JP5227741B2 - Optical compensation film manufacturing method and optical compensation film - Google Patents

Description

  The present invention relates to an optical compensation film manufacturing method and an optical compensation film that can be suitably used for an optical device such as a liquid crystal display device and an optical pickup.

  In various optical devices such as liquid crystal display devices and optical pickups, an optical compensation film for compensating for birefringence caused by other components in the device is generally used. Such an optical compensation film is used, for example, for widening the viewing angle, preventing color leakage during black display, and the like.

  By the way, in order to use the optical compensation film for preventing discoloration during display of a liquid crystal display device or the like, it is necessary to control the phase difference (wavelength dispersion of the phase difference) with respect to each wavelength of light. As an example of such, there is a retardation plate or the like whose phase difference is 1/4 of the wavelength for each wavelength of light. Examples of such a controlled phase difference in a wide band include, for example, (retardation in light with a wavelength of 450 nm) / (retardation in light with a wavelength of 550 nm) and films having different retardations and their optical axes intersect. In this state, there are retardation plates that are laminated in a state (see, for example, Patent Document 1).

  Another example is a ¼ wavelength film produced by uniaxially stretching a film formed from a mixture of a polymer having a positive intrinsic birefringence value and a polymer having a negative intrinsic birefringence value ( For example, see Patent Document 2 and Non-Patent Document 1). Here, a polymer having a positive intrinsic birefringence value means that when the main chain of the polymer extends to the ideal state (refractive index related to the polarization component in the direction parallel to the alignment direction of the polymer main chain) − (Refractive index related to polarization component in a direction perpendicular to the orientation direction of the polymer main chain)> 0, for example, polyvinyl chloride. In addition, a polymer having a negative intrinsic birefringence value means that when the main chain of the polymer is extended and oriented to an ideal state (refractive index related to a polarization component in a direction parallel to the orientation direction of the polymer main chain) − ( The refractive index of the polarization component in the direction perpendicular to the orientation direction of the polymer main chain) is <0, for example, polymethyl methacrylate.

  In addition, examples of films composed of a polymer compound including a monomer unit of a polymer compound having positive refractive index anisotropy and a monomer unit of a polymer compound having negative refractive index anisotropy are also mentioned ( For example, see Patent Document 3). Moreover, the example of the film which extended | stretched the polymer film which disperse | distributed the liquid crystal substantially uniformly inside to one direction is also mentioned (refer patent document 4).

Another example is a surface relief hologram using structural birefringence (see, for example, Patent Document 5).
Japanese Patent Laid-Open No. 5-27118 (published February 5, 1993) JP 56-125702 A (released on October 2, 1981) International Publication No. WO00 / 26705 (published on May 11, 2000) Japanese Patent Laid-Open No. 5-257013 (released on October 8, 1993) Japanese Patent Application Laid-Open No. Sho 62-212940 (published on September 18, 1987) Takashi Inoue, Taku Saito, “Design of Low Birefringent Plastics”, Functional Materials, Vol. 7, No. 3, p21-29, 1987

  However, in the film described in Patent Document 1, there is a complexity of aligning the optical axes of a plurality of films.

  In addition, in the films described in Patent Document 2 and Non-Patent Document 1, when the film is uniaxially stretched, the sign of the phase difference of each polymer is reversed, so that the phase difference of the entire film is reduced as a result of addition, In order to obtain a necessary phase difference, it is necessary to increase the film thickness. As a result, problems such as high material costs and increased thickness of the display device arise.

  Further, even in the film described in Patent Document 3, since the sign of the phase difference of each monomer unit is reversed, the phase difference of the entire film is reduced as a result of addition, and the necessary phase difference is obtained in the same manner as in the above example. In order to obtain this, it is necessary to increase the film thickness.

  The retardation plate described in Patent Document 4 has a characteristic that combines the refractive index of a stretched polymer film and its wavelength dependence, and the refractive index and wavelength dependence of a liquid crystal in which molecules are aligned in the stretching direction. Therefore, in order to obtain the required wavelength dependence, there arises a problem that the selection between the polymer film and the liquid crystal is limited.

  In the case of the technique described in Patent Document 5, it is necessary to finely process the light to a wavelength level size, and it is difficult to produce a seamless roll film by processing.

  The present invention has been made in view of the above problems, and its purpose is not to require a complicated process of bonding two retardation films with the optical axis aligned, and is inexpensive. An object of the present invention is to provide an optical compensation film manufacturing method and an optical compensation film in which the thickness of an optical device does not unnecessarily increase during use, and the phase difference for each wavelength of light can be easily controlled.

  The method for producing an optical compensation film according to the present invention includes the following inventions in order to solve the above problems.

  [1] The film surface has a concavo-convex shape in which a concave portion and a convex portion are repeated, and when divided into a plurality of unit regions along a direction parallel to the film surface, there is a phase difference with respect to light of the same wavelength. A method for producing an optical compensation film in which a plurality of unit regions different from each other by 10 nm or more from adjacent unit regions, the method comprising: forming a concavo-convex shape in which concave portions and convex portions are repeated on the film surface; and a stretching step A method for producing an optical compensation film.

  [2] In the film, there are a plurality of hollow regions having different lengths in the thickness direction of the film along the direction parallel to the film surface, and divided into a plurality of unit regions along the direction parallel to the film surface. Is a method for producing an optical compensation film in which a plurality of unit regions differing by 10 nm or more from adjacent unit regions with respect to light of the same wavelength, wherein the lengths are different in the thickness direction of the film. The manufacturing method of the optical compensation film characterized by including the film manufacturing process which manufactures the film in which a plurality of airspace exists along the direction parallel to the film surface, and an extending process.

  [3] A plurality of types of polymer compounds having the same orientation birefringence value and different orientation birefringence values, and having the same wavelength when divided into a plurality of unit regions along a direction parallel to the film surface Is a method for producing an optical compensation film in which a plurality of unit regions having a phase difference with respect to light adjacent to each other by 10 nm or more exist, wherein the signs of the orientation birefringence values are the same and the orientation birefringence values are different. An extrusion step of extruding a polymer compound to form a film, and a stretching step of stretching the film obtained in the extrusion step, wherein the extrusion step has the same sign of the orientation birefringence value, and the orientation A method for producing an optical compensation film, comprising extruding a plurality of types of polymer compounds having different birefringence values while changing a ratio of the plurality of types of polymer compounds over time.

  [4] A plurality of types of polymer compounds having the same orientation birefringence value and different orientation birefringence values, and having the same wavelength when divided into a plurality of unit regions along a direction parallel to the film surface Is a method for producing an optical compensation film in which a plurality of unit regions having a phase difference with respect to light adjacent to each other by 10 nm or more exist, wherein the signs of the orientation birefringence values are the same and the orientation birefringence values are different. An extrusion process for extruding the polymer compound to form a film, and a stretching process for stretching the film obtained in the extrusion process. The extrusion process includes two adjacent extrusions in the film cross section by multilayer extrusion molding. In the unit region, the signs of the orientation birefringence values are the same inside the film so that the ratios in the thickness direction of the plural types of polymer compounds contained in the unit regions are different, and the orientation birefringence values differ. Method of manufacturing an optical compensation film characterized by extruding the region that.

  [5] An optical compensation film produced using the production method according to any one of [1] to [4].

[6] When the combined phase difference with respect to light of wavelength λ nm in the entire region is R (λ), the following formula (1)
R (548) ≦ 350 nm Formula (1)
The optical compensation film according to [5], wherein

[7] In the optical compensation film or film having a concavo-convex shape in which concave portions and convex portions are repeated on the film surface, hollow regions having different lengths in the thickness direction of the film are in a direction parallel to the film surface. A plurality of optical compensation films along the direction, wherein the convex portion or the adjacent hollow region in the region where the length in the thickness direction is short is a phase difference with respect to light of wavelength λ nm, and the concave portion Alternatively, the phase difference with respect to light having a wavelength of λ nm in a region where the length of the adjacent hollow region in the thickness direction is long is defined as r ′ (λ), and the combined phase difference with respect to light having a wavelength of λ nm in all regions is defined as R (λ). When the following mathematical formulas (2), (3) and (4)
r (548) <r (447) (2)
r ′ (548) <r ′ (447) (3)
R (548) ≧ R (447) (4)
The optical compensation film according to [5] or [6], wherein

[8] An optical compensation film including a plurality of types of polymer compounds having the same sign of the orientation birefringence value and different orientation birefringence values, and formed of each of the plurality of types of polymer compounds. When the stretched product obtained by uniaxially stretching the film is defined as R ₀ (λ) for the phase difference with respect to the light with the wavelength λnm and R (λ) with respect to the combined phase difference with respect to the light with the wavelength λnm in the entire region, the following formula (5 ) And (6)
R ₀ (548) <R ₀ (447) (5)
R (548) ≧ R (447) (6)
The optical compensation film according to [5] or [6], wherein

[9] When the combined phase difference with respect to light of wavelength λ nm in all regions is R (λ), the following formula (7)
R (628) ≧ R (548) ≧ R (447) (7)
The optical compensation film according to any one of [5] to [8], wherein

  Moreover, the manufacturing method of the optical compensation film of [1] according to the present invention may include the following methods.

