JP4595362B2 - Liquid crystal display element - Google Patents

Description

  The present invention relates to a liquid crystal display element, and more particularly to a liquid crystal display element including a liquid crystal / cured material composite layer.

  A transmission-scattering type optical element has been proposed in which a liquid crystal and a transparent polymer are combined to cause a difference in refractive index between the polymer and the liquid crystal, or inside the liquid crystal (between microregions). It is called a liquid crystal / polymer composite element, a liquid crystal / resin composite element, or a dispersed liquid crystal element. Since this element does not require a polarizing plate in principle, it has a great advantage that light absorption loss is small, high scattering performance is obtained, and light use efficiency in the entire element is high.

  Taking advantage of this characteristic, it is used for light control glass, optical shutters, laser devices, display devices and the like. Those in a scattering state when no voltage was applied and in a transparent state when a voltage was applied were commercialized.

  Further, Patent Document 1 discloses an element using a liquid crystal and a polymerizable liquid crystal. In this prior art, when no voltage is applied, the liquid crystal in the element and the polymerized liquid crystal have the same alignment direction, and thus the transparent state is exhibited when the element is viewed from any direction. When a voltage is applied, the orientation of the liquid crystal in the element is controlled by an electric field, and the arrangement direction of the liquid crystal molecules changes variously in a minute region, whereby the element exhibits a scattering state.

  It has also been disclosed that the contrast ratio is improved by adding a chiral agent to provide a helical structure in the initial orientation. This element is called “anisotropic gel” or “liquid crystal gel”. In this prior art, a mesogenic monomer having an acryloyl group at the terminal is used.

  Patent Document 2 also discloses an element having a similar configuration. The operation mode is the same as in Patent Document 1, and a small amount of polymer is dispersed in a chiral nematic liquid crystal to obtain a transparent state when no voltage is applied and a scattering state when a voltage is applied. This element is called PSCT (Polymer Stabilized Cholesteric Texture). This document also disclosed a mesogenic monomer having an acryloyl group at its terminal.

  In a liquid crystal display element, a mixture of a liquid crystal and a photocurable resin is sandwiched between a pair of substrates having electrodes. And in order to improve the contrast by increasing the difference in transmittance between the transmissive state and the scattering state, exposure and photocuring are performed (Patent Document 3). In this liquid crystal display element, when no voltage is applied, the liquid crystal is aligned perpendicular to the substrate and is in a transmissive state. On the other hand, when a voltage is applied, the liquid crystal is randomly oriented and enters a scattering state.

  In addition, a manufacturing method of a liquid crystal display element that is exposed to seal an opening for injecting liquid crystal is disclosed (Patent Document 4). In this method, an opening for injecting a liquid mixture containing a liquid crystal composition and a photocurable compound is exposed to ultraviolet rays to seal the opening. Then, the entire liquid crystal cell is irradiated with ultraviolet rays to form a liquid crystal resin composite layer serving as an electro-optical functional layer by a photopolymerization reaction. Thus, a liquid crystal display element is manufactured by two exposure steps.

  Since such a liquid crystal display element is in a transmissive state that transmits light when no voltage is applied, it is used as a front panel for instrument panels and pachinko machines that display automobile meters, such as show windows and showcases that display various products. It has become so. When used in such applications, the impact resistance of the liquid crystal display element becomes a problem. That is, the pair of substrates of the liquid crystal display element is distorted in the alignment of the liquid crystal due to the impact. Thereby, the display characteristic of the part will deteriorate. For example, the area around the place where the impact is applied remains cloudy and does not return to transparency. Thus, the conventional liquid crystal display device has a problem that the impact resistance is low, and it is difficult to manufacture a liquid crystal display device having a sufficient impact resistance.

US Pat. No. 5,188,760 International Publication No. 92/19695 Pamphlet JP 2000-119656 A JP-A-8-129184

  As described above, the conventional liquid crystal display device has a problem in that the display characteristics of the portion subjected to the impact deteriorate.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a liquid crystal display element having high impact resistance.

