JP2013238784A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a VA (vertical alignment) type liquid crystal display element capable of carrying out a positive display with high contrast.SOLUTION: A retardation plate is disposed at least on one side outside a liquid crystal layer; and the retardation plate is disposed in such a manner that a stretching axis of the retardation plate is substantially orthogonal to the direction where an alignment treatment is performed. The retardation plate thus disposed has a total retardation ranging from 200 to 320 nm. A pair of polarizing plates is disposed on both sides outside the liquid crystal layer, with the respective absorption axes substantially orthogonal to each other, in which each polarizing plate disposed with the direction of the absorption axis and the alignment treatment direction forming approximately an angle of 45°. When the retardation plate is disposed, the polarizing plate is disposed at an opposite side of the retardation plate to the liquid crystal layer.

Description

  The present invention relates to a VA (Vertical Alignment) type liquid crystal display element.

  As a liquid crystal display element, there is a liquid crystal display element in which the alignment (initial alignment) of liquid crystal molecules in a liquid crystal layer when no voltage is applied is a vertical alignment substantially perpendicular to the substrate surface. Such a liquid crystal display element is called a VA (Vertical Alignment) type liquid crystal display element. In the VA liquid crystal display element, a liquid crystal having negative dielectric anisotropy is used. Then, by applying a voltage to the liquid crystal layer, the alignment direction of the liquid crystal (liquid crystal molecules) is changed in a direction parallel to the substrate surface. An example of such a VA liquid crystal display element is described in Patent Document 1. Compared with TN (Twisted Nematic) type liquid crystal display elements and STN (Super Twisted Nematic) type liquid crystal display elements, VA type liquid crystal display elements have higher responsiveness and can realize high contrast display (patent) Reference 2).

If the orientation of the liquid crystal when no voltage is applied is completely perpendicular to the substrate, the direction in which the liquid crystal tilts when a voltage is applied cannot be defined. As a result, the alignment of the liquid crystal is not uniform and the display quality is lowered. Therefore, it is necessary to provide a pretilt angle by some method or to define the direction in which the liquid crystal tilts when a voltage is applied. As a method of providing a pretilt angle or a method of defining the direction in which the liquid crystal is tilted when a voltage is applied, an oblique electric field method in which the electric field direction due to the applied voltage is inclined with respect to the substrate surface, a rib method in which a rib structure is provided on an electrode, etc. There is an oblique deposition method in which SiO ₂ ) is obliquely deposited on a substrate. In addition, the alignment direction of the liquid crystal can be defined by performing a rubbing treatment on the vertical alignment film.

JP 2003-207782 A (paragraphs 0002-0004) JP 2006-11362 A (paragraph 0014)

  In general, a VA liquid crystal display element can obtain a good light shielding degree and black display when no voltage is applied (that is, when the power is turned off), and when a voltage is applied to the liquid crystal (that is, when the power is turned on). A negative display that provides a bright white display is performed.

  On the other hand, the VA liquid crystal display element has a very good light shielding degree when no voltage is applied (when the power is turned off), and thus is not suitable for a transflective type using external light or the like or a reflective type. Therefore, it is difficult to perform positive display with high contrast using a VA liquid crystal display element.

  Therefore, an object of the present invention is to provide a VA liquid crystal display element capable of performing positive display with high contrast.

  The liquid crystal display element according to the present invention faces a first transparent substrate (for example, the first transparent substrate 1) on which a first transparent electrode (for example, the first transparent electrode 3) is disposed, and the first transparent electrode. Sealed between a second transparent substrate (for example, second transparent substrate 2) on which a second transparent electrode (for example, second transparent electrode 4) is disposed, and the first transparent substrate and the second transparent substrate. A liquid crystal layer (for example, liquid crystal layer 7) containing a liquid crystal having negative dielectric anisotropy that is vertically aligned when no voltage is applied, and the liquid crystal is vertically aligned with a predetermined pretilt angle. The phase difference plate (for example, the first phase difference plate 5 and the second phase difference plate 6) is disposed on at least one of the outer sides of the liquid crystal layer, and the phase difference plate is subjected to the alignment treatment. The arranged phase and the phase difference plate are arranged in a direction almost orthogonal to each other, and the arranged phase A pair of polarizing plates is arranged on both outer sides of the liquid crystal layer such that the total retardation of the plates satisfies 200 to 320 nm so that the absorption axes thereof are substantially orthogonal to each other. When the angle between the absorption axis direction and the phase difference plate is approximately 45 °, the voltage is not applied to the liquid crystal layer by disposing the phase difference plate on the opposite side of the liquid crystal layer. In this case, positive display is performed in which white display is performed and black display is performed when a voltage is applied to the liquid crystal layer.

