JP2009230069A - Liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display element which is can show a monostable property and showing an electro-optical properties in which transmitted light amount against an impressed voltage is asymmetrical during the drive of the liquid crystal display element even though a ferroelectric liquid crystal is used. <P>SOLUTION: The liquid crystal display element has a first alignment treatment substrate 11a having a first electrode layer 4a and a first alignment film 3a; a second alignment treatment substrate 11b having a second base material, a second electrode layer 4b and a second alignment film 3b; and a liquid crystal layer 5 including a ferroelectric liquid crystal. The first and the second alignment films have compositions in which the constituent materials are different from each other. When the ferroelectric liquid crystal shows a monostable property and the constituent materials of the first and the second alignment films have the same composition, V shaped switching properties are shown during the drive of the liquid crystal display element, and by making the first and the second alignment films have the compositions in which the constituent materials are different from each other, the ferroelectric liquid crystal shows half-V shaped switching properties during the drive of the liquid crystal display element. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a liquid crystal display element using monostable ferroelectric liquid crystal having spontaneous polarization.

  Liquid crystal display elements have been widely used from large displays to portable information terminals because of their thinness and low power consumption, and their development is actively underway. So far, liquid crystal display elements have been developed and put to practical use, such as TN mode, STN multiplex drive, and active matrix drive using thin layer transistors (TFTs) for TN, but these use nematic liquid crystals. In addition, the response speed of the liquid crystal material is as slow as several ms to several tens of ms, and it cannot be said that it is sufficiently compatible with moving image display.

  Ferroelectric liquid crystal (FLC) is a liquid crystal suitable for high-speed devices because its response speed is as short as μs order. Ferroelectric liquid crystal is widely known as a bistable one proposed by Clark and Lagerwol, which has two stable states when no voltage is applied (FIG. 18), but is limited to switching in two states, light and dark. However, although it has a memory property, it has a problem that gradation display cannot be performed.

  In recent years, the state of the liquid crystal layer when no voltage is applied is stabilized in a single state (hereinafter referred to as “monostable”). ) Is continuously changed, and the transmitted light intensity is analog-modulated to attract gradation (see Non-Patent Document 1, FIGS. 2 and 3).

  For example, as shown in FIG. 2, the ferroelectric liquid crystal exhibiting monostability has an electro-optical characteristic in which the amount of transmitted light is asymmetric with respect to the applied voltage so that the liquid crystal molecules operate only when a positive or negative voltage is applied. For example, as shown in FIG. 3, there are an electro-optical characteristic in which the amount of transmitted light is symmetrical with respect to the applied voltage so that the liquid crystal molecules operate when either positive or negative voltage is applied. In particular, the ferroelectric liquid crystal exhibiting electro-optical characteristics in which the amount of transmitted light with respect to the applied voltage is asymmetric has an advantage that the opening time as a black and white shutter can be sufficiently long.

  In recent years, color liquid crystal display elements have been actively developed. As a method for realizing color display, there are generally a color filter method and a field sequential color method. In the color filter system, a white light source is used as a backlight, and color display is realized by attaching R, G, B micro color filters to each pixel. On the other hand, the field sequential color system switches the backlight to R, G, B, R, G, B ... in time, and opens and closes the black and white shutter of the ferroelectric liquid crystal to synchronize with it, and the afterimage effect of the retina Thus, the colors are mixed temporally to realize color display. In this field sequential color system, color display is possible with one pixel, and it is not necessary to use a color filter with low transmittance. Therefore, bright and high-definition color display is possible, and low power consumption and low cost can be realized. Useful in terms.

  In the field sequential color system, one pixel is time-divided, so that a liquid crystal as a black and white shutter needs to have high-speed response in order to obtain good moving image display characteristics. If a ferroelectric liquid crystal is used, this problem can be solved. As the ferroelectric liquid crystal used in this case, it is desirable that the liquid crystal display is monostable in order to enable gradation display by analog modulation as described above and realize high-definition color display. As described above, among the ferroelectric liquid crystals exhibiting monostability, those showing electro-optical characteristics in which the amount of transmitted light is asymmetric with respect to the applied voltage are particularly desirable.

NONAKA, T., LI, J., OGAWA, A., HORNUNG, B., SCHMIDT, W., WINGEN, R., and DUBAL, H., 1999, Liq. Cryst., 26, 1599.

  If a ferroelectric liquid crystal exhibiting electro-optical characteristics with a symmetric amount of transmitted light with respect to an applied voltage can exhibit an electro-optical characteristic with an asymmetric amount of transmitted light with respect to the applied voltage when driving a liquid crystal display element, it exhibits monostability. Regardless of which ferroelectric liquid crystal is used, the opening time as a black and white shutter can be made sufficiently long.

  The present invention has been made in view of such various points, and even when using a ferroelectric liquid crystal exhibiting monostability and exhibiting electro-optical characteristics in which the amount of transmitted light with respect to an applied voltage is symmetric, when driving a liquid crystal display element, A main object is to provide a liquid crystal display element capable of exhibiting electro-optical characteristics in which the amount of transmitted light with respect to an applied voltage is asymmetric.

  In order to achieve the above object, the present invention includes a first base material, a first electrode layer formed on the first base material, and a first alignment film formed on the first electrode layer. A first alignment treatment substrate; a second substrate; a second electrode layer formed on the second substrate; and a second alignment film formed on the second electrode layer. Formed between the first alignment film and the second alignment film disposed so that the first alignment film and the second alignment film face the alignment process substrate; A liquid crystal layer including a dielectric liquid crystal, wherein the constituent material of the first alignment film and the constituent material of the second alignment film have different compositions from each other, the ferroelectric liquid crystal Are monostable, and the constituent material of the first alignment film and the constituent material of the second alignment film are the same. When the liquid crystal display element is driven, the liquid crystal display element exhibits V-shaped switching characteristics, and the constituent material of the first alignment film and the constituent material of the second alignment film have different compositions. By providing the liquid crystal display element, the ferroelectric liquid crystal exhibits a half V-shaped switching characteristic when the liquid crystal display element is driven.

  According to the present invention, since the constituent material of the first alignment film and the constituent material of the second alignment film have different compositions, the surface polarities of the first alignment film and the second alignment film can be made different from each other. Accordingly, when the constituent material of the first alignment film and the constituent material of the second alignment film have the same composition, a ferroelectric liquid crystal exhibiting V-shaped switching characteristics is converted into a half V-shaped when the liquid crystal display element is driven. It is possible to exhibit switching characteristics.

  In the above invention, the second alignment film is formed on the reactive liquid crystal alignment film formed on the second base material and the reactive liquid crystal alignment film, and is fixed by fixing the reactive liquid crystal. It is preferable to consist of a liquid crystal layer. It is considered that the fixed liquid crystal layer tends to have a positive polarity stronger than an alignment film generally used for a liquid crystal display element, for example, a photo-alignment film or a rubbing alignment film. Therefore, the direction of the spontaneous polarization of the ferroelectric liquid crystal can be controlled by using the second alignment film in which the alignment film for reactive liquid crystal and the fixed liquid crystal layer are laminated. Therefore, the ferroelectric liquid crystal can effectively exhibit a half V-shaped switching characteristic.

  In the above case, the first alignment film is preferably a photo-alignment film. The direction of spontaneous polarization of the ferroelectric liquid crystal is effectively controlled by stacking the first alignment film as a photo-alignment film and the second alignment film as a reactive liquid crystal alignment film and a fixed liquid crystal layer. Because it can.

  In the present invention, it is also preferable that the first alignment film is a photo-alignment film using a photoisomerizable material, and the second alignment film is a photo-alignment film using a photodimerization material. Photo-alignment films using photodimerized materials tend to have a stronger positive polarity than photo-alignment films using photoisomerization-type materials, which can change the direction of spontaneous polarization of ferroelectric liquid crystals. Can be controlled. Therefore, the ferroelectric liquid crystal can effectively exhibit a half V-shaped switching characteristic.

  Furthermore, in the present invention, it is also preferable that the first alignment film is a photo-alignment film using a photoisomerizable material and the second alignment film is a rubbing-processed alignment film. The rubbing-treated alignment film is considered to have a stronger positive polarity than the photo-alignment film using the photoisomerization type material, thereby controlling the direction of spontaneous polarization of the ferroelectric liquid crystal. it can. Therefore, the ferroelectric liquid crystal can effectively exhibit a half V-shaped switching characteristic.

  In the present invention, it is also preferable that the first alignment film is a rubbing alignment film, and the second alignment film is a photo-alignment film using a photodimerization type material. A photo-alignment film using a photodimerization type material is considered to have a stronger positive polarity than a rubbing-processed alignment film, thereby controlling the direction of spontaneous polarization of the ferroelectric liquid crystal. . Therefore, the ferroelectric liquid crystal can effectively exhibit a half V-shaped switching characteristic.

  In the above case, it is preferable that the alignment film subjected to the rubbing treatment contains polyimide. The rubbing-treated alignment film preferably contains nylon. This is because such a configuration makes it easier for the ferroelectric liquid crystal to be oriented in the azimuth direction.

  Furthermore, in the present invention, it is preferable to perform display when a negative voltage is applied to the second electrode layer. As described above, by using the first alignment film and the second alignment film as predetermined alignment films, the second alignment film tends to have a relatively positive polarity, and the spontaneous polarization of the ferroelectric liquid crystal Can be controlled. In this way, when the second alignment film tends to have a relatively positive polarity, the inclination angle of the liquid crystal molecules from the mono-stabilized state when the negative voltage of the second electrode layer is applied is When the positive voltage of the second electrode layer is applied, the inclination angle of the liquid crystal molecules from the mono-stabilized state becomes larger. Therefore, it is preferable to perform display when a negative voltage is applied to the second electrode layer, in which the tilt angle from the mono-stabilized state of the liquid crystal molecules becomes larger.

  In the present invention, the constituent material of the first alignment film and the constituent material of the second alignment film have different compositions from each other, so that the surface of the first alignment film and the second alignment film according to these constituent materials. The polarities can be different. As a result, the direction of spontaneous polarization of the ferroelectric liquid crystal can be controlled by the polar surface interaction. Therefore, the constituent material of the first alignment film and the constituent material of the second alignment film have the same composition by making the constituent material of the first alignment film and the constituent material of the second alignment film different from each other. In such a case, the ferroelectric liquid crystal exhibiting the V-shaped switching characteristics can exhibit the half V-shaped switching characteristics.

