JP2005221588A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display of high display quality, suitable for a transmission type having wide visible angle characteristics and moreover attaining high transmittance. <P>SOLUTION: The liquid crystal device has a liquid crystal layer between a first substrate and a second substrate, displays substantially a vertical orientation state with respect to the substrate by making liquid crystal molecules constituting the liquid crystal layer lower than threshold voltage, and displays radial orientation state at threshold voltage or higher. The liquid crystal display provides an irregularity structure on the substrate, formed of an organic insulation film or the like fitted via the liquid crystal layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a liquid crystal display device. More specifically, the present invention relates to a high display quality liquid crystal display device which has a wide viewing angle characteristic and can be widely applied to TVs, personal computer displays and the like.

In recent years, liquid crystal display devices have been widely used due to the advantages of being thin and lightweight for displays such as personal computers, car navigation systems, and mobile information terminals such as mobile phones, and have become indispensable for various display means. In such a liquid crystal display device, the conventional twisted nematic method (TN method) and the super twisted nematic method (STN method) have a narrow viewing angle, and various technical developments have been made to solve this problem.
For example, as a typical technique for improving the viewing angle characteristics of a TN liquid crystal display device or an STN liquid crystal display device, there is a method of adding an optical compensation plate. However, there is room for improvement in the wide viewing angle range and the objectivity in the vertical viewing angle direction, and it is desired to further improve the display quality.

As an improvement technique in a conventional liquid crystal display device, there is an in-plane switching (IPS) system in which an electric field in a horizontal direction with respect to a substrate surface is applied to a liquid crystal layer. As another technique, there is a DAP (Deformation of Vertical Aligned Phase) method in which a nematic liquid crystal material having negative dielectric anisotropy is used as a liquid crystal material and a vertical alignment film is used as an alignment film. This is one of the voltage controlled birefringence (ECB) method, and controls the transmittance by utilizing the birefringence of liquid crystal molecules.
These two improved technologies have been adopted for TV and personal computer displays, and mass production has been realized in recent years.

However, since the IPS method is a method in which a horizontal electric field is applied within one picture element, at least two electrodes having different potentials must be provided at a certain interval only on one substrate. In order to apply a lateral electric field, it is necessary to divide into a large number of electrodes. At this time, since a horizontal electric field is not applied to the upper part of the electrode, a region (opening area) in which the amount of transmitted light can be controlled is greatly reduced, and the liquid crystal display is compared with the conventional TN method or STN method. The transmittance as a device is reduced.

On the other hand, in the DAP method, a method of providing a slit (opening) in a picture element electrode is disclosed in order to control the transmittance and perform uniform and stable vertical alignment control (for example, patents). Reference 1 to 3). Separately, the first electrode on the first substrate is divided into a plurality of parts, and a second electrode is provided on the second substrate, and each pixel divided on the first substrate is projected on the second electrode. A method of providing a part is also disclosed (for example, see Patent Documents 4 and 5). In these two methods, there is room for contrivance in this respect because the transmittance is reduced as a liquid crystal display element as compared with the conventional TN method and STN method due to slits and pixel division. .

That is, in the DAP type liquid crystal display device, a method of controlling liquid crystal molecules is disclosed for vertical alignment when no voltage is applied and radial tilt alignment when a voltage is applied (see, for example, Patent Documents 2 and 3). One pixel electrode to be controlled by one active element is divided into a plurality by slits, and the radial orientation is stably controlled in units of divided pixel electrodes. However, the slit width for obtaining a stable radial orientation needs to be 5 to 10 μm, and since almost no voltage is applied to this slit region, it does not contribute as a transmissive opening, leading to a decrease in transmittance. .

In addition, as shown in FIGS. 10A and 10B, regarding the division of the pixel electrode by the convex portion, as shown in FIGS. 10A and 10B, for the liquid crystal display device that shares the transmissive display and the reflective display, the optical path of the transmissive display portion and the reflective display portion It is disclosed that a convex portion is provided to make the length constant (see, for example, Patent Document 5). In such a liquid crystal display device, one pixel is divided into a plurality of sub-pixels.
However, since it is preferable for a transflective liquid crystal display device (transflective type), for example, in a preferred embodiment, the pixel is divided into a transmissive region and a reflective region, and the liquid crystal layer Will be different within one pixel (multi-gap). Therefore, a DAP type liquid crystal display device that can be suitably applied to a transmissive type and is required to have a high display quality by suppressing a decrease in transmittance.

