JP2005037657A - Optical laminate, its manufacturing method, and luminance improved film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical laminate uniformly and inexpensively manufactured and having a liquid crystal layer set in a specified oriented state, and its manufacturing method, a luminance improved film using the optical laminated body, and a polarization light source device and a liquid crystal display device. <P>SOLUTION: The optical laminate has the liquid crystal layer set in a 2nd oriented state different from a 1st oriented state by changing the layer shape of the liquid crystal layer after forming the liquid crystal layer having the 1st oriented state on transparent base material. The optical laminated body and its manufacturing method are provided. The luminance improved film includes the liquid crystal layer set in the 2nd oriented state different from the 1st oriented state by changing the layer shape after forming the liquid crystal layer having the 1st oriented state on the transparent base material, a phase difference element set so that Rth defined by expression (1) is -20nm to -1000nm, and a 1/4 wavelength plate. The luminance improved film, and the polarizing light source device and the liquid crystal display device equipped with the luminance improved film are provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical laminate having a liquid crystal layer whose orientation is controlled on a transparent substrate, a method for producing the same, a brightness enhancement film using the optical laminate, a polarized light source device, and a liquid crystal display device.

  Liquid crystal display devices are used in many display devices, and the demand for display characteristics is increasing. Along with this, there are increasing demands on the performance, productivity, and manufacturing cost of optical films such as polarizing plates, viewing angle compensation films, broadband quarter-wave plates, and brightness enhancement films used in liquid crystal display devices.

  As these optical films, retardation films for controlling the polarization state of light used for display are known. This retardation film can be roughly classified into a film obtained by stretching a polymer film and a film in which a liquid crystal layer whose orientation is controlled is formed on a transparent substrate. The latter retardation film uses a liquid crystalline compound and has a feature that various polarization states can be controlled by variously controlling the alignment state of the liquid crystal layer.

  Conventionally, as a retardation film using a liquid crystalline compound, a viewing angle compensation film disclosed in Patent Document 1, an optical anisotropic element disclosed in Patent Document 2, and Patent Document 3 are disclosed. Examples include a quarter wave plate and a polarization separation film disclosed in Patent Document 4. Each of these optical films has a liquid crystal layer formed by fixing an alignment state that is uniquely determined by the composition of the liquid crystal composition and a substance that contacts one or both sides of the liquid crystal layer. However, in these optical films, the alignment state of the liquid crystal layer is very susceptible to noise caused by the environment and materials. In particular, the structure in which the optical axis of liquid crystal molecules is tilted with respect to the layer normal is unstable, and it is technically difficult to uniformly and efficiently produce an optical film having a liquid crystal layer having such a structure. there were.

  Incidentally, as an optical film, in addition to a film that controls the polarization state of light used for display, a brightness enhancement film for increasing the brightness at the time of display is known. As the brightness enhancement film, a film having a polarization separation film for separating incident light into transmitted light and reflected light according to the polarization state is currently on the market.

  Examples of the polarization separation film include a linear polarization separation film in which many anisotropic polymer layers disclosed in Patent Document 5 are stacked, a circular polarization separation film using a cholesteric liquid crystal layer disclosed in Patent Documents 4 and 6, and the like. Are known. Among these, the former linearly polarized light separating layer has a problem that it is necessary to stack several hundred anisotropic layers and is very expensive.

  The latter circularly polarized light separating film has a liquid crystal layer having a structure in which a liquid crystal group of a rod-like liquid crystal molecule or a side chain type liquid crystalline polymer is twisted in a thickness direction with a helical axis parallel to the layer normal as a rotation axis. By utilizing the selective reflection characteristic, the circularly polarized light rotated left and right is separated into transmitted light and reflected light. However, when this selective reflection layer is formed using ordinary liquid crystal, the selective reflection wavelength range of this selective reflection layer is about several tens of nm, and cannot be used as a brightness enhancement film as it is. Therefore, in order to perform circularly polarized light separation over the entire visible light region, it is necessary to widen the reflection band in the visible region.

  For this purpose, a selective reflection layer having a wide band can be formed by a method of providing a plurality of liquid crystal layers having different reflection bands, a method of gradually changing the helical pitch of the cholesteric liquid crystal layer in the thickness direction, or the like. Has been tried. However, the present situation is that both methods still have problems regarding productivity and cost. In addition, in the case of a circularly polarized light separation layer using a cholesteric liquid crystal layer, it does not affect display characteristics for light incident in a direction parallel to the layer normal, but for obliquely incident light. Since the phase difference is generated by the action of the cholesteric liquid crystal layer itself, the display characteristics are deteriorated, and there is a problem of coloring in an oblique direction.

JP-A-8-338913 JP-A-8-209127 JP 2000-66192 A JP-A-8-271731 US 6335999 gazette JP-A-6-235900

  The present invention has been made in view of such problems of the prior art, and is an optical laminate having a liquid crystal layer in a specific alignment state, which can be produced uniformly and at low cost, a method for producing the same, and an optical laminate comprising the optical laminate. It is an object to provide a brightness enhancement film to be used, a polarized light source device, and a liquid crystal display device.

  As a result of intensive studies to solve the above problems, the present inventors have formed a liquid crystal layer having a first alignment state on a transparent substrate, and then a member having a convex portion in the surface of the liquid crystal layer. It was found that a liquid crystal layer having the desired second alignment state can be obtained simply and reliably by bringing the layer into contact with each other to change the layer shape. Further, by applying this method to a liquid crystal layer of a cholesteric phase having the first alignment state, it has been found that a brightness enhancement film excellent in display characteristics can be easily obtained, and the present invention has been completed.

  Thus, according to the first aspect of the present invention, an optical laminate having a liquid crystal layer on a transparent substrate, the liquid crystal layer forming a liquid crystal layer having a first alignment state on the transparent substrate, By changing the layer shape of the liquid crystal layer, an optical layered body is provided which is a liquid crystal layer having a second alignment state different from the first alignment state.

In the optical layered body of the present invention, the liquid crystal layer having the first alignment state is preferably a liquid crystal layer having a cholesteric phase, a nematic phase, or a smectic phase.
In the optical layered body of the present invention, the liquid crystal layer is formed by forming a cholesteric phase liquid crystal layer in which the spiral axis and the layer normal are substantially parallel, and then changing the shape of the layer to change the spiral axis and the layer. It is more preferable that the liquid crystal layer has a cholesteric phase including at least a portion that is not parallel to the normal line.

  According to a second aspect of the present invention, there is provided a method for producing an optical laminate in which a liquid crystal layer is formed on a transparent substrate, the step of forming a liquid crystal layer having a first alignment state on the transparent substrate (1 And a step (2) of changing the shape of the liquid crystal layer to change the alignment state to a second alignment state different from the first alignment state. A manufacturing method is provided.

  In the method for producing an optical laminate of the present invention, the step (1) preferably forms a cholesteric phase, nematic phase or smectic phase liquid crystal layer on a transparent substrate. ) Includes a step of bringing a liquid crystal layer having the first alignment state into contact with a member having an in-plane convex portion.

  According to the third aspect of the present invention, after forming the cholesteric phase liquid crystal layer having the first alignment state on the transparent substrate, the second shape different from the first alignment state is obtained by changing the layer shape. A liquid crystal layer in an aligned state and a formula: Rth = {(nx + ny) / 2−nz} × d (where nx and ny represent refractive indexes in two directions perpendicular to the thickness direction and nx> ny. Nz represents a refractive index in the thickness direction, and d represents a film thickness.) Rth defined by -20 nm to -1000 nm and a quarter wavelength plate are included. A brightness enhancement film is provided.

  In the brightness enhancement film of the present invention, the liquid crystal layer is formed by forming a cholesteric phase liquid crystal layer in which the spiral axis and the layer normal are substantially parallel, and then changing the shape of the layer, thereby changing the spiral axis and the layer method. A liquid crystal layer having a cholesteric phase including at least a portion that is not parallel to the line is preferable.

According to a fourth aspect of the present invention, there is provided a polarized light source device comprising the brightness enhancement film of the present invention.
According to a fifth aspect of the present invention, there is provided a liquid crystal display device comprising the polarized light source device of the present invention and further comprising a liquid crystal cell above it.

  As a result of the inventor's research, after aligning the liquid crystal layer once on the substrate, the optical axis of the liquid crystal molecules is changed to the layer method by changing the layer shape by contacting a member having a convex portion in the plane. A structure tilted with respect to the line can be easily obtained, and it has become possible to produce the structure uniformly and efficiently. In addition, when this is applied to a cholesteric liquid crystal layer, a structure in which the angle formed by the spiral axis and the layer normal gradually changes in the thickness direction is obtained. As a result, a broadband circularly polarized light separation film can be manufactured uniformly and efficiently. It became possible to do. By integrating the retardation element having the Rth defined as the broadband circularly polarized light separating film and the quarter wavelength plate, it becomes possible to produce a brightness enhancement film with good viewing angle characteristics that achieves both performance and cost. It was.

  Hereinafter, the present invention will be described in detail by dividing it into 1) an optical laminate, 2) a method for producing an optical laminate, 3) a brightness enhancement film, 4) a polarized light source device, and 5) a liquid crystal display device.

1) Optical laminate The optical laminate of the present invention is a laminate having a liquid crystal layer on a transparent substrate, and the liquid crystal layer formed a liquid crystal layer having a first alignment state on the transparent substrate. After that, the liquid crystal layer is characterized in that the liquid crystal layer is changed to a second alignment state different from the first alignment state by changing the layer shape of the liquid crystal layer.

(1) Liquid crystal layer The liquid crystal layer of the optical layered body of the present invention is different from the first alignment state by changing the layer shape of the liquid crystal layer after forming the liquid crystal layer having the first alignment state. This is the second orientation state.

