JPH10219397A - Steel sheet for shadow mask, shadow mask, and picture tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive steel sheet for shadow mask, having stable etching characteristic, a shadow mask, and a picture tube incorporating the shadow mask. SOLUTION: The steel sheet for shadow mask has a composition consisting of >=0.015wt.% Cu and the balance Fe. Moreover, the characteristic of this steel sheet can be improved to a greater extent when an aluminum-killed steel having Cu content higher by >=0.02wt.% than S content is used. This steel sheet can be obtained by carrying out hot rolling, acid pickling, annealing, primary cold rolling, decarburizing annealing, and finish cold rolling in the order named. A shadow mask, prepared by using this steel sheet, has excellent etching characteristic. A picture tube, incorporating this shadow mask, is free from color bleeding and has extremely excellent image clarity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a steel plate used for a shadow mask of a color picture tube, a shadow mask, and a color picture tube incorporating the same. More specifically, aluminum killed, which excels in etching properties when processing dot holes in shadow masks and also has excellent press forming workability that can prevent the occurrence of stretcher strain when press forming into flat masks The present invention relates to a steel plate for a shadow mask made of steel, a shadow mask, and a color picture tube incorporating the same.

[0002]

SUMMARY OF THE INVENTION A color picture tube (hereinafter C)
As a material for the shadow mask used for the RT), a thin plate made of an Invar alloy or aluminum killed steel is used. The material for shadow masks made of aluminum-killed steel is a series of hot-pressed aluminum-killed steels, pickling, removing scale, annealing, then primary cold rolling, and finishing cold rolling after decarburizing annealing. It is manufactured through a process. A flat mask can be obtained by perforating dot holes in the thin sheet of aluminum-killed steel obtained as described above by using a photo-etching method. This flat mask is annealed, press-formed into a desired shape, blackened, and then incorporated into a CRT.

[0003] The shadow mask serves as an anode for generating an electron beam by applying a voltage, and as a stop when the electron beam passing through the dot hole is applied to a dot of a fluorescent paint applied on a front panel. It also has the role of. The latter role directly affects the sharpness, color bleeding, and brightness unevenness of an image displayed on a CRT, so that the dot holes require extremely high dimensional accuracy. The dot hole has a small diameter portion (hereinafter referred to as a small dot) on the surface facing the cathode side of the thin mask plate, a large diameter portion (hereinafter referred to as the large dot), and a small dot on the surface facing the panel side. The hole (Break)
Through Hole (hereinafter referred to as Br Th hole). The BrTh hole actually plays the role of the shadow mask as an electron beam aperture.

[0004] Etching of a steel plate for a shadow mask is performed as follows. First, a steel plate is subjected to a pretreatment such as degreasing, and a resist is applied to both surfaces and dried. Then
After exposing the master pattern of the dot holes, developing and baking the master pattern exposing the steel plate only to the portions corresponding to the dot holes, spraying a ferric chloride solution to remove the steel plate portion corresponding to the dot holes. Etch and drill.
Usually, the thickness of the steel plate for shadow mask is about 100 to 250 μm, and the above-mentioned Br Th hole is formed in the thickness direction by 15 to
It is located near a large dot of about 25 μm, and its diameter is 120 μm for a high-definition shadow mask and 14 mm for a medium-definition shadow mask.
It is about 0 μm. Hundreds of thousands of Br Th holes are formed in one shadow mask, and their dimensional accuracy such as position, diameter, and roundness must be strictly controlled.
Therefore, in order to obtain an accurate and small variation in the shape of the holes, in the various steps of the etching process, it is necessary to not only strictly control the steps such as the concentration of the ferric chloride solution, but also to etch the steel plate itself for the shadow mask. Improvement of characteristics is indispensable. As a method for improving the etching characteristics of an aluminum killed steel sheet for a shadow mask, for example, JP-A-58-81926, JP-A-6-330167, and JP-A-63-286
No. 524, etc., various techniques have been proposed, but there is no technique that specifically teaches improvement of the etching characteristics of the steel plate for shadow mask itself.

