JP2018036295A - Liquid crystal display device and method for manufacturing liquid crystal display device - Google Patents

Abstract

A liquid crystal display device capable of improving a contrast ratio in a liquid crystal panel that controls display by generating an electric field parallel to a liquid crystal layer and a method of manufacturing the liquid crystal display device. A liquid crystal display device includes a pair of glass substrates opposed to each other with a liquid crystal layer interposed therebetween, and applies a voltage between a plurality of electrodes formed on one of the pair of glass substrates so as to be parallel to the liquid crystal layer. A liquid crystal display device comprising a liquid crystal panel that controls display by generating a strong electric field, between a liquid crystal panel and a backlight unit that irradiates the liquid crystal panel from the back or side, with a long axis direction and a short axis direction. With the optical film containing dichroic dyes with different light absorptivity of molecules, the major axis direction where the light absorptance of dichroic dyes is relatively large is oriented perpendicular to the film surface of the optical film . [Selection diagram] Fig. 1

Description

  The present invention relates to a liquid crystal display device that controls display by generating an electric field parallel to a liquid crystal layer, and a method for manufacturing the same.

  As a liquid crystal panel control method, a TN (Twisted Nematic) method, a VA (Vertical Aligned) method, or the like that generates an electric field between a pair of glass substrates facing each other with a liquid crystal layer interposed therebetween is known. These vertical electric field type liquid crystal panels have a feature that the contrast ratio of the liquid crystal panel is high, but have a problem that viewing angle characteristics are low.

  In order to solve such a problem of viewing angle characteristics, for example, in the liquid crystal display device of Patent Document 1, an optical film including a dichroic dye oriented in a substantially vertical direction is provided between a liquid crystal panel and a backlight light source. It is arranged. Thereby, the hue change when observed from a wide angle is compensated.

JP 2009-1116015 A JP-A-5-273602 JP-A-11-160538

  As a control method for a liquid crystal panel different from the vertical electric field method, an IPS (In-Plane Switching) method, an FFS (Fringe Field Switching) method, and the like that generate an electric field parallel to the liquid crystal layer to control display are known. These horizontal electric field type liquid crystal panels have a feature of excellent viewing angle characteristics because the apparent length of liquid crystal molecules (refractive index ellipsoid) is almost constant regardless of the viewing angle direction of the liquid crystal panel. .

  The problem of the horizontal electric field type liquid crystal panel is that the contrast ratio (hereinafter referred to as “front contrast ratio”) when the liquid crystal panel is viewed from the front direction is lower than that of the vertical electric field type liquid crystal panel. One of the factors that lower the front contrast ratio of a horizontal electric field type liquid crystal panel is a linear electrode for generating a horizontal electric field formed in large numbers on a glass substrate of the liquid crystal panel. Since the refractive index is different between the linear electrode and the glass substrate, the light incident on the liquid crystal panel from a wide angle and reflected / scattered at the edge of the linear electrode and emitted in the front direction of the liquid crystal panel lowers the front contrast ratio. .

  In particular, the polarizing plates provided on both surfaces of the liquid crystal panel have a significant decrease in polarizing ability with respect to light incident from an oblique direction with respect to the absorption axis. For this reason, light incident on the polarizing plate on the back side of the liquid crystal panel from a wide angle may not be sufficiently polarized, and when reflected / scattered at the edge of the linear electrode, it is absorbed by the polarizing plate on the front side of the liquid crystal panel. Without being emitted in the front direction of the liquid crystal panel. As a result of this phenomenon occurring during black display, the front contrast ratio decreases.

  In the horizontal electric field type liquid crystal panel, such a method for reducing the light incident on the liquid crystal panel from a wide angle and reflected / scattered at the edge of the linear electrode and emitted in the front direction of the liquid crystal panel has been described so far. There was no consideration. Accordingly, the applicant has studied a method for reducing the light incident on the liquid crystal panel from a wide angle and improving the contrast ratio in the horizontal electric field type liquid crystal panel.

