JP2006330310A - Liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display element which can be driven by lower voltage, the liquid crystal display element using a ferroelectric liquid crystal exhibiting monostable properties. <P>SOLUTION: In the liquid crystal display element wherein a first substrate having a first base material, a first electrode layer formed on the first base material and a first alignment layer formed on the first electrode layer and a second substrate having a second base material, a second electrode layer formed on the second base material and a second alignment layer formed on the second electrode layer are disposed so that the first and the second alignment layers may be opposed to each other and that a liquid crystal layer containing the ferroelectric liquid crystal may be interposed between the first and the second alignment layers. The ferroelectric liquid crystal in the liquid crystal layer exhibits monostable properties and a spontaneous polarization direction of the ferroelectric liquid crystal is opposite to a reference direction regulated by the first and the second alignment layers. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display element in which the orientation of ferroelectric liquid crystal is controlled and which has a low driving voltage.

  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 crystals proposed by Clark and Lagerwol are widely known as bistable ones that have two stable states when no voltage is applied, but are limited to switching in two states, light and dark, and have a memory property. However, 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). As such a liquid crystal exhibiting monostability, generally, a ferroelectric liquid crystal that changes phase with a cholesteric phase (Ch) -chiral smectic C (SmC ^* ) phase in the temperature lowering process and does not pass through a smectic A (SmA) phase. Used (upper part of FIG. 5).

On the other hand, the ferroelectric liquid crystal is a liquid crystal that undergoes a phase change between the cholesteric phase (Ch) -smectic A (SmA) phase-chiral smectic C (SmC ^* ) phase in the temperature lowering process and exhibits the SmC ^* phase via the SmA phase. There are materials. Among the ferroelectric liquid crystals currently reported, the liquid crystal material having a phase series that passes through the latter SmA phase is more than the former liquid crystal material that does not pass through the SmA phase. It is known that a ferroelectric liquid crystal having a phase sequence passing through the latter SmA phase usually has two stable states with respect to a single-layer normal (the lower part of FIG. 5) and exhibits bistability. .

  Here, the ferroelectric liquid crystal is expected to be a material suitable for realizing color display by the field sequential color method which has been actively researched in recent years because the ferroelectric liquid layer has high-speed response. ing. In the field sequential color system, the backlight is switched in time with R, G, B, R, G, B, etc., and the black-and-white shutter of the ferroelectric liquid crystal is opened and closed in synchronization with it, and the color is timed by the afterimage effect of the retina. Thus, color display is realized. This field-sequential color system is useful in that color display can be performed with one pixel and a color filter with low transmittance is not required, so that bright and high-definition color display is possible.

  Under such circumstances, in a liquid crystal display element adopting a field sequential color system, a liquid crystal display element excellent in power saving that can be driven at a lower voltage is desired, and a ferroelectric that can be driven at a lower voltage than before. It is desired to realize the alignment state of the conductive liquid crystal.

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

  The present invention has been made in view of the above situation, and provides a liquid crystal display element using a ferroelectric liquid crystal exhibiting monostability, which can be driven at a lower voltage. The main purpose.

In order to achieve the above object, the present invention comprises a first base material, a first electrode layer formed on the first base material, and a first alignment layer formed on the first electrode layer. A second substrate having a first substrate, a second substrate, a second electrode layer formed on the second substrate, and a second alignment layer formed on the second electrode layer. A liquid crystal formed by placing the first alignment layer and the second alignment layer facing each other, and sandwiching a liquid crystal layer containing a ferroelectric liquid crystal between the first alignment layer and the second alignment layer. A display element,
The ferroelectric liquid crystal exhibits monostability in the liquid crystal layer, and the direction of spontaneous polarization of the ferroelectric liquid crystal is relative to a reference direction defined by the first alignment layer and the second alignment layer. A liquid crystal display element characterized by being directed in the opposite direction is provided.

  According to the present invention, the direction of spontaneous polarization of the ferroelectric liquid crystal in the liquid crystal layer is opposite to the reference direction defined by the first alignment layer and the second alignment layer. Thus, the ferroelectric liquid crystal can be driven at a lower voltage. Further, according to the present invention, since the ferroelectric liquid crystal exhibits monostability in the liquid crystal layer, the director of the liquid crystal (inclination of the molecular axis) is continuously changed by voltage change, and the transmitted light intensity is analog-modulated. Thus, gradation display is possible. Therefore, according to the present invention, it is possible to obtain a liquid crystal display element that has a high response speed and can be driven with low power consumption.

  In the above invention, the liquid crystal layer may contain a polymer of actinic radiation curable monomer. By containing a polymer of the active radiation curable monomer in the liquid crystal layer, the alignment of the ferroelectric liquid crystal can be further stabilized in a state where the direction of spontaneous polarization is opposite to the reference direction. Because it can.

  In the present invention, it is preferable that the constituent materials of the first alignment layer and the second alignment layer have different compositions. Since the first alignment layer and the second alignment layer are made of materials having different compositions with the ferroelectric liquid crystal sandwiched therebetween, the ferroelectric liquid crystal can be aligned without forming alignment defects. This is because a proper orientation state can be obtained.

  Further, in the present invention, at least one of the first alignment layer and the second alignment layer is composed of an alignment film and a reactive liquid crystal film formed on the alignment film and fixing a reactive liquid crystal. It may be. According to such an alignment layer, since the reactive liquid crystal is aligned by the alignment film and the alignment state is fixed, the reactive liquid crystal film functions as an alignment film for aligning the ferroelectric liquid crystal. Because it can be done. In addition, the reactive liquid crystal has a relatively similar structure to the ferroelectric liquid crystal, so it has a strong interaction with the ferroelectric liquid crystal and is more effective than the case where only the alignment film is used. This is because the alignment of the liquid crystal can be controlled.

  In the present invention, it is preferable that the first alignment layer and the second alignment layer have a photo-alignment film. This is because the photo-alignment process at the time of forming the photo-alignment film is a non-contact alignment process, so that it is useful in that there is no generation of static electricity and dust and quantitative alignment control is possible.

  Furthermore, in the above invention, the constituent material of the photo-alignment film is a photo-reactive material that imparts anisotropy to the photo-alignment film by causing a photoreaction, or the photo-alignment by causing a photoisomerization reaction. A photoisomerization type material containing a photoisomerization reactive compound that imparts anisotropy to the film is preferable. It is because anisotropy can be easily imparted to the photo-alignment film by using such a material.

  In the present invention, it is preferable that the ferroelectric liquid crystal does not have a smectic A phase in the phase series. By using a ferroelectric liquid crystal that shows monostability and does not have a smectic A phase in the phase series, it becomes possible to drive by an active matrix method using thin film transistors (TFT), and to control gradation by voltage modulation This is because high-definition and high-quality display can be realized.

  In addition, the liquid crystal display element of the present invention is preferably driven by an active matrix method using a thin film transistor (TFT). This is because by adopting an active matrix system using a TFT element, a target pixel can be reliably turned on and off, so that a high-quality display is possible. Furthermore, a TFT substrate in which TFT elements are arranged in a matrix on one substrate and a common electrode substrate in which a common electrode is formed over the entire display portion on the other substrate are combined, and the common electrode substrate is shared. A micro color filter in which a matrix of TFT elements is arranged between an electrode and a substrate can be formed and used as a color liquid crystal display element.

  The liquid crystal display element of the present invention is preferably driven by a field sequential color system. The above ferroelectric liquid crystal is monostable, so it can display gray scales, and it can be driven by the field sequential color method to display a bright and high-definition color video with low power consumption, low cost, wide viewing angle, and wide viewing angle. It is because it is realizable.

Furthermore, the present invention provides a first substrate having a first substrate, a first electrode layer formed on the first substrate, and a first alignment layer formed on the first electrode layer, and A second substrate having a second substrate, a second electrode layer formed on the second substrate, and a second alignment layer formed on the second electrode layer; and A method for manufacturing a liquid crystal display device, wherein the liquid crystal display element is disposed so as to face the second alignment layer, and a liquid crystal layer containing a ferroelectric liquid crystal is sandwiched between the first alignment layer and the second alignment layer. And
A liquid crystal encapsulation step of encapsulating a composition for forming a liquid crystal layer containing the ferroelectric liquid crystal having monostability and an actinic radiation curable monomer between the first alignment layer and the second alignment layer;
A first alignment step in which the ferroelectric liquid crystal is heated to a temperature higher than the transition temperature from the chiral smectic C phase to the nematic phase before or after the liquid crystal encapsulation step, and the encapsulated ferroelectric liquid crystal is cooled;
After the first alignment step, a voltage is applied to the ferroelectric liquid crystal so that the direction of spontaneous polarization is opposite to the reference direction defined by the first alignment layer and the second alignment layer. A second alignment step in which the ferroelectric liquid crystal is heated and cooled to a temperature higher than the transition temperature from the chiral smectic C phase to the nematic phase while a voltage is applied;
And a polymerization step of polymerizing the actinic radiation curable monomer in a state where the ferroelectric liquid crystal is in a chiral smectic C phase.

  According to the present invention, the ferroelectric liquid crystal is polymerized with the actinic radiation curable monomer in the state of chiral smectic C phase, so that the direction of spontaneous polarization in the liquid crystal layer is the first alignment layer and the second alignment layer. Thus, it is possible to easily manufacture a liquid crystal display element in which the ferroelectric liquid crystal is mono-stabilized in a state in which the ferroelectric liquid crystal is oriented in the opposite direction to the reference direction defined by the above.

  In the said invention, it is preferable that the said superposition | polymerization process superposes | polymerizes the said active radiation curable monomer in the state which applied the voltage between the said 1st board | substrate and the said 2nd board | substrate. This is because it is easy to form a liquid crystal layer in which the ferroelectric liquid crystal is mono-stabilized by polymerizing the actinic radiation curable monomer in a state where a voltage is applied between the first substrate and the second substrate. .

