JP2010250104A - Optical functional film, method for manufacturing optical functional film, and polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical functional film which is a retardation film using a substrate comprising a cellulose derivative and has an optically biaxial property of high degree of freedom in optical characteristic design. <P>SOLUTION: The optical functional film includes a substrate 1 comprising a cellulose derivative and an optical functional layer 2 directly formed on the substrate 1 and containing a rod-shaped compound 3 and has an optically biaxial property, and the rod-shaped compound 3 forms irregular random homogenous orientation in the optical functional layer 2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical functional film exhibiting optical biaxiality mainly used in liquid crystal display devices and the like, and more specifically, a base material made of a cellulose derivative is used, and a rod-like compound is irregular random homogeneous alignment. The present invention relates to an optical functional film having a novel arrangement form.

  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 a general liquid crystal display device, as shown in FIG. 7, a liquid crystal display device having an incident side polarizing plate 102 </ b> A, an outgoing side polarizing plate 102 </ b> B, and a liquid crystal cell 104 can be exemplified. The polarizing plates 102A and 102B are configured to selectively transmit only linearly polarized light 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 101 includes a large number of cells corresponding to the pixels, and is disposed between the polarizing plates 102A and 102B.

  As such a liquid crystal display device, those using various driving methods are known depending on the arrangement form of the liquid crystal material used in the liquid crystal cell. The main ones of liquid crystal display devices that are popular today are classified into TN, STN, MVA, IPS, OCB, and the like. In particular, today, those having the MVA and IPS driving methods have come into widespread use.

  On the other hand, the liquid crystal display device has a problem of viewing angle dependency due to the refractive index anisotropy of the liquid crystal cell and the polarizing plate as a specific problem. This problem of viewing angle dependency is a problem that the color and contrast of an image that is visually recognized change when the liquid crystal display device is viewed from the front and when viewed from an oblique direction. Such a problem of viewing angle characteristics has become more serious as the liquid crystal display device has recently been enlarged.

  Various techniques have been developed so far to improve the viewing angle dependency problem. As a typical method, there is a method using a retardation film. In the method using this retardation film, for example, as shown in FIG. 8, a retardation film 103 having predetermined optical characteristics is disposed between the liquid crystal cell 101 and the polarizing plates 102A and 102B, thereby depending on the viewing angle. It is a way to improve sex problems. Since such a method can improve the viewing angle dependency problem only by incorporating the retardation film 103 in the liquid crystal display device, it can be easily obtained as a liquid crystal display device having excellent viewing angle characteristics. It has been widely used.

  As a method for improving viewing angle characteristics using a retardation film, a method of separately arranging a retardation film and a polarizing plate as shown in FIG. 8 has been the mainstream. A system in which a film is also used as a polarizing plate protective film constituting the polarizing plate has become mainstream. That is, as illustrated in FIG. 9, a general liquid crystal display device has a configuration in which polarizing plates 102 </ b> A and 102 </ b> B are arranged on both sides of the liquid crystal cell 101. The polarizer 111 is sandwiched between two polarizing plate protective films 112a and 112b (FIG. 9A). When the viewing angle characteristic of the liquid crystal display device is improved using the retardation film 103, as illustrated in FIG. 9B, the inner polarizing plate of the two polarizing plate protective films 112a and 112b. The use of polarizing plates 102A ′ and 102B ′ in which the retardation film 103 is used as the protective film 112a has become the mainstream in recent years.

Here, the optical characteristics required for the retardation film depend on the type of the liquid crystal display device to be improved in viewing angle characteristics. For example, in an IPS (In-Plane Switching) type liquid crystal display device, a retardation film having the properties of an optically A plate and a positive C plate is used. In Patent Documents 1 to 3, a retardation film used in such an IPS liquid crystal display device is optically formed on a transparent substrate made of a cycloolefin resin optically having a property as an A plate. In which a retardation layer having properties as a positive C plate is formed is disclosed.
The retardation film using a transparent substrate made of a cycloolefin resin having such a configuration is less likely to absorb and expand even under a high-temperature and high-humidity atmosphere, and also has an advantage that the durability of optical properties is also good. It is what has.
However, on the other hand, since the transparent substrate made of such a cycloolefin resin has extremely low moisture permeability, the retardation film using such a transparent substrate is also used as the polarizing plate protective film as described above. Then, in the process of manufacturing the polarizing plate, the moisture contained in the polarizer cannot pass through the polarizing plate protective film and evaporate, resulting in a phenomenon that the liquid crystal is sealed inside the polarizing plate. was there. Further, when such a phenomenon occurs, the durability of the polarizing plate is remarkably lowered, and as a result, there is a problem that the stability with time of the liquid crystal display device itself is impaired.

  In this respect, a retardation film composed of a film made of a cellulose derivative, which is a member of a typical optical film for liquid crystal display devices, has excellent moisture permeability, so that the above-described durability problem hardly occurs. On the other hand, there has been a problem that it is difficult to produce a retardation film having desired optical characteristics.

JP 2002-174725 A JP 2003-121853 A JP-A-2005-70098

  The present invention has been made in view of the above problems, and is a retardation film using a substrate made of a cellulose derivative, and has an optical function exhibiting optical biaxiality with a high degree of freedom in optical property design. The main purpose is to provide a film.

  In order to solve the above-described problems, the present invention provides an optical functional film having a base composed of a cellulose derivative and an optical functional layer directly formed on the base and having a rod-like compound, and exhibiting optical biaxiality. And the said rod-shaped compound forms the irregular random homogeneous orientation in the said optical function layer, The optical function film characterized by the above-mentioned is provided.

According to the present invention, since the rod-like compound forms an irregular random homogeneous orientation in the optical functional layer, the optical biaxiality is excellent using a substrate having arbitrary optical characteristics. An optical functional film can be obtained.
Further, according to the present invention, when the substrate is made of a cellulose derivative having excellent moisture permeability, for example, when a polarizing plate is produced using the optical functional film of the present invention as a polarizing plate protective film, it is contained in a polarizer. Moistened water can be volatilized through the polarizing plate protective film. Moreover, since it has good adhesion to a polarizer mainly composed of PVA and does not require a liner unlike a norbornene-based resin, there is an advantage that the problem of foreign matters is small and the yield is good.
For this reason, according to the present invention, a substrate made of a cellulose derivative is used, and an optical functional film exhibiting optical biaxiality with a high degree of freedom in optical property design can be obtained.

  The optical functional film of the present invention has a relationship of nx> ny> nz to the refractive index nx in the slow axis direction in the in-plane direction, the refractive index ny in the fast axis direction in the in-plane direction, and the refractive index nz in the thickness direction. Is preferably established. This is because the optical functional film of the present invention can be made more excellent in optical biaxiality.

  The optical functional film of the present invention preferably has an in-plane retardation (Re) in the range of 70 nm to 180 nm. The retardation in the thickness direction (Rth) is preferably in the range of 75 nm to 300 nm. This is because it becomes easy to set the optical characteristics expressed by the optical functional film of the present invention within a range suitable for use as an optical compensation film of a liquid crystal display device, for example. Further, for example, by controlling the values of in-plane retardation (Re) and retardation in the thickness direction (Rth) to make the relationship of refractive index close to nx> ny ≧ nz, it is used for an IPS liquid crystal display device. There is also an advantage that it can be used as an A plate of a retardation film.

  The optical functional film of the present invention preferably has an Nz coefficient in the range of 1.0 to 2.5. This is because it becomes easy to set the optical characteristics expressed by the optical functional film of the present invention within a range suitable for use as an optical compensation film of a liquid crystal display device, for example.

  Moreover, in this invention, it is preferable that the said rod-shaped compound is what has a polymeric functional group. Since the rod-shaped compound has a polymerizable functional group, the rod-shaped compound can be polymerized and fixed, so that the rod-shaped compound forms an irregular random homogeneous orientation in the optical function layer. This is because, by fixing, it is possible to obtain an optical functional film that is excellent in alignment stability and hardly changes in optical characteristics.

  In the present invention, the rod-like compound preferably has a structure in which a polymerizable functional group and a mesogenic group are bonded via an alkyl chain having 4 or more carbon atoms. This is because the use of the rod-shaped compound having such a structure makes it easy to arrange the rod-shaped compounds in an embodiment that exhibits optical biaxiality as the entire optical functional film of the present invention. .

  In the present invention, the rod-like compound is preferably a liquid crystal material. 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.

  In the present invention, the wavelength dependence of in-plane retardation (Re) is preferably a positive dispersion type. This is because the optical properties of the optical functional film of the present invention can be made suitable as an optical compensation film for a liquid crystal display device.

In the present invention, the rod-shaped compound has a rod-shaped main skeleton to which two or more benzene rings are bonded, and the in-plane slow axis direction Raman peak intensity in the optical functional layer. The ratio (1605 cm ⁻¹ / 2942 cm ⁻¹ ) is preferably 1.1 times or more of the in-plane fast axis direction Raman peak intensity ratio (1605 cm ⁻¹ / 2942 cm ⁻¹ ). This is because the optical functional layer in the present invention can be made excellent in in-plane retardation (Re) expression.

In the present invention, the rod-shaped compound has a rod-shaped main skeleton to which two or more benzene rings are bonded, and the thickness direction of the cut surface in the thickness direction of the optical function layer is relative to the thickness direction. that the Raman peak intensity ratio in the vertical direction ^{(1605cm -1} / ^2942cm -1), is not less than 1.1 times the Raman peak intensity ratio in the parallel direction to the thickness direction ^{(1605cm -1} / ^2942cm -1) Te preferable. This is because the optical functional layer in the present invention can be made excellent in the expression of retardation (Rth) in the thickness direction.

