KR20110112219A - Liquid crystal diplay and method of manufacturing liquid crystal display - Google Patents

Abstract

The present invention provides a liquid crystal display device and a method for manufacturing a liquid crystal display device capable of realizing high transmittance while maintaining good voltage response characteristics. The liquid crystal display device of the present invention includes a liquid crystal layer, first and second substrates facing each other with the liquid crystal layer interposed therebetween, a plurality of pixel electrodes provided on the liquid crystal layer side of the first substrate, and the plurality of pixels. The counter electrode provided in the said 2nd board | substrate is provided opposite an electrode, and the surface of the said liquid crystal layer side of one or both of the said pixel electrode and the said counter electrode has an uneven structure.

Description

Liquid crystal display device, the manufacturing method of a liquid crystal display device {LIQUID CRYSTAL DIPLAY AND METHOD OF MANUFACTURING LIQUID CRYSTAL DISPLAY}

TECHNICAL FIELD This invention relates to the liquid crystal display device which used the liquid crystal of VA mode, for example, and its manufacturing method.

In recent years, for example, VA (Vertical Alignment: vertical alignment) mode is used in a liquid crystal display (LCD). In a liquid crystal display device, a liquid crystal layer having refractive index anisotropy is sealed between a substrate having a pixel electrode and a substrate having a counter electrode, and the transmittance of light passing there through by applying a voltage to the liquid crystal layer to change the axis of refractive index anisotropy. To control. In this way, the liquid crystal display device is a display device which uses electrical stimulation for optical switching.

In the VA mode liquid crystal display device, the liquid crystal layer has negative dielectric anisotropy, that is, the dielectric constant of the liquid crystal molecules is smaller in the major axis direction than the minor axis direction. Thus, in the liquid crystal layer, when no voltage is applied (off state), the long axis direction of the liquid crystal molecules is aligned in a direction substantially perpendicular to the substrate surface, and when voltage is applied (on state), the liquid crystal responds to the magnitude of the voltage. The molecule is in an inclined (tilted) orientation.

By the way, when a voltage is applied to the liquid crystal layer in a state where no voltage is applied, the liquid crystal molecules oriented almost perpendicular to the substrate surface incline, but the inclination direction is arbitrary. For this reason, the orientation of a liquid crystal molecule is disturbed, and a response, such as a response to a voltage is slowed or a desired transmittance | permeability is hard to produce, etc. generate | occur | produce.

Therefore, various proposals have been made so far as a method of regulating the orientation of liquid crystal molecules at the time of voltage response. For example, a technique using a multi-domain vertical aliasing (MVA) method, a patterned vertical aliasing (PVA) method, or a photo-alignment film (for example, see Japanese Patent Application Laid-Open No. 5-232473) Proposed. In the PVA method, a high viewing angle is realized while performing orientation control by using a slit or a rib. Recently, in addition, a structure (so-called fine slit structure) in which a plurality of fine slits are provided on the pixel electrode and the counter electrode is a beta electrode without slits has been proposed (for example, Japanese Patent Laid-Open No. 2002). -357830 publication).

However, in the above-described method, the voltage response characteristic can be improved, but in the portion corresponding to the slit (just above the slit) in the liquid crystal layer, no voltage is applied and the liquid crystal molecules are difficult to align ( Hard to tilt). For this reason, there exists a problem that a dark line (region where light transmittance is small locally) arises corresponding to a slit position, and high transmittance is hard to be obtained.

This invention is made | formed in view of such a problem, and the objective is to provide the liquid crystal display device and the manufacturing method of a liquid crystal display device which can implement | achieve a high transmittance, maintaining a favorable voltage response characteristic.

The liquid crystal display device of the present invention includes a liquid crystal layer, first and second substrates sandwiched by sandwiching the liquid crystal layer, a plurality of pixel electrodes provided on the liquid crystal layer side of the first substrate, and a plurality of pixel electrodes. It is provided with a counter electrode provided on the second substrate. The surface on the liquid crystal layer side of one or both of the pixel electrode and the counter electrode has an uneven structure.

The manufacturing method of the liquid crystal display device of this invention is a process of forming a some pixel electrode on a 1st board | substrate, forming a counter electrode on a 2nd board | substrate, and between a 1st and 2nd board | substrate. Sealing the liquid crystal layer by opposing the pixel electrode and the counter electrode; and exposing the liquid crystal layer by applying a voltage to the liquid crystal layer through the pixel electrode and the counter electrode, thereby providing pre-tilt to the liquid crystal layer. It includes a step and forms an uneven structure on the surface of the liquid crystal layer side of one or both of a pixel electrode and a counter electrode.

In the liquid crystal display device and the manufacturing method thereof of the present invention, the concave and convex portions of the concave-convex structure in the concave-convex structure are provided in the liquid crystal layer at the time of voltage application by providing the concave-convex structure on the side of the liquid crystal layer on either or both of the pixel electrode and the counter electrode. Due to the height difference (step difference) between the surfaces, electric field distortion (lateral electric field) occurs. On the other hand, since an electrode notch portion such as a slit does not exist, the region where no voltage is applied in the liquid crystal layer is eliminated, and insufficient alignment of the liquid crystal molecules in the local region is suppressed.

According to the liquid crystal display device and the manufacturing method of the liquid crystal display device of the present invention, since the concave-convex structure is provided on the side of the liquid crystal layer on one or both sides of the pixel electrode and the counter electrode, the electric field distortion is applied to the liquid crystal layer at the time of voltage application. And pretilt can be efficiently performed by this. Moreover, since it becomes possible to suppress that orientation of liquid crystal molecules is insufficient in a local area | region, as a result, the fall of a transmittance | permeability can be suppressed. Therefore, it is possible to realize high transmittance while maintaining good voltage response characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows the whole structure of the liquid crystal display device which concerns on one Embodiment of this invention.
FIG. 2 is a cross-sectional view illustrating a partial region of the pixel illustrated in FIG. 1. FIG.
3A to 3C are plan views and cross-sectional enlarged views of the pixel electrode shown in FIG. 2;
4A and 4B are plan views illustrating another configuration of the pixel electrode.
5A to 5E are plan views illustrating another configuration of the pixel electrode.
6A and 6B are plan views illustrating another configuration of the pixel electrode.
7 is a schematic diagram for explaining a tilt angle of liquid crystal molecules.
8A to 8C are cross-sectional views for explaining a method for forming a liquid crystal display device (process for forming a pixel electrode) shown in FIG. 1.
9A and 9B are cross-sectional schematic diagrams for explaining a step (pretilt applying step) subsequent to Figs. 8A to 8C.
10 is a cross-sectional view showing a partial region of a pixel in a liquid crystal display device according to a comparative example.
11 is a plan view and a sectional view schematically illustrating the alignment state of liquid crystal molecules near an electrode in a comparative example.
12 is a plan view and a cross-sectional view schematically showing the alignment state of liquid crystal molecules near an electrode in the embodiment;
FIG. 13 is a characteristic diagram showing an electric field distribution (equal potential distribution) in the embodiment; FIG.
14 is a characteristic diagram showing electric field distribution (equal potential distribution) in a comparative example.
15A and 15B are characteristic diagrams showing the relationship between voltage and response time, and characteristic diagrams showing relationship between voltage and transmittance.
16A and 16B are plan views showing measurement results of transmittance distribution.
17 is a cross-sectional view showing a portion of a pixel in a liquid crystal display panel according to Modification Example 1. FIG.
18A to 18C are cross-sectional views for explaining a process for forming a pixel electrode shown in FIG. 17.
19A to 19C are cross-sectional views illustrating a process of forming a pixel electrode according to Modification Example 2. FIGS.
20 is a cross-sectional view showing a portion of a pixel in a liquid crystal display panel according to Modification Example 3. FIG.
21 is a plan view showing a measurement result of transmittance distribution of the liquid crystal display panel shown in FIG. 20;
FIG. 22 is a cross-sectional view showing a portion of a pixel in a liquid crystal display panel according to Modification Example 4. FIG.
23 is a cross-sectional view illustrating a concave-convex structure according to Modification Example 5-1.
24A and 24B are sectional views for explaining the concave-convex structure according to Modification 5-2.
25 is a cross-sectional view illustrating a concave-convex structure according to Modification Example 5-3.
26 is a cross-sectional view illustrating a concave-convex structure according to Modification Example 5-4.
27 is a cross-sectional view illustrating a concave-convex structure according to Modification 5-5.
28A and 28B are a perspective view and a plan view for explaining a pixel electrode (electrode end structure) according to Modification 6. FIG.
29 is a perspective view illustrating a structure of a sample having a fine slit structure.
30 is a characteristic diagram showing the relationship between the voltage and transmittance of a sample using the pixel electrodes shown in FIGS. 28A and 28B.
Fig. 31 is a characteristic diagram showing a relationship between the voltage and the tilt angle of a sample using the pixel electrodes shown in Figs. 28A and 28B.
32 is a characteristic diagram showing a relationship between a voltage and a response speed of a sample using the pixel electrodes shown in FIGS. 28A and 28B.
33A to 33C are diagrams showing simulation results showing the inclination of liquid crystal molecules at the time of voltage response.
34A and 34B are schematic diagrams showing an alignment state of liquid crystal molecules near an electrode.
35A to 35C are schematic views for explaining an alignment state in the case of a fine slit structure.
36A and 36B are a perspective view and a plan view for illustrating another structural example of the pixel electrode shown in FIGS. 28A and eh 28B.
37 is a characteristic diagram showing a relationship between a level difference (nm) and transmittance according to Example 1. FIG.
38 is a cross-sectional view for illustrating a scale of the uneven structure according to the second embodiment.
39 is a characteristic diagram showing the relationship between the width of the convex surface and the transmittance according to Example 2. FIG.
40 is a cross-sectional view for illustrating a scale of the uneven structure according to the third embodiment.
41 is a characteristic diagram showing a relationship between a step height of a convex surface and a transmittance according to Example 3. FIG.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail with reference to drawings. The description will be made in the following order.

