Optical element and liquid crystal display device having the same

Abstract

Provided is an optical element capable of suppressing a decrease in contrast in a front direction and a decrease in transmittance of white display at azimuth angles of 0° to 180°, and a liquid crystal display device provided with the optical element. The optical element is provided with, in order from an observation surface side to a back surface side, an observation surface side polarizer, a phase difference plate, and a back surface side polarizer, the transmission axis of the observation surface side polarizer being parallel to the transmission axis of the back surface side polarizer, the average angle θ of the angle θ1 between the optical axis at the back surface side of the phase difference plate and the back surface side and the angle θ2 between the optical axis at the observation surface side of the phase difference plate and the observation surface side being more than 0° and less than 90°.

Description

Technical Field

[0001] The following disclosure relates to optical elements and liquid crystal display devices incorporating optical elements. Background Technology

[0002] Liquid crystal display (LCD) devices typically consist of a liquid crystal panel, a backlight, and optical components such as polarizers and phase retardation plates. Due to their superior display characteristics, LCD devices are widely used in electronic devices such as monitors, projectors, mobile phones, and portable digital assistants (PDAs).

[0003] Furthermore, techniques for controlling the viewing angle characteristics of light emitted from a backlight source using optical elements such as polarizers and phase retardation plates are known. Specifically, for example, Patent Document 1 discloses an optical element comprising a first polarizer, a birefringent layer, and a second polarizer, wherein the first polarizer, the birefringent layer, and the second polarizer are stacked in this order, the transmission axis of the first polarizer is parallel to the transmission axis of the second polarizer, the biaxiality parameter NZ of the birefringent layer satisfies 10≤NZ or NZ≤-9, and the absolute value of the phase difference |Rth| in the thickness direction of the birefringent layer satisfies |Rth|≥200nm.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2012 / 090769 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] Liquid crystal displays generally have low contrast ratio (CR), especially when displaying dark images, blacks do not appear truly black, and there is room for improvement in this regard.

[0009] The reasons are as follows. Figure 16 This diagram illustrates an example of the transmittance viewing angle in a black display state of a conventional liquid crystal display device. Because the liquid crystal panel of the liquid crystal display device has a viewing angle-dependent polarizing plate, when viewed from an angle in a black display state, as... Figure 16 As shown, light leakage occurs in the tilted direction. Because the shutter function of the liquid crystal panel is incomplete in the tilted direction, light leakage occurs in black display mode. Part of the tilted light leakage changes direction towards the normal direction of the liquid crystal panel through scattering, thus also causing light leakage in the normal direction, resulting in a decrease in contrast in the front view.

[0010] Furthermore, in liquid crystal display devices used in vehicles, it is required to suppress the decrease in transmittance (brightness) of white display at an orientation of 0° to 180° (especially 45° and 135°) equivalent to looking down at the liquid crystal display device from above.

[0011] While Patent Document 1 discloses a technique for controlling the viewing angle characteristics of light emitted from a backlight using an optical element equipped with a polarizing plate and a phase retardation plate, it makes no disclosure or suggestion regarding countermeasures for light leakage in the tilt direction. There is room for improvement in suppressing the decrease in contrast in the front direction and suppressing the decrease in transmittance of white displays at 0° to 180°.

[0012] The present invention was made in view of the above-mentioned situation, and its object is to provide an optical element capable of suppressing the decrease in contrast in the front direction and the decrease in transmittance of white display at an orientation of 0° to 180°, and a liquid crystal display device having the optical element.

[0013] Solution for solving the problem

[0014] (1) One embodiment of the present invention is an optical element comprising, in sequence from the observation surface side to the back side: an observation surface side polarizer, a phase retardation plate, and a back side polarizer, wherein the transmission axis of the observation surface side polarizer is parallel to the transmission axis of the back side polarizer, and when the angle between the optical axis at the back side surface of the phase retardation plate and the back side surface is set as θ1, and the angle between the optical axis at the observation surface surface of the phase retardation plate and the observation surface surface is set as θ2, the average angle θ of the angles θ1 and θ2 exceeds 0° and is less than 90°.

[0015] (2) In addition, one embodiment of the present invention is an optical element in which the average angle θ is 40° or more and 80° or less, based on the configuration described in (1) above.

[0016] (3) In addition, one embodiment of the present invention is an optical element in which the angle θ1 is different from the angle θ2, based on the configuration described in (1) or (2) above.

[0017] (4) In addition, in one embodiment of the present invention, an optical element is provided in which the angle θ1 is larger than the angle θ2, based on the configuration described in (1), (2) or (3) above.

[0018] (5) In addition, in one embodiment of the present invention, an optical element is provided in which the difference between the angle θ1 and the angle θ2 is 60° or more and 80° or less, based on the configuration of (1), (2), (3) or (4) above.

[0019] (6) In addition, one embodiment of the present invention is an optical element in which, based on the configuration of (1), (2), (3), (4) or (5) above, the orientation of the optical axis at the back side of the phase retardation plate is parallel to the orientation of the optical axis at the observation side of the phase retardation plate, and is orthogonal or parallel to the transmission axis of the observation side polarizer.

[0020] (7) In addition, one embodiment of the present invention is an optical element in which the phase retardation plate contains a cured polymeric liquid crystal, based on the configuration of (1), (2), (3), (4), (5) or (6) described above.

[0021] (8) In addition, in a certain embodiment of the present invention, an optical element is provided, based on the configuration of (1), (2), (3), (4), (5), (6) or (7) above, wherein the observation surface side polarizer or the back side polarizer is a reflective polarizer.

[0022] (9) In addition, another embodiment of the present invention is a liquid crystal display device comprising: an optical element as described in any one of (1), (2), (3), (4), (5), (6), (7), and (8) above; a liquid crystal panel disposed on the observation surface side of the observation surface side polarizer of the optical element; and a polarizer disposed on the observation surface side of the liquid crystal panel.

[0023] (10) In addition, one embodiment of the present invention is a liquid crystal display device. Based on the above configuration (9), when the horizontal right direction of the image of the liquid crystal panel is set to 0°, the counterclockwise direction is set to a positive angle, and the clockwise direction is set to a negative angle, the orientation of the optical axis at the back side of the phase difference plate and the orientation of the optical axis at the observation side of the phase difference plate are 90°±3°.

[0024] Invention Effects

[0025] According to the present invention, an optical element and a liquid crystal display device are provided that can suppress the decrease in contrast in the front direction and suppress the decrease in transmittance of white display at an orientation of 0° to 180°. Attached Figure Description

[0026] Figure 1 This is a cross-sectional schematic diagram showing an example of the configuration of the liquid crystal display device according to Embodiment 1.

[0027] Figure 2This is a cross-sectional schematic diagram illustrating the phase difference plate of the polarization grating in Embodiment 1.

[0028] Figure 3 This is a cross-sectional schematic diagram showing an example of the configuration of a liquid crystal display device according to reference method 1.

[0029] Figure 4 This is an example of a calculation result that normalizes the transmittance angle of the polarizer grating in Reference Method 1 to the transmittance angle of the polarizer grating including the second and third polarizers.

[0030] Figure 5 This is an example of a calculation result that normalizes the transmittance angle of the polarizer grating in Embodiment 1 to the transmittance angle of the polarizer grating including the second polarizer and the third polarizer.

[0031] Figure 6A This is a diagram illustrating the configuration of the liquid crystal display device in Comparative Example 1.

[0032] Figure 6B The results are the calculated transmittance angle of the optical element of Comparative Example 1 and the calculated transmittance angle of the optical element of Comparative Example 1 after normalization with the optical element of Comparative Example 1.

[0033] Figure 7A This is a diagram used to illustrate the configuration of the liquid crystal display device in Reference Example 1.

