JP2008175837A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of efficiently inducing a splay-bend transition. <P>SOLUTION: A plurality of minute structural bodies 31 are formed on a TFT substrate 3. The minute structural body 31 includes a side (a) along a rubbing direction X in which rubbing treatment is performed first and a side (b) along a rubbing direction Y in which rubbing treatment is performed second and an angle θ1 formed by the rubbing directions X and Y is specified to be an angle (a vertex angle) θ2 formed between the sides (a) and (b). Two minute regions having twisted structures having twisted arrangements of liquid crystal molecules different from each other when voltage is applied can be formed by performing rubbing treatment using the minute structural bodies 31. The splay-bend transition can be induced by forming the two minute regions. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an OCB (Optically Compensated Birefringence or Optically Compensated Bend) mode liquid crystal display device that realizes a wide viewing angle and high-speed response.

  In recent years, in a liquid crystal display device, a display method called an OCB mode has attracted attention (see, for example, Non-Patent Documents 1 and 2). In this OCB mode, a liquid crystal panel in which a liquid crystal layer sandwiched between a pair of substrates is in a splay alignment state and transitions to a bend alignment state when a driving voltage is applied is combined with an optical compensation film that performs optical compensation of the liquid crystal panel. In this way, wide viewing angle and high speed response are realized. However, in this OCB mode, when a normal alignment treatment is performed, it is not easy to quickly transfer the liquid crystal layer in the initial splay alignment state to the bend alignment state, and the pretilt angle on the substrate is about 10 °. Even if it is set to, a high voltage of 10V or more, for example, about 20V is required. It is very difficult to apply such a high voltage in terms of controlling the driving voltage. In addition, it is not easy to cause such a transition of the liquid crystal layer in all the pixels, and some of the pixels that remain without the transition of the liquid crystal layer will greatly deteriorate the display quality of the panel.

In order to solve such a problem, for example, in Non-Patent Document 3, a post spacer is provided on the alignment control layer (alignment film), and the rubbing process is performed three times in three directions different from each other. It is disclosed to form a twist orientation to induce a splay-bend transition.
SID 93 Digest p277, Y. Yamaguchi et al. “Wide-Viewing-Angle Display Mode for the Active-Matrix LCD Using Bend-Alignment Liquid Crystal Cell” SID 94 Digest p927, CL. Kuo et al. “Improvement of Gray-Scale performance of Optically Compensated Birefringence (OCB) Display Mode for AMLCDs” 2005 Japan Liquid Crystal Society Annual Meeting, 3A03 Kuboki, Miyashita, Ishibe, Uchida “Formation of twist disclination for spray-bend transition and its application to OCB cell”

  In order to induce the splay-bend transition, it is necessary to form two micro regions (a left twist alignment region and a right twist alignment region) having a twist structure in which the twist alignment of liquid crystal molecules is different from each other when a voltage is applied. It is necessary to form two minute regions more efficiently.

  The present invention has been made in view of such a point, and an object thereof is to provide a liquid crystal display device capable of efficiently inducing a spray-bend transition.

  The liquid crystal display device of the present invention is a liquid crystal display device in which a liquid crystal layer having positive dielectric anisotropy is sandwiched between a pair of substrates each having an electrode and an alignment control layer disposed thereon, and the alignment of one substrate The control layer has a microstructure that forms two microregions having a twisted structure in which the twisted arrangement of liquid crystal molecules is different from each other when a voltage is applied, and the microstructure has a structure of the one substrate in a plan view. A first side along the first rubbing direction of the first rubbing treatment applied to the orientation control layer, and a second rubbing direction of the second rubbing treatment applied to the orientation control layer of the one substrate. And an angle formed between the first rubbing direction and the second rubbing direction is an angle formed between the first side and the second side. And

  According to this configuration, since the microstructure having an appropriate shape is provided, it is possible to reliably form two minute regions that induce the spray-bend transition by a predetermined rubbing process. As a result, it is possible to quickly shift to bend alignment over the entire screen.

  In the liquid crystal display device of the present invention, it is preferable that the second rubbing process is performed after the first rubbing process, and the strength of the first rubbing process is equal to or less than the strength of the second rubbing process. .

  In the liquid crystal display device of the present invention, it is preferable that in the microstructure, the length of the first side is equal to or longer than the length of the second side.

  In the liquid crystal display device of the present invention, the width of the microstructure is preferably 5 μm or more.

