JPS6235435A - Color picture tube - Google Patents

Abstract

PURPOSE:To obtain a color picture tube with a superior emission life by coating the inner surface of a shadow mask with a ceramic layer baked at low temperature and forming a thin conductive layer on the ceramic layer so as to prevent any deformation of the shadow mask and to improve its purity drift. CONSTITUTION:A shadow mask 15 is made by forming a penetrating hole in a soft steel plate by usual photoetching and then curving the plate into a given shape by pressing. Next, after a liquid suspension such as an aqueous silicon oxide suspension is applied to the electron-gun-16-side surface of the shadow mask 15 by spraying, the shadow mask 15 is baked at low temperature to form a baked ceramic layer 22. After that, a thin conductive film 23 is formed on the layer 22.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a color picture tube, and particularly to a shadow mask thereof.

[Technical background and problems of the invention]

A general shadow mask type color picture tube has an electron gun that generates three electron beams inside the tube, a shadow mask that selects the electron beams according to color and has a large number of holes, and excites the electron beams to produce red and IL blue. It has a phosphor screen that emits light in three colors, and is structured so that the image projected on the screen can be observed through the panel of the envelope. The holes in the shadow mask and the phosphor patterns of each color on the screen correspond precisely. Therefore, the effective amount of electron beams passing through the through hole is less than 173°C due to the operation of the picture tube, and the remaining electron beams impinge on the shadow mask and are converted into thermal energy, heating the shadow mask to 80° C. or more. The shadow mask is formed from a thin plate with a thickness of 0.1 mm to 0.3 # made of cold-rolled mild steel with a coefficient of thermal expansion of about 1.2xlo-5/'C, and a mask that supports this shadow mask. The frame is also made of cold-rolled steel with a thickness of about 1 s and a strong cross-sectional blackening treatment. Therefore, a heated shadow mask easily undergoes thermal expansion, but since its periphery is joined to a mask frame with a large heat capacity that has been subjected to a blackening process, heat is transferred from the periphery of the shadow mask to the mask frame due to radiation and conduction. The temperature around the shadow mask becomes lower than that at the center of the mask. For this reason, a temperature difference occurs between the central portion and the peripheral portion of the shadow mask, resulting in a so-called doming phenomenon in which the central portion is heated and expanded relatively, resulting in a purity drift. As a result, the distance between the shadow mask and the phosphor screen changes, disturbing the accurate landing of the electron beam and causing deterioration of color purity. This phenomenon is particularly noticeable in the early stages of operation of a color picture tube. Furthermore, when a locally high-luminance image is projected, a local doming phenomenon also occurs in the shadow mask.

Regarding the doming phenomenon of color picture tubes,
Many proposals have been made from the viewpoint of promoting heat radiation from the center of the shadow mask and preventing heat conduction to the shadow mask. For example, US Pat. No. 2,826,538 proposes providing a black layer made of graphite or carbon coating on the surface of a shadow mask to promote heat radiation from the shadow mask. In such a color picture tube, this graphite layer acts as a good heat sink, so for the shadow mask, for example, as disclosed in Japanese Patent Application Laid-Open No. 60-54139, lead borate, which has a lower coefficient of thermal expansion than iron, is used on the shadow mask surface. It is proposed to apply glass.

Using this technology, we were able to improve the purity drift characteristics and anti-stretching properties of iron sheet shadow masks and amber shadow masks. variation (
- There was a problem in that clouding, ie, variations in residual stress, caused wrinkle-like deformation at the boundary between the coated and non-coated areas of the glass layer. Since this kind of shadow mask has a structure that leaves stress between the iron sheet and the glass layer, it is said that the thickness of the glass layer must be at least 10p, and in fact it is necessary to coat it on average at least 20p. There is. In such a conventional mask, as shown in Fig. 6, the glass layer (32) applied to the surface of the iron sheet (25) has an uneven thickness such that it is thicker in the center, and furthermore, the thickness is uneven after coating. , there is a problem in that the residual stress in the coated part becomes large because of the high-temperature heat treatment, and the difference in residual stress between the coated part and the non-coated part becomes large.

Furthermore, since this glass layer is heated to a high temperature, it melts and softens and becomes convex as shown in Figure 6. When a getter film (33) is formed on this glass layer, the thickness of the getter film varies depending on the direction in which the getter is scattered. Getter r!
(33) is formed to make the glass layer (32) conductive, and if there is any "unevenness" in this getter film, an insulating part will be formed in some parts and the electron beam will be deflected, leading to mis-landing. It causes

In order to eliminate such "unevenness", it is possible to make the getter film thicker, but the effect of preventing heat generation in the mask due to the formation of a resistive layer (a resistive layer formed by forming a thin getter film) is lost. In other words, the resistive layer has the effect of suppressing the heat generation of the shadow mask by lowering the potential of the resistor layer than that of the shadow mask and reducing the impingement speed of the electron beam that impinges on the shadow mask. Necessary and sufficient resistance is required. However, there is a problem in that the effect becomes smaller if there is unevenness.

