JPS58177471A - Etching method of shadow mask - Google Patents

Abstract

PURPOSE:To obtain a small hole which is smaller than the thickness of a metallic plate with good accuracy in the stage of punching fine holes differing in aperture area on both sides of a metallic plate, by etching the plate to the midway from the large hole side then etching the plate further so as to penetrate through the plate from the small hole to large hole side. CONSTITUTION:Thin films 6, 7 exposed with metallic surfaces 14, 15 corresponding to a part for forming a small hole and a part for forming a large hole are formed on both main surfaces of a metallic plate 5 having a prescribed thickness T. An etching soln. 16 is sprayed only from the lower large hole side to form a recess 17 and the 1st stage is completed. A means for preventing sticking of the soln. 16 on the surface on the opposite side of the plate 15 is provided in this stage. The soln. 16 is further sprayed from both surfaces 14, 15 and the 2nd stage is completed. Thus, the hole having the hole diameter smaller than the thickness T is punched easily and the unfluctuated hole size is obtained.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method of etching a shadow mask for a color picture tube.

Technical background and problems of the invention Shadow! The square-shaped color receiver tube focuses three electron beams corresponding to red, green, and blue, respectively, into one of the many pores of the shadow mask, and disperses them again to produce red, green, and one color, respectively. A common method is to project a color image by correctly hitting each emitting phosphor with a corresponding electron beam. For this purpose, a large number of regularly arranged pores must be drilled with high precision within the effective area of the shadow mask. Since the electron beam is deflected and scanned within the effective area, the holes must be formed so that the opening areas are different on both sides of the shadow mask.

The aperture area on the fluorescent surface side is larger than that on the electron gun side (hereinafter, the aperture area on the fluorescent surface side will be referred to as a large hole, and that on the electron gun side will be referred to as a small hole). By the way, making the pores of the shadow mask even finer is considered to be an effective means of achieving higher definition in a color picture tube. However, in addition to the fact that it is difficult to uniformly drill pores with complex shapes as described above within the entire effective area, etching is generally used to drill holes smaller than the thickness of the shadow mask. It is said to be difficult to drill. As an example of a method for drilling such a hole smaller than the thickness of the plate, Japanese Patent Laid-Open No. 51-9035 proposes a process as shown in FIG. 1. That is, in the first step (3) of etching, the iron plate (1) is partially etched from one side, and the iron plate (
The protruding portions of the photoresist film and the iron plate located on the opposite side of 1) are completely protected from etching by the protective shield (2). Then, in the latter stage (4), the shield (2) is stripped off and etching continues from both sides until the RIP dimensions are obtained. Moreover, the protective shield (2) has a device mechanism that can be used continuously. Rubber belts containing magnetized particles or pressure-sensitive polyester, vinyl chloride and vinyl acetate films are suitable as the protective shield. In this process, a protective shield is used to prevent the etching solution from adhering to the small hole side when etching is performed only from the large hole side in the previous stage, but this increases the weight of the running iron plate and prevents the etching inside the etching chamber. In this case, the iron plate tends to bend, and the distance between the iron plate and the spray nozzle varies, which tends to disturb the uniform etching state. To avoid this, if the steel plate is pulled harder than usual, excessive strain is applied to the steel plate, causing molding defects during the press forming process. There is also a method of installing a support roller in the etching chamber to prevent the iron plate from bending, but in this case, the etching liquid is not applied to the iron plate located on a part of the support roller, and the etching liquid that has hit a part of the support roller is removed. It is difficult to maintain uniform etching because the spray pattern is disrupted. Furthermore, when implementing a process to enable the reuse of the protective shield, it is important to completely remove dirt from the protective shield and dry it before it can cause defects such as clogged pores and enlarged pores. Therefore, by simplifying the cleaning and drying process of the protective shield, it is possible to achieve a ratio of 1::1, which naturally has the disadvantage of increasing equipment costs as the length of the shield increases. In addition, when etching is performed only from the large hole side in the first stage, and when etching is performed from both sides of the large and small holes in the latter stage, if the flow rate of etching liquid on the small hole side is lower than that on the large hole side, as is usually done, the large hole is etched after passing through the large hole. The spray liquid from the lower side blows through the through hole to the upper side. As a result, Figure 2 (1
) and (b), the distance (hereinafter referred to as ■) from the surface of the iron plate on the small hole side of the matching part of the large and small holes decreases as etching progresses, and when the desired hole diameter is finally obtained, the cross section of the hole The shape is knife-etched. Therefore, if the etching conditions vary, the hole diameter of the knife edge part tends to change due to its thin wall thickness, which has the disadvantage that it is difficult to obtain a stable hole diameter.

