JP5250277B2 - Liquid crystal panel and polarizing plate with retardation layer - Google Patents

Description

  The present invention includes a liquid crystal cell in which a liquid crystal layer containing liquid crystal molecules aligned in a twist alignment in the absence of an electric field is sandwiched between a pair of alignment substrates, and a pair of polarizing plates that sandwich the liquid crystal cell. The present invention relates to a liquid crystal panel with improved contrast characteristics. Furthermore, this invention relates to the polarizing plate with a phase difference layer which can be used suitably for this liquid crystal panel, and its manufacturing method.

  A liquid crystal display device combines a liquid crystal panel with a light source such as a backlight, a reflector for using external light, etc., and the liquid crystal panel generally has a configuration having a liquid crystal cell between a pair of polarizing plates. It has been adopted. In a liquid crystal panel, by applying a voltage to the liquid crystal cell, the polarization state of the light transmitted through the liquid crystal cell changes as the alignment state of the liquid crystal molecules in the liquid crystal cell changes. The brightness and darkness of the image can be adjusted to display characters and images. Such conversion of the polarization state by the liquid crystal cell utilizes birefringence of liquid crystal molecules. Since birefringence has an angle dependency, the liquid crystal display device has a problem that display characteristics change depending on the direction of viewing the screen (viewing angle), that is, has a viewing angle dependency. For this reason, even if the display characteristics in the front direction of the screen are excellent, when the screen is viewed from an oblique direction, the contrast may be lowered or a color shift may occur.

  In order to reduce such viewing angle dependency as much as possible and improve visibility from an oblique direction, methods using various optical compensation films (retardation films) between the liquid crystal cell and the polarizing plate have been proposed. ing. For example, in a liquid crystal display device in twisted nematic (TN) mode in which liquid crystal molecules are aligned in a 90 ° twist alignment in the absence of an electric field in the liquid crystal cell, nematic liquid crystal compounds and discotic liquid crystal compounds are tilted and aligned. A method of enlarging the viewing angle by using an inclined alignment layer (so-called O plate) has been proposed (for example, see Patent Documents 1 to 4).

Thus, by using an optical compensation film, it is possible to improve the viewing angle characteristics of a liquid crystal panel having a liquid crystal cell in which the liquid crystal layer is aligned in a twisted arrangement in the absence of an electric field, but in the front direction The contrast was not good enough.
Japanese Patent Laid-Open No. 9-21914 JP-A-9-26572 JP 7-287120 A JP-A-8-95032

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a liquid crystal panel having a high front contrast, a liquid crystal display device, and a polarizing plate with a retardation layer suitably used for forming the liquid crystal panel. To do.

  The inventors of the present application analyzed the relationship between the gradation (that is, the voltage applied to the liquid crystal cell) and the luminance (sometimes referred to as “VT characteristics”) in the liquid crystal display device. In an ideal liquid crystal display device, a graph in which gradation is plotted on the horizontal axis and luminance is plotted on the vertical axis is a substantially quadratic curve (parabola) that has the minimum luminance in black display (0 gradation). In the case of the liquid crystal panel, since the luminance is minimum at a voltage other than the 0 gradation, the black luminance at the 0 gradation is increased, and as a result, the contrast is decreased (hereinafter, this phenomenon is observed). May be referred to as “tone characteristic abnormality”). As a result of intensive studies in view of such a viewpoint, the present inventors have found that the above problem can be solved by arranging the liquid crystal cell, the polarizing plate, and the retardation layer at a predetermined angle.

  The present invention includes a liquid crystal cell having a liquid crystal layer including liquid crystal molecules aligned in a twisted arrangement in the absence of an electric field between a first alignment substrate and a second alignment substrate whose alignment directions are orthogonal to each other; A first polarizing plate disposed on the first alignment substrate side of the liquid crystal cell; a second polarizing plate disposed on the second alignment substrate side of the liquid crystal cell; and the liquid crystal cell and the first The present invention relates to a liquid crystal panel having a first retardation layer disposed between a polarizing plate and a second retardation layer disposed between the liquid crystal cell and the second polarizing plate.

In the liquid crystal panel of the present invention, the first retardation layer and the second retardation layer are liquid crystal optical compensation layers obtained by obliquely aligning the optical axis of the liquid crystal, and the liquid crystal cell, The polarizing plate, the second polarizing plate, the first retardation layer, and the second retardation layer satisfy all of the following (A) to (C).
(A) The absorption axis direction of the first polarizing plate and the absorption axis direction of the second polarizing plate are orthogonal to each other. (B) The absorption axis direction of the first polarizing plate, the alignment direction of the first retardation layer, and the first (B-1) Absorption axis of the first polarizing plate The absorption axis direction of the polarizing plate 2 and the orientation direction of the second retardation layer satisfy either of the following (B-1) or (B-2): And the alignment direction of the liquid crystal molecules of the first retardation layer are parallel, and the absorption axis direction of the second polarizing plate and the alignment direction of the liquid crystal molecules of the second retardation layer are parallel. 2) The absorption axis direction of the first polarizing plate and the alignment direction of the liquid crystal molecules of the first retardation layer are orthogonal, and the absorption axis direction of the second polarizing plate and the liquid crystal molecules of the second retardation layer (C) The angle formed by the alignment direction of the second alignment substrate and the absorption axis direction of the second polarizing plate is 0.5 to 2.5 ° or 87.5 to 99.5 °. is there

  In the liquid crystal panel of the present invention, the first retardation layer and the second retardation layer preferably contain a liquid crystal material that exhibits optically negative uniaxiality, and the optically negative uniaxiality. It is more preferable that the liquid crystal material exhibiting the above is a discotic liquid crystal compound.

  In the liquid crystal panel of the present invention, it is preferable that an angle formed by the alignment direction of the second alignment substrate and the alignment direction of the liquid crystal molecules of the second retardation layer is 0.5 to 2.5 °. With this configuration, it is possible to obtain a liquid crystal panel excellent in display characteristics in an oblique direction, that is, viewing angle characteristics as well as in the front.

  In the liquid crystal panel of the present invention, it is further preferable that the absorption axis direction of the second polarizing plate and the alignment direction of the liquid crystal molecules of the second retardation layer are parallel. By adopting this configuration, the polarizing plate with a retardation layer used in the liquid crystal panel can be laminated by roll-to-roll, and the workability and productivity are excellent. Further, it is excellent in optical characteristics such as viewing angle characteristics.

  Furthermore, the present invention relates to a liquid crystal display device having the liquid crystal panel.

  Moreover, this invention relates to the polarizing plate with a phase difference layer which can be used suitably for the said liquid crystal panel. The polarizing plate with a retardation layer of the present invention includes a polarizing plate and a retardation layer composed of a liquid crystal optical compensation layer obtained by tilting and aligning the optical axis of the liquid crystal. The polarizing plate is rectangular, and the angle formed between the absorption axis direction of the polarizing plate and the long side direction of the rectangular is 42.5 to 44.5 °, or 45.5 to 47.5 °.

  In the polarizing plate with a retardation layer of the present invention, the retardation layer preferably contains a liquid crystal material exhibiting optically negative uniaxiality, and the liquid crystal material exhibiting optically negative uniaxiality is disco. More preferably, it is a tick liquid crystal compound.

  Furthermore, this invention relates to the manufacturing method of the said polarizing plate with a phase difference layer. In the method for producing a polarizing plate with a retardation layer of the present invention, roll-to-roll so that the absorption axis direction of the polarizing plate and the alignment direction of the retardation layer obtained by tilting the optical axis of the liquid crystal are parallel to each other. The step of obtaining a long laminated polarizing plate by laminating with a roll, and the angle formed between the longitudinal direction of the long laminated polarizing plate and the long side of the rectangle is 42.5 to 44.5 °, or 45.5 to 47. A step of cutting a rectangular polarizing plate so as to be 5 °.

  According to the present invention, by shifting the angle formed between the axial direction of the polarizing plate and the retardation layer and the alignment direction of the alignment substrate of the liquid crystal cell in a range of 0.5 to 2.5 ° from parallel or orthogonal, An abnormality in the gradation characteristics of the panel is suppressed, and the brightness at the 0th gradation, that is, the black brightness is reduced, so that the contrast of the liquid crystal panel can be improved. In addition, according to the method for manufacturing a polarizing plate with a retardation layer of the present invention, it is possible to manufacture a liquid crystal panel in which the above-described gradation characteristic abnormality is suppressed without significantly changing the manufacturing process of the conventional liquid crystal panel. Is possible.

[Configuration overview of LCD panel]
1A and 1B show examples of schematic perspective views of the liquid crystal panel of the present invention. In FIG. 1, in order to facilitate understanding of the relative relationship of the arrangement angle of the configuration of the present application, the liquid crystal cell is rectangular, and the side direction of the rectangle, the orientation direction of each component member, the absorption axis direction, and the like are approximately. Although illustrated so as to be parallel, in an actual configuration, as will be described later in the embodiments of the present specification, the side direction of the rectangle and the optical axis direction of each component member are approximately 45 ° or approximately 135. Note that they can be arranged at a predetermined angle such as °.

  The liquid crystal cell 10 includes a liquid crystal layer 13 including liquid crystal molecules aligned in a twist arrangement in the absence of an electric field between a first alignment substrate 11 and a second alignment substrate 12. The liquid crystal panel 100 includes a first polarizing plate 21 on the first alignment substrate 11 side of the liquid crystal cell 10 and a second polarizing plate 22 on the second alignment substrate 12 side. A first retardation layer 31 is disposed between the liquid crystal cell 10 and the first polarizing plate 21, and a second retardation is disposed between the liquid crystal cell 10 and the second polarizing plate 22. Layer 32 is disposed.

[Liquid Crystal Cell]
Referring to FIGS. 1A and 1B, the liquid crystal cell 10 includes a liquid crystal layer 13, a first alignment substrate 11 disposed on the liquid crystal layer 13 on the first polarizing plate 21 side, and a liquid crystal layer 13. And the second alignment substrate 12 disposed on the second polarizing plate 22 side. One substrate (active matrix substrate) preferably has a switching element (typically a TFT) for controlling the electro-optical characteristics of the liquid crystal, a scanning line for supplying a gate signal to the switching element, and a signal line for supplying a source signal. Are provided (both not shown). The other substrate (color filter substrate) is provided with a color filter (not shown). Note that the color filter may be provided on the active matrix substrate. Alternatively, for example, when an RGB three-color light source (which may include a multicolor light source) is used as the illumination means of the liquid crystal display device as in the field sequential method, the color filter is omitted. Can do. In the case of a monochrome liquid crystal display device, the color filter can be omitted. The distance (cell gap) between the two substrates can be controlled by a spacer or the like.

  As the first alignment substrate 11 and the second alignment substrate 12, those subjected to alignment treatment are preferably used. As the means for the alignment treatment, any method can be adopted as long as the liquid crystal molecules are arranged in a certain alignment state on the surface of the substrate. An alignment film is preferably provided on the layer 13 side, and the alignment film is preferably subjected to an alignment treatment. As the alignment film, a film coated with an alignment polymer such as polyimide or polyvinyl alcohol is preferable. Further, as the alignment means, a “rubbing method” in which the alignment film is rubbed in one direction with a fiber such as nylon or polyester is preferably used. For example, when the rubbing method is used as the alignment process, the alignment direction is substantially equal to the rubbing direction.

