JP2005157103A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semitransmission type liquid crystal display wherein a color filter layer having respectively suitable characteristics in a reflection part and a transmission part is formed in one display pixel and the color filter layer realizing display having excellent brightness and color purity in both reflection and transmission is formed. <P>SOLUTION: In the semitransmission type liquid crystal display having first and second substrates disposed opposite to each other across a liquid crystal layer, wherein pixel electrodes each having an auxiliary capacitance electrode Cs, a reflection part reflecting external light and a transmission part transmitting light from a backlight in one pixel are formed on the first substrate and the color filter layer CF is formed on the second substrate, a region CF<SB>H</SB>where the color filter layer CF is not formed is formed in the region opposed to the auxiliary capacitance electrode Cs on the second substrate. The region CF<SB>H</SB>where the color filter layer CF is not formed is formed by a slit and a circular or rectangular pinhole. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a transflective liquid crystal display device having both functions of a reflective type and a transmissive type, and more particularly to a transflective liquid crystal display device which realizes a bright color display with high color purity.

  A liquid crystal display device having both functions of a reflective type and a transmissive type, that is, a so-called transflective type liquid crystal display device, includes a reflective portion that reflects external light to one display pixel, and a transmission that transmits light from a backlight. When the surroundings are dark, the image is displayed using the light from the backlight that passes through the transmission part. When the external light is dark, the light is transmitted through the transmission part and reflected by the reflection part. The image is displayed using the reflected external light, and when the external light is bright, the image is displayed by the external light reflected by the reflecting part, so it is always excellent regardless of the brightness of the external light. In addition, it is possible to display an image, and since it is not necessary to always turn on the backlight, there is an advantage that power consumption can be greatly reduced.

  On the other hand, however, when color display is attempted with this transflective liquid crystal display device, the transmittance of the color filter differs between the reflective portion and the transmissive portion, so that the color purity is bright in both the transmissive and reflective types. It has become difficult to achieve high color display. That is, in the transflective liquid crystal display device capable of color display, since the color filter layer overlaps the entire area of the reflective electrode and the transmissive electrode of each pixel, in the color filter layer corresponding to the transmissive portion, While the light from the backlight is transmitted once, the color filter layer corresponding to the reflecting portion transmits twice when external light enters and exits. Therefore, the transmittance of the color filter is about 30% even after the visibility correction, and when this is used as it is as a color filter in a reflective liquid crystal display device, the transmittance is reduced to about 17%. As a result, the display becomes very dark, and it is impossible to realize a bright and high color purity color display in both the transmission type and the reflection type.

  As a method for solving this problem, a method of mixing colors with a color filter having high transmittance, high brightness, and low color purity, or a color for transmission type having high color purity in an area corresponding to a reflection portion on a color filter substrate. A method is known in which a region where a filter layer is formed and a region where a color filter layer is not formed are provided, white is displayed in a region where no color filter layer is formed, and color mixing is performed with a color filter layer having high color purity. A transflective liquid crystal display device adopting the latter method is introduced in, for example, Patent Document 1.

  5 and 6 are transflective liquid crystal display devices described in Patent Document 1, wherein FIG. 5 is an enlarged plan view of the liquid crystal panel, and FIG. 6 is a cross-sectional view taken along the line AA ′ of FIG. is there. In the plan view of FIG. 5, the transparent electrode, the liquid crystal layer, the light shielding layer, and the alignment layer on the color filter substrate side are omitted in order to facilitate understanding of the positional relationship between the pixel electrode and the color filter layer.

  As shown in FIG. 6, the transflective liquid crystal display device 70 includes a pair of substrates 51 and 52 disposed to face each other with a liquid crystal layer 55 interposed therebetween, and is vertically disposed on one lower substrate 51. A thin film transistor (hereinafter referred to as TFT) 73 and pixel electrodes 53 and 58 are formed in the vicinity of the formed signal electrode 71, the scanning electrode 72 formed in the horizontal direction, and the intersection of these electrodes 71 and 72. . The pixel electrodes 53 and 58 are made of two kinds of materials. One pixel electrode 53 is formed of a reflective electrode using an Al alloy, and the other pixel electrode 58 is formed of a transparent electrode using ITO.

  Reference numerals 61A, 61B, and 61C in the figure are R, G, and B color filter layers, respectively, and the transparent electrode 58 is overlapped in the entire region. It is overlapped in stripes at a rate of about 87.5% of the total area.

