JPH0817084B2 - Projection type cathode ray tube - Google Patents

Description

The present invention relates to a projection cathode ray tube (hereinafter, referred to as a projection cathode ray tube used for a video projector for enlarging and projecting an image of a phosphor screen on a screen).
"CRT").

[Prior Art] FIG. 2 is a diagram showing a configuration of a typical video projector. In the figure, (1) is a projection type CRT (cathode ray tube)
Device, (1R), (1G), (1B) are R
(Red), G (green), B (blue) monochromatic image light source. (2)
Is a projection lens, (3) is a screen, CRT (1)
A large-screen color image is realized by enlarging and projecting the image of (1) on the screen (3) placed in front by the projection lens (2).

FIG. 3 is a cross-sectional configuration diagram of the projection type CRT device (1). The device (1) is composed of a vacuum envelope (4) and an electron gun (5) enclosed therein. A phosphor layer (7) is formed on the inner surface of the face plate (6) that constitutes a part of the vacuum envelope (4), and on the phosphor layer (7),
A metal back film (8) made of a vapor deposition film of aluminum is formed as a high voltage electrode and a reflection film. The phosphor (7) is excited by the energy of the electron beam emitted from the electron gun (5) arranged opposite to the metal back film (8),
A light emission output is obtained.

[Problems to be Solved by the Invention] While video projectors are capable of obtaining large-screen color images, there is an increasing demand for high-definition images. For this purpose, it is necessary to increase the definition of the image of the projection CRT device (1) itself, and it is expected that the diameter of the light emission spot will be reduced. However, controlling halos is an issue here.

Therefore, the state of halo generation in the current projection type CRT device will be described with reference to FIG. FIG. 4 is an enlarged sectional view of the vicinity of the phosphor layer (7) of the CRT device (1) of FIG. The green projection CRT device (1G) will be described below as an example.

(70) is a phosphor particle, which usually has a diameter of 8 to 20 μm. The electron beam irradiated from the metal back film (8) side excites the phosphor particles (70) to emit light. Now, focusing only on the shaded phosphor particles, among the emitted light flux, the light flux that passes through the boundary surface (11) between the face plate (6) and the phosphor layer (7) passes through the projection lens (not shown) and passes through the screen. To reach.

The light flux from the shaded particle (70) emits light in multiple directions, but for the video projector, the
The intensity of the light flux (9) that passes through 1) is the strongest and dominates the shape of the light emission spot, and has the intensity distribution shown by the solid line in FIG. 5, for example.

However, in reality, as shown by the dotted arrow in FIG. 4, the light flux (10) reflected by the boundary surface (11) and reflected by the phosphor, or after multiple reflection, is transmitted through the boundary surface (11). There is also a luminous flux.

This luminous flux (10) causes a halo, and the shape of the light emission spot has an intensity distribution shown by the broken line in FIG. 5, which increases the spot diameter, which hinders the high definition of the image.

In order to improve the brightness of the video projector, an optical interference filter (14) is provided on the boundary surface (11) as shown in Fig. 1, and the boundary surface (11) is incident almost vertically (about ± 30 °). A plan for increasing the transmittance of a light beam is described in, for example, Japanese Patent Application Laid-Open No. 58-207750.

FIG. 6 shows the spectral characteristics of the optical interference filter (14) (1
Figure 2) is a drawing of the phosphor emission spectrum (13),
In the figure, θ is the angle of incidence on the face plate.

This optical interference filter (14) increases the transmittance of a light beam that enters the boundary surface (11) almost vertically, but the transmittance decreases sharply as the incident angle θ increases, that is, the reflection intensity at the boundary surface (11). Becomes stronger, and the halo increases due to the above action. That is, there is a problem that the diameter of the light emission spot becomes larger due to the influence of the halo than in the case where the optical interference filter (14) is not provided.

As described above, the halo is caused by the reflected light at the boundary surface (11), and its spread is approximately the size of the vacuum gap between the phosphor particles (12) near the boundary surface (11). In the case of a phosphor having a particle size of 8 to 20 μm, the clearance is 10 to
The size of 20 μm is generated, the spread of the emission spot diameter due to the halo reaches about ± 10 to 20 μm, and the emission spot diameter is 200
In the case of the projection type CRT device of μm, the deterioration caused by the halo is 10 to 20%.

As a measure to suppress the halo, if the diameter of the phosphor particles (70) is reduced to, for example, about 5 μm, the clearance between the phosphor particles (70) near the boundary surface (11) will also be about 5 μm, and the halo emission spot. The diameter deterioration will be halved.

However, a phosphor having a small particle size has a low luminous efficiency and deteriorates the brightness of the video projector. Further, if the thickness of the phosphor layer (7) is increased to increase the number of light emitting particles, the transmittance in the layer thickness direction is drastically reduced, and the brightness is also deteriorated.

The present invention has been made to solve the above problems, and an object thereof is to obtain a projection type CRT device capable of suppressing a halo without reducing the light amount.

[Means for Solving the Problems] In a projection CRT device according to the present invention, a phosphor (71) having a small particle size is applied to a boundary surface (11) formed by one surface of an optical interference filter (14). And a first phosphor layer (7a) formed by depositing a layer having a thickness approximately equal to the particle size of the phosphor, and a large particle size with good luminous efficiency on the first phosphor layer (7a). And a second phosphor layer (7b) formed of the phosphor (70).

