JP2022029054A - Resin film, method of manufacturing the same, and liquid crystal panel - Google Patents

Abstract

To provide a resin film capable of controlling wavelength dispersion characteristics of retardation both in the in-plane direction and thickness direction thereof.SOLUTION: A resin film is provided, comprising a resin 131 and particles 132. The resin 131 and particles 132 are aligned in the resin film to have different birefringence wavelength dispersion characteristics between the in-plane direction and the thickness direction of the resin film.SELECTED DRAWING: Figure 2

Description

The present invention relates to a resin film or the like. More specifically, the present invention relates to, for example, a resin film that compensates for the polarization characteristics of a polarizing film.

For example, in a display device provided with a liquid crystal panel, a polarizing film for polarizing light may be provided in order to display an image. At this time, a retardation film may be used to compensate for the polarization characteristics of the light transmitted through the polarizing film. By using the retardation film, it is possible to suppress a decrease in contrast and an inversion phenomenon of intermediate gradations when the liquid crystal panel is viewed from an oblique direction.

Patent Document 1 discloses a biaxial retardation compensation film. This means that the refractive indexes nx and ny on the surface of the film and the refractive index nz in the thickness direction are nx>ny> nz. Further, it has a reverse wavelength dispersion characteristic in which the phase difference value on the surface increases as the wavelength increases within the range of visible light. Further, it has a negative value of the normal wavelength dispersion characteristic in which the absolute value of the phase difference value in the thickness direction decreases. Then, the total of the phase difference values in the thickness direction including the phase difference values in the thickness direction of the biaxial compensation film and the vertically oriented panel is proportional to the wavelength within the range of visible light. In this case, it has a value in the range of 30 nm to 150 nm.
Patent Document 2 discloses a retardation film. The retardation film is a film obtained by dispersing a rod-shaped inorganic substance having refractive index anisotropy in a polymer medium.

Japanese Patent Publication No. 2006-515686 Japanese Unexamined Patent Publication No. 2005-227427

However, a resin film such as a retardation film has a wavelength dispersion characteristic in which the phase difference differs depending on the wavelength of light. Further, with the conventional method, it is difficult to control each of the wavelength dispersion characteristics in the in-plane direction of the resin film and the thickness direction of the resin film with respect to the phase difference. As a result, a phenomenon occurs in which the colors look different depending on the viewing angle of the liquid crystal panel. For example, the invention of Patent Document 1 is also rejected because there is a defect in the description of the specific realization method. As described above, it has been conventionally considered difficult to realize a method for actually controlling the wavelength dispersion characteristics of the in-plane direction of the resin film and the thickness direction of the resin film separately.
The present invention is intended to provide a resin film or the like capable of controlling the wavelength dispersion characteristics of the resin film in the in-plane direction and the thickness direction of the resin film with respect to the phase difference.

The resin film of the present invention has at least a resin and particles. The resin and particles are oriented in the resin film. As a result, the wavelength dispersion characteristic of birefringence in the in-plane direction of the resin film and the wavelength dispersion characteristic of birefringence in the thickness direction of the resin film are different.

The resin and particles have anisotropy of the refractive index. The resin and the particles are oriented in the resin film so that the direction of the anisotropy of the resin and the direction of the anisotropy of the particles are different.

Here, the refractive index ellipsoid of the resin can have an ellipsoidal shape, and the refractive index ellipsoid of the particles can have a disk shape.
Further, it is preferable that the major axis direction of the ellipsoidal sphere of the resin is oriented along the in-plane direction of the resin film. Further, it is preferable that the particles are oriented in the axial direction of the disk shape along the thickness direction of the resin film.
Further, the refractive index in the in-plane direction of the resin film of the resin and the refractive index in the thickness direction of the resin film can all be different. Further, the refractive index ellipsoid of the particles can be formed into a disk shape.
Then, the resin and the particles can have at least one of the refractive index in the in-plane direction of the resin film and the refractive index in the thickness direction of the resin film different from the others.
Further, the refractive index of the resin in the in-plane direction of the resin film is n _x1 and n _y1 , and the refractive index of the resin film in the thickness direction is n _z1 . At this time, n _x1 > n _y1 ≧ n _z1 can be set.
Further, the refractive indexes of the particles in the in-plane direction of the resin film are n _x2 and n _y2 , and the refractive indexes in the thickness direction of the resin film are n _z2 . At this time, n _x2 ≧ n _y2 > n _z2 can be set.
The particles can then contain smectite.
Further, the resin can be made to contain at least one of cycloolefin polymer, triacetyl cellulose, diacetyl cellulose, polycarbonate and polyester.
Further, the phase difference with respect to the wavelength λ (nm) of light in the in-plane direction of the resin film is Re (λ), and the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the resin film is Rth (λ). .. At this time, Re (450) / Re (550) <Rth (450) / Rth (550) can be set. Further, when only the resin is used as a film, the phase difference with respect to the wavelength λ (nm) of light in the in-plane direction of the film of this resin only is defined as Re_poly (λ). Further, the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the film of this resin only is defined as Rth_poly (λ). At this time, (Re_poly (450) / Re_poly (550)) / (Re (450) / Re (550))> (Rth_poly (450) / Rth_poly (550)) / (Rth (450) / Rth (550)) Can be.
Further, the phase difference with respect to the wavelength λ (nm) of light in the in-plane direction of the resin film is Re (λ), and the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the resin film is Rth (λ). .. At this time, Re (650) / Re (550)> Rth (650) / Rth (550) can be set. Further, when only the resin is used as a film, the phase difference with respect to the wavelength λ (nm) of light in the in-plane direction of the film of this resin only is defined as Re_poly (λ). Further, the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the film of this resin only is defined as Rth_poly (λ). At this time, (Re_poly (650) / Re_poly (550)) / (Re (650) / Re (550)) <(Rth_poly (650) / Rth_poly (550)) / (Rth (650) / Rth (550)) Can be.
The resin can have birefringence having a reverse wavelength dispersion characteristic, and the particles can have birefringence having a positive wavelength dispersion characteristic.
Further, the wavelength dispersion characteristic of birefringence in the in-plane direction of the resin film is mainly determined by the wavelength dispersion characteristic of the resin. The wavelength dispersion characteristic of birefringence in the thickness direction of the resin film is determined by the mixing ratio of the resin and the particles.

It also has at least a resin and particles. The refractive index ellipsoid of the resin can be shaped like an ellipsoidal sphere. Further, the refractive index ellipsoid of the particles can be formed into a disk shape. Then, the refractive index ellipsoid of the resin and the refractive index ellipsoid of the particles are oriented so that the longitudinal direction thereof is along the in-plane direction of the resin film in the resin film.

The method for producing a resin film of the present invention includes a preparation step, a coating step, and a stretching step. The coating solution contains a resin, particles, and a solvent. The particles are oriented by the flow of the material in the coating and drying steps. The resin may also be oriented at the time of application depending on the characteristics of the material. Further, the resin and particles are oriented in the resin film when stretched in the stretching step. As a result, the wavelength dispersion characteristic of the birefringence in the in-plane direction of the resin film and the wavelength dispersion characteristic of the birefringence in the thickness direction of the resin film become different. The solvent disperses the resin and particles.
Further, the method for producing a resin film of the present invention includes a preparation step, a coating step, and a stretching step. In the preparation step, a coating solution for preparing a resin film is prepared. In the coating step, the coating solution is applied to form a film-like body. In the stretching step, the film-like body is stretched to form a resin film. The coating solution contains a resin, particles, and a solvent. The resin is oriented in the resin film when it is stretched in the stretching step. As a result, in the resin, the refractive index ellipsoid becomes an ellipsoidal shape. The particles are oriented in the film when stretched in the flow and stretching steps of the material during the coating and drying steps. As a result, the particles have a disk-shaped refractive index ellipsoid. The solvent disperses the resin and particles.
Further, the method for producing a resin film of the present invention includes a preparation step, a coating step, and a stretching step. In the preparation step, a coating solution for preparing a resin film is prepared. In the coating step, the coating solution is applied to form a film-like body. In the stretching step, the film-like body is stretched to form a resin film. The coating solution contains a resin, particles, and a solvent. The resin is oriented in the resin film when it is stretched in the stretching step. As a result, the refractive index of the resin film in the in-plane direction and the refractive index in the thickness direction of the resin film are all different. The particles are oriented by the flow of the material during the coating and drying steps and are oriented in the membrane when further stretched. As a result, the particles have a disk-shaped refractive index ellipsoid. The solvent disperses the resin and particles.
Here, in the stretching step, the resin film may have a biaxial phase difference by performing uniaxial stretching.
Further, in the stretching step, the resin film may have a biaxial phase difference by performing biaxial stretching.
Further, the refractive indexes of the particles in the film-like body before the stretching step in the in-plane direction of the film-like body are set to n _{x 2} and n _y 2. Further, the refractive index in the thickness direction of the film-like body is _nz2 . At this time, n _x2 = n _y2 > n _z2 can be set.
Further, the resin film may be a c-plate after coating. Depending on the material, it may be fluid-oriented during the coating step and the drying step to form a c-plate, and the refractive index ellipsoid after coating becomes a disk shape. In that case, it may have a biaxial phase difference by stretching uniaxially. In this case, the refractive index ellipsoid becomes an ellipsoid in which the ellipsoidal sphere is crushed and approaches the disk.
Further, even if the coating film is a c-plate, it may be similarly biaxially stretched to have a biaxial phase difference.
The wavelength dispersion characteristic of birefringence in the thickness direction of the resin film may be adjusted by the mixing ratio of the resin and the particles.

The liquid crystal panel of the present invention includes a liquid crystal display, a polarizing means, and a retardation film. The liquid crystal controls the state of light transmission. The polarizing means polarizes the light. The retardation film has at least a resin and particles. The resin and particles are oriented in the retardation film. As a result, the wavelength dispersion characteristic of birefringence in the in-plane direction of the retardation film and the wavelength dispersion characteristic of birefringence in the thickness direction of the retardation film are different.
The liquid crystals may be arranged vertically without applying a voltage.
Here, the mixing ratio of the resin and the particles in the retardation film can be determined according to the phase difference obtained in the thickness direction of the liquid crystal display.
Then, the wavelength dispersion characteristic of the phase difference in the thickness direction of the liquid crystal and the wavelength dispersion characteristic of the phase difference in the thickness direction of the retardation film are considered. At this time, both can be set to have positive wavelength dispersion characteristics.
Further, the wavelength dispersion characteristic of the phase difference in the thickness direction of the liquid crystal and the wavelength dispersion characteristic of the phase difference in the thickness direction of the retardation film will be considered. At this time, both can be flat.
Further, the phase difference with respect to the wavelength λ (nm) of light in the in-plane direction of the retardation film is defined as Re (λ). Further, the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the liquid crystal is defined as Rth_p (λ). At this time, Re (450) / Re (550) <Rth_p (450) / Rth_p (550) can be set.
Further, the phase difference with respect to the wavelength λ (nm) of light in the in-plane direction of the retardation film is defined as Re (λ). Further, the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the liquid crystal is defined as Rth_p (λ). At this time, Re (650) / Re (550)> Rth_p (650) / Rth_p (550) can be set.
Then, the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the retardation film is defined as Rth (λ). Further, the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the liquid crystal is defined as Rth_p (λ). At this time, (Re (450) / Re (550)) / (Rth_p (450) / Rth_p (550)) <(Rth_p (450) / Rth_p (550)) / (Rth (450) / Rth (550)) Can be.
Further, the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the retardation film is defined as Rth (λ). Further, the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the liquid crystal is defined as Rth_p (λ). At this time, (Re (650) / Re (550)) / (Rth_p (650) / Rth_p (550))> (Rth_p (650) / Rth_p (550)) / (Rth (650) / Rth (550)) Can be.

The optical member of the present invention includes a substrate and the resin film provided on the substrate.

Further, the polarizing member of the present invention includes a polarizing means for polarizing light and the resin film provided on the substrate.

The coating solution for forming a resin film of the present invention contains a resin, particles, and a solvent. The particles flow in the material during the coating and drying steps, and the resin and particles are oriented in the resin film when the film-like body containing the resin and particles is stretched to form a resin film. As a result, the wavelength dispersion characteristic of the birefringence in the in-plane direction of the resin film and the wavelength dispersion characteristic of the birefringence in the thickness direction of the resin film become different. The solvent disperses the resin and particles.
Further, the coating solution for forming a resin film of the present invention contains a resin, particles, and a solvent. The particles are oriented in the resin film when the flow of the material during the coating step and the drying step, and the film-like body containing the resin and the particles are stretched to form a resin film. As a result, in the resin, the refractive index ellipsoid becomes an ellipsoidal shape. Then, the particles have a disk-shaped refractive index ellipsoid. The solvent disperses the resin and particles.
Further, the coating solution for forming a resin film of the present invention contains a resin, particles, and a solvent. The particles flow in the material during the coating and drying steps, and the resin and particles are oriented in the resin film when the film containing the resin and particles is stretched. As a result, the refractive index of the resin film in the in-plane direction and the refractive index in the thickness direction of the resin film are all different. The particles have a disk-shaped refractive index ellipsoid. The solvent disperses the resin and particles.
The particles can then contain smectite.
Further, the resin can be made to contain at least one of cycloolefin polymer, triacetyl cellulose, diacetyl cellulose, polycarbonate and polyester.

