JPH03283349A - Illumination light source - Google Patents

Abstract

PURPOSE:To obtain an illumination light source of flat type whose unevenness of luminance is small by using as an emission source a micro cold cathode tube having an emitter for field emission and a collector both arranged in a plane, and causing the emission source to emit light from a plane as a whole. CONSTITUTION:An electron emitter 12, an electron collector electrode 15 and a thin film 16 of light-emitting material, etc., are formed on respective portions of a base 11. An electron beam emitted from the electron emitter 12 is urged to collide with the electron collector electrode 15 with energy corresponding to the potential difference between the emitter 12 and the electron collector electrode 15 and thereby the thin film 16 of light-emitting material on the collector electrode 15 is excited to emit light and the light is emitted to the outside through a transparent sealing body 18. Because the thin film 16 of light-emitting material is formed over roughly the whole surface of the base 11, light emission as from a plane is possible and the thin film 16 acts as a planar light source. An illumination light source of flat type whose unevenness of luminance is small is thus obtained.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a flattened illumination light source, and particularly to a planar illumination light source suitable for use as a backlight of a liquid crystal display. .

(Conventional technology) With the progress of the information society, display devices are becoming more and more
It has now become indispensable as a machine interface. As the application of display devices to various uses progresses, requirements for display quality and performance have become stricter and more sophisticated. As the current direction of development,
Improvements in performance such as larger size and higher definition, and flat panel displays are being actively developed.

Various technologies and methods have been tried in the development of flat panel displays, such as liquid crystal displays (
LCD), plasma display (FDP), EL display, fluorescent display tube (VFD), etc., each of which has its advantages and disadvantages, has been put into practical use. Among them, LCDs using active matrix are seen as promising not only as displays for man-machine interfaces but also as screens for home televisions. However, the brightness and contrast of the LCD screen is
There are weaknesses in terms of performance, which are far behind RT displays.

Therefore, recently, as a means to cover the weaknesses of LCDs, backlight type LCDs in which a light source is provided on the back side of a liquid crystal panel have been developed. For example, as shown in FIG. 6, this backlight type LCD is composed of a liquid crystal active matrix 61 equipped with drive elements and drive circuits using TPT formed on a transparent substrate, and a backlight using a plurality of fluorescent lamps 62. There is. With this configuration, the brightness and contrast performance of the screen can be significantly improved compared to a reflective LCD.

However, this type of display has the following problems. That is, because fluorescent lamps are used as backlights, flattening is insufficient, and because a small number of thin fluorescent lamps are used close to the liquid crystal active matrix, there is a problem of large uneven brightness on the display surface. there were.

(Problem to be solved by the invention) As described above, conventionally, a flat light source with no uneven brightness is required for the backlight of a liquid crystal display, but it is difficult to satisfy this requirement with a conventional light source using a fluorescent lamp. Met.

The present invention has been made in consideration of the above circumstances, and its object is to provide a light source for illumination that can be applied to backlights of liquid crystal displays, etc., and has relatively small unevenness in brightness.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to apply an ultra-small cold cathode tube in which an emitter and a collector for field emission are arranged in a plane as a light emitting source, and to generate a surface-emitting light as a whole. The aim is to realize this.

That is, the present invention provides a planar illumination light source used for backlights of liquid crystal displays, etc., which includes a plurality of electron-emitting emitters provided on one principal surface of a substrate and emitting electrons upon application of an electric field; an electron collector electrode provided on one main surface of the substrate excluding the installation part and collecting the electron beam emitted from the emitter; a light-emitting thin film provided on the collector electrode and emitting light upon excitation of the electron beam;
The present invention is characterized in that it includes a transparent sealing body which is disposed opposite to the entire surface of the substrate and maintains a region in which the emitter, collector electrode, and light emitting thin film are arranged in a vacuum.

Further, in a preferred embodiment of the present invention, at least three electron collector electrodes are provided for one electron emission emitter.
It is characterized by forming R, G, and B light emitting thin films on different collector electrodes for one electron-emitting emitter, and emitting either R, G, or B light by selecting the electron collector electrode. shall be. Furthermore, at least a part of the surface of the transparent sealing body facing the substrate is formed of a conductive material, and this conductive part is set at a positive potential to cause electrons to collide to generate secondary electrons and deflect the electrons. It is characterized by

(Function) According to the present invention having the above configuration, it is possible to realize a flat planar light source with small unevenness in brightness for the following reasons.

First, flattening will be explained. In the present invention, a plurality of electron-emitting emitters are installed on the substrate surface, and an electron collector electrode and a light-emitting thin film are formed for each emitter. Therefore, the scanning range of the electron source is small; A large distance between the light emitting surfaces is not required. Moreover, since the electron source and the light emitting surface are arranged in the planar direction of the substrate rather than in the thickness direction, there is no need to increase the void ffjJ in the thickness direction, and the overall structure can therefore be made flat. Also,
In a preferred embodiment of the present invention, secondary electrons are generated by causing electrons to collide with a transparent sealing body facing the substrate, and as a result, the direction of the electrons is changed, so that the trajectory is not restricted by the energy of the electron beam. This makes electron scanning much easier, and flattening can be performed more easily.