[Operation] In the first phosphor layer having a small particle diameter according to the present invention, the luminous flux generated from the phosphor particles of the second phosphor layer having a large particle diameter and the phosphor particles of the first phosphor layer and The halo is reduced because it suppresses the multiple reflection and spread with the boundary surface.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a partially enlarged sectional view in the vicinity of the phosphor layer of this embodiment. In the figure, (14) is an optical interference filter which is provided on the interface between the face plate (6) and the phosphor layer (7), and one of which constitutes the interface (11),
(7a) is a first phosphor layer composed of phosphor particles (71) having a particle diameter of about 5 μm, and is formed on the optical interference filter (14). (7b) is a second phosphor layer composed of phosphor particles (70) having a particle diameter of 8 to 20 μm.

The first phosphor layer (7a) is formed to have a layer thickness of about the diameter of the phosphor particles (71) and is thinner than the second phosphor layer (7b).
Further, the coating density of the particles (71) is small, and the coating amount is controlled so that the gap between the phosphor particles is approximately the particle diameter.

Therefore, the phosphor layer (7) in the conventional example shown in FIG. 4 corresponds to the second phosphor layer (7b) in the present embodiment, and the second phosphor particle (70) and the boundary surface (11). It is formed so that the first phosphor particles (71) are inserted into the gap of the vacuum generated during (1).

Next, similar to the conventional example, the halo control action will be described by focusing on the phosphor particles (70) of the second phosphor layer (7b) which are shaded.

An electron beam (not shown) passes through the metal back film (8),
By exciting the phosphor particles (70) of the second phosphor layer (7b),
Make it glow.

Of the emitted luminous flux, the luminous flux (9) that has passed through the gaps between the phosphor particles (70) and reached the face plate (6) is used as a video signal.

However, since the phosphor particles (70) generate luminous flux in multiple directions, there is also a luminous flux (10) of a component reflected by the boundary surface (11) with the face plate (6). However, in this embodiment, since the phosphor particles (71) having a small particle size are formed in the vicinity of the boundary surface (11) so as to fill the gaps between the phosphor particles (70), reflection by the boundary surface (11) is caused. The light flux (10) is scattered and reflected by the phosphor particles (71) without spreading in the gaps between the second phosphor particles (70), so the halo light (10) that passes through the face plate (6).
Is dramatically reduced compared to the conventional one.

In addition, since the phosphor particles (70) of the second phosphor layer (7b) mainly perform the light emitting action, and have a sufficient particle size,
The same luminous efficiency as the conventional one can be obtained. Furthermore, the first
In the phosphor layer (7a), the particle diameter of the phosphor particles (71) is 5 μm.
Since the layer thickness is small and the layer thickness is as thin as approximately the particle size, and the formation density is appropriately controlled to provide a gap, the luminous flux emitted from the second phosphor layer (7b) should be sufficiently transmitted. There is no danger of reducing the amount of light.

The CRT device having the above configuration is particularly effective when applied to a projection type CRT device using an optical interference filter (14), and there is a problem in that the increase in halo due to the increase in reflectance for a light beam with a large incident angle Since it can be suppressed by the action, only the advantage of increasing the originally required light amount of the light flux (9) can be utilized.

In addition, although the green projection type CRT device has been described in the above embodiment, it can be applied to the red and blue projection type CRT devices, and the same effect can be obtained.

As described above, according to the projection cathode ray tube of the present invention,
A first phosphor layer formed by applying a phosphor having a small particle size to a boundary surface formed by one surface of the optical interference filter and forming a layer thickness to a thickness of about the particle size of the phosphor. Since the first phosphor layer and the second phosphor layer formed of a phosphor having a large particle size with good light emission efficiency are provided on the first phosphor layer, the luminous flux emitted from the second phosphor layer is It can be sufficiently transmitted and does not reduce the light quantity (that is, without deteriorating the brightness), and can suppress the halo light due to multiple reflection in the gap between the phosphor particles having a large particle diameter and the face plate, There is an effect that a projection type CRT device capable of obtaining a high definition image can be obtained.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view showing the structure of a phosphor screen according to an embodiment of the present invention, FIG. 2 is a structural view of a typical video projector, and FIG. 3 is a sectional view of a conventional projection type CRT device, FIG. 4 is a partially enlarged cross-sectional view showing a fluorescent screen structure of a conventional projection CRT device, FIG. 5 is a light emission spot intensity distribution diagram in the conventional projection CRT device, and FIG. 6 is a phosphor spectrum example and optical interference. It is a spectral characteristic diagram of a filter. (1) ... projection cathode ray tube, (4) ... vacuum envelope,
(5) ... electron gun, (6) ... face plate,
(7) ... Phosphor layer, (7a) ... First phosphor layer, (7
b) ... second phosphor layer, (11) ... boundary surface, (14) ...
… Optical interference filter, (70) …… Large particle size phosphor, (7
1) ...... Small particle size phosphor. In each drawing, the same reference numerals indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-152350 (JP, A) JP-A-61-273837 (JP, A) JP-A-60-74241 (JP, A)

Claims (1)

[Claims] 1. A projection type cathode ray tube in which an optical interference filter is provided on a boundary surface between a face plate and a phosphor layer, wherein fluorescent light having a small particle size is formed on the boundary surface formed by one surface of the optical interference filter. A first phosphor layer formed by applying a body to a layer thickness of about the particle diameter of the phosphor, and the first phosphor layer.
And a second phosphor layer formed of a phosphor having a large particle size and having a high luminous efficiency on the phosphor layer.