JPS60257043A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To give directivity to emission of light of phosphorescent surface by providing a multi-layer optical film where silicon oxide film and tantalum oxide film are alternately formed between a face plate glass and phosphor material layer. CONSTITUTION:While a phase plate glass which is used as a substrate is heated up to about 300 deg.C, tantalum oxide and silicon dioxide are alternately vacuum deposited through heating by electron beam in the designed constant thickness and an optical interference film is formed by the six-layer coating. Thereby, an optical interference film for very stable cathode-ray tube phosphor surface providing both heat resistance characteristic and chemical resistance property can be obtained, it is also possible to give dependency on angle to distribution of luminousity of light emission of phosphor surface. As a result, a high quality cathode-ray tube for terminal and projection type cathode-ray tube can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to the structure of a cathode ray tube in which light emitted from a fluorescent surface is given directionality.

[Prior art]

FIG. 1 is a schematic cross-sectional view showing the operating principle of a conventional cathode ray tube. Referring to this figure, a phosphor layer (4) is formed on the circular surface of the face plate glass (2) that constitutes a part of the glass bulb (1) that serves as the vacuum envelope.
On this phosphor layer (4), a high-voltage electrode and a metal back film (5) consisting of a vapor-deposited film of aluminum (An) as a light reflecting film are formed to constitute a phosphor surface (3). The phosphor layer (4) is excited by the energy of the electron beam (7) emitted from the electron gun (6) which is placed opposite to the inner surface of the metal bank film (5) side of the phosphor surface (3), and the phosphor layer (4) Luminous output can be obtained. Since such a phosphor layer (4) is usually close to a completely diffusing surface, for example, in the case of light emission excited by an electron beam (7) at point (N in the figure), the luminous intensity with respect to the divergence angle of the light is The distribution follows LAMBERT's law, and as shown in the figure (, (2) the distribution is proportional to θ.
It is well known that the brightness distribution in each angular direction in this case is a constant value, that is, the brightness is the same no matter which direction the fluorescent surface is viewed from. For ordinary home television receivers, it is an essential condition that the brightness of the image projected on the fluorescent surface (3) appears almost the same no matter what direction it is viewed from. However, depending on the type of use, the brightness of the fluorescent surface (3) is not necessarily the same depending on the viewing angle, and in some cases it is preferable to have angle dependence. An example is a cathode ray tube for terminals such as computers.

In the case of a display for a terminal such as a computer, as shown in FIG.
Since the operator (9) performs the work while looking at the information displayed on the screen, the operator (9) actually sees the visual information of approximately ±C of the light emitted from the fluorescent surface (3) at the center of the screen. Even if the periphery of the screen is considered, the light emission is within a divergence angle range of about ±80° at most. therefore,
Light emission outside this range can be said to be meaningless light emission for computer terminal work. If the luminous flux outside the divergence angle of about ±8♂ can be concentrated within the divergence angle of ±80′ as shown in Fig. 8, angular dependence will occur in the luminance distribution, and the fluorescence on the operator (9) side will The brightness of the surface can be significantly improved, which can also lead to energy savings. Further, it is preferable that the luminance distribution of the fluorescent surface has angular dependence. Another example is a projection cathode ray tube.

FIG. 4 is a schematic sectional view showing the principle of construction of a projection television set. The projection cathode ray tube θυ transmits the image projected on its fluorescent surface (3) to the projection lens unit @
The image is enlarged and projected onto a screen (6) installed in front of the screen. This projection lens unit (6) is usually configured as a compound lens incorporating about 8 to 8 optical lenses.

In the case of such a projection lens (unit) Q"2J, it is difficult to choose a lens aperture that is too large compared to the size of the fluorescent surface (3) of the projection cathode ray tube Qυ due to aberration problems, cost, and space problems. It is difficult.

For this reason, the useful angle for capturing the light emitted from the fluorescent surface (3) into the projection lens unit (6) is extremely limited. For example, in the case of light emission at the center of the fluorescent surface (3), optically useful light emission occurs at the light emitting point on the fluorescent surface (3).
The range is approximately ±15 to ±2" with respect to the normal line set on the surface. Similarly, when emitting light around the fluorescent surface (3), The range is about 80. Therefore, even if both the central part and the peripheral part of the fluorescent surface (3) are considered, the range is about ±8 with respect to the normal to the fluorescent surface (3) at the light emitting point. Light emitted with a larger divergence angle than the male is unnecessary light that cannot take an optically useful optical path of the projection lens unit (6).

As shown in Figure 8, the luminous flux outside the divergence angle of about ±8♂ is
If the luminance can be concentrated within a divergence angle of ±80', angular dependence will occur in the luminance distribution, making it possible to significantly improve the brightness of the image enlarged and projected onto the screen θ.

Of the luminous flux of the fluorescent surface (3) as described above, those with a large divergence angle are concentrated into the direction with a small divergence angle, and the brightness in the direction with a small divergence angle is increased. As a method to make the luminance distribution of angular dependence, JP-A-55
The method disclosed in ``Cathode ray tube face plate structure for suppressing halo and method for suppressing the same'' of No. 150582 is very suggestive. That is, as shown in Figure 8,
By forming an optical interference film 00 between the face plate glass (2) of the fluorescent surface (3) and the fluorescent layer (4), angular dependence is imparted to the luminance distribution of the fluorescent surface (3). It has been suggested that This optical interference film QO transmits as much of the light that is incident on the film from the phosphor layer (4) as possible with a small angle of incidence, and reflects the light that has a large angle of incidence and reflects the light that enters the film from the phosphor layer (4). 4) Acts to return it to the side. The light that enters the optical interference film M at a large angle of incidence and is reflected toward the phosphor layer (4) is diffusely reflected again on the phosphor surface. Only those with small angles of incidence are transmitted; the rest are also reflected. By repeating this process, a luminance distribution with angular dependence is realized, as shown in FIG. 8, in which the luminous flux is concentrated in a range with a small divergence angle.

