JP2009080251A - Retardation film and liquid crystal display device - Google Patents

Abstract

A main object of the present invention is to provide a retardation film capable of easily adjusting optical characteristics within a desired range, and a liquid crystal display device excellent in viewing angle characteristics.
The present invention is a retardation film having a configuration in which two optical functional films having a base material and an optical functional layer directly formed on the base material and containing a rod-shaped compound are laminated, In the optical functional layer, the rod-shaped compound forms a random homogeneous orientation, and at least one of the two optical functional films has an optical property as an A plate. By providing the above, the above object is achieved.
[Selection] Figure 1

Description

  The present invention relates to a retardation film and a liquid crystal display device using the same.

  The liquid crystal display device has features such as power saving, light weight, thinness, and the like, and has rapidly spread in recent years in place of the conventional CRT display. As shown in FIG. 10, a typical liquid crystal display device 100 may include a liquid crystal cell 104 having 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 the pixels, and is disposed between the polarizing plates 102A and 102B.

  Various types of liquid crystal display devices have been put into practical use depending on the arrangement form of liquid crystal molecules constituting the liquid crystal cell, but in recent years, the VA (Vertical Alignment) method has become the mainstream. Such a VA liquid crystal display device has been widely used mainly for liquid crystal television applications.

  In the liquid crystal cell used in the VA liquid crystal display device, since the liquid crystal molecules are vertically aligned, the entire liquid crystal cell has optical characteristics that act as an optically positive C plate. For example, if the liquid crystal cell 104 of the liquid crystal display device 100 shown in FIG. 10 has such optical characteristics, the linearly polarized light that has passed through the incident-side polarizing plate 102A is the non-driven cell portion of the liquid crystal cell 104. When transmitting, the light is transmitted without being phase-shifted, and is blocked by the output-side polarizing plate 102B. On the other hand, when the liquid crystal cell 104 is transmitted through the cell portion in the driving state, the linearly polarized light is phase-shifted, and an amount of light corresponding to the phase shift amount is transmitted through the polarizing plate 102B on the emission side and emitted. The Thereby, the drive voltage of the liquid crystal cell 104 can be appropriately controlled for each cell, and a desired image can be displayed on the exit-side polarizing plate 102B side.

  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 acts as an optically positive C plate as described above. Since it has optical characteristics, light incident along the normal line of the liquid crystal cell 104 among the linearly polarized light transmitted through the incident-side polarizing plate 102A is transmitted without being phase-shifted, but is incident-side polarizing plate 102A. Of the linearly polarized light transmitted through the liquid crystal cell 104, light incident in a direction inclined from the normal line of the liquid crystal cell 104 undergoes a phase difference when passing through the liquid crystal cell 104 and becomes elliptically polarized light. Accordingly, even if 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 output-side polarizing plate 102B. 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 lower than the image observed from the front. There was a problem that it worsened by (viewing angle dependency problem).

  In order to improve the problem of viewing angle dependency in such a liquid crystal display device, various techniques have been developed so far, and a representative method is a method using a retardation film. As a method of improving the viewing angle dependency of the liquid crystal display device adopting the VA method using a retardation film, a retardation film having properties as an optically negative C plate, and optically A method using two retardation films with a retardation film having properties as an A plate is used. As a method of using such two retardation films, for example, a liquid crystal cell 104 as shown in FIG. 11A is used as a retardation film 41 having a function as a negative C plate and an A plate. As shown in FIG. 11B, a retardation film 41 having a function as a negative C plate and a retardation film 41 having a function as a negative C plate as shown in FIG. A method of laminating a retardation film 42 having a function has been used.

  A method for improving the viewing angle dependency problem using such two retardation films is to change the combination of the retardation films so that the liquid crystal display device using liquid crystal cells having various optical characteristics is used. It is useful in that it can improve the problem of viewing angle dependency and is still widely used today. On the other hand, in such a method, it is required to strictly adjust each of the two retardation films within a predetermined range, so that the retardation film can control optical characteristics accurately. It was desired.

In this regard, conventionally, as the retardation film, as shown in FIG. 12, an alignment layer 106 is provided on an arbitrary substrate 105, and a retardation layer 107 having liquid crystal molecules is further formed on the alignment layer 106. In general, the liquid crystal molecules are aligned by the alignment regulating force of the alignment layer so as to exhibit a desired refractive index anisotropy. As such a retardation film, for example, as disclosed in Patent Document 1 or Patent Document 2, a retardation layer having a cholesteric regular molecular structure (a retardation layer exhibiting birefringence) is used as an alignment layer. A retardation film formed on a substrate having the same is disclosed. Patent Document 3 discloses a retardation film in which a retardation layer composed of a discotic compound (a retardation layer exhibiting birefringence) is formed on a substrate having an alignment layer. Moreover, what has the structure which expressed the phase difference by extending | stretching the film which consists of cycloolefin type resin and polycarbonate resin is also known.
However, the retardation film having such a configuration has a problem that it is difficult to adjust the optical characteristics within a desired range, and a method for improving viewing angle characteristics using the two retardation films. It was unsuitable for. In addition, in the retardation film having the alignment layer and the retardation layer, it is useful in that the alignment layer makes it easy to align the liquid crystal molecules, but the adhesion between the alignment layer and the retardation layer is useful. There was a problem.

JP-A-3-67219 JP-A-4-322223 Japanese Patent Laid-Open No. 10-312166

  The present invention has been made in view of such circumstances, and provides a retardation film capable of easily adjusting optical characteristics to a desired range, and a liquid crystal display device excellent in viewing angle characteristics. This is the main purpose.

  In order to solve the above problems, the present invention is a retardation film having a configuration in which two optical functional films having a base material and an optical functional layer formed directly on the base material and containing a rod-shaped compound are laminated. In the optical functional layer, the rod-like compound forms a random homogeneous orientation, and at least one of the two optical functional films has an optical property as an A plate. A retardation film is provided.

According to the present invention, since the optical functional film has an optical functional layer containing a rod-shaped compound having the random homogeneous orientation, it is easy to adjust the optical characteristics of the optical functional film within a predetermined range. become. In the retardation film of the present invention, two optical functional films that can easily adjust the optical characteristics are used, and at least one of the optical functional films has an optical property as an A plate. By being a thing, it becomes easy to achieve the arbitrary optical characteristics by arbitrarily adjusting the optical characteristics of the two optical functional films.
Therefore, according to the present invention, it is possible to obtain a retardation film capable of easily adjusting optical characteristics to a desired range.

  In the present invention, at least one of the two optical functional films has an optical property as an A plate and a negative C plate, and the other has an optically negative C plate. It is preferable that it has only the property as. This is because the retardation film of the present invention can be suitably used as a viewing angle compensation film for a VA liquid crystal display device.

  Moreover, in this invention, it is preferable that the said base material consists of a cellulose derivative. When the base material is made of a cellulose derivative, for example, when the retardation film of the present invention is also used as a polarizing plate protective film, the adhesion between the polarizer and the polarizing plate protective film can be improved. Because.

  In order to solve the above problems, the present invention provides a liquid crystal cell, a polarizer disposed on both sides of the liquid crystal cell, and one side of the liquid crystal cell, and is disposed between the liquid crystal cell and the polarizer. A liquid crystal display device having a retardation film, wherein the retardation film is the retardation film according to the invention.

  According to the present invention, since the retardation film according to the present invention is used, the optical characteristics of the retardation film can be arbitrarily adjusted according to the mode of the liquid crystal cell. Therefore, according to the present invention, a liquid crystal display device having excellent viewing angle characteristics can be provided.

  In order to solve the above problems, the present invention provides a liquid crystal cell, a polarizer disposed on both sides of the liquid crystal cell, and both sides of the liquid crystal cell, and disposed between the liquid crystal cell and the polarizer. A liquid crystal display device comprising at least two optical functional films, wherein the optical functional film includes a base material, and an optical functional layer including a rod-like compound that is directly formed on the base material and has a random homogeneous orientation; Further, the liquid crystal display device is characterized in that the optical functional film disposed on at least one side of the liquid crystal cell optically has a property as an A plate.

  According to the present invention, at least two optical functional films including an optical functional layer including a rod-shaped compound having the above-described random homogeneous alignment formed on both sides of a liquid crystal cell are used, and the optical functional film is disposed on at least one side. Optically having the properties of an A plate, the optical characteristics of the two optical functional films are arbitrarily adjusted, and the optical characteristics of the two optical functional films are predetermined according to the mode of the liquid crystal cell. It becomes easy to adjust to the range. Therefore, according to the present invention, a liquid crystal display device having excellent viewing angle characteristics can be provided.

  INDUSTRIAL APPLICATION This invention has the effect that the liquid crystal display device excellent in the retardation film which can adjust an optical characteristic easily to a desired range, and the viewing angle characteristic can be provided.

  The present invention relates to a retardation film and a liquid crystal display device. Hereinafter, the retardation film of the present invention and the liquid crystal display device will be described in order.

A. Retardation Film First, the retardation film of the present invention will be described. The retardation film of the present invention is a retardation film having a configuration in which two optical functional films having a base material and an optical functional layer formed directly on the base material and containing a rod-shaped compound are laminated, In the optical functional layer, the rod-shaped compound forms a random homogeneous orientation, and at least one of the two optical functional films has an optical property as an A plate. .

Such a retardation film of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing an example of the retardation film of the present invention. As illustrated in FIG. 1, the retardation film 10 of the present invention has a configuration in which two optical function films 1 are laminated via an adhesive layer 2.
Here, the optical functional film 1 has a base 1a and an optical functional layer 1b containing a rod-shaped compound formed on the base 1a and having a random homogeneous orientation.
In such an example, the retardation film 10 of the present invention is characterized in that at least one of the two optical functional films 1 has an optical property as an A plate.

