KR200308060Y1 - LCD back light by using electro organic electro lminescence element - Google Patents

Abstract

The present invention is a flat light source made of a linear organic electroluminescence element instead of a conventional light source by a light emitting diode (LED) or a fluorescent lamp (CCFL) surface contact the light incident surface of the light guide to uniformity and A low power consumption LCD backlight with greatly improved brightness.

Description

LCD back light by using electro organic electro lminescence element

The present invention relates to a backlight panel used as a light source of a liquid crystal display (LCD), and in particular, a linear organic electroluminescent device (organic electroluminescent device) instead of a conventional light source by a light emitting diode (LED) or a fluorescent lamp (CCFL) It is to provide a low-power LCD backlight with uniformity and brightness greatly improved by the plane contact of the lminescence element surface contact with the light incident surface of the light guide.

As the development of the information society accelerates, people are exposed to a variety of information. Representative devices that allow a person to be in direct contact with such information include a display for visually presenting the various types of information as images.

Conventionally, a cathode ray tube (Cathod Ray Tube) has been most commonly used as such a display device, but recently, a flat panel display (FPD: Flat Panel Display) has a problem of heavy weight and bulkiness and high power consumption. Is being replaced.

The flat panel display includes a liquid crystal display (LCD), a plasma display (PDP), a vacuum fluorescent display (VFD), a field emission display (FED), and an electroluminescence display (ELD). Among them, LCD, which is low in power consumption, bulky and low voltage, is widely used, and is known to occupy more than 80% of the flat panel display market.

However, unlike other flat panel displays, LCDs do not have self-luminous capability and require a back light. Currently used LCD backlights include a light guide plate backlight using an LED light source or a CCFL light source, and an electroluminescent (EL) backlight in the form of a sheet.

The light guide plate backlight is mainly used for a large area display or a color display such as a TFT-LCD, and is also widely used when a luminance of 1,000 cd / m ² or more is required.

In addition, the EL backlight is widely used for black and white LCDs, PCS terminals, portable communication devices and measuring devices such as pagers requiring luminance of about tens of cd / m ² , but the luminance is 60 cd / m ² to 80 cd / m ² is very low, so the color LCD, there do not apply.

In addition, LED backlight is used for color because its brightness is about hundreds of cd / m ² higher than that of EL. However, when the number of LEL chips is increased, the power consumption is disadvantageous. have.

As a backlight for small LCDs such as mobile phones and DPAs, distributed thick film EL or LED backlights have been mainly used.

Recently, due to the colorization of LCDs, the thick film type EL is not used because of low luminance, and a backlight using an LED chip has become the mainstream.

The LCD module is a structure in which an LCD panel, a light guide plate, a light source, a back light, and a printed circuit board (PCB) are mounted and mounted on a square frame shaped mold frame. Here, LED panel is mainly used in small LCD, and the power terminal of LED panel is inserted into the insertion hole of PCB and fixed by soldering.

The LED panel is formed in a structure in which a PCB substrate having an LED chip is fixed to both sides of a rectangular light guide plate. In addition, the light guide plate of the LED panel diffusely reflects the light generated from the LED to improve the uniformity of the brightness, so that the optically designed light reflection pattern is printed on the lower surface of the light guide plate with an ink such as acrylic, so I am controlling the amount.

1 shows a plan view of a conventional LCD backlight 2 composed of a light guide plate and an LED light source.

First, the rectangular light guide 20 accommodated in the mold frame 8 is an opaque plate material coated with a suspension coating film such as acrylic, and the LED 4 as a light source on one side or both sides of the light guide 20. A large number of mounted PCB 6 is installed. In addition, the light guide body 20 corresponding to the LED 4 has a structure in which a semicircular shape 20b is recessed for efficient incidence of light.

However, in the conventional light guide 20, the luminance gradually decreases as the light emitted from the LED 4, which is a light source, moves away from the light source.

In addition, due to the difference in the spatial distance between the LED and the LED, the brightness of the center portion 20a of the front of the LCD is relatively lowered, resulting in a hot spot phenomenon that causes an overall brightness unevenness.

In addition, the electroluminescent device can be used as a display of mobile communication equipment such as a mobile phone, PDA, etc., because the power consumption is low, lightweight and thin, and can also be used as a display of a computer monitor and a television receiver.

