JPH01283747A - Shadow mask of color picture tube - Google Patents

Abstract

PURPOSE:To make it possible to suppress the temperature rise of a shadow mask and to relax the doming phenomenon by forming a phosphor layer on the surface of the shadow mask on which electron beams are radiated. CONSTITUTION:This shadow mask is formed by coating a phosphor 4 which converts electron beams into a photo-energy on the surface of the shadow mask where electron beams are radiated. As a result, the electron beams radiated on the shadow mask 2 make the phosphor 4 illuminate, and the major part of the energy can be converted to the photo-energy. Consequently, the temperature rise of the shadow mask 2 is suppressed without using a heavy metal, and a color picture tube which can relax the doming phenomenon and prevent a color slippage, with a long service life, is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a shadow mask for a color picture tube, and more particularly to an improvement in a method for reducing thermal deformation of a shadow mask.

[Conventional technology]

Conventionally, in a shadow mask type color picture tube, it is known that the temperature of the shadow mask increases due to the impact of an electron beam, causing thermal deformation.

Since this thermal deformation causes color misregistration, which is generally called misregistration, it is desirable to take measures for each cause. One of the above thermal deformations is called doming. This is because during the operation of a color picture tube, only a part of the image reproduction screen (generally a relatively large part with a size of several minutes to several tens of minutes of the total effective screen area) is larger than other parts. This is a phenomenon in which when an extremely bright (or very still) image continues for a long time, the shadow mask corresponding to the bright area is locally thermally deformed.

Figure 2 (δl, (bl) is a diagram showing the relationship between the image reproduced on the color picture tube screen and the doming of the shadow mask, and 1
2 is a panel whose inner surface is coated with phosphor, and 2 is a shadow mask made of a metal plate such as iron, which has countless small holes 3 arranged in a row. Note that parts such as the holding mechanism of the shadow mask 2 and the electron gun are omitted.

On the other hand, in the image of the mountain map, 10 shows an image part that is significantly brighter than other parts, such as a white cloud in a blue sky, and this state lasts a little longer (more than 5 seconds) and is almost stationary. If this continues, the part corresponding to the image 10 of the shadow mask 2 will be hit by the electron beam more often than other parts, so the temperature will locally rise and the shape of the dotted line 21 will change. As a result, the small hole 3 in the shadow mask 2 cannot maintain its fixed position, and therefore the electron beam that has passed through the small hole 3 moves to the irradiation point on the phosphor dot. (Misregistration that results in color misregistration) occurs. In a general shadow mask, this deformation occurs in a direction in which a portion of the shadow mask corresponding to a bright screen bulges toward the phosphor screen. This phenomenon becomes rapidly noticeable as the deflection angle increases, and as in recent years, 11
This is a very serious problem in color picture tubes that have a wide angle such as 0° deflection or have a flat screen.

A method for reducing the above-mentioned doming phenomenon is, for example, as disclosed in Japanese Patent Publication No. 61-6969, in which when an electron beam impinges on a shadow mask, electrons are applied to the mask surface to prevent the mask temperature from rising. A method of applying a reflective substance is known. A typical method is to apply an oxide of a heavy metal such as lead or bismuth to the t4 beam incident side of a shadow mask. This takes advantage of the fact that materials with large atomic caps have a strong ability to reflect electrons. Oxides are used because single metals are unstable when heated in the air, or are difficult to melt and hold in place, so it is difficult to achieve the desired performance after the color picture tube manufacturing process. This is because it is difficult to make full use of it.

[Problem to be solved by the invention]

However, the method of applying heavy metal oxides has the following problems.

First, heavy metal oxides are not necessarily stable against electron bombardment in a vacuum, and often decompose and release harmful gases, which can shorten the life of the picture tube. This is not only because the oxygen in the oxides is released into the picture tube, but also because these metals take in carbon dioxide gas from the air during the process, turning the oxides into carbonates. It must also be taken into consideration that it is difficult to control these phenomena due to the effects of moisture and the substances used as binders, and that it is difficult to create a film that is completely stable against electron beam impact in a vacuum.

Secondly, the ions of these heavy metals are often harmful to the human body and must be handled with care. Therefore, equipment costs are high, and the color picture tube as a whole becomes a costly amplifier.

In particular, heavy metal substances usually lack chemical stability when added to water, so it is recommended to apply by spraying, which can be applied and dried within a short time after mixing, in order to improve the performance of color picture tubes. Preferably, in this case, the influence of dust on workers becomes a problem.

