JP6824658B2 - Liquid crystal display device and manufacturing method of liquid crystal display device - Google Patents

Description

The present invention relates to a liquid crystal display device for controlling a display by generating an electric field parallel to the liquid crystal panel surface, and a method for manufacturing the liquid crystal display device.

As a display method of a liquid crystal panel, an IPS (In-Plane Switching) method is known in which a voltage is applied to an electrode provided on a glass substrate to generate an electric field parallel to the liquid crystal layer to control the display. In the IPS system, the apparent length of the liquid crystal molecules (refractive index ellipsoid) is almost constant regardless of the viewing angle direction of the liquid crystal panel, so that the viewing angle characteristics are excellent.

However, in the IPS method, since the lateral component of the electric field for generating the electric field becomes relatively small just above the electrode, the operability of the liquid crystal molecules directly above the electrode becomes low, and when the voltage of the electrode is ON (displayed in white). There was a problem that the brightness was insufficient.

In order to solve such a problem, for example, in Patent Document 1, the anchoring energy (Anchoring Energy) of the alignment film for aligning the liquid crystal molecules is reduced to weaken the orientation regulating force of the liquid crystal molecules. As a result, even when the lateral component of the electric field is small, the liquid crystal molecules on the electrode-forming substrate can easily operate in response to the lateral electric field, so that sufficient brightness can be obtained even immediately above the electrode.

JP-A-2009-271390

The anchoring energy of the alignment film of the liquid crystal panel provides a restoring force that aligns the orientation direction of the liquid crystal molecules in a certain direction when the voltage of the electrode is OFF (displayed in black). In Patent Document 1, by reducing the anchoring energy, this restoring force is reduced to facilitate the operation of the liquid crystal molecules. However, when the magnitude of the anchoring energy is changed in the liquid crystal layer, the orientation characteristics of the liquid crystal molecules also change in the liquid crystal layer. Therefore, although the brightness of the liquid crystal display is improved, the viewing angle characteristic, which is a feature of the IPS system, may be affected.

Patent Document 1 does not mention any effect on the viewing angle characteristics by reducing the anchoring energy of the alignment film. Therefore, the applicant investigated the effect on the viewing angle characteristics when the anchoring energy of the alignment film of the liquid crystal panel was reduced.

The liquid crystal display device according to the present invention has a first orientation that orients the first glass substrate and the second glass substrate that face each other with the liquid crystal layer interposed therebetween and the liquid crystal molecules on the side of the first glass substrate of the liquid crystal layer in the first direction. A film, a second alignment film for aligning liquid crystal molecules on the side of the second glass substrate of the liquid crystal layer in the first direction, a first polarizing plate provided on the first glass substrate and having a first absorption axis, and a first polarizing plate. A second polarizing plate provided on the two glass substrates and having a second absorption axis orthogonal to the first absorption axis is provided, and a voltage is applied to the electrodes provided on the first glass substrate to generate an electric field parallel to the liquid crystal layer. A liquid crystal display device that controls display by generating, the anchoring energy of the first alignment film is smaller than the anchoring energy of the second alignment film, and the direction of the absorption axis of the first polarizing plate is the first. It is characterized in that it is parallel to the direction of.

Further, the method for manufacturing a liquid crystal display device according to the present invention includes a first glass substrate and a second glass substrate facing each other with the liquid crystal layer sandwiched therein, and applies a voltage to an electrode provided on the first glass substrate to form a liquid crystal layer. A method of manufacturing a liquid crystal display device that controls display by generating parallel electric fields, in which liquid crystal molecules on the side of the first glass substrate of the liquid crystal layer are oriented in the first direction by a relatively small anchoring energy. A step of providing a first alignment film to be aligned, a step of providing a second alignment film for aligning the liquid crystal molecules on the side of the second glass substrate of the liquid crystal layer in the first direction with a relatively large anchoring energy, and an absorption axis. The step of providing the first polarizing plate on the first glass substrate so that the direction of is parallel to the first direction, and the second polarizing plate of the second polarizing plate so that the direction of the absorption axis is perpendicular to the first direction. It is characterized by having a step provided on the substrate.

According to the present invention, it is possible to obtain a liquid crystal display device and a method for manufacturing a liquid crystal display device capable of improving the brightness and viewing angle characteristics of the liquid crystal display.