The liquid crystal display element according to the first aspect of the present invention is formed by exposing a mixture of a nematic liquid crystal sandwiched between a pair of substrates, at least one of which is transparent, and a photocurable compound of the formula (1). A liquid crystal display element comprising the liquid crystal photocured composite, wherein the liquid crystal photocured composite is in a transparent state when no voltage is applied and is in a scattering state when a voltage is applied (for example, implementation of the present invention). The liquid crystal immobilization has the same component ratio as that of the operating region and includes the nematic liquid crystal immobilized on the polymer of the photocurable compound, and the transmittance does not change depending on the voltage. A region (for example, the impact resistant structure 5 in the embodiment of the present invention). Thereby, impact resistance can be improved without degrading the display characteristics of the liquid crystal display element.
_{A 1 - (OR 1) n} -O-Z-O- (R 2 O) m -A 2 ··· Equation (1)
(However, (A ₁ , A ₂ ) is each independently an acryloyl group, a methacryloyl group, a glycidyl group, and an allyl group, R 1 and R 2 are each independently an alkylene group having 2 to 6 carbon atoms, and Z is A divalent mesogen structure, wherein n and m are each independently an integer of 1 to 10 )

  A liquid crystal display element according to a second aspect of the present invention is the above-described liquid crystal display element, wherein an area of the operation region is 60% or more of a total area of the liquid crystal fixed region and the operation region in the display region. 85% or less. As a result, a liquid crystal display element having excellent display characteristics and excellent impact resistance can be provided.

  A liquid crystal display element according to a third aspect of the present invention is the above liquid crystal display element, wherein the liquid crystal has negative dielectric anisotropy, and at least one alignment film for aligning the liquid crystal perpendicular to the substrate surface is provided. It is provided on the surface of the substrate. Thereby, the display characteristic of a liquid crystal display element can be improved.

  A liquid crystal display element according to a fourth aspect of the present invention is the above liquid crystal display element, wherein the liquid crystal immobilization region is formed by pattern exposure from substantially the same composition as the mixture. Thereby, it is possible to improve the impact resistance without deteriorating the display characteristics of the liquid crystal display element with a simple configuration.

  The liquid crystal display element according to the fifth aspect of the present invention is the above liquid crystal display element, wherein the mass of the liquid crystal in the liquid crystal immobilization region is 50% or more based on the total mass of the liquid crystal and the photocurable compound. It is what is.

  A liquid crystal display element according to a sixth aspect of the present invention is the above liquid crystal display element, wherein the liquid crystal immobilization region has a transmittance of 50% or more. The display characteristics of the liquid crystal display element can be improved.

  A liquid crystal display element according to a seventh aspect of the present invention is the above liquid crystal display element, wherein the liquid crystal immobilization region is optically isotropic. The display characteristics of the liquid crystal display element can be improved.

  The liquid crystal display element according to an eighth aspect of the present invention is the above liquid crystal display element, wherein the liquid crystal immobilization region has a polygonal continuous junction shape. Thereby, impact resistance can be improved.

A liquid crystal display element according to a ninth aspect of the present invention is the above liquid crystal display element, wherein the polygon is a regular hexagon. Thereby, impact resistance can be improved.
In the method for producing a liquid crystal display element according to the tenth aspect of the present invention, a mixture of a nematic liquid crystal sandwiched between a pair of substrates at least one of which is transparent and a photocurable compound of the formula (1) is exposed. A method of manufacturing a liquid crystal display device comprising a liquid crystal photocured composite formed by exposing the mixture between the pair of substrates at a temperature at which the nematic liquid crystal exhibits an isotropic state, A first exposure step for forming a liquid crystal fixed region that includes the fixed nematic liquid crystal and whose transmittance does not change depending on a voltage; and after the liquid crystal fixed region is formed, than the first exposure step. By exposing the mixture at a low illuminance and a temperature showing a liquid crystal state, the mixture has almost the same component ratio as the liquid crystal immobilization region, becomes transparent when no voltage is applied, and when a voltage is applied A second exposure step of forming an operating region to be a scattering state, but with a. Thereby, impact resistance can be improved.
_{A 1 - (OR 1) n} -O-Z-O- (R 2 O) m -A 2 ··· Equation (1)
(However, (A ₁ , A ₂ ) is each independently an acryloyl group, a methacryloyl group, a glycidyl group, and an allyl group, R 1 and R 2 are each independently an alkylene group having 2 to 6 carbon atoms, and Z is A divalent mesogen structure, wherein n and m are each independently an integer of 1 to 10 )

  According to the present invention, a liquid crystal display element having high impact resistance can be provided.

