JPWO2017150313A1 - Depolarizing film and method for producing the same - Google Patents

Abstract

  A substrate film, and a depolarization layer formed on at least one surface of the substrate film and having a function of converting linearly polarized light into partially polarized light or non-polarized light, wherein the depolarizing layer is a liquid crystalline compound. Alternatively, the liquid crystal compound includes an alignment fixing compound, the base film includes a surface treatment layer into which oxygen atoms are introduced, and the surface treatment layer and the depolarization layer are in direct contact with each other. the film.

Description

  The present invention relates to a depolarizing film and a method for producing the same.

  Patent Document 1 describes a depolarizing film using a liquid crystal compound. In Patent Document 1, a depolarization layer formed by applying a coating liquid containing a liquid crystalline compound on the surface of a transparent resin film that has not been subjected to an alignment treatment is a linearly polarized light that is partially polarized or non-polarized. It describes that it can exhibit the depolarization function of converting to.

JP2011-257479A

  However, when the inventor has verified the technique described in Patent Document 1, when a depolarizing film is manufactured by the method described in Patent Document 1, it may be difficult to exhibit the depolarizing function uniformly in the plane. found. Specifically, in the depolarization film manufactured by the method described in Patent Document 1, a part of the surface of the depolarization layer does not have the depolarization function or is inferior in the depolarization function. There was a thing.

  The present invention has been made in view of the above-mentioned problems, and has as its first object to provide a depolarizing film that can uniformly exhibit a depolarizing function in a plane and a manufacturing method thereof.

  When the resin film is stretched, various advantages such as improvement in mechanical strength and reduction in thickness can be obtained. Therefore, a technique for producing a depolarizing film using a stretched transparent resin film is required. However, when the resin film is stretched, the polymer molecules contained in the resin film are usually oriented in the stretching direction. And the surface of the resin film in which the polymer molecules are aligned in this way can express an alignment regulating force that can align the liquid crystalline compound on the surface. As described above, since the stretching process is a kind of orientation process, it is difficult to obtain a depolarizing film using the stretched film as the transparent resin film in the technique described in Patent Document 1.

  In addition, when the resin film is stretched, usually, a large in-plane retardation Re is expressed by orienting polymer molecules contained in the resin film. However, when a depolarizing film is to be provided in a liquid crystal display device, if the depolarizing film includes a transparent resin film having a large in-plane retardation Re, an image is displayed by being transmitted through the transparent resin film. The polarization state of the polarization changes, and the image may cause unintentional coloring. Therefore, when the depolarizing film includes a stretched film, the in-plane retardation Re of the stretched film is desirably small.

  The second object of the present invention is to provide a depolarizing film including a stretched film having a small in-plane retardation Re and a method for producing the same.

The inventor has intensively studied to solve the above problems. As a result, the present inventor can exhibit the depolarization function uniformly in the plane by providing a depolarization layer containing a liquid crystalline compound or an alignment fixing compound on the surface of the film into which oxygen has been introduced by the surface treatment. The inventors have found that a depolarizing film can be obtained and completed the present invention.
That is, from the viewpoint of achieving the first invention, the present invention is as follows.

[1] A base film, and a depolarization layer formed on at least one surface of the base film, and having a function of converting linearly polarized light into partially polarized light or non-polarized light,
The depolarizing layer includes a liquid crystal compound or an alignment fixing compound of the liquid crystal compound,
The base film includes a surface treatment layer into which oxygen atoms are introduced,
The depolarization film in which the surface treatment layer and the depolarization layer are in direct contact.
[2] The depolarizing film according to [1], wherein the amount of oxygen atoms introduced into the surface treatment layer is 5 atom% to 20 atom%.
[3] The depolarizing film according to [1] or [2], wherein the in-plane retardation of the substrate film is 30 nm or less.
[4] The base film is selected from the group consisting of an alicyclic structure-containing polymer and a block copolymer having an aromatic vinyl compound hydride unit (a) and a diene compound hydride unit (b). The depolarizing film according to any one of [1] to [3], including at least one polymer.
[5] The depolarizing film according to any one of [1] to [4], wherein the base film is a stretched film.
[6] The depolarizing film according to any one of [1] to [5], which is a long film.
[7] A step of performing a surface treatment for introducing oxygen atoms on at least one surface of the pre-treatment film;
Applying a coating liquid containing a liquid crystalline compound to the surface subjected to the surface treatment to form a depolarization layer,
The method for producing a depolarizing film, wherein the depolarizing layer has a function of converting linearly polarized light into partially polarized light or non-polarized light.
[8] The method for producing a depolarizing film according to [7], wherein the surface treatment is a corona treatment.

Further, from the viewpoint of achieving the second object, the present invention is as follows.
[9] A base film, and a depolarization layer formed on at least one surface of the base film, and having a function of converting linearly polarized light into partially polarized light or non-polarized light,
The depolarizing layer includes a liquid crystal compound or an alignment fixing compound of the liquid crystal compound,
The base film is a stretched film,
The depolarization film whose in-plane retardation of the said base film is 30 nm or less.
[10] The depolarizing film according to [9], wherein the base film includes a block copolymer having an aromatic vinyl compound hydride unit (a) and a diene compound hydride unit (b).
[11] The base film includes a surface treatment layer into which oxygen atoms are introduced,
The depolarizing film according to [9] or [10], wherein the surface treatment layer and the depolarizing layer are in direct contact with each other.
[12] The depolarizing film according to [11], wherein the amount of oxygen atoms introduced into the surface treatment layer is 5 atom% to 20 atom%.
[13] The depolarizing film according to any one of [9] to [12], wherein the haze is 15% or less.
[14] Stretching the film before stretching to obtain a base film;
Applying a surface treatment for introducing oxygen atoms to at least one surface of the base film;
Applying a coating liquid containing a liquid crystalline compound to the surface subjected to the surface treatment to form a depolarizing layer, and
The method for producing a depolarizing film, wherein the depolarizing layer has a function of converting linearly polarized light into partially polarized light or non-polarized light.

ADVANTAGE OF THE INVENTION According to this invention, the depolarization film which can exhibit a depolarization function uniformly in a surface, and its manufacturing method can be provided.
Or according to this invention, the depolarizing film provided with the stretched film with small in-plane retardation Re, and its manufacturing method can be provided.

FIG. 1 is a cross-sectional view schematically showing a depolarizing film according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing a depolarizing film according to the second embodiment of the present invention.

  Hereinafter, the present invention will be described in detail with reference to embodiments and examples. However, the present invention is not limited to the following embodiments and exemplifications, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof.

  In the following description, retardation represents in-plane retardation Re unless otherwise specified. The in-plane retardation Re of a certain film is a value represented by Re = (nx−ny) × d unless otherwise specified. Here, nx represents a refractive index in a direction (in-plane direction) perpendicular to the thickness direction of the film and giving a maximum refractive index. ny represents the refractive index in the in-plane direction of the film and perpendicular to the nx direction. d represents the thickness of the film. The measurement wavelength is 550 nm unless otherwise specified.

  In the following description, the “polarizing plate” includes not only a rigid member but also a flexible member such as a resin film, unless otherwise specified.

[1. Description of First Embodiment of the Present Invention]
Hereinafter, a first embodiment of the present invention will be described.

[1.1. Overview of depolarization film according to first embodiment]
FIG. 1 is a cross-sectional view schematically showing a depolarizing film 10 according to the first embodiment of the present invention.
As shown in FIG. 1, the depolarizing film 10 according to the first embodiment of the present invention includes a base film 100 and a depolarizing layer 200 formed on at least one surface 100U of the base film 100. The depolarizing layer 200 is a layer having a function of converting linearly polarized light into partially polarized light or non-polarized light (that is, a depolarizing function). Therefore, the depolarization layer 200 can convert at least a part or all of the linearly polarized light L1 incident on the depolarization layer 200 into partially polarized light or non-polarized light L2 and emit it.

  “Polarized light” refers to light whose electric field vibrates only in a specific direction, and is classified into linearly polarized light, circularly polarized light, and elliptically polarized light. “Linearly polarized light” represents light in which the vibration direction of the electric field is constant in one direction, and “circularly polarized light” represents light that draws a circle as the vibration of the electric field propagates. Further, “elliptical polarized light” is light that is in an intermediate state between linearly polarized light and circularly polarized light, and the vibration of the electric field draws an ellipse with respect to time.

  On the other hand, “non-polarized light” refers to light having no regularity that can be observed in the electric field component. In other words, non-polarized light is random light in which no dominant specific polarization state is observed. Further, “partially polarized light” refers to light in a state between polarized light and non-polarized light, and means light in which at least one of linearly polarized light, circularly polarized light, and elliptically polarized light is mixed with non-polarized light. Since the depolarization layer 200 has a function of converting linearly polarized light into partially polarized light or non-polarized light, when the light emitted from the depolarized layer 200 is partially polarized light, the partially polarized light is usually not linearly polarized light and non-polarized light. Often the light is mixed with polarized light.

  In addition, the layer having the function of converting linearly polarized light into partially polarized light has a degree of polarization of linearly polarized light having a degree of polarization of 99.90% or more when evaluated by the method described in Examples described later. It means a layer that can be reduced to less than 0.000%. Further, a layer having a function of converting linearly polarized light into non-polarized light has a degree of polarization of linearly polarized light having a degree of polarization of 99.90% or more when evaluated by the method described in Examples described later. Means a layer that can be reduced to less than 0%. Further, the degree of polarization means a degree of polarization that has been corrected for visibility by a two-degree field of view (C light source) of JIS Z 8701, unless otherwise specified.

  In general, a decrease in the degree of polarization can be observed not only when linearly polarized light is converted into partially polarized light or non-polarized light but also when linearly polarized light is converted into circularly polarized light or elliptically polarized light. However, the depolarization function of the depolarization layer 200 is distinguished from the function of converting linearly polarized light into circularly polarized light or elliptically polarized light. Whether the decrease in the degree of polarization is due to conversion to partially polarized light or non-polarized light, or due to conversion to circularly polarized light or elliptically polarized light can be determined by the determination method described in the examples described later. When the depolarization film 10 is evaluated using the determination method, it is determined that the degree of polarization is reduced due to conversion to partially polarized light or non-polarized light.

  The depolarizing layer 200 includes a liquid crystal compound or an alignment fixing compound of the liquid crystal compound. Here, the alignment fixing compound of a liquid crystalline compound means a compound in which the alignment state of the liquid crystalline compound is fixed, and examples thereof include a polymer obtained by polymerizing a liquid crystalline compound. The depolarizing layer 200 usually includes a large number of micro liquid crystal domains composed of a plurality of liquid crystal compounds having alignment states or alignment fixing compounds thereof. The alignment state of these liquid crystal domains is usually random. Therefore, the alignment states of the liquid crystal domains cancel each other, so that the depolarization layer 200 can be a non-aligned layer (that is, a layer having no orientation) from a macro viewpoint.

  In the depolarization layer 200 including the liquid crystal domains having a random alignment state as described above, since the alignment state of the liquid crystalline compound is random or almost random from a macro viewpoint, an electric field of linearly polarized light incident on the depolarization layer 200 is obtained. Randomness can be imparted to some or all of the components. Therefore, the depolarization layer 200 can exhibit a depolarization function that converts part or all of the linearly polarized light incident on the depolarization layer 200 into partially polarized light or non-polarized light. The liquid crystal alignment structure of the depolarizing layer 200 is clearly distinguished from a λ / 4 wavelength plate that converts linearly polarized light into circularly polarized light or elliptically polarized light because the entire liquid crystalline compound is aligned in one direction. The

  Furthermore, in the depolarization film 10, the base film 100 includes a surface treatment layer 110 into which oxygen atoms are introduced, and the surface treatment layer 110 and the depolarization layer 200 are in direct contact with each other. Since oxygen atoms are introduced, the abundance ratio of the oxygen element in the surface treatment layer 110 is usually larger than the layer portion 120 of the base film 100 other than the surface treatment layer 110. Further, that the surface treatment layer 110 and the depolarization layer 200 are in direct contact means that there is no other layer between the surface treatment layer 110 and the depolarization layer 200.

  Since the base film 100 includes the surface treatment layer 110 into which oxygen atoms are introduced, and the surface treatment layer 110 and the depolarization layer 200 are in direct contact with each other, the depolarization film 10 has a depolarization function. Can be exhibited uniformly in the plane. According to the present inventor, the mechanism for obtaining such an effect is assumed as follows. However, the technical scope of the present invention is not limited by the following description of the mechanism.

  In the technique described in Patent Document 1, a depolarizing layer is formed by applying a coating liquid containing a liquid crystalline compound to the surface of a transparent resin film that has not been subjected to an alignment treatment such as a rubbing treatment. However, in general, even if the transparent resin film is not subjected to an alignment treatment, molecules contained in the transparent resin film can be aligned on the surface of the transparent resin film. For example, in general, when a transparent resin film is transported, the transparent resin film contacts a member such as a transport roll. Moreover, when winding a elongate transparent resin film in roll shape, the laminated | stacked transparent resin films contact. Since the friction force is generated by these contacts, the molecules on the surface of the transparent resin film can be oriented by the friction force. In particular, depending on factors such as film vibration during conveyance and roll shape during winding, the contact pressure at the time of contact may increase momentarily. The degree of molecular orientation on the surface of the resin film is increased. The surface on which the molecules are aligned generally has an alignment regulating force that can align the liquid crystalline compound on the surface. Therefore, the liquid crystalline compound in the coating liquid applied to the surface of the transparent resin film is partially oriented, and a part of the surface of the depolarization layer does not have a depolarization function or polarized light. In some cases, the resolution function was inferior.

  On the other hand, in the depolarizing film 10 shown in FIG. 1, the base film 100 includes a surface treatment layer 110 into which oxygen atoms are introduced by a surface treatment such as a corona treatment. In such a surface treatment layer 110, the orientation state of molecules is uniformly disturbed by introducing oxygen atoms. Therefore, when a coating liquid containing a liquid crystal compound is applied to the surface treatment layer 110, the liquid crystal compound is difficult to align with regularity. Therefore, since the depolarization layer 200 which has the liquid crystal domain which has a random orientation state uniformly in a plane is formed, the depolarization film 10 can exhibit a depolarization function uniformly in a plane.

[1.2. Base film of depolarizing film according to first embodiment]
[1.2.1. Composition of base film]
As the base film, a resin film is usually used. As the resin, a thermoplastic resin is preferable. Therefore, the base film is preferably a resin film containing a thermoplastic polymer and optional components as necessary.

