JPS5927057B2 - correction lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a correction lens used when forming phosphor dots or stripes on the phosphor surface of a color picture tube.

It is well known that the fluorescent surface of a shadow mask type color picture tube is usually formed by coating three color phosphors using a photo printing method.

Exposure for forming this fluorescent surface is carried out using an exposure apparatus usually called a light house or an exposure table as shown in FIG. The exposure apparatus 1 shown in FIG. 1 includes a light source section 2 and a light source section 2.
The exposure apparatus 1 is composed of a lens section 4 including a correction lens 3 for matching the light beam (not shown) emitted from the electron beam with the trajectory of the actual electron beam, and a shadow mask 5 is attached to the exposure apparatus 1 having such a structure. This is done by placing the panel 6 on it. This type of correction lens 3 is necessary to make the exposure light beam match the trajectory of the actual electron beam, and the color purity of the color picture tube is affected by the quality of this correction lens. It is well known.

Therefore, the curved surface of this correction lens 3 is usually very complicated. Conventionally, this correction lens generally has a continuous curved surface. Such a correction lens curved surface is usually expressed by a function as shown in the following equation. xoΣΣAmn7
' mcosnθ Here, Amn is a coefficient, m−n is an order, and X is a displacement in the thickness direction of the correction lens.

However, it is impossible for a correction lens having a continuous curved surface represented by the above function to approximate the trajectory of the exposure light beam and the actual electron beam over the entire effective surface of the color picture tube.

In other words, a color picture tube in which a fluorescent surface is formed using a correction lens having such a continuous curved surface has the disadvantage that high quality color purity cannot be obtained.

An example of a means to solve these shortcomings is the
A correction lens as shown in No. 4459, or a correction lens as described in Japanese Patent Publication No. 47-40983, that is, a correction lens having a discontinuous stepped surface in the circumferential direction or in two or more directions, has been devised. Although it is possible to approximate the trajectory of the actual electron beam over the entire effective surface of the color picture tube in the continuous curved surface area of the correction lens by providing the discontinuous stepped surface, it has the disadvantages detailed below. has. That is, as shown in FIG. 2, when the light ray 10 emitted from the light source section 2 of FIG. Reflect or scatter.

Because of this undesirable reflection and scattering phenomenon, for example, a color picture tube in which a fluorescent surface is formed using a correction lens with discontinuous steps as shown in Fig. 3 has a lattice pattern as shown in Fig. 4. 7 is visible on the screen and has the disadvantage that the quality of the fluorescent surface is significantly degraded. As a means to solve the above-mentioned drawbacks, there are two steps: to minimize the step difference in the stepwise discontinuous area, or to correct it using a special optical filter that corrects a lattice pattern, or to use an arbitrary correction lens itself. A method of vibrating in the direction of is used. However, when the above-mentioned solution is used, there are drawbacks as detailed below.

In other words, in order to minimize the level difference in the discontinuous area, it is necessary to increase the number of areas to be divided, which requires a lot of time in designing the curved surface of the correction lens, and at the same time, the amount of the level difference itself becomes large. It is necessary to test it every day.

In addition, the method of correcting using a special optical filter has the disadvantage that the filter itself is difficult to manufacture, while the method of vibrating the correction lens itself in an arbitrary direction has the drawback that the mechanism of the exposure device becomes complicated. There is. On the other hand, a method for manufacturing a correction lens having a discontinuous stepped surface, for example, Japanese Patent Publication No. 47-4098
As shown in 3, in the manufacturing method where a block-shaped mold is first made and then a resin such as plastic or glass material is melted and solidified based on the mold, it takes a lot of effort to manufacture the correction lens. I have no choice but to spend it. The present invention was devised in view of the above points, and it is possible to achieve a discontinuous phosphor surface with good quality and high-order approximation without having to vibrate the correction lens in any direction or use a special filter. A correction lens having a cross section is provided, in which at least one correction lens with a small effective area is layered on a large correction lens whose effective area is a continuous plane or curved surface via an adhesive member. The present invention relates to a correction lens characterized by being cemented.

Hereinafter, the correction lens of the present invention will be specifically explained in detail using the drawings.

FIG. 5 shows a correction lens according to the present invention, and the first correction lens 12 is a part of the correction lens whose effective area is a large continuous curved surface or a flat surface. The second correction lens 13 is a correction lens whose effective area is smaller than the effective area of the first correction lens 12, and there is a step 17 within the effective area of the first correction lens 12.
has. The second correction lens 13 is preferably made of an adhesive material 14, such as a material with relatively high light transmittance, such as balsam.
When such a correction lens is used to form the fluorescent surface of a color picture tube, the area where the adhesive member 14 is interposed is at least a few times larger than the area where the adhesive member is not interposed. Since the light transmittance decreases, the effective area is the stepped surface 1 of the second correction lens.
7, the amount of reflected and scattered light decreases, and as a result, undesirable unevenness on the fluorescent surface (such as the one shown in Figure 4) formed by reflection and scattering of light rays due to the step simply reduces the light transmittance. It has been experimentally found that the reduction is not only by a minute but also more than expected.

In other words, in the past, reflection and scattering from the steps caused linear unevenness on the fluorescent surface depending on the presence or absence of the steps, but by using the adhesive member 14 with low light transmittance, the reflection and scattering from the steps can be reduced. As a result, the linear unevenness of the fluorescent surface was reduced, so the difference in light transmittance with the area 18 without the adhesive member 14 was several degrees. However, it can be assumed that this is due to the unevenness of the fluorescent surface, which can be visually ignored.