  The liquid crystal layer 13 includes liquid crystal molecules aligned in a twist arrangement in the absence of an electric field. In the twist alignment, generally, the liquid crystal molecules in the liquid crystal layer are aligned substantially parallel to both substrate surfaces, and the alignment direction is twisted at a predetermined angle (for example, 90 ° or 270 °) on both substrate surfaces. Say what you are. A liquid crystal cell including a liquid crystal layer in such an alignment state is typically a twisted nematic (TN) mode or super twisted nematic (STN) mode liquid crystal cell. In the present invention, the characteristics of the constituent members are exhibited synergistically, and from the viewpoint of realizing the optical compensation that is the object of the present invention, the alignment direction of the liquid crystal molecules is substantially 90 ° twisted. A liquid crystal cell is preferred.

  FIG. 2 is a schematic perspective view illustrating the alignment state of liquid crystal molecules in a TN mode liquid crystal cell. The first alignment substrate 11 and the second alignment substrate 12 are arranged so that the alignment directions 1 and 2 thereof are orthogonal to each other. In such a liquid crystal cell, as shown in FIG. 2A, the liquid crystal molecules of the liquid crystal layer 13 are in an alignment state having a substantially twisted structure of 90 °. That is, as the distance from the center in the thickness direction of the liquid crystal layer increases, the thickness gradually changes along the thickness direction of the liquid crystal layer so as to be substantially parallel to the alignment direction of the opposing substrate surface. Such an alignment state can be realized by arranging a nematic liquid crystal having a positive dielectric anisotropy between alignment films having a predetermined alignment regulating force. In this state, when light is incident from the surface of the second alignment substrate 12, the liquid crystal molecules are birefringent with respect to the linearly polarized light that has passed through the second polarizing plate 22 and entered the liquid crystal layer 13. The polarization state of incident light changes according to the twist of the liquid crystal molecules. The light passing through the liquid crystal layer when no voltage is applied becomes, for example, linearly polarized light whose polarization direction is rotated by 90 °. When the absorption axis direction 3 of the first polarizing plate 21 and the absorption axis direction 4 of the second polarizing plate 22 are orthogonal (normally white mode), the polarization direction of the light transmitted through the second polarizing plate is liquid crystal. By being rotated by 90 ° by the cell, the light passes through the first polarizing plate 21, and thus a bright display can be obtained.

  In the liquid crystal panel of the present invention, the first alignment substrate 11 can be disposed on either the light source side or the viewing side. However, in order to facilitate understanding of the content of the present invention, unless otherwise noted. The first alignment substrate 11 (and the first polarizing plate 21 and the first retardation layer 31) are arranged on the viewing side of the liquid crystal layer 13, and the second alignment substrate 12 (and the second polarizing plate 22). The second retardation layer 32) is described as being disposed on the light source side of the liquid crystal layer 13.

  As described above, when the liquid crystal molecules of the liquid crystal layer 13 have positive dielectric anisotropy, when a voltage is applied between the electrodes, the liquid crystal molecules of the liquid crystal layer 13 are changed as shown in FIG. The first alignment substrate 11 and the second alignment substrate 12 are aligned perpendicular to the surfaces. When light is incident from the surface of the second alignment substrate 12 in such a state, the linearly polarized light that has passed through the second polarizing plate 22 and entered the liquid crystal layer 13 is vertically aligned liquid crystal molecules. Proceed along the direction of the major axis. Since birefringence does not occur in the major axis direction of the liquid crystal molecules, incident light travels without changing the polarization direction. When the absorption axis direction 3 of the first polarizing plate 21 and the absorption axis direction 4 of the second polarizing plate 22 are orthogonal to each other, the light transmitted through the second polarizing plate 22 is absorbed by the first polarizing plate 21. Is done. Thereby, a dark display can be obtained when a voltage is applied. When the voltage is not applied again, the display can be returned to the bright state by the orientation regulating force. Further, gradation display can be performed by changing the intensity of transmitted light from the first polarizing plate 21 by changing the applied voltage to control the inclination of the liquid crystal molecules. In the present invention, a TN mode liquid crystal cell mounted on a commercially available liquid crystal display device can be used as it is.

  Here, the orientation direction of the liquid crystal molecules in the liquid crystal cell in the present specification is defined. FIG. 3 schematically shows a state in which the TN mode liquid crystal cell of FIG. 2A in which no voltage is applied is viewed from the first alignment substrate 11 side. In the liquid crystal layer 13, the liquid crystal molecules are aligned parallel to the alignment direction 11 (left and right direction on the paper surface) on the first alignment substrate 11 side, and the alignment direction 12 (up and down direction on the paper surface) on the second alignment substrate 12 side. Orientated parallel. Then, at the center of the liquid crystal layer 13 in the thickness direction, the liquid crystal molecules are oriented in a 45 ° direction oblique to the paper surface. The alignment direction of the liquid crystal molecules changes gradually and continuously along the thickness direction of the liquid crystal layer, and the direction obtained by averaging these alignment directions is defined as the “average alignment direction” of the liquid crystal cell (FIG. 3). (Indicated by a double-headed arrow 9). When the alignment direction 1 of the first alignment substrate 11 and the alignment direction 2 of the second alignment substrate 12 are orthogonal, the angle formed by the average alignment direction 9 and the alignment direction 1 of the first alignment substrate is about 45 °. It becomes. Similarly, the angle formed by the average alignment direction 9 and the alignment direction 2 of the second alignment substrate is about 45 °, but the sign (positive / negative) of the angle is opposite. The angle sign will be described later. In FIG. 3, when the right side of the page is defined as an azimuth angle of 0 ° and a counterclockwise direction as positive, the average orientation direction is a direction of 45 ° (225 °).

[Arrangement of polarizing plate and retardation layer]
The liquid crystal panel of the present invention is characterized in that the axial direction of the polarizing plate and the retardation layer is not strictly parallel or orthogonal to the alignment direction of the alignment substrate of the liquid crystal cell, but is deviated from the parallel or orthogonal by a predetermined angle. To do. Hereinafter, the arrangement of each optical layer will be described.

(A. Arrangement of polarizing plate)
The absorption axis direction 3 of the first polarizing plate 21 and the absorption axis direction 4 of the second polarizing plate 22 are orthogonal to each other. By making both orthogonal, the luminance during black display can be reduced.

(B. Relative arrangement angle of retardation layer and polarizing plate)
The absorption axis direction 3 of the first polarizing plate 21 and the alignment direction 5 of the first retardation layer 31 are parallel or orthogonal. When the absorption axis direction 3 of the first polarizing plate 21 and the alignment direction 5 of the first retardation layer 31 are parallel, the absorption axis direction 4 of the second polarizing plate 22 and the alignment of the second retardation layer 32 The direction 6 is also parallel (B-1, hereinafter may be referred to as “parallel configuration”). When the absorption axis direction 3 of the first polarizing plate 21 and the alignment direction 5 of the first retardation layer 31 are orthogonal, the absorption axis direction 4 of the second polarizing plate 22 and the alignment direction of the second retardation layer 32 6 are also orthogonal (B-2, hereinafter referred to as “orthogonal configuration”). FIGS. 1A and 1B both show a parallel configuration (B-1). These arrangement angles may be either a parallel configuration or an orthogonal configuration. However, as described later, from the viewpoint of productivity of a polarizing plate with a retardation layer in which a polarizing plate and a retardation layer are laminated, the parallel configuration is preferably used. Can be adopted.

  In the present specification and claims, “parallel” includes not only completely parallel but also substantially parallel, and the angle is generally within 0.3 °. Yes, preferably within 0.2 °, more preferably within 0.1 °. In addition, the term “orthogonal” includes not only completely orthogonal but also substantially orthogonal, and the angle is generally in the range of 90 ± 0.3 °, preferably 90 ± 0.2 °. More preferably, the range is 90 ± 0.1 °.

  In the present specification and claims, unless otherwise specified, when the liquid crystal panel is viewed from the first polarizing plate side (viewing side), the counterclockwise direction is the angle “+”, the clockwise direction. Is defined as an angle “−”. Moreover, when a positive / negative sign is not attached to an angle, it means that either positive or negative may be sufficient.

(C. Relative arrangement angle of polarizing plate and liquid crystal cell)
The liquid crystal panel of the present invention may be in a so-called “O mode” or “E mode”. The “O-mode liquid crystal panel” refers to a panel in which the absorption axis direction of the polarizing plate disposed on the light source side of the liquid crystal cell and the alignment direction of the alignment substrate on the light source side of the liquid crystal cell are substantially parallel. The “E-mode liquid crystal panel” refers to a panel in which the absorption axis direction of the polarizing plate disposed on the light source side of the liquid crystal cell is substantially orthogonal to the alignment direction of the alignment substrate on the light source side of the liquid crystal cell.

(O mode configuration)
First, a case where the liquid crystal panel adopts the O mode will be described. In the case of a conventional O-mode liquid crystal panel, it is preferable that the absorption axis direction of the polarizing plate and the alignment direction of the alignment substrate of the liquid crystal cell are strictly parallel, and generally the angle formed by both is within 0.3 °. . On the other hand, when the O mode is adopted in the liquid crystal panel of the present invention, the absorption axis direction 4 of the second polarizing plate 22 is the second axis of the liquid crystal cell 10 as schematically shown in FIG. It forms a predetermined angle with the alignment direction 2 of the alignment substrate 12, and the angle is in the range of 0.5 to 2.5 °.

  By adopting such an angular arrangement, the gradation characteristic abnormality is suppressed and the luminance is minimized as compared with the case where the absorption axis direction of the polarizing plate and the alignment direction of the alignment substrate of the liquid crystal cell are strictly parallel. Can be a low gradation close to 0 gradation. Note that a liquid crystal panel in which the luminance is the lowest in black display, that is, 0 gradation, is ideal, but from this point of view, the alignment direction 2 of the second alignment substrate 12 and the absorption of the second polarizing plate 22 The angle formed by the axial direction 4 is preferably 0.5 to 2.0 °, and more preferably 0.7 to 1.5 °.

  As described above, in the liquid crystal panel of the present invention, the absorption axis direction 3 of the first polarizing plate 21 and the absorption axis direction 4 of the second polarizing plate 22 are orthogonal to each other. The angle formed by the orientation direction 2 and the absorption axis direction 3 of the first polarizing plate 21 is in the range of 90 ° ± 0.5 ° to 90 ° ± 2.5 °. When the alignment direction 1 of the first alignment substrate 11 and the alignment direction 2 of the second alignment substrate 12 are orthogonal to each other, the alignment direction 1 of the first alignment substrate 11 and the absorption axis of the first polarizing plate 21 are used. The direction 3 is 0.5 to 2.5 °, preferably 0.5 to 2.0 °, and more preferably 0.7 to 1.5 °.

