JP4666554B2 - Transmission and reflection type liquid crystal display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transmissive / reflective liquid crystal display device, and more particularly to a liquid crystal display device capable of switching between a reflective type and a transmissive type.
[0002]
[Prior art]
In the field of liquid crystal display devices, for example, in a liquid crystal display device for a mobile phone, a transmissive / reflective liquid crystal display device that allows a user to selectively use a reflective type and a transmissive type depending on circumstances such as the environment is known.
[0003]
One of them is that when a transflective mirror is placed on the back side of the transmissive liquid crystal display element and used in the reflective type, external light on the viewing side of the liquid crystal display element is reflected to the observing side by the transflective mirror on the back side In this case, when the display is used in a transmissive type, a backlight disposed on the back side of the semi-transmissive mirror is turned on so that the display can be observed with light transmitted through the semi-transmissive mirror.
[0004]
Another transmissive / reflective liquid crystal display device is configured by providing an opening in a reflective layer disposed on the side opposite to the observation side of each pixel of a reflective liquid crystal display element. The external light on the observation side of the element is reflected to the observation side by a reflection layer other than the opening on the back surface to enable the display to be observed, and when used in a transmission type, the backlight arranged on the back side of the reflection layer is turned on The display can be observed with the light transmitted through the opening (for example, “FLAT-PANEL DISPLAY 2001” pp. 123-124).
[0005]
In the latter case, R (red), G (green), and B (blue) color filters are uniformly provided as colored layers in the portions corresponding to the reflective layer openings of each pixel and the portions other than the openings. ing.
[0006]
[Problems to be solved by the invention]
By the way, as shown in FIGS. 3A and 3B, the transmittance distribution of a realistic color filter is related to the height of a mountain corresponding to a desired color (R, G, B) and other valleys. Typically, it is roughly divided into two types. (1) Mountains are high (100%) but valleys are high (not close to 0%) (Fig. 3 (b)), (2) Valleys are low (close to 0%), but mountains are low ( (It is not close to 100%) (FIG. 3A). (1) is a reflection type that originally has poor color reproducibility due to the use of external light. Since light needs to be transmitted twice back and forth, priority is given to the transmittance. Reproducibility is poor. (2) is adapted to the good color reproducibility of the transmissive type, but the luminance of the transmissive and reflective types decreases. This decrease in luminance is contrary to the reduction in power consumption required for mobile phones and the like, particularly in the case of a transmission type.
[0007]
As described above, when the reflective layer is provided with the opening and the liquid crystal display device of the transmissive type and the reflective type is used, if the same color filter is uniformly arranged in the opening and the non-opening, the one shown in FIG. If used, the luminance will decrease, particularly when used as a reflective type. On the other hand, when the one shown in FIG. 3B is used, there is a problem that the color reproducibility is deteriorated particularly when it is used as a transmission type.
[0008]
The present invention has been made in view of such problems of the prior art, and the object thereof is to provide a liquid crystal display device that is also used as a transmission type by providing an opening in the reflective layer of each pixel of a reflective liquid crystal display element. It is to obtain optimum color reproducibility and luminance regardless of whether the reflection type or the transmission type is used.
[0009]
[Means for Solving the Problems]
The transmissive / reflective liquid crystal display device of the present invention that achieves the above object includes a plurality of pixels of different colors in which different color filters are arranged on the observation side of the liquid crystal layer and a reflection layer is arranged on the opposite side of the liquid crystal layer. In a liquid crystal display device comprising a combination of
The reflection layer of each pixel is provided with an opening, and the wavelength distribution of the transmittance of the colored layer corresponding to the opening of the color filter of each pixel is different from that of the colored layer not corresponding to the opening. It is what.
[0010]
In this case, it is desirable that the transmittance of the colored layer in the portion not corresponding to the opening of the color filter of each pixel is set higher than the transmittance of the colored layer in the portion corresponding to the opening.
