JP6697216B2 - Retardation film - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a retardation film, and relates to a retardation film having an alignment film having a novel structure.

  In recent years, as a retardation film applied to a flat panel display or the like, there has been provided a retardation film that imparts a desired retardation to transmitted light by a retardation layer to ensure desired optical characteristics (for example, see Patent Document 1). ). In this type of retardation film, an alignment film is formed on the surface of a base material such as a transparent film, and the retardation layer is formed by curing the liquid crystal material in the aligned state by the alignment regulating force of the alignment film. A liquid crystal material applied to such a retardation layer usually has a positive wavelength dispersion characteristic, but in recent years, a liquid crystal material having an inverse dispersion characteristic has been proposed (for example, see Patent Documents 2 and 3). .. Here, the inverse dispersion characteristic is a wavelength dispersion characteristic with a smaller phase difference in transmitted light on the shorter wavelength side, and more specifically, a retardation (R450) at a wavelength of 450 nm and a retardation (R550) at a wavelength of 550 nm. The relationship is R450 <R550.

  Further, in the image display panel, there has been proposed a method of improving various optical characteristics such as a viewing angle characteristic and a tint by using an A plate, a C plate and the like. A device for optical compensation of an IPS liquid crystal display device using a C plate has been proposed. Here, the optical compensation is a configuration for reducing light leakage in an oblique direction from the linear polarizing plate during black display. The C plate is represented by nx = ny <nz or nx = ny> nz, where nx = ny <nz is a positive C plate and nx = ny> nz is a negative C plate. The A plate is represented by nx> ny = nz or nz = nx> ny, where nx> ny = nz is a positive A plate and nz = nx> ny is a negative A plate. Note that nx and ny (nx ≧ ny) are in-plane refractive indices, and nz is a thickness-wise refractive index.

  Among them, the positive A plate is manufactured by using a liquid crystal material having a positive wavelength dispersion characteristic and a liquid crystal material having a reverse dispersion characteristic applied to the retardation layer, and having a positive wavelength dispersion characteristic and a reverse dispersion characteristic, respectively. be able to. Further, the positive C plate can be manufactured by applying a coating liquid of a so-called C plate liquid crystal material and drying and curing the coating liquid. Further, in a vertical alignment (VA) liquid crystal display device or the like, a liquid crystal material is vertically aligned by a vertical alignment film, and various ideas for the vertical alignment film for VA liquid crystal have been proposed.

  Now, in such a retardation film, it is important to surely and exactly orient the molecules of the liquid crystal compound in the retardation layer in a predetermined direction. On the other hand, in a certain aspect, it is important to appropriately control the thickness of the alignment film, the thickness of the alignment film can be appropriately controlled, and the alignment regulating force is effectively exerted on the liquid crystal compound in the retardation layer. There is a demand for a retardation film having an alignment film having a novel structure that enables the above.

Japanese Patent Laid-Open No. 10-68816 U.S. Pat. No. 8119026 Japanese Patent Publication No. 2010-522892 Japanese Patent Publication No. 2006-520008 JP, 2005-49865, A JP, 2007-156234, A

  It is an object of the present invention to provide a retardation film having a novel alignment film. Then, in a certain aspect, it is an object to provide a retardation film capable of appropriately controlling the film thickness of the orientation film and effectively exerting an orientation regulating force on the liquid crystal compound in the retardation layer. ..

  (1) In the present invention, a base material, an alignment film, and a retardation layer are laminated in this order, and the alignment film is made of a mixed material of an ultraviolet curable resin and a thermosetting resin. Is a retardation film.

  (2) Further, the present invention is the retardation film according to the invention of (1), wherein the ultraviolet curable resin and the thermosetting resin are phase-separated in the alignment film.

  (3) Further, the present invention is the retardation film according to the invention of (1) or (2), wherein the thermosetting resin contained in the alignment film exhibits vertical alignment.

  (4) Further, in the invention according to any one of (1) to (3), the base material is subjected to a blocking prevention treatment and has irregularities, and the alignment film has a thickness of It is a retardation film having a size equal to or larger than the height of the convex portion on the surface of the base material.

  (5) Further, in the invention according to any one of (1) to (4), the retardation film is a transfer laminate for an optical film having a transfer layer, the alignment film and the retardation layer. The retardation film is characterized in that the base material and the alignment film are separated from each other by using the interface of as the separation interface.

  (6) Further, the present invention is the retardation film according to the invention of (5), wherein the transfer layer is transferred to an optical functional layer which imparts a retardation of ¼ wavelength.

  According to the present invention, it is possible to provide a retardation film having an alignment film having a novel structure. Further, in one aspect, the film thickness of the alignment film can be appropriately controlled, and the alignment regulating force can be effectively exerted on the liquid crystal compound in the retardation layer.