It is the schematic which shows the structure of the liquid crystal display device which concerns on 1st Embodiment. It is a figure which shows the light passing characteristic of the liquid crystal display device which concerns on 1st Embodiment. It is a figure which shows the viewing angle characteristic of the liquid crystal display device which concerns on 1st Embodiment. It is the schematic which shows the structure of the liquid crystal display device which concerns on 2nd Embodiment. It is a figure which shows the light passing characteristic of the liquid crystal display device which concerns on 2nd Embodiment. It is a figure which shows the viewing angle characteristic of the liquid crystal display device which concerns on 2nd Embodiment. It is a figure which shows the light passing characteristic 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. The present invention is not limited to the following embodiments, and can be appropriately modified without departing from the gist thereof. Further, in the drawings described below, those having the same function may be designated 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. 1 to 3. FIG. 1 is a schematic view showing a configuration of a liquid crystal display device according to the first embodiment. FIG. 1A schematically shows the cross section of the liquid crystal display device, and FIG. 1B schematically shows the orientation of the liquid crystal molecules on the plane of the liquid crystal layer 11 of the liquid crystal display device. FIG. 1 (a) is a cross-sectional view taken along the line AA'shown in FIG. 1 (b).

The liquid crystal display device shown in FIG. 1A includes a liquid crystal panel 1 and a backlight unit 2. A light diffusion sheet, a prism sheet, or the like may be arranged between the liquid crystal panel 1 and the backlight unit 2.

The liquid crystal panel 1 has a pair of glass substrates 12a and 12b that face each other with the liquid crystal layer 11 interposed therebetween. Of the glass substrates 12a and 12b, the glass substrate 12a on the backlight unit 2 side is provided with a plurality of electrodes 10. The control unit (not shown) of the liquid crystal display device applies a voltage between the electrodes 10 of the glass substrate 12a to generate an electric field parallel to the surface of the liquid crystal layer 11, and rotates the liquid crystal molecules in the surface of the liquid crystal layer 11. The display of the liquid crystal display device is controlled by the operation.

The liquid crystal panel 1 is provided with polarizing plates 14a and 14b, respectively, so as to sandwich the glass substrates 12a and 12b from the outside. The orientations of the polarization axes of the polarizing plates 14a and 14b are arranged so that the light illuminated from the backlight unit 2 passes or is blocked when a voltage is applied to the electrodes 10. For example, in the embodiment shown in FIG. 1A, the polarization axes of the polarizing plates 14a and 14b are orthogonal to each other, and the illumination light from the backlight unit 2 passes through when a voltage is applied to the electrode 10. ..

Alignment films 13a and 13b are provided between the glass substrates 12a and 12b of the liquid crystal panel 1 and the liquid crystal layer 11, respectively. The alignment films 13a and 13b orient the liquid crystal molecules of the liquid crystal layer 11 when the voltage of the electrode 10 is OFF in a predetermined direction. Further, a color filter 15 is provided between the glass substrate 12b of the liquid crystal panel 1 and the alignment film 13b. The color filter 15 passes light in the wavelength range of the three primary colors of R (red) / G (green) / B (blue) among the light illuminated by the backlight unit 2.

The backlight unit 2 is an edge light type backlight, and includes an LED light source 22 having an LED element at an end portion of the light guide plate 21. The LED light source 22 supplies the light that illuminates the liquid crystal panel 1 through the light guide plate 21.

The liquid crystal panel 1 of the present embodiment shown in FIG. 1 generates a transverse electric field parallel to the liquid crystal layer 11, and rotates the liquid crystal molecules in the plane of the liquid crystal layer 11 to control the display (IPS mode, AH-). It is a liquid crystal display device of IPS mode). However, as described above, in the IPS method, since the lateral component of the electric field is relatively small immediately above the electrode 10, the liquid crystal molecules directly above the electrode 10 are difficult to respond to the lateral electric field, and the brightness in the white display is insufficient. Resulting in.

Therefore, in the present embodiment, as shown in FIG. 1A, the anchoring energy of the alignment film 13a is reduced to weaken the alignment regulating force of the liquid crystal molecules on the glass substrate 12a side. As a result, even when the lateral component of the electric field is small, the liquid crystal molecules on the glass substrate 12a side easily operate in response to the lateral electric field, so that sufficient brightness can be ensured even immediately above the electrode 10.

Next, a method of manufacturing the liquid crystal display device of the present embodiment shown in FIG. 1 will be described. First, a nematic liquid crystal material having a positive dielectric anisotropy (dielectric anisotropy Δε = 10, refractive index anisotropy Δn = 0.100) is sealed between a pair of glass substrates 12a and 12b facing each other. The liquid crystal layer 11 was formed. The thickness of the glass substrates 12a and 12b was 0.5 (mm), and the thickness of the liquid crystal layer 11 was 4.8 (μm).