  Specifically, retardation plates may be disposed on both outer sides of the liquid crystal layer. In this case, among the retardation plates, the first polarizing plate is disposed on the opposite side of the liquid crystal layer in one retardation plate, and the second polarizing plate is disposed on the opposite side of the liquid crystal layer in the other retardation plate. The first polarizing plate and the second polarizing plate are arranged so that their absorption axes are substantially orthogonal to each other.

  In addition, a retardation plate may be disposed on either one of the outer sides of the liquid crystal layer. In this case, the first polarizing plate is disposed on the opposite side of the liquid crystal layer in the retardation plate, and the second polarizing plate is disposed on the outer side of the liquid crystal layer different from the side on which the retardation plate is disposed. The polarizing plate and the second polarizing plate are arranged so that their absorption axes are substantially orthogonal to each other.

The refractive indices _n x in the plane direction of the retardation _{plate, n y (n x> n} y), and, when the refractive index in the thickness direction is _{n z, 1.4 ≦ (n x} -n z) / preferably satisfies the _{(n x -n y) ≦ 2.4} .

  According to the present invention, positive display with high contrast can be performed.

FIG. 3 is a schematic cross-sectional view illustrating a configuration example of a liquid crystal display element of the present invention. Explanatory drawing which shows the example of axial arrangement | positioning of the polarizing plate and phase difference plate in a liquid crystal display element. Explanatory drawing which shows the refractive index of a phase difference plate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing a configuration example of a liquid crystal display element of the present invention. The liquid crystal display element of the present invention is a VA type. The liquid crystal display element includes a first transparent substrate 1 and a second transparent substrate 2, and a liquid crystal layer 7 is sealed between the first transparent substrate 1 and the second transparent substrate 2.

  Hereinafter, the first transparent substrate 1 and the second transparent substrate 2 may be simply referred to as transparent substrates 1 and 2. In addition, the illustration of the peripheral sealing material used for sealing the liquid crystal layer 7 between the transparent substrates 1 and 2 is omitted.

  A first transparent electrode 3 is disposed on the first transparent substrate 1. A second transparent electrode 4 is disposed on the second transparent substrate 2 so as to face the first transparent electrode 3. In this embodiment, a case where segment display is performed using a VA liquid crystal display element will be described as an example.

  Specifically, one or more first transparent electrodes 3 (segment electrodes) are provided in accordance with the shape of the display pattern, and the second transparent electrode 4 (common electrode) is at least in a region facing the display pattern. Be placed. Note that the first transparent electrode 3 may be a common electrode, and the second transparent electrode 4 may be a segment electrode.

  However, display content performed using the VA liquid crystal display element is not limited to segment display. Full-dot display may be performed using a VA liquid crystal display element. In this case, a plurality of column electrodes are arranged as the first transparent electrode 3, and a plurality of row electrodes orthogonal to the column electrode are arranged as the second transparent electrode 4. Note that a plurality of row electrodes may be arranged as the first transparent electrode 3, and a plurality of column electrodes orthogonal to the row electrode may be arranged as the second transparent electrode 4.

  The transparent substrates 1 and 2 are, for example, glass substrates. The first transparent electrode 3 and the second transparent electrode 4 are made of, for example, ITO (Indium Tin Oxide).

  The liquid crystal of the liquid crystal layer 7 has a negative dielectric anisotropy that becomes vertical alignment when no voltage is applied, and is subjected to alignment treatment so as to be vertically aligned with a predetermined pretilt angle. The alignment state of the liquid crystal can also be defined by, for example, rubbing the vertical alignment film. In this case, the liquid crystal is inclined in the rubbing process direction. That is, this direction is a direction in which the liquid crystal tilts when an electric field is applied.

