JPH1152133A - Elliptic polarizing element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an elliptic polarizing element capable of forming a liquid crystal display device which lessens the reflection loss of light, is excellent in utilization efficiency of light and is excellent in brightness and display grade. SOLUTION: The elliptic polarizing element 5 consists of a laminate formed by adhering a polarized light separating film 3 which consists of a cholesteric liquid crystal layer having parts indicating the max. value or min. value by inversion and change of a spiral pitch at the intermediate of the layer and a quarter-wave plate 4 via a tacky adhesive 2 having a stress relieving property and has a polarizing plate at need on the quarter-wave plate 4 side. The element has further a light transmission plate 1 which has a reflection 11 on the rear surface and emits light from the surface on the polarized light separating film 3 side. As a result, the polarized light separating film lessens the coloration of display by correcting the distortion in the reflection characteristic by a blue shift. The quarter-wave plate polarizes the circularly polarized light emitted therefrom to linearly polarized light. The reflection loss at the respective boundaries is lessened and the occurrence of the display unevenness by the heat from a light source is substantially prevented by the lamination and integration via the tacky adhesive layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an elliptically polarizing element excellent in light use efficiency and suitable for a transmission type liquid crystal display device and the like.

[0002]

BACKGROUND OF THE INVENTION Hitherto, there has been known a polarization separation film utilizing a characteristic that a cholesteric liquid crystal layer separates incident light into left and right circularly polarized lights, transmits one of them, and reflects the other.
Attempts have been made to use it to improve the brightness of liquid crystal displays. By the way, circularly polarized light by the polarization separation film can be converted to linearly polarized light by transmitting through a 1/4 wavelength plate.
By making the vibration direction coincide with the transmission axis, the absorption loss by the polarizing plate can be reduced, and the brightness of the liquid crystal display can be improved by increasing the amount of transmitted light.

[0003] However, the blue shift characteristic of the cholesteric liquid crystal layer, that is, the wavelength of light obliquely incident on the cholesteric liquid crystal layer shifts to the short wavelength side and is transmitted, so that the elliptically polarizing element using the polarization separation film can be used as a liquid crystal. When applied to a display device, there is a problem that the display in the oblique direction is colored by a blue shift, thereby deteriorating the display quality.

[0004]

SUMMARY OF THE INVENTION The present invention relates to an elliptically polarizing element capable of forming a liquid crystal display device which has a small reflection loss of light, is excellent in light use efficiency, is less likely to be colored by blue shift, and is excellent in brightness and display quality. Development is an issue.

[0005]

According to the present invention, there is provided a polarized light separating film comprising a cholesteric liquid crystal layer having a portion in which the helical pitch is inverted and changed to show a maximum value or a minimum value in the middle of the layer, and a quarter-wave plate. It consists of a laminate bonded via an adhesive layer with excellent stress relaxation properties, has a polarizing plate on the quarter wavelength plate side if necessary, and further has a reflective layer on the back surface on the polarization separation film side if necessary. An elliptically polarizing element having a light guide plate that emits light from the surface.

[0006]

According to the above construction, the polarized light separating film comprises:
Light incident through the light guide plate or the like is separated into left and right circularly polarized lights, one of which is transmitted, and the other is reflected. As a result, the reflected light is confined between the polarization separation film and the reflection layer of the light guide plate,
In the meantime, while being repeatedly reflected, it is converted into a predetermined circularly polarized light and can be transmitted through the polarization separation film, and is emitted together with the circularly polarized light in the predetermined state from the beginning in the incident light,
This reduces the amount of unused light due to reflection loss.

On the other hand, the circularly polarized light emitted from the polarized light separating film is converted into a state having a large amount of linearly polarized light components such as linearly polarized light and flat elliptically polarized light through a quarter-wave plate. When the direction of the linearly polarized light coincides with the transmission axis of the polarizing plate, the converted light passes through the polarizing plate without being absorbed, thereby reducing unused light due to absorption loss. As a result, light that has conventionally been a reflection loss or an absorption loss can be effectively used, and the light use efficiency can be improved.

In the above, in the elliptically polarizing element of the present invention,
Since the polarization separation film is made of a cholesteric liquid crystal layer having a helical pitch characteristic of a quadratic curve showing a maximum value or a minimum value, it is possible to correct the distortion of the reflection characteristic due to the blue shift and reduce the coloring of the display. it can. This result is surprising because, in the past, a helical pitch characteristic of a unidirectional change such as a gradual decrease or a gradual increase has been preferred,
The mechanism for suppressing blue shift is also unknown.

