JP2011013442A - Liquid crystal display panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display panel that has high view angle characteristics and superior contrast, and is reduced in power consumption.SOLUTION: The liquid crystal display panel 100 includes a TFT substrate 10, a counter substrate 20, a first liquid crystal layer 15 containing first liquid crystal arranged between both substrates 10 and 20, alignment control layers 14 and 24 formed on the first liquid crystal layer 15 side of both substrates 10 and 20, and a compensation plate 40 that is arranged on the counter substrate 20 on the opposite side to the first liquid crystal layer 15 and formed of a second liquid crystal layer containing second liquid crystal. Each of a plurality of pixels includes a first region 5 and a second region 6. The expression θ-5°≤θ≤θ+5° is established, where θis a tilt angle of the first liquid crystal with respect to a substrate surface of the counter substrate 20 in the first region 5 when voltage is not applied to the first liquid crystal layer 15, and θis a tilt angle of the optical axis closer to the direction perpendicular to the substrate surface on a refractive index ellipsoid of the second liquid crystal layer.

Description

  The present invention relates to a vertical alignment type liquid crystal display panel.

  In recent years, thin and light liquid crystal display devices have been used as display devices for televisions, computers, portable information terminal devices, and the like. Conventional liquid crystal display devices include twisted nematic type (TN type) and super twisted nematic type (STN type) liquid crystal display devices, but various techniques have been proposed to solve the drawback of the narrow viewing angle. Development has been done.

  A liquid crystal display device having a vertical alignment type liquid crystal layer is known as a liquid crystal display device with improved viewing angle characteristics. The vertical alignment type liquid crystal display device is called a VA (Vertical Alignment) mode liquid crystal display device. An example of a VA mode liquid crystal display device is described in Patent Document 1. Further, as another example of the VA mode liquid crystal display device, an alignment division type MVA (Multi-domain Vertical Alignment) mode liquid crystal display device is disclosed in Patent Document 2.

  In the MVA mode, an alignment regulating structure that regulates the alignment of liquid crystal molecules is provided on each of a pair of substrates opposed via a liquid crystal layer. Specifically, the orientation regulating structure is a protruding structure (convex portion) formed on the electrode or a slit formed on the electrode. By providing such an alignment regulating structure, when a voltage is applied to the liquid crystal layer, it is possible to form a plurality of regions having different orientations in which the liquid crystal molecules are inclined, and the viewing angle characteristics are improved.

  Further, Patent Document 3 discloses a liquid crystal display device in which an alignment control layer made of a polymer structure is formed on a substrate surface in contact with a liquid crystal layer in order to define the alignment direction of liquid crystal molecules. The alignment control layer is formed by polymerizing a polymerizable composition previously mixed in the liquid crystal layer by irradiation with UV light or the like after the panel is formed. A method of controlling the alignment of liquid crystal molecules using an alignment control layer formed by this method is called a PSA (Polymer-Sustained Alignment) method.

  In the PSA type liquid crystal display device, the alignment control layer defines the pretilt angle (polar angle) and pretilt direction (azimuth angle) of the liquid crystal molecules when no voltage is applied, and the liquid crystal molecules are aligned in the pretilt direction when a voltage is applied. Along the substrate surface. According to the PSA method, alignment stability and response characteristics in a VA mode liquid crystal display device can be improved.

JP-A-11-352328 Japanese Patent Laid-Open No. 11-242225 JP 2006-317866 A

  In the liquid crystal display device of Patent Document 3, the voltage-transmittance characteristics (VT characteristics) when the substrate is viewed from the front (polar angle 90 ° direction) and the substrate from an oblique direction (for example, polar angle 30 ° direction). In order to reduce the difference between the VT characteristics when viewed and reduce the brightness difference when viewed from both directions, the following characteristics are provided.

  The liquid crystal display device of Patent Document 3 includes a vertical alignment layer (first alignment control layer) formed on the liquid crystal layer side of the substrate, and an alignment control layer (second alignment control layer) formed on the vertical alignment layer. ). The alignment control layer is formed by encapsulating a mixture of liquid crystal and monomer between a pair of substrates and then irradiating the liquid crystal layer with ultraviolet rays to cure the monomer. At this time, a potential difference is applied between the two substrates, and the liquid crystal is slightly oriented with respect to the substrate surface in accordance with the potential difference. Therefore, as the alignment control layer is formed, the liquid crystal in the vicinity of the alignment control layer is fixed in a slightly aligned state, so that the alignment of the liquid crystal is memorized, and a constant alignment (pretilt) of the liquid crystal when no voltage is applied is realized. . In Patent Document 3, in order to obtain a high contrast, it is essential that the pretilt angle is 86 ° or more.

