JP2006003883A - Method for manufacturing optical laminated body, optical element, polarizing light source device and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently manufacturing an optical laminated body, having a cholesteric liquid crystal layer having a wide-band circularly polarized light separating function, suitable as a member for a luminance improving film, in a short time, having proper productivity, and to provide an optical element functioning as the luminance improving film having the optical laminate. <P>SOLUTION: The method for manufacturing the optical laminated body includes (A) a step of forming a coating layer by using a coating liquid containing at least a light absorbent and a photopolymerizable cholesteric liquid crystal compound on base material, (B) a step of photopolymerizing the photopolymerizable cholesteric liquid crystal compound by irradiating the coating layer with active light in a wavelength region where the average molecular extinction coefficient of the light absorbent in the coating layer is ≥9,000(mol<SP>-1</SP>L cm<SP>-1</SP>) with irradiating quantity which exceeds 0 and is under 10mJ/cm<SP>2</SP>, and (C) a step of changing the pitch of the photopolymerized cholesteric liquid crystal layer. The optical element has the optical laminated body and a 1/4-wave plate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical laminate manufacturing method, an optical element, a polarized light source device, and a liquid crystal display device.

Liquid crystal display devices are used in many devices, and there is an increasing demand for their display characteristics. In connection with this, the performance of optical films, such as a polarizing plate used for a liquid crystal display device, a viewing angle compensation film, a quarter wavelength plate, a brightness enhancement film, and a cost are also increasing. In particular, a brightness enhancement film for increasing the brightness at the time of display is an important element for suppressing the power consumption of a liquid crystal display device, and the demand for quality and cost is high. A brightness enhancement film having a polarization separation layer for separating incident light into transmitted light and reflected light according to the polarization state is known as a constituent element.
These polarization separation layers include, for example, a linear polarization separation layer (see, for example, Patent Document 1) in which a large number of anisotropic polymer layers are laminated, and a circular polarization separation film using a cholesteric liquid crystal layer (for example, Patent Document 2, Patent Document). 3) is known. However, the former linearly polarized light separating layer needs to be laminated with several hundred anisotropic layers, and has a problem that it 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. When this selective reflection layer is formed using a normal liquid crystal, the wavelength range of selective reflection is about several tens of nanometers and cannot be applied as it is for the purpose of a brightness enhancement film. 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 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, and the like are known. However, the present situation is that both methods still have problems regarding productivity and cost.
On the other hand, as a means for increasing the brightness of a liquid crystal display device or the like, a method is known in which an optical element composed of a cholesteric liquid crystal layer having a Grand Jean structure and a quarter-wave plate is disposed on a surface light source (for example, a patent) Reference 4). This method utilizes the property of separating the incident natural light shown by the cholesteric liquid crystal layer into right and left circularly polarized light components as reflected light and transmitted light, and circularly polarizes the outgoing light from the surface light source, which is converted into a quarter-wave plate. In this way, the light is linearly polarized through and supplied to the polarizing plate, thereby suppressing the absorption loss due to the polarizing plate and improving the luminance.
Japanese National Patent Publication No. 9-506837 JP-A-6-235900 JP-A-8-271731 JP-A-6-281814

  Under such circumstances, the present invention can efficiently produce an optical laminate having a cholesteric liquid crystal layer having a broadband circularly polarized light separation function suitable as a member of a brightness enhancement film in a short time with high productivity. And an optical element as a brightness enhancement film having the optical laminate obtained by this manufacturing method, having the optical element and having high brightness, and making it difficult to cause color unevenness with a wide viewing angle. A polarized light source device suitably used as a backlight unit of a liquid crystal display device, and a liquid crystal display device having the polarized light source device, which has excellent luminance and can improve display characteristics such as viewing angle dependency It was made for the purpose of providing.

As a result of intensive studies to achieve the above object, the inventors of the present invention applied a coating layer containing a light absorber having a large average molecular extinction coefficient and a photopolymerizable cholesteric liquid crystal compound to a wavelength having a large extinction coefficient. It has been found that an optical laminate having a broadband circularly polarized light separation function can be efficiently obtained in a short time by performing a simple operation of irradiating weak active light in the band and then performing heat treatment.
In addition, an optical element obtained by combining the optical laminate obtained in this manner with a quarter-wave plate and preferably a retardation element having a specific property has high luminance and color unevenness with a wide viewing angle. It has been found that it is less likely to occur and is useful as a brightness enhancement film for a polarized light source device suitable as a backlight unit of a liquid crystal display device.
The present invention has been completed based on such findings.
That is, the present invention
(1) (A) A step of forming a coating layer on a substrate using a coating liquid containing at least a light absorber and a photopolymerizable cholesteric liquid crystal compound, (B) Irradiating active light in a wavelength region in which the average molecular extinction coefficient of the light absorber is 9000 (mol ⁻¹ · L · cm ⁻¹ ) or more at an irradiation dose of more than 0 and less than 10 mJ / cm ² , A process for photopolymerizing a photopolymerizable cholesteric liquid crystal compound, and (C) a method for producing an optical laminate comprising a step of changing the pitch of the photopolymerized cholesteric liquid crystal layer,
(2) The method for producing an optical layered product according to item (1), wherein the irradiation dose in step (B) is more than 0 and not more than 1 mJ / cm ² ,
(3) In the step (B), the method for producing an optical laminate according to the above (1) or (2), wherein the polymerization rate after irradiation with active light is more than 0% and less than 85%,
(4) After the step (C), (D) the step (1), (2) comprising a step of photopolymerizing a photopolymerizable cholesteric liquid crystal compound by irradiating active light at an irradiation dose of 10 mJ / cm ² or more. ) Or the method for producing an optical layered product according to item (3),
(5) An optical element comprising the optical laminate according to any one of (1) to (4) above and a quarter-wave plate,
(6) The optical element according to (5) above, wherein the quarter-wave plate is a broadband quarter-wave plate.
(7) In addition the main refractive indices n _x, n _y and n _z (however, n _x is one of the inner largest orthogonal axis direction of the refractive index in the plane, n _y is of the orthogonal axis direction of the refractive index in the plane and the minimum of, n _z is a refractive index in the thickness direction.) relationship n _z> n _{x of, n z> n y, n} x is a ≒ n _y above having a phase difference element (5) or The optical element according to item (6),
(8) the phase difference element is essentially no in-plane retardation and Rth = _{[[(n x + n y)} / 2] -n z ] × D
(However, D is the thickness of the retardation element.)
The optical element according to item (7), wherein the retardation in the thickness direction defined by is in the range of -20 to -1000 nm,
(9) A polarized light source device having the optical element according to any one of (5) to (8) above, and (10) the polarized light source device according to (9) above. Liquid crystal display device,
Is to provide.

According to the present invention, it is possible to provide a method for efficiently and efficiently producing an optical laminate having a cholesteric liquid crystal layer having a broadband circularly polarized light separation function suitable as a member of a brightness enhancement film in a short time. it can.
In addition, according to the present invention, an optical element as a brightness enhancement film formed by combining the optical laminate obtained by the above-described manufacturing method, a quarter-wave plate, and a phase difference element having a specific property in some cases, the optical element A polarized light source device that is suitable for use as a backlight unit of a liquid crystal display device, etc. In addition, it is possible to provide a liquid crystal display device that is excellent in luminance and can improve display characteristics such as viewing angle dependency.

