KR101904355B1 - Liquid crystal display device and Method of fabricating the same - Google Patents

Abstract

An object of the present invention is to provide a liquid crystal display device and a method of manufacturing a liquid crystal display device which are capable of improving the contrast ratio in a liquid crystal panel that generates an electric field parallel to the liquid crystal layer and controls display.
A pair of glass substrates opposed to each other with a liquid crystal layer interposed therebetween, a voltage is applied between a plurality of electrodes formed on one of the pair of glass substrates to generate an electric field parallel to the liquid crystal layer, An optical film containing a dichroic dye different in light absorption ratio of molecules in the major axis direction and the minor axis direction is provided between the backlight unit and the liquid crystal panel for irradiating the liquid crystal panel from the back surface or the side surface, And a direction in which the light absorption rate of the dichroic dye is relatively large is oriented perpendicular to the film surface of the optical film.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a manufacturing method of a liquid crystal display device,

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

As a control method of the liquid crystal panel, TN (Twisted Nematic) and VA (Vertically Aligned) methods are known in which an electric field is generated between a pair of glass substrates opposed to each other with a liquid crystal layer interposed therebetween to control display. These conventional vertical (vertical electric field) type liquid crystal panels have a feature that the contrast ratio of the liquid crystal panel is high and the viewing angle characteristics are low.

In order to solve such a viewing angle characteristic problem, for example, in a liquid crystal display device of Patent Document 1, an optical film including a dichroic dye oriented in a substantially vertical direction is disposed between a liquid crystal panel and a backlight source. Thus, the color change when observed from the wide angle (wide viewing angle) is compensated.

Patent Document 1: JP-A No. 2009-116015 Patent Document 2: Japanese Patent Application Laid-Open No. 5-273602 Patent Document 3: Japanese Patent Application Laid-Open No. 11-160538

As an example of a liquid crystal panel control system different from the conventional system, there is known an IPS (In-Plane Switching) system and an FFS (Fringe Field Switching) system in which an electric field parallel to the liquid crystal layer is generated to control display. In these transverse electric field type liquid crystal panels, the apparent length (refractive index ellipsoid) of the liquid crystal molecules is almost constant irrespective of the viewing angle direction of the liquid crystal panel, so that the viewing angle characteristic is excellent.

The problem of the transverse electric field type liquid crystal panel is that the contrast ratio (hereinafter referred to as " front contrast ratio ") of the liquid crystal panel when viewed from the front direction is lower than that of the conventional system liquid crystal panel. One of the factors for lowering the front contrast ratio of the transverse electric field type liquid crystal panel is a line electrode for generating a transverse electric field formed on the glass substrate of the liquid crystal panel. Since the linear electrodes and the glass substrate have different refractive indices, light incident on the liquid crystal panel from the wide angle and reflected / scattered at the edges of the linear electrodes and emitted in the front direction of the liquid crystal panel lower the front contrast ratio.

Particularly, in the polarizing plate provided on both surfaces of the liquid crystal panel, the polarizing power is greatly lowered with respect to the light incident from the diagonal direction with respect to the absorption axis. Therefore, the light incident on the back-surface-side polarizer of the liquid crystal panel may not be sufficiently polarized. When reflected / scattered at the edge of the line-shaped electrode, the light is not absorbed in the front- . When such a phenomenon occurs at the time of black display, the front contrast ratio is lowered.

A method of reducing the light incident on the liquid crystal panel from such a wide angle and reflected / scattered at the edge of the line-shaped electrode and emitted in the frontal direction of the liquid crystal panel has not been studied in the transverse electric field type liquid crystal panel. Therefore, the Applicant has studied a method for improving the contrast ratio by reducing the light incident on the liquid crystal panel from the wide angle in the transverse electric field type liquid crystal panel.

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, a voltage is applied between a plurality of electrodes formed on one glass substrate among a pair of glass substrates, A liquid crystal display comprising a liquid crystal panel for controlling a display by generating a parallel electric field, the liquid crystal display comprising: a backlight unit for irradiating a liquid crystal panel from a back surface or a side surface; And an optical film containing a coloring dye, wherein a direction in which a light absorptivity of the dichroic dye is relatively large is oriented perpendicular to the film surface of the optical film.