1. Embodiment (the example which provided the uneven structure on the surface of a pixel electrode, and made the back surface flat)

2. Modification 1 (Example of providing an uneven structure on the foundation layer (flattening film) of the pixel electrode)

3. Modification 2 (Example in which the uneven structure of the pixel electrode was formed by a two-step process)

4. Modification 3 (Example in which the uneven structure of the pixel electrode has a taper)

5. Modification 4 (Example in which the uneven structure of the pixel electrode has an inverse taper)

6. Modifications 5-1 to 5-5 (detailed configuration example in the case of providing an uneven structure in the underlying layer of the pixel electrode)

7. Modification 6 (Structural example of pixel electrode end)

8. Example

Example 1 (Measurement Result of Transmittance in Case of Changing Steps of Uneven Structure)

Example 2 (result of measurement of transmittance when the width of the upper floor was changed in the modification 3)

Example 3 (Measurement Result of Transmittance When Step Changes in Variant 3)

<1. Embodiment of embodiment>

[Configuration of Liquid Crystal Display Device 1]

FIG. 1: shows the whole structure of the liquid crystal display device (liquid crystal display device 1) which concerns on one Embodiment of this invention. The liquid crystal display device 1 includes, for example, a liquid crystal display panel 2, a backlight 3, a data driver 51, a gate driver 52, a timing controller 61, and a backlight driver 62, The video display is performed based on the external input signal Din.

The backlight 3 is a light source that irradiates light toward the liquid crystal display panel 2, and is disposed on the rear surface (surface of the polarizing plate 19 side described later) of the liquid crystal display panel 2. The backlight 3 includes, for example, a light emitting diode (LED), a cold cathode fluorescent lamp (CCFL), or the like. The backlight driver 62 controls the lighting operation (light emitting operation) of the backlight 3.

The timing controller 61 controls the driving timing of the gate driver 52, the data driver 51, and the backlight driver 62, and transmits a video signal based on the external input signal Din to the data driver 51. To supply.

The gate driver 52 drives each pixel 10 in the liquid crystal display panel 2 according to the timing control by the timing control part 61. The data driver 51 performs D / A conversion on the video signal (video signal based on the external input signal Din) supplied from the timing controller 61, and performs the video signal after the D / A conversion. It outputs to each pixel 10 of the liquid crystal display panel 2.

The liquid crystal display panel 2 modulates the light emitted from the backlight 3 based on the drive signal supplied from the gate driver 52 and the video signal supplied from the data driver 51. The liquid crystal display panel 2 includes a plurality of pixels 10 arranged in a matrix as a whole.

2 shows a cross-sectional structure of the liquid crystal display panel 2. In FIG. 2, only a partial region of the pixel 10 is shown. The liquid crystal display panel 2 sandwiches the liquid crystal layer 15 between the driving substrate 11 and the opposing substrate 18, and the polarizing plate 19 is located outside the driving substrate 11 and the opposing substrate 18. And the polarizing plate 20 are bonded to each other. On the drive substrate 11, the planarization film 12 is formed covering the surface of the drive substrate 11. The pixel electrode 13 is arrange | positioned for every pixel 10 on this planarization film 12, and the oriented film 14 is formed covering the surface of this pixel electrode 13. As shown in FIG. On the surface of the counter substrate 18 on the side of the liquid crystal layer 15, the counter electrode 17 is provided over almost the entire surface of the effective display area, and the alignment film 16 is formed covering the surface of the counter electrode 17. It is.

The driving substrate 11 is, for example, a driving circuit for driving the pixel 10 on a glass substrate, for example, the gate driver 52, the data driver 51, the timing controller 61, and the backlight controller described above. (62) is excreted. On this drive substrate 11, each pixel electrode 13 includes wirings such as gate lines and source lines through which the drive signals from the gate driver 52 and the data driver 51 are transmitted, and TFTs (thin film transistors). (Not shown in any of them) and the like are connected.

The planarization film 12 is an overcoat film which planarizes the surface of the drive board 11 in which the above drive circuits, wirings, etc. were arrange | positioned. The planarization film 12 is an insulating film made of an organic film made of a thermosetting resin or a photoreactive resin, and has a thickness of, for example, 1 µm to 10 µm. Alternatively, an inorganic insulating film such as silicon oxide film (SiO ₂ ), silicon nitride film (SiN), silicon oxynitride film (SiON) or the like may be provided instead of the planarization film 12 made of such an organic film.

(Configuration of Pixel Electrode)

The pixel electrode 13 consists of transparent conductive films, such as ITO (indium tin oxide) and IZO, for example, and has an uneven structure on the surface (surface of the liquid crystal layer 15 side). In the present embodiment, the uneven structure has a concave surface 13a and a convex surface 13b that are alternately arranged in a direction parallel to the substrate surface, and the stepped portion therebetween is a substrate surface. It is a vertical surface 13c perpendicular | vertical to. In addition, only the surface on the liquid crystal layer 15 side of the pixel electrode 13 has an uneven structure, and the surface on the flattening film 12 side is flat.

3A schematically illustrates an example of a planar configuration of the pixel electrode 13. Thus, the uneven structure provided in the pixel electrode 13 is formed in a predetermined pattern (uneven pattern), for example. That is, the concave surface 13a is provided extending along the some direction (here, four directions A1 to A4) in an electrode surface, and the other part is the convex surface 13b. By having such an uneven | corrugated pattern, since the area | region different from orientation direction is formed (orientation division) in the pixel 10, a viewing angle characteristic improves.

3B enlarges a part of the cross-sectional structure of the pixel electrode 13. The width S of the concave surface 13a is preferably 1 µm to 20 µm, for example, and the width L of the convex surface 13b extending in the same direction as the concave surface 13a (= concave) It is preferable that the space | interval (pitch) of surface 13a comrades is 1 micrometer-20 micrometers, for example. If the widths S and L are narrower than 1 mu m, the formation of the pixel electrode 13 becomes difficult, and it becomes difficult to secure a sufficient yield. On the other hand, when the widths S and L are wider than 20 µm, when a driving voltage is applied, a good inclined electric field is hardly generated between the pixel electrode 13 and the counter electrode, and the orientation of the entire liquid crystal molecules is slightly It becomes easy to be distracted. In particular, while width S is 2 micrometers or more and 10 micrometers or less, it is more preferable that width L is 2 micrometers or more and 10 micrometers or less. This is because the orientation of the liquid crystal molecules at the time of applying the driving voltage becomes better while ensuring a sufficient yield.

It is preferable that the distance (thickness Ta) from the concave surface 13a to the back surface of the pixel electrode 13 is 50 nm to 250 nm, for example, and from the convex surface 13b to the back surface of the pixel electrode 13 It is preferable that distance (thickness Tb) is 100 nm-300 nm, for example. Although details are mentioned later, the transmittance | permeability in the liquid crystal layer 15 at the time of voltage application changes with the step (difference of thickness Ta and Tb) between these concave surface 13a and the convex surface 13b. However, it is preferable that the level | step difference is 50 nm or more. It is because favorable orientation control can be attained, sufficient yield can be ensured, and the fall of a transmittance | permeability and prolongation of a process time can be prevented.

(Another uneven pattern at the pixel electrode)

As the concave-convex pattern, the concave surface 13a is not limited to a pattern extending along four directions, and various patterns such as a stripe shape or a V-shape can be adopted. The width S of the concave surface 13a, the number thereof, the width L of the convex surface 13b, and the number thereof can be arbitrarily set.

In addition, you may set each planar shape of the concave surface 13a and the convex surface 13b as follows, for example. For example, as shown in FIG. 4A, in the edge portion EE of the pixel electrode 13, the outer end E1 of the concave surface 13a1 and the convex surface 13b1 has their extending directions (here, the direction A structure (hereinafter referred to as a right angle structure) may be cut along the direction orthogonal to (A4)). Here, as shown in FIG. 3C, for example, in the case where the outer end E0 is obliquely cut along the sides of the rectangular shape of the pixel electrode 13 at the edge portion EE, the outer end ( The liquid crystal molecules in the vicinity of E0 are inclined in the direction of the arrow (thick line), which may cause an obstacle in the orientation control. Thus, by making the outer end E1 in the right angle structure as described above, it is shown in Fig. 4E. As described above, the liquid crystal molecules near the outer end E1 tend to be inclined along the direction A4, and the alignment control becomes easy.

