KR20060080129A - Liquid crystal display - Google Patents

Abstract

The present invention provides a liquid crystal display device which quickly and stably generates a transition from a spray alignment state to a band alignment state of a liquid crystal layer without applying a high driving voltage.

To this end, the present invention is a pair of substrates (3, 4) and a pair of substrates (3, 4), which are disposed to face each other and have electrodes (19, 25) and alignment layers (21, 26) formed on opposite surfaces thereof, respectively. 4) Spray alignment of the nematic liquid crystal encapsulated between the alignment layers 21 and 26 and transfer of the spray-oriented nematic liquid crystal to the band alignment by the driving voltage applied between the electrodes 19 and 25. And a liquid crystal panel 2 having a liquid crystal layer 5 in an OCB mode and a spacer 6 arranged in the liquid crystal layer 5 and maintaining the opposing intervals of the pair of substrates 3 and 4 uniformly. The spacer 6 is subjected to a surface treatment for promoting the transition from the spray alignment state of the liquid crystal layer 5 to the band alignment state.

Description

Liquid Crystal Display {LIQUID CRYSTAL DISPLAY}

1 is a cross-sectional view showing the configuration of a liquid crystal display device to which the present invention is applied;

2 is an active matrix substrate diagram;

3 is a perspective view showing an uneven shape formed on the alignment film;

4 is a schematic diagram showing a cross-sectional shape in the first direction of the convex portion;

5 is a schematic diagram showing a state in which the liquid crystal layer is spray-oriented;

6 is a schematic diagram showing a state in which a liquid crystal layer is band aligned;

7 is a cross-sectional view showing an alignment state of liquid crystal molecules in a liquid crystal panel of the present invention subjected to surface treatment on a spacer;

8 is a cross-sectional view showing an alignment state of liquid crystal molecules in a conventional liquid crystal panel in which no surface treatment is applied to the spacer.

※ Explanation of code for main part of drawing

1 liquid crystal display 2 liquid crystal panel

3: One side (back side) board | substrate 4: The other side (front side) board | substrate

5: liquid crystal layer 5a: liquid crystal molecules

6 spacer 7 TFT

15 scanning line 16 signal line

19 pixel electrode 21 alignment film

23 black matrix layer 24 color filter layer

25 counter electrode 26 alignment layer

28: convex part 28a: normal part

28b: first inclined plane 28c: second inclined plane

31a, 31b: optical compensation plate 32a, 32b: polarizing plate

33: backlight

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a liquid crystal display of OCB (0ptically Compensated Birefringence) mode that realizes wide viewing angle and high speed response.

In recent years, the notation system called OCB mode attracts attention in a liquid crystal display device (for example, refer patent document 1, 2). In this OCB mode, a liquid crystal layer sandwiched between a pair of substrates is placed in a spray alignment state, and a liquid crystal panel (n cell) for transitioning to a band alignment state when a driving voltage is applied, and optical compensation for optical compensation of the liquid crystal panel. By combining films, wide viewing angle and high speed response are realized. However, in this OCB mode, it is not easy to quickly transfer the liquid crystal layer in the initial spray alignment state to the band alignment state, and a high voltage of about 10V is required, but applying such a high voltage is necessary to control the driving voltage. Very difficult on the In addition, it is not easy to generate such a transition of the liquid crystal layer in all the pixels, and some of the pixels left unchanged in the liquid crystal layer greatly deteriorate the display quality of the panel.

Therefore, in the liquid crystal panel of patent document 1, in order to promote the transition from the spray orientation state of a liquid crystal layer to a band alignment state, it is proposed to provide the convex part formed from the material whose dielectric constant is larger than this liquid crystal layer. In this liquid crystal panel, however, such a convex portion is used as a starting point to promote the transition from the spray alignment state of the liquid crystal layer to the band alignment state, but the plurality of spacers dispersed in the liquid crystal layer in order to maintain a uniform gap between the pair of substrates. The problem arises that the transition stops along the way. Therefore, in order to generate such a transition quickly in all the pixels, it is necessary to continuously apply the high driving voltage. Moreover, such a convex part has a narrow selection of material, and when it forms on a board | substrate, it raises a cost by adding several processes. In addition, when the conductive convex portions as described in Patent Literature 1 are formed, there is a high possibility of being connected to a fatal defect such as a leak shape between the substrates, and it is virtually impossible to introduce a process for forming such convex portions.

On the other hand, in the liquid crystal panel described in Patent Literature 2, the rising side of the liquid crystal molecules at the time of applying the voltage so that the liquid crystal layer easily transitions from the spray alignment state to the band alignment state by application of an initialization voltage of about V is the liquid crystal molecules around It has been proposed to provide a region opposite to the rising side of at the interface of the alignment film. However, when such an area is provided at the interface of the alignment film, it is necessary to perform rubbing treatments in different directions for each divided region of the alignment film, but it is usual to ensure the positional accuracy of the alignment treatment at the boundary of the area. Very difficult. For example, in mask rubbing using a perforated mask (template), it is very difficult to control the area boundary with a position accuracy of 5 to 10 µm or less. For example, even if position control is possible, an area is used in the orientation processing by a rubbing cloth. It is not possible to partition the boundary clearly. As a result, drops of light appear on the boundary of the area at a level that can be observed with the naked eye.

