JP5584502B2 - Liquid crystal display element, method for manufacturing liquid crystal display element, and driving method - Google Patents

Description

  The present invention relates to a liquid crystal display element. The present invention also relates to a manufacturing method and a driving method thereof.

  Depending on the relationship between the chiral agent and the alignment angle, the direction of rotation of the liquid crystal molecules (the first direction of rotation) regulated by the combination of the directions of the alignment treatment applied to the pair of transparent electrode substrates sandwiching the liquid crystal layer (the first direction of rotation) ( An invention of a liquid crystal display element in which liquid crystal molecules are twisted in the second turning direction) is disclosed (for example, see Patent Document 1). In the liquid crystal display element described in Patent Document 1, the alignment state in which the liquid crystal molecules are twisted in the first turning direction is unstable. By applying a high voltage, it is possible to obtain an alignment state that is twisted in the first rotation direction, but as time passes, the liquid crystal molecules transition to an alignment state that is twisted in the second rotation direction.

  A liquid crystal element that increases the distortion in the liquid crystal layer and greatly reduces the driving voltage by arranging the chiral agent that rotates the liquid crystal molecules in the second rotation direction while arranging the chiral agent in the first rotation direction. Is known (see, for example, Patent Document 2). Also in the liquid crystal element described in Patent Document 2, the arrangement state of the liquid crystal molecules twisted in the second turning direction is stable, and the arrangement state twisted in the second turning direction is changed to the arrangement state twisted in the first turning direction. After a few seconds after the application of the voltage to be transferred is stopped, the state is re-transferred to the original array state (an array state twisted in the second turning direction). When driving the liquid crystal element in an arrangement state twisted in the second turning direction, a high driving voltage is required.

  In a reverse twisted nematic (RTN) type liquid crystal display element as described in Patent Documents 1 and 2, generally, the liquid crystal molecules are arranged in a twisted state (reverse twisted state). ) And the arrangement state twisted in the second turning direction (spray twist arrangement state), there is no significant difference in the appearance display state (light transmittance), and it is difficult to obtain a high contrast ratio even if bistability is given.

Japanese Patent No. 2510150 JP 2007-293278 A

  An object of the present invention is to provide a liquid crystal display element with high display quality.

  Moreover, it is providing the manufacturing method of a liquid crystal display element with high display quality.

  It is another object of the present invention to provide a method for driving a liquid crystal display element that can reduce power consumption.

According to one aspect of the present invention, a first substrate including a first electrode and subjected to an alignment process is disposed opposite to and parallel to the first substrate, and includes a second electrode and includes a second electrode. A liquid crystal layer that is disposed between the first substrate and the second substrate, includes a chiral agent and is twist-aligned, and the liquid crystal layer does not include the chiral agent. In addition, when the swirl direction in which the liquid crystal molecules are twisted by the alignment treatment is the first swivel direction, the chiral agent swirls in the liquid crystal molecules of the liquid crystal layer in the second swirl direction opposite to the first swirl direction. The first substrate and the second substrate are aligned so that a pretilt angle of 20 ° to 45 ° is expressed, and the liquid crystal layer includes the first electrode and the second substrate. 2 to generate an electric field in the thickness direction of the liquid crystal layer. And switching the direction in which the liquid crystal molecules of the liquid crystal layer are twisted from the second swivel direction to the first swivel direction, and displaying at least one of the first substrate and the second substrate. On the other hand, by applying a voltage, an electric field in a direction perpendicular to the thickness direction of the liquid crystal layer is generated , and the direction in which the liquid crystal molecules of the liquid crystal layer are twisted is switched from the first turning direction to the second turning direction. Thus, a liquid crystal display element in which an electrode capable of performing display is formed is provided.

According to another aspect of the present invention, a first substrate including a first electrode and subjected to an alignment treatment is disposed opposite to and parallel to the first substrate, and includes a second electrode. And a liquid crystal layer that is disposed between the first substrate and the second substrate and includes a chiral agent and is twist-aligned, and the liquid crystal layer includes the chiral agent. If the swirl direction in which the liquid crystal molecules are twisted by the alignment treatment is defined as the first swirl direction, the chiral agent is applied to the liquid crystal molecules of the liquid crystal layer in the second swirl direction opposite to the first swirl direction. The first substrate and the second substrate are aligned so that a pretilt angle of 20 ° or more and 45 ° or less is developed, and the liquid crystal layer includes the first electrode. And a voltage applied to the second electrode, the voltage in the thickness direction of the liquid crystal layer is applied. It is possible to perform display by switching the direction in which the liquid crystal molecules of the liquid crystal layer are twisted from the second turning direction to the first turning direction . An electric field in a direction perpendicular to the thickness direction of the liquid crystal layer is generated by applying a voltage to at least one of the substrates, and the direction in which the liquid crystal molecules of the liquid crystal layer are twisted is changed from the first turning direction to the second turning direction. A method for manufacturing a liquid crystal display element in which an electrode capable of performing display by switching in a direction is formed, wherein an alignment film subjected to alignment treatment on the first substrate and the second substrate is 160 ° C. or higher. A method for manufacturing a liquid crystal display element is provided, which is formed at a baking temperature of 180 ° C. or lower.

Further, according to another aspect of the present invention, a first substrate including a first electrode and subjected to an alignment process is disposed opposite to and parallel to the first substrate, and includes a second electrode. And a liquid crystal layer that is disposed between the first substrate and the second substrate and includes a chiral agent and is twist-aligned, and the liquid crystal layer includes the chiral agent. If the swirl direction in which the liquid crystal molecules are twisted by the alignment treatment is defined as the first swirl direction, the chiral agent is applied to the liquid crystal molecules of the liquid crystal layer in the second swirl direction opposite to the first swirl direction. The first substrate and the second substrate are aligned so that a pretilt angle of 20 ° or more and 45 ° or less is developed, and the liquid crystal layer includes the first electrode. And a voltage applied to the second electrode, the voltage in the thickness direction of the liquid crystal layer is applied. It is possible to perform display by switching the direction in which the liquid crystal molecules of the liquid crystal layer are twisted from the second turning direction to the first turning direction . An electric field in a direction perpendicular to the thickness direction of the liquid crystal layer is generated by applying a voltage to at least one of the substrates, and the direction in which the liquid crystal molecules of the liquid crystal layer are twisted is changed from the first turning direction to the second turning direction. A method for driving a liquid crystal display element in which electrodes capable of performing display by switching in a direction are formed, and when switching from white display to black display , an electric field in the thickness direction of the liquid crystal layer is generated, and black When switching from display to white display , there is provided a method for driving a liquid crystal display element, wherein an electric field in a direction perpendicular to the thickness direction of the liquid crystal layer is generated.

  According to the present invention, a liquid crystal display element with high display quality can be provided.

  In addition, a method for manufacturing a liquid crystal display element with high display quality can be provided.

  Furthermore, a method for driving a liquid crystal display element that can reduce power consumption can be provided.

