JPH0554820A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To enhance the contrast of a fluorescent screen by restraining scattering of external surrounding light at the fluorescent screen. CONSTITUTION:On a glass panel 1 where carbon stripes 2 are formed at a predetermined pitch in advance, a phosphor layer 4 made of phosphor particles 3 is formed at the portion of the panel 1 where on carbon stripe 2 is formed. The phosphor layer 4 is obtained when a coat of a phosphor slurry wherein the phosphor particles 3 are dispersed is exposed and developed using an aperture grill as an optical mask. Voids in the phosphor layer 4 (voids among the phosphor particles 3 and the void between the phosphor layer 4 and the glass panel 1) are filled with a medium 5 the refractive index of which is close to that of phosphor particles 3 (normally 2.3 to 2.4). An inorganic coating agent wherein an inorganic material whose refractive index is greater than 1 is dispersed is used as such a medium 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode ray tube, and more particularly to improving the contrast of a fluorescent screen.

[0002]

2. Description of the Related Art For example, a phosphor screen of a cathode ray tube panel in a color television receiver or the like has a phosphor slurry containing phosphor fine particles and a photosensitive binder on a glass panel on which a carbon matrix is formed in a predetermined pattern. It is obtained by forming a phosphor layer on a portion where the carbon matrix is not formed by applying, selectively exposing and developing. On the fluorescent screen of such a cathode ray tube panel, there is a problem that the contrast is lowered due to reflection of external ambient light on the fluorescent screen. For example, when watching a television in a general home, when external ambient light such as indoor lighting is reflected on the fluorescent surface of the cathode ray tube panel, the reflected light is mixed with the light emitted from the fluorescent material, and the contrast is apparently lowered.

On the other hand, recently, in order to improve the contrast of the fluorescent screen, black tends to be emphasized. For example, a gray filter is arranged on the front surface of the glass panel so that the glass panel is A method of reducing the transmittance or adding or adhering an absorbing material to the phosphor fine particles themselves is mainly adopted.

[0004]

As described above, in the method of mounting the filter on the front surface of the glass panel, since the external ambient light passes through the filter twice in the process of reflecting on the fluorescent screen, this reflected light amount Can be significantly attenuated. However, in this case, since the light emitted from the phosphor also passes through the filter, there is a drawback that the emission brightness of the phosphor is reduced.

In addition, the method of adding or adhering an absorbing material to the phosphor fine particles themselves does not absorb the light emitted from the phosphor as the absorbing material but selects a wavelength that absorbs light of other wavelengths. Unless a conventional dye absorber is used, the above-mentioned absorbing material absorbs the external ambient light incident on the phosphor layer and also absorbs the light emitted from the phosphor, so that it is not practical.

Therefore, the present invention has been proposed in view of the above conventional circumstances, and an object thereof is to provide a cathode ray tube in which the contrast of the phosphor screen is improved and a good image quality can be obtained. To do.

[0007]

Means for Solving the Problems As a result of studies to achieve the above-mentioned object, the present inventors have found that, in the glass panel surface on which the phosphor layer is formed, the space between the phosphors and the glass panel The inventors have found that filling the voids with a material having a refractive index close to that of a phosphor can suppress light scattering on the phosphor screen and improve the contrast, and completed the present invention.

That is, the cathode ray tube according to the present invention is characterized in that the voids in the phosphor layer on the phosphor screen are filled with an inorganic material having a refractive index larger than 1. In the cathode ray tube of the present invention, the fluorescent surface is formed on a glass panel in which a phosphor layer made of phosphor fine particles is formed in advance with a carbon matrix in a predetermined pattern, and the gap between the phosphor layer and the glass panel and the above The gap between the phosphor fine particles is filled with an inorganic material.

The phosphor layer is formed by coating a phosphor slurry containing phosphor fine particles on the glass panel, drying it, and then performing selective exposure / development to only a portion where the carbon matrix is not formed. It is formed by leaving it.

The gap between the phosphor layer and the glass panel and the gap between the phosphor fine particles are covered with an organic substance when the phosphor slurry is applied, but the organic substance is removed by subsequent firing, Almost vacuum state.
Therefore, if the gap between these phosphor layers is filled with a material having a refractive index close to that of the phosphor fine particles forming the phosphor layer,
It is possible to reduce the light scattering of the external ambient light that has entered the phosphor layer.

Therefore, the refractive index of the inorganic material is set to a value larger than 1, which is the refractive index in the vacuum state, and it is particularly preferable that the difference from the refractive index of the phosphor fine particles is 1.2 or less. ..