  The liquid crystal display device according to the present invention has a pair of glass substrates facing each other with a liquid crystal layer interposed therebetween, and a voltage is applied between a plurality of electrodes formed on one glass substrate of the pair of glass substrates, A liquid crystal display device comprising a liquid crystal panel that controls display by generating an electric field parallel to the liquid crystal layer, the major axis direction between the backlight unit that irradiates the liquid crystal panel from the back or side and the liquid crystal panel And an optical film containing a dichroic dye having different molecular light absorption rates in the short axis direction, and the long axis direction in which the light absorption rate of the dichroic dye is relatively large is perpendicular to the film surface of the optical film It is characterized by being oriented.

  The method for manufacturing a liquid crystal display device according to the present invention includes a pair of glass substrates facing each other with a liquid crystal layer interposed therebetween, and a voltage between a plurality of electrodes formed on one glass substrate of the pair of glass substrates. And a liquid crystal display device comprising a liquid crystal panel that controls display by generating an electric field parallel to the liquid crystal layer, wherein the light absorption rate of molecules in the major axis direction and the minor axis direction is Forming an optical film containing different dichroic dyes so that the major axis direction where the light absorption rate of the dichroic dyes is relatively large is aligned perpendicular to the film surface of the optical film; and And a step of disposing an optical film between the backlight unit that irradiates from the back surface or the side surface and the liquid crystal panel.

  ADVANTAGE OF THE INVENTION According to this invention, in the liquid crystal panel which produces | generates an electric field parallel to a liquid-crystal layer and controls a display, the liquid crystal display device which can improve a contrast ratio, and the manufacturing method of a liquid crystal display device can be obtained.

It is a schematic diagram which shows the structure of the liquid crystal display device which concerns on 1st Embodiment. It is a schematic diagram which shows the layout of the electrode in the liquid crystal display device which concerns on 1st Embodiment. It is a schematic diagram which shows the difference in the apparent shape when the dichroic dye used for the liquid crystal display device which concerns on 1st Embodiment is seen from a major axis direction, and when it sees from a diagonal direction with respect to a major axis. . It is the schematic which shows the light transmission characteristic of the dichroic dye used for the liquid crystal display device which concerns on 1st Embodiment. It is the schematic which shows the viewing angle characteristic of the liquid crystal display device which concerns on 1st Embodiment. It is the schematic which shows the viewing angle characteristic of the conventional liquid crystal display device. It is a schematic diagram which shows the structure of the liquid crystal display device which concerns on 2nd Embodiment. It is a schematic diagram which shows the layout of the electrode in the liquid crystal display device which concerns on 2nd Embodiment. It is a schematic diagram which shows the structure of the liquid crystal display device which concerns on 3rd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited to the following embodiment, In the range which does not deviate from the summary, it can change suitably. In the drawings described below, components having the same function are denoted by the same reference numerals, and the description thereof may be omitted or simplified.

(First embodiment)
The liquid crystal display device according to the first embodiment will be described with reference to FIGS. FIG. 1 is a schematic diagram showing the configuration of the liquid crystal display device according to the first embodiment. The liquid crystal display device of this embodiment includes a liquid crystal panel 1, a backlight unit 2, a prism sheet 3, and an optical film 4. A light diffusion sheet or the like may be further disposed between the backlight unit 2 and the prism sheet 3.

  The liquid crystal panel 1 has a pair of glass substrates 12a and 12b that face each other with the liquid crystal layer 11 in between. The liquid crystal layer 11 is made of nematic liquid crystal having a positive dielectric anisotropy as a main material, and in black display in which no voltage is applied to the electrode 10, the liquid crystal layer 11 has a homogeneous alignment in which all liquid crystal molecules are aligned in approximately the same direction. . A color filter 15 is provided between the glass substrate 12b and the liquid crystal layer 11 to emit light in the wavelength range of the three primary colors R (red) / G (green) / B (blue) illuminated from the backlight unit 2. Pass through every pixel.

  The backlight unit 2 is an edge light type backlight, and includes an LED light source 22 including an LED element at an end portion of the light guide plate 21. A light reflecting sheet or the like may be further arranged on the back side of the light guide plate 21. The backlight unit 2 is not limited to the edge type backlight, and may be any unit that irradiates the liquid crystal panel 1 from the back surface or the side surface. For example, the backlight unit 2 can be a direct type backlight.

