JP2009092815A - Liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of enhancing contrast and responsivity to voltage with good balance. <P>SOLUTION: A liquid crystal layer 40 is sealed between a TFT substrate 20 and a CF substrate 30. The liquid crystal layer 40 contains liquid crystal molecules 41A held by a polymer 42A fixed to an alignment layer 22 covering the TFT substrate 20, liquid crystal molecules 41B held by a polymer 42B fixed to an alignment layer 32 covering the CF substrate 30 and liquid crystal molecules 41C positioned in an intermediate region in the thickness direction of the liquid crystal layer 40. A pretilt angle θ1 is imparted to the liquid crystal molecules 41A by presence of the polymer 42A and a pretilt angle θ2 smaller than the pretilt angle θ1 is imparted to the liquid crystal molecules 41B by presence of the polymer 42B. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display element in which a liquid crystal layer is sealed between a pair of substrates.

  In recent years, a liquid crystal display (LCD) is often used as a display monitor for liquid crystal televisions, notebook computers, car navigation systems, and the like. Liquid crystal displays are classified into various modes (methods) according to the molecular arrangement between the panel substrates. For example, a TN (Twisted Nematic) mode in which liquid crystal molecules are twisted and aligned when no voltage is applied. Is well known. In this TN mode, the liquid crystal molecules have a positive dielectric anisotropy, that is, the property that the dielectric constant in the major axis direction of the molecules is larger than that in the minor axis direction, and the in-plane parallel to the substrate surface The liquid crystal molecules are aligned in the direction perpendicular to the surface of the substrate while sequentially rotating the orientation direction of the liquid crystal molecules.

  On the other hand, attention has been focused on a VA (Vertical Alignment) mode in which liquid crystal molecules in a state where no voltage is applied are aligned perpendicularly to the surface of the substrate. In the vertical alignment type VA mode, the liquid crystal molecules have a negative dielectric anisotropy, that is, the property that the dielectric constant in the major axis direction of the molecules is smaller than that in the minor axis direction. A corner can be realized.

  In such a VA mode liquid crystal display, when a voltage is applied, the liquid crystal molecules aligned perpendicular to the substrate are tilted (raised) in a direction parallel to the substrate due to negative dielectric anisotropy. By responding like this, it is the structure which permeate | transmits light. However, since the direction in which the liquid crystal molecules aligned in the direction perpendicular to the substrate is tilted is arbitrary, the alignment of the liquid crystal molecules is disturbed by the application of a voltage, which is a factor of deteriorating the response characteristics to the voltage.

Therefore, as a means for regulating the direction of tilting in response to a voltage, a polymer having a predetermined structure is formed on the opposite surface side of the substrate, and liquid crystal molecules are tilted in a specific direction from a direction perpendicular to the substrate (so-called pretilt). A technique for providing corners is disclosed. With such a configuration, the direction in which the liquid crystal molecules fall when a voltage is applied can be determined in advance, and the response characteristics with respect to the voltage can be improved.
Japanese Patent Laid-Open No. 2003-177408

  However, in the configuration of Patent Document 1 described above, the liquid crystal molecules are aligned slightly tilted with respect to the substrate normal even when not driven (black display), so that the response speed to voltage is improved. However, there is a problem that the light is slightly transmitted during black display and the contrast is lowered. Therefore, it is desired to realize a liquid crystal display element capable of improving the contrast and the response speed with respect to voltage in a well-balanced manner and a manufacturing method thereof.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a liquid crystal display element capable of improving the contrast and the response speed to the voltage in a balanced manner.

  The liquid crystal display element of the present invention has a pair of substrates arranged opposite to each other and a liquid crystal layer provided between the pair of substrates and containing liquid crystal molecules. Here, the liquid crystal molecules located on one side of the pair of substrates have a different pretilt angle than the liquid crystal molecules located on the other side of the pair of substrates. The pretilt angle refers to an inclination angle with respect to the normal line of the substrate in the axial direction serving as a reference for liquid crystal molecules.

