JP4064687B2 - Liquid crystal display device and manufacturing method thereof - Google Patents

Abstract

The invention relates to a liquid crystal display device and method for manufacturing the same. The liquid crystal display device is a liquid crystal display device formed by jointing a first substrate having a first electrode and a second substrate having a second electrode through an orientation film and a liquid crystal layer, which is characterized in that the liquid crystal layer forms a polymer structure for orientating the liquid crystal molecules according to the appointed direction in the liquid crystal, and the liquid crystal molecules have the approximately identical pre-elevation angle at the display position and peripheral position of the liquid crystal layer.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device that uses a polymer to define the alignment direction when driving liquid crystal molecules, and a method for manufacturing the same.
[0002]
[Prior art]
In order to realize a multi-domain vertical alignment mode liquid crystal display device capable of high-intensity and high-speed response, a method for defining the alignment direction when driving liquid crystal molecules using a polymer has been proposed. Yes. In this method, a liquid crystal material in which liquid crystal and a photopolymerizable monomer are mixed is sealed between two substrates. In a state where a predetermined voltage is applied between the substrates to tilt the liquid crystal molecules, the liquid crystal layer is irradiated with UV light to polymerize the monomer to form a polymer. The polymer formed in the vicinity of the surface of the substrate can provide a liquid crystal layer having a predetermined alignment direction and a pretilt angle even when voltage application is removed. For this reason, the rubbing process of an alignment film becomes unnecessary.
[0003]
[Problems to be solved by the invention]
FIG. 7 shows a display area of a conventional MVA mode liquid crystal display device. The liquid crystal material mixed with the monomer is injected from a liquid crystal injection port 12 formed at one end of the panel. As the liquid crystal material diffuses in the narrow cell gap, the monomer distribution in the display region 10 becomes non-uniform. In particular, in the region β in the vicinity of the two corners on the side facing the liquid crystal injection port 12, the monomer concentration is lower than in the other regions α. For this reason, in the region β, the pretilt angle of the liquid crystal molecules obtained after irradiating UV light to form a polymer is larger than that in the other regions α. Here, the pretilt angle is an inclination angle of the liquid crystal molecules from the substrate surface when no voltage is applied to the liquid crystal layer. That is, when the pretilt angle is 90 °, the liquid crystal molecules are aligned perpendicular to the substrate surface.
[0004]
FIG. 8 shows the luminance distribution on the line AA ′ of the display screen of the liquid crystal display device shown in FIG. The horizontal axis represents the position on the AA ′ line, and the vertical axis represents the luminance. The left end of the display area 10 on the line AA ′ is A0, the boundary between the area α and the area β is A1, and the right end of the display area 10 is A2. This liquid crystal display device is in a normally black mode, and the same gradation is displayed on the entire display area 10. As shown in FIG. 8, a substantially uniform luminance distribution is obtained in the region α, but the luminance is lowered in the region β as compared with the region α by the amount that the pretilt angle of the liquid crystal molecules is larger than the region α. For this reason, it is visually recognized as luminance unevenness on the display screen.
[0005]
Further, in a conventional color liquid crystal display device, coloring is visually recognized when a halftone (grayscale) is displayed. That is, the chromaticity has changed due to the change in gradation from white to black. This phenomenon indicates that different colors are reproduced not only for achromatic colors but also for chromatic colors, and there is a problem that a desired display image cannot be obtained. This is because the wavelength of the light transmitted through each color of the color filter (CF) resin layer is different, so that the substantial size of the retardation including the liquid crystal layer is different for each color, and the transmittance characteristic (T-V This is because the characteristics are different for each color.
[0006]
As a countermeasure against the above-described problem, a multi-gap technique has been proposed in which a cell gap is changed for each pixel having a different color. However, manufacturing by controlling the cell gap for each pixel has a problem that the process becomes complicated and the manufacturing cost increases.
[0007]
As another countermeasure, there is a method in which an input signal is converted by a signal conversion element such as a scaler IC to adjust a TV characteristic for each color. However, a scaler IC having a frame memory is expensive and lacks versatility.
[0008]
An object of the present invention is to provide a liquid crystal display device capable of obtaining good display characteristics and a method for manufacturing the same.