A color filter 15 for passing light in the wavelength ranges of the three primary colors of R (red) / G (green) / B (blue) was formed between the glass substrate 12b and the liquid crystal layer 11. On the other hand, a linear electrode 10 for generating an electric field parallel to the liquid crystal layer 11 was formed between the glass substrate 12a and the liquid crystal layer 11. The electrodes 10 are configured such that pixel electrodes and common electrodes are alternately arranged and a voltage is applied between the pixel electrodes and the common electrodes. The width of the electrodes 10 is 3 (μm), and the distance between the electrodes 10 is 10 (μm). did.

Further, an alignment film 13a was formed between the glass substrate 12a and the liquid crystal layer 11, and an alignment film 13b was formed between the glass substrate 12b and the liquid crystal layer 11. The anchoring energy of the alignment film 13a was relatively small at ^10-7 (J / m ² ), and the anchoring energy of the alignment film 13b was relatively large at ^10-2 (J / m ² ). Further, the alignment film 13a and the alignment film 13b were oriented in substantially the same direction to obtain a homogeneous orientation in which all the liquid crystal molecules of the liquid crystal layer 11 were oriented in substantially the same direction when the voltage was turned off.

At this time, the anchoring energy of the alignment film 13a was made smaller than the anchoring energy of the alignment film 13b by the following procedure. First, to form a polyimide film having anchoring energy of ¹⁰ -2 (J / ^{m 2)} on the glass substrate 12a. Then, the polyimide film is subjected to a rubbing treatment so that the liquid crystal molecules of the liquid crystal layer 11 are uniformly oriented at an angle α = about 20 degrees with respect to the longitudinal direction of the linear electrode 10 as shown in FIG. 1 (b). did. Subsequently, the polyimide film was irradiated with UV light of about 1000 (mJ / m ² ) by mask exposure to reduce the anchoring energy of the alignment film 13a to ^10-7 (J / m ² ).

After that, the polarizing plates 14a and 14b were arranged so as to sandwich the glass substrates 12a and 12b. In the polarizing plates 14a and 14b, typically, one absorption axis of the polarizing plates 14a and 14b is parallel to the orientation direction of the liquid crystal molecules of the liquid crystal layer 11, and the other absorption axis is the liquid crystal molecules of the liquid crystal layer 11. It is arranged so as to be orthogonal to the orientation direction. In the present embodiment, as shown in FIG. 1 (b), the direction 18 of the absorption axis of the polarizing plate 14a is made parallel to the orientation direction of the liquid crystal molecules of the liquid crystal layer 11. Then, the backlight unit 2 provided with the white LED light source 22 at the end of the light guide plate 21 is arranged on the back side of the liquid crystal panel 1.

FIG. 2 is a diagram showing light passing characteristics of the liquid crystal display device according to the first embodiment. FIG. 2 shows an actually measured value of the light transmittance (%) of the liquid crystal panel 1 when a voltage difference of 0 to 10 (V) is applied between the adjacent electrodes 10. The light passage characteristic T1 of the liquid crystal panel 1 in the present embodiment was measured by reducing the anchoring energy to ^10-7 (J / m ² ) over the entire area of the alignment film 13a (weakly). On the other hand, the conventional light passage characteristic T2 was measured by increasing the anchoring energy to ^10-2 (J / m ² ) over the entire area of the alignment film 13a (strongly). The anchoring energy of the alignment film 13b was as large (strong) as ^10-2 (J / m ² ) in the entire area in the measurement of the light passing characteristics T1 and T2.

As shown in FIG. 2, the light passing characteristic T1 of the liquid crystal panel 1 of the present embodiment is greatly improved as compared with the light passing characteristic T2 of the conventional liquid crystal panel. It is considered that this is because the anchoring energy of the alignment film 13a is reduced so that the liquid crystal molecules directly above the electrode 10 can easily respond to the transverse electric field.

Next, the viewing angle characteristics when the anchoring energy of the alignment film 13a of the liquid crystal panel 1 was reduced were examined. In the configuration shown in FIG. 1 in which the anchoring energy of the alignment film 13a is relatively small, the alignment characteristics of the liquid crystal layer 11 are asymmetrical between the side of the polarizing plate 14a and the side of the polarizing plate 14b. Therefore, the direction of the absorption axis of the polarizing plate 14a is parallel to the orientation direction of the liquid crystal molecules of the liquid crystal layer 11, and the direction of the absorption axis of the polarizing plate 14a is perpendicular to the orientation direction of the liquid crystal molecules of the liquid crystal layer 11. The viewing angle characteristics of the liquid crystal display device may differ depending on the case. Therefore, the applicant reduced the anchoring energy of the alignment film 13a of the liquid crystal panel 1 and measured the viewing angle characteristics by changing the direction of the absorption axis of the polarizing plate 14a with respect to the orientation direction of the liquid crystal molecules.

