JP2010039217A - Liquid crystal panel and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal panel having the high usage efficiency of a polarizing plate and excellent display characteristics. <P>SOLUTION: The liquid crystal panel is provided with a liquid crystal cell 10 having a liquid crystal layer 13 between first and second alignment substrates 11 and 12, a first polarizing plate 21 disposed at the first alignment substrate side of the liquid crystal cell 10, a second polarizing plate 22 disposed at the second alignment substrate side of the liquid crystal cell, a first optical rotation element 31 disposed between the liquid crystal cell and the first polarizing plate 21 and a second optical rotation element 32 disposed between the liquid crystal cell and the second polarizing plate 22. Each of the first and the second optical rotation elements is a chiral nematic liquid crystal layer wherein the alignment direction of a liquid crystal molecule is gradually continuously changed along the layer thickness direction and the liquid crystal layer has a prescribed thickness. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystal panel and a liquid crystal display device excellent in productivity.

  A liquid crystal display device has a structure in which a liquid crystal cell is sandwiched between two polarizing plates (a light source side polarizing plate and a viewing side polarizing plate). In general, the two polarizing plates have their absorption axes orthogonal or parallel. It is arranged to be. Since a polarizing plate is generally produced continuously in a long shape, the film width is limited and is limited to a few meters at most, and is generally about 1 to 1.5 m in width. On the other hand, in recent years, there has been an increasing demand for a large screen for a liquid crystal display device. For example, a polarizing plate applicable to a size exceeding 65 inches (about 1640 mm) diagonal has been demanded. Such a trend toward an increase in size has been prominent in liquid crystal panels that employ in-plane switching (IPS) mode or vertical alignment (VA) mode liquid crystal cells having excellent viewing angle characteristics.

  On the other hand, twisted nematic (TN) type liquid crystal panels tend to be inferior in viewing angle characteristics as compared to VA mode and IPS mode liquid crystal panels. Mainly used in display devices. However, technologies for improving the viewing angle characteristics of TN mode liquid crystal panels are also progressing day by day, and TN mode liquid crystal panels are now used in liquid crystal display devices of 30 inches or more (for example, non-patent documents). 1). The use of such a TN mode liquid crystal panel in a large screen liquid crystal display device is expected to expand further in the future.

  By the way, in the TN mode liquid crystal panel, the orientation direction of the substrate of the liquid crystal cell and the optical axis such as the absorption axis of the polarizing plate are oblique directions of the screen from the viewpoint of uniform visibility on the left and right sides of the screen. In particular, an arrangement that is in the direction of 45 ° is mainly adopted. In order to employ such an arrangement in a liquid crystal display device having a rectangular screen, as shown in FIG. 1A, a polarizing plate P produced in a long shape is rectangularly polarized at an angle of 45 °. Since it is necessary to cut out as the board P1, the part which cannot use the edge part of a polarizing plate as a product arises. This problem becomes more prominent as the screen size increases.

  In order to solve these problems, a polarizing plate having an absorption axis in a 45 ° direction with respect to the longitudinal direction of the long film has been proposed by oblique stretching, rubbing treatment in an oblique direction, or the like (for example, Patent Document 1). To 3). However, it has been difficult for these methods to obtain a polarizing plate having a sufficient degree of polarization due to uniformity in the direction of the polarization axis and lack of molecular orientation.

  On the other hand, as shown in FIG. 1B, the polarizing plate cut out so that the longitudinal direction (absorption axis A direction) of the long polarizing plate and the side direction of the rectangle are parallel or perpendicular to each other, There has also been proposed a method for solving the above problem by combining optical rotatory elements having an optical rotatory action for rotating the shaft by 45 ° (see, for example, Patent Document 4).

Fuji Film Research Report No. 51 (2006) 59-62 Japanese Patent Laid-Open No. 2000-9912 JP 2002-86554 A JP 2004-151573 A JP-A-7-333427

  In the case of using the optical rotatory element as described in Patent Document 4, a conventional polarizing plate can be used as it is, so that the problems of the productivity and the degree of polarization of the polarizing plate are solved. However, it has been found that when an optical rotatory element is actually used in a liquid crystal display device, the screen is colored or the contrast is lowered when the screen is viewed from an oblique direction.

  In view of the above, an object of the present invention is to provide a liquid crystal panel with high use efficiency of a polarizing plate and excellent display characteristics, particularly a liquid crystal panel using a twisted nematic (TN) mode liquid crystal cell.

  As a result of intensive studies, the present inventors have found that the above problems can be solved by a liquid crystal display device using an optical rotatory element that satisfies a predetermined condition, and have reached the present invention.

That is, the present invention provides a liquid crystal cell having a liquid crystal layer between a first alignment substrate and a second alignment substrate, 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 optical rotatory element disposed between the liquid crystal cell and the first polarizing plate; A second optical rotator arranged between the polarizing plate and the first optical rotator and the second optical rotator, wherein the alignment direction of the liquid crystal molecules is gradually continuous along the thickness direction of the layer. The present invention relates to a liquid crystal panel that is a chiral nematic liquid crystal layer that has been changed. In one form of the liquid crystal panel of the present invention, the product of the birefringence Δn _{545 at} a wavelength of 545 nm and the thickness d of the liquid crystal layer of the nematic liquid crystalline material forming the chiral nematic liquid crystal layer is 1400 nm or more.

  In the liquid crystal panel of the present invention, the orientation direction of the liquid crystal molecules on the first polarizing plate side surface of the first optical rotator is preferably parallel or orthogonal to the absorption axis direction of the first polarizing plate. . Furthermore, it is preferable that the alignment direction of the liquid crystal molecules on the second polarizing plate side surface of the second optical rotator is parallel or orthogonal to the absorption axis direction of the second polarizing plate.

  In the liquid crystal panel of the present invention, the alignment direction of the liquid crystal molecules on the surface on the liquid crystal cell side of the first optical rotation element is parallel or orthogonal to the alignment direction of the first alignment substrate of the liquid crystal cell. Is preferred. Furthermore, it is preferable that the alignment direction of the liquid crystal molecules on the surface on the liquid crystal cell side of the second optical rotatory element is parallel or orthogonal to the alignment direction of the second alignment substrate of the liquid crystal cell.

  In one embodiment of the liquid crystal panel of the present invention, the twist angle of the chiral nematic liquid crystal layer in the first optical rotator and the second optical rotator is preferably about 45 °.

  Furthermore, in one embodiment of the liquid crystal panel of the present invention, it is preferable that the absorption axis direction of the first polarizing plate and the absorption axis direction of the second polarizing plate are parallel.

  In one embodiment of the liquid crystal panel of the present invention, the liquid crystal cell is preferably a TN mode liquid crystal.

  In the liquid crystal panel of the present invention, a first retardation layer is provided between the liquid crystal cell and the first optical rotator, and between the liquid crystal cell and the second optical rotator. In addition, it is preferable to have a second retardation layer. More preferably, the first retardation layer and the second retardation layer have a liquid crystal layer in which the optical axes of the liquid crystals are hybrid-aligned.

  In one embodiment of the liquid crystal panel of the present invention, the first polarizing plate and the second polarizing plate are rectangular, and the long side direction of the rectangle and the absorption axis direction of the polarizing plate are parallel or orthogonal. Is preferred. By setting it as this structure, the rectangular polarizing plate for liquid crystal panels can be efficiently acquired from a elongate polarizing plate.

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

  The liquid crystal panel of the present invention has an optical rotation element that converts linearly polarized light into linearly polarized light at a different angle, so that the absorption axis of the polarizing plate can be obtained even when using a liquid crystal cell in which the orientation direction of the substrate is an oblique direction of the screen. The direction can be parallel or orthogonal to the long sides of the rectangle. Therefore, the product efficiency and productivity of the polarizing plate used for the liquid crystal panel can be improved. Furthermore, in the present invention, a liquid crystal display device having display characteristics comparable to those of conventional liquid crystal display devices can be obtained by adjusting the thickness of the optical rotatory element.

[Overview of the entire LCD panel]
FIG. 2 is a schematic cross-sectional view of a liquid crystal panel according to an embodiment of the present invention. The liquid crystal panel 100 of the present invention includes a liquid crystal cell 10, a first polarizing plate 21 disposed on one side of the liquid crystal cell 10, and a second polarizing plate 22 disposed on the other side of the liquid crystal cell 10. A first optical rotation element 31 between the liquid crystal cell 10 and the first polarizing plate 21, and a second optical rotation element 32 between the liquid crystal cell 10 and the second polarizing plate 22.

  In a preferred embodiment of the liquid crystal panel of the present invention, from the viewpoint of improving the viewing angle of the liquid crystal display device, the first retardation is provided between the first polarizing plate 21 and the liquid crystal cell 10 as shown in FIG. It is preferable to have the layer 41, and in addition, it is more preferable to have the second retardation layer 42 between the second polarizing plate 22 and the liquid crystal cell 10. The arrangement of the first and second retardation layers may be between the optical rotator 31 or 32 and the liquid crystal cell 10 as shown in FIG. 3A, or as shown in FIG. 3 may be between the polarizing plate 21 or 22 and the optical rotator 31 or 32. From the viewpoint that appropriate optical compensation can be performed by the retardation layer similar to that used in the conventional liquid crystal panel, FIG. As in (a), it is preferable to have a retardation layer between the optical rotator and the liquid crystal cell.

  Moreover, in one Embodiment of the liquid crystal panel of this invention, it is preferable that the absorption axis direction of the said 1st polarizing plate 21 and the 2nd polarizing plate 22 is parallel. By making both parallel, the removal rate of the polarizing plate can be increased when applied to a rectangular liquid crystal panel in which the left and right and top and bottom lengths of the screen are different.

  In the present specification and claims, “parallel” includes not only completely parallel but also substantially parallel, and the angle is generally within ± 3 °. , Preferably within ± 2 °, more preferably within ± 1 °, and even more preferably within ± 0.5 °. The term “orthogonal” includes not only completely orthogonal but also substantially orthogonal, and the angle is generally in the range of 90 ± 3 °, preferably 90 ± 2 °, more preferably The range is 90 ± 1 °, more preferably 90 ± 0.5 °. Similarly, the case where it is described as approximately 45 °, approximately 90 °, etc. includes a range of ± 3 ° from the angle, preferably ± 2 °, more preferably ± 1 °, still more preferably ± The range of 0.5 ° is included.

  Furthermore, according to the configuration in which the absorption axis directions of the first polarizing plate 21 and the second polarizing plate 22 are parallel, the problem of warping of the liquid crystal panel having a large screen size can be solved. In a liquid crystal panel in which the absorption axes of two polarizing plates are orthogonal to each other, the liquid crystal panel may be warped due to a difference in the heating dimension change direction of the polarizing plates arranged on the front and back of the liquid crystal cell. In other words, the polarizing plate has anisotropy, but the commonly used polarizing plate develops anisotropy by stretching a film adsorbing a dichroic substance such as iodine or a dichroic dye. Yes. A liquid crystal panel is combined with a light source such as a backlight to form a liquid crystal display device. However, the polarizing plate tends to contract or expand in the stretching direction due to heat from the light source or the external environment. Therefore, in the liquid crystal panel arranged so that the absorption axes of the two polarizing plates are orthogonal to the front and back of the liquid crystal cell, deformation stress is generated in different directions on the front and back of the liquid crystal cell, so that the peripheral portion of the liquid crystal panel is distorted. There are cases. Such distortion causes the panel to warp, and there is a problem that display defects such as light leakage are likely to occur in the peripheral portion of the panel. In particular, in a large-sized liquid crystal panel, the stress caused by such shrinkage or expansion becomes large, and thus the problem of such warpage and display defect tends to become remarkable.

  On the other hand, by making the absorption axis directions of the first polarizing plate 21 and the second polarizing plate 22 parallel, even if the polarizing plate contracts or expands due to heating or the like, the liquid crystal cell is accompanied accordingly. Since the direction of the applied stress is the same on the front and back of the liquid crystal cell, the occurrence of distortion of the liquid crystal panel can be suppressed, and the warpage of the panel and display defects can be suppressed.

  The liquid crystal panel of the present invention may be in a so-called “O mode” or “E mode”. 4A and 4B are schematic perspective views of the liquid crystal panel according to the embodiment shown in FIG. 3A. FIG. 4A shows an O-mode liquid crystal panel, and FIG. 4B shows an E-mode liquid crystal panel. Represents. In addition, the aspect ratio of each structural member in these figures and the ratio of thickness are described differently from reality for simplicity.

  In general, an “O-mode liquid crystal panel” is one in which the absorption axis direction of a polarizing plate usually 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 parallel. In the liquid crystal panel of the present invention, it refers to a liquid crystal panel in which the vibration direction of linearly polarized light incident on the liquid crystal cell via the polarizing plate is orthogonal to the alignment direction of the alignment substrate on the light source side of the liquid crystal cell. Similarly, an “E-mode liquid crystal panel” is one in which the absorption axis direction of the polarizing plate normally disposed on the light source side of the liquid crystal cell is orthogonal to the alignment direction of the alignment substrate on the light source side of the liquid crystal cell. However, in the liquid crystal panel of the present invention, the liquid crystal panel in which the vibration direction of the linearly polarized light incident on the liquid crystal cell from the light source through the polarizing plate is parallel to the alignment direction of the alignment substrate on the light source side of the liquid crystal cell.