It is a flowchart which shows the manufacturing method of the liquid crystal display element by an Example. It is a table | surface which shows the combination of the calcination temperature at the time of alignment film formation, and the pushing amount at the time of a rubbing process. (A)-(C) are the pictures which show the external appearance of the produced some liquid crystal display element. (A)-(F) are the table | surface which shows the preparation conditions of a liquid crystal display element, and the table | surface and photograph which show an observation result. It is a schematic sectional drawing in one pixel of the liquid crystal display element by an Example. It is a schematic top view which shows the pattern of the ITO film | membrane formed on the upper side transparent substrate 11a. It is a schematic top view which shows the pattern of the ITO film | membrane formed on the lower transparent substrate 11b. It is a schematic top view which shows the photomask used for the etching of an ITO film | membrane. It is a schematic top view which shows a part of formation area of the lower alignment film 14b formed in the lower substrate 10b. It is a schematic plan view which shows the structure of the liquid crystal display element by an Example. (A)-(C) are the external appearance photographs of the liquid crystal display element by an Example, (D)-(F) is schematic sectional drawing which shows the electric field direction at the time of a voltage application. (A)-(D) are the graphs which show the voltage-light transmittance characteristic of the liquid crystal display element by an Example, and the liquid crystal display element produced on the other preferable conditions. (A) And (B) is a graph which shows the viewing angle-contrast characteristic of the liquid crystal display element by an Example.

  The twist direction of the liquid crystal molecules (first rotation direction) determined by the combination of the alignment treatment direction and the pretilt angle of the pair of alignment films, and the twist direction of the liquid crystal molecules (second rotation direction) induced by the optically active substance (chiral agent) For example, by applying a physical action to the liquid crystal layer so that the liquid crystal molecules are twisted in each direction (reverse twist (uniform twist) The liquid crystal display element in which the arrangement state and the spray twist arrangement state in the second turning direction) can be realized interchangeably is referred to as a reverse twisted nematic (RTN) type liquid crystal display element. The first turning direction is a turning direction in which liquid crystal molecules are twisted when no optically active substance (chiral agent) is added to the liquid crystal layer.

  FIG. 1 is a flowchart illustrating a method for manufacturing a liquid crystal display device according to an embodiment. The inventors of the present application first manufactured a plurality of liquid crystal display elements according to the flowchart shown in this figure, and preliminarily considered the range of pretilt angles for realizing good display.

  Two transparent substrates on which transparent electrodes, for example, ITO (indium tin oxide) electrodes are formed, are prepared (step S101). Here, a test cell having parallel plate type electrodes was used, and the two transparent substrates were washed and dried (step S102).

  An alignment film material is applied on the transparent substrate so as to cover the ITO electrode (step S103). The alignment film material was applied by spin coating. You may perform using flexographic printing or inkjet printing. Normally, the side chain density of the polyimide alignment film material used for forming the vertical alignment film is lowered and used as the alignment film material. The alignment film material was applied so that the alignment film had a thickness of 500 to 800 mm. Temporary baking (step S104) and main baking (step S105) of the transparent substrate coated with the alignment film material are performed. The main baking was performed under four conditions of 160 ° C., 180 ° C., 200 ° C., and 220 ° C. Thus, an alignment film covering the ITO electrode was formed (steps S103 to S105).

  Next, a rubbing process (orientation process) is performed (step S106). The rubbing process is a process of rotating a cylindrical roll wound with a cloth at a high speed and rubbing on the alignment film, whereby the liquid crystal molecules in contact with the substrate can be aligned (aligned) in one direction. The rubbing treatment was performed under three conditions with the indentation amount being 0.4 mm, 0.8 mm, and 1.2 mm. The rubbing treatment was performed so that the twist angle of the liquid crystal display element was 90 °.

  FIG. 2 is a table showing combinations of the firing temperature at the time of forming the alignment film and the indentation amount at the time of the rubbing treatment. The inventors of the present application have no. 1-No. A liquid crystal display element was produced under 9 conditions.

  Refer to FIG. 1 again. In order to keep the thickness (inter-substrate distance) of the liquid crystal cell constant, a gap control material is sprayed on one transparent substrate surface by, for example, a dry spraying method (step S107). A plastic ball having a particle diameter of 4 μm was used as the gap control material.

  A sealant is printed on the other transparent substrate surface to form a main seal pattern (step S108). For example, a thermosetting sealing material containing glass fiber having a particle diameter of 4 μm is printed by a screen printing method. A sealing material can also be applied using a dispenser. Further, instead of thermosetting, a photo-curing sealing material or a light / heat combined curing type sealing material may be used.

  The transparent substrates are overlaid (step S109). Two transparent substrates are overlapped at a predetermined position to form a cell, and heat treatment is performed in a pressed state to cure the sealing material. For example, the sealing material is thermally cured using a hot press method. An empty cell is thus produced.

  For example, nematic liquid crystal is injected into the empty cell by vacuum injection (step S110). ZLI2293 manufactured by Merck Co., Ltd. was used as the liquid crystal material. A chiral agent was added to the liquid crystal. CB15 manufactured by Merck & Co., Inc. was used as the chiral agent. The addition amount of the chiral agent was adjusted so that d / p was 0.16 or 0.25, assuming that the chiral pitch was p and the thickness (cell thickness) of the liquid crystal layer was d.

  The liquid crystal inlet is sealed with, for example, an ultraviolet (UV) curable end seal material (step S111), and the cell is heated to a temperature higher than the phase transition temperature of the liquid crystal in order to adjust the alignment of the liquid crystal molecules (step S112). Then, it breaks along the crack | wound attached to the transparent substrate with a scriber device, and divides it into individual cells.

  Chamfering (step S113) and cleaning (step S114) are performed on the subdivided cells.

  Finally, a polarizing plate is attached to the surface of the two transparent substrates opposite to the liquid crystal layer (step S115). The two polarizing plates were arranged in crossed Nicols so that the direction of the transmission axis was parallel to the rubbing direction. It can also be arranged so as to be orthogonal. A power source was connected between the ITO electrodes of both transparent substrates.

  3A to 3C are photographs showing the appearance of the plurality of liquid crystal display elements that were produced. The manufactured liquid crystal display element is in a spray twist alignment state in the initial state. When a voltage equal to or higher than the saturation voltage value is applied between the ITO electrodes of both transparent substrates, a transition to the reverse twist arrangement state is made.

  Reference is made to FIG. No. in the table shown in FIG. No. 1 (baking temperature 160 ° C., pushing amount during rubbing treatment 0.8 mm), and No. 1 The liquid crystal display device manufactured under the condition 3 (baking temperature 180 ° C., push-in amount at the time of rubbing treatment 0.8 mm) is in a reverse twist arrangement state regardless of whether d / p is 0.16 or 0.25. When no voltage was applied, the appearance as shown in the figure, that is, a relatively dark black display was exhibited. When the light transmittance was measured, it was about 4%. In addition, a very dark black display was observed when a voltage was applied in the reverse twist arrangement state. The light transmittance could be reduced to almost 0%. Furthermore, when the light transmittance in the spray twist arrangement state was measured, it was about 18% when no voltage was applied. No. 1 and no. It can be seen that the liquid crystal display element manufactured under the condition 3 can perform a display with a greatly different appearance in the reverse twist arrangement state and the spray twist arrangement state. That is, it is possible to perform black display in the reverse twist arrangement state and white display in the spray twist arrangement state. When measured by a spectroscopic ellipso method, it was found that a pretilt angle of 23 to 35 ° was developed in these liquid crystal display elements.

  Reference is made to FIG. No. in the table shown in FIG. The liquid crystal display device manufactured under the conditions of 2 (baking temperature 180 ° C., push amount 0.4 mm during rubbing treatment) is dark from the initial state regardless of whether d / p is 0.16 or 0.25. Displayed. Since the amount of pushing during the rubbing process is small and the pretilt angle is high, it is considered that the liquid crystal molecule alignment state is close to vertical alignment. There was no significant change in display brightness due to the application of voltage, and the light transmittance was about 1% or less regardless of the presence or absence of the applied voltage and the applied voltage value.