  In the liquid crystal display device of the present invention, it is preferable that the microstructure has a height of 2 μm or more and a panel gap or less.

  In the liquid crystal display device of the present invention, it is preferable that the microstructure has a shape with a base angle in a cross section of 45 ° to 110 °.

  In the liquid crystal display device of the present invention, the two minute regions are preferably a homogeneous twist region and a spray twist region.

  According to the present invention, there is provided a liquid crystal display device in which a liquid crystal layer having positive dielectric anisotropy is sandwiched between a pair of substrates each having an electrode and an alignment control layer disposed thereon, the alignment control layer of one substrate Has a microstructure that forms two minute regions having twist structures in which the twist arrangement of liquid crystal molecules is different from each other when a voltage is applied, and the microstructure controls the orientation of the one substrate in a plan view. A first side along a first rubbing direction of the first rubbing treatment applied to the layer, and a second side of the second rubbing treatment applied to the orientation control layer of the one substrate along the second rubbing direction. And an angle formed between the first rubbing direction and the second rubbing direction is defined as an angle formed between the first side and the second side. Liquid crystal display device capable of efficiently inducing transition It can be realized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings used in the following description, in order to make the characteristics easy to understand, the characteristic portions are enlarged as necessary.

  As shown in FIG. 1, a liquid crystal display device 1 according to the present invention includes an OCB mode liquid crystal panel 2. The liquid crystal panel 2 is a transmissive color liquid crystal panel adopting, for example, an active matrix driving method, and one unit pixel (pixel) is formed by three dots (sub-pixels) corresponding to the three primary colors of red, green, and blue. In addition, an active drive element is provided for each dot, and a color display is performed by controlling the lighting state of each pixel. Although FIG. 1 illustrates an example in which each red, green, and blue subpixel is arranged in a stripe shape, the subpixels may be arranged diagonally or in a triangle shape.

  The liquid crystal panel 2 includes a pair of substrates 3 and 4 arranged to face each other, a liquid crystal layer 5 as a light modulation layer sandwiched between the pair of substrates 3 and 4, and a rear side substrate (view side) At least one polarizing plate 7 disposed on the front side substrate (viewing side substrate: CF (color filter) substrate) 4 and a light source 6 disposed below the opposite substrate: TFT substrate) 3. The retardation plate 8, the polarizing plate 9 disposed below the lower substrate 3, at least one retardation plate 10, and the like. The pair of substrates 3 and 4 are rectangular transmissive substrates such as glass and plastic, and are mutually dispersed in the liquid crystal layer 5 by spherical spacers (not shown) that are dispersed or fixed in place. The facing distance is kept uniform, and the peripheral part is sealed and integrated with a sealing agent (not shown) made of epoxy resin or the like. Although not shown, the front substrate 4 is provided with a transparent electrode on the entire surface, and a predetermined liquid crystal alignment state is controlled on each surface of the substrates 3 and 4 facing the liquid crystal layer 5. Orientation control layers 23 and 24 (see FIG. 2) are provided.

Of the pair of substrates 3 and 4, one (back side) substrate 3 is a so-called active matrix substrate as shown in FIGS. 2 and 3, and a switching element is provided on the surface facing the liquid crystal layer 5. A plurality of thin film transistors (TFTs) 11 are formed in a matrix. The TFT 11 includes an inverted staggered structure in which a gate electrode 12, a gate insulating layer 13, a semiconductor layer 14, and a source electrode 15 and a drain electrode 16 are stacked via a semiconductor layer (n ⁺ layer) 28 in this order from the substrate 3 side. Has a mold structure. That is, in this structure, an island-shaped semiconductor layer 14 is formed on the gate insulating layer 13 covering the lowermost gate electrode 12 so as to block the gate electrode 12, and is formed on one end side of the semiconductor layer 14. The source electrode 15 is formed through the semiconductor layers 14 and 28, and the drain electrode 16 is formed at the other end of the semiconductor layer 14 through the semiconductor layers 14 and 28. Note that an island-shaped insulating layer 17 is formed on the semiconductor layer 14, and this insulating layer functions as an etch stopper layer when forming a channel between the source electrode and the drain electrode.