  Hereinafter, embodiments to which the present invention can be applied will be described. The following description is to describe the embodiment of the present invention, and the present invention is not limited to the following embodiment. For clarity of explanation, the following description is omitted and simplified as appropriate. Further, those skilled in the art will be able to easily change, add, and convert each element of the following embodiments within the scope of the present invention. In addition, what attached | subjected the same code | symbol in each figure has shown the same element, and abbreviate | omits description suitably.

  The photocurable compound suitable for the present invention will be described. In the present invention, by introducing an oxyalkylene structure having high molecular mobility between the mesogen structure portion and the cured site in the uncured curable compound, the molecular mobility of the cured site in the curing process is improved, Even in a short-time curing reaction, a liquid crystal optical element can be obtained in which the state during application / non-application of the electric field is stable and reliable, and the contrast is high. The chemical formula of this curable compound is shown in Formula (1).

The curing site (A ₁ , A ₂ ) of the chemical formula (1) may be any of the above functional groups that can be photocured and thermally cured together with a curing catalyst, and in particular, the temperature during curing can be controlled. To acryloyl group and methacryloyl group suitable for photocuring. Further, the cured site (A ₁ , A ₂ ) may be a glycidyl group or an allyl group.

The number of carbon atoms of R ₁ and R _{2 in} the oxyalkylene moiety of formula (1) is preferably 2 to 6 independently from the mobility, and further, a chain of ethylene groups having 2 carbon atoms and a propylene group having 3 carbon atoms are preferred. preferable.

  As the mesogen structure part (Z) of the formula (1), divalent polyphenylene in which two or more 1,4-phenylene groups are linked is preferable. Further, a divalent organic group in which a part of the 1,4-phenylene group in the polyphenylene group is substituted with a 1,4-cyclohexylene group may be used.

  Some or all of the hydrogen atoms of these polyphenylene groups and divalent organic groups may be substituted with substituents such as alkyl groups having 1 to 2 carbon atoms, halogen atoms, carboxyl groups, and alkoxycarbonyl groups. Preferred Z is a biphenylene group in which two 1,4-phenylene groups are linked (hereinafter referred to as 4,4′-biphenylene group), a terphenylene group in which three 1,4-phenylene groups are linked, and 1 to 4 of these hydrogen atoms. It is a divalent organic group substituted by an alkyl group having 1 to 2 carbon atoms, a fluorine atom, a chlorine atom or a carboxyl group. Most preferred Z is a 4,4′-biphenylene group having no substituent.

  If n and m in the formula (1) are too large, the compatibility with the liquid crystal is lowered. Therefore, each is independently 1 to 10, and 1 to 4 is more preferable in consideration of element characteristics after curing.

  A mixture of liquid crystal and an uncured curable compound may contain a curing catalyst. In the case of photocuring, a photopolymerization initiator generally used for photocuring resins such as benzoin ether, acetophenone, and phosphine oxide. Can be used.

  The content of the curing catalyst is preferably 20 wt% or less of the uncured curable compound to be contained, and more preferably 1 to 10 wt% when a high molecular weight or high specific resistance of the cured product after curing is required. . Further, a chiral agent can be added to a mixture of liquid crystal and an uncured curable compound in order to improve the contrast of the device when an electric field is applied / not applied.

  In order to improve the compatibility with the liquid crystal, the uncured curable compound in the mixture of the liquid crystal and the uncured curable compound includes a plurality of uncured curable compounds having different n and m in the formula (1). May be included, thereby further improving the contrast.

  On the other hand, the mixture of the liquid crystal and the uncured curable compound is preferably a homogeneous solution after mixing. Moreover, the mixture of a liquid crystal and an uncured curable compound may exhibit a liquid crystal phase when sandwiched between substrates with electrodes. As the liquid crystal, for example, a nematic liquid crystal having a negative dielectric anisotropy can be used. As a suitable example, the mixing ratio of the liquid crystal and the curable compound is 80 to 85 wt% for the liquid crystal and 15 to 20 wt% for the curable mixture. The mass of the liquid crystal is preferably 50% or more of the total mass of the liquid crystal and the curable compound.

