JPH03129647A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To heighten the mechanical strength of a vacuum envelope made of glass without thickening the wall of the glass by providing the vacuum envelope with a covering layer that generates stress strain due to the difference of coefficient of thermal expansion. CONSTITUTION:An inner conductive film 33 of coefficient of thermal expansion smaller than that of glass from which a glass envelope comprising a panel 10 and a funnel 11 is made is formed on the inner wall surface 32 of the funnel from the neck portion 14 of the funnel 11 to near the junction face 23 of the funnel 11 and the panel 10. The inner conductive film 33 provides compressive stress to the surface of the glass envelope comprising the panel 10 and the funnel 11, thereby effectively attenuating tensile stress generated during high temperature treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a cathode ray tube, and particularly to a glass envelope for a cathode ray tube with improved mechanical strength.

(Prior Art) Generally, a color cathode ray tube has a glass envelope consisting of a panel and a funnel. , a phosphor screen made of three-color phosphor layers that emits red light is formed. Also, there are 3 inside the neck of the funnel.
An electron gun structure for emitting electron beams is provided, and the three electron beams emitted from each electron gun are deflected in horizontal and vertical directions by a deflection device attached to the outside of the boundary between the cone and neck of the funnel. The structure is such that a color image is displayed by scanning a phosphor screen.

Usually, the inner wall surface of the funnel of the color cathode ray tube mentioned above has
An internal conductive coating is formed whose main components are graphite and water glass. A high voltage is applied to this internal conductive coating from the outside via an anode button embedded in the funnel, and this high voltage is further applied to the accelerating electrode of the electron gun body via a valve spacer contact to generate three electron beams. To accelerate.

Meanwhile, in the manufacturing process of the color cathode ray tube, the glass envelope undergoes several high-temperature processes. In particular, the temperature is heated to 300° to 500° C. in the sealing process in which the panel and the funnel are fused and bonded via low-melting glass, and in the exhaust process in which the interior is evacuated to a high vacuum after the electron gun assembly is sealed. In this high-temperature process, especially the temperature rising and cooling processes,
Various stresses act on the inside of the glass depending on the temperature distribution inside the glass.

Furthermore, during the evacuation process, stress is applied due to the difference in air pressure between the inside and outside of the glass envelope, and these stresses may mechanically break the glass envelope.

That is, as shown in FIGS. 6(a) to (c), glass is first applied to the outer and inner walls of the panel (50) and funnel (51) as shown in FIG. A temperature difference occurs depending on the wall thickness of the funnel, and tensile stress (F4) acts on the inner wall of the funnel where the temperature is low. Compressive stress (F2) acts on the outer surface. At this time, if the coefficient of thermal expansion of the internal conductive coating (53) adhered to the inner wall surface of the funnel is larger than the coefficient of thermal expansion of the glass forming the funnel (51), the inner wall surface of the funnel is subjected to additional tensile stress. works. This tensile stress causes strain on the glass surface and causes micro-cracks to occur, and when micro-cracks exist, it causes destruction due to stress concentration.

In addition, in the temperature decreasing process of the above-mentioned high temperature step, Fig. 6 (b
), the outer surface is under tensile stress (FL).

Compressive stress (F2) acts on the inner surface. Further, in the exhaust furnace, as shown in FIG. 6(c), compressive and tensile stresses are complexly applied due to deformation caused by the difference in pressure between the inside and outside of the envelope.

(Problem to be Solved by the Invention) The influence of stress as described above was small and could be ignored in conventional small tubes, but it can no longer be ignored in recent large picture tubes and high-definition picture tubes.

One way to deal with this problem is to increase the thickness of the glass to improve its strength, but the problem remains in terms of weight.

Therefore, in recent years, there has been an increasing demand for glass envelopes that are lightweight and can maintain strength. The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a glass envelope that can maintain strength even when the glass wall thickness is reduced and the weight is reduced.

[Structure of the invention]

(Means for solving problem m1) The present invention has a vacuum envelope made of glass, and a coating M that generates distortion due to the difference in thermal expansion coefficient with the glass envelope is provided on the glass envelope. It is a cathode ray tube with

(Operation) The operation of the present invention when the glass envelope configured as described above passes through a high temperature process such as a sealing process and an exhaust process will be explained using FIGS. 2 to 5.