[0005]

As described above, the CRT
A technical problem in the production of shadow masks for use is the improvement of the etching characteristics of steel plates for shadow mass. S is well known as an element contained in steel that inhibits the etching characteristics of an aluminum-killed steel sheet for shadow mass, and a technique for limiting the content is disclosed. Normally, S is removed by desulfurization in the iron making and steel making processes.However, in the steel making operation of aluminum killed steel for shadow masks, the yield of molten metal is sacrificed in order to give priority to the reduction of S, and material costs are reduced. It has resulted in raising. Therefore, it is impossible to supply an inexpensive aluminum masked steel sheet for a shadow mask with an improved etching characteristic by a manufacturing method in which the S content is simply reduced.

Accordingly, an object of the present invention is to provide an aluminum killed steel plate for a shadow mask which is inexpensive and has stable etching characteristics. More specifically, the reduction of S, which inhibits the etching characteristics, is achieved by adding other inexpensive alloying elements to the remaining S harmfulness while maintaining the molten metal yield in the desulfurization process at a normal level that does not reduce the material cost. By achieving detoxification, the object of the above-mentioned subject is achieved.

[0007]

According to a first aspect of the present invention, there is provided a steel plate for a shadow mask, wherein an aluminum killed steel comprising 0.015% by weight or more of Cu and a balance of Fe is used. The steel plate for a shadow mask according to claim 2 is characterized in that an aluminum killed steel having a Cu content of 0.02% by weight or more with respect to the S content is used. A shadow mask according to a third aspect uses the steel plate according to the first or second aspect. A color picture tube according to a fourth aspect is characterized by incorporating the shadow mask according to the third aspect.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, by using a steel sheet in which Cu is uniformly dissolved in aluminum-killed steel,
The etching characteristics when spraying an aqueous ferric chloride solution are remarkably improved. The effect of the solid solution of Cu compensates for the etching inhibition of S and further increases the S content if the S content in the steel is within the range of 0.025% by weight or less in ordinary aluminum-killed steel.
The effect of improvement over the inhibition of the above is obtained, and as a result, stable etching characteristics are obtained. In addition, the S content is 0.025
% By weight or less, the Cu content is 0.02
If the amount exceeds the weight percentage, the effect of improving the etching characteristics by adding Cu becomes clearer. In order to quantitatively evaluate such a fact, a method of measuring an etch factor value is well known as a means for evaluating the etching characteristic. In the present invention, the etching characteristic was evaluated using the etch factor value. The method of measuring the etch factor value is shown by etching one side of a steel plate and determining the etch depth and the side etch ratio. Etch factor = (etch depth) / (side etch) (1) As shown in the above equation (1), a material having an excellent etching characteristic has an amount to be etched in the depth direction (plate thickness direction). On the other hand, since the amount etched in the side direction (plane direction) decreases, the etch factor value shows a large value. vice versa,
A material having poor etching characteristics has a large amount of side etch, and thus has a small etch factor value. That is,
For materials with high etch factor values, deeper dot holes can be obtained when etched under conditions that keep the diameter of the dot holes constant, which not only excels in perforation, but also reduces the pitch between each dot hole. It is possible to cope with the high-definition shadow mask. Further, the etch factor affects the shape of the Br Th hole, which is most important for the image quality of the CRT, and when the etch factor value is large, the Br Th hole becomes closer to a perfect circle, and a clear high image quality is obtained. Show the trend.