  Here, the alignment state means, for example, homeotropic alignment in which the major axis direction of the liquid crystal molecule group is perpendicular to the transparent substrate surface; the major axis direction of the liquid crystal molecule group is parallel to the transparent substrate surface. Homogeneous alignment; bend alignment in which the liquid crystal molecule group is bent near the center of the liquid crystal layer; the major axis direction of the liquid crystal molecule group is parallel on one side and vertical on the other side Hybrid alignment; twisted orientation in which the major axis direction of the liquid crystal molecule group is parallel to the transparent substrate surface and twisted between the upper and lower sides; the angle formed by the major axis of the liquid crystal molecule group and the normal of the layer is from one layer interface The orientation state of the liquid crystal molecule group in the liquid crystal layer, such as orientation (splay orientation etc.) gradually changing toward the other layer interface.

The first alignment state is an alignment state of a liquid crystal layer obtained by applying a coating liquid containing a liquid crystalline compound on a transparent substrate, and drying and heating.
The liquid crystal layer formed on the transparent substrate exhibits various alignment states depending on the characteristics and temperature of the liquid crystalline compound and other materials. Further, among liquid crystal compounds, those that exhibit a specific alignment state depending on temperature (the temperature at which each phase develops is called a phase transition temperature) are known. These are called thermotropic liquid crystals. Therefore, when using the thermotropic liquid crystal, a desired first alignment state can be obtained by heating to a predetermined temperature.

The second alignment state is an alignment state different from the first alignment state, which is obtained by changing the layer shape of the first alignment state.
As the second alignment state, various layers can be formed as long as the layer shape is changed as long as the alignment state is different from the first alignment state. In the present invention, as the second alignment state, JP-A-8-338913, JP-A-8-209127 and JP2000-2000A depend on the nature of the contact interface (alignment film side and the interface facing the interface). An alignment state in which the angle formed by the major axis of the liquid crystalline compound and the normal line of the layer gradually changes from one layer interface toward the other layer interface, as described in JP-A-66192 Is preferred.

  Since the liquid crystal layer of the optical layered body of the present invention can realize a wide reflection band, the layer shape of the liquid crystal layer of the cholesteric phase having the first alignment state is changed, and the major axis of the layer and the normal of the layer A liquid crystal layer having an orientation state in which the angle formed by the layer gradually changes from one layer interface to the other layer interface is preferable, and a liquid crystal layer having a cholesteric phase in which the helical axis is substantially parallel to the layer normal direction It is particularly preferable that the liquid crystal layer has a cholesteric phase including at least a portion where the spiral axis and the layer normal are not parallel by changing the layer shape after forming the layer.

As will be described later, the liquid crystal layer can be formed by applying a coating liquid appropriately containing a liquid crystalline compound, a solvent, a surfactant, a polymerization initiator, an alignment regulator, and the like on a transparent substrate.
The liquid crystal compound to be used is not particularly limited and can be appropriately selected depending on the target alignment state. For example, a rod-like liquid crystal compound, a disk-like liquid crystal compound, a polymer liquid crystal, and the like can be given.

Examples of the rod-like liquid crystalline compound include compounds represented by the formula (I): R1-B1-A1-B3-M-B4-A2-B2-R2.
In formula (1), R1 and R2 represent a polymerizable group. Specific examples of the polymerizable groups R1 and R2 include (r-1) to (r-15) shown below, but are not limited thereto.

  B1, B2, B3 and B4 each independently represent a single bond or a divalent linking group. Moreover, it is preferable that at least one of B3 and B4 is —O—CO—O—.

  A1 and A2 represent a spacer group having 2 to 20 carbon atoms. Examples of the spacer group include a polymethylene group and a polyoxymethylene group. The number of carbon atoms contained in the structural unit forming the spacer group is appropriately determined depending on the chemical structure of the mesogenic group, and is generally 0 to 20, preferably 2 to 12, in the case of a polymethylene group. In the case of a group, it has 0 to 10 carbon atoms, preferably 1 to 3 carbon atoms.

  M represents a mesogenic group. The material for forming the mesogenic group M is not particularly limited, but azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines Alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used.

  Examples of the discotic liquid crystalline compound include various documents (for example, C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10, Section 2 (1994); Liquid Crystal Handbook Editorial Committee, Liquid Crystal Handbook, Chapter 2, Section 2.1.1 (2000) The thing which introduce | transduced the connection group similar to what was mentioned by the above-mentioned rod-shaped liquid crystalline compound, a spacer group, and a polymeric group can be used for a thing.

  The polymer liquid crystal is not particularly limited, and various types can be used. For example, liquid crystal handbooks, edited by Liquid Crystal Handbook Editorial Committee, Chapter 3, Section 3.8 (2000) can be used. From the viewpoint of alignment uniformity, side chain polymer liquid crystals are used. preferable.

In the present invention, the liquid crystal layer having the first alignment state is preferably a cholesteric phase, nematic phase or smectic phase liquid crystal layer.
The cholesteric phase is a state in which the position of the center of gravity of the liquid crystal molecules is disordered and the major axis of the molecules is twisted in a certain direction between the molecules. The nematic phase is a state in which the position of the center of gravity of the liquid crystal molecules is disordered and the long axes of the molecules are uniaxially aligned. The smectic phase is characterized by having a layer structure in a state where a one-dimensional order exists at the position of the center of gravity in addition to the order in the direction of the nematic phase.

  Among these, in the present invention, as the liquid crystal layer having the first alignment state, a cholesteric phase liquid crystal layer is more preferable, which has a circularly polarized light separation function over the entire wavelength region of visible light, that is, a wavelength of 410 to 470 nm. A cholesteric phase liquid crystal layer having a circularly polarized light separation function is particularly preferable for light in any wavelength region of wavelengths 520 to 580 nm and wavelengths 600 to 660 nm.

  As such a cholesteric liquid crystal layer, (i) a combination of cholesteric liquid crystal layers having different central wavelengths of selectively reflected light, and (ii) a single cholesteric liquid crystal layer having a helical pitch in the thickness direction. Are continuously or stepwise changing.

In the case of the type (i) above, from the viewpoint of increasing the amount of polarized light in a usable state by aligning the phase state of the circularly polarized light reflected by each layer and preventing different polarization states in each wavelength region, It is preferable to combine those that reflect circularly polarized light in the same direction. In this case, it is more preferable that the cholesteric liquid crystal layers are laminated in the wavelength order based on the center wavelength of the reflected light from the viewpoint of suppressing the wavelength shift at the large viewing angle.

  As a method of laminating the cholesteric liquid crystal layers in the wavelength order based on the center wavelength of the reflected light, for example, cholesteric liquid crystal layers having the center wavelengths of the reflected light of 470 nm, 550 nm, 640 nm, and 770 nm are respectively produced, and these cholesteric liquid crystal layers Is arbitrarily selected, and 3 to 7 layers are laminated in the order of the center wavelength of the reflected light. Examples of a method of laminating a plurality of cholesteric liquid crystal layers having different center wavelengths of reflected light include methods such as simple placement and adhesion via an adhesive such as an adhesive.

  The cholesteric liquid crystal layer (ii) can be formed as follows. First, the irradiation light intensity is continuously applied in the depth direction from the surface (ultraviolet irradiation surface) side to a liquid crystal layer containing a compound that becomes a chiral agent by being irradiated with ultraviolet rays of a specific wavelength, a liquid crystal, and an ultraviolet absorber. Is irradiated with ultraviolet rays of the specific wavelength so that the light is attenuated. As a result, a liquid crystal layer in which the amount of the chiral agent existing continuously decreases in the depth direction from the surface side, that is, a state in which the spiral pitch of the liquid crystal continuously changes in the thickness direction of the liquid crystal layer is obtained. Next, the liquid crystal layer is irradiated with ultraviolet light having a wavelength different from that of the specific wavelength to cure the entire liquid crystal layer, thereby fixing the state in which the spiral pitch is changed in an inclined manner. The cholesteric liquid crystal layer thus obtained has a helical structure whose pitch is continuously changed in the depth direction, and has a circularly polarized light separation function in all the wavelength bands of the visible light range.

  Examples of such a type of cholesteric liquid crystal layer include SID'95, Asia Display. , P735 (1995), Liquid Crystal, Vol. 2, No. 2, pp. 32-39 (1998).

  As a material for the cholesteric liquid crystal, a liquid crystal polymer is preferable. The liquid crystal polymer is not particularly limited, and a liquid crystal polymer in which a conjugated linear atomic group (mesogen) imparting liquid crystal orientation is introduced into the main chain of the polymer, and a type in which the mesogen is introduced into the side chain of the polymer. Various liquid crystal polymers can be used.

  As a liquid crystal polymer in which a mesogen is introduced into the main chain of the polymer, a polyester system or a polyamide system having a structure in which a mesogen group composed of a para-substituted cyclic compound or the like is bonded via a spacer portion that imparts flexibility as necessary, Examples of the polymer include polycarbonate-based and polyesterimide-based polymers.

  In addition, as a liquid crystal polymer in which mesogen is introduced into the side chain of the polymer, the main chain skeleton is polyacrylate, polymethacrylate, polysiloxane, polymalonate, etc., and a spacer part composed of a conjugated atomic group as a side chain as necessary Having a low molecular crystal compound (mesogen part) composed of a para-substituted cyclic compound, etc., a nematic liquid crystal polymer containing a low molecular chiral agent, a liquid crystal polymer incorporating a chiral component, a mixed liquid crystal polymer of nematic and cholesteric, etc. Is mentioned.

