JP2008170675A - Liquid crystal device and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transflective liquid crystal device capable of exhibiting excellent visibility both in a transmission display region and in a reflection display region and having excellent reliability and to provide an electronic device. <P>SOLUTION: In the transflective liquid crystal device provided with first and second electrodes provided on either of a TFT array substrate 10 or a counter substrate 20 and driving a liquid crystal layer 30, a reflection layer 13 provided in the reflection display region R and an in-plane retardation layer 28 superposed on the reflection layer 13: the polarization axis of a first polarizing plate 25 is orthogonal to the polarization axis of a second polarizing plate 24; an end part of the in-plane retardation layer 28 has an inclined part 28A; the inclined part 28A is positioned in the transmission display region T; the slow phase axis of the inclined part 28A is made to be parallel to either one polarization axis of the first and the second polarizing plates 25 or 24 and the slow phase axis of the in-plane retardation layer 28 positioned in the reflection display region R is made to cross the polarization axes of the first and the second polarizing plates 25 and 24. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal device and an electronic apparatus.

2. Description of the Related Art Conventionally, transflective liquid crystal devices have been used in which external light is used in bright places and display is visible using an internal light source such as a backlight in dark places. This transflective liquid crystal device employs a display system that has both a reflective type and a transmissive type. By switching to either the reflective mode or the transmissive mode depending on the ambient brightness, It is possible to display clearly even when the surroundings are dark while reducing power.

In such a transflective liquid crystal device, a transmissive display region for performing transmissive display and a reflective display region for performing reflective display are provided in one pixel region. In order to efficiently perform reflective display and transmissive display with a transflective liquid crystal device, the phase difference between display modes must be adjusted to achieve reflective display and transmissive display using a single liquid crystal layer. is necessary. Therefore, in Patent Document 1 below, by forming an internal retardation layer having a retardation of half wavelength in the reflective display region and setting the retardation of the liquid crystal layer in the reflective display region to a quarter wavelength, It enables display in a wide range of environments including dark places, and enables high-quality transmissive display with a wide viewing angle.
JP 2005-338256 A

  However, in the inner surface retardation layer as described above, an inclined portion in which the film thickness gradually changes is usually formed at the end portion. Since the film thickness changes continuously in such an inclined part, the retardation changes according to the film thickness change, and the retardation as the design value of the main body cannot be obtained as the entire reflection display region. There is.

In addition, it is conceivable to provide a retardation layer so that the inclined portion is not formed. In such a case, the angle formed by the end surface of the retardation layer with respect to the substrate surface becomes large, so that the adhesion of the inner surface retardation layer to the substrate is increased. Is significantly reduced, causing the internal retardation layer to peel off. In addition, it is difficult to provide the retardation layer so as not to form the inclined portion, which causes an increase in the manufacturing process and cost.

  The present invention has been made in view of the above-described problems, and the object thereof is to provide excellent translucency that can exhibit excellent visibility in both the transmissive display area and the reflective display area. An object of the present invention is to provide a liquid crystal device and an electronic device.

  In order to solve the above problem, it is also conceivable that only the inclined portion of the inner surface retardation layer disposed in the reflective display region is positioned in the transmissive display region. Thereby, it is possible to prevent the light reflection efficiency from being lowered by the inclined portion on the reflective display region side. Generally, the retardation axis of the retardation layer is arranged so as to intersect the polarization axis of the polarizing plate. However, in such a case, a difference in phase difference occurs between a region where the inclined portion exists and a region where the inclined portion does not exist in the transmissive display region.

  Therefore, in order to solve this problem, the liquid crystal device of the present invention includes a liquid crystal layer sandwiched between a first substrate and a second substrate facing each other, and a first substrate provided on the first substrate side with respect to the liquid crystal layer. A transflective liquid crystal comprising a polarizing plate and a second polarizing plate provided on the second substrate side with respect to the liquid crystal layer, and having a transmissive display region and a reflective display region in one pixel region. An apparatus, provided on one of the first substrate and the second substrate, for driving the liquid crystal layer, a first electrode and a second electrode, a reflective layer provided in the reflective display region, A retardation layer overlapping the reflective layer, a polarization axis of the first polarizing plate being orthogonal to a polarization axis of the second polarizing plate, and an end portion of the retardation layer having an inclined portion. The inclined portion is located in the transmissive display area, and the slow axis of the inclined portion is the first offset. A slow axis of the retardation layer located in the reflective display region is parallel to the polarization axis of one of the plate and the second polarizing plate, and the first polarizing plate and the second polarizing plate It intersects with the polarization axis of the plate.

  According to the liquid crystal device of the present invention, since the inclined portion of the retardation layer whose film thickness gradually changes is positioned in the transmissive display region, the change in the retardation in the inclined portion in the reflective display region. Does not occur. Therefore, it is possible to avoid a decrease in contrast on the reflective display region side. In addition, no voltage is applied by setting the slow axis in the inclined part to be parallel to the polarization axis of either the first polarizing plate or the second polarizing plate (substrate on the light incident side). In this case, a good display can be maintained without being affected by the retardation fluctuation in the inclined portion. Therefore, the occurrence of light leakage due to the inclined portion in the transmissive display area is prevented.

Further, since the slow axis of the retardation layer other than the inclined portion located in the reflective display region is set so as to intersect with the polarization axes of the first polarizing plate and the second polarizing plate, the reflective display region The phase difference between the side and the transmissive display area is adjusted well. From the above, high contrast can be realized in the reflective display area and the transmissive display area, and excellent visibility can be exhibited. In addition, since the angle of the edge part of a phase difference layer becomes small with respect to a substrate surface by an inclination part, the adhesiveness with respect to the board | substrate of a phase difference layer becomes favorable.

