JP2001004845A - Polarized light guiding plate and surface light source for polarized light - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide plate which can obtain emitted light composed of linearly polarized light and which can arbitrarily control the direction of the polarized light (plane of oscillation). SOLUTION: A polarized light guiding plate is provided with a layered body 4 and a mirror reflection layer 5 which is disposed on one surface of the layered body 4, wherein the layered body 4 is comprised of a double-refractive optically transparent resin plate 1 and a polarized light scattering plate 3 which is disposed on one or both surfaces of the resin plate 1 and which contains dispersed double-reflective minute regions to show scattering anisotropy. A surface light source for polarized light 6 is provided on at least one side of the polarized light guiding plate. Accordingly, it is possible to form an excellent liquid crystal display element which can make natural light incident on from one side and allow efficient outgoing of linearly polarized light from either the front surface or the back, without the necessity of forming a special light emission means such as reflection dots on the resin plate 1, and which can arbitrarily control the oscillation direction of the linearly polarized light through an optical axis of the polarized light scattering plate 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarized light guide plate suitable for forming a backlight of a liquid crystal display device by emitting linearly polarized light with incident light from the side surface being controlled from one of the front and back surfaces and the vibrating surface being controlled. And a polarization plane light source.

[0002]

2. Description of the Related Art Conventionally, as a side light type light guide plate which can be used as a backlight of a liquid crystal display device, a light emitting plate formed of a reflective dot containing a high reflectance pigment such as titanium oxide or barium sulfate on a translucent resin plate. There has been known a device in which a transmission means is provided by means of the light emitting means and emitted from one of the front and back sides of the plate by scattering or the like due to total reflection in the plate. However, the emitted light is natural light having almost no polarization characteristics, and it is necessary to convert it into linearly polarized light through a polarizing plate during liquid crystal display. However, there was a problem that it could not exceed 50%.

[0003] In view of the above, there has been proposed a system in which a polarization converter combining a polarization separation plate and a retardation plate capable of obtaining linearly polarized light by using the Brewster angle is used (Japanese Patent Laid-Open No. Hei 6-18873). Gazette, JP-A-6-16084
0, JP-A-6-265892, JP-A-7-
JP-A-72475, JP-A-7-261122, JP-A-7-270792, JP-A-9-54556, JP-A-9-105933, JP-A-9-13
8406, JP-A-9-152604, JP-A-9-293406, JP-A-9-326205 and JP-A-10-78581. However, such a backlight has a problem in that it is not practically used because sufficient polarization cannot be obtained and it is difficult to control the polarization direction.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to develop a light guide plate capable of obtaining emission light composed of linearly polarized light and controlling the polarization direction (oscillation plane) of the light arbitrarily.

[0005]

According to the present invention, a birefringent translucent resin plate is provided on one or both sides thereof with a polarizing scattering plate that contains a birefringent fine region in a dispersed manner and exhibits scattering anisotropy depending on the polarization direction. The present invention provides a polarizing light guide plate having a specular reflection layer on one side of a laminate comprising the above, and a polarizing light source having a light source on at least one side of the polarizing light guide plate.

[0006]

According to the present invention, with the above structure, natural light is made to enter from the side surface without forming any special light emitting means such as reflective dots on the translucent resin plate, and the mirror reflection layers on the front and back surfaces are provided. It is possible to efficiently emit linearly polarized light from the other side, and to obtain linearly polarized light in the vibration direction according to the optical axis of the polarization scattering plate used together. Therefore, the oscillation direction of the linearly polarized light can be arbitrarily changed by controlling the optical axis of the polarization scattering plate.

That is, in the above, the incident light from the side surface is totally reflected by the difference in the refractive index from the air interface and is transmitted through the light guide plate while being incident on the polarization scattering plate. The axial direction (△ n1) indicating the rate difference (△ n1)
The linearly polarized light having the vibration plane parallel to the direction is selectively and strongly scattered, and a part thereof becomes an angle smaller than the total reflection angle and is emitted from the light guide plate. In that case, on the side where the specular reflection layer is provided, the outgoing light is blocked and supplied to the opposite surface, and the outgoing light is concentrated on that surface (one of the front and back surfaces of the light guide plate having no specular reflection layer). Emit light efficiently.

On the other hand, the light scattered at a large angle in the △ n1 direction, the light that satisfies the △ n1 direction condition but is not scattered, and the light having a vibration direction other than the △ n1 direction Then, it is confined in the light guide plate and transmitted while repeating total reflection, and the polarization state is canceled by the birefringence phase difference due to the resin plate or the polarization scattering plate, and the opportunity to emit light satisfying the above-mentioned Δn1 direction condition is waited. By repeating the above, linearly polarized light having a predetermined vibration plane is efficiently emitted from the light guide plate. In this case, in the present invention, the translucent resin plate efficiently cancels the polarization state due to its birefringence, thereby increasing the above-mentioned emission opportunity and improving the luminance.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polarized light guide plate according to the present invention is a polarized light exhibiting scattering anisotropy depending on the polarization direction by dispersing a birefringent fine region on one or both sides of a birefringent translucent resin plate. The laminate having the scattering plate is provided with a specular reflection layer on one surface. An example is shown in FIG. 1 is a translucent resin plate, 3 is a polarization scattering plate, 4 is a laminate thereof,
5 is a specular reflection layer and 2 is an adhesive layer. FIG. 1
Exemplifies a polarizing plane light source, and 6 denotes a light source.