It is generally recognized as a high quality display used for special applications such as computers, military, avionics and aerospace industries where features such as high reliability, low weight and low power consumption are important.

In addition, electroluminescent displays have particular advantages over other displays, such as cathode ray tubes (CRTs) and liquid crystal displays (LCDs), so their use is expanding in automotive, personal computers, and other industries.

Inorganic electroluminescent devices (inorganic ELDs), which are inorganic phosphors such as ZnS and Mn, which are a class of electroluminescent devices, are developed and commercialized in various models, but operate in electric fields of several tens of volts and have various color expressions. Due to the disadvantage of difficulty, there is a limitation as a color display element, and in recent years, the color expression part has been greatly improved by the color filter combination type, but there is a problem that it is still difficult to overcome the characteristics of operating in the high field.

Against this backdrop, (thin film) organic electroluminescence (OLEM) devices with organic phosphors as their light emission centers have recently been developed and applied to various industrial fields with active research, and have been recognized for their infinite potential as display devices.

For example, Eastman Kodak's Tang et al. Developed an organic thin film electroluminescent device having a laminated structure having an amorphous light emitting layer capable of emitting light with high brightness and being driven by low voltage power in 1987. .

Since then, research and development have been conducted to obtain red, green, and blue trichromatic light emission, increase in luminescence stability, and luminance in each direction, and a lot of research and development have been carried out regarding suitable lamination structure and manufacturing method, and suitable lamination structure and manufacturing method. R & D has been performed on the back.

It is essential that the organic electroluminescent device is capable of stable emission of three primary colors, that is, red, green, and blue. However, there have been no reports on materials capable of stable emission of red or blue with good chromaticity with good luminance besides green emission.

New organic materials have been invented through molecular design and the like, and active research has begun to enable the application of thin organic electroluminescent display devices having excellent characteristics including self-luminescence for color displays.

In general, an organic electroluminescent device is composed of a plurality of layers of different materials. This layer typically consists of a transparent front electrode layer, an electroluminescent layer and a back electrode layer.

When a voltage is applied to these electrodes, the electroluminescent layer is activated to convert some of the electrical energy passing through the electroluminescent layer into light.

This light is then emitted through the front electrode layer, which is transparent to the emitted light so that the user of the device can see it.

In the case of the organic light emitting device, the luminance is thousands of cd / m ² is very high compared to the conventional thick film type EL backlight, it can be manufactured thin, and the direct current (DC) drive is possible, no inverter is required. In addition, the driving voltage is about 10V, low power consumption, and has the advantages of not generating noise to the LCD module or circuit components.

Therefore, the present invention uses a flat light source using an organic light emitting device to contact or bond the light incident surface of the light guide (light guide plate, etc.) and use it as a light source of the backlight, so that the LCD backlight of high brightness is uniform even at low power consumption. The purpose is to provide.

In addition, the present invention is a light source using an organic light emitting device is configured in a linear or line shape in accordance with the thickness and length of the light guide to contact or bonded to the light incident surface of the light guide to achieve a total light incident. do.

In addition, an object of the present invention is to use a plurality of linear organic electroluminescent devices to greatly improve luminance and luminance uniformity.

In order to achieve the above object, an organic electroluminescent device as a light source is formed by forming an ITO electrode layer, a hole transport layer, an electroluminescent layer, an electron transport layer, and a metal electrode layer on a transparent glass substrate. It becomes a heterostructure.

The organic light emitting diode is configured to have a linear or line shape having the same length or the same area as the light incident surface of the light guide so as to be incident to the light guide in full surface contact.

Further, when the driving power source DC is applied to the anode ITO transparent electrode layer and the cathode metal electrode layer, holes as the charge carriers move to the electroluminescent layer through the hole transport layer, and the electrons of the metal electrode layer are the electron transport layer. The light of a predetermined wavelength, which is generated by recombination of electrons and holes through the ITO transparent electrode layer and the glass substrate, is incident to the light guide (light guide plate) through the ITO transparent electrode layer and then is reflected and diffusely reflected on the front surface of the light guide so that high luminance is achieved even at low power consumption. Of uniform illumination is achieved.

The electroluminescent layer may be made of a light emitting material such as anthracene, naphthalene, phenanthrene, pyrene, chrysene, perylene, butadiene, coumarin, acridine, stilbene, and the electron transport layer may contain such a light emitting material. .

