JP2005049866A - Phase difference layer and liquid crystal display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase difference layer capable of effectively suppressing the deterioration of display quality without producing a contrast pattern in a display image even when being arranged between a liquid crystal cell and a polarizing plate. <P>SOLUTION: The phase difference layer 10 is composed of a plurality of micro domains 12 having a molecular structure with cholesteric regularity. In the phase difference layer 10, helical pitch of the molecular structure is adjusted so that selective reflection wavelength of selective reflection light due to the molecular structure becomes smaller than the wavelength of incident light which is made incident on the phase difference layer 10. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a retardation layer used by being incorporated in a liquid crystal display device or the like, and in particular, includes a retardation layer that acts as a negative C plate made of cholesteric regularity, and has a direction inclined from a normal line of a liquid crystal cell. The present invention relates to a retardation layer that compensates the polarization state of light and a liquid crystal display device including the retardation layer.

  As a conventional general liquid crystal display device, as shown in FIG. 15, a liquid crystal display device having an incident side polarizing plate 102 </ b> A, an output side polarizing plate 102 </ b> B, and a liquid crystal cell 104 can be exemplified. The polarizing plates 102A and 102B are configured to selectively transmit only linearly polarized light (schematically illustrated by arrows in the figure) having a vibration surface in a predetermined vibration direction. They are arranged to face each other in a crossed Nicol state so as to have a right angle relationship with each other. The liquid crystal cell 104 includes a large number of cells corresponding to the pixels, and is disposed between the polarizing plates 102A and 102B.

  Here, in such a liquid crystal display device 100, the liquid crystal cell 104 has a VA (Vertical Alignment) method in which nematic liquid crystal having negative dielectric anisotropy is sealed (a liquid crystal director is schematically shown by a dotted line in the figure). As an example, the linearly polarized light transmitted through the incident-side polarizing plate 102A is phase-shifted when passing through the non-driven cell portion of the liquid crystal cell 104. And is blocked by the output-side polarizing plate 102B. On the other hand, when the liquid crystal cell 104 is transmitted through the portion of the driven cell, the linearly polarized light is phase-shifted, and an amount of light corresponding to the amount of the phase shift is transmitted through the polarizing plate 102B on the emission side. Emitted. Thereby, by appropriately controlling the driving voltage of the liquid crystal cell 104 for each cell, a desired image can be displayed on the exit side polarizing plate 102B side. The liquid crystal display device 100 is not limited to the above-described light transmission and blocking modes, and light emitted from the non-driven cell portion of the liquid crystal cell 104 is emitted from the polarizing plate on the emission side. There has also been devised a liquid crystal display device configured so that light emitted from the portion of the cell in the driving state is blocked by the polarizing plate 102B on the emission side while being emitted through 102B.

  By the way, considering the case where linearly polarized light is transmitted through the non-driven cell portion of the VA liquid crystal cell 104 as described above, the liquid crystal cell 104 has birefringence and is refracted in the thickness direction. Since the refractive index and the refractive index in the plane direction are different, the light incident along the normal line of the liquid crystal cell 104 out of the linearly polarized light transmitted through the polarizing plate 102A on the incident side is transmitted without being phase-shifted. Of the linearly polarized light transmitted through the polarizing plate 102 </ b> A, light incident in a direction tilted from the normal line of the liquid crystal cell 104 has a phase difference when passing through the liquid crystal cell 104 and becomes elliptically polarized light. This phenomenon is caused by the fact that the liquid crystal molecules aligned in the vertical direction in the liquid crystal cell 104 act as a positive C plate. Note that the magnitude of the phase difference generated with respect to light transmitted through the liquid crystal cell 104 (transmitted light) depends on the birefringence value of the liquid crystal molecules sealed in the liquid crystal cell 104, the thickness of the liquid crystal cell 104, and the transmitted light. It is also affected by the wavelength.

  Due to the above phenomenon, even when a certain cell in the liquid crystal cell 104 is in a non-driven state, the linearly polarized light is essentially transmitted as it is and should be blocked by the polarizing plate 102B on the output side. A part of the light emitted in the direction inclined from the normal line leaks from the polarizing plate 102B on the emission side.

  For this reason, in the conventional liquid crystal display device 100 as described above, the display quality of the image observed from the direction inclined from the normal line of the liquid crystal cell 104 is mainly lower than the image observed from the front. There was a problem (problem of viewing angle dependency) that it was worsened by doing.

  Various techniques have been developed so far to improve the viewing angle dependency problem in the conventional liquid crystal display device 100 as described above, and one of them is disclosed in, for example, Patent Document 1 or Patent Document 2. As shown in the figure, a phase difference layer having a cholesteric regular molecular structure (a phase difference layer exhibiting birefringence) is used, and such a phase difference layer is disposed between the liquid crystal cell and the polarizing plate. There has been known a liquid crystal display device configured to perform the above.

  Here, in a phase difference optical element having a cholesteric regular molecular structure, λ = nav · p (p: helical pitch in the helical structure of liquid crystal molecules, nav: average refraction in a plane perpendicular to the helical axis For example, as disclosed in Patent Document 1 or Patent Document 2, the selective reflection wavelength represented by (rate) is adjusted to be smaller or larger than the wavelength of transmitted light.

  In the retardation optical element as described above, as in the case of the liquid crystal cell described above, the linearly polarized light incident in the direction inclined from the normal line of the retardation layer causes a retardation when transmitted through the retardation layer. Becomes elliptically polarized light. This phenomenon is caused by the fact that the cholesteric regular molecular structure acts as a negative C plate. Note that the magnitude of the phase difference generated with respect to the light transmitted through the retardation layer (transmitted light) depends on the birefringence value of the liquid crystal molecules in the retardation layer, the thickness of the retardation layer, the wavelength of the transmitted light, and the like. Is also affected.

  Therefore, if the phase difference optical element as described above is used, the phase difference generated in the VA liquid crystal cell acting as the positive C plate and the phase difference caused in the phase difference layer acting as the negative C plate cancel each other. Thus, by appropriately designing the retardation layer, it is possible to greatly improve the problem of the viewing angle dependency of the liquid crystal display device.

  On the other hand, Patent Document 3 discloses a TN (Twisted Nematic) type liquid crystal cell, which is a liquid crystal display element having a large number of unfixed micro domains having a diameter of several μm to several tens of μm. The chiral nematic liquid crystal layer used as the TN liquid crystal is set so as to act as an optical rotation layer and not as a retardation layer. Therefore, the twist angle of the TN liquid crystal is set so that the twist angles of the many microdomains coincide with each other in a range of 0 degree to about 270 degrees (0 to 0.75 pitch when converted to a chiral pitch). When the chiral pitch of the TN liquid crystal is assumed to be 1 pitch or more, the selective reflection wavelength of the TN liquid crystal is longer than the wavelength of incident visible light.

  Non-Patent Document 1 discloses a liquid crystal display element comprising an amorphous liquid crystal layer that is not fixed as a TN liquid crystal cell forming method. The chiral nematic liquid crystal layer used as the TN liquid crystal is set so as to act as an optical rotation layer and not as a retardation layer. Therefore, the twist angle of the TN liquid crystal is set to 90 degrees (0.5 pitch when converted to a chiral pitch). The TN system includes a normally black mode in which a TN cell is sandwiched between two polarizing plates made parallel to each other, and a normally white mode in which a TN cell is sandwiched between polarizer crossed Nicols. In Patent Document 1, when a TN liquid crystal display element composed of an amorphous liquid crystal layer that is not fixed is set to a normally black mode, the transmittance is as high as 3%, resulting in a decrease in contrast. When the chiral pitch of the TN liquid crystal is assumed to be 1 pitch or more, the selective reflection wavelength of the TN liquid crystal is longer than the wavelength of incident visible light.

  Non-Patent Document 2 also discloses a liquid crystal display element composed of an amorphous liquid crystal layer as a TN liquid crystal cell forming method. The liquid crystal layer in the amorphous state has a brush width of 10 to 100 μm, and several domains exist between them, and the directors of adjacent domains are almost continuous. The chiral nematic liquid crystal layer used as the TN liquid crystal is set so as to act as an optical rotation layer and not as a retardation layer. Therefore, the twist angle of the TN liquid crystal is set to 90 degrees (0.5 pitch when converted to a chiral pitch). When the chiral pitch of the TN liquid crystal is assumed to be 1 pitch or more, the selective reflection wavelength of the TN liquid crystal is longer than the wavelength of incident visible light.

  Patent Document 4 discloses a circularly polarized light extracting optical element in which the director of liquid crystal molecules in the entire range of the liquid crystal layer surface having cholesteric regularity is made to be a monodomain. By doing so, the light and dark pattern observed when the cholesteric liquid crystal is sandwiched between the polarizing plates in a crossed Nicol state is eliminated.

  However, when the retardation optical element (retardation layer having a cholesteric regular molecular structure) as described above is disposed between the liquid crystal cell and the polarizing plate, the problem of viewing angle dependency can be improved. However, except for the case of Patent Document 4, there is a problem that a bright and dark pattern is generated in the display image and the display quality is remarkably lowered.

JP-A-3-67219 JP-A-4-322223 JP-A-7-175065 JP 2002-258053 A R. Holding et al., SID '93 Digest, 622 (1993) Y. Iimura et al., SID '94 Digest, 915 (1994)

  The present invention has been made in consideration of such problems, and even when a retardation layer is disposed between a liquid crystal cell and a polarizing plate, a bright and dark pattern is not generated in a display image, and display quality is improved. An object of the present invention is to provide a retardation layer capable of effectively suppressing the decrease in the phase difference, a retardation optical element using the retardation layer, and a liquid crystal display device.

  In order to achieve the above object, the present invention provides a retardation layer functioning as a negative C plate having a fixed cholesteric structure, wherein at least one of the two main surfaces of the retardation layer is predetermined. The retardation layer is characterized in that the directors of the liquid crystal molecules do not substantially coincide with each other.

  According to the present invention, since the retardation layer has a liquid crystal molecule director that does not substantially match within a predetermined interval on at least one surface, the film thickness is, for example, for manufacturing reasons. Even when a retardation optical element having a retardation layer with a distribution of ± 5% is arranged between a liquid crystal cell and a polarizing plate, liquid crystal molecules with different directors exist within a minute interval, so Since the pattern is virtually invisible to the human eye, it is possible to surely make it difficult to see the bright and dark pattern generated in the display image, and thus it is possible to suppress deterioration in the display quality of the appearance.

  Furthermore, among the two main surfaces of the retardation layer, it is preferable that the other surface has a liquid crystal molecule director that does not substantially match within a predetermined interval. This is because it is possible to make it more difficult to see the bright and dark pattern generated in the display image more effectively, and thus it is possible to more effectively suppress the deterioration in display quality.

  The present invention also provides a retardation layer that functions as a negative C plate with a fixed cholesteric structure, and is within a region of a predetermined radius on at least one of the two main surfaces of the retardation layer. There is provided a retardation layer characterized by the presence of liquid crystal molecules whose directors do not substantially coincide.

  According to the present invention, the retardation layer includes a liquid crystal molecule whose director does not substantially match within a region having a predetermined radius on at least one surface. Even when a retardation optical element having a retardation layer with a film thickness distribution of ± 5% is disposed between a liquid crystal cell and a polarizing plate, liquid crystal molecules having different directors exist in a minute region. Thus, it is possible to make it difficult to see the bright and dark pattern generated in the display image, and thus it is possible to suppress a decrease in the visual display quality.

  Furthermore, the present invention provides a retardation layer that functions as a negative C plate having a fixed cholesteric structure, and the twist angle in the cholesteric structure is substantially at a position within a predetermined interval on the main surface of the retardation layer. There is provided a retardation layer characterized in that there is a material that does not match the above.