On the other hand, in order to clearly divide this area boundary part, the alignment film image is first oriented in the first direction, and then a mask with a resist is formed on the alignment film, and then the alignment film image is aligned in the second direction, Lastly, a method of removing the resist has been proposed. (See Patent Document 3, for example.) However, in the case of a wet alignment treatment using such a resist, it is easy to cause liquid residue or stain marks on the alignment film. In addition, it is impossible to completely remove these from the alignment film. Since these not only cause in-plane unevenness of the display, but also lead to an increase in the current consumption value, for example, display unevenness occurs due to an increase in the current value during high temperature operation.

[Patent Document 1]

Japanese Patent No. 3417218

[Patent Document 2]

Japanese Patent Application Laid-Open No. 2000-66208

[Patent Document 3]

Japanese Patent Application Laid-Open No. 7-28067

Accordingly, the present invention has been proposed in view of such a conventional situation, and an object thereof is to provide a liquid crystal capable of quickly and stably generating a transition from the spray alignment state to the band alignment state of the liquid crystal layer without applying a high driving voltage. It is to provide a display device.

In order to achieve this object, the liquid crystal display device of the present invention comprises a pair of substrates arranged opposite to each other and having an electrode and an alignment layer formed on opposite surfaces thereof, and a nematic liquid crystal encapsulated between the pair of substrates to form an alignment layer. The liquid crystal layer of the OCB mode which transfers the spray-oriented nematic liquid crystal to the band alignment at the same time as the spray orientation and the drive voltage applied between the electrodes, and the opposing intervals of the pair of substrates arranged in the liquid crystal layer. A liquid crystal panel having a spacer to be held uniformly is provided, and the spacer is characterized in that the surface treatment for prompting the transition from the spray alignment state of the liquid crystal layer to the band alignment state is performed.

In addition, the liquid crystal display device of the present invention is characterized in that the surface treatment is performed in which the liquid crystal molecules of the liquid crystal layer are oriented substantially horizontally along the surface of the spacer.

Moreover, the liquid crystal display device of this invention is characterized by the spacer being spherical.

In addition, the liquid crystal display device of the present invention has an uneven shape in which the alignment film alternately repeats the concave portion and the convex portion along the first direction in which the alignment film gives at least the liquid crystal molecules of the liquid crystal layer, and in the first direction of each convex portion. The cross-sectional shape in this case is characterized by being asymmetrical left and right across the top.

In addition, the liquid crystal display device of the present invention has a first inclined surface in which the convex portion is inclined toward the first direction from the top portion, and a second inclined surface inclined in the opposite direction from the top portion to the first direction, and the first inclined surface is first The inclination angle with respect to the said board | substrate is made larger than 2 inclined surfaces, It is characterized by the above-mentioned.

In addition, the liquid crystal display of the present invention has an uneven shape in which the concave portion and the convex portion are alternately repeated along the second direction in which the alignment film intersects the first direction, and the pitch of the uneven shape repeated along the first direction is It is characterized by being longer than the pitch of the uneven shape repeated along the second direction.

In addition, the liquid crystal display device of the present invention has a direction in which pretilt is applied to liquid crystal molecules of the liquid crystal layer by an alignment film on one substrate side, and a direction in which pretilt is applied to liquid crystal molecules of the liquid crystal layer by an alignment film on the other substrate side. The alignment film on the one substrate side and the alignment film on the other substrate side are provided with pre-tilt angles opposite to each other so as to be in the same direction as each other.

Moreover, the liquid crystal display device of this invention is characterized by the nematic liquid crystal having positive dielectric anisotropy.

EMBODIMENT OF THE INVENTION Hereinafter, the liquid crystal display which applied this invention is demonstrated in detail with reference to drawings. In addition, the drawings used in the following description may expand and show the part which becomes a characteristic for convenience in order to make a characteristic clear, and it does not restrict that the dimension ratio of each component etc. are the same as actual.

As shown in FIG. 1, the liquid crystal display device 1 to which this invention is applied is provided with the liquid crystal panel 2 of OCB mode. The liquid crystal panel 2 is, for example, a transmissive color liquid crystal display panel employing an active matrix driving method, and includes one unit pixel (pixel) by three dots (sub pixels) corresponding to three primary colors of red, green, and blue. ) And an active element is provided in each dot to control the lighting of each pixel to perform color display.

Specifically, the liquid crystal panel 2 includes a pair of substrates 3 and 4 disposed to face each other and a liquid crystal layer 5 as an optical modulation layer sandwiched between the pair of substrates 3 and 4. have. In addition, the pair of substrates 3 and 4 is made of a rectangular transmissive substrate such as glass or plastic, and a plurality of spacers 6 dispersed in the liquid crystal layer 5 maintain a uniform gap between them. The circumferential edge part is sealed by the sealing material (not shown), and is joined together.

