JPH10197722A - Polarized light reflecting element, elliptic polarizing element, and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the optical element for both reflection and transmission which has a reflection factor equal to that of a mirror surface, etc., and superior light transmissivity. SOLUTION: These are a polarized light reflecting element which is constituted by arranging a polarized light separating film 1 formed of a cholesteric liquid crystal layer and a polarizing film 3 across a 1/4-wavelength plate 2 so that the polarizing film 3 is arranged in orthogonal Nicol relation with polarized light passed through the polarized light separating film 1 and 1/4-wavelength plate 2, and an elliptic polarizing element which has a phase difference film on the side of the polarizing film of the polarized light reflecting element. Consequently, the sunshine, etc., transmitted through the polarizing film 3 is converted through the 1/4-wavelength plate 2 into one of right and left circular polarized lights, and the circular polarized light is reflected specularly by the polarized light separating film 1 to obtain a reflected light in a linear polarized state for the reflection mode of a liquid crystal display device, etc. Then lights other than a vertical light among lights such as a back light made incident on the polarized light separating film 1 are transmitted as elliptic polarized lights to obtain a transmitted light in a linear polarized state for the transmission mode of the liquid crystal display device, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing reflection element and an elliptically polarizing element suitable for a liquid crystal display device for both reflection and transmission.

[0002]

BACKGROUND OF THE INVENTION In a portable liquid crystal display device such as a mobile phone using a storage battery, a transmissive liquid crystal display device in which a backlight is lit and visually recognized consumes a large amount of power, frequently replaces a battery, and disconnects a call on a mobile phone. Since a serious problem such as the occurrence of such a problem may occur, a backlight is provided according to a reflective liquid crystal display device that is visually recognized using external light, but a transflective reflector is provided on the light side via a polarizing plate. A reflective / transmissive liquid crystal display device has been proposed in which a backlight is turned off under sunlight or the like, and the backlight is turned on in a transmission mode at night or in a dark room. .

Heretofore, as the above-mentioned semi-transmissive reflection plate, those provided with a metal vapor-deposited film or a resin layer containing a pearl pigment have been known. However, in any case, there is a trade-off between reflection and transmission, and it is necessary to balance the reflectance and the transmittance while balancing the visibility between the reflection / transmission modes. There was a problem that visibility in the reflection mode was poor.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to develop a reflection / transmission optical element which exhibits a reflectance comparable to a mirror surface or the like and is excellent in light transmittance.

[0005]

[MEANS FOR SOLVING PROBLEMS] The present invention provides a method using a 1/4 wavelength plate,
A polarization separation film composed of a cholesteric liquid crystal layer and a polarization film are arranged, and the polarization film is arranged in a perpendicular Nicols relationship with the polarization separation film and polarized light through a quarter-wave plate. And an elliptically polarizing element having a retardation film on the polarizing film side of the polarizing reflecting element.

[0006]

According to the present invention, as shown by an arrow A in FIGS. 1 and 5, when external light such as sunlight enters a polarizing film, a part of the light is transmitted as linearly polarized light, and the transmitted light is reduced by 1 /. The light is converted into one of left and right circularly polarized light via a four-wavelength plate. When the circularly polarized light is one of the left and right circularly polarized lights that satisfies the reflection condition of the polarized light separating film, the light is specularly reflected by the polarized light separating film, and the reflected light is linearly polarized through a quarter-wave plate and polarized. Transmitted light in a linearly polarized state, which reenters the film and can be used for visual recognition in a reflection mode of a liquid crystal display device or the like, is obtained.

On the other hand, as shown by an arrow B in FIGS. 1 and 5, of the light incident on the polarization splitting film via a backlight or the like, light other than the vertical direction is transmitted as elliptically polarized light, and the transmitted light is reduced to 1/4. The light is converted into linearly polarized light via the wavelength plate and is incident on the polarizing film, so that transmitted light in a linearly polarized state that can be used for viewing in a transmission mode of a liquid crystal display device or the like is obtained. The light vertically incident on the polarization splitting film is separated into left and right circularly polarized lights and one of them is transmitted. When the transmitted light is linearly polarized through a quarter-wave plate, the polarizing films are arranged in orthogonal Nicols. And cannot be transmitted.