The birefringent translucent resin plate may be a plate-like material formed of an appropriate material exhibiting transparency according to the wavelength range of the light source. In the visible light region, for example, a plate made of an acrylic resin, a polycarbonate resin, a styrene resin, a polyester resin, or an epoxy resin can be preferably used. From the viewpoint of light transmittance, a plate made of a resin having a refractive index as small as possible is preferable.

[0011] The translucent resin plate is used to improve the brightness by eliminating the polarization state of the light transmitted through the light guide plate and increasing the chance of exiting the light from the scattering polarizer to improve the luminance. Those exhibiting refraction are used. It is preferable that the retardation due to birefringence is 50 nm or more, particularly 60 nm or more, particularly 70 nm or more, based on the average in-plane retardation, from the viewpoint of efficiently eliminating polarized light. Further, it is preferable that the phase difference unevenness is as small as possible from the viewpoint of preventing the brightness unevenness.

The birefringent translucent resin plate is formed by, for example, a method of causing orientation birefringence due to distortion or the like during the molding of the plate, a method of stretching, a method of rolling, and a method under the action of an electric field or a magnetic field. It can be performed by an appropriate method such as a method of aligning the resin. Above all, a method of generating birefringence by molding distortion is preferable from the viewpoint of mass productivity of the resin plate, and an acrylic resin or a polycarbonate resin can be preferably used from such a point.

The shape of the translucent resin plate can be appropriately determined according to the size of the liquid crystal cell, the characteristics of the light source, and the uniformity of the luminance of the emitted light, and is not particularly limited. A flat plate or a wedge-shaped plate is preferred from the viewpoint of ease of molding. The thickness of the plate can also be appropriately determined according to the size of the light source or the liquid crystal cell, etc., and is not particularly limited. However, it is preferably as thin as possible for the purpose of thinning and weight reduction, particularly 10 mm or less, particularly 0.5 to 5 mm. Is preferred.

The transparent resin plate is formed by, for example, an injection molding method, a casting molding method, an extrusion molding method, a casting molding method,
It can be performed by an appropriate method such as a rolling molding method, a roll coating molding method, a transfer molding method, and a reaction injection molding method (RIM). In the formation, appropriate additives such as, for example, a discoloration inhibitor, an antioxidant, an ultraviolet absorber, and a release agent can be added as needed.

On the other hand, as the polarized light scattering plate, a suitable one can be used which contains a birefringent minute region in a dispersed manner and exhibits scattering anisotropy depending on the polarization direction. Incidentally, examples thereof include those in which a birefringent minute region is dispersed and contained in a transparent film. The formation of such a polarized light scattering plate is made of, for example, one of suitable materials having excellent transparency such as polymers and liquid crystals.
The method can be carried out by an appropriate method such as a method of obtaining an oriented film by using a combination of two or more kinds in which a region having a different birefringence is formed by an appropriate orientation treatment such as a stretching treatment.

Incidentally, examples of the above-mentioned combination include a combination of polymers and liquid crystals, a combination of an isotropic polymer and an anisotropic polymer, and a combination of anisotropic polymers. From the viewpoint of the dispersion distribution of the minute region, a combination that separates phases is preferable, and the dispersion distribution can be controlled by the compatibility of the materials to be combined. The phase separation can be performed by an appropriate method such as a method in which an incompatible material is made into a solution with a solvent or a method in which the incompatible material is mixed while being heated and melted.

In the case of performing the orientation treatment by the stretching method in the above-mentioned combination, the combination of the polymer and the liquid crystal and the combination of the isotropic polymer and the anisotropic polymer can be carried out at an arbitrary stretching temperature and stretching ratio. In the combination of the two, the desired polarization scattering plate can be formed by appropriately controlling the stretching conditions. Note that anisotropic polymers are classified into positive and negative based on the characteristics of refractive index change in the stretching direction.In the present invention, any positive or negative anisotropic polymer can be used. It can be used in any of the combinations.

Examples of the above-mentioned polymers include ester polymers such as polyethylene terephthalate and polyethylene naphthalate, styrene polymers such as polystyrene and acrylonitrile-styrene copolymer (AS polymers), polyethylene, polypropylene, cyclo and Polyolefins having a norbornene structure, such as olefin polymers such as ethylene-propylene copolymer, acrylic polymers such as polymethyl methacrylate, cellulose polymers such as cellulose diacetate and cellulose triacetate, and amide polymers such as nylon and aromatic polyamide Is raised.

Further, carbonate polymers, vinyl chloride polymers, imide polymers and sulfone polymers,
Polyether sulfone or polyether ether ketone,
Polyphenylene sulfide, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene,
Silicone-based polymers and urethane-based polymers, ether-based polymers and vinyl acetate-based polymers, blends of the above polymers, or thermosetting types such as phenol-based or melamine-based, acrylic- or urethane-based, urethane-acrylic-based, epoxy- or silicone-based Or UV-curable polymers are also examples of the above-mentioned transparent polymer.

