WO1999047720A1

WO1999047720A1 - Steel sheet for shadow mask, shadow mask, and picture tube

Info

Publication number: WO1999047720A1
Application number: PCT/JP1998/001196
Authority: WO
Inventors: Tsuneyuki Ide; Hironao Okayama; Hiroaki Ikenaga; Susumu Shigemasa; Yasuo Tahara; Hiroshi Fujishige; Akira Ikeda
Original assignee: Toyo Kohan Co., Ltd.
Priority date: 1998-03-19
Filing date: 1998-03-19
Publication date: 1999-09-23
Also published as: AU6420098A

Abstract

A steel sheet for a shadow mask which is inexpensive and has stable etching characteristics, a shadow mask, and a picture tube incorporating the shadow mask are disclosed. The steel sheet contains at least 0.015 weight % of Cu and the balance of Fe. When an aluminum killed steel having a Cu content which is higher by at least 0.02 weight % than the S content is used as this steel sheet, the characteristics can be further improved. This steel sheet is produced through hot rolling, pickling, annealing, primary cold rolling, decarburization annealing, and finish cold rolling in this order. A shadow mask using this steel sheet has excellent etching characteristics. A picture tube incorporating this shadow mask has extremely high sharpness without blur of colors.

Description

Description Steel plates for shadow masks, shadow masks and picture tubes Background technology

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, it has excellent etching properties when processing the dot holes of shadow masks, and also has excellent press forming properties that can prevent the occurrence of strain strain when press forming into flat masks. The present invention relates to a shadow mask steel sheet made of aluminum killed steel, a shadow mask, and a color picture tube incorporating the same.

As a shadow mask material used for a color picture tube (hereinafter referred to as CRT), a thin plate made of Invar alloy or aluminum killed steel is used. The material for shadow masks made of aluminum-killed steel is hot-pressed, pickled to remove scale by pickling, then annealed, then subjected to primary cold rolling, decarburized annealing, and finished cold-rolled It is manufactured through a series of steps. A flat mask can be obtained by drilling a hole in the thus obtained thin sheet of aluminum-killed steel using a photo-etching method. This flat mask is annealed, press-formed into a desired shape, blackened, and then incorporated into a CRT.

The shadow mask functions as an anode that generates an electron beam when a voltage is applied, and a diaphragm when the electron beam that has passed through the dot hole is applied to the dot of fluorescent paint applied to the front panel. It also has a role. In the latter role, the dot hole requires extremely high dimensional accuracy because it directly affects the sharpness, color blur, and uneven brightness of the image displayed on the CRT. The dot hole has a small diameter portion (hereinafter referred to as a small dot) on the surface facing the negative electrode side of the thin mask plate, and faces the panel side. On the other hand, it has a structure that consists of a large-diameter part (hereinafter, referred to as a large dot) and a hole (Break Through Hole, hereafter referred to as a Br Th hole) that meets a small dot and a large dot. The Br Th hole actually plays the role of the shadow mask as an electron beam aperture.

The etching process of the steel plate for shadow mask is performed as follows. First, the steel plate is subjected to pretreatment such as degreasing, and a resist is applied to both sides and dried. Next, the master pattern of the dot hole is exposed and developed, and a master pattern in which the steel sheet is exposed only in the portion corresponding to the dot hole is baked. Then, a ferric chloride solution is sprayed to correspond to the dot hole. The part of the steel plate is etched and perforated. Normally, the thickness of the steel plate for shadow mask is about 100 to 250 // 111, and the above-mentioned Br Th hole is located about 15 to 25 <m in the thickness direction from the small dot to the large dot, and its diameter is Is 120 m for a high-definition shadow mask and 140 in for a medium-definition shadow mask. Hundreds of thousands of these Br Th holes are drilled in a single shadow mask, and their dimensional accuracy, such as position, diameter, and roundness, must be strictly controlled. Therefore, in order to obtain accurate and small-varied hole shapes, it is necessary to not only strictly control the ferric chloride solution concentration and other processes in the etching process, but also to use the steel plate for shadow mask itself. It is indispensable to improve the etching characteristics. As a method of improving the etching characteristics of the aluminum-killed steel sheet for a shadow mask, so far, for example, JP-58 - 81926 Patent, JP-6 330 167 No., are various techniques have proposed in JP-63- 28652 No. ^4, etc. However, there is no technology that specifically teaches the improvement of the etching characteristics of the steel plate for shadow masks.