It is a cross-sectional schematic diagram which shows an example of a retardation film. Regarding a retardation film in which a PET base material, an alignment film formed of a mixed material of an ultraviolet curable resin and a thermosetting resin, and a liquid crystal layer are laminated, when peeled at the interface between the alignment film and the liquid crystal layer FIG. 6 is a graph showing the analysis results by X-ray photoelectron spectroscopy at the liquid crystal layer side interface (A) and the alignment film side interface (B). (A) shows a reference peak of a vertically aligned thermosetting material, and (B) is a graph showing a reference peak of a UV curable material. It is a flowchart which shows the flow of the manufacturing process of a retardation film. It is a figure for demonstrating the flow which produces an optical film by the transfer method using a retardation film as a transfer laminated body for optical films.

Hereinafter, specific embodiments of the retardation film according to the present invention (hereinafter referred to as “the present embodiment”) will be described in detail in the following order. The present invention is not limited to the following embodiments, and various modifications can be made without changing the gist of the present invention.
1. Structure of retardation film 2. Alignment film 3. 3. Method for producing retardation film Application as a transfer laminate for optical films

<< 1. Structure of retardation film ≫
FIG. 1 is a sectional view schematically showing an example of the retardation film 1 according to the present embodiment. As shown in FIG. 1, the retardation film 1 is formed by laminating a base material 11 made of a transparent film material, an alignment film 12, and a retardation layer (liquid crystal layer) 13 in this order.

  The retardation film 1 according to the present embodiment is characterized in that the alignment film 12 laminated on the base material 11 is made of a mixed material of an ultraviolet curable resin and a thermosetting resin. In the retardation film 1 as described above, the ultraviolet curable resin and the thermosetting resin are present in the alignment film 12 in a phase-separated manner. Specifically, in the alignment film 12, the thermosetting resin is unevenly distributed on the interface side between the alignment film 12 and the retardation layer 13.

  In the retardation film 1 having the novel alignment film 12 made of such a mixed material of two kinds of different resins, that is, an ultraviolet curable resin and a thermosetting resin, the ultraviolet curable resin is provided in the alignment film 12. The following retardation film can be produced by utilizing the property that the phase-separated thermosetting resin and the thermosetting resin exist. That is, as will be described later in detail, as an example, the alignment film is a vertical alignment film for effectively homeotropically aligning the molecular axes of the liquid crystal compound molecules in the retardation layer, and the alignment film has a predetermined thickness. A retardation film which is a film and can effectively suppress the occurrence of cissing of the coating liquid (the retardation layer forming coating liquid) when forming the retardation layer 13 can be obtained.

  Hereinafter, the configuration of the retardation film 1 according to the present embodiment will be sequentially described.

<1-1. Substrate>
The base material 11 has a function of supporting the alignment film 12, and is a long transparent film material. For example, when the retardation film 1 is used for transfer, the base material 11 functions as a releasable support, supports the alignment layer 12 and the retardation layer 13 for transfer, and has a surface thereof. It is preferable that the adhesive has such an adhesive strength that it can be peeled off.

  Examples of the film material that constitutes the base material 11 include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, and polyarylate, polyolefins such as polyethylene, polypropylene, and polymethylpentene, triacetyl cellulose, and acrylics. Examples thereof include polymers. The base material 11 may be a single layer made of these materials, or may be a laminated body in which two or more kinds of materials are laminated. Further, in the case of forming a laminated body of a plurality of layers, layers having the same composition may be laminated.

  The thickness of the base material 11 is not particularly limited, but is preferably in the range of 20 μm to 200 μm, for example. When the thickness of the base material 11 is less than 20 μm, it may not be possible to impart the minimum self-supporting property required for the optical film transfer laminate. On the other hand, when the thickness of the transfer laminate for optical film is 200 μm or more, when the transfer laminate for optical film is elongated, the transfer laminate for optical film is cut and processed to be a single-layer transfer laminate for optical film. In this case, the processing waste may increase or the cutting blade may wear faster.

  Here, the base material 11 may be subjected to various blocking prevention treatments. Examples of the blocking prevention treatment include an easy adhesion treatment, a treatment for preventing blocking by kneading a filler and the like, and a knurling treatment. By applying such a blocking prevention treatment to the base material 11, sticking of the base materials when winding the base material 11, so-called blocking, can be effectively prevented, and the retardation film with high productivity can be obtained. It becomes possible to manufacture.

  When the anti-blocking treatment is applied to the base material 11 in this manner, irregularities are formed on the surface of the base material 11. The height (size) of the convex portion on the surface of the substrate 11 that has been subjected to the blocking prevention treatment is not particularly limited, but is generally about 0.5 μm to 1.5 μm.

<1-2. Alignment film>
The alignment film 12 is obtained by applying the composition for an alignment film (alignment film composition) on the above-mentioned base material 11 and curing it, and develops an alignment regulating force. Here, the orientation regulating force is a function of aligning (orienting) the liquid crystal compound in a predetermined direction when a layer (retardation layer 13) made of a polymerizable liquid crystal compound (liquid crystal material) is formed on the orientation film 12. Say.