[0009]
[Means for Solving the Problems]
The purpose is to seal a liquid crystal layer containing a polymerizable component that is polymerized by light between two substrates disposed opposite to each other, and irradiate a predetermined light while applying a voltage to the liquid crystal layer under a predetermined voltage application condition. When irradiating the light under conditions to polymerize the polymerizable component and defining the pretilt angle of liquid crystal molecules and / or the alignment direction during driving, at least one of the voltage application condition and the light irradiation condition is a region. It is achieved by a manufacturing method of a liquid crystal display device characterized by being changed every time.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
A liquid crystal display device and a manufacturing method thereof according to a first embodiment of the present invention will be described with reference to FIGS. In this embodiment, the same pretilt angle is applied to the liquid crystal layer in the entire display region by varying the irradiation intensity of the UV light irradiated when forming a polymer that defines the alignment of liquid crystal molecules during driving. Has been granted. Thereby, uniform TV characteristics can be obtained over the entire display area.
[0011]
First, the principle of the manufacturing method of the liquid crystal display device according to the present embodiment will be described. FIG. 1 is a graph showing the relationship between the irradiation intensity of UV light and the pretilt angle of liquid crystal molecules. The horizontal axis represents the UV light irradiation intensity (mW / cm ² ), and the vertical axis represents the pretilt angle (deg.) Of the liquid crystal molecules obtained after the UV light irradiation. Note that a voltage (for example, 5 V) is applied to the liquid crystal layer so that the display screen has white luminance. Moreover, the irradiation time of UV light is 100 seconds. As shown in FIG. 1, the pretilt angle of the liquid crystal molecules obtained after UV light irradiation becomes smaller as the UV light irradiation intensity increases. However, the pretilt angle of the liquid crystal molecules becomes almost constant at an irradiation intensity of 50 mW / cm ² or more.
[0012]
In this embodiment, the region α shown in FIG. 7 is irradiated with UV light having an irradiation intensity B, and the region β is irradiated with UV light having an irradiation intensity B ′ (B ′> B) higher than the irradiation intensity B. The monomer is polymerized. As a result, even in the region β where the monomer concentration is lower than the region α, by irradiating UV light having an irradiation intensity B ′ higher than the irradiation intensity B, a pretilt angle almost the same as that in the region α can be obtained. That is, the TV characteristic of the region α and the TV characteristic of the region β are almost the same, and the luminance unevenness generated on the display screen can be reduced.
[0013]
Next, the manufacturing method of the liquid crystal display device according to the present embodiment will be described more specifically. FIG. 2 shows a schematic cross-sectional configuration of the liquid crystal display panel 1 used in the present embodiment. As shown in FIG. 2, the liquid crystal display panel 1 includes a thin film transistor (TFT) substrate 2 and a CF substrate 4 disposed to face the TFT substrate 2. The TFT substrate 2 has a pixel electrode 20 formed for each pixel on the glass substrate 16. The CF substrate 4 has a light shielding film 24 for defining each pixel on the glass substrate 17. Each pixel is formed with one of red (R), green (G), and blue (B) CF resin layers. A common electrode 22 is formed on the CF resin layers R, G, and B.
[0014]
A liquid crystal layer 6 in which a liquid crystal and a photopolymerizable monomer are mixed is sealed between the TFT substrate 2 and the CF substrate 4. The liquid crystal layer 6 is injected from a liquid crystal injection port 12 (not shown in FIG. 2) formed at one end of the liquid crystal display panel 1.
[0015]
First, a voltage that causes the display screen to have white luminance is applied between the pixel electrode 20 on the TFT substrate 2 and the common electrode 22 on the CF substrate 4. Subsequently, in a state where a voltage is applied between both electrodes 20 and 22, UV light is irradiated through a predetermined mask to polymerize the monomer in the liquid crystal layer 6. A gray mask drawing pattern is formed on the mask such that the transmittance of the region β shown in FIG. 7 is higher than the transmittance of the region α. As a result, the intensity of the UV light applied to the liquid crystal layer 6 is higher in the region β than in the region α. A liquid crystal display device is completed through the above steps.
[0016]
FIG. 3 is a graph corresponding to FIG. 8 showing the luminance distribution of a liquid crystal display device manufactured using the method for manufacturing a liquid crystal display device according to the present embodiment. As shown in FIG. 3, according to the present embodiment, the luminance in the region β is improved, and a substantially uniform luminance distribution is obtained in the entire display region 10. Therefore, a liquid crystal display device having good display characteristics without uneven brightness can be obtained.