Hereinafter, the liquid crystal display element of the present invention will be described in detail.
The liquid crystal display element of the present invention includes a first alignment treatment including a first substrate, a first electrode layer formed on the first substrate, and a first alignment film formed on the first electrode layer. A substrate, a second base material, a second electrode layer formed on the second base material, and a second alignment film formed on the second electrode layer; On the other hand, a ferroelectric liquid crystal is formed between the second alignment treatment substrate disposed so that the first alignment film and the second alignment film face each other, and the first alignment film and the second alignment film. A liquid crystal layer, and the constituent material of the first alignment film and the constituent material of the second alignment film have different compositions, wherein the ferroelectric liquid crystal is monostable And the constituent material of the first alignment film and the constituent material of the second alignment film have the same composition When the liquid crystal display device is driven, it exhibits V-shaped switching characteristics, and the constituent material of the first alignment film and the constituent material of the second alignment film have different compositions from each other. Thus, the ferroelectric liquid crystal exhibits a half V-shaped switching characteristic when the liquid crystal display element is driven.

The liquid crystal display element of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing an example of the liquid crystal display element of the present invention. As illustrated in FIG. 1, the liquid crystal display element 1 includes a first alignment treatment substrate 11a in which a first electrode layer 3a and a first alignment film 4a are formed on a first substrate 2a, and a second substrate 2b. The liquid crystal layer 5 is formed between the second alignment processing substrate 11b on which the second electrode layer 3b and the second alignment film 4b are formed, and the first alignment film 4a and the second alignment film 4b, and includes a ferroelectric liquid crystal. It has. Here, the first alignment film 4a and the second alignment film 4b are different in composition of the constituent materials.

  The ferroelectric liquid crystal contained in the liquid crystal layer 5 exhibits monostability, and exhibits a half V-shaped switching characteristic when the liquid crystal display element is driven as illustrated in FIGS. 2 (a) and 2 (b). . Further, this ferroelectric liquid crystal is illustrated in FIG. 3 when the constituent materials of the first alignment film and the second alignment film in the liquid crystal display element 1 illustrated in FIG. 1 have the same composition. It also shows V-shaped switching characteristics when the liquid crystal display element is driven.

  “Showing monostability” means a state in which the state of the ferroelectric liquid crystal when no voltage is applied is stabilized in one state. In the ferroelectric liquid crystal, as illustrated in FIG. 4, the liquid crystal molecules 25 are tilted from the layer normal z and rotate along a cone ridge having a bottom surface perpendicular to the layer normal z. In such a cone, the tilt angle of the liquid crystal molecules 25 with respect to the layer normal z is referred to as a tilt angle θ. Thus, the liquid crystal molecules 25 can operate on the cone between two states inclined by a tilt angle ± θ with respect to the layer normal z. Specifically, the expression of monostability refers to a state in which the liquid crystal molecules 25 are stabilized in any one state on the cone when no voltage is applied.

“Half V-shaped switching characteristics” refers to the transmitted light amount of the applied voltage when the transmitted light amount is small out of the transmitted light amount with respect to the applied voltage when a positive and negative voltage of 10 V is applied to the liquid crystal layer. When the transmitted light amount of the applied voltage when B is large is B, the B / A is 2 or more. Those shown in FIGS. 2A and 2B that exhibit the electro-optical characteristics are said to exhibit half V-shaped switching characteristics.
On the other hand, “V-shaped switching characteristics” refers to the transmitted light amount of the applied voltage when the transmitted light amount is small among the transmitted light amounts with respect to the applied voltage when a positive and negative voltage of 10 V is applied to the liquid crystal layer. When the transmitted light amount of the applied voltage when B is large is B, the B / A is 1.5 or less. The electro-optical characteristic illustrated in FIG. 3 is a V-shaped switching characteristic.

For example, as shown in FIG. 5 (a), the V-shaped switching characteristic is the orientation state (i) when no voltage is applied, and the orientation state (ii) when a positive voltage is applied. Oriented from the back to the front of the paper (marked with ● in Fig. 5 (a)). When a negative voltage is applied, the orientation state is (iii), and the spontaneous polarization is directed from the front of the paper to the back (Fig. 5 (a)). X). That is, the spontaneous polarization is oriented in the horizontal direction with respect to the paper surface when no voltage is applied, and the spontaneous polarization is oriented in the direction perpendicular to the paper surface when a positive or negative voltage is applied.
On the other hand, as shown in FIG. 5 (b), for example, as shown in FIG. 5 (b), the half V-shaped switching characteristic is the orientation state (i), and the spontaneous polarization is directed from the front side to the back side of the page ( When a positive voltage is applied, the orientation state (ii) is obtained, and the spontaneous polarization is directed from the back of the paper to the front (● mark in FIG. 5 (b)), and a negative voltage is applied. In some cases, the orientation state (i) is also reached, and the spontaneous polarization is directed from the front side to the back side (marked with x in FIG. 5 (b)). That is, when no voltage is applied and when a positive and negative voltage is applied, the spontaneous polarization is directed in a direction perpendicular to the paper surface.

  In the present invention, the constituent material of the first alignment film and the constituent material of the second alignment film have different compositions from each other, and the ferroelectric liquid crystal and the first alignment film are different between the first alignment film and the second alignment film. It is considered that the polar surface interaction, which is the interaction between the film surface and the second alignment film surface, is different. Therefore, in the first alignment film and the second alignment film, when the second alignment film tends to have a relatively positive polarity, as illustrated in FIG. It is considered that the positive polarity of the spontaneous polarization Ps of the liquid crystal molecules 25 faces the first alignment film 4a side due to the polar surface interaction. On the other hand, in the first alignment film and the second alignment film, when the first alignment film tends to have a relatively positive polarity, as illustrated in FIG. It is considered that the positive polarity of the spontaneous polarization Ps of the liquid crystal molecules 25 faces the second alignment film 4b side due to the polar surface interaction. The direction of spontaneous polarization is such a direction because the direction of spontaneous polarization is the direction in which the polarization of the ferroelectric liquid crystal and the polarization of the alignment film are electrically balanced, and the liquid crystal molecules are in an electrically stable state. It is thought that it is to become. 6 and 7, liquid crystal molecules are shown for the ferroelectric liquid crystal.

  On the other hand, when the constituent material of the first alignment film and the constituent material of the second alignment film have the same composition, the first alignment film and the second alignment film have the same surface polarity. The interaction is considered to be the same. Therefore, it is considered that the spontaneous polarization does not easily turn in any direction due to the polar surface interaction between the first alignment film and the second alignment film.

  Therefore, in the case of using a ferroelectric liquid crystal exhibiting V-shaped switching characteristics as shown in the alignment state illustrated in FIG. 5A, the constituent material of the first alignment film and the configuration of the second alignment film are used. When the materials have the same composition, the first alignment film and the second alignment film have the same surface polarity. Therefore, the spontaneous polarization is caused by the polar surface interaction between the first alignment film and the second alignment film. It is considered that the orientation is not controlled and the V-shaped switching characteristic is exhibited when the liquid crystal display element is driven.

  On the other hand, a ferroelectric liquid crystal exhibiting V-shaped switching characteristics as shown in the alignment state illustrated in FIG. 5A is used, and the constituent material of the first alignment film and the second alignment film If the constituent materials have different compositions, the first alignment film and the second alignment film have different surface polarities, so that the direction of spontaneous polarization is controlled by the polar surface interaction. It is considered that a half V-shaped switching characteristic is exhibited when the display element is driven.

  As described above, in the present invention, the constituent material of the first alignment film and the constituent material of the second alignment film have different compositions from each other. A ferroelectric liquid crystal exhibiting a V-shaped switching characteristic when the material has the same composition can exhibit a half V-shaped switching characteristic.

  In the present invention, when the first alignment film and the second alignment film tend to have a relatively positive polarity in the second alignment film, a negative voltage is applied to the second electrode layer. It is preferable to perform display.

  FIG. 8 is a schematic diagram showing an example of the alignment state of a ferroelectric liquid crystal exhibiting monostability. 8A shows a case where no voltage is applied, FIG. 8B shows a case where a negative voltage is applied to the second electrode layer, and FIG. 8C shows a case where a positive voltage is applied to the second electrode layer. Each is shown. When no voltage is applied, the liquid crystal molecules 25 are stabilized in one state on the cone (FIG. 8 (a)). When a negative voltage is applied to the second electrode layer, the liquid crystal molecules 25 are inclined from the stabilized state (broken line) to one side (FIG. 8 (b)). In addition, when a positive voltage is applied to the second electrode layer, the liquid crystal molecules 25 are tilted from the stabilized state (broken line) to the opposite side when a negative voltage is applied to the second electrode layer (see FIG. 8 (c)). At this time, the inclination angle δ when a negative voltage is applied to the second electrode layer is larger than the inclination angle ω when a positive voltage is applied to the second electrode layer. In FIG. 8, d indicates the alignment treatment direction, and z indicates the layer normal.

In this way, when the second alignment film tends to have a relatively positive polarity, the inclination angle of the liquid crystal molecules from the mono-stabilized state when the negative voltage of the second electrode layer is applied is When the positive voltage of the second electrode layer is applied, the inclination angle of the liquid crystal molecules from the mono-stabilized state becomes larger.
At this time, in the polarizing plates respectively disposed on the first alignment treatment substrate side and the second alignment treatment substrate side of the liquid crystal layer, the polarization axes of the respective polarization plates are substantially vertical, The polarizing plate is arranged so that the alignment direction of the liquid crystal molecules in a monostabilized state is substantially parallel.
When no voltage is applied, the linearly polarized light transmitted through one polarizing plate and the alignment direction of the liquid crystal molecules coincide with each other, so that the refractive index anisotropy of the liquid crystal molecules is not expressed. As it passes through the liquid crystal molecules, it is blocked by the other polarizing plate and becomes dark. On the other hand, in the voltage application state, the liquid crystal molecules move on the cone, and the linearly polarized light transmitted through one polarizing plate and the alignment direction of the liquid crystal molecules have a predetermined angle, and thus transmitted through one polarizing plate. Linearly polarized light becomes elliptically polarized light due to the birefringence of liquid crystal molecules. Of the elliptically polarized light, only the linearly polarized light that matches the polarization axis of the other polarizing plate is transmitted through the other polarizing plate and becomes a bright state.
As described above, when the second alignment film tends to have a relatively positive polarity, the inclination of the liquid crystal molecules from the mono-stabilized state when the negative voltage of the second electrode layer is applied. The angle becomes larger than the tilt angle from the mono-stabilized state of the liquid crystal molecules when the positive voltage of the second electrode layer is applied. Therefore, when a negative voltage is applied to the second electrode layer, the amount of transmitted light is larger than when a positive voltage is applied to the second electrode layer. That is, when a positive voltage is applied to the second electrode layer, the amount of transmitted light is less than when a negative voltage is applied to the second electrode layer. For this reason, when a positive voltage is applied to the second electrode layer, it is more disadvantageous for display than when a negative voltage is applied to the second electrode layer.
Therefore, it is preferable to perform display when a negative voltage is applied to the second electrode layer, in which the tilt angle from the mono-stabilized state of the liquid crystal molecules becomes larger.