1 is a plan view of a conventional LCD backlight using an LED light source.

2 is an external perspective view of an LCD backlight having a linear organic electroluminescent device of the present invention as a light source.

3 is a perspective view of another embodiment of the present invention FIG. 2.

4 is a cross-sectional view of an organic light emitting display device of the present invention.

5 is a block diagram of a linear organic electroluminescent device of the present invention.

6 is a light emission principle of the present invention.

<Explanation of symbols for the main parts of the drawings>

(10)-light source (organic electroluminescent element) (11)-glass substrate

(12)-ITO transparent electrode layer (anode layer) (13)-hole transport layer

(14)-Electroluminescent Layer (15)-Electron Transport Layer

(16)-metal electrode layer (cathode layer) (19)-LCD module

(20)-Light guide (light guide plate)

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 and 3 are perspective views of the present invention using the thin film organic electroluminescent device as the light source 10.

FIG. 2 is an external perspective view of the thin film type light source 10 in contact with or bonded to one light incident surface of the light guide 20 so as to be illuminated, and FIG. 3 illustrates the thin film type light source 10 of the light guide 20. It is an external perspective view of the state which contacted or bonded to both light incident surfaces, respectively, and was made to illuminate with high brightness and high uniformity.

The light source 10 forms a gap between the LCD module and the light guide 20, and then inserts the organic light emitting device into close or interference fit to prevent the flow thereof, or to the light incident surface of the light guide 20. The light source 10 may be contacted or bonded and then mounted in the LCD module 19.

In addition, the light source 10 is brought into contact with the light incident surface of the light guide 20 by using a separate gripping means or clamping means, or the light source 10 is light incident by the light guide 20 using a transparent binder. It can be fixed by bonding to a surface.

Since the light source 10 is very thin and flexible, having a thickness of about 1 μm or less, the light source 10 may be bonded or contacted as a single body even if the light incident surface of the light guide 20 is curved or curved.

Therefore, the shape of the light guide 20 can be diversified into a circle, a triangle, a polygon, an oval or a shape in which they are deformed.

In addition, the light source 10 using the organic light emitting device is formed in a linear or line shape in accordance with the thickness and length of the light guide 20 so that the entire light incident on the side surface of the light guide 20 is achieved by a hot spot ( In addition to preventing hot spots, the luminance and luminance uniformity are greatly improved, and power consumption is greatly reduced.

The light source 10 converts electrical energy, which is an ideal feature of the self-luminous display element, into optical energy when the current is supplied, and has a thickness of 1 μm or less, and has a luminance of 1,000 cd / m ² or more with sufficient color image expression. Has In addition, the inverter is unnecessary because the DC drive is possible, and the driving voltage is about 10V, so the power consumption is low, so that noise is not generated in the LCD module 19 or various circuit components.

In addition, the light guide 20 and the light source 10 are accommodated or embedded in the interior space of the LCD module 19, and a reflective surface (mirror) is formed or mirror-treated on the inner wall of the LCD module 19 so that light Loss is prevented as much as possible.

In the case of FIG. 3, the light sources 10 are respectively provided on both light incident surfaces of the light guide 20, but, of course, although not shown in the drawing, not only both sides of the light guide 20 are provided. Each light source 10 may also be contacted or bonded to the front and rear surfaces of 20) to greatly increase the luminance and uniformity of the luminance.

The organic light emitting device used as the light source 10 in the present invention is composed of a plurality of layered materials of different physical properties. 4 is a cross-sectional view illustrating a layer structure of the organic light emitting display device, and FIG. 6 illustrates a light emission principle of the organic light emitting display device.

Looking at the layer structure of the organic electroluminescent device, ITO (Indium Tin Dxide) (In ₂ O ₃ : SnO ₂ ) transparent electrode layer (anode layer) 12, holes on the glass substrate 11 that is a transparent protective plate The low work function metal electrode layer (cathode) 16, such as the transport layer (HTL) 13, the electroluminescent layer (EML) 14, the electron transport layer (ETL) 15, and the aluminum electrode, has a single hetero structure. After the layer structure, it is manufactured into a thin film having a thickness of 1 μm or less by a vacuum deposition method, a printing method, or a spin coating method.