According to the present invention, since the optical functional film has an optical functional layer containing a rod-shaped compound having the random homogeneous orientation, it is easy to adjust the optical characteristics of the optical functional film within a predetermined range. become. In the retardation film of the present invention, two optical functional films that can easily adjust the optical characteristics are used, and at least one of the optical functional films has an optical property as an A plate. By being a thing, it becomes easy to achieve the arbitrary optical characteristics by arbitrarily adjusting the optical characteristics of the two optical functional films.
Therefore, according to the present invention, it is possible to obtain a retardation film capable of easily adjusting optical characteristics to a desired range.

In the present invention, “having optical properties as an A plate” means that the in-plane retardation (Re) is 5 nm or more.
Here, the in-plane retardation (Re) is a refractive index nx in the slow axis direction in the plane, a refractive index ny in the fast axis direction in the plane, and the thickness d of the target configuration, Re = It is represented by (nx−ny) × d.

The retardation film of the present invention is one in which at least two of the optical functional films are used, and may have other configurations as necessary.
Hereafter, each structure used for this invention is demonstrated in detail.

1. Optical Function Film First, the optical function film used in the present invention will be described. The optical functional film used in the present invention has a base material and an optical functional layer formed directly on the base material and containing a rod-shaped compound, and the rod-shaped compound is randomly homogeneously oriented in the optical functional layer. It is what forms. Since the retardation film of the present invention uses such an optical functional film, it becomes easy to adjust the optical characteristics within the range of wear.

  Such an optical functional film used in the present invention will be described with reference to the drawings. FIG. 2 is a schematic view showing an example of an optical functional film used in the present invention. As illustrated in FIG. 2, the optical functional film 1 used in the present invention includes a base material 1a and an optical functional layer 1b formed on the base material 1a. The rod-shaped compound 1c having a random homogeneous orientation is included.

Here, “directly formed” means that the base material and the optical functional layer are in direct contact with each other between the base material and the optical functional layer without using another layer such as an alignment layer, for example. It means that it is formed to do. In this invention, it has the advantage that the adhesiveness of the said optical function layer and the said base material can be improved by forming the said optical function layer directly on the said base material in this way.
Hereinafter, such an optical functional film will be described.

(1) Optical functional layer First, the optical functional layer will be described. The optical functional layer used in the present invention is formed directly on the substrate described later, contains a rod-shaped compound, and the rod-shaped compound forms a random homogeneous orientation in the optical functional layer. It is characterized by.

a. Random homogeneous orientation The “random homogeneous orientation” will be described. The random homogeneous alignment in the present invention refers to an alignment state formed by the rod-shaped compound contained in the optical functional layer. As a result of the rod-shaped compound having such an orientation state, it becomes easy to subsequently adjust the optical characteristics of the optical functional layer. As a result, the retardation film of the present invention adjusts the optical characteristics within a predetermined range. Is easier.

  In the random homogeneous orientation, at least the size of the domain formed by the rod-shaped compound molecules in the optical functional layer is smaller than the wavelength in the visible light region (hereinafter, sometimes simply referred to as “dispersibility”), and In the optical functional layer, rod-like compound molecules are present in a plane parallel to the surface of the optical functional layer (in the example of FIG. 1, a plane parallel to the xy plane) (hereinafter simply referred to as “in-plane orientation”). In some cases).

  Such random homogeneous orientation will be described with reference to the drawings. FIG. 3A is a schematic view when the optical functional film used in the present invention is viewed from the normal direction of the optical functional layer represented by A in FIG. 2 described above. 3B and 3C are cross-sectional views taken along line B-B 'in FIG.

  First, the “dispersibility” of the random homogeneous orientation in the present invention will be described with reference to FIG. As shown in FIG. 3A, the above “dispersibility” indicates that when the rod-shaped compound 1c forms the domain b in the optical functional layer 1b, the size of the domain b is smaller than the wavelength in the visible light region. It shows that. In the present invention, the smaller the size of the domain b, the more preferable, and the most preferable state is that the rod-like compound is dispersed as a single molecule without forming a domain.

  Next, the “in-plane orientation” possessed by the random homogeneous orientation in the present invention will be described with reference to FIG. As shown in FIG. 3B, the “in-plane orientation” is such that the rod-like compound 1c in the optical functional layer 1b is substantially perpendicular to the normal direction A of the molecular axis a of the optical functional layer 1b. It means that it is oriented. As the “in-plane orientation” in the present invention, as shown in FIG. 3B, the molecular axes a of all the rod-like compounds 1c in the optical functional layer 1b are substantially perpendicular to the normal direction A. The rod-like compound 1c whose molecular axis a ′ is not perpendicular to the normal direction A was present in the optical functional layer 1b, for example, as shown in FIG. 3C. However, the case where the average direction of the molecular axis a of the rod-shaped compound 1c existing in the optical functional layer 1b is substantially perpendicular to the normal direction A is included.

  Next, a method for confirming that the rod-like compound contained in the optical functional layer has such “dispersibility” and “in-plane orientation” will be described.

First, a method for confirming the “dispersibility” of the random homogeneous orientation in the present invention will be described. The “dispersibility” can be confirmed by the haze value of the optical functional layer being within a range indicating that the size of the domain of the rod-shaped compound is not more than the wavelength in the visible light region. Especially in this invention, it is preferable that the haze value of an optical function layer exists in the range of 0.1%-1%.
Here, as the haze value, a value measured in accordance with JIS K7105 is used.

  In addition, the haze value of the said optical function layer can be calculated | required by subtracting the haze value of layers other than an optical function layer from the haze value of an optical function film, for example. That is, the haze value of the entire optical functional film and the optical functional layer obtained by cutting the optical functional layer is measured, and the haze value of the optical functional layer is obtained by subtracting the latter haze value from the former haze value. it can. As the haze value, a value measured according to JIS K7105 is used.

Next, a method for confirming “in-plane orientation” possessed by random homogeneous orientation in the present invention will be described. The “in-plane orientation” can be confirmed by having a retardation (Rth) value in the thickness direction in which the optical functional layer exhibits properties as an optically negative C plate. Here, “showing properties as a negative C plate” in the present invention means that the retardation in the thickness direction (Rth) is 50 nm or more, and in particular, the optical function in the present invention. The thickness direction retardation (Rth) of the layer is preferably in the range of 50 nm to 300 nm.
The retardation in the thickness direction (Rth) is the refractive index Nx in the fast axis direction (the direction in which the refractive index is the smallest) in the plane of the optical functional layer constituting the retardation film of the present invention, and the slow phase. Rth = {(nx + ny) / 2−nz} × d based on the refractive index Ny in the axial direction (direction in which the refractive index is the largest), the refractive index Nz in the thickness direction, and the thickness d (nm) of the optical function layer. It is a value represented by an expression. The Rth value in the present invention indicates the absolute value of the value represented by the above formula.

  The Rth of the optical function layer can be obtained, for example, by subtracting Rth indicated by a layer other than the optical function layer from Rth of the optical function film. That is, the Rth of the optical functional layer can be obtained by measuring Rth of the entire optical functional film and the optical functional film from which the optical functional layer has been removed, and subtracting the latter Rth from the former Rth. Rth can be measured by, for example, the parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments.

When the rod-like compound has a rod-like main skeleton in which two or more benzene rings are bonded, the “in-plane orientation” is the Raman peak in the thickness direction of the optical function layer. It can also be confirmed by measuring the intensity ratio (1605 cm ⁻¹ / 2942 cm ⁻¹ ). That is, the Raman peak intensity ratio (1605 cm ⁻¹ / 2942 cm ⁻¹ ) in the direction perpendicular to the thickness direction in the cut surface in the thickness direction of the optical functional layer is the Raman peak intensity ratio (1605 cm) in the direction parallel to the thickness direction. by greater than ^-1 / ^{2942cm -1),} it can be seen that with the "in-plane orientation". In particular, in the present invention, the Raman peak intensity ratio (1605 cm ⁻¹ / 2942 cm ⁻¹ ) in the direction perpendicular to the thickness direction on the cut surface in the thickness direction of the optical functional layer is Raman in the direction parallel to the thickness direction. It is preferably 1.1 times or more of the peak intensity ratio (1605 cm ⁻¹ / 2942 cm ⁻¹ ), particularly preferably 1.50 times or more, and further within a range of 1.20 times to 3.00 times. Preferably there is.

Here, the "Raman peak intensity ratio ^{(1605cm -1} / 2942cm -1)" means the ratio of the in the Raman spectrum (spectral light intensity of the spectral light intensity / wave number 2942cm ^-1 in wavenumber 1605 cm ^-1) To do.

Here, the Raman peak intensity ratio (1605 cm ⁻¹ / 2942 cm ⁻¹ ) in the present invention is obtained by using, for example, a laser Raman spectrophotometer (JASCO: NRS-3000), and the linearly polarized electric field vibration surface has an optical function. The measurement light is incident on the cut surface in the thickness direction of the layer so as to coincide with the parallel direction and the vertical direction with respect to the thickness direction. After measuring the Raman spectroscopic spectrum, the peak intensity of 1605 cm ⁻¹ (C—H bond-derived peak) and the peak intensity of 2942 cm ⁻¹ (benzene ring-derived peak) can be determined. The conditions for measuring a Raman spectrum using the laser Raman spectrophotometer are an exposure time of 15 seconds, an integration count of 8 times, and an excitation wavelength of 532.11 nm.
The Raman peak intensity ratio of the optical functional layer can be determined by, for example, measuring the Raman spectrum of only the portion corresponding to the optical functional layer after cutting the optical functional film in the thickness direction and preparing a section. Can be sought.

As described above, since the optical functional layer in the present invention has the rod-like compound having the random homogeneous orientation, it has at least the property as an optically negative C plate. The optical properties of the layer can be optically combined with the properties of the A plate by controlling the arrangement regularity of the rod-shaped compound in the optical functional layer (note that the properties of the optical plate are optically (In some cases, optically having the property as a C plate is simply expressed as “optically having a property as a B plate”.)
More specifically, when the rod-like compounds are randomly arranged in the optical functional layer (hereinafter, this case may be referred to as “isotropic”), the optical functional layer is optical. In the case where the rod-like compounds are arranged so that the molecular axes are averagely oriented in one direction in the optical functional layer (hereinafter, such as this) The case may be referred to as “anisotropic”.), And the optical functional layer has optical properties as a B plate.

