JPS5935496B2 - Manufacturing method of correction filter for exposure equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for adjusting a correction filter for adjusting the amount of exposure in an exposure apparatus used for forming a fluorescent surface of a color picture tube.

In the process of forming the fluorescent surface of a color picture tube, a phosphor suspension uniformly applied to the inner surface of the face panel is exposed to ultraviolet light through an attached shadow mask, and then subjected to development and other processing steps. By repeating this process, a fluorescent surface with many dots or stripes is produced.

FIG. 1 schematically shows the exposure state in the above process.
1 is a face panel, 2 is a phosphor suspension layer applied to the inner surface of the face panel, 3 is a shadow mask attached, and the exposure device is 4 a point light source, 5 a correction lens,
6 is a correction filter.

This correction filter 6 has a characteristic that the transmittance is low at the center and high at the periphery, and is used for the purpose of averaging the amount of light over the entire surface of the phosphor suspension layer 2. The correction filter 6 has a metal thin film 8 on a transparent substrate T such as glass.
Metals such as Inconel, chromel, platinum, etc. are evaporated from a circular evaporation source in vacuum, and the metal is deposited on the surface of a transparent substrate T such as glass through a evaporation mask with star-shaped holes. The thin film 8 was formed by vapor deposition.

In addition to the above, nickel, chromium, rhodium, rubidium, and the like are known as vapor deposition materials, but Inconel and chromel have traditionally been widely used because of their cost and ease of vapor deposition.

In general, the correction filter 6 is formed by a curve 9 shown as a solid line in FIG.
It is formed to have a transmittance distribution that is low in the center and high in the periphery, as shown in Figure 2.However, if it is used in the exposure process for a long time, it will change over time.Curve 1 shown by the broken line in Figure 2
0, the transmittance increases and the original characteristics are lost.

When the change in transmittance over time is shown in FIG. 3, both the transmittance curve 11 in the central part of the correction filter 6 and the transmittance curve 12 in the peripheral part gradually increase with the passage of time. The reason for this change over time is that since an ultra-high pressure mercury lamp or the like is used as the point light source 4 during exposure, the temperature of the exposure apparatus increases due to radiant heat and conduction heat, and the temperature of the correction filter 6 reaches 40 to 60 degrees Celsius. Therefore, during use, the metal thin film 8 was gradually oxidized and the transmittance increased. According to the conventional manufacturing method, as mentioned above, the transmittance of the correction filter 6 changes over time.
Industrially, there were major problems with quality and mass production efficiency.

In order to deal with the above-mentioned changes over time, the present inventors created a thin film by depositing chromel or the like on a transparent substrate, and made the thin film thicker so that the transmittance was lower than the target value (dashed line 13 in Figure 4). A manufacturing method for obtaining a correction filter by forcibly oxidizing the thin film surface to increase the transmittance as shown by the solid line 14 in FIG. 4 has already been proposed in patent application No. 87638 of 1978. There is. When examining the change over time of the correction filter obtained by the manufacturing method shown in the above specification, it was found that the fifth
As shown in the figure, the transmittance hardly changes under normal usage conditions. A transmittance curve 15 shows the values at the center of the correction filter, and a transmittance curve 16 shows the values at the periphery. In this way, with the above manufacturing method, a correction filter with very little change over time can be obtained.8 In order to obtain the target transmittance distribution (solid line 14) through heat treatment, the thickness and transmittance of the deposited film, the heating temperature, and the It was necessary to investigate and calculate the correlation between 1 and the time, which resulted in a slight decrease in mass production effectiveness and workability. The present invention is a manufacturing method for obtaining a correction filter with a target transmittance by heating while measuring the transmittance, and one embodiment thereof will be described below.

FIG. 6 is an example of an apparatus implementing the present invention.

17 is an electric furnace, 18 is a shielding glass plate fitted into a through hole provided on the upper surface of the electric furnace 17, and 19 is also a shielding glass plate similarly provided on the lower surface of the electric furnace 17.

20 is connected to the meter 21, and the upper shielding glass plate 18
A photocell 22 is a light source device of an ultra-high pressure mercury lamp used in the exposure process of the color picture tube, and is provided at the lower shielding glass plate 19.

Reference numeral 23 denotes a correction filter, on the surface of which a thin metal film 24 is formed to be thick enough to slightly lower transmittance.

The correction filter 23 is held in an electric furnace and heated in an oxygen-containing atmosphere, and at the same time, the transmittance of light from the light source device 22 is measured at every moment by the photocell 20 via the correction filter 23.

At this time, b1 is provided with a stirring fan in the electric furnace 17.
A mechanism for rotating the correction filter 23 may be provided to achieve more uniform heating. Metal thin film 24 of correction filter 23
The surface of the film is gradually oxidized and the transmittance measured by the photocell 20 gradually increases, but the heat treatment is terminated when the target value shown by the solid line 14 in FIG. 4 is reached. According to the above manufacturing method, it is possible to always obtain a correction filter with a constant transmittance, and the quality of the correction filter can be kept constant, which has a large economical effect.

It is also easy to automate the heating by feeding back the output of the measuring part (the photocell 20, etc.) to the heating device and stopping the heating when a certain transmittance is reached. Furthermore, the metal thin film 24 deposited in advance must have a transmittance lower than the target value, but this value does not have to be exact because it can be adjusted accurately later during heat treatment, making it easier to work. It also improves. If a correction filter with a highly accurate transmittance distribution is first obtained using the manufacturing method described above, there will be very little change over time when used in an exposure device, resulting in the economical mass production of high-quality color picture tubes. It becomes possible.

As described above, the present invention provides a method for manufacturing a correction filter in which a metal thin film is deposited on a transparent substrate of the correction filter so that the transmittance is lower than the target transmittance, and then heat treatment is performed in an atmosphere containing oxygen. During the heat treatment, transmittance measurement is performed using an ultra-high pressure mercury lamp for exposure as a light source, and the heat treatment is terminated when the measured value of the transmittance measurement reaches the target transmittance. The present invention provides a method of manufacturing a correction filter for an exposure apparatus, which is extremely advantageous in the D1 industry, in which the change in transmittance over time is extremely small and the quality of the correction filter is constant.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing the exposure state, Fig. 2 is a transmittance distribution curve diagram of a correction filter made by a conventional manufacturing method, Fig. 3 is a transmittance change diagram over time of a conventional correction filter, and Fig. 4 is a diagram of the present invention. FIG. 5 is a transmittance distribution curve diagram of a correction filter according to an embodiment of the manufacturing method of the invention. FIG. FIG. 17... Electric furnace, 20... Photo cell, 22...
Light source device, 23... correction filter.

Claims (1)

[Claims] 1. In the production of correction filters, in which a metal thin film is deposited on the transparent substrate of the correction filter to have a transmittance lower than the target transmittance, and then heat-treated in an oxygen-containing atmosphere, an ultra-high pressure mercury lamp for exposure is used. Manufacturing a correction filter for an exposure apparatus, characterized in that transmittance measurement using a light source is performed during the heat treatment period, and the heat treatment is terminated when the measured value of the transmittance measurement reaches the target transmittance. Method.