JPS59149637A - Manufacture of shadow mask - Google Patents

Abstract

PURPOSE:To obtain a high quality shadow mask by providing means for suppressing promotion of dark reaction at more than one positions behind photosensitive film forming process, back/for of exposure process and before developing process. CONSTITUTION:Means for suppressing aging due to dark reaction at non-exposed section of photo-sensitive film are provided on at least one position behind photo- sensitive film forming process, back/for of exposure process and before developing process. For example original negative pattern 17 positioned with black dot 16 is contacted tightly on both faces of shadow mask metal plate 14 fed through a roller 15 then exposed by light from an ultraviolet light source to harden the photo-sensitive film except black dot 16 section optically. While suction and exhaust tubes 211, 212 are provided in a dark box 18 at the winding side while an air-conditioner 26 comprising an evaporator 22, fan 23, refrigerator 24 and electric heater 25 is placed in the suction tube 211 to maintain the environment in the dark chamber 18 below 18 deg.C and relative humidity of 40- 60% under the condition for suppressing aging of the non-exposed section of photo-sensitive film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a shadow mask for a color picture tube.

[Technical background of the invention and its problems]

The shadow masks used in general (two-color picture tubes) are represented by those with circular electron beam passage holes and those with rectangular electron beam passage holes. It has a large hole and a small hole with a small diameter on the surface facing the electron gun, and the electron beam passage hole is completed by passing through the small hole and the large hole.

On the other hand, in recent years, shadow masks used in color picture tubes for various displays and monitors are required to have extremely fine and highly accurate electron beam passage holes. A shadow mask with a circular electron beam passage hole uses a fine one with a pitch of 0.2 to 0.3 mm and a hole diameter on the electron gun side of 0.090 to 0.14 Q II*. There is.

When manufacturing a shower mask having such a fine and highly accurate electron beam passage hole, for example, a diameter of 4 to 5 μm is required.
After the large-hole side original I/GA pattern and the small-hole side original negative pattern are closely attached to both sides of a long metal plate for a shadow mask on which a photosensitive film of a certain thickness has been deposited, exposure and development are performed.

For example, when forming an image using a dichromate photosensitive dye, a dichromate such as ammonium dichromate or sodium dichromate is used as a photosensitive agent, and a film forming agent such as alkali milk caseinate or polyvinyl chloride is used. A photosensitive film M made of a water-soluble polymer substance such as alcohol (uses the property that when UV rays are irradiated through a mask pattern, the exposed areas harden and the unexposed areas become insoluble in cold water or hot water used as a developer) The mechanism of this photocuring reaction is a chemical change in which a trivalent chromium (Cr) compound is produced by a photochemical reaction of dichromate, that is, hexavalent chromium (Cr+s) absorbs ultraviolet energy and This trivalent chromium is reduced to trivalent chromium (Cr), and this trivalent chromium is combined with a water-soluble polymer substance such as milk caseinate alkali, which is a film-forming agent. On the other hand, in unexposed areas that are not exposed to light, the photosensitive coating does not harden and is washed away by the development process.

Therefore, by exposing using a negative original plate with a mask pattern that does not irradiate the part where the openings are to be formed, but irradiates the parts other than the openings, and then passing it through a developing process such as hot water. The photosensitive film in the area where the hole is to be formed is dissolved and removed, and the desired hole is formed in the next etching step.

However, as mentioned above, the photosensitive film becomes water-insoluble when irradiated with ultraviolet rays, but other than that, irradiation with ultraviolet rays also depends on environmental conditions such as temperature, humidity, and 1 uJ during residence after the photosensitive film is formed. There is a phenomenon in which a substance becomes water-insoluble, which is generally called a dark reaction.

Under normal working environment, for example, room temperature is 22℃ and relative humidity is 55%.
The photosensitive film was applied and dried for 48 hours under the following conditions, and the sensitivity was checked using a Kodak Photographic Step Tablet 1-NO2, and the sensitivity changed by 0.5 to 1.0 steps. This skewer means that the entire photosensitive film has been weakly exposed to light, and this is because the parts of the photosensitive film where holes should be formed are also exposed, and what should be completely water-soluble becomes somewhat water-insoluble. It is. At the time of image formation, the photosensitive film in the portion where the opening is to be formed is not completely dissolved and removed and a portion remains, resulting in variations in the progress of etching of individual openings and deterioration of the quality of the mask unevenness. Approximately 210 mJ/d under the above environment
After exposure, I left it for 10 hours, and then developed it.The result was Kodak Photographic Step Tablets)'NO.
2, the sensitivity changed from 4 steps to 5 to 6 steps, that is, the sensitivity changed from 1 to 2 steps. This is because, as mentioned above, the development performance worsens due to the progress of the dark reaction, and furthermore, the dark reaction progresses at the boundary line between exposed and unexposed areas. Exposed part (1) (opening forming part) and exposed part (2)
The dimensions of the dark reaction progressing portion (3) become smaller than the intended size, and the dimensions vary. As a result, especially when manufacturing a high-definition mask with small aperture dimensions, the dimensional accuracy of the apertures decreases, resulting in a final mask that is unusable.