First, the manufacturing method of the optical laminated body of this invention is demonstrated.
In the method for producing an optical layered body of the present invention, (A) a step of forming a coating layer on a substrate using a coating liquid containing at least a light absorber and a photopolymerizable cholesteric liquid crystal compound; B) Active light in a wavelength region where the average molecular extinction coefficient of the light absorber in the coating layer is 9000 (mol ⁻¹ · L · cm ⁻¹ ) or more is applied to this coating layer, exceeding 0 and less than 10 mJ / cm ² (C) a step of changing the pitch of the photopolymerized cholesteric liquid crystal layer, and (D) an active light of 10 mJ / A step of further photopolymerizing the photopolymerizable cholesteric liquid crystal compound by irradiation with an irradiation dose of cm ² or more is performed.

  As the coating liquid in the step (A), a coating liquid appropriately containing a chiral agent, a surfactant, an alignment regulator, a solvent and the like in addition to the light absorber and the photopolymerizable cholesteric liquid crystal compound is used.

The light absorber causes a phenomenon in which when the light travels through the substance, the energy of the light is changed to the energy of the substance and the intensity of the light is reduced. Examples of such a light absorber include a photopolymerization initiator, a photosensitizer, and an ultraviolet absorber. Among these, a photopolymerization initiator having a function as a polymerization initiator is preferable. . In the present invention, a light absorber having an average molecular extinction coefficient of 9000 (mol ⁻¹ · L · cm ⁻¹ ) or more is used. The average molecular extinction coefficient is light having a ratio of (light transmission intensity when using a bandpass filter) / (light transmission intensity transmitted without a bandpass filter) of 0.01 or more. Is the average value of the molecular extinction coefficient (mol ⁻¹ · L · cm ⁻¹ ) of the light absorbent in the wavelength region.

In the present invention, examples of the light absorber include acetophenones, benzophenones, alkylaminobenzophenones, benzyls, benzoins, benzoin ethers, benzyldimethylacetals, benzoyl benzoates, α-acyloxime esters, and the like. Average molecular absorption among the aryl ketone photopolymerization initiators, sulfur-containing photopolymerization initiators such as sulfides and thioxanthones, acylphosphine oxides such as acyldiarylphosphine oxide, anthraquinones, and other photopolymerization initiators. One having a coefficient of 9000 (mol ⁻¹ · L · cm ⁻¹ ) or more can be appropriately selected and used.

  Although there is no restriction | limiting in particular about the usage-amount of this light absorber, Usually 0.001-50 weight part with respect to 100 weight part of monomer components which consist of a photopolymerizable cholesteric liquid crystal compound mentioned later and a chiral agent, Preferably it is 0. It is selected in the range of 0.01 to 20 parts by weight, more preferably 0.5 to 5 parts by weight.

等が挙げられるが、これに限定されるものではない。 As the photopolymerizable cholesteric liquid crystal compound which is a constituent component in the coating liquid, a rod-like liquid crystal compound, a discotic liquid crystal compound or a polymer liquid crystal in which a polymerizable functional group is introduced into the molecule can be used.
As the rod-like liquid crystal compound, a compound represented by the following formula [1] R1-L1-S1-L3-M-L4-S2-L2-R2 [1]
In the formula, R1 and R2 represent a polymerizable group, and L1, L2, L3, and L4 each represent a single bond or a divalent linking group, but at least one of L3 or L4 represents —O—CO—O—. , S1 and S2 represent spacer groups having 2 to 20 carbon atoms, and M represents a mesogenic group. The mesogenic group M includes azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyl Dioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. Specific examples of the polymerizable groups R1 and R2

However, it is not limited to this.

As a discotic liquid crystalline compound, various documents (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); edited by The Chemical Society of Japan, Quarterly Chemical Review, No. 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 same linking group, spacer group and polymerizable group as those mentioned for the rod-like liquid crystalline compound can be used.
As the polymer liquid crystal, those described in the Liquid Crystal Handbook Editorial Committee, Liquid Crystal Handbook, Chapter 3, Section 3.8 (2000) can be used, but are not limited thereto. From the viewpoint of alignment uniformity, a side chain type polymer liquid crystal is preferably used.

In the case of a cholesteric phase, a method using a liquid crystalline compound containing an optically active site in the molecule and a method of adding an optically active substance to a liquid crystalline compound having no optically active site are known. The optically active substance is also called a chiral agent. As an example of the chiral agent, those having a large HTP, which is an index representing the efficiency of twisting the liquid crystal compound, are preferable from the viewpoint of economy. HTP is represented by Formula [2].
HTP = 1 / P · c [2]

Here, P represents the pitch length of the spiral of the cholesteric phase, and c represents the concentration of the chiral agent. In order to avoid an unintended change in the phase transition temperature due to the addition of the chiral agent, it is preferable to use a chiral agent that exhibits liquid crystallinity.
This chiral agent may or may not have a polymerizable functional group in the molecule.
As the solvent used for preparing the coating liquid, an organic solvent is preferably used. Examples of the organic solvent include ketones, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, and ethers. In particular, ketones are preferable in consideration of environmental load. Two or more organic solvents may be used in combination.

As the surfactant for adjusting the surface tension of the coating liquid and the liquid crystal layer before polymerization, a commercially available surfactant can be used, but a nonionic surfactant is particularly preferable, and the molecular weight is several thousand. It is preferable to be an oligomer of a degree. Examples of such a surfactant include KH-40 manufactured by Seimi Chemical Co., Ltd.
The alignment regulator is for controlling the alignment state of the air-side surface of the liquid crystal layer formed on the substrate, and may also serve as the surfactant. Is used. As such a resin, polyvinyl alcohol, polyvinyl butyral, or a modified product thereof is used, but not limited thereto.

  In the present invention, the substrate used for the optical laminate is not particularly limited as long as it is an optically transparent substrate, but is a long film to efficiently produce the liquid crystal layer. It is preferable. In order to avoid an unnecessary change in the polarization state, an optically isotropic film having a small phase difference due to birefringence is more preferable. Further, from the viewpoint of material cost and reduction in thickness and weight, the thickness is preferably 5 to 300 μm, and more preferably 30 to 200 μm. Such a transparent substrate 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, a polymer having an alicyclic structure, a chain olefin such as polyethylene or polypropylene Single-layer or multi-layer film made of synthetic resin such as polymer, triacetylcellulose, polyvinyl alcohol, polyimide, polyarylate, polyester, polycarbonate, polysulfone, polyethersulfone, modified acrylic polymer, epoxy resin, glass plate, etc. Is mentioned. Among these, a polymer having an alicyclic structure or a chain olefin polymer is preferable, and a polymer having an alicyclic structure is particularly preferable from the viewpoint of transparency, low hygroscopicity, dimensional stability, lightness, and the like. preferable.

  A polymer having an alicyclic structure has an alicyclic structure in the repeating unit of the polymer, and a polymer having an alicyclic structure in the main chain and a polymer having an alicyclic structure in the side chain. Any of the combinations 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 5-15 pieces.

