CN103424933A - Liquid crystal element and liquid crystal display - Google Patents

Abstract

The invention provides a liquid crystal element and a liquid crystal display device, and improves the memory performance of the liquid crystal element utilizing the transition between two alignment states and the liquid crystal display device using the liquid crystal element in a high-temperature environment. The liquid crystal element includes: a first substrate and a second substrate arranged oppositely, and the respective surfaces of the first substrate and the second substrate have been subjected to orientation treatment; a liquid crystal layer disposed between one surface of the first substrate and one surface of the second substrate ; and a plurality of columnar spacers disposed between one side of the first substrate and one side of the second substrate. The direction of the alignment treatment of the first substrate and the second substrate is set to produce the first alignment state in which the liquid crystal molecules of the liquid crystal layer are twisted in the first direction, and each of them imparts the liquid crystal layer at the interface with the liquid crystal layer. The pretilt angle of the liquid crystal molecules is 20° or more. The liquid crystal layer contains a chiral material having a property of producing a second alignment state in which liquid crystal molecules are twisted in a second direction opposite to the first direction.

Description

Liquid crystal element, liquid crystal display device

technical field

The present invention relates to a technology for improving electro-optic characteristics in liquid crystal elements and liquid crystal display devices.

Background technique

JP 2011-203547 A (Patent Document 1) discloses a novel liquid crystal display element (reverse TN type liquid crystal element) utilizing transition between two alignment states. The liquid crystal display element of this conventional example has a first substrate and a second substrate subjected to alignment treatment, and a liquid crystal layer arranged between them and subjected to twist alignment, and a chiral material is contained in the liquid crystal layer. Furthermore, when the rotation direction in which liquid crystal molecules are twisted when no chiral material is included in the liquid crystal layer is the first rotation direction, the chiral material imparts rotation to the liquid crystal molecules in a second rotation direction opposite to the first rotation direction. In addition, the first substrate and the second substrate were subjected to orientation treatment so as to generate pretilt angles of 20° to 45°, respectively. Electrodes capable of generating electric fields in the thickness direction of the liquid crystal layer and in a direction perpendicular thereto are provided on the first substrate and the second substrate. According to this configuration, it is possible to realize a liquid crystal display element having a memory capable of maintaining a display state, and obtaining a high-contrast liquid crystal display element with excellent display quality.

However, although the liquid crystal display elements of the above-mentioned conventional examples have high memory at room temperature, when the ambient temperature becomes high (for example, 60° C. or higher), the memory may decrease, and some display states may not be maintained. Therefore, for example, the memory performance is insufficient under usage conditions such as in-vehicle use, aircraft use, and outdoor use where the ambient temperature changes greatly. In addition, in the liquid crystal display element of the conventional example, the disclination lines generated between the gap materials scattered between the substrates sometimes result in a region of splay twist orientation twisted in the above-mentioned second rotation direction. The transmittance in is reduced, and there is room for improvement in this regard. Furthermore, the boundary line between the reverse twist (reverse twist) oriented region twisted in the above-mentioned first rotation direction and the splay twist oriented region reflects the shape of the disclination line, so that the boundary line may become uneven, Resulting in lower display quality, there is also room for improvement in this regard.

[Patent Document 1] Japanese Patent Laid-Open No. 2011-203547

Contents of the invention

One of the objects of a specific embodiment of the present invention is to provide a technology capable of improving the memory properties of a liquid crystal element utilizing transition between two alignment states and a liquid crystal display device using the liquid crystal element in a high-temperature environment.

One of the objects of a specific aspect of the present invention is to provide a technology capable of preventing degradation of display quality due to disclination lines in a liquid crystal element utilizing transition between two alignment states and a liquid crystal display device using the liquid crystal element. .

A liquid crystal element according to one aspect of the present invention includes: (a) a first substrate and a second substrate disposed opposite to each other, and the respective surfaces of the first substrate and the second substrate are subjected to alignment treatment; (b) a liquid crystal layer provided on between one surface of the first substrate and one surface of the second substrate; and (c) a plurality of columnar spacers disposed between one surface of the first substrate and one surface of the second substrate, (d) the first substrate and the second substrate The direction of the alignment treatment of the substrates is set so as to generate a first alignment state in which the liquid crystal molecules of the liquid crystal layer are twisted in the first direction, and the first substrate and the second substrate are respectively provided at interfaces with the liquid crystal layer. The liquid crystal molecules of the liquid crystal layer have a pretilt angle of 20° or more, and (e) the liquid crystal layer contains a chiral material having a property of generating a second direction in which the liquid crystal molecules are twisted in a second direction opposite to the first direction. orientation status.

In the above-mentioned liquid crystal element, the gap between the first substrate and the second substrate is maintained by using a plurality of columnar spacers, so that the columnar space arranged near the boundary between the region of the first alignment state and the region of the second alignment state The object acts like a partition wall, capable of producing a state in which the two orientation states are discontinuous. Thereby, the transition of the orientation state can be blocked bidirectionally, and the memory property can be improved, so that each orientation state can be stably maintained even in a high-temperature state. Therefore, it can also be applied to applications requiring high reliability, such as in-vehicle use, aircraft use, and outdoor use. In addition, compared with the case where spherical spacers are used as the gap material, the disclination lines between the gap materials are eliminated, so it is possible to avoid a decrease in display quality due to the shape of the disclination lines. Furthermore, the weak scattering due to the disclination line disappears, so the transmittance in the region of the second orientation state (splay-twist state) increases, and the contrast between the regions of the first orientation state and the second orientation state improves.