By the way, in these types of liquid crystal display devices, since commercialization has progressed mainly for TVs and personal computer displays that require a wide viewing angle and high-quality display characteristics, a backlight system used in these devices has been developed. It was also possible to compensate for the decrease in the transmittance by devising the light source. However, in recent years, in personal digital assistants (cell phones, etc.) and mobile notebook personal computers, in addition to the conventional requirements of low power consumption (power source duration), small size and light weight, a wide viewing angle is high. Although there is an increasing demand for quality display, it is incompatible with the reduction in power consumption and reduction in size and weight to compensate for a decrease in transmittance with a light source device in the DAP method capable of realizing a wide viewing angle. Also from such a point, a liquid crystal display device with high display quality that can achieve both wide viewing angle and high transmittance is demanded.
Japanese Patent Laid-Open No. 6-301036 (pages 1, 6 and 1, 2) JP 2000-47217 A (pages 1, 9, 10 and 1, 4) Japanese Patent Laid-Open No. 2002-55343 (pages 1, 44, 45, FIGS. 1, 14) Japanese Patent Laying-Open No. 2003-43525 (15-17, page 30, FIG. 13) Japanese Patent Laid-Open No. 2003-167253 (pages 1, 24, FIG. 17)

The present invention has been made in view of the above problems, and provides a liquid crystal display device having a wide viewing angle characteristic, a high transmittance, and a high display quality suitable for a transmission type. It is for the purpose.

The present inventors have made various studies on a liquid crystal display device having a wide viewing angle characteristic, in particular, a DAP-type transmissive liquid crystal display device. For example, one pixel electrode controlled by one active element is divided into a plurality of pixel electrodes. Then, attention was first paid to the fact that the alignment direction is easily determined due to the separation and individualization of the radial alignment state of the liquid crystal molecules at the time of voltage application, and stable alignment control can be performed. If the separation of the picture element electrodes is performed by providing slits as in the conventional case, the transmittance will be reduced, but one picture element electrode controlled by one active element is divided into a plurality of parts. As a technique to achieve this, if the substrate is provided with an uneven structure that is fitted via a liquid crystal layer, or has a cross-sectional structure in which liquid crystal layers are alternately formed, stable alignment control and high The inventors have found that the transmittance can be realized, and have conceived that the above problems can be solved brilliantly, and have reached the present invention. For example, when the pixel electrode unit to be divided is provided with uneven portions in a checkered pattern, the division loss can be greatly reduced as compared with the division method using a slit, and DAP having a wide viewing angle characteristic. Among the methods, it can be suitably applied to a transmissive liquid crystal display device in which the thickness of the liquid crystal layer is preferably constant.

That is, the present invention has a liquid crystal layer between the first substrate and the second substrate, the liquid crystal molecules constituting the liquid crystal layer take a substantially vertical alignment state with respect to the substrate at a voltage lower than the threshold voltage, and the threshold value A liquid crystal display device having a radial alignment state at a voltage or higher, wherein the liquid crystal display device has a concavo-convex structure fitted on a substrate via a liquid crystal layer.
The present invention also has a liquid crystal layer between the first substrate and the second substrate, and the liquid crystal molecules constituting the liquid crystal layer take a substantially vertical alignment state with respect to the substrate when the threshold voltage is lower than the threshold voltage. A liquid crystal display device having a radial alignment state as described above, which is also a liquid crystal display device having a cross-sectional structure in which liquid crystal layers are alternately formed.
The present invention is described in detail below.

The liquid crystal display device of the present invention can be suitably applied as a DAP liquid crystal display device. That is, it has a liquid crystal layer between the first substrate and the second substrate, and the liquid crystal molecules constituting the liquid crystal layer take a substantially vertical alignment state with respect to the substrate below the threshold voltage, and radiate above the threshold voltage. It is configured to take an orientation state. In the configuration of the two substrates and the liquid crystal layer, a pixel electrode, a common electrode, a signal line, a scanning line, and the like are usually provided on the substrate. At least one of the first substrate and the second substrate preferably has an active element, and preferably has an active element on one side and a common electrode on the other side.
The present invention is suitable as a transmissive liquid crystal display device, but can be applied to a transmissive / reflective type (semi-transmissive type) having a transmissive display portion and a reflective display portion. The configuration of such a liquid crystal display device is not particularly limited as long as such components are formed as essential, and may or may not include other components. Absent.

The liquid crystal layer is mainly composed of liquid crystal molecules, and the liquid crystal molecules take a substantially vertical alignment state with respect to the substrate when the threshold voltage is lower than the threshold voltage, and take a radial alignment state when the threshold voltage or higher. In the present invention, it is preferable that no voltage is applied to the electrode when the voltage applied to the electrode is less than the threshold voltage. A wide viewing angle characteristic is realized due to the liquid crystal molecules being in a substantially vertical alignment state. In addition, the radial alignment state above the threshold voltage contributes to stable liquid crystal molecule alignment control.
In the present invention, the substantially vertical alignment state is preferably a state in which the liquid crystal molecules are evaluated to be substantially perpendicular to the substrate in the liquid crystal layer, but as long as the effects of the present invention are exhibited. As a similar form, it includes a state having a predetermined angle. The radial alignment state may be any state that is advantageous for controlling the alignment of liquid crystal molecules, and it is preferable that at least one pixel electrode has at least two radial alignment states.