In the temperature raising process of the high-temperature process, since the funnel (U) has a certain wall thickness, a certain certain amount is required for the heat applied to the funnel outer wall surface (31) to be conducted to the funnel inner wall surface (32). It takes time. For this purpose, a temperature difference occurs between the funnel outer wall surface (31) and the inner ball surface (32), and the lower temperature inner wall surface (32) has a tensile force as shown in Figure 2 due to the difference in the amount of expansion caused by the temperature difference. Stress <34) acts. At this time, the coefficient of thermal expansion (α) of the internal conductive coating (33) adhered to the funnel inner wall surface (32) is
), tensile stress acts on the funnel inner wall surface (32) and aggravates the tensile stress.

This tensile stress (34) causes micro-cracks (39) in a portion of the glass surface (38) which is not completely uniform as shown in FIG. Tensile stress concentrates on the micro cracks (39) generated on the surface (40) L, and eventually a stress greater than the bonding force between atoms acts, resulting in mechanical destruction of the glass. Here, as in the configuration of the present invention, if the thermal expansion coefficient (α.) of the internal conductive coating (33) is smaller than the thermal expansion coefficient (αg) of the funnel glass (11),
Compressive stress (36) acts on the funnel inner wall surface (32) and can cancel out the tensile stress (34).

In the subsequent constant temperature process, the temperature difference between the glass outer wall surface (31) and the inner wall surface (32) disappears, and as shown in FIG. Only the compressive strain (41) caused by the difference in thermal expansion coefficients (33) remains.

Furthermore, in the cooling process accompanied by contraction, tensile stress (42) acts on the funnel inner wall surface (32) due to the difference in thermal expansion coefficients, contrary to the heating process, but this tensile stress (42) does not occur in the constant temperature process. Since it is used to release the remaining compressive strain (41〉), it does not destroy the glass.

As described above, by forming a coating layer with a low coefficient of thermal expansion on the surface of the glass envelope, compressive stress is applied to the surface of the glass envelope, effectively relieving the tensile stress generated during the high-temperature treatment process. Strength can be improved.

(Example) Hereinafter, the present invention will be described based on an example with reference to the drawings. FIG. 1 shows an in-line color cathode ray tube device which is an embodiment of the present invention.

This color cathode ray tube device has a glass envelope consisting of a panel (10) and a funnel (11) integrally joined to the panel (10) via a low melting point glass (23). The inner surface of the panel (10) is colored blue and green.

A phosphor screen (12) consisting of a three-color phosphor layer that emits red light is formed, and a shadow serving as a color selection electrode is formed opposite to this phosphor screen (12) and has a large number of electron beam passing holes formed inside the phosphor screen (12). A mask (13) is worn.

In addition, in the neck (14) of the funnel (11), there is a center beam (8G) passing on the same horizontal plane and a pair of side beams (8B), (8R) arranged in three rows.
An electron gun (15) that emits an electron beam is provided.

Further, on the outside of the boundary between the cone portion (24) and the neck (14) of the funnel (11), there is a deflection device (18) for deflecting the three electron beams emitted from the electron gun (15).
is installed.

Further, the funnel inner wall surface (32) of the color cathode ray tube device of this embodiment has a neck (14) of the funnel (11>).
) from the panel (lO) and the funnel (lO) to the vicinity of the joint surface (23) of the funnel (11) and the panel (lO).
11), the thermal expansion coefficient (α
g) An internal conductive coating (33) is formed which has a smaller coefficient of thermal expansion (α.). This internal conductive coating (
33) passes a high voltage applied from the outside via an anode button (26) buried in the funnel (11) to the electron gun structure (27) through a valve spacer contact (27).
15) and to the shadow mask (13) through the contact spring (28), and absorbs secondary electrons generated from the shadow mask (13), etc., and the secondary electrons are emitted onto the phosphor screen (12). It has the function of preventing sudden deterioration of color purity.

In this example, oxidation, which is a conductive material, is used as an example of a material forming the internal conductive coating (33) having a coefficient of thermal expansion (α.) smaller than the coefficient of thermal expansion (αg) of the glass constituting the glass envelope. A lead borate glass with tin (SnO□) and antimony oxide (sbzoz) was chosen.