  In the liquid crystal display element of the present invention, in the liquid crystal layer provided between the pair of substrates, the liquid crystal molecules located on one substrate side have a different pretilt angle than the liquid crystal molecules located on the other substrate side. The transmission amount of light in the non-driving state (black display state) is reduced without deteriorating the response speed to.

  According to the liquid crystal display element of the present invention, in the liquid crystal layer, the pretilt angle of the liquid crystal molecules located on the other substrate side can be further reduced while the pretilt angle of the liquid crystal molecules located on the one substrate side is further increased. Therefore, the response speed to the voltage and the contrast can be improved in a balanced manner.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a schematic cross-sectional view of a liquid crystal display element according to the first embodiment of the present invention. This liquid crystal display element has a plurality of pixels 10 (10A, 10B, 10C...) And is arranged between a TFT (Thin Film Transistor) substrate 20 and a CF (Color Filter) substrate 30. Further, the liquid crystal layer 40 is provided through the alignment films 22 and 32. The display mode of this liquid crystal display element is a so-called vertical alignment (VA) mode. FIG. 1 shows a non-driving state in which no driving voltage is applied. In addition, in this specification including FIG. 1, the illustration about the specific structure in the TFT substrate 20 and the CF substrate 30 is abbreviate | omitted.

  The TFT substrate 20 has a plurality of pixel electrodes 20B arranged in a matrix, for example, on the surface of the glass substrate 20A on the side facing the CF substrate 30. Further, the plurality of pixel electrodes 20B are provided with a TFT switching element having a gate, a source, a drain and the like for driving each pixel electrode, and a gate line and a source line (not shown) connected to the TFT switching element. Has been. The pixel electrode 20B is provided for each pixel electrically separated by the pixel separation unit 50 on the glass substrate 20A, and is formed of a transparent electrode such as ITO (indium tin oxide). The pixel electrode 20B is provided with a slit portion 21 (a portion where no electrode is formed) having, for example, a stripe shape or a V-shaped pattern in each pixel.

  The CF substrate 30 is a color filter (not shown) in which, for example, red (R), green (G), and blue (B) filters are provided in a stripe pattern on the surface of the glass substrate 30A on the side facing the TFT substrate 20. And the counter electrode 30B is disposed over almost the entire effective display area. The counter electrode 30B is configured by a transparent electrode such as ITO (indium tin oxide). In each pixel, the slit portion 31 is provided in the same pattern as the pixel electrode 20B. In this case, the slit portions 21 and 31 of the pixel electrode 20B and the counter electrode 30B are arranged so as not to face each other between the substrates. As a result, when a driving voltage is applied, an oblique electric field is applied to the long axis of the liquid crystal molecules, thereby improving the response speed to the voltage and forming regions with different alignment directions in the pixels (alignment). Viewing angle characteristics are improved.

  The liquid crystal layer 40 is composed of a vertically aligned liquid crystal, and has, for example, a rotationally symmetric shape with a major axis and a minor axis orthogonal to each other as central axes, and a liquid crystal molecule 41 having a negative dielectric anisotropy and an alignment. Polymers 42A and 42B are provided on the surfaces of the films 22 and 32 and hold the liquid crystal molecules 41 in the vicinity thereof.