  On the surface of the substrate 3 facing the liquid crystal layer 5, a plurality of scanning lines 18, which are wirings electrically connected to the gate electrodes 12 of the respective TFTs 11, are arranged in parallel with each other in the arrow X direction (row direction) in FIG. 3. A plurality of signal lines 19 that are electrically connected to the source electrode 15 of each TFT 11 are formed side by side in the arrow Y direction (column direction) in FIG. The TFT 11 is formed in the vicinity of the intersection of the signal line 19 and the signal line 19. In addition, each rectangular area partitioned by the scanning lines 18 and the signal lines 19 forms a dot corresponding area on the substrate 3 side corresponding to each dot. By arranging a plurality of regions in a matrix, a display region of the liquid crystal panel 2 is formed as a whole. Although not shown, a scanning driver that applies a selection pulse to each scanning line 18 and a signal driver that applies a signal voltage to each signal line 19 are provided outside the display area. .

  An insulating film 20 that covers the TFT 11, the scanning line 18, and the signal line 19 is formed on the surface of the substrate 3 that faces the liquid crystal layer 5. In addition, a contact hole 21 that faces the drain electrode 16 of each TFT 11 is formed in the insulating film 20. On the insulating film 20, a plurality of pixel electrodes 22 electrically connected to the drain electrodes 16 of the respective TFTs 11 through the contact holes 21 are formed in a matrix corresponding to the respective dots. Yes. The pixel electrode 22 is made of a transparent conductive material such as ITO (Indium-Tin Oxide), and is formed in a rectangular shape so as to cover almost the entire area corresponding to each dot. On the substrate 3 on which the pixel electrode 22 is formed, an orientation control layer 23 that has been processed as described later is formed.

  On the other hand, the other surface (front side) of the substrate 4 facing the liquid crystal layer 5 is made of an alignment control layer 24 that has been processed later and a transparent conductive material such as ITO (Indium-Tin Oxide). For example, red (R), green (G), blue, which are defined by the counter electrode 27, the light-shielding black matrix layer 25 that partitions the dot corresponding area corresponding to each dot, and the black matrix layer 25. The color filter layers 26R and 26G (26B are not shown) of (B) are formed in order. Specifically, each rectangular area partitioned in a rectangular pattern by the rectangular black matrix layer 25 forms a dot corresponding area on the substrate 4 side corresponding to each dot. The black matrix layer 25 is a light shielding wall for preventing light color mixing between the color filters, and is a dot of any one of the red (R), green (G), and blue (B) colors. Is embedded. The color filter layers 26R and 26G (26B not shown) have a structure in which layers of different colors are periodically arranged in a mosaic shape such as a stripe shape, a diagonal shape, or a triangle shape. Therefore, the display color of each pixel is controlled by controlling the drive voltage applied between the pixel electrode 22 and the counter electrode 27 for each of the three dot corresponding regions corresponding to red, green, and blue of each pixel. Thus, a desired image can be displayed.

  The liquid crystal layer 5 includes a nematic liquid crystal composition having positive dielectric anisotropy enclosed between the alignment control layer 23 of one substrate 3 and the alignment control layer 24 of the counter substrate 4. Furthermore, the liquid crystal layer 5 is in a splay arrangement in which the pretilt angles of the liquid crystal molecules are opposite to each other on each of the substrates 3 and 4 in an initial state (no voltage application state or a low voltage state in which the alignment state does not change). The orientation is controlled so that

  In the liquid crystal display device of the present invention, a plurality of retardation plates, polarizing plates, etc. are provided so as to satisfy an appropriate optical compensation condition according to the liquid crystal driving voltage for a panel provided with liquid crystal molecular orientation as described later. An optical film is placed.

For example, when a display is performed in a transmissive normally black mode, a liquid crystal layer in the panel is formed with respect to a panel (a nematic liquid crystal composition having positive dielectric anisotropy sandwiched between two substrates). And a biaxial optical compensation film ( _nx > _ny > _nz , where the optical axes are set in directions orthogonal to the rubbing direction, respectively, so that the birefringence phase difference becomes zero in total X and y represent the directions in the panel surface, and z represents the thickness direction of the panel). In particular, the optical films described above are configured so that black display is performed at the lowest voltage (OFF voltage) that maintains the bend alignment state, and white display is performed at a voltage (ON voltage) at which the liquid crystal molecules sufficiently rise from the bend alignment. Conditions (mutual optical axis direction, phase difference value, etc.) are set. For example, when the panel has a phase difference of 960 nm when no voltage is applied (splay alignment state) and the ON voltage is 5.0 V, the phase difference of the biaxial optical compensation film is 50 nm and the Nz coefficient is 7.5. Then, the birefringence phase difference between the liquid crystal layer of the panel and the biaxial optical compensation film becomes zero in total. Here, the Nz coefficient is Nz = (nx−) where the refractive index in the slow axis direction, the refractive index in the fast axis direction, and the refractive index in the thickness direction are nx, ny, and nz, respectively. nz) / (nx-ny). Needless to say, in the case of so-called normally white, the above conditions for black display and white display are reversed. Further, a laminated body in which a polarizing plate and a quarter wavelength plate (1 / 4λ plate) are set so that the optical axes of both are set to about 45 ° and a circular polarizing plate is formed is placed on both sides of the above. Deploy.