  Examples of the polymer include an alicyclic structure-containing polymer, cellulose ester, polyvinyl alcohol, polyimide, polycarbonate, polysulfone, polyethersulfone, epoxy polymer, polystyrene, acrylic polymer, methacrylic polymer, polyethylene, polypropylene, and the like. Is mentioned. Moreover, a polymer may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  The polymer contained in the base film is selected from the group consisting of alicyclic structure-containing polymers and block copolymers having aromatic vinyl compound hydride units (a) and diene compound hydride units (b). At least one polymer is preferred. In the following description, a block copolymer having an aromatic vinyl compound hydride unit (a) and a diene compound hydride unit (b) may be referred to as a “specific block copolymer” as appropriate.

Hereinafter, the alicyclic structure-containing polymer will be described.
The alicyclic structure-containing polymer is a polymer in which the structural unit of the polymer has an alicyclic structure. The alicyclic structure-containing polymer is, for example, a polymer having an alicyclic structure in the main chain, a polymer having an alicyclic structure in the side chain, a polymer having an alicyclic structure in the main chain and the side chain, In addition, a mixture of any two or more of these may be used. Among these, from the viewpoint of mechanical strength and heat resistance, a polymer having an alicyclic structure in the main chain is preferable.

  Examples of the alicyclic structure include a saturated alicyclic hydrocarbon (cycloalkane) structure and an unsaturated alicyclic hydrocarbon (cycloalkene, cycloalkyne) structure. Among these, from the viewpoint of mechanical strength and heat resistance, a cycloalkane structure and a cycloalkene structure are preferable, and a cycloalkane structure is particularly preferable.

  The number of carbon atoms constituting the alicyclic structure is preferably 4 or more, more preferably 5 or more, preferably 30 or less, more preferably 20 or less, particularly preferably per alicyclic structure. Is 15 or less. When the number of carbon atoms constituting the alicyclic structure is within this range, the mechanical strength, heat resistance and moldability of the base film are highly balanced.

  In the alicyclic structure-containing polymer, the proportion of the structural unit having an alicyclic structure is preferably 55% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight or more. When the ratio of the structural unit having an alicyclic structure in the alicyclic structure-containing polymer is in this range, the transparency and heat resistance of the base film are improved.

  Among the alicyclic structure-containing polymers, preferred are norbornene polymers, monocyclic olefin polymers, cyclic conjugated diene polymers, vinyl alicyclic hydrocarbon polymers, and hydrides thereof. Can be mentioned. Among these, norbornene-based polymers are particularly suitable because of their good transparency and moldability.

  Examples of the norbornene-based polymer include a ring-opening polymer of a monomer having a norbornene structure and a hydride thereof; an addition polymer of a monomer having a norbornene structure and a hydride thereof. Examples of a ring-opening polymer of a monomer having a norbornene structure include a ring-opening homopolymer of one kind of monomer having a norbornene structure and a ring-opening of two or more kinds of monomers having a norbornene structure. Examples thereof include a copolymer and a ring-opening copolymer of a monomer having a norbornene structure and an arbitrary monomer copolymerizable therewith. Furthermore, examples of the addition polymer of a monomer having a norbornene structure include an addition homopolymer of one kind of monomer having a norbornene structure and an addition copolymer of two or more kinds of monomers having a norbornene structure. And addition copolymers of a monomer having a norbornene structure and an arbitrary monomer copolymerizable therewith. Examples of these polymers include polymers disclosed in Japanese Patent Application Laid-Open No. 2002-321302. Among these, a hydride of a ring-opening polymer of a monomer having a norbornene structure is particularly suitable from the viewpoints of transparency, moldability, heat resistance, low hygroscopicity, dimensional stability, lightness, and the like. .

Examples of the monomer having a norbornene structure include bicyclo [2.2.1] hept-2-ene (common name: norbornene), tricyclo [4.3.0.1 ^2,5 ] deca-3,7. -Diene (common name: dicyclopentadiene), 7,8-benzotricyclo [4.3.0.1 ^2,5 ] dec-3-ene (common name: methanotetrahydrofluorene), tetracyclo [4.4. 0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene (common name: tetracyclododecene) and derivatives of these compounds (for example, those having a substituent in the ring). Here, examples of the substituent include an alkyl group, an alkylene group, and a polar group. Moreover, these substituents may be the same or different, and a plurality thereof may be bonded to the ring. One type of monomer having a norbornene structure may be used alone, or two or more types may be used in combination at any ratio.

  Examples of the polar group include heteroatoms and atomic groups having heteroatoms. Examples of the hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, and a halogen atom. Specific examples of polar groups include carboxyl groups, carbonyloxycarbonyl groups, epoxy groups, hydroxyl groups, oxy groups, ester groups, silanol groups, silyl groups, amino groups, amide groups, imide groups, nitrile groups, and sulfonic acid groups. Is mentioned.

  Examples of monomers capable of ring-opening copolymerization with monomers having a norbornene structure include monocyclic olefins such as cyclohexene, cycloheptene, and cyclooctene and derivatives thereof; cyclic conjugated dienes such as cyclohexadiene and cycloheptadiene; And derivatives thereof. As the monomer having a norbornene structure and a monomer capable of ring-opening copolymerization, one kind may be used alone, or two or more kinds may be used in combination at any ratio.

  A ring-opening polymer of a monomer having a norbornene structure can be produced, for example, by polymerizing or copolymerizing a monomer in the presence of a ring-opening polymerization catalyst.

  Examples of monomers that can be addition copolymerized with a monomer having a norbornene structure include α-olefins having 2 to 20 carbon atoms such as ethylene, propylene, and 1-butene, and derivatives thereof; cyclobutene, cyclopentene, and cyclohexene. And non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, and the like. Among these, α-olefin is preferable and ethylene is more preferable. Moreover, the monomer which can carry out addition copolymerization with the monomer which has a norbornene structure may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  An addition polymer of a monomer having a norbornene structure can be produced, for example, by polymerizing or copolymerizing a monomer in the presence of an addition polymerization catalyst.

  The hydride of the ring-opening polymer and the addition polymer described above is, for example, in the presence of a hydrogenation catalyst containing a transition metal such as nickel or palladium in a solution of these ring-opening polymer and addition polymer. The carbon unsaturated bond can be produced by hydrogenating preferably 90% or more.

Among norbornene-based polymers, as structural units, X: bicyclo [3.3.0] octane-2,4-diyl-ethylene structure and Y: tricyclo [4.3.0.1 ^2,5 ] decane- Having a 9,9-diyl-ethylene structure, the amount of these structural units being 90% by weight or more based on the total structural units of the norbornene polymer, and the ratio of X and Y It is preferable that the ratio is 100: 0 to 40:60 by weight ratio of X: Y. By using such a polymer, it is possible to make the substrate film excellent in stability of optical characteristics without long-term dimensional change.

  The weight average molecular weight (Mw) of the alicyclic structure-containing polymer is preferably 10,000 or more, more preferably 15,000 or more, particularly preferably 20,000 or more, preferably 100,000 or less, more preferably. Is 80,000 or less, particularly preferably 50,000 or less. When the weight average molecular weight of the alicyclic structure-containing polymer is in such a range, the mechanical strength and molding processability of the base film are highly balanced, which is preferable. Here, the weight average molecular weight is a polyisoprene or polystyrene converted weight average molecular weight measured by gel permeation chromatography using cyclohexane as a solvent. In the gel permeation chromatography, when the sample does not dissolve in cyclohexane, toluene may be used as a solvent.

  The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the alicyclic structure-containing polymer is preferably 1 or more, more preferably 1.2 or more, preferably 10 or less, more preferably 4 or less, particularly preferably 3.5 or less.

Next, the specific block copolymer having an aromatic vinyl compound hydride unit (a) and a diene compound hydride unit (b) will be described.
The aromatic vinyl compound hydride unit (a) is a structural unit having a structure obtained by polymerizing an aromatic vinyl compound and hydrogenating an unsaturated bond thereof. However, the aromatic vinyl compound hydride unit (a) includes units obtained by any production method as long as it has the structure.
Similarly, in the present application, for example, a structural unit having a structure obtained by polymerizing styrene and hydrogenating the unsaturated bond may be referred to as a styrene hydride unit. The styrene hydride unit also includes a unit obtained by any production method as long as it has the structure.
Examples of the aromatic vinyl compound hydride unit (a) include a structural unit represented by the following structural formula (1).

In the structural formula (1), R ^c represents an alicyclic hydrocarbon group. Examples of R ^c include cyclohexyl groups such as cyclohexyl group; decahydronaphthyl groups and the like.

In the structural formula (1), R ¹ , R ² and R ³ are each independently a hydrogen atom, a chain hydrocarbon group, a halogen atom, an alkoxy group, a hydroxyl group, an ester group, a cyano group, an amide group or an imide group. Represents a chain hydrocarbon group substituted with a silyl group or a polar group (halogen atom, alkoxy group, hydroxyl group, ester group, cyano group, amide group, imide group, or silyl group). Among them, R ¹ , R ² and R ³ are preferably a hydrogen atom and a chain hydrocarbon group having 1 to 6 carbon atoms from the viewpoints of heat resistance, low birefringence, mechanical strength and the like. The chain hydrocarbon group is preferably a saturated hydrocarbon group, and more preferably an alkyl group.

  A more specific example of the aromatic vinyl compound hydride unit (a) includes a structural unit represented by the following formula (1-1). The structural unit represented by Formula (1-1) is a styrene hydride unit.

  Any of the examples of the aromatic vinyl compound hydride unit (a) having a stereoisomer can use any stereoisomer. Only one type of aromatic vinyl compound hydride unit (a) may be used, or two or more types may be used in combination at any ratio.

The diene compound hydride unit (b) is a structural unit having a structure obtained by polymerizing a diene compound and hydrogenating the unsaturated bond if the obtained polymer has an unsaturated bond. However, the diene compound hydride unit (b) includes units obtained by any production method as long as it has the structure.
Similarly, in the present application, for example, a structural unit having a structure obtained by polymerizing isoprene and hydrogenating the unsaturated bond may be referred to as an isoprene hydride unit. The isoprene hydride unit also includes a unit obtained by any production method as long as it has the structure.

  The diene compound hydride unit (b) preferably has a structure obtained by polymerizing a conjugated diene compound such as a linear conjugated diene compound and hydrogenating the unsaturated bond. Examples thereof include a structural unit represented by the following structural formula (2) and a structural unit represented by the structural formula (3).

In Structural Formula (2), R ^{4 to} R ⁹ are each independently a hydrogen atom, a chain hydrocarbon group, a halogen atom, an alkoxy group, a hydroxyl group, an ester group, a cyano group, an amide group, an imide group, or a silyl group. Or a chain hydrocarbon group substituted with a polar group (halogen atom, alkoxy group, hydroxyl group, ester group, cyano group, amide group, imide group, or silyl group). Among them, R ^{4 to} R ⁹ are preferably a hydrogen atom and a chain hydrocarbon group having 1 to 6 carbon atoms from the viewpoints of heat resistance, low birefringence, mechanical strength, and the like. The chain hydrocarbon group is preferably a saturated hydrocarbon group, and more preferably an alkyl group.

In the structural formula (3), R ^{10 to} R ¹⁵ each independently represent a hydrogen atom, a chain hydrocarbon group, a halogen atom, an alkoxy group, a hydroxyl group, an ester group, a cyano group, an amide group, an imide group, or a silyl group. Or a chain hydrocarbon group substituted with a polar group (halogen atom, alkoxy group, hydroxyl group, ester group, cyano group, amide group, imide group, or silyl group). Among them, R ^{10 to} R ¹⁵ are preferably a hydrogen atom and a chain hydrocarbon group having 1 to 6 carbon atoms from the viewpoints of heat resistance, low birefringence, mechanical strength, and the like. The chain hydrocarbon group is preferably a saturated hydrocarbon group, and more preferably an alkyl group.

  More specific examples of the diene compound hydride unit (b) include structural units represented by the following formulas (2-1) to (2-3). The structural units represented by the formulas (2-1) to (2-3) are isoprene hydride units.

  In the example of the diene compound hydride unit (b), any one having a stereoisomer can be used. As the diene compound hydride unit (b), only one type may be used, or two or more types may be used in combination at any ratio.

  The specific block copolymer is a block copolymer having the aforementioned aromatic vinyl compound hydride unit (a) and diene compound hydride unit (b). The specific block copolymer includes a block A having an aromatic vinyl compound hydride unit (a), a copolymer block B having an aromatic vinyl compound hydride unit (a) and a diene compound hydride unit (b), and It is preferable to contain. Further, the specific block copolymer preferably has a triblock molecular structure having one copolymer block B per molecule and two blocks A per molecule linked to both ends thereof.

  The specific block copolymer having a triblock molecular structure has a block A1 and a block A2 as two blocks A per molecule, and the weight ratio A1 / A2 between the block A1 and the block A2 is within a specific range. It is preferable that A1 / A2 is preferably 60/5 to 85/5, more preferably 65/5 to 80/5. When the specific block copolymer has a triblock molecular structure and A1 / A2 falls within such a range, a base film excellent in the above various characteristics, particularly in heat resistance, can be easily obtained.

  In the specific block copolymer, the weight ratio (a) / (b) between the aromatic vinyl compound hydride unit (a) and the diene compound hydride unit (b) is preferably within a specific range. . (A) / (b) is preferably 70/30 to 95/5. When (a) / (b) is within such a range, a substrate film excellent in the above-mentioned various properties can be easily obtained. Further, when (a) / (b) is within such a range, a base film having high tear strength and impact strength and low retardation can be easily obtained.

  The molecular weight of the specific block copolymer is preferably 60,000 or more, more preferably 70,000 or more. The upper limit of the molecular weight is preferably 150,000 or less, more preferably 140,000 or less. When the molecular weight is within such a range, particularly when the value is equal to or more than the lower limit, a base film excellent in the above various characteristics, particularly in heat resistance, can be easily obtained. As the molecular weight of the specific block copolymer here, a polystyrene-reduced weight average molecular weight measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent can be adopted.

  The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the specific block copolymer is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1.2 or less. The lower limit of the molecular weight distribution can be 1.0 or more. Thereby, a polymer viscosity can be lowered | hung and a moldability can be improved.

  The block A preferably comprises only the aromatic vinyl compound hydride unit (a), but may contain any unit other than the aromatic vinyl compound hydride unit (a). Examples of the arbitrary structural unit include structural units based on vinyl compounds other than the aromatic vinyl compound hydride unit (a). The content of any structural unit in the block A is preferably 10% by weight or less, more preferably 5% by weight or less, and particularly preferably 1% by weight or less.