  Specifically, the liquid crystal molecules 41 are arranged in the vicinity of the interface between the liquid crystal layer 41A in the liquid crystal layer 40 and the alignment film 32 in the liquid crystal layer 40 and in the vicinity of the interface between the alignment film 32 in the liquid crystal layer 40 and the polymer 42B. Can be classified into the liquid crystal molecules 41B held by and the other liquid crystal molecules 41C. The liquid crystal molecules 41C are located in an intermediate region in the thickness direction of the liquid crystal layer 40, and are arranged so that the major axis of the liquid crystal molecules 41C is substantially perpendicular to the glass substrates 20A and 30A when the driving voltage is off. When the driving voltage is turned on, the liquid crystal molecules 41C are tilted and aligned so that the major axis is parallel to the glass substrates 20A and 30A. Such a behavior is attributed to the fact that the liquid crystal molecules 41C have a property that the dielectric constant in the major axis direction is larger than that in the minor axis direction. Since the liquid crystal molecules 41A and 41B have similar properties, the liquid crystal molecules 41A and 41B basically exhibit the same behavior as the liquid crystal molecules 41C according to the on / off state change of the drive voltage. However, in a state where the driving voltage is off, the liquid crystal molecules 41A are given a pretilt angle θ1 due to the presence of the polymer 42A, and the major axis thereof is inclined from the normal direction of the glass substrates 20A and 30A. Similarly, the liquid crystal molecules 41B are given a pretilt angle θ2 due to the presence of the polymer 42B, and the major axis thereof is inclined from the normal direction of the glass substrates 20A and 30A. As shown in FIG. 2, the pretilt angle θ (θ1, θ2) is a liquid crystal molecule 41 with respect to the Z direction when the direction (normal direction) perpendicular to the surfaces of the glass substrates 20A and 30A is Z. The inclination angle in the major axis direction D of (41A to 41C) shall be said.

  In the present embodiment, both the pretilt angles θ1 and θ2 have values larger than 0 °, and the pretilt angle θ1 applied to the liquid crystal molecules 41A on the TFT substrate 20 side is the liquid crystal molecules on the CF substrate 30 side. It is configured to be larger than the pretilt angle θ2 given to 41B. That is, the pretilt angles θ1 and θ2 satisfy the relationship 0 <θ2 <θ1. In particular, the pretilt angle θ1 is preferably 1 ° or more and 4 ° or less. In such a range, the response speed with respect to the application of the drive voltage is improved as compared with the case where both the pretilt angles θ1 and θ2 are 0 °, and almost the same as when both the pretilt angles θ1 and θ2 are 0 °. This is because an equivalent contrast can be obtained.

  The polymers 42A and 42B are made of a polymer material obtained by polymerizing a radical polymerizable monomer having a property of being polymerized by irradiation with ultraviolet light.

  The alignment films 22 and 32 are vertical alignment films that align the liquid crystal molecules 41 in a direction perpendicular to the substrate surface, and are made of an organic material such as polyimide, for example. The alignment films 22 and 32 may be further subjected to a process for regulating the alignment direction such as rubbing.

  In the liquid crystal display element of the present embodiment having such a configuration, when a drive voltage is applied between the pixel electrode 20B and the counter electrode 30B based on image data, the liquid crystal molecules 41 in the liquid crystal layer 40 are tilted. In response, display is performed by transmitting and modulating light. At this time, in the liquid crystal layer 40 provided between the TFT substrate 20 and the CF substrate 30, the liquid crystal molecules 41A and 41B have predetermined pretilt angles θ1 and θ2, respectively. Compared with a liquid crystal display element that is not, the response speed to the drive voltage can be greatly improved. On the other hand, the liquid crystal molecules 41B have a pretilt angle θ2 smaller than the pretilt angle θ1 of the liquid crystal molecules 41A and are aligned in a state close to the normal direction of the glass substrates 20A and 30A. The amount of transmitted light can be reduced, and the contrast can be improved.

  In other words, conventionally, the same pretilt angle is given to the liquid crystal molecules located on both sides of the counter substrate (TFT substrate and CF substrate), so that the response speed is increased by increasing the pretilt angle. On the other hand, contrast was deteriorated. On the other hand, in the liquid crystal display element of the present embodiment, in the liquid crystal layer 40, for example, the response speed is improved by increasing the pretilt angle θ1 of the liquid crystal molecules 41A located on the TFT substrate 20 side, and the CF substrate 30 is improved. The contrast can be improved by further reducing the pretilt angle θ2 of the liquid crystal molecules 41B located on the side. Therefore, the response speed to the voltage and the contrast can be improved with a good balance.