  On the glass substrate 12a on the backlight unit 2 side of the liquid crystal panel 1, at least a pair of electrodes 10 is formed for each pixel. The liquid crystal panel 1 shown in FIG. 1 assumes an IPS (In-Plane Switching) method, and the electrode 10 of the liquid crystal panel 1 includes a linear pixel electrode 10a and a common electrode 10b. A control unit (not shown) of the liquid crystal display device applies a voltage between the pixel electrode 10a and the common electrode 10b to generate an electric field parallel to the surface of the liquid crystal layer 11, and rotates liquid crystal molecules within the surface of the liquid crystal layer 11. By controlling the full color display of the liquid crystal display device.

  FIG. 2 is a schematic diagram showing a layout of the electrodes 10 in the liquid crystal display device according to the first embodiment. 2A shows a cross section of the pixel electrode 10a along the line XX 'shown in FIG. 1, and FIG. 2B shows the cross section of the common electrode 10b along the line YY' shown in FIG. A cross section is shown. The pixel electrode 10a and the common electrode 10b are formed in different wiring layers, and are electrically insulated from each other by an insulating layer 13 made of, for example, a SiNx film. The plurality of pixel electrodes 10a actually have a comb shape as shown in FIG. 2A, and are electrically connected to each other for each pixel. The same applies to the common electrode 10b. The pixel electrodes 10a and the common electrodes 10b are alternately arranged in a plan view as shown in FIG.

  The liquid crystal panel 1 is provided with polarizing plates 14a and 14b so as to sandwich the glass substrates 12a and 12b from outside. The absorption axis 5a of the polarizing plate 14a and the absorption axis 5b of the polarizing plate 14b are orthogonal to each other, and are illuminated from the backlight unit 2 in white display in which a voltage is applied between the pixel electrode 10a and the common electrode 10b. Light passes through.

  By the way, as described above, in the IPS system in which the display is controlled by applying a lateral voltage between the electrodes, the liquid crystal panel 1 is incident on the liquid crystal panel 1 from a wide angle and is reflected / scattered by the edge of the electrode 10. The light that exits to the front reduces the front contrast ratio.

  In particular, the polarizing ability of the polarizing plate 14a shown in FIG. 1 is greatly reduced with respect to the light 6b incident from the oblique direction with respect to the absorption axis 5a from the wide angle in the horizontal direction of FIG. For this reason, the light 6b incident from an oblique direction with respect to the absorption axis 5a from a wide angle is not sufficiently polarized, and is reflected / scattered at the edge of the electrode 10 to be emitted in the front direction of the liquid crystal panel 1, and the alignment state of the liquid crystal molecules Regardless, it passes through the polarizing plate 14b. As a result, in the IPS liquid crystal panel 1, the front contrast ratio is lowered. The polarizing plate 14a does not deteriorate the polarization ability with respect to the light 6a incident perpendicularly to the absorption axis 5a.

  Therefore, the liquid crystal display device of this embodiment includes a prism sheet 3 between the liquid crystal panel 1 and the backlight unit 2 as shown in FIG. The prism sheet 3 collects light emitted from the backlight unit 2 in the front direction of the liquid crystal panel 1. Thereby, the light which enters into the liquid crystal panel 1 from a wide angle can be reduced.

  Furthermore, the liquid crystal display device of the present embodiment includes an optical film 4 between the liquid crystal panel 1 and the backlight unit 2 as shown in FIG. The optical film 4 includes a dichroic dye having different molecular light absorption rates in the major axis direction and the minor axis direction, and the major axis direction in which the light absorption rate of the dichroic dye is relatively large is the optical film 4. The film is oriented perpendicular to the film surface. Typically, a dichroic dye has an elongated molecular shape, and this anisotropy absorbs light polarized in the major axis direction relatively much and relatively absorbs light polarized in the minor axis direction. It has the property of absorbing small.

  FIG. 3 shows the difference in apparent shape when the dichroic dye used in the liquid crystal display device according to the first embodiment is viewed from the long axis direction and when viewed from an oblique direction with respect to the long axis. It is a schematic diagram. 3A shows the anisotropy of apparent light absorption when the dichroic dye molecule is viewed from the long axis direction, and FIG. 3B shows the dichroic dye molecule as the long axis. On the other hand, the anisotropy of apparent light absorption when viewed from an oblique direction is shown. Comparing FIG. 3A and FIG. 3B, the dichroic dye has a larger apparent anisotropy as light enters from an oblique direction with respect to the major axis, and light that vibrates in the major axis direction. It can be seen that a relatively large amount is absorbed. Accordingly, the dichroic dyes having different molecular light absorption rates in the major axis direction and the minor axis direction are aligned perpendicularly to the film surface of the optical film 4 so as to enter the liquid crystal panel 1 from a wide angle. Can absorb a relatively large amount of light.