  For example, the alignment process is performed by rubbing the alignment film formed on the surface of the first transparent substrate 1 on the liquid crystal layer side in a direction perpendicular to the long side direction of the liquid crystal display element. The alignment treatment may be performed by subjecting the alignment film formed on the surface of the liquid crystal layer to a rubbing treatment in a direction opposite to the vertical direction described above.

  By doing so, the liquid crystal molecules of the liquid crystal layer 7 are vertically aligned when no voltage is applied, and are horizontal with respect to the first transparent substrate 1 and the second transparent substrate 2 when a voltage is applied. Orient.

Note that the method for defining the alignment state of the liquid crystal is not limited to the rubbing treatment. An oblique electric field method in which an electric field direction by an applied voltage is inclined with respect to the substrate surface, a rib method in which a rib structure is provided on an electrode, an oblique deposition method in which silicon oxide (SiO ₂ ) is obliquely deposited on a substrate, etc. The orientation direction can be defined.

  The pretilt angle of the liquid crystal is preferably 85 ° to 89.8 °. This is because when the pretilt angle of the liquid crystal is smaller than 85 °, the brightness when no voltage is applied or when the liquid crystal is off becomes dark and the contrast ratio is lowered. In addition, when the pretilt angle of the liquid crystal is larger than 89.8 °, particularly when the angle is 90 °, the direction in which the liquid crystal molecules are tilted when a voltage is applied varies, resulting in alignment disorder and domains, and the display quality deteriorates. It is.

  The first transparent substrate 1 is provided with a first retardation plate 5 on the surface opposite to the liquid crystal layer 7. The second transparent substrate 2 is also provided with a second retardation plate 6 on the surface opposite to the liquid crystal layer 7.

  In the present embodiment, the case where the liquid crystal display element is provided with two phase difference plates of the first phase difference plate 5 and the second phase difference plate 6 will be described. Any one retardation plate of the plate 5 and the second retardation plate 6 may be provided. In other words, the phase difference plate is disposed outside one of the liquid crystal layers 7 or both outside the liquid crystal layer 7.

  When both the first phase difference plate 5 and the second phase difference plate 6 are provided in the liquid crystal display element, each phase difference plate (the first phase difference plate 5 and the second phase difference plate 6) is the liquid crystal layer 7. The direction in which the alignment treatment is performed so that the liquid crystal is vertically aligned and the stretching axis of the retardation plate itself are arranged in a direction substantially orthogonal to each other. With this arrangement, a black display with low transmittance can be obtained when a voltage is applied to the liquid crystal.

  In addition, when one phase difference plate of the 1st phase difference plate 5 and the 2nd phase difference plate 6 is provided in a liquid crystal display element (namely, when there is one phase difference plate), the phase difference of the one sheet Regarding the plate, it is only necessary that the direction in which the alignment treatment is performed so that the liquid crystal of the liquid crystal layer 7 is vertically aligned and the direction in which the stretching axis of the retardation plate itself is substantially orthogonal.

  Furthermore, a first polarizing plate 8 is provided on the surface of the first retardation plate 5 opposite to the first transparent substrate 1. A second polarizing plate 9 is provided on the surface of the second retardation plate 6 opposite to the second transparent substrate 2. The polarizing plates 8 and 9 are disposed so that the absorption axes thereof are substantially orthogonal to each other, and the angle formed by the orientation processing direction and the absorption axis direction is disposed in a direction of approximately 45 °.

  In other words, the polarizing plates 8 and 9 are arranged so that their polarization axes are substantially orthogonal to each other, and the angle formed by the orientation processing direction and the polarization axis direction is arranged in a direction of approximately 45 °.

  As described above, the liquid crystal display element only needs to be provided with one of the first retardation plate 5 and the second retardation plate 6. For this reason, the pair of polarizing plates 8 and 9 are arranged on the opposite side of the liquid crystal layer 7 in the first retardation plate 5 or the second retardation plate 6 in the direction in which the absorption axes thereof are substantially orthogonal to each other.

