JPH07226168A - Member for cathode-ray tube - Google Patents

Abstract

PURPOSE:To restrain the falling-off of particulates of an oxide film to an almost nothing condition, and significantly reduce the abrasion of a metal mold in press work. CONSTITUTION:A member for a cathod-ray tube where an oxide film is formed on a surface by using iron as a base body, is arranged in the cathod-ray tube. Surface roughness Ra of the oxide film is set in 0.15 to 0.5mum, and maximum roughness Rmax is set not more than 5mum, and an average film thickness is formed in 0.5 to 2.0mum. The oxide film is formed as a two-layer structure of magnetite and hematite or a three-layer structure of wustite, magnetite and hematite.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shadow mask, an inner shield, etc. arranged in a color picture tube.
The present invention relates to a member for a cathode ray tube, which has an oxide film formed on the surface of iron as a base.

[0002]

2. Description of the Related Art Generally, in a cathode ray tube, many members are arranged in the tube. A shadow mask as a color selection electrode arranged to face the phosphor screen of the color picture tube, and an inner shield arranged between the shadow mask and the electron gun in order to prevent the influence of geomagnetism on the electron beam, This is an example. The shadow mask is usually composed of a mask body having a large number of electron beam passage holes, and a mask frame attached to the peripheral portion of the mask body.

The mask body, mask frame, and inner shield of this color cathode ray tube are usually made of a mild steel plate as a base, with some exceptions. As shown in FIG. An oxide film 4 having a two-layer structure of (Fe ₃ O ₄ ) and hematite 3 (Fe ₂ O ₃ ) and having a film thickness of 3 to 5 μm is formed. The reason for forming such an oxide film 4 is to prevent rusting during storage of members and in the manufacturing process of the color picture tube, and to reduce radiant heat and electron beam reflection that occur during operation of the color picture tube.

Generally, this oxide film is formed in a oxidizing furnace in an oxidizing gas atmosphere after processing a mild steel material into a predetermined shape.

Further, in the specification of Japanese Patent Application No. 2-291965, as shown in FIG. 6, an oxide film having a three-layer structure composed mainly of wustite 5 (Fe 2 O) and composed of wustite 5, magnetite 2 and hematite 3 is shown. It is shown that 4 is formed in advance on the surface of a mild steel material and is processed into a mask frame or an inner shield. The method of previously forming the oxide film 4 having the three-layer structure on the surface of the mild steel material and then processing the oxide film 4 does not require an oxidation furnace or a step of forming an oxide film in the assembly process of the color picture tube, This is advantageous over a method of forming a two-layered oxide film composed of magnetite and hematite after processing a mild steel material. In addition, the formed oxide film 4 has better adhesion to the substrate than the two-layer structure oxide film composed of magnetite and hematite, and even in the impact test after the production of the color picture tube, the oxide film particles are less likely to fall off. In addition, it is possible to reduce the deterioration of the withstand voltage characteristics caused by the clogging of the shadow mask and the foreign substances in the tube, and it is possible to improve the quality of the cathode ray tube and reduce the cost.

However, the above magnetite 2 and hematite 3
For the oxide film 4 having a two-layer structure composed of
Regarding the oxide film 4 having a three-layer structure composed of wustite 5, magnetite 2 and hematite 3 in (a), as shown in the surface roughness profiles 7 and 8 in FIG. The unevenness is large. Therefore, when these members having the oxide film 4 formed therein are arranged in the tube, the oxide film 4 will not be exposed when shock or vibration is applied to the color picture tube.
There is a problem that the fine particles are lost due to mutual friction and the like, which causes clogging of the shadow mask and deterioration of withstand voltage characteristics. In particular, the three-layer oxide film 4 consisting of wustite 5, magnetite 2 and hematite 3 has a film thickness of 3 to 5 μm for the purpose of corrosion resistance and reduction of radiant heat generated during operation of the cathode ray tube and reflection of electron beam. Therefore, there is a problem that the die for press working is worn down and productivity is drastically reduced.