  Next, the manufacturing method of the liquid crystal display element having such a configuration will be described with reference to the schematic cross-sectional views shown in FIGS. 4 to 6 together with the flowchart shown in FIG. 4 to 6 show only one pixel for simplification.

  First, as shown in FIG. 4, a liquid crystal material is sealed between the TFT substrate 20 and the CF substrate 30 via the alignment films 22 and 32 (step S101).

  Specifically, the pixel substrate 20B and the counter electrode 30B having predetermined slit portions 21 and 31, respectively, are provided on the glass substrate 20A and the glass substrate 30A, for example, in a matrix form, so that the TFT substrate 20 and the CF substrate 30 are formed. After the formation, the alignment films 22 and 32 are formed on the surfaces of the pixel electrode 20B and the counter electrode 30B by applying a vertical alignment agent or printing and baking a vertical alignment film on the substrate. On the other hand, a liquid crystal material is prepared by mixing liquid crystal molecules 41, a monomer 43, and an ultraviolet light absorber 44 as a material constituting the liquid crystal layer 40. The monomer 43 has a property of being polymerized (radical polymerization) by irradiation with ultraviolet light to become polymers 42A and 42B. Examples of the monomer 43 include acrylic monomers such as hexamethylene diacrylate (trade name: manufactured by Shin-Nakamura Chemical Co., Ltd.). The ultraviolet light absorber 44 has a property of absorbing ultraviolet light. For example, an anthracene having a structure represented by Chemical Formula 1 or 2- (2-hydroxy-5- 5 having a structure represented by Chemical Formula 2 is used. t-butylphenyl) -2H-benzotriazole and the like. A photopolymerization initiator (radical polymerization initiator) or the like may be further added to the liquid crystal material.

  Next, spacer projections for securing a cell gap, such as plastic beads, are sprayed on the surface of the TFT substrate 20 or the CF substrate 30 where the alignment films 22 and 32 are formed. For example, the seal portion is printed using an epoxy adhesive or the like by a screen printing method. After that, the TFT substrate 20 and the CF substrate 30 are bonded together via spacer protrusions and a seal portion so that the alignment films 22 and 32 are opposed to each other, and the liquid crystal material is injected. Then, the liquid crystal material is sealed between the TFT substrate 20 and the CF substrate 30 by curing the seal portion by heating or the like.

  Next, as shown in FIG. 5A, a DC voltage V1 is applied between the pixel electrode 20B and the counter electrode 30B using the voltage applying unit 1 (step S102). The DC voltage V1 is applied with a magnitude of, for example, 5 to 30 (V). As a result, a DC electric field is formed in a direction that forms a predetermined angle with respect to the surfaces of the glass substrates 20A and 30A, and the liquid crystal molecules 41 are oriented in a predetermined direction with respect to the normal direction of the glass substrates 20A and 30A. The tilt angle of the liquid crystal molecules 41 at this time is approximately equal to the pretilt angle θ1 given to the liquid crystal molecules 41A in a process described later. Therefore, it is possible to control the magnitude of the pretilt angle θ1 of the liquid crystal molecules 41A by appropriately adjusting the magnitude of the DC voltage V1.

  Furthermore, as shown in FIG. 5B, the monomer 43 is polymerized by irradiating the liquid crystal layer 40 with ultraviolet light UV from the outside of the TFT substrate 20 while the DC voltage V1 is applied. A polymer 42A adhered to the surface is formed (step S103). Here, since the ultraviolet light absorber 44 is contained in the liquid crystal layer 40, the illuminance distribution of the ultraviolet light UV occurs in the thickness direction of the liquid crystal layer 40. Specifically, the illuminance distribution is inclined so that the illuminance of the ultraviolet light UV decreases from the TFT substrate 20 toward the CF substrate 30. For this reason, the monomer 43 moves to the TFT substrate 20 side on which the ultraviolet light UV is incident, and is polymerized. The polymer 42A thus formed is chemically bonded to the alignment film 22 and has a function of imparting a pretilt angle θ1 to the liquid crystal molecules 41A located in the vicinity of the interface with the alignment film 22 in the liquid crystal layer 40 in a non-driven state. Have.