On the other hand, in the case of reflection type (normally black) display, the inner surface of the substrate (on the opposite side to the observation side of the panel (a nematic liquid crystal composition having positive dielectric anisotropy sandwiched between two substrates) ( to form a reflective layer on the side of the surface) or the substrate outer surface in contact with the liquid crystal layer, the liquid crystal layer and the biaxial optical compensation film, such as its birefringence phase difference becomes zero in total in the panel (n _x> n _y > N _z , where x and y represent the panel surface, and z represents the thickness direction of the panel. For example, when the phase difference in the voltage non-application state (splay alignment state) of the panel is 480 nm and the ON voltage is 5.0 V, the phase difference of the biaxial optical compensation film is 50 nm and the Nz coefficient is 7.5. The birefringence phase difference between the liquid crystal layer of the panel and the biaxial optical compensation film becomes zero in total. Further, on the upper surface (surface close to the observation side), a polarizing plate and a quarter wavelength plate (1 / 4λ plate) are set so that both optical axes are about 45 °. The laminated body formed with is disposed. In the case of normally white, the above-described relationship between the black display and the white display is reversed as described above.

  FIG. 4 is a plan view showing a microstructure in the liquid crystal display device according to the embodiment of the present invention. FIG. 4 is a so-called film top view in which the surface on which the orientation control layer is provided is on the paper surface. A plurality of the microstructures 31 are formed on one substrate, for example, the TFT substrate 3. The microstructure 31 includes a side a along the rubbing direction X of the first rubbing process, and a side b along the rubbing direction Y of the second rubbing process, and the rubbing direction X and the rubbing direction Y The angle θ1 formed between them is defined as an angle (vertical angle) θ2 formed between the side a and the side b. By performing the rubbing process using the microstructure 31, it is possible to form two minute regions having twist structures in which the twist arrangement of liquid crystal molecules is different from each other when a voltage is applied. By forming these two minute regions, the spray-bend transition can be induced.

  In FIG. 4, the side a has an angle α with respect to the reference direction (the vertical direction in FIG. 4). That is, the first rubbing direction is a direction having an angle α with respect to the reference direction. The side b has an angle β with respect to the reference direction (the vertical direction in FIG. 4). That is, the second rubbing direction is a direction having an angle β with respect to the reference direction. Therefore, the angle θ2 formed corresponds to the sum of the angle α and the angle β. Further, a third rubbing process is performed along the reference direction (vertical direction in FIG. 4) (rubbing direction Z). The rubbing direction Z is the same direction as the rubbing direction in the CF substrate 4 which is the counter substrate.

  In FIG. 4, a polygon ABCD is the outer shape of the microstructure 31. The BCH region 32 is a shadow portion of rubbing formed for the second rubbing process and the third rubbing process. That is, in the second rubbing process and the third rubbing process, the microstructure 31 becomes an obstacle, and the rubbing process in the rubbing direction Y and the rubbing direction Z is not performed. Therefore, only the first rubbing process is performed on the BCH region, and the alignment in the rubbing direction X is formed.

  An EDGF region 33 is a rubbing shadow formed for the third rubbing process. That is, in the third rubbing process, the micro structure 31 becomes an obstacle, and the rubbing process in the rubbing direction Z is not performed. Therefore, the first rubbing process and the second rubbing process are performed on the EDGF region.

  Further, the BCDGFE region (region surrounded by a portion corresponding to the lengths of BCHF and DG) is a rubbing shadow formed for the third rubbing process. That is, in the third rubbing process, the micro structure 31 becomes an obstacle, and the rubbing process in the rubbing direction Z is not performed.

