JP2001118526A - Image display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image display having low brightness saturation caused by strong excitation by an electron beam and a low deterioration of a fluorescence membrane. SOLUTION: An image display has a fluorescence membrane of two-layer structure of a first fluorescent body layer 3, disposed on a face plate 4 and a second fluorescent body layer 2 which is disposed on the first fluorescent body layer, an average particle diameter of the first fluorescent body composing the first fluorescent body layer 3 being larger than the average particle diameter of the second fluorescent body constituting the second fluorescent body layer 2, preferably in the range of 20-200%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device having a phosphor film on which at least two phosphor layers are laminated. Here, the image display device is a device that excites a phosphor by irradiating an electron beam and emits light to display image information. For example, not only a cathode ray tube (CRT) but also a fluorescent display tube (VFD) And a field emitter display (FED).

[0002]

2. Description of the Related Art In recent years, CRTs for displaying color images have recently been developed.
Higher definition and higher brightness are being promoted due to growing needs. Such a CRT reduces the spot diameter of an electron beam,
Due to the increase in the intensity of the excited electron beam, luminance saturation and luminance deterioration become remarkable, and the deterioration of image quality has become a problem. For this reason,
The phosphor is required to have improved characteristics such as color tone, luminance saturation, and luminance degradation. Further, it is necessary to improve the light extraction efficiency from the fluorescent film in order to improve the luminance.

In a CRT, the intensity of luminance is controlled by the current value of an excited electron beam. Therefore, the luminance of the phosphor needs to increase linearly with the current value. However, in general, when the intensity of excitation by the electron beam increases, luminance saturation occurs in the phosphor, and linearity of luminance is lost. Further, when an image is displayed with a strong excitation intensity, the phosphor material is greatly deteriorated, and the luminance and the color development are deteriorated during use.

[0004] Luminance saturation and deterioration characteristics vary greatly depending on the type of phosphor material, manufacturing method, additives, composition, and the like. Conventionally, in order to improve the above-mentioned problems, selection of a phosphor having better characteristics and improvement of the composition and manufacturing method have been studied. However, at present, it is difficult to fully satisfy all the properties required by a single phosphor material.

Further, in order to improve the light extraction efficiency and the apparent luminance, it is necessary to increase the particle size of the phosphor. However, if the particle size of the entire film is increased, the packing density of the phosphor becomes low, which causes a phenomenon of light emission and does not improve luminance.

[0006] Further, if an attempt is made to solve such a problem by improving the structure of the fluorescent film, the cost is increased due to an increase in the number of procedures and the like, resulting in a loss of price competitiveness.

Hereinafter, the case of a green light-emitting phosphor (abbreviated as a green phosphor, and the same applies to other colors) will be described as an example. The same is true when using the body.

Now, since the green phosphor occupies 70% of luminance on a white screen, improvement of the above problem is particularly important for improvement of an image display device. Materials that have been used as green phosphors for CRTs to date include Zn ₂ SiO ₄ : Mn-based phosphor, Gd ₂ O ₂ S: Tb-based phosphor, and Y ₂ SiO ₅ : Tb.
Phosphors and Y ₃ (Al _x Ga _{1 -x} ) ₅ O ₁₂ : Tb phosphor (where x is a numerical value from 0 to 1).

Among them, Y ₃ (Al _x Ga _{1 -x} ) ₅ O ₁₂ : Tb-based phosphor which is hardly deteriorated and has low luminance saturation (where x is 0
), The problems of luminance degradation and luminance saturation can be solved to some extent. However, this phosphor has a yellowish color and poor color reproduction, and it is not preferable to use it alone in an image display device (display). Therefore, for example, Japanese Patent Application Laid-Open No. 59-49279 discloses a method in which a Zn ₂ SiO ₄ : Mn-based phosphor having good coloring is mixed and used.

In addition, Gd ₂ O _{2 having} good luminous efficiency in a low current region
S: Tb phosphor, poor emission efficiency at high current range, Y ₂ S
The iO ₅ : Tb phosphor has good luminous efficiency in a high current range, but has poor luminous efficiency in a low current range. Therefore, Japanese Patent Application Laid-Open No. 4-35
As disclosed in Japanese Patent No. 9845, a wide fluorescent film is formed by using a two-layer fluorescent film in which a Gd ₂ O ₂ S: Tb phosphor is formed on a face plate side and a Y ₂ SiO ₅ : Tb phosphor layer is formed on an aluminum back side. The luminous efficiency in the current region is improved.