According to the present invention, it is possible to provide a resin film or the like capable of controlling the wavelength dispersion characteristics of the resin film in the in-plane direction and the thickness direction of the resin film with respect to the phase difference.

(A) is a figure explaining the display device to which this embodiment is applied. (B) is a cross-sectional view taken along the line Ib-Ib of FIG. 1A, showing an example of the configuration of a liquid crystal panel to which the present embodiment is applied. (A) to (c) are schematic views showing the structure of the retardation film. (A)-(b) is a figure which showed the refractive index ellipsoid of a resin and a particle. (C) is a figure which showed the calculation formula of the refractive index in the in-plane direction and the thickness direction of a retardation film. (A) is a diagram showing the wavelength dependence of birefringence of the resin alone. (B) is a figure showing the wavelength dependence of birefringence of a particle alone. FIGS. (C) to (e) are diagrams showing the wavelength dependence of birefringence when the resin and the particles are mixed. It is a flowchart explaining the method of making the retardation film of this embodiment. (A) to (b) are diagrams showing the wavelength dispersion characteristic of the vertical phase difference Rth of the liquid crystal when the cell gap is not changed. (A) to (c) are diagrams showing the wavelength dispersion characteristic of the retardation film. (A) to (c) are diagrams showing the luminance viewing angle distribution of the chromaticity at the time of black display. (D) to (f) are diagrams showing the spectral distribution of the locations indicated by the respective points of (a) to (c). (A)-(b) is a figure which showed the other example of the refractive index ellipsoid of a resin. (A)-(b) is a figure which showed the other example of the refractive index ellipsoid of a resin. (A) is a conceptual diagram in the case where the particles have a rectangular shape. (B) is a refractive index ellipsoid of the particles after being stretched in the stretching step. It is a figure which showed the structure of a liquid crystal display. a) to (b) are diagrams showing the wavelength dispersion characteristics of the vertical phase difference Rth of the liquid crystal display when the cell gap is changed. (A) to (b) are diagrams showing the wavelength dispersion characteristic of the retardation film. (A) is a display showing the luminance and chromaticity at the time of black display when the conventional retardation film shown in FIG. 14 (a) is used. (B) is a display showing the luminance and chromaticity at the time of black display when the retardation film of the present embodiment shown in FIG. 14 (b) is used. FIGS. (A) to (b) are diagrams for evaluating the wavelength-dependent characteristics of the in-plane phase difference and the vertical phase difference. FIGS. (A) to (b) are diagrams showing wavelength-dependent characteristics of in-plane phase difference and longitudinal phase difference. FIG. 3 is a diagram for evaluating the wavelength-dependent characteristics of in-plane phase difference and longitudinal phase difference with respect to Example 3. FIG. 4 is a diagram for evaluating the wavelength-dependent characteristics of in-plane phase difference and longitudinal phase difference with respect to Example 4. FIG. 5 is a diagram for evaluating the wavelength-dependent characteristics of in-plane phase difference and longitudinal phase difference with respect to Example 5. FIG. 6 is a diagram for evaluating the wavelength-dependent characteristics of in-plane phase difference and longitudinal phase difference with respect to Example 6. FIG. 3 is a diagram for evaluating the wavelength-dependent characteristics of in-plane phase difference and vertical phase difference with respect to Comparative Example 3. It is a figure which evaluated the wavelength dependence characteristic of the in-plane phase difference and the vertical phase difference about the comparative example 4. FIG. 7 is a diagram for evaluating the wavelength-dependent characteristics of in-plane phase difference and longitudinal phase difference with respect to Example 7. FIG. 8 is a diagram for evaluating the wavelength-dependent characteristics of in-plane phase difference and longitudinal phase difference with respect to Example 8. It is a figure which evaluated the wavelength dependence characteristic of the in-plane phase difference and the vertical phase difference about the comparative example 5.

Hereinafter, embodiments for carrying out the present invention will be described in detail. The present invention is not limited to the following embodiments. In addition, it can be modified in various ways within the scope of the gist. Further, the drawings used are for explaining the present embodiment and do not represent the actual size.

<Explanation of display device>
FIG. 1A is a diagram illustrating a display device 1 to which the present embodiment is applied.
The illustrated display device 1 is, for example, a liquid crystal display for a PC (Personal Computer), a liquid crystal television, or the like. The display device 1 displays an image on the liquid crystal panel 1a.

<Explanation of liquid crystal panel 1a>
FIG. 1B is a cross-sectional view taken along the line Ib-Ib of FIG. 1A, showing an example of the configuration of the liquid crystal panel 1a to which the present embodiment is applied.
The liquid crystal panel 1a of the present embodiment is, for example, a VA type liquid crystal panel. The illustrated liquid crystal panel 1a has a backlight 11 and a polarizing film 12a. Further, the liquid crystal panel 1a includes a retardation film 13a, a liquid crystal 14, a retardation film 13b, and a polarizing film 12b. And these have a structure which is laminated in this order. Hereinafter, when the polarizing film 12a and the polarizing film 12b are not distinguished, they may be simply referred to as the polarizing film 12. Further, when the retardation film 13a and the retardation film 13b are not distinguished, it may be simply referred to as the retardation film 13. Further, the liquid crystal 14 generally has a cell structure in which a liquid crystal layer is sandwiched between two glass substrates.

The backlight 11 irradiates the liquid crystal 14 with light. The backlight 11 is, for example, a cold cathode fluorescent lamp or a white LED (Light Emitting Diode).
The polarizing film 12a and the polarizing film 12b are examples of polarizing means for polarizing light. The polarization directions of the polarizing film 12a and the polarizing film 12b are orthogonal to each other. The polarizing film 12a and the polarizing film 12b include, for example, a resin film in which an iodine compound molecule is contained in polyvinyl alcohol (PVA). Then, this is sandwiched and bonded with a resin film made of triacetylcellulose (TAC). Light is polarized by including iodine compound molecules. In the case of a VA type liquid crystal panel, among these TACs, the one on the liquid crystal 14 side is often used in combination with the retardation film 13a of the present embodiment. Generally, a TAC stretched or a COP (cyclo olefin polymer) biaxially stretched is used.

A power supply (not shown) is connected to the liquid crystal 14, and when a voltage is applied by this power supply, the arrangement direction of the liquid crystal 14 changes. The liquid crystal display 14 controls the light transmission state by this.
In the case of the VA type liquid crystal panel, when no voltage is applied to the liquid crystal 14 (voltage OFF), the liquid crystal molecules are arranged in the vertical direction in the figure. Then, when the light is irradiated from the backlight 11, the light first passes through the polarizing film 12a and becomes polarized. Then, the polarized light passes through the liquid crystal 14 as it is. Further, since the polarizing film 12b has a different polarization direction, this polarization is blocked. In this case, the user who sees the liquid crystal panel 1a cannot visually recognize this light. That is, when no voltage is applied to the liquid crystal 14, the color of the liquid crystal is "black".

On the other hand, when the maximum voltage is applied to the liquid crystal 14, the liquid crystal molecules are arranged in the horizontal direction in the figure. The polarization of the polarized light that has passed through the polarizing film 12a is rotated by 90 degrees due to the action of the liquid crystal display 14. Therefore, the polarizing film 12b does not block this polarization but allows it to pass through. In this case, the user who sees the liquid crystal panel 1a can visually recognize this light. That is, when the maximum voltage is applied to the liquid crystal 14, the color of the liquid crystal is "white". The voltage can also be between the voltage OFF and the maximum voltage. In this case, the liquid crystal display 14 is in a state between the vertical direction in the figure and the vertical direction with respect to the vertical direction in the figure. That is, the liquid crystals 14 are arranged in an oblique direction, which is a direction that intersects both the vertical direction and the vertical direction. In this state, the color of the liquid crystal is "gray". Therefore, by adjusting the voltage applied to the liquid crystal 14 between OFF and the maximum voltage, it is possible to express intermediate gradations in addition to black and white. Then, the image is displayed by this.

Although not shown, a color image can be displayed by using a color filter. Further, a hard coat layer or a low refractive index layer can be formed on the upper side of the polarizing film 12b in the drawing.

The illustrated polarizing film 12 and the retardation film 13 can be integrally formed. As will be described in detail later, the retardation film 13 can be formed by, for example, coating on a substrate. That is, the retardation film 13 can be formed on the polarizing film 12. Therefore, the polarizing film 12 and the retardation film 13 can be taken together as an example of the polarizing member. Further, if the polarizing film 12 is taken as an example of a substrate, the substrate and the retardation film 13 can be taken together as an example of an optical member. The substrate is not limited to the film, and may be, for example, glass. In this case, for example, the optical member is a lens or an optical element.

However, the light transmitted through the liquid crystal 14 changes its polarization state from linearly polarized light to elliptically polarized light. For example, when the liquid crystal panel 1a is displayed in black, the liquid crystal panel 1a looks black when viewed from the vertical direction. On the other hand, when the liquid crystal panel 1a is viewed from an oblique direction, the retardation of the liquid crystal 14 occurs. Also, the axis of the polarizing film 12 is not 90 °. Therefore, there arises a problem that light is lost, the image becomes white, and the contrast is lowered. That is, the liquid crystal panel 1a has a viewing angle dependence. The retardation films 13a and 13b have a function of returning the elliptically polarized light to linearly polarized light. By providing the retardation films 13a and 13b, the viewing angle dependence of the liquid crystal panel 1a can be compensated. As will be described in detail later, the retardation film 13 of the present embodiment has different wavelength dispersion characteristics of the phase difference in the in-plane direction and the phase difference in the thickness direction. This makes it possible to compensate for the wavelength dispersion characteristics of the liquid crystal 14 and the polarizing film 12 when observing from an angle. Then, it becomes possible to suppress light leakage over the entire wavelength range.

<Detailed description of the retardation film 13>
Next, the retardation film 13 of the present embodiment will be described in detail.
2 (a) to 2 (c) are schematic views showing the structure of the retardation film 13.
The retardation film 13 of the present embodiment is an example of a resin film or a film. The retardation film 13 has a resin 131 and particles 132. Further, the retardation film 13 may contain an unreacted monomer or the like, which is a raw material of the resin 131, in addition to the resin 131 and the particles 132. Further, the retardation film 13 may contain additives such as a dispersant, an antifoaming agent, and a leveling agent. The resin 131 is also the main component of the retardation film 13. Therefore, it can be said that the particles 132 are dispersed in the resin 131. However, the particles 132 are not always completely dispersed and may be partially aggregated. Then, what is aggregated to some extent may be distributed in the resin 131. Here, the resin 131 is shown as a linear shape, and the particles 132 are shown as a disk shape. However, for convenience of explanation, the resin 131 is shown in such a shape. Therefore, it does not necessarily represent the actual shapes of the resin 131 and the particles 132. When the particles 132 are smectites, which will be described in detail later, smectites can be regarded as flat disc-shaped particles. Further, the flat surfaces of the smectite disc-shaped particles are arranged substantially horizontally with respect to the film surface of the retardation film 13.

Further, FIG. 2A shows a case where the particles 132 are uniformly dispersed in the resin 131. That is, in this case, the particles 132 are not unevenly distributed in the resin 131. Further, FIG. 2B shows a case where the particles 132 are unevenly distributed on the upper side in the resin 131. Further, FIG. 2C shows a case where the particles 132 are unevenly distributed downward in the resin 131. Even in the cases shown in FIGS. 2 (b) and 2 (c), the function of the retardation film 13 can be exhibited.

The resin 131 and the particles 132 have anisotropy of the refractive index, and are oriented in the retardation film 13 so that the direction of the anisotropy of the resin 131 and the direction of the anisotropy of the particles 132 are different. Hereinafter, this matter will be described in detail.

3 (a) to 3 (b) are views showing the refractive index ellipsoids of the resin 131 and the particles 132.
FIG. 3A is a diagram showing the refractive index ellipse of the resin 131, and FIG. 3B is a diagram showing the refractive index ellipse of the particles 132.
The refractive index ellipsoid represents the distribution of the refractive index when the in-plane direction and the thickness direction of the retardation film 13 are the xy direction and the z direction, respectively. That is, the refractive index ellipsoid represents the refractive index in any direction in the xyz Cartesian coordinate system. The "in-plane direction" is a predetermined biaxial direction along the surface of the retardation film 13, and here, there are two directions, the x direction and the y direction. Here, the x-direction and the y-direction are collectively referred to as the xy-direction.

As shown in FIG. 3A, the refractive index ellipsoid of the resin 131 has an ellipsoidal shape. Then, in the resin 131, the ellipsoidal long axis C1 direction is oriented in the direction along the in-plane direction of the retardation film 13. It can also be said that the resin 131 is oriented in the longitudinal direction of the ellipsoidal sphere along the in-plane direction of the retardation film 13. It can also be said that the molecules of the resin 131 are oriented in such an orientation. As shown in the figure, the ellipsoidal sphere-shaped short axis C2 direction is the thickness direction of the retardation film 13. It can also be said that the ellipsoidal sphere-shaped short axis C2 direction is the out-of-plane direction of the retardation film 13.