Purpose of the invention - The present invention enables the second step to be performed without attaching a special protective shield to the small hole side to prevent etching liquid from adhering to the small hole side before the first step of etching. The purpose is to make maximum use of the effect of spray etching in the latter stage of etching to uniformly drill holes smaller than the thickness of the shadow mask.

Summary of the Invention The present invention involves performing 1iK etching on the side of the running part of the iron plate Km in order to prevent the etching solution from the large hole side from adhering to the small hole side when performing the first stage of etching, which is the first step, only on the large hole side. Etching should be done with a prevention plate provided for the liquid blowout, and then the second step, which is etching from both sides of the large and small holes, should be performed so that the etching liquid flows from the small hole side to the large hole side. K effectively makes holes smaller than the thickness of the shadow mask plate.

Embodiment of the Invention Figure 3 ((trans) to (f)K shows the process of the etching method of the present invention. Milk casein or polyvinyl is coated on both main surfaces between smooth metal plates such as iron having a predetermined thickness T5. A photosensitive solution consisting of ammonium alcoholic dichromate or sodium bithalamic acid is applied and dried to form a photosensitive film layer (61, (71) on one main surface of the bale and metal plate (5) of a predetermined thickness. A negative original plate (8) having a negative hole with a small diameter *(II) is placed on one main surface, and a negative original plate (9) having a negative image α force with a large diameter hole is placed on the other main surface, Using a light source such as ultraviolet light, each negative image M, αD is transferred to a photoresist film layer (61,
(7) Burn K. Next, the unexposed and uncured portions α2. of the photosensitive film layers (6) and (7) are exposed. The α tank is dissolved and removed using hot water, etc., and the metal surface Q4 corresponding to the small hole forming part and the large hole forming part is formed on both main surfaces of the metal plate (5). After that, in order to improve the etching resistance of the remaining photoresist film layer and its adhesion to the metal plate (5), and to prevent decomposition and peeling due to the etching solution, the remaining photoresist layer was subjected to a heat treatment process called baking. After that, etching is performed using an etching solution αe such as ferric chloride.The first stage of etching is performed only from the large hole side, that is, from the lower etching hole side. For example, the thickness of the metal plate (
Etching is continued to a depth of approximately half of the temperature of 100°C to form a recessed surface. When etching only the large hole side, if the etching liquid aI adheres to the small hole side, that is, to the upper side of the metal plate (5), etching progresses at the place where it has adhered, eventually causing variations in the hole diameter. In order to prevent this, in the etching chamber, an etching blowhole shown in FIG. 4 (51) is provided with an α value prevention plate on the side wall where the metal plate (5) runs. The structure of this parking WaS can be variously considered, including the structure shown in Fig. 4(b), but the metal plate (5) and the prevention plate α value rub against each other when the metal plate runs, and the photoresist film layer peels off. To prevent this, #C is mackerel 4 diagram (C
) is suitable as an a-lar prevention device (2). After forming the depression II (I?) on the large hole side to the desired depth, etching is performed from both the large and small holes in the second step.For example, the spray conditions for each Masochold on the small hole side are The pressure is 1~2 k/al, the etching liquid flow rate is 15~3°//m1m, and the spray conditions for each maw hold on the large hole side are gentler than those on the small hole side, such as the spray pressure and etching liquid for each maw hold. Etching is carried out at the platform to obtain the desired hole diameter under the condition that the flow I is compared to the small hole side and becomes approximately 1111 square meters. When compared to immersion etching, the mold in spray etching is that the amount of etching in the direction of the material to be etched is large.Furthermore, in the case of a shadow mask, the large and small holes are exposed to the surface, and the areas where these large and small holes meet (21) are exposed to the etching solution. In combination with the etching ability of K, the mechanical roar of the spray allows for preferential etching. In other words, as etching progresses in the depth direction, the metal plate (5
), the photoresist film layer (6), and f71. Etching, generally called side etching, also progresses at the contact surface between the photoresist film layer (6) and f71. In other words, as shown in Fig. 5, if the etch factor [F] is set as F = B/A as a method for quantifying the amount of side etching, the larger the F value, the smaller the amount of side etching and the closer it is to ideal etching. However, when spray etching is performed to obtain the desired hole diameter, the F value becomes smaller as the thickness of the metal plate increases.