[Principle of the composition of this application]
FIG. 5 schematically shows how the light from the light source reaches the viewing side while changing the polarization state by each optical element in the conventional liquid crystal panel of the present invention. In FIG. 5, a case of a normally white mode O-mode liquid crystal panel in which white display is obtained in a state where the liquid crystal cell 10 is in the TN mode and no voltage is applied to the liquid crystal cell will be described as an example.

  FIG. 5 (a) shows the change in the polarization state when no voltage is applied to the liquid crystal cell of the liquid crystal panel, that is, a white display is obtained when the liquid crystal layer in the liquid crystal cell is twisted by approximately 90 °. It is a figure explaining typically. In the present specification and claims, unless otherwise specified, the right direction of the screen of the liquid crystal panel is defined as an angle reference (0 °), and the liquid crystal panel is viewed from the second polarizing plate side (viewing side). When viewed, the counterclockwise direction is defined as an angle “+”, and 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.

Naturally polarized light (r1) emitted from a light source (not shown) enters the first polarizing plate 21.
Since the first polarizing plate 21 has the absorption axis 3 in the horizontal direction of the paper, it absorbs light in the horizontal direction of the paper and emits linearly polarized light in the vertical direction of the paper as transmitted light (r2).
The linearly polarized light transmitted through the first polarizing plate 21 is incident on the first optical rotation element (r3). In the case where the first optical rotation element rotates the polarization direction of linearly polarized light by −45 °, the incident light (r3) is emitted as linearly polarized light (r4) rotated by −45 °.
The linearly polarized light whose polarization direction has been converted by the first optical rotation element 31 enters the liquid crystal cell 10 from the first alignment substrate 11 side (r5). In a twisted nematic (TN) mode liquid crystal panel, liquid crystal molecules are aligned in a 90 ° twist alignment in the absence of an electric field in the liquid crystal cell, so that light incident on the liquid crystal layer is rotated by the optical rotation of the liquid crystal layer. The light whose polarization direction is rotated by 90 ° is (r6) and is emitted from the second alignment substrate side of the liquid crystal cell 10.
The linearly polarized light emitted from the liquid crystal cell 10 enters the second optical rotator 32 (r7). When the second optical rotation element rotates the polarization direction of linearly polarized light by −45 °, the incident light (r7) is emitted as linearly polarized light (r8) rotated by −45 °.
The linearly polarized light whose polarization direction has been converted by the second optical rotation element 32 enters the second polarizing plate 22 (r9). Since the second polarizing plate 22 has the absorption axis 4 in the left-right direction on the paper surface, the linearly polarized light (r9) is not absorbed by the second polarizing plate 22 (r10), so that it reaches the viewing side and is bright (white). ) Display is obtained.

  FIG. 5B shows that in the same liquid crystal panel, a voltage is applied to the TN mode liquid crystal cell, that is, black display is performed in a state where the liquid crystal layer in the liquid crystal cell is aligned perpendicular to the substrate. It is a figure which illustrates typically the change of a polarization state about being obtained.

The process until the naturally polarized light (r1) emitted from the light source (not shown) is incident on the liquid crystal cell (r5) is the same as that in FIG.
In a twisted nematic (TN) mode liquid crystal panel, when a voltage is applied to the liquid crystal cell, the liquid crystal molecules are aligned in the electric field direction, so that the liquid crystal layer in the liquid crystal cell is aligned perpendicular to the substrate. Therefore, since the linearly polarized light (r5) incident on the liquid crystal cell travels along the direction of the major axis of the liquid crystal molecules, the incident light exits the liquid crystal cell without changing the polarization direction (r6 ′).
The linearly polarized light emitted from the liquid crystal cell 10 enters the second optical rotator 32 (r7 ′). When the second optical rotation element rotates the polarization direction of linearly polarized light by −45 °, the incident light (r7) is emitted as linearly polarized light (r8 ′) rotated by −45 °.
The linearly polarized light whose polarization direction is converted by the second optical rotator 32 is incident on the second polarizing plate 22 (r9 ′). Since the second polarizing plate 22 has the absorption axis 4 in the horizontal direction of the paper, linearly polarized light (r9 ′) is absorbed by the second polarizing plate 22 (r10), and does not reach the viewing side. A dark (black) display is obtained.

  Thus, even if the absorption axis and transmission axis directions of the polarizing plate and the alignment direction of the liquid crystal cell are neither parallel nor perpendicular, the polarization direction can be changed by arranging the optical rotation element between the liquid crystal cell and the polarizing plate. By rotating, the polarized light in a direction parallel or perpendicular to the alignment direction of the liquid crystal cell can be incident on the liquid crystal cell. Further, the light emitted from the liquid crystal cell is rotated in the direction of deflection by the optical rotatory element, so that a light-dark display can be obtained even if the polarizing plate has an absorption axis in the vertical direction or the horizontal direction of the screen.

Therefore, the longitudinal direction (absorption axis A) of the long polarizing plate P as shown in FIG. 1B is also applied to the liquid crystal cell in which the orientation direction of the substrate of the liquid crystal cell is an oblique direction (for example, 45 ° direction) of the screen. Direction) and the side of the rectangle are parallel or orthogonal to each other, and a liquid crystal panel can be formed using the polarizing plate cut out so that the product efficiency and productivity of the polarizing plate can be improved. In the present invention, a liquid crystal display device having display characteristics comparable to those of a conventional liquid crystal display device can be obtained by adjusting the thickness of the optical rotatory element used in the liquid crystal panel. This will be described in detail later.
Hereinafter, the liquid crystal cell, the polarizing plate, and the optical rotator constituting the liquid crystal panel of the present invention will be described.

[Liquid Crystal Cell]
2 to 4, 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 second liquid crystal layer 13. And the second alignment substrate 12 disposed on the 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. However, the liquid crystal of each of the first alignment substrate 11 and the second alignment substrate 12 is used. 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 homeotropic alignment, a homogeneous alignment, or a twist alignment in the absence of an electric field. In the liquid crystal panel of the present invention, the liquid crystal layer 13 includes liquid crystal molecules aligned in a twist alignment. Preferably used.

  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, TN mode liquid crystal cell in which the alignment direction of the liquid crystal molecules is twisted by approximately 90 ° from the viewpoint that the characteristics of the constituent members are synergistically exhibited and the optical compensation targeted by the present invention can be realized. Is preferred.

  In a TN mode liquid crystal cell in which the liquid crystal cell is twisted by 90 ° between the first alignment substrate 11 and the second alignment substrate 12, the first alignment substrate and the second alignment substrate are aligned in the alignment direction 1 of both. 2 are arranged so as to be orthogonal to each other. In a state where no voltage is applied between the substrates, the liquid crystal layer becomes substantially parallel to the alignment direction of the opposing substrate surface as the distance from the center in the thickness direction increases between the first alignment substrate and the second alignment substrate. In this way, it gradually changes along the thickness direction of the liquid crystal layer. 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 first alignment substrate 11, the liquid crystal molecules are birefringent with respect to the linearly polarized light that has passed through the first polarizing plate 21 and is incident on 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 °.

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

  As described above, when the liquid crystal molecules of the liquid crystal layer 13 have a positive dielectric anisotropy, when a voltage is applied between the electrodes, the surfaces of the first alignment substrate 11 and the second alignment substrate 12 are perpendicular to each other. Oriented to In this state, when light is incident from the surface of the first alignment substrate 11, linearly polarized light that has passed through the first polarizing plate 21 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. Then, when no voltage is applied again, the original liquid crystal can be returned to the display of 90 ° twisted by the alignment regulating force. Further, by changing the applied voltage to control the tilt of the liquid crystal molecules, the transmitted light intensity from the second polarizing plate 22 is changed by setting the polarization state between the voltage application and non-application states. Gradation display is possible.

  The above example describes the case where the liquid crystal layer is twisted by 90 ° between the first alignment substrate 11 and the second alignment substrate 12. However, in the present invention, the twist angle is not limited to 90 °. Liquid crystal cells having various twist angles can be used. For example, in a transflective liquid crystal display device, a device having a twist angle of less than 90 ° is preferably used. 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.

[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 as the first polarizing plate and the second polarizing plate 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 the polarizer protective film described later, the upper limit is approximately 43.2%.

  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 for measuring the degree of polarization, the parallel transmittance (H ₀ ) and orthogonal transmittance (H ₉₀ ) of the polarizing plate are measured, and the formula: degree of polarization (%) = {(H ₀ -H ₉₀ ) / (H ₀ + H ₉₀ )} ^1/2 × 100. The parallel transmittance (H ₀ ) 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 (H ₉₀ ) 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.

(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. In addition, a guest / host type polarizer in which a liquid crystal composition containing a dichroic substance and a liquid crystal compound disclosed in US Pat. No. 5,523,863 is aligned in a certain direction can 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 (hereinafter sometimes simply referred to as “iodine polarizer”) is preferably used. Polyvinyl alcohol or a derivative thereof is used as a material for the polyvinyl alcohol film applied to the polarizer. Derivatives of polyvinyl alcohol include polyvinyl formal, polyvinyl acetal, and the like, olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, and their alkyl esters and acrylamide. Things. Polyvinyl alcohol having a polymerization degree of about 1000 to 10000 and a saponification degree of about 80 to 100 mol% is generally used.

  The polyvinyl alcohol film may contain an additive such as a plasticizer. Examples of the plasticizer include polyols and condensates thereof, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The amount of the plasticizer used is not particularly limited, but is preferably 20% by weight or less in the polyvinyl alcohol film.

  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 iodine-based polarizer has the property of absorbing polarized light in the stretching direction (absorption axis) and transmitting light in the direction orthogonal to the stretching direction (transmission axis). When the polarizer is continuously produced in a long form (roll form), from the viewpoint of increasing productivity and the degree of polarization, a longitudinal stretching method in which the film is uniaxially stretched in the longitudinal direction, that is, the transport direction is generally used. The polarizer thus obtained by longitudinal stretching has an absorption axis in the film transport direction (longitudinal direction) and a transmission axis in the width direction.

(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.

  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 plate) 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 a preferable configuration that the substrate film as a support for a liquid crystal layer as a polarizing element described later, or the function of an alignment film is also used 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 for laminating the polarizer and the protective film is not particularly limited, but from the viewpoint of workability and light utilization efficiency, it is desirable to laminate the layers without using an air gap. 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.

  Moreover, it is preferable that an adhesive agent contains a crosslinking agent. Examples of the crosslinking agent include alkylenediamines having two alkylene groups and two amino groups, such as ethylenediamine, triethylenediamine, and hexamethylenediamine; tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane tolylene diisocyanate adduct, triphenyl Isocyanates such as methane triisocyanate, methylene bis (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-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether Epoxies such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde; glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde, maleidialdehyde, phthaldialdehyde Dialdehydes such as: methylol urea, methylol melamine, alkylated methylol urea, alkylated methylolated melamine, acetoguanamine, condensates of benzoguanamine and formaldehyde, and the like; further sodium, potassium, magnesium, calcium, Examples thereof include salts of divalent metals such as aluminum, iron, nickel, or trivalent metals and oxides thereof, among which amino-formaldehyde Fats and dialdehydes are preferred, amino-formaldehyde resins are preferably compounds having a methylol group, and dialdehydes are preferably glyoxal, particularly methylol melamine, which is a compound having a methylol group. .

  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. Attaching the pressure-sensitive adhesive layer or adhesive layer to the film can be performed by an appropriate method.

  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. .

[Optical Rotator]
In the liquid crystal panel of the present invention, the optical rotator used as the first optical rotator and the second optical rotator converts linearly polarized light into linearly polarized light having a different direction. “Optical rotation” refers to a phenomenon in which the plane of polarization rotates as polarized light travels through a medium. The rotation angle is referred to as “optical rotation angle”. The optical rotation angle is determined by considering the arrangement and twist angle of the liquid crystal layer in the liquid crystal cell or the arrangement angle of the liquid crystal cell in the liquid crystal panel. It can select suitably in the range which can be achieved. That is, it is preferable to select the optical rotation angle so that the absorption axis direction of the polarizing plate in the liquid crystal panel is parallel or orthogonal to the side direction of the screen, and the liquid crystal layer as described above has a twist angle of 90 °. In the liquid crystal panel, the optical rotation element preferably has an optical rotation angle of about 45 °. Such an optical rotatory element having an optical rotation angle of approximately 45 ° is useful not only for a TN mode liquid crystal panel but also for an STN mode liquid crystal panel. Furthermore, it can be suitably employed in a liquid crystal panel in which circularly polarized light or elliptically polarized light is incident on a liquid crystal cell, such as an optical compensation bend (OCB) mode or a hybrid alignment (HAN) mode.