  The alignment film 12 is not particularly limited, but may be, for example, a vertical alignment film that causes homeotropic alignment (vertical alignment) of the molecular axes of the liquid crystal compound molecules in the retardation layer 13. As the vertical alignment film, various kinds of vertical alignment films applied to a VA liquid crystal display device or the like can be applied, and for example, a polyimide alignment film, an alignment film of an LB film, or the like can be applied.

  As described above, the alignment film 12 is not limited to the vertical alignment film, and may be an alignment film that causes the molecular axis of the liquid crystal compound to be homogeneously aligned (horizontal alignment). It may be an alignment film for hybrid alignment (tilt alignment).

  The solvent (diluting solvent) used in the alignment film composition is not particularly limited as long as it can dissolve the alignment material to a desired concentration, and examples thereof include hydrocarbon solvents such as benzene and hexane, methyl ethyl ketone, Ketone-based solvents such as methyl isobutyl ketone and cyclohexanone (CHN), ether-based solvents such as tetrahydrofuran, 1,2-dimethoxyethane and propylene glycol monoethyl ether (PGME), alkyl halide solvents such as chloroform and dichloromethane, methyl acetate , Ethyl acetate, butyl acetate, ester solvents such as propylene glycol monomethyl ether acetate (PGMEA), amide solvents such as N, N-dimethylformamide, sulfoxide solvents such as dimethyl sulfoxide, anone solvents such as cyclohexane, Methanol, ethanol can be exemplified an alcohol solvent such as isopropyl alcohol. Further, the solvent may be one kind or a mixed solvent of two or more kinds of solvents.

  Such an alignment film 12 is produced by applying a coating liquid of an alignment film composition containing the above-mentioned materials to the base material 11 and drying it, and then performing a predetermined curing treatment. The alignment film 12 is composed of the cured product produced in this manner.

  Here, the retardation film 1 according to the present embodiment is characterized in that the alignment film 12 is made of a mixed material of an ultraviolet curable resin and a thermosetting resin. As will be described later in detail, according to the retardation film 1 having the alignment film 12 made of such a mixed material of the ultraviolet curable resin and the thermosetting resin, the ultraviolet curable film is hardened in the film. The resin and the thermosetting resin are phase-separated, and in particular, the thermosetting resin is unevenly distributed on the interface side between the alignment film 12 and the retardation layer 13.

<1-3. Retardation layer (liquid crystal layer)>
The retardation layer (liquid crystal layer) 13 contains a polymerizable liquid crystal composition. This polymerizable liquid crystal composition contains a liquid crystal compound (rod-like compound) which exhibits liquid crystallinity and has a polymerizable functional group in the molecule.

  The liquid crystal compound has a refractive index anisotropy and has a function of imparting a desired retardation by being regularly arranged. Examples of the liquid crystal compound include materials exhibiting a liquid crystal phase such as a nematic phase and a smectic phase. However, nematic phase is preferable because it is easy to arrange regularly as compared with other liquid crystal compounds exhibiting a liquid crystal phase. It is preferable to use a material exhibiting liquid crystallinity. The liquid crystal compound exhibiting a nematic phase is preferably a material having spacers at both ends of the mesogen. Since the liquid crystal compound having spacers at both ends of the mesogen has excellent flexibility, the retardation film 1 can have excellent transparency.

  Further, for example, when the above-mentioned alignment film 12 is composed of a vertical alignment film and the liquid crystal compound is homeotropically aligned, a homeotropic liquid crystal material capable of forming homeotropic alignment is particularly preferable as the liquid crystal compound. Not limited. Examples of homeotropic liquid crystal materials include those that can form homeotropic alignment without using a vertical alignment film and those that can form homeotropic alignment by using a vertical alignment film. Either one can be preferably used.

  The liquid crystal compound is a polymerizable liquid crystal compound having a polymerizable functional group in the molecule as described above. Since the liquid crystal compound can be polymerized and fixed by having the polymerizable functional group, the alignment stability is excellent and the retardation hardly changes with time. Further, the polymerizable liquid crystal compound more preferably has a polymerizable functional group capable of three-dimensional crosslinking in the molecule. By having a three-dimensionally crosslinkable polymerizable functional group, sequence stability can be further enhanced. The term "three-dimensional cross-linking" means that liquid crystal molecules are polymerized three-dimensionally with each other to form a network structure.

  Examples of the polymerizable functional group include those that are polymerized by the action of ionizing radiation such as ultraviolet rays or electron beams, or the action of heat. Examples of these polymerizable functional groups include radically polymerizable functional groups and cationically polymerizable functional groups. Representative examples of the radically polymerizable functional group include a functional group having at least one addition-polymerizable ethylenically unsaturated double bond, and examples thereof include a vinyl group with or without a substituent and an acrylate group (acryloyl). Group, methacryloyl group, acryloyloxy group, methacryloyloxy group) and the like. Moreover, an epoxy group etc. are mentioned as a specific example of a cationically polymerizable functional group. Other examples of the polymerizable functional group include an isocyanate group and an unsaturated triple bond. Among them, a functional group having an ethylenically unsaturated double bond is preferably used from the viewpoint of the process.