The above-mentioned inorganic material has a good light-transmitting property, and its complex refractive index n-ik (n represents a refractive index, k
Represents the extinction coefficient. ), The extinction coefficient k is 0.001
It is preferably less than.

In addition to the above, the above-mentioned inorganic material is a material that absorbs light at a wavelength position deviating from the emission wavelength of the phosphor fine particles in the visible light wavelength region more than absorption at the emission wavelength position. Heating temperature during heat treatment (400 ℃
Degree) and sufficient stability against electron beam irradiation, and the fact that no gas is released, etc., therefore, an inorganic dielectric material can be cited as a material satisfying such conditions. Inorganic pigments and the like are particularly suitable.

As a method for filling the gaps in the phosphor layer with such an inorganic material, for example, the inorganic material is dispersed in an inorganic coating agent having an inorganic glass structure after sintering, and the inorganic coating agent is used for the fluorescent material. There is a method of applying from the surface of the body layer and curing.

In this case, examples of the inorganic coating agent include those mainly containing SiO ₂ , TiO ₂ , or a mixture thereof.

Further, in the cathode ray tube of the present invention, for the purpose of improving the brightness of the screen, preventing ion burning and stabilizing the phosphor surface potential, a metal back consisting of a conductive reflection film on the phosphor layer is used. It is preferable to form a layer. As the conductive reflection film, for example, an aluminum thin film can be used, but in the present invention, a material having a lower reflectance than the aluminum thin film is used, or as shown in FIG. 2, it is formed on the glass panel 11. Alternatively, a structure may be employed in which the reflectance of the aluminum thin film is reduced by interposing a carbon film 13 or the like between the phosphor layer 12 (the gap is filled with the inorganic material 15) and the aluminum thin film 14. In this case, the purpose of providing the metal back layer can be sufficiently achieved, and the scattering from the metal back layer can be suppressed, which is more preferable for improving the contrast.

Furthermore, the cathode ray tube of the present invention is shown in FIG.
The same constituent materials as those shown in FIG. 2 are designated by the same reference numerals. ), A circularly polarizing plate 16 may be provided on the front surface of the glass panel 11. As the circularly polarizing plate 16, a combination of a 90 ° phase difference plate 16a and a polarizing plate 16b is used, and these are sequentially laminated on the glass panel 11. As a result, the amount of light emitted from the phosphor (indicated by a white arrow in the figure) is halved when it is emitted from the screen by passing through the circular polarizing plate 16, but the circular polarizing plate 16 The amount of external ambient light (indicated by a black arrow in the figure) incident on the phosphor screen via the is reduced to 1/4 of that at the time of being reflected from the phosphor screen and emitted from the screen again. As a result, the contrast is improved.

[0018]

The fluorescent screen of the cathode ray tube looks bright when it does not emit light because external ambient light enters the fluorescent screen, is scattered, and is emitted again to the outside to increase the scattering intensity of the fluorescent screen. As described above, it is considered that the scattering (reflection) on the surface of the phosphor fine particles forming the phosphor layer has a considerable influence as a factor for increasing the scattering intensity of the phosphor screen.

The periphery of the phosphor fine particles is filled with an organic substance at the time of application, but the organic substance is removed by subsequent firing, and the gap between the phosphor fine particles and the glass panel and the fluorescent light formed on the glass panel are removed. The gap with the body layer is almost in a vacuum state.

Here, since the scattering intensity on the surface of the phosphor fine particles is approximately proportional to the square of the difference in the refractive index at the interface (Fresnel reflection), the gap between the phosphor layers (the difference between the phosphor fine particles is If the scattering on the surface of the phosphor fine particles is suppressed by filling the gap or the space between the phosphor layer and the glass panel) with a medium having a refractive index as close as possible to the phosphor fine particles, the scattering intensity of the phosphor screen is significantly reduced. It is thought that.

Therefore, by filling the gap of the phosphor layer with at least an inorganic material having a refractive index higher than that in a vacuum state, that is, an inorganic material having a refractive index higher than 1, light scattering on the phosphor screen is reduced.

[0022]

EXAMPLES Preferred examples of the present invention will be described below based on experimental results. In the cathode ray tube of this embodiment, as shown in FIG. 1, the phosphor screen has carbon stripes 2 formed on a panel substrate 1 made of glass or the like at a predetermined pitch. The carbon stripe 2 functions as a light absorbing layer, and its thickness is usually about 1 μm.

