JP5439891B2 - Liquid crystal display element - Google Patents

Description

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

  Ferroelectric liquid crystal (FLC) is a liquid crystal suitable for high-speed devices because its response speed is as short as μs order. In particular, the field sequential color method, which is one of the methods for realizing color display, divides one pixel in time, so that a liquid crystal as a black-and-white shutter has high-speed response in order to obtain good moving image display characteristics. It is necessary to have a ferroelectric liquid crystal.

  Ferroelectric liquid crystal is widely known as a bistable one having two stable states when no voltage is applied, as proposed by Clark and Lagerwol (FIG. 14 (a)). However, there is a problem that gradation display cannot be performed although it has a memory property.

In recent years, the state of the liquid crystal layer when no voltage is applied is stabilized in a single state (hereinafter referred to as “monostable”). ) Is continuously changed, and the transmitted light intensity is analog-modulated to attract gradation (see Non-Patent Document 1, FIGS. 14B and 14C). As the liquid crystal exhibiting monostability, generally, a ferroelectric liquid crystal that changes phase with the cholesteric (Ch) phase-chiral smectic C (SmC ^* ) phase in the temperature lowering process and does not pass through the smectic A (SmA) phase is used ( FIG. 15 top).

On the other hand, as the ferroelectric liquid crystal, a material that changes in phase from a cholesteric (Ch) phase to a smectic A (SmA) phase to a chiral smectic C (SmC ^* ) phase in the temperature lowering process and exhibits an SmC ^* phase via the SmA phase. (The lower part of FIG. 15). Most of the ferroelectric liquid crystal materials currently reported have a phase series that passes through the latter SmA phase compared to the former 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 and exhibits bistability.

As described above, the ferroelectric liquid crystal used in the field sequential color system preferably has monostability in order to enable gradation display by analog modulation and realize high-definition color display. .
There are two types of ferroelectric liquid crystal exhibiting monostability, one that responds to positive and negative voltages (FIG. 14C) and one that responds only to positive and negative voltages (FIG. 14B). is there. In particular, when a ferroelectric liquid crystal is driven using a thin film transistor (TFT) element, it is particularly preferable to respond to a voltage of either positive or negative polarity because the influence of reversal current due to spontaneous polarization is small.

  Here, FIG. 16 shows an example of a driving sequence of a liquid crystal display element by a field sequential color system using TFT elements. In FIG. 16, it is assumed that the voltage applied to the liquid crystal display element is 0 to ± V (V), data writing scanning is performed with a positive polarity voltage, and data erasing scanning is performed with a negative polarity voltage. It is assumed that a ferroelectric liquid crystal that exhibits monostability and responds only to a positive or negative voltage is used.

  As a response of the ferroelectric liquid crystal which shows monostability and responds only to a voltage of either positive or negative polarity, as illustrated in FIG. 11 (a)) and a bright state in response to a negative polarity voltage (FIG. 11 (b)). Therefore, as shown in FIG. 16, when the ferroelectric liquid crystal showing the response (liquid crystal response 1) of FIG. 11 (a) is used, a bright state is obtained when a positive polarity voltage is applied, and FIG. When a ferroelectric liquid crystal exhibiting a response (liquid crystal response 2) is used, a bright state is obtained when a negative polarity voltage is applied.

The ferroelectric liquid crystal using the TFT element is driven by applying a constant voltage to the common electrode of the common electrode substrate facing the TFT substrate and applying a voltage to the pixel electrode of each pixel of the TFT substrate. Here, when the pixel electrode voltage is relatively high with respect to the common electrode, a positive polarity voltage application is applied, and when the pixel electrode voltage is relatively low, a negative polarity voltage application is applied.
When using a ferroelectric liquid crystal that responds only to positive polarity voltage, positive polarity voltage application (writing) and negative polarity voltage application (erasing) are alternated to balance the charge. To do. When a TFT element is used, voltage cannot be written to all pixels at the same time, so scanning is performed for each line. Therefore, the writing of the first line and the writing of the L line are out of timing. The same applies to erasure. In the example shown in FIG. 16, erasing is performed from the first line after writing of all lines is completed.
Further, in the field sequential color method, writing and erasing are performed in synchronization with the flashing of the backlight. In FIG. 16, + (R) indicates that writing scanning (application of a positive polarity voltage) is performed in synchronization with the R (red) backlight, and − (R) indicates synchronization with the R backlight. This indicates that erase scanning (application of a negative polarity voltage) was performed. Similarly, + (G), − (G), + (B), and − (B) indicate that scanning is performed in synchronization with the backlights of G (green) and B (blue), respectively.

As described above, in the field sequential color system, the ferroelectric liquid crystal is made to respond by performing the write scan and the erase scan in synchronization with the temporal switching of the backlight R, G, B. When scanning in synchronism, if a ferroelectric liquid crystal showing a liquid crystal response 1 is used, the writing scan of the first line (+ (R)) and the writing scan of the L line (+ (R)) are performed. In any case, a bright state is obtained while the R backlight is lit. On the other hand, when the ferroelectric liquid crystal showing the liquid crystal response 2 is used, the write scan (+ (R)) and the erase scan (− (R)) are shifted in time between the first line and the L line. The L-line erase scan (-(R)) synchronized with the R backlight results in a bright state when the G backlight is turned on (thick frame in FIG. 16). Further, when scanning in synchronization with the G backlight, the L-line erasing scan (-(G)) synchronized with the G backlight results in a bright state when the B backlight is turned on. (Thick frame in FIG. 16).
In FIG. 16, bright (R) indicates a bright state by scanning synchronized with the R (red) backlight, and dark indicates R (red), G (green), and B (blue). ) Indicates a dark state by scanning synchronized with each backlight. Similarly, bright (G) and bright (B) are also shown to be in a bright state by scanning synchronized with G (green) and B (blue) backlights, respectively.

  In a normal liquid crystal display device, it is determined which of the positive polarity voltage and the negative polarity voltage is used for writing scanning or erasing scanning and cannot be easily changed. In order to avoid this, it is necessary to match the polarity of the voltage to which the ferroelectric liquid crystal exhibiting monostability responds to the polarity of the applied voltage. Since the response of the ferroelectric liquid crystal is determined by the direction of spontaneous polarization of the ferroelectric liquid crystal, the polarity of the voltage to which the ferroelectric liquid crystal responds can be controlled if the direction of spontaneous polarization can be controlled. .

  However, ferroelectric liquid crystals are difficult to align because they have higher molecular ordering than nematic liquid crystals. In particular, in a ferroelectric liquid crystal that does not pass through the SmA phase, two regions having different layer normal directions (hereinafter referred to as “double domain”) are generated. Such a double domain becomes a serious problem because black-and-white inversion is displayed during driving. For this reason, various alignment processing methods have been studied.

  For example, as a method for improving the double domain, an electric field applied slow cooling method is known in which a liquid crystal cell is heated to a temperature equal to or higher than the cholesteric phase and gradually cooled while a DC voltage is applied (see Non-Patent Document 2). When this electric field application annealing method is used, the direction of spontaneous polarization can be controlled by the direction of the applied electric field. However, in this method, if the temperature rises again above the phase transition point, alignment disturbance occurs, and the manufacturing process becomes complicated, and alignment disturbance occurs in a portion where the electric field between the pixel electrodes does not act. There's a problem.

Therefore, the present inventors have proposed a method of using a photo-alignment film as the upper and lower alignment films and using materials having different compositions for these photo-alignment films as a method of mono-domaining the ferroelectric liquid crystal. (See Patent Documents 1 to 3). Furthermore, as another method for making the ferroelectric liquid crystal monodomain, the present inventors fixed the alignment state of the reactive liquid crystal by applying and aligning the reactive liquid crystal on only one of the upper and lower alignment films. Forming a fixed liquid crystal layer, and allowing the fixed liquid crystal layer to act as an alignment film of a ferroelectric liquid crystal, and forming a fixed liquid crystal layer on both the upper and lower alignment films. A method of using materials having different compositions for each layer has been proposed (see Patent Document 4). In these methods, the ferroelectric liquid crystal is aligned without using the electric field applied slow cooling method, so that the alignment can be maintained even if the temperature is increased beyond the phase transition.
In the above method, the reason why a favorable alignment state of the ferroelectric liquid crystal is obtained is not clear, but the interaction between the ferroelectric liquid crystal and each of the upper and lower alignment layers in direct contact with the ferroelectric liquid crystal is not clear. This is probably due to the difference.
However, in the liquid crystal display element obtained by the above-described method, the direction of spontaneous polarization of the ferroelectric liquid crystal cannot be known unless it is actually driven.

  In order to solve this problem, the present inventors have intensively studied and proposed a method for controlling the direction of spontaneous polarization by specifying the combination of the upper and lower alignment layers in direct contact with the ferroelectric liquid crystal. (See Patent Documents 5 to 7).

JP 2005-208353 A JP 2005-234549 A JP 2005-234550 A JP 2005-258428 A JP 2006-350322 A JP 2008-107634 A JP 2008-129529 A

NONAKA, T., LI, J., OGAWA, A., HORNUNG, B., SCHMIDT, W., WINGEN, R., and DUBAL, H., 1999, Liq. Cryst., 26, 1599. PATEL, J., and GOODBY, J. W., 1986, J. Appl. Phys., 59, 2355.

  As a result of further studies on a method for improving the double domain and controlling the direction of spontaneous polarization, the present inventors have found that either one of the upper and lower alignment layers in direct contact with the ferroelectric liquid crystal It was found that the monodomain alignment of the ferroelectric liquid crystal can be obtained even if the alignment treatment is not performed. Furthermore, it has been found that the direction of spontaneous polarization can be controlled by specifying a combination of an alignment layer and an unaligned treatment layer that are in direct contact with the ferroelectric liquid crystal.