FIG. 3 is a diagram showing the viewing angle characteristics of the liquid crystal display device according to the first embodiment. FIG. 3 shows actual measurements of the contrast ratio of the electrode 10 when the voltage is ON (white display) and when the voltage is OFF (black display) in a viewing angle range of 0 to 360 ° in azimuth and 0 to 90 ° in polar angle. Shows the value.

Of FIGS. 3 (a) to 3 (d), FIGS. 3 (a) and 3 (b) show the measurement results of the viewing angle characteristics when the anchoring energy of the alignment film 13a is relatively small. ing. FIG. 3A shows the viewing angle characteristic C1 of the liquid crystal panel 1 of the present embodiment in which the direction of the absorption axis of the polarizing plate 14a is parallel to the orientation direction of the liquid crystal molecules, and FIG. 3B shows the polarizing plate 14a. The viewing angle characteristic C2 when the direction of the absorption axis of is perpendicular to the orientation direction of the liquid crystal molecules is shown.

Further, FIGS. 3 (c) and 3 (d) show the measurement results of the viewing angle characteristics of the conventional liquid crystal panel while keeping the anchoring energy of the alignment film 13a increased. FIG. 3C shows the viewing angle characteristic C3 when the direction of the absorption axis of the polarizing plate 14a is parallel to the orientation direction of the liquid crystal molecules, and FIG. 3D shows the direction of the absorption axis of the polarizing plate 14a. The viewing angle characteristic C4 when it is perpendicular to the orientation direction of the liquid crystal molecules is shown. In any of the measurements of FIGS. 3A to 3D, the absorption axis of the polarizing plate 14a and the absorption axis of the polarizing plate 14b are orthogonal to each other.

In the viewing angle characteristics C1 and C2 shown in FIG. 3, the region where the contrast ratio C / R = 1000 or more is larger than the viewing angle characteristics C3 and C4. That is, it can be seen that the viewing angle characteristics C1 and C2 of the liquid crystal panel 1 in which the anchoring energy of the alignment film 13a is reduced are superior to the viewing angle characteristics C3 and C4 of the conventional liquid crystal panel. It is considered that this is because the brightness of the liquid crystal panel 1 when the voltage is ON (white display) is improved and the contrast ratio C / R is improved.

Further, in the viewing angle characteristic C1 shown in FIG. 3, the region where the contrast ratio C / R = 10 or less is smaller than the viewing angle characteristic C2. That is, the viewing angle characteristic C1 of the liquid crystal panel 1 of the present embodiment in which the direction of the absorption axis of the polarizing plate 14a is parallel to the orientation direction of the liquid crystal molecules is such that the direction of the absorption axis of the polarizing plate 14a is the orientation direction of the liquid crystal molecules. It can be seen that it is superior to the viewing angle characteristic C2 when it is perpendicular to. This is because only the anchoring energy on the side of the alignment film 13a is relatively small, so that the liquid crystal orientation in the white display becomes asymmetric between the side of the polarizing plate 14a and the side of the polarizing plate 14b, and the viewing angle characteristic C1 and the field of view It is probable that there was a difference from the angular characteristic C2.

As described above, in the configuration of the liquid crystal panel 1 in which the anchoring energy of the alignment film 13a shown in FIG. 1A is reduced, the absorption axis of the polarizing plate 14a is set to the direction of liquid crystal orientation as shown in FIG. 1B. It was found that the viewing angle characteristics were improved when they were arranged in parallel. On the other hand, in the conventional configuration in which the alignment film 13a and the alignment film 13b have the same anchoring energy, the viewing angle characteristic C3 in which the absorption axis of the polarizing plate 14a is parallel to the orientation direction of the liquid crystal molecules and the orientation direction of the liquid crystal molecules There was almost no difference from the vertical viewing angle characteristic C4.

As described above, in the liquid crystal display device of the present embodiment, the anchoring energy of the first alignment film (alignment film 13a) is made smaller than the anchoring energy of the second alignment film (alignment film 13b). The direction of the absorption axis of the first polarizing plate (polarizing plate 14a) is parallel to the orientation direction of the first alignment film and the second alignment film. As a result, it is possible to obtain a liquid crystal display device and a method for manufacturing the liquid crystal display device, which can improve the brightness and viewing angle characteristics of the liquid crystal display. In addition, since the liquid crystal molecules immediately above the electrodes are more likely to respond, the electric field applied between the electrodes can be made smaller, and the power consumption of the liquid crystal display device can be reduced.

In the above description, the plurality of electrodes 10 are formed in the same wiring layer, but the pixel electrode and the common electrode may be separately formed in different wiring layers insulated from each other by an insulating film such as SiNx or SiOx. ..