  Reference is made to FIG. No. in the table shown in FIG. 1-No. A liquid crystal display device manufactured under conditions other than 3 has a large difference in light transmittance between the spray twist arrangement state and the reverse twist arrangement state regardless of whether the d / p value is 0.16 or 0.25. Was not recognized, and the display appearance was almost equal. The light transmittance when no voltage was applied was about 25% in both arrangement states, and by applying voltage, the light transmittance in both arrangement states could be lowered to about 1% or less. This figure shows the appearance of display (light blue display) when no voltage is applied in the reverse twist arrangement state. No. in the table shown in FIG. 1-No. When the pretilt angle of the liquid crystal display device produced under conditions other than the condition 3 was measured by a spectroscopic ellipso method, it was found that a pretilt angle of 8 to 15 ° was developed.

  The inventors of the present application measured the pretilt angle for many liquid crystal display elements, and the range of the pretilt angle that can preferably display black when no voltage is applied in the reverse twist arrangement state is 31.5 ° to 36.2 °. there were. The maximum pretilt angle at which black display cannot be performed when no voltage is applied in the reverse twist arrangement state is 17.1 °. Furthermore, the minimum value of the pretilt angle displayed in black even when no voltage was applied in the spray twist arrangement state was 48 °.

  For these reasons, the RTN type liquid crystal display element is manufactured by setting the pretilt angle applied to the upper and lower substrates to 20 ° to 45 °, more preferably 31 ° to 37 °, so that no voltage is applied in the reverse twist arrangement state. It can be considered that it is possible to realize black display in white and white display when no voltage is applied in the spray twist arrangement state (when no vertical electric field is applied).

  In the RTN liquid crystal display element having the pretilt angle range described above, the principle of realizing a relatively dark black display when no voltage is applied in the reverse twist arrangement state is not completely clarified, but the RTN liquid crystal The display element has such a property that the threshold value at the time of falling (reverse twist arrangement state) is lower than the threshold value at the time of rising (spray twist arrangement state), and the threshold value is lower than 0 V due to special conditions. Is presumed to be realized.

  In general, in the reverse twist alignment state, a large distortion is generated in the liquid crystal layer due to the pretilt angle given by the alignment treatment of the substrate and the twisting force given by the chiral agent, and even when no voltage is applied due to this distortion. The liquid crystal molecules near the center in the thickness direction of the liquid crystal layer are considered to be inclined with respect to the substrate plane. In an RTN liquid crystal display element having a high pretilt angle of 20 ° or more, it is presumed that the tilt angle of liquid crystal molecules near the center in the thickness direction of the liquid crystal layer is very large and rises almost perpendicularly to the substrate. For this reason, it is considered that a relatively dark black display can be obtained even when no voltage is applied. In general, in the reverse twist arrangement state, the inclination angle in the bulk is higher than the pretilt angle at the interface with the substrate. This has also been confirmed by liquid crystal molecular alignment simulation based on continuum theory.

  Next, the inventors of the present application have listed No. 1 in the table shown in FIG. 1 or No. Assuming the condition 3, a plurality of liquid crystal display elements are manufactured according to the flowchart shown in FIG. 1, and the firing temperature at which a relatively dark black display is maintained is realized when no voltage is applied in the reverse twist arrangement state. In addition, the twist angle and the cell thickness (the thickness of the liquid crystal layer) were preliminarily considered. 4A to 4F show manufacturing conditions and observation results of the liquid crystal display element.

  FIG. 4A is a table showing conditions for manufacturing the liquid crystal display element. First, two transparent substrates on which ITO electrodes were formed were prepared. Again, using a test cell having parallel plate type electrodes, the two transparent substrates were washed and dried.

  An alignment film material was applied on the transparent substrate so as to cover the ITO electrode. The alignment film material was applied by spin coating. Normally, the side chain density of the polyimide alignment film material used for forming the vertical alignment film is lowered and used as the alignment film material. The alignment film material was applied so that the alignment film had a thickness of 500 to 800 mm. Temporary baking and main baking were performed on the transparent substrate coated with the alignment film material. As shown in FIG. 4A, the main baking was performed at 160 ° C. or 180 ° C. Thus, an alignment film covering the ITO electrode was formed.

  Subsequently, the rubbing treatment was performed with the indentation amount set to 0.8 mm. As shown in FIG. 4A, the rubbing process was performed under three conditions in which the twist angles between the upper and lower substrates were 80 °, 90 °, and 100 °.

  A gap control material was sprayed on one transparent substrate surface. A plastic ball having a particle size of 3 μm, 4 μm, and 5 μm was used as the gap control material, and a plurality of liquid crystal display elements having cell thicknesses of 3 μm, 4 μm, and 5 μm were manufactured as shown in FIG. On the other transparent substrate surface, a thermosetting seal material containing glass fibers was printed by a screen printing method to form a main seal pattern. Two transparent substrates were overlapped at a predetermined position, and heat treatment was performed to cure the sealing material, thereby producing an empty cell.

  Nematic liquid crystal was injected into the empty cell by vacuum injection. ZLI2293 manufactured by Merck Co., Ltd. was used as the liquid crystal material. A chiral agent was added to the liquid crystal. CB15 manufactured by Merck & Co., Inc. was used as the chiral agent. The addition amount of the chiral agent was adjusted so that d / p was 0.04, 0.08, 0.125, 0.16, 0.20, 0.25, and 0.33.

  The liquid crystal injection port was sealed with an ultraviolet curable end seal material, and the cell was heated to a temperature higher than the phase transition temperature of the liquid crystal. Breaking was done along the scratches on the transparent substrate with a scriber device, and it was subdivided into individual cells.

  The cleaved cell was chamfered and washed, and a polarizing plate was attached to the surface of the two transparent substrates opposite to the liquid crystal layer. The two polarizing plates were arranged in crossed Nicols so that the direction of the transmission axis was parallel to the rubbing direction. A power source was connected between the ITO electrodes of both transparent substrates. By applying an AC voltage of 5 V between the ITO electrodes of the liquid crystal display element thus manufactured, it is possible to transition from the spray twist arrangement state to the reverse twist arrangement state (relatively dark black display).

  FIG. 4B is a table showing the results of measuring the retention time of a relatively dark black display (reverse twist alignment state) when the amount of the chiral agent added to the liquid crystal material is changed.

  A liquid crystal display element manufactured under condition A shown in FIG. 4A and a liquid crystal display element manufactured under condition B are compared. The liquid crystal display device manufactured under the condition A has four cases where d / p = 0.08, 0.125, 0.16, and 0.20, and the reverse twist arrangement state (relatively black display) from the spray twist arrangement state. ), The reverse twist arrangement state is maintained as it is for several weeks (displayed as “∞” in the table). Further, in the case of d / p = 0.04, a desired operation is partially performed, but a portion that is in a black display state from the beginning is mixed. From this, it can be considered that d / p = 0.04 is a boundary condition for obtaining uniformity for use as a display element.

  On the other hand, the liquid crystal display element manufactured under the condition B maintains the reverse twist alignment state for several weeks or more when d / p = 0.08 and 0.125. Also in condition B, as in condition A, in the case of d / p = 0.04, there were mixed portions that were in a black display state from the beginning.