  For example, as schematically shown in FIG. 5, the alignment direction 1 of the first alignment substrate 11 is −45 ° direction and the alignment direction 2 of the second alignment substrate 12 is +45 with respect to the long side direction of the screen. In the TN mode liquid crystal panel, the angle of rotation of the first optical rotator and the second optical rotator is 45 ° so that the absorption axis direction of the polarizing plate in the liquid crystal panel is parallel to the long side direction of the screen. Can be arranged as follows. Further, the optical rotation angle has a sign (positive or negative), but in the present specification, a sign that rotates the polarization direction counterclockwise when viewed from the second polarizing plate side (viewing side) is defined as a positive sign. . The sign of the optical rotation direction of the optical rotatory element can be appropriately selected according to the design such as the arrangement angle of the polarizing plate.

  Examples of the optically rotatory substance include inorganic crystals such as garnet single crystals, quartz crystals, saccharides represented by glucose, chiral (optically active) organic molecules such as polylactic acid and helicene, and the like. In the liquid crystal layer, a liquid crystal layer in which the orientation direction of liquid crystal molecules is gradually changed along the thickness direction of the layer is used from the viewpoint of productivity, handling properties, and display characteristics. Examples of such a liquid crystal layer include those in which nematic liquid crystal molecules are twisted and aligned (sometimes referred to as “chiral nematic liquid crystal” or “cholesteric liquid crystal”). As such a liquid crystal layer, a nematic liquid crystal material (a liquid crystal material in which the liquid crystal phase is a nematic phase) obtained by adding a chiral agent and fixing the alignment state is preferably used.

  When a chiral nematic liquid crystal layer in which a chiral agent is added to a nematic liquid crystalline material is used as the optical rotatory element, the twist angle of the liquid crystal in the liquid crystal layer, that is, the optical rotation angle of the optical rotatory element depends on the addition amount of the chiral agent and the liquid crystal layer. The thickness can be adjusted. That is, the twisting pitch of the liquid crystal layer (sometimes referred to as “cholesteric pitch”) is adjusted by the amount of the chiral agent added, but the thickness of the liquid crystal layer is cholesteric pitch (equal to the thickness at which the liquid crystal is twisted 360 °) Is adjusted so that the liquid crystal is twisted by 45 °, a chiral nematic liquid crystal layer can be formed, and this can be used as an optical rotation element having an optical rotation angle of 45 °. Note that, from the viewpoint of achieving the object of the present invention, the optical rotation angle of the optical rotator is not limited to 45 ° as described above, but hereinafter, for easy understanding, the optical rotation angle is 45 °. An example of the element will be described.

In the embodiment of the present invention, the product (Δn ₅₄₅ × d) of birefringence Δn _{545 at} a wavelength of 545 nm and the thickness d of the optical rotatory element of the nematic liquid crystalline material used for the liquid crystal layer as the optical rotatory element is 1400 nm or more. In the case of optical rotation using chiral nematic liquid crystal, due to the birefringence of the liquid crystal layer, a phenomenon of light leakage may occur even when the chiral nematic liquid crystal layer has a 45 ° twist angle. On the other hand, in a liquid crystal layer in which the liquid crystal layer is twisted by 45 °, light leakage due to such birefringence can be reduced by increasing the thickness. This point will be described below.

In a configuration in which an optical rotatory element using a chiral nematic liquid crystal layer exists between two polarizing plates arranged in parallel with each other as in the liquid crystal panel of the present application, when the thickness d satisfies the following formula (1): The transmittance of monochromatic light of wavelength λ is theoretically zero.

However, in said formula (1), m is an integer greater than or equal to 1, and (DELTA) n ( _lambda) is birefringence in wavelength (lambda).

  The above equation (1) shows the condition that T (λ) = 0 in the following equation (2) representing the transmittance at the wavelength λ. This equation (2) is used when determining the thickness (cell gap) of a liquid crystal cell in a twisted nematic (TN) mode liquid crystal display device or the like [C. H. Gooch and H.C. A. Tally, Appl. Phys., Vol. 8, 1575-1584 (1975)], and θ = π / 4 (45 °) is substituted.

Usually, in the TN mode liquid crystal cell and the optical rotatory element, a thickness d (sometimes referred to as “first minimum”) such that m = 1 in the above formula (1) is employed. For example, when the light leakage at a wavelength of 545 nm is minimized, the thickness of the optical rotation element is designed so that the value of (Δn ₅₄₅ × d) is about 527 nm. On the other hand, since the refractive index has a so-called “wavelength dependency” that varies depending on the wavelength, the birefringence Δn _λ also has a wavelength dependency. Therefore, the thickness d satisfying the above equation (1) varies depending on the wavelength λ. Therefore, even if the thickness of the optical rotation element is set so that the transmittance at a predetermined wavelength in the visible light region is theoretically zero, the transmittance at other wavelengths does not become zero, resulting in light leakage. Will occur. In addition, when the light leakage of a specific wavelength increases, the display may be colored.

  The present invention is based on the new finding that good display characteristics can be obtained by increasing the thickness d of the optical rotation layer in consideration of the influence of the wavelength dependence of the birefringence. In other words, the amount of transmitted light (transmittance T) at a specific wavelength λ is as expressed by the above formula (2), and the Y value considering this over the entire wavelength range of the visible light region is the optical rotation element. This is based on the knowledge that it depends on the thickness d. The Y value is a tristimulus value Y of the XYZ color system corresponding to “brightness” in human vision, and can be expressed as the following equation (3).

The relationship between the Y value and the thickness d of the optical rotatory element will be described based on an example in a later embodiment, but the thickness at which the transmittance is minimum at a predetermined wavelength is different from the thickness at which the Y value is minimum. ing. Therefore, even if the thickness d is selected so that m in Formula (1) is an integer in order to minimize the transmittance at a predetermined wavelength (λ), the Y value is not necessarily minimized. On the other hand, when the product of the optical rotatory element and the birefringence (Δn ₅₄₅ × d) increases, the Y value tends to decrease as the thickness increases, and the thickness at which m = 1 in formula (1) (first) -Y value is smaller than in the case of minimum). Such a decrease in the Y value by adjusting the thickness is conceptually explained by the locus of polarization state conversion on the Poincare sphere. Hereinafter, with respect to the principle of the present invention and the fact that light leakage is reduced by increasing the thickness as described above, a retardation plate (1) having a retardation of ½ of the wavelength when using an optical rotator. A description will be given based on the trajectory conversion on the Poincare sphere while comparing with the case of using a / 2 wavelength plate.

The Poincare sphere is a method of expressing the polarization state of light rays by points on the sphere. When this sphere is viewed as the Earth, the North and South Pole points indicate circularly polarized light, and the equator points indicate linearly polarized light. The north or south pole and the equator point show elliptically polarized light, and the greater the latitude, the smaller the ellipticity, that is, the elliptically polarized light close to a perfect circle. The longitude on the equator corresponds to twice the angle of linearly polarized light. That is, two points having longitudes of 180 ° on the equator correspond to two orthogonal linearly polarized lights. Each point on the Poincare sphere is represented by _three Stokes parameters (S ₁ , S ₂ , S ₃ ). The Stokes parameter S ₀ = (S ₁ ² + S ₂ ² + S ₃ ² ) ^1/2 relates to the light intensity, but here, S ₀ = 1 is constant, that is, the Poincare sphere is represented as a sphere having a radius of 1.

  1/2 wavelength plate (or 3/2 wavelength plate, 5/2 wavelength plate) so that the optical axis (slow axis) direction is 22.5 ° (half of 45 °) with respect to the polarization direction of linearly polarized light. Etc.), linearly polarized light is converted into linearly polarized light orthogonal thereto, as in the case of using an optical rotator as in the present application. However, when such a half-wave plate or the like is used, the above-described Y value tends to increase as compared to the case where an optical rotatory element as in the present application is used.

FIG. 6 shows a half-wave plate for a monochromatic light having a predetermined wavelength (for example, 545 nm) having an angle of 22.5 ° with respect to the polarization direction and a retardation of 1/2. Thus, the linearly polarized light at point A: (S ₁ , S ₂ , S ₃ ) = (− 1, 0, 0) on the Poincare sphere becomes point B: (S ₁ , S ₂ , S ₃ ) = (0, The trajectory when converted into linearly polarized light of (1,0) is shown. In FIG. 6 (a) perspective, (b) the projection of the _S 2 -S ₃ sides, (c) the projection of the _S 3 -S ₁ surface, (d) is to _S 1 -S ₂ sides (The same applies to FIGS. 7 and 8 below).

The light transmitted through the incident side polarizing plate (incident linearly polarized light) is represented by a point A: (S ₁ , S ₂ , S ₃ ) = (− 1, 0, 0). This incident linearly polarized light moves south on the Poincare sphere while changing the longitude as it travels in the thickness direction along the half-wave plate. This represents a state in which linearly polarized light is converted into elliptically polarized light as the thickness direction proceeds, and the major axis direction of the ellipse changes while increasing the ellipticity. And it becomes the elliptically polarized light represented by the point M where the longitude moved 45 ° from the point A at the intermediate point in the thickness direction of the half-wave plate (corresponding to the retardation of the quarter wavelength). When the thickness direction of the half-wave plate further proceeds, the major axis direction changes while decreasing the ellipticity, and the ellipticity becomes zero, that is, approaches the linearly polarized light as the thickness direction of the half-wave plate is advanced. . Finally, the light is emitted from the half-wave plate as a linearly polarized light of point B: (S ₁ , S ₂ , S ₃ ) = (0, −1, 0). This point B exists on the equator like the point A representing the linearly polarized light incident on the half-wave plate and has a 90 ° longitude difference from the point A. Corresponds to linearly polarized light. The linearly polarized light represented by this point B reaches the exit side polarizing plate. Since the liquid crystal panel of the present invention includes the two optical rotatory elements, the first optical rotatory element and the second optical rotatory element, the polarization state conversion as described above is performed twice, resulting in a straight line rotated by 90 °. Polarized light is obtained. Therefore, when the absorption axis direction of the incident-side polarizing plate and the emission-side polarizing plate is parallel, light is absorbed and dark display is obtained.

On the other hand, FIG. 7 shows that the linearly polarized light at point A forms an angle of 45 ° with the Poincare sphere when the thickness d of the optical rotation element satisfies the condition of m = 1 in the above formula (1). The locus | trajectory in the case of converting into B linearly polarized light is shown. When an optical rotatory element having an optical rotation angle of 45 ° is used, as the linearly polarized light at point A: (S ₁ , S ₂ , S ₃ ) = (− 1, 0, 0) advances through the optical rotatory element in the thickness direction, The latitude on the Poincare sphere is smaller than that of the half-wave plate, that is, the longitude is converted through a state close to linear polarization, in other words, the major axis direction of the ellipse is rotated. Become. Then, at an intermediate point in the thickness direction of the optical rotatory element, linearly polarized light B having an angle of 45 ° via a midpoint M whose longitude is 45 ° different from the point A: (S ₁ , S ₂ , S ₃ ) = ( 0, -1, 0) and emitted from the optical rotator. This light is converted into linearly polarized light rotated by 90 ° by two optical rotators as in the case of the half-wave plate, and dark display can be obtained.

Further, FIG. 8 shows a straight line in which the linearly polarized light at the point A on the Poincare sphere forms an angle of 45 ° represented by the point B in the above formula (1) when the thickness of the optical rotatory element satisfies the condition of m = 4. The locus when converted into polarized light is shown. In this case, the longitude is converted on the Poincare sphere while the latitude is kept smaller than in the case of m = 1. Then, at 1/4 of the thickness of the optical rotatory element, it once reaches the point M ₁ on the equator, that is, becomes linearly polarized light, and further at an intermediate point M _{2 having} a thickness of 1/2 and a point M _{3 having a} thickness of 3/4. Is also linearly polarized light, and finally converted to point B: (S ₁ , S ₂ , S ₃ ) = (0, −1, 0) and emitted from the optical rotation element. This light is converted into linearly polarized light rotated by 90 ° by two optical rotators as in the case described above, and a dark display can be obtained.

The case where m = 4 has been described above. However, in the case where m = 2 and 3, the point B is orthogonal with the latitude being smaller than that when m = 1 and the latitude being larger than when m = 4. S ₁ , S ₂ , S ₃ ) = (0, −1, 0) is converted into linearly polarized light and emitted from the optical rotator. In addition, when m = 5 or more, the latitude is further reduced, that is, it is converted to linearly polarized light having an angle of 45 ° through a path close to the equator. Theoretically, when m = ∞, The locus on the Poincare sphere moves 90 ° on the equator. Thus, it can be seen that as m is larger, that is, the thickness of the optical rotation element is larger, the polarization state is converted in a state closer to linearly polarized light.

  Next, when the wavelength dependence of birefringence is taken into consideration, it will be described below that the Y value can be reduced by using an optical rotatory element. As described above, the birefringence of the polymer or the liquid crystal molecule has wavelength dependency, and the birefringence generally increases as the wavelength becomes shorter. Therefore, for example, when green light near a wavelength of 545 nm is designed to minimize light leakage, for blue light near a wavelength of 440 nm, birefringence is a value suitable for minimizing light leakage. Tend to be larger. On the other hand, for red light near the wavelength of 650 nm, birefringence tends to be smaller than a value suitable for minimizing light leakage.

