JP3953338B2 - Liquid crystal display - Google Patents

Liquid crystal display Download PDF

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JP3953338B2
JP3953338B2 JP2002057306A JP2002057306A JP3953338B2 JP 3953338 B2 JP3953338 B2 JP 3953338B2 JP 2002057306 A JP2002057306 A JP 2002057306A JP 2002057306 A JP2002057306 A JP 2002057306A JP 3953338 B2 JP3953338 B2 JP 3953338B2
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Prior art keywords
electrode
liquid crystal
pixel
switch element
reflective
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JP2003255375A (en
Inventor
和弘 井上
真司 小川
信彦 小田
徳夫 小間
徹 山下
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三洋電機株式会社
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Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a configuration of a reflective or transflective liquid crystal display device having a reflective function.
[0002]
[Prior art]
Liquid crystal display devices (hereinafter referred to as LCDs) are characterized by being thin and have low power consumption, and are currently widely used as monitors for computer monitors and portable information devices. In such an LCD, liquid crystal is sealed between a pair of substrates, and display is performed by controlling the orientation of the liquid crystal formed on each substrate and positioned between the electrodes, such as a CRT (cathode ray tube) display, Unlike an electroluminescence (hereinafter, EL) display or the like, since it does not emit light in principle, a light source is required to display an image to an observer.
[0003]
Therefore, in a transmissive LCD, a transparent electrode is adopted as an electrode formed on each substrate, a light source is disposed behind or on the side of the liquid crystal display panel, and the amount of light transmitted through the light source is controlled by the liquid crystal panel. Bright display is possible even in the dark. However, since the display is always performed by turning on the light source, power consumption by the light source is inevitable, and sufficient contrast cannot be secured in an environment where the outside light is very strong such as outdoors in the daytime. .
[0004]
On the other hand, the reflective LCD employs external light such as the sun and room light as a light source, and reflects the ambient light incident on the liquid crystal panel by a reflective electrode formed on the substrate on the non-observation surface side. Then, display is performed by controlling the amount of light emitted from the liquid crystal panel, which is incident on the liquid crystal layer and reflected by the reflective electrode, for each pixel. As described above, since the reflective LCD employs external light as the light source, the display cannot be seen without external light. However, unlike the transmissive LCD, the power consumption by the light source is very low and the power consumption is very low. If the surroundings are bright, sufficient contrast can be obtained. However, this reflection type LCD has a problem that it is insufficient in comparison with a transmission type in terms of general display quality such as color reproducibility and display luminance.
[0005]
On the other hand, reflective LCDs with lower power consumption than transmissive LCDs are advantageous in situations where the demand for lower power consumption of devices is further strengthened, so attempts have been made to adopt them for high-definition monitor applications in portable devices. R & D is being conducted to improve display quality.
[0006]
FIG. 5 shows a planar structure (first substrate side) per pixel of a conventional active matrix reflective LCD having a thin film transistor (TFT) for each pixel. FIG. 5 shows a schematic cross-sectional structure of a reflective LCD at a position along line 5 of CC.
[0007]
The reflective LCD is configured such that a liquid crystal layer 300 is sealed between a first substrate 100 and a second substrate 200 which are bonded to each other with a predetermined gap. As the first and second substrates 100 and 200, a glass substrate, a plastic substrate, or the like is used. At least in this example, a transparent substrate is used as the second substrate 200 disposed on the observation surface side.
[0008]
On the liquid crystal side surface of the first substrate 100, a TFT 110 is formed for each pixel. A data line 136 for supplying a data signal to each pixel is connected to, for example, a drain region of the active layer 120 of the TFT 110 via a contact hole formed in the interlayer insulating film 134. 134 and a contact hole formed so as to penetrate the planarization insulating film 138, the pixel is connected to a first electrode (pixel electrode) 150 formed in an individual pattern for each pixel.
[0009]
As the first electrode 150, Al, Ag or the like having a reflection function is used, and an alignment film 160 for controlling the initial alignment of the liquid crystal layer 300 is formed on the reflection electrode 150.
[0010]
In the case of a color display device, color filters (R, G, B) 210 are formed corresponding to each pixel electrode 150 on the liquid crystal side of the second substrate 200 disposed opposite to the first substrate 100. A transparent electrode 250 using a transparent conductive material such as ITO (Indium Tin Oxide) is formed on the second electrode. On the transparent electrode 250, an alignment film 260 similar to that on the first substrate side is formed.