[0017]
In addition, according to the present embodiment, the TV characteristics can be improved by changing the pretilt angle of the liquid crystal molecules even in a region where the cell gap is different from other regions, for example, in the vicinity of the liquid crystal injection port 12 or the vicinity of the sealing material. Can be almost the same as other areas. Therefore, good display characteristics with no luminance unevenness can be obtained in the vicinity of the liquid crystal inlet 12 or the frame in the display area 10.
[0018]
If the method for manufacturing a liquid crystal display device according to the present embodiment is used, luminance unevenness in the display region 10 caused by the luminance distribution of a light source device such as a backlight unit can be reduced. If the luminance distribution on the display region 10 of the light source device is grasped in advance, a high irradiation intensity corresponding to the luminance distribution has a high irradiation intensity so that the pretilt angle of the liquid crystal molecules is small in the relatively high luminance region. Irradiate with UV light. A region having a relatively low luminance is irradiated with UV light having a low irradiation intensity so that the pretilt angle of the liquid crystal molecules is increased. As described above, by intentionally changing the TV characteristic for each region of the liquid crystal display panel 1 in accordance with the luminance distribution of the light source device, the luminance unevenness generated on the display screen can be reduced, and good display characteristics can be obtained. Is obtained.
[0019]
Next, a method for manufacturing a liquid crystal display device according to the second embodiment of the present invention will be described with reference to FIGS. In this embodiment, a pixel in which an R CF resin layer is formed (hereinafter referred to as an R pixel), a pixel in which a G CF resin layer is formed (hereinafter referred to as a G pixel), and a B CF resin layer are formed. In order to give different pretilt angles to the liquid crystal molecules of the pixels (hereinafter referred to as B pixels), different voltages are applied to the liquid crystal layer 6 for each color when the monomers are polymerized by irradiating UV light.
[0020]
FIG. 4 is a graph showing the relationship between the applied voltage and the pretilt angle of the liquid crystal molecules. The horizontal axis represents the voltage (V) applied to the liquid crystal layer 6, and the vertical axis represents the pretilt angle (deg.) Of liquid crystal molecules obtained after irradiation with a predetermined amount of UV light. As shown in FIG. 4, the pretilt angle of the liquid crystal molecules decreases as the voltage applied to the liquid crystal layer 6 when UV light is irradiated increases.
[0021]
In the present embodiment, for example, a predetermined voltage Vr is applied to the liquid crystal layer 6 of the R pixel, a voltage Vg having an absolute value smaller than the voltage Vr is applied to the liquid crystal layer 6 of the G pixel, and a voltage is applied to the liquid crystal layer 6 of the B pixel. A voltage Vb having an absolute value smaller than Vg is applied (| Vr |> | Vg |> | Vb |). When the monomer is polymerized by irradiating with UV light in this state, the pretilt angle of the liquid crystal molecules of the R pixel becomes relatively small, and the pretilt angle of the liquid crystal molecules becomes larger in the order of the G pixel and B pixel. This increases the retardation generated in the liquid crystal layer 6 of the R pixel that transmits red light that has a refractive index relatively smaller than green, and the liquid crystal of B pixel that transmits blue light that has a refractive index relatively larger than green. The retardation that occurs in layer 6 is reduced. In this way, by correcting the refractive index of light different for each color, the substantial size of retardation generated in the liquid crystal layer 6 of each pixel can be made substantially the same. Therefore, the TV characteristics in the display area can be made uniform, and a desired display image can be obtained.
[0022]
Next, the manufacturing method of the liquid crystal display device according to the present embodiment will be described more specifically with reference to FIG. First, as shown in FIG. 2, voltages Vr, Vg, and Vb (| Vr |> | Vg |> | Vb |) are respectively applied to the liquid crystal layers 6 of the R, G, and B pixels. Subsequently, with a voltage applied to the liquid crystal layer 6, a predetermined amount of UV light is irradiated to polymerize the monomer in the liquid crystal layer 6. A liquid crystal display device is completed through the above steps.
[0023]
Next, a modification of the method for manufacturing the liquid crystal display device according to the present embodiment and a liquid crystal display device used therefor will be described. In the CF substrate 4 used in this modification, for example, the CF resin layers R, G, and B are formed with different formation materials or film thicknesses. When the transmissivities of the R, G, and B pixels of the CF substrate 4 are Tr, Tg, and Tb, Tr>Tg> Tb. When the liquid crystal layer 6 is irradiated with UV light from the CF substrate 2 side, the irradiation intensity of the UV light to the liquid crystal layer 6 is relatively increased in the R pixel and is decreased in the order of the G pixel and the B pixel. For this reason, as shown in FIG. 1, the pretilt angle of the liquid crystal molecules of the R pixel becomes relatively small, and the pretilt angle of the liquid crystal molecules becomes large in the order of the G pixel and the B pixel. Therefore, the effect similar to the said embodiment is acquired also by this modification.
