JP4595586B2 - REFLECTIVE POLARIZER AND METHOD FOR MANUFACTURING THE SAME, APPARATUS FOR PRODUCING REFLECTIVE POLARIZER, AND LIQUID CRYSTAL DISPLAY - Google Patents

Description

  The present invention relates to a reflective polarizer that controls the vibration direction of light, a method for manufacturing the same, a manufacturing apparatus for the reflective polarizer, and a liquid crystal display device.

  In a liquid crystal display (LCD), a polarizer is an indispensable important member. Conventionally, as this polarizer, one that exhibits absorption dichroism in which one polarization component of light is absorbed and the other polarization component is transmitted is generally used. In this type of polarizer, 50% of light is absorbed in principle to obtain linearly polarized light, and as a result, half of the input light is lost as heat energy. The light absorption by the polarizer is a main factor of the poor light utilization efficiency of the liquid crystal display device.

  In view of this, a reflective polarizer has been proposed for the purpose of increasing the light utilization efficiency. This reflective polarizer is provided between the liquid crystal panel and the backlight, passes only one of the orthogonally polarized components of the light emitted from the backlight, reflects the other, and re-enters the backlight. Then, the light is incident again on the reflective polarizer by diffuse reflection. By repeating this reflection, the light that is originally absorbed can be recycled to improve the luminance of the liquid crystal display device.

  In recent years, as the reflective polarizer, those utilizing the birefringence of a stretched resin film have been widely used (see, for example, Patent Document 1). This reflective polarizer is formed by alternately laminating optically anisotropic films and optically isotropic films. The optically anisotropic film can be obtained by drawing a crystalline naphthalenedicarboxylic acid ester such as polyethylene naphthalate (PEN) into a film by a melt extrusion method and then stretching it. The optically isotropic form can be obtained by drawing a naphthalenedicarboxylic acid and a copolyester of terephthalic acid or isotalic acid (coPEN) into a film by melt extrusion and then stretching.

Japanese Patent No. 3448626

  However, the above-described reflective polarizer requires 800 or more layers in order to cover the visible light band. For this reason, it has been difficult to reduce the thickness and size of the reflective polarizer and improve the productivity.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a reflective polarizer capable of realizing a reduction in thickness, size and productivity, a method for manufacturing the same, a manufacturing apparatus for the reflective polarizer, and a liquid crystal display device including the reflective polarizer. Is to provide.

In order to solve the above-mentioned problem, the first invention
A transparent support, and a first optical anisotropic film and a second optical anisotropic film laminated alternately on the transparent support,
The first and second optically anisotropic layer, for to have an equal correct refractive index on one surface in the direction of the plane direction orthogonal to each other, different refractive index to the other in-plane direction Have
In the first optical anisotropic film, the refractive index in the other in-plane direction is smaller than the refractive index in one in-plane direction,
In the second optical anisotropic film, the refractive index in the other in-plane direction is larger than the refractive index in one in-plane direction,
The first optical anisotropic film has a columnar structure inclined in the other in-plane direction with respect to one main surface of the transparent support,
The second optically anisotropic film is a reflective polarizer characterized by having a columnar structure inclined in one in-plane direction with respect to one main surface of the transparent support.

  In the first invention, the refractive index is uniform for one in-plane direction among the in-plane directions orthogonal to each other, and the refractive index difference is large for the other in-plane direction among the in-plane directions orthogonal to each other. As described above, since the first and second optically anisotropic films are laminated, the refractive index difference in the other in-plane direction can be made larger than that of the conventional reflective polarizer.

  In the first invention, it is preferable that the first and second optical anisotropic films are made of a dielectric material. Moreover, it is preferable that a transparent support is further provided, and the first and second optically anisotropic films are alternately laminated on the transparent support. Further, the first optical anisotropic film is an optical anisotropic film formed by injecting an inorganic material obliquely from the other in-plane direction with respect to one main surface of the transparent support, and the second optical anisotropic film It is preferable that the conductive film is an optically anisotropic film formed by injecting an inorganic material obliquely from one in-plane direction with respect to one main surface of the transparent support.

  In the first invention, the first optical anisotropic film has a columnar structure inclined in the other in-plane direction with respect to one main surface of the transparent support, and the second optical anisotropic film is It is preferable to have a columnar structure inclined in one in-plane direction with respect to one main surface of the transparent support. Moreover, it is preferable that the difference in refractive index between the first optical anisotropic film and the second optical anisotropic film in the other in-plane direction is 0.05 or more. In addition, the positional relationship between the major axis and the minor axis of the refractive index ellipsoid cut surface with respect to light incident from the optical axis direction is reversed between the first optical anisotropic film and the second optical anisotropic film. Preferably it is.

The second invention is
Using the first vaporization source, the step of causing the inorganic material to enter obliquely from one in-plane direction among the in-plane directions perpendicular to each other with respect to one main surface of the transparent support;
Injecting an inorganic material obliquely from the other in-plane direction among the in-plane directions perpendicular to each other with respect to one main surface of the transparent support using the second vaporization source;
By alternately repeating the steps , the first optical anisotropic film and the second optical anisotropic film are alternately and repeatedly stacked,
The first optical anisotropic film has a columnar structure inclined in the other in-plane direction with respect to one main surface of the transparent support,
The second optically anisotropic film has a columnar structure inclined in one in-plane direction with respect to one main surface of the transparent support , and is a method for producing a reflective polarizer.

  In the second invention, the first optical anisotropic film obtained by growing the inorganic material obliquely in one in-plane direction among the in-plane directions orthogonal to each other and the other of the in-plane directions orthogonal to each other The second optically anisotropic film formed by growing an inorganic material obliquely in the in-plane direction can be alternately and repeatedly stacked.

  In the second invention, it is preferable to repeat the two steps alternately by running the transparent support so as to periodically pass over the first vaporization source and the second vaporization source. Moreover, it is preferable to use a dielectric material as the inorganic material.

  In the second invention, it is preferable to form a film using a vacuum thin film production technique such as sputtering, chemical vapor deposition, vacuum deposition, or ion plating.