[0011]

The above conventional Y ₃ (Al _x
The technology using a phosphor film in which a Ga _1-x ) ₅ O ₁₂ : Tb-based phosphor (where x is a numerical value from 0 to 1) and a Zn ₂ SiO ₄ : Mn-based phosphor is used. When both phosphors are evenly irradiated, there is an undesired phenomenon that the Zn ₂ SiO ₄ : Mn phosphor causes luminance saturation. Further, there is an undesired phenomenon that the color tone and the luminance are deteriorated when the Zn ₂ SiO ₄ : Mn-based phosphor is deteriorated first. Furthermore, in order to obtain a sufficient color tone, Zn ₂ SiO _4: Increasing the mixing ratio of Mn phosphor, Zn ₂ SiO _4: Characteristics of Mn based phosphor manifested strong,
There was an undesired phenomenon that the afterglow was long and the fluorescent film became severely degraded.

Also, the above-mentioned conventional technology using a two-layer phosphor film in which a Gd ₂ O ₂ S: Tb phosphor is formed on a face plate side and a Y ₂ SiO ₅ : Tb phosphor layer is formed on an aluminum back side is as follows.
Since the emission of the Gd ₂ O ₂ S: Tb phosphor on the face plate side was yellow-green, the color tone was not preferable.

A first object of the present invention is to provide an image display device having a fluorescent film which has less luminance saturation and less deterioration due to strong excitation by an electron beam. A second object of the present invention is to provide an image display device having a green phosphor film having a good color tone.

[0014]

In order to achieve the first object, an image display apparatus according to the present invention comprises a first phosphor layer disposed on a face plate and a first phosphor layer disposed on the face plate. A first phosphor constituting a first phosphor layer, comprising: a phosphor film having a two-layer structure including a second phosphor layer disposed thereon; and means for irradiating the phosphor film with an electron beam to emit light. Is set to be larger than the average particle diameter of the second phosphor constituting the second phosphor layer.

[0015] The first phosphor and the second phosphor may be phosphors having the same composition or phosphors having different compositions. The average particle size of the first phosphor is 20 to 20 times larger than the average particle size of the second phosphor.
It is preferable to be large in the range of 200%. If it is less than 20%, a special effect due to the difference in the average particle diameter between the first phosphor layer and the second phosphor layer does not appear remarkably.
On the other hand, if it exceeds 200%, the particle size of the first layer becomes large, so that the density of the fluorescent film becomes small and the display resolution becomes poor.
The practical upper limit is about 200%. The average particle diameter of the phosphor constituting the second phosphor layer is usually 1 to 15 μm.
It is.

In such a phosphor film, the scattering of light of the first phosphor layer on the face plate side is smaller than the scattering of light of the second phosphor layer, and light is extracted to the face plate side. , All having the same particle size. In addition, since the particle size on the electron beam irradiation side does not increase, the filling rate of the phosphor particles does not change significantly. As a result, since the light emission amounts are the same, the apparent luminance can be improved.

The fluorescent film may be at least two layers. For example, a layer made of a phosphor having an average particle diameter smaller than the average particle diameter of the second phosphor may be provided on the second phosphor layer. Between the two phosphor layers, there may be a layer made of a phosphor having an average particle diameter that is intermediate between the average particle diameters of the two phosphors, and the first phosphor layer is provided under the first phosphor layer. There may be a layer made of a phosphor having an average particle size larger than the average particle size.

The ratio of the thickness of the first phosphor layer to the thickness of the second phosphor layer is preferably in the range of 2: 8 to 8: 2, and preferably is 2: 8 to 6: 4. More preferably, it is within the range.

In this image display device, the first phosphor and the second phosphor
Of the first phosphor is made larger than that of the second phosphor by making the y-value of the xy chromaticity coordinate of the first phosphor larger than that of the second phosphor, so that the green phosphor having excellent color tone is obtained. An image display device having a film can be obtained. It is preferable that the y value of the first phosphor is 0.1 or more larger than that of the second phosphor. Also, the upper limit is that the y value of the second phosphor is the pure y value of point G in the xy chromaticity coordinates, but is preferably about 0.75 in practical use.