Of the pair of substrates 3 and 4, one of the substrates 3 is a so-called active matrix substrate as shown in Figs. 1 and 2, and a TFT (Thin) which is a switching element on the surface facing the liquid crystal layer 5 A plurality of film transistors 7 are arranged in a matrix. The TFT 7 includes the gate electrode 8, the gate insulating layer 9, the semiconductor layers 10 and 11, the source electrode 12, and the drain electrode 13 in order from the substrate 3 side. It has a stacked inverse staggered structure. That is, on the gate insulating layer 9 covering the lowermost gate electrode 8, an island-like semiconductor layer 10 is formed so as to ride over the gate electrode 8, and at one end of the semiconductor layer 10, a semiconductor is formed. The source electrode 12 is formed through the layer 11, and the drain electrode 13 is formed on the other end side of the semiconductor layer 10 via the semiconductor layer 11. In addition, an island-shaped insulating layer 14 is formed on the semiconductor layer 11, and the insulating layer 14 is insulated between the source electrode 12 and the drain electrode 13. Moreover, this insulating layer 14 has a function as an etching stopper which protects this semiconductor layer 11 when forming the semiconductor layer 11.

Moreover, the scanning line 15 electrically connected to the gate electrode 8 of each TFT 7 is the arrow X direction (row direction) in the surface which opposes the liquid crystal layer 5 of the board | substrate 3 in FIG. And a plurality of signal lines 16 electrically connected to the source electrodes 12 of the respective TFTs 7 in the arrow Y direction (column direction) in FIG. Formed. That is, the scanning lines 15 and the signal lines 16 are formed in a plurality in a direction orthogonal to each other, and the TFTs 7 are formed near the intersection positions of the scanning lines 15 and the signal lines 16. have. In addition, one rectangular area partitioned by the scanning line 15 and the signal line 16 into a checkerboard shape forms a dot correspondence area on the side of the substrate 3 corresponding to each dot. The display area of the liquid crystal panel 2 is formed as a whole by being arranged in plural in a matrix form. In the area outside of the display area, a scan driver for applying a selection pulse to each scan line 15 and a signal driver for applying a display voltage to each signal line 16 are provided.

The insulating film 17 covering the TFT 7, the scan line 15, and the signal line 16 is formed on the surface of the substrate 3 that faces the liquid crystal layer 5. In this insulating film 17, a contact hole 18 facing the drain electrode 13 of each TFT 7 is formed. On the insulating film 17, a plurality of pixel electrodes 19 electrically connected to the drain electrodes 13 of the TFTs 7 through the contact holes 18 are formed in a plurality of matrix arrays corresponding to the dots. It is. The pixel electrode 19 is made of a transparent conductive material such as ITO (Indium-Tin 0xide), and is formed in a rectangular shape so as to cover approximately the entire area of each of the dot correspondence regions. On the substrate 3 on which the pixel electrode 19 is formed, a resin layer 20 having a concave-convex shape described in detail later, and an alignment film 21 for controlling the alignment of the liquid crystal layer 5 are formed in this order. .

On the other hand, the surface facing the liquid crystal layer 5 of the other (front side) substrate 4 is divided into a resin layer 22 having a concave-convex shape to be described later in detail, and a dot corresponding region corresponding to each dot. For example, red (R), green (G), and blue (B) for each of the light-blocking black matrix layers 23 and the dot correspondence regions of the resin layer 22 partitioned by the black matrix layers 23. ) And a color filter of 24), a color filter layer 24 in which these color filters are arranged periodically, a counter electrode 25 made of a transparent conductive material such as ITO (Indium-Tin 0xide), and a liquid crystal layer 5 The alignment film 26 which controls the orientation of) is laminated in order. Specifically, the resin layer 22 is divided into a checkerboard shape by a stripe-shaped black matrix layer 23, and one rectangular area partitioned by the black matrix layer 23 corresponds to each dot. The dot correspondence area | region on the board | substrate 4 side is formed. In addition, the black matrix layer 23 is a light shielding wall for preventing the mixing of light between the color filters, and red (R) and green (G) in each dot correspondence area partitioned by the black matrix layer 23. ), Any one of the color filters of blue (B) is embedded. The color filter layer 24 has a structure in which color filters of these different colors are periodically arranged in a stripe shape or a mosaic shape. Therefore, the display color of each pixel is controlled by controlling the driving voltage applied between the pixel electrode 19 and the counter electrode 25 for each of the three dot correspondence areas corresponding to the red, green, and blue of each pixel. Thereby, the color display of the liquid crystal panel 2 can be performed.

The liquid crystal layer 5 is made of a nematic liquid crystal having positive dielectric anisotropy enclosed between the alignment film 21 on the one substrate 3 side and the alignment film 26 on the other substrate 4 side, The nematic liquid crystal is spray-oriented by the alignment films 21 and 26. On the other hand, by applying a driving voltage between the pixel electrode 19 and the counter electrode 25, this spray-oriented nematic liquid crystal can be transferred to band orientation.