  The copolymer block B preferably comprises only the aromatic vinyl compound hydride unit (a) and the diene compound hydride unit (b), but may contain any other unit. Examples of the arbitrary structural unit include structural units based on vinyl compounds other than the aromatic vinyl compound hydride unit (a). The content of any structural unit in the block B is preferably 10% by weight or less, more preferably 5% by weight or less, and particularly preferably 1% by weight or less.

  The specific block copolymer is prepared, for example, by preparing monomers corresponding to the aromatic vinyl compound hydride unit (a) and the diene compound hydride unit (b), and polymerizing them, and the resulting polymer is hydrogenated. Can be manufactured.

  As a monomer corresponding to the aromatic vinyl compound hydride unit (a), an aromatic vinyl compound can be used. Examples thereof include styrene, α-methylstyrene, α-ethylstyrene, α-propylstyrene, α-isopropylstyrene, α-t-butylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2 , 4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, monochlorostyrene, dichlorostyrene, monofluorostyrene, and 4-phenylstyrene Vinylcyclohexanes such as vinylcyclohexane and 3-methylisopropenylcyclohexane; and 4-vinylcyclohexene, 4-isopropenylcyclohexene, 1-methyl-4-vinylcyclohexene, 1-methyl-4-isopropenylcyclohexene, 2- Methyl And vinylcyclohexenes such as 4-vinylcyclohexene and 2-methyl-4-isopropenylcyclohexene. These monomers may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Examples of monomers corresponding to the diene compound hydride unit (b) include chains such as butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. Conjugated dienes. These monomers may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  In general, anionic polymerization can be employed as a polymerization reaction mode. The polymerization may be performed by any of bulk polymerization, solution polymerization and the like. Among these, solution polymerization is preferable in order to continuously perform the polymerization reaction and the hydrogenation reaction.

Examples of reaction solvents for polymerization include aliphatic hydrocarbon solvents such as n-butane, n-pentane, isopentane, n-hexane, n-heptane, and isooctane; cyclopentane, cyclohexane, methylcyclopentane, methylcyclohexane, and And alicyclic hydrocarbon solvents such as decalin; and aromatic hydrocarbon solvents such as benzene and toluene. Among these, an aliphatic hydrocarbon solvent and an alicyclic hydrocarbon solvent are preferable because they can be used as they are as an inert solvent for the hydrogenation reaction.
A reaction solvent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
The reaction solvent is usually used at a ratio of 200 parts by weight to 10,000 parts by weight with respect to 100 parts by weight of the total monomers.

  In the polymerization, a polymerization initiator is usually used. Examples of polymerization initiators include monoorganolithiums such as n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, and phenyllithium; and dilithiomethane, 1,4-diobane, and 1,4-dilithio Polyfunctional organolithium compounds such as -2-ethylcyclohexane are listed. A polymerization initiator may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  As an example of the manufacturing method in the case of manufacturing the triblock copolymer containing block A1 and A2 and the copolymerization block B as a specific block copolymer, the manufacturing method including the following 1st process-3rd process is mentioned. It is done. Here, the material called “monomer composition” includes not only a mixture of two or more substances but also a material composed of a single substance.

First step: A step of polymerizing the monomer composition (a1) containing an aromatic vinyl compound to form the block A.
Second step: A step of polymerizing a monomer composition containing an aromatic vinyl compound and a diene compound to form a copolymer block B at one end of the block A to form a diblock polymer of AB.
Third step: A step of obtaining a specific block copolymer by polymerizing the monomer composition (a2) containing an aromatic vinyl compound at the terminal of the copolymer block B of the diblock polymer. However, the monomer composition (a1) and the monomer composition (a2) may be the same or different.

  When polymerizing each polymer block, a polymerization accelerator and a randomizer can be used in order to suppress an excessively long chain of one component in each block. For example, when the polymerization is carried out by anionic polymerization, a Lewis base compound can be used as a randomizer. Specific examples of Lewis base compounds include ether compounds such as dimethyl ether, diethyl ether, diisopropyl ether, dibutyl ether, tetrahydrofuran, diphenyl ether, ethylene glycol diethyl ether, and ethylene glycol methyl phenyl ether; tetramethylethylenediamine, trimethylamine, triethylamine, and pyridine. Tertiary amine compounds such as potassium-t-amyl oxide, and alkali metal alkoxide compounds such as potassium-t-butyl oxide; and phosphine compounds such as triphenylphosphine. One of these may be used alone, or two or more of these may be used in combination at any ratio.

  The polymerization temperature is not limited as long as the polymerization proceeds, but is usually 0 ° C. or higher, preferably 20 ° C. or higher, and is usually 200 ° C. or lower, preferably 100 ° C. or lower, more preferably 80 ° C. or lower.

  After the polymerization, the polymer can be recovered from the reaction mixture by any method. Examples of the recovery method include a steam stripping method, a direct desolvation method, and an alcohol coagulation method. Further, when a solvent inert to the hydrogenation reaction is used as a reaction solvent during the polymerization, the polymer may not be recovered from the polymerization solution and may be directly used in the hydrogenation step.

  There is no restriction | limiting in the hydrogenation method of a polymer, Arbitrary methods are employable. Hydrogenation can be performed, for example, using a suitable hydrogenation catalyst. More specifically, hydrogenation is performed using a hydrogenation catalyst containing at least one metal selected from the group consisting of nickel, cobalt, iron, rhodium, palladium, platinum, ruthenium, and rhenium in an organic solvent. sell. The hydrogenation catalyst may be a heterogeneous catalyst or a homogeneous catalyst. A hydrogenation catalyst may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The heterogeneous catalyst may be used as it is as a metal or a metal compound, or may be used by being supported on an appropriate carrier. Examples of the carrier include activated carbon, silica, alumina, calcium carbide, titania, magnesia, zirconia, diatomaceous earth, and silicon carbide. The amount of the catalyst supported on the carrier is usually 0.01% by weight or more, preferably 0.05% by weight or more, and usually 80% by weight or less, preferably 60% by weight or less.

Examples of homogeneous catalysts include catalysts combining nickel, cobalt, or iron compounds with organometallic compounds (eg, organoaluminum compounds, organolithium compounds); and rhodium, palladium, platinum, ruthenium, rhenium, etc. An organometallic complex catalyst is mentioned. Examples of nickel, cobalt, or iron compounds include acetylacetone salts, naphthenates, cyclopentadienyl compounds, and cyclopentadienyl dichloro compounds of these metals. Examples of organoaluminum compounds include alkylaluminums such as triethylaluminum and triisobutylaluminum; aluminum halides such as diethylaluminum chloride and ethylaluminum dichloride; and alkylaluminum hydrides such as diisobutylaluminum hydride.
Examples of the organometallic complex catalyst include metal complexes such as γ-dichloro-π-benzene complex, dichloro-tris (triphenylphosphine) complex, hydrido-chloro-triphenylphosphine) complex of each of the above metals. .

  The amount of the hydrogenation catalyst used is usually 0.01 parts by weight or more, preferably 0.05 parts by weight or more, more preferably 0.1 parts by weight or more, and usually 100 parts by weight with respect to 100 parts by weight of the polymer. Hereinafter, it is preferably 50 parts by weight or less, more preferably 30 parts by weight or less.

The reaction temperature during the hydrogenation reaction is usually 10 ° C. to 250 ° C., but is preferably 50 ° C. or more, more preferably, because the hydrogenation rate can be increased and the polymer chain scission reaction can be reduced. It is 80 degreeC or more, Preferably it is 200 degrees C or less, More preferably, it is 180 degrees C or less. Further, the pressure during the reaction is usually 0.1 MPa to 30 MPa, but in addition to the above reasons, from the viewpoint of operability, it is preferably 1 MPa or more, more preferably 2 MPa or more, preferably 20 MPa or less, more preferably 10 MPa or less.
The hydrogenation rate is usually 90% or more, preferably 95% or more, more preferably 97% or more. By increasing the hydrogenation rate, the low birefringence and thermal stability of the vinyl alicyclic hydrocarbon polymer can be enhanced. The hydrogenation rate can be measured by ¹ H-NMR.

  The amount of the weight body in the resin forming the base film is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, and particularly preferably 90% by weight to 100% by weight. By making the ratio of a polymer into the said range, a base film can acquire sufficient heat resistance and transparency. Among these, when a specific block copolymer is used as the polymer, the amount of the specific block copolymer in the resin forming the base film is preferably 95% by weight to 100% by weight, more preferably 97% by weight to 100% by weight.

  The resin forming the base film can contain an optional component in addition to the polymers listed above. Examples of optional components include antioxidants, heat stabilizers, light stabilizers, UV absorbers, antistatic agents, dispersants, chlorine scavengers, flame retardants, crystallization nucleating agents, reinforcing agents, antiblocking agents, Examples include antifogging agents, mold release agents, pigments, organic or inorganic fillers, neutralizing agents, lubricants, decomposition agents, metal deactivators, antifouling agents, and antibacterial agents. These components may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. The ratio of the arbitrary component can be appropriately adjusted within a range in which the ratio of the polymer in the resin is a preferable ratio.

  The glass transition temperature of the resin forming the base film is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, preferably 250 ° C. or lower, more preferably 230 ° C. or lower. A base film formed of a resin having a glass transition temperature in such a range is excellent in durability because deformation and stress generation during use at high temperatures are suppressed.

[1.2.2. Surface treatment layer included in base film]
The base film includes a surface treatment layer as a layer in contact with the depolarization layer. The surface treatment layer is the outermost surface layer on the depolarization layer side of the base film. The surface treatment layer is a layer into which oxygen atoms are introduced. By introducing oxygen atoms in this manner, the orientation state of molecules such as polymers is disturbed on the surface of the surface treatment layer.

  The surface treatment layer can be formed by performing an appropriate surface treatment capable of introducing oxygen atoms on the surface of the base film. Examples of such surface treatment include corona treatment and plasma treatment.

  The amount of oxygen atoms introduced into the surface treatment layer is usually 5 atom% or more, preferably 6 atom% or more, more preferably 7 atom% or more, and usually 20 atom% or less, preferably 19 atom% or less, more preferably 18 atom% or less. . By introducing oxygen atoms in such an introduction amount, the alignment state of the molecules is effectively disturbed on the surface of the surface treatment layer, and the alignment state of the liquid crystalline compound and the alignment fixing compound in the depolarization layer is randomly changed. it can.

The amount of oxygen atoms introduced into the surface treatment layer can be measured by the following method.
Before and after performing the surface treatment on the surface of the base film, the elements present on the surface of the base film are identified and the abundance ratio of the existing elements is measured by XPS (X-ray photoelectric spectroscopy). Specifically, the surface of the pre-treatment film before the surface treatment and the surface of the base film obtained by subjecting the surface to the surface treatment are analyzed by the XPS method and exist on the surface. Measure the abundance ratio of elements to be used. Then, the difference in the abundance ratio of oxygen elements existing on the surface before and after the surface treatment can be calculated as the oxygen atom introduction amount.

  In addition, when the oxygen element abundance ratio before the surface treatment is unknown, the amount of oxygen atoms introduced into the surface treatment layer is determined based on the oxygen element abundance ratio in the surface treatment layer and the substrate film other than the surface treatment layer. It can be measured by calculating the difference from the abundance ratio of the oxygen element in the layer portion. For example, the surface treatment layer is obtained by measuring the abundance ratio of oxygen element on both the surface of the base film on the surface treatment layer side and the surface opposite to the surface treatment layer by XPS method and calculating the difference between them. The amount of oxygen atoms introduced in may be measured.

  The thickness of the surface treatment layer is not particularly limited and is arbitrary. In the XPS method, since the abundance ratio of elements at a depth of several nanometers on the sample surface is generally measured, the surface treatment layer is formed at least in the range of several nanometers in the thickness of the substrate film surface. .

[1.2.3. Characteristics of base film
The base film is usually a transparent film. Therefore, usually, the total light transmittance of the base film is high, and the haze of the base film is low. Specifically, the total light transmittance of the base film is preferably 70% to 100%, more preferably 80% to 100%, and particularly preferably 90% to 100%. Further, the haze of the base film is preferably 0.0% to 3.0%, more preferably 0.0% to 1.0%.
The total light transmittance and haze of the film can be measured according to JIS K 7361 and JIS K 7136, respectively.

  The in-plane retardation Re of the base film is preferably small. Specifically, the in-plane retardation Re of the substrate film is preferably 30 nm or less, more preferably 25 nm or less, and particularly preferably 20 nm or less. Since the in-plane retardation Re of the base film is small as described above, the depolarization layer can be made thin.

  The tensile modulus of the base film is preferably 1,500 MPa or more, more preferably 1,800 MPa or more, particularly preferably 2,000 MPa or more, and preferably 5,000 MPa or less, more preferably 4,500 MPa or less. Particularly preferably, it is 4,000 MPa or less. The tensile elastic modulus of the base film may vary depending on the tensile direction. In that case, the base film preferably has the tensile elastic modulus in at least one direction within the plane. When the tensile modulus of the base film is equal to or higher than the lower limit of the above range, the base film has high rigidity. Therefore, even when the area is increased, deformation such as bending hardly occurs, and mechanical durability is also achieved. Excellent. Moreover, when the tensile elasticity modulus of a base film is below the upper limit of the said range, brittleness can be made small and the mechanical strength of a base film can be improved.

The tensile modulus of the film can be measured by the following method.
According to JIS K7162, the film is punched into a dumbbell shape to obtain a test piece. About this test piece, a tensile test is done at a tensile speed of 5 mm / min using a tensile tester. The tensile modulus can be measured from the slope of the SS curve (stress-strain curve) obtained in the tensile test.

  The base film preferably has a high impact strength. Here, the impact strength of the film is a steel ball at a boundary height h when the film is not torn and when the film is torn in an impact test in which the steel ball is dropped onto the film from various heights h. Is the potential energy (mJ). In the impact test, the film is fixed horizontally to a jig that can be supported horizontally, and a steel ball (pachinko ball, weight 5 g, diameter 11 mm) is placed in the center of the film fixed to the jig. It is a test to drop from various heights h. The impact strength of the base film can be preferably 14 mJ or more, more preferably 15 mJ or more. The upper limit of impact strength is not particularly limited, but may be, for example, 80 mJ or less. By having such high impact strength, it is possible to obtain high durability that does not cause defects in the manufacturing process of the display device.

  The base film may be a stretched film that has been stretched. By stretching, physical properties such as mechanical strength of the base film can be adjusted. In general, when a stretching treatment is performed, the molecules contained in the stretched film are oriented, so that it has been difficult to form a depolarization layer on the stretched film by a conventional technique such as Patent Document 1. On the other hand, the base film including the surface treatment layer can form a depolarization layer on the surface treatment layer even if the base film is a stretched film subjected to a stretching treatment.