On the other hand, by laminating and integrating through an adhesive layer, reflection loss at each interface is small, foreign matter and the like can be prevented from entering the interface, and deterioration in display quality can be prevented. The conversion efficiency can be prevented from lowering. In addition, by laminating and unifying through an adhesive layer that is excellent in stress relaxation, the stress generated in the polarization separation film, quarter-wave plate, and even the polarizing plate due to heat from the light source can be suppressed, and the refractive index generated by photoelastic deformation Can be prevented from changing. As a result of the above,
A liquid crystal display device which is bright and has excellent visibility and reliability of display quality can be formed.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The elliptically polarizing element of the present invention comprises a cholesteric liquid crystal layer having a cholesteric liquid crystal layer having a portion where the helical pitch reversely changes and shows a maximum value or a minimum value in the middle of the layer, and a quarter-wave plate. It consists of a laminate bonded via an adhesive layer with excellent stress relaxation properties, has a polarizing plate on the quarter wavelength plate side if necessary, and further has a reflective layer on the back surface on the polarization separation film side if necessary. And a light guide plate that emits light from the surface.

FIGS. 1 and 2 show an elliptically polarizing element 5 according to the present invention.
Was exemplified. 2,20,21,22,23,24 are adhesive layers, 3 is a polarization separation film, 4 is a quarter wavelength plate,
1 is a light guide plate as needed, and 6 is a polarizing plate as needed. As shown in FIG. 2, the polarization separation film 3 may be formed as a superimposed layer of a plurality of cholesteric liquid crystal layers 31, 32, and 33, and the quarter-wave plate 4 may be formed of a superimposed layer of a plurality of retardation layers 42 and 43. It may be formed as.

According to the elliptically polarizing element 5 in which the light guide plate 1 of the above-described example is arranged, predetermined circularly polarized light of the light emitted from the surface of the light guide plate 1 is converted into the polarized light separating film 3 arranged on the surface side of the light guide plate. And is transmitted to the outside via the ４ wavelength plate 4. On the other hand, non-predetermined circularly polarized light is reflected by the polarization separation film 3, and the reflected light is re-incident on the light guide plate, is reflected through the reflection layer 11 on the back surface, and re-enters the polarization separation film 3 as return light. .

The light reflected by the polarization splitting film is:
When the light is reflected by the back surface of the light guide plate, the polarization state is changed, and a part or all of the reflected light becomes a predetermined circularly polarized light that can pass through the polarization splitting film. Therefore, the light reflected by the polarized light separating film is confined between the polarized light separating film and the light guide plate until the light becomes a predetermined circularly polarized light that can pass through the polarized light separating film, and the light is repeatedly reflected between them.

On the other hand, the circularly polarized light emitted from the polarization splitting film enters the quarter-wave plate 4 and undergoes a phase change. Light having a wavelength corresponding to the quarter-wavelength change is converted into linearly polarized light. , Light of other wavelengths are converted to elliptically polarized light.
The elliptically polarized light becomes flatter elliptically polarized light as it approaches the wavelength of the light converted into the linearly polarized light. As a result, light containing a large amount of linearly polarized light component that can be transmitted through the polarizing plate is emitted from the quarter-wave plate.

In the present invention, the polarized light separating film and 1 /
The components of the four-wavelength plate and, if necessary, the light guide plate and the polarizing plate are laminated and integrated via an adhesive layer having excellent stress relaxation properties. In that case, the light guide plate 1 is arranged so that its surface (light emission) side is located on the polarization separation film 3 side of the elliptically polarizing element 5. The polarizing plate 6 is arranged on the quarter wavelength plate 4 side.

As the polarized light separating film, as shown in FIG. 3, a film composed of a cholesteric liquid crystal layer having a portion where the helical pitch reversely changes and shows a maximum value or a minimum value in the middle of the layer is used. According to the cholesteric liquid crystal layer, the left and right circularly polarized light can be selectively separated into either one of the two through transmission and reflection, and has an advantage of a wide viewing angle.
In the case of a cholesteric liquid crystal layer, a change in optical characteristics with respect to a change in viewing angle is small, and thus the cholesteric liquid crystal layer is suitable for a direct-view type liquid crystal display device that can be directly observed even from an oblique direction.

As the cholesteric liquid crystal, an appropriate one can be used, and there is no particular limitation. The use of a liquid crystal polymer is advantageous from the viewpoint of the superposition efficiency of the liquid crystal layer and the thinning of the liquid crystal layer. Cholesteric liquid crystal molecules having a large birefringence are preferable because the wavelength range of the selective reflection is widened. Examples of the polarization separation film that can be preferably used include a film made of a cholesteric liquid crystal polymer and a film provided with a layer made of a cholesteric liquid crystal polymer on a transparent substrate such as a film.

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

The cholesteric liquid crystal layer can be formed by a method according to a conventional alignment treatment. Incidentally, examples thereof include a film formed by forming a film of polyimide or polyvinyl alcohol on a substrate and rubbing with a rayon cloth or the like,
A liquid crystal polymer is spread on an appropriate alignment film composed of an obliquely deposited layer of iO ₂ and heated to a temperature equal to or higher than the glass transition temperature and lower than the isotropic phase transition temperature. A method of cooling to a glass state by cooling to a temperature lower than the temperature to form a solidified layer in which the orientation is fixed is exemplified.