The third invention is
Traveling means for traveling the transparent support;
A first vaporization source that causes the inorganic material to enter obliquely from one of the in-plane directions perpendicular to each other with respect to the transparent support that is traveled by the travel means;
A second vaporization source that causes the inorganic material to enter obliquely from the other in-plane direction of the in-plane directions perpendicular to each other with respect to the transparent support that is traveled by the travel means;
With
The traveling means travels the transparent support so that the transparent support periodically passes over the first vaporization source and the second vaporization source, whereby the first optical anisotropic film and the second The optically anisotropic film is laminated alternately and repeatedly,
The first optical anisotropic film has a columnar structure inclined in the other in-plane direction with respect to one main surface of the transparent support,
The second optically anisotropic film has a columnar structure inclined in one in-plane direction with respect to one main surface of the transparent support, and is a reflective polarizer manufacturing apparatus.

  In the third invention, the first optical anisotropic film obtained by growing the inorganic material obliquely in one in-plane direction among the in-plane directions orthogonal to each other and the other of the in-plane directions orthogonal to each other The second optically anisotropic film formed by growing an inorganic material obliquely in the in-plane direction can be alternately and repeatedly stacked.

  In the third invention, it is preferable to use a dielectric material as the inorganic material. In the third invention, it is preferable to form a film using a vacuum thin film production technique such as sputtering, chemical vapor deposition, vacuum deposition, or ion plating.

  As described above, according to the present invention, the first and second optical anisotropic films have the same refractive index in one in-plane direction out of the in-plane directions perpendicular to each other. In the optically anisotropic film, the refractive index in the other in-plane direction is made smaller than the refractive index in the one in-plane direction, and in the second optically anisotropic film, the refractive index in the other in-plane direction is made smaller. Since the refractive index in the in-plane direction is increased, the refractive index difference in the other in-plane direction can be further increased as compared with the conventional reflective polarizer. Therefore, the number of stacked layers can be reduced. That is, the reflective polarizer can be made thinner, more compact, and more productive.

  First, in order to facilitate understanding of the present invention, an outline of the present invention will be described. Conventionally, as a reflective polarizer, a laminate obtained by laminating stretched films made of organic materials is widely known. However, as described above, this reflective polarizer has a problem that it is difficult to reduce the thickness, make it compact, and improve the productivity.

  In view of this, the present inventor has studied a reflective polarizer in which an optical anisotropic film made of an inorganic material and an optical isotropic film are alternately laminated. According to the knowledge of the present inventor, in this reflective polarizer, it is possible to reduce the number of stacked layers of 800 layers or more conventionally required to cover the visible light band to about 300 layers. That is, the reflective polarizer can be made thinner, more compact, and improved in productivity.

  However, it is necessary to further reduce the number of stacked layers in order to achieve further thinning, compactness, and improvement in productivity. Therefore, the present inventor has intensively studied to further reduce the number of laminated optical thin films. As a result, a configuration in which the first optical anisotropic thin film and the second optical anisotropic thin film are alternately stacked is adopted instead of the configuration in which the anisotropic thin film and the isotropic thin film are alternately stacked. As a result, the number of layers necessary to cover the visible light band is further reduced, and for example, it has been found that it can be made about 100 layers. The present invention has been devised based on the above studies.

Embodiments of the present invention will be described in the following order.
(1) Configuration of liquid crystal display device (2) Configuration of reflective polarizer (3) Reflective polarizer manufacturing device (4) Reflective polarizer manufacturing method

(1) Configuration of Liquid Crystal Display Device FIG. 1 is a cross-sectional view showing a configuration example of a liquid crystal display device 1 according to an embodiment of the present invention.
Hereinafter, the configuration of the liquid crystal display device 1 will be described with reference to FIG.

  As shown in FIG. 1, the liquid crystal display device 1 is a so-called transmissive liquid crystal display device, and includes a liquid crystal panel 2, a backlight 7 that is a light source, and a reflective polarizer 24.

  The backlight 7 is, for example, a cold cathode fluorescent lamp (CCFL) or an LED (Light Emitting Diode), and is disposed immediately below the liquid crystal panel 2. Here, an example of a method of arranging the backlight 7 directly under the liquid crystal panel 2 (directly under type) is shown, but the method of the backlight is not limited to this example, and one end side (edge) of the liquid crystal panel 2 is shown. A backlight (7) such as a cold cathode tube or an LED may be disposed on the side), and a method (edge type) in which light from the backlight 7 is spread over the entire surface of the liquid crystal panel 2 through a light guide plate. In addition, when the liquid crystal panel 2 is a large-sized liquid crystal panel for television use or the like, the backlight is preferably a direct type.

  The liquid crystal panel 2 is formed by sealing liquid crystal between the first substrate 3 and the second substrate 4 and the first substrate 3 and the second substrate 4 that are opposed to each other with a spacer 5 spaced apart from each other. A liquid crystal layer 6. The spacer 5 is for maintaining a predetermined distance between the first substrate 3 and the second substrate 4. The liquid crystal layer 6 is made of, for example, a liquid crystal such as a nematic liquid crystal, and its arrangement changes according to the voltage applied between the first substrate 3 and the second substrate 4.

  The first substrate 3 is a semiconductor element substrate such as a TFT (Thin Film Transistor) substrate. The first substrate 3 includes a substrate 21 made of glass, plastic, or the like. A transparent electrode 22 and an alignment film 23 are sequentially stacked on one main surface of the substrate 21, and a reflective polarizer is formed on the other main surface. 24 is provided. Although illustration is omitted for convenience, a semiconductor element such as a TFT, a signal line, and a scanning line are provided on one main surface of the substrate 21.

  The second substrate 4 is a color filter substrate (CF substrate). The second substrate 4 includes a substrate 11. A color filter 12, a transparent electrode 13, and an alignment film 14 are sequentially stacked on one main surface of the substrate 11. A polarizer is formed on the other main surface of the substrate 11. 15 is provided.