  From these facts, the liquid crystal display element is manufactured at 160 ° C. rather than the liquid crystal display device at a baking temperature of 180 ° C. In order to stabilize the reverse twist alignment state, that is, the reverse twist alignment state and the spray twist alignment state. It can be seen that the d / p margin for obtaining stability is wide. Note that FIG. 4C shows a display appearance in a reverse twist arrangement state held in a liquid crystal display element manufactured under condition A and d / p = 0.125. By producing a liquid crystal display element at a baking temperature of at least 160 ° C. and 180 ° C., black display can be maintained for a long time when no voltage is applied in a reverse twist arrangement state.

  Next, liquid crystal display elements manufactured under conditions A, C, and D are compared. In the liquid crystal display device manufactured under the condition C, the reverse twist alignment state was not maintained for a long time at any d / p. It can be seen that when a liquid crystal display element is manufactured with a twist angle of 80 °, it is difficult to obtain bistability in both alignment states.

  On the other hand, a large difference in holding time was not recognized between the liquid crystal display device manufactured under condition A and that manufactured under condition D. However, in the case of Condition D, the liquid crystal display element manufactured at d / p = 0.125 showed a dark display from the initial state as in the example shown in the photograph in FIG. In addition, the holding times when d / p = 0.25 and 0.33 were slightly shorter than those under condition A. Therefore, by producing a liquid crystal display element with a twist angle of at least 90 ° and not more than 100 °, black display can be maintained for a long time when no voltage is applied in a reverse twist arrangement state, and the twist angle is 100 °. It can be seen that the bistability of the reverse twist alignment state and the spray twist alignment state is slightly more easily obtained when the liquid crystal display element is manufactured at 90 ° than when the liquid crystal display element is manufactured.

  Subsequently, a comparison is made based on the cell thickness. When the cell thickness was as thin as 3 μm (condition E), there was no clear difference in retention depending on the value of d / p, and the reverse twist arrangement state was maintained for several weeks or more at all d / p. FIG. 4D shows a display appearance of a liquid crystal display element manufactured under conditions E and d / p = 0.125. However, under the condition E, when the value of d / p is as large as 0.20 and 0.25, the phenomenon that the reverse twist arrangement state gradually spreads to the region outside the electrode is observed even though no voltage is applied. It was. This is shown in FIG. If the reverse twist arrangement state spreads to the region outside the electrode, it is difficult to control that portion, so care must be taken.

  When the cell thickness is as thick as 5 μm (Condition F), the range of d / p with a long holding time is narrow compared with Condition A and Condition E, and only the liquid crystal display device manufactured with d / p = 0.16 is reversed. The twisted array state was maintained for several weeks. FIG. 4F shows a display appearance of the liquid crystal display element. As a result of observation by the inventors of the present application, even when the cell thickness is thick (Condition F) and thin (Condition E), as in the liquid crystal display device manufactured under Condition A, when no voltage is applied in the reverse twist arrangement state, A relatively dark black display was obtained. From this, it can be seen that even if the cell thickness of the liquid crystal display element is somewhat uneven, for example, a bistable display with a high contrast ratio is possible. From the observations shown in the table of FIG. 4B, it is possible to maintain a black display for a long time when no voltage is applied in a reverse twist arrangement state by manufacturing a liquid crystal display element with a cell thickness of at least 3 μm to 5 μm. It was confirmed that it was possible.

  Regarding d / p, although depending on other conditions, for example, from the black display holding time of the liquid crystal display element manufactured under conditions A, D, and E, it is preferably more than 0.04 and less than 0.25. Would be considered.

  Based on the above preliminary considerations, the inventors of the present application produced liquid crystal display elements according to the examples.

  FIG. 5 is a schematic cross-sectional view in one pixel of the liquid crystal display device according to the embodiment.

  The liquid crystal display device according to the embodiment includes an upper substrate 10a, a lower substrate 10b, and a twisted nematic liquid crystal layer 15 sandwiched between the substrates 10a and 10b.

  The upper substrate 10a includes an upper transparent substrate 11a, an upper solid electrode 12a formed on the upper transparent substrate 11a, and an upper alignment film 14a formed on the upper solid electrode 12a. The lower substrate 10b is formed on the lower transparent substrate 11b, the lower solid electrode 12b formed on the lower transparent substrate 11b, the insulating film 13 formed on the lower solid electrode 12b, and the insulating film 13. The lower alignment film 14b formed on the insulating film 13 so as to cover the first and second comb electrodes 12c and 12d and the first and second comb electrodes 12c and 12d is included.

  The upper and lower transparent substrates 11a and 11b are made of glass, for example. The upper and lower solid electrodes 12a and 12b and the first and second comb electrodes 12c and 12d are formed of a transparent conductive material such as ITO, for example. The first and second comb electrodes 12c and 12d are comb electrodes each having a plurality of comb portions. The comb-tooth portions of the first and second comb-tooth electrodes 12c and 12d are alternately arranged along the horizontal direction of the figure.

  The liquid crystal layer 15 is disposed between the upper alignment film 14a of the upper substrate 10a and the lower alignment film 14b of the lower substrate 10b.

  The upper and lower alignment films 14a and 14b are subjected to an alignment process by rubbing. The alignment treatment directions of the upper alignment film 14a and the lower alignment film 14b are orthogonal to each other when viewed from the normal direction of the upper and lower substrates 10a and 10b. When the rubbing direction of the upper alignment film 14a is the first direction and the rubbing direction of the lower alignment film 14b is the second direction, the second direction is the first direction when viewed from the normal direction of the upper substrate 10a. The direction is 90 ° counterclockwise with respect to the reference. The alignment state of the liquid crystal molecules of the liquid crystal layer 15 defined by the combination of the alignment processing direction and the pretilt angle of the upper and lower substrates 10a and 10b is twisted by 90 ° to the right when viewed from the normal direction of the upper substrate 10a. Uniform twist (reverse twist) arrangement.

  A chiral agent is added to the liquid crystal material forming the liquid crystal layer 15. The alignment state of the liquid crystal molecules generated under the influence of the chiral agent is a splay that twists in the left twist direction along the direction from the upper substrate 10a to the lower substrate 10b when viewed from the normal direction of the upper substrate 10a. Twisted array.

  The twist direction of the liquid crystal molecules in the completed liquid crystal cell was left twist (spray twist arrangement) in the same direction as the twist direction by the chiral agent.

  A power source 20 is electrically connected to the upper and lower solid electrodes 12a and 12b and the first and second comb electrodes 12c and 12d. A voltage can be applied to the electrodes 12a to 12d by the power source 20. For example, by applying an AC voltage equal to or higher than the threshold voltage between the solid electrodes 12a and 12b, the alignment state of the liquid crystal molecules can be transferred from the spray twist alignment to the uniform twist (reverse twist) alignment.

  An upper polarizing plate 16a and a lower polarizing plate 16b are disposed on the surfaces of the upper substrate 10a and the lower substrate 10b opposite to the liquid crystal layer 15, respectively. Both polarizing plates 16a and 16b are arranged in a crossed Nicol manner so that the light transmission axis is parallel to the rubbing direction of the upper and lower substrates 10a and 10b. The liquid crystal display element according to the embodiment is a normally white type liquid crystal display element.

  With reference to FIGS. 6-10, the structure and manufacturing method of the liquid crystal display element by an Example are demonstrated in detail.