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

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

The thickness of the cholesteric liquid crystal layer is from 0.5 to 100 μm, preferably from 1 to 100 μm, from the viewpoints of preventing alignment disorder and a decrease in transmittance, and selectively reflecting (wavelength range showing circular dichroism). 70 μm, particularly preferably 1 to 50 μm. The polarization separation film to be formed is preferably formed as a flat layer from the viewpoint of uniformization of separation performance including oblique incident light, and even when formed as two or more superposed layers, each layer is flat. Is preferable. When forming the cholesteric liquid crystal layer or the polarized light separating film, various additives such as stabilizers, plasticizers, and metals can be added as necessary.

A cholesteric liquid crystal layer having a cholesteric liquid crystal layer having a portion in which the helical pitch reversely changes and shows a maximum value or a minimum value in the middle of the layer can be formed, for example, by using a cholesteric liquid crystal layer having a different selective reflection center wavelength. A method of superimposing the cholesteric liquid crystal layer having a short selective reflection center wavelength on the long wavelength side of the superimposed layer and / or a selective reflection center on the short wavelength side of the superimposed layer based on the wavelength. It can be performed by a method in which a cholesteric liquid crystal layer having a long wavelength is superimposed.

The change in the helical pitch of the cholesteric liquid crystal layer forming the polarization splitting film increases from one end in the thickness direction toward the end on the quarter wavelength plate side as shown in FIG. After that, it may decrease, or as shown in FIG. 3B, １ ／ from one end in the thickness direction.
It may decrease toward the end of the wave plate and reach a minimum value and then increase, or may have both the maximum value portion and the minimum value portion.

The change in the helical pitch may be gradual as illustrated by the solid line and the imaginary line in FIG. 3, or may be continuous, or a combination of a gradual portion and a continuous portion. And so on. A helical pitch that changes stepwise can be obtained, for example, by a method of superimposing selective reflections having a difference in the wavelength range ends in a predetermined wavelength order.

On the other hand, in the case where the helical pitch changes continuously, for example, the above-mentioned superposed body in which the helical pitch changes stepwise is formed in a state where the cholesteric liquid crystal layers are directly in close contact with each other, and then the superposed body is heated. And a re-orientation treatment. That is, the wavelength range of the selective reflection is made to adhere the cholesteric liquid crystal polymer layers that are discontinuous to each other via thermocompression bonding or the like, and the width of the discontinuous wavelength range can be reduced by heating the cholesteric liquid crystal polymer layers. It is also possible to make the area continuous.

In order to form a cholesteric liquid crystal layer exhibiting a helical pitch characteristic exhibiting a maximum value or a minimum value by the above-described superposition method, it is necessary to superimpose three or more cholesteric liquid crystal layers. The upper limit of the number of superimpositions is not particularly limited, and is generally 50 layers or less, especially 20 layers or less, particularly 4 to 10 layers in terms of light transmittance (brightness) and the like.

The above-described superposition of the cholesteric liquid crystal layer is also effective in a case where the center function of light reflected as circularly polarized light other than a predetermined wavelength is superimposed in a different combination to broaden the wavelength separation function. That is, in a single cholesteric liquid crystal layer, there is usually a limit to a wavelength region showing selective reflection (circular dichroism), and the limit may be a wide range up to a wavelength region of about 100 nm. However, since it does not cover the entire range of visible light desired when applied to liquid crystal display devices, etc., in such a case, a cholesteric liquid crystal layer with different selective reflection is superimposed to expand the wavelength range showing circular dichroism. Can be done.

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

Therefore, as the polarized light separating film, a film in which the wavelength range of light that can be reflected as circularly polarized light outside the predetermined range matches as much as possible the wavelength range of emitted light based on the light guide plate can be preferably used. If the emitted light has a dominant wavelength such as a bright line spectrum, it is necessary to match the wavelength of the reflected light based on the cholesteric liquid crystal phase or the like to one or more dominant wavelengths such as efficiency of polarization separation. It is the next best solution from the point,
This is also advantageous for making the polarization separation film thinner by reducing the required number of superpositions. In this case, it is preferable that the degree of coincidence of the wavelengths of the reflected light is within a range of 20 nm or less for one or two or more types of main wavelength light of the light guide plate.

In the above, it has been pointed out that when the polarization separation film is formed as a superposed layer of the cholesteric liquid crystal layer, a combination of those which reflect circularly polarized light having the same polarization direction is used. This aligns the phase state of the circularly polarized light reflected by each layer to prevent different polarization states in each wavelength range,
The aim is to increase the available polarization. As described above, a suitable cholesteric liquid crystal may be used, but a cholesteric liquid crystal molecule having a larger phase difference has a wider wavelength range of selective reflection, such as a reduction in the number of layers and a margin for a wavelength shift at a large viewing angle. It can be preferably used from the point of view.

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

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

A quarter arranged on one side of the polarized light separating film
The wavelength plate is intended to change the phase of the circularly polarized light emitted from the polarization splitting film as described above to convert it into a state having a large amount of linearly polarized light components. Can be obtained.