As described above, the optical functional layer in the present invention makes the regularity of the rod-like compound “isotropic” or “anisotropic” because the rod-like compound forms a random homogeneous orientation. Depending on the degree of “anisotropy”, depending on the degree of “anisotropy”, the optically negative A-plate is maintained while maintaining the property as an optically negative C plate. It becomes possible to give the property as a plate to an arbitrary degree. And since it is possible to adjust arbitrarily the optical characteristic which an optical functional layer can express in this way, the retardation film of this invention becomes easy to adjust to a desired optical characteristic.
Hereinafter, the “isotropic” and “anisotropic” will be described in order.

  First, the “isotropic property” will be described. As described above, “isotropic” in the present invention means that the rod-like compounds are randomly arranged in the optical functional layer.

The “isotropy” of the rod-shaped compound will be described with reference to FIG. As illustrated in FIG. 4A, the “isotropic” indicates that the rod-shaped compounds 1 c are randomly arranged in the optical function layer 1 b.
Here, in the present invention, in order to explain the arrangement direction of the rod-shaped compound 1c, the molecular major axis direction (hereinafter referred to as the molecular axis) represented by a in FIG. . Therefore, the arrangement direction of the rod-shaped compound being random means that the molecular axis a of the rod-shaped compound 1c included in the optical functional layer is randomly oriented.

  In addition to the arrangement state illustrated in FIG. 4A, the direction of the molecular axis is random as a whole even when the rod-shaped compound has a cholesteric structure. “Isotropic” corresponds to “isotropic”, but “isotropic” in the present invention does not include a form resulting from a cholesteric structure.

  The fact that the rod-shaped compound used in the present invention has the above-mentioned “isotropic” is to evaluate the in-plane retardation (Re) evaluation of the optical functional layer and the presence or absence of a selective reflection wavelength due to the cholesteric structure. Can be confirmed. This can be confirmed by the in-plane retardation (Re) evaluation of the optical functional layer that the rod-shaped compound is randomly oriented, and the rod-shaped compound does not form a cholesteric structure depending on the presence or absence of the selective reflection wavelength. This is because it can be confirmed.

  It can be confirmed that the rod-like compound is randomly oriented by having an in-plane retardation (Re) value within a range indicating that the rod-like compound is randomly oriented. Especially, in this invention, it is preferable that the in-plane retardation (Re) of an optical function layer is 0 nm-5 nm.

  The in-plane retardation (Re) of the optical functional layer can be obtained, for example, by subtracting the in-plane retardation (Re) exhibited by the layers other than the optical functional layer from the in-plane retardation (Re) of the optical functional film. it can. That is, in-plane retardation (Re) is measured for the entire optical functional film and for the optical functional film cut out from the optical functional film, and the former in-plane retardation (Re) is measured from the former in-plane retardation (Re). Re of the optical functional layer can be obtained by subtracting. Re can be measured, for example, by the parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments.

  Moreover, the rod-shaped compound does not have a cholesteric structure, for example, using an ultraviolet-visible gold-infrared spectrophotometer (UV-3100, etc.) manufactured by Shimadzu Corporation, and the optical functional layer in the present invention has a selective reflection wavelength. It can be evaluated by confirming that it does not have. This is because the cholesteric structure has a selective reflection wavelength that depends on the helical pitch of the cholesteric structure.

  Next, the “anisotropy” will be described. As described above, “anisotropy” in the present invention means a case where the rod-shaped compounds are arranged in the optical functional layer so that molecular axes are averagely oriented in one direction.

Such “anisotropy” will be described with reference to FIG. As illustrated in FIG. 4B, the “anisotropy” indicates that the rod-shaped compound 1c is an average in the optical functional layer 1b when the optical functional film is viewed from the direction perpendicular to the surface of the optical functional layer 1b. It shows that it is arranged in one direction.
Here, as described above, in order to explain the arrangement direction of the rod-shaped compound 1c in the present invention, since the molecular long axis direction represented by a in FIG. Arranging in the direction means that the molecular axis a of the rod-shaped compound 1c contained in the optical functional layer 1b is oriented in one direction on average.

  The fact that the rod-shaped compound has the above-mentioned “anisotropy” is evaluated by the in-plane retardation (Re) value of the optical functional layer that the optical functional layer has an optical property as an A plate. This can be confirmed. Here, “having optical properties as an A plate” in the present invention means that the value of in-plane retardation (Re) is 5 nm or more. In particular, in the present invention, an optical functional layer is used. The in-plane retardation (Re) is preferably in the range of 5 nm to 300 nm, more preferably in the range of 10 nm to 200 nm, and particularly in the range of 40 nm to 150 nm. preferable.

In addition, when the rod-shaped compound having a rod-shaped main skeleton to which two or more benzene rings are bonded is used, the “isotropic” and “anisotropy” This can also be confirmed by measuring the Raman peak intensity ratio (1605 cm ⁻¹ / 2942 cm ⁻¹ ) in the in-plane direction.
Namely, the Raman peak intensity ratio in the in-plane slow axis direction of the optical functional layer in the present invention ^{(1605cm -1} / ^2942cm -1) is, fast axis direction Raman peak intensity ratio of the plane ^(1605cm -1 / ^2942cm It can be confirmed that the above-mentioned “anisotropy” is provided by confirming that it is larger than ⁻¹ ). In particular, in the present invention, the Raman peak intensity ratio in the in-plane slow axis direction of the optical functional layer ^{(1605cm -1} / ^2942cm -1) is the Raman peak intensity ratio of the fast axis direction in the plane (1605 cm ^-1 / 2942 cm ⁻¹ ) is preferably 1.1 times or more, particularly preferably 1.15 times or more, and more preferably in the range of 1.20 times to 3.00 times.
On the other hand, the Raman peak intensity ratio in the in-plane slow axis direction of the optical functional layer in the present invention and ^{(1605cm -1} / ^2942cm -1), the fast axis direction Raman peak intensity ratio of the plane ^(1605cm -1 / ^{2942cm -1} ) is substantially equivalent, it can be confirmed that the above-mentioned "isotropic" is provided.

Here, the Raman peak intensity ratio (1605 cm ⁻¹ / 2942 cm ⁻¹ ) in the present invention is obtained by using, for example, a laser Raman spectrophotometer (JASCO: NRS-3000), and the linearly polarized electric field vibration surface has an optical function. Measure the Raman spectrum for each of the in-plane fast axis direction and the in-plane fast axis direction by entering the measurement light so that it matches the slow axis direction and the fast axis direction in the plane of the layer. Then, it can be determined by evaluating the peak intensity of 1605 cm ⁻¹ (C—H bond-derived peak) and the peak intensity of 2942 cm ⁻¹ (benzene ring-derived peak). The conditions for measuring a Raman spectrum using the laser Raman spectrophotometer are an exposure time of 15 seconds, an integration count of 8 times, and an excitation wavelength of 532.11 nm.
The Raman peak intensity ratio of the optical function layer can be determined, for example, by subtracting the Raman peak intensity ratio indicated by layers other than the optical function layer from the Raman peak intensity ratio of the entire optical function film. That is, the Raman peak intensity ratio is measured for the entire optical functional film and the optical functional layer cut out from the optical functional film, and the Raman peak intensity ratio of the optical functional layer is determined by subtracting the latter value from the former value. Can be sought.

b. Next, the rod-shaped compound used in the present invention will be described. The rod-shaped compound used in the present invention is not particularly limited as long as it can form a random homogeneous alignment in the optical functional layer.
Here, the “rod-like compound” in the present invention refers to a rod having a main skeleton of a molecular structure, and examples of the compound having such a rod-like main skeleton include azomethines, azoxys, and cyanobiphenyl. Cyanophenyl esters, benzoic acid esters, cyclohexane carboxylic acid phenyl esters, cyanophenyl cyclohexanes, cyano substituted phenyl pyrimidines, alkoxy substituted phenyl pyrimidines, phenyl dioxanes, tolanes and alkenyl cyclohexyl benzonitriles be able to. Moreover, not only the above low molecular liquid crystalline compound but a high molecular liquid crystalline compound can also be used.

  In the present invention, any rod-like compound belonging to any of the above-mentioned categories can be suitably used, and in particular, it has a rod-like main skeleton to which two or more benzene rings are bonded. In particular, it is preferable that two or more benzene rings have a rod-like main skeleton in which ester bonds are bonded to each other. Since the rod-shaped compound having such a structure has a large refractive index anisotropy in the molecule, it is possible to impart high retardation to the optical functional layer by being arranged in the optical functional layer. It is.

As the rod-shaped compound used in the present invention, a compound having a relatively small molecular weight is preferably used. Specifically, a compound having a molecular weight in the range of 200 to 1200, particularly in the range of 400 to 800 is preferably used. When the molecular weight is within the above range, the affinity of the rod-like compound for the material constituting the base material described later can be improved, so that the adhesion between the base material and the optical functional layer can be improved. Because it can.
In addition, when a rod-shaped compound is a material which has the polymeric functional group mentioned later, the said molecular weight shall show the molecular weight before superposition | polymerization.

  In addition, the rod-like compound used in the present invention is preferably a liquid crystalline material exhibiting liquid crystallinity. This is because, when the rod-shaped compound is a liquid crystalline material, the optical functional layer can be made excellent in expression of optical characteristics per unit thickness. The rod-like compound in the present invention is preferably a liquid crystalline material exhibiting a nematic phase among the above liquid crystalline materials. This is because a liquid crystalline material exhibiting a nematic phase is relatively easy to form a random homogeneous alignment.

  Further, the liquid crystalline material exhibiting the nematic phase is preferably a molecule having spacers at both mesogenic ends. This is because the liquid crystalline material having spacers at both ends of the mesogen is excellent in flexibility and can effectively prevent the optical functional layer in the present invention from becoming clouded.