When the liquid crystal panel employs an O-mode configuration as described above, the angular arrangement is represented by the following (C-1) or (C-2) with a positive / negative sign.
(C-1) The angle formed by the alignment direction of the second alignment substrate and the absorption axis direction of the second polarizing plate is +0.5 to + 2.5 °, and the alignment direction of the second alignment substrate and the first alignment substrate The angle between the absorption axis direction of the polarizing plate and the alignment direction of the second alignment substrate is +90.5 to + 92.5 °
(C-2) The angle formed by the alignment direction of the second alignment substrate and the absorption axis direction of the second polarizing plate is −2.5 to −0.5 °, and the alignment direction of the second alignment substrate The angle between the absorption axis direction of the polarizing plate 1 and the alignment direction of the second alignment substrate is +87.5 to + 89.5 °

(E mode configuration)
Next, a case where the liquid crystal panel adopts the E mode will be described. In the case of a conventional E-mode liquid crystal panel, it is preferable that the absorption axis direction of the polarizing plate and the alignment direction of the alignment substrate of the liquid crystal cell are strictly orthogonal, and the angle formed by both is generally within 90 ± 0.3 °. is there. On the other hand, when the E mode is adopted in the liquid crystal panel of the present invention, the absorption axis direction of the polarizing plate is strictly the same as the alignment direction of the alignment substrate of the liquid crystal cell 10 as schematically shown in FIG. Are not orthogonal and deviate by a predetermined angle from ± 90 °, and the angle is in the range of 90 ± 0.5 to 90 ± 2.5 °.

  By adopting such an angular arrangement, the gradation characteristic abnormality is suppressed and the luminance is minimized as compared with the case where the absorption axis direction of the polarizing plate and the alignment direction of the alignment substrate of the liquid crystal cell are strictly orthogonal. The gradation can be made a low gradation closer to 0 gradation. Note that, in order to obtain a black display, that is, a liquid crystal panel having the lowest luminance at 0 gradation, the alignment direction 2 of the second alignment substrate 12 and the absorption axis direction 4 of the second polarizing plate 22 are formed. The angle is preferably 90 ± 0.5 to 90 ± 2.0 °, and more preferably 90 ± 0.7 to 90 ± 1.5 °.

  As described above, in the liquid crystal panel of the present invention, the absorption axis direction 3 of the first polarizing plate 21 and the absorption axis direction 4 of the second polarizing plate 22 are orthogonal to each other. The angle formed by the orientation direction 2 and the absorption axis direction 3 of the first polarizing plate 21 is in the range of ± 0.5 ° to ± 2.5 °. When the alignment direction 1 of the first alignment substrate 11 and the alignment direction 2 of the second alignment substrate 12 are orthogonal to each other, the alignment direction 1 of the first alignment substrate 11 and the absorption axis of the first polarizing plate 21 are used. The direction 3 is 87.5 to 89.5 °, preferably 88.0 to 89.5 °, and more preferably 88.5 to 89.3 °.

When the liquid crystal panel adopts the E mode configuration as described above, the angular arrangement is represented by the following (C-3) or (C-4) with a positive or negative sign.
(C-3) The angle formed between the alignment direction of the second alignment substrate and the absorption axis direction of the second polarizing plate is −89.5 to −87.5 °, and the alignment direction of the second alignment substrate The angle between the absorption axis direction of the polarizing plate 1 and the alignment direction of the second alignment substrate is +0.5 to + 2.5 °
(C-4) The angle formed by the alignment direction of the second alignment substrate and the absorption axis direction of the second polarizing plate is +87.5 to + 89.5 °, and the alignment direction of the first alignment substrate and the second alignment substrate The angle formed by the absorption axis direction of the polarizing plate and the alignment direction of the second alignment substrate is −2.5 to −0.5 °.

  As in the above (C-1) to (C-4), in the liquid crystal panel of the present invention, the alignment direction of the alignment substrate of the liquid crystal cell and the absorption axis direction of the polarizing plate are 0.5 to 2 from parallel or orthogonal. Although arranged at an angle shifted by 5 °, as described above in (B-1) and (B-2), the absorption axis direction of the polarizing plate and the alignment direction of the retardation layer are parallel or orthogonal. Therefore, the alignment direction of the alignment substrate of the liquid crystal cell and the alignment direction of the retardation layer are 0.5 to 2.5 °, preferably 0.5 to 2.0 °, more preferably 0.7 to 0.5 ° from parallel or orthogonal. It will be arranged at an angle shifted by 1.5 °.

In the liquid crystal panel of the present invention, the orientation direction of the second orientation substrate and the second phase difference as shown in FIGS. 1A and 1B in both the O mode and the E mode. The angle formed by the alignment direction of the liquid crystal molecules in the layer is preferably 0.5 to 2.5. With such an arrangement, the optical compensation of the liquid crystal cell by the retardation layer is appropriately performed, and the viewing angle characteristics of the liquid crystal display device can be improved. In order to obtain a black display, that is, a liquid crystal panel having the lowest luminance at 0 gradation, the angle formed by the alignment direction of the liquid crystal molecules in the second retardation layer is 0.5 to 2.0. It is preferable that it is (degree), and it is more preferable that it is 0.7-1.5 degree.

  From the above, when the liquid crystal panel of the present invention adopts the O mode (the C-1 or C-2), as shown in FIG. 1A, it may have a parallel configuration (the B-1). Preferably, when the liquid crystal panel of the present invention adopts the E mode (the C-3 or C-4), it is preferably an orthogonal configuration (the B-2) as shown in FIG. . In addition, from the viewpoint of productivity of the polarizing plate with a retardation layer in which a polarizing plate and a retardation layer are laminated, the above parallel configuration (B-1) can be suitably employed. It is preferable to employ the O mode as shown in FIG. When the O mode is employed, not only is the productivity of the polarizing plate with a retardation layer excellent, but also the front contrast and viewing angle characteristics tend to be superior to those when the E mode is employed.

  In addition, regarding the relationship between the alignment direction of the liquid crystal molecules in the liquid crystal cell and the absorption axis direction of the polarizing plate, according to the definition of the sign of the previous angle, in the conventional liquid crystal display device, the average alignment direction of the liquid crystal cell is a reference (angle). 0 °), if the absorption axis direction of the viewing side polarizing plate is + 45 °, the absorption axis direction of the light source side polarizing plate is −45 ° (135 °), and the absorption axis direction of the viewing side polarizing plate is − If it is 45 ° (135 °), the absorption axis direction of the light source side polarizing plate is + 45 °. On the other hand, in the liquid crystal panel of the present invention, if the absorption axis direction of the first polarizing plate is +42.5 to + 44.5 °, the absorption axis direction of the second polarizing plate is −47.5 to −45. 5 ° (132.5 to 134.5 °) and the absorption axis direction of the first polarizing plate is −44.5 to −42.5 ° (135.5 to 137.5 °), The absorption axis direction of the second polarizing plate is +45.5 to + 47.5 °. In addition, a configuration in which the absorption axis direction of the first polarizing plate is +45.5 to + 47.5 °, or −47.5 to −45.5 ° may be employed.

  As described above, the present invention eliminates the gradation characteristic abnormality in the black display and obtains a liquid crystal panel with high contrast by disposing the polarizing plate and the retardation layer at an angle different from that of the conventional liquid crystal panel. is there. Hereinafter, preferred configurations such as a polarizing plate and a retardation layer constituting the liquid crystal panel of the present invention are shown.

[Polarizer]
In the present specification and claims, the term “polarizing plate” refers to an element that can convert natural light or polarized light into arbitrary polarized light. The polarizing plate used in the liquid crystal panel of the present invention is not particularly limited, but preferably converts natural light or polarized light into linearly polarized light. Such a polarizing plate has a function of transmitting one of the polarized components when incident light is divided into two orthogonal polarized components, and absorbing, reflecting, and scattering the other polarized component. At least one function selected from the functions to be performed.

  The transmittance at a wavelength of 440 nm (also referred to as single transmittance) of the polarizing plate used in the present invention is preferably 41.0% or more, and more preferably 42.0% or more. Although the theoretical upper limit of the single transmittance is 50%, in practice, reflection due to the difference between the refractive index of air and the polarizing plate occurs, so the single transmittance does not become 50%. When a triacetyl cellulose film is used as a polarizer protective film described later, 43.2% is the upper limit.

  Further, the degree of polarization is preferably 99.8 to 100%, and more preferably 99.9 to 100%. If it is said range, the contrast of a front direction can be made still higher when it uses for a liquid crystal display device.

  The single transmittance and the degree of polarization can be measured using a spectrophotometer. As a specific method of measuring the degree of polarization, the parallel transmittance (H0) and orthogonal transmittance (H90) of the polarizing plate are measured, and the formula: degree of polarization (%) = {(H0−H90) / (H0 + H90). )} 1/2 × 100. The parallel transmittance (H0) is a transmittance value of a parallel laminated polarizing plate produced by superposing two identical polarizing plates so that their absorption axes are parallel to each other. The orthogonal transmittance (H90) is a value of the transmittance of an orthogonal laminated polarizing plate produced by superposing two identical polarizing plates so that their absorption axes are orthogonal to each other.

  In the present invention, it is preferable that the polarizing plate alone has the above-described single transmittance and degree of polarization, and the polarizing plate with the retardation layer in which the retardation layer is laminated on the polarizing plate has the same optical properties. It is preferable to have characteristics.

(Polarizer)
The function of converting natural light or polarized light of the polarizing plate into linearly polarized light is achieved by a polarizer. A polarizing plate is obtained by laminating a transparent film as a polarizer protective film on one or both sides of a polarizer as required. Any appropriate polarizer may be adopted as the polarizer depending on the purpose. For example, dichroic substances such as iodine and dichroic dyes are adsorbed on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films. And a polyene-based oriented film such as a uniaxially stretched product, a polyvinyl alcohol dehydrated product or a polyvinyl chloride dehydrochlorinated product. Further, a guest / host type O-type polarizer in which a liquid crystalline composition containing a dichroic substance and a liquid crystalline compound disclosed in US Pat. No. 5,523,863 is aligned in a certain direction, US Pat. An E-type polarizer or the like in which lyotropic liquid crystals disclosed in US Pat. No. 6,049,428 are aligned in a certain direction can also be used. Among such polarizers, from the viewpoint of having a high degree of polarization, a polarizer made of a polyvinyl alcohol film containing iodine is preferably used.

  In the production of a polarizer using a polyvinyl alcohol film containing iodine, the polyvinyl alcohol film (unstretched film) is at least subjected to uniaxial stretching treatment and iodine dyeing treatment according to a conventional method. Furthermore, boric acid treatment and iodine ion treatment can be performed. Moreover, the polyvinyl alcohol film (stretched film) subjected to the treatment is dried according to a conventional method to form a polarizer.

  The stretching method in the uniaxial stretching treatment is not particularly limited, and either a wet stretching method or a dry stretching method can be employed. Examples of the stretching means of the dry stretching method include an inter-roll stretching method, a heated roll stretching method, and a compression stretching method. Stretching can also be performed in multiple stages. In the stretching means, the unstretched film is usually heated. Usually, an unstretched film having a thickness of about 30 to 150 μm is used. The stretch ratio of the stretched film can be appropriately set according to the purpose, but the stretch ratio (total stretch ratio) is about 2 to 8 times, preferably 3 to 6.5 times, more preferably 3.5 to 6 times. Is desirable.