  The amount of the polymerizable liquid crystal compound is not particularly limited as long as the viscosity of the retardation layer forming coating liquid (liquid crystal composition) can be adjusted to a desired value according to the coating method applied on the alignment film 12. For example, the amount in the liquid crystal composition can be in the range of about 5 to 40 parts by mass. The polymerizable liquid crystal compound may be used alone or in combination of two or more.

  The above-mentioned liquid crystal compound is usually dissolved in a solvent (diluting solvent). The solvent is not particularly limited as long as it can uniformly disperse the liquid crystal compound and the like, and examples thereof include hydrocarbon solvents such as benzene and hexane, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone (CHN). Solvents, ether solvents such as tetrahydrofuran, 1,2-dimethoxyethane, propylene glycol monoethyl ether (PGME), alkyl halide solvents such as chloroform and dichloromethane, methyl acetate, ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate (PGMEA) and other ester solvents, N, N-dimethylformamide and other amide solvents, dimethylsulfoxide and other sulfoxide solvents, cyclohexane and other anone solvents, methanol, ethanol, isopropyl It can be exemplified an alcohol solvent such as alcohol, but is not limited thereto. Further, the solvent may be one kind alone or a mixed solvent of two or more kinds.

  The amount of the solvent is not particularly limited and can be, for example, about 66 parts by mass to 900 parts by mass with respect to 100 parts by mass of the liquid crystal compound. If the amount of the solvent is less than 66 parts by mass, the liquid crystal compound may not be uniformly dissolved, which is not preferable. On the other hand, when it exceeds 900 parts by mass, a part of the solvent remains, which may reduce reliability and may not be uniformly applied, which is not preferable.

  In addition, the liquid crystal composition may contain other compounds as necessary, as long as they do not impair the alignment order of the liquid crystal compound. For example, a polymerization inhibitor, a plasticizer, a surfactant, a silane coupling agent, etc. can be mentioned.

  The thickness of the retardation layer 13 formed by applying the liquid crystal composition as described above on the alignment film 12 is not particularly limited, but in order to obtain appropriate alignment performance, it is 500 nm to It is preferably about 2000 nm.

<< 2. About alignment film ≫
(Structure of the alignment film 12)
As described above, in the retardation film 1 according to the present embodiment, the alignment film 12 is made of a mixed material of the ultraviolet curable resin and the thermosetting resin.

  In the alignment film 12 made of such a mixed material of the ultraviolet curable resin and the thermosetting resin, the ultraviolet curable resin and the thermosetting resin are phase-separated in the film of the alignment film 12. Will exist. More specifically, the ultraviolet curable resin is phase-separated on the substrate 11 side, and the thermosetting resin is phase-separated on the interface side between the alignment film 12 and the retardation layer 13. It is considered that this is because the thermosetting resin migrates more easily to the atmosphere side (comparatively hydrophobic) than the side of the substrate 11 which is relatively hydrophilic, and is more easily stabilized.

  Here, in FIG. 2, a retardation film obtained by laminating a PET substrate, an alignment film made of a mixed material of an ultraviolet curable resin and a thermosetting resin, and a retardation layer (liquid crystal layer) in this order. The results of analysis by X-ray photoelectron spectroscopy (XPS) at the liquid crystal layer-side interface and the alignment film-side interface when peeled at the interface between the alignment film and the liquid crystal layer are shown below. Specifically, in this XPS analysis, an ultraviolet (UV) curable material (referred to as “UV curable material (a)”) and a thermosetting material exhibiting vertical alignment (“thermosetting material (b)”). And a mixture material mixed in a weight ratio of 1: 100 is applied as a material for the alignment film onto a PET substrate so that the thickness of the alignment film is 3 μm. Then, the alignment film was formed by irradiating and curing with ultraviolet rays.

  As shown in the XPS analysis result of FIG. 2, the thermosetting material (in the interface of the liquid crystal layer side (FIG. 2A)) and the interface of the alignment film side (FIG. 2B) also exhibits the vertical alignment property ( It can be seen that the peak whose main component is b) is detected. Note that FIG. 3A shows the reference peak of the UV curable material (a), and FIG. 3B shows the reference peak of the thermosetting material (b) exhibiting vertical alignment.

  From this, in the alignment film composed of the mixed material of the ultraviolet curable resin and the thermosetting resin, the ultraviolet curable resin and the thermosetting resin are phase-separated in the film, and the thermosetting resin is It can be seen that the film is unevenly distributed on the interface side between the liquid crystal layer and the alignment film.