  Further, in this liquid crystal display device, each pixel has two regions having different threshold voltages in order to obtain good viewing angle characteristics. Here, the threshold voltage refers to an applied voltage when the liquid crystal starts to be aligned in a direction parallel to the substrate surface from the pretilt state, that is, a minimum voltage for aligning the liquid crystal. Since the two regions have different pretilt angles and threshold voltages, the VT characteristics are also different. Accordingly, by appropriately adjusting the pretilt angles of both regions, a display with good viewing angle characteristics with less viewing angle dependency of luminance or gradation can be obtained.

  The above two regions are formed as follows. First, when forming the alignment control layer, only the first region is selectively opened by masking, and ultraviolet irradiation is performed while applying the first applied voltage, thereby forming the alignment control layer in the first region. . Next, ultraviolet irradiation is performed while applying a second applied voltage different from the first applied voltage to the second region, thereby forming the orientation control layer in the second region. In this way, two regions having different pretilt angles and threshold voltages are formed in one pixel.

  According to the liquid crystal display device of Patent Document 3, good viewing angle characteristics can be obtained. However, in this liquid crystal display device, the pretilt angle is small overall (close to the direction perpendicular to the substrate surface (polar angle 90 ° direction)). There is a problem that the driving voltage is high and the power consumption is large because anchoring by the control layer (binding by liquid crystal sticking) is strong.

  An object of the present invention is to provide a liquid crystal display device having good display characteristics and low power consumption.

A liquid crystal display panel according to the present invention is a vertical alignment type liquid crystal display panel having a plurality of pixels, and includes a TFT substrate, a counter substrate disposed opposite to the TFT substrate, the TFT substrate, and the counter substrate. A first liquid crystal layer including a first liquid crystal disposed between, an alignment control layer formed on a surface of the TFT substrate and the counter substrate on the first liquid crystal layer side, and the first substrate of the counter substrate A compensation plate made of a second liquid crystal layer including a second liquid crystal disposed on a side opposite to the liquid crystal layer, wherein each of the plurality of pixels includes a first region and a second region, The tilt angle of the first liquid crystal when the voltage is not applied to the first liquid crystal layer with respect to the substrate surface of the counter substrate is θ ₁ , and the substrate surface of the refractive index ellipsoid of the second liquid crystal layer The tilt angle of the optical axis closer to the direction perpendicular to θ ₂ , If
θ ₁ -5 ° ≦ θ ₂ ≦ θ ₁ + 5 °
Meet.

In one embodiment, the inclination angle θ ₁ is not less than 75 ° and not more than 85 °.

In one embodiment, when the inclination angle of the first liquid crystal with respect to the substrate surface in the second region when no voltage is applied to the first liquid crystal layer is θ ₃ , the inclination angle θ ₃ is It is larger than the inclination angle θ ₁ .

In one embodiment, when the tilt angle of the optical axis closer to the direction perpendicular to the substrate surface of the refractive index ellipsoid of the second liquid crystal layer in the second region is θ ₄ , the tilt angle θ ₄ is It is larger than the inclination angle θ ₂ .

In one embodiment, the second liquid crystal is a discotic liquid crystal, and the tilt angle θ ₂ is a tilt angle of an optical axis closer to a direction perpendicular to the substrate surface of the discotic liquid crystal.

In one embodiment, the second liquid crystal is a chiral nematic liquid crystal, and the tilt angle θ ₂ is the tilt angle of the helical axis of the chiral nematic liquid crystal.

  In one embodiment, in the first region, the retardation of the compensation plate is 50% or more and 80% or less of the retardation of the first liquid crystal layer.

  In one embodiment, the alignment control layer is a polymer layer formed by curing a monomer mixed with the first liquid crystal in the first liquid crystal layer while applying a voltage to the first liquid crystal layer. .

  In the liquid crystal display panel according to the present invention, since the pretilt angle of the first liquid crystal is larger than the conventional one (polar angle is small) in at least a part of the pixels, the threshold voltage for liquid crystal alignment can be lowered. A decrease in contrast caused by this is prevented by appropriately tilting the optical axis of the refractive index ellipsoid of the compensation plate.