[0007]

As described above, as a member arranged inside the cathode ray tube, there is a member having an oxide film formed on the surface of mild steel (iron) as a base. The oxide film consists of magnetite and hematite 2
There are a layered oxide film and a three-layered oxide film mainly composed of wustite, which is composed of wustite, magnetite, and hematite.

However, when a member having such an oxide film is arranged in the cathode ray tube, the conventional oxide film is
In both cases, the roughness of the surface roughness is large, so when impact or vibration is applied to the cathode ray tube, the fine particles are lost due to friction between the oxide films, which may cause clogging of the shadow mask and deterioration of withstand voltage characteristics. It causes it. In addition, especially for a three-layer oxide film composed of wustite, magnetite, and hematite, the three-layer structure is used for the purpose of corrosion resistance and reduction of radiation heat and electron beam reflection generated during operation of the cathode ray tube.
Since the material having a film thickness of ˜5 μm and having the oxide film formed thereon is subjected to press working, there is a problem that the die is worn and productivity is remarkably lowered.

The present invention has been made in order to solve the above-mentioned problems, and reduces the loss of the oxide film and pre-oxidizes it for a member having an oxide film formed on the surface of iron as a base. An object of the present invention is to make the wear of the die for press working to a normal level even when the member on which the coating is formed is pressed.

[0010]

In a cathode ray tube member in which an oxide film is formed on the surface of iron as a base and is arranged in a cathode ray tube, the surface roughness Ra of the oxide film is 0.15.
.About.0.5 .mu.m, maximum roughness Rmax of 5 .mu.m or less, and average film thickness of 0.5 to 2.0 .mu.m.

The oxide film has a two-layer structure of magnetite and hematite or a three-layer structure of wustite, magnetite and hematite, and the surface roughness Ra of these oxide films is 0.15 to 0.5 μm and the maximum roughness is Rmax is 5μ
The average film thickness was 0.5 to 2.0 μm.

[0012]

As described above, whether the oxide film has the two-layer structure of magnetite and hematite or the three-layer structure of wustite, magnetite and hematite, the surface roughness Ra of the oxide film is 0.15 to 0.15. When 0.5 μm and the maximum roughness Rmax are 5 μm or less, even if the oxide coatings or the oxide coating and other members rub against each other due to shock or vibration, the oxide coating particles are almost completely prevented from falling off. You can The average film thickness of the oxide film is 0.5 to 2.
By setting the thickness to 0 μm, even if the oxide film is formed in advance and then press working is performed, the wear of the die for the press working can be significantly reduced, the productivity is not deteriorated, and the required oxide film is obtained. Can be processed without impairing the function of.

[0013]

EXAMPLES As an example of a cathode ray tube in which a member having an iron oxide as a base material and an oxide film formed on the surface thereof was provided in the tube, foreign matter in the tube of a color picture tube was investigated. This color picture tube has a base member made of iron and has an oxide film formed on its surface.
As shown in FIG. 3, a mask body 10 in which a large number of electron beam passage holes are formed in a mild steel plate and a mask frame 11 attached to the peripheral portion of the mask body 10 are emitted, and the electron beam is emitted from a shadow mask 12. A hollow trapezoidal inner shield 15 attached to the mask frame 11 is provided in order to prevent the influence of geomagnetism on the generated electron beam 14. This oxide film is mainly for the purpose of preventing rusting during storage and in the manufacturing process of color picture tubes, and also for preventing reflection of radiant heat and electron beams generated during operation of color picture tubes.
_A two-layer oxide film composed of ₃ O ₄ ) and hematite (Fe ₂ O ₃ ) is formed. An elastic support 13 for holding the shadow mask 12 in the tube is attached to the mask frame 11.

The in-tube foreign matter generated in such a color picture tube had burrs and the like of the base metal generated during processing, but most of them were hematite. Further, as a result of investigating the place where the foreign matter in the pipe is generated, a spot-like missing portion was recognized at the contact portion between the mask frame 11 and the inner shield 15, but an oxide film still remained at this missing portion, and this missing portion It was found that the film thickness hardly changed.