  For example, when the first retardation plate 5 is provided in the liquid crystal display element, the polarizing plate 8 is disposed on the opposite side of the liquid crystal layer 7 in the first retardation plate 5. The polarizing plate 9 is disposed outside the liquid crystal layer 7 different from the side where the first retardation plate 5 is disposed (specifically, outside the second transparent substrate 2). And the polarizing plate 8 and the polarizing plate 9 are arrange | positioned in the direction where a mutual absorption axis is substantially orthogonal.

  On the other hand, when the second retardation plate 6 is provided in the liquid crystal display element, the polarizing plate 9 is disposed on the opposite side of the liquid crystal layer 7 in the second retardation plate 6. The polarizing plate 8 is disposed outside the liquid crystal layer 7 different from the side where the second retardation plate 6 is disposed (specifically, outside the first transparent substrate 1). And the polarizing plate 8 and the polarizing plate 9 are arrange | positioned in the direction where a mutual absorption axis is substantially orthogonal.

  Hereinafter, the case where an image is observed from the direction of the surface on the first polarizing plate 8 side will be described as an example. In this case, as illustrated in FIG. 1, the backlight 11 is disposed on the second polarizing plate 9 side, and the transflective plate 10 is disposed between the second polarizing plate 9 and the backlight 11. However, the structure may be such that the transflective plate 10 and the backlight 11 are provided on the first polarizing plate 8 side, and the image is observed from the surface on the second polarizing plate 9 side.

  FIG. 2 is an explanatory diagram illustrating an example of an axial arrangement of a polarizing plate and a retardation plate in a liquid crystal display element. In the example shown in FIG. 2, the liquid crystal display element is observed from the front direction on the first polarizing plate 8 side. In addition, the liquid crystal display element illustrated in FIG. 2 is provided with both the first retardation plate 5 and the second retardation plate 6. Further, the first transparent substrate 1 and the second transparent substrate 2 and the portion sandwiched between these transparent substrates may be collectively referred to as a liquid crystal display panel 12.

  When the liquid crystal display element illustrated in FIG. 1 is observed from the front direction on the first polarizing plate 8 side, the liquid crystal display panel 12 has a downward direction on the alignment film formed on the liquid crystal layer side surface of the first transparent substrate 1. An alignment process (arrow O2 in FIG. 2) is performed, and an alignment process in the upward direction (arrow O1 in FIG. 2) is performed on the alignment film formed on the liquid crystal layer side surface of the second transparent substrate 2. That is, in FIG. 2, in the liquid crystal display panel 12, a downward orientation process is performed on the viewing side surface, and an upward orientation that is 180 ° different from the orientation processing direction of the viewing side surface on the non-viewing side surface. Indicates that processing is being performed.

  In the example shown in FIG. 2, the first retardation plate 5 and the second retardation plate 6 are arranged in the direction in which the alignment treatment is performed in the liquid crystal display panel 12 (arrow O <b> 3 in FIG. 2) and the stretching axis A <b> 1 of each retardation plate. , A2 are arranged in a direction orthogonal to each other.

  Further, in the example shown in FIG. 2, a pair of absorption axes A3 and A4 are orthogonal to the opposite sides of the first retardation plate 5 and the second retardation plate 6 to the liquid crystal display panel 12 (liquid crystal layer 7). It is shown that the polarizing plates 8 and 9 are arranged. Furthermore, in the example shown in FIG. 2, each polarizing plate indicates that the angle formed by the direction in which the alignment treatment is performed (arrow O <b> 3 in FIG. 2) and the absorption axis direction is 45 °.

  With the arrangement as shown in FIG. 2, the liquid crystal display element performs a positive display in which white display is performed when no voltage is applied to the liquid crystal layer 7 and black display is performed when a voltage is applied to the liquid crystal layer 7. .

  As described above, the liquid crystal display element only needs to include one of the first retardation plate 5 and the second retardation plate 6. In this case, the liquid crystal display element illustrated in FIG. 2 only needs to include either the first retardation plate 5 or the second retardation plate 6. In this case, the directions of the axes of the polarizing plates and the phase difference plate are the same as those illustrated in FIG. Also in this case, the liquid crystal display element can perform positive display.