The refractive index of the resin 131 in the x direction is n _x1 , the refractive index in the y direction is n _y1 , and the refractive index in the z direction is n _z1 . When the resin 131 is oriented in this way in the retardation film 13, the relationship of n _x1 > n _y1 = n _z1 is established as shown in the equation (1). It is also possible to combine the refractive index n _y1 in the y direction and the refractive index n _z1 in the z direction so that _{ny = z1} . In this case, as shown in the equation (1)', the relationship of n _x1 > _{ny = z1} is established.

Further, as shown in FIG. 3B, the refractive index ellipsoid of the particles 132 has a disk shape. Then, in the particles 132, the disk-shaped axis C3 direction is oriented in the direction along the thickness direction of the retardation film 13. It can also be said that the particles 132 are oriented in the longitudinal direction of the disk shape along the in-plane direction of the retardation film 13.

Let the refractive index of the particles 132 in the x direction be n _x2 , the refractive index in the y direction be n _y2 , and the refractive index in the z direction be n _z2 . When the particles 132 are oriented in this way in the retardation film 13, the relationship of n _x2 = n _y2 > n _z2 is established as shown in the equation (2). It is also possible to combine the refractive index n _x2 in the x direction and the refractive index n _y2 in the y direction so that n _{x = y2} . In this case, as shown in the equation (2)', the relationship of n _{x = y2} > n _z2 is established.

Regarding the ellipsoidal sphere shape and the disk shape, this shape is not required in a strict sense. That is, even if the shape is slightly different from the ellipsoidal shape and the disk shape, there is usually no problem in using the retardation film 13. Therefore, the ellipsoidal sphere shape and the disk shape are concepts including the substantially ellipsoidal sphere shape and the substantially ellipsoidal shape.

From the above description, the resin 131 and the particles 132 have a bidirectional index of refraction in the in-plane direction of the retardation film 13 (in this case, n _x1 , n _y1 and n _x2 , n _y2 ) and the thickness of the retardation film 13. It can be said that at least one of the refractive indexes in the direction (in this case, n _z1 and n _z2 ) is different from the others. That is, in the resin 131, the refractive index n _x1 is different from the other refractive indexes _ny1 and _nz1 . Further, in the particle 132, the refractive index n _z2 is different from the other refractive indexes n _{x 2} and n _y 2.

Then, such a resin 131 and the particles 132 are mixed in a ratio of a: 1-a. Here, the refractive index in the in-plane direction of the retardation film 13 and the thickness direction of the retardation film 13 at this time is considered.
FIG. 3C is a diagram showing a calculation formula of the refractive index in the in-plane direction and the thickness direction of the retardation film 13. Here, the refractive indexes of the resin 131 and the particles 132 in the x-direction, y-direction, and z-direction when a: 1-a are mixed are calculated.

Here, the refractive index in the x direction in which the resin 131 and the particles 132 are mixed is defined as the refractive index n _xm . At this time, the refractive index n _xm is n _x1 * a + n _x2 * (1-a) as shown in the equation (3). This can also be expressed as n _x1 * a + n _{x = y2} * (1-a) as shown by the equation (3)'.
Further, the refractive index in the y direction in which the resin 131 and the particles 132 are mixed is defined as the refractive index n _ym . At this time, the refractive index n _ym is n _y1 * a + n _y2 * (1-a) as shown by the equation (4). Further, this can also be expressed as n _{y = z1} * a + n _{x = y2} * (1-a) as shown by the equation (4)'.
Further, the refractive index in the z direction in which the resin 131 and the particles 132 are mixed is defined as the refractive index n _zm . At this time, the refractive index n _zm is n _z1 * a + n _z2 * (1-a) as shown in the equation (5). Further, this can also be expressed as ny _{= z1} * a + n _z2 * (1-a) as shown by the equation (5)'.

Then, the birefringence Δn in the xy direction, which is the in-plane direction, is n _mxm − n _ym as shown in the equation (6). Then, when this is transformed into an equation, the birefringence Δn becomes (n _x1 - _ny1 ) * a as shown in the equation (7).
Further, the birefringence P in the z direction, which is the thickness direction of the retardation film 13, is (n _xm + n _ym ) / 2-n _zm as shown by the equation (8). Then, when this is transformed, the birefringence P becomes (n _{x1 -ny = z1} ) * a / 2 + (n _{x = y2-} n _z2 ) * (1-a) as shown in the equation (9). Will be.

Looking at the equation (7), the birefringence Δn in the xy direction, which is the in-plane direction, depends on the refractive indexes n _x1 and _ny1 of the resin 131. The birefringence Δn becomes smaller in proportion to the amount of the particles 132 added. That is, the birefringence Δn is multiplied by a. On the other hand, it does not affect the wavelength dispersion characteristics. Therefore, the in-plane birefringence Δn coincides with the slope of the wavelength dispersion characteristic of the birefringence Δn of the resin 131.
Further, when looking at the equation (9), the birefringence P in the z direction, which is the thickness direction of the retardation film 13, depends on both the refractive indexes of the resin 131 and the particles 132. That is, the birefringence P is represented by the refractive indexes n _x1 and _{ny = z1} of the resin 131 and the refractive indexes n _{x = y2} and _nz2 of the particles 132.

When the particles 132 are placed in the retardation film 13, the slope of the wavelength dispersion characteristic of the in-plane retardation, which is the in-plane retardation, does not change. On the other hand, the slope of the wavelength dispersion characteristic of the vertical retardation, which is the phase difference in the thickness direction of the retardation film 13, changes.
This is due to the following reasons.
That is, assuming that the birefringence (refractive index anisotropy) at the wavelength λ is Δn _λ and P _λ , the following equation 1 relationship holds. Here, C _nano , Δn _{nano, λ} , C _poly , Δn _{poly, and λ} are C _nano = 1-a, Δn _{nano, λ} = n _{x2, λ} −n _{y2, λ} , C _poly = a, Δn _poly =. There is a relationship of n _{x1, λ} -n _{y1, λ} . The subscript of λ means that it is a value at the wavelength λ.

Therefore, the wavelength-dependent characteristic of birefringence in the in-plane direction of the retardation film 13 to which the particles 132 are added becomes equal to the wavelength-dependent characteristic of the material of the resin 131.
On the other hand, the birefringence P in the thickness direction of the retardation film 13 has the following relation of the following equation (2). Here, P _{nano, λ} , P _{poly, and λ} can be calculated by the following equations and three equations, respectively.

Whether the wavelength dispersion characteristic is a positive wavelength dispersion characteristic or an inverse positive wavelength dispersion characteristic is determined by | C _nano (P _{nano, λ} -P _{nano, 550} ) | and | C _poly (P _{poly, λ} -P _poly ). ₅₅₀ ) | Although it depends on the magnitude relationship, it approaches the positive wavelength dispersion characteristic as compared with the wavelength dependence of the retardation film 13 of the resin 131 alone.

FIG. 4A is a diagram showing the wavelength dependence of birefringence of the resin 131 alone. The value of birefringence is standardized with the birefringence of 550 nm as 1.
Here, as the refractive index of the resin 131 alone, the birefringence Δn in the xy direction, which is the in-plane direction, is shown. Further, the birefringence P in the z direction, which is the thickness direction of the retardation film 13, is shown. In this case, the wavelength dependence of the birefringence Δn and the birefringence P is the same. Therefore, both lines overlap and are represented as one line. As for the refractive index of the resin 131 alone, the birefringence Δn and the birefringence P increase as the wavelength of light increases. In this case, it can be said that the birefringence Δn and the birefringence P of the resin 131 alone have the inverse wavelength dispersion characteristic.

Further, FIG. 4B is a diagram showing the wavelength dependence of birefringence of the particle 132 alone.
Here, as the birefringence of the particles 132 alone, the birefringence P in the z direction, which is the thickness direction of the retardation film 13, is shown. The birefringence P of the particle 132 alone becomes smaller as the wavelength of light increases. In this case, it can be said that the birefringence P of the particle 132 alone has a positive wavelength dispersion characteristic. The birefringence Δn has a value of almost 0.

4 (c) to 4 (e) are diagrams showing the wavelength dependence of birefringence when the resin 131 and the particles 132 are mixed.
Of these, FIG. 4C shows the wavelength dependence of birefringence when the resin 131 is 95% and the particles 132 are 5% in terms of mass ratio. Further, FIG. 4D shows the wavelength dependence of birefringence when the resin 131 is 90% and the particles 132 are 10%. Further, FIG. 4 (e) shows the wavelength dependence of birefringence when the resin 131 is 80% and the particles 132 are 20%. 4 (c) to 4 (e) show birefringence Δn in the xy direction, which is the in-plane direction, respectively. Further, the birefringence P in the z direction, which is the thickness direction of the retardation film 13, is shown in the figure.

Comparing FIGS. 4 (c) to 4 (e), the wavelength dependence of the birefringence Δn does not change even if the content of the particles 132 increases. That is, the result shows that the birefringence Δn depends on the refractive index of the resin 131, and the refractive index of the particles 132 has no effect.
On the other hand, comparing FIGS. 4 (c) to 4 (e), the slope of the birefringence P increases as the content of the particles 132 increases. Further, it can be said that the birefringence P decreases as the content of the particles 132 increases. That is, the birefringence P is represented by the refractive indexes n _x1 and _{ny = z1} of the resin 131 and the refractive indexes n _{x = y2} and _nz2 of the particles 132. Therefore, the change in the birefringence P shows that as the content of the particles 132 increases, the contribution ratio of the resin 131 decreases and the contribution ratio of the particles 132 increases.

As described above, the retardation film 13 of the present embodiment can independently control the wavelength dependence of birefringence in the in-plane direction of the retardation film 13 and the thickness direction of the retardation film 13. It can also be said that the retardation film 13 of the present embodiment can independently control in-plane birefringence and out-of-plane birefringence.
In the retardation film 13 of the present embodiment, as shown in FIG. 4, the wavelength dispersion characteristic of the birefringence Δn in the in-plane direction of the retardation film 13 is mainly determined by the wavelength dispersion characteristic of the resin 131. On the other hand, the wavelength dispersion characteristic of the birefringence P in the thickness direction of the retardation film 13 is determined by the mixing ratio of the resin 131 and the particles 132. That is, the wavelength dispersion characteristic of the birefringence P in the thickness direction of the retardation film 13 can be controlled by the mixing ratio of the resin 131 and the particles 132.

Further, the retardation film 13 of the present embodiment has a wavelength dispersion characteristic of birefringence in the in-plane direction of the retardation film 13 (in this case, birefringence Δn) and birefringence in the thickness direction of the retardation film 13. In this case, it can be said that the wavelength dispersion characteristic of the birefringence P) is different.

In the above-mentioned example, it is assumed that the relationship of n _x1 > n _y1 = n _z1 is established for the resin 131 as shown in the equation (1) of FIG. However, for n _y1 = n _z1 , it does not have to be exactly the same, and it may be almost the same. That is, depending on the shape of the resin 131, _ny1 and _nz1 may have different numerical values. Therefore, from this point of view, it can be said that the relationship of n _x1 , n _y1 , and n _z1 holds the relationship of n _x1 > n _y1 ≧ n _z1 .
Similarly, for the particle 132, as shown in the equation (2) of FIG. 3, it is assumed that the relationship of n _x2 = n _y2 > n _z2 is established. However, for n _x2 = n _y2 , it does not have to be exactly the same, and it may be almost the same. That is, depending on the shape of the particle 132, n _{x 2} and n _y 2 may have different numerical values. Therefore, from this point of view, it can be said that the relationship of n _x2 , n _y2 , and n _z2 holds the relationship of n _x2 ≧ n _y2 > n _z2 .

An example of the resin 131 having the above-mentioned properties is a polymer such as a cycloolefin polymer (COP). Further, it is a polymer such as triacetylcellulose (TAC), diacetylcellulose, polycarbonate, and polyester. These may be used alone or in combination of two or more.
Further, as an example of the particles 132 having the above-mentioned properties, smectite can be mentioned. The particles 132 are fine particles and can be further made into nanoparticles. The particle size of the particles 132 can be, for example, 1 nm to 400 nm.
Examples of substances that can be used other than smectite include smectite minerals, and specific examples thereof include hectorite, montmorillonite, and bentonite. Examples thereof include kaolinite and antigonite, which are kaolinite minerals, and mica, which is a mica mineral.
Of these, in the present embodiment, organic smectite obtained by artificial synthesis can be particularly preferably used. Examples of the organic smectite include dimethylstearylammonium hectorite. In addition, lithium silicate, sodium, magnesium, trioctylmethylammonium can be mentioned. Further, lithium silicate / sodium / magnesium chloride dipolyoxyethylene coconut alkylmethylammonium can be mentioned.

Next, a method of creating the retardation film 13 will be described.
FIG. 5 is a flowchart illustrating a method of creating the retardation film 13 of the present embodiment.
First, a coating solution for forming the retardation film 13 is prepared (step 101: preparation step). This coating solution is an example of a coating solution for forming a resin film. Further, here, "preparation" includes not only the case of preparing by preparing a coating solution but also the case of purchasing and preparing a coating solution.
The coating solution contains the resin 131, the particles 132, and a solvent that disperses the resin 131 and the particles 132. The solvent is not particularly limited as long as it can disperse the resin 131 and the particles 132. As the solvent, for example, methylene chloride, toluene, xylene, ethyl acetate, butyl acetate, or acetone can be used. In addition, MEK (methyl ethyl ketone), ethanol, methanol, and normal propyl alcohol can be used. In addition, isopropyl alcohol, butanol, mineral spirits and oleic acid can be used. Furthermore, NMP (N-methyl-2-pyrrolidone) and DMP (dimethyl phthalate) can be used. Further, the coating solution may contain a dispersant, an antifoaming agent, a leveling agent and the like.
At this time, the wavelength dispersion characteristic of the birefringence P in the thickness direction of the retardation film 13 can be adjusted by the mixing ratio of the resin 131 and the particles 132.

