JP2007188066A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of effectively suppressing light leakage even when a liquid crystal can not completely maintain a homeotropic alignment state but is fixed. <P>SOLUTION: The liquid crystal display device 1 includes substrates (3, 4) opposing to each other to sandwich a liquid crystal layer 2 containing a liquid crystal with a variable alignment state, and a first polarizing plate 5 and a second polarizing plate 6 interposing the opposing substrates with the absorption axes of the polarizing plates intersecting orthogonal to each other, wherein a birefringent layer 7 is formed by polymerizing a polymerizable liquid crystal with an optical axis inclined with respect to the thickness direction of the birefringent layer 7 between the first polarizing plate 5 and the second polarizing plate 6. Since the optical axis of the birefringent layer 7 is inclined in the direction of the absorption axis of either the first polarizing plate 5 or the second polarizing plate 6 with respect to the thickness direction of the layer 7, the liquid crystal display device 1 can effectively suppress light leakage even when the liquid crystal can not completely maintain a homeotropic alignment state but is fixed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device in which a birefringence layer is formed.

  Liquid crystal display devices (LCDs) are used in various fields such as televisions and medical devices because they have advantages such as being easy to reduce the thickness and weight, reducing power consumption, and preventing flicker. However, depending on the angle at which the user views the liquid crystal display screen, light leakage and gradation inversion occur, and the viewing angle is narrow. In addition, the liquid crystal display screen has uneven color and contrast. We had problems such as decline.

In order to solve these problems, a liquid crystal display device provided with an optical element for controlling the state of light emitted from the liquid crystal cell and light incident on the liquid crystal cell has been proposed.
In that case, as an optical element, in addition to a film material obtained by subjecting a triacetyl cellulose (TAC) film to uniaxial stretching or biaxial stretching treatment, an optical element using a layer in which liquid crystal molecules are aligned and fixed in a specific direction is proposed. ing.

  Patent Document 1 proposes a viewing angle compensation film made of a nematic liquid crystal polymer having a positive intrinsic refractive index value in which molecular chains are aligned in the normal direction of the film surface. In Patent Document 1, this viewing angle compensation film is formed by forming a vertical alignment film on the surface of a glass substrate or the like with an alkyl silicone type or fluoroalkyl silicone type surface treatment agent, thereby producing a cell, and liquid crystal in the cell. It is disclosed that it is obtained by encapsulating molecules and photopolymerizing liquid crystal molecules.

  Patent Document 2 proposes a method of manufacturing a liquid crystal layer in which a liquid crystal compound is homeotropically aligned by coating a polymerizable liquid crystal compound on a vertical alignment film formed on a substrate. In this method, a long-chain alkyl type dendrimer derivative is used as a vertical alignment film forming agent. Patent Document 2 discloses that according to this method, a film material having a homeotropically aligned liquid crystal layer is obtained, and the film material can be used as an optical film such as a retardation film. ing.

  Patent Document 3 discloses a side chain type liquid crystal polymer containing a monomer unit containing a liquid crystalline fragment side chain and a monomer unit containing a non-liquid crystalline fragment side chain on a substrate not provided with a vertical alignment film. A method has been proposed in which a homeotropic alignment liquid crystal film is produced by coating, further aligning the liquid crystal polymer in a homeotropic state in a liquid crystal state, and then fixing the liquid crystal polymer in a state in which the alignment state is maintained.

  In Patent Document 4, a binder layer and then an anchor coat layer are formed from a substrate side on a substrate not provided with a vertical alignment film, and a side chain type liquid crystal polymer is applied to the anchor coat layer to cause homeotropic alignment. After that, a method for producing a homeotropic alignment liquid crystal film by fixing the homeotropic alignment state is proposed. In this method, as the side chain type liquid crystal polymer, one capable of forming a homeotropic alignment liquid crystal layer on a substrate not provided with a vertical alignment film is used.

JP-A-5-142531 JP 2002-174724 A JP 2002-174725 A JP 2003-121852 A

  However, the viewing angle compensation film of Patent Document 1 is a cell produced by using two substrates having an alignment film, liquid crystal molecules are enclosed in the empty cell, the liquid crystal molecules are vertically aligned, and the state is maintained. The liquid crystal molecules are obtained after a series of steps of photopolymerizing each other. Thus, since the viewing angle compensation film of Patent Document 1 is finally obtained through many manufacturing steps, there is a problem that the production cost is remarkably increased. Moreover, since the visual compensation film is a film material, it must be fixed with an adhesive when used in a liquid crystal display device, and a special one is selected as this adhesive to increase the contrast of the liquid crystal screen of the liquid crystal display device. There is a need to.

  In the method of Patent Document 2, it is necessary to use a special material called a long-chain alkyl-type dendrimer derivative in order to obtain a homeotropic alignment liquid crystal layer by providing a vertical alignment film on a substrate. Then, when obtaining a homeotropic alignment liquid crystal layer by this method, there is a problem that the production cost is remarkably increased.

The homeotropic alignment liquid crystal film obtained by the method described in Patent Document 3 is composed of a side-chain liquid crystal polymer, and its fluidity increases as the temperature rises even if it is fixed in a homeotropic alignment state. Since the characteristics are easily affected, the temperature range in which the desired birefringence characteristics can be maintained is relatively narrow, and the orientation of the liquid crystal polymer in the portion where the liquid crystal polymer is fixed tends to be nonuniform. Then, the homeotropic alignment liquid crystal film obtained by this method is difficult to use in a liquid crystal display device that requires high heat resistance, and the liquid crystal display devices that can use this liquid crystal film are limited. Further, this method has the same problem as the method described in Patent Document 1 described above.

  Further, when the homeotropic alignment liquid crystal film obtained by this method is used for a liquid crystal display device, it is necessary to prevent the film from being placed in a high temperature environment. Difficult to do. For this reason, the homeotropic alignment liquid crystal film obtained by the method of Patent Document 3 also has a problem that the position where it can be installed in the liquid crystal cell is limited.

Since the homeotropic alignment liquid crystal film obtained by the method described in Patent Document 4 is composed of a side chain type liquid crystal polymer, this method has the same problem as the method described in Patent Document 3 described above. . Further, this method has the same problem as the method described in Patent Document 1 described above.

  Further, when a homeotropic alignment liquid crystal film obtained by the method described in Patent Documents 1 to 4 is laid on the liquid crystal display device to increase the viewing angle of the liquid crystal screen, the liquid crystal display device separates such a film. It is necessary to attach a new body using an adhesive material or the like. The greater the need to add a separate body, the greater the risk that a member that reflects light somewhat will be arranged. As a result, the liquid crystal display device has a large possibility that the color unevenness of the liquid crystal display screen becomes large or the contrast is lowered.

Further, in such a homeotropic alignment liquid crystal film, liquid crystal molecules are fixed and held in a homeotropic alignment state by applying some method such as a polymerization reaction to the liquid crystal molecules. However, it is difficult to maintain the homeotropic alignment state when fixing the liquid crystal in a state in which the liquid crystal is almost completely homeotropically aligned, and the liquid crystal molecules are in an alignment state having an inclination with respect to the homeotropic alignment state. There is a problem of becoming.
In such a case, the homeotropic alignment liquid crystal film has an optical axis inclined with respect to the thickness direction of the film surface, which causes light leakage during black display on the liquid crystal display screen.

  Therefore, even when the birefringence layer in which the liquid crystal is completely homeotropically aligned is not formed, the liquid crystal display screen can prevent light leakage and display black, and suppress the occurrence of color unevenness. A liquid crystal display device with improved contrast has been studied and the present invention has been completed.

  An object of the present invention is to provide a liquid crystal display device capable of effectively suppressing light leakage even when a liquid crystal is fixed without being completely maintained in a homeotropic alignment state.

  The present invention includes (1) a substrate that is opposed to a liquid crystal layer containing a liquid crystal having a variable orientation state, and the first polarizing plate and the second polarizing plate are orthogonal to each other with the absorption axes orthogonal to each other with the opposing substrate interposed therebetween. In the liquid crystal display device, the birefringence layer is formed by polymerizing polymerizable liquid crystal between the first polarizing plate and the second polarizing plate, and the birefringence layer. The optical axis of the birefringent layer is the first polarizing plate or the second polarizing plate with respect to the thickness direction of the birefringent layer. (2) The birefringence layer is formed by polymerizing a polymerizable liquid crystal in a homeotropic alignment state (1). The liquid crystal display device according to (3), (3) the birefringent layer is obtained by three-dimensionally cross-linking polymerizing liquid crystal having a rod-like molecular shape The liquid crystal display device according to the above (1) or (2), (4) the optical axis of the birefringent layer is uniformly inclined over the entire surface of the birefringent layer (1) to (3) (5) The liquid crystal display device according to any one of (1) to (4), wherein the birefringent layer is laminated between opposing substrates, (6) The liquid crystal display device according to any one of (1) to (5) above, wherein a colored layer is formed on at least one of the opposing substrates, and (7) a birefringence layer is formed on the colored layer surface. The liquid crystal display device according to (6) above, (8) the colored layer is provided with colored pixels that are arranged in a stripe arrangement pattern and transmit light of a predetermined wavelength, and the first polarization The direction of the absorption axis of either the plate or the second polarizing plate is in the longitudinal direction of the striped colored pixel The liquid crystal display device according to the above (7), (9) a birefringence in which a different birefringence layer having an optical axis different from the birefringence layer having an inclined optical axis has an inclined optical axis. The liquid crystal display device according to any one of (1) to (8) formed between the layer and the first polarizing plate, and (10) a birefringence layer having an inclined optical axis formed a colored layer. A birefringence layer formed between the substrate and the liquid crystal layer and having an optical axis different from the birefringence layer having an inclined optical axis is formed between the substrate on which the colored layer is formed and the first polarization The liquid crystal display device according to any one of (6) to (8) formed between the plates, (11) the optical axis of the different birefringence layer is the absorption of the first polarizing plate or the second polarizing plate. The liquid crystal display device according to (9) or (10), wherein the direction and the direction of the axis are aligned, and (12) a different birefringence layer Is summarized in the liquid crystal display device according to any one of (9) to (11) above, which includes a film material.

  According to the liquid crystal display device of the present invention, since the optical axis of the birefringent layer is inclined in the absorption axis direction of the first polarizing plate or the second polarizing plate with respect to the thickness direction, the polymerizable liquid crystal Even when the polymerizable liquid crystal is in an incomplete homeotropic alignment state in the birefringent layer formed by polymerization reaction of the birefringent layer with respect to the thickness direction of the birefringent layer during black display It is possible to prevent light leakage, and it is also possible to prevent a decrease in front contrast.

  According to the liquid crystal display device of the present invention, a polymerizable liquid crystal is polymerized on a substrate surface to form a birefringent layer, whereby the birefringent layer is manufactured separately and pasted using an adhesive or the like. This eliminates the need to reduce the interfacial reflection of the light due to the multilayering due to the presence of a layer such as an adhesive, and further suppress the decrease in front contrast. In this case, the liquid crystal display device can form the birefringence layer by three-dimensionally cross-linking the polymerizable liquid crystal, so that the structure of the birefringence layer can be further strengthened. .

  According to the liquid crystal display device of the present invention, the birefringence layer may be formed by crosslinking polymerization of a thermotropic liquid crystal that can be polymerized by irradiation with ultraviolet rays. The orientation is hardly affected by heat, and for example, a liquid crystal display device applicable to an optical apparatus used in an environment where the temperature tends to be relatively high such as in a car can be obtained.

  According to the liquid crystal display device of the present invention, the molecules of the polymerizable liquid crystal form a uniformly tilted alignment state, that is, the optical axis of the birefringent layer is uniformly tilted over the entire surface. A difference in position on the refractive index layer surface makes it difficult to produce a difference in the ability to suppress light leakage in the thickness direction of the birefringence layer, and light leakage from the liquid crystal display device can be suppressed evenly.

