JPH02288049A - Luminous screen - Google Patents

Abstract

PURPOSE:To improve luminance by filling the periphery of a dot or a stripe with metal excellent in heat conductivity and electric conductivity when forming a fluorescent film in dot or stripe shape on a glass substrate to make it into a luminous screen, and then covering the surface of the structure, being made this way, with an aluminum reflection film. CONSTITUTION:On a glass substrate 1 being cleaned enough, a thin aluminum layer 2 by heating deposition in low vacuum and a thick aluminum layer 3 by heating deposition in high vacuum are stacked, and the light absorption factor of the layer 3 is made small beforehand. Next, the space surrounded by this laminate is formed by etching this laminate, and phosphors 4, 5 and 6 are stuffed in these spaces, respectively. Thereafter, the whole face of these phosphors and the laminate where the surfaces are exposed is covered with an aluminum film 7 being a reflective film, and is heat-treated at about 450 deg.C into a fluorescent film. This way, a screen excellent in relative luminous output, luminance maintenance factor, nonelectrification factor, etc., is obtained easily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fluorescent film that emits light by irradiation with a charged particle beam, and a luminescent screen that particularly requires high brightness in display devices.

[Conventional technology]

In the case of color cathode ray tubes, which are the most well-known display devices using fluorescent films, graphite is used as a light-emitting absorbing layer between each pixel to improve the contrast of the emitting pixels. (black matrix, hereinafter referred to as BM). The above-mentioned BM invention was groundbreaking at the time, and achieved a significant improvement in contrast. However, as the need for large-screen, high-definition color cathode ray tubes increases, insufficient screen brightness has become a chronic problem. Therefore, B.M.
A method of improving brightness has been proposed by forming an aluminum film with high reflectance on the surface and then applying a slurry of phosphor (Patent Nα1435540).

Furthermore, the current of the irradiated electron beam is increasing year by year, and there is a strong demand for countermeasures against the brightness life (deterioration) of the fluorescent film.

[Problem to be solved by the invention]

In order to improve the brightness of the fluorescent surface, measures have been taken to increase the irradiation energy of the electron beam. This includes an increase in the electron acceleration voltage and an increase in the current density of the electron beam. However, both of these strategies cause heat to accumulate on the phosphor surface and also tend to charge the phosphor particle surface. In general, the efficiency of phosphors tends to decrease as the temperature increases, and heat accelerates the formation of defects on the crystal surface, making them susceptible to deterioration. On the other hand, charging of the surface of the phosphor particles generates a strong electric field inside the crystal, resulting in defects on the crystal surface.

Furthermore, charging of the surface of the phosphor particles leads to a decrease in brightness. Therefore, in order to solve these problems, there is a need for a phosphor film having a structure in which heat is not accumulated in the phosphor film even when irradiated with high-energy electron beams, and the phosphor film is not easily charged.

In the prior art, the BM around the phosphor dots or stripes is graphite powder. A laminated film with a higher packing density is more effective than powder in order to suppress temperature rise and charging of the fluorescent film. However, when a material having high thermal and electrical conductivity and high reflectance is laminated on the BM in the form of a film with a high packing density of several μm, the laminated film easily peels off. Therefore, the present invention has realized a structure that can satisfy the above requirements in a fluorescent film that does not use BM.

An object of the present invention is to obtain a luminescent screen having a structure in which heat is not accumulated in the fluorescent film even when irradiated with a high-energy electron beam, and the fluorescent film is not easily charged.

[Means to solve the problem]

The above object is achieved by using a metal with excellent thermal conductivity and electrical conductivity in place of the conventional BM.

However, when a metal film with high reflectance is directly deposited on a glass substrate, a mirror surface is created.

The display screen becomes very difficult to see due to the reflection of external light. In order to solve this problem, a layer with high light absorption must be provided in a portion close to the substrate.

The metal is preferably a substance that can be easily formed into a film by a heating vapor deposition method, such as aluminum. Furthermore, when aluminum is vapor-deposited, a black aluminum film with high light absorption can be formed by vapor-depositing it in a low vacuum, so it is the most suitable material for achieving the above object. It is sufficient for the black aluminum film to have a thickness of 0.5 μm; if it is thicker than that, it will absorb the light emitted from the sides of the phosphor layer, reducing the brightness of the phosphor layer. . The black aluminum film can also be formed by thermal evaporation or sputtering in a low vacuum.

[For production]

When a phosphor film is irradiated with a charged particle beam such as an electron beam at high density, the surface of the phosphor particles becomes charged to varying degrees. This obstructs the entry of the -order particle beam and becomes a factor in impairing the luminescence of the phosphor. However, if there is a metal layer close to the surface of the phosphor particles, the charged state is relaxed and does not interfere with light emission. On the other hand, heat is accumulated in the phosphor film due to high-density irradiation, and the action of the heat promotes the formation of defects in the phosphor crystal. Therefore, by using a metal with excellent thermal conductivity and surrounding the phosphor dots or stripes in the form of a laminated film, it is possible to absorb and dissipate heat and prevent heat accumulation.

〔Example〕 Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view conceptually showing an embodiment of a luminescent screen according to the present invention.

FIRST EXAMPLE In FIG. 1, an aluminum layer 2 was deposited by heating on a glass substrate 1 which had been thoroughly cleaned.

Initially, aluminum was laminated to a thickness of about 0.1 μm under low vacuum (several mTorr), but under this condition, the aluminum turned into black aluminum with high light absorption.