  According to the present invention, since the retardation layer has a layer in which the twist angles in the cholesteric structure do not substantially coincide with each other at a position within a predetermined interval, the film thickness distribution is, for example, for manufacturing reasons. Even when a retardation optical element having a retardation layer of ± 5% is arranged between the liquid crystal cell and the polarizing plate, there are things with different twist angles within a minute interval, so the light and dark pattern is human. Therefore, it is difficult to see the bright and dark pattern generated in the display image, and thus it is possible to suppress the deterioration of the display quality.

  The present invention also provides a retardation layer functioning as a negative C plate having a fixed cholesteric structure, wherein the twist angle in the cholesteric structure is located at a position within a predetermined radius region on the main surface of the retardation layer. There is provided a retardation layer characterized in that there is a material that does not substantially match.

  According to the present invention, since the cholesteric structure does not substantially coincide with the twist angle at a position within a predetermined radius region, the film thickness distribution is ± 5% for manufacturing reasons, for example. Even when a phase difference optical element having a phase difference layer is arranged between a liquid crystal cell and a polarizing plate, there is a thing with a different twist angle in a minute region, so that a bright and dark pattern generated in a display image is not generated. It is possible to make it difficult to see, and therefore, it is possible to suppress a decrease in visual display quality.

  In addition, the present invention provides a retardation layer that functions as a negative C plate with a fixed cholesteric structure, and the normal line is within a region of a predetermined radius in a cross section including a normal line standing on the surface of the retardation layer. And the helical axis of the helical axis structure region having the cholesteric structure has an acute angle clockwise with respect to the normal direction, and an acute angle counterclockwise with respect to the normal direction. A retardation layer comprising the helical axis structure region as described above.

  According to the present invention, the retardation layer is formed between the normal line and the helical axis of the helical axis structure region having a cholesteric structure in a region having a predetermined radius in a cross section including the normal line standing on the surface of the retardation layer. The angular axis has a helical axis structure area that is acute clockwise with respect to the normal direction and a helical axis structure area that is acute counterclockwise with respect to the normal direction. It is possible to prevent the helical axis structure regions from being combined into a large domain. Thereby, for example, even when the retardation layer having a film thickness distribution of ± 5% for manufacturing reasons is disposed between the liquid crystal cell and the polarizing plate, a bright and dark pattern is not generated in the display image. A decrease in display quality can be effectively suppressed.

  In the above-described invention, it is preferable that a plurality of minute units (domains) having the cholesteric structure exist. For example, the directors of the liquid crystal molecules between the minute units (domains) do not substantially match or the twist angles in the cholesteric structure between the minute units (domains) do not substantially match. This is because if there are a plurality of units (domains) in contact with each other, it is possible to more reliably make it difficult to see the bright and dark pattern generated in the display image, and thus it is possible to more reliably suppress the deterioration of display quality. .

  Furthermore, the present invention is a retardation layer that functions as a negative C plate fixed in a range in which the helical pitch of the cholesteric structure is 1 pitch or more, and there are a plurality of micro units (domains) having the cholesteric structure. A retardation layer is provided.

  According to the present invention, since the retardation layer includes a plurality of micro units (domains) having the cholesteric structure, the retardation layer has a thickness distribution of ± 5% for manufacturing reasons, for example. Even when the phase difference optical element is arranged between the liquid crystal cell and the polarizing plate, the domain is very small, so that a bright and dark pattern is not generated in the display image, and deterioration of display quality is effectively suppressed. Can do.

  In the above-described invention, it is preferable that the selective reflection wavelength of the selective reflection light having the cholesteric structure is shorter than the wavelength of the incident light. When the selective reflection wavelength of the selective reflected light is set to be shorter than the wavelength of the incident light, the minute unit (domain) is smaller than the case where the selective reflection wavelength of the selective reflected light is set to be longer than the wavelength of the incident light. This is because it becomes considerably small and the bright and dark pattern as described above is not observed.

  In the above-described invention, the maximum major axis of the inscribed ellipse on the surface of the minute unit (domain) is preferably 40 μm or less. As a result, even when the retardation layer is disposed between the liquid crystal cell and the polarizing plate, it is possible to effectively prevent the display quality from being deteriorated without recognizing a bright and dark pattern in the display image. Because it can.

  At this time, it is more preferable that the maximum major axis of the inscribed ellipse on the surface of the minute unit (domain) is not more than the wavelength of the incident light. Thereby, when the said phase difference layer is arrange | positioned between a liquid crystal cell and a polarizing plate, it can avoid generating the bright and dark pattern resulting from the magnitude | size of a domain. The reason is that it is difficult to identify the size of the domain by light because the size of the domain is not more than the wavelength of the incident light.

  In the above-described invention, it is preferable that the distance of the alignment defect (disclination) between the minute units (domains) is not more than the wavelength of the incident light. Thereby, when the said phase difference layer is arrange | positioned between a liquid crystal cell and a polarizing plate, it can avoid generating the scattering resulting from disclination. This is because the disclination is less than the wavelength of the incident light and it is difficult to identify the disclination with light.

  Furthermore, in the above-described invention, it is preferable that the haze value when the retardation layer is measured according to JIS-K7105 is 2% or less. Thereby, even when the retardation layer is disposed between the liquid crystal cell and the polarizing plate, a decrease in contrast can be effectively suppressed.

  In the above-described invention, the leakage light when measured from the normal direction with the polarizing plate in the crossed Nicol state is 0%, and the leakage light when measured from the normal direction with the polarizing plate in the parallel state is 100%. The maximum value of leakage light measured in the range of 380 nm to 700 nm when the retardation layer is sandwiched between the polarizing plate crossed Nicol states is preferably 1% or less. Thereby, even when the retardation layer is disposed between the liquid crystal cell and the polarizing plate, a decrease in contrast can be effectively suppressed.

  Furthermore, in the above-described invention, it is preferable that the helical axis of the minute unit (domain) having the cholesteric structure does not substantially coincide with the normal line standing on the surface of the retardation layer. Especially, it is preferable that the average value of the angle formed by the helical axis of the minute unit (domain) having the cholesteric structure and the normal line standing on the surface of the retardation layer is substantially 0 degree. Thereby, even when the retardation layer is disposed between the liquid crystal cell and the polarizing plate, it is possible to effectively prevent the display quality from being deteriorated without generating a bright and dark pattern on the display image. Because it can.

  In the above-described invention, a laminated retardation layer may be formed by further laminating a second retardation layer on the main surface of the retardation layer. This is because it is possible to realize a phase difference amount that cannot be expressed in a single layer.

  Furthermore, in the above-described invention, it is preferable that the selective reflection light of the retardation layer and the second retardation layer both have substantially the same selective reflection wavelength. This is because it is possible to suppress deterioration of the optical characteristics when mass transfer occurs between the two retardation layers.

  In the above-described invention, the retardation layer preferably has a molecular structure in which chiral nematic liquid crystal is three-dimensionally cross-linked or a molecular state in which polymer cholesteric liquid crystal is in a glass state. This is because the molecular structure of the cholesteric regularity can be kept stable.

  Furthermore, the present invention provides a retardation optical element comprising a transparent substrate and the above-described retardation layer formed on the surface of the transparent substrate.

  At this time, an alignment film is preferably formed between the transparent base material and the retardation layer. This is because the molecular structure of cholesteric regularity can be kept mechanically stable.

  Furthermore, it is preferable that a color filter layer is formed between the transparent substrate and the retardation layer. Thereby, the surface reflection between the transparent substrate, the color filter layer, and the retardation layer can be prevented, and the transmittance can be further increased.

  The present invention also provides a polarizing element characterized in that a polarizing layer is disposed on the surface of the transparent substrate of the retardation optical element described above on the side where the retardation layer is not formed. According to the present invention, since the polarizing layer is provided on at least one surface of the retardation optical element, reflection on the surface of the retardation optical element is extremely reduced, and the occurrence of bright and dark patterns is effectively suppressed and contrast is increased. Can be improved, and the deterioration of display quality can be effectively suppressed.

  Furthermore, the present invention provides a liquid crystal cell, a pair of polarizing plates disposed so as to sandwich the liquid crystal cell, and the phase difference described above disposed between at least one of the liquid crystal cell and the pair of polarizing plates. A liquid crystal display device including an optical element is provided. Thereby, the occurrence of bright and dark patterns in the liquid crystal display device can be suppressed and the contrast can be improved, and the deterioration of display quality can be suppressed.

  The present invention also provides an alignment film forming step of forming an alignment film on a transparent substrate, and a retardation layer forming coating comprising a liquid crystal material having a cholesteric regularity for forming a cholesteric liquid crystal structure on the alignment film An application process for applying the liquid without rubbing the alignment film, an alignment process for applying an alignment process to the retardation layer formed on the alignment film by the application process, and the alignment process. And a fixing step of fixing the cholesteric liquid crystal structure expressed in a liquid crystal phase in the retardation layer by solidifying the aligned retardation layer by solidification treatment. A manufacturing method is provided.

  According to the present invention, since the retardation layer is formed on the alignment film that is not subjected to the rubbing treatment, it is possible to obtain a retardation layer having a small minute unit (domain), such as a liquid crystal display device. When used in the above, a retardation optical element having good display quality can be produced.

  Even when the retardation layer of the present invention is disposed between the liquid crystal cell and the polarizing plate, it does not generate a bright and dark pattern on the display image, and effectively suppresses deterioration in display quality. There is an effect that can be done.

  The present invention includes a retardation layer, a retardation optical element using the retardation layer, and a liquid crystal display device. Each will be described in detail below.

A. Retardation Layer First, the retardation layer of the present invention will be described. The retardation layer of the present invention can be divided into six embodiments. Each embodiment will be described below.

1. First Embodiment A first embodiment of the retardation layer of the present invention is a retardation layer that functions as a negative C plate fixed in a range in which the helical pitch of the cholesteric structure is 1 pitch or more, and the cholesteric structure It is characterized in that a plurality of minute units (domains) having s are present. Further, it is better if the selective reflection wavelength of the selective reflection light of the cholesteric structure is shorter than the wavelength of the main incident light.

  According to this embodiment, since the retardation layer includes a plurality of minute units (domains) having the cholesteric structure, for example, the retardation layer having a thickness distribution of ± 5% for manufacturing reasons is provided. Even when it is arranged between the liquid crystal cell and the polarizing plate, since the domain is very small, a bright and dark pattern is not generated in the display image, and deterioration of display quality can be effectively suppressed. The reason is that if the selective reflection wavelength of the selective reflection light is set to be shorter than the wavelength of the incident light, the minute unit (domain) is set so that the selective reflection wavelength of the selective reflection light is longer than the wavelength of the incident light. For example, the uneven pattern as seen in FIG. 2 of Y. Iimura et al., SID '94 Digest, 915 (1994) described above is not observed, and the bright and dark pattern is not generated. It is.

  Although there is currently no clear evidence as to why the above phenomenon occurs, it can be considered as follows. In other words, when the selective reflection wavelength of the cholesteric structure is set to the long wavelength side, the size of the minute unit (domain) formed on the alignment film not subjected to the rubbing process is relatively large and can be visually observed. Yes, white turbidity occurs due to the scattering phenomenon. On the other hand, when the selective reflection wavelength of the cholesteric structure is set on the short wavelength side, the size of the minute unit (domain) formed on the alignment film not subjected to the rubbing process is relatively small and cannot be visually observed. And no scattering phenomenon occurs.

Hereinafter, the retardation layer of this embodiment will be described in detail with reference to the drawings.
FIG. 1 is a schematic view showing a cross section of an example of the retardation layer of the present embodiment. As shown in FIG. 1, the retardation layer 10 of this embodiment is composed of a large number of micro units (domains) 12 having a cholesteric regular molecular structure (helical structure).