A method of 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 is applied between a plurality of electrodes formed on one glass substrate among a pair of glass substrates, And a liquid crystal panel for controlling the display by generating an electric field parallel to the liquid crystal layer, the method comprising the steps of: forming an optical film containing a dichroic dye having a light absorptance ratio of molecules in the long axis direction and the short axis direction, A step of forming a direction in which the light absorption rate of the coloring material is relatively large in a direction perpendicular to the film surface of the optical film and a step of disposing an optical film between the backlight unit and the liquid crystal panel for irradiating the liquid crystal panel from the back surface or the side surface .

According to the present invention, it is possible to obtain a liquid crystal display device and a liquid crystal display device manufacturing method capable of improving a contrast ratio in a liquid crystal panel which generates an electric field parallel to a liquid crystal layer to control display.

1 is a schematic diagram showing a configuration of a liquid crystal display device according to the first embodiment.
2 is a schematic diagram showing an electrode layout in the liquid crystal display device according to the first embodiment.
Fig. 3 is a schematic diagram showing the difference in the 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 the diagonal direction with respect to the long axis.
4 is a schematic view showing light transmission characteristics of a dichroic dye used in the liquid crystal display device according to the first embodiment.
5 is a schematic view showing the viewing angle characteristics of the liquid crystal display device according to the first embodiment.
6 is a schematic view showing viewing angle characteristics of a conventional liquid crystal display device.
7 is a schematic diagram showing a configuration of a liquid crystal display device according to the second embodiment.
8 is a schematic diagram showing the electrode layout in the liquid crystal display device according to the second embodiment.
Fig. 9 is a schematic diagram showing a configuration of a liquid crystal display device according to the third embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and can be appropriately changed without departing from the gist of the present invention. In the drawings described below, those having the same functions are denoted by the same reference numerals and the description thereof may be omitted or simplified.

≪ First Embodiment >

A liquid crystal display device according to a first embodiment will be described with reference to Figs. 1 to 6. Fig. 1 is a schematic diagram showing a configuration of a liquid crystal display device according to the first embodiment. The liquid crystal display device of the present embodiment comprises 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 opposed to each other with a liquid crystal layer 11 interposed therebetween. The liquid crystal layer 11 is made of a nematic liquid crystal having a positive dielectric anisotropy as a main material and a liquid crystal layer 11 having a homogeneous alignment in which all the liquid crystal molecules are oriented in substantially the same direction in a black display in which no voltage is applied to the electrode 10 Respectively. Between the glass substrate 12b and the liquid crystal layer 11 is provided a color filter 15 and a color filter 15 is disposed between the glass substrate 12b and the liquid crystal layer 11 to emit light in the three primary color wavelength ranges R (red) / G (green) / B Pass light through each pixel.

The backlight unit 2 is an edge light type backlight, and an LED light source 22 including an LED element is provided at an end of the light guide plate 21. [ On the back side of the light guide plate 21, a light reflecting sheet or the like may be further disposed. Further, the backlight unit 2 is not limited to the edge-type backlight, and may be any one that irradiates the liquid crystal panel 1 from the back surface or the side surface. For example, the backlight unit 2 may be a direct-type backlight.

At least one pair of electrodes 10 is formed in the glass substrate 12a on the backlight unit 2 side of the liquid crystal panel 1 for each pixel. The liquid crystal panel 1 shown in Fig. 1 assumes an IPS (In-Plane Switching) system 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 plane of the liquid crystal layer 11, And controls the full color display of the liquid crystal display device by rotating the liquid crystal molecules.

Fig. 2 is a schematic diagram showing the layout of the electrodes 10 in the liquid crystal display device according to the first embodiment. FIG. 2 (a) is a cross-sectional view of the pixel electrode 10a taken along line XX 'of FIG. 1, and FIG. 2 (b) is a cross-sectional view of the common electrode 10b along line YY' Respectively. 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. 2 (a), and are electrically connected to each other for each pixel. The same applies to the common electrode 10b. The pixel electrode 10a and the common electrode 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, respectively, as if glass substrates 12a and 12b are interposed therebetween. 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 in the white display in which a voltage is applied between the pixel electrode 10a and the common electrode 10b, (2).

