JPS62133645A - Shadow mask structure - Google Patents

Abstract

PURPOSE:To reduce the beam landing error resulting from a thermal expansion of the shadow mask, by composing a shadow mask applied with a tension and a mask frame to hold the shadow mask by combining low thermal expansion materials. CONSTITUTION:A tension imposed to a shadow mask 22, a mask frame 23, an extension 24, and frame supporters 25 are composed by combining low thermal expansion materials respectively. Metallic materials for the shadow mask 22 and for the mask frame 23 are both a metal having a winding point of the thermal expansion curve below 500 deg.C, and a material of a lower temperature winding point is used for the shadow mask 22 while that of a higher temperature winding point for the mask frame 23. Since the mask frame 23 keeps its balance in the condition bending inward as shown in the broken line 23', the tension of the shadow mask 22 is relaxed by moving in the direction of the arrow 29 when the shadow mask 22 is expanded by heating.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a shadow mask structure, and particularly to a shadow mask structure that can improve color purity reproduction characteristics when incorporated into a color picture tube and used. be.

[Technical background of the invention and its problems]

Generally, in a color picture tube using a shadow mask method,
The electron beam emitted from the electron gun forms part of the shadow mask.
After passing through the apertures, the light hits the phosphor layers that emit light in three colors, red, green, and blue, formed on the inner surface of the panel facing the shadow mask, causing each of the phosphor layers to emit light. It has become.

Therefore, in order to achieve good color reproduction, the relative positional relationship between the many apertures of the shadow mask and the three color phosphor layers corresponding to each of these apertures must be in a predetermined matching relationship, and the electron beam passing through the apertures must be aligned. must land accurately on a predetermined phosphor layer.

However, the shadow mask transmittance of the electron beam is usually 1
5% to 20%, and most of the other electron beams impinge on the shadow mask, causing the shadow mask to heat and expand. This heating expansion becomes particularly large when the anode voltage and beam current of the color picture tube are increased to obtain a bright screen, and as a result, the landing position of the electron beam on the phosphor layer fluctuates greatly, resulting in a decrease in color purity. This will cause deterioration.

Next, an example of a normal shadow mask type color picture tube will be explained with reference to FIGS. 4 and 5.

That is, a panel (1) has a phosphor screen (2) formed on its inner surface made of a band-shaped or dot-shaped phosphor layer that emits light in three colors of red, green, and blue, and this phosphor screen (2). Shadow masks (3) arranged at predetermined intervals and a mask frame (4) to which the shadow masks (3) are fixed.
a shadow mask structure (5) consisting of a frame support (5) that supports this mask frame (4) on panel pins;
6) and an electron gun (9) provided within the neck (8).

In such a color picture tube, the electron beam (11)
When the shadow mask (3) is heated by the impact of a large portion of Since it is transmitted from to panel (1),
Temperature differences occur in each part, causing the parts to deform, and the electron beam (1
A so-called landing error occurs in which the position where the light emitting device 1) lands on the phosphor screen (2) through the aperture deviates from a predetermined position.

This landing error changes over time, and the shadow mask (3) undergoes rapid thermal expansion immediately after operation or when a locally bright portion occurs on the screen.

However, the temperature of the mask frame (4), which has a relatively large heat capacity, does not rise quickly, so the shadow mask (3)
bulges out toward the position (3'), that is, toward the phosphor screen (2). As a result, the electron beam passing through the same aperture (
11) transitions to (11'), and the landing position also changes to (1
2) to (12'), resulting in a landing error. Furthermore, if the color picture tube continues to be operated, the mask frame (4) will also thermally expand after a sufficiently long period of time has elapsed, so that the landing position will change in the opposite direction to that immediately after the above-mentioned operation.

The amount of variation in this landing position is several tens of micrometers to 100 micrometers.
m, causing deterioration of color purity. In addition, as the anode voltage of the color picture tube increases and the beam current increases in an attempt to obtain a bright screen, the energy that collides with the shadow mask (3) also increases, increasing the landing error and deteriorating color purity. It becomes noticeable.

On the other hand, in order to realize a high-definition image, it is necessary to reduce the distance between the apertures of the shadow mask (3) and increase the number of picture elements. This reduces the spacing between the three color phosphor layers deposited on the phosphor screen (2) and the landing tolerance of each phosphor layer. Therefore, high-definition color picture tubes require more accurate beam landing.