Next, the coating solution is applied to prepare a film-like body (step 102: coating step). This film-like body is a resin film before stretching. The method of coating is not particularly limited, but the coating solution can be dropped onto the substrate and coated with a bar coater. Further, it is also possible to adopt a method of dropping a coating solution onto the substrate, rotating the substrate, and creating a film-like body having a uniform thickness by centrifugal force. Further, in order to produce a film-like body in mass production, a solution casting method can be used in which a film is formed by applying Roll to Roll using a slit coater. In this case, a thin film is applied to a metal band or a metal drum whose surface is made of stainless steel or the like.

Further, the applied coating film is dried (step 103: drying step). Drying can be carried out by a method of volatilizing the solvent by leaving it at room temperature, or a method of forcibly removing the solvent by heating or evacuation.
In the present embodiment, the coating film can also be formed by a melt extrusion method (melt method). The melt extrusion method (melt method) is a method in which a film can be formed simply by extruding the melted resin 131 from an apparatus and contacting a roll. The solution casting method or the melt method can be selected depending on the resin 131.
The particles 132 are oriented by the flow of the material in the coating and drying steps. Depending on the type of the resin 131, the resin 131 may be oriented in a c-plat state having a phase difference in the thickness direction.

Then, the film-like body is stretched (step 104: stretching step). As a result, the resin 131 and the particles 132 are oriented to cause a retardation in the film-like body, resulting in a retardation film 13 having an in-plane axis. By the above steps, the retardation film 13 can be produced. Stretching can be performed by a known method using a stretching device or the like.

6 (a) to 6 (b) are views showing the wavelength dispersion characteristic of the vertical phase difference Rth_p of the liquid crystal display 14.
As shown in the figure, the vertical phase difference Rth_p of the liquid crystal 14 has a positive wavelength dispersion characteristic. The vertical phase difference Rth_p of the liquid crystal 14 in this case will be described in detail later, but it corresponds to the case where the cell gap is not changed. In this case, it is preferable that the longitudinal retardation Rth of the retardation film 13 also has a positive wavelength dispersion characteristic. As a result, as will be described in detail later, the light leakage is reduced, and the color is tinted and difficult to see.
That is, it is preferable to match the wavelength dispersion characteristic of the longitudinal retardation Rth of the retardation film 13 with the wavelength dispersion characteristic of the longitudinal retardation Rth_p of the liquid crystal 14.

7 (a) to 7 (c) are diagrams showing the wavelength dispersion characteristics of the retardation film 13. In FIGS. 7A to 7C, the horizontal axis represents the wavelength and the vertical axis represents the phase difference. 7 (a) to 7 (c) show the in-plane phase difference Re, which is the phase difference in the in-plane direction of the retardation film 13. Further, FIGS. 7 (a) to 7 (c) show the vertical phase difference Rth, which is the phase difference in the thickness direction of the retardation film 13.
Further, FIGS. 8A to 8C are diagrams showing the luminance viewing angle distribution of the chromaticity at the time of displaying black. The "brightness viewing angle distribution" refers to the state in which the screen of the liquid crystal panel 1a is viewed vertically at the center of a circle, and the direction in which the field of view is viewed on the hemisphere placed on the liquid crystal panel 1a. FIG. 8A, which is represented in a plane, shows the brightness viewing angle distribution of the liquid crystal panel 1a when the retardation film 13 having the wavelength dispersion characteristic shown in FIG. 7A is used. Further, FIG. 8B is a luminance viewing angle distribution of the liquid crystal panel 1a when the retardation film 13 having the wavelength dispersion characteristic shown in FIG. 7B is used. Further, FIG. 8C is a luminance viewing angle distribution of the liquid crystal panel 1a when the retardation film 13 having the wavelength dispersion characteristic shown in FIG. 7C is used. Further, here, the time when the screen of the liquid crystal panel 1a is viewed vertically is defined as the 0 ° direction, and the brightness when viewed from the angles of the 30 ° direction and the 60 ° direction is shown. Further, the maximum brightness in the circle representing the luminance viewing angle distribution is shown as Max. The viewing angle distribution of the chromaticity at the time of black display represents light leakage in the diagonal direction of the liquid crystal, and the higher the luminance value is, the worse the viewing angle characteristic of the contrast is.
8 (d) to 8 (f) are diagrams showing the spectral distribution of the points shown by the points T1 to T3 in FIGS. 8 (a) to 8 (c), respectively.

The configuration of the liquid crystal panel 1a at this time was as shown in FIG. 1 (b). The liquid crystal 14 is vertically oriented without applying a voltage. Regarding the polarizing film 12, the polarizing film 12a and the polarizing film 12b were arranged so that their axes were orthogonal to each other. As the retardation films 13a and 13b, those having the characteristics shown in FIG. 7 were used. Then, the retardation films 13a and 13b were arranged between the liquid crystal 14 and the polarizing films 12a and 12b, and their respective axes were arranged so as to be orthogonal to each other. The adjacent polarizing film 12a and the retardation film 13a are arranged so that the absorption axis of the polarizing film 12a and the slow axis of the retardation film 13a are orthogonal to each other. Further, the adjacent polarizing film 12b and the retardation film 13b have the same configuration.

FIG. 7A is a diagram showing a retardation film 13 having a flat wavelength dispersion characteristic. That is, in the retardation film 13 of FIG. 7A, both the in-plane retardation Re and the longitudinal retardation Rth have no wavelength dependence. Therefore, the phase difference is almost constant regardless of the wavelength. In this case, the wavelength dispersion characteristic is "Flat".
Looking at the viewing angle characteristics shown in FIG. 8A and the spectral distribution shown in FIG. 8D, for example, the portion indicated by the point T1 is red or blue. However, when comparing the wavelength of 450 nm and the wavelength of 650 nm, the light intensity at 450 nm is higher. The brightness in the 30 ° direction is 0.005, the brightness in the 60 ° direction is 0.022, and the maximum brightness is 0.023. In this case, when it is displayed in black, it looks bluish when viewed from an angle.

FIG. 7B is a diagram showing the retardation film 13 whose wavelength dispersion characteristic is the reverse wavelength dispersion characteristic. That is, in the retardation film 13 of FIG. 7B, the in-plane retardation Re and the longitudinal retardation Rth increase as the wavelength increases.
Looking at the viewing angle characteristics shown in FIG. 8 (b) and the spectral distribution shown in FIG. 8 (e), for example, the portion indicated by the point T2 is a magenta color in which red and blue are mixed. Here, the luminance in the 30 ° direction is 0.008, the luminance in the 60 ° direction is 0.048, and the maximum luminance is 0.059. That is, the brightness is larger than that in FIG. 7 (a). In this case, for example, when the liquid crystal panel 1a is viewed from an oblique direction when the liquid crystal panel 1a is displayed in black, the magenta color appears to be tinged.

FIG. 7C is a diagram showing the retardation film 13 of the present embodiment. That is, it is a case where the resin 131 having the reverse wavelength dispersion characteristic and the particles 132 having the positive wavelength dispersion characteristic are included. In this case, the wavelength dispersion characteristics as shown in FIG. 7 (c) are shown from the characteristics of the birefringence Δn and the birefringence P shown in FIGS. 4 (c) to 4 (e). That is, in the retardation film 13 of FIG. 7C, the in-plane retardation Re increases and the longitudinal retardation Rth decreases as the wavelength increases.
Looking at the viewing angle characteristics shown in FIG. 8 (c) and the spectral distribution shown in FIG. 8 (f), for example, the portion indicated by the point T3 is uncolored and achromatic. That is, as compared with FIGS. 7 (a) and 7 (b), light leakage is suppressed in the entire wavelength range. Further, here, the luminance in the 30 ° direction is 0.004, the luminance in the 60 ° direction is 0.010, and the maximum luminance is 0.010. That is, the brightness is smaller than that in FIG. 7 (a). In this case, for example, when the liquid crystal panel 1a is viewed from an oblique direction when the liquid crystal panel 1a is displayed in black, there is no uneven coloring.

The in-plane retardation Re changes depending on the thickness of the retardation film 13. Further, when the particles 132 are added, the in-plane phase difference Re is reduced by the amount of the addition. For example, when the resin 131 is 90% and the particles 132 are 10% in terms of mass ratio, the in-plane phase difference Re is 90% when the resin 131 has the same thickness as compared with the case where the resin 131 is 100%. Become. In order to suppress this, it is necessary to increase the thickness of the retardation film 13.

In the retardation film 13 of the present embodiment, the wavelength-dependent characteristics of the retardation can be independently controlled in the in-plane direction of the retardation film 13 and the thickness direction of the retardation film 13. It can also be said that in the retardation film 13, the wavelength-dependent characteristics of the retardation can be controlled independently in the in-plane direction of the retardation film 13 and in the out-of-plane direction of the retardation film 13. .. Further, the retardation film 13 of the present embodiment can independently control the wavelength-dependent characteristics of the retardation in the in-plane direction of the retardation film 13 and the thickness direction of the retardation film 13. You can also. Further, it can be said that the retardation film 13 of the present embodiment can independently control the wavelength-dependent characteristics of the longitudinal retardation Rth and the in-plane retardation Re. So to speak, the retardation film 13 of the present embodiment is a retardation film having a biaxial retardation, and the two retardations can be controlled independently.

Further, in the stretching step, there are a method of stretching the film-like body by uniaxial stretching and a method of stretching by biaxial stretching. In either case, the retardation film 13 having the wavelength dispersion characteristic shown in FIG. 7C can be produced.

In uniaxial stretching, the longitudinal phase difference Rth of the resin 131 alone becomes ½ of the in-plane retardation Re. At this time, by adding the particles 132, the birefringence Δn becomes smaller. Then, the in-plane phase difference Re becomes smaller accordingly. When the thickness of the retardation film 13 is increased in order to maintain the in-plane retardation Re, the longitudinal retardation Rth changes greatly depending on the amount of the particles 132 added.
This results in the biaxial retardation film 13 described above.

On the other hand, in the biaxial stretching, the longitudinal phase difference Rth of the resin 131 alone can be set to other than 1/2 of the in-plane retardation Re. As described above, the in-plane retardation Re of the retardation film 13 changes depending on the thickness. Therefore, the in-plane retardation Re can be controlled by the thickness of the retardation film 13. Therefore, these two methods improve the degree of freedom in designing the vertical retardation Rth of the retardation film 13. That is, in the biaxial stretching, the longitudinal retardation Rth of the retardation film 13 can be controlled not only by the addition amount of the particles 132 but also by the stretching step. For example, the wavelength dispersion characteristic of the retardation film 13 can be adjusted by the amount of particles 132 added, and the birefringence P can be adjusted by biaxial stretching.

In the above-mentioned example, the refractive index ellipsoid of the resin 131 had an ellipsoidal shape. In this case, two of the three refractive indexes, which are the refractive index in the in-plane direction of the retardation film 13 and the refractive index in the thickness direction of the retardation film 13, are the same or substantially the same. However, the present invention is not limited to this, and all three refractive indexes can be made different.

9 (a) to 9 (b) are views showing another example of the refractive index ellipsoid of the resin 131.
Of these, FIG. 9A shows the refractive index ellipsoid of the resin 131 before stretching. That is, the refractive index ellipsoid of the above-mentioned film-like body is shown. Again, the refractive index of the resin 131 in the x direction is n _x1 , the refractive index in the y direction is n _y1 , and the refractive index in the z direction is n _z1 . In this case, as shown in the figure, n _x1 = n _y1 > n _z1 . In such a case, the membranous body may be referred to as a c-plate.

Further, FIG. 9B shows a refractive index ellipsoid of the resin 131 after stretching. That is, the refractive index ellipsoid of the above-mentioned retardation film 13 is shown. In this case, as shown in the figure, n _x1 > n _y1 > n _z1 . In this case, the retardation film 13 is a retardation film having a biaxial retardation with the resin 131 alone. In this case, the three refractive indexes of n _x 1, _{ny 1} , and n _z 1, which are the refractive indexes when stretched, are all different. At this time, Re (λ) / Re (550) and Rth (λ) / Rth (550) are substantially the same regardless of the wavelength λ. When n _x1 > n _y1 > n _z1 , the refractive index ellipsoid may be said to have two axes.

On the other hand, when the above-mentioned particles 132 are added, a retardation film having a biaxial retardation is similarly obtained. However, in the in-plane phase difference Re, the refractive index of the resin 131 is in a state in which a contribution amount corresponding to the addition amount of the particles 132 is added. Further, the value of the thickness direction phase difference Rth also changes when the particles 132 are added, and the wavelength dispersion characteristic also changes depending on the amount thereof. Therefore, when the refractive index of the resin 131 is the reverse wavelength dispersion characteristic and the wavelength dispersion characteristic of the particles 132 is the positive wavelength dispersion characteristic, Re (λ) / Re (550) and Rth (λ) / Rth ( It is different from 550). Therefore, for example, when the wavelength λ is 450 nm and 550 nm, Re (450) / Re (550) <Rth (450) / Rth (550). Further, when comparing the case where the wavelength λ is 650 nm and the case where the wavelength λ is 550 nm, Re (650) / Re (550)> Rth (650) / Rth (550).