In the above-mentioned liquid crystal element, each of the plurality of columnar spacers has a linear or dot-like outer shape in plan view, for example.

The above-mentioned liquid crystal element further includes a voltage applying unit for applying a voltage to the liquid crystal layer in order to generate an electric field. An electric field is generated in a direction, thereby causing the liquid crystal layer to transition to the first alignment state, and an electric field is generated in a direction substantially parallel to the respective surfaces of the first substrate and the second substrate, thereby making the liquid crystal layer The liquid crystal layer transitions to the second alignment state.

A liquid crystal display device according to one aspect of the present invention has a plurality of pixel units each configured using the above-mentioned liquid crystal element of the present invention.

According to the above-mentioned structure, it is possible to obtain a liquid crystal display device as follows: By using the bistability (memory) of the two alignment states of the liquid crystal element, it basically does not require electric power except when the display is rewritten, and it does not require much power at high temperatures. Will reduce the memory, display quality is also very good.

Description of drawings

FIG. 1 is a schematic diagram schematically showing the operation of an inverse TN type liquid crystal element.

FIG. 2 is a conceptual diagram for explaining the relationship between the alignment state of the liquid crystal layer and the direction of the electric field at the time of transition from the reverse twisted state to the spread twisted state.

3 is a cross-sectional view showing a structural example of an inverse TN type liquid crystal element.

FIG. 4 is a schematic diagram showing a planar shape of a columnar spacer.

5 is a schematic cross-sectional view illustrating an electric field applied to a liquid crystal layer using electrodes.

FIG. 6 is a diagram schematically showing a configuration example of a liquid crystal display device.

FIG. 7 is a view showing a microscope observation image of the liquid crystal element of Example 1. FIG.

FIG. 8 is a view showing a microscope observation image of a liquid crystal element of Example 2. FIG.

Label description

1: Upper substrate

2: Lower side substrate

3: Liquid crystal layer

51: 1st substrate

52: 1st electrode

53, 57: Alignment film

54: 2nd substrate

55: 2nd electrode

56: insulating film

58: 3rd electrode

59: 4th electrode

60: liquid crystal layer

61: columnar spacer

71, 72, 73: Drivers

74: Pixel Department

A1～An, B1～Bm, C1～Cn, D1～Dn: control line

Detailed ways

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

FIG. 1 is a schematic diagram schematically showing the operation of a reverse TN (RTN) type liquid crystal element. As a basic structure of an inverse TN type liquid crystal element, there are an upper substrate 1 and a lower substrate 2 arranged opposite to each other, and a liquid crystal layer 3 provided therebetween. The surfaces of the upper substrate 1 and the lower substrate 2 are subjected to orientation treatment such as rubbing treatment. The upper substrate 1 and the lower substrate 2 are arranged facing each other so as to cross each other at an angle of 90° in front and rear in accordance with their orientation processing directions (indicated by arrows in the figure). The liquid crystal layer 3 is formed by injecting a nematic liquid crystal material between the upper substrate 1 and the lower substrate 2 . In this liquid crystal layer 3, a liquid crystal material to which a chiral material is added is used, and the chiral material produces the following effect: the liquid crystal molecules are aligned in a specific direction (in the example of FIG. distortion. In such an inverse TN-type liquid crystal element, the liquid crystal layer 3 is in a splay-twisted state in which the liquid crystal layer 3 is twisted while being splay-aligned in the initial state due to the action of the chiral material. When a voltage exceeding the saturation voltage is applied in the layer thickness direction to the liquid crystal layer 3 in the spread twist state, the liquid crystal molecules shift to a reverse twist state (uniform twist state) twisted in the left-hand direction. In the liquid crystal layer 3 in such a reverse twist state, the liquid crystal molecules in the bulk are tilted, so the effect of lowering the driving voltage of the liquid crystal element is exhibited.

FIG. 2 is a conceptual diagram for explaining the relationship between the alignment state of the liquid crystal layer and the direction of the electric field at the time of transition from the reverse twisted state to the spread twisted state. As shown in Figure 2(A), for the electric field in the horizontal direction relative to the substrate surface, the direction of application of the electric field is set so that it is as far as possible from the layer thickness direction of the liquid crystal layer in the reverse twisted state. The major axes of liquid crystal molecules in the approximate center of the liquid crystal molecules (the liquid crystal molecules with patterns in the figure) are parallel to each other, but become vertical or nearly vertical. As a result, the liquid crystal molecules in the substantially center of the liquid crystal layer in the layer thickness direction are re-aligned along the direction of the electric field, so as shown in FIG. In addition, when an electric field is applied to the liquid crystal layer in the reverse twisted state in a state parallel to or nearly parallel to the major axis direction of the liquid crystal molecules in the approximate center of the layer thickness direction, it is difficult to change from the reverse twisted state to the splay twisted state. change. This is because, at substantially the center of the liquid crystal layer in the layer thickness direction, reorientation of the liquid crystal molecules hardly occurs due to the electric field. According to the above situation, in order to switch freely between the two alignment states in the reverse TN type liquid crystal element, it is necessary to generate an electric field (longitudinal electric field) corresponding to the layer thickness direction of the liquid crystal layer and an electric field (lateral electric field) in a direction perpendicular to it. ), and for the lateral electric field, it is necessary to be substantially vertical or close to the vertical direction to the long axis direction of the liquid crystal molecules in the approximate center of the liquid crystal layer in the reverse twisted state in the layer thickness direction. The device structure for freely applying these vertical electric fields and horizontal electric fields will be described below with specific examples.