Further, in the present embodiment, IZO (indium zinc oxide) having a high light transmittance T of 85% is adopted as the main material of the electrode 10, but the present invention is not limited to this. The electrode 10 may be a conductor film having a high light transmittance. Instead of IZO, for example, ITO (Indium tin oxide, T = 88%) or AZO (aluminum doped zinc oxide, T = 92%) can be used. Alternatively, GZO (gallium doped zinc oxide, T = 92%), ATO (antimony tin oxide, T = 87%) and the like may be used.

(Second Embodiment)
Next, the liquid crystal display device according to the second embodiment will be described with reference to FIGS. 4 to 6. FIG. 4 is a schematic view showing the configuration of the liquid crystal display device according to the second embodiment. FIG. 4A schematically shows the cross section of the liquid crystal display device, and FIG. 4B schematically shows the orientation of the liquid crystal molecules on the plane of the liquid crystal layer 11 of the liquid crystal display device. FIG. 4A is a cross-sectional view taken along the line AA'shown in FIG. 4B. The liquid crystal display device shown in FIG. 4 is mainly different in the structure of the electrodes 10 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 IPS type liquid crystal panel 1, the material and thickness of the liquid crystal layer 11 are changed. Hereinafter, a configuration different from that of the first embodiment will be described.

In the first embodiment described above, as shown in FIG. 1, a plurality of linear electrodes 10 are formed in the wiring layer between the glass substrate 12a and the liquid crystal layer 11. On the other hand, in the liquid crystal display device of the present embodiment, as shown in FIG. 4, a plurality of linear pixel electrodes 10a are formed in the first wiring layer between the glass substrate 12a and the liquid crystal layer 11. A rectangular common electrode 10b was formed on a second wiring layer different from the first wiring layer. Then, a voltage was applied between the pixel electrode 10a and the common electrode 10b to control the display. As a result, in the present embodiment, as shown in FIG. 4A, the closer to the pixel electrode 10a, the shorter the distance to the common electrode 10b and the stronger the electric field, so that the operability of the liquid crystal molecules in the vicinity of the pixel electrode 10a is improved. It can be improved further. Hereinafter, a method for manufacturing the liquid crystal display device of the present embodiment shown in FIG. 4 will be described.

First, a nematic liquid crystal material having a negative dielectric anisotropy (dielectric anisotropy Δε = -3, refractive index anisotropy Δn = 0.100) is placed between a pair of glass substrates 12a and 12b facing each other. It was sealed to form a liquid crystal layer 11. The thickness of the glass substrates 12a and 12b was 0.5 (mm), and the thickness of the liquid crystal layer 11 was 4.2 (μm). Since there are few types of nematic liquid crystal materials with negative dielectric anisotropy, the degree of freedom in selecting the liquid crystal material is reduced, but by using nematic liquid crystal materials with negative dielectric anisotropy, the liquid crystal with respect to the electric field of the liquid crystal molecules It is possible to improve the operability of.

A color filter 15 for passing light in the wavelength ranges of the three primary colors of R (red) / G (green) / B (blue) was formed between the glass substrate 12b and the liquid crystal layer 11. On the other hand, a linear pixel electrode 10a was formed on the first wiring layer between the glass substrate 12a and the liquid crystal layer 11. Then, a rectangular common electrode 10b was formed on the second wiring layer different from the first wiring layer. The width of the pixel electrodes 10a was 2 (μm), and the spacing between the pixel electrodes 10a was 4 (μm). An insulating layer 16 made of a SiNx film having a thickness of 3000 (Å) was formed between the first wiring layer and the second wiring layer. As shown in FIG. 4, the pixel electrode 10a and the common electrode 10b have a region that overlaps with each other in a plan view from a direction perpendicular to the surface of the glass substrate 12a.

Further, an alignment film 13a was formed between the glass substrate 12a and the liquid crystal layer 11, and an alignment film 13b was formed between the glass substrate 12b and the liquid crystal layer 11. The anchoring energy of the alignment film 13a was relatively small at ^10-6 (J / m ² ), and the anchoring energy of the alignment film 13b was relatively large at 10 ³ (J / m ² ). Further, the alignment film 13a and the alignment film 13b were oriented in substantially the same direction to obtain a homogeneous orientation in which all the liquid crystal molecules of the liquid crystal layer 11 were oriented in substantially the same direction when the voltage was turned off.

At this time, the anchoring energy of the alignment film 13a was made smaller than the anchoring energy of the alignment film 13b by the following procedure. First, a polymer brush having a small anchoring energy was formed on the glass substrate 12a. After that, the entire area of the polymer brush is subjected to rubbing treatment, and as shown in FIG. 4B, the liquid crystal molecules of the liquid crystal layer 11 are uniformly oriented at an angle α = about 83 degrees with respect to the longitudinal direction of the linear pixel electrode 10a. I tried to do it.