  That is, the present invention suppresses the occurrence of alignment defects such as double domains in a liquid crystal display element using a ferroelectric liquid crystal that exhibits monostability and does not pass through the SmA phase, and spontaneous polarization of the ferroelectric liquid crystal. It is a main object to provide a novel liquid crystal display element capable of controlling the orientation of the liquid crystal display.

In order to achieve the above object, the present invention includes a first substrate, a first substrate having an unoriented treatment layer formed on the first substrate and not subjected to an orientation treatment, and a second substrate. Material, a second electrode layer formed on the second substrate, a reactive liquid crystal alignment film formed on the second electrode layer, and a reactive liquid crystal alignment film formed on the reactive liquid crystal alignment film. A second substrate having an immobilized liquid crystal layer formed by immobilizing liquid crystal and disposed so that the unoriented treatment layer and the immobilized liquid crystal layer face the first substrate; and the unoriented treatment layer And a liquid crystal layer including a ferroelectric liquid crystal formed between the fixed liquid crystal layers, and the ferroelectric liquid crystal exhibits an SmC ^* phase without passing through an SmA phase in a temperature lowering process, and , which shows a single stability in the SmC ^* phase, further, the ferroelectric liquid crystal, the above When a negative voltage is applied to the two-electrode layer, the liquid crystal molecules tilt to one side from the monostable state, and when a positive voltage is applied to the second electrode layer, the liquid crystal molecules Maintaining a state exhibiting monostability, or inclining to the opposite side when a negative voltage is applied to the second electrode layer from the state exhibiting monostability, and applying a negative voltage to the second electrode layer Provided is a liquid crystal display element characterized in that the amount of transmitted light when applied is larger than the amount of transmitted light when a positive voltage is applied to the second electrode layer.

  According to the present invention, it is possible to control the direction of spontaneous polarization of liquid crystal molecules by utilizing the fact that the positive polarity of the spontaneous polarization of the ferroelectric liquid crystal tends to be directed to the unaligned treatment layer side. Since the direction of spontaneous polarization can be controlled, the monodomain alignment of the ferroelectric liquid crystal can be obtained without causing alignment defects such as double domains. Further, since the ferroelectric liquid crystal has a larger amount of transmitted light when a negative voltage is applied to the second electrode layer, it is greater than the amount of transmitted light when a positive voltage is applied to the second electrode layer. When the liquid crystal display element is driven by a field sequential color system, the direction of spontaneous polarization of liquid crystal molecules can be controlled, so that the problems described in the background art section can be avoided. .

  In the above invention, the unoriented treatment layer contains a photoisomerization-reactive compound having an azobenzene skeleton in the molecule, and a first electrode layer is formed between the first base material and the unoriented treatment layer. It is preferable. 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 direction of spontaneous polarization of ferroelectric liquid crystal. In addition, since the unaligned layer is not subjected to the alignment process, it is not necessary to perform the alignment process in the manufacturing process of the first substrate. Therefore, the manufacturing process of the liquid crystal display element can be simplified. In particular, large-sized mother glass is often used when manufacturing liquid crystal display elements, and since the increase in size of this mother glass is progressing year by year, a larger mother glass is used when performing photo-alignment treatment. Although it is necessary to develop a corresponding exposure apparatus and there is a concern in recent years that capital investment will increase with the increase in the size of the mother glass, it is not necessary to perform an alignment treatment, so that the cost can be reduced.

  Moreover, in the said invention, it is preferable that the said non-oriented process layer consists of an inorganic compound which has electroconductivity, and the said non-oriented process layer is a 1st electrode layer. In this case, the inorganic compound is preferably indium tin oxide (ITO) or indium zinc oxide (IZO). Similar to the above case, it is not necessary to perform the alignment process in the manufacturing process of the first substrate, and the manufacturing process of the liquid crystal display element can be simplified and the cost can be reduced.

Further, according to the present invention, an unoriented treatment layer containing a photoisomerization-reactive compound having an azobenzene skeleton in the molecule is formed on the first substrate on which the first electrode layer is formed. A first substrate preparation step of preparing a first substrate in which the first electrode layer and the non-orientation treatment layer are sequentially laminated on the first base material without performing a photo-alignment treatment on the first substrate; A reactive liquid crystal alignment film is formed on the formed second substrate, a reactive liquid crystal layer containing a reactive liquid crystal is formed on the reactive liquid crystal alignment film, and the reactive liquid crystal layer includes the reactive liquid crystal layer. Alignment of the reactive liquid crystal, fixing the alignment state of the reactive liquid crystal, and fixing the second electrode layer, the alignment film for reactive liquid crystal, and the reactive liquid crystal on the second substrate A second substrate preparation step of preparing a second substrate on which liquid crystal layers are sequentially laminated; A ferroelectric liquid crystal is sandwiched between the non-oriented treatment layer and the fixed liquid crystal layer of the second substrate, the ferroelectric liquid crystal is oriented without performing an electric field application treatment, and the liquid crystal containing the ferroelectric liquid crystal A liquid crystal layer forming step of forming a layer, wherein the ferroelectric liquid crystal exhibits an SmC ^* phase without passing through an SmA phase in a temperature lowering process, and exhibits monostability in the SmC ^* phase. Further, the ferroelectric liquid crystal is inclined when the negative voltage is applied to the second electrode layer, and the liquid crystal molecules are tilted to one side from the monostable state, and the second electrode layer When a positive voltage is applied to the liquid crystal molecules, the liquid crystal molecules maintain the monostable state or a negative voltage is applied to the second electrode layer from the monostable state. The amount of transmitted light when tilted to the opposite side and a negative voltage is applied to the second electrode layer is A method of manufacturing a liquid crystal display element, characterized in that the amount of transmitted light is larger than that when a positive voltage is applied to the second electrode layer.

  According to the present invention, in addition to the above-described effects, the ferroelectric liquid crystal is aligned without performing an electric field application treatment, so that the alignment is maintained even when the temperature is raised above the phase transition temperature, and alignment defects are generated. It is possible to suppress.

  In the present invention, when the ferroelectric liquid crystal is sandwiched between the unaligned treatment layer and the fixed liquid crystal layer, the positive polarity of the spontaneous polarization of the ferroelectric liquid crystal tends to face the unaligned treatment layer side. As a result, the direction of spontaneous polarization of the ferroelectric liquid crystal can be controlled.

It is a schematic sectional drawing which shows an example of the liquid crystal display element of this invention. It is a schematic sectional drawing which shows the other example of the liquid crystal display element of this invention. It is a schematic diagram which shows an example of the orientation state of a ferroelectric liquid crystal. It is a schematic diagram which shows the other example of the orientation state of a ferroelectric liquid crystal. It is a schematic diagram which shows the spontaneous polarization of a ferroelectric liquid crystal. It is a schematic diagram which shows the other example of the orientation state of a ferroelectric liquid crystal. It is a conceptual diagram which shows the drive sequence of the liquid crystal display element by a field sequential color system. It is a schematic diagram which shows the behavior of a liquid crystal molecule. It is a schematic diagram which shows the other example of the orientation state of a ferroelectric liquid crystal. It is a schematic sectional drawing which shows the other example of the liquid crystal display element of this invention. It is the graph which showed the change of the transmitted light amount with respect to the applied voltage of a ferroelectric liquid crystal. It is a schematic perspective view which shows the other example of the liquid crystal display element of this invention. It is a schematic diagram which shows the spontaneous polarization of a ferroelectric liquid crystal. It is the graph which showed the change of the transmitted light amount with respect to the applied voltage of a ferroelectric liquid crystal. It is the figure which showed the difference in orientation by the difference in the phase sequence which a ferroelectric liquid crystal has. It is a conceptual diagram which shows the drive sequence of the liquid crystal display element by a field sequential color system.

  Hereinafter, the liquid crystal display element of the present invention and the method for manufacturing the liquid crystal display element 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, a first substrate formed on the first substrate and having an unaligned treatment layer that has not been subjected to an alignment treatment, a second substrate, and the first substrate. 2 The second electrode layer formed on the substrate, the alignment film for reactive liquid crystal formed on the second electrode layer, and the reactive liquid crystal formed on the alignment film for reactive liquid crystal A second substrate disposed so that the non-oriented treatment layer and the fixed liquid crystal layer face the first substrate, the non-oriented treatment layer, and the immobilization layer. A liquid crystal layer including a ferroelectric liquid crystal formed between the liquid crystal layers, wherein the ferroelectric liquid crystal exhibits an SmC ^* phase without passing through an SmA phase in a temperature lowering process, and the SmC ^* The ferroelectric liquid crystal is formed on the second electrode layer. When the voltage is applied, the liquid crystal molecules are tilted to one side from the state showing the monostability, and when a positive voltage is applied to the second electrode layer, the liquid crystal molecules show the monostability. When the negative voltage is applied to the second electrode layer from the state where the state is maintained or the monostable state is exhibited, the transmission is inclined when the negative voltage is applied to the second electrode layer. The amount of light is larger than the amount of transmitted light when a positive voltage is applied to the second electrode layer.

The liquid crystal display element of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing an example of the liquid crystal display element of the present invention. As illustrated in FIG. 1, the liquid crystal display element 10 includes a first substrate 9 in which a first electrode layer 3 and an unoriented treatment layer 4 are sequentially formed on a first substrate 2, and a second substrate 12. It is formed between the second substrate 19 on which the second electrode layer 13, the reactive liquid crystal alignment film 14 and the fixed liquid crystal layer 15 are formed in this order, and the unaligned treatment layer 4 and the fixed liquid crystal layer 15, and is ferroelectric. And a liquid crystal layer 20 containing liquid crystal. The unaligned layer 4 is not subjected to an alignment process, and contains a photoisomerization reactive compound having an azobenzene skeleton in the molecule. The fixed liquid crystal layer 15 is obtained by fixing the alignment state of the reactive liquid crystal.