[0011]
The reflective LCD has the above-described configuration, and performs a desired display by controlling the amount of light incident on the liquid crystal panel, reflected by the reflective electrode 150, and again emitted from the liquid crystal panel for each pixel. .
[0012]
[Problems to be solved by the invention]
The LCD is not limited to the reflective type, and the liquid crystal is driven with an AC voltage to prevent burn-in. In the transmissive LCD, both the first electrode on the first substrate and the second electrode on the second substrate are required to be transparent, and both employ ITO as an electrode material. Therefore, when the liquid crystal is AC driven, the first and second electrodes can apply positive and negative voltages to the liquid crystal under substantially the same conditions.
[0013]
However, as shown in FIG. 6, in a reflective LCD using a reflective electrode made of a metal material as the first electrode 150 and a transparent electrode made of a transparent metal oxide material such as ITO as the second electrode 250, depending on driving conditions, In some cases, display flickering or liquid crystal burn-in problems occur. This is remarkable, for example, when the liquid crystal is driven at a critical flicker frequency (CFF) or less recently reported. The driving below CFF is a liquid crystal driving frequency (≈ liquid crystal (liquid crystal capacitance) in each pixel formed in a region facing the first and second electrodes for the purpose of further reducing power consumption in the LCD. The data write frequency) is lower than CHz that can be perceived as flicker by human eyes, for example, 40 Hz to 30 Hz, for example, lower than 60 Hz, which is standard in the NTSC standard. However, when each pixel of the conventional reflective liquid crystal panel is driven at such a frequency below CFF, it has been found that the above flicker and liquid crystal burn-in problems become prominent and cause a significant decrease in display quality. .
[0014]
As a result of the applicant's research on the causes of flicker and liquid crystal burn-in in the reflective LCD as shown in FIGS. 5 and 6, these are the electrical properties of the first and second electrodes for the liquid crystal layer 300 as described above. It has been found that this asymmetry is one of the causes. This asymmetry is that the work function of a transparent metal oxide such as ITO used for the second electrode 250 is about 4.7 eV to 5.2 eV, whereas the work of a metal such as Al used for the first electrode 150 is about. This is considered to be due to the large difference between the functions of about 4.2 eV to 4.3 eV. The difference in work function causes a difference in charge actually induced at the liquid crystal interface via the alignment films 160 and 260 when the same voltage is applied to each electrode. Then, due to the difference in charge induced at the liquid crystal alignment film interface, impurity ions and the like in the liquid crystal layer are biased toward one electrode, and as a result, a residual DC voltage is accumulated in the liquid crystal layer 300. The lower the driving frequency of the liquid crystal, the greater the influence of the residual DC on the liquid crystal and the more noticeable flicker and liquid crystal burn-in occur. In particular, driving below CFF was practically difficult. .
[0015]
As a reflection type LCD, a structure in which ITO is used for the first and second electrodes like a transmission type LCD and a reflection plate is separately provided outside the first substrate (on the side not facing the liquid crystal) is conventionally known. ing. However, when a reflecting plate is provided outside the first substrate, the optical path length is increased by the thickness of the transparent first electrode 150 and the transparent first substrate, and display quality is likely to deteriorate due to parallax. Therefore, reflective LCDs for display applications that require high display quality use reflective electrodes as pixel electrodes, and if the drive frequency is lowered as described above, flicker or the like occurs, so that it is driven to reduce power consumption. The frequency could not be reduced.
[0016]
In order to solve the above-described problems, the present invention provides a liquid crystal display device that has the electrical characteristics of the first and second electrodes with respect to the liquid crystal layer, eliminates the influence of flicker and parallax, and enables high-quality display and low power consumption. It aims at realizing.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is configured by enclosing a liquid crystal layer between a first substrate having an individual first electrode for each pixel and a second substrate having a second electrode. In the liquid crystal display device for performing display, the first substrate further covers a switch element provided for each pixel and one pixel region, and is electrically connected to the switch element on the switch element. A reflective electrode that reflects light incident on the liquid crystal layer from the second substrate side, and a transparent conductive material is interposed between the reflective electrode and the reflective electrode via an insulating film as the first electrode. The transparent electrode is capacitively coupled to the reflective electrode, and the voltage supplied from the switch element to the reflective electrode is disposed with the insulating film interposed therebetween. And through a capacitor composed of the first electrode It is applied to the transparent electrode.