3 is a cross-sectional view showing a structural example of an inverse TN type liquid crystal element. The liquid crystal element shown in FIG. 3 has a basic structure in which a liquid crystal layer 60 is interposed between a first substrate (upper substrate) 51 and a second substrate (lower substrate) 54 . Hereinafter, the structure of the liquid crystal element will be described in further detail. In addition, illustration and description of components such as a sealing material that seals the periphery of the liquid crystal layer 60 are omitted.

The first substrate 51 and the second substrate 54 are transparent substrates such as glass substrates and plastic substrates, respectively. As shown in the figure, the first substrate 51 and the second substrate 54 are bonded with a predetermined gap (for example, several μm) provided so that their surfaces face each other. In addition, although particular illustration is omitted, switching elements such as thin film transistors may be formed on any one of the substrates.

The first electrode 52 is provided on one side of the first substrate 51 . In addition, the second electrode 55 is provided on one side of the second substrate 54 . The first electrode 52 and the second electrode 55 are each formed by patterning a transparent conductive film such as indium tin oxide (ITO), for example.

An insulating film (insulating layer) 56 is provided on the second substrate 54 to cover the second electrode 55 . The insulating film 56 is, for example, an inorganic insulating film such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a laminated film thereof, or an organic insulating film (for example, an acrylic organic insulating film).

The third electrode 58 and the fourth electrode 59 are respectively provided on the above-mentioned insulating film 56 on the second substrate 54 . The third electrode 58 and the fourth electrode 59 in this embodiment are comb-shaped electrodes each having a plurality of electrode branches, and are arranged such that the electrode branches are alternately arranged (see FIG. 4 described later). The third electrode 58 and the fourth electrode 59 are each formed by patterning a transparent conductive film such as indium tin oxide (ITO), for example. The respective electrode branches of the third electrode 58 and the fourth electrode 59 are arranged with a width of, for example, 20 μm and an electrode interval of 20 μm.

The alignment film 53 is provided on one side of the first substrate 51 so as to cover the first electrode 52 . In addition, the alignment film 57 is provided on one surface side of the second substrate 54 so as to cover the third electrode 58 and the fourth electrode 59 . A predetermined alignment treatment (for example, rubbing treatment) is performed on each of the alignment films 53 and 57 .

The liquid crystal layer 60 is provided between the first substrate 51 and the second substrate 54 . The dielectric constant anisotropy Δε of the liquid crystal material constituting the liquid crystal layer 60 is positive (Δε>0). A chiral material for twisting liquid crystal molecules is added to the liquid crystal material.

The columnar spacer 61 is arranged between the first substrate 51 and the second substrate 54 to maintain a gap therebetween at a predetermined cell thickness (for example, several μm). These columnar spacers 61 are formed using, for example, a photosensitive resin material. In this embodiment, each columnar spacer 61 is formed on the first substrate 51 in advance.

FIG. 4(A) and FIG. 4(B) are schematic diagrams each showing the shape of the columnar spacer in plan view. For example, as shown in FIG. 4(A), each columnar spacer 61 is formed in a linear shape (in the illustrated example, a long rectangular shape) extending in the first direction, and is equally spaced in the second direction. configuration. In addition, the arrangement intervals of the columnar spacers 61 may not be equal intervals. In addition, for example, as shown in FIG. 4(B) , each columnar spacer 61 may be formed in a dot shape (square shape in the illustrated example) and arranged in a matrix at equal intervals. In addition, the shape of each columnar spacer 61 is not limited to a square shape, and the arrangement interval may not be equal. Even if columnar spacers 61 of any shape are used, it is desirable that the total area of each columnar spacer 61 in plan view in the region used for light modulation such as display accounts for the total area of the region from the viewpoint of stabilizing the cell thickness. 3.8% or more.

5 is a schematic cross-sectional view illustrating an electric field applied to a liquid crystal layer using electrodes. FIG. 5(A) is a schematic diagram showing the arrangement of the first to fourth electrodes in plan view. 5(B) to 5(D) are schematic diagrams showing the arrangement of the first to fourth electrodes in cross-section. The 1st electrode 52 and the 2nd electrode 55 are arrange|positioned facing each other, and the 3rd electrode 58 and the 4th electrode 59 are arrange|positioned in the area where both overlap. In addition, the plurality of electrode branches of the third electrode 58 and the plurality of electrode branches of the fourth electrode 59 are alternately arranged one by one repeatedly.

As shown in FIG. 5(B) , by applying a voltage between the first electrode 52 and the second electrode 55 , an electric field can be generated between both electrodes. As shown in the figure, the electric field at this time is an electric field along the thickness direction (cell thickness direction) of the first substrate 51 and the second substrate 54 , that is, a “vertical electric field”.