Further, when a film containing only the resin 131 is used, the phase difference with respect to the wavelength λ (nm) of light in the in-plane direction of the film containing only the resin 131 is defined as Re_poly (λ). Then, the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the film of the resin 131 only is defined as Rth_poly (λ). At this time, (Re_poly (450) / Re_poly (550)) / (Re (450) / Re (550))> (Rth_poly (450) / Rth_poly (550)) / (Rth (450) / Rth (550)) Is preferable.
Then, in (Re_poly (650) / Re_poly (550)) / (Re (650) / Re (550)) <(Rth_poly (650) / Rth_poly (550)) / (Rth (650) / Rth (550)) Is preferable.

FIG. 10 is a diagram showing a case where the birefringence of the retardation film 13 is calculated when the resin 131 shown in FIG. 9 is used.

The refractive index ellipsoid of the resin 131 is the same as in FIG. 9B. The refractive index of the resin 131 in the x direction is n _x1 , the refractive index in the y direction is n _y1 , and the refractive index in the z direction is n _z1 . At this time, as shown in the equation (11), the relationship of n _x1 > n _y1 > n _z1 is established.

Further, the refractive index ellipsoid of the particle 132 is the same as in FIG. 3 (b). The refractive index ellipsoid of the particles 132 has a disk shape. Then, in the particles 132, the disk-shaped axis C3 direction is oriented in the direction along the thickness direction of the retardation film 13.

Let the refractive index of the particles 132 in the x direction be n _x2 , the refractive index in the y direction be n _y2 , and the refractive index in the z direction be n _z2 . When the particles 132 are oriented in this way in the retardation film 13, the relationship of n _x2 = n _y2 > n _z2 is established as shown in the equation (12). It is also possible to combine the refractive index n _x2 in the x direction and the refractive index n _y2 in the y direction so that n _{x = y2} . In this case, as shown in the equation (12)', the relationship of n _{x = y2} > n _z2 is established. This is the same as in FIG.

Then, such a resin 131 and the particles 132 are mixed in a ratio of a: 1-a. Here, the refractive index in the in-plane direction of the retardation film 13 and the thickness direction of the retardation film 13 at this time is considered.
FIG. 10 (c) is a diagram showing a calculation formula of the refractive index in the in-plane direction and the thickness direction of the retardation film 13. Here, the refractive indexes of the resin 131 and the particles 132 in the x-direction, y-direction, and z-direction when a: 1-a are mixed are calculated.

Here, the refractive index in the x direction in which the resin 131 and the particles 132 are mixed is defined as the refractive index n _xm . At this time, the refractive index n _xm is n _x1 * a + n _x2 * (1-a) as shown by the equation (13). This can also be expressed as n _x1 * a + n _{x = y2} * (1-a) as shown by the equation (13)'.
Further, the refractive index in the y direction in which the resin 131 and the particles 132 are mixed is defined as the refractive index n _ym . At this time, the refractive index n _ym is n _y1 * a + n _y2 * (1-a) as shown by the equation (14). This can also be expressed as n _y1 * a + n _{x = y2} * (1-a) as shown by the equation (14)'.
Further, the refractive index in the z direction in which the resin 131 and the particles 132 are mixed is defined as the refractive index n _zm . At this time, the refractive index n _zm is n _z1 * a + n _z2 * (1-a) as shown by the equation (15).

Then, the birefringence Δn in the xy direction, which is the in-plane direction, is n _xm − n _ym as shown by the equation (16). Then, when this is transformed into an equation, the birefringence Δn becomes (n _x1 - _ny1 ) * a as shown in the equation (17). Equation (17) is the same as equation (7) in FIG.
Further, the birefringence P in the z direction, which is the thickness direction of the retardation film 13, is (n _xm + n _ym ) / 2-n _zm as shown by the equation (18). Then, when this is transformed, the birefringence P becomes ((n _x1 + n _y1 ) / 2-n _z1 ) * a + (n _{x = y2-} n _z2 ) * (1-) as shown in the equation (19). a). Equation (19) is different from equation (9) in FIG.

Looking at the equation (17), the birefringence Δn in the xy direction, which is the in-plane direction, depends on the refractive indexes n _x1 and _ny1 of the resin 131. The birefringence Δn becomes smaller in proportion to the amount of the particles 132 added, but the birefringence Δn does not affect the wavelength dispersion characteristics. This is the same for both uniaxial stretching and biaxial stretching.
On the other hand, when looking at the equation (19), the birefringence P in the z direction, which is the thickness direction of the retardation film 13, depends on both the refractive indexes of the resin 131 and the particles 132. That is, the birefringence P is represented by the refractive indexes n _x1 , n _y1 , n _z1 of the resin 131 and the refractive indexes n _{x = y2} , n _z2 of the particles 132.

Also in this case, the retardation film 13 to which the particles 132 are added can independently control the wavelength dependence of birefringence in the in-plane direction and the film thickness direction. In addition to this, it is possible to adjust the total value of birefringence P by controlling ny1 and nz1 respectively by biaxial stretching. Therefore, it is also possible to adjust the wavelength dependence of the birefringence P by the amount of the particles 132 added, and adjust the value of the birefringence P by biaxial stretching.

It should be noted that n _x1 > _ny1 = n _z1 , which is the relationship of the refractive index of the resin 131 shown in the equation (1) of FIG. 3, is established when the stretching ratio in the stretching step is approximately 100% or more. From this, when the draw ratio is low, as shown in the equation (11) of FIG. 10, the relationship is n _x1 > n _y1 > n _z1 .

In the case of biaxial stretching, n _x1 , _ny1 , and _nz1 of the resin 131 are further changed by stretching. Therefore, the birefringence P and its wavelength dispersion characteristics can be further adjusted.
Further, the effect on biaxial stretching is the same even when the c-plate is uniaxially stretched.
This time, FIG. 9 shows an embodiment in the case where the refractive index ellipsoid of the resin 131 has two axes (n _x1 > n _y1 > n _z1 ). However, it is conceivable that the refractive index ellipsoid of the particles 132 is not a perfect disk shape but has two axes. That is, in the above embodiment, the case of n _x2 = n _y2 > n _z2 is shown, but there is a case where n _x2 > n _y2 > n _z2 . Even in such a case, the wavelength dispersion characteristics in the in-plane direction and the thickness direction due to the addition of the particles 132 can be independently controlled. That is, the same effect as the above-mentioned case can be obtained. In this case, the case where the particle 132 has a rectangular shape is exemplified. FIG. 11A is a conceptual diagram when the particles 132 have a rectangular shape. The refractive index ellipsoid after stretching in the stretching step is shown in FIG. 11 (b). In this refractive index ellipsoid, n _x2 > n _y2 > n _z2 .
When the solution containing the particles 132 having the relationship of n _x2 > n _y2 > n _z2 is applied, a film-like body having a disk-shaped refractive index ellipsoid is formed by flow orientation in the application step and the drying step. In this case, since the in-plane is random and the in-plane refractive index is averaged, n _x2 = n _y2 > n _z2 . When this film-like body is stretched, the particles are further oriented in the stretching direction depending on the stretching conditions, and the relationship of the refractive index of the particles 132 as a whole of the retardation film 13 is n _x2 ≧ n _y2 > n. It becomes _z2 .

Next, the relationship between the liquid crystal 14 and the retardation film 13 will be described.
FIG. 12 is a diagram showing the structure of the liquid crystal display 14.
As shown in the figure, the liquid crystal 14 has a cell structure in which the liquid crystal layer 142 is sandwiched between a pair of glass substrates 141a and 141b. The liquid crystal 14 is also called a liquid crystal cell. In addition, the liquid crystal 14 includes color filters 143B, 143G, and 143R. The color filters 143B, 143G, and 143R are blue (B), green (G), and red (R) color filters, respectively. Further, the liquid crystal display 14 includes a TFT (Thin Film Transistor) 144, a pair of transparent electrodes 145a and 145b, and a pair of alignment films 146a and 146b. Further, the liquid crystal display 14 includes an interlayer insulating film 147 and a gluck matrix 148.

In the liquid crystal 14 having this structure, the thickness (cell gap) of the liquid crystal layer 142 can be changed by changing the thickness of the color filters 143B, 143G, and 143R. As a result, the wavelength dispersion characteristic of the vertical phase difference Rth of the liquid crystal 14 can be changed.

13 (a) to 13 (b) are diagrams showing the wavelength dispersion characteristics of the vertical phase difference Rth_p of the liquid crystal 14 when the cell gap is changed. In FIG. 13A, the horizontal axis represents the wavelength, and the vertical axis represents the vertical phase difference Rth_p, which is the phase difference in the thickness direction of the liquid crystal display 14. Further, in FIG. 13B, the horizontal axis represents the wavelength and the vertical axis represents Rth_p (λ) / Rth_p (550). Here, Rth_p (λ) is a phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the liquid crystal 14.
In FIG. 13A, the vertical phase difference Rth_p is almost constant regardless of the wavelength. Further, in FIG. 13B, Rth_p (λ) / Rth_p (550) is almost constant regardless of the wavelength. In this case, the wavelength dispersion characteristic of the liquid crystal 14 is, so to speak, "Flat". By changing the thickness (cell gap) of the liquid crystal layer 142 or the like, the vertical phase difference Rth_p of the liquid crystal 14 can be set to "Flat". A normal driving liquid crystal material has a positive wavelength dispersion, but the wavelength dispersion can be adjusted by such a method.

14 (a) to 14 (b) are views showing the wavelength dispersion characteristics of the retardation film 13. Of these, FIG. 14A is a diagram showing the wavelength dispersion characteristics of the conventional retardation film 13. Further, FIG. 14B is a diagram showing the wavelength dispersion characteristics of the retardation film 13 suitable for the liquid crystal display 14 shown in FIG.
In FIGS. 14A to 14B, the horizontal axis represents wavelength and the vertical axis represents phase difference. 14 (a) to 14 (b) show the in-plane phase difference Re, which is the phase difference in the in-plane direction of the retardation film 13. Further, FIGS. 14A to 14B show the longitudinal phase difference Rth, which is the phase difference in the thickness direction of the retardation film 13.

The wavelength dispersion characteristics of the conventional retardation film 13 shown in FIG. 14 (a) are similar to those shown in FIG. 7 (b). That is, it is a case where the wavelength dispersion characteristic becomes the reverse wavelength dispersion characteristic. At this time, as the wavelength increases, the in-plane phase difference Re and the vertical phase difference Rth increase.
On the other hand, in the wavelength dispersion characteristic of the retardation film 13 of the present embodiment shown in FIG. 14B, the in-plane retardation Re increases as the wavelength increases, but the longitudinal retardation Rth is not so large. It does not change and is almost "Flat".

FIG. 15A is a display showing the luminance and chromaticity at the time of black display when the conventional retardation film 13 shown in FIG. 14A is used. Further, FIG. 15B is a display showing the luminance and chromaticity at the time of black display when the retardation film 13 of the present embodiment shown in FIG. 14B is used. Here, the vertical view of the screen of the liquid crystal panel 1a is defined as the 0 ° direction, and the luminance and color difference when viewed from the angles of the 30 ° direction and the 60 ° direction are shown. Further, the maximum luminance in the range from 0 ° to 90 ° is shown as Max, and the color difference at that time is shown. In this case, the higher the luminance value, the more light is lost, and the poorer the viewing angle characteristic of the contrast. Also, the larger the color difference, the more tinted it looks.

Further, FIG. 15 (c) is a diagram showing a spectral distribution of chromaticity at the time of black display when the conventional retardation film 13 shown in FIG. 14 (a) is used. Furthermore, FIG. 15 (d) is a diagram showing the spectral distribution of the chromaticity at the time of black display when the retardation film 13 of the present embodiment shown in FIG. 14 (b) is used.

Comparing FIG. 15A and FIG. 15B, in this case, the luminance of the retardation film 13 of the present embodiment is smaller than that of the conventional retardation film 13. That is, the light leakage is small and the viewing angle characteristic of the contrast is good. Further, the color difference is smaller when the retardation film 13 of the present embodiment is used than when the retardation film 13 of the present embodiment is used. In other words, it is difficult to see because of its color.
Further, FIG. 15 (c) and FIG. 15 (d) are compared. In this case, the luminance of the retardation film 13 of the present embodiment is lower than that of the conventional retardation film 13 in the vicinity of the wavelength of 450 nm and the wavelength of the vicinity of the wavelength of 650 nm. That is, the light leakage of blue or red is small. In other words, it is difficult to see because of its color.