As this side etching progresses and the number of photoresist film layer portions α which do not come into contact with the metal plate (5) increases, the sprayed etching solution Oe is removed from the metal plate (5).
and photoresist film layer f61. (7) It works to prevent contact near the contact surface. As a result, the progress of side etching is greatly suppressed, and the metal parts that are directly hit by the sprayed etching solution Oe, as well as the thin large and small hole matching parts c! D is preferentially etched. As mentioned above, by performing the 11-stage etching under the condition that the etching liquid blows from the small hole side to the large hole side, the large and small hole matching area 01) is preferentially etched, and as the etching progresses, the large and small hole matching area Qυ As for the opening width, the printing of the photoresist film layer (6) on the small hole side begins to be regulated by the width, and as the wall thickness of the one large and small inclusion part C2p becomes thicker, variations in etching conditions occur, resulting in one hole diameter. The effect on the shadow mask is small, and it is possible to obtain holes having a uniform diameter with little dimensional variation over the entire surface of the shadow mask. In addition, when etching from both sides of the large and small holes in the subsequent stage, the thickness of the metal plate at the location to be etched is thinner than the initial metal plate thickness, so the hole has a smaller diameter than the metal plate thickness. A shadow mask can be easily obtained.

In the above embodiments, the later double-sided etching was explained using spray etching, but the etching on the large hole side can be done by using the etching solution in a spray form to eliminate the mechanical effect.

Effects of the Invention As described above, according to Book 1 [K], when etching only from the large hole side of the previous stage, the thickness of the metal plate can be reduced by only partially modifying the conventional chamber structure without requiring large-scale work 1. Holes having smaller diameters can be IK-drilled, and stable hole sizes can be obtained even if etching conditions are disturbed. 1+ When etching from both sides of the large and small holes in the latter stage,
Because the plate thickness is thinner, the amount of side etching on the small hole side is required to obtain the desired hole diameter, and as a result, the negative dimensions of the small hole can be increased, improving the quality of the negative original plate, and therefore A shadow mask having apertures of high quality and high precision can be obtained.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a conventional etching device, and Figure 2 (
M) and (b) are schematic diagrams showing the progress of conventional etching, FIGS. 3(a) to (f) are schematic diagrams showing the progress of hole drilling in the embodiment of the present invention, and FIG. a), (b), and (C) are schematic diagrams of the main parts of the etching liquid blowout showing the prevention plate, and Fig. 5 is a schematic diagram for explaining the etching depth. (1)... Iron plate ( 2)... Maintenance shield (3)... Pre-stage etching chamber (4)... Bale stage etching chamber (5)... Metal plate (
61, (7)... Photoresist film layer (8), +9)... Negative original plate 01. αF...Negative image αri, I...Uncured light-uncured area (14,0j...Exposed metal image...Etching liquid a7), Recessed area Ol...Photoresist film area
0...The atrium is a prevention plate (to)...The atrium is a prevention device Qυ...Large and small hole matching part (7317) Representative Patent Attorney Noriyuki Noriyuki (and 1 other person) Figure 2
Figure 4 390 Figure 3

Claims (1)

[Claims] In a shadow mask etching method in which a large number of pores with different opening areas on both sides are bored in a predetermined area of a metal plate in an etching chamber, the metal surface on the side having a corrosion-resistant pattern defining a large opening area is used. a first step of etching only the first step; and a second step of etching from both sides of the metal surface, each having a corrosion-resistant pattern defining a large aperture area and a small aperture area, respectively. means for preventing the etching solution from adhering to the opposite side of the metal plate in the second step, and means for allowing the etching solution in the second step to blow through from the small opening area side of the front plate to the large opening area side. A shadow mask etching method having the following characteristics.