The proportion of the repeating unit having an alicyclic structure in the polymer having an alicyclic structure is appropriately selected according to 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 the number of repeating units having an alicyclic structure is excessively small, heat resistance may be reduced.
Polymers having an alicyclic structure include (1) norbornene polymers, (2) monocyclic olefin polymers, (3) cyclic conjugated diene polymers, and (4) vinyl alicyclic hydrocarbons. Examples thereof include 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 monomers. Among these, from the viewpoint of heat resistance and transparency, ring-opening polymer hydrogenated products of norbornene monomers and ring-opening copolymer hydrogenated products of norbornene-based monomers and other monomers capable of ring-opening copolymerization are the most. preferable.
The polymer having the alicyclic structure is selected from known polymers disclosed in, for example, JP-A No. 2002-321302.

  These substrates are preferably provided with an alignment film for aligning the liquid crystal compound. The alignment film can be provided 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 the Langmuir-Blodgett method (LB film). Furthermore, it is also possible to use an alignment film in which an alignment function is generated by application of an electric field or a magnetic field or light irradiation. Further, in order to provide adhesion between the substrate and the alignment film, it is preferable to surface-treat the substrate in advance, and means for this purpose include glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment, flame Processing etc. are known. It is also effective to provide an adhesive layer (undercoat layer) on the substrate.

From the viewpoint of enabling continuous treatment, an alignment film formed by rubbing treatment of a coatable polymer is preferable. The rubbing process is achieved by rubbing the surface of the polymer layer with a cloth in a certain direction. The type of polymer used as such an alignment film is not particularly limited, but a polymer according to the type of liquid crystal compound and the desired alignment can be selected. Further, these alignment films preferably have a polymerizable group for the purpose of imparting adhesion between the liquid crystal compound and the substrate. The thickness of the alignment film is preferably 0.001 to 5 μm, and more preferably 0.01 to 2 μm.
Application of the coating liquid to the substrate can be performed by a known method such as extrusion coating, direct gravure coating, reverse gravure coating, and die coating.

In the present invention, as the step (B), the average molecular extinction coefficient of the light absorbent in the coating layer thus provided on the substrate is 9000 (mol ⁻¹ · L · cm ^−1). ) The step of photopolymerizing the photopolymerizable cholesteric liquid crystal compound by irradiating active light in the above wavelength region with an irradiation amount exceeding 0 and less than 10 mJ / cm ² is performed. As the active light, ultraviolet rays are usually used. Then, in order to irradiate the active light in a wavelength region where the average molecular extinction coefficient of the light absorber is 9000 (mol ⁻¹ · L · cm ⁻¹ ) or more, use ultraviolet rays that have passed through a predetermined bandpass filter. Is preferred. When the irradiation amount of the active light is 10 mJ / cm ² or more, an optical laminate having a broadband circularly polarized light separation function cannot be obtained, and the object of the present invention cannot be achieved. A preferable irradiation amount is more than 0 and 1 mJ / cm ² or less.

In this way, the active light in the wavelength region in which the average molecular extinction coefficient of the light absorber in the coating layer is 9000 (mol ⁻¹ · L · cm ⁻¹ ) or more is irradiated with the above-mentioned weak dose. As a result, light intensity distribution is generated in the depth direction of the film (see FIG. 3), and as a result, cholesteric liquid crystal layers having different degrees of crosslinking are formed in the depth direction of the film. The shape of this cholesteric liquid crystal layer is the same as that before irradiation with active light, and it is considered that selective reflection is performed in a narrow band. Therefore, in the present invention, in the next step (C), a step of changing the pitch of the photopolymerized cholesteric liquid crystal layer is performed. The polymerization rate in step (B) is preferably more than 0% and less than 85%.
The polymerization rate is a value calculated according to the following method.
<Calculation method of polymerization rate>
The polymerization rate is measured by the ATR method using an FT-IR apparatus [“Nicolet AVATER 360” manufactured by Thermo Co.]. For the calculation of the polymerization rate, a transmittance peak of about 1400 cm ⁻¹ is used, and the absorption rate is calculated from the absorption rate (%) = 100−transmittance (%). Next, the polymerization rate is calculated from the following equation based on the calculated absorption rate.
Polymerization rate (%) = [1− (absorption rate of sample−absorption rate when irradiated unirradiated sample at 70 mW / cm ² for 30 seconds) / (absorption rate at unirradiated−70 mW / unirradiated sample) Absorption rate when irradiated for 30 seconds at cm ² )] × 100

(C) As a step of changing the pitch of the cholesteric liquid crystal layer, which is a step, (1) a step of performing a heat treatment at a temperature higher than the liquid crystal phase, (2) a step of further applying a liquid crystal compound to the cholesteric liquid crystal layer, (3) A step of applying a non-liquid crystal compound to the cholesteric liquid crystal layer can be exemplified. In this step, one type may be used, a repeated operation thereof, or a combination of two or more types of steps may be used. Among these, it is preferable to perform the heat treatment at a temperature equal to or higher than the temperature (1) showing the liquid crystal phase from the viewpoint of simple operation and effects.
As heat treatment conditions, considering productivity as well as the effect of broadening the band, the temperature is usually about 0.001 to 20 minutes at a temperature of 65 to 115 ° C., preferably 0.001 to 10 minutes at a temperature of 65 to 115 ° C. Preferably, it is 0.01 to 5 minutes at a temperature of 65 to 115 ° C. However, since the temperature range in which the liquid crystal phase is expressed varies depending on the type of cholesteric liquid crystal compound that forms the cholesteric liquid crystal layer, the processing temperature and processing time also vary accordingly.

Thus, by changing the pitch of the cholesteric liquid crystal layer, an optical laminate having a broadband circularly polarized light separation function can be obtained.
In the present invention, if necessary, after the step (C), as the step (D), actinic light is irradiated at an irradiation dose of 10 mJ / cm ² or more to photopolymerize a photopolymerizable cholesteric liquid crystal and cure. The process to make can be given. In this case, the dose of active light is preferably 10~1000mJ / cm ^2, more preferably is selected in the range of 50 to 800 mJ / cm ^2.

By further curing in this manner, an optical laminate having excellent mechanical properties can be obtained without significantly degrading the broadband.
The thickness of the cholesteric liquid crystal layer in the optical layered body is usually 1 to 100 μm, preferably 1 to 100 μm, from the viewpoints of preventing disorder of alignment and transmittance reduction, and the wide range of the selective reflection wavelength range (reflection wavelength range). It is 50 micrometers, More preferably, it is 1-20 micrometers. Moreover, the total thickness including the base material is usually 20 to 300 μm, preferably 20 to 200 μm, more preferably 30 to 100 μm.
According to the method of the present invention, an optical laminate having a cholesteric liquid crystal layer having a broadband circularly polarized light separation function can be produced efficiently in a short time with high productivity.

