JPH0195439A - Manufacture of shadow mask - Google Patents

Abstract

PURPOSE:To make it possible to restrict the progress of dark reaction in a photosensitive film caused by heat when forming the photosensitive resin layer by feeding a signal obtained by measuring and detecting the amount of the dark reaction progress in the photosensitive film caused by heat back to a temperature control section of a drying furnace. CONSTITUTION:A continuous strip of metallic thin plate 1 as shadow mask material is dipped in a photosensitive liquid in an application trough 4, drawn out, and passed through a drying furnace 6 to form a photosensitive film on both surface of the continuous strip of metallic thin plate 1. The amount of progress of dark reaction in the photosensitive film is measured and detected with a dark reaction meter 8 installed in the middle of a path along which the strip is introduced to a winder 9 and signal feedback is sent to a drying furnace heat source control section so that said amount becomes below an allowable value. This makes it possible to obtain the shadow mask of a high quality as the progress of the dark reaction in the photosensitive film due to heat can be restricted to eliminate the dimensional variance of portions where a shadow mask base material is exposed and corresponding to the portions where electron beam passing holes are to be bored in later process of developing the photosensitive film, and the photosensitive film is totally removed.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a method for manufacturing a shadow mask.

(Prior Art) Shadow masks are generally manufactured by a method called photoetching. This is usually done by forming a photoresist film of a certain thickness on both sides of a shadow mask, which is a thin metal plate, and then printing the desired electron beam passage hole pattern on it with light, developing, drying, and burning it. In this method, the exposed surface of the mask material is chemically etched with an etching solution to produce a shadow mask having a large number of electron beam passage holes of a desired size.

By the way, various methods for forming photoresist films have been proposed;
- Inside the shell is divided into two ways. The first method, as shown in FIG. 3, is to move a continuous strip-shaped metal thin plate 10, which is a shadow mask material, laterally at right angles to the floor, and to drip a photosensitive liquid 11 from the top of this metal thin plate 10. A photosensitive liquid 11 is applied to both sides of a thin metal plate 10, and the photosensitive liquid 11 is passed through a drying oven 12 to form a photosensitive film.

In the second method, as shown in FIG. 4, a continuous thin metal plate 13 serving as a shadow mask material moving parallel to the floor is pulled upward via a turn roller 14, and a coating tank 15 containing a photosensitive liquid is filled. A photosensitive liquid is applied to both sides of the thin metal plate 13 by passing it through the metal plate 13, and a photosensitive film is formed by passing it through a drying oven 16.Known examples include Japanese Patent Publication No. 61-33633 and Japanese Patent Publication No. 61-45512. Can be mentioned.

(Problems to be Solved by the Invention) The quality of the photoresist film is one of the important factors that determines the quality of the shadow mask, especially the uniformity of the film thickness and the absence of dark reaction due to heat (thermal fog). It is hoped that The photosensitive film is generally made of polyvinyl alcohol ammonium decachromate or milk casein ammonium decachromate;
Valent chromium is reduced to trivalent chromium, which becomes insoluble in water by combining with resin.

However, this phenomenon occurs not only with ultraviolet rays, but also with heat above a certain temperature, and as a result, the photoresist film remains in the area corresponding to the electron beam passage hole, which must be washed away during development. This causes variations in hole size and hole shape, significantly reducing the quality of the shadow mask.

Therefore, it is very important to suppress this heat-induced dark reaction and obtain a photoresist film with a uniform thickness.

The first method has the drawback that the photosensitive liquid 11 is dripped, so the upper part is thinner and the lower part is thicker, resulting in a difference in film thickness between the upper and lower parts. Further, during drying, the temperature of the upper part of the drying oven 12, which is installed horizontally, is not higher than that of the lower part, and the upper part, where the film is thin, is more likely to cause a dark reaction. For this reason, it is common to try to reduce the temperature difference by changing the heater temperature between the top and bottom, but it is very difficult to obtain a uniform temperature distribution.