[0034] Figure 7B The results are the calculated transmittance angle of the polarizer grating of Reference Example 1 and the calculated transmittance angle of the polarizer grating of Reference Example 1, which has been normalized with the optical element of Comparative Example 1.

[0035] Figure 8A This is a diagram illustrating the configuration of the liquid crystal display device in Embodiment 1.

[0036] Figure 8B These are the calculated results of the transmittance angle of the polarizing grating of Example 1, and the calculated results of the transmittance angle of the polarizing grating of Example 1, which were normalized using the optical element of Comparative Example 1.

[0037] Figure 9A This is a diagram illustrating the configuration of the liquid crystal display device in Embodiment 2.

[0038] Figure 9B The results are the calculated transmittance angle of the polarizing grating of Example 2 and the calculated transmittance angle of the polarizing grating of Example 2, which has been normalized with the optical element of Comparative Example 1.

[0039] Figure 10AThis is a diagram illustrating the configuration of the liquid crystal display device in Embodiment 3.

[0040] Figure 10B These are the calculated results of the transmittance angle of the polarizing grating of Example 3, and the calculated results of the transmittance angle of the polarizing grating of Example 3, which were normalized using the optical element of Comparative Example 1.

[0041] Figure 11A This is a diagram illustrating the configuration of the liquid crystal display device in Embodiment 4.

[0042] Figure 11B These are the calculated results of the transmittance angle of the polarizing grating of Example 4, and the calculated results of the transmittance angle of the polarizing grating of Example 4, which were normalized using the optical element of Comparative Example 1.

[0043] Figure 12A This is a diagram illustrating the configuration of the liquid crystal display device in Embodiment 5.

[0044] Figure 12B The results are the calculated transmittance angle of the polarizing grating of Example 5 and the calculated transmittance angle of the polarizing grating of Example 5, which has been normalized with the optical element of Comparative Example 1.

[0045] Figure 13A This is a diagram illustrating the configuration of the liquid crystal display device in Embodiment 6.

[0046] Figure 13B These are the calculated results of the transmittance angle of the polarizing grating of Example 6, and the calculated results of the transmittance angle of the polarizing grating of Example 6, which were normalized using the optical element of Comparative Example 1.

[0047] Figure 14A This is a diagram illustrating the configuration of the liquid crystal display device in Embodiment 7.

[0048] Figure 14B The results are the calculated transmittance angle of the polarizing grating of Example 7 and the calculated transmittance angle of the polarizing grating of Example 7, which has been normalized with the optical element of Comparative Example 1.

[0049] Figure 15A This is a diagram illustrating the configuration of the liquid crystal display device in Embodiment 8.

[0050] Figure 15B These are the calculated results of the transmittance angle of the polarizing grating of Example 8, and the calculated results of the transmittance angle of the polarizing grating of Example 8, which were normalized using the optical element of Comparative Example 1.

[0051] Figure 16This is a diagram showing an example of the transmittance viewing angle in the black display state of a conventional liquid crystal display device.

[0052] Explanation of reference numerals in the attached figures

[0053] 1, 1R, 1S: Liquid Crystal Display Device

[0054] 11: First polarizer

[0055] 11A, 12A, 13A: Axis orientation

[0056] 12: Second polarizer

[0057] 13: Third polarizer

[0058] 20: LCD panel

[0059] 30: Phase retardation plate (tilted phase retardation plate)

[0060] 30L: Polymerized liquid crystal

[0061] 30S: Phase Difference Plate

[0062] 30SA, 30XA, 30YA: Optical axis (hysteresis axis)

[0063] 30X, 30Y: Face

[0064] 40: Backlight

[0065] 100, 100S: Polarizing grating

[0066] 100R: Optical components

[0067] θ: Mean angle

[0068] θ1, θ2: Angles. Detailed Implementation

[0069] The present invention will now be described in more detail with reference to the accompanying drawings, but the present invention is not limited to these embodiments.

[0070] [Definition of the term]

[0071] In this specification, a polarizer means a device that extracts polarized light (linearly polarized light) that vibrates only in a specific direction from unpolarized light (natural light), partially polarized light, or polarized light, as opposed to a circular polarizer (circular polarizing plate). Unless otherwise stated, the term "polarizer" in this specification does not include a protective film and refers only to an element with polarization function. An absorption polarizer is a polarizer that absorbs light vibrating in a specific direction and allows polarized light (linearly polarized light) vibrating in a direction perpendicular to that specific direction to pass through. A reflection polarizer is a polarizer that reflects light vibrating in a specific direction and allows polarized light (linearly polarized light) vibrating in a direction perpendicular to that specific direction to pass through.

[0072] In this specification, the in-plane phase difference Rp is defined as Rp = (ns - nf)d. The thickness-direction phase difference Rth is defined as Rth = (nz - (nx + ny) / 2)d. ns refers to the larger of nx and ny, and nf refers to the smaller of nx and ny. Furthermore, nx and ny represent the in-plane principal refractive indices of the birefringent layer (including the retardation plate and the liquid crystal panel), nz represents the out-of-plane principal refractive index (i.e., the direction perpendicular to the plane of the birefringent layer), and d represents the thickness of the birefringent layer.

[0073] Furthermore, unless otherwise specified, the wavelength for measuring optical parameters such as principal refractive index and phase difference is set to 550 nm in this specification.

[0074] In this specification, a birefringent layer refers to a layer with optical anisotropy, encompassing both a phase retardation plate and a liquid crystal panel. A birefringent layer means a layer in which either the absolute value of the in-plane phase difference or the absolute value of the phase difference in the thickness direction is greater than 10 nm, preferably a layer in which either the absolute value of the in-plane phase difference or the absolute value of the phase difference in the thickness direction is greater than 20 nm.

[0075] In this specification, the viewing side means the side closer to the screen (display surface) of the liquid crystal display device, and the rear side means the side farther away from the screen (display surface) of the liquid crystal display device.

[0076] In this specification, polar angle refers to the angle between the direction of the object (e.g., the measurement direction) and the normal direction of the liquid crystal panel screen. Azimuth refers to the direction in which the direction of the object is projected onto the liquid crystal panel screen, expressed as the angle (azimuth angle) between it and the reference azimuth. Here, the reference azimuth (0°) is set to the horizontal right direction of the liquid crystal panel screen. Angles and azimuth angles are positive counterclockwise and negative clockwise. Both counterclockwise and clockwise directions indicate the rotation direction when viewing the liquid crystal panel screen from the viewing side (front). Furthermore, angles represent values ​​measured when looking down at the liquid crystal panel; two straight lines (including axes, directions, and edges) being orthogonal to each other mean that they are orthogonal when looking down at the liquid crystal panel.

[0077] In this specification, unless otherwise stated, axis orientation means the orientation of the absorption axis (reflection axis) of the polarizer or the optical axis (hysteresis axis) of the phase retardation plate.

[0078] In this specification, two orthogonal axes mean that the angle between them is 90°±3°, preferably 90°±1°, more preferably 90°±0.5°, and particularly preferably 90° (completely orthogonal). Two parallel axes mean that the angle between them is 0°±3°, preferably 0°±1°, more preferably 0°±0.5°, and particularly preferably 0° (completely parallel).

[0079] The following describes embodiments of the present invention. The present invention is not limited to the contents described in the following embodiments, and appropriate design changes can be made within the scope of satisfying the structure of the present invention.

[0080] <Implementation Method 1>

[0081] Figure 1 This is a cross-sectional schematic diagram showing an example of the configuration of the liquid crystal display device according to Embodiment 1.

[0082] Figure 2 This is a cross-sectional schematic diagram illustrating the phase retardation plate included in the polarizing grating of Embodiment 1. The liquid crystal display device 1 of this embodiment is a transmissive liquid crystal display device, such as... Figure 1 As shown, the structure, from the observation surface side to the back surface side, includes a first polarizer 11, a liquid crystal panel 20 containing a liquid crystal layer, a second polarizer 12 serving as the observation surface side polarizer, a phase retardation plate (tilted phase retardation plate) 30, a third polarizer 13 serving as the back surface side polarizer, and a backlight 40. The first polarizer 11 corresponds to the polarizer disposed on the observation surface side of the liquid crystal panel 20.