As mentioned above, a technical problem in the production of shadow masks for CRTs is the improvement of the etching characteristics of the steel plates for shadow masks. S is well known as an element contained in steel that inhibits the etching characteristics of aluminum-killed steel sheets for shadow mass, and a technique for limiting its content has been disclosed. Normally, S is removed by desulfurization in the ironmaking and steelmaking process, but the production of aluminum-killed steel for shadow masks In the work, the yield of molten metal is sacrificed in order to prioritize the reduction of S, resulting in higher material costs. Therefore, it is not possible to supply an inexpensive aluminum-killed steel sheet for shadow masks with improved etching characteristics by simply reducing the s content.

As described above, an object of the present invention is to provide an aluminum-killed steel sheet for shadow masks which is inexpensive and has stable etching characteristics. More specifically, the reduction of S, which hinders the etching characteristics, reduces the harmfulness of the remaining s to other inexpensive alloy elements while maintaining the melt yield in the desulfurization process at a normal level that does not reduce the material cost. The objective of the above-mentioned subject is achieved by making it harmless by adding. Disclosure of the invention

The steel plate for a shadow mask according to claim 1 is characterized in that an aluminum killed steel comprising 0.015% by weight or more of Cu and the balance of Fe is used.

Shadow mask steel sheet according to claim 2 is characterized by using the content of C u relative to the content of S is 0 ² wt% or more often aluminum killed steel.

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. 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 improves the S inhibition if the S content in the steel is within the range of 0.025% by weight or less in ordinary aluminum-killed steel. As a result, stable etching characteristics can be obtained. In addition, when the S content is 0.025% by weight or less, and when the added amount of Cu exceeds the S content by 0.02% by weight or more, the effect of improving the etching characteristics by the addition of 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 of 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 by the ratio of the etch depth and the side etch.

One etch factor = (etch depth) / (side etch)… (1)

As shown in the above equation (1), a material with excellent etching characteristics has a smaller amount of etching in the side direction (plane direction) than the amount of etching in the depth direction (plate thickness direction). Therefore, the value of the etch factor is large. Conversely, a material with poor etching characteristics has a large amount of side etch, so that the value of the etch factor is small. In other words, with a material having a high etch factor, when etching is performed under the condition that the diameter of the dot hole is constant, a deeper dot hole can be obtained, which not only excels in drilling property but also improves each dot hole. It is possible to cope with a high-definition shadow mask in which the pitch between them is narrowed. Furthermore, the etch factor affects the shape of the Br Th hole, which is the most important for the image quality of the CRT. 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. This shows the tendency to be obtained.

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 shadow masks for CRTs of the present invention, is prepared by melting the molten metal that has been subjected to ordinary iron making, steelmaking, or obtained by electric furnace melting using a steel scrap, etc. After passing through, A1 is a deoxidized aluminum killed steel. After solidification, the alloying elements contained in the steel should be adjusted to an alloy composition such that the steel contains at least 0.015% by weight of C11 and the balance consists of Fe and other unavoidable elements, or the Cu content becomes S Adjust the alloy composition so that it is 0.02% by weight higher than the content, with the balance being Fe and other unavoidable elements. Normal continuous construction or inggo A continuous slab or ingot solidified and formed by a toughening method is hot-rolled to obtain a hot-rolled steel sheet. After the descaling process, the hot-rolled steel sheet is cold-rolled to a predetermined thickness, wound into an open coil so that the overlapping steel sheets do not come into contact with each other when winding into a coil, and a box-type annealing furnace is used. Used for decarburization annealing. However, the annealing furnace is not limited to a box furnace, and the use of a continuous annealing furnace will not be hampered as long as it has the same processing capacity. The decarburization annealing is usually performed in a non-oxidizing atmosphere with the dew point adjusted, with a heat history of (630 to 700) ^ (5 to 20) hours + (700 to 860) for (5 to 10) hours. After decarburization annealing, the C content must be reduced to 0.001% by weight or less. Then, the steel sheet is cold-rolled to a predetermined thickness for a shadow mask steel sheet. At the same time, the surface of the steel sheet is finished to a surface roughness that takes into account the adhesion of the resist film applied thereon. In the following, inevitable elements such as elements and impurities added to the aluminum-killed steel sheet used for the shadow mask for CRT of the present invention, and the reasons for limiting the amount or content of the elements will be described.