  In addition, para-substituted cyclic compounds that impart nematic orientation such as para-substituted aromatic units and para-substituted cyclohexyl units such as azomethine, azo, azoxy, ester, biphenyl, phenylcyclohexane, and bicyclohexane. Cholesteric orientation can be obtained by introducing an appropriate chiral component composed of a compound having an asymmetric carbon, a low molecular chiral agent, or the like into a compound having an asymmetric carbon (JP-A-55-21479). U.S. Pat. No. 5,332,522). Here, examples of the terminal substituent at the para position in the para-substituted cyclic compound include a cyano group, an alkyl group, and an alkoxyl group.

  Examples of the spacer portion include a polymethylene chain and a polyoxymethylene chain. The number of carbon atoms contained in the structural unit forming the spacer portion is appropriately determined depending on the chemical structure of the mesogen portion, and is generally 0 to 20, preferably 2 to 12 in the case of a polymethylene chain. In the case of a chain, the carbon number is 0 to 10, preferably 1 to 3.

  Examples of a method for producing a polymer of a type in which mesogen is introduced into the polymer main chain include a method in which component monomers are polymerized by radical polymerization, cationic polymerization, anionic polymerization, or the like. In addition, as a method of producing a polymer of a type in which mesogen is introduced into the side chain of the polymer, a monomer in which a mesogenic group is introduced into a vinyl monomer such as an ester of acrylic acid or methacrylic acid through a spacer portion as desired. Via a radical polymerization method, a method of addition reaction of a vinyl-substituted mesogen monomer in the presence of a platinum-based catalyst via the Si-H bond of polyoxymethylsilylene, via a functional group imparted to the main chain polymer Examples include a method of introducing a mesogen group by an esterification reaction using a phase transfer catalyst, a method of subjecting a part of malonic acid to a polycondensation reaction between a monomer having a mesogen group introduced via a spacer group and a diol as necessary. .

  The chiral agent is not particularly limited, and conventionally known agents can be used. Examples thereof include a chiral monomer described in JP-A-6-281814, a chiral agent described in JP-A-8-209127, and a photoreactive chiral compound described in JP-A-2003-131187.

  Further, as the chiral agent, in order to avoid an unintended change of the phase transition temperature due to the addition of the chiral agent, a chiral agent that exhibits liquid crystallinity is preferable. Further, from the viewpoint of economy, a material having a large HTP defined by the formula (II): HTP = 1 / P · c, which is an index representing the efficiency of twisting the liquid crystal compound, is preferable. Here, P represents the pitch length of the spiral of the cholesteric phase, and c represents the concentration of the chiral agent.

  In the liquid crystal layer having the first alignment state (particularly, the cholesteric phase liquid crystal layer), the basic structure of the liquid crystal phase (the spiral structure of the cholesteric phase itself) can be maintained as much as possible in the subsequent step of deforming the layer shape. preferable. For this purpose, it is preferable to fix the first alignment state to some extent. This fixing method includes a method in which the type of polymerizable group, the number of polymerizable groups per molecule adjusted, is used as a liquid crystalline compound, and is fixed by heating or light irradiation. Examples include a method of fixing by heating or light irradiation using a mixture with a crystalline liquid crystal, and a method of fixing by rapidly cooling when a first alignment state is obtained using a polymer liquid crystal. It is done.

  The thickness of the liquid crystal layer (the total thickness in the case where the liquid crystal layer is composed of a plurality of layers) is from the viewpoint of orientation disorder and prevention of transmittance reduction, the range of the selective reflection wavelength range (reflection wavelength range), etc. Usually, it is 1-50 micrometers, Preferably it is 2-30 micrometers, More preferably, it is 2-10 micrometers. Moreover, when it has a support base material, the total thickness including the base material is 20-200 micrometers normally, Preferably it is 25-150 micrometers, More preferably, it is 30-100 micrometers.

(2) Transparent substrate The transparent substrate used in the present invention is not particularly limited as long as it is an optically transparent substrate, but in order to avoid an unnecessary change in the polarization state, the phase difference due to birefringence is small, Those that are optically isotropic are preferred. Examples of such a transparent substrate include a transparent resin film and a glass substrate, and a long transparent resin film is more preferable from the viewpoint of efficiently producing a liquid crystal layer. The transparent resin film may be a single-layer film or a multi-layer film in which a plurality of films are laminated, but preferably has a thickness of 1 mm and a total light transmittance of 80% or more.

  The resin material of the transparent resin film includes an alicyclic structure-containing polymer resin, a chain olefin polymer such as polyethylene and polypropylene, triacetyl cellulose, polyvinyl alcohol, polyimide, polyarylate, polyester, polycarbonate, polysulfone, and polyether. Examples include sulfone, amorphous polyolefin, modified acrylic polymer, and epoxy resin. These can be used alone or in combination of two or more. Among these, an alicyclic structure-containing polymer resin or a chain olefin polymer is preferable, and an alicyclic structure-containing polymer resin is more preferable from the viewpoint of transparency, low hygroscopicity, dimensional stability, lightness, and the like. preferable.

  The alicyclic structure-containing polymer resin has an alicyclic structure in the repeating unit of the polymer resin, and the polymer resin having an alicyclic structure in the main chain and an alicyclic structure in the side chain. Any polymer resin can be used. Examples of the alicyclic structure include a cycloalkane structure and a cycloalkene structure, and a cycloalkane structure is preferable from the viewpoint of thermal stability. Although there is no restriction | limiting in particular in carbon number which comprises an alicyclic structure, Usually, 4-30 pieces, Preferably it is 5-20 pieces, More preferably, it is 6-15 pieces.

  The proportion of the repeating unit having an alicyclic structure in the polymer resin having an alicyclic structure is appropriately selected depending on the purpose of use, but is usually 50% by weight or more, preferably 70% by weight or more, more preferably 90%. % By weight or more. When there are too few repeating units having an alicyclic structure, the heat resistance of the film may be reduced.

  Specifically, the polymer resin having an alicyclic structure includes (1) a norbornene polymer, (2) a monocyclic olefin polymer, (3) a cyclic conjugated diene polymer, and (4) vinyl. Examples thereof include alicyclic hydrocarbon polymers and hydrogenated products thereof. Among these, norbornene-based polymers are more preferable from the viewpoints of transparency and moldability.

Specific examples of the norbornene-based polymer include ring-opening polymers of norbornene-based monomers, ring-opening copolymers of norbornene-based monomers and other monomers capable of ring-opening copolymerization, and hydrogenated products thereof, norbornene-based polymers Examples include addition polymers of monomers and addition copolymers with other monomers copolymerizable with norbornene-based monomers. Among these, from the viewpoint of transparency, a ring-opening polymer hydrogenated product of a norbornene-based monomer is most preferable.
The polymer having the alicyclic structure is selected from known polymers disclosed in, for example, JP-A No. 2002-321302.

  The glass transition temperature of the resin material of the transparent resin film suitably used in the present invention is preferably 80 ° C. or higher, more preferably 100 to 250 ° C. A substrate made of a transparent resin having a glass transition temperature in such a range is excellent in durability without causing deformation or stress in use at high temperatures.

  The molecular weight of the resin material of the transparent resin film suitably used in the present invention is abbreviated as gel permeation chromatography (hereinafter referred to as “GPC”) using cyclohexane (toluene when the polymer resin is not dissolved) as a solvent. The weight average molecular weight (Mw) in terms of polyisoprene or polystyrene measured in (1) is usually 10,000 to 100,000, preferably 25,000 to 80,000, more preferably 25,000 to 50,000. When the weight average molecular weight is in such a range, the mechanical strength and moldability of the film are highly balanced and suitable.

  The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the resin material of the transparent resin film suitably used in the present invention is not particularly limited, but is usually 1.0 to 10.0, preferably 1.0. It is -4.0, More preferably, it is the range of 1.2-3.5.

  The alicyclic structure-containing polymer resin suitably used in the present invention has a resin component (that is, oligomer component) having a molecular weight of 2,000 or less, preferably 5% by weight or less, more preferably 3% by weight or less. More preferably, it is 2% by weight or less. When the amount of the oligomer one component is large, when the resin laminate is stretched, fine convex portions are generated on the surface or unevenness of the thickness occurs, resulting in poor surface accuracy. In order to reduce the amount of the oligomer component, the selection of the polymerization catalyst and the hydrogenation catalyst, the reaction conditions such as polymerization and hydrogenation, and the temperature conditions in the step of pelletizing the resin as a molding material may be optimized. . The amount of the oligomer component can be measured by GPC using cyclohexane (toluene if the polymer resin does not dissolve).

  The thickness of the transparent substrate used in the present invention is not particularly limited, but the thickness is usually 1 to 1000 μm, preferably 5 to 300 μm, more preferably 30 to 100 μm, from the viewpoint of material cost and reduction in thickness and weight.

  In addition, the transparent substrate used in the present invention is preferably subjected to surface treatment in advance. By performing the surface treatment, the adhesion between the transparent substrate and the alignment film can be enhanced. Examples of the surface treatment include glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment, flame treatment) and the like. It is also preferable to provide an adhesive layer (undercoat layer) on the transparent support in order to improve the adhesion between the transparent substrate and the alignment film.

  It is preferable to provide an alignment film for aligning the liquid crystal compound on the surface of the transparent substrate. The alignment film can be formed by means such as rubbing treatment of an organic compound, oblique vapor deposition of an inorganic compound, formation of a micro group, or accumulation of an organic compound by a Langmuir-Blodgett method. In addition, an alignment film in which an alignment function is generated by application of an electric field or a magnetic field or light irradiation can be provided. Among these, the alignment film formed on the transparent substrate is preferably formed by applying a polymer and rubbing it from the viewpoint of enabling continuous treatment. The rubbing treatment can be performed by rubbing the surface of the polymer layer with a cloth in a certain direction.

  The polymer used for forming the alignment film is not particularly limited, and a polymer corresponding to the type of liquid crystal compound to be used and the desired alignment can be appropriately selected. The alignment film preferably has a polymerizable group for the purpose of imparting adhesion between the liquid crystal compound and the substrate. The thickness of the alignment film is usually 0.001 to 50 μm, preferably 0.01 to 5 μm, more preferably 0.05 to 1 μm.