  In the example shown in FIG. 2, the relationship between the direction of the absorption axis of each polarizing plate and the direction in which the alignment treatment is performed in the liquid crystal display panel 12 is shown. A similar relationship is established with the direction in which the alignment process is performed in FIG.

  The total retardation Δnf · df of the first phase difference plate 5 and the second phase difference plate 6 is preferably the same value as the half-wave plate. Specifically, the total of retardation Δnf · df preferably satisfies 200 to 320 nm. In particular, it is more preferable that the total of retardation Δnf · df satisfies 220 to 300 nm. This is because when the retardation Δnf · df is less than 200 nm, the transmittance when no voltage is applied (when the power is off) is lowered. On the other hand, when the retardation Δnf · df is larger than 320 nm, the background color when no voltage is applied (when the power is off) is easy to be colored from yellow to orange. It is because it becomes easier to color.

  When only one of the first retardation plate 5 and the second retardation plate 6 is provided on the liquid crystal display element, the total of retardation Δnf · df is the retardation of the retardation plate provided only on one of them. It corresponds to Δnf · df.

FIG. 3 is an explanatory diagram showing the refractive index of the retardation plate. As shown in the example of FIG. 3, the refractive indexes in the two orthogonal directions x and y within the plane of each phase difference plate are n _x and n _y (where n _x > _ny ), respectively, and the thickness direction (d direction) If the refractive index of the set to n _z, n _x, the value Nz is calculated using n _y and n _z preferably satisfies the relationship of equation 1 shown below. Incidentally, n _x direction, the same as the stretching axis direction of the retardation plate. Further, retardation of the retardation plate satisfying the relation of _{Δnf · df = (n x -n} y) · d.

_{Nz = (n x -n z)} / (n x -n y) = 1.4~2.4 ( Equation 1)

In particular, Nz is preferably set within a range of 1.4 to 2.0. _N x so Nz is 1.4 to 2.4, _{by n y} and _{n z} are set, and the background color when no voltage is applied (power off), the background color of the viewed from the lateral direction Since coloring can be reduced, a good white display can be obtained.

  When two retardation plates are provided in the liquid crystal display element, Nz for each retardation plate may be the same or different.

Moreover, the relationship shown in Formula 1 is effective when the retardation Δn _LC · d _LC of the liquid crystal layer is large. When the retardation Δn _LC · d _LC of the liquid crystal layer is increased, the steepness of the transmittance characteristic with respect to the voltage is improved, so that the duty can be increased and more information can be displayed. Specifically, the retardation Δn _LC · d _LC of the liquid crystal layer is large when Δn _LC · d _LC ≧ 480 nm, and the high duty means driving exceeding 1/8 duty.

  With the above configuration, a positive display is obtained in which white display is performed when no voltage is applied to the liquid crystal layer 7 and black display is performed when a voltage is applied to the liquid crystal layer 7. That is, in a VA liquid crystal display element, outside light or the like is effectively used without a backlight, and a bright white display is obtained when no voltage is applied (when the power is turned off), and when a voltage is applied (when the power is turned on). In addition, a positive display (normally white) that can provide a black display can be performed.

  Specifically, the liquid crystal display element of the present embodiment has a phase difference plate on either or both sides of the liquid crystal layer 7 in a direction in which the direction in which the alignment treatment is performed and the stretching axis of the phase difference plate are substantially orthogonal. With the arrangement, a black display with low transmittance can be obtained when a voltage is applied (when the power is turned on).

  Moreover, a favorable white display can be obtained by setting the total retardation Δnf · df of the retardation film to 200 to 320 nm.

Further, for each phase difference plate, n _x , _ny and _nz are set so as to satisfy the relationship of the above-described formula 1, whereby a good white display can be obtained. The relationship shown in Formula 1 is effective when the retardation Δn _LC · d _LC of the liquid crystal layer 7 is large. If the retardation Δn _LC · d _LC of the liquid crystal layer 7 can be increased, the steepness of the transmittance characteristic with respect to the voltage is improved, so that the duty can be increased and more information can be displayed.