  [10] A surface processing step for forming a concavo-convex shape in which a concave portion and a convex portion are repeated on the film surface by sandblasting the film surface, and a film on which the concavo-convex shape is formed is stretched after the surface processing step. A method for producing an optical compensation film as described in [1], comprising a stretching step.

  [11] A stretching step for stretching the film, and a surface processing step for forming a concavo-convex shape in which the concave portion and the convex portion are repeated on the film surface by sandblasting the film surface after the stretching step. [1] The method for producing an optical compensation film according to [1].

  [12] A surface processing step for forming a concave-convex shape in which concave portions and convex portions are repeated on the film surface by attaching a molten resin to the film surface, and a film on which the concave-convex shape is formed after the surface processing step. The method for producing an optical compensation film according to [1], comprising a step of stretching.

  [13] A mixture comprising a plurality of types of polymer compounds or a copolymer comprising a plurality of types of polymer chains is formed on a film, and the plurality of types of polymer compounds or the plurality of types of polymer chains are formed. A film forming step for producing a film in which the copolymer is phase-separated into a sea-island structure, and the film contains n types of polymer compounds or a copolymer composed of n types of polymer chains. In this case, one or more (n-1) or less types of polymer compounds or polymer chains contained in the film obtained in the film forming step are removed by dissolution treatment or dry etching treatment to form island portions. By removing only the surface processing step for forming the concave-convex shape in which the concave portion and the convex portion are repeated on the film surface, and after the surface processing step, the film having the concave-convex shape is stretched Method of manufacturing an optical compensation film as described in [1], which comprises the extension step.

  [14] A mixture comprising a plurality of types of polymer compounds or a copolymer comprising a plurality of types of polymer chains is formed on a film, and the plurality of types of polymer compounds or the plurality of types of polymer chains are formed. A film forming step for producing a film in which the copolymer is phase-separated into a sea-island structure, a stretching step for stretching the film obtained in the film forming step, and n kinds of polymer compounds are contained in the film. Alternatively, when a copolymer composed of n types of polymer chains is included, one or more (n−1) types of polymer compounds or high polymers included in the film obtained in the film forming step A surface processing step for forming a concavo-convex shape in which a concave portion and a convex portion are repeated on the film surface by removing only the island portion by removing the molecular chain by dissolution treatment or dry etching treatment, Method of manufacturing an optical compensation film as described in [1], which comprises.

  Moreover, the manufacturing method of the optical compensation film of [2] according to the present invention may include the following methods.

  [15] In the film manufacturing process, the polymer compound melt containing the foaming agent is extruded after the foaming agent is vaporized, or the foaming agent is vaporized after the extrusion molding, whereby the film has a thickness direction. The method for producing an optical compensation film according to [2], wherein a film having a plurality of hollow regions having different lengths along a direction parallel to the film surface is produced.

  [16] In the film manufacturing process, the stretched film is allowed to exist in a low-temperature liquefied gas in a stretched state, and then exposed to the atmosphere to be foamed. The method for producing an optical compensation film as described in [2], wherein a film having a plurality of hollow regions having different lengths along a direction parallel to the film surface is produced.

  [17] In the film production process, the film has a moisture absorption, and by vaporizing water by dielectric heating and foaming, a hollow region having a length different in the thickness direction of the film is parallel to the film surface. A method for producing an optical compensation film according to [2], wherein a plurality of films are produced along the line.

  Moreover, the manufacturing method of the optical compensation film concerning this invention can include the following methods.

  [18] A plurality of types of polymer compounds having the same orientation birefringence value and different orientation birefringence values, and having the same wavelength when divided into a plurality of unit regions along a direction parallel to the film surface Is a method for producing an optical compensation film in which a plurality of unit regions differing by 10 nm or more from adjacent unit regions with respect to the light of [13], [14], [2], [15] to [17] A film produced by the method according to any one of the above, or before performing the stretching step in the method according to any one of [13], [14], [2], [15], [16] and [17] An impregnation step of impregnating a film having the same sign of an orientation birefringence value with a material having a different orientation birefringence value and a stretching step of stretching the film obtained in the impregnation step. With features including Method of manufacturing an optical compensation film that.

  As described above, the method for producing an optical compensation film according to the present invention has a concavo-convex shape in which a concave portion and a convex portion are repeated on the film surface, and a plurality of unit regions along a direction parallel to the film surface. Is a method of manufacturing an optical compensation film in which a plurality of unit regions different in phase difference by 10 nm or more from adjacent unit regions with respect to light of the same wavelength are present, and concave portions and convex portions are repeated on the film surface Since it has a configuration including a step of forming a concavo-convex shape and a stretching step, it does not require a complicated step of bonding two retardation films together with the optical axis, and is inexpensive. It is possible to provide an optical compensation film manufacturing method and an optical compensation film in which the thickness of the optical device is not unnecessarily increased during use, and the phase difference for each wavelength of light can be easily controlled.

  In the method for producing an optical compensation film according to the present invention, as described above, a plurality of hollow regions having different lengths in the film thickness direction exist in the film along the direction parallel to the film surface. When the optical compensation film is divided into a plurality of unit regions along a direction parallel to the surface, the optical compensation film has a plurality of unit regions different in phase difference by 10 nm or more from adjacent unit regions with respect to light having the same wavelength, A film manufacturing process for manufacturing a film in which a plurality of hollow regions having different lengths in the thickness direction of the film exist in a direction parallel to the film surface, and the film obtained in the film manufacturing process is stretched A stretching process, so that a complicated process of bonding two retardation films with the optical axis aligned is not required, and is inexpensive and usable. Sometimes the thickness of the optical device without increasing unnecessarily, it is possible to provide a manufacturing method and an optical compensation film easy optical compensation film control of the phase difference for each wavelength of light.

  As described above, the method for producing an optical compensation film according to the present invention includes a plurality of types of polymer compounds having the same sign of the orientation birefringence value and different orientation birefringence values, in a direction parallel to the film surface. A method of manufacturing an optical compensation film in which a plurality of unit regions having a phase difference of 10 nm or more from adjacent unit regions with respect to light of the same wavelength when divided into a plurality of unit regions along the same direction, And extruding a plurality of types of polymer compounds having different orientation birefringence values to form a film, and a stretching step of stretching the film obtained in the extrusion step, and the above-mentioned extrusion step Extrude at least a plurality of polymer compounds having the same orientation birefringence value sign and different orientation birefringence values while changing the ratio of the plurality of polymer compounds over time. Because it has a configuration, it does not require a complicated process of bonding two retardation films with the optical axis aligned, and it is inexpensive and does not unnecessarily increase the thickness of the optical device during use. It is possible to provide a method for producing an optical compensation film and an optical compensation film in which the phase difference for each wavelength of light can be easily controlled.

  In addition, as described above, the method for producing an optical compensation film according to the present invention includes a plurality of types of polymer compounds having the same sign of the orientation birefringence value and different orientation birefringence values, and is parallel to the film surface. A method for producing an optical compensation film in which when divided into a plurality of unit regions along a direction, a plurality of unit regions having a phase difference with respect to light of the same wavelength differing by 10 nm or more from adjacent unit regions, the orientation birefringence value Including an extrusion step of extruding a plurality of types of polymer compounds having the same sign and different orientation birefringence values to form a film, and a stretching step of stretching the film obtained in the extrusion step, The extrusion process is performed by multi-layer extrusion so that the ratios in the thickness direction of the plural kinds of polymer compounds contained in the two adjacent unit regions in the film cross section are different. Since it has a structure for extruding regions having the same orientation birefringence value and different orientation birefringence values, the complicated process of attaching two retardation films together with the optical axis aligned. To provide an optical compensation film manufacturing method and an optical compensation film, which are not required, are inexpensive, and do not unnecessarily increase the thickness of an optical device during use, and allow easy control of a phase difference for each wavelength of light. Can do.

  One embodiment of the method for producing an optical compensation film and the optical compensation film of the present invention will be described below with reference to FIGS.

(I) Optical compensation film produced in the present invention The optical compensation film produced in the present invention is one in which one surface of the film is used as a light incident surface, and the film surface that is the light incident surface. It is a film whose phase difference changes in at least one direction. Here, the amount of change in the phase difference only needs to exceed a degree of mere manufacturing variation.

  More specifically, in the present invention, the optical compensation film means that when divided into a plurality of unit regions along a direction parallel to the film surface, the phase difference for light of the same wavelength is 10 nm or more from the adjacent unit region. A film having a plurality of different unit areas.

  Hereinafter, the optical compensation film of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing an example of the optical compensation film of the present invention. The optical compensation film 1 shown in FIG. 1A has a two-dimensionally spread film shape, and one surface thereof is used as a light incident surface. FIG. 1B is a plan view of the optical compensation film 1 viewed from a direction perpendicular to the light incident surface. Moreover, (c) of FIG. 1 is an arrow sectional view of the AA line in (b).

  As shown in FIGS. 1B and 1C, the optical compensation film 1 includes a plurality of unit regions 2 (2-1, 2-2,..., 2- N) are mixed along the direction parallel to the light incident surface. Here, region numbers n (n = 1 to N) are assigned to each unit region in order from one end of the film to the other end. Further, as shown in FIG. 1C, the phase difference with respect to light of wavelength λ in the unit region of region number n is r (n, λ).