  Further, in the liquid crystal display panel according to the present invention, two regions having different pretilt angles of the first liquid crystal can be formed in one pixel, so two types of VT characteristics are obtained in one pixel. Therefore, good gradation characteristics can be obtained.

  According to the present invention, in the liquid crystal display panel, it is possible to reduce the driving voltage for liquid crystal alignment of at least a part of the pixels while maintaining the viewing angle characteristics and contrast of the liquid crystal display panel at a high level. Therefore, it is possible to provide a liquid crystal display panel that is excellent in viewing angle characteristics and contrast and has reduced power consumption.

1 is a perspective view schematically showing a configuration of a liquid crystal display device 1 according to an embodiment of the present invention. 1 is a perspective view schematically showing a layer configuration of a liquid crystal display panel 100 according to an embodiment of the present invention. 4 is a cross-sectional view schematically showing a layer configuration of one pixel 7 in the liquid crystal display panel 100. FIG. 4 is a cross-sectional view illustrating a method of forming alignment control layers 14 and 24 of the liquid crystal display panel 100. FIG. It is a figure for demonstrating the effect of the liquid crystal display panel 100, and is a graph showing the relationship between VT characteristic and the pretilt angle of a liquid crystal. It is a figure for demonstrating the effect of the liquid crystal display panel 100, the difference of the threshold voltage (vertical axis: (DELTA) V) in the 1st area | region 5 and the 2nd area | region 6 of the pixel 7, and the pretilt of the liquid crystal 16a in the 1st area | region 5 ( It is a graph showing the relationship with horizontal axis: PT1). It is a figure for demonstrating the effect of the liquid crystal display panel 100, and the average ratio (vertical axis:%) of the leak light at the time of black display in the 1st area | region 5, and the angle difference of the pretilt of the liquid crystal layer 15 and the liquid crystal layer 45 It is a graph showing the relationship with (horizontal axis: ΔPT (°)). It is a figure for demonstrating the effect of the liquid crystal display panel 100, and the average ratio (vertical axis:%) of the leakage light at the time of black display in the 1st area | region 5, and the pretilt angle (horizontal axis: PT2) in the liquid crystal layer 15. It is the graph showing the relationship with. It is a figure for demonstrating the effect of the liquid crystal display panel 100, The average ratio (vertical axis:%) of the leakage light at the time of black display in the 1st area | region 5, and the retardation of the compensation board 40 with respect to the retardation of the liquid crystal layer 15 It is a graph showing the relationship with a ratio (horizontal axis:%).

  Hereinafter, a liquid crystal display device 1 and a liquid crystal display panel 100 according to an embodiment of the present invention will be described with reference to the drawings. However, the scope of the present invention is not limited to the following embodiments.

  FIG. 1 is a perspective view schematically showing the configuration of the liquid crystal display device 1. As shown in FIG. 1, a liquid crystal display device 1 includes a TFT substrate 10 and a counter substrate (CF substrate) facing each other across a liquid crystal layer (first liquid crystal layer) 15 (which will be described later with reference to FIG. 2). 20, a first polarizing plate 60 and a second polarizing plate 70 disposed outside the TFT substrate 10 and the counter substrate 20, and a backlight unit 90 that emits display light toward the first polarizing plate 60. And.

  A plurality of scanning lines (gate bus lines) and a plurality of signal lines (data bus lines) are arranged on the TFT substrate 10 so as to be orthogonal to each other. Near each intersection of the plurality of scanning lines and the plurality of signal lines, a TFT as an active element is formed for each pixel 7 (described later with reference to FIG. 3). Here, one pixel 7 is defined as a region delimited by two adjacent scanning lines and two adjacent signal lines. Each pixel 7 is provided with a pixel electrode 12 made of, for example, ITO (Indium Tin Oxide), which is electrically connected to the drain electrode of the TFT (described later with reference to FIG. 3). A storage capacitor line (also referred to as a storage capacitor line or a Cs line) may extend in parallel with the scan line between two adjacent scan lines.