  FIG. 6 is a schematic plan view showing a pattern of an ITO film formed on the upper transparent substrate 11a. In the ITO film shown in this figure, for example, a pixel electrode (an electrode that forms the upper solid electrode 12a in each pixel) and an extraction electrode for the pixel electrode are formed.

The ITO film pattern is formed, for example, such that the ITO film extends in a stripe shape in the left-right direction in the figure. In this figure, the ITO films constituting the pixel electrodes are indicated by reference numerals 12A ₁ to 12A ₁₀ .

  The ITO film was patterned using a photolithography process after washing the glass substrate with ITO. Etching of ITO was performed by wet etching using ferric chloride. Patterning may be performed by irradiating a laser beam and removing the ITO film.

  FIG. 7 is a schematic plan view showing a pattern of an ITO film formed on the lower transparent substrate 11b. With the ITO film shown in this figure, for example, a pixel electrode (an electrode forming the lower solid electrode 12b in each pixel) and an extraction electrode for the pixel electrode are formed.

The ITO film pattern is formed, for example, such that the ITO film extends in a stripe shape in the vertical direction of the figure. In this figure, reference numerals 12B ₁ to 12B ₉ are attached to a part of the ITO film constituting the pixel electrode. In addition, the up-down direction of this figure and the left-right direction of FIG. 6 are directions orthogonal to each other.

  The ITO film can be patterned by the same method as the ITO film pattern forming method described with reference to FIG.

After patterning the ITO film, an insulating film 13 is formed on the lower transparent substrate 11b including the ITO film. The insulating film 13 is not formed on the extraction electrodes 12BT _{1 to} 12BT ₉ (terminal portion), for example. In this figure, the region where the insulating film 13 is not formed is hatched. The insulating film 13 can be formed by a method in which a resist is formed on the extraction electrode portion and the resist is removed by lift-off after forming the insulating film, or a method in which the extraction electrode portion is covered by a metal mask and formed by sputtering. . The insulating film 13 can be an organic insulating film or an inorganic insulating film such as SiO ₂ or SiN _x . You may form by those combination. In the example, a laminated film of an acrylic organic insulating film and SiO ₂ was used as the insulating film 13.

In the examples, a heat-resistant film (polyimide tape) was first attached to the extraction electrode portion and the like, and an organic insulating film was spin-coated (spun at 2000 rpm for 30 seconds) to a thickness of 1 μm. Next, the lower transparent substrate 11b on which the organic insulating film is spin-coated is baked at 220 ° C. for 1 hour in a clean oven, and then the lower transparent substrate 11b is heated to 80 ° C. with the heat-resistant film attached. A SiO ₂ film was formed to a thickness of 1000 mm by a sputtering method (AC discharge). The SiO ₂ film can also be formed using a vacuum deposition method, an ion beam method, a CVD method, or the like.

Here, when the heat-resistant film was peeled off, the organic insulating film and the SiO ₂ film were able to be removed at the location where the heat-resistant film was applied. Subsequently, in order to improve the insulation and transparency of the SiO ₂ film, the lower transparent substrate 11b was baked at 220 ° C. for 1 hour in a clean oven.

The formation of the SiO ₂ film is not essential, but the insulating property of the insulating film 13 can be improved by forming the SiO ₂ film. In addition, it is possible to improve the adhesion and patterning properties of the first and second comb electrodes 12c and 12d formed on the insulating film 13.

Instead of forming the organic insulating film, the insulating film 13 may be composed of only the SiO ₂ film. Since the SiO ₂ film tends to be porous, in this case, the thickness of the SiO ₂ film is desirably 4000 to 8000 mm. An inorganic insulating film 13 made of a laminate of a SiO ₂ film and a SiN _x film can also be used.

  An ITO film was formed on the insulating film 13. The ITO film was formed on the entire surface of the substrate by heating the lower transparent substrate 11b to 100 ° C. and sputtering (AC discharge). The film thickness was about 1200 mm. The ITO film can also be formed using a vacuum deposition method, an ion beam method, a CVD method, or the like. This ITO film was patterned by a photolithography process to form a first comb electrode 12c, a second comb electrode 12d, and extraction electrodes for these electrodes 12c and 12d.

  FIG. 8 is a schematic plan view showing a photomask used for etching the ITO film. The photomask includes a portion corresponding to the first comb electrode 12c, a portion corresponding to the second comb electrode 12d, a portion corresponding to the extraction electrode of the first comb electrode 12c, a portion corresponding to the extraction electrode of the second comb electrode 12d, and a lower solid. A portion corresponding to the extraction electrode of the electrode 12b is included. At the time of etching, an electrode is formed with an ITO film covered with each corresponding portion. In addition, the inventors of the present invention have electrode widths of 20 μm, 30 μm, and comb electrode portions of the comb-like electrode, and electrode intervals when the comb-tooth portions of the two comb-like electrodes are alternately arranged are 20 μm, 30 μm, 50 μm, 100 μm, The 1st comb-tooth electrode 12c and the 2nd comb-tooth electrode 12d were produced with the several electrode pattern set to 200 micrometers.

  Through the steps as described above, two substrates with electrodes were prepared (step S101 in FIG. 1). The two substrates with electrodes are washed and dried (step S102). In the case of water washing, pure water washing is performed. You may carry out using a detergent. It can be cleaned by either brush cleaning or spray cleaning. Then drain and drain. As a method other than water washing, UV washing and IR drying can be performed.

  On the two substrates with electrodes, an alignment film material was applied so as to cover the ITO electrodes (step S103). The alignment film material was applied by spin coating. You may perform using flexographic printing or inkjet printing. Normally, the side chain density of the polyimide alignment film material used for forming the vertical alignment film is lowered and used as the alignment film material. The alignment film material was applied so that the alignment film had a thickness of 500 to 800 mm. Temporary baking (step S104) and main baking (step S105) of the substrate with electrodes coated with the alignment film material were performed. The main baking was performed at 160 ° C. for 1 hour. You may carry out at the temperature of 160 degreeC or more and 180 degrees C or less. Thus, an alignment film covering the ITO electrode was formed (steps S103 to S105).

  FIG. 9 is a schematic plan view showing a part of a formation region of the lower alignment film 14b formed on the lower substrate 10b. The lower alignment film 14b is formed, for example, in a region where the first and second comb electrodes 12c and 12d are arranged and pixels are defined. In this figure, only the upper left portion is shown as the formation region of the lower alignment film 14b, but the same applies to the other regions where the comb electrodes 12c and 12d are arranged.

  Next, a rubbing process (orientation process) was performed (step S106). The rubbing treatment was performed with the indentation amount being 0.8 mm. Moreover, it implemented so that the twist angle of a liquid crystal display element might be set to 90 degrees.

  In order to set the cell thickness to 4 μm, a gap control material having a particle size of 4 μm was sprayed on one substrate surface (step S107). In order to set the cell thickness to 3 μm or more and 5 μm or less, it is possible to spray a gap control material having a particle size of 3 μm or more and 5 μm or less. A sealant was printed on the other substrate surface to form a main seal pattern (step S108). The two substrates were overlapped at a predetermined position (step S109), and the sealing material was cured.

  When the two substrates are stacked, the rubbing direction of the upper alignment film 14a is such that the alignment of the liquid crystal molecules is a uniform twist (reverse twist) alignment that is twisted by 90 ° to the right as viewed from the normal direction of the upper substrate. Is the first direction, and the rubbing direction of the lower alignment film 14b is the second direction, the second direction is viewed from the normal direction of the upper substrate 10a, and the counterclockwise direction is based on the first direction. The direction was 90 °. The twist angle can be 90 ° or more and 100 ° or less.