In the liquid crystal display device, a concavo-convex structure fitted through a liquid crystal layer is provided on a substrate.
As a result, picture element division by the concavo-convex portion is introduced into the liquid crystal display device. In the present invention, when a voltage higher than the threshold voltage is applied to the pixel electrode, the liquid crystal molecules take a radial alignment state. The radial alignment state is on the liquid crystal layer side of the first substrate and the second substrate. Separation and individualization are performed by the provided uneven structure (part), and alignment control of liquid crystal molecules is performed by this separation and individualization. In addition, it is preferable that at least two or more concavo-convex structures fitted to at least one picture element electrode are provided on the substrate.

In the concavo-convex structure, a concave portion is provided on one of the first substrate and the second substrate, and a convex portion is provided on the other substrate so as to face the concave portion. The fitting is performed with the liquid crystal layer formed. For example, at least two or more uneven structures are alternately formed on the liquid crystal layer side of the first substrate, and an uneven structure opposite to the uneven structure on the first substrate is formed on the second substrate. The concavo-convex structure formed in this way may be the same even if the size and shape of the concave and convex portions alternately formed on the liquid crystal layer side of the first substrate are different or formed on the second substrate. The size and shape of the uneven structure to be formed may be different from or the same as the size and shape of the corresponding uneven structure in the first substrate.

The liquid crystal display device may have a cross-sectional structure in which liquid crystal layers are alternately formed.
In this case, the cross-sectional structure of the substrate and the liquid crystal layer may be a structure in which the liquid crystal layers are alternately formed. For example, in the cross section of the region where one pixel electrode is formed, the cross-sectional structure of the substrate and the liquid crystal layer is more than that of the first substrate. The formation of the liquid crystal layer is alternately repeated such that the liquid crystal layer is formed at a position close to the second substrate, and then the liquid crystal layer is formed at a position closer to the first substrate than the second substrate. Become. Thereby, the radial alignment state of the liquid crystal molecules is separated and individualized. Such a form is preferably implemented by a form in which the above-described concavo-convex structure is provided on the substrate, but exhibits the effect of the present invention of separation and individualization of the radial alignment state of liquid crystal molecules by pixel division. As long as it becomes, it is not limited to this.

As a preferable configuration of the liquid crystal display device of the present invention, the pixel is divided by the concavo-convex shape provided on the first substrate, and a convex portion is provided on the surface of the second substrate facing the first substrate, relative to the concave portion provided on the first substrate. By disposing them so as to face each other, the thickness of the liquid crystal layer of each pixel electrode section divided in the concavo-convex shape becomes a transmission type optical path length. As a result, the division loss due to the conventional slit is required to be 5 to 10 μm. However, the division loss as the uneven portion (tapered portion) can be 3 μm or less, and the division loss is reduced. Since the region corresponds to the tapered portion of the concave portion, when the pixel electrode is also provided in the tapered portion, the transmittance of 30 to 50% of the main pixel electrode portion can be obtained. Therefore, the conventional TN method or STN method As a result, almost the same transmittance can be obtained.

A preferred embodiment of the liquid crystal display device of the present invention will be described in detail below.
At least one of the first substrate and the second substrate preferably has a structure that expresses a radial alignment state of liquid crystal molecules on the liquid crystal layer side. In addition, the structure that expresses the radial alignment state of the liquid crystal molecules is preferably at least one structure selected from the group consisting of a convex portion, a concave portion, and a partially extracted structure of the pixel electrode. Thereby, the radial alignment state of the liquid crystal molecules can be expressed by the substrate or the electrode structure. In the present invention, this radial alignment state is separated and individualized as described above. In addition, the convex portion, the concave portion, and the partial extraction structure of the pixel electrode that express the radial orientation state are provided separately from the concave-convex structure that separates and individualizes the radial orientation state, for example, the radial orientation state. In addition to the concavo-convex structure that separates and separates, at least one of a convex portion, a concave portion, and a partial extraction structure of the pixel electrode is provided.

The liquid crystal display device preferably has an inclined portion on the liquid crystal layer side of the substrate, and the pixel electrode is provided on a part or all of the inclined portion. An inclined portion is an inclined portion of a step portion formed in a concavo-convex structure that separates and separates radial alignment states. In this case, in the substrate having the picture element electrode, the picture element electrode covers a part or all of the inclined portion of the stepped portion. Thereby, the fall of the transmittance | permeability can be suppressed in the inclination part formed by an uneven structure.
In addition, it is preferable that the pixel electrode is provided in the entire inclined portion from the viewpoint of sufficiently suppressing the decrease in transmittance.

In the present invention, the thickness of the liquid crystal layer is preferably substantially constant. As a result, when the present invention is applied to a transmissive liquid crystal display device, the optical path length in the liquid crystal layer is substantially constant, and the display quality is improved. Note that “substantially constant” means that when applied to a transmissive liquid crystal display device, the thickness of the liquid crystal layer is constant in each region to such an extent that deterioration in display quality due to a difference in optical path length in each region of the liquid crystal layer is suppressed. For example, at least two or more concavo-convex structures are alternately formed on the liquid crystal layer side of the first substrate, and a concavo-convex structure opposite to the concavo-convex structure in the first substrate is formed on the second substrate. What is necessary is just to make it a structure which does not become what is called a multi-gap.