Therefore, the quarter-wave plate can form a large amount of linearly polarized light corresponding to the phase difference of the quarter-wavelength circularly-polarized light emitted from the polarization separation film, and can convert the light of other wavelengths into the linearly-polarized light. Those having a major axis direction as parallel as possible to polarized light and capable of converting into flat elliptically polarized light as close to linearly polarized light as possible can be preferably used. By using such a 波長 wavelength plate, the linearly polarized light direction and the major axis direction of the elliptically polarized light of the emitted light can be arranged so as to be as parallel as possible to the transmission axis of the polarizing plate, and can be transmitted through the polarizing plate. Light with a large amount of linearly polarized light components can be obtained.

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

In some cases, the retardation layer is colored depending on the viewing angle, and from the viewpoint of preventing the coloring, the formula: N _z =
_{(N x -n z) / (} n x -n y) is defined by N _z is, N _z ≦
A quarter-wave plate made of a refractive index ellipsoid satisfying 1.1 can be preferably used. Note in the above formulas, n _x is the maximum refractive index in the plane of the retardation layer, n _y is a refractive index in a direction perpendicular to n _x direction, n _z denotes a refractive index in the thickness direction.

The quarter-wave plate is composed of a single-layer retardation layer or, as illustrated in FIG. 2, has a different phase difference for the purpose of expanding the wavelength range that can function as a quarter-wave plate. It can be obtained as a laminate of two or more retardation layers. Incidentally, as a superimposition type quarter-wave plate that can function as a quarter-wave plate in a wide range of visible light, for example, a retardation layer that gives a half-wave phase difference to light having a wavelength of 550 nm can be used. , A combination of a plurality of retardation layers in combination with a retardation layer providing a quarter-wave retardation, and a plurality of retardation layers superimposed with their optical axes crossing each other.

[0039] In the above, from the viewpoint of obtaining a quarter-wave plate of superposition type for preventing coloration due viewing angle, the N _z ≦ 1.
A retardation layer that provides a quarter-wave retardation that satisfies 1.
It is preferable to use a superimposed body using one or two or more retardation layers that provide a half-wave retardation.

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

Incidentally, specific examples of the above-mentioned polymer film include polycarbonate, polyester, polysulfone, polyethersulfone, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene and other polyolefins, cellulose acetate polymers, polyvinyl chloride, and polyvinyl chloride. Examples thereof include films made of a suitable transparent plastic such as arylate and polyamide.

In the present invention, the quarter-wave plate may have a roughened surface, if necessary, at least on the outer surface on the side of the polarizing plate.
It may be. The surface roughening is effective in preventing the occurrence of a spot pattern or color unevenness due to the sticking phenomenon due to the close contact between the elliptically polarizing element and the polarizing plate when the liquid crystal cell is arranged on the elliptically polarizing element via the polarizing plate. . The roughening of the surface of the quarter-wave plate can be performed on both the front and back surfaces of the quarter-wave plate, if necessary.

The surface roughening 41 of the quarter-wave plate can be performed, for example, by a method in which fine particles are dispersed and fixed on the surface of the quarter-wave plate via a binder or the like, a method in which fine particles are contained in the quarter-wave plate, It can be performed by giving a fine uneven structure to one or both surfaces by an appropriate method such as embossing or sand blasting the surface of the 波長 wavelength plate. Therefore, the rough surface of the quarter-wave plate may conform to the anti-glare treatment performed for the purpose of preventing glare on the viewing side of the liquid crystal display device.

The fine particles may have, for example, an average particle size of 0.3.
5-20 μm silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, inorganic fine particles which may be conductive such as antimony oxide, and organic fine particles such as crosslinked or uncrosslinked polymers. Can be used.

From the viewpoint of preventing the occurrence of spot patterns and color unevenness by preventing adhesion to the polarizing plate, the preferred rough surface of the quarter-wave plate has a center line average roughness (Ra).
And a roughness state of 1 μm or more based on 10-point average roughness (Rz). The same effect can be obtained by roughening the surface of the quarter-wave plate instead of or together with the method of roughening the surface of the polarizing plate.

In the elliptically polarizing element of the present invention, as shown in the drawing, the light guide plate, which is adhered and arranged as necessary on the polarization separation film side, has a reflective layer on the back surface and emits light to the front surface side. Any suitable one can be used. Preferably, one that efficiently emits light without absorption is used.

(Cold, hot) A linear light source such as a cathode ray tube or a light source such as a light emitting diode is disposed on the side surface of the light guide plate 1, and the light transmitted through the light guide plate is diffused, reflected or diffracted by the light guide plate. An example of the light guide plate is a side light type backlight known in liquid crystal display devices, which emits light to one side of the plate due to interference or the like.

In the above, the light guide plate which emits the internal transmission light to one side is provided with, for example, a dot-shaped or stripe-shaped diffuser on the light-emitting surface of a transparent or translucent resin plate or on the back surface thereof. It can be obtained as a substrate or a substrate having a concave and convex structure, particularly an array structure of fine prisms, provided on the back surface of a resin plate.

The light guide plate which emits light to one surface side can have a function of converting the light reflected by the polarization splitting film by itself, but by providing the reflection layer 11 on the back surface of the light guide plate. Reflection loss can be almost completely prevented. A reflection layer such as a diffuse reflection layer or a specular reflection layer is excellent in the function of converting the light reflected by the polarization separation film into a polarized light, and is preferable in the present invention.

