JPH0822784A - Projecting cathode-ray tube and projection display device using the projecting cathode-ray tube - Google Patents

Abstract

PURPOSE:To provide a projecting cathode-ray tube by which image contrast can be improved, and a projection display device by which image contrast on a screen can be improved. CONSTITUTION:In a projecting cathode-ray tube of a projection display device, carbon films 22 and 25 having the atomic number smaller than aluminium films 23 and 26 are formed on an inside surface between a funnel 28 and the aluminium film 23 of an image forming area 31 in which an image is formed when an electron beam 21 from an electron gun 20 is made incident on a phosphor layer 24. Therefore, these carbon films 22 and 25 absorb secondary reflected electrons of the aluminium films 23 and 26 or the phosphor film 24, and reduce the generating rate, and also reduce average energy of the reflected electrons, and reduce unnecessary exciting light emission in the phosphor layer 24 by the reflected electrons.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type display device for projecting an image formed on a projection cathode ray tube on a screen by a projection lens.

[0002]

2. Description of the Related Art FIG. 6 shows the structure of a conventional projection cathode ray tube. Face plate 1 for cathode ray tube for projection
A glass bulb 4 composed of a funnel 2 and a neck 3 and an electron gun 5 enclosed in the neck 3 are provided. On the inner surface of the face plate 1, a phosphor layer 7 made of a phosphor that is excited by the electron beam 6 from the electron gun 5 and emits light is formed. An aluminum film 8 is formed as a metal film on the phosphor layer 7 and the inner surface of the funnel 2.

In this structure, the electron beam 6 emitted from the electron gun 5 according to the video signal passes through the aluminum film 8 and enters the phosphor layer 7. The phosphor excited by the electron beam 6 emits light to form an image. The aluminum film 8 formed on the phosphor layer 7 reflects the light emitted to the electron gun 5 side by the phosphor layer 7 and emits the light to the face plate 1 side to increase the emission brightness of the phosphor layer 7. .

In order to increase the contrast of an image on a projection display device in which an image formed on a projection cathode ray tube is enlarged and projected on a screen by using a projection lens, a face plate 1 of the projection cathode ray tube is generally used. An optical coupling technique that optically couples a projection lens is used. The optical coupling uses a transparent liquid such as ethylene glycol as an optical coupling material to reduce the difference in refractive index between the face plate 1, the liquid, and the lens surface, and reduces unnecessary reflected light to the phosphor layer 7.

Although the contrast of the projected image is improved by this technique, the contrast is not sufficient for viewing images. Further, some methods have been disclosed as methods for improving contrast. For example, JP
According to Japanese Patent Laid-Open No. 4-63248, by smoothing the inner surface of the face plate on which the phosphor layer of the projection cathode ray tube is formed, unnecessary reflected light from the projection lens is irregularly reflected on the inner surface of the face plate. It shows that the contrast reduction of the projected image is improved.

Further, in Japanese Patent Laid-Open No. 3-224384, a light absorbing material is mixed and colored in a concave lens arranged on the projection cathode ray tube side in a projection lens composed of a plurality of lenses. Unnecessary reflected light at the boundary surface between the concave lens and air is absorbed by the light absorbing material of the concave lens,
This shows that the unnecessary diffuse reflection brightness of the phosphor layer is reduced, and the contrast reduction of the projected image is improved.

[0007]

However, the factors that lower the contrast of the projected image of the projection display device are the inner surface roughness of the face plate, the interface between the face plate and the liquid, and the unwanted reflection at the interface between the projection lenses. Not only due to light.

The electron beam 6 emitted from the electron gun 5 of the conventional projection cathode ray tube shown in FIG. 6 passes through the aluminum film 8 and enters the phosphor layer 7 to excite the phosphor to emit light.
The incident electron beam 6 is applied to the aluminum film 8 and the phosphor layer 7
Emits secondary electrons. The energy of the emitted secondary electrons is divided into true secondary electrons emitted by the electrons in the shell of the incident material being excited and incident electrons that are elastically or inelastically scattered backward. The electrons elastically scattered backward are called backscattered electrons 9.

The energy of the true secondary electron is several tens of eV, but the energy of the reflected electron 9 is about the same as the energy of the incident electron. The generation rate of the reflected electrons 9 is determined by the atomic number of the incident substance, the energy of the incident electron, the surface roughness of the incident substance, and the like. The incident electron beam 6 produces reflected electrons 9 on the aluminum film 8. The surface of the aluminum film 8 formed on the phosphor layer 7 is rough, and the reflected electrons 9 are reflected in all directions. The reflected electrons 9 are generated by the aluminum film 8 formed on the inner surface of the funnel 2. The backscattered electrons 10 again pass through the aluminum film 8 on the phosphor layer 7 and enter the phosphor layer 7 to excite the phosphor to emit light.

