JPS62193053A - Flat light source - Google Patents

Abstract

PURPOSE:To provide a flat light source having a uniform luminance and shaped as a thin plate, by determining the distance between linear electrodes, the width of each linear electrode, the length thereof, the pressure of a hermetically enclosed gas and the magnitude of a discharge current in accordance with prescribed conditions. CONSTITUTION:A plurality of linear conductors 18a disposed at equal intervals in parallel with each other are coated with electric insulation layers 18b and dielectric layers 18c of high secondary electron emission ratio so that linear electrodes 18 are constituted. A fluorescent material is applied to an inside surface of a discharge container 14, which faces the linear electrodes 18. In order to realize a luminous surface of uniform luminance, the distance d(mm) between the linear electrodes 18, the width W(mm) of each of the electrodes, the length l(mm) thereof, the pressure P(torr) of a hermetically enclosed gas and the magnitude I(mA) of a discharge current are determined in accordance with conditions represented by formulae I-IV, and voltages different in polarity are applied to the adjacent electrodes.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a flat light source with a completely new structure, such as a rear light source for a transmissive color liquid crystal display device, a reading light source for information equipment, and a general illumination light source. This relates to products used in fields that require uniform brightness and thin flat plates.

[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 and thermal energy and exhibit polarizing properties.Currently, light is received through the liquid crystal display surface and reflected at the rear. Two types of systems have been put into practical use: a reflective type that allows the user to recognize turns, and a transmissive type that allows light to enter and pass through the rear of the liquid crystal to recognize the display and turn.

However, although liquid crystals switch light, they do not emit light by themselves, so a light source is essential to achieve a bright display. 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.

In FIG. 2, 1 is a liquid crystal display section, which includes a first liquid crystal-filled vacuum container 2, a first transparent electrode 3 formed on the inner surface of the first liquid-crystal-filled vacuum container 2, and a first transparent electrode 1. 3, a second liquid crystal-filled vacuum container 5 disposed opposite to the first liquid-crystal-filled vacuum container 2, and a second liquid crystal-filled vacuum container 2. A plurality of second transparent electrodes 6a, 6b, 6 formed in a matrix on the inner surface of 5
c.

. . . and colored layers 7a, 7b, 7c, . . . formed on the upper surfaces of the second transparent electrodes 6a, 6b, 6c, .
and the second transparent electrodes 6a, 6b, 6c,... and the colored layer? a, 7b, 7c, . . . , a second liquid crystal alignment film 8 provided to cover It is composed of a first polarizing plate 10 disposed on the outer surface side of the liquid crystal-filled vacuum container 2 and a second polarizing plate 11 disposed on the outer surface side of the second liquid crystal-filled vacuum container 5. Reference numeral 12 denotes a straight tube-shaped fluorescent rung which serves as a rear light source and is disposed behind the liquid crystal display section 1, that is, on the side of the second polarizing plate 11, and a plurality of fluorescent rungs are arranged in parallel according to the display area of the liquid crystal display section 1. has been done. 13 is the liquid crystal display section 1
This is a light diffusing plate disposed between the fluorescent rungs 12 and the fluorescent rungs 12 to make the light flux from the plurality of fluorescent rungs 12 uniform.

In the transmissive color liquid crystal display device having the above configuration, the fluorescent rung 12 is turned on, and the first transparent electrode 3 and the second transparent electrode 6a, 6b, 6 are connected in accordance with a desired display pattern.
Apply a potential between c,...

Here, for example, if no potential is generated between the first and second transparent electrodes 3 and 6c, but a potential is generated between the first and second transparent electrodes 3 and 6b, the liquid crystal molecules between the transparent electrodes 3 and 6c The liquid crystal molecules 9a remain in a molecular crystal structure that does not transmit light, and the liquid crystal molecules 9b between the transparent electrodes 3 and 6b have a molecular crystal structure that transmits light. As a result, no light is emitted from the portion facing the second transparent electrode 6a, and light corresponding to the color of the colored layer 7b is emitted from the portion facing the second transparent electrode 6b as indicated by the arrow A.
The desired display angle can be obtained.