  After forming the polymer 42A, as shown in FIG. 6A, the DC voltage V2 is applied between the pixel electrode 20B and the counter electrode 30B using the voltage applying means 1 (step S104). As a result, the liquid crystal molecules 41 (excluding the liquid crystal molecules 41A) are aligned in a predetermined direction with respect to the normal direction of the glass substrates 20A and 30A. At this time, the DC voltage V2 is set to a value smaller than the DC voltage V1, so that the tilt angle of the liquid crystal molecules 41 (excluding the liquid crystal molecules 41A) is smaller than the pretilt angle θ1 applied to the liquid crystal molecules 41A. At this time, the tilt angle of the liquid crystal molecules 41 (excluding the liquid crystal molecules 41A) is substantially equal to the pretilt angle θ2 applied to the liquid crystal molecules 41B in a later-described process, and therefore by appropriately adjusting the magnitude of the DC voltage V2, It is possible to control the magnitude of the pretilt angle θ2 of the liquid crystal molecules 41B.

  While the DC voltage V2 is applied, the liquid crystal layer 40 is irradiated with ultraviolet light UV from the outside of the CF substrate 30 as shown in FIG. As a result, the monomer 43 remaining without being polymerized in step S103 is polymerized to form a polymer 42B fixed to the surface of the alignment film 32 (step S105). In this step, since the illuminance distribution of the ultraviolet light UV attenuates as it goes from the CF substrate 30 to the TFT substrate 20 due to the action of the ultraviolet light absorber 44 described above, the monomer 43 of the CF substrate 30 on which the ultraviolet light UV is incident. Will move to the side and polymerize. The polymer 42B thus formed is chemically bonded to the alignment film 32 and has a function of imparting a pretilt angle θ2 to the liquid crystal molecules 41B located in the vicinity of the interface of the liquid crystal layer 40 with the alignment film 32 in the non-driven state. Have.

  Through the above steps, the liquid crystal display element shown in FIG. 1 is completed. Thus, according to the manufacturing method of the liquid crystal display element of this Embodiment, the liquid crystal display element which can exhibit the outstanding response speed performance and contrast performance with sufficient balance can be manufactured efficiently.

  In the present embodiment, the ultraviolet light absorber 44 is added separately from the monomer 43, but the monomer 43 that also has a function as a light absorbing material may be used. Further, the polymer 42A on the TFT substrate 20 side is formed first, but the polymer 42B on the CF substrate 30 side may be formed first. Furthermore, the pretilt angle θ1 is made larger than the pretilt angle θ2, but the magnitude relationship between them may be reversed. In addition, although the DC voltage V1 is applied between the pixel electrode 20B and the counter electrode 30B to apply the DC electric field to the liquid crystal layer 40, the present invention is not limited to this. An AC electric field may be applied to the liquid crystal layer 40 by applying an AC voltage of an asymmetric rectangular wave.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 7 is a schematic cross-sectional view of the liquid crystal display element according to the present embodiment.

  In the present embodiment, the pretilt angle θ1 applied to the liquid crystal molecules 41A on the TFT substrate 20 side is 1 ° or more and 4 ° or less, while the pretilt angle θ2 applied to the liquid crystal molecules 41B on the CF substrate 30 side is 0 °. It is comprised so that. That is, in this liquid crystal display element, there is no equivalent to the polymer 42B in the first embodiment. For this reason, the liquid crystal display element of this Embodiment can obtain a higher contrast compared with the liquid crystal display element in 1st Embodiment, and can be manufactured more simply.