Its specific composition is as follows.

mA/lead borate glass; 70wt%PbO: 74
．． 9 B, 0. : 8.6 ZnO: 12.6 Sin2: 2.0 ao: L, 9 conductive material; 30wt% SnO3: 95.0 Sb20. : 5.0 The coefficient of thermal expansion (αg) of the glass covering the panel (10) and funnel (11) is approximately 10 x 10-'deg-
The coefficient of thermal expansion of the lead borate glass in this example is approximately 7.7×to-'deg-''. Since the thermal expansion coefficient and specific resistance decrease as the content increases, an internal conductive coating with desired properties can be obtained by adjusting the content.

Such an internal conductive coating (33) is applied to the inner wall (32) of the funnel portion which has been cleaned with a cleaning agent such as hydrogen fluoride.
It is formed by applying a slurry containing a substance having the above composition having a low coefficient of thermal expansion (αg) by a spray method or the like. After that, this inner wall conductive coating (33) is
The panel (10) and funnel (11) are made of low melting point glass (
In the temperature raising process of the sealing step 23), it is sintered and bonded to the funnel glass inner wall (32). This coating has different effects depending on its thickness even if the coefficient of thermal expansion is the same. However, the effect becomes saturated when the thickness exceeds a certain level. In the case of this embodiment, about 5 to 20 μs is appropriate. The coefficient of thermal expansion is difficult to define and measure when there is a large amount of powder and voids inside the coating, as in the case of conventional internal conductive coatings, but when glass is the main component, as in this example, it is difficult to define and measure the coefficient of thermal expansion. Since it is thought that there are not many voids in , the coefficient of thermal expansion after sintering is approximately 8. OX 1 (1'''6deg-1 is expected. The sintered internal conductive coating (33) with a low coefficient of thermal expansion applies compressive stress (36) to the funnel glass inner wall (32) during the subsequent temperature increase process. , Q inside the funnel glass due to the temperature difference inside and outside the funnel glass.
(32) acts to cancel the tensile stress (34) generated in the glass envelope, suppresses the generation and growth of microcracks, and improves the resistance of the glass envelope against mechanical breakage. Further, in the constant temperature process, compressive strain (41) remains on the inner wall surface of the funnel, and in the subsequent temperature cooling process, the compressive strain (41) is released, so that it acts effectively in the entire process of the high temperature process. moreover,
This effect is also applicable to the evacuation process, in which the inside of the cathode ray tube is evacuated to high vacuum at high temperature, and stress is added due to the pressure difference between the inside and outside of the glass envelope.

This action and effect will be explained in more detail.

When a glass envelope is coated with a substance made of oxide, metal, or other powder and glass, and the temperature does not rise above the transposition point of the glass, stress is applied at high temperatures to prevent the bulb from heating during heat treatment. It can be expected to have the effect of preventing destruction.

When such a substance is applied and the temperature is raised, the glass in the applied material is diffused during the heating process, sintering the powder particles and the glass envelope. If the coefficient of thermal expansion of the coated material is smaller than that of the glass envelope in the subsequent heat treatment, compressive stress will act on the surface of the glass envelope due to the difference in thermal expansion, and tensile stress will be concentrated on the micro cracks existing on the surface. It has a soothing effect.

However, if the temperature is raised above the glass transition temperature of the glass in the coated material, the glass will have fluidity and the particles will be rearranged, and the compressive stress will be relaxed. , the temperature should not be raised above the glass transition temperature. Conversely, during the cooling process after heat treatment, tensile stress is applied to the glass surface, but this is not a problem because it is used to release the compressive strain generated at high temperatures.

However, such a coating layer is not suitable for the outer surface of the glass, as it is better not to deposit it in areas where tensile stress is applied during cooling. From now on, the layer that exerts stress under high temperature conditions to prevent the bulb from breaking during heat treatment will be referred to as the "first coating layer."

In this example, tin oxide (SnO□) is used as the conductive substance contained in the substance forming the internal conductive film.

Although antimony oxide (sb2o,) was selected, it is not limited to this substance; for example, rhenium oxide (R
eOi)-nickel oxide (NiO), vanadium oxide (v203), etc. can also be used.

Next, another example of this example will be described.

A second coating that is applied when the glass envelope is in a high temperature state, applies stress at room temperature, and improves the static pressure resistance characteristics of the envelope.
The case of forming the coating layer will be explained.

