JPH06251730A - Picture tube for projection television - Google Patents

Abstract

PURPOSE:To double light utilization factor to drastically reduce stray light, and to achieve easily visible high contrast. CONSTITUTION:Very small lenticular lenses 4 are accumulated on the side of the phosphor surface of a panel glass sheet 1, and the boundary 4A of the lens is coated with a film 5 on which a black-color substance is applied, to shut stray light causing lower contrast. Since the phosphor surface is formed by the directivity of the lenticular lens, the light utilization factor can be doubled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a picture tube for a projection TV which enlarges and uses a screen, and more particularly to a high contrast of the picture tube for a projection TV.

[0002]

2. Description of the Related Art FIG. 4 is a schematic sectional view showing a structure of a fluorescent screen in a conventional picture tube for projection TV. This is a complete diffusion surface because the fluorescent substance 2 and the aluminum reflection film (hereinafter referred to as Al reflection film) 3 are formed on the flat surface (display surface) of the panel glass 1 and the fluorescent surface is flat. .

[0003]

However, in the picture tube for projection TV as shown in FIG. 4, since the fluorescent screen constitutes a perfect diffusion surface, about 20% of the luminous flux emitted from the picture tube for projection TV is used. However, the remaining about 80% of the luminous flux becomes stray light, which lowers the contrast of the display screen and makes it difficult to see.

The present invention overcomes these drawbacks of the prior art,
It is an object of the present invention to provide a picture tube for a projection TV which is easy to see by doubling the light utilization rate of the picture tube for a projection TV and significantly reducing stray light.

[0005]

In order to achieve the above object, the present invention arranges minute lenticular lenses integrated on the phosphor screen side of a panel, and covers each boundary with a coating film of a black substance to prevent stray light. It is characterized by being absorbed and having high contrast.

The diameters of the minute lenticular lenses contact each other in the shape of a sphere or a semi-cylindrical shape of 20 to 60 μm, and a coating film of a black substance having an area ratio of 20 to 40% is provided on the boundary of the lenticular lenses. Has been formed.

The fluorescent screen and the lenticular lens are independent of each other, and the distance between the fluorescent screen and the lenticular lens is formed to be larger than the focal length f of the lenticular lens and smaller than 3f.

[0008]

According to the present invention, the fluorescent screen of the picture tube for projection TV has a directivity from a perfect diffusing surface so that a large amount of light flux emitted from the picture tube for projection TV enters the projection lens. For example, it is achieved by using a lenticular lens.

[0009]

FIG. 1 is a schematic cross-sectional view showing the structure of the fluorescent screen of a picture tube for projection TV in one embodiment of the present invention, in which the display surface side of the panel glass 1 is a fine spherical or chamfered lenticular lens ( In the example of the drawing, it is formed into a semi-cylindrical shape 4 and a black material coating film 5 is formed on the boundary 4A of each lenticular lens. The phosphor 2 and the Al reflection film 3 are integrally formed on each of the lenticular lenses 4.

In this case, the diameter of the lenticular lens 4 must be smaller than the electron beam spot diameter of the projection TV picture tube in order not to deteriorate the resolution of the projection TV picture tube. In the present embodiment, the aperture of the lenticular lens is set in the range of ⅓ or less of the electron beam spot diameter to twice or more of the average particle diameter R of the phosphor 2 to avoid deterioration of resolution due to the lenticular lens 4. That is, the electron beam spot diameter of the picture tube for projection TV (projection tube) is about
Since the average particle diameter R of the phosphor 2 is about 10 μm at 200 μm, the diameter of the lenticular lens is set to a value of 20 to 60 μm.

Further, in order to reduce stray light, in the present embodiment, the lenticular lens 4 is used to improve the light utilization rate, and at the same time, the black material coating film 5 is formed on the periphery of the boundary 4A of the lenticular lenses contacting each other. It blocks stray light that forms and reduces contrast. Here, when the coating area of the black pigment as the black substance increases, the stray light decreases but the luminance also decreases, so the area ratio was set to 20-40%.

Next, r ₁ shown in FIG. 1 is the lens curvature radius of the lenticular lens 4, P is the light emitting surface of the phosphor 2, and A is A.
1 is the aluminum reflection surface of the reflection film 3, F is the lens focus of the lenticular lens 4, f is the focal length, and G is the virtual image plane of the fluorescent surface of the phosphor 2. Further, R is the average particle size of the phosphor 2, and the relationship between the average particle size R and the P, A and G is set to P = 0.8R, A = 1.6R and G = 2.4R. .

Next, an optical system using the lenticular lens 4 of FIG. 1 will be described with reference to FIG. 2. The left side of FIG.
The lenticular lens 4 (1) is spherical and the right side (2) is semi-cylindrical.