  A method for manufacturing the liquid crystal display element will be described with reference to the schematic cross-sectional views shown in FIGS. 9 to 11 together with the flowchart shown in FIG. 9 to 11 show only one pixel for simplification. In the following, points different from the first embodiment will be described in detail, and other points will be omitted as appropriate.

  First, as shown in FIG. 9, a liquid crystal material is sealed between the TFT substrate 20 and the CF substrate 30 via the alignment films 22 and 32 (step S201).

  Specifically, the pixel substrate 20B and the counter electrode 30B having predetermined slit portions 21 and 31, respectively, are provided on the glass substrate 20A and the glass substrate 30A, for example, in a matrix form, so that the TFT substrate 20 and the CF substrate 30 are formed. After the formation, the alignment films 22 and 32 are formed on the surfaces of the pixel electrode 20B and the counter electrode 30B by applying a vertical alignment agent or printing and baking a vertical alignment film on the substrate. On the other hand, a liquid crystal material is prepared by mixing liquid crystal molecules 41 and an ion polymerizable monomer 45 as a material constituting the liquid crystal layer 40. An ionic polymerization initiator (not shown) or the like may be further added to the liquid crystal material. The ion polymerizable monomer 45 has a property of being polymerized by irradiation with ultraviolet light to become a polymer 42A. Examples of the ion polymerizable monomer 45 include an anionic monomer having the structure shown in Chemical Formula 3 and a cationic monomer having the structure shown in Chemical Formula 4.

  After producing the liquid crystal material, sealing is performed between the TFT substrate 20 and the CF substrate 30 in the same manner as in the first embodiment.

  Next, as shown in FIG. 10A, a DC voltage V1 is applied between the pixel electrode 20B and the counter electrode 30B using the voltage applying means 1 (step S202). At this time, for example, the pixel electrode 20 </ b> B is set to have a polarity with a sign opposite to the charge of the ion polymerizable monomer 45. As a result, the ion polymerizable monomer 45 moves to the vicinity of the interface with the alignment film 22 in the liquid crystal layer 40. At the same time, an electric field in a direction forming a predetermined angle with respect to the surfaces of the glass substrates 20A and 30A is generated, and the liquid crystal molecules 41 are oriented in a predetermined direction from the normal direction of the glass substrates 20A and 30A.

  Further, as shown in FIG. 10B, the ion polymerizable monomer 45 is polymerized by irradiating the liquid crystal layer 40 with ultraviolet light UV, for example, from the outside of the TFT substrate 20 with the DC voltage V1 applied. Then, the polymer 42A fixed to the surface of the alignment film 22 is formed (step S203).

  Through the above steps, the liquid crystal display element shown in FIG. 7 is completed. Thus, according to the manufacturing method of the liquid crystal display element of this Embodiment, the liquid crystal display element which can exhibit the outstanding response speed performance and contrast performance with sufficient balance can be manufactured efficiently.

  In the present embodiment, the polymer 42A is formed so as to be fixed to the alignment film 22 covering the TFT substrate 20, and the pretilt angle θ1 is applied to the liquid crystal molecules 41A located closest to the TFT substrate 20 in the liquid crystal layer 40. However, the present invention is not limited to this. In other words, a polymer is formed so as to be fixed to the alignment film 32 covering the CF substrate 30, and a pretilt angle θ2 is given to the liquid crystal molecules 41B located closest to the CF substrate 30 in the liquid crystal layer 40. Good. However, since the TFT substrate 20 is provided with TFT switching elements and various bus lines and various lateral electric fields are generated during driving, it is desirable to provide the polymer 42A on the TFT substrate 20 side. By doing so, the alignment disorder of the liquid crystal molecules 41 due to such a transverse electric field can be effectively reduced.