In the liquid crystal display device, the convex shape of the substrate is preferably smaller than the concave shape.
For example, when the concavo-convex structure is alternately formed on the liquid crystal layer side of the first substrate and the concavo-convex structure opposite to the concavo-convex structure in the first substrate is formed on the second substrate, the convex shape is contrary to that. If it is larger than the concave shape to be fitted, a discontinuous region of liquid crystal molecule alignment appears in the vicinity of the inclined portion forming the convex step, and the stability of the liquid crystal molecule in the radial alignment state may be lowered. In the present invention, since the convex shape formed on the substrate is smaller than the concave shape fitted in the opposite direction, separation and individualization are performed while stabilizing the radial alignment state of the liquid crystal molecules. It becomes possible.

With respect to the wiring and electrode structure in the liquid crystal display device of the present invention, (1) at least one of the first substrate and the second substrate has an active element, and the liquid crystal display device has an inclined portion of the substrate and / or Alternatively, at least one of the signal line and the scanning line is provided at a position having a convex shape, and the pixel electrode is provided in a part or all of the inclined portion and / or the convex shape, 2) At least one of the first substrate and the second substrate has an active element, and the liquid crystal display device includes at least one of a signal line and a scanning line at a position where the substrate has a concave shape, In addition, it is preferable that the pixel electrode is provided in a region other than the region where the signal line and the scanning line are provided. With these configurations, in the wiring and electrode configuration formed in layers on the substrate, a state in which an area where a signal line or a scanning line (scanning signal line) overlaps with a pixel electrode is generated is avoided, and the signal line In addition, an increase in electrical parasitic capacitance between the scanning line and the pixel electrode can be suppressed. That is, it is possible to suppress the action of the signal line and the scanning line on the pixel electrode, and to suppress problems such as the occurrence of crosstalk due to this.

Further, in the electrode structure in the liquid crystal display device of the present invention, the first substrate and the second substrate have an active element and a pixel electrode on one side and a common electrode on the other side, and the common electrode and / or The pixel electrode is preferably provided on the convex liquid crystal layer side.
That is, when the concavo-convex structure is alternately formed on the liquid crystal layer side of the first substrate and the concavo-convex structure opposite to the concavo-convex structure in the first substrate is formed on the second substrate, the concavo-convex structure of the first substrate or the second substrate These electrodes are formed along the liquid crystal layer side of the concavo-convex structure or the rugged structure so that the common electrode and / or the pixel electrode, preferably both are formed on the liquid crystal layer side of the substrate. It is preferable to adopt a form. As a result, the liquid crystal molecules in the liquid crystal layer can be sufficiently controlled, and the liquid crystal display device of the present invention can sufficiently exhibit the above-described effects, so that the portable device such as a TV, a personal computer, a mobile notebook personal computer, and a mobile phone can be used. It can be suitably applied to a display such as an information terminal.

Since the liquid crystal display device of the present invention has the above-described configuration, the radial alignment state of liquid crystal molecules can be separated and individualized in a DAP-type transmissive liquid crystal display device, for example, within one pixel region. Is divided into picture elements with checkered pattern uneven steps, enabling stable control of the alignment of the liquid crystal molecules in the radial direction and greatly improving the transmittance, which is almost equivalent to the conventional TN and STN methods. Transmittance. As a result, it is possible to realize a liquid crystal display device having a wide viewing angle and a high contrast, which are features of the DAP method, and having excellent display performance.

Hereinafter, the present invention will be described in more detail with reference to the drawings with reference to examples. However, the present invention is not limited only to these examples.
In the following embodiments, an active matrix liquid crystal display device using a thin film transistor (TFT) will be described. However, the present invention is not limited to this, and an active matrix liquid crystal display device or a simple matrix liquid crystal display using an MIM is described. It can be applied to the device. In the following, a transmissive liquid crystal display device will be described as an example. However, the present invention is not limited to this, and can be applied to a transmissive / reflective liquid crystal display device and a reflective liquid crystal display device.

(Production of liquid crystal display device)
First, in an active matrix liquid crystal display device using thin film transistors (TFTs), the structure of one picture element region in the liquid crystal display device 100 will be described with reference to FIGS. 1 (a), (b) and (c). .
FIG. 1A is a conceptual top view of a picture element portion of a liquid crystal display device according to a preferred embodiment of the present invention as viewed from the normal direction of the substrate, and FIG. 1B is a picture shown in FIG. FIG. 3 is a conceptual cross-sectional view of the element part cut along a line segment 1A-1A ′.