  The iodine staining treatment is performed by immersing the polyvinyl alcohol film in an iodine solution containing iodine and potassium iodide. The iodine solution is usually an iodine aqueous solution, and contains iodine and potassium iodide as a dissolution aid. The iodine concentration is about 0.01 to 1% by weight, preferably 0.02 to 0.5% by weight. The potassium iodide concentration is about 0.01 to 10% by weight, and further 0.02 to 8% by weight. It is preferable to use it.

  In the iodine dyeing treatment, the temperature of the iodine solution is usually about 20 to 50 ° C, preferably 25 to 40 ° C. The immersion time is usually about 10 to 300 seconds, preferably 20 to 240 seconds. In the iodine dyeing treatment, the iodine content and potassium content in the polyvinyl alcohol film are within the above ranges by adjusting the conditions such as the concentration of the iodine solution, the immersion temperature of the polyvinyl alcohol film in the iodine solution, and the immersion time. Adjust as follows. The iodine dyeing process may be performed at any stage before the uniaxial stretching process, during the uniaxial stretching process, or after the uniaxial stretching process.

  The boric acid treatment is performed by immersing a polyvinyl alcohol film in an aqueous boric acid solution. The boric acid concentration in the boric acid aqueous solution is about 2 to 15% by weight, preferably 3 to 10% by weight. The aqueous boric acid solution can contain potassium ions and iodine ions with potassium iodide. The potassium iodide concentration in the boric acid aqueous solution is preferably about 0.5 to 10% by weight, more preferably 1 to 8% by weight. A boric acid aqueous solution containing potassium iodide can provide a lightly colored polarizer, that is, a so-called neutral gray polarizer having a substantially constant absorbance over almost the entire wavelength range of visible light.

  For the iodine ion treatment, for example, an aqueous solution containing iodine ions with potassium iodide or the like is used. The potassium iodide concentration is preferably about 0.5 to 10% by weight, more preferably 1 to 8% by weight. In the iodine ion impregnation treatment, the temperature of the aqueous solution is usually about 15 to 60 ° C, preferably 25 to 40 ° C. The immersion time is usually about 1 to 120 seconds, preferably 3 to 90 seconds. The stage of iodine ion treatment is not particularly limited as long as it is before the drying process. It can also be performed after water washing described later.

  From the viewpoint of obtaining a polarizing plate having a high degree of polarization and a high hue neutrality, the iodine content (I) and the potassium content (K) in the polarizer have a weight ratio (K / I) of 0. It is preferable that it is 200-0.235. Such a numerical value can be achieved by adjusting the contents of iodine and potassium by the boric acid treatment or the like.

  The treated polyvinyl alcohol film (stretched film) can be subjected to a water washing step and a drying step according to a conventional method.

  The water washing step is usually performed by immersing a polyvinyl alcohol film in pure water. The water washing temperature is usually in the range of 5 to 50 ° C, preferably 10 to 45 ° C, more preferably 15 to 40 ° C. The immersion time is usually about 10 to 300 seconds, preferably about 20 to 240 seconds.

  Arbitrary appropriate drying methods, for example, natural drying, ventilation drying, heat drying, etc., can be adopted as the drying step. For example, in the case of heat drying, the drying temperature is typically 20 to 80 ° C., preferably 25 to 70 ° C., and the drying time is typically about 1 to 10 minutes. Further, the moisture content of the polarizer after drying is preferably 10 to 30% by weight, more preferably 12 to 28% by weight, and even more preferably 16 to 25% by weight. When the moisture content is excessively large, a laminated laminate in which a polarizer is bonded to an optical element or an isotropic film through an adhesive layer as described later, that is, when the polarizing plate is dried, the polarizer is dried. Accordingly, the degree of polarization tends to decrease. In particular, the orthogonal transmittance increases in a short wavelength region of 500 nm or less, that is, light of a short wavelength leaks, so that black display tends to be colored blue. On the other hand, if the moisture content of the polarizer is excessively small, problems such as local uneven defects (knic defects) are likely to occur.

  In this invention, arbitrary appropriate thickness can be employ | adopted for the thickness of the polarizer of a 1st polarizing plate and a 2nd polarizing plate. The thickness of the polarizer is typically 5 to 80 μm, preferably 10 to 50 μm, and more preferably 20 to 40 μm. If it is said range, it is excellent in an optical characteristic and mechanical strength.

(Protective film)
The protective film for the polarizer is appropriately used for the purpose of preventing the polarizer from being damaged or deteriorated. In particular, an iodine-based polarizer or a polarizer using a liquid crystal material preferably has a protective film on both sides from the viewpoint of preventing sublimation of the dichroic substance and ensuring film strength.

  As a material constituting the protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, and the like is used. Specific examples of such thermoplastic resins include polycarbonate resins, polyvinyl alcohol resins, cellulose resins, polyester resins, polyarylate resins, polyimide resins, cyclic polyolefin resins, polysulfone resins, polyether sulfones. Resin, polyolefin resin, polystyrene resin, polyvinyl alcohol resin, and mixtures thereof. Further, a thermosetting resin such as urethane, acrylic urethane, epoxy, or silicone, or an ultraviolet curable resin can also be used. The protective film may contain one or more arbitrary appropriate additives. Examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a mold release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a coloring agent. The content of the thermoplastic resin in the protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. When content of the said thermoplastic resin in a protective film is 50 weight% or less, the high transparency etc. which a thermoplastic resin originally has may not fully be expressed.

  Moreover, as a protective film arrange | positioned at the liquid crystal cell side of a polarizer, it is preferable to use a thing with high optical uniformity. If the protective film disposed between the polarizer and the liquid crystal cell has birefringence, the birefringence may affect the display characteristics of the liquid crystal panel. From such a viewpoint, as the protective film, a film having a small birefringence, that is, having optical isotropy is preferably used, and among these, a cellulose resin is generally used. As the cellulose resin, an ester of cellulose and a fatty acid is preferable. Specific examples of the cellulose ester resin include triacetyl cellulose, diacetyl cellulose, tripropionyl cellulose, dipropionyl cellulose, and the like. Among these, triacetyl cellulose is particularly preferable. Many products of triacetylcellulose are commercially available, which is advantageous in terms of availability and cost. In general, these triacetyl celluloses have almost no in-plane retardation, but have a thickness direction retardation of about 60 nm.

  As the cellulose film, for example, a method of annealing the cellulose resin by heating or solvent treatment, addition of an additive such as a retardation adjusting agent, a method of controlling the degree of substitution of the fatty acid cellulose resin with a fatty acid, etc. What controlled the thickness direction phase difference small can also be used.

  As the protective film, a film having a phase difference can be used instead of the optically isotropic film as described above. That is, by using the birefringence of the protective film disposed between the polarizer and the liquid crystal cell for optical compensation of the liquid crystal cell, the functions of the protective film of the polarizer and the optical compensation film (retardation film) are combined into one sheet. This can be achieved with a film, and can contribute to reducing the thickness, weight, and cost of the liquid crystal panel. Furthermore, in the present invention, it is also preferable to use a substrate film as a support for a retardation layer (liquid crystal optical compensation layer) described later as a protective film for a polarizer.

  Although the thickness of a protective film can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and a handleability, and thin-layer property. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable. If the thickness of the protective film is excessively small, the polarizer may be inferior in durability in a high-temperature and high-humidity environment, or may cause problems such as local unevenness defects (knic defects).

  The same protective film may be used on both sides of the polarizer, or different ones may be used. In addition, a laminate of two or more layers can be used on one surface.

(Lamination of polarizer and protective film)
The method of laminating the polarizer and the protective film and the method of laminating the polarizer and the protective film are not particularly limited, but from the viewpoint of workability and light utilization efficiency, an adhesive or a pressure-sensitive adhesive is used. Thus, it is desirable to laminate each layer without air gaps. In the case of using an adhesive or a pressure-sensitive adhesive, the type thereof is not particularly limited, and various types can be used, but an adhesive is suitably used for laminating the polarizer and the protective film.

  Examples of the adhesive include acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyvinyl ether, vinyl acetate / vinyl chloride copolymer, modified polyolefin, epoxy-based, fluorine-based, natural rubber-based, and synthetic rubber. Those using a rubber-based polymer as a base polymer can be appropriately selected and used. In particular, a water-based adhesive is preferably used for laminating the polarizer and the optically isotropic film. Among them, those mainly composed of polyvinyl alcohol resin are used.

  Examples of the polyvinyl alcohol resin used for the adhesive include a polyvinyl alcohol resin and a polyvinyl alcohol resin having an acetoacetyl group. A polyvinyl alcohol resin having an acetoacetyl group is a polyvinyl alcohol-based adhesive having a highly reactive functional group, and is preferable because durability of the polarizing plate is improved.

  Polyvinyl alcohol resin is polyvinyl alcohol obtained by saponifying polyvinyl acetate; a derivative thereof; a saponified product of a copolymer of vinyl acetate and a monomer having copolymerizability; Examples thereof include modified polyvinyl alcohols that have been converted into ethers, ethers, grafts, or phosphoric esters. Examples of the monomer include unsaturated carboxylic acids such as (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, (meth) acrylic acid, and esters thereof; α-olefins such as ethylene and propylene, (meth) Examples include allyl sulfonic acid (soda), sulfonic acid soda (monoalkyl malate), disulfonic acid soda alkyl maleate, N-methylol acrylamide, acrylamide alkyl sulfonic acid alkali salt, N-vinyl pyrrolidone, N-vinyl pyrrolidone derivatives, and the like. . These polyvinyl alcohol resins can be used alone or in combination of two or more.

  The polyvinyl alcohol-based resin is not particularly limited, but from the viewpoint of adhesiveness, the average degree of polymerization is about 100 to 5000, preferably 1000 to 4000, the average saponification degree is about 85 to 100 mol%, preferably 90 to 100 mol%. It is.

  A polyvinyl alcohol resin containing an acetoacetyl group is obtained by reacting a polyvinyl alcohol resin and diketene by a known method. For example, a method in which polyvinyl alcohol resin is dispersed in a solvent such as acetic acid and diketene is added thereto, and a method in which polyvinyl alcohol resin is previously dissolved in a solvent such as dimethylformamide or dioxane and diketene is added thereto. Etc. Moreover, the method of making diketene gas or liquid diketene contact directly to polyvinyl alcohol is mentioned.

  The degree of acetoacetylation of the polyvinyl alcohol resin containing an acetoacetyl group is not particularly limited as long as it is 0.1 mol% or more. If it is less than 0.1 mol%, the water resistance of the adhesive layer tends to be insufficient. The degree of acetoacetylation is preferably about 0.1 to 40 mol%, more preferably 1 to 20 mol%, and particularly preferably 2 to 7 mol%. If the degree of acetoacetylation exceeds 40 mol%, the effect of improving water resistance may not be sufficiently obtained. The degree of acetoacetylation can be quantified by NMR.