After that, the polarizing plates 14a and 14b were arranged so as to sandwich the glass substrates 12a and 12b. In the present embodiment, as shown in FIG. 4B, the direction 18 of the absorption axis of the polarizing plate 14a is made parallel to the orientation direction of the liquid crystal molecules of the liquid crystal layer 11. Then, the backlight unit 2 provided with the white LED light source 22 at the end of the light guide plate 21 is arranged on the back side of the liquid crystal panel 1.

FIG. 5 is a diagram showing light passing characteristics of the liquid crystal display device according to the second embodiment. Further, FIG. 6 is a diagram showing the viewing angle characteristics of the liquid crystal display device according to the second embodiment. The measurement in the liquid crystal display device of the present embodiment shown in FIGS. 5 and 6 was performed by basically the same method and under the same conditions as the measurement in the liquid crystal display device of the first embodiment shown in FIGS. 2 and 3.

As shown in FIGS. 5 and 6, the light passage characteristic T1 and the viewing angle characteristic C1 of the liquid crystal panel 1 of the present embodiment are further improved as compared with the case of the first embodiment shown in FIGS. 2 and 3. You can see that. It is considered that this is because the operability of the liquid crystal molecules in the vicinity of the pixel electrode 10a is further improved by improving the structure of the electrode 10.

Further, the viewing angle characteristic C1 of the liquid crystal panel 1 of the present embodiment shown in FIG. 6 has the largest region having a contrast ratio C / R = 1000 or more and the smallest region having a contrast ratio C / R = 10 or less. You can see that there is. That is, also in this embodiment, the viewing angle characteristic C1 in which the anchoring energy of the alignment film 13a is reduced and the absorption axis of the polarizing plate 14a is parallel to the orientation direction of the liquid crystal molecules is the other viewing angle characteristics C2 to C4. It turns out to be better than. In this way, in the configuration in which the anchoring energy of the alignment film 13a is reduced, the absorption axis of the polarizing plate 14a is arranged parallel to the direction of the liquid crystal orientation as shown in FIG. 4B regardless of other configurations. It was found that the viewing angle characteristics were improved by doing so.

As described above, in the liquid crystal display device of the present embodiment, the linear pixel electrodes provided on the first wiring layer of the first glass substrate are provided on the second wiring layer different from the first wiring layer. The display is controlled by applying a voltage between the common electrode and the rectangular common electrode. As a result, it is possible to obtain a liquid crystal display device and a method for manufacturing the liquid crystal display device, which can further improve the brightness and viewing angle characteristics of the liquid crystal display.

In the present embodiment, ITO (Indium tin oxide) having a high light transmittance T of 88% is adopted as the main material of the pixel electrode 10a and the common electrode 10b, but the present invention is not limited to this. The pixel electrode 10a and the common electrode 10b may be any conductor film having high light transmittance. For example, IZO (indium zinc oxide T = 85%) and AZO (aluminum bonded zinc oxide, T = 92%) can be used instead of ITO. Alternatively, GZO (gallium doped zinc oxide, T = 92%), ATO (antimony tin oxide, T = 87%) and the like may be used.

(Third Embodiment)
In this embodiment, the influence of the magnitude of anchoring energy on the light passing characteristics of the liquid crystal panel 1 is examined. The configuration of the liquid crystal display device of this embodiment is basically the same as the configuration of the second embodiment shown in FIG. However, 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 IPS type liquid crystal panel 1, the material and thickness of the liquid crystal layer 11 are changed. Hereinafter, the parts different from the second embodiment will be described.

First, a nematic liquid crystal material having a positive dielectric anisotropy (dielectric anisotropy Δε = 10, refractive index anisotropy Δn = 0.100) is sealed between a pair of glass substrates 12a and 12b facing each other. The liquid crystal layer 11 was formed. The thickness of the glass substrates 12a and 12b was 0.5 (mm), and the thickness of the liquid crystal layer 11 was 4.4 (μm).

A color filter 15 for passing light in the wavelength ranges of the three primary colors of R (red) / G (green) / B (blue) was formed between the glass substrate 12b and the liquid crystal layer 11. On the other hand, a linear pixel electrode 10a was formed on the first wiring layer between the glass substrate 12a and the liquid crystal layer 11. Then, a rectangular common electrode 10b was formed on the second wiring layer different from the first wiring layer. The width of the pixel electrodes 10a was 2 (μm), and the spacing between the pixel electrodes 10a was 4 (μm). An insulating layer 16 made of a SiNx film having a thickness of 3000 (Å) was formed between the first wiring layer and the second wiring layer. As shown in FIG. 4, the pixel electrode 10a and the common electrode 10b have a region that overlaps with each other in a plan view from a direction perpendicular to the surface of the glass substrate 12a.