Alternatively, a planar configuration as shown in Figs. 5A to 5E may be used. 5A and 5B show a planar structure of the entire pixel electrode, FIG. 5C shows a part of the pixel electrode, and FIG. 5D shows an enlarged view of one concave surface. As shown in FIGS. 5A and 5B, the convex surfaces 13b2 and 13b3 may be connected to each other at the edge of the pixel electrode 13. In addition, although not shown in figure, concave surfaces 13a2 and 13a3 may be respectively connected in the edge part.

In addition, as shown in FIG. 5C, the inner end E2 (part corresponding to the area EC in FIG. 3A) of the concave surface 13a4 has a concave surface 13a4 similar to the outer end E1. It may be a right angle structure cut along the direction orthogonal to the extending | stretching direction (here A1). In addition, both the outer end E1 and the inner end E2 of the concave surface 13a4 may have a right angle structure.

Further, in addition to the above-described right angle structure, for example, as shown in FIG. 5D, the outer end portion E3 of each convex surface 13b5 may have an R shape in which a round shape is formed. Thereby, liquid crystal molecules can be oriented in arbitrary directions as shown by the arrow of FIG. 5 (D). Alternatively, the outer end E4 may have a polygonal shape, for example, as shown in FIG. 5E, without being limited to such an R shape. In addition, although not shown in figure, one or both of the outer edge part and the inner edge part of each concave surface may have R shape and polygon shape as mentioned above.

In addition, in the above description, the pixel electrode structure (structure divided into four regions) provided with concave and convex surfaces extending along the four directions A1 to A4 is taken as an example, but the concave and convex surfaces are extended. The direction is not limited to this. For example, as shown in FIG. 6A, the concave surface 13a7 is provided extending along two directions A5 and A6 in the electrode surface, and the other part becomes the convex surface 13b7 ( Structure oriented in two regions). In addition, as shown in Fig. 6B, the convex surface 13b8 may be connected at the edge of the pixel electrode. In the case of these two-divided structures, the optical axes of the polarizing plates 19 and 20 are shifted by 45 degrees from the optical axis in the case of the four-divided structure.

The counter substrate 18 is, for example, a filter of red (R), green (G), and blue (B) on the surface of the glass substrate (the surface on the counter electrode 17 side or the surface on the polarizing plate 20 side). Has a color filter (not shown) which is arranged. However, this color filter may be provided in the opposing board | substrate 18, but may be provided in the drive board | substrate 11 (CoA (Color Filter On Array) structure) may be sufficient.

The counter electrode 17 consists of transparent conductive films, such as ITO, for example, and is provided in the pixel 10 (as opposed to all the pixel electrodes 13) as a common electrode. The surface on the side of the liquid crystal layer 15 of the counter electrode 17 is a flat surface without a slit, a gap, or the like here. However, the counter electrode 17 may be an electrode having no electrode notched portion such as a gap or a slit. For example, the surface on the liquid crystal layer 15 side may be an uneven surface, or a step may be formed.

The alignment films 14 and 16 are, for example, vertical alignment films, and the liquid crystal molecules (in particular, liquid crystal molecules in the vicinity of the alignment films 14 and 16) in the liquid crystal layer 15 are long-axis directions (directors). It is oriented so as to be substantially perpendicular to this substrate surface. As such alignment films 14 and 16, vertical alignment agents, such as a polyimide and polysiloxane, are used, for example.

The liquid crystal layer 15 contains liquid crystal molecules of vertical alignment type, for example. In this liquid crystal layer 15, liquid crystal molecules have a rotationally symmetrical shape, for example, with the major axis and the minor axis as the central axis, respectively, and the negative dielectric anisotropy (the dielectric constant in the major axis direction is smaller than the minor axis direction). ).

In this liquid crystal layer 15, as shown in FIG. 7, the liquid crystal molecules (liquid crystal molecules 15a) near the interface with the alignment films 14 and 16 have a long axis due to restrictions from the alignment films 14 and 16. While the orientation D1 is oriented so as to be substantially perpendicular to the substrate surface, it is kept inclined slightly in the vertical direction. That is, so-called pretilt is provided near the interface with the alignment films 14 and 16 of the liquid crystal layer 15, and the inclination angle (tilt angle) θ in the vertical direction of the liquid crystal molecules 15a is given as an example. For example, 1 ° to 4 °. The larger the tilt angle [theta], the faster the response speed at the start, but since the black luminance at the time of no voltage application is lowered, the contrast deteriorates. Such a pretilt is held by the polymer near the interface with the alignment films 14 and 16 of the liquid crystal layer 15, and mimics the alignment of the liquid crystal molecules near the interface to form other liquid crystal molecules (for example, liquid crystal layer ( Liquid crystal molecules near the center in the thickness direction of 15) are also aligned in the same direction.

The polarizing plate 19 and the polarizing plate 20 are arrange | positioned in the state of the cross nicol mutually, for example, block the light from the backlight 3 in the voltage free state (off state), and apply a voltage. In the state (on state), it is made to transmit. That is, the polarizing plate 19 and the polarizing plate 20 are joined to the drive board | substrate 11 and the opposing board | substrate 18 so that it may become normally black type.

[Manufacturing Method of Liquid Crystal Display Device 1]

(1.panel sealing process)

The liquid crystal display device 1 can be manufactured as follows, for example. That is, as shown in FIG. 8A, the planarization film 12 is formed into a film by the spin coat method, for example so that the surface of the drive substrate 11 may be covered. In addition, when forming an inorganic insulating film instead of this planarization film 12, what is necessary is just to form the silicon oxide film mentioned above by the CVD method, for example. Subsequently, as shown in FIG. 8B, the pixel electrode 13 made of, for example, ITO is formed over the entire surface on the planarization film 12 by, for example, a vapor deposition method or a sputtering method. Subsequently, as shown in FIG. 8C, the concave surface is removed by removing the selected region (region corresponding to the concave surface 13a) of the pixel electrode 13 by, for example, a half etching method by photolithography. The uneven structure which consists of 13a, the convex surface 13b, and the vertical surface 13c is formed. In addition, a contact hole is provided in the planarization film 12, and the pixel electrode 13 is electrically connected to the driving circuit formed on the driving substrate 11, respectively, through the contact hole.

In order to cover the surface of the pixel electrode 13 formed in this way, specifically, the concave surface 13a, the convex surface 13b, and the vertical surface 13c, a vertical alignment agent is apply | coated by the spin coat method, for example. By baking, the alignment film 14 is formed.

On the other hand, after the counter electrode 17 is formed into a film by the vapor deposition method or the sputtering method on the surface of the counter substrate 18, a vertical alignment agent is applied to the surface of this counter electrode 17, for example by the spin coat method. Is applied, and the alignment film 16 is formed by baking.

Thereafter, for example, a UV curable or thermosetting seal portion is printed in the peripheral region of the drive substrate 11, and, for example, a UV curable monomer is mixed in the region surrounded by the seal portion. The injected liquid crystal layer 15 is dripped. Thereafter, the opposing substrate 18 is laminated on the drive substrate 11 via a spacer made of, for example, a photosensitive acrylic resin, and the seal portion is cured. In this way, a panel seal body in which the liquid crystal layer 15 is sealed is formed between the drive substrate 11 and the counter substrate 18.

(2.Pretilt giving process)

Subsequently, in the panel sealing body formed as mentioned above, the pretilt is given to the liquid crystal layer 15 by exposure (UV irradiation), applying a voltage to the liquid crystal layer 15. Specifically, as shown in FIG. 9A, the voltage V is applied to the liquid crystal layer 15 through the counter electrode 17 and the pixel electrode 13.

This voltage application causes electric field distortion (transverse electric field) in the liquid crystal layer 15 due to the height difference (step difference) between the concave surface 13a and the convex surface 13b formed on the surface of the pixel electrode 13. do. As a result, the liquid crystal molecules 15a are inclined in response to the uneven pattern of the pixel electrode 13. By performing UV irradiation in the state in which this liquid crystal molecule 15a was inclined, the monomer mixed in the liquid crystal layer 15 hardens in the vicinity of the interface with the alignment films 14 and 16. Thereafter, as shown in FIG. 9B, when the liquid crystal layer 15 is returned to the voltage-free state, the polymer formed near the interface keeps the liquid crystal molecules 15a slightly inclined in the vertical direction. In this manner, the tilt angle θ as shown in FIG. 7 is given to the liquid crystal molecules 15a.

As described above, the polarizing plates 20 are bonded to the surfaces of the polarizing plates 19 and the opposing substrates 18 on the back surface of the driving substrate 11 of the panel sealing body after the pretilt application so as to have a cross nicol arrangement. Thereby, the liquid crystal display device 1 shown in FIG. 1 is completed.