  The transparent electrodes 13 and 22 are, for example, an alloy oxide (ITO: Indium Tin Oxide) of indium and tin. The alignment films 14 and 23 are films for aligning liquid crystal molecules in a certain direction, and are made of a polymer such as polyimide, for example.

  The color filter 12 is for color display. For example, R (red), G (green), and B (blue) elements are arranged corresponding to the pixels. Each pixel is composed of three sub-pixels of R (red), G (green), and B (blue). The size of the sub-pixel depends on the screen size and the number of pixels, but is about several tens of μm, for example.

The polarizer 15a and the polarizer 15b allow only one of orthogonally polarized components of incident light to pass therethrough and shield the other by absorption. For example, the polarizer 15a and the polarizer 15b are provided so that their transmission axes are orthogonal to each other. The reflective polarizer 24 allows only one of the orthogonal polarization components of incident light to pass and reflects the other. The reflective polarizer 24 is provided between the liquid crystal panel 2 and the backlight 7. For example, the polarizer 15b and the reflective polarizer 24 are provided so that their transmission axes are parallel to each other. In FIG. 1, L is light incident on the reflective polarizer 24 from the backlight 7, l ₁ is light transmitted through the reflective polarizer 24 among the incident light L, and l ₂ is incident light L. Among these, the light reflected by the reflective polarizer 24 is shown.

(2) Configuration of the reflective polarizer First, in order to facilitate understanding of the reflective polarizer formed by alternately laminating the first optical anisotropic film and the second optical anisotropic film on the support. A reflective polarizer in which an optical anisotropic film and an optical isotropic film are alternately laminated on a support will be described.

FIG. 2 is a cross-sectional view showing a configuration example of a reflective polarizer in which the optical anisotropic film 32 and the optical isotropic film 33 are alternately stacked on the support 31. In FIG. 2, n _1x and n _1y indicate the refractive index in the x-axis direction and the refractive index in the y-axis direction of the optically anisotropic film 32, respectively. N _2x and n _2y represent the refractive index in the x-axis direction and the refractive index in the y-axis direction of the optical isotropic film 33, respectively.

  As shown in FIG. 2, this reflective polarizer is formed by alternately laminating optical anisotropic films 32 and optical isotropic films 33 on a support 31. The reflective polarizer transmits the x-polarized component of the light incident on the reflective polarizer, while reflecting the y-polarized component. Hereinafter, in the support 31, one main surface on the side where the optical anisotropic film 32 and the optical isotropic film 33 are laminated is referred to as a film formation surface.

The optically anisotropic film 32 has different refractive indexes, that is, birefringence in the x-axis direction and the y-axis direction. On the other hand, the optical isotropic film 33 has the same refractive index in the x-axis direction and the y-axis direction. The refractive indexes n _1x and n _{2x in the} x-axis direction and the refractive indexes n _1y and n _2y in the y-axis direction of the optical anisotropic film 32 and the optical isotropic film 33 and the refractive index difference Δn between the films in the y-axis direction. For example, the following relationship is satisfied.
n _1x > n _1y , n _2x = n _2y
n _1x = n _2x , n _1y <n _2y
Δn = n _2y −n _1y

  The first optically anisotropic film 32 is a film in which an inorganic material is incident obliquely from the y-axis direction with respect to the film formation surface of the support 31, that is, the inorganic material is inclined obliquely toward the y-axis direction. It is an obliquely grown film that is grown, and has, for example, a columnar structure inclined in the y-axis direction or a structure in which granular materials are deposited.

  The second optically isotropic film 33 is a film in which an inorganic material is incident perpendicularly to the film-forming surface of the support 31 from the direction of the optical axis, that is, an inorganic material perpendicular to the z-axis direction. For example, the film has a columnar structure perpendicular to the film formation surface of the support 31 or a uniform structure in the surface.

Here, the optical anisotropic film 32 and the optical isotropic film 33 will be described using specific numerical values as examples. For example, the optically anisotropic film 32 has a refractive index n _1x = 2.0 as a refractive index in the _x -axis direction and a refractive index n _1y = 1.8 as a refractive index in the y-axis direction. The optical isotropic film 33 has, for example, a refractive index n _2x = 2.0 as a refractive index in the _x -axis direction and a refractive index n _2y = 2.0 as a refractive index in the y-axis direction. In this case, the refractive index difference between the films in the x-axis direction is Δn = 2.0−2.0 = 0, whereas the refractive index difference between the films is Δn = 2 in the y-axis direction. 0.0-1.8 = 0.2. With these optical characteristics, the multilayer laminate functions as a reflective polarizer that reflects only the y-polarized component of incident light and transmits the x-polarized component.

  The number of layers required for covering the visible light band is defined by the value of the refractive index difference Δn between the films. However, in the configuration in which the optically anisotropic film 32 and the optically isotropic film 33 are stacked, the refractive index difference Δn between the films cannot be increased so much. For example, the refractive index difference between the films is Δn = 0. In the case of .2, 200 or more layers are required. For this reason, in the reflective polarizer having the above-described configuration, it has been difficult to make the reflective polarizer thinner, more compact, and improve productivity.

  Therefore, in the reflective polarizer according to an embodiment of the present invention, the refractive index difference Δn between the films is further increased as compared with the above-described reflective polarizer, thereby further reducing the number of laminated optical thin films and further reflecting polarized light. This makes it possible to make the child thinner, more compact, and improve productivity.

FIG. 3 is a cross-sectional view showing a configuration example of the reflective polarizer 24 according to the embodiment of the present invention. In FIG. 3, n _1x and n _1y respectively indicate the refractive index in the x-axis direction and the refractive index in the y-axis direction of the first optical anisotropic film 42. Further, n _2x and n _2y represent the refractive index in the x-axis direction and the refractive index in the y-axis direction of the second optical anisotropic film 43, respectively.

  As shown in FIG. 3, the reflective polarizer 24 is formed by alternately stacking first optical anisotropic films 42 and second optical anisotropic films 43 on a support 41. The reflective polarizer 24 transmits the x-polarized component of the light incident on the reflective polarizer 24, while reflecting the y-polarized component. Hereinafter, in the support 41, one main surface on the side where the first optical anisotropic film 42 and the second optical anisotropic film 43 are laminated is referred to as a film formation surface.