On the other hand, examples of the liquid crystal include nematic phase and smectic phase at room temperature or high temperature such as cyanobiphenyl type, cyanophenylcyclohexane type, cyanophenyl ester type, benzoic acid phenyl ester type, phenylpyrimidine type and mixtures thereof. And a liquid crystal polymer exhibiting a nematic phase or a smectic phase at room temperature or high temperature. The above-mentioned crosslinkable liquid crystal monomer is usually subjected to an alignment treatment, and then subjected to a crosslinking treatment by an appropriate method such as heat or light to form a polymer.

From the viewpoint of obtaining a polarized light scattering plate having excellent heat resistance and durability, the glass transition temperature is 50 ° C. or more, especially 80 ° C.
As described above, it is particularly preferable to use a combination of polymers having a temperature of 120 ° C. or higher and a crosslinkable liquid crystal monomer or liquid crystal polymer. As the liquid crystal polymer, an appropriate one such as a main chain type or a side chain type can be used, and the type thereof is not particularly limited. A liquid crystal polymer which can be preferably used in view of the formability and thermal stability of fine regions having excellent uniformity of particle size distribution, the formability into a film, and the ease of alignment treatment, has a degree of polymerization of 8 or more, especially 10 Above, especially those of 15 to 5000.

The formation of the polarized light scattering plate using the liquid crystal polymer is performed, for example, by mixing one or more kinds of polymers and one or more kinds of liquid crystal polymers for forming minute regions, Can be performed by a method of forming a polymer film containing dispersedly in the form of a fine region, orienting the film by an appropriate method, and forming a region having a different birefringence.

In view of the above-mentioned controllability of the refractive index differences Δn1 and Δn2 by the alignment treatment, the glass transition temperature is 50 ° C. or higher and the glass transition temperature is lower than the glass transition temperature of the polymers used in combination. Those exhibiting a nematic liquid crystal phase can be preferably used. Incidentally, specific examples thereof include a side chain type liquid crystal polymer having a monomer unit represented by the following general formula.

General formula:

In the above general formula, X is a skeletal group forming the main chain of the liquid crystal polymer, and may be formed by a suitable connecting chain such as linear, branched or cyclic. Incidentally, examples thereof include polyacrylates and polymethacrylates, poly-α-haloacrylates and poly-α-cyanoacrylates, polyacrylamides and polyacrylonitriles, polymethacrylonitriles and polyamides, polyesters and Examples include polyurethanes, polyethers, polyimides, and polysiloxanes.

Y is a spacer group branched from the main chain, and a preferable spacer group Y in view of the formability of a polarizing scattering plate such as control of the refractive index is, for example, ethylene, propylene, butylene, pentylene, hexylene or octylene. ,
These include decylene, undecylene, dodecylene, octadecylene, ethoxyethylene, methoxybutylene and the like.

On the other hand, Z is a mesogen group for imparting liquid crystal orientation, and examples thereof include the following compounds.

The terminal substituent A in the compound may be, for example, a cyano group, an alkyl group, an alkenyl group, an alkoxy group, an oxaalkyl group, a haloalkyl group in which at least one of hydrogen is substituted by fluorine or chlorine, a haloalkoxy group, It may be an appropriate one such as a haloalkenyl group.

In the above, the spacer group Y and the mesogen group Z
May be linked via an ether bond, that is, -O-. In the phenyl group in the mesogen group Z, one or two hydrogens may be substituted with a halogen. In this case, the halogen is preferably chlorine or fluorine.

The side chain type liquid crystal polymer having nematic alignment described above may be any suitable thermoplastic polymer such as a homopolymer or a copolymer having a monomer unit represented by the above general formula. Excellent ones are preferred.

The formation of the polarizing scattering plate using the liquid crystal polymer having the nematic alignment described above includes, for example, forming a polymer for forming a polymer film and a nematic liquid crystal phase in a temperature range lower than the glass transition temperature of the polymer. A liquid crystal polymer having a glass transition temperature of 50 ° C. or higher, particularly 60 ° C. or higher, particularly 70 ° C. or higher is mixed to form a polymer film containing the liquid crystal polymer dispersed in a fine region, and then the fine region is formed. The liquid crystal polymer can be subjected to a heat treatment to align the liquid crystal polymer into a nematic liquid crystal phase, and the alignment state can be fixed by cooling.

The formation of the above-mentioned polymer film containing fine domains dispersed therein, that is, a film to be subjected to an orientation treatment is carried out by
For example, it can be obtained by an appropriate method such as a casting method, an extrusion molding method, an injection molding method, a roll molding method, a cast molding method, etc., developed in a monomer state, and polymerized by heat treatment or radiation treatment such as ultraviolet rays. It can also be performed by a method of forming a film into a film.

From the viewpoint of obtaining a polarized light scattering plate excellent in uniform distribution of minute regions, a method of forming a mixed solution of a forming material through a solvent by a casting method, a casting method, or the like is preferable. In this case, the size and distribution of the minute region can be controlled by the type of the solvent, the viscosity of the mixed solution, the drying speed of the mixed solution developing layer, and the like. Incidentally, in order to reduce the area of the minute region, it is advantageous to lower the viscosity of the mixed liquid and to increase the drying rate of the mixed liquid developing layer.