  As the rod-like compound used in the present invention, those having a polymerizable functional group in the molecule are suitably used, and those having a polymerizable functional group capable of three-dimensional crosslinking are particularly preferable. Since the rod-shaped compound has a polymerizable functional group, the rod-shaped compound can be polymerized and fixed. Therefore, by fixing the rod-shaped compound in a state of forming a random homogeneous orientation, an array is obtained. This is because an optical functional film that is excellent in stability and hardly changes in optical properties can be obtained. In the present invention, the rod-shaped compound having the polymerizable functional group may be mixed with the rod-shaped compound having no polymerizable functional group.

The “three-dimensional crosslinking” means that liquid crystal molecules are polymerized three-dimensionally to form a network (network) structure.

  Such a polymerizable functional group is not particularly limited, and various polymerizable functional groups that are polymerized by the action of ionizing radiation such as ultraviolet rays and electron beams, or heat are used. Representative examples of these polymerizable functional groups include radically polymerizable functional groups or cationic polymerizable functional groups. Further, representative examples of radically polymerizable functional groups include functional groups having at least one addition-polymerizable ethylenically unsaturated double bond, and specific examples include vinyl groups having or not having substituents, An acrylate group (generic name including an acryloyl group, a methacryloyl group, an acryloyloxy group, and a methacryloyloxy group) and the like can be given. Specific examples of the cationic polymerizable functional group include an epoxy group. In addition, examples of the polymerizable functional group include an isocyanate group and an unsaturated triple bond. Among these, from the viewpoint of the process, a functional group having an ethylenically unsaturated double bond is preferably used.

  The rod-like compound in the present invention is a liquid crystalline material exhibiting liquid crystallinity and particularly preferably has a polymerizable functional group at the terminal. For example, if nematic liquid crystalline materials having polymerizable functional groups at both ends are used, they can be polymerized three-dimensionally to form a network structure, have alignment stability, and have optical properties. An optical functional layer having excellent expression can be obtained. Moreover, even if it has a polymerizable functional group at one end, it can be cross-linked with other molecules to stabilize the sequence. Examples of such rod-shaped compounds include compounds represented by the following formulas (1) to (6).

  Here, the liquid crystalline materials represented by the chemical formulas (1), (2), (5) and (6) are disclosed in DJ Broer et al., Makromol. Chem. 190, 3201-3215 (1989), or DJ Broer et al., Makromol. Chem. 190, 2250 (1989), or can be prepared similarly. The preparation of liquid crystalline materials represented by the chemical formulas (3) and (4) is disclosed in DE 195,04,224.

Specific examples of the nematic liquid crystalline material having an acrylate group at the terminal include those represented by the following chemical formulas (7) to (17).

In the present invention, the rod-shaped compound may be used alone or in combination of two or more.
For example, when the rod-shaped compound is used by mixing a liquid crystalline material having one or more polymerizable functional groups at both ends and a liquid crystalline material having one or more polymerizable functional groups at one end, The polymerization density (crosslink density) and the optical characteristics can be arbitrarily adjusted by adjusting the ratio, which is preferable.

c. Other compounds The optical functional layer in the present invention may contain other compounds in addition to the rod-shaped compound. Such other compounds are not particularly limited as long as they do not disturb the random homogeneous orientation of the rod-shaped compound. Examples of such other compounds include a photopolymerization initiator, a polymerization inhibitor, a leveling agent, a chiral agent, and a silane coupling agent.

  Moreover, the optical function layer in the present invention may contain a material constituting a base material to be described later.

d. Optical Functional Layer The thickness of the optical functional layer in the present invention is not particularly limited as long as it is within a range in which desired optical characteristics can be imparted to the optical functional layer, depending on the type of the rod-shaped compound. In particular, in the present invention, the thickness of the optical functional layer is preferably in the range of 0.5 μm to 10 μm, more preferably in the range of 0.5 μm to 8 μm, and particularly in the range of 0.5 μm to 6 μm. It is preferable to be within. This is because if the thickness of the optical functional layer is larger than the above range, “in-plane orientation”, which is one of the characteristics of random homogeneous orientation, is impaired, and desired optical characteristics may not be obtained. On the other hand, if the thickness is less than the above range, the target optical characteristics may not be obtained depending on the kind of the rod-shaped compound.

  The configuration of the optical functional layer in the present invention is not limited to a configuration composed of a single layer, and may have a configuration in which a plurality of layers are laminated. When it has the structure by which the several layer was laminated | stacked, the layer of the same composition may be laminated | stacked, and the several layer which has a different composition may be laminated | stacked.

(2) Substrate Next, the substrate used in the present invention will be described. The base material used for this invention will not be specifically limited if it has desired transparency and can form the said optical function layer directly. In particular, the substrate used in the present invention preferably has a transmittance in the visible light region of 80% or more, and more preferably 90% or more. This is because if the transmittance is low, the selection range of the rod-like compound or the like may be narrowed.
Here, the transmittance | permeability of a base material can be measured by JISK7361-1 (the test method of the total light transmittance of a plastic transparent material).

  The thickness of the base material used in the present invention is not particularly limited as long as it has necessary self-supporting properties depending on the use of the retardation film of the present invention. In particular, in the present invention, the range of 10 μm to 188 μm is preferable, the range of 20 μm to 125 μm is particularly preferable, and the range of 30 μm to 100 μm is particularly preferable. This is because if the thickness of the substrate is thinner than the above range, the self-supporting property required for the retardation film of the present invention may not be obtained. Further, if the thickness is thicker than the above range, for example, when cutting the retardation film of the present invention, processing waste may increase or the cutting blade may be worn quickly.

  Further, the base material used in the present invention can be a flexible material having flexibility or a rigid material having no flexibility, but it is preferable to use a flexible material. By using a flexible material, it is because the manufacturing process of the retardation film of this invention can be made into a roll-to-roll process, and the retardation film excellent in productivity can be obtained.

  The materials constituting the flexible material include cellulose derivatives, norbornene polymers, cycloolefin polymers, polymethyl methacrylate, polyvinyl alcohol, polyimide, polyarylate, polyethylene terephthalate, polysulfone, polyethersulfone, amorphous polyolefin, and modified acrylic polymers. , Polystyrene, epoxy resin, polycarbonate, polyesters and the like can be exemplified, but in the present invention, cellulose derivatives and norbornene polymers can be preferably used.

  Examples of the norbornene-based polymer include cycloolefin polymer (COP) and cycloolefin copolymer (COC). In the present invention, it is preferable to use a cycloolefin polymer. Since the cycloolefin polymer has low moisture absorption and permeability, the substrate used in the present invention is composed of the cycloolefin polymer, so that the retardation film of the present invention has excellent optical characteristics over time. Because it can be made.

  Specific examples of the cycloolefin polymer used in the present invention include, for example, JSR Corporation trade name: ARTON; Nippon Zeon Corporation trade name: Zeonoa; Sekisui Chemical Co., Ltd. trade name: Essina Can do.

  As the cellulose derivative, a cellulose ester is preferably used, and among the cellulose esters, cellulose acylates are preferably used. This is because cellulose acylates are advantageous in terms of availability because they are widely used industrially.

  As said cellulose acylates, C2-C4 lower fatty acid ester is preferable. The lower fatty acid ester may include only a single lower fatty acid ester such as cellulose acetate, and may include a plurality of fatty acid esters such as cellulose acetate butyrate and cellulose acetate propionate. There may be.

  In the present invention, cellulose acetate can be particularly preferably used among the above lower fatty acid esters. As the cellulose acetate, it is most preferable to use triacetyl cellulose having an average acetylation degree of 57.5 to 62.5% (substitution degree: 2.6 to 3.0). Since triacetyl cellulose has a molecular structure having a relatively bulky side chain, by constituting the base material from triacetyl cellulose, the rod-shaped compound forming the optical functional layer easily penetrates into the base material. This is because the adhesion between the substrate and the optical functional layer can be further improved. Moreover, since triacetylcellulose is easy to express the property as a negative C plate, it becomes easy to form the random homogeneous orientation of the said rod-shaped compound. Here, the degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation can be determined by measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like).

  The base material used in the present invention is preferably subjected to a stretching treatment. Since the rod-shaped compound is easily penetrated into the base material by being subjected to the stretching treatment, the rod-shaped compound has a more uniform random homogeneous orientation with excellent adhesion between the base material and the optical functional layer. It is because it can form.

  The stretching treatment is not particularly limited and may be arbitrarily determined according to the material constituting the substrate. Examples of such a stretching process include a uniaxial stretching process and a biaxial stretching process.

  The stretching conditions for the stretching treatment are not particularly limited as long as the base material can be imparted with desired properties as an A plate or B plate and properties as a negative C plate.

The structure of the base material in the present invention is not limited to a structure composed of a single layer, and may have a structure in which a plurality of layers are laminated. When it has the structure by which the several layer was laminated | stacked, the layer of the same composition may be laminated | stacked, and the several layer which has a different composition may be laminated | stacked.
As the structure of the base material in which a plurality of layers having different compositions are laminated, for example, a film made of a material for randomly orienting the rod-like compound such as triacetyl cellulose and a cycloolefin polymer having excellent water permeability are used. A mode of laminating with the support can be exemplified.

(3) Optical functional film The optical characteristics of the optical functional film used in the present invention depend on the optical characteristics of the optical functional layer and the base material. In the optical functional layer, the rod-like compound has random homogeneous orientation. Since it is formed, it has at least the property as an optically negative C plate. Then, whether the rod-shaped compound has “isotropic” or “anisotropic” has an optical property as an A plate is determined. Therefore, normally, the optical characteristics of the optical functional film used in the present invention are either in the case of having only the property as an optically negative C-method rate or in the case of having the property as an optically B plate. Become.

When the optical functional film used in the present invention has only the property as an optically negative C plate, the thickness direction retardation (Rth) of the optical functional film is preferably in the range of 60 nm to 450 nm, and more preferably 70 nm to A range of 400 nm is preferable, and a range of 80 nm to 200 nm is particularly preferable.
The in-plane retardation (Re) is preferably in the range of 0 nm to 60 nm, more preferably in the range of 0 nm to 30 nm, and particularly preferably in the range of 0 nm to 10 nm.