  Further, the retardation layer is made of a liquid crystal material, an alignment film for aligning the liquid crystal material is provided on the lower layer side of the retardation layer, and the alignment direction of the alignment film located in the reflective display region is The alignment direction of the alignment film that intersects the polarization axis of the first polarizing plate and the second polarizing plate and is positioned in the transmissive display region is either the first polarizing plate or the second polarizing plate. It is also preferable to be parallel to one polarization axis.

  According to such a configuration, the liquid crystal material constituting the retardation layer is aligned according to the alignment treatment applied to the surface of the alignment film. Therefore, the retardation layer located on the reflective display region side has a slow axis that intersects with the polarization axis of either the first polarizing plate or the second polarizing plate, and the retardation layer located on the transmissive display region side, That is, the inclined portion has a slow axis parallel to the polarization axis of either the first polarizing plate or the second polarizing plate. Thereby, when no voltage is applied, it is possible to maintain a good display without being affected by the retardation fluctuation in the inclined portion located in the transmissive display region.

Moreover, it is also preferable that the first electrode and the second electrode are arranged so as to avoid a region overlapping the inclined portion.

  According to such a configuration, when a voltage is applied, the electric field strength of the region where the inclined portion exists is weaker than the region where the electrode is arranged without the inclined portion (and the reflective display region). Alternatively, since the electric field is hardly applied, the alignment direction of the liquid crystal positioned on the inclined portion is regulated by the alignment film. For this reason, on the inclined portion, even when a voltage is applied, the alignment direction of the liquid crystal hardly changes, and the alignment direction is substantially the same as when no voltage is applied.

  That is, when the first electrode and the second electrode are arranged in the region where the inclined portion of the retardation layer is formed, the liquid crystal molecules on the inclined portion exist in the transmissive display region when a voltage is applied. The orientation is controlled in the same way as molecules. Then, the retardation of the region where the retardation layer is present differs from the retardation of the region where the retardation layer is not present. Since light transmitted through the inclined portion is also used for displaying the transmissive display area, it is difficult to perform gradation (orientation) control even if a predetermined gradation is obtained in the entire transmissive display area.

However, in the present invention, the alignment of the liquid crystal molecules on the inclined portion is not controlled by not arranging the electrode in the region where the inclined portion of the retardation layer is formed. For this reason, the alignment direction of the liquid crystal positioned on the inclined portion is regulated by the alignment film, and dark display tends to occur. Therefore, the influence of the light transmitted through the inclined portion on the display in the transmissive display area can be made constant. Thereby, when a constant gradation is obtained in the entire pixel region, a desired gradation can be obtained accurately.

It is also preferable that the same voltage be applied to the electrodes facing each other across the region overlapping the inclined portion.
According to such a configuration, even when a voltage is applied, no electric field is generated in the region having the inclined portion. Therefore, alignment control of the liquid crystal on the inclined portion is not performed, and dark display is obtained even when a voltage is applied. Thereby, it can avoid more reliably that the light which permeate | transmitted the inclination part affects the display in a transmissive display area. Therefore, the desired gradation can be obtained more accurately when a constant gradation is obtained in the entire pixel region.

It is also preferable that the retardation layer functions as a liquid crystal layer thickness adjusting layer for adjusting the layer thickness of the liquid crystal layer between the reflective display region and the transmissive display region.
According to such a configuration, it is not necessary to separately provide a liquid crystal layer thickness adjusting layer made of an insulating layer, so that the device configuration and the manufacturing process can be simplified. In addition, since most of the retardation layer is provided on the reflective display region side, by adjusting the thickness of the retardation layer, the retardation layer itself is used to reduce the thickness of the liquid crystal layer on the reflective display region side. It can function as a liquid crystal layer thickness adjusting layer.

An electronic apparatus according to the present invention includes the liquid crystal device as described above.
According to the electronic device of the present invention, since the liquid crystal device that exhibits excellent visibility in the transmissive display region and the reflective display region is provided, it is possible to provide an electronic device with excellent reliability.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, each layer or each member has a different scale so that each layer and each member can be recognized on the drawing. In the following description, the liquid crystal layer side in each component of the liquid crystal device is referred to as the inner side, and the opposite side is referred to as the outer side. An area serving as a minimum unit of image display is referred to as a “sub-pixel area”, and a set of a plurality of sub-pixel areas including each color filter is referred to as an “image display area”. In the sub-pixel region, a region where display using light incident from the display surface side of the liquid crystal device can be performed is called a “reflective display region”, and the light is incident from the back side (the side opposite to the display surface) of the liquid crystal device. An area that can be displayed using light is referred to as a “transmission display area”.

[First Embodiment]
First, the liquid crystal device of this embodiment will be described.
FIG. 1 is a cross-sectional view showing a schematic configuration of the liquid crystal device of the present embodiment, and FIG. 2 is a plan view showing an electrode configuration of a TFT array substrate in the liquid crystal device of the present embodiment. FIG. 3 is an explanatory diagram showing the slow axis of the inner surface retardation layer. In FIGS. 1 and 2, in order to make one subpixel region enlarged and to make the drawing easy to see, specific parts are highlighted, and the film thicknesses and dimensional ratios of the respective components are as follows. It is different as appropriate.

The liquid crystal device of this embodiment is an example of an active matrix liquid crystal device using a thin film transistor (hereinafter abbreviated as TFT) as a switching element.