The thickness of the film to be subjected to the alignment treatment can be determined as appropriate, but is generally 1 μm
３3 mm, especially 5 μm to 1 mm, especially 10 to 500 μm. In forming the film, for example, appropriate additives such as a dispersant, a surfactant, an ultraviolet absorber, a color tone adjuster, a flame retardant, a release agent, and an antioxidant can be blended.

As described above, the orientation treatment is performed, for example, for one axis or two axes.
Stretching method and rolling method using two axes, sequential two axes, Z axis, etc.
Applying an electric or magnetic field at a temperature higher than the glass transition temperature or liquid crystal transition temperature to quench and fix the alignment, or apply a flow alignment at the time of film formation, or self-align the liquid crystal based on the slight alignment of the isotropic polymer. It can be performed using one or two or more of appropriate methods such as a method for controlling the refractive index depending on the orientation. Therefore, the obtained polarized light scattering plate may be a stretched film or a non-stretched film. When a stretched film is used, a brittle polymer may be used, but a polymer having excellent extensibility can be particularly preferably used.

When the fine regions are composed of the liquid crystal polymer described above, for example, the liquid crystal polymer dispersed and distributed as the fine regions in the polymer film is heated and melted to a temperature at which a desired liquid crystal phase such as a nematic phase is exhibited. Can be performed by orienting under the action of an alignment regulating force and quenching to fix the alignment state. It is preferable that the orientation state of the minute region is as mono-domain state as possible from the viewpoint of preventing variation in optical characteristics.

As the above-mentioned alignment regulating force, for example, a stretching force by a method of stretching a polymer film at an appropriate magnification, a sharing force at the time of film formation, an electric field or a magnetic field, etc. A regulating force can be applied, and the alignment treatment of the liquid crystal polymer can be performed by applying one or more kinds of the regulating force.

Therefore, portions other than the minute regions in the polarized light scattering plate may exhibit birefringence or may be isotropic. The whole of the polarizing scattering plate exhibits birefringence, can be obtained by the molecular orientation in the film forming process described above using a polymer for film formation having an orientation birefringence, if necessary, for example, stretching Birefringence can be imparted or controlled by adding known orientation means such as treatment.

The isotropic polarizing scattering plate having a portion other than the minute region is, for example, an isotropic polymer for forming a film, and the film is formed in a temperature region below the glass transition temperature of the polymer. And a method of stretching.

The polarization scattering plate that can be preferably used is a refractive index difference Δn in each optical axis direction of the minute region between the minute region and the other portion, that is, the portion made of the polymer film.
1, Δn2 and Δn3 are 0.03 or more (Δn1) in the axial direction (Δn1 direction) at which the maximum value is obtained, and the remaining two axial directions (Δn2 direction and Δn direction) orthogonal to the Δn1 direction.
50% or less (△ n2, △
n3), and it is more preferable that Δn2 is equal to Δn3.

By setting the refractive index difference, Δn1
The linearly polarized light in the direction is strongly scattered and is scattered at an angle smaller than the total reflection angle, so that the amount of light emitted from the light guide plate can be increased. Can be trapped inside.

In the above description, the difference in the refractive index between the direction of each optical axis of the minute region and the portion other than the minute region is determined when the polymer forming the film is optically isotropic. The difference between the axial refractive index and the average refractive index of the polymer film.If the polymer forming the film is optically anisotropic, the main optical axis direction of the polymer film and the main Since the direction of the optical axis usually coincides with the direction of the optical axis, it means the difference between the refractive indexes in the respective axial directions.

From the point of total reflection described above, the refractive index difference Δn1 in the Δn1 direction is preferably moderately large, more preferably 0.035 to 1, especially 0.045 to 0.5. It is preferred that It is preferable that the refractive index differences Δn2 and Δn3 between the Δn2 direction and the Δn3 direction are appropriately small. Such a difference in the refractive index can be controlled by the refractive index of the material to be used, the above-described alignment operation, and the like.

The above-mentioned Δn1 direction is a vibration plane of linearly polarized light emitted from the light guide plate.
The direction is preferably parallel to the plane of the polarized light scattering plate. Note that the Δn1 direction in the plane can be an appropriate direction according to a target liquid crystal cell or the like.

It is preferable that the minute regions in the polarized light scattering plate are dispersed and distributed as uniformly as possible in view of the homogeneity of the scattering effect and the like. The size of the minute region, particularly the length in the △ n1 direction, which is the scattering direction, is related to backscattering (reflection) and wavelength dependency.

The improvement of light use efficiency, prevention of coloring due to wavelength dependency, prevention of visual inhibition of fine regions or prevention of clear display, and furthermore, preferable of fine regions from the viewpoint of film forming property and film strength. The size, particularly the preferred length in the Δn1 direction, is 0.05 to 500 μm, preferably 0.1 to 500 μm.
２５０250 μm, especially 1 １〜100 μm. Note that the minute region is usually present in the polarization scattering plate in the state of a domain,
The length in the Δn2 direction or the like is not particularly limited.

The ratio of the minute area in the polarized light scattering plate is as follows:
Δn1 can be appropriately determined from the viewpoint of scattering properties in the direction,
Generally, the content is 0.1 to 70% by weight, preferably 0.5 to 50% by weight, particularly 1 to 30% by weight in consideration of the film strength and the like.