  The present invention also provides an optical film having a base material composed of a cellulose derivative 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 optically uniaxial. , The refractive index nx in the slow axis direction in the in-plane direction, the refractive index ny in the fast axis direction and the refractive index nz in the thickness direction in the in-plane direction, nx ≠ ny, Alternatively, an optical functional layer including a base material in which a relationship of nx ≠ ny ≠ nz is established, and a rod-shaped compound that is directly formed on the base material and has an irregular random homogeneous orientation, and further exhibits optical biaxiality; A method for producing an optical functional film is provided, which comprises producing an optical functional film having:

  According to the present invention, an optical film having a base material made of a cellulose derivative 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 that exhibits optical uniaxiality. And stretching the substrate, the refractive index nx in the slow axis direction in the in-plane direction, the refractive index ny in the fast axis direction in the in-plane direction, and the refractive index nz in the thickness direction are set to nx ≠ The relationship of ny or nx ≠ ny ≠ nz can be established. Furthermore, since the random homogeneous orientation can be changed to an irregular random homogeneous orientation by stretching, optical biaxiality can be imparted to the optical functional layer. Therefore, according to the present invention, the refractive index nx in the slow axis direction in the in-plane direction, the refractive index ny in the fast axis direction in the in-plane direction, and the refractive index nz in the thickness direction are nx ≠ ny or nx ≠ It is possible to easily form an optical functional film in which an optical functional layer having an optical biaxial property is formed on a base material in which the relationship of ny ≠ nz is established and a rod-like compound that is irregularly homogeneously oriented on the base material. Therefore, an optical functional film having a high degree of freedom in optical property design can be easily produced.

  The present invention comprises the optical functional film of the present invention, a polarizer formed on any surface of the optical functional film, and a polarizing plate protective film formed on the polarizer surface. A polarizing plate is provided.

  According to the present invention, by using the optical functional film of the present invention, a polarizing plate having a viewing angle compensation function of a liquid crystal display device and excellent in durability can be obtained.

  The present invention provides a retardation film using a base material made of a cellulose derivative, and can provide an optical functional film exhibiting optical biaxiality with a high degree of freedom in optical property design.

It is a schematic sectional drawing which shows an example of the optical function film of this invention. It is a schematic sectional drawing which shows the other example of the optical function film of this invention. It is the schematic which shows an example of the manufacturing method of the optical function film of this invention. It is the schematic which shows an example of the optical film used for the manufacturing method of an optical function film in this invention. It is a schematic sectional drawing which shows an example of the polarizing plate of this invention. It is an example of the in-plane Raman spectroscopy spectrum of the optical function film of this invention. It is the schematic showing an example of a common liquid crystal display device. It is the schematic which shows an example of the liquid crystal display device in which the phase difference film was used. It is the schematic which shows the other example of the liquid crystal display device with which the phase difference film was used.

The present invention relates to an optical functional film, a method for producing the optical functional film, and a polarizing plate.
Hereinafter, the optical functional film, the method for producing the optical functional film, and the polarizing plate of the present invention will be described in detail.

A. Optical Function Film First, the optical function film of the present invention will be described. The optical functional film of the present invention has a base material composed of a cellulose derivative and an optical functional layer directly formed on the base material and having a rod-like compound, and exhibits optical biaxiality. The rod-like compound forms an irregular random homogeneous orientation in the optical functional layer.

Next, the optical functional film of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view showing an example of the optical functional film of the present invention. As shown in FIG. 1, the optical functional film 10 of the present invention has a base material 1 made of a cellulose derivative and an optical functional layer 2 directly formed on the base material 1.
In such an example, the optical functional film 10 of the present invention includes the rod-shaped compound 3 in which the optical functional layer 2 has formed an irregular random homogeneous orientation, and the optical functional film 10 as a whole has optical biaxiality. It is characterized by showing.

According to the present invention, since the rod-like compound forms an irregular random homogeneous orientation in the optical functional layer, the optical biaxiality is excellent using a substrate having arbitrary optical characteristics. An optical functional film can be obtained.
Further, according to the present invention, when the substrate is made of a cellulose derivative having excellent moisture permeability, for example, when a polarizing plate is produced using the optical functional film of the present invention as a polarizing plate protective film, it is contained in a polarizer. Moistened water can be volatilized through the polarizing plate protective film. Moreover, since it has good adhesion to a polarizer mainly composed of PVA and does not require a liner unlike a norbornene-based resin, there is an advantage that the problem of foreign matters is small and the yield is good.
For this reason, according to the present invention, a substrate made of a cellulose derivative is used, and an optical functional film exhibiting optical biaxiality with a high degree of freedom in optical property design can be obtained.

Here, the optical biaxiality in the present invention means having two optically isotropic optical axes. The optical functional film of the present invention is characterized by exhibiting optical biaxiality. However, exhibiting optical biaxiality means that the refractive index in the slow axis direction of the optical functional film is nx, and the refractive index in the fast axis direction. Can be evaluated by confirming that the relationship of nx ≠ ny ≠ nz holds, where ny is the refractive index in the thickness direction and nz is the refractive index in the thickness direction.
Here, the establishment of the above relationship in nx, ny and nz can be measured, for example, by the parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments.

  Next, the irregular random homogeneous orientation in the present invention will be described. The irregular random homogeneous alignment in the present invention is an alignment state formed by the rod-shaped compound contained in the optical functional layer. By having such an alignment state, the optical functional film of the present invention is used without using an alignment film. Optical biaxiality can be imparted.

The irregular random homogeneous orientation of the rod-like compound in the present invention has at least the following three characteristics. That is, the anomalous random homogeneous orientation in the present invention is
First, when the optical functional layer is viewed from the direction perpendicular to the surface of the optical functional layer, the arrangement direction of the rod-shaped compounds has anisotropy (hereinafter, sometimes simply referred to as “anisotropic”). ),
Second, the size of the domain formed by the rod-shaped compound in the optical functional layer is smaller than the wavelength in the visible light region (hereinafter, sometimes simply referred to as “dispersibility”),
Third, in the optical functional layer, the rod-like compound molecules are present on 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 property”). ”),
At least.

  Next, the irregular random homogeneous orientation in the present invention will be described with reference to the drawings. FIG. 2A shows a case where the optical functional film of the present invention is viewed from the direction perpendicular to the surface (xy plane) of the optical functional layer represented by A in FIG. 1 (xy plane). FIG. 2B and 2C are cross-sectional views taken along line B-B 'in FIG.

First, “anisotropy” possessed by the irregular random homogeneous orientation in the present invention will be described with reference to FIG. As shown in FIG. 2A, the above “anisotropy” indicates that the rod-like compound is formed in the optical functional layer 2 when the optical functional film 10 of the present invention is viewed from the direction perpendicular to the surface of the optical functional layer 2. 3 shows an average arrangement in one direction.
That is, when the probability distribution function (probability density function) of each rod-like compound molecule oriented in each direction in the xy plane (surface of the optical functional layer) is obtained, the probability distribution function is determined in a specific direction (example in FIG. 2) in the xy plane. In this case, it is distributed so as to have a peak (average orientation direction) in the x direction and a predetermined dispersion (variation width in the orientation direction) in the orientation direction. Furthermore, in other words, the orientation direction of the long axis of the rod-like compound molecule is not completely aligned in parallel, nor is it completely disordered. An example thereof is shown in FIG.
Here, in the present invention, in order to explain the arrangement direction of the rod-shaped compounds 3, the molecular major axis direction (hereinafter referred to as molecular axis) represented by a in FIG. . Therefore, the fact that the rod-shaped compounds are arranged in one direction means that the molecular axis a of the rod-shaped compound 3 contained in the optical functional layer is oriented in one direction on average.
As described above, the “anisotropy” in the present invention does not require that the rod-like compounds are completely arranged in one direction, and the arrangement directions of the rod-like compounds are arranged in one direction on average. It is sufficient that the optical functional layer is provided with desired optical biaxiality. The degree of such anisotropy will be described later.

  Next, the “dispersibility” possessed by the irregular random homogeneous orientation in the present invention will be described with reference to FIG. As shown in FIG. 2A, the above “dispersibility” means that when the rod-shaped compound 3 forms the domain b in the optical functional layer 2, 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 is, the more preferable, and the state where the rod-like compound is dispersed in a single molecule is the most preferable.

Next, the “in-plane orientation” possessed by the irregular random homogeneous orientation in the present invention will be described with reference to FIG. As shown in FIG. 2B, the above-mentioned “in-plane orientation” means that the rod-like compound 3 in the optical functional layer 2 has a molecular axis a with respect to the normal direction A of the optical functional layer 3 (z direction in FIG. 1). It is oriented so as to be substantially perpendicular (corresponding to the xy plane in FIG. 1). As the “in-plane orientation” in the present invention, as shown in FIG. 2B, the molecular axes a of all the rod-like compounds 3 in the optical functional layer 2 are substantially perpendicular to the normal direction A. The rod-like compound 3 whose molecular axis a ′ is not perpendicular to the normal direction A was present in the optical functional layer 2 as shown in FIG. 2C, for example. However, the case where the average direction of the molecular axis a of the rod-shaped compound 3 existing in the optical functional layer 3 is substantially perpendicular to the normal direction A is included.
That is, in FIG. 2, even if the molecular axis direction of each rod-like compound molecule has a distribution, the molecular axis direction averaged over all the molecules of the rod-like compound exists substantially in the xy plane.

  In the optical functional film of the present invention, the rod-shaped compound forms an irregular random homogeneous orientation, so that the refractive index nx in the x direction, the refractive index ny in the y direction, and the refractive index nz in the z direction shown in FIG. In addition, since it is easy to establish the relationship of nx> ny> nz, the optical functional film of the present invention exhibits optical biaxiality.

  As described above, the irregular random homogeneous orientation in the present invention is characterized by exhibiting the above-mentioned “anisotropic”, “dispersibility” and “in-plane orientation”, but the rod-like compound is irregular random homogeneous orientation. The formation of can be confirmed by the following method.

  First, a method for confirming “anisotropy” possessed by the irregular random homogeneous orientation in the present invention will be described. The “anisotropy” can be confirmed by evaluating the in-plane retardation of the optical functional layer constituting the optical functional film of the present invention (hereinafter sometimes simply referred to as “Re”).