Hereinafter, the present invention will be described in detail. First, the manufacturing method will be described. The aluminum killed steel sheet, which is a steel sheet for a shadow mask for a CRT of the present invention, is prepared by ladle refining, vacuum degassing, and the like, which are performed by ordinary ironmaking, molten metal that has undergone a steelmaking process, or molten metal obtained by electric furnace melting using a steel scrap. This is an aluminum killed steel that has been Al deoxidized.
After solidification, the elemental component contained in the steel is Cu at 0.015% by weight.
Adjust the alloy composition so that the above content is contained and the balance is composed of Fe and other unavoidable elements, or the Cu content is 0.02% by weight greater than the S content and the balance is Fe and other unavoidable elements. The alloy composition is adjusted so that A continuously cast slab or ingot solidified and formed by a usual continuous casting method or ingot casting method is hot-rolled to obtain a hot-rolled steel sheet. This hot-rolled steel sheet is descaled, cold-rolled to a predetermined thickness, and wound into an open coil so that the steel sheet surfaces that overlap each other do not come into contact when winding into a coil, using a box-type annealing furnace. Carbide annealing treatment. However, the annealing furnace is not limited to the box furnace,
Having the same processing capacity does not prevent the use of a continuous annealing furnace. Decarburization annealing is usually performed in a non-oxidizing atmosphere with a dew point adjusted (630 to 700) ° C × (5 to 20) hours + (700 to 8
60) C. x (5-10) hours of heat history. After decarburizing annealing, the C content needs to be reduced to 0.001% by weight or less. Next, the steel sheet is subjected to cold rolling to finish the steel sheet for a predetermined thickness for a shadow mask. At the same time, the steel plate surface is finished to a surface roughness in consideration of the adhesion of the resist film applied thereon. The inevitable elements such as elements and impurities added to the aluminum-killed steel sheet used for the CRT shadow mask of the present invention, and the reasons for limiting the amount or content of the elements will be described below.

[0010] By uniformly dissolving Cu in steel, Cu has the effect of significantly improving the etching characteristics. In particular, since the etching rate has the function of making the etching rate uniform macroscopically and microscopically, the etched surface has a flat and fine texture. This effect depends on the added amount of Cu, and as the added amount increases, the etching surface roughness, for example, the Ra value shows a remarkably small value, and the steel sheet surface becomes finely textured. Therefore, the added amount of Cu is
Limited to 0.015% by weight or more. The amount of Cu added is 0.015% by weight
If it is less than 10%, the effect is small, so the lower limit is 0.015% by weight. More preferably, the content is 0.018% by weight or more, and a still more desirable range is 0.020% by weight or more. The upper limit is not particularly limited, but if it exceeds 1.0% by weight, it is a main cause of deterioration of the etching solution, and causes a decrease in etching rate. Therefore,
If it is necessary to limit the upper limit of the Cu content, 1.
0% by weight. More preferably 0.95% by weight or less,
Further, a desirable range is 0.90% by weight or less. Further, the effect of inhibiting the etching characteristics of S is compensated for by the addition of Cu, so Cu is added in an amount exceeding the S content. Specifically, the difference between the Cu content and the S content is
Cu is added so as to be 0.02% by weight or more. The preferred difference in content is 0.022% by weight or more. More preferably
0.023% by weight or more.

S is an element that remains in steel and roughens the etched surface, thereby impairing the etching property. further,
Since S embrittles steel materials and lowers mechanical properties, it is desirable that the S content be as small as possible. If it is necessary to limit the S content, the S content is limited to 0.030% by weight or less. The content is more preferably 0.028% by weight or less, and an even more desirable range is 0.025% by weight or less.