  Here, a minute unit (domain) having a molecular structure of cholesteric regularity is based on a physical molecular arrangement (planar arrangement) of liquid crystal molecules, and an optical rotation component (circularly polarized light component) in one direction, and the reverse direction. The optical rotation selection characteristics (polarization separation characteristics) for separating the optical rotation components of the optical rotation components. Such a phenomenon is known as circular dichroism, and when a rotation direction in the helical structure of liquid crystal molecules is appropriately selected, a circularly polarized component having the same optical rotation direction as that of the rotation direction is selectively reflected.

In this case, the maximum optical polarization polarization light scattering (selective reflection peak) occurs at the wavelength λ ₀ of the following equation (1).
λ ₀ = nav · p (1)
Here, p is a helical pitch in the helical structure of liquid crystal molecules, and nav is an average refractive index in a plane perpendicular to the helical axis.

On the other hand, the wavelength bandwidth Δλ of the selectively reflected light at this time is expressed by the following equation (2).
Δλ = Δn · p (2)
Here, Δn is a birefringence value expressed as a difference between the refractive index for ordinary light and the refractive index for extraordinary light.

That is, in such a small unit (domain) having a cholesteric regular molecular structure, the incident non-polarized light is in the range of the wavelength bandwidth Δλ centered on the selective reflection wavelength λ ₀ in accordance with the polarization separation characteristics as described above. One of the right-handed and left-handed circularly polarized light components is reflected, and the other circularly polarized light component and light in a wavelength region other than the selective reflection wavelength (unpolarized light) are transmitted. The reflected right-handed or left-handed circularly polarized light component is reflected without reversing the turning direction, unlike normal reflection.

  In this embodiment, the minute unit (domain) is a spiral of the molecular structure so that the selective reflection wavelength of the selectively reflected light caused by the molecular structure is shorter than the wavelength of the incident light incident on the minute unit (domain). The pitch is adjusted.

  In this embodiment, it is preferable that the selective reflection wavelength of the selective reflection light is shorter than the wavelength of incident light. In addition, since the incident light is generally visible light, the selective reflection wavelength is preferably shorter than the wavelength of visible light, specifically, preferably 380 nm or less, particularly 280 nm or less. It is preferable. The lower limit is not particularly limited, but is usually 150 nm or more.

  Thus, there are the following three reasons for adjusting the selective reflection wavelength of the selective reflection light so as to be smaller than the wavelength of incident light, particularly visible light.

  The first reason is that the selective reflection wavelength is made smaller or larger than the wavelength of the incident light in order to prevent the incident light from being reflected by the selective reflection due to the molecular structure of cholesteric regularity. It is necessary. Therefore, when the incident light incident on the minute unit (domain) is visible light (wavelength bandwidth: 380 nm to 780 nm), it is preferable to remove the bandwidth in the above range, and the selective reflection wavelength is smaller than 380 nm or 780 nm. Larger is preferred.

  The second reason is that the selective reflection wavelength is incident in order to cause the micro unit (domain) to act as a negative C plate (act as a retardation layer) and not to cause the optical rotation action like TN liquid crystal. It is because it is preferable to make it smaller than the wavelength of light. When the incident light incident on the minute unit (domain) is visible light, the selective reflection wavelength is preferably 380 nm or less as described above.

  The third reason is that if the selective reflection wavelength is set to be shorter than the wavelength of the incident light, the minute unit (domain) is set so that the selective reflection wavelength of the selective reflected light is longer than the wavelength of the incident light. This is because it becomes considerably smaller than that, and the bright and dark pattern is not observed. Although there is currently no clear evidence as to why the above phenomenon occurs, it can be considered as follows.

  That is, when the selective reflection wavelength of the cholesteric structure is set to the long wavelength side, the size of the minute unit (domain) formed on the alignment film not subjected to the rubbing process is relatively large and is visually observable. Thus, white turbidity due to the scattering phenomenon occurs. On the other hand, when the selective reflection wavelength of the cholesteric structure is set on the short wavelength side, the size of the minute unit (domain) formed on the alignment film not subjected to the rubbing process is relatively small and cannot be visually observed. Then, the scattering phenomenon does not occur.

  In the present embodiment, as shown in FIG. 1, the plurality of minute units (domains) 12 existing in the retardation layer 10 do not use an optical rotation action like TN liquid crystal. The film thickness is adjusted to be 1 pitch or more, preferably 5 pitch or more. The specific number of pitches can be calculated from the desired film thickness (see K. Kashima et al., IDW '02, 413 (2002)).

  In the present embodiment, the twist angles in the cholesteric structure of a plurality of minute units (domains) existing in the retardation layer may not substantially coincide.

  For example, as shown in FIG. 2, when the retardation layer 10 has a film thickness distribution, the twist angles of the minute units (domains) 12 do not match. Such a situation is a fatal defect in the case of a TN mode liquid crystal using an optical rotation action. However, in the present invention, the purpose is not to use the optical rotation action but to shift the phase of polarization. This is because only a slight shift in the phase shift amount causes no major problem.

  As shown in FIG. 1, the retardation layer 10 has two main surfaces (wider surfaces) 12 </ b> A and 12 </ b> B facing each other and arranged so as to be orthogonal to the thickness direction. In this embodiment, among the two main surfaces 12A and 12B of the retardation layer 10, the direction of the director Da of the liquid crystal molecules of the plurality of micro units (domains) 12 on one surface 12A is substantially the same. Preferably, the direction of the director Db of the liquid crystal molecules of the micro units (domains) 12 on the other surface 12B is not substantially coincident. In the present embodiment, the director of the liquid crystal molecules on the surface of each minute unit (domain) 12 is preferably substantially random.

  When there is a film thickness distribution in the above retardation layer, if you try to create a monodomain by matching the directors of all the liquid crystal molecules on the surface of the retardation layer, multiple large island domains (domain surface that cannot be monodomain) The maximum major axis of the inscribed ellipse is visually recognized as a bright and dark pattern. On the other hand, in the present invention, a plurality of minute units (domains) exist in the retardation layer, and the directors of the liquid crystal molecules on the surfaces of the plurality of minute units (domains) do not coincide with each other. Even when there is a film thickness distribution, there is an advantage that it is possible to suppress deterioration in display quality without causing bright and dark patterns.

  If a monodomain is to be formed, an alignment film subjected to rubbing treatment may be used. If a plurality of minute units (domains) are to be formed, an alignment film not subjected to rubbing treatment may be used. These are disclosed in JP-A-7-175065, R. Holding et al., SID '93 Digest, 622 (1993), Y. Iimura et al., SID '94 Digest, 915 (1994). Therefore, although explanation here is omitted, in short, the alignment film not subjected to the rubbing treatment has a horizontal alignment regulating force for the liquid crystal molecules, but the direction of the force is random in the plane. This is due to the fact that

  Here, whether or not the directions of the directors of the liquid crystal molecules on the surface of the minute unit (domain) substantially coincide can be determined by observing the cross section of the retardation layer with a transmission electron microscope. it can. Specifically, for example, as shown in FIG. 3, when a cross-section of the retardation layer 10 solidified with a cholesteric regular molecular structure is observed with a transmission electron microscope, a molecular spiral peculiar to the cholesteric regular molecular structure is observed. A bright and dark pattern corresponding to the pitch of is observed. Therefore, at this time, if the density of light and darkness varies along the surface on each surface (for example, the surface 12A), it can be determined that the directors of the liquid crystal molecules in the surface do not substantially match. it can.

  The term “liquid crystal molecule” is generally used to mean a molecule having both fluidity of liquid and anisotropy of crystal. In this specification, the term “liquid crystal molecule” has fluidity. For the sake of convenience, the term “liquid crystal molecule” is also used for molecules that have been solidified while maintaining the anisotropy. As a method of solidifying while maintaining the anisotropy that the molecule has in the fluid state, for example, a liquid crystal molecule (polymerizable monomer molecule or polymerizable oligomer molecule) having a polymerizable group is crosslinked. And a method of cooling a polymer liquid crystal (liquid crystal polymer) to a glass transition temperature or lower.

  Further, the retardation layer having a cholesteric regular molecular structure of the present embodiment has anisotropy, that is, birefringence, and the refractive index in the thickness direction and the refractive index in the plane direction are different. Acts as a negative C plate.

  Here, the retardation layer is classified according to the direction of the optical axis and the magnitude of the refractive index in the optical axis direction with respect to the refractive index in the direction orthogonal to the optical axis. When the direction of the optical axis is along the plane of the retardation layer, the A plate, when the direction of the optical axis is in the normal direction perpendicular to the retardation layer, the C plate, the direction of the optical axis is the normal direction The one tilted from the side is called an O plate. A plate having a refractive index in the direction of the optical axis larger than the refractive index in the direction perpendicular to the optical axis is called a positive plate, and a plate having a refractive index in the direction of the optical axis smaller than that in the direction perpendicular to the optical axis is called a negative plate. . Therefore, there is a distinction between a positive A plate, a negative A plate, a positive C plate, a negative C plate, a positive O plate, and a negative O plate. In this embodiment, the retardation layer functions as a negative C plate. In the negative C plate, the direction of the optical axis is in the normal direction perpendicular to the retardation layer, and the refractive index in the optical axis direction is smaller than the refractive index in the direction perpendicular to the optical axis.

  That is, in the three-dimensional orthogonal coordinate system, assuming that the refractive index in the surface direction of the retardation layer is Nx, Ny, and the refractive index in the thickness direction is Nz, the relationship is Nz <Nx = Ny. Therefore, for example, as shown in FIG. 1, when linearly polarized light is incident on the retardation layer 10, the linearly polarized light incident in the direction of the normal line 12C of the retardation layer 10 is transmitted without being phase-shifted. The linearly polarized light incident in the direction inclined from the normal line 12C of the phase difference layer 12 generates a phase difference when passing through the phase difference layer 10 and becomes elliptically polarized light. Conversely, when elliptically polarized light is incident in a direction inclined from the normal line 12C of the retardation layer 10, the incident elliptically polarized light can be converted into linearly polarized light.

  In each minute unit (domain) 12 of the retardation layer 10, the directions of the directors Da and Db of the liquid crystal molecules in the entire range of the main surfaces 12A and 12B substantially coincide.

  Here, 12D in FIG. 1 indicates a boundary between each minute unit (domain) 12, and 12E in FIG. 1 indicates a helical axis of each minute unit (domain) 12.

  In the present embodiment, the size of the surface of the minute unit (domain) is preferably such that it cannot be visually determined. Specifically, the maximum major axis of the inscribed ellipse is 40 μm or less, preferably 20 μm or less, more preferably 10 μm or less, and particularly preferably 5 μm or less. Since the size of the surface of the minute unit (domain) is within the above range, it is impossible to visually distinguish the minute unit (domain), and the bright and dark pattern cannot be captured visually. It is because the malfunction resulting from a pattern can be suppressed.

  Further, the size of the surface of the minute unit (domain) is preferably not more than the incident wavelength, and particularly preferably not more than the wavelength of visible light, that is, not more than 380 nm. In this case as well, the fact that the size of the surface of the minute unit (domain) is in the above range can suppress the actual occurrence of a bright and dark pattern.

  Thus, when it is desired to reduce the size of the surface of the minute unit (domain), the selective reflection wavelength may be shortened as described above. Specifically, the selective reflection wavelength is preferably 380 nm or less, preferably Should be 280 nm or less.

  As the size of the surface of the minute unit (domain) in this embodiment, an actual measurement value with a polarizing microscope can be used. When the size of the surface of the minute unit (domain) cannot be identified with a polarizing microscope, an analysis method using electrons or the like instead of light such as AFM, SEM, or TEM is used.

  In the present embodiment, it is preferable that the helical axis of each of the plurality of minute units (domains) and the normal line standing on the surface of the retardation layer do not substantially match. For example, as shown in FIG. 1, if the helical axes 12E of a plurality of minute units (domains) 12 and the normal line 12C standing on the surface of the retardation layer are not substantially coincident, a plurality of minute units are obtained. This is because it can be further reduced. This is because it is possible to prevent a plurality of adjacent minute units (domains) from being combined to form a larger domain.