Various proposals have been made to reduce the above-mentioned beam landing error. For example, by blackening the shadow mask or coating it with black to improve heat dissipation and reduce the temperature rise of the shadow mask, by adjusting the thickness and length of the side wall of the shadow mask, or by providing holes, notches, etc. There are structures that reduce heat capacity to achieve uniform heat, and structures that use materials with a low coefficient of thermal expansion. However, these measures have not been sufficient for applications that require high brightness and are used under bright external light, such as in aircraft or vehicles.

As a structure to solve this problem, "Avi Brightness Shadow Mask Color C, R, T Color Cockpit Display Digest of Papers of 1983, Symposium of Society For Information Display 9.5" by R. C. and Robinder.
A color picture tube equipped with an improved shadow mask structure was announced.

As shown in FIG. 3, this color picture tube is equipped with a flat shadow mask (13) fixed to a mask frame (14) under tension.
Thermal expansion of the shadow mask structure (15) is absorbed by tension relaxation, thereby realizing a shadow mask structure (15) that does not deform even under high brightness. It is reported that this color picture tube has significantly improved landing error compared to a conventional color picture tube equipped with a dome-shaped shadow mask.

This type of shadow mask structure (15) includes a step in which it is heated to 400° C. to 500° C. in the manufacturing process of the color picture tube, and this heating may significantly reduce the tension of the shadow mask.

The reason for this decrease in tension due to heating is thought to be that the yield strength of the metal at high temperatures is lower than the yield strength at room temperature. In other words, the change in yield strength due to temperature of Amber (36% NiFe alloy), a metal material suitable as a material for the shadow mask (13), is 18.7 kg/m at room temperature.
m2 is 14.4kg/mm” at 400℃, 500
℃ is 13.0 kg/mm''.In other words, the decrease in yield strength is approximately 70% at 500℃ compared to at room temperature.This decrease in tension is determined by measuring the tension of the shadow mask. However, as a result of heating a shadow mask structure in which the shadow mask and mask frame were prototyped from amber material at 500°C, the same temperature as a color picture tube, the tension in the shadow mask before and after heating was halved.

Such a color picture tube in which tension is applied to the shadow mask is made up of a balance between tension relaxation due to thermal expansion of the shadow mask and stress in the mask frame in response to an increase in input to the shadow mask. Therefore, the thermal expansion of the shadow mask becomes large, and when the shadow mask becomes loose, the beam landing will shift by a large amount.

The beam landing tolerance for a shadow mask type color picture tube is determined at the time of design, and it is necessary that the shadow mask be within this range and that tension be applied to the shadow mask.

However, when welding the shadow mask to the mask frame by first increasing the tension of the shadow mask in anticipation of a decrease in tension due to heat treatment, a problem occurred in which the shadow mask broke and the yield decreased. This fracture of the shadow mask occurs not only during the process of welding the mask frame, but also during the heat treatment process after welding. Although there is a problem with increasing the tension of the shadow mask in this way, if the tension is not increased, the input increase to obtain a high-brightness image is only several times that of a conventional shadow mask.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned problems, and by configuring a shadow mask to which tension is applied and a mask frame that supports it from a combination of low thermal expansion materials, the thermal expansion of the shadow mask is reduced. The object of the present invention is to provide a shadow mask structure that reduces beam landing errors caused by.

[Summary of the invention]

The present invention provides a shadow mask structure mainly composed of a shadow mask to which tension is applied and a mask frame that supports this shadow mask, in which the metal materials used for the shadow mask and the mask frame each have a thermal expansion curve of up to 500°C. The shadow mask uses a material with a low temperature at the bending point, and the mask frame uses a material with a high temperature at the bending point, resulting in good performance with little beam landing error under high brightness conditions. A color picture tube was obtained.

[Embodiments of the invention]

Next, an embodiment of the shadow mask structure of the present invention will be described with reference to FIG.

That is, the shadow mask (22) is welded under tension to one side of the mask frame (23) to form a shadow mask structure, and the four sides of the mask frame (23) are welded to the other side of the mask frame (23). An extending portion (24) is provided at the center of the. Frame support (25) C, this extension part (2
4), and is fixed to a panel pin of a color picture tube through a pin hole (26) provided near the other end.

The tension applied to the shadow mask (22), the mask frame (23), the extension part (24), and the frame support (
25) are characterized in that they are each constructed from a combination of low thermal expansion materials.