  Moreover, it is preferable that an adhesive agent contains a crosslinking agent. As a crosslinking agent, what is used for the polyvinyl alcohol-type adhesive agent can be especially used without a restriction | limiting. A compound having at least two functional groups having reactivity with the polyvinyl alcohol resin can be used. For example, alkylene diamines having two alkylene groups and two amino groups such as ethylene diamine, triethylene diamine and hexamethylene diamine; tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane tolylene diisocyanate adduct, triphenylmethane triisocyanate, methylene bis (Isocyanates such as 4-phenylmethane triisocyanate, isophorone diisocyanate and their ketoxime block product or phenol block product; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di or triglycidyl ether, 1,6-hexane Diol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl Epoxys such as aniline and diglycidylamine; monoaldehydes such as formaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde; Amino-formaldehyde resins such as methylolurea, methylolmelamine, alkylated methylolurea, alkylated methylolated melamine, acetoguanamine, condensate of benzoguanamine and formaldehyde; further sodium, potassium, magnesium, calcium, aluminum, iron, Examples thereof include divalent metals such as nickel or salts of trivalent metals and oxides thereof, among which amino-formaldehyde resins and dialaldehydes. S is preferably an amino -.. Is preferably a compound having a methylol group as a formaldehyde resin, the dialdehydes are preferred glyoxal is inter alia a compound having a methylol group, methylol melamine is particularly preferred.

  The amount of the crosslinking agent can be appropriately designed according to the type of the polyvinyl alcohol resin in the adhesive and the like, but is usually about 10 to 60 parts by weight, preferably 20 with respect to 100 parts by weight of the polyvinyl alcohol resin. ~ 50 parts by weight. In such a range, good adhesiveness can be obtained.

  Furthermore, from the viewpoint of suppressing the occurrence of uneven defects (knics), it is also preferable to include a metal colloid in the adhesive. Examples of such metal colloids include alumina colloid, silica colloid, zirconia colloid, titania colloid and tin oxide colloid. Specifically, those described in JP-A-2008-15383 can be suitably used.

  It is preferable to apply the adhesive so that the thickness of the adhesive layer after drying is about 10 to 300 nm. The thickness of the adhesive layer is more preferably from 10 to 200 nm, and even more preferably from 20 to 150 nm, from the viewpoint of obtaining a uniform in-plane thickness and sufficient adhesive strength.

  In the present invention, each of the polarizer, protective film, adhesive layer, pressure-sensitive adhesive layer, and the like includes, for example, salicylic acid ester compounds, benzophenol compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex compounds. It may be one having a UV absorbing ability by a method such as a method of treating with a UV absorber.

  Attaching the pressure-sensitive adhesive layer or adhesive layer to the film can be performed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of an appropriate solvent alone or a mixture such as toluene and ethyl acetate is prepared. Examples include a method in which it is directly attached on a film by an appropriate development method such as a casting method or a coating method, or a method in which an adhesive layer is formed on a separator according to the above and transferred (transferred). It is done.

  The pressure-sensitive adhesive layer and the adhesive layer can also be provided on one side or both sides of the film as an overlapping layer of different compositions or types. Moreover, when providing in both surfaces, it can also be set as adhesive layers, such as a different composition, a kind, and thickness, in the front and back of a film.

  Further, the protective film may be subjected to a surface modification treatment such as hydrophilization for the purpose of improving the adhesiveness before attaching the adhesive or the pressure-sensitive adhesive. Specific examples of the treatment include corona treatment, plasma treatment, primer treatment, and saponification treatment.

(Surface treatment layer)
Furthermore, a surface of the protective film on which the polarizer is not adhered may be provided with a hard coat layer, antireflection treatment, antisticking, or a surface treatment layer for the purpose of diffusion or antiglare.

  The hard coat layer is provided for the purpose of preventing scratches on the surface of the polarizing plate. For example, a hard film with an appropriate UV curable resin such as acrylic or silicone is applied to the surface of the protective film. It can be formed by a method added to the above. The antireflection layer is provided for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the prior art. The anti-sticking layer is provided for the purpose of preventing adhesion with an adjacent layer (for example, a diffusion plate).

  The anti-glare layer is provided for the purpose of preventing external light from being reflected on the surface of the polarizing plate and hindering the viewing of the light transmitted through the polarizing plate. For example, a roughening method using a sandblasting method or an embossing method, It can be formed by imparting a fine concavo-convex structure to the surface of the protective film by an appropriate method such as a blending method of transparent fine particles. The fine particles to be included in the formation of the surface fine concavo-convex structure are, for example, conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle diameter of 0.5 to 20 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like are used. When forming the surface fine uneven structure, the amount of fine particles used is generally about 2 to 70 parts by weight, preferably 5 to 50 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure.

  The antireflection layer, anti-sticking layer, surface treatment layer such as a diffusion layer and an antiglare layer can be provided on the protective film itself, and can also be provided as a separate optical layer from the protective film. .

[Phase difference layer]
The retardation layer used in the liquid crystal panel of the present invention is obtained by tilting the optical axis of the liquid crystal. As such a liquid crystal optical compensation layer, an O plate is used. As an O plate, for example, a plate formed of a liquid crystal material that exhibits optically positive or negative uniaxial properties and having a portion in which the material is tilted and aligned can be used. An optically positive uniaxial material is a material in which the refractive index of the principal axis in one direction is larger than the refractive indexes in the other two directions in the three-dimensional refractive index ellipsoid. An optically negative uniaxial material refers to a material in which the refractive index of the principal axis in one direction is smaller than the refractive indexes in the other two directions in the three-dimensional refractive index ellipsoid. In addition, a material in which such a material as a main component is mixed and reacted with another oligomer or polymer to fix a state in which a material exhibiting positive or negative uniaxiality is tilt-oriented is fixed to form a film. In using a liquid crystal compound, the tilted alignment state of the liquid crystal molecules is determined depending on the molecular structure, the type of alignment film, and the use of additives (for example, plasticizers, binders, surfactants) that are appropriately added to the optically anisotropic layer. Can be controlled by.

  The liquid crystal optical compensation layer is formed of a liquid crystal material that exhibits optically positive or negative uniaxiality, but it is preferable to use a liquid crystal material that exhibits optically negative uniaxiality. As the liquid crystal material exhibiting optically negative uniaxiality, a liquid crystal material such as a discotic liquid crystal compound is preferable.

(Discotic liquid crystal layer)
The discotic liquid crystal layer is usually formed by alignment and curing of a discotic liquid crystal compound having a polymerizable unsaturated group. The discotic liquid crystal layer is useful as a liquid crystal optical compensation layer and can improve the viewing angle, contrast, brightness, and the like. The discotic liquid crystal layer is preferably one in which a discotic liquid crystal compound is tilted. The thickness of the discotic liquid crystal layer is usually about 0.5 to 10 μm.

  The discotic liquid crystal compound has a negative refractive index anisotropy (uniaxiality). Destrade et al., Mol. Cryst. 71, 111 (1981), benzene derivatives and B.I. Kohne et al., Angew. Chem. 96, page 70 (1984) and the cyclohexane derivatives described in J. Am. M.M. Lehn et al. Chem. Commun. , 1794 (1985), J. Am. Zhang et al., J. Am. Chem. Soc. 116, 2655 (1994), such as azacrown and phenylacetylene macrocycles, etc., which are generally used as a mother nucleus at the center of a molecule, and are linear alkyl groups, alkoxy groups, substituted A structure in which a benzoyloxy group or the like is radially substituted as a straight chain thereof exhibits liquid crystallinity and includes what is generally called a discotic liquid crystal. However, the molecule itself is not limited to the above description as long as the molecule itself has negative uniaxiality and can give a certain orientation. In the present invention, as the discotic liquid crystal compound, one having a polymerizable unsaturated group (for example, acryloyl group, methacryloyl group, vinyl group, allyl group, etc.) that undergoes a curing reaction with heat, light or the like is usually used. It is done. Note that the discotic liquid crystal layer does not necessarily need to be the final compound, and includes a liquid crystal layer that has been polymerized or cross-linked by the reaction of a polymerizable unsaturated group to increase the molecular weight and lose liquid crystallinity.

  In addition, the discotic liquid crystal compounds are optical molecules such as reaction products of discotic liquid crystals that no longer exhibit liquid crystallinity due to reaction with various discotic liquid crystal compounds and other low molecular compounds and polymers. In general, it means all compounds having negative uniaxiality.

(Nematic liquid crystal layer)
On the other hand, a liquid crystal material exhibiting optically positive uniaxiality includes a nematic liquid crystal compound. Examples of the nematic liquid crystal compound include nematic liquid crystal monomers and / or polymers.

  Examples of the nematic liquid crystalline monomer include those having a polymerizable functional group such as an acryloyl group or a methacryloyl group at the terminal and a mesogenic group composed of a cyclic unit or the like. In addition, as a polymerizable functional group, one having two or more acryloyl groups, methacryloyl groups and the like can be used to introduce a crosslinked structure to improve durability. Examples of the cyclic unit serving as a mesogenic group include biphenyl, phenylbenzoate, phenylcyclohexane, azoxybenzene, azomethine, azobenzene, phenylpyrimidine, diphenylacetylene, diphenylbenzoate, and bicyclohexane. Cyclohexyl benzene, terphenyl, and the like. In addition, the terminal of these cyclic units may have substituents, such as a cyano group, an alkyl group, an alkoxy group, a halogen group, for example.

  Examples of the main chain type liquid crystal polymer include condensed polymers having a structure in which mesogenic groups composed of aromatic units and the like are bonded, for example, polyester-based, polyamide-based, polycarbonate-based, and polyesterimide-based polymers. Examples of the aromatic unit that becomes a mesogenic group include phenyl, biphenyl, and naphthalene types, and these aromatic units have substituents such as a cyano group, an alkyl group, an alkoxy group, and a halogen group. May be.

  Examples of the side chain type liquid crystal polymer include those having a polyacrylate-based, polymethacrylate-based, polysiloxane-based, or polymalonate-based main chain as a skeleton, and having a mesogenic group composed of a cyclic unit or the like in the side chain. Examples of the cyclic unit serving as a mesogenic group include biphenyl, phenylbenzoate, phenylcyclohexane, azoxybenzene, azomethine, azobenzene, phenylpyrimidine, diphenylacetylene, diphenylbenzoate, and bicyclohexane. Cyclohexyl benzene, terphenyl, and the like. In addition, the terminal of these cyclic units may have substituents, such as a cyano group, an alkyl group, an alkoxy group, a halogen group, for example.

  Any mesogenic group of the polymerizable liquid crystal monomer or the liquid crystal polymer may be bonded via a spacer portion that imparts flexibility. Examples of the spacer portion include a polymethylene chain and a polyoxymethylene chain. The number of repeating structural units forming the spacer portion is appropriately determined depending on the chemical structure of the mesogenic portion, but the repeating unit of the polymethylene chain is 0 to 20, preferably 2 to 12, and the repeating unit of the polyoxymethylene chain is 0 to 0. 10, preferably 1-3.