  As described above, in order to prevent the helical axes of a plurality of minute units (domains) and the normal line standing on the surface of the retardation layer from being substantially coincident, when the retardation layer is manufactured, A method such as applying wind to the surface of the phase difference layer may be used.

  Furthermore, it is preferable that an average value of angles formed between the helical axes of the plurality of minute units (domains) having a cholesteric structure and a normal line standing on the surface of the retardation layer is substantially 0 degree. If the average value of the angle formed between the helical axis of each of the plurality of minute units (domains) having a cholesteric structure and the normal line standing on the surface of the retardation layer is substantially 0 degree, the liquid crystal cell, the polarizing plate, This is because even when the retardation layer is disposed between the two, the bright and dark pattern is not generated in the display image, and the deterioration of the display quality can be further effectively suppressed.

  In the present embodiment, the distance between orientation defects (disclinations) between minute units (domains) is preferably equal to or less than the wavelength of incident light. Specifically, it is preferably not more than the wavelength of visible light, that is, not more than 380 nm, and more preferably not more than 280 nm. This is because scattering due to disclination does not occur when the distance between orientation defects (disclination) between minute units (domains) is within the above range.

  As described above, when it is desired to reduce the distance of alignment defects (disclinations) between minute units (domains) as described above, the selective reflection wavelength may be shortened as described above. The reflection wavelength may be 380 nm or less, preferably 280 nm or less.

  Moreover, it is preferable that the haze value at the time of measuring the said phase difference layer based on JIS-K7105 is 10% or less, and it is especially preferable that it is 2% or less, especially 1% or less. When the haze value is in the above-described range, scattering due to disclination between minute units (domains) does not occur, and even when the retardation layer is disposed between the liquid crystal cell and the polarizing plate, the contrast is reduced. It is because it can suppress effectively.

  By suppressing scattering due to disclination between the micro units (domains), the haze value when measured according to JIS-K7105 can be suppressed to 10% or less, particularly 2% or less, and further 1% or less. However, as described above, the selective reflection wavelength may be shortened as described above. Specifically, the selective reflection wavelength may be 380 nm or less, preferably 280 nm or less.

  In this embodiment, when the leakage light when measured from the normal direction in the crossed Nicol state is 0%, the leakage light when measured from the normal direction in the polarization plate parallel state is 100%, The maximum value of leakage light measured in the range of 380 nm to 700 nm when measured by sandwiching the retardation layer between polarizing plates in a crossed Nicol state is preferably 1% or less, and more preferably 0.1% or less. It is preferable. This is because, when the maximum value of the leakage light is in the above-described range, even when the retardation layer is disposed between the liquid crystal cell and the polarizing plate, a decrease in contrast can be effectively suppressed.

  By reducing the haze value, the maximum value of the leaked light can be suppressed to 1% or less, and further to 0.1% or less. For that purpose, the selective reflection wavelength should be made shorter. Specifically, the selective reflection wavelength may be 380 nm or less, preferably 280 nm or less.

  In addition, as a material used for the retardation layer, a liquid crystal material exhibiting a cholesteric liquid crystal phase can be used. Such a liquid crystal material is not particularly limited as long as it has cholesteric regularity, and a polymerizable liquid crystal material (polymerizable monomer or polymerizable oligomer) or liquid crystal polymer can be used.

  In this embodiment, among the above materials, it is preferable to use a polymerizable monomer or polymerizable oligomer that can be three-dimensionally cross-linked. This is because the liquid crystal molecules can be optically fixed in the state of cholesteric liquid crystal, and can be made into a film-like film that is easy to handle as an optical film and stable at room temperature. The term “three-dimensional crosslinking” means that polymerizable monomer molecules or polymerizable oligomer molecules are three-dimensionally polymerized to form a network (network) structure.

  Alternatively, a liquid crystal polymer (polymer cholesteric liquid crystal) that can be solidified into a glass state by cooling can be used. Similarly, in this case, the liquid crystal molecules can be optically fixed in the state of cholesteric liquid crystal, and it is easy to handle as an optical film, and a film-like film stable at room temperature can be obtained. is there.

  Examples of the three-dimensionally crosslinkable polymerizable monomer are disclosed in JP-A-7-258638, JP-A-11-513019, JP-A-9-506088, and JP-A-10-508882. Mixtures of liquid crystalline monomers and chiral compounds can be used. For example, a chiral nematic liquid crystal (cholesteric liquid crystal) can be obtained by adding a chiral agent to a liquid crystalline monomer exhibiting a nematic liquid crystal phase. A method for producing a cholesteric thin film is also described in JP-A Nos. 2001-5684 and 2001-10045. As such a liquid crystalline monomer, for example, compounds represented by the general formulas (1) to (11) can be used. Here, in the case of the liquid crystalline monomer represented by the general formula (11), X is preferably 2 to 5 (integer).

Moreover, as said chiral agent, it is preferable to use the compound shown, for example in General formula (12)-(14). In the case of the chiral agent represented by the general formulas (12) and (13), X is preferably 2 to 12 (integer), and in the case of the chiral agent represented by the general formula (14), X is It is preferable that it is 2-5 (integer). Here, in the general formula (12), R ⁴ represents hydrogen or a methyl group.

  Examples of the three-dimensionally crosslinkable polymerizable oligomer include cyclic organopolysiloxane compounds having a cholesteric phase as disclosed in JP-A-57-165480.

  Further, the liquid crystal polymer includes a polymer in which a mesogen group exhibiting liquid crystal is introduced into the main chain, a side chain, or both positions of the main chain and the side chain, a polymer cholesteric liquid crystal in which a cholesteryl group is introduced into the side chain, A liquid crystalline polymer as disclosed in Kaihei 9-133810, a liquid crystalline polymer as disclosed in JP-A-11-293252, or the like can be used.

  The retardation layer of the present embodiment is not limited to a single layer, and a second retardation layer and, if necessary, a plurality of retardation layers are laminated on the main surface of the retardation layer. It may be a laminated retardation layer formed in the above manner.

  In this way, by making the retardation layer a laminate of a plurality of retardation layers, various optical compensations can be realized by using each retardation layer having different birefringence values, helical pitches, and the like. .

  In the multilayer retardation layer having such a multilayer structure, the two main surfaces facing each other located on the outermost surface of each retardation layer are substantially the directors of the liquid crystal molecules in each minute unit (domain). However, the directors of each minute unit (domain) do not substantially match.

  In addition, it is preferable that the selective reflection light of the retardation layer and the second retardation layer both have substantially the same selective reflection wavelength, and the liquid crystalline material used for forming each retardation layer is It is preferable that they are substantially the same component. Thereby, almost no mass transfer between the retardation layer and the second retardation layer can be eliminated, and a laminated retardation layer as a uniform laminate of retardation layers can be produced. .

2. Second Embodiment A second embodiment of the retardation layer of the present invention is a retardation layer that functions as a negative C plate having a fixed cholesteric structure, and includes at least one of the two main surfaces of the retardation layer. One of the surfaces is characterized in that the directors of the liquid crystal molecules do not substantially coincide within an interval of 100 μm, preferably within an interval of 10 μm.

  Moreover, it is preferable that among the two main surfaces of the retardation layer, the other surface has liquid crystal molecule directors that do not substantially coincide within a predetermined interval.

  At this time, the retardation layer includes a plurality of minute units (domains) having the cholesteric structure, and the directors of the liquid crystal molecules substantially coincide within the minute units (domains). It is preferable that the minute units (domains) are close to each other.

  Furthermore, it is better if the selective reflection wavelength of the selective reflection light of the cholesteric structure is shorter than the wavelength of the incident light.

  According to the present embodiment, since the director of the liquid crystal molecules does not substantially match within a predetermined interval on the main surface of the retardation layer, the film thickness distribution is, for example, for manufacturing reasons. Even when a retardation layer of ± 5% is placed between the liquid crystal cell and the polarizing plate, liquid crystal molecules with different directors exist within a minute interval, so that a bright and dark pattern is generated in the display image. Therefore, it is possible to effectively suppress the deterioration of display quality. The reason is that liquid crystal molecules with different directors exist within a minute interval, so that the bright and dark pattern cannot be identified by the human eye, and the selective reflection wavelength of the selective reflection light of the cholesteric structure is shorter than the wavelength of the incident light. If so, the minute unit (domain) is considerably smaller than the case where the selective reflection wavelength of the selective reflected light is set to be longer than the wavelength of the incident light, for example, Y. Iimura et al., Described above. This is because the uneven pattern as seen in FIG. 2 of SID '94 Digest, 915 (1994) is not observed, and the bright and dark pattern is not generated.

  In addition, it can be confirmed by observing the cross section of the retardation layer with a transmission electron microscope that the directors of the liquid crystal molecules do not substantially coincide with each other, as in the first embodiment. it can.

  In the present embodiment, the fact that the directors of the liquid crystal molecules do not substantially coincide means that the directors of the liquid crystal molecules are different within a range of 10 degrees to 170 degrees.

  Since the other points of the retardation layer are the same as those described in the first embodiment, description thereof is omitted here.

3. Third Embodiment A third embodiment of the retardation layer of the present invention is a retardation layer that functions as a negative C plate with a fixed cholesteric structure, and includes at least one of the two main surfaces of the retardation layer. One of the surfaces is characterized in that the directors of the liquid crystal molecules do not substantially coincide within a region having a radius of 50 μm, preferably within a region having a radius of 5 μm.

  Moreover, it is preferable that among the two main surfaces of the retardation layer, the other surface has a liquid crystal molecule director that does not substantially match within a predetermined radius.

  At this time, the retardation layer includes a plurality of minute units (domains) having the cholesteric structure, and the directors of the liquid crystal molecules substantially coincide within the minute units (domains). It is preferable that the minute units (domains) are close to each other.

  Furthermore, it is better if the selective reflection wavelength of the selective reflection light of the cholesteric structure is shorter than the wavelength of the incident light.

  According to this embodiment, since there is a liquid crystal molecule director that does not substantially match within a region of a predetermined radius on the main surface of the retardation layer, the film thickness is, for example, for manufacturing reasons. Even when a phase difference layer with a distribution of ± 5% is placed between the liquid crystal cell and the polarizing plate, liquid crystal molecules with different directors exist in a minute area, resulting in a bright and dark pattern on the display image. The display quality can be effectively suppressed from being lowered. The reason for this is that liquid crystal molecules with different directors exist in a minute area, so that the bright and dark pattern cannot be identified by the human eye, and the selective reflection wavelength of the selective reflection light of the cholesteric structure is shorter than the wavelength of the incident light. If so, the minute unit (domain) is considerably smaller than the case where the selective reflection wavelength of the selective reflected light is set to be longer than the wavelength of the incident light, for example, Y. Iimura et al., Described above. This is because the uneven pattern as seen in FIG. 2 of SID '94 Digest, 915 (1994) is not observed, and the bright and dark pattern is not generated.

  In addition, it can be confirmed by observing the cross section of the retardation layer with a transmission electron microscope that the directors of the liquid crystal molecules do not substantially coincide with each other, as in the first embodiment. it can.

  Further, the fact that the directors of the liquid crystal molecules do not substantially coincide has the same meaning as described in the section of the second embodiment.

  In this embodiment, it is preferable that 10% or more of the liquid crystal molecule directors do not substantially coincide with each other in a predetermined radius region, and more preferably 50% or more. This is because, if the liquid crystal molecule directors that do not substantially coincide with each other are present in the above range, it is possible to reliably make it difficult to see the bright and dark pattern generated in the display image.

  Since the other points of the retardation layer are the same as those described in the first embodiment, description thereof is omitted here.

4). Fourth Embodiment A fourth embodiment of the retardation layer of the present invention is a retardation layer that functions as a negative C plate with a fixed cholesteric structure, and is within a distance of 100 μm on the main surface of the retardation layer. Preferably, there are those in which the twist angles in the cholesteric structure do not substantially coincide with each other at a position within an interval of 10 μm.