  Furthermore, according to the liquid crystal display device of the present invention, the polarizing plate is birefringent in the step of arranging the polarizing plate or the like so as to sandwich the substrate by forming the birefringent layer between the opposing substrates. The possibility of colliding with the refractive index layer is suppressed, and the possibility that the birefringent layer is damaged is suppressed.

  In the liquid crystal display device of the present invention, a colored layer may be laminated on at least one of the opposing substrates, and a birefringent layer may be laminated on the colored layer surface. In this case, according to this liquid crystal display device, the birefringent layer does not need to be laminated with an adhesive as a separate retardation film or the like, and the adhesive is provided between the colored layer and the birefringent layer. Since it is possible to form a liquid crystal display device without forming a layer such as, the number of interfaces between different members such as the interface between the retardation film and the adhesive layer can be reduced, and the colored layer and birefringence can be reduced. It is possible to suppress the occurrence of interface reflection for light traveling between the rate layers.

  The liquid crystal display device of the present invention has a birefringence layer as a birefringence layer having a different optical axis between the substrate on which the colored layer is formed and the liquid crystal layer and between the substrate on which the colored layer is formed and the polarizing plate. A layer and a heterobirefringence layer may be provided. In particular, a different birefringence layer is formed between the substrate on which the colored layer is formed and the polarizing plate, and this is a so-called + A plate, and the birefringence is formed between the substrate on which the colored layer is formed and the liquid crystal layer. If a layer is formed and this is a so-called + C plate, light leakage from the liquid crystal display device can be more efficiently reduced.

The liquid crystal display device of the present invention (referred to as the liquid crystal display device of the first embodiment) will be described in detail.
FIG. 1 is a schematic explanatory diagram for explaining a liquid crystal display device of the present invention.
FIG. 2 is a schematic explanatory diagram for explaining the relationship between the absorption axis direction of the polarizing plate and the refractive index ellipsoid of the birefringent layer in the liquid crystal display device of the present invention when viewed in the F direction of FIG.
As an example of the liquid crystal display device according to the first aspect, a case where a birefringence layer is formed on one of opposing substrates will be described.

The liquid crystal display device 1 includes a first substrate 3 and a second substrate 4 (hereinafter sometimes simply referred to as a substrate) that are opposed to each other with a liquid crystal layer 2 (sometimes referred to as a driving liquid crystal layer) interposed therebetween. A first polarizing plate 5 and a second polarizing plate 6 are disposed between the first substrate 3 and the second substrate 4 (on the outer surface of the substrate). A birefringent layer 7 is formed between the polarizing plate 6 and the polarizing plate 6.
In the liquid crystal display device, the inner side surface and the outer side surface are the inner and outer surfaces specified in accordance with the definition of the inner and outer directions when the inner and outer directions are directed from the side closer to the liquid crystal layer 2 to the far side. To do.

  The first substrate 3 and the second substrate 4 include a layer made of a light-transmitting base material and have a multilayer structure in which a large number of base materials are stacked even if the first substrate 3 and the second substrate 4 have a structure made of a single base material layer. Even if comprised, it may be comprised by laminating | stacking the functional layer provided with the predetermined function on the layer which consists of base materials. In the substrate, functional layers may be formed on both sides of the base material, or functional layers may be formed on one side of the base material.

  The light transmittance of the substrate can be appropriately selected. The base material may be partially provided with a light shielding region or the like.

As a base material, the plate-shaped body which consists of various materials other than a glass substrate (glass material) can be selected suitably. Specifically, for example, a non-flexible member (rigid material) such as quartz glass, borosilicate glass, or synthetic quartz plate, or a flexible member (flexible material) such as a resin film or a resin plate is used. it can.
In addition, when using a base material for a liquid crystal display device, it is preferable that a base material is an alkali free glass.

  When the substrate is a member using a resin such as a resin film or a resin plate, the resin used for the substrate is specifically a polyester polymer such as polycarbonate polymer, polyarylate or polyethylene terephthalate (PET). Molecules, polyimide polymers such as polyimide and polyamideimide, polysulfone polymers, polyethersulfone polymers, polystyrene polymers, polyolefin polymers such as polyethylene and polypropylene, polyetherketone polymers, polyvinyl alcohol Examples thereof include thermoplastic polymers such as polymers, cellulose acetate polymers, polyvinyl chloride polymers, polymethyl methacrylate polymers, triacetyl cellulose (TAC) films, and liquid crystal polymers.

Moreover, as a base material, what uniaxially stretched or biaxially stretched the resin film which consists of resin mentioned above may be used.
In this case, it is preferable that the resin film is a film made of polyethylene terephthalate from the viewpoints of a wide range of stretch ratio and availability.

  The functional layer is a layer having a function of changing the state of light, and is a layer having a different configuration from the birefringence layer 7, a colored layer, a layer made of cholesteric liquid crystal in which the orientation of the liquid crystal is fixed, light Specific examples include a reflecting plate, a polarizing plate, and the like that reflect the light. Moreover, the functional layer may be provided not only on the entire surface of the substrate but also partially on the surface of the substrate.

  Further, the functional layer may be an alignment film such as a horizontal alignment film that horizontally aligns liquid crystal molecules constituting the liquid crystal layer 2 or a vertical alignment film that vertically aligns liquid crystal molecules.

  As the alignment film, polyimide, polyamide, polyvinyl alcohol or the like is usually used. When polyimide is used as the alignment film, it must have a long-chain alkyl group. When the liquid crystal molecules are fixed and the birefringence layer is formed on the substrate, the thickness of the birefringence layer is reduced. A wide range can be selected, which is preferable.

  The alignment film is prepared by adjusting the film composition liquid constituting the alignment film, and applying the film composition liquid on the substrate surface by a method such as flexographic printing or spin coating to form a coating film. It can be formed by curing. Examples of membrane composition liquids include polyimides such as SE-7511 and SE-1211 manufactured by Nissan Chemical Co., Ltd., JALS-2021-R2 manufactured by JSR, QL and LX manufactured by Hitachi Chemical DuPont Microsystems, etc. The Rixon aligner made by Chisso Co., Ltd. or the like can be specifically exemplified.

  The alignment film preferably has a thickness in the range of about 0.01 to 1 μm. If the film thickness of the alignment film is less than 0.01 μm, it may be difficult to impart desired alignment to the liquid crystal contained in a layer such as a birefringence layer in contact with the alignment film. Further, if the thickness of the alignment film is greater than 1 μm, the alignment film itself may diffusely reflect light, and the light transmittance of the liquid crystal display device may be greatly reduced.

  The first polarizing plate 5 and the second polarizing plate 6 (sometimes simply referred to as a polarizing plate) are those polarizing plates 5 and 6 as shown in FIGS. 1 and 2A and 2B. Is disposed so that the absorption axes P1 and P2 of the polarizing plates 5 and 6 are orthogonal to each other when viewed in the thickness direction of the birefringent layer 7 (when viewed in the direction of arrow F in FIG. 1). In this case, the transmission axes of the polarizing plates 5 and 6 are formed perpendicularly to the absorption axes P1 and P2 on the polarizing plate surface, respectively. That is, the first polarizing plate 5 and the second polarizing plate 6 are arranged in crossed Nicols.

  In FIG. 1, the birefringence layer 7 is formed between the first substrate 3 and the liquid crystal layer 2.

  The birefringent layer 7 is a polymer obtained by polymerizing liquid crystal molecules in a homeotropic alignment with liquid crystal molecules (sometimes referred to as polymerizable liquid crystals) that are polymerizable and have a slightly elongated molecular shape. Provide structure. In this case, the polymer structure may form a three-dimensional structure (crosslinked polymer structure) by crosslinking polymerization of polymerizable liquid crystal molecules.

  As the polymerizable liquid crystal, any of monomers, oligomers, and polymers of polymerizable liquid crystal may be used, and these may be used in appropriate combination.

  In the crosslinked polymer structure of the birefringence layer 7, the degree of crosslinking of the liquid crystal molecules is preferably about 80 or more, and more preferably about 90 or more. If the degree of crosslinking of the liquid crystal molecules is less than 80, there is a possibility that uniform orientation cannot be sufficiently maintained.

  The birefringence layer 7 has a birefringence characteristic (birefringence characteristic) according to the refractive index anisotropy of the liquid crystal molecules constituting the birefringence layer and its alignment state. Using the refractive index ellipsoid A, it is specified according to the state of the refractive index ellipsoid A (FIG. 1).

  The state of the refractive index ellipsoid A can be specified at each position on the surface of the birefringent layer 7. The state of the refractive index ellipsoid A representing the birefringence characteristics in the birefringent layer 7 is approximately the average of the states of the refractive index ellipsoid A specified for each preselected position of the birefringent layer 7. It can be specified as a state.

  For example, the average state of the refractive index ellipsoid A is selected by selecting a plurality of different positions on the birefringence layer surface to be the measurement target positions (measurement positions) of the refractive index ellipsoid, and the refraction at each measurement position. It is specified by measuring and averaging the state of the rate ellipsoid A.

Here, the state of the refractive index ellipsoid A is shown by the shape of the refractive index ellipsoid A and the inclined state of the refractive index ellipsoid A.

  The refractive index ellipsoid A has a z-axis (indicated by z in FIG. 1) in the thickness direction of the birefringent layer 7 and an x-axis and a y-axis on a plane having the z-axis as a normal line. When a space specified by the x-axis, y-axis, and z-axis is considered by intersecting them (indicated by x and y in FIG. 1) at right angles to each other and intersecting the z-axis, the space In the figure, it is specified as an ellipsoid corresponding to the value of the refractive index (indicated by nx, ny, nz in FIG. 1). The refractive indexes nx, ny, and nz are assumed to be birefringent layers when the optical axes of the liquid crystal molecules constituting the birefringent layer 7 are parallel (aligned) with the z-axis direction. It is specified as the refractive index of light in the x-axis, y-axis, and z-axis directions in the index layer. In this space, the x-axis and the y-axis are designated so as to overlap with the absorption axes P1 and P2 of the polarizing plates 5 and 6, respectively, when viewed from the z-axis direction.

  The inclination state of the refractive index ellipsoid A in the space is specified by the inclination state of the major axis a (indicating the optical axis), and the inclination state of the major axis a is indicated by the inclination angle (indicated by φ in FIG. 1). And an azimuth angle (indicated by θ in FIG. 2). Here, the inclination angle φ is an angle formed by the major axis a of the refractive index ellipsoid A and the z axis. Further, the azimuth angle θ is viewed from the first polarizing plate 5 to the second polarizing plate 6 in the z-axis direction (in the F direction) while viewing the long axis a when the value of the inclination angle φ is other than zero. The rotation angle necessary for rotating the refractive index ellipsoid A counterclockwise around the z axis and superimposing the major axis a on the x axis (the absorption axis P1 of the first polarizing plate 5) is shown.

  In the birefringent layer 7, the value of the inclination angle φ of the refractive index ellipsoid A is ideally 0 (zero), but the liquid crystal molecules are arranged in the birefringent layer 7 in the thickness direction (FIG. 1). In such a case, the birefringence layer 7 has a tilt angle φ of a value other than zero, and the optical axis tilted with respect to the thickness direction is inclined. Will have.

  Thus, when the inclination angle φ of the birefringent layer 7 is a value other than zero, the birefringent layer 7 has the major axis a (optical axis) of the refractive index ellipsoid A when viewed in the thickness direction. The first polarizing plate 5 and the second polarizing plate 6 are oriented in the same direction (aligned) as one of the absorption axes P1 and P2 (FIGS. 2A and 2B). )). That is, the approximate value of the azimuth angle θ of the major axis a in the refractive index ellipsoid A of the birefringent layer 7 is one of 0 °, 90 °, 180 °, and 270 °.