  The support 41 is a transparent substrate or film. As the material of the support 41, transparent glass or plastic can be used. As the glass, for example, soda lime glass, lead glass, hard glass, quartz glass, or liquid crystallized glass can be used. As the plastic, for example, polycarbonate, polyolefin, acrylic resin, or the like can be used.

The first optical anisotropic film 42 and the second optical anisotropic film 43 have different refractive indexes, that is, birefringence in the x-axis direction and the y-axis direction. Refractive indexes n _1x and n _{2x in the} x-axis direction and refractive indexes n _1y and n _2y in the y-axis direction of the first optical anisotropic film 42 and the second optical anisotropic film 43, and a film in the y-axis direction For example, the refractive index difference Δn satisfies the following relationship.
n _1x > n _1y , n _2x <n _2y
n _1x = n _2x , n _1y <n _2y
Δn = n _2y −n _1y

  By satisfying this relationship, it is possible to reflect the y-polarized component oscillating in the y-axis direction while transmitting the x-polarized component oscillating in the x-axis direction among the light incident on the reflective polarizer 24. Further, the refractive index difference Δn between the films in the y-axis direction can be increased, and the number of stacked layers can be reduced.

  The optical axis of the first optical anisotropic film 42 is inclined in the y-axis direction, for example. The optical axis of the second optical anisotropic film 43 is inclined, for example, in the x-axis direction. Specifically, for example, the optical axis of the second optical anisotropic film 43 is at a position obtained by rotating the optical axis of the first optical anisotropic film 42 by approximately 90 degrees about the optical axis. Therefore, the positional relationship between the major axis and the minor axis of the cut surface of the refractive index ellipsoid with respect to the light incident from the optical axis direction is reversed between the first optical anisotropic film 42 and the second optical anisotropic film 43. is doing.

  4A and 4B are perspective views for explaining a method of forming the first optical anisotropic film 42 and the second optical anisotropic film 43. FIG. 4A and 4B, the direction of the arrow indicates the incident direction of an inorganic material such as a dielectric material.

  The first optically anisotropic film 42 is a film in which an inorganic material is incident obliquely from the y-axis direction with respect to the film formation surface of the support 41, that is, the inorganic material is inclined obliquely toward the y-axis direction. It is an obliquely grown film that is grown, and has, for example, a columnar structure inclined in the y-axis direction or a structure in which granular materials are deposited. The second optical anisotropic film 43 is a film in which an inorganic material is incident obliquely from the x-axis direction with respect to the film formation surface of the support 41, that is, the inorganic material is inclined obliquely toward the x-axis direction. It is an obliquely grown film formed by growth, and has, for example, a columnar structure inclined in the x-axis direction or a structure in which granular materials are deposited.

  As described above, when an inorganic thin film made of a dielectric material or the like is grown in an oblique direction with respect to the film formation surface of the support 41, the optical film is optically oriented with respect to the in-plane orientation of the support 41 due to its unique internal structure. Anisotropy can be expressed (see JP-A-59-49508).

The structure possessed by the first optical anisotropic film 42 and the second optical anisotropic film 43 can be made by appropriately selecting materials and the like. For example, a columnar structure grown in an oblique direction can be obtained by making Ta ₂ O ₅ incident on the film formation surface of the support 41 from an oblique direction. The structure in which the granular material is deposited can be obtained, for example, by allowing a mixture of Ta ₂ O ₅ and CeO ₂ to enter the film forming surface of the support 41 from an oblique direction.

Here, the first optical anisotropic film 42 and the second optical anisotropic film 43 will be described using specific numerical values as an example. The first optical anisotropic film 42 has, for example, a refractive index n _1x = 1.8 as a refractive index in the _x -axis direction and a refractive index n _1y = 1.6 as a refractive index in the y-axis direction. The second optically anisotropic film 43 has, for example, a refractive index n _2x = 1.8 as a refractive index in the _x -axis direction and n _2y = 2.0 as a refractive index in the y-axis direction. In this case, the refractive index difference between the films in the x-axis direction is Δn = 1.8−1.8 = 0, whereas the refractive index difference between the films in the y-axis direction is Δn = 2.0−1. .6 = 0.4. Thus, since a large refractive index difference Δn can be obtained in the y-axis direction, the function as a reflective polarizer that transmits one polarization component and reflects the other polarization component is about 100 layers. The number of layers can be obtained. That is, the required number of layers can be greatly reduced.

  The first optical anisotropic film 42 and the second optical anisotropic film 43 are made of different inorganic materials, for example. As this inorganic material, a transparent inorganic material, for example, a transparent dielectric material can be used, and more specifically, for example, a transparent oxide, sulfide or fluoride is used. Can do.

Examples of the oxide include an oxide of tantalum (Ta), titanium (Ti), zirconium (Zr), niobium (Nb), cerium (Ce), aluminum (Al), silicon (Si), or zinc (Zn) or A mixture thereof can be used, and more specifically, for example, tantalum pentoxide (Ta ₂ O ₅ ), trititanium pentoxide (Ti ₃ O ₅ ), dititanium trioxide (Ti ₂ O ₃ ), monoxide titanium (TiO), titanium dioxide (TiO _2), zirconium dioxide (ZrO _2), niobium pentoxide (Nb ₂ O _5), cerium dioxide (CeO _2), aluminum oxide (Al ₂ O _3), silicon dioxide (SiO ₂ ), Silicon monoxide (SiO), ZnO (zinc oxide), or a mixture thereof.

As the sulfide, for example, a sulfide of zinc (Zn) or cadmium (Cd) or a mixture thereof can be used, and more specifically, for example, zinc sulfide (ZnS), cadmium sulfide (CdS) or a mixture thereof. Mixtures can be used. As the fluoride, a fluoride of magnesium (Mg), cerium (Ce), barium (Ba), calcium (Ca) or neodymium (Nd) or a mixture thereof can be used, and more specifically, for example, fluoride. Magnesium fluoride (MgF ₂ ), cerium fluoride (CeF ₃ ), barium fluoride (BaF ₂ ), calcium fluoride (CaF ₂ ), neodymium fluoride (NdF ₃ ), or a mixture thereof can be used.