It is preferable to match the wavelength dispersion characteristic of the longitudinal retardation Rth of the retardation film 13 with the inclination of the wavelength dispersion characteristic of the longitudinal retardation Rth_p of the liquid crystal 14.
As shown in FIG. 13, the wavelength dispersion characteristic of the vertical phase difference Rth_p of the liquid crystal 14 may be "Flat". At this time, the wavelength dispersion characteristic of the vertical phase difference Rth of the retardation film 13 is determined. As shown in FIG. 14 (b), it is set to "Flat". When the wavelength dispersion characteristic is Flat, it means that the vertical phase difference Rth and the vertical phase difference Rth_p hardly change with respect to the wavelength. It can also be said that there is almost no wavelength dependence of the vertical phase difference Rth and the vertical phase difference Rth_p. Further, the wavelength dispersion characteristic of the phase difference in the thickness direction (longitudinal phase difference Rth_p) of the liquid crystal 14 is considered. Further, consider the wavelength dispersion characteristic of the phase difference (longitudinal phase difference Rth) in the thickness direction of the retardation film 13. At this time, it can be said that both are flat.
Further, as shown in FIG. 6, the wavelength dispersion characteristic of the vertical phase difference Rth_p of the liquid crystal 14 may be a positive wavelength dispersion characteristic. At this time, the wavelength dispersion characteristic of the longitudinal retardation Rth of the retardation film 13 is set to the positive wavelength dispersion characteristic. This considers the wavelength dispersion characteristic of the phase difference in the thickness direction (longitudinal phase difference Rth_p) of the liquid crystal 14. Further, consider the wavelength dispersion characteristic of the phase difference (longitudinal phase difference Rth) in the thickness direction of the retardation film 13. At this time, it can be said that both have positive wavelength dispersion characteristics. Further, the vertical phase difference Rth_p of the liquid crystal 14 may be a monotonically decreasing function with respect to the wavelength (λ). At this time, it can be said that the directionality of the inclination of the wavelength dispersion characteristic of the longitudinal retardation Rth of the retardation film 13 is a monotonically decreasing function with respect to the wavelength (λ).

Let it be the phase difference (in-plane phase difference) Re (λ) in the in-plane direction with respect to the wavelength λ (nm) of the retardation film 13. Further, the phase difference (longitudinal phase difference) with respect to the wavelength λ (nm) of light in the thickness direction of the liquid crystal 14 is defined as Rth_p (λ). At this time, it is preferable that Re (450) / Re (550) <Rth_p (450) / Rth_p (550). Further, it is preferable that Re (650) / Re (550)> Rth_p (650) / Rth_p (550).

Further, the phase difference (longitudinal phase difference) with respect to the wavelength λ (nm) of light in the thickness direction of the retardation film 13 is defined as Rth (λ). At this time, (Re (450) / Re (550)) / (Rth_p (450) / Rth_p (550)) <(Rth_p (450) / Rth_p (550)) / (Rth (450) / Rth (550)) Is preferable. Further, in (Re (650) / Re (550)) / (Rth_p (650) / Rth_p (550))> (Rth_p (650) / Rth_p (550)) / (Rth (650) / Rth (550)) Is preferable.

To do the above, the mixing ratio of the resin 131 and the particles 132 in the retardation film 13 is adjusted. Thereby, the vertical retardation Rth of the retardation film 13 is controlled. In other words, the mixing ratio of the resin 131 and the particles 132 in the retardation film 13 is determined according to the wavelength dispersion characteristic of the vertical retardation Rth_p of the liquid crystal 14.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to these examples as long as the gist of the present invention is not exceeded.

[Preparation of coating solution]
(Example 1)
As the resin 131, a polyester resin containing fluorene manufactured by Osaka Gas Chemical Co., Ltd. was prepared. Further, as the particles 132, smectite manufactured by Kunimine Industries, Ltd. was prepared. Further, methylene chloride was prepared as a solvent. Then, the resin 131 and the particles 132 were added to the solvent at a ratio of 100 parts by mass and 8 parts by mass, respectively. In this case, the target was to have a solid content of 25% by mass.
Then, using a stirrer, stirring was performed for 4 hours at a rotation speed of 500 rpm to 1000 rpm. Further, after stirring, the pressure was reduced by an oil vacuum pump to perform defoaming treatment.
As a result, a coating solution for forming the retardation film 13 was prepared.
Specifically, 7.00 g of the resin 131 and 0.568 g of the particles 132 were used. In addition, 25.81 g of the coating solution could be prepared, and the solid content concentration was 23.6% by mass.

(Comparative Example 1)
A coating solution was prepared in the same manner as in Example 1 except that the particles 132 were not used and the stirring time was 3.5 hours. That is, in Comparative Example 1, the retardation film 13 is produced by using the resin 131 alone.
7.52 g of the resin 131 was used. In addition, 25.48 g of the coating solution could be prepared, and the solid content concentration was 23.9% by mass.

[Applying and drying]
A PET (polyethylene terephthalate) film was placed on the stainless steel plate as a substrate. Then, the prepared coating solution was further applied onto it. As the PET film, a release PET film PET-01-BU manufactured by Shikoku Tohcello Corporation was used. Further, at the time of coating, the coating solution was dropped onto the PET film and coated with a bar coater. At this time, an applicator with an automatic micrometer was used as the coating device. The coating speed was 50 mm / s, and the coating thickness was 700 μm.
Then, after application, as primary drying, it was naturally dried in an oven with a duct for 3 days. Further, as secondary drying, drying was performed at 50 ° C. for 24 hours. As a result, a film-like body before stretching was created.
Both Example 1 and Comparative Example 1 were coated and dried in this way. As a result, in Example 1, the film thickness was 102.8 μm, and in Comparative Example 1, the film thickness was 94.0 μm.

[Stretching]
The film-like body was uniaxially stretched by a stretching device. At this time, the film-like body before stretching had a size of 20 mm × 20 mm. Then, the temperature was set to 70 ° C., which is the glass transition point (Tg) of the resin 131 + 5 ° C., and after achieving this temperature, the waiting time was set to 30 minutes, and then stretching was performed. At this time, the stretching speed was set to 30 mm / s, and the stretching was performed so that the stretching ratio was 250%. The maximum stress in this case was 10.1 N in Example 1 and 5.3 N in Comparative Example 1.
As a result, the film thickness changed from 90 μm to 48 μm in the case of Example 1. Further, in the case of Comparative Example 1, it was changed from 83 μm to 47 μm. The width of the film-like body was 20 mm to 11 mm for both. As described above, a retardation film was prepared for Example 1 and Comparative Example 1.

〔evaluation〕
The wavelength-dependent characteristics of the in-plane phase difference Re and the vertical phase difference Rth were measured. In Example 1, the in-plane phase difference Re and the vertical phase difference Rth are as shown in FIG. 7 (c). That is, the in-plane phase difference Re is an upward-sloping curve, and the vertical phase difference Rth is a downward-sloping curve. On the other hand, in Comparative Example 1, the in-plane phase difference Re was ½ of the vertical phase difference Rth, and both became downward-sloping curves.

16a) to 16b are diagrams for evaluating the wavelength-dependent characteristics of the in-plane phase difference Re and the vertical phase difference Rth.
Here, the ratio between the time when the wavelength of light is 450 nm and the time when the wavelength of light is 550 nm is considered. In this case, the in-plane phase difference Re with respect to the wavelength λ (nm) of light is Re (λ). Further, the vertical phase difference Rth with respect to the wavelength λ (nm) of light is defined as Rth (λ).

At this time, Re (450) / Re (550) <Rth (450) / Rth (550) should be satisfied. As shown in FIG. 16A, when the wavelength of light is smaller than 550 nm, the in-plane phase difference Re is smaller than when the wavelength of light is 550 nm. Therefore, Re (λ) / Re (550) is smaller than 1. On the other hand, when the wavelength of light is smaller than 550 nm, the vertical phase difference Rth is larger when the wavelength of light is 550 nm. Therefore, Rth (λ) / Rth (550) is larger than 1. Therefore, when the wavelength of light is smaller than 550 nm, and when the representative value of the wavelength is 450 nm, Re (450) / Re (550) <Rth (450) / Rth (550).

It can also be said that Re (650) / Re (550)> Rth (650) / Rth (550). That is, as shown in FIG. 16A, when the wavelength of light is larger than 550 nm, the in-plane phase difference Re is larger when the wavelength of light is 550 nm. Therefore, Re (λ) / Re (550) is larger than 1. On the other hand, when the wavelength of light is larger than 550 nm, the vertical phase difference Rth is smaller than when the wavelength of light is 550 nm. Therefore, Rth (λ) / Rth (550) is smaller than 1. Therefore, when the wavelength of light is larger than 550 nm, and when the representative value of the wavelength is 650 nm, Re (650) / Re (550)> Rth (650) / Rth (550).

In the first embodiment, this relationship is satisfied. However, in Comparative Example 1, as shown in FIG. 16B, Re (450) / Re (550)> Rth (450) / Rth (550). Therefore, the direction of the inequality sign is opposite to that of the first embodiment. Further, in Comparative Example 1, Re (650) / Re (550) <Rth (650) / Rth (550). Therefore, the direction of the inequality sign is opposite to that of the first embodiment. By considering such an inequality, it is possible to evaluate whether or not the in-plane phase difference Re and the vertical phase difference Rth are in the state shown in FIG. 7 (c).

(Example 2)
A 10% dichloroethane solution of Smectite SPN manufactured by Kunimine Industries, Ltd. was prepared in the same manner as in Example 1. Further, a resin prepared as a mixture of a polymethylmethacrate (PMMA) resin and a resin MS600 manufactured by Toyo Styrene Co., Ltd. at a weight ratio of 60:40 was prepared. Then, it was added and dissolved in the above solution so that the weight of smectite SPN was 64: 100 with respect to the weight of the resin. As a result, a coating solution for preparing a retardation film was prepared.
Using the obtained coating solution, coating, drying, and stretching were performed in the same manner as in Example 1. At this time, the stretching ratio was set to 200%. As a result, a retardation film having a film thickness of 64 μm could be produced.

(Comparative Example 2)
A coating solution was prepared in the same manner as in Example 1 except that the particles 132 were not used. That is, in Comparative Example 1, the resin film is formed by the resin 131 alone.
Then, a resin film was prepared based on the coating solutions prepared according to the compositions shown in Example 2 and Comparative Example 2.

17 (a) to 17 (b) are diagrams showing the wavelength-dependent characteristics of the in-plane phase difference Re and the longitudinal phase difference Rth.
Here, FIG. 17A illustrates the wavelength-dependent characteristics of the in-plane phase difference Re of Example 2 and Comparative Example 2. Further, FIG. 17B illustrates the wavelength-dependent characteristics of the longitudinal phase difference Rth of Example 2 and Comparative Example 2.

The styrene methacrylic acid copolymer used as the resin 131 in Example 2 and Comparative Example 2 has a positive wavelength dispersion characteristic. The particles 132 also have a positive wavelength dispersion characteristic. Therefore, in this case, the effect of the particles 132 is smaller than that in the case where the resin 131 has the reverse wavelength dispersion characteristic. That is, the effect of changing the wavelength-dependent characteristics of the in-plane phase difference Re and the vertical phase difference Rth by the particles 132 is small.

Further, the resin film of Example 2 is difficult to use as the retardation film 13 due to its characteristics. However, even in this case, the effect that the wavelength-dependent characteristics of the phase difference can be independently controlled in the in-plane direction of the film and the thickness direction of the film by adding the particles 132 still occurs. Further, from this viewpoint, both the resin 131 and the particles 132 may have reverse wavelength dispersion characteristics. That is, it may be the case shown in FIG. 7 (b). Further, the resin 131 may have a positive wavelength dispersion characteristic, and the particles 132 may have a reverse wavelength dispersion characteristic. Such a resin film is expected to be used as an optical film.

In addition, the following Examples 3 to 6 and Comparative Examples 3 to 4 were performed. The production conditions and evaluation results of Examples 3 to 6 and Comparative Examples 3 to 4 are summarized in Table 1 below.

[Preparation of coating solution]
(Examples 3 to 6)
Cellulose acetate (product number L-20) manufactured by Daicel Corporation was prepared as the resin 131. Further, as the particles 132, smectite manufactured by Kunimine Industries, Ltd. was prepared. Further, methylene chloride was prepared as a solvent. In addition, methanol was prepared as an auxiliary solvent.
Then, methylene chloride as a solvent and methanol as an auxiliary solvent were mixed and used as a mixed solvent. The ratio at this time was 20 parts by mass of methanol as an auxiliary solvent with respect to 100 parts by mass of methylene chloride as a solvent.
Then, the resin 131 and the particles 132 were added to the mixed solvent at a ratio of 100 parts by mass and 32 parts by mass, respectively, to prepare a coating solution. In this case, the target was to have a solid content of 14%.
Actually, 7.00 g of the resin 131 and 2.24 g of the particles 132 were used. As the mixed solvent, a mixture of 47.32 g of methylene chloride and 9.45 g of methanol was used. As a result, 66.01 g of the coating solution could be prepared, and the solid content concentration was 14.0% by mass.

More specifically, the particles 132 were put into the above-mentioned mixed solvent, allowed to stand for 4 to 5 days, and then stirred with a stirrer for 6 hours to obtain a uniform solution. Further, the resin 131 having a solid content of 14% was added to the obtained solution. Then, using a stirrer, stirring was performed for 24 hours at a rotation speed of 500 rpm to 1000 rpm. It was allowed to stand for another day. As a result, a coating solution for forming the retardation film 13 was prepared.