Next, the optical element of the present invention will be described.
The optical element of the present invention is an element obtained by combining the optical laminate obtained by the above-described method of the present invention, a quarter wavelength plate, and preferably a retardation element.
As the ¼ wavelength plate, a broadband ¼ wavelength plate is particularly suitable. 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 has at least one layer (A layer) made of a material having a positive intrinsic birefringence value and at least one layer (B layer) made of a material having a negative intrinsic birefringence value. And the orientation directions of the molecular chains in the A layer and the B layer are the same.
A material having a positive intrinsic birefringence value constituting the A layer (hereinafter sometimes simply referred to as a positive material) exhibits optically positive uniaxiality when molecules are oriented in a uniaxial order. It has a characteristic. Examples of materials having a positive intrinsic birefringence value include rod-shaped liquid crystals, rod-shaped liquid crystal polymers, polymers having an alicyclic structure, chain olefin polymers, polyester polymers, polyarylene sulfide polymers, polyvinyl Alcohol polymer, polycarbonate polymer, polyarylate polymer, cellulose ester polymer, polyethersulfone polymer, polysulfone polymer, polyallylsulfone polymer, polyvinyl chloride polymer, or these Multi-component (binary, ternary, etc.) copolymers. These can be used alone or in combination of two or more.

In the present invention, among these, a polymer having an alicyclic structure or a chain olefin polymer is preferable, and from the viewpoint of light transmittance characteristics, heat resistance, dimensional stability, photoelastic characteristics, and the like, A polymer having a formula structure is more preferred.
About the polymer which has this alicyclic structure, it is as having demonstrated in the base material of the said optical laminated body.
The glass transition temperature Tg _A of the polymer having an alicyclic structure suitably used in the present invention is preferably 80 ° C. or higher, more preferably 100 to 250 ° C., further preferably, from the viewpoint of obtaining excellent optical properties. It is the range of 120-200 degreeC.

On the other hand, materials having a negative intrinsic birefringence value constituting the layer (B) include discotic liquid crystals, discotic liquid crystal polymers, aromatic vinyl polymers, polyacrylonitrile polymers, polymethacrylate polymers, cellulose esters. And a multi-component (binary, ternary, etc.) copolymer thereof. 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. Among these, an aromatic vinyl polymer is more preferable from the viewpoint of high birefringence.

  The aromatic vinyl polymer refers to a polymer of an aromatic vinyl monomer or a copolymer of an aromatic vinyl monomer and a monomer copolymerizable therewith. 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. You may use these individually or in combination of 2 or more types.

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 the aromatic vinyl polymers, a copolymer of styrene and / or a styrene derivative and maleic anhydride is preferable from the viewpoint of high heat resistance.
The glass transition temperature Tg _B of the aromatic vinyl polymer suitably used in the present invention is preferably 110 ° C. or higher, more preferably 120 ° C. or higher, from the viewpoint of obtaining excellent optical properties.
In the quarter wavelength plate used in the present invention, it is preferable that the difference between the glass transition temperature Tg _A of the material constituting the A layer and the glass transition temperature Tg _{B of} the material constituting the B layer is small. Specifically, it is preferably 10 ° C. or lower, more preferably 5 ° C. or lower.

The method for producing a quarter-wave plate used in the present invention is not particularly limited. For example, (a) A layer and B layer are separately formed, and dry lamination is performed through an adhesive layer (C layer). Examples include a method of stacking and obtaining a laminate, and (b) a method of forming a film by coextrusion to obtain a laminate and stretching the laminate. Among these, the film forming method by the co-extrusion method (b) is preferable because a laminate having a high delamination strength can be obtained and the production efficiency is excellent. Specifically, a method for obtaining a laminate by a coextrusion method is to use a plurality of extruders and extrude a material having a positive intrinsic birefringence value and a material having a negative intrinsic birefringence value from a multilayer die. A film is formed.
Thus, the thickness of the laminated body obtained can be suitably determined according to the intended purpose etc. of the laminated body obtained. The thickness of the film is preferably 10 to 300 μm, more preferably 30 to 200 μm, from the viewpoint of obtaining a uniform stretched film by a stable stretching process.

In this case, various additives and other thermoplastic resins and elastomers can be added within a range not impairing the object of the present invention. Examples of various additives include plasticizers and deterioration inhibitors.
The additive amount of these additives is usually 0 to 20% by weight, preferably 0 to 10% by weight, more preferably 0 to 5% by weight with respect to a material having a positive intrinsic birefringence value and / or a negative material. It is.

  In order to laminate a layer made of a material having a positive intrinsic birefringence value (A layer) and a layer made of a material having a negative intrinsic birefringence value (B layer) with their 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, the quarter-wave plate is a laminate of layers (A layer and B layer) made of materials having different intrinsic birefringence values, so that the stretching directions of the A layer and the B layer coincide with each other. The slow axes of the two layers can necessarily be orthogonal.

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.
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 A layer and B layer. The temperature range is from Tg-20) ° C to (Tg + 50) ° C. The draw ratio is usually 1.01 to 30 times, preferably 1.01 to 10 times, and more preferably 1.01 to 5 times. In the case of performing longitudinal uniaxial stretching, the draw ratio is preferably from 1.1 to 3, and more preferably from 1.2 to 2.2.

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 A layer and at least one B layer, and is an optical laminate having the same molecular chain orientation in the A layer and the B layer. However, it is preferable to have a layer configuration of A layer / B layer / A layer or B layer / A layer / B layer. In addition, a C layer (adhesive layer) is further provided between the A layer and the B layer, and a three layer structure of A layer-C layer-B layer, or A layer-C layer-B layer-C layer- A five-layer structure of A layer or B layer-C layer-A layer-C layer-B layer or a five-layer structure of A layer-C layer-B layer-C layer-A layer can be adopted.

The adhesive constituting the C layer preferably has an affinity for both the A layer and the B layer. For example, ethylene- (meth) acrylate copolymer such as ethylene- (meth) acrylate methyl copolymer, ethylene- (meth) ethyl acrylate copolymer; ethylene-vinyl acetate copolymer, ethylene-styrene copolymer An ethylene copolymer such as a polymerization holiday; other olefin copolymers. In addition, modified products obtained by modifying these copolymers by oxidation, saponification, chlorination, chlorosulfonation or the like can also be used.
The thickness of the adhesive layer (C layer) is preferably 1 to 50 μm, more preferably 5 to 30 μm.

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

In the optical element of the present invention, the main refractive indexes _nx , _ny, and _nz (where _nx is the largest refractive index in the in-plane orthogonal axis direction and _ny is in the in-plane orthogonal axis direction). are those inner minimum refractive index, n _z is a refractive index in the thickness direction.) the relationship of _{n z> n x, n z} > n y, a phase difference element is n _x ≒ n _y, further Can be combined. In the case where the retardation element is composed of a plurality of layers, the main refractive index of the average value 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 the n _X ≒ n _y, the refractive index difference is, usually within 0.0002, preferably 0.0001, more preferably within it within 0.00005.
The phase difference element is substantially free of in-plane retardation and Rth = _{[[(n x + n y)} / 2] -n z ] × D (although, D is a thickness of the phase difference element It is preferable that the retardation in the thickness direction defined by (1) is in the range of -20 to -1000 nm. Plane retardation Re is defined by _{Re = (n x -n y)} × D. Having substantially no in-plane retardation means that the Re is usually 20 nm or less, preferably 10 nm or less, more preferably 5 nm or less. Further, the retardation Rth in the thickness direction is appropriately set according to the purpose of use, but is preferably in the range of −20 to −1000 nm, particularly in the range of −50 to −500 nm, in order to fulfill the function as a retardation compensation member. A range is preferred.