Incidentally, in a diffuse reflection layer represented by an uneven surface or the like, the polarization states are randomly mixed based on the diffusion and form a state in which the polarization is eliminated. When a circularly polarized light is reflected, the polarization state of a mirror reflection layer represented by a metal layer made of a vapor deposited layer of aluminum, silver, or the like, a resin plate provided with the layer, a metal foil, or the like is inverted.

When the light guide plate is formed, a prism sheet for controlling the light emission direction, a diffusion plate for obtaining uniform light emission, a reflection means for returning leaked light, and a light source for emitting light from the light source to the light guide plate. It is also possible to provide a combination body in which one or two or more layers of appropriate auxiliary means such as a light source holder for guiding to the side face are arranged at predetermined positions as necessary. In addition, a prism sheet or a diffusion plate disposed on the surface side (light emission side) of the light guide plate, or dots provided on the light guide plate can function as polarization conversion means for changing the phase of reflected light by a diffusion effect or the like.

In the elliptically polarizing element of the present invention, the components of the polarized light separating film and the quarter-wave plate and, if necessary, the light guide plate and the polarizing plate are separated via an adhesive layer having excellent stress relaxation properties. It was bonded to form a laminate. When the materials forming the polarization separation film, the quarter-wave plate, the light guide plate, and the polarizing plate are not in a tightly integrated state but in a separated state, an adhesive layer that is also used for the tightly integrated state is preferably used. Can be

For the formation of the pressure-sensitive adhesive layer, a transparent pressure-sensitive adhesive having excellent stress relaxation properties is used, for example, using an appropriate polymer such as an acrylic polymer, a silicone polymer, polyester, polyurethane, polyether or synthetic rubber. sell. Above all, an acrylic pressure-sensitive adhesive can be preferably used in terms of optical transparency, pressure-sensitive adhesive properties, weather resistance and the like. The adhesive layer has a relaxation elastic modulus of 2 × 10 ⁵ to 1 × 10 ⁷ dyne / cm ² , especially from the viewpoint of preventing photoelastic deformation due to relaxation of internal stress generated inside the laminate due to heat. 2 × 10 ⁶ -8 ×
Those having 10 ⁶ dyne / cm ² are preferred.

Specific examples of the acrylic polymer forming the acrylic pressure-sensitive adhesive include methyl group, ethyl group, n-propyl group and isopropyl group, n-butyl group and 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, isodecanyl group, especially those having 2 to 2 carbon atoms. One or two or more esters of acrylic acid or methacrylic acid having 14 alkyl groups may be substituted with one or more
Examples thereof include those subjected to polymerization treatment together with one or more species.

Specific examples of the modifying monomer include:
2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate,
12-hydroxylauryl (meth) acrylate and (4-
Hydroxyl group-containing monomers such as hydroxymethylcyclohexyl) -methyl acrylate, acrylic acid and methacrylic acid, carboxyethyl acrylate and carboxypentyl acrylate, carboxyl group-containing monomers such as itaconic acid, maleic acid and crotonic acid, maleic anhydride and itaconic anhydride Acid anhydride monomers such as
Examples thereof include sulfonic acid group-containing monomers such as acrylamide-2-methylpropanesulfonic acid, and phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate.

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

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

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

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

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

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

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

The thickness of the adhesive layer may be determined as appropriate. Generally, the thickness is 1 to 500 μm, particularly 2 to 200 μm, particularly 5 to 100 μm from the viewpoint of adhesive strength and thinning. If necessary, a tackifier such as petroleum resin, rosin resin, terpene resin, coumarone indene resin, phenol resin, xylene resin, alkyd resin, phthalate ester or phosphorus An appropriate additive such as an acid ester, a softening agent such as chlorinated paraffin, polybutene, or polyisobutylene, or other various fillers or an antioxidant can be blended.

The elliptically polarizing element is formed by, for example, transferring a pressure-sensitive adhesive layer provided on a separator obtained by surface-treating a thin film such as a film with a release agent to the bonding surface of the polarization separation film, and then forming a ４ It can be performed by a method in which a wave plate is arranged and pressed.

An adhesive layer provided on a parator is transferred to an adhesive surface of a light guide plate or the like, and a polarization separation film is disposed thereon and pressed, and then the adhesive layer is transferred thereon in the same manner. 1
A system in which a quarter-wave plate or a polarizing plate is arranged and pressure-bonded sequentially, or an adherend such as a polarization separation film, a quarter-wave plate, a polarizing plate, or a light guide plate via an adhesive layer provided on a predetermined adhesive surface in advance. Are laminated in a predetermined order, and the laminate is press-processed and pressure-bonded collectively.

In the present invention, the processing order and the like are not particularly limited, except that the components forming the elliptically polarizing element are bonded and laminated in a predetermined arrangement order via a predetermined adhesive layer. The elliptically polarizing element may be formed in a manner.
In addition, even when the polarization separation film, the quarter-wave plate, the light guide plate, the polarization plate, and the like are formed of a plurality of separation materials, it is preferable to form them as an integrated adhesive through an adhesive layer.