  INDUSTRIAL APPLICABILITY The present invention is advantageous in that a liquid crystal display element using a ferroelectric liquid crystal exhibiting monostability and capable of being driven at a lower voltage can be obtained.

  Hereinafter, the liquid crystal display element of the present invention and the manufacturing method thereof will be described in detail.

A. Liquid Crystal Display Element First, the liquid crystal display element of the present invention will be described.
The liquid crystal display element of the present invention includes a first substrate having a first substrate, a first electrode layer formed on the first substrate, and a first alignment layer formed on the first electrode layer. And a second substrate having a second substrate, a second electrode layer formed on the second substrate, and a second alignment layer formed on the second electrode layer. The liquid crystal display element is formed by disposing an alignment layer and the second alignment layer so as to face each other and sandwiching a liquid crystal layer containing a ferroelectric liquid crystal between the first alignment layer and the second alignment layer. And
The ferroelectric liquid crystal exhibits monostability in the liquid crystal layer, and the direction of spontaneous polarization of the ferroelectric liquid crystal is relative to a reference direction defined by the first alignment layer and the second alignment layer. It is characterized by facing in the opposite direction.

  The liquid crystal display element of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an example of the liquid crystal display element of the present invention. As shown in FIG. 1, the liquid crystal display element 10 of the present invention includes a first substrate 11 in which a first electrode layer 2a and a first alignment layer 3a are sequentially formed on a first substrate 1a, and a second substrate 1b. The second substrate 12 on which the second electrode layer 2b and the second alignment layer 3b are formed in order is opposed to the first electrode. The first alignment layer 3a of the first substrate 11 and the second alignment layer 3b of the second substrate 12 are opposed to each other. And a liquid crystal layer 5 containing a ferroelectric liquid crystal is sandwiched therebetween. Further, as illustrated in FIG. 1, the liquid crystal display element of the present invention may include polarizing plates 6a and 6b.

  In the present invention, the ferroelectric liquid crystal exhibits monostability in the liquid crystal layer, and the direction of spontaneous polarization of the ferroelectric liquid crystal is defined by the first alignment layer and the second alignment layer. It is characterized by being directed in the opposite direction with respect to the reference direction.

  In the present invention, “showing monostability” means a state in which the state of the ferroelectric liquid crystal when no voltage is applied is stabilized in one state. Specifically, as illustrated in FIG. 2, the ferroelectric liquid crystal 8 can operate on a cone between two states inclined by a tilt angle ± θ with respect to the layer normal z, but no voltage is applied. Sometimes the ferroelectric liquid crystal 8 is stabilized in any one state on the cone.

  The present invention is characterized in that in the liquid crystal layer, the direction of spontaneous polarization of the ferroelectric liquid crystal is opposite to the reference direction defined by the first alignment layer and the second alignment layer. It is said. The “reference direction” in the present invention is the direction of spontaneous polarization of the ferroelectric liquid crystal when the ferroelectric liquid crystal is sandwiched between the first alignment layer and the second alignment layer. And the direction of spontaneous polarization when no voltage is applied between the second alignment layers. Such a reference direction is defined by the first alignment layer and the second alignment layer.

Next, the “reference direction” in the present invention will be specifically described with reference to the drawings.
FIG. 3 is a schematic view illustrating the alignment state of the ferroelectric liquid crystal in the liquid crystal layer sandwiched between the first alignment layer 3a and the second alignment layer 3b. The first alignment layer 3a and the second alignment layer 3b in the present invention have different polarities depending on the materials constituting them, but in FIG. 3, for example, the second alignment layer 3b is more exemplary than the first alignment layer. Is assumed to have a relatively large positive polarity. In such a case, when no voltage is applied between the first alignment layer 3a and the second alignment layer 3b, the ferroelectric liquid crystal 8 existing between the first alignment layer 3a and the second alignment layer 3b is The molecules are arranged so that the positive electrodes of the molecules face the direction of the first alignment layer 3a (FIG. 3A). The direction of the spontaneous polarization is such a direction because the direction of the spontaneous polarization Ps is a direction in which the polarization of the ferroelectric liquid crystal and the polarization of the alignment layer are electrically balanced. This is because is in an electrically stable state.

  In the present invention, as shown in FIG. 3A, when the ferroelectric liquid crystal is sandwiched between the first alignment layer and the second alignment layer, the first alignment layer and the second alignment layer A direction indicated by the direction of spontaneous polarization in a state where no voltage is applied to is defined as a “reference direction”.

  In the present invention, the spontaneous polarization direction is opposite to the reference direction. Such an alignment state of the ferroelectric liquid crystal will be specifically described with reference to the example shown in FIG. FIG. 3B is a schematic view illustrating the alignment state of the ferroelectric liquid crystal in the invention. In FIG. 3B, the ferroelectric liquid crystal 8 existing between the first alignment layer 3a and the second alignment layer 3b is arranged so that the positive electrode of the molecule faces the direction of the second alignment layer 3b. . In such a case, the direction Ps of spontaneous polarization of the ferroelectric liquid crystal is directed in the opposite direction to the reference direction (the direction of spontaneous polarization Ps of the ferroelectric liquid crystal shown in FIG. 3A). .

  As shown in FIG. 3B, the direction of spontaneous polarization of the ferroelectric liquid crystal according to the present invention is directed in the opposite direction to the reference direction.

  When the direction of the spontaneous polarization is opposite to the reference direction, the direction of the spontaneous polarization Ps is a direction in which the polarization of the ferroelectric liquid crystal and the polarization of the alignment layer are electrically repelled. The ferroelectric liquid crystal is in a relatively electrically unstable state.

  Next, a method for examining whether the spontaneous polarization of the ferroelectric liquid crystal in an arbitrary liquid crystal display element is oriented in the reference direction or in the opposite direction to the reference direction will be described.

The direction of spontaneous polarization of the ferroelectric liquid crystal in an arbitrary liquid crystal display element (hereinafter referred to as an evaluated liquid crystal display element) is determined by performing a realignment process of the ferroelectric liquid crystal on the evaluated liquid crystal display element. This can be investigated by comparing the direction of the electric field driven by the ferroelectric liquid crystal before and after the alignment treatment (hereinafter referred to as the liquid crystal driving electric field direction).
Specifically, the liquid crystal display element to be evaluated is heated to a temperature that is 10 ° C. to 20 ° C. higher than the nematic to isotropic phase transition temperature of the ferroelectric liquid crystal contained in the liquid crystal layer of the liquid crystal display element to be evaluated. The ferroelectric liquid crystal is realigned by slowly cooling it to an ordinary temperature without applying an electric field. When the liquid crystal driving electric field direction is reversed by performing such realignment treatment, the spontaneous polarization of the ferroelectric liquid crystal in the liquid crystal display element to be evaluated is directed in the opposite direction to the reference direction. become. On the other hand, when the liquid crystal driving electric field direction does not change due to the realignment treatment, the spontaneous polarization of the ferroelectric liquid crystal in the liquid crystal display element to be evaluated is directed to the reference direction.

Next, a method for evaluating the liquid crystal driving electric field direction will be described.
First, a method for evaluating the liquid crystal drive electric field direction before the realignment process will be described. The liquid crystal driving electric field direction before the realignment treatment is arranged between two polarizing plates in which the liquid crystal display element to be evaluated is arranged in a crossed Nicol state, and is in a dark state without applying an electric field. Evaluation is carried out by applying an electric field to. By applying an electric field, the ferroelectric liquid crystal is driven 2θ ± 5 °, and the direction of the electric field in the bright state becomes the liquid crystal driving electric field direction before the realignment treatment. Here, when the liquid crystal display element to be evaluated is placed between two polarizing plates arranged in crossed Nicols and is in a dark state, the intensity of transmitted light changes by rotating the liquid crystal display element to be evaluated. In this state, the intensity of transmitted light is minimized. In addition, the θ is an angle formed by the layer normal line z of the ferroelectric liquid crystal and the alignment processing direction d of the alignment layer, as shown in FIG.

Next, an evaluation method of the liquid crystal driving electric field direction after the realignment process will be described. The liquid crystal driving electric field direction after the realignment treatment is disposed between two polarizing plates arranged in crossed Nicols and the liquid crystal display element to be evaluated subjected to the above realignment treatment is darkened without applying an electric field. Evaluation is performed by applying an electric field to the liquid crystal display element to be evaluated. By applying an electric field, the ferroelectric liquid crystal is driven 2θ ± 5 °, and the direction of the electric field when 51% or more of the display area of the liquid crystal display element to be evaluated is in the bright state is the liquid crystal driving after the realignment treatment. The electric field direction.
Here, when the liquid crystal display element to be evaluated that has been subjected to the above realignment treatment is disposed between two polarizing plates arranged in a crossed Nicol state, and the dark liquid is in a dark state, the liquid crystal display element is rotated to rotate the liquid crystal display element. When the intensity changes, the transmitted light intensity is the smallest. In addition, as a method for confirming that 51% or more of the display area of the liquid crystal display element to be evaluated becomes bright when an electric field is applied, for example, the display state of the liquid crystal display element to be evaluated when the electric field is applied is observed with a polarizing microscope. By doing this, it can be confirmed by calculating the white / black area of black and white (bright and dark) display and calculating the ratio of the bright state.