  At this time, the optical compensation film 1 has a difference of | r (n, λ) −r (n + 1, λ) | between two adjacent unit regions, that is, a phase difference in the region of region number n and a phase difference in the region of n + 1. Is designed so that there is a unit region 2 in which the thickness is 10 nm or more. Usually, even when an optical compensation film having a uniform thickness is manufactured, the phase difference slightly changes along the surface direction of the film due to manufacturing variations. However, the change in phase difference due to such manufacturing variations is usually in the range of less than 10 nm. The optical compensation film of the present invention does not utilize such a change in retardation due to manufacturing variations, but is designed so that the phase difference between adjacent unit regions is intentionally different by 10 nm or more. Note that the phase difference between adjacent unit regions needs to be different by 10 nm or more, but two unit regions that are not adjacent may have the same phase difference. Usually, as shown in FIG. 2 and the like, the optical compensation film can exhibit its function by uniformly distributing two types of unit regions having different phase differences. However, of course, the optical compensation film produced in the present invention may have three or more types of unit regions having different phase differences uniformly.

  The phase difference described here is a phase difference when viewed from a direction perpendicular to the surface of the optical compensation film. In this specification, when there is no particular reference to the angle with respect to the light incident surface, the “phase difference” means a phase difference when viewed from a direction perpendicular to the surface of the optical compensation film.

  The adjacent unit regions of the optical compensation film, for example, the phase difference r (λ) nm of 2-1 and 2-2, for example, can be obtained as follows.

An optical compensation film having a phase difference ref (nm) is arranged between a pair of polarizing plates whose polarization directions are parallel so that the slow axis is deviated by 45 ° from the polarization direction of the polarizing plate, and the wavelength λ (nm from one polarizing plate ) Of the linearly polarized light transmitted through the optical compensation film and the other polarizing plate, and the relationship between the phase difference ref for the light of wavelength λ,
I (λ) = 1/2 + 1/2 · cos (2πref / λ)
In the case of the optical compensation film of the present invention in which a plurality of unit regions 2-1 and 2-2 consisting of a high retardation region and a low retardation region are present, the transmittance due to the retardation r (λ) is The phase difference indicating the transmittance may be calculated based on the above relational expression, and the value may be used as the phase difference r (λ).

  Or when measuring the phase difference of a minute unit area, it can measure using a micro polarization spectrophotometer. For example, by using a liquid crystal cell gap measuring device (TFM-120AFT-PC) using a micro-polarization spectrophotometer manufactured by Oak Manufacturing Co., Ltd., it is possible to measure the phase difference of a minute region up to about 10 μm square. is there.

  In general, the optical axis of each unit region is preferably in the same direction. The variation of the optical axis is preferably within ± 10 °, more preferably ± 5 °, and further preferably within ± 1 °. Further, if necessary, the optical axes of each other can be orthogonal to 90 °.

  Then, the optical compensation film of the present invention appropriately selects the phase difference of each unit region and the ratio of the area of each unit region to the area of the entire region where all the unit regions are combined, so that the optical compensation film as a whole is positioned. The wavelength dispersion (wavelength dependence) of the phase difference (combined phase difference described later) is made different from the wavelength dispersion of any unit region. That is, by appropriately selecting the phase difference r (n, λ) and the area ratio of each unit region, an optical compensation film having a desired wavelength dispersion of wavelength dispersion can be easily manufactured.

  The wavelength dispersion of the phase difference has been determined by the material so far. However, according to the optical compensation film, an optical compensation film having a wavelength dispersion different from that of the material used in each unit region can be produced. That is, the wavelength dispersion of the phase difference of the entire optical element can be designed without being limited by the wavelength dispersion characteristics of the material.

  As a result, since materials were selected so as to satisfy chromatic dispersion so far, characteristics other than chromatic dispersion (photoelastic coefficient and glass transition point) were also determined by the material. However, it is possible to select those having other desired characteristics. That is, the range of material selection is expanded. For example, a material having a small photoelastic coefficient or a material having a glass transition point (Tg) of 130 ° C. or higher can be used, and the wavelength dispersion of the retardation can be made desired.

  The arrangement of the unit regions having different phase differences is not particularly limited. A stripe shape as shown in FIG. 1B or a matrix shape may be used, and an arbitrary arrangement may be adopted.

  Next, a specific example of a method of causing a plurality of unit regions having different phase differences for light of the same wavelength along a direction parallel to the film surface that is a light incident surface will be described.

The phase difference is the product of the birefringence and the thickness of the film (phase difference) = (birefringence) × (thickness)
It is represented by

  Therefore, unit regions having different phase differences can be mixed by making at least one of birefringence or thickness different.

  FIG. 2 is a diagram illustrating an example of an optical compensation film in which unit regions having different retardations are mixed by varying the thickness. 2A is a perspective view, and FIG. 2B is a cross-sectional view. The optical compensation film 1 shown in FIG. 2 is a film in which unit regions having different retardations are mixed by forming an uneven shape in which a concave portion and a convex portion are repeated, thereby varying the thickness. In the example of FIG. 2, the unit areas 2 (2-1, 2-2,...) Having different thicknesses are alternately arranged in a stripe shape, and as shown in FIG. The thickness is uniform.

  Of course, the optical compensation film having an uneven shape in which the concave portion and the convex portion are repeated is not limited to the configuration arranged in the stripe shape shown in FIG. 2, and by having the uneven shape, the optical compensation film is parallel to the film surface. The structure is not particularly limited as long as it is divided into a plurality of unit regions having different phase differences along the direction. The optical compensation film having such an uneven shape may be, for example, an optical compensation film in which protrusions having a triangular cross section are formed at predetermined intervals on a flat film surface. In this case, the optical compensation film is divided into a unit region where the protrusion is not formed and a unit region where the protrusion is formed. Moreover, the optical compensation film having the uneven shape may be an optical compensation film in which a cross section of one surface of the film is formed in a sawtooth shape. Such an optical compensation film includes a unit region having a width of half of a sawtooth-like period around the maximum point of thickness, and a width of half of a sawtooth-like period including a minimum point of the thickness. It is divided into unit areas having Alternatively, the optical compensation film having the concavo-convex shape may be an optical compensation film in which bullet-shaped projections are formed at a predetermined interval on a flat film surface. Such an optical compensation film is divided into a unit region in which no protrusion is formed and a unit region in which a protrusion is formed.

  FIG. 3, FIG. 7 and FIG. 8 are diagrams showing an example of an optical compensation film in which unit regions having different retardations are mixed by making birefringence different for each region. The optical compensation film 1 shown in FIG. 3 includes a plurality of types of polymer compounds having different orientation birefringence values. In addition, as will be described later, various polymer compounds included in the optical compensation film 1 have the same sign of the orientation birefringence value and different orientation birefringence values. In the optical compensation film 1 shown in FIG. 3, the polymer compound A having a relatively large blending ratio forms a sea portion, and the polymer compound B having a relatively small blending ratio forms an island portion. In addition, in this specification, a compounding ratio means the ratio of the weight of each high molecular compound with respect to the total weight of the said multiple types of high molecular compound contained in an optical compensation film.

  In the optical compensation film 1, the polymer compounds A and B having the same sign of the orientation birefringence value and having different orientation birefringence values are present along the direction parallel to the film surface. The mixing ratio of B changes and the phase difference changes. Thus, in the optical compensation film 1, a plurality of unit regions having different phase differences with respect to light of the same wavelength are present along a direction parallel to the film surface (light incident surface).

  That is, the mixing ratio of various polymer compounds existing in the thickness direction is different at an arbitrary point on the film surface of the optical compensation film 1 in FIG. For example, the mixing ratio of the polymer compound A at the point X in FIG. 1 is 1.0, and the mixing ratio of the polymer compound B at the point Y is about 0.5. Therefore, a region where the polymer compounds having a mixing ratio larger than the corresponding blending ratio are the same and is continuous along the film surface is set as one unit region. In the case of FIG. 3, for example, if the blending ratio of A and B is A: B = 0.8: 0.2, in region a, the blending ratio of the polymer compound A is larger than the corresponding blending ratio. . For this reason, the area a may be set as one unit area. On the other hand, in the region b, the mixing ratio of the polymer compound B is larger than the corresponding blending ratio. For this reason, the region b may be set as one unit region. By setting the unit region in this way, two adjacent unit regions have different mixing ratios of a plurality of types of polymer compounds contained therein. Here, since the polymer compounds A and B have different birefringence values, the phase difference between two adjacent unit regions is different. In addition, when there are three or more kinds of polymer compounds constituting the optical compensation film 1, the polymer has a mixing ratio larger than the corresponding blending ratio, and the difference between the blending ratio and the blending ratio is the largest. A region where the compounds are the same and is continuous along the film surface may be set as one unit region.

  Of course, the distribution state of a plurality of types of polymer compounds is not limited to this, and includes various distribution states. For example, when each type of polymer compound is phase-separated so as to continuously exist from one side of the film to the other side along the thickness direction of the film, each type of polymer A region where the compound is continuously present may be defined as one unit region.

  Other configurations that make the birefringence different from region to region include, for example, in a polymer film having a uniform retardation, hollow regions having different lengths in the film thickness direction are parallel to the film surface. There may be a configuration in which a plurality exist. In this case, since the hollow region is filled with air, the region has a phase difference of 0 nm.