Furthermore, a high vacuum (IXIO 5 Torr) was applied and aluminum was again laminated to a thickness of about 25 μm.

An aluminum vapor-deposited film 3, which is a thermally and electrically conductive film, was formed, a commonly used ultraviolet photoresist was applied onto the vapor-deposited film 3, and ultraviolet rays were irradiated through a mask. Then, a dot pattern for applying the phosphor was formed by etching.

The phosphor was applied using a slurry method. That is, polyvinyl alcohol (PVA) and ammonium dichromate are added to the phosphor, mixed, and phosphors of each luminescent color are attached by UV irradiation through a mask matched to a predetermined luminescent color dot. I let it happen. The phosphor used was ZnS
: Ag, CQ (blue), Zn S: Cu, Au
, Aff (green), Y, 02S: E u (red). The above phosphors are applied in the order of blue phosphor 4, green phosphor 5, and red phosphor 6. After that, an organic film is used for filming, and then an aluminum film 7, which is a reflective film, is applied in the order of The layers were laminated to a thickness of about 0.4 μm. Further, heat treatment at 450° C. was performed to thermally decompose the filmed organic film, and a fluorescent film having a cross section as shown in FIG. 1 was prepared.

The fluorescent film obtained by the above method was set in an electron beam irradiation device, and a 10×10 electron beam was applied at an acceleration voltage of 27 kV and a current of 1 μA.
The luminous output of the fluorescent film was examined by irradiating with a X10 raster.

For comparison, a fluorescent film produced by a conventional process using BM was examined. Also, set the current to 100/AA and 1
The fluorescent film was forcibly degraded for 0 minutes, and the luminous output ratio (referred to as brightness maintenance rate) before and after irradiation was examined. The value of the luminance maintenance factor is a scale indicating that the closer the value is to 1, the more difficult the fluorescent film is to deteriorate. On the other hand, in order to investigate the charging state of the fluorescent film, the emission output ratio (referred to as uncharged rate) due to reflection and secondary electron beam before and after high-intensity irradiation was also determined. This uncharged rate value is a measure indicating that the closer it is to 1, the less likely the fluorescent film is to be charged.

Table 1 shows the results of comparing the characteristics of the fluorescent films constituting the luminescent screen.

According to the present invention, a fluorescent film using aluminum instead of BM has a higher luminous output and is less likely to deteriorate in brightness, and
It turns out that it is difficult to charge. moreover.

As a result of considering gold, copper, and silver as metals other than aluminum, except for the points regarding black aluminum,
It was confirmed that it had the same effect as aluminum.

Second Embodiment Approximately zero black aluminum 2 is applied to the inner surface of a thoroughly cleaned face plate glass 1 of a cathode ray tube by heating vapor deposition.
．． The aluminum layer 3 was laminated to a thickness of about 1 .mu.m, and then an aluminum layer 3 of about 0.5 .mu.m thick was formed by electroless plating and about 25 .mu.m thick by electrolytic plating on the above film.

Next, battening and phosphor coating were carried out in the same manner as in the first example, and a color cathode ray tube was manufactured using a process similar to that used for manufacturing well-known color cathode ray tubes.

The light emitting output of the prototype cathode ray tube was evaluated using an accelerating voltage of 27 kV, a cathode current of 500 μA, and a 20-inch rusk. In addition, as an evaluation similar to the first example, the brightness maintenance rate was measured using forced irradiation with a current of 1 mA and a 1-inch rusk, and the comparison results are shown in Table 2.

According to this example, it can be seen that even when the phosphor film according to the present invention is applied to a color cathode ray tube using a face plate glass, the luminescence characteristics are superior to that of the phosphor film made using the conventional BM method. .

〔Effect of the invention〕

As described above, the luminescent screen according to the present invention has a fluorescent film formed in the form of dots or stripes on a glass substrate, and the area around the fluorescent dots or stripes has excellent thermal conductivity and electrical conductivity. By using a structure in which the buried layer is in contact with the aluminum reflective film formed on the phosphor dots or stripes, the brightness can be increased several times without significantly reducing the contrast of the phosphor dots or stripes. % to more than 10%, and furthermore, it has a brightness life characteristic of almost 90%, which has the effect of helping to further improve the quality of large-screen, high-definition display devices.

[Brief explanation of the drawing]

FIG. 1 is a sectional view conceptually showing an embodiment of the luminescent screen according to the present invention. 1...Glass substrate 3...Metal with excellent thermal and electrical conductivity 4.5.6
...Fluorescent material 7...Aluminum reflective film

Claims (1)

[Claims] 1. In a luminescent screen in which a fluorescent film is formed in the form of dots or stripes on a glass substrate, the area around the fluorescent dots or stripes has excellent thermal conductivity and electrical conductivity. 1. A luminescent screen, characterized in that the embedded metal layer is in contact with an aluminum reflective film formed on the phosphor dots or phosphor stripes. 2. The luminescent screen as set forth in claim 1, wherein the metal layer is made of aluminum and is formed together with a black aluminum coating directly on the glass substrate. 3. A color cathode ray tube comprising a luminescent screen according to claim 1 or 2. 4. The metal layer described in claim 1 or 2 is formed on glass by either electrolytic plating or electroless plating, a combination thereof, or a combination with a heating vapor deposition method. A method for manufacturing a luminescent screen, characterized in that a fluorescent film is applied between these metal layers after forming the luminescent screen directly on a substrate.