Therefore, unnecessary light emission is generated in the phosphor layer 7, and the contrast of the image formed on the projection cathode ray tube is lowered. Further, the contrast of the projection image of the projection display device in which the image on the projection cathode ray tube is enlarged and projected by the projection lens is also reduced. With respect to these problems, it has been a problem to reduce the reflected electrons 9 and 10 on the aluminum film 8 and the phosphor layer 7 of the projection cathode ray tube to improve the contrast.

In view of the above problems, the present invention can display a high-contrast image on a screen by using a projection cathode ray tube capable of improving the contrast of an image and the projection cathode ray tube. It is an object to provide a projection display device.

[0012]

In order to achieve the above object, a projection cathode ray tube according to claim 1 of the present invention comprises an electron gun for emitting an electron beam, a face plate and the face plate. A glass bulb composed of a funnel and a neck that is connected to the funnel and in which the electron gun is enclosed, and a phosphor that is formed on the inner surface of the face plate and excited by the electron beam emitted from the electron gun to emit light. A phosphor layer and a metal film formed on the phosphor layer, and the metal film and the funnel in an image forming region where the electron beam is incident to form an image on the phosphor layer. On the inner surface of the metal film, the electron beam is composed of an element having an atomic number smaller than that of the metal film, and the electron beam reduces reflected electrons scattered and reflected by the metal film or the phosphor layer. Morphism and formed with the structure of the electron barrier layer.

A projection display device according to a fourth aspect of the present invention includes three cathode ray tubes and a projection lens that receives light emitted from the cathode ray tubes and projects an image on a screen. The cathode ray tube according to claim 1 is constituted by the projection cathode ray tube according to any one of claims 1 to 3, and each of the blue, green and red images formed on the screen by each cathode ray tube is displayed on the screen. It is configured to form an image.

[0014]

According to the above construction, the projection type display device according to claim 4 is provided.
In the projection cathode ray tube according to any one of claims 1 to 3, which constitutes a book cathode ray tube, the backscattered electron prevention film is emitted from the electron gun by an element having an atomic number smaller than that of the substance forming the metal film. Since the electron beam is incident on the inner surface of the funnel and the metal film in the image forming region where an image is formed on the phosphor layer, the backscattered electron preventing film is formed on the inner surface of the metal film or the phosphor layer. It absorbs secondary reflected electrons to reduce the generation rate thereof, and also reduces the average energy of the reflected electrons, thereby reducing unnecessary excited light emission in the phosphor layer due to the reflected electrons.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A projection cathode ray tube and a projection type display device using the same in the embodiments of the present invention will be described below with reference to the drawings.

First, the projection cathode ray tube of this embodiment will be described. FIG. 1 shows the structure of a projection cathode ray tube in this embodiment. In FIG. 1, 20 is an electron gun, 21 is an electron beam, 22 and 25 are carbon films which are reflection electron prevention films, 23 and 26 are aluminum films which are metal films, 24 is a phosphor layer made of a phosphor, and 27 is A face plate, 28 is a funnel, 29 is a neck, 30 is a glass bulb formed by sealingly bonding the face plate 27, the funnel 28, and the neck 29, 31 is an image forming region, and the phosphor layer 24 is formed by the electron beam 21. The region where the phosphor of (1) is excited to emit light to form an image is shown.

Here, the phosphor of the phosphor layer 24 is ZnS: AgAl which emits blue light among the three primary color lights. The phosphor layer 24 is formed on the face plate 2 by a precipitation coating method or the like.
It is formed on the inner surface of 7. Phosphor layer 2 in image forming area 31
The aluminum film 23 on 4 prevents the effective acceleration voltage from lowering, prevents the phosphor layer 24 from being ion-burned, reflects the light from the phosphor layer 24 toward the face plate 27, and reflects the phosphor layer 24.
It has the function of increasing the emission brightness from the. The thickness of the aluminum film 23 formed on the phosphor layer 24 is 0.2 μm, and the surface roughness is about 2 μm. Aluminum film 26 formed on the inner surface of funnel 28
Does not have the function of the aluminum film 23 in the image forming area 31, but has the function of transmitting and supplying the anode voltage of the projection cathode ray tube to the phosphor layer 24 and the function of keeping the inner surface of the funnel 28 at the same potential. The carbon films 22 and 25 are formed on the aluminum film 23 in the image forming area 31 and on the aluminum film 26 on the inner surface of the funnel 28.