[Purpose of the invention]

The present invention has been made in view of the above points, and an object of the present invention is to suppress the progress of dark reactions and produce a high-quality shadow mask.

[Summary of the invention]

The present invention provides means for suppressing the progress of the dark reaction in at least one or more so-called retention areas after the photosensitive film forming step, after the exposure step [1], and before the development step.
The embodiment of this is the retention part'l: i
Partial air conditioning under specific conditions of a mf degree of 18 degrees Celsius or less and a relative humidity of 40% to 60% is used to suppress the progression of cyclone to a practically acceptable range.

[Embodiments of the invention]

Observing that the hexavalent chromium ions in the photosensitive film made of milk caseate alkali and ammonium dichromate were reduced to trivalent chromium ions as the dark reaction progressed, infrared spectral analysis was performed and left for 10 hours. The results of examining subsequent changes in the amounts of hexavalent chromium ions and trivalent chromium ions by varying the temperature and relative humidity are shown in Figures 2 and 3. Figure 2 shows the 1nif degree and the amount of residual hexavalent chromium ions, and Figure 3 shows the relative humidity and the amount of residual hexavalent chromium ions.Characteristics (a) and (b) show the relative humidity of 40% and the amount of residual hexavalent chromium ions, respectively. 80% constant, and characteristic (C1) and characteristic (d) are under the condition that the temperature is constant at 10'C and 40℃, respectively.If the dark reaction does not proceed, l2 in the photosensitive film is 100% hexavalent chromium ion. should exist, but at a temperature of 1.0°C and a relative humidity of 40
Approximately 98% in %, approximately 25 at a temperature of 40°C and a relative humidity of 80%
Only % of hexavalent chromium ions remain.

These results show that the progress of dark reactions is greatly influenced by temperature, and that relative humidity has an effect when the temperature is high, but the effect is slight at low temperatures.

Next, FIGS. 4 and 5 show changes in the sensitivity of the Kodak Photographic Step Tablet N02 when the relative humidity is kept constant at 50% and the temperature is varied in order to actually correlate with the Shadow Mask.

In FIG. 4, the horizontal axis represents the residence time, and the vertical axis represents the C Nicoduck step tablet value. Characteristics (e), (g), and (g) are for temperatures of 15°C, 20°C, and 25°C, respectively. FIG. 5 shows the change in the number of stages of the Kodak Step Tablet from FIG. 4, and the characteristics (h), (i+ and (j) are for temperatures of 15°C, 20°C and 25°C, respectively.

It can be seen from FIGS. 4 and 5 that there is a correlation with the change characteristics of the amount of residual hexavalent chromium ions.

From the above results, in order to suppress the change in dark reaction over time, it is desirable to maintain the shadow mask material at as low temperature and low humidity as possible from after the photosensitive film is applied and before development. However, in reality, the dark reaction progression 11 is as shown in Figure 1 [b].
It is extremely difficult to completely remove the
Moreover, the equipment and energy required for this purpose are large. Also, the influence of temperature is greater than that of relative humidity.

As a result of further investigation from the above points of view, if the residual hexavalent chromium ion content is 80% or more and the change in the number of stages of Kodak Photographic Step Tablet N02 is within one stage,
It was confirmed that there is no problem in practical use even if the dark reaction progresses. In this case, the dust conditions are preferably controlled to a relative humidity of 40% to 60% and a temperature of 18.degree.

Next, inspections will be conducted according to the actual situation at each process.

The manufacturing process for a metal plate for a shadow mask is started by winding a long strip of metal into a roll. From the point of view of suppressing dark reactions, it is best to move the unwound metal plate at a constant speed and pass through each process in sequence, and after the etching process is complete (pick off the etching process at the unwound outer frame to obtain a flat mask). Most preferred because it requires the least residence time between each step.

In this case, it is very uneconomical to adjust all the environments in each process, that is, to starve the entire room, so from after the photosensitive film is applied to before the exposure process, and from after the exposure process to before the development process. It is economical to install partial air conditioning. Furthermore, since the residence time between each step is minimized and the dark reaction progresses less, it is effective to provide partial air conditioning at least one location between each step, for example, at least one location before and after the exposure step.

On the other hand, when manufacturing various types of shadow masks, each process is often performed independently, and a certain amount of time is required for residence between each process, so adjustment of environmental conditions is particularly important.