The polarized light scattering plate can be formed of a single layer of a film exhibiting the above-described birefringence characteristics, or can be formed as a laminate of two or more such films. By superimposing the films, a synergistic scattering effect of increasing the thickness or more can be exerted.

The above-mentioned superimposed body may be obtained by superposing the films at an arbitrary arrangement angle such as the △ n1 direction or the △ n2 direction. It is preferable that the layers are overlapped so as to be in a parallel relationship. The number of superimposed films can be an appropriate number of two or more layers.

The film to be superimposed is Δn1 or Δn
2 and the like may be the same or different. The parallel relationship between the upper and lower layers in the Δn1 direction and the like is preferably as parallel as possible, but deviation due to a work error is allowed. If there is variation in the △ n1 direction or the like, it is based on the average direction.

The film in the superposed body is bonded via an adhesive layer or the like so that the total reflection interface is the outermost surface.
For the bonding, for example, a suitable adhesive such as a hot melt type or an adhesive type can be used. From the viewpoint of suppressing the reflection loss, an adhesive layer having a refractive index difference as small as possible from the film is preferable, and the film and the polymer forming the minute region thereof can be bonded.

The polarizing light guide plate according to the present invention uses a laminate of a light-transmitting resin plate and a polarization scattering plate. When the light-guiding plate is formed, as shown in FIG. In order to suppress reflection at the interface with the scattering plate as much as possible, that is, to facilitate transmission of transmission light between the light-transmitting resin plate and the polarized light scattering plate, the surface of the laminated body composed of a close-adhesive body is easily formed. In order to achieve total reflection on the back surface, it is preferable that the adhesive is bonded with an adhesive having a refractive index as close as possible. The bonding process is
This is more effective than the prevention of misalignment of the shaft relationship.

The above-mentioned bonding treatment is carried out by appropriately bonding a transparent adhesive such as an acrylic, silicone, polyester, polyurethane, polyether, or rubber based on the above-mentioned superposition type polarizing scattering plate. An agent can be used, and there is no particular limitation. From the viewpoint of preventing a change in optical properties, a material that does not require a high-temperature process for curing and drying and does not require long-time curing or drying treatment is preferable. Further, a material which does not cause a peeling problem such as floating or peeling under heating or humidifying conditions is preferable.

In view of the above, an alkyl ester of (meth) acrylic acid having an alkyl group having 20 or less carbon atoms, such as a methyl group, an ethyl group, or a butyl group, and (meth) acrylic acid or hydroxy (meth) acrylate. An acrylic monomer composed of an improving component such as ethyl was added to a glass transition temperature of 0.
Acrylic pressure-sensitive adhesives having a weight average molecular weight of 100,000 or more and having an acrylic polymer as a base polymer, which is obtained by copolymerization in a combination of not more than ° C, are preferably used. Acrylic pressure-sensitive adhesives also have the advantage of being excellent in transparency, weather resistance, heat resistance, and the like.

The attachment of the pressure-sensitive adhesive layer to the light-transmitting resin plate and / or the polarized light scattering plate can be performed by an appropriate method. Examples thereof include dissolving or dispersing an adhesive component in a solvent consisting of an appropriate solvent alone or a mixture such as toluene or ethyl acetate to prepare an adhesive liquid of about 10 to 40% by weight, A method of directly attaching on a light-transmitting resin plate or a polarizing scattering plate by an appropriate development method such as a rolling method or a coating method, or forming an adhesive layer on a separator according to the above and forming it on a light-transmitting resin plate. And a method of transferring the light onto a polarizing scattering plate. The provided adhesive layer may be a superposed layer of different compositions or types.

The thickness of the adhesive layer can be appropriately determined according to the adhesive strength and the like, and is generally from 1 to 500 μm. The adhesive layer, if necessary, for example, natural or synthetic resins, glass fibers or glass beads, fillers or pigments made of metal powder or other inorganic powder, etc. Additives can also be included. Further, an adhesive layer showing light diffusing properties may be formed by incorporating fine particles.

In forming the laminate of the light-transmitting resin plate and the polarization scattering plate in the above, the average slow axis direction of the light-transmitting resin plate and the polarization scattering are considered in order to efficiently eliminate the polarization state of the transmitted light. It is preferable to arrange the plate so that the optical axis direction (the direction of the plane of oscillation of the output polarized light) has an intersection angle of 5 degrees or more, particularly 10 to 80 degrees, particularly 15 to 75 degrees. When forming the polarized light guide plate, as shown in FIG.
The polarizing scattering plate 3 can be provided on both the front and back surfaces of the above.

As shown in FIG. 1, a specular reflection layer 5 provided on one surface of a laminate 4 of a light-transmitting resin plate 1 and a polarization scattering plate 3 polarizes light emitted from the side where the reflection layer is disposed via the specular reflection layer. It is an object of the present invention to improve the brightness by inverting the emitted light without changing the state and concentrating the emitted light on one of the front and back surfaces of the polarizing light guide plate.

The reflecting layer is preferably a mirror surface as much as possible from the viewpoint of maintaining the polarization state, and a reflecting surface made of metal is particularly preferable from this point. As the metal, for example, an appropriate material such as aluminum, silver, chromium, gold, copper, tin, zinc, indium, palladium, platinum, or an alloy thereof can be used.