The hole transport layer 13 serves to transfer holes of the ITO transparent electrode layer 12 to the electroluminescent layer 14, and the electron transport layer 15 transfers electrons of the metal electrode layer 16 to the electroluminescent layer 14. Will pass.

Accordingly, when the driving voltage DC is applied to the two electrode layers 12 and 16, the electroluminescent layer 14 is activated, and in this state, the charge carrier hole moves to the electroluminescent layer 14 through the hole transport layer 13. The electrons of the metal electrode layer 16 move to the electroluminescent layer 14 through the electron transport layer 15 to recombine electrons and holes. When holes and electrons recombine, excitons are formed, and light of a predetermined wavelength is emitted by radiative recombination of the excitons through the ITO transparent electrode layer 12 and the glass substrate 11 positioned at the front surface. Most of incident light is incident on the light incident surface of the light guide 20 so that the LCD is uniformly illuminated with high brightness (luminance of 1,000 cd / m ² or more).

The electroluminescent layer 14 may be made of a light emitting material such as anthracene, naphthalene, phenanthrene, pyrene, chrysene, perylene, butadiene, coumarin, acridine, stilbene, and the like. In addition, the electron transport layer may contain such a light emitting material.

In addition, since the organic light emitting device is a linear organic light emitting device, a reflection shade for reflecting light of a light emitting source to a light guide plate is unnecessary as in the prior art, and it is not necessary to form the recessed groove of the semicircular shape 20b in the light guide portion facing the light source. .

And, since the light source 10 of the present invention is a thin film type, not only can reduce the volume and weight, but also the thin film type light source 10 is brought into contact with the light incident surface of the light guide 20 so that the installation is simple and easy to maintain. Has the advantage.

In addition, the present invention has a brightness of thousands of cd / m ² , which is very high compared to the conventional thick film type EL backlight, can be manufactured thinly, and can be driven by direct current (DC), thus eliminating the need for an inverter and having a low driving voltage of 10V. The power consumption is low, and there is an advantage such as not generating noise to the LCD module 19 or the circuit components.

The present invention as described above is not limited to the present embodiment and the accompanying drawings, various substitutions, modifications and changes are possible within the scope without departing from the technical spirit of the present invention, which is usually in the art It is self-evident for those who have knowledge.

As described above, the present invention uses a linear organic electroluminescent element, which is a planar light source, as an LCD backlight, so that the uniformity and uniformity of conventional LCD backlights using light emitting diodes (LEDs) or fluorescent lamps (CCFLs) can be achieved. The brightness is greatly improved and power consumption is greatly reduced.

In addition, the present invention has an effect that the hot spot phenomenon is prevented because the light source has a uniform linear luminance and thus greatly improves the uniformity of the luminance.

In addition, the present invention is a planar light source, so it is easy to design and manufacture the light guide, and the shape of the light guide is circular, triangular, polygonal, elliptical, or various modifications thereof.

In addition, the present invention does not need to use a raw member such as a PCB can reduce the manufacturing cost, there is an effect that the design of the electrode unit for driving can be easily and freely.

In addition, the present invention is a useful design that can simplify the manufacturing process of the backlight module, increase the effective area of the backlight, free the entire design, and the like.

Claims (5)

In constructing the backlight of the LCD in which the light source is installed in the light incident surface of the light guide; An LCD backlight having a light source as an organic light emitting device, characterized in that the backlight light source is an organic light emitting device that is in contact with the light incident surface of the light guide. The method according to claim 1; An organic electroluminescent device is an LCD backlight using a linear organic electroluminescent device as a light source, characterized in that the linear organic electroluminescent device. The method according to claim 2; The linear organic electroluminescent device is an LED backlight using a linear organic electroluminescent device as a light source, wherein the linear organic electroluminescent device is a single heterostructure in which an ITO transparent electrode layer, a hole transport layer, an electroluminescent layer, an electron transport layer, and a metal electrode layer are layered on a glass substrate. The method according to claim 1 or 2; An LCD backlight using a linear organic electroluminescent device as a light source, characterized in that at least one light source is in surface contact with the light incident surface of the light guide. The method according to claim 1 or 2; An organic light emitting diode is an LCD backlight using a linear organic light emitting diode as a light source, characterized in that the flexible thin film type.