[0083] The components from the second polarizer 12 to the third polarizer 13 together function as an optical louver, and are therefore referred to as polarizing louvers below. That is, the optical element having the second polarizer 12, the phase retardation plate 30, and the third polarizer 13 is also called the polarizing louver 100.

[0084] The first polarizer 11 has a first transmission axis and a first absorption axis or a first reflection axis orthogonal to the first transmission axis; the second polarizer 12 has a second transmission axis and a second absorption axis or a second reflection axis orthogonal to the second transmission axis; and the third polarizer 13 has a third transmission axis and a third absorption axis or a third reflection axis orthogonal to the third transmission axis.

[0085] like Figure 1 and Figure 2 As shown, in the polarizing grating 100, the transmission axis of the second polarizer 12 is parallel to the transmission axis of the third polarizer 13. When the angle between the optical axis 30XA at ​​the back surface surface 30X of the phase retardation plate 30 and the back surface surface 30X is set to θ1, and the angle between the optical axis 30YA at the observation surface surface 30Y of the phase retardation plate 30 and the observation surface surface 30Y is set to θ2, the average angle θ of angles θ1 and θ2 exceeds 0° and is less than 90°. By adopting this scheme, the decrease in contrast in the front direction can be suppressed, and the decrease in transmittance of white display in the azimuth range of 0° to 180° can be suppressed. In this specification, the optical axis is also referred to as the hysteresis axis.

[0086] A phase retardation plate with an average angle θ greater than 0° but less than 90° is also called a phase retardation plate or a tilted phase retardation plate whose optical axis is tilted from the normal direction of the display device (the normal direction of the phase retardation plate). A phase retardation plate with an average angle θ of 90° is also called a phase retardation plate whose optical axis is aligned with the normal direction of the display device (the normal direction of the phase retardation plate). The phase retardation plate 30 in this embodiment is a tilted phase retardation plate.

[0087] Figure 3 This is a cross-sectional schematic diagram showing an example of the configuration of a liquid crystal display device according to reference method 1.

[0088] Figure 4 This is an example of a calculation result where the transmittance angle of the polarizer grating in Reference Method 1 is normalized to the transmittance angle of the polarizer grating including the second and third polarizers. The inventors of this invention have made the following improvements... Figure 3 The polarization grating 100S of the reference method 1, which has a phase retardation plate 30S with an average angle θ of 90° between the second polarizer 12 and the third polarizer 13, i.e., the optical axis 30SA (specifically the principal axis or hysteresis axis of the refractive index ellipsoid) is aligned with the normal direction of the display device, was studied.

[0089] The results showed that the polarizing grating 100S in reference method 1 limits the amount of light incident from the backlight 40 onto the liquid crystal panel 20 from an oblique direction. Specifically, as Figure 4 As shown, it was found that the polarizing grating 100S of Reference Method 1 can improve the contrast in the front direction by symmetrically and equally reducing the amount of tilted light at 45°, 135°, 225°, and 315°. However, in Reference Method 1, there is a problem that the white display becomes darker in the tilted direction.

[0090] Figure 5 This is an example of a calculation result that normalizes the transmittance angle of the polarizing grating in Embodiment 1 to the transmittance angle of the polarizing grating including the second and third polarizers. In this embodiment, the aforementioned problem is solved by selectively reducing the amount of light at azimuths 225° and 315° using a phase retardation plate 30 with an average angle θ greater than 0° and less than 90°, i.e., a phase retardation plate 30 whose optical axis is tilted from the normal direction of the display device. For example... Figure 5 As shown, the polarizing grating 100 of this embodiment operates by keeping the amount of light above (0° to 180°) constant while reducing the amount of light below (especially at 225° and 315°). Therefore, it not only sufficiently ensures the white brightness above (0° to 180°), i.e., not only suppresses the decrease in transmittance of white display at 0° to 180°, but also improves light leakage in black display and contrast in the front direction. Thus, in this embodiment, the white brightness viewing angle is improved by asymmetric light reduction. For example, the polarizing grating 100 of this embodiment can suppress the decrease in transmittance (brightness) of white display at 45° and 135°, which are important for automotive displays. Furthermore, the viewing angle characteristics of the liquid crystal display device 1 of this embodiment become... Figure 16 and Figure 5 The perspective characteristics after multiplication.

[0091] The following is a detailed description of the liquid crystal display device 1.

[0092] The first polarizer 11 and the second polarizer 12 are orthogonally Nichols. That is, the first transmission axis (or the first absorption axis or the first reflection axis) of the first polarizer 11 is orthogonal to the second transmission axis (or the second absorption axis or the second reflection axis) of the second polarizer 12. More specifically, they form an angle within a range of 90° ± 3° (preferably within a range of 90° ± 1°).

[0093] Furthermore, the first polarizer 11 and the second polarizer 12 can also be configured in parallel Nichols, but from the viewpoint of obtaining high contrast, it is preferable to configure them in orthogonal Nichols.

[0094] The second polarizer 12 and the third polarizer 13 are arranged in a parallel Nicol configuration. That is, the second transmission axis (or second absorption axis or second reflection axis) of the second polarizer 12, which serves as the transmission axis of the observation plane-side polarizer, is parallel to the third transmission axis (or third absorption axis or third reflection axis) of the third polarizer 13, which serves as the transmission axis of the back-side polarizer. More specifically, this forms an angle within a range of 0° ± 10° (preferably within a range of 0° ± 5°).

[0095] The axial orientations of the second polarizer 12 and the third polarizer 13 can be appropriately set, but preferably within the range of 0°±10° or 90°±10°, more preferably within the range of 0°±5° or 90°±5°, and particularly preferably substantially set to 0° or 90°. This allows for a bright display in both the normal direction and the vertical and horizontal directions. For example, the axial orientation 11A of the first polarizer 11 is 0°, and the axial orientations 12A of the second polarizer 12 and 13A of the third polarizer 13 are 90°.

[0096] There are no particular limitations on the materials or optical properties of polarizers 11, 12, and 13; for example, absorptive polarizers and reflective polarizers can be used appropriately. Specifically, in addition to absorptive polarizers, which are formed by adsorbing anisotropic materials such as dichroic iodine complexes onto a polyvinyl alcohol (PVA) film and orienting them, reflective polarizers (e.g., APCF manufactured by Nitto Denko Corporation or DBEF manufactured by 3M Corporation), which are obtained by uniaxially stretching a co-extruded film comprising two resins, and reflective polarizers (so-called wire grid polarizers), which are formed by periodically arranging fine metal wires, can also be used. Furthermore, polarizers formed by stacking absorptive polarizers and reflective polarizers can also be used.

[0097] Preferably, the second polarizer 12 or the third polarizer 13 is a reflective polarizer. Here, light supplied from the backlight (generally unpolarized light) is absorbed by 50% and lost due to the absorption polarizer disposed on the back side of the liquid crystal panel. However, since the second polarizer 12 or the third polarizer 13 is a reflective polarizer, the absorption of light supplied from the backlight by the polarizer disposed on the back side of the liquid crystal panel can be suppressed, thus improving light utilization efficiency. This reflective polarizer disposed on the back side of the liquid crystal panel is also called a brightness-enhancing film.

[0098] More preferably, the third polarizer 13 is a reflective polarizer. By adopting this configuration, the function of a brightness-enhancing film can be added to the third polarizer 13 of the polarizing plate grating 100, thereby suppressing the increase in manufacturing cost or thickness of the liquid crystal display device 1.