Next, the “dark state” and the “bright state” will be described. For example, as shown in FIG. 1, polarizing plates 6a and 6b are provided outside the first substrate 11 and the second substrate 12, and light is incident from the polarizing plate 6a side, and light is emitted from the polarizing plate 6b side. . In the two polarizing plates 6a and 6b, the respective polarizing axes are substantially perpendicular, and the polarizing axis of the polarizing plate 6a and the alignment treatment direction of the first alignment film 3a (the alignment direction of the ferroelectric liquid crystal) are approximately parallel. It is arranged to be.
When no voltage is applied, the linearly polarized light transmitted through the polarizing plate 6a and the alignment direction of the ferroelectric liquid crystal coincide with each other. Therefore, the refractive index anisotropy of the ferroelectric liquid crystal does not appear, and the straight line transmitted through the polarizing plate 6a. The polarized light passes through the liquid crystal layer 5 as it is and is blocked by the polarizing plate 6b.
On the other hand, in the voltage application state, the ferroelectric liquid crystal moves on the cone, and the linearly polarized light transmitted through the polarizing plate 6a and the alignment direction of the ferroelectric liquid crystal have a predetermined angle. The transmitted linearly polarized light becomes elliptically polarized light due to the birefringence of the ferroelectric liquid crystal. Of the elliptically polarized light, only linearly polarized light that matches the polarization axis of the polarizing plate 6b is transmitted through the polarizing plate 6b.
In the present invention, a state in which incident light is blocked by polarizing plates in a crossed Nicol state is referred to as a “dark state”, and a state in which incident light is transmitted through a polarizing plate in a crossed Nicol state is referred to as a “bright state”. And

  In the evaluation method of the liquid crystal driving electric field direction, it is confirmed that the ferroelectric liquid crystal is driven by 2θ ± 5 ° by evaluating the driving angle of the ferroelectric liquid crystal. The drive angle can be evaluated as follows. First, the liquid crystal display element to be evaluated is placed between two polarizing plates arranged in crossed Nicols. At this time, it arrange | positions so that the polarization axis of one polarizing plate and the orientation direction of the ferroelectric liquid crystal of a liquid-crystal layer may become parallel, and this position is made into a reference | standard. When an electric field is applied to the liquid crystal display element to be evaluated, the ferroelectric liquid crystal has a predetermined angle with respect to 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 electric field applied, the liquid crystal display element is rotated to make it dark. And the angle which rotated the liquid crystal display element at this time is measured. The angle at which the liquid crystal display element is rotated is the driving angle of the ferroelectric liquid crystal. The drive angle of the liquid crystal display element to be evaluated after the realignment treatment may be evaluated for a bright state portion that is 51% or more of the display area.

  For the liquid crystal display element to be evaluated, when the alignment of the ferroelectric liquid crystal cannot be changed by the realignment process, for example, when the liquid crystal layer is stabilized with a polymer, the liquid crystal display to be evaluated A liquid crystal display element having the same configuration as the element may be duplicated, and the above evaluation may be performed on the duplicated liquid crystal display element. Since the reference direction depends on the constituent materials of the first alignment layer and the second alignment layer and the type of the ferroelectric liquid crystal, at least the first alignment layer and the second alignment layer are replicated when the liquid crystal display element is replicated. It is sufficient that the constituent material and the type of the ferroelectric liquid crystal are the same as those of the liquid crystal display element to be evaluated, and the other configurations are not necessarily the same.

  According to the present invention, when the direction of spontaneous polarization of the ferroelectric liquid crystal is opposite to the reference direction in the liquid crystal layer, a voltage is applied to drive the ferroelectric liquid crystal. In addition, the ferroelectric liquid crystal is driven in a direction in which the direction of spontaneous polarization Ps is electrically balanced from the direction in which the polarization of the ferroelectric liquid crystal and the polarization of the alignment layer are electrically repelled. That is, the ferroelectric liquid crystal is driven from a relatively unstable state to a stable state. With such a mechanism, the liquid crystal display element of the present invention can be driven at a lower voltage.

  Further, according to the present invention, since the ferroelectric liquid crystal exhibits monostability in the liquid crystal layer, the director of the liquid crystal (inclination of the molecular axis) is continuously changed by voltage change, and the transmitted light intensity is analog-modulated. Thus, gradation display is possible.

  As described above, according to the present invention, it is possible to obtain a liquid crystal display element that has a high response speed and can be driven with power saving. Hereinafter, each structure of the liquid crystal display element of this invention is demonstrated.

1. Liquid Crystal Layer The liquid crystal layer used in the present invention is constituted by being sandwiched between the first alignment layer and the second alignment layer, and includes a ferroelectric liquid crystal. The liquid crystal layer used in the present invention may contain a polymer of actinic radiation curable monomer. By containing a polymer of the active radiation curable monomer in the liquid crystal layer, the alignment of the ferroelectric liquid crystal can be further stabilized in a state where the direction of spontaneous polarization is opposite to the reference direction. Because it can.

(1) Ferroelectric liquid crystal The ferroelectric liquid crystal used in the present invention is not particularly limited as long as it exhibits monostability and exhibits a chiral smectic C phase (SmC ^* ) phase. Of these, those having no smectic A phase in the phase sequence are preferred in the present invention. By using a ferroelectric liquid crystal that does not go through the smectic A phase, it becomes possible to drive by an active matrix method using thin film transistors (TFTs), and to control gradation by voltage modulation, so that high definition and high quality are possible. This is because the display can be realized. Examples of such ferroelectric liquid crystal include those in which the phase series changes from a nematic phase (N) -cholesteric phase (Ch) -chiral smectic C phase (SmC ^* ), or a nematic phase (N) -chiral smectic. Examples thereof include those that change phase with C phase (SmC ^* ).

Further, the ferroelectric liquid crystal has a half-V shaped switching (hereinafter referred to as HV-shaped switching) characteristic in which liquid crystal molecules operate only when a positive or negative voltage as shown in FIG. 4 is applied, for example. It is preferable to show this. When the ferroelectric liquid crystal exhibiting such HV-shaped switching characteristics is used, the opening time as a black and white shutter can be made sufficiently long, whereby each color that can be temporally switched can be displayed brighter. A bright color liquid crystal display element can be realized.
Here, the “HV-shaped switching characteristic” refers to an electro-optical characteristic in which the light transmittance with respect to the applied voltage is asymmetric.

  Such a ferroelectric liquid crystal can be variously selected from generally known liquid crystal materials according to required characteristics. Specific examples of the ferroelectric liquid crystal used in the present invention include “R2301” manufactured by AZ Electronic Materials.

(2) Polymer of actinic radiation curable monomer The polymer of actinic radiation curable monomer contained in the liquid crystal layer has a function of stabilizing the alignment of the ferroelectric liquid crystal in the liquid crystal layer.

  The actinic radiation curable monomer used in the polymer of the actinic radiation curable monomer forms a polymer by causing a polymerization reaction upon irradiation with actinic radiation, and stabilizes the alignment state of the ferroelectric liquid crystal. There is no particular limitation as long as it is possible. Examples of such actinic radiation curable monomers include an electron beam curable monomer that undergoes a polymerization reaction upon irradiation with an electron beam, and a photocurable monomer that undergoes a polymerization reaction upon irradiation with light. In particular, in the present invention, it is preferable to use a photocurable monomer. It is because the manufacturing method of the liquid crystal display element of this invention can be simplified by using a photocurable monomer.

  The photocurable monomer is not particularly limited as long as it causes a polymerization reaction when irradiated with light having a wavelength in the range of 150 nm to 500 nm. In particular, in the present invention, it is preferable to use an ultraviolet curable monomer that undergoes a polymerization reaction when irradiated with light having a wavelength in the range of 250 nm to 450 nm, particularly in the range of 300 nm to 400 nm. This is because it has advantages in terms of the ease of the irradiation apparatus.

  The polymerizable functional group possessed by the ultraviolet curable monomer is not particularly limited as long as it causes a polymerization reaction when irradiated with ultraviolet rays in the wavelength region. In the present invention, it is preferable to use an ultraviolet curable monomer having an acrylate group.

  The ultraviolet curable monomer may be a monofunctional monomer having one polymerizable functional group in one molecule, or a polyfunctional monomer having two or more polymerizable functional groups in one molecule. May be. In particular, in the present invention, it is preferable to use a polyfunctional monomer. By using a polyfunctional monomer, it becomes possible to form a stronger polymer network in the liquid crystal layer, so that the intermolecular force and the polymer network at the interface of the first alignment layer can be strengthened. Therefore, by using a polyfunctional monomer, it is possible to prevent the alignment of the ferroelectric liquid crystal from being disturbed by the temperature change of the liquid crystal layer.

  In the present invention, among the polyfunctional monomers, a bifunctional monomer having a polymerizable functional group at both ends of the molecule is preferable. By having the above functional groups at both ends of the molecule, a polymer network with a wide interval between the polymers can be formed, so that the driving voltage of the ferroelectric liquid crystal by containing a polymer of active radiation curable monomer in the liquid crystal layer It is because the fall of can be prevented.

  In the present invention, among the ultraviolet curable monomers, it is preferable to use an ultraviolet curable liquid crystal monomer that exhibits liquid crystallinity. The reason why such an ultraviolet curable liquid crystal monomer is preferable is as follows. That is, since the ultraviolet curable liquid crystal monomer exhibits liquid crystallinity, it can be regularly arranged by the alignment regulating force of the first alignment layer or the second alignment layer. Therefore, after the ultraviolet curable liquid crystal monomer is regularly arranged and then a polymerization reaction is caused, it can be fixed in the liquid crystal layer while maintaining the regular arrangement state. Since the polymer having such a regular alignment state is present in the liquid crystal layer, the alignment stability of the ferroelectric liquid crystal can be improved. It is because it can be made excellent in impact.

  The liquid crystal phase exhibited by the ultraviolet curable liquid crystal monomer is not particularly limited, and examples thereof include a nematic phase, an SmA phase, and an SmC phase.

  As said ultraviolet curable liquid crystal monomer used for this invention, the compound shown to a following formula can be mentioned, for example.

In the above formula, A, B, D, E and F represent benzene, cyclohexane or pyrimidine, and these may have a substituent such as halogen. A and B, or D and E may be bonded via a bonding group such as an acetylene group, a methylene group, or an ester group. M ¹ and M ² may be any of a hydrogen atom, an alkyl group having 3 to 9 carbon atoms, an alkoxycarbonyl group having 3 to 9 carbon atoms, or a cyano group. Furthermore, the acryloyloxy group at the end of the molecular chain and A or D may be bonded via a spacer such as an alkylene group having 3 to 6 carbon atoms.