  By performing the rubbing process three times, the BCH region 32 becomes a left-handed homogeneous alignment region, and the EDGF region 33 becomes a right-handed splay alignment region. The CH line 34 is a boundary between the left twisted homogeneous alignment region and the right twist splay alignment region, and the CH line can be secured with a sufficient length and / or the BCH region 32 with a sufficient width. By being able to ensure, the spray-bend transition can be induced efficiently.

  Making the boundary line (CH line) 34 between the two microregions as the nucleus of the spray-bend transition sufficiently long, making the BCH region 32 sufficiently wide, and stabilizing the spray-bend transition. In consideration of what is performed, the angle α and the angle β constituting the apex angle θ2 of the microstructure 31 are preferably in the range of 50 ° to 80 °. The angle α is particularly preferably 55 ° to 75 °. Note that the angle α and the angle β are not necessarily equal.

  For the formation of the BCH region 32 and the CH line 34, it is important how the shadow portion described above is formed. The shadow varies depending on the height of the microstructure 31, the pile length of the rubbing cloth, the amount of pushing of the rubbing roll onto the substrate, and the height of the microstructure 31 is typically described later. In the case of the range, it is formed with a width of about 5 μm to 20 μm in the vicinity of the microstructure 31.

  The height of the microstructure 31 is 2 μm or more, preferably 3 μm or more and preferably less than the panel gap in consideration of the formation of shadows for generating effective nuclei for the spray-bend transition and the setting of the panel gap. preferable. That is, the height h in FIG. 5 is 2 μm or more, preferably 3 μm or more and preferably less than the panel gap.

  The microstructure 31 preferably has a shape with a base angle in the cross section of 45 ° to 110 ° in consideration of formation of a shadow portion and reduction of damage due to rubbing. That is, the base angle θ3 in FIG. 5 is preferably 45 ° to 110 °.

  The width of the microstructure 31 (the width in the direction along the rubbing direction Z) is preferably 5 μm or more, preferably 7 μm or more in consideration of the formation of shadows. That is, the width W in FIG. 5 is 5 μm or more, preferably 7 μm or more. Note that the width of the microstructure 31 (the width in the direction along the rubbing direction Z) may be 30 μm or less in consideration of a reduction in the area of the effective display portion and the fact that the microstructure is not visually visible. preferable.

  In the microstructure 31, the length of the side a is preferably equal to or longer than the length of the side b. As a result, the BCH region (left-handed homogeneous region) 32 is formed wider than the EDGF region (right-handed splay region) 33, and the transition to the bend state becomes easier to proceed.

  In the present invention, the angle α, the angle β, the side a, the side b, the height h, the width W, and the like of the microstructure 31 are appropriately selected so that the left-twisted homogeneous alignment region is as wide as possible within the above-described range. It is desirable to set them.

  All of these rubbing processes are performed on an alignment film (for example, a polymer alignment film such as polyvinyl alcohol, polyamide, or polyimide) that is the alignment control layer 23 of the TFT substrate 3. First, with the rubbing direction X, that is, the rubbing direction Z as a reference direction, a first rubbing process is performed in a direction having an angle α with respect to the reference direction. Next, a second rubbing process is performed in a direction having an angle β with respect to the reference direction with the rubbing direction Y, that is, the rubbing direction Z as a reference direction. Thereafter, a third rubbing process is performed in the rubbing direction Z.

  Of the sides constituting ABCD in the microstructure 31, two sides BC and side CD forming at least one apex angle are along a direction substantially equal to the directions of these angles α and β, and the apex angle BCD (θ2 ) Is set approximately equal to α + β. In the present invention, the rubbing direction and the direction of the side of the microstructure 31 are set to be approximately equal. In this case, the rubbing direction is satisfied if the variation in the rubbing direction due to the micro structure 31 is in a range in which the micro structure 31 is not significant, or if the micro structure 31 is not broken or peeled off by the shearing force of the rubbing. The object of the present invention can be achieved even when there is a predetermined angle, for example, within ± 10 °, preferably within ± 5 °, between the edge of the micro structure 31 and the direction of the side of the microstructure 31.

  The alignment control layer 24 of the CF substrate 4 facing the TFT substrate 3 is rubbed on the entire surface in the rubbing direction Z. As a result, in FIG. 4, the entire region excluding the microstructure ABCD and the shaded portion BEFGDC is a full surface splay alignment region as shown in FIG. 6C. In FIG. 4, the BCH region 32 is a left-twisted homogeneous alignment region having an angle of about α between the CF substrate 4 and the TFT substrate 3 when projected from the CF substrate 4 side, for example. ing. FIG. 6A is a view of the panel cross section along the AF line as viewed from the direction D. FIG. On the other hand, in the region of HCDGF, the liquid crystal molecules 41 between the CF substrate 4 and the TFT substrate 3 have an angle of about β (actually a value slightly larger than β due to the effect of rubbing in the rubbing direction X). It is a twisted splay alignment region. FIG. 6B is a view of the panel cross section along the AF line as viewed from the direction D.