  The mixture of liquid crystal and uncured curable compound may exhibit a liquid crystal phase when cured. The function of aligning the liquid crystal on the electrode surface by directly polishing the electrode surface of the substrate with the electrode holding the mixture of liquid crystal and uncured curable compound, or by providing a resin thin film or rubbing it. Can also be granted,

  Further, the combination of the alignment directions of the pair of alignment-treated substrates may be either parallel or orthogonal, and the angle may be set so that the unevenness when the mixture is held is minimized.

  The distance between the electrodes can be held by a spacer or the like, and the interval is preferably 2 to 50 μm, more preferably 4 to 30 μm. When the electrode interval is too small, the contrast is lowered, and when it is too large, the drive voltage is increased.

  The structure of the liquid crystal display element according to the present invention will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing a configuration of a liquid crystal optical element according to the present invention. 1A and 1B are substrates, 2A and 2B are electrodes, 3A and 3B are alignment films, 4 is a composite layer of liquid crystal and a curable compound, 5 is an impact-resistant structure portion, and 6 is a scattering display portion.

  The substrates 1A and 1B that support the electrodes may be, for example, a transparent glass substrate or a resin substrate, or a combination of a glass substrate and a resin substrate. Alternatively, one may be a reflective electrode made of aluminum or a dielectric multilayer film.

  In the case of a film substrate, a substrate with electrodes to be continuously supplied is sandwiched between two rubber rolls, and a mixture of a liquid crystal containing a spacer and dispersed therein and an uncured curable compound is sandwiched between the substrates, and then sandwiched continuously. Productivity is high because it can be cured with

  In the case of a glass substrate, a small amount of spacers are scattered on the electrode surface, and the four sides of the opposed substrate are sealed with a sealing agent such as epoxy resin, and one of the cutouts of the seals provided at two or more locations is liquid crystal A liquid crystal optical element can be obtained by immersing in a mixture of curable compound and uncured curable compound and sucking from the other to fill the cell with the mixture and cure. A vacuum injection method can also be used.

  Patterns of electrodes 2A and 2B are formed on the substrates 1A and 1B. The electrodes 2A and 2B are formed of a transparent conductive film such as ITO. The electrodes 2A and 2B may be patterned corresponding to the display screen. Alignment films 3A and 3B for aligning liquid crystals are provided on the electrodes 2A and 2B, respectively. The alignment films 3A and 3B are respectively formed on the surfaces of the substrates 1A and 1B so as to be in contact with the liquid crystal. It is desirable that at least one of the alignment films 3A and 3B aligns the liquid crystal perpendicular to the substrate surface. Thereby, display characteristics can be improved.

  A composite layer 4 formed by exposing a mixture of liquid crystal and a curable compound is sandwiched between the two substrates. The composite 4 is divided into an impact resistant structure 5 and a scattering display 6. The impact-resistant structural part 5 remains substantially transparent with almost no change in transmittance between when voltage is applied and when voltage is not applied. Therefore, the impact resistant structure 5 becomes a liquid crystal fixing region where the liquid crystal is fixed. On the other hand, the scattering display unit 6 is in a transparent state when no voltage is applied, but the transmittance is changed to be in a scattering state when a voltage is applied. Therefore, the scattering display unit 6 becomes an operation region in which the liquid crystal operates by voltage. Since the impact-resistant structure portion 5 and the scattering display portion 6 are formed by the difference in exposure conditions in the following exposure process, they have substantially the same component ratio.

  When a voltage is applied to the electrodes 2A and 2B, the liquid crystal is randomly oriented by the electric field between the electrodes, and the scattering display unit 6 enters a scattering state. On the other hand, when no voltage is applied to the electrodes 2A and 2B, since the liquid crystal is aligned, the scattering display section 6 is in a transparent state. The transparent scattering display section 6 has substantially the same transmittance as the impact-resistant structure section 5, and the back surface of the liquid crystal display element can be observed. As described above, since the scattering state and the transparent state change depending on whether the voltage is applied or not, a desired image can be displayed according to the pattern of the formed electrodes 2A and 2B.

  A method for manufacturing the above-described liquid crystal display element will be described with reference to FIG. FIG. 2 is a cross-sectional view schematically showing the configuration of the liquid crystal display element in the manufacturing process. 7 is a mask, 8 is an antireflection plate, 9 is a diffusion plate, and 10 is a liquid crystal display element.