  The other substrate 52 is a color filter substrate on which a color filter layer is formed. As shown in FIG. 6, a color filter layer 61 is formed on the substrate 52 except for the region B. In the figure, reference numeral 54 denotes a counter electrode, 56 denotes a deflection plate, and 57 denotes a quarter wavelength plate.

  According to this configuration, the color purity and brightness can be freely set by changing the area of the region B where the color filter layer 61 is not formed in the region corresponding to the reflective electrode 53 on the color filter substrate 52. In addition, the brightness increases in proportion to the increase in the area and the color purity decreases, so that this value can be freely designed according to the intended use of the liquid crystal display device. Therefore, by forming the region B where the color filter layer 61 is not formed on the color filter substrate 52, the region B where the color filter layer 61 is not formed and the color filter layer 61 with high color purity are mixed. Thus, it is possible to realize a necessary bright display in the reflection region of the transflective liquid crystal display device including the reflection part and the transmission part.

However, in this configuration, the layer thickness of the liquid crystal layer 55 where the color filter layer 61 is formed is different from the layer thickness of the liquid crystal layer 55 in the region B where the color filter layer 61 is not formed. The retardation is different. That is, if the layer thickness of the liquid crystal layer 55 in which the color filter layer 61 is formed is represented by dT ₁ , and the layer thickness of the liquid crystal layer 55 in the region B in which the color filter layer 61 is not formed is represented by dT ₂ , dT ₁ <DT ₂ , and the electro-optical characteristics at this time are shifted due to the difference in the layer thickness of the liquid crystal layer 55.

  This same state also occurs in a region where an auxiliary capacitance electrode is provided, although not shown in FIGS. That is, a reflective layer is usually formed above the auxiliary capacitance electrode through an interlayer film. The thickness of the liquid crystal layer in the region where the auxiliary capacitance electrode is formed and the region shifted from the auxiliary capacitance electrode The layer thickness of the liquid crystal layer is different.

For this reason, even in the region where the auxiliary capacitance electrode is provided, the electro-optical characteristic shift occurs, and uniform display cannot be realized in the dark state, the gradation region, and the bright state, and higher contrast is realized. There is a problem that cannot be done.
JP 2000-111902 A (FIGS. 1, 14, [0106], [0115])

  The present invention has been made in order to solve the problems of the prior art, and an object of the invention is to provide a color filter layer having characteristics suitable for the reflective portion and the transmissive portion in one display pixel. It is an object of the present invention to provide a transflective liquid crystal display device in which a color filter layer is formed and a display with excellent brightness and color purity is realized in both a reflection portion and a transmission portion.

  A transflective liquid crystal display device according to claim 1 of the present application has first and second substrates disposed opposite to each other with a liquid crystal layer interposed therebetween, and each pixel is disposed on the first substrate. A transflective electrode in which a pixel electrode having an auxiliary capacitance electrode, a reflective portion that reflects external light, and a transmissive portion that transmits light from a backlight is formed, and a color filter layer is formed on the second substrate. In the liquid crystal display device, the auxiliary capacitance electrode is located below the reflective portion of the pixel electrode, and a region in which no color filter layer is formed is provided in each pixel on the second substrate. A region where the filter layer is not formed is disposed above the auxiliary capacitance electrode.

  The invention according to claim 2 of the present application is the transflective liquid crystal display device according to claim 1, wherein the area of the region where the color filter layer is not formed is 1 to 0. 0 of the area of the auxiliary capacitance electrode. It is selected within the range of 1 times.

  The invention according to claim 3 of the present application is the transflective liquid crystal display device according to claim 1 or 2, wherein the area where the color filter layer is not formed is a slit having a predetermined width, A center line in the longitudinal direction of the slit is located on the auxiliary capacitance electrode.

  The invention according to claim 4 of the present application is the transflective liquid crystal display device according to claim 1 or 2, wherein the region where the color filter layer is not formed has a circular or square shape having a predetermined size. It is formed by the pinhole of this.

  The invention according to claim 5 of the present application is the transflective liquid crystal display device according to claim 4, characterized in that there are one or more pinholes.

  Furthermore, the invention according to claim 6 of the present application is the transflective liquid crystal display device according to any one of claims 1 to 5, wherein the reflection portion is configured by a concavo-convex structure so as to diffuse light. It is characterized by being.