The specular reflection layer can be directly adhered to the laminate as an additional layer of a metal thin film by a vapor deposition method or the like. However, complete reflection is difficult, and a slight absorption by the reflection layer also occurs, and repetition due to total reflection is taken into consideration. Then, there is a concern about absorption loss, and it is preferable to use an arrangement method in which an air layer in which the reflectors are simply stacked is interposed, rather than preventing the loss.

Accordingly, from this point of view, the specular reflection layer may preferably be a plate-like material such as a reflector having a metal thin film provided on a supporting substrate by a sputtering method or a vapor deposition method, or a metal foil or a rolled metal sheet. . An appropriate material such as a glass plate or a resin sheet can be used as the supporting base material of the above-mentioned reflective layer. Above all, silver, aluminum, and the like, which are deposited on a resin sheet, can be preferably used in terms of reflectance, color, handling, and the like. Note that the reflective layer may be disposed on either side of the laminate.

The polarized light guide plate according to the present invention can be preferably used for forming a polarized surface light source because it exhibits the characteristic that incident light from the side surface is emitted as linearly polarized light from one of the front and back surfaces as described above. The polarization plane light source can be formed by arranging the light source 6 on at least one side surface of the polarization light guide plate as illustrated in FIG.

As the light source, for example, a (cold, hot) cathode tube, which can be disposed on the side surface of the polarizing light guide plate,
Appropriate devices such as a linear or planar array body such as a light emitting diode and an incandescent bulb can be used. In particular, a cold cathode tube can be preferably used in terms of luminous efficiency, low power consumption, small diameter, and the like. The light source may be arranged on a plurality of side surfaces such as two opposing side surfaces of the polarizing light guide plate or three side surfaces of a U-shaped tube or the like in view of brightness and uniformity thereof.

In forming the polarization plane light source, if necessary, appropriate auxiliary means such as a reflector 61 surrounding the light source 6 are arranged to guide the divergent light from the light source to the side surface of the polarization light guide plate as shown in the figure. You can also. For the reflector, a resin sheet or a metal foil provided with a metal thin film having a high reflectance is generally used. In addition, a reflector may be provided on the lower surface of the polarization light guide plate to serve also as a mirror reflection layer. The reflector is also useful as a light source fixing means or the like.

In forming the polarizing plane light source, one or two or more of the same or different optical layers can be arranged at appropriate positions. The optical layer is not particularly limited, and for example, an appropriate layer used for forming a light diffusion layer, a lens sheet, a polarizing plate, a retardation plate, a liquid crystal display device such as a liquid crystal cell, or the like can be used. Such an optical layer is usually disposed on the light emission side of the polarizing light guide plate, that is, on the side having no specular reflection layer, and an example is shown in FIG. In this polarization plane light source, a light diffusion layer 7 and a lens sheet 8 are arranged on the light emission side of a polarization light guide plate.

The light diffusing layer is arranged as necessary for the purpose of uniforming luminance by diffusing outgoing light and improving visibility by alleviating visual irregularities of the lens sheet uneven pattern. Also, the lens sheet controls the optical path of the scattered outgoing light (linearly polarized light) from the polarizing light guide plate to improve the directivity in the frontal direction, which is advantageous for visual recognition, and makes the intensity peak of the scattered outgoing light equal to the frontal direction. It is arranged as needed for the purpose of doing.

In the present invention, since the linearly polarized light emitted from the polarizing light guide plate is effectively used, the optical layer disposed on the light emitting side of the polarizing light guide plate, particularly, when the polarizing plate is provided, the polarizing plate and the polarizing light guide are disposed. As the optical layer disposed between the optical plates, one having excellent light transmittance and maintaining the linearly polarized state (degree of polarization) of the emitted light as much as possible is preferably used.
In particular, the total light transmittance is 80% or more, particularly 85% or more, particularly 90% or more, and the leakage light (transmittance) due to depolarization when placed between crossed Nicols is 5% or less, especially 2%. Hereinafter, it is particularly preferable that the optical layer is 1% or less.

In view of the fact that the above-described polarization cancellation is usually caused by birefringence or multiple scattering, the optical layer exhibiting the polarization maintaining property should reduce birefringence as much as possible, This can be achieved by, for example, reducing the number of average reflections (scatterings). From this point, in forming the optical layer, a resin having low birefringence (resin having good optical isotropy) such as cellulose triacetate resin, polymethyl methacrylate, polycarbonate or norbornene resin is used. preferable. One or more resins can be used.

Incidentally, the light diffusion layer having excellent polarization maintaining properties is
For example, it can be obtained as a material having a fine concavo-convex structure on the surface by an appropriate method such as a method in which transparent particles are dispersed and contained in a layer made of a resin having a small birefringence or a method in which a resin layer is roughened. The transparent particles include, for example, silica or glass, alumina, titania or zirconia, tin oxide or indium oxide, inorganic fine particles that may be conductive such as cadmium oxide or antimony oxide, or acrylic polymer or polyacrylonitrile, Organic fine particles such as polyester or epoxy resin, melamine resin or urethane resin, polycarbonate or polystyrene, silicone resin or crosslinked or uncrosslinked polymer such as benzoguanamine, melamine / benzoguanamine condensate or benzoguanamine / formaldehyde condensate, etc. May be used alone or in combination of two or more.

