JP4183329B2 - 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]
A liquid crystal display device according to the present invention includes a display pixel region in which a plurality of gate signal lines made of a reflective material and a plurality of drain signal lines made of a reflective material are surrounded and arranged in a matrix. A thin film transistor connected to the thin film transistor, a first substrate provided with a transparent electrode connected to the thin film transistor in the display pixel region, and a reflective display electrode made of a reflective material provided in an island shape facing the transparent electrodes And a second substrate having an opening disposed between the reflective display electrodes and in a position overlapping with the drain signal line or the gate signal line, and has a negative dielectric anisotropy. In addition, a liquid crystal aligned perpendicularly to the first and second substrates is filled, and a polarizing plate and a retardation plate are provided on the side of the first and second substrates not filled with the liquid crystal, respectively. The bias Plate and retardation plate are those arranged to produce the same direction of the circularly polarized light when viewed from the second substrate side.
[0017]
The present invention is the liquid crystal display device in which a material that does not cause a phase difference of light incident from the second substrate side is disposed between the drain signal line or the gate signal line and the opening. .
[0018]
Furthermore, the present invention is a 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, a reflective display electrode 50 is provided in a display pixel region surrounded by a plurality of gate signal lines G and a plurality of drain signal lines D.
[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 one insulating substrate (TFT substrate) 10 to the formation of the planarization insulating film 17 is the same as the conventional structure, the description thereof is omitted.
[0024]
On the planarizing insulating film 17, a transparent electrode 34 made of a transparent conductive material such as ITO connected to the source 13s of the active layer 13 made of a polycrystalline silicon film is formed.
[0025]
Further, as shown in FIGS. 1 and 3, the drain signal line D surrounding the display pixel region is disposed so as to be positioned in the opening 60 between the reflective display electrodes 50. Therefore, light incident from the counter electrode substrate 30 side passes through the opening 60 and reaches the drain signal line D. Since the drain signal line D is made of a reflective material such as Al, it reflects the light transmitted through the opening 60.
[0026]
The other counter electrode substrate 30 is made of a conductive reflective material such as Al or silver (Ag) on the side where the liquid crystal 21 is provided, and the reflective display electrode 50 is formed at a position corresponding to the transparent electrode 34. On the reflective display electrode 50, a color filter 31 having R, G, and B colors is provided. A protective film 33 made of an acrylic resin or the like for protecting the color filter 31 is provided on the color filter 31, and an alignment film 35 made of polyimide or the like for aligning the liquid crystal 21 is formed thereon.
[0027]
Further, a phase difference (λ / 4) plate 43 and a polarizing plate 44 are provided in this order from the counter electrode substrate 30 side on the side where the liquid crystal 21 is not disposed.
[0028]
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.
[0029]
Here, how light travels when used as a reflective liquid crystal display device in the above-described liquid crystal display device will be described.
[0030]
Natural light 100 incident from the viewer 101 side enters from the polarizing plate 24 on the viewer 101 side as shown by a dotted arrow in FIG. 3, passes through the phase difference plate 23, and further enters the TFT substrate 10 and the gate. The reflective display electrode 50 made of a reflective material is transmitted through the insulating film 12, the interlayer insulating film 15, the planarizing insulating film 17, the transparent electrode 19, the alignment film 20, the liquid crystal 21, the alignment film 35, the protective film 33, and the color filter 31. To reach. The light that has reached there is reflected by the reflective display electrode 50, followed by a reverse optical path that is incident again, and then emitted to the outside and observed by the observer 101.
[0031]
Here, the polarization state of light when used as a reflection type will be described.
[0032]
Light incident from the TFT substrate 10 side passes through the polarizing plate 24 to become linearly polarized light, and becomes, for example, clockwise circularly polarized light by the phase difference plate 23, and circularly polarized light becomes 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 to invert the phase. By passing through the liquid crystal 21 again, it becomes counterclockwise circularly polarized light and reaches the phase difference plate 23 again. Then, it is transmitted as linearly polarized light that vibrates in the same direction as the transmission axis of the polarizing plate 24 and is emitted to the outside.
[0033]
Next, how light travels when the above-described liquid crystal display device is used as a transmission type will be described.