The foreign matter in the tube is generated in such a state as shown in FIG. 5, in the oxide film 4 having a two-layer structure consisting of magnetite 1 and hematite 2, the surface layer is composed of hematite 2. Moreover, as shown in FIG. 7A, the surface of the oxide film 4 having the two-layer structure has large irregularities in the surface roughness, and the convex portions grow like needles. Therefore, it is considered that at the contact portion between the mask frame 11 and the inner shield 15 due to impact or vibration, the convex portions on the surface of the oxide film rub against each other, and the convex portions are lost to become foreign matter in the tube.

In addition to the occurrence of foreign matter in the tube, the hardness of the oxide film was investigated and found to be wustite (Fe 2 O 3).
The three-layer oxide film mainly composed of wustite, magnetite and hematite has a Vickers hardness of about 250 measured by a micro hardness tester, which is about 700 as compared with the two-layer oxide film composed of magnetite and hematite. It turned out to be soft and hard to drop out.

This means that the oxide film having a three-layer structure composed of wustite, magnetite, and hematite can be formed into an oxide film or an oxide film and another member by impact or vibration by appropriately reducing the unevenness of the surface. It suggests that even if friction occurs due to the contact of the oxide film, it is possible to form an oxide film that can prevent chipping.

Further, as another problem, in the press working of a mild steel sheet on which an oxide film of a three-layer structure composed of wustite, magnetite and hematite is formed, the die wear is severe and burrs are generated on the worked member. As a result of studying the wear of the die and the occurrence of burrs on the processed member, it was found that the process would proceed in the following steps (a) to (e). (A) If the oxide film is hard and the surface has large irregularities and the film thickness is large, for example, the material pressing in punching becomes insufficient, and material slippage occurs due to the impact of the punching punch (upper die). ) The edge of the die (lower die) begins to wear due to the material slippage (c) Then, the die wear progresses, and the clearance between the die and the punch increases (d) When the clearance increases, the flow of material increases, Wear of the die and punch rapidly progresses due to the thick oxide film. (E) Due to wear of the die and punch, burrs of the base metal are likely to occur. Normally, a die for press working has clearance adjustment. The die is softer than the punch to make it easier. Therefore, in order to reduce the wear of the mold and the occurrence of burrs, the point is how to suppress the wear of the die. For that purpose, one solution is to strengthen the material presser, but there is a limit to the strengthening of the material presser due to the configuration of the press working apparatus.

Therefore, as a result of searching for a method for suppressing the slippage of the material by improving the oxide film formed on the surface of the mild steel material, it has been found that this is possible. For example, the surface roughness Ra of the oxide film is 0.3 μm, the maximum roughness Rmax is 4.0 μm or less, and the average film thickness is 1.0 μm.
It has been found that it is possible to suppress slippage of the material. However, as the oxide film of the members arranged inside the cathode ray tube, basically, the characteristics required for the cathode ray tube such as rust prevention, radiant heat generated during operation of the cathode ray tube and reflection of electron beam are retained. At the same time, it is difficult to generate foreign matter in the pipe,
Further, it is necessary to reduce the wear of the press die.

Therefore, as a result of repeatedly conducting various experiments based on the above-mentioned investigations and views, the surface roughness Ra of the oxide film on the surface of the iron-based member arranged in the cathode ray tube is 0. 15-0.5 μm, maximum roughness Rmax is 5.0
μm or less, average film thickness 0.5 to 2.0 μm, preferably surface roughness Ra 0.2 to 0.4 μm, maximum roughness Rma
When x is 4.0 μm or less and the average film thickness is 0.5 to 1.5 μm, the basic characteristics required for the cathode ray tube are maintained, foreign matter in the tube is unlikely to occur, and a die for press working is used. It can be applied to both a two-layered oxide film composed of magnetite and hematite, and a three-layered oxide film composed mainly of wustite, magnetite and hematite, which can reduce the wear of aluminum. found.