In addition, as shown in FIG. 5(C) , by applying a voltage between the third electrode 58 and the fourth electrode 59 , an electric field can be generated between both electrodes. As shown in the figure, the electric field at this time is an electric field in a direction approximately parallel to the respective surfaces of the first substrate 51 and the second substrate 54 , that is, a “lateral electric field”. Hereinafter, the mode using such an electric field may be referred to as "IPS mode".

In addition, as shown in FIG. 5(D) , by applying a voltage between the second electrode 55 , the third electrode 58 , and the fourth electrode 59 that are arranged to face each other with the insulating film 56 interposed therebetween, an electric field can be generated between the two electrodes. As shown in the figure, the electric field at this time is an electric field along a direction substantially parallel to the respective surfaces of the first substrate 51 and the second substrate 54 , that is, a “lateral electric field”. Hereinafter, the mode using such an electric field may be referred to as "FFS mode".

In the liquid crystal element of this embodiment, in the initial state, the liquid crystal molecules of the liquid crystal layer 60 are aligned in a spread-twisted state. On the other hand, when the vertical electric field is generated using the first electrode 52 and the second electrode 55 as described above, the alignment state of the liquid crystal molecules in the liquid crystal layer 60 transitions to the reverse twist state. Thereafter, when a transverse electric field is generated using the third electrode 58 and the fourth electrode 59 (IPS mode), the alignment state of the liquid crystal layer 60 transitions to a splay-twisted state. Also, even when a lateral electric field is generated using the second electrode 55 , the third electrode 58 , and the fourth electrode 59 (FFS mode), the alignment state of the liquid crystal layer 60 similarly transitions from the reverse twisted state to the spread twisted state. In comparison with the IPS mode, the FFS mode tends to enable more uniform transition of the alignment state of the liquid crystal layer 60 . This is because a lateral electric field is also applied to each of the third electrode 58 and the fourth electrode 59 . Therefore, considering the aperture ratio (transmittance, contrast), it can be said that the FFS mode is more suitable.

The reason why the alignment state of the liquid crystal layer 60 can be switched between the splay twist state and the reverse twist state is considered as follows. In the splay twisted state, the liquid crystal molecules in the approximate center of the layer thickness direction of the liquid crystal layer 60 are aligned approximately horizontally, and after being reversed twisted by the longitudinal electric field, the liquid crystal molecules in the approximate center of the layer thickness direction are aligned in the vertical direction. tilt. Thereafter, a transverse electric field is applied to the liquid crystal molecules in the approximate center of the liquid crystal layer 60 in the reverse twist state in the layer thickness direction by the transverse electric field in the IPS mode or the FFS mode, and the liquid crystal molecules in the approximate center of the liquid crystal layer 60 in the spread twist state The liquid crystal molecules are oriented in the proper director direction, and thus transition to the splay-twisted state which is the initial state again. From this, it can be seen that the splay twisted state and the reverse twisted state can be switched by making full use of the longitudinal electric field and the transverse electric field.

Next, an example of the manufacturing method of a liquid crystal element is demonstrated in detail.

The first substrate 51 having the first electrode 52 is produced by patterning the ITO film of the glass substrate with the ITO film. Here, the patterning of the ITO film can be performed by a general photolithography technique. As an ITO etching method, wet etching (ferric chloride) was used. In the shape pattern of the first electrode 52 here, the ITO film remains in the extraction electrode portion and the portion corresponding to the display pixel. Similarly, the second substrate 54 having the second electrode 55 is produced by patterning the ITO film of the glass substrate with the ITO film.

Columnar spacers 61 are formed on the first electrodes 52 of the first substrate 51 . For example, a transparent negative photosensitive resin is applied on one side of the first substrate 51 with a spin coater (for example, the spinner is rotated for 30 seconds), and prebaked (for example, at 100° C. for 120 seconds). In addition, by adjusting the rotational speed of the spin coater, it is possible to uniformly form a film within the range of about 0.5 μm to 5 μm in film thickness. Instead of coating with a spin coater, a slit coater can also be used. In this case, a film can be uniformly formed to a film thickness of about 10 μm. After film formation, the photosensitive resin film is irradiated with ultraviolet rays by a contact exposure machine using a high-pressure mercury lamp as a light source through a photomask having an exposure pattern corresponding to columnar spacers 61 of a desired shape. The exposure conditions are, for example, irradiated at an illuminance of 5.79 mW/cm ² for 35 seconds (200 mJ/cm ² ). Afterwards, the photosensitive resin was developed by immersing in a 1% tetramethylammonium hydroxide aqueous solution, and rinsed with pure water. After the substrate was dried, it was mainly dried in a dust-free oven at 220°C for 30 minutes. bake. Thereby, a plurality of columnar spacers 61 are formed on one surface of the first substrate 51 .

An insulating film 56 is formed on the second electrode 55 of the second substrate 54 . At this time, measures need to be taken in order not to form the insulating film 56 at the extraction electrode portion. As the method, the following methods can be mentioned: a method of forming a resist in advance on the lead-out electrode portion, and then peeling off after forming the insulating film 56; A method of forming the insulating film 56 and the like. In addition, examples of the insulating film 56 include organic insulating films, inorganic insulating films such as silicon oxide films and silicon nitride films, combinations thereof, and the like. Here, a laminated film of an acrylic organic insulating film and a silicon oxide film (SiO ₂ film) is used as the insulating film 56 .