  The plurality of scanning lines and the plurality of signal lines are respectively connected to the scanning line driving circuit 80 and the signal line driving circuit 82, and the scanning line driving circuit 80 and the signal line driving circuit 82 are connected to the control circuit 84. . In accordance with control by the control circuit 84, a scanning signal for switching on / off of the TFT is supplied from the scanning line driving circuit 80 to the plurality of scanning lines. In addition, a display signal (voltage applied to the pixel electrode 12) is supplied from the signal line driving circuit 82 to the plurality of signal lines in accordance with control by the control circuit 84.

  The counter substrate 20 includes a color filter and a common electrode 22 (which will be described later with reference to FIG. 3). In the case of displaying three primary colors, the color filter includes an R (red) filter, a G (green) filter, and a B (blue) filter, each of which is arranged corresponding to the pixel 7. The common electrode 22 is formed so as to cover the plurality of pixel electrodes 12. In accordance with the potential difference applied between the common electrode 22 and each pixel electrode 12, the liquid crystal molecules between both electrodes are aligned for each pixel 7 and display is performed.

  FIG. 2 is a perspective view schematically showing the layer configuration of the liquid crystal display panel 100 according to the present invention, and FIG. 3 is a cross-sectional view schematically showing the layer configuration of one pixel 7 in the liquid crystal display panel 100. is there. The liquid crystal display panel 100 corresponds to a portion sandwiched between the first polarizing plate 60 and the second polarizing plate 70 excluding the backlight unit 90 in the liquid crystal display device 1.

  2 and 3, the liquid crystal display panel 100 includes a first polarizing plate 60, a TFT substrate 10, a counter substrate 20, a liquid crystal layer 15 disposed between the TFT substrate 10 and the counter substrate 20, and a first Two polarizing plates 70 are provided. The liquid crystal layer 15 includes a vertical alignment type liquid crystal (first liquid crystal) 16 having negative dielectric anisotropy. The TFT substrate 10 includes a transparent substrate 11, a pixel electrode 12 disposed for each pixel 7 on the transparent substrate 11, an alignment layer 13 that is a vertical alignment film formed so as to cover the pixel electrode 12, and a liquid crystal of the alignment layer 13. The orientation control layer 14 formed on the layer 15 side is included. Each pixel 7 is divided into two regions, a first region 5 and a second region 6. The alignment control layer 14 includes a first alignment control layer 14 a formed in the first region 5 of the pixel 7 and a second alignment control layer 14 b formed in the second region 6.

  The counter substrate 20 includes a transparent substrate 21, a retardation plate 50 disposed on the liquid crystal layer 15 side of the transparent substrate 21, a compensation plate 40 disposed on the liquid crystal layer 15 side of the retardation plate 50, and a liquid crystal layer of the compensation plate 40. A laminated substrate 30 is provided on the 15 side. As shown in FIG. 2, a liquid crystal layer (second liquid crystal layer) 45 including a liquid crystal (second liquid crystal) 43 is formed between the pair of substrates 41 and 42 of the compensation plate 40. The liquid crystal 43 is a discotic liquid crystal, but a chiral nematic liquid crystal (cholesteric liquid crystal) may be used instead.

  The laminated substrate 30 includes a common electrode 22, an alignment layer 23 that is a vertical alignment film formed on the liquid crystal layer 15 side of the common electrode 22, and an alignment control layer 24 formed on the liquid crystal layer 15 side of the alignment layer 23. . The alignment control layer 24 includes a first alignment control layer 24 a formed in the first region 5 of the pixel 7 and a second alignment control layer 24 b formed in the second region 6. The compensation plate 40 includes a first compensation layer 40 a formed in the first region 5 and a second compensation layer 40 b formed in the second region 6.

  The alignment layers 13 and 23 are vertical alignment films applied on the opposing surfaces of both substrates before the TFT substrate 10 and the counter substrate 20 are bonded, and the liquid crystal 16 contained in the liquid crystal layer 15 is perpendicular to the substrate surface. It has a function of aligning in the z direction shown in FIG. The alignment control layers 14 and 24 are polymer layers formed by the PSA method described above, and give the liquid crystal 16 a pretilt inclined by a predetermined angle 17 from a direction perpendicular to the substrate surface. The azimuth angle of the pretilt (in the xy plane which is the substrate surface) is 45 °, 135 °, 225 °, or 315 °, where the x axis is 0 ° and the counterclockwise direction is the positive direction.