As described above, the elliptically polarizing element of the present invention is used in combination with an appropriate light source, such as a light guide plate, to convert the circularly polarized light reflected by the polarization separation film into a polarized light, and to reuse the converted light as the outgoing light. Loss is prevented, the output light is phase-controlled through a quarter-wave plate, and converted to a state containing a linearly polarized component that is transparent to the polarizer, thereby preventing absorption loss by the polarizer and improving light use efficiency. It is intended to be able to measure improvement.

Therefore, it is possible to provide light that is excellent in light use efficiency and easily transmit through a polarizing plate, and it is easy to enlarge the area. Therefore, it is preferably used in various devices as a backlight system in a liquid crystal display device or the like. Can be. In this case, 65% or more, especially 7%, of the linearly polarized light component that can be transmitted through the polarizing plate as linearly polarized light or elliptically polarized light in the major axis direction is used, rather than using the light emitted from the quarter wavelength plate as a light source.
It is preferable to contain 0% or more.

FIG. 4 illustrates a liquid crystal display device using the elliptically polarizing element of the present invention in a backlight system. this is,
The light source 12 is provided on the side surface of the light guide plate 1 provided on the elliptically polarizing element 5 to form a backlight system. 6, 61 are polarizing plates, 7 is a liquid crystal cell, and 13, 15, 25, 26, 2
7 and 28 are adhesive layers, 14 and 9 are light diffusion plates, 16 is a prism sheet, and 8 is a retardation film. As shown in the figure, the liquid crystal cell is arranged on the side of the 楕 円 wavelength plate 4 in the elliptically polarizing element.

A liquid crystal display device is generally formed by appropriately assembling components such as a polarizing plate, a liquid crystal cell, a backlight, and, if necessary, a compensating retardation film and incorporating a driving circuit. In the present invention, there is no particular limitation except that the liquid crystal cell is provided on the ４ wavelength plate side of the elliptically polarizing element via a polarizing plate, and a liquid crystal display device can be formed according to the conventional method. It is preferable that they are bonded and integrated via an adhesive layer. As shown in FIG. 4, the elliptically polarizing element of the present invention comprises polarizing plates 6 and 61 on both sides of the liquid crystal cell 7.
Can be particularly preferably used for forming a liquid crystal display device having

The elliptically polarizing element of the present invention can be preferably used for a liquid crystal cell in which light in a polarized state needs to be incident, for example, a liquid crystal cell using a twisted nematic liquid crystal or a super twisted nematic liquid crystal. And a guest-host type liquid crystal in which a dichroic substance is dispersed in a liquid crystal, or a liquid crystal using a ferroelectric liquid crystal. There is no particular limitation on the driving method of the liquid crystal.

In forming a liquid crystal display device, for example, a light diffusion plate or an anti-glare layer provided on a polarizing plate on the viewing side,
Appropriate optical elements such as an antireflection film, a protective layer or a protective plate, or a compensating retardation plate provided between the liquid crystal cell and the polarizing plate on the viewing side or / and the backlight side can be appropriately disposed.

The light diffusing plate is intended to diffuse light and homogenize luminance, expand the direction of light emission, and the like. Therefore, the light diffusion plate, for example, such as a polarization separation film or the upper surface of the light guide plate,
One layer or two or more layers can be arranged at appropriate positions on the surface or inside of the elliptically polarizing element. As a light diffusion plate, 1 /
Any suitable material such as a transparent film having a diffusion structure by an appropriate method such as a fine uneven structure exemplified by a four-wavelength plate or a diffusion structure exemplified by a light guide plate can be used, and any known light diffusion plate can be used. . The compensating retardation plate is used for compensating birefringence of a liquid crystal cell or the like to prevent coloring of a display and the like, and can be obtained as a stretched film or the like according to the above-described quarter-wave plate.

As shown in FIG. 2, the polarizing plate 6 provided on the elliptically polarizing element 5 as necessary may be provided on the liquid crystal cell side. When arranging the liquid crystal cell and the elliptically polarizing element via the polarizing plate, the arrangement angle of the polarizing axis of the polarizing plate with respect to the fast axis or slow axis of the quarter-wave plate is determined by the phase difference characteristic of the quarter-wave plate or the like. Although it can be appropriately determined according to the characteristics of the circularly polarized light incident thereon, the transmission of the linearly polarized light through the quarter-wave plate with respect to the polarization direction of the light through the quarter-wave plate from the viewpoint of improving the light use efficiency. It is preferable to arrange the axes as parallel as possible.

In the present invention, an adhesive layer for forming an elliptically polarizing element, a polarization separation film, a quarter-wave plate, or other components such as a light guide plate, a polarization plate, a retardation plate, and a light diffusion plate may be used. For example, salicylic acid ester compounds, benzophenol compounds, benzotriazole compounds,
Ultraviolet absorbing ability can be provided by a method of treating with an ultraviolet absorbing agent such as a cyanoacrylate compound or a nickel complex compound.