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, the material having a negative intrinsic birefringence value is as described in the quarter-wave plate.
As the retardation element used in the present invention, a film or sheet made of the negative material is uniaxially stretched or unbalanced biaxially stretched and orthogonal to the stretching direction (direction in which the refractive index is maximized or minimized). A laminate of two sheets 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. However, in view of mechanical strength, it is preferable to laminate a layer made of a transparent resin material on at least one side of a layer obtained by stretching and orientation of the negative material.

The transparent resin material 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, a polymer having an alicyclic structure, a chain olefin heavy polymer such as polyethylene or polypropylene, and the like. Polymers, polycarbonate polymers, polyester polymers, polysulfone polymers, polyethersulfone polymers, polyvinyl alcohol polymers, cellulose acetate polymers, polyvinyl chloride polymers, polymethacrylate polymers, etc. Can be mentioned. Among these, a polymer having an alicyclic structure or a chain olefin polymer is preferable, and a polymer having an alicyclic structure is particularly preferable from the viewpoint of transparency, low hygroscopicity, dimensional stability, lightness, and the like. preferable.
About the polymer which has the said alicyclic structure, it is as having demonstrated in the base material of the above-mentioned optical laminated body.

In the present invention, the thickness of the layer (E layer) made of the transparent resin material used for the retardation element is not particularly limited, but is usually 15 to 250 μm, preferably 25 to 150 μm.
In the case where the retardation element used in the present invention has a laminated structure of such a layer made of a negative material (D layer) and a layer made of a transparent resin material (E layer), the thickness of the D layer is Although not particularly limited, it is usually 5 to 400 μm, preferably 15 to 250 μm.

Furthermore, when the retardation element used in the present invention includes a laminated structure of such a layer made of a negative material (D layer) and a layer made of a transparent resin material (E layer), the intrinsic birefringence used for the D layer The glass transition temperature Tg _D of the material having a negative value and the glass transition temperature Tg _E of the transparent resin material used for the E layer are preferably Tg _D > Tg _E , and Tg _D −20 ≧ Tg _E Is more preferable. When Tg _E is equal to or greater than Tg _D , particularly when the intrinsic birefringence value of the transparent resin material used for the E layer is positive, the refractive index anisotropy of the E layer developed by stretching is different from that of the D layer. There is a risk that the relationship between the target refractive index in the plane direction and the refractive index in the thickness direction cannot be obtained.

Further, when the retardation element used in the present invention includes a laminated structure of such a layer made of a negative material (D layer) and a layer made of a transparent resin material (E layer), moisture absorption, temperature change, or aging From the viewpoint of preventing warping due to change, it is preferable that a layer (E layer) made of a transparent resin material is laminated on both sides of a layer (D layer) made of a material having a negative intrinsic birefringence value. In this case, the thickness of the two E layers is preferably substantially equal. Moreover, when laminating | stacking E layer only on one side, although the number of the E layer to pile up is not restricted, it is usually 1 layer.
For the material having a negative intrinsic birefringence value and / or transparent resin material used in the present invention, an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, an antistatic agent, and a dispersing agent are optionally added. , Chlorine scavengers, flame retardants, crystallization nucleating agents, antiblocking agents, antifogging agents, mold release agents, pigments, organic or inorganic fillers, neutralizing agents, lubricants, decomposition agents, metal deactivators, contamination Known additive components such as an inhibitor, an antibacterial agent, other resins, and a heat-numerable elastomer 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 (F layer) between a layer (D layer) made of a material having a negative intrinsic birefringence value and a layer (E layer) made of a transparent resin material. It may be provided.
The adhesive layer (F layer) can be formed from a material having an affinity for both the material having a negative intrinsic birefringence value used for the D layer and the transparent resin material used for the E layer. Specifically, the same ones as exemplified as the adhesive in the description of the quarter-wave plate described above can be given. The thickness of this adhesive layer (F layer) is preferably 1 to 50 μm, more preferably 5 to 30 μm.

Further, when the retardation element used in the present invention includes the adhesive layer (F layer), the glass transition temperature or softening point Tg _F of the adhesive used for the F layer is Tg _D > Tg _F. Preferably, Tg _D −20 ≧ Tg _F is more preferable.
A method for producing the retardation element used in the present invention is not particularly limited. However, as a preferred production method, a transparent resin material is used on at least one surface of a layer (D layer) made of a material having a negative intrinsic birefringence value. The layer (E layer) to be obtained is laminated to obtain an unstretched laminate, and this is uniaxially or biaxially stretched.

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 a 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 stretching temperature is not particularly limited, but when the retardation element has the laminated structure, (Tg _D −10) (° C.) to (Tg) with respect to the glass transition temperature Tg _D of the material having a negative intrinsic birefringence. The range of ( _D + 20) (° C.) is preferable, and the range of (Tg _D −5) (° C.) to (Tg _D +15) (° C.) is more preferable. By setting the stretching temperature within the above range, it is possible to make it difficult for the E layer to exhibit refractive index anisotropy 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.
Here, 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.

  As described above, an optical element obtained by combining the optical laminate obtained by the method of the present invention with a quarter wavelength plate and optionally a retardation element is suitable as a luminance improving member, a backlight unit of a liquid crystal display device, and the like. Used in polarized light source devices and the like. A polarized light source device provided with the optical element can provide a liquid crystal display device that has high luminance and is less likely to cause color unevenness with a wide viewing angle.

The present invention also provides a polarized light source device having the above-described optical element of the present invention and a liquid crystal display device having the polarized light source device.
FIG. 1 is a cross-sectional view showing a configuration of an example of a polarized light source device of the present invention. In the polarized light source device 30, the light source 4 is disposed on the incident end surface side of the light guide plate 1 provided with the light reflecting layer 2 a on the back surface side, and the light diffusion sheet 3 a, The optical laminate 5, the retardation element 6, the quarter-wave plate 7, and the polarizing plate 8 are sequentially disposed. Reference numeral 9 denotes a light source holder.

  The light from the light source 4 arranged on the incident end face side of the light guide plate 1 enters the light guide plate 1 and exits to the light diffusion sheet 3a side. The light that has passed through the light diffusion sheet 3 a and entered the optical laminate 5 is transmitted through either the left or right circularly polarized light, and the other circularly polarized light is reflected and reenters the light guide plate 1. The light that reenters the light guide plate 1 is reflected by the light reflecting layer 2 a provided on the back side of the light guide plate 1, enters the optical laminate 5 again, and is separated again into transmitted light and reflected light. By repeating this, the light emitted from the light source 4 is effectively used, and the effect of improving the luminance can be obtained. The circularly polarized light transmitted through the optical laminated body 5 is transmitted through the phase difference element 6, the phase difference is compensated, and further converted into linearly polarized light by the quarter wavelength plate 7 and transmitted through the polarizing plate 8. The light diffusion sheet 3a and the polarizing plate 8 can be omitted. The phase difference element 6 may be disposed on the light transmission side of the quarter wavelength plate. Furthermore, if necessary, a prism sheet can be disposed on the light transmission side of the light diffusion sheet 3a.