  Further, since the steepness of the transmittance characteristic with respect to the voltage becomes better than that of the TN liquid crystal display element, the duty can be increased, and more information can be displayed.

  The first example is an example in which the liquid crystal display element of the above embodiment is realized.

  In the first embodiment, predetermined segment electrodes and common electrodes were patterned on the transparent substrates 1 and 2 in order to perform segment display.

Next, a vertical alignment film is formed on the surfaces of the first transparent substrate 1 and the second transparent substrate 2 on the liquid crystal layer side, and an anti-parallel (anti-parallel) rubbing process is performed in one direction to set a pretilt angle. 89.6 °, retardation Δn _LC · d _LC was 400 nm. A liquid crystal material having a dielectric anisotropy (Δε) of −5.6 was used, and the liquid crystal layer 7 (see FIG. 1) was sealed between the first transparent substrate and the second transparent substrate.

As the first polarizing plate 8, SWQ1423CUAG30G manufactured by Nitto Denko Corporation was used, and as the second polarizing plate 9, SWQ1423CU manufactured by Nitto Denko Corporation was used. Further, a retardation plate manufactured by Nippon Zeon Co., Ltd. that satisfies retardation Δn _F · d _F = 135 nm and Nz = 1.0 was used. In this embodiment, the phase difference plates are arranged on both outer sides of the liquid crystal layer 7. Therefore, the total of retardation Δnf · df arranged on both outer sides of the liquid crystal layer 7 is 270 nm.

  Assuming that the counterclockwise angle from the reference axis when viewed from the observer direction to the absorption axis of the first polarizing plate 8 (see FIG. 1) is θ1 with the long side direction of the liquid crystal display element as the reference axis, θ1 The first polarizing plate 8 was arranged so that = 45 °. Further, when the counterclockwise angle from the reference axis to the absorption axis of the second polarizing plate 9 (see FIG. 1) is θ2, the second polarizing plate 9 is arranged so that θ2 = 135 °. In this embodiment, the first polarizing plate 8 and the second polarizing plate 9 are disposed so that the absorption axes thereof are orthogonal to each other, but the first polarizing plate 8 and the second polarizing plate 9 are disposed so that the polarization axes are orthogonal to each other. May be.

  Further, with the long side direction of the liquid crystal display element as the reference axis, the counterclockwise angle from the reference axis when viewed from the observer direction to the extending axis of the first retardation plate 5 (see FIG. 1) is θ3. In this case, the first retardation plate 5 was arranged so that θ3 = 0 °. Further, when the counterclockwise angle from the reference axis to the extending axis of the second retardation plate 6 (see FIG. 1) is θ4, the second retardation plate 6 is arranged so that θ4 = 0 °.

  Furthermore, LTO-FW1 manufactured by Tsujiden Co., Ltd. was disposed as the transflective plate 10 (see FIG. 1).

  When the liquid crystal display element manufactured as described above was driven at a duty ratio of 1/4, good visibility was obtained. That is, a good white display was obtained when no voltage was applied or the power was turned off, and a black display was obtained when the power was turned on and a voltage was applied to the liquid crystal. In addition, compared with the case of the comparative example described later, the display quality with high contrast was obtained because of the low transmittance when the power was turned on.

  The second example is also an example in which the liquid crystal display element of the above embodiment is realized. However, the second embodiment is an example in which a retardation plate is disposed only on one outer side of the liquid crystal layer 7. That is, the second embodiment is different from the first embodiment in that the second retardation plate 6 is not provided as compared with the first embodiment.

  In the second embodiment, similar to the first embodiment, predetermined segment electrodes and common electrodes were patterned on the transparent substrates 1 and 2 in order to perform segment display.

  The alignment films formed on the transparent substrates 1 and 2, the alignment film alignment method, and the liquid crystal material sealed in the liquid crystal layer 7 are the same as in the first embodiment. The materials and arrangement methods used for the first polarizing plate 8 and the second polarizing plate 9 are the same as in the first embodiment. The material of the transflective plate 10 (see FIG. 1) to be arranged is the same as that in the first embodiment.