The influence of this wavelength dependence will be described first based on the locus of light on the Poincare sphere when a phase difference plate is used. FIG. 9 shows that when the retardation is larger than ½ of the wavelength, the linearly polarized light of the point A: (S ₁ , S ₂ , S ₃ ) = (− 1, 0, 0) on the Poincare sphere is the point B. The locus | trajectory in the case of converting into ₁ elliptically polarized light is shown. For example, when a half-wave plate having a retardation of 1/2 is used for monochromatic light having a predetermined wavelength (for example, 545 nm) as described above, at other wavelengths (for example, 440 nm) This corresponds to the case where the retardation is larger than ½ of the wavelength.

The linearly polarized light incident on the retardation plate follows the same locus as that of the half-wave plate shown in FIG. 6 and moves on the Poincare sphere as it travels in the thickness direction. Retardation results in linearly polarized light of (S ₁ , S ₂ , S ₃ ) = B (0, −1, 0). However, since the retardation of the retardation plate is larger than ½ of the wavelength, it goes further north over the equator on the Poincare sphere and reaches the point B ₁ in the northern hemisphere. This indicates that the light emitted from the wave plate is elliptically polarized light. Then, the latitude difference between points B and B ₁ is equivalent to ellipticity of elliptically polarized light, the longitude difference between the points B and B ₁ is, corresponds to the long axis direction of the deviation of the ellipse. The distance between the point B and the point B ₁ increases as the retardation deviates from ½ of the wavelength. The elliptically polarized light represented by the point B ₁ represents, not completely absorbed by the exit side polarizing plate, the transmitted light is to be observed as light leakage. As the distance between the points B and B ₁ is increased this light leakage tends to increase.

Next, the influence of wavelength dependency when an optical rotatory element is used will be described. First, the case where the thickness d of the optical rotatory element satisfies the condition of m = 1 in the expression (1) at the predetermined wavelength λ has been described with reference to FIG. Is generally larger than 1 (not necessarily an integer) due to the wavelength dependence of birefringence. FIG. 10 shows that the linearly polarized light at point A: (S ₁ , S ₂ , S ₃ ) = (− 1, 0, 0) on the Poincare sphere when m is greater than 1 and not an integer. It shows the trace when being converted into elliptically polarized light at the point B _2. As the linearly polarized light at point A travels through the optical rotatory element in the thickness direction, it follows a locus similar to the case of m = 1 in FIG. 7 and reaches the point M ′ on the equator with a thickness corresponding to m = 1. When further proceeding in the thickness direction, the southern hemisphere is moved in the same trajectory shape as before while changing the latitude, and reaches a point B ₂ where the latitude on the same meridian is different from that of the point B. As in the previous FIG. 9, the light leakage increases as the distance between the points B and B ₂ becomes large.

On the other hand, the case where the thickness d of the optical rotatory element satisfies the condition of m = 4 in the formula (1) at the predetermined wavelength λ has been described above with reference to FIG. In addition, on the shorter wavelength side than λ, m is generally larger than 4 (not necessarily an integer). FIG. 11 shows that when m is larger than 4 and is not an integer, the linearly polarized light of point A: (S ₁ , S ₂ , S ₃ ) = (− 1, 0, 0) on the Poincare sphere is It shows the trace when being converted into elliptically polarized light of B _3. As the linearly polarized light at point A travels through the optical rotatory element in the thickness direction, it follows a similar trajectory as in the case of m = 4 in FIG. 8, and at the thicknesses corresponding to m = 1, 2, 3, 4 respectively via points, latitude on the same meridian and the point B to reach the different B _3. Then, the light leakage increases as the distance between the point B and B ₃ is increased. Here, it can be seen that the distance between the points B and B ₃ is smaller than the distance between the points B and B ₁ or the points B and B _{2 described above} .

  As described above, this is related to the fact that as the value of m increases, the polarization state is converted while maintaining a locus closer to the equator on the Poincare sphere, in other words, a state close to linear polarization. The greater the value of m in Equation (1), that is, the greater the thickness of the optical rotator, the smaller the deviation from linearly polarized light even when m deviates from the integer value. Therefore, even if the birefringence has wavelength dependence, the light leakage, that is, the Y value for the entire visible light region is reduced.

In a liquid crystal panel using a prior art optical rotatory element, the thickness of the optical rotatory element was designed to satisfy m = 1 (first minimum) in the formula (1), but it is conceptual using a Poincare sphere. As shown in FIG. 5, when m = 1, the difference from the case where the phase difference plate is used is small, that is, the distance between the points B and B ₁ and the distance between the points B and B ₂ are substantially the same. . On the other hand, by increasing the thickness, light leakage can be reduced at other wavelengths, and as a result, the Y value is reduced. The thickness at which the Y value is smaller than in the case of the first minimum varies depending on the wavelength dispersion of the liquid crystal compound forming the liquid crystal layer, but as will be shown later in the examples, the product of birefringence and thickness of the optical rotation element (Δn ₅₄₅ When xd) is 1400 nm or more, the Y value tends to be small. The product of birefringence and thickness (Δn ₅₄₅ × d) of the optical rotatory element is more preferably 1500 nm or more, further preferably 1600 nm or more, and particularly preferably 1700 nm or more. In such a range, the Y value tends to show a monotonous decrease as the thickness of the optical rotatory element increases.

In the liquid crystal panel of the present invention, (Δn ₅₄₅ × d) of the optical rotatory element is 1400 nm or more, but the present invention is caused by the wavelength dependence of birefringence by increasing the thickness d of the optical rotatory layer. This is based on the new knowledge that the influence of light leakage occurring at each wavelength in the visible light region can be reduced, and as a result, the Y value can be reduced.

  In addition, when λ satisfying the above formula (1) is included in the visible light region, the transmittance T at the time of black display at the wavelength λ can be reduced, so that good display characteristics are obtained. In general, in a liquid crystal panel, color display is possible by using three color filters of red (R), green (G), and blue (B), but the design is based on the transmission wavelength of the color filter. From the viewpoint, it is preferable that λ satisfying the above formula (1) exists in the range of 450 to 650 nm. Further, from the viewpoint of optimally designing green light having the highest visibility among the above three colors, it is preferable that λ satisfying the above formula (1) exists in the range of 530 to 570 nm. Since light with a green wavelength (near 545 nm) has high visibility in human vision, it is possible to obtain a display with excellent visibility by reducing light leakage in the green wavelength region (resulting in a Y value). Tends to be smaller).

When (Δn ₅₄₅ × d) of the optical rotatory element is less than 1400 nm, the visible light region (380 to 780 nm), preferably 450 to 650 nm, more preferably 500 to 600 nm, still more preferably 530 to 570 nm. If the wavelength λ is m = 2 in the above formula (1) in the above range, the Y value can be made smaller than in the case of the first minimum. However, the Y value tends to be higher than when (Δn ₅₄₅ × d) is 1400 nm or more.

  Further, by increasing the thickness, light leakage in black display can be suppressed and the Y value can be reduced. In addition, it is also possible to suppress the influence of the characteristic change due to the thickness variation of the optical rotation element. That is, when a liquid crystal layer is used as an optical rotatory element, the thickness is generally in the range of 0.1 to several tens of micrometers as will be described in detail later, but when the liquid crystal layer is produced in a large area, It is difficult to make the thickness completely uniform, and variations in thickness occur in the same liquid crystal layer or between products with separately prepared liquid crystal layers. The variation in thickness causes the twist angle of the liquid crystal layer in the optical rotation layer, that is, the variation in the optical rotation angle and the deviation from the thickness d that satisfies the condition of the above formula (1). May be uneven. Such variation in thickness within a product or between products can be suppressed by adopting an optical rotatory element composed of a liquid crystal layer having a large thickness.

  From the viewpoint of obtaining good display characteristics by reducing the Y value, as described above, it is preferable that the thickness d is larger. However, from the viewpoint of productivity of the optical rotatory element, the thickness d is preferably 10 μm or less. More preferably, it is 7 μm or less.

(Optical rotation element placement angle)
When using an optical rotatory element that includes a liquid crystal layer in which the orientation direction of liquid crystal molecules gradually changes along the thickness direction of the layer, the orientation direction of liquid crystal molecules on one side and the other side of the optical rotatory element However, in the liquid crystal panel of the present invention, as schematically shown in FIG. 4, the alignment direction 5a of the liquid crystal molecules on the surface of the first optical rotator 31 on the first polarizing plate 21 side is The alignment direction 6a of the liquid crystal molecules on the second polarizing plate 22 side surface of the second optical rotator 32 is parallel or perpendicular to the absorption axis direction 3 of the first polarizing plate 21 and the second polarizing plate It is preferable to be parallel or orthogonal to the absorption axis direction 4 of 22. The alignment direction 5b of the liquid crystal molecules on the first alignment substrate 11 side surface of the first optical rotation element 31 is parallel or orthogonal to the alignment direction 1 of the first alignment substrate 11, and the second optical rotation. The alignment direction 6 b of the liquid crystal molecules on the surface of the element 32 on the first alignment substrate 12 side is preferably parallel or orthogonal to the alignment direction 2 of the second alignment substrate 12. By adopting such an angular arrangement, the contrast of the liquid crystal display device of the present invention can be set to a level comparable to that of the conventional one. Further, the optical rotation angles of the first optical rotation element 31 and the second optical rotation element 32 can be appropriately selected according to the design of the liquid crystal panel so as to satisfy the above-described angular relationship.

(Optical rotator manufacturing method)
Although the material and manufacturing method of the liquid crystal layer as the optical rotatory element are not particularly limited, as described above, a liquid crystal material (nematic liquid crystal material) having a nematic liquid crystal phase is preferably used. As such a liquid crystalline material, for example, a liquid crystalline polymer or a liquid crystalline monomer can be used. The liquid crystal material may have a liquid crystallinity manifestation mechanism that may be either lyotropic or thermotropic.

  The liquid crystalline material is preferably a liquid crystalline monomer (for example, a polymerizable monomer and a crosslinkable monomer). This is because the alignment state of the liquid crystalline monomer can be fixed by polymerizing or crosslinking the liquid crystalline monomer, as will be described later. After aligning the liquid crystalline monomers, for example, if the liquid crystalline monomers are polymerized or crosslinked, the alignment state can be fixed thereby. Here, a polymer is formed by polymerization and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystalline. Therefore, in the formed liquid crystal layer, for example, a transition to a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change specific to the liquid crystal compound does not occur. As a result, the liquid crystal layer is an optical compensation layer that is not affected by temperature changes and has excellent stability.

  The liquid crystalline monomer is not particularly limited, and any appropriate liquid crystalline monomer can be adopted. For example, Japanese translations of PCT publication No. 2002-533742 (International Publication No. 00/37585), European Patent No. 358208 (US Pat. No. 5,211,877), European Patent No. 66137 (US Pat. No. 4,388,453), International Publication No. 93/22397, European Patent No. 0261712. Polymerizable mesogenic compounds described in German Patent No. 19504224, German Patent No. 4408171, British Patent No. 2280445, and the like can be used. Specific examples of such a polymerizable mesogenic compound include, for example, trade name Paliocolor LC242 from BASF, trade name E7 from Merck, and trade name LC-Silicon-CC3767 from Wacker-Chem. Moreover, the following materials can also be used suitably as a monofunctional or bifunctional reactive mesogenic compound.

  For the purpose of aligning the nematic liquid crystal with chiral nematic alignment, it is preferable to use a chiral agent. The content of the chiral agent can be appropriately selected depending on the kind of the chiral agent and nematic liquid crystal to be used, the thickness of the optical rotator (liquid crystal layer), etc., but forms a cholesteric pitch suitable for twisting the liquid crystal layer by 45 °. From the viewpoint, the addition amount of the chiral agent is preferably 0.0005 to 0.5 parts by weight, more preferably 0.001 to 0.3 parts by weight with respect to 100 parts by weight of the nematic liquid crystalline material. More preferred is 005 to 0.12 parts by weight. If the addition amount of the chiral agent is excessively low, the twist of the liquid crystal becomes small. For example, it is necessary to excessively increase the thickness for obtaining a liquid crystal layer twisted by 45 °. May be inferior. In addition, if the amount of the chiral agent added is excessively high, the liquid crystalline material becomes difficult to exhibit a liquid crystal state (the temperature range showing the liquid crystal phase becomes narrow), and thus it is necessary to perform temperature control at the time of manufacturing with extremely high precision. There is a case. Further, since the thickness for reducing the liquid crystal layer twisted by 45 ° is reduced, the Y value of the liquid crystal display device is increased, and a good black display may not be obtained. In addition, a chiral agent can be used individually or in combination of 2 or more types.

  As the chiral agent, any appropriate material capable of aligning the liquid crystalline material in a desired chiral nematic orientation can be adopted. As the chiral agent to be added, those having an optically active group and not disturbing the orientation when mixed with a liquid crystal compound can be suitably used. The chiral agent may or may not have liquid crystallinity. Any chiral agent having a reactive group can be used, but those having a reactive group can be suitably used from the viewpoint of heat resistance and solvent resistance of the optical rotatory element (liquid crystal layer). Examples of the reactive group include a (meth) acryloyloxy group, an azide group, and an epoxy group, and the same (meth) acryloyloxy group as the polymerizable reactive group of the polymerizable liquid crystal compound is preferable. From the viewpoint of heat resistance and solvent resistance, those having two or more polymerization reactive groups are preferable.

Examples of the chiral agent having two or more polymerizable functional groups include the following materials.