As a result, it is possible to obtain reflected light having excellent reflection characteristics and excellent brightness which enables visual recognition in the reflection mode by using external light having a brightness such as indoor lighting, and a required ratio of visual recognition in the transmission mode. Thus, a liquid crystal display device which is low in power consumption, can reduce power consumption, and is excellent in practical use for both reflection and transmission, which can extend the life of a storage battery, can be formed.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polarizing reflection element of the present invention comprises a polarizing film composed of a cholesteric liquid crystal layer and a polarizing film arranged via a quarter-wave plate. It is composed of those arranged in a crossed Nicols relationship with the polarized light passing through the wavelength plate.
Examples thereof are shown in FIGS. 1, 2 and 3. 1 is a polarization separation film, 2 is a 1/4 wavelength plate, and 3 is a polarization film. 4, 41 to 44 are adhesive layers, and 5 is a separator.

As the polarized light separating film, a film composed of a cholesteric liquid crystal layer is used. According to the cholesteric liquid crystal layer, the left and right circularly polarized lights can be selectively separated into one of the two through transmission and reflection. As the cholesteric liquid crystal, an appropriate one can be used, and there is no particular limitation. The use of a liquid crystal polymer is advantageous from the viewpoint of the superposition efficiency of the liquid crystal layer and the thinning of the liquid crystal layer. Cholesteric liquid crystal molecules having a large birefringence are preferable because the wavelength range of the selective reflection is widened. Examples of the polarization separation film that can be preferably used include a film made of a liquid crystal polymer exhibiting a cholesteric phase, and a film provided with a layer made of a cholesteric liquid crystal polymer on a transparent substrate such as a film.

As the liquid crystal polymer, for example, a main chain type liquid crystal polymer such as polyester, a side chain type liquid crystal polymer having an acrylic main chain, a methacryl main chain, a siloxane main chain, etc., a nematic liquid crystal polymer containing a low molecular weight chiral agent, Examples of the liquid crystal polymer include a chiral component-introduced liquid crystal and a mixed liquid crystal polymer of a nematic type and a cholesteric type. From the viewpoint of handleability, the glass transition temperature is 30 to 150.
The liquid crystal polymer of ° C. can be preferably used.

The cholesteric liquid crystal layer can be formed by a method according to a conventional alignment treatment. Incidentally, examples thereof include a film formed by forming a film of polyimide or polyvinyl alcohol on a substrate and rubbing with a rayon cloth or the like,
A liquid crystal polymer is spread on an appropriate alignment film composed of an obliquely deposited layer of iO and heated to a temperature equal to or higher than the glass transition temperature and lower than the isotropic phase transition temperature. Cooling to a glass state to form a solidified layer in which the orientation is fixed.

As the substrate, for example, a film made of a plastic such as triacetyl cellulose, polyvinyl alcohol, polyimide, polyarylate, polyester, polycarbonate, polysulfone, polyethersulfone, or epoxy resin, or a suitable substrate such as a glass plate Can be used. When the substrate is formed of a film, the solidified layer of the liquid crystal polymer formed on the substrate can be used as a polarization separation film as it is, or can be peeled off from the substrate and used as a polarization separation film formed of a film or the like. . When it is formed as an integral body with a film substrate, it is preferable to use a film having a phase difference as small as possible from the viewpoint of prevention of a change in the state of polarization.

The liquid crystal polymer may be developed by a heating and melting method or may be developed as a solution using a solvent. As the solvent, for example, an appropriate solvent such as methylene chloride, cyclohexanone, trichloroethylene, tetrachloroethane, N-methylpyrrolidone, tetrahydrofuran, or the like can be used. The development can be performed by a suitable coating machine such as a bar coater, a spinner, a roll coater, and a gravure printing method. Upon development, a cholesteric liquid crystal layer superimposing method via an alignment film may be used as necessary.

The thickness of the cholesteric liquid crystal layer is from 0.5 to 100 μm, preferably from 1 to 100 μm, in view of prevention of disorder of alignment and decrease in transmittance, and selective reflection (wavelength range showing circular dichroism). 70 μm, particularly preferably 1 to 50 μm. In forming the cholesteric liquid crystal layer or the polarized light separating film, various additives including a stabilizer, a plasticizer, and metals can be blended as necessary.

As shown in FIG.
It can also be formed as a layer or a superposition of three or more cholesteric liquid crystal layers 11, 12. The superimposition is advantageous from the viewpoint of broadening the reflection wavelength, and in that case, it is preferable to superimpose in a combination in which the center wavelengths of light reflected as non-predetermined circularly polarized light are different. That is, in a single cholesteric liquid crystal layer, there is usually a limit to a wavelength region showing selective reflection (circular dichroism), and the limit may be a wide range up to a wavelength region of about 100 nm. However, since it does not cover the entire range of visible light desired when applied to liquid crystal display devices, etc., in such a case, a cholesteric liquid crystal layer with different selective reflection is superimposed to expand the wavelength range showing circular dichroism. Can be done.