  Moreover, the orientation birefringence value of the polymer compound contained in the optical compensation film 1 according to the present embodiment has the same sign. Thereby, the composite phase difference does not become too small, and it is not necessary to increase the film thickness of the optical compensation film in order to obtain a necessary composite phase difference.

(II) Manufacturing method of optical compensation film (II-1) Method including the process of forming uneven | corrugated shape on the film surface One embodiment of the manufacturing method of the optical compensation film concerning this invention is a film surface, a recessed part and a convex part. Have a concavo-convex shape that is repeated, and when divided into a plurality of unit regions along a direction parallel to the film surface, a unit region whose phase difference with respect to light of the same wavelength differs from the adjacent unit region by 10 nm or more A method for producing a plurality of optical compensation films, which includes a step of forming a concavo-convex shape in which concave portions and convex portions are repeated on the film surface, and a stretching step.

  By forming an uneven shape in which concave and convex portions are repeated on the film surface, it is possible to manufacture an optical compensation film in which unit areas having different retardations are mixed with different thicknesses.

  According to the above configuration, when the distance between the optical compensation film and the person viewing the optical compensation film is ensured so that the convex portion and the concave portion cannot be visually recognized by human eyes, the human The entire area including this is viewed macroscopically.

  At this time, the combined phase difference R of the entire region including the convex portion and the concave portion indicates a phase difference corresponding to the average birefringence of the birefringence due to the phase difference between the convex portion and the concave portion. Therefore, the wavelength dependence of the phase difference in the convex part and the concave part is different from the wavelength dependence of the combined phase difference R in the entire region including all the convex parts and the concave part.

  The wavelength dependence (wavelength dispersion) of the composite phase difference is determined by the difference in phase difference between the convex portion and the concave portion and the area ratio of the convex portion and the concave portion with respect to the entire region. Therefore, the chromatic dispersion of the composite phase difference can be easily controlled without being restricted by the material.

  As described above, according to the present invention, the phase difference for each wavelength of light can be controlled by a simple manufacturing method including a step of forming a concavo-convex shape in which concave portions and convex portions are repeated on the film surface and a stretching step. Can provide an easy optical compensation film.

  Here, the step of forming a concave / convex shape in which the concave portion and the convex portion are repeated on the film surface is formed by forming the concave / convex shape in which the concave portion and the convex portion are repeated, thereby varying the thickness and different units of retardation. There is no particular limitation as long as the regions can be mixed.

  The stretching step in each embodiment of the present invention is for orienting the main chain of the polymer constituting the film and imparting birefringence, and the method is not particularly limited, and uniaxial stretching Or biaxial stretching may be sufficient. Further, the conditions may be appropriately selected depending on the desired optical compensation film, the material of the film to be used, and the like.

  In addition, the optical compensation film manufactured in the present embodiment has an uneven surface shape with a material having a relatively low phase difference (ideally 0 is preferable) relative to the phase difference of the film (that is, a light incident surface). The surface of the optical compensation film may be made uniform by filling it with a material that does not exhibit birefringence when viewed from a direction perpendicular to the surface, for example, a resin that can be cured with ultraviolet rays or electron beams such as acrylic resin. Thereby, scattering of light can be prevented.

<Method by sandblasting>
In the method for producing an optical compensation film according to the present embodiment, an example of a method for forming a concavo-convex shape in which concave portions and convex portions are repeated on the film surface is a method of sandblasting the film surface. In such a method, the stretching step may be performed after the film surface is sandblasted to form an uneven shape, or the film surface of the film after the stretching step may be sandblasted.

  That is, the method for manufacturing an optical compensation film according to the present embodiment includes a surface processing step of forming a concave and convex shape in which concave portions and convex portions are repeated on the film surface by sandblasting the film surface, and the surface processing step. Later, the method may include a stretching step of stretching the film on which the irregular shape is formed, or the film surface may be sandblasted after the stretching step, and the film surface may be sandblasted after the stretching step. A method including a surface processing step of forming an uneven shape in which a concave portion and a convex portion are repeated may be used.

  The film that can be used in the present embodiment is, for example, a polycarbonate polymer obtained by polycondensation of bisphenol A and carbonyl chloride; poly (meth) acrylate such as polymethyl acrylate and polymethyl methacrylate A condensation or lactone of a dibasic acid such as adipic acid, phthalic acid, isophthalic acid, terephthalic acid or 2,6-naphthalenedicarboxylic acid with a glycol such as ethylene glycol, diethylene glycol, propylene glycol, tetramethylene glycol or neopentyl glycol Polymers obtained by ring-opening polymerization of polymers; styrene polymers such as polystyrene and poly (α-methylstyrene); copolymers of acrylic acid esters and styrene; polyethylene, polypropylene, norbornene resins, Polyolefin polymers such as olefin polymers, hydrogenated polyisoprene, hydrogenated polybutadiene, etc .; cellulose resins such as triacetyl cellulose and ethyl cellulose; polyamides such as nylon 6 and nylon 66; polyimides; polyamide imides; Polyvinylsulfone; polysulfone; polyethersulfone; polyarylate; epoxy resin; silicone resin; compounds described in WO 01/37007 are preferred.

  FIG. 4 is a diagram schematically illustrating an example of sandblasting used in the present embodiment. In this embodiment, as shown in FIG. 4, the sandblasting agent 4 is run along with a fluid such as air or water by an ejector (not shown) while running the film 3 to be formed with an uneven shape in the direction of the arrow. The film 3 is sprayed on the surface. Thereby, the part which the sandblasting agent on the surface of the film 3 collided is shaved, and becomes a recessed part, and uneven | corrugated shape is formed in the film 3 surface. By appropriately selecting the traveling direction and traveling speed of the film 3, the position of the surface of the film 3 on which the sandblasting treatment is performed, the sandblasting agent to be used, the amount and type of the fluid, the spraying amount and the spraying speed of the sandblasting agent, etc. What is necessary is just to form a shape. For example, when an optical compensation film as shown in FIG. 2 is manufactured, a plurality of ejectors are arranged at equal intervals, and the sandblasting process may be performed while the film 3 is running.

  Here, the sandblasting agent is not particularly limited, and a conventionally known agent can be suitably used. For example, alundum (alumina), carborundum (silicon carbide), ceramic beads, silica sand glass A metal etc. can be illustrated. The said sandblasting agent should just be a particulate form, and the average particle diameter should just be 1 micrometer-100 micrometers normally.

  Moreover, it is preferable that the temperature of a film when performing a sandblasting process is below the glass transition temperature Tg of a film. Thereby, since a desired uneven | corrugated shape can be formed, without deform | transforming a film, it is preferable.

  The fluid is not limited to air and water, and any fluid may be used as long as it does not adversely affect the formation of the uneven shape on the film surface.

  Further, as the sandblast treatment, instead of injecting the sandblast treatment agent together with the fluid onto the surface of the film traveling by the ejector, a method of projecting the sandblast treatment agent by applying centrifugal force on a rotating disk may be used. Good.

  Furthermore, as described in JP-A-50-15190, a method of bringing a contact material into contact with the back surface of the sandblasting agent for the film can also be suitably used.

<Method by adhesion of molten resin>
In the method for producing an optical compensation film according to the present embodiment, another example of a method for forming a concavo-convex shape in which concave portions and convex portions are repeated on the film surface is a method in which a molten resin is attached to the film surface.

  That is, the method for producing an optical compensation film according to the present embodiment includes a surface processing step for forming a concave and convex shape in which concave portions and convex portions are repeated on the film surface by attaching a molten resin to the film surface; And a step of stretching the film on which the concavo-convex shape is formed after the processing step.

  The method for adhering the molten resin to the film surface is not particularly limited as long as it is a method capable of forming an irregular shape by attaching the molten resin to the film surface and using the portion where the molten resin is adhered as a convex portion. Absent. For example, as shown in FIG. 5, a plurality of thread-shaped molten resins 6 extruded from the die 5 are attached to the traveling film 3 to form convex portions, whereby the concave and convex portions are repeated. Form a shape.

  In FIG. 5, the film 3 is run and the die 5 is fixed, but the film 3 may be fixed and the die 5 may be run.

  As the film and the molten resin that can be used in the present embodiment, the same materials as the film described in the embodiment using the sandblast treatment can be suitably used. Further, the molten resin may be the same resin as the film to which it is attached, or may be a different resin. When the molten resin and the film are different resins, materials having different orientation birefringence simultaneously with the thickness are formed on the film surface.

  Of course, the method of adhering the molten resin to the film surface is not limited to the method shown in FIG. 5. For example, the molten resin is formed into bullet-like projections at a predetermined interval on the fixed film surface. A method of extruding from a die having a plurality of openings and attaching it to form bullet-shaped convex portions at a predetermined interval can also be suitably used.

<Method by dissolution of phase separation film or dry etching>
In the method for producing an optical compensation film according to the present embodiment, still another example of the method for forming a concavo-convex shape in which concave portions and convex portions are repeated on the film surface is a plurality of types of polymer compounds or a plurality of types of polymers. From a film in which a chain copolymer is phase-separated into a sea-island structure, the film contains n types of polymer compounds or a copolymer consisting of n types of polymer chains In addition, by removing one or more types (n-1) or less of polymer compounds or polymer chains by dissolution treatment or dry etching treatment, and removing only the island portions, Is a method of forming an uneven shape in which is repeated.