As shown in FIG. 3, the alignment films 21 and 26 that control the alignment of the liquid crystal layer 5 have the concave portion 27 and the convex portion along the first direction of giving pretilt to the liquid crystal molecules of the liquid crystal layer 5. It has an uneven shape which alternately repeats (28), and an uneven shape which alternately repeats the recessed part 29 and the convex part 30 along the 2nd direction which cross | intersects this 1st direction. Moreover, the uneven | corrugated pitch P1 repeated along a 1st direction is longer than the uneven pitch P2 repeated along a 2nd direction. Thus, the pre-tilt angle described later becomes easy to control by making pitch P1 of the uneven shape repeated along a 1st direction longer than the pitch P2 of the uneven shape repeated along a 2nd direction. Moreover, it is preferable that pitch P1 is 50 micrometers or less, and it is preferable that pitch P2 is 3.0 micrometers or less. More preferably, the pitch P1 is 20 micrometers or less, and the pitch P2 is 1.2 micrometers or less. Moreover, the height dimension d1 of the recessed part 27 and the convex part 28 in a 1st direction, and the height dimension d2 of the recessed part 29 and the convex part 30 in a 2nd direction are respectively, It is preferable that it is 0.5 micrometer or less.

Moreover, the cross-sectional shape in the 1st direction of each convex part 28 is asymmetrically left and right across the top part 28a as shown typically in FIG. That is, the convex part 28 has the 1st inclined surface 28b which inclines toward the 1st direction from the top part 28a, and the 2nd inclined surface 28c which inclines toward the reverse direction from the top part 28a to a 1st direction. In addition, the first inclined surface 28b is formed such that the inclination angle θ with respect to the substrates 3 and 4 becomes larger than the second inclined surface 28c. That is, the cross-sectional shape in the 1st direction of each convex part 28 is a right-left angle ratio (r1 / r2) of the right angle divided | segmented by the waterline A lowered from the vertex part 28a. Has a bilateral asymmetric triangle shape that is greater than one. Thus, the orientation of the liquid crystal layer 5 can be improved by making the cross-sectional shape in the 1st direction of each convex part 28 into the asymmetrical shape across the top part 28a. In addition, it is preferable that the inclination angle (theta) with respect to the board | substrates 3 and 4 of the 2nd inclination surface 28c is 0.01 degrees-30 degrees. In addition, it is preferable that the said ratio (r1 / r2) is 1.2 or more in optimizing the pretilt angle demonstrated later. In addition, the cross-sectional shape in the 2nd direction of each convex part 28 can be made into the shape similar to sin wave, various shapes, such as a comb-tooth shape and a triangle shape. The double triangular shape is most preferable for improving the orientation of the liquid crystal layer 5, and in some cases, the top of the triangle may be rounded or flattened.

By the way, the uneven | corrugated shape of these alignment films 21 and 26 is formed by transferring the uneven | corrugated shape of the insulating layers 20 and 22 formed under it. Specifically, as the formation method of these alignment films 21 and 26, for example, the transfer mold having the fine concavo-convex shape to be transferred on the surface is pressed against the resin layers 20 and 22 formed on the substrates 3 and 4 to make this fine. After transferring the uneven shape to the resin layers 20 and 22, the alignment films 21 and 26 are formed thereon, and the rubbing treatment in the first direction is performed on the surfaces of the alignment films 21 and 26. FIG. Can be mentioned.

The alignment films 21 and 26 are polymer films such as polyimide-based, polyamide-based, polyvinyl alcohol-based, epoxy-based, modified epoxy-based, polystyrene-based, polyurethane-based, polyolefin-based, acryl-based, and the like that have been given shape anisotropy to their surfaces. Is done. Moreover, the film thickness of these alignment films 21 and 26 is about 0.05-0.07 micrometer. In addition, the liquid crystal layer 5 is provided by the alignment film 21 on the one side of the substrate 3 and the direction of giving pretilt to the liquid crystal molecules of the liquid crystal layer 5, and the alignment layer 26 on the other side of the substrate 4. The pretilt angles of opposite directions are given to the alignment film 21 on the one side of the substrate 3 and the alignment film 26 on the other side of the substrate 4 so that the directions of giving pretilts to the liquid crystal molecules in the same direction are the same. . Moreover, this pretilt angle is controlled in the angle range of 1-10 degrees, for example. These alignment films 21 and 26 align the liquid crystal layer 5 by horizontally aligning the liquid crystal molecules of the liquid crystal layer 5 along the second inclined surface 28c of the convex portion 28 in the first direction. It is in the spray orientation state.

Specifically, as shown schematically in FIG. 5, the alignment film 21 on one side of the substrate 3 is closer to the second inclined surface 28c because the second inclined surface 28c of the convex portion 28 becomes the right upward gradient. The liquid crystal molecules 5a of the liquid crystal layer 5 at the position are aligned to the right upward by giving a pretilt angle of about 1 ° to 10 °. On the other hand, in the alignment film 26 on the other substrate 4 side, the liquid crystal layer 5 at the position close to the second inclined surface 28c is formed by the second inclined surface 28c of the convex portion 28 becoming a downward downward slope on the right side. ) Liquid crystal molecules 5a are oriented rightward downward with a pretilt angle of about 1 ° to 10 °. In addition, the liquid crystal molecules 5a near the center of the liquid crystal layer 5 are in a substantially horizontally aligned state. As described above, the liquid crystal layer 5 between the alignment film 21 on the one substrate 3 side and the alignment film 26 on the other substrate 4 side is spray-oriented as shown in FIG. 5 when no voltage is applied. It is in a state.