In the case of a cholesteric liquid crystal layer, the central wavelength of selective reflection based on the liquid crystal layer is 300 to 900.
nm is a combination that reflects circularly polarized light in the same polarization direction,
And the central wavelength of selective reflection is different, especially 50nm each
By using different combinations as described above and superimposing two to six kinds thereof, it is possible to efficiently form a polarization separation film that can cover a wide wavelength range. For the superposition of the cholesteric liquid crystal layer, the use of a liquid crystal polymer is particularly advantageous from the viewpoints of production efficiency and thinning.

Therefore, as the polarized light separating film, a film in which the wavelength range of light which can be reflected as circularly polarized light outside the predetermined range matches as much as possible the wavelength range of light used for visual recognition or the like can be preferably used. In the above description, it has been pointed out that when the polarization separation film is formed as a superposition layer of the cholesteric liquid crystal layer, a combination of those that reflect circularly polarized light having the same polarization direction is used. This aims at aligning the phase state of the circularly polarized light reflected by each layer to prevent different polarization states in each wavelength region, and to increase the amount of polarized light that can be used.

The polarized light separating film used in the present invention may be, for example, a cell in which a cholesteric liquid crystal layer composed of a low molecular weight substance is sandwiched between transparent substrates such as a film, a form in which a cholesteric liquid crystal layer composed of a liquid crystal polymer is supported by a transparent substrate, The cholesteric liquid crystal layer may be formed in an appropriate form such as a form formed of a liquid crystal polymer film, or a form in which these forms are overlapped in an appropriate combination.

In the above case, the cholesteric liquid crystal layer can be held by one or more supports depending on the strength and operability. When a support having two or more layers is used, the retardation is as small as possible, for example, a non-oriented film or a triacetate film having a small birefringence even when oriented, in order to prevent a change in the state of polarization. Those can be preferably used.

A quarter arranged on one side of the polarized light separating film
The wave plate makes the light incident from the polarizing film circularly polarized as described above to enable reflection by the polarization separating film (reflection mode), and changes the phase of the elliptically polarized light incident from the polarization separating film to change the linearly polarized light component. The purpose is to convert to a large number of states, whereby light or the like that easily passes through the polarizing film can be obtained.

The quarter-wave plate can be formed of an appropriate material.
Those which are transparent and give a uniform phase difference are preferred. The phase difference of the 波長 wavelength plate can be appropriately determined according to the wavelength range of light to be used. Incidentally, in the visible light region, a quarter-wave plate for light having a wavelength of 550 nm is preferable.

The retardation layer may be colored depending on the viewing angle. To prevent the coloring, the formula: N _z =
_{(N x -n z) / (} n x -n y) N z defined by the -2
A quarter-wave plate satisfying <N _z <5 can be preferably used. Note in the above formulas, n _x is the maximum refractive index in the plane of the retardation layer, n _y is a refractive index in a direction perpendicular to n _x direction, n _z denotes a refractive index in the thickness direction.

The quarter-wave plate has a single-layer retardation layer or, as shown in FIG. 2, has a different phase difference for the purpose of expanding the wavelength range that can function as a quarter-wave plate. It can be obtained as a laminate of two or more retardation layers 21 and 22 or the like. By the way, 1 /
As a superimposition type quarter-wave plate that can function as a four-wavelength plate, for example, a phase difference layer that gives a half-wave phase difference to light having a wavelength of 550 nm and a phase difference layer that gives a quarter-wave phase difference are provided. In combination with the retardation layer, a plurality of retardation layers are superimposed with their optical axes crossing each other.

In the above, from the viewpoint of obtaining a superimposition type quarter-wave plate in which coloring due to a viewing angle is prevented, the relation of −2 <N _{z is} satisfied.
One or two of a retardation layer providing a quarter-wave retardation satisfying <5 and a retardation layer providing a half-wave retardation
It is preferable to form a superposed product using at least two layers.

As described above, the quarter-wave plate can be obtained as a single layer or a superposed layer of a retardation layer. For example, a retardation film or the like is used for forming the retardation layer. The retardation film can be obtained as a film obtained by appropriately stretching a polymer film uniaxially or biaxially, or a liquid crystal polymer film. Appropriate materials can be used as the polymer film or the liquid crystal polymer film.

