4<Fe3O4> + (O
2) = 6<Fe2O3>
(XI) Next, oxidation treatment (hereinafter referred to as oxidation treatment 2) is performed at a temperature equal to or lower than the temperature of the oxidation heat treatment 1 in an oxidizing gas atmosphere without adding air. The term "equivalent" refers to a processing temperature range of approximately 5°C.

[0023] As the oxidizing gas, the above-mentioned DX is usually used.
Gas etc. are used. The oxidizing gas flow rate used in oxidation treatment 2 is about 1.5 times the oxidizing gas flow rate in oxidation heat treatment 1, compared to heat treatment in air in the manufacturing process of products incorporating the treated product. This is preferable because the emissivity of the product is stable.

The treatment temperature in oxidation treatment 2 is, for example, 600 to 6 when the temperature in oxidation heat treatment 1 is 650°C.
50°C is preferred. If the treatment temperature is too low, the emissivity of the treated product tends to decrease due to the heat treatment in the air during the manufacturing process of the product incorporating the treated product, and if it exceeds 650° C., the emissivity decreases.

[0025] The treatment time is 10 times the treatment time of oxidation heat treatment 1.
~30% is preferred. If the treatment time is too short, the emissivity of the treated product tends to decrease due to heat treatment in air during the manufacturing process of a product incorporating the treated product, and if it is too long, the treated product tends to be thermally deformed.

Here, FIG. 4 shows that the Invar material is subjected to oxidation heat treatment 1.
The results are shown below of the results of examining the emissivity of parts obtained by changing the holding time of oxidation treatment 2 and the temperature of the treated product after oxidation treatment was carried out at 650° C. for 20 minutes. In the figure, 13 is a graph of retention time of 3 minutes,
14 is a graph for a retention time of 5 minutes. It can be seen from FIG. 4 that as the treatment temperature of oxidation treatment 2 increases, the emissivity decreases. In addition, if the holding time is 5 minutes, in order to make the emissivity of the invar material higher than the emissivity of the iron material (0.7), 650
It can be seen that it is preferable to perform the treatment at a temperature below .degree.

The present invention will be explained in more detail below based on examples.

[Example 1] Invar material was blackened using the furnace shown in FIG.

FIG. 1A is a schematic sectional view of a furnace used for the thermal oxidation treatment. In the figure, a, b, c, d are heating zones, 1, 2, 3 are exhaust pipes for discharging the gas inside the furnace to the outside, 4 is a boundary plate that divides the atmosphere inside the furnace, 5,
6 is a pipe for guiding air to the heating zone a or b in the furnace, and 7 is a mesh belt for conveying the shadow mask 8 to be processed in the direction of the arrow. In addition, a, b,
Pipes for introducing DX gas to c and d and a heater for heating this furnace are not shown.

The set temperature of the furnace is heating zones a, b, c, d.
550℃, 655℃, 650℃, 63℃ respectively
0°C, and DX gas with the composition shown in Table 1 and a dew point of 55±10°C was supplied to heating zones a, b, and c at a rate of 110 Nm3/hour, and air was further supplied to heating zones a and b at 22°C.
The same DX as above was supplied to the heating zone d.
Gas was supplied at 150 Nm3/h. Belt speed was set at 350 mm/min.

FIG. 1B shows the actual temperature trend of the treated Invar material (solid line 9). In the figure, the vertical axis indicates temperature (° C.), and the horizontal axis indicates elapsed time of treatment.

The emissivity of the treated and blackened invar material is 0.
．． 75, and even when this shadow mask was passed through a furnace in air at around 400° C. during the manufacturing process of color cathode ray tubes, the emissivity hardly deteriorated.

Note that since the control temperature varies depending on the structure of the furnace, it goes without saying that the actual temperature has priority over the oxidation treatment.

[Comparative Example 1] Invar material was treated so that the actual temperature trend was as shown by the dotted line 10 in FIG. 1B. That is, the actual temperature in heating zones a, b, and c was 650° C. and the keeping time was 23 minutes, and the actual temperature in heating zone d was a maximum of 680° C. and the keeping time above 650° C. was about 5 minutes.

The emissivity of the treated and blackened invar material is 0.
．． It was 45-0.55.

[0036]

According to the method of the present invention, electronic components for color cathode ray tubes having emissivity that is stable throughout the year can be manufactured, and color cathode ray tubes with stable doming characteristics can be manufactured at all times.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the configuration of a furnace used in the blackening method of the present invention, and a graph showing the actual temperature trend of a shadow mask to be processed.

FIG. 2 is a graph showing the relationship between the emissivity and the doming rate of a shadow mask made of Invar material.

FIG. 3 is a graph showing the relationship between the emissivity of a shadow mask and the heat flow rate between the shadow mask and a panel facing it.

FIG. 4 is a graph showing the relationship between the temperature or holding time of the treated product in oxidation treatment 2 and the emissivity of the treated shadow mask.

Claims (1)

[Claims] [Claim 1] A method for blackening electronic components for color cathode ray tubes based on Fe or an alloy containing Fe and Ni as the main components, in which oxidation heat treatment is performed in an atmosphere in which air is mixed with an oxidizing gas atmosphere. . A method for blackening electronic components for color cathode ray tubes, characterized in that oxidation treatment is then performed in an oxidizing gas atmosphere without mixing air at a temperature equal to or lower than the temperature of the oxidation heat treatment.