此处，当剥离耐热性薄膜时，能够将有机绝缘膜、SiO₂膜一起干净地剥离。之后，在无尘烘烤箱中进行烘烤（例如，220℃、1小时）。这是为了提高SiO₂膜的绝缘性和透明性。虽然不是必须形成SiO₂膜，但通过形成SiO₂膜，能够提高其上形成的ITO膜的密接性和构图性，因此优选形成SiO₂膜。并且，绝缘性也提高。另一方面，也可以考虑不形成有机绝缘膜而仅通过SiO₂膜来获得绝缘性的方法，不过此时，由于SiO₂膜容易成为多孔质，因此优选将膜厚确保为

左右。另外，也可以成为与SiNx的层叠膜。另外，作为无机绝缘膜的形成方法，虽然叙述了溅射法，但是也可以使用真空蒸镀法、离子束法、CVD法（化学气相沉积法）等形成方法。A heat-resistant film (polyimide tape) is attached to the lead-out electrode part (terminal part), and the material liquid of the organic insulating film is spin-coated in this state. For example, under the condition of spinning at 2000 rpm for 30 seconds, a film thickness of 1 μm is obtained. Bake them in a dust-free oven (eg, 220 °C for 1 hour). A _SiO2 film is formed by sputtering (AC discharge) with a heat-resistant film attached. For example, the substrate is heated to 80°C to form

Here, when the heat-resistant thin film is peeled off, the organic insulating film and the SiO ₂ film can be cleanly peeled off together. Thereafter, baking is performed in a dust-free oven (for example, 220° C. for 1 hour). This is to improve the insulation and transparency of the _SiO2 film. Although it is not necessary to form the SiO ₂ film, the adhesion and patterning of the ITO film formed thereon can be improved by forming the SiO ₂ film, so the formation of the SiO ₂ film is preferable. In addition, insulation is also improved. On the other hand, it is also conceivable to obtain insulation only by the _SiO2 film without forming an organic insulating film _.

about. In addition, it may be a laminated film with SiNx. In addition, although the sputtering method was described as the method for forming the inorganic insulating film, a method such as a vacuum evaporation method, an ion beam method, and a CVD method (chemical vapor deposition method) may also be used.

Next, the third electrode 58 and the fourth electrode 59 are formed on the insulating film 56 . Specifically, first, an ITO film is formed on the insulating film 56 by a sputtering method (alternating current discharge). For example, the substrate is heated to 100°C to form about left and right ITO films. This ITO film is patterned by a general photolithography technique. As the photomask at this time, a photomask having a light-shielding portion corresponding to the above-mentioned comb-shaped electrode shown in FIG. 5 is used. Regarding the comb-shaped electrodes, for example, the width of the electrode branch can be 20 μm to 30 μm, and the electrode interval can be 20 μm to 200 μm. Also, if there is no pattern on the extraction electrode portion, the ITO film on the lower side will also be removed by etching, so a photomask in which a pattern is also formed on the extraction electrode portion is used.

The first substrate 51 and the second substrate 54 fabricated as described above are cleaned. Specifically, water washing (brushing or spray washing, pure water washing) is performed first, UV washing is performed after removing moisture, and finally IR drying is performed.

接着，对各取向膜53、57进行作为取向处理的摩擦处理。摩擦时的压入量例如设定为0.8mm。由此，各取向膜53、57能够使得液晶分子产生20°～60°左右的预倾角。Next, alignment films 53 and 57 are formed on the first substrate 51 and the second substrate 54, respectively. As the alignment films 53 and 57 , for example, a polyimide film obtained by reducing the side chain density of a material generally used as a vertical alignment film is used. A material solution for an alignment film (orientation material) is applied to one surface of each of the first substrate 51 and the second substrate 54, and they are baked in a dust-free oven (eg, 160° C., 1 hour). As a coating method of the material liquid for the alignment film, flexographic printing, inkjet printing, or spin coating can be used. Although the spin coating method is used here, the result is the same even if other methods are used. The thickness of the alignment films 53 and 57 is, for example,

Next, a rubbing treatment as an alignment treatment is performed on each of the alignment films 53 and 57 . The press-in amount at the time of friction is set to 0.8 mm, for example. Accordingly, the alignment films 53 and 57 can cause the liquid crystal molecules to have a pretilt angle of about 20° to 60°.

Next, the first substrate 51 and the second substrate 54 are bonded together. A sealing material is printed in advance on the first substrate 51 . Next, a liquid crystal material is injected between the first substrate 51 and the second substrate 54 to form the liquid crystal layer 60 . In the liquid crystal material, for example, CB15 is added as a chiral material.

Thus, the liquid crystal element of this embodiment is completed. When such a liquid crystal element of this embodiment is completed, the liquid crystal layer 60 is oriented in a spread-twisted state. At this time, the transmittance (or reflectance) is relatively low, and the appearance is in a dark state. Also, when a vertical electric field is applied to the liquid crystal layer 60 , the alignment of the liquid crystal layer 60 changes to a reverse twist state, and this state is maintained even after the electric field is turned off. At this time, the transmittance (or reflectance) is relatively high, and the appearance becomes brighter. Next, when a transverse electric field is applied to the liquid crystal layer 60 , the orientation of the liquid crystal layer 60 changes to the spread-twisted state again, and this state is maintained even after the electric field is turned off. The contrast at this time tends to be the highest when the pretilt angle is around 45°, and the contrast decreases as the pretilt angle decreases. In particular, when the pretilt angle is less than 20°, the contrast is significantly lowered, and the difference in transmittance (or the difference in reflectance) between the splayed twisted state and the reverse twisted state almost disappears, and insufficient display performance was confirmed.

