JPS61165945A - Flat light source - Google Patents

Abstract

PURPOSE:To produce a flat light source with a long life by using an insulating sheet for preventing any sputtering upon the electrode-protecting layer, a phosphor for increasing the luminance and a dielectric sheet for protecting the phosphor from ionic impact. CONSTITUTION:A flat discharge case 21 consists of a side wall 25 and planar plates 22 and 23. Over the flat plate 23, a matrix-like electrode 18 of m lines n rows, a dielectric film 30, a protection layer 19, an insulating sheet 28 having through holes 29 at most 10% of the holes of the protection layer 19, a phorphor layer 31 and a dielectric sheet 32 transmitting ultraviolet rays in that order. The inner surface of the flat plate 22 is coated with a phosphor 20 excited by ultraviolet rays. A flat light source is produced by placing the flat plates 22 and 23 facing each other. The insulating sheet 28 prevents any sputtering upon the protection layer 19 and the phosphor layer 31 increases the luminance of the light source. Besides, the dielectric sheet 32 prevents the deterioration of the phosphor layer 31, thereby increasing the life of the light source.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is applicable to thin flat plates such as rear light sources of transmissive liquid crystal display devices, pixels of large screen display panels, reading light sources for information equipment, and light sources for general illumination. The present invention relates to a flat light source used in a field in which it is required.

[Conventional technology]

For example, liquid crystal display devices utilize the optical switch function of liquid crystals, which undergo a phase transition under the action of electric fields and thermal energy and exhibit polarizing properties.

Two methods have been put into practical use: a reflective type that receives light from the liquid crystal display surface and reflects it behind the LCD to make the displayed pattern clearer, and a transmissive type that allows light to enter and pass through the back of the liquid crystal to make the displayed pattern clearer. ing.

However, although liquid crystals switch light, they do not emit light by themselves, so a light source is essential to realize a bright display pattern. In particular, the transmissive type is used as an OA terminal, and a transmissive color liquid crystal display device as shown in FIG. 2 is currently being proposed.

@2 In Figure 2, (1) is a liquid crystal display section, which includes a first liquid crystal-filled vacuum container (2) and this first liquid crystal-filled vacuum container (2).
) and the first transparent electrode (3) formed on the inner surface of the g
A first liquid crystal alignment film (4) provided to cover the Xl transparent electrode (3), and a second liquid crystal-filled vacuum container disposed opposite to the first liquid-crystal-filled vacuum container (2). (5) and.

A plurality of second transparent electrodes (6a), (6b) formed in a matrix on the inner surface of the second liquid crystal-filled vacuum container (5).
).

(6c), - and the second transparent electrode (6a), (
6b), (6c).

Colored layers (7a) and (
7b).

(7c) , -・- and the second transparent electrode (6a) ,
(6b), (6c).

... and colored layers (7a), (7b), (7
c)] and the second liquid crystal alignment film (8) provided to cover the first and second liquid crystal-filled vacuum vessels +21, (5
1, the first polarizing plate α1 disposed on the outer surface side of the first liquid crystal-filled vacuum container (2), and the outer surface of the second liquid crystal-filled vacuum container (5). l@ placed on the side
It is composed of two polarizing plates αυ. α is the liquid crystal display (
A straight tube-shaped fluorescent lamp that serves as a rear light source is arranged behind 1), that is, on the side of the second polarizing plate aD, and a plurality of them are arranged in parallel according to the display area of the liquid crystal display section (1). . (I3
is a light diffusing plate that is disposed between the fluorescent lamp α2 and the liquid crystal display portion fl) and makes uniform the luminous flux from the plurality of fluorescent lamps (I3).

In a transmissive color liquid crystal display device having the above configuration.

While lighting the fluorescent lamp α side, the first transparent electrode (3) and the second transparent electrode (6) are connected according to the desired display pattern.
A potential is applied between a), (6b), (6c), and so on.

Here, 1. For example, no potential is generated between the first transparent electrode (3) and the second transparent electrode (6a), and the first transparent electrode (3)
) and the second transparent electrode (6b), the liquid crystal molecules (9a) between the transparent electrodes (31, (6a))
remains in the molecular crystal structure that allows light to pass through, and the liquid crystal molecule (9b) between the transparent electrodes (31, (6b) becomes a molecular crystal structure that allows light to pass through. As a result, the second transparent electrode (
No light is emitted from the part facing the second transparent electrode (6b), and light corresponding to the color of the colored layer (7b) is emitted from the part facing the second transparent electrode (6b), so that the desired display can be achieved. A pattern is obtained.