  Therefore, the boundary line where these two minute regions are in contact forms the disclination line CH. When a voltage higher than a predetermined value is applied to this alignment state, a stable homogeneous region spreads to the splay side all at once, so that the entire display screen quickly transitions to the bend state. The reason is that the twisted homogeneous orientation is more energetically stable than the twisted splay orientation when a voltage is applied, and the energy required for the transition from spray to bend by passing through a twisted state of 90 ° or more. This is due to the smaller barrier.

  Note that the position of the end portion H of the disclination line slightly varies depending on the roll pressing amount in rubbing in the rubbing direction Y, the pile length of the rubbing cloth, and the like. This is because with respect to rubbing in the rubbing direction Y, the end of the rubbing shadow portion formed in the vicinity of the microstructure 31 corresponds to the starting point at which rubbing starts.

  7A to 7I are plan views showing a microstructure in the liquid crystal display device of the present invention. In these figures, the first, second and third rubbing directions are the same as those shown in FIG. 4 (in FIG. 7, only the third rubbing direction Z is indicated by an arrow). In addition, the length of the side substantially along the rubbing direction X of the first rubbing process is denoted by a, and the length of the side along the rubbing direction Y of the second rubbing process is denoted by b.

  The microstructure 31 shown in FIGS. 7A and 7B is the most basic shape, and is a quadrangle in which the side a is set longer than the side b, and particularly in the shape shown in FIG. 7B. The length of side a is considerably longer than side b. The shape shown in FIG. 7C has an arc-shaped side at least in the rubbing direction Y and the rubbing direction Z (the portion where the pile of the rubbing cloth abuts is arc-shaped), and is formed by rubbing on the microstructure 31. This is preferable from the viewpoint of reducing damage.

  The shape shown in FIG. 7D has a substantially triangular outer shape and satisfies the relationship described above with respect to angle α, angle β, side a, side b, and the like. Further, in order to prevent peeling or damage due to rubbing, a length may be provided in the Z direction as shown in FIG. 7 (e). Further, like the shapes shown in FIGS. 7F and 7G, in consideration of prevention of damage due to rubbing, the side subjected to the third rubbing treatment may be formed into a concave shape.

  Furthermore, as shown in FIGS. 7H and 7I, the microstructure 31 may be configured by a plurality of small structures. The arrangement of the small structures satisfies the relationship between the angles α and β, and the length of the small structure aggregate substantially satisfies the relationship between the sides a and b. If the space between the small structures is an interval (for example, 10 μm) at which the pile of the rubbing cloth does not pass therethrough, the same effect as the structure shown in FIGS. 7A to 7G can be obtained.

  The rubbing strength is set so that the rubbing strength of the second rubbing treatment is larger than the rubbing strength of the first rubbing treatment, and the rubbing strength of the third rubbing treatment is larger than the rubbing strength of the second rubbing treatment. It is preferable to do. That is, with respect to the alignment regulating force (anchoring) for the liquid crystal molecules in each region after the rubbing treatment, the HCDGF region has a stronger alignment regulating force than the BCH region, and the entire region other than the BCDGFE region is oriented. By setting the restricting force strongly, the region rubbed in the rubbing direction Z is most dominant (wide), and the BCH region rubbed in the rubbing direction X and the rubbing treatment in the rubbing direction Y The EFGD region thus formed is formed in an island shape.

Various methods can be used to change the orientation regulating force. For example, in the case of rubbing, the orientation regulating force is a “rubbing strength parameter” (Y. Sato, K) that semiquantitatively represents the degree of rubbing treatment. Sato and T. Uchida: Jpn. J. Appl. Phys., 31 (1992) L579). This rubbing strength parameter (L) is generally expressed by the following equation. Note that all the units related to the length are mm.
L = N × l × (l + 2πrn / 60v)
Here, N (mm) represents the number of times of rubbing, l (mm) represents the depth of depression (pushing amount) into the rubbing cloth, r (mm) represents the radius of the rubbing roll, and n (rpm) is The number of rotations of the roll is represented, and v represents the moving speed of the substrate stage. As a result, the rubbing strength parameter is an amount related to the length (mm) of the rubbing cloth passing through one point on the substrate. As is clear from the above equation, the strength of the orientation regulation force can be controlled by increasing or decreasing the number of rubbing and the amount of pushing, increasing or decreasing the rubbing roll diameter or rotation speed, or changing the substrate feed speed. Is possible.