[Problem that the invention seeks to solve]

However, in the conventional device described above, since a plurality of fluorescent lamps 12 are arranged according to the display area, the light diffusing plate 13
Brightness unevenness tends to occur on the top. Possible methods for preventing this uneven brightness include increasing the distance between the fluorescent rungs 12 and the light diffusing plate 13, or increasing the number of fluorescent rungs 12 to increase their arrangement density. However, in the former method, the device itself becomes large, especially in the thickness direction, and one of the advantages of using the liquid crystal display section 1 as the device is lost. In addition, in the latter method, the fluorescent rung 12
As the power consumption increases as a light source consisting of
One of the advantages of using a light source is low power consumption, but this is not foolish, and the efficiency of the fluorescent lamp 12 deteriorates due to the rise in temperature of the light source, causing damage to the area around the liquid crystal display 10 and the light diffusing plate 13. This caused the problem of deterioration. Also, depending on the size of the display section, the fluorescent rung 1
It was necessary to prepare 2.

In addition, although the above conventional example uses an ordinary fluorescent rung as a light source, in order to maintain the lifespan of a TV as a light source, a transmission type liquid crystal display device uses a glow discharge fluorescent rung using a cold cathode. A device for use as a rear power source has also been proposed. However, with fluorescent lamps that use glow discharge, as the distance between the electrodes increases to match the enlargement of the display surface, the starting voltage increases, making starting difficult, and restarting becomes difficult. The voltage also increases, causing noise to the liquid crystal drive circuit, causing malfunctions of the display device, and it is not suitable for large transmissive liquid crystal display devices such as office automation display terminals. there were.

This invention was made to solve the above-mentioned problems, and is suitable for the rear light source of a liquid crystal display device, and can realize a thin and uniform brightness surface, as well as discharge at a low starting voltage. The purpose is to obtain a flat light source that can

[Failure to solve the problem]

In the flat light source according to the present invention, each linear conductor formed on one inner plane of a flat discharge vessel filled with a rare gas or a rare gas and mercury is layered with an insulating layer and a dielectric material with a high secondary electron emission rate. to form each linear electrode, and coat the other opposing inner surface of the discharge vessel with a phosphor.
In order to achieve a light emitting surface with uniform brightness, the distance between the two linear electrodes is set to ``du'', the electrode width is set to ``W'', the length of the linear electrode is set to ``l'', the pressure of the filled gas is set to P Torr, and the discharge current is adjusted to When I mA, 0.5≦P≦100 (1)
0.5≦W≦d(2) 0.5≦t (3
)0.5≦Work≦100 (4
), and voltages with different polarities are applied to adjacent electrodes.

[Effect]

In the flat light source according to the present invention, each linear electrode is formed by coating a linear conductor with an insulating layer and a dielectric layer with a high secondary electron emission rate, and voltages of different polarities are applied between adjacent electrodes. By doing so, it is possible to realize a light source that generates discharge simultaneously between multiple electrodes and emits light from the surface of the apparent metal plate, and by satisfying the above four conditions, the stability of the discharge,
Achieving longer life of the electrode and lower starting voltage.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. 1st
In the figure, reference numeral 14 denotes a flat discharge vessel in which a rare gas or mercury 17 and a rare gas are sealed. , a light reflective white plate 15b facing this, and a flat plate 1
5a and the white plate 15b, an exhaust pipe 19 attached to the side wall plate 16, and a linear electrode 1 formed on the white plate 15b facing the light emitting surface.
The flat plate 15a, white plate 15b and side wall plate 16 are sealed with powdered glass to maintain airtightness. After the discharge vessel 14 is evacuated through an exhaust pipe 19, it is filled with a rare gas or rare gas and mercury 17. Moreover, the linear electrode 18 is made of Ni, A/? , a plurality of linear conductors 18a made of conductive material such as Cu and formed at equal intervals in parallel on a white plate 15b, an insulating layer 18b covering the linear conductors 18a, and an insulating layer 18b coated with high secondary electron emission characteristics. The dielectric layer 18c has a multilayer structure.