  According to the first aspect of the present invention, even if the reflection layer on the auxiliary capacitance electrode arranged on the first substrate rises due to the arrangement of the auxiliary capacitance electrode, the second substrate facing this portion has a color on the second substrate. The filter layer is not formed and becomes a depression, and the layer thickness of the liquid crystal layer is almost equal to the other area in this rise and depression, that is, the layer thickness of the liquid crystal layer in the area where the rise and depression face each other, and this auxiliary Since the thickness of the liquid crystal layer in the region shifted from the capacitor electrode is substantially equal, the retardation in each region is equal.

  As a result, even in the liquid crystal layer in the region where the auxiliary capacitance electrode is provided, a uniform display can be performed over the dark state, the gradation region, and the bright state without causing a shift in electro-optical characteristics. A high contrast transflective liquid crystal display device can be realized.

  According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, the area of the region where the color filter layer is not formed is in the range of 1 to 0.1 times the area of the auxiliary capacitance electrode. By selecting so as to be within, color purity and brightness can be freely set. That is, the brightness increases in proportion to the increase in the area, and the color purity decreases. On the other hand, the area is changed, and a region in which no color filter layer is formed and a color filter layer with a high color purity are provided. By mixing the colors, it is possible to realize display with necessary brightness in the reflective region of the transflective liquid crystal display device having the reflective portion and the transmissive portion.

According to a third aspect of the present invention, the area where the slits of the color filter substrate are formed is in a depressed state due to the provision of the slits, while the portion of the opposing substrate where the auxiliary capacitance electrode is provided Is raised, but the depression of the slit and the raised portion of the portion where the auxiliary capacitance electrode is provided are opposed to each other, a liquid crystal layer is formed therebetween, and the layer thickness of the liquid crystal layer in which the slit is formed is represented by dT ₃ , Denoting the thickness of the liquid crystal layer in a region where the color filter layer is formed by dT _4, substantially equal, a dT ₃ ≒ dT _4. Therefore, the retardation in each region becomes equal.

  As a result, even in the liquid crystal layer in the region where the auxiliary capacitance electrode is provided, a uniform display can be realized in the dark state, the gradation region, and the bright state without causing a shift in electro-optical characteristics, and higher contrast. Can be realized.

  Furthermore, by making the area where the color filter layer is not formed into a slit, it is possible to mix the color filter layer with high color purity according to the shape, so that the semi-transmission having a reflection part and a transmission part It is possible to realize a display with a necessary brightness in the reflection region of the liquid crystal display device.

  According to the invention described in claim 4, in addition to the effect of the invention of claim 1 or 2, by forming the region where the color filter layer is not formed into a circular or square pinhole, these shapes are obtained. By mixing colors with a color filter layer having high matching color purity, it is possible to realize a bright display necessary in the reflection region of a transflective liquid crystal display device having a reflection portion and a transmission portion.

  According to the invention of claim 5, in addition to the effect of the invention of claim 4, by providing a plurality of pinholes in a region where the color filter layer is not formed, a color filter layer having a high color purity according to this number. As a result, the bright display necessary in the reflective region of the transflective liquid crystal display device having the reflective portion and the transmissive portion can be realized.

  According to the invention described in claim 6, in addition to the effects of the invention described in claims 1-5, a display with good reflection efficiency can be performed.

FIG. 1 is an enlarged plan view of one pixel constituting a liquid crystal panel in a transflective liquid crystal display device according to an embodiment of the present invention, and FIG. 2 is a schematic enlarged cross-sectional view taken along line AA ′ of FIG. It is.

As shown in FIG. 2, a liquid crystal panel 10 constituting a transflective liquid crystal display device has a liquid crystal layer 40 formed between a TFT substrate 12 and a color filter substrate 11 arranged to face each other. On the TFT substrate 12, a pixel electrode 18 having an auxiliary capacitance electrode C _S in each pixel, a reflection portion R that reflects external light, and a transmission portion T that transmits light from a backlight (not shown). A color filter layer CF is formed on each color filter substrate 11.

  The TFT substrate 12 is made of a transparent insulating glass material. On the substrate 12, as shown in FIG. 1, a plurality of gate bus wirings 32 made of a metal such as aluminum or chromium are arranged at substantially equal intervals. An auxiliary capacitance electrode Cs is formed in parallel to the gate bus line 32 and slightly below the center between the adjacent gate bus lines 32. A gate electrode G extends from the gate bus line 32.