  In the above formula, Y is hydrogen, alkyl having 1 to 20 carbon atoms, alkenyl having 1 to 20 carbon atoms, alkyloxy having 1 to 20 carbon atoms, alkyloxycarbonyl having 1 to 20 carbon atoms, formyl, 1 to 1 carbon atoms. It represents 20 alkylcarbonyl, C1-20 alkylcarbonyloxy, halogen, cyano or nitro.

  Among the compounds represented by the above formula, specific compounds that can be suitably used in the present invention include compounds represented by the following formula.

  The polymer of actinic radiation curable monomers used in the present invention may be a polymer of a single actinic radiation curable monomer, or may be a polymer of two or more different actinic radiation curable monomers. . In the case of using a polymer of two or more different actinic radiation curable monomers, for example, a polymer of the above ultraviolet curable liquid crystal monomer and another ultraviolet curable monomer can be exemplified.

  When the above-mentioned ultraviolet curable liquid crystal monomer is used as the active radiation curable monomer, the polymer of the active radiation curable monomer used in the present invention has an atomic group exhibiting liquid crystallinity in the main chain, so that the main chain is liquid crystal. A main chain liquid crystal polymer exhibiting liquidity may be used, or a side chain liquid crystal polymer exhibiting liquid crystallinity in the side chain by having an atomic group exhibiting liquid crystallinity in the side chain may be used. Among these, in the present invention, a side chain liquid crystal polymer is preferable. This is because the presence of an atomic group exhibiting liquid crystallinity in the side chain increases the degree of freedom of the atomic group, so that the atomic group exhibiting liquid crystallinity is easily aligned in the liquid crystal layer. Further, as a result, the alignment stability of the ferroelectric liquid crystal in the liquid crystal layer can be improved.

The abundance of the polymer of active radiation curable monomer in the liquid crystal layer is not particularly limited as long as it is within a range in which the alignment stability of the ferroelectric liquid crystal can be brought to a desired level, but usually 0 in the liquid crystal layer. It is preferably in the range of 5% by mass to 30% by mass, particularly preferably in the range of 1% by mass to 20% by mass, and particularly preferably in the range of 1% by mass to 10% by mass. This is because if it exceeds the above range, the driving voltage of the ferroelectric liquid crystal may increase or the response speed may decrease. On the other hand, if the amount is less than the above range, the alignment stability of the ferroelectric liquid crystal becomes insufficient, and the heat resistance and impact resistance of the liquid crystal display element of the present invention may be impaired.
Here, the abundance of the polymer of active radiation curable monomer in the liquid crystal layer is determined by washing the weight of the polymer of active radiation curable monomer remaining after washing the monomolecular liquid crystal in the liquid crystal layer with a solvent. It can be calculated from the remaining amount obtained by surveying and the total mass of the liquid crystal layer.

  The liquid crystal layer used in the present invention may contain other compounds as long as the object of the present invention is not impaired. Examples of such other compounds include unreacted actinic radiation curable monomers, photopolymerization initiators, reaction initiators, and reaction inhibitors. Examples of the compound used as the photopolymerization initiator include compounds described in the reactive liquid crystal film of “2. First substrate” described later.

(3) Others The thickness of the liquid crystal layer composed of the ferroelectric liquid crystal is preferably in the range of 1.2 μm to 3.0 μm, more preferably 1.3 μm to 2.5 μm, and even more preferably 1. Within the range of 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 a spacer such as beads.

2. First substrate A first substrate used in the present invention includes a first base material, a first electrode layer formed on the first base material, and a first alignment layer formed on the first electrode layer. I have it. Hereinafter, each configuration of the first substrate will be described.

(1) First alignment layer The first alignment layer used in the present invention is not particularly limited as long as the alignment of the ferroelectric liquid crystal can be controlled.
The first alignment layer used in the present invention may be composed of an alignment film alone, and is composed of an alignment film and a reactive liquid crystal film formed by fixing a reactive liquid crystal on the alignment film. It may be a thing.

a. Alignment Film As the alignment film used for the first alignment layer, for example, a rubbing alignment film subjected to rubbing treatment, a photo alignment film subjected to photo alignment treatment, or the like can be used. Among these, it is preferable to use a photo-alignment film. This is because the photo-alignment process is a non-contact alignment process, which is useful in that there is no generation of static electricity or dust and quantitative control of the alignment process is possible. Hereinafter, the photo-alignment film will be described.

(I) Photo-alignment film A photo-alignment film is obtained by irradiating a substrate coated with a constituent material of a photo-alignment film, 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 constituent material of the photo-alignment film used in the present invention is particularly limited as long as it has the effect of aligning the ferroelectric liquid crystal (photo-alignment) by irradiating light and causing a photoexcitation reaction. However, such materials are large, photoreactive materials that impart anisotropy to the photoalignment film by causing a photoreaction, and anisotropic to the photoalignment film by causing a photoisomerization reaction. It can be divided into photoisomerization type materials that impart properties.

The wavelength region of light that causes the photoexcitation reaction of the constituent material of the photo-alignment film 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.
Hereinafter, the photoreactive material and the photoisomerization type material will be described.

(Photoreactive type)
First, a photoreactive component material will be described. As described above, the photoreactive component material is a material that imparts anisotropy to the photoalignment film by causing a photoreaction. The photoreactive type constituent material used in the present invention is not particularly limited as long as it has such characteristics, but among these, the above light can be produced by causing a photodimerization reaction or a photolysis reaction. A material that imparts anisotropy to the alignment film is preferred.

  Here, the photodimerization reaction refers to a reaction in which a 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 photo-alignment film different. It is possible to impart directionality. The photolysis reaction is a reaction that decomposes molecular chains such as polyimide oriented in the polarization direction by light irradiation. This reaction leaves a molecular chain oriented in the direction perpendicular to the polarization direction, and is different from the photo-alignment film. It is possible to impart directionality. 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 photoreactive material utilizing such a photodimerization reaction is not particularly limited as long as it is a material that can impart anisotropy to the photoalignment film by the photodimerization reaction, but is radically polymerizable. It is preferable that the photodimerization reactive compound which has the dichroism which has the functional group of this and has dichroism which makes absorption different with polarization directions is included. This is because by radical polymerization of the reaction site oriented in the polarization direction, the orientation of the photodimerization reactive compound is stabilized and anisotropy can be easily imparted to the photo-alignment 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 photo-alignment film by radical polymerization of α and β unsaturated ketone double bonds aligned 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 appropriate anisotropy to the photo-alignment film. On the other hand, if it is too large, the viscosity of the coating liquid at the time of forming the photo-alignment film becomes high and it may be difficult to form a uniform coating film.

  As a dimerization reactive polymer, the compound represented by a following formula can be illustrated.

In the above formula, M ¹¹ and M ¹² each independently represent a monomer unit of a monopolymer or a copolymer. Examples thereof include ethylene, acrylate, methacrylate, 2-chloroacrylate, acrylamide, methacrylamide, 2-chloroacrylamide, styrene derivatives, maleic acid derivatives, and siloxane. M ¹² may be acrylonitrile, methacrylonitrile, methacrylate, methyl methacrylate, hydroxyalkyl acrylate or hydroxyalkyl methacrylate. x and y represent the molar ratio of each monomer unit in the case of a copolymer, and are numbers satisfying 0 <x ≦ 1, 0 ≦ y <1 and satisfying x + y = 1, respectively. It is. n represents an integer of 4 to 30,000. D ¹ and D ² represent spacer units.

R ¹ is a group represented by -A ^1- (Z ¹ -B ¹ ) _z -Z ^2- , and R ² is represented by -A ^1- (Z ¹ -B ¹ ) _z -Z ^3-. It is a group. Here, A ¹ and B ¹ are each independently a covalent single bond, pyridine-2,5-diyl, pyrimidine-2,5-diyl, 1,4-cyclohexylene, 1,3-dioxane-2, It represents 5-diyl or 1,4-phenylene which may have a substituent. Z ¹ and Z ² are each independently a covalent single bond, —CH ₂ —CH ₂ —, —CH ₂ O—, —OCH ₂ —, —CONR—, —RNCO—, —COO— or — Represents OOC-. R is a hydrogen atom or a lower alkyl group, and Z ³ is a hydrogen atom or an alkyl or alkoxy having 1 to 12 carbon atoms, which may have a substituent, cyano, nitro, or halogen. z is an integer of 0-4. E ¹ represents a photodimerization reaction site, and examples thereof include cinnamic acid ester, coumarin, quinoline, chalcone group, cinnamoyl group and the like. j and k are each independently 0 or 1.

  As such a dimerization reactive polymer, More preferably, the compound represented by a following formula can be mentioned.

  Among the dimerization reactive polymers, at least one of the compounds (1) to (4) represented by the following formula is particularly preferable.

  In the present invention, as the photodimerization reactive compound, various photodimerization reaction sites and substituents can be selected from the above-mentioned compounds according to required characteristics. Moreover, the photodimerization reactive compound can also be used individually by 1 type or in combination of 2 or more types.

  In addition to the photodimerization reactive compound, the photoreactive material using photodimerization reaction may contain an additive within a range that does not interfere with the photoalignment property of the photoalignment film. 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.

  Specific examples of the photodimerization reactive compound used in the present invention include “ROP103” and “ROP102” manufactured by Rolic.

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

(Photoisomerization type)
Next, the photoisomerization type material will be described. The photoisomerization type material here is a material that imparts anisotropy to the photo-alignment film by causing a photoisomerization reaction as described above, and is particularly limited as long as it has such characteristics. However, it is preferable to include a photoisomerization reactive compound that imparts anisotropy to the photoalignment film by causing a photoisomerization reaction. By including such a photoisomerization-reactive compound, a stable isomer among a plurality of isomers is increased by light irradiation, so that anisotropy can be easily imparted to the photo-alignment film. It is.

  Such a 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 light It is preferable that a photoisomerization reaction is caused by irradiation. This is because anisotropy can be easily imparted to the photo-alignment film by causing isomerization of the reaction site oriented in the polarization direction of the photoisomerization-reactive compound having such characteristics.