  “Display when a negative voltage is applied to the second electrode layer” means that liquid crystal molecules are stabilized in one state on the cone when no voltage is applied, and the second electrode layer is negative. When the voltage is applied, the liquid crystal molecules tilt from the mono-stabilized state to one side on the cone, and the liquid crystal molecules maintain the mono-stabilized state when a positive voltage is applied to the second electrode layer. Or tilted from the mono-stabilized state to the opposite side of the negative voltage applied to the second electrode layer, and tilted from the mono-stabilized state of the liquid crystal molecules when a negative voltage is applied to the second electrode layer. It means that the angle is larger than the tilt angle from the mono-stabilized state of the liquid crystal molecules when a positive voltage is applied to the second electrode layer. At this time, the alignment direction in the mono-stabilized state of the liquid crystal molecules and the polarization axis of one polarizing plate are made substantially parallel.

  In the first alignment film and the second alignment film, when the second alignment film tends to have a relatively positive polarity, as shown in FIG. Therefore, the spontaneous polarization Ps of the liquid crystal molecules 25 tends to face the first alignment film 4a side. Further, when a negative voltage is applied to the second electrode layer 3b, the spontaneous polarization Ps of the liquid crystal molecules 25 is directed toward the second alignment film 4b due to the influence of the polarity of the applied voltage, as illustrated in FIG. . Furthermore, when a positive voltage is applied to the second electrode layer 3b, the spontaneous polarization Ps of the liquid crystal molecules 25 is directed toward the first alignment film 4a due to the influence of the polarity of the applied voltage, as illustrated in FIG. . In this case, the direction of spontaneous polarization is the same as that in the state where no voltage is applied. The direction of spontaneous polarization is such a direction, as described above, the direction of spontaneous polarization is the direction in which the polarization of the ferroelectric liquid crystal and the polarization of the alignment film or the polarity of the voltage are electrically balanced, This is because the liquid crystal molecules are in an electrically stable state.

  From the no-voltage applied state or the positive voltage applied state to the second electrode layer (FIG. 6) to the negative voltage applied state to the second electrode layer (FIG. 7), the negative polarity of this applied voltage, Due to the repulsion of the spontaneous polarization of the liquid crystal molecules with the negative polarity, the liquid crystal molecules 25 rotate about an angle of about 2θ as illustrated in FIG. That is, when a negative voltage is applied to the second electrode layer, the molecular direction of the ferroelectric liquid crystal changes parallel to the surface of the first alignment treatment substrate and changes approximately twice the tilt angle θ of the ferroelectric liquid crystal. To do.

  Thus, when the second alignment film tends to have a relatively positive polarity between the first alignment film and the second alignment film, the spontaneous polarization of the ferroelectric liquid crystal is directed to the first alignment film side. By utilizing this tendency, it is possible to control the direction of spontaneous polarization of liquid crystal molecules.

  In general, in a liquid crystal display element using ferroelectric liquid crystal, two opposing alignment films are arranged so that their alignment treatment directions are parallel to each other. For example, in the liquid crystal display element shown in FIG. 1, when no voltage is applied, the liquid crystal molecules 25 are aligned along the alignment treatment direction d of the first alignment film and the second alignment film as illustrated in FIG. A uniform orientation state is obtained. When a negative voltage is applied to the second electrode layer, the direction of the spontaneous polarization Ps is reversed due to the influence of the polarity of the applied voltage, as illustrated in FIG. 10B. Also in this case, the liquid crystal molecules 25 are in a uniform alignment state. Furthermore, when a positive voltage is applied to the second electrode layer, the direction of the spontaneous polarization Ps is reversed due to the influence of the polarity of the applied voltage, as illustrated in FIG. In this case, the liquid crystal molecules 25 are in an alignment state similar to that in the state where no voltage is applied. FIG. 10A is a schematic diagram showing the alignment state of the liquid crystal molecules from the upper surface of FIG. 6, and the spontaneous polarization Ps is directed from the front side to the back side of the drawing (the mark “X” in FIG. 10A). ). FIG. 10 (b) is a schematic diagram showing the alignment state of the liquid crystal molecules from the upper surface of FIG. 7, and the spontaneous polarization Ps is directed from the back of the page to the near side (marked with ● in FIG. 10 (b)). ).

  When a negative voltage is applied to the second electrode layer, it is preferable that there are 70% or more, more preferably 80% or more, more preferably, the molecular direction of the ferroelectric liquid crystal changes about twice the tilt angle. 90% or more, most preferably 95% or more. This is because a favorable contrast ratio can be obtained within the above range.

In addition, said ratio can be measured as follows.
For example, as shown in FIG. 11, a first alignment substrate 11a in which a first electrode layer 3a and a first alignment film 4a are laminated on a first substrate 2a, and a second electrode layer 3b on a second substrate 2b. In the liquid crystal display element 1 in which the liquid crystal layer 5 containing ferroelectric liquid crystal is formed between the second alignment processing substrate 11b and the second alignment film 4b, the first alignment processing substrate 11a and the second alignment processing substrate 11b are formed. It is assumed that polarizing plates 17a and 17b are respectively provided on the outside of the processing substrate 11b so that light is incident from the polarizing plate 17a side and light is emitted from the polarizing plate 17b side. The two polarizing plates 17a and 17b have their polarization axes substantially perpendicular to each other, and the polarization axis of the polarizing plate 17a and the alignment treatment direction (the alignment direction of the liquid crystal molecules) of the first alignment film 4a are substantially parallel. Are arranged as follows.

  When no voltage is applied, the linearly polarized light transmitted through the polarizing plate 17a coincides with the alignment direction of the liquid crystal molecules. Therefore, the refractive index anisotropy of the liquid crystal molecules does not appear, and the linearly polarized light transmitted through the polarizing plate 17a remains as it is. It passes through the molecules, is blocked by the polarizing plate 17b, and enters a dark state. On the other hand, in the voltage application state, the liquid crystal molecules move on the cone, and the linearly polarized light transmitted through the polarizing plate 17a and the alignment direction of the liquid crystal molecules have a predetermined angle. Therefore, the linearly polarized light transmitted through the polarizing plate 17a. Becomes elliptically polarized light due to the birefringence of the liquid crystal molecules. Of the elliptically polarized light, only linearly polarized light that coincides with the polarization axis of the polarizing plate 17b is transmitted through the polarizing plate 17b and becomes bright.

  For this reason, when a negative voltage is applied to the second electrode layer, a bright state is obtained when the molecular direction of the ferroelectric liquid crystal changes approximately twice the tilt angle. On the other hand, when a negative voltage is applied to the second electrode layer, for example, when a portion of the ferroelectric liquid crystal whose molecular direction does not change partially exists, a dark state is partially obtained. Therefore, the molecular direction of the ferroelectric liquid crystal changes approximately twice the tilt angle when a negative voltage is applied to the second electrode layer, based on the black / white (bright / dark) display white / black area ratio obtained when the voltage is applied. The ratio of things can be calculated.

  When a negative voltage is applied to the second electrode layer, the liquid crystal molecules are tilted from the mono-stabilized state to one side on the cone at an angle corresponding to the magnitude of the applied voltage. Further, in the ferroelectric liquid crystal, as illustrated in FIG. 8A, the position A (direction of the liquid crystal molecules 25), the position B (alignment processing direction d), and the position C do not necessarily match. Absent. Therefore, as illustrated in FIG. 8B, the maximum tilt angle δ when a negative voltage is applied to the second electrode layer is about twice the tilt angle θ.

  The angle at which the molecular direction of the ferroelectric liquid crystal changes in parallel to the first alignment processing substrate surface can be measured as follows. First, a polarizing microscope and a liquid crystal display element in which polarizing plates are arranged in crossed Nicols are arranged so that the polarization axis of one polarizing plate and the alignment direction of liquid crystal molecules in the liquid crystal layer are parallel, and this position is used as a reference. . When a voltage is applied, the liquid crystal molecules come to have a predetermined angle with the polarization axis, so that the polarized light transmitted through one polarizing plate is transmitted through the other polarizing plate to be in a bright state. With this voltage applied, the liquid crystal display element is rotated to a dark state. And the angle which rotated the liquid crystal display element at this time is measured. The angle by which the liquid crystal display element is rotated is an angle at which the molecular direction of the ferroelectric liquid crystal changes in parallel to the first alignment processing substrate surface.

  As described above, when a negative voltage is applied to the second electrode layer, the liquid crystal molecules are inclined from the mono-stabilized state to one side on the cone at an angle according to the magnitude of the applied voltage. When driving the liquid crystal display element, the direction of the liquid crystal molecules does not change about twice the tilt angle when a negative voltage is applied to the second electrode layer.

In a liquid crystal display element using a ferroelectric liquid crystal exhibiting monostability, the amount of transmitted light depends on the tilt angle of liquid crystal molecules when a voltage is applied. When either positive or negative voltage is applied, the liquid crystal molecules are tilted on the cone. Therefore, as shown in FIG. 2, for example, the tilt angle of the liquid crystal molecules changes according to the magnitude of the applied voltage, and the transmitted light amount changes. At this time, the amount of transmitted light is maximized when the inclination angle of the liquid crystal molecules from the monostable state is 45 °.
Therefore, in order to realize a high amount of transmitted light, a ferroelectric liquid crystal whose tilt angle from a monostable state of liquid crystal molecules can be 45 ° when a negative voltage is applied to the second electrode layer during actual driving. Is preferably used.
For example, when a ferroelectric liquid crystal having a maximum tilt angle δ from a monostable state of liquid crystal molecules as shown in FIG. 8 is larger than 45 °, when the liquid crystal display element is actually driven, When a negative voltage is applied to the second electrode layer, the tilt angle of the liquid crystal molecules from the monostable state can be set to 45 °. This is because, as described above, when a negative voltage is applied to the second electrode layer during actual driving, the direction of the liquid crystal molecules does not change approximately twice the tilt angle.

  Hereinafter, each structure of the liquid crystal display element of this invention is demonstrated.

1. First alignment film and second alignment film In the present invention, the constituent material of the first alignment film and the constituent material of the second alignment film have different compositions.

  The first alignment film and the second alignment film are not particularly limited as long as the constituent materials have different compositions from each other and can align the ferroelectric liquid crystal. As these first alignment film and second alignment film, for example, a photo-alignment film, a rubbing-treated alignment film, an oblique deposition alignment film, a reactive liquid crystal alignment film for aligning reactive liquid crystals, and a reactivity Examples include a laminate of a fixed liquid crystal layer in which liquid crystal is fixed. Hereinafter, the composition of these alignment films and the constituent materials of the first alignment film and the second alignment film will be described.

(1) Photo-alignment film A photo-alignment film is a film obtained by irradiating a substrate coated with a photo-alignment material, which will be described later, with light whose polarization is controlled to cause a photoexcitation reaction (decomposition, isomerization, dimerization). The liquid crystal molecules on the film are aligned by imparting anisotropy to the film. The photo-alignment film is useful in that since the photo-alignment process is a non-contact alignment process, there is no generation of static electricity or dust, and the quantitative alignment process can be controlled.