  On the TFT substrate 12, a gate insulating film 13 made of silicon nitride, silicon oxide or the like is laminated so as to cover the gate bus wiring 32, the auxiliary capacitance electrode Cs, and the gate electrode G. A semiconductor layer 14 made of amorphous silicon, polycrystalline silicon, or the like is formed through the insulating film 13. A plurality of source bus lines 34 are formed on the gate insulating film 13 so as to be orthogonal to the gate bus lines 32. A source electrode S extends from the source bus line 34, and the source electrode S is connected to the semiconductor layer 14. Further, the drain electrode D is provided on the gate insulating film 13 and connected to the semiconductor layer 14.

  Here, a region surrounded by the gate bus wiring 32 and the source bus wiring 34 corresponds to one pixel. The gate electrode G, the gate insulating film 13, the semiconductor layer 14, the source electrode S, and the drain electrode D constitute a TFT element 15 serving as a switching element, and the TFT element 15 is formed in each pixel. In this case, an auxiliary capacitance is formed by the drain electrode D and the auxiliary capacitance electrode Cs.

  An interlayer insulating film 16 (protective film) made of, for example, an inorganic insulating film is laminated so as to cover the source bus wiring 34, the TFT element 15, and the gate insulating film 13, and an interlayer made of an organic insulating film is formed on the interlayer insulating film 16. A film 20 is laminated. In the interlayer insulating film 16 and the interlayer film 20, a contact hole 21 is formed at a position corresponding to the drain electrode D of the TFT element 15, and a groove 22 is formed in a rectangular shape at a position away from the TFT element 15. The rectangular groove portion 22 forms a transmission portion T.

  In each pixel, the reflective electrode 17 made of aluminum is provided on the interlayer film 20 and the contact hole 21 so as to be in contact with the interlayer insulating film 16 but not to the drain electrode D of the TFT element 15. . Aluminum is used as a material for the reflective electrode because of its high reflectivity and low resistance. Other materials for the reflective electrode 17 may be an alloy containing aluminum.

  A backlight device having a well-known light source, a light guide plate, a diffusion sheet and the like (not shown) is disposed below the TFT substrate 12.

On the color filter substrate 11, an alignment film (not shown) is laminated so as to cover all the pixels, and R, G, B3 color filter layers CF are formed corresponding to each pixel. The color filter layer CF is the area color filter layer CF is not formed CF _H is provided in a region opposed to the storage capacitor electrode C _S. The color filter layer CF region is not formed CF _H is be any size and shape, for example a slit or a circular or rectangular pinholes are preferable.

3 and 4, shows the shape of the color filter layer CF is not formed region CF _H, 3 is a plan view schematically showing a region CF _H color filter layer CF in FIG. 1 is not formed, FIG. 4 other areas CF _H color filter layer CF is not formed shape is a plan view schematically showing.

If region CF _H color filter layer CF is not formed is slit, as shown in FIG. 3, the center line L in the length direction of the slit is formed so as to be located above the storage capacitor electrode C _S, It is formed such that the area of the auxiliary capacitance electrode C _S and approximately the same area as or slightly smaller area.

The area CF _H color filter layer CF is not formed a rectangular pinhole, is smaller than the area of the auxiliary capacitance electrode C _S, as shown in FIG. 4, located on the auxiliary capacitance electrode C _S Formed as follows. Incidentally, in FIG. 4 is a region rectangular color filter layer CF is not formed CF _H showed one thing, the number may be two or more.

  In the present invention, it is desirable to provide a region where the color filter layer CF is not formed in a region overlapping with the auxiliary capacitance electrode as much as possible. In FIG. 3, the effect of the present invention can be obtained as long as most of the region (about 80% or more) in which the color filter layer CF is not formed in the pixel is in a region overlapping with the auxiliary capacitance electrode.

  In the case where the region where the color filter layer CF is not formed is provided in the region overlapping with the auxiliary capacitance electrode, the area of the region where the color filter layer CF is not formed is within 1 to 0.1 times the area of the auxiliary capacitance electrode in each pixel. It is desirable to select within. By selecting this area within a range of 1 to 0.1 times, color purity and brightness can be freely set. As an example in which the area ratio is 1, there is a region in which the color filter layer CF is not formed in all regions on the auxiliary capacitance electrode in one pixel electrode. That is, the brightness increases in proportion to the area ratio increasing (approaching 1), and the color purity decreases. On the other hand, the area ratio is changed, and the color purity of the area where the color filter layer is not formed is reduced. By mixing colors with a high color filter layer, it is possible to realize display with necessary brightness in the reflection region of the transflective liquid crystal display device including the reflection portion and the transmission portion.