On the other hand, in this example, a retardation plate manufactured by Nippon Zeon Co., Ltd. that satisfies retardation Δn _F · d _F = 270 nm and Nz = 1.0 was used. In the present embodiment, only the first retardation plate is disposed on the first polarizing plate 8 side (that is, between the first transparent substrate 1 and the first polarizing plate 8) on the outside of the liquid crystal layer 7. Therefore, the total of retardation Δnf · df arranged on one outer side of the liquid crystal layer 7 is 270 nm.

  When the long side direction of the liquid crystal display element is the reference axis, and the counterclockwise angle from the reference axis when viewed from the observer direction to the extending axis of the first retardation plate 5 (see FIG. 1) is θ3, The first retardation plate 5 was arranged so that θ3 = 0 °.

  When the liquid crystal display element manufactured as described above was driven at a duty ratio of 1/4, good visibility was obtained. That is, a good white display was obtained when no voltage was applied or the power was turned off, and a black display was obtained when the power was turned on and a voltage was applied to the liquid crystal. In addition, compared with the case of the comparative example described later, the display quality with high contrast was obtained because of the low transmittance when the power was turned on.

  In the third embodiment, in order to perform full dot display, a plurality of strip-shaped column electrodes extending in the vertical direction and a plurality of strip-shaped row electrodes intersecting with the transparent substrates 1 and 2 were respectively patterned. Specifically, each column electrode and each row electrode had a line width of 350 μm and a line spacing of 10 μm.

Next, a vertical alignment film is formed on the surfaces of the first transparent substrate 1 and the second transparent substrate 2 on the liquid crystal layer side, and an anti-parallel (anti-parallel) rubbing process is performed in one direction to set a pretilt angle. 89.6 °, retardation Δn _LC · d _LC was 590 nm. A liquid crystal material having a dielectric anisotropy (Δε) of −2.7 was used, and the liquid crystal layer 7 (see FIG. 1) was sealed between the first transparent substrate and the second transparent substrate.

Further, a retardation plate manufactured by Nippon Zeon Co., Ltd. that satisfies retardation Δn _F · d _F = 140 nm and Nz = 1.55 was used. In this embodiment, the phase difference plates are arranged on both outer sides of the liquid crystal layer 7. Therefore, the total of retardation Δnf · df arranged on both outer sides of the liquid crystal layer 7 is 280 nm.

  In addition, the raw material used for the 1st polarizing plate 8 and the 2nd polarizing plate 9 and the arrangement | positioning method are the same as that of a 1st Example. The arrangement method of the first retardation plate 5 (see FIG. 1) and the second retardation plate 6 (see FIG. 1) is also the same as that of the first embodiment. The material of the transflective plate 10 (see FIG. 1) to be arranged is the same as that in the first embodiment.

  When the liquid crystal display device manufactured as described above was driven at a duty ratio of 1/16, good visibility was obtained. That is, a good white display was obtained when no voltage was applied or the power was turned off, and a black display was obtained when the power was turned on and a voltage was applied to the liquid crystal. Even in the configuration of this example, since the transmittance at power-on was low, display quality with high contrast was obtained.

[Comparative example]
In the comparative example, the liquid crystal display element is not provided with a retardation plate. Specifically, the comparative example is different from the first embodiment in that the first retardation plate 5 and the second retardation plate 6 are not provided. The rest is the same as in the first embodiment.

  That is, the method of patterning electrodes on the transparent substrates 1 and 2, the alignment film formed on the transparent substrates 1 and 2, the alignment film alignment method, and the liquid crystal material sealed in the liquid crystal layer 7 are the first embodiment. Similar to the example. The materials used for the first polarizing plate 8 and the second polarizing plate 9 and the material of the transflective plate 10 (see FIG. 1) to be arranged are the same as in the first embodiment.