  Also in the present embodiment, as in the first embodiment, the ultraviolet light absorber 44 may be included in the liquid crystal layer 40. However, in that case, the ultraviolet light UV is always irradiated from the outside of the substrate (TFT substrate 20 in this embodiment) having a polarity different from that of the ion polymerizable monomer 45. In such a case, a larger amount of the ion polymerizable monomer 45 is collected on the substrate that is irradiated with the ultraviolet light UV (in this embodiment, the TFT substrate 20).

  Hereinafter, specific examples of the present invention will be described.

  In this example, a vertical alignment film was applied to each of a TFT substrate with a 4 μm spacer protrusion and a substrate with an ITO electrode disposed on a color filter. A slit pattern is formed on the ITO so that an electric field is applied obliquely, and the line width is 60 μm and the line is 10 μm. A seal is formed on the substrate, and a liquid crystal material consisting of a negative liquid crystal, an ionic polymerizable monomer that is polymerized by ultraviolet light, and a photopolymerization initiator is dropped into a portion surrounded by the seal, and the substrates are bonded together and sealed. Was cured. The liquid crystal panel thus prepared was irradiated with ultraviolet light with an asymmetric rectangular wave alternating electric field applied to polymerize the ion polymerizable monomer to form a polymer on the surface of the alignment film on the TFT substrate side. . As a result, a liquid crystal display element in which the liquid crystal molecules on the TFT substrate side formed a pretilt angle in a non-driven state was obtained.

  When the liquid crystal display device thus manufactured was driven, the response time (ms; millisecond) and contrast showed behavior as shown in FIG. 11 according to the pretilt angle (°). The drive voltage was 5V. In FIG. 11, a curve C11 represents the relationship between the contrast and the pretilt angle, and curves C12 to C14 represent the relationship between the response speed and the pretilt angle. In detail, the curve 12 represents the time required to reach 90% of the required transmittance after the driving voltage is applied (response time of 0 to 90%), and the curve 13 represents the time when the driving voltage is applied. Represents the time required to reach 10% of the required transmittance (0-10% response time), and curve 14 shows 10% of the required transmittance after the drive voltage is applied. It represents the time (from 10 to 90% response time) until reaching 90% of the required transmittance.

  As a comparative example to this example, the liquid crystal molecules in the liquid crystal layer are configured to have the same pretilt angle both in the vicinity of the interface with the alignment film on the TFT substrate side and in the vicinity of the interface with the alignment film on the CF substrate side. The manufactured liquid crystal display element was produced and the same investigation was performed. The result is shown in FIG. In FIG. 12, the curve C21 represents the relationship between the contrast and the pretilt angle, and the curves C22 to C24 represent the relationship between the response speed and the pretilt angle. In detail, the curve 22 represents the time from when the drive voltage is applied until it reaches 90% of the required transmittance (0 to 90% response time), and the curve 23 represents the time when the drive voltage is applied. Represents the time required to reach 10% of the required transmittance (0-10% response time), and the curve 24 shows 10% of the required transmittance after the drive voltage is applied. It represents the time (from 10 to 90% response time) until reaching 90% of the required transmittance.

  When the curves C12 to C14 (FIG. 11) of the example are compared with the curves C22 to C24 (FIG. 12) of the comparative example, the pretilt angle is larger in the example although the response time is slightly longer overall than the comparative example. The tendency for the response speed to improve is the same as in the comparative example. On the other hand, the contrast deteriorates greatly when the pretilt angle exceeds 3 ° in the comparative example (curve C21), whereas in this example (curve C11), the pretilt angle is substantially constant in the range of 0 ° to 6 °. Value (about 1150). As a result, in the liquid crystal layer, by giving a pretilt angle to the liquid crystal molecules located on either side of the TFT substrate or the CF substrate, the liquid crystal layer has the same pretilt angle on both the TFT substrate side and the CF substrate side. It was found that the contrast and the response speed to voltage can be improved in a better balance than when applied to molecules.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to these embodiments and the like, and various modifications are possible. For example, in the above embodiment, a DC voltage is applied to the liquid crystal layer by applying a DC voltage between the pixel electrode and the counter electrode, but a magnetic field is applied to the liquid crystal layer instead of the electric field. May be.