Other unavoidable elements include C, S
Elements normally contained in steel materials such as i, Mn, P, N, Al, and the like, and Cr, Ni, Mo, Ti, V, Nb, W contained in iron scrap used as a part of the melting raw material
And other alloying elements of steel materials. C is decarburized in a decarburization annealing step when manufacturing an aluminum killed steel sheet for a shadow mask, so its content is usually 0.001% by weight or less. If it is necessary to limit the C content, the content is set to 0.001% by weight or less. C forms a solid solution in the steel in an interstitial form and is a main cause of stretcher strain during press forming of a flat mask, which causes uneven elongation. Therefore, its content must be strictly controlled. . Mn is added as a deoxidizer in the steelmaking process.
Mn remaining in the steel has the effect of solid solution strengthening.
Further, S has an effect of preventing hot brittleness. Therefore, if it is necessary to limit the amount of Mn added, its content is
It is limited to the range of 0.025 to 0.35% by weight. 0.025 lower limit
In order to form MnS necessary for preventing deterioration of mechanical properties, the upper limit of the S content is 0.025%.
When the content is% by weight, at least the same content as that of S is required. The upper limit of 0.35% by weight is
This is because productivity in shaping the shadow mask by solid solution hardening is hindered. Si reacts with the etchant,
This leads to deterioration of the ferric chloride aqueous solution. In addition, since Si dissolves in steel and embrittles steel, the smaller the content, the better. S
When the i content is 0.04% by weight or more, the above-mentioned effect becomes significant. Therefore, the Si content is limited to 0.04% by weight or less. P is an element that significantly embrittles steel, and its content must be strictly controlled. In a normal steelmaking process, a steel having a P content of 0.015% by weight or less can be obtained.
Therefore, if it is necessary to limit the P content, it is limited to 0.015% by weight or less. Since N has the same effect as C, its content must be strictly controlled. In a normal steelmaking process, the content of N can be reliably obtained at 0.009% by weight or less. Therefore, if it is necessary to limit the N content, it is limited to 0.009% by weight or less. Al is used in the steelmaking process as a deoxidizer and has the effect of improving the cleanliness of the steel. Further, Al remaining in the steel combines with N to form AlN and has an effect of preventing uneven elongation due to N. However, when contained in a large amount, embrittlement due to solid solution hardening occurs and etching characteristics are deteriorated.
Since the Al content can be reliably reduced to 0.1% by weight or less after a normal steelmaking process, if it is necessary to limit the Al content, it is limited to 0.1% by weight or less.

[0013] Cr, Ni, Mo, Ti, V, Nb, and W are not elements to be positively added, and those contained in scraps and the like used as melting raw materials for aluminum-killed steel sheets remain. It is about to do. These elements are solid-solution hardened by forming a solid solution in the steel, and thus have an effect of improving the strength of the steel. Therefore, if it is necessary to limit the content, each element is limited to 0.5% by weight or less. It is more preferably at most 0.3% by weight.

Hereinafter, the method for producing the aluminum-killed steel sheet for a shadow mask of the present invention will be described with some supplementary explanations. The thermal history of open coil annealing is (630-700)
C. × (5 to 20) hours + (700 to 860) ° C. × (5 to 10) hours is used for the following reason. The annealing temperature (630 to 700) ° C. in the first annealing is mainly for decarburization, and the annealing temperature (700 to 860) ° C. in the second annealing is for diffusion and dispersion of segregated elements. If the temperature is 630 ° C or lower, the decarburization reaction rate is slow. If the temperature is 860 ° C or higher, the steel sheets are likely to adhere to each other due to deformation of the steel sheets. Therefore, the upper limit is 860 ° C. However, this does not preclude the use of single-stage annealing in order to improve productivity during annealing. If the C content in the hot-rolled steel sheet is about 0.04% by weight, almost all the steel becomes α-Fe in the range of (600-830) ° C, so the heat history is (600-830)
Decarburization and diffusion of segregation can be sufficiently performed only by single-stage decarburization annealing such as C × (5 to 20) hours.

[0015]