The birefringence layer 7 corresponds to the birefringence characteristics and can cause retardation with respect to light (incident light) incident on the birefringence layer 7. Retardation is an optical path difference between ordinary light and extraordinary light generated with respect to incident light, and the magnitude of retardation (retardation value) is birefringence Δn (no) when the refractive index no of ordinary light and the refractive index ne of extraordinary light are used. And the difference between ne and ne) and d (film thickness of the birefringent layer 7). Here, the correspondence between the values of no and ne and the values of nx, ny and nz are no = nx = ny and ne = nz.
Therefore, in the birefringence layer 7, when the birefringence characteristics are controlled by appropriately selecting the type of liquid crystal molecules, the degree of orientation of the liquid crystal molecules, the film thickness of the birefringence layer 7, etc., this is handled. The size of the retardation is controlled.

  The magnitude | size of retardation can be measured using commercially available measuring apparatuses, such as RETS-1250VA (made by Otsuka Electronics) and KOBRA-21 (made by Oji Scientific Instruments). In this case, the retardation is measured by irradiating the birefringent layer with incident light having a specific wavelength. The measurement wavelength is preferably in the visible region (380 to 780 nm), and particularly has the highest specific luminous efficiency. It is more preferable to measure at around 550 nm.

  In the birefringence layer 7, from the viewpoint of obtaining the birefringence layer 7 in which the liquid crystal molecules are brought closer to the homeotropic alignment state more uniformly, the size of the retardation is 1 nm or less. Is preferably 0.1 nm or less, and ideally zero.

  The film thickness of the birefringent layer 7 is preferably selected as appropriate within a range in which liquid crystal molecules can be homeotropically aligned, specifically within a range in which the retardation in the thickness direction is 1 nm or less. Is more preferably selected within a range of about 0.1 nm or less.

  The birefringent layer 7 preferably has substantially the same gradient state of the refractive index ellipsoid at different positions on the surface thereof, and has a small variation in the gradient state of the refractive index ellipsoid. Specifically, the variation in the inclination angle of the refractive index ellipsoid at each position is preferably within a range of about 2 °. In such a case, when the liquid crystal display device is viewed from a direction other than the front direction (F direction) during black display, the light leakage may be slightly uneven, or the optical compensation may be uneven even when other than black display. When the range of variation exceeds 2 °, there is a risk that such unevenness can be recognized with the naked eye.

  When the birefringent layer 7 is formed on the vertical alignment film, the liquid crystal molecules contained in the birefringent layer 7 are strongly homeotropically aligned (tilt angle φ) as long as the molecules are close to the vertical alignment film. Is approximately 0). Further, when the liquid crystal molecules are located away from the vertical alignment film, the homeotropic alignment is weakened. Therefore, if the liquid crystal molecules located away from the vertical alignment film 7 are also strongly homeotropically aligned, The birefringent layer 7 has a uniform tilt angle of the liquid crystal molecules, and the liquid crystal molecules are uniformly homeotropically aligned.

  In the birefringence layer 7, the tilt angle of the liquid crystal molecules that are the units constituting the crosslinked polymer structure, the tilt angle of the liquid crystal molecules that is closest to the interface with the vertical alignment film of the birefringence layer 7, It is preferable that the tilt angle of the liquid crystal molecules located farthest in the thickness direction of the birefringence layer with respect to the liquid crystal molecules is substantially equal. In this case, the tilt angle of each liquid crystal molecule in the birefringence layer 7 is approximately uniform in the thickness direction. In such a case, the birefringence layer 7 can easily make the birefringence characteristics uniform in the surface direction, and can easily suppress unevenness in the ability to suppress light leakage.

  The birefringent layer 7 preferably has the tilt angles of the liquid crystal molecules in the birefringent layer 7 equal to each other in the plane direction, and is equal throughout the entire birefringent layer 7. More preferred. In such a case, the state of the refractive index ellipsoid A is approximately the same at different positions on the surface of the birefringent layer 7, and the birefringence characteristics of the birefringent layer 7 are uniform in the surface direction. . That is, the optical axis of the birefringent layer 7 is substantially uniform regardless of the position on the birefringent layer 7 surface. As a result, unevenness in the ability to suppress light leakage according to the position on the surface of the birefringent layer 7 is less likely to occur.

  In the birefringent layer 7, the azimuth angle θ of the optical axis of the birefringent layer A is approximately one of 0 °, 90 °, 180 °, and 270 ° as described above. In some cases, the azimuth of the optical axis of each liquid crystal molecule contained in the birefringence layer 7 is uniformly approximately 0 °, 90 °, 180 °, or 270 ° regardless of the position of the liquid crystal molecules. Value (first case), and the azimuth of the optical axis of the liquid crystal molecules is approximately 0 °, 90 °, 180 °, or 270 ° for liquid crystal molecules with different positions. The azimuth angle θ of the optical axis of the birefringence layer 7 as a whole is one of the above values. (The second case), and the birefringence layer 7 may be equivalent to the first case even if it corresponds to the first case. It may correspond to the scan, but preferably corresponds to the first case.

  Further, in both cases of the first case and the second case, the variation in the tilt state of the optical axis of the liquid crystal molecules is approximately the above values of 0 °, 90 °, 180 °, and 270 °. In contrast, it is preferable that the azimuth angle of the liquid crystal molecules is within a range of 2 °. In the first case, taking the case where the azimuth angle of the optical axis of the liquid crystal molecules is uniformly approximately 0 ° as an example, all the liquid crystal molecules in the birefringence layer 7 are all selected even if the liquid crystal molecules exist. It is preferable that the azimuth angle of the optical axis of the liquid crystal molecules is within the range of 2 ° before and after 0 ° at the position. Further, in the second case, when the major axis a of the refractive index ellipsoid A of the birefringent layer 7 is oriented in the same direction as the absorption axis P1 of the first polarizing plate 5, the optical axis of the liquid crystal molecules. Is approximately 0 ° or 180 °, and the major axis a of the refractive index ellipsoid A of the birefringent layer 7 is the same as the direction of the absorption axis P 2 of the second polarizing plate 6. When the direction is directed, the approximate value of the azimuth angle of the optical axis of the liquid crystal molecules is 90 ° or 270 °, and it is preferable that each value of the azimuth angle is within a range of 2 ° before and after. . For example, in the second case, when the azimuth angle of the liquid crystal molecules is a combination of approximately 0 ° and 180 °, all the positions of the birefringence layer 7 may be selected even if many are selected as the positions of the liquid crystal molecules. In this case, the azimuth angle of the optical axis of the liquid crystal molecules is preferably in the range of 2 ° before and after 0 ° or in the range of 2 ° before and after 180 °.

  The state of the optical axis of the birefringent layer 7 is approximately the average state of the optical axis specified for each position selected in advance on the surface of the birefringent layer 7 as described above (optical axis). Can be defined as an average value of values such as φ, θ, etc.), but the inclined state of the optical axis of the birefringent layer 7 at different positions on the surface of the birefringent layer 7 is substantially the same. In this case, the tilt state of the optical axis measured at one place on the surface of the birefringence layer 7 can indicate the tilt state of the optical axis of the birefringence layer 7.

  In addition, regarding the tilted state of the optical axis of the liquid crystal molecules at different positions in the birefringence layer 7, the tilted state of the optical axis (the state of the optical axis determined by the tilt angle, the azimuth angle, and the refractive index) is an average state. In these states, the tilt state of the optical axis of the liquid crystal molecules of the birefringent layer 7 can be defined. Specifically, the azimuth angle of the optical axis of the liquid crystal molecules contained in the birefringent layer 7 has two values of 0 ° and 180 ° selected from 0 °, 90 °, 180 °, and 270 °. Taking such a case as an example, the tilted state of the optical axis of the liquid crystal molecules of the birefringent layer 7 can be specifically defined as a state in which the azimuth is a combination of 0 ° and 180 °. it can.

As the liquid crystal molecules constituting the birefringent layer 7, those having an unsaturated double bond in the molecular structure and capable of being crosslinked in a liquid crystal state are used. Accordingly, a polymerizable liquid crystal having an unsaturated double bond at the end of the molecule is used.
The liquid crystal molecules preferably have a birefringence Δn of about 0.03 to 0.20, more preferably about 0.05 to 0.15. Specific examples of such liquid crystal molecules include compounds represented by the following formulas 1 to 11. From the viewpoint of heat resistance, those capable of three-dimensional crosslinking are preferred, and those having two or more unsaturated double bonds at the molecular ends are used.
Furthermore, as the liquid crystal molecules constituting the birefringence layer 7, a plurality of types of compounds represented by the following chemical formulas (Chemical Formula 1) to (Chemical Formula 11) may be selected.

（なお、Xは、４から６の整数である。）

(X is an integer from 4 to 6.)

  The birefringence layer 7 is not limited to the case where it is formed by polymerizing liquid crystal molecules over the entire surface of the vertical alignment film, but is patterned on the vertical alignment film using various printing methods or photolithography methods. It may be formed.

  In the liquid crystal display device of the present invention, if the birefringence layer 7 is formed between the first polarizing plate 5 and the second polarizing plate 4, the first substrate 3 as shown in FIG. The birefringence layer 7 is not limited to the case where it is laminated between the liquid crystal layer 2 and the birefringence layer 7 is provided between the first substrate 3 and the first polarizing plate 5 or between the second substrate and the second polarization. It can also be laminated between the plate 4 and the like.

  The birefringence layer 7 may be formed between the opposing substrates (first substrate and second substrate). Specifically, the birefringence layer 7 may be formed between the first substrate 3 and the liquid crystal layer 2 or may be formed between the second substrate and the liquid crystal layer 2.

  In the liquid crystal display device, when the birefringence layer 7 is formed between the first substrate 3 and the liquid crystal layer 2 or between the second substrate 4 and the liquid crystal layer 2, It is possible to prevent exposure to the outer surface of the substrate 1 and to receive an external force during the assembly process or use of the liquid crystal display device such as attaching the polarizing plates 5 and 6 to the substrates 3 and 4. In addition, the possibility that the birefringent layer is easily damaged can be suppressed.

  The liquid crystal layer 2 is formed by sealing a liquid crystal between the first substrate 3 on which the birefringence layer 7 is laminated and the second substrate 4.

  The liquid crystal sealed in the liquid crystal layer 2 is appropriately selected, and specific examples thereof include ZLI-2293 (manufactured by Merck).

  The liquid crystal constituting the liquid crystal layer 2 has an alignment state that is variable according to an external electric field. This enables the liquid crystal display device to control the phase difference of light traveling through the liquid crystal layer.

  As shown in FIG. 4A, alignment films 50 and 51 may be formed between the substrates 3 and 4 and the liquid crystal layer 2 so as to be in contact with the interface of the liquid crystal layer 2. The liquid crystal layer 2 formed between the substrates 3 and 4 is a horizontal alignment film for horizontally aligning the liquid crystal or a vertical alignment film for vertically aligning the liquid crystal. Whether the horizontal alignment film or the vertical alignment film is used as the alignment film can be appropriately selected.

  In this liquid crystal display device, for example, when light is incident in the direction from the second substrate 4 toward the first substrate 3, the light emitted from the light source 62 and the light source 62 is transmitted to the second polarizing plate 6. A light irradiator 63 including a light guide plate 60 that guides the light while diffusing in the surface direction, and a light reflecting plate 61 that advances light guided by the light guide plate 60 in the direction of the second substrate 4 may be provided. (FIG. 4 (A)). In this case, when light is incident on the second polarizing plate 6 from the light irradiation unit 63, light that passes through the second substrate 4 and the liquid crystal layer 2 and vibrates perpendicularly to the absorption axis of the first polarizing plate 5. Can be made. Further, the light passes through the colored layer 10 and light having a predetermined wavelength is emitted toward the outside of the first polarizing plate 5.

  In the liquid crystal display device of the present invention, a birefringent layer having a structure in which liquid crystal molecules are crosslinked and polymerized is provided on a substrate, so that a liquid crystal display device having relatively high heat resistance can be manufactured at low cost. To be able to get to. In addition, it becomes possible to manufacture a liquid crystal display device without interposing a retardation control film manufactured separately for optical compensation, and the liquid crystal display device can be made thin. Adhesives such as adhesives that had to be applied at the time of phase difference control film material installation are also unnecessary, so that the interface reflection due to the presence of layers such as adhesives can be reduced. As a result, the display characteristics of the liquid crystal display screen such as contrast can be further improved.

