JP2004125963A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive liquid crystal display device in which double images hardly occur and besides the utilization factors of the external light and that of an organic EL device are heightened and which is thin in thickness. <P>SOLUTION: The liquid crystal display device is provided with a liquid crystal panel part A and a polymer network liquid crystal part C and the organic EL device D are integrally formed on the rear side thereof. In the polymer network liquid crystal part C, a polymer network liquid crystal layer 12 is formed between a transparent electrode 11 and a transparent electrode 13. The transparent electrode 13 functions as a common electrode and a positive electrode side of a power source 18 is connected thereto via a switch 17. A negative electrode side of the power source 18 is connected to the transparent electrode 11 and a reflection electrode 15. The polymer network liquid crystal layer 12 is constructed in such a way that when no voltage is applied thereto, it scatters and reflects incident external light L1 so as to form backscattering light L2, and when voltage is applied thereto, it transmits light emitted at an organic light emitting layer 14. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device that appropriately uses light from an internal organic EL (electroluminescence) element while using external light.
[0002]
[Prior art]
Conventionally, there is a liquid crystal display device that uses external light and appropriately uses light from an internal organic EL element to secure visibility and reduce power consumption. FIG. 1 shows a longitudinal section of the liquid crystal display device of FIG.
This liquid crystal display device includes a liquid crystal panel part A and an organic EL element B provided behind the liquid crystal panel part A.
The liquid crystal panel section A is formed by sealing a liquid crystal with transparent electrodes 2 formed on a pair of glass substrates 1 to form a liquid crystal layer 3, and attaching a polarizing plate 4 to the outside of the glass substrate 1.
The organic EL element B is configured by sequentially laminating a transparent electrode 6, an organic light emitting layer 7, and a reflective electrode 8 on a transparent substrate 5. The organic light emitting layer 7 emits light by applying a voltage between the transparent electrode 6 and the reflective electrode 8, and the light is used as a backlight. The reflective electrode 8 reflects external light incident on the liquid crystal panel portion A or light emitted from the organic light emitting layer 7 and emits the light to the liquid crystal panel portion A.
[0003]
In such a liquid crystal display device, in a bright place where the amount of external light is large, liquid crystal display using only external light is performed. That is, the light emitted from the organic EL element B is not emitted, and the external light incident on the liquid crystal panel section A is reflected by the reflective electrode 8 located at the rear end of the organic EL element B. After passing through the transparent electrode 6 and the transparent substrate 5, the light enters the liquid crystal panel portion A again, and display light according to the orientation state of the liquid crystal layer 3 is emitted from the liquid crystal panel portion A to perform liquid crystal display.
On the other hand, in a dark place where the amount of external light is small, liquid crystal display is performed by utilizing light emission from the organic EL element B. That is, a voltage is applied between the transparent electrode 6 and the reflective electrode 8 to cause the organic light-emitting layer 7 to emit light, and the light is reflected directly or by the reflective electrode 8 and enters the liquid crystal panel portion A, and the liquid crystal layer Liquid crystal display according to the alignment state of No. 3 is performed.
As described above, the visibility of the liquid crystal display is ensured by using the light emission of the organic EL element B only when the external light is weak, and the power consumption is suppressed without emitting the organic EL element B when the external light is strong. .
[0004]
However, in the above-described liquid crystal display device, since the surface of the reflective electrode 8 of the organic EL element B has a smooth surface and reflects the incoming external light like a mirror surface, it is necessary to specify the direction according to the direction of the external light. The intensity of the reflected light in the direction becomes strong, the illumination becomes non-uniform, and the viewing angle of the liquid crystal panel part A becomes narrow. Therefore, for example, in a liquid crystal display device disclosed in Patent Document 1, a diffusion plate is arranged between a liquid crystal panel section A and an organic EL element B to diffuse the direction of transmitted external light to perform uniform illumination and liquid crystal. The view angle of the panel section A is enlarged.
[0005]
[Patent Document 1]
JP-A-9-50031
[Problems to be solved by the invention]
However, the external light incident on the liquid crystal panel part A is transmitted through the liquid crystal panel part A, and then scattered in various directions by the diffusion plate, so that the transparent substrate 5, the transparent electrode 6, and the organic light emitting layer of the organic EL element B are formed. 7 is reflected by the reflective electrode 8, and then returns to the liquid crystal panel section A along the reverse path for use. For this reason, there is a problem in that light loss occurs in each of the above-described elements through which the external light passes, and the amount of the external light decreases, thereby reducing the light use efficiency.