  As a material for the alignment layers 13 and 23, for example, a polyimide vertical alignment film manufactured by JSR is used. As a means for giving a pretilt to the liquid crystal 16, an MVA method or a VA method in which the liquid crystal 16 is aligned using protrusions or slits of electrodes, a method of giving a pretilt by rubbing, or the like may be used. For the liquid crystal 16, ZLI-4792 manufactured by Merck is used. The thickness of the liquid crystal layer 15 is, for example, 4 μm. As the spacer for maintaining the thickness of the liquid crystal layer 15, a spherical spacer such as micropearl is used. Moreover, as a monomer mixed in the liquid crystal layer 15, for example, a bifunctional methacryloyl monomer is used. The monomer is added in an amount of 0.3 wt% or more with respect to the liquid crystal 16.

  The 1st polarizing plate 60 and the 2nd polarizing plate 70 are mutually arrange | positioned at cross Nicol. The absorption axis of the first polarizing plate 60 extends in the y direction (azimuth angle 90 ° direction), and the absorption axis of the second polarizing plate 70 extends in the x direction (azimuth angle 0 ° direction). By arranging both polarizing plates in this way, a normally black liquid crystal display panel 100 (a black display is made when no voltage is applied to the liquid crystal layer 15) is obtained. In addition, since the pretilt azimuth angle of the liquid crystal 16 and the absorption axes of both polarizing plates are arranged to be different by 45 °, display with less light leakage is possible.

The retardation of the liquid crystal layer 15 (Δn · d: Δn is birefringence in the liquid crystal layer 15 and d is the thickness of the liquid crystal layer 15) is 290 nm. The liquid crystal 16a of the liquid crystal layer 15 in the first region 5 is given a pretilt (θ ₁ ) of 80 ° by the alignment control layers 14a and 24a (the substrate surface is 0 ° and the z direction is 90 °). In addition, the liquid crystal 16b in the second region 6 is given a pretilt (θ ₃ ) with a polar angle of 89 ° by the alignment control layers 14b and 24b.

  Next, a method for forming the orientation control layers 14 and 24 will be described with reference to FIG.

First, a mask 96 that transmits, for example, irradiation light 95 that is, for example, UV light (ultraviolet light) is disposed only on the first region 5 above the transparent substrate 21, and the liquid crystal layer 15 is provided with, for example, 20 J through the mask 96. Irradiate with UV light of / cm ² or more. At this time, predetermined voltage V1 (e.g., 20V) are applied, the liquid crystal 16 is oriented in a predetermined angle theta ₁ is provided between the pixel electrode 12 and the common electrode 22. By irradiation with UV light, the monomer contained in the liquid crystal layer 15 in the first region 5 is cured to form the alignment control layers 14 a and 24 a, and a pretilt of an angle θ ₁ (polar angle 80 °) is given to the first region 5. It is done.

Next, the position of the mask 96 is shifted, and the irradiation light 95 is selectively transmitted only to the second region 6. At this time, a voltage V2 smaller than the voltage V1 is applied between the pixel electrode 12 and the common electrode 22, and the liquid crystal 16 has a polar angle larger than the angle θ ₁ (more perpendicular to the substrate surface). An orientation of (close) angle θ ₃ is given. The monomer contained in the liquid crystal layer 15 in the second region 6 is cured by the irradiation light 95 to form the alignment control layers 14 b and 24 b, and a pretilt of an angle θ ₃ (polar angle 89 °) is given to the second region 6. . After the alignment control layers 14 and 24 are formed, it is desirable to further irradiate the liquid crystal 16 with ultraviolet rays for several hours with a black light in order to reduce the residual monomer.

  The retardation plate 50 is a uniaxial retardation plate, and the retardation of the retardation plate 50 (Δn · d: Δn is birefringence in the retardation plate 50, and d is the thickness of the retardation plate 50) is 100 nm. The optical axis of the phase difference plate 50 extends in the x direction.

The compensation plate 40 includes a liquid crystal layer 45 including a liquid crystal 43 that is a discotic liquid crystal, which is sealed between two substrates 41 and 42. As the liquid crystal 43, a chiral nematic liquid crystal may be used. x-direction, when the y-direction, and z-direction of the refractive index, which is a n _x, n _y, and n _z, respectively, compensation plate 40, n _x = n _y> of n _z, the refractive index ellipsoid of the so-called cushion-shaped An optical layer having a body. The compensation plate 40 includes a first compensation layer 40 a provided in the first region 5 and a second compensation layer 40 b provided in the second region 6.

