JP4183330B2 - Liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device integrally provided with reflection and transmission.
[0002]
[Prior art]
Conventionally, there is a so-called reflective liquid crystal display device having a function of reflecting light incident from the observation direction and viewing the display, and a function of viewing light by transmitting light from the opposite side of the observer and viewing the display. A reflection type and transmission type liquid crystal display device in which a so-called transmission type liquid crystal display device is integrated has been proposed.
[0003]
4 is a cross-sectional view of a conventional reflective and transmissive liquid crystal display device taken along line AA in FIG. 1, and FIG. 5 is a cross-sectional view taken along line BB in FIG.
[0004]
As shown in FIGS. 4 and 5, a conventional reflective and transmissive liquid crystal display device has a thin film transistor (hereinafter referred to as “TFT”) as a switching element on an insulating substrate 10 made of quartz glass, non-alkali glass or the like. .) Is formed.
[0005]
First, a gate electrode 11 made of a refractory metal such as chromium (Cr) and molybdenum (Mo), a gate insulating film 12 and an active layer 13 made of a polycrystalline silicon film are sequentially formed on an insulating substrate (TFT substrate) 10. Form.
[0006]
The active layer 13 is provided with a channel 13c above the gate electrode 11, and on both sides of the channel 13c, a source 13s and a drain 13d formed by ion implantation using the stopper insulating film 14 on the channel 13c as a mask. ing.
[0007]
Then, an interlayer insulating film 15 in which an SiO ₂ film, an SiN film, and an SiO ₂ film are stacked in this order is formed on the entire surface of the gate insulating film 12, the active layer 13, and the stopper insulating film 14, and provided corresponding to the drain 13d. The drain electrode 16 is formed by filling the contact hole with a metal such as aluminum (Al). Further, a planarizing insulating film 17 made of, for example, an organic resin and flattening the surface is formed on the entire surface. Then, a contact hole is formed at a position corresponding to the source 13s of the planarization insulating film 17, and it is a transparent electrode made of ITO (Indium Tin Oxide) in contact with the source 13s through the contact hole and also serving as the source electrode. A transparent display electrode 19 is formed on the planarization insulating film 17. Then, an alignment film 20 made of an organic resin such as polyimide is aligned on the transparent display electrode 19 to align the liquid crystal 21. Further, on the side opposite to the side on which the transparent display electrode 19 is provided, a retardation plate 22, a polarizing plate 23, and a semi-transmissive mirror 24 are laminated in this order from the TFT substrate 10 side. The semi-transmissive mirror 24 has a function of reflecting and transmitting incident light.
[0008]
Further, the counter electrode substrate 30 made of an insulating substrate facing the TFT substrate 10 is provided with a black matrix 32 having red (R), green (G), and blue (B) colors and a light shielding function on the TFT substrate 10 side. And a protective film 33 made of resin formed thereon, a counter electrode 34 made of ITO and an alignment film 35 formed on the entire surface of the color filter 31, and the opposite side, that is, the observer A polarizing plate 44 is arranged on the side 101. Then, the periphery of the counter electrode substrate 30 and the TFT substrate 10 is bonded with a seal adhesive (not shown), and the gap formed thereby is filled with twisted nematic (TN) liquid crystal 21.
[0009]
A backlight 51 as a light source is provided on the TFT substrate 10 side of the liquid crystal display device thus completed.
[0010]
Here, how light travels when used as a reflective liquid crystal display device will be described.
[0011]
Natural light 100 incident from the outside is incident from the polarizing plate 44 on the viewer 101 side as indicated by a broken-line arrow in FIG. 5, and is opposed to the counter electrode substrate 30, the color filter 31, the protective film 33, the counter electrode 34, and the orientation. The film 35, the TN liquid crystal 21, the alignment film 20 on the TFT substrate 10, the transparent display electrode 19, the planarization insulating film 17, the interlayer insulating film 15, the gate insulating film 12, the TFT substrate 10 and the polarizing plate 23 are transmitted and semi-transmissive. The light is reflected by the mirror 24, then passes through each layer in the direction opposite to the incident direction, is emitted from the polarizing plate 44 on the counter electrode substrate 30, and enters the observer's eyes 101.
[0012]
Further, when used as a transmissive liquid crystal display device, when the light 102 of the backlight 51 is incident from the TFT substrate 10 side, it is transmitted through the semi-transmissive mirror 24 as shown by the solid line arrow in FIG. Further, the polarizing plate 23, the TFT substrate 10, the gate insulating film 12, the interlayer insulating film 15, the planarizing insulating film 17, the transparent display electrode 19, the alignment film 20, the TN liquid crystal 21, the alignment film 35, the counter electrode 34, and the protective film 33. The light passes through the color filter 31, the counter electrode substrate 30, and the polarizing plate 44 and enters the eyes of the observer 101.