(Comparative Examples 3 to 4)
A coating solution was prepared in the same manner as in Examples 3 to 6 except that the particles 132 were not used. That is, Comparative Examples 3 to 4 are cases where the retardation film 13 is manufactured from the resin 131 alone. 7.00 g of the resin 131 was used. As the solvent, 36.00 g of methylene chloride and 7.00 g of methanol were used. As a result, the coating solution was 50.0 g, and the solid content concentration was 14.0% by mass.

[Apply / Dry]
A PET film was placed as a substrate on a stainless steel plate. Further, the prepared coating solution was applied onto it. At the time of coating, the coating solution was dropped onto the PET film and coated with a bar coater. At this time, as the coating device, the automatic coating device PI-1210 manufactured by Tester Sangyo Co., Ltd. was used. In addition, an applicator with a micrometer was used as a bar coater. The coating speed was 50 mm / s, and the coating thickness was 700 μm. After coating, the mixture was placed in an oven with a duct and dried at 40 ° C. for 30 minutes as primary drying. Further, as secondary drying, drying was performed at 100 ° C. for 30 minutes. As a result, a film-like body before stretching was produced.

[Stretching]
The produced film-like body was uniaxially stretched by a stretching device. At this time, the film-like body had a size of 20 mm × 20 mm. Then, in Example 3, the temperature was set to 165 ° C., and after the temperature was achieved, the waiting time was set to 30 minutes, and then stretching was performed. At this time, the stretching speed was set to 0.5 mm / s, and in Example 3, stretching was performed so that the stretching rate was 60%. Further, in Example 4, stretching was performed so that the stretching ratio was 15%. Further, in Example 5, stretching was performed so that the stretching ratio was 30%. Further, in Example 6, the temperature was set to 155 ° C., and the stretching was performed so that the stretching ratio was 15%.
Further, in Comparative Example 3, the draw ratio was set to 60%. Further, in Comparative Example 4, the draw ratio was set to 15%. As described above, the retardation films 13 of Examples 3 to 6 and Comparative Examples 3 to 4 were produced.

[evaluation]
The values of the in-plane phase difference Re and the vertical phase difference Rth and the wavelength-dependent characteristics of each value were measured. Table 1 shows the film thickness of each of the retardation films 13, the values of the in-plane retardation Re and the longitudinal retardation Rth at a wavelength of 550 nm. In Examples 3 to 6, the retardation film 13 is in the range of Re> 30 nm and Rth <300 nm, and is effective as an optical compensation film for a VA type liquid crystal panel. Further, the vertical phase difference Rth is slightly larger than that of Comparative Examples 3 and 4, which is due to the addition of smectite.
FIG. 18 is a diagram in which the wavelength-dependent characteristics of the in-plane phase difference Re and the vertical phase difference Rth are evaluated for Example 3.
Further, FIG. 19 is a diagram in which the same evaluation was performed for Example 4. Further, FIG. 20 is a diagram in which the same evaluation was performed for Example 5. Furthermore, FIG. 21 is a diagram in which the same evaluation was performed for Example 6. FIG. 22 is a diagram in which Comparative Example 3 is evaluated in the same manner. FIG. 23 is a diagram in which Comparative Example 4 is evaluated in the same manner.
In Examples 3 to 6, the in-plane phase difference Re became a curve rising to the right, and the vertical phase difference Rth became a curve almost horizontal.
On the other hand, in Comparative Examples 3 to 4, the wavelength dependences of the in-plane phase difference Re and the vertical phase difference Rth were almost equal, and both of them had an upward-sloping curve.

Then, for each of the in-plane phase difference Re and the vertical phase difference Rth, the ratio between the time when the wavelength of light is 450 nm and the time when the wavelength is 550 nm is considered. In this case, the in-plane phase difference Re at the wavelength λ (nm) of light is Re (λ). Further, the vertical phase difference Rth with respect to the wavelength λ (nm) of light is defined as Rth (λ).

At this time, it is evaluated that Re (450) / Re (550) <Rth (450) / Rth (550) should be satisfied.
As illustrated in FIGS. 18 to 21, in Examples 3 to 6, when the wavelength of light is smaller than 550 nm, the in-plane phase difference Re is smaller than when the wavelength of light is 550 nm. For example, at 450 nm, when the value at 550 nm is 1, it becomes 0.95. On the other hand, the vertical phase difference Rth has almost no change. For example, assuming that the vertical phase difference Rth at 550 nm is 1, it is almost 1 at 450 nm.
Here, the representative value of the wavelength when the wavelength of light is smaller than 550 nm is 450 nm. Then, in Examples 3 to 6, Re (450) / Re (550) <Rth (450) / Rth (550).

Further, in Examples 3 to 6, it can be said that Re (650) / Re (550)> Rth (650) / Rth (550). That is, as shown in FIGS. 18 to 21, when the wavelength of light is larger than 550 nm, the in-plane phase difference Re is larger when the wavelength of light is 550 nm. Therefore, Re (λ) / Re (550) is larger than 1. For example, the in-plane phase difference Re at 650 nm is 1.025, where 1 is at 550 nm. On the other hand, the vertical phase difference Rth hardly changes with wavelength. For example, assuming that the vertical phase difference Rth at 550 nm is 1, the vertical phase difference is approximately 1 at 650 nm.
Here, the representative value of the wavelength when the wavelength of light is larger than 550 nm is 650 nm. Then, in Examples 3 to 6, Re (650) / Re (550)> Rth (650) / Rth (550).

As described above, Examples 3 to 6 satisfy such a relationship. However, in Comparative Examples 3 to 4, as shown in FIGS. 22 to 23, there is almost no difference in wavelength dependence between the in-plane phase difference Re and the longitudinal phase difference Rth.
That is, assuming that the in-plane phase difference Re at 550 nm is 1, the in-plane phase difference Re at 450 nm is 0.95. On the other hand, even in the vertical phase difference Rth, when the vertical phase difference Rth at 550 nm is 1, the value at 450 nm is 0.95. Assuming that the in-plane phase difference Re at 550 nm is 1, the in-plane phase difference Re at 650 nm is 1.025. On the other hand, even in the vertical phase difference Rth, assuming that the vertical phase difference Rth at 550 nm is 1, the value at 650 nm is 1.025.

As described above, in Examples 3 to 6, it is possible to realize different wavelength dependences in the in-plane phase difference Re and the vertical phase difference Rth. On the other hand, in Comparative Examples 3 to 4, the wavelength dependence of the in-plane phase difference Re and the vertical phase difference Rth are almost the same.
Therefore, in Examples 3 to 6, when combined with the liquid crystal display 14 having the characteristics shown in FIG. 13, the wavelength dispersion characteristics such as the retardation film 13 in FIG. 14 (b), which is optimal for this, are subjected to the phase difference. It can be realized by adjusting the value. Then, it becomes possible to obtain a viewing angle characteristic that suppresses oblique light leakage as shown in FIG. 15 (b).

On the other hand, Comparative Examples 3 to 4 have characteristics similar to those of the retardation film of FIG. 14 (a), and therefore, when combined with the liquid crystal 14 having the wavelength dispersion characteristics as shown in FIG. 13, FIG. 15 (a). The viewing angle characteristics are as follows. Then, blue and red light escape occurs in the diagonal direction.

Further, Examples 3 to 6 are compared with Comparative Examples 3 to 4 in which the particles 132 are not used and only the resin 131 is used. When a film containing only the resin 131 is used, the phase difference with respect to the wavelength λ (nm) of light in the in-plane direction of the film containing only the resin 131 is Re_poly (λ). Further, the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the film of the resin 131 only is defined as Rth_poly (λ). At this time, (Re_poly (450) / Re_poly (550)) / (Re (450) / Re (550))> (Rth_poly (450) / Rth_poly (550)) / (Rth (450) / Rth (550)) You can see that it is. As described above, depending on the presence or absence of the addition of the particles 132, the wavelength dependence of the longitudinal phase difference Rth becomes flat in Examples 3 to 6 of the addition of the particles 132 as compared with the difference in the wavelength dependence of the in-plane phase difference Re. .. Then, it can be seen that the relationship is as shown in the above equation.

In addition, (Re_poly (650) / Re_poly (550)) / (Re (650) / Re (550)) <(Rth_poly (650) / Rth_poly (550)) / (Rth (650) / Rth (550)) You can see that it is. Even on the long wavelength side, the wavelength dependence of the longitudinal phase difference Rth is larger than the wavelength dependence difference of the in-plane phase difference Re depending on the addition or absence of the particles 132 in Examples 3 to 6 of the addition of the particles 132. Become flat. Then, it can be seen that the relationship is as shown in the above equation.

In addition, the following Examples 7 and 8 and Comparative Example 5 were performed. The manufacturing conditions and evaluation results of Examples 7 and 8 and Comparative Example 5 are summarized in Table 2 below.

[Preparation of coating solution]
(Examples 7 and 8)
As the resin 131, a 50:50 mixture of cellulose acetate (product number L-20) manufactured by Daicel Corporation and cellulose acetate (product number TL-105) was prepared. Further, smectite manufactured by Kunimine Industries, Ltd. was prepared as the particles 132. Further, methylene chloride was prepared as a solvent. In addition, methanol was prepared as an auxiliary solvent. Then, methylene chloride as a solvent and methanol as an auxiliary solvent were mixed and used as a mixed solvent. The ratio at this time was 100 parts by mass of methylene chloride as a solvent and 4 parts by mass of methanol as an auxiliary solvent.
Then, the resin 131 and the particles 132 were added to the mixed solvent at a ratio of 100 parts by mass and 32 parts by mass, respectively, to prepare a coating solution. In this case, the target was to have a solid content of 14%.
Actually, 3.18 g of the resin 131 and 1.02 g of the particles 132 were used. As the mixed solvent, a mixture of 25.38 g of methylene chloride and 1.04 g of methanol was used. As a result, 30.62 g of the coating solution could be prepared, and the solid content concentration was 14% by mass.

More specifically, the particles 132 were put into the above-mentioned mixed solvent, allowed to stand for 4 to 5 days, and then stirred with a stirrer for 6 hours to obtain a uniform solution. Further, the resin 131 having a solid content of 14% was added to the obtained solution. Then, using a stirrer, stirring was performed for 24 hours at a rotation speed of 500 rpm to 1000 rpm. It was allowed to stand for another day. As a result, a coating solution for forming the retardation film 13 was prepared.

(Comparative Example 5)
A coating solution was prepared in the same manner as in Examples 7 and 8 except that the particles 132 were not used. That is, Comparative Example 5 is a case where the retardation film 13 is manufactured from the resin 131 alone. 4.20 g of the resin 131 was used. As the solvent, 21.6 g of methylene chloride and 4.2 g of methanol were used. As a result, the coating solution was 30.0 g, and the solid content concentration was 14% by mass.

[Apply / Dry]
A PET film was placed as a substrate on a stainless steel plate. Further, the prepared coating solution was applied onto it. At the time of coating, the coating solution was dropped onto the PET film and coated with a bar coater. At this time, as the coating device, the automatic coating device PI-1210 manufactured by Tester Sangyo Co., Ltd. was used. In addition, an applicator with a micrometer was used as a bar coater. The coating speed was 50 mm / s, and the coating thickness was 900 μm. After coating, the mixture was placed in an oven with a duct and dried at 40 ° C. for 30 minutes as primary drying. Further, as secondary drying, drying was performed at 100 ° C. for 30 minutes. As a result, a film-like body before stretching was produced.

[Stretching]
The produced film-like body was uniaxially stretched by a stretching device. At this time, the film-like body had a size of 20 mm × 20 mm. Then, the temperature was set to 165 ° C., and after the temperature was achieved, the waiting time was set to 30 minutes, and then stretching was performed. At this time, the stretching speed was set to 0.5 mm / s, and in Example 7, stretching was performed so that the stretching rate was 15%. Further, in Example 8, the draw ratio was set to 60%. The maximum stress in this case was 31.5N in Example 7 and 49.6N in Example 8. As a result, the film thickness changed from 87 μm to 83 μm in the case of Example 7. Further, in Example 8, the film thickness was changed from 91 μm to 77 μm.
In Comparative Example 5, stretching was performed so that the stretching ratio was 15%. The maximum stress in this case was 48.2N. As a result, the film thickness changed from 87 μm to 83 μm in the case of Comparative Example 5.
As described above, the retardation film 13 of Examples 7 and 8 and Comparative Example 5 was produced.

[evaluation]
The values of the in-plane phase difference Re and the vertical phase difference Rth and the wavelength-dependent characteristics of each value were measured. Table 2 shows the film thickness of each of the retardation films 13, the values of the in-plane retardation Re and the longitudinal retardation Rth at a wavelength of 550 nm. In Examples 7 and 8, the values of Re> 30 nm and Rth <300 nm are both, which is an effective retardation film 13 as an optical compensation film for a VA type liquid crystal panel.

When Examples 7 and 8 are compared with Comparative Example 5, (Re_poly (450) / Re_poly (550)) / (Re (450) / Re (550))> (Rth_poly (450) / Rth_poly (550)) It can be seen that / (Rth (450) / Rth (550)). As described above, depending on the presence or absence of the addition of the particles 132, the wavelength dependence of Rth becomes flat in Examples 7 and 8 of the addition of the particles 132 as compared with the difference in the wavelength dependence of Re. Then, it can be seen that the relationship is as shown in the above equation.