  In the liquid crystal display element 10, as shown in FIG. 1, a composite layer 4 of liquid crystal and a curable compound is sandwiched between a pair of substrates. The internal configuration of the liquid crystal display element 10 is the same as that shown in FIG. An exposure mask 7 is provided on the surface side of the liquid crystal display element 10. As a light source for exposure, an ultraviolet light source having a dominant wavelength of 365 nm is used. In the first exposure process, in order to form the pattern of the impact-resistant structure 5, a light beam parallel to the liquid crystal display element 10 is irradiated through the mask 7 as shown in FIG.

  As the mask 7, a normal exposure mask is used. For example, a transparent glass substrate provided with a light shielding pattern corresponding to the pattern of the scattering display portion can be used as the mask 7. Further, a black antireflection plate 8 is provided on the back side of the substrate for preventing the light transmitted through the liquid crystal display element 10 from being reflected. The antireflection plate 8 is a plate formed of a material that absorbs 365 nm as an exposure wavelength. By providing the antireflection plate 8, light transmitted through the liquid crystal display element 10 is absorbed, and therefore, it is possible to prevent the light from being reflected in the direction of the liquid crystal display element 10 and being irradiated outside the pattern of the mask 7. it can. Therefore, a desired pattern can be exposed with high accuracy.

  According to the pattern of the mask 7 described above, the mixture of the portion irradiated with light crosslinks and polymerizes a curable compound as a monomer to form a polymer. The portion irradiated with light becomes the impact resistant structure 5. The impact resistant structure 5 may be transparent or in a scattering state, but is preferably in a transparent state. Furthermore, it is preferable that the impact resistant structure 5 is optically isotropic. That is, the optical characteristics are preferably the same in any direction. In the exposure for forming the impact-resistant structure 5, the exposure is performed in a state where the temperature of the liquid crystal display element 10 is set to 80 ° C., for example. Therefore, since the polymerization reaction proceeds in an isotropic state, the impact resistant structure 5 is formed. The impact resistant structure 5 serves as an impact resistant structure for improving the impact resistance of the liquid crystal display element 10. That is, the impact resistant structure 5 formed by mask polymerization serves as a wall or a column that supports the substrates, and improves the impact resistance of the liquid crystal display element.

  Next, in order to perform the second exposure, the diffusion plate 9 is disposed in front of the liquid crystal display element 10 instead of the mask 7. Further, the antireflection plate 8 is removed. Then, the liquid crystal display element 10 is irradiated with light from the same light source via the diffusion plate 9. Since there is no mask in the second exposure process, the entire surface of the liquid crystal display element 10 is irradiated with light. When irradiated with light, if already polymerized, the curable compound is cross-linked and polymerized except for the impact-resistant structure 5. As a result, the unpolymerized portion is polymerized, and the entire curable compound of the liquid crystal display element 10 becomes a polymer.

  In the second exposure, the exposure is performed in a state where the temperature of the liquid crystal display element 10 is lower than the first exposure temperature. Thereby, since the polymerization reaction proceeds in a liquid crystal state, the scattering display portion 6 is formed. Therefore, the composite layer 4 having different characteristics is formed. The condition for the second exposure can be a condition that places importance on the display characteristics of the liquid crystal display element 10. In this case, it is desirable to perform the second exposure with a lower illuminance than the illuminance in the first exposure step. Further, since the parallel light flux from the light source is uniformly applied to the liquid crystal display element 10 by the diffusion plate 9, the illuminance can be made uniform. Thereby, the display characteristics of the liquid crystal display element 10 can be made uniform.

  The impact resistant structure 5 is formed to support two substrates and improve the impact resistance of the liquid crystal display element 10. The impact resistant structure 5 is also formed in the display area of the liquid crystal display element 10. Since the impact resistant structure 5 maintains a transparent state regardless of whether a voltage is applied or not, the area is preferably small from the viewpoint of the display performance of the liquid crystal display element 10. However, if the area of the impact resistant structure 5 is small, sufficient impact resistance cannot be obtained. Therefore, when the ratio of the scattering display portion 6 in the display area of the liquid crystal display element 10 is an aperture ratio, that is, (scattering display portion) / (impact structure portion + scattering display portion) = aperture ratio, the aperture ratio is 0. It may be 01 to 0.99, and is preferably 0.1 to 0.9. When the aperture ratio is small, there is a usage method in which the whole is transparent and a part is lit. In this case, the liquid crystal display element 10 having high impact resistance can be obtained.