The light guide plate 1 preferably has a shape (wedge shape) in which the shape of the side end facing the incident surface is thinner than that of the incident surface. Moreover, the thing of the structure which has fine prism-shaped unevenness | corrugation from the viewpoint of being excellent in the output efficiency from an output surface, being excellent in the perpendicularity with respect to the output surface, and aiming at the effective utilization of an emitted light is preferable. The light guide plate 1 can be formed of a transparent material such as a norbornene polymer, polymethyl methacrylate, polycarbonate, or polystyrene. The light reflecting layer 2a 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. This light reflection layer may be integrated with the surface facing the light exit surface of the light guide plate, or may be formed as a light reflection sheet or the like superimposed on the light guide plate.
The polarized light source device of the present invention has an excellent brightness enhancement effect and is provided with a phase difference element. Therefore, when used as a backlight unit of a liquid crystal display device, color unevenness with wide viewing angles in the front and perspective. It is possible to provide a high-brightness liquid crystal display device that is less likely to cause the phenomenon.

The liquid crystal display device of the present invention has the polarized light source device of the present invention as a backlight unit, and there is no particular limitation on the configuration thereof.
FIG. 2 is a cross-sectional view showing a configuration of an example of the liquid crystal display device of the present invention. In the liquid crystal display device 40, the polarized light source device 30 of the present invention is disposed on the back side of the liquid crystal cell 10 as a backlight unit, and the polarizing plate 11 and the light diffusion sheet 12 are provided on the surface side of the liquid crystal cell 10. Are arranged in order. The light diffusion sheet 12 can be omitted.

The liquid crystal mode used is not particularly limited. As the liquid crystal mode, for example, TN (Twisted nematic) type, STN (Super Twisted Nematic) type, HAN (hybrid aligned nematic) type, VA (Vertical Aligned Bench type, IPS (In Plane Swing C, B) ) Type.
Moreover, it does not restrict | limit especially as a polarizing plate (8, 11), A conventionally well-known thing can be used.
Since the liquid crystal display device of the present invention has the polarized light source device of the present invention as a backlight unit, an excellent luminance improvement effect can be obtained and the luminance improvement effect can be stably exhibited over a long period of time. it can. In addition, the occurrence of color unevenness is suppressed at a wide viewing angle from the front and perspective, and the display quality is excellent.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Reference Example 1 Relationship between Average Molecular Absorption Coefficient of Light Absorbing Agent and Depth of Film and Light Intensity According to Lambert-Beer's law, the average molecular extinction coefficient of light absorbing agent and film depth are expressed by the following equations. And the relationship with the light intensity.
log (I / I ₀ ) = εcd
Where I ₀ : intensity of incident light
I: Intensity of transmitted light
ε: Average molecular extinction coefficient
c: Concentration of light absorber (mol / L)
d: Distance in the depth direction from the light incident side (cm)
The results are shown graphically in FIG.

  From FIG. 3, it can be seen that as the average molecular extinction coefficient of the light absorber increases, the light intensity distribution is generated in the depth direction of the film. This makes it possible to produce cholesteric liquid crystal layers having different degrees of crosslinking in the depth direction of the film. Further, after this operation, the shape of the cholesteric liquid crystal layer is considered to be the same as that before ultraviolet irradiation, and it is expected that selective reflection in a narrow band will be achieved. Therefore, in the present invention, after the ultraviolet irradiation, the band is broadened by preferably performing a heat treatment.

Reference Example 2 Light Transmission Region of Band Pass Filter In the examples and comparative examples shown below, two types of a 313 nm band pass filter and a 365 nm band pass filter were used. FIG. 4 is a graph showing the relationship between the wavelength and transmittance in these bandpass filters. When the light transmission region is defined as a region having a transmittance of 1% or more, the light transmission region in the 313 nm bandpass filter is 299 to 345 nm, the bandwidth is 46 nm, and the light transmission region in the 365 nm bandpass filter is 348 to 403 nm. The bandwidth is 57 nm.
That is, it was confirmed that the two types of band-pass filters used in the examples and comparative examples transmit with a bandwidth of about 50 nm and can be set to different light irradiation regions.

Reference Example 3 Relationship Between Wavelength and Average Molecular Absorption Coefficient in Light Absorber Three kinds of light absorbers “Irgacure 184” used in the following examples and comparative examples [trade name, manufactured by Ciba Specialty Chemicals, 1-hydroxycyclohexyl phenyl ketone], “Irgacure 907” [trade name, manufactured by Ciba Specialty Chemicals, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one] And “Irgacure 1850” [trade name, manufactured by Ciba Specialty Chemicals, weight of bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide and 1-hydroxycyclohexyl phenyl ketone The ratio of the wavelength and the molecular extinction coefficient FIG. 5 is a graph.

From FIG. 5, the average molecular extinction coefficient (mol ⁻¹ · L · cm ⁻¹ ) in the wavelength range of 299 to 345 nm (313 nm bandpass filter) is 1.04 × 10 ^{2 for} Irgacure 184, and 1.0 for Irgacure 1850. It was 36 × 10 ³ and Irgacure 907 was 9.37 × 10 ³ . The average molecular extinction coefficient (mol ⁻¹ · L · cm ⁻¹ ) in the wavelength region of 346 to 403 nm (365 nm bandpass filter) was 2.14 × 10 ² for Irgacure 907. The results are shown in Table 1.
The average molecular extinction coefficient was determined using an ultraviolet-visible spectrophotometer [manufactured by JASCO Corporation, apparatus name “JASCO V-550”].

Example 1
95.63 parts by weight of a nematic liquid crystal compound represented by the following formula [3], 4.37 parts by weight of a chiral agent represented by the following formula [4], 3.10 weights of a light absorber “Irgacure 907” (supra). And 0.1 part by weight of a surfactant [trade name “KH-40” manufactured by Seimi Chemical Co., Ltd.] in 155 parts by weight of methyl ethyl ketone, and then this is a CD / X syringe made of polytetrafluoroethylene having a pore diameter of 2 μm. A liquid crystal coating solution was prepared by filtering with a filter.

Next, using a norbornene polymer film [manufactured by Nippon Zeon Co., Ltd., trade name “Zeonor film ZF14-100”] having a thickness of 100 μm as a substrate, plasma treatment was performed on both surfaces of the substrate. Then, an alignment film coating solution consisting of 10 parts by weight of polyvinyl alcohol and 371 parts by weight of water was applied to one side of the substrate and dried to form an alignment film having a thickness of 1 μm. Thereafter, a rubbing treatment was performed on the alignment film. Next, the liquid crystal coating liquid is applied on the alignment film subjected to the alignment treatment so that the dry thickness is 4 μm, and then dried by heating at 100 ° C. for 2 minutes in an oven. A layer was provided.
Next, the liquid crystal coating layer was irradiated with ultraviolet rays at 0.2 mW / cm ² for 1 second using an ultraviolet (UV) irradiation device [manufactured by HOYA SHOT, device name “EXECURE 3000”]. At that time, a 313 nm band pass filter was used.

About the optical layered body thus obtained, the reflection band is measured.
Measuring instrument: Otsuka Electronics Co., Ltd., apparatus name “MCPD-3000”
Microscope used: Nikon Corporation, apparatus name "Eclipse E-600POL"
Made using. As a result, the selective reflection band was 130 nm.
Note that the selective reflection band is a band of 400 to 750 nm, in which “maximum transmittance−minimum transmittance” is calculated as the reflectance, and the width of the band is ½ or more of the reflectance. The same applies hereinafter.