[0018]
As described above, on the first substrate side, the transparent first electrode having the same characteristics as the second electrode of the second substrate is disposed on the liquid crystal layer side, and the reflective layer is disposed on the lower layer of the first electrode. The liquid crystal layer can be driven with good symmetry by the first electrode and the second electrode. The difference between the work function of the transparent conductive material of the first electrode and the work function of the transparent conductive material of the second electrode formed on the liquid crystal layer side of the second substrate is 0.5 eV or less. Is particularly effective for driving with excellent symmetry. Further, by adopting such a configuration, even when the driving frequency of the liquid crystal layer in each pixel is set lower than 60 Hz, for example, high quality display can be performed without causing flicker. The present invention further employs a configuration in which a voltage for driving liquid crystal is applied to the transparent first electrode using a capacitive coupling via a reflective electrode connected to the switch element. Therefore, although the electrode on the first substrate side is constituted by the multilayer structure of the reflective electrode and the transparent first electrode, the connection structure between the switch element and the reflective electrode is a conventional structure using a metal reflective electrode for the pixel electrode. A structure almost the same as that of the reflective liquid crystal display device can be adopted, and display quality can be improved and power consumption can be reduced with minimal design changes.
[0019]
In another aspect of the present invention, a liquid crystal layer is formed by sealing a liquid crystal layer between a first substrate having an individual first electrode for each pixel and a second substrate having a second electrode, and performing display for each pixel. In the display device, the first substrate further includes a switch element provided for each pixel, and is electrically connected to the switch element on the switch element, and is incident on the liquid crystal layer from the second substrate side. A transparent electrode made of a transparent conductive material is formed on the reflective electrode with an insulating film interposed between the reflective electrode and the transparent electrode. A voltage that is capacitively coupled to the reflective electrode and is supplied from the switch element to the reflective electrode is passed through a capacitor composed of the reflective electrode and the first electrode disposed with the insulating film interposed therebetween. Applied to the transparent electrode, and the liquid crystal layer is sandwiched between them. In the pixel capacitance of the capacitance C1 formed by the oppositely disposed the first electrode and the second electrode, and the capacitance value C2 of the capacitor constituted by the first electrode and the reflective electrode,
C2> 100 × C1
Satisfy the relationship.
[0020]
In another aspect of the present invention, a liquid crystal layer is formed by sealing a liquid crystal layer between a first substrate having an individual first electrode for each pixel and a second substrate having a second electrode, and performing display for each pixel. In the display device, the first substrate further includes a switch element provided for each pixel, and is electrically connected to the switch element on the switch element, and is incident on the liquid crystal layer from the second substrate side. A transparent electrode made of a transparent conductive material is formed on the reflective electrode with an insulating film interposed between the reflective electrode and the transparent electrode. The capacitively coupled to the reflective electrode, a voltage supplied from the switch element to the reflective electrode is applied to the transparent electrode by the capacitive coupling, and is disposed opposite to the second electrode with the liquid crystal layer interposed therebetween The insulating film between the area S1 of the first electrode And overlapping area S2 between the reflective electrode and the first electrode being sandwiched therebetween opposite arrangement,
S2> 0.1 × S1
Satisfy the relationship.
[0021]
When a transparent conductive material is formed on a reflective electrode made of a metal material, a natural oxide film is formed on the surface of the reflective electrode, so that the reflective electrode and the transparent first electrode are insulated. However, by designing the capacitance value and the area so as to satisfy the relationship as described above, the reflective electrode connected to the switch element is sufficient to drive the liquid crystal to the transparent first electrode via capacitive coupling. A voltage can be applied.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments (hereinafter referred to as embodiments) of the invention will be described with reference to the drawings.
[0023]
FIG. 1 is a part of a planar configuration on the first substrate side of a reflective active matrix LCD as a reflective LCD according to the present embodiment, and FIG. 2 is a schematic cross section of the LCD at a position along the line AA in FIG. The configuration is shown. In an active matrix LCD, a plurality of pixels are provided in a matrix in a display area, and a switch element such as a TFT is provided for each pixel. The switch element is formed for each pixel on one of the first and second substrates, for example, the first substrate 100 side, and an interlayer insulating film 34 and a planarizing insulating film 38 are formed on each switch element. Reflective electrodes 44 made of a reflective metal material respectively formed on the insulating film 38 are connected to this switch element. Further, a transparent first electrode 50 made of a transparent conductive material formed in an individual pattern with an insulating film 46 interposed therebetween is formed on the reflective electrode 44.