On the other hand, when voltage is applied, the liquid crystal layer 5 in the spray alignment state is transferred to the band alignment state. Specifically, as shown schematically in FIG. 6, when a driving voltage is applied between the pixel electrode 19 and the counter electrode 25 described above, the convex portion 28 is provided on the side of the alignment film 21 on one substrate 3 side. The liquid crystal molecules 5a of the liquid crystal layer 5 at a position close to the second inclined surface 28c of the C1 are raised with respect to the inclined surface 28c, and are convex on the alignment film 26 side of the other substrate 4 side. The liquid crystal molecules 5a of the liquid crystal layer 5 at the position close to the second inclined surface 28c of the portion 28 are in a state where they are raised with respect to the inclined surface 28c. The liquid crystal molecules 5a in between are oriented along these raised liquid crystal molecules 5a to be in a state of being arranged in a bow shape as a whole. The liquid crystal molecules 5a near the center of the liquid crystal layer 5 are in a substantially vertically aligned state. As described above, the liquid crystal layer 5 between the alignment film 21 on the one substrate 3 side and the alignment film 26 on the other substrate 4 side has a band alignment as shown in FIG. 6 at the time of voltage application. Transition to state.

By the way, the spacer 6 dispersed in the liquid crystal layer 5 is subjected to a surface treatment for promoting the transition from the spray alignment state of the liquid crystal layer 5 to the band alignment state. Specifically, the spacer 6 is subjected to a surface treatment for aligning the liquid crystal molecules 5a of the liquid crystal layer 5 substantially horizontally along the spherical surface. This surface treatment includes, for example, a silane coupling agent having two polar functional groups (-NH ₂ , -CONH, etc.) capable of bonding with the surface of the spacer 6, for example, γ-methacryloxypropyltrimethoxy Silane, (gamma)-glycidoxy propyl trimethoxysilane, 4-aminophenyl propyl trimethoxysilane, N- (trimethoxy silylpropyl)-ethylenediamine, etc. can be used. In addition, they use water, mixed liquid of water and methanol, or ethanol etc. as a solvent, and all are used in the density | concentration of 0.01-2 wt%. Moreover, the density | concentration of the alcohols in a solvent is 1-20 wt%. Moreover, about N- (trimethoxysilylpropyl) -ethylenediamine, there exists a tendency for a good result of a solvent of an aqueous system to be obtained. In addition, these are 2-10 (more preferably about 4-8) of organic groups couple | bonded with a silanol group by carbon chain equivalent. Moreover, when larger than this, it exists in the tendency to show vertical orientation, but the reason is qualitatively considered that the hydrophobicity becomes strong, when the ratio of carbon atoms of an organic group increases. Moreover, it has both an affinity compound which has an aromatic or olefinic unsaturated bond group at the center of a molecule, and has at least 2 bond groups at the terminal of a molecule | numerator, for example, a C15 or more long-chain alkyl group, and has a strong polar group (-OH, -CN, NH ₂ etc.) etc. can be used. And using such surfactant, the film which has a polar group which horizontally orients the liquid crystal molecule 5a of the liquid crystal layer 5 with respect to the surface is formed in the surface of the spacer 6. As shown in FIG. Alternatively, the surface of the spacer 6 may be blasted in an antistatic atmosphere. In addition, the spacer 6 is not necessarily limited to the above-mentioned spherical thing, For example, what was surface-treated to the spacer 6 of rectangular shape (rib) or columnar shape (photospacer) can be used.

In the liquid crystal panel 2, a plurality of spacers 6 dispersed in the liquid crystal layer 5 without causing scattering of the alignment of the liquid crystal molecules 5a around the spacer 6 subjected to the surface treatment upon application of voltage. As a starting point, the transition from the spray alignment state of the liquid crystal layer 5 to the band alignment state is promoted. Therefore, in the liquid crystal panel 2, the transition from the spray alignment state of the liquid crystal layer 5 to the band alignment state is rapidly and stably performed without applying a high driving voltage by the spacer 6 subjected to such surface treatment. Can be generated.

The optical compensating plate 31a and the polarizing plate 32a are arranged on the back side of the liquid crystal panel 2 having the above structure, that is, the surface opposite to the surface facing the liquid crystal layer 5 of one substrate 3. It is laminated as it is and installed. On the other hand, the optical compensation plate 31b and the polarizing plate 32b are sequentially stacked on the front side of the liquid crystal panel 2, that is, on the surface opposite to the surface facing the liquid crystal layer 5 of the other substrate 4. It is. Of these, the optical compensation plates 31a and 31b perform optical compensation on the liquid crystal layer 5, and are made of a retardation film having birefringence. The optical compensating plates 31a and 31b may be arranged on only one of the rear side and the front side of the liquid crystal panel 2 as necessary. The polarization directions of the polarizing plates 32a and 32b are set to each other with respect to the liquid crystal panel 2 so as to display in the so-called normally black mode, which gives a black level when no voltage is applied, for example. In some cases, it is also possible to set the polarization directions of each other to display in the so-called normally white mode.