Incidentally, specific examples of the above-mentioned polymer film include polycarbonate polymers, polyester polymers, polysulfone polymers and polyethersulfone polymers, polyvinyl alcohol polymers and polystyrene polymers, polymethyl methacrylate polymers and polyolefins. And a film made of an appropriate transparent plastic such as a cellulose-based polymer, a cellulose acetate-based polymer, a polyvinyl chloride-based polymer, a polyarylate-based polymer, or a polyamide-based polymer.

As the polarizing film disposed on the quarter-wave plate side, an appropriate film such as an absorption polarizing film containing a dichroic substance, a polyene oriented film, or a film provided with a transparent protective layer on the film is used. sell. Incidentally, examples of the absorption type polarizing film include a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, an ethylene-vinyl acetate copolymer-based partially saponified film, iodine and a dichroic dye, etc. And a film stretched by adsorbing the dichroic substance. Examples of the oriented polyene film include dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride.

A material having a high degree of polarization, such as a polarizing film containing a dichroic substance, is preferably used in view of the achievement of bright reflected light and transmitted light by the polarizing reflection element.
In particular, the light transmittance is 40% or more, the degree of polarization is 90% or more,
Among them, a polarizing film of 95% or more, particularly 99% or more is preferably used. The degree of polarization (P) is calculated by the equation: P =
Defined by _{SQR [(T p -T c)} / (T p + T c)]. Wherein, T _p, the light transmittance in the case of arranging the same polarizing film parallel Nicols, the T _c is the light transmittance when placed crossed Nicols. The thickness of the polarizing film is usually 5
８０80 μm, but is not limited to this.

The above-mentioned transparent protective layer is provided for the purpose of protection especially when the water resistance is poor such as a polarizing film containing a dichroic substance. It may be formed in any suitable manner. When it is formed of a separated material such as a film, it is preferable to laminate and integrate with an adhesive layer from the viewpoint of preventing reflection loss and the like. The thickness of the transparent protective layer may be determined as appropriate, and is generally 1 mm or less, particularly 500 μm or less, particularly 1 to 300 μm.

The transparent resin layer can also be formed in the form of a fine surface unevenness by a method containing fine particles. The fine particles have, for example, an average particle size of 0.5 to 5 μm.
In a transparent resin layer such as inorganic fine particles that may be conductive such as silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, and antimony oxide, and organic fine particles such as a crosslinked or uncrosslinked polymer. What shows transparency is used. The content of the fine particles is 2 to 25.
% By weight, especially 5 to 20% by weight.

In order to obtain reflected light which allows visual recognition in the reflection mode, the polarizing film is used in combination with the polarized light separating film.
It is arranged in a crossed Nicols relationship with respect to polarized light via a four-wavelength plate. That is, when the circularly polarized light transmitted through the polarized light separating film is transmitted through the quarter-wave plate and becomes linearly polarized light, the polarizing film is arranged so as not to transmit the linearly polarized light.

As described above, when the light incident from the polarizing film side passes through the quarter-wave plate and becomes circularly polarized light, it becomes circularly polarized light reflected by the polarization separation film and serves as return light via the reflection. The reflected light is obtained. The above arrangement of the orthogonal Nicols relationship can be achieved by making the transmission axis of the polarizing film orthogonal to the linearly polarized light transmitted through the 偏光 wavelength plate. In forming the orthogonal state, an angle deviation based on a variation in an optical axis of a polarizing film, a quarter-wave plate, or the like, an operation error, and the like is allowed.

As shown in FIG. 3, the polarizing reflection element has one or more layers for diffusing light to an appropriate position on the surface or between layers for the purpose of homogenizing luminance and expanding the direction of light emission. Of light diffusion layers 6 can be arranged. The light diffusing layer is also effective for, for example, reducing the viewing angle characteristics due to the incident angle dependence of the polarization separation film. As the light diffusing layer, an additional layer having an appropriate diffusing structure such as a fine concavo-convex structure or a diffraction grating-shaped one exemplified in the transparent protective layer of the polarizing film described above, an internal diffusion type or a pearl pigment-containing type, An appropriate material such as a diffusion plate can be used, and any known light diffusion layer can be used.