[0076]

【Example】

Example 1 A cold cathode tube having a diameter of 2.4 mm was arranged on a side surface of a light guide plate having a thickness of 3 mm made of polymethyl methacrylate provided with a reflective layer made of an Al vapor-deposited layer on the back surface. After surrounding the side and the cold cathode tube, a polarizing separation film showing selective reflectivity in the wavelength range of 400 to 700 nm and a quarter-wave plate are sequentially arranged on the surface of the light guide plate via an acrylic adhesive layer having a thickness of 20 μm. Then, the resultant was press-pressed and laminated and integrated to obtain an elliptically polarizing element. The polarization separation film is composed of a cholesteric liquid crystal layer in which the helical pitch increases from the light guide plate side toward the quarter wavelength plate side, reaches a maximum value, and then decreases.

The above-mentioned polarized light separating film has a selective reflection wavelength range (A) based on the difference in the ratio of the optically active mesogen.
400-470 nm, (B) 470-550 nm, (C) 5
Spin a 20 wt% tetrahydrofuran solution of an athacrylic thermotropic cholesteric liquid crystal polymer of 50 to 640 nm or (D) 640 to 740 nm on a polyvinyl alcohol rubbed surface (0.1 μm) of a 50 μm thick triacetyl cellulose film. Coating by coating method, heat orientation at 160 ° C for 5 minutes, thickness 5μ
m cholesteric liquid crystal layer is formed, and four types of cholesteric liquid crystal layers exhibiting a mirror-like selective reflection state and reflecting left-handed circularly polarized light are obtained. The two cholesteric liquid crystal layers are brought into close contact with each other and heated. After pressing, one of the triacetyl cellulose films was peeled off, and the next cholesteric liquid crystal layer was heated and pressed with the liquid crystal layers in close contact with each other, and the operation was repeated to repeat the order of A layer-B layer-D layer-C layer. And a 1/4 wavelength plate was arranged on the C layer.

The 波長 wavelength plate is provided with a フ ィ ル ム wavelength retardation to 550 nm wavelength light obtained by uniaxially stretching a 100 μm thick polycarbonate film 1.05 times at 160 ° C. A phase difference film cut out to have an axis of 17.5 degrees, and a polycarbonate film having a thickness of 100 μm are uniaxially stretched by a factor of 1.09 at 160 ° C. to a wavelength of 550 nm, which is １ ／ wavelength. This is obtained by pressing and laminating a phase difference film cut to give a phase difference so that the stretching axis becomes 80 degrees via an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm and integrated.

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

Example 2 The helical pitch increased from the light guide plate side to the 波長 wavelength plate side and became the maximum value, superimposed in the order of A layer-B layer-C layer-D layer-C layer. An elliptically polarizing element was obtained in the same manner as in Example 1 except that a quarter-wave plate was disposed on the C layer outside the polarization separation film composed of cholesteric liquid crystal, which subsequently decreased.

Example 3 A-layer, B-layer, C-layer, D-layer, and B-layer were superimposed in this order, and the helical pitch increased from the light guide plate side to the 波長 wavelength plate side and reached a maximum value. An elliptically polarizing element was obtained in the same manner as in Example 1 except that a quarter-wave plate was disposed on the B layer outside the polarization separation film composed of cholesteric liquid crystal, which subsequently decreased.

Example 4 A layer-B layer-D layer-C layer-B layer was superposed in this order, and the helical pitch increased from the light guide plate side to the 波長 wavelength plate side and reached a maximum value. An elliptically polarizing element was obtained in the same manner as in Example 1 except that a quarter-wave plate was disposed on the B layer outside the polarization separation film composed of cholesteric liquid crystal, which subsequently decreased.

Example 5 The spiral pitch increases from the light guide plate side to the quarter wavelength plate side and overlaps with the maximum value by superimposing in the order of A layer-B layer-C layer-D layer-C layer-B layer. An elliptically polarizing element was obtained in the same manner as in Example 1, except that a quarter-wave plate was disposed on the outer B layer of the polarization separation film composed of cholesteric liquid crystal, which decreased after.

Example 6 The helical pitch decreases in the order of D layer-C layer-A layer-B layer in order from the light guide plate side to the 波長 wavelength plate side, reaches a minimum value, and then increases. An elliptically polarizing element was obtained in the same manner as in Example 1 except that a quarter-wave plate was disposed on the layer B of the polarization separation film composed of cholesteric liquid crystal.

Example 7 The helical pitch decreased from the light guide plate side to the １ ／ wavelength plate side and became the minimum value by superimposing in order of D layer-C layer-B layer-A layer-B layer. An elliptically polarizing element was obtained in the same manner as in Example 1 except that a quarter-wave plate was disposed on the layer B of the polarization separation film composed of cholesteric liquid crystal, which subsequently increased.

Example 8 The helical pitch decreased from the light guide plate side to the 波長 wavelength plate side and became the minimum value by superimposing in the order of D layer-C layer-B layer-A layer-C layer. An elliptically polarizing element was obtained in the same manner as in Example 1 except that a quarter-wave plate was arranged on the outer C layer of the polarization separation film composed of cholesteric liquid crystal which subsequently increased.