  The photo-alignment material used in the present invention is not particularly limited as long as it has an effect of aligning ferroelectric liquid crystal (photoalignment) by irradiating light and causing a photoexcitation reaction. Absent. As such materials, there are large photoreactive materials that impart anisotropy to a film by causing a photoreaction, and photoisomerizable materials that impart anisotropy to a film by causing a photoisomerization reaction. And can be divided into In the following, description will be made separately for photoreactive materials and photoisomerizable materials.

(I) Photoreactive Material A photoreactive material is a material that imparts anisotropy to a film by causing a photoreaction. The photoreactive material used in the present invention is not particularly limited as long as it has such characteristics, but among these, the film is anisotropic by causing a photodimerization reaction or a photodecomposition reaction. It is preferable that the material imparts properties.

  Here, the photodimerization reaction is a reaction in which the reaction site oriented in the polarization direction by light irradiation undergoes radical polymerization and two molecules are polymerized. This reaction stabilizes the orientation in the polarization direction and makes the film anisotropic. Can be provided. The photodecomposition reaction is a reaction that decomposes molecular chains such as polyimide oriented in the polarization direction by light irradiation. This reaction leaves molecular chains oriented in the direction perpendicular to the polarization direction, and makes the film anisotropic. Can be provided. In the present invention, among these photoreactive materials, it is more preferable to use a material that imparts anisotropy to the photoalignment film by a photodimerization reaction because of high exposure sensitivity and a wide range of material selection. .

  The photodimerization type material used in the present invention is not particularly limited as long as it can impart anisotropy to the film by a photodimerization reaction, but has a radical polymerizable functional group, And it is preferable that the photodimerization reactive compound which has the dichroism which makes absorption differ with polarization directions is included. This is because radical polymerization of the reaction sites oriented in the polarization direction stabilizes the orientation of the photodimerization reactive compound and can easily impart anisotropy to the film.

  Examples of the photodimerization reactive compound having such characteristics include a dimerization reactive polymer having at least one reactive site selected from cinnamate ester, coumarin, quinoline, chalcone group and cinnamoyl group as a side chain. Can do.

  Among these, the photodimerization reactive compound is preferably a dimerization reactive polymer containing cinnamate, coumarin or quinoline as a side chain. This is because anisotropy can be easily imparted to the film by radical polymerization of α, β unsaturated ketone double bonds oriented in the polarization direction as reaction sites.

  The main chain of the dimerization reactive polymer is not particularly limited as long as it is generally known as a polymer main chain, but the reaction sites of the side chains such as aromatic hydrocarbon groups are not limited. It is preferable that it does not have a substituent containing a lot of π electrons that hinders the interaction.

  The weight average molecular weight of the dimerization reactive polymer is not particularly limited, but is preferably in the range of 5,000 to 40,000, and is preferably in the range of 10,000 to 20,000. Is more preferable. The weight average molecular weight can be measured by a gel permeation chromatography (GPC) method. If the weight average molecular weight of the dimerization reactive polymer is too small, it may not be possible to impart an appropriate anisotropy to the film. On the other hand, if it is too large, the viscosity of the coating solution at the time of forming the alignment film increases, and it may be difficult to form a uniform coating film.

  Examples of the dimerization reactive polymer are the same as those described in JP-A-2006-350322, JP-A-2006-323214, JP-A-2005-258429, JP-A-2005-258428, and the like.

  As the photodimerization reactive compound, various photodimerization reaction sites and substituents can be selected from the above compounds according to the required properties. Moreover, the photodimerization reactive compound can also be used individually by 1 type or in combination of 2 or more types.

  Further, the photodimerization type material may contain an additive in addition to the photodimerization reactive compound as long as the photoalignment of the alignment film is not hindered. Examples of the additive include a polymerization initiator and a polymerization inhibitor.

  The polymerization initiator or polymerization inhibitor may be appropriately selected from generally known compounds according to the type of the photodimerization reactive compound. The addition amount of the polymerization initiator or the polymerization inhibitor is preferably in the range of 0.001% by mass to 20% by mass, and in the range of 0.1% by mass to 5% by mass with respect to the photodimerization reactive compound. It is more preferable that This is because if the addition amount of the polymerization initiator or polymerization inhibitor is too small, the polymerization may not be started (prohibited), whereas if too large, the reaction may be inhibited.

  Examples of the photoreactive material utilizing photolysis reaction include polyimide “RN1199” manufactured by Nissan Chemical Industries, Ltd.

  The wavelength region of light that causes photoreaction of the photoreactive material is preferably in the range of ultraviolet light, that is, in the range of 10 nm to 400 nm, and more preferably in the range of 250 nm to 380 nm.

  Next, the photo-alignment processing method will be described. First, a coating liquid for forming a photo-alignment film obtained by diluting the above-mentioned photoreactive material with an organic solvent is applied on the first electrode layer or the second electrode layer and dried.

  The content of the photodimerization reactive compound in the coating liquid for forming a photoalignment film is preferably in the range of 0.05% by mass to 10% by mass, and in the range of 0.2% by mass to 2% by mass. It is more preferable that If the content is less than the above range, it will be difficult to impart an appropriate anisotropy to the film. Conversely, if the content is more than the above range, the viscosity of the coating solution will increase, and a uniform coating film will be formed. Because it becomes difficult to do.

  Examples of the coating method for forming the coating liquid for forming a photo-alignment film include spin coating, roll coating, rod bar coating, spray coating, air knife coating, slot die coating, wire bar coating, ink jet, and flexo. A printing method, a screen printing method, or the like can be used.

  The film obtained by applying the coating liquid for forming a photo-alignment film can impart anisotropy by causing a photoreaction by irradiating light with controlled polarization. The polarization direction is not particularly limited as long as it can cause a photoreaction.

  The thickness of the photo-alignment film is preferably in the range of 1 nm to 1000 nm, more preferably in the range of 3 nm to 100 nm. If the thickness of the photo-alignment film is smaller than the above range, sufficient optical alignment may not be obtained. Conversely, if the thickness of the photo-alignment film is larger than the above range, the cost may be disadvantageous. is there.

(Ii) Photoisomerizable material A photoisomerizable material is a material that imparts anisotropy to a film by causing a photoisomerization reaction. The photoisomerization type material used in the present invention is not particularly limited as long as it imparts anisotropy to the film by causing a photoisomerization reaction, but the film is anisotropic by causing a photoisomerization reaction. It is preferable that the compound contains a photoisomerization-reactive compound that imparts properties. By including such a photoisomerization reactive compound, a stable isomer among a plurality of isomers is increased by light irradiation, whereby anisotropy can be easily imparted to the film. .

  The photoisomerization reactive compound is not particularly limited as long as it is a material having the above-mentioned characteristics, but has a dichroism that makes absorption different depending on the polarization direction, and can be irradiated by light irradiation. It is preferable that it causes an isomerization reaction. This is because anisotropy can be easily imparted to the film by causing isomerization of the reaction site oriented in the polarization direction of the photoisomerization reactive compound having such characteristics.

  Further, the photoisomerization reaction in which the photoisomerization reactive compound is generated is preferably a cis-trans isomerization reaction. This is because irradiation with light increases the isomer of either the cis-isomer or the trans-isomer, thereby imparting anisotropy to the film.

  Examples of such photoisomerization-reactive compounds include monomolecular compounds and polymerizable monomers that are polymerized by light or heat. These may be appropriately selected according to the type of ferroelectric liquid crystal used, but the anisotropy can be stabilized by polymerizing after imparting anisotropy to the film by light irradiation. Therefore, it is preferable to use a polymerizable monomer. Among such polymerizable monomers, an acrylate monomer and a methacrylate monomer are preferable because anisotropy is imparted to the film and the polymer can be easily polymerized while maintaining the anisotropy in a good state.

  The polymerizable monomer may be a monofunctional monomer or a polyfunctional monomer. However, since the anisotropy of the alignment film due to polymerization becomes more stable, it is a bifunctional monomer. Preferably there is.

  Specific examples of such a photoisomerization-reactive compound include compounds having a cis-trans isomerization-reactive skeleton such as an azobenzene skeleton or a stilbene skeleton.

  In this case, the number of cis-trans isomerization reactive skeletons contained in the molecule may be one or two or more, but the alignment control of the ferroelectric liquid crystal becomes easy. Two are preferable.

  The cis-trans isomerization reactive skeleton may have a substituent in order to further enhance the interaction with the liquid crystal molecules. The substituent is not particularly limited as long as it can enhance the interaction with the liquid crystal molecules and does not interfere with the orientation of the cis-trans isomerization reactive skeleton, and examples thereof include a carboxyl group and a sulfonic acid. A sodium group, a hydroxyl group, etc. are mentioned. These structures can be appropriately selected depending on the type of ferroelectric liquid crystal used.

In addition to the cis-trans isomerization reactive skeleton, the photoisomerization reactive compound contains many π electrons such as aromatic hydrocarbon groups so that the interaction with the liquid crystal molecules can be further enhanced. It may have an included group, and the cis-trans isomerization reactive skeleton and the aromatic hydrocarbon group may be bonded via a bonding group. The bonding group is not particularly limited as long as it can enhance the interaction with the liquid crystal molecule. For example, —COO—, —OCO—, —O—, —C≡C—, —CH ₂ —CH _2- , —CH ₂ O—, —OCH ₂ — and the like can be mentioned.

  In addition, when using a polymerizable monomer as a photoisomerization reactive compound, it is preferable to have the said cis-trans isomerization reactive skeleton as a side chain. By having the cis-trans isomerization reactive skeleton as a side chain, the effect of anisotropy imparted to the film becomes larger, and it is particularly suitable for the alignment control of ferroelectric liquid crystals. Because. In this case, the aromatic hydrocarbon group or bonding group contained in the molecule is contained in the side chain together with the cis-trans isomerization reactive skeleton so that the interaction with the liquid crystal molecule is enhanced. It is preferable.

  Further, the side chain of the polymerizable monomer may have an aliphatic hydrocarbon group such as an alkylene group as a spacer so that the cis-trans isomerization reactive skeleton can be easily oriented.

  Among the photoisomerization reactive compounds of the monomolecular compound or polymerizable monomer as described above, the photoisomerization reactive compound used in the present invention is preferably a compound having an azobenzene skeleton in the molecule. This is because the azobenzene skeleton contains a lot of π electrons, and thus has a high interaction with liquid crystal molecules and is particularly suitable for controlling the alignment of ferroelectric liquid crystals.

Among the compounds having an azobenzene skeleton in the molecule, as monomolecular compounds, JP-A-2006-350322, JP-A-2006-323214, JP-A-2005-258429, JP-A-2005-258428, etc. Similar to those described.
Examples of the polymerizable monomer having an azobenzene skeleton as a side chain include those described in JP-A-2006-350322, JP-A-2006-323214, JP-A-2005-258429, JP-A-2005-258428, and the like. It is the same as that.