  As shown in FIG. 1, the liquid crystal device 1 includes, for example, a pseudo-device between a TFT array substrate 10 (first substrate) and a counter substrate 20 (second substrate) disposed to face the TFT array substrate 10 (first substrate). A liquid crystal layer 30 composed of an isotropic liquid crystal material or the like is sandwiched. The TFT array substrate 10 generates an electric field (lateral electric field) in an in-plane direction (a direction parallel to the surface direction of the substrate) with respect to the substrate, and changes the alignment state of the liquid crystal material by this lateral electric field, thereby performing optical switching. An electrode configuration of an in-plane switching (hereinafter abbreviated as “IPS”) system that has a function is employed.

  In the IPS system, when a voltage is applied, the alignment state of the liquid crystal material changes in a direction parallel to the substrate. Therefore, in addition to a wide viewing angle, there is a change in color tone depending on the viewing direction and a change in color tone in all gradations from white to black. A small viewing angle (for example, about 170 degrees in the vertical and horizontal directions) can be obtained, and a natural image can be displayed.

An electrode configuration in the TFT array substrate 10 is shown in FIG.
A plurality of subpixel regions S are arranged in a matrix on the inner surface of the TFT array substrate 10. In plan view, the plurality of data lines 2 extending in the longitudinal direction of the sub-pixel region S having a rectangular shape and the plurality of scanning lines 3 extending in the short direction of the sub-pixel region S intersect each other. Is provided. The data line 2 has a function of supplying an image signal to the sub-pixel regions S in each column, and the scanning line 3 has a function of supplying a scanning signal to the TFT elements 5 in the sub-pixel regions S in each row. ing. In the vicinity of the intersection between the data line 2 and the scanning line 3, the scanning line 3 branches inward into the sub-pixel region S to form the gate electrode 4, and constitutes a TFT element 5 for pixel switching.

  In the TFT element 5 in each sub-pixel region S, one of the source electrode and the drain electrode is connected to the data line 2 and the other is connected to the first electrode 6. The first electrode 6 has a plurality of electrode fingers 6 a extending along the scanning line 3 and is connected to the drain electrode of the TFT element 5, for example.

  A comb-like second electrode 7 having a plurality of electrode fingers 7 a extending along the scanning line 3 is provided. The electrode fingers 7a of the second electrode 7 are arranged at positions between the electrode fingers 6a of the first electrode 6 in a plan view. In this way, the electrode fingers 6a that are pixel electrodes and the electrode fingers 7a that are common electrodes alternately exist in the extending direction of the data line 2.

  Here, each electrode finger 7a is connected to the common electrode line 7b. The second electrodes 7 are connected to each other between the sub-pixel regions S, and are configured to be kept at a constant potential in the entire image display region. That is, the first electrode 6 (electrode finger 6a) is a pixel electrode, and the second electrode 7 (electrode finger 7a) is a common electrode. The data line 2, the scanning line 3, the first electrode 6 (electrode finger 6 a), the second electrode 7 (electrode finger 7 a, common electrode line 7 b), and the TFT element 5 are all provided on the TFT array substrate 10. It has been.

  An area surrounded by the data lines 2 and the scanning lines 3 (area surrounded by a two-dot chain line in FIG. 2) constitutes one sub-pixel area S of the liquid crystal device 1 of the present embodiment. In this sub-pixel region S, one colored layer of the three primary colors is disposed corresponding to one sub-pixel region S, and each of the colored layers, blue (B), green A pixel region including (G) and red (R) is formed.

  As shown in FIG. 1, the TFT array substrate 10 has a reflective layer 13 made of a highly reflective metal material such as aluminum on the surface of a substrate body 11 made of a light transmissive material such as quartz or glass. In this configuration, the insulating layer 12 is partially formed of a resin material or the like. A region where the reflective layer 13 is formed becomes a reflective display region R, and a region where the reflective layer 13 is not formed becomes a transmissive display region T. Thus, the liquid crystal device 1 is a transflective liquid crystal device 1 that enables reflective display and transmissive display.

  The insulating layer 12 formed on the substrate body 11 has an uneven shape 12a on its surface, and the surface of the reflective layer 13 has an uneven portion 13a corresponding to the uneven shape 12a. Since the reflected light is scattered by such an uneven portion 13a, reflection from the outside is prevented, and a wide viewing angle display can be obtained. The uneven shape 12 a is further covered with a resin layer 14. By the resin layer 14, the uneven portion 13 a of the reflective layer 13 is flattened, and the first electrode 6 and the second electrode 7 are formed on the flat surface of the resin layer 14.

  The first electrode 6 as a pixel electrode and the second electrode 7 as a common electrode are made of a transparent conductive material such as indium tin oxide (hereinafter abbreviated as ITO).

  On the other hand, in the transmissive display region T, the reflective layer 13 is not formed on the surface of the insulating layer 12, and the surface is covered with the resin layer 14. That is, in the transmissive display region T, the first electrode 6 and the second electrode 7 made of a transparent conductive material are formed as pixel electrodes on the resin layer 14 covering the insulating layer 12 (uneven shape 12a). As described above, each of the first electrode 6 and the second electrode 7 has a plurality of electrode fingers 6 a and 7 a, and the electrode finger 6 a of the second electrode 6 is planarly arranged with the electrode finger of the first electrode 7. 7a. Therefore, in the longitudinal direction of the sub-pixel region S (the extending direction of the data line 2), the electrode fingers 6a and the electrode fingers 7a are alternately present.

Further, on the TFT array substrate 10, a first alignment film 19 made of polyimide or the like is formed on the boundary surface with the liquid crystal layer 30 so as to cover the first electrode 6 and the second electrode 7. The first alignment film 19 is rubbed in a predetermined direction, and the initial alignment (alignment when no voltage is applied) of the liquid crystal molecules 31 of the liquid crystal layer 30 is set to the first electrode 6 and the second electrode. The electrode 7 is restricted in a direction inclined at a predetermined angle with respect to the extending direction of the electrode fingers 6a, 7a.