However, in the above device, since a plurality of fluorescent lamps (I3) are arranged according to the display area, uneven brightness tends to occur on the light diffusion plate a:1. Possible methods include increasing the distance between the light diffusing plate a3 and the light diffusing plate a3, or increasing the number of fluorescent lamps (I3) to increase the arrangement density.

However, in the former method, the device itself becomes large, especially in the thickness direction, and the liquid crystal display part f
One of the advantages of using l) is lost.

In addition, in the latter method, the power consumption of the fluorescent lamp fI3 as a light source increases, and not only is it impossible to take advantage of low power consumption, which is one advantage of using the liquid crystal display part fl), but also the light source The movement of fluorescent lamps < 13 becomes worse due to the temperature rise in the area.

A problem occurred in that the periphery of the liquid crystal display section (1) and the light diffusing plate αj were deteriorated. In addition, it was necessary to prepare a narrow light lamp t1 to match the size of the display section 9.

In addition, although the conventional example above uses a normal fluorescent lamp as the light source, in order to maintain the lifespan of a television, a glow discharge fluorescent lamp using a cold cathode is used as the light source behind the transmissive liquid crystal display device. It has also been proposed to use it as a power source. However.

In fluorescent lamps that use such glow discharge, as the distance between the electrodes increases to accommodate the expansion of the display screen, the starting voltage increases, making it difficult to start, and the discharge restriking voltage also increases. This causes noise to be applied to the liquid crystal's rapid circuit, causing malfunction of the display device, making it unsuitable for large-scale transmissive liquid crystal display devices such as office automation display terminals.

Therefore, it has been desired to develop a light source that has a thin, uniform brightness surface and discharges at a low starting voltage as a rear light source for a liquid crystal display cover. Therefore, a surface discharge type rear light source as shown in FIGS. 3 and 4 can be considered. In the figure, (14 is a discharge vessel made of flat glass with mercury and rare gas sealed inside.

It consists of a first container (α→) and a second container (le) sealed with flanges.

Each container (19, (II is a pair of opposing inner planes (15a
) , (ISa). (18,,)~(18
mn) is a plurality of electrodes provided in a matrix of m rows and n columns on one inner plane (16a) of the discharge vessel (14);
Each electrode (18,1) to (18mn) has a protective layer (19
4,) to (19 mn). (to) is a phosphor coated on the inner surface of the discharge vessel a◆ except for the electrodes (181,) to (18 mn). Protective layer (194,) ~
(19 mn) is formed from a dielectric material having excellent secondary electron emission characteristics as electrodes (1811) to (18 mn).

In the flat light source with the above configuration, each electrode (1B, , )
By applying a voltage to (18 mn) to cause discharge and excite the phosphor (a), light emission occurs, and a thin flat light source having a uniform brightness surface can be obtained with a low starting voltage.

[Problem that the invention seeks to solve]

However, in the flat light source described above, electric field concentration tends to occur at the boundary around the electrode during discharge.

The electrode protective layer and insulating layer are sputtered, making it impossible to stably emit secondary electrons, making the discharge unstable and eventually ceasing to turn on, resulting in a short lifespan.Furthermore, ultraviolet rays are only used on the light-emitting surface. Therefore, there is a problem in that it is not possible to fully satisfy the demand for a high-intensity light source and the more advanced demand for uniformity of brightness.

This invention aims to solve the above-mentioned problems.

It is an object of the present invention to provide a long-life thin surface discharge flat light source having a structure that can increase the brightness of a light emitting surface and improve the uniformity of brightness at the same time.

[Means for Solving the Problem] In the present invention, a plate-like discharge vessel having a thickness made of glass or ceramic having a through-hole 10% or more smaller than the protective layer size corresponding to the electrode position on the electrode-side inner surface of the flat discharge vessel. An insulating sheet with a thickness of 1 m or less is brought into close contact with the electrode, a phosphor with a thickness of 20 μm or more is covered on the surface of the insulating sheet excluding the through holes, and a phosphor with a thickness of 1 m IT +
Cover with a dielectric film that can transmit the following 60 am to 360 am ultraviolet rays.

The other inner surface is coated with phosphor.