[0099] When the second polarizer 12 is an absorptive polarizer and the third polarizer 13 is a reflective polarizer, it is preferable that the transmission axis of the second polarizer 12 and the transmission axis of the third polarizer 13 are arranged parallel to each other. By adopting this arrangement, the light utilization efficiency can be further improved. More specifically, the polarized light emitted from the backlight source 40 that vibrates in an azimuth parallel to the transmission axis of the third polarizer 13 (which is a reflective polarizer) passes sequentially through the third polarizer 13 and the second polarizer 12. On the other hand, the polarized light that vibrates in an azimuth orthogonal to the transmission axis of the third polarizer 13 is reflected by the third polarizer 13 and returns to the backlight source 40 side. The light returning to the backlight source 40 side is then emitted again from the backlight source 40 towards the third polarizer 13 side after its polarization state has been changed in the reflective or diffuser provided with the backlight source 40. In this process, polarized light vibrating in an azimuth parallel to the transmission axis of the third polarizer 13 is sequentially transmitted through the third polarizer 13 and the second polarizer 12, but polarized light vibrating in an azimuth orthogonal to the transmission axis of the third polarizer 13 is reflected again. By repeating this process, the utilization efficiency of the light from the backlight 40 can be further improved.

[0100] Absorption-type polarizers are preferred for the first polarizer 11 and the second polarizer 12, and reflection-type polarizers are preferred for the third polarizer 13. By adopting this configuration, as described above, both light utilization efficiency and contrast degradation can be suppressed. In this case, the first polarizer 11 has a first transmission axis and a first absorption axis orthogonal to the first transmission axis; the second polarizer 12 has a second transmission axis and a second absorption axis orthogonal to the second transmission axis; and the third polarizer 13 has a third transmission axis and a third reflection axis orthogonal to the third transmission axis.

[0101] Alternatively, multiple third polarizers 13 can be used, stacked together. In this case, the third transmission axes of the multiple third polarizers 13 are set to substantially the same orientation.

[0102] In addition, to ensure mechanical strength or resistance to damp heat, a protective film such as a triacetyl cellulose (TAC) film (not shown) may be laminated on at least one of the observation surface side and the back side side of each polarizer 11, 12, 13. The protective film is attached to the polarizers 11, 12, 13 via any suitable adhesive layer (not shown).

[0103] Furthermore, in this specification, "adhesive layer" refers to a layer that joins the surfaces of adjacent components together and integrates them using sufficient adhesive force and bonding time for practical purposes. Examples of materials forming the adhesive layer include adhesives and anchor coating agents. The adhesive layer can be a multi-layered structure, such as an anchor coating layer formed on the surface of the bonded objects, with an adhesive layer formed on top of the anchor coating layer. Alternatively, it can be a thin layer that is not visible to the naked eye.

[0104] The liquid crystal mode of the liquid crystal panel 20 is not particularly limited. It can be a mode in which the liquid crystal molecules in the liquid crystal layer are aligned perpendicularly to the substrate surface to achieve black display, or a mode in which the liquid crystal molecules in the liquid crystal layer are aligned parallel to the substrate surface, or aligned in a direction that is neither perpendicular nor parallel to the substrate surface to achieve black display. In addition, as for the driving method of the liquid crystal panel, besides the TFT method (active matrix method), it can also be a simple matrix method (passive matrix method), plasma addressing method, etc.

[0105] As for the configuration of the liquid crystal panel 20, examples include a configuration in which a liquid crystal layer is sandwiched between a pair of substrates on one substrate having pixel electrodes and a common electrode, and a voltage is applied between the pixel electrodes and the common electrode to apply a lateral electric field (including an edge electric field) to the liquid crystal layer for display; and a configuration in which a liquid crystal layer is sandwiched between a pair of substrates on one substrate having pixel electrodes and another substrate having a common electrode, and a voltage is applied between the pixel electrodes and the common electrode to apply a vertical electric field to the liquid crystal layer for display. More specifically, as a lateral electric field method, examples include the FFS (Fringe Field Switching) mode or the IPS (In Plane Switching) mode in which the liquid crystal molecules in the liquid crystal layer are aligned parallel to the substrate surface when no voltage is applied; and as a vertical electric field method, examples include the vertical alignment (VA) mode in which the liquid crystal molecules in the liquid crystal layer are aligned perpendicular to the substrate surface when no voltage is applied.

[0106] Phase retardation plate 30 is a phase retardation plate with an average angle θ exceeding 0° but less than 90°. That is, phase retardation plate 30 is a phase retardation plate having an optical axis tilted from the normal direction of the phase retardation plate 30. For example, phase retardation plate 30 is a phase retardation plate in which molecules are tilted and oriented, also known as an O-plate (Oblique plate).

[0107] Preferably, the average angle θ is 40° or more and 80° or less. By setting it in this way, not only can the white brightness at the top (0° to 180°) be sufficiently ensured, that is, not only can the decrease in the transmittance of the white display at the 0° to 180° be suppressed, but also the light leakage of the black display and the contrast in the front direction can be improved. More preferably, the average angle θ is 45° or more and 75° or less, and even more preferably, 50° or more and 70° or less.

[0108] The retardation plate 30 may be a cured product containing a polymeric liquid crystal. A polymeric liquid crystal is a compound having polymeric groups and mesocrystalline groups. Examples of polymeric liquid crystals include rod-shaped liquid crystal molecules having polymeric groups and disk-shaped liquid crystal molecules having polymeric groups. The retardation plate 30 may be obtained, for example, by coating a retardation plate forming composition containing a polymeric liquid crystal onto an alignment film and then curing the polymeric liquid crystal. Examples of retardation plates 30 include a cured layer in which the polymeric liquid crystal 30L is uniformly tilted and aligned, such as... Figure 2 The polymeric liquid crystal 30L shown has an oriented curing layer and the like arranged in a mixed pattern. Figure 2 The polymeric liquid crystal 30L shown is a polymeric liquid crystal in which at least a portion of the polymeric groups have been polymerized. The aforementioned cured layer refers to a cured layer in which part or all of the liquid crystal composition has been cross-linked by heat, catalyst, light and / or radiation, resulting in an insoluble, infusible, or poorly soluble and refractory state.

[0109] In this specification, "mixed arrangement" refers to an arrangement in which the tilt angle (tilt angle) of the polymeric liquid crystal 30L increases or decreases continuously or intermittently in the thickness direction. It is an arrangement where the tilt angle of the polymeric liquid crystal 30L on one side of the phase retardation plate differs from the tilt angle of the polymeric liquid crystal 30L on the other side. The representative arrangement of the rod-shaped liquid crystal compound molecules in the mixed arrangement is shown in... Figure 2 The diagram is schematically shown. Here, the tilt angle refers to the angle between the physical axis of symmetry of the polymeric liquid crystal 30L and the interface of the retardation plate. Specifically, the tilt angle represents the angle between adjacent layers and the major axis (optical axis) of the polymeric liquid crystal 30L, with 0° set for the case where the polymeric liquid crystal 30L is arranged parallel to each other in the plane. Since the major axis of the polymeric liquid crystal 30L is the direction of the optical axis, the tilt angle of the polymeric liquid crystal 30L on one side of the retardation plate corresponds to the aforementioned angle θ1, and the tilt angle of the polymeric liquid crystal 30L on the other side corresponds to the aforementioned angle θ2. That is, the difference between the tilt angle of the polymeric liquid crystal 30L on one side of the retardation plate and the tilt angle of the polymeric liquid crystal 30L on the other side means that the aforementioned angle θ1 and the aforementioned angle θ2 are different.

[0110] The aforementioned rod-shaped liquid crystal molecules with polymerizable groups have, for example, a structure represented by the following general formula (I).