  The compensation plate 40 is formed as follows. First, after an alignment film is applied to the inside of the substrates 41 and 42, a discotic liquid crystal is applied on the alignment film. The discotic liquid crystal is polymerized by irradiating with UV light in a state where a pretilt is applied to the discotic liquid crystal by a method such as voltage application. The pretilt to the discotic liquid crystal may be given as follows.

  First, after an alignment film including a cinnamoyl group is applied to the inside of the substrates 41 and 42, only the substrates 41 and 42 in the first region 5 are irradiated with UV light from a direction with a small polar angle. Next, only the substrates 41 and 42 in the second region 6 are irradiated with UV light from a direction having a large polar angle. Thereafter, by injecting a discotic liquid crystal between the alignment films thus aligned, two different pretilts are given to the liquid crystal molecules. The pretilt angle in the first region 5 is, for example, 80 °, and the pretilt angle in the second region 6 is, for example, 89 °.

  Alternatively, the first compensation layer 40a and the second compensation layer 40b having different pretilt angles may be formed by patterning the alignment film. In order to vary the pretilt, it is possible to partially cover the compensation plate 40 by disposing a plastic substrate that can be peeled off via a spacer, and then irradiate UV light thereon. As the polymerizable discotic liquid crystal, the liquid crystal described in Patent Document 1 can be used.

A pretilt is also given to the liquid crystal 43 in the liquid crystal layer 45. The pretilt angle 44 of the liquid crystal 43 in the first compensation layer 40a is larger than the pretilt angle 44 of the liquid crystal 43 in the second compensation layer 40b (closer to the substrate surface). The inclination angle (polar angle when the direction perpendicular to the substrate surface is 90 °) θ ₂ of the optical axis closer to the z direction of the refractive index ellipsoid in the first compensation layer 40a is, for example, 80 °. The inclination angle θ ₄ of the optical axis closer to the z direction of the refractive index ellipsoid in the second compensation layer 40b with respect to the substrate surface is, for example, 89 °.

Here, when the liquid crystal 43 of the compensation plate 40 is a discotic liquid crystal, the tilt angle θ ₂ is the tilt angle of the optical axis closer to the z axis of the discotic liquid crystal. When the liquid crystal 43 is a chiral nematic liquid crystal, the tilt angle θ ₂ is the tilt angle of the helical axis of the chiral nematic liquid crystal.

In the first region 5, the pretilt angle θ ₁ of the liquid crystal layer 15 and the tilt angle θ ₂ of the optical axis in the first compensation layer 40 a of the compensation plate 40 are preferably substantially the same,
θ ₁ -5 ° ≦ θ ₂ ≦ θ ₁ + 5 °
It is preferable that the relationship is satisfied. By setting both angles in this way, light leakage by the liquid crystal layer 15 in the first region 5 can be efficiently prevented by the first compensation layer 40a.

Since the pretilt angle of the liquid crystal 16a in the first region 5 is relatively large, the threshold voltage of the liquid crystal alignment is relatively low in the first region 5, and the power consumption by display can be reduced. Along with this, in the first region 5, there is a risk that light leakage during black display may increase, but light leakage can be prevented by the first compensation layer 40a formed in the first region, so that the contrast is increased. Can be maintained. The pretilt angle θ ₁ in the first region 5 is preferably 75 ° to 85 °. As a result, it is possible to provide the liquid crystal display panel 100 with a sufficiently high contrast and low power consumption.

The tilt angle θ ₃ of the liquid crystal 16 b of the liquid crystal layer 15 in the second region 6 is set larger than the tilt angle θ ₁ of the liquid crystal 16 a in the first region. Since the two tilt angles are different, different VT characteristics can be obtained in the two regions 5 and 6, and a display with less dependence on luminance or gradation on the viewing angle can be obtained. In order to obtain a sufficient viewing angle characteristic, it is preferable to give a difference of 0.3 V or more between the threshold voltage in the first region 5 and the threshold voltage in the second region 6.

Further, the inclination angle θ ₄ of the refractive index ellipsoid in the second compensation layer 40b is also different from the inclination angle θ ₂ in accordance with the difference between the inclination angle θ ₁ and the inclination angle θ ₃ (θ ₄ > θ ₂ ), Light leakage by the liquid crystal layer 15 in the second region 6 is prevented by the second compensation layer 40b.