  Next, the counter substrate 20 side is provided with a color filter CF and a retardation layer alignment film on a substrate main body 21 (an inner surface of the substrate main body 21 on the liquid crystal layer 30 side) made of a translucent material such as glass or quartz. 27, an inner surface retardation layer 28 (retardation layer), and a second alignment film 29 are provided in this order. Here, the color filter CF is partitioned by the black matrix BM corresponding to the sub-pixel region S, and the boundary of each sub-pixel region S is formed by this black matrix BM.

  Further, a retardation layer alignment film 27 is formed on the inner surface side of the color filter CF (the surface side sandwiching the liquid crystal layer 30). The alignment film 27 for the retardation layer is subjected to different alignment treatments in the transmissive display region T and the reflective display region R by using a rubbing method or the like. Here, the alignment layer 27 for the retardation layer has a function of determining the slow axis of the inner surface retardation layer 28. 3A and 3B, the rubbing direction of the retardation layer alignment film 27 located on the reflective display region R side is indicated by an arrow O in the drawing, and the retardation layer orientation located on the transmissive display region T side is shown. The rubbing direction of the film 27 is indicated by an arrow P in the figure. The rubbing direction on the reflective display region R side is along the extending direction of the data line 2 (see FIG. 2), and the rubbing direction on the transmissive display region T side is a predetermined angle θ (with respect to the extending direction of the data line 2). The direction is inclined at about 45 °. Specifically, a rubbing process is performed in a direction parallel to the polarization axis L of a first polarizing plate 24 described later disposed on the outer surface side of the counter substrate 20 shown in FIG.

As shown in FIGS. 1 and 3A and 3B, the inner surface retardation layer 28 is provided on the inner surface of the color filter CF on the reflective display region R side in each sub-pixel region S, and the liquid crystal layer 30. A phase difference of ½ wavelength is given to visible light incident on the light. The inner surface retardation layer 28 is composed of a polymer liquid crystal formed by photopolymerizing a liquid crystalline monomer. The inner surface retardation layer 28 includes an inclined portion 28A having an inclined surface 28a inclined at a predetermined angle with respect to the substrate surface at an end thereof, and the entire inclined portion 28A is disposed in the transmissive display region T. Has been. Further, the inner surface retardation layer 28 of the present embodiment has a function of optimizing the retardation imparted to the light transmitted through the liquid crystal layer 30 in each of the reflective display region R and the transmissive display region T, and adjusts the liquid crystal layer thickness. Acts as a layer. Here, the liquid crystal layer 30 on the reflective display region R side is adjusted so that the phase difference of the liquid crystal layer 30 in the reflective display region R is λ / 4 and the phase difference of the liquid crystal layer 30 in the transmissive display region T is λ / 2. is doing. The liquid crystal layer thickness in the reflective display region R is approximately ½ of the liquid crystal layer thickness in the transmissive display region T. Where λ is the wavelength of light.

  The slow axis of the inner surface retardation layer 28 is subjected to an alignment process corresponding to the rubbing direction of the alignment layer 27 for the retardation layer in the reflective display region R and the transmissive display region T, respectively. In the present embodiment, although the slow axis (arrow O in FIG. 3) of the inner surface retardation layer 28 existing on the reflective display region R side is along the extending direction of the data line 2 (see FIG. 2). On the other hand, the slow axis (arrow P1 in FIG. 3) of the inclined portion 28A of the inner surface retardation layer 28 existing on the transmissive display region T side is the slow axis (arrow P2 in FIG. 3) on the reflective display region R side. ) With a predetermined angle (about 45 °) and coincides with a polarization axis L of the first polarizing plate 24 described later.

  Here, a method of forming the inner surface retardation layer 28 on the counter substrate 20 on which the color filter CF is formed will be described. On the color filter CF, as described above, the retardation layer alignment film 27 that is rubbed in different directions in the reflective display region R and the transmissive display region T is formed. For example, a photoreactive liquid crystalline monomer is applied onto the alignment layer 27 for the retardation layer, heated at a predetermined temperature, and then cooled to cool the liquid crystal monomer in the rubbing direction of the alignment layer 27 for the retardation layer. Orient in the appropriate direction. Next, the liquid crystalline monomer is locally photopolymerized by performing exposure with ultraviolet light using a photomask, and then developed using an organic solvent to form a liquid crystalline monomer polymer on the reflective display region R side. Remain. At this time, the liquid crystalline monomer polymer remains so that the end portion on the transmissive display region T side protrudes to the transmissive display region T side, reflecting the pattern of the photomask. Therefore, an inclined surface is formed at the end of the liquid crystalline monomer polymer that protrudes toward the transmissive display region T so that the film thickness gradually decreases. Thereby, the inner surface retardation layer 28 in which the inclined portion 28A is located in the transmissive display region T is formed. Here, since the alignment direction of the liquid crystal monomer in the inclined portion 28A of the inner surface retardation layer 28 is always along the rubbing direction of the alignment layer 27 for the retardation layer on the transmissive display region T side, An inner surface retardation layer 28 having a different alignment direction from the existing liquid crystal monomer is formed.

The second alignment film 29 is made of polyimide or the like so as to cover the inner surface retardation layer 28 and the exposed surface of the color filter CF. The second alignment film 29 is rubbed along a predetermined direction, and the initial alignment of liquid crystal molecules in the liquid crystal layer 30 (alignment when no voltage is applied) is applied to the first electrode 6 and the first electrode. The two electrodes 7 are restricted in a direction inclined at a predetermined angle (about 45 °) with respect to the extending direction of the electrode fingers 6a, 7a. That is, in detail, a rubbing process in a direction parallel to the polarization axis L of the first polarizing plate 24 described later disposed on the outer surface side of the counter substrate 20 is performed. Note that the rubbing direction of the first alignment film 19 and the rubbing direction of the second alignment film 29 are the same in plan view.