  The inorganic material constituting the first optical anisotropic film 42 and the second optical anisotropic film 43 is preferably selected so that the refractive index difference Δn between the films increases in the y-axis direction. The refractive index difference Δn is selected to be, for example, 0.05 or more, preferably 0.2 or more, more preferably 0.44 or more. By setting the refractive index difference Δn to 0.2 or more, it is possible to reduce the number of laminated layers required to make the reflectance of one polarized light to 97% or more over the entire visible light band. By setting the refractive index difference Δn to 0.44 or more, the number of stacked layers necessary for making the reflectance of one polarized light 97% or more in the entire visible light band can be made 100 or less.

In order to increase the refractive index difference Δn between the films as described above, examples of oxides constituting the first optical anisotropic film 42 include cerium dioxide (CeO ₂ ), tantalum pentoxide (Ta ₂ O _5). ), Niobium pentoxide (Nb ₂ O ₅ ) or zinc oxide (ZnO), and as the oxide constituting the second optical anisotropic film 43, for example, titanium dioxide (TiO ₂ ) is used. .

  The optical performance of the reflective polarizer 24 is determined by the optical thickness (refractive index × thickness) of each optical film. If the optical film has an optical thickness that is smaller than the wavelength of light, structural interference can be utilized to enhance the optical performance of the reflective polarizer 24 at the selected wavelength. As a film forming method for forming a uniform film having an optical thickness thinner than the wavelength of light, for example, a vacuum thin film forming technique can be used. As a vacuum thin film formation technique, for example, a sputtering method, a chemical vapor deposition method, a vacuum deposition method, an ion plating method, or the like can be used.

  Specifically, the structural interference is caused by the optical thickness of the paired optical films (the optical thickness of the first optical anisotropic film 42 + the optical thickness of the second optical anisotropic film 43). Is) half of the wavelength of the incident light. This half-wavelength condition results in narrowband structural interference centered on the design wavelength λ. Broadband optical performance can be obtained by stacking multiple narrowband combinations. For example, the first group having the same thickness (the optical thickness of the first optical anisotropic film 42 + the optical thickness of the second optical anisotropic film 43 = λ / 2) is changed to a different thickness. By stacking in a second group having (the optical thickness of the first optical anisotropic film 42 + the optical thickness of the second optical anisotropic film 43 = λ ′ / 2), λ and Two types of bands centering on λ ′ are combined to increase the bandwidth.

For example, in order to obtain broadband optical characteristics, a first laminated body and a film obtained by alternately laminating first optical anisotropic films 42 and second optical anisotropic films 43 having a film thickness d ₁ A _second laminate formed by alternately laminating the first optical anisotropic film 42 and the second optical anisotropic film 43 having the thickness d ₂ ,..., The first having the film thickness d _n An nth stacked body in which the optically anisotropic films 42 and the second optically anisotropic films 43 are alternately stacked is sequentially stacked on the support 41. The thickness _{d 1, d 2, ···,} d n is appropriately selected depending on the band to be desired.

More specifically, for example, in order to obtain a broadband optical characteristic covering white light emitted from the backlight 7, the first optical anisotropic film 42 having the film thickness d ₁ and the second optical anisotropic film 42. first laminate the anisotropic film 43 formed by laminating alternately formed by laminating a first optically anisotropic layer 42 and a second optically anisotropic layer 43 having a thickness d ₂ alternately first A second laminated body, a _third laminated body obtained by alternately laminating a first optical anisotropic film 42 and a second optical anisotropic film 43 having a film thickness d _3, and a first film having a film thickness d ₄ . It is preferable that a fourth laminate formed by alternately laminating the first optical anisotropic film 42 and the second optical anisotropic film 43 is sequentially laminated on the support 41. Here, the film thicknesses d ₁ , d ₂ , d ₃ , and d ₄ are appropriately selected according to the band corresponding to white light.

  FIG. 5 is a cross-sectional view of the reflective polarizer 24 having a columnar structure in the xz plane. FIG. 6 is a cross-sectional view of the reflective polarizer 24 having a columnar structure in the yz plane. 5 and 6 show an example in which the number of stacked layers of the first optical anisotropic film 42 and the second optical anisotropic film 43 is four for convenience.

The first optical anisotropic film 42 has a columnar structure grown perpendicular to the x-axis and inclined with respect to the y-axis. Optical anisotropy can be obtained by obliquely growing the columnar structure in this way. Specifically, the refractive index n _1y in the y-axis direction can be made smaller than the refractive index n _{1x in the} x-axis direction. it can. The columnar structure of the first optically anisotropic film 42 is inclined in the range of 5 degrees to 85 degrees in the y-axis direction with respect to the normal line of the film-forming surface of the support 41 (that is, the z-axis), for example. ing.

The second optically isotropic film 43 has a columnar structure that is inclined with respect to the x-axis and grown perpendicular to the y-axis. Thus, the optical anisotropy can be obtained by obliquely growing the columnar structure. Specifically, the refractive index n _2y in the y-axis direction can be made larger than the refractive index n _{2x in the} x-axis direction. it can. For example, the columnar structure of the second optically anisotropic film 43 is inclined in the range of 5 degrees to 85 degrees in the x-axis direction with respect to the normal line (that is, the z-axis) of the film formation surface of the support 41. ing.

(3) Reflective Polarizer Manufacturing Apparatus FIG. 7 is a schematic diagram showing a configuration example of a reflective polarizer manufacturing apparatus 101 according to an embodiment of the present invention. FIG. 8 is a schematic cross-sectional view parallel to the paper surface of FIG. FIG. 9 is a schematic cross-sectional view taken along line IX-IX in FIG. The reflective polarizer manufacturing apparatus 101 is a sputtering apparatus that can alternately stack the first optical anisotropic film 42 and the second optical anisotropic film 43 on the support 41.