(Objective of the Invention) The present invention provides a color picture tube that prevents deformation of the shadow mask due to residual stress and suppresses expansion caused by heat generation of the shadow mask due to electron beam impingement, thereby improving utility drift characteristics. It is.

[Summary of the invention]

The present invention includes a phosphor screen, a shadow mask having a large number of through holes provided close to the screen, and a hole provided on the side of the shadow mask opposite to the phosphor screen.
The color picture tube is equipped with an electron gun, and the electron beam emitted from the electron gun hits the screen through a large number of holes in the shadow mask. It has a ceramic layer and a conductive thin film layer formed on the ceramic layer.

It is particularly effective to use the low-temperature fired ceramic layer as an insulating layer.

The low temperature fired ceramic layer is deposited on the electron gun side surface of the shadow mask, but it can also be deposited on the screen side surface.

(Embodiments of the invention) Examples of the invention will be described below with reference to the drawings. As shown in FIG. 2, the shadow mask type color picture tube of this embodiment has an envelope θΦ made of glass, which has a substantially rectangular panel 01), a funnel-shaped funnel 02), and a neck 03). It consists of The inner surface of the panel (11) is provided with striped phosphor screens O0 that emit light in red, green, and blue, respectively, while the net 03) is provided with striped phosphor screens O0 that emit light in red, green, and blue. An in-line electron gun OΦ that emits three electron beams (30) corresponding to , edge, and blue is provided. Further, a shadow mask CΦ having a main surface with a large number of through holes is disposed in close opposition to the screen θ. The shadow mask (the peripheral part of the IG has a skirt part θ which is bent in accordance with the outer shape of the panel, and this skirt part C) is supported and fixed by a mask frame (b) consisting of a cross-sectional cross-sectional shape. , the mask frame (I7) is locked by a pin CΦ embedded in the inner wall of the panel 01 via a spring (!l). Note that the symbol (20) indicates an inner shield. In such a color picture tube, the three electron beams (30) emitted from the electron gun Oe are deflected by a deflection device (not shown) disposed outside near the funnel 02. a substantially rectangular panel (6) deflected by a substantially rectangular panel (6
), and colors are sorted through a shadow mask (1G through-hole (10a)), and each color light-emitting striped phosphor is projected correctly to reveal a color image.

Shadow mask 00 is 0.1# to 0.3# e.g. 0
．． It is made of a 12 m long mild steel plate, and after holes are bored through it by conventional etching, it is pressed into a predetermined curved surface. On the surface of the formed shadow mask OS on the electron gun Oe side, a low temperature firing ceramic layer @ is applied and adhered as shown in FIG. 1(2).

The coating is carried out by a spray method, and the following is used as a component of the low-temperature fired ceramic, for example, a solution in which silicon oxide (S!Oz) is dispersed.
And so.

5iOz 500gr isopropyl alcohol 400! llrll after replay 5
Forced heating was performed at a temperature of 0° C. for about 10 to 20 minutes, and by this heating, 1 q of a low temperature fired ceramic layer with a thickness of about 4 mm was formed. A conductive thin film layer (23) as shown in FIG. 1 is formed on this ceramic 115 (221). For example, a getter film is formed on the ceramic E (221) by scattering a getter agent.

A portion of the ceramic layer @ may wrap around the inner wall of the shadow mask through hole θΦa during spray coating, and may also partially adhere to the back surface on the screen side. The degree of wrap-around varies depending on the setting of the ceramic layer thickness, but it does not pose a problem as long as the holes are not clogged, and is effective in preventing electron scattering on the inner walls of the holes.

In order to confirm the effect of this example, a mild steel shadow mask with a conventional structure without a ceramic layer was used as a comparison amount.
A test was conducted on a type 0 color picture tube.

First, in order to examine the utility drift characteristics of this example, the difference in the amount of beam movement from the comparative amount was measured. As reproduction screen patterns, the full white pattern shown in FIG. 3 (8) and the partially white pattern shown in FIG. 3 (B) were used. In CB), a strip (51) with a width of 75 m in the horizontal direction is reproduced on the screen so that it is positioned in two places on the left and right, each spaced 140 mm apart from the center. The remaining part is black, that is, a non-light-emitting part. X marks indicate measurement points. Table 1 shows the measurement results of the amount of beam movement. The measurement conditions are Eb=26.5kV11k is pattern (8) and 1
500 μA, and 1100 μA in pattern (8).

It can be seen from Table 1 that the amount of beam change can be reduced in this example.

FIG. 5 shows the relationship between the thickness of the SiQ 2 ceramic layer and the amount of movement of the electron beam used in the purity drift characteristic test. It can be seen from the figure that the thickness of the ceramic layer is preferably 1- or more, preferably 5JiI11 or more. If it is made too thick, the shadow mask through-holes will be clogged, so it is only necessary to make it as thick as possible so as not to interfere with operation. According to the inventor's experiments, the mask hole pitch is 0.65M and the hole diameter is 175 deep.
No clogging occurred even when the temperature reached 0.