In addition, the method for giving pretilt is not limited to the above-mentioned thing, What is necessary is just to include the process of exposing, applying a voltage at least after liquid crystal sealing. For example, pretilt may be provided using the following special orientation film. That is, in the side chain, an alignment film having a polymer containing a group for pretilt provision and a group (photosensitive group) for fixing the pretilt, or an alignment film containing a photosensitive monomer may be used. Can be. Such a special alignment film is formed on one or both sides of the driving substrate 11 side and the opposing substrate 18 side (however, when only one substrate side is formed, a vertical alignment film is formed on the other substrate side), After sealing the VA type liquid crystal which does not contain a monomer, exposure is performed, applying a voltage. Also by such a method, pretilt can be provided.

[Operation of the liquid crystal display device 1]

(Video display action)

In the liquid crystal display device 1, an image is displayed by applying a driving voltage based on an external input signal Din between the pixel electrode 13 and the counter electrode 17 in the following manner. Specifically, in response to the control of the timing controller 61, the gate driver 52 sequentially supplies scan signals to the gate lines connected to the respective pixels 10, and the data driver 51 supplies an external input. The video signal based on the signal Din is supplied to a predetermined source line. As a result, the pixel 10 positioned at the intersection of the source line supplied with the video signal and the gate line supplied with the scan signal is selected, and a driving voltage is applied to the pixel 10.

In the selected pixel 10, when a driving voltage is applied, the alignment state of the liquid crystal molecules 15a included in the liquid crystal layer 15 changes in response to the voltage between the pixel electrode 13 and the counter electrode 17. Specifically, when the driving voltage is applied from the voltage-free state, the liquid crystal molecules 15a positioned in the vicinity of the alignment films 14 and 16 are inclined, and the center portion in the thickness direction of the liquid crystal layer 15 so as to mimic its operation. Towards the liquid crystal molecules 15a are inclined sequentially. At this time, since the tilt angle is given to the liquid crystal molecules 15a, the liquid crystal molecules 15a tend to be inclined in their own inclined direction, so that the response time to the driving voltage is shortened. As a result, the optical characteristics in the liquid crystal layer 15 change, and the light incident on the liquid crystal display panel 2 from the backlight 3 is modulated and emitted. In the liquid crystal display device 1, an image is thus displayed.

Here, the liquid crystal display device which concerns on a comparative example is demonstrated. FIG. 10 shows a part of a cross-sectional structure of a pixel of a liquid crystal display device according to a comparative example. In this liquid crystal display device, the liquid crystal layer 105 is sandwiched between the drive substrate 101 and the counter substrate 108, and the incident side polarizer 109 is disposed outside the drive substrate 101 and the counter substrate 108. And the emission-side polarizing plate 110 are bonded to each other. On the surface of the liquid crystal layer 105 of the driving substrate 101, the pixel electrode 103 is disposed for each pixel through the planarization film 102, and the alignment film 104 covers the surface of the pixel electrode 103. Formed. On the surface of the counter substrate 108 on the side of the liquid crystal layer 105, the counter electrode 107 is provided over almost the entire surface of the effective display area, and the alignment film 106 is formed covering the surface of the counter electrode 107. It is. That is, in the liquid crystal display device of the comparative example, a so-called fine slit structure in which the pixel electrode 103 has a plurality of slits 103a is adopted.

Fig. 11 schematically shows the aspect of the alignment of liquid crystal molecules at the time of voltage application of the comparative example. 11A shows the vicinity of the pixel electrode 103 of the area | region B in FIG. 10 from the upper surface, and FIG. 11B is corresponded in the cross-sectional structure. In addition, the alignment film 104 is not shown for simplicity. As described above, in the comparative example, since the slit 103a, that is, the portion in which the electrode is notched, exists in the pixel electrode 103, no voltage is applied to the region immediately above the liquid crystal molecules and the liquid crystal molecules are oriented in the desired direction. It is hard (it is hard to tilt). Therefore, the liquid crystal molecules 15a are not inclined and are oriented so as to stand in a direction substantially perpendicular to the substrate surface. In such an orientation state, since the light transmittance decreases in the region corresponding to the slit 103a, the transmittance decreases.

In contrast, in the present embodiment, the alignment state of the liquid crystal molecules 15a at the time of voltage application is as follows. FIG. 12 schematically illustrates the orientation of the liquid crystal molecules 15a at the time of voltage application in the present embodiment. 12A shows the vicinity of the pixel electrode 13 from the upper surface, and FIG. 12B corresponds to the cross-sectional structure. In addition, for the sake of simplicity, the alignment film 14 is not shown. As described above, the pixel electrode 13 has an uneven structure on the surface thereof, but since there is no electrode notch portion such as a slit, the applied voltage is insufficient not only on the convex surface 13b but also on the concave surface 13a. Can be suppressed. For this reason, the liquid crystal molecule 15a also inclines on the concave surface 13a. Therefore, the fall of the transmittance accompanying the insufficient orientation of liquid crystal molecules in a local area | region as mentioned above is suppressed.

Here, FIG. 13 shows the electric field distribution (equal potential distribution) of the liquid crystal layer 15 at the time of voltage application. However, in each figure, X (micrometer) has shown the scale in the direction orthogonal to the extending direction of the concave surface 13a in a board | substrate surface. Z (μm) is a scale in the thickness direction of the liquid crystal layer 15, Z = 0 is the pixel electrode 13 side (alignment film 14 side), and Z = 3.5 μm is the opposite electrode 17 side (alignment film ( 16) side). The width S of the concave surface 13a of the pixel electrode 13 is 4 μm, the thickness Ta is 50 nm, the width L of the convex surface 13b is 4 μm, and the thickness Tb is 300 μm. It was set to nm. The alignment films 14 and 16 are coated with a vertical alignment film (manufactured by JALS2131-R6: JSR) on the first sub-electrode 12A and dried at 80 ° C. for 80 seconds on a hot plate, and then placed in a clean oven in a nitrogen atmosphere. It was formed by baking at 200 ° C. for 60 minutes. As the liquid crystal layer 15, the thickness of the liquid crystal layer 15 was 3.5 micrometers using what mix | blended 0.3 wt% of acrylic monomers (A-BP-2E: Shin-Nakamura Chemical Co., Ltd.) to VA liquid crystal material. 14, the electric field distribution of the liquid crystal layer 105 of the said comparative example is shown. In addition, structural conditions and process conditions other than a pixel electrode were similar to the above. As can be seen from FIG. 14, in the comparative example, particularly in the region on the pixel electrode side, the voltage applied to the electrode portion 103b is lower than the region corresponding to the slit 103a. Able to know. On the other hand, in this embodiment shown in FIG. 13, it turns out that the voltage which is about the same as the area | region corresponding to the convex surface 13b is applied also in the area | region corresponding to the concave surface 13a.

15A shows the relationship between the voltage V and the response time (ms: milliseconds), and FIG. 15B shows the relationship between the voltage V and the transmittance (%). As for the voltage response, as shown in Fig. 15A, it can be seen that better characteristics can be realized than the comparative example having the fine slit structure. On the other hand, as shown in FIG. 15B, the transmittance was significantly improved in the present embodiment compared with the comparative example.

As an example, the simulation result regarding the transmittance distribution is shown in Fig. 16A. However, Y (micrometer) represents the extending direction of the concave surface 13a in a board | substrate surface, The dimension in the X, Y plane of the pixel electrode 13 is 30x30 micrometers, concave surface 13a, and a convex surface. Each width | variety of (13b) was 4 micrometers. Moreover, the thickness of the liquid crystal layer 15 was 3.5 micrometers, the applied voltage was 7.5V, and the wavelength of incident light was 550 micrometers. FIG. 16B is a transmittance distribution relating to a fine slit structure in which slits each having a width of 4 m are provided at intervals of 4 m on the pixel electrode. In this fine slit structure, the above conditions were set except that slits were provided in the pixel electrodes. In this way, by providing the concave-convex structure in the pixel electrode, compared with the fine slit structure, the dark line is reduced, the transmittance is improved, and the uniform transmittance distribution can be easily realized. In each drawing, however, the transmittance distribution is shown in black and white shades (the closer to white, the higher the transmittance, and the closer to black, the lower the transmittance).

As described above, in the present embodiment, the concave-convex structure, specifically, the concave surface 13a, the convex surface 13b and the vertical surface 13c, is formed on the surface of the pixel electrode 13 on the liquid crystal layer 15 side. Since the uneven structure is provided, electric field distortion can be generated in the liquid crystal layer 15 when voltage is applied. Therefore, pretilt provision can be performed efficiently. On the other hand, since the fall of the applied voltage in a local area can be suppressed, as a result, the fall of a transmittance | permeability can be suppressed. Therefore, it is possible to realize high transmittance while maintaining good voltage response characteristics.

Hereinafter, modification examples (modification examples 1 to 4) of the above embodiment will be described. In addition, about the component similar to the said embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted suitably.

