JPH04249850A - Display tube for light source - Google Patents

Abstract

PURPOSE:To reduce the lowering of luminous brightness due to the temperature rise of a fluorescent screen by providing a heat conductive film on a glass base substance, and laminating and forming in order a fluorescent film and a metal-backed film on the heat conductive film. CONSTITUTION:Powder of a high-heat conductor is film-formed by sedimentation on a glass base substance 1 to form a heat conductive film 5. Next, a phosphor film 2 for a high-speed electron beam is formed on the film 5, a filming film 3 is formed on the film 2, and an Al metal-backed film 4 is formed on the film 3. After that, baking is made to burn and decompose the film 3, and the film 4 is sticked on the film 2 to form a fluorescent screen. This causes the escape of most of heat generated in the film 2 to outside the base substance 1 via the film 5 through the glass base substance 1, and the reduction of the temperature rise degree of a fluorescent screen, of temperature quenching, and of lowering luminous brightness.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source display tube having a metal back film on a phosphor screen, and more particularly to a heat dissipation structure of the phosphor screen.

0002

2. Description of the Related Art FIG. 2 is a sectional view of a main part showing the structure of a conventional display tube for a light source. In the figure, 1 is a glass substrate, 2
3 is a phosphor film, 3 is a filming film, and 4 is an Al metal back film. Note that the filming film 3 is formed to temporarily support the Al metal back film 4 formed thereon, and will disappear after the phosphor screen is fired and will not remain for convenience of explanation. Above, illustrated. Therefore, after the phosphor screen is formed, the Al metal back film 4 is placed directly on the phosphor film 2.

0003

[Problems to be Solved by the Invention] However, the phosphor screen of a conventional light source display tube has a phosphor film 2 on a glass substrate 1.
was formed, and an Al metal back film 4 was formed on this phosphor film 2 to form a phosphor screen, so that when electrons generated from a cathode (not shown) are accelerated and hit the phosphor screen, the following occurs. There was a problem as shown. (1) During the excitation process of the phosphor by the electron beam, the current that does not contribute to light emission becomes heat and increases the temperature of the phosphor screen, and this temperature increase causes temperature quenching of the phosphor and significantly reduces the luminance. . For example, the temperature of the phosphor screen in an excited state varies depending on the current density, scanning speed, etc., so it cannot be said with certainty, but it is generally around 150° C., and the brightness reduction rate at that time is 10 to 50%. (2) When a mixed phosphor is used in the phosphor screen (for example, a mixture of blue and pink phosphors is used to obtain white light), each phosphor has a different degree of temperature quenching, so the temperature of the phosphor screen The increase causes a shift in color balance. (3) Materials of the phosphor screen and its surroundings (glass substrate 1, A
As the temperature of the metal back film 4) rises, gas is released from the surface, and if the degree of gas release is large, the degree of vacuum will be lowered, and as a result, the relationship between the constituent members or between the cathode and the constituent members will decrease. Abnormal discharge will occur between the two, leading to deterioration or burnout of the cathode. (4) The temperature of the glass substrate 1 near the phosphor screen increases significantly, and as a result, the glass substrate 1 is affected by external physical factors (for example, rain, snow, etc. hitting the surface of the glass substrate 1).
In some cases, cracks may occur, which can be a fatal defect.

0004

[Means for Solving the Problems] In order to solve these problems, the light source display tube according to the present invention has a thermally conductive film with high thermal conductivity between the glass substrate and the phosphor film. be.

[0005]

[Operation] In the present invention, the heat generated by the phosphor screen is quickly released to the outside through the heat conductive film.

[0006]

Embodiments Hereinafter, embodiments of the present invention will be explained in detail with reference to the drawings. FIG. 1 is a sectional view of a main part of a phosphor screen showing the structure of an embodiment of a display tube for a light source according to the present invention, and the same parts as in the previous figures are given the same reference numerals. In the same figure,
A thermally conductive film 5 is formed on the glass substrate 1 by depositing powder of a highly thermally conductive substance by a precipitation method. The powder of the thermally conductive film 5 preferably has particles that are approximately the same as or slightly larger than the phosphor particles. Further, on this heat conductive film 5, a phosphor for high-speed electron beam is precipitated by a precipitation method to form a phosphor film 2 having a predetermined thickness. After drying, wetting the
A filming film 3 is formed on the phosphor film 2. Next, for example, Al evaporation is performed on the filming film 3 to form an Al
A metal back film 4 is formed. Then about 460℃, 10
Baking is performed for about 1 minute to burn and decompose the filming film 3, and the Al metal back film 4 is deposited on the phosphor film 2 to form a phosphor screen of a display tube for a light source.