  Furthermore, since the dichroic dye absorbs light incident obliquely with respect to the major axis direction, it has a polarization ability to polarize light incident obliquely with respect to the major axis direction. As shown in FIG. 3A, since the apparent dichroic dye shape with respect to light incident from the direction along the long axis of the dichroic dye is circular, no anisotropy occurs. On the other hand, as shown in FIG. 3B, since the apparent dichroic dye shape with respect to light incident obliquely with respect to the long axis direction of the dichroic dye is an elongated ellipse, anisotropy occurs. Thus, the polarization ability is generated in the direction of the absorption axis 7 shown in FIG. Accordingly, by aligning the dichroic dye having such polarization ability perpendicularly to the film surface of the optical film 4, the light incident on the liquid crystal panel 1 from a wide angle is polarized, and the front side of the liquid crystal panel 1. Can be absorbed by the polarizing plate 14b. That is, by providing the optical film 4, it is possible to compensate for a decrease in the polarization ability of the polarizing plate 14a with respect to light incident from a wide angle.

  FIG. 4 is a schematic diagram showing light transmission characteristics of the dichroic dye used in the liquid crystal display device according to the first embodiment. The light transmission characteristic T1 indicates an actual measurement value of the light transmittance of the dichroic dye when irradiated with light polarized in a direction parallel to the long axis of the dichroic dye, and the light transmission characteristic T2 indicates the dichroic dye. The measured value of the light transmittance of the dichroic dye when irradiated with the light polarized in the direction perpendicular to the major axis is shown. The light transmission characteristics T1 and T2 shown in FIG. 4 were measured by the following method. First, a dichroic dye was added to a polymer liquid crystal (nematic liquid crystal E7) at a concentration of 2.0% by weight to prepare a parallel alignment cell (cell gap 2.0 μm). And the spectrum when a polarizing plate (G1220Du Nitto Denko) was piled up on this parallel alignment cell was measured.

  As shown in FIG. 4, the dichroic dye used in the liquid crystal display device of this embodiment has a light transmittance of about 10% for light polarized in a direction parallel to the long axis of the molecule, whereas The light transmittance with respect to light polarized in the direction perpendicular to the major axis was approximately 30%. That is, it was confirmed that the dichroic dye of this embodiment has a property of absorbing light polarized in the major axis direction relatively large and absorbing light polarized in the minor axis direction relatively small.

  Further, it can be seen that the dichroic dye used in the liquid crystal display device of the present embodiment absorbs light in the visible light region substantially uniformly as shown in FIG. The optical film 4 having such a neutral color characteristic can be obtained by mixing at least two kinds of dichroic dyes having different absorption wavelengths in the visible light region. For example, at least two kinds of materials shown in [Chemical 9] of Patent Document 2 may be mixed. Alternatively, at least two kinds of materials shown in [FIG. 4] of Patent Document 3 may be mixed.

  In order to align the long axis direction of the molecules of the dichroic dye perpendicularly to the film surface of the optical film 4, for example, a polymer liquid crystal to which a dichroic dye is added using, for example, a vertically oriented polyimide ( The liquid crystal polymer) can be vertically aligned with respect to the optical film 4. As the polymer liquid crystal, for example, materials shown in [Chemical Formula 1] to [Chemical Formula 4] of Patent Document 2 can be used. Alternatively, the material shown in FIG. 3 of Patent Document 3 may be used.

  An example of the manufacturing method of the optical film 4 of this embodiment is demonstrated below. First, a solution for forming a polymer liquid crystal layer is prepared by adding and dissolving a dichroic dye at a concentration of 2.0% by weight in a predetermined polymer liquid crystal solvent. Next, a vertical alignment polyimide alignment film is formed on an isotropic and non-retarded film such as triacetyl cellulose or norbornene film to obtain a base film of the optical film 4.