This is done by coating a glass envelope with a low-melting glass whose coefficient of thermal expansion is smaller than that of the glass envelope, raising the temperature above the glass transition temperature, and making the low-melting glass have fluidity. The coating is applied to a thickness of 5 to 20 mm. in this case,
No stress is applied at high temperatures.

When this is cooled, the thermal expansion coefficient of the coating layer is smaller than that of the glass envelope, so tensile stress acts on the interface between the coating layer and the glass envelope on the glass envelope side due to the difference in the amount of shrinkage. , compressive stress acts on the coating layer side. However, in this case,
Since the interface between the coating layer and the glass envelope is uniformly bonded, microcracks on the surface become a problem on the surface of the coating layer.

In this case, the thickness of the coating layer should not be too thick.

After being cooled to room temperature, the surface of the coating layer becomes a glass surface, and compressive stress acts on this area, which has the effect of increasing static pressure resistance.

In this case, it is better to apply a separate heat treatment to the glass envelope and apply compressive stress in advance before the heat treatment during the manufacturing process.

An example in which such a second coating layer is applied to a glass envelope will be described with reference to FIGS. 6(c) and 7. That is, as shown in FIG. 6(c), a strong tensile stress (F3) acts on the glass envelope, especially around the outer surface of the panel, during the cooling process in the exhaust furnace. The second coating layer (60) is formed over the entire circumference of this portion, that is, the outer peripheral portion of the panel (10) shown in FIG. In Figure 7, (
33) is the first coating layer, which is coated by heat treatment during the manufacturing process. Since the second coating layer (60) partially covers the front surface of the panel, it is preferable to use transparent low-melting glass, and the second coating layer (60) is preferably made of transparent low-melting glass, and is made to have a strong hardness by applying heat treatment before heat treatment during manufacturing processes such as sealing and exhaust. It is desirable to cover it with adhesive strength.

In addition, since tensile stress acts on the outer surface of the funnel (11) during the cooling process of the sealing furnace, it is not preferable to use the same type of coating layer as the first coating layer.
It is preferable to form the same type as the second covering layer.

Furthermore, at the center of the inner surface of the panel, the type of first coating layer described above may be used, but it must be transparent, so it is preferable to coat it with transparent low-melting point glass in advance.

Still other examples include those that utilize a conventional internal conductive membrane with low thermal expansion glass frit powder mixed into the material that makes up the membrane, or lead-based materials with low thermal expansion other than borate glass. The glass envelope may be coated with melting point glass mixed with a conductive substance and heat treated to provide a strong adhesive force.

〔Effect of the invention〕

The present invention improves the mechanical strength of the glass envelope, which has become a problem as color cathode ray tubes have become larger in recent years, without particularly increasing the wall thickness of the glass, and by a relatively simple method. be able to.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the configuration of a color cathode ray tube device, which is a detailed illustration of the present invention, and FIGS. 2 to 5 are partial cross-sectional views for explaining the operation of the embodiment of the present invention. Figure 2 is a diagram showing the stress acting in the temperature rising process of the high temperature process, Figure 3 is a diagram showing the stress and strain acting in the constant temperature process of the high temperature process, and Figure 4 is a diagram showing the stress and strain acting in the constant temperature process of the high temperature process.
The figure shows the stress acting during the cooling process in a high-temperature process. Figure 5 shows the micro-cracks and stress concentration that occur on the glass surface. Figure 6 (a), (b), and (c) show the glass surface. FIG. 6(a) is a diagram illustrating the stress acting on the envelope; FIG. 6(a) shows the temperature rising process in the high-temperature process, FIG. 6(b) shows the temperature decreasing process, and FIG. 6(c) shows the outer envelope in the exhaust furnace. FIG. 7 is a schematic sectional view illustrating another embodiment of the present invention.

Claims (1)

[Claims] (1) A vacuum envelope made of glass and evacuated at high temperature;
In a cathode ray tube comprising a phosphor screen formed within the envelope and an electron gun that emits electrons at a position opposite to the phosphor screen to cause the phosphor screen to emit light, the glass envelope includes an outer A cathode ray tube characterized by having a coating layer that generates stress strain due to a difference in thermal expansion coefficient between the cathode ray tube and the cathode ray tube.