  Furthermore, when considering both display characteristics and impact resistance, it is preferable to set the aperture ratio to about 60 to 85%. If the aperture ratio is less than 60%, the impact-resistant structure portion is visually recognized, and the display characteristics may be deteriorated. On the other hand, if the aperture ratio exceeds 85%, sufficient impact resistance may not be obtained.

  The impact resistance can be improved by patterning so as to create an enclosure surrounding the scattering display portion 6 with the impact resistant structure portion 5. Moreover, impact resistance can be improved by making the shape of the above-mentioned impact resistant structure part 5 into a honeycomb shape as shown in FIG. When the impact resistant structure 5 is formed in a honeycomb shape as shown in FIG. 3, an enclosure surrounding the hexagonal scattering display part 6 is formed by the impact resistant structure 5. By making the impact resistant structure portion 5 into a honeycomb shape, for example, the impact resistance can be improved as compared with the case where the impact resistant structure portion 5 is a lattice-shaped enclosure surrounding the scattering display portion 6. That is, in the honeycomb-shaped and lattice-shaped liquid crystal display elements 10 having the same aperture ratio, the honeycomb-shaped liquid crystal display element 10 has higher impact resistance than the lattice-shaped liquid crystal display element 10. Furthermore, by making the honeycomb shape, the visibility of the impact-resistant structure portion 5 is lowered even with the same aperture ratio, so that display characteristics can be improved. That is, when the impact resistant structure portion 5 is formed in a honeycomb shape, it becomes less visible to an observer, and thus, for example, the appearance is significantly better than the liquid crystal display element 10 having the lattice-like impact resistant structure portion 5.

  Such a honeycomb-like impact resistant structure 5 can be formed based on the pattern of the mask 7. Here, one of the hexagonal light shielding portions was set to 270 μm, and the width of the opening of the mask surrounding the mask was set to 30 μm. As a result, the pattern of the composite layer becomes a honeycomb shape in which 300 μm hexagons as unit patterns are continuous. When the aperture ratio is the same, the impact resistance can be improved as the unit pattern is smaller. That is, even if the aperture ratio is the same, the impact resistance can be improved as the width of the impact resistant structure 5 is narrower. Therefore, from the viewpoint of impact resistance, it is desirable to reduce the width of the impact resistant structure 5 by reducing one honeycomb-shaped hexagon.

  The cross section of the impact resistant structure 5 is not limited to the honeycomb shape. The cross section of the impact resistant structure 5 is preferably, for example, a polygonal continuous joint shape. In the case of a regular hexagon, it has a honeycomb shape as shown in the figure. Further, the cross section of the impact resistant structure 5 may be a shape in which a plurality of circles are joined.

In the first exposure process, a structure having a higher impact resistance at a high temperature and high illuminance can be obtained. However, considering the display characteristics of the liquid crystal display element, it is desirable that the exposure temperature is 80 ° C., which is 3 ° C. higher than the phase transition temperature, and the illuminance is about 10 mW / cm ² . By performing exposure for 10 minutes under the above-described conditions, it is possible to manufacture the liquid crystal display element 10 having excellent impact resistance and display characteristics.

  If the waiting time from the first exposure process to the second exposure process is long, polymerization proceeds and problems such as a phenomenon of display area and unevenness occur. Therefore, it is desirable to perform exposure by changing the temperature within 2 hours as much as possible between the first pattern exposure and the second entire surface exposure. Furthermore, it is desirable that the time be within 1 hour. Moreover, temperature control can be easily performed by mounting a liquid crystal display element on a hot plate, for example.

  As described above, by performing pattern exposure and overall exposure under different conditions, even a composite layer having the same composition can be separated into portions having different functions. When forming portions having such different functions, it is desirable to change the substrate temperature during exposure. Furthermore, portions having different functions can be formed by changing exposure conditions such as illuminance and exposure time.

Example A liquid crystal display element was manufactured by changing the exposure conditions in the first exposure step by the above-described method for manufacturing a liquid crystal display element, and the impact resistance of each liquid crystal display element was tested. Here, in the second exposure process, the test was performed with the temperature of the liquid crystal display element at the time of exposure being 40 ° C., the exposure illuminance being 1 mW / cm ² , and the exposure time being 10 minutes. Further, in the first exposure, exposure was performed using the mask 7 so that the impact-resistant structure portion had a honeycomb shape. An impact resistance test was performed by changing the exposure conditions of pattern exposure. The results of the impact resistance test are as shown in Table 1.