[Effect]

The insulating sheet prevents electric field concentration that tends to occur at the boundary around the electrode, and prevents sputtering of the protective layer and insulating layer.Furthermore, the phosphor coated on the insulating sheet prevents the light from emitting light. Due to the diffusion effect, the uniformity of the brightness of the light emitting surface emitted from the other plane to the outside is improved, and the increase in the area of the phosphor increases the conversion of ultraviolet rays into visible light, which improves the brightness of the light emitting surface. The insulation sheet isolates the phosphor on the surface from direct ion bombardment, making it easier to discharge.
Deterioration can be prevented.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

In Figure 1, an is a flat discharge vessel with a side wall (C) open on two sides, a flat plate made of glass that emits light and closes the other opening, and the side wall (C) above. It is formed by a flat plate made of glass or ceramics that closes one opening surface. (18,1) ~ (18mn
) is a plurality of electrodes arranged in a 1 mm matrix on the flat plate force, and the distance between each electrode is 20 to 100+
nm range, taken as H3Omm in this example, with a thickness of 2~
A 10 μm thick film of aluminum or other conductive metal is formed by vapor deposition or thick film printing, and a discharge is generated between the two electrodes by driving in 7 time divisions. ■ is this electrode (181
, ) ~ (18 mm) with a thickness of 0.1 to 100 μm, 2 uniformly accumulates surface charge, and speeds up the response characteristics of the discharge application pulse. 9 It is Ta205, 5i02 or Si3N4. +I
I is a protective layer made of an inorganic oxide such as MgO, 0eO20aO or (8r, 0a)O on top of this lightning arrester single film (■), and has a thickness of 1G to 800 nm, @ is this protective layer + IIO
An insulating sheet with a thickness of 1 mm or less and having through holes (2) corresponding to the electrodes (18,) to (18 mn) and having a ti value of 10% or less of the ti value of this protective layer is closely attached to the top of the protective layer. Protect the interface from direct ion bombardment. Furthermore, a phosphor layer 0υ is provided on the upper surface of this insulating sheet (through), which is coated with phosphor having a thickness of 20 μm or more using a thick film printing method or the like, except for the through holes. (to) is 60am to 36mm provided on the upper layer of this phosphor 011 layer.
A dielectric material with a thickness of 1 mm or less that transmits 0 nm ultraviolet rays, such as MgF2. Consists of 8102SiO□ sheet.

■ was applied to the inner surface of the flat plate @. It is a phosphor that is excited by ultraviolet light.

The side wall (to) and the flat plates (2) and (to) are sealed with a glass frit, and the thermal expansion coefficient of this glass frit is the difference between the coefficient of thermal expansion of the side wall (c) and the flat plates a and t23. 20% or less is used. Insulator sheet (
(2) also has a coefficient of thermal expansion of 20% or less between the side wall and the flat plate (2).

CI'll evacuates the inside of the flat discharge vessel t21).

This is an exhaust pipe for sealing mercury or rare gas inside.

Note that the phosphor (3) is colored layers (7a) and (7b) shown in FIG. 2 so that color display can be efficiently realized.

(7C) It is an ultraviolet-excited three-wavelength range emitting phosphor based on the original three primary colors that matches the spectral transmittance of 445
A first range of 525 nm or more and 555 nm or less, and a second range of 595 nm or more 6
It is mainly emitted in the third range of 25 nm or less, and this
The sum of radiant energy in two ranges is 380 nm or more7
45% for radiant energy in the range below 80 nm
It has the above spectral distribution.

For example, 30 wt% Y2O2: Fiu3+ phosphor, 49 wt% Lapo4: o e3+, Tb'+ phosphor 21 wt% (8r, Ba), (PO4
)68rO12: A material consisting of a Bu2+ phosphor is coated to a thickness of 100 μm or less, for example 60 μm.

Furthermore, in the flat discharge vessel QD, there is a mixture of mercury in a range capable of maintaining a saturated vapor pressure of 5 mg or more and a rare gas in a range of 1 to several IQ Torr, or one to several HI that does not contain mercury.
OTorr, for example, 50 Torr of a mixed rare gas mainly composed of helium and xenon is sealed.

In this example, 10 mg of mercury and 20 Torr of a mixed rare gas mainly composed of argon and neon are sealed.

In the flat light source configured as above.

Each of the electrodes (18, 1) to (18n1n) is connected to a drive circuit (not shown) in which time-division driving is performed sequentially between the two electrodes, and two adjacent electrodes are sequentially selected and these two electrodes are Time division discharge will be performed between the two. The selected 2 poles then move sequentially to generate a discharge.