[0024]
As the switch element, in this embodiment, a polycrystalline silicon TFT 110 using polycrystalline silicon for the active layer 20 including the channel 20c and the drain / source regions 20d and 20s is employed. Of course, it is not limited to polycrystalline silicon, and may be an amorphous silicon TFT.
[0025]
When a gate signal (scanning signal) is applied to the gate electrode 32 of the TFT 110, the TFT 110 is turned on, so that, for example, a voltage on the source electrode 40 side is applied to the drain electrode (data line) 36. Equal to the voltage. Since the reflective electrode 44 is connected to the source electrode 40, this source voltage is applied to the reflective electrode 44.
[0026]
The reflective electrode 44 is covered with an insulating film 46 for the reason described later, and a transparent first electrode 50 made of a transparent conductive material is formed on the insulating film 46. In this embodiment, the reflective electrode 44 and the first electrode 50 are capacitively coupled with the insulating film 46 interposed therebetween, and a data voltage corresponding to the display content applied to the reflective electrode 44 is supplied to the first electrode 50 via this capacitance. Is applied.
[0027]
A transparent substrate such as glass is used for the first and second substrates 100 and 200, and a color filter 210 is provided on the second substrate 200 side facing the first substrate 100 in the case of a color type as in the conventional case. The second electrode 250 made of a transparent conductive material is formed on the color filter 210. As the transparent conductive material of the second electrode 250, IZO (Indium Zinc Oxide), ITO, or the like is employed. In the active matrix type, the second electrode 250 is formed as a common electrode for each pixel. Further, an alignment film 260 made of polyimide or the like is formed on the second electrode 250.
[0028]
In contrast to the second substrate side having the above-described configuration, in the present embodiment, an electrode structure is adopted so that the electrical characteristics of the liquid crystal layer 300 on the first substrate side are aligned. Specifically, as shown in FIG. 2, a material having a work function similar to that of the second electrode 250, i.e., IZO, is not provided directly below the alignment film on the first substrate 100. A first electrode 50 made of the same transparent conductive material as the second electrode 250, such as ITO or ITO, is formed. The reflective electrode 44 that reflects incident light from the second substrate side is formed below the first electrode 50.
[0029]
The material used as the first electrode 50 is the same as the material of the second electrode 250, so that an electrode having the same work function is disposed with respect to the liquid crystal layer 300 through the alignment films 60 and 260. Therefore, the liquid crystal layer 300 can be AC driven with very good symmetry by the first electrode 50 and the second electrode 250. However, the first electrode 50 and the second electrode 250 may be approximated as long as the liquid crystal layer 300 can be driven with good symmetry even if their work functions are not completely the same. For example, if the difference between the work functions of both electrodes is about 0.5 eV or less, even if the liquid crystal drive frequency is CFF or less as described above, high-quality display is possible without flicker or liquid crystal burn-in. It becomes possible.
[0030]
As the first electrode 50 and the second electrode 250 that satisfy such conditions, for example, IZO (work function 4.7 eV to 5.2 eV) is used for the first electrode 50 and ITO (work function 4.7 eV) is used for the second electrode 250. -5.0 eV), or vice versa, and in selecting the material, select the material to be used for each electrode in consideration of process characteristics such as transmittance, patterning accuracy, manufacturing cost, etc. Also good.
[0031]
As the reflective electrode 44, a material having excellent reflection characteristics such as Al, Ag, and an alloy thereof (Al—Nd alloy in this embodiment) is used at least on the surface side (liquid crystal layer side). The reflective electrode 44 may be a single layer of a metal material such as Al, but a refractory metal layer such as Mo may be provided as a base layer in contact with the planarization insulating film 38. By forming such a base layer, the adhesion between the reflective electrode 44 and the planarization insulating film 38 is improved, so that the reliability of the element can be improved. In the configuration of FIG. 2, an inclined surface having a desired angle is formed in each pixel region of the planarizing insulating film 38 formed on the interlayer insulating film 34, and covers the planarizing insulating film 38. By laminating the reflective electrode 44, a similar inclination is formed on the surface of the reflective electrode 44. If such an inclined surface is formed at an optimum angle and position, it is possible to collect and emit external light for each pixel. For example, it is possible to improve the display brightness at the front position of the display. is there. Of course, such an inclined surface does not necessarily exist.