  In the present invention, the place where the microstructure is arranged is not particularly limited. For example, it can be arranged on unit pixels such as RGB called display pixels or sub-pixels, or source electrode wiring (or gate electrode wiring) which is an electrode wiring of an active element. In the case of being arranged on the pixel electrode, it is desirable to consider the aperture ratio and contrast.

  In the above description, the case where at least one spray-bend transition start point is formed corresponding to each pixel is described. However, the present invention is not limited to this, and the present invention is not limited to the physical property values ( The arrangement density can be appropriately changed according to the elastic constant, dielectric anisotropy, etc.), the panel gap, the pretilt angle of the liquid crystal molecules, the alignment regulating force, and the like. For example, the number of transition start points may be one per 3 to 10 pixels. Also, by providing 2 to 4 pixels per pixel, there are relatively many starting points for bend transition, and the time to bend transition can be substantially shortened. For example, when the pretilt angle is large (4 ° or 5 ° to 15 °), the splay-bend transition is very likely to occur. Therefore, even when the arrangement density of the transition start points is 10 or more, it is effective. .

  In the above description, the case where the microstructure is provided on the TFT substrate on which the active element is formed is described. However, in the present invention, the microstructure may be provided on the CF substrate which is the counter substrate.

Next, examples performed for clarifying the effects of the present invention will be described.
A general CF substrate in which red, green, and blue filters are formed on sub-pixels is manufactured, and the dimensions are 10 μm × 10 μm (the side a in FIG. 4 is 10 μm and the side b is 10 μm), and the height is 4 μm. Structures (column spacers) were formed at a pitch of 60 μm for each subpixel. The apex angle (θ2 in FIG. 4) of this column spacer was 120 °, the angle α was 60 °, and the angle β was 60 °. The width of the column spacer (the width in the direction along the rubbing direction Z) was 6 μm.

This column spacer is exposed to transparent negative resist CL-016S (manufactured by TOK) at 100 mJ / cm ² , developed with a 0.5% aqueous solution of N-A3K (trade name) for 60 seconds, and then post-treated at 300 mJ / cm ² . It formed by exposing and performing a post-baking at 220 degreeC for 1 hour. The base angle (θ3 in FIG. 5) in the cross section of the obtained column spacer was 60 °.

  As shown in FIG. 4, the CF substrate was subjected to the first rubbing process in the rubbing direction X, the second rubbing process in the rubbing direction Y, and the third rubbing process in the rubbing direction Z. . The rubbing strength was 100 cm (pushing amount 0.2 mm) for all three rubbing treatments.

  Next, a TFT substrate on which a source electrode, a gate electrode, a pixel electrode, a TFT element and the like were formed was produced by a normal method. The TFT substrate was rubbed in the rubbing direction Z shown in FIG. 4 with a rubbing strength of 300 cm (pushing amount 0.6 mm).

  Next, the CF substrate and the TFT substrate were overlapped using the column spacer formed on the CF substrate as a gap material between the substrates. Next, after the stacked substrates were cut into panel units, a liquid crystal material (manufactured by Chisso Corporation) was injected between both substrates by a vacuum injection method to produce an OCB liquid crystal panel.

  Each OCB liquid crystal panel was produced in the same manner as described above except that the angle α was changed to 50 °, 55 °, 70 °, 75 °, and 80 °. Each OCB liquid crystal panel was produced in the same manner as described above except that the angle β was changed to 50 °, 55 °, 70 °, 75 °, and 80 °.

  The OCB liquid crystal panel thus obtained was examined by an optical microscope to determine whether a spray-bend transition was induced by applying a voltage of 5 V to each pixel electrode and source electrode line. As a result, in all OCB liquid crystal panels, immediately after voltage application, a splay-bend transition occurs from the point where the post spacer formation region of the CF substrate intersects with the pixel electrode space, and all the panel pixels bend in about 0.5 seconds. Transitioned to orientation.