2) Method for Producing Optical Laminate The method for producing an optical laminate of the present invention includes a step (1) of forming a liquid crystal layer having a first alignment state on a transparent substrate, and a layer shape of the liquid crystal layer. And (2) changing the alignment state into a second alignment state different from the first alignment state. The production method of the present invention is particularly suitable for the production of the optical laminate of the present invention.

(A) Step (1)
Step (1) forms a liquid crystal layer having a first alignment state on a transparent substrate. The liquid crystal layer can be formed by applying a coating liquid appropriately containing a liquid crystalline compound, a solvent, a surfactant, a polymerization initiator, an alignment regulator, and the like on a transparent substrate.

As the liquid crystal compound, the same compounds as described above can be used.
The surfactant is used to adjust the surface tension of the coating liquid and the liquid crystal layer before polymerization. The surfactant is not particularly limited, and a commercially available one can be used, but the use of a nonionic surfactant is preferable. Among these, the use of a nonionic surfactant which is an oligomer having a molecular weight of about several thousand is particularly preferable. Examples of such surfactants include nonionic surfactants (trade name: KH-40) manufactured by Seimi Chemical Co., Ltd.

  As the polymerization initiator, either a thermal polymerization initiator or a photopolymerization initiator can be used. Use of a photoinitiator is preferred because the polymerization reaction is rapid. Examples of photopolymerization initiators include polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), oxadiazole compounds (described in US Pat. No. 4,212,970), α-carbonyl compounds ( U.S. Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in U.S. Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin compound (as described in U.S. Pat. No. 2,722,512) ), Combinations of triarylimidazole dimers and p-aminophenyl ketone (described in US Pat. No. 3,549,367), acridine and phenazine compounds (described in Japanese Patent Application Laid-Open No. 60-105667, US Pat. No. 4,239,850) ) And the like. The usage-amount of a polymerization initiator is 0.001 to 50 weight% normally with respect to solid content of a coating liquid, Preferably it is 0.01 to 20 weight%, More preferably, it is 0.5 to 5 weight%.

  The alignment regulator is for controlling the alignment state of the air side surface of the liquid crystal layer formed on the substrate. The alignment regulator may also serve as the surfactant. The alignment regulator is not particularly limited, and various types can be used depending on the target alignment state. Examples thereof include resins such as polyvinyl alcohol, polyvinyl butyral, and modified products thereof.

  As the solvent used for preparing the coating solution, an organic solvent is preferable. Examples of the organic solvent include ketones, halogenated hydrocarbons, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, ethers, and the like. These may be used alone or in combination of two or more. Among these, in consideration of environmental load, it is preferable to use ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.

  The method for applying the coating solution on the transparent substrate is not particularly limited, and spin coating method, roll coating method, flow coating method, printing method, dip coating method, casting film forming method, bar coating method, gravure printing method. A known coating method such as the above can be employed.

  In addition, as a method for forming the liquid crystal layer, a heated melt of a liquid crystal polymer, preferably a heated melt exhibiting an isotropic phase, is formed on the base film by a method according to the above-described coating method. In addition, it is possible to employ a method of further developing and solidifying into a thin layer while maintaining the melting temperature as necessary.

  A liquid crystal layer can be formed by drying and heat-treating a coating film obtained by applying the coating liquid on a transparent substrate. The temperature of the heat treatment is a temperature range from the glass transition temperature to the isotropic phase transition temperature of the liquid crystal polymer, that is, a temperature range in which the liquid crystal polymer exhibits liquid crystal.

  In the method for producing an optical layered body of the present invention, the step (1) preferably forms a cholesteric phase, nematic phase or smectic phase liquid crystal layer on a transparent substrate. The liquid crystal layer in the cholesteric phase, nematic phase or smectic phase is as described above.

  In order to fix the first alignment state, it is preferable to solidify with heat or ultraviolet rays in the target alignment state. For this purpose, a liquid crystalline compound having a polymerizable functional group introduced in the molecule is used. It is preferable to use it.

By polymerizing a liquid crystal compound having a polymerizable group, the first alignment state can be fixed to some extent. That is, when a thermal polymerization initiator is used as the polymerization initiator, the coating film is heated to a predetermined temperature, and when a photopolymerization initiator is used, the coating film is irradiated with light, thereby obtaining a liquid crystalline property. The compound can be polymerized. From the viewpoint of rapidity, a method using light irradiation is preferable, and a method using ultraviolet rays is more preferable. The light irradiation energy is usually 1 mJ / cm ^{2 to} 50 J / cm ² , preferably 1 mJ / cm ^{2 to} 800 mJ / cm ² .

(B) Step (2)
In the step (2), the alignment state is changed to a second alignment state different from the first alignment state by changing the layer shape of the liquid crystal layer having the first alignment state formed in the step (1). Is.

  As the second alignment state, various layers may exist as long as the layer shape is changed and the alignment state is different from the first alignment state. Among them, the angle formed between the major axis of the liquid crystal compound similar to the liquid crystal layer of the optical layered body of the present invention and the normal line of the layer gradually changes from one layer interface to the other layer interface. Since the alignment state is preferable and a wide reflection band can be realized, the layer shape of the liquid crystal layer of the cholesteric phase having the first alignment state is changed so that the angle formed between the major axis of the layer and the normal of the layer is one layer. An alignment state that gradually changes from the interface toward the other layer interface is particularly preferable.

  Hereinafter, with respect to the step (2), the layer shape of the liquid crystal layer of the cholesteric phase having the first alignment state is changed so that the angle formed between the major axis of the layer and the normal of the layer is changed from one layer interface to the other layer. A case where an alignment state (second alignment state) that gradually changes toward the interface is formed will be described as an example.

  A schematic representation of a general cholesteric phase liquid crystal layer is shown in FIG. Here, the liquid crystal molecules 2 in contact with the alignment treatment surface 1 applied to the substrate surface are drawn so as to align the major axes of the liquid crystal molecules in the direction corresponding to the alignment treatment. Furthermore, the liquid crystal molecules form a twisted orientation with a helical pitch P corresponding to the chiral agent HTP between the orientation-treated surface side interface and the surface facing it.

  It is known that when light is incident on the liquid crystal layer 1 exhibiting such a cholesteric phase, it exhibits a reflection characteristic (selective reflection) only with respect to any circularly polarized light around the left and right of a specific wavelength region. . This will be described with reference to FIG. In FIG. 2, θ1 is an incident angle when white incident light L1 is incident, L2 is selectively reflected circularly polarized light, and θ2 is a progression of incident light when the incident light L1 is refracted in the liquid crystal layer 1 according to Snell's law. It represents the angle formed by the direction and the layer normal 3. When the spiral axis 4 representing the rotation axis when the liquid crystal compound is twisted is perpendicular to the layer, the layer normal 3 and the spiral axis 4 are parallel. In this case, it can be said that θ2 is an angle formed by the spiral axis inside the liquid crystal layer and the incident light.

  The central wavelength λ of the circularly polarized light L2 subjected to selective reflection is expressed by the formula (III): λ = n × P × cos θ2, and the reflection band is expressed by the formula (IV): no × P × cos θ2 ≦ λ ≦ ne × P ×. It is represented by cos θ2. Here, n = (ne + no) / 2 (wherein, no represents the refractive index in the minor axis direction of the rod-like liquid crystalline compound, ne represents the refractive index in the major axis direction of the rod-like liquid crystalline compound, and P represents the helical pitch. Represents the length.)

  As apparent from the above formula (IV), the wavelength of the reflected light with respect to the light incident obliquely is shorter than the wavelength of the reflected light with respect to the light incident parallel to the helical axis (θ2 = 0). Shift to the side. As a result, the transmission spectrum 5 for light incident obliquely with respect to the helical axis shifts the peak position to the short wave side with respect to the transmission spectrum 6 for light incident in parallel (θ2 = 0). This is shown in FIG. In FIG. 3, the horizontal axis indicates the measurement wavelength (nm), and the vertical axis indicates the transmittance (%).

  Here, it is considered that the selective reflection wavelength range Δλ (ne × P × cos θ2−no × P × cos θ2) is extended to the entire visible wavelength range (wide band). For this, the following methods (a) to (c) are conceivable.

(A) The first is a method of increasing Δn (birefringence) which is the difference between ne and no of the rod-like liquid crystal compound. However, at present, no liquid crystal compound having a large Δn that exhibits a selective reflection characteristic in the entire visible region in a single layer has been found. Therefore, a cholesteric liquid crystal layer using such a liquid crystal compound is known. Not.

(B) The second is a method disclosed in JP-A-6-235900. This method has a structure in which the helical pitch P gradually changes in the thickness direction of the layer. In such a structure, since there are regions having different spiral pitches P in the thickness direction, a broadband reflection characteristic can be obtained as the sum of the wavelength regions λ of reflected light in each region. This can be said to be a result of controlling the helical pitch P in the formula (IV).

(C) The third is a method of controlling cos θ2 in the above formula (IV). In the above formula (IV), θ2 is an angle formed between the incident light inside the liquid crystal layer and the spiral axis, so that the spiral axis of the liquid crystal layer is changed so that θ2 gradually changes in the path of the incident light inside the layer. In the case of an inclined structure, it is considered that incident light has different reflection bands in different θ2 regions on the path.

  As shown in the equations (III), (IV) and FIG. 3, the incident angle dependence of the wavelength of the selectively reflected light shifts to the short wave side as the incident angle, that is, θ2 increases. Therefore, the inclination angle of the spiral axis of the liquid crystal layer Further, it is possible to broaden the band by adjusting the helical pitch length over the entire path of incident light. This is shown in FIG. FIG. 4 illustrates a state in which the angle θ2 formed by the spiral axis and L1 changes as a, b, and c (a> b> c) as the incident light L1 travels through the liquid crystal layer. Since the wavelength of the selectively reflected light is shifted to the short wave side as θ2 is larger, the wavelength of each reflected light is shorter in θ2 = a than in θ2 = c.