  Subsequently, the prepared solution is coated on the base film on which the alignment film of the vertically aligning polyimide is formed, thereby forming a coating film containing a polymer liquid crystal and a dichroic dye. Thereafter, the coating film containing the polymer liquid crystal and the dichroic dye is irradiated with ultraviolet light having a predetermined wavelength to cure the coating film. As a result, the molecules of the polymer liquid crystal are aligned perpendicular to the base film, and the molecules of the dichroic dye are aligned perpendicular to the base film.

  The above-described manufacturing method is an example of a method for manufacturing the optical film 4 according to this embodiment, and may be a method capable of aligning a polymer liquid crystal and a dichroic dye perpendicularly to the base film. For example, it is possible to use a manufacturing method other than the above-described method. For example, instead of using vertical alignment polyimide or the like, a polymer liquid crystal that spontaneously exhibits vertical alignment may be used. Alternatively, the orientation direction of the polymer liquid crystal or the dichroic dye may be controlled by an external electric field or an external magnetic field. In this embodiment, the polymer liquid crystal added with the dichroic dye is aligned vertically on the base film having no retardation, but the base film and the polymer added with the dichroic dye from the backlight unit 2 side. When the liquid crystals are arranged in order, a base film having a phase difference may be used.

  FIG. 5 is a schematic diagram showing viewing angle characteristics of the liquid crystal display device according to the first embodiment. FIG. 6 is a schematic view showing viewing angle characteristics of a conventional liquid crystal display device. 5 and 6 both show actual measurement values of the angle dependence of the luminance of the liquid crystal panel 1 in white display. The viewing angle characteristic IH indicates the angle dependency of the luminance of the liquid crystal panel 1 in the horizontal direction (left and right direction), and the viewing angle characteristic IV indicates the angle dependency of the luminance of the liquid crystal panel 1 in the vertical direction (vertical direction). Comparing FIG. 5 and FIG. 6, the viewing angle characteristics IH and IV of the liquid crystal display device of the present embodiment shown in FIG. 5 have poor quality appearing in the viewing angle characteristics IH and IV of the conventional liquid crystal display device shown in FIG. It can be seen that wide-angle light is reduced. Thus, it was confirmed that the light incident on the liquid crystal panel 1 from a wide angle is reduced by providing the prism sheet 3 and the optical film 4 between the liquid crystal panel 1 and the backlight unit 2.

  The front contrast ratio measured using the liquid crystal display device of this embodiment shown in FIG. On the other hand, the front contrast ratio measured using the conventional liquid crystal display device shown in FIG. Thus, by providing the prism sheet 3 and the optical film 4 between the liquid crystal panel 1 and the backlight unit 2, the light reflected / scattered at the edge of the electrode 10 and emitted in the front direction of the liquid crystal panel 1 is reduced. It was confirmed that the contrast ratio of the liquid crystal display was improved. In addition, although it is desirable that the prism sheet 3 and the optical film 4 include both, the prism sheet 3 may be omitted. If at least the optical film 4 is provided, the effects of the present invention can be obtained.

  As described above, the liquid crystal display device of the present embodiment has two colors in which the major axis of molecules is aligned perpendicularly to the film surface between the backlight unit that irradiates the liquid crystal panel from the back or side and the liquid crystal panel. The optical film containing a sex pigment is provided. As a result, a liquid crystal display device capable of improving the contrast ratio of the liquid crystal display and a method for manufacturing the liquid crystal display device can be obtained.

  In the above description, it is assumed that the control method of the liquid crystal panel 1 is the IPS method, but the present invention is not limited to this. In the present invention, the above-described excellent effect can be obtained if the liquid crystal panel 1 has the linear electrode 10 for generating an electric field parallel to the liquid crystal layer 11 formed on the glass substrate 12a.

  The dichroic dye has a property of absorbing light polarized in the major axis direction relatively large and absorbing light polarized in the minor axis direction relatively small, but is not limited thereto. The dichroic dye only needs to have at least two axes having different light absorption coefficients. For example, the dichroic dye absorbs light polarized in the major axis direction relatively small and relatively reflects light polarized in the minor axis direction. It may be one that absorbs significantly.