Cu has an effect of significantly improving the etching characteristics by being uniformly dissolved in steel. In particular, it has the effect of making the etching rate uniform both macroscopically and microscopically, so that the etched surface has a flat and fine surface texture. This effect depends on the added amount of Cu, and as the added amount increases, the roughness of the etched surface, for example, the Ra value shows a remarkably small value, and the steel sheet surface becomes finely textured. Therefore, the amount of Cu added is limited to 0.015 weight or more. If the Cu content is less than 0.015% by weight, the effect is small, so the lower limit is set to 0.015% by weight. More preferably, it is at least 0.018% by weight, and a more desirable range is at least 0.020% by weight. The upper limit is not particularly limited, but if it exceeds 1.0% by weight, it will be the main cause of the deterioration of the etching solution, resulting in a decrease in the etching rate. Therefore, if it is necessary to limit the upper limit of the Cu content, the content is set to 1.0% by weight. The content is more preferably 0.95% by weight or less, and a desirable range is 0.90% by weight or less. In addition, the addition of Cu compensates for the effect of inhibiting the etching properties of S, so that Cu is in excess of the S content. Add in. Specifically, Cu is added so that the difference between the Cu content and the S content is 0.02% by weight or more. A preferred content difference is 0.022% by weight or more. More preferably, it is 0.023 weight or more.

S remains in the steel to roughen the etched surface, which is a factor that inhibits the etching properties. Furthermore, since S embrittles steel materials and lowers mechanical properties, it is desirable that the S content be as low as possible. If it is necessary to limit the S content, the S content is limited to 0.030% by weight or less. It is more preferably at most 0.028% by weight, and a still more desirable range is at most 0.025% by weight.

Other unavoidable elements include C, Si, Mn, P, N, A1, etc., which are usually contained in trace amounts in steel materials, and C contained in iron scrap used as part of dissolved materials. Includes alloying elements of steel materials such as r, Ni, Mo, Ti, V, Nb, and W. C is decarburized in the decarburization annealing step when manufacturing aluminum-killed steel sheets for shadow masks, so its content is usually 0.001% by weight or less. If it is necessary to limit the C content, make it 0.001% by weight or less. C forms a solid solution in the steel in an interstitial form, and is a major cause of the formation of strain strain during flat mask press forming, which leads to non-uniform elongation. Must be managed. Mn is added as a deoxidizer in the steel making process. Mn remaining in the steel has the effect of solid solution strengthening. In addition, S has the effect of preventing hot brittleness. Therefore, if it is necessary to limit the amount of Mn added, its content is limited to the range of 0.025 to 0.35% by weight. The lower limit is set to 0.025% by weight. First, in order to form MnS necessary to prevent deterioration of mechanical properties, if the upper limit of the S content is 0.025% by weight, at least the same amount as S This is because the content is required. The upper limit is set to 0.35% by weight because productivity in shaping a shadow mask by solid solution hardening is hindered. Si reacts with the etching solution to cause deterioration of the ferric chloride aqueous solution. Also, since Si forms a solid solution in the steel and embrittles the steel, the smaller the content, the better. If S i content is 0.0 ^4% by weight or more, the above effect becomes remarkable. Therefore, The content of Si is limited to 0 · (Μ% by weight or less. Ρ is an element that remarkably embrittles steel, and its content must be strictly controlled. In a normal steelmaking process, the content of i Therefore, if the content of Ρ needs to be limited, it should be limited to 0.015% by weight or less. Ν has the same effect as C, so its content is strictly controlled. In the normal steelmaking process, the content of Ν can be reliably obtained at 0.009% by weight or less, so if it is necessary to limit the Ν content, limit it to 0.009% by weight or less. It is used in the steelmaking process as a material and has the effect of improving the cleanliness of the steel.Also, A1 remaining in the steel combines with N to form AIN and has the effect of preventing non-uniform elongation due to N. However, it contains a large amount In addition, it causes embrittlement due to solid solution hardening and deteriorates etching characteristics.A1 content is limited to 0.1% by weight or less after normal steel making process, so limit A1 content. If necessary, limit to 0.1% by weight or less.

Cr, Ni, Mo, Ti, V, Nb, and W are not elements that are actively added, but are included in scraps used as a raw material for melting aluminum killed steel sheets. To the extent that remains. Since these elements form a solid solution in the steel to form a solid solution, they have the 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, a few supplementary explanations will be added for the method for producing an aluminum killed steel sheet for a shadow mask of the present invention. The thermal history of open coil annealing is (630-700) ° CX (5-20) hours + (700-860) ° CX (5-10) hours, for the following reasons. The annealing temperature (630-700) ° C in the first annealing is mainly for decarburization, and the annealing temperature (700-860) ° C in the second annealing is for diffusion and dispersion of segregated elements. . Below 630, the decarburization reaction rate is slow, and above 860 ° C, the deformation of the steel sheet tends to cause adhesion between the steel sheets. However, this does not preclude the use of single-stage annealing to improve productivity during annealing. Hot rolled steel sheet If the C content in the steel is about 0.04% by weight, almost all the steel becomes α-Fe in the range of (600 to 830) ° C, so the heat history is (600 to 830) ° CX (5 to 20). ) Decarburization and diffusion of segregation are sufficiently possible only by single-stage decarburization annealing such as time.