The structure for providing the pretilt angle may be as follows. For example, alignment films having different orientations may be provided on the TFT substrate side and the CF substrate side. For such an alignment film, for example, a crystal such as silicon oxide (SiO ₂ ) constituting the alignment film may be deposited on each substrate so that the growth direction (growth angle with respect to the substrate surface) is different. The alignment film thus deposited functions to give a pretilt angle to the liquid crystal molecules in the vicinity of the surface in accordance with the crystal growth angle. Alternatively, a photo-alignment film in which anisotropy is induced by irradiation of polarized light may be provided on the TFT substrate side and the CF substrate side. At that time, if a photo-alignment film having different anisotropy directions is provided on the TFT substrate side and the CF substrate side, each photo-alignment film has a different pretilt angle on the liquid crystal molecules in the vicinity of the surface. Can be granted. Further, by providing protrusions (ribs) on the surface of the TFT substrate and the CF substrate that are in contact with the liquid crystal layer, a pretilt angle may be given to the liquid crystal molecules in the vicinity of the protrusions.

It is a cross-sectional schematic diagram of the liquid crystal display element device as 1st Embodiment in this invention. It is a schematic diagram for demonstrating the pretilt angle of a liquid crystal molecule. 2 is a flowchart for explaining a manufacturing method of the liquid crystal display element of FIG. 1. It is a cross-sectional schematic diagram for demonstrating the manufacturing method of the liquid crystal display element of FIG. FIG. 5 is a schematic cross-sectional view for explaining a process following the process in FIG. 4. FIG. 6 is a schematic cross-sectional view for explaining a process following the process in FIG. 5. It is a cross-sectional schematic diagram of the liquid crystal display element device as 2nd Embodiment in this invention. It is a flowchart for demonstrating the manufacturing method of the liquid crystal display element of FIG. It is a cross-sectional schematic diagram for demonstrating the manufacturing method of the liquid crystal display element of FIG. FIG. 10 is a schematic cross-sectional view for illustrating a step following the step in FIG. 9. It is a characteristic view showing the pretilt angle dependency of response time and contrast in the example. It is a characteristic view showing the pretilt angle dependence of response time and contrast in a comparative example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Voltage application means, 10A, 10B ... Pixel, 20 ... TFT substrate, 30 ... CF substrate, 20A, 30A ... Glass substrate, 20B ... Pixel electrode, 30B ... Counter electrode, 22, 32 ... Alignment film, 40 ... Liquid crystal layer 41 (41A, 41B, 41C) ... liquid crystal molecules, 42A, 42B ... polymer, 43 ... monomer, 44 ... ultraviolet light absorber, 45 ... ion polymerizable monomer.

Claims (4)

A pair of substrates disposed opposite to each other, and a liquid crystal layer provided between the pair of substrates and including liquid crystal molecules,
The liquid crystal display, wherein the liquid crystal molecules located on one side of the pair of substrates have a pretilt angle different from that of the liquid crystal molecules located on the other side of the pair of substrates. element. The liquid crystal display element according to claim 1, wherein a pretilt angle of the liquid crystal molecules located on one side of the pair of substrates is 0 (°). The pair of substrates, one is a semiconductor element mounting substrate on which a semiconductor element that drives a plurality of pixel electrodes is mounted, and the other is a color filter mounting substrate having a color filter,
The liquid crystal display element according to claim 1, wherein a pretilt angle of the liquid crystal molecules located on the color filter mounting substrate side is 0 (°). The liquid crystal display element according to claim 1, wherein the liquid crystal layer includes a polymer that imparts a pretilt angle to the liquid crystal molecules.

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