Next, a configuration example of a liquid crystal display device capable of driving with low power consumption utilizing the memory characteristic of the above-mentioned liquid crystal element will be described.

FIG. 6 is a diagram schematically showing a configuration example of a liquid crystal display device. The liquid crystal display device shown in FIG. 6 is a pure matrix type liquid crystal display device configured by arranging a plurality of pixel units 74 in a matrix, and uses the above-mentioned liquid crystal element as each pixel unit 74 . Specifically, the liquid crystal display device is configured to include: m control lines B1 to Bm extending in the X direction; a driver 71 for supplying control signals to these control lines B1 to Bm; n control lines A1-An extending in the Y direction; a driver 72 for supplying control signals to these control lines A1-An; n control lines C1-Cn and D1 extending in the Y direction crossing the control lines B1-Bm respectively ˜Dn; a driver 73 that supplies control signals to these control lines C1 ˜Cn and D1 ˜Dn; and a pixel portion 74 provided at each intersection of the control lines B1 ˜Bm and the control lines A1 ˜An.

Each of the control lines B1 to Bm, A1 to An, C1 to Cn, and D1 to Dn is made of, for example, a transparent conductive film such as ITO formed in a stripe shape. Portions where the control lines B1 to Bm intersect A1 to An function as the aforementioned first electrodes 52 and second electrodes 55 (see FIG. 3 ). In addition, the control lines C1 to Cn are provided in regions corresponding to the respective pixel portions 74 , and are connected to comb-shaped electrode branches (not shown in FIG. 6 ) as the third electrodes 58 . Similarly, the control lines D1 to Dn are provided in regions corresponding to the respective pixel portions 74 , and are connected to comb-shaped electrode branches (not shown in FIG. 6 ) as the fourth electrodes 59 .

Various methods can be considered as a driving method of the liquid crystal display device having the structure shown in FIG. 6 . For example, a method of performing display rewriting for each of the control lines B1 , B2 , B3 . . . (line sequential driving method) will be described. At this time, it is only necessary to apply a vertical electric field to the pixel portion 74 for relatively bright display (reverse twist state), and apply a horizontal electric field for pixel portion 74 for relatively dark display (splay twist state).

For example, a rectangular wave voltage (for example, about 5 V and 150 Hz) is applied to the control line B1 to such an extent that no transition of the orientation state occurs, and the control lines A1 to An, C1 to Cn, and D1 to Dn are applied to the control lines A1 to An, C1 to Cn, and D1 to Dn synchronously or half-shifted. A rectangular wave voltage around the threshold voltage of one cycle (for example, about 5V and 150Hz).

Specifically, a rectangular wave voltage shifted by a half cycle from the rectangular wave voltage applied to the control line B1 is applied to the control line corresponding to the pixel portion 74 desired to display brighter among the control lines A1 to An. At this time, no voltage is applied to the control lines C1 to Cn and D1 to Dn. As a result, a voltage of about 10 V (vertical electric field) is actually applied to the liquid crystal element of the pixel portion 74 . When this voltage is equal to or higher than the saturation voltage, the liquid crystal layer 60 undergoes a transition of the alignment state, and the transmittance of the pixel portion 74 can be changed. On the other hand, a rectangular wave voltage synchronized with the rectangular wave voltage applied to the control line B1 is applied to the control line corresponding to the pixel portion 74 that does not need to change the display among the control lines A1 to An. At this time, no voltage is applied to the control lines C1 to Cn and D1 to Dn. As a result, the pixel portion 74 is in a state where no voltage is actually applied. Therefore, the transition of the alignment state does not occur in the liquid crystal layer 60, and the transmittance does not change.

In addition, a rectangular wave voltage shifted by a half cycle from the rectangular wave voltage applied to the control line B1 is applied to the control line corresponding to the pixel portion 74 desired to display darker among the control lines C1 to Cn and D1 to Dn. At this time, no voltage is applied to the control lines A1 to An. Thereby, a voltage (lateral electric field) of about 10 V is actually applied to the liquid crystal element of the pixel portion 74 . When this voltage is equal to or higher than the saturation voltage, the liquid crystal layer 60 undergoes a transition of the alignment state, and the transmittance of the pixel portion 74 can be changed. On the other hand, a rectangular wave voltage synchronized with the rectangular wave voltage applied to the control line B1 is applied to the control line corresponding to the pixel portion 74 that does not need to change the display among the control lines C1 to Cn and D1 to Dn. At this time, no voltage is applied to the control lines A1 to An. As a result, the pixel portion 74 is in a state where no voltage is actually applied. Therefore, the transition of the alignment state does not occur in the liquid crystal layer 60, and the transmittance does not change.