  Nematic liquid crystal was injected by a vacuum injection method (step S110). ZLI2293 manufactured by Merck Co., Ltd. was used as the liquid crystal material. A chiral agent was added to the liquid crystal. CB15 manufactured by Merck & Co., Inc. was used as the chiral agent. The addition amount of the chiral agent was adjusted so that d / p was 0.16, where p was the chiral pitch and d was the thickness of the liquid crystal layer. It can be more than 0.04 and less than 0.25.

  The liquid crystal injection port was sealed with an ultraviolet curing type end seal material (step S111), and the cell was heated to a temperature higher than the phase transition temperature of the liquid crystal in order to adjust the alignment of the liquid crystal molecules (step S112). Then, it broke along the crack | wound attached to the transparent substrate with the scriber apparatus, and subdivided into the individual cell. Chamfering (step S113) and cleaning (step S114) were performed on the subdivided cells.

  Finally, a polarizing plate was attached to the surface opposite to the liquid crystal layer of the two substrates (step S115). The two polarizing plates were arranged in crossed Nicols so that the direction of the transmission axis was parallel to the rubbing direction. It can also be arranged so as to be orthogonal. A power source was connected to the ITO electrodes (upper and lower solid electrodes 12a and 12b and first and second comb electrodes 12c and 12d) of both substrates.

FIG. 10 is a schematic plan view showing the structure of the liquid crystal display device according to the embodiment. FIG. 10 shows all the structures shown in FIGS. One pixel is defined by a horizontal electrode extending in the left-right direction and a vertical electrode extending in the vertical direction. In the figure, indicated by reference numeral of _12A 1 _{~12A 10} next electrode, shown in a part of the vertical electrodes are denoted by the sign of the _12B 1 _{~12B 9.} The arrows indicate pixels defined in a region where the horizontal electrode 12A ₉ and the vertical electrode 12B ₈ overlap when viewed from the substrate normal direction. Horizontal electrode 12A ₉ in the pixel corresponds to the upper solid electrode 12a of FIG. 5, the vertical electrode 12B ₈ corresponds to the lower solid electrode 12b.

  FIGS. 11A to 11C are external appearance photographs of the liquid crystal display element according to the example, and FIGS. 11D to 11F are schematic cross-sectional views showing the electric field direction when a voltage is applied. Note that FIGS. (A) to (C) show that the electrode widths of the comb teeth of the first and second comb electrodes 12c and 12d are 20 μm, and the comb teeth of both the comb electrodes 12c and 12d are alternately arranged. 2 is a photograph of the appearance of a region where comb electrodes 12c and 12d are formed in a liquid crystal display device manufactured with an electrode spacing of 20 μm when arranged in a.

  FIG. 11A shows an appearance photograph of the liquid crystal display element in a completed state (initial state). In the initial state, the liquid crystal molecules are in a spray twist alignment state.

  In this state, as shown in FIG. 11D, a voltage was applied between the upper solid electrode 12a and the lower solid electrode 12b. By applying a voltage to both electrodes 12a and 12b, a vertical electric field (electric field in the thickness direction of the liquid crystal layer) is generated in the liquid crystal layer.

  FIG. 11B is an appearance photograph after voltage is applied to the electrodes 12a and 12b. It can be seen that the whole has transitioned from the spray twist arrangement state to the reverse twist arrangement state. Conversely, this confirms that a vertical electric field is generated in the liquid crystal layer when a voltage is applied to both electrodes 12a and 12b.

  Next, as shown in FIG. 11E, a voltage was applied between the first comb electrode 12c and the second comb electrode 12d. By applying a voltage to both electrodes 12c and 12d, a lateral electric field (an electric field in a direction orthogonal to the thickness direction of the liquid crystal layer, an electric field in the substrate plane) is generated in the liquid crystal layer. A driving mode for driving the liquid crystal display element by generating a lateral electric field in the liquid crystal layer by applying a voltage to the first and second comb electrodes 12c and 12d is called an IPS mode (in-plane switching mode). .

  When the liquid crystal display element in the state shown in FIG. 11B was driven in the IPS mode, it was confirmed that the liquid crystal display element re-transitioned to the same state (spray twist arrangement state) as the initial state.

  Further, as shown in FIG. 11F, a voltage was applied to the lower solid electrode 12b, the first comb electrode 12c, and the second comb electrode 12d. A lateral electric field is also generated in the liquid crystal layer by applying a voltage to the electrodes 12b, 12c, and 12d. Note that a driving mode in which a liquid crystal layer is driven by applying a voltage to the electrodes 12b, 12c, and 12d to drive the liquid crystal display element is called an FFS mode (fringe field switching mode).

  FIG. 11C is an appearance photograph after the liquid crystal display element in the state shown in FIG. 11B is driven in the FFS mode. It can be seen that the entire surface re-transitions to the same state (spray twist arrangement state) as the initial state.

  As a result of observation by the inventors of the present application, when driven in the IPS mode, the entire surface did not change to the spray twist arrangement state, but changed to the spray twist arrangement state in a stripe shape corresponding to the pattern of the comb electrode. In the IPS mode, it is considered that a lateral electric field is generated only between the comb electrodes 12c and 12d. On the other hand, when driven in the FFS mode, the entire surface transitions to the spray twist arrangement state because the lateral electric field is also generated on the comb-tooth electrodes 12c and 12d in the FFS mode. The liquid crystal display element according to the embodiment is a liquid crystal display element capable of switching between a spray twist arrangement state and a reverse twist arrangement state. By applying a vertical electric field, the former can be changed to the latter. Moreover, the latter can be changed to the former by application of a transverse electric field. Regarding application of the lateral electric field, driving in the FFS mode is preferable to the IPS mode in terms of aperture ratio, light transmittance, contrast ratio, and the like.

  The liquid crystal molecules near the center in the thickness direction of the liquid crystal layer are considered to be switched from the spray twist alignment state to the reverse twist alignment state by tilting from the horizontal direction to the vertical direction by applying a vertical electric field. In addition, the liquid crystal molecules near the center in the thickness direction of the liquid crystal layer are considered to be switched from the reverse twist alignment state to the spray twist alignment state by tilting from the vertical direction to the horizontal direction due to the addition of a horizontal electric field. It is done.

  The liquid crystal display element according to the embodiment is a liquid crystal display element in which a spray twist arrangement state and a reverse twist arrangement state are shifted to each other depending on the direction of an applied electric field, and each state is stably maintained. In the liquid crystal display element according to the embodiment, for example, display utilizing memory property is possible.

  Pixels that are to be displayed in white are in a spray twist arrangement state, and pixels that are to be displayed in black are in a reverse twist arrangement state. A vertical electric field is applied to at least a pixel to be changed from white display to black display. A vertical electric field may be applied to a pixel for which black display is to be maintained. On the contrary, a horizontal electric field is applied to at least a pixel to be changed from black display to white display. A lateral electric field may be applied to a pixel for which white display is to be maintained.