  The thickness of the base film is preferably 5 μm or more, more preferably 10 μm or more, preferably 150 μm or less, more preferably 100 μm or less. When the thickness of the base film is equal to or higher than the lower limit of the range, the mechanical strength of the base film can be sufficiently increased, and when the thickness of the base film is equal to or lower than the upper limit of the range, The thickness can be reduced.

[1.3. Depolarization Layer of Depolarization Film According to First Embodiment]
A depolarization layer is a layer containing the liquid crystalline compound or its orientation fixing compound formed on the surface of the surface treatment layer of the base film. In the depolarization layer, the liquid crystalline compound and the alignment fixing compound form a liquid crystal domain having a random alignment state as described above. Therefore, the depolarization layer can exhibit a depolarization function.

As the liquid crystal compound, any compound can be used as long as the depolarization function is obtained. Moreover, a liquid crystalline compound may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. Among these, a liquid crystalline compound having a polymerizable functional group is preferable. As a particularly suitable liquid crystalline compound, a polymerizable functional group represented by the following formulas (D-1) to (D-5), a mesogenic group, and a linking group that connects these polymerizable functional group and mesogen The compound which has these. In the following formulas (D-1) to (D-3), R ^{a1 to} R ^a5 each independently represents an alkyl group having 1 to 4 carbon atoms or a hydrogen atom.

  Specific examples of suitable liquid crystalline compounds having the polymerizable functional group, the mesogenic group, and a linking group for linking these polymerizable functional group and mesogen include liquid crystal manuals (edited by the Liquid Crystal Handbook Editorial Committee, Maruzen). Of the liquid crystal compounds described in “3.2 Non-chiral rod-like liquid crystal molecules” and “3.3 Chiral rod-like liquid crystal molecules” in “Chapter 3 Molecular structure and liquid crystal properties” of October 30, 2000), The compound which has the said polymeric functional group is mentioned.

When the specific example of the liquid crystalline compound used preferably is shown, the liquid crystalline compound containing group represented by following formula (4) is mentioned, for example. Hereinafter, the liquid crystal compound containing a group represented by the formula (4) may be appropriately referred to as “compound (4)”. The compound (4) is a nematic liquid crystal compound having a polymerizable functional group at the terminal.
^{P 11 -B 11 -E 11 -B 12} -A 11 -B 13 - (4)

In the formula (4), P ¹¹ represents a polymerizable functional group represented by any one of the above formulas (D-1) to (D-5).

In the formula (4), A ¹¹ represents a divalent alicyclic hydrocarbon group or a divalent aromatic hydrocarbon group. The hydrogen atom contained in the divalent alicyclic hydrocarbon group and divalent aromatic hydrocarbon group is a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, cyano It may be substituted with a group or a nitro group. The hydrogen atom contained in the alkyl group having 1 to 6 carbon atoms and the alkoxy group having 1 to 6 carbon atoms may be substituted with a fluorine atom.

The number of carbon atoms of the alicyclic hydrocarbon group and the aromatic hydrocarbon group of A ¹¹ is, for example, 3 to 18, preferably 5 to 12, and more preferably 5 or 6. A ¹¹ is particularly preferably a cyclohexane-1,4-diyl group or a 1,4-phenylene group.

In the formula (4), B ¹¹ is —O—, —S—, —C (═O) —O—, —O—C (═) O—, —O—C (═O) —O—, -C (= O) -NR < ¹⁶ >-, -NR < ¹⁶ > -C (= O)-, -C (= O)-, -CS- or a single bond is represented. R ¹⁶ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

In the formula ^{(4), B 12} and ^{B 13} are each _{independently, -C≡C -, - CH = CH} -, - CH 2 -CH 2 -, - O -, - S -, - C (= O )-, -C (= O) -O-, -O-C (= O)-, -O-C (= O) -O-, -CH = N-, -N = CH-, -N = N—, —C (═O) —NR ¹⁷ —, —NR ¹⁷ —C (═O) —, —OCH ₂ —, —OCF ₂ —, —CH ₂ O—, —CF ₂ O—, —CH═ It represents CH—C (═O) —O—, —O—C (═O) —CH═CH— or a single bond. R ¹⁷ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

In formula (4), E ¹¹ represents an alkanediyl group having 1 to 12 carbon atoms. The hydrogen atom contained in the alkanediyl group may be substituted with an alkyl group having 1 to 5 carbon atoms or an alkoxy group having 1 to 5 carbon atoms. Moreover, the hydrogen atom contained in the alkyl group and alkoxy group may be substituted with a halogen atom. Furthermore, —CH ₂ — contained in the alkanediyl group may be replaced by —O— or —C (═O) —.

E ¹¹ is preferably a linear alkanediyl group having 1 to 12 carbon atoms. —CH ₂ — contained in the alkanediyl group may be replaced by —O—. Examples of the linear alkanediyl group having 1 to 12 carbon atoms in which —CH ₂ — may be replaced by —O— include, for example, methylene group, ethylene group, propane-1,3-diyl group, butane -1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1, 9-diyl group, decane-1,10-diyl group, undecane-1,11-diyl group, dodecane-1,12-diyl group, —CH ₂ —CH ₂ —O—CH ₂ —CH ₂ —, —CH _{2 -CH 2 -O-CH 2 -CH} 2 -O-CH 2 -CH 2 -, _{and, -CH 2 -CH 2 -O-CH} 2 -CH 2 -O-CH 2 -CH 2 -O-CH ₂ -CH ₂ - and the like.

Examples of the compound (4) include compounds represented by any of the following formula (I), formula (II), formula (III), formula (IV), formula (V) and formula (VI). .
^{(I): P 11 -B 11} -E 11 -B 12 -A 11 -B 13 -A 12 -B 14 -A 13 -B 15 -A 14 -B 16 -E 12 -B 17 -P 12
^{(II): P 11 -B 11} -E 11 -B 12 -A 11 -B 13 -A 12 -B 14 -A 13 -B 15 -A 14 -F 11
^{(III) P 11 -B 11 -E} 11 -B 12 -A 11 -B 13 -A 12 -B 14 -A 13 -B 15 -E 12 -B 17 -P 12
^{(IV): P 11 -B 11} -E 11 -B 12 -A 11 -B 13 -A 12 -B 14 -A 13 -F 11
^{(V): P 11 -B 11} -E 11 -B 12 -A 11 -B 13 -A 12 -B 14 -E 12 -B 17 -P 12
^{(VI) P 11 -B 11 -E} 11 -B 12 -A 11 -B 13 -A 12 -F 11

In the formulas (I) to (VI), A ¹² , A ¹³ and A ¹⁴ are synonymous with the above A ¹¹ , B ¹⁴ , B ¹⁵ and B ¹⁶ are synonymous with the above B ¹² , and B ¹⁷ is has the same meaning as above ^{B 11, E 12} have the same meanings as ^{E 11.} F ¹¹ is a hydrogen atom, an alkyl group having 1 to 13 carbon atoms, an alkoxy group having 1 to 13 carbon atoms, a cyano group, a nitro group, a trifluoromethyl group, a dimethylamino group, a hydroxy group, a methylol group, or a formyl group. , A sulfo group (—SO ₃ H), a carboxy group, an alkoxycarbonyl group having 1 to 10 carbon atoms or a halogen atom, —CH ₂ — contained in the alkyl group and alkoxy group is replaced by —O—. It may be. ^{Also, P 12} have the same meanings as in ^{P 11.}

  Examples of the compound (4) include the following formula (I-1) to formula (I-4), formula (II-1) to formula (II-4), formula (III-1) to formula (III- 26), compounds represented by formula (IV-1) to formula (IV-19), formula (V-1) to formula (V-2), formula (VI-1) to formula (VI-6), etc. Is mentioned. In the following formula, k1 and k2 each independently represent an integer of 2 to 12. Since these liquid crystalline compounds are easy to manufacture or are commercially available, they are easily available.

  In the depolarization layer, the liquid crystalline compound may be an alignment-fixed compound in which the alignment state of the liquid crystalline compound is fixed. Such an alignment state can be fixed by polymerizing a liquid crystalline compound having a polymerizable functional group at the terminal as described above. When such polymerization is performed, a polymer of a liquid crystal compound is obtained as an alignment fixing compound.

  The thickness of the depolarizing layer is preferably 0.3 μm or more, more preferably 0.5 μm or more, particularly preferably 0.8 μm or more, preferably 10 μm or less, more preferably 8 μm or less, particularly preferably 5 μm or less. . Since the depolarizing layer can be formed as a layer containing a liquid crystalline compound or an alignment fixing compound thereof, the thickness can be reduced as described above. When the thickness of the depolarization layer is equal to or greater than the lower limit value of the range, linearly polarized light incident on the depolarization layer can be effectively converted into partially polarized light or non-polarized light, and is equal to or less than the upper limit value of the range. Thus, the thickness can be reduced.

[1.4. Arbitrary Layer of Depolarization Film According to First Embodiment]
The depolarizing film may further include an arbitrary layer in combination with the base film and the depolarizing layer. For example, the depolarizing film may have an arbitrary layer on the side opposite to the depolarizing layer of the base film and on the side opposite to the base film of the depolarizing layer.

[1.5. Characteristics of depolarizing film according to first embodiment]
Since the depolarization film includes a depolarization layer, it has a depolarization function. Therefore, the depolarizing film can emit at least part or all of the linearly polarized light incident on the depolarizing film after being converted into partially polarized light or non-polarized light.

  Moreover, the depolarization film can exhibit the said depolarization function uniformly in a surface. Therefore, the depolarization film can suppress that the part which cannot exhibit a depolarization function arises locally in the surface of the said depolarization film.

It can be confirmed by the following method that the depolarizing film can exhibit the depolarizing function uniformly in the plane.
Two polarizing plates are placed on the light table. The orientation of the polarizing plate is adjusted so that the polarization transmission axis of one polarizing plate and the polarization transmission axis of the other polarizing plate are perpendicular to each other. A depolarizing film cut to 100 mm × 100 mm is installed between the polarizing plates. While the light table is turned on, the depolarization film is visually observed while being rotated 360 ° in the in-plane direction. As a result of the observation, it can be determined that the depolarization film can exhibit the depolarization function uniformly in the plane when there is no darkened portion over the entire surface of the depolarization film at any angle.

  The depolarizing film preferably has high transparency. Therefore, the depolarizing film preferably has a high total light transmittance, and preferably has a low haze. The specific total light transmittance of the depolarizing film is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more. The specific haze of the depolarizing film is preferably 15% or less, more preferably 13% or less, and particularly preferably 10% or less. Since the depolarization film has high transparency as described above, when the depolarization film is provided in the image display device, the white luminance of the image display device can be increased, so that the screen can be brightened.

  The in-plane retardation Re of the depolarizing film is preferably 30 nm or less, more preferably 10 nm or less. Since the depolarizing film has the small in-plane retardation Re as described above, when the depolarizing film is provided in the image display device, the optical isotropy of light emitted from the image display device is increased. be able to. Therefore, the angle dependency of visibility and image quality can be reduced.

  The tensile elastic modulus of the depolarizing film is preferably 1,500 MPa or more, more preferably 1,800 MPa or more, particularly preferably 2,000 MPa or more, and preferably 5,000 MPa or less, more preferably 4,500 MPa or less. Particularly preferably, it is 4,000 MPa or less. The tensile elastic modulus of the depolarizing film may vary depending on the tensile direction. In this case, the depolarizing film preferably has the tensile elastic modulus in at least one direction within the plane. When the tensile modulus of the depolarizing film is equal to or higher than the lower limit of the above range, the depolarizing film has high rigidity, so that deformation such as bending hardly occurs even when the area is increased, and mechanical durability is also achieved. Excellent. Moreover, when the tensile elasticity modulus of a depolarizing film is below the upper limit of the said range, brittleness can be made small and the mechanical strength of a depolarizing film can be raised.

  The depolarizing film preferably has a high impact strength. The impact strength of the depolarizing film is preferably 14 mJ or more, more preferably 15 mJ or more. The upper limit of impact strength is not particularly limited, but may be, for example, 80 mJ or less. By having such high impact strength, it is possible to obtain high durability that does not cause defects in the manufacturing process of the display device.

[1.6. Dimensions of depolarizing film according to first embodiment]
The depolarizing film is preferably a long film. The “long” film means a film having a length of 5 times or more with respect to the width, preferably 10 times or more, and specifically wound in a roll shape. A film having a length that can be stored or transported. The upper limit of the length of the long film is not particularly limited, and can be, for example, 100,000 times or less with respect to the width.

  Conventionally, it has been difficult for such a long depolarizing film to exhibit the depolarizing function uniformly in a plane. Generally, a long base film is wound up at the time of manufacture to become a roll, and after being stored in the state of the roll, it is unwound from the roll and used. In any of the above-described winding, storage, and unwinding, a frictional force is generated on the surface of the base film by contact between the films, and molecules are oriented in a part of the film surface. Therefore, conventionally, in a depolarizing film manufactured using a long base film, it has been difficult to form a depolarizing layer uniformly in the entire surface. It was difficult to perform evenly. On the other hand, if the substrate film includes a surface treatment layer as in the first embodiment of the present invention, the orientation state due to the frictional force can be eliminated, so that the depolarization function can be exhibited uniformly in the plane. A long depolarizing film is obtained. Therefore, the fact that the depolarizing film according to the first embodiment of the present invention is a long film is technically significant in that it can solve problems that have been difficult to solve in the past.

  The thickness of the depolarizing film is preferably 5 μm or more, more preferably 8 μm or more, particularly preferably 10 μm or more, preferably 200 μm or less, more preferably 150 μm or less, and particularly preferably 100 μm or less. When the thickness of the depolarizing film is equal to or higher than the lower limit of the range, the handleability of the depolarizing film can be improved, and by being equal to or lower than the upper limit of the range, the transparency of the depolarizing film is increased. Or promote thinning.

[1.7. Manufacturing method of depolarizing film according to first embodiment]
The depolarizing film includes a step of preparing a pre-treatment film from which the base film including the surface treatment layer is obtained by performing a surface treatment; surface treatment is performed on at least one surface of the pre-treatment film, A step of obtaining a base film containing a layer; and a step of applying a coating liquid containing a liquid crystalline compound to the surface subjected to the surface treatment to form a depolarizing layer; Can be manufactured.

[1.7.1. Preparation of film before processing)
The pre-treatment film is a film from which the above-described base film can be obtained by performing an appropriate surface treatment. As this pre-treatment film, a film similar to the base film can be used except that the surface treatment layer is not included.