In particular, in order to improve productivity in recent years, if the drying temperature is increased without increasing the length of the furnace to speed up the formation of a photoresist film, it becomes more difficult to obtain a uniform temperature distribution. The disadvantage is that reactions are likely to occur and it is difficult to control the furnace temperature.

The second method has the advantage of being able to form a uniform film thickness, but since the drying oven 16 is vertical, the heated air rises due to the chimney effect. As a result, heat is trapped in the upper part and the photoresist film is exposed to a high temperature atmosphere even after drying, resulting in a drawback that dark reactions due to heat are likely to occur. Furthermore, as with the first method, if the drying temperature is increased without increasing the length of the furnace in order to improve productivity, it will result in difficulty in controlling the temperature, which has the disadvantage that dark reactions are likely to proceed. There is.

The general temperature control of a drying oven is to measure the oven temperature with a thermocouple inserted into the oven, and if this temperature becomes higher than the set value, the heater power is turned off, and if it becomes lower, the power is turned on. This is done by If the thermocouple comes into contact with the photoresist film, it will damage the film surface, so taking into consideration the fluctuations caused by the passage of the thin metal plate, the thermocouple is installed at a distance equivalent to the length of the photoresist film.

Therefore, since the ambient temperature in the furnace is detected, the set temperature is a value determined empirically from the quality of the mask obtained, and does not indicate the allowable upper limit temperature of the photoresist film itself. In other words, temperature control is not performed in consideration of the heat-induced dark reaction of the photoresist film.

Further, the temperature atmosphere inside the furnace reacts sensitively to changes in the temperature, humidity, and amount of air sucked in from outside the furnace and is disturbed. In terms of manufacturing conditions, the temperature is kept high to prevent the photosensitive film from adhering to the thin metal plate holding rollers installed in the production line due to insufficient drying and causing stain defects. Generally, the photoresist film is dried completely. As a result, the overall disadvantage is that dark reactions due to heat tend to occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a shadow mask that suppresses the progress of dark reaction in a photoresist film due to heat.

[Structure of the Invention] (Means for Solving the Problems) This invention provides a method of degreasing both main surfaces of a continuous strip-shaped thin metal plate and washing them with water.
In the process of applying and drying a photosensitive resin liquid to form a photosensitive film with a desired thickness, the amount of dark reaction progressed on the photosensitive film is detected, and the obtained signal is fed to the temperature control section of the drying oven. This is a method for manufacturing a shadow mask that suppresses the progress of dark reactions.

(Function) According to the present invention, in the step of forming a photoresist film on both sides of a continuous strip-shaped thin metal plate that is a shadow mask material, the progress of dark reaction of the photoresist film due to heat is suppressed, so that the subsequent development of the photoresist film is prevented. In the process, there is no dimensional variation in the exposed part of the shadow mask material corresponding to the part where the electron beam passage hole is made by etching, and the photoresist film is completely removed, so a high-quality shadow mask can be manufactured. is possible.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

The method for manufacturing a shadow mask according to the present invention is constructed as shown in FIG.
Spray a high-temperature alkaline solution at 0°C or higher to degrease the rust preventive oil applied to the surface.

Thereafter, it is washed with water in a water washing chamber 3 to clean the surface of the continuous strip-shaped thin metal plate 1.

Next, it is pulled up while being immersed in a coating tank 4 containing a photosensitive solution consisting of milk casein and ammonium dichromate.

Next, a film is formed by passing it through a drying oven 6 using a sheathed heater and an infrastein heater 5 as heat sources.
A photoresist film having a thickness of 8 μm is formed on both sides of a continuous strip-shaped thin metal plate 1.

After that, a dark reaction measuring device 8 installed on the way to the winding machine 9 via the turn roller 7 measures and detects the progress of the dark reaction of the photoresist film, and controls the heat source of the drying oven so that the amount is below the allowable amount. A signal to lower the temperature is fed back to the unit.

The dark reaction measuring device 8 is composed of an infrared irradiation section, a detection section for measuring the intensity of the reflected infrared rays, an arithmetic circuit, a signal generation circuit, etc., and the obtained reflection spectrum has irregularities.