  The TFT array substrate 10 and the counter substrate 20 described above are bonded together by a sealing material (not shown), and liquid crystal molecules 31 are injected from a liquid crystal injection port formed in the sealing material, whereby a liquid crystal panel 35 is obtained.

The liquid crystal panel 35 is provided with a first polarizing plate 24 and a second polarizing plate 25 on the outer surface sides of the TFT array substrate 10 and the counter substrate 20, respectively. As shown in FIG. The transmission axes L and N are arranged so as to be orthogonal to each other. In the first polarizing plate 24 and the second polarizing plate 25, the light transmittance of the liquid crystal device 1 when no voltage is applied is approximately 0%, and the light transmittance of the liquid crystal device 1 when the voltage is applied is approximately 50%. Further, the light transmission axes L and N of the first polarizing plate 24 and the second polarizing plate 25 are arranged in directions intersecting the scanning line 3 and the data line 2 at a predetermined angle (about 45 °), respectively. As described above, the first polarizing plate 24 and the second polarizing plate 25 are set in a crossed Nicols state by sandwiching the TFT array substrate 10 and the counter substrate 20 between both sides of the TFT array substrate 10 and the counter substrate 20 shown in FIG. The liquid crystal device 1 of this embodiment is bonded. In this embodiment, the first polarizing plate 24 and the second polarizing plate 25 are disposed outside the TFT array substrate 10 and the counter substrate 20, respectively. However, the wire grid polarizing layer or the like is used as the TFT array substrate 10 and the counter substrate. It is good also as a structure arrange | positioned at the 20 liquid crystal layer side. As shown in FIG. 2, the polarization axis L of the first polarizing plate 24 disposed outside the counter substrate 20 has a rubbing direction on the transmissive display region T side of the retardation layer alignment film 27 and an internal phase difference. It is substantially coincident with the slow axis O of the layer 28.

A backlight (not shown) serving as a light source for transmissive display is provided outside the second polarizing plate 25 provided on the TFT array substrate 10.

  Such a liquid crystal device 1 employs an IPS-type electrode configuration in which the first electrode 6 and the second electrode 7 are arranged on the same plane on the TFT array substrate 10. Accordingly, the liquid crystal layer 30 is driven by a lateral electric field F generated by the first electrode 6 (electrode finger 6a) and the second electrode 7 (electrode finger 7a).

  In the transmissive display region T of the present embodiment, when the region where the inclined portion 28A of the inner surface retardation layer 28 exists is the first region T1, and the other transmissive display region T where the inclined portion 28A does not exist is the second region T2, Either the pixel electrode or the common electrode is arranged also in the first region T1 where the inclined portion 28A exists. In the present embodiment, as shown in FIG. 2, electrode fingers 6a (first electrodes 6) as pixel electrodes are present in the first region T1.

  However, the multi-gap liquid crystal device 1 has a problem that the phase difference of light passing through the liquid crystal layer 30 in the reflective display region R and the phase difference of light passing through the liquid crystal layer 30 in the transmissive display region T are different. . Here, for example, when the thickness of the liquid crystal layer 30 is d and the refractive index anisotropy of the liquid crystal is Δn, the phase difference (retardation) of light is represented by the product Δn · d. Therefore, in this embodiment, the refractive index anisotropy Δn and the cell gap of the liquid crystal layer 30 are set so that the phase difference of the liquid crystal layer 30 is ¼ wavelength in the reflective display region R and ½ wavelength in the transmissive display region T. d is set.

  As the liquid crystal molecules constituting the liquid crystal layer 30, positive type liquid crystal molecules 31 having positive dielectric anisotropy are used. When the voltage is applied, the liquid crystal molecules are aligned along the electric field direction and no voltage is applied. In the state, the first alignment film 19 and the second alignment film 29 are aligned along the rubbing direction.

[Operation of liquid crystal device]
Next, the operation of the liquid crystal device 1 having the above configuration will be described.
As shown in FIG. 1, the liquid crystal device 1 according to the present embodiment is a horizontal electric field type liquid crystal device 1 using an IPS method, and an image signal (voltage) is applied to a first electrode 6 as a pixel electrode via a TFT element 5. ) Is generated between the electrode fingers 6a and the electrode fingers 7a, and an electric field E is generated along the direction in which the electrode fingers 6a and 7a face each other (the surface direction of the substrate). To drive. Then, the liquid crystal device 1 performs display by polarizing the transmittance for each sub-pixel region S. That is, in a state where no voltage is applied to the first electrode 6 (pixel electrode), the liquid crystal molecules 31 constituting the liquid crystal layer 30 are rubbed between the TFT array substrate 10 and the counter substrate 20 (in the data line 2 shown in FIG. 2). (In a direction inclined by approximately 45 ° with respect to the substrate surface). Since the first alignment film 19 and the second alignment film 29 that face each other with the liquid crystal layer 30 interposed therebetween are rubbed in the same direction in plan view, the liquid crystal molecules 31 are horizontally aligned in one direction between the substrates. ing.

  An electric field E is applied to the liquid crystal layer 30 in such an alignment state via the pixel electrode (first electrode 6) and the common electrode (second electrode 7). As shown in FIG. 2, in the transmissive display region T (first region T1, second region T2) and the reflective display region R, the extending direction of the electrode finger 6a constituting the pixel electrode and the electrode finger 7a constituting the common electrode When the electric field E along the direction orthogonal to the liquid crystal layer 30 is generated, the liquid crystal molecules 31 are aligned along the direction of the electric field E.