However, in the IPS system in which the display is controlled by applying the lateral voltage between the electrodes as described above, the light is incident on the liquid crystal panel 1 from the wide angle and reflected / scattered at the edge of the electrode 10, So that the front contrast ratio is lowered.

Particularly, in the polarizing plate 14a shown in Fig. 1, the polarizing power greatly decreases from the wide angle in the lateral direction in Fig. 1 to the light 6b incident from the diagonal direction with respect to the absorption axis 5a. Therefore, the light 6b incident on the absorption axis 5a in the diagonal direction from the wide angle is not sufficiently polarized. When the light 6b is reflected / scattered at the edge of the electrode 10 and exits in the front direction of the liquid crystal panel 1, Regardless of the alignment state of the polarizer 14b. As a result, in the IPS liquid crystal panel 1, the front contrast ratio decreases. In addition, the polarizing plate 14a does not lower the polarization capability with respect to the light 6a incident perpendicularly to the absorption axis 5a.

The liquid crystal display device of the present embodiment is provided with a prism sheet 3 between the liquid crystal panel 1 and the backlight unit 2 as shown in Fig. The prism sheet 3 condenses the light emitted from the backlight unit 2 in the front direction of the liquid crystal panel 1. [ Thus, the light incident on the liquid crystal panel 1 from the wide angle can be reduced.

Furthermore, the liquid crystal display device of the present embodiment is provided with the optical film 4 between the liquid crystal panel 1 and the backlight unit 2 as shown in Fig. The optical film 4 includes dichroic dyes having different light absorption ratios of the 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 4 (The surface facing the liquid crystal panel 1 or the backlight unit 2). Typically, the dichroic dye has an elongated molecular shape. The anisotropic property absorbs relatively large light polarized in the long axis direction and absorbs light polarized in the short axis direction relatively small.

Fig. 3 is a schematic diagram showing 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 major axis direction and when viewed from the diagonal direction with respect to the major axis. Fig. 3 (a) shows the apparent anisotropy of light absorption when the dichroic dye molecule is viewed from the long axis direction, and Fig. 3 (b) shows the apparent anisotropy of light absorption when the dichroic dye molecule is viewed from the diagonal direction with respect to the long axis. Anisotropy. 3 (a) and FIG. 3 (b), the dichroic dye has a larger apparent anisotropy as the light enters from the diagonal direction with respect to the long axis, and absorbs light oscillating in the major axis direction relatively have. Therefore, by aligning the dichroic dye having different light absorptivity of molecules in the major axis direction and the minor axis direction perpendicularly to the film surface of the optical film 4, light incident from the wide angle to the liquid crystal panel 1 is relatively absorbed can do.

Furthermore, since the dichroic dye absorbs light incident from the diagonal direction with respect to the long axis direction, it has a polarizing ability to polarize light incident diagonally to the long axis direction. As shown in Fig. 3 (a), since the apparent shape of the dichroic dye with respect to the 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. 3 (b), the apparent shape of the dichroic dye with respect to the light incident from the diagonal with respect to the major axis direction of the dichroic dye is an elongated elliptical shape, And a polarizing capability is generated in the direction of the axis 7. Therefore, by orienting the dichroic dye having such a polarizing function perpendicularly to the film surface of the optical film 4, the light incident on the liquid crystal panel 1 from the wide angle is polarized, and the front side of the liquid crystal panel 1 And can be absorbed by the polarizing plate 14b. That is, by providing the optical film 4, it is possible to compensate for the lowering of the polarization performance of the polarizing plate 14a with respect to the light incident from the wide angle.

4 is a schematic view showing light transmission characteristics of a dichroic dye used in a liquid crystal display device according to the first embodiment. The light transmission property T1 is an actual measured value of the light transmittance of the dichroic dye when light polarized in a direction parallel to the long axis of the dichroic dye is irradiated, and the light transmittance T2 is a value perpendicular to the long axis of the dichroic dye And the light transmittance of the dichroic dye when irradiated with polarized light. The light transmission characteristics T1 and T2 shown in Fig. 4 were measured by the following methods. First, in a polymer liquid crystal (nematic liquid crystal E7), a dichroic dye was added at a concentration of 2.0 wt% to prepare a parallel alignment cell (cell gap 2.0 μm). Then, the spectral spectrum when one polarizing plate (G1220Du, Nitto Denko Co.) was superimposed on this parallel alignment cell was measured.