[0013]
[Problems to be solved by the invention]
However, as shown in FIG. 5, in the case of using as a reflection type, when the incident natural light enters and travels as indicated by the dashed arrow 100, the light reflected by the semi-transmissive mirror 24 is emitted from the glass. The TFT substrate 10 is transmitted again. For this reason, there has been a drawback that parallax due to the thickness of the glass substrate occurs between the incident light and the emitted light.
[0014]
Further, for example, light incident on the red display pixel (R) is emitted to the adjacent green display pixel (G), and as a result, blurring of R and G colors occurs as a display. There was a drawback of becoming.
[0015]
Accordingly, the present invention has been made in view of the above-described conventional drawbacks, and an object of the present invention is to provide a reflection / transmission integrated liquid crystal display device capable of obtaining a display with no parallax and no color blur. .
[0016]
[Means for Solving the Problems]
The liquid crystal display device of the present invention includes a first substrate including a thin film transistor connected to a plurality of gate signal lines and a plurality of drain signal lines, and an island-shaped reflective display electrode made of a reflective material connected to the thin film transistor, A counter electrode made of a transparent conductive material provided to face each of the reflective display electrodes, and a reflector for reflecting light incident from the first substrate side to the first substrate side. And a second substrate provided at a location corresponding to the first substrate, filled with a liquid crystal having negative dielectric anisotropy and oriented perpendicularly to the first and second substrates. A polarizing plate and a retardation plate are respectively provided on the sides of the first and second substrates that are not filled with the liquid crystal, and the polarizing plate and the retardation plate are circularly polarized in the same direction as viewed from the second substrate side. Are arranged so as to produce
[0017]
Further, the present invention is a liquid crystal display device in which a material that does not cause a phase difference of light incident from the first substrate side is disposed between the reflector and the reflective display electrode.
[0018]
Furthermore, the present invention is the liquid crystal display device in which the material that does not cause the phase difference is an acrylic resin.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
A liquid crystal display device having both the reflection and transmission functions of the present invention will be described below.
[0020]
FIG. 1 is a plan view of the liquid crystal display device of the present invention, FIG. 2 is a sectional view taken along line AA in FIG. 1, and FIG. 3 is a sectional view taken along line BB in FIG. Indicates.
[0021]
As shown in FIG. 1, the reflective display electrode 50 connected to the TFT provided near the intersection of the plurality of gate signal lines G and the plurality of drain signal lines D is provided in an island shape. Accordingly, an opening 60 is formed between the reflective display electrodes 50. Light from a backlight 51 described later is transmitted through the opening 60. The opening 60 is provided so as to overlap with the reflector 61 provided above the opening 60. The reflector 61 is formed in a band shape with a reflective material such as Al. It is preferable that the width of the drain signal line D is larger than the width of the opening 60 so that incident light can be completely reflected.
[0022]
Further, as shown in FIG. 2, a TFT as a switching element is formed on an insulating substrate 10 made of quartz glass, non-alkali glass or the like.
[0023]
Since the process from the formation of the gate electrode 11 made of a refractory metal such as Cr or Mo on the one insulating substrate (TFT substrate) 10 to the formation of the planarization insulating film 17 is the same as the conventional structure, the description is omitted. .
[0024]
On the planarization insulating film 17, a reflective display electrode 50 made of a conductive reflective material such as Al or silver (Ag) connected to the source 13s of the active layer 13 made of a polycrystalline silicon film is formed. As shown in FIGS. 1 and 3, the reflective display electrode 50 is provided with a window 60 formed by removing a part of the central portion of the reflective display electrode 50 from the conductive reflective material. On the reflective display electrode 50, a color filter 31 having R, G, and B colors is provided. Note that the color filter 31 is not provided on the window 60. A protective film 33 made of acrylic resin or the like for protecting the color filter 31 is provided on the color filter 31 and the window 60, and an alignment film 20 made of polyimide or the like for aligning the liquid crystal 21 is formed thereon.
[0025]
The other counter electrode substrate 30 is provided with a reflector 61 made of a metal such as Al that reflects light and having a shape corresponding to the window 60 provided in each reflective display electrode 50 on the side where the liquid crystal 21 is provided. The surface of the reflector 61, that is, the TFT substrate 10 side, may have an uneven shape in order to diffuse incident light. Further, the cross-sectional shape of the reflector 61 may be a hemispherical shape or a triangular shape other than that shown in FIG. In a region other than the reflector 61, a counter electrode 34 facing each reflective display electrode 50 is provided. Further, an alignment film 35 made of polyimide is formed on the entire surface. A black matrix 32 made of black resin or the like is provided between the reflective display electrodes 50, that is, around the reflective display electrodes 50 at positions corresponding to the drain signal lines D in order to improve the contrast by shielding light. ing.