In order to achieve the second object,
The image display device according to the present invention has a two-layered fluorescent film including a first phosphor layer disposed on a face plate and a second phosphor layer disposed on the first phosphor layer, and the fluorescent film. Means for irradiating the film with an electron beam to emit light;
The first phosphor constituting the phosphor layer and the second phosphor constituting the second phosphor layer are green light-emitting phosphors having different compositions, and the xy chromaticity of the first phosphor is The y value of the coordinate
Is larger than that of the phosphor.

It is preferable that the y value of the first phosphor is larger than that of the second phosphor by 0.1 or more. Also, the upper limit is that the y value of the second phosphor is pure G in xy chromaticity coordinates.
The y value of the point is practically preferably about 0.75.

The ratio of the thickness of the first phosphor layer to the thickness of the second phosphor layer is preferably in the range of 2: 8 to 5: 5.

In this image display device, when the average particle size of the first phosphor is larger than the average particle size of the second phosphor, a fluorescent film having less luminance saturation and less deterioration due to strong excitation by an electron beam is provided. An image display device can be provided. At this time, it is preferable that the average particle size of the first phosphor is larger than the average particle size of the second phosphor by 20 to 200%.
If it is less than 20%, a special effect due to the difference in the average particle diameter between the first phosphor layer and the second phosphor layer does not appear remarkably. On the other hand, if it exceeds 200%, the particle size of the first layer becomes large, so that the density of the fluorescent film becomes small and the display resolution becomes poor. Is about 200%.

In the present invention, for example, Y ₃ (Al, Ga) ₅
A phosphor such as O ₁₂ : Tb-based phosphor, which has less luminance saturation and luminance degradation, is provided on the second phosphor layer (aluminum back side).
A _two- layer fluorescent material in which a fluorescent material having a good color tone, such as n ₂ SiO ₄ : Mn-based fluorescent material, which has relatively poor luminance saturation and luminance degradation characteristics but has a good color tone, is formed on the first fluorescent layer (face plate side). It is possible to obtain a film that satisfies both luminance saturation, luminance deterioration, and color tone.

In the CRT using the phosphor film having the above-described structure, an electron beam (primary electron beam) emitted from the cathode is first irradiated on the phosphor in the second layer to emit light. An electron beam is irradiated on the first layer. The secondary electron beam is
Excitation energy is weaker than the primary electron beam irradiated first. Therefore, the phosphor of the second layer, which has relatively low luminance saturation and is hardly deteriorated, is excited by the strong primary electron beam, and the first layer has relatively high luminance saturation and is easily deteriorated.
The phosphor in the layer will be excited by the weak secondary electron beam.

The first layer phosphor, which mainly relates to the color tone when viewed from the face plate, has a small temperature rise,
Less change in color due to less degradation. By these effects, a CRT with less luminance saturation, less degradation, and good color tone can be obtained.

In addition to the above structure, the ratio of the luminance of the phosphor constituting the second phosphor layer to the initial luminance after irradiating an electron beam of 300 μA for 30 minutes with an 8m × 8m raster is as follows.
The use of a phosphor that is at least 1% higher than the same ratio of the phosphors constituting the first phosphor layer can further improve the luminance degradation characteristics.

As an example showing a specific material of the present invention, a green-emitting Zn ₂ SiO ₄ : Mn phosphor (hereinafter referred to as EIA)
(Abbreviated as P1 according to the number) (first layer) and Y
₃ (Al _x Ga ( _{1 -x} )) ₅ O ₁₂ : Tb (where x is a number from 0 to 1) Phosphor (hereinafter also abbreviated as P53)
(A second phosphor layer) composed of two layers. By irradiating the phosphor layer with an electron beam from the P53 phosphor layer side (second phosphor layer side) and exciting it, a CRT with less luminance saturation, less degradation, less color change, and better color tone Can be obtained.

In addition, the same effect as that of the green phosphor can be obtained for phosphors such as Y ₂ O ₃ : Eu phosphor which emits red light and ZnS: Ag and Al which emit blue light.