In other words, it can be assumed that the visual difference is due to the difference between linear and planar shapes.
In addition, for the light beam 16 in FIG. 5 that passes through the boundary surface of the adhesive member 14, the adhesive member 14 may be applied over a wide area as necessary, and the area to which the adhesive member is applied can be determined by experiment. You just have to decide accordingly.

When using the correction lens according to the present invention, it is possible to counteract the unevenness of the fluorescent surface, which is the biggest drawback of conventional correction lenses having this type of step, without vibrating the correction lens or using a special filter. can. FIG. 9 shows another embodiment of the present invention, and FIG.
Figure b shows an embodiment in which two or more layers are adhesively fixed via an adhesive member 14, and the present invention is also effective in this type of correction lens. The correction lens of the present invention further has the following advantages.

In a color picture tube, the fluorescent light used to form the fluorescent surface is corrected by a correction lens so that it matches the trajectory of the electron beam as much as possible. This correction amount (△Z) usually has the characteristics as shown in Figure 6, and is typically represented by the D axis 19 (diagonal axis of the picture tube), the H axis 21 (horizontal axis), and the 30° axis 20. As shown in the example, it is customary to be different for each axis. Here, γf is the eccentric distance from the center of the screen, and △Z is the horizontal axis (H-axis) direction of a color picture tube that has a striped fluorescent surface (recent color picture tubes have a striped fluorescent surface). This is the amount of correction by the correction lens (the amount of correction is designated as △Z to make it easier to understand, since it is the mainstream that has the following).
The necessary correction amount of the above-mentioned correction lens is shown schematically in FIG. Here, arrow 22 indicates a correction vector. In other words, as shown in Fig. 7, the correction amount (△Z) ideally corresponds to each axis (
The representative axes are the H axis, the D axis, and the 30° axis), but if the fluorescent surface of a color picture tube is divided into the first quadrant, second, third, and fourth, each quadrant is symmetrical. I understand. However, in general color picture tubes, metal parts such as a shadow mask are secured to panel pins installed on the side wall of the panel of the picture tube, so they are susceptible to deformation due to mechanical twisting or the like.

It is also locally magnetized to electrically weld internal magnetic shields, etc. As a result, the correction amount of the correction lens, which should ideally be symmetrical with each quadrant as shown in FIG. 7, becomes as shown in FIG. 8.

That is, the required correction amount 23 differs for each quadrant.
The imbalance of this correction amount is actually about 40μ for a 90° tube.
, for a 110° tube, it is close to 70μ, and especially for a 110° deflection color tube, there is a guard pad between the electron beam and the phosphor strip (a landing error between the electron beam and the phosphor strip that can guarantee color purity). Since it is about 50μ, it becomes a factor that significantly reduces the color purity of the color picture tube.

This unbalance is caused by the above-mentioned factors, and it has been experienced that if the same system color picture tube is used but only the screen size differs between cars, this unbalance pattern will change even if the basic correction amount shown in Figure 6 is the same. It is clearly determined. Therefore, it is desirable that the second correction lens 13, which is used when forming the fluorescent surface of a color picture tube that differs only in screen size, be detachable so that the asymmetric component can be easily changed as in the present invention.

As described above, the present invention provides a first correction lens 12 that is made of a continuous curved surface or a flat surface in the effective area of the correction lens.
The feature is that at least one or more second correction lenses 13 with a small effective area are adhesively fixed on the upper surface via an adhesive member, and it is easy to manufacture and can be used for other tube types with different unbalance patterns. It has many applications,
In addition, it provides a correction lens that can reduce the unevenness of the fluorescent surface, which was the biggest drawback of conventional lenses of this type, without moving special optical filters or correction lenses, and its industrial value is extremely great. be.

[Brief explanation of drawings]

Fig. 1 is a simplified cross-sectional view of an exposure stage to explain the exposure process during the formation of the fluorescent surface of a color picture tube, and Fig. 2 shows the essentials of a conventionally used correction lens having a stepwise discontinuous surface. 3 is a plan view and a sectional view of a correction lens having a lattice-like discontinuous surface, which is an example of the correction lens shown in FIG. An explanatory diagram showing the unevenness of the fluorescent surface that occurs when the optical surface is formed. FIG.
The figure is a curve diagram showing the correction amount of the correction lens, FIG. 7 is an explanatory diagram showing the correction amount of the correction lens of an ideal color picture tube, and FIG.
The figure is an explanatory diagram showing the amount of correction required for an actual color picture tube, and FIG. 9 is an enlarged sectional view of a main part showing another embodiment of the correction lens of the present invention. 12...First correction lens, 13...
Second correction lens, 14...Adhesive member.

Claims (1)

[Scope of Claims] 1. A first correction lens having a continuous curved surface or a flat surface within an effective area, and one or more correction lenses fixed to at least one principal surface of the first correction lens via an adhesive member. A correction lens comprising: a second correction lens. 2. Claim 1, characterized in that at least one of the second correction lenses is composed of two or more layers of correction lenses.
Correction lens described in section. 3. The correction lens according to claim 1, wherein the adhesive member extends over the first correction lens at a desired position.