As shown in Fig. 4, the dichroic dye used in the liquid crystal display device of the present embodiment has a light transmittance of about 10% to light polarized in a direction parallel to the long axis of the molecule, Lt; RTI ID = 0.0 > 30%. ≪ / RTI > That is, it was confirmed that the dichroic dye of the present embodiment has a property of relatively absorbing light polarized in the major axis direction and absorbing light polarized in the minor axis direction relatively small.

It is also understood 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 is 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 or more of the materials shown in the chemical formula (9) of Patent Document 2 may be mixed. Or at least two kinds of materials shown in FIG. 4 of Patent Document 3 may be mixed.

In order to align the major axis direction of the dichroic dye molecule vertically with respect to the film surface of the optical film 4, for example, a vertically oriented polyimide or the like is used and a polymer liquid crystal (liquid crystal polymer) , It is possible to vertically align the optical film (4). As the polymer liquid crystal, for example, the materials shown in 'Formula 1' to 'Formula 4' of Patent Document 2 can be used. Or the material shown in FIG. 3 of Patent Document 3 may be used.

An example of a manufacturing method of the optical film 4 of the present embodiment will be described below. First, a dichroic dye is added to a predetermined polymer liquid crystal solvent at a concentration of 2.0 wt% and dissolved to prepare a solution for forming a polymer liquid crystal layer. Next, a vertically aligning polyimide alignment film is formed on a film having an isotropic phase difference such as triacetyl cellulose and a norbornene film to obtain a base film of the optical film (4).

Subsequently, the base film on which the vertically aligning polyimide alignment film is formed is coated with the adjusted solution to form a coating film containing the polymer liquid crystal and the dichroic dye. Then, the coating film containing the polymer liquid crystal and the dichroic dye is irradiated with ultraviolet light of a predetermined wavelength to cure the coating film. As a result, the polymer liquid crystal molecules are oriented perpendicular to the base film while the dichroic dye molecules are oriented perpendicular to the base film.

The manufacturing method described above is an example of a method of manufacturing the optical film 4 according to the present embodiment, in which a manufacturing method other than the above-described method is used as long as the method can orient the polymer liquid crystal and the dichroic dye in a direction perpendicular to the base film It is also possible. For example, instead of using a vertically oriented polyimide or the like, a polymer liquid crystal showing spontaneous vertical orientation 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 the present embodiment, the polymer liquid crystal to which the dichroic dye is added is vertically oriented on the base film having no phase difference. When the base film and the polymer liquid crystal in which the dichroic dye are added are arranged in this order from the backlight unit 2 side , A base film having a phase difference may be used.

5 is a schematic view showing the viewing angle characteristics of the liquid crystal display device according to the first embodiment. 6 is a schematic view showing viewing angle characteristics of a conventional liquid crystal display device. Both FIGS. 5 and 6 show measured values of the angle dependency of the luminance of the liquid crystal panel 1 in white display. The viewing angle characteristic IH represents the angle dependence of the luminance of the liquid crystal panel 1 in the horizontal direction (left-right direction), and the viewing angle characteristic IV represents the angle dependence of the luminance of the liquid crystal panel 1 in the vertical direction (up-down direction). 5 and FIG. 6, the viewing angle characteristics IH and IV of the liquid crystal display device of this embodiment shown in FIG. 5 are inferior to those of the conventional liquid crystal display device of FIG. 6 in terms of viewing angle characteristics IH and IV It can be seen that the wide-angle light is reduced. It has been confirmed that the light incident on the liquid crystal panel 1 from the 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 as described above.

The front contrast ratio measured using the liquid crystal display device of this embodiment shown in Fig. 5 was 2100. On the other hand, the front contrast ratio measured using the conventional liquid crystal display apparatus shown in Fig. 6 was 1600. By providing the prism sheet 3 and the optical film 4 between the liquid crystal panel 1 and the backlight unit 2 as described above, the light is reflected / scattered at the edge of the electrode 10, It was confirmed that the contrast ratio of the liquid crystal display was improved. It is preferable that both the prism sheet 3 and the optical film 4 are provided, but the prism sheet 3 may be omitted. The effect of the present invention can be obtained if at least the optical film 4 is provided.