  At this time, the retardation layer includes a plurality of minute units (domains) having the cholesteric structure, and the twist angles in the cholesteric structure are substantially the same in the minute units (domains). It is preferable that the minute units (domains) are close to each other.

  Furthermore, it is better if the selective reflection wavelength of the selective reflection light of the cholesteric structure is shorter than the wavelength of the incident light.

  According to this embodiment, since there exists a film in which the twist angles in the cholesteric structure do not substantially coincide with each other at a position within a predetermined interval on the main surface of the retardation layer, for example, the film for manufacturing reasons. Even when a retardation layer with a thickness distribution of ± 5% is placed between the liquid crystal cell and the polarizing plate, there are light and dark patterns in the displayed image because there are those with different twist angles within a minute interval. The display quality can be effectively suppressed from being lowered. The reason for this is that since there are those with different twist angles within a minute interval, the bright and dark pattern cannot be identified by the human eye, and the selective reflection wavelength of the selective reflection light of the cholesteric structure is shorter than the wavelength of the incident light. In this case, the minute unit (domain) is considerably smaller than the case where the selective reflection wavelength of the selective reflection light is set to be longer than the wavelength of the incident light, for example, Y. Iimura et al., SID described above. This is because the uneven pattern as seen in FIG. 2 of '94 Digest, 915 (1994) is not observed, and a bright and dark pattern is not generated.

  Here, it can be confirmed by observing the cross section of the retardation layer with a transmission electron microscope that the twist angles in the cholesteric structure do not substantially coincide with each other. Specifically, for example, as shown in FIG. 4, when a cross-section of the retardation layer 10 solidified with a cholesteric regular molecular structure is observed with a transmission electron microscope, a molecular spiral peculiar to the cholesteric regular molecular structure is observed. A bright and dark pattern corresponding to the pitch of is observed. Therefore, if there are those having different pitches, it can be determined that there are those in which the twist angles in the cholesteric structure do not substantially coincide. In FIG. 4, 12 </ b> A and 12 </ b> B are main surfaces of the retardation layer 10, and the retardation layer 10 has a film thickness distribution. Reference numeral 13 denotes a TAC film and an alignment film, which are laminated in the order of the TAC film, the alignment film, and the retardation layer.

  Further, in the present embodiment, the fact that the twist angles in the cholesteric structure do not substantially coincide means that the twist angles differ by 10 degrees or more, and among them, it is preferable that they differ by 90 degrees or more.

  Since the other points of the retardation layer are the same as those described in the first embodiment, description thereof is omitted here.

5. Fifth Embodiment A fifth embodiment of the retardation layer of the present invention is a retardation layer that functions as a negative C plate with a fixed cholesteric structure, and is in a region having a radius of 50 μm on the main surface of the retardation layer. The twist angle in the cholesteric structure does not substantially coincide at a position preferably within a region having a radius of 5 μm.

  At this time, the retardation layer includes a plurality of minute units (domains) having the cholesteric structure, and the twist angles in the cholesteric structure are substantially the same in the minute units (domains). It is preferable that the minute units (domains) are close to each other.

  Furthermore, it is better if the selective reflection wavelength of the selective reflection light of the cholesteric structure is shorter than the wavelength of the incident light.

  According to the present embodiment, since there are those in which the twist angles in the cholesteric structure do not substantially coincide with each other at a position within a predetermined radius region on the main surface of the retardation layer, for example, for manufacturing reasons Even when a retardation layer with a film thickness distribution of ± 5% is placed between the liquid crystal cell and the polarizing plate, there are things with different twist angles in a small area, so the display image has a light and dark pattern. The display quality can be effectively prevented from being lowered. The reason for this is that there are things with different twist angles in a minute region, so that the bright and dark pattern cannot be identified by the human eye, and the selective reflection wavelength of the selective reflection light of the cholesteric structure is shorter than the wavelength of the incident light. In this case, the minute unit (domain) is considerably smaller than the case where the selective reflection wavelength of the selective reflection light is set to be longer than the wavelength of the incident light, for example, Y. Iimura et al., SID described above. This is because the uneven pattern as seen in FIG. 2 of '94 Digest, 915 (1994) is not observed, and a bright and dark pattern is not generated.

  Here, it is confirmed by observing the cross-section of the retardation layer with a transmission electron microscope that the twist angle in the cholesteric structure does not substantially match, as in the fourth embodiment. Can do.

  In addition, the fact that the twist angles in the cholesteric structure do not substantially coincide has the same meaning as described in the fourth embodiment.

  In the present embodiment, it is preferable that 10% or more of the cholesteric structures in which the twist angles do not substantially coincide exist within a predetermined radius region, and more preferably 50% or more. This is because it is possible to surely make it difficult to see the bright and dark pattern generated in the display image if the twist angle in the cholesteric structure does not substantially match in the above range.

  Since the other points of the retardation layer are the same as those described in the first embodiment, description thereof is omitted here.

6). Sixth Embodiment A sixth embodiment of the retardation layer of the present invention is a retardation layer that functions as a negative C plate with a fixed cholesteric structure, and includes a cross-section including a normal line standing on the surface of the retardation layer. In the region having a radius of 50 μm, preferably in the region having a radius of 5 μm, the angle formed by the normal line and the helical axis of the helical axis structure region having the cholesteric structure is an acute angle clockwise with respect to the normal direction. It has the helical axis structure area and the helical axis structure area having an acute angle counterclockwise with respect to the normal direction.

  Here, the helical axis structure region in this embodiment is a cholesteric liquid crystal block structure H having a helical axis 12E in a substantially constant direction in the cholesteric structure, for example, as shown in FIG. It shall mean a thing substantially 1 pitch or more.

  Further, for example, as illustrated in FIG. 5, the retardation layer 10 includes a helical axis structure region H in which a helical axis 12 </ b> E forms an acute angle α in a clockwise direction with respect to a normal line 12 </ b> C of the retardation layer 10, and a helical axis. 12E has a helical axis structure region H that forms an acute angle β in the counterclockwise direction with respect to the normal line 12E of the retardation layer 10.

  At this time, the retardation layer includes a plurality of minute units (domains) having the cholesteric structure, and the angles of the helical axes of the helical axis structure region substantially coincide with each other in the minute units (domains). It is preferable that such minute units (domains) are close to each other.

  Furthermore, it is better if the selective reflection wavelength of the selective reflection light of the cholesteric structure is shorter than the wavelength of the incident light.

  According to this embodiment, the retardation layer has a normal radius and a helical axis of a helical axis structure region having a cholesteric structure in a region of a predetermined radius in a cross section including a normal line standing on the surface of the retardation layer. Since the formed angle has a helical axis structure region that is acute clockwise with respect to the normal direction and a helical axis structure region that is acute counterclockwise with respect to the normal direction, a plurality of adjacent It is possible to prevent the helical axis structure regions from being combined into a large domain. Thereby, for example, even when the retardation layer having a film thickness distribution of ± 5% for manufacturing reasons is disposed between the liquid crystal cell and the polarizing plate, a bright and dark pattern is not generated in the display image. A decrease in display quality can be effectively suppressed. The reason is that the retardation layer has a plurality of helical axis structure regions having different helical axis angles in a minute region, so that a bright and dark pattern cannot be identified by the human eye, and the selectively reflected light of the cholesteric structure If the selective reflection wavelength is set to be shorter than the wavelength of the incident light, the minute unit (domain) is considerably smaller than when the selective reflection wavelength of the selective reflection light is set to be longer than the wavelength of the incident light, For example, the uneven pattern as seen in FIG. 2 of Y. Iimura et al., SID '94 Digest, 915 (1994) described above is not observed, and a bright and dark pattern is not generated.

  In this embodiment, the retardation layer may also have a helical axis structure region H having a helical axis 12E in the normal direction of the retardation layer 10 as shown in FIG.

  Here, as the angle formed by the helical axis and the normal line standing on the surface of the retardation layer, specifically, the helical axis structure is in the range of 0 degrees to 30 degrees, particularly in the range of 0 degrees to 10 degrees. It is preferable to have a region. This is because if the angle is too large, wide disclination occurs, and a bright and dark pattern is generated, or the haze value increases to cause light leakage.

  Moreover, it is preferable that the average value of the angle formed by each helical axis of the helical axis structure region and the normal line standing on the surface of the retardation layer is substantially 0 degree. Thereby, even when it arrange | positions between a liquid crystal cell and a polarizing plate, it is because the display image does not produce a bright-dark pattern and can suppress the fall of display quality still more effectively.

  In this embodiment, it is preferable that the helical shaft structure region having the above angle is contained in an area having a predetermined radius of 10% or more, particularly 50% or more. This is because if the helical axis structure region having the above angle is contained within the above range, it is possible to reliably make it difficult to see the bright and dark pattern generated in the display image.

  Note that the angle of the helical axis is determined from the photograph of the cross-sectional structure taken with a transmission electron microscope, as shown in FIG. 6, for example, the helical axis of the helical axis structure region in which the helical pitch of the cholesteric structure is substantially 1 pitch or more. The value obtained by measuring the angle between 12E and the normal line 12C raised on the surface of the retardation layer 10 is referred to. Here, in the transmission electron microscope, for example, as shown in FIG. 6, the spiral pitch of the cholesteric structure is a pitch consisting of a line observed in white and a line observed in black, which is one pitch. . The axial direction of the helical shaft 12E is a perpendicular direction of a line observed in white or a line observed in black. In FIG. 6, reference numeral 13 denotes a TAC film and an alignment film, which are laminated in the order of the TAC film, the alignment film, and the retardation layer.

  Since the other points of the retardation layer are the same as those described in the first embodiment, description thereof is omitted here.

B. Next, the retardation optical element of the present invention will be described. The retardation optical element of the present invention is characterized by having a transparent base material and a retardation layer formed on the surface of the transparent base material and described in the above section “A. Retardation layer”. is there.

  In the retardation optical element of the present invention, it is preferable that an alignment film is formed on the transparent substrate, and the above-described retardation layer is formed on the surface thereof. Hereinafter, these base materials and alignment films will be described. The retardation layer is the same as that described in the section “A. Retardation layer”, and thus the description thereof is omitted here.

1. Transparent substrate The transparent substrate used in the retardation optical element of the present invention is not particularly limited as long as it is a material that transmits visible light, but is preferably formed of a material with few optical defects. Specifically, a polymer film such as a glass substrate or a TAC (cellulose triacetate) film is preferably used.

2. Alignment film Although the alignment film used for this invention is not specifically limited, For example, PI (polyimide), PVA (polyvinyl alcohol), HEC (hydroxyethylcellulose), PC (polycarbonate), PS (polystyrene), PMMA (Polymethyl methacrylate), PE (polyester), PVCi (polyvinyl cinnamate), PVK (polyvinyl carbazole), polysilane containing cinnamoyl, coumarin, chalcone and the like used as known alignment films can be used.

  In the present invention, an alignment film that has not been particularly rubbed is preferably used. This is because minute units (domains) in the retardation layer can be reduced, and the occurrence of bright and dark patterns can be suppressed.

3. Others In the present invention, a color filter layer may be formed between the transparent substrate and the retardation layer. Thereby, the surface reflection between the transparent substrate, the color filter layer, and the retardation layer can be prevented, and the transmittance can be further increased.

C. Next, a method for producing a retardation optical element of the present invention will be described.
The method for producing a retardation optical element of the present invention includes an alignment film forming step for forming an alignment film on a transparent substrate, and a liquid crystal material having a cholesteric regularity for forming a cholesteric liquid crystal structure on the alignment film. An application process for applying the coating liquid for forming the retardation layer without subjecting the alignment film to a rubbing process, and an alignment process process for applying an alignment process to the retardation layer formed on the alignment film by the application process. And a fixing step of fixing the cholesteric liquid crystal structure expressed in the state of the liquid crystal phase in the retardation layer by solidifying the retardation layer oriented by the orientation treatment by solidification. To do.