The present invention will be described in more detail with reference to the following examples. An aluminum killed steel sheet having the chemical composition shown in Table 1 was produced through a series of steps of melting, refining, continuous casting, hot rolling, primary cold rolling, decarburizing annealing, and secondary cold rolling. In the refining process, adjustment of the S content, vacuum degassing, and Al deoxidation were performed. The sheet thickness after hot rolling was 2.0 mm, and the sheet thickness was 0.6 mm by primary cold rolling. The decarburization annealing conditions were set to 650 ° C x 10 hours + 750 ° C x 6 hours, and the thickness of both sheets was 0.12 in the secondary cold rolling for finishing.
The range is from 4 to 0.126mm. In the obtained aluminum-killed steel sheets shown in Table 1, Sample Nos. 1 to 7 have adjusted S and Cu contents within the scope of the present invention, and Comparative Materials are shown in Sample Nos. 8 to 11. Table 2 shows the etch factors measured for the test materials shown in Table 1, the variation thereof, and the content difference between Cu and S (Cu-S) wt%. The etching conditions were as follows: the hole diameter of the photoresist pattern on the surface of the aluminum-killed steel plate as the test material was 110 μm, an aqueous solution of ferric chloride was used as an etching solution, the concentration was 48 ° Be (degree of Baume), and the temperature of the solution was 70 μm.
After adjusting to ° C., etching was performed at a spray pressure of 0.3 MPa for 100 seconds. For the etch factor, 300 holes were measured for each test material, and the average value and variation (σ value) were determined.

[0016]

[Table 1]

[0017]

[Table 2]

Sample Nos. 1 to 7 were adjusted so that the S content was 0.025% by weight or less and the Cu addition amount was 0.017 to 0.978% by weight. Sample Nos. 8 to 11 are test materials in which the content of S or Cu is out of the range of the alloy composition of the present invention. From Table 2, it can be seen that all the materials having the alloy composition of the present invention show an etch factor value exceeding 2.85, and the variation is within about 0.12 to 0.14, which means that they have excellent etching characteristics. Sample Nos. 8 to 11 are all Cu
The content is 0.011% by weight or less, and the effect of Cu is in a range where the effect is not recognized. In this case, although the S content is reduced and the etch factor is improved, even in the test material No. 11 (S content 0.0051% by weight) for the purpose of reducing the S content, the etch factor is only about 2.80. Absent. From these results, it was found that there is a limit to the effect of improving the etching characteristics by reducing the S content. Further, reducing the S content to 0.0051% by weight requires advanced refining technology, and inevitably lowers the yield of molten metal. Therefore, it has been clarified that a method for stably improving the etching characteristics of an aluminum-killed steel sheet for shadow masks at low cost is to set the S content to a normal level and to add an appropriate amount of Cu.

[0019]

As described above, the steel sheet of claim 1 uses aluminum killed steel containing 0.015% by weight or more of Cu and the balance Fe, and the steel sheet of claim 2 has an S content. On the other hand, since the Cu content is 0.02% by weight or more, these steel sheets are excellent in etching characteristics, and are excellent in dot hole piercing properties during etching in the flat mask manufacturing process. Further, these steel plates have a high etch factor value, a small number of side etches, and a deep etch depth, so that they can be used for manufacturing a high-definition shadow mask in which the pitch between dots is narrowed. Furthermore, shadow masks using these steel plates have good quality and little variation in Br Th holes in the dot holes, and a picture tube incorporating this shadow mask can provide high quality images.

Continued on the front page. (72) Inventor Susumu Shigemasa 1296-1, Toyoi Higashi-Toyoi, Kudamatsu City, Yamaguchi Prefecture Inside the Technical Research Center of Toyo Kohan Co., Ltd. In the laboratory (72) Inventor Hiroshi Fujishige 1302 Higashi Toyoi, Kudamatsu City, Yamaguchi Prefecture Toyo Kohan Co., Ltd. Kudamatsu Plant (72) Inventor Akira Ikeda 1-4-3 Kasumigaseki, Chiyoda-ku, Tokyo Toyo Kohan Co., Ltd.

Claims (4)

[Claims] (1) Cu of 0.015% by weight or more, and the balance being F
e. A steel plate for a shadow mask using an aluminum killed steel made of e. 2. The Cu content is 0.02 with respect to the S content.
2. The steel sheet for a shadow mask according to claim 1, wherein the steel sheet is made of aluminum killed steel in an amount of at least% by weight. 3. A shadow mask using the steel sheet according to claim 1. 4. A color picture tube incorporating the shadow mask according to claim 3.