[0111] [Chemical Formula 1]

[0112] Z 1 -Y 1 -A 1 -Y 3 -MY 4 -A 2 -Y 2 -Z 2 (1)

[0113] (In the formula, Z) 1 and Z 2 Y represents a polymerizable group. 1 Y 2 Y 3 and Y 4 Each of these can independently represent a single bond, oxygen, sulfur, -O-CO-, -CO-O-, -O-CO-O-, -CO-NR-, -NR-CO-, -O-CO-NR-, -NR-CO-O-, or -NR-CO-NR-, Y 3 and Y 4 At least one of them represents -O-CO-O-, -O-CO-NR-, -NR-CO-O-, or -NR-CO-NR-, A 1 and A 2 Each of these can be used independently to represent a spacer having 2 to 30 carbon atoms, where M represents a mesocrystalline group and R represents an alkyl group having 1 to 4 carbon atoms.

[0114] The mesocrystalline group M described above has, for example, a structure represented by the following general formula (Ia).

[0115] [Chemical Formula 2]

[0116]

[0117] (In the formula, T represents a divalent saturated or unsaturated heterocyclic group or heterocyclic group, Y) 5 The symbols represent single bonds, oxygen, sulfur, -O-CO-, -CO-O-, -O-CO-O-, -CO-NR-, -NR-CO-, -O-CO-NR-, -NR-CO-O-, -NR-CO-NR-, -O-CH2-, -CH2-O-, -CH=N-, -N=CH-, or -N=N-, where r represents 0, 1, 2, or 3.

[0118] In the above general formula (Ia), when r is greater than 0, T can be the same or different, and Y 5 They can be the same or different.

[0119] The aforementioned disk-shaped liquid crystal molecules with polymerizable groups have, for example, a structure represented by the following general formula (II).

[0120] [Chemical Formula 3]

[0121]

[0122] (In the formula, Y) 11 Y 12 and Y 13 Each can independently represent either the methine or the nitrogen atom, R 11 R 12 and R 13 Each of the following general formulas (A), (B), (C), or hydrogen atoms can be represented independently, where R 11 R 12 and R 13 At least two of them are general formulas (A), (B), or (C) below.

[0123] [Chemical Formula 4]

[0124]

[0125] (In the formula, A) 11 and A 12 Each can be used independently to represent either a nitrogen atom or a methine; A 13 A 14 A 15 And A 16 Each can be used independently to represent either a nitrogen atom or a methine (where the hydrogen atom of the methine can be represented by a substituent -L). 11 -L 12 -Q 11 (replace); X 1 Indicates an oxygen atom, a sulfur atom, a methylene group, or an imino group; L 11 A group representing a five-membered heterocyclic ring; L 12 This indicates an alkylene or alkenylene group, wherein one or more non-adjacent CH2 groups present in these alkylene or alkenylene groups can be represented by -O-, -COO-, -OCO-, -OCOO-, -CO-, -S-, -SO2-, or -NR, respectively. A -、-NR A SO2- or -SO2NR A -(R A This indicates substitution of hydrogen atoms or alkyl groups having 1 to 4 carbon atoms. Additionally, one or more hydrogen atoms present in these groups may be substituted with halogen atoms; Q 11 Each of the following can independently represent a polymerizable group, a hydrogen atom, an OH group, a COOH group, or a halogen atom, with at least one Q. 11 (This indicates a polymerizable group.)

[0126] [Chemical Formula 5]

[0127]

[0128] (In the formula, A) 21 and A 22 Each can be used independently to represent either a nitrogen atom or a methine; A 23 A 24 A 25 And A 26 Each can be used independently to represent either a nitrogen atom or a methine (where the hydrogen atom of the methine can be represented by a substituent -L). 21 -L 22 -Q 21 (replace); X 2 Indicates an oxygen atom, a sulfur atom, a methylene group, or an imino group; L 21 A group representing a five-membered heterocyclic ring; L 22 This indicates an alkylene or alkenylene group, wherein one or more non-adjacent CH2 groups present in these alkylene or alkenylene groups can be represented by -O-, -COO-, -OCO-, -OCOO-, -CO-, -S-, -SO2-, or -NR. B -、-NR B SO2- or -SO2NR B -(R B This indicates substitution of hydrogen atoms or alkyl groups having 1 to 4 carbon atoms. Additionally, one or more hydrogen atoms present in these groups may be substituted with halogen atoms; Q 21 Each of the following can independently represent a polymerizable group, a hydrogen atom, an OH group, a COOH group, or a halogen atom, with at least one Q. 21 (This indicates a polymerizable group.)

[0129] [Chemical Formula 6]

[0130]

[0131] (In the formula, A) 31 and A 32 Each can be used independently to represent either a nitrogen atom or a methine, A 33 A 34 A 35 And A 36 Each can be used independently to represent either a nitrogen atom or a methine (where the hydrogen atom of the methine can be represented by a substituent -L). 31 -L 32 -Q 31 (replace); X 3 Indicates an oxygen atom, a sulfur atom, a methylene group, or an imino group; L 31 A group representing a five-membered heterocyclic ring; L 32This indicates an alkylene or alkenylene group. The presence of one or more non-adjacent CH2 groups in these alkylene or alkenylene groups can also be represented by -O-, -COO-, -OCO-, -OCOO-, -CO-, -S-, -SO2-, or -NR. C -、-NR C SO2- or -SO2NR C -(R C (These are substitutions of hydrogen atoms or alkyl groups having 1 to 4 carbon atoms). Additionally, one or more hydrogen atoms present in these groups can be substituted with halogen atoms; Q 31 Each of the following can independently represent a polymerizable group, a hydrogen atom, an OH group, a COOH group, or a halogen atom, with at least one Q. 31 (This indicates a polymerizable group.)

[0132] When the polymerizable liquid crystal 30L is uniformly tilted and aligned, angle θ1 is the same as angle θ2. When the polymerizable liquid crystal 30L is mixed and aligned, angle θ1 is different from angle θ2. By adopting this configuration, compared to the case where angles θ1 and θ2 are equal, it is easier to adjust the average angle θ to an optimal value. When the polymerizable liquid crystal 30L is mixed and aligned, it is preferable that angle θ1 is larger than angle θ2.

[0133] When the polymeric liquid crystal 30L is mixed and oriented, it is preferable that the difference between angle θ1 and angle θ2 is 0° or more and 90° or less.

[0134] Preferably, the orientation of the optical axis 30XA at ​​the back surface 30X of the phase retardation plate 30 is parallel to the orientation of the optical axis 30YA at the observation surface 30Y of the phase retardation plate 30, and is orthogonal to or parallel to the second transmission axis of the second polarizer 12. By adopting this configuration, the decrease in contrast in the front direction can be further suppressed.

[0135] Preferably, the orientation of the optical axis 30XA at ​​the back surface 30X of the phase retardation plate 30 and the orientation of the optical axis 30YA at the observation surface 30Y of the phase retardation plate 30 are 90°±3°. By adopting this configuration, the amount of light below (especially at azimuths 225° and 315°) can be further reduced without changing the amount of light above (azimuth 0° to 180°), thus further suppressing the decrease in contrast in the front direction. The orientation of the optical axis 30XA and the orientation of the optical axis 30YA are preferably 90°±1°, and more preferably 90°±0.5°.

[0136] Preferably, the orientation of the optical axis 30XA at ​​the back surface 30X of the phase retardation plate 30 and the orientation of the optical axis 30YA at the observation surface 30Y of the phase retardation plate 30 are 90°±3°. The orientation of the transmission axis of the second polarizer 12 is 0°±3° (i.e., the orientation of the absorption axis is 90°±3°), and the orientation of the transmission axis of the third polarizer 13 is 0°±3° (i.e., the orientation of the reflection axis is 90°±3°). By adopting this configuration, the amount of light below (especially at azimuths 225° and 315°) can be further reduced without changing the amount of light above (azimuth 0° to 180°), thus further suppressing the decrease in contrast in the front direction. Preferably, the orientation of the optical axis 30XA and the optical axis 30YA is 90°±1°, and the orientation of the transmission axis of the second polarizer 12 and the transmission axis of the third polarizer 13 is 0°±1°. More preferably, the orientation of the optical axis 30XA and the optical axis 30YA is 90°±0.5°, and the orientation of the transmission axis of the second polarizer 12 and the transmission axis of the third polarizer 13 is 0°±0.5°.