  Further, as the chiral agent, a commercially available product such as a trade name “Pariocolor LC756” manufactured by BASF Corporation may be used.

The torsional force of such a chiral agent is preferably 1 × 10 ⁻⁸ nm ⁻¹ · (wt%) ⁻¹ or more, and more preferably 1 × 10 ⁻⁷ nm ⁻¹ · (wt%) ⁻¹ to 1 × 10 ⁻² nm ⁻¹ · (wt%) ⁻¹ , most preferably 1 × 10 ⁻⁶ nm ⁻¹ · (wt%) ⁻¹ to 1 × 10 ⁻³ nm ⁻¹ · (wt%) ^-1 . By using a chiral agent having such a twisting force, the cholesteric pitch of the liquid crystal layer can be controlled within a desired range.

  In forming the liquid crystal layer, a method of applying a liquid obtained by dissolving or dispersing a liquid crystal composition containing the above liquid crystalline compound, chiral agent and other additives in a solvent onto a substrate is suitably used. Such a liquid crystal composition preferably contains a polymerization initiator, a crosslinking agent (curing agent) and the like. By using a polymerization initiator or a crosslinking agent, a liquid crystal layer formed of a liquid crystal material in a liquid crystal state can be fixed. As such a polymerization initiator or crosslinking agent, any appropriate substance can be adopted as long as the effects of the present invention can be obtained. Examples of the polymerization initiator include benzoyl peroxide (BPO) and azobisisobutyronitrile (AIBN). Commercially available polymerization initiators such as trade names Irgacure 184, Irgacure 907, Irgacure 369, and Irgacure 651 manufactured by Ciba Japan can also be suitably used. Examples of the crosslinking agent (curing agent) include an ultraviolet curing agent, a photocuring agent, and a thermosetting agent. More specifically, an isocyanate type crosslinking agent, an epoxy type crosslinking agent, a metal chelate crosslinking agent, etc. are mentioned. These may be used alone or in combination of two or more.

  The content of the polymerization initiator or the crosslinking agent is preferably 0.01 to 15% by weight, more preferably 0.1 to 10% by weight, and still more preferably based on 100 parts by weight of the nematic liquid crystal compound. 1 to 7% by weight. If the content of the polymerization initiator or the crosslinking agent is too small, the liquid crystal layer may not be sufficiently fixed. In addition, when the content of the polymerization initiator or the crosslinking agent is excessively large, the temperature range in which the liquid crystalline material exhibits a liquid crystal phase is narrowed, and it may be difficult to control the temperature when forming the liquid crystal layer.

  The liquid crystal composition may further contain any appropriate additive as required. Examples of the additive include a deterioration inhibitor, a modifier, a surfactant, a dye, a pigment, a discoloration inhibitor, and an ultraviolet absorber. These additives may be used alone or in combination of two or more. More specifically, examples of the deterioration inhibitor include phenol compounds, amine compounds, organic sulfur compounds, and phosphine compounds. Examples of the modifier include glycols, silicones, and alcohols. The surfactant is added for the purpose of smoothing the surface of the optical compensation layer. For example, silicone-based, acrylic-based, and fluorine-based surfactants can be used.

  As a method for forming the liquid crystal layer, any appropriate method can be adopted as long as the effects of the present invention are not impaired. A typical forming method includes a step of spreading a solution obtained by dissolving the liquid crystal composition in a solvent on a substrate to form a spread layer, and a liquid crystalline material in the liquid crystal composition exhibiting a chiral nematic liquid crystal phase. And a step of heating the spreading layer. Such heating may also serve as drying of the solvent. Furthermore, the step of arbitrarily subjecting the spreading layer to at least one of a polymerization treatment and a crosslinking treatment to fix the orientation of the liquid crystalline material, the step of transferring the liquid crystal layer formed on the substrate to another substrate, It is preferable to contain. Hereinafter, a specific procedure of the forming method will be described.

  First, a liquid crystal coating liquid is prepared by dissolving or dispersing a liquid crystal material, a chiral agent, and, if necessary, a polymerization initiator or a crosslinking agent and various additives in a solvent. The liquid crystal material, the chiral agent, the polymerization initiator, the crosslinking agent, and the additive are as described above. The solvent used for the liquid crystal coating liquid is not particularly limited. Specific examples include halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, methylene chloride, trichloroethylene, tetrachloroethylene, chlorobenzene, orthodichlorobenzene, phenol, p-chlorophenol, o-chlorophenol, m. -Phenols such as cresol, o-cresol, p-cresol, aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, 1,2-dimethoxybenzene, acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone, cyclohexanone Ketone solvents such as cyclopentanone, 2-pyrrolidone and N-methyl-2-pyrrolidone, ester solvents such as ethyl acetate and butyl acetate, t-butyl alcohol, glycerin, Tylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, alcohol solvents such as 2-methyl-2,4-pentanediol, amide solvents such as dimethylformamide and dimethylacetamide Nitrile solvents such as acetonitrile and butyronitrile, ether solvents such as diethyl ether, dibutyl ether, tetrahydrofuran and dioxane, carbon disulfide, ethyl cellosolve, butyl cellosolve and the like. Among these, toluene, xylene, mesitylene, MEK, methyl isobutyl ketone, cyclohexanone, cyclopentanone, ethyl cellosolve, butyl cellosolve, ethyl acetate, butyl acetate, propyl acetate, and ethyl cellosolve are preferable. These solvents may be used alone or in combination of two or more.

  Next, the liquid crystal coating solution is coated on the substrate to form a spread layer. As a method for forming the spreading layer, any appropriate method (typically, a method in which a coating solution is fluidly developed) can be employed. Specific examples include a roll coating method, a die coating method, a spin coating method, a wire bar coating method, a dip coating method, an extrusion method, a curtain coating method, and a spray coating method.

Any appropriate substrate capable of aligning the liquid crystalline material can be adopted as the substrate. Typically, various plastic films are mentioned. Although it does not restrict | limit especially as a plastic, For example, polyolefin, such as a triacetyl cellulose (TAC), polyethylene, a polypropylene, poly (4-methyl pentene-1), a polyimide, a polyimide amide, polyether imide, polyamide, polyether ether ketone , Polyether ketone, polyketone sulfide, polyether sulfone, polysulfone, polyphenylene sulfide, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyacetal, polycarbonate, polyarylate, acrylic resin, polyvinyl alcohol, polypropylene, cellulose resin, An epoxy resin, a phenol resin, etc. are mentioned. Moreover, what arrange | positioned the above plastic films and sheet | seats on the surfaces, such as metal substrates, such as aluminum, copper, and iron, a ceramic substrate, and a glass substrate, can also be used. Can also be used that form a SiO ₂ oblique deposition film on the substrate or the plastic film or surface of the sheet. The thickness of the substrate is preferably 5 μm to 500 μm, more preferably 10 μm to 200 μm, and most preferably 15 μm to 150 μm. If it is such thickness, since it has sufficient intensity | strength as a board | substrate, generation | occurrence | production of problems, such as a fracture | rupture at the time of manufacture, can be prevented, for example.

  Moreover, it is preferable that the said board | substrate is equipped with a liquid crystal aligning film. Various conventionally known alignment films can be used. For example, a film formed by rubbing a thin film made of polyimide, polyvinyl alcohol or the like on a substrate, a stretched film, a cinnamate skeleton In addition, a polymer having an azobenzene skeleton or a polyimide irradiated with polarized ultraviolet rays can be used.

  In the case where the liquid crystal layer is formed in a long roll shape, the alignment film preferably has an alignment direction in the film longitudinal direction, that is, the transport direction, from the viewpoint of productivity. Moreover, if it has an orientation direction in a film conveyance direction, it can laminate | stack with a long polarizing plate and roll tow roll which have an absorption axis in a longitudinal direction, and can be made into a long laminated polarizing plate provided with an optical rotation element. This is also preferable in terms of points. As the alignment film, a stretched film can be used as described above. Furthermore, for example, since an iodine-based polarizer is stretched in the longitudinal direction of the film, it is possible to replace the polarizer with a liquid crystal alignment film and apply a liquid crystal coating liquid on the polarizer. In addition, the number of liquid crystal panel production steps and the number of laminated films can be reduced by using, as alignment films, components used in liquid crystal panels such as polarizer protective films and optical compensation layers (optical compensation films) described later. can do.

  The coating amount of the liquid crystal coating liquid can be appropriately set according to the concentration of the coating liquid, the thickness of the target layer, and the like, but from the viewpoint of making the thickness of the liquid crystal layer uniform, the coating thickness (wet thickness) is 1. It is preferably ˜100 μm, and more preferably 2 to 50 μm. In the present invention, as described above, it may be necessary to increase the thickness from the viewpoint of preventing coloring of black display. In such a case, when the coating thickness exceeds the above range, it is preferable to employ a method of performing coating with the thickness within the above range a plurality of times from the viewpoint of making the thickness uniform. For example, when manufacturing a liquid crystal layer having a 45 ° twist angle, a method of applying twice with a thickness of 22.5 ° or a method of applying three times with a thickness of 15 ° is employed. can do. For example, in the case of a method of coating three times with a thickness that gives a twist angle of 15 °, the first layer is 0 to 15 °, the second layer is 15 to 30 °, the third layer is 30 to 45 °, and each layer is 15 °. A twist angle of 45 ° can be achieved by rotating each rotation.

  In this case, the second layer and the third layer can be applied in a wet state before the first layer is dried. From the viewpoint of uniformity of thickness, the first layer is once dried and necessary. And then applying the second layer after fixing the orientation of the liquid crystal layer and then applying the third layer after fixing the orientation of the second liquid crystal layer. It is preferable to sequentially perform fixing. In the case of sequential application in this way, an alignment film may be formed before application of each layer. However, if the alignment of the liquid crystal is fixed, the liquid crystal alignment layer is the same as the alignment film. Therefore, the target twist angle (45 °) can be achieved without forming an alignment film. For example, when three 15 ° liquid crystal layers are applied, the liquid crystal molecules are oriented in the direction of 15 ° on the surface layer of the first layer, and therefore on the surface adjacent to the first layer in the second development layer. Has a twist angle of 15 to 30 ° when the liquid crystal molecules are oriented at 15 ° and the spread layer is solidified. Similarly, the second surface layer in which liquid crystal molecules are aligned in the direction of 30 ° serves as an alignment film, and the third layer can be a liquid crystal layer having a twist angle of 30 to 45 °. In addition, although the case where three liquid crystal layers having a twist angle of 15 ° are applied has been described as an example, the same applies to the case where a liquid crystal layer having another twist angle is applied a plurality of times.

  In addition, when a plurality of liquid crystal layers are prepared in advance and three liquid crystal layers having a predetermined angle, for example, a twist angle of 15 °, are laminated, each layer is rotated by 15 ° and disposed. , A liquid crystal layer having a twist angle of 45 °.

  By applying heat treatment to the development layer developed on the base material (alignment film), the liquid crystalline material can be aligned in a state showing a liquid crystal phase. Since the spread layer contains a chiral agent together with the liquid crystalline material, the liquid crystalline material is twisted and aligned in a state showing a liquid crystal phase. As a result, the spread layer (liquid crystal material constituting the layer) exhibits chiral nematic alignment (helical alignment).

  The temperature condition for the heat treatment can be appropriately set according to the type of the liquid crystalline material. Specifically, it is preferable to heat the liquid crystalline material to a temperature exhibiting liquid crystallinity. For example, in the case of the liquid crystalline material described above as “Chemical Formula 1”, the temperature range exhibiting liquid crystallinity is generally in the range of 90 to 185 ° C. It is preferable to heat within this range, and from the viewpoint of imparting sufficient orientation to the liquid crystalline material, the heating temperature is more preferably 120 ° C. or higher, considering the heat resistance of the substrate, From the viewpoint of expanding the selection range, the heating temperature is preferably 160 ° C. or lower. The heating time is preferably 30 seconds or longer, and more preferably 1 minute or longer. If the treatment time is excessively short, the liquid crystal material may not take a sufficient liquid crystal state. On the other hand, the heating time is preferably 10 minutes or less, more preferably 8 minutes or less, and most preferably 7 minutes or less. If the heating time is excessively long, problems such as sublimation of the additive may occur.

  Next, in a state where the liquid crystalline material exhibits chiral nematic alignment, the development layer is subjected to polymerization treatment or crosslinking treatment to fix the alignment of the liquid crystalline material. More specifically, by performing the polymerization treatment, the liquid crystalline material (polymerizable monomer) and / or chiral agent (polymerizable chiral agent) is polymerized, and the polymerizable monomer and / or polymerizable chiral agent becomes a polymer molecule. Fixed as a repeating unit. Further, by performing a crosslinking treatment, the liquid crystalline material (crosslinkable monomer) and / or the chiral agent forms a three-dimensional network structure, and the crosslinking monomer and / or the chiral agent is fixed as a part of the crosslinked structure. Is done. As a result, the alignment state of the liquid crystal material is fixed. Note that a polymer or a three-dimensional network structure formed by polymerizing or cross-linking a liquid crystalline material does not cause a phase state transition and is strictly “non-liquid crystalline”. Therefore, in the formed liquid crystal layer, for example, transition to a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change peculiar to liquid crystal molecules does not occur, and an orientation change due to temperature does not occur. As a result, the formed liquid crystal layer is not affected by temperature and can exhibit stable optical rotation.