Comparative Examples 1 and 2
In the same manner as in Example 1, a liquid crystal coating layer was provided on the substrate, and then left untreated (Comparative Example 1) and irradiated with ultraviolet light through a 365 nm bandpass filter at 0.2 mW / cm ² for 1 second. After irradiation, heat treatment was performed at 100 ° C. for 1 minute in an oven (Comparative Example 2), an optical laminate was produced, and the reflection band was measured.

The ultraviolet irradiation, heat treatment conditions and results are shown in Table 1 together with Example 1.
Moreover, in FIG. 6, the relationship between the wavelength and the transmittance | permeability in the optical laminated body obtained in Example 1 and Comparative Example 1 is shown with a graph.

Examples 2 to 5 and Comparative Examples 3 to 11
An optical laminate was produced in the same manner as in Example 1 except that the conditions shown in Table 2 (light absorber, bandpass filter, irradiation condition, heating condition) were used, and the selective reflection band was measured. The results are shown in Table 2.
In addition, the polymerization rate after ultraviolet irradiation in Comparative Example 9 was 81.5%, and the polymerization rate after ultraviolet irradiation in Comparative Examples 10 and 11 was 95.3%.

From the results of Table 2, according to Example 1, the ultraviolet light in the wavelength region where the average molecular extinction coefficient of the light absorber is 9000 (mol ⁻¹ · L · cm ⁻¹ ) or more exceeds 0 and is 10 mJ / cm ^2. By irradiating with an irradiation dose of less than, and then performing a heat treatment, the selective reflection band is more than doubled compared to those not performing ultraviolet irradiation (B process) and heat treatment (C process) (Comparative Example 1). ing. Further, it can be seen from FIG. 6 that although the selective reflection band is slightly shifted to the longer wavelength side as compared with Comparative Example 1, the center wavelength of the selective reflection band is almost widened without moving.
In addition, it can be seen that the selective reflection bands are also increased in other Examples 2 to 5.
On the other hand, those irradiated with ultraviolet rays in a wavelength range where the average molecular extinction coefficient of the light absorber is less than 9000 (mol ⁻¹ · L · cm ⁻¹ ) (Comparative Examples 2, 4 to 7), The ultraviolet rays in the wavelength region where the average molecular extinction coefficient is 9000 (mol ⁻¹ · L · cm ⁻¹ ) or more are irradiated at an irradiation dose exceeding 0 and less than 10 mJ / cm ^2, but the heat treatment (Step C) is performed. What is not performed (Comparative Examples 3 and 9), what is subjected to heat treatment (Step C) but not subjected to ultraviolet irradiation (Step B) (Comparative Example 8), and the average molecular extinction coefficient of the light absorber is The ultraviolet rays in the wavelength range of 9000 (mol ⁻¹ · L · cm ⁻¹ ) or more are irradiated, but those with an irradiation amount exceeding 10 mJ / cm ² (Comparative Examples 10 and 11) have a selective reflection band. It has not changed.

Examples 6 and 7 and Comparative Examples 12 and 13
In the same manner as in Example 1, after providing a liquid crystal coating layer on the substrate, ultraviolet irradiation was performed under the conditions shown in Table 3, followed by heat treatment at 100 ° C. for 1 minute in an oven. Then, the nematic liquid crystal compound (supra) powder is added to the liquid crystal layer, and further, the liquid crystal layer is heated at 100 ° C. until the liquid crystal is sufficiently melted. Bandwidth measurement was performed. The results are shown in Table 3.

  From the results in Table 3, it was confirmed that the broadening of the liquid crystal also occurred in the swelling of the liquid crystal.

Examples 8 and 9 and Comparative Examples 14 and 15
In the same manner as in Example 1, after providing a liquid crystal coating layer on the substrate, ultraviolet irradiation was performed under the conditions shown in Table 4. Next, a bisphenol type epoxy acrylate represented by the following formula [5] [manufactured by Shin-Nakamura Chemical Co., Ltd., trade name “EA1020”] is added to the liquid crystal layer, and heat treatment is performed at 100 ° C. for 1 minute in an oven. Thus, an optical laminated body was produced, and the selective reflection band was measured. The results are shown in Table 4.

  From the results in Table 4, it was confirmed that a broad band occurs even when treatment is performed using a non-liquid crystal compound.

Example 10 and Comparative Examples 16 and 17
In the same manner as in Example 1, after providing a liquid crystal coating layer on the substrate, after performing ultraviolet irradiation and heat treatment under the conditions shown in Table 5, the ultraviolet light was irradiated at a dose of 150 mJ / cm ² . An optical laminate was produced by post-irradiation, and the selective reflection band was measured. The results are shown in Table 5.

From Table 5, it can be seen that when the irradiation amount of ultraviolet rays in the semi-curing process is 0.2 mJ / cm ² , the effect of broadening the bandwidth is maintained even after the curing process.

Production Example 1 Production of Retardation Element (Positive Letterer) As a material having a negative intrinsic birefringence value, a styrene-maleic anhydride copolymer [“Dilark D332”, manufactured by Nova Chemical Co., Tg = 131 ° C.], transparent resin material And a norbornene resin layer (thickness 50 μm) / styrene-maleic anhydride copolymer layer (thickness 200 μm) by a coextrusion method using a norbornene resin [“ZEONOR 1020”, manufactured by Nippon Zeon Co., Ltd., Tg = 105 ° C.]. / The laminated body which has a three-layer structure of a norbornene-type resin layer (thickness 50 micrometers) was obtained.
Next, the mixture was sequentially fed into a zone-heated longitudinal uniaxial stretching apparatus and a tenter stretching (transverse 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 laminated body (retardation element) after stretching was 120 μm, the refractive index in the plane direction was n _x = 1.5732, n _y = 1.5731, and the refractive index in the thickness direction was n _z = 1.5757. It was. The in-plane Re = 10 nm and the thickness direction Rth = −300 nm.

Production Example 2 Production of Broadband 1/4 Wave Plate As a material having a positive intrinsic birefringence value, a norbornene resin [“Zeonor 1420”, manufactured by Nippon Zeon Co., Ltd., Tg = 136 ° C.] and a material having a negative intrinsic birefringence value , A styrene-maleic anhydride copolymer [“DAILARK D332”, manufactured by Nova Chemical Co., 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 storing 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-layer 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 longitudinally uniaxially stretched at 125 ° C. for 70%, 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 is obtained.