Dot matrix display can be performed by sequentially performing the driving as described above in accordance with the control lines B2, B3, . . . The display state rewritten by driving as described above can be held semi-permanently. When rewriting the display, the above-mentioned control may be executed again from the control line B1. In addition, although an example in which the present invention is applied to a so-called pure matrix liquid crystal display device is shown here, the present invention can also be applied to an active matrix liquid crystal display device using a thin film transistor or the like. In the case of an active-matrix liquid crystal display device, it is not necessary to rewrite each line such as the control line B1, so that rewriting time can be shortened. In addition, since a voltage twice or more than the threshold value can be applied, higher-speed rewriting can be performed. However, since the electrodes for the lateral electric field and the vertical electric field are present on one substrate, two thin film transistors and the like are required for one pixel.

(Example 1)

接着进行了摩擦处理。摩擦时的压入量为0..8mm，扭曲角

为70°。单元厚度d为4μm。在注入的液晶材料中添加了手性材料。手性材料的添加量为d/p=0.20～0.53。关于偏振板，以彼此的透射轴大致正交、且各偏振板的透射轴与摩擦方向成15°的方式进行了配置。A liquid crystal element having linear columnar spacers extending in one direction was manufactured. In this embodiment, columnar spacers with a height of about 4 μm are formed on one side of the substrate. When applying the photosensitive resin material, the rotation speed of the spin coater was set to 600 rpm. In addition, exposure was performed using a negative photomask (line width: 40 μm, line pitch: 400 μm) having linear openings corresponding to the shapes of the columnar spacers. Other steps are the same as those in the above-mentioned embodiment. It is preferable not to form the linear columnar spacers in the part of the main sealing material for sealing the liquid crystal layer. Next, as an alignment film, a polyimide film obtained by adjusting the side chain density of a material generally used as a vertical alignment film so that an appropriate pretilt angle can be generated was used. Set the baking temperature between 160°C and 260°C. As a method for forming the alignment film, flexographic printing, inkjet printing, or spin coating can be used. Although the spin coating method was used here, the result is the same even if other methods are used. The film thickness of the alignment film is

This was followed by a rubbing treatment. The press-in amount during friction is 0..8mm, and the twist angle

is 70°. The cell thickness d is 4 μm. A chiral material is added to the injected liquid crystal material. The amount of chiral material added is d/p=0.20-0.53. The polarizing plates were arranged so that their transmission axes were substantially perpendicular to each other, and the transmission axis of each polarizing plate was at 15° to the rubbing direction.

7(A) to 7(D) are diagrams showing microscopic observation images of the liquid crystal element of Example 1. FIG. In each figure, areas that appear relatively bright correspond to the splay twist state (initial orientation), and areas that appear dark correspond to the reverse twist state (area switched by the longitudinal electric field). In the past, the boundary between the two domains was disorganized and jagged, but when this part was carefully observed, it was observed that randomly scattered spherical spacers connected to form the boundary line of the domain, and the orientation was maintained depending on the position of the spherical spacers state of memory. On the other hand, as shown in FIGS. 7(A) to 7(D), in Example 1, it was observed that the transition from the reverse twisted state to the splayed twisted state was along the linear column spacer And was blocked. In detail, states at the time of application of an electric field are shown in chronological order in the order of FIG. 7(A), FIG. 7(B), FIG. 7(C), and FIG. 7(D). Although it is also related to the position of the electrode for generating the longitudinal electric field, by making the extension direction of the partition wall realized by the columnar spacer and the boundary portion between the region of the splay twist state and the region of the reverse twist state (that is, The ends of the electrodes to which the longitudinal electric field can be applied) are consistent, the two alignment regions can be made discontinuous, the transition of the alignment state can be bidirectionally blocked by the columnar spacer, and the memory of the alignment state can be improved. The liquid crystal element of Example 1 was observed by heating at 90°C for about 30 minutes in order to investigate the stability of maintaining the orientation state. Before and after, there is no change in the boundary portion between the splay twist region and the reverse twist region (see FIG. 7(D) ). In addition, it was found that the disclination lines observed in the spread-twisted alignment region of the conventional liquid crystal element were not observed in the liquid crystal element of Example 1 at all. It is known that disclination lines are formed by connecting spherical spacers as a gap control material, but in the liquid crystal element of the first embodiment which does not require a gap control material, the disclination lines can be eliminated.

(Example 2)

点密度为3.8%左右），进行了曝光。除此以外的工序与上述情况相同。优选不在用于密封液晶层的主密封材料的部分中形成该点状的柱状间隔物。除此以外的制造条件与实施例1的情况相同。A liquid crystal element having dot-like columnar spacers arranged in a matrix was manufactured. In this embodiment, columnar spacers with a height of about 4 μm are formed on one side of the substrate. When applying the photosensitive resin material, the rotation speed of the spin coater was set to 600 rpm. In addition, a negative photomask with dots opening corresponding to the shape of the columnar spacers (dot size of

The dot density is about 3.8%), and the exposure was performed. The steps other than that are the same as in the above case. It is preferable not to form the dot-like columnar spacers in the portion of the main sealing material for sealing the liquid crystal layer. The manufacturing conditions other than that are the same as in the case of Example 1.