As described above, it is obvious that the structure in which the spiral axis is inclined with respect to the incident light is effective as a method for widening the bandwidth.
In general, the orientation state in which the angle formed between the major axis of the liquid crystal compound and the normal of the layer gradually changes from one layer interface to the other layer interface is the alignment layer side interface of the liquid crystal layer and the interface This can be realized by changing the alignment state of the liquid crystal molecules at the facing interface. As this method, conventionally, when one interface is an interface with an alignment film and the other is an interface with air, a material that horizontally adsorbs liquid crystal compound molecules on the alignment film surface is selected for the alignment film, A method is known in which an alignment regulator is selected so that liquid crystal compound molecules are obliquely aligned with respect to the air interface at the air side interface, and added in advance to a coating solution for forming a liquid crystal layer (for example, JP-A-8-209127, JP-A-8-338913). However, the alignment state of the liquid crystal layer is very susceptible to noise caused by the environment and materials. In particular, the structure in which the optical axis of the liquid crystal molecules is tilted with respect to the layer normal is unstable, and it is technically difficult to manufacture a liquid crystal layer having such a structure uniformly and efficiently.

In addition, when the cholesteric phase liquid crystal layer having the first alignment state is formed as the liquid crystal layer, the tilt angle range necessary for inclining the spiral axis of the cholesteric liquid crystal layer to increase the bandwidth for visible light is as follows. For example, when the spiral pitch P is 470 nm and n is 1.5, θ _{2 (700)} (upper limit wavelength of reflection band), θ _{2 (400)} (lower limit wavelength of reflection band) from the formula (III) Are θ _{2 (700)} ≈0 ° and θ _{2 (400)} ≈56 °, respectively. Therefore, it is preferable that the inclination θ2 of the spiral axis of the liquid crystal layer with respect to the traveling direction of incident light inside the layer has a distribution including at least 0 ° to 56 °. However, it is difficult to form a cholesteric liquid crystal layer having such a large tilt angle distribution by the known method described above.

  Therefore, in the present invention, after the liquid crystal layer having the first alignment state is formed on the substrate, a method of changing to the second alignment state by changing the layer shape is adopted. According to this method, a liquid crystal layer having a desired second alignment state can be easily and reliably formed.

  After forming the liquid crystal layer having the first alignment state on the substrate, as a specific means for changing to the second alignment state by changing the layer shape, a member having a convex portion in the plane is used. A preferred example is a method of bringing the liquid crystal layer into the first alignment state into contact.

  The material of the member having a convex portion in the surface is not particularly limited as long as it can be processed into a concave and convex portion, but is optically transparent when used in an integrated state with the liquid crystal layer having the second alignment state. A material having the smallest possible phase difference due to birefringence is preferable.

  Such materials include alicyclic structure-containing polymer resins, chain olefin polymers such as polyethylene and polypropylene, triacetyl cellulose, polyvinyl alcohol, polyimide, polyarylate, polyester, polycarbonate, polysulfone, polyethersulfone, Examples thereof include a single layer or laminated film made of a synthetic resin such as an amorphous polyolefin, a modified acrylic polymer, and an epoxy resin, and a glass plate. Among these, an alicyclic structure-containing polymer resin or a chain olefin polymer is preferable, and an alicyclic structure-containing polymer resin is particularly preferable from the viewpoints of transparency, low hygroscopicity, dimensional stability, lightness, and the like. preferable. From the viewpoint of enabling continuous processing, it is preferably a long film.

  The shape of the convex portion is not particularly limited as long as the inclination of the spiral axis is generated. Examples include a pyramid shape, a hemispherical shape, and a dome shape. When the phase difference in the front direction that occurs as a result of changing the shape is canceled in-plane to prevent the appearance of an apparent phase difference, the rotationally symmetric axis is in the normal direction of the substrate as the convex shape. Some are preferred.

  As the height of the convex portion, the height from the bottom surface of the convex portion to the apex is preferably 0.1 μm to 10 μm, more preferably 0.5 μm to 3 μm. The in-plane period of the convex portion is preferably 0.1 μm to 10 μm, and more preferably 0.5 to 3 μm.

  FIG. 5 is a cross-sectional view showing a state in which the member 7 having a convex portion in the surface is integrated with the liquid crystal layer having the second alignment state. Here, a curve 4 crossing the liquid crystal layer 1 represents the helical axis of the cholesteric liquid crystal layer. As shown in FIG. 5, the planar first alignment state in which the spiral axis is parallel to the normal line of the liquid crystal layer is deformed by the convex surface of the member 7 and is the second alignment state. The spiral axis of this has a curved structure.

  As a means for bringing a member having a convex portion in the surface into contact with the liquid crystal layer, a method of pressing with a press machine generally used with a member having a convex portion in the surface facing the liquid crystal layer, or between rolls A laminating method of heating and pressurizing can be applied. In addition, a method in which an embossing roll or the like is pressure-bonded to the liquid crystal layer in which the first alignment state is formed, and a convex shape on the embossing roll can be transferred.

  As described above, after forming the cholesteric liquid crystal layer in the first alignment state in which the spiral axis is parallel to the layer normal direction on the transparent substrate, the spiral shape and the layer are changed by changing the layer shape. A liquid crystal layer having a cholesteric phase including at least a portion that is not parallel to the normal can be easily and reliably formed.

  As described above, in the step (2), by changing the layer shape of the liquid crystal layer of the cholesteric phase having the first alignment state, the angle formed between the major axis of the layer and the normal of the layer is changed from one layer interface to the other layer. The case where an alignment state that gradually changes toward the interface is formed has been described as an example. The present invention is not limited to this, and a second liquid crystal layer different from the first alignment state is formed by forming a liquid crystal layer having the first alignment state on a transparent substrate and changing the layer shape thereof. An optical laminate having various liquid crystal layers having an alignment state can be produced.

  The shape of the optical laminate of the present invention is not particularly limited, but is preferably a film. As described below, the film-shaped optical laminate of the present invention is useful as a raw material for producing a brightness enhancement film and a liquid crystal display device.

3) Brightness-enhancing film The brightness-enhancing film of the present invention is different from the first oriented state by forming a liquid crystal layer having the first oriented state on a transparent substrate and then changing the layer shape. And the formula: Rth = {(nx + ny) / 2−nz} × d (where nx and ny represent the refractive indexes in two directions perpendicular to the thickness direction and nx> nz represents a refractive index in the thickness direction, and d represents a film thickness.) Rth defined by -20 nm to -1000 nm, and a quarter-wave plate. It is characterized by.

  In the optical layered body of the present invention described above, after forming the cholesteric liquid crystal layer in the first alignment state in which the spiral axis is parallel to the layer normal direction, the spiral shape and the layer are changed by changing the layer shape. An optical laminate having a cholesteric phase liquid crystal layer containing at least a portion that is not parallel to the normal can be used as a brightness enhancement film by being combined with a quarter-wave plate.

  The retardation element used for the brightness enhancement film of the present invention has substantially no in-plane retardation, and has the formula: Rth = {(nx + ny) / 2−nz} × d (where nx, ny Represents a refractive index in two directions perpendicular to the thickness direction and orthogonal to each other, nx> ny, nz represents a refractive index in the thickness direction, and d represents a film thickness.) Rth defined by −20 nm It is in the range of ˜−1000 nm, preferably -50 nm to −500 nm. The retardation element having Rth in such a range has a function of compensating for a phase difference of light incident obliquely on the quarter wavelength plate from the light source side.

  In the retardation element used in the brightness enhancement film of the present invention, the relationship between the main refractive indexes nx, ny and nz (nx, ny and nz are the same as described above) is nz> nx, nz> ny, nx≈ It is necessary to satisfy ny. When this retardation element is composed of a plurality of layers, the main refractive index of each layer is different, but in the present invention, the refractive index of the entire element only needs to satisfy the above relationship. This main refractive index can be measured by an automatic birefringence meter [for example, “KOBRA series” manufactured by Oji Scientific Instruments Co., Ltd.]. Note that nx≈ny means that the refractive index difference is usually within 0.0002, preferably within 0.0001, and more preferably within 0.00005.

  Further, the in-plane retardation Re defined by the formula: Re = (nx−ny) × d (nx, ny and d have the same meaning as described above) of the retardation element used in the brightness enhancement film of the present invention. Is usually 20 nm or less, preferably 10 nm or less, more preferably 5 nm or less.

  Examples of the retardation element having such optical characteristics include a layer including a layer obtained by stretching and orientation of a material having at least a negative intrinsic birefringence value (hereinafter, sometimes referred to simply as a negative material). be able to.

  Here, a material having a negative intrinsic birefringence value refers to a material having a characteristic that exhibits optically negative uniaxiality when molecules are oriented in a uniaxial order. Examples of materials having a negative intrinsic birefringence value include discotic liquid crystals, discotic liquid crystal polymers, aromatic vinyl polymers, polyacrylonitrile polymers, polymethacrylate polymers, cellulose ester polymers, and their multiple (two Original, ternary, etc.) and the like. These can be used alone or in combination of two or more. Among these, at least one selected from an aromatic vinyl polymer, a polyacrylonitrile polymer, and a polymethyl methacrylate polymer is preferable. Of these, aromatic vinyl polymers are more preferable from the viewpoint of high birefringence.