The liquid crystal display device 100 includes an active matrix substrate (hereinafter also referred to as “TFT substrate”) 10, a counter substrate (hereinafter also referred to as “color filter substrate”) 20, and the TFT substrate 10 and the color filter substrate 20. The liquid crystal layer 30 is provided therebetween. The liquid crystal molecules 31 of the liquid crystal layer 30 have negative dielectric anisotropy, and are provided on the surface of the TFT substrate 10 and the color filter substrate 20 on the liquid crystal layer 30 side when no voltage is applied to the liquid crystal layer 30. As shown in FIG. 1B, the vertical alignment film 32 aligns perpendicularly to the surface of the vertical alignment film.
“Aligned perpendicularly to the surface of the vertical alignment film” refers to a state in which the liquid crystal molecular axes are aligned at an angle of about 85 ° or more with respect to the surface of the vertical alignment film.

The TFT substrate 10 in the liquid crystal display device 100 includes a transparent substrate (for example, a glass substrate) 11, a TFT 12 formed on the surface, an organic insulating film 13, a pixel electrode 14, a signal line 15, a scanning line 16, and an inorganic insulating film 18. And auxiliary capacitance wiring 19. The color filter substrate 20 includes a transparent substrate (for example, a glass substrate) 21, a color layer 22 formed on the surface thereof, a transparent convex member 23, a counter electrode 24, and a radial orientation forming central member (hereinafter also referred to as “rivet”). 25, a structural member for controlling the gap between the TFT substrate 10 and the color filter substrate 20 (hereinafter also referred to as “spacer”) (not shown), and black provided at the boundary portion of the color layer 22 It has a matrix 27.

The organic insulating film 13 on the TFT substrate 10 of the liquid crystal display device 100 is provided with a thickness of about 1 to 4 μm, and alternately forms a picture element division region for forming a radial alignment so as to form a checkered pattern. An organic insulating film recess 17 is formed. The color filter substrate 20 facing this is provided with a transparent convex member 23 which is opposite to the organic insulating film concave portion 17 formed of the organic insulating film 13 of the TFT substrate 10. Specifically, the transparent convex member 23 is provided with the same film thickness as that of the organic insulating film 13 so that the convex portion comes above the concave portion 17 formed of the organic insulating film 13. As a result, the thickness of the liquid crystal layer 30 in the picture element region (hereinafter also referred to as “cell thickness”) is made constant. In addition, the cell thickness D1 in the organic insulating film convex part of the liquid crystal layer 30 and the cell thickness D2 in the concave part 17 are the same thickness.
In such a liquid crystal display device, the liquid crystal layer 30 of each pixel region is in accordance with the voltage applied to the pixel electrode 14 and the counter electrode 24 arranged to face each other through the liquid crystal layer 30. The orientation state changes. Display is performed using a phenomenon in which the polarization state and amount of light transmitted through the liquid crystal layer 30 change in accordance with the change in the alignment state of the liquid crystal layer 30.

Further, as shown in FIG. 1 (c), even in the structure in which the pixel electrode extraction portion 41 is provided in the pixel electrode 14 of the TFT substrate 10 in order to obtain the radial orientation without using the rivet 25, the conventional technique ( Needless to say, for example, the area of the pixel electrode 14 is greatly improved as compared with FIG.

(Measurement of transmittance)
Using the liquid crystal display device 100 of the present invention obtained as described above, and the liquid crystal display devices 200 and 300 for comparison, the transmittance improvement effect was evaluated as follows.
First, the structure and the like of these liquid crystal display devices will be described.
The liquid crystal display device 100 includes a 7-inch transmissive liquid crystal display device, an effective display screen size: horizontal 154.080 mm × vertical 87.048 mm, the number of picture elements: 480 × RGB × 234 = 336960, and the pixel size: 0. The basic design is 107 mm × length 0.372 mm.
In this liquid crystal display device 100, the organic insulating film 13 of the TFT substrate 10 is a photosensitive acrylic resin having a dielectric constant ε of 3.7 and has a thickness of 2 μm. Further, the boundary portion (inclined portion) of the concave portion 17 formed of the organic insulating film 13 was formed with a width of 2 μm. Further, the pixel electrode 14 was formed of indium tin oxide (ITO) on these upper layers.
In the color filter substrate 20, the color layer 22 and the black matrix 27 are obtained by adding a pigment to an acrylic resin, the transparent convex member 23 is made of a transparent acrylic resin, and the step of the convex portion is formed on the organic insulating film 13. And 2 μm of the same thickness. Further, the counter electrode 24 was formed of indium tin oxide (ITO) on the liquid crystal layer 30 side, and the rivet 25 was further made of acrylic resin with a diameter of 15 μm and a maximum thickness of 1.3 μm. The spacers were made of acrylic resin in a cylindrical shape having a diameter of 12 μm and a thickness of 3.7 μm.