[0011]
Further, it is desirable that the transmittance is set so that the colored layer in the portion corresponding to the opening of the color filter of each pixel gives priority to color reproduction, and the colored layer in the portion not corresponding to the opening gives priority to light use efficiency.
[0012]
In addition, it is desirable to arrange a lighting device capable of lighting control on the opposite side of the reflection layer of each pixel to the observation side.
[0013]
In that case, a spectroscopic unit that splits light from the illumination device and makes the light incident on the opening of the reflection layer of the corresponding color pixel may be disposed.
[0014]
As the spectroscopic means, for example, there is a hologram color filter.
[0015]
In that case, it is desirable that a colored layer corresponding to the opening of the color filter of each pixel is a transparent layer.
[0016]
In the present invention, an opening is provided in the reflective layer of each pixel so that the wavelength distribution of transmittance differs between a colored layer corresponding to the color filter opening of each pixel and a colored layer corresponding to the opening of the color filter of each pixel. Therefore, when used as a reflection type liquid crystal display device, it is equivalent to a normal reflection type liquid crystal display device by using a colored layer having a wavelength distribution of transmittance corresponding to the reflection type in a portion not corresponding to the opening. Brightness, color reproducibility can be displayed, and when used as a transmissive liquid crystal display device, by using a colored layer having a wavelength distribution of transmittance corresponding to the transmissive type in a portion corresponding to the opening, Brightness and color reproducibility display equivalent to those of a normal transmissive liquid crystal display device can be achieved, and optimum color reproducibility and luminance can be obtained in any use form.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the transmissive / reflective liquid crystal display device of the present invention will be described below.
[0018]
FIG. 1 is a partial cross-sectional view (a) showing the configuration of a transmissive / reflective liquid crystal display device according to one embodiment of the present invention, and a plan view (b) showing the configuration of the color filter. This transmissive / reflective liquid crystal display device includes a liquid crystal display element 1 and a backlight light source 2 disposed on the back surface thereof. The liquid crystal display element 1 includes, for example, a TN liquid crystal display element or an STN liquid crystal display element. A liquid crystal layer 13 is sandwiched and sealed between the side transparent substrate 11 and the opposite transparent substrate 12. As shown in FIG. 1A, the liquid crystal layer 13 is virtually divided by a broken line, and the liquid crystal display element 1 is composed of R, G, and B pixels 3R, 3G, and 3B that are periodically repeated. A liquid crystal display element for color display. On the inner surface of the observation-side transparent substrate 11 on the liquid crystal layer 13 side, R, G, B color filters 14R, 14G, corresponding to the R, G, B pixels 3R, 3G, 3B, 14B is provided in a periodically repeating arrangement. The configuration of each color filter 14R, 14G, 14B will be described later. A transparent counter electrode or a transparent matrix electrode 15 is provided on the surface of the color filter layer 14 having such a repetitive arrangement of R, G, B color filters 14R, 14G, 14B, and an alignment layer (not shown) is provided on the surface. ing. On the other hand, a reflective layer 16 is provided on the inner surface of the opposite transparent substrate 12 on the liquid crystal layer 13 side, and this reflective layer 16 is provided with an opening 17 at the center of each pixel 3R, 3G, 3B. . A transparent pixel electrode or a transparent matrix electrode 18 is provided on the surface of the reflective layer 16, and an orientation layer (not shown) is provided on the surface. Further, polarizing plates 19 and 20 are arranged outside the transparent substrates 11 and 12 in a parallel Nicols state or a crossed Nicols state.
[0019]
The R, G, and B color filters 14R, 14G, and 14B are R, G, and B transmissive filters 14Ra, 14Ga, and 14Ba that are provided in portions corresponding to the openings 17 of the reflective layer 16, respectively. And R, G, and B reflective filters 14Rb, 14Gb, and 14Bb that cover the R, G, and B pixels 3R, 3G, and 3B. The transmission filters 14Ra, 14Ga, and 14Ba are respectively It has the transmittance distribution characteristics of R, G, and B shown in FIG. 3A, and the reflection type filters 14Rb, 14Gb, and 14Bb are respectively R, G, and B shown in FIG. It has transmittance distribution characteristics.