  A mixture containing a plurality of types of polymer compounds or a copolymer such as a block copolymer comprising a plurality of types of polymer chains is likely to undergo phase separation in the production process. And the uneven | corrugated shape can be easily formed in the film surface by removing the island part which carried out phase separation.

  That is, in the method for producing an optical compensation film according to the present embodiment, a mixture containing a plurality of types of polymer compounds or a copolymer composed of a plurality of types of polymer chains is formed on the film, and the plurality of types of high compensation films are formed. A film forming step for producing a film in which a molecular compound or a copolymer comprising a plurality of kinds of polymer chains is phase-separated into a sea-island structure, and the film contains n kinds of polymer compounds, or n kinds When a copolymer consisting of a polymer chain is included, one or more (n-1) types of polymer compounds or polymer chains are removed by dissolution treatment or dry etching treatment, and only the island portion is removed. By removing the surface, a surface processing step for forming a concave-convex shape in which concave and convex portions are repeated on the film surface, and a film on which the concave-convex shape is formed after the surface processing step is stretched And Shin step may be a method comprising the.

  Moreover, the manufacturing method of the optical compensation film according to the present embodiment may be a method of performing the stretching step after the film forming step and before the surface processing step, instead of performing the stretching step after the surface processing step. . That is, the method for producing an optical compensation film according to the present embodiment includes the film forming step, a stretching step of stretching the film obtained in the film forming step, and the surface processing step after the stretching step. It may be.

  In the film formation step, a mixture containing a plurality of types of polymer compounds or a copolymer comprising a plurality of types of polymer chains is formed on a film, and the plurality of types of polymer compounds or the plurality of types of polymers are formed. A film is produced in which a chain copolymer is phase-separated into a sea-island structure. Here, as a method for forming the mixture or a copolymer such as the block copolymer into a film, a conventionally known method can be suitably used. For example, the mixture or the copolymer can be used. Examples thereof include a method in which a polymer solution is applied on a substrate and then peeled off from the substrate after heating, a method in which a cast film is melt cast, heated to an order-disorder transition temperature, and then cooled.

  By appropriately selecting the kind and ratio of the polymer compound to be mixed, a film in which the plurality of kinds of polymer compounds are phase-separated into a sea-island structure can be produced. Such a combination of polymer compounds is not particularly limited as long as it is phase-separated into a sea-island structure, and examples thereof include a combination of polycarbonate and cycloolefin polymer.

  In addition, by appropriately selecting the type of polymer chain contained in the block copolymer, the length of each polymer chain, and the ratio of the length of each polymer chain, the block copolymer is self-assembled. A film in which the plurality of types of polymer chains are phase-separated into a regular sea-island structure, that is, a film having a microphase-separated structure can be produced. Examples of such a block copolymer include a block copolymer containing at least polystyrene and polymethyl methacrylate, a block copolymer of polystyrene and polyisoprene, and the like. FIG. 6A shows an example of a film that is formed by self-assembly of a block copolymer composed of two types of polymer chains A and B and is phase-separated into a sea-island structure. In the film shown in FIG. 6A, the polymer chain A forms the sea part and the polymer chain B forms the island part. Such a film is manufactured by applying a solution of a block copolymer consisting of polymer chains A and B onto a substrate such as silicon, for example, so that the film thickness is substantially the same as the diameter of the dots forming the islands. After the film is formed, it can be manufactured by heating at a temperature higher than any of the glass transition temperatures of A and B to form a microphase separation structure and then peeling from the substrate. In addition, after forming a micro phase-separation structure, you may peel the film in which the uneven | corrugated shape was formed from the board | substrate after performing a melt | dissolution process or a dry etching process, without peeling a film from a board | substrate.

  The film phase-separated into the sea-island structure formed in the film forming step is left as it is or when the polymer compound or polymer chain contained in the film is n types after stretching, One or more (n-1) or less types of polymer compounds or polymer chains contained in the film obtained in the film forming step are removed by dissolution treatment or dry etching treatment to remove only the islands. Thereby, the removed island part becomes a recessed part, and the uneven | corrugated shape in which a recessed part and a convex part are repeated can be formed in the film surface. For example, FIG. 6B shows the film after removing the polymer chain B forming the island portion in the film shown in FIG.

(II-2) A method comprising a step of producing a film in which a plurality of hollow regions having different lengths in the thickness direction of the film are present in the film. The second embodiment of the method for producing an optical compensation film according to the present invention comprises: In the film, there are a plurality of hollow regions having different lengths in the thickness direction of the film along a direction parallel to the film surface, and when divided into a plurality of unit regions along the direction parallel to the film surface. A method for producing an optical compensation film in which there are a plurality of unit regions different in phase difference by 10 nm or more from adjacent unit regions with respect to light of the same wavelength, and in the film, hollow regions having different lengths in the thickness direction of the film, It includes a film manufacturing process and a stretching process for manufacturing a plurality of films along a direction parallel to the film surface. Here, the stretching process may be performed at least before, during and after the film manufacturing process. For example, the stretching step may stretch the film obtained in the film manufacturing step.

  The film has multiple hollow areas with different lengths in the film thickness direction along the direction parallel to the film surface, thereby making the birefringence different and mixing unit regions with different retardations. An optical compensation film can be produced.

  Here, the film production process is particularly suitable if the film can produce a film in which a plurality of hollow regions having different lengths in the thickness direction of the film exist in a direction parallel to the film surface. It is not limited. As an example of a film in which a plurality of hollow regions having different lengths in the film thickness direction exist in the film along a direction parallel to the film surface, for example, a portion B in FIG. 3 is a hollow region. Such a film can be mentioned. Further, the method of dividing into unit regions having different phase differences with respect to light of the same wavelength may be performed in the same manner as the method described with reference to FIG.

  Moreover, as a film which can be used in this embodiment, the film similar to the film demonstrated in embodiment using the said sandblasting process can be used conveniently.

<Method by vaporizing the foaming agent>
In the method for producing an optical compensation film according to the present embodiment, an example of a method for producing a film in which a plurality of hollow regions having different lengths in the thickness direction of the film exist in a direction parallel to the film surface is provided in the film. And a method of extruding a polymer compound melt containing a foaming agent after vaporizing the foaming agent, or a method of vaporizing the foaming agent after extrusion.

  That is, in the method for producing an optical compensation film according to the present embodiment, the melt of the polymer compound containing the foaming agent is extruded after the foaming agent is vaporized, or the foaming agent is vaporized after the extrusion molding. Alternatively, a method may be used in which a film having a plurality of hollow regions having different lengths in the thickness direction of the film is produced along a direction parallel to the film surface, and the obtained film is stretched.

  As the foaming agent, conventionally known foaming agents can be suitably used, and examples thereof include sodium hydrogen carbonate, ammonium hydrogen carbonate, N, N-dinitrosopentamethylenetetramine, azodicarbonamide and the like.

  Further, the method for vaporizing the foaming agent is not particularly limited, and a conventionally known method may be used. As a method for vaporizing the foaming agent after extrusion molding of the polymer compound melt containing the foaming agent, for example, the method described in JP-A-48-45561 can also be suitably used.

<Method by foaming using low temperature liquefied gas>
In the method for producing an optical compensation film according to the present embodiment, another method for producing a film in which a plurality of hollow regions having different lengths in the thickness direction of the film exist in a direction parallel to the film surface in the film. An example is a method in which a film is allowed to exist in a low-temperature liquefied gas in a stretched state, and then exposed to the atmosphere for foaming.

  That is, in the method for producing an optical compensation film according to the present embodiment, the stretched film is present in a low-temperature liquefied gas in a stretched state, and then exposed to the atmosphere to be foamed. A method may be used in which a film in which a plurality of hollow regions having different lengths in the thickness direction of the film are present along a direction parallel to the film surface is produced, and the obtained film is further stretched as necessary.

  In this method, the stretched film is present in a low-temperature liquefied gas such as liquid nitrogen or liquid helium in a stretched state, and the low-temperature liquefied gas is infiltrated into the film. Thereafter, the film infiltrated with the low-temperature liquefied gas is exposed to the atmosphere, the liquefied gas infiltrated into the film is expanded and foamed, and then further stretched as necessary.

<Method by evaporating and foaming water from a moisture-absorbed film>
In the method for producing an optical compensation film according to the present embodiment, still another method for producing a film in which a plurality of hollow regions having different lengths in the thickness direction of the film exist in a direction parallel to the film surface. One example is a method in which the film absorbs moisture and vaporizes water by dielectric heating to cause foaming.

  That is, in the method for producing an optical compensation film according to the present embodiment, a hollow region having a different length in the thickness direction of the film is formed in the film by absorbing the moisture and evaporating water by dielectric heating and foaming. A method of producing a plurality of films along a direction parallel to the film surface and stretching the obtained film may be used.

  In this method, the film is impregnated in water, for example, and the film absorbs moisture. Thereafter, for example, microwaves may be radiated to the moisture-absorbed film to evaporate water by dielectric heating, that is, heat generated by the molecular motion of the substance itself, and then stretched.

