JP3071251B2 - Backlight unit for liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit for a liquid crystal display.

[0002]

2. Description of the Related Art A backlight unit used in a liquid crystal display comprises a light guide section, a reflection / diffusion section and a light source section.
Conventionally, light emitting diodes, tungsten balls, cold cathode tubes or hot cathode tubes have been used.

However, a backlight unit for a liquid crystal display using a tungsten bulb or a heat or cold cathode tube as a light source is difficult to make the display as a whole thin and lightweight. Also, the configuration has many parts, etc.
It is complicated and has problems in terms of cost.

In the case of a backlight unit for a full-color liquid crystal display, a white light source is required as a light source unit. However, there is a problem in weight reduction and cost, and a device using a light emitting diode also has problems in luminance and whitening.

The present invention has been made in view of such circumstances of the prior art, and can be made thinner, lighter, and lower in cost, and has very good luminance and color reproducibility. It is an object to provide a backlight unit for a liquid crystal display.

[0006] The present inventors have found that a result of extensive investigations to solve the above problems, back for a full-color liquid crystal display
The light generated by the light source is reflected and expanded as a light unit.
The light is reflected and diffused by the diffuser, and the light guide is
Full color LCD display buckler that functions as a guide
Light unit in the light source unit
Thus, and the organic electroluminescent element is an anode and
Cathode and at least one organic layer sandwiched between them
And an organic electroluminescent device comprising an end portion of the light guide portion.
Monolithically formed organic with three primary colors
An organic electroluminescent device comprising an electroluminescent element,
A member in which one electrode of the element and the reflection diffusion portion are continuous
Full-color liquid crystal display
By using the backlight unit for spray ,
The inventors have found that the above object can be achieved, and have completed the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIGS. 1A and 1B are a cross-sectional view and a plan view, respectively, showing an outline of a configuration example of a backlight unit for a liquid crystal display according to the present invention. In the figure, reference numeral 1 denotes a light guide portion, which can be made of a suitable material such as plastic or glass as needed. Further, in order to obtain a uniform light emitting surface, one or both surfaces may be subjected to diffusion processing or light guiding processing, or such a layer may be provided adjacently. Reference numeral 2 denotes a reflection / diffusion unit, and a metal mirror, a white diffusion plate, or the like can be used.
Reference numeral 3 denotes a light-emitting portion using an organic electroluminescent element, and its cross section is shown in an enlarged scale in FIG. As shown in FIG. 2, the light emitting section 3 composed of the organic electroluminescent element is formed by sequentially laminating a transparent anode 5, a hole transport layer 6, a light emitting layer 7, and a cathode 8 on a glass substrate 4. Conventionally known components can be used for each component, and different layer configurations such as providing an electron transport layer depending on the material used can also be used. In this backlight unit, the light source may be arranged on both sides as shown in FIG. 1 or only on one side if a sufficient amount of light can be obtained.
In addition, four sides may be surrounded to make the light emission more uniform.

In the case where a single light source color is used in the backlight unit, the light emitting portion 3 can be configured in a line shape. When a white light source color is desired, as shown in FIG. In this case, the organic electroluminescent elements of the three primary colors of R, G, and B are alternately arranged. In the latter case, it is very effective as a backlight unit for a full-color liquid crystal display. In this case, an appropriate pattern may be selected in consideration of workability and whitening.

FIG. 4 is a cross-sectional view showing a backlight unit of another configuration example according to the present invention, and the same components as those in FIG. 1 are denoted by the same reference numerals. This configuration example is different from the configuration example of FIG.
Is that the light guide portion 1 is formed monolithically using the end portion as a substrate. Therefore, the light generated by the light emission of the light emitting unit 3 is guided to the light guide unit 1 with high efficiency, and a backlight having higher performance can be obtained. Incidentally, 9 in the figure is a light shielding portion.

FIG. 5 is a sectional view showing a backlight unit of still another configuration example according to the present invention, and the same components as those in FIG. 1 are denoted by the same reference numerals. This configuration example is different from the configuration example of FIG. 1 in that the light emitting section 3 using the organic electroluminescent element is formed monolithically using the end of the light guide section 1 as a substrate, and one of the electrodes of the light source section 3 is reflected and diffused. This is a point formed in common with the part 2. Therefore, the configuration of the backlight unit is simpler, and the productivity is improved.

