JP3376233B2 - Polarizing reflection element, elliptically polarizing element, and liquid crystal display - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

BACKGROUND OF THE INVENTION In a liquid crystal display device for portable use such as a mobile phone which uses a storage battery, a transmissive liquid crystal display device in which a backlight is turned on and visually recognized consumes a lot of power and requires frequent battery replacement, resulting in disconnection of the call on the mobile phone. Since a fatal problem such as is caused, a semi-transmissive reflection plate is provided according to a reflection type liquid crystal display device that visually recognizes by using external light, though a backlight is provided but a polarizing plate is provided on the light side of the backlight. , A liquid crystal display device for both reflection / transmission has been proposed which can be visually recognized in a reflection mode in which the backlight is turned off under sunlight or the like and in a transmission mode in which the backlight is turned on at night or in a dark room. .

Conventionally, as the above-mentioned semi-transmissive reflection plate, a metal vapor deposition film or a film provided with a resin layer containing a pearl pigment has been known. However, in both cases, there is a trade-off relationship between reflection and transmission, and it is necessary to harmonize the visibility between reflection / transmission modes while balancing the reflectance and the transmittance. There was a problem of poor visibility in the reflection mode.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to develop an optical element for both reflection and transmission, which has a reflectance comparable to that of a mirror surface and the like and is excellent in the transmittance of light.

[0005]

According to the present invention , the maximum in- plane refractive index is n.
x, the refractive index in the orthogonal direction is ny, and the refractive index in the thickness direction is n
z and (nx-nz) / (nx-ny) = Nz,
-2 <Nz <5 A polarization separation film composed of a cholesteric liquid crystal layer and a polarization film are arranged through a quarter-wave plate having a retardation layer, and the polarization film serves as a polarization separation film. It is characterized in that it is arranged in a crossed Nicol relationship with respect to the polarized light passing through the quarter-wave plate, and that it has a retardation film on the polarizing film side of the polarizing reflection element. An elliptically polarizing element is provided.

[0006]

According to the present invention, as shown by an arrow A in FIGS. 1 and 5, when external light such as sunlight is incident on the polarizing film, a part thereof is transmitted as linearly polarized light, and the transmitted light is It is converted into left and right circularly polarized light through a four-wave plate. When the circularly polarized light is one of left and right circularly polarized light that satisfies the reflection condition of the polarization separation film, it is specularly reflected by the polarization separation film, and the reflected light is linearly polarized through a quarter wavelength plate and polarized. Re-incident on the film, it is possible to obtain a linearly polarized transmitted light that can be used for visual recognition in a reflection mode of a liquid crystal display device or the like.

On the other hand, as indicated by arrow B in FIGS. 1 and 5, of the light incident on the polarization separation film through the backlight or the like, the light other than the vertical direction is transmitted as elliptically polarized light, and the transmitted light is ¼ Linearly polarized light passes through the wave plate and enters the polarizing film to obtain transmitted light in a linearly polarized state that can be visually recognized in a transmission mode of a liquid crystal display device or the like. Note that the light vertically incident on the polarization separation film is separated into left and right circularly polarized light and one of them is transmitted, but when the transmitted light is linearly polarized through a quarter-wave plate, the polarizing film is arranged in crossed Nicols. It cannot be penetrated because it is made.

As a result of the above, reflected light having excellent reflection characteristics and excellent brightness that enables visual recognition in the reflection mode by using external light of brightness such as interior lighting is obtained, and a necessary ratio of visual recognition in the transmission mode is obtained. Therefore, it is possible to form a liquid crystal display device that is excellent in practicability for both reflection and transmission, which can reduce the power consumption because it can reduce the power consumption and extend the life of the storage battery. Well
To prevent coloring due to the viewing angle through the 1/4 wave plate
You can

[0009]