[0137] The orientation state of the polymeric liquid crystal 30L in the retardation plate 30 can be controlled by the surface energy of the surface (e.g., the support surface, air surface, etc.) in contact with the coating of the retardation plate forming composition, and by the combination of the types of polymeric liquid crystals included in the retardation plate forming composition, thereby enabling changes in the tilt degree of the liquid crystal molecules, such as mixed orientation. For example, the tilt angle of the polymeric liquid crystal 30L on the support surface side of the retardation plate 30 can be adjusted by selecting the material of the polymeric liquid crystal, the material of the alignment film, the rubbing treatment method of the alignment film, and the photoalignment treatment method of the alignment film. Furthermore, the tilt angle of the liquid crystal molecules on the surface side (air surface side) of the retardation plate 30 can be adjusted by selecting the polymeric liquid crystal and other compounds used with the polymeric liquid crystal (e.g., plasticizers, surfactants, polymeric monomers, and polymeric polymers). Moreover, the degree of change in the tilt angle can also be adjusted by the above selections.

[0138] More specifically, the tilt angle on the support side can be adjusted by optimizing the type of alignment film and surface energy. Furthermore, the tilt angle on the air side can be adjusted by biasing the air interface alignment control agent (described later) onto the air interface side. Additionally, in the method of Example 1 disclosed in Japanese Patent Application Publication No. 2013-47758, the tilt angle can be adjusted by optimizing various parameters.

[0139] To achieve the desired orientation of the polymerizable liquid crystal 30L in the retardation plate 30, and to improve the coatability or curability of the retardation plate forming composition, the retardation plate forming composition may contain one or more additives. To achieve mixed orientation of the polymerizable liquid crystal 30L, an additive capable of controlling the orientation of the air interface side of the layer (hereinafter referred to as an "air interface orientation control agent") may be added. Examples of such additives include low-molecular-weight or high-molecular-weight compounds having hydrophilic groups such as fluorinated alkyl groups and sulfonyl groups.

[0140] In the retardation plate 30 containing a polymeric liquid crystal 30L with a fixed orientation state, it is difficult to directly and accurately measure angles θ1 and θ2. Therefore, in this specification, angles θ1 and θ2 are calculated using the following method. Although this method does not accurately represent the actual orientation state, it is effective as a means of representing the relative relationships of some optical characteristics possessed by an optical element. In this method, for ease of calculation, the following two points are assumed and set as the tilt angles at the two interfaces of the retardation plate.

[0141] 1. Assume that the phase retardation plate is a multilayer structure composed of layers containing liquid crystal molecules such as polymeric liquid crystals. Furthermore, assume that the smallest unit layer (assuming that the tilt angle of the liquid crystal molecules is uniform within the layer) is optically uniaxial.

[0142] 2. Assume that the tilt angle of each layer changes monotonically as a linear function along the thickness direction of the phase difference plate. The specific calculation method is as follows.

[0143] (1) In a plane where the tilt angle of each layer monotonically changes along the thickness direction of the retardation plate as a linear function, the incident angle of the measurement light toward the retardation plate is varied, and the delay value is measured using three or more measurement angles. To simplify the measurement and calculation, it is preferable to set the normal direction relative to the retardation plate to 90° and measure the delay value using three measurement angles of 50°, 90°, and 130°. This measurement can be performed, for example, using a KOBRA-21ADH, a KOBRA-WR (manufactured by Oji Measurement Machinery Co., Ltd.), or an AxoScan (manufactured by Axometrics Co., Ltd.).

[0144] (2) The refractive index of ordinary light in each layer is set to no, and the refractive index of anomalous light in each layer is set to ne (no and ne are set to the same value in all layers). The thickness of the entire multilayer is set to d. Moreover, based on the assumption that the tilt direction in each layer is consistent with the uniaxial optical axis direction of that layer, the angle θ1 on one side of the phase retardation plate, the angle θ2 on the other side, and the thickness d are used as variables to fit and calculate θ1, θ2, and d, so that the calculated polar angle dependence of the retardation value of the phase retardation plate is consistent with the measured value.

[0145] Although the phase retardation plate 30 is a single layer (more specifically, a single layer formed as a film), as described above, the optical axis at the back side surface and the optical axis at the observation side surface of the phase retardation plate 30 can be defined based on the premise that the phase retardation plate 30 is imagined as a stack of multiple thin layers and each thin layer has an optical axis.

[0146] The backlight 40 includes a reflector, a diffuser, and a light source unit that includes a light guide plate and a light source.

[0147] In addition to the components described above, the liquid crystal display device 1 of this embodiment also includes external circuits such as TCP (bandwidth package) and PCB (printed circuit board); optical films such as viewing angle enhancement film and brightness enhancement film; and multiple components such as an outer frame. Depending on the components, they may sometimes be assembled with other components. There are no particular limitations on components other than those already described, and components commonly used in the field of liquid crystal display devices can be used, so their description is omitted.

[0148] Example

[0149] The present invention is illustrated in more detail by providing examples and comparative examples, but the present invention is not limited to these examples.

[0150] (Example 1, Comparative Example 1, and Reference Example 1)

[0151] The configurations of the liquid crystal display devices in Comparative Example 1, Reference Example 1, and Embodiment 1 are respectively as follows: Figure 6A , Figure 7A as well as Figure 8A As shown. Figure 6A This is a diagram illustrating the configuration of the liquid crystal display device in Comparative Example 1. Figure 7A This is a diagram used to illustrate the configuration of the liquid crystal display device in Reference Example 1. Figure 8A This diagram illustrates the configuration of the liquid crystal display device of Embodiment 1. The axial orientations of each component are shown in the cross-sectional view. The axial orientation of the absorption polarizer represents the orientation of the absorption axis, the axial orientation of the retardation plate represents the orientation of the optical axis (the orientation of the in-plane hysteresis axis), the axial orientation of the reflection polarizer represents the orientation of the reflection axis, and the axial orientation of the liquid crystal panel represents the orientation of the hysteresis axis. In the diagram, d represents the thickness of the retardation plate, and R represents the phase difference.

[0152] Furthermore, in the case of a phase retardation plate with an average angle θ = 90°, i.e., a so-called C-plate where the optical axis is aligned with the normal direction, the in-plane hysteresis axis is not defined, nor is the axial orientation of the phase retardation plate defined. However, in the case where the optical axis is uniformly tilted in a specific orientation, as in the phase retardation plate 30 of Embodiment 1 and Embodiments 2 to 8 described later, or in the case where the tilt angle of the optical axis is not uniform but the tilt orientation is uniform, this tilt orientation becomes the in-plane hysteresis axis, and the axial orientation of the phase retardation plate can be defined.

[0153] In the diagram, the phase difference R of the phase difference plates outside plate C represents the in-plane phase difference Rp. In the case of plate C, since the in-plane phase difference becomes 0, the phase difference R represents the thickness-direction phase difference Rth.

[0154] The phase difference R was measured using a polarimeter (manufactured by Axometrics, trade name: Axo-scan) employing a dual-rotating-retarder method. The in-plane phase difference Rp was measured directly from the normal direction of the birefringent layer. The thickness-direction phase difference Rth was measured from the normal direction of the birefringent layer at various tilt directions from -50° to 50°, and calculated using a known elliptic curve fitting method for the refractive index. The tilt orientation was set to be orthogonal to the in-plane hysteresis axis. Furthermore, while the thickness-direction phase difference Rth depends on the average refractive index given as the calculation condition for curve fitting (nx + ny + nz) / 3, the average refractive index of each birefringent layer was uniformly set to 1.5 for calculation. For birefringent layers with an actual average refractive index different from 1.5, an average refractive index of 1.5 was also assumed and converted accordingly.