  In the present invention, various cis-trans isomerization reactive skeletons and substituents can be selected from such photoisomerization reactive compounds according to required characteristics. In addition, these photoisomerization reactive compounds can also be used individually by 1 type or in combination of 2 or more types.

  In addition to the photoisomerization reactive compound, the photoisomerization type material may contain an additive within a range that does not interfere with the photoalignment of the alignment film. When a polymerizable monomer is used as the photoisomerization reactive compound, examples of the additive include a polymerization initiator and a polymerization inhibitor.

  The polymerization initiator or polymerization inhibitor may be appropriately selected from generally known compounds according to the type of photoisomerization reactive compound. The addition amount of the polymerization initiator or polymerization inhibitor is preferably in the range of 0.001% by mass to 20% by mass, and in the range of 0.1% by mass to 5% by mass with respect to the photoisomerization reactive compound. More preferably, it is within. This is because if the addition amount of the polymerization initiator or polymerization inhibitor is too small, the polymerization may not be started (prohibited), whereas if too large, the reaction may be inhibited.

  The wavelength region of the light that causes the photoisomerization reaction of the photoisomerizable material is preferably in the ultraviolet light range, that is, in the range of 10 nm to 400 nm, and more preferably in the range of 250 nm to 380 nm. .

  Next, the photo-alignment processing method will be described. First, a coating liquid for forming a photo-alignment film obtained by diluting the above-mentioned photoisomerizable material with an organic solvent is applied on the first electrode layer or the second electrode layer and dried.

  The content of the photoisomerization-reactive compound in the coating liquid for forming a photoalignment film is preferably in the range of 0.05% by mass to 10% by mass, and in the range of 0.2% by mass to 2% by mass. More preferably, it is within. If the content is less than the above range, it will be difficult to impart an appropriate anisotropy to the film. Conversely, if the content is more than the above range, the viscosity of the coating solution will increase, and a uniform coating film will be formed. Because it becomes difficult to do.

  Examples of the coating method for forming the coating liquid for forming a photo-alignment film include spin coating, roll coating, rod bar coating, spray coating, air knife coating, slot die coating, wire bar coating, ink jet, and flexo. A printing method, a screen printing method, or the like can be used.

  A film obtained by applying the coating liquid for forming a photo-alignment film can be imparted with anisotropy by causing a photoisomerization reaction by irradiating light with controlled polarization. The polarization direction is not particularly limited as long as it can cause a photoisomerization reaction.

  Further, when a polymerizable monomer is used as the photoisomerization type material among the above photoisomerization reactive compounds, it is polymerized by heating after photoalignment treatment and applied to the alignment film. Anisotropy can be stabilized.

  The thickness of the photo-alignment film is preferably in the range of 1 nm to 1000 nm, more preferably in the range of 3 nm to 100 nm. If the thickness of the photo-alignment film is smaller than the above range, sufficient optical alignment may not be obtained. Conversely, if the thickness of the photo-alignment film is larger than the above range, the cost may be disadvantageous. is there.

(2) Rubbing-treated alignment film The rubbing-treated alignment film is useful in that a relatively high pretilt angle can be realized.

  The material used for the alignment film subjected to rubbing treatment is not particularly limited as long as it can impart anisotropy to the film by rubbing treatment. For example, nylon, polyimide, polyamide, polyamideimide, Examples include polyetherimide, polyvinyl alcohol, and polyurethane. These may be used alone or in combination of two or more.

  Among them, the rubbing-treated alignment film preferably contains nylon or polyimide. This is because the ferroelectric liquid crystal is easily aligned in the azimuth direction. That is, the ferroelectric liquid crystal is easily arranged in a certain direction.

As the rubbing treatment method, a method is used in which a film containing the above material is formed on the first electrode layer or the second electrode layer, and this film is rubbed with a rubbing cloth in a certain direction to impart anisotropy to the film. be able to.
As the rubbing cloth, for example, a cloth made of a fiber such as nylon resin, vinyl resin, rayon, or cotton can be used. For example, by rotating a drum wound with such a rubbing cloth and bringing it into contact with the surface of the film containing the above material, fine grooves are formed in one direction on the film surface, and anisotropy is imparted to the film. The

  The thickness of the alignment film subjected to the rubbing treatment is set to about 1 nm to 1000 nm, and preferably in the range of 50 nm to 100 nm.

(3) Oblique deposition alignment film The oblique deposition alignment film is formed by an oblique deposition method. The oblique deposition film is useful in that a relatively high pretilt angle can be realized.

The oblique deposition alignment film is not particularly limited as long as it can align the ferroelectric liquid crystal. As a constituent material of the oblique deposition film, an inorganic material that can be formed by an oblique deposition method is used, and examples thereof include silicon monoxide (SiO), silicon dioxide (SiO ₂ ), and titanium dioxide (TiO ₂ ). be able to. Of these, SiO is preferably used.

  It is known that the oblique deposition alignment film has a groove structure and a columnar structure, and the groove structure and the columnar structure change depending on the deposition angle, and the alignment direction of the liquid crystal changes. It is also known that the angle and density of the columnar microstructure change depending on the angle of the vapor deposition direction with respect to the normal of the substrate surface. Therefore, in order to set the pretilt angle of the liquid crystal molecules within a desired range, it is important to adjust the angle and density of the columnar microstructure of the oblique deposition alignment film. As for the oblique deposition alignment film, “Liquid Crystal Handbook” edited by the Liquid Crystal Handbook Editorial Committee Maruzen Co., Ltd. October 30, 2000 p. Reference may be made to 229-230.

  The oblique deposition alignment film can control the pretilt angle of the liquid crystal molecules by changing the angle of the deposition direction (deposition angle) with respect to the normal of the substrate surface. This deposition angle can be set at about 40 ° to 60 °, preferably about 50 ° to 60 °. By adjusting the deposition angle within the above range, the pretilt angle of the liquid crystal molecules can be controlled within a desired range.

  As a method of forming the oblique vapor deposition alignment film, an oblique vapor deposition method is used. For example, the normal direction of the first substrate surface or the second substrate surface is a predetermined angle with respect to the incident direction (deposition direction) of the vapor deposition particles. In this manner, the first base material or the second base material is tilted by rotating the first base material or the second base material with respect to the deposition direction so that the oblique deposition orientation film is obliquely formed with respect to the first base material or the second base material surface. Can be formed.

  The thickness of the oblique deposition alignment film is set to about 10 nm to 500 nm, and preferably in the range of 30 nm to 200 nm.

(4) Reactive liquid crystal alignment film and immobilized liquid crystal layer At least one of the first alignment film and the second alignment film is formed on the first base material or the second base material. And a fixed liquid crystal layer formed on the reactive liquid crystal alignment film and formed by fixing the reactive liquid crystal. For example, in FIG. 12, the second alignment film 4b is formed by laminating a reactive liquid crystal alignment film 14a and a fixed liquid crystal layer 14b. When forming the fixed liquid crystal layer on the alignment film for reactive liquid crystal, the reactive liquid crystal is aligned by the alignment film for reactive liquid crystal, and the reactive liquid crystal is polymerized by irradiating ultraviolet rays, for example. The orientation state can be fixed. Therefore, the alignment regulating force of the alignment film for reactive liquid crystal can be imparted to the fixed liquid crystal layer, and the fixed liquid crystal layer can act as an alignment film for aligning the ferroelectric liquid crystal. Further, since the reactive liquid crystal is fixed, it has an advantage that it is not affected by temperature or the like. In addition, reactive liquid crystals are relatively similar in structure to ferroelectric liquid crystals, and interact more strongly with ferroelectric liquid crystals, so that ferroelectrics are more effective than using single-layer alignment films. The orientation of the crystalline liquid crystal can be controlled. Hereinafter, the description will be divided into the alignment film for reactive liquid crystal and the fixed liquid crystal layer.

(I) Immobilized liquid crystal layer The immobilized liquid crystal layer used in the present invention is formed on an alignment film for reactive liquid crystal, and is formed by immobilizing reactive liquid crystal.

  The reactive liquid crystal used in the present invention preferably exhibits a nematic phase. This is because the nematic phase is relatively easy to control the alignment among the liquid crystal phases.

  The reactive liquid crystal preferably contains a polymerizable liquid crystal material. This is because the alignment state of the reactive liquid crystal can be fixed. As the polymerizable liquid crystal material, any of a polymerizable liquid crystal monomer, a polymerizable liquid crystal oligomer, and a polymerizable liquid crystal polymer can be used, and among them, a polymerizable liquid crystal monomer is preferably used. The polymerizable liquid crystal monomer can be aligned at a lower temperature than other polymerizable liquid crystal materials, that is, a polymerizable liquid crystal oligomer and a polymerizable liquid crystal polymer, and has high sensitivity in alignment, and can be easily aligned. Because you can.

  The polymerizable liquid crystal monomer is not particularly limited as long as it is a liquid crystal monomer having a polymerizable functional group, and examples thereof include a monoacrylate monomer and a diacrylate monomer. These polymerizable liquid crystal monomers may be used alone or in combination of two or more.

  Monoacrylate monomers and diacrylate monomers are the same as those described in JP-A-2006-350322, JP-A-2006-323214, JP-A-2005-258429, JP-A-2005-258428, and the like. .

  In the present invention, a diacrylate monomer is preferred among the polymerizable liquid crystal monomers. This is because the diacrylate monomer can be easily polymerized while maintaining the orientation state in a good state.

  The polymerizable liquid crystal monomer described above does not have to exhibit a nematic phase. These polymerizable liquid crystal monomers may be used as a mixture of two or more kinds as described above, because the composition in which these are mixed, that is, the reactive liquid crystal may exhibit a nematic phase. It is.

  Furthermore, in this invention, you may add a photoinitiator, a polymerization inhibitor, etc. to the said reactive liquid crystal as needed. For example, when polymerizing a polymerizable liquid crystal material by electron beam irradiation, a photopolymerization initiator may not be necessary, but in the case of polymerization by, for example, ultraviolet irradiation, usually photopolymerization is started. This is because the agent is used for promoting the polymerization. As the photopolymerization initiator, for example, a photopolymerization initiator described in JP-A-2005-258428 can be used. Moreover, it is also possible to add a sensitizer other than a photoinitiator in the range which does not impair the objective of this invention.

  The amount of the photopolymerization initiator added is generally 0.01 to 20% by mass, preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass. It can be added to the liquid crystal.

  The thickness of the fixed liquid crystal layer is appropriately adjusted according to the target anisotropy, and can be set, for example, within a range of 1 nm to 1000 nm, and preferably within a range of 3 nm to 100 nm. This is because if the fixed liquid crystal layer is too thick, anisotropy more than necessary occurs, and if the fixed liquid crystal layer is too thin, the predetermined anisotropy may not be obtained.