In the present invention, an elliptically polarizing element in which a retardation film 7 is provided on the polarizing film 3 side of the polarizing reflection element as illustrated in FIG. Such a retardation film converts linearly polarized light transmitted through the polarizing film into elliptically polarized light, adjusts the plane of polarization of light incident on the liquid crystal cell, and compensates for optical characteristics due to birefringence of the liquid crystal cell. Thus, they are arranged for the purpose of improving light use efficiency and visibility. As the retardation film, those exemplified above as the quarter-wave plate can be appropriately used according to the wavelength range or the like. The retardation film may be formed as one layer or two or more layers. In addition, 45 in the figure is an adhesive layer.

In the present invention, components such as a polarizing beam splitter, a quarter-wave plate, a polarizing film, a light diffusing layer, a retardation film, and an adhesive layer, which will be described later, for forming a polarizing reflecting element or an elliptically polarizing element include: For example, it may have ultraviolet absorbing ability by a method of treating with an ultraviolet absorbent such as a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, a nickel complex compound, or the like.

Each component such as a polarization separating film, a quarter-wave plate, a polarizing film and a retardation film in a polarizing reflection element or an elliptically polarizing element can be laminated and integrated via an adhesive layer or the like as necessary. . The lamination and integration are more preferable in preventing deviation of the optical axis during use. As illustrated in FIG. 2, an adhesive layer 44 for bonding to another component may be provided on one or both of the front and back sides of the polarizing reflection element and the elliptically polarizing element which are laminated and integrated. In this case, it is preferable to temporarily attach the separator 5 or the like to protect the surface.

For the lamination and integration, an appropriate adhesive or the like may be used, but it is excellent in stress relaxation from the viewpoint of preventing photoelastic deformation due to relaxation of internal stress generated inside the laminate by heat. Adhesive layer, especially, relaxation elastic modulus 2 × 10 ⁵ -1
× 10 ⁷ dyne / cm ² , especially 2 × 10 ⁶ to 8 × 10 ⁶ dyne / cm
It is preferable to form a laminate bonded through the ^second adhesive layer. Such an adhesive layer can be usually formed of an adhesive having a glass transition temperature of 0 ° C. or less.

The above-mentioned lamination and integration via the adhesive layer having excellent stress relaxation properties is performed by heat from a light source or the like.
Stress generated in a / 4 wavelength plate, a polarizing film, etc. can be suppressed,
In addition to preventing changes in the refractive index caused by photoelastic deformation, it is also effective in preventing reflection loss at each interface, preventing foreign matter from entering the interface, and preventing deterioration in display quality of liquid crystal display devices and the like. is there. Furthermore, the lamination and integration method by pre-adhesion has an advantage that a device with stable quality and excellent reliability can be obtained as compared with the sequential adhesion method in an assembly line of a liquid crystal display device or the like.

In order to form the pressure-sensitive adhesive layer having an excellent stress relaxation property, for example, an appropriate polymer having an excellent transparency can be obtained by using an appropriate polymer such as an acrylic polymer, a silicone polymer, polyester, polyurethane, polyether or synthetic rubber. A suitable adhesive can be used. Above all, acrylic pressure-sensitive adhesives are preferred from the viewpoints of optical transparency, adhesive properties, weather resistance and the like.

Specific examples of the acrylic polymer forming the acrylic pressure-sensitive adhesive include a methyl group, an ethyl group, an n-propyl group and an isopropyl group, an n-butyl group and an isobutyl group, a pentyl group and an isoamyl group, Alkyl groups such as hexyl group, heptyl group, cyclohexyl group, 2-ethylhexyl group, octyl group, isooctyl group, nonyl group, isononyl group, lauryl group, dodecyl group, decanyl group, isodecanyl group, especially those having 2 to 2 carbon atoms. One obtained by polymerizing one or more of acrylic acid esters and methacrylic acid esters having 14 alkyl groups together with one or two or more types of modifying monomers as necessary.

Specific examples of the modifying monomer which is copolymerized with the (meth) acrylic acid ester as needed in the formation of the above-mentioned acrylic copolymer include 2-hydroxyethyl (meth) acrylate and (meth) acrylic acid. ) 2-hydroxypropyl acrylate, 4-hydroxybutyl (meth) acrylate or 6-hydroxyhexyl (meth) acrylate,
8-hydroxyoctyl (meth) acrylate or (meth)
Hydroxyl group-containing monomers such as 10-hydroxydecyl acrylate, 12-hydroxylauryl (meth) acrylate and (4-hydroxymethylcyclohexyl) -methyl acrylate, acrylic acid and methacrylic acid, carboxyethyl acrylate and carboxypentyl acrylate, and itaconic acid Carboxyl group-containing monomers such as maleic acid and maleic acid and crotonic acid; acid anhydride monomers such as maleic anhydride and itaconic anhydride; 2-acrylamide-
Examples thereof include a sulfonic acid group-containing monomer such as 2-methylpropanesulfonic acid, and a phosphoric acid group-containing monomer such as 2-hydroxyethylacryloyl phosphate.