  Such a method for producing a retardation optical element of the present invention has different modes depending on the type of liquid crystal material used for the retardation layer, the number of retardation layers, and the like. Hereinafter, the method for producing a retardation optical element of the present invention will be described in each embodiment.

1. 1st aspect The 1st aspect of the manufacturing method of the retardation optical element of this invention is an aspect which forms one phase difference layer using a polymerizable monomer or a polymerizable oligomer.

  FIG. 7 is a process diagram showing an example of a method for producing the retardation optical element of this aspect. First, the alignment film 16 is formed on the transparent substrate 14 (FIG. 7A: alignment film forming process), and the polymerizable monomer or the polymerizable oligomer 18 is coated on the alignment film 16 (application process). Alignment is performed by the alignment regulating force of the alignment film 16 (FIG. 7B: alignment processing step). At this time, the coated polymerizable monomer or polymerizable oligomer 18 constitutes a liquid crystal layer. Next, in this orientation state, the polymerizable monomer or polymerizable oligomer 18 is polymerized by the photopolymerization initiator added in advance and the ultraviolet ray 110 irradiated from the outside, or the electron beam 110 is used. When the polymerization is directly initiated and solidified by three-dimensional crosslinking (polymerization), one phase difference layer 10 acting as a negative C plate as described above is formed (FIG. 7C: fixed). Process).

  In this aspect, if the direction of the alignment regulating force of the alignment film is left in a random state without rubbing, the direction of the director of the liquid crystal molecules in contact with the alignment film is substantially random within the contact surface. A plurality of minute units (domains) can be created.

  In addition, the polymerizable monomer or polymerizable oligomer used in this embodiment may be dissolved in a solvent to form a coating solution in order to reduce the viscosity so that coating is easy. In this case, a drying step for evaporating the solvent is required before three-dimensional crosslinking is performed by irradiation with ultraviolet rays or electron beams. Preferably, after performing the coating process for coating the coating liquid, a drying process for evaporating the solvent is performed, and then an alignment process for aligning the liquid crystal is performed.

  Furthermore, when the polymerizable monomer or polymerizable oligomer is formed into a liquid crystal layer at a predetermined temperature, this becomes a nematic state. If an arbitrary chiral agent is added here, a chiral nematic liquid crystal phase (cholesteric liquid crystal phase) is obtained. It becomes. Specifically, a chiral agent may be added to the polymerizable monomer or the polymerizable oligomer in the range of several percent to 20%. In addition, the selective reflection wavelength resulting from the molecular structure of the polymerizable monomer or polymerizable oligomer can be controlled by changing the chiral power by changing the type of the chiral agent or by changing the concentration of the chiral agent. In this embodiment, the selective reflection wavelength is preferably 380 nm or less, preferably 280 nm or less.

  Further, the alignment film used in this embodiment can be formed by a conventionally known method. For example, PI (polyimide), PVA (polyvinyl alcohol), HEC (hydroxyethyl cellulose), PC (polycarbonate), PS (polystyrene), PMMA (polymethyl methacrylate), PE (polyester), PVCi (polyvinyl cinnamate) ), PVK (polyvinylcarbazole), polysilane containing cinnamoyl, coumarin, chalcone, or the like, which can be used as a known alignment film, and a method that does not rub, can be used.

  When a polymer film such as a TAC film is used as the substrate, a barrier layer is provided on the substrate so that the substrate is not attacked by the solvent in the coating solution in which the polymerizable monomer or polymerizable oligomer is dissolved. It is preferable. In this case, the alignment film may also serve as a barrier layer. For example, a water-soluble substance such as PVA may be used as the alignment film.

2. Second Aspect Next, a second aspect of the method for producing a retardation optical element of the present invention will be described. The second aspect of the method for producing a retardation optical element of the present invention is an aspect in which a single retardation layer is formed using a liquid crystal polymer.

  FIG. 8 is a process diagram showing an example of a method of manufacturing a retardation optical element according to this aspect. First, the alignment film 16 is formed on the transparent substrate 14 (FIG. 8A: alignment film forming process), and then the liquid crystal polymer 34 having cholesteric regularity is coated on the alignment film 16 (application process). ), Alignment is performed by the alignment regulating force of the alignment film 16 (FIG. 8B: alignment processing step). At this time, the coated liquid crystal polymer 34 constitutes a liquid crystal layer. Thereafter, when the liquid crystal polymer 34 is cooled to a glass transition temperature (Tg) or lower to be in a glass state, one phase difference layer 10 is formed (FIG. 8C: fixing step).

  The liquid crystal polymer used in this embodiment may be dissolved in a solvent and used as a coating liquid in order to reduce the viscosity so that it can be easily coated. In this case, a drying step for evaporating the solvent is required before cooling. Preferably, after performing the coating process for coating the coating liquid, a drying process for evaporating the solvent is performed, and then an alignment process for aligning the liquid crystal is performed.

  When a polymer film such as a TAC film is used as the base material used in this embodiment, a barrier layer is provided on the base material so that the base material is not attacked by the solvent in the coating solution in which the liquid crystal polymer is dissolved. It is preferable to coat the liquid crystal thereon. In this case, the alignment film may also serve as a barrier layer. For example, a water-soluble substance such as PVA may be used as the alignment film.

  As the liquid crystal polymer used in this embodiment, a cholesteric liquid crystal polymer itself having a chiral ability may be used, or a mixture of a nematic liquid crystal polymer and a cholesteric liquid crystal polymer may be used. is there.

  Such a liquid crystal polymer changes its state depending on the temperature. For example, when the glass transition temperature is 90 ° C. and the isotropic transition temperature is 200 ° C., it exhibits a cholesteric liquid crystal state between 90 ° C. and 200 ° C. If it cools to room temperature, it can be solidified to a glass state with having a cholesteric structure.

  In addition, as a method for adjusting the selective reflection wavelength of incident light due to the cholesteric regular molecular structure of the liquid crystal polymer, when using a cholesteric liquid crystal polymer, the chiral power in the liquid crystal molecule is adjusted by a known method. What should I do? When a mixture of a nematic liquid crystal polymer and a cholesteric liquid crystal polymer is used, the mixing ratio may be adjusted. In this embodiment, the selective reflection wavelength is 380 nm or less, preferably 280 nm or less.

  In addition, if the direction of the alignment regulating force of the alignment film used in this embodiment is random in the entire range on the alignment film, the director of the liquid crystal molecules on one surface of the retardation layer in contact with the alignment film is contacted. A plurality of minute units (domains) can be formed in a substantially random manner in the plane.

3. Third Aspect Next, a third aspect of the method for producing a retardation optical element of the present invention will be described. In the third aspect of the method for producing a retardation optical element of the present invention, a multilayer laminated retardation layer is formed using a polymerizable monomer or a polymerizable oligomer.

  The retardation optical elements in the first and second aspects described above are both methods for producing a single-layer retardation optical element composed of a single retardation layer, but the present invention is limited to this. In addition, a method for manufacturing a retardation optical element having a multilayer laminated retardation layer is also included.

  Specifically, as shown in FIG. 9E, a plurality of retardation layers 42 and 44 having a planar-oriented cholesteric regular molecular structure may be directly laminated in sequence. In the multilayer retardation layer 40 having such a multilayer structure, various optical compensations can be realized by using the retardation layers 42 and 44 having different birefringence values, helical pitches, and the like.

  In the retardation layer 40 having such a multilayer structure, the two main surfaces facing each other located on the outermost surfaces of the retardation layers 42 and 44 are substantially the directors of the liquid crystal molecules in each minute unit (domain). However, the directors of each minute unit (domain) do not substantially match.

  FIG. 9 is a process diagram showing an example of a method for producing the retardation optical element of this aspect. First, an alignment film 16 is formed on the transparent substrate 14 (FIG. 9A: alignment film forming step), and a coating liquid 18 containing a polymerizable monomer or polymerizable oligomer as a liquid crystal molecule on the alignment film 16. Is applied (application process) and is aligned by the alignment regulating force of the alignment film 16 (FIG. 9B: alignment treatment process). Next, in this orientation state, if the polymerizable monomer or polymerizable oligomer 18 is three-dimensionally cross-linked and solidified by irradiation with ultraviolet light 110 using a photopolymerization initiator or single irradiation with an electron beam 110, 1 retardation layer 42 is formed (FIG. 9C: fixing step). Further, the second coating liquid 19 containing another polymerizable monomer molecule or polymerizable oligomer molecule separately prepared on the three-dimensionally crosslinked first retardation layer 42 is directly coated (FIG. 9 ( D)). At this time, as shown in FIG. 10, alignment is performed by the alignment regulating force of the surface of each micro unit (domain) of the three-dimensionally crosslinked retardation layer 42, and in this state, irradiation with ultraviolet rays using a photopolymerization initiator is performed. When solidified by three-dimensional crosslinking by irradiation with 110 or electron beam 110 alone, the second retardation layer 44 is formed (FIG. 9E).

  In the case of a multi-layer structure having three or more layers, the same steps (FIGS. 9D to 9E) as described above are repeated, and the necessary number of retardation layers may be sequentially stacked. It is.

  The polymerizable monomer or polymerizable oligomer used in this embodiment may be dissolved in a solvent to form a coating solution in order to reduce the viscosity so that coating is easy. In this case, three-dimensional crosslinking is performed by irradiation with ultraviolet rays or electron beams. A drying step for evaporating the solvent is necessary before the operation. Preferably, after performing the coating process for coating the coating liquid, a drying process for evaporating the solvent is performed, and then an alignment process for aligning the liquid crystal is performed.

  In addition, if the direction of the alignment regulating force of the alignment film used in this embodiment is made substantially random in the entire range on the alignment film, the director of the liquid crystal molecules that are in contact with the alignment film is substantially within the contact surface. Can be random.

  Moreover, it is preferable that the liquid crystalline materials used for forming the retardation layer and the second retardation layer are substantially the same component. Thereby, almost no mass transfer between the phase difference layer 42 and the second phase difference layer 44 can be eliminated, and a phase difference optical element as a laminated body of uniform phase difference layers can be manufactured. .

4). Fourth Aspect Next, a fourth aspect of the method for producing a retardation optical element of the present invention will be described. In a third aspect of the method for producing a retardation optical element of the present invention, a multilayer laminated retardation layer is formed using a liquid crystal polymer.

  FIG. 11 is a process diagram showing an example of a method for producing the retardation optical element of this aspect. First, the alignment film 16 is formed on the transparent substrate 14 (FIG. 11A: alignment film forming process), and then the alignment film 16 is coated with a liquid crystal polymer 32 having cholesteric regularity (application process), The first retardation layer is aligned by the alignment regulating force of the alignment film 16 (FIG. 11B: alignment processing step), and the liquid crystal polymer 32 is cooled to a glass transition temperature (Tg) or lower to be in a glass state. 42 'is formed (FIG. 11C: immobilization process). Thereafter, another liquid crystal polymer 34 having a cholesteric regularity, which is separately prepared, is directly coated on the first retardation layer 42 ′ to control the alignment of the surface of the first liquid crystal layer 42 ′ in a glass state. The second retardation layer 44 ′ is formed by aligning with a force (FIG. 11D) and cooling the liquid crystal polymer 34 to a glass transition temperature (Tg) or lower to bring it into a glass state (FIG. 11 (FIG. 11 (D)). E)).

  Further, when the retardation layer has a multilayer structure of three or more layers, the same steps as described above (FIGS. 11D to 11E) may be repeated.

  If the direction of the alignment regulating force of the alignment film used in this embodiment is made substantially random in the entire range on the alignment film, the director of the liquid crystal molecules in contact therewith is substantially random within the contact surface. Can be.

D. Next, the polarizing element of the present invention will be described.
In the polarizing element of the present invention, a polarizing layer is disposed on the surface of the transparent substrate of the retardation optical element described in the above section “B. Retardation optical element” on the side where the retardation layer is not formed. It is characterized by being.