The operation of the projection cathode ray tube configured as described above will be described below. The electron beam 21 emitted from the electron gun 20 passes through the carbon film 22 and the aluminum film 23 and enters the phosphor layer 24. The phosphor of the phosphor layer 24 is excited to emit light by the electron beam 21. The electron gun 20 controls the electron beam 21 according to the video signal to form an image on the phosphor layer 23.

When the electron beam 21 emitted from the electron gun 20 is incident on the carbon film 22, the aluminum film 23 and the phosphor layer 24, reflected electrons are generated in each layer. The directions of the reflected electrons are reflected in various directions inside the glass bulb 30 because the surfaces of the aluminum film 23 and the phosphor layer 24 are rough.

In FIG. 1, backscattered electrons 32 generated in the carbon film 22, the aluminum film 23, and the phosphor layer 24 are emitted into the glass bulb 30, and are incident on the carbon film 25 on the inner surface of the funnel 28. The reflected electrons 33 are generated as a result, and the reflected electrons 33 again pass through the carbon film 22 and the aluminum film 23 in the image forming area 31 and enter the phosphor layer 24.

Generally, the reflected electron generation rate η is the atomic number of the incident substance of the electron beam 21, the energy of the incident electron, the roughness of the surface of the incident substance (incident angle of the incident electron to the incident substance).
Etc. The relationship between the atomic number Z and the generation rate of backscattered electrons and the average energy of backscattered electrons has long been known as T.E.E.V. Heart (J.A.F.
1483-1490,1960) (TEEVERHART (J. Applied Physics, vo
l.31, No.8, PP.1483-1490, 1960)).

The relationship between the atomic number Z and the backscattered electron generation rate η is
It is expressed by the following equation.

[0023]

[Equation 1]

Here, a is expressed by the following equation.

[0025]

[Equation 2]

Where Z is the atomic number of the incident substance, e is the charge of the electron, N _A is the Avogadro constant, m is the mass of the electron,
A is represented by the atomic weight of the incident material, and c is represented by a constant determined by the velocity of electrons and the density of the incident material. When the experimentally obtained constant c is used, it is approximately represented by the following equation.

[0027]

(Equation 3)

FIG. 2 shows the reflection electron generation rate η with respect to the atomic number.
About. The reflected electron generation rate η increases almost in proportion to the atomic number. Since the atomic number Z of carbon is Z = 6, the atomic number Z of aluminum is Z = 13, and the average atomic number Zn of ZnS is Z = 23, the reflection electron generation rate η is 0.
It will be 08, 0.16, and 0.26. The reflected electron generation rate η of carbon is as low as 50% of aluminum and 31% of ZnS.

FIG. 3 shows the relationship between the atomic number Z and the average energy ratio of reflected electrons. The energy of the reflected electrons is represented by using the average energy because it has an energy distribution. The average energy ratio k of backscattered electrons represents the average energy of backscattered electrons per incident electron energy per unit backscattered electron generation rate. The energy ratio k of the reflected electrons is higher as the incident angle θ of the electrons is larger when the atomic number Z is about 25 or less. When the incident angle of the electron beam on the incident material is θ = 0 °,
The energy ratios k of the reflected electrons of carbon, aluminum and ZnS are 0.55, 0.61 and 0.69, respectively.

The average energy ratio of backscattered electrons of carbon is as low as 90% of aluminum and 80% of ZnS. If the product of the generation rate η of backscattered electrons and the average energy ratio k of the backscattered electrons is the backscattered electron energy rate R, the backscattered electron energy rates R of carbon, aluminum and ZnS are R _C respectively.
= 0.044, R _Al = 0.098, R _ZnS = 0.179
Becomes

Therefore, the backscattered electron energy rates of the backscattered electrons generated in the carbon film 22 are 45% and 25% lower than the backscattered electron energy rates in the aluminum film 23 and the phosphor layer 24, respectively.

Therefore, as compared with the case where the carbon film 22 is not formed, both the amount of backscattered electrons generated inside the glass bulb 30 and the energy are reduced. Glass bulb 30
The backscattered electrons 32 emitted to the inside of the are incident on the carbon film 25 on the inner surface of the funnel 28. By forming the carbon film 25, the secondary reflected electrons 33 generated on the inner surface of the funnel 28 are attenuated both in the amount of generation and the energy as compared with the case of only the aluminum film 26.