The rod-shaped compound has the above-mentioned “anisotropy” because the in-plane retardation (Re) value of the optical functional layer is within a range in which the optical functional layer can exhibit optical biaxiality. This can be confirmed. In particular, in the present invention, the in-plane retardation (Re) of the optical functional layer is preferably in the range of 5 nm to 300 nm, and more preferably in the range of 10 nm to 200 nm. It is preferably within the range of 40 nm to 150 nm.
Here, Re represents the refractive index nx in the slow axis direction (direction in which the refractive index is largest) and the fast axis direction (with the highest refractive index) in the plane of the optical functional layer constituting the optical functional film of the present invention. The refractive index ny in the small direction) and the thickness d (nm) of the optical function layer are values represented by the equation Re = (nx−ny) × d.

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

When the rod-shaped compound having a rod-shaped main skeleton to which two or more benzene rings are bonded is used, the “anisotropy” is the Raman peak in the in-plane direction of the optical functional layer. It can also be confirmed by measuring the intensity ratio (1605 cm ⁻¹ / 2942 cm ⁻¹ ). 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.

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. 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.

  Next, a method for confirming “dispersibility” of the irregular random homogeneous orientation in the present invention will be described. The above “dispersibility” means that the haze value of the optical functional layer constituting the optical functional film of the present invention is 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. Can be confirmed. In particular, in the present invention, the haze value of the optical functional layer is preferably in the range of 0% to 5%, particularly preferably in the range of 0% to 1%, and more preferably 0% to It is preferable to be within the range of 0.5%.

  Here, the haze value of the optical function layer can be obtained, for example, by subtracting the haze value of a layer other than the optical function layer from the haze value of the optical function film. 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.

  The size of the domain in the present invention is less than or equal to the wavelength of visible light, but the specific size is preferably 380 nm or less, more preferably 350 nm or less, particularly 200 nm or less. Preferably there is. In the present invention, since the rod-shaped compound is preferably monomolecularly dispersed, the lower limit value of the domain size is the size of a single molecule of the rod-shaped compound. The size of such a domain can be evaluated by observing the optical functional layer with a polarizing microscope, AFM, SEM, or TEM.

Next, a method for confirming “in-plane orientation” possessed by the irregular random homogeneous orientation in the present invention will be described. The above “in-plane orientation” means that the Re of the optical functional layer constituting the optical functional film of the present invention is in the above-described range, and that the optical functional layer in the present invention exhibits optical biaxiality. This can be confirmed by having a retardation in the thickness direction as much as possible (hereinafter, sometimes simply referred to as “Rth”). In particular, the Rth of the optical functional layer in the present invention is preferably in the range of 50 nm to 400 nm, more preferably in the range of 75 nm to 300 nm, and particularly preferably in the range of 100 nm to 250 nm. .
Here, Rth is a refractive index nx in the slow axis direction (direction in which the refractive index is the largest) and a fast axis direction (refractive index) in the plane of the optical functional layer constituting the optical functional film of the present invention. Is expressed by the following formula: Rth = {(nx + ny) / 2−nz} × d, based on the refractive index ny in the smallest direction), the refractive index nz in the thickness direction, and the thickness d (nm) of the optical function layer. Value.
The Rth value in the present invention refers to 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, the optical functional film of the present invention has a base material and an optical functional layer directly formed on the base material. Hereinafter, each configuration of the optical functional film of the present invention will be described in detail.

1. Optical functional layer First, the optical functional layer constituting the optical functional film of the present invention will be described. The optical functional layer in the present invention is directly formed on a substrate to be described later, and includes a rod-shaped compound having an irregular random homogeneous orientation.
Hereinafter, such an optical functional layer will be described in detail.

(1) Rod-shaped compound The rod-shaped compound used for this invention is demonstrated. The rod-shaped compound used in the present invention is not particularly limited as long as it can form irregular random homogeneous orientation in the optical functional layer and has refractive index anisotropy in the molecule.
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-like compound used in the present invention, those having a relatively small molecular weight are 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 rod-shaped compound easily penetrates into the base material to be described later, so that it becomes easy to form a “mixed” state at the bonding site between the base material and the optical functional layer. This is because the adhesion to the layer can be improved.
In addition, it is a material which has the polymeric functional group mentioned later, Comprising: About the rod-shaped compound superposed | polymerized in an optical function layer, the molecular weight before superposition | polymerization shall be shown.

  Moreover, the rod-shaped compound used in the present invention is preferably a polymerizable rod-shaped compound having a polymerizable functional group in the molecule, and particularly preferably has a polymerizable functional group capable of three-dimensional crosslinking. Since the rod-shaped compound has a polymerizable functional group, it becomes possible to polymerize and fix the rod-shaped compound. Therefore, by fixing the rod-shaped compound in a state of forming an irregular random homogeneous orientation, This is because it is possible to obtain an optical functional film that is excellent in array stability and hardly changes in optical characteristics. 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.

  The 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.

  Examples of the polymerizable rod-shaped compound used in the present invention include a polyfunctional polymerizable rod-shaped compound having a plurality of polymerizable functional groups and a monofunctional polymerizable rod-shaped compound having a single polymerizable functional group. In the present invention, any of them can be suitably used.

  The polymerizable rod-like compound used in the present invention is not particularly limited as long as it has the above-described polymerizable functional group, and in particular, the polymerizable functional group and the mesogenic group are bonded with an alkyl chain. Those having a molecular structure are preferably used. This is because by using a film having such a structure, it becomes easy to arrange the rod-shaped compounds in an embodiment that exhibits optical biaxiality as the entire optical functional film of the present invention.

The length of the alkyl chain can be arbitrarily determined to such an extent that desired optical properties can be exhibited, depending on the use of the optical functional film of the present invention. Especially, in this invention, it is preferable that carbon number which comprises the said alkyl chain is 4 or more, It is more preferable in the range of 5-12, It is further more preferable in the range of 6-10. When the number of carbon atoms is within the above range, the mesogenic group of the polymerizable rod-shaped compound can be made to have a higher degree of freedom in molecular orientation, further improving the expression of optical anisotropy of the optical functional layer. Because it can be done.
In the present invention, the “number of carbon atoms constituting the alkyl chain” means the number of carbon atoms constituting the main chain portion of the alkyl group that binds the polymerizable functional group and the mesogenic group. . Therefore, for example, when the alkyl group is a branched chain having a side chain, the number of carbon atoms constituting the side chain is not included in the “number of carbon atoms constituting the alkyl chain”.

  The alkyl chain used in the present invention is not particularly limited as long as the carbon number is within the above range. Therefore, the alkyl chain used in the present invention may be a straight chain having no side chain or a branched chain having a side chain. Moreover, the saturated alkyl chain which consists only of a saturated bond may be sufficient, or the unsaturated alkyl chain which has an unsaturated bond may be sufficient. Furthermore, it may have a structure in which an arbitrary functional group is bonded to a hydrocarbon chain.

  Moreover, when using the said polyfunctional polymerizable rod-shaped compound in this invention, all the carbon number which comprises the alkyl chain couple | bonded with each polymerizable functional group may be the same, or may differ.

  The mesogenic group used in the polymerizable rod-like compound is particularly limited as long as it has a rod-like structure and can give a predetermined optical anisotropy to the optically anisotropic layer by regular arrangement. It is not a thing. Among them, the mesogenic group used in the present invention is preferably a mesogenic group having a rod-like structure and exhibiting liquid crystallinity. By using a mesogenic group exhibiting liquid crystallinity, the rod-like compound used in the present invention can be made into a liquid crystalline material exhibiting liquid crystallinity, so that the optical functional layer has excellent expression of optical characteristics per unit thickness. Because it can be made.

  When using what has liquid crystallinity as said mesogenic group, the kind of liquid crystal phase which the said mesogenic group shows is not specifically limited. Examples of such a liquid crystal phase include a nematic phase, a cholesteric phase, and a smectic phase. In the present invention, any mesogenic group exhibiting any of these liquid crystal phases can be preferably used, but among them, a mesogenic group exhibiting a nematic phase is preferably used. This is because mesogenic groups exhibiting a nematic phase can be easily arranged regularly as compared with mesogenic groups exhibiting other liquid crystal phases.

  Specific examples of such a mesogenic group include those in which two or more ring structures represented by the following formulas (1) to (11) are connected directly or via a bonding group.

Wherein any hydrogen in the ring structure of the above formula (1) to (11) has _{halogen, -CN, -CF 3, -CF 2} H, -NO 2, or 1 to 7 carbon atoms It may be replaced with alkyl. In the alkyl having 1 to 7 carbon atoms, arbitrary —CH ₂ — may be replaced by —O—, —CH═CH— or —C≡C—, and arbitrary hydrogen may be replaced by halogen. May be.

  The linking group is not particularly limited as long as it can bond the ring structure at a predetermined distance. Examples of such a linking group include those represented by the following formulas (12) to (23).

  Specific examples of the rod-shaped compound used in the present invention include compounds represented by the following formulas (a) to (f).

  Here, the liquid crystalline materials represented by the chemical formulas (a), (b), (e) and (f) are D.I. J. et al. Broer et al., Makromol. Chem. 190,3201-3215 (1989), or DJ Broer et al., Makromol. Chem. 190,2255-2268 (1989), or can be prepared similarly. The preparation of liquid crystalline materials represented by the chemical formulas (c) and (d) 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 (g) to (q).

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 (crosslinking density) and the optical characteristics can be arbitrarily adjusted by adjusting the ratio, which is preferable.

(2) 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 irregular random homogeneous orientation of the rod-shaped compound. Examples of such other compounds include polymerizable materials generally used for hard coat agents.

  Examples of the polymerizable material include polyester (meth) acrylates obtained by reacting (meth) acrylic acid with polyester prepolymers obtained by condensing polyhydric alcohols with monobasic acids or polybasic acids; Polyurethane (meth) acrylate obtained by reacting a compound having a polyol group and 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, novolac type epoxy resin, polycarboxylic acid polyglycidyl ester, polyol polyglycidyl ether, aliphatic or cycloaliphatic epoxy resin, amino group epoxy resin, triphenolmethane type epoxy resin, dihydroxybenzene type epoxy resin and the like , (Meta) It may be mentioned a photopolymerizable liquid crystal compound having an acryl group or a methacryl group or the like; photopolymerizable compounds such as epoxy (meth) acrylates obtained by reacting an acrylic acid.