The backlight 33 is disposed on the back side of the liquid crystal panel 2, that is, on the outside of the polarizing plate 2a on the back side. The backlight 33 has a light guide plate made of a flat transparent acrylic resin or the like, and a light source made of a cathode fluorescent tube, a light emitting diode (LED), or the like. The back side of the panel 2 is irradiated.

In the liquid crystal display device 1 having the above structure, the light emitted from the backlight 33 passes through the polarizing plate 32a and becomes linearly polarized light, and then passes through the optical compensating plate 31a to form an elliptical polarization. It enters into the back side of (2). Light incident on the liquid crystal panel 2 is emitted from the front side of the liquid crystal panel 2 while passing through the liquid crystal layer 5. Light emitted from the liquid crystal panel 2 passes through the optical compensation plate 31b, becomes linearly polarized light, and enters the polarizing plate 32b. Here, when no voltage is applied, the light that is finally linearly polarized by the optical compensation plate 31b is blocked by the polarizing plate 32b. As a result, black display called normally black mode is performed. On the other hand, when no voltage is applied, the light finally linearly polarized by the optical compensation plate 31b passes through the polarizing plate 32b. This gives a back level.

The liquid crystal display device 1 can quickly and easily transition from the spray alignment state of the liquid crystal layer 5 to the band alignment state without applying a high driving voltage by the spacer 6 subjected to the surface treatment as described above. It can be generated stably. Therefore, in this liquid crystal display device 1, the viewing angle of the liquid crystal panel 2 can be widened and the response speed can be significantly improved. In the liquid crystal display device 1, since the orientation of the liquid crystal molecules 5a around the spacer 6 is controlled by the spacer 6 subjected to surface treatment, the liquid crystal display device is displayed in the normally black mode described above. Even in this case, leakage of light from the liquid crystal panel 2 when no voltage is applied can be prevented. Therefore, the liquid crystal display device 1 can achieve higher contrast and higher picture quality.

In addition, this invention is not necessarily limited to what was applied to the above-mentioned transmissive liquid crystal panel 2, For example, it is applicable also to a reflective or semi-transmissive liquid crystal panel. In addition, the present invention is to prepare a light source (LED) corresponding to the three primary colors of red (R), green (G), blue (B), and to change the color of the light emitted by these light sources without using a color filter The present invention can also be applied to a liquid crystal panel of a so-called field sequential driving method for displaying color.

Hereinafter, one or more of the effects of the present invention by examples, the following examples do not limit the technical scope of the present invention.

(Example 1)

In Example 1, a liquid crystal panel having a diagonal real dimension of about 55 mm (2.2 inches) and a pixel number of 176 x 128 (XRGB) was produced. Specifically, when fabricating this liquid crystal panel, first, an active matrix substrate having TFTs, scanning lines, and signal lines formed on one main surface side is prepared, and a transparent pixel electrode made of ITO is formed on the active matrix substrate via an insulating film. Next, a photosensitive acrylic resin is formed on this active matrix substrate, and the fine concavo-convex shape to be transferred to the film-formed resin layer is pressurized by a transfer mold formed on the surface, and the fine concave-convex shape is transferred to the resin layer. In addition, this uneven | corrugated shape is the same shape as the said liquid crystal panel 2 shown in FIG. 3, The uneven | corrugated pitch P1 repeated along the 1st direction is 0.27 micrometer, and the recessed part in a 1st direction The height dimension d1 with the convex portion is 0.1 μm. On the other hand, the pitch P2 of the uneven shape repeated along the second direction is 1.4 m, and the height dimension d2 of the concave portion and the convex portion in the second direction is 0.1 m. Incidentally, the inclination angle θ is 4.8 °. Next, an alignment film made of polyimide is formed on the resin layer at a film thickness of about 0.07 μm, and a rubbing treatment is performed on the surface of the alignment film. In this rubbing process, a YA18R manufactured by Yoshikawa Kago was used as a rubbing cloth, and a substrate was pressed about 30 mm while rotating a rubbing roll of about 100 mm in diameter at a rotation speed of about 500 rpm while pressing the rubbing cloth to the alignment film at a pressure of about 0.15 mm. By sending at a feed rate of / sec, rubbing treatment was performed as weaker than normal as rubbing strength.

Next, an opposing substrate facing the active matrix substrate is prepared, and a photosensitive acrylic resin is formed on the opposing substrate, and a fine concavo-convex shape to be transferred to the formed resin layer is pressed to press the transfer mold formed on the surface. The uneven shape is transferred to the resin layer. In addition, this uneven | corrugated shape was formed by substantially the same method as the uneven shape formed in the resin layer on the side of the said active matrix board | substrate except that the 1st and 2nd directions are reversed. Next, a black matrix layer, a color filter layer, and a transparent counter electrode made of ITO were laminated on the resin layer in this order, and an alignment film made of polyimide was formed at a film thickness of about 0.07 μm and rubbed against the surface of the alignment film. Carry out processing. In this rubbing process, a substantially identical method was used except that the direction in which the pretilt angle was applied was opposite to that of the alignment film on the active matrix substrate side.