(Application Example of Retardation Film 1 Having Alignment Film 12)
By the way, generally, in the retardation film, the base material thereof is subjected to various anti-blocking treatments for winding to prevent blocking and the like. However, conventionally, when a retardation film is formed using a substrate that has been subjected to such a blocking prevention treatment, unevenness is formed on the substrate surface by the blocking prevention treatment, and an alignment film is coated on the substrate. If an alignment layer is to be formed by using the protrusions on the surface of the base material, the surface of the alignment layer (contact surface with the retardation layer) becomes uneven. When a coating liquid for forming a retardation layer containing a liquid crystal composition is applied onto the alignment layer having such unevenness and increased surface roughness (Ra), the unevenness on the surface of the alignment film is followed. As a result, the coating liquid for forming the retardation layer cannot be uniformly applied onto the alignment layer, and the alignment layer is exposed, so-called “repellency” occurs. Occurrence of coating defects such as cissing reduces the yield of the retardation film, and when a visual inspection is performed by laminating a polarizing plate on the optical film having cissing, the phase difference of the part where cissing occurs is small. As a result, defects and the like are generated, resulting in poor appearance.

  In order to solve such a conventional problem, in the present embodiment, the blocking prevention treatment is applied to the alignment film 12 made of the mixed material of the ultraviolet curable resin and the thermosetting resin. It is formed so as to have a thickness (film thickness) greater than or equal to the height of the convex portion on the surface of the base material 11. By thus forming the alignment film 12 having a film thickness equal to or larger than the height of the protrusions on the surface of the base material 11, the surface roughness of the alignment film 12 caused by the unevenness of the base material 11 is reduced. You can That is, by forming the alignment layer 12 having a predetermined film thickness or more, the unevenness of the base material 11 is embedded in the alignment film 12 and can be canceled. As a result, it is possible to effectively suppress the occurrence of cissing when the liquid crystal composition is coated on the alignment film 12.

  Here, in the retardation film, it is required to reliably align the molecules of the liquid crystal compound in the retardation layer in a desired direction. For example, the liquid crystal compound is reliably and strictly homeotropically aligned (vertical alignment). Is required. The alignment direction of the molecules of the liquid crystal compound is not limited to vertical alignment, and may be either homogeneous alignment (horizontal alignment) or hybrid alignment (tilt alignment). However, in order to align the liquid crystal compound in a desired direction, in order to form an alignment film using a thermosetting resin exhibiting the orientation in the desired direction, from the viewpoint of high viscosity of the thermosetting resin, etc. The thickness of the alignment film that can be formed only with the thermosetting resin is limited, and it is not possible to form a sufficiently thick alignment film. From this, in order to effectively suppress the occurrence of cissing when forming the retardation layer as described above, in the conventional retardation film, a film thickness equal to or higher than the height of the convex portion on the surface of the base material. Cannot be effectively formed.

  In this regard, in the retardation film 1 according to the present embodiment, as described above, by having the alignment film 12 formed of the mixed material of the ultraviolet curable resin and the thermosetting resin, repelling is prevented. In addition to being effectively suppressed, the molecules of the liquid crystal compound in the retardation layer can be reliably aligned in a predetermined direction.

  That is, for example, the thermosetting resin that constitutes the alignment film 12 is a thermosetting resin that exhibits vertical alignment that homeotropically aligns the molecular axes of the liquid crystal compound molecules in the retardation layer 13. In the retardation film 1, the alignment film 12 is made of a mixed material of an ultraviolet curable resin and a thermosetting resin having such a vertical alignment property. The curable resin is phase-separated and exists, and in particular, the thermosetting resin exhibiting vertical alignment is unevenly distributed on the interface side between the alignment film 12 and the retardation layer 13. On the other hand, since the alignment film 12 is composed of the mixed material of the ultraviolet curable resin and the thermosetting resin, the alignment film 12 having the vertical alignment property has the ultraviolet curable resin (on the base material 11 side). The film thickness of the alignment film 12 can be increased by the amount of the separated resin. That is, the thermosetting resin exhibiting vertical alignment that is unevenly distributed on the interface side between the alignment film 12 and the retardation layer 13 effectively exerts the alignment regulating force on the liquid crystal compound, and the ultraviolet curable resin allows the alignment film to be aligned. It is possible to control the film thickness of 12 to a predetermined thickness, and for example, it is possible to effectively form an alignment film having a film thickness equal to or greater than the height of the convex portion on the surface of the substrate.

  This makes it possible to effectively suppress the occurrence of cissing during coating of the liquid crystal composition as described above, and at the same time, by the thermosetting resin exhibiting vertical alignment unevenly distributed on the retardation layer 13 side, The liquid crystal compound in the liquid crystal layer formed on the alignment film 12 can be reliably and strictly homeotropically aligned.

  It should be noted that the use example of the retardation film 1 having such an alignment film 12 is merely an example and is not limited to this.