(3) Optical functional layer The optical functional layer in this invention is directly formed on the base material mentioned later. By forming the optical functional layer directly on the substrate, the optical functional film of the present invention can be excellent in adhesion between the optical functional layer and the substrate.
Thus, it is understood that the adhesion mechanism between the two is improved by forming the optical functional layer directly on the base material by the following mechanism. That is, when the optical functional layer is directly formed on the base material, rod-like molecules contained in the optical functional layer penetrate into the base material from the surface of the base material or are used when forming the optical functional layer. Depending on the solvent, the surface of the base material can be dissolved, and the rod-shaped compound and the base material can be mixed. Therefore, there is no clear interface at the bonding portion between the base material and the optical functional layer, and both are mixed. "" For this reason, it is considered that the adhesion is remarkably improved as compared with the adhesion by the conventional interface interaction.

  Furthermore, in the conventional optical functional film having an alignment layer, there is a problem in that light is multiple-reflected at the interface between the alignment layer and the optical functional layer or at the interface between the alignment layer and the substrate, resulting in interference unevenness. However, the optical functional film of the present invention does not have an alignment layer, and there is no clear interface because the bonded portion between the substrate and the optical functional layer is in a “mixed” state. Therefore, the optical functional film of the present invention has the advantage that the multiple reflection does not occur and the quality is not deteriorated due to interference unevenness.

  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 according to the kind 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 5 μm, particularly in the range of 1 μm to 3 μm. Preferably there is. If the thickness of the optical functional layer is larger than the above range, “in-plane orientation”, which is one of the characteristics of irregular random homogeneous orientation, is impaired, and the desired optical characteristics may not be obtained. is there. On the other hand, if the thickness is smaller than the above range, the target optical characteristics may not be obtained depending on the kind of the rod-shaped compound.

  The in-plane retardation (Re) of the optical functional layer in the present invention is within the range of 5 nm to 300 nm as described above from the viewpoints of “anisotropic” and “in-plane orientation” possessed by the irregular random homogeneous orientation. Among these, a range of 10 nm to 200 nm is preferable, and a range of 40 nm to 150 nm is particularly preferable. Here, since the definition of Re value and the measuring method are as described above, the description thereof is omitted here.

  In the optical functional layer in the present invention, the value (Re / d) obtained by dividing the retardation value (Re (nm)) of the optical functional layer by the thickness (d (μm)) of the optical functional layer is 0.5 to It is preferably in the range of 600, particularly preferably in the range of 2 to 400, and particularly preferably in the range of 13 to 150.

In addition, the retardation (Rth) in the thickness direction of the optical functional layer in the present invention is preferably in the range of 50 nm to 400 nm as described above from the viewpoint of “in-plane orientation” possessed by the irregular random homogeneous orientation. However, the range of 75 nm to 300 nm is preferable, and the range of 100 nm to 250 nm is particularly preferable.
Here, the definition and measurement method of the Rth value are as described above, and thus the description thereof is omitted here.

  The optical functional layer in the present invention has a value (Rth / d) obtained by dividing the retardation value (Rth (nm)) in the thickness direction of the optical functional layer by the thickness (d (μm)) of the optical functional layer. It is preferably in the range of ˜800, more preferably in the range of 15 to 600, and particularly preferably in the range of 33 to 250.

  In addition, the haze of the optical functional layer in the present invention is preferably in the range of 0% to 5% as described above from the viewpoint of “dispersibility” possessed by the irregular random homogeneous orientation, and in particular, 0% to 1%. Is preferably within the range of 0% to 0.5%. Here, since the definition of haze and the measuring method are as described above, description thereof is omitted here.

  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. When the optical functional layer is composed of a plurality of layers, at least the optical functional layer directly laminated on the substrate only needs to have a rod-shaped compound in which an irregular random homogeneous orientation is formed.

2. Substrate Next, the substrate used in the present invention will be described. The base material used in the present invention is made of a cellulose derivative. The cellulose derivative used in the present invention is not particularly limited as long as desired optical characteristics and physical characteristics can be imparted to the substrate. Of these, cellulose esters are preferably used as the cellulose derivative in the present invention. Furthermore, it is preferable that cellulose acylates are used among cellulose esters. This is because cellulose acylates are advantageous in terms of availability because they are widely used industrially.

  As the cellulose acylates, C 2-4 lower fatty acid esters are preferably used. Such a lower fatty acid ester may contain only a single lower fatty acid ester, for example, cellulose acetate, or a plurality of lower fatty acid esters such as cellulose acetate butyrate and cellulose acetate propionate. May be included.

  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. In addition, triacetyl cellulose easily develops properties as an optically negative C plate, and therefore, it becomes easy to form an irregular random homogeneous orientation of the 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). In addition, the acetylation degree of the triacetyl cellulose which comprises a triacetyl cellulose film can be calculated | required by said method, after removing impurities, such as a plasticizer contained in a film.

As a base material used for this invention, what has arbitrary optical characteristics can be used according to the optical characteristic calculated | required by the optical function film of this invention. In particular, in the present invention, the refractive index nx in the slow axis direction in the in-plane direction and the refractive index ny in the fast axis direction in the in-plane direction have a relationship of nx ≠ ny, or the retardation in the in-plane direction. It is preferable that the relationship of nx ≠ ny ≠ nz holds in the refractive index nx in the phase axis direction, the refractive index ny in the fast axis direction in the in-plane direction, and the refractive index nz in the thickness direction.
Here, when the relationship of nx ≠ ny is established between nx and ny, the base material used in the present invention optically has a property as an A plate. Further, when the relationship of nx ≠ ny ≠ nz is established for nx, ny, and nx, the base material used in the present invention optically has a property as a B plate, that is, optical biaxiality. The above-mentioned “characteristic as the optically B plate” specifically refers to a state where Rth ≠ (Re / 2).
The above nx ≠ ny ≠ nz means nx ≠ ny, ny ≠ nz, and nz ≠ nx.

The in-plane retardation (Re) of the substrate used in the present invention 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. Preferably there is. This is because, when the in-plane retardation (Re) of the substrate is within the above range, it becomes easy to form irregular random homogeneous alignment in the optical functional layer regardless of the type of the rod-shaped compound.
In addition, since it is the same as that of the measuring method of Re of the optical function layer mentioned above as the measuring method of Re of the said base material, description here is abbreviate | omitted.

In addition, from the viewpoint of forming a homogeneous irregular random homogeneous orientation, Re is in the above range, and the thickness direction retardation (Rth) of the base material is in the range of 2.5 nm to 150 nm. In particular, it is preferably in the range of 5 nm to 100 nm, and more preferably in the range of 20 nm to 75 nm.
Here, the definition of Rth and the measurement method are the same as those described in the above section “1. Optical functional layer”, and thus the description thereof is omitted here.

  The transparency of the substrate used in the present invention may be arbitrarily determined according to the transparency required for the optical functional film of the present invention, but it is usually preferable that the transmittance in the visible light region is 80% or more. 90% or more is more preferable. 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 substrate used in the present invention is not particularly limited as long as it has the necessary self-supporting property depending on the use of the optical functional film of the present invention, but is preferably in the range of 10 μm to 188 μm. In particular, the range of 20 μm to 125 μm is preferable, and the range of 30 μm to 80 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 optical functional film of the present invention may not be obtained. Moreover, when the thickness is thicker than the above range, for example, when cutting the optical functional film of the present invention, there is a case where processing waste increases or wear of the cutting blade is accelerated.

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.
Examples of the structure of the base material in which a plurality of layers having different compositions are laminated include, for example, a film made of a material that irregularly and homogeneously aligns the rod-shaped compound such as triacetyl cellulose, and a support excellent in water permeability and self-supporting property. A mode of laminating the body can be exemplified.

3. Optical functional film The optical functional film of the present invention is characterized in that the optical functional layer is directly formed on the base material. Therefore, the rod-shaped compound contained in the optical functional layer penetrates the base material, A mixed region in which both are “mixed” is formed at the bonding portion between the material and the optical functional layer. The thickness of such a mixed region is not particularly limited as long as the irregular random homogeneous orientation can be formed and the adhesive force between the substrate and the optical functional layer can be within a desired range. In particular, in the present invention, the thickness of the mixed region is preferably in the range of 0.1 μm to 10 μm, particularly preferably in the range of 0.5 μm to 5 μm, and more preferably in the range of 1 μm to 3 μm. It is preferable that

  The distribution state of the rod-shaped compound in the mixed region is also particularly limited as long as the irregular random homogeneous orientation can be formed and the adhesion between the base material and the optical functional layer can be in a desired range. Not. Examples of the distribution state of the rod-shaped compound include an aspect that exists uniformly in the thickness direction of the base material and an aspect that has a concentration gradient in the thickness direction of the base material. Can also be suitably used.

  In addition, confirmation of the presence of the mixed region and confirmation of the distribution state of the rod-shaped compound in the mixed region can be confirmed by a TOF-SIMS method.

  The optical functional film of the present invention may have other layers in addition to the substrate and the optical functional layer. Examples of such other layers include an antireflection layer, an ultraviolet absorption layer, an infrared absorption layer, and an antistatic 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 the 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.

  Examples of the antistatic layer used in the present invention include various cationic antistatic agents having cationic groups such as quaternary ammonium salts, pyridinium salts, and primary to tertiary amino groups; sulfonate groups, Anionic antistatic agents having an anionic group such as sulfate ester base, phosphate ester base, phosphonate base; amphoteric antistatic agents such as amino acid and aminosulfate esters; amino alcohols, glycerols, polyethylene glycols, etc. A nonionic antistatic agent, a high molecular weight antistatic agent obtained by increasing the molecular weight of the antistatic agent, a monomer or an oligomer having a tertiary amino group or a quaternary ammonium group and capable of being polymerized by ionizing radiation, For example, N, N-dialkylaminoalkyl (meth) acrylate monomers, polymerizable antistatics such as quaternary compounds thereof It was added an antistatic agent and the like that were formed.