  Next, a method for forming the fixed liquid crystal layer will be described. The fixed liquid crystal layer is formed by applying a reactive liquid crystal composition containing the reactive liquid crystal on the alignment film for reactive liquid crystal, performing an alignment treatment, and fixing the alignment state of the reactive liquid crystal. Can do.

  Further, instead of applying the reactive liquid crystal composition, a method of forming a dry film or the like in advance and laminating the film on the reactive liquid crystal alignment film can also be used. From the viewpoint of the simplicity of the manufacturing process, it is possible to prepare a reactive liquid crystal composition by dissolving a reactive liquid crystal in a solvent, apply this onto a reactive liquid crystal alignment film, and use a method of removing the solvent. preferable.

  The solvent used in the reactive liquid crystal composition is not particularly limited as long as it can dissolve the reactive liquid crystal and the like and does not inhibit the alignment ability of the alignment film for reactive liquid crystal. As such a solvent, for example, a solvent described in JP-A-2005-258428 can be used. A solvent may be used independently and may use 2 or more types together.

  Further, if only a single kind of solvent is used, the solubility of the reactive liquid crystal or the like may be insufficient, or the reactive liquid crystal alignment film may be eroded as described above. In this case, this inconvenience can be avoided by using a mixture of two or more solvents. Among the above-mentioned solvents, hydrocarbons and glycol monoether acetate solvents are preferable as the sole solvent, and a mixed system of ethers or ketones and glycol solvent is preferable as the mixed solvent. It is.

  Although the concentration of the reactive liquid crystal composition depends on the solubility of the reactive liquid crystal and the thickness of the immobilized liquid crystal layer, it cannot be defined unconditionally. % Is adjusted. If the concentration of the reactive liquid crystal composition is lower than the above range, the reactive liquid crystal may be difficult to align. Conversely, if the concentration of the reactive liquid crystal composition is higher than the above range, the viscosity of the reactive liquid crystal composition is low. It is because it becomes high and it may become difficult to form a uniform coating film.

  Furthermore, a compound such as that described in JP-A-2005-258428 can be added to the reactive liquid crystal composition as long as the object of the present invention is not impaired. The amount of these compounds added to the reactive liquid crystal is selected within a range that does not impair the object of the present invention. Addition of these compounds improves the curability of the reactive liquid crystal, increases the mechanical strength of the resulting fixed liquid crystal layer, and improves its stability.

  Examples of a method for applying such a reactive liquid crystal composition include spin coating, roll coating, printing, dip coating, die coating, casting, bar coating, blade coating, spray coating, and gravure. Examples thereof include a coating method, a reverse coating method, an extrusion coating method, an ink jet method, a flexographic printing method, and a screen printing method.

  In addition, the solvent is removed after the reactive liquid crystal composition is applied, and the removal of the solvent is performed by, for example, removal under reduced pressure or removal by heating, or a combination thereof.

  In the present invention, the reactive liquid crystal applied as described above is aligned by the alignment film for reactive liquid crystal so as to have liquid crystal regularity. That is, a nematic phase is developed in the reactive liquid crystal. This is usually performed by a method such as a method of performing a heat treatment below the NI transition point. Here, the NI transition point indicates the temperature at which the liquid crystal phase transitions to the isotropic phase.

  As described above, the reactive liquid crystal has a polymerizable liquid crystal material, and in order to fix the alignment state of such a polymerizable liquid crystal material, a method of irradiating active radiation that activates polymerization is used. . The active radiation as used herein refers to radiation capable of causing polymerization of the polymerizable liquid crystal material. If necessary, a photopolymerization initiator may be included in the polymerizable liquid crystal material.

  The actinic radiation is not particularly limited as long as it is a radiation capable of polymerizing the polymerizable liquid crystal material, but usually ultraviolet light or visible light is used from the viewpoint of the ease of the apparatus. Irradiation light having a wavelength of 150 to 500 nm, preferably 250 to 450 nm, and more preferably 300 to 400 nm is used.

  In the present invention, a method of irradiating ultraviolet rays with active radiation to a polymerizable liquid crystal material in which the photopolymerization initiator generates radicals with ultraviolet rays and the polymerizable liquid crystal material undergoes radical polymerization is a preferable method. . This is because the method using ultraviolet rays as actinic radiation is an already established technique, and therefore it can be easily applied to the present invention including the photopolymerization initiator to be used.

  As the light source of this irradiation light, low pressure mercury lamp (sterilization lamp, fluorescent chemical lamp, black light), high pressure discharge lamp (high pressure mercury lamp, metal halide lamp), short arc discharge lamp (super high pressure mercury lamp, xenon lamp, mercury xenon) Lamp). In particular, the use of metal halide lamps, xenon lamps, high-pressure mercury lamps, etc. is recommended. The irradiation intensity is appropriately adjusted according to the composition of the reactive liquid crystal and the amount of photopolymerization initiator.

  Such irradiation with active radiation may be performed under a temperature condition in which the polymerizable liquid crystal material becomes a liquid crystal phase, or may be performed at a temperature lower than the temperature at which the liquid crystal phase is formed. This is because the alignment state of the polymerizable liquid crystal material once in the liquid crystal phase is not disturbed suddenly even if the temperature is lowered thereafter.

  As a method for fixing the alignment state of the polymerizable liquid crystal material, in addition to the method of irradiating the active radiation, a method of polymerizing the polymerizable liquid crystal material by heating can also be used. As the reactive liquid crystal used in this case, it is preferable that the polymerizable liquid crystal monomer contained in the reactive liquid crystal is thermally polymerized below the NI transition point of the reactive liquid crystal.

(Ii) Alignment film for reactive liquid crystal As the alignment film for reactive liquid crystal used in the present invention, the above-mentioned reactive liquid crystal can be aligned, and there is an adverse effect in fixing the alignment state of the above-mentioned reactive liquid crystal. There is no particular limitation as long as it does not reach. As the alignment film for reactive liquid crystal, for example, the above-described photo-alignment film, a rubbing-treated alignment film, an oblique deposition alignment film, or the like can be used.

(5) Composition of constituent materials of first alignment film and second alignment film In the present invention, the constituent materials of the first alignment film and the second alignment film have different compositions. By forming the first alignment film and the second alignment film using materials having different compositions, the polarities of the first alignment film surface and the second alignment film surface can be made different depending on the respective materials. As a result, the polar surface interaction between the ferroelectric liquid crystal and the first alignment film is different from the polar surface interaction between the ferroelectric liquid crystal and the second alignment film, so that the first alignment film and the second alignment film When the material of the first alignment film and the second alignment film has the same composition, the ferroelectric liquid crystal exhibiting V-shaped switching characteristics is reduced to half by V-shaped switching characteristics may be exhibited.

  In order to change the composition of the constituent materials of the first alignment film and the second alignment film, for example, one is a photo-alignment film and the other is a rubbing-treated alignment film, or one is for reactive liquid crystal The alignment film and the fixed liquid crystal layer may be stacked, and the other may be a photo-alignment film, a rubbing-treated alignment film, or an oblique deposition alignment film. Also, for example, both are rubbed alignment films, the composition materials of the rubbed alignment films are different; both are photoalignment films, and the composition of the photo alignment film is different Both are obliquely deposited alignment films, and the composition of the constituent materials of the photo-alignment film is different; or both are formed by laminating an alignment film for reactive liquid crystal and an immobilized liquid crystal layer, What is necessary is just to make the composition of the constituent material of a layer different.

  Further, when the first alignment film and the second alignment film are photo-alignment films, for example, by using a photoisomerizable material for one photo-alignment film and a photo-reactive material for the other photo-alignment film, The composition of the constituent material of the alignment film can be different.

  Furthermore, when the first alignment film and the second alignment film are photo-alignment films using a photoisomerization type material, cis-trans isomerization reactivity is selected from photoisomerization-reactive compounds according to required characteristics. By selecting various skeletons and substituents, the composition of the constituent materials of the photo-alignment film can be made different. Furthermore, the composition can be changed by changing the amount of the additive added.

  Furthermore, when the first alignment film and the second alignment film are photo-alignment films using a photo-dimerization-type material, by selecting various photo-dimerization reactive compounds, for example, photo-dimerization-reactive polymers, The composition of the constituent materials can be different. Furthermore, the composition can be changed by changing the amount of the additive added.

  As a combination of materials used for the first alignment film and the second alignment film, among the above, one of the alignment films for the reactive liquid crystal and the fixed liquid crystal layer is laminated, and the other is the photo-alignment film and the rubbing. Processed alignment film or oblique deposition alignment film; one is a photo-alignment film using a photodimerization type material and the other is a photoalignment film using a photoisomerization type material; one is a photodimerization type It is preferable that a photo-alignment film using a material is used and the other is a rubbing-treated alignment film; one is a photo-alignment film using a photoisomerizable material and the other is a rubbing-processed alignment film.

The fixed liquid crystal layer tends to have a stronger positive polarity than the photo-alignment film, the rubbing-treated alignment film, or the oblique deposition alignment film. Therefore, in the case of this combination, the spontaneous polarization of the ferroelectric liquid crystal tends to be directed to the photo-alignment film, the rubbing-treated alignment film, or the oblique deposition alignment film side due to the polar surface interaction.
In addition, a photo-alignment film using a photodimerization type material tends to have a relatively positive polarity compared to a photo-alignment film using a photoisomerization type material. Due to the action, the spontaneous polarization of the ferroelectric liquid crystal tends to face the photo-alignment film side using the photoisomerizable material.
Furthermore, since the photo-alignment film using the photodimerization type material tends to have a relatively positive polarity relative to the alignment film subjected to the rubbing treatment, the spontaneous polarization of the ferroelectric liquid crystal is caused by the polar surface interaction, There is a tendency to face the rubbing-treated alignment film side.
In addition, rubbing alignment films tend to have a relatively positive polarity compared to photo-alignment films using photoisomerizable materials, so that the spontaneous polarization of the ferroelectric liquid crystal is caused by the polar surface interaction. There is a tendency to face the photo-alignment film side using the photoisomerization type material.
In such a combination, the direction of spontaneous polarization of the ferroelectric liquid crystal can be controlled. Therefore, when the constituent materials of the first alignment film and the second alignment film have the same composition, V A ferroelectric liquid crystal exhibiting a letter-shaped switching characteristic can exhibit a half V-shaped switching characteristic.

In the present invention, as described above, when the second alignment film tends to have a relatively positive polarity between the first alignment film and the second alignment film, the second electrode layer has a negative polarity. It is preferable to perform display when the above voltage is applied.
In the case where the first alignment film and the second alignment film have a tendency that the second alignment film tends to have a relatively positive polarity, the combination described above can be given. A photo-alignment film, a rubbing-treated alignment film, or an oblique deposition film, and the second alignment film is formed by laminating a reactive liquid crystal alignment film and an immobilized liquid crystal layer; A photo-alignment film using an isomerized material and a second alignment film as a photo-alignment film using a photo-dimerization type material; a first alignment film as a rubbed alignment film and a second alignment film as a photo-dimerization Preferably, a photo-alignment film using a mold material is used; alternatively, the first alignment film is a photo-alignment film using a photoisomerization-type material, and the second alignment film is preferably a rubbing-processed alignment film.