Polarized reflection element of the present invention embodiments of the Invention, in-plane
The maximum refractive index is nx, the refractive index in the orthogonal direction is ny, and the thickness is
Direction refractive index nz, and (nx-nz) / (nx-ny) =
When Nz, a retardation layer satisfying −2 <Nz <5 is used.
A polarization separation film composed of a cholesteric liquid crystal layer and a polarization film are arranged through a 1/4 wavelength plate provided, and the polarization film is orthogonal to the polarization through the polarization separation film and the quarter wavelength plate. It consists of those arranged in a Nicole relationship. Examples thereof are shown in FIGS. 1, 2 and 3. 1
Is a polarization separation film, 2 is a quarter 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 made of a cholesteric liquid crystal layer is used. According to the cholesteric liquid crystal layer, left and right circularly polarized light can be selectively separated into either one through transmission and reflection. As the cholesteric liquid crystal, an appropriate one can be used without any particular limitation. The use of a liquid crystal polymer is advantageous in terms of the superposition efficiency of the liquid crystal layer and the thinning. In addition, a cholesteric liquid crystal molecule having a large birefringence is preferable because the wavelength range of selective reflection becomes wider. 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 including an acrylic main chain, a methacrylic main chain, a siloxane main chain, a nematic liquid crystal polymer containing a low molecular weight chiral agent, Examples include liquid crystal polymers having a chiral component introduced therein, and nematic and cholesteric mixed liquid crystal polymers. From the viewpoint of handleability, the glass transition temperature is 30 to 150.
A liquid crystal polymer having a temperature of ° C can be preferably used.

The cholesteric liquid crystal layer can be formed by a method similar to the conventional alignment treatment. By the way, as an example, a film formed of polyimide or polyvinyl alcohol on a substrate and rubbed with rayon cloth or S,
A liquid crystal polymer is spread on an appropriate orientation film such as an oblique vapor deposition layer of iO and heated to a temperature not lower than the glass transition temperature and lower than the isotropic phase transition temperature, and the glass transition temperature is in a state where the liquid crystal polymer molecules are Grandjean aligned. A method of forming a solidified layer in which the orientation is fixed by cooling the glass to a glass state by cooling it to a lower temperature can be mentioned.

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

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

The thickness of the cholesteric liquid crystal layer is 0.5 to 100 μm, especially 1 to 1 from the viewpoints of preventing alignment disorder and transmittance reduction, and selective reflectivity (wavelength range showing circular dichroism). 70 μm, particularly preferably 1 to 50 μm. When forming the cholesteric liquid crystal layer or the polarization separation film, various additives such as stabilizers, plasticizers, and metals can be blended as necessary.

The polarized light separating film is composed of 2 as shown in FIG.
It can also be formed as a layer or as a superposition of three or more cholesteric liquid crystal layers 11 and 12. The superposition is advantageous in terms of widening the reflection wavelength, and in that case, it is preferable to superimpose the light with a different central wavelength of the light reflected as the circularly polarized light outside the predetermined range. That is, a single-layer cholesteric liquid crystal layer usually has a limit in the wavelength range exhibiting selective reflection (circular dichroism), and the limit may be a wide range extending to a wavelength range of about 100 nm. However, when it is applied to liquid crystal display devices, etc., it does not reach the entire range of visible light, so in such a case a wavelength range showing circular dichroism is expanded by overlapping cholesteric liquid crystal layers with different selective reflection properties. Can be made.

Incidentally, 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.
A combination that reflects circularly polarized light of the same polarization direction with the nm one,
And the central wavelength of selective reflection is different, especially 50nm each.
It is possible to efficiently form a polarization separation film capable of covering a wide wavelength range by using the above different combinations and superposing 2 to 6 types thereof. For the superposition of the cholesteric liquid crystal layer, the use of a liquid crystal polymer is particularly advantageous in terms of production efficiency and thinning.

Therefore, as the polarized light separating film, one in which the wavelength range of the light which can be reflected as the circularly polarized light outside the predetermined range coincides with the wavelength range of the light used for visual recognition or the like can be preferably used. In the above description, it was pointed out that when the polarization separation film was formed as a superposed layer of the cholesteric liquid crystal layer, it was used in combination with those which reflect circularly polarized light of the same polarization direction. This aims to increase the amount of polarized light in a usable state by preventing the circularly polarized light reflected by each layer from having different phase states in each wavelength range by aligning the phase states.

The polarization separation film used in the present invention is, for example, a cell form in which a cholesteric liquid crystal layer made of a low molecular weight material is sandwiched by a transparent substrate such as a film, a form in which a cholesteric liquid crystal layer made of a liquid crystal polymer is supported by a transparent substrate, The cholesteric liquid crystal layer may have a suitable form such as a film made of a liquid crystal polymer film or a form in which these forms are superposed in an appropriate combination.