  The photoisomerization reaction that produces such a photoisomerization-reactive compound is preferably a cis-trans isomerization reaction. This is because either the cis isomer or the trans isomer is increased by light irradiation, whereby anisotropy can be imparted to the photo-alignment film.

  Examples of such photoisomerization-reactive compounds include monomolecular compounds and polymerizable monomers that are polymerized by light or heat. These may be selected as appropriate according to the type of ferroelectric liquid crystal used, but the anisotropy is imparted to the photo-alignment film by light irradiation, and then the anisotropy is stabilized by polymerizing. 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 photo-alignment 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 photo-alignment film due to polymerization becomes more stable, the bifunctional monomer It is preferable that

  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 photo-alignment film becomes larger, and is particularly suitable for controlling the alignment of ferroelectric liquid crystals Because it becomes. 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.

  Hereinafter, the reason why anisotropy can be imparted to the photo-alignment film by causing the azobenzene skeleton to undergo a photoisomerization reaction will be described. First, when the azobenzene skeleton is irradiated with linearly polarized ultraviolet light, the trans azobenzene skeleton having the molecular long axis oriented in the polarization direction is changed to a cis isomer as shown in the following formula.

  Since the cis isomer of the azobenzene skeleton is chemically unstable compared to the trans isomer, it thermally or absorbs visible light and returns to the trans isomer. Whether to become the right transformer body occurs with the same probability. Therefore, if the ultraviolet light is continuously absorbed, the ratio of the right-side trans isomer increases, and the average orientation direction of the azobenzene skeleton becomes perpendicular to the polarization direction of the ultraviolet light. In the present invention, by utilizing this phenomenon, the alignment direction of the azobenzene skeleton is aligned, anisotropy is imparted to the photo-alignment film, and the alignment of liquid crystal molecules on the film can be controlled.

  Among such compounds having an azobenzene skeleton in the molecule, examples of the monomolecular compound include compounds represented by the following formula.

  Moreover, as a polymerizable monomer which has the said azobenzene skeleton as a side chain, the compound represented by a following formula can be mentioned, for example.

  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.

  The photoisomerization type material used in the present invention may contain additives in addition to the above-mentioned photoisomerization reactive compound as long as the photoalignment property of the photoalignment film is not hindered. 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 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 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.

(Ii) Composition of the constituent material of the alignment film In the present invention, the constituent materials of the first alignment layer and the second alignment layer described later preferably have different compositions. In general, a ferroelectric liquid crystal having a phase sequence that does not pass through an SmA phase as exemplified in the upper part of FIG. 5 is likely to generate two regions (double domains) having different layer normal directions. In the present invention, since the first alignment layer and the second alignment layer are made of materials having different compositions, the alignment of the ferroelectric liquid crystal is made simple without causing such alignment defects. Can be stabilized.

  In order to change the composition of the constituent materials of the first alignment layer and the second alignment layer, for example, one may be a photo-alignment film and the other may be a rubbing alignment film. Moreover, both can be made into a rubbing alignment film, and the composition of the constituent material of a rubbing alignment film can be made different, or both can be made into a photo-alignment film and the composition of the constituent material of a photo-alignment film can be made different.

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

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

  Furthermore, when the first alignment layer and the second alignment layer are made of a photo-alignment film using a photo-reactive material, the light dimerization-reactive compound, for example, the photo-dimerization-reactive polymer, can be selected by various selection. The composition of the constituent material of the alignment film can be different. Furthermore, the composition can be changed by changing the amount of the additive described above.

b. Reactive Liquid Crystal Film The first alignment layer in the present invention may be composed of the alignment film and a reactive liquid crystal film formed on the alignment film and formed by fixing reactive liquid crystals. An embodiment in which the first alignment layer is composed of the alignment film and the reactive liquid crystal film will be described with reference to the drawings. FIG. 6 is a schematic cross-sectional view showing an example in which the first alignment layer is composed of an alignment film and a reactive liquid crystal film. As illustrated in FIG. 6, the first alignment layer 3a in the present invention may have a configuration in which a reactive liquid crystal film 32a formed by fixing a reactive liquid crystal is formed on an alignment film 31a.

  The reactive liquid crystal film is aligned by being formed on the alignment film. For example, the reactive liquid crystal film can be formed by irradiating ultraviolet rays to polymerize the reactive liquid crystal and fixing the alignment state. it can. Since the reactive liquid crystal film is formed by fixing the alignment state of the reactive liquid crystal as described above, it functions 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. Furthermore, the reactive liquid crystal is relatively similar in structure to the ferroelectric liquid crystal and has a strong interaction with the ferroelectric liquid crystal, so that it is more effective than the case where the first alignment layer is composed only of the alignment film. The alignment of the dielectric liquid crystal can be controlled.

  The reactive liquid crystal used for the reactive alignment film 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.

  As a monoacrylate monomer, the compound represented, for example by a following formula can be illustrated.

In the above formula, A, B, D, E and F represent benzene, cyclohexane or pyrimidine, and these may have a substituent such as halogen. A and B, or D and E may be bonded via a bonding group such as an acetylene group, a methylene group, or an ester group. M ¹ and M ² may be any of a hydrogen atom, an alkyl group having 3 to 9 carbon atoms, an alkoxycarbonyl group having 3 to 9 carbon atoms, or a cyano group. Furthermore, the acryloyloxy group at the end of the molecular chain and A or D may be bonded via a spacer such as an alkylene group having 3 to 6 carbon atoms.

  Moreover, as a diacrylate monomer, the compound shown to following formula (5)-(7) can be mentioned, for example.

  In the above formulas (5) and (6), X and Y are hydrogen, alkyl having 1 to 20 carbons, alkenyl having 1 to 20 carbons, alkyloxy having 1 to 20 carbons, or alkyl having 1 to 20 carbons. It represents oxycarbonyl, formyl, alkylcarbonyl having 1 to 20 carbons, alkylcarbonyloxy having 1 to 20 carbons, halogen, cyano or nitro. M represents an integer in the range of 2-20.

In the formula (7), Z ²¹ and Z ²² are each independently directly bonded —COO—, —OCO—, —O—, —CH ₂ CH ₂ —, —CH═CH—, —C≡C—, —OCH ₂ —, —CH ₂ O—, —CH ₂ CH ₂ COO—, —OCOCH ₂ CH ₂ — is represented. l and m represent 0 or 1, and n represents an integer in the range of 2-8. In the above formula, R represents hydrogen or alkyl having 1 to 5 carbon atoms.

Among the above, compounds represented by the above formulas (5) and (7) are preferably used. In the case of the compound represented by the above formula (5), X is preferably an alkyloxycarbonyl having 1 to 20 carbon atoms, methyl or chlorine, and especially an alkyloxycarbonyl having 1 to 20 carbon atoms, particularly CH _3. Preferably it is (CH ₂ ) ₄ OCO. Specific examples of the compound represented by the formula (7) include Adeka Kiracol PLC-7209 (Asahi Denka Kogyo Co., Ltd.), Adeka Kiracol PCL-7183 (Asahi Denka Kogyo Co., Ltd.) and the like. it can. As the reactive liquid crystal, ROF-5101 (manufactured by Rolic) or the like can also be suitably used.

  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.

  Examples of the photopolymerization initiator that can be used in the present invention include benzyl (also referred to as bibenzoyl), benzoin isobutyl ether, benzoin isopropyl ether, benzophenone, benzoylbenzoic acid, benzoylmethyl benzoate, and 4-benzoyl-4′-methyldiphenyl. Sulfide, benzylmethyl ketal, dimethylaminomethylbenzoate, 2-n-butoxyethyl-4-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 3,3′-dimethyl-4-methoxybenzophenone, methylobenzoylformate, 2-methyl-1- (4- (methylthio) phenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 1- (4-dodecylphenyl) -2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropyl Phenyl) -2-hydroxy-2-methylpropan-1-one, 2-chlorothioxanthone, 2,4-diethylthioxanthone 2,4-diisopropylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 1-chloro-4- And propoxythioxanthone. In addition to the photopolymerization initiator, it is also possible to add a sensitizer as long as the object of the present invention is not impaired.

  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.

  Furthermore, when using the said photoinitiator, a photoinitiator adjuvant can be used together. Examples of such photopolymerization initiation assistants include tertiary amines such as triethanolamine and methyldiethanolamine, and benzoic acid derivatives such as ethyl 2-dimethylaminoethylbenzoate and ethyl 4-dimethylamidebenzoate. Yes, but not limited to these.

  The thickness of the reactive liquid crystal film 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 reactive liquid crystal film is too thick, anisotropy more than necessary occurs, and if the reactive liquid crystal film is too thin, the predetermined anisotropy may not be obtained.

(2) 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, but the first electrode layer and the first electrode layer described later. It is preferable that at least one of the two electrode layers is 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 of the present invention is an active matrix type liquid crystal display element using TFTs, one of the first electrode layer and the second electrode layer to be described later is entirely formed of the transparent conductor. On the other side, an x electrode and a y electrode are arranged in a matrix, and a TFT element and a pixel electrode are arranged in a portion surrounded by the x electrode and the y electrode.

(3) 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 mentioned preferably. It is done.

3. Second substrate The second substrate used in the present invention includes a second base material, a second electrode layer formed on the second base material, and a second alignment layer formed on the second electrode layer. It is what has.
The second substrate, the second electrode layer, and the second alignment layer that constitute the second substrate are the same as the first substrate, the first electrode layer, and the first alignment layer of the first substrate. Since there is, explanation here is omitted.

4). Driving Method of Liquid Crystal Display Element The liquid crystal display element of the present invention is preferably driven by an active matrix method using a thin film transistor (TFT). This is because by adopting an active matrix system using a TFT element, a target pixel can be reliably turned on and off, so that a high-quality display is possible.