  The thickness of the optical functional film of the present invention is not particularly limited as long as it is within a range in which desired optical characteristics can be expressed, but it is usually preferably within a range of 10 μm to 200 μm, particularly 20 μm to 135 μm. It is preferable that it exists in the range, and also it is preferable that it exists in the range of 30 micrometers-90 micrometers.

  The optical functional film of the present invention preferably has a haze value measured in accordance with JIS K7105 in the range of 0% to 5%, particularly preferably in the range of 0% to 1%. However, it is preferably in the range of 0% to 0.5%.

Further, the retardation (Rth) in the thickness direction of the optical functional film of the present invention is preferably in the range of 50 nm to 400 nm, more preferably in the range of 75 nm to 300 nm, particularly 100 nm to 250 nm. It is preferable to be within the range. Furthermore, 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 preferably in the range of 70 to 180 nm.
This is because, when Re and Rth are within the above ranges, the optical functional film of the present invention can be used as a retardation film suitable for improving the viewing angle characteristics of a liquid crystal display device.
Here, since the definition of Re value and Rth value and the measuring method are as described above, description thereof is omitted here.

  The in-plane retardation (Re) value and the thickness direction retardation value (Rth) may have wavelength dependency. The wavelength dependency may be reverse dispersion having a larger value on the long wavelength side than that on the short wavelength side, or may be positive dispersion having a value on the short wavelength side larger than that on the long wavelength side. In particular, the optical functional film of the present invention is preferably a positive dispersion type in terms of wavelength dependency of in-plane retardation (Re). This is because the optical properties of the optical functional film of the present invention can be made suitable as an optical compensation film for a liquid crystal display device.

  The optical functional film of the present invention has a value (Rth / d) obtained by dividing the retardation value (Rth (nm)) in the thickness direction by the thickness (d (μm)) within a range of 0.25 to 40. It is preferable that it is within a range of 0.6 to 15, particularly preferably within a range of 1.1 to 8.3.

  In the optical functional film of the present invention, the value (Re / d) obtained by dividing the retardation value (Re (nm)) by the thickness (d (μm)) is in the range of 0.025 to 30. In particular, it is preferably in the range of 0.05 to 10, particularly preferably in the range of 0.44 to 5.

Furthermore, the optical functional film of the present invention preferably has an Nz coefficient in the range of 1.0 to 2.5. Here, the Nz coefficient is a parameter indicating the shape of the refractive index ellipsoid provided in the optical functional film of the present invention,
Nz = (Rth / Re) +0.5
It is represented by the formula of

4). Application of optical functional film The application of the optical functional film of the present invention is not particularly limited, and can be used as an optical functional film for various applications. Specific applications of the optical functional film of the present invention include, for example, an optical compensator (for example, a viewing angle compensator) used in a liquid crystal display device, an elliptically polarizing plate, a luminance improving plate, etc. It can be used as an A plate or B plate. Thus, when used as an optical compensator which is an A plate or a B plate, it is suitably used for a liquid crystal display device having a liquid crystal layer such as a VA mode or an OCB mode.

  Moreover, the optical functional film of this invention can be used also for the use as a polarizing film by bonding with a polarizing layer. The 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 layer on one side as the optical functional film described above, 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.

5). Production method of optical functional film The production method of the optical functional film of the present invention is not particularly limited as long as it is a method capable of producing one having the above-described configuration. For example, “B. Production method of optical functional film” described later is used. It can be produced by the method described in the item.

B. Next, a method for producing the optical functional film of the present invention will be described. The method for producing an optical functional film of the present invention includes a base material composed of a cellulose derivative, a rod-shaped compound that is directly formed on the base material and has a random homogeneous orientation, and has an optical uniaxial property. By stretching the optical film, the refractive index nx in the slow axis direction in the in-plane direction, the refractive index ny in the fast axis direction in the in-plane direction, and the refractive index nz in the thickness direction are obtained. , Nx ≠ ny or nx ≠ ny ≠ nz, and a rod-like compound that is directly formed on the substrate and has an irregular random homogeneous orientation, and further exhibits optical biaxiality. An optical functional film having an optical functional layer is produced.

  Next, the method for producing the optical functional film of the present invention will be described with reference to the drawings. FIG. 3 is a schematic view showing an example of a method for producing an optical functional film of the present invention. As illustrated in FIG. 3, the method for producing an optical functional film of the present invention includes an optical functional layer that includes a rod-shaped compound 3 having a random homogeneous orientation formed on a substrate 1 ′ made of a cellulose derivative and exhibits optical uniaxiality. By using the optical film 20 on which 2 ′ is formed (FIG. 3A), and uniaxially stretching it in the x direction (FIG. 3B), the refractive index nx in the slow axis direction in the in-plane direction, An irregular random homogeneous orientation was formed on the base material 1 in which the relationship of nx ≠ ny or nx ≠ ny ≠ nz is established between the refractive index ny in the fast axis direction and the refractive index nz in the thickness direction in the in-plane direction. In this method, the optical functional film 10 including the rod-shaped compound 3 and the optical functional layer 2 exhibiting optical biaxiality is formed.

According to the present invention, an optical film having a base material made of a cellulose derivative 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 that exhibits optical uniaxiality. And stretching the substrate, the refractive index nx in the slow axis direction in the in-plane direction, the refractive index ny in the fast axis direction in the in-plane direction, and the refractive index nz in the thickness direction are set to nx ≠ The relationship of ny or nx ≠ ny ≠ nz can be established.
Furthermore, since the random homogeneous orientation can be changed to an irregular random homogeneous orientation by stretching, optical biaxiality can be imparted to the optical functional layer.
Therefore, according to the present invention, the refractive index nx in the slow axis direction in the in-plane direction, the refractive index ny in the fast axis direction in the in-plane direction, and the refractive index nz in the thickness direction are nx ≠ ny or nx ≠ It is possible to easily form an optical functional film in which an optical functional layer having an optical biaxial property is formed on a base material in which the relationship of ny ≠ nz is established and a rod-like compound that is irregularly homogeneously oriented on the base material. Therefore, an optical functional film having a high degree of freedom in optical property design can be easily produced.

  Hereafter, the manufacturing method of the optical function film of this invention is demonstrated in detail.

1. Optical film First, the optical film used for the manufacturing method of the optical function film of this invention is demonstrated. The optical film used in the present invention comprises a base material composed of a cellulose derivative, and an optical functional layer that is formed directly on the base material and includes a rod-like compound that has formed a random homogeneous orientation and exhibits optical uniaxiality. I have it.

(1) Base material The base material used for the said optical film consists of a cellulose derivative, and has a function as what is called an alignment film for the said rod-shaped compound to form random homogeneous orientation.

  Although the base material used for the said optical film will not be specifically limited if it consists of a cellulose derivative, It is preferable that it has a property as an optically negative C plate especially. Here, in the present invention, “having properties as an optically negative C plate” means an arbitrary X direction in the plane of the base sheet and a refractive index in the Y direction perpendicular to the X direction in the plane nx. , Ny, when the refractive index in the thickness direction is nz, it means that the relationship of nx = ny> nz, nx> ny> nz, or ny> nx> nz is established.

  The base material used for the optical film is one having an optically negative C plate property for the following reason. That is, as described above, the substrate in the present invention functions as a so-called alignment film for the rod-shaped compound to form a random homogeneous alignment, but the substrate is a property as an optically negative C plate. This is because the above rod-like compound cannot form a random homogeneous orientation without the presence of.

In the present invention, it is not clear about the mechanism by which the rod-shaped compound forms a random homogeneous orientation by forming an optical functional layer containing the rod-shaped compound on a substrate having the property as an optically negative C plate. Although not, it is thought to be based on the following mechanism.
That is, for example, considering the case where the base material is formed of a polymer material, when the base material has a property as an optically negative C plate, the polymer material constituting the base material is specified in the in-plane direction. Most of them are considered to be randomly arranged. When the rod-shaped compound is applied onto a substrate having a polymer material that is arranged in the in-plane direction at random on the surface, the rod-shaped compound partially penetrates into the substrate and the molecular axis is random. It is thought that the polymer material is arranged along the molecular axis of By such a mechanism, it is considered that a substrate having an optically negative C plate exhibits a function as an alignment film for forming a random homogeneous alignment.

Due to the mechanism described above, the base material is considered to have a function as an alignment film that forms a random homogeneous orientation of the rod-shaped compound. Therefore, the base material used for the optical film is oriented with respect to the rod-shaped compound. It must have a structure in which the constituent material of the base material that has a force and exhibits the properties of an optically negative C plate is present on the surface of the base material. Therefore, even when the optically functional layer is formed on the substrate, the rod-shaped compound has an alignment regulating force with respect to the rod-shaped compound even if it has properties as an optically negative C plate. Those that cannot come into contact with the constituent material of the substrate cannot be used as the substrate in the optical film.
As a base material that cannot be used for such an optical film, for example, a support made of only a polymer material and having a function as an optically negative C plate, and a refractive index anisotropy on the support are described. The base material which has the structure by which the phase difference layer containing the optically anisotropic material which has this was laminated | stacked can be mentioned. In the base material having such a configuration, the polymer material constituting the support is a constituent material of the base material having an orientation regulating force for the rod-shaped compound, but the optical functional layer is formed on the retardation layer. Is formed, the rod-shaped compound cannot contact the polymer material due to the presence of the retardation layer. Therefore, the base material having such a configuration is not included in the base material used for the optical film even if it has the property as an optically negative C plate.