<Modification 1>

FIG. 17: shows the cross-sectional structure (corresponding to a part of pixel) of the liquid crystal display panel in the liquid crystal display device which concerns on the modification 1. As shown in FIG. In the liquid crystal display panel of the present modification, the liquid crystal layer 15 is sandwiched between the driving substrate 11 and the opposing substrate 18 similarly to the liquid crystal display panel 2 of the above embodiment, and the driving substrate 11 and The polarizing plates 19 and 20 are bonded to the outer side of the opposing board | substrate 18. As shown in FIG. The planarization film 21 is formed on the drive substrate 11 to cover the surface of the drive substrate 11, and the pixel electrode 22 is provided for each pixel 10 on the planarization film 21. . In such a configuration, also in this modification, the surface on the liquid crystal layer 15 side of the pixel electrode 22 has an uneven structure, and the surface on the liquid crystal layer 15 side of the counter electrode 17 is flat.

In this modification, however, the uneven structure is formed on the surface of the planarization film 21 serving as the underlayer of the pixel electrode 22, and the pixel electrode 22 is formed on the planarization film 21 with the surface shape thereof. It mimics and is provided in substantially the same thickness. Specifically, the planarization film 21 has a concave-convex structure in which the surfaces are alternately arranged with the concave surface 21a and the convex surface 21b along the direction parallel to the substrate surface. The surface of the pixel electrode 22 has a concave surface 22a corresponding to the concave surface 21a of the planarization film 21 and a convex surface 22b corresponding to the convex surface 21b of the planarization film 21. The uneven structure is formed. In addition, this planarization film 21 is comprised with the organic insulating film similar to the planarization film 12 of the said embodiment. However, instead of this planarization film 21, inorganic insulating films, such as a silicon oxide film, a silicon nitride film, and a silicon oxynitride film, for example, may be provided.

The uneven structure of the pixel electrode 22 can be formed as follows, for example. That is, first, as shown in FIG. 18A, the planarization film 21 is formed on the drive board 11 by the same method as the above embodiment. Subsequently, as shown in FIG. 18B, the selected region (region corresponding to the concave surface 21a) of the planarization film 21 is etched by a predetermined depth, for example, to thereby form the planarization film 21. The concave surface 21a and the convex surface 21b are formed in the surface. Thereafter, as shown in FIG. 18C, the pixel electrode 22 is formed by, for example, a vapor deposition method, a sputtering method, or the like so as to cover the uneven structure of the planarization film 21. (22) is formed.

Also in this modification, the uneven structure which has the concave surface 22a and the convex surface 22b is formed in the surface by the side of the liquid crystal layer 15 of the pixel electrode 22 similarly to the said embodiment, and a voltage At the time of application, the electric field distortion which is effective in giving pretilt to the liquid crystal layer 15 arises. On the other hand, since the electrode notch part like a slit does not exist as the whole pixel electrode 22, the fall of the transmittance | permeability in the local area | region of the liquid crystal layer 15 is suppressed. Therefore, the effect equivalent to the said embodiment can be acquired.

<Modification 2>

19A to 19C show another manufacturing method of the pixel electrode 13 in the liquid crystal display device according to the modification 2 in the order of steps. In the above embodiment, the uneven structure of the pixel electrode 13 is formed by half-etching the pixel electrode 13 after forming the entire surface of the pixel electrode 13 on the planarization film 12. However, it is also possible to form as follows. . That is, as shown in FIG. 19A, after the planarization film 12 is formed on the drive substrate 11, the electrode layer 130 made of ITO is formed over the entire surface of the planarization film 12. For example, it forms by a vapor deposition method or a sputtering method. Subsequently, as shown in FIG. 19B, the selected region (the region corresponding to the concave surface 13a) of the electrode layer 130 is removed by etching using, for example, a photolithography method. After that, as shown in Fig. 19C, an electrode layer 131 made of ITO is formed by, for example, a vapor deposition method or a sputtering method. Thereby, the exposed surface of the planarization film 12 is covered by the electrode layer 131, and the uneven structure which has the concave surface 13a and the convex surface 13b is formed.

Thus, the uneven structure of the pixel electrode 13 is not limited to what was described by the said embodiment, It can form by various methods. That is, if the surface on the liquid crystal layer 15 side of the pixel electrode 13 has an uneven structure, the same effect as the above embodiment can be obtained.

<Modification 3>

FIG. 20: shows the cross-sectional structure (corresponding to a part of pixel) of the liquid crystal display panel in the liquid crystal display device which concerns on the modification 3. As shown in FIG. In the liquid crystal display panel of the present modification, the liquid crystal layer 15 is sandwiched between the driving substrate 11 and the opposing substrate 18 similarly to the liquid crystal display panel 2 of the above embodiment, and the driving substrate 11 and The polarizing plates 19 and 20 are bonded to the outer side of the opposing board | substrate 18. As shown in FIG. In addition, on the driving substrate 11, the pixel electrode 23 is provided for each pixel 10 through the planarization film 12. In such a configuration, also in this modification, the surface on the liquid crystal layer 15 side of the pixel electrode 23 has an uneven structure, and the surface on the liquid crystal layer 15 side of the counter electrode 17 is flat.

However, in this modification, the uneven structure of the pixel electrode 23 has a taper. Specifically, the uneven structure has a concave surface 23a and a convex surface 23b that are alternately arranged in a direction parallel to the substrate surface, and the stepped portion therebetween is a tapered surface 23c. . The taper angle (the direction perpendicular to the substrate surface is 0 °) of the tapered surface 23c is, for example, larger than 0 ° and 80 ° or less. That is, in this modification, the concave-convex structure in which the convex parts which make trapezoidal cross section shape are arrange | positioned at predetermined space | interval is formed in the surface of the pixel electrode 23. As shown in FIG.

Such uneven structure of the pixel electrode 23 can be formed by etching by photolithography, for example.

Also in this modification, the uneven structure which has the concave surface 23a and the convex surface 23b is formed in the surface on the liquid crystal layer 15 side of the pixel electrode 23 similarly to the said embodiment, and the voltage At the time of application, the electric field distortion which is effective in giving pretilt to the liquid crystal layer 15 arises. On the other hand, since the electrode notch part like a slit does not exist as the whole pixel electrode 23, the fall of the transmittance | permeability in the local area | region of the liquid crystal layer 15 is suppressed. Therefore, the effect equivalent to the said embodiment can be acquired.

Here, the simulation result regarding the transmittance distribution is shown in FIG. In addition, the conditions, such as the dimension of the pixel electrode 13, the uneven structure, the thickness of the liquid crystal layer 15, the applied voltage, the wavelength of incident light, etc. were made like the simulation (FIG. 16A) in the said embodiment. However, the taper angle was inclined 30 ° in the direction perpendicular to the substrate surface. As described above, even when the uneven structure having the tapered surface is provided in the stepped portion, the dark line is reduced, the transmittance is improved, and the uniform transmittance distribution can be easily realized as in the above-described embodiment.

<Modification 4>

FIG. 22: shows the cross-sectional structure (corresponding to a part of pixel) of the liquid crystal display panel in the liquid crystal display device which concerns on the modification 4. As shown in FIG. In the liquid crystal display panel of the present modification, the liquid crystal layer 15 is sandwiched between the driving substrate 11 and the opposing substrate 18 similarly to the liquid crystal display panel 2 of the above embodiment, and the driving substrate 11 and The polarizing plates 19 and 20 are bonded to the outer side of the opposing board | substrate 18. As shown in FIG. In addition, on the drive substrate 11, the pixel electrode 24 is provided for each pixel 10 via the planarization film 12. In such a configuration, also in this modification, the surface on the liquid crystal layer 15 side of the pixel electrode 24 has an uneven structure, and the surface on the liquid crystal layer 15 side of the counter electrode 17 is flat.

However, in this modification, the uneven structure of the pixel electrode 24 has an inverse taper. Specifically, the uneven structure has a concave surface 24a and a convex surface 24b that are alternately arranged in a direction parallel to the substrate surface, and the stepped portion therebetween becomes an inverse tapered surface 24c. have. That is, in this modification, the concavo-convex structure in which the convex part which makes an inverted trapezoidal cross-sectional shape are arrange | positioned at predetermined intervals is formed in the surface of the pixel electrode 24. As shown in FIG.

Such uneven structure of the pixel electrode 24 can be formed by the etching by photolithography, for example.

Also in this modification, the uneven structure which has concave surface 24a and convex surface 24b is formed in the surface of the pixel electrode 24 at the liquid crystal layer 15 side similarly to the said embodiment, and a voltage At the time of application, the electric field distortion which is effective in giving pretilt to the liquid crystal layer 15 arises. On the other hand, since the electrode notch part like a slit does not exist as the whole pixel electrode 22, the fall of the transmittance | permeability in the local area | region of the liquid crystal layer 15 is suppressed. Therefore, the effect equivalent to the said embodiment can be acquired. In addition, since the stepped portion is an inverse tapered surface, electric field distortion can be generated with a small step compared with the case of the vertical surface. For this reason, orientation control is attained, without increasing the film thickness of the whole pixel electrode.