On the other hand, when the optical functional film used in the present invention optically has the property as a B plate, the thickness direction retardation (Rth) of the optical functional film is preferably in the range of 60 nm to 450 nm, particularly 70 nm to 400 nm. Is preferable, and the range of 80 nm to 300 nm is particularly preferable.
The in-plane retardation (Re) is preferably in the range of 40 nm to 400 nm, more preferably in the range of 60 nm to 200 nm, and particularly preferably in the range of 80 nm to 160 nm.
Further, the Nz factor is preferably in the range of 1.0 to 3.0, more preferably in the range of 1.0 to 2.5, and particularly preferably in the range of 1.0 to 2.0.

  Moreover, in the optical functional film used in the present invention, as an aspect in which the optical functional layer is laminated on the base material, the base material and the optical functional layer are laminated so as to form a clear interface. Alternatively, there is no clear interface between the base material and the optical functional layer, and the layer is formed so that the concentration of the rod-shaped compound continuously changes in the thickness direction. An aspect may be sufficient.

2. Retardation Film The retardation film of the present invention has a structure in which two optical functional films described above are laminated, and at least one of them is optically characterized as an A plate. However, the mode in which the two optical functional films are laminated can be appropriately determined according to the use of the retardation film of the present invention, and is not particularly limited. Therefore, in the retardation film of the present invention, the two optical functional films may be laminated so that the two optical functional films are in contact with each other, or the two optical functional films are laminated. The aspect by which the functional film was laminated | stacked through the other layer may be sufficient. Furthermore, in the present invention, an aspect in which the above-mentioned optical functional layer is formed on both surfaces of the substrate and the optical functional layer formed on at least one surface optically has a property as an A plate is also referred to as “optical”. It shall be included in the “configuration in which two functional films are laminated”.

  Further, the two optical functional films used for the retardation film of the present invention may be any film as long as at least one of them has optical properties as an A plate. Accordingly, in the present invention, only one of the optical functional films may be optically A-plate properties, or both optical functional films may be optically A-plate properties. You may have. In particular, in the present invention, at least one of the two optical functional films has an optical property as an A plate and a negative C plate, and the other is optically negative. It is preferable that it has only the property as a C plate. This is because the retardation film of the present invention can be suitably used as a viewing angle compensation film for a VA liquid crystal display device.

  The retardation film of the present invention may have other configurations in addition to the optical function film. Examples of such other configurations include an antireflection layer, an ultraviolet absorption layer, an infrared absorption layer, an antistatic layer, and an adhesive layer.

  The antireflection layer used in the present invention is not particularly limited. For example, a transparent base film formed with a low refractive index layer made of a material having a lower refractive index than the transparent base film, or a transparent base On the material film, a high refractive index layer made of a substance having a higher refractive index than that of the transparent substrate, and a low refractive index layer made of a substance having a lower refractive index than that of the transparent substrate, in this order, alternately, Examples include those in which one or more layers are laminated. These high-refractive index layers and low-refractive index layers are vacuum-deposited so that the optical thickness represented by the product of the geometric thickness and refractive index of the layer is 1/4 of the wavelength of light to be prevented from being reflected. It is formed by coating or the like. As the constituent material of the high refractive index layer, titanium oxide, zinc sulfide and the like are used, and as the constituent material of the low refractive index layer, magnesium fluoride, cryolite and the like are used.

  The ultraviolet absorbing layer used in the present invention is not particularly limited. For example, an ultraviolet absorber made of a benzotriazole compound, a benzophenone compound, a salicylate compound, or the like is used in a film such as a polyester resin or an acrylic resin. Addition and film formation are mentioned.

  Moreover, it does not specifically limit as an infrared rays absorption layer used for this invention, For example, what formed the infrared rays absorption layer by coating etc. on film base materials, such as a polyester resin, is mentioned. As the infrared absorbing layer, for example, a film formed by adding an infrared absorber made of a diimmonium compound, a phthalocyanine compound or the like into a binder resin made of an acrylic resin, a polyester resin or the like is used.

  In addition, the adhesive layer used in the present invention is not particularly limited as long as the optical functional film and other layers can be bonded to each other. In this invention, what consists of a well-known adhesive agent can be used as such an adhesive layer.

  The thickness of the retardation film of the present invention is not particularly limited as long as it is within a range in which desired optical properties can be expressed, but usually within a range of 20 μm to 150 μm, and particularly within a range of 25 μm to 130 μm. In particular, it is preferable to be in the range of 30 μm to 110 μm.

  The retardation film of the present invention preferably has a haze value measured according to JIS K7105 in the range of 0% to 2%, particularly preferably in the range of 0% to 1.5%. In particular, it is preferably in the range of 0% to 1%.

  The retardation in the thickness direction of the retardation film of the present invention may be appropriately selected according to the use of the present invention, and is not particularly limited. In particular, in the present invention, the retardation in the thickness direction (Rth) is preferably in the range of 60 nm to 450 nm, more preferably in the range of 70 nm to 400 nm, and particularly preferably in the range of 80 nm to 350 nm. Since the retardation (Rth) in the thickness direction is within the above range, the retardation film of the present invention can be made suitable for improving the viewing angle characteristics of a VA (Vertical Alignment) type liquid crystal display device. is there.

  Further, the in-plane retardation (Re) of the retardation film of the present invention may be appropriately selected according to the use of the retardation film of the present invention, and is not particularly limited. In particular, in the present invention, the in-plane retardation (Re) is preferably in the range of 20 nm to 200 nm, more preferably in the range of 30 nm to 180 nm, and particularly preferably in the range of 40 nm to 150 nm. When the in-plane retardation (Re) is within the above range, the retardation film of the present invention is used as a retardation film suitable for improving the viewing angle characteristics of a VA (Vertical Alignment) liquid crystal display device. Because it can.

  The in-plane retardation (Re) value may have wavelength dependency. For example, the long wavelength side may have a larger value than the short wavelength side, and the short wavelength side may have a larger value than the long wavelength side. This is because the viewing angle characteristics of the liquid crystal display device can be improved in the entire visible light region by having the wavelength dependency of the in-plane retardation (Re) value.

3. Use of the phase film The use of the retardation film of the present invention is not particularly limited. For example, an optical compensator (for example, a viewing angle compensator) used in a liquid crystal display device, an elliptically polarizing plate, a brightness improving plate, etc. Can be mentioned. In particular, the retardation film of the present invention can be suitably used as an optical compensator for improving the viewing angle dependency of a liquid crystal display device. In particular, the retardation film of the present invention is an optically negative C plate. Since it has properties and optical properties as an A plate, it can be most suitably used as an optical compensator for a VA liquid crystal display device.

  Moreover, the retardation film of this invention can be used also for the use as a polarizing film by bonding with a polarizing layer. A polarizing film is usually formed by forming a polarizing layer and protective layers on both surfaces thereof. In the present invention, for example, by forming the protective film on one side as the above-described retardation film, for example, a liquid crystal display. It can be set as the polarizing film which has the optical compensation function which improves the viewing angle characteristic of an apparatus.

  Although it does not specifically limit as said polarizing layer, For example, an iodine type polarizing layer, a dye type polarizing layer using a dichroic dye, a polyene type polarizing layer, etc. can be used. The iodine-based polarizing layer and the dye-based polarizing layer are generally produced using polyvinyl alcohol.

4). Next, a method for producing the retardation film of the present invention will be described. The retardation film of the present invention can be produced, for example, by using two optical functional films and bonding them together via an adhesive layer.

  Moreover, as a method of producing the said optical function film, the method of apply | coating the composition for optical function layer formation prepared by melt | dissolving the said rod-shaped compound in the solvent on the said base material, for example is used. According to such a method, the rod-shaped compound can be infiltrated into the base material together with the solvent, so that the interaction between the rod-shaped compound and the material constituting the base material can be enhanced. This is because it becomes easier to form a random homogeneous orientation of the rod-like compound.

  The composition for forming an optical functional layer usually comprises the rod-like compound and a solvent, and may contain other compounds as necessary. The solvent used in the composition for forming an optical functional layer is not particularly limited as long as it can dissolve the rod-like compound at a desired concentration and does not corrode the substrate. Examples of the solvent used in the present invention include hydrocarbon solvents such as benzene and hexane, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, ether solvents such as tetrahydrofuran and 1,2-dimethoxyethane, chloroform, Alkyl halide solvents such as dichloromethane, ester solvents such as methyl acetate, ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, amide solvents such as N, N-dimethylformamide, and sulfoxide solvents such as dimethyl sulfoxide, Examples thereof include, but are not limited to, ananone solvents such as cyclohexane, and alcohol solvents such as methanol, ethanol, and propanol. Further, the solvent used in the present invention may be one kind or a mixed solvent of two or more kinds of solvents. In the present invention, among these solvents, a ketone solvent is preferably used, and cyclohexane is preferably used.

  The content of the rod-shaped compound in the composition for forming an optical functional layer is desired for the viscosity of the composition for forming an optical functional layer according to a coating method or the like for applying the optical functional layer formation on a substrate. If it is in the range which can be made into the value of, it will not be limited especially. In particular, in the present invention, the content of the rod-like compound is preferably in the range of 10% by mass to 30% by mass in the composition for forming an optical functional layer, and particularly in the range of 10% by mass to 25% by mass. It is preferable that it is in the range of 10 mass%-20 mass% especially.