The particle size of the transparent particles is preferably 1 to 20 μm from the viewpoints of light diffusivity and uniformity of the diffusion. Although the particle shape is arbitrary, a (true) spherical shape or a secondary aggregate thereof is generally used. Particularly, transparent particles having a refractive index ratio of 0.9 to 1.1 with respect to the resin can be preferably used from the viewpoint of the polarization maintaining property.

The light-diffusing layer containing transparent particles is formed, for example, by mixing transparent particles with a resin melt and extruding the mixture into a sheet or the like, or by mixing the resin solution or monomer with the transparent particles and casting the mixture into a sheet or the like. It can be formed by an appropriate method according to the related art, such as a method of performing a polymerization treatment as needed, or a method of applying a resin liquid containing transparent particles to a predetermined surface or a polarization-maintaining support film.

The light diffusion layer having a rough surface having a fine surface irregularity structure is formed by, for example, a method of roughening the surface of a resin sheet by buffing or embossing with sand blasting or the like. Can be formed by an appropriate method such as a method of forming a layer of a light-transmitting material having However, a method of forming irregularities (projections) having a large difference in refractive index from bubbles such as air or a resin such as titanium oxide fine particles is not preferable because polarized light can be easily eliminated.

The fine uneven structure on the surface of the light diffusing layer is formed from irregularities having a surface roughness of not less than the wavelength of incident light and not more than 100 μm and having no periodicity in terms of light diffusivity and uniformity of the diffusion. Are preferred. When forming the transparent particle-containing type or rough surface type light diffusion layer described above, it is necessary to minimize the occurrence of an increase in retardation due to photoelasticity and orientation in the base layer made of the resin. It is preferable from the viewpoint of maintainability and the like.

On the other hand, the lens sheet controls the optical path of the scattered light incident from one surface (back surface) so that the scattered light is efficiently emitted from the other surface (front surface) in a direction as perpendicular (front) as possible to the sheet surface. Any suitable one can be used. Therefore, except for the polarization maintaining property, any of various lens forms used in the conventional sidelight type light guide plate can be used (for example, Japanese Patent Application Laid-Open No. 5-169015).

In particular, one or both sides of the sheet 8 as shown in FIG.
In particular, a lens having a lens configuration 81 having an uneven structure on one surface can be preferably used. The concavo-convex structure forming the lens form may be any as long as it has a function of controlling the optical path of the light transmitted through the sheet and condensing the transmitted light in the front direction.

Incidentally, examples of the above-mentioned uneven structure include those in which a large number of linear grooves or projections having a triangular cross section or the like are arranged in a stripe shape or a lattice shape, or a bottom surface such as a triangular pyramid, a quadrangular pyramid, or another polygonal pyramid or a cone. One in which a large number of conical small protrusions having a shape are arranged in a dot-like manner may be used. The linear or dot-like uneven structure may be a spherical lens, an aspherical lens, a semi-cylindrical lens, or the like, and may have an appropriate lens form.

The above-mentioned lens sheet having a linear or dot-like uneven structure can be formed, for example, by filling a mold formed so as to form a predetermined uneven structure with a resin liquid or a monomer for forming a resin. An appropriate method such as a method of transferring the concavo-convex structure of the mold by polymerization treatment or a method of transferring the concavo-convex structure by heat-pressing a resin sheet to the mold and transferring the concavo-convex structure can be used. The lens sheet may be formed as an overlapping layer of two or more resin layers of the same or different types, such as a sheet obtained by adding a lens form to a support sheet.

As described above, one or two or more optical layers such as a light diffusion layer and a lens sheet can be arranged on the light exit side of the polarizing light guide plate. When two or more layers of the same type are arranged, the same layer is used. Alternatively, different materials may be used, but it is preferable to maintain the polarization maintaining properties as a whole.

In the arrangement of the optical layer, the optical layer adjacent to the polarizing light guide plate can be adhered through an adhesive layer or the like. Is preferably arranged so that Preferably, the gap is sufficiently larger than the wavelength of the incident light than the point of total reflection.

The optical layer which is not adjacent to the polarizing light guide plate may be subjected to an adhesion treatment via an adhesive layer or the like, if necessary. However, it is preferable that the optical layer having irregularities on the surface, such as the above-mentioned light diffusion layer having a fine irregularities on the surface or a lens sheet having an irregular structure, be arranged with the above-mentioned voids. Therefore, an optical layer such as a light diffusion layer can be arranged as an independent layer of a plate-like object or the like, or can be arranged as a subordinate layer that is tightly integrated with another optical layer.

When the light diffusion layer 7 and the lens sheet 8 are used together as shown in FIG. 3, one or more light diffusion layers are disposed between the lens sheet and the polarizing light guide plate and / or on the light exit side of the lens sheet. can do. For a lens sheet having a lens form having a linear concavo-convex structure,
From the viewpoint of controlling the optical path in the front direction, it is preferable to arrange the polarization scattering plate so that its linear direction is parallel or orthogonal to the optical axis direction of the polarization scattering plate. Further, when two or more such lens sheets are arranged, it is preferable to arrange them so that the line directions of the upper and lower layers intersect from the viewpoint of the efficiency of optical path control.