  FIG. 2 is a cross-sectional view showing another example of the liquid crystal display element of the present invention. As illustrated in FIG. 2, the liquid crystal display element 10 includes a first substrate 9 in which the non-oriented treatment layer 4 is formed on the first base material 2, a second electrode layer 13 on the second base material 12, and a reaction. A liquid crystal layer 20 including a ferroelectric liquid crystal formed between the second substrate 19 on which the alignment film 14 for the liquid crystal and the fixed liquid crystal layer 15 are sequentially formed, and the non-aligned treatment layer 4 and the fixed liquid crystal layer 15; It is what has. The unoriented treatment layer 4 is not subjected to the orientation treatment, is made of an inorganic compound having conductivity, and also serves as the first electrode layer 3. The fixed liquid crystal layer 15 is obtained by fixing the alignment state of the reactive liquid crystal.

The ferroelectric liquid crystal contained in the liquid crystal layer 20 exhibits an SmC ^* phase without passing through the SmA phase in the temperature lowering process, and exhibits monostability in the SmC ^* phase. Further, when a negative voltage is applied to the second electrode layer, the ferroelectric liquid crystal is tilted to one side from a state where the liquid crystal molecules exhibit monostability, and a positive voltage is applied to the second electrode layer. In addition, the liquid crystal molecules maintain a state exhibiting monostability or are tilted to the opposite side to the case where a negative voltage is applied to the second electrode layer from the state exhibiting monostability, and the liquid crystal molecules are negatively applied to the second electrode layer. The amount of transmitted light when the above voltage is applied is larger than the amount of transmitted light when a positive voltage is applied to the second electrode layer.

FIGS. 3A and 3B and FIGS. 4A and 4B are schematic views showing examples of the alignment state of the ferroelectric liquid crystal used in the present invention. In FIGS. 3A and 3B and FIGS. 4A and 4B, the ferroelectric liquid crystal indicates liquid crystal molecules.
As a result of intensive studies by the present inventors, for example, the fixed liquid crystal layer is more relative to the non-oriented treatment layer and the fixed liquid crystal layer containing a photoisomerization-reactive compound or inorganic compound having an azobenzene skeleton in the molecule. It was found that the positive polarity tends to be strong. This is the interaction between the ferroelectric liquid crystal and the surface of the unaligned treated layer and the immobilized liquid crystal layer that contains a photoisomerization-reactive compound or inorganic compound having an azobenzene skeleton in the molecule. Is considered to have influenced. Therefore, in the liquid crystal display element illustrated in FIG. 1, when no voltage is applied, the spontaneous polarization Ps of the liquid crystal molecules 1 is caused to be on the unaligned treatment layer 4 side by the polar surface interaction as illustrated in FIG. Tend to face. Further, in the liquid crystal display element illustrated in FIG. 2, when no voltage is applied, the spontaneous polarization Ps of the liquid crystal molecules 1 is caused to be on the unaligned treatment layer 4 side due to the polar surface interaction as illustrated in FIG. Tend to face.
At this time, when a positive voltage is applied to the first electrode layer 3 and a negative voltage is applied to the second electrode layer 13, as illustrated in FIG. 3B and FIG. 4B, due to the influence of the polarity of the applied voltage. The spontaneous polarization Ps of the liquid crystal molecules 1 comes to face the fixed liquid crystal layer 15 side.
On the other hand, when a negative voltage is applied to the first electrode layer and a positive voltage is applied to the second electrode layer, liquid crystal molecules as shown in FIG. 3A and FIG. 4A due to the influence of the polarity of the applied voltage. 1 spontaneous polarization Ps is directed to the non-oriented treatment layer 4 side. In this case, the direction of spontaneous polarization is the same as that in the state where no voltage is applied.
The direction of spontaneous polarization is in this direction because the direction of spontaneous polarization is such that the polarization of the ferroelectric liquid crystal and the polarization of the layer in direct contact with the ferroelectric liquid crystal or the polarity of the voltage are electrically balanced. This is because the liquid crystal molecules are in an electrically stable state.

  From a state where no voltage is applied or a state where a positive polarity voltage is applied to the second electrode layer (FIGS. 3A and 4B), a state where a negative polarity voltage is applied to the second electrode layer (FIG. 3 ( When the negative polarity of the applied voltage and the negative polarity of the spontaneous polarization of the liquid crystal molecules are repelled by b) and FIG. 4B), the direction of the liquid crystal molecules 1 is changed as illustrated in FIG. The angle changes by about 2θ. That is, when a negative voltage is applied to the second electrode layer, the liquid crystal molecules tilt to one side from a state exhibiting monostability, and when a positive voltage is applied to the second electrode layer, the liquid crystal molecules are When the state showing monostability is maintained, or when a negative voltage is applied to the second electrode layer from the state showing monostability and the negative voltage is applied to the second electrode layer The inclination angle from the state showing the monostability of the liquid crystal molecules is larger than the inclination angle from the state showing the monostability of the liquid crystal molecules when a positive voltage is applied to the second electrode layer. That is, the amount of transmitted light when a negative voltage is applied to the second electrode layer is greater than the amount of transmitted light when a positive voltage is applied to the second electrode layer.

6A and 6B are schematic views showing an example of the alignment state of the ferroelectric liquid crystal used in the present invention. 6A is a schematic diagram showing the alignment state of the liquid crystal molecules from the upper surface of FIGS. 3A and 4A, and the spontaneous polarization Ps is directed from the front side to the back side of the page ( (X mark in Fig.6 (a)). FIG. 6B is a schematic diagram showing the alignment state of the liquid crystal molecules from the upper surface of FIGS. 3B and 4B, and the spontaneous polarization Ps is directed from the back to the front of the page ( (● mark in FIG.6 (b)).
For example, in the liquid crystal display element shown in FIGS. 1 and 2, in the state where no voltage is applied, the liquid crystal molecules 1 are aligned along the alignment treatment direction d of the alignment film for reactive liquid crystal as illustrated in FIG. A uniform orientation state is obtained. Further, when a positive voltage is applied to the first electrode layer and a negative voltage is applied to the second electrode layer, the direction of the spontaneous polarization Ps is reversed due to the influence of the polarity of the applied voltage, as illustrated in FIG. 6B. Also in this case, the liquid crystal molecules 1 are in a uniform alignment state. Furthermore, when a negative voltage is applied to the first electrode layer and a positive voltage is applied to the second electrode layer, the direction of the spontaneous polarization Ps is reversed due to the influence of the polarity of the applied voltage as illustrated in FIG. In this case, the liquid crystal molecules 1 are in the same alignment state as in the voltage-free state.

  Thus, in the present invention, for example, the positive polarity of the spontaneous polarization of the ferroelectric liquid crystal tends to be directed to the non-aligned treatment layer side containing a photoisomerization reactive compound having an azobenzene skeleton in the molecule or an inorganic compound. By utilizing this, it is possible to control the direction of spontaneous polarization of liquid crystal molecules. In the present invention, since the direction of spontaneous polarization can be controlled, the monodomain alignment of the ferroelectric liquid crystal can be obtained without causing alignment defects such as double domains. At this time, since the ferroelectric liquid crystal is aligned without using the electric field applied slow cooling method, there is an advantage that the alignment can be maintained even if the temperature is raised to the phase transition temperature or higher, and the occurrence of alignment defects can be suppressed.

  In addition, when the immobilized liquid crystal layer is formed on the reactive liquid crystal alignment film, the reactive liquid crystal is aligned by the reactive liquid crystal alignment film, and the reaction is performed by, for example, irradiating ultraviolet rays to polymerize the reactive liquid crystal. The alignment state of the conductive liquid crystal can be fixed. Therefore, the alignment regulating force of the alignment film for reactive liquid crystal can be imparted to the fixed liquid crystal layer, and the fixed liquid crystal layer can act as an alignment film for aligning the ferroelectric liquid crystal. Further, since the reactive liquid crystal is fixed, it has an advantage that it is not affected by temperature or the like. In addition, reactive liquid crystals are relatively similar in structure to ferroelectric liquid crystals, and the interaction with ferroelectric liquid crystals becomes stronger, so that the direction of spontaneous polarization of ferroelectric liquid crystals can be controlled effectively. Can do.

Furthermore, in the present invention, the direction of spontaneous polarization of the ferroelectric liquid crystal can be controlled as described above. In a liquid crystal display element having a polarizing plate, no voltage is applied and the positive polarity to the second electrode layer When the voltage is applied, a dark state is obtained, and when a negative polarity voltage is applied to the second electrode layer, the light state is obtained. Therefore, when the liquid crystal display element is driven by the field sequential color system, as illustrated in FIG. 7, for example, when the G (green) backlight is turned on, the liquid crystal display element is brightened by scanning synchronized with the R (red) backlight. It is possible to avoid the state.
Note that the symbols and the like in FIG. 7 are the same as the symbols and the like shown in FIG.

  In the present invention, since the ferroelectric liquid crystal exhibits monostability, gradation control can be performed by voltage modulation, and high-definition and high-quality display can be realized. That is, since the ferroelectric liquid crystal is mono-stabilized in the liquid crystal layer, the transmitted light intensity can be analog-modulated by continuously changing the director of the liquid crystal due to voltage change, and gradation display is possible. .

  The phrase “ferroelectric liquid crystal exhibits monostability” means a state in which the state of the ferroelectric liquid crystal when no voltage is applied is stabilized in one state. In the ferroelectric liquid crystal, as illustrated in FIG. 8, the liquid crystal molecules 1 are tilted from the layer normal z, and rotate along a cone ridge having a bottom surface perpendicular to the layer normal z. In such a cone, the tilt angle of the liquid crystal molecules 1 with respect to the layer normal z is referred to as a tilt angle θ. Thus, the liquid crystal molecules 1 can operate on the cone between two states inclined by a tilt angle ± θ with respect to the layer normal z. Specifically, showing monostability means a state where the liquid crystal molecules 1 are stabilized in any one state on the cone when no voltage is applied.