[0034]
As shown by a solid line in FIG. 3, the light 102 emitted from the backlight is a polarizing plate 44, a retardation plate 43, a counter electrode substrate 30, a protective film 33, an alignment film 35, a liquid crystal 21, an alignment film 20, and planarization. The light passes through the insulating film 17 and reaches the drain signal line D. The reached light is reflected to the counter electrode substrate 30 side by the drain signal line D and reaches the reflective display electrode 50, and further reflected by the reflective display electrode 50, the color filter 31, the protective film 33, the alignment film 35, and the liquid crystal. 21, the alignment film 20, the transparent electrode 19, the planarization insulating film 17, the interlayer insulating film 15, the gate insulating film 12, the TFT substrate 10, the phase difference plate 23, and the polarizing plate 24, and are emitted to the viewer 101 side.
[0035]
Here, the polarization state of light when used as a transmission type will be described.
[0036]
As indicated by a solid line in FIG. 3, the light 102 emitted from the backlight 51 passes through the polarizing plate 44 and becomes linearly polarized light, and then becomes counterclockwise circularly polarized light by the phase difference plate 43. Thereafter, it passes through the opening 60 and passes through the liquid crystal 21 of the liquid crystal layer to reach the drain signal line D. 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.
[0037]
Then, the light whose phase is inverted by the drain signal line D to become clockwise circularly polarized light changes from circularly polarized light to elliptically polarized light when passing through the liquid crystal 21. 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 23, becomes linearly polarized light that vibrates in the same direction as the transmission axis of the polarizing plate 24, and is transmitted to the outside.
[0038]
In the above description, the direction of the circularly polarized light has been described with respect to the traveling direction of each light. Further, in the description of the case of using as the reflection type, the case where the circularly polarized light is turned clockwise by the phase difference plate 23 is shown. However, as in the case of the transmission type, the circularly polarized light after being reflected by the drain signal line D is shown. In the case of the reflective type, the direction of the circularly polarized light after passing through the phase difference plate 43 may be set to be the same as that of the counterclockwise circularly polarized light.
[0039]
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.
[0040]
Further, since the reflective display electrode 50 is provided on the inner side of the counter electrode substrate 30, that is, on the liquid crystal layer 21 side, the occurrence of parallax due to the thickness of the glass substrate is suppressed even when the reflective display electrode 50 is 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.
[0041]
In the above-described embodiment, the case where the liquid crystal 21 is disposed between the opening 60 between the reflective display electrodes 50 and the drain signal line D corresponding to the opening 60 has been described. The present invention is not limited, and the same effects as those of the present invention can be obtained even when a substance such as an acrylic resin that does not cause a phase difference is inserted therein. 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.
[0042]
In this embodiment mode, 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 by using a semiconductor material such as amorphous silicon. It plays.
[0043]
Furthermore, in the present invention, a conductive reflective material other than Al and silver may be used as the reflective display electrode material.
[0044]
In the present embodiment, the case where the light incident from the counter electrode substrate 30 is reflected by the drain signal line D has been described. However, the present invention is not limited to this, and the openings between the reflective display electrodes 50 are not limited thereto. The present invention can also be applied to the case where the light transmitted through the portion 60 is reflected by the gate signal line G, and the same effects as those of the drain signal line D can be obtained.
[0045]
【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 G Gate Signal line D Drain signal line

Claims (3)

A plurality of gate signal lines made of a reflective material and a plurality of drain signal lines made of a reflective material, each having a display pixel region arranged in a matrix and intersecting with each other; and a thin film transistor connected to both the signal lines; and A first substrate provided with a transparent electrode connected to a thin film transistor in the display pixel region, a reflective display electrode made of a reflective material provided in an island shape facing the transparent electrodes, and between the reflective display electrodes And a second substrate having an opening disposed at a position overlapping the drain signal line or the gate signal line, and having a negative dielectric anisotropy and the first and second Comprising a liquid crystal aligned perpendicular to the substrate, each having a polarizing plate and a retardation plate on the side of the first and second substrates not filled with the liquid crystal,
The polarizing plate and the retardation plate provided on the first and second substrates, respectively, enter from the second substrate side, pass through the opening, and are reflected by the drain signal line or the gate signal line. After that, the light reflected by the reflective display electrode and emitted to the first substrate side is incident on the first substrate side, is reflected by the reflective display electrode, and is emitted to the first substrate side. the liquid crystal display device comprising a light, characterized in that that will be arranged to produce the same direction of the circularly polarized light when viewed from the second substrate side.   2. The material according to claim 1, wherein a material that does not cause a phase difference of light incident from the second substrate side is disposed between the drain signal line or the gate signal line and the opening. Liquid crystal display device.   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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