2. Liquid Crystal Layer The liquid crystal layer in the present invention is formed between the first alignment film of the first alignment processing substrate and the second alignment film of the second alignment processing substrate, and includes a ferroelectric liquid crystal. In addition, the ferroelectric liquid crystal exhibits monostability. Furthermore, this ferroelectric liquid crystal exhibits V-shaped switching characteristics when the liquid crystal display element is driven when the constituent material of the first alignment film and the constituent material of the second alignment film have the same composition. In addition, the liquid crystal display element driving of the present invention exhibits a half V-shaped switching characteristic.

The phase series of the ferroelectric liquid crystal is not particularly limited as long as it exhibits a chiral smectic C phase (SmC ^* ). For example, the phase sequence changes in phase with the nematic phase (N) -cholesteric phase (Ch) -chiral smectic C phase (SmC ^* ) in the temperature lowering process, the nematic phase (N) -chiral smectic C phase (SmC ^* ) , Nematic phase (N) -smectic A phase (SmA) -chiral smectic C phase (SmC ^* ), phase change, nematic phase (N) -cholesteric phase (Ch) -smectic A phase (SmA ) -Chiral smectic C phase (SmC ^* ) and the like.

  Such a ferroelectric liquid crystal can be variously selected from generally known liquid crystal materials according to required characteristics. Specifically, “R3201” manufactured by AZ Electronic Materials may be mentioned.

  The thickness of the liquid crystal layer is preferably in the range of 1.2 μm to 3.0 μm, more preferably 1.3 μm to 2.5 μm, and still more preferably in the range of 1.4 μm to 2.0 μm. This is because if the thickness of the liquid crystal layer is too thin, the contrast may be lowered. Conversely, if the thickness of the liquid crystal layer is too thick, the ferroelectric liquid crystal may be difficult to align. The thickness of the liquid crystal layer can be adjusted by bead spacers, columnar spacers, partition walls, or the like.

As a method for forming the liquid crystal layer, a method generally used as a method for manufacturing a liquid crystal cell can be used. For example, a vacuum injection method, a liquid crystal dropping method, or the like can be used.
In the vacuum injection method, for example, a ferroelectric liquid crystal that is made an isotropic liquid by heating is applied to a liquid crystal cell that has been prepared using a first alignment processing substrate and a second alignment processing substrate in advance by utilizing the capillary effect. The liquid crystal layer can be formed by pouring and sealing with an adhesive.
Further, in the liquid crystal dropping method, for example, a heated ferroelectric liquid crystal is dropped on the second alignment film of the second alignment processing substrate, a sealant is applied to the peripheral portion of the first alignment processing substrate, and the first is applied under reduced pressure. A liquid crystal layer can be formed by superimposing the first alignment treatment substrate and the second alignment treatment substrate and bonding them with a sealant.

When aligning the ferroelectric liquid crystal, if a polymerizable monomer is added to the ferroelectric liquid crystal, the ferroelectric liquid crystal is aligned and then the polymerizable monomer is polymerized. The polymerization method of the polymerizable monomer is appropriately selected according to the type of the polymerizable monomer. For example, when an ultraviolet curable resin monomer is used as the polymerizable monomer, the polymerizable monomer can be polymerized by ultraviolet irradiation. .
Further, when polymerizing the polymerizable monomer, a voltage may or may not be applied to the liquid crystal layer composed of the ferroelectric liquid crystal, but no voltage is applied to the liquid crystal layer. It is preferable to polymerize a polymerizable monomer.

  In the present invention, since the ferroelectric liquid crystal exhibits monostability, a liquid crystal display element that can be driven by an active matrix method using a thin film transistor (TFT) and can control gradation by voltage modulation is provided. Obtainable.

3. First alignment processing substrate The first alignment processing substrate used in the present invention includes a first base material, a first electrode layer formed on the first base material, and a first electrode layer formed on the first electrode layer. And one alignment film.
Since the first alignment film has been described above, the description thereof is omitted here. Hereinafter, another configuration of the first alignment processing substrate will be described.

(1) First electrode layer The first electrode layer used in the present invention is not particularly limited as long as it is generally used as an electrode of a liquid crystal display element. At least one of the electrode layer and the second electrode layer of the second alignment treatment substrate is preferably formed of a transparent conductor. Preferred examples of the transparent conductor material include indium oxide, tin oxide, indium tin oxide (ITO), and the like.

  When the liquid crystal display element obtained by the present invention is driven by an active matrix system using TFTs, one of the first alignment processing substrate and the second alignment processing substrate is formed on the entire surface formed of the transparent conductor. An electrode is provided, and on the other side, a gate electrode and a source electrode are arranged in a matrix, and a TFT element and a pixel electrode are provided in a portion surrounded by the gate electrode and the source electrode.

  Examples of the method for forming the first electrode layer include chemical vapor deposition (CVD), physical vapor deposition (PVD) such as sputtering, ion plating, and vacuum deposition.

(2) 1st base material The 1st base material used for this invention will not be specifically limited if generally used as a base material of a liquid crystal display element, For example, a glass plate, a plastic plate, etc. are preferable. Can be mentioned.

(3) Other Configurations In the first alignment substrate in the present invention, partition walls or columnar spacers may be formed on the first base material. When the partition or columnar spacer is formed on the second base material in the second alignment processing substrate, the partition or columnar spacer is not formed on the first base material in the first alignment processing substrate. That is, partition walls or columnar spacers may be formed on the first alignment processing substrate, and partition walls or columnar spacers may be formed on the second alignment processing substrate.
As the partition walls and columnar spacers, general partition walls and columnar spacers can be applied.

Moreover, in the 1st orientation processing board | substrate in this invention, the colored layer may be formed on the 1st base material. When the colored layer is formed on the second base material in the second alignment processing substrate, the coloring layer is not formed on the first base material in the first alignment processing substrate. That is, a colored layer may be formed on the first alignment processing substrate, and a coloring layer may be formed on the second alignment processing substrate.
When the colored layer is formed, a color filter type liquid crystal display element capable of realizing color display by the colored layer can be obtained.
As a method for forming the colored layer, a method for forming a colored layer in a general color filter can be used. For example, a pigment dispersion method (color resist method, etching method), a printing method, an inkjet method, or the like can be used. it can.

4). Second alignment treatment substrate The second alignment treatment substrate used in the present invention includes a second base material, a second electrode layer formed on the second base material, and a second electrode layer formed on the second electrode layer. And two alignment films.
Since the second alignment film has been described above, description thereof is omitted here. The second base material, the second electrode layer, and other configurations are the same as the first base material, the first electrode layer, and other configurations in the first alignment processing substrate, respectively. Description is omitted.

5. Other Configurations The liquid crystal display element of the present invention may have a polarizing plate as illustrated in FIG.
The polarizing plate used in the present invention is not particularly limited as long as it transmits only a specific direction among the wave of light, and a polarizing plate generally used as a polarizing plate of a liquid crystal display element should be used. Can do.

6). Method for Driving Liquid Crystal Display Element As a method for driving the liquid crystal display element of the present invention, the high-speed response of ferroelectric liquid crystal can be used. A field sequential color system that particularly requires high-speed response is suitable.

  Further, the driving method of the liquid crystal display element of the present invention is not limited to the field sequential method, and may be a color filter method that performs color display using a colored layer.

  As a driving method of the liquid crystal display element of the present invention, an active matrix system using a thin film transistor (TFT) is preferable. This is because by adopting an active matrix system using TFTs, the target pixel can be reliably turned on and off, and a high-quality display becomes possible.

  In the present invention, the first alignment treatment substrate may be a TFT substrate, the second alignment treatment substrate may be a common electrode substrate, the first alignment treatment substrate is a common electrode substrate, and the second alignment treatment substrate is a TFT substrate. Also good. In particular, when the first alignment film and the second alignment film tend to have a relatively positive polarity in the second alignment film, the first alignment process substrate is common to the TFT substrate and the second alignment process substrate. An electrode substrate is preferred.

  For example, in the liquid crystal display element 1 shown in FIG. 13, when the gate electrode 26x is set to a high potential of about 30 V, the TFT element 27 is switched on, and a signal voltage is applied to the ferroelectric liquid crystal by the source electrode 26y. Is set to a low potential of about −10 V, the TFT element 27 is switched off. In the switch-off state, as illustrated in FIG. 14, a voltage is applied between the common electrode (second electrode layer 3a) and the gate electrode 26x so that the common electrode (second electrode layer 3a) side is positive. . Since the ferroelectric liquid crystal does not operate in this switch-off state, the pixel is in a dark state.

  In the first alignment film and the second alignment film, when the second alignment film tends to have a relatively positive polarity, the spontaneous polarization of the ferroelectric liquid crystal is caused by the polar surface interaction when no voltage is applied. Tends to face the first alignment film side. That is, in the switch-off state, as illustrated in FIG. 14, the spontaneous polarization Ps of the liquid crystal molecules 25 faces the TFT substrate (first alignment processing substrate 11a) side. Therefore, the direction of spontaneous polarization is not affected by the voltage applied between the common electrode (second electrode layer 3a) and the gate electrode 26x.

  On the other hand, in the first alignment film and the second alignment film, the second alignment film tends to have a relatively strong positive polarity, and the first alignment processing substrate is the common electrode substrate and the second alignment film. When the processing substrate is a TFT substrate, the spontaneous polarization of the ferroelectric liquid crystal faces the common electrode substrate (second alignment processing substrate) side when no voltage is applied. Due to the influence of the voltage applied between the electrodes, the direction of spontaneous polarization is reversed in the vicinity of the region where the gate electrode is provided. Then, in the vicinity of the region where the gate electrode is provided, the ferroelectric liquid crystal operates and light leakage occurs even though the switch is off.

  On the other hand, in the first alignment film and the second alignment film, the second alignment film tends to have a relatively positive polarity, and the first alignment processing substrate is the TFT substrate, and the second alignment film is the second alignment film. When the alignment substrate is a common electrode substrate, the direction of spontaneous polarization is not affected by the voltage applied between the common electrode and the gate electrode, so that no light leakage occurs. Therefore, by controlling the direction of spontaneous polarization and using the first alignment processing substrate as the TFT substrate and the second alignment processing substrate as the common electrode substrate, light leakage near the gate electrode can be prevented.