That is, the metal plate is unwinded, a photosensitive film is applied, and then the metal plate is once wound. Next (unwinding before the second exposure step and winding once after the exposure is completed).

Furthermore, unwinding is performed before the second development step, and etching is started immediately after the development is completed, or wine-gaining is performed once. This is because when manufacturing a wide variety of shadow masks, the width of the metal plate and the mask pattern for exposure are different.
This is because it is more efficient as a manufacturing line if each process is independent. In this case, since the dark reaction progresses quickly after the exposure, at least partial air conditioning is required in this area. In addition, although the dark reaction progresses relatively slowly in a wound metal plate, if the residence time until the next process is long, it is of course necessary to provide air conditioning to the storage area of the metal plate.

An embodiment in which partial air conditioning is applied to the next exposure step will be described with reference to FIG. 6. However, since the basic mechanism of the exposure apparatus is almost the same as that of the conventional one, the drawings and explanations are also simplified.

That is, the exposure device αD has a dark box (121) on the winding side, in which a long shadow mask metal plate (14+) with a photosensitive coating formed on both sides is wound around the rotation of the shaft (13). A (winding) roller αω is housed, and black dots t, i are formed on both sides of the (unwinding) shadow mask metal plate sent out from this roller α5).
6) are placed in close contact with the large hole side and small hole side original negative patterns a′0 (the figure shows one original negative pattern), and then exposed to uniform light from an ultraviolet light source (not shown), The photosensitive coating is photocured except for 00 parts of the black dots. Also, in the dark box (18) on the winding side, the axis σ
It is almost the same as a conventional exposure device in that it is equipped with a winding roller (20) that winds up a long shadow mask metal plate (14g) in the exposure area by rotating in the direction of the arrow. In the embodiment, the intake pipe (21+) and exhaust pipe (212) are marked in the dark box 0 on the winding side.
), and one pumporator inside this intake pipe (211) @
Fan + 23) An air conditioner (261) consisting of a refrigerator @ and an electric heater (c) is installed in the atmosphere inside the dark box αa, at a temperature of 18°C or less, which is a condition that can suppress the aging of the unexposed part of the photosensitive coating. The humidity is maintained at 40% to 60%.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to effectively suppress the dark reaction of the photosensitive film within a practically acceptable range, and the shadow mask has extremely high quality electron beam passing holes. can be manufactured.

[Brief explanation of drawings]

Figures 1(a) and 1(b) are schematic diagrams for explaining the exposure state of the photosensitive film, and Figure 2 shows the amount of residual hexavalent ROM ions in the unexposed area of the photosensitive film and the fM degree. Figure 3 is a characteristic diagram showing the relationship between the amount of residual hexavalent chromium ions in the unexposed area of the photosensitive film and relative humidity, and Figure 4 is the sensitivity of the photosensitive film depending on residence time (Kodak Step Taplet)N
Figure 5 shows the residence time (sensitivity of photosensitive film due to two factors (Kodak Step Tablet) NO2).
FIG. 6 is a schematic configuration diagram showing an embodiment of an exposure apparatus to which the present invention is applied. (1)...Unexposed area (2)...Exposed area (
3)...Dark reaction progress department (141), (142), (148)...Metal plate agent Patent attorney Noriyuki Chika (and 1 other person)

Claims (1)

[Scope of Claims] 1) A step of coating and forming a photosensitive film on a long metal plate, a step of exposing the metal plate coated with the photosensitive film to light through a mask pattern, and a step of exposing the exposed photosensitive film to light through a mask pattern. In the method for manufacturing a shadow mask, which comprises a step of developing and a step of etching the developed photosensitive film along the mask pattern, the following steps are performed: after the photosensitive film is applied, before and after the exposure step, and before and after the development step. A method for manufacturing a shadow mask, comprising means for suppressing changes over time due to dark reactions in unexposed areas of the photosensitive film at at least one or more locations. 2) The first aspect of the present invention is characterized in that the means for suppressing changes over time due to dark reactions in unexposed areas of the photosensitive film is partial air conditioning at a temperature of 18° C. or less and a relative humidity of 40% to 60%. A method for manufacturing a shadow mask as described in Section 1. 3) A part of the winding of the long metal plate after the photosensitive film has been applied and formed, a part of the unwinder before being attached to the exposure device in the exposure step, and a part of the winding after exposure and the developing device in the developing step. Claim 1, characterized in that at least one of the unwinding part of the long metal plate and the unwinding part of the long metal plate is subjected to two-part air conditioning before installation. How to make a shadow mask. 4) The method of manufacturing a shadow mask according to claim 1, characterized in that the unwinding part and the winding part of the long metal plate before and after the exposure step are partially air-conditioned.