  The composition for forming an optical functional layer may contain a photopolymerization initiator as necessary. In particular, when a treatment for curing the optical functional layer by ultraviolet irradiation is performed, it is preferable to include a photopolymerization initiator. Examples of the photopolymerization initiator used in the present invention include benzophenone, methyl o-benzoylbenzoate, 4,4-bis (dimethylamine) benzophenone, 4,4-bis (diethylamine) benzophenone, α-amino acetophenone, 4, 4-dichlorobenzophenone, 4-benzoyl-4-methyldiphenyl ketone, dibenzyl ketone, fluorenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methylpropiophenone P-tert-butyldichloroacetophenone, thioxanthone, 2-methylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, diethylthioxanthone, benzyldimethyl ketal, benzylmethoxyethyl acetal Benzoin methyl ether, benzoin butyl ether, anthraquinone, 2-tert-butylanthraquinone, 2-amylanthraquinone, β-chloroanthraquinone, anthrone, benzanthrone, dibenzsuberone, methyleneanthrone, 4-azidobenzylacetophenone, 2,6-bis (p- Azidobenzylidene) cyclohexane, 2,6-bis (p-azidobenzylidene) -4-methylcyclohexanone, 2-phenyl-1,2-butadion-2- (o-methoxycarbonyl) oxime, 1-phenyl-propanedione-2 -(O-ethoxycarbonyl) oxime, 1,3-diphenyl-propanetrione-2- (o-ethoxycarbonyl) oxime, 1-phenyl-3-ethoxy-propanetrione-2- (o-benzoy ) Oxime, Michler's ketone, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone, Naphthalene sulfonyl chloride, quinoline sulfonyl chloride, n-phenylthioacridone, 4,4-azobisisobutyronitrile, diphenyl disulfide, benzthiazole disulfide, triphenylphosphine, camphorquinone, Adeca N1717, carbon tetrabromide, Examples include combinations of photoreducing dyes such as tribromophenylsulfone, benzoin peroxide, eosin, and methylene blue with reducing agents such as ascorbic acid and triethanolamine. In this invention, these photoinitiators can be used 1 type or in combination of 2 or more types.

  Furthermore, when using the said photoinitiator, a photoinitiator adjuvant can be used together. Examples of such photopolymerization initiation assistants include tertiary amines such as triethanolamine and methyldiethanolamine, and benzoic acid derivatives such as ethyl 2-dimethylaminoethylbenzoate and ethyl 4-dimethylamidebenzoate. Yes, but not limited to these.

  To the composition for forming an optical functional layer, compounds as shown below can be added within a range not impairing the object of the present invention. Examples of compounds that can be added include polyester (meth) acrylate obtained by reacting (meth) acrylic acid with a polyester prepolymer obtained by condensing polyhydric alcohol and monobasic acid or polybasic acid; A polyurethane (meth) acrylate obtained by reacting a compound having two isocyanate groups with each other and then reacting the reaction product with (meth) acrylic acid; bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak Type epoxy resins, polycarboxylic acid polyglycidyl esters, polyol polyglycidyl ethers, aliphatic or cycloaliphatic epoxy resins, amino group epoxy resins, triphenolmethane type epoxy resins, dihydroxybenzene type epoxy resins and the like (meta Acu Photopolymerizable compounds such as epoxy (meth) acrylate obtained by reacting Le acid; photopolymerizable liquid crystal compound having an acryl group or methacryl group and the like. The amount of these compounds added to the composition for forming an optical functional layer can be determined within a range that does not impair the object of the present invention. By adding such a compound, the mechanical strength of the optical functional layer is improved, and the stability may be improved.

  The composition for forming an optical functional layer may contain a compound other than the above if necessary. The other compound is not particularly limited as long as it does not impair the optical properties of the optical functional layer according to the use of the retardation film of the present invention.

  The coating method for coating the optical functional layer-forming composition on the alignment layer is not particularly limited as long as it can achieve a desired flatness. Specifically, gravure coating method, reverse coating method, knife coating method, dip coating method, spray coating method, air knife coating method, spin coating method, roll coating method, printing method, dip pulling method, curtain coating method, die coating Examples thereof include, but are not limited to, a method, a casting method, a bar coating method, an extrusion coating method, and an E-type coating method.

  The thickness of the coating film of the composition for forming an optical functional layer is not particularly limited as long as the desired flatness can be achieved, but is preferably in the range of 0.1 μm to 50 μm, In particular, the range of 0.5 μm to 30 μm is preferable, and the range of 0.5 μm to 10 μm is particularly preferable. If the thickness of the coating film of the composition for forming an optical functional layer is thinner than the above range, the planarity of the optical functional layer may be impaired. If the thickness is thicker than the above range, the drying load of the solvent increases and production This is because the performance may deteriorate.

  As a method for drying the coating film of the composition for forming an optical functional layer, a commonly used drying method such as a heat drying method, a reduced pressure drying method, a gap drying method, or the like can be used. In addition, the drying method in the present invention is not limited to a single method, and a plurality of drying methods may be employed, for example, by changing the drying method sequentially according to the amount of solvent remaining.

  When a polymerizable material is used as the rod-shaped compound, a method for polymerizing the polymerizable material is not particularly limited, and may be arbitrarily determined according to the type of polymerizable functional group of the polymerizable material. . In particular, in the present invention, a method of curing by irradiation with actinic radiation is preferable. The actinic radiation is not particularly limited as long as it is a radiation capable of polymerizing a polymerizable material, but it is usually preferable to use ultraviolet light or visible light from the viewpoint of the ease of the device, etc. Among them, it is preferable to use irradiation light having a wavelength of 150 to 500 nm, preferably 250 to 450 nm, and more preferably 300 to 400 nm.

  As the light source of this irradiation light, low pressure mercury lamp (sterilization lamp, fluorescent chemical lamp, black light), high pressure discharge lamp (high pressure mercury lamp, metal halide lamp), short arc discharge lamp (super high pressure mercury lamp, xenon lamp, mercury xenon) Lamp). Among these, use of a metal halide lamp, a xenon lamp, a high-pressure mercury lamp, etc. is recommended. The irradiation intensity can be appropriately adjusted according to the content of the photopolymerization initiator.

  In the optical functional film thus produced, the rod-shaped compound usually shows “isotropic” and has only the property as an optically negative C plate. By stretching the film, a predetermined “anisotropy” can be easily imparted to the rod-shaped compound, and the rod-shaped compound can be optically provided with a property as a B plate.

B. Next, the liquid crystal display device of the present invention will be described. The liquid crystal display device of the present invention can be classified into two modes according to the mode.
Therefore, the liquid crystal display device of the present invention will be described below in each embodiment.

B-1: Liquid Crystal Display Device of First Aspect First, the liquid crystal display device of the first aspect of the present invention will be described. The liquid crystal display device of this aspect includes a liquid crystal cell, a polarizer disposed on both sides of the liquid crystal cell, a retardation film disposed on one side of the liquid crystal cell and disposed between the liquid crystal cell and the polarizer, The retardation film is the retardation film according to the present invention.

  Such a liquid crystal display device of this embodiment will be described with reference to the drawings. FIG. 5 is a schematic view showing an example of the liquid crystal display device of this embodiment. As illustrated in FIG. 5, the liquid crystal display device 20 a of this aspect includes a liquid crystal cell 21 and a polarizing plate 30 that is disposed on both sides of the liquid crystal cell 21 and a polarizing plate protective film 23 is bonded to both surfaces of the polarizer 22. The retardation film 10 according to the present invention is disposed between the liquid crystal cell 21 and the polarizing plate 30 on one side of the liquid crystal cell 21.

  According to the liquid crystal display device of this aspect, the retardation film according to the present invention is used as the retardation film, so that the optical properties of the retardation film are arbitrarily adjusted according to the aspect of the liquid crystal cell. It becomes possible to do. Therefore, according to the present variety, a liquid crystal display device having excellent viewing angle characteristics can be obtained.

The liquid crystal display device of this embodiment has at least a liquid crystal cell, a polarizer, and a retardation film.
Hereinafter, each of these components will be described in order.
In addition, about the retardation film used for this aspect, since it is the same as that of what was demonstrated in the term of the said "A. retardation film", description here is abbreviate | omitted.

1. Polarizer First, the polarizer used in this embodiment will be described. The polarizer used in this embodiment is not particularly limited as long as it has predetermined polarization characteristics, and a polarizer generally used in a liquid crystal display device can be used. As such a polarizer, usually, a film made of polyvinyl alcohol is impregnated with iodine and uniaxially stretched to form a complex of polyvinyl alcohol and iodine.

  The form of the polarizer used in this embodiment is not particularly limited as long as it can maintain a predetermined polarization characteristic for a long period of time. Usually, the form of a polarizing plate in which a polarizing plate protective film is bonded to both sides. Used as

When the polarizer used in this embodiment is used in the form of the polarizing plate, the polarizing plate protective film is particularly limited as long as it can protect the polarizer and has desired transparency. Is not to be done. Among them, the polarizing plate protective film used in the present invention preferably has a transmittance in the visible light region of 80% or more, and more preferably 90% or more.
Here, the transmittance of the polarizing plate protective film can be measured by JIS K7361-1 (Testing method of total light transmittance of plastic-transparent material).

  As a material constituting the polarizing plate protective film used in the present invention, for example, cellulose derivative, cycloolefin resin, polymethyl methacrylate, polyvinyl alcohol, polyimide, polyarylate, polyethylene terephthalate, polysulfone, polyethersulfone, amorphous polyolefin, Examples thereof include modified acrylic polymers, polystyrene, epoxy resins, polycarbonates and polyesters. In particular, in the present invention, it is preferable to use a cellulose derivative or a cycloolefin resin as the resin material.

  Here, the cellulose derivative and the cycloolefin-based resin are the same as those described as those used for the base material in the section “A. Retardation film”, and thus the description thereof is omitted here. .

  The configuration of the polarizing plate protective film used in this embodiment is not limited to a configuration composed of a single layer, and may have a configuration in which a plurality of layers are laminated. Moreover, when it has the structure by which the several layer was laminated | stacked, the layer of the same composition may be laminated | stacked, and the several layer which has a different composition may be laminated | stacked.

  In addition, the thickness of the polarizing plate protective film used in this embodiment can make the polarizing plate of this embodiment flexible within a desired range, and can be bonded to the polarizer described later. There is no particular limitation as long as the dimensional change can be within a predetermined range. In particular, the thickness of the polarizing plate protective film used in this embodiment is preferably in the range of 5 μm to 200 μm, particularly preferably in the range of 15 μm to 150 μm, and more preferably in the range of 30 μm to 100 μm. Is preferred. This is because if the thickness is smaller than the above range, the dimensional change of the polarizing plate of this embodiment may be large. Moreover, when thickness is thicker than said range, when cutting the polarizing plate of this aspect, for example, when processing scrap increases, wear of a cutting blade may become quick.