  The liquid crystal device 1 performs bright and dark display using birefringence based on the difference in the alignment state of the liquid crystal molecules 31, and a voltage is applied between the transmissive display region T and the reflective display region R. By changing the operation of the liquid crystal molecules 31 in the state, appropriate transmittance / reflectance can be obtained in each region.

[Display operation of liquid crystal device]
Next, a display operation of the liquid crystal device having the above configuration will be specifically described with reference to FIGS.
First, transmissive display (transmission mode) will be described.
In the liquid crystal device 1, the light emitted from the backlight passes through the second polarizing plate 25, is converted into linearly polarized light parallel to the polarization axis N of the second polarizing plate 25, and enters the liquid crystal layer 30. .

  In the transmissive display region T, when the liquid crystal layer 30 is in the non-application state (non-selection state), the linearly polarized light incident on the liquid crystal layer 30 is emitted from the liquid crystal layer 30 in the same polarization state as that at the time of incidence. At this time, in the second region T2 where the inclined portion 28A of the inner phase difference layer 28 is not located, the linearly polarized light transmitted through the liquid crystal layer 30 is directed to the first polarizing plate 24, but the inclined portion 28A is located. In the first region T1, the linearly polarized light emitted from the liquid crystal layer 30 enters the inclined portion 28A. The linearly polarized light transmitted through the liquid crystal layer 30 in the second region T2 is absorbed by the first polarizing plate 24 having a transmission axis orthogonal to the linearly polarized light, and the second region T2 becomes a dark display. In the first region T1, since the slow axis of the inclined portion 28A coincides with the polarization axis of the first polarizing plate 24, the liquid crystal layer is not affected by the retardation of the inclined portion 28A and is the same as the second region T2. The linearly polarized light transmitted through the light 30 is absorbed by the first polarizing plate 24 having a transmission axis perpendicular to the linearly polarized light, and dark display is obtained.

  Therefore, the linearly polarized light transmitted through the liquid crystal layer 30 in the first region T1 and the second region T2 is absorbed by the first polarizing plate 24 having a transmission axis orthogonal to the linearly polarized light, and the transmissive display region T (first The sub-pixel region S including the region T1 and the second region T2) and the reflective display region R is darkly displayed.

    On the other hand, if the liquid crystal layer 30 is in an applied state (selected state), the linearly polarized light incident on the liquid crystal layer 30 is given a predetermined phase difference (1/2 wavelength) by the liquid crystal layer 30 and the polarization direction at the time of incidence. Is converted into linearly polarized light rotated by 90 ° from the liquid crystal layer 30 and emitted from the liquid crystal layer 30. Since this linearly polarized light is parallel to the transmission axis of the first polarizing plate 24, the linearly polarized light passes through the first polarizing plate 24 and is visually recognized as display light, so that the sub-pixel region S is brightly displayed. In the inclined portion 28A, since the cell thickness is smaller than λ / 2, it is not completely black, and a bright display is achieved with a lower transmittance than the second region T2.

Next, reflection display (reflection mode) will be described.
In the reflective display region R, light incident from above (outside) the first polarizing plate 24 is converted into linearly polarized light parallel to the polarization axis of the second polarizing plate 25 by passing through the first polarizing plate 24, and thus the inner surface. The light enters the phase difference layer 28. The inner retardation layer 28 is a so-called λ / 2 retardation layer that gives a half-wave retardation to the light passing through the inner retardation layer 28, and thus linearly polarized light that passes through the inner retardation layer 28. Is converted into linearly polarized light orthogonal thereto, is emitted from the inner surface retardation layer 28, and enters the liquid crystal layer 30.

  If the voltage of the liquid crystal layer 30 is not applied (non-selected state), the linearly polarized light converted by the inner surface retardation layer 28 is given a predetermined retardation (λ / 4) by the liquid crystal layer 30. Converted to clockwise circularly polarized light. In the case of this embodiment, since the inner retardation layer 28 has a multi-gap structure that functions as a liquid crystal layer thickness adjusting layer, the retardation of the liquid crystal layer 30 in the reflective display region R is half of the retardation in the transmissive display region T. Since it is set, linearly polarized light is converted into circularly polarized light by passing through the liquid crystal layer 30.

  The light emitted from the liquid crystal layer 30 as clockwise circularly polarized light is reflected by the reflective layer 13, but at this time, the rotation direction viewed from the first polarizing plate 24 is reversed to become counterclockwise circularly polarized light. Then, it enters the liquid crystal layer 30 again. Thereafter, a predetermined phase difference is given by the liquid crystal layer 30 and the inner surface retardation layer 28, converted into linearly polarized light, and returned to the first polarizing plate 24. Since the linearly polarized light that has reached the first polarizing plate 24 is converted into linearly polarized light in a direction orthogonal to the transmission axis of the second polarizing plate 25, the linearly polarized light is absorbed by the first polarizing plate 24 and the sub-pixel region S is The display is dark.

    On the other hand, when the voltage of the liquid crystal layer 30 is in the applied state (selected state), the liquid crystal layer 30 is emitted from the liquid crystal layer 30 and reflected in the same polarization state as the linearly polarized light to which the phase difference of λ / 2 is given by the inner surface retardation layer 28. Reach the layer. Then, the light reflected by the reflective layer 13 passes through the liquid crystal layer 30 again and enters the inner surface retardation layer 28. Then, again, a phase difference of λ / 2 is given by the inner surface phase difference layer 28 and converted into linearly polarized light. Since the linearly polarized light is linearly polarized light parallel to the transmission axis of the first polarizing plate 24, the linearly polarized light is viewed through the first polarizing plate 24, and the sub-pixel region S is brightly displayed.