[0032]
The reflective electrode 44 is made of a conductive material such as an Al—Nd alloy as described above, but the first electrode 50 laminated on the reflective electrode 44 and the reflective electrode 44 are electrically insulated. ing. The reason for the insulation is that when IZO, ITO, or the like is used as the material of the first electrode 50, these are formed by sputtering. That is, the reflective electrode 44 made of Al or the like is exposed to a sputtering atmosphere, so that an oxidation reaction takes place on the surface and is covered with a natural oxide film (insulating film) 46.
[0033]
In the present embodiment, the reflective electrode 44 is connected to the TFT 110 (here, the source electrode 40) in the same manner as the reflective electrode on the first substrate side that drives the liquid crystal in the conventional reflective LCD. The reflective electrode 44 and the first electrode 50 are insulated by the natural oxide film 46, and the reflective electrode 44 and the first electrode 50 constitute a second capacitor (C2) with the natural oxide film 46 formed therebetween. . Further, the first capacitor 50 and the second electrode 250 that are arranged to face each other with the liquid crystal layer 300 interposed therebetween constitute a first capacitor (pixel capacitor) (C1). The first capacitor (C1) and the second capacitor (C2) are equivalent to a circuit electrically connected in series to an AC power source in one pixel as shown in FIG. Where [Equation 1]
V = V1 (first capacity voltage) + V2 (second capacity voltage) (1)
It is. The capacitance value C between the electrodes is expressed by the following general formula (2)
[Expression 2]
C = ε × ε 0 × (S / d) (2)
(Where ε is the dielectric constant of the interelectrode material, ε 0 is the dielectric constant in vacuum, S is the capacitance area, and d is the distance between the electrodes)
It is represented by And V1 is
[Equation 3]
V1 = (C2 / C1) × V2 (3)
It is represented by
[0034]
From equation (3), it can be seen that if C2 is sufficiently larger than C1, a sufficiently high voltage V1 can be applied to the first capacitor via the second capacitor. For example, the capacitance values of the first capacitor and the second capacitor are expressed by the following formula (4).
[Expression 4]
C2> 100 × C1 (4)
If the relationship is satisfied, the liquid crystal layer 300 can be driven substantially the same as the case where the liquid crystal layer 300 is directly driven by the reflective electrode 44 via the first electrode 50. Here, since the natural oxide film 46 between the reflective electrode 44 and the first electrode 50 can be formed very thin, the second capacitance value C2 should be a very large value even if the area is small. Can do. Therefore, the second capacitor C2 can satisfy the above formula (4). In particular, as shown in FIG. 1, in the reflective LCD, since the overlap (capacitance area) between the reflective electrode 44 and the first electrode 50 is large, the capacitance value C2 is sufficiently large, and the relationship of the above equation (4) is satisfied. it can.
[0035]
Further, for example, in order to satisfy the relationship of the above formula (4), the area of the first capacitor, that is, the area S1 of the first electrode 50 formed in an individual pattern for each pixel, and the area of the second capacitor, That is, the overlapping area S2 between the reflective electrode 44 and the first electrode 50 is expressed by the following equation (5).
[Equation 5]
S2> 0.1 × S1 (5)
It is preferable to set the areas of the reflective electrode 44 and the first electrode 50 so as to satisfy the above relationship. Of course, in the reflective LCD as shown in FIG. 1 in which the reflective electrode 44 has substantially the same area as the first electrode 50, the relationship of the above equation (5) can be satisfied.
[0036]
In the above equations (4) and (5), the voltage loss is 1% or less. For example, the distance between the first electrode 50 and the second electrode 250 (the thickness of the liquid crystal layer 300) d1 is 5 μm, and the liquid crystal The dielectric constant ε 1 (liquid crystal average dielectric constant) of the layer is 5, the distance between the reflective electrode 44 and the first electrode 50 (film thickness of the natural oxide film 46, etc.) d2 is 50 nm, and the distance between the reflective electrode 44 and the first electrode 50 It is satisfied when the dielectric constant between them (natural oxide film or other average dielectric constant) ε 2 is 5. Of course, the first electrode 50 can be sufficiently driven from the reflective electrode 44 by capacitive coupling without satisfying all of these conditions.
