JPS6042577B2 - Method for forming fluorescent surface of color picture tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a phosphor screen of a color picture tube, in which an attached area of phosphor dots or phosphor strips of a first emission color and a phosphor screen of a second emission color are formed. In order to correct the positional deviation of the area where the body dots or phosphor strips are attached from their respective optimal attachment areas, approximately half of the shadow mask during each exposure process is cooled with cold air, and approximately the other half is cooled with cold air. The main feature is that the shadow mask is heated with hot air and deformed by thermal distortion.

Generally, in a color picture tube in which three electron guns are arranged in a Ξ-gonal arrangement, g and b are arranged in a triangular arrangement in the trio of electron beams generated on the fluorescent surface S, as shown in FIG.

However, in the electron beam trio generated at the center of the fluorescent surface S, the line connecting the beam centers forms a regular Ξ-gon;
The line connecting the beam centers of the electron beam trio generated at the periphery does not form a regular Ξ-gon, but is distorted in different directions depending on the location.
Therefore, when forming three types of phosphor dots that emit red, green, and blue light, it is necessary to add g to the electron beam trio.
, b requires complicated consideration in order to obtain a dot arrangement that correctly matches the arrangement of the dots.

However, no matter how intricately designed a correction lens is used in the exposure process, it is true that a trio of phosphor dots with an arrangement that correctly matches the arrangement of the electron beam trio can be obtained over the entire area of the phosphor surface. It was impossible. For this reason,
Normally, lenses are designed to have a compromise arrangement between the center and the periphery of the phosphor surface, and the correction error is minimized over the entire phosphor surface area. The trio of body dots is arranged as shown by R, G, and B in FIG. However, when a color picture tube with such a compromise dot arrangement emits a locally bright image part over a long period of time in the center of the phosphor surface, a large beam current flows in this part. This causes thermal expansion, especially in the center of the shadow mask, causing the electron beam trio to
g and b are fluorescent dot trios R and G as shown in Figure 3.
, B and exceeds a practical tolerance, causing color blurring.

The occurrence of such color shift is particularly noticeable in high-definition color picture tubes and wide deflection angle color picture tubes in which mask apertures are arranged at an ultra-fine pitch. The present invention provides a method for forming a phosphor screen that can solve the above-mentioned conventional problems at low cost, and will be described below with reference to embodiments shown in the drawings.

In Fig. 4, 1 is a point light source for exposure, 2 is a correction lens,
3 is a face panel for a color picture tube, 4a and 4b are nozzles for jetting cold air, and 5a and 5b are nozzles for jetting warm air.

In addition, a prescribed shadow mask (
(not shown), and the tip openings of the nozzles 4a and 5a are located approximately in the center A of the left half of the shadow mask.
The tip openings of the nozzles 4b and 5b are directed toward approximately the center B of the right half of the shadow mask. Of the three types of phosphor dots, the red-emitting phosphor dot is first formed by an exposure method. During this exposure process, cold air is jetted from nozzle 4b, and warm air is jetted from nozzle 5a. Make it spray.

Therefore, the right side of the shadow mask is cooled and causes thermal contraction, and the left side is warmed and causes thermal expansion. Therefore, the shadow mask deforms as shown by the broken line 6 in FIG. 5 due to thermal distortion, and the distance between the plate surface of the shadow mask and the inner surface of the face panel becomes larger on the right side than the designed distance. It becomes smaller on the left side. Due to this behavior of the shadow mask, the red-emitting phosphor dots R are formed slightly shifted to the right from the initial position Rd on both the left and right sides, as shown in FIG. Note that the dashed dotted line 7 in FIG. 5 indicates the shadow mask before deformation. Then,
The point light source 1 for exposure is moved to a predetermined second position to form phosphor dots that emit green light, but in this exposure process, contrary to the above, cold air is jetted from the nozzle 4a. , hot air is jetted from the nozzle 5b.

For this reason, Shadowmas! The right side of the block is heated and causes thermal expansion, and the left side is cooled and causes thermal contraction, resulting in deformation as shown by the broken line 8 in FIG. As a result, the green-emitting phosphor dots G are formed on both the left and right sides with a slight deviation to the left from the original Gd 3, as shown in FIG. Next, the point light source 1 is moved to a predetermined third position to form blue-emitting phosphor dots, but in this exposure process, all nozzles 4a, 4b, 5a, 5b
The ejection operation is stopped, and the exposure process is performed in the same manner as in the conventional method 4, and the blue-emitting phosphor dots B are formed at the initial positions.

As is clear from FIG. 2, the trio distortion of the phosphor dot trios R, G, and B on the phosphor surface formed in this manner is particularly noticeable in the central region of the phosphor surface. This approximates the trio distortion of g and b, and the occurrence of color shift is greatly alleviated.

The present invention was applied to the formation of a fluorescent surface in a 20-inch 90-degree deflection type high-definition color picture tube (at room temperature of 36°C).
(using hot air at 36°C and cold air at 24°C), the positional deviation between the two dots R and G of approximately 8 pm, which conventionally existed on the central horizontal axis of the fluorescent surface, was almost completely eliminated. was completed. Moreover, the temperature of the exposure apparatus as a whole can be maintained, and the exposure process can be performed with high accuracy without disturbing the temperature balance of the entire shadow mask and face panel.

Although the formation of phosphor dots has been described above, it goes without saying that the present invention is equally applicable to the formation of phosphor strips and black matrices.

[Brief explanation of drawings]

Figure 1 is a plan view for explaining the arrangement of electron beam trios formed on the fluorescent surface of a color picture tube, and Figure 2 is an arrangement of phosphor dot trios formed on the fluorescent surface of a conventional color picture tube. FIG. 3 is a plan view for explaining the positional shift of the phosphor dot trio during thermal expansion of the shadow mask of the same color picture tube; FIG. 5 is a perspective view showing an embodiment of the fluorescent surface forming method of the present invention, FIGS. 5 and 7 are side sectional views showing modified forms of a shadow mask modified by carrying out the present invention, and FIGS. 6 and 8 are FIG. 2 is a plan view for explaining the positional relationship between phosphor dots formed by implementing the present invention and conventional phosphor dots. 1... Point light source for exposure, 3... Face panel, 4a, 4b... Cold air injection nozzle, 5a
, 5b... Hot air injection nozzle, 6, 8...
...A transformed shadow mask.

Claims (1)

[Claims] 1. A method for forming a fluorescent surface of a color picture tube, characterized in that during exposure processing, approximately half of the shadow mask is cooled with cold air, and the other half is heated with warm air, so that the shadow mask is deformed by thermal distortion.