An amide monomer such as (meth) acrylamide or N-substituted (meth) acrylamide;
Maleimide monomers such as cyclohexylmaleimide and N-isopropylmaleimide, N-laurylmaleimide and N-phenylmaleimide, N-methylitaconimide and N-ethylitaconimide, N-butylitaconimide and N-octylitaconimide, N-2 -Ethylhexylitaconimide, N-cyclohexylitaconimide, itaconimide monomers such as N-laurylitaconimide, N- (meth) acryloyloxymethylene succinimide, N- (meth) acryloyl-6-oxyhexamethylene succinimide, N- (meta) S) A succinimide-based monomer such as acryloyl-8-oxyoctamethylene succinimide is also exemplified as a modifying monomer.

Furthermore, vinyl monomers such as vinyl acetate, N-vinyl pyrrolidone, N-vinyl carboxylic acid amides and styrene, divinyl monomers such as divinyl benzene, 1,4-butyl diacrylate and 1,6-hexyl di Diacrylate monomers such as acrylates,
Glycidyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, polyethylene glycol (meth) acrylate and polypropylene glycol (meth)
An acrylate monomer such as acrylate, fluorine (meth) acrylate or silicone (meth) acrylate, or an ester group different from the above-mentioned main component monomer such as methyl (meth) acrylate or octadecyl (meth) acrylate (meth) ) Acrylates and the like are also examples of the modifying monomer.

Among the above-mentioned modifying monomers, monomers having a functional group capable of reacting with an intermolecular crosslinking agent and capable of participating in intermolecular crosslinking of an acrylic copolymer, such as the above-mentioned carboxyl group-containing monomer and acid anhydride Product monomers, glycidyl (meth) acrylate, hydroxyl group-containing monomers, and the like can be preferably used. Above all, monomers having high crosslinking reactivity such as carboxyethyl acrylate and 6-hydroxyhexyl (meth) acrylate can impart necessary crosslinking properties with a small amount of copolymerization. It is difficult to increase the relaxation modulus, and it is particularly preferably used.

The method of preparing the acrylic polymer is arbitrary, and an appropriate method such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, or a suspension polymerization method can be employed. In the polymerization, for example, hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) ) Polyfunctional monomers such as acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, epoxy acrylate, polyester acrylate and urethane acrylate may also be used.

In the polymerization treatment, a polymerization initiator can be used as required. The amount used can be according to the ordinary law,
Generally, 0.001 to 5% by weight of the monomer component is used. Examples of the polymerization initiator include benzoyl peroxide and t
-Butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-
Propyl peroxy dicarbonate, di (2-ethoxyethyl) peroxy dicarbonate, t-butyl peroxy neodecalate, t-butyl peroxy vivalate, (3,5,5-trimethylhexanoyl) peroxide and dipropionyl Organic peroxides such as peroxide and diacetyl peroxide can be mentioned.

Further, 2,2′-azobisisobutyronitrile and 2,2′-azobis (2-methylbutyronitrile),
1'-azobis (cyclohexane 1-carbonitrile)
And 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethyl-4-methoxyvaleronitrile) and dimethyl 2,2′-azobis (2
-Methylpropionate), 4,4'-azobis (4-cyanovaleric acid) and 2,2'-azobis (2-hydroxymethylpropionitrile), 2,2'-azobis [2-
An azo compound such as (2-imidazolin-2-yl) propane], potassium persulfate, ammonium persulfate, hydrogen peroxide, or the like, or a redox initiator using a reducing agent in combination therewith, may be mentioned as the polymerization initiator.

The acrylic polymer which can be preferably used from the viewpoint of wet heat resistance and the like has a weight-average molecular weight of 10 or more, especially 200,000 or more, especially 400,000 or more. In addition, such an acrylic polymer may be subjected to a crosslinking treatment with an intermolecular crosslinking agent or the like, if necessary, to improve the adhesive properties by increasing the molecular weight or the like. Incidentally, examples of the intermolecular crosslinking agent include polyfunctional isocyanate crosslinking agents such as tolylene diisocyanate and trimethylolpropane tolylene diisocyanate, diphenylmethane triisocyanate, polyethylene glycol diglycidyl ether and diglycidyl ether, and trimethylolpropane triglycidyl ether. Suitable crosslinkers such as epoxy crosslinkers, melamine resin crosslinkers, metal salt crosslinkers, metal chelate crosslinkers, amino resin crosslinkers and the like can be used.