  In order to realize a fast response speed and a lower driving voltage, a certain amount of pretilt is given to the liquid crystal 43 of the second compensation layer 40b also in the second region 6. In order to ensure high contrast in the second region 6, the pretilt angle is preferably 87 ° or more and less than 90 °. Therefore, in the present embodiment, the pretilt angle in the second region 6 is set to 89 °.

  The VT characteristics were evaluated by applying a voltage with a transmittance of 10% when the transmittance at a voltage of 0 V was 0% and the transmittance at a voltage of 5 V was 100%.

  FIG. 5 is a graph showing the relationship between the VT characteristic and the pretilt angle of the liquid crystal 16. This graph shows the transmittance (vertical axis:%) and applied voltage (horizontal) when the pretilt angles are 89 ° (a), 80 ° (b), 70 ° (c), and 60 ° (d). Each correspondence with the axis: V) is shown.

  FIG. 5 shows that when the pretilt angle is 60 ° and 70 °, black display (transmittance 0%) cannot be obtained when the applied voltage is 0 V, and when the pretilt angle is 80 ° and 89 °, the voltage is applied. It is shown that sufficient black display can be obtained even when the voltage is 0V. This shows that a pretilt angle of about 75 ° or more is necessary to obtain a black display when no voltage is applied. Therefore, it is necessary to give a pretilt angle of about 75 ° or more to both the liquid crystal 16a in the first region 5 and the liquid crystal 16b in the second region 6.

  FIG. 6 is a graph showing the relationship between the threshold voltage difference (vertical axis: ΔV) in the first region 5 and the second region 6 and the pretilt (horizontal axis: PT1) of the liquid crystal 16a in the first region 5. This graph shows that a threshold voltage difference (ΔV) of 0.3 V or more is obtained when the pretilt angle is 85 ° or less. The pretilt angle of the second region 6 is 89 °.

  It is desirable to set the pretilt angle smaller for ease of manufacturing. Further, when the pretilt angle is large, there is a problem that a gradation display compensation effect cannot be obtained sufficiently. Furthermore, in order to realize a sufficient gradation display compensation effect, ΔV (also referred to as voltage shift) of 0.3 V or more is necessary. Therefore, the liquid crystal 16a in the first region 5 needs a pretilt angle of 85 ° or less.

Based on the above examination, in the present embodiment, the pretilt angle θ ₁ in the first region 5 is set within the range of 75 ° to 85 °.

FIG. 7 shows the average ratio of leakage light (vertical axis:%) during black display in the first region 5 and the angle difference between the pretilts of the liquid crystal layer 15 and the liquid crystal layer 45 (horizontal axis: ΔPT (°)). Represents a relationship. This angle difference (ΔPT) is equal to the pretilt angle (θ ₁ ) given by the first alignment control layer 14a in the first region 5 and the optical axis closer to the z direction of the refractive index ellipsoid in the first compensation layer 40a. It can also be said to be a difference from the inclination angle (θ ₂ ).

Referring to FIG. 7, when the angle difference (ΔPT) is within a range of ± 5 °, that is, θ ₁ and θ ₂ are
θ ₁ -5 ° ≦ θ ₂ ≦ θ ₁ + 5 °
It can be seen that the ratio of leakage light is 0.3% or less when the above relationship is satisfied. The lower limit of the contrast that does not cause discomfort in the image display is 100. In order to realize a contrast of 100 or more, the leakage light needs to be 0.3% or less. Therefore, in order to obtain a contrast that does not cause discomfort, the angle difference (ΔPT) is within ± 5 °. Must be set to a range.

FIG. 8 shows the relationship between the average ratio of leakage light (vertical axis:%) during black display and the pretilt angle (horizontal axis: PT2 = θ ₁ ) in the liquid crystal layer 15 in the first region 5. Here, the average ratio of leaked light during black display is the average ratio of leaked light after compensation by the compensation plate 40.

  From FIG. 8, when the pretilt angle becomes 75 ° or less, the average value of the leaked light rapidly increases exceeding 0.3% even if compensation is performed by the compensator 40 to which the pretilt of substantially the same angle is given. I understand. As described above, the contrast value that does not cause discomfort is 100 or more. In order to realize this, it is necessary that leakage light is 0.3% or less, that is, the pretilt angle of the liquid crystal is larger than 75 °.