  In this embodiment, the dichroic dye is added to the polymer liquid crystal at a concentration of 2.0% by weight. However, the concentration of the dichroic dye in the polymer liquid crystal is not limited to this value. If the concentration of the dichroic dye in the polymer liquid crystal is at least 2.0% by weight or more, the front contrast ratio of the liquid crystal display can be improved. However, if the concentration of the dichroic dye in the polymer liquid crystal is increased too much, the brightness of the liquid crystal display decreases.

(Second Embodiment)
Next, a liquid crystal display device according to a second embodiment will be described with reference to FIGS. FIG. 7 is a schematic diagram showing the configuration of the liquid crystal display device according to the second embodiment. The liquid crystal display device shown in FIG. 7 is mainly different from the liquid crystal display device of the first embodiment shown in FIG. Further, in order to show that the effect of the present invention can be obtained regardless of other configurations or the like in the case of the horizontal electric field type liquid crystal panel 1b, the material of the nematic liquid crystal is changed. Hereinafter, a configuration different from the first embodiment will be described.

  In the first embodiment, the display method of the liquid crystal panel 1 is the IPS method, and as shown in FIG. 1, the linear pixel electrode 10a and the linear common electrode are formed on the glass substrate 12a on the backlight unit 2 side. 10b was formed. On the other hand, in the liquid crystal display device of the present embodiment, the display method of the liquid crystal panel 1b is the FFS (Fringe Field Switching) method.

  That is, in the present embodiment, the linear pixel electrodes 10c are arranged at shorter intervals, and the common electrode 10d is not linear but rectangular. The display was controlled by applying a voltage between the pixel electrode 10c and the common electrode 10d. Accordingly, as shown in FIG. 7, the distance from the pixel electrode 10c to the common electrode 10d is shortened and the electric field is increased, so that the operability of the liquid crystal molecules can be improved. As a result, the brightness and responsiveness of the liquid crystal display are improved.

  FIG. 8 is a schematic diagram showing a layout of the electrodes 10 in the liquid crystal display device according to the second embodiment. 8A shows a cross section of the pixel electrode 10c along the line XX ′ shown in FIG. 7, and FIG. 8B shows the cross section of the common electrode 10d along the line YY ′ shown in FIG. A cross section is shown. The pixel electrode 10c and the common electrode 10d are formed in different wiring layers, and are electrically insulated from each other by an insulating layer 13 made of, for example, a SiNx film. The plurality of pixel electrodes 10c are actually shaped as shown in FIG. 8A, and are electrically connected to each other for each pixel. As shown in FIG. 7, the pixel electrode 10c and the common electrode 10d have an overlapping region in plan view.

  As shown in FIG. 8A, the FFS mode liquid crystal panel 1b has a large factor for reflecting / scattering light incident on the liquid crystal panel 1b from a wide angle because the interval between the linear pixel electrodes 10c is short. . Therefore, in this embodiment as well, as in the first embodiment, a prism sheet 3 and an optical film 4 are provided between the liquid crystal panel 1b and the backlight unit 2 in order to reduce light incident on the liquid crystal panel 1b from a wide angle. It was.

  In the liquid crystal display device of this embodiment, a liquid crystal layer 11 is formed by enclosing a nematic liquid crystal material having a negative dielectric anisotropy between a pair of opposing glass substrates 12a and 12b. Although there are few types of nematic liquid crystal materials with negative dielectric anisotropy, the degree of freedom in selecting liquid crystal materials is reduced, but by using nematic liquid crystal materials with negative dielectric anisotropy, liquid crystal against the electric field of liquid crystal molecules can be used. Operability can be improved.

  The front contrast ratio measured using the liquid crystal display device of this embodiment shown in FIG. On the other hand, the front contrast ratio measured using a conventional FFS liquid crystal display device was 1300. As described above, in the FFS liquid crystal display device, the front contrast ratio is significantly improved by including the prism sheet 3 and the optical film 4 as compared with the IPS liquid crystal display device. This is because in the FFS type liquid crystal panel 1b, the interval between the linear pixel electrodes 10c is short, and light that enters the liquid crystal panel 1b from a wide angle and is reflected / scattered at the edge of the electrode 10 increases. And the effect by the optical film 4 is thought to have increased. In addition, although it is desirable that the prism sheet 3 and the optical film 4 include both, the prism sheet 3 may be omitted. If at least the optical film 4 is provided, the effects of the present invention can be obtained.