  Hereinafter, the configuration of the reflective polarizer manufacturing apparatus 101 according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 7, the reflective polarizer manufacturing apparatus 101 includes a vacuum chamber 103, and a vacuum exhaust system 102 is provided on a side surface of the vacuum chamber 103. By this evacuation system 102, the inside of the vacuum chamber 103 is brought into a high vacuum state.

  Inside the vacuum chamber 103, guide rolls 104 and 105, tension adjusting rolls 106 and 107, and a cooling can 108 are provided. By the guide rolls 104 and 105, the tension adjusting rolls 106 and 107, and the cooling can 108, the support body 41 travels in a counterclockwise direction, for example. The belt-like support body 41 is attached to the cooling can 108 by connecting both ends in the longitudinal direction thereof with, for example, an adhesive tape to form a ring shape.

  The cooling can 108 is configured to be rotatable, and the support body 41 travels on the peripheral surface of the cooling can 108 at a constant speed as the cooling can 108 rotates. A cooling mechanism (not shown) is provided inside the cooling can 108, and the cooling mechanism is cooled by an external cooling device (not shown). Thereby, the deformation | transformation etc. by the temperature rise of the support body 41 can be suppressed.

  The tension adjusting rolls 106 and 107 control the tension of the support body 41 so that the support body 41 travels smoothly without deformation. The tension adjusting rolls 106 and 107 are appropriately controlled by a tension adjusting mechanism (not shown). The guide rolls 104 and 105, the tension adjusting rolls 106 and 107, and the cooling can 108 have, for example, a cylindrical shape larger than the width of the support body 41.

  In the vacuum chamber 103, a first target 109, which is a first vaporization source, and a second target 110, which is a second vaporization source, are provided. As the first target 109 and the second target 110, an oxide target or a metal target can be used. When a metal target is used, a DC sputtering method, an AC sputtering method, or the like can be used. From the viewpoint of film formation speed, it is preferable to use a metal target.

  The first target 109 is for forming the first optical anisotropic film 42 on the support body 41 that travels on the peripheral surface of the cooling can 108 at a constant speed. The first optical anisotropic film 42 is made of a material.

  The second target 110 is for forming the second optical anisotropic film 43 on the support 41 that travels at a constant speed on the peripheral surface of the cooling can 108, and the second target 110 is , And a material corresponding to the second optical anisotropic film 43.

  As shown in FIG. 8, the first target 109 is arranged so that the sputtered atoms ejected from the first target 109 are obliquely incident on the traveling surface of the cooling can 108 from the traveling direction or the opposite direction. Is provided. For example, the sputtered atoms are incident from the normal line n of the traveling surface of the cooling can 108 from the direction inclined by the angle θ in the traveling direction or the opposite direction. Here, the angle θ is selected from a range of 5 degrees to 85 degrees, for example. By making the sputter atoms enter in this way, the inorganic material 110 can be grown obliquely on the film formation surface of the support 41.

  As shown in FIG. 9, the second target 110 is provided so that the sputtered atoms ejected from the second target 110 are obliquely incident on the traveling surface of the cooling can 108 from the side. . The sputtered atoms are incident, for example, from a direction inclined at an angle θ from the normal line n of the traveling surface of the cooling can 108. Here, the angle θ is selected from a range of 5 degrees to 85 degrees, for example. By making the sputter atoms enter in this way, the inorganic material 110 can be grown obliquely on the film formation surface of the support 41.

  Further, between the cooling can 108 and the first target 109, a shutter 111a and a shutter 111b are provided in the vicinity of the cooling can 108. The shutter 111a and the shutter 111b are provided so as to cover a predetermined region of the support body 41 that travels on the peripheral surface of the cooling can 108 at a constant speed. With the shutter 111a and the shutter 111b, sputtering atoms that have jumped out from the first target 109 can be incident obliquely on the support 41 within a predetermined angle range.

  In addition, a shutter 111 a and a shutter 111 c are provided in the vicinity of the cooling can 108 between the cooling can 108 and the second target 110. The shutter 111a and the shutter 111c are provided so as to cover a predetermined region of the support body 41 that travels on the peripheral surface of the cooling can 108 at a constant speed. By means of the shutter 111a and the shutter 111c, sputtering atoms that have jumped out from the second target 110 can be incident on the support 41 obliquely within a predetermined angle range.

(4) Manufacturing method of reflective polarizer Next, the manufacturing method of the reflective polarizer by one Embodiment of this invention is demonstrated.

  First, both ends in the longitudinal direction of the support body 41 having a belt shape are connected to the cooling can 108 in a ring shape by joining, for example, with an adhesive tape. Next, the inside of the vacuum chamber 103 is evacuated to a predetermined degree of vacuum by the vacuum exhaust system 102, and then the support body 41 is caused to travel at a constant speed by the cooling can 108.

  Next, the first optical anisotropic film 42 and the second optical anisotropic film are formed by introducing a discharge gas into the vacuum chamber 103 and performing sputtering while running the support 41 at a constant speed. 43 are alternately laminated on the support 41. Here, the film thickness, refractive index, and refractive index difference Δn of each film can be controlled by the film forming conditions. Thus, the target reflective polarizer 24 can be obtained.

According to one embodiment of the present invention, the following effects can be obtained.
Since the reflective polarizer 24 is produced by alternately laminating the first optical anisotropic film 42 and the second optical anisotropic film 43, the optical anisotropic film and the optical isotropic film are alternately laminated. Since the refractive index difference Δn between the films can be made larger than that of the reflective polarizer, the number of layers necessary for reflecting the visible light band can be reduced. Therefore, it is possible to improve productivity and reduce costs.

  Further, since the first optical anisotropic film 42 and the second optical anisotropic film 43 are made of an inorganic material such as a dielectric material, they are excellent in that there is no UV degradation or deformation due to heat peculiar to organic matter. Weather resistance can be realized. In addition, unlike a reflective polarizer in which an optical thin film made of an organic material is laminated, light in the ultraviolet band is not absorbed, so that the transmittance of blue light is not reduced. Therefore, it has high transparency over the entire visible light pair. Further, it can be easily combined with another optical thin film, for example, combined with a polarizing plate.