  Since such a polarizing element is provided with a polarizing layer on at least one surface of the retardation optical element, reflection on the surface of the retardation optical element is extremely reduced, and the generation of bright and dark patterns is effectively prevented. In addition to being able to suppress, the contrast can be improved, and the deterioration of display quality can be effectively suppressed.

  FIG. 12 is a schematic perspective view showing an example of the polarizing element of the present invention. As shown in FIG. 12, the polarizing element 50 of the present invention has a polarizing layer 51A and a retardation optical element 20 disposed on the light incident side surface of the polarizing layer 51A. In FIG. 12, the phase difference optical element 20 and the polarizing layer 51 </ b> A are drawn apart from each other, but are assumed to be configured to be bonded to each other.

  In this way, if the polarizing layer 51A is bonded to the surface of the transparent substrate of the retardation optical element 20 on which the retardation layer is not formed, reflection on the surface of the retardation optical element 20 is prevented. It can be extremely reduced, the occurrence of bright and dark patterns can be effectively suppressed and the contrast can be improved, and the deterioration of display quality can be effectively suppressed.

  In addition, the polarizing layer used at this time can use what is normally used in the liquid crystal display device. Further, the phase difference optical element used in the present invention is the same as that described in “A. Phase difference optical element” described above, and therefore the description thereof is omitted here.

E. Liquid Crystal Display Device Finally, the liquid crystal display device of the present invention will be described.
The liquid crystal display device of the present invention is the liquid crystal cell, the pair of polarizing plates arranged so as to sandwich the liquid crystal cell, and the liquid crystal cell and at least one of the pair of polarizing plates, The phase difference optical element compensates the polarization state of light in a direction inclined from the normal line of the liquid crystal cell. Thereby, the occurrence of bright and dark patterns in the liquid crystal display device can be suppressed and the contrast can be improved, and the deterioration of display quality can be suppressed.

  FIG. 13 is a perspective view showing an example of the liquid crystal display device of the present invention. As shown in FIG. 13, the liquid crystal display device 60 of the present invention includes an incident side polarizing plate 102 </ b> A, an output side polarizing plate 102 </ b> B, and a liquid crystal cell 104. The polarizing plates 102A and 102B are configured to selectively transmit only linearly polarized light having a vibration surface in a predetermined vibration direction, and crossed Nicols so that the vibration directions are perpendicular to each other. It is arranged to face each other. The liquid crystal cell 104 includes a large number of cells corresponding to pixels, and is disposed between the polarizing plates 102A and 102B.

  Here, in the liquid crystal display device 60, the liquid crystal cell 104 employs a VA method in which nematic liquid crystal having negative dielectric anisotropy is sealed, and linearly polarized light transmitted through the incident-side polarizing plate 102A is When transmitting through the non-driven cell portion of the liquid crystal cell 104, the light is transmitted without being phase-shifted and blocked by the output-side polarizing plate 102B. On the other hand, when the liquid crystal cell 104 is transmitted through the portion of the driven cell, the linearly polarized light is phase-shifted, and an amount of light corresponding to the amount of the phase shift is transmitted through the polarizing plate 102B on the emission side. Emitted. Thereby, by appropriately controlling the driving voltage of the liquid crystal cell 104 for each cell, a desired image can be displayed on the exit side polarizing plate 102B side.

  In the liquid crystal display device 60 having such a configuration, between the liquid crystal cell 104 and the polarizing plate 102B on the emission side (polarizing plate that selectively transmits light in a predetermined polarization state emitted from the liquid crystal cell 104), The phase difference optical element 20 according to the above-described embodiment is arranged, and the phase difference optical element 20 is inclined from the normal line of the liquid crystal cell 104 among the light in a predetermined polarization state emitted from the liquid crystal cell 104. It is possible to compensate for the polarization state of the light emitted to.

  As described above, according to the liquid crystal display device 60 having the above-described configuration, the retardation optical element 20 according to the above-described embodiment is provided between the liquid crystal cell 104 of the liquid crystal display device 60 and the output-side polarizing plate 102B. Since the polarization state of the light emitted from the liquid crystal cell 104 in the direction inclined from the normal line of the liquid crystal cell 104 is compensated for, the liquid crystal cell 104 is effectively improved with respect to the viewing angle dependency problem. It is possible to suppress the occurrence of bright and dark patterns in the display device 60 and improve the contrast, thereby suppressing the deterioration of display quality.

  Note that the liquid crystal display device 60 illustrated in FIG. 13 is a transmission type in which light is transmitted from one side to the other side in the thickness direction, but the present embodiment is not limited to this, and is described above. The retardation optical element 20 according to the embodiment can be used by being incorporated in a reflective liquid crystal display device in the same manner.

  In the liquid crystal display device 60 shown in FIG. 13, the phase difference optical element 20 according to the above-described embodiment is disposed between the liquid crystal cell 104 and the exit-side polarizing plate 102B. The retardation optical element 20 may be disposed between the liquid crystal cell 104 and the polarizing plate 102A on the incident side. Further, the phase difference optical element 20 may be disposed on both sides of the liquid crystal cell 104 (between the liquid crystal cell 104 and the incident side polarizing plate 102A and between the liquid crystal cell 104 and the outgoing side polarizing plate 102B). The number of retardation optical elements arranged between the liquid crystal cell 104 and the incident-side polarizing plate 102A or between the liquid crystal cell 104 and the outgoing-side polarizing plate 102B is not limited to one, and a plurality of retardation optical elements are arranged. Also good.

  In the present invention, the liquid crystal cell 104 is particularly preferably formed of a VA (Vertical Alignment) type liquid crystal layer. This is because it is possible to suppress the occurrence of bright and dark patterns in the liquid crystal display device and improve the contrast, and to further suppress the deterioration of display quality.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

Next, the present invention will be described with reference to examples and comparative examples.
(Example 1)
In Example 1, a single-layer retardation layer was formed on a glass substrate.
A monomer molecule having a polymerizable acrylate at both ends and a spacer between the mesogen in the central part and the acrylate and having a nematic-isotropic transition temperature of 110 ° C. (a molecule as represented by the chemical formula (11) above) A toluene solution in which 90 parts by weight of a compound having a structure and 10 parts by weight of a chiral agent molecule having a polymerizable acrylate at both ends (a compound having a molecular structure represented by the above chemical formula (14)) is dissolved. Got ready. In addition, 5 weight% of photoinitiators (the Ciba Specialty Chemicals make, Irgacure (trademark) 907) were added to the said toluene solution with respect to the said monomer molecule. On the other hand, on a transparent glass substrate, polyimide (Optomer (registered trademark) AL1254, manufactured by JSR Corporation) dissolved in a solvent was spin-coated with a spin coater, dried, and then formed at 200 ° C. (film thickness 0.1 μm) ), But the alignment film was not rubbed.

  Then, such a glass substrate with an alignment film was set on a spin coater, and a toluene solution in which the monomer molecules and the like were dissolved was spin-coated under conditions such that the film thickness was as constant as possible. Next, toluene in the toluene solution was evaporated at 80 ° C.

  Then, the retardation optical element having a single retardation layer is formed by irradiating the coating film with ultraviolet rays, three-dimensionally cross-linking the monomer molecule acrylate with radicals generated from the photopolymerization initiator in the coating film, and polymerizing the polymer film. Produced. The thickness of the coating film at this time was 2 μm ± 1.5%. Moreover, when measured with the spectrophotometer, the center wavelength of the selective reflection wavelength of the coating film was 280 nm. Since the refractive index of the cured liquid crystal molecules was about 1.5, the film thickness per pitch calculated from P = λ / n was about 190 nm, so the pitch number of the retardation layer was 2000/190 = About 11 pitches.

  Moreover, when the retardation optical element thus produced was measured using an automatic birefringence measuring apparatus (manufactured by Oji Scientific Instruments Co., Ltd., KOBRA (registered trademark) 21ADH), the phase difference in the plane direction was 1 nm. It was within the error range of the measuring device, and the phase difference in the thickness direction was about 100 nm, confirming that it was acting as a negative C plate.

  When the cross section of the produced retardation layer was observed with a transmission electron microscope, a plurality of minute units (domains) were observed, and the directors on the surface did not match in a random state. ) The twist angles of each other did not match. The size of the surface of the minute unit (domain) was not visible with the naked eye.

  The haze value measured for the prepared retardation layer in accordance with JIS-K7105 was 2%, the leakage light when measured from the normal direction with the polarizing plate in a crossed Nicol state, and the polarizing plate in the parallel state. Leakage light when measured from the normal direction is 100%, and the maximum value of leakage light measured in the range of 380 nm to 700 nm when the retardation layer is sandwiched between the polarizing plate crossed Nicol states is 1% was.

  Further, as shown in FIG. 14, the linearly polarizing plates 70A and 70B are placed in a crossed Nicol state, and the produced retardation optical element 20 is sandwiched between the linearly polarizing plates 70A and 70B. There was no bright and dark pattern.

(Example 2)
In Example 2, a single-layer retardation layer composed of polymerizable monomer molecules was formed on a polymer film. That is, a PVA solution dissolved in pure water so as to have a concentration of 2% by weight is coated on a transparent TAC film by bar coating, dried, and formed at 100 ° C. (film thickness 0.2 μm). A phase difference optical element was produced in the same manner as in Example 1 except that it functioned as a film. As a result, in the retardation optical element manufactured in this way, the same results as in Example 1 were obtained, but the haze value and the maximum value of leakage light were smaller than those in Example 1 and were 1%, It was 0.8%. When the retardation layer produced in Example 1 was compared with the retardation layer produced in Example 2 with a polarizing microscope, the size of the plurality of minute units (domains) was smaller in Example 2, and the minute units (domains) were smaller. The maximum major axis of the inscribed ellipse was 5 μm, but light leakage was observed from the disclination between a plurality of minute units (domains).

(Example 3)
In Example 3, a retardation optical element was produced in the same manner as in Example 2 except that HEC (hydroxyethylcellulose) functions as an alignment film. As a result, in the retardation optical element manufactured in this way, the same results as in Example 2 were obtained, but the haze value and the maximum value of leakage light were smaller than those in Example 2, and each was 0.5. It was 0.08%. When the phase difference layer produced in Example 2 and the phase difference layer produced in Example 3 were compared with a polarizing microscope, the size of a plurality of minute units (domains) was smaller in Example 3, and was actually measured with a TEM photograph. As a result, the maximum major axis of the inscribed ellipse of the minute unit (domain) was 1.5 μm. Further, the disclination was such that it could not be measured from the TEM photograph.

(Example 4)
In Example 4, the film thickness of the single phase retardation layer composed of polymerizable monomer molecules was made non-uniform. That is, the retardation optical element produced in the same manner as in Example 1 except that the film thickness was changed to 2 μm ± 5% by changing the conditions of the spin coater was observed in the same manner. The bright and dark pattern was not observed, but when the cross section of the prepared retardation layer was observed with a transmission electron microscope, the helical axis of multiple micro units (domains) and the normals set up on the surface of the retardation layer were Although not in agreement, the average angle between each helical axis and the normal was 0 degree.

(Comparative Example 1)
In Comparative Example 1, the alignment film on which a single phase retardation layer composed of polymerizable monomer molecules was formed was rubbed so that the directors of the liquid crystal molecules were matched. That is, when the retardation optical element produced in the same manner as in Example 1 was observed in the same manner except that the rubbing direction of the alignment film was made uniform in the plane, a clear light and dark pattern was observed in the plane.

(Example 5)
In Example 5, a retardation element having a multilayer retardation layer composed of polymerizable monomer molecules was produced.
Using the retardation layer produced in Example 1 as the first retardation layer, spin the toluene solution prepared in the same manner as in Example 1 on the surface opposite to the alignment film at a faster rotational speed than in Example 1. Coated. Next, toluene in the toluene solution was evaporated at 80 ° C.