  According to this liquid crystal display device, since the birefringent layer has a structure in which the liquid crystal is homeotropically aligned and crosslinked and polymerized, xyz orthogonal coordinates with the thickness direction of the birefringent layer as the z axis are provided. When the value of the inclination angle φ of the refractive index ellipsoid A is zero, the refractive indexes nx, ny, and nz of the refractive index ellipsoid A are parallel to the x-axis direction, the y-axis direction, and the z-axis direction, respectively. In addition, the refractive index nx in the x-axis direction and the refractive index ny in the y-axis direction are almost the same value, and the refractive index nz in the z-axis direction can be made larger than the refractive indexes nx and ny. .

  Therefore, in such a case, the birefringence layer 7 is a layer having a birefringence characteristic such that the refractive index is nz> nx = ny, that is, a layer having an optical axis in the thickness direction (z-axis direction). And a layer having uniaxial birefringence characteristics, which can function as a so-called “+ C plate”, and can be optically compensated for retardation of light. It can function as a liquid crystal display device having a control function.

Furthermore, in this liquid crystal display device, when the value of the inclination angle φ of the refractive index ellipsoid A takes a value other than zero, the azimuth angle θ is approximately 0 °, 90 °, 180 °, or 270 °. Take.
Here, when the azimuth angle θ is other than these values, as shown by a broken line in FIG. 2, when viewed from the z-axis direction (as viewed from the direction of arrow F in FIG. 1), the long axis a (optical axis) ) Does not overlap either absorption axis P1 or absorption axis P2. Then, a phase difference is given to the light passing through the birefringence layer 7, a light component perpendicular to the absorption axis P1 (parallel to the transmission axis of the first polarizing plate 5) is generated, and light leakage occurs. .
On the other hand, in this liquid crystal display layer device, since the azimuth angle θ is configured to take the above-described value, the risk of light leakage in the thickness direction of the birefringent layer 7 is suppressed. The

  Therefore, in this liquid crystal display device, the function as the + C plate can be further ensured.

  The liquid crystal display device of the present invention may have a plurality of birefringent layers.

  In this case, the plurality of birefringence layers may be layers having different birefringence characteristics. Hereinafter, a layer having a birefringence characteristic different from that of the birefringence layer 7 may be referred to as a different birefringence layer. That is, the different birefringence layer is a layer having a birefringence characteristic different from the birefringence characteristic (+ C plate) of the birefringence layer 7 in the first embodiment.

  In this case, the different birefringence layer has an optical axis different from that of the birefringence layer 7 having an inclined optical axis.

  Specifically, the different birefringence layer is a layer having a birefringence characteristic such that the above-described refractive index is nz = nx <ny or nz = ny <nx, that is, a layer functioning as a so-called “+ A plate”. Alternatively, it may be a layer having a birefringence characteristic such that the above-mentioned refractive index is nz <nx = ny, that is, a layer functioning as a so-called “-C plate”.

  The different birefringence layer functioning as the so-called “+ A plate” described above is, for example, between the first polarizing plate 5 and the first substrate 3 or between the first substrate 3 and the birefringence layer 7. It can be formed between the first polarizing plate and the birefringence layer 7 such as a position between them.

  Specifically, the so-called + A plate, for example, uses a resin material or a film material capable of horizontally aligning liquid crystals to form a coating film for forming a horizontal alignment film on the surface thereof, thereby forming a horizontal alignment film. The surface of the coating film is rubbed or photo-aligned to obtain a horizontal alignment film, and a solution in which liquid crystal is dissolved in a solvent is applied onto the horizontal alignment film, and liquid crystal molecules are homogeneously aligned and fixed. Can be obtained.

  The + A plate is obtained by forming a horizontal alignment film on the outer or inner surface of the first substrate 3 and fixing the liquid crystal molecules homogeneously on the horizontal alignment film. be able to.

  In the liquid crystal display device, such a + A plate is arranged so that the direction of the optical axis thereof is aligned (coincided) with the direction of the absorption axis of the first polarizing plate 5 or the second polarizing plate 6. .

  When the liquid crystal display device is configured in this way, the light that has passed through the second polarizing plate, the second substrate, and the liquid crystal layer in this order passes through the + C plate and then passes through the + A plate and proceeds to the first polarizing plate. The liquid crystal display device can exhibit an optical compensation function that suppresses light leakage in an oblique direction with respect to the thickness of the liquid crystal display device, by a combined structure of the + C plate and the + A plate. The viewing angle of the device is enlarged.

  When a plurality of birefringent layers (birefringent layer 7 and different birefringent layer 31) having different optical axes are formed, the birefringent layer 7 and the different birefringent layer 31 are in contact with each other. Although it may be laminated (FIG. 3 (A)), it is not limited to this, the position between the first substrate 3 and the first polarizing plate 5, the first substrate 3 and the liquid crystal layer 2. Unlike the birefringence layer 7, the layers may be laminated while interposing a different layer from the different birefringence layer 31 at a position such as between the liquid crystal layer 2 and the second polarizing plate 6. (Fig. 3 (B), (C)).

  In order to protect the surface of the birefringent layer 7, a protective layer (not shown) such as an insulating film such as an acrylic photosensitive resin may be laminated on the surface of the birefringent layer 7.

Next, the manufacturing method of the liquid crystal display device of the present invention will be described in detail.
The liquid crystal display device of the present invention can be manufactured as follows.

  First, as a base material for constituting the first substrate 3 on which the birefringent layer 7 is laminated, a base material to which orientation is imparted is prepared in advance. For example, as the base material, a uniaxially stretched film, a biaxially stretched film such as a film provided with orientation itself, or a film irradiated with polarized light using a photo-alignment film is prepared.

  In addition, as a base material, the process which makes the orientation of a liquid crystal easier according to the kind of the liquid crystal contained in the birefringence layer 7 formed on the base-material surface, and the orientation which is going to provide to a liquid crystal. (Orientation facilitating step) may be performed in advance, and a product obtained as a result of the orientation facilitating step may be used.

  As the substrate on which the alignment facilitating step has been performed, a substrate that has been subjected to a treatment for forming an alignment film on the substrate to enable alignment of liquid crystal may be adjusted. In this way, according to the alignment film formed on the base material and having the alignment ability, by selecting various composition liquids constituting the alignment film, it is possible to select a relatively wide range of alignment directions. There is an advantage that it is possible.

  The treatment for forming the alignment film performed as the alignment facilitating step is carried out by appropriately selecting conditions according to the type of liquid crystal contained in the birefringence layer 7 and the like. That is, for example, when the birefringent layer 7 is configured by fixing the liquid crystal contained therein in a homeotropic alignment state, a process for forming a vertical alignment film is selected as the alignment facilitating step. It is preferred that

  The vertical alignment film is formed on the substrate surface as shown below. In other words, a film composition liquid containing polyimide is prepared using the materials described above, and this is applied to the surface of a light-transmitting base material by a method such as flexographic printing or spin coating to apply a coating for a vertical alignment film. A base material (vertical orientation film forming base material) in which a vertical orientation film is formed on a base material is obtained by preparing a work film and further curing the coating film for vertical orientation film.

  When forming the alignment film on the substrate, if the surface of the alignment film has high water repellency or oil repellency, the liquid crystal can be preliminarily subjected to UV cleaning or plasma treatment as long as it can be homeotropically aligned. The wettability of the alignment film surface may be increased in advance.

When the base material is thus prepared, the birefringence layer 7 is laminated on the base material through the following steps.
First, the liquid crystal constituting the birefringent layer 7 laminated on the substrate is dispersed in a solvent to prepare a birefringent layer composition liquid. And this birefringence layer composition liquid is apply | coated to a base-material surface, and a coating film is formed (coating film formation process). More specifically, for example, a vertical alignment film forming base material is prepared as a base material, and further a liquid crystal molecule and polyimide are dissolved in a solvent to prepare a birefringence layer composition liquid, which is used as the vertical alignment film forming base material. A coating film is prepared by coating on the vertical alignment film surface.

  In the coating film forming step, a known coating method can be used as a coating method of the birefringence layer composition liquid. Specifically, a spin coating method, a die coating method, a slit coating method, a roll coating method, The coating liquid can be applied onto the substrate by each method such as a gravure coating method, a slide coating method, and an immersion method, or a method in which these are appropriately combined. In order to improve the adhesion between the base material and the coating film, an adhesive layer is provided on the base material as described in JP-A-8-278491, and the birefringence is further provided on the adhesive layer. A layer composition liquid can also be applied.

  The weight ratio of the liquid crystal in the birefringence layer composition liquid is 5% by weight to 50% by weight. If it exceeds 50% by weight, the film thickness distribution of the birefringent layer 7 may be increased, and if it is less than 5% by weight, coating unevenness may occur. Considering this, the weight ratio of the liquid crystal is preferably 5 to 50 parts by weight, and more preferably 10 to 30 parts by weight.

  The solvent is not particularly limited as long as it can dissolve the polymerizable liquid crystal, and an organic solvent can be appropriately selected. When a spin coating method is used to form a coating film by applying a birefringence layer composition liquid on a substrate, the solvent is 3-methoxybutyl acetate, diethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate, cyclohexanone. Etc. are preferably used.

  The birefringent layer composition liquid may contain a polyimide having an alkyl group in the side chain in order to effectively homeotropically align liquid crystal molecules. In this case, in the birefringence layer composition liquid, the blending ratio of the polyimide having an alkyl group in the side chain and the liquid crystal is 1/7 to 1/3 by weight. Further, the blending amount of the polyimide in the birefringence layer composition liquid is preferably 12.5 to 25% by weight, more preferably 15 to 22.5% by weight with respect to the total amount of liquid crystal in the birefringence layer composition liquid. preferable. If the blending amount of the polyimide is less than 12.5% by weight, it may be difficult to obtain a birefringent composition that is homeotropically oriented sufficiently. If it is greater than 25% by weight, the light transmittance decreases. There is a risk of doing.

  It is preferable that a photopolymerization initiator is added to the birefringence layer composition liquid.

  As the photopolymerization initiator, a radical polymerizable initiator can be preferably used. The radical polymerizable initiator generates free radicals by energy such as ultraviolet rays. For example, benzyl (also referred to as bibenzoyl), benzoin isobutyl ether, benzoin isopropyl ether, benzophenone, benzoyl benzoic acid, methyl benzoyl benzoate, 4 -Benzoyl-4'-methyldiphenyl sulfide, benzylmethyl ketal, dimethylaminomethylbenzoate, 2-n-butoxyethyl-4-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 3,3'-dimethyl-4-methoxy Benzophenone, methylobenzoyl formate, 2-methyl-1- (4- (methylthio) phenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-mol Olinophenyl) -butan-1-one, 1- (4-dodecylphenyl) -2hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropane- 1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2,4-dimethyl Examples thereof include thioxanthone, isopropylthioxanthone, 1-chloro-4-propoxythioxanthone and the like. In the present invention, a commercially available photopolymerization initiator can also be used as appropriate. For example, “Irgacure 184 (substance name: 1-hydroxycyclohexyl phenyl ketone)”, “Irgacure 369 (substance name: 2-benzyl-2-dimethylamino-1- (4-morpholino) manufactured by Ciba Specialty Chemicals, Inc. Phenyl) -butan-1-one) ”,“ Irgacure 651 (substance name: 2,2-dimethoxy-1,2-diphenylethane-1-one) ”,“ Irgacure 907 (substance name: 2-methyl-1-) Ketones such as (4- (methylthio) phenyl) -2-morpholinopropan-1-one), “Darocur 1173 (substance name: 2-hydroxy-2-methyl-1-phenylpropan-1-one)” Compounds, 2,2'-bis (o-chlorophenyl) -4,5,4'-tetraphenyl-1,2'biimidazole (Kurokin Kasei Co., Ltd.) You may use biimidazole type compounds, such as a company make.