Next, the spherical resin spacer having a diameter of about 6 μm was sprinkled with a density of about 120 particles / mm 2, and then the active matrix substrate and the opposing substrate were pasted together, and the peripheral edge was sealed with a sealing material, thereby providing a panel gap of 6 mm. An empty cell which becomes 탆 is produced. The resin spacer is subjected to a surface treatment in which the liquid crystal molecules of the liquid crystal layer are aligned substantially horizontally along the spherical surface. In this surface treatment, a silane coupling agent having a concentration of 0.02 wt% in which γ-methacryloxypropyltrimethoxysilane was dissolved in a mixed solvent of water and methanol (10%) was prepared. After immersion and air drying, the silane coupling process was performed on the surface of the resin spacer by drying at about 120 degreeC for about 1 hour.

Next, a fluorine-based nematic liquid crystal (no chiral product) made by Chisso Petrochemical is injected into the empty cell, and the mixture is cooled to room temperature after being maintained at a temperature equal to or higher than the N-I point (isotropic transition temperature). The refractive index anisotropy (Δn) of this nematic liquid crystal is 0.15, and the dielectric anisotropy (Δε) is 8. The liquid crystal panel of Example 1 was produced through the above processes. Moreover, the liquid crystal panel of this Example 1 was about 5.6 degrees when the pretilt angle of the liquid crystal injected in the panel was measured by the crystal rotation method. Moreover, as a result of visual observation using a polarizing plate and observation using a polarizing microscope, it was a uniform spray orientation state in the whole panel.

(Example 2)

In Example 2, the liquid crystal panel was produced like Example 1 except having set the concentration of (gamma)-methacryloxypropyl trimethoxysilane used for the surface treatment of a spacer to 0.1 wt% and 0.3 wt%.

(Example 3)

In Example 3, the liquid crystal panel was produced like Example 1 except having used the aqueous solution of (gamma)-glycidoxy propyl trimethoxysilane of concentration 0.03wt% for the surface treatment of a spacer material.

(Example 4)

In Example 4, the liquid crystal panel was produced like Example 1 except having used 0.3 wt% of aqueous solution of (gamma)-glycidoxy propyl trimethoxysilane for the surface treatment of a spacer material.

(Example 5)

In Example 5, Example 1 was used for the surface treatment of the spacer material except that a silane coupling agent having a concentration of 0.03 wt% in which 4-aminophenylpropyltrimethoxysilane was dissolved in a mixed solvent of water and methanol (5%) was used. In the same manner as in the liquid crystal panel was produced.

(Example 6)

In Example 6, the pitch P1 of the concave-convex shape repeated in the first direction among the concave-convex shape of the alignment film is 0.3 μm, and the height dimension d1 of the concave portion and the convex portion in the first direction is set. It is set to 0.2 micrometer, the uneven | corrugated pitch P2 repeated along a 2nd direction is 5 micrometers, and the height dimension d2 of the concave part and convex part in a 2nd direction is 0.3 micrometer, and an inclination angle A liquid crystal panel was produced in the same manner as in Example 1 except that (θ) was 4 °.

(Comparative Example 1)

In Comparative Example 1, a liquid crystal panel was produced in the same manner as in Example 1 except that no fine concavo-convex shape was provided to the alignment film and no surface treatment was performed on the spacer.

Then, the transition time from the spray alignment state to the band alignment state when the driving voltage was applied to the liquid crystal panels of Examples 1 to 6 and Comparative Example 1 was measured.

Specifically, in Example 1, when a driving voltage of about 10 V (1 kHz, square wave) was applied to the liquid crystal panel, the transition time from the spray alignment state to the band alignment state was about 5 seconds. The starting point of the transition is a spacer in a certain direction (the end direction of the rubbing process) with respect to the rubbing direction. In addition, in Example 1, the driving voltage was changed in the range of 2 to 30V in order to see the voltage dependence on the transition from the spray alignment state to the band alignment state, and the driving time increased from about 300 seconds to about 0.2 seconds. It was found to decrease exponentially accordingly. In Example 1, no alignment defect was observed when the liquid crystal panel was observed with a polarization microscope, and the transition from the spray alignment state to the band alignment state occurred uniformly over the entire panel.

On the other hand, in Example 2, when the same driving voltage as in Example 1 was applied to the liquid crystal panel, the transition time from the spray alignment state to the band alignment state was about 4.5 seconds. In Example 2, when the frequency of the driving voltage was changed in the range of 0.5 Hz to 6 kHz, the transition time was reduced from the low frequency side (0.5 Hz) to 1.0 to 1.2 kHz, and then to the high frequency side (6 kHz). The transition time tended to increase slightly. In addition, the starting point number of the transition in the liquid crystal panel tends to be changed by the frequency of the driving voltage applied. That is, near about 1 kHz, the starting point number of the transition increased with frequency, and then the starting point number of the transition tended to decrease slightly.

On the other hand, in Example 3, when the same drive voltage as in Example 1 was applied to the liquid crystal panel, the transition time from the spray alignment state to the band alignment state was about 4.3 seconds.

On the other hand, in Example 4, when the same drive voltage as in Example 1 was applied to the liquid crystal panel, the transition time from the spray alignment state to the band alignment state was about 5.2 seconds.