[0020]
With such a configuration, in a state where the backlight light source 2 is not turned on, the external light 21 from the observation side of the liquid crystal display element 1 is incident on the liquid crystal display element 1, and for example, the external light 21 incident on the G pixel 3G is The G color filter 14G is incident on the liquid crystal layer 13 through the reflective filter 14Gb and the transmissive filter 14Ga and reaches the reflective layer 16 on the back surface thereof, but the light that has passed through the transmissive filter 14Ga is reflected by the reflective layer 16. And will not be used because it will come back to the back surface. On the other hand, the external light 21 that has reached the reflection layer 16 through the reflection type filter 14Gb reaches the reflection layer 16 other than the opening 17 and is reflected, passes through the liquid crystal layer 13 from the opposite side again, and passes through the reflection type filter 14Gb to be reflected. Return to. Therefore, the reflected light is modulated by the liquid crystal layer 13 in accordance with the voltage state applied between the electrodes 15 and 18 of the pixel 3G, and the modulation is converted into intensity modulation by the polarizing plate 19. On the other hand, in a state where the backlight light source 2 is turned on, the liquid crystal display element 1 is illuminated with white illumination light 22 from the back surface, enters the liquid crystal layer 13 through the opening 17 of the reflective layer 16, and is observed through the transmission filter 14Ga. Go out to the side. Therefore, the transmitted light is modulated by the liquid crystal layer 13 in accordance with the voltage state applied between the electrodes 15 and 18 of the pixel 3G, and the modulation is converted into intensity modulation by the polarizing plate 19. The other R pixels 3R and B pixels 3B are the same in both the reflective type and the transmissive type, and in the case of the reflective type by combining the modulation states of these R, G, B pixels 3R, 3G, and 3B. Is capable of color display with high luminance, and in the case of a transmission type, color display with good color reproducibility is possible.
[0021]
FIG. 2 is a partial cross-sectional view showing a configuration of another embodiment in which a hologram color filter is arranged between the liquid crystal display element and the backlight to greatly improve the utilization efficiency of the backlight. In this embodiment, the hologram color filter proposed by the present applicant in Japanese Patent Laid-Open No. 6-222361 is premised. However, the present invention can be similarly applied to the case of using a hologram color filter of another principle. It will become clear from the following description.
[0022]
In the configuration of FIG. 2, the liquid crystal display element 1 includes R, G, B color filters 14R, 14G, 14B corresponding to the openings 17 of the reflective layer 16 in the case of FIG. The transmission type filters 14Ra, 14Ga, and 14Ba are different from each other in that the transparent portions 14Rt, 14Gt, and 14Bt are not colored in the case of FIG. 2, and the other configurations are the same. On the back side of the liquid crystal display element 1, a hologram color filter 30 is disposed in parallel away from the reflective layer 16 by the focal length of the light-collecting hologram element 30a. Here, the hologram color filter 30 is composed of an array of transmissive condensing hologram elements 30a. The hologram color filter 30 has a parallel white light from the light source when a backlight light source (not shown) is lit. Illumination light 22 is illuminated so as to be incident at a predetermined oblique incident angle. Therefore, the illumination light 22 is angle-divided into three convergent lights 22R, 22G, and 22B of R, G, and B by each hologram element 30a of the hologram color filter 30, and the three lights 22R, 22G, and 22B are R, G, and B, respectively. It is configured to enter the liquid crystal layer 13 through the openings 17 of the B pixels 3R, 3G, and 3B, and exit to the observation side without attenuation through the transparent portions 14Rt, 14Gt, and 14Bt of the color filters 14R, 14G, and 14B, respectively. . Therefore, the transmitted light is subjected to intensity modulation according to the modulation state of the pixels 3R, 3G, and 3B, and color display with higher efficiency, higher luminance, and good color reproducibility is possible. When the backlight light source (not shown) is not turned on, color display with high luminance can be performed in the same manner as in FIG.