  The manufacturing method of the film before a process is arbitrary. For example, when a pre-treatment film is produced from a resin, the pre-treatment film can be produced by molding the resin by any molding method. Examples of the molding method include a melt molding method and a solution casting method. More specifically, the melt molding method can be classified into an extrusion molding method, a press molding method, an inflation molding method, an injection molding method, a blow molding method, a stretch molding method, and the like. Among these methods, since a pre-treatment film having excellent mechanical strength and surface accuracy can be obtained, the extrusion molding method, the inflation molding method and the press molding method are preferable, and among them, the expression of in-plane retardation Re is more reliably suppressed. However, the extrusion molding method is particularly preferable from the viewpoint that a pre-treatment film can be produced efficiently and easily. When forming by an extrusion method, a long unprocessed film can usually be obtained.

  The film before treatment may be subjected to surface treatment after being subjected to any treatment as required. For example, the pre-treatment film may be subjected to a stretching treatment before the surface treatment. The stretching conditions for performing the stretching treatment are not particularly limited, and can be appropriately adjusted so that a desired product is obtained. The stretching performed in the stretching process can be uniaxial stretching, biaxial stretching, or other stretching. The stretching direction can be set in any direction. For example, when the pre-processed film before stretching is a long film, the stretching direction may be any of the film longitudinal direction, the film width direction, and other oblique directions. The angle formed by the two stretching directions when biaxial stretching is performed can usually be an angle orthogonal to each other, but is not limited thereto, and may be an arbitrary angle. Biaxial stretching may be sequential biaxial stretching or simultaneous biaxial stretching. From the viewpoint of high productivity, simultaneous biaxial stretching is preferred.

  The stretching ratio in the case of performing the stretching treatment can be appropriately adjusted according to desired conditions. For example, the draw ratio is preferably 1.5 times or more, more preferably 2 times or more, preferably 5 times or less, more preferably 3 times or less. In the case of biaxial stretching, the magnification in each of the two stretching directions can be within this range. By setting the draw ratio within the range, a high-quality depolarizing film can be efficiently produced. The stretching temperature may be Tg−5 ° C. to Tg + 20 ° C. based on the glass transition temperature Tg of the resin.

[1.7.2. surface treatment〕
After preparing the film before a process, the process of surface-treating at least one surface of the film before a process is performed. This surface treatment is a treatment for introducing oxygen atoms into the surface of the pre-treatment film. By performing this surface treatment, a surface treatment layer is formed as the film outermost layer, and thus a base film including the surface treatment layer is obtained.

  Examples of the surface treatment include corona treatment and plasma treatment. Among these, the corona treatment is preferable because the surface treatment layer can be easily formed.

The treatment conditions for the surface treatment are arbitrary as long as oxygen atoms can be introduced. Therefore, for example, when the corona treatment is performed as the surface treatment, the discharge amount in the corona treatment can be arbitrarily set. When showing a specific example of the range of the discharge amount in the corona treatment, for example, it may be a ^{50W · min / m 2 ~500W ·} min / m 2.

  In general, the surface treatment does not change optical properties such as retardation of the film.

[1.7.3. (Coating liquid application)
After the surface treatment, a step of applying a coating liquid containing a liquid crystalline compound to the surface subjected to the surface treatment is performed. By applying the coating liquid, it is possible to form a depolarizing layer containing a liquid crystalline compound that is in direct contact with the surface treatment layer. And thereby, a depolarization film provided with the base film containing a surface treatment layer and the depolarization layer provided in the surface treatment layer side of the said base film is obtained. Since the molecules contained in the surface treatment layer are not oriented, the liquid crystalline compound contained in the depolarizing layer is not oriented. Therefore, the depolarization layer is a layer including a liquid crystal domain having a random alignment state, and thus can exhibit a depolarization function.

As a coating liquid, the liquid containing the liquid crystalline compound mentioned above is used. Moreover, a coating liquid can contain arbitrary components in combination with a liquid crystalline compound.
The coating liquid can contain a solvent, for example. As the solvent, those capable of dissolving the liquid crystalline compound are preferable, and those inert to the polymerization reaction of the liquid crystalline compound are more preferable. Examples of suitable solvents include: water; alcohol solvents such as methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, methyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether; ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, Ester solvents such as γ-butyrolactone, propylene glycol methyl ether acetate, and ethyl lactate; Ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, methyl amyl ketone, and methyl isobutyl ketone; Aliphatics such as pentane, hexane, and heptane Hydrocarbon solvents; aromatic solvents such as toluene and xylene; nitrile solvents such as acetonitrile; ethers such as tetrahydrofuran and dimethoxyethane Ether-based solvents; like; and chloroform, chlorinated hydrocarbon solvents such as chlorobenzene. Moreover, a solvent may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  The amount of the solvent is preferably 40 parts by weight or more, more preferably 70 parts by weight or more, particularly preferably 100 parts by weight or more, preferably 1,200 parts by weight or less, based on 100 parts by weight of the liquid crystalline compound. The amount is preferably 1,100 parts by weight or less, particularly preferably 1,000 parts by weight or less. By using such an amount of solvent, the coating property of the coating liquid can be improved.

  The coating liquid can contain, for example, a polymerization initiator. Since the polymerization of the liquid crystal compound can be promoted by using the polymerization initiator, the alignment state of the liquid crystal compound can be easily fixed. As the polymerization initiator, a photopolymerization initiator may be used, or a thermal polymerization initiator may be used. Moreover, a polymerization initiator may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Examples of the photopolymerization initiator include benzoins, benzophenones, benzyl ketals, α-hydroxyketones, α-aminoketones, iodonium salts, sulfonium salts, and the like. Examples of commercially available photopolymerization initiators include “Irgacure 907”, “Irgacure 184”, “Irgacure 651”, “Irgacure 819”, “Irgacure 250”, “Irgacure 369” manufactured by Ciba Specialty Chemicals; “SEIKALL BZ”, “SEIKALL Z”, “SEIKALL BEE” manufactured by Seiko Chemical Co., Ltd .; “Kayacure BP100” manufactured by Nippon Kayaku Co., Ltd .; “Kayacure UVI-6992” manufactured by Dow Corporation; manufactured by Asahi Denka Co., Ltd. “Adekaoptomer SP-152”, “Adekaoptomer SP-170”;

  Examples of the thermal polymerization initiator include azo initiators such as 2,2′-azobis (isobutyronitrile) and 4,4′-azobis (4-cyanovaleric acid); peroxides such as benzoyl peroxide And so on.

  The amount of the polymerization initiator is preferably 0.1 parts by weight or more, more preferably 0.5 parts by weight or more, preferably 30 parts by weight or less, more preferably 10 parts by weight with respect to 100 parts by weight of the liquid crystalline compound. Or less. By using such an amount of the polymerization initiator, the polymerization reaction can proceed while suppressing the change in the alignment state of the liquid crystalline compound.

  The coating liquid can contain a polymerization inhibitor, for example. By using a polymerization inhibitor, the polymerization of the liquid crystal compound can be controlled, and the stability of the depolarizing layer can be improved, or the stability of the coating solution before coating can be improved. Moreover, a polymerization inhibitor may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Examples of the polymerization inhibitor include hydroquinone, hydroquinones such as hydroquinone having a substituent (alkyl group and the like); catechols such as catechol (butyl catechol and the like) having a substituent (alkyl group and the like); pyrogallols; And radical scavengers such as 2,6,6-tetramethyl-1-piperidinyloxy radical; thiophenols; β-naphthylamines; and β-naphthols.

  The amount of the polymerization inhibitor is preferably 0.1 parts by weight or more, more preferably 0.5 parts by weight or more, preferably 30 parts by weight or less, more preferably 10 parts by weight with respect to 100 parts by weight of the liquid crystalline compound. Or less. By using such an amount of the polymerization inhibitor, a change in the alignment state of the liquid crystal compound can be suppressed during the polymerization reaction.

  When using a photoinitiator, a coating liquid can contain a photosensitizer, for example. By using a photosensitizer, the polymerization of the liquid crystalline compound can be made highly sensitive. Moreover, a photosensitizer may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  Examples of the photosensitizer include xanthones such as xanthone and thioxanthone; anthracene such as anthracene having a substituent such as anthracene and alkoxy group; phenothiazine; and rubrene.

  The amount of the photosensitizer is preferably 0.1 parts by weight or more, more preferably 0.5 parts by weight or more, preferably 30 parts by weight or less, more preferably 10 parts by weight with respect to 100 parts by weight of the liquid crystalline compound. Less than parts by weight. By using such a quantity of photosensitizer, the polymerization reaction can be advanced while suppressing a change in the alignment state of the liquid crystalline compound.

  The coating liquid can contain a surfactant, for example. By using a surfactant, it is possible to control the size of the micro liquid crystal domain contained in the depolarization layer.

  As a coating method of the coating liquid, for example, a micro gravure coating method, a die coating method, a comma coating method, a lip coating method, a spin coating method, a bar coating method, or the like can be used.

  However, during the period from the surface treatment to the application of the coating liquid, the surface of the surface treatment layer of the base film (that is, the surface subjected to the surface treatment) is not in contact with any member. It is preferable not to give a frictional force by making the contact state. Thereby, since the orientation by the frictional force of the molecule | numerator contained in a surface treatment layer can be suppressed, a highly uniform depolarizing layer can be formed easily.

[1.7.4. Arbitrary process]
The method for producing a depolarizing film may further include an optional step in combination with the above-described steps.
For example, the method for producing a depolarizing film may include a drying step of drying the depolarizing layer after application of the coating liquid. By the drying step, volatility such as a solvent can be removed from the depolarizing layer formed by coating the coating liquid. The drying temperature is preferably 30 ° C. or higher, more preferably 50 ° C. or higher from the viewpoint of efficiently performing drying, and preferably 250 ° C. or lower from the viewpoint of suppressing thermal deterioration of the base film and the liquid crystalline compound. More preferably, it is 180 degrees C or less.

  For example, the method for producing a depolarizing film may include a step of fixing the alignment state of the liquid crystal compound contained in the depolarizing layer formed by coating the coating liquid. The alignment state of the liquid crystal compound can be fixed by polymerizing the liquid crystal compound. By fixing the alignment state of the liquid crystalline compound in this way, a depolarization layer containing the alignment fixing compound of the liquid crystalline compound is obtained. As described above, since the depolarizing layer containing the orientation fixing compound is usually a solid layer having high rigidity, high mechanical strength can be obtained.

  The polymerization of the liquid crystalline compound may be photopolymerization or thermal polymerization. Among these, photopolymerization is preferable because the polymerization reaction can be stably carried out at a low temperature. In photopolymerization, the alignment state of the liquid crystalline compound can be effectively fixed by irradiating the depolarizing layer with light containing a large amount of light having a wavelength that enables cleavage of the photopolymerization initiator. The light source can be selected according to the type of photopolymerization initiator used, and for example, an ultraviolet lamp such as a high-pressure mercury lamp, a metal halide lamp, or a fusion lamp can be suitably used. On the other hand, in the thermal polymerization, it is preferable to heat the depolarization layer to a temperature at which the thermal polymerization initiator is cleaved and the polymerization is started.

  Furthermore, the method for producing a depolarizing film may further include a step of providing an arbitrary layer.

[1.7.5. (Implementation with long film)
According to the manufacturing method mentioned above, a depolarization film provided with a base film and the depolarization layer containing the liquid crystalline compound provided on this base film or its orientation fixed compound is obtained. Moreover, when using a elongate film as a film before a process, it is possible to perform each process which the manufacturing method mentioned above conveys the film before a process in a film longitudinal direction. In this way, when the pre-treatment film is conveyed, the surface of the pre-treatment film may be in contact with a member such as a conveyance roll, and the molecules of the surface may be oriented. Therefore, it is possible to manufacture the film while conveying it. Therefore, since the manufacturing method of the depolarizing film mentioned above can be continuously manufactured by the roll-to-roll method, it is excellent in productivity.

[1.8. Application of depolarizing film according to first embodiment]
The depolarizing film is preferably provided in a liquid crystal display device. In a liquid crystal display device, an image is usually displayed by linearly polarized light that has passed through a linear polarizer. Therefore, an observer wearing polarized sunglasses may not be able to visually recognize an image displayed on the liquid crystal display device. On the other hand, when a depolarizing film is provided in the liquid crystal display device, an image is displayed by non-polarized light or partially polarized light, so that an observer wearing polarized sunglasses can clearly see the image.

  By the way, when a λ / 4 wavelength plate is appropriately provided on the screen of the liquid crystal display device, the liquid crystal display device can display an image by circularly polarized light or elliptically polarized light. Therefore, when a λ / 4 wavelength plate is provided in the liquid crystal display device, an observer wearing polarized sunglasses can visually recognize an image. However, in order to display an image by circularly polarized light or elliptically polarized light, the polarization transmission axis of the linear polarizer provided in the liquid crystal display device and the slow axis of the λ / 4 wavelength plate are aligned. Therefore, it is required to accurately adjust the angle formed between the polarization transmission axis of the linear polarizer and the slow axis of the λ / 4 wavelength plate. Therefore, the liquid crystal display device capable of displaying an image by circularly polarized light or elliptically polarized light as described above is difficult to manufacture because of complicated operation and condition adjustment for manufacturing. On the other hand, the depolarizing film does not require the above-described axis alignment and can be provided in the liquid crystal display device in an arbitrary direction. Therefore, the depolarizing film is excellent in that it can facilitate the production of a liquid crystal display device having excellent visibility when viewed with polarized sunglasses.

  When providing a depolarizing film in a liquid crystal display device, the depolarizing film is usually provided so that the liquid crystal cell, the viewing-side linear polarizer and the depolarizing film are in this order. Thereby, the linearly polarized light for displaying the image which permeate | transmitted the liquid crystal cell and the visual recognition side linear polarizer can be converted into partial polarized light or non-polarized light by a depolarization film. Such a liquid crystal display device can be manufactured by laminating a linear polarizer and a depolarization film to produce a multilayer film, and using this multilayer film to assemble a liquid crystal display device.

  A linear polarizer is an optical member having a polarization transmission axis and a polarization absorption axis, absorbs linearly polarized light having a vibration direction parallel to the polarization absorption axis, and passes linearly polarized light having a vibration direction parallel to the polarization transmission axis. sell. Here, the vibration direction of linearly polarized light means the vibration direction of the electric field of linearly polarized light. As a linear polarizer, for example, a film of an appropriate vinyl alcohol polymer such as polyvinyl alcohol or partially formalized polyvinyl alcohol, dyeing treatment with dichroic substances such as iodine and dichroic dye, stretching treatment, crosslinking treatment The film which performed appropriate processes, such as these by the appropriate order and system, can be used. Usually, in the stretching process for producing a linear polarizer, the film is stretched in the longitudinal direction, so that the obtained linear polarizer has a polarization absorption axis parallel to the longitudinal direction of the linear polarizer and the width of the linear polarizer. A polarization transmission axis parallel to the direction can be developed. This linear polarizer is preferably excellent in the degree of polarization. The thickness of the linear polarizer is generally 5 μm to 80 μm, but is not limited thereto.