[0037]
FIG. 4 shows a schematic plan configuration of an active matrix type transflective LCD. The only difference from the configuration of FIG. 1 is that the reflective electrode 44 formed below the first electrode 50 is smaller than one pixel region and there is a region where the reflective electrode 44 is not formed. Since the formation area of the reflective electrode 44 in one pixel region is small, the second capacitance is smaller than in the case of a reflective LCD. However, the distance d2 between the reflective electrode 44 and the transparent electrode 50 is only 1/100 in the above example with respect to the thickness d1 of the liquid crystal layer, and the value of C2 can satisfy the above formula (4).
[0038]
In addition, the transflective LCD needs to exhibit both a light transmission function and a light reflection function. In particular, the reflection function is required to further improve the brightness, and the reflective electrode 44 has at least 10 pixel area area. Designed larger than%. Therefore, this can also be satisfied for the condition of the above equation (5).
[0039]
As described above, even in a transflective LCD, the reflective electrode 44 may be connected to the pixel TFT 110 with the same connection structure (manufacturing method) as in the reflective type. Further, the natural oxide film 46 is left as it is between the reflective electrode 44 and the first electrode 50, thereby reflecting through the second capacitor (C 2) formed between the reflective electrode 44 and the first electrode 50. A voltage corresponding to the display content can be applied from the electrode 44 to the first electrode 50. Of course, since the first electrode 50 made of a transparent conductive material is formed closer to the liquid crystal layer 300 than the reflective electrode 44, the liquid crystal layer 300 can be driven with good symmetry by the first electrode 50 and the second electrode 250. It is possible. Therefore, it is possible to improve display quality by increasing the symmetry of driving the liquid crystal at a very low cost. For this reason, the second capacitor sufficient to drive the first electrode 50 can be formed without forming the special reflective electrode large, and sufficient luminance can be obtained when the transmissive type is used.
[0040]
【The invention's effect】
As described above, according to the present invention, the first and second electrodes made of the transparent conductive material having a similar work function are disposed on the opposite side of the liquid crystal on both the first substrate side and the second substrate side. Can be driven with good symmetry by the first electrode and the second electrode. A reflective electrode that is connected to the switch element and reflects light incident from the second substrate side is formed under the first electrode.
[0041]
The first electrode is electrically insulated from the reflection electrode due to the presence of an insulating layer such as a natural oxide film formed between the reflection electrode and the first electrode. ), A voltage approximately equal to the voltage corresponding to the display content can be applied to the first electrode from the reflective electrode. In addition, a reflective or transflective LCD can be configured by the presence of the reflective electrode, and the reflective first electrode is formed on the reflective electrode in order to realize a highly symmetric drive with respect to the liquid crystal. It is not necessary to change the connection structure between the reflective electrode and the switch element in the case of the type LCD. Accordingly, it is possible to obtain a reflective or transflective liquid crystal display device with a simple configuration, high display quality, and low power consumption while realizing a reduction in manufacturing cost.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic planar configuration of a first substrate side of an active matrix reflective LCD according to an embodiment of the present invention.
2 is a diagram showing a schematic cross-sectional configuration of a reflective LCD at a position along the line AA in FIG.
FIG. 3 is a diagram showing an equivalent circuit of one pixel according to the embodiment of the present invention.
FIG. 4 is a diagram showing a schematic planar configuration on the first substrate side of the active matrix transflective LCD according to the embodiment of the present invention.
FIG. 5 is a diagram showing a partial planar structure on the first substrate side in a conventional active matrix reflective LCD.
6 is a diagram showing a schematic cross-sectional structure of a conventional reflective LCD at a position along line CC in FIG.
[Explanation of symbols]
20 active layer (p-Si layer), 30 gate insulating film, 32 gate electrode (gate line), 34 interlayer insulating film, 36 drain electrode (data line), 38 planarizing insulating film, 40 source electrode, 44 reflective electrode, 46 insulating film (natural oxide film), 50 first electrode, 60, 260 alignment film, 100 first substrate, 110 TFT, 200 second substrate, 210 color filter, 250 second electrode, 300 liquid crystal layer.

Claims (5)

  1. A liquid crystal display device configured to display a pixel by pixel, in which a liquid crystal layer is sealed between a first substrate having an individual first electrode for each pixel and a second substrate having a second electrode,
    The first substrate further includes:
    A switch element provided for each pixel;
    A reflective electrode that partially covers one pixel region, is electrically connected to the switch element on the switch element, and reflects light incident on the liquid crystal layer from the second substrate side;
    Have
    As the first electrode, a transparent electrode made of a transparent conductive material is formed on the reflective electrode with a natural oxide film interposed therebetween. The transparent electrode is capacitively coupled to the reflective electrode, and is connected to the switch element from the switch element. The voltage supplied to the reflective electrode is applied to the transparent electrode through a capacitor composed of the reflective electrode and the first electrode disposed with the natural oxide film interposed therebetween. Liquid crystal display device.