FIG. 8 is a view showing a microscope observation image of a liquid crystal element of Example 2. FIG. In the figure, areas that appear relatively brighter correspond to the splay twist state (initial orientation), and areas that appear darker correspond to the reverse twist state (areas switched by the longitudinal electric field). As can be seen from FIG. 8 , the boundary line between the region in the splay twist state and the region in the reverse twist state becomes a clear straight line. Here, it can be seen that the boundary line observed in FIG. 8 roughly coincides with the end of the electrode for applying the longitudinal electric field. Thus, by making the position of the dot-shaped columnar spacer coincide with the position of the electrode, the splay-twisted state and the electrode can be adjusted. The boundary line of the reverse twisted state becomes clear. In addition, in order to obtain the arrangement of the columnar spacers as described above, it is only necessary to adjust the position of the photomask in accordance with the positions of the electrodes during the exposure at the time of forming the columnar spacers, and no special additional steps are required. Although the case where the shape of the end portion of the electrode is linear has been described here, the shape of the end portion of the electrode may be curved. In this case, it is only necessary to use a photomask designed to arrange dot-shaped columnar spacers in accordance with the positions of the curves. In addition, even if the positions of the columnar spacers are slightly changed, as long as the dot density is made approximately the same, performance and display quality will not be affected. In addition, regarding the position of the columnar spacer at this time, it is preferable that the columnar spacer facing the inside of the electrode at the shortest distance from the electrode end is arranged within 100 μm from the electrode end. In addition, as shown in the example of FIG. 8 , if the columnar spacers are planarly arranged at a pitch of 100 μm, the above conditions can be satisfied at any position, so it is not necessary to align the positions of the electrodes and the columnar spacers with high precision. Even if the pitch of the columnar spacers is larger than 100 μm or irregular, there is no problem if the arrangement is adopted such that, in the region within 100 μm from the end of the electrode forming the pixel, at the shortest distance The columnar spacers conform to the shape of the ends of the electrodes. Also, as shown in Example 2, when dot-shaped columnar spacers are used, it is easier to inject the liquid crystal material than when linear columnar spacers like Example 1 are used. This is because there are few factors that hinder the flow of the liquid crystal material.

As described above, according to the present embodiment and each of the examples, it is possible to improve the memory performance of a liquid crystal element utilizing the transition between two alignment states in a high-temperature environment, and to prevent a decrease in display quality due to disclination lines.

In addition, the manufacturing process of a liquid crystal element is basically the same as the manufacturing process of a general liquid crystal element, and there are few factors leading to an increase in cost. That is, it can be manufactured at low cost by the same manufacturing technology as that of a general liquid crystal element.

In addition, in the liquid crystal element of the present embodiment and the like, since no power is required except when rewriting the display, ultra-low power consumption driving can be realized, and the liquid crystal element suitable for either a transmissive display or a reflective display can be realized. display. Especially when applied to reflective displays, the advantages are obvious.

In addition, since a driving method (line sequential rewriting method, etc.) that utilizes the memory of the alignment state can be applied, it is not necessary to use switching elements such as thin film transistors, and large-capacity dot matrix display can be performed by pure matrix display. Therefore, large-capacity display can be realized at low cost.

In addition, this invention is not limited to the content of the said embodiment, Various deformation|transformation can be carried out within the range of the summary of this invention. For example, in the above-mentioned embodiments and the like, rubbing treatment was mentioned as a specific example of alignment treatment, but other alignment treatments (for example, photo-alignment method, oblique vapor deposition method, etc.) may be used. In addition, the numerical conditions and the like mentioned in the description are only suitable examples, and are not necessarily limited thereto. In addition, a material (monomer) polymerizable by ultraviolet light or the like may be added to the liquid crystal material constituting the liquid crystal layer, and the monomer may be polymerized by irradiating ultraviolet light or the like after injecting the liquid crystal material between the substrates. In this case, the memory property of the orientation state can be further improved.

Claims (4)

1. a liquid crystal cell, this liquid crystal cell comprises:

The 1st substrate and the 2nd substrate that relatively configure, the 1st substrate and the 2nd substrate one side separately have been implemented orientation process;

Be arranged on the liquid crystal layer between the one side of the one side of described the 1st substrate and described the 2nd substrate; And

Be arranged on a plurality of column spacers between the one side of the one side of described the 1st substrate and described the 2nd substrate,

About described the 1st substrate and described the 2nd substrate, the direction of described orientation process is set to the 1st state of orientation of the liquid crystal molecule distortion on the 1st direction that produces described liquid crystal layer, and, described the 1st substrate and described the 2nd substrate respectively with the interface of described liquid crystal layer, the tilt angle that is given to the liquid crystal molecule of this liquid crystal layer is more than 20 °

Described liquid crystal layer contains chiral material, and this chiral material has following character: the 2nd state of orientation that produces the distortion on the 2nd direction with described the 1st opposite direction of described liquid crystal molecule.

2. liquid crystal cell according to claim 1, wherein,

Described a plurality of column spacer has respectively the profile of wire or point-like when overlooking.

3. liquid crystal cell according to claim 1 and 2, wherein,

This liquid crystal cell also comprises voltage applying unit, and this voltage applying unit applies voltage in order to produce electric field to described liquid crystal layer,

Produce electric field by described voltage applying unit on the direction substantially vertical with described the 1st substrate and described the 2nd substrate one side separately, make thus described liquid crystal layer change to described the 1st state of orientation, by on the direction with described the 1st substrate and described the 2nd a substrate almost parallel separately, producing electric field, make thus described liquid crystal layer change to described the 2nd state of orientation.

4. a liquid crystal indicator, this liquid crystal indicator has a plurality of pixel section, and the other right to use of the plurality of pixel portion requires the described liquid crystal cell of any one in 1～3 and forms.

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