A polyimide alignment film 32 having a vertical alignment property is formed on each surface of the TFT substrate 10 and the color filter substrate 20 thus manufactured to a thickness of about 600 mm (600 × 10 ⁻¹⁰ m), and is thermosetting. The TFT substrate 10 and the color filter substrate 20 were bonded together with a sealing resin.
A liquid crystal layer 30 is provided in the gap between the TFT substrate 10 and the color filter substrate 20 using a vacuum injection method. As the liquid crystal molecules 31 of the liquid crystal layer 30, those having a birefringence Δn of 0.11, a negative dielectric anisotropy and a Δε of −3.6 were used. The phase difference Δnd of the liquid crystal layer 30 was set to 0.407 μm of 0.11 × 3.7 μm. Further, the liquid crystal molecules 31 contained a cholesteric component so as to cause a one-turn twist with a thickness of 12 μm.
The opening area ratio of the liquid crystal display device 100 is 65.1%, and the boundary portion (inclined portion) due to the uneven step is 4.0%.

For comparison, a conventional DAP liquid crystal display device 200 and a conventional TN liquid crystal display device 300 were used.
FIG. 8 is a top conceptual view of a conventional DAP liquid crystal display device 200 as viewed from the normal direction of the substrate. In this liquid crystal display device 200, the picture element electrode 14 of the TFT substrate 10 is divided into two horizontal parts and eight vertical parts, and the division slit width is 7 μm. The slit width is determined depending on whether a stable axially symmetric orientation can be obtained around the rivet 25. As a result, the aperture area ratio of the manufactured liquid crystal display device 200 was 50.7%.
FIG. 9 is a conceptual top view of a conventional TN liquid crystal display device 300 as viewed from the normal direction of the substrate. The opening area ratio of the liquid crystal display device 300 is 65.1%.

Next, the transmittance of these liquid crystal display devices was measured with a luminance meter BM5 manufactured by Topcon Corporation. As a result, the liquid crystal display device 100 of the present invention was 6.15%, and the conventional DAP liquid crystal display device 200 was 5.19. Thus, the liquid crystal display device 100 according to the present invention was able to realize a transmittance improvement of 18.5% over the conventional DAP method. Further, the transmittance of the conventional TN liquid crystal display device 300 is 6.30%, and it was confirmed that the liquid crystal display device 100 according to the present invention can obtain almost the same transmittance.

(Production of liquid crystal display device)
A liquid crystal display device was produced in the same manner as in Example 1 (production of a liquid crystal display device).
In the liquid crystal display device 100, the organic insulating film 13 of the TFT substrate 10 is provided with a thickness of about 2 μm, and the pixel division regions for forming the radial alignment are alternately formed in a checkered pattern. A recess 17 is formed. On the color filter substrate 20 facing this, a transparent convex member 23 opposite to the concave portion 17 formed of the organic insulating film 13 of the TFT substrate 10 is provided. Specifically, the transparent convex member 23 is provided with the same film thickness as that of the organic insulating film 13 so that the convex portion comes above the concave portion 17 formed of the organic insulating film 13. Thus, the thickness of the liquid crystal layer 30 in the picture element region is made constant.

(Stability evaluation of radial orientation)
The size of the transparent convex member 23 in this liquid crystal display device was made larger or smaller than the size of the concave portion 17 provided with the organic insulating film 13 in the TFT substrate 10 to confirm the stability of the radial alignment.
The stability of the radial orientation was measured as the time from when the black display state when no voltage was applied to when the transmittance became steady when the white display state when voltage was applied. Table 1 shows the results.

The “resize amount of the transparent convex member 23 relative to the concave portion 17” in Table 1 is expressed by the following formula when the size of the convex portion is x and the size of the concave portion 17 is y, as shown in FIG. (1);
Resizing amount of transparent convex member 23 with respect to concave portion 17 (μm) = (xy) / 2 (2)
It can ask for.
From Table 1, when the transparent convex member 23 became larger than the size of the recessed part 17 provided with the organic insulating film 13, the tendency for the time until the transmittance | permeability became steady to become long was confirmed.
This result will be described with reference to FIGS. 2 (a) and 2 (b).
2A is a conceptual cross-sectional view of a picture element portion when the size of the transparent convex member 23 is smaller than the size of the concave portion 17 provided in the organic insulating film 13 of the TFT substrate 10 in the liquid crystal display device according to the second embodiment. It is. In this picture element portion, as shown by a line segment (A) in FIG. 2A, the inclined portion of the rivet 25, the inclined portion of the concave portion 17 provided with the organic insulating film 13, and the transparent convex member 23 The alignment axis directions of the liquid crystal molecules 31 in the inclined portion are the same. On the other hand, FIG. 2B shows a cross section of the picture element portion when the size of the transparent convex member 23 is larger than the size of the concave portion 17 provided in the organic insulating film 13 of the TFT substrate 10 in the liquid crystal display device according to the second embodiment. It is a conceptual diagram. In this picture element portion, as shown by the line (B) in FIG. 2B, the liquid crystal molecules 31 in the inclined portion of the rivet 25 and the inclined portion of the concave portion 17 provided with the organic insulating film 13 It can be seen that, although the alignment axis directions coincide with each other, these alignment axis directions and the alignment axis directions of the liquid crystal molecules 31 in the inclined portion of the transparent convex member 23 are opposite to each other.
From these results, it was found that a stable radial orientation can be obtained when the transparent convex member 23 is smaller than the size of the concave portion 17 provided with the organic insulating film 13.