The properties of the substrate used in the optical film as an optically negative C plate depend on the type of rod-shaped compound used in the optical functional layer, the optical characteristics required for the optical functional film produced according to the present invention, and the like. May be appropriately selected and used. In particular, in the present invention, the thickness direction retardation (Rth) of the substrate is preferably in the range of 2.5 nm to 150 nm, particularly preferably in the range of 5 nm to 100 nm, and in particular, 20 nm. It is preferable to be within a range of ˜75 nm. This is because when the retardation (Rth) in the thickness direction of the substrate is within the above range, it becomes easy to form random homogeneous alignment in the optical functional layer regardless of the type of the rod-shaped compound. . Moreover, it is because a homogeneous random homogeneous orientation can be formed when Rth of the said base material exists in the said range.
Here, the definition of Rth and the measuring method are the same as those described in the section “A. Optical Functional Film”, and therefore the description thereof is omitted here.

  In addition, from the viewpoint of forming a homogeneous random homogeneous orientation, in addition to Rth being in the above range, in-plane retardation (Re) is preferably in the range of 0 nm to 300 nm, particularly 0 nm to It is preferably in the range of 150 nm, and particularly preferably in the range of 0 nm to 125 nm.

  Here, the transparency and thickness of the base material used for the optical film are the same as those described in the above section “A. Optical functional film”, and thus the description thereof is omitted here.

  Moreover, the material which comprises the base material used for the said optical film will not be specifically limited if it has the said optical characteristic. The material specifically used is the same as the material exemplified in the section “Substrate” of the above “A. Optical functional film”, and thus the description thereof is omitted here.

(2) Optical functional layer The optical functional layer used for the optical film will be described. The optical functional layer used for the optical film includes a rod-like compound that is directly formed on the base material and has a random homogeneous orientation, and exhibits optical uniaxiality.

The random homogeneous orientation in the optical function layer will be described. The irregular random homogeneous orientation having the three characteristics of “anisotropic”, “dispersibility” and “in-plane orientation” has been described in the section “A. Optical functional film”. The random homogeneous orientation in the above has “irregularity” instead of the above “anisotropic”. Therefore, it can be said that the random homogeneous orientation in the optical functional layer of the optical film has three characteristics of “irregularity”, “dispersibility”, and “in-plane orientation”.
Here, the above “irregularity” means that the arrangement direction of the rod-shaped compounds is random when the optical functional layer is viewed from the direction perpendicular to the surface of the optical functional layer.

The “irregularity” will be described with reference to the drawings. FIG. 4 is a schematic view when the optical film 20 is viewed from the perpendicular direction A with respect to the surface of the optical functional layer of the optical film 20 illustrated in FIG. As shown in FIG. 4, the “irregularity” means that the rod-shaped compound 3 in the optical functional layer 2 ′ when the optical film 20 of the present invention is viewed from the direction perpendicular to the surface of the optical functional layer 2 ′. Indicates that they are randomly arranged.
Here, in the present invention, in order to describe the arrangement direction of the rod-shaped compound 3, the molecular major axis direction (hereinafter referred to as a molecular axis) represented by a in FIG. 4 is considered as a reference. Therefore, that the arrangement direction of the rod-shaped compounds is random means that the molecular axes a of the rod-shaped compounds 3 included in the optical functional layer are randomly oriented.

  In addition to the arrangement state as illustrated in FIG. 4, even if the rod-like compound has a cholesteric structure, the direction of the molecular axis a is random as a whole. However, the above “irregularity” does not include a form resulting from a cholesteric structure.

Next, a method for confirming the “irregularity” will be described. The “irregularity” can be confirmed by evaluating the in-plane retardation (Re) of the optical functional layer constituting the optical film and the presence or absence of a selective reflection wavelength due to the cholesteric structure.
That is, it can be confirmed that the rod-like compound is randomly oriented by Re evaluation of the optical functional layer constituting the optical film, and it is confirmed that the rod-like compound does not form a cholesteric structure by the presence or absence of the selective reflection wavelength. be able to.

  It is confirmed that the rod-shaped compound is randomly oriented by checking that the in-plane retardation (Re) value of the optical functional layer is within a range indicating that the rod-like compound is oriented randomly. Can do. In particular, in the present invention, the in-plane retardation (Re) of the optical functional layer is preferably in the range of 0 nm to 5 nm. Here, the definition and measurement method of Re are the same as those described in the section “A. Optical Function Film”, and thus the description thereof is omitted here.

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

  The “dispersibility” and “in-plane orientation” of the random homogeneous orientation are the same as those described in the section “A. Optical functional film”, and thus the description thereof is omitted here.

The optical uniaxiality exhibited by the optical functional layer in the optical film means that it has one optically isotropic optical axis. Here, the optical uniaxiality in the present invention means having one optically isotropic optical axis. The optical functional layer exhibits optical uniaxiality when the refractive index in the slow axis direction of the optical functional layer is nx, the refractive index in the fast axis direction is ny, and the refractive index in the thickness direction is nz. , Nx = ny ≠ nz can be evaluated by confirming that the relationship is established.
Here, the establishment of the above relationship in nx, ny and nz can be measured, for example, by the parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments.

  Further, the rod-like compound contained in the optical functional layer in the optical film and other matters relating to the optical functional layer are the same as the contents described in the above section “A. Optical functional film”. Is omitted.

(3) Method for Producing Optical Film Next, a method for producing an optical film used in the present invention will be described. The method for producing an optical film used in the present invention is not particularly limited as long as it is a method capable of forming an optical functional layer having random homogeneous orientation on the above-mentioned base material. Usually, the rod-shaped compound is formed on the base material. A method of coating a composition for forming an optical functional layer prepared by dissolving in a solvent 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 easy to form an irregular random homogeneous orientation of the rod-like compound. Hereinafter, the manufacturing method of such an optical film is demonstrated.

  The composition for forming an optical functional layer usually comprises a rod-like compound and a solvent, and may contain other compounds as necessary. The rod-shaped compound and the base material used in the composition for forming an optical functional layer are the same as those described in the above sections “1. Base material” and “2. Optical functional layer”. The description in is omitted.

  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. Examples of such solvents 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, dichloromethane, and the like. Alkyl halide solvents, ester solvents such as methyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, amide solvents such as N, N-dimethylformamide, and sulfoxide solvents such as dimethyl sulfoxide. However, it is not limited to these. 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 the above solvents, a ketone solvent is preferably used, and among them, cyclohexanone is preferably used.

  The content of the rod-shaped compound in the composition for forming an optical functional layer depends on the coating method for applying the composition for forming an optical functional layer on a substrate, etc. If it is in the range which can make a viscosity into a desired value, it will not be limited especially. In particular, in the present invention, the content of the rod-shaped compound is preferably in the range of 20% by mass to 90% by mass, and particularly in the range of 30% by mass to 80% by mass in the optical functional layer forming composition. It is preferable that it is in the range of 40 mass%-70 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) acrylates obtained by reacting (meth) acrylic acid with polyester prepolymers obtained by condensing polyhydric alcohols with monobasic acids or polybasic acids; polyol groups And a compound having two isocyanate groups are reacted with each other, and then a polyurethane (meth) acrylate obtained by reacting the reaction product with (meth) acrylic acid; bisphenol A type epoxy resin, bisphenol F type epoxy resin, Epoxy resins such as novolac type epoxy resin, polycarboxylic acid polyglycidyl ester, polyol polyglycidyl ether, aliphatic or cycloaliphatic epoxy resin, amino group epoxy resin, triphenolmethane type epoxy resin, dihydroxybenzene type epoxy resin, ( Meta) Epoxy obtained by reacting an acrylic acid (meth) photopolymerizable compound such as acrylate; 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. Other compounds are not particularly limited as long as they do not impair the optical properties of the optical functional layer, depending on the application of the optical functional 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). Of these, use of metal halide lamps, xenon lamps, high-pressure mercury lamps, etc. is recommended. The irradiation intensity can be appropriately adjusted according to the content of the photopolymerization initiator.

2. Next, a method for stretching the optical film in the method for producing an optical functional film of the present invention will be described.

  As the stretching method, the base material constituting the optical film is set to have a refractive index nx in the slow axis direction in the in-plane direction, a refractive index ny in the fast axis direction in the in-plane direction, and a refractive index nz in the thickness direction. nx ≠ ny or nx ≠ ny ≠ nz, and a method capable of imparting optical biaxiality to the optical functional layer by changing the random homogeneous orientation to an irregular random homogeneous orientation. If there is no particular limitation. Such a method may be a biaxial stretching method or a uniaxial stretching method, but the uniaxial stretching method is preferred in the present invention.

  The uniaxial stretching method may be a method of stretching in the flow direction of the film, or a method of stretching the film in the width direction of the film while fixing the interval in the flow direction of the film.

  What is necessary is just to adjust arbitrarily the draw ratio which stretches the said optical film according to the optical characteristic calculated | required by the optical function film manufactured by this invention.

3. Next, the optical functional film manufactured by the manufacturing method of the present invention will be described. The optical functional film produced according to the present invention includes a substrate having at least the property of optically as an A plate or a B plate, and a rod-shaped compound directly formed on the substrate and having an irregular random homogeneous orientation, Furthermore, it has an optical functional layer showing optical biaxiality.
Such an optical functional film produced according to the present invention is the same as that described in the above section “A. Optical functional film”, and thus the description thereof is omitted here.

C. Next, the polarizing plate of the present invention will be described. In the polarizing plate of the present invention, the optical functional film according to the present invention is used as a polarizing plate protective film.
That is, the polarizing plate of the present invention includes an optical functional film according to the present invention, a polarizer formed on any surface of the optical functional film, and a polarizing plate protective film formed on the polarizer. , Characterized by having.

Such a polarizing plate of the present invention will be described with reference to the drawings. FIG. 5 is a schematic sectional view showing an example of the polarizing plate of the present invention. As illustrated in FIG. 5, the polarizing plate 20 of the present invention includes an optical functional film 10, a polarizer 11 formed on the optical functional film 10, and a polarizing plate protective film formed on the polarizer 11. 12.
In such an example, the polarizing plate 20 of the present invention is characterized in that the optical functional film 10 of the present invention is used as the optical functional film 10.