Further, since the organic EL element B has a certain thickness, an image formed by the incident light of the external light entering the liquid crystal panel section A and the external light entering the liquid crystal panel section A are reflected by the reflective electrode 8. There is also a problem that a double image with an image formed by the reflected light returning to the liquid crystal panel unit A is displayed from the liquid crystal panel unit A.
Furthermore, in the case of performing liquid crystal display using light emission from the organic EL element B, there is also a problem that the emitted light transmits through the diffusion plate to cause light loss, and the amount of light reaching the liquid crystal panel unit A decreases. there were.
In addition, there is a demand for an inexpensive, thin and thin liquid crystal display device, and it is desired that the liquid crystal display device has a simple internal structure and a dimension in the thickness direction as small as possible.
[0007]
SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a liquid crystal display device having a small thickness and an inexpensive liquid crystal display device which is less likely to generate a double image, improves external light and the light use efficiency of an organic EL element. The purpose is to provide.
[0008]
[Means for Solving the Problems]
A liquid crystal display device according to the present invention is a liquid crystal display device including a liquid crystal panel unit, an organic light emitting layer, and an organic EL element having a pair of organic EL electrodes sandwiching the organic light emitting layer. A polymer having a pair of network liquid crystal electrodes sandwiching the polymer network liquid crystal layer, and the polymer network liquid crystal layer performing one of back light scattering and light transmission depending on whether or not a voltage is applied to the pair of network liquid crystal electrodes. A network liquid crystal unit is provided between the liquid crystal panel unit and the organic EL element, and one of the network liquid crystal electrodes forms a common electrode integrated with one of the organic EL electrodes. .
Preferably, an organic light emitting layer, a common electrode, and a polymer network liquid crystal layer are stacked in this order toward the liquid crystal panel.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows the entire structure of a liquid crystal display device according to an embodiment of the present invention.
This liquid crystal display device includes a liquid crystal panel section A, and a polymer network liquid crystal section C and an organic EL element D are integrally formed behind the liquid crystal panel section A.
The liquid crystal panel portion A is a known one. For example, a liquid crystal layer 3 is formed by enclosing liquid crystal with transparent electrodes 2 formed on a pair of glass substrates 1 respectively, and a polarizing plate 4 is attached to the outside of the glass substrate 1. It is composed.
In the polymer network liquid crystal part C, a polymer network liquid crystal layer 12 is formed between a transparent electrode 11 made of ITO formed on a glass substrate 10 and a transparent electrode 13 also made of ITO. The polymer network liquid crystal layer 12 is a polymer network liquid crystal that is a liquid crystal / polymer composite material, and includes a mixture of liquid crystal molecular parts 12a and polymer network parts 12b. When no voltage is applied, the polymer network liquid crystal layer 12 scatters and reflects the incident external light L1, causing backward light scattering. On the other hand, when a voltage is applied, the polymer network liquid crystal layer 12 is configured to transmit light emitted from the organic light emitting layer 14.
As the polymer network liquid crystal part C, for example, PNLCD manufactured by Dainippon Ink and Chemicals, Inc. can be used. Here, the transparent electrodes 11 and 13 constitute a network liquid crystal electrode.
[0010]
The organic EL element D includes a transparent electrode 13 constituting a part of the polymer network liquid crystal part C as a component thereof, and an organic light emitting layer 14 is disposed on a lower surface of the transparent electrode 13. On its lower surface, an organic EL electrode for emitting light from the organic light emitting layer 14 and a reflective electrode 15 having a mirror surface made of, for example, a MgIn thin film functioning as a light reflecting plate are arranged, and a substrate 16 is further arranged.
The transparent electrode 13 functions as a common electrode between the network liquid crystal electrode and the organic EL electrode, and the positive electrode side of the power supply 18 is connected via the switch 17. The negative electrode side of the power supply 18 is connected to the transparent electrode 11 and the reflective electrode 15.
[0011]
Next, the operation of the liquid crystal display device according to the embodiment of the present invention will be described with reference to FIGS.
When liquid crystal display is performed using external light, the switch 17 is opened as shown in FIG. In this case, since no voltage is applied to the organic light emitting layer 14, the organic light emitting layer 14 does not emit light.
Since no voltage is applied to the polymer network liquid crystal layer 12, the liquid crystal molecules of the liquid crystal molecule portion 12a are arranged along the polymer network surface of the polymer network portion 12b, thereby causing a refractive index mismatch between the liquid crystal molecules and the polymer network. The external light L1 incident from the liquid crystal panel unit A is reflected toward the liquid crystal panel unit A in a scattered state, reenters the liquid crystal panel unit A, and the display light according to the alignment state of the liquid crystal layer 3 is converted to liquid crystal. The light is emitted from the panel unit A and a liquid crystal display is performed.