That is, the surface roughness of the oxide film is necessary to prevent the reflection of radiant heat and electron beams, and for that purpose, the surface roughness Ra of the oxide film must be 0.15 μm or more. Was found as a result of the experiment. However, as is clear from the above-mentioned investigation, when the surface roughness becomes rough, the convex portions of the oxide film are rubbed against each other, and the convex portions are lost, and become foreign matter in the tube. Also, the die for press working is severely worn.
However, in FIG. 3, the relationship between the surface roughness Ra and the generation of foreign matter in the pipe is shown in broken line 1 for different oxide coating members.
As shown in Nos. 8 and 19, when the surface roughness Ra is 0.5 μm or less, even if a shock or vibration is applied, the oxide films are abraded by friction between the oxide films, resulting in a decrease in the protrusions. The generation of foreign matter is significantly reduced. Further, it was found from an experiment result that the wear of the mold is significantly reduced by setting the surface roughness Ra to 0.5 μm or less. The smaller the maximum surface roughness Rmax is, the more preferable it is, but it is 5 μm.
It was confirmed that the number of protrusions due to the friction between the oxide films was significantly reduced as long as it was below.

The thickness of the oxide film is important for preventing rusting during the manufacturing process of the cathode ray tube during the storage of the member,
As a result of experiments, it has been found that the thickness of the oxide film needs to be 0.5 μm or more for this purpose. However, the film thickness is 2
When the thickness is thicker than μm, the effect of the irregularities on the upper and lower mold surfaces of the mold on the processing material is weakened, and the material pressing becomes insufficient and slippery. As a result, wear of the mold becomes severe. The slippage of this material can be solved by providing a bead or a pressing pin in the press working apparatus as described above, but when the bead or the pressing pin is provided in this way, cracking or peeling of the oxide film occurs. As a result of experiments, it was found that the film thickness of the oxide film needs to be 2.0 μm or less in order to reduce the wear of the mold without making a special improvement to the conventionally used press working apparatus.

In the case of forming an oxide film having a two-layer structure composed of magnetite and hematite after processing the material into a predetermined shape, if the oxide film is thick, it may be oxidized due to slight bending. It was found that problems such as cracking and peeling off of the coating tend to occur, but this can also be greatly reduced by setting the thickness of the oxide coating to 2 μm or less.

That is, when the results of the above investigations and experiments are combined, the surface roughness Ra of the oxide film is 0.15 to 0.5 μm,
The maximum roughness Rmax is 5 μm or less, and the average film thickness is 0.5 to 2.
By setting the thickness to 0 μm, even if the oxide films contact with each other or the oxide film and other members cause friction due to shock or vibration, it is possible to make almost no loss of fine particles in the oxide film, and press molding is possible. It is possible to significantly reduce the wear of the die during processing, to perform processing without lowering the productivity and without impairing the required function of the oxide film.

A specific example will be described below.

Concrete Example 1. As a mask frame material for a shadow mask of a color picture tube, wustite is mainly contained on both surfaces of a mild steel plate (corresponding to SPCE material) having a thickness t of 0.50 mm, and is composed of wustite, magnetite and hematite. 3
A layered oxide film was formed aiming at a surface roughness Ra of 0.15 μm and a film thickness of 0.8 μm. This oxide film is formed by cleaning the mild steel plate to remove surface scale and rolling oil, and then putting it in a heating furnace and raising the temperature to about 800 ° C in an oxidizing atmosphere such as a mixed gas of CO and CO _2. Then, the temperature was rapidly cooled to about 80 ° C., and the surface roughness Ra and the film thickness were controlled by adjusting the temperature rising rate and the gas flow rate.

Table 1 shows the composition of the oxide-coated mild steel sheet of this example (specific example 1) in which an oxide film of a three-layer structure composed of wustite, magnetite and hematite was formed by the above-mentioned method by a conventional method. Compared with an oxide film-coated mild steel sheet that formed an oxide film later (conventional example 1) and an oxide film-coated mild steel sheet that had a three-layer oxide film formed of wustite, magnetite, and hematite before processing (conventional example 2) Indicate. Further, Table 2 shows the characteristics of the respective oxide films in comparison.