In the above case, the cholesteric liquid crystal layer may be held by one or two 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 if oriented, from the viewpoint of preventing a change in the polarization state. Those can be preferably used.

1/4 placed on one side of the polarized light separating film
As described above, the wave plate circularly polarizes the light incident from the polarizing film and enables the light to be reflected by the polarization separation film (reflection mode), and also changes the phase of the elliptically polarized light incident from the polarization separation film to change the linear polarization component. For the purpose of converting into a large amount, it is possible to obtain light or the like that easily passes through the polarizing film.

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

[0023] The phase difference layer, there is a case to be colored depending on the viewing angle, Ri'll point to prevent the coloring, the formula: Nz =
Nz defined by (nx-nz) / (nx-ny) is -2
<¼ wavelength plate satisfying the Nz <5 is Ru is used. In the above equation, nx means the maximum refractive index in the plane of the retardation layer, ny means the refractive index in the direction orthogonal to the nx direction, and nz means the refractive index in the thickness direction.

The quarter-wave plate is composed of a single retardation layer, or has a different phase difference for the purpose of expanding the wavelength range capable of functioning as the quarter-wave plate as illustrated in FIG. It can be obtained as a laminate of two or more retardation layers 21 and 22. By the way, in the wide visible light range 1 /
As a superposed type quarter-wave plate that can function as a four-wave 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. Examples thereof include a combination of a plurality of retardation layers in combination with the retardation layer in a state where their optical axes intersect with each other.

In the above, from the point of obtaining a superposed type quarter-wave plate in which coloring due to the viewing angle is prevented, the above -2 <N _z
1 layer or 2 layers of a retardation layer which satisfies <5 and gives a retardation of ¼ wavelength and a retardation layer which gives a retardation of ½ wavelength.
It is preferable to use a layered product composed of two or more layers.

As described above, the quarter-wave plate can be obtained as a single layer product or a superposed product of retardation layers, and 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, a liquid crystal polymer film, or the like. Appropriate materials can be used as the polymer film and the liquid crystal polymer film.

Incidentally, specific examples of the above-mentioned polymer film include polycarbonate type polymers, polyester type polymers, polysulfone type polymers, polyether sulfone type polymers, polyvinyl alcohol type polymers, polystyrene type polymers, polymethylmethacrylate type polymers and polyolefins. Examples thereof include films made of appropriate transparent plastics such as polymer-based polymers, cellulose acetate-based polymers, polyvinyl chloride-based polymers, polyarylate-based polymers and polyamide-based polymers.

As the polarizing film arranged on the quarter wavelength plate side, an appropriate polarizing film such as an absorptive polarizing film containing a dichroic material, a polyene oriented film, or a transparent protective layer provided on the film is used. sell. By the way, examples of the absorption type polarizing film include hydrophilic polymer films such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film and ethylene / vinyl acetate copolymer partially saponified film, iodine and dichroic dye. Examples include films stretched by adsorbing the dichroic substance. Further, examples of the polyene oriented film include a dehydrated product of polyvinyl alcohol and a dehydrochlorinated product of polyvinyl chloride.

From the standpoint of achieving bright reflected light and transmitted light by the polarized light reflecting element, a polarizing film having a high degree of polarization such as a polarizing film containing a dichroic substance is preferably used.
Above all, the light transmittance is 40% or more, the polarization degree is 90% or more,
Above all, a polarizing film of 95% or more, particularly 99% or more is preferably used. The degree of polarization (P) is calculated by the formula: P =
It is defined by SQR [(T _p −T _c ) / (T _p + T _c )]. In the formula, T _p is the light transmittance when the same polarizing films are arranged in parallel Nicols, and T _c is the light transmittance when they are arranged in orthogonal Nicols. The thickness of the polarizing film is usually 5
˜80 μm, but not limited to this.

The above-mentioned transparent protective layer is provided for the purpose of protection especially in the case of poor water resistance such as a dichroic substance-containing polarizing film, and is appropriately applied by a plastic coating method or a film laminating method. It may be formed by any method. When it is formed of a separated material such as a film, it is preferable that the adhesive layer is laminated and integrated to prevent reflection loss. The thickness of the transparent protective layer may be appropriately determined and is generally 1 mm or less, preferably 500 μm or less, particularly 1 to 300 μm.