  Also, since the first optical anisotropic film 42 and the second optical anisotropic film 43 are laminated by making the inorganic material incident on the support 41, the axial location irregularity unique to the stretched film, There is no decrease in the accuracy of the phase difference setting due to the unevenness of the film thickness. Therefore, the thickness of the reflective polarizer can be controlled on the nano order. In addition, since an anisotropic thin film having no unevenness in the axial direction can be obtained, a highly accurate phase difference can be set according to the film formation time. In addition, a high-performance reflective polarizer with small incident angle dependency can be produced. In addition, high-performance polarized light separation characteristics can be obtained over the entire visible light range.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples. In the following examples and comparative examples, the in-plane direction of the transparent support 41 will be described using the coordinate system shown in FIG.

Example 1
Sputtering atoms are incident on the film formation surface obliquely from the y-axis direction by sputtering, and a first optical anisotropic film 42 made of CeO ₂ is formed, and sputtering is performed obliquely from the x-axis direction by sputtering. A process of forming the second optical anisotropic film 42 made of TiO ₂ by causing atoms to enter the film forming surface is alternately repeated to form a laminate on the transparent support 41, The number of layers necessary for the reflectance of polarized light in the y-axis direction to be 97% or more over the entire visible light band was evaluated.

Example 2
Sputtering atoms are incident on the film formation surface obliquely from the y-axis direction by sputtering to form the first optical anisotropic film 42 made of Ta ₂ O ₅ , and oblique from the x-axis direction by sputtering The step of making the sputtered atoms incident on the film formation surface and forming the second optical anisotropic film 42 made of TiO ₂ alternately is repeated to form a laminate on the transparent support 41. Thus, the number of layers necessary for the reflectance of polarized light in the y-axis direction to be 97% or more in the entire visible light band was evaluated.

Example 3
Sputtering atoms are incident on the film formation surface obliquely from the y-axis direction by sputtering, and the first optical anisotropic film 42 made of Nb ₂ O _{5 is formed} and obliquely from the x-axis direction by sputtering. A process of forming the second optical anisotropic film 42 made of TiO ₂ by causing the sputtering atoms to enter the film formation surface is alternately repeated to form a laminate on the transparent support 41. The number of layers necessary for the reflectance of polarized light in the y-axis direction to be 97% or more over the entire visible light band was evaluated.

Example 4
Sputtering atoms are incident on the film formation surface obliquely from the y-axis direction by sputtering, and a first optical anisotropic film 42 made of ZnO is formed, and sputtering atoms are obliquely formed from the x-axis direction by sputtering. Is incident on the film formation surface, and the step of forming the second optical anisotropic film 42 made of TiO ₂ is alternately repeated to form a laminate on the transparent support 41, and visible The number of layers necessary for the reflectance of polarized light in the y-axis direction to be 97% or more over the entire optical band was evaluated.

Example 5
Sputtering atoms are incident on the film formation surface obliquely from the y-axis direction by sputtering, and the first optical anisotropic film 42 made of Nb ₂ O ₅ is formed, and obliquely from the x-axis direction by sputtering. A layer is formed on the transparent support 41 by alternately repeating the step of making the sputtered atoms incident on the film formation surface and forming the second optical anisotropic film 42 made of CeO ₂ alternately. Thus, the number of layers necessary for the reflectance of polarized light in the y-axis direction to be 97% or more in the entire visible light band was evaluated.

Comparative Example 1
Sputtering atoms are incident on the film formation surface obliquely from the y-axis direction by sputtering to form the first optical anisotropic film 42 made of Ta ₂ O ₅ , and oblique from the x-axis direction by sputtering A layer is formed on the transparent support 41 by alternately repeating the step of making the sputtered atoms incident on the film formation surface and forming the second optical anisotropic film 42 made of CeO ₂ alternately. Thus, the number of layers necessary for the reflectance of polarized light in the y-axis direction to be 97% or more in the entire visible light band was evaluated.

Comparative Example 2
Sputtering atoms are incident on the deposition surface obliquely from the y-axis direction by sputtering to form an optically anisotropic film 42 made of Ta ₂ O _5, and sputtering atoms perpendicular to the z-axis direction by sputtering Is incident on the film forming surface, and the step of forming the optically isotropic film made of Ta ₂ O ₅ is alternately repeated to form a laminate on the transparent support 41, and the visible light band. The number of layers necessary for the reflectance of polarized light in the y-axis direction to be 97% or more over the entire region was evaluated.

Further, the refractive index (n _1x , n _1y ) of the first optical anisotropic film 42 and the refractive index (n _2x , n _2y ) of the second optical anisotropic film 43 in the above-described examples and comparative examples, The refractive index difference Δn (= n _2y −n _1y ) between the films in the y-axis direction was also evaluated. Note that a spectroscopic ellipsometer (manufactured by J. A. Woollam Japan, trade name: M-2000) was used for the measurement of the refractive index. Table 1 shows the film configuration, refractive index, and required number of layers of the reflective polarizers according to the examples and comparative examples.

Table 1 shows the following.
(1) In Examples 1 to 5 in which the first optical anisotropic film and the second optical anisotropic film are laminated on the transparent support, the optical anisotropic film and the optical isotropic film are used as the transparent support. It can be seen that the refractive index difference Δn can be further increased and the required number of layers can be reduced as compared with Comparative Examples 1 and 2 stacked above.
(2) In Examples 1 to 5, the refractive index difference Δn between the films in the y-axis direction can be 0.2 or more, and the reflectance of polarized light in the y-axis direction is 97% or more over the entire visible light band. It can be seen that the number of layers required for the reduction can be reduced to 200 layers or less. That is, it can be seen that the required number of layers can be reduced as compared with the conventional case.
(3) In Example 1, Example 2, and Example 4, the refractive index difference Δn in the y-axis direction between the films can be 0.44 or more, and the reflection of polarized light in the y-axis direction over the entire visible light band. It can be seen that the number of stacked layers required for the rate to be 97% or more can be reduced to 100 layers or less. That is, it can be seen that the required number of layers can be greatly reduced as compared with the conventional case.