Production Example 3 Production of Optical Laminate Using a norbornene polymer base material [manufactured by Nippon Zeon Co., Ltd., “ZEONOR FILM ZF14-100”] having a thickness of 100 μm, a width of 680 mm, and a length of 500 m, on both sides of this base material Plasma treatment was performed. Thereafter, an alignment film coating solution comprising 10 parts by weight of polyvinyl alcohol and 371 parts by weight of water was continuously applied to both surfaces of the substrate and dried to form alignment films each having a thickness of 1 μm. Thereafter, rubbing treatment was performed on both alignment films.
96.08 parts by weight of a nematic liquid crystal compound represented by the formula [3], 3.92 parts by weight of a chiral agent represented by the formula [4], a light absorber (photopolymerization initiator) “Irgacure 907” (supra) 3. Prepared by filtering a coating solution consisting of 1 part by weight and a surfactant (trade name “KH-40” manufactured by Seimi Chemical Co., Ltd.) and 0.1 part by weight of methyl ethyl ketone with a filter of 0.5 μm. did. Then, the liquid crystal coating layer was formed by coating so that the dry thickness might be set to 4 micrometers on alignment film. Next, using an ultraviolet (UV) irradiation device, the liquid crystal coating layer was irradiated with ultraviolet rays at 0.2 mW / cm ² for 1 second. At that time, a 313 nm band pass filter was used. Then, it heated at 100 degreeC for 1 minute. Then, ultraviolet irradiation and heating were performed again under the same conditions, and after irradiation at 150 mW / cm ² for 2 seconds, a cholesteric liquid crystal layer 1 was obtained. The obtained cholesteric liquid crystal layer 1 had a selective reflection center near 625 nm and a selective reflection band of about 190 nm.
Thereafter, 94.89 parts by weight of a nematic liquid crystal compound represented by the formula [3], 5.11 parts by weight of a chiral agent represented by the following formula [4], a light absorber (photopolymerization initiator) “Irgacure 907” (previous Out) 3.1 parts by weight and a surfactant (trade name “KH-40”, manufactured by Seimi Chemical Co., Ltd.) 0.1 parts by weight and methyl ethyl ketone 155 parts by weight were filtered in the same manner. A cholesteric liquid crystal layer 2 was obtained by applying, broadening and curing the other surface in the same manner. The obtained cholesteric liquid crystal layer 2 had a selective reflection center in the vicinity of 560 nm, and the selective reflection band was about 300 nm or more.

Example 11
A light diffusing sheet, an optical laminate obtained in Production Example 3, and a commercially available light emitting sheet are sequentially disposed on a light-emitting surface side of a general-purpose light guide plate in which a cold cathode tube is disposed on the incident end surface side and a light reflecting sheet is provided on the back surface side. A polarized light source device was manufactured by arranging a quarter-wave plate. Further, a polarizing plate, a viewing angle widening film [manufactured by Fuji Photo Film Co., Ltd., “WV film”], a transmissive TN liquid crystal display element, and a polarizing plate are sequentially arranged on the ¼ wavelength plate side to produce a liquid crystal display device. did.
When the liquid crystal display device was observed in the white display mode from the light exit surface side, the brightness was 3, and the color viewing angle was slightly colored.
In the evaluation of the characteristics of the liquid crystal display device, the brightness is evaluated in five stages of 1, 2, 3, 4, and 5, with 5 being the brightest and 1 being the darkest.

Example 12
In Example 11, a liquid crystal display device was produced in the same manner as in Example 11 except that the broadband quarter wavelength plate obtained in Production Example 2 was used instead of the commercially available quarter wavelength plate.
When the liquid crystal display device was observed in the white display mode from the light exit surface side, the brightness was 4 and the color viewing angle was good.

Example 13
In Example 11, a liquid crystal display device was produced in the same manner as in Example 11 except that the retardation element obtained in Production Example 1 was disposed between the optical laminate and a commercially available quarter-wave plate. did.
When this liquid crystal display device was observed in the white display mode from the light exit surface side, the brightness was 4 and the color viewing angle was good.

Example 14
In Example 13, a liquid crystal display device was produced in the same manner as in Example 13 except that the broadband quarter wave plate obtained in Production Example 2 was used instead of the commercially available quarter wave plate.
When this liquid crystal display device was observed in the white display mode from the light exit surface side, the brightness was 5, the color viewing angle was very good, and there was no coloration over the entire display surface.

  According to the method of the present invention, an optical laminate having a cholesteric liquid crystal layer having a broadband circularly polarized light separation function suitable as a member for a brightness enhancement film can be efficiently produced in a short time with high productivity. In addition, an optical element obtained by combining the optical laminate, the quarter-wave plate, and the retardation element obtained by this method is a polarized light source device used as a brightness improving member, a backlight unit such as a liquid crystal display device, etc. Is preferably used.

It is sectional drawing which shows the structure of one example of the polarized light source device of this invention. It is sectional drawing which shows the structure of one example of the liquid crystal display device of this invention. It is a graph which shows an example of the relationship between the average molecular extinction coefficient of a light absorber, the depth of a film | membrane, and the intensity | strength of light. It is a graph which shows an example of the relationship between the wavelength and the transmittance | permeability in a band pass filter. It is a graph which shows the relationship between the wavelength in each light absorber, and a molecular extinction coefficient. It is a graph which shows the relationship between the wavelength in the optical laminated body obtained by Example 1 and Comparative Example 1, and the transmittance | permeability.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light guide plate 2a Light reflection layer 3a Light diffusion sheet 4 Light source 5 Optical laminated body 6 Phase difference element 7 1/4 wavelength plate 8 Polarizing plate 9 Light source holder 10 Liquid crystal cell 11 Polarizing plate 12 Light diffusion sheet 30 Polarized light source device 40 Liquid crystal display apparatus

Claims (10)

(A) A step of forming a coating layer on a base material using a coating liquid containing at least a light absorber and a photopolymerizable cholesteric liquid crystal compound, (B) a light contained in the coating layer. Photopolymerization is possible by irradiating active light in a wavelength range where the average molecular extinction coefficient of the absorbent is 9000 (mol ⁻¹ · L · cm ⁻¹ ) or more with an irradiation dose of more than 0 and less than 10 mJ / cm ^2. A method for producing an optical laminate comprising the steps of: photopolymerizing a cholesteric liquid crystal compound, and (C) changing the pitch of the photopolymerized cholesteric liquid crystal layer. (B) The manufacturing method of the optical laminated body of Claim 1 whose irradiation amount in a process exceeds 0 and is 1 mJ / cm < ² > or less.   The method for producing an optical laminate according to claim 1 or 2, wherein in the step (B), the polymerization rate after irradiation with active light is more than 0% and less than 85%. 4. The method according to claim 1, comprising a step of (C) photopolymerizing a photopolymerizable cholesteric liquid crystal compound by irradiating active light with an irradiation dose of 10 mJ / cm ² or more after the step (C). Manufacturing method of optical laminated body.   An optical element comprising the optical laminate according to claim 1 and a quarter-wave plate.   The optical element according to claim 5, wherein the quarter-wave plate is a broadband quarter-wave plate. Further, the main refractive indexes _nx , _ny and _nz (where _nx is the highest refractive index in the orthogonal axis direction in the plane, _ny is the lowest refractive index in the orthogonal axis direction in the plane) in and, n _z is a refractive index in the thickness direction.) the relationship of _{n z> n x, n z} > n y, according to claim 5 or 6 having a phase difference element is n _x ≒ n _y Optical element. Retardation element is essentially no in-plane retardation and Rth = _{[[(n x + n y)} / 2] -n z ] × D
(However, D is the thickness of the retardation element.)
The optical element according to claim 7, wherein the retardation in the thickness direction defined by is in the range of −20 to −1000 nm.   A polarized light source device comprising the optical element according to claim 5.   A liquid crystal display device comprising the polarized light source device according to claim 9.

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