  A cholesteric liquid crystalline monomer and a chiral agent can be blended with the nematic liquid crystalline monomer and the liquid crystalline polymer so as to exhibit a cholesteric phase in a liquid crystal state. A cholesteric liquid crystalline polymer can also be used. The obtained cholesteric liquid crystal layer is used as a selective reflection film. The chiral agent is not particularly limited as long as it has an optically active group and does not disturb the alignment of a nematic liquid crystalline monomer or the like. The chiral agent may or may not have liquid crystallinity, but those exhibiting cholesteric liquid crystallinity can be preferably used. As the chiral agent, those having or not having a reactive group can be used, but those having a reactive group are preferred from the viewpoint of heat resistance and solvent resistance of a cholesteric liquid crystal alignment film obtained by curing. Examples of the reactive group include an acryloyl group, a methacryloyl group, an azide group, and an epoxy group.

(Method for producing liquid crystal optical compensation layer)
The first and second retardation layers used in the liquid crystal panel of the present invention are not particularly limited as long as they are obtained by tilting and aligning the optical axis of the liquid crystal as described above. As a means for forming a tilted alignment layer of discotic or nematic liquid crystal, for example, an electric field or magnetic field is applied or a support is rubbed, or an alignment film is applied and rubbed or irradiated with ultraviolet rays. Thus, it is possible to use a method such as aligning a polymerizable liquid crystal or a polymer liquid crystal in a predetermined direction, and then fixing the alignment state of the liquid crystal by light or heat in the former case, or rapid cooling in the latter case. . In particular, from the viewpoint of uniformity of alignment, a method of applying the liquid crystalline composition on a support on which an alignment film is formed, and fixing the alignment by solidification (drying) and curing can be suitably used as necessary.

  The transparent support is not particularly limited as long as it is optically transparent, and those exemplified as the protective film for the polarizing plate can be used. The transparent support can also serve as the protective film for the polarizing plate.

  In order to align the liquid crystal layer in a predetermined direction, a method using an electric field or a magnetic field, a rubbing process, an alignment film, or the like can be used as described above. From the viewpoint of alignment uniformity, an alignment film is used. It is preferable. As the alignment film, various kinds of conventionally known films can be used, and examples thereof include an inorganic oblique deposition film or an alignment film rubbed with a specific organic polymer film. There is a thin film in which isomerization is caused by light and molecules are uniformly arranged with directionality, such as an LB film made of an azobenzene derivative. Examples of organic polymer alignment films include polyimide films and organic polymer films such as alkyl chain-modified poval, polyvinyl butyral, polymethyl methacrylate, and polyvinyl alcohol. In addition, as the inorganic oblique deposition film, an SiO oblique deposition film or the like can be used.

  It is also possible to form a discotic liquid crystal or nematic liquid crystal on another alignment substrate by tilting and then transferring it onto a transparent support using an optically transparent adhesive or adhesive. It is.

  In the liquid crystal optical compensation layer obtained by tilting the optical axis of the liquid crystal in this way, as shown in FIGS. 1A and 1B, the direction in which the director direction of the liquid crystal compound is projected onto the liquid crystal cell surface is The film is substantially parallel to the alignment treatment direction of the alignment film or the like. The “director direction” means the alignment orientation of the entire liquid crystal molecules as viewed statistically.

  FIG. 4 schematically illustrates the direction of the director, and FIG. 4A shows the case of a liquid crystal material exhibiting optically negative uniaxiality typified by the discotic liquid crystal. For example, the discotic liquid crystal 15 has the optical axis 17 in the normal direction of the molecule, but the average of the vector directions is the director direction 7 (or 8). That is, the director direction is, in other words, a statistical average of vectors of the optical axis (C axis) of liquid crystal molecules. FIG. 4B shows the case of a liquid crystal material that exhibits optically positive uniaxiality, typified by the nematic liquid crystal. For example, the nematic liquid crystal 16 has an optical axis 18 in the molecular alignment direction, and the average of the vector directions is the director direction 7 (or 8). In FIG. 1 and FIG. 4, the director directions 7 and 8 are indicated by unidirectional single arrows. The direction of the arrow is from the smaller tilt angle of the liquid crystal molecules in the O plate to the larger tilt angle. Define it as heading.

  In the first retardation layer 31, the director direction 7 projected onto the liquid crystal cell surface (indicated by a broken-line arrow with 7 ′ in FIGS. 1A and 1B) is the first It becomes substantially parallel to the alignment direction 5 of the retardation layer. Further, in the second retardation layer 32, the director direction 8 projected onto the liquid crystal cell surface (indicated by a broken line arrow with 8 ′ in FIGS. 1A and 1B) is as follows. It becomes substantially parallel to the alignment direction 6 of the second retardation layer.

In FIGS. 1A and 1B, the liquid crystal molecules in the first retardation layer 31 and the second retardation layer 32 have an inclination angle (θ _LC ) on the liquid crystal cell side and an inclination angle on the polarizing plate side. Although it is smaller than (θ _P ), that is, the arrow in the director direction is drawn from the polarizing plate 21 (or 22) side to the liquid crystal cell side 10, the tilt angle (θ _P of the polarizing plate side of the liquid crystal molecules is drawn. ) May be arranged on the liquid crystal panel so that the tilt angle (θ _LC ) on the liquid crystal cell side becomes small. Such a magnitude relationship between the tilt angles can be adjusted by the type of liquid crystal molecules, the method of tilting the liquid crystal, and the like. Further, according to the transfer method described above, since the front and back of the liquid crystal layer is reversed, it is also possible to adjust the magnitude relationship between theta _P and theta _LC by the number of transfers. The director directions 7 and 8 in FIGS. 1A and 1B schematically represent the case where a liquid crystal material exhibiting negative uniaxiality is used for the retardation layer.

  Regardless of whether the liquid crystal optical compensation layer is a liquid crystal material that exhibits optically positive uniaxiality or a liquid crystal material that exhibits negative uniaxiality, the liquid crystal molecules tend to be aligned in the alignment treatment direction of the alignment film. There is. Therefore, when a liquid crystal material that exhibits positive uniaxiality, such as nematic liquid crystal, is used, the alignment direction of the alignment film is the same as the slow axis direction of the retardation layer, and negative uniaxiality, like discotic liquid crystal. When the liquid crystal material showing is used, the alignment direction of the alignment film tends to be equal to the fast axis direction of the retardation layer.

  As the discotic liquid crystal layer, those described in JP-A-8-95032 and JP-A-7-287120 are preferably used. A wide view film manufactured by Fuji Film Co., Ltd. is one in which such an inclined alignment layer of discotic liquid crystal is formed on a cellulose film. As the nematic liquid crystal layer, those described in JP-A-9-21914, JP-A-9-26572 and the like are preferably used. An NH film manufactured by Nippon Oil Corporation is an example of such a nematic liquid crystal tilted alignment layer formed on a cellulose film.

[Formation of liquid crystal panel]
FIG. 5 shows an example of a schematic cross-sectional view of the liquid crystal panel of the present invention. The liquid crystal panel of the present invention uses the liquid crystal cell 10, the first polarizing plate 21, the second polarizing plate 22, the first retardation layer 31, and the second retardation layer 32, and any appropriate It can be formed by a method. In addition, the liquid crystal panel of the present invention can include an optical layer other than the above and other members. Examples thereof include the above-described antireflection layer, antisticking layer, surface treatment layer such as a diffusion layer and an antiglare layer, and a brightness enhancement film. Moreover, in the range which does not impair the objective of this invention, retardation layers (retardation film) other than a 1st phase difference layer and a 2nd phase difference layer, an optically isotropic film, etc. can also be included.

  The brightness enhancement film is not particularly limited, and transmits linearly polarized light having a predetermined polarization axis such as a dielectric multilayer thin film or a multilayer laminate of thin film films having different refractive index anisotropy. Other materials that reflect light can be used. As such a brightness enhancement film, for example, trade name “D-BEF” manufactured by 3M Co., Ltd. may be mentioned. Further, a cholesteric liquid crystal layer, in particular, an oriented film of a cholesteric liquid crystalline polymer, or a film in which the oriented liquid crystal layer is supported on a film substrate can be used. These reflect the right and left circularly polarized light and transmit the other light. For example, the product name “PCF350” manufactured by Nitto Denko Corporation, the product name “Transmax” manufactured by Merck, etc. Can be mentioned.

  Each member is preferably laminated via an adhesive layer, a pressure-sensitive adhesive layer, or the like. In that case, the adhesive or pressure-sensitive adhesive is transparent, has no absorption in the visible light region, and the refractive index is desirably as close as possible to the refractive index of each layer from the viewpoint of suppressing surface reflection. As the adhesive, those described above in the lamination of the polarizer and the protective film can be suitably used. As the pressure-sensitive adhesive, an acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer can be appropriately selected and used. In particular, those having excellent optical transparency, such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and having excellent weather resistance, heat resistance and the like can be preferably used.

  In addition to the above, from the viewpoints of prevention of foaming and peeling phenomenon due to moisture absorption, deterioration of optical characteristics due to thermal expansion difference and the like, prevention of warpage of liquid crystal cells, and formation of liquid crystal display devices with high quality and excellent durability. An adhesive layer having a low moisture absorption rate and excellent heat resistance is preferred.

  The pressure-sensitive adhesive layer is, for example, a natural or synthetic resin, in particular, a tackifier resin, a filler, a pigment, a colorant, an antioxidant made of glass fiber, glass beads, metal powder, or other inorganic powders. An additive to be added to the pressure-sensitive adhesive layer may be contained. Moreover, the adhesive layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient. Although the thickness of an adhesive layer can be suitably determined according to a use purpose, adhesive force, etc., generally it is 1-500 micrometers, 5-200 micrometers is preferable, and 10-100 micrometers is more preferable.

(Liquid crystal panel formation order)
In the present invention, the order in which the liquid crystal panels are formed is not particularly limited, and the liquid crystal panels may be formed by a method of sequentially laminating each member separately, or a material obtained by laminating several members in advance may be used. In addition, although the stacking order is not particularly limited, in the present invention, a polarizing plate and a retardation layer, and a polarizing plate with a retardation layer in which a surface treatment layer, a brightness enhancement film and the like are laminated in advance, are prepared in advance. By laminating this with a liquid crystal cell, it is possible to achieve excellent quality stability and assembly workability. A polarizing plate with a viewing angle compensation film “NWF series” manufactured by Nitto Denko is commercially available as a laminate in which a polarizing plate and a retardation layer obtained by tilting and aligning the optical axes of liquid crystals are laminated.

  In addition, it is preferable to laminate | stack the said polarizing plate with a phase difference layer, and a liquid crystal cell through an adhesive, especially an acrylic adhesive layer as mentioned above. In particular, from the viewpoint of productivity and workability, as shown in FIG. 6, the pressure-sensitive adhesive layer is formed on the surface of the polarizing plate with the retardation layer that is bonded to the liquid crystal cell, that is, on the surface of the retardation layer 31 (or 32) side. It is preferable to prepare in advance as a retardation layer-attached polarization 91 (92) provided with a pressure-sensitive adhesive layer provided with, and laminate it with a liquid crystal cell. In FIG. 6, the protective film 50 of the polarizing plate and the support film of the retardation layers 31 and 32 are a single film, but the protective film and the support film are separated from each other. Can also be adopted.