  The specific procedure for the polymerization treatment or the crosslinking treatment can be appropriately selected depending on the kind of the polymerization initiator and the crosslinking agent to be used. For example, when a photopolymerization initiator or a photocrosslinking agent is used, light irradiation may be performed. When an ultraviolet polymerization initiator or an ultraviolet crosslinking agent is used, ultraviolet irradiation may be performed. When a cross-linking agent is used, heating may be performed. Light or ultraviolet irradiation time, irradiation intensity, total irradiation amount, and the like can be appropriately set according to the type of liquid crystal material, the type of substrate, the characteristics desired for the liquid crystal layer, and the like. Similarly, the heating temperature, the heating time, and the like can be appropriately set according to the purpose.

  The liquid crystal layer formed on the substrate (alignment film) in this way may be used as it is, or may be peeled off from the substrate. Furthermore, it can be transferred to another film such as a polarizing plate, a liquid crystal cell, or other film. Further, the transfer can be performed a plurality of times to adjust the orientation angle of the liquid crystal layer and the front and back of the surface. The transfer is preferably performed via an adhesive, and when the transfer is performed a plurality of times, for example, a method of using an adhesive having a high adhesive force in sequence can be suitably employed.

[Formation of liquid crystal panel]
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 optical rotator 31, and the second optical rotator 32 by any appropriate method. Can be formed. 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, an optically isotropic film, a phase difference layer (optical compensation film), etc. can also be included. In particular, in the liquid crystal panel of the present invention, the retardation layer has a retardation between one or both of the first polarizing plate 21 and the liquid crystal cell 10 and between the second polarizing plate 22 and the liquid crystal cell 10. It is preferable to have a layer.

[Phase difference layer]
Examples of the retardation layer include a stretched retardation film obtained by uniaxially or biaxially stretching a polymer material, a liquid crystal polymer alignment film, and a liquid crystal polymer alignment layer supported by a film. The stretching treatment can be performed by, for example, a roll stretching method, a long gap stretching method, a tenter stretching method, a tubular stretching method, or the like. In the case of uniaxial stretching, the stretching ratio is generally about 1.1 to 3 times. The thickness of the optical compensation layer is not particularly limited, but when a stretched film is employed as the retardation plate, the thickness is generally 10 to 200 μm, preferably 20 to 100 μm.

  Examples of the polymer material used for the retardation layer include polyvinyl alcohol, polyvinyl butyral, polymethyl vinyl ether, polyhydroxyethyl acrylate, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, polycarbonate, polyarylate, polysulfone, polyethylene terephthalate, polyethylene naphthalate. Phthalate, polyethersulfone, polyphenylene sulfide, polyphenylene oxide, polyallylsulfone, polyvinyl alcohol, polyamide, polyimide, polyolefin, polyvinyl chloride, cellulosic resin, or any of these binary and ternary copolymers, grafts Examples include copolymers and blends. These polymer materials become oriented products (stretched films) by stretching or the like.

  Examples of the liquid crystalline polymer include various main chain types and side chain types in which a conjugated linear atomic group (mesogen) imparting liquid crystal alignment is introduced into the main chain or side chain of the polymer. Can be mentioned. Specific examples of the main chain type liquid crystalline polymer include, for example, a nematic alignment polyester liquid crystalline polymer, a discotic liquid crystalline polymer, and a cholesteric liquid crystalline polymer having a structure in which a mesogen group is bonded at a spacer portion that imparts flexibility. Etc. Specific examples of the side chain type liquid crystalline polymer include polysiloxane, polyacrylate, polymethacrylate, or polymalonate as a main chain skeleton, and a nematic alignment imparting paraffin through a spacer portion composed of a conjugated atomic group as a side chain. Examples thereof include those having a mesogen moiety composed of a substituted cyclic compound unit. These liquid crystalline polymers are, for example, solutions of liquid crystalline polymers on alignment treatment surfaces such as those obtained by rubbing the surface of a thin film such as polyimide or polyvinyl alcohol formed on a glass substrate, or those obtained by obliquely depositing silicon oxide. It is performed by developing and heat-treating.

  The retardation layer may have an appropriate retardation according to the purpose of use, such as for the purpose of compensating for coloring or viewing angle due to birefringence of various wave plates and liquid crystal layers, for example. What laminated | stacked the phase difference plate and controlled optical characteristics, such as phase difference, etc. may be used. As the retardation plate, not only a film but also a polymer coating layer can be used. Further, as described above, the transparent film as the polarizer protective film may have a function as a retardation layer.

  The viewing angle compensation layer is a kind of retardation layer, and is used to widen the viewing angle so that the image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction rather than perpendicular to the screen. It is a film. Such a viewing angle compensation layer is composed of an alignment film such as a liquid crystalline polymer or a support in which an alignment layer such as a liquid crystalline polymer is supported on a transparent substrate. In general, the retardation layer is a birefringent polymer film that is uniaxially stretched in the plane direction, whereas the retardation layer that is used as a viewing angle compensation layer is biaxially stretched in the plane direction. A polymer film having birefringence, a polymer having birefringence with a controlled refractive index in the thickness direction that is uniaxially stretched in the plane direction and also stretched in the thickness direction, and a bi-directionally stretched film such as a tilted orientation film are suitable. Used. Examples of the tilted alignment film include a film obtained by bonding a heat-shrinkable film to a polymer film and stretching or / and shrinking the polymer film under the action of the contraction force by heating, or a film obtained by obliquely aligning a liquid crystalline polymer. Is mentioned. The raw material polymer of the phase difference plate is the same as the polymer described in the previous phase difference plate, preventing coloration due to a change in the viewing angle based on the phase difference by the liquid crystal cell and expanding the viewing angle for good viewing. An appropriate one for the purpose can be used.

  In particular, in a TN mode liquid crystal panel, it is preferable to use a so-called O plate in which the optical axes of the liquid crystal are hybrid-aligned in view of achieving a wide viewing angle with good visibility. 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.

  Such an O plate 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.

(Method for producing liquid crystal optical compensation layer)
When a liquid crystal layer in which the optical axis of the liquid crystal is tilted and aligned is used as the retardation layer in the liquid crystal panel of the present invention, its manufacturing method is not particularly limited, but a hybrid alignment layer of discotic or nematic liquid crystal is formed on a transparent support. Means include, for example, applying a rubbing treatment to the support under the application of an electric field or a magnetic field, or applying an alignment film and applying the rubbing treatment or irradiating it with ultraviolet rays to bring the polymerizable liquid crystal or polymer liquid crystal in a predetermined direction. A method of aligning the liquid crystal and then fixing the alignment state of the liquid crystal by light or heat in the former case and rapid cooling in the latter case can be used. In particular, from the viewpoint of uniformity of alignment, a method in which the liquid crystal composition is applied onto a support on which an alignment film is formed, and the alignment is fixed by solidification (drying) and curing as necessary can be used.

  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.

  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. As a product obtained by forming such a discotic liquid crystal hybrid alignment layer on a cellulose film, there is a trade name “Wide View Film” manufactured by Fuji Film. As the nematic liquid crystal layer, those described in JP-A-9-21914, JP-A-9-26572 and the like are preferably used. As a product obtained by forming such a nematic liquid crystal hybrid alignment layer on a cellulose film, there is a trade name “NH film” manufactured by Nippon Oil Corporation.

(Arrangement of retardation layer)
The retardation layer can be disposed between the polarizing plate and the optical rotator, or between the optical rotator and the polarizing plate, as long as it is between the polarizing plate and the liquid crystal cell. From the viewpoint of performing optical compensation using the same retardation layer as that of the conventional liquid crystal panel, it is preferable to dispose the retardation layer between the liquid crystal cell and the optical rotator. On the other hand, when the retardation layer is disposed between the polarizing plate and the optical rotatory element, a configuration in which the optical axes of the polarizing plate and the retardation layer are disposed in parallel or orthogonal to each other in the liquid crystal panel can be suitably employed. Therefore, it is excellent in productivity in that a laminated polarizing plate in which a polarizing plate and a retardation layer are laminated can be produced by roll-to-roll.

  When the liquid crystal panel of the present invention employs a TN mode liquid crystal cell, a retardation layer may be disposed between the liquid crystal cell and the optical rotator from the viewpoint of optically compensating for the birefringence of liquid crystal molecules near the substrate. preferable. Further, when the liquid crystal panel employs a TN mode liquid crystal cell, as the retardation layer, as described above, an O plate in which liquid crystal molecules are hybrid-aligned is preferable. In a particularly preferred configuration, as shown in FIG. 3A and FIG. 4, a first retardation layer 41 is provided between the liquid crystal cell 10 and the first optical rotator 31, and the liquid crystal cell 10 and the second The first retardation layer 42 is provided between the optical rotatory elements 32. By setting it as such a structure, it can be set as the liquid crystal display device which is excellent in front contrast and excellent in the visibility from an oblique direction.

  Further, in the case of adopting an O plate in which liquid crystal molecules are hybrid-aligned as a retardation layer in a TN mode liquid crystal panel, the projection of the alignment direction of the liquid crystal molecules on the film surface is the absorption axis direction of the polarizing plate or the liquid crystal It is preferably parallel or orthogonal to the orientation direction of the cell substrate.

  More specifically, as shown in FIG. 3A, the first retardation layer 41 is provided between the liquid crystal cell 10 and the first optical rotation element 31, and the liquid crystal cell 10 and the second optical rotation element are included. When the first retardation layer 42 is provided between the first retardation layer 41 and the first retardation layer 41, the projection 7 on the film surface of the orientation direction of the liquid crystal molecules in the first retardation layer 41 is the orientation direction of the first orientation substrate 11 of the liquid crystal cell 10. And the projection 8 on the film surface of the alignment direction of the liquid crystal molecules in the second retardation layer 42 is preferably parallel to the alignment direction of the second alignment substrate 12 of the liquid crystal cell 10. . In particular, as shown in FIGS. 4A and 4B, it is preferable to arrange the liquid crystal molecules in the vicinity of both substrates so that the projections in the director direction are antiparallel.

  Further, as shown in FIG. 3B, the first retardation layer 41 is provided between the first polarizing plate 21 and the first optical rotator 31, and the second polarizing plate 22 and the second polarizing plate 22 are provided. When the first retardation layer 42 is provided between the optical rotator 32 and the first retardation layer 41, the projection 7 onto the film surface in the orientation direction of the liquid crystal molecules in the first retardation layer 41 is the absorption axis orientation direction of the first polarizing plate 21. 3 in which the projection 8 of the alignment direction of the liquid crystal molecules in the second retardation layer 42 onto the film surface is parallel to the absorption axis direction 4 of the second polarizing plate 22, or the first retardation The projection 7 of the alignment direction of the liquid crystal molecules in the layer 41 on the film surface is orthogonal to the absorption axis alignment direction 3 of the first polarizing plate 21, and the alignment direction of the liquid crystal molecules in the second retardation layer 42 onto the film surface. A configuration in which the projection 8 is orthogonal to the absorption axis direction 4 of the second polarizing plate 22 is suitable. By setting it as such a structure, it can be set as the liquid crystal display device which is excellent in front contrast and excellent in the visibility from an oblique direction.

  The projections 7 and 8 of the liquid crystal molecules on the film surface in the director direction in the retardation layer are substantially equal to the slow axis direction of the retardation layer when a liquid crystal material exhibiting positive uniaxiality is used. When a liquid crystal material exhibiting negative uniaxiality is used, it tends to be substantially equal to the fast axis direction of the retardation layer. Therefore, as a result, the projection of the alignment direction onto the film surface is substantially equal to the alignment direction of the alignment film when the liquid crystal layer of the O plate is formed.

(Brightness enhancement film)
The brightness enhancement film is not particularly limited. For example, it transmits linearly polarized light in a predetermined polarization direction 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, particularly an oriented film of a cholesteric liquid crystalline polymer, or a film in which the oriented 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.

(Lamination of each member)
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, 2-200 micrometers is preferable, 3-100 micrometers is more preferable, and 4-50 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 an optical rotator, and if necessary, a laminated polarizing plate in which a surface treatment layer, a retardation layer, a brightness enhancement film and the like are prepared in advance, By laminating this with a liquid crystal cell, it is possible to achieve excellent quality stability and assembly workability.

  In addition, it is preferable to laminate | stack the said polarizing plate or a laminated polarizing plate, and a liquid crystal cell through an adhesive and especially an acrylic adhesive layer as mentioned above. In particular, from the viewpoint of productivity and workability, it is preferable to prepare in advance as a pressure-sensitive adhesive layer on the side of the polarizing plate to be bonded to the liquid crystal cell, and to laminate this with the liquid crystal cell.

  Further, in the present invention, a laminated polarizing plate in which a polarizing plate and an optical rotatory element and, if necessary, other optical layers are laminated, is laminated in a roll-to-roll manner from the viewpoint of productivity. Thus, it is preferably used as a long laminated polarizing plate. Further, as described above, a protective film for a polarizer and an optical compensation layer (retardation plate) are used as a support (alignment film), and a liquid crystal coating liquid for forming a liquid crystal layer as an optical rotation element is continuously applied thereto. Thus, a long laminated polarizing plate having an optical rotatory element can be obtained.