  2. A liquid crystal display device configured to display a pixel by pixel, in which a liquid crystal layer is sealed between a first substrate having an individual first electrode for each pixel and a second substrate having a second electrode,
    The first substrate further includes:
    A switch element provided for each pixel;
    A reflective electrode that is electrically connected to the switch element on the switch element and reflects light incident on the liquid crystal layer from the second substrate side;
    As the first electrode, a transparent electrode made of a transparent conductive material is formed on the reflective electrode with a natural oxide film interposed therebetween. The transparent electrode is capacitively coupled to the reflective electrode, and is connected to the switch element from the switch element. A voltage supplied to the reflective electrode is applied to the transparent electrode through a capacitor composed of the reflective electrode and the first electrode arranged with the natural oxide film interposed therebetween,
    A capacitance value C1 of a pixel capacitance composed of the first electrode and the second electrode arranged opposite to each other with the liquid crystal layer interposed therebetween, and a capacitance of a capacitance composed of the reflection electrode and the first electrode The value C2 is
    C2> 100 × C1
    A liquid crystal display device satisfying the relationship:
  3. A liquid crystal display device configured to display a pixel by pixel, in which a liquid crystal layer is sealed between a first substrate having an individual first electrode for each pixel and a second substrate having a second electrode,
    The first substrate further includes:
    A switch element provided for each pixel;
    A reflective electrode that is electrically connected to the switch element on the switch element and reflects light incident on the liquid crystal layer from the second substrate side;
    As the first electrode, a transparent electrode made of a transparent conductive material is formed on the reflective electrode with a natural oxide film interposed therebetween. The transparent electrode is capacitively coupled to the reflective electrode, and is connected to the switch element from the switch element. A voltage supplied to the reflective electrode is applied to the transparent electrode through a capacitor composed of the reflective electrode and the first electrode arranged with the natural oxide film interposed therebetween,
    An area S1 of the first electrode disposed opposite to the second electrode with the liquid crystal layer interposed therebetween, and an overlap between the reflective electrode and the first electrode disposed opposite to each other with the natural oxide film interposed therebetween Area S2 is
    S2> 0.1 × S1
    A liquid crystal display device satisfying the relationship:
  4. In the liquid crystal display device according to any one of claims 1 to 3,
    The difference between the work function of the transparent conductive material of the first electrode and the work function of the transparent conductive material of the second electrode formed on the liquid crystal layer side of the second substrate is 0.5 eV or less. A liquid crystal display device characterized by the above.
  5. The liquid crystal display device according to claim 4.
    A liquid crystal display device, wherein a driving frequency of a liquid crystal layer in each pixel is lower than 60 Hz.
JP2002057306A 2002-03-04 2002-03-04 Liquid crystal display Active JP3953338B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2002057306A JP3953338B2 (en) 2002-03-04 2002-03-04 Liquid crystal display

Applications Claiming Priority (7)

Application Number Priority Date Filing Date Title
JP2002057306A JP3953338B2 (en) 2002-03-04 2002-03-04 Liquid crystal display
TW92103758A TWI230304B (en) 2002-03-04 2003-02-24 Display device with reflecting layer
US10/376,721 US7133094B2 (en) 2002-03-04 2003-02-28 Liquid crystal display apparatus having a transparent layer covering a reflective layer
KR20030013007A KR100582131B1 (en) 2002-03-04 2003-03-03 A display apparatus having reflective layer
CN 03107054 CN1239946C (en) 2002-03-04 2003-03-04 Display device with reflection layer
CN 200510080737 CN100523963C (en) 2002-03-04 2003-03-04 Display apparatus having reflective layer
US11/522,871 US7482746B2 (en) 2002-03-04 2006-09-18 Liquid crystal display apparatus having reflective layer

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JP2006091063A (en) 2004-09-21 2006-04-06 Casio Comput Co Ltd Liquid crystal display element
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US7429753B2 (en) 2005-05-20 2008-09-30 Sanyo Electric Co., Ltd. Display device
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