[0011]

Next, embodiments of the present invention will be described. Example 1 On a glass substrate, a transparent anode made of ITO, a hole transport layer made of a compound represented by the following formula 1 (500 °), a light emitting layer made of a compound represented by the following chemical formula 2 (500 °),
A cathode (1500 °) made of aluminum was sequentially laminated to form a linear light source section (light emitting section) using an organic electroluminescent device having a configuration as shown in FIG. In addition, ITO was formed by sputtering, and the others were formed by vacuum evaporation. This light source unit was used in a configuration as shown in FIG. 1 to provide a backlight unit according to the present invention. When the backlight unit was driven by being connected to a power supply, a uniform green high-luminance planar light-emitting unit could be obtained.

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Example 2 A backlight unit according to the present invention was produced in the same manner as in Example 1, except that organic electroluminescent elements of the following three primary colors were alternately arranged at a pitch of 4 mm as a light source. . The configuration of the green light emitting section was the same as that of the first embodiment. The red light emitting portion was configured so that the light emitting layer of Example 1 was doped with a compound represented by the following formula (3). Further, the blue light emitting portion was configured to use a compound represented by the following formula 4 as the light emitting layer and a compound represented by the following formula 5 as the electron transport layer. When the backlight unit manufactured as described above was connected to a power supply and driven, a uniform white high-luminance planar light-emitting unit could be obtained.

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Embodiment 3 Embodiment 1 is the same as Embodiment 1 except that the light source section is monolithically formed at the end of the light guide section using the light guide section as a substrate as shown in FIG.
In the same manner as in the above, a backlight unit according to the present invention was produced. When the backlight unit was connected to a power supply and driven, a uniform green planar light emitting unit with higher luminance could be obtained.

Embodiment 4 As shown in FIG. 5, the light source section of Embodiment 1 is formed monolithically at the end of the light guide section using the light guide section as a substrate, and furthermore, the electrodes of the light source section are formed in common with the reflection section. A backlight unit according to the present invention was manufactured in the same manner as in Example 1, except that the electrode and the reflecting portion were continuous members. When the backlight unit was driven by connecting a power source, it exhibited the same performance as that of the third embodiment.

[0015]

According to the first to third and fourth aspects of the present invention,
With the above structure, a thin, light-weight, high-brightness planar illuminant can be obtained, which is very useful as a backlight unit for a liquid crystal display. According to the second aspect of the present invention, in addition to these effects, a white planar illuminant having high luminance and excellent color reproducibility can be obtained, which is very useful as a backlight unit for a full-color liquid crystal display. is there.

[Brief description of the drawings]

FIGS. 1A and 1B are a cross-sectional view and a plan view, respectively, showing a configuration of a backlight unit of one configuration example according to the present invention.

FIG. 2 is a cross-sectional view illustrating a structure of a light emitting unit using an organic electroluminescent element.

FIG. 3 is a diagram showing an arrangement of R, G, and B organic electroluminescent elements when a white light source color is used.

FIG. 4 is a cross-sectional view illustrating a configuration of a backlight unit of another configuration example according to the present invention.

FIG. 5 is a cross-sectional view illustrating a configuration of a backlight unit of still another configuration example according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light-guide part 2 Reflection-diffusion part 3 Light-emitting part 4 Glass substrate 5 Transparent anode 6 Hole transport layer 7 Light-emitting layer 8 Cathode 9 Light-shielding part

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshihiko Takahashi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (72) Inventor Taketo Yamaguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (56) References JP-A-60-130715 (JP, A) JP-A-58-50475 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1 / 13357 G09F 13/22 F21V 8/00 601

Claims (1)

(57) [Claims] 1. The light generated by a light source section is reflected by a reflection / diffusion section.
The light is diffused and guided to the back of the display by the light guide section.
Backlight unit for full color LCD
The light source unit is constituted by an organic electroluminescent element.
And the organic electroluminescent element is an anode and a cathode.
At least one organic compound layer sandwiched between them
And the organic electroluminescent element forms an end of the light guide with a substrate.
Monolithically formed organic electroluminescence of three primary colors
And an organic electroluminescent device.
One electrode and the reflection diffusion portion are formed by a continuous member.
Full color liquid crystal display characterized by being
Backlight unit.