In the plurality of linear electrodes 18 described above, in order to maintain the brightness as a light source, the discharge current I mA is 0.5≦min≦
Make it flow within the range of 100. For this reason, the thickness of the linear conductor 18a is 1 to 2 μm, the width W is 0.5≦W, and the distance between the linear electrodes 18, that is, the distance dw1 between the linear droplets 18a is W
≦d. In addition, in order to maintain uniform discharge between the linear electrodes 18, charges can be uniformly accumulated on the electrodes 18.
An insulating layer 18b with a thickness of 1000 to 2 μm is provided, and a dielectric layer 18c with a high secondary electron emission rate of 1000 to 2 μm in thickness is further provided on the upper surface of the insulating layer 18b for the purpose of lowering the starting voltage and the discharge sustaining voltage. . Here, metal lead 18
a is, for example, Cr (100 people)/AJ (2 μm), Cr (
100^)/Ni (2ttm), Cr (100^)
/Ni (1000^)/Cu (2ttm)/Ni
(1000^) or the like, and Cr is provided to improve adhesion to the white plate 15b.

The insulating layer 18b is made of, for example, Al2O5 (2 μm), SiS
102C2tt, Ta205 (2ttm) etc. 3~
A material having a dielectric strength of 7×106 (V/c+++) is used, and the dielectric layer 18c is Lab6 (5000 people).
Mr, (3000 people), (Sr, Ca) O(1
A secondary electron emitting material such as 0000^) was used. In addition, for the purpose of suppressing the discharge starting voltage below the dielectric strength voltage and optimizing the efficiency of sunlight, the rare gas filling pressure P Tor
r was set to 0.5≦P≦100.

When the pressure P is less than 0.5 Torr, pBschen's law regarding the discharge starting voltage vb (Vb=f (Pa
) exists which determines Vb (min). ), but since the gas is weakly ionized, it has a large kinetic energy (the mean free path becomes long).The dielectric layer 18c is snocked by the particles, and the life of the electrode 18 is less than 1000 hrs. , and if P exceeds 100 Torr, pasc
According to the henO law, if b is large, the distance d between the linear electrodes 18 is large.

If it is not less than 0.5 rua, practical problems such as exceeding the dielectric breakdown voltage will occur. Further, in the case of W>d, although the discharge can be maintained, there is a problem that a practical uniform brightness light source cannot be realized due to the existence of the dark electrode part peculiar to the discharge. Also, the length I of the linear electrode 18! If it is less than 0.5 ms, there are problems such as its meaning as a flat light source diminishes and the brightness cannot be increased. After all, 0.5≦P≦100
(1) 0.5≦W≦d
(2) 0.5≦1 (3) 0.5≦Work≦100 (4) It is necessary that the light source be a flat plate light source. Moreover, the linear electrode 1
8 applies voltages so that adjacent electrodes have different polarities or different potentials, as shown in FIG. When a voltage is applied in this way, a discharge occurs simultaneously between the plurality of linear electrodes 18, and the ultraviolet rays emitted from the rare gas or mercury atoms due to this discharge irradiate the phosphor 20 coated on the inner surface of the discharge vessel 14. The phosphor 20 emits visible light.

For example, in the linear electrode 18, Ne-Ar(A
r 70 Vat%) The pressure of the mixed rare gas is 20 Torr.
r, space perpendicular to the discharge axis H = = 5x, distance between electrodes 18 d = 50rtts, length of electrode 18 1 = 60vts,
When the width W of the electrode 18 is 21i1jl and the number of electrodes 18 is 10, the effective value of the discharge voltage Veff is 180V, and the effective value of the discharge current Ieff =
Characteristics of 30 mA and a life of 5000 hrs or more were obtained.