  The embodiment of the present invention has been specifically described above, but the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible.

  For example, the numerical values given in the above-described embodiment are merely examples, and different numerical values may be used as necessary.

  Further, in the above-described embodiment, the case where the first optical anisotropic film 42 and the second optical anisotropic film 43 are made of an inorganic material has been described as an example. The film 42 and the second optical anisotropic film 43 may be made of an organic material. In this case, as the first optical anisotropic film 42 and the second optical anisotropic film 43, for example, a uniaxially stretched sheet made of crystalline naphthalene dicarboxylic acid polyester such as polyethylene naphthalate (PEN) is used. Can do.

It is sectional drawing which shows one structural example of the liquid crystal display device by one Embodiment of this invention. It is sectional drawing which shows one structural example of the reflective polarizer formed by laminating | stacking an optically anisotropic film-forming and an optically isotropic film on a support body alternately. It is sectional drawing which shows one structural example of the reflective polarizer by one Embodiment of this invention. It is a perspective view for demonstrating the film-forming method of a 1st optically anisotropic film and a 2nd optically anisotropic film. It is sectional drawing in the xz plane of the reflective polarizer which has a columnar structure. It is sectional drawing in yz plane of the reflective polarizer which has a columnar structure. It is a schematic diagram which shows one structural example of the manufacturing apparatus of the reflective polarizer by one Embodiment of this invention. It is a schematic sectional drawing which shows the positional relationship of the 1st target which is a 1st vaporization source, and a cooling can. It is a schematic sectional drawing which shows the positional relationship of the 2nd target which is a 2nd vaporization source, and a cooling can.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 Liquid crystal panel 3 1st board | substrate 4 2nd board | substrate 5 Spacer 6 Liquid crystal layer 7 Backlight 24 Reflective polarizer 41 Support body 42 Optical anisotropic film 43 Optical isotropic film 101 Manufacture of reflective polarizer Device 108 Cooling can 109, 110 Target

Claims (12)

A transparent support, and a first optical anisotropic film and a second optical anisotropic film laminated alternately on the transparent support,
Said the first and second optically anisotropic layer, different for to have an equal correct refractive index on one surface in the direction of the plane direction orthogonal to each other, the other in-plane direction refraction Have a rate,
In the first optical anisotropic film, the refractive index in the other in-plane direction is smaller than the refractive index in the one in-plane direction,
In the second optical anisotropic film, the refractive index in the other in-plane direction is larger than the refractive index in the one in-plane direction,
The first optical anisotropic film has a columnar structure inclined in the other in-plane direction with respect to one main surface of the transparent support,
The reflective polarizer, wherein the second optically anisotropic film has a columnar structure inclined in the one in-plane direction with respect to one main surface of the transparent support.   The reflective polarizer according to claim 1, wherein the first and second optically anisotropic films are made of a dielectric material. The reflection material according to claim 2, wherein a bulk material refractive index difference between dielectric materials constituting the first optical anisotropic film and the second optical anisotropic film is 0.05 or more. Polarizer. The first optical anisotropic film is an optical anisotropic film formed by injecting an inorganic material obliquely from the other in-plane direction with respect to one main surface of the transparent support,
The second optically anisotropic film is an optically anisotropic film formed by injecting an inorganic material obliquely from the one in-plane direction with respect to one main surface of the transparent support. The reflective polarizer according to claim 1 . The reflection according to claim 1, wherein a difference in refractive index between the first optical anisotropic film and the second optical anisotropic film in the other in-plane direction is 0.2 or more. Polarizer.   The positional relationship between the major axis and the minor axis of the cut surface of the refractive index ellipsoid with respect to light incident from the optical axis direction is reversed between the first optical anisotropic film and the second optical anisotropic film. The reflective polarizer according to claim 1. A liquid crystal display device comprising the reflective polarizer according to any one of claims 1 to 6 between a liquid crystal panel and a light source. Using the first vaporization source, the step of causing the inorganic material to enter obliquely from one in-plane direction among the in-plane directions perpendicular to each other with respect to one main surface of the transparent support;
Injecting an inorganic material obliquely from the other in-plane direction among the in-plane directions perpendicular to each other with respect to one main surface of the transparent support using a second vaporization source;
By alternately repeating the steps , the first optical anisotropic film and the second optical anisotropic film are alternately and repeatedly stacked,
The first optical anisotropic film has a columnar structure inclined in the other in-plane direction with respect to one main surface of the transparent support,
The method for producing a reflective polarizer, wherein the second optically anisotropic film has a columnar structure inclined in the one in-plane direction with respect to one main surface of the transparent support . The reflection according to claim 8, wherein the two steps are alternately repeated by running the transparent support so as to periodically pass over the first vaporization source and the second vaporization source. A method for producing a polarizer. The method of manufacturing a reflective polarizer according to claim 8 , wherein the inorganic material is a dielectric material. Traveling means for traveling the transparent support;
A first vaporization source that causes the inorganic material to enter obliquely from one of the in-plane directions perpendicular to each other with respect to the transparent support that is traveled by the travel means;
A second vaporization source that causes the inorganic material to enter obliquely from the other in-plane direction of the in-plane directions perpendicular to each other, with respect to the transparent support that is traveled by the travel means;
With
The traveling means travels the transparent support so that the transparent support periodically passes over the first vaporization source and the second vaporization source, whereby the first optical anisotropic film And the second optically anisotropic film are alternately and repeatedly laminated,
The first optical anisotropic film has a columnar structure inclined in the other in-plane direction with respect to one main surface of the transparent support,
The apparatus for manufacturing a reflective polarizer, wherein the second optical anisotropic film has a columnar structure inclined in the one in-plane direction with respect to one main surface of the transparent support . The reflective polarizer manufacturing apparatus according to claim 11 , wherein the inorganic material is a dielectric material.

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