(Example)

Hereinafter, the present invention will be described in more detail with reference to Examples. An aluminum-killed steel sheet having the chemical composition shown in Table 1 was manufactured through a series of steps of melting, refining, continuous forming, hot rolling, primary cold rolling, decarburizing annealing, and secondary cold rolling. In the scouring process, S content adjustment, vacuum degassing, and A1 deoxidation were performed. The plate thickness after hot rolling was 2.0 mm, and the plate thickness was reduced to 0.6 by primary cold rolling. Decarburization annealing conditions were set at 650 ° CX 10 hours + 750 ° CX 6 hours, in the secondary cold rolling finish, Re Izu plate thickness is also aligned in the range of 0.12 ⁴ to 0.1 ² 6 negation Was. Sample numbers 1 to 7 of the obtained Almkilled steel sheets shown in Table 1 have S and Cu contents adjusted within the scope of the present invention, and comparative materials are shown by sample numbers 8 to 11. Table 2 shows the measured etch factors of the test materials shown in Table 1, their variations, and the difference between the Cu and S contents (Cu-S) wt%. The etching conditions were as follows: the hole diameter of the photoresist pattern on the surface of the aluminum-killed steel sheet to be tested was 110 / m, an aqueous solution of ferric chloride was used as an etching solution, and the concentration was 48 ° B e (both degree). After adjusting the liquid temperature to 70 ° C, etching was performed for 100 seconds at a spray pressure of 0.3 MPa. For the etch factor, 300 holes were measured for each test material, and the average value and the variation were determined.

Table 1 Chemical composition of test material (steel plate)

Characteristic evaluation result of test material Sample Etch factor 1

Cu-S (% by weight) Category number Etch factor one value Variation (σ)

1 0.1023 2.86 0.13 The present invention

2 0.0461 3.04 0.12 The present invention

3 0.0310 2.90 0.13 The present invention

4 0.0430 2.93 0.14 The present invention

5 0.0610 2.89 0.14 The present invention

6 0.1060 3.05 0.13 The present invention

7 0.9540 3.11 0.13 The present invention

8 -0.0170 2.31 0.22 Comparative material

9 1 0.0050 2.49 0.19 Comparative material

10 0.0010 2.65 0.21 Comparative material

11 0.0039 2.80 0.14 Comparative material 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 whose S or Cu content is out of the range of the alloy composition of the present invention. From Table 2, materials having alloy set configuration of the present invention are both show the etch factor one value greater than 2.85, Matabara with also falls within 0.1 ² to 0.1 approximately ^4, it can be seen that excellent etching characteristics. Sample No. 8 or later: L1 has a Cu content of 0.011% by weight or less in all cases, and the effect of Cu is not recognized. In this case, although the S content was reduced, the etch factor was improved, but the test factor No. 11 (S content 0.0051 wt%) aimed at reducing the S content had an etched factor of about 2.80. It's just From these results, it was found that there is a limit to the effect of improving the etching characteristics by reducing the S content. Also, reducing the S content to 0.0051% by weight requires advanced refining technology, and inevitably reduces the yield of molten metal. Therefore, it was clarified that the method of improving the etching characteristics of aluminum-killed steel sheets for shadow masks inexpensively and stably is to keep the S content at a normal level and add an appropriate amount of Cu. Industrial applicability

As described above, the steel sheet of claim 1 uses aluminum-killed steel consisting of 0.015% by weight or more of Cu and the balance of Fe, and the steel sheet of claim 2 is based on the S content. Since the Cu content is higher than 0.02% by weight, these steel sheets have excellent etching characteristics and excellent drilling properties of the dot holes during the etching process in the flat mask manufacturing process.

In addition, since these steel sheets have a high etch factor, a small side etch, and a deep etch depth, they can be used for manufacturing a high-definition shadow mask in which the pitch between dots is narrow.

Furthermore, shadow masks using these steel plates have good Br Th holes in the dot holes and low variance. High quality images can be obtained.

Claims

The scope of the claims

1. A steel sheet for shadow masks made of aluminum killed steel consisting of at least 0.015% by weight of Cu and the balance Fe.

2. The steel sheet for a shadow mask according to claim 1, wherein an aluminum killed steel having a Cu content of 0.02% by weight or more with respect to an S content is used.

3. A shadow mask using the steel sheet according to claim 1 or 2.

4. An empty picture tube incorporating the shadow mask according to claim 3.