To explain in more detail, the shadow mask (22) includes:
A mask frame (2
For 3), a shadow mask structure was assembled using Kovar with a plate thickness of 1°2 mrn. When such a shadow mask structure was heated at 500° C. to reduce the tension of the shadow mask in a greenhouse, the amount of decrease in tension before and after the heat treatment was 10%. This was about 50% when the material of the mask frame (23) was amber, but it was found that the tension remaining in the shadow mask (22) was significantly higher. Furthermore, a color picture tube incorporating this shadow mask structure can achieve the same level of brightness even when the power input to the phosphor screen is increased by 10 times compared to a color picture tube equipped with a conventional dome-shaped shadow mask. It was found that the landing error was

The reason why the tension decreased by 10% before and after this heat treatment is that tension relaxation occurred due to the difference in thermal expansion properties between Kovar and Amber, and the tension in the shadow mask (22) decreased by 10%. it is conceivable that.

As shown in Figure 2, this thermal expansion characteristic is a straight line as shown in (31) when the horizontal axis is the temperature and the vertical axis is the elongation (ΔQ/Q) at each temperature from room temperature. , Fe
-Ni alloy Amber, 42 alloy, Fe-Ni
-Co alloy Kovar (32
) (33) As shown in (34), there is an inflection point, and the lower temperature side of this inflection point shows a lower expansion coefficient, and the higher temperature side has a higher expansion coefficient.

Next, the operation of the color picture tube will be described.

That is, in FIG. 3, the shadow mask (22) is balanced with the mask frame (23) curved inward as shown by the dashed line (23'). Therefore, when the shadow mask (22) thermally expands, the arrow (29) in the figure
), and the tension on the shadow mask (22) is relaxed. This thermal deformation is a change due to temperature increase,
When considering the temperature rise time, it occurs in proportion to the heat capacity of the shadow mask (22) and mask frame (23). That is, the heat capacity of the shadow mask (22) is small, and the arrow (
29) changes occur in a short period of time.

On the other hand, since the mask frame (23) has a large heat capacity, the temperature rise takes a longer time than that of the shadow mask (22), several tens of times longer. Therefore, when a high intensity input occurs for a short time, the tension of the shadow mask (22) is relaxed, and when a relatively low intensity input is applied for a long time, thermal expansion of the mask frame (23) occurs. . in this case,
As the stress in the mask frame (23) increases in a stress relationship that was balanced with the tension in the shadow mask (22), the tension in the shadow mask (22) increases due to thermal expansion, which increases the input limit that causes loosening. become. That is, in the case of the example, a mask frame made of Kovar (
Thermal expansion of 23) acts to give tension to the shadow mask (22) made of amber. This is because the thermal expansion curves of both are on the low temperature side, and Kovar has a larger thermal expansion than Amber.

In the embodiment described above, the shadow mask is amber.

Kovar is used for the mask frame (23), but it is not limited to this.The thermal expansion curve up to SOO℃ shows the bending point, and the shadow mask has a low bending point temperature, and the mask frame A similar effect can be obtained by using a material with a high bending line temperature.

〔Effect of the invention〕

As described above, it is an object of the present invention to provide a shadow mask structure capable of realizing a color picture tube with small beam landing errors and good color purity under extremely high brightness conditions under bright external light such as when mounted on an aircraft vehicle. I can do it.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an embodiment of the shadow mask structure of the present invention, Fig. 2 is a thermal expansion curve diagram of Fa, amber, Kovar, and 42 alloy, and Fig. 3 is a diagram of the shadow mask structure of Fig. 1 when heated. 4 is a sectional view showing a color picture tube equipped with a conventional shadow mask structure, FIG. 5 is an explanatory view showing a beam landing state, and FIG. 6 is another conventional shadow mask structure. FIG. 2 is a sectional view of a main part of a color picture tube equipped with a color picture tube. 3.22...Shadow mask 4,23...Mask frame 6.25...Frame support

Claims (1)

[Claims] In a shadow mask structure mainly composed of a shadow mask to which tension is applied and a mask frame that supports this shadow mask, the metal materials used for the shadow mask and the mask frame each have a thermal expansion curve of up to 500°C. A shadow mask structure having a line, the shadow mask using a material having a low temperature at the bending point, and the mask frame using a material having a high temperature at the bending point. .