FIG. 7 is a schematic perspective view showing an example of an active matrix liquid crystal display element using the TFT of the present invention. The liquid crystal display element 20 illustrated in FIG. 7 includes a TFT substrate 21a in which TFTs 25 are arranged in a matrix on one base material 22a, and a common electrode substrate 21b in which a common electrode 23 is formed on the other base material 22b. It is what has. An x electrode 24x, a y electrode 24y, and a pixel electrode 24t are formed on the TFT substrate 21a. In such a liquid crystal display element 20, the x electrode 24x and the y electrode 24y are arranged vertically and horizontally, respectively, and the TFT element 25 is operated by applying a signal to these electrodes 24x and 24y to drive the ferroelectric liquid crystal. Can be made. A portion where the x electrode 24x and the y electrode 24y intersect with each other is insulated by an insulating layer (not shown), and the signal of the x electrode 24x and the signal of the y electrode 24y can operate independently. A portion surrounded by the x electrode 24x and the y electrode 24y is a pixel which is a minimum unit for driving the liquid crystal display element of the present invention, and at least one TFT element 25 and a pixel electrode 24t are formed in each pixel. ing. In this liquid crystal display element 20, the TFT element 25 of each pixel can be operated by sequentially applying a signal voltage to the x electrode 24x and the y electrode 24y.
In the present invention, either the TFT substrate or the common electrode substrate may be the first substrate or the second substrate. In FIG. 7, the liquid crystal layer and the alignment layer are omitted.

  Furthermore, the liquid crystal display element of the present invention can be a liquid crystal display element capable of color display by adopting a color filter system or a field sequential color system. For example, in the liquid crystal display element shown in FIG. 7, color display is possible by arranging a micro color filter on the TFT substrate side or the common electrode substrate side.

  The liquid crystal display element of the present invention is particularly preferably driven by a field sequential color system. In the field sequential color system, one pixel is time-divided, and high-speed response is required to obtain good moving image display characteristics. In the present invention, by using the high-speed response of the ferroelectric liquid crystal, color display is possible by combining with an LED light source without using a micro color filter. In addition, since the ferroelectric liquid crystal can be aligned without causing alignment defects, a wide viewing angle, high-speed response, and high-definition color display can be realized.

  The liquid crystal display element of the present invention is basically driven by an active matrix system using TFTs, but can also be driven by a segment system.

5. Method for Producing Liquid Crystal Display Element The method for producing the liquid crystal display element of the present invention is not particularly limited, and a general method can be used. For example, it is described in the section “B. Method for producing liquid crystal display element” described later. It can manufacture by the method to do.

B. Next, a method for manufacturing a liquid crystal display element of the present invention will be described.
The manufacturing method of the liquid crystal display element of this invention has a 1st base material, the 1st electrode layer formed on the said 1st base material, and the 1st orientation layer formed on the said 1st electrode layer. A second substrate having a first substrate, a second substrate, a second electrode layer formed on the second substrate, and a second alignment layer formed on the second electrode layer; A liquid crystal display in which the first alignment layer and the second alignment layer are disposed to face each other, and a liquid crystal layer containing a ferroelectric liquid crystal is sandwiched between the first alignment layer and the second alignment layer. A method for manufacturing an element, comprising:
A liquid crystal encapsulation step of encapsulating a composition for forming a liquid crystal layer containing the ferroelectric liquid crystal having monostability and an actinic radiation curable monomer between the first alignment layer and the second alignment layer;
A first alignment step in which the ferroelectric liquid crystal is heated to a temperature higher than the transition temperature from the chiral smectic C phase to the nematic phase before or after the liquid crystal encapsulation step, and the encapsulated ferroelectric liquid crystal is cooled;
After the first alignment step, a voltage is applied to the ferroelectric liquid crystal so that the direction of spontaneous polarization is opposite to the reference direction defined by the first alignment layer and the second alignment layer. A second alignment step in which the ferroelectric liquid crystal is heated and cooled to a temperature higher than the transition temperature from the chiral smectic C phase to the nematic phase while a voltage is applied;
The ferroelectric liquid crystal has a polymerization step of polymerizing the actinic radiation curable monomer in a chiral smectic C phase.

  In the present invention, a composition for forming a liquid crystal layer comprising, for example, a ferroelectric liquid crystal exhibiting monostability and an actinic radiation curable monomer between the first alignment layer and the second alignment layer is used. After the liquid crystal is sealed in an isotropic liquid state (after the liquid crystal sealing step), the first alignment step and the second alignment step are performed, and the actinic radiation is in the state of chiral smectic C phase. Polymerize the curable monomer.

Next, the first alignment step and the second alignment step will be described with reference to the drawings. FIG. 8 is a schematic view showing an example of the alignment state of the ferroelectric liquid crystal in the first alignment step and the second alignment step in the method for manufacturing a liquid crystal display element of the present invention. In the first alignment step, after the liquid crystal encapsulating step, the ferroelectric liquid crystal is heated to a temperature higher than the transition temperature from the chiral smectic C phase to the nematic phase, and the ferroelectric liquid crystal is cooled, so that FIG. As shown, the ferroelectric liquid crystal 8 is uniformly aligned along the alignment processing direction d of the alignment layer (first alignment step). FIG. 8A shows a state in which the spontaneous polarization Ps of the ferroelectric liquid crystal 8 is directed from the front of the paper to the back direction, and the direction of the spontaneous polarization Ps is the first alignment layer, the second alignment layer, and the like. The reference direction is defined by Here, the reference direction is the same as that described in the above-mentioned section “A. Liquid crystal display element”, and thus description thereof is omitted here.
Next, in the second alignment step, a voltage is applied to the ferroelectric liquid crystal so that the direction of spontaneous polarization is opposite to the reference direction. Then, while applying this voltage, the ferroelectric liquid crystal is heated to a temperature higher than the transition temperature from the chiral smectic C phase to the nematic phase and cooled, so that the ferroelectric liquid crystal 8 is formed as shown in FIG. The spontaneous polarization direction is opposite to the reference direction, and the chiral smectic C phase is set. In FIG. 8B, the spontaneous polarization Ps of the ferroelectric liquid crystal 8 is directed from the back of the page to the front (marked with ● in FIG. 8B).

  The present invention has a polymerization step of polymerizing the actinic radiation curable monomer in a state where the ferroelectric liquid crystal is in a chiral smectic C phase by the first alignment step and the second alignment step. Thus, a liquid crystal display element is manufactured.

  According to the present invention, by polymerizing the actinic radiation curable monomer in a state in which the ferroelectric liquid crystal is in a chiral smectic C phase, the direction of spontaneous polarization in the liquid crystal layer is opposite to the reference direction. A liquid crystal display element in which the ferroelectric liquid crystal is stabilized in the state can be easily manufactured.

  Hereinafter, each process of the manufacturing method of the liquid crystal display element of this invention is demonstrated.

1. Liquid Crystal Encapsulation Process In this process, first, a first substrate is formed by sequentially forming a first electrode layer and a first alignment layer on a first substrate (first substrate formation process). In addition, a second electrode layer and a second alignment layer are sequentially formed on the second base material to produce a second substrate (second substrate forming step). Next, the first substrate and the second substrate are arranged at predetermined positions (substrate arrangement step). And it is the process of enclosing the composition for liquid crystal layer formation containing the ferroelectric liquid crystal which has monostability, and the actinic radiation curable monomer between the 1st board | substrate and the 2nd board | substrate.

(1) 1st board | substrate formation process The 1st board | substrate formation process in this invention forms the 1st alignment layer on the 1st electrode layer and the electrode layer formation process which forms a 1st electrode layer on a 1st base material. A first alignment layer forming step. Hereinafter, each step will be described.

a. First electrode layer forming step The first electrode layer forming step is a step of forming the first electrode layer on the first substrate. As a formation method of the 1st electrode layer in this process, physical vapor deposition (PVD) methods, such as a chemical vapor deposition (CVD) method, sputtering method, an ion plating method, a vacuum evaporation method, etc. can be mentioned, for example. Moreover, as a patterning method of the first electrode layer, a general electrode patterning method can be applied.

  Since the other points of the first substrate and the first electrode layer are the same as those described in the column of the first electrode layer of the “A. Liquid crystal display element”, description thereof is omitted here. .

b. First alignment layer forming step The first alignment layer forming step is a step of forming a first alignment layer on the first electrode layer. As described in the column of the first alignment layer of the “A. Liquid crystal display element”, the first alignment layer only needs to be capable of controlling the alignment of the ferroelectric liquid crystal. As the alignment layer, a first alignment layer composed only of an alignment film may be formed, or a first alignment layer composed of an alignment film and a reactive liquid crystal film may be formed.

(I) Method for forming alignment film In this step, a rubbing alignment film or a photo-alignment film may be formed as the alignment film. Hereinafter, a method for forming the photo-alignment film will be described.

  In order to form the photo-alignment film in this step, first, a photo-alignment film-forming coating solution obtained by diluting the constituent material of the photo-alignment film with an organic solvent is applied and dried. In this case, the content of the photodimerization reactive compound or photoisomerization reactive compound in the photoalignment film-forming coating solution is preferably in the range of 0.05% by mass to 10% by mass, More preferably, it is in the range of 2% by mass to 2% by mass. If the content is less than the above range, it becomes difficult to impart appropriate anisotropy to the photo-alignment film. Conversely, if the content is more than the above range, the viscosity of the photo-alignment film-forming coating liquid increases. This is because it becomes difficult to form a uniform coating film.

  As a coating method of the photo-alignment film forming coating solution, for example, a spin coating method, a roll coating method, a rod bar coating method, a spray coating method, an air knife coating method, a slot die coating method, a wire bar coating method and the like can be used. .

  The thickness of the film obtained by applying the coating liquid for forming a photo-alignment film is preferably in the range of 1 nm to 2000 nm, more preferably in the range of 3 nm to 100 nm. This is because if the thickness of the film is thinner than the above range, sufficient optical alignment may not be obtained, and conversely, if the thickness is thicker than the above range, it may be disadvantageous in cost.