  The bonding between the linear polarizer and the depolarizing film can be performed by any method, and for example, can be performed by bonding using an adhesive or a pressure-sensitive adhesive. In particular, it is preferable to bond a long linear polarizer and a long depolarizing film because a multilayer film can be manufactured by a roll-to-roll method. A long multilayer film produced by using a roll-to-roll method is usually cut into an appropriate size and incorporated in a liquid crystal display device.

[2. Description of Second Embodiment of the Present Invention]
Next, a second embodiment of the present invention will be described.

[2.1. Outline of Depolarization Film According to Second Embodiment]
FIG. 2 is a cross-sectional view schematically showing a depolarizing film 20 according to the second embodiment of the present invention.
As shown in FIG. 2, the depolarization film 20 which concerns on 2nd embodiment of this invention is the base film 300 as a stretched film, and the depolarization layer 400 formed in the at least one surface 300U of the base film 300. As shown in FIG. With. The depolarization layer 400 is a layer having a function of converting linearly polarized light into partially polarized light or non-polarized light (that is, a depolarization function). Therefore, the depolarization layer 400 can convert at least a part or all of the linearly polarized light L1 incident on the depolarization layer 400 into partially polarized light or non-polarized light L2 and emit it.

  Since the depolarization layer 400 has a function of converting linearly polarized light into partially polarized light or non-polarized light, when the light emitted from the depolarized layer 400 is partially polarized light, the partially polarized light is usually not linearly polarized light and non-polarized light. Often the light is mixed with polarized light.

  The depolarization function of the depolarization layer 400 is distinguished from the function of converting linearly polarized light into circularly polarized light or elliptically polarized light. Whether the decrease in the degree of polarization is due to conversion to partially polarized light or non-polarized light, or due to conversion to circularly polarized light or elliptically polarized light can be determined by the determination method described in the examples described later. When the depolarization film 20 is evaluated using the determination method, it is determined that the degree of polarization is reduced due to conversion to partially polarized light or non-polarized light.

  As the depolarization layer 400, the same one as the depolarization layer 200 described in the first embodiment is usually used. Therefore, the depolarizing layer 400 usually includes a large number of micro liquid crystal domains composed of a plurality of liquid crystal compounds having aligned states or alignment fixing compounds thereof. The alignment state of these liquid crystal domains is usually random. Therefore, the alignment states of the liquid crystal domains cancel each other, so that the depolarization layer 400 can be a non-oriented layer (that is, a layer having no orientation) from a macro viewpoint.

  In the depolarization layer 400 including the liquid crystal domains having a random alignment state as described above, the alignment state of the liquid crystalline compound is random or almost random from a macro viewpoint. Randomness can be imparted to some or all of the components. Therefore, the depolarization layer 400 can exhibit a depolarization function that converts part or all of the linearly polarized light incident on the depolarization layer 400 into partially polarized light or non-polarized light. The liquid crystal alignment structure of the depolarizing layer 400 is clearly distinguished from a λ / 4 wavelength plate that converts linearly polarized light into circularly polarized light or elliptically polarized light because the entire liquid crystalline compound is aligned in one direction. The

  Further, the base film 300 provided in the depolarizing film 20 is a stretched film, but its in-plane retardation Re is small. Thus, when the in-plane retardation Re which the base film 300 has is small, the change of the polarization state of the light which permeate | transmits the base film 300 can be suppressed. Therefore, when the depolarizing film 20 is provided in a display device such as a liquid crystal display device, unintentional coloring of the image can be suppressed.

  The base film 300 preferably includes a surface treatment layer 310 into which oxygen atoms have been introduced, and the surface treatment layer 310 and the depolarization layer 400 are preferably in direct contact with each other. Since oxygen atoms are introduced, the abundance ratio of the oxygen element in the surface treatment layer 310 is usually larger than the layer portion 320 of the base film 300 other than the surface treatment layer 310. In addition, the fact that the surface treatment layer 310 and the depolarization layer 400 are in direct contact means that there is no other layer between the surface treatment layer 310 and the depolarization layer 400. When the base film 300 includes such a surface treatment layer 310, the alignment state of the liquid crystal domains in the depolarization layer 400 can be easily randomized. Moreover, by using the base film 300 provided with the surface treatment layer 310, the depolarization film 20 can normally exhibit a depolarization function uniformly in a surface.

[2.2. Base film of depolarizing film according to second embodiment]
[2.2.1. Composition of base film]
As the base film, a resin film is usually used. As the resin, a thermoplastic resin is preferable. Therefore, the base film is preferably a resin film containing a thermoplastic polymer and optional components as necessary.

  Examples of the polymer include the same polymers as described in the first embodiment. Moreover, a polymer may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  Especially, as a polymer, the block copolymer which has an aromatic vinyl compound hydride unit (a) and a diene compound hydride unit (b) is preferable. That is, the specific block copolymer is preferable as the polymer contained in the base film. Since the specific block copolymer hardly develops the in-plane retardation Re even when stretched, the in-plane retardation Re of the base film can be easily reduced by using the specific block copolymer.

  As a specific block copolymer, what was demonstrated by 1st embodiment can be used, and the advantage similar to having demonstrated by 1st embodiment can be acquired by this.

  The amount of the weight body in the resin forming the base film can be in the same range as described in the first embodiment, and thereby has the same advantages as described in the first embodiment. Can be obtained.

  The resin forming the base film can contain an optional component in addition to the polymers listed above. Examples of optional components include the same components as described in the first embodiment. These components may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. The ratio of the arbitrary component can be appropriately adjusted within a range in which the ratio of the polymer in the resin is a preferable ratio.

  The glass transition temperature of the resin forming the base film can be in the same range as described in the first embodiment, thereby obtaining the same advantages as described in the first embodiment. it can.

[2.2.2. Surface treatment layer that can be contained in base film]
The base film preferably includes a surface treatment layer as a layer in contact with the depolarization layer. The surface treatment layer is the outermost surface layer on the depolarization layer side of the base film. The surface treatment layer is a layer into which oxygen atoms are introduced. By introducing oxygen atoms in this manner, the orientation state of molecules such as polymers is disturbed on the surface of the surface treatment layer. Therefore, it is possible to effectively suppress the alignment of the liquid crystalline compound in the depolarization layer provided on the surface of the surface treatment layer. Therefore, although the base film is a stretched film, the depolarization layer can be easily formed on the base film.

  Moreover, when a base film is provided with a surface treatment layer, a depolarization film can usually exhibit a depolarization function uniformly in a surface. When oxygen atoms are introduced as described above, disorder of molecules in the surface treatment layer occurs uniformly in the plane. Therefore, it can suppress that the part which the molecule | numerator orientated occurs locally on the surface of a base film. Therefore, when a coating liquid containing a liquid crystal compound is applied to this surface treatment layer, liquid crystal domains having a random alignment state can be formed uniformly in the plane, so that the depolarizing film has a depolarizing function. Uniform in the plane. In general, even if the film is not subjected to orientation treatment due to friction between the films and friction due to contact with the transport roll, a portion where molecules are locally oriented is formed on the surface of the film. In view of the above, it is a great advantage that the depolarization function can be uniformly exhibited in the plane as described above.

  The surface treatment layer can be formed by performing an appropriate surface treatment capable of introducing oxygen atoms on the surface of the base film. Examples of such surface treatment include the same treatment as described in the first embodiment.

  The amount of oxygen atoms introduced into the surface treatment layer can be in the same range as described in the first embodiment, and thereby the same advantages as described in the first embodiment can be obtained.

  The amount of oxygen atoms introduced into the surface treatment layer can be measured by the same method as described in the first embodiment.

  The thickness of the surface treatment layer is not particularly limited and is arbitrary. In the XPS method used in the method for measuring the introduction amount of oxygen atoms in the surface treatment layer, since the abundance ratio of elements at a depth of several nanometers on the sample surface is generally measured, the surface treatment layer is at least a substrate film. The surface has a thickness of several nanometers.

[2.2.3. Characteristics of base film
In the second embodiment, the base film is a stretched film that has been stretched. Since the stretching process is performed, the base film usually has excellent mechanical strength. However, in general, when the stretching treatment is performed, the molecules contained in the film are oriented, so that it has been difficult to form a depolarization layer on the stretched film by the conventional technique such as Patent Document 1. On the other hand, in the second embodiment of the present invention, even if the base film is a stretched film by a technique such as forming a surface treatment layer, a depolarizing layer is formed on the stretched film. It is possible to form.

  The in-plane retardation Re of the substrate film is usually 30 nm or less, preferably 20 nm or less, more preferably 10 nm or less. Since the in-plane retardation Re of the base film is small as described above, the depolarization layer can be made thin.

  The base film as a stretched film having a small in-plane retardation Re as described above can be realized by using, for example, the specific block copolymer described above.

The base film is usually a transparent film. Therefore, usually, the total light transmittance of the base film is high, and the haze of the base film is low. Specifically, the total light transmittance and haze of the base film can be in the same range as described in the first embodiment.
The total light transmittance and haze of the film can be measured in the same manner as described in the first embodiment.

  The tensile elastic modulus of the base film can be in the same range as described in the first embodiment, and thereby, the same advantage as described in the first embodiment can be obtained.

  The tensile elastic modulus of the film can be measured by the same method as described in the first embodiment.

  The base film preferably has a high impact strength. Here, the impact strength of the film is synonymous with the impact strength described in the first embodiment. The impact strength of the base film can be in the same range as described in the first embodiment, and thereby the same advantages as described in the first embodiment can be obtained.

  The thickness of the base film can be in the same range as described in the first embodiment, and thereby the same advantages as described in the first embodiment can be obtained.

[2.3. Depolarization Layer of Depolarization Film According to Second Embodiment]
The depolarizing layer is a layer containing a liquid crystalline compound or an alignment fixing compound formed on the surface of the base film. As the depolarization layer, generally, the same depolarization layer as described in the first embodiment can be used, whereby the same advantages as described in the first embodiment can be obtained.

[2.4. Arbitrary Layer of Depolarizing Film According to Second Embodiment]
The depolarizing film may further include an arbitrary layer in combination with the base film and the depolarizing layer. For example, the depolarizing film may have an arbitrary layer on the side opposite to the depolarizing layer of the base film and on the side opposite to the base film of the depolarizing layer.

[2.5. Characteristics of the depolarizing film according to the second embodiment]
Since the depolarization film includes a depolarization layer, it has a depolarization function. Therefore, the depolarizing film can emit at least part or all of the linearly polarized light incident on the depolarizing film after being converted into partially polarized light or non-polarized light.

  Moreover, the depolarizing film can usually exhibit the above-mentioned depolarizing function uniformly in the plane. Therefore, the depolarization film can suppress that the part which cannot exhibit a depolarization function arises locally in the surface of the said depolarization film.

  It can be confirmed by the same method as in the first embodiment that the depolarization film can exhibit the depolarization function uniformly in the plane.

  The depolarizing film preferably has high transparency. Therefore, the depolarizing film preferably has a high total light transmittance, and preferably has a low haze. The specific total light transmittance and haze of the depolarizing film can be in the same range as described in the first embodiment, thereby obtaining the same advantages as described in the first embodiment. be able to.

  The in-plane retardation Re of the depolarizing film can be in the same range as described in the first embodiment, and thereby, the same advantages as described in the first embodiment can be obtained.

  The tensile elastic modulus of the depolarizing film can be in the same range as described in the first embodiment, thereby obtaining the same advantages as described in the first embodiment.

  The depolarizing film preferably has a high impact strength. The impact strength of the depolarizing film can be in the same range as described in the first embodiment, and thereby the same advantages as described in the first embodiment can be obtained.

[2.6. Dimensions of depolarizing film according to second embodiment]
The depolarizing film is preferably a long film.

  The thickness of the depolarizing film can be in the same range as described in the first embodiment, and thereby, the same advantage as described in the first embodiment can be obtained.

[2.7. Manufacturing method of depolarizing film according to second embodiment]
The depolarizing film is prepared by, for example, preparing a pre-stretch film from which a base film is obtained by stretching; stretching a pre-stretch film to obtain a base film; surface on at least one surface of the base film A step of forming a surface treatment layer by applying a treatment; and a step of forming a depolarization layer by applying a coating liquid containing a liquid crystal compound to the surface subjected to the surface treatment. It can be manufactured by a method. Moreover, the said manufacturing method is normally performed, conveying a film before extending | stretching and a base film in a film longitudinal direction. Hereinafter, this manufacturing method will be described in detail.

[2.7.1. Preparation of film before stretching)
The film before stretching is a film from which the above-described base film can be obtained by stretching. As this pre-stretch film, a film made of the same resin as the base film described above can be used.

  The manufacturing method of the film before extending | stretching is arbitrary. The pre-stretch film can be produced, for example, by the same method as the pre-treatment film production method described in the first embodiment, thereby obtaining the same advantages as the pre-treatment film production method described in the first embodiment. be able to.

[7.2. Stretching process]
After the pre-stretching film is prepared, the pre-stretching film is stretched to obtain a base film. The stretching conditions are not particularly limited and can be appropriately adjusted so that a desired product is obtained.

  Stretching may be performed by uniaxial stretching processing in which stretching processing is performed only in one direction, or biaxial stretching processing in which stretching processing is performed in two different directions. In addition, in the biaxial stretching process, a simultaneous biaxial stretching process in which stretching processes are performed simultaneously in two directions may be performed, and a sequential biaxial stretching process in which a stretching process is performed in one direction and then a stretching process is performed in another direction. May be performed. Further, the stretching is a longitudinal stretching process in which the stretching process is performed in the longitudinal direction of the film before stretching, a lateral stretching process in which the stretching process is performed in the width direction of the film before stretching, and an oblique direction that is neither parallel nor perpendicular to the width direction of the film before stretching. Any of the oblique stretching treatments for stretching may be performed, or a combination of these may be performed.

  The draw ratio can be arbitrarily set according to the physical properties required for the base film. When showing a specific range of the draw ratio, it is preferably 1.2 times or more, more preferably 1.5 times or more, particularly preferably 2.0 times or more, preferably 10 times or less, more preferably 8 times. Hereinafter, it is particularly preferably 5 times or less. In the stretched film stretched at such a large stretch ratio, the polymer molecules in the film are largely oriented, but even when such a stretched film is used as a base film, by providing a surface treatment layer, A depolarizing layer can be easily formed on the base film.