  On the other hand, the arrangement method of the 1st polarizing plate 8 and the 2nd polarizing plate 9 differs from a 1st Example. Specifically, with the long side direction of the liquid crystal display element as the reference axis, the counterclockwise angle from the reference axis when viewed from the observer direction to the absorption axis of the first polarizing plate 8 (see FIG. 1) is θ1. In this case, the first polarizing plate 8 was arranged so that θ1 = 45 °. In addition, when the counterclockwise angle from the reference axis to the absorption axis of the second polarizing plate 9 (see FIG. 1) is θ2, the second polarizing plate 9 is arranged so that θ2 = 45 °. In the present embodiment, the first polarizing plate 8 and the second polarizing plate 9 are arranged so that the absorption axes thereof are parallel, but the first polarizing plate 8 and the second polarizing plate 9 have parallel polarization axes. You may arrange in.

  When the liquid crystal display element manufactured as described above was driven at a duty ratio of 1/4, good visibility was obtained. That is, a good white display was obtained when no voltage was applied or the power was turned off. However, when the power was turned on and a voltage was applied to the liquid crystal, a brown-blue-violet display having a slightly higher transmittance than that of the black display was obtained, resulting in a lower contrast.

  From this result, as shown in the above embodiment, the phase difference plate is arranged on either one or both outer sides of the liquid crystal layer 7 in the direction in which the orientation-treated direction and the stretching axis of the phase difference plate are substantially orthogonal to each other. Thus, when a voltage is applied (when the power is turned on), a black display with low transmittance can be obtained.

  The present invention can be suitably applied to a VA liquid crystal display element.

DESCRIPTION OF SYMBOLS 1 1st transparent substrate 2 2nd transparent substrate 3 1st transparent electrode 4 2nd transparent electrode 5 1st phase difference plate 6 2nd phase difference plate 7 Liquid crystal layer 8 1st polarizing plate 9 2nd polarizing plate 10 Semi-transmissive Reflector 11 Backlight

Claims (4)

A first transparent substrate on which a first transparent electrode is disposed;
A second transparent substrate on which a second transparent electrode facing the first transparent electrode is disposed;
A liquid crystal layer that is sealed between the first transparent substrate and the second transparent substrate and includes a liquid crystal having negative dielectric anisotropy that is vertically aligned when no voltage is applied;
The liquid crystal is aligned so as to be vertically aligned with a predetermined pretilt angle,
A phase difference plate is disposed on at least one of both outer sides of the liquid crystal layer,
The retardation plate is arranged in a direction in which the orientation treatment and the stretching axis of the retardation plate are substantially perpendicular to each other, and the total retardation of the arranged retardation plates satisfies 200 to 320 nm,
A pair of polarizing plates are arranged on both outer sides of the liquid crystal layer so that the absorption axes thereof are substantially orthogonal to each other,
Each polarizing plate is disposed at an angle of approximately 45 ° between the direction in which the alignment treatment is performed and the absorption axis direction. When the retardation plate is disposed, the opposite of the liquid crystal layer in the retardation plate. By being placed on the side,
A liquid crystal display element that performs a positive display in which white display is performed when no voltage is applied to the liquid crystal layer and black display is performed when a voltage is applied to the liquid crystal layer. Retardation plates are arranged on both outer sides of the liquid crystal layer,
Among the retardation plates, a first polarizing plate is disposed on the opposite side of the liquid crystal layer in one retardation plate, and a second polarizing plate is disposed on the opposite side of the liquid crystal layer in the other retardation plate,
The liquid crystal display element according to claim 1, wherein the first polarizing plate and the second polarizing plate are arranged so that their absorption axes are substantially orthogonal to each other. A phase difference plate is arranged on either one of both outer sides of the liquid crystal layer,
A first polarizing plate is disposed on the opposite side of the liquid crystal layer in the retardation plate,
A second polarizing plate is arranged outside the liquid crystal layer different from the side where the retardation plate is arranged,
The liquid crystal display element according to claim 1, wherein the first polarizing plate and the second polarizing plate are arranged so that their absorption axes are substantially orthogonal to each other. Refractive index in the in-plane direction of the retardation plate _{n x, n y (n x} > n y), and, when the refractive index in the thickness direction is _{n z,}
1.4 ≦ (n _x −n _z ) / (n _x −n _y ) ≦ 2.4
The liquid crystal display element according to any one of claims 1 to 3, wherein:

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