(Production of liquid crystal display device)
A liquid crystal display device was produced in the same manner as in Example 1 (production of a liquid crystal display device).
In the liquid crystal display device 100, the organic insulating film 13 of the TFT substrate 10 is provided with a thickness of about 2 μm, and the pixel division regions for forming the radial alignment are alternately formed in a checkered pattern. A recess 17 is formed. On the color filter substrate 20 facing this, a transparent convex member 23 opposite to the concave portion 17 formed of the organic insulating film 13 of the TFT substrate 10 is provided. Specifically, the transparent convex member 23 is provided with the same film thickness as that of the organic insulating film 13 so that the convex portion comes above the concave portion 17 formed of the organic insulating film 13. Thus, the thickness of the liquid crystal layer 30 in the picture element region is made constant.
If the concave portion 17 formed in the organic insulating film 13 of the TFT substrate 10 has a region overlapping with the signal line 15 and the scanning line 16, the parasitic capacitance with the pixel electrode increases and crosstalk is likely to occur. In the liquid crystal display device 100, since the organic insulating film 13 has a relatively low dielectric constant and is formed with a film thickness of several μm, the parasitic capacitance can be reduced to such an extent that crosstalk does not occur. .

(Measurement of crosstalk rate)
The crosstalk ratio in the following liquid crystal display devices 400, 500, 600 and 700 was measured with a luminance meter BM5 manufactured by Topcon Corporation. The results are shown in Table 2.
Liquid crystal display device 400: As shown in FIG. 3, the liquid crystal display device has a structure in which the recesses 17 and the pixel electrodes 14 overlap the signal lines 15 and the scanning lines 16.
Liquid crystal display device 500: a liquid crystal display device having a structure in which the pixel electrode 14 overlaps the signal line 15 and the scanning line 16 in the inclined region of the recess 17, as shown in FIG.
Liquid crystal display device 600: As shown in FIG. 5, the liquid crystal display device has a structure in which the recesses 17 and the pixel electrodes 14 do not completely overlap the signal lines 15 and the scanning lines 16.
Liquid crystal display device 700: a liquid crystal display device having a structure in which the recess 17 overlaps with the signal line 15 and the scanning line 16, but the pixel electrode 14 does not overlap with the signal line 15 and the scanning line 16, as shown in FIG.

As shown in FIG. 7, the crosstalk rate is a state in which a black pattern is displayed on a white background, the periphery of the display screen 50 is a white display area 51, and the center of the display screen 50 is a black display area 52. When the brightness T0 of the white display area 51 of the background is compared with the brightness T1 of the upper, lower, left, and right areas (black stroke generation areas) 53 where the shadow of the black display area 52 is likely to occur, the following formula (2):
Crosstalk rate (%) = (T1-T0 / T0) × 100 (2)
It can ask for.

From Table 2, the crosstalk rate is 3.6% in the liquid crystal display device 400 shown in FIG. 3 (a liquid crystal display device having a structure in which the concave portions 17 and the pixel electrodes 14 overlap the signal lines 15 and the scanning lines 16). In the structure of 3% or less. Accordingly, as shown in FIGS. 4 to 6, if a liquid crystal display device having a structure in which the pixel electrode 14 does not overlap with the signal line 15 and the scanning line 16 and the concave portion 17, the display performance can be further improved. I understood.

It is the conceptual diagram which showed typically the pixel part of the liquid crystal display device in the suitable form of this invention, and is the upper surface conceptual diagram which looked at the pixel part from the substrate normal line direction. It is the conceptual diagram which showed typically the pixel part of the liquid crystal display device in the suitable form of this invention, and the cross-sectional conceptual diagram (voltage) which cut | disconnected the pixel part shown to FIG. 1-a by line segment 1A-1A ' No application). It is the conceptual diagram which showed typically the pixel part of the liquid crystal display device in the suitable form of this invention, and is a cross-sectional conceptual diagram (voltage no application) of the form different from FIG. FIG. 6 is a conceptual diagram schematically showing a picture element portion in a liquid crystal display device manufactured in Example 2, where the size of the transparent convex member 23 is smaller than the size of the concave portion 17 provided by the organic insulating film 13 of the TFT substrate 10. FIG. 3 is a conceptual cross-sectional view (no voltage applied) of the picture element portion of FIG. FIG. 5 is a conceptual diagram schematically showing a picture element portion in a liquid crystal display device manufactured in Example 2, where the size of the transparent convex member 23 is larger than the size of the concave portion 17 provided in the organic insulating film 13 of the TFT substrate 10. FIG. 3 is a conceptual cross-sectional view (no voltage applied) of the picture element portion of FIG. In the liquid crystal display device manufactured in Example 3, the cross-sectional conceptual diagram (no voltage applied) of the picture element portion of the liquid crystal display device 400 in which the concave portion 17 and the picture element electrode 14 overlap with the signal line 15 and the scanning line 16. is there. In the liquid crystal display device manufactured in Example 3, the cross-sectional conceptual diagram of the pixel portion of the liquid crystal display device 500 having a structure in which the pixel electrode 14 overlaps the signal line 15 and the scanning line 16 in the inclined region of the recess 17 ( No voltage is applied). In the liquid crystal display device manufactured in Example 3, the cross-sectional conceptual diagram of the pixel portion of the liquid crystal display device 600 having a structure in which the concave portion 17 and the pixel electrode 14 do not completely overlap with the signal line 15 and the scanning line 16 (no voltage mark) )). In the liquid crystal display device manufactured in Example 3, the concave portion 17 overlaps with the signal line 15 and the scanning line 16, but the pixel electrode 14 has a structure that does not overlap with the signal line 15 and the scanning line 16. FIG. In Example 3, it is a conceptual diagram of the crosstalk display used when demonstrating a crosstalk rate. It is the upper surface conceptual diagram which looked at the conventional liquid crystal display device 200 of the DAP system from the substrate normal direction. It is the upper surface conceptual diagram which looked at the liquid crystal display device 300 of the conventional TN system from the substrate normal line direction. It is the conceptual diagram which showed typically the pixel part in the liquid crystal display device which shares the conventional transmissive display and reflective display, and is the upper surface conceptual diagram which looked at the pixel part from the board | substrate normal line direction. It is the conceptual diagram which showed typically the pixel part in the liquid crystal display device which shares the conventional transmissive display and reflective display, and cut | disconnected the pixel part shown to FIG. 10-a by line segment 2A-2A ' It is a cross-sectional conceptual diagram (no voltage applied).