(II-3) A method comprising a step of producing a film containing a plurality of types of polymer compounds having different orientation birefringence values The third embodiment of the method for producing an optical compensation film according to the present invention has an orientation birefringence value of Including a plurality of types of polymer compounds having the same sign and different orientation birefringence values, when divided into a plurality of unit regions along a direction parallel to the film surface, the phase difference for light of the same wavelength is adjacent A method for producing an optical compensation film having a plurality of unit regions different from a unit region by 10 nm or more, wherein a plurality of types of polymer compounds having the same sign of orientation birefringence values and different orientation birefringence values are extruded to form a film And a stretching step for stretching the film obtained in the extrusion step, wherein the extrusion step has the same sign of the orientation birefringence value and a plurality of different orientation birefringence values. This is a method of extruding various types of polymer compounds while changing the ratio of the plurality of types of polymer compounds over time.

  In addition, the third embodiment of the method for producing an optical compensation film according to the present invention includes a plurality of types of polymer compounds having the same orientation birefringence sign and different orientation birefringence values, and is parallel to the film surface. A method for producing an optical compensation film comprising a plurality of unit regions having a phase difference of 10 nm or more from an adjacent unit region when the light is divided into a plurality of unit regions along a specific direction. An extrusion process of extruding a plurality of types of polymer compounds having the same value sign and different orientation birefringence values to form a film, and a stretching process of stretching the film obtained in the extrusion process, The extrusion process is performed by multilayer extrusion so that the ratio in the thickness direction of the plurality of types of polymer compounds contained in two adjacent unit regions in the film cross section is different. Lum inside the sign of orientation birefringence values are the same, or a method of extruding a region where the orientation birefringence values are different.

  Manufactures an optical compensation film that includes different types of phase difference and mixed unit areas with different phase differences by including multiple types of polymer compounds with the same orientation birefringence value and different orientation birefringence values. can do.

  Hereinafter, the orientation birefringence value will be described. In general, a polymer compound has the property that the main chain of the polymer compound is oriented and birefringence occurs due to stress such as tensile stress acting during stretching and shrinkage stress after thermoforming. This is because the refractive index relating to the polarization component in the direction parallel to the orientation direction of the main chain of the polymer compound subjected to the stress as described above is different from the refractive index relating to the polarization component in the direction perpendicular to the orientation direction. Is. The orientation birefringence value indicates birefringence due to orientation, and is represented by a difference between these two refractive indexes. In the present specification, (refractive index related to the polarization component in the direction parallel to the orientation direction of the main chain of the polymer compound) − (refractive index related to the polarization component in the direction perpendicular to the orientation direction of the main chain of the polymer compound) )> 0 is the positive value of the orientation birefringence when a relationship of 0 is obtained, and (refractive index relating to the polarization component in the direction parallel to the orientation direction of the main chain of the polymer compound) − (main chain of the polymer compound) The orientation birefringence value when a relationship of <refractive index regarding the polarization component in the direction perpendicular to the orientation direction> <0 is obtained is a negative value.

  For example, a uniaxially stretched polymer film will be specifically described as an example. In a polymer film in which the main chain of the polymer compound is oriented by uniaxial stretching, the stretching direction is 0 degree direction, and the angle of the direction in which the refractive index related to the polarization component is maximum in the film plane with respect to the stretching direction Is expressed as “azimuth angle of orientation birefringence”. In this case, when the direction in which the refractive index relating to the polarization component is maximum in the film plane substantially coincides with the direction parallel to the orientation direction (stretching direction) of the main chain of the polymer compound, the orientation birefringence value is obtained from the above definition. Is a positive value. The azimuth angle of orientation birefringence is almost 0 degrees. In addition, when the direction in which the refractive index relating to the polarization component is maximum in the film plane substantially coincides with the direction perpendicular to the orientation direction (stretching direction) of the polymer main chain, the orientation birefringence value is negative from the above definition. Value. The orientation birefringence azimuth is approximately 90 degrees or approximately -90 degrees (a counterclockwise angle from the stretching direction is a positive value and a clockwise angle is a negative value). Therefore, the sign (positive or negative) of the orientation birefringence value can be determined by measuring the azimuth angle of the orientation birefringence.

Further, the absolute value of the orientation birefringence value can be obtained by measuring the phase difference and the thickness from the relationship of (phase difference) = (birefringence) × (thickness). In this specification, the value obtained by dividing the phase difference (R ₀ (548) (nm)) in the direction perpendicular to the film surface measured by light having a wavelength of 548 nm by the thickness (d (nm)) of the film is oriented birefringence. The absolute value.

  Here, as a method of forming a film using a plurality of types of polymer compounds having the same orientation birefringence value and different orientation birefringence values, the orientation birefringence value has the same sign. A method of extruding a plurality of types of polymer compounds having different refractive values, and a copolymer comprising a plurality of types of polymer compounds or a plurality of types of polymer chains obtained in (II-1) above is phase-separated into a sea-island structure. A film obtained by removing a part of a polymer compound or a polymer chain from a film by dissolving or dry etching to remove only the island part has the same sign for the sea part and the orientation birefringence value. The method of stretching after impregnating materials with different orientation birefringence values, or the film obtained by the above (II-2) having a plurality of hollow regions in the film has the same sign of the orientation birefringence value There can be used a method of impregnating the materials with different orientation birefringence value.

  In addition, as the plurality of polymer compounds that can be used in the present embodiment, a plurality of types of polymer compounds selected from the polymer compounds used in the film described in the embodiment using the sandblast treatment may be used.

<Method by extruding while changing the ratio of the polymer compound over time>
In the method for producing an optical compensation film according to the present embodiment, an example of a method for forming a film by extruding a plurality of types of polymer compounds having the same sign of the orientation birefringence value and different orientation birefringence values is as follows. This is a method of extruding at least two types of polymer compounds having the same refraction value sign and different orientation birefringence values while changing the ratio of the two types of polymer compounds over time.

  That is, in the method for producing an optical compensation film according to the present embodiment, at least two types of polymer compounds having the same sign of the orientation birefringence value and different orientation birefringence values are used as a ratio of the two types of polymer compounds. When dividing into a plurality of unit regions along the direction parallel to the film surface by extruding while changing the time, a unit region whose phase difference with respect to light of the same wavelength differs by 10 nm or more from the adjacent unit region A method including an extrusion process for producing a plurality of films and a stretching process for stretching the film obtained in the extrusion process may be used.

  In the extrusion process, when two types of polymer compounds melted in the extruder are extruded into a film using a die provided at the outlet of the extruder, the ratio of the two types of polymer compounds is changed over time. Anything can be used. As a method for changing the ratio of the two types of polymer compounds over time, for example, the ratio of the two types of polymer compounds supplied to the extruder may be changed over time. For that purpose, for example, a method of alternately supplying each polymer compound to the extruder, a method of continuously supplying a certain amount of one polymer compound, and simultaneously supplying the other polymer compound intermittently, etc. are used. Can do.

  In FIG. 7, two types of polymer compounds A and B having the same sign of the orientation birefringence value and different orientation birefringence values are alternately supplied to the extruder, melted and extruded, thereby making the birefringence region. An example of the film made different for each is shown. In FIG. 7, the direction indicated by the arrow is the film extrusion direction.

  A supplied to the extruder is first extruded alone to form region a in FIG. Subsequently, B is supplied to the extruder, but since A remains in the extruder at that time, A and B are extruded together until all the remaining A is extruded, and the region b in FIG. Form. Then, after all A in the extruder has been extruded, B is extruded alone to form region c in FIG. Thereafter, when A is supplied to the extruder, A and B are similarly extruded to form the region d. Thus, the formed regions a, b, c, and d have different mixing ratios of A and B. Here, since the signs of the orientation birefringence values are the same for the polymer compounds A and B, and the orientation birefringence values are different, the optical compensation film obtained by performing the stretching treatment after extrusion is used between adjacent regions. The birefringence will be different. Therefore, if each of the regions a, b, c, d,... Is set as one unit region, the phase difference between the two adjacent unit regions will be different. Thereby, the obtained optical compensation film has a plurality of unit regions having different phase differences with respect to light of the same wavelength along a direction parallel to the film surface (light incident surface).

<Method by extruding so that the ratios in the thickness direction of the above-mentioned plural kinds of polymer compounds contained> are different>
In the method for producing an optical compensation film according to the present embodiment, another example of a method of forming a film by extruding a plurality of types of polymer compounds having the same orientation birefringence value and different orientation birefringence values, In the two adjacent unit regions in the cross section of the film by multilayer extrusion molding, the signs of the orientation birefringence values are the same in the film so that the ratio in the thickness direction of the plurality of types of polymer compounds contained is different, This is a method of extruding regions having different orientation birefringence values.

  That is, in the method for producing an optical compensation film according to this embodiment, the ratio in the thickness direction of the plurality of types of polymer compounds contained in the two adjacent unit regions in the film cross section is different by multilayer extrusion. When the film is divided into a plurality of unit regions along the direction parallel to the film surface by using a method of extruding to form regions having the same orientation birefringence value and different orientation birefringence values inside the film. In addition, an extrusion process for producing a film in which a plurality of unit areas different in phase difference by 10 nm or more from a unit area having a phase difference adjacent to light of the same wavelength exists, and a stretching process for stretching the film obtained in the extrusion process There may be.