Subsequently, a detailed configuration in the case where the underlayer of the pixel electrode has the uneven structure as described in the first modified example 1 will be described taking the following modified examples 5-1 to 5-5 as an example.

<Modification 5-1>

It is sectional drawing for demonstrating the example of the uneven | corrugated structure which concerns on the modification 5-1. This modification is a detailed structural example of having the same uneven structure as that of the first modified example (when the uneven structure 21ab is provided on the surface of the flattening film 21 which is the underlayer of the pixel electrode 22). As shown in FIG. 23, the planarization film 21 is provided so that the transistor 120 (TFT), wiring which is not shown in figure, etc. on the board | substrate 11a may be covered. The transistor 120 includes, for example, the semiconductor layer 123 on the gate electrode 121 through the gate insulating film 122. The source / drain electrodes 124 are provided on the semiconductor layer 123, and they are covered by the protective film 125. The transistor 120 is not limited to the bottom gate type, but may be a top gate type.

The planarization film 21 is provided with a contact hole H1 for ensuring electrical conduction between the transistor 120 (source / drain electrode 124) and the pixel electrode 22. On the planarization film 21, the pixel electrode 22 embeds the bottom part of the contact hole H1, mimics the surface shape of the uneven structure 21ab, and is formed in substantially constant thickness.

In such a planarization film 21, the uneven structure 21ab can be formed as follows, for example. That is, although not shown, first, the planarization film 21 is formed on the drive substrate 11 by the above-described method, and then the photolithography method is used on the surface of the planarization film 21. The uneven structure 21ab and the contact hole H1 are formed. Specifically, first, a photoresist is applied and formed on the planarization film 21, and exposure and development are performed using a predetermined photomask to pattern the photoresist. At this time, the photomask has a transmissive region (a transmittance of about 100%) corresponding to the contact hole H1 and a semi-transmissive region (several percent to several tens of percent) corresponding to the formation region of the uneven structure 21ab. Use a mask having a. The region corresponding to the uneven structure 21ab is a so-called half-tone mask. Thereafter, etching is performed to remove the photoresist, whereby a contact hole H1 penetrating to the surface of the source / drain electrode 124 is formed in a portion of the planarization film 21, while in another selected region. The predetermined uneven structure 21ab is formed on the surface. The recess depth (projection height) and recess width (projection width) in this uneven structure 21ab can be adjusted with the transmittance | permeability of the semi-transmissive area | region in the said photo mask, or its pattern. Thereafter, the pixel electrode 22 may be formed on the flat film 21.

As in this modification, in the case of providing the uneven structure 21ab in the underlayer (flattening film 21) of the pixel electrode 22, the contact hole H1 is employed by using the photolithography method using a halftone mask. With the formation of, the uneven structure 21ab can be formed. That is, it is possible to form the uneven structure 21ab in the planarization film 21 without newly increasing a manufacturing process.

<Modification 5-2>

24A is a cross-sectional view for illustrating a concave-convex structure example according to Modification Example 5-2. This modification has a concave-convex structure in the underlying layer of the pixel electrode 22 similarly to the modification 5-1, but differs from the modification 5-1 in the following points. That is, in this modification, the surface of the planarization film 12 is flat, and the photoresist 25 which comprises the uneven structure 25ab is provided on this planarization film 12. The planarization film 12 is provided with the contact hole H1 for ensuring electrical conduction between the pixel electrode 22 and the source / drain electrode 124 similarly to the modification 5-1. The photoresist 25 has an opening in a region corresponding to the contact hole H1 and is patterned in another selected region to form the uneven structure 25ab. The pixel electrode 22 is formed on the photoresist 25 with the bottom of the contact hole H1 imitating the shape of the uneven structure 25ab and having a substantially constant thickness.

The uneven structure 25ab using such a photoresist 25 can be formed as follows, for example. That is, although not shown, first, the planarization film 12 is formed on the drive substrate 11 by the above-described method, and then the contact hole H1 is formed by the photolithography method. Subsequently, after the photoresist 25 is applied and formed on the planarization film 12, the photoresist 25 is exposed and developed, and the surface of the source / drain electrode 124 is formed in the contact hole H1. While exposing, patterning is performed so that the surface of the planarization film 12 is exposed in the region where the uneven structure 25ab is formed. As a result, the uneven structure 25ab using the photoresist 25 is formed on the planarization film 12.

In the case where the uneven structure is provided in the underlying layer of the pixel electrode 22, the uneven structure 21ab may be provided in the planarization film 21 itself as described in the modified example 5-1. In addition, the uneven structure 25ab may be formed using the photoresist 25. Thereby, the uneven structure 25ab can be formed without passing through an etching process. In addition, in this modification, the recess depth (convex part height) and recess width (convex part width) in the uneven structure 25ab can be adjusted by the film thickness and pattern of the photoresist 25. Here, in the uneven structure 25ab, the photoresist 25 is removed from the selected region to the surface of the planarization film 12 (a part of the surface of the planarization film 12 is in contact with the pixel electrode). The resist 25 may not necessarily be completely removed to the surface of the planarization film 12. That is, as shown in FIG. 24B, an uneven structure 25ab may be provided on at least a part of the pixel electrode 22 side of the photoresist 25, and the surface on the planarization film 12 side may be flat.

<Modification example 5-3>

25A is a cross-sectional view for illustrating a concave-convex structure example according to Modification 5-3. In this modification, similarly to the modifications 5-1 and 5-2, the underlayer of the pixel electrode 22 has an uneven structure. In addition, similarly to the modification 5-2, the surface of the planarization film 12 is flat, and the uneven structure is formed on the planarization film 12 separately. However, in this modification, the inorganic insulating film 26 is provided on the planarization film 12, and the uneven structure 26ab is formed in the inorganic insulating film 26. The inorganic insulating film 26 is made of, for example, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or the like, and is patterned in a region corresponding to the contact hole H1 and a region constituting the uneven structure 26ab. . The pixel electrode 22 is formed on the inorganic insulating film 26 with the bottom of the contact hole H1, and mimics the shape of the uneven structure 26ab and is formed to have a substantially constant thickness.

The uneven structure 26ab using such an inorganic insulating film 26 can be formed as follows, for example. That is, although not shown, first, the planarization film 12 is formed on the drive substrate 11 by the above-described method, and then the contact hole H1 is formed by the photolithography method. Subsequently, after forming the inorganic insulating film 26 on the planarization film 12 by CVD method etc., this inorganic insulating film 26 is the area | region corresponding to the contact hole H1 by the photolithography method. And etching in the formation region of the uneven structure 26ab. As a result, an uneven structure 26ab using the inorganic insulating film 26 is formed on the planarization film 12.

In the case where the uneven structure is provided in the underlayer of the pixel electrode 22, the uneven structure 26ab may be formed using the inorganic insulating film 26 provided on the planarization film 12 as in this modification. By using the inorganic insulating film 26, it is easy to form a desired uneven | corrugated shape in the uneven structure 26ab, and shape stability also becomes high. In addition, the inorganic insulating film 26 also does not necessarily have to be removed from the uneven structure 26ab to the surface of the planarization film 12 similarly to the photoresist 25 of the modification 5-2. ) May be provided only on at least a portion of the pixel electrode 22 side. In addition, an organic insulating film may be used, without being limited to an inorganic insulating film.

<Modification 5-4>

It is sectional drawing for demonstrating the uneven structure example which concerns on the modification 5-4. In this modification, similarly to the modifications 5-1 to 5-3, the underlayer of the pixel electrode 22 has an uneven structure. However, this modified example is an application example to the COA structure which has the color filter layer 27 on the drive board 11 unlike the said modified examples 5-1 to 5-3. In this modification, the color filter layer 27 is formed so that the transistor 120 provided on the board | substrate 11 may be covered. On this color filter layer 27, the insulating film 28 as a protective layer of this color filter 27 is provided, and this insulating film 28 has the uneven structure 28ab. The color filter layer 27 contains a resin material, a pigment, dye, etc., for example, and is classified and colored by any one color of R, G, and B for every pixel. The insulating film 28 is made of, for example, an organic film such as a thermosetting resin or a photoreactive resin, or an inorganic film such as a silicon oxide film, a silicon nitride film, or a silicon oxynitride film, and includes a region corresponding to the contact hole H1 and unevenness. Each is patterned in the areas constituting the structure 28ab. The pixel electrode 22 is formed on the insulating film 28 with a bottom portion of the contact hole H1, mimicking the shape of the uneven structure 28ab, and having a substantially constant thickness.

The uneven structure 28ab using such an insulating film 28 can be formed as follows, for example. That is, although not shown, first, after forming the color filter layer 27 on the drive substrate 11, the insulating film 28 which consists of organic films, for example is apply | coated. Thereafter, the contact hole H1 is formed using the photolithography method, and the uneven structure 28ab is formed. As a result, an uneven structure 28ab using the insulating film 28 is formed on the color filter layer 27. In addition, by forming the uneven structure 28ab by patterning the insulating film 28, a part of the surface of the color filter layer 27 is exposed from the insulating film 28 serving as a protective film. The exposed color filter surface is finally exposed. It is covered by the pixel electrode 22. That is, since the pixel electrode 22 (for example, ITO) functions as a protective film, the color filter layer 27 does not easily deteriorate by the formation of the uneven structure 28ab.