  Here, the impact resistance is the impact of an iron ball (pachinko ball) colliding with the free fall from above the liquid crystal display element, and the haze value of the cloudy part around the impact application point generated by the impact is twice that before the test. Acceleration was calculated and used as an index. The strength of the impact force applied by changing the falling height of the iron ball was changed. Furthermore, the impact force generated by the free fall of the iron ball was quantified as acceleration by an acceleration sensor. By colliding an iron ball through a silicon rubber sheet having a thickness of 1 mm, an impact waveform close to that when a human hit the cell with a fist was obtained. The impact duration was about 500 μsec. In the drop test, in order to approximate the installation state in actual use, the outer peripheral portion of the liquid crystal display element 10 was installed on a metal test stand on the frame, and the impact application point was floated inside.

The pattern exposure exposure conditions of the liquid crystal display element used in the first test were a temperature of 80 ° C., an illuminance of 10 mW / cm ² , and an exposure time of 10 minutes. The liquid crystal display element of the first test had an aperture ratio of 70% and an impact resistance of 1880G. Since the liquid crystal display element manufactured by the conventional method for manufacturing a liquid crystal display element without pattern exposure has an impact resistance of about 500 G in the same impact resistance test, the impact resistance could be improved. Further, even when observed from the front and oblique directions, the boundary between the impact-resistant structure portion and the scattering display portion could not be visually recognized, and thus the display characteristics did not deteriorate.

In the second test, a liquid crystal display element formed with a lower exposure illuminance than the first test was used. Specifically, the pattern exposure conditions were a temperature of 80 ° C., an illuminance of 5 mW / cm ² , and an exposure time of 10 minutes. The liquid crystal display element in the second test had an aperture ratio of 68% and an impact resistance of 1430G. The impact resistance when exposed at 10 mW / cm ² is improved compared to the conventional liquid crystal display element, but even when the aperture ratio is similar to that when exposed at the first 10 mW / cm ² , The impact has become slightly lower. Thus, it is desirable to expose with high illuminance from the viewpoint of impact resistance.

In the third test, exposure was performed in a state where the temperature of the liquid crystal display element 10 was lower than that in the first test. That is, the exposure conditions for pattern exposure were a temperature of 60 ° C., an illuminance of 10 mW / cm ² , and an exposure time of 10 minutes. The liquid crystal display element in the third test had an aperture ratio of 70% and an impact resistance of 800G. Although the impact resistance when the temperature is 60 degrees is improved over the conventional liquid crystal display element, the impact resistance is improved even when the aperture ratio is comparable as compared with the first exposure at 80 ° C. It has become low.

In the fourth test, the exposure time was made longer than in the first test. That is, the exposure conditions for pattern exposure were set to a temperature of 80 ° C., an illuminance of 10 mW / cm ² , and an exposure time of 20 minutes. The liquid crystal display element in the fourth test had an aperture ratio of 63% and an impact resistance of 2000 G or more. The impact resistance when the exposure time was 20 minutes was very good. However, the aperture ratio was lower than that in the first exposure for 10 minutes.

  As described above, in the pattern exposure process, it is desirable to irradiate light at a high temperature and high illuminance for a long time from the viewpoint of impact resistance. However, it is desirable from the viewpoint of the display characteristics of the liquid crystal display element that the aperture ratio is not lowered and the impact resistant structure is not visually recognized. In the above-described curable compound, for example, an exposure temperature of 80 ° C., an illuminance of 10 mW, and a time of 10 minutes are desirable from the viewpoint of both impact resistance and aperture ratio. Of course, pattern exposure may be performed under conditions other than those described above.

  Furthermore, it goes without saying that suitable exposure conditions vary depending on the material and mixing ratio of the liquid crystal and the curable compound. In the present invention, the exposure conditions, the material of the mixture, the mixing ratio, and the like can be selected according to the required impact resistance and aperture ratio. In the manufacturing method described above, the pattern exposure is performed in the first exposure process, but the pattern exposure may be performed in the second exposure process. In this case, for example, the first exposure process is not the entire surface exposure, but the exposure is performed using a mask having a pattern opposite to the pattern exposure. Furthermore, the exposure may be performed not only from one side but also from both sides through a mask.