The thickness of the adhesive layer may be determined as appropriate. Generally, the thickness is 1 to 500 μm, particularly 2 to 200 μm, particularly 5 to 100 μm from the viewpoint of adhesive strength and thinning. If necessary, a tackifier such as petroleum resin, rosin resin, terpene resin, cumarone indene resin, phenol resin, xylene resin, alkyd resin, phthalate ester or phosphoric acid Softeners such as esters, paraffin chloride, polybutene and polyisobutylene, or other appropriate additives such as other various fillers and antioxidants can be blended.

When a polarization separation film, a quarter-wave plate, a polarization film, a retardation film and the like are formed of a plurality of separation materials, they are preferably formed as an integrated adhesive with an adhesive layer interposed therebetween.

As described above, the polarized light reflecting element and the elliptically polarized light element of the present invention can be preferably used for forming a liquid crystal display device for both reflection and transmission. FIG. 5 shows an example of the liquid crystal display device. 8 is a liquid crystal cell, and 9 is a backlight. 61 is a light diffusion layer, 31 is a polarizing plate, and 46, 47 and 48 are adhesive layers.

A liquid crystal display device for both reflection and transmission is generally
A polarizing plate is arranged on both sides of the liquid crystal cell, a backlight is arranged on the bottom surface, and a structure in which a compensation retardation film or the like is added as necessary is formed as a basic form,
In the present invention, the polarizing plate on the backlight side is not particularly limited except that the above-mentioned polarizing reflection element or elliptically polarizing plate is used, and can be formed according to a conventional method. In that case, as shown in FIG. 5, the polarizing reflection element or the elliptically polarizing plate is disposed between the liquid crystal cell 8 and the backlight 9 with the polarizing film side 3 or the retardation film side 6 as the liquid crystal cell side.

Accordingly, as the liquid crystal cell, for example, a twisted nematic liquid crystal, a super twisted nematic liquid crystal, a non-twist type liquid crystal, a guest-host type liquid crystal in which a dichroic substance is dispersed in a liquid crystal, or a ferroelectric liquid crystal is used. Any appropriate driving method may be used, and the driving method is not particularly limited. Further, the backlight may be a suitable one such as a sidelight type light guide plate or the like.

[0055]

【Example】

Example 1 A polarized light separating film showing selective reflectivity in a wavelength range of 400 to 700 nm, and a broadband type quarter-wave plate (manufactured by Nitto Denko Corporation,
NRF-QF02A) and a polyvinyl alcohol-based polarizing film (manufactured by Nitto Denko Corporation, NPF) are sequentially arranged via an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm, and they are press-pressed to be laminated and integrated to obtain a polarizing reflection element. Was. The polarizing film was arranged such that the transmission axis was orthogonal (orthogonal Nicols) to the linearly polarized light transmitted through the quarter-wave plate via the polarization separation film.

The above-mentioned polarizing beam splitting film is prepared by adding a tetrachloroethane solution obtained by adding a chiral agent (CM-32, manufactured by Chisso Corporation) to a side chain type nematic liquid crystal polymer having a methacrylic main chain, and forming a 50 μm-thick triacetyl cellulose film. Is applied by a spin coating method on a polyimide rubbed surface, and dried and cured at 150 ° C. for 10 minutes to obtain a thickness of 5 μm.
In the method of forming a cholesteric liquid crystal layer of μm, the central wavelength of selective reflection exhibiting a mirror-like selective reflection state is 450 n.
This is obtained by obtaining three types of films having a cholesteric liquid crystal layer of m, 550 nm, or 650 nm, and by crimping and laminating them through an acrylic adhesive layer having a thickness of 20 μm. The adjustment of the central wavelength of the selective reflection is as follows:
This was performed by changing the amount of the chiral agent added.

The は wavelength plate gives a phase difference of １ ／ wavelength to light of 550 nm wavelength obtained by uniaxially stretching a polycarbonate film having a thickness of 100 μm 1.05 times at 160 ° C. A retardation film cut out so that the stretching axis becomes 17.5 degrees, and a polycarbonate film having a thickness of 100 μm are uniaxially stretched 1.09 times at 160 ° C. and are に 対 し of a light having a wavelength of 550 nm obtained by a uniaxial stretching treatment. It is obtained by pressing and laminating a retardation film cut to give a wavelength retardation so that the stretching axis is 80 degrees through an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm and integrated.