The powder of the highly thermally conductive material constituting the highly thermally conductive film 5 used here: (1) does not react with the fluorescent material and does not attack the glass substrate 1; (2) It is transparent in the visible light range and can sufficiently transmit the light emitted from the phosphor film 2. (3) The particle size can be adjusted to an appropriate size. (4) It can be formed to an appropriate thickness by a precipitation method. (5) Good thermal conductivity and heat resistance, and can be obtained at low cost. The following characteristics are required, and aluminum oxide is an example of a material that meets this condition. This aluminum oxide (hereinafter referred to as alumina) has a thermal conductivity of approximately 0.
3W/cm・deg, for example, 0.0 of SiO2
The thermal conductivity is 2.1 to 4.2 times better than that of 7 to 0.014.

[0008]Although the particle size and particle form of alumina can be selected from various options, the inventor's alumina precipitation experiments revealed the following. (1) The particle diameter of alumina is preferably equal to or slightly larger than that of the phosphor particles. This is because the precipitation method differs from the printing method in that the unevenness of the powder particles remains on the surface, so the phosphor particles fit into the unevenness, increasing the contact area between the phosphor particles and alumina particles, and thus increasing the heat dissipation cross section. becomes larger, making heat dissipation even more effective. (2) The thickness of the alumina layer is an extremely important factor. If this film is too thick, it will interfere with light emission, and
If it is too thin, the heat dissipation effect will not be achieved. As a result of various experiments, it was found that the appropriate thickness of the alumina layer is about 5 to 15 μm (at this thickness, 2 to 6 alumina particles overlap and precipitate).

When accelerated electrons from a cathode (not shown) are bombarded with the phosphor screen constructed in this manner, the accelerated electrons pass through the Al metal back film 4 and strike the phosphor film 2.
It collides with the object, causing it to emit light. The generated light is transmitted through the thermally conductive film 5 and the glass substrate 1 and radiated, and the light directed toward the Al metal back film 4 is reflected by the Al vapor deposition surface and radiated from the glass substrate 1 through the phosphor film 2. be done.

According to this structure, by providing the heat conductive film 5 on the glass substrate 1, part of the heat generated in the phosphor film 2 is conducted through the Al metal back film 4 and transferred to the outside of the glass substrate 1. However, most of the heat escapes to the outside of the glass substrate 1 through the glass substrate 1 via the heat conductive film 5. Since the thermal conductivity of alumina is several times higher than that of the phosphor, the generated heat can be quickly conducted to the glass substrate 1, and therefore the degree of temperature rise of the phosphor screen can be reduced.

Next, explanation will be given using a specific example. First, a diameter of 20 mm and a length of 60 mm was formed with an anode electrode formed on a part of the inner surface.
Inject 2 ml of an aqueous solution containing potassium silicate into the head of a glass tube with one end sealed, and then inject a precipitating solution containing a mixture of white lumpy alumina powder (particle size 2 to 6 μm) and barium acetate. Let stand for 15 minutes. After the specified time has passed,
The supernatant liquid is removed by a decanting method and dried to form a thermally conductive film 5 made of an alumina powder layer. Next, a phosphor for high-speed electron beam (Y3(Al,Ga)5O12
: Tb (green light emitting) is formed by precipitation coating method, with a film thickness of about 1
A 5 μm phosphor film 2 is obtained. After forming the phosphor film 2 and the heat conductive film 5 as described above, a light source display tube is formed by a normal display tube manufacturing process.

[0012] In the above-mentioned embodiment, the thermally conductive film 5 was formed using alumina, but the present invention is not limited thereto; for example, Al, Mg, Be, Si, etc. , In, and Sn, the same effect as described above can be obtained.

[0013]

[Effects of the Invention] As explained above, according to the present invention,
By providing a heat conductive film on a glass substrate and sequentially laminating a phosphor film and a metal back film on this heat conductive film, extremely excellent effects as shown below can be obtained. (1) In the process of excitation of the phosphor film by an electron beam, the degree of temperature rise in the phosphor film due to current that does not contribute to light emission can be suppressed to a low level, so that temperature quenching is small and reduction in luminance of light emission is relatively small. (2) Even when mixed phosphors are used, there is little deviation in color balance and display quality is improved. (3) Since gas emission from the phosphor screen and its surrounding members is reduced, the occurrence of defects due to abnormal discharge is reduced. (4) The crack occurrence rate due to temperature rise of the glass substrate wall is reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a phosphor screen showing the structure of an embodiment of a display tube for a light source according to the present invention.

FIG. 2 is a sectional view of a main part of a fluorescent screen showing the configuration of a conventional light source display tube.

[Explanation of symbols]

1 Glass substrate 2. Phosphor film 3 Filming film 4 Al metal back film 5 Thermal conductive film

Claims (1)

[Claims] 1. A display tube for a light source, characterized in that a heat conductive film is provided on a glass substrate, and a phosphor film and a metal back film are sequentially laminated on the heat conductive film.