Similarly, Ar10Torr, H=5WjR,d=
100m1.1=60Tu1, W=21LI, number of electrodes: 4, Veff=350V, Ieff” 40
mA and a lifetime of 5,000 hrs or more.

Also, Ar-Ne (Ne 50 Vat%) 100
Torr, H=5 rtm.

d=5mm, /=200&lI, W=1M, number of electrodes 10, Veff=400V, Ieff=10
mA and a lifespan of 5000 hrs or more were obtained.

In addition, as a result of many experiments within the range of satisfying Equations (1) to (4), we obtained a uniformly high-intensity light source with a long life.Also, in each case, the luminous efficiency as a light source is 20～
30I! m/W. In the lighting circuit shown in Fig. 3 used in the experiment, Cs and C2 are capacitors, Tr,
, Tr2 is a transistor, L is a coil, T is a transformer, R+, & is a resistor.

In the above embodiment, only the application to a backlight was explained, but since this light source can freely change the color of the light emitted by the phosphor 20, it is possible to create a system by preparing and combining three primary color light sources of red, green, and blue. , it goes without saying that it can itself become a pixel and form a display. Furthermore, by combining the vacuum ultraviolet radiation of a rare gas with a vacuum ultraviolet-excited phosphor for light emission by discharge, a thin flat plate light source that is not affected by the ambient temperature can be realized, and the same effect as that of the embodiment can be achieved. Not only can it be used to play music, but it can also be used for a wide range of other purposes.

〔Effect of the invention〕

As described above, according to the present invention, the sealed gas pressure P To
rr, distance between linear electrodes do, electrode length 1u, electrode width W1i
IjI, discharge, current I mA, and when the linear electrode is formed by covering the linear conductor with an insulating layer and a dielectric layer, 0.5≦P≦100 (1)
0.5≦W≦d (2)0.
5≦1(3) 0.5≦Work≦100
By configuring the structure to satisfy the relationship (4), a thin planar light source with stable and uniform brightness can be realized, and a reduction in starting voltage and a longer life can also be achieved.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1(a) and 1(b) are a perspective view and a sectional view of a flat light source according to the present invention, FIG. 2 is a sectional view of a conventional liquid crystal display device, and FIG. 3 is a sectional view of a flat light source according to the present invention. FIG. 3 is a lighting circuit diagram of a flat light source according to the invention. 14...Discharge vessel, 15a...Flat plate, 15b...
White plate, 17...Mercury, 18... Linear electrode, 18a
... Linear conductor, ISB... Insulating layer, 18C... Dielectric layer, 20... Fluorescent material. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A flat discharge vessel having at least one pair of opposing inner planes and filled with a rare gas or a rare gas and mercury, and a plurality of linear electrodes provided on one inner plane of the discharge vessel. and a phosphor coated on at least the other inner plane of the discharge vessel, and the plurality of linear electrodes include a plurality of linear conductors provided in parallel on the one inner plane and coated with an insulating layer. Furthermore, a dielectric layer with excellent secondary electron emission characteristics is coated on top of the dielectric layer, and voltages are applied so that adjacent linear electrodes have different potentials or polarities, and each linear electrode simultaneously The conditions for discharging and for simultaneously causing uniform discharge between the linear electrodes are as follows: the distance between each linear electrode is dmm, the linear electrode width is Wmm, the length of each linear electrode is lmm, and the pressure of the filled gas is set as follows. When PTorr is PTorr and ImA is discharge current, 0.5≦P≦100 (1) 0.5≦W≦d (2) 0.5≦l (3) 0.5≦I≦100 (4) A flat power source characterized by being configured to satisfy the following relationship.