  “Applying a negative voltage to the second electrode layer” means that the voltage of the second electrode layer is relatively lower than that of the first electrode layer. Further, “applying a positive voltage to the second electrode layer” means that the voltage of the second electrode layer is relatively higher than that of the first electrode layer.

  “When a negative voltage is applied to the second electrode layer, the liquid crystal molecules are tilted to one side from a state exhibiting monostability, and when a positive voltage is applied to the second electrode layer, the liquid crystal molecules are When the negative voltage is applied to the second electrode layer when the negative voltage is applied to the second electrode layer when the negative voltage is applied to the second electrode layer from the state where the stability is maintained “The amount of transmitted light is larger than the amount of transmitted light when a positive voltage is applied to the second electrode layer” means that the liquid crystal molecules are stabilized in one state on the cone when no voltage is applied. When a negative voltage is applied, the liquid crystal molecules tilt from the monostable state to one side on the cone, and when a positive voltage is applied to the second electrode layer, the liquid crystal molecules maintain the monostable state. Or when the negative voltage is applied to the second electrode layer from the mono-stabilized state, The amount of transmitted light at the time of applying a negative voltage to the electrode layer, say greater than the amount of transmitted light when a positive voltage is applied to the second electrode layer.

FIGS. 9A to 9C are schematic views showing an example of the alignment state of the ferroelectric liquid crystal exhibiting monostability. 9A to 9C, liquid crystal molecules are shown for the ferroelectric liquid crystal. 9A shows the case where no voltage is applied, FIG. 9B shows the case where a negative voltage is applied to the second electrode layer, and FIG. 9C shows the case where a positive voltage is applied to the second electrode layer. Each is shown.
When no voltage is applied, the liquid crystal molecules 1 are stabilized in one state on the cone (FIG. 9A). When a negative voltage is applied to the second electrode layer, the liquid crystal molecules 1 are inclined from the stabilized state (broken line) to one side (FIG. 9B). In addition, when a positive voltage is applied to the second electrode layer, the liquid crystal molecules 1 are tilted from the stabilized state (broken line) to the opposite side when a negative voltage is applied to the second electrode layer (see FIG. 9 (c)). At this time, the inclination angle δ when a negative voltage is applied to the second electrode layer is larger than the inclination angle ω when a positive voltage is applied to the second electrode layer. 9A to 9C, d represents the alignment treatment direction of the reactive liquid crystal alignment film, and z represents the layer normal.

As illustrated in FIGS. 9A and 9B, when a negative voltage is applied to the second electrode layer, the liquid crystal molecules 1 are cone-shaped from the mono-stabilized state at an angle according to the magnitude of the applied voltage. Tilt to one side above. On the other hand, in the ferroelectric liquid crystal, as illustrated in FIG. 9A, the position A (the direction of the liquid crystal molecules 1), the position B (the alignment treatment direction d of the alignment film for reactive liquid crystal), the position C, However, they do not necessarily match. Therefore, as illustrated in FIG. 9B, the maximum tilt angle δ when a negative voltage is applied to the second electrode layer is about twice the tilt angle θ.
When a negative voltage is applied to the second electrode layer, the liquid crystal molecules are tilted from the mono-stabilized state to one side on the cone at an angle corresponding to the magnitude of the applied voltage. When driving the element, when a negative voltage is applied to the second electrode layer, the direction of the liquid crystal molecules does not change about twice the tilt angle.

Here, “the tilt angle from the mono-stabilized state of the liquid crystal molecules when a negative voltage is applied to the second electrode layer” and “the liquid crystal molecules when a positive voltage is applied to the second electrode layer” The “inclination angle from the mono-stabilized state” can be measured as follows.
That is, first, the polarization axis of one polarizing plate and the alignment direction of the liquid crystal molecules of the liquid crystal layer are set so that the polarizing microscope and the liquid crystal display element in which the polarizing plates are arranged in crossed Nicols are dark when no voltage is applied. Are arranged parallel to each other, and this position is used as a reference. When a voltage is applied, the liquid crystal molecules come to have a predetermined angle with the polarization axis, so that the polarized light transmitted through one polarizing plate is transmitted through the other polarizing plate to be in a bright state. With this voltage applied, the liquid crystal display element is rotated to a dark state. And the angle which rotated the liquid crystal display element at this time is measured. The angle at which the liquid crystal display element is rotated is the tilt angle.

The inclination angle δ when a negative voltage is applied to the second electrode layer may be larger than the inclination angle ω when a positive voltage is applied to the second electrode layer. If the inclination angle when a voltage of 10 V is applied is δ ₁ , and the inclination angle when a positive voltage of 10 V is applied to the second electrode layer is ω ₁ , δ ₁ / ω ₁ is preferably 2 or more.

Further, “the amount of transmitted light when a negative voltage is applied to the second electrode layer” and “the amount of transmitted light when a positive voltage is applied to the second electrode layer” can be measured as follows. it can.
That is, first, the polarization axis of one polarizing plate and the alignment direction of the liquid crystal molecules of the liquid crystal layer are set so that the polarizing microscope and the liquid crystal display element in which the polarizing plates are arranged in crossed Nicols are dark when no voltage is applied. Are arranged parallel to each other, and this position is used as a reference. When a voltage is applied, the liquid crystal molecules come to have a predetermined angle with the polarization axis, so that the polarized light transmitted through one polarizing plate is transmitted through the other polarizing plate to be in a bright state. Then, the amount of transmitted light at this time is measured. This transmitted light amount is the above-described transmitted light amount.

  The amount of transmitted light when a negative voltage is applied to the second electrode layer need only be larger than the amount of transmitted light when a positive voltage is applied to the second electrode layer, but in particular, a positive voltage of 10 V is applied to the second electrode layer. It is preferable that B / A is 2 or more, where A is the amount of transmitted light when A is applied and B is the amount of transmitted light when a negative voltage of 10 V is applied to the second electrode layer.

  Hereinafter, each component of the liquid crystal display element of the present invention will be described in detail.

1. Liquid Crystal Layer The liquid crystal layer in the present invention is formed between the non-oriented treatment layer of the first substrate and the fixed liquid crystal layer of the second substrate, and contains a ferroelectric liquid crystal. The ferroelectric liquid crystal, express SmC ^* phase without passing through the SmA phase in the cooling process, and shows a single stability in SmC ^* phase. In addition, when a negative voltage is applied to the second electrode layer, the ferroelectric liquid crystal is tilted to one side from a state where the liquid crystal molecules exhibit monostability, and a positive voltage is applied to the second electrode layer. In addition, the liquid crystal molecules maintain a state exhibiting monostability or are tilted to the opposite side to the case where a negative voltage is applied to the second electrode layer from the state exhibiting monostability, and the liquid crystal molecules are negatively applied to the second electrode layer. The amount of transmitted light when the above voltage is applied is larger than the amount of transmitted light when a positive voltage is applied to the second electrode layer.

As described above, the ferroelectric liquid crystal is such that the amount of transmitted light when a negative voltage is applied to the second electrode layer is larger than the amount of transmitted light when a positive voltage is applied to the second electrode layer. Good.
Note that the amount of transmitted light when a negative voltage is applied to the second electrode layer is greater than the amount of transmitted light when a positive voltage is applied to the second electrode layer is 80% or more in the entire liquid crystal display element. Preferably, it is 90% or more, more preferably 95% or more. This is because a favorable contrast ratio can be obtained within the above range.

Here, the above ratio can be measured as follows.
That is, for example, as shown in FIG. 10, the first substrate 9 in which the first electrode layer 3 and the non-oriented treatment layer 4 are laminated on the first base material 2, and the second electrode layer 13 on the second base material 12. In the liquid crystal display element in which the liquid crystal layer 10 containing ferroelectric liquid crystal is formed between the alignment layer 14 for reactive liquid crystal and the second substrate 19 on which the fixed liquid crystal layer 15 is laminated, the first substrate 9 and It is assumed that polarizing plates 21a and 21b are provided on the outside of the second substrate 19 so that light is incident from the polarizing plate 21a side and light is emitted from the polarizing plate 21b side. The two polarizing plates 21a and 21b are arranged such that their polarization axes are substantially perpendicular, and the polarization axis of the polarizing plate 21a and the alignment direction of the liquid crystal molecules are substantially parallel.

  When no voltage is applied, the linearly polarized light transmitted through the polarizing plate 21a coincides with the alignment direction of the liquid crystal molecules. Therefore, the refractive index anisotropy of the liquid crystal molecules is not exhibited, and the linearly polarized light transmitted through the polarizing plate 21a remains as it is. It passes through the molecules, is blocked by the polarizing plate 21b, and enters a dark state. On the other hand, in the voltage application state, the liquid crystal molecules move on the cone, and the linearly polarized light transmitted through the polarizing plate 21a and the alignment direction of the liquid crystal molecules have a predetermined angle. Therefore, the linearly polarized light transmitted through the polarizing plate 21a. Becomes elliptically polarized light due to the birefringence of the liquid crystal molecules. Of the elliptically polarized light, only linearly polarized light that coincides with the polarization axis of the polarizing plate 21b is transmitted through the polarizing plate 21b to be in a bright state.