Example 9 The helical pitch decreased from the light guide plate side to the 波長 wavelength plate side and became the minimum value by superimposing in the order of D layer-C layer-A layer-B layer-C layer. An elliptically polarizing element was obtained in the same manner as in Example 1 except that a quarter-wave plate was arranged on the outer C layer of the polarization separation film composed of cholesteric liquid crystal which subsequently increased.

Example 10 The spiral pitch decreases from the light guide plate side to the quarter wavelength plate side and overlaps with the minimum value by superimposing in the order of D layer-C layer-B layer-A layer-B layer-C layer. An elliptically polarizing element was obtained in the same manner as in Example 1 except that a quarter-wave plate was arranged on the outer C layer of the polarization separation film composed of cholesteric liquid crystal, which increased after.

Comparative Example 1 A polarization separation film made of a cholesteric liquid crystal in which the helical pitch is increased from the light guide plate side toward the 波長 wavelength plate side so as to overlap in the order of A layer-B layer-C layer-D layer. An elliptically polarizing element was obtained according to Example 1, except that a 1/4 wavelength plate was disposed on the D layer.

Comparative Example 2 A polarization separation film made of a cholesteric liquid crystal in which the helical pitch is reduced from the light guide plate side toward the ４ wavelength plate side by overlapping in the order of D layer-C layer-B layer-A layer. An elliptically polarizing element was obtained in the same manner as in Example 1 except that a 配置 wavelength plate was disposed on the A layer.

Evaluation Test Front Luminance Ratio A polarizing plate was arranged on the quarter-wave plate of the elliptically polarizing element obtained in each of Examples and Comparative Examples in the axial direction showing the maximum luminance, and the front luminance when the backlight was turned on was measured. Measure the polarized light separating film and 1
The front luminance ratio (improvement degree) to the front luminance when the quarter wave plate was not arranged was examined.

Chromaticity difference Front direction (x ₀ ,
y ₀ ) and the chromaticity in the 45 ° oblique direction (x ₄₅ , y ₄₅ ) are measured, and the chromaticity difference is calculated from the following: {(x ₀ −x ₄₅ ) ² + (y ₀ −y ₄₅ ) ² } Was.

The results are shown in the following table.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of an elliptically polarizing element.

FIG. 2 is a cross-sectional view of another example of an elliptically polarizing element.

FIG. 3 is an explanatory diagram of a changing state of a helical pitch.

FIG. 4 is a cross-sectional view of an example of a liquid crystal display device.

[Explanation of symbols]

 1: light guide plate 11: reflection layer 14: light diffusion plate 16: prism sheet 5: elliptically polarizing element 2, 13, 15, 20 to 28: adhesive layer 3: polarization separation film 31, 32, 33: cholesteric liquid crystal layer 4: 1/4 wavelength plate 41: rough surface 42, 43: retardation layer 6, 61: polarizing plate 7: liquid crystal cell 8: retardation plate 9: light diffusion plate

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Naoki Takahashi 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation

Claims (9)

[Claims] 1. A polarizing separation film composed of a cholesteric liquid crystal layer having a portion in which the helical pitch changes and shows a maximum value or a minimum value in the middle of the layer, and a ４ wavelength plate comprising an adhesive layer having an excellent stress relaxation property. An elliptically polarizing element comprising a laminate adhered through the intermediary. 2. The cholesteric liquid crystal layer according to claim 1, wherein the helical pitch increases stepwise or continuously from one end in the thickness direction toward the end of the quarter-wave plate, reaches a maximum value, and then decreases. Elliptically polarizing element. 3. The cholesteric liquid crystal layer according to claim 1, wherein the helical pitch decreases stepwise or continuously from one end in the thickness direction toward the end of the 波長 wavelength plate, reaches a minimum value, and then increases. Elliptically polarizing element. 4. The method of claim 1 to 3, 1/4 wave plate, a maximum refractive index in the film plane n _x, a refractive index of the direction perpendicular n _y, the refractive index in the thickness direction n _z Then, the formula:
_{N z = (n x -n z} ) / (n x -n y) represented by N _z is 1.
An elliptically polarizing element using a retardation film of 1 or less. 5. The elliptically polarizing element according to claim 1, wherein the quarter-wave plate is a single layer of a retardation film or a laminate of two or more adhesives having a retardation difference. 6. The superimposed body according to claim 5, wherein the quarter-wave plate is a quarter-wave plate satisfying N _z ≦ 1.1 and one or more half-wave plates. An elliptically polarizing element comprising: 7. The elliptically polarizing element according to claim 1, wherein a polarizing plate is adhered to the quarter wavelength plate via an adhesive layer having excellent stress relaxation. 8. The elliptically polarized light according to claim 1, wherein a light guide plate having a reflection layer on the back surface and emitting light from the front surface is bonded to the polarization separation film side via an adhesive layer having excellent stress relaxation properties. element. 9. The method according to claim 1, wherein the pressure-sensitive adhesive layer is 2 × 1.
An elliptically polarizing element having a relaxation modulus of from 0 ⁵ to 1 × 10 ⁷ dyne / cm ² .