On the panel substrate 1 on which the carbon stripes 2 are not formed, a phosphor layer 4 composed of phosphor fine particles 3 is formed. The phosphor layer 4 includes the panel substrate 1 including a phosphor slurry in which the phosphor fine particles 3 are dispersed together with a photosensitizer on the carbon stripes 2.
It is formed by applying it to the entire surface of, and drying it, and then using an aperture grill provided with thin vertical stripe slits as an optical mask, exposing it with a light source corresponding to each color phosphor, and developing it.

On the phosphor screen of a normal cathode ray tube, the periphery of the phosphor fine particles 3 constituting the phosphor layer 4 as described above is filled with an organic substance at the time of application, but the organic substance is removed by subsequent firing. It is removed, and the gap is almost close to the vacuum state. On the other hand, in the present embodiment, the refractive index of the phosphor fine particles 3 (usually 2.3 to 10) is set in the gaps between the phosphor fine particles 3 and the gap between the phosphor layer 4 and the panel substrate 1. The inorganic material 5 close to 2.4) is filled. As a result, the scattering on the surface of the fluorescent fine particles 3 is reduced, and the scattering intensity on the fluorescent surface can be remarkably reduced.

The inorganic material 5 has a refractive index of 1
(Refractive index in vacuum state), and a material having a larger absorption at a wavelength position deviating from the emission wavelength position of the phosphor fine particles in the visible light wavelength region than at the emission wavelength position of the phosphor fine particle, and heat treatment Has sufficient stability against the heating temperature (about 400 ° C) and electron beam irradiation at the time of
It is required that no gas be released. As a material satisfying such characteristics, an inorganic dielectric material can be used, and an inorganic pigment or the like is particularly preferable.

Such an inorganic material 5 is, for example, Si.
The phosphor layer 4 is dispersed in an inorganic coating agent mainly containing O ₂ , TiO ₂ or a mixture thereof, applied from the surface of the phosphor layer 4, and baked and cured at a predetermined temperature to form the phosphor layer. Fill the gap.

At this time, the inorganic coating agent is applied thickly so that the surface of the phosphor layer 4 is sufficiently covered, so that the primer treatment step (aluminum reflective film described later) usually performed in the manufacturing process of the cathode ray tube. 6 is omitted, the step of forming a thermally decomposable intermediate film such as nitrocellulose in order to eliminate the surface irregularities of the phosphor layer 4 and flatten it before forming 6), and simplify the manufacturing process. Is possible.

An aluminum reflection film (metal back layer) 6 having a film thickness of 3000 Å is formed on the entire surface of the phosphor layer 4 whose gaps are filled with the inorganic material 5 so as to cover the surface by a vacuum deposition method or the like. It

The aluminum reflection film 6 is formed to improve the brightness of the phosphor screen, and is made of a material having a high light reflectance and a high electron transmittance. As a result, of the light emitted by the fluorescent fine particles 3 excited by the electron beam and the external ambient light that has penetrated through the glass substrate 1 and is directed toward the back surface, the component directed toward the back surface is reflected forward, and the screen brightness is increased. In addition to improving the quality, it is possible to prevent ion burning and stabilize the fluorescent surface potential.

In order to fully exhibit the function of the aluminum reflective film 6, it is essential that the aluminum reflective film 6 is formed into a mirror-finished state. For this purpose, it is necessary to flatten the surface irregularities of the phosphor layer 4, but as described above, if the film thickness of the inorganic coating agent is made sufficiently thick, without performing primer treatment,
The aluminum reflection film 6 can be formed in a mirror-like manner on the coating film of this inorganic coating agent.

Therefore, in a cathode ray tube having such a structure, the following experiment was conducted in order to investigate the effect of filling the above-mentioned inorganic coating agent in the gap of the phosphor layer.

First, the aluminum coat film formed on the phosphor layer of a commercially available 4-inch color cathode ray tube panel (baked. Stripes L & S, 50 μm) was peeled off, and the exposed surface of the phosphor layer was covered with the following Table 1. Various inorganic coating agents a to e (manufactured by Nissan Kagaku Co., Ltd.) having the characteristics shown in (3) were dropped and allowed to naturally develop, and then dried at 300 ° C. for about 30 minutes (the above inorganic coating agent is completely baked). Although the temperature is about 500 ° C., it is sufficiently cured even at the above temperature (however, in this case, the refractive index is slightly lower than that in the completely baked state). At this time, as shown in FIG.
A portion A in which the thickness of the inorganic coating agent is changed so that the surface of the phosphor layer is sufficiently covered so as to be applied.
And a thinly applied portion B was formed so that the phosphor fine particles on the surface of the phosphor layer were slightly exposed. Also,
For comparison, a portion not coated with the above inorganic coating agent was also formed.