(UV curable resin material)
The ultraviolet curable resin material forming the alignment film 12 is not particularly limited as long as it can be cured by irradiation with ultraviolet rays, and examples thereof include acrylate-based and methacrylate-based monomers, prepolymers, or these. It is possible to use a mixture obtained by adding a photopolymerization initiator such as acetophenone, benzophenone, or aromatic iodonium to the mixture.

  More specifically, for example, trimethylolpropane tri (meth) acrylate, hexanediol (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipenta Resins such as erythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate and neopentyl glycol di (meth) acrylate can be used.

(Thermosetting resin material)
As described above, the thermosetting resin forming the alignment film 12 is a component that becomes unevenly distributed in the alignment film 12 on the interface side between the alignment film 12 and the retardation layer 13. Therefore, the thermosetting resin affects the orientation of the molecules of the liquid crystal compound in the retardation layer 13 and the like. From this, the thermosetting resin is not particularly limited as long as it can be cured by heat, but in order to exert the alignment regulating force for aligning the liquid crystal compound of the retardation layer 13 in a desired direction. It is preferable to select the most suitable resin.

  For example, in order to vertically align the liquid crystal compound, it is preferable to select a thermosetting resin exhibiting vertical alignment. Specifically, the thermosetting resin exhibiting vertical alignment property is not particularly limited as long as it can be cured by heat to cause homeotropic alignment of the liquid crystal compound, and examples thereof include thermosetting polyimide and long-chain alkyl. Examples thereof include a polyamic acid having a group or an alicyclic structure in its side chain. Further, as the thermosetting resin material exhibiting vertical orientation, for example, lecithin, a silane-based surfactant, a titanate-based surfactant, a pyridinium salt-based polymer surfactant, n- A silane coupling agent such as octadecyltriethoxysilane can also be mixed.

  Note that the orientation direction of the molecules of the liquid crystal compound is not limited to vertical orientation, and may be homogeneous orientation (horizontal orientation) or hybrid orientation (tilted orientation), and exhibits the orientation to orient in the desired direction. It is preferable to select a thermosetting resin.

(Mixing ratio of UV curable resin material and thermosetting resin material)
The mixing ratio of the ultraviolet curable resin material and the thermosetting resin material in the mixed material forming the alignment film 12 is not particularly limited, but the weight ratio of the ultraviolet curable resin material 100 to the ultraviolet curable resin material 100 is set to that of the thermosetting resin material. The resin materials are preferably mixed in a ratio of 0.1-10, more preferably 1-5.

  Regarding this mixing ratio, when the mixing amount of the thermosetting resin material is less than 0.1 with respect to the ultraviolet curable resin material 100 in weight ratio, the alignment regulating force in the alignment film becomes weak and the retardation layer. There is a possibility that the liquid crystal compound in 13 cannot be sufficiently oriented in a predetermined direction. On the other hand, when the mixing amount of the thermosetting resin material is more than 10 with respect to the ultraviolet curable resin material 100 in a weight ratio, the mixed material becomes turbid and gels, which is effective on the substrate. There is a possibility that it cannot be applied and an alignment film that exhibits the desired effect cannot be formed.

<< 3. Method of manufacturing retardation film >>
Next, a method for manufacturing the retardation film 1 will be described. FIG. 4 is a flowchart showing a flow of manufacturing steps of the retardation film 1. In the following description of the manufacturing method, the case where the alignment film 12 is composed of a vertical alignment film will be described as an example, but the present invention is not limited to this.

  As shown in FIG. 4, in the production of the retardation film 1, first, a base material 11 such as a PET film is provided from a long film wound on a roll (S1).

  Next, in the alignment film forming step (S2), the coating liquid (alignment film composition) for forming the alignment film is applied onto the base material 11 fed from the roll, dried and then cured. Thereby, the alignment film 12 is formed on the base material 11. At this time, in the present embodiment, an alignment film composition composed of a mixed material of an ultraviolet curable resin and a thermosetting resin is applied onto the base material 11, dried, and then exposed to ultraviolet rays. And then cured to form the alignment film 12. The thermosetting resin in the mixed material forming the alignment film 12 can be effectively cured by the heat accompanying the irradiation of ultraviolet rays.

  Next, in the retardation layer forming step (S3), a coating liquid of a liquid crystal composition containing a liquid crystal compound (a retardation layer forming coating liquid) is applied onto the alignment film 12. Then, the retardation layer (liquid crystal layer) 13 is formed by drying and curing by irradiation with ultraviolet rays or the like. Before the ultraviolet irradiation process, a leveling process for making the layer thickness of the retardation layer 13 uniform may be performed.

  Here, in the present embodiment, as described above, the orientation film 12 is formed by applying the orientation film composition composed of the mixed material of the ultraviolet curable resin and the thermosetting resin on the base material 11. Is formed. That is, the alignment film 12 is made of a mixed material of an ultraviolet curable resin and a thermosetting resin. In such an alignment film 12, the ultraviolet curable resin and the thermosetting resin are present in a phase-separated state in the film, and in particular, the thermosetting resin is aligned with the alignment film 12 and the retardation layer 13. It becomes unevenly distributed on the interface side with.