  The stretching temperature can be arbitrarily set according to the physical properties required for the base film. Specifically, the range of the stretching temperature is preferably TgA-30 ° C or higher, more preferably TgA-20 ° C or higher, particularly preferably TgA-15 ° C or higher, preferably TgA + 70 ° C or lower, more preferably TgA + 60 ° C. Hereinafter, TgA + 50 ° C. or less is particularly preferable. Here, TgA represents the glass transition temperature of the resin contained in the film before stretching and the base film. In a stretched film stretched in such a temperature range, polymer molecules in the film are largely oriented. Even when such a stretched film is used as a base film, by providing a surface treatment layer, A depolarizing layer can be easily formed on a base film.

[2.7.3. Surface treatment process)
After obtaining the base film by stretching the pre-stretch film, it is preferable to perform a step of performing a surface treatment on at least one surface of the base film. This surface treatment is a treatment for introducing oxygen atoms into the surface of the base film. By performing this surface treatment, a surface treatment layer is formed as the outermost layer of the base film. Since the molecular alignment state is disturbed on the surface of the surface treatment layer, the alignment regulating force on this surface can be reduced.

  The surface treatment can be performed in the same manner as described in the first embodiment, for example.

[2.7.4. (Coating liquid coating process)
After the surface treatment, a step of applying a coating liquid containing a liquid crystalline compound to the surface subjected to the surface treatment is performed. By applying the coating solution, a depolarizing layer containing a liquid crystalline compound can be formed on the surface treatment layer. And thereby, a depolarization film provided with a base film and a depolarization layer is obtained. Since the molecules contained in the surface treatment layer are not oriented, the liquid crystalline compound contained in the depolarizing layer is not oriented. Therefore, the depolarization layer is a layer including a liquid crystal domain having a random alignment state, and thus can exhibit a depolarization function.

  As a coating liquid, the liquid containing the liquid crystalline compound mentioned above is used. Moreover, a coating liquid can contain arbitrary components in combination with a liquid crystalline compound. As the coating liquid, the same ones as described in the first embodiment can be usually used, whereby the same advantages as described in the first embodiment can be obtained.

  Examples of the coating method of the coating liquid include the same method as described in the first embodiment.

  However, during the period from the surface treatment to the application of the coating liquid, the surface of the surface treatment layer of the base film (that is, the surface subjected to the surface treatment) is not in contact with any member. It is preferable not to give a frictional force by making the contact state. Thereby, since the orientation by the frictional force of the molecule | numerator contained in a surface treatment layer can be suppressed, a highly uniform depolarizing layer can be formed easily.

[7.5. Arbitrary process]
The method for producing a depolarizing film may further include an optional step in combination with the above-described steps. As an arbitrary process, the process similar to 1st embodiment is mentioned, for example, By this, the advantage similar to having demonstrated in 1st embodiment can be acquired.

[2.8. Application of depolarizing film according to second embodiment]
The depolarizing film can be used for the same application as that described in the first embodiment, and thereby, the same advantages as those described in the first embodiment can be obtained.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof. In the following description, “%” and “part” representing amounts are based on weight unless otherwise specified. Further, the operations described below were performed in a normal temperature and pressure atmosphere unless otherwise specified.

[Evaluation method]
[Measurement method of in-plane retardation of film]
The in-plane retardation Re of the film was measured using a polarimeter (“AxoScan” manufactured by AXOMETRICS) at a measurement wavelength of 550 nm.
Moreover, in the Example shown below, there exists what measures the in-plane retardation Re of the film before a corona treatment before a process. Usually, since the in-plane retardation Re does not change by corona treatment, the measured value of the in-plane retardation of the film before treatment can be adopted as the in-plane retardation of the base film.

[Measurement method of oxygen atom introduction amount on film surface]
Before and after performing the surface treatment on the film surface, an XPS measurement analyzer (“PHI Bearsaprobe II” manufactured by ULVAC-PHI) was used to identify the elements present on the film surface and measure the abundance ratio of the existing elements. The difference in the ratio of oxygen elements present on the film surface before and after the surface treatment was calculated as the amount of oxygen atoms introduced.

[Measurement method of total light transmittance of film]
The total light transmittance of the film was measured using a haze meter (“Haze Guard II” manufactured by Toyo Seiki Seisakusho Co., Ltd.) according to JIS K 7361.

[Method for measuring haze of film]
The haze of the film was measured using a haze meter (“Haze Guard II” manufactured by Toyo Seiki Seisakusho) according to JIS K 7136.

[Method for measuring tensile modulus of film]
According to JIS K7162, the film was punched into a dumbbell shape to obtain a test piece. The test piece was subjected to a tensile test at a tensile speed of 5 mm / min using a tensile tester (“Tensile Tester 5564” manufactured by Instron Japan). The tensile modulus was measured from the slope of the SS curve (stress-strain curve) obtained in the tensile test. Moreover, especially about the stretched film, in order to manufacture the stretched film, the tensile elasticity modulus in the direction which stretched | stretched the film before extending | stretching was measured.

[Measurement method of impact strength]
The film was fixed horizontally using a jig. An impact test was conducted in which a steel ball (pachinko ball, weight 5 g, diameter 11 mm) was dropped from various heights h at the center of the film fixed to the jig. In this impact test, the height h of the boundary when the film was not torn and when the film was torn was determined. The potential energy (kmJ) of the steel ball at the boundary height h was measured as the impact strength of the film.

[Evaluation method of depolarization function]
An ultraviolet-visible spectrophotometer (a kit in which an ultraviolet-visible spectrophotometer “V7200” manufactured by JASCO Corporation is set with a polarization measurement option “VAP-7070”) was prepared. A polarizing prism (Gran Thompson prism) was installed on the light source side of this apparatus. In addition, a polarizing plate having a polarization degree of 99.90% or more was attached as an analyzer to a rotary holder installed on the light receiving side of the polarizing prism.

This state is emitting light source by using the ultraviolet-visible spectrophotometer, linearly polarized light emitted from the polarizing prism was measured MD transmittance T _MD and TD transmittance T _TD transmits an analyzer. Here, the MD transmittance T _MD is a transmittance when the vibration direction of the linearly polarized light emitted from the polarizing prism and the polarization transmission axis of the analyzer are parallel. The TD transmittance T _TD is a transmittance when the vibration direction of the linearly polarized light emitted from the polarizing prism and the polarization transmission axis of the analyzer are perpendicular to each other. Measurement of MD transmittance _{T MD} and TD transmittance _{T TD} was carried out in the range of measurement wavelength 380 nm to 780 nm.

From the measured MD transmittance _{T MD} and TD transmittance _{T TD,} the formula (A) below, to calculate the degree of polarization _{D P} before correction, addition, viewing the two-degree field of JIS Z 8701 (C light source) Sensitivity correction was performed to determine the corrected degree of polarization. Hereinafter, the degree of polarization measured without installing a sample film between the polarizing prism and the analyzer may be referred to as “blank polarization degree” as appropriate. It was confirmed that the polarization value of this blank was 99.90% or more.
_{D P (%) = {(} T MD -T TD) / (T MD + T TD)} 1/2 × 100 (A)

Next, the sample film to be measured between the polarization prism and the analyzer is installed, similar to the above, measurement of the MD transmittance T _MD and TD transmittance T _TD, correction calculation of the previous polarization D _P In addition, the visibility was corrected, and the corrected degree of polarization at a measurement angle of 0 ° was obtained.
Thereafter, the sample film is rotated by measurement angles of 45 °, 90 °, 135 °, and 180 ° around the rotation axis perpendicular to the main surface of the sample film, and at each measurement angle as described above. The corrected degree of polarization was determined.

  The degree of polarization of the blank measured without installing the sample film indicates the degree of polarization of the linearly polarized light itself emitted from the polarizing prism. Further, the degree of polarization measured by installing the sample film indicates the degree of polarization of light after the linearly polarized light emitted from the polarizing prism is transmitted through the sample film. Therefore, when the sample film has a depolarization function, the degree of polarization measured by installing the sample film is lower than the degree of polarization of the blank measured without installing the sample film by the amount of depolarization. When the degree of polarization measured by installing the sample film is less than 90.00%, the sample film can be judged as “having a function of converting linearly polarized light into partially polarized light”. In particular, when the degree of polarization measured by installing a sample film is less than 5.0%, it is difficult to say that preferentially polarized light is observed anymore, so “has a function of converting linearly polarized light into non-polarized light”. It can be judged.

  Even if the sample film does not have a depolarization function, if the sample film has a circular polarization conversion function for converting linearly polarized light into circularly polarized light or elliptically polarized light, the degree of polarization measured by installing the sample film is It can be lower than the polarization degree of the blank. Whether such a decrease in the degree of polarization is due to the depolarization function or the circular polarization conversion function can be determined by the following determination method.

  The difference between the maximum value and the minimum value is calculated from the degree of polarization measured at the measurement angles of 0 °, 45 °, 90 °, 135 °, and 180 °. When this difference is less than 10.00%, it can be determined that the sample film has a depolarization function that converts linearly polarized light into partially polarized light or non-polarized light. On the other hand, when the difference is 10.00% or more, the sample film has in-plane retardation, which indicates that the observable slow axis direction exists clearly. This sample film can be judged to have a circularly polarized light conversion function for converting linearly polarized light into circularly polarized light or elliptically polarized light.

[Evaluation method of in-plane uniformity of depolarization function]
Two polarizing plates were placed on the light table. The orientation of the polarizing plate was adjusted so that the polarized light transmission axis of one polarizing plate and the polarized light transmission axis of the other polarizing plate were perpendicular to each other. A film cut to 100 mm × 100 mm was placed between the polarizing plates. With the light table turned on, the film was visually observed while being rotated 360 ° in the in-plane direction. From the observation results, the in-plane uniformity of the depolarization function of the film was evaluated based on the following criteria.
“Good”: The extinction position cannot be obtained. That is, there is no darkened portion over the entire surface regardless of the angle of the film.
"Bad": The extinction position can be taken. That is, when the film is at an angle, there is a portion that becomes dark.

[1. Production Examples, Examples, and Comparative Examples Regarding First Embodiment]
[Production Example 1-1. Production of pre-treatment film 1-1]
A pellet of an alicyclic structure-containing polymer resin (“ZEONOR 1430” manufactured by Nippon Zeon Co., Ltd .; glass transition temperature: 135 ° C.) was dried at 70 ° C. for 2 hours using a hot air dryer in which air was circulated. Thereafter, the dried resin was subjected to molding conditions of a molten resin temperature of 270 ° C. and a T die width of 500 mm using a T-die type film melt extrusion molding machine having a resin melt kneader equipped with a 65 mm diameter screw. A pre-treatment film 1-1 having a thickness of 40 μm and a length of 1000 m was produced by molding into a film. When the abundance ratio of the oxygen element on the surface of the untreated film 1-1 was measured, it was 0 atom%. The in-plane retardation Re of this untreated film 1-1 was measured by the method described above.

[Production Example 1-2. Production of pre-treatment film 1-2]
(1-2-1. First Stage Polymerization Reaction: Elongation of Block A1)
A stainless steel reactor equipped with a stirrer and thoroughly dried and purged with nitrogen was charged with 320 parts of dehydrated cyclohexane, 65 parts of styrene, and 0.38 part of dibutyl ether, and stirred at 60 ° C. to obtain an n-butyllithium solution. (15 wt% hexane solution) 0.41 part was added to initiate the polymerization reaction, and the first stage polymerization reaction was carried out. At 1 hour after the start of the reaction, a sample was sampled from the reaction mixture and analyzed by gas chromatography (GC). As a result, the polymerization conversion was 99.5%.

(1-2-2. Second Stage Reaction: Extension of Block B)
To the reaction mixture obtained in the step (1-2-1), 40 parts of a mixed monomer consisting of 15 parts of styrene and 15 parts of isoprene was added, and then the second stage polymerization reaction was started. At 1 hour after the start of the second stage polymerization reaction, a sample was sampled from the reaction mixture and analyzed by GC. As a result, the polymerization conversion was 99.5%.

(1-2-3. Third stage reaction: extension of block A2)
5 parts of styrene was added to the reaction mixture obtained in the step (1-2-2), and the third stage polymerization reaction was subsequently started. At 1 hour after the start of the third stage polymerization reaction, a sample was sampled from the reaction mixture, and the weight average molecular weight Mw and number average molecular weight Mn of the polymer were measured. Moreover, as a result of analyzing the sample sampled at this time by GC, the polymerization conversion was almost 100%. Immediately thereafter, 0.2 part of isopropyl alcohol was added to the reaction mixture to stop the reaction. This obtained the mixture containing the block copolymer which has a triblock molecular structure of A1-B-A2.

In the steps (1-1-1) and (1-1-2), since the polymerization reaction was sufficiently advanced, the polymerization conversion rate was about 100%. Therefore, the weight ratio of St / Ip in the block B was It is considered to be 20/20. Here, “St” represents styrene, and “Ip” represents isoprene.
From these values, it was found that the obtained block copolymer was a polymer having a triblock molecular structure of St- (St / Ip) -St = 65- (15/15) -5. The weight average molecular weight (Mw (3)) of the block copolymer was 105,500, and the molecular weight distribution (Mw / Mn) was 1.04.

  Next, the mixture containing the above block copolymer was transferred to a pressure-resistant reactor equipped with a stirrer, and a diatomaceous earth-supported nickel catalyst (“E22U” manufactured by JGC Catalysts & Chemicals, 60% nickel support) as a hydrogenation catalyst. 8.0 parts and 100 parts dehydrated cyclohexane were added and mixed. The inside of the reactor was replaced with hydrogen gas, and hydrogen was supplied while stirring the solution. A hydrogenation reaction was performed at a temperature of 190 ° C. and a pressure of 4.5 MPa for 6 hours. Thereby, the hydrogenation reaction of the block copolymer proceeded to obtain a reaction solution containing the specific block copolymer. The weight average molecular weight (Mw) of the specific block copolymer contained in this reaction solution was 111,800, and the molecular weight distribution (Mw / Mn) was 1.05.

After completion of the hydrogenation reaction, the reaction solution was filtered to remove the hydrogenation catalyst, and then the phenol-based antioxidant pentaerythrityl tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl). ) Propionate] ("Songnox 1010" manufactured by Matsubara Sangyo Co., Ltd.) 2.0 parts of xylene solution in which 0.1 part was dissolved was added and dissolved.
Next, the above solution is dried at a temperature of 260 ° C. and a pressure of 0.001 MPa or less using a cylindrical concentrating dryer (“Contro” manufactured by Hitachi, Ltd.). From the solution, the solvents cyclohexane and xylene, and others Volatile components were removed.