  For this reason, when a negative voltage is applied to the second electrode layer, a bright state is obtained if the molecular direction of the ferroelectric liquid crystal changes. At this time, if the transmitted light amount when a negative voltage is applied to the second electrode layer is larger than the transmitted light amount when a positive voltage is applied to the second electrode layer, that is, the second electrode layer The tilt angle from the state showing the monostability of the liquid crystal molecules when a negative voltage is applied to the tilt angle from the state showing the monostability of the liquid crystal molecules when a positive voltage is applied to the second electrode layer If it is larger than that, the molecular direction of the ferroelectric liquid crystal changes greatly when a negative voltage is applied to the second electrode layer. On the other hand, for example, if the transmitted light amount when a negative voltage is applied to the second electrode layer is smaller than the transmitted light amount when a positive voltage is applied to the second electrode layer, that is, the second electrode The tilt angle from the state showing the monostability of the liquid crystal molecules when a negative voltage is applied to the layer is tilted from the state showing the monostability of the liquid crystal molecules when a positive voltage is applied to the second electrode layer If the angle is smaller than the angle, the molecular direction of the ferroelectric liquid crystal does not change when the negative voltage is applied to the second electrode layer, or the molecular direction of the ferroelectric liquid crystal changes only slightly. It is. Thus, for example, there are some cases where the molecular direction of the ferroelectric liquid crystal does not change when a negative voltage is applied to the second electrode layer, or where the molecular direction of the ferroelectric liquid crystal changes only slightly. In this case, a dark state is partially obtained. Therefore, the amount of transmitted light when a negative voltage is applied to the second electrode layer is determined from the white / black area ratio of black and white (bright / dark) display obtained when a negative voltage is applied to the second electrode layer. It is possible to calculate the ratio of the amount that is larger than the amount of transmitted light when a positive voltage is applied to the electrode layer.

The phase sequence of the ferroelectric liquid crystal is not particularly limited as long as it exhibits the chiral smectic C (SmC ^* ) phase without passing through the smectic A (SmA) phase in the temperature lowering process. For example, the phase sequence changes in phase with a nematic (N) phase-cholesteric (Ch) phase-chiral smectic C (SmC ^* ) phase, a nematic (N) phase-chiral smectic C (SmC ^* ) phase And those that change phase.

In addition, the ferroelectric liquid crystal may be any liquid crystal as long as it exhibits monostability in the SmC ^* phase, but in particular, when either positive or negative voltage as illustrated in FIGS. 11A and 11B is applied. It is preferable that only the liquid crystal molecules operate and exhibit half V-shaped switching characteristics. Using a ferroelectric liquid crystal exhibiting such a half V-shaped switching characteristic, it is possible to take a sufficiently long opening time as a black and white shutter, thereby making it possible to display each color that is temporally switched brighter. In addition, a bright color display liquid crystal display element can be realized.

  “Half V-shaped switching characteristics” refers to electro-optical characteristics in which the amount of transmitted light is asymmetric with respect to the applied voltage. Specifically, among the transmitted light amounts with respect to the applied voltage when a positive and negative voltage of 10 V is applied to the liquid crystal layer, A is the transmitted light amount of the applied voltage when the transmitted light amount is small, and the applied voltage is transmitted when the transmitted light amount is large. When the amount of light is B, B / A is 2 or more. The electro-optical characteristics illustrated in FIGS. 11A and 11B are half V-shaped switching characteristics.

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

In addition to the ferroelectric liquid crystal, the liquid crystal layer may contain a compound having any function depending on the function required for the liquid crystal display element. Examples of such a compound include a polymerized polymerizable monomer. By containing such a polymerizable monomer polymer in the liquid crystal layer, the alignment of the liquid crystal material is so-called “polymer stabilization”, and a liquid crystal display device excellent in alignment stability can be obtained.
The case where the liquid crystal layer contains a ferroelectric liquid crystal and a polymer of a polymerizable monomer is the same as that described in JP-A-2006-323215.

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

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

In the present invention, since the fixed liquid crystal layer tends to have a relatively positive polarity in the non-oriented treatment layer and the fixed liquid crystal layer, when a negative voltage is applied to the second electrode layer It is preferable to perform display.
As described above, the amount of transmitted light when the negative voltage of the second electrode layer is applied is larger than the amount of transmitted light when the positive voltage of the second electrode layer is applied. That is, when a positive voltage is applied to the second electrode layer, the amount of transmitted light is less than when a negative voltage is applied to the second electrode layer. For this reason, when a positive voltage is applied to the second electrode layer, it is more disadvantageous for display than when a negative voltage is applied to the second electrode layer.
Therefore, it is preferable to perform display when a negative voltage is applied to the second electrode layer where the amount of transmitted light is larger.

In a liquid crystal display element using a ferroelectric liquid crystal exhibiting monostability, the amount of transmitted light depends on the tilt angle of liquid crystal molecules when a voltage is applied. When either positive or negative voltage is applied, the liquid crystal molecules tilt on the cone. For example, as shown in FIGS. 9A to 9C, the tilt angle of the liquid crystal molecules changes according to the magnitude of the applied voltage, and the transmitted light amount Changes. At this time, the amount of transmitted light is maximized when the inclination angle of the liquid crystal molecules from the monostable state is 45 °.
Therefore, in order to realize a high amount of transmitted light, a ferroelectric liquid crystal whose tilt angle from a monostable state of liquid crystal molecules can be 45 ° when a negative voltage is applied to the second electrode layer during actual driving. Is preferably used.
In the example shown in FIG. 9B, when a ferroelectric liquid crystal having a maximum tilt angle δ from the monostable state of the liquid crystal molecules is larger than 45 °, the liquid crystal display element is actually driven. At this time, when a negative voltage is applied to the second electrode layer, the tilt angle of the liquid crystal molecules from the monostable state can be set to 45 °. This is because the direction of the liquid crystal molecules does not change approximately twice the tilt angle when a negative voltage is applied to the second electrode layer during actual driving.

2. 1st board | substrate The 1st board | substrate used for this invention has a 1st base material and the non-orientation processing layer which is formed on the said 1st base material and the orientation process is not performed.

  The 1st board | substrate in this invention can be divided into two aspects by the structure of an unoriented process layer. In the first aspect, the non-oriented treatment layer contains a photoisomerization-reactive compound having an azobenzene skeleton in the molecule, and the first electrode layer is formed between the first substrate and the non-oriented treatment layer. It is. A 2nd aspect is a case where an unoriented processing layer consists of an inorganic compound which has electroconductivity, and an unoriented processing layer is a 1st electrode layer. Hereinafter, the description will be made separately for each aspect.

(1) 1st aspect The 1st board | substrate of this aspect is formed on the 1st base material, the 1st electrode layer formed on the said 1st base material, the said 1st electrode layer, and azobenzene in a molecule | numerator. It contains a photoisomerization-reactive compound having a skeleton and an unaligned treatment layer that has not been subjected to photo-alignment treatment.

In this aspect, since the unaligned layer is not subjected to the photo-alignment process, it is not necessary to perform the photo-alignment process in the manufacturing process of the first substrate of this aspect. Therefore, the manufacturing process of the liquid crystal display element can be simplified. In particular, large-sized mother glass is often used when manufacturing liquid crystal display elements, and since the increase in size of this mother glass is progressing year by year, a larger mother glass is used when performing photo-alignment treatment. In recent years, it is necessary to develop a corresponding exposure apparatus, and there is a concern that the capital investment will increase as the size of the mother glass increases. In this mode, however, it is not necessary to carry out photo-alignment treatment, so costs can be reduced. It becomes.
Further, since the azobenzene skeleton contains many π electrons, it has an advantage that it has a high interaction with liquid crystal molecules and is particularly suitable for controlling the direction of spontaneous polarization of ferroelectric liquid crystal.
Hereinafter, each configuration of the first substrate will be described.

(I) Unoriented treatment layer The unoriented treatment layer used in this embodiment is formed on the first electrode layer, contains a photoisomerization-reactive compound having an azobenzene skeleton in the molecule, and is subjected to a photoalignment treatment. It is not.

  In addition, it can be confirmed by measuring the polarized ultraviolet / visible absorption spectrum of the non-oriented treatment layer that “the non-oriented treatment layer has not been subjected to the photo-alignment treatment”. That is, using a UV-visible spectrophotometer (V7100: manufactured by JASCO Corporation), the non-oriented treatment layer is irradiated with polarized ultraviolet rays, and polarized ultraviolet / visible absorption spectra parallel and perpendicular to the polarization direction of the ultraviolet rays are obtained. taking measurement. If the ratio of the absorption peak of the spectrum in the vertical direction and the horizontal direction is 1.2 or less, it is assumed that the photo-alignment treatment has not been performed.

  The ratio of the absorption peak of the spectrum in the vertical direction and the horizontal direction is preferably 1.2 or less, more preferably 1.1 or less. Note that the non-oriented treatment layer may have some anisotropy depending on the application method of the non-oriented treatment layer forming coating liquid when forming the non-oriented treatment layer. The lower limit of the ratio of the absorption peak of the spectrum in the direction and the horizontal direction is not particularly limited.

  The photoisomerization reactive compound used in this embodiment is not particularly limited as long as it has an azobenzene skeleton in the molecule. The photoisomerization reaction in which this photoisomerization reactive compound is generated is a cis-trans isomerization reaction.

Examples of the photoisomerization-reactive compound include a monomolecular compound or a polymerizable monomer that is polymerized by light or heat. These may be appropriately selected according to the type of ferroelectric liquid crystal used.
For example, when a polymerizable monomer is used, the film can be stabilized by polymerization. Moreover, when an acrylate monomer or a methacrylate monomer is used among the polymerizable monomers, it can be easily polymerized. The polymerizable monomer may be a monofunctional monomer or a polyfunctional monomer, but is preferably a bifunctional monomer because the film becomes more stable by polymerization.

  The number of azobenzene skeletons contained in the molecule is not particularly limited, and may be one or two, for example.

  The azobenzene 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 azobenzene skeleton, and examples thereof include a carboxyl group, a sodium sulfonate group, and a hydroxyl group. Can be mentioned. These structures can be appropriately selected depending on the type of ferroelectric liquid crystal used.

In addition to the azobenzene skeleton, the photoisomerization-reactive compound has a group containing many π electrons such as an aromatic hydrocarbon group so that the interaction with the liquid crystal molecule can be further enhanced. The azobenzene 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.