  Moreover, in this invention, it is preferable from a viewpoint of productivity to laminate | stack a polarizing plate and retardation layer with a roll-to-roll, and to set it as a elongate laminated polarizing plate. In order to laminate both of them in a roll-to-roll manner, in the liquid crystal panel of the present invention, the absorption axis direction of the first polarizing plate and the alignment direction of the first retardation layer are parallel, and the second It is preferable to adopt a configuration in which the absorption axis direction of the polarizing plate and the orientation direction of the second retardation layer are parallel.

  Usually, a polarizing plate uses a polarizer stretched in the transport direction (longitudinal direction) from the viewpoint of increasing the degree of polarization or improving the productivity, but such a polarizing plate has a transport direction and an absorption axis direction that are stretch directions. Are equal. On the other hand, a liquid crystal optical compensation layer obtained by tilting and orienting the optical axes of liquid crystals used as the first retardation layer and the second retardation layer is a base material that is oriented in the transport direction from the viewpoint of productivity. It is often produced using Therefore, as a result, the alignment direction (projection in the director direction) of the liquid crystal molecules in the retardation layer and the transport direction (longitudinal direction) are parallel.

  Therefore, when the liquid crystal panel of the present invention adopts the above configuration, a long polarizing plate with a retardation layer having a desired angular arrangement is obtained by laminating a polarizing plate and a retardation layer by roll-to-roll. Can be obtained.

  The long retardation film with retardation layer thus obtained is preferably bonded to a liquid crystal panel after being processed into a predetermined size. Usually, in a TN mode liquid crystal panel, a polarizing plate cut out into a rectangle so as to match the screen size is used. In particular, in the present invention, from the viewpoint of achieving the angular arrangement of any one of (C-1) to (C-4) above, the longitudinal direction of the long polarizing plate with a retardation layer and the long side of the rectangle The polarizing plate is adjusted so that the angle formed by is 42.5 to 44.5 °, or 45.5 to 47.5 ° (or 132.5 to 144.5 °, or 135.5 to 137.5 °). It is preferable to cut out.

  The liquid crystal panel is usually rectangular, but in the case of a TN mode liquid crystal panel, the alignment direction 1 of the first alignment substrate 11 of the liquid crystal cell, with the long side direction (right side of the screen) of the rectangle as a reference of 0 °, and The alignment direction 2 of the second alignment substrate 12 is often 45 ° or 135 °. In the case of a conventional TN mode liquid crystal panel, since the alignment direction of the alignment substrate of the liquid crystal cell and the absorption axis direction of the polarizing plate are parallel or orthogonal, the longitudinal direction of the long polarizing plate with a retardation layer and the rectangular length It was cut out and used so that the angle formed by the side would be 45 °. On the other hand, in the present invention, by changing the angle at which the polarizing plate is cut out as described above, it is possible to obtain a liquid crystal panel with high contrast by suppressing gradation abnormality without changing other steps.

  The method for cutting the polarizing plate to the above angle is not particularly limited. For example, the above conditions are set using a method of cutting a blade or laser at a predetermined angle for each side, or using a blade with a predetermined size. A method of punching at a filling angle or the like can be suitably employed.

  When the pressure-sensitive adhesive layer for laminating the liquid crystal cell is provided on the polarizing plate with the retardation layer, the adhesive can be attached either before or after the rectangular polarizing plate is cut out from the long laminated polarizing plate. From the viewpoint of workability and workability, it is preferable to attach an adhesive layer before cutting out the polarizing plate. By forming a long polarizing plate with a retardation layer provided with an adhesive layer and cutting it out to a predetermined size, the productivity and workability of the liquid crystal panel can be improved.

  The exposed surface of the pressure-sensitive adhesive layer is preferably covered with a separator for the purpose of preventing contamination until it is practically used. Thereby, it can prevent contacting an adhesive layer in the usual handling state. As the separator, for example, a suitable thin leaf body such as a plastic film, rubber sheet, paper, cloth, nonwoven fabric, net, foamed sheet, metal foil, laminate thereof, or the like, silicone-based or long-chain alkyl-based, fluorine-based An appropriate material according to the prior art, such as those coated with an appropriate release agent such as molybdenum sulfide or molybdenum sulfide, can be used.

[Liquid Crystal Display]
The liquid crystal display device of the present invention includes the liquid crystal panel and means for supplying light to the liquid crystal panel such as a light source or a reflector. As an example of the liquid crystal display device of the present invention, a transmissive liquid crystal display device including a light source will be described. FIG. 7 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. The liquid crystal display device 300 includes at least a liquid crystal panel 100 and a backlight unit 200 disposed on one side of the liquid crystal panel 100. In the illustrated example, the case where the direct type is adopted as the backlight unit is shown, but this may be a side light type, for example.

  When the direct method is employed, the backlight unit 200 preferably includes a light source 81, a reflective film 82, a diffusion plate 83, and a prism sheet 84. Although not shown, it is also preferable to have a brightness enhancement film. When the sidelight system is adopted, preferably, the backlight unit further includes a light guide plate and a light reflector in addition to the above configuration. In addition, as long as the effect of this invention is acquired, the optical member illustrated in FIG. 7 may be partly omitted depending on the design of the illumination method or the like of the liquid crystal display device, or may be replaced with another optical member. Can be done.

  As described above, the liquid crystal display device of the present invention includes the liquid crystal panel in which the polarizing plate and the retardation layer are arranged at a predetermined angle, so that the gradation characteristic abnormality is suppressed and the luminance in the black display is small. Have.

  Since the liquid crystal display device of the present invention has such characteristics, the applications that can be used for any appropriate application include, for example, personal computer monitors, notebook computers, OA devices such as copy machines, mobile phones, watches, digital cameras, Personal digital assistants (PDAs), portable devices such as portable game machines, household electrical equipment such as video cameras, televisions, and microwave ovens, back monitors, monitors for car navigation systems, in-car devices such as car audio, and information for commercial stores Display equipment such as medical monitors, security equipment such as monitoring monitors, nursing care and medical equipment such as nursing monitors and medical monitors.

  The present invention will be further described using examples and comparative examples, but the present invention is not limited to the following examples. In addition, the measured value etc. which were used in the Example were obtained by the following methods.

(Measurement method of single transmittance of polarizing plate)
From a central part in the width direction of the polarizing plate with a retardation layer, a rectangular sample is cut out with a size of 50 mm × 25 mm so that the absorption axis direction of the polarizing plate is 45 ° with respect to the long side, and integrating sphere type single transmission It measured using the rate measuring apparatus (Murakami Color Research Institute make brand name "Dot-3C").

(Measurement method in the axial direction of the polarizing plate)
The absorption axis direction of the polarizing plate was measured with a phase difference measuring device (manufactured by Oji Scientific Instruments, trade name “KOBRA 31WPR”) with the long side of the polarizing plate aligned with the reference axis of the phase difference measuring device field.

(Measurement of brightness)
One hour after the backlight is turned on after turning on the power of the liquid crystal display device, the gradation of the panel is gradually changed from 0 gradation (black display) to 12 gradations, and the product name “Conoscope” manufactured by AUTRONIC-MELCHERS The brightness in the front direction of the central portion of the liquid crystal panel at each gradation was measured.

[Production example]
(Creating a polarizer)
A polyvinyl alcohol film having an average polymerization degree of 2400, a saponification degree of 99.9 mol% and a thickness of 75 microns was immersed in warm water of 30 ° C. for 60 seconds to swell. Next, the film was dyed while being immersed in an aqueous solution having a concentration of 0.3% by weight containing iodine / potassium iodide at a weight ratio of 1/16, and stretching to 3.5 times the original length. Then, it extended | stretched so that it might become 6 times the original length in 65 degreeC borate ester aqueous solution. After extending | stretching, it dried in 40 degreeC oven for 3 minutes, and obtained the polarizer. The single transmittance of the polarizer was 42.4%.

(Transparent protective film)
As one transparent protective film, a 80 μm thick triacetyl cellulose film (manufactured by Fuji Film, trade name “Fujitac TD80UL”) was used.

(Transparent protective film with retardation layer)
An optical compensation film (trade name “Wide View Film EA” manufactured by Fuji Film Co., Ltd.) in which an ultraviolet curable discotic liquid crystal compound is tilted and aligned on a triacetyl cellulose base film through an alignment film made of a crosslinkable polyvinyl alcohol film. Using.

(Polyvinyl alcohol adhesive)
30 parts by weight of methylol melamine as a cross-linking agent with respect to 100 parts by weight of polyvinyl alcohol resin containing acetoacetyl groups (average polymerization degree 120, saponification degree 98.5 mol%, acetoacetylation degree 5 mol%) An aqueous adhesive solution was prepared by dissolving in pure water under a temperature condition of 0 ° C. and adjusting the solid content concentration to 4% by weight.

(Creation of polarizing plate with retardation layer)
The polyvinyl alcohol adhesive aqueous solution was applied to one side of the transparent protective film (triacetyl cellulose film) so that the adhesive thickness after drying was 80 nm. On the other hand, the thickness of the adhesive layer after drying the polyvinyl alcohol-based adhesive aqueous solution is 80 nm on the surface of the transparent protective film with a retardation layer on the side where the liquid crystal layer of the triacetyl cellulose film is not formed. It was applied to. In addition, application | coating of each adhesive agent was performed on 30 degreeC temperature conditions 30 minutes after the preparation. Next, under the temperature condition of 30 ° C., after the transparent protective film is bonded to one main surface of the polarizer and the transparent protective film with retardation layer is bonded to the other main surface with a roll bonding machine, In a state where tension was applied so that the tension was 100 N, drying was performed at 70 ° C. for 5 minutes to obtain a polarizing plate with a retardation layer.

(Preparation of adhesive)
In a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer and a stirrer, 99 parts by weight of butyl acrylate, 1 part by weight of 4-hydroxybutyl acrylate, and 2,2-azobisisobutyronitrile (AIBN) 0 .3 parts by weight with ethyl acetate and reacted at 60 ° C. for 4 hours in a nitrogen gas atmosphere, and then ethyl acetate was added to the reaction solution to obtain a solid content concentration containing an acrylic polymer having a weight average molecular weight of 1,650,000. A 30% solution was obtained. 0.15 parts by weight of dibenzoyl peroxide per 100 parts by weight of the acrylic polymer (trade name “Nyver BO-Y” manufactured by NOF Corporation), 0.02 parts by weight of trimethylolpropane xylene diisocyanate (trade name “Mitsui Takeda Chemicals” Takenate D110N ”) and 0.2 part by weight of an acetoacetyl group-containing silane coupling agent (trade name“ A100 ”manufactured by Soken Chemical Co., Ltd.) were blended to obtain an acrylic pressure-sensitive adhesive.

  The above-mentioned pressure-sensitive adhesive was applied onto a separator made of a polyester film which was release-treated with a silicone release agent, and dried at 155 ° C. for 3 minutes to obtain a pressure-sensitive adhesive layer having a thickness of 20 μm. A separator having a pressure-sensitive adhesive layer was transferred to the alignment liquid crystal layer of the above-mentioned polarizing plate with a phase difference layer, to prepare a polarizing plate with a phase difference layer provided with the pressure-sensitive adhesive layer. The gel fraction of the pressure-sensitive adhesive layer was 60% by weight. The single transmittance of the obtained polarizing plate was 42.10%.