  The specific block copolymer obtained after drying was melted, extruded into a strand from a die, cooled, and then molded by a pelletizer to produce 95 parts of a specific block copolymer pellet. The resulting pellet-like specific block copolymer had a weight average molecular weight (Mw) of 110,300, a molecular weight distribution (Mw / Mn) of 1.10, and a hydrogenation rate of almost 100%.

  The pre-treatment film 1-2 having a thickness of 50 μm and a length of 1000 m was produced by extruding the specific block copolymer. When the abundance ratio of the oxygen element on the surface of the untreated film 1-2 was measured, it was 0 atom%. The in-plane retardation Re of this untreated film 1-2 was measured by the method described above.

[Production Example 1-3. Production of pre-treated film 1-3]
A tenter stretching machine equipped with a clip capable of gripping both ends of the long film in the width direction was prepared. The unprocessed film 1-2 obtained in Production Example 1-2 is supplied to the tenter stretching machine, and both ends of the unprocessed film 1-2 in the width direction are gripped by clips and pulled in the film width direction. Thus, a uniaxial stretching process was performed. The stretching conditions at this time were a stretching temperature of 130 ° C. and a stretching ratio of 2.0 times. Thereby, the film 1-3 before a process as a stretched film was obtained. When the abundance ratio of the oxygen element on the surface of the untreated film 1-3 was measured, it was 0 atom%. In-plane retardation Re of this untreated film 1-3 was measured by the method described above.

[Example 1-1]
(Preparation of coating solution)
100 parts by weight of a liquid crystal compound ("LC242" manufactured by BASF), 3 parts by weight of a photopolymerization initiator ("Irgacure 369" manufactured by Ciba Japan), 0.5 parts by weight of a leveling agent ("F-477" manufactured by DIC) And 260 parts by weight of cyclopentanone as a solvent were mixed to obtain a coating liquid for the depolarization layer.

(Surface treatment; production of substrate film)
One side of the untreated film 1-1 produced in Production Example 1-1 was subjected to corona treatment at a discharge amount of 50 W · min / m ² using a corona treatment device (manufactured by Kasuga Denki Co., Ltd.). By the corona treatment, the surface portion of the pre-treatment film 1-1 became a surface treatment layer, and a base film 1-1 was obtained. It was 5 atom% when the existence ratio of the oxygen element of the surface which gave the corona treatment of this base film 1-1 was measured. The tensile elastic modulus of the base film 1-1 thus obtained was measured by the method described above.

(Coating liquid application)
The coating liquid was applied to the surface of the base film 1-1 subjected to the corona treatment by a die coating method so that the wet film thickness was 3.2 μm to form a coating liquid layer. Thereafter, the film is dried in a hot air oven at 60 ° C. for 1 minute, and further, the depolarizing layer is formed on the substrate film 1-1 by irradiating the coating liquid layer by irradiating with 1000 mJ / cm ² ultraviolet rays at room temperature. And the depolarization film provided with the base film 1-1 and the depolarization layer was obtained. The total light transmittance, haze, in-plane retardation Re, depolarization function, and in-plane uniformity of the depolarization function of the obtained depolarization film were evaluated by the methods described above.

[Example 1-2]
A depolarizing film was manufactured and evaluated in the same manner as in Example 1-1 except that the discharge amount in the corona treatment was changed to 500 W · min / m ² . In Example 1-2, the abundance ratio of the oxygen element on the surface of the base film 1-1 subjected to the corona treatment was 20 atom%.

[Example 1-3]
Instead of the untreated film 1-1, the untreated film 1-2 produced in Production Example 1-2 was used. Moreover, the discharge amount in the corona treatment was changed to 300 W · min / m ² . Except for the above items, a depolarizing film was produced and evaluated in the same manner as in Example 1-1.

[Example 1-4]
Instead of the untreated film 1-1, the untreated film 1-3 produced in Production Example 1-3 was used. Moreover, the discharge amount in the corona treatment was changed to 300 W · min / m ² . Except for the above items, a depolarizing film was produced and evaluated in the same manner as in Example 1-1.

[Comparative Example 1-1]
Instead of the pre-treatment film 1-1, a triacetyl cellulose film (“KC4UY” manufactured by Konica Minolta Opto) having a thickness of 40 μm and a length of 1000 m was used. Moreover, the corona treatment was not performed. Except for the above items, a depolarizing film was produced and evaluated in the same manner as in Example 1-1.

[Comparative Example 1-2]
Instead of the depolarizing film, a retardation film (“ESCINA TER-140” manufactured by Sekisui Chemical Co., Ltd.), which is a λ / 4 wavelength plate, was evaluated.

[result]
The results of Examples and Comparative Examples are shown in Table 1 below. In Table 1, the meanings of the abbreviations are as follows.
Re: In-plane retardation.
Oxygen atom introduction amount: The amount of oxygen atoms introduced by corona treatment.
Polarization degree (0 ° direction): degree of polarization at a measurement angle of 0 °.
Polarization degree (45 ° direction): degree of polarization at a measurement angle of 45 °.
Polarization degree (90 ° direction): degree of polarization at a measurement angle of 90 °.
Polarization degree (135 ° direction): degree of polarization at a measurement angle of 135 °.
Polarization degree (180 ° direction): degree of polarization at a measurement angle of 180 °.

[Examination of Examples and Comparative Examples According to First Embodiment]
In Comparative Example 1-1, a part having no depolarization function was observed in a part of the plane. In this part, it is considered that the molecules on the film surface were oriented by the friction between the films at the time of winding or unwinding the triacetyl cellulose film, and the orientation regulating force was generated. On the other hand, in Examples 1-1 to 1-4, the depolarization function can be exhibited uniformly in the plane. From this result, it was confirmed that the present invention can realize a depolarization film that can exhibit the depolarization function uniformly in the plane.

[2. Production Examples, Examples and Comparative Examples Regarding Second Embodiment]
[Production Example 2-1. Production of base film 2-1]
(2-1-1. Production of film before stretching)
By extruding the pellet-shaped specific block copolymer obtained in [Production Example 1-2], a pre-stretching film 2-1 having a thickness of 50 μm and a length of 1000 m was produced. When the abundance ratio of oxygen element on the surface of the pre-stretching film 2-1 was measured, it was 0 atom%. The in-plane retardation Re of the unstretched film 2-1 was 3 nm as measured by the method described above. Furthermore, the tensile elastic modulus and impact strength of the film 2-1 before stretching thus obtained were measured by the method described above.

(2-1-2. Stretching)
A tenter stretching machine equipped with a clip capable of gripping both ends of the long film in the width direction was prepared. The unstretched film 2-1 was supplied to the tenter stretching machine, and both ends in the width direction of the unstretched film 2-1 were gripped by clips and pulled in the film width direction to perform uniaxial stretching. . The stretching conditions at this time were a stretching temperature of 140 ° C. and a stretching ratio of 2.0 times. Thereby, the base film 2-1 as a stretched film was obtained. When the abundance ratio of oxygen element on the surface of the base film 2-1 was measured, it was 0 atom%. Moreover, it was 10 nm when the in-plane retardation of this base film 2-1 was measured by the method mentioned above. Furthermore, the tensile elasticity modulus and impact strength of the base film 2-1 obtained in this way were measured by the method described above.

[Production Example 2-2. Production of base film 2-2]
A pellet of an alicyclic structure-containing polymer resin (“ZEONOR 1430” manufactured by Nippon Zeon Co., Ltd .; glass transition temperature: 135 ° C.) was dried at 70 ° C. for 2 hours using a hot air dryer in which air was circulated. Thereafter, the dried resin was subjected to molding conditions of a molten resin temperature of 270 ° C. and a T die width of 500 mm using a T-die type film melt extrusion molding machine having a resin melt kneader equipped with a 65 mm diameter screw. A film 2-2 having a thickness of 100 μm and a length of 1000 m was produced by molding into a film.

  A tenter stretching machine similar to that used in Production Example 2-1 was prepared. The unstretched film 2-2 was supplied to the tenter stretching machine, and both ends in the width direction of the unstretched film 2-2 were gripped by clips and pulled in the film width direction to perform a uniaxial stretching process. . The stretching conditions at this time were a stretching temperature of 140 ° C. and a stretching ratio of 2.0 times. Thereby, the base film 2-2 as a stretched film was obtained. When the abundance ratio of the oxygen element on the surface of the base film 2-2 was measured, it was 0 atom%. Moreover, it was 50 nm when the in-plane retardation of this base film 2-2 was measured by the method mentioned above. Furthermore, the tensile modulus and impact strength of the base film 2-2 thus obtained were measured by the methods described above.

[Example 2-1]
(Preparation of coating solution)
100 parts by weight of a liquid crystal compound ("LC242" manufactured by BASF), 3 parts by weight of a photopolymerization initiator ("Irgacure 369" manufactured by Ciba Japan), 0.5 parts by weight of a leveling agent ("F-477" manufactured by DIC) Part and 260 parts by weight of cyclopentanone as a solvent were mixed to obtain a coating solution for the depolarizing layer.

(surface treatment)
One side of the base film 2-1 produced in Production Example 2-1 is subjected to corona treatment at a discharge amount of 300 W · min / m ² using a corona treatment device (manufactured by Kasuga Denki Co., Ltd.). The surface part of the material film 2-1 was used as the surface treatment layer. When the abundance ratio of the oxygen element on the surface subjected to the corona treatment was measured, it was 10 atom%.

(Coating of coating layer)
The coating liquid was applied to the surface of the substrate film 2-1 that had been subjected to the corona treatment by a die coating method so that the wet film thickness was 3.2 μm to form a coating liquid layer. Thereafter, the film is dried in a hot air oven at 60 ° C. for 1 minute, and further, a depolarizing layer is formed on the base film 2-1 by curing the coating liquid layer by irradiating with 1000 mJ / cm ² ultraviolet rays at room temperature. Thus, a depolarizing film was obtained. The total light transmittance, haze, in-plane retardation Re, depolarization function, and in-plane uniformity of the depolarization function of the obtained depolarization film were evaluated by the methods described above.

[Example 2-2]
A depolarizing film was produced and evaluated in the same manner as in Example 2-1, except that the discharge amount in the corona treatment was changed to 50 W · min / m ² . In Example 2-2, the abundance ratio of the oxygen element on the surface of the base film 2-1 subjected to the corona treatment was 7 atom%.

[Example 2-3]
A depolarizing film was produced and evaluated in the same manner as in Example 2-1, except that the discharge amount in the corona treatment was changed to 500 W · min / m ² . In Example 2-3, the abundance ratio of the oxygen element on the surface of the base film 2-1 subjected to the corona treatment was 17 atom%.

[Comparative Example 2-1]
In the same manner as in Example 2-1, except that the base film 2-2 manufactured in Manufacturing Example 2-2 was used instead of the base film 2-1 manufactured in Manufacturing Example 2-1, polarized light was used. The release film was manufactured and evaluated.

[Comparative Example 2-2]
In the same manner as in Example 2-1, except that the pre-stretching film 2-1 produced in Production Example 2-1 was used instead of the base film 2-1 produced in Production Example 2-1, polarized light was used. The release film was manufactured and evaluated.

[result]
The results of Examples and Comparative Examples are shown in Table 2 below. In Table 2, the meanings of the abbreviations are as follows.
Re: In-plane retardation.
Oxygen atom introduction amount: The amount of oxygen atoms introduced by corona treatment.
Polarization degree (0 ° direction): degree of polarization at a measurement angle of 0 °.
Polarization degree (45 ° direction): degree of polarization at a measurement angle of 45 °.
Polarization degree (90 ° direction): degree of polarization at a measurement angle of 90 °.
Polarization degree (135 ° direction): degree of polarization at a measurement angle of 135 °.
Polarization degree (180 ° direction): degree of polarization at a measurement angle of 180 °.

10, 20 Depolarization film 100, 300 Base film 110, 310 Surface treatment layer 120, 320 Layer portion of base film other than surface treatment layer 200, 400 Depolarization layer

Claims (14)

A base film, and a depolarization layer formed on at least one surface of the base film, and having a function of converting linearly polarized light into partially polarized light or non-polarized light,
The depolarizing layer includes a liquid crystal compound or an alignment fixing compound of the liquid crystal compound,
The base film includes a surface treatment layer into which oxygen atoms are introduced,
The depolarization film in which the surface treatment layer and the depolarization layer are in direct contact.   The depolarizing film according to claim 1, wherein an introduction amount of oxygen atoms in the surface treatment layer is 5 atom% to 20 atom%.   The depolarization film of Claim 1 or 2 whose in-plane retardation of the said base film is 30 nm or less.   The base film is at least one selected from the group consisting of an alicyclic structure-containing polymer and a block copolymer having an aromatic vinyl compound hydride unit (a) and a diene compound hydride unit (b). The depolarization film as described in any one of Claims 1-3 containing the polymer of.   The depolarizing film according to any one of claims 1 to 4, wherein the base film is a stretched film.   The depolarizing film according to any one of claims 1 to 5, which is a long film. Applying a surface treatment to introduce oxygen atoms on at least one surface of the pre-treatment film;
Applying a coating liquid containing a liquid crystalline compound to the surface subjected to the surface treatment to form a depolarization layer,
The method for producing a depolarizing film, wherein the depolarizing layer has a function of converting linearly polarized light into partially polarized light or non-polarized light.   The method for producing a depolarizing film according to claim 7, wherein the surface treatment is a corona treatment. A base film, and a depolarization layer formed on at least one surface of the base film, and having a function of converting linearly polarized light into partially polarized light or non-polarized light,
The depolarizing layer includes a liquid crystal compound or an alignment fixing compound of the liquid crystal compound,
The base film is a stretched film,
The depolarization film whose in-plane retardation of the said base film is 30 nm or less.   The depolarizing film according to claim 9, wherein the base film comprises a block copolymer having an aromatic vinyl compound hydride unit (a) and a diene compound hydride unit (b). The base film includes a surface treatment layer into which oxygen atoms are introduced,
The depolarizing film according to claim 9 or 10, wherein the surface treatment layer and the depolarizing layer are in direct contact with each other.   The depolarizing film according to claim 11, wherein an introduction amount of oxygen atoms in the surface treatment layer is 5 atom% to 20 atom%.   The depolarizing film according to any one of claims 9 to 12, wherein the haze is 15% or less. Stretching the film before stretching to obtain a base film;
Applying a surface treatment for introducing oxygen atoms to at least one surface of the base film;
Applying a coating liquid containing a liquid crystalline compound to the surface subjected to the surface treatment to form a depolarizing layer, and
The method for producing a depolarizing film, wherein the depolarizing layer has a function of converting linearly polarized light into partially polarized light or non-polarized light.

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