When a discharge occurs between the final electrodes, it returns between the first electrodes,
repeated. By the way, this 2'! ! The discharge current between the electrodes exceeds too many people and the electrodes (18,,) to (18m
Since the deterioration of n) progresses and it becomes difficult to maintain the life of the light source for 10,000 hours, it is necessary to reduce the current to N) OmA or less. In addition, the scan period of the discharge (for example, the pole (1
8,, ), (18,□) starts from the discharge of the electrode (1
8 mn, ), (18 mn) discharge is one scan. ) is required to be 30 Hz or higher because if it is less than 301-13, you will experience light flickering and cause eye fatigue when using an OA display terminal for a long time.

The phosphor is excited by the ultraviolet rays generated by the time-sharing discharge between the two electrodes arranged in a matrix, and the outside of the discharge vessel r2υ has uniform brightness. Light is irradiated. Furthermore, due to the phosphor layer 6υ provided on the upper surface of the insulating sheet (to).

Converts the ultraviolet rays generated within the discharge vessel into visible light.

By scattering and reflecting the visible light generated inside the container to the opposing light emitting surface, uniform brightness and high brightness of the light emitting surface can be achieved at the same time. Moreover, since this phosphor is covered with a dielectric layer that transmits ultraviolet light, it is not directly exposed to the discharge space and is easily discharged by direct ion bombardment.

Sputtering of the phosphor layer is prevented, and the dielectric material also reduces the firing voltage. In addition, the insulating sheet prevents electric field concentration that tends to occur at the boundary around the electrode, eliminates sputtering of the electrode protective layer and insulating layer, stabilizes discharge, and extends life.

〔Effect of the invention〕

As described above, in the present invention, one inner surface of a flat discharge vessel having a pair of opposing inner surfaces is coated with a protective layer, and the protective layer is coated on a plurality of electrodes arranged in a matrix. An insulating sheet with through holes of 10% or less of the layer at potentials corresponding to each electrode is provided in close contact with the protective layer.

A phosphor layer is provided on the upper surface of this insulating sheet, a dielectric layer is further provided on the upper surface of this phosphor layer, and the phosphor is coated on the other inner surface of the flat discharge vessel. The insulating sheet prevents sputtering of the electrode protective layer and insulating layer due to the generation of a concentrated electric field at the boundary around the electrode, resulting in a longer service life.Furthermore, the phosphor layer converts the ultraviolet rays generated within the discharge vessel into visible light. Since this visible light is scattered and reflected to the opposing light emitting surface, the brightness of the light emitting surface can be further made uniform and high. In addition, this phosphor is covered with a dielectric layer that transmits ultraviolet rays and is not exposed to the discharge space, so it is easy to discharge and prevents deterioration of the phosphor from direct ion bombardment. It also has the effect of lowering voltage.

It is possible to realize a long-life flat light source that can stably maintain brightness uniformity and high brightness over a long period of time.

[Brief explanation of drawings]

Fig. 1 is an exploded perspective view and a longitudinal sectional view with the middle part omitted, showing an embodiment of the present invention, Fig. wc2 is a longitudinal sectional view showing a transmissive color liquid crystal display device, and Fig. 3 is a longitudinal sectional view of a conventional flat light source. FIG. 4 is a partial plan view of the electrode section. Codes (1811) to (18mn) in the figure: Electrodes, (I
Protective layer. (to)...phosphor, 12t flat discharge vessel, 23.
(to)...flat plate. (To)...Side wall, -...Exhaust pipe, @...Insulator sheet, @...Through hole, (To)...Dielectric layer,
G...phosphor layer, ■...dielectric layer. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (3)

[Claims] (1) A flat discharge vessel that has a pair of opposing inner planes and is filled with rare gas or rare gas mercury, and is provided on one inner plane of this discharge vessel to protect the parts necessary for discharge. The layer is coated with a plurality of electrodes arranged in a matrix, and has a through hole at a position corresponding to each electrode and having a size of 10% or less of the protective layer, and is tightly attached to the upper surface of the protective layer. an insulating sheet, a phosphor coated with a thickness of 20 μm or more on the upper surface of the insulator sheet other than through holes, a dielectric material coated on the upper surface of the phosphor with a thickness of 1 mm or less, and a phosphor coated on the other inner surface. (2) Claim 1, characterized in that the insulating sheet has a thickness of 1 mm or less and is made of glass or ceramic material with a thermal expansion coefficient difference of no more than 20% from the discharge vessel. The flat light source described. (3) The electrodes are made of a conductor with a distance between each electrode in the range of 1 to 100 mm and a discharge current of 1 to 100 mA. The flat light source described in Section 1.