  Then, the coating film is irradiated with ultraviolet rays, and the acrylate of the monomer molecule is three-dimensionally cross-linked by radicals generated from the photopolymerization initiator in the coating film, thereby forming a second retardation layer, A phase difference optical element was produced. The total film thickness at this time was 3.5 μm ± 1.5%. Further, when measured with a spectrophotometer, the center wavelength of the selective reflection wavelength of the coating film of the multilayered retardation layer was 280 nm.

  When the cross sections of the prepared retardation layers were observed with a transmission electron microscope, the light and dark patterns between the polymerized retardation layers were parallel to each other (from this, the directions of the helical axes coincided) However, no fault was observed between the retardation layers (which indicates that the directors of the liquid crystal molecules coincide between the surfaces of the adjacent retardation layers). In addition, a plurality of minute units (domains) were observed.

  Further, as shown in FIG. 14, the linearly polarizing plates 70A and 70B are placed in a crossed Nicol state, and the produced retardation optical element 20 is sandwiched between the linearly polarizing plates 70A and 70B. There was no bright and dark pattern.

(Example 6)
In Example 6, the thickness of the multilayer retardation layer composed of polymerizable monomer molecules was made non-uniform. That is, the retardation optical element produced in the same manner as in Example 4 except that the total film thickness was changed to 3.5 μm ± 5% by changing the conditions of the spin coater was observed in the same manner. Was not observed.

(Example 7)
In Example 7, a multilayer retardation layer made of a liquid crystal polymer was produced.
A toluene solution in which an acrylic side-chain liquid crystal polymer having a glass transition temperature of 80 ° C. and an isotropic transition temperature of 200 ° C. was dissolved was prepared. On the other hand, on a transparent glass substrate, polyimide (Optomer (registered trademark) AL1254, manufactured by JSR Corporation) dissolved in a solvent was spin-coated with a spin coater, dried, and then formed at 200 ° C. (film thickness 0.1 μm) ), But functioned as an alignment film, but not rubbed.

  Then, such a glass substrate with an alignment film was set on a spin coater, and a toluene solution in which the liquid crystal polymer was dissolved was spin-coated under conditions such that the film thickness was as constant as possible.

  Next, toluene in the toluene solution was evaporated at 90 ° C., and the coating film formed on the alignment film was held at 150 ° C. for 10 minutes. Furthermore, the coating film was cooled to room temperature, and the liquid crystal polymer was fixed in a glass state to form a retardation layer. The film thickness at this time was 2 μm ± 1.5%. Further, when measured with a spectrophotometer, the center wavelength of the selective reflection wavelength of the first retardation layer was 370 nm.

  Furthermore, a toluene solution in which an acrylic side-chain liquid crystal polymer having a glass transition temperature of 75 ° C. and an isotropic transition temperature of 190 ° C. is dissolved on the retardation layer fixed in a glass state from the previous time. Was spin-coated at high speed.

  Next, toluene in the toluene solution was evaporated at 90 ° C., and the coating film was held at 150 ° C. for 10 minutes. Further, the coating film was cooled to room temperature, and the liquid crystal polymer was fixed in a glass state to form a second retardation layer, thereby producing a multilayer retardation optical element. The total film thickness at this time was 3.5 μm ± 1.5%. Further, when measured with a spectrophotometer, the central wavelength of the selective reflection wavelength of the coating film of the multilayered retardation layer was 370 nm.

  When the cross sections of the prepared retardation layers were observed with a transmission electron microscope, the light and dark patterns between the fixed retardation layers were parallel to each other. However, no fault was observed between the retardation layers (this shows that the directors of the liquid crystal molecules coincide between the surfaces of the adjacent liquid crystal layers). In addition, a plurality of minute units (domains) were observed.

  Further, as shown in FIG. 14, the linearly polarizing plates 70A and 70B are placed in a crossed Nicol state, and the produced retardation optical element 20 is sandwiched between the linearly polarizing plates 70A and 70B. There was no bright and dark pattern.

(Example 8)
In Example 8, the thickness of the multilayer liquid crystal layer made of the liquid crystal polymer was made non-uniform, and the director of the liquid crystal molecules was disturbed. That is, when the retardation optical element produced in the same manner as in Example 6 was observed except that the total film thickness was changed to 3.5 μm ± 5% by changing the conditions of the spin coater, a bright and dark pattern was observed in the plane. Was not observed.

(Comparative Example 2)
In Comparative Example 2, a retardation layer was produced in the same manner as in Example 1 except that the selective reflection wavelengths of the cholesteric structure were 600 nm and 800 nm, respectively. As a result, a retardation layer having a selective reflection wavelength of 600 nm or 800 nm has a clear white turbidity phenomenon, and the degree of white turbidity is larger in the retardation layer having a selective reflection wavelength of 800 nm and can be used as a retardation layer. There was no level. In addition, the retardation layer having a selective reflection wavelength of 600 nm reflects green light, which is also at a level that cannot be used as a retardation layer.

It is the typical sectional view which expanded a part of phase contrast layer as an example of the present invention. It is the typical sectional view which expanded a part of phase contrast layer as other examples of the present invention. It is a transmission electron micrograph which shows an example of the cross section of the phase difference layer of this invention. It is a transmission electron micrograph which shows the other example of the cross section of the phase difference layer of this invention. It is explanatory drawing for demonstrating the phase difference layer of this invention. It is a transmission electron micrograph which shows the other example of the cross section of the phase difference layer of this invention. It is process drawing for demonstrating an example of the manufacturing method of the phase difference optical element of this invention. It is process drawing for demonstrating the other example of the manufacturing method of the phase difference optical element of this invention. It is process drawing for demonstrating the other example of the manufacturing method of the phase difference optical element of this invention. It is a schematic diagram which shows the director of the liquid crystal molecule in the adjacent surface between layers in the phase difference layer of a multilayer structure among the phase difference layers which concern on an example of this invention. It is process drawing for demonstrating the other example of the manufacturing method of the phase difference optical element of this invention. It is a schematic exploded perspective view which shows an example of the polarizing element provided with the phase difference layer of this invention. It is a schematic exploded perspective view which shows an example of the liquid crystal display device provided with the phase difference layer of this invention. It is a schematic exploded perspective view which shows the structure in the case of observing with a retardation optical element sandwiched between polarizing plates. It is a general | schematic disassembled perspective view which shows the conventional liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 40, 40 '... Retardation layer 20 ... Retardation optical element 14 ... Transparent substrate 16 ... Orientation film 42, 42' ... Retardation layer 44, 44 '... 2nd retardation layer 50 ... Polarizing element 60, 100 ... Liquid crystal display devices 70A, 70B, 102A, 102B ... Polarizing plate

Claims (26)

  A retardation layer functioning as a negative C plate having a fixed cholesteric structure, wherein at least one of the two main surfaces of the retardation layer has a liquid crystal molecule director substantially within an interval of 100 μm. A retardation layer characterized in that there is a layer that does not match the above.   2. The liquid crystal molecule director does not substantially coincide within an interval of 100 μm on the other surface of the two main surfaces of the retardation layer, according to claim 1. Retardation layer.   A retardation layer functioning as a negative C plate having a fixed cholesteric structure, wherein a director of liquid crystal molecules is substantially formed in a region having a radius of 50 μm on at least one of the two main surfaces of the retardation layer. Retardation layer, characterized in that there is something that does not match.   A retardation layer functioning as a negative C plate with a fixed cholesteric structure, wherein the twist angle in the cholesteric structure does not substantially coincide with a position within an interval of 100 μm on the main surface of the retardation layer A retardation layer, wherein:   A retardation layer functioning as a negative C plate having a fixed cholesteric structure, wherein the twist angle in the cholesteric structure does not substantially coincide with a position in a region having a radius of 50 μm on the main surface of the retardation layer A phase difference layer characterized by the presence of a thing.   A retardation layer functioning as a negative C plate having a fixed cholesteric structure, the helical layer having the normal and the cholesteric structure in a region having a radius of 50 μm in a cross section including a normal standing on the surface of the retardation layer The helical axis structure region having an acute angle clockwise with respect to the normal direction, and the helical axis structure region having an acute angle counterclockwise with respect to the normal direction. And a retardation layer.   The retardation layer according to any one of claims 1 to 6, wherein a plurality of micro units (domains) having the cholesteric structure are present.   A retardation layer functioning as a negative C plate fixed in a range in which a spiral pitch of a cholesteric structure is 1 pitch or more, wherein a plurality of minute units (domains) having the cholesteric structure exist. Retardation layer.   The retardation layer according to any one of claims 1 to 8, wherein a selective reflection wavelength of the selective reflection light of the cholesteric structure is shorter than a wavelength of incident light.   The retardation layer according to any one of claims 7 to 9, wherein a maximum major axis of an inscribed ellipse on the surface of the minute unit (domain) is 40 µm or less.   The retardation layer according to claim 10, wherein a maximum major axis of an inscribed ellipse on the surface of the minute unit (domain) is equal to or less than a wavelength of the incident light.   The distance of the orientation defect (disclination) between the minute units (domains) is equal to or less than the wavelength of the incident light, The claim according to any one of claims 7 to 11, Retardation layer.   The phase difference layer according to any one of claims 1 to 12, wherein a haze value when the phase difference layer is measured in accordance with JIS-K7105 is 2% or less.   Leakage light when measured from the normal direction with the polarizing plate in a crossed Nicol state is 0%, leakage light when the polarizing plate is measured from the normal direction with the parallel state is 100%, and the retardation layer is the polarizing plate The maximum value of leaked light measured in the range of 380 nm to 700 nm when measured by being sandwiched between the crossed Nicol states is 1% or less. The retardation layer described in 1.   The helical axis of the minute unit (domain) having the cholesteric structure and a normal line standing on the surface of the retardation layer do not substantially coincide with each other. The retardation layer according to claim.   The average value of the angle formed by the helical axis of the minute unit (domain) having the cholesteric structure and the normal line standing on the surface of the retardation layer is substantially 0 degree. Retardation layer.   The retardation layer according to any one of claims 1 to 16, wherein a second retardation layer is further laminated on the main surface of the retardation layer.   The retardation layer according to claim 16, wherein the selective reflection lights of the retardation layer and the second retardation layer both have substantially the same selective reflection wavelength.   The retardation layer according to any one of claims 1 to 18, wherein the retardation layer has a molecular structure in which chiral nematic liquid crystal is three-dimensionally crosslinked.   The retardation layer according to any one of claims 1 to 18, wherein the retardation layer has a molecular state in which polymer cholesteric liquid crystal is in a glass state.   A retardation optical element comprising: a transparent substrate; and the retardation layer according to any one of claims 1 to 20 formed on a surface of the transparent substrate.   The retardation optical element according to claim 21, wherein an alignment film is formed between the transparent substrate and the retardation layer.   23. The retardation optical element according to claim 21, wherein a color filter layer is formed between the transparent substrate and the retardation layer.   The polarizing layer is arrange | positioned at the surface of the transparent base material of the phase difference optical element as described in any one of Claim 21 to 23 in which the phase difference layer is not formed. A polarizing element.   The liquid crystal cell, a pair of polarizing plates arranged so as to sandwich the liquid crystal cell, and at least one of the liquid crystal cell and the pair of polarizing plates, any one of claims 21 to 23 A liquid crystal display device comprising the retardation optical element according to claim 1. An alignment film forming step for forming an alignment film on a transparent substrate, and a coating solution for forming a retardation layer containing a liquid crystal material having a cholesteric regularity for forming a cholesteric liquid crystal structure on the alignment film, A coating process in which the film is not subjected to a rubbing process, an alignment process process in which an alignment process is performed on the retardation layer formed on the alignment film by the coating process, and a retardation layer that is aligned in the alignment process And a solidifying process to solidify the cholesteric liquid crystal structure expressed in a liquid crystal phase in the retardation layer, and a method for producing a retardation optical element.

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