Secondary reflected electrons 33 generated from the carbon film 25 are incident on the carbon film 22 in the image forming area 31 again. The reflected electrons 33 are absorbed by the carbon film 22, attenuated, pass through the aluminum film 23 in the image forming area 31, and enter the phosphor layer 24. In the process in which the reflected electrons 32 are incident on the aluminum film 23 on the image forming area 31 again, they are transmitted through the carbon film 22 and are attenuated by the carbon film 25 on the inner surface of the funnel 28, so that the phosphor layer 2 is formed.
The number and energy of the backscattered electrons 32 incident on 4 are greatly attenuated.

Therefore, unnecessary excited light emission in the phosphor layer 24 due to reflected electrons is sufficiently reduced. Image forming area 3
Since the carbon film 22 of No. 1 also lowers the energy of the incident electron beam 21, the emission luminance is lowered due to the formation of the carbon film 22. Therefore, in order to suppress the energy reduction of the incident electron beam 21 and reduce unnecessary excitation and emission in the phosphor layer 24 due to reflected electrons, the carbon film 22 is used.
It is necessary to select the thickness of.

FIG. 4 shows the relationship between the thickness of the carbon film and the electron energy transmittance τ. Anode voltage of projection cathode ray tube is 2
It is used at 5 kV to 34 kV. Considering the case of the minimum anode voltage, the electron energy transmittance τ when the anode voltage is 25 kV is shown. The thickness of the carbon film 22 is about 0.8μ
If formed with m or less, electron energy transmittance τ> 0.8
Becomes If the carbon film 22 is formed to have a thickness of 0.8 to 1 μm, the energy loss of the incident electron beam will be about 20% or less. The incident electron energy is attenuated in proportion to the electron energy transmissivity τ of the carbon film 22, but the energy at which the reflected electrons enter the phosphor layer 24 again is attenuated in proportion to the transmissivity τ ² .

Therefore, it is possible to suppress a decrease in emission luminance and reduce unnecessary excitation and emission in the phosphor layer due to reflected electrons.
The carbon film 25 formed on the inner surface of the funnel 28 has a thickness that absorbs the energy of electrons entering the inside of the carbon film 25 and does not generate reflected electrons at the aluminum film 26.

Due to the carbon film 22 formed on the aluminum film 23 in the image forming area 31 and the carbon film 25 formed on the inner surface of the funnel 28, compared with the reflected electrons of the conventional projection cathode ray tube shown in FIG. The number and energy of the above can be sufficiently reduced, unnecessary excitation and emission in the phosphor layer 24 can be reduced, and the contrast of the image of the projection cathode ray tube can be increased.

The carbon films 22 and 25 are made of black graphite or carbon black, or a mixture thereof. The black carbon films 22 and 25 absorb weak light from the phosphor layer 24 that passes through the aluminum film 23 and is emitted into the glass bulb 30. Therefore, the diffused light of the phosphor layer 24 due to unnecessary light into the glass bulb 30 can be reduced, and the contrast of the image of the projection cathode ray tube can be increased.

In the cathode ray tube for projection shown in FIG. 1, carbon films 22 and 25 are formed on the aluminum film 23 in the image forming area 31 and the inner surface of the funnel 28, respectively, but only one of these areas is formed. A carbon film may be formed on.

In this case, the effect of reducing backscattered electrons is smaller than that of the projection cathode ray tube shown in FIG. 1, but compared with the conventional projection cathode ray tube shown in FIG.
Unnecessary excitation light emission in can be reduced.

Aluminum film 2 on the inner surface of funnel 28
6 need only have a conductive function of transmitting and supplying an anode voltage to the aluminum film 23 of the image forming area 31.
The inner surface of the funnel 28 may be the carbon film 25 only.

Although the projection cathode ray tube for forming a blue image has been described here, the green and red projection cathode ray tubes have the same effect as the carbon film.

Further, as the backscattered electron prevention film, any other substance such as boron may be used as long as it is a substance composed of an element having an atomic number smaller than that of the metal film of the image forming area 31 or the metal film of the inner surface of the funnel. Good.

Next, the projection type display device of this embodiment will be described. FIG. 5 shows the configuration of the projection display apparatus of this embodiment. In FIG. 5, reference numerals 40, 41, and 42 are blue, green, and red projection cathode ray tubes, 44, 45, and 46 are projection lenses corresponding to blue, green, and red projection cathode ray tubes, respectively, and 47 is a screen. .

Here, three projection cathode ray tubes 40, 4 are used.
1 and 42 show the case where the projection cathode ray tube of this embodiment shown in FIG. 1 is used. That is, the projection cathode ray tube 4
Aluminum film 2 in image forming area 31 of 0, 41, 42
Carbon films 22 and 25 are formed on the inner surface of the funnel 28 and the inner surface of the funnel 28, respectively.