  In the extrusion process, the sign of the orientation birefringence value is set inside the film so that the ratios in the thickness direction of the plurality of types of polymer compounds contained in the two adjacent unit regions in the film cross section are different by multilayer extrusion. Are the same, and there is no particular limitation as long as it is a method of extruding regions having different orientation birefringence values.

  In FIG. 8, the polymer compound A is formed by multilayer extrusion molding so that the ratio in the thickness direction of the two kinds of polymer compounds A and B contained in the two adjacent unit regions a and b in the film cross section is different. The birefringence varies from region to region by extruding so as to form a plurality of cores made of the polymer compound B having the same sign of the orientation birefringence value and different orientation birefringence values inside the film as the sheath. An example of such a film is shown. In FIG. 8, the direction indicated by the arrow is the film extrusion direction. Therefore, the film cross section may be a cross section perpendicular to the extrusion direction, for example.

  This film is a composite resin stream consisting of A and B in which polymer compounds A and B are melted in separate extruders, and then polymer compound A is a sheath and polymer compound B is arranged on a plurality of cores. For example, it can be formed by supplying and extruding to a die such as a T-die. Here, in order to form a composite resin flow composed of A and B in which the polymer compound A is a sheath and the polymer compound B is arranged on a plurality of cores, feeds mounted between each extruder and a die. As the block, for example, a feed block in which a plurality of feed blocks for forming a core-sheath composite resin flow are arranged can be suitably used. As a feed block for forming such a core-sheath type composite resin flow, for example, a conventionally known one having a circular cross section, a feed block described in JP-A-59-31157, or the like can be used.

  In the film thus formed, as shown in FIG. 8, the ratio of the polymer compound A and B in the thickness direction differs between the region a and the adjacent region b. Since the high molecular compound A and the high molecular compound B have the same sign of the orientation birefringence value and different orientation birefringence values, the optical compensation film obtained by performing a stretching process after extrusion is used between adjacent regions. The birefringence will be different. Therefore, if the regions a, b,... Are set as one unit region, the phase difference between the two adjacent unit regions will be different. Thereby, the obtained optical compensation film has a plurality of unit regions having different phase differences with respect to light of the same wavelength along a direction parallel to the film surface (light incident surface).

<Method by impregnating a film obtained by removing only islands with materials having different orientation birefringence values>
In the method for producing an optical compensation film according to this embodiment, a plurality of types of polymer compounds or a copolymer composed of a plurality of types of polymer chains obtained in (II-1) above are phase-separated into a sea-island structure. From the film, when there are n types of polymer compounds or polymer chains contained in the film, one or more (n-1) types of high compounds contained in the film obtained in the film forming step are used. A film obtained by removing a molecular compound or a polymer chain by dissolution treatment or dry etching treatment and removing only the island portion, or a film obtained by stretching the film, the material constituting the film and the orientation birefringence value It may be a method including an impregnation step of impregnating materials having the same sign and different orientation birefringence values, and a stretching step of stretching a film obtained in the impregnation step.

  Thereby, the material having the same birefringence value as that of the material constituting the film and the material having a different orientation birefringence value are formed in the concave portions of the film having an uneven shape obtained by removing only the island portion. As a result, the birefringence is different between adjacent regions of the obtained optical compensation film. Therefore, the phase difference is different between two adjacent unit regions, and an optical compensation film having a plurality of unit regions having different phase differences with respect to light of the same wavelength can be obtained.

  In addition, by using such a method, it is possible to fill the concave portions of the film with the same sign of arbitrary orientation birefringence values and different materials with different orientation birefringence values, so that the range of selection of materials is widened. effective. Furthermore, as a film that is phase-separated into a sea-island structure, if a film in which a block copolymer is self-assembled and micro-phase-separated into a regular sea-island structure is used, it has a highly irregular shape easily. A film can be obtained. Furthermore, for example, a block copolymer having a polystyrene structure, which is easy to produce a block copolymer, is processed into a film that is phase-separated into a sea-island structure, and then the polystyrene is removed by dry etching, and a desired material is placed in the recess. If it fills, the optical compensation film which has a desired characteristic can be manufactured easily.

  Furthermore, the method according to the present embodiment can be applied not only to a film that is microphase-separated into a sea-island structure but also to a film that is microphase-separated into a vertical (thickness) cylinder structure or a vertical lamella structure. it can. For example, by removing one polymer chain by dissolution treatment or dry etching treatment from a film formed on a substrate and microphase-separated into a vertical (thickness) cylinder structure or vertical lamella structure, respectively. A film having regular microholes or nanoholes penetrating in the thickness direction of the film, or a film in which a cylinder composed of domains of polymer chains that have not been removed forms regular protrusions on the substrate, or Thus, a film in which the domains of the polymer chains that have not been removed are arranged in a stripe pattern on the substrate is obtained. By impregnating these films or a film obtained by stretching the film with a material having the same sign of the orientation birefringence value as that of the material constituting the film and having a different orientation birefringence value, the removed domains are aligned in the orientation. It is possible to form a film in which the birefringence value has the same sign and is replaced with a material having a different orientation birefringence value.

  In the method for producing an optical compensation film according to the present embodiment, the sign of the orientation birefringence value is the same as that obtained in the above (II-2) and having a plurality of hollow regions in the film or a film obtained by stretching the film. There may be a method including an impregnation step of impregnating materials having different orientation birefringence values and a stretching step of stretching the film obtained in the impregnation step.

  As a result, a plurality of the above hollow regions existing in the film are filled with a material having the same sign of the orientation birefringence value as that of the material constituting the film and having a different orientation birefringence value. The birefringence is different between adjacent regions. Therefore, the phase difference is different between two adjacent unit regions, and an optical compensation film having a plurality of unit regions having different phase differences with respect to light of the same wavelength can be obtained.

  Here, in the impregnation step, the sign of the orientation birefringence value is the same, and the method of impregnating materials having different orientation birefringence values is not particularly limited, and the sign of the orientation birefringence value is the same, A method of impregnating the film with a melted resin having different orientation birefringence values, a method of impregnating the film with a solution of materials having the same orientation birefringence value and different orientation birefringence values, etc. Can be mentioned. In addition, films impregnated with materials having the same orientation birefringence value and different orientation birefringence values may be stretched after heating and / or drying.

(III) Wavelength dispersion of retardation of optical compensation film In the optical compensation film produced by the above method, the birefringence and / or thickness of the film is made different, and unit regions having different retardations are mixed, thereby easily. It is possible to control the wavelength dispersion of the entire retardation of the optical compensation film. Therefore, such an optical compensation film is also included in the present invention. Hereinafter, how the wavelength dispersion of the entire retardation is determined in the optical compensation film of the present invention will be described. The details of this principle are as described in the international application by the present inventors: PCT / JP2007 / 073246, and therefore will be described in a simplified manner.

  The optical compensation film of the present invention has a concavo-convex shape in which a concave portion and a convex portion that exist along a direction parallel to the film surface are repeated, and a length in the thickness direction of the film that exists in a plurality along the direction parallel to the film surface. By having a plurality of types of polymer compounds having different hollow regions and / or having the same sign of the orientation birefringence value and different orientation birefringence values, the phase difference with respect to light of the same wavelength is different from that of the adjacent unit region. It differs by 10 nm or more. Then, the fact that the wavelength dependence of the phase difference in the adjacent unit areas is different from the wavelength dependence of the combined phase difference R (λ) in the entire area including all the unit areas is used.

  In the optical compensation film having a concavo-convex shape in which a concave portion and a convex portion are repeated on the film surface, r (λ) is a phase difference of the convex portion measured with light having a wavelength λ (nm), and r ′ It is assumed that (λ) is the phase difference of the recess measured with light of wavelength λ (nm), and R (λ) is the combined phase difference in the film surface measured with light of wavelength λ (nm). In the case of an optical compensation film in which a plurality of hollow regions having different lengths in the film thickness direction exist in the film along a direction parallel to the film surface, r (λ) is a wavelength λ ( nm) is a phase difference in a region where the length in the thickness direction of the hollow region is short, and r ′ (λ) is a length in the thickness direction of the hollow region measured with light of wavelength λ (nm). Is a phase difference in a long region, and R (λ) is a combined phase difference in the film surface measured with light of wavelength λ (nm).

  The phase difference described here is a phase difference when viewed from a direction perpendicular to the light incident surface (in this specification, “phase difference” means the light incident surface unless there is an angle with respect to the light incident surface). It means the phase difference when viewed from the direction perpendicular to. The composite phase difference is a phase difference when the entire region is viewed macroscopically.

  At this time, the composite phase difference R (λ) is the average birefringence due to the phase difference between the concave portions and the convex portions, or the phase difference between the short region and the long region in the thickness direction of the hollow region. The phase difference corresponding to refraction is shown. Here, even if the phase difference is the same, different birefringence is exhibited if the wavelength of light incident thereon is different.

  For example, as a characteristic quantity indicating birefringence, a film having a phase difference re (nm) between two polarizing plates whose polarizing axes are parallel to each other (parallel Nicol state), and whose slow axis is polarized Consider the transmittance I (θ, λ) of wavelength λ (nm) when it is placed at an angle θ (rad) with the transmission axis of the plate. At this time, the transmittance is given by the following equation.