  In this way, a laminated body film in which the substrate 11 / alignment film 12 / retardation layer 13 is laminated in this order is manufactured, and the obtained film is wound up by a take-up reel or the like, and then a desired size is obtained. The cutting process is carried out. The retardation film 1 is manufactured through these steps.

  The method for applying the alignment film composition on the base material 11 and the method for applying the retardation layer forming coating liquid on the alignment film 12 are not particularly limited, and examples thereof include die coating. Method, gravure coating method, reverse coating method, knife coating method, dip coating method, spray coating method, air knife coating method, spin coating method, roll coating method, printing method, immersion pulling method, curtain coating method, casting method, bar A coating method, an extrusion coating method, an E-type coating method or the like can be used.

<< 4. Application as a transfer laminate for optical films >>
Now, as an optical film applied to a flat panel display or the like, for example, a transfer laminate for an optical film having a transfer layer transferred to an optical functional layer such as a linear polarizing plate having a function as a linear polarizing plate is used. It can be produced by a transfer method. The transfer method is, for example, when a desired layer is formed on a predetermined base material, the desired layer is not directly formed on the base material, but is temporarily released from a releasable support (support The base material to be finally laminated with the layer formed on the support according to the process, demand, etc. This is a method of forming a desired layer on a predetermined base material by adhering and laminating on a (transferred base material) and then peeling and removing the support. It is considered that an optical film having a small overall thickness can be provided by producing an optical film by such a transfer method. The optical film produced by the transfer method is described in Patent Document 5 and Patent Document 6, for example.

  The retardation film 1 according to the present embodiment can be applied as an optical film transfer laminate used when an optical film is produced by a transfer method. As described above, the transfer laminate for an optical film includes a retardation layer or the like constituting the retardation film, a base material having releasability (releasing base material) or an alignment film and any other base material. Is used to form a retardation layer on the arbitrary substrate. In the transfer laminate for an optical film, for example, an optical functional layer of a linear polarizing plate, an inverse dispersion stretched film, or a laminate of a λ / 2 retardation plate and a λ / 4 retardation plate, etc. The transfer layer can be transferred by bonding it to an optical functional layer or the like that gives a phase difference of four wavelengths. In addition, in such a transfer laminate for an optical film, although not particularly limited, for example, the interface between the alignment film 12 and the retardation layer 13 serves as a peeling interface, and when the optical film is produced, the transfer laminate for an optical film is formed. After transferring the transfer layer (retardation layer 13) to a substrate such as a reverse dispersion stretched film, the substrate 11 and the alignment film 12 are peeled from the retardation layer 13.

  More specifically, a method for producing an optical film by a transfer method using the retardation film 1 according to the present embodiment as a transfer laminate for an optical film will be described. In addition, below, the transfer laminate for optical films is demonstrated as "transfer laminate 1A for optical films."

  FIG. 5 shows an optical film obtained by transferring the transfer layer of the optical film transfer laminate 1A to an optical functional layer that imparts a phase difference of 1/4 wavelength to transmitted light using the optical film transfer laminate 1A. It is a figure which shows the flow of the process at the time of manufacturing. Note that FIG. 5 is a diagram showing a cross section of the film, and is a diagram showing the flow of the process while showing the layer structure of the film in each process. The layer structure of the film is not limited to this.

  First, as shown in FIG. 5A, an alignment film 12 made of, for example, a vertical alignment film is formed on a substrate 11 made of a PET film or the like, and a phase difference containing a liquid crystal composition is formed on the alignment film 12. The layer forming coating liquid is applied to form the retardation layer (liquid crystal layer) 13 to prepare the optical film transfer laminate 1A. Here, as described above, in the production of the optical film transfer laminate 1A, the alignment film 12 is formed by using the alignment film composition made of the mixed material of the ultraviolet curable resin and the thermosetting resin. There is.

  Next, as shown in FIG. 5B, an adhesive layer 21 containing, for example, a UV adhesive is formed on the retardation layer 13 of the produced optical film transfer laminate 1A, and the adhesive layer 21 is formed on the adhesive layer 21. Then, for example, the reverse dispersion stretched film 22 is formed, and the optical film transfer laminate 1A is transferred.

  As the adhesive layer 21, various adhesives such as an ultraviolet curable resin, a thermosetting resin, and a pressure sensitive adhesive can be widely applied. Among them, ultraviolet rays (UV) are used from the viewpoint of reducing the overall thickness. It is preferable to apply a curable resin to form a UV adhesive layer. In this case, an adhesive layer having a thickness of about 1 μm can be produced. An adhesive layer may be applied to the adhesive layer 21.