Further, an alignment film 13a was formed between the glass substrate 12a and the liquid crystal layer 11, and an alignment film 13b was formed between the glass substrate 12b and the liquid crystal layer 11. The anchoring energy of the alignment film 13a was relatively small, ^10-8 to 10 ^-1 (J / m ² ), and the anchoring energy of the alignment film 13b was relatively large, 10 ³ (J / m ² ). .. Further, the alignment film 13a and the alignment film 13b were oriented in substantially the same direction to obtain a homogeneous orientation in which all the liquid crystal molecules of the liquid crystal layer 11 were oriented in substantially the same direction when the voltage was turned off.

At this time, the anchoring energy of the alignment film 13a was made smaller than the anchoring energy of the alignment film 13b by the following procedure. First, a polymer brush having a small anchoring energy was formed on the alignment film 13a. After that, the entire area of the polymer brush is subjected to rubbing treatment, and as shown in FIG. 4B, the liquid crystal molecules of the liquid crystal layer 11 are uniformly oriented at an angle α = about 83 degrees with respect to the longitudinal direction of the linear pixel electrode 10a. I tried to do it.

After that, the polarizing plates 14a and 14b were arranged so as to sandwich the glass substrates 12a and 12b. In the present embodiment, as shown in FIG. 4B, the direction 18 of the absorption axis of the polarizing plate 14a is made parallel to the orientation direction of the liquid crystal molecules of the liquid crystal layer 11. Then, the backlight unit 2 provided with the white LED light source 22 at the end of the light guide plate 21 is arranged on the back side of the liquid crystal panel 1.

FIG. 7 is a diagram showing light passing characteristics of the liquid crystal display device according to the third embodiment. FIG. 7 shows an actually measured value of the light transmittance (%) of the liquid crystal panel 1 when a voltage difference of 0 to 10 (V) is applied between the pixel electrode 10a and the common electrode 10b. In FIG. 7, the anchoring energies of the alignment film 13a are ^10-8 , ^10-7 , ^10-6 , ^10-5 , ^10-4 , ^10-3 , ^10-2 , and 10 ^-1 (J / m ² ). The light passing characteristics of the liquid crystal panel 1 were measured in the case of.

As shown in FIG. 7, when the anchoring energy of the alignment film 13a is 10 ^-3 (J / m ² ) or more, the light passing characteristic of the liquid crystal display device of the present embodiment increases the anchoring energy over the entire range. It was almost the same as the conventional light passing characteristics. Next, when the anchoring energy of the alignment film 13a was set to 10 ^-4 or less, the light transmittance improved as the anchoring energy was reduced. However, even if the anchoring energy of the alignment film 13a was reduced to ^10-6 (J / m ² ) or less, the light transmittance was not further improved. As described above, it was found that when the anchoring energy of the alignment film 13a is ^10-6 (J / m ² ) or less, the brightness of the liquid crystal display can be greatly improved.

As described above, in the liquid crystal display device of the present embodiment, the brightness of the liquid crystal display can be greatly improved by setting the anchoring energy of the first alignment film to ^10-6 (J / m ² ) or less. .. Further, when the anchoring energy is ^10-6 (J / m ² ) or less, the light transmittance hardly changes, so that the influence of the change due to the variation of the anchoring energy on the light passing characteristics can be suppressed. As a result, it is possible to obtain a liquid crystal display device in which display unevenness is less likely to occur and a manufacturing margin is wide.

(Other embodiments)
The above-described embodiments are merely examples of embodiment in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner by these. That is, the present invention can be implemented in various forms without departing from the technical idea or its main features.

For example, in the above-described embodiment, only the anchoring energy directly above the electrode 10 (or the pixel electrode 10a) of the alignment film 13a may be relatively small. That is, by keeping the anchoring energy in the region other than directly above the electrode 10 of the alignment film 13a large, the restoring force of the liquid crystal molecules when the voltage of the electrode 10 is turned off is hardly reduced, and the responsiveness of the liquid crystal display is lowered. Can be suppressed. That is, both the brightness of the liquid crystal display and the responsiveness can be achieved.

In order to make the anchoring energy of the alignment film 13a relatively small only directly above the electrode 10, for example, the alignment film 13a is formed by the following procedure. First, a polyimide film having anchoring energy of ¹⁰ -2 (J / ^{m 2)} on the glass substrate 12a. Then, the polyimide film is subjected to a rubbing treatment so that the liquid crystal molecules of the liquid crystal layer 11 are uniformly oriented at a predetermined angle α with respect to the longitudinal direction of the linear electrode 10. Subsequently, by mask exposure, only the polyimide film directly above the electrode 10 is irradiated with UV light of about 1000 (mJ / m ² ), and the anchoring energy directly above the electrode 10 is set to ^10-7 (J / m ² ). Make it smaller.