I (θ, λ) = cos4θ + sin4θ + 1/2 · cos (2πre / λ) · sin2 (2θ)
Here, when θ is π / 4 rad (= 45 °), the transmittance is given by the following equation and is represented by a trigonometric function.

I (π / 4, λ) = 1/2 + 1/2 · cos (2πre / λ)
However, the period differs depending on the wavelength. Even if the phase difference in each unit region has the same value regardless of the wavelength, the combined phase difference changes depending on the wavelength. Conversely, even if the phase difference indicates positive chromatic dispersion in each unit region, the combined phase difference may not change with wavelength. In the present specification, “positive wavelength dispersion” is a long wavelength when the phase difference measured with light of a wavelength of 548 nm is 1 and the phase difference measured with light of another wavelength is expressed as its relative value. This means that the relative value becomes smaller. On the contrary, the case where the relative value becomes large is referred to as “reverse wavelength dispersion”.

  The wavelength dependence (wavelength dispersion) of the combined phase difference is determined by the difference in phase difference between the unit regions and the area ratio of each unit region with respect to the entire region. The difference in phase difference of each unit region depends on the thickness and / or birefringence difference.

For example, when a polymer compound film having rectangular irregularities on the surface is formed of the same material, the ten-point average roughness was measured at the convex part of the film by RzJIS (μm), a contact-type film thickness meter or the like. When the average film thickness is d (μm), the birefringence of the concave portion and the convex portion is equal, and the ratio of the average magnitude of the phase difference of the unit region is expressed by the ratio of the thickness of each part. That is,
(D-RzJIS) / d = 1-RzJIS / d
It becomes. Therefore, by controlling RzJIS / d, the ratio of the phase difference between the concave portion and the convex portion can be controlled.

R (548) -R (447)> r (548) -r (447) Formula A
From the viewpoint of obtaining this relationship, the lower limit of RzJIS / d is preferably 0.05, more preferably 0.1, and even more preferably 0.15. If RzJIS / d is smaller than 0.05, the difference in phase difference between adjacent unit regions may not be sufficiently obtained, and the relationship of Formula A tends to be not obtained. The upper limit is not particularly limited as long as it is smaller than 1. When RzJIS / d = 1, since there is no single film, the upper limit needs to be smaller than 1.

  From the above, the wavelength dispersion of the composite phase difference can be easily controlled without being restricted by the material.

  Further, since the chromatic dispersion of the combined phase difference in the entire region can be controlled by the phase difference and area ratio of each unit region, there is no restriction by the material. That is, the material can be selected so that properties other than wavelength dispersion, for example, various physical properties such as glass transition temperature and photoelastic coefficient, are intended.

  For example, in the case of an optical compensation film formed in each unit region having different birefringence, the birefringence of each unit region depends on the type of polymer used when the optical compensation film is manufactured. Therefore, the birefringence of each unit region can be selected by appropriately selecting the polymer to be used. At this time, since the wavelength dispersion of the combined phase difference is determined by the phase difference and the area ratio of each unit region, it is not necessary to consider so much the wavelength dispersion of birefringence due to the single polymer used. As a result, the range of selection of the polymer to be used is expanded. Therefore, the polymer can be selected so that properties other than wavelength dispersion, for example, various physical properties such as glass transition temperature and photoelastic coefficient are intended.

  Thus, the present invention utilizes the wavelength dependence of the combined phase difference R (λ) viewed macroscopically with the entire region as one element.

A plurality of hollow regions having different lengths in the thickness direction of the film are provided along the direction parallel to the film surface in the optical compensation film or film having a concavo-convex shape in which concave and convex portions are repeated on the film surface. In the existing optical compensation film, r (λ) is a phase difference with respect to light having a wavelength of λ nm in a region where the length in the thickness direction of the convex portion or the adjacent hollow region is short, and the concave portion or the adjacent medium In the region where the length of the airspace in the thickness direction is long, the phase difference with respect to the light with the wavelength λ nm is r ′ (λ), and the combined phase difference with respect to the light with the wavelength λ nm in the entire region is R (λ). The optical compensation film of the following formulas (2), (3) and (4)
r (548) <r (447) (2)
r ′ (548) <r ′ (447) (3)
R (548) ≧ R (447) (4)
It satisfies.

  The phase difference when many polymer compounds are oriented exhibits positive wavelength dispersion. Therefore, since many numerical formulas (2) and (3) are satisfied, a large number of polymer compounds can be used, and the range of selection of materials is widened.

  On the other hand, as described above, the wavelength dependence (wavelength dispersion) of the combined phase difference R is determined by the phase difference of each unit region and the area ratio of each unit region to the entire region. It is easily controlled by appropriately selecting. And when satisfy | filling Numerical formula (4), a synthetic | combination phase difference will show reverse wavelength dispersion. That is, the optical compensation film can be used as a retardation film exhibiting reverse wavelength dispersion.

In addition, in an optical compensation film including a plurality of types of polymer compounds having the same sign of the orientation birefringence value and different orientation birefringence values, a film formed of each of the plurality of types of polymer compounds is used as a single film. When the phase difference of the axially stretched stretched product with respect to light with a wavelength of λnm is R ₀ (λ) and the combined retardation with respect to light with a wavelength of λnm in all regions is R (λ), the optical compensation film of the present invention is as follows. Equations (5) and (6)
R ₀ (548) <R ₀ (447) (5)
R (548) ≧ R (447) (6)
It satisfies.

  The phase difference when many polymer compounds are uniaxially stretched exhibits positive wavelength dispersion. Therefore, since the mathematical formula (5) is satisfied, many polymer compounds can be used, and the range of selection of materials is widened.

  On the other hand, the chromatic dispersion of the composite phase difference is determined by the phase difference difference between the unit regions and the area ratio of various unit regions to the entire region, and can be easily selected by appropriately selecting these. Be controlled. And when satisfy | filling Numerical formula (6), a synthetic | combination phase difference will show reverse wavelength dispersion. That is, the optical compensation film can be used as a retardation film exhibiting reverse wavelength dispersion.

Further, the optical compensation film of the present invention has a wavelength dependency of the synthetic retardation R (λ),
R (447) ≦ R (548) ≦ R (628)
It may satisfy.

  This makes it possible to easily realize an optical compensation film exhibiting reverse wavelength dispersion and to control the degree of wavelength dispersion. In addition, a larger inverse chromatic dispersion can be easily realized as compared with the case where the chromatic dispersion is controlled by a conventional material.

  Further, the present invention provides optical compensation for a liquid crystal display device having high image quality such as a TN (Twisted Nematic) method, a VA (Vertical Alignment) method, an IPS (In-Plane Switching) method, an OCB (Optically Compensated Birefringence) method, and the like. In the case of using a film, the retardation is generally required to be 350 nm or less. Therefore, the combined phase difference R (548) is preferably 350 nm or less.

  This makes it possible to easily realize an optical compensation film exhibiting reverse wavelength dispersion and to control the degree of wavelength dispersion. In addition, an optical compensation film exhibiting chromatic dispersion having a large slope can be easily realized in a graph with the phase difference on the vertical axis and the wavelength on the horizontal axis.

R (548) -R (447)> r (548) -r (447)
From the viewpoint of obtaining the above relationship, the difference in phase difference between adjacent unit regions is preferably a lower limit of 10 nm, more preferably a lower limit of 50 nm, and even more preferably a lower limit of 100 nm.

  Furthermore, since the optical axis of each unit region is preferably in the same direction, the variation of the optical axis is preferably within ± 5 degrees, more preferably within ± 3 degrees, and further preferably within ± 1 degree.

  The present invention can be applied to a film for compensating for birefringence caused by other configurations in various optical devices such as a liquid crystal display device.

BRIEF DESCRIPTION OF THE DRAWINGS The optical compensation film concerning one Embodiment of this invention is shown, (a) is a perspective view, (b) is a top view, (c) is sectional drawing. The optical compensation film concerning one Embodiment of this invention is shown, (a) is a perspective view, (b) is sectional drawing. It is sectional drawing of the optical compensation film concerning one Embodiment of this invention. It is a figure which shows typically an example of the manufacturing method of the optical compensation film concerning one Embodiment of this invention. It is a figure which shows typically an example of the manufacturing method of the optical compensation film concerning one Embodiment of this invention. It is sectional drawing of the optical compensation film concerning one Embodiment of this invention. It is sectional drawing of the optical compensation film concerning one Embodiment of this invention. It is sectional drawing of the optical compensation film concerning one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical compensation film 2 Unit area | region 3 Film 4 Sand blasting agent 5 Die 6 Molten resin

Claims (2)

A unit having a concave and convex shape in which concave and convex portions are repeated on the film surface, and a phase difference for light of the same wavelength is adjacent when divided into a plurality of unit regions along a direction parallel to the film surface A method for producing an optical compensation film having a plurality of unit regions different from each other by 10 nm or more,
Forming a concavo-convex shape in which concave and convex portions are repeated on the film surface;
Stretching step,
In the step of forming the concavo-convex shape, RzJIS / d is 0.05 or more and less than 1 when the ten-point average roughness is RzJIS (μm) and the average film thickness measured by the convex portion is d (μm). And a method for producing an optical compensation film, wherein an uneven shape is formed . An optical compensation film manufactured using the manufacturing method according to claim 1 .

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