  In the manufacturing method of the liquid crystal display device described above, the exposure is performed twice, but the exposure may be performed in three or more exposure steps. It is also possible to form the composite layer 4 having three or more different characteristics by exposing three or more times.

It is sectional drawing which shows the structure of the liquid crystal display element concerning this invention. It is sectional drawing which shows the process of the liquid crystal display element in the manufacturing process of the liquid crystal display element concerning this invention. It is a top view which shows the structure of the composite layer of the liquid crystal display element concerning this invention.

Explanation of symbols

1A substrate 1B substrate 2A electrode 2B electrode 3A orientation film 3B orientation film,
4 Composite layer 5 Impact resistant structure 6 Scattering display 7 Mask 8 Anti-reflection plate 9 Diffusion plate
10 Liquid crystal display elements

Claims (10)

A liquid crystal display element comprising a liquid crystal photocured composite formed by exposing a mixture of a nematic liquid crystal sandwiched between a pair of transparent substrates at least one and a photocurable compound of formula (1) There,
The liquid crystal photocured composite is
An operating region that becomes transparent when no voltage is applied, and is in a scattering state when voltage is applied,
A liquid crystal display element comprising: a liquid crystal fixed region having the same component ratio as that of the operation region and including the nematic liquid crystal fixed to the polymer of the photocurable compound and having a transmittance that does not change depending on voltage.
_{A 1 - (OR 1) n} -O-Z-O- (R 2 O) m -A 2 ··· Equation (1)
(However, A ₁ and A ₂ are each independently an acryloyl group, a methacryloyl group, a glycidyl group, and an allyl group, R 1 and R 2 are each independently an alkylene group having 2 to 6 carbon atoms, and Z is a divalent group. And n and m are each independently an integer of 1 to 10. )   2. The liquid crystal display element according to claim 1, wherein an area of the operation region is 60% or more and 85% or less of a total area of the liquid crystal fixing region and the operation region in the display region. The liquid crystal has negative dielectric anisotropy;
The liquid crystal display element according to claim 1, wherein an alignment film for aligning the liquid crystal perpendicularly to the substrate surface is provided on a surface of at least one substrate.   4. The liquid crystal display element according to claim 1, wherein the liquid crystal immobilization region is formed by pattern exposure from substantially the same composition as the mixture.   5. The liquid crystal display element according to claim 1, wherein a mass of the liquid crystal in the liquid crystal immobilization region is 50% or more with respect to a total mass of the liquid crystal and the photocurable compound.   The liquid crystal display element according to claim 1, wherein the transmittance of the liquid crystal immobilization region is 50% or more.   The liquid crystal display element according to claim 1, wherein the liquid crystal immobilization region is optically isotropic.   The liquid crystal display element according to any one of claims 1 to 4, wherein the liquid crystal fixing region has a polygonal continuous bonding shape.   The liquid crystal display element according to claim 8, wherein the polygon is a regular hexagon. A liquid crystal display element comprising a liquid crystal photocured composite formed by exposing a mixture of a nematic liquid crystal sandwiched between a pair of substrates at least one of which is transparent and a photocurable compound of formula (1) A manufacturing method comprising:
A liquid crystal immobilization region including the nematic liquid crystal immobilized by pattern exposure of the mixture between the pair of substrates at a temperature at which the nematic liquid crystal exhibits an isotropic state and having a transmittance that does not change depending on voltage. A first exposure step to form;
After the liquid crystal immobilization region is formed, the mixture is exposed at a temperature lower than that of the first exposure step and showing a liquid crystal state, thereby having substantially the same component ratio as the liquid crystal immobilization region. And a second exposure step of forming an operation region that is transparent when no voltage is applied and is in a scattering state when a voltage is applied.
_{A 1 - (OR 1) n} -O-Z-O- (R 2 O) m -A 2 ··· Equation (1)
(However, (A ₁ , A ₂ ) is each independently an acryloyl group, a methacryloyl group, a glycidyl group, and an allyl group, R 1 and R 2 are each independently an alkylene group having 2 to 6 carbon atoms, and Z is A divalent mesogen structure, wherein n and m are each independently an integer of 1 to 10 )

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