In the present invention, each layer forming the polarizing light guide plate or the polarizing surface light source may be provided with, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, a nickel complex compound, etc., if necessary. An ultraviolet absorbing agent can be blended to have an ultraviolet absorbing ability.

The polarized light guide plate and the polarized light source according to the present invention
Since the linearly polarized light is provided in a state where the vibration plane (polarization axis) is controlled as described above, an appropriate device or application utilizing the linearly polarized light, such as formation of a liquid crystal display device, based on its features. Can be used.

[0084]

EXAMPLE 1 950 parts (parts by weight, hereinafter the same) of a norbornene resin (arton, glass transition temperature: 182 ° C., manufactured by JSR Corporation) and a liquid crystal polymer represented by the following formula (glass transition temperature: 80 ° C., nematic liquid crystal) A 100-μm-thick film was formed by a casting method using a 20% by weight dichloromethane solution in which 50 parts of a solution was dissolved.
After a stretching treatment at a temperature of 3 ° C., the film was rapidly cooled to obtain a polarized light scattering plate.

The above-mentioned polarization scattering plate comprises a transparent film made of a norbornene resin in which a liquid crystal polymer is dispersed in a domain having substantially the same shape in a state of having a long axis in a stretching direction, and has a refractive index difference Δn1 of 0. .23, Δn2 and Δn3 were 0.029. Further, when the average diameter of the minute region was measured by coloring based on the phase difference by observation with a polarizing microscope, the length in the Δn1 direction was about 5 μm.

Next, the above-mentioned polarized light scattering plate was bonded to one surface of a commercially available polycarbonate plate having a thickness of 2 mm with an acrylic adhesive layer interposed therebetween so that the Δn1 direction had a 45 ° intersection angle with the end face to form a laminate. A polarizing light guide plate is obtained by arranging a mirror-reflective sheet obtained by depositing silver on a PET sheet on the lower surface thereof, and fixed on one side of the laminate by a lamp reflector composed of a PET-based reflective sheet in which a cold-cathode tube is matted. As a result, a polarizing surface light source was obtained. The average in-plane retardation of the polycarbonate plate is 80 nm, and the average slow axis direction is parallel to the end face (0 degree direction).

Comparative Example 1 A commercially available acrylic resin plate having a thickness of 2 mm was printed on one surface with reflection ink mixed with titanium white in the form of dots.
A surface light source was obtained in the same manner as in Example 1 except that a light guide plate provided with a white reflector made of ET was used.

Comparative Example 2 A polarized light guide plate and a polarized surface light source were obtained in the same manner as in Example 1 except that an acrylic resin plate (in-plane average retardation: 5 nm or less) was used instead of the polycarbonate plate.

Evaluation Test A commercially available absorption-type polarizing plate was arranged on the (polarized) surface light source obtained in each of the examples and comparative examples so that the transmission axis was at 45 degrees, and the luminance in the front direction was visually compared. However, Example 1> Comparative Example 2
> The order was that of Comparative Example 1, and the difference in luminance could be clearly seen visually. Further, the luminance difference between Comparative Example 2 and Comparative Example 1 was clearly larger than the luminance difference between Example 1 and Comparative Example 2.

In the case where no polarizing plate is provided, the luminance in the frontal direction of Example 1 and Comparative Examples 1 and 2 is almost the same, it is difficult to distinguish them, and the polarizing plate is provided. From the luminance difference between Example 1 and Comparative Example 1 in this case, it can be seen that in Example 1, linearly polarized light was emitted and the luminance when passing through the polarizing plate was dramatically improved. From the above, it can be seen that the use of the polarizing surface light source according to the present invention as a backlight of a liquid crystal display device significantly improves the luminance and achieves a very bright display.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of a polarized plane light source.

FIG. 2 is a cross-sectional view of another example of the polarized light guide plate.

FIG. 3 is a cross-sectional view of another example of a polarization plane light source.

[Explanation of symbols]

 4: Laminated body 1: Translucent resin plate 2: Adhesive layer 3: Polarized light scattering plate 5: Specular reflection layer 6: Light source 7: Light diffusion layer 8: Lens sheet

Continued on the front page F-term (reference) 2H038 AA55 BA06 2H049 BA02 BA44 BB06 BC22 2H091 FA07Z FA16Z FA23Z FA32Z FA42Z FB02 FC17 FD06 LA17 LA18 4F100 AK01B AK41 AK45 AK80 AL05 AR00A AR00C AR00J10 BA05D10 BA00N JN10C JN18B JN30A JN30C

Claims (4)

[Claims] 1. A laminated body comprising a birefringent light-transmitting resin plate and a polarizing scattering plate provided on one or both sides of the birefringent light-transmitting resin plate and containing a birefringent fine region in a dispersed manner and exhibiting scattering anisotropy depending on the polarization direction. A polarized light guide plate having a specular reflection layer on one surface. 2. The method according to claim 1, wherein the phase difference due to the birefringence of the translucent resin plate is 50 nm based on the in-plane average phase difference.
The polarized light guide plate described above. 3. The polarizing light guide plate according to claim 1, wherein the average slow axis direction of the light-transmitting resin plate in the laminate and the optical axis direction of the polarization scattering plate have an intersection angle of 5 degrees or more. 4. A polarized light source comprising a light source provided on at least one side of the polarized light guide plate according to claim 1.