[0012]
As described above, the external light L1 incident on the liquid crystal panel unit A is reflected by the polymer network liquid crystal unit C, and returned to the liquid crystal panel unit A as backscattered light L2. Therefore, the light passes through the transparent electrode 13 and the organic light emitting layer 14, is reflected by the reflective electrode 15, and is transmitted again through the organic light emitting layer 14, the transparent electrode 13 and the polymer network liquid crystal part C and returned to the liquid crystal panel part A. Therefore, light energy is not absorbed by each element of the organic EL element D, and the amount of external light is hardly reduced and the light use efficiency is hardly reduced.
Further, since the distance from the liquid crystal panel part A to the polymer network liquid crystal part C is shorter than the distance from the liquid crystal panel part A to the reflective electrode 15 of the organic EL element D, the direct light of the external light and the polymer network liquid crystal part C Since the optical path difference from the reflected light at the optical path becomes short, the occurrence of double images is reduced.
[0013]
On the other hand, when performing liquid crystal display using light emission from the organic EL element D, the switch 17 is closed as shown in FIG. In this case, a voltage is applied between the transparent electrode 13 and the reflective electrode 15, and the organic light emitting layer 14 emits light.
Also, a voltage is applied between the transparent electrode 13 and the transparent electrode 11, the liquid crystal molecules of the liquid crystal molecule portion 12 a in the polymer network liquid crystal layer 12 are oriented in the direction of the electric field, and the refraction between the liquid crystal molecules and the polymer network is caused. Since the rates match, a state in which light is transmitted is formed in the polymer network liquid crystal part C.
Therefore, the light L3 emitted from the organic light emitting layer 7 passes through the polymer network liquid crystal part C toward the liquid crystal panel part A, and a liquid crystal display according to the alignment state of the liquid crystal layer 3 is performed.
As described above, since the liquid crystal of the polymer network liquid crystal part C is oriented in the direction of the electric field, light loss in the polymer network liquid crystal part C is small.
Further, by laminating the organic light emitting layer 14 and the polymer network liquid crystal layer 12 sequentially with the transparent electrode 13 as a common electrode interposed therebetween, one of the electrodes of the polymer network liquid crystal part C and the organic EL element D is formed. Can be shared. As a result, one electrode can be reduced, so that the cost can be reduced, the internal structure can be simplified, and the thickness of the liquid crystal display device can be reduced.
[0014]
【The invention's effect】
As described above, the liquid crystal display device according to the present invention has a polymer network liquid crystal having a polymer network liquid crystal layer and a pair of network liquid crystal electrodes sandwiching the polymer network liquid crystal layer between the liquid crystal panel and the organic EL element. Portion, and one of the network liquid crystal electrodes of the polymer network liquid crystal portion forms a common electrode integrated with one of the organic EL electrodes. It is possible to provide a thin and inexpensive liquid crystal display device while improving the light use efficiency.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a configuration of a liquid crystal display device according to an embodiment of the present invention and a state where no voltage is applied.
FIG. 2 is a longitudinal sectional view showing a state where a voltage is applied to the liquid crystal display device according to the embodiment of the present invention.
FIG. 3 is a longitudinal sectional view showing a configuration of a conventional liquid crystal display device.
[Explanation of symbols]
11: Transparent electrode (network liquid crystal electrode), 12: Polymer network liquid crystal layer, 13: Transparent electrode (network liquid crystal electrode, organic EL electrode, common electrode), 14: Organic light emitting layer, 15: Reflective electrode (organic EL) Electrodes), A: liquid crystal panel section, C: polymer network liquid crystal section, D: organic EL element.

Claims (2)

In a liquid crystal display device including a liquid crystal panel portion and an organic EL element having an organic light emitting layer and a pair of organic EL electrodes sandwiching the organic light emitting layer,
It has a polymer network liquid crystal layer and a pair of network liquid crystal electrodes sandwiching the polymer network liquid crystal layer, and depending on whether or not a voltage is applied to the pair of network liquid crystal electrodes, the polymer network liquid crystal layer can perform either backward light scattering or light transmission. A polymer network liquid crystal part performing the above operation is provided between the liquid crystal panel part and the organic EL element,
A liquid crystal display device wherein one of the network liquid crystal electrodes forms a common electrode integrated with one of the organic EL electrodes. 2. The liquid crystal display device according to claim 1, wherein an organic light emitting layer, a common electrode, and a polymer network liquid crystal layer are stacked in that order toward the liquid crystal panel portion.

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