The effect of reducing beam movement (i.e., reduction of utility drift) is due to the thermal expansion coefficient of the 5iQ2 ceramic layer of 0.55.
xlo-5 and about half that of mild steel 1.2X10-5, the thermal expansion of the seed mask is suppressed, and S! The thermal conductivity of 02 is approximately 1.0 cal/cm-s
ec °C and 0.144 Cal/cm of mild steel plate.
The reason is that it is larger than sec 'C and allows the heat generated by the shadow mask to escape easily.

The thermal conductivity of 5iQ2 is considerably higher than the thermal conductivity of 0.002 Cat/cm-3eC'C of lead (IIIM salt glass (commonly known as frit glass) described as the prior art).

Next, after continuously operating the color picture tube of this example for 3000 hours, the residual emission rate was measured.
It was found that the improvement was 80% compared to the initial operation. Conventionally, 70% has been considered the standard, so this represents an improvement of more than -00%. This is presumed to be because the ceramic layer of this example absorbed gas, but it is thought that silicon oxide (S!Oz) acted effectively.

It is also thought that gas generation was suppressed because a dense ceramic layer was formed on the surface of the shadow mask.

Although the embodiments have been described above, even if the SiQ 2 ceramic layer is applied to the inner shield that causes electron scattering, it is expected that the dark area luminance will be reduced and the transmission characteristics will be improved.

Furthermore, by mixing a black substance such as graphite or manganese oxide into the SiQ 2 ceramic layer, the body color can be made into a dark part and a radiation effect can be achieved.

Furthermore, the application of 5iQ2 ceramic is as shown in the example.
The effect can be improved even if the coating is applied not to the entire shadow mask but to a localized portion (32) of the mask surface (31), as shown in FIG. In addition, it is also possible to compensate for the locally occurring purity trit by attaching C to the electron gun side of the shadow mask, and by locally attaching M to the screen side.

In such low-temperature-fired ceramics, the solution containing the material as its main component hydrolyzes and hardens in the car chassis without softening or melting, and at the same time the diluent evaporates, making it difficult to apply.
Since the thickness becomes thinner, it is possible to form a thin ceramic layer with a uniform thickness from the painted state shown in Fig. 1 (c) to that shown in Fig. 1 (c). In addition, the heating temperature of the above) small is 150℃
The temperature difference between the shadow mask temperature and the shadow mask temperature during operation of a color picture tube can be reduced, and the residual stress between the shadow mask material and the ceramic layer can also be reduced. However, in this case, a certain amount of residual stress exists to suppress doming due to thermal expansion of the shadow mask. Therefore, the difference in residual stress between the coated area and the non-coated area became small, and deformation of the shadow mask no longer occurred. In addition, since the ceramic layer can be formed uniformly and thinly in this way, the getter film formed on the ceramic layer also becomes uniform and even, and it becomes easy to make it thin as a whole. In other words, it is possible to form the getter film thinly so that the resistance value of the getter film increases.

In addition, by using the above ceramic layer as an insulator and forming an even and thin getter film on it, the insulating layer is not charged due to the impact of electrons, and the speed of impact of the electron beam on the seed mask is suppressed. Thus, it is possible to obtain an excellent shadow mask that suppresses heat generation of the shadow mask, which eliminates the disadvantages of having the surface of the shadow mask be an insulator or a conductor.

Therefore, it is possible to obtain a color picture tube in which deformation of the shadow mask is prevented and the purity drift characteristics are improved.

(Effects of the Invention) As described above, according to the present invention, by forming a low-temperature fired ceramic layer on the surface of the shadow mask and further forming a conductive thin film layer thereon, defective deformation of the shadow mask can be prevented. improved the utility drift characteristics, and
A color picture tube with good emission life characteristics can be obtained.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view of a shadow mask showing an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view of a color picture tube showing an embodiment of the present invention, and FIG. FIG. 4 is a schematic plan view of a shadow mask showing another embodiment of the present invention, and FIG. 5 is a schematic diagram of a reproduced image pattern explaining the utility drift characteristics of an embodiment of the present invention. A curve diagram showing the relationship between the thickness of the ceramic layer and the amount of beam movement,
FIG. 6 is a partially enlarged cross section of a conventional sit mask. 15...shadow mask, 15a...through hole, 22.
...Ceramic layer, 23.33...Getter film, 32
...Crow layer. Agent: Patent Attorney: Nori Chika 1: Norio Ogo Figure 1 Figure 6 Figure 4 (B) Figure 3 Cerami = t7A1! J (Am) Figure 5

Claims (5)

[Claims] (1) It comprises at least a phosphor screen, a shadow mask installed close to the phosphor screen, and an electron gun that causes an electron beam to strike the phosphor screen through the shadow mask to emit light. 1. A color picture tube, characterized in that the shadow mask has a low-temperature fired ceramic layer on the surface thereof, and a conductive thin film layer is formed on the low-temperature fired ceramic layer. (2) The color picture tube according to claim 1, wherein the low-temperature fired ceramic layer is an insulating layer. (3) The color picture tube according to claim 1, wherein the low-temperature fired ceramic layer contains silicon oxide as a main component. (4) A color picture tube according to claim 1, wherein a low-temperature fired ceramic layer is adhered to a part of the surface of the shadow mask. (5) The color picture tube according to claim 1, wherein the conductive thin film layer is a getter film.