  According to the present invention, by using the optical functional film of the present invention, a polarizing plate having a viewing angle compensation function of a liquid crystal display device and excellent in durability can be obtained.

  Although FIG. 5 shows an example in which the polarizer is formed on the base material of the optical functional film, the polarizing plate of the present invention is not limited to such an embodiment. Therefore, the polarizing plate of the present invention may have a configuration in which a polarizer is formed on the optical functional layer of the optical functional film, and a polarizing plate protective film is disposed on the polarizer.

The polarizing plate of the present invention has at least the optical function film, a polarizer, and a polarizing plate protective film.
Hereinafter, each structure used for the polarizing plate of this invention is demonstrated.

  In addition, about the optical function film used for this invention, since it is the same as that of what was demonstrated in the term of the said "A. optical function film", description here is abbreviate | omitted.

1. Polarizing plate protective film First, the polarizing plate protective film used in the present invention will be described. The polarizing plate protective film used in the present invention has a function of preventing the polarizer from being exposed to moisture in the air in the polarizing plate of the present invention and a function of preventing dimensional change of the polarizer. is there.

The polarizing plate protective film used in the present invention is not particularly limited as long as it can protect the polarizer in the polarizing plate of the present invention and has desired transparency. 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.

  As said cellulose derivative, the thing similar to what was demonstrated as a cellulose derivative which comprises the transparent substrate used for the optically anisotropic film in the said "A. optical function film" item can be used, for example.

On the other hand, the cycloolefin resin is not particularly limited as long as it is a resin having a monomer unit composed of a cyclic olefin (cycloolefin). Examples of such a monomer comprising a cyclic olefin include norbornene and polycyclic norbornene monomers.
Further, as the cycloolefin resin used in the present invention, either a cycloolefin polymer (COP) or a cycloolefin copolymer (COC) can be suitably used.

  The cycloolefin resin used in the present invention may be a homopolymer of a monomer composed of the above cyclic olefin or a copolymer.

In addition, the cycloolefin resin used in the present invention preferably has a saturated water absorption at 23 ° C. of 1% by mass or less, and in particular, has a range of 0.1% by mass to 0.7% by mass. preferable. This is because by using such a cycloolefin-based resin, it is possible to make the polarizing plate of the present invention less susceptible to changes in optical properties and dimensions due to water absorption.
Here, the saturated water absorption is obtained by immersing in 23 ° C. water for 1 week according to ASTM D570 and measuring the increased weight.

  Furthermore, the cycloolefin resin used in the present invention preferably has a glass transition point in the range of 100 ° C to 200 ° C, particularly preferably in the range of 100 ° C to 180 ° C, and in particular, 100 ° C. What is in the range of -150 degreeC is preferable. This is because, when the glass transition point is within the above range, the polarizing plate of the present invention can be made more excellent in heat resistance and processability.

  Specific examples of the polarizing plate protective film made of cycloolefin-based resin used in the present invention include, for example, Ticona Topas, JSR Arton, Nippon Zeon Corporation ZEONOR, Nippon Zeon Corporation ZEONEX, Mitsui Chemicals, Inc. Examples include apels.

As the polarizing plate protective film used in the present invention, any of those composed of the above cellulose derivatives and those composed of the above cycloolefin-based resins can be suitably used. It is preferable to use one made of a resin. The reason is as follows. That is, the polarizing plate of the present invention uses the optical functional film according to the present invention as one polarizing plate protective film, but the optical functional film according to the present invention has a transparent substrate made of a cellulose derivative. The optically anisotropic film used is used. Therefore, when the polarizing plate protective film is composed of the cellulose derivative, the polarizing plate protective film on both sides in the polarizing plate of the present invention is composed of the cellulose derivative, and as a result, the durability of the optical properties, etc. May be damaged.
In this regard, by using a polarizing plate protective film made of the cycloolefin resin or acrylic resin, the polarizing plate protective film made of cycloolefin resin or acrylic resin is used on one side of the polarizing plate of the present invention, This is because the phase film of the present invention in which the cellulose derivative is used on the other surface is used, and thus there are few concerns as described above.

The configuration of the polarizing plate protective film 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.
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.

2. Next, the polarizer used in the present invention will be described. The polarizer used in the present invention has a function of imparting polarization characteristics to the polarizing plate of the present invention.

  The polarizer used in the present invention is not particularly limited as long as it can impart desired polarization characteristics to the polarizing plate of the present invention, and in particular, those that are generally used for polarizing plates in liquid crystal display devices are limited. Can be used. In the present invention, as such a polarizer, a polyvinyl alcohol film is usually stretched, and a polarizer containing iodine is used.

3. Production method of polarizing plate The production method of the polarizing plate of the present invention is not particularly limited as long as it is a method capable of producing a polarizing plate having the above-described configuration. As such a method, the method of bonding the polarizing plate protective film and the optical functional film to the polarizer with an adhesive is usually used.
The optical functional film and the polarizer are usually bonded together so that the slow axis direction of the optical functional film and the absorption axis direction of the polarizer are perpendicular to each other.
In addition, about the method of bonding the said polarizing plate protective film, the said optical function film, and the said polarizer, the method used when manufacturing the polarizing plate generally used for a liquid crystal display device can be used. As such a method, for example, a method described in Japanese Patent No. 3132122 can be used.

  Moreover, when producing the polarizing plate like this invention industrially, usually, a polarizer, a polarizing plate protective film, and an optical functional film formed in a long length are used, and these are bonded in a long state. Thus, a method of manufacturing a polarizing plate wound up in a roll shape is used. When the polarizing plate of the present invention is produced by such a method, a polarizer having the absorption axis direction parallel to the longitudinal direction is used as the polarizer, and the slow axis direction is long as the optical functional film. By using a material perpendicular to the direction, the polarizing plate of the present invention can be efficiently produced by the Roll to Roll process.

  As a preferable usage pattern of the polarizing plate of the present invention, the optical functional film is disposed on the liquid crystal cell side, and the polarizing plate protective film is disposed on the side opposite to the liquid crystal cell. By using it in such a mode, it is possible to achieve both the durability of the polarizing plate and the discharge of moisture during the production of the polarizing plate.

  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 specifically described with reference to examples.

1. Example 1
(Production of optical film)
As a rod-like compound, a photopolymerizable liquid crystal compound (a mixture of the following compound (I) and compound (II)) is dissolved in a mixed solvent of cyclohexanone and cyclopentanone in an amount of 15% by mass, and is dissolved in a TAC film (product name: TF80UL, manufactured by Fuji Film). The bar coating was applied so that the coating amount after drying was 2.7 g / m ² . Subsequently, the solvent was dried and removed by heating at 40 ° C. for 1 minute and 80 ° C. for 1 minute, and the liquid crystal compound was mixed and aligned with the polymer on the substrate surface. Furthermore, the photopolymerizable liquid crystal compound was fixed by irradiating the coated surface with ultraviolet rays to produce an optical film.

  About the produced optical film and the said TAC film, Rth and Re were measured by the parallel Nicol rotation method using KOBRA-WR by Oji Scientific Instruments. Here, for the measurement of Re and Rth, a product name: KOBRA-21ADH manufactured by Oji Scientific Instruments Co., Ltd. was used. Moreover, Nippon Denshoku Industries Co., Ltd. brand name: NDH2000 was used for the measurement of the said haze. Furthermore, Shimadzu Corporation brand name: UV-3100PC was used for confirmation of the presence or absence of the selective reflection wavelength. As a result, Rth = 104 nm and Re = 0 nm. The haze was 0.2%, and it was further confirmed that the retardation film did not have a selective reflection wavelength by an ultraviolet-visible near-infrared spectrophotometer (UV-3100) manufactured by Shimadzu Corporation. Thereby, in the retardation layer of the produced optical film, it confirmed that the said compounds (I) and (II) formed random homogeneous orientation.

(Stretching of optical film)
Next, the optical film was heated on a hot plate at 160 ° C. for 5 minutes and stretched so that the stretch ratio was 1.30 times, thereby producing an optical functional film. Using the produced optical functional film as a sample, the following items were evaluated.

(1) Optical biaxiality The three-dimensional refractive index of the retardation of the produced optical functional film was measured with an automatic birefringence measuring apparatus (manufactured by Oji Scientific Instruments, trade name: KOBRA-21ADH). As a result, nx = 1.60, ny = 1.58, and nz = 1.52.

(2) Unusual Random Homogeneous Orientation About the produced optical functional film and the TD80UF, Rth and Re were measured by a parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments. Here, for the measurement of Re and Rth, a product name: KOBRA-21ADH manufactured by Oji Scientific Instruments Co., Ltd. was used. Moreover, Nippon Denshoku Industries Co., Ltd. brand name: NDH2000 was used for the measurement of the said haze. Furthermore, Shimadzu Corporation brand name: UV-3100PC was used for confirmation of the presence or absence of the selective reflection wavelength. As a result of calculating Rth and Re of the optical functional layer from the measurement results, Rth = 104.8 nm, Re = 1115.2 nm, and the Nz coefficient were 1.41. The haze was 0.4%.
Furthermore, it was confirmed that the optical functional film did not have a selective reflection wavelength by an ultraviolet-visible near-infrared spectrophotometer (UV-3100 manufactured by Shimadzu Corporation).

(3) Adhesion test In order to investigate the adhesiveness of a base material and an optical function layer about the produced optical function film, the peeling test was done. As a peel test, a 1 mm square cut is put in a grid pattern in the obtained sample, an adhesive tape (manufactured by Nichiban Co., Ltd., cello tape (registered trademark)) is applied to the liquid crystal surface, and then the tape is peeled off by visual inspection. Observed. As a result, the degree of adhesion was 100%.
Adhesion degree (%) = (part which was not peeled / area where tape was applied) × 100

(4) Moisture and heat resistance test-1
The sample was immersed in hot water at 90 ° C. for 60 minutes, and the optical properties and adhesion were measured by the method described above. As a result, there was no change in optical properties and adhesion before and after the test.