  In addition, although it is not particularly limited as long as it plays a role as a retardation layer for a quarter-wave plate, for example, a stretched film having reverse dispersion characteristics (hereinafter, also referred to as “reverse dispersion stretched film 22”) is formed on the adhesive layer 21. Can be formed. This reverse dispersion stretched film 22 is formed of, for example, a PC (polycarbonate) film stretched in the longitudinal direction, the transverse direction, or obliquely stretched in a desired direction, and the slow axis is relative to the absorption axis of the linear polarizing plate. Are arranged so as to form an angle of about 45 degrees, and play a role as a retardation layer for a 1/4 wavelength plate that imparts a retardation of 1/4 wavelength to transmitted light. By using such a reverse dispersion stretched film 22, for example, the constitution of the base material, the resin layer for the quarter-wave plate, and the alignment film for the quarter-wave plate can be omitted. The layer thickness can be reduced.

  The reverse dispersion stretched film 22 is laminated on the transfer laminate for optical film 1A and transferred, and then, as shown in FIG. 5C, the base material 11 and the alignment film 12 of the transfer laminate for optical film 1A are peeled off. To do. The transfer laminate 1A for optical film is a base material that plays a role as a releasable support in order to transfer the transfer layer (retardation layer 13) to another base material (polymer film or the like) in this manner. 11 and the alignment film 12 are peeled off. The base material 11 and the alignment film 12 may be peeled off after laminating a linear polarizing plate described later.

  Then, when the base material 11 and the alignment film 12 of the optical film transfer laminate 1A are peeled off, next, as shown in FIG. 5D, a linear polarizing plate having an adhesive layer 31 is laminated.

  As the linear polarizing plate, an optical functional layer is arranged after the lower surface side of a base material 34 made of a transparent film such as TAC (triacetyl cellulose) is saponified. The base material 34 includes methyl poly (meth) acrylate, poly (meth) butyl acrylate, methyl (meth) acrylate-butyl (meth) acrylate copolymer, methyl (meth) acrylate-styrene copolymer. It is also possible to apply a resin such as an acrylic resin for coalescing, a glass such as soda glass, potassium glass, lead glass, and quartz glass.

  The optical functional layer is a portion that has an optical function as a linear polarizing plate, and for example, a layer in which a polarizer 33 and a transparent protective film (base material) 32 made of an acrylic resin or the like are sequentially laminated is used. You can Such a linear polarizing plate is attached to the reverse dispersion stretched film 22 via the adhesive layer 31.

  By using the retardation film 1 as a transfer laminate for an optical film based on the above steps, an optical film can be easily produced based on the transfer method.

  As described above, it is assumed that the optical film transfer laminate 1A has the alignment film 12 composed of the vertical alignment film, and the reverse layer is formed on the retardation layer 13 of the optical film transfer laminate 1A with the adhesive layer 21 interposed therebetween. By stacking the dispersion stretched film 22 and providing a linear polarizing plate having the polarizer 33 sandwiched between the base materials 32 and 34 made of transparent films on the reverse dispersion stretched film 22, it is possible to easily and highly productively. Therefore, an optical film having a positive C plate having a reverse dispersion characteristic can be obtained.

  Further, in the above-described example, the case where the base material 11 and the alignment film 12 are separated after transfer is described by taking the interface between the alignment film 12 and the retardation layer 13 as the separation interface, but the separation interface is not limited to this. Instead, the interface between the base material 11 and the alignment film 12 may be used as a peeling interface, and only the base material 11 may be peeled off after transfer to transfer the alignment film 12 and the retardation layer 13 to another base material.

DESCRIPTION OF SYMBOLS 1 Retardation film 1A Transfer laminate for optical film 11 Base material 12 Alignment film 13 Retardation layer (liquid crystal layer)

Claims (4)

The base material, the alignment film, and the retardation layer are laminated in this order,
The alignment film is composed of a cured product of a mixed material of an ultraviolet curable resin and a thermosetting resin for vertically aligning a liquid crystal compound ,
The material of the thermosetting resin is a polyamic acid having a long chain alkyl group or an alicyclic structure in its side chain, or the thermosetting resin is a thermosetting polyimide,
In the alignment film, the cured product of the ultraviolet curable resin is phase-separated on the base material side, and the cured product of the thermosetting resin is phase-separated on the interface side between the alignment film and the retardation layer. Retardation film. The base material has an unevenness by being subjected to a blocking prevention treatment,
The retardation film according to claim 1, wherein the thickness of the alignment layer, characterized in that the height or the size of the convex portion of the surface of the substrate. The retardation film is a transfer laminate for an optical film having a transfer layer,
The retardation film according to claim 1 or 2 , wherein the base material and the alignment film are peeled from the retardation layer by using an interface between the alignment film and the retardation layer as a peeling interface. The retardation film according to claim 3 , wherein the transfer layer is transferred to an optical functional layer that imparts a retardation of ¼ wavelength.

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