  The photopolymerization initiator is preferably added within a range that does not significantly impair the liquid crystal regularity of the polymerizable liquid crystal. The addition amount of the photopolymerization initiator is generally 0.01 to 10% by weight, preferably 0.1 to 7% by weight, and more preferably 0.5 to 5% by weight, added to the birefringence layer composition liquid. Can do.

  In addition to the photopolymerization initiator, a sensitizer can also be added to the birefringence layer composition liquid within a range that does not impair the object of the present invention. Specifically, the range is from 0.01 to 1% by weight. Selected within.

  Moreover, only 1 type may be used for a photoinitiator and a sensitizer, respectively, and 2 or more types may be used together.

It is preferable that a surfactant is added to the birefringence layer composition liquid. By adding a surfactant to the birefringent layer composition liquid, the orientation of liquid crystal molecules at the air interface can be controlled in a coating film formed by applying the surfactant.
The surfactant is not particularly limited as long as it does not impair the liquid crystal expression of the polymerizable liquid crystal. For example, polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene derivative, polyoxyethylene / polyoxypropylene block polymer, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyoxyethylene fatty acid ester , Nonionic surfactant such as polyoxyethylene alkylamine, fatty acid salt, alkyl sulfate ester salt, alkylbenzene sulfonate, alkyl naphthalene sulfonate, alkyl sulfosuccinate, alkyl diphenyl ether disulfonate, alkyl phosphate, Polyoxyethylene alkyl sulfate ester salt, naphthalenesulfonic acid formalin condensate, special polycarboxylic acid type polymer surfactant, polyoxyethylene Anionic surfactants such as alkyl phosphates.
The amount of the surfactant added is generally 0.01 to 1% by weight, preferably 0.05 to 0.5% by weight, and can be added to the fixed liquid crystal layer composition liquid.

  When the coating film is formed on the substrate in the coating film forming step, the liquid crystal contained in the coating film is brought into a liquid crystal phase and, for example, the liquid crystal is brought into a homeotropic alignment state as shown below.

  That is, by heating the coating film, the temperature of the coating film is equal to or higher than the temperature at which the liquid crystal in the coating film becomes a liquid crystal phase (liquid crystal phase temperature), and the liquid crystal in the coating film is in an isotropic phase (liquid The liquid crystal is homeotropically aligned at a temperature lower than the temperature of the phase. At this time, the means for heating the coating film is not particularly limited, and may be a means for placing in a heating atmosphere or a means for heating with infrared rays.

  The method for homeotropic alignment of the liquid crystal is not limited to the above method, but can also be applied to the coating film by a method of drying the coating film under reduced pressure according to the liquid crystal contained in the coating film or the state of the coating film. It can also be realized by a method of applying an electric field or a magnetic field from a predetermined direction.

  When the liquid crystal is homeotropically aligned by drying the coating film under reduced pressure, the coating film can be brought into a supercooled state by setting a reduced pressure state, and the liquid crystal in the coating film is homeotropically aligned. The coated film can be further cooled to room temperature while maintaining the state. Then, it is possible to prevent the liquid crystal from being efficiently homeotropically aligned until the liquid crystal is subjected to a crosslinking reaction.

  The liquid crystal that is homeotropically aligned in the coating film is then crosslinked and fixed as shown below to form the birefringent layer 7 (referred to as a birefringent layer forming step).

  This crosslinking reaction proceeds by irradiating (exposure) light having a photosensitive wavelength of liquid crystal to the coating film. At this time, the wavelength of light applied to the coating film is appropriately selected according to the type of liquid crystal contained in the coating film. The light applied to the coating film is not limited to monochromatic light, but may be light having a certain wavelength range including the photosensitive wavelength of the liquid crystal.

The light used for the exposure is preferably ionizing radiation because of the magnitude of the excitation energy, and the amount of ionizing radiation is appropriately selected according to the polymerizable liquid crystal used, but when using ultraviolet rays as the ionizing radiation, In general, the irradiation amount is preferably adjusted so that the exposure amount of the liquid crystal phase expected site is about 10 to 1000 mJ / cm ² , and the wavelength is preferably about 200 to 450 nm.

  In addition, as a method of curing the liquid crystal contained in the coating film, a method of curing the coating film by irradiating an electron beam of about 50 to 500 Gy may be used.

  The cross-linking reaction of the liquid crystal is preferably performed while the coating film is heated to a temperature 1 to 10 ° C. lower than the temperature at which the liquid crystal transitions from the liquid crystal phase to the isotropic phase. By doing so, disorder of homeotropic alignment of the liquid crystal can be reduced during the crosslinking reaction. From this point of view, the temperature at which the crosslinking reaction is performed is more preferably 3 to 6 ° C. lower than the temperature at which the liquid crystal transitions from the liquid crystal phase to the isotropic phase.

  In addition to the method described above, the crosslinking reaction of the liquid crystal is a method of irradiating the coating film with light having a photosensitive wavelength of liquid crystal while heating the coating film to the liquid crystal phase temperature in an inert gas atmosphere ( (Method A).

  In Method A, the liquid crystal is cross-linked under an inert atmosphere, and the disorder of the alignment of liquid crystal molecules is further suppressed as compared with the case where the liquid crystal is cross-linked under an air atmosphere.

  In addition, the cross-linking reaction of the liquid crystal is carried out by partially irradiating the coating film with light of the photosensitive wavelength of the liquid crystal while heating the coating film to the liquid crystal phase temperature in an inert gas atmosphere or air atmosphere. The coating film is cooled to a temperature (Tc) at which the liquid crystal becomes a crystalline phase after the partial crosslinking process, and in this state, light with a photosensitive wavelength is further irradiated to the coating film. The method may be carried out by a method of completing the crosslinking reaction (referred to as method B). The temperature Tc described above is a temperature at which the liquid crystal becomes a crystal phase in the coating film before the crosslinking reaction proceeds.

  In the partial crosslinking step, the crosslinking reaction proceeds to such an extent that the orientation of the liquid crystal contained in the coating film is maintained even when the coating film is cooled to the temperature Tc. Accordingly, the degree of progress of the cross-linking reaction in the partial cross-linking step is appropriately selected according to the type of liquid crystal in the coating film, the film thickness of the coating film, and the like. The crosslinking reaction is preferably allowed to proceed until the degree of cross-linking becomes 5-50.

  Method B can be carried out in an inert gas atmosphere or an air atmosphere. However, when the method B is carried out in an air atmosphere, the equipment for carrying out the step of performing the crosslinking reaction can be simplified, and the liquid crystal display device can be produced. This is preferable from the viewpoint of cost reduction.

  When the birefringence layer forming step is performed in this way, the polymerizable liquid crystal in the coating film formed on the substrate is cross-linked and cured to form the birefringence layer 7. The provided first substrate 3 is formed.

  Next, a base material constituting the second substrate 4 is prepared. As this base material, the thing similar to the 1st board | substrate 3 may be used, and a different thing may be used.

A liquid crystal layer is formed as follows using the first substrate 3 and the second substrate 4 provided with the birefringence layer 7.
First, the first substrate 3 and the second substrate 4 are arranged to face each other with a slight space therebetween, and a spacer (for example, a spherical spacer or a columnar spacer) is arranged in the gap between the first substrate 3 and the second substrate 4. Then, the separation distance (cell gap) between the first substrate 3 and the second substrate 4 is fixed.

  Next, a space section partitioned by the sealing material is formed between the two substrates (the first substrate 3 and the second substrate 4) using a sealing material (thermosetting resin). Then, by filling the space portion with a liquid crystal material, liquid crystal is sealed and the liquid crystal layer 2 is formed.

  Further, when the first polarizing plate 5 and the second polarizing plate 6 are viewed in the thickness direction of the liquid crystal layer 2, the outer surface of the first substrate 3 and the second polarizing plate 6 are arranged so that the absorption axes P 1 and P 2 are orthogonal to each other. The two substrates 4 are disposed on the outer surface of the second substrate 4 so as to sandwich the substrates 3 and 4 therebetween. At this time, both polarizing plates (the first polarizing plate 5 and the second polarizing plate 6) are arranged in crossed Nicols. Further, the thickness direction of the birefringence layer 7 is aligned with the thickness direction of the liquid crystal layer 2, and both polarizing plates 5 and 6 are arranged in crossed Nicols when viewed in the thickness direction of the birefringence layer 7. .

  In the birefringence layer forming step, when the liquid crystal molecules are almost completely fixed in a homeotropic alignment state, the birefringence layer 7 is inclined by a refractive index ellipsoid specifying its birefringence characteristics. The angle φ is approximately 0 °, and the first polarizing plate and the second polarizing plate can be installed without considering the state of the refractive index ellipsoid of the birefringent layer.

  In the birefringence layer forming step, when the birefringence layer 7 is formed such that the inclination angle φ of the refractive index ellipsoid specifying the birefringence characteristics is other than 0 °, the first polarizing plate 5 and the second polarizing plate 6 are installed so that the approximate value of the azimuth angle θ in the refractive index ellipsoid of the birefringent layer 7 is 0 °, 90 °, 180 °, or 270 °. The That is, when the refractive index ellipsoid of the birefringent layer 7 is viewed in the thickness direction of the birefringent layer 7, either the absorption axis P1 of the first polarizing plate 5 or the absorption axis P2 of the second polarizing plate 6 is selected. Are aligned with (overlapping with) the direction of the major axis a (optical axis) of the refractive index ellipsoid of the birefringent layer 7, the first polarizing plate 5 and the second polarizing plate 6 are installed.

  Thus, the liquid crystal display device 1 of the present invention is manufactured.

The liquid crystal display device according to the first embodiment of the present invention may be one in which the colored layer 8 is formed on at least one of the opposing substrates (referred to as the second embodiment).
FIG. 4B is a schematic diagram showing a cross-sectional structure in an example of the liquid crystal display device of the second mode.

  In this liquid crystal display device 1, the colored layer 10 is laminated as a functional layer on the base material 30 constituting one of the opposing substrates (for example, the first substrate 3), and the birefringence layer 7 is colored. It is further laminated on the surface of the layer 10. A different birefringence layer 31 is formed between the substrate on which the colored layer 10 is formed and the first polarizing plate 5.

  The colored layer 10 includes a colored pixel portion 8 that transmits visible light in a predetermined wavelength region, and a light shielding portion 9 (sometimes referred to as a black matrix or BM).

The colored pixel portion 8 has a predetermined pattern of colored pixels (referred to as a red colored pixel 8a, a green colored pixel 8b, and a blue colored pixel 8c, respectively) that transmit light of each color wavelength band for red, green, and blue, respectively. 30. Various arrangement patterns such as a stripe type, a mosaic type, and a triangle type can be selected as the arrangement form of the red color pixel 8a, the blue color pixel 8b, and the green color pixel 8c constituting the color pixel unit 8.
Further, instead of these colored pixels (8a, 8b, 8c), it is also possible to use colored pixels that transmit light in the complementary wavelength band of each color.

  The coloring pixel unit 8 patterns a coating film of a coloring material dispersion obtained by dispersing a coloring material of a coloring pixel in a solvent into a predetermined shape for each coloring pixel (8a, 8b, 8c) of each color, for example, by a photolithography method. It is formed by doing.

  In addition to the photolithography method, the colored pixel portion 8 can be formed by applying a coloring material dispersion liquid in a predetermined shape for each colored pixel (8a, 8b, 8c) of each color.

  The light-shielding portion 9 prevents overlapping of the colored pixels (8a, 8b, 8c), fills in the gaps between the colored pixels, suppresses light leakage (leakage light) between adjacent colored pixels, and In the case of being provided in an active matrix driving type liquid crystal display device, light degradation of the active element is suppressed.