Next, unevenness in brightness will be explained. In the present invention, a plurality of electron-emitting emitters are formed on the substrate surface, and these emitters can be formed in extremely precise alignment using, for example, Si micromachining technology. Therefore,
It is possible to reduce the unevenness in brightness caused by the density of the light emitting parts. In addition, since the light is extracted from the light-emitting surface side of the light-emitting thin film, rather than from the opposite side of the light-emitting surface like in a CRT, there is no attenuation of light due to the thickness of the light-emitting thin film, and the light emission efficiency is improved. It becomes possible to reduce uneven brightness.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is for explaining the schematic structure of the iJ< surface light source according to the first embodiment of the present invention, (a) is a plan view, (a) is a plan view;
b) is a sectional view. In the figure, reference numeral 11 denotes a Si substrate, and a plurality of electron-emitting emitters 12 are formed on this substrate 11. The electron emitters 12 are, for example, electron emitters of a field emission mechanism formed by silicon micromachining technology, and are arranged in a matrix on the substrate 11.

An insulating film 1 is formed on the substrate 11 except for the emitter 12.
3 is formed, and an electron collector electrode 15 is formed on this insulator film 13. The end of this collector electrode 15 does not coincide with the end of the insulator film 13, and
It is located far inward from the edge of the A light-emitting thin film 16 is formed on the electron collector electrode 15 to be excited and emit light when irradiated with an electron beam. As this light emitter #film 16, for example, a phosphor that emits white light is used.

Above the substrate 11, a transparent sealing body 18 made of, for example, glass is arranged to face the substrate 11, and the space between them is kept in a vacuum. Although not shown in the figure, the substrate 1
1 includes a drive element and a drive circuit, and each drive element is electrically connected to an electron emission emitter 12 and an electron collector electrode 15. The potential of each electrode is, for example, a negative potential for the electron emission emitter 12, and a positive potential for the electron collector electrode 15 suitable for the material of the light emitter.

In the plane light source configured in this way, the electron beam emitted from the electron emitter 12 is
The electron collides with the electron collector electrode 15 with energy corresponding to the potential difference between the electron beam and the electron collector electrode 15. At this time, the light emitter thin film 16 on the collector electrode 15 is excited and emits light. This light is then emitted to the outside through the transparent sealing body 18. Here, since the light-emitting thin film 16 is formed on substantially the entire surface of the substrate, surface light emission is possible and it functions as a flat light source.

Thus, according to this embodiment, the electron-emitting emitters 12 . An electron collector electrode 15, a light emitter thin film 16, etc. are formed, and electrons from the emitter 12 are transferred to the collector electrode 15.
By causing the light-emitting thin film 16 to emit light by colliding with
A flat light source can be realized. And in this case,
Since the light-emitting thin film 16 is formed on substantially the entire surface of the substrate surface, it is possible to make the light emission uniform on the substrate surface, and it is possible to extremely reduce unevenness in brightness as a light source. Furthermore, since light is extracted from the light emitting surface side of the light emitting thin film 16, it is also possible to improve the light emission efficiency.

FIG. 2 is for explaining a second embodiment of the present invention, in which (a) is a plan view and (b) is a sectional view. In addition, the first
The same parts as those in the figures are given the same reference numerals, and detailed explanation thereof will be omitted. In this embodiment, the emitted light is colored.

In the previous embodiment, the collector electrode was common to all emitters, but in this embodiment, a collector electrode is provided for each emitter to form a unit light emitting element, and these unit light emitting elements are arranged in a matrix. ing.

That is, an electron emitting emitter 12 is provided at the center of the unit light emitting device.
are formed, and four control electrodes 14 are independently formed around this electron emitting emitter 12 with an insulating film 13 interposed therebetween. Around the control electrode 14, four electron collector electrodes 1 having different areas are arranged with an insulating film 13 interposed therebetween.
5 is formed. And these collector electrodes 1
A light-emitting thin film 16 is formed on each of the light-emitting elements 5, which is excited by the electron beam and emits one of RGB.

The potentials applied to the electron collector electrode 15 are R and G, respectively.
, B to obtain an electron beam with energy suitable for the material of the light emitter. The area of the electron collector electrode 15 on which R, G, and B light emitting films are formed is the same as that of each light emitting thin film 1.
．． 6, it is formed in proportion to the product of the luminous efficiency for the electron beam with each energy and the human visual sensitivity.

An electronic shield 17 consisting of one electrode is formed around the electron collector electrode 15 with an insulating film 13 interposed therebetween. This electronic shield 17 includes each electron collector electrode 15.
It is also formed between the electrodes 15, and not only isolates the unit light emitting elements but also isolates the electron beam between the electrodes 15.

With such a configuration, by appropriately setting the potential of each electrode 12, 14, 15, the electron beam emitted from the electron emitter 12 is guided to the electron collector electrode 15, and the light emitter thin film on the collector electrode 16 can be made to emit light.