  Anisotropy is imparted to the obtained film by performing photo-alignment treatment. Specifically, by irradiating light with controlled polarization, an anisotropy can be imparted by causing a photoexcitation reaction. The wavelength range of the light to be irradiated may be appropriately selected according to the constituent material of the photo-alignment film to be used, but is preferably in the ultraviolet light range, that is, in the range of 100 nm to 400 nm, more preferably 250 nm. Within the range of ˜380 nm.

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

  Since the other points of the photo-alignment film are the same as those described in the column of the first alignment layer of “A. Liquid crystal display element”, description thereof is omitted here.

(ii) Reactive Liquid Crystal Film Forming Method In this step, the reactive liquid crystal film is formed by forming a reactive liquid crystal film on the alignment film. It is formed by applying a coating liquid for forming a liquid crystal film, performing an alignment treatment, and fixing the alignment state of the reactive liquid crystal. Further, instead of applying the coating liquid for forming the reactive liquid crystal film, a reactive liquid crystal film may be formed by forming a dry film or the like in advance and laminating it on the alignment film. From the viewpoint of the simplicity of the manufacturing process, a method of preparing a reactive liquid crystal film forming coating solution by dissolving a reactive liquid crystal in a solvent, applying this on the alignment film, and removing the solvent is used. Is preferred.

  The solvent used in the coating liquid for forming the reactive liquid crystal film 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 example, hydrocarbons such as benzene, toluene, xylene, n-butylbenzene, diethylbenzene and tetralin; ethers such as methoxybenzene, 1,2-dimethoxybenzene and diethylene glycol dimethyl ether; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, 2 Ketones such as 1,4-pentanedione; esters such as ethyl acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, γ-butyrolactone; 2-pyrrolidone, N-methyl-2-pyrrolidone, dimethylformamide, dimethyl Amide solvents such as acetamide; t-butyl alcohol, diacetone alcohol, glycerin, monoacetin, ethylene glycol, triethyleneglycol 1 or 2 types of alcohols such as phenol and hexylene glycol; phenols such as phenol and parachlorophenol; cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, and ethylene glycol monomethyl ether acetate; is there.

  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 alignment film may be eroded. 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.

  The concentration of the coating liquid for forming the reactive liquid crystal film depends on the solubility of the reactive liquid crystal and the thickness of the reactive liquid crystal film, but cannot be defined unconditionally, but is usually 0.1 to 40% by mass, preferably It adjusts in the range of 1-20 mass%. If the concentration of the reactive liquid crystal film-forming coating liquid is lower than the above range, the reactive liquid crystal may be difficult to align, and conversely if the concentration of the reactive liquid crystal film-forming coating liquid is higher than the above range, This is because the viscosity of the coating liquid for forming a reactive liquid crystal film is increased, so that it may be difficult to form a uniform coating film.

Furthermore, the following compounds can be added to the reactive liquid crystal film-forming coating liquid within the range not impairing the object of the present invention. Examples of compounds that can be added include polyester (meth) acrylate obtained by reacting (meth) acrylic acid with a polyester prepolymer obtained by condensing polyhydric alcohol and monobasic acid or polybasic acid; A polyurethane (meth) acrylate obtained by reacting a compound having two isocyanate groups with each other and then reacting the reaction product with (meth) acrylic acid; bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak Type epoxy resins, polycarboxylic acid polyglycidyl esters, polyol polyglycidyl ethers, aliphatic or cycloaliphatic epoxy resins, amine epoxy resins, triphenolmethane type epoxy resins, dihydroxybenzene type epoxy resins and the like (meth) Acry Photopolymerizable compound in epoxy (meth) acrylate obtained by reacting an acid; photopolymerizable liquid crystal compound having an acryl group and a methacryl group; and the like.
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 reactive liquid crystal film, and improves its stability.

  Examples of the coating method for the reactive liquid crystal film forming coating liquid include spin coating, roll coating, printing, dip coating, die coating, casting, bar coating, blade coating, and spray coating. Method, gravure coating method, reverse coating method, extrusion coating method and the like.

  In addition, the solvent is removed after the reactive liquid crystal film-forming coating solution 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 this step, the reactive liquid crystal applied as described above is aligned by the alignment film 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.

  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 actinic radiation that activates polymerization is used. As used herein, active radiation refers to radiation that has the ability to cause polymerization of a 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 this step, it can be said that a preferable method is to irradiate a polymerizable liquid crystal material in which the photopolymerization initiator generates radicals with ultraviolet rays and radically polymerizes the polymerizable liquid crystal material with ultraviolet rays as active radiation. . 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.

  Further, 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 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.

  Since the other points of the reactive liquid crystal film are the same as those described in the column of the reactive liquid crystal film in the above “A. Liquid crystal display element”, description thereof is omitted here.

(2) Second substrate forming step The second substrate forming step includes a second electrode layer forming step of forming the second electrode layer on the second base material, and a second alignment layer forming of the second alignment layer on the second electrode layer. A two-alignment layer forming step.
The second electrode layer forming step and the second alignment layer forming step are the same as the first electrode layer forming step and the second alignment layer forming step in the first substrate forming step, respectively. Omitted.

(3) Substrate Arrangement Step The substrate arrangement step in this step is a step of arranging the first substrate and the second substrate so that the first alignment layer and the second alignment layer face each other. The arrangement method of the first substrate and the second substrate is not particularly limited as long as it can be arranged at a predetermined position.

(4) Method of Encapsulating Composition for Forming Liquid Crystal Layer In this step, a ferroelectric liquid crystal having monostability between the first alignment layer of the first substrate and the second alignment layer of the second substrate, and active The method for encapsulating the liquid crystal layer forming composition containing the radiation curable monomer is not particularly limited. For example, the ferroelectric liquid crystal is made isotropic liquid by heating the composition for forming the liquid crystal layer in a liquid crystal cell prepared using the first substrate and the second substrate in advance, and the capillary effect is utilized from the injection port. The composition for forming a liquid crystal layer can be encapsulated by injecting. In this case, the inlet is sealed with an adhesive.

  The composition for forming a liquid crystal layer used in this step contains a ferroelectric liquid crystal and an actinic radiation curable monomer. The ferroelectric liquid crystal and the active radiation curable monomer used in the liquid crystal layer forming composition are the same as those described in the above section “A. Liquid crystal display element 1. Liquid crystal layer”. Description is omitted.

  The amount of the actinic radiation curable monomer contained in the liquid crystal layer forming composition is arbitrarily determined according to the amount necessary for stabilizing the alignment of the ferroelectric liquid crystal after the liquid crystal layer is formed. That's fine. Especially in this invention, the inside of the range of 0.5 mass%-30 mass% is preferable in the said composition for liquid-crystal layer formation, Especially the inside of the range of 1 mass%-20 mass% is preferable, and especially 1 mass%- A range of 10% by mass is preferable. If the content of the actinic radiation curable monomer is more than the above range, the driving voltage of the ferroelectric liquid crystal becomes high after the liquid crystal layer is formed, which may impair the performance of the liquid crystal display device manufactured according to the present invention. Because there is. On the other hand, if it is lower than the above range, the stability of the alignment of the ferroelectric liquid crystal becomes insufficient, and as a result, the heat resistance, impact resistance, etc. of the liquid crystal display device produced according to the present invention may be lowered. Because.

  The composition for forming a liquid crystal layer may contain a photopolymerization initiator. In particular, when an ultraviolet curable monomer is used as the actinic radiation curable monomer, a photopolymerization initiator is preferably contained. The photopolymerization initiator used in the composition for forming a liquid crystal layer is the same as that described in the section of the reactive liquid crystal film in “A. Liquid crystal display element 2. First substrate”. Description is omitted.

2. First Alignment Step In the first alignment step of the present invention, the ferroelectric liquid crystal contained in the liquid crystal layer forming composition is added at a temperature higher than the transition temperature from the chiral smectic C phase to the nematic phase before or after the liquid crystal encapsulation step. This is a step of heating and cooling the encapsulated ferroelectric liquid crystal. In this step, by heating and cooling the ferroelectric liquid crystal at a predetermined temperature, it is possible to obtain a uniform alignment state in which the ferroelectric liquid crystal is aligned along the alignment treatment direction of the alignment layer. After this step, the ferroelectric liquid crystal becomes monostable in a state where the direction of spontaneous polarization Ps is in the reference direction and shows a chiral smectic C phase.

  In this step, first, the ferroelectric liquid crystal is heated to a temperature equal to or higher than the transition temperature from the chiral smectic C phase to the nematic phase. The temperature may be equal to or higher than the transition temperature from the chiral smectic C phase to the nematic phase, and usually the ferroelectric liquid crystal is heated so as to be in an isotropic phase or a nematic phase, preferably the chiral smectic C phase. To a nematic phase transition temperature of 10 to 20 ° C. The specific temperature differs depending on the type of ferroelectric liquid crystal and is appropriately selected. The heating of the ferroelectric liquid crystal may be performed before the liquid crystal sealing step or after the liquid crystal sealing step.

  Although the heated ferroelectric liquid crystal is cooled, it is usually gradually cooled to room temperature (about 25 ° C.).

3. Second Alignment Step In the second alignment step of the present invention, after the first alignment step, a voltage is applied to the ferroelectric liquid crystal so that the direction of spontaneous polarization is opposite to the reference direction. In this step, the ferroelectric liquid crystal is heated to a temperature higher than the transition temperature from the chiral smectic C phase to the nematic phase while being applied. In this step, while applying a predetermined voltage to the ferroelectric liquid crystal, heating and cooling at a predetermined temperature, the direction of the spontaneous polarization is directed in the opposite direction to the reference direction, and A mono-stabilized ferroelectric liquid crystal alignment state can be obtained in a state showing a chiral smectic C phase.