The transparent resin layer can also be formed in the form of a surface fine uneven structure by a method of 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 have conductivity such as m, silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, or organic fine particles such as crosslinked or uncrosslinked polymer The one showing transparency is used. The content of fine particles is 2 to 25
%, Especially 5 to 20% by weight is common.

The polarizing film is combined with a polarization separating film to obtain a reflected light that enables visual recognition in the reflection mode.
It is arranged in a relationship of orthogonal Nicols with respect to the polarized light passing through the four-wave plate. That is, the polarizing film is arranged in a state in which, when the circularly polarized light transmitted through the polarization separation film is transmitted through the quarter wavelength plate and becomes linearly polarized light, the linearly polarized light is not transmitted.

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 which is reflected by the polarization separation film, and as a return light through the reflection. The reflected light will be obtained. The above-mentioned arrangement in the crossed Nicols relation can be achieved by setting the transmission axis of the polarizing film in an orthogonal state with respect to the linearly polarized light transmitted through the quarter-wave plate. When forming the orthogonal state, the deviation of the angle due to the variation of the optical axis of the polarizing film, the quarter-wave plate, etc., the work error, etc. is allowed.

As shown in FIG. 3, the polarizing / reflecting element has one or more layers for the purpose of homogenizing the brightness and expanding the light emitting direction by diffusing light at appropriate positions between the surface and the layers. The light diffusing layer 6 can be arranged. The light diffusion layer is also effective for alleviating the viewing angle characteristics due to the incident angle dependency of the polarization separation film. As the light diffusion layer, a fine concavo-convex structure or a diffraction grating-like one exemplified in the transparent protective layer of the above-mentioned polarizing film, an additional layer having an appropriate diffusion structure such as an internal diffusion type or a pearl pigment-containing type, or the like. An appropriate one 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 having a retardation film 7 on the polarizing film 3 side of the polarizing / reflecting element as shown in FIG. 4 may be used. Such a retardation film converts linearly polarized light transmitted through the polarizing film into elliptically polarized light, adjusts the polarization plane of light incident on the liquid crystal cell, and compensates optical characteristics due to the birefringence of the liquid crystal cell. And is arranged for the purpose of improving the light utilization efficiency and visibility. As the retardation film, those exemplified above as the quarter-wave plate can be appropriately used according to the wavelength range and the like. The retardation film may be formed as one layer or a superposed layer of two or more layers. Note that reference numeral 45 in the figure is an adhesive layer.

In the present invention, the forming components such as the polarization separation film and the quarter-wave plate that form the polarization reflection element and the elliptical polarization element, the polarization film and the light diffusion layer, the retardation film and the adhesive layer described later are For example, it may have ultraviolet absorption ability by a method of treatment with an ultraviolet absorber such as salicylate compound, benzophenol compound, benzotriazole compound, cyanoacrylate compound, nickel complex salt compound.

The respective components such as the polarization separation film, the quarter-wave plate, the polarization film and the retardation film in the polarization reflection element or the elliptically polarization element can be laminated and integrated through an adhesive layer or the like, if necessary. . Stacking and unifying is preferable because it prevents misalignment of the optical axis during use. Note that, as illustrated in FIG. 2, an adhesive layer 44 for adhering to other components may be provided on one or both of the front and back of the polarization reflection element and the elliptical polarization element that are laminated and integrated. In that case, it is preferable to temporarily attach the separator 5 or the like to protect the surface.

An appropriate adhesive or the like may be used for the above-mentioned lamination integration, but it is excellent in stress relaxation because of the prevention of photoelastic deformation due to relaxation of internal stress generated inside the laminate by heat. Adhesive layer, especially, relaxation elastic modulus of 2 × 10 ⁵ -1
× 10 ⁷ dyne / cm ² , especially 2 × 10 ⁶ to 8 × 10 ⁶ dyne / cm
It is preferable that the laminated body is adhered via the adhesive layer of ² . Such an adhesive layer can be usually formed from an adhesive having a glass transition temperature of 0 ° C. or lower.