  Each OCB liquid crystal panel was fabricated in the same manner as described above except that the length of the side a of the column spacer was changed to 12 μm and 15 μm. Each OCB liquid crystal panel was prepared in the same manner as described above except that the width of the column spacer (the width in the direction along the rubbing direction Z) was changed to 5 μm, 7 μm, 10 μm, and 15 μm. Each OCB liquid crystal panel was fabricated in the same manner as described above except that the column spacer height was changed to 3 μm, 3.5 μm, 4.5 μm, 5 μm, and 5.5 μm. Further, each OCB liquid crystal panel was produced in the same manner as described above except that the base angle (θ3 in FIG. 5) in the cross section of the column spacer was changed to 45 °, 90 °, 100 °, and 110 °.

  The OCB liquid crystal panel thus obtained was examined by an optical microscope to determine whether a spray-bend transition was induced by applying a voltage of 5 V to each pixel electrode and source electrode line. As a result, in all OCB liquid crystal panels, immediately after voltage application, a splay-bend transition occurs from the point where the post spacer formation region of the CF substrate intersects with the pixel electrode space, and all the panel pixels bend in about 0.5 seconds. Transitioned to orientation.

  As described above, in the liquid crystal display device of the present invention, since a microstructure having an appropriate shape is provided, two minute regions that induce a spray-bend transition by a predetermined rubbing process, that is, a left twisted homogeneous region In addition, the right twisted spray region can be reliably formed. As a result, it is possible to quickly shift to bend alignment over the entire screen.

  The present invention is not limited to the embodiment described above, and can be implemented with various modifications. For example, the numerical values and materials described in the above embodiments, the configuration of the liquid crystal display device, and the like are not particularly limited. Other modifications may be made as appropriate without departing from the scope of the object of the present invention.

1 is an exploded perspective view showing a schematic configuration of a liquid crystal display device according to an embodiment of the present invention. It is sectional drawing of the liquid crystal display device shown in FIG. FIG. 2 is an enlarged view showing an active matrix substrate of the liquid crystal display device shown in FIG. 1. It is a figure for demonstrating the microstructure of the liquid crystal display device which concerns on embodiment of this invention. It is a figure for demonstrating the microstructure of the liquid crystal display device which concerns on embodiment of this invention. (A)-(c) is a figure for demonstrating the orientation state of a liquid crystal molecule. (A)-(i) is a figure for demonstrating the other example of the microstructure of the liquid crystal display device which concerns on embodiment of this invention.

Explanation of symbols

3,4 substrate 5 liquid crystal layer 11 TFT
DESCRIPTION OF SYMBOLS 12 Gate electrode 13 Gate insulating film 14 Semiconductor layer 15 Source electrode 16 Drain electrode 17 Insulating layer 18 Scan line 19 Signal line 22 Pixel electrode 23, 24 Orientation control layer 25 Black matrix layer 26R, 26G Color filter layer 27 Counter electrode 31 Microstructure Body 32 BCH region 33 EDGF region 34 CH line 41 Liquid crystal molecule

Claims (7)

  A liquid crystal display device in which a liquid crystal layer having positive dielectric anisotropy is sandwiched between a pair of substrates on which an electrode and an alignment control layer are respectively disposed, and the alignment control layer of one substrate is a liquid crystal when a voltage is applied A microstructure that forms two microregions having a twisted structure with different molecular twisting arrangements, and the microstructure has a first structure applied to the orientation control layer of the one substrate in a plan view; A first side along a first rubbing direction of one rubbing process, and a second side along a second rubbing direction of a second rubbing process applied to the orientation control layer of the one substrate. In addition, an angle formed between the first rubbing direction and the second rubbing direction is an angle formed between the first side and the second side.   2. The liquid crystal display according to claim 1, wherein the second rubbing process is performed after the first rubbing process, and the intensity of the first rubbing process is equal to or less than the intensity of the second rubbing process. apparatus.   3. The liquid crystal display device according to claim 1, wherein in the microstructure, the length of the first side is equal to or longer than the length of the second side.   The liquid crystal display device according to claim 1, wherein a width of the microstructure is 5 μm or more.   The liquid crystal display device according to claim 1, wherein a height of the microstructure is 2 μm or more and a panel gap or less.   The liquid crystal display device according to claim 1, wherein the microstructure has a shape with a base angle in a cross section of 45 ° to 110 °.   7. The liquid crystal display device according to claim 1, wherein the two minute regions are a homogeneous-twist region and a spray-twist region.

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