  As described above, the liquid crystal device 1 employs a multi-gap structure so that the phase difference of the liquid crystal layer 30 in the reflective display region R is approximately ½ of the phase difference of the liquid crystal layer 30 in the transmissive display region T. There is a difference in the substantial phase difference imparted to the display light between the reflective display using the light transmitted through the layer 30 twice as the display light and the transmissive display using the light transmitted only once through the liquid crystal layer 30 as the display light. Does not occur.

  In the liquid crystal device 1 of the present embodiment, since the inclined portion 28A of the inner surface retardation layer 28 does not exist on the reflective display region R side, a change in retardation imparted to the reflected light in the inclined portion 28A does not occur. Therefore, it is possible to avoid a decrease in contrast due to light leakage in the reflective display region R. In addition, since the slow axis in the inclined portion 28A coincides with the polarization axis of the first polarizing plate 24, the state of light transmitted through the inclined portion 28A is changed when no voltage is applied. Can be kept in good condition. For this reason, even if the inclined portion 28A exists in the transmissive display region T, there is no deviation in polarization due to the inclined portion 28A in the first region T1 and the second region T2 of the transmissive display region T.

  In this way, the influence of the retardation variation due to the inclined portion 28A of the inner surface retardation layer 28 is avoided on the reflective display region R side, so that the difference in image display quality between the reflective display region R and the transmissive display region T is eliminated. Thus, high-quality display can be obtained by both transmissive display and reflective display.

According to such a configuration, the phase difference in the reflective display region R and the phase difference in the transmissive display region T can be made substantially equal. Thereby, the light utilization efficiency can be improved most, and the transmissive display can be the brightest. In addition, a display with high contrast can be obtained. Furthermore, the visibility of the reflective display can be sufficiently secured. In addition, since the above-described liquid crystal device 1 employs the horizontal electric field method, an effect of good visibility can be obtained.

  Here, in the above embodiment, as shown in FIG. 1, the cell gap d1 of the first region T1 and the cell gap d2 of the second region T2 in the transmissive display region T are caused by the inclined portion 28A of the inner surface retardation layer 28. Is different. Therefore, the phase difference value Δnd2 of the second region T2 is larger than the phase difference value Δnd1 of the first region T1. That is, in the state where the voltage is applied, the liquid crystal molecules 31 in the first region T1 where the inclined portion 28A is located are controlled in the same manner as the liquid crystal molecules 31 in the second region T2 where the inclined portion 28A is not located. There is a difference between the retardation of the liquid crystal layer in the region T1 and the retardation of the liquid crystal layer in the second region T2. Since light transmitted through the inclined portion 28A is also used for transmissive display, even if an attempt is made to obtain a constant gradation in the entire transmissive display region T, the gradation (light transmitted through the first polarizing plate 24) due to the difference in retardation. The light in the first region T1 that cannot be controlled) is added to the display, making it difficult to display a desired gradation. Therefore, in the following second embodiment, an electrode is not provided in the first region T1 where the inclined portion 28A exists.

[Second Embodiment]
Next, a liquid crystal device according to a second embodiment of the invention will be described with reference to the drawings. Here, FIGS. 4 to 6 are cross-sectional views showing the electrode configuration of the liquid crystal device in the second embodiment. In this embodiment, since the configuration of the sub-pixel region S of the first embodiment is different, this point will be mainly described, and the same reference numerals are given to the components described in the above-described embodiment, and the description will be given. Is omitted. FIG. 5 shows the alignment direction of the liquid crystal with no voltage applied, and FIG. 6 shows the alignment direction of the liquid crystal with the voltage applied.

  As shown in FIGS. 4 and 5, in the liquid crystal device 50 of the present embodiment, in the transmissive display region T, any of the pixel electrode and the common electrode is disposed in the first region T1 where the inclined portion 28A of the inner surface retardation layer 28 exists. Also not arranged. In the transmissive display area T and the reflective display area R, the electrode finger 6a (first electrode 6) as a pixel electrode and the electrode finger 7a (second electrode 7) as a common electrode are extended from the data line 2 in the same manner as in the above embodiment. Alternating in the present direction.

In the reflective display region R, the electrode fingers 7a of the second electrode 7 are arranged at the boundary on the transmissive display region T side. In the transmissive display region T, in the second region T2 where the inclined portion 28A does not exist, the electrode finger 7a of the second electrode 7 is disposed on the boundary side with the first region T1 where the inclined portion 28A exists. In the present embodiment, the electrode fingers 7a of the second electrode 7 are arranged to face each other on both sides of the first region T1.

Thus, by arranging the electrode fingers 7a so as to face each other on both sides of the first region T1, no voltage is applied to the first region T1 when a voltage is applied as shown in FIG. It will be. Thereby, the alignment direction of the liquid crystal molecules 31 existing in the first region T1 in the voltage application state is the same as the alignment direction of the liquid crystal molecules 31 when no voltage is applied. That is, by arranging the electrode fingers 7a and 7a having the same potential on both sides of the first region T1, no voltage is applied to the liquid crystal layer 30 in the first region T1, so that the liquid crystal alignment is not controlled. Therefore, in the first region T1, dark display is performed even when a voltage is applied. Therefore, it is possible to prevent the light in the region (first region T1) that cannot be controlled by the inclined portion 28A from being added to the transmissive display.

Here, in the reflective display region R and the second region T2 (transmission display region T), the electrode fingers 6a as the pixel electrodes and the electrode fingers 7a as the common electrodes are alternately arranged. An electric field perpendicular to the extending direction of the electrode fingers 6a and 7a acts between the electrodes 7a, and the liquid crystal molecules 31 are aligned in the electric field direction. Therefore, in the reflective display region R and the second region T2 (transmissive display region T), a bright display is obtained when a voltage is applied.