(5) Moist heat resistance test-2
The sample was allowed to stand for 24 hours in an environment of 80 ° C. and 95% humidity, and the optical properties and adhesion were measured by the methods described above. As a result, there was no change in optical properties and adhesion before and after the test. Moreover, neither the exudation of the refractive index anisotropic material nor the white turbidity was observed after the test.

(6) Water resistance test The sample was immersed in pure water for 1 day at room temperature (23.5 ° C), and the optical properties and adhesion were measured by the methods described above. As a result, there was no change in optical properties and adhesion before and after the test.

(7) Alkali resistance test The sample was immersed in an aqueous alkaline solution (1.5N aqueous sodium hydroxide) at 55 ° C for 3 minutes, washed with water and dried, and the optical properties and adhesion were measured by the methods described above. As a result, there was no change in optical properties and adhesion before and after the test. Also, no coloring was seen.

(8) Raman peak intensity ratio The in-plane direction and thickness direction Raman spectroscopic spectra of the optical functional layer in the sample were measured using a laser Raman spectrophotometer (JASCO NRS-3000). Measurement conditions were such that the exposure time was 15 seconds, the number of integrations was 8, and the excitation wavelength was 532.11 nm.
Here, the Raman spectral spectrum in the in-plane direction is obtained by injecting the measurement light so that the linearly polarized electric field vibration plane coincides with the slow axis direction and the fast axis direction in the plane of the optical functional layer. Measured in each of the fast axis direction and the in-plane fast axis direction. Then, from the obtained spectrum was calculated Raman peak intensity ratio ^{(1605cm -1} / 2942cm -1) from the peak intensity at 1605 cm ^-1 and 2942cm ^-1.

Further, the Raman spectral spectrum in the thickness direction is obtained by making the measurement light incident so that the electric field vibration surface of the linearly polarized light is parallel to and perpendicular to the thickness direction at the cut surface in the thickness direction of the optical functional layer. The Raman spectrum was measured for each of the direction parallel to and perpendicular to the thickness direction on the cut surface in the thickness direction, and then calculated from the peak intensities of 1605 cm ⁻¹ and 2942 cm ⁻¹ . The results are shown in Table 1 below.
Table 1 also shows the Raman peak intensity ratio for the substrate and the optical film before stretching.

  Here, “the slow axis direction cut surface” in Table 1 means a cut surface when the optical functional film is cut in a direction parallel to the slow axis direction in the plane of the optical functional 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.

An example of the Raman spectrum is shown in FIG. FIG. 6 is a Raman spectral spectrum in the in-plane direction of the entire optical functional film, and FIG. 6 (a) is measured with the measurement light incident so that the electric field vibration plane of linearly polarized light coincides with the slow axis direction. FIG. 6B shows the measurement with the measurement light incident so that the electric field vibration plane of the linearly polarized light coincides with the fast axis direction. 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.

2. Example 2
A liquid crystal mixture of 50% by mass of a side chain polymer represented by the following formula (A) and 50% by mass of a photopolymerizable liquid crystal represented by the following formula (B), a photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Irgacure 907, 5 mass% with respect to the photopolymerizable compound) was dissolved in a cyclohexanone solution so as to have a solid content of 20%, and a leveling agent was further added to obtain a coating solution for forming a retardation layer. After coating the retardation layer forming coating solution on the optical functional film prepared in Example 1, the liquid crystal mixture is homeotropically aligned by drying at 100 ° C. for 1 minute and then cooling to room temperature. I let you. Furthermore, it hardened | cured by 100 mJ / cm < ² > UV, and produced the optical function film with a phase difference layer by forming a phase difference layer with a thickness of 1 micrometer on the said optically anisotropic layer.

3. Comparative Example 1
75 parts by weight of a liquid crystal material (formula III below) having polymerizable acrylate groups at both ends and a spacer between the mesogen at the center and the acrylate, Irgacure Irg184 (manufactured by Chiba Specialty Chemicals) as a photopolymerization initiator 1 part by weight and 25 parts by weight of toluene as a solvent are mixed, and further 10 parts by weight of a chiral agent having a polymerizable acrylate group at both ends (formula IV below) is added as a chiral agent. A working solution was prepared.

Using a substrate made of a cycloolefin polymer having a thickness of 80 μm having no in-plane retardation (Re) (manufactured by JSR Corporation, trade name: Arton), the coating solution for forming the optical functional layer is used as the substrate. It was applied on top using a spin coating method. Next, the film coated with the coating solution for forming an optical functional layer was heated on a hot plate at 100 ° C. for 5 minutes to remove the residual solvent, and a twist-aligned liquid crystal structure was developed. Then, ultraviolet rays are irradiated to the coating film (20 mJ / cm ^2, wavelength 365 nm), the liquid crystal material to obtain a chiral nematic (cholesteric) 4.0 .mu.m thick optical functional layer of the array. At this time, the spiral pitch of the liquid crystal material was 180 nm, and the reflection wavelength of the optical functional layer was 280 nm.
In addition, as a result of heating the base material in which the said optical functional layer was formed at 145 degreeC for 1 minute and extending | stretching 1.5 time, peeling generate | occur | produced between a base material and an optical functional layer, It could not be produced.

4). Comparative Example 2
Using a substrate made of norbornene-based resin with Re = 120 nm as an optically anisotropic film (trade name: ZEONOR manufactured by Nippon Zeon Co., Ltd.), a retardation layer is formed on the anisotropic film by the same method as in Example 2. Thus, an optical functional film was produced.

5). Evaluation A polarizing plate was prepared using each optical function film as a polarizing plate protective film on one side, and an environmental test was performed in which the polarizing plate was left in an environment of a temperature of 90 ° C. and a humidity of 90% RH for 100 hours, and frame unevenness evaluation was performed. In the frame unevenness evaluation, light leakage during black display was visually evaluated. As a result, when the films prepared in Examples 1 and 2 were used as a polarizing plate protective film, no significant change was visually observed on the entire polarizing plate with respect to light leakage during black display before and after the environmental test.
Here, when producing a polarizing plate using the optical functional films of Examples 1 and 2, a polarizing plate protective film made of a cycloolefin resin could be used as the other polarizing plate protective film.
However, when producing a polarizing plate using the optical functional film produced in Comparative Examples 1 and 2, a polarizing plate protective film made of triacetyl cellulose is used as the other polarizing plate protective film due to moisture permeability. There was nothing else.

DESCRIPTION OF SYMBOLS 1, 1 '... Base material 2, 2' ... Optical functional layer 3 ... Rod-shaped compound 10 ... Optical functional film 11 ... Polarizer 12 ... Polarizing plate protective film 20 ... Optical film 101 ... Liquid crystal cell 102A, 102A ', 102B, 102B '... Polarizing plate 103 ... Retardation film 111 ... Polarizer 112a, 112b ... Polarizing plate protective film

Claims (13)

An optical functional film having a base material composed of a cellulose derivative and an optical functional layer formed directly on the base material and having a rod-like compound, and exhibiting optical biaxiality,
The optical functional film, wherein the rod-like compound forms irregular random homogeneous orientation in the optical functional layer.   The relationship of nx> ny> nz is established among the refractive index nx in the slow axis direction in the in-plane direction, the refractive index ny in the fast axis direction in the in-plane direction, and the refractive index nz in the thickness direction. The optical functional film according to claim 1.   The optical functional film according to claim 1 or 2, wherein an in-plane retardation (Re) is in a range of 70 nm to 180 nm.   The optical functional film according to any one of claims 1 to 3, wherein a retardation (Rth) in a thickness direction is in a range of 75 nm to 300 nm.   The optical functional film according to any one of claims 1 to 4, wherein the Nz coefficient is within a range of 1.0 to 2.5.   The optical functional film according to any one of claims 1 to 5, wherein the rod-shaped compound has a polymerizable functional group.   The rod-shaped compound has a structure in which a polymerizable functional group and a mesogenic group are bonded via an alkyl chain having 4 or more carbon atoms, wherein the rod-shaped compound is any one of claims 1 to 6. The optical functional film according to claim 1.   The optical functional film according to any one of claims 1 to 7, wherein the rod-shaped compound is a liquid crystalline material.   The optical functional film according to any one of claims 1 to 8, wherein the wavelength dependency of in-plane retardation (Re) is a positive dispersion type. The rod-shaped compound has a rod-shaped main skeleton to which two or more benzene rings are bonded, and an in-plane slow axis direction Raman peak intensity ratio (1605 cm ⁻¹ / ¹⁾ in the optical functional layer. 2942 cm ⁻¹ ) is 1.1 times or more of the in-plane fast axis direction Raman peak intensity ratio (1605 cm ⁻¹ / 2942 cm ⁻¹ ), The optical functional film according to any one of claims. The rod-shaped compound has a rod-shaped main skeleton to which two or more benzene rings are bonded, and a Raman peak in a direction perpendicular to the thickness direction in a cut surface in the thickness direction of the optical function layer The intensity ratio (1605 cm ^-1 / 2942 cm ^-1 ) is 1.1 times or more of the Raman peak intensity ratio (1605 cm ^-1 / 2942 cm ^-1 ) in the direction parallel to the thickness direction. The optical functional film according to any one of claims 1 to 10. Using an optical film having a base material composed of a cellulose derivative, a rod-shaped compound that is directly formed on the base material and having a random homogeneous orientation, and an optical functional layer that is optically uniaxial,
By stretching the optical film, the refractive index nx in the slow axis direction in the in-plane direction, the refractive index ny in the fast axis direction in the in-plane direction, and the refractive index nz in the thickness direction are set to nx ≠ ny or nx An optical material comprising: a base material satisfying a relationship of ≠ ny ≠ nz; and an optical functional layer that is formed directly on the base material and includes a rod-like compound having an irregular random homogeneous orientation and further exhibits optical biaxiality. A method for producing an optical functional film, comprising producing a functional film.   The optical functional film according to any one of claims 1 to 11, a polarizer formed on any surface of the optical functional film, and a polarizing plate formed on the polarizer And a protective film.

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