  The (laminate) polarizing plate thus obtained is preferably bonded to a liquid crystal cell after being processed to a predetermined size. In the present invention, as described above, it is preferable to cut the polarizing plate into a rectangle in which the absorption axis direction of the polarizing plate and the long side direction of the rectangle are parallel or orthogonal. By adopting such a configuration, it is possible to increase the productivity and use efficiency of the polarizing plate, and it becomes easy to cope with a large liquid crystal panel.

  When a pressure-sensitive adhesive layer for laminating a liquid crystal cell is provided on the (laminate) polarizing plate, the pressure-sensitive adhesive can be attached either before or after the polarizing plate is cut out from the long laminated polarizing plate. From the viewpoint of property, it is preferable to attach an adhesive layer before cutting out the polarizing plate. By forming a long (laminated) polarizing plate provided with an adhesive layer and cutting it into 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. 12 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 and a prism sheet 84. Although not shown, it is preferable to have a reflector, a diffuser, a brightness enhancement film, and the like. 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 the present invention is obtained, a part of the optical member illustrated in FIG. 12 can be omitted depending on the design of the illumination method of the liquid crystal display device, or can be replaced with another optical member. Can be done.

  The liquid crystal display device of the present invention can be used for any appropriate application, for example, OA equipment such as a monitor for a personal computer, a notebook personal computer, a copy machine, a mobile phone, a clock, a digital camera, a personal digital assistant (PDA). ), Portable devices such as portable game machines, household electric devices such as video cameras, televisions, microwave ovens, back monitors, car navigation system monitors, car audio and other in-vehicle devices, information displays for commercial stores, etc. Equipment, security equipment such as monitoring monitors, nursing care / medical equipment such as nursing monitors and medical monitors. In particular, the liquid crystal display device of the present invention can be suitably used for large liquid crystal display devices such as televisions and information monitors.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the examples shown below. In addition, the measured value etc. which were used in the Example were obtained by the following methods.

[Measuring method]
(Optical rotation angle)
The optical rotation angle of the optical rotatory element was measured by the trade name “OPTIPRO” manufactured by Shintech.

(Thickness)
The thickness of the optical rotatory element was measured with a film thickness meter (trade name “MCPD2000” manufactured by Otsuka Electronics Co., Ltd.).

(Transmittance and Y value)
One hour after the backlight was turned on with the power of the liquid crystal display device turned on, the liquid crystal panel was displayed in black, and the transmittance and Y value at each viewing angle were measured using a trade name “EZ-contrast” manufactured by ELDIM. Note that the transmittance and the Y value are based on the luminance (100%) of the backlight unit of the liquid crystal display device (when the liquid crystal panel is not interposed).

[Creation of optical rotation element]
[Production Example 1]
(Preparation of liquid crystal coating liquid)
99.956 parts by weight of nematic liquid crystalline material [trade name “Pariocolor LC242” manufactured by BASF (Δn ₅₄₅ = 0.1)], 0.0444 parts by weight of chiral agent [trade name “Pariocolor LC756 manufactured by BASF” 216 parts by weight of 5 parts by weight of a UV polymerization initiator [trade name “Irgacure 907” manufactured by Ciba Japan], 0.5 parts by weight of a leveling agent [trade name “BYK370” manufactured by Big Chemie] A liquid crystal coating solution A having a concentration of 31.6% by weight was prepared.

(Formation of liquid crystal layer)
The obtained liquid crystal coating solution was applied onto an alignment film of polyvinyl alcohol using a # 14 wire bar. The liquid crystal layer was aligned while being dried in an oven at 90 ° C. for 3 minutes, and cured by irradiating 300 mJ / cm ² of UV light to obtain an optical rotatory element. The obtained optical rotatory element is referred to as an optical rotatory element A. The film thickness of the obtained optical rotatory element A was 4.42 μm.

[Production Example 2]
(Preparation of liquid crystal coating liquid and formation of liquid crystal layer)
As shown in Table 3, a liquid crystal coating liquid B was prepared in the same manner as in Production Example 1 except that the contents of the liquid crystal material and the chiral agent in the liquid crystal coating liquid were changed. The obtained liquid crystal coating liquid B was applied onto an alignment film of polyvinyl alcohol using a # 28 wire bar. This was dried in an oven at 90 ° C. for 5 minutes to align the liquid crystal layer while drying the liquid crystal layer, and cured by irradiation with 300 mJ / cm ² of UV light to obtain an optical rotation element. The obtained optical rotatory element is referred to as an optical rotatory element B. The film thickness of the obtained optical rotatory element B was 9.06 μm.

[Production Example 3]
(Preparation of liquid crystal coating liquid and formation of liquid crystal layer)
As shown in Table 3, a liquid crystal coating liquid C was prepared in the same manner as in Production Example 1 except that the contents of the liquid crystal material and the chiral agent in the crystal coating liquid were changed.
(Formation of liquid crystal layer)
The obtained liquid crystal coating liquid C was applied onto an alignment film of polyvinyl alcohol using a # 21 wire bar. The liquid crystal layer is oriented while being dried in an oven at 90 ° C. for 5 minutes, and cured by irradiating 300 mJ / cm ² of UV light, and a liquid crystal solidified layer (liquid crystal layer having a liquid crystal twist angle of 22.5 °) did. The liquid crystal coating liquid C is further applied onto the obtained liquid crystal solidified layer using a # 21 wire bar, then dried again in an oven at 90 ° C. for 5 minutes, and irradiated with 300 mJ / cm ² UV light. To obtain a liquid crystal layer having a twist angle of 45 ° for the liquid crystal. This is an optical rotation element C. The film thickness of the obtained optical rotatory element C was 13.66 μm.

[Production Example 4]
(Preparation of liquid crystal coating liquid and formation of liquid crystal layer)
A liquid crystal coating solution D was prepared in the same manner as in Production Example 1 except that the composition of the coating solution was changed as shown in Table 3. The obtained liquid crystal coating layer D was coated, dried and cured twice using the # 28 wire bar in the same manner as in Production Example 3 to produce a liquid crystal layer having a liquid crystal twist angle of 45 °. . This is an optical rotation element D. The film thickness of the obtained optical rotatory element D was 18.24 μm.

[Production Example 5]
(Preparation of liquid crystal coating liquid and formation of liquid crystal layer)
A liquid crystal coating solution E was prepared in the same manner as in Production Example 1 except that the composition of the coating solution was changed as shown in Table 3.
(Formation of liquid crystal layer)
The obtained liquid crystal coating liquid E was applied onto an alignment film of polyvinyl alcohol using a # 23 wire bar. The liquid crystal layer was oriented while being dried in an oven at 90 ° C. for 5 minutes, and cured by irradiating UV light of 300 mJ / cm ² to obtain a liquid crystal solidified layer (liquid crystal layer having a liquid crystal twist angle of 15 °). On the obtained liquid crystal solidified layer, the liquid crystal coating liquid E was further applied using a # 23 wire bar, and then the drying and curing process was repeated twice to produce a liquid crystal layer having a liquid crystal twist angle of 45 °. . This is an optical rotation element E. The film thickness of the obtained optical rotatory element E was 22.80 μm.

[Production Example 6]
(Preparation of liquid crystal coating liquid and formation of liquid crystal layer)
A liquid crystal coating solution F was prepared in the same manner as in Production Example 1 except that the composition of the coating solution was changed as shown in Table 3. Using the # 28 wire bar, the obtained liquid crystal coating layer F was coated, dried and cured three times in the same manner as in Production Example 5 to produce a liquid crystal layer having a liquid crystal twist angle of 45 °. . This is an optical rotation element F. The film thickness of the obtained optical rotatory element F was 27.39 μm.

  The thicknesses of the optical rotators A to F obtained in Production Examples 1 to 6 are m = 1, 2, 3, 4, 5, 6 when the wavelength λ = 545 nm in the formula (1), respectively. It corresponds to the thickness. In addition, in the optical rotator A of Production Example 1, in the formula (1), m = 1 was satisfied, but a wavelength satisfying m ≧ 2 did not exist in the visible light region.

[Production Examples 7 to 11]
In the production example 1, the following compound (Δn ₅₄₅ = 0.3) was used as the nematic liquid crystalline material instead of “Pariocolor LC242”, the composition ratio of the liquid crystal coating liquids G to L, and the wire bar used for coating A liquid crystal layer having a liquid crystal twist angle of 45 ° was produced in the same manner as in Production Example 1 except that the count and the number of coatings were as shown in Table 2. These are optical rotation elements G to K, respectively.

[Production Examples 13 to 14]
In Production Example 3, the following compound (Δn ₅₄₅ = 0.3) was used as the nematic liquid crystal material in place of “Palocoll LC242”, the composition ratio of liquid crystal coating liquids L, M, and N, and the wire used for coating The liquid crystal layer was repeatedly applied, dried and cured in the same manner as in Production Example 3 except that the bar counts were as shown in Table 2. Thus, a liquid crystal layer having a liquid crystal twist angle of 45 ° was produced. These are optical rotation elements L, M, and N, respectively.

  The thicknesses of the optical rotatory elements G to L obtained in the above Production Examples 7 to 12 are m = 1, 2, 3, 4, 5, 6 when the wavelength λ = 545 nm in the formula (1), respectively. It corresponds to the thickness. In addition, in the optical rotator A of Production Example 1, in the formula (1), m = 1 was satisfied, but a wavelength satisfying m ≧ 2 did not exist in the visible light region. The optical rotatory element N obtained in Production Example 14 corresponds to a thickness of m = 11. On the other hand, in the thickness of the optical rotatory element M obtained in Production Example 13, m is not an integer when the wavelength λ = 545 nm in the formula (1), and the optical rotatory element M has a thickness of m = 8.26. It corresponds to.

[Reference Example 1]
When the optical rotation element having a twist angle (optical rotation angle) of 45 ° for the liquid crystal layer is manufactured by the nematic liquid crystalline material used in the manufacture of the optical rotation elements in Production Examples 1 to 6, the thickness d of the optical rotation element is variously changed. In this case, transmittance T (%) and Y value (%) at a wavelength of 545 nm were calculated based on the above formulas (2) and (3). FIG. 13 shows the calculation results represented in a graph of horizontal axis: thickness, vertical axis: transmittance T or Y value. 13A and 13B are obtained by changing the scale of the horizontal axis (thickness) of the same graph.

[Reference Example 2]
When the optical rotation element whose twist angle (optical rotation angle) of the liquid crystal layer is 45 ° is manufactured by the nematic liquid crystalline material used in the manufacture of the optical rotation elements of the manufacturing examples 7 to 14, the thickness d of the optical rotation element is variously changed. In this case, the transmittance T (%) and the Y value (%) at a wavelength of 545 nm were calculated based on the equations (2) and (3). FIG. 14 shows the calculation results in a graph of horizontal axis: thickness, vertical axis: transmittance T or Y value. 14A and 14B are obtained by changing the scale of the horizontal axis (thickness) of the same graph.

As understood from FIGS. 13 and 14, the transmittance T has a minimum value in the thickness where m is an integer in the equation (1), whereas the Y value is in a region where the thickness is small. Although it shows a tendency to increase or decrease similar to the transmittance T, the behavior differs from the transmittance T as the thickness increases. As the thickness increases, a monotonic decrease appears. The change point appears in a region where Δn ₅₄₅ × d = 1400 nm.

[Creation of laminated polarizing plate, liquid crystal panel, and liquid crystal display device]
[Comparative Example 1]
(Preparation of polarizing plate with optical rotation element)
The optical rotatory element A obtained in Production Example 1 is substantially optically isotropic (front phase difference is 0.5 nm or less, thickness direction retardation is 1.0 nm or less) as protective films on both sides of the polarizer. In the commercial polarizing plate [trade name “NPF SIG1423DU” manufactured by Nitto Denko, single transmittance: 42.6%, polarization degree: 99.99%, manufactured by] Is transferred using an acrylic adhesive so that the alignment direction of the liquid crystal molecules on the surface facing the polarizing plate is parallel, and an optical rotatory element having a twist angle of 45 ° is laminated on the polarizing plate. A laminated polarizing plate A was prepared. In addition, when laminating the optical rotatory element on the polarizing plate, transfer was performed twice so that the surface on the alignment film side at the time of preparing the optical rotatory element was opposed to the polarizing plate.

(Lamination of retardation layer)
As a retardation layer, an optical compensation film 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 [trade name “Wide View Film EA "] was used. This retardation layer was laminated on a polarizing plate provided with the above optical rotatory element using an acrylic adhesive to obtain a laminated polarizing plate. When laminating both, the optical rotation element and the triacetyl cellulose base film of the retardation layer face each other, and the rubbing direction of the alignment film of the retardation layer and the side facing the retardation layer of the optical rotation element Lamination was performed such that the alignment directions of the liquid crystals at the interface were parallel. The stacking order of the obtained laminated polarizing plates and the arrangement relationship when viewed from the phase difference layer side with the absorption axis of the polarizing plate as the angle reference (0 °) are as shown in Table 3.