  The photoisomerization reactive compound may have the azobenzene skeleton as a main chain or a side chain. In the case where a polymerizable monomer is used as the photoisomerization-reactive compound and has the azobenzene skeleton as a side chain, the aromatic hydrocarbon group or bonding group contained in the molecule described above is a liquid crystal molecule. It is preferable that it is contained in the side chain together with the azobenzene skeleton so as to enhance the interaction with. In this case, the side chain of the polymerizable monomer may have an aliphatic hydrocarbon group such as an alkylene group as a spacer so that the azobenzene skeleton is easily oriented.

Among the compounds having an azobenzene skeleton in the molecule, as monomolecular compounds, JP-A-2006-350322, JP-A-2006-323214, JP-A-2005-258429, JP-A-2005-258428, etc. Those described can be used.
Examples of the polymerizable monomer having an azobenzene skeleton as a side chain include those described in JP-A-2006-350322, JP-A-2006-323214, JP-A-2005-258429, JP-A-2005-258428, and the like. Things can be used.

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

  Further, the non-oriented treatment layer may contain an additive in addition to the photoisomerization reactive compound. When a polymerizable monomer is used as the photoisomerization reactive compound, examples of the additive include a polymerization initiator and a polymerization inhibitor.

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

  The thickness of the unoriented treatment layer is preferably in the range of 1 nm to 1000 nm, more preferably in the range of 3 nm to 100 nm. If the thickness of the unaligned layer is thinner than the above range, the direction of spontaneous polarization of the ferroelectric liquid crystal may not be sufficiently controlled. Conversely, if the thickness of the unaligned layer is larger than the above range, it is disadvantageous in terms of cost. It is because it may become.

(Ii) First electrode layer The first electrode layer used in this embodiment 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 of the first substrate. Preferably, at least one of the second electrode layers of the second substrate 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 driven by an active matrix method using TFTs, one of the first substrate and the second substrate is provided with the entire surface common electrode formed of the transparent conductor, and the other is provided with the other. The gate electrode and the source electrode are arranged in a matrix, and a TFT element and a pixel electrode are provided in a portion surrounded by the gate electrode and the source electrode.

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

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

(Iv) Other Configurations In the first substrate of this aspect, partition walls or columnar spacers may be formed on the first base material. In the case where the partition walls or columnar spacers are formed on the second base material in the second substrate, the partition walls or columnar spacers are not formed on the first base material in the first substrate. That is, partition walls or columnar spacers may be formed on the first substrate, and partition walls or columnar spacers may be formed on the second substrate.
As the partition walls and columnar spacers, general partition walls and columnar spacers can be applied.

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

(2) 2nd aspect The 1st board | substrate of this aspect is a non-orientated treatment layer which is formed on the 1st base material and the said 1st base material, consists of an inorganic compound which has electroconductivity, and the orientation process is not given. And the unoriented treatment layer is the first electrode layer.

  In this embodiment, since the unaligned layer is not subjected to alignment treatment, it is not necessary to perform alignment treatment in the manufacturing process of the first substrate of this embodiment. Therefore, the manufacturing process of the liquid crystal display element can be simplified. In particular, large-sized mother glass is often used when manufacturing liquid crystal display elements. Since this mother glass has been increasing in size year by year, it is compatible with larger mother glass when orientation processing is performed. In recent years, there is a concern that capital investment will increase as the size of the mother glass increases. However, in this mode, it is not necessary to perform orientation treatment, which can reduce costs. It becomes.

  The first base material is the same as that in the first aspect, and the description thereof is omitted here. Hereinafter, other configurations of the first substrate will be described.

(I) Unoriented processing layer The unoriented processing layer used for this aspect is formed on the 1st substrate, consists of an inorganic compound which has electroconductivity, has not been subjected to orientation processing, and is the 1st electrode. It also serves as a layer.

  In addition, it can be confirmed by measuring the polarized ultraviolet / visible absorption spectrum of the unoriented treatment layer that the “unoriented treatment layer is not subjected to the orientation treatment” as in the first embodiment. it can.

  The inorganic compound used in this embodiment is not particularly limited as long as it has electrical conductivity. However, since the non-oriented treatment layer also serves as the first electrode layer, it is generally used as an electrode of a liquid crystal display element. It is preferable to apply what is used. Specifically, indium oxide, tin oxide, indium tin oxide (ITO), indium zinc oxide (IZO), and the like can be given.

  The thickness of the non-oriented treatment layer can be the same as the thickness of an electrode of a general liquid crystal display element.

(Ii) Other Configurations In the first substrate of this aspect, partition walls or columnar spacers may be formed on the first base material. Moreover, in the 1st board | substrate of this aspect, the colored layer may be formed on the 1st base material.
Since these members are the same as those described in the first aspect, description thereof is omitted here.

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 an alignment for reactive liquid crystal formed on the second electrode layer. A film and a fixed liquid crystal layer formed on the reactive liquid crystal alignment film and formed by fixing the reactive liquid crystal. The second substrate is disposed so that the unoriented processing layer of the first substrate and the fixed liquid crystal layer of the second substrate face the first substrate.

  Note that the second base material, the second electrode layer, and other configurations are the same as the first base material, the first electrode layer, and other configurations of the first substrate, respectively. Omitted. Hereinafter, other configurations of the second substrate will be described.

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

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

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

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

  As the monoacrylate monomer and diacrylate monomer, those described in JP 2006-350322 A, JP 2006-323214 A, JP 2005-258429 A, JP 2005-258428 A, and the like are used. it can.

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

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

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

  The addition amount of such a photopolymerization initiator is generally 0.01% by mass to 20% by mass, preferably 0.1% by mass to 10% by mass, more preferably 0.5% by mass to 5% by mass. % Can be added to the reactive liquid crystal.

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

(2) Alignment film for reactive liquid crystal As the alignment film for reactive liquid crystal used in the present invention, the above-mentioned reactive liquid crystal can be aligned, and there is an adverse effect in fixing the alignment state of the above-mentioned reactive liquid crystal. There is no particular limitation as long as it does not reach. As the alignment film for reactive liquid crystal, for example, a rubbing-treated alignment film, a photo-alignment-treated photo-alignment film, or the like can be used. Among these, in consideration of the capital investment accompanying the increase in size of the mother glass, a rubbing-treated alignment film is preferably used.

  The rubbing-treated alignment film is useful in that a relatively high pretilt angle can be realized. As the alignment film subjected to the rubbing treatment, for example, those described in JP-A-2008-129529 can be used.

  The photo-alignment film irradiates a substrate coated with a photo-excited reaction type material with light with controlled polarization to cause photo-excited reaction (decomposition, isomerization, dimerization) and to give anisotropy to the obtained film. This aligns the liquid crystal molecules on the film. The photo-alignment film is useful in that since the photo-alignment process is a non-contact alignment process, there is no generation of static electricity or dust, and the quantitative alignment process can be controlled. Photoexcitation materials used for photo-alignment films include photoisomerization materials that impart anisotropy to the film by photoisomerization reaction, and anisotropy to the film by photodimerization reaction. And a photodecomposable material that imparts anisotropy to the film by causing a photodecomposition reaction. As the photo-alignment film, for example, those described in JP-A-2006-350322, JP-A-2006-323214, JP-A-2005-258429, and JP-A-2005-258428 can be used.

4). Other Configurations The liquid crystal display element of the present invention may have polarizing plates 21a and 21b as illustrated in FIG.
The polarizing plate used in the present invention is not particularly limited as long as it transmits only a specific direction among the wave of light, and a polarizing plate generally used as a polarizing plate of a liquid crystal display element should be used. Can do.

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

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

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

  In the present invention, the first substrate may be a TFT substrate, the second substrate may be a common electrode substrate, the first substrate may be a common electrode substrate, and the second substrate may be a TFT substrate. In particular, in the case where the fixed liquid crystal layer tends to have a relatively positive polarity between the non-oriented treatment layer and the fixed liquid crystal layer, the first substrate is the TFT substrate and the second substrate is the common electrode substrate. It is preferable.

  FIG. 12 is a schematic perspective view showing an example of an active matrix liquid crystal display element using TFTs. The liquid crystal display element 10 illustrated in FIG. 12 includes a TFT substrate 9a (first substrate) in which TFT elements 31 are arranged in a matrix on the first base material 2, and a common electrode 32 (first electrode) on the second base material 12. And a common electrode substrate 19a (second substrate) on which two electrode layers are formed. A gate electrode 33x, a source electrode 33y, and a pixel electrode 34 (first electrode layer) are formed on the TFT substrate 9a (first substrate). The gate electrode 33x and the source electrode 33y are arranged vertically and horizontally, respectively, and by applying a signal to the gate electrode 33x and the source electrode 33y, the TFT element 31 can be operated to drive the ferroelectric liquid crystal. A portion where the gate electrode 33x and the source electrode 33y intersect is insulated by an insulating layer (not shown), and the signal of the gate electrode 33x and the signal of the source electrode 33y can operate independently. A portion surrounded by the gate electrode 33x and the source electrode 33y is a pixel that is a minimum unit for driving the liquid crystal display element of the present invention. Each pixel includes at least one TFT element 31 and a pixel electrode 34 (first electrode). Electrode layer) is formed. Then, by sequentially applying a signal voltage to the gate electrode and the source electrode, the TFT element of each pixel can be operated. In FIG. 12, the liquid crystal layer, the unaligned treatment layer, the reactive liquid crystal alignment film, and the fixed liquid crystal layer are omitted.