[Comparative Example 1]
(Punching of polarizing plate)
The polarizing plate with the retardation layer obtained in the above production example is set in a punching device so that the pressure-sensitive adhesive layer is on the front surface, and the polarizing plate is formed by using a blade type set to 19 inch wide size (408 mm × 255 mm). I punched one piece. The blade mold was set so that the long side direction was 135 ° as shown in FIG. The absorption axis direction of the obtained two polarizing plates was 135.1 °.

(Creation of LCD panel)
A liquid crystal panel is taken out from a commercially available 19-inch wide-size liquid crystal display device (manufactured by Shanghai Guangden (Group) Co., Ltd., product name “SVA190WX02TB”) equipped with an 8-bit gray scale (256 gray scale) TN mode liquid crystal panel. All the optical films arranged above and below were removed, and the glass surfaces (front and back) of the liquid crystal cell were washed and used.

(Creation of liquid crystal display device)
The two polarizing plates with retardation layers punched out above were laminated on the viewing side and the light source side of the liquid crystal cell so that the absorption axes of the two were orthogonal to each other. In addition, the lamination of the liquid crystal cell and the polarizing plate with the retardation layer was mounted so that the long side of the polarizing plate and the long side of the liquid crystal cell coincided with each other so as to have the angular arrangement shown in Table 1.

  FIG. 10A schematically shows the optical axial relationship among the polarizing plate, the retardation layer, and the liquid crystal cell of the obtained display device. As shown in FIG. 10, the right side of the liquid crystal panel is defined as an azimuth angle of 0 ° and the counterclockwise direction as positive (+).

[Example 1]
(Punching of polarizing plate)
Using the polarizing plate with retardation layer obtained in the above production example, the same as in Comparative Example 1 except that the blade shape was set so that the long side direction was 136 ° as shown in FIG. 9A. A single polarizing plate was punched out. Further, as shown in FIG. 9B, the blade mold was set so that the long side direction was 134 °, and one polarizing plate was punched out. The absorption axis direction of the polarizing plate punched at 136 ° was 136.0 °, and the absorption axis direction of the polarizing plate punched at 134 ° was 134.0 °.

  9A and 9B are drawn so as to be different from the actual angles in order to easily understand the difference in angle from FIG.

(Creation of liquid crystal display device)
Using the same liquid crystal cell as in Comparative Example 1, the polarizing plate punched at 136 ° was used as the viewing side, the polarizing plate punched out at 134 ° was used as the polarizing plate on the light source side, and the angular arrangement shown in Table 2 was obtained. Mounting was performed so that the long side of the polarizing plate and the long side of the liquid crystal cell coincided. FIG. 10B schematically shows the optical axial relationship between the polarizing plate, the retardation layer, and the liquid crystal cell of the obtained display device. In FIG. 10B, in order to facilitate understanding of the difference in angle from FIG. 10A, it is drawn so as to be different from the actual angle.

[Examples 2 to 4, Comparative Examples 2 to 5]
Except that the punching angle of the polarizing plate on the viewing side and the light source side was changed in increments of 1 ° as shown in Table 3, a rectangular polarizing plate was prepared in the same manner as in Example 1 and Comparative Example 1, and the liquid crystal display device Created. The punching angle in Table 3 is not the angle at which the blade shape is set, but the angle in the absorption axis direction measured using a polarizing plate actually punched. In Examples and Comparative Examples, the tolerance of the absorption axis of the polarizing plate was within 0.2 °.

[Evaluation results]
Table 3 shows the arrangement of the polarizing plates of the liquid crystal display devices obtained in Examples and Comparative Examples, the luminance value at 0 gradation (black display), and the gradation at which the luminance is minimized. Further, FIG. 11 and FIG. 12 show plots of luminance with respect to gradation of the liquid crystal display devices of Examples 1 and 2 and Comparative Examples 1 to 3. Note that FIG. 12 is obtained by changing the scale of the vertical axis (luminance) for the same data as FIG.

  In Comparative Example 1, which has the same angular arrangement as the conventional liquid crystal display device, an abnormality in the gradation characteristics in which the luminance is minimum at 7 gradations was observed, whereas in the liquid crystal display device of Example 1, The brightness was minimized at 0 gradation, and no gradation characteristic abnormality was observed. Therefore, it can be seen that the brightness at 0 gradation is lower than that of Comparative Example 1, and as a result, a liquid crystal display device with high contrast can be obtained.

  Further, in Comparative Example 3, although no gradation characteristic abnormality is observed, the luminance at the 0th gradation is increased because the absorption axes of the polarizing plate on the viewing side and the light source side are not orthogonal to each other. . Similarly, in Comparative Example 2, an increase in luminance is observed.

  As described above, the liquid crystal display device including the liquid crystal panel according to the present invention has a high contrast because the gradation characteristic abnormality in the black display is suppressed and the luminance of the black display is reduced. Therefore, the liquid crystal display device is suitably used for various displays. be able to.

It is a schematic perspective view of the liquid crystal panel in the liquid crystal display device of this invention. (A) represents an example of an O mode, and (b) represents an example of an E mode. It is a schematic perspective view explaining the orientation state of the liquid crystal molecule in the TN mode liquid crystal cell. It is a conceptual diagram for demonstrating the average orientation direction of the liquid crystal molecule in the liquid crystal cell of TN mode. It is a conceptual diagram for demonstrating the director direction in a phase difference layer. (A) represents the case of a liquid crystal material exhibiting optically negative uniaxiality, and (b) represents the case of a liquid crystal material exhibiting optically positive uniaxiality. It is a schematic sectional drawing of the liquid crystal panel by preferable embodiment of this invention. It is a schematic sectional drawing of the polarizing plate with a phase difference layer by preferable embodiment of this invention. 1 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. It is a figure for demonstrating the punching angle of the polarizing plate in the comparative example 1. FIG. 6 is a diagram for explaining a punching angle of a polarizing plate in Example 1. FIG. (A) is a schematic diagram which shows the optical axial relationship of each layer in the liquid crystal panel in the comparative example 1. FIG. (B) is a schematic diagram which shows the optical axial relationship of each layer in the liquid crystal panel in Example 1. FIG. 6 is a graph showing luminance at each gradation of the liquid crystal display devices of Examples 1 and 2 and Comparative Examples 1, 2, and 3. 6 is a graph showing luminance at each gradation of the liquid crystal display devices of Examples 1 and 2 and Comparative Examples 1 and 2.

Explanation of symbols

1, 2 Orientation direction of alignment substrate 3, 4 Absorption axis (direction)
5, 6 Orientation (direction) of liquid crystal molecules in retardation layer
7, 8 Director direction 7 ', 8' Director direction projection 9 Average alignment direction 10 Liquid crystal cell 11, 12 Alignment substrate 13 Liquid crystal layer 15, 16 Liquid crystal molecule 17, 18 Optical axis 20 Polarizer 21, 22 Polarizing plate 31, 32 Retardation layer 50 Protective film 60 Adhesive layer 65 Adhesive layer 70 Surface treatment layer 80 Backlight unit 81 Light source 82 Reflective film 83 Diffuser plate 84 Prism sheet 85 Brightness enhancement film 100 Liquid crystal panel 200 Backlight unit 300 Liquid crystal display device

Claims (10)

A liquid crystal cell having a liquid crystal layer including liquid crystal molecules aligned in a twist arrangement in the absence of an electric field between a first alignment substrate and a second alignment substrate whose alignment directions are orthogonal to each other;
A first polarizing plate disposed on the first alignment substrate side of the liquid crystal cell;
A second polarizing plate disposed on the second alignment substrate side of the liquid crystal cell;
A first retardation layer disposed between the liquid crystal cell and the first polarizing plate;
A second retardation layer disposed between the liquid crystal cell and the second polarizing plate,
The first retardation layer and the second retardation layer are liquid crystal optical compensation layers obtained by tilt-aligning the optical axis of the liquid crystal,
The liquid crystal cell, the first polarizing plate, the second polarizing plate, the first retardation layer, and the second retardation layer are arranged so as to satisfy all of the following (A) to (C). LCD panel.
(A) The absorption axis direction of the first polarizing plate and the absorption axis direction of the second polarizing plate are orthogonal to each other. (B) The absorption axis direction of the first polarizing plate, the alignment direction of the first retardation layer, and the first (B-1) Absorption axis of the first polarizing plate The absorption axis direction of the polarizing plate 2 and the orientation direction of the second retardation layer satisfy either of the following (B-1) or (B-2): And the alignment direction of the liquid crystal molecules of the first retardation layer are parallel, and the absorption axis direction of the second polarizing plate and the alignment direction of the liquid crystal molecules of the second retardation layer are parallel. 2) The absorption axis direction of the first polarizing plate and the alignment direction of the liquid crystal molecules of the first retardation layer are orthogonal, and the absorption axis direction of the second polarizing plate and the liquid crystal molecules of the second retardation layer (C) The angle formed by the alignment direction of the second alignment substrate and the absorption axis direction of the second polarizing plate is 0.5 to 2.5 ° or 87.5 to 89.5 °. is there   The liquid crystal panel according to claim 1, wherein the first retardation layer and the second retardation layer contain a liquid crystal material that exhibits optically negative uniaxiality.   The liquid crystal panel according to claim 2, wherein the optically negative liquid crystal material is a discotic liquid crystal compound.   The liquid crystal panel according to claim 1, wherein an angle formed by an alignment direction of the second alignment substrate and an alignment direction of liquid crystal molecules of the second retardation layer is 0.5 to 2.5 °. .   The liquid crystal panel according to any one of claims 1 to 4, wherein an absorption axis direction of the second polarizing plate and an alignment direction of liquid crystal molecules of the second retardation layer are parallel to each other.   A liquid crystal display device comprising the liquid crystal panel according to claim 1. A retardation layer composed of a polarizing plate and a liquid crystal optical compensation layer obtained by tilting the optical axis of the liquid crystal is laminated,
The polarizing plate is rectangular,
A polarizing plate with a retardation layer, wherein an angle formed between an absorption axis direction of the polarizing plate and a long side direction of the rectangle is 42.5 to 44.5 °, or 45.5 to 47.5 °.   The polarizing plate with a retardation layer according to claim 7, wherein the retardation layer contains a liquid crystal material that exhibits optically negative uniaxiality.   The polarizing plate with a retardation layer according to claim 8, wherein the optically negative uniaxial liquid crystal material is a discotic liquid crystal compound. A method for producing a polarizing plate with a retardation layer according to any one of claims 7 to 9,
A step of obtaining a long laminated polarizing plate by laminating with a roll-to-roll so that the absorption axis direction of the polarizing plate and the alignment direction of the retardation layer obtained by tilting the optical axis of the liquid crystal are parallel, and A step of cutting out the rectangular polarizing plate so that the angle formed between the longitudinal direction of the long laminated polarizing plate and the long side of the rectangular is 42.5 to 44.5 °, or 45.5 to 47.5 ° ,
The manufacturing method of the polarizing plate with a phase difference layer which has this.