As described above, in the liquid crystal display device of the present embodiment, an optical film containing a dichroic dye whose major axis is oriented perpendicularly to the film surface is provided between the backlight unit for irradiating the liquid crystal panel from the back surface or the side surface and the liquid crystal panel Respectively. This makes it possible to obtain a liquid crystal display device and a liquid crystal display device manufacturing method capable of improving the contrast ratio of the liquid crystal display.

In the above description, it is assumed that the liquid crystal panel 1 is controlled by the IPS system, but the present invention is not limited thereto. The above-described excellent effect can be obtained when the linear electrode 10 for generating an electric field parallel to the liquid crystal layer 11 is the liquid crystal panel 1 formed on the glass substrate 12a.

The dichroic dye has a property of relatively absorbing light polarized in the major axis direction and absorbing light polarized in the minor axis direction relatively small, but the present invention is not limited thereto. The dichroic dye may have at least two axes having different light absorption coefficients. For example, the dichroic dye may absorb relatively large light polarized in the long axis direction and absorb relatively large polarized light in the short axis direction.

In the present embodiment, a dichroic dye is added to the polymer liquid crystal at a concentration of 2.0 wt%, but the dichroic dye concentration in the polymer liquid crystal is not limited to this value. When the dichroic dye concentration in the polymer liquid crystal is at least 2.0 wt% 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 too large, the brightness of the liquid crystal display is reduced.

≪ Second Embodiment >

Next, a liquid crystal display device according to the second embodiment will be described with reference to Figs. 7 and 8. Fig. 7 is a schematic diagram showing a configuration of a liquid crystal display device according to the second embodiment. The liquid crystal display device shown in Fig. 7 differs from the liquid crystal display device of the first embodiment shown in Fig. 1 mainly in the structure of the electrode 10 mainly. In addition, the nematic liquid crystal material or the like is changed to indicate that the effect of the present invention can be obtained regardless of the other constitution or the like if the liquid crystal panel 1b is the transverse electric field type. Hereinafter, configurations that are different from those of the first embodiment will be described.

The display method of the liquid crystal panel 1 according to the first embodiment of the present invention is an IPS system in which the linearly arranged pixel electrodes 10a and the linearly arranged pixel electrodes 10a are formed on the glass substrate 12a on the backlight unit 2 side, Thereby forming an electrode 10b. On the other hand, in the liquid crystal display device of the present embodiment, the display method of the liquid crystal panel 1b is a FFS (Fringe Field Switching) method.

That is, in the present embodiment, the line-shaped pixel electrodes 10c are arranged at a shorter interval, while the common electrode 10d is formed in a rectangular shape (plate shape) instead of a line shape. A voltage was applied between the pixel electrode 10c and the common electrode 10d to control the display. As a result, as shown in Fig. 7, the distance from the pixel electrode 10c to the common electrode 10d is shortened and the electric field is strengthened, so that it is possible to improve the workability of the liquid crystal molecules. As a result, brightness and responsiveness of the liquid crystal display are improved.

8 is a schematic diagram showing the layout of the electrodes 10 in the liquid crystal display device according to the second embodiment. 8A is a sectional view of the pixel electrode 10c taken along the line XX 'in FIG. 7, and FIG. 8B is a cross-sectional view of the common electrode 10d along the line YY' Respectively. 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 actually have a shape as shown in Fig. 8 (a), and are electrically connected to each other for each pixel. As shown in Fig. 7, the pixel electrode 10c and the common electrode 10d overlap each other when viewed in plan.

Since the interval between the linear pixel electrodes 10c is short as shown in Fig. 8 (a), the FFS type liquid crystal panel 1b has a large factor of reflecting / scattering the light incident on the liquid crystal panel 1b from the wide angle . The prism sheet 3 and the optical film (not shown) are interposed between the liquid crystal panel 1b and the backlight unit 2 in order to reduce the light incident on the liquid crystal panel 1b from the wide angle similarly to the first embodiment, 4) was installed.