[0028]

[Table 1]

[Table 2] As is clear from Table 1, the composition of the oxide film-coated mild steel sheet of this example is not significantly different from that of Conventional Example 1. The formed oxide film varied in thickness from 0.5 to 1.5 μm, but the average film thickness was almost the target value. Further, as shown by the surface roughness profile 21 in FIG. 1, the surface roughness R
a was 0.16 μm and maximum roughness Rmax was 1.5 μm.

This three-layer oxide-coated mild steel sheet consisting of wustite, magnetite, and hematite was molded into a mask frame of a shadow mask of a color picture tube. The mold wear was remarkable, and many burrs were generated on the molded mask frame. In the case of the oxide film-coated mild steel sheet having a three-layer structure of this example, although the mold was slightly worn, it was molded. There was no problem with the mask frame, and the required mask frame could be used. Further, in the conventional three-layer oxide-coated mild steel sheet, since the surface roughness Ra is large, it was difficult for the working oil to be removed by washing after processing. However, the three-layer oxide-coated mild steel sheet of this example was washed. Well done and left no problems. Further, in the color picture tube in which the mask frame formed of the oxide film-coated mild steel sheet having the three-layer structure of this example is incorporated, the foreign matter in the tube incorporates the mask frame formed of the oxide film-coated mild steel sheet of Conventional Example 1. Compared to a color picture tube, it is about 1/7 less. In addition, it was confirmed that no rusting was observed even though the film thickness was as thin as 0.5 μm, and that there was no problem with heat radiation or electron beam reflection due to the reduced surface roughness. .

Concrete Example 2. As an inner shield material for a color picture tube, phosphorus (P) of 0.2% by weight or less is added to both sides of a mild steel plate having a thickness t of 0.145 mm. Surface roughness Ra of 0.30 μm with a layered oxide film,
The target film thickness was 1.5 μm. The formation of this oxide film was carried out by almost the same method as the formation of the oxide film described in Example 1. However, in this case, in order to form the oxide film as described above, it is necessary to raise the temperature and heat it up to about 800 ° C. At this temperature, the mild steel sheet is softened, corrugated in the heating furnace, and sometimes cut. Accidents such as accidents may occur. The addition of phosphorus is for strengthening the heat resistance of the mild steel sheet, and the purpose can be achieved by adding a trace amount. In addition to phosphorus, there are silicon (Si) and manganese (Mn) as the heat resistance-enhancing elements of mild steel sheets, but in the case of an inner shield for magnetic shielding, manganese, carbon (C), nitrogen (N), etc. However, since the magnetic properties deteriorate, it cannot be added easily. Further, silicon impairs the adhesion of the oxide film formed.

Table 1 shows the composition of the oxide-coated mild steel sheet (Example 1) having a three-layer structure consisting of wustite, magnetite and hematite of Example 2, and Table 2 shows the characteristics of the oxide film.

As shown in Table 1, the composition of the oxide film-coated mild steel sheet of this example is the same as that of Conventional Example 2. As shown in Table 2, the formed oxide film has almost the target value. The film thickness is 0.8 μm, which is thinner than the film thickness of Conventional Example 2. As shown by the surface roughness profile 22 in FIG. 2, Ra is 0.3 μm and maximum roughness Rmax is 3.5 μm.
Became.

When the three-layered oxide-coated mild steel sheet of wustite, magnetite and hematite was formed into an inner shield by pressing, the three-layered oxide-coated mild steel sheet of Conventional Example 2 had about 500 punches. When it exceeded the limit, the mold started to wear, and it was necessary to readjust the clearance with approximately 1,500 punches. With the oxide film-coated mild steel sheet of this example, however, the wear of the mold was slightly observed after 50,000 punches. However, there was no need to readjust the clearance. Further, in the case of the oxide film-coated mild steel sheet having the three-layer structure of Conventional Example 2, since the surface roughness Ra is as large as 1.5 μm,
Although it was difficult to remove the processing oil by washing after processing and oil could not be applied, the oxide layer-coated mild steel sheet with a three-layer structure of this example could be easily removed by washing even if oil was applied, It was possible to reduce the wear of the mold. Further, in the color picture tube incorporating the inner shield formed from the oxide layer-coated mild steel sheet having the three-layer structure of this example, the inner shield having the two-layer structure oxide layer formed of the magnetite and hematite after the foreign matter in the tube is processed. Compared to a color picture tube that incorporates
It was as small as about 1/10, and it was about 1/3 or less as compared with the color picture tube incorporating the inner shield formed from the oxide film-coated mild steel sheet of Conventional Example 2. Also, despite the thin film thickness of 1.5 μm, no rusting was observed,
Also, there was no problem with heat radiation or electron beam reflection due to the reduced surface roughness. It was confirmed that the addition of phosphorus had no problem on the magnetic properties and other properties.