The above-mentioned lamination and integration through the pressure-sensitive adhesive layer having an excellent stress relaxation property can be achieved by using a polarized light separating film or 1
/ 4 wavelength plate and polarizing film can be suppressed stress,
In addition to preventing changes in the refractive index caused by photoelastic deformation, it is also effective in suppressing reflection loss at each interface, preventing foreign matter from entering the interface, and preventing deterioration of the display quality of liquid crystal display devices. is there. Further, the laminated integration method by pre-adhesion has an advantage that an element having stable quality and excellent reliability can be obtained as compared with a sequential adhesion method in an assembly line of a liquid crystal display device or the like.

For the formation of the above-mentioned pressure-sensitive adhesive layer having excellent stress relaxation property, for example, an acrylic polymer, a silicone polymer, polyester, polyurethane, polyether, synthetic rubber or the like is used. Any adhesive can be used. Above all, acrylic adhesives are preferable 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 methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, pentyl group and 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 and isodecanyl group, especially having 2 to 2 carbon atoms. Examples thereof include those obtained by polymerizing one or two or more of acrylic acid esters and methacrylic acid esters having 14 alkyl groups with one or more modifying monomers as necessary.

Specific examples of the modifying monomer that is copolymerized with the (meth) acrylic ester at the time of forming the above-mentioned acrylic copolymer include 2-hydroxyethyl (meth) acrylate and (meth) acrylic acid. ) 2-hydroxypropyl acrylate, 4-hydroxybutyl (meth) acrylate and 6-hydroxyhexyl (meth) acrylate,
8-Hydroxyoctyl (meth) acrylate and (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, itaconic acid Carboxyl group-containing monomers such as and maleic acid and crotonic acid, acid anhydride monomers such as maleic anhydride and itaconic anhydride, 2-acrylamido-
Examples thereof include sulfonic acid group-containing monomers such as 2-methylpropanesulfonic acid and phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate.

In addition, amide-based monomers such as (meth) acrylamide and N-substituted (meth) acrylamide, N-
Maleimide-based monomers such as cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide and N-phenylmaleimide, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2. Itaconimide-based monomers such as -ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide, N- (meth) acryloyloxymethylenesuccinimide, N- (meth) acryloyl-6-oxyhexamethylenesuccinimide, N- (meth ) A succinimide-based monomer such as acryloyl-8-oxyoctamethylene succinimide can also be used as the modifying monomer.

Further, vinyl-based monomers such as vinyl acetate, N-vinylpyrrolidone, N-vinylcarboxylic acid amides and styrene, divinyl-based monomers such as divinylbenzene, 1,4-butyldiacrylate and 1,6-hexyldiene. Diacrylate-based monomer such as acrylate,
Glycidyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, polyethylene glycol (meth) acrylate and polypropylene glycol (meth)
Acrylic ester type monomers such as acrylate, fluorine (meth) acrylate and silicone (meth) acrylate, and ester groups different from those of the above-mentioned main component monomers such as methyl (meth) acrylate and octadecyl (meth) acrylate (meth). ) Acrylic acid esters and the like are also mentioned as the modifying monomer.

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

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 adopted. 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) acrylate, etc. ) Polyfunctional monomers such as acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, epoxy acrylate, polyester acrylate and urethane acrylate can also be used.

In the polymerization treatment, a polymerization initiator may be used if necessary. The amount used can be in accordance with the usual method,
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-
Propylperoxydicarbonate, di (2-ethoxyethyl) peroxydicarbonate, t-butylperoxyneodecalyate, t-butylperoxyvibrate, (3,5,5-trimethylhexanoyl) peroxide and dipropionyl Examples thereof include organic peroxides such as peroxide and diacetyl peroxide.

Further, 2,2'-azobisisobutyronitrile and 2,2'-azobis (2-methylbutyronitrile), 1,2'-azobis (2-methylbutyronitrile)
1'-azobis (cyclohexane 1-carbonitrile)
Or 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethyl-4-methoxyvaleronitrile) or dimethyl 2,2'-azobis (2
-Methylpropionate), 4,4'-azobis (4-cyanovaleric acid) and 2,2'-azobis (2-hydroxymethylpropionitrile), 2,2'-azobis [2-
Examples of the polymerization initiator include azo compounds such as (2-imidazolin-2-yl) propane], potassium persulfate, ammonium persulfate, hydrogen peroxide, and the like, and redox initiators in which they are used in combination with a reducing agent.