[0024]
In the first and second embodiments, the UV characteristics in the display region are made uniform by changing the irradiation intensity of UV light and the applied voltage for each region, but other methods can also be used. .
[0025]
FIG. 5 is a graph showing the relationship between the irradiation wavelength of UV light and the pretilt angle of liquid crystal molecules. The horizontal axis represents the irradiation wavelength (nm) of UV light, and the vertical axis represents the pretilt angle (deg.) Of liquid crystal molecules obtained after irradiation with UV light. A predetermined voltage is applied to the liquid crystal layer 6 to irradiate a predetermined amount of UV light. As shown in FIG. 5, when UV light having an irradiation wavelength of about 365 nm is irradiated, the pretilt angle of the liquid crystal molecules becomes the smallest. Note that the irradiation wavelength at which the pretilt angle of the liquid crystal molecules becomes the smallest varies depending on the monomer mixed in the liquid crystal.
[0026]
When irradiating the UV light, the irradiation wavelength of the UV light applied to the liquid crystal layer 6 can be controlled by using a filter that transmits light having different irradiation wavelengths depending on the region. As described above, the same effects as those of the first and second embodiments can be obtained by changing the irradiation wavelength of the UV light for each region.
[0027]
FIG. 6 shows the relationship between the UV light irradiation time and the pretilt angle of the liquid crystal molecules. The horizontal axis represents the light irradiation time (sec), and the vertical axis represents the pretilt angle (deg.) Of the liquid crystal molecules obtained after the UV light irradiation. Note that a predetermined voltage is applied to the liquid crystal layer 6 and UV light having a predetermined irradiation intensity is irradiated. As shown in FIG. 6, the pretilt angle of the liquid crystal molecules decreases with increasing irradiation time up to about 100 seconds. However, the pretilt angle of the liquid crystal molecules hardly changes when the irradiation time exceeds 100 seconds.
[0028]
By irradiating UV light while moving a mask formed with a predetermined drawing pattern, the irradiation time can be changed depending on the region, and the boundary portion may be conspicuous on the display screen of the completed liquid crystal display device. Absent. As described above, the same effects as those of the first and second embodiments can be obtained by changing the irradiation time of the UV light for each region.
[0029]
The present invention is not limited to the above embodiment, and various modifications can be made.
For example, in the above-described embodiment, a normally black mode liquid crystal display device has been described as an example. However, the present invention is not limited to this, and can be applied to a normally white mode liquid crystal display device.
[0030]
In the above embodiment, a transmissive liquid crystal display device is taken as an example. However, the present invention is not limited to this, and can be applied to other liquid crystal display devices such as a reflective type and a transflective type.
In the above embodiment, the monomer is used as an example of the polymerizable component. However, an oligomer may be included in the liquid crystal layer as the polymerizable component.
[0031]
The manufacturing method of the liquid crystal display device according to the embodiment described above can be summarized as follows.
(Appendix 1)
A liquid crystal layer containing a polymerizable component that is polymerized by light is sealed between two substrates disposed opposite to each other;
The polymerizable component is polymerized by irradiating the light under a predetermined light irradiation condition while applying a voltage to the liquid crystal layer under a predetermined voltage application condition, thereby defining a pretilt angle of liquid crystal molecules and / or an alignment direction during driving. In this case, at least one of the voltage application condition and the light irradiation condition is changed for each region.
[0032]
(Appendix 2)
In the method for manufacturing a liquid crystal display device according to attachment 1,
The method for manufacturing a liquid crystal display device, wherein the light irradiation condition includes an irradiation intensity of the light.
[0033]
(Appendix 3)
In the method for manufacturing a liquid crystal display device according to appendix 1 or 2,
The method for manufacturing a liquid crystal display device, wherein the light irradiation condition includes an irradiation time of the light.
[0034]
(Appendix 4)
In the method for manufacturing a liquid crystal display device according to any one of appendices 1 to 3,
The method of manufacturing a liquid crystal display device, wherein the light irradiation condition includes an irradiation wavelength of the light.