  In this step, a voltage is applied to the ferroelectric liquid crystal so that the direction of spontaneous polarization is opposite to the reference direction. The magnitude of the applied voltage is not particularly limited as long as the direction of spontaneous polarization is the opposite direction, and the kind of the ferroelectric liquid crystal, the first alignment layer, and the second alignment layer are not limited. It varies depending on the type and the like and is appropriately selected. The upper limit of the applied voltage is determined by the withstand voltage of the ferroelectric liquid crystal, and it is not necessary to make it larger than the withstand voltage. Usually, a sufficiently uniform alignment state can be obtained if it is about 5V to 10V.

  In this step, the ferroelectric liquid crystal is heated to a temperature higher than the transition temperature from the chiral smectic C phase to the nematic phase while the above voltage is applied. The heating temperature may be equal to or higher than the transition temperature from the chiral smectic C phase to the nematic phase, and is particularly preferably a temperature that is 10 ° C. to 20 ° C. higher than the transition temperature from the chiral smectic C phase to the nematic phase. The specific temperature differs depending on the type of ferroelectric liquid crystal and is appropriately selected.

  The heated ferroelectric liquid crystal is cooled and normally cooled gradually to room temperature (about 25 ° C.).

4). Polymerization step In the polymerization step of the present invention, the actinic radiation curable monomer is used in the state in which the ferroelectric liquid crystal is oriented in the direction opposite to the reference direction and the chiral smectic C phase. This is a process of polymerization. The method for polymerizing the actinic radiation curable monomer in this step may be arbitrarily determined according to the type of the actinic radiation curable monomer, for example, when an ultraviolet curable monomer is used as the actinic radiation curable monomer, Polymerization can be performed by ultraviolet irradiation.
Such polymerization of the actinic radiation curable monomer may be performed with a voltage applied between the first substrate and the second substrate, or may be performed with no voltage applied. It is preferable to carry out in a state where a voltage is applied. This is because it is easy to form a liquid crystal layer in which the ferroelectric liquid crystal is mono-stabilized by polymerization in a state where a voltage is applied between the first substrate and the second substrate.

  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.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

(Example)
A solution of ROP103 (2% by mass cyclopentanone solution: manufactured by Rolic) was spin-coated on two glass substrates coated with ITO at 1500 rpm for 15 seconds and dried on a hot plate at 130 ° C. for 15 minutes. Then, 100 mJ / cm ^{2 was} exposed to polarized ultraviolet rays at 25 ° C. Furthermore, a solution of 5% by mass of reactive liquid crystal ROF-5101 (manufactured by Rolic) dissolved in cyclopentanone was spin-coated at a rotation speed of 1500 rpm for 15 seconds on one glass substrate, and dried at 55 ° C. for 3 minutes. Then, non-polarized ultraviolet rays were exposed to 1000 mJ / cm ² at 55 ° C.

Thereafter, a 1.5 μm spacer was sprayed on one substrate, and a sealing material was applied to the other substrate with a seal dispenser. The substrate was assembled in a state parallel to the polarized UV irradiation direction and thermocompression bonded. The liquid crystal used was a mixture of “R2301” (manufactured by AZ Electronic Materials) and 5% by mass of polymerizable liquid crystal “UCL-001” (manufactured by Dainippon Ink & Chemicals, Inc.). Liquid crystal was adhered to the upper part of the inlet, and injection was performed at a temperature 10 ° C. to 20 ° C. higher than the nematic phase-isotropic phase transition temperature using an oven, and the temperature was slowly returned to room temperature. After that, while applying an electric field so that the direction of spontaneous polarization of the liquid crystal is opposite to that of the reference direction, the temperature higher by 10 ° C. to 20 ° C. than the nematic phase-isotropic phase transition temperature is heated and slowly returned to room temperature. . Thereafter, non-polarized ultraviolet rays were exposed to 1000 mJ / cm ² at 25 ° C., and the above “UCL-001” was polymerized to produce a liquid crystal display element. The liquid crystal display device thus fabricated had a saturation voltage of 2.5V.

(Comparative example)
A solution of ROP103 (2% by mass cyclopentanone solution: manufactured by Rolic) was spin-coated on two glass substrates coated with ITO at 1500 rpm for 15 seconds and dried on a hot plate at 130 ° C. for 15 minutes. Then, 100 mJ / cm ^{2 was} exposed to polarized ultraviolet rays at 25 ° C. Furthermore, a solution of 5% by mass of reactive liquid crystal ROF-5101 (manufactured by Rolic) dissolved in cyclopentanone was spin-coated at a rotation speed of 1500 rpm for 15 seconds on one glass substrate, and dried at 55 ° C. for 3 minutes. Then, non-polarized ultraviolet rays were exposed to 1000 mJ / cm ² at 55 ° C.

Thereafter, a 1.5 μm spacer was sprayed on one substrate, and a sealing material was applied to the other substrate with a seal dispenser. The substrate was assembled in a state parallel to the polarized UV irradiation direction and thermocompression bonded. The liquid crystal used was a mixture of “R2301” (manufactured by AZ Electronic Materials) and 5% by mass of polymerizable liquid crystal “UCL-001” (manufactured by Dainippon Ink & Chemicals, Inc.). Liquid crystal was adhered to the upper part of the inlet, and injection was performed at a temperature 10 ° C. to 20 ° C. higher than the nematic phase-isotropic phase transition temperature using an oven, and the temperature was slowly returned to room temperature. A non-polarized ultraviolet ray was exposed to 1000 mJ / cm ² at 25 ° C. to polymerize the “UCL-001” to produce a liquid crystal display element. The liquid crystal display device thus produced had a saturation voltage of 5V.

It is a schematic sectional drawing which shows an example of the liquid crystal display element of this invention. 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 the graph which showed the change of the transmittance | permeability with respect to the applied voltage of ferroelectric liquid crystal. It is the figure which showed the difference in orientation by the difference in the phase sequence which a ferroelectric liquid crystal has. 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 an example of the liquid crystal display element of this invention. It is the schematic showing the alignment state of the ferroelectric liquid crystal in the manufacturing method of the liquid crystal display element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a ... 1st base material 1b ... 2nd base material 2a ... 1st electrode layer 2b ... 2nd electrode layer 3a ... 1st orientation layer 3b ... 2nd orientation layer 5 ... Liquid crystal layer 6a ... 1st polarizing plate 6b ... 2nd Polarizing plate 8 ... Ferroelectric liquid crystal 10 ... Liquid crystal display element 11 ... First substrate 12 ... Second substrate 31a ... Alignment film 32a ... Reactive liquid crystal film d ... Alignment treatment direction n ... Ferroelectric liquid crystal molecular direction z ... Layer Normal Ps ... Spontaneous polarization

Claims (11)

A first substrate having a first substrate, a first electrode layer formed on the first substrate, a first alignment layer formed on the first electrode layer, and a second substrate; A second substrate having a second electrode layer formed on the second base material and a second alignment layer formed on the second electrode layer, the first alignment layer and the second alignment layer. And a liquid crystal display element comprising a liquid crystal layer containing a ferroelectric liquid crystal sandwiched between the first alignment layer and the second alignment layer,
The ferroelectric liquid crystal exhibits monostability in the liquid crystal layer, and the direction of spontaneous polarization of the ferroelectric liquid crystal is relative to a reference direction defined by the first alignment layer and the second alignment layer. A liquid crystal display element characterized by facing in the opposite direction.   The liquid crystal display element according to claim 1, wherein the liquid crystal layer contains a polymer of an active radiation curable monomer.   The liquid crystal display element according to claim 1, wherein the constituent materials of the first alignment layer and the second alignment layer have different compositions.   The at least one of the first alignment layer and the second alignment layer includes an alignment film and a reactive liquid crystal film formed on the alignment film and having a reactive liquid crystal fixed thereon. The liquid crystal display element according to any one of claims 1 to 3.   The liquid crystal display element according to any one of claims 1 to 4, wherein the first alignment layer or the second alignment layer has a photo-alignment film.   The constituent material of the photo-alignment film is a photoreactive material that imparts anisotropy to the photo-alignment film by causing a photoreaction, or anisotropy to the photo-alignment film by causing a photoisomerization reaction. 6. The liquid crystal display element according to claim 5, which is a photoisomerization type material containing a photoisomerization reactive compound to be imparted.   The liquid crystal display element according to any one of claims 1 to 6, wherein the ferroelectric liquid crystal does not have a smectic A phase in a phase sequence.   The liquid crystal display element according to any one of claims 1 to 7, wherein the liquid crystal display element is driven by an active matrix method using a thin film transistor.   9. The liquid crystal display element according to claim 1, wherein the liquid crystal display element is driven by a field sequential color system. A first substrate having a first substrate, a first electrode layer formed on the first substrate, a first alignment layer formed on the first electrode layer, and a second substrate; A second substrate having a second electrode layer formed on the second base material and a second alignment layer formed on the second electrode layer, the first alignment layer and the second alignment layer. And a liquid crystal display element comprising a liquid crystal layer containing a ferroelectric liquid crystal sandwiched between the first alignment layer and the second alignment layer,
A liquid crystal encapsulation step of encapsulating a composition for forming a liquid crystal layer containing the ferroelectric liquid crystal having monostability and an actinic radiation curable monomer between the first alignment layer and the second alignment layer;
A first alignment step in which the ferroelectric liquid crystal is heated to a temperature higher than a transition temperature from a chiral smectic C phase to a nematic phase before or after the liquid crystal encapsulation step, and the encapsulated ferroelectric liquid crystal is cooled;
After the first alignment step, a voltage is applied to the ferroelectric liquid crystal so that the direction of spontaneous polarization is opposite to the reference direction defined by the first alignment layer and the second alignment layer. A second alignment step in which the ferroelectric liquid crystal is heated and cooled to a temperature equal to or higher than the transition temperature from the chiral smectic C phase to the nematic phase while a voltage is applied;
And a polymerization step of polymerizing the actinic radiation curable monomer in a state where the ferroelectric liquid crystal is in a chiral smectic C phase. The method of manufacturing a liquid crystal display element according to claim 10, wherein the polymerization step polymerizes the actinic radiation curable monomer in a state where a voltage is applied between the first substrate and the second substrate.

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