[0155] Depending on the manufacturing method, the tilt angle of the optical axis of the phase retardation plate 30 is not limited to being uniform relative to the thickness direction of the phase retardation plate. Therefore, the tilt angle of the optical axis of the phase retardation plate 30 on the side closer to the back light source 40 (the side facing away from the back light source), that is, the angle between the optical axis of the side facing away from the back light source 40 and the side facing away from the back light source 40, is set as angle θ1. The tilt angle of the optical axis of the phase retardation plate 30 on the side closer to the observer, that is, the angle between the optical axis of the side facing away from the observer and the side facing away from the observer, is set as angle θ2. The average value of these two angles is set as the average angle θ, which is marked in the figure.

[0156] The first and second polarizers were absorption-type polarizers formed by adsorbing and orienting dichroic iodine complexes onto a polyvinyl alcohol (PVA) film. The liquid crystal panel was an FFS (Free-Flush-Side) mode liquid crystal panel using a lateral electric field. The third polarizer was a reflective polarizer (APF) manufactured by 3M. An LED light source was used as the backlight.

[0157] The phase décor plate 30S of Reference Example 1 was manufactured using the same method as the positive C plate described in paragraphs

[0082] to

[0089] of International Publication No. 2016 / 158300. Specifically, firstly, an alignment film coating solution (B) of the following composition was continuously coated onto a cellulose acylated membrane that had not undergone alkaline saponification treatment using a #14 wire rod. Then, the cellulose acylated membrane coated with the alignment film coating solution (B) was dried under warm air at 60°C for 60 seconds, and then dried under warm air at 100°C for 120 seconds to form an alignment film.

[0158] (Composition of Orientation Film Coating Solution (B))

[0159]

[0160] [Chemical Formula 7]

[0161]

[0162] An optical anisotropic layer coating solution (C) comprising a rod-shaped liquid crystal compound with the following composition was continuously coated onto the alignment film prepared above using a #5.0 wire rod. The film transport speed (V) was set to 26 m / min. To dry the solvent of the coating solution and to ripen the alignment of the rod-shaped liquid crystal compound, the film coated with the optical anisotropic layer coating solution (C) was heated under warm air at 60°C for 60 seconds. Afterwards, the resulting film was subjected to UV irradiation at 60°C to fix the alignment of the rod-shaped liquid crystal compound, thus fabricating the phase retardation plate 30S of Reference Example 1.

[0163] (Composition of the optical anisotropic layer coating solution (C))

[0164]

[0165] [Chemical Formula 8]

[0166]

[0167] [Chemical Formula 9]

[0168]

[0169] [Chemical Formula 10]

[0170]

[0171] Liquid crystal display devices (LCD 1R of Comparative Example 1 and LCD 1S of Reference Example 1) were fabricated, and the contrast ratio (CR) in the front direction of the LCD devices of Comparative Example 1 and Reference Example 1 was measured. Specifically, the brightness of white and black displays was measured using a viewing angle measuring device (manufactured by ELDIM Corporation, trade name: EZContrast160), and the ratio of the two was set as the contrast ratio (CR) in the front direction. In addition, the contrast ratio in the front direction of the LCD device of Example 1 was calculated by simulation. A liquid crystal optical simulator (LCD Master, manufactured by SHINTECH Corporation) was used in the calculation of the contrast ratio in the front direction. The contrast ratio in the front direction was 1520 in Comparative Example 1, 1657 in Reference Example 1, and 1626 in Example 1.

[0172] Furthermore, in order to understand the light distribution of the backlight incident on the liquid crystal panel of the liquid crystal display devices of Comparative Example 1, Reference Example 1, and Embodiment 1, the transmittance and viewing angle characteristics of the optical elements (parts located below the liquid crystal panel, i.e., optical elements including the components from the second polarizer 12 to the third polarizer 13, particularly optical elements having a phase retardation plate between the second polarizer 12 and the third polarizer 13, are also referred to as polarizing gratings) are calculated. The results are presented in... Figure 6B , Figure 7B as well as Figure 8B As shown in the image. Figure 6B The results are the calculated transmittance angle of the optical element of Comparative Example 1 and the calculated transmittance angle of the optical element of Comparative Example 1 after normalization with the optical element of Comparative Example 1. Figure 7B The results are the calculated transmittance angle of the polarizer grating of Reference Example 1 and the calculated transmittance angle of the polarizer grating of Reference Example 1, which has been normalized with the optical element of Comparative Example 1. Figure 8B These are the calculated results of the transmittance viewing angle of the polarizer grating of Example 1, and the calculated results of the transmittance viewing angle of the polarizer grating of Example 1 normalized to the optical element of Comparative Example 1. A liquid crystal optical simulator (LCD Master, manufactured by SHIINTECH) was used in the calculation of the transmittance viewing angle characteristics. It was assumed that the retardation plate 30 of Example 1 was composed of a rod-shaped liquid crystal compound, and that the refractive index and thickness were set to fixed values ​​of ne = 1.6, no = 1.5, Δn = 0.1, and d = 2 μm.

[0173] Furthermore, the viewing angle characteristics in the bottom section of the figure are normalized from the viewing angle characteristics of Comparative Example 1, and therefore correspond to the relative transmittance viewing angle characteristics for Comparative Example 1. Unless otherwise stated, the following description refers to the normalized viewing angle characteristics.

[0174] In Comparative Example 1, which uses an optical element 100R including a second polarizer 12 and a third polarizer 13, sufficient contrast in the front direction was not obtained. In Reference Example 1, which uses a polarizing grating 100S including a second polarizer 12, a phase retardation plate 30S, and a third polarizer 13, sufficient contrast in the front direction was obtained, but... Figure 7B As shown, the light distribution characteristics of the polarizing grating 100S in Reference Example 1 are approximately cross-shaped, and the incident light onto the liquid crystal panel at azimuths of 45°, 135°, 225°, and 315° is restricted. That is, it is unable to suppress the decrease in transmittance of white display at azimuths of 0° to 180°.

[0175] On the other hand, it is known that the liquid crystal display device 1 of Embodiment 1, which has a phase retardation plate 30 with its optical axis tilted from the normal direction, sufficiently achieves contrast in the front direction. Furthermore, the polarizing grating 100 of Embodiment 1 selectively reduces the amount of light at azimuths 225° and 315°, without causing a decrease in transmittance (brightness) of white display at azimuths 45° and 135°, which is important for automotive displays. Thus, in Embodiment 1, the amount of light below (especially at azimuths 225° and 315°) can be suppressed while keeping the amount of light above (azimuths 0° to 180°) constant, thereby satisfying the white brightness above and suppressing light leakage during black display, thereby improving contrast in the front direction.

[0176] (Examples 2-8)

[0177] The liquid crystal display devices in Examples 2 to 8 are configured as follows: Figure 9A , Figure 10A , Figure 11A , Figure 12A , Figure 13A , Figure 14A as well as Figure 15A As shown. Except that the angles θ1, θ2 and the average angle θ are various, and the phase difference plate 30 (tilted phase difference plate) with an average angle θ of more than 0° and less than 90° is used, the liquid crystal display devices of Embodiments 2 to 8 have the same configuration as Embodiment 1. Figure 9A This is a diagram illustrating the configuration of the liquid crystal display device in Embodiment 2. Figure 10A This is a diagram illustrating the configuration of the liquid crystal display device in Embodiment 3. Figure 11A This is a diagram illustrating the configuration of the liquid crystal display device in Embodiment 4. Figure 12A This is a diagram illustrating the configuration of the liquid crystal display device in Embodiment 5. Figure 13A This is a diagram illustrating the configuration of the liquid crystal display device in Embodiment 6. Figure 14A This is a diagram illustrating the configuration of the liquid crystal display device in Embodiment 7. Figure 15A This is a diagram illustrating the configuration of the liquid crystal display device in Embodiment 8.