[0035]
(Appendix 5)
In the method for manufacturing a liquid crystal display device according to any one of appendices 1 to 4,
A method of manufacturing a liquid crystal display device, wherein at least one of the voltage application condition and the light irradiation condition is changed for each color filter formed in each pixel.
[0036]
(Appendix 6)
In the method for manufacturing a liquid crystal display device according to any one of appendices 1 to 5,
A method of manufacturing a liquid crystal display device, wherein at least one of the voltage application condition and the light irradiation condition is changed between a corner region on the side facing the liquid crystal injection port and another region.
[0037]
(Appendix 7)
In the method for manufacturing a liquid crystal display device according to any one of appendices 1 to 6,
The method for manufacturing a liquid crystal display device, wherein the light is ultraviolet light.
[0038]
(Appendix 8)
A substrate for sandwiching a liquid crystal layer containing a polymer polymerized by ultraviolet light so as to define a pretilt angle of liquid crystal molecules and / or an alignment direction at the time of driving together with a substrate disposed oppositely;
A color filter resin layer formed on the substrate;
A liquid crystal display substrate, comprising: a pixel region arranged in a matrix on the substrate and having a different transmittance of the ultraviolet light for each color of the color filter resin layer.
[0039]
(Appendix 9)
In the substrate for liquid crystal display device according to appendix 8,
For the liquid crystal display device, the pixel region is Tr>Tg> Tb, where Tr is the transmittance of red pixels, Tg is the transmittance of green pixels, and Tb is the transmittance of blue pixels. substrate.
[0040]
(Appendix 10)
In the liquid crystal display substrate according to appendix 8 or 9,
A substrate for a liquid crystal display device, wherein the color filter resin layer has a different material for each color.
[0041]
(Appendix 11)
The substrate for a liquid crystal display device according to any one of appendices 8 to 10,
The substrate for a liquid crystal display device, wherein the color filter resin layer has a different film thickness for each color.
[0042]
(Appendix 12)
In a liquid crystal display device having two substrates opposed to each other and a liquid crystal layer sealed between the substrates,
A liquid crystal display device, wherein the substrate for a liquid crystal display device according to any one of appendices 8 to 11 is used on one of the substrates.
[0043]
【The invention's effect】
As described above, according to the present invention, it is possible to realize a method for manufacturing a liquid crystal display device capable of obtaining good display characteristics.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the irradiation intensity of UV light and the pretilt angle of liquid crystal molecules.
FIG. 2 is a cross-sectional view showing a schematic configuration of the liquid crystal display device according to the first embodiment of the invention.
FIG. 3 is a graph showing a luminance distribution of a display area of the liquid crystal display device according to the first embodiment of the present invention.
FIG. 4 is a graph showing a relationship between an applied voltage and a pretilt angle of liquid crystal molecules.
FIG. 5 is a graph showing the relationship between the irradiation wavelength of UV light and the pretilt angle of liquid crystal molecules.
FIG. 6 is a graph showing the relationship between the irradiation time of UV light and the pretilt angle of liquid crystal molecules.
FIG. 7 is a diagram showing a display area of a conventional liquid crystal display device.
FIG. 8 is a graph showing a luminance distribution in a display area of a conventional liquid crystal display device.
[Explanation of symbols]
2 TFT substrate 4 CF substrate 6 Liquid crystal layer 10 Display region 12 Liquid crystal injection port 16, 17 Glass substrate 20 Pixel electrode 22 Common electrode 24 Light shielding film

Claims (3)

A liquid crystal layer containing a polymerizable component that is polymerized by light is sealed between two substrates disposed opposite to each other;
The polymerizable component is polymerized by irradiating the light under a predetermined light irradiation condition while applying a voltage to the liquid crystal layer under a predetermined voltage application condition, thereby defining a pretilt angle of liquid crystal molecules and / or an alignment direction during driving. to time, as the transmittance characteristic of each region is substantially uniform, a method of manufacturing a liquid crystal display device characterized by varying at least one of the voltage applying condition or the light irradiation condition for each of the areas. In the manufacturing method of the liquid crystal display device of Claim 1,
A method for manufacturing a liquid crystal display device, wherein at least one of the voltage application condition and the light irradiation condition is changed for each color filter formed in each pixel. In the manufacturing method of the liquid crystal display device of Claim 1 or 2,
A method for manufacturing a liquid crystal display device, wherein at least one of the voltage application condition and the light irradiation condition is changed between a corner region on the side facing the liquid crystal injection port and another region.

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