As described above, when the second alignment film tends to have a relatively positive polarity in the first alignment film and the second alignment film, a negative voltage is applied to the second electrode layer. Sometimes it is preferable to display. That is, when a negative voltage is applied to the second electrode layer of the ferroelectric liquid crystal, the molecular direction of the ferroelectric liquid crystal is parallel to the first alignment treatment substrate surface and is approximately equal to the tilt angle of the ferroelectric liquid crystal. It is preferable to change 2 times.
If the pixel electrode voltage is relatively high with respect to the common electrode, a positive polarity voltage application is assumed, and if the pixel electrode voltage is relatively low, a negative polarity voltage application is assumed. In this definition, when the first alignment processing substrate is a common electrode substrate and the second alignment processing substrate is a TFT substrate, the ferroelectric liquid crystal has a pixel electrode voltage relatively lower than the common electrode. That is, when a negative polarity voltage is applied, the molecular direction of the ferroelectric liquid crystal changes approximately twice the tilt angle of the ferroelectric liquid crystal in parallel with the first alignment processing substrate surface. Further, when the first alignment processing substrate is a TFT substrate and the second alignment processing substrate is a common electrode substrate, the ferroelectric liquid crystal has a pixel electrode voltage relatively higher than the common electrode, that is, a positive electrode. When a polarity voltage is applied, the molecular direction of the ferroelectric liquid crystal changes approximately twice the tilt angle of the ferroelectric liquid crystal parallel to the first alignment substrate surface.

  Further, the driving method of the liquid crystal display element of the present invention may be a segment method.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

The following examples illustrate the present invention in more detail.
[Example 1]
(Production of first alignment processing substrate)
The glass substrate on which the ITO electrode was formed was thoroughly washed, and a transparent resist (manufactured by JSR, trade name: NN780) was spin coated on the glass substrate, dried under reduced pressure, and prebaked at 90 ° C. for 3 minutes. Subsequently, it exposed to a mask with 100 mJ / cm ² ultraviolet rays, developed with an inorganic alkali solution, and post-baked at 230 ° C. for 30 minutes. Thereby, a columnar spacer having a height of 1.5 μm was formed.
Next, a photo-alignment material (manufactured by DIC, trade name: LIA01) is spin-coated at 1000 rpm for 20 seconds on a glass substrate on which columnar spacers are formed, dried at 100 ° C. for 3 minutes, and then linearly polarized ultraviolet rays. Was irradiated with about 1000 mJ / cm ² to perform alignment treatment.

(Preparation of second alignment processing substrate)
The glass substrate on which the ITO electrode is formed is thoroughly washed, and on this glass substrate, a photo-alignment material (manufactured by DIC, product name: LIA01) is spin-coated at 1000 rpm for 20 seconds and dried at 100 ° C. for 3 minutes. After that, alignment treatment was performed by irradiating with linearly polarized ultraviolet rays of about 1000 mJ / cm ² . Further, a polymerizable liquid crystal (trade name: ROF5101, manufactured by ROLIC Technology Co., Ltd.) is spin-coated at 1000 rpm for 20 seconds on the alignment film using the photoalignable material, dried at 100 ° C. for 3 minutes, and then non-polarized light. The alignment treatment was performed by irradiating with ultraviolet rays of about 1000 mJ / cm ² .

(Production of liquid crystal display element)
A cell was fabricated by combining the first alignment treatment substrate and the second alignment treatment substrate so that the respective alignment treatment directions were parallel. The produced cell was heated to a temperature 10 ° C. higher than the nematic phase-isotropic phase transition temperature of the ferroelectric liquid crystal, and a ferroelectric liquid crystal material (manufactured by AZ Electronic Materials, trade name: R3201) was injected.

(Evaluation)
When the liquid crystal drive characteristics of the manufactured liquid crystal display element were measured, the drive characteristics showed a half V-shaped switching characteristic.
FIG. 15 shows the relationship between the applied voltage and the amount of transmitted light in this liquid crystal display element. FIG. 16 shows a photograph showing the alignment state of the ferroelectric liquid crystal in the liquid crystal display element.

[Comparative Example 1]
A liquid crystal display device was produced in the same manner as in Example 1 except that in the production of the second alignment treatment substrate, a layer using a polymerizable liquid crystal was not formed on an alignment film using a photo-alignment material.
When the liquid crystal drive characteristics of the manufactured liquid crystal display element were measured, the drive characteristics showed V-shaped switching characteristics.
FIG. 15 shows the relationship between the applied voltage and the amount of transmitted light in this liquid crystal display element. FIG. 17 shows a photograph showing the alignment state of the ferroelectric liquid crystal in the liquid crystal display element.

[Example 2]
In the production of the second alignment treatment substrate, the same as in Example 1 except that instead of forming an alignment film using a photo-alignment material and a layer using a polymerizable liquid crystal, an alignment film was formed as shown below. A liquid crystal display element was produced by the method described above.
A photo-alignment material (product name: ROP103, manufactured by ROLIC Technology, Inc.) is spin-coated on a glass substrate for 20 seconds at a rotation speed of 1000 rpm, dried at 100 ° C. for 3 minutes, and then irradiated with polarized ultraviolet rays for about 100 mJ / cm ^2. Then, the orientation treatment was performed.

When the liquid crystal drive characteristics of the manufactured liquid crystal display element were measured, the drive characteristics showed a half V-shaped switching characteristic.
FIG. 15 shows the relationship between the applied voltage and the amount of transmitted light in this liquid crystal display element.

[Example 3]
In the production of the second alignment treatment substrate, the same as in Example 1 except that instead of forming an alignment film using a photo-alignment material and a layer using a polymerizable liquid crystal, an alignment film was formed as shown below. A liquid crystal display element was produced by the method described above.
A glass substrate is spin-coated with a 2 wt% trichloroethanol solution of nylon 6 (manufactured by Aldrich) at a rotation speed of 1000 rpm for 20 seconds, dried at 100 ° C. for 3 minutes, then rubbed, and the rubbed alignment film is formed. Formed.
When the liquid crystal drive characteristics of the manufactured liquid crystal display element were measured, the drive characteristics showed a half V-shaped switching characteristic.

[Example 4]
In the production of the second alignment treatment substrate, the same as in Example 1 except that instead of forming an alignment film using a photo-alignment material and a layer using a polymerizable liquid crystal, an alignment film was formed as shown below. A liquid crystal display element was produced by the method described above.
2% by weight of poly (trimellitic anhydride chloride-co-4,4'-methylenedianiline) (manufactured by Aldrich) on a glass substrate The N-methylpyrrolidinone solution was spin-coated at a rotation speed of 1000 rpm for 20 seconds, dried at 100 ° C. for 3 minutes, and baked at 230 ° C. for 1 hour in an oven, followed by rubbing treatment to form a rubbing-treated alignment film.
When the liquid crystal drive characteristics of the manufactured liquid crystal display element were measured, the drive characteristics showed a half V-shaped switching characteristic.

It is a schematic sectional drawing which shows an example of the liquid crystal display element of this invention. It is the graph which showed the change of the transmitted light amount with respect to the applied voltage of a ferroelectric liquid crystal. It is the graph which showed the change of the transmitted light amount with respect to the applied voltage of a ferroelectric liquid crystal. It is a schematic diagram which shows the behavior of a liquid crystal molecule. It is a schematic diagram which shows an example of the orientation state of a ferroelectric liquid crystal. It is a schematic diagram which shows the other example of the orientation state of a ferroelectric liquid crystal. It is a schematic diagram which shows the other example of the orientation state of a ferroelectric liquid crystal. It is a schematic diagram which shows the other example of the orientation state of a ferroelectric liquid crystal. It is a schematic diagram which shows the spontaneous polarization of a ferroelectric liquid crystal. It is a schematic diagram which shows the other example of the orientation state of a ferroelectric liquid crystal. It is a schematic sectional drawing which shows the other example of the liquid crystal display element of this invention. It is a schematic sectional drawing which shows the other example of the liquid crystal display element of this invention. It is a schematic perspective view which shows the other example of the liquid crystal display element of this invention. It is a schematic diagram which shows the other example of the orientation state of a ferroelectric liquid crystal. 6 is a graph showing changes in the amount of transmitted light with respect to applied voltages of the liquid crystal display elements of Examples 1 and 2 and Comparative Example 1. 3 is a photograph showing the alignment state of the ferroelectric liquid crystal of Example 1. FIG. 6 is a photograph showing the alignment state of the ferroelectric liquid crystal of Comparative Example 1. It is the graph which showed the change of the transmitted light amount with respect to the applied voltage of a ferroelectric liquid crystal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display element 2a ... 1st base material 2b ... 2nd base material 3a ... 1st orientation film 3b ... 2nd orientation film 4a ... 1st electrode layer 4b ... 2nd electrode layer 5 ... Liquid crystal layer 11a ... 1st orientation Processing substrate 11b ... Second alignment processing substrate 25 ... Liquid crystal molecule z ... Layer normal Ps ... Spontaneous polarization

Claims (9)

A first alignment treatment substrate having a first substrate, a first electrode layer formed on the first substrate, and a first alignment film formed on the first electrode layer;
A second base material, a second electrode layer formed on the second base material, and a second alignment film formed on the second electrode layer; A second alignment treatment substrate disposed so that the first alignment film and the second alignment film face each other;
A liquid crystal layer formed between the first alignment film and the second alignment film and including a ferroelectric liquid crystal;
A liquid crystal display element in which the constituent material of the first alignment film and the constituent material of the second alignment film have different compositions,
When the ferroelectric liquid crystal is monostable and the constituent material of the first alignment film and the constituent material of the second alignment film have the same composition, the liquid crystal display element is driven. V-shaped switching characteristics,
By making the constituent material of the first alignment film and the constituent material of the second alignment film have different compositions, the ferroelectric liquid crystal exhibits a half V-shaped switching characteristic when the liquid crystal display element is driven. A liquid crystal display element characterized by comprising.   The second alignment film includes a reactive liquid crystal alignment film formed on the second substrate, and a fixed liquid crystal layer formed on the reactive liquid crystal alignment film and having the reactive liquid crystal fixed thereon. The liquid crystal display element according to claim 1, wherein   The liquid crystal display element according to claim 2, wherein the first alignment film is a photo-alignment film.   2. The liquid crystal according to claim 1, wherein the first alignment film is a photo-alignment film using a photoisomerizable material, and the second alignment film is a photo-alignment film using a photodimerization material. Display element.   The liquid crystal display element according to claim 1, wherein the first alignment film is a photo-alignment film using a photoisomerizable material, and the second alignment film is a rubbing-processed alignment film.   The liquid crystal display element according to claim 1, wherein the first alignment film is a rubbing alignment film, and the second alignment film is a photo-alignment film using a photodimerization type material.   The liquid crystal display element according to claim 5, wherein the alignment film subjected to the rubbing treatment contains polyimide.   7. The liquid crystal display element according to claim 5, wherein the alignment film subjected to the rubbing treatment contains nylon.   The liquid crystal display element according to claim 2, wherein display is performed when a negative voltage is applied to the second electrode layer.