[0033]

[Table 1]

Subsequently, an aluminum reflective film having a film thickness of about 3000 Å was formed again on the coating film of the above inorganic coating agent by a vacuum deposition method. When the TiO ₂ -containing inorganic coating agent d and the inorganic coating agent e were used in the obtained cathode ray tube panel, yellowing was observed in the inorganic coating agent d and the inorganic coating agent e after drying. , Inorganic coating agents a to c excluding these
In case of using, the scattering intensity of the phosphor screen of the cathode ray tube panel when the phosphor screen was irradiated with external ambient light was measured. The results are shown in Table 2.

At the time of measurement, two 40 W indoor fluorescent lamps were used as light sources of external ambient light, and the scattering intensity of the fluorescent surface was measured by a luminance meter (trade name: Luminescence Meter BM-5) manufactured by Tokyo Optics. The installation positions of these luminance meters and indoor fluorescent lamps are shown in FIG. As shown in FIG. 5, the luminance meter 21 is installed at a position 6 m apart horizontally from the surface 22a of the cathode ray tube panel 22, and the indoor fluorescent lamp 23 is installed through the surface 22a of the cathode ray tube panel 22. It was installed at a position where the angle θ with the luminance meter 21 was 70 ° and the distance from the surface 22a of the cathode ray tube panel 22 was 1.2 m.

[0036]

[Table 2]

As shown in Table 2, it was found that the scattering strength of the phosphor screen was remarkably reduced by filling the gaps in the phosphor layer with the above inorganic coating agents a to c. Also,
When the illuminance of the fluorescent screen with respect to the illuminance of the indoor fluorescent lamp was determined, it became clear that light scattering on the fluorescent screen could be suppressed to about 50%.

[0038]

As is apparent from the above description, in the cathode ray tube of the present invention, the space between the phosphor layers is filled with a medium having a refractive index close to that of the fine phosphor particles forming the phosphor layer. Therefore, the scattering of the external ambient light on the surface of the phosphor fine particles is significantly suppressed. Therefore, the contrast is improved and a good image can be obtained.

If the inorganic coating agent used for filling the gaps in the phosphor layer is applied thickly,
Since the conductive reflection film can be formed on the phosphor layer as a mirror surface, the primer treatment that is performed in the existing phosphor screen forming step is unnecessary, and the working process can be simplified.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing the structure of a phosphor screen in a cathode ray tube of the present invention.

FIG. 2 is a cross-sectional view of essential parts showing an example of a structure for reducing the reflectance of an aluminum reflective film formed on a phosphor layer.

FIG. 3 is a schematic diagram for explaining a state of light emitted from a fluorescent screen when a circularly polarizing plate is arranged on the front surface of a panel substrate.

FIG. 4 is a cross-sectional view showing a film thickness of an inorganic coating applied on the phosphor layer and a formation state of an aluminum reflective film formed on the phosphor layer.

FIG. 5 is a schematic diagram showing the arrangement of a measurement system when measuring the scattering intensity of a fluorescent screen with a luminance meter.

[Explanation of symbols]

 1 ... Panel substrate 2 ... Carbon stripe 3 ... Phosphor fine particles 4 ... Phosphor layer 5 ... Inorganic material 6 ... Aluminum reflection film

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[Procedure amendment]

[Submission date] August 12, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction content]

At the time of measurement, two 40 W indoor fluorescent lamps were used as light sources of external ambient light, and the scattering intensity of the fluorescent surface was measured by a luminance meter (trade name: Luminescence Meter BM-5) manufactured by Tokyo Optics. The installation positions of these luminance meters and indoor fluorescent lamps are shown in FIG. As shown in FIG. 5, the luminance meter 21 is installed at a position 0.6 m apart from the surface 22a of the cathode ray tube panel 22 in the horizontal direction,
The indoor fluorescent lamp 23 is the surface 22 of the cathode ray tube panel 22.
It was installed at a position where the angle θ formed with the luminance meter 21 through a was 70 ° and the distance from the surface 22a of the cathode ray tube panel 22 was 1.2 m.

Claims (1)

[Claims] 1. A cathode ray tube, characterized in that voids of a phosphor layer on a phosphor screen are filled with an inorganic material having a refractive index of more than 1.