Acrylic polymers which can be preferably used in view of resistance to moist heat and the like have a weight average molecular weight of 10 or more, preferably 200,000 or more, particularly 400,000 or more. If necessary, the acrylic polymer may be subjected to a crosslinking treatment with an intermolecular crosslinking agent or the like to improve the adhesive property by increasing the molecular weight. Incidentally, examples of the intermolecular cross-linking agent, tolylene diisocyanate and trimethylol propane tolylene diisocyanate, polyfunctional isocyanate-based cross-linking agents such as diphenylmethane triisocyanate, polyethylene glycol diglycidyl ether and diglycidyl ether, trimethylol propane triglycidyl ether Other appropriate epoxy crosslinking agents such as melamine resin crosslinking agents, metal salt crosslinking agents, metal chelate crosslinking agents and amino resin crosslinking agents may be used.

The thickness of the adhesive layer may be appropriately determined. Generally, the thickness is from 1 to 500 μm, especially from 2 to 200 μm, and particularly from 5 to 100 μm in view of adhesive strength and thinning. The adhesive layer may contain tackifiers such as petroleum-based resins, rosin-based resins, terpene-based resins, coumarone-indene-based resins, phenol-based resins, xylene-based resins, alkyd-based resins, phthalates and phosphoric acid as needed. Ester, chloroparaffin, polybutene, softening agents such as polyisobutylene, or other appropriate additives such as various fillers and antiaging agents can be added.

Even when the polarized light separating film, the quarter-wave plate, the polarizing film, the retardation film and the like are made of a plurality of separating materials, it is preferable to form them as an integrated adhesive product via an adhesive layer.

As described above, the polarizing / reflecting element and the elliptically polarizing element of the present invention can be preferably used for forming a reflective / transmissive liquid crystal display device. An example of the liquid crystal display device is shown in FIG. 8 is a liquid crystal cell, and 9 is a backlight. Further, 61 is a light diffusion layer, 31 is a polarizing plate, and 46, 47 and 48 are adhesive layers.

A reflective / transmissive liquid crystal display device 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 retardation film for compensation or the like is added is formed as a basic form,
In the present invention, the polarizing plate on the backlight side is not particularly limited except that the polarizing reflection element or the elliptically polarizing plate described above is used, and it can be formed according to the conventional method. In that case, the polarizing reflection element or the elliptically polarizing plate is arranged between the liquid crystal cell 8 and the backlight 9 with the polarizing film side 3 or the retardation film side 6 thereof as the liquid crystal cell side, as shown in FIG.

Therefore, as the liquid crystal cell, for example, twisted nematic liquid crystal, super twisted nematic liquid crystal, non-twisted liquid crystal, guest-host liquid crystal in which a dichroic substance is dispersed in liquid crystal, or ferroelectric liquid crystal is used. However, the driving method is not particularly limited. Further, the backlight may be an appropriate one such as a side light type with a light guide plate or the like.

[0055]

【Example】

Example 1 A polarization separation film showing selective reflectivity in the 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 (NPF, NPF) are sequentially arranged via an acrylic adhesive layer having a thickness of 20 μm, which is press-bonded to be laminated and integrated to obtain a polarizing reflection element. It was The polarizing film was arranged such that the transmission axis was orthogonal (orthogonal Nicol) to the linearly polarized light transmitted through the quarter-wave plate through the polarization separation film.

The polarized light separating film was prepared by adding a tetrachloroethane solution prepared by adding a chiral agent (CM-32, manufactured by Chisso Co.) to a side chain type nematic liquid crystal polymer having a methacrylic main chain and using a 50 μm thick triacetyl cellulose film. It is applied to the polyimide rubbing treated surface of No. 3 by a spin coating method, dried and cured at 150 ° C. for 10 minutes to have a thickness of 5
A method for forming a cholesteric liquid crystal layer of μm, the selective reflection having a mirror-like selective reflection state has a central wavelength of 450 n.
It was obtained by obtaining three kinds of cholesteric liquid crystal layer-attached films of m, 550 nm, or 650 nm, and pressure-bonding and laminating them with an acrylic adhesive layer having a thickness of 20 μm. The adjustment of the central wavelength of the selective reflection is
It was performed by changing the addition amount of the chiral agent.