Further, the acrylic pressure-sensitive adhesive layer was placed in a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer and a stirrer, in an amount of 99.9 parts by weight of butyl acrylate / 0.1 part by weight of 6-hydroxyhexyl acrylate / 0.3 parts by weight of 2,2-azobisisobutyronitrile were added together with 120 parts by weight of ethyl acetate, and the mixture was placed at 60 ° C. for 4 hours under a nitrogen gas stream, then at 70 ° C.
To the solution obtained by reacting for 2 hours, 114 parts by weight of ethyl acetate was added to adjust the solid concentration to 30% by weight, and 0.3 parts by weight of trimethylolpropane tolylene diisocyanate was added to 100 parts by weight of the solids. The acrylic pressure-sensitive adhesive obtained above was coated on a polyester film separator surface-treated with a silicone-based release agent,
It was formed by heating and drying for minutes. The relaxation modulus of the acrylic pressure-sensitive adhesive layer was 6 × 10 ⁶ dyne / cm ² .

COMPARATIVE EXAMPLE The same procedure as in Example 1 was carried out except that the polarizing film was arranged so that the transmission axis became parallel (parallel Nicol) to the linearly polarized light transmitted through the quarter-wave plate via the polarization separation film. A polarizing element was obtained.

Evaluation Test When the light was irradiated in the dark room from the polarizing film side of the polarizing (reflection) element obtained in Example 1 and Comparative Example, in Example 1, good reflected light based on the reflection law was obtained. Although the reflectance was excellent, substantially no reflected light was observed in the comparative example. Further, when light was irradiated from the polarization separation film side in a dark room, good transmitted light was obtained in Example 1 and Comparative Example.

[Brief description of the drawings]

FIG. 1 is a sectional view of an example of a polarization reflection element.

FIG. 2 is a cross-sectional view of another example of a polarization reflection element.

FIG. 3 is a cross-sectional view of yet another example of a polarization reflection element.

FIG. 4 is a cross-sectional view of an example of an elliptically polarizing element.

FIG. 5 is a cross-sectional view of an example of a liquid crystal display device.

[Explanation of symbols]

 1: Polarization separation film 11, 12: Cholesteric liquid crystal layer 2: Quarter wave plate 3, 31: Polarization film 4, 41 to 48: Adhesive layer 6, 61: Light diffusion layer 7: Retardation film 8: Liquid crystal cell 9 :Backlight

Claims (9)

[Claims] 1. A polarizing separation film comprising a cholesteric liquid crystal layer and a polarizing film are arranged via a quarter-wave plate.
A polarized light reflecting element, wherein the polarized light reflecting element is disposed in a relationship of orthogonal Nicols with respect to polarized light passing through a / 4 wavelength plate. 2. The polarization reflection element according to claim 1, wherein the polarization separation film comprises two or more cholesteric liquid crystal layers having different selective reflection center wavelengths, and the polarization film comprises a dichroic substance-containing material. 3. The method of claim 1 or 2, 1/4 wave plate, a maximum refractive index in the film plane n _x, a refractive index of the direction perpendicular n _y, the refractive index in the thickness direction n _z Then, the formula:
_{N z = (n x -n z} ) / (n x -n y) represented by N _z is -
A retardation film that satisfies 2 <N _z <5, or a polarizing reflection element comprising the retardation film and one or more half-wave plates. 4. The polarizing reflection element according to claim 1, wherein the polarizing film has a light transmittance of 40% or more and a degree of polarization of 90% or more. 5. The method according to claim 1, wherein the polarized light separating film, the quarter-wave plate and the polarized film are 2 × 10 ⁵ to 1 × 1.
0 ⁷ dyne / cm polarized reflection element comprising a laminate formed by bonding through an adhesive layer having a ^second relaxation modulus. 6. The polarization reflection element according to claim 1, wherein one or two or more light diffusion layers are provided on the surface or between the layers. 7. An elliptically polarizing element comprising the polarizing reflection element according to claim 1 and a retardation film on the polarizing film side. 8. The polarizing reflection element according to claim 1,
A liquid crystal display device for both reflection and transmission, wherein the polarizing film side is provided between the liquid crystal cell and the backlight as the liquid crystal cell side. 9. A liquid crystal display device for both reflection and transmission, wherein the elliptically polarizing element according to claim 7 is provided between the liquid crystal cell and the backlight with the retardation film side as the liquid crystal cell side.