[0026]
A phase difference (λ / 4) plate 43 and a polarizing plate 44 are sequentially provided from the counter electrode substrate 30 side on the side of the counter electrode substrate 30 where the liquid crystal 21 is not disposed, that is, the viewer 101 side.
[0027]
The counter electrode substrate 30 thus formed and the periphery of the TFT substrate 10 are bonded with a seal adhesive (not shown), and the liquid crystal 21 is filled into the gap formed thereby to complete a reflection / transmission integrated liquid crystal display device. Let The liquid crystal 21 has negative dielectric anisotropy and is a liquid crystal aligned perpendicular to both the TFT substrate 10 and the counter electrode substrate 30. A light source 51 such as a backlight is provided on the TFT substrate 10 side.
[0028]
Here, how light travels when used as a reflective liquid crystal display device in the above-described liquid crystal display device will be described.
[0029]
Natural light 100 incident from the counter electrode substrate 30 side on the viewer 101 side enters from the polarizing plate 44 on the viewer 101 side as shown by a dotted arrow in FIG. It passes through the counter electrode substrate 30, the alignment film 35, the liquid crystal 21, the alignment film 20, the protective film 33, and the color filter 31 to reach the reflective display electrode 50 made of a reflective material. The reached light is reflected by the reflective display electrode 50, travels along the reverse optical path that is incident again, exits to the outside, and is observed by the observer 101.
[0030]
Here, the polarization state of light when used as a reflection type will be described. In the following description of the polarization state, a case where a voltage is applied to the liquid crystal will be described.
[0031]
Light incident from the counter electrode substrate 30 side on the viewer 101 side passes through the polarizing plate 44 and becomes linearly polarized light, and becomes, for example, clockwise circularly polarized light by the phase difference plate 43 and passes through the liquid crystal 21 of the liquid crystal layer. The light becomes elliptically polarized light. In the polarization state, the light reaches the reflective display electrode 50 and is reflected to invert the phase. By passing through the liquid crystal 21 again, it becomes counterclockwise circularly polarized light and reaches the phase difference plate 43 again. Then, it is transmitted as linearly polarized light that vibrates in the same direction as the transmission axis of the polarizing plate 44 and is emitted to the viewer 101 side.
[0032]
Next, how light travels when the above-described liquid crystal display device is used as a transmission type will be described.
[0033]
As shown by a solid line in FIG. 3, the light 102 emitted from the backlight 51 includes a polarizing plate 23, a retardation plate 22, a TFT substrate 10, a gate insulating film 12, an interlayer insulating film 15, a planarizing insulating film 17, Then, the light passes through the opening 60 between the reflective display electrodes 50, is reflected by the reflector 61 formed on the counter electrode substrate 30, enters the color filter 31, and reaches the reflective display electrode 50. Then, it is reflected again and passes through the color filter 31, the protective film 33, the alignment film 20, and the liquid crystal 21, and the alignment film 35 on the counter electrode substrate 30, the counter electrode 34, the counter electrode substrate 30, the retardation plate 43, and the polarization The light is transmitted through the plate 44 and is observed by the observer 101.
[0034]
Here, the polarization state of light when used as a transmission type will be described.
[0035]
As indicated by a solid line in FIG. 3, the light 102 emitted from the backlight 51 passes through the polarizing plate 23 to become linearly polarized light, and then becomes, for example, clockwise circularly polarized light by the phase difference plate 22. Thereafter, the light passes through the opening 60, passes through the liquid crystal 21 of the liquid crystal layer, and reaches the reflector 61. At this time, since there is no electrode in the region of the opening 60, no voltage is applied to the liquid crystal 21 in the region of the opening 60. Since the liquid crystal 21 is a liquid crystal having a negative dielectric anisotropy, the liquid crystal 21 is aligned perpendicular to both the substrates 10 and 30 when no voltage is applied, and therefore there is a phase difference between the opening 60 and the reflector 61. Does not occur. Accordingly, the light reaches the reflector 61 while being left-handed circularly polarized light, and the phase is inverted by the reflector 61 to become right-handed circularly polarized light.
[0036]
Then, the light whose phase is reversed by the reflector 61 to become clockwise circularly polarized light changes from circularly polarized light to elliptically polarized light when passing through the liquid crystal 21 of the liquid crystal layer. In the polarization state, the light reaches the reflective display electrode 50 and is reflected there to reverse the phase. Thereafter, the light passes through the liquid crystal 21 again to become counterclockwise circularly polarized light, reaches the phase difference plate 43, becomes linearly polarized light that vibrates in the same direction as the transmission axis of the polarizing plate 44, passes through, and exits to the viewer 101 side. .