Explanation of symbols

10: TFT substrate 11: Glass substrate 12: TFT
13: organic insulating film 14: picture element electrode 15: signal line 16: scanning line 17: organic insulating film recess 18: inorganic insulating film 19: auxiliary capacitance wiring 20: color filter substrate 21: glass substrate 22: color layer 23: transparent Convex member 24: counter electrode 25: rivet 27: black matrix 30: liquid crystal layer 31: liquid crystal molecule 32: vertical alignment film 40a: reflective electrode 40b: transmissive electrode 41: picture element electrode extraction part 50: display screen 51: white display area 52: Black display region 53: Crosstalk generation region 100: Liquid crystal display device 110: Liquid crystal display device 200: Conventional DAP liquid crystal display device 300: Conventional TN liquid crystal display device 400: Liquid crystal display device 500: Liquid crystal display Device 600: Liquid crystal display device 700: Liquid crystal display device 800: Conventional liquid crystal display device

Claims (10)

A liquid crystal layer is provided between the first substrate and the second substrate, and the liquid crystal molecules constituting the liquid crystal layer take a substantially vertical alignment state with respect to the substrate when the threshold voltage is lower than the threshold voltage, and the radial alignment state when the threshold voltage is higher than the threshold voltage A liquid crystal display device taking
The liquid crystal display device is characterized in that a concave-convex shape fitted through a liquid crystal layer is provided on a substrate. A liquid crystal layer is provided between the first substrate and the second substrate, and the liquid crystal molecules constituting the liquid crystal layer take a substantially vertical alignment state with respect to the substrate when the threshold voltage is lower than the threshold voltage, and the radial alignment state when the threshold voltage is higher than the threshold voltage A liquid crystal display device taking
The liquid crystal display device has a cross-sectional structure in which liquid crystal layers are alternately formed. 3. The liquid crystal display device according to claim 1, wherein at least one of the first substrate and the second substrate has a structure that develops a radial alignment state of liquid crystal molecules on the liquid crystal layer side. 4. 4. The structure that expresses the radial alignment state of the liquid crystal molecules is at least one structure selected from the group consisting of a convex portion, a concave portion, and a partial extraction structure of a pixel electrode. The liquid crystal display device described. 3. The liquid crystal display according to claim 1, wherein the liquid crystal display device has an inclined portion on the liquid crystal layer side of the substrate, and the pixel electrode is provided on a part or all of the inclined portion. apparatus. 3. The liquid crystal display device according to claim 1, wherein the thickness of the liquid crystal layer is substantially constant. 2. The liquid crystal display device according to claim 1, wherein the convex shape of the substrate is smaller than the concave shape. At least one of the first substrate and the second substrate has an active element,
In the liquid crystal display device, at least one of a signal line and a scanning line is provided at a position where the inclined portion and / or convex shape of the substrate is present, and the pixel electrode is provided on a part or all of the inclined portion and / or convex shape. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device. At least one of the first substrate and the second substrate has an active element,
In the liquid crystal display device, at least one of a signal line and a scanning line is provided at a position where the substrate has a concave shape, and a pixel electrode is provided in a region other than the region where the signal line and the scanning line are provided. The liquid crystal display device according to claim 1. The first substrate and the second substrate have an active element and a pixel electrode on one side and a common electrode on the other side,
2. The liquid crystal display device according to claim 1, wherein the common electrode and / or the pixel electrode are provided on a convex liquid crystal layer side.

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