  The polarizing plate protective film used in this embodiment may have retardation. By using a polarizing plate protective film having retardation, there is an advantage that the polarizing plate of this embodiment can have a viewing angle compensation function of a liquid crystal display device.

  The aspect in which the polarizing plate protective film used in this aspect has a phase difference is not particularly limited as long as a desired phase difference can be exhibited. As such an aspect, for example, it has a configuration composed of a single layer and includes an optical property developing agent that exhibits retardation, and has retardation, and the above-described transparent resin material. A mode having retardation can be given by having a configuration in which a retardation layer containing a compound having refractive index anisotropy is laminated on a substrate. In the present embodiment, any of these embodiments can be suitably used.

2. Liquid Crystal Cell The liquid crystal cell used in this embodiment is not particularly limited, and any liquid crystal cell of any driving system can be used as long as it is a liquid crystal cell generally used in a liquid crystal display device. Especially, since the retardation film according to the present invention is used in the liquid crystal display device of this embodiment, it is preferable to use a VA liquid crystal cell.

3. Liquid crystal display device The liquid crystal display device of the present embodiment uses the retardation film according to the present invention, and the embodiment in which the retardation film is used is appropriately determined according to the type of the liquid crystal cell. It can be used in such a manner that the viewing angle characteristics can be expressed. Such an embodiment may be an embodiment in which the retardation film according to the present invention is disposed between the liquid crystal cell and the polarizing plate using the polarizer having the form of the polarizing plate, Alternatively, the polarizer may be in the form of a polarizing plate in which the retardation film according to the present invention is used as a polarizing plate protective film, and the polarizing plate may be disposed on the liquid crystal cell.

  The usage mode of such a retardation film will be described with reference to the drawings. FIG. 6 is a schematic view showing an example of an embodiment in which a retardation film is used in the present invention in the liquid crystal display device of this embodiment. As illustrated in FIG. 6, in the liquid crystal display element 20 a of this embodiment, the polarizing plate 30 in which the polarizing plate protective film 23 is bonded to both surfaces of the polarizer 22 is used as the polarizer, and the liquid crystal cell 21 and the polarizing plate are used. The aspect which arrange | positions the retardation film 10 which concerns on this invention between the board | plates 30 may be sufficient (FIG.6 (a)), or the retardation film 10 which concerns on this invention as a polarizer is a polarizing plate protective film. Alternatively, the polarizing plate 31 bonded to the polarizer 21 may be used, and the polarizing plate 31 may be disposed on the liquid crystal cell 21 (FIG. 6B).

  As a use mode of the retardation film in this embodiment, any of the above-described embodiments can be suitably used. Among them, the retardation film according to the present invention is used as a polarizing plate protective film as the polarizer. An embodiment in which a polarizing plate is used and the polarizing plate is disposed on the liquid crystal cell is preferable. This is because the liquid crystal display device can be thinned by using the retardation film according to the present invention also as a polarizing plate protective film.

B-2: Liquid Crystal Display Device of Second Aspect Next, the liquid crystal display device of the second aspect of the present invention will be described. The liquid crystal display device according to this aspect includes a liquid crystal cell, a polarizer disposed on both sides of the liquid crystal cell, and at least two sheets disposed on both sides of the liquid crystal cell and disposed between the liquid crystal cell and the polarizer. An optical functional film, wherein the optical functional film has a base material and an optical functional layer including a rod-shaped compound that is formed directly on the base material and has a random homogeneous orientation, Further, the optical functional film disposed on at least one side of the liquid crystal cell is optically characterized as an A plate.

Such a liquid crystal display device of this embodiment will be described with reference to the drawings. FIG. 7 is a schematic view showing an example of the liquid crystal display device of this embodiment. As illustrated in FIG. 7, the liquid crystal display device 20 b of this embodiment includes a liquid crystal cell 21, a polarizing plate 30 that is disposed on both sides of the liquid crystal cell 21, and a polarizing plate protective film 23 is bonded to both surfaces of the polarizer 22. The two optical functional films 1 are disposed on both sides of the liquid crystal cell 21 and between the liquid crystal cell 21 and the polarizing plate 30.
In such an example, the liquid crystal display device 20b of the present embodiment includes an optical functional layer in which the optical functional film 1 includes a substrate 1a and a rod-like compound that is formed directly on the substrate 1a and has a random homogeneous orientation. 1b, and the optical functional film 1 disposed on at least one side of the liquid crystal cell 21 is optically characterized as an A-plate.

  According to this aspect, the optical functional film including the optical functional layer including the rod-shaped compound having the random homogeneous alignment formed on both sides of the liquid crystal cell is used, and the optical functional film disposed on at least one side is optical. The optical characteristics of the two optical functional films can be arbitrarily adjusted by having the properties as the A plate, and the optical characteristics of the two optical functional films can be adjusted according to the mode of the liquid crystal cell. It becomes easy to adjust to the range. For this reason, according to this aspect, a liquid crystal display device excellent in viewing angle characteristics can be provided.

The liquid crystal display device of this embodiment has at least a liquid crystal cell, two optical functional films, and a polarizer.
Here, the optical functional film used in this embodiment is the same as that described in the above section “A. Retardation film”, and thus the description thereof is omitted here.
Further, the liquid crystal cell and the polarizer used in this embodiment are the same as those described in the section “B-1: Liquid crystal display device of first embodiment”, and the description thereof is omitted here.

  As described above, the liquid crystal display device according to this aspect is characterized in that an optical functional film is used on both surfaces of the liquid crystal cell, and at least one of them has an optically A-plate property. The two optical functional films used in the liquid crystal display device of this embodiment may be any film as long as at least one of them has optical properties as an A plate. Therefore, in this embodiment, only one of the optical functional films may be optically A-plate properties, or both optical functional films may be optically A-plate properties. You may have.

  In the liquid crystal display device according to this aspect, the optical functional film can be used in such a manner that a predetermined viewing angle characteristic can be appropriately exhibited according to the type of the liquid crystal cell, depending on the type of the liquid crystal cell. . Such an embodiment may be an embodiment in which the polarizer has the form of the polarizing plate, and the optical functional film is disposed between the liquid crystal cell and the polarizing plate. A polarizing plate in which the optical functional film is used as a polarizing plate protective film as a polarizer may be used, and the polarizing plate may be disposed on the liquid crystal cell.

  The usage mode of such an optical functional film will be described with reference to the drawings. FIG. 8 is a schematic view showing an example of a mode in which a retardation film is used in the present invention in the liquid crystal display device of the present aspect. As illustrated in FIG. 8, the liquid crystal display device 20 b of this embodiment uses a polarizing plate 30 in which a polarizing plate protective film 23 is bonded to both surfaces of a polarizer 22 as a polarizer, and the liquid crystal cell 21 and the polarizing plate. The optical functional film 1 may be disposed between the optical functional film 1 and the optical functional film 1 (FIG. 8A). Alternatively, as the polarizer, the optical functional film 1 is bonded to the polarizer 21 as a polarizing plate protective film. An embodiment in which the polarizing plate 32 is used and the polarizing plate 32 is disposed on the liquid crystal cell 21 may be used (FIG. 8B).

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the technical idea described in the claims of the present invention has substantially the same configuration and exhibits the same function and effect regardless of the case. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described in more detail by showing examples.

1. Example 1
(Preparation of optical functional film 1)
A photopolymerizable liquid crystal compound (compound (I) below) is used as a rod-like compound, which is dissolved in cyclohexanone by 15% by mass, and applied to a TAC film (Konica Minolta, trade name: KC4UYW) after drying by bar coating. The coating was performed so that the amount was 5 g / m ² . Subsequently, the rod-shaped compound was mixed and oriented with the polymer on the surface of the substrate by heating at 40 ° C. for 1 minute and at 80 ° C. for 1 minute to remove the solvent by drying. Furthermore, the optical functional film 1 was produced by immobilizing the rod-shaped compound by irradiating the coated surface with ultraviolet rays.

  As a result of measuring the phase difference of the produced optical functional film 1 with an automatic birefringence measuring device (manufactured by Oji Scientific Instruments Co., Ltd., trade name: KOBRA-WR), the measurement light was incident on the sample surface vertically or obliquely. The anisotropy that increases the retardation of the base film was confirmed from the chart of the optical retardation and the incident angle of the measuring light. Moreover, the phase difference was measured with the same measuring apparatus. As a result, nx = 1.508, ny = 1.508, nz = 1.504, nx = ny> nz, and it was confirmed that an optically negative C plate was provided. The phase difference values were Re = 1.2 nm and Rth = 143 nm.

(Check adhesion)
In order to examine the adhesion, a peel test was performed. For the peel test, put the obtained sample into a 1 mm square cut grid, apply an adhesive tape (manufactured by Nichiban Co., Ltd., Cellotape (registered trademark)) to the liquid crystal surface, then peel off the tape and visually observe it. did. As a result, the degree of adhesion was 100%. The degree of adhesion described here is expressed by the following equation.
Adhesion degree (%) = (part which was not peeled / area where tape was applied) × 100

Preparation of (Optical Function Film 2) A photopolymerizable liquid crystal compound (the following compound (II)) is used as a rod-like compound, which is dissolved in 15% by mass in cyclohexanone, and a TAC film (manufactured by Konica Minolta, trade name: KC8UX2MW). Coating was performed by bar coating so that the coating amount after drying was 3.8 g / m ² . Subsequently, the rod-shaped compound was mixed and oriented with the polymer on the surface of the substrate by heating at 40 ° C. for 1 minute and at 80 ° C. for 1 minute to remove the solvent by drying. Further, the rod-shaped compound was immobilized by irradiating the coated surface with ultraviolet rays. This was uniaxially stretched in the in-plane direction while being heated at 165 ° C. so that the stretch ratio was 1.2 times by a stretching experiment machine, and the optical functional film 2 was produced.