Alternatively, instead of irradiating UV directly above the electrode 10 of the alignment film 13a, a polymer brush having a small anchoring energy may be formed in a region directly above the electrode 10 of the alignment film 13a by using a photolithography method. Alternatively, a polymer brush having a small anchoring energy may be selectively formed in the region directly above the electrode 10 of the alignment film 13a by using an inkjet method.

In this way, by making the anchoring energy directly above the electrodes 10 of the alignment film 13a smaller than the anchoring energy between the electrodes 10 of the alignment film 13a, the liquid crystal display can be displayed while suppressing a decrease in the responsiveness of the liquid crystal display. Brightness and viewing angle characteristics can be improved.

1: Liquid crystal panel 2: Backlight unit 10: Electrode 10a: Pixel electrode 10b: Common electrode 11: Liquid crystal layer 12a, 12b: Glass substrate 13a, 13b: Alignment film 14a, 14b: Polarizing plate

Claims (10)

The first glass substrate and the second glass substrate facing each other across the liquid crystal layer,
A first alignment film that orients the liquid crystal molecules on the side of the first glass substrate of the liquid crystal layer in the first direction,
A second alignment film that orients the liquid crystal molecules on the side of the second glass substrate of the liquid crystal layer in the first direction,
A first polarizing plate provided on the first glass substrate and having a first absorption axis,
A second polarizing plate provided on the second glass substrate and having a second absorption axis orthogonal to the first absorption axis,
A liquid crystal display device that controls display by applying a voltage to an electrode provided on the first glass substrate to generate a transverse electric field in the liquid crystal layer.
The anchoring energy of the first alignment film is smaller than the anchoring energy of the second alignment film.
Direction of absorption axis of the first polarizer, Ri said first direction and parallel der,
The anchoring energy directly above the electrodes of the first alignment film is smaller than the anchoring energy between the electrodes of the first alignment film.
Liquid crystal display device. The liquid crystal display device according to claim 1, wherein the anchoring energy immediately above the electrodes of the first alignment film is ^10-6 (J / m ² ) or less. The electrode is a linear pixel electrode provided on the first wiring layer of the first glass substrate, and is a rectangular common common provided on a second wiring layer different from the first wiring layer. The liquid crystal display device according to claim 1 or 2, wherein the display is controlled by applying a voltage between the electrodes and the pixel electrodes. The liquid crystal display device according to claim 3, wherein the pixel electrode and the common electrode have an overlapping region in a plan view. The liquid crystal display device according to any one of claims 1 to 4, wherein the electrode is made of any one of ITO, IZO, AZO, GZO, and ATO as a main material. The liquid crystal display device according to any one of claims 1 to 5 , wherein the anchoring energy between the electrodes of the first alignment film is equal to the anchoring energy of the second alignment film. The first alignment film
A polymer brush formed directly above the electrode and
With the polyimide formed in the region between the electrodes
The liquid crystal display device according to any one of claims 1 to 6, comprising the above. A first glass substrate and a second glass substrate facing each other across the liquid crystal layer are provided, and a voltage is applied to the electrodes provided on the first glass substrate to generate a transverse electric field in the liquid crystal layer to control the display. It is a manufacturing method of a liquid crystal display device.
A step of providing a first alignment film that orients the liquid crystal molecules on the side of the first glass substrate of the liquid crystal layer in the first direction by a relatively small anchoring energy.
A step of providing a second alignment film that orients the liquid crystal molecules on the side of the second glass substrate of the liquid crystal layer in the first direction by a relatively large anchoring energy.
A step of providing a first polarizing plate on the first glass substrate so that the direction of the absorption axis is parallel to the first direction.
A step of providing a second polarizing plate on the second glass substrate so that the direction of the absorption axis is perpendicular to the first direction.
A method for manufacturing a liquid crystal display device, which has an alignment step in which the anchoring energy immediately above the electrodes of the first alignment film is smaller than the anchoring energy between the electrodes of the first alignment film . The orientation step
The first step of forming the polyimide film on the first glass substrate and
The second step of rubbing the polyimide film and
The third step of irradiating the region directly above the electrodes of the polyimide film with UV to make the anchoring energy directly above the electrodes of the polyimide film smaller than the anchoring energy between the electrodes of the polyimide film.
The method for manufacturing a liquid crystal display device according to claim 8 . The first alignment film
A polymer brush formed directly above the electrode and
With the polyimide formed in the region between the electrodes
8. The method for manufacturing a liquid crystal display device according to claim 8.

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