  Therefore, the light-shielding part 9 is formed so as to partition the area corresponding to the position where the colored pixels are arranged on the surface of the base material 30 for each colored pixel (8a, 8b, 8c) in plan view. . The colored pixels (8a, 8b, 8c) of the respective colors cover the regions in plan view according to the formation positions of the regions on the surface of the base material 30 partitioned by the light shielding unit 9, respectively. Be placed.

  The light shielding part 9 can be formed, for example, by patterning a metal thin film having a light shielding property or light absorbing property such as a metal chromium thin film or a tungsten thin film on the surface of the substrate 30 in a predetermined shape. Moreover, the light shielding part 9 can also be formed by printing an organic material such as black resin in a predetermined shape.

  According to the liquid crystal display device of the second embodiment in which such a colored layer 10 is formed, color display is possible.

  In the liquid crystal display device according to the second embodiment, the colored pixels (the red colored pixels 8a, the blue colored pixels 8b, and the green colored pixels 8c) constituting the colored pixel portion 8 of the colored layer 10 are arranged in a stripe arrangement pattern. In the case where they are arranged, the red colored pixels 8a, the blue colored pixels 8b, and the green colored pixels 8c are linearly arranged. In such a liquid crystal display device, as shown in FIG. The direction of the absorption axis (P1, P2) of one of the polarizing plate and the second polarizing plate (indicated by arrows P1, P2 in FIG. 6) is the longitudinal direction of the striped colored pixels (8a, 8b, 8c) ( Preferably, it coincides with the arrow J in FIG. In the example of FIG. 6, in the liquid crystal display device 1, the longitudinal direction of the stripe-type colored pixels (8a, 8b, 8c) coincides with the absorption axis P1 of the first polarizing plate. These may coincide with the absorption axis P2 of the second polarizing plate.

  Here, when the birefringence layer 4 is formed on the colored layer 10 including the colored pixel portion 8 in which the stripe-shaped colored pixels are arranged, the present inventors are perpendicular to the longitudinal direction of the colored pixels in plan view. It has been found that there is a phenomenon in which the optical axis a of the birefringent layer 4 is directed. The liquid crystal display device 1 is an invention that has been completed by applying this phenomenon, and has the effect of becoming an efficiently manufacturable device. In other words, by adopting a stripe type as the arrangement pattern of the colored pixels and aligning the absorption axis direction of the polarizing plate with the longitudinal direction of the colored pixels, which is easy to visually recognize, the birefringence can be reliably and easily obtained. The tilt direction of the optical axis of the layer 4 can be made to coincide with the absorption axis of either the first polarizing plate or the second polarizing plate, and an efficiently manufactured liquid crystal display device is provided.

  In addition, when forming the birefringence layer 4 on the colored layer 10 provided with the colored pixel part 8 which has arrange | positioned the stripe-type colored pixel, the birefringent layer 4 in the direction orthogonal to the longitudinal direction of a colored pixel. The details of the cause of the easy orientation of the optical axis a is unknown, but it is thought that the shape of the colored pixel 8, the method of creating the colored pixel 8, and the conditions thereof are factors.

In the liquid crystal display devices according to the first and second embodiments of the present invention, the switching circuit 20 may be provided on the first substrate 3 or the second substrate 4 (referred to as the third embodiment) (FIG. 5 ( A), (B)).
As the switching circuit 20, a pixel electrode and an electrode for forming an electric field on the liquid crystal layer opposite to the pixel electrode are not disposed on the same substrate surface (for example, TN (Twisted Nematic) mode, VA (Virtical Alignment) mode) ) (Referred to as a first mode) and those in which these are disposed on the same substrate surface (for example, an IPS (In-Plane-Switching) mode) (referred to as a second mode).

  A case where the pixel electrode constituting the electrode portion and the electrode (common electrode) opposed to the pixel electrode are not provided on the same substrate will be described (FIG. 5A).

  The switching circuit 20 in the first mode is laminated on the substrate 30 corresponding to the pixel electrode 18 provided for each pixel, and is configured in layers, and is electrically connected to the pixel electrode 18. An element substrate as a functional layer is formed together with various elements such as signal lines and scanning lines.

  The switching circuit 20 is supplied with an electrical signal from the scanning line 13 and controls the energization state of the signal line 12 and the electrode unit 11. Specific examples of the switching circuit 20 include active elements such as a three-terminal element such as a thin film transistor (TFT) and a two-terminal element such as a MIM (Metal Insulator Metal) diode.

  When the switching circuit 20 is a thin film transistor, the switching circuit 20 includes a drain electrode 15 connected to each pixel electrode 18, a source electrode 16 that receives an electric signal from the signal line 12, and the drain electrode 15 and the source electrode 16. A semiconductor that interposes between and connects the two electrodes is laminated on a base material, and a gate electrode 17 is laminated on the semiconductor via an insulating layer (not shown). Note that the gate electrode is connected to the scanning line 13.

  The electrode unit 11 includes a pixel electrode 18 and a common electrode (not shown). As the electrode unit 11, a transparent electrode such as an ITO (Indium Tin Oxide) electrode can be preferably used. It can be formed by laying over almost the entire area to be formed. The electrode part 11 can also be formed by laying a thin transparent electrode on the edge of each pixel region.

  Next, the switching circuit 20 in the second mode in which the pixel electrode and the common electrode constituting the electrode portion are provided on the same substrate will be described (FIG. 5B). The element substrate on which the switching circuit 20 is formed is configured in the same manner as in the first mode except for the region where the electrode portion 11 is formed in the same pixel region. Both the pixel electrode and the opposing electrode are stacked on the same pixel region.

  That is, in the electrode unit 11 including the pixel electrode 18 and the common electrode 19, the common electrode 19 is provided so as to face the pixel electrode 18 connected to the drain electrode 15 on the same substrate surface. As shown in FIG. 5B, the common electrode 19 is disposed so as to face one pixel electrode 18 in two directions (in the example of FIG. 5B, the direction approaching and away from the signal line 12). The In FIG. 5B, the electrode portion 11 is provided with a pixel electrode 18 and a common electrode 19 in a comb shape. Note that an insulating layer is provided in a region where the pixel electrode 18 and the common electrode 19 overlap so that the switching circuit 20 is not short-circuited.

  If the switching circuit 20 in the first mode or the second mode is provided on the first substrate 3 or the second substrate 4 to constitute the liquid crystal display device of the third mode, the liquid crystal display device is energized by the switching circuit. The liquid crystal display is controlled according to the state.

Example 1.
As shown below, a birefringence layer and an alignment film were sequentially laminated on a base material to produce a first substrate having a birefringence layer.

<Preparation of vertical alignment film>
A solution of the vertical alignment film (JLS, JALS-2021-R2) is diluted twice with γ-butyrolactone to prepare an alignment film composition liquid.
On the surface of a glass substrate (7059 glass manufactured by Corning Co., Ltd.) (size is 550 mm × 650 mm) as a base material to be the first substrate, the above-mentioned alignment film composition liquid is applied to form an alignment film forming coating film. The glass substrate on which the coating film for forming the alignment film is formed is baked at 180 ° C. for 1 hour to obtain a base material on which the vertical alignment film is formed (referred to as a vertical alignment film forming base material).

<Preparation of birefringent layer forming coating film>
As a solution containing polyimide, a solution obtained by diluting a vertically aligned film solution (JLS, JALS-2021-R2) 8 times with diethylene glycol dimethyl ether is prepared.
As a polymerizable liquid crystal molecule (polymerizable liquid crystal) exhibiting a nematic liquid crystal phase, 20 parts by weight of a compound represented by the above chemical formula (Formula 11) (where X is a compound having a value of 6) and a photopolymerization initiator (Ciba Geigy) Manufactured by “Irgacure 907”), 59.2 parts by weight of chlorobenzene as a solvent, and 20 parts by weight of a solution containing the polyimide are mixed to prepare a birefringence layer composition liquid.

  A substrate for forming a vertical alignment film was placed on a spin coater, and a birefringence layer composition liquid was spin-coated on the vertical alignment film to prepare a coating film (referred to as a coating film for forming a birefringence layer). The birefringence layer forming coating film obtained at this time was cloudy. A coater system (manufactured by Tokyo Ohka Kogyo Co., Ltd., “trade name TR40000F”) was used to produce a coating film by spin coating. This coater system is a system that integrally performs bar coating of a birefringence layer composition liquid on the surface of a base material for forming a vertical alignment film, spin coating, and vacuum drying of a coating film for forming a birefringence layer.

  The film thickness of the produced birefringent layer forming coating film was about 1.5 μm when dried. The film thickness was measured using a stylus type step gauge (manufactured by Sloan, product name “DEKTAK”).

<Formation of homeotropic alignment state of liquid crystal>
The substrate for forming the vertical alignment film on which the coating film for forming the birefringent layer is formed is heated at 100 ° C. for 3 minutes, and the liquid crystal molecules in the coating film for forming the birefringent layer are transferred to the liquid crystal phase. It was confirmed that an alignment state was formed. At this time, it was visually confirmed that the coating film for forming a birefringent layer was changed from a cloudy state to a transparent state.

<Crosslink polymerization reaction of liquid crystal>
Next, in an air atmosphere, UV light with an output of 20 mW / cm ² is applied to the transparent birefringent layer forming coating film using an ultraviolet irradiation device (trade name TOSCURE751 manufactured by Harrison Toshiba Lighting Co., Ltd.). The birefringent layer was formed by irradiating for 10 seconds to cause the liquid crystal in the coating film for forming a birefringent layer to undergo a crosslinking polymerization reaction to fix the orientation of the molecules of the liquid crystal. The base material on which the birefringence layer thus obtained was formed was baked in an oven at 230 ° C. for 30 minutes to improve the adhesion between the birefringence layer and the base material.

  In this way, a base material having a birefringent layer formed thereon is obtained. For this, nx, ny, nz, and φ indicating the state of a refractive index ellipsoid that specifies the birefringence characteristics of the birefringent layer are obtained. The value is specified as follows:

  The refractive index (nx, ny, nz) indicating the shape of the refractive index ellipsoid of the birefringent layer is specified by determining the refractive index according to the molecules of the liquid crystal.

Next, the tilt state of the refractive index ellipsoid of the birefringence layer is specified by determining the tilt angle φ.
First, it is determined whether or not there is an inclination in the major axis (optical axis) of the refractive index ellipsoid by measuring the amount of retardation in the front direction using a phase difference measuring machine. That is, the measured retardation amount is a value assumed when there is no inclination in the optical axis of the birefringent layer based on the refractive index and the film thickness of the birefringent layer (when the inclination angle φ = 0). If the value is different from, it is determined that the optical axis of the birefringent layer is inclined.

  When it is determined that the optical axis of the birefringent layer is inclined, the inclination angle φ with respect to the optical axis is specified by measuring the phase difference using a phase difference measuring machine as shown below.

  The position where the phase difference is to be measured is selected in advance on the birefringence layer surface. This selected position is taken as a measurement point. The phase difference of light (wavelength 589 nm) in the 45 ° polar angle direction at this measurement point is measured in four different directions.

Here, four orientations different from the polar angle are defined as follows.
That is, taking the measurement point as the origin, taking the z-axis in the thickness direction of the birefringence layer, taking the x-axis and y-axis intersecting at the origin on the birefringence layer surface and orthogonal to each other, When considering a space formed by the z-axis, the polar angle for the position (K) in the space is 0 ° when K is on the z-axis, with respect to the z-axis of the straight line connecting the origin and K Defined as tilt angle.

  The four different azimuths are two azimuths (azimuth X1, azimuth X2) facing each other across the origin in the x-axis direction and two azimuths (azimuth Y1, azimuth Y2) facing each other across the origin in the y-axis direction. Defined.

  Inclination angle φ is the value of phase difference (phase difference with respect to azimuth X1, azimuth X2, azimuth Y1, azimuth Y2) measured at a position of 45 ° polar angle for each of four azimuths (azimuths X1, X2, Y1, Y2) Are determined by combinations of Δn (X1), Δn (X2), Δn (Y1), and Δn (Y2)).