In the above-mentioned specific example 1, the case where an oxide film of a three-layer structure composed of wustite, magnetite and hematite was formed on both front and back surfaces of a mild steel plate was described. The surface roughness and film thickness of the oxide film formed on the front and back of the mild steel plate may be different, such as forming only on the surfaces that are in contact with each other.
The oxide film on the surface where the oxide films do not contact each other may be different oxide films such as a two-layer structure composed of magnetite and hematite.

[0035]

EFFECTS OF THE INVENTION In a cathode ray tube member in which an oxide film is formed on the surface of iron as a base and is arranged in the cathode ray tube,
The surface roughness Ra of the oxide film is 0.15 to 0.5 μm,
The maximum roughness Rmax is 5 μm or less, and the average film thickness is 0.5 to 2.
When it is formed to 0 μm, regardless of whether the oxide film has a two-layer structure of magnetite and hematite or a three-layer structure of wustite, magnetite and hematite, the oxide film and the oxide film and other members may be separated by shock or vibration. Even if the particles are rubbed, the oxide particles can be almost completely removed. Also, by setting the average film thickness of the oxide film to 0.5 to 2.0 μm, the wear of the die during press working can be greatly reduced, and the required function of the oxide film can be achieved without lowering the productivity. It can be processed without damage.

[Brief description of drawings]

FIG. 1 is a diagram showing the surface roughness of an oxide film of Example 1 of the present invention.

FIG. 2 is a diagram showing the surface roughness of an oxide film of Example 2 of the present invention.

FIG. 3 is a diagram showing the relationship between the surface roughness of an oxide film formed on the surface of a mild steel plate as a substrate and foreign matter in the tube.

FIG. 4 is a diagram for explaining the configuration of a color picture tube.

FIG. 5 is a view showing a structure of an oxide film having a two-layer structure formed on the surface of a mild steel plate.

FIG. 6 is a diagram showing a structure of an oxide film having a three-layer structure formed on the surface of a mild steel plate.

FIG. 7 (a) is a diagram showing the surface roughness of an oxide film having a two-layer structure formed on the surface of a conventional mild steel plate, and FIG. 7 (b) is a surface roughness of an oxide film having a three-layer structure. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Mask body 11 ... Mask frame 12 ... Shadow mask 13 ... Electron gun 14 ... Electron beam 15 ... Inner shield 16 ... Elastic support 21 ... Surface roughness profile 22 ... Surface roughness profile

Claims (2)

[Claims] 1. A cathode ray tube member having an iron oxide as a base material and having an oxide film formed on the surface thereof, the oxide oxide film having a surface roughness Ra of 0.15 to 0.5 μm.
The maximum roughness Rmax is 5 μm or less, and the average film thickness is 0.5 to 2.
A member for a cathode ray tube, which is formed to have a thickness of 0 μm. 2. A cathode ray tube in which an oxide film is formed on a surface of iron as a base, and the oxide film is arranged in a cathode ray tube having a two-layer structure of magnetite and hematite or a three-layer structure of wustite, magnetite and hematite. In the member, the oxide film has a surface roughness Ra of 0.15 to 0.5 μm,
The maximum roughness Rmax is 5 μm or less, and the average film thickness is 0.5 to 2.
A member for a cathode ray tube, which is formed to have a thickness of 0 μm.