For example, the potential of each electrode is set such that the electron emitter 12 is at a negative potential, the control electrode 14 is also at a negative potential, the electron collector electrode 15 is at a positive potential suitable for each of the R, G, and B light emitter materials, and the electron shield 17 is at a negative potential. Suppose that In this case, the electrons emitted from the electron emitter 12 are quantitatively controlled and deflected by the negative potential of the control electrode 14, and then sent to a certain electron collector electrode 15 due to the potential difference between the electron emitter 12 and the electron collector electrode 15. They collide with corresponding energy. At this time, the light-emitting thin film 16 on the collector electrode 15 is excited to emit specific R, G, and B light, and this light is emitted to the outside through the transparent sealing body 18.

Thus, according to this embodiment, it is possible to emit light of any one of R, G, and B, and it is also possible to emit light of other colors or white by combining not just one of R, G, and B but a plurality of them. Therefore, it can be used as a color light source that can change the color of emitted light.

FIG. 3 is a sectional view showing a schematic configuration of a third embodiment of the present invention. Note that the same parts as in FIG. 2 are given the same reference numerals, and detailed explanation thereof will be omitted.

The feature of this embodiment is that the transparent sealing body 1 facing the substrate 11
The reason is that a part 34 of the surface of 8 is made conductive. In this case, by setting a positive potential on the conductive surface 34, electrons are caused to collide with the surface 34 to generate secondary electrons,
It can multiply and deflect electrons. In this example, since the energy of the electron beam necessary for light emission can be selected based on the potential difference between the conductive surface 34 and the electron collector electrode 15, there is an advantage that the degree of freedom regarding the potential of the electron-emitting emitter 12 is greatly increased. Furthermore, since it uses electron collision, it is possible to send electrons to the substrate side without applying an unreasonable electric field. Note that the conductive surface 34 may be at a constant potential throughout the device. The conductive surface 34 can also be formed, for example, by slightly reducing glass with heat in a hydrogen atmosphere and then etching away unnecessary portions.

FIG. 4 is a sectional view showing a schematic configuration of a fourth embodiment of the present invention. Note that the same parts as in FIG. 3 are given the same reference numerals, and detailed explanation thereof will be omitted. In addition to the configuration shown in FIG. 3, this embodiment is characterized in that at least a portion 35 of the conductive surface 34 on which electrons collide is processed into a convex shape to facilitate horizontal deflection of secondary electrons. It is in. If you do this,
It is also possible to keep the thickness of the vacuum part to 10 μm or less.

FIG. 5 is for explaining the fifth embodiment of the present invention, and is a perspective view showing an example in which the flat light source according to the present invention is applied to a backlight of a liquid crystal display. The liquid crystal display device is composed of a liquid crystal active matrix 61 formed on a transparent substrate and provided with driving elements and driving circuits using TPT, and a flat light source 62 according to the present invention.

Note that 63 in the figure indicates the position of the electron emission emitter.

As a feature of this embodiment, by using the transparent substrate of the liquid crystal active matrix 61 as the transparent sealing body of the flat light source 62 according to the present invention, further flattening can be realized.

Note that the present invention is not limited to the embodiments described above. In the embodiment, an example has been described in which the present invention is applied to a backlight of a liquid crystal display, but the present invention is not limited to backlights and can be used for indoor lighting, etc. In addition, in the example, an electron emitting emitter, an electron collector electrode, a light emitter thin film, etc. were formed on a flat substrate surface, but by forming these on a curved substrate surface, it is possible to create a curved planar light source. It is also possible to realize In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, an ultra-small cold cathode tube in which an emitter and a collector for field emission are arranged in a plane is applied as a light source, and surface emission is achieved as a whole. Therefore, it is possible to realize a flat illumination light source with small brightness unevenness, which can be applied to backlights of liquid crystal displays, etc.

[Brief explanation of the drawing]

FIG. 1 is for explaining the schematic configuration of a flat light source according to the first embodiment of the present invention, (a) is a plan view, (b) is a plan view.
2 is a sectional view, FIG. 2 is a plan view, (b) is a sectional view, and FIG. 3 is a third embodiment of the present invention. 4th cross-sectional view showing the schematic configuration of
The figure is a sectional view showing a schematic configuration of a fourth embodiment of the present invention, Figure 5 is a perspective view showing an example in which the present invention is applied to a backlight of a liquid crystal display, and Figure 6 is a backlight using the conventional technology 1 is a perspective view showing the structure of a type liquid crystal display. DESCRIPTION OF SYMBOLS 11... Substrate, 12... Electron emission emitter, 13... Insulator film, 14... Control electrode, 15... Electron collector electrode, 16... Luminescent thin film, 17... Electron Shield, 18... Transparent sealing body, 34... Conductive surface, 35... Convex portion.

Claims (1)

[Claims] A plurality of electron-emitting emitters are provided on one main surface of a substrate and emit electrons upon application of an electric field, and electron beams emitted from the emitters are collected on one main surface of the substrate excluding a portion where the emitters are installed. an electron collector electrode provided on the collector electrode that emits light upon excitation of an electron beam, and a region where the emitter, the collector electrode, and the light emitter thin film, which are arranged to face one main surface of the substrate, are placed in a vacuum. 1. A light source for illumination, comprising: a transparent sealing body for holding the material.