In the liquid crystal display device of the present embodiment, a nematic liquid crystal material having a negative dielectric constant anisotropy is sealed between the pair of opposed glass substrates 12a and 12b to form the liquid crystal layer 11. [ The nematic liquid crystal material having a negative dielectric constant anisotropy has a small number of kinds and therefore the degree of freedom in selecting the liquid crystal material is reduced. However, by using a nematic liquid crystal material having a negative dielectric anisotropy, it is possible to improve the liquid crystal composition of the liquid crystal molecules against the electric field .

The front contrast ratio measured using the liquid crystal display device of this embodiment shown in Fig. 7 was 2000. On the other hand, the front contrast ratio measured using the conventional FFS type liquid crystal display was 1300. As described above, in the FFS type liquid crystal display device, the improvement of the front contrast ratio due to the provision of the prism sheet 3 and the optical film 4 was remarkable in the IPS type liquid crystal display device. This is because, in the FFS type liquid crystal panel 1b, since the interval between the linear pixel electrodes 10c is short and the light incident on the liquid crystal panel 1b from the wide angle and reflected / scattered at the edge of the electrode 10 increases, 3) and the optical film (4) are increased. It is preferable that both the prism sheet 3 and the optical film 4 are provided, but the prism sheet 3 may be omitted. The effect of the present invention can be obtained if at least the optical film 4 is provided.

As described above, in the liquid crystal display device of the present embodiment, display is controlled by applying a voltage between a linear pixel electrode formed on a glass substrate and a rectangular common electrode formed on a wiring layer different from the pixel electrode. This makes it possible to obtain a liquid crystal display device and a liquid crystal display device manufacturing method capable of further improving the contrast ratio of the liquid crystal display.

In the above description, the control method of the liquid crystal panel 1b is assumed to be the FSS method, but the present invention is not limited thereto. The above-described excellent effect can be obtained when 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. 9 is a schematic diagram showing a configuration of a liquid crystal display device according to the third embodiment. The liquid crystal display device shown in Fig. 9 differs 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, configurations that are different from those of the first embodiment will be described.

Local dimming refers to dividing the irradiated area of the backlight unit 2b that irradiates the liquid crystal panel 1 from the back surface or the side surface into a plurality of sections and adjusting the amount of light irradiated by the LED light sources 22a to 22c for each section, Dynamic Range). The number of divisions of the backlight unit 2b to be divided is typically small compared with the number of pixels, and is, for example, 16x9 = 144. For example, in the case of displaying the night view on the liquid crystal panel 1, the illumination light quantity of the section displaying the relatively bright image such as the moon is increased while the illumination light quantity is reduced in the section displaying the dark image. As a result, the contrast ratio of the entire image can be improved.

The problem of the local dimming method is that light is leaked to a neighboring region where the amount of irradiated light is low when the amount of irradiated light of a specific section of the backlight unit 2b is increased. Therefore, in this embodiment, similarly to 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 into adjacent compartments. As a result, in the liquid crystal display device shown in Fig. 9, the amount of light leaking into the adjacent compartments can be reduced to about one third 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 area irradiated with the liquid crystal panel 1 is divided into a plurality of sections, and according to the brightness distribution of the image to be displayed on the liquid crystal panel 1, 1) is adjusted for each section. As a result, the light reflected / scattered at the edge of the electrode can be reduced to reduce the light emitted to the front surface of the liquid crystal panel, thereby improving the contrast ratio and reducing the light leaked to the adjacent sections, thereby further improving the contrast ratio.

In the above description, it is assumed that the liquid crystal panel 1 is controlled by the IPS system, but the present invention is not limited thereto. The above-described excellent effect can be obtained when the linear electrodes 10 for generating an electric field parallel to the liquid crystal layer 11 are the liquid crystal panel 1 formed on the glass substrate 12a. The backlight unit 2b may be an edge-type backlight or a direct-type backlight as long as it irradiates the liquid crystal panel 1 from the back surface or the side surface.

<Other Embodiments>

All of the above-described embodiments are merely illustrative of specific embodiments of 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 carried out in various forms without departing from the technical idea or the main features thereof.