This invention was made to solve the above-mentioned problems, and the purpose is to obtain a shadow mask for a color picture tube that can suppress the temperature rise of the shadow mask and alleviate the doming phenomenon without using heavy metals. shall be.

[Means to solve the problem]

In the shadow mask according to the present invention, a phosphor that converts the electron beam into light energy is coated on the shadow mask surface on which the electron beam impinges.

[For production]

In this invention, the electron beam impinging on the shadow mask causes the phosphor to emit light, and most of the energy can be converted into light energy, thereby reducing the temperature rise of the shadow mask.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows a partially enlarged cross-sectional view of a shadow mask according to the present invention, and the shadow mask 2 is composed of a first surface 2a serving as an electron beam projection surface and a second surface 2b on the opposite side. 3
are numerous aligned small holes penetrating both surfaces 2a and 2b. 4 is a phosphor layer formed on the first surface 2a,
This layer 4 is made of a phosphor that converts the energy of the electron beam into light energy, such as a green-emitting Cu and a ZnS phosphor activated with A1, or a green-emitting Tb7:
! The activated Y1S403 phosphor is provided in a thickness of 5 to 20 pm. Further, the energy efficiency of the phosphor layer 4 in emitting light as a phosphor reaches 20% at maximum. That is, the energy of the electron beam that impinges on the shadow mask 2 is converted into energy of [1] at a considerable rate. Therefore, the temperature rise of the shadow mask 2 is suppressed by that much, and the doming phenomenon is reduced.

Further, the phosphor layer 4 is usually a poor conductor of heat, and therefore, due to the impact of the electron beam, the temperature of the portion of the thickness of the layer 4 that is close to the surface that is not in contact with the first surface 2a of the shadow mask 2 is increased. The rise is remarkable, and this is caused by radiant heat that is absorbed by the phosphor layer 4
This increases the heat escaping from the shadow mask 2 and contributes to suppressing the temperature rise of the shadow mask 2. Furthermore, if the phosphor layer 4 is composed of a phosphor containing a substance with a relatively large atomic weight, such as indolium Y, it can be expected to have the effect of repelling incident electrons, which has been known in the past. A doming reduction effect of about 30% can be obtained compared to the case where nothing is applied to the surface of the shadow mask 2.

-S phosphors have been studied as one of the most important elements of picture tubes, and their stability against electron beam stimulation in vacuum has been completely resolved, and therefore the lifespan of color picture tubes due to the generation of decomposition gas has been completely resolved. The problem can be almost completely removed. Furthermore, there is no problem with the stability when the phosphor is mixed with water, and the binder technology used to form the phosphor layer 4 on the shadow mask 2 is conventionally known as a method for coating the phosphor screen of picture tubes. The method can be used as is. Therefore, a sufficiently stable film can be formed without using a conventional method that generates dust, such as spraying.

In addition, in this invention, when the phosphor coated on the back surface of the shadow mask emits light due to the stimulation of the electron beam, this light may leak to the outside or reflect within the thickness of the glass pulp and reach the front of the panel 1. It is necessary to be careful not to enclose the image and change the contrast of the original screen. However, in general color picture tubes, it is common to provide an internal conductive film made of black graphite on the shadow mask side of the phosphor film on the inner surface of the panel, and this problem can be solved in a relatively simple manner. Needless to say, when the present invention is applied to the aluminum smoke-coated film and the conductive film, a more preferable arrangement form can be considered from the viewpoint of light leakage, which is different from the conventional method.

〔Effect of the invention〕

As explained above, according to the present invention, a phosphor film that converts the electron beam into light energy is formed on the electron beam emitting surface of the shadow mask, so the temperature rise of the shadow mask is suppressed without using heavy metals, and doming is prevented. This alleviates the phenomenon and prevents color shift, resulting in a long-life color picture tube. In addition, since materials such as phosphors are stable and have well-established handling methods, technology has been established to prevent dust from affecting workers, making it possible to reduce costs and obtain high-performance color picture tubes.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of a portion of a shadow mask of a color picture tube according to an embodiment of the present invention, and FIG. 2 fa1. (b
1 is a sectional view and a screen view of a picture tube for explaining the doming phenomenon, which is a drawback of the conventional art. 2...Shadow mask, 3...Small hole, 4...phosphor layer. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Masuo Oiwa Figure 1 4 “Grudge Book N”

Claims (1)

[Claims] In a shadow mask having a surface on which the electron beam strikes and a countless number of aligned small holes through which the electron beam passes, a phosphor that converts the electron beam into light energy is placed on the surface on which the electron beam strikes. A color picture tube shadow mask characterized by the formation of layers.