  Since the refractive index (nx, ny, nz) of the refractive index ellipsoid is specified according to the type of liquid crystal and the like, the shape of the refractive index ellipsoid is specified, and the phase difference of the four different orientations as described above is specified. If the value is specified, the value of (Δn (X1) −Δn (X2)) and (Δn (Y1) −Δn (Y2)) will determine how much the optical axis of the refractive index ellipsoid is azimuth X1 or It is inclined toward the azimuth X2, and how much it is inclined toward the azimuth Y1 or the azimuth Y2 is specified. From this, it can be specified how much the optical axis of the refractive index ellipsoid is inclined with respect to the z-axis.

  For example, nx = ny <nz, (Δn (X1) −Δn (X2)) = ε> 0 (zero), and the value of (Δn (Y1) −Δn (Y2)) is 0 (zero). Alternatively, when it is almost 0, the refractive index ellipsoid is specified as a state in which the refractive index ellipsoid is inclined according to the value of ε in the azimuth X2 and is hardly inclined in either the azimuth Y1 or the azimuth Y2. Is determined.

  In addition, about the base material in which the birefringence layer was formed, the measurement point was taken at the approximate center position (W) of the substrate, and the inclination angle φ of the refractive index ellipsoid at the position W was measured. The value of was approximately 1 °.

  In addition, for the base material on which the birefringence layer is formed, the inclination state (inclination state of the optical axis) of the refractive index ellipsoid at a plurality of different positions on the birefringence layer surface is measured, and the uniformity of the inclination state is measured. Was evaluated.

<Evaluation of uniformity in tilted state>
First, in the base material on which the birefringence layer is formed, a total of 35 measurement points (35 points) of 5 points × 7 points which are different from each other in a lattice shape with a spacing of 100 mm in the plane direction on the surface of the birefringence layer. At the same time, the position of the center point among the 35 measurement points is matched with the position W. Then, the phase difference (Δn (X1), Δn (X2), Δn (Y1), Δn (Y2)) is measured for each measurement point from four directions, and the standard deviation for the phase difference Δn (X1) is calculated. , And for each measurement point, the magnitude relation of the phase difference value is compared.

As a result, the standard deviation of Δn (X1) was 0.29. In this case, it is expected that the variation in the inclination angle of the refractive index ellipsoidal state and the optical axis state at different positions on the birefringent layer surface can be suppressed to a range of approximately 0.4 °.
Further, at all the 35 measurement points, (Δn (X1) −Δn (X2)) = ε> 0 (zero) and (Δn (Y1) −Δn (Y2)) are almost zero (zero). )Met.

  Therefore, in the base material on which the birefringent layer is formed, the optical axis at each measurement point of the birefringent layer corresponds to a case where the optical axis is approximately uniform and tilted in the same direction, and at each measurement point of the birefringent layer. It shows that there is almost no variation in the tilted state of the optical axis. In this base material, the inclination angle of the refractive index ellipsoid at the approximate center position of the birefringence layer directly indicates the inclination angle of the optical axis of the birefringence layer.

<Production of horizontal alignment film>
The base material on which the birefringent layer formed as described above is formed is cut into a size of 20 mm × 20 mm, and a horizontal alignment film is produced on the surface of the birefringent layer as shown below. did.
First, a horizontal alignment film composition liquid (AL1254 (manufactured by JSR)) is applied to the base material surface on which the birefringence layer is formed by using flexographic printing to form a coating film (horizontal alignment film coating film). The horizontal alignment film was formed by baking the glass substrate on which the coating film for horizontal alignment film was formed in an oven at 230 ° C. for 1 hour.

<Rubbing treatment>
In the direction of the major axis (optical axis) of the refractive index ellipsoid that specifies the birefringence characteristics of the birefringent layer when viewed in the thickness direction of the birefringent layer with respect to the base material on which the horizontal alignment film is formed A rubbing process was performed using a rubbing apparatus (RLYY-3 (manufactured by Iinuma Gauge Co., Ltd.)) so that the rubbing directions were parallel (aligned), and thus a first substrate having a birefringence layer was obtained.

  Next, a base material (glass substrate) of the same type as that used for forming the first substrate was prepared, and used as a base material for forming the second substrate, to produce a second substrate.

  First, a horizontal alignment film was produced on the base material surface used for the second substrate through the same process as the process for producing the horizontal alignment film on the birefringence layer surface of the first substrate. Further, a rubbing treatment was performed on the horizontal alignment film provided on the second substrate base material in the same manner as the first substrate to produce a second substrate.

  A first substrate provided with a birefringent layer and a second substrate were cut into a size of approximately 20 mm × 20 mm, and a liquid crystal layer was formed using them as follows.

<Preparation of liquid crystal layer>
The seal material made of thermosetting resin (Mitsui Chemicals Co., Ltd .; trade name: XN-5A) contains 0.4% by weight of spacer for the seal part (Sekisui Chemical Co., Ltd .; Micropearl SP-2035). Then, a composition liquid (seal part composition liquid) was prepared, and a seal part composition liquid was applied to the second substrate along the peripheral edge of the horizontal alignment film to create a coating part (seal liquid coating part). When creating the seal liquid coating part, a part (referred to as non-coating part) where the seal part composition liquid was not applied was left at a part of the peripheral edge of the horizontal alignment film.

The first substrate and the second substrate are disposed so that the surfaces subjected to the rubbing treatment face each other so that the directions in which the liquid crystals are aligned by rubbing treatment are aligned, and the seal liquid coating portion of the second substrate is disposed on the first substrate. The first and second substrates were heated to 140 ° C. while pressing the first substrate and the second substrate at a pressure of 20 kPa / cm ² so as to maintain this contact state, and the sealing material was cured. As a result, an integrated body (referred to as a cell) of the first substrate and the second substrate was produced. The obtained cell has a size of about 2 cm × about 2 cm and a cell gap of 3.5 μm.

  As a result, the first substrate and the second substrate are arranged facing each other at a slight interval, and an opening is formed at the position of the non-application portion between the first substrate and the second substrate. A space portion partitioned by the seal portion is formed. Then, liquid crystal is injected into this space portion to form a liquid crystal layer (driving liquid crystal layer). In injecting the liquid crystal constituting the liquid crystal layer, an opening is used as a liquid crystal injection port.

  As the liquid crystal constituting the liquid crystal layer, a liquid crystal having a positive dielectric anisotropy (manufactured by Merck; trade name ZLI-2293; Δn = 0.132, λ = 590 nm) was used. In addition, a dispenser method may be used to inject liquid crystal, but a vacuum injection method is used here.

  Formation of the liquid crystal layer by the vacuum injection method was performed as follows. That is, a cell that does not contain liquid crystal is placed in a container containing liquid crystal with the liquid crystal injection port facing downward. At this time, the liquid crystal injection port is not immersed in the liquid crystal. Next, this container is sealed and the air in the container is evacuated to a state close to vacuum. In that state, the liquid crystal inlet of the cell is immersed in the liquid crystal. Then, the pressure in the container is returned to normal pressure while the liquid crystal inlet is maintained immersed in the liquid crystal. As a result, the liquid crystal is gradually injected into the panel from the liquid crystal injection port by the pressure and the capillary management phenomenon, and the liquid crystal is filled in the space portion of the cell.

After the cell is filled with liquid crystal, UV curable resin (product name: LCB-610) is applied to the liquid crystal injection port, and the applied position (position where the liquid crystal injection port is formed) is irradiated with ultraviolet light. As a result, the ultraviolet curable resin at that position was fixed and the space was sealed.
Thus, a cell in which a liquid crystal layer was formed was obtained.

<Disposition of retardation film and polarizing plate>
A retardation film (manufactured by JSR; trade name Arton) as “+ A plate” was attached to the outer surface of the first substrate of the cell on which the liquid crystal layer was formed. At this time, the direction of the optical axis of the retardation film is the direction of the optical axis of the birefringent layer when the birefringent layer is viewed in the thickness direction of the liquid crystal layer or the birefringent layer (inclination direction of the optical axis). The retardation film is attached to the outer surface of the first substrate so that they are aligned.

  Then, a polarizing plate (manufactured by Sanlitz Co., Ltd .; trade name HLC2-5618) is pasted on the surface of the retardation film on the cell on which the retardation film is pasted (this polarizing plate is referred to as a first polarizing plate). The same polarizing plate is also attached to the outer surface of the second substrate (this polarizing plate is referred to as a second polarizing plate). These polarizing plates are disposed so that the absorption axis of the first polarizing plate and the absorption axis of the second polarizing plate are orthogonal to each other when viewed in the thickness direction of the birefringence layer. . At this time, the first polarizing plate is aligned such that the absorption axis direction of the first polarizing plate is aligned with the tilt direction of the optical axis of the birefringence layer when the birefringence layer is viewed in the thickness direction of the birefringence layer. The polarizing plate is affixed on the retardation film surface.

  Thus, a polarizing plate was attached to the outer position of the cell, and a liquid crystal display device was obtained.

  About the obtained liquid crystal display device, the state of light leakage when viewed from the thickness direction of the birefringent layer was measured by measuring the front luminance. The front luminance was measured as follows.

<Measurement of front brightness>
The measurement of the front luminance was carried out using a luminance measurement system constructed by a luminance measuring device and a light irradiation unit that irradiates light to the liquid crystal display device.

  In the luminance measurement system, the luminance measuring device includes an optical sensor that detects light that has passed through the liquid crystal display device among light emitted from the light irradiation unit, and a measurement unit that measures luminance based on a signal detected by the optical sensor. Is provided. Specifically, “BM-9” manufactured by Topcon Corporation was used as a luminance measuring instrument for measuring luminance.

Using the luminance measurement system, the front luminance was measured as follows.
First, the light irradiating unit is arranged at the outer side of the second polarizing plate of the liquid crystal display device, and the light is irradiated to the outer side of the first polarizing plate at a position facing the thickness direction of the liquid crystal layer across the liquid crystal display device. A sensor was placed.

Light with a wavelength of 550 nm is emitted from the light irradiation unit toward the liquid crystal display device, and the light sensor passes through the first polarizing plate from the outer side of the second polarizing plate and is detected by the optical sensor. The front luminance is measured by measuring the amount of light (luminance) measured by the measuring unit.
As a result of such measurement, the front luminance of the liquid crystal display device was 0.23 cd / m ² .

Example 2
4 except that the colored layer is formed as follows on the base material surface constituting the first substrate and the birefringence layer is formed on the colored layer surface. A liquid crystal display device including a first substrate and a second substrate as shown in FIG.

<Preparation of colored layer>
<Adjustment of coloring material dispersion used for forming colored layer>
A pigment-dispersed photoresist was used as a coloring material dispersion for the black matrix (BM) and red (R), green (G), and blue (B) colored pixels. The pigment-dispersed photoresist uses a pigment as a coloring material, adds beads to a dispersion composition (containing a pigment, a dispersant, and a solvent), disperses with a disperser for 3 hours, and then removes the beads. It was obtained by mixing with a clear resist composition (containing polymer, monomer, additive, initiator and solvent). The obtained pigment-dispersed photoresist has a composition as shown below. A paint shaker (manufactured by Asada Tekko Co., Ltd.) was used as the disperser.