The display can be rewritten, for example, for each line. As an example, in FIG. 10, one of the vertical electrode _12B 1 _{~12B 9,} for example, the vertical electrodes 12B _1, applies a rectangular wave of a degree that transition arrangement state does not occur (e.g. 150 Hz, about 5V). Along with this, the lateral electrode _12A 6 _{~12A 10} or the first and second comb electrodes, is applied to the longitudinal electrodes 12B ₁ voltage synchronized with or half cycle shifted square wave (e.g. 150 Hz, about 5V) is applied to.

In the pixel plus vertical electrode 12B waveform synchronized with waveforms added to _1, the display for a state of effectively voltage is not applied is not changed, the waveform and the half period shift made to the vertical electrodes 12B ₁ In the pixel to which the waveform is added, since a voltage of about 10 V is effectively applied, the voltage becomes equal to or higher than the saturation voltage and can be changed between white display and black display.

For example, a rectangular wave shifted by a half cycle is applied to the first and second comb electrodes and no voltage is applied to the horizontal electrodes 12A _{6 to} 12A ₁₀ to the pixels that are desired to be displayed in white. The pixel to be black display, a square wave shifted by a half period in the horizontal electrode 12A ₆ ~12A ₁₀ is applied, first, no voltage is applied to the second comb electrodes.

After the vertical electrodes 12B _1, also by applying a rectangular wave with respect to the longitudinal electrodes _12B 2 _{~12B 9,} by driving in the same manner, a matrix display can be performed. The rewritten display can be held semipermanently.

  The liquid crystal display element according to the embodiment can be driven by a driving method using memory characteristics such as the above-described line-sequential rewriting method (line-sequential driving). Ultra-low power consumption driving is possible that does not consume power except during display rewriting. Particularly when applied to a reflective display, the merit is great. Further, large-capacity dot matrix display can be performed by simple matrix display without using expensive TFTs or the like. That is, a large-capacity display can be performed at low cost. Furthermore, the liquid crystal display element according to the embodiment can be manufactured at low cost by the manufacturing method described with reference to FIGS. 1 and 6 to 10, for example.

  12A to 12D are graphs showing voltage-light transmittance characteristics of the liquid crystal display elements according to the examples and liquid crystal display elements manufactured under other preferable conditions. The horizontal axis of each graph indicates the applied voltage in the unit “V”, and the vertical axis indicates the light transmittance in the unit “%”. A curve indicated by a solid line represents a voltage-light transmittance characteristic in a reverse twist arrangement state (indicated as “after transition” in the figure), and a curve indicated by a broken line represents a spray twist arrangement state (in the figure as “before transition”). It represents that in the display. Shown are electro-optical characteristics when a voltage is applied between the upper and lower solid electrodes 12a and 12b to generate a longitudinal electric field in each arrangement state. The numbers given before “before transition” and “after transition” represent the value of d / p in FIGS. 12A to 12C and the cell thickness in FIG. 12D. Moreover, LCD5200 which is a liquid crystal element electro-optical characteristic measuring apparatus made from Otsuka Electronics Co., Ltd. was used for the measurement.

  FIG. 12A shows the electro-optical characteristics of the liquid crystal display element (liquid crystal display element according to the example) manufactured under the condition A in FIG. It can be seen that the light transmittances of the two arrangement states when no voltage is applied are greatly different, and display with a high contrast ratio is possible. The liquid crystal display element according to the embodiment is a liquid crystal display element that can easily realize a high-quality display having a high contrast ratio and stable in both the white display state and the black display state. The black display is dark and easy to display clearly.

  FIG. 12B shows electro-optical characteristics of the liquid crystal display element manufactured under the condition B in FIG. Although slightly inferior to the example shown in FIG. 12A, the light transmittance in both arrangement states when no voltage is applied is greatly different, and display with a high contrast ratio and high quality is possible. Note that the tendency of the dependence of light transmittance on d / p is reversed between the electro-optical characteristics shown in FIG. 12A and that shown in FIG. Although the details of the cause are unknown, it can be seen that the d / p tendency for obtaining optimum electro-optical characteristics varies depending on the manufacturing conditions.

  FIG. 12C shows electro-optical characteristics of the liquid crystal display element manufactured under Condition D in FIG. It is not significantly different from the example shown in FIG. 12A, and high contrast ratio and high quality display is possible. In the example shown in FIG. 12C, it can be seen that the dependency of the light transmittance on d / p is small and stable with respect to d / p.

  FIG. 12D shows the difference in electro-optical characteristics depending on the cell thickness. It can be seen that when the cell thickness is 3 μm, 4 μm, or 5 μm, a relatively dark black display is obtained when no voltage is applied in the reverse twist arrangement state. By optimizing the liquid crystal material, it is considered that a relatively bright light transmittance and a high contrast ratio can be achieved at any cell thickness.

  13A and 13B are graphs showing viewing angle-contrast characteristics of the liquid crystal display elements according to the examples. In both graphs, the horizontal axis represents the viewing angle (polar angle, tilt angle from the substrate normal direction) in the best viewing direction in the unit of “°”. In the reverse twist alignment state, the direction in which the liquid crystal molecules at the center in the liquid crystal layer thickness direction rises is the best viewing direction. The vertical axis represents the contrast ratio. The contrast ratio is a value obtained by dividing the light transmittance in the spray twist arrangement state (white display) by the light transmittance in the reverse twist arrangement state (black display).

  As shown in FIG. 13A, in the liquid crystal display element according to the example, a contrast ratio of 16 or more is obtained at a viewing angle (polar angle) of about 40 °.

  FIG. 13B shows the viewing angle-contrast characteristics (solid line) of the liquid crystal display element according to the embodiment, and the viewing angle-contrast characteristics (broken line) of the conventional liquid crystal display element whose display appearance is shown in FIG. Indicates. As shown in the figure, the conventional liquid crystal display element has a contrast ratio of about 1 regardless of the viewing angle (polar angle). The maximum value of the contrast ratio of the conventional liquid crystal display element was 1.09. It can be seen that the liquid crystal display element according to the example is a liquid crystal display element with high display quality in which a high contrast ratio is realized in a wide viewing angle range.

    As mentioned above, although this invention was demonstrated along the Example, this invention is not limited to these.

  For example, in the embodiments, the polarizing plates are arranged in crossed Nicols to obtain a normally white display liquid crystal display element, but the polarizing plates may be arranged in parallel Nicols to form a normally black display liquid crystal display element. However, it would be easier to achieve a display with a high contrast ratio if it is normally white. In the case of normally white display, in order to obtain good black display, the angle formed by the transmission axis directions of the upper and lower polarizing plates 16a and 16b is preferably about 90 °.

  In the embodiment, since the upper and lower polarizing plates 16a and 16b are of a type having a relatively low light transmittance, for example, as shown in FIG. 12A, the light transmittance of white display (spray twist arrangement state). However, if a type having a relatively high light transmittance is used, the light transmittance for white display can be set to, for example, about 25% to 30%.

  In the embodiment, the twist angle is 90 °, but other angles may be used. In that case, it is necessary to adjust the retardation value in the liquid crystal layer in order to increase the brightness in white display.

  Furthermore, in the embodiment, an electrode for generating a lateral electric field is formed only on the lower substrate 10b, but it can be formed not only on the lower substrate 10b but also on the upper substrate 10a. The electrode that generates the lateral electric field may be formed on at least one of the upper substrate 10a and the lower substrate 10b.

    It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like are possible.

  It can be used for all liquid crystal display elements, for example, all liquid crystal display elements that perform simple matrix driving. Further, it can be used for a liquid crystal display element that requires low power consumption, wide viewing angle characteristics, low price, and the like.