In addition, (Re_poly (650) / Re_poly (550)) / (Re (650) / Re (550)) <(Rth_poly (650) / Rth_poly (550)) / (Rth (650) / Rth (550)) You can see that it is. Even on the long wavelength side, the wavelength dependence of Rth becomes flat in Examples 7 and 8 of the addition of the particles 132, as compared with the difference in the wavelength dependence of Re, depending on the presence or absence of the addition of the particles 132. Then, it can be seen that the relationship is as shown in the above equation.

Similar to Examples 3 to 6, it is possible to realize different wavelength dependences in the in-plane phase difference Re and the vertical phase difference Rth in Examples 7 and 8. On the other hand, in Comparative Example 5, the wavelength dependence of the in-plane phase difference Re and the longitudinal phase difference Rth are almost the same as in Comparative Examples 3 and 4.

Therefore, in Examples 7 and 8, when combined with the liquid crystal display 14 having the characteristics shown in FIG. 13, the wavelength dispersion characteristics such as the retardation film 13 in FIG. 14 (b), which is optimal for this, are subjected to the phase difference. It can be realized by adjusting the value. Then, it becomes possible to obtain a viewing angle characteristic that suppresses oblique light leakage as shown in FIG. 15 (b).

On the other hand, Comparative Example 5 has characteristics similar to those of the retardation film of FIG. 14 (a), and therefore, when combined with the liquid crystal 14 having the wavelength dispersion characteristics as shown in FIG. 13, it is as shown in FIG. 15 (a). It has a good viewing angle characteristic. Then, blue and red light escape occurs in the diagonal direction.

FIG. 24 is a diagram in which the wavelength-dependent characteristics of the in-plane phase difference Re and the vertical phase difference Rth are evaluated for Example 7. Further, FIG. 25 is a diagram in which the wavelength-dependent characteristics of the in-plane phase difference Re and the vertical phase difference Rth are evaluated for Example 8. Further, FIG. 26 is a diagram in which the wavelength-dependent characteristics of the in-plane phase difference Re and the longitudinal phase difference Rth are evaluated for the comparative example.
In Examples 7 and 8, the in-plane phase difference Re became a curve rising to the right, and the vertical phase difference Rth became a curve almost horizontal.
On the other hand, in Comparative Example 5, the wavelength dependences of the in-plane phase difference Re and the vertical phase difference Rth were almost equal, and both of them had an upward-sloping curve.

Also in Examples 7 and 8, Re (450) / Re (550) <Rth (450) / Rth (550). Further, also in Examples 7 and 8, Re (650) / Re (550)> Rth (650) / Rth (550).

1 ... Display device, 1a ... Liquid crystal panel, 11 ... Backlight, 12, 12a, 12b ... Polarizing film, 13, 13a, 13b ... Phase difference film, 14 ... Liquid crystal, 131 ... Resin, 132 ... Particles, Re ... In-plane Phase difference, Rth ... Vertical phase difference

Claims (38)

In a resin film having at least a resin and particles,
The resin and the particles are oriented in the resin film, so that the wavelength dispersion characteristic of birefringence in the in-plane direction of the resin film and the wavelength dispersion characteristic of birefringence in the thickness direction of the resin film are different. A resin film characterized by. The resin and the particles have anisotropy of the refractive index, and are oriented in the resin film so that the direction of the anisotropy of the resin and the direction of the anisotropy of the particles are different. The resin film according to claim 1. The resin film according to claim 2, wherein the refractive index ellipsoid of the resin has an ellipsoidal shape, and the refractive index ellipsoid of the particles has a disk shape. In the resin, the long axis direction of the elliptical sphere is oriented along the in-plane direction of the resin film, and in the particles, the axial direction of the disk shape is along the thickness direction of the resin film. The resin film according to claim 3, wherein the resin film is oriented in the direction of 1. The refractive index of the resin in the in-plane direction of the resin film and the refractive index in the thickness direction of the resin film are all different, and the refractive index ellipsoid of the particles has a disk shape. The resin film according to any one of claims 2 to 4. The resin according to claim 1, wherein the resin and the particles differ from each other in at least one of the refractive index in two directions in the in-plane direction of the resin film and the refractive index in the thickness direction of the resin film. film. When the refractive index of the resin in the in-plane direction of the resin film is n _x1 and n _y1 , and the refractive index of the resin film in the thickness direction is _nz1 , n _x1 > n _y1 ≧ n. The resin film according to claim 6, wherein the resin film is _z1 . When the refractive index of the particles in the in-plane direction of the resin film is n _x2 and n _y2 and the refractive index of the resin film in the thickness direction is _nz2 , n _x2 ≧ n _y2 > n. The resin film according to claim 6, wherein the resin film is _z2 . The resin film according to any one of claims 1 to 8, wherein the particles contain smectite. The resin film according to any one of claims 1 to 9, wherein the resin contains at least one of a cycloolefin polymer, triacetyl cellulose, diacetyl cellulose, polycarbonate and polyester. When the phase difference with respect to the wavelength λ (nm) of light in the in-plane direction of the resin film is Re (λ), and the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the resin film is Rth (λ). In addition, when Re (450) / Re (550) <Rth (450) / Rth (550) and only the resin is used as a film, the wavelength λ of light in the in-plane direction of the film of the resin alone ( When the phase difference with respect to nm) is Re_poly (λ) and the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the film of the resin only is Rth_poly (λ), (Re_poly (450) / Re_poly (550). )) / (Re (450) / Re (550))> (Rth_poly (450) / Rth_poly (550)) / (Rth (450) / Rth (550)). The resin film according to any one of the above items. When the phase difference with respect to the wavelength λ (nm) of light in the in-plane direction of the resin film is Re (λ), and the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the resin film is Rth (λ). In addition, when Re (650) / Re (550)> Rth (650) / Rth (550) and only the resin is used as a film, the wavelength λ of light in the in-plane direction of the film of the resin alone ( When the phase difference with respect to nm) is Re_poly (λ) and the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the film of the resin only is Rth_poly (λ), (Re_poly (650) / Re_poly (550). )) / (Re (650) / Re (550)) <(Rth_poly (650) / Rth_poly (550)) / (Rth (650) / Rth (550)). The resin film according to any one of the above items. The resin film according to any one of claims 1 to 12, wherein the resin has a birefringence having a reverse wavelength dispersion characteristic, and the particles have a birefringence having a positive wavelength dispersion characteristic. The wavelength dispersion characteristic of birefringence in the in-plane direction of the resin film is mainly determined by the wavelength dispersion characteristic of the resin.
The resin film according to any one of claims 1 to 13, wherein the wavelength dispersion characteristic of birefringence in the thickness direction of the resin film is determined by the mixing ratio of the resin and the particles. In a resin film having at least a resin and particles,
The refractive index ellipsoid of the resin has an ellipsoidal shape, the refractive index ellipsoid of the particles has a disk shape, and the refractive index ellipsoid of the resin and the refractive index ellipsoid of the particles are the resin film. A resin film characterized in that the longitudinal direction thereof is oriented along the in-plane direction of the resin film. The preparatory step to prepare the coating solution for creating the resin film,
The coating process of applying the coating solution to form a film-like body, and
The stretching step of stretching the film-like body to obtain the resin film, and
Have,
The coating solution is oriented in the resin film when stretched in the stretching step, so that the wavelength dispersion characteristic of birefringence in the in-plane direction of the resin film and the wavelength of birefringence in the thickness direction of the resin film are used. A resin and particles having different dispersion characteristics, and a solvent for dispersing the resin and the particles,
How to make a resin film containing. The preparatory process for preparing the coating solution for creating the resin film,
The coating process of applying the coating solution to form a film-like body, and
The stretching step of stretching the film-like body to obtain the resin film, and
Have,
The coating solution is oriented in the resin film when stretched in the stretching step so that the refractive index ellipsoid has an ellipsoidal shape and the refractive index ellipsoid has a disk shape. Particles, the resin and the solvent that disperses the particles,
How to make a resin film containing. The preparatory process for preparing the coating solution for creating the resin film,
The coating process of applying the coating solution to form a film-like body, and
The stretching step of stretching the film-like body to obtain the resin film, and
Have,
By orienting the coating solution in the resin film when it is stretched in the stretching step, the refractive index in the in-plane direction of the resin film and the refractive index in the thickness direction of the resin film are all set. A resin that becomes different, particles that form a disk-shaped refractive index ellipse, and a resin that disperses the resin and the particles, and a solvent that disperses the particles.
How to make a resin film containing. The preparation of the resin film according to any one of claims 16 to 18, wherein the stretching step is performed by uniaxial stretching so that the resin film has a biaxial phase difference. Method. The preparation of the resin film according to any one of claims 16 to 18, wherein the stretching step causes the resin film to have a biaxial phase difference by performing biaxial stretching. Method. The refractive index of the particles in the film-like body before the stretching step in the in-plane direction of the film-like body is n _x2 and n _y2 , and the refractive index of the film-like body in the thickness direction is n. The method for producing a resin film according to any one of claims 16 to 20, wherein n _x2 = n _y2 > n _z2 when _z2 is set. The resin film according to any one of claims 16 to 21, wherein the wavelength dispersion characteristic of birefringence in the thickness direction of the resin film is adjusted by the mixing ratio of the resin and the particles. How to make. A liquid crystal display that controls the state of light transmission,
A polarizing means that polarizes light, and
A retardation film having at least a resin and particles,
Equipped with
The retardation film is
By orienting the resin and the particles in the retardation film, the wavelength dispersion characteristic of birefringence in the in-plane direction of the retardation film and the wavelength dispersion characteristic of birefringence in the thickness direction of the retardation film can be obtained. Different LCD panels. The liquid crystal panel according to claim 23, wherein the liquid crystals are arranged vertically without applying a voltage. The liquid crystal panel according to claim 24, wherein the mixing ratio of the resin and the particles in the retardation film is determined according to the wavelength dispersion characteristic of the phase difference in the thickness direction of the liquid crystal. 24 or 25 according to claim 24 or 25, wherein the wavelength dispersion characteristic of the phase difference in the thickness direction of the liquid crystal display and the wavelength dispersion characteristic of the phase difference in the thickness direction of the retardation film are both positive wavelength dispersion characteristics. LCD panel. The liquid crystal panel according to claim 24 or 25, wherein the wavelength dispersion characteristic of the phase difference in the thickness direction of the liquid crystal and the wavelength dispersion characteristic of the phase difference in the thickness direction of the retardation film are both flat. .. When the phase difference with respect to the wavelength λ (nm) of light in the in-plane direction of the retardation film is Re (λ), and the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the liquid crystal is Rth_p (λ). The liquid crystal panel according to any one of claims 24 to 27, wherein Re (450) / Re (550) <Rth_p (450) / Rth_p (550). When the phase difference with respect to the wavelength λ (nm) of light in the in-plane direction of the retardation film is Re (λ), and the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the liquid crystal is Rth_p (λ). The liquid crystal panel according to any one of claims 24 to 28, wherein Re (650) / Re (550)> Rth_p (650) / Rth_p (550). When the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the retardation film is Rth (λ), and the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the liquid crystal is Rth_p (λ). To (Re (450) / Re (550)) / (Rth_p (450) / Rth_p (550)) <(Rth_p (450) / Rth_p (550)) / (Rth (450) / Rth (550)) The liquid crystal panel according to any one of claims 24 to 29. When the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the retardation film is Rth (λ), and the phase difference with respect to the wavelength λ (nm) of light in the thickness direction of the liquid crystal is Rth_p (λ). In addition, (Re (650) / Re (550)) / (Rth_p (650) / Rth_p (550))> (Rth_p (650) / Rth_p (550)) / (Rth (650) / Rth (550)) The liquid crystal panel according to any one of claims 24 to 30, wherein the liquid crystal panel is characterized by the above. With the board
The resin film provided on the substrate and according to any one of claims 1 to 14.
An optical member comprising. A polarizing means that polarizes light, and
The resin film provided on the polarizing means and according to any one of claims 1 to 14.
A polarizing member comprising. The resin, the particles, the resin, and the solvent that disperses the particles,
Including
The resin and the particles are oriented in the resin film when the resin and the film-like body containing the particles are stretched to form a resin film, thereby causing birefringence wavelength dispersion characteristics in the in-plane direction of the resin film. And a coating solution for forming a resin film in which the wavelength dispersion characteristics of birefringence in the thickness direction of the resin film are different. The resin, the particles, the resin, and the solvent that disperses the particles,
Including
The resin and the particles are oriented in the resin film when the resin and the film-like body containing the particles are stretched to form a resin film, so that the refractive index ellipsoid of the resin forms an ellipsoidal shape. A coating solution for forming a resin film that causes the ellipsoidal refractive index of the particles to form a disk shape. The resin, the particles, the resin, and the solvent that disperses the particles,
Including
The resin and the particles are oriented in the resin film when the resin and the film-like body containing the particles are stretched to form a resin film, whereby the resin is oriented in two directions in the in-plane direction of the resin film. A coating solution for forming a resin film, in which the refractive index of the resin film and the refractive index in the thickness direction of the resin film are all different, and the refractive index ellipses of the particles form a disk shape. The coating solution for forming a resin film according to any one of claims 34 to 36, wherein the particles contain smectite. The coating solution for forming a resin film according to any one of claims 34 to 37, wherein the resin contains at least one of a cycloolefin polymer, triacetyl cellulose, diacetyl cellulose, polycarbonate and polyester.

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