The 1/4 wave plate gives a phase difference of 1/4 wavelength to a light having a wavelength of 550 nm obtained by uniaxially stretching a polycarbonate film having a thickness of 100 μm by 1.05 times at 160 ° C., Half of the retardation film cut so that the stretching axis is 17.5 degrees and a polycarbonate film having a thickness of 100 μm are uniaxially stretched 1.06 times at 160 ° C. to a light having a wavelength of 550 nm. It is obtained by pressure-bonding and laminating a retardation film, which is cut so that the stretching axis is 80 degrees and which gives a retardation of wavelength, with an acrylic adhesive layer having a thickness of 20 μm to be integrated.

Further, the acrylic adhesive layer was prepared by adding 99.9 parts by weight of butyl acrylate / 0.1 part by weight of 6-hydroxyhexyl acrylate / to a reaction vessel equipped with a cooling pipe, a nitrogen introducing pipe, a thermometer and a stirrer. 0.32 parts by weight of 2,2-azobisisobutyronitrile was added together with 120 parts by weight of ethyl acetate, and the mixture was put in a nitrogen gas stream at 60 ° C. for 4 hours and then at 70 ° C.
114% by weight of ethyl acetate was added to the solution obtained by the reaction for 2 hours to adjust the solid content concentration to 30% by weight, and 0.3 parts by weight of trimethylolpropane tolylene diisocyanate was added to 100 parts by weight of the solid content. The acrylic pressure-sensitive adhesive obtained in this way was applied onto a polyester film separator whose surface was treated with a silicone-based release agent, and the temperature was adjusted to 3 at 120 ° C.
It is formed by heating and drying for a minute. The relaxation elastic modulus of the acrylic pressure-sensitive adhesive layer was 6 × 10 ⁶ dyne / cm ² .

Comparative Example According to Example 1, except that the polarizing film was arranged so that the transmission axis was parallel (parallel Nicol) to the linearly polarized light transmitted through the quarter-wave plate through the polarization separation film. A polarizing element was obtained.

Evaluation test When a light was irradiated from the polarizing film side of the polarizing (reflection) elements obtained in Example 1 and Comparative Example in a dark room, good reflected light based on the law of reflection was obtained in Example 1, and Although it was also excellent in reflectance, 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 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 still 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 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: 1/4 wave plate 3,31: Polarizing film 4,41-48: Adhesive layer 6,61: Light diffusion layer 7: Retardation film 8: Liquid crystal cell 9: Backlight

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-271731 (JP, A) JP-A-9-189811 (JP, A) JP-A-10-3079 (JP, A) JP-A-9- 329779 (JP, A) JP-A-7-35925 (JP, A) JP-A-10-68816 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 5/30 G02F 1 / 1335

Claims (9)

(57) [Claims] 1. The maximum in-plane refractive index is nx, and its orthogonal direction
, Ny, the refractive index in the thickness direction is nz, and (nx−
nz) / (nx-ny) = Nz, -2 <Nz <5
Via a quarter wave plate having a retardation layer satisfying
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 crossed Nicols relationship with respect to the polarization through the polarization separation film and the quarter wavelength plate. And a polarized light reflection element. 2. The polarization reflection element according to claim 1, wherein the polarization separation film is composed of two or more cholesteric liquid crystal layers having different selective reflection central wavelengths, and the polarization film is composed of a dichroic substance-containing material. 3. The polarizing reflection element according to claim 1, wherein the quarter wave plate has a retardation film satisfying the Nz , or 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 polarization degree of 90% or more. 5. The polarized light separating film, the quarter wavelength plate and the polarizing film according to claim 1, wherein the polarizing film is 2 × 10 ⁵ to 1 × 1.
A polarization reflection element comprising a laminated body adhered via an adhesive layer having a relaxation elastic modulus of 0 ⁷ dyne / cm ² . 6. The polarization reflection element according to claim 1, which has one or more light diffusion layers on the surface or between the layers. 7. An elliptically polarizing element having a retardation film on the polarizing film side of the polarizing and reflecting element according to claim 1. 8. The polarization reflection element according to claim 1,
A reflective / transmissive liquid crystal display device having the polarizing film side as a liquid crystal cell side between a liquid crystal cell and a backlight. 9. A reflective / transmissive liquid crystal display device comprising the elliptically polarizing element according to claim 7 between the liquid crystal cell and a backlight, with the retardation film side being the liquid crystal cell side.