[0030]

Embodiment 1 As a first embodiment of the present invention, a fluorescent film having a two-layer structure of a CRT was formed by changing the thickness of each film, and the light emission characteristics were examined. FIG. 1 shows a schematic diagram of a cross section of the fluorescent film portion. In this embodiment, a CRT for a projection type cathode ray tube (hereinafter, referred to as a CRT) made of a green phosphor is used.
Abbreviated as a projection tube).

On the face plate 4 of the 7-inch bulb, P1 (Zn ₂ Si) was used as the phosphor of the first phosphor layer 3.
P53 (Y ₃ (Al _0.63 Ga _0.37 ) ₅ O ₁₂ : Tb phosphor) is used as the phosphor of the second phosphor layer 2 using O ₄ : Mn phosphor as the phosphor of the second phosphor layer 2. A two-layer fluorescent film was formed.

The y value of the xy chromaticity coordinates of P53 is 0.5
5, and the y value of P1 is 0.73.

As the average particle diameter of the phosphor, the length average particle diameter of the biaxial average diameter of each particle measured by a scanning electron microscope was used. The average particle size of P1 is 13.2 μm,
Has an average particle size of 8.4 μm.

Further, the fluorescent film is subjected to a filming process, an aluminum back 1 is provided, electrodes for irradiating the fluorescent film with an electron beam are set, and a predetermined process is performed on the bulb to complete a CRT. Was examined.

Light emission characteristics are as follows: raster size 8 mm × 8 mm
And illuminate the center of the raster 5m using a luminance meter.
The circular part of mΦ was measured.

FIG. 2 shows the relationship between the irradiation current and the luminance. First
The ratio of the thickness of the phosphor layer 3 to the thickness of the second phosphor layer 2 is 2: 8,
The characteristic curves of the 4: 6, 5: 5, 6: 4, and 8: 2 are shown as a, b, c, d, and e. The total thickness of the first phosphor layer 3 and the second phosphor layer 2 is 30 μm.
It is.

For comparison, as a conventional technique, data of a CRT using a phosphor in which P1 and P53 which are currently practically used are mixed at a ratio of 1: 9 is shown as f. In the CRT of the present embodiment, the luminance saturation is lower than that of the conventional product at all film thickness ratios. In addition, when the thickness ratio is 6: 4 or more and the second phosphor layer is thick, as shown by the characteristic curves a, b, c, and d, the luminance is higher than that of the conventional product.

Next, the color tone was compared. The color tone of the phosphor is generally represented using xy chromaticity coordinates. The green phosphor is closer to pure green as the chromaticity value y is larger,
Good color tone. FIG. 3 shows the relationship between the irradiation current and the chromaticity value y.
Data a to f shown in the same figure are for a projection tube having the same film thickness ratio as that shown in FIG.

It can be seen that the color tone of most of the projection tubes of this embodiment is not deteriorated even when the irradiation current is increased as compared with the conventional product. In addition, when the thickness ratio is 5: 5 or more and the second phosphor layer is thick, as shown by the characteristic curves a, b, and c, it can be seen that the color tone is better than the conventional product at all irradiation currents.

Next, a comparison of luminance degradation was made. 8mm x 8
The difference between the degradation characteristics due to irradiation was compared by taking the ratio of the luminance after irradiation with an electron beam of 300 μA for 30 minutes with the raster of mm and the luminance at the beginning of irradiation. This irradiation current is a current value which is higher by about one digit than that when actually used for display, and is a condition under which more severe deterioration than usual occurs.
Table 1 shows a comparison of the results.

[0041]

[Table 1]

The data a to f are those of a projection tube having the same film thickness ratio as that shown in FIG. It can be seen that all the projection tubes of this embodiment have a higher ratio of luminance after 30 minutes irradiation than the conventional products. From this, it can be seen that the phosphor film according to the present invention has a small decrease in luminance due to electron beam irradiation, that is, has a good deterioration characteristic.

<Example 2> A projection tube composed of a monochromatic film was prepared in the same manner as in Example 1 except that the red phosphor Y ₂ O ₃ : Eu was used instead of the green phosphor. That is, the phosphor constituting the first phosphor layer 3 has an average particle diameter of 12.9 μm,
The average particle size of the phosphor layer 2 was 9.4 μm, and the thickness of each layer was 15 μm for the former and 15 μm for the latter, and the total thickness of the two-layer film was 30 μm. In this case, the luminance was improved by 5% compared with the conventional product due to the improvement of the light extraction efficiency.