In the case where the uneven structure is provided in the underlying layer of the pixel electrode 22, it is also applicable to the same COA structure as the present modification, and in this case, the uneven structure 28ab is provided in the insulating film 28 provided on the color filter layer 27. May be formed. In addition, also in this insulating film 28, in the uneven structure 28ab, it is not necessary to necessarily remove even to the surface of the color filter layer 27 similarly to the modification 5-2, The pixel electrode 22 of the insulating film 28 The uneven structure 28ab may be provided only in at least one part of the side.

In addition, when using an inorganic film as the insulating film 28, after forming the color filter layer 27 on the drive board 11, the contact hole H1 is formed in the color filter layer 27 first. Subsequently, an inorganic film as described above may be formed on the color filter layer 27 by, for example, CVD, and then patterned to form an uneven structure 28ab.

<Modification 5-5>

In addition, as shown in FIG. 27, in the COA structure described in the modification 5-4, the uneven structure 29ab may be formed directly on the surface of the color filter layer 29. In this case, the uneven structure 29ab can be collectively formed in the same process as the contact hole H1 by using the predetermined photomask described in the modification 5-1. In addition, in this modification, the pixel electrode 22 covers the whole surface of the color filter layer 29, and this pixel electrode 22 functions as a protective film of the color filter layer 29. As shown in FIG. Thus, the uneven structure 29ab may be provided in the color filter layer 29 itself.

In addition, although the case where the uneven | corrugated structure was provided in the underlayer of the pixel electrode 22 was demonstrated in the said modified examples 5-1 to 5-5, this is also the case when forming an uneven | corrugated pattern in the counter electrode 17 side. Applicable For example, when a color filter layer is provided on the opposing substrate 18 side, the counter electrode 17 is formed on the surface of the color filter layer or the surface of the protective film of the color filter layer to cover the formed uneven structure. It is good to form.

<Modification 6>

28A and 28B are schematic diagrams for explaining the structure of the pixel electrode end portion. FIG. 28A shows a perspective configuration, and FIG. 28B shows a pixel electrode 22 provided on the driving substrate 11 through the planarization film 21. Is seen from the side of the pixel electrode 22. In the pixel electrode described in the above embodiments and modifications, the end portion (specifically, a non-display portion facing the black matrix layer) may be removed. In addition, as a pixel electrode, the pixel electrode (pixel electrode 22) provided on the base layer which has an uneven structure demonstrated by the said modified example 1 and modified examples 5-1 to 5-5 is mentioned below. Specifically, the pixel electrode 22 has a base having an uneven structure such as a flattening film, and the pixel electrode 22 having the electrode end 22E (peripheral portion) having such an electrode end 22E. After forming the pixel electrode 22 on the layer, the end portion is formed by etching removal.

Thus, by having the electrode end 22E patterned by the pixel electrode 22, the gradient electric field becomes strong at a pixel edge part, and it becomes easy to orientate a liquid crystal in a desired direction.

Here, on the planarization film 21 of the modification 5-1, the following sample which forms the pixel electrode 22 which has the electrode end 22E was produced, and the measurement experiment and simulation were performed. That is, first, the thermosetting resin (SS3969 by JSR Corporation) was apply | coated by the spin coat method on the glass substrate, and it prebaked (90 degreeC, 90 second) using the hotplate. Then, it baked in the oven set to 230 degreeC for 1 hour, and formed the planarization film 21 with a film thickness of 2 micrometers. On the surface of this planarization film 21, by patterning a stripe-shaped recess (groove) with a width of 4 µm (the width of the convex portion also 4 µm) and a depth of 100 nm, the ITO was 100. It formed over the whole surface in thickness of nm, and only the edge part was etched away by the photolithographic method. An alignment film (FPA material manufactured by JSR) was applied to each electrode surface of the pixel electrode 22 to be formed and a counter substrate (a substrate on which a non-patterned solid counter electrode was formed) prepared separately. Then, the liquid crystal material (MLC-7026 by a mark company) was sealed between these pixel electrode 22 and the counter electrode. Thereafter, UV exposure was performed while supplying a voltage to the liquid crystal through the pixel electrode 22 and the counter electrode, thereby pretilting the liquid crystal molecules near the alignment film. In the thus produced sample (sample (A): groove depth 100 nm), the transmittance, tilt angle, and response characteristics were respectively measured. In addition, the same measurement is carried out with respect to the sample B (groove depth 200 nm) and the sample C (groove depth 300 nm) produced on the conditions similar to the above except the depth of the groove | channel formed in the planarization film 21. Was performed.

In addition, as a comparative example of the said samples (A-C), the following sample (D) was produced and the same measurement was performed. As the structure on the driving substrate side in the sample D, as shown in FIG. 29, the planarization film 102 is formed on the substrate 101, and the fine slit structure is formed on the planarization film 102. The pixel electrode 103 which has the same was provided. Specifically, first, a flattening film 102 (without concave-convex structure) having a film thickness of 2 μm is formed on the glass substrate in the same manner as described above, and then ITO is coated over the entire surface of the flattening film 102. It formed into a film in thickness of nm. Thereafter, the formed ITO was patterned by the photolithography method, and the stripe region and the end region corresponding to the slit 103a were selectively etched away. In addition, the width of this slit 103a is made equal to the said samples A-C, and the structure of the counter electrode side, the material of an orientation film and a liquid crystal, voltage application conditions, UV exposure conditions are the said samples (A-C). ).

The transmittance | permeability, tilt angle, and response characteristic which were measured as mentioned above are shown in FIGS. 30-32, respectively. In addition, the tilt angle shows the voltage applied to each electrode at the time of UV exposure, and the tilt angle provided by it. In addition, as a measured value of this tilt angle, each tilt angle of the liquid crystal molecule which exists in a certain area | region is measured, and what averaged it is shown.

As shown in FIG. 30, the transmittance | permeability improved about 17% in the samples A-C which have an uneven | corrugated pattern in a pixel electrode compared with the sample D using a fine slit structure.

31, it turns out that the tilt angle provided is large in the samples A-C compared with the sample D. As shown in FIG. Although this is mentioned later in detail, it is considered that in a sample (D), a disorder arises in the orientation state of a liquid crystal molecule, and in a sample (A-C), it is because it is easy to arrange | position an orientation state to a fixed state. As described above, since the tilt angle is an average value of the tilt angles of the liquid crystal molecules present in a certain region, when the tilt direction of the liquid crystal molecules deviates or there are liquid crystal molecules which do not tilt, their average values are small values. It is easy to become. On the other hand, when the inclination direction of the liquid crystal molecules is arranged in a constant direction, the actual tilt angle of the liquid crystal molecules and the average value thereof tend to be close to the values.

Further, as shown in FIG. 32, it can be seen that the response to the voltage is faster in the samples A to C than in the sample D. FIG. This is considered to be because liquid crystal molecules tend to be inclined in a fixed direction due to the existence of the orientation of the pretilt. In addition, it was found that little difference was observed between the samples A to C with groove depths of 100 nm, 200 nm, and 300 nm in terms of this response characteristic and transmittance.

As proof of these results, the simulation about the orientation of the liquid crystal molecule in the case of changing the voltage at the time of pretilting (5V, 7.5V, 10V) is shown to FIG. 33B and FIG. 33C. 33B shows an electrode having a fine slit structure, FIG. 33C shows an electrode having an uneven pattern, and FIGS. 33B and 33C show the boundary between the convex portion and the concave portion of the electrode as shown in FIG. 33A. The region S1 in the vicinity (in the fine slit, near the boundary between the electrode portion and the slit portion) is shown. In addition, each figure shows typically a liquid crystal molecule using the line segment D1 which shows the direction of a director, and the edge part D21, D22 in a long-axis direction. For example, the liquid crystal molecules in which the length (the length of the line segment D1) between the ends D21 and D22 are relatively long indicate that the liquid crystal molecules are inclined at a larger angle in the direction along the line segment D1. Also from these simulation results, it is understood that a larger tilt angle is given to the liquid crystal molecules in the case of having an uneven structure as compared with the fine slit structure. In addition, in the fine slit structure, in addition to the liquid crystal molecules inclined along the electrode long side direction (slit extension direction), there are also a large number of liquid crystal molecules inclined in the direction orthogonal to the electrode long side direction. It can be seen that there is a disturbance in the direction. On the other hand, in the case of the uneven structure, it can be seen that the liquid crystal molecules are inclined almost along the electrode long side direction (the extending direction of the recessed portion).