  In the above liquid crystal display element, for example, when the gate electrode is set to a high potential of about 30 V, the TFT element is switched on, a signal voltage is applied to the ferroelectric liquid crystal by the source electrode, and the gate electrode is set to a low level of about −10 V. When the potential is set, the TFT element is turned off. In the switch-off state, as illustrated in FIG. 13, a voltage is applied between the common electrode 32 (second electrode layer) and the gate electrode 33x so that the common electrode 32 (second electrode layer) side is positive. . Since the ferroelectric liquid crystal does not operate in this switch-off state, the pixel is in a dark state.

  In the present invention, as described above, when no voltage is applied, the spontaneous polarization of the liquid crystal molecules tends to face the unaligned treatment layer side (first substrate side) due to the polar surface interaction. That is, in the switch-off state, as illustrated in FIG. 13, the spontaneous polarization Ps of the liquid crystal molecules 1 faces the TFT substrate 9a (first substrate) side. Therefore, the direction of spontaneous polarization is not affected by the voltage applied between the common electrode 32 (second electrode layer) and the gate electrode 33x.

  On the other hand, for example, when the spontaneous polarization is directed to the fixed liquid crystal layer side (the common electrode substrate side) in the state where no voltage is applied, due to the influence of the voltage applied between the common electrode and the gate electrode in the switch-off state, The direction of spontaneous polarization is reversed near the region where the gate electrode is provided. Then, in the vicinity of the region where the gate electrode is provided, the ferroelectric liquid crystal operates and light leakage occurs even though the switch is off.

  On the other hand, as described above, in the present invention, the direction of spontaneous polarization is not affected by the voltage applied between the common electrode and the gate electrode, so that no light leakage occurs. Therefore, in the present invention, light leakage near the gate electrode can be prevented by controlling the direction of spontaneous polarization and using the second substrate as a common electrode substrate.

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

B. Next, a method for manufacturing a liquid crystal display element of the present invention will be described.
In the method for producing a liquid crystal display element of the present invention, an unoriented treatment layer containing a photoisomerization-reactive compound having an azobenzene skeleton in the molecule is formed on the first substrate on which the first electrode layer is formed, A first substrate preparation step of preparing a first substrate in which the first electrode layer and the non-oriented treatment layer are sequentially laminated on the first base material without performing a photo-alignment treatment on the non-oriented treatment layer; A reactive liquid crystal alignment film is formed on the second substrate on which the second electrode layer is formed, and a reactive liquid crystal layer containing a reactive liquid crystal is formed on the reactive liquid crystal alignment film. The reactive liquid crystal in the liquid crystal layer is aligned, the alignment state of the reactive liquid crystal is fixed, and the second electrode layer, the reactive liquid crystal alignment film, and the reactive liquid crystal are fixed on the second substrate. Second substrate preparation process for preparing a second substrate in which fixed liquid crystal layers are sequentially laminated And sandwiching a ferroelectric liquid crystal between the unoriented treatment layer of the first substrate and the fixed liquid crystal layer of the second substrate, aligning the ferroelectric liquid crystal without performing an electric field application treatment, and A liquid crystal layer forming step of forming a liquid crystal layer including a dielectric liquid crystal, wherein the ferroelectric liquid crystal exhibits an SmC ^* phase without passing through an SmA phase in a temperature lowering process, and the SmC ^* phase Furthermore, the ferroelectric liquid crystal is tilted to one side from a state where the liquid crystal molecules exhibit monostability when a negative voltage is applied to the second electrode layer. When a positive voltage is applied to the second electrode layer, the liquid crystal molecules maintain the monostable state or the negative voltage is applied to the second electrode layer from the monostable state. Was applied to the second electrode layer, and the negative voltage was applied to the second electrode layer. The transmitted light amount is larger than the transmitted light amount when a positive voltage is applied to the second electrode layer.

  In the present invention, by utilizing the fact that the positive polarity of the spontaneous polarization of the ferroelectric liquid crystal tends to be directed to the non-oriented treatment layer side containing the photoisomerization-reactive compound having an azobenzene skeleton in the molecule, It is possible to control the direction of spontaneous polarization of the molecule. Since the direction of spontaneous polarization can be controlled, the monodomain alignment of the ferroelectric liquid crystal can be obtained without causing alignment defects such as double domains.

  In addition, according to the present invention, only by slowly cooling the ferroelectric liquid crystal without performing an electric field application treatment, the alignment ability of the fixed liquid crystal layer and the ferroelectric liquid crystal of the non-aligned processed layer and the fixed liquid crystal layer can be obtained. Due to the surface polarity interaction, the ferroelectric liquid crystal can be aligned and the direction of spontaneous polarization can be controlled. Therefore, since the ferroelectric liquid crystal is aligned without performing an electric field application treatment, the alignment can be maintained even when the temperature is raised to the phase transition temperature or higher, and the occurrence of alignment defects can be suppressed.

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

1. First substrate preparation step The first substrate preparation step in the present invention is an unoriented treatment layer containing a photoisomerization-reactive compound having an azobenzene skeleton in the molecule on the first base material on which the first electrode layer is formed. And preparing a first substrate in which the first electrode layer and the non-oriented layer are sequentially laminated on the first base material without subjecting the non-oriented layer to a photo-alignment treatment. .

  The non-oriented treatment layer is formed by applying a non-oriented treatment layer forming coating solution obtained by diluting a photoisomerization reactive compound with an organic solvent onto the first base material on which the first electrode layer is formed, and drying the coating solution. Can be formed.

  The content of the photoisomerization-reactive compound in the coating liquid for forming an unoriented treatment layer is preferably in the range of 0.05% by mass to 10% by mass, and is 0.2% by mass to 2% by mass. More preferably within the range. If the content is less than the above range, it becomes difficult to control the direction of spontaneous polarization of the ferroelectric liquid crystal, and conversely if the content is more than the above range, the viscosity of the coating liquid increases, so that a uniform coating film is obtained. It is because it becomes difficult to form.

  As an application method of the coating liquid for forming the non-oriented treatment layer, for example, spin coating method, roll coating method, rod bar coating method, spray coating method, air knife coating method, slot die coating method, wire bar coating method, ink jet method, A flexographic printing method, a screen printing method, or the like can be used.

  Furthermore, when a polymerizable monomer is used among the above-mentioned photoisomerization-reactive compounds, the film can be polymerized and stabilized by heating after coating.

2. Second substrate preparation step In the second substrate preparation step in the present invention, a reactive liquid crystal alignment film is formed on the second substrate on which the second electrode layer is formed, and the reactive liquid crystal alignment film is reactive. A reactive liquid crystal layer containing liquid crystal is formed, the reactive liquid crystal in the reactive liquid crystal layer is aligned, the alignment state of the reactive liquid crystal is fixed, and the second electrode layer is formed on the second substrate. This is a step of preparing a second substrate in which the alignment film for reactive liquid crystal and the immobilized liquid crystal layer formed by immobilizing the reactive liquid crystal are sequentially laminated.

  The method for forming the alignment film for reactive liquid crystal is appropriately selected according to the type of alignment film for reactive liquid crystal. In addition, since each formation method of the alignment film by which the rubbing process used as an alignment film for reactive liquid crystals, a photo-alignment film, and an oblique vapor deposition alignment film was described in the above-mentioned "A. liquid crystal display element" section. Explanation here is omitted.

  The fixed liquid crystal layer is formed by applying a reactive liquid crystal composition containing the reactive liquid crystal on the reactive liquid crystal alignment film to form a reactive liquid crystal layer, and aligning the reactive liquid crystal in the reactive liquid crystal layer. It can be formed by fixing the alignment state of the reactive liquid crystal.

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

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

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

  Although the concentration of the reactive liquid crystal composition depends on the solubility of the reactive liquid crystal and the thickness of the immobilized liquid crystal layer, it cannot be defined unconditionally, but is usually 0.1% by mass to 40% by mass, preferably 1% by mass. It adjusts in the range of% -20 mass%. If the concentration of the reactive liquid crystal composition is lower than the above range, the reactive liquid crystal may be difficult to align. Conversely, if the concentration of the reactive liquid crystal composition is higher than the above range, the viscosity of the reactive liquid crystal composition is low. It is because it becomes high and it may become difficult to form a uniform coating film.

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

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

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

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

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

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

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

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

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

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

3. Liquid crystal layer forming step In the liquid crystal layer forming step of the present invention, a ferroelectric liquid crystal is sandwiched between the non-oriented treatment layer of the first substrate and the fixed liquid crystal layer of the second substrate, and an electric field application treatment is not performed. In this step, the ferroelectric liquid crystal is aligned to form a liquid crystal layer containing the ferroelectric liquid crystal.

  As a method for sandwiching the ferroelectric liquid crystal between the unaligned treatment layer of the first substrate and the fixed liquid crystal layer of the second substrate, a method generally used as a method for producing a liquid crystal cell can be used. An injection method or the like can be used. In the vacuum injection method, for example, a ferroelectric liquid crystal, which is made an isotropic liquid by heating, is injected into a liquid crystal cell prepared using a first substrate and a second substrate in advance by using the capillary effect and bonded. By blocking with the agent, the ferroelectric liquid crystal can be sandwiched between the first substrate and the second substrate.

  After the ferroelectric liquid crystal is sandwiched between the first substrate and the second substrate, the ferroelectric liquid crystal is aligned. At this time, the encapsulated ferroelectric liquid crystal can be aligned by slowly cooling the liquid crystal cell to room temperature. That is, in the present invention, in order to align the ferroelectric liquid crystal, it is not necessary to perform an electric field application treatment, and only slow cooling is required.

  When a polymerizable monomer is added to the ferroelectric liquid crystal, the polymerizable monomer is polymerized after aligning the ferroelectric liquid crystal. The polymerization method of the polymerizable monomer is appropriately selected according to the type of the polymerizable monomer. For example, when an ultraviolet curable resin monomer is used as the polymerizable monomer, the polymerizable monomer can be polymerized by ultraviolet irradiation. .