  From the point of having memory properties, it can be preferably applied to reflective, transmissive, and projection displays, such as the display surface of information equipment (personal computer, portable information terminal, etc.) that does not require frequent rewriting, for example, with low power consumption. is there. Further, it can be used for information display surfaces of magnetically recorded or electrically recorded cards, toys for children, electronic paper, and the like.

10a Upper substrate 10b Lower substrate 11a Upper transparent substrate 11b Lower transparent substrate 12a Upper solid electrode 12b Lower solid electrode 12c First comb electrode 12d Second comb electrode 13 Insulating film 14a Upper alignment film 14b Lower alignment film 15 Liquid crystal layer 16a Upper polarizing plate 16b Lower polarizing plate 20 Power supply

Claims (14)

A first substrate comprising a first electrode and subjected to orientation treatment;
A second substrate disposed in parallel and opposite to the first substrate, provided with a second electrode, and subjected to an orientation treatment;
A liquid crystal layer that is disposed between the first substrate and the second substrate, includes a chiral agent, and has a twist alignment;
In the case where the liquid crystal layer does not contain the chiral agent, when the swirl direction in which the liquid crystal molecules are twisted by the alignment treatment is defined as the first swirl direction, the chiral agent is added to the liquid crystal molecules in the liquid crystal layer. Giving a turnability in the second turning direction opposite to the direction,
The first substrate and the second substrate are subjected to an orientation treatment so that a pretilt angle of 20 ° to 45 ° is expressed,
In the liquid crystal layer, by applying a voltage to the first electrode and the second electrode, an electric field in the thickness direction of the liquid crystal layer is generated , and the direction in which the liquid crystal molecules of the liquid crystal layer are twisted is changed. It is possible to display by switching from the second turning direction to the first turning direction ,
At least one of the first substrate and the second substrate is caused to generate an electric field in a direction perpendicular to the thickness direction of the liquid crystal layer by applying a voltage, so that the liquid crystal molecules in the liquid crystal layer are twisted. The liquid crystal display element in which the electrode which can be switched and displayed from the said 1st turning direction to the said 2nd turning direction is formed. The second substrate is
A transparent substrate;
The second electrode formed on the transparent substrate;
An insulating film formed on the second electrode;
First and second comb electrodes formed on the insulating film, wherein the comb teeth portions are alternately arranged; and
The liquid crystal display element according to claim 1, further comprising an alignment film formed on the insulating film so as to cover the first and second comb electrodes.   The liquid crystal display element according to claim 1, wherein the first substrate and the second substrate are aligned so that a pretilt angle of 31 ° to 37 ° is developed.   The angle formed between the alignment treatment direction of the first substrate and the alignment treatment direction of the second substrate is 90 ° or more and 100 ° or less when viewed from the normal direction of the first and second substrates. The liquid crystal display element according to claim 1.   The angle formed by the alignment treatment direction of the first substrate and the alignment treatment direction of the second substrate is 90 ° when viewed from the normal direction of the first and second substrates. A liquid crystal display element according to 1.   The amount of the chiral agent added to the liquid crystal layer is adjusted so that d / p is more than 0.04 and less than 0.25 when the chiral pitch is p and the thickness of the liquid crystal layer is d. The liquid crystal display element according to claim 1.   The liquid crystal display element according to claim 1, wherein a thickness of the liquid crystal layer is 3 μm or more and 5 μm or less. A first substrate having a first electrode and subjected to an alignment treatment; a second substrate having a second electrode and being subjected to an alignment treatment; disposed opposite to and parallel to the first substrate; and the first substrate is disposed between the substrate and the second substrate includes a chiral agent, and a liquid crystal layer of twist orientation, when the liquid crystal layer did not contain the chiral agent, the liquid crystal molecules by the alignment treatment When the twisting turning direction is the first turning direction, the chiral agent gives the liquid crystal molecules of the liquid crystal layer a turning property in the second turning direction opposite to the first turning direction, and the first substrate. And the second substrate are subjected to an alignment treatment so that a pretilt angle of 20 ° to 45 ° is developed, and a voltage is applied to the liquid crystal layer between the first electrode and the second electrode. Thus, an electric field in the thickness direction of the liquid crystal layer is generated , and the liquid crystal component of the liquid crystal layer is It is possible to display by switching the direction in which the child is twisted from the second turning direction to the first turning direction, and voltage is applied to at least one of the first substrate and the second substrate. To generate an electric field in a direction perpendicular to the thickness direction of the liquid crystal layer, and to switch the direction in which the liquid crystal molecules of the liquid crystal layer are twisted from the first turning direction to the second turning direction, thereby performing display. A method of manufacturing a liquid crystal display element in which possible electrodes are formed,
A method for manufacturing a liquid crystal display element, comprising forming an alignment film on which alignment treatment is performed on the first substrate and the second substrate at a baking temperature of 160 ° C. to 180 ° C.   In the liquid crystal layer, when the chiral pitch of the chiral agent is p and the thickness of the liquid crystal layer is d, the chiral agent is added so that d / p is more than 0.04 and less than 0.25. The manufacturing method of the liquid crystal display element of Claim 8 formed.   The method for manufacturing a liquid crystal display element according to claim 8 or 9, wherein the alignment treatment of the first substrate and the second substrate is performed by rubbing with an indentation amount of 0.8 mm.   The direction of the alignment treatment of the first substrate and the direction of the alignment treatment of the second substrate form an angle of 90 ° or more and 100 ° or less when viewed from the normal direction of the first and second substrates. The method for manufacturing a liquid crystal display element according to claim 8, wherein the first and second substrates are bonded in parallel.   The method for manufacturing a liquid crystal display element according to claim 8, wherein the first substrate and the second substrate are bonded to each other with an interval of 3 μm or more and 5 μm or less. A first substrate having a first electrode and subjected to an alignment treatment; a second substrate having a second electrode and being subjected to an alignment treatment; disposed opposite to and parallel to the first substrate; and the first substrate is disposed between the substrate and the second substrate includes a chiral agent, and a liquid crystal layer of twist orientation, when the liquid crystal layer did not contain the chiral agent, the liquid crystal molecules by the alignment treatment When the twisting turning direction is the first turning direction, the chiral agent gives the liquid crystal molecules of the liquid crystal layer a turning property in the second turning direction opposite to the first turning direction, and the first substrate. And the second substrate are subjected to an alignment treatment so that a pretilt angle of 20 ° to 45 ° is developed, and a voltage is applied to the liquid crystal layer between the first electrode and the second electrode. Thus, an electric field in the thickness direction of the liquid crystal layer is generated , and the liquid crystal component of the liquid crystal layer is It is possible to display by switching the direction in which the child is twisted from the second turning direction to the first turning direction, and voltage is applied to at least one of the first substrate and the second substrate. To generate an electric field in a direction perpendicular to the thickness direction of the liquid crystal layer, and to switch the direction in which the liquid crystal molecules of the liquid crystal layer are twisted from the first turning direction to the second turning direction, thereby performing display. A method of driving a liquid crystal display element on which possible electrodes are formed,
When switching from white display to black display , an electric field in the thickness direction of the liquid crystal layer is generated,
A method for driving a liquid crystal display element, wherein an electric field in a direction orthogonal to the thickness direction of the liquid crystal layer is generated when switching from black display to white display . Switching to black display from a white display, and method of driving a liquid crystal display device according to claim 13 for switching to the white display, a line sequential driving.