The operation of the projection type display device having the above components will be described below. The fluorescent layers 43B, 43G, 43R of the respective projection cathode ray tubes 40, 41, 42 are formed in accordance with the video signals input to the blue, green, and red projection cathode ray tubes 40, 41, 42. The image includes three projection lenses 44, 4 corresponding to each image.
It is incident on 5, 46 and is enlarged and projected on the screen 47. In this way, the magnified and projected blue, green, and red images are combined on the screen 47 to obtain a full-color projected image.

Since the carbon films 22 and 25 are respectively formed on the aluminum film 23 and the inner surface of the funnel 28 in the image forming area 31 of the projection cathode ray tubes 40, 41 and 42, the projection cathode ray tubes 40 and 41 are formed. , 42, the generation of reflected electrons is suppressed, and unnecessary excited light emission in the phosphor layer 23 due to the reflected electrons is sufficiently reduced.

As described above, the contrast of the image displayed in the image forming area 31 of the projection cathode ray tube can be increased. Further, the contrast of the image on the screen 47 of the projection type display device using this projection cathode ray tube can be increased. Actually, in the projection display device shown in FIG. 5, when the contrast of the display image was measured, it was 10% to 3% as compared with the conventional projection display device.
A 0% improvement in contrast was obtained.

Further, a transmissive screen is used as the screen 47 of the projection display device shown in FIG. 5, and the projection cathode ray tubes 40, 41 and 42, the projection lenses 44, 45 and 46, and the screen 47 are incorporated inside the cabinet. A rear projection display device can also be configured, and the same effect as the projection display device shown in FIG. 5 can be obtained.

[0050]

As described above, according to the present invention, in the projection cathode ray tube constituting the three cathode ray tubes of the projection type display device, the backscattered electron prevention film has an atomic number higher than that of the substance constituting the metal film. The small element is formed on the inner surface of the metal film and the funnel in the image forming area where the electron beam emitted from the electron gun is incident and the image is formed on the phosphor layer. It is possible to absorb the secondary backscattered electrons in (3) and reduce the generation rate thereof, and also reduce the average energy of the backscattered electrons, thereby reducing unnecessary excitation and emission in the phosphor layer due to the backscattered electrons.

Therefore, the projection cathode ray tube can improve the contrast of an image, and by using the projection cathode ray tube, the projection display device can display a high-contrast image on the screen. .

[Brief description of drawings]

FIG. 1 is a configuration diagram of a projection cathode ray tube according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of the backscattered electron generation rate with respect to the atomic number of a metal.

FIG. 3 is a characteristic diagram of the average energy ratio of reflected electrons to the atomic number of a metal.

FIG. 4 is a characteristic diagram of electron energy transmittance with respect to carbon film thickness.

FIG. 5 is a configuration diagram of a projection display device according to an embodiment of the present invention.

FIG. 6 is a configuration diagram of a conventional projection cathode ray tube.

[Explanation of symbols]

 20 electron gun 22, 25 carbon film 23, 26 aluminum film 24, 43B, 43G, 43R phosphor layer 30 glass bulb

Claims (4)

[Claims] 1. A glass bulb comprising an electron gun for emitting an electron beam, a face plate, a funnel coupled to the face plate, and a neck coupled to the funnel for enclosing the electron gun, and the face plate. A phosphor layer formed of a phosphor that is formed on the inner surface of the phosphor and is excited by the electron beam emitted from the electron gun to emit light; and a metal film formed on the phosphor layer. On the inner surfaces of the metal film and the funnel in the image forming area where an image is formed on the phosphor layer, the electron beam is composed of an element having an atomic number smaller than that of the metal film, and the electron beam is the metal film or the metal film. A projection cathode ray tube having a backscattered electron prevention film for reducing backscattered electrons scattered and reflected by a phosphor layer. 2. The metal film is composed of an aluminum film, and the backscattered electron prevention film is composed of at least one of graphite and carbon black, which is a carbon film.
The cathode ray tube for projection according to. 3. The reflection electron prevention film formed on the metal film in the image forming area has a thickness of 0.8 μm to 1 μm.
Alternatively, the projection cathode ray tube according to claim 2. 4. A cathode ray tube comprising three cathode ray tubes and a projection lens for projecting an image on a screen upon receipt of light emitted from said cathode ray tube, said three cathode ray tubes comprising: And a cathode ray tube for projection according to any one of
A projection display device configured to form an image on the screen by blue, green, and red images formed by each cathode ray tube based on a video signal.