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

The following examples illustrate the present invention in more detail.
[Example 1]
The two glass substrates on which the ITO electrodes were formed were washed, an unaligned treatment layer was formed on one substrate, and a reactive liquid crystal alignment film and an immobilized liquid crystal layer were formed on the other substrate. As the material for the unoriented treatment layer, compounds i to v represented by the following structural formula were used.

(Production of substrate 1)
With respect to the non-oriented treatment layer using the compounds i to v, the non-oriented treatment layer was formed as follows.
The glass substrate on which the ITO electrode is formed is thoroughly washed, and a solution of 10% by mass of compounds iv dissolved in N-methyl-2-pyrrolidinone is spin-coated on the glass substrate for 30 seconds at a rotation speed of 1000 rpm. did. Then, it was dried at 100 ° C. for 10 minutes on a hot plate.

(Preparation of substrate 2)
The glass substrate on which the ITO electrode was formed was thoroughly washed, and on this glass substrate, a photo-alignment material (product name: ROP-103, manufactured by ROLIC Technology Co., Ltd.) was spin-coated for 20 seconds at a rotation speed of 1000 rpm, and at 100 ° C. After drying for 3 minutes, alignment treatment was performed by irradiating with linearly polarized ultraviolet rays of about 1000 mJ / cm ² . Further, a polymerizable liquid crystal (trade name: ROF5101, manufactured by ROLIC Technology Co., Ltd.) is spin-coated at 1000 rpm for 20 seconds on the alignment film using the photoalignable material, dried at 100 ° C. for 3 minutes, and then non-polarized light. Ultraviolet rays were irradiated at about 1000 mJ / cm ² for polymerization.

(Production of liquid crystal display element)
Thereafter, 1.5 μm bead spacers were sprayed on one substrate, and a sealing material was applied to the other substrate with a seal dispenser. The substrate 1 and the substrate 2 were assembled so that the UV polarized light irradiation direction of the substrate 2 and the liquid crystal injection direction were parallel, and thermocompression bonded to produce a 1-inch test cell. The ferroelectric liquid crystal is “R2301” (manufactured by Clariant), the ferroelectric liquid crystal is attached to the upper part of the injection port, and the oven is used at a temperature 10 ° C. to 20 ° C. higher than the nematic phase-isotropic phase transition temperature. Injection was performed and the temperature was slowly returned to room temperature.

(Evaluation)
The double domain defect was observed by applying a voltage of 5 V to the produced test cell under crossed Nicols. At this time, the area ratios of the light transmission region (white) and the non-transmission region (black) were calculated, and the larger one of the regions was expressed as a percentage. This percentage was taken as the monodomain rate. The closer the monodomain ratio is to 100%, the more the double domain defect is improved.
Contrast was observed under crossed Nicols with the fabricated test cell, and the ratio between the minimum value and maximum value of the amount of transmitted light was calculated.

[Example 2]
(Production of substrate 1)
The glass substrate on which the ITO electrode or the IZO electrode was formed was washed.

(Preparation of substrate 2)
The glass substrate on which the ITO electrode was formed was thoroughly washed, and on this glass substrate, a photo-alignment material (product name: ROP-103, manufactured by ROLIC Technology Co., Ltd.) was spin-coated for 20 seconds at a rotation speed of 1000 rpm, and at 100 ° C. After drying for 3 minutes, alignment treatment was performed by irradiating with linearly polarized ultraviolet rays of about 1000 mJ / cm ² . Further, a polymerizable liquid crystal (trade name: ROF5101, manufactured by ROLIC Technology Co., Ltd.) is spin-coated at 1000 rpm for 20 seconds on the alignment film using the photoalignable material, dried at 100 ° C. for 3 minutes, and then non-polarized light. Ultraviolet rays were irradiated at about 1000 mJ / cm ² for polymerization.

(Production of liquid crystal display element)
Thereafter, 1.5 μm bead spacers were sprayed on one substrate, and a sealing material was applied to the other substrate with a seal dispenser. The substrate 1 and the substrate 2 were assembled so that the UV polarized light irradiation direction of the substrate 2 and the liquid crystal injection direction were parallel, and thermocompression bonded to produce a 1-inch test cell. The ferroelectric liquid crystal is “R2301” (manufactured by Clariant), the ferroelectric liquid crystal is attached to the upper part of the injection port, and the oven is used at a temperature 10 ° C. to 20 ° C. higher than the nematic phase-isotropic phase transition temperature. Injection was performed and the temperature was slowly returned to room temperature.

(Evaluation)
The double domain defect was observed by applying a voltage of 5 V to the produced test cell under crossed Nicols. At this time, the area ratios of the light transmission region (white) and the non-transmission region (black) were calculated, and the larger one of the regions was expressed as a percentage. This percentage was taken as the monodomain rate. The closer the monodomain ratio is to 100%, the more the double domain defect is improved.
Contrast was observed under crossed Nicols with the fabricated test cell, and the ratio between the minimum value and maximum value of the amount of transmitted light was calculated.

  In Example 2, as in Example 1, a high monodomain ratio was obtained.

[Comparative Example 1]
A liquid crystal display device was produced in the same manner as in Example 1 except that in the production of the substrate 1, the film using the compounds iv was subjected to a rubbing treatment.

  In Example 1 and Comparative Example 1, the monodomain ratio did not change, but a decrease in contrast was observed due to scratches caused by rubbing.

[Comparative Example 2]
A liquid crystal display device was produced in the same manner as in Example 1 except that in the production of the substrate 1, a film using the compounds i to v was irradiated with polarized ultraviolet rays and subjected to photo-alignment treatment.

In Example 1 and Comparative Example 2, there was almost no change in the monodomain ratio and contrast, and it was confirmed that the direction of spontaneous polarization of the ferroelectric liquid crystal could be controlled without performing photo-alignment treatment.
Further, in any of the results of Examples and Comparative Examples, when a negative voltage is applied to the electrode of the substrate 2, the liquid crystal molecules transmit tilted light, and when a positive voltage is applied to the electrode of the substrate 2, The liquid crystal molecules were not tilted and maintained a black state.

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal molecule 2 ... 1st base material 3 ... 1st electrode layer 4 ... Non-alignment process layer 9 ... 1st board | substrate 10 ... Liquid crystal display element 12 ... 2nd base material 13 ... 2nd electrode layer 14 ... For reactive liquid crystal Alignment film 15 ... immobilized liquid crystal layer 19 ... second substrate 20 ... liquid crystal layer z ... layer normal line Ps ... spontaneous polarization

Claims (2)

A first substrate, and a first substrate having an unoriented treatment layer formed on the first substrate and not subjected to an orientation treatment;
Formed on the second substrate, the second electrode layer formed on the second substrate, the alignment film for reactive liquid crystal formed on the second electrode layer, and the alignment film for reactive liquid crystal A second substrate having an immobilized liquid crystal layer formed by immobilizing a reactive liquid crystal and disposed so that the unaligned treatment layer and the immobilized liquid crystal layer face the first substrate;
A liquid crystal layer formed between the unaligned treatment layer and the fixed liquid crystal layer and containing a ferroelectric liquid crystal;
The ferroelectric liquid crystal exhibits a chiral smectic C phase without passing through a smectic A phase in the temperature lowering process, and exhibits monostability in the chiral smectic C phase,
Further, when a negative voltage is applied to the second electrode layer, the ferroelectric liquid crystal is tilted to one side from a state where the liquid crystal molecules exhibit monostability, and a positive voltage is applied to the second electrode layer. When the liquid crystal molecules maintain a state showing the monostability or when a negative voltage is applied to the second electrode layer from the state showing the monostability, the liquid crystal molecules are inclined to the opposite side. The amount of transmitted light when a negative voltage is applied to the second electrode layer is greater than the amount of transmitted light when a positive voltage is applied to the second electrode layer,
The unoriented treatment layer contains a photoisomerization-reactive compound having an azobenzene skeleton in the molecule, and a first electrode layer is formed between the first substrate and the unoriented treatment layer. and to that liquid crystal display element. On the first substrate on which the first electrode layer is formed, an unoriented treatment layer containing a photoisomerization-reactive compound having an azobenzene skeleton in the molecule is formed, and the unaligned treatment layer is subjected to a photoalignment treatment. Without preparing a first substrate in which the first electrode layer and the unoriented treatment layer are sequentially laminated on the first base material,
A reactive liquid crystal alignment film is formed on the second substrate on which the second electrode layer is formed, a reactive liquid crystal layer containing a reactive liquid crystal is formed on the reactive liquid crystal alignment film, and the reactivity The reactive liquid crystal in the liquid crystal layer is aligned, the alignment state of the reactive liquid crystal is fixed, and the second electrode layer, the alignment film for reactive liquid crystal, and the reactive liquid crystal are fixed on the second substrate. A second substrate preparation step of preparing a second substrate on which fixed liquid crystal layers formed in order are laminated;
A ferroelectric liquid crystal is sandwiched between an unaligned treatment layer of the first substrate and a fixed liquid crystal layer of the second substrate, and the ferroelectric liquid crystal is oriented without performing an electric field application treatment. A liquid crystal layer forming step of forming a liquid crystal layer containing liquid crystal,
The ferroelectric liquid crystal exhibits a chiral smectic C phase without passing through a smectic A phase in the temperature lowering process, and exhibits monostability in the chiral smectic C phase,
Further, when a negative voltage is applied to the second electrode layer, the ferroelectric liquid crystal is tilted to one side from a state where the liquid crystal molecules exhibit monostability, and a positive voltage is applied to the second electrode layer. When the liquid crystal molecules maintain a state showing the monostability or when a negative voltage is applied to the second electrode layer from the state showing the monostability, the liquid crystal molecules are inclined to the opposite side. A transmitted light amount when a negative voltage is applied to the second electrode layer is larger than a transmitted light amount when a positive voltage is applied to the second electrode layer. Production method.

Images