The absorption axis direction of the polarizing plate 14a and the wiring direction of the linear electrode 10 are set so that the ratio between the absorption axis direction of the polarizing plate 14a and the linear direction of the linear electrode 10 is It may be approximated in parallel. Although the drawing of the embodiment described above is drawn so that the absorption axis direction of the polarizing plate 14a and the wiring direction of the linear electrode 10 are perpendicular to each other for the sake of convenience of explanation, And the absorption axis direction is at a predetermined angle. This angle is mainly determined depending on the type of liquid crystal molecules of the liquid crystal layer 11 and the like. However, by making the angle close to 0 or 180 degrees, it is possible to prevent reflection / scattering at the edge of the electrode 10, It is possible to reduce the ratio of light to be emitted.

For example, in a liquid crystal display device for a vehicle in which a horizontal viewing angle characteristic of the liquid crystal panel 1 is required, the absorption axis direction of the front-side polarizing plate 14b of the liquid crystal panel 1 may be set to be vertical. This makes it possible to suppress a decrease in the polarization performance of the polarizing plate 14b with respect to light incident diagonally on the polarizing plate 14b from the wide angle in the horizontal direction.

1, 1b: liquid crystal panel 2, 2b: backlight unit
3: prism sheet 4: optical film
10: electrodes 10a and 10c: pixel electrodes
10b, 10d: common electrode 11: liquid crystal layer
12a, 12b: glass substrate 13: insulating layer
14a, 14b: polarizer 15: color filter
21: light guide plate 22: LED light source

Claims (13)

A liquid crystal display device comprising: first and second glass substrates facing each other with a liquid crystal layer interposed therebetween; a line-shaped pixel electrode formed on the first substrate; and a second electrode formed on the first substrate in a rectangular shape A liquid crystal panel for applying a voltage between the line-shaped pixel electrode and the rectangular common electrode to control the display;
A backlight unit including a plurality of LEDs for irradiating the liquid crystal panel from a rear surface or a side surface;
And an optical film including a dichroic dye having a light absorptance ratio of molecules in the major axis direction and the minor axis direction between the backlight unit and the liquid crystal panel,
A direction in which the light absorptivity of the dichroic dye is relatively large is oriented perpendicular to the film surface of the optical film,
Wherein the backlight unit includes a liquid crystal display panel in which an area irradiated with the liquid crystal panel is divided into a plurality of sections and an amount of light of the LEDs irradiating the liquid crystal panel is adjusted for each section according to a brightness distribution of an image to be displayed on the liquid crystal panel. .

delete delete delete The method according to claim 1,
Wherein the optical film comprises a polymer liquid crystal to which the dichroic dye is added, and the polymer liquid crystal is oriented perpendicular to the film surface of the optical film.
6. The method of claim 5,
Wherein a concentration of the dichroic dye added to the polymer liquid crystal is 2.0 wt% or more.
The method according to claim 1,
Wherein the optical film contains two or more kinds of the dichroic dye having different absorption wavelengths in the visible light region.
The method according to any one of claims 1, 5, and 6,
Further comprising a prism sheet between the optical film and the backlight unit for condensing light from the backlight unit in a front direction of the liquid crystal panel.
The method according to any one of claims 1, 5, and 6,
Wherein the absorption axis of the polarizing plate provided on the one glass substrate and the absorption axis of the polarizing plate provided on the other glass substrate are orthogonal to each other among the pair of glass substrates.
delete delete The method according to claim 1,
Wherein the liquid crystal panel comprises a first polarizing plate positioned on an outer surface of a glass substrate positioned on the backlight unit side and having a first absorption axis and a second absorption plate located on an outer surface of another glass substrate and having a second absorption axis perpendicular to the first absorption axis And a second polarizer plate,
Wherein light incident from the backlight unit in a direction inclined with respect to a direction perpendicular to the film surface of the optical film among light incident toward the liquid crystal panel is polarized by the dichroic dye in a direction parallel to the second absorption axis .
The method according to claim 1,
Wherein the dichroic dye has a first absorption rate with respect to light polarized in the major axis direction and a second absorption rate with respect to light polarized in the minor axis direction that is smaller than the first absorption rate.

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