[0178] The phase retardation plate 30 of Example 4 was fabricated as follows. An alignment agent for photoalignment films (manufactured by Rolic, trade name "ROF103") was applied to the surface of a substrate (a polymer film with triacetyl cellulose as the main component, manufactured by Fujifilm) with a thickness of 80 μm using a spin coater (conditions: 3000 rpm for 1 minute). The film was then dried in an air-circulating constant-temperature oven at 100°C for 10 minutes, forming a photoalignment film with a thickness of 70 nm. Next, the photoalignment film was irradiated with polarized ultraviolet light (irradiation dose: 100 mJ / cm²) from an angle of 140° relative to the substrate plane. 2 The tilting and orientation treatment was implemented.

[0179] Next, a coating solution (concentration: 20% by weight) comprising a liquid crystal composition (manufactured by Rolic, trade name "ROP5101" (liquid crystal temperature range 30°C to 57°C)) and cyclopentanone was prepared. The liquid crystal composition contained a polymerization initiator and rod-shaped liquid crystal compounds having two crosslinking functional groups in their molecular structure. This coating solution was then applied to the surface of the aforementioned photoalignment film. The mixture was heated to 50°C with the interface of the coating solution opposite to the substrate side exposed to air, and held at this temperature for 2 minutes, forming a cured layer of rod-shaped liquid crystal compounds aligned in a mixed arrangement. This cured layer was then irradiated with ultraviolet light (irradiation dose: 500 mJ / cm²) under a nitrogen atmosphere. 2 A phase retardation plate 30 with a thickness of 1.1 μm was formed on a substrate (the aforementioned polymer film with triacetyl cellulose as the main component) at 365 nm. In Example 4, the phase retardation plate 30 was removed from the substrate and transferred to the second polarizer 12 via an adhesive.

[0180] For the liquid crystal display device of Example 4, the front contrast ratio was measured in the same manner as in Comparative Example 1. Furthermore, for the liquid crystal display devices of Examples 2-3 and 5-8, the front contrast ratio was calculated in the same manner as in Example 1. The front contrast ratios of Examples 2-8 are all to the same degree as in Example 1, exhibiting sufficient front contrast ratio.

[0181] For Examples 2-8, the transmittance-viewing angle characteristics of the polarizer grating were calculated in the same manner as in Example 1. The results are presented in... Figure 9B , Figure 10B , Figure 11B , Figure 12B , Figure 13B , Figure 14B as well as Figure 15B As shown in the image. Figure 9BThe results are the calculated transmittance angle of the polarizing grating of Example 2 and the calculated transmittance angle of the polarizing grating of Example 2, which has been normalized with the optical element of Comparative Example 1. Figure 10B These are the calculated results of the transmittance angle of the polarizing grating of Example 3, and the calculated results of the transmittance angle of the polarizing grating of Example 3, which were normalized using the optical element of Comparative Example 1. Figure 11B These are the calculated results of the transmittance angle of the polarizing grating of Example 4, and the calculated results of the transmittance angle of the polarizing grating of Example 4, which were normalized using the optical element of Comparative Example 1. Figure 12B The results are the calculated transmittance angle of the polarizing grating of Example 5 and the calculated transmittance angle of the polarizing grating of Example 5, which has been normalized with the optical element of Comparative Example 1. Figure 13B These are the calculated results of the transmittance angle of the polarizing grating of Example 6, and the calculated results of the transmittance angle of the polarizing grating of Example 6, which were normalized using the optical element of Comparative Example 1. Figure 14B The results are the calculated transmittance angle of the polarizing grating of Example 7 and the calculated transmittance angle of the polarizing grating of Example 7, which has been normalized with the optical element of Comparative Example 1. Figure 15B These are the calculated results of the transmittance viewing angle of the polarizing grating in Example 8, and the calculated results of the transmittance viewing angle of the polarizing grating in Example 8, which were normalized using the optical element of Comparative Example 1. In the calculation of the transmittance viewing angle characteristics in Examples 2 to 8, it was assumed, as in Example 1, that the phase retardation plate 30 was composed of a rod-shaped liquid crystal compound, and the refractive index was set to a fixed value of ne = 1.6, no = 1.5, Δn = 0.1, and d = 2 μm, and only the angles θ1, θ2, and the average angle θ were varied.

[0182] For the polarizing grating 100 of Examples 2 to 8, similar to Example 1, it is also possible to suppress the amount of light below (especially at azimuths 225° and 315°) while keeping the amount of light above (0° to 180°) constant, thereby satisfying the white brightness above and suppressing light leakage when displaying black, thus improving the contrast in the front direction.

[0183] Furthermore, it was confirmed that the larger the average angle θ, the wider the range of angles with low transmittance below, and the greater the effect. In particular, it was confirmed that the liquid crystal display device 1 of Embodiment 4 has a higher contrast ratio in the front direction compared to Comparative Example 1, and a wider white brightness viewing angle compared to Reference Example 1, indicating that the upward viewing angle is wide. By evaluating the actually manufactured liquid crystal display devices of Comparative Example 1, Reference Example 1, and Embodiment 4, it was confirmed that the liquid crystal display device of Embodiment 4 has a higher front contrast ratio compared to Comparative Example 1, and a wider white brightness viewing angle compared to Reference Example 1. In particular, it was confirmed that the upward viewing angle of the liquid crystal display device of Embodiment 4 is wide.

Claims

1. A liquid crystal display device, characterized in that, have: Optical elements, which are provided sequentially from the observation surface side to the back surface side: Observe the surface-side polarizer, the phase retardation plate, and the back-side polarizer. The transmission axis of the observation plane-side polarizer is parallel to the transmission axis of the back-side polarizer. When the angle between the optical axis at the back side of the phase retardation plate and the back side of the plate is defined as θ1, and the angle between the optical axis at the observation side of the phase retardation plate and the observation side of the plate is defined as θ2, The average angle θ of the above angles θ1 and θ2 exceeds 0° but is less than 90°; A liquid crystal panel is disposed on the observation surface side of the observation surface side polarizer of the aforementioned optical element; as well as A polarizer is disposed on the viewing surface side of the aforementioned liquid crystal panel. When the horizontal right direction of the LCD panel screen is set to 0°, the counter-clockwise direction is set to a positive angle, and the clockwise direction is set to a negative angle, The orientation of the optical axis at the back side of the phase retardation plate and the orientation of the optical axis at the observation side of the phase retardation plate are 90°±3°.

2. The liquid crystal display device according to claim 1, characterized in that, The average angle θ mentioned above is above 40° and below 80°.

3. The liquid crystal display device according to claim 1, characterized in that, The angle θ1 mentioned above is different from the angle θ2 mentioned above.

4. The liquid crystal display device according to claim 3, characterized in that, The angle θ1 mentioned above is larger than the angle θ2 mentioned above.

5. The liquid crystal display device according to claim 3, characterized in that, The difference between the aforementioned angle θ1 and the aforementioned angle θ2 is greater than 60° and less than 80°.

6. The liquid crystal display device according to any one of claims 1 to 5, characterized in that, The orientation of the optical axis on the back side of the phase retardation plate is parallel to the orientation of the optical axis on the observation side of the phase retardation plate, and is orthogonal to or parallel to the transmission axis of the observation side polarizer.

7. The liquid crystal display device according to any one of claims 1 to 5, characterized in that, The aforementioned phase retardation plate contains a cured polymeric liquid crystal.

8. The liquid crystal display device according to any one of claims 1 to 5, characterized in that, The aforementioned observation-side polarizer or the aforementioned back-side polarizer is a reflective polarizer.

Images