As a specific example of such an optical interference film, the above-mentioned Japanese Patent Application Laid-Open No. 55-150582 uses silicon dioxide (Sin2) as a low refractive index layer and titanium dioxide (T) as a high refractive index layer.
An example of a six-layer coating consisting of a combination of i02) is disclosed.

On the other hand, when such an optical interference film is applied to the fluorescent surface of a cathode ray tube, two important performances are required of the optical interference film in addition to the required optical properties. One of them is heat resistance. Normally, the manufacturing process for cathode ray tubes requires approximately 400
It must pass through a heat treatment step at least twice in which the temperature is raised to ~450°C. Therefore, such a heat treatment step must not cause any change in the optical properties of the optical interference film formed on the fluorescent surface.

From the point of view of such heat resistance, silicon dioxide (Si02
) and titanium dioxide (Ti02) are unstable, and it has been revealed that even holding the temperature at 400°C for 80 minutes causes significant fluctuations in optical properties. Also,
Another important performance required of such an optical interference film is chemical resistance.

Usually, when forming the phosphor surface (3) of a cathode ray tube, the inner surface of the glass bulb (1) is cleaned with an acidic solution such as hydrofluoric acid (IF) before forming the phosphor layer (4). be done.

This cleaning is an essential step to ensure the operational life of the 5its tube. This cleaning of the inner surface of the glass bulb (1) is carried out immediately before the formation of the phosphor layer (4), so that the optical interference formed in advance on the inner surface of the face plate glass (2) of the glass bulb (1) The membrane will also be subjected to cleaning, such as with HF, and the optical properties of the membrane must not be impaired due to this. However, in the case of a multilayer film consisting of silicon dioxide (Sin2) and titanium dioxide (TiO2), about 1.0 wt% of hydrofluoric acid (HF)
After being immersed in water for only about 1 minute, the film decomposes and peels off.
It is also extremely unsatisfactory from the viewpoint of chemical resistance. Therefore, silicon dioxide (Si02) and titanium dioxide (T
Although the optical interference film consisting of a multilayer film described in i02) can sufficiently meet the initial properties of the film, it does not meet the required performance such as heat resistance and chemical resistance, which are naturally required in the manufacturing process of cathode ray tubes. Therefore, it is extremely difficult to apply it to the fluorescent surface of a cathode ray tube.

[Summary of the Invention] This invention provides an optical interference film between the face plate glass and the phosphor layer of the fluorescent surface of a cathode ray tube to make the luminance distribution of the fluorescent surface angularly dependent. This was developed in view of the instability of optical interference film properties that could not be resolved using conventional technology, and was developed to provide an extremely stable optical system for cathode ray tube phosphor screens that is both heat resistant and chemical resistant. The purpose of this invention is to provide a targeted interference film.

[Embodiments of the invention]

In order to obtain an optical film that has both heat resistance and chemical resistance that can be applied to the fluorescent surface of cathode ray tubes, we conducted experiments on films actually deposited using various metal oxides.
Silicon dioxide (S i02 ) is used as the low refractive index layer, and tantalum oxide (Ta02 or Ta2's) is used as the high refractive index layer.
) has excellent heat resistance and chemical resistance, and has been confirmed to be fully applicable to the fluorescent surface of cathode ray tubes.

Tantalum oxide (Ta02 or Ta203) is heated to approximately 800°C while the face plate glass serving as the substrate is heated.
In the case of an optical interference film formed by coating 6 layers by alternately depositing silicon dioxide (Si02) and silicon dioxide (Si02) at a constant film thickness using electron beam heating, a temperature cycle of holding at 450°C for 80 minutes was performed. Even if this was repeated 8 times and 5 minutes of immersion in a 2.0 wt % hydrofluoric acid (HF) solution was added during this period, no abnormality occurred in the properties of the optical interference film or other properties.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to apply an optical interference film with excellent heat resistance and chemical resistance to the fluorescent surface of a #polar ray tube, and the luminance distribution of the light emitted from the fluorescent surface can be changed. Angular dependence can be provided, and as a result, it becomes possible to provide high-quality terminal cathode ray tubes and projection type cathode ray tubes.

[Brief explanation of drawings]

Figure 1 is a schematic sectional view showing the operating principle of a conventional cathode ray tube, Figure 2 is a diagram showing the working status of a terminal display such as a computer, and Figure 8 is the luminance of the fluorescent surface of the cathode ray tube. FIG. 4 is a schematic cross-sectional view showing the principle of construction of a projection television set. (1)... Glass bulb, (2)... Face plate glass, (3)... Fluorescent surface, (4)... Fluorescent layer, 0I... Optical interference film. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa

Claims (1)

[Claims] (1) A multilayer optical film formed by alternately forming a silicon dioxide (Si02) film and a tantalum oxide (Ta02 or Ta203) film is provided between the face plate glass that constitutes the fluorescent surface and the phosphor layer. A cathode ray tube characterized by having a fluorescent surface that emits light with directionality.