34A and 34B schematically show the alignment states of the liquid crystal molecules in each case of the fine slit structure and the concave-convex structure. As shown in Fig. 34A, in the fine slit structure, the liquid crystal molecules are twisted (oriented while rotating the director from the pixel electrode to the counter electrode) near the boundary between the electrode portion and the slit portion. Further, since the electrode portion and the slit portion are alternately arranged in succession, the twist of the right winding (R1) and the twist of the left winding (L1) alternately appear. 35B to 35D show the alignment state of liquid crystal molecules in such a fine slit structure as seen from different angles. 35B has shown the orientation state seen by the arrow F1 of FIG. 35A, FIG. 35C, the arrow F2, and FIG. 35D, the arrow F3, respectively. As described above, in the fine slit structure, the inclination direction of the liquid crystal molecules changes, which causes a decrease in response speed.

On the other hand, as shown in Fig. 34B, in the case of the uneven structure, the liquid crystal molecules are oriented and inclined in a substantially constant direction, which shows that a flexible voltage response is realized.

In addition, although the structure in which the electrode end 22E (peripheral part) of the pixel electrode 22 was patterned was demonstrated in the said modification 6, it is not limited to such a structure, As shown to FIG. 36A and FIG. 36B. The perimeter does not have to be removed.

<8. Example>

Hereinafter, the Example (Examples 1-3) of the liquid crystal display device which concerns on the said embodiment and modification is demonstrated.

(Example 1)

37, the transmittance | permeability at the time of changing the step | step (difference between the thickness Tb of the convex surface 13b and the thickness Ta of the concave surface 13a) in the liquid crystal display panel 2 which concerns on the said embodiment. The measurement result of is shown. At this time, the width S of the concave surface 13a of the pixel electrode 13 made of ITO is 4 µm, the width L of the convex surface 13b is 4 µm, the thickness of the liquid crystal layer 15 is 3.5 µm, The applied voltage was 7.5V and the wavelength of incident light was 550 nm. In addition, the level | step difference was changed by 50 nm in the range of 50 nm-500 nm, and was changed by 500 nm in the range of 1000 nm-3000 nm. In addition, in the range of 500 nm-800 nm, the measurement was performed at two points of 750 nm and 800 nm. In either case, the liquid crystals were oriented without problems, but as the level became larger, the transmittance tended to decrease. Here, since the transmittance higher than the transmittance (REF = 0.71) in the fine slit structure can be realized, the step is preferably in the range of 50 nm to 750 nm. More preferably, they are 50 nm-300 nm. The tact time in the film forming step and the etching step can be shortened, and the step difference can be reduced, so that the surface shape is closer to the structure of the beta electrode, whereby the transmittance can be improved.

(Example 2)

As Example 2, the transmittance | permeability at the time of changing the taper angle (theta) t of the tapered surface 23c in the pixel electrode 23 demonstrated in the said modification 3 was measured. Specifically, as shown in FIG. 38, the width S (4 μm), the thickness Ta (50 nm) of the concave surface 23a, and the pitch (= bottom of the trapezoidal convex portion) are shown. Width: 4 mu m) and the thickness Tb (200 nm) of the convex surface 23b were fixed, and the width Da of the convex surface 23b was varied to change the taper angle θt. . At this time, the width Da was changed by 0.5 µm in the range of 3.5 to 1 µm. In either case, the liquid crystals were oriented without problems, and as shown in FIG. 39, high transmittance was obtained. In addition, the transmittance was highest when the width Da was 1 µm.

(Example 3)

As Example 3, the transmittance | permeability when the taper angle (theta) t of the taper surface 23c was changed similarly to the said Example 2 was measured. However, in this embodiment, as shown in Fig. 40, the width S (4 mu m), the thickness Ta (50 nm) of the concave surface 23a, and the pitch (= bottom of the trapezoidal convex portion) are shown. The width | variety (4 micrometers) and the width | variety (1 micrometer) of the convex surface 23b were fixed, the thickness Tb of the convex surface 23b was made variable, and the step | step difference (= Tb-50) was changed. The step was made to change by 20 nm in the range of 200-60 nm. In either case, the liquid crystals were oriented without problems, and as shown in FIG. 41, high transmittance was obtained. In addition, as the step became smaller, higher transmittance was shown.

As mentioned above, although this invention was demonstrated based on embodiment and a modification, this invention is not limited to these embodiment etc., Various modifications are possible. For example, in the above embodiment, the case where the uneven structure is formed only on the surface of the pixel electrode has been described as an example, but the uneven structure may be provided on the surface of the counter electrode. That is, the uneven structure may be provided on the surface of the counter electrode and the surface of the pixel electrode may be flat, or the uneven structure may be provided on both the surface of the pixel electrode and the counter electrode.

In addition, although the above-mentioned embodiment demonstrated the case where the step part of the uneven structure was made into any one of a vertical surface, a taper surface, and an inverse taper surface as an example, it is not limited to this, A curved surface may be sufficient. The uneven structure having the stepped portion as a tapered surface has been described using an example in which the cross-sectional shape becomes a trapezoidal shape, but the cross-sectional shape may be triangular (that is, a shape without a top).

In addition, the material, thickness, a dimension, etc. of each layer in the liquid crystal display device of this invention are not limited to what was mentioned above. For example, in the pixel electrode, the case where the width S of the concave surface and the width L of the convex surface are equivalent to each other (S = L = 4 μm) has been described as an example. However, the width S of the slit and the electrode The width L of the portions may be different from each other.

Claims (20)

A liquid crystal layer,
First and second substrates sandwiched with the liquid crystal layer;
A plurality of pixel electrodes provided on the liquid crystal layer side of the first substrate;
A counter electrode provided on the second substrate so as to face the plurality of pixel electrodes;
The liquid crystal display device characterized in that the surface on the side of the liquid crystal layer on one or both sides of the pixel electrode and the counter electrode has an uneven structure. The method of claim 1,
Each pixel electrode has the uneven structure,
A liquid crystal display device wherein the surface of the counter electrode on the side of the liquid crystal layer is flat. The method of claim 2,
A stepped portion between the concave and convex surfaces of the uneven structure is perpendicular to the substrate surface. The method of claim 2,
A stepped portion between the concave and convex surfaces of the uneven structure is a tapered surface. The method of claim 2,
The step portion between the concave and convex surfaces of the uneven structure is an inverted taper surface. The method of claim 2,
A surface on the side opposite to the liquid crystal layer of the pixel electrode is flat. The method of claim 2,
Further having a foundation layer having an uneven structure between the plurality of pixel electrodes and the first substrate,
A surface on the liquid crystal layer side of each pixel electrode has a concave-convex structure that mimics the surface shape of the concave-convex structure of the base layer. The method of claim 7, wherein
And said base layer is a planarization film covering the surface of said first substrate. The method of claim 7, wherein
It further has a planarization film which covers the surface of a said 1st board | substrate,
The photoresist film is provided on the said planarization film as said base layer, The liquid crystal display device characterized by the above-mentioned. The method of claim 7, wherein
It further has a planarization film which covers the surface of a said 1st board | substrate,
An insulating film is provided as said base layer on the said planarization film, The liquid crystal display device characterized by the above-mentioned. The method of claim 7, wherein
And said base layer is a color filter layer provided on said first substrate. The method of claim 7, wherein
Further having a color filter layer on the first substrate,
An insulating film is provided as said base layer on the said color filter layer, The liquid crystal display device characterized by the above-mentioned. The method of claim 1,
In said liquid crystal layer, pretilt is provided in the vicinity of the said pixel electrode and the said counter electrode, The liquid crystal display device characterized by the above-mentioned. Forming a plurality of pixel electrodes on the first substrate,
Forming a counter electrode on a second substrate;
Sealing the liquid crystal layer by opposing the pixel electrode and the counter electrode between the first and second substrates;
A step of applying pretilt to the liquid crystal layer by exposing the liquid crystal layer while applying a voltage to the liquid crystal layer through the pixel electrode and the counter electrode,
The uneven structure is formed in the surface on the side of the said liquid crystal layer of one or both of the said pixel electrode and the said counter electrode, The manufacturing method of the liquid crystal display device characterized by the above-mentioned. The method of claim 14,
The concave-convex structure is formed on each pixel electrode,
The surface of the said liquid crystal layer side of the said counter electrode is made flat, The manufacturing method of the liquid crystal display device characterized by the above-mentioned. 16. The method of claim 15,
And a step portion between the concave and convex surfaces of the uneven structure is perpendicular to the substrate surface. 16. The method of claim 15,
A stepped portion between the concave and convex surfaces of the uneven structure is a tapered surface. 16. The method of claim 15,
A stepped portion between the concave surface and the convex surface in the concave-convex structure is an inverse tapered surface manufacturing method of a liquid crystal display device. 16. The method of claim 15,
And a surface opposite to the liquid crystal layer of the pixel electrode is flattened. 16. The method of claim 15,
As a base layer of the plurality of pixel electrodes, after forming a planarization film covering the surface of the first substrate, an uneven structure is formed on the surface of the planarization film,
In the step of forming the plurality of pixel electrodes,
Each pixel electrode is formed on the planarizing film so that the surface on the liquid crystal layer side has an uneven structure that mimics the uneven structure of the planarizing film.

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