On the other hand, in Example 5, when the same drive voltage as in Example 1 was applied to the liquid crystal panel, the transition time from the spray alignment state to the band alignment state was about 4.2 seconds.

In addition, when a driving voltage of about 15 V was applied to each of the liquid crystal panels of Examples 1 to 5, the transition time until the entire panel transitioned from the spray alignment state to the band alignment state was all 3.0 to 4.5 seconds. It was in range. When a driving voltage of about 20 V was applied to each liquid crystal panel, the transition time from the spray alignment state to the band alignment state was all in the range of 1 second.

On the other hand, in Example 6, when a driving voltage of about 10 V was applied to the liquid crystal panel, the transition time from the spray alignment state to the band alignment state was about 6 seconds. When a driving voltage of about 15 V was applied to the liquid crystal panel, the transition time from the spray alignment state to the band alignment state was about 1.7 seconds.

On the other hand, in Comparative Example 1, when a driving voltage of about 10 V was applied to the liquid crystal panel, the liquid crystal panel gradually transitioned from the spray alignment state to the band alignment state. Transition line) occurred, and after about 10 seconds, only 5 to 10% of the front panel was transferred. Then, about 280 seconds were required for the entire panel to transition to the band alignment state uniformly.

In the liquid crystal panel of the present invention, the liquid crystal molecules 5a of the liquid crystal layer 5 are oriented substantially horizontally along the surface of the spacer 6 subjected to the surface treatment, as shown schematically in FIG. Dispersion of the orientation of the liquid crystal molecules 5a is unlikely to occur around the spacer 6. As a result, when the voltage is applied, the spray alignment state is directed from the liquid crystal layer 5 on one side (left side in the drawing) to the liquid crystal layer 5 on the other side (right side in the drawing) with the spacer 6 interposed therebetween. Transition to the band alignment state easily occurs.

On the other hand, in the conventional liquid crystal panel, as shown schematically in FIG. 8, the liquid crystal molecules 5a of the liquid crystal layer 5 are randomly (horizontally and vertically) on the surface of the spacer 6 which is not surface treated. Because of orientation, scattering of the alignment of the liquid crystal molecules 5a occurs around the spacer 6. As a result, when the voltage is applied, the transition from the spray alignment state to the band alignment state is inhibited by the spacer 6.

From the above, the surface treatment of the liquid crystal layer of the liquid crystal layer in the surface of the liquid crystal layer is substantially horizontally oriented to form a large number of spacers dispersed in the liquid crystal layer, starting from the spray alignment state of the liquid crystal layer to the band alignment state. It is clear that is promoted.

As described above, the liquid crystal display of the present invention can quickly and stably generate a transition from the spray alignment state to the band alignment state of the liquid crystal layer without applying a high driving voltage by the spacer subjected to the surface treatment. Therefore, in this liquid crystal display device, the viewing angle of the liquid crystal panel can be widened and the response speed can be significantly improved.

Claims (8)

A pair of substrates disposed to face each other and having electrodes and alignment films formed on opposite surfaces thereof, In the OCB mode, the nematic liquid crystal encapsulated between the pair of substrates is spray-oriented by the alignment layer, and the spray-oriented nematic liquid crystal is transferred to band alignment by a driving voltage applied between the electrodes. A liquid crystal layer, A liquid crystal panel having a spacer disposed in the liquid crystal layer, the spacer having a uniform gap between the pair of substrates; The spacer is subjected to a surface treatment for prompting a transition from the spray alignment state to the band alignment state of the liquid crystal layer. The method of claim 1, The spacer is subjected to a surface treatment for aligning the liquid crystal molecules of the liquid crystal layer substantially horizontally along the surface thereof. The method of claim 1, The spacer is a spherical liquid crystal display, characterized in that. The method of claim 1, The alignment film has an uneven shape which alternately repeats the concave portion and the convex portion along the first direction of giving pretilt to the liquid crystal molecules of the liquid crystal layer, and the cross-sectional shape in the first direction of each convex portion is A liquid crystal display device characterized by being asymmetrical left and right with its top portion interposed therebetween. The method of claim 4, wherein The convex portion has a first inclined surface that is inclined from the top to the first direction, and a second inclined surface that is inclined in the opposite direction from the top to the first direction, and the first inclined surface is the second inclined surface. The inclination angle with respect to the said board | substrate is made larger than this, The liquid crystal display device characterized by the above-mentioned. The method of claim 4, wherein The alignment film has a concave-convex shape that alternately repeats the concave portion and the convex portion along a second direction crossing the first direction, and the pitch of the concave-convex shape repeated along the first direction is along the second direction. A liquid crystal display device, wherein the liquid crystal display device has a length longer than a repeated pitch of irregularities. The method of claim 1, The direction in which the pretilt is applied to the liquid crystal molecules of the liquid crystal layer by the alignment film on the one substrate side and the direction in which the pretilt is applied to the liquid crystal molecules of the liquid crystal layer by the alignment film on the other substrate side are the same. And a pretilt angle in opposite directions to the alignment film on the one substrate side and the alignment film on the other substrate side. The method of claim 1, And said nematic liquid crystal has positive dielectric anisotropy.

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