  An aromatic vinyl polymer is a homopolymer of an aromatic vinyl monomer, a copolymer of two or more of these, or a copolymer of an aromatic vinyl monomer and a monomer copolymerizable therewith. Refers to a polymer. Examples of the aromatic vinyl monomer include styrene; styrene derivatives such as 4-methylstyrene, 4-chlorostyrene, 3-methylstyrene, 4-methoxystyrene, 4-tert-butoxystyrene, and α-methylstyrene; It is done. Two or more of these may be used in combination.

Monomers copolymerizable with aromatic vinyl monomers include propylene, butene; acrylonitrile; (meth) acrylic acid, maleic anhydride; (meth) acrylic acid ester; maleimide; vinyl acetate, vinyl chloride; Can be mentioned. Among these, from the viewpoint of high heat resistance, a copolymer of styrene and / or a styrene derivative and maleic anhydride is preferable.
The glass transition temperature Tg _A of the aromatic vinyl polymer is preferably 110 ° C. or higher, more preferably 120 ° C. or higher, from the viewpoint of obtaining excellent optical properties.

  As a retardation element, a film or sheet made of a material having a negative intrinsic birefringence value is uniaxially stretched or unbalanced biaxially stretched, and the stretching directions (directions in which the refractive index is maximum or minimum) are orthogonal to each other. Two layers laminated, or a balance biaxially stretched (stretched so that the refractive index is substantially equal in any direction in the plane) can be used as a single layer. Among them, in view of mechanical strength, a layer in which a reinforcing layer (B layer) made of a transparent resin material is laminated on at least one side of a layer (A layer) obtained by stretching and orientation of the negative material is used. From the viewpoint of preventing warping due to moisture absorption, temperature change, or change over time, a layer (B) made of a transparent resin material on both sides of a layer (A layer) made of a material having a negative intrinsic birefringence value (B) More preferably, the layer) is laminated.

The transparent resin material used here is not particularly limited as long as it has a thickness of 1 mm and a total light transmittance of 80% or more. For example, the thing similar to what was listed as what can be used as a material of the transparent base material of the optical laminated body of the said invention can be used.
Although the thickness of the layer (B layer) which consists of transparent resin materials is not specifically limited, Usually, 15-250 micrometers, Preferably it is 25-150 micrometers.

  The material having the negative intrinsic birefringence value and / or the transparent resin material may include an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, an antistatic agent, a dispersant, and a chlorine scavenger as necessary. , Flame retardant, crystallization nucleating agent, antiblocking agent, antifogging agent, mold release agent, pigment, organic or inorganic filler, neutralizing agent, lubricant, decomposition agent, metal deactivator, antifouling agent, antibacterial Known additives such as an agent, other resins, and thermoplastic elastomers can be added as long as the effects of the present invention are not impaired.

  The retardation element used in the present invention has an adhesive layer (C layer) between a layer (A layer) made of a material having a negative intrinsic birefringence value and a layer (B layer) made of a transparent resin material. It may be provided. The adhesive layer (C layer) can be formed from a material having an affinity for both the material having a negative intrinsic birefringence value used for the A layer and the transparent resin material used for the B layer. For example, ethylene- (meth) acrylic acid ester copolymer such as ethylene- (meth) acrylic acid methyl copolymer, ethylene- (meth) ethyl acrylate copolymer; ethylene-vinyl acetate copolymer, ethylene-styrene An ethylene copolymer such as a copolymer may be mentioned. In addition, modified products obtained by modifying these copolymers by oxidation, saponification, chlorination, chlorosulfonation, or the like can also be used. In the present invention, when the ethylene copolymer is modified, the handling property at the time of forming the laminated structure and the heat resistance deterioration property of the adhesive force can be improved. The thickness of the adhesive layer (C layer) is preferably 1 to 50 μm, more preferably 5 to 30 μm.

  A method for producing the retardation element is not particularly limited, but a layer (B layer) made of a transparent resin material is not laminated on at least one side of a layer (A layer) made of a material having a negative intrinsic birefringence value. A method of obtaining a stretched laminate and stretching it uniaxially or biaxially is preferable.

  As a method for obtaining an unstretched laminate, a coextrusion T die method, a coextrusion inflation method, a coextrusion molding method such as a coextrusion lamination method, a film lamination molding method such as dry lamination, and a base resin film A known method such as a coating molding method for coating a resin solution can be appropriately used. Among these, from the viewpoint of production efficiency and the like, a molding method by coextrusion is preferable. The extrusion temperature may be appropriately selected according to the material having a negative intrinsic birefringence value, a transparent resin material, and the type of adhesive used as necessary.

  There is no restriction | limiting in particular in the method of extending | stretching the said unstretched laminated body, A conventionally well-known method may be applied. Specifically, a uniaxial stretching method such as a method of uniaxial stretching in the longitudinal direction using the difference in peripheral speed on the roll side, a method of uniaxial stretching in the lateral direction using a tenter, etc .; At the same time as stretching in the longitudinal direction, use the simultaneous biaxial stretching method that stretches in the transverse direction according to the spread angle of the guide rail or the longitudinal direction using the difference in peripheral speed between the rolls, and then grip the both ends of the clip And a biaxial stretching method such as a sequential biaxial stretching method of stretching in the transverse direction using a tenter. The biaxial stretching method is preferred for balancing the refractive index in the plane direction and making the in-plane retardation substantially zero (positive letterer).

The stretching temperature is not particularly limited. However, when the retardation element has the above-described laminated structure, assuming that the glass transition temperature Tg _A of the material having a negative intrinsic birefringence is (Tg _A −10) (° C.) to (Tg _A +20). ) (° C.) is preferable, and the range of (Tg _A −5) (° C.) to (Tg _A +15) (° C.) is more preferable. By setting the stretching temperature in the above range, refractive index anisotropy can be made difficult to develop in the B layer during stretching, and the relationship between the target in-plane orthogonal axis direction and the refractive index in the thickness direction can be easily achieved. Obtainable.

  The draw ratio is usually 1.1 to 30 times, preferably 1.3 to 10 times. If the draw ratio is out of the above range, the orientation may be insufficient, the refractive index anisotropy, and thus the retardation may be insufficiently developed, or the laminate may be broken.

  The quarter-wave plate used in the present invention is not particularly limited as long as it provides a quarter-wave phase difference with respect to incident light, but a broadband quarter-wave plate is preferable. Here, the broadband quarter-wave plate is a quarter-wave plate in which the retardation (retardation) is almost ¼ wavelength in the entire visible light region including the wavelength of 410 to 660 nm.

  The quarter-wave plate used in the present invention includes at least one layer (D layer) made of a material having a positive intrinsic birefringence value and a layer (E layer) made of a material having a negative intrinsic birefringence value. And having the same orientation direction of molecular chains in the D layer and the E layer are preferable.

  The material having a positive intrinsic birefringence value constituting the D layer refers to a material having optically positive uniaxial characteristics when molecules are oriented in a uniaxial order. Examples of the material having a positive intrinsic birefringence value include a rod-like liquid crystal, a rod-like liquid crystal polymer, an alicyclic structure-containing polymer resin, an olefin polymer, a polyester polymer, a polyarylene sulfide polymer, and a polyvinyl alcohol type. Polymer, polycarbonate polymer, polyarylate polymer, cellulose ester polymer, polyethersulfone polymer, polysulfone polymer, polyallylsulfone polymer, polyvinyl chloride polymer, or their multiple (Binary, ternary, etc.) copolymers and the like. These can be used alone or in combination of two or more.

  In the present invention, among these, it is preferable to use an alicyclic structure-containing polymer resin or an olefin polymer. From the viewpoint of light transmittance characteristics, heat resistance, dimensional stability, photoelastic characteristics, and the like, The use of a polymer resin containing a formula structure is more preferred. As an alicyclic structure containing polymer resin used here, the thing similar to what was listed as what can be used as a material of the transparent base material of the said optical laminated body of the said invention can be used. The glass transition temperature of the alicyclic structure-containing polymer resin may be appropriately selected depending on the purpose of use, but is preferably 80 ° C. or higher, more preferably 100 to 250 ° C. from the viewpoint of obtaining excellent optical properties. More preferably, it is the range of 120-200 degreeC.

  Moreover, about the material which has the negative intrinsic birefringence value which comprises the (E) layer, use of an aromatic vinyl polymer is preferable. Examples of the aromatic vinyl polymer include the same ones listed in the retardation element.

  The method for producing a quarter-wave plate used in the present invention is not particularly limited. For example, (i) a D layer and an E layer are separately formed, and dry lamination is performed through an adhesive layer (F layer). Examples include a method of laminating to form a laminate, and (ii) a method of forming a laminate by coextrusion to obtain a laminate. Among these, the film-forming method by the co-extrusion method (ii) is preferable because a laminate having a high delamination strength can be obtained and the production efficiency is excellent. Specifically, a method of obtaining a laminate by a coextrusion method is to extrude a material having a positive intrinsic birefringence value and a material having a negative intrinsic birefringence value from a multilayer die using a plurality of extruders. Thus, a film is formed.

  In the case of producing a quarter-wave plate used in the present invention, various additives and other thermoplastic resins and elastomers are added to the D layer and / or E layer within a range not impairing the object of the present invention. can do. Examples of various additives include plasticizers and deterioration inhibitors. The addition amount of these additives is usually 0 to 20% by weight, preferably 0 to 10% by weight, and more preferably 0 to 5% by weight with respect to the alicyclic structure-containing polymer resin.

  In order to laminate a layer made of a material having a positive intrinsic birefringence value (D layer) and a layer made of a material having a negative intrinsic birefringence value (E layer) with the slow axes orthogonal to each other, the molecular chain of each layer It is sufficient to make the orientation directions of the same. That is, since the quarter wave plate is a laminate of layers (D layer and E layer) made of materials having different intrinsic birefringence values, the stretching direction of the D layer and the E layer should be matched. The slow phases of the two phases can inevitably be orthogonal.