Example 3 In the same manner as in Example 1, a projection tube composed of a monochromatic film was prepared using the blue phosphor ZnS: Ag and Al instead of the green phosphor. That is, the average particle diameter of the phosphor constituting the first phosphor layer 3 is 14.1 μm.
m, the average particle size of the second phosphor layer 2 is 11.2 μm, and the thickness of each of these layers is 15 μm for the former and 15 μm for the latter.
m, the total thickness of the two-layer film was 30 μm. In this case, the luminance was improved by 6% compared to the conventional product due to the improvement of the light extraction efficiency.

In each of the above embodiments, the projection tube has been described as an example of the image display device. However, in addition to the above, a similar fluorescent film is formed, for example, a direct-view CRT, a flat emission type fluorescent display tube (VFD), or the like. It goes without saying that the present invention can be similarly applied to an image display device (FED) using a field emitter.

[0046]

As described above, according to the present invention, an image display device which has less luminance saturation and less deterioration and is suitable for high current density excitation can be obtained. Further, according to the present invention, an image display device having an excellent color tone was obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of a fluorescent film of a cathode ray tube according to one embodiment of the present invention.

FIG. 2 is a characteristic curve diagram showing a relationship between irradiation current and luminance in one embodiment of the present invention and a conventional example.

FIG. 3 is a characteristic curve diagram showing a relationship between an irradiation current and a chromaticity value y according to an embodiment of the present invention and a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Aluminum back 2 ... 2nd fluorescent substance layer 3 ... 1st fluorescent substance layer 4 ... Face plate

Claims (11)

[Claims] 1. A two-layer phosphor film comprising a first phosphor layer disposed on a face plate and a second phosphor layer disposed on the first phosphor layer. Means for irradiating an electron beam to emit light, wherein the average particle diameter of the first phosphor constituting the first phosphor layer is set to the second particle constituting the second phosphor layer. An image display device characterized in that the average particle diameter is larger than the average particle diameter of the phosphor. 2. The method according to claim 1, wherein the first phosphor has an average particle size of the second phosphor.
2. The image display device according to claim 1, wherein the average particle size is larger than the average particle size of the phosphor in the range of 20 to 200%. 3. The method according to claim 1, wherein the ratio of the thickness of the first phosphor layer to the thickness of the second phosphor layer is in the range of 2: 8 to 8: 2. 2. The image display device according to 2. 4. The method according to claim 1, wherein the ratio of the thickness of the first phosphor layer to the thickness of the second phosphor layer is in the range of 2: 8 to 6: 4. 2. The image display device according to 2. 5. The first phosphor and the second phosphor,
3. The phosphor according to claim 1, wherein the phosphors are green light-emitting phosphors having different compositions, and the y-value of the xy chromaticity coordinates of the first phosphor is larger than that of the second phosphor. 4. Image display device. 6. The image display apparatus according to claim 5, wherein the y value of the first phosphor is larger than the y value of the second phosphor by 0.1 or more. 7. A phosphor film having a two-layer structure comprising a first phosphor layer disposed on a face plate and a second phosphor layer disposed on the first phosphor layer. In an image display device having means for irradiating an electron beam and emitting light, a first phosphor constituting the first phosphor layer and a second phosphor constituting the second phosphor layer are: A green light-emitting phosphor having a different composition, and x-
An image display device wherein the y value of the y chromaticity coordinate is larger than that of the second phosphor. 8. The image display device according to claim 7, wherein the y value of the first phosphor is larger than the y value of the second phosphor by 0.1 or more. 9. The method according to claim 7, wherein the ratio of the thickness of the first phosphor layer to the thickness of the second phosphor layer is in the range of 2: 8 to 5: 5. 9. The image display device according to 8. 10. The image display device according to claim 7, wherein an average particle diameter of said first phosphor is larger than an average particle diameter of said second phosphor. 11. The image display device according to claim 10, wherein the average particle size of the first phosphor is larger than the average particle size of the second phosphor in a range of 20% to 200%.