JPH0425660B2 - - Google Patents

Description

[Detailed description of the invention] Technical field The present invention relates to a refractive projection cathode ray tube.

Background Art A refractive projection cathode ray tube uses a magnifying lens to form an image formed on the face of the cathode ray tube onto a screen to obtain an enlarged image. An example of this cathode ray tube will be explained with reference to FIG. Reference numeral 1 designates a bulb in which a face portion 1a having a fluorescent film 2 formed on its inner surface and a neck portion 1a housing an electron gun 3 for supplying an electron beam to the fluorescent film 2 are hermetically connected to both ends of a funnel portion 1c. It is. Reference numeral 4 indicates a metal back layer laminated on the fluorescent film 2, and reference numeral 5 indicates an exterior conductive film formed on the outer peripheral surface of the funnel portion 1c.

Although not shown, a magnifying lens group is mounted in front of the cathode ray tube via a support frame, and a screen is further arranged in front of the cathode ray tube.

This cathode ray tube is the same as a general cathode ray tube for receiving television broadcast images, but a high resolution one is used for the electron gun 3, a higher acceleration voltage is applied to the electron gun 3, and the fluorescent film 2 is The difference is that a high-luminance phosphor is used.

Incidentally, since the brightness of an image on a screen decreases depending on the light transmittance and magnification of the magnifying lens, high brightness is required.

Therefore, we use phosphors with high luminous efficiency,
The amount of electron beam supplied from the electron gun 3 is increased to improve the brightness.

However, as the amount of electron beam increases, the amount of heat generated at the face part also increases, and the luminous efficiency of the phosphor decreases due to the temperature rise, resulting in saturation at low brightness.
On the contrary, there were problems such as a decrease in brightness.

In addition, when multiple cathode ray tubes with different emission colors are used and the images are superimposed on a screen to obtain a color image, each cathode ray tube has a different temperature rise, which causes the problem of unbalanced emission levels and color shifts. .

Further, heat generation tends to concentrate in the center of the face portion 1a, but if the temperature difference between the center and the peripheral portion of the face portion 1a becomes large, thermal expansion causes the face portion 1a to
There was also the problem that it caused distortion and was prone to cracking even with the slightest scratch on the surface.

Therefore, a cathode ray tube shown in FIG. 2 has been proposed. That is, a light-transmitting plate 7 is airtightly connected in front of the face part 1a with an adhesive 8 via an annular radiator 6 having a light-transmitting part in the center, and cooling is carried out between the face part 1a and the plate 7. It is filled with a liquid 9, and 10 indicates a spacer for regulating the distance between the plate 7 and the radiator 6, and between the radiator 6 and the face portion 1a.

This cathode ray tube has a face section 1 where the temperature rises significantly.
a The heat in the center is transferred to the radiator 6 on the periphery by the convection of the coolant 9, and then the heat is transferred to the outside of the valve 1 by the radiator 6 with a good heat conduction chamber, and the heat dissipation effect is significantly improved. be done.

However, this cathode ray tube had the following drawbacks. That is, when the temperature of the valve 1 rises during storage or operation, the temperature of the coolant 9 in the closed space also rises and thermally expands, damaging the seal and causing liquid leakage or damaging the plate 7 or the valve 1. Ta.

As the coolant 9, an aqueous solution of ethylene glycol, which is generally used as an antifreeze, is suitable. If an aqueous solution of water and ethylene glycol is used in a volume ratio of 7:3, the body expansion coefficient will be 0.21×10 ^-3 /
℃, 0.64×10 ^-3 /℃, the cooling liquid 9 expands in volume by about 2% for a temperature change of 60℃.

For example, in a cathode ray tube with a screen size of 5 inches, the sealed space is approximately 25 c.c., and if this is completely filled with coolant 9, the volume will increase by approximately 0.5 cc. Damage to the valve 1 cannot be prevented. Therefore, if the cooling liquid 9 is filled so that there are some voids, the increased volume will be absorbed by the voids, but the vapor pressure within the voids will rise and the internal pressure will rise, which may damage the sealing or damage the panel 7.
In some cases, valve 1 was damaged. This means that the vapor pressure of ethylene glycol is 20 mmHg even at 106°C and can be ignored, but the vapor pressure of water is 17.5 mmHg at 20°C and 40°C.
55.3mmHg at ℃, 149.5mmHg at 60℃, 355.3 at 80℃
mmHg, 760mmHg at 100℃, which is because the pressure increases rapidly as the temperature increases.

For this purpose, the volume of the void can be increased, but
In this case, bubbles would form in the light emitting area of the cathode ray tube, which was undesirable, and there was a limit.

DISCLOSURE OF THE INVENTION The present invention has been proposed in view of the above drawbacks, and provides a projection type cathode ray tube that eliminates the above drawbacks.

The present invention airtightly connects a light-transmitting plate to the front of a bulb face with a fluorescent film formed on its inner surface through an annular radiator having a light-transmitting window in the center, and creates a space between the face and the plate. It is characterized by filling the gap with cooling liquid and reducing the pressure inside the gap.

With the above configuration, the present invention can prevent leakage of the coolant and damage to the plates and valves.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be applied to the apparatus shown in FIG. 2 and explained from FIG. 3 below. In the figure, the same reference numerals as in FIG. 2 indicate the same parts, and the explanation will be omitted. What is different from the apparatus shown in FIG.
The only thing that happened was that the inside of the tank was evacuated.

For example, for a cathode ray tube with a screen size of 5 inches,
A 25 c.c. sealed space is filled with 24 c.c. of an aqueous solution containing 30% ethylene glycol to create a void 11 of about 1 c.c. Then, the pressure inside this gap 11 is reduced to, for example, 0.5 atmospheres.

As a result, the volume increase of approximately 0.5 cc of the coolant 9 is absorbed by compressing the void 11. At this time, the pressure in the gap 11 increases by the amount of compression, and the vapor pressure of the cooling liquid 9 is added, causing the internal pressure to increase. However, since the pressure has been reduced in advance, the pressure increase is suppressed, and the sealing is not impaired. Panel 7 and valve 1
damage is also prevented.

In addition, heat conduction to the radiator 6 cannot be carried out sufficiently in the gap 11, but by reducing the pressure, the heat can be transferred to the gap 11.
can be made smaller and the heat dissipation effect can be improved.

[Brief explanation of drawings]

FIG. 1 is a partially sectional side view showing a conventional cathode ray tube, FIG. 2 is a partially sectional side view of a projection type cathode ray tube which is the premise of the present invention, and FIG. 3 is a partially sectional side view showing an embodiment of the present invention. A partial cross-sectional side view is shown. DESCRIPTION OF SYMBOLS 1... Bulb, 1a... Face part, 2... Fluorescent film, 6... Radiator, 6a... Window, 7... Plate, 9... Coolant, 11... Gap.

Claims (1)

[Claims] 1. A light-transmitting plate is airtightly connected in front of a bulb face portion having a fluorescent film formed on its inner surface via an annular radiator having a light-transmitting window in the center, and the face portion and the plate A projection type cathode ray tube having a cooling liquid filled between the projection type cathode ray tube, characterized in that the projection type cathode ray tube has a reduced pressure gap between the face portion and the plate.