Incidentally, the reflection spectrum obtained from the photoresist film in which the dark reaction has not progressed is used as a reference spectrum, and is compared with the reflection spectrum actually measured after drying on the production line. Infrared reflectance spectra suggest the presence of various chemical species, but when using ammonium dichromate, 6
The valent chromium is reduced to trivalent chromium by ultraviolet irradiation,
When a photoresist film becomes insoluble in water, a similar change occurs under heat, so the spectral intensity at a wavelength corresponding to Cr6+→Cr3+ can be measured on the photoresist film after drying. Specifically, spectral changes due to chromium reduction appear at wavelengths around 935 cm-1 and 890 m-1, but these wavelengths are good in terms of sensitivity.

As shown in FIGS. 2(a) and (b), the relative intensity from the baseline of the spectrum actually measured on the production line is Ic,
The relative intensity obtained with an unexposed photoresist film in which no dark reaction has progressed is I', and the amount of dark reaction progress (Δd) is the intensity ratio of the two (I
c/Ir).

On the other hand, if the baseline tends to have movement errors for each measurement, 935
The intensity from the baseline of the first peak at a wavelength shorter than cm-1 is IO
As, I C-1c/I'o and IR-1r
/ I □ may be obtained and the dark reaction progress amount Δd-IC/IR may be obtained. Ir or IR can be determined in advance and stored in memory within the arithmetic circuit.

The values actually measured on the manufacturing line enter this arithmetic circuit to calculate the amount of deviation from the reference spectrum, and the obtained analog signal is converted into a digital signal through an AD converter.

Finally, this signal is sent to a controller that adjusts the heater temperature of the drying oven, varying the voltage or current. That is, the temperature of the heater is controlled so that the dark reaction does not proceed or is within an allowable amount. The heaters in the drying oven are divided into blocks, but it is better to control this dark reaction in the final heater block of the drying oven. or,
The longer the dark reaction is exposed to high temperatures, the more it progresses.In the case of a furnace structure with an air cooling zone at the top of the drying furnace, this method can also be used to control the temperature or volume of cold air. It is possible using

In the above embodiment, the method of forming a photoresist film by vertically pulling up the continuous strip metal sheet 1 was given as an example, but the present invention can also be applied to the conventional example (FIG. 3).

Of course, it is also possible to check the amount of dark reaction on the front and back sides and control the temperature individually.

[Effects of the Invention] According to the present invention, in the step of forming a photoresist film on both sides of a continuous strip-shaped thin metal plate that is a shadow mask material, progress of dark reaction of the photoresist film due to heat is suppressed, so that subsequent exposure to light is prevented. In the film development process, there is no dimensional variation in the exposed part of the shadow mask material corresponding to the part where the electron beam passage holes are made by etching, and the photoresist film is completely removed, producing a high-quality shadow mask. It is possible to do so.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a method for manufacturing a shadow mask according to an embodiment of the present invention, FIGS. 3 and 4 are schematic configuration diagrams showing a conventional shadow mask manufacturing method. DESCRIPTION OF SYMBOLS 1... Continuous strip metal thin plate, 2... Degreasing chamber, 3... Washing chamber, 4... Coating tank, 5... Sheath heater and Infrastein heater, 6... Drying oven, 7... ... Turn roller, 8... Dark reaction measuring device, 9... Winding machine. Applicant's representative Patent attorney Takehiko Suzue RS Figure 1 Figure 4 Liquid length (C vinegar 1) (a) Δd=Ic/Ir or Δd= No. :IC/IR Figure 2

Claims (2)

[Claims] (1) A method for manufacturing a shadow mask, which comprises at least the step of forming a photosensitive resin layer by applying a photosensitive resin liquid and drying both principal surfaces of a continuous strip-shaped thin metal plate after degreasing and washing with water. When forming a photoresist layer, the progress of the dark reaction in the photosensitive film due to heat is measured and detected, and the obtained signal is fed back to the temperature control section of the drying oven to suppress the progress of the dark reaction. A method for producing a shadow mask characterized by: (2) The method for manufacturing a shadow mask according to claim 1, wherein the measurement of the progress of the dark reaction is performed using an infrared reflection spectrum.