  Such a quarter-wave plate can be produced by stretching the laminate. There is no restriction | limiting in particular in the method of extending | stretching a laminated body, A conventionally well-known method is employable. Examples of the stretching method include a method of uniaxial stretching in the longitudinal direction using a difference in peripheral speed on the roll side, and a method of uniaxial stretching in the lateral direction using a tenter. Among these, uniaxial stretching in the longitudinal direction is preferable. Although there is no restriction | limiting in particular in the draw ratio of uniaxial stretching, it is preferable that it is 1.1 to 3.0 times, and it is more preferable that it is 1.2 to 2.2 times.

  The temperature at which the laminate is stretched is preferably between (Tg-30) ° C and (Tg + 60) ° C, more preferably (Tg + 60) ° C, where Tg is the glass transition temperature of the resin constituting the D layer and E layer. The temperature range is from Tg-10) ° C to (Tg + 50) ° C. Moreover, a draw ratio is 1.01-30 times normally, Preferably it is 1.01-10 times, More preferably, it is 1.01-5 times.

  In addition, when the laminate is manufactured by the above-described coextrusion method, operations such as cutting out a stretched film chip and pasting the cut chip, which are necessary when manufacturing a conventional quarter-wave plate, are performed. Is not necessary, and a long quarter-wave plate can be continuously produced by a so-called roll-to-roll method.

  The quarter-wave plate is particularly limited to the layer structure as long as it has at least one D layer and at least one E layer, and the optical layered body has the same molecular chain orientation in the D layer and the E layer. However, it is preferable to have a layer structure of D layer / E layer / D layer or E layer / D layer / E layer. In addition, an F layer (adhesive layer) is further provided between the D layer and the E layer, and a three-layer structure of D layer-F layer-E layer, or D layer-F layer-E layer-F layer- A five-layer structure of D layer or E layer-F layer-D layer-F layer-E layer can be employed. About the adhesive which comprises the said F layer, the thing similar to what was listed in the said phase difference element can be used.

  The thickness of the quarter-wave plate obtained as described above can be appropriately determined according to the purpose of use. From the viewpoint of obtaining a homogeneous stretched film by a stable stretching treatment, the thickness is preferably 10 to 300 μm, more preferably 30 to 200 μm.

  In the present invention, in addition to the above-described broadband quarter-wave plate, a half-wave plate and a quarter wavelength described in JP-A-5-100114, JP-A-11-231132, etc. A laminate of plates or a broadband retardation film WRF (manufactured by Teijin Ltd.) can also be used suitably.

The brightness enhancement film of the present invention includes the above-described liquid crystal layer, the above-described retardation element, and a quarter-wave plate.
An example of the layer structure of the brightness enhancement film of the present invention is shown in FIG. In FIG. 6, 9 is a cholesteric liquid crystal layer, 12 is a retardation element, and 10 is a quarter-wave plate. For example, as shown in FIG. 7, the brightness enhancement film 14 shown in FIG. 6 can be used by sequentially arranging the light source A, the diffusion plate 8, the brightness enhancement film 14, the prism sheet 13, and the polarizing plate 11. The light beam L emitted from the light source A is converted into diffused light having a uniform distribution by passing through the diffusion plate 8. Next, the light incident on the quarter-wave plate 10 is separated into circularly polarized light having different rotational directions, circularly polarized light in one rotational direction is transmitted, and circularly polarized light in the other rotational direction is reflected. The transmitted circularly polarized light is converted by the quarter wavelength plate 10 into linearly polarized light parallel to the transmission axis of the polarizing plate 11. On the other hand, the reflected circularly polarized light is depolarized by being depolarized by the diffusing plate 8 and then emitted again to the diffusing plate side by the reflecting plate B disposed on the back side of the light source A to be reused. As a result, the light emitted from the light source can be effectively used, and the display luminance can be improved.

  The brightness enhancement film shown in FIG. 6 can be manufactured, for example, as follows. First, an alignment film is formed on a transparent substrate, a liquid crystal layer having a first alignment state is formed on the alignment film, and then the layer shape is changed so that the spiral axis is substantially the same as the layer normal direction. After the parallel cholesteric liquid crystal layer is formed, the layer shape is changed to form a costelic liquid crystal layer including at least one portion where the helical axis and the layer normal are not parallel. Next, directly or via an adhesive layer or an adhesive layer, the formula: Rth = {(nx + ny) / 2−nz} × d (where nx and ny are two directions perpendicular to the thickness direction and perpendicular to each other) Nx> ny, nz represents the refractive index in the thickness direction, and d represents the film thickness.) Rth defined by Rth is −20 nm to −1000 nm is laminated. Thereby, a phase difference element is formed. Next, a desired wavelength enhancement film can be obtained by laminating a quarter wavelength plate directly or via an adhesive layer or an adhesive layer on the retardation element.

  By using the brightness enhancement film of the present invention in combination with an appropriate surface light source such as a side light type light guide plate, the reflection circular loss by depolarizing the reflected circularly polarized light by the cholesteric liquid crystal layer and reusing it as the output light is reflected. Can be eliminated. Moreover, the loss of absorption by the polarizing plate is prevented by controlling the phase of the emitted light through an optical layered body laminated on the cholesteric liquid crystal layer and converting it into a state containing a large amount of linearly polarized light that is transparent to the polarizing plate. Therefore, the luminance can be improved.

3) Polarized light source device The polarized light source device of the present invention includes the brightness enhancement film of the present invention. The polarized light source device of the present invention includes a light reflection layer, a light source, and the brightness enhancement film of the present invention, and the light emitted from the light source is incident from the cholesteric liquid crystal layer side of the brightness enhancement film and reflected by the brightness enhancement film. The light reflecting layer, the light source, and the brightness enhancement film are preferably arranged so that the light reflection layer is reflected by the light reflection layer and reenters the brightness enhancement film.

  An example of the layer structure of the polarized light source device of the present invention is shown in FIG. In FIG. 8, 15 is a light source, 16 is a light source holder, 17 is a light guide plate, 18 is a reflection layer, 14 is a brightness enhancement film, and 11 is a polarizing plate. The brightness enhancement film 14 includes a cholesteric liquid crystal layer 9, a retardation element 12, and a quarter wavelength plate 10.

The light from the light source 15 arranged on the side surface enters the light guide plate 17 and exits upward (to the cholesteric liquid crystal layer 9 side). The light incident on the cholesteric liquid crystal layer 9 is transmitted through one of the left and right circularly polarized light, and the other circularly polarized light is reflected and reenters the light guide plate 17. The light that re-enters the light guide plate is reflected by the reflective layer 18 on the lower surface, is incident again on the cholesteric liquid crystal layer 9, and is separated again into transmitted light and reflected light. Thereby, the effective utilization of the light emitted from the light source 15 is achieved, and an excellent luminance improvement effect can be obtained.
The light source 15 is not particularly limited, and a conventionally known light source 15 can be used.

  As the light guide plate 17, it is preferable that the shape of the side end portion facing the incident surface is thinner than that of the incident surface (wedge type). Moreover, the thing of the structure which has a fine prism-shaped convex part from viewpoints, such as being excellent in the output efficiency from an output surface, excellent in the perpendicularity with respect to the output surface, and aiming at effective utilization of an emitted light, is preferable. The light guide plate 17 can be formed of a transparent material such as norbornene-based polymer, polymethyl methacrylate, polycarbonate, polystyrene. Moreover, the reflective layer 18 can be appropriately formed by, for example, a plating layer, a metal vapor deposition layer, a metal foil, a metal vapor deposition sheet, a plating sheet, or the like. The reflection layer may be integrated with the opposite surface of the light guide plate, or may be formed as a reflection sheet or the like so as to overlap the light guide plate.

  Since the polarized light source device of the present invention is provided with the brightness enhancement film of the present invention, it has an excellent brightness enhancement effect and has a wide viewing angle characteristic.

4) Liquid crystal display device The liquid crystal display device of the present invention has the polarized light source device of the present invention, and further includes a liquid crystal cell above it. In general, a liquid crystal display device can be manufactured by combining a liquid crystal cell that functions as a liquid crystal shutter, and accompanying components such as a driving device, a polarizing plate, a backlight, and a retardation plate for compensation as necessary. . The liquid crystal display device of the present invention is not particularly limited except that the optical laminate of the present invention is used, and can be produced by a method according to a conventional method.

  An example of the layer structure of the liquid crystal display device of the present invention is shown in FIG. The liquid crystal display device shown in FIG. 9 uses the polarized light source device of the present invention in a backlight system. In FIG. 9, 19 is a liquid crystal cell, 11a is a lower polarizing plate, 11b is an upper polarizing plate, and 8a and 8b are diffusion plates. The lower polarizing plate 11a and the diffusion plates (8a, 8b) can be omitted.

  The liquid crystal mode to be used is not particularly limited. Examples of the liquid crystal mode include a TN (Twisted Nematic) type, a STN (Super Twisted Nematic) type, and a HAN (Hybrid Aligned Nematic) type. Moreover, it does not restrict | limit especially as a polarizing plate (11a, 11b), A conventionally well-known thing can be used.

  Since the liquid crystal display device of the present invention has the optical layered body of the present invention, it is possible to obtain an excellent brightness improvement effect and to obtain a wide viewing angle characteristic.

(Creation of polarization separation layer)
[Example 1]
An optically isotropic alicyclic structure-containing polymer resin having a thickness of 100 μm, a width of 680 mm, and a length of 500 m was used as a transparent support. After performing plasma discharge treatment on both surfaces of the transparent support, an alignment film coating solution having the following composition was continuously applied to one surface of the transparent support and dried to form an alignment film having a thickness of 1 μm. Next, a rubbing treatment was performed on the alignment film continuously in a direction parallel to the longitudinal direction of the transparent support.