A color filter layer CF is not formed region CF _H is formed the color filter layer CF is covered with an insulating film 30 having optical transparency, the counter electrode 19 is formed thereon. A transparent electrode material using ITO is used for the counter electrode 19.

  The color filter substrate 11 is opposed to the TFT substrate 12, the substrates 11 and 12 are bonded together, and liquid crystal is injected between the substrates to form a liquid crystal layer 40, thereby forming a transflective liquid crystal panel.

According to this arrangement, the region area CF _H color filter layer CF of the color filter substrate 1 is not formed is formed is in a state recessed by providing this region CF _H, whereas, in the TFT substrate 12 The portion where the auxiliary capacitance electrode _CS is provided is raised. Then, the depression and the auxiliary capacitance electrodes C _S raised portion of the portion provided with a region CF _H color filter layer CF is not formed face each other, the liquid crystal layer 40 is formed therebetween.

Therefore, it represents the thickness of the liquid crystal layer 40 which region CF _H color filter layer CF is not formed is formed with dT _3, the thickness of the liquid crystal layer 40 in the region where the color filter layer 11 is formed by dT ₄ Expressed approximately equal, dT ₃ ≈dT ₄ . Therefore, since the layer thickness of the liquid crystal layer in which the color filter layer is formed and the layer thickness of the liquid crystal layer in the region where the color filter layer is not formed are substantially equal, the retardation in each region is equal.

  As a result, even in the liquid crystal layer in the region where the auxiliary capacitance electrode is provided, a uniform display can be realized in the dark state, the gradation region, and the bright state without causing a shift in electro-optical characteristics, and higher contrast can be realized. Can be realized.

1 is an enlarged plan view of one pixel constituting a liquid crystal panel in a transflective liquid crystal display device according to an embodiment of the present invention. FIG. 2 is an enlarged schematic cross-sectional view taken along line A-A ′ of FIG. 1. The area CF _H color filter layer CF in FIG. 1 is not formed is a plan view schematically showing. Is a plan view showing another shape of the color filter layer CF is not formed region CF _H schematically. It is a top view of the transflective liquid crystal display device of a prior art. FIG. 6 is a cross-sectional view taken along line A-A ′ of FIG. 5.

Explanation of symbols

10 Liquid crystal panel 11 Color filter substrate 12 TFT substrate 15 TFT element 16 Interlayer insulating film (protective film)
17 Reflective electrode 18 Transparent electrode 22 Groove portion 26 Reflective electrode 32 Gate bus wiring 34 Source bus wiring 40 Liquid crystal layer Cs Auxiliary capacitance electrode CF Color filter layer CF _H Color filter layer CF is not formed D Drain electrode G Gate electrode S Source electrode

Claims (6)

  There are first and second substrates disposed opposite to each other with a liquid crystal layer interposed therebetween. On the first substrate, an auxiliary capacitance electrode in each pixel, a reflection part for reflecting external light, and a backlight A transflective liquid crystal display device in which a pixel electrode having a transmissive portion that transmits light from the transmissive portion is formed and a color filter layer is formed on the second substrate, wherein the auxiliary capacitance electrode is a reflective portion of the pixel electrode In each pixel on the second substrate, a region in which no color filter layer is formed is provided, and a region in which no color filter layer is formed is disposed above the auxiliary capacitance electrode. A transflective liquid crystal display device characterized by the above.   2. The transflective liquid crystal display device according to claim 1, wherein the area of the region where the color filter layer is not formed is selected within a range of 1 to 0.1 times the area of the auxiliary capacitance electrode. .   2. The area where the color filter layer is not formed is a slit having a predetermined width, and a center line in the length direction of the slit is located on the auxiliary capacitance electrode. Or the transflective liquid crystal display device of 2.   3. The transflective liquid crystal display device according to claim 1, wherein the area where the color filter layer is not formed is formed by a circular or square pinhole having a predetermined size.   5. The transflective liquid crystal display device according to claim 4, wherein the number of the pinholes is one or more.   The transflective liquid crystal display device according to any one of claims 1 to 5, wherein the reflection portion is configured by an uneven structure so as to diffuse light.

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