(Creation of LCD panel)
All the optical films arranged above and below the liquid crystal cell of a commercially available liquid crystal display device [trade name “FP74VW” manufactured by BENQ Co., Ltd.] equipped with a TN mode liquid crystal panel were removed, and the glass surfaces (front and back) of the liquid crystal cell were washed. A liquid crystal cell was used. In such a liquid crystal cell, the orientation directions of the two substrates were orthogonal to each other, and the angles formed by the long side direction of the liquid crystal cell were + 45 ° and −45 °.

  Two of the laminated polarizing plates obtained above were cut out in accordance with the size of the liquid crystal cell so as to be a rectangle having a long side in the absorption axis direction of the polarizing plate. One laminated polarizing plate was cut out on each side of the liquid crystal cell via an acrylic adhesive to prepare a liquid crystal panel. This was assembled with the backlight unit of the original liquid crystal display device to obtain a liquid crystal display device. Table 4 shows the stacking order of the obtained liquid crystal panels and the arrangement relationship when viewed from the viewing side with the long side direction (right side) of the screen as the angle reference (0 °). In Table 4, the alignment direction of the liquid crystal layer of the retardation layer and the alignment direction of the substrate in the liquid crystal cell both represent the projection of the director of the liquid crystal at the substrate interface, and the retardation layer and the liquid crystal adjacent thereto It arrange | positions so that the director direction of the board | substrate of a cell may become antiparallel. The same applies to Tables 5 and 6 described later.

[Creation of laminated polarizing plate, liquid crystal panel, and liquid crystal display device]
[Examples 1 to 10, Comparative Examples 2 to 4]
(Preparation of polarizing plate with optical rotation element)
In the comparative example 1, the optical rotatory element is transferred to the polarizing plate in the same manner as in the comparative example 1 except that the optical rotatory elements B to N are used as shown in Table 7 instead of the optical rotatory element A. A plate was produced, a laminated polarizing plate using the same, a liquid crystal panel, and a liquid crystal display device were produced.

[Reference Example 3]
(Preparation of laminated polarizing plate)
A commercially available polarizing plate (trade name “NPF SIG1423DU” manufactured by Nitto Denko) and a retardation layer (trade name “Wide View Film EA” manufactured by Fuji Film) similar to the above are used as the absorption axis of the polarizing plate and the orientation of the retardation layer. Lamination was performed using an acrylic adhesive so that the rubbing direction of the film was parallel to obtain a laminated polarizing plate.

(Production of liquid crystal panel and liquid crystal display device)
A liquid crystal display device was produced in the same manner as in Comparative Example 1 except that the obtained laminated polarizing plate was used and the order of arrangement of the liquid crystal panels and the arrangement relationship were changed as shown in Table 5.

[Comparative Example 5]
(Preparation of polarizing plate provided with stretched retardation film)
A polycarbonate film [trade name “manufactured by Kaneka Co., Ltd., manufactured by Kaneka Co., Ltd.] having a phase difference at 545 nm of 273 nm and an Nz coefficient of 1, which is uniaxially stretched on a commercially available polarizing plate (trade name“ NPF SIG1423DU ”manufactured by Nitto Denko) as described above. Elmec R film ”] is laminated using an acrylic pressure-sensitive adhesive so that the angle formed by the absorption axis direction of the polarizing plate and the slow axis direction of the stretched retardation film is 22.5 °. A polarizing plate provided with a retardation film was produced.

(Preparation of laminated polarizing plate)
As the retardation layer, an optical compensation film similar to the above [trade name “Wide View Film EA” manufactured by Fuji Film] was used. This retardation layer was laminated on a polarizing plate provided with the stretched retardation film using an acrylic pressure-sensitive adhesive to obtain a laminated polarizing plate. In addition, when laminating both, the angle formed by the rubbing direction of the alignment film of the retardation layer and the slow axis direction of the stretched retardation film is such that the triacetyl cellulose base film of the retardation layer faces each other. The layers were laminated so that the angle formed by 22.5 ° and the absorption axis of the polarizing plate was 45 °.

(Production of liquid crystal panel and liquid crystal display)
A liquid crystal panel and a liquid crystal display device were produced in the same manner as in Comparative Example 1 except that the laminated polarizing plate obtained above was used and the order of lamination and the arrangement relationship were changed as shown in Table 6.

[Comparative Example 6]
In Comparative Example 5, in place of the stretched polycarbonate film, a norbornene-based resin film (trade name “Zeonor Film” manufactured by Optes, Inc.) having a retardation at 545 nm of 273 nm and an Nz coefficient of 1 is used. A laminated polarizing plate and a liquid crystal panel and a liquid crystal display device were produced in the same manner as in Comparative Example 3 except for the above.

[Evaluation results]
Measurement results of Y type (%) of liquid crystal display device, and types of optical rotatory elements (or retardation plates) used for forming the liquid crystal panels of Examples 1 to 10, Comparative Examples 1 to 6, and Reference Example 3 Is shown in Table 7. Moreover, the viewing angle distribution (cone diagram) of the measurement result of Y value is shown in FIGS. In Table 7 and FIGS. 15 to 31, the long side direction (right side) of the liquid crystal display device is the azimuth angle reference (0 °), and the normal direction of the screen (front view) is the polar angle reference (0 °). It represents as.

  As described above, the liquid crystal panel using the optical rotatory element of the present invention can be used by using the optical rotatory element even when the long side direction when the polarizing plate is cut out and the absorption axis direction of the polarizing plate are parallel. Compared with the conventional liquid crystal display device as shown in Reference Example 3, a black display comparable to that of the conventional liquid crystal display device can be obtained. Further, as compared with the case where the polarization direction is rotated by the half-wave plate as in Comparative Examples 5 and 6, the Y value in black display is reduced by the optical rotatory element, and a liquid crystal display device with small light leakage is obtained. I understand that Further, as is clear from the comparison between each example and Comparative Examples 1 to 4, a good black display with little coloration can be obtained by adjusting the thickness of the liquid crystal layer in the optical rotator.

  In each of the above examples, the polarizer protective film and the optical compensation layer were provided separately in all the examples in order to facilitate the comparison of differences depending on the configuration. As described above, the protective film of the polarizer, the optical compensation layer, and the alignment substrate of the liquid crystal layer forming the optical rotator can be provided with a plurality of functions.

  As described above, the liquid crystal panel of the present invention contributes to an increase in size and an improvement in the removal rate of a polarizing plate by using an optical rotatory element having a predetermined thickness, and has a display comparable to that of a conventional liquid crystal display device. Characteristics can be obtained.

It is a conceptual diagram showing a mode that a polarizing plate is cut out from a elongate polarizing plate. (A) represents a state in which a polarizing plate used in a TN type liquid crystal panel in the prior art is cut out at an angle of 45 °, and (b) in the present invention, the absorption axis of the polarizing plate is parallel to the rectangular side direction. It represents the case of cutting out like this. 1 is a schematic cross-sectional view of a liquid crystal panel according to an embodiment of the present invention. 1 is a schematic cross-sectional view of a liquid crystal panel according to an embodiment of the present invention. 1 is a schematic perspective view of a liquid crystal panel according to an embodiment of the present invention. In the liquid crystal display device using the liquid crystal panel of this invention, it is a conceptual diagram which represents typically the principle in which (a) white display and (b) black display are obtained. It is a conceptual diagram showing the conversion of the polarization state on Poincare when a phase difference plate is used. (A) is a sketch, (b) is a projection onto the S ₂ -S ₃ plane, (c) is a projection onto the S ₃ -S ₁ plane, and (d) is a projection onto the S ₁ -S ₂ plane. Represents It is a conceptual diagram showing conversion of the polarization state on Poincare at the time of using an optical rotatory element. (A) is a sketch, (b) is a projection onto the S ₂ -S ₃ plane, (c) is a projection onto the S ₃ -S ₁ plane, and (d) is a projection onto the S ₁ -S ₂ plane. Represents It is a conceptual diagram showing conversion of the polarization state on Poincare at the time of using an optical rotatory element. (A) is a sketch, (b) is a projection onto the S ₂ -S ₃ plane, (c) is a projection onto the S ₃ -S ₁ plane, and (d) is a projection onto the S ₁ -S ₂ plane. Represents It is a conceptual diagram showing the conversion of the polarization state on Poincare when a phase difference plate is used. It is a conceptual diagram showing conversion of the polarization state on Poincare at the time of using an optical rotatory element. It is a conceptual diagram showing conversion of the polarization state on Poincare at the time of using an optical rotatory element. It is a schematic sectional drawing showing an example of the liquid crystal display device by embodiment of this invention. In Reference Example 1, transmittance T (%) and Y value at a wavelength of 545 nm in the case where an optical rotatory element having a twist angle of 90 ° for the liquid crystal layer was produced by changing the thickness d of the optical rotatory element with nematic liquid crystal materials. It is a graph showing the calculation result of (%). (A) And (b) changes the scale of the horizontal axis (thickness) of the same graph. In Reference Example 2, the transmittance T (%) and the Y value at a wavelength of 545 nm in the case where an optical rotatory element having a twist angle of 90 ° in the liquid crystal layer was produced by changing the thickness of the optical rotatory element with a nematic liquid crystal material. %) Is a graph showing a calculation result. (A) And (b) changes the scale of the horizontal axis (thickness) of the same graph. It is a figure showing the measurement result of Y value in the liquid crystal display of comparative example 1. It is a figure showing the measurement result of Y value in the liquid crystal display of comparative example 2. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 1. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 2. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 3. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 4. It is a figure showing the measurement result of Y value in the liquid crystal display of comparative example 3. It is a figure showing the measurement result of Y value in the liquid crystal display of comparative example 4. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 5. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 6. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 7. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 8. It is a figure showing the measurement result of Y value in the liquid crystal display of Example 9. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 10. It is a figure showing the measurement result of Y value in the liquid crystal display of reference example 3. It is a figure showing the measurement result of Y value in the liquid crystal display of comparative example 5. It is a figure showing the measurement result of Y value in the liquid crystal display of comparative example 6.

Explanation of symbols

1 Orientation (rubbing) direction 2 Orientation (rubbing) direction 3 Absorption axis (direction)
4 Absorption axis (direction)
5a, 5b Orientation directions of liquid crystal molecules 6a, 6b Orientation directions of liquid crystal molecules 10 Liquid crystal cell 11 Substrate 12 Substrate 13 Liquid crystal layer 21 Polarizing plate 22 Polarizing plate 31 Optical rotator 32 Optical rotator 41 Phase difference layer 42 Phase difference layer 81 Light source 82 Reflection Film 83 Diffusion plate 84 Prism sheet 100 Liquid crystal panel 200 Light source 300 Liquid crystal display device

Claims (10)

A liquid crystal cell having a liquid crystal layer between the first alignment substrate and the second alignment substrate; 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 optical rotator arranged between the liquid crystal cell and the first polarizing plate;
A second optical rotator disposed between the liquid crystal cell and the second polarizing plate,
The first optical rotatory element and the second optical rotatory element are chiral nematic liquid crystal layers in which the alignment direction of liquid crystal molecules gradually changes along the thickness direction of the layer, and the chiral nematic liquid crystal layer is A liquid crystal panel in which a product of birefringence Δn _{545 at} a wavelength of 545 nm of a nematic liquid crystalline material to be formed and a thickness d of a liquid crystal layer is 1400 nm or more.   The alignment direction of the liquid crystal molecules on the first polarizing plate side surface of the first optical rotation element is parallel or orthogonal to the absorption axis direction of the first polarizing plate, and the second optical rotation element The liquid crystal panel according to claim 1, wherein the alignment direction of the liquid crystal molecules on the second polarizing plate side surface is parallel or orthogonal to the absorption axis direction of the second polarizing plate.   The alignment direction of the liquid crystal molecules on the liquid crystal cell side surface of the first optical rotation element is parallel or orthogonal to the alignment direction of the first alignment substrate of the liquid crystal cell, and the second optical rotation element The liquid crystal panel according to claim 1 or 2, wherein the alignment direction of the liquid crystal molecules on the surface on the liquid crystal cell side is parallel or orthogonal to the alignment direction of the second alignment substrate of the liquid crystal cell.   The liquid crystal panel according to claim 1, wherein the twist angle of the chiral nematic liquid crystal layer in the first optical rotator and the second optical rotator is approximately 45 °.   The liquid crystal panel according to claim 1, wherein an absorption axis direction of the first polarizing plate and an absorption axis direction of the second polarizing plate are parallel.   The liquid crystal panel according to claim 1, wherein the liquid crystal cell is a TN mode liquid crystal cell.   A first retardation layer is provided between the liquid crystal cell and the first optical rotation element, and a second retardation layer is provided between the liquid crystal cell and the second optical rotation element. The liquid crystal panel according to claim 1, comprising:   The liquid crystal panel according to claim 7, wherein the first retardation layer and the second retardation layer include a liquid crystal layer in which an optical axis of liquid crystal is hybrid-aligned.   The liquid crystal panel according to claim 1, wherein the first polarizing plate and the second polarizing plate are rectangular, and the long side direction of the rectangle and the absorption axis direction of the polarizing plate are parallel or orthogonal. .   A liquid crystal display device comprising the liquid crystal panel according to claim 1.