Alignment film coating solution composition Polyvinyl alcohol 10% by weight
371% by weight of water

  On the alignment film, a coating solution having the following composition is continuously applied using a bar coater, dried and heated (alignment aging), and further irradiated with ultraviolet rays to give a cholesteric liquid crystal layer (A) having a thickness of 5.0 μm. Formed. The cholesteric liquid crystal layer (A) had a helical axis in the layer normal direction.

Coating liquid composition for cholesteric liquid crystal layer (A) Liquid crystalline compound (Compound 1) 81.5 parts by weight Photopolymerization initiator (Compound 2) 3.1 parts by weight Surfactant (KH-40 manufactured by Seimi Chemical Co.) 0.1 Parts by weight Chiral agent (compound 3) 18.5 parts by weight Methyl ethyl ketone 240.8 parts by weight

  A member in which a quadrangular pyramid having an apex angle of about 70 ° and a height of 3 μm is formed of a polymer resin containing an alicyclic structure with respect to the cholesteric liquid crystal layer (A) is a surface on which the quadrangular pyramid is formed. The circularly polarized light separating layer (B) was arranged so as to face the layer surface and the shape of the layer was changed by pressure bonding. The circularly polarized light separating layer (B) had a helical axis inclined with respect to the layer normal.

(Production of retardation film)
Styrene-maleic anhydride copolymer [“Dairaku D332”, manufactured by Nopa Chemical Co., Tg = 131 ° C.] as a material having a negative intrinsic birefringence value, norbornene-based resin (trade name: ZEONOR 1020, Nippon Zeon) as a transparent resin layer material Co., Ltd., Tb = 105 ° C., and a norbornene resin layer (thickness 50 μm) / styrene-maleic anhydride copolymer layer (thickness 200 μm) / norbornene resin layer (thickness) A laminate having a three-layer structure of 50 μm) was obtained.

  Next, the mixture was sequentially fed into a zone-heated longitudinal uniaxial stretching apparatus and a tenter stretching (lateral uniaxial stretching) apparatus to perform sequential biaxial stretching. The stretching temperature was 140 ° C. for both longitudinal stretching and lateral stretching, and the stretching ratio was 1.8 times for longitudinal stretching and 1.5 times for lateral stretching.

  The average thickness of the stretched laminate (retardation film (D)) is 120 μm, the refractive index in the plane direction is nx = 1.732, ny = 1.5731, and the refractive index in the thickness direction is nz = 1.5757. there were. In the retardation, the in-plane Re was 10 nm and the thickness direction Rth was -300 nm.

(Preparation of quarter wave plate)
As a material having a positive intrinsic birefringence value, norbornene-based resin (trade name: ZEONOR 1420, manufactured by Nippon Zeon Co., Ltd., Tg = 136 ° C.) and as a material having a negative intrinsic birefringence value, styrene-maleic anhydride A copolymer (trade name: Dailark D332, manufactured by Nova Chemical Co., Ltd., Tg = 131 ° C.) was used. First, the norbornene-based resin and the styrene-maleic anhydride copolymer in a molten state were respectively stored in the extruders of the extrusion dies in which two extruders were integrally combined with the extrusion die. The extrusion flow path of the extruder containing the norbornene-based resin is branched into two, and the norbornene-based resin extruded from the branched flow path is styrene-maleic anhydride co-polymer extruded from another extruder. The union was sandwiched and a three-layer laminate was formed inside the extrusion die. In addition, a filter is disposed at a communication port to the extrusion die of the two extruders, and the norbornene resin and the styrene-maleic anhydride copolymer are passed through the filter and then extruded into the extrusion die. I made it.

  The thickness unevenness of the three-layered laminate extruded from the extrusion die was measured using a scanning thickness meter. The measurement was performed by continuously scanning in the longitudinal direction of the laminate. The obtained laminate had a thickness average of 120 μm, and the thickness unevenness was 2.5% with respect to the thickness average.

  Next, when the obtained laminate was stretched 70% at 125 ° C., the ratio of retardation to wavelength at wavelengths λ = 450 nm, 550 nm, and 650 nm was 0.235, 0.250, and 0.232, respectively. A broadband quarter-wave plate (E) was obtained.

(Production of brightness enhancement film)
The circularly polarized light separating layer (B) obtained in Example 1 was laminated with the retardation film (D) and the broadband quarter-wave plate (E) prepared in the above order, and the brightness enhancement film (F) and did.

[Comparative Example 1]
A cholesteric liquid crystal layer (A) is produced by the same material and method as in Example 1, and a circularly polarized light separating layer (C ) Was produced. The circularly polarized light separating layer (C) had a helical axis in the layer normal direction. The circularly polarized light separating layer (C) was laminated with the retardation film (D) and the broadband quarter wave plate (E) in the same manner as in Example 1 to obtain a brightness enhancement film (G).

(Performance comparison)
The light diffusion sheet and the brightness enhancement film (F) obtained in Example 1 are sequentially applied to the light-emitting plate side where the cold cathode tube is disposed on the incident end surface side and the light reflecting sheet is provided on the back surface side. A polarized light source device was produced by laminating the polarization separation layer so that it faces the diffusion sheet. Further, a polarizing plate, a viewing angle widening film (trade name: WV film, manufactured by Fuji Photo Film Co., Ltd.), a transmission type TN liquid crystal display element, and a polarizing plate are sequentially arranged on the quarter wavelength plate side to display a liquid crystal display. A device was made.

  When this liquid crystal display device was observed in the white display mode from the light exit surface side, there was no coloration over the entire display surface, and good white display was achieved. When the liquid crystal display device was produced and observed in exactly the same manner except that the brightness enhancement film (G) produced in Comparative Example 1 was used as the brightness enhancement film, it was colored over the entire display surface of the liquid crystal display device, and a good display was obtained. I could not.

It is the schematic which shows a general cholesteric liquid crystal layer. It is the schematic which shows the selective reflection of a general cholesteric liquid crystal layer. It is the schematic which shows the viewing angle dependence of selective reflection. It is the schematic which shows the cholesteric liquid crystal layer in which the spiral axis inclined. It is the schematic which shows an example of the method of this invention which inclines a helical axis. It is the schematic which shows the principle and structure of a brightness enhancement film. It is a figure which shows the layer structure of the brightness enhancement film of this invention. It is a figure which shows the layer structure of the polarized light source device of this invention. It is a figure which shows the layer structure of the liquid crystal display device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Orientation processing surface of base material, 2 ... Liquid crystal molecule, 3 ... Layer normal line, 4 ... Spiral axis, 5 ... Transmission spectrum with respect to oblique incident light, 6 ... Transmission spectrum with respect to parallel incident light, 7 ... Convex part in plane 8, 8a, 8b ... diffusion plate, 9 ... cholesteric liquid crystal layer, 10 ... 1/4 wavelength plate, 11, 11a, 11b ... polarizing plate, 12 ... phase difference element, 13 ... prism sheet, P ... spiral Pitch, L1 ... white incident light, L2 ... reflected circularly polarized light, .theta.1 ... incident angle to the layer surface, .theta.2 ... incident angle inside the layer, a ... incident angle inside the layer (upper layer), b ... inside layer (middle layer) , C ... incident angle inside the layer (lower layer), A, 15 ... light source, B, 18 ... reflector (reflective layer), 16 ... light source holder, 17 ... light guide plate, 19 ... liquid crystal cell

Claims (10)

  An optical laminate having a liquid crystal layer on a transparent substrate, wherein the liquid crystal layer forms a liquid crystal layer having a first alignment state on the transparent substrate, and then the first shape is changed by changing the layer shape. An optical laminate, which is a liquid crystal layer having a second alignment state different from the alignment state.   2. The optical laminate according to claim 1, wherein the liquid crystal layer having the first alignment state is a liquid crystal layer of a cholesteric phase, a nematic phase, or a smectic phase.   After the liquid crystal layer forms a cholesteric phase liquid crystal layer in which the spiral axis and the layer normal are substantially parallel, the layer shape is changed, so that at least one portion where the spiral axis and the layer normal are not parallel is changed. The optical layered body according to claim 1, wherein the optical layered body is a liquid crystal layer having a cholesteric phase contained in a part.   A method for producing an optical laminate in which a liquid crystal layer is formed on a transparent substrate, the step (1) of forming a liquid crystal layer having a first alignment state on the transparent substrate, and the layer shape of the liquid crystal layer And (2) changing the orientation state to a second orientation state different from the first orientation state, thereby producing an optical laminate manufacturing method.   5. The method for producing an optical laminate according to claim 4, wherein the step (1) forms a cholesteric phase, nematic phase or smectic phase liquid crystal layer on a transparent substrate.   6. The optical layered body according to claim 4, wherein the step (2) includes a step of bringing a member having a convex portion in contact with the liquid crystal layer having the first alignment state. Production method.   After forming a cholesteric phase liquid crystal layer having a first alignment state on a transparent substrate, the cholesteric phase liquid crystal layer having a second alignment state different from the first alignment state by changing the layer shape And the formula: Rth = {(nx + ny) / 2−nz} × d (where nx and ny represent refractive indexes in two directions perpendicular to the thickness direction and perpendicular to each other, and nx> ny. The brightness improvement characterized by including the phase difference element whose Rth defined by the refractive index of thickness direction and d represents a film thickness is -20 nm--1000 nm, and a quarter wavelength plate. the film.   After the liquid crystal layer forms a cholesteric phase liquid crystal layer in which the spiral axis and the layer normal are substantially parallel, the layer shape is changed, so that at least one portion where the spiral axis and the layer normal are not parallel is changed. The brightness enhancement film according to claim 7, which is a liquid crystal layer having a cholesteric phase contained in a part.   A polarized light source device comprising the brightness enhancement film according to claim 7. A liquid crystal display device comprising the polarized light source device according to claim 9 and further comprising a liquid crystal cell thereabove.

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