(Photoresist for black matrix)
Black pigment: 14.0 parts by weight (manufactured by Dainichi Seika Kogyo Co., Ltd., TM Black # 95550)
・ Dispersant: 1.2 parts by weight (Bic Chemie, Disperbyk 111)
・ Polymer 2.8 parts by weight (Showa Polymer Co., Ltd., VR60)
-Monomer 3.5 parts by weight (Sartomer Co., Ltd., SR399)
・ Additive: 0.7 parts by weight (L-20 manufactured by Soken Chemical Co., Ltd.)
Initiator: 1.6 parts by weight (2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1)
・ Initiator: 0.3 parts by weight (4,4′-diethylaminobenzophenone)
・ Initiator: 0.1 parts by weight (2,4-diethylthioxanthone)
・ Solvent: 75.8 parts by weight (ethylene glycol monobutyl ether)

(Photoresist for red (R) colored pixels)
・ Red pigment: 4.8 parts by weight (CIPR254 (manufactured by Ciba Specialty Chemicals, Chromophthal DPP Red BP))
・ Yellow pigment: 1.2 parts by weight (CI PY139 (manufactured by BASF, Paliotor Yellow D1819))
・ Dispersant: 3.0 parts by weight (manufactured by Zeneca Corporation, Solsperse 24000)
・ Monomer: 4.0 parts by weight (Sartomer Co., Ltd., SR399)
-Polymer 1-5.0 parts by weight-Initiator-1.4 parts by weight (Irgacure 907, manufactured by Ciba Geigy)
Initiator: 0.6 parts by weight (2,2′-bis (o-chlorophenyl) -4,5,4 ′, 5′-tetraphenyl-1,2′-biimidazole)
・ Solvent: 80.0 parts by weight (propylene glycol monomethyl ether acetate)

(Photoresist for green (G) colored pixels)
Green pigment: 3.7 parts by weight (CIPG7 (manufactured by Dainichi Seika, Seika Fast Green 5316P))
・ Yellow pigment: 2.3 parts by weight (CI PY139 (manufactured by BASF, Paliotor Yellow D1819))
・ Dispersant: 3.0 parts by weight (manufactured by Zeneca Corporation, Solsperse 24000)
・ Monomer: 4.0 parts by weight (Sartomer Co., Ltd., SR399)
-Polymer 1-5.0 parts by weight-Initiator-1.4 parts by weight (Irgacure 907, manufactured by Ciba Geigy)
Initiator: 0.6 parts by weight (2,2′-bis (o-chlorophenyl) -4,5,4 ′, 5′-tetraphenyl-1,2′-biimidazole)
・ Solvent: 80.0 parts by weight (propylene glycol monomethyl ether acetate)

(Blue (B) colored pixel photoresist)
・ Blue pigment: 4.6 parts by weight (CI PB15: 6 (manufactured by BASF, heliogen blue L6700F))
・ Purple pigment: 1.4 parts by weight (CIPV23 (manufactured by Clariant, Foster Palm RL-NF))
Pigment derivative: 0.6 parts by weight (manufactured by Zeneca Corporation, Solsperse 12000)
・ Dispersant: 2.4 parts by weight (Zeneca Co., Ltd., Solsperse 24000)
・ Monomer: 4.0 parts by weight (Sartomer Co., Ltd., SR399)
-Polymer 1-5.0 parts by weight-Initiator-1.4 parts by weight (Irgacure 907, manufactured by Ciba Geigy)
Initiator: 0.6 parts by weight (2,2′-bis (o-chlorophenyl) -4,5,4 ′, 5′-tetraphenyl-1,2′-biimidazole)
・ Solvent: 80.0 parts by weight (propylene glycol monomethyl ether acetate)

  The polymer 1 is based on 100 mol% of a copolymer of benzyl methacrylate: styrene: acrylic acid: 2-hydroxyethyl methacrylate = 15.6: 37.0: 30.5: 16.9 (molar ratio). 2-methacryloyloxyethyl isocyanate was added at 16.9 mol%, and the weight average molecular weight was 42500.

<Formation of colored layer>
Prepare a glass substrate (7059 glass, manufactured by Corning) as a base material that has been subjected to a cleaning treatment, and apply a colored material dispersion for each color on the upper surface of the glass substrate as shown below. Were laminated.
First, the BM photoresist prepared above is applied to a glass substrate by spin coating, pre-baked (pre-baked) at 90 ° C. for 3 minutes, and exposed using a mask formed in a predetermined pattern ( 100 mJ / cm ² ), followed by spray development using 0.05% KOH aqueous solution for 60 seconds, followed by post-baking (baking) at 200 ° C. for 30 minutes to form a BM having a thickness of 1.2 μm A base material (BM forming base material) was produced.

Next, a red (R) pigment-dispersed photoresist that has been adjusted in advance so as to correspond to the position corresponding to the red colored pixel is applied on the BM-forming substrate by spin coating, and the conditions of 80 ° C. and 3 minutes are applied. And pre-baked with UV exposure (300 mJ / cm ² ) using a predetermined coloring pattern photomask corresponding to each color pattern. Further, spray development using a 0.1% KOH aqueous solution was performed for 60 seconds, followed by post-baking (baking) at 200 ° C. for 60 minutes, and a red (R) film having a thickness of 2.6 μm at a predetermined position with respect to the BM pattern. ) A colored pixel pattern was formed.

  Subsequently, a pattern was formed for each of the green (G) colored pixels and the blue (B) colored pixels by using the same method as the pattern forming method of the red (R) colored pixels. Thus, a colored layer composed of BM, red colored pixels, green colored pixels, and blue colored pixels was formed on the glass substrate.

  Using the base material on which the colored layer thus obtained was formed, a first substrate was produced in the same manner as in Example 1.

Further, a liquid crystal display device was obtained in the same manner as in Example 1 using the first substrate.
With respect to the obtained liquid crystal display device, the front luminance was measured in the same manner as in Example 1.
The front luminance was 0.20 cd / m ² .

Example 3
A first substrate was produced in the same manner as in Example 2 except that a base material on which a colored layer provided with colored pixels of each color arranged in a stripe pattern was used. The birefringence layer was formed on the colored layer forming surface side of the substrate.

  Further, a liquid crystal display device was obtained in the same manner as in Example 1 except that the first substrate was used and the polarizing plate was disposed as shown below.

<Disposition of polarizing plate>
In the same manner as in Example 1, a polarizing plate (manufactured by Sanlitz Co., Ltd .; trade name HLC2-5618) was pasted on the retardation film surface to the cell on which the retardation film (manufactured by JSR; trade name Arton) was pasted (No. 1 And a similar polarizing plate is also attached to the second substrate outer surface (second polarizing plate). These polarizing plates are disposed so that the absorption axis of the first polarizing plate and the absorption axis of the second polarizing plate are orthogonal to each other when viewed in the thickness direction of the birefringence layer. . However, in this example, the first polarizing plate was stuck on the retardation film surface so that the absorption axis direction of the first polarizing plate coincided with the longitudinal direction of the stripe-type colored pixels.

With respect to the obtained liquid crystal display device, the front luminance was measured in the same manner as in Example 1.
The front luminance was 0.20 cd / m ² .

Comparative Example 1
In Example 1, when viewed in the thickness direction of the liquid crystal layer, the absorption axis of the first polarizing plate is disposed at a position shifted by 45 ° with respect to the direction of inclination of the optical axis of the refractive index ellipsoid of the birefringence layer. And the liquid crystal display device which stuck the 1st polarizing plate and the 2nd polarizing plate to the cell so that the absorption axis of the 1st polarizing plate and the absorption axis of the 2nd polarizing plate was orthogonally crossed was obtained.
With respect to the obtained liquid crystal display device, the front luminance was measured in the same manner as in Example 1.
Front luminance was 0.28cd / m ^2.

Comparative Example 2
A liquid crystal display device was obtained in the same manner as in Example 3 except that the first substrate obtained in Example 3 was used and the polarizing plate was arranged as follows. That is, in this comparative example, when viewed in the thickness direction of the liquid crystal layer, the absorption axis of the first polarizing plate is disposed at a position shifted by 45 ° with respect to the longitudinal direction of the stripe-type colored pixels, and the first The first polarizing plate and the second polarizing plate were attached to the cell so that the absorption axis of the polarizing plate and the absorption axis of the second polarizing plate were orthogonal to each other.

With respect to the obtained liquid crystal display device, the front luminance was measured in the same manner as in Example 1.
The front luminance was 0.27 cd / m ² .

  Thus, Examples 1, 2, 3 and Comparative Examples 1 and 2 show that light leakage is suppressed in the liquid crystal display device of the present invention.

It is a decomposition explanatory view for explaining the structure of the liquid crystal display layer device of the present invention. (A) It is explanatory drawing explaining the relationship between the absorption axis seen from the F direction in FIG. 1, and a refractive index ellipsoid in the Example of the liquid crystal display device of this invention. (B) It is explanatory drawing explaining the relationship between the absorption axis seen from the F direction in FIG. 1, and a refractive index ellipsoid in the other Example of the liquid crystal display device of this invention. (A) It is a schematic sectional drawing for demonstrating the installation position of a birefringence layer. (B) It is a schematic sectional drawing for demonstrating the installation position of a birefringence layer. (C) It is a schematic sectional drawing for demonstrating the installation position of a birefringence layer. (A) It is a schematic sectional drawing for demonstrating one of the Examples of the liquid crystal display device provided with the different birefringence layer. (B) It is a schematic sectional drawing for demonstrating one of the Examples of the liquid crystal display device provided with the colored layer. (A) It is a schematic plan view explaining the switching circuit in the liquid crystal display device of this invention. (B) It is a schematic plan view explaining the other switching circuit in the liquid crystal display device of this invention. It is a figure for demonstrating the arrangement | positioning relationship of a colored layer and a polarizing plate in a liquid crystal display device provided with the colored layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 Liquid crystal layer 3 1st board | substrate 4 2nd board | substrate 5 1st polarizing plate 6 2nd polarizing plate 7 Birefringence layer 8 Colored pixel 9 Light-shielding part 10 Colored layer 20 Switching circuit 30 Base material 31 Different birefringence layers

Claims (12)

Provided are substrates that are opposed to each other with a liquid crystal layer containing a liquid crystal having a variable orientation state, and the first polarizing plate and the second polarizing plate are disposed with their absorption axes orthogonal to each other with the opposing substrate interposed therebetween. In liquid crystal display devices,
Between the first polarizing plate and the second polarizing plate, a birefringent layer is formed by polymerizing a polymerizable liquid crystal and has an optical axis inclined with respect to the thickness direction of the birefringent layer. Is formed,
The optical axis of the birefringent layer is inclined in the direction of the absorption axis of either the first polarizing plate or the second polarizing plate with respect to the thickness direction of the birefringent layer. Display device.   The liquid crystal display device according to claim 1, wherein the birefringent layer is formed by polymerizing a polymerizable liquid crystal in a homeotropic alignment state.   The liquid crystal display device according to claim 1, wherein the birefringent layer is formed by three-dimensionally cross-linking polymerizing liquid crystal having a rod-like molecular shape.   4. The liquid crystal display device according to claim 1, wherein an optical axis of the birefringent layer is uniformly inclined over the entire surface of the birefringent layer.   5. The liquid crystal display device according to claim 1, wherein the birefringent layer is laminated between opposing substrates.   The liquid crystal display device according to claim 1, wherein a colored layer is formed on at least one of the opposing substrates.   The liquid crystal display device according to claim 6, wherein the birefringence layer is formed on the colored layer surface.   The colored layer includes colored pixels that are arranged in a stripe-type arrangement pattern and transmit light of a predetermined wavelength, and the direction of the absorption axis of either the first polarizing plate or the second polarizing plate The liquid crystal display device according to claim 7, which corresponds to a longitudinal direction of a stripe-type colored pixel.   9. The birefringence layer having an optical axis different from the birefringence layer having an inclined optical axis is formed between the birefringence layer having an inclined optical axis and the first polarizing plate. A liquid crystal display device according to any one of the above.   A birefringent layer having an inclined optical axis is formed between the substrate on which the colored layer is formed and the liquid crystal layer, and has a different optical axis from the birefringent layer having the inclined optical axis. 9. The liquid crystal display device according to claim 6, wherein the birefringent layer is formed between the substrate on which the colored layer is formed and the first polarizing plate.   The liquid crystal display device according to claim 9 or 10, wherein the optical axis of the different birefringence layer is aligned with the direction of the absorption axis of the first polarizing plate or the second polarizing plate.   The liquid crystal display device according to claim 9, wherein the different birefringence layer includes a film material.

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