  As described above, in the liquid crystal display device of this embodiment, a voltage is applied between the linear pixel electrode formed on the glass substrate and the rectangular common electrode formed on a wiring layer different from the pixel electrode. To control the display. Thereby, the liquid crystal display device and the manufacturing method of a liquid crystal display device which can further improve the contrast ratio of a liquid crystal display can be obtained.

  In the above description, it is assumed that the control method of the liquid crystal panel 1b is the FSS method, but the present invention is not limited to this. In the present invention, the above-described excellent effect can be obtained if the linear electrode 10 for generating an electric field parallel to the liquid crystal layer 11 is the liquid crystal panel 1b formed on the glass substrate 12a.

(Third embodiment)
Next, a liquid crystal display device according to a third embodiment will be described with reference to FIG. FIG. 9 is a schematic diagram illustrating a configuration of a liquid crystal display device according to the third embodiment. The liquid crystal display device shown in FIG. 9 is different from the liquid crystal display device of the first embodiment shown in FIG. 1 in that the backlight unit 2b corresponds to a so-called local dimming function. Hereinafter, a configuration different from the first embodiment will be described.

  In local dimming, the irradiation area of the backlight unit 2b that irradiates the liquid crystal panel 1 from the back surface or the side surface is divided into a plurality of sections, and the irradiation light quantity of the LED light sources 22a to 22c is adjusted for each section. This is a function for realizing (Dynamic Range). The number of sections of the backlight unit 2b to be divided is typically smaller than the number of pixels, for example, horizontal 16 × vertical 9 = 144. For example, when a night view is displayed on the liquid crystal panel 1, the irradiation light amount is increased in a section displaying a relatively bright image such as the moon, while the irradiation light amount is decreased in a section displaying a dark image. To do. Thereby, the contrast ratio of the whole image can be improved.

  The problem of the local dimming method is that when the irradiation light amount of a specific section of the backlight unit 2b is increased, light leaks to an adjacent region where the irradiation light amount is low. Therefore, in this embodiment as well, as in the first embodiment, the optical film 4 is provided between the liquid crystal panel 1 and the backlight unit 2b in order to reduce the light leaking to the adjacent section. As a result, in the liquid crystal display device shown in FIG. 9, the amount of light leaking to the adjacent section can be reduced to about 約 as compared with the case where the optical film 4 is not provided.

  As described above, in the backlight unit of the liquid crystal display device of the present embodiment, the region that illuminates the liquid crystal panel 1 is divided into a plurality of sections, and according to the brightness distribution of the image displayed on the liquid crystal panel 1, The amount of light that irradiates the liquid crystal panel 1 is adjusted for each section. As a result, the contrast ratio is improved by reducing the light reflected / scattered at the edge of the electrode and emitted to the front surface of the liquid crystal panel, and the contrast ratio is further improved by reducing the light leaking to the adjacent section. it can.

  In the above description, it is assumed that the control method of the liquid crystal panel 1 is the IPS method, but the present invention is not limited to this. In the present invention, the above-described excellent effect can be obtained if the liquid crystal panel 1 has the linear electrode 10 for generating an electric field parallel to the liquid crystal layer 11 formed on the glass substrate 12a. Moreover, the backlight unit 2b should just irradiate the liquid crystal panel 1 from a back surface or a side surface, for example, can be made into an edge type backlight or a direct type backlight.

(Other embodiments)
The above-described embodiments are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

  For example, in order to reduce the proportion of light that enters the liquid crystal panel 1 from a wide angle and is reflected / scattered at the edge of the electrode 10, the direction of the absorption axis of the polarizing plate 14a and the wiring direction of the linear electrode 10 are parallel. It should be close to. In the drawings of the above-described embodiment, for convenience of explanation, the direction of the absorption axis of the polarizing plate 14a and the wiring direction of the linear electrode 10 are drawn so as to be orthogonal. However, the actual polarizing plate 14a is a linear electrode. The direction of the absorption axis is arranged at a predetermined angle with respect to the ten wiring directions. This angle is mainly determined according to the type of liquid crystal molecules of the liquid crystal layer 11 and the like, but by approaching this angle to 0 ° or 180 °, it enters the liquid crystal panel 1 from a wide angle and is at the edge of the electrode 10. The proportion of light reflected / scattered can be reduced.