[0037]
In the above description, the direction of the circular polarization of light indicates the direction with respect to the traveling direction of light. Further, in the description of the case of using the reflection type as described above, the case where the circularly polarized light is clockwise rotated by the phase difference plate 43 is shown, but the direction of the circularly polarized light after being reflected by the reflector 61 and the case of the reflection type are shown. If the direction of circularly polarized light after passing through the phase difference plate 43 is set to be the same, the case of counterclockwise circularly polarized light may be used.
[0038]
As described above, the polarization state of light reaching the reflective display electrode 50 when used as a reflective liquid crystal display device is the same as the polarization state of light reaching the reflective display electrode 50 when used as a transmissive type. One liquid crystal display device can have both a reflection type and a transmission type function.
[0039]
Further, since the reflective display electrode 50 is provided on the inner side of the TFT substrate 10, that is, on the liquid crystal layer 21 side, it is possible to suppress the occurrence of parallax due to the thickness of the glass substrate even when used as a reflective type. In addition, it is possible to suppress color bleeding caused by light transmitted through a display pixel of a certain color being transmitted through an adjacent display pixel and emitted.
[0040]
In the above-described embodiment, the case where the liquid crystal 21 is disposed between the opening 60 and the reflector 61 corresponding to the opening 60 has been described. However, the present invention is not limited thereto, and Even if a material such as an acrylic resin that does not cause a phase difference is inserted, the same effect as in the present invention can be obtained. Specifically, when the acrylic resin is formed on the TFT substrate 30 and the counter electrode substrate 30 and the periphery of both substrates are bonded together, the acrylic resin is applied on the protective film 33 and then the photolithography technique is used. An acrylic resin having a rectangular or square cross section is formed between the drain signal line D and the drain signal line D.
[0041]
In this embodiment, polycrystalline silicon is used as the active layer of the TFT. However, the present invention is not limited to this, and the effect of the present invention can be achieved even if a semiconductor material such as amorphous silicon is used. It plays.
[0042]
Furthermore, in the present invention, a conductive reflective material other than Al and silver may be used as the reflective display electrode material.
[0043]
Further, in the present embodiment, the case where the opening is provided between the reflective display electrodes adjacent in the row direction is shown, but the present invention is not limited to this, and between the reflective display electrodes adjacent in the column direction. It can also be adopted when an opening is provided in the.
[0044]
【The invention's effect】
According to the present invention, it is possible to obtain a liquid crystal display device having no parallax, no color blur, and both functions of reflection and transmission.
[Brief description of the drawings]
FIG. 1 is a plan view of a liquid crystal display device integrated with reflection and transmission according to the present invention.
FIG. 2 is a cross-sectional view of the reflective and transmissive integrated liquid crystal display device of the present invention along the line AA in FIG.
FIG. 3 is a cross-sectional view of the reflective and transmissive integrated liquid crystal display device of the present invention along the line BB in FIG. 1;
4 is a cross-sectional view of a conventional reflective and transmissive integrated liquid crystal display device corresponding to line AA in FIG.
5 is a cross-sectional view of a conventional reflective and transmissive integrated liquid crystal display device corresponding to the line BB in FIG. 1. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 TFT substrate 13 Active layer 15 Interlayer insulating film 16 Drain electrode 17 Flattening insulating film 19 Transparent electrode 21 Liquid crystal 30 Counter electrode substrate 31 Color filter 22, 43 Phase difference plate 23, 44 Polarizing plate 50 Reflective display electrode 60 Opening 61 Reflection Body G Gate signal line D Drain signal line

Claims (3)

Each connected plurality of thin film transistors to a plurality of gate signal lines and a plurality of drain signal lines, and a first substrate having a plurality of island-shaped reflective display electrode made of a reflective material connected to each of said plurality of thin film transistors A counter electrode made of a transparent conductive material provided to face each of the reflective display electrodes, and a reflector that reflects light incident from the first substrate side to the first substrate side. A second substrate provided at a location corresponding to the intermediate substrate, and filled with a liquid crystal having negative dielectric anisotropy and aligned perpendicularly to the first and second substrates, On the side of the first and second substrates not filled with the liquid crystal , a retardation plate and a polarizing plate are provided in order from the respective substrates ,
The phase difference plate and polarizing plate convert light incident on the liquid crystal into substantially circularly polarized light,
The retardation plate and the polarizing plate are incident from the second substrate side, reflected from the reflective display electrode and emitted to the second substrate side, and incident from the first substrate side. The light reflected by the reflector and the reflective display electrode and emitted to the second substrate side is viewed from the second substrate side before passing through the polarizing plate on the second substrate side. A liquid crystal display device arranged to generate circularly polarized light in the same direction.   The liquid crystal display device according to claim 1, wherein a material that does not cause a phase difference of light incident from the first substrate side is disposed between the reflector and the reflective display electrode.   The liquid crystal display device according to claim 2, wherein the material that does not cause the phase difference is an acrylic resin.

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