  As a result of measuring the phase difference of the optical functional film 2 with an automatic birefringence measuring device (trade name: KOBRA-WR, manufactured by Oji Scientific Instruments Co., Ltd.) Anisotropy that increases the retardation of the base film was confirmed from the chart of the optical retardation and the incident angle of the measuring light. Moreover, the phase difference was measured with the same measuring apparatus. As a result, nx = 1.515 (stretching direction), ny = 1.510, nz = 1.508, nx> ny> nz, and confirmed to have properties as an optically negative B plate did. The phase difference values were Re = 100 nm and Rth = 170 nm at this time.

(Confirmation of liquid crystal alignment state of optical functional films 1 and 2)
The arrangement state of the rod-like compounds in the optical functional layers of the optical functional films 1 and 2 was confirmed by measuring the Raman spectrum by the following procedure. Here, the Raman spectrum was measured with a laser Raman spectrophotometer (JASCO NRS-3000). The exposure time was 15 seconds, the number of integrations was 8, and the excitation wavelength was 532.11 nm.

First, a cross section of TAC (manufactured by Konica Minolta Co., Ltd.) as a base material was cut out, and incident on the cross section so that the electric field vibration surface of linearly polarized light was parallel or perpendicular to the film surface, and a Raman spectrum was obtained.
Next, the cross section of the optical functional film 1 is taken out, and similarly, the light is incident on the cross section of the optical functional layer, which is a mixed layer of liquid crystal and TAC, so that the electric field vibration plane of linearly polarized light is parallel or perpendicular to the film plane. Got.
Next, the linearly polarized electric field vibrating surface was incident from the coating surface side from the film surface of the optical functional film 2 so as to be parallel or perpendicular to the axial direction, and a Raman spectrum was obtained. Each peak intensity and calculated peak intensity ratio obtained from them are shown in Table 1.

FIG. 9 shows an example of the Raman spectrum. Here, FIG. 9 (a) shows the measurement with the measurement light incident so that the electric field vibration plane of the linearly polarized light coincides with the slow axis direction, and FIG. 9 (b) shows the linearly polarized light in the fast axis direction. The measurement light is incident and measured so that the electric field vibration planes coincide with each other. The Raman peak intensity ratio is obtained by reading peak intensities at 1605 cm ⁻¹ and 2942 cm ⁻¹ from a spectrum and calculating from these values.

  Here, the “slow axis direction cut surface” in Table 1 means a cut surface when the optical function film is cut in a direction parallel to the slow axis direction in the plane of the optical function film. On the other hand, the “fast axis direction cut surface” means a cut surface when the presence or absence of the optical function film is cut in a direction perpendicular to the slow axis direction in the plane of the optical function film.

In Raman spectroscopy, when monochromatic light (ν ₀ ) such as laser light hits a substance, strong light having the same wavelength as the incident light (Rayleigh scattered light ν ₀ ) and weak light having a different wavelength from the incident light (Raman scattered light ν _0). ± ν) is scattered, and the Raman scattered light appears to deviate from the incident light by a certain wave number based on the vibration and rotation of the molecules constituting the substance. This wave number is called Raman shift. In this measurement, Raman spectroscopy was measured for the purpose of confirming the alignment state of the liquid crystal. That is, from the retardation value of each sample, it was considered that the liquid crystal in this sample was randomly homogeneously oriented, and that the molecules were oriented to some extent in the stretching direction by further stretching. In this measurement, the linearly polarized light whose electric field vibration plane was changed was incident on the sample, and the alignment state of the liquid crystal was observed by comparing the peak intensity ratio considered to be mainly the benzene ring-derived peak and the CH-derived peak of the liquid crystal, This idea was verified.

(1) Even if linearly polarized light is incident from the coating surface and the electric field vibration surface is changed, the difference in peak intensity ratio is small. This result suggests that the liquid crystal molecules are oriented in random directions. (Vibration plane parallel: 0.775, vertical: 0.756)
(2) When linearly polarized light is incident from the cross section and the electric field vibration plane is changed perpendicularly to the film surface (peak intensity ratio 0.467) and parallel (peak intensity ratio 1.033), the peak intensity ratio is It became bigger.
The results of (1) and (2) suggest that the liquid crystal molecules are randomly oriented in the plane, but the liquid crystal molecules are oriented horizontally with respect to the film plane.

  As described above, when linearly polarized light is incident from the film application surface, no difference is observed in the peak intensity ratio even if the electric field vibration surface of the linearly polarized light is changed before stretching (optical functional film 1). When the electric field vibration surface of linearly polarized light is made parallel to the stretching direction by stretching (optical functional film 2), the peak intensity is 1.534, and when the electric field vibration surface is aligned in the vertical direction, it is larger than 1.117. This suggests that the liquid crystal molecules are aligned in the stretching direction.

(Production of retardation film)
The optical functional film 1 and the optical functional film 2 were bonded together to produce the retardation film of the present invention. At this time, the optical functional film 1 and the optical functional film 2 were bonded using a transparent double-sided adhesive tape (CS9621 manufactured by Nitto Denko Corporation) as an adhesive layer, and first the light release liner of the transparent double-sided adhesive tape was peeled off, The optical functional film 1 was bonded to the transparent double-sided adhesive tape, then the heavy release liner of the transparent double-sided adhesive tape was peeled off, and then the optical functional film 2 was bonded.

(Production of liquid crystal display device)
A liquid crystal display device was produced using the produced retardation film. At this time, the configuration of the liquid crystal display device uses a TAC film (manufactured by Konica Minolta, trade name: KC8UX2MW) as a polarizing plate protective film, and the polarizing plate 1 arranged on both sides of a polarizer made of PVA, and the above A retardation film is used as a polarizing plate protective film on one side, and a polarizing plate protective film made of a TAC film (manufactured by Konica Minolta, trade name: KC8UX2MW) is used as the other polarizing plate protective film, and these are made of PVA. The polarizing plates 2 arranged on both sides of the VA liquid crystal cell were respectively arranged on both sides of the VA liquid crystal cell. In this example, the polarizing plate 1 was used as the backlight-side polarizing plate, and the polarizing plate 2 was used as the display-side polarizing plate. The polarizing plate 1 was disposed such that the retardation film side was directed to the liquid crystal cell side.

2. Comparative Example A liquid crystal display device was produced in the same manner as in Example except that a TAC film (manufactured by Konica Minolta, trade name: KC8UX2MW) was used instead of the retardation film.

3. Evaluation Using a light source of 450 nm as B (blue), 550 nm as G (green), and 610 nm as R (red), and using EZContrast 160R (manufactured by ELDIM) for the measurement, the liquid crystal display devices prepared in the above examples and comparative examples The light leakage at that time was verified. The azimuth angles of the absorption axes of the two polarizing plates are 45 ° and 135 °. At each wavelength, it was found that light leakage at azimuth angles of 0 °, 90 °, 180 °, and 270 ° was significantly reduced in the example in comparison with the comparative example. It was also found that there was almost no color shift even when R, G, and B were displayed and viewed obliquely from each azimuth direction. In particular, compared to the case where a positive A plate and a negative C plate were separately prepared and bonded with an adhesive, the contrast was excellent and no unevenness was observed.

It is the schematic which shows an example of the retardation film of this invention. It is the schematic which shows an example of the optical function film used for this invention. It is the schematic which shows the other example of the optical function film used for this invention. It is the schematic which shows the other example of the optical function film used for this invention. It is the schematic which shows an example of the liquid crystal display device of the 1st aspect of this invention. It is the schematic which shows the other example of the liquid crystal display device of the 1st aspect of this invention. It is the schematic which shows an example of the liquid crystal display device of the 2nd aspect of this invention. It is the schematic which shows the other example of the liquid crystal display device of the 2nd aspect of this invention. It is a graph which shows an example of the Raman spectrum of the optical function film used for this invention. It is the schematic showing an example of a common liquid crystal display device. It is a schematic sectional drawing which shows an example of the liquid crystal display device using two retardation films. It is a schematic sectional drawing which shows an example of the conventional phase difference film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical function film 1a ... Base material 1b ... Optical function layer 1c ... Rod-shaped compound 2 ... Adhesion layer 10 ... Phase difference film 20a, 20b ... Liquid crystal display device 21 ... Liquid crystal cell 22 ... Polarizer 23 ... Polarizing plate protective film 41, DESCRIPTION OF SYMBOLS 42 ... Retardation film 100 ... Liquid crystal display device 102A, 102B ... Polarizing plate 104 ... Liquid crystal cell 105 ... Base material 106 ... Orientation layer 107 ... Retardation layer

Claims (5)

A retardation film having a configuration in which two optical functional films having a base material and an optical functional layer formed directly on the base material and containing a rod-shaped compound are laminated,
In the optical functional layer, the rod-like compound forms a random homogeneous orientation, and at least one of the two optical functional films optically has a property as an A plate. the film.   Of the two optical functional films, at least one has the property as an optically A plate and the property as a negative C plate, and the other has only the property as an optically negative C plate. The retardation film according to claim 1, wherein the retardation film has a retardation film.   The retardation film according to claim 1, wherein the substrate is made of a cellulose derivative. A liquid crystal display device comprising: a liquid crystal cell; a polarizer disposed on both sides of the liquid crystal cell; and a retardation film on one side of the liquid crystal cell and disposed between the liquid crystal cell and the polarizer. ,
A liquid crystal display device, wherein the retardation film is the retardation film according to any one of claims 1 to 3. A liquid crystal display comprising a liquid crystal cell, a polarizer disposed on both sides of the liquid crystal cell, and at least two optical functional films disposed on both sides of the liquid crystal cell and between the liquid crystal cell and the polarizer A device,
The optical functional film has a base material and an optical functional layer that is directly formed on the base material and includes a rod-like compound having a random homogeneous orientation, and is further disposed on at least one side of the liquid crystal cell. The liquid crystal display device, wherein the optical functional film has optical properties as an A plate.

Images