According to the configuration of the liquid crystal device 50 of the present embodiment, even when a voltage is applied, the display of the first region T1 where the inclined portion 28A is present can be made dark, so the first region T1. The transmitted light is prevented from affecting the transmissive display. For this reason, when a certain gradation is obtained in the sub-pixel region S, a desired gradation can be obtained accurately.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but it goes without saying that the present invention is not limited to such examples. Various shapes, combinations, and the like of the constituent members shown in the above-described examples are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

For example, in the above-described embodiments, an example of a transflective color liquid crystal device has been described. However, the present invention can be applied regardless of monochrome / color. That is, it is not always necessary to provide a color filter as in the above embodiment.
In the above-described embodiment, the configuration in which the first electrode and the pixel switching TFT element are electrically connected has been described as an example. However, the present invention is not limited to this configuration, and the second electrode and the pixel switching TFT element are used. And may be electrically connected.

Furthermore, regarding specific descriptions such as the shape, size, and number of electrode fingers of each component such as the first electrode, the second electrode, the data line, and the gate line, the design is appropriately changed without being limited to the example of the embodiment. Is possible.
In the second embodiment, the electrode finger 7a (second electrode) as a common electrode is disposed opposite to both sides of the first region T1 in the transmissive display region T. However, the electrode finger 6a (first electrode) as a pixel electrode is disposed. ) May be arranged opposite to each other.

[Electronics]
FIG. 7 is a perspective view showing an example of an electronic apparatus according to the present invention. A cellular phone 1300 in the figure includes the liquid crystal device of the present invention as a small-sized display portion 1301, and includes a plurality of operation buttons 1302, an earpiece 1303, and a mouthpiece 1304. The display device of each of the above embodiments is not limited to the mobile phone, but is an electronic book, a personal computer, a digital still camera, a liquid crystal television, a viewfinder type or a monitor direct view type video tape recorder, a car navigation device, a pager, and an electronic notebook. , Calculators, word processors, workstations, video phones, POS terminals, devices equipped with touch panels, etc., and can be suitably used as image display means. In any electronic device, it is bright, has high contrast, and has a wide viewing angle. Image display is possible.

It is sectional drawing which shows schematic structure of the liquid crystal device which concerns on 1st Embodiment. It is a top view which shows the electrode structure of the TFT array substrate of the liquid crystal device which concerns on 1st Embodiment. It is explanatory drawing which shows the slow axis of the inner surface phase difference layer which concerns on 1st Embodiment. It is sectional drawing which shows schematic structure of the liquid crystal device which concerns on 2nd Embodiment. It is a top view which shows the electrode state of the liquid crystal device which concerns on 2nd Embodiment, and shows the orientation state of the liquid crystal of a voltage no application state. It is a top view which shows the orientation state of the liquid crystal of a voltage application state while showing the electrode structure of the liquid crystal device which concerns on 2nd Embodiment. It is a schematic block diagram which shows the mobile telephone which concerns on the electronic device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,50 ... Liquid crystal device, 10 ... TFT array substrate (first substrate), 20 ... Counter substrate (second substrate), 30 ... Liquid crystal layer, S ... Pixel region, T ... Transmission display region, T1 ... First region, T2 ... second region, R ... reflective display region, 13 ... reflective layer, 28 ... inner surface retardation layer (retardation layer), 24 ... first polarizing plate, 25 ... second polarizing plate, 28A ... inclined portion, 27 ... Alignment film for retardation layer, 1300 ... mobile phone (electronic equipment)

Claims (6)

A liquid crystal layer is sandwiched between a first substrate and a second substrate facing each other, a first polarizing plate provided on the first substrate side with respect to the liquid crystal layer, and the second substrate side with respect to the liquid crystal layer A transflective liquid crystal device having a transmissive display region and a reflective display region in one pixel region,
A first electrode and a second electrode which are provided on any one of the first substrate and the second substrate and drive the liquid crystal layer;
A reflective layer provided in the reflective display area;
A retardation layer overlapping the reflective layer,
The polarization axis of the first polarizing plate is orthogonal to the polarization axis of the second polarizing plate,
An end portion of the retardation layer has an inclined portion, and the inclined portion is located in the transmissive display area,
The slow axis of the inclined portion is parallel to the polarization axis of either the first polarizing plate or the second polarizing plate,
The liquid crystal device, wherein a slow axis of the retardation layer located in the reflective display region intersects with polarization axes of the first polarizing plate and the second polarizing plate. The retardation layer is made of a liquid crystal material,
An alignment film for aligning the liquid crystal material is provided on the lower layer side of the retardation layer,
The alignment direction of the alignment film located in the reflective display region intersects the polarization axis of the first polarizing plate and the second polarizing plate,
2. The liquid crystal according to claim 1, wherein an alignment direction of the alignment film located in the transmissive display region is parallel to a polarization axis of one of the first polarizing plate and the second polarizing plate. apparatus.   3. The liquid crystal device according to claim 1, wherein the first electrode and the second electrode are disposed so as to avoid a region overlapping the inclined portion.   4. The liquid crystal device according to claim 3, wherein the same voltage is applied to electrodes facing each other across a region overlapping with the inclined portion.   5. The liquid crystal layer thickness adjusting layer according to claim 1, wherein the retardation layer functions as a liquid crystal layer thickness adjusting layer for adjusting a layer thickness of the liquid crystal layer between the reflective display region and the transmissive display region. The liquid crystal device according to item.   An electronic apparatus comprising the liquid crystal device according to claim 1.

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