Where n is the refractive index of the glass 1.54 r ₁ : is the radius of curvature of the lens 10 to 30 μm r ₂ : is the radius of curvature of the lens ∞ (plane) d is the thickness of the lens 10 mm f is the focal length The relationship is established.

[0015]

1 / f = (n−1) (1 / r ₁ −1 / r ₂ ) + (n−1) ²
d / nr ₁ r ₂ Here, r ₂ is infinite, so 1 / r ₂ = 0, and
The expression of becomes the expression of Equation 2.

[0016]

## EQU2 ## 1 / f = (n-1) / r _{1 When} the refractive index of glass n = 1.54 is substituted into this equation, the focal length f is given by the equation 3.

[0017]

F = r ₁ /0.54 r ₁ is 10 to 30 μm, so the focal length f is 18.5 to 55.6 μ.
becomes m.

On the other hand, as for the phosphor screen, as shown in FIG. 1, the phosphor emission surface P having the highest brightness in the transmissive phosphor screen having the Al reflection film 3 has a film thickness of 1.6 of the average particle diameter R of the phosphor 2. Double
(1.6R). Since the phosphor 2 having an average particle diameter of 10 μm is used and the light emission from the phosphor surface is emitted from each part of the phosphor layer, if the light is averaged and emitted from the center of the phosphor layer, the virtual image of the phosphor surface by the Al reflection film 3 in FIG. The distance between the surface G and the lenticular lens 4 (assuming D) is D when the average particle diameter of the phosphor is R.
= 1.6R + 0.8R = 2.4R.

Therefore, if the average particle diameter R of the phosphor is properly selected, it is possible to satisfy the condition that the luminous flux of D ≧ f has directivity. This condition is 2.4R ≧ r ₁ /0.54, that is, R ≧ 0.
It can be expressed as 77r _1, and it is important that the average particle size R of the phosphor is larger than 0.77 times the radius of curvature r ₁ of the lenticular lens.

FIG. 3 shows a projection T according to another embodiment of the present invention.
It is a schematic cross section which shows the structure of the fluorescent surface of the V picture tube. In FIG. 3, reference numeral 6 denotes a phosphor screen substrate (made of glass) completely separated from the lenticular lens 4, and has a structure in which the phosphor 2 and the Al reflection film 3 are formed on the substrate. here,
PA is the front surface of the light emission and PB is the virtual image surface of the front light emission.
F indicates the triple point of the lens focal length.

In the present embodiment, the lenticular lens 4 and the phosphor screen substrate 6 forming a phosphor screen for completely directing all the luminous flux emitted from the phosphor 2 are completely separated to form a phosphor screen. The lens interval is set to a value larger than the focal length f of the lenticular lens 4 and smaller than 3f. If this value is too large, the luminous flux incident on the lenticular lens 4 is reduced and the brightness is lowered. If it is too small, directivity cannot be added to the emitted luminous flux. Therefore, it is necessary to balance the distance between the fluorescent screen and the lenticular lens with the focal length f of this lens.

[0022]

As described above, in the picture tube for projection TV of the present invention, the fluorescent screen is changed from the perfect diffusing surface to the surface having directivity so that as much light as possible can be emitted from the picture tube for projection TV to enter the projection lens. Since it is changed, the light utilization rate can be doubled, stray light can be significantly reduced, and high contrast and high brightness can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a configuration of a fluorescent screen of a picture tube for projection TV in an embodiment of the present invention.

FIG. 2 is a perspective view showing the shape of the lenticular lens of FIG. 1 and a diagram showing values of glass, lenses, and the like.

FIG. 3 is a schematic cross-sectional view showing a configuration of a fluorescent screen of a picture tube for projection TV in another embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view showing the structure of a fluorescent screen in a conventional projection TV picture tube.

[Explanation of symbols]

1 ... Panel glass, 2 ... Phosphor, 3 ... Al reflective film,
4 ... Lenticular lens, 4A ... Boundary of lenticular lens, 5 ... Coating film of black substance, 6 ... Phosphor screen substrate.

Claims (3)

[Claims] 1. A projection TV characterized in that minute lenticular lenses integrated on the phosphor screen side of a panel are arranged, and each boundary thereof is covered with a coating film of a black substance to absorb stray light to provide high contrast. Picture tube. 2. The minute lenticular lens has a diameter of 20 to 60 μm and is in contact with each other in a spherical or semi-cylindrical shape.
The picture tube for projection TV according to claim 1, wherein a coating film of 20 to 40% of a black substance is formed. 3. An image receiving apparatus for projection TV, characterized in that the fluorescent screen and the lenticular lens are independent of each other, and the distance between the fluorescent screen and the lenticular lens is larger than the focal length f of the lenticular lens and smaller than 3f. tube.