  Further, for example, in an automobile liquid crystal display device that requires a horizontal viewing angle characteristic of the liquid crystal panel 1, the absorption axis direction of the polarizing plate 14 b on the front side of the liquid crystal panel 1 may be made vertical. As a result, it is possible to suppress a reduction in polarization ability of the polarizing plate 14b with respect to light that is obliquely incident on the polarizing plate 14b from a horizontal wide angle.

1, 1b: Liquid crystal panel 2, 2b: Backlight unit 3: Prism sheet 4: Optical film 10: Electrode 10a, 10c: Pixel electrode 10b, 10d: Common electrode 11: Liquid crystal layer 12a, 12b: Glass substrate 13: Insulating layer 14a, 14b: Polarizing plate 15: Color filter 21: Light guide plate 22: LED light source

Claims (11)

A pair of glass substrates facing each other with a liquid crystal layer interposed therebetween, and a voltage is applied between a plurality of electrodes formed on one glass substrate of the pair of glass substrates to generate an electric field parallel to the liquid crystal layer. A liquid crystal display device comprising a liquid crystal panel that controls display by generating,
Between the backlight unit that irradiates the liquid crystal panel from the back or side and the liquid crystal panel, an optical film containing a dichroic dye having different molecular light absorption rates in the major axis direction and the minor axis direction,
A liquid crystal display device in which a major axis direction in which the light absorption rate of the dichroic dye is relatively large is aligned perpendicularly to the film surface of the optical film. The electrode includes a linear pixel electrode and a linear common electrode formed on the glass substrate on the backlight unit side of the pair of glass substrates,
The liquid crystal display device according to claim 1, wherein a display is controlled by applying a voltage between the pixel electrode and the common electrode. The electrode includes a linear pixel electrode formed on a glass substrate on the backlight unit side of the pair of glass substrates, and a rectangular common electrode formed on a wiring layer different from the pixel electrode. ,
The liquid crystal display device according to claim 1, wherein a display is controlled by applying a voltage between the pixel electrode and the common electrode. In the backlight unit, an area that illuminates the liquid crystal panel is divided into a plurality of sections,
4. The liquid crystal display device according to claim 1, wherein the amount of light applied to the liquid crystal panel is adjusted for each of the sections according to a brightness distribution of an image displayed on the liquid crystal panel. 5. 5. The optical film includes a polymer liquid crystal to which the dichroic dye is added, and the polymer liquid crystal is aligned perpendicularly to a film surface of the optical film. A liquid crystal display device according to 1. The liquid crystal display device according to claim 5, wherein a concentration of the dichroic dye added to the polymer liquid crystal is 2.0% by weight or more. The liquid crystal display device according to claim 1, wherein the optical film includes two or more types of the dichroic dyes having different absorption wavelengths in the visible light region. The liquid crystal display according to any one of claims 1 to 7, further comprising a prism sheet that condenses light from the backlight unit in a front direction of the liquid crystal panel between the optical film and the backlight unit. apparatus. The absorption axis of a polarizing plate provided on one glass substrate of the pair of glass substrates and an absorption axis of a polarizing plate provided on the other glass substrate are orthogonal to each other. The liquid crystal display device according to any one of the above. A pair of glass substrates facing each other with a liquid crystal layer interposed therebetween, and a voltage is applied between a plurality of electrodes formed on one glass substrate of the pair of glass substrates to generate an electric field parallel to the liquid crystal layer. A method of manufacturing a liquid crystal display device including a liquid crystal panel that controls display by generating,
An optical film containing a dichroic dye having different light absorption rates of molecules in the major axis direction and the minor axis direction, and the major axis direction in which the light absorption rate of the dichroic dye is relatively large is the film surface of the optical film. Forming so as to be oriented perpendicular to
Arranging the optical film between a backlight unit that irradiates the liquid crystal panel from the back or side and the liquid crystal panel;
A method of manufacturing a liquid crystal display device having Forming the optical film comprises:
Forming a vertical alignment polyimide alignment film on a base film;
Coating the alignment film with a polymer liquid crystal solution to which the dichroic dye is added, and forming a coating film on the base film;
Irradiating the coating film with ultraviolet light to cure the coating film;
The manufacturing method of the liquid crystal display device of Claim 10 which has these.

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