  FIG. 9 shows the relationship between the average ratio of leakage light during black display (vertical axis:%) and the ratio of retardation of the compensation plate 40 to the retardation of the liquid crystal layer 15 (horizontal axis:%) in the first region 5. Represents.

  FIG. 9 shows that when the retardation of the compensation plate 40 is not in the range of 50% to 80% with respect to the retardation of the liquid crystal layer 15, the average ratio of leaked light exceeds 0.3%. Therefore, in the present embodiment, the retardation of the compensation plate is set in the range of 50% to 80% of the retardation of the liquid crystal layer 15.

  According to the present invention, power consumption of a liquid crystal display panel and a liquid crystal display device excellent in viewing angle characteristics and contrast can be reduced.

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 5 1st area | region 6 2nd area | region 7 Pixel 10 TFT substrate 11 Transparent substrate 12 Pixel electrode 13 Orientation layer 14 Orientation control layer 14a 1st orientation control layer 14b 2nd orientation control layer 15 Liquid crystal layer 16, 16a, 16b Liquid crystal 17 Pretilt angle 20 Counter substrate 21 Transparent substrate 22 Common electrode 23 Alignment layer 24 Alignment control layer 24a First alignment control layer 24b Second alignment control layer 30 Multilayer substrate 40 Compensation plate 40a First compensation layer 40b Second compensation layer 41, 42 substrate 43 liquid crystal 44 pretilt angle 45 liquid crystal layer 50 phase difference plate 60 first polarizing plate 70 second polarizing plate 80 scanning line driving circuit 82 signal line driving circuit 84 control circuit 90 backlight unit 95 irradiation light 96 mask 100 liquid crystal display panel

Claims (8)

A vertical alignment type liquid crystal display panel having a plurality of pixels,
A TFT substrate;
A counter substrate disposed opposite the TFT substrate;
A first liquid crystal layer including a first liquid crystal disposed between the TFT substrate and the counter substrate;
An alignment control layer formed on the first liquid crystal layer side surface of the TFT substrate and the counter substrate;
A compensator made of a second liquid crystal layer including a second liquid crystal, disposed on the opposite substrate to the opposite side of the first liquid crystal layer,
Each of the plurality of pixels includes a first region and a second region;
The tilt angle of the first liquid crystal when the voltage is not applied to the first liquid crystal layer with respect to the substrate surface of the counter substrate in the first region is θ ₁ , and the refractive index ellipsoid of the second liquid crystal layer is When the inclination angle of the optical axis closer to the direction perpendicular to the substrate surface is θ ₂ ,
θ ₁ -5 ° ≦ θ ₂ ≦ θ ₁ + 5 °
Meet the LCD panel. The liquid crystal display panel according to claim 1, wherein the inclination angle θ ₁ is not less than 75 ° and not more than 85 °. In the second region, when the inclination angle of the first liquid crystal with respect to the substrate surface when no voltage is applied to the first liquid crystal layer is θ ₃ , the inclination angle θ ₃ is the inclination angle θ _1. The liquid crystal display panel according to claim 1, wherein the liquid crystal display panel is larger than the liquid crystal display panel. When the tilt angle of the optical axis closer to the direction perpendicular to the substrate surface of the refractive index ellipsoid of the second liquid crystal layer in the second region is θ ₄ , the tilt angle θ ₄ is the tilt angle θ _2. The liquid crystal display panel according to claim 1, wherein the liquid crystal display panel is larger than the liquid crystal display panel. The second liquid crystal is a discotic liquid crystal, and the tilt angle θ ₂ is a tilt angle of an optical axis closer to a direction perpendicular to the substrate surface of the discotic liquid crystal. LCD panel. 5. The liquid crystal display panel according to claim 1, wherein the second liquid crystal is a chiral nematic liquid crystal, and the tilt angle θ ₂ is a tilt angle of a helical axis of the chiral nematic liquid crystal.   7. The liquid crystal display panel according to claim 1, wherein in the first region, the retardation of the compensation plate is 50% or more and 80% or less of the retardation of the first liquid crystal layer.   The alignment control layer is a polymer layer formed by curing a monomer mixed with the first liquid crystal in the first liquid crystal layer while applying a voltage to the first liquid crystal layer. 8. A liquid crystal display panel according to any one of 7 above.

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