[0023]
As described above, in the above embodiment, the hologram color filter 30 is considered to be composed of an array of transmissive condensing hologram elements 30a, but is composed of a combination of a uniform diffraction grating and a microlens. Diffractive white using a characteristic of high wavelength selectivity of diffraction angle, consisting of three layers of volume holograms having diffraction wavelength selectivity and angle selectivity, or one volume hologram You may use what diffracts the color component from which the incident angle in light differs in a different angle, and performs color spectroscopy.
[0024]
The transmissive / reflective liquid crystal display device of the present invention has been described based on the embodiments. However, the present invention is not limited to these embodiments, and various modifications can be made. The liquid crystal display element itself is not limited to the TN liquid crystal display element and the STN liquid crystal display element of the above embodiment, and can be applied to various known principles.
[0025]
【The invention's effect】
As is clear from the above description, according to the transmissive / reflective liquid crystal display device of the present invention, the reflective layer of each pixel is provided with an opening, and the colored layer corresponding to the opening of the color filter of each pixel Since the wavelength distribution of the transmittance is different from that of the colored layer in the portion not corresponding to the opening, when using as a reflective liquid crystal display device, the colored layer having the transmittance wavelength distribution corresponding to the reflective type is opened. When used as a transmissive liquid crystal display device, it is possible to display the same brightness and color reproducibility as a normal reflective liquid crystal display device. By using a colored layer with a wavelength distribution of the ratio in the part corresponding to the aperture, it becomes possible to display the same brightness and color reproducibility as a normal transmission type liquid crystal display device, and optimal color reproduction in any use form And brightness So as to.
[Brief description of the drawings]
FIG. 1 is a partial sectional view showing a configuration of a transmissive / reflective liquid crystal display device according to an embodiment of the present invention and a plan view showing a configuration of a color filter thereof.
FIG. 2 is a partial cross-sectional view showing a configuration of a transmissive / reflective liquid crystal display device according to another embodiment of the present invention.
FIG. 3 is a diagram illustrating an example of transmittance distribution of a color filter used in a transmissive liquid crystal display device and a reflective liquid crystal display device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display element 2 ... Backlight light source 3R, 3G, 3B ... R, G, B pixel 11 ... Observation side transparent substrate 12 ... Opposite side transparent substrate 13 ... Liquid crystal layer 14 ... Color filter layer 14R, 14G, 14B ... R , G, B color filters 14Ra, 14Ga, 14Ba... R, G, B transmissive filters 14Rb, 14Gb, 14Bb ... R, G, B reflective filters 14Rt, 14Gt, 14Bt ... Transparent portion 15 ... Transparent counter electrode or Transparent matrix electrode 16 ... reflective layer 17 ... opening 18 ... transparent pixel electrode or transparent matrix electrode 19,20 ... polarizing plate 21 ... external light 22 ... white illumination light 22R, 22G, 22B ... converged light 30 of R, G, B ... Hologram color filter 30a ... Light-collecting hologram element

Claims (2)

In a liquid crystal display device comprising a combination of a plurality of pixels of different colors in which different color filters are arranged on the observation side of the liquid crystal layer and a reflection layer is arranged on the opposite side of the liquid crystal layer,
An opening is provided in the reflective layer of each pixel,
An illumination device capable of controlling lighting is disposed on the opposite side to the observation side of the reflection layer of each pixel,
Dispersing the light from the illuminating device, and placing the spectroscopic means for entering the aperture of the reflective layer of the corresponding color pixel,
A transmissive / reflective liquid crystal display device , wherein a colored layer corresponding to the opening of the color filter of each pixel is a transparent layer . Transmissive and reflective type liquid crystal display device according to claim 1, wherein the spectroscopic means is equal to or der hologram color filter.

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