JP2000275436A - Polarizing member and optical member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing member and an optical member which are excellent in contrast in a reflective display mode using a reflecting polarizing plate and also excellent in brightness in a transmissive display mode. SOLUTION: A polarizing member 1 comprises a reflecting polarizing plate 11 for separating incident natural light into reflected light consisting of polarized light and transmitted light and an absorbing polarizing element disposed on one side of the reflecting polarizing plate 11 in such a way as to transmit the polarized light consisting of the transmitted light, and an optical member comprises a quarter wavelength plate 3 or both an absorbing polarizing plate and the quarter wavelength plate 3 disposed on the absorbing polarizing element side of the polarizing member, with the absorbing polarizing plate in axial relationship for transmitting the transmitted polarized light produced by the absorbing polarizing element. This arrangement achieves a display of high contrast and brightness in a transmissive display mode while achieving functions of a semitranslucent reflecting polarizer by use of the reflecting polarizing plate 11, and allows unwanted reflected external light (return light) in a reflective display mode to be efficiently absorbed and cut.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing member and an optical member which can prevent a decrease in contrast due to unnecessary reflected light and are suitable for forming a transflective liquid crystal display or the like.

[0002]

BACKGROUND OF THE INVENTION Conventionally, when a reflective or semi-transmissive liquid crystal display device is formed by using a reflective polarizing plate that separates incident natural light into reflected light and transmitted light composed of polarized light, the light passes through the reflective polarizing plate. As a countermeasure to prevent the reflected light from being reflected by the lower surface or the like and becoming unnecessary return light, which lowers the level of black display and lowers the contrast, a method of providing an absorbing layer on the lower surface side of the reflective polarizing plate has been proposed. Was known.

However, in a transflective liquid crystal display device, it is necessary to use a light transmissive light absorbing layer in order to secure visibility in a transmissive display mode via an illumination device. There has been a problem that it is difficult to prevent a decrease in contrast in black display or the like.

[0004]

According to the present invention, a transflective liquid crystal display device having excellent contrast in a reflective display mode and excellent luminance in a transmissive display mode can be formed using a reflective polarizing plate. An object is to develop a polarizing member and an optical member.

[0005]

According to the present invention, an absorptive polarizing element is disposed on one side of a reflective polarizing plate for separating incident natural light into reflected light and transmitted light composed of polarized light so as to transmit the polarized light composed of the transmitted light. A polarizing member, characterized in that a quarter-wave plate or an absorption-type polarizing plate and a quarter-wave plate are arranged on the absorption-type polarizing element side of the polarizing member, and the absorption-type polarizing plate is It is an object of the present invention to provide an optical member having an axial relationship for transmitting transmitted polarized light by an absorption type polarizing element.

[0006]

According to the present invention, the function as a transflective polarizer is achieved by using a reflective polarizer, and the degree of polarization is maintained by maintaining the degree of polarization by the absorptive polarizer in the transmissive display mode. , And high-luminance display can be achieved by high utilization of illumination light due to high light transmittance. In addition, the optical member efficiently absorbs and cuts off unnecessary reflected light (return light) from an external light illuminating device or the like in the reflective display mode to prevent a decrease in contrast in a black display or the like, and provides a high contrast high quality display. Provide dignity.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A polarizing member according to the present invention is provided on one side of a reflective polarizing plate for separating incident natural light into reflected light and transmitted light composed of polarized light. The optical member is provided with 1 /
A four-wavelength plate or an absorption-type polarizing plate and a quarter-wavelength plate are arranged, and the absorption-type polarizing plate has an axial relationship that allows transmission of polarized light transmitted by the absorption-type polarizing element.

FIGS. 1 and 2 show examples of the above-mentioned polarizing member, and FIGS. 3 to 6 show examples of the optical member. 1 is a reflective polarizer, 11 and 12 are linear or circular polarizers forming it, 2 is an absorptive polarizer, and 21 and 22 are absorptive polarizers or 1/4 that form it. This is a circularly polarizing plate including a wavelength plate 23 and an absorption type polarizing plate 24. Reference numeral 3 denotes a 波長 wavelength plate, and reference numeral 4 denotes an absorption type polarizing plate. Reference numeral 5 denotes a lighting device.

As shown in the drawing, the polarizing member has an absorption type polarizing element disposed on one side of a reflection type polarizing plate for separating incident natural light into reflected light and transmitted light composed of polarized light so as to transmit the polarized light composed of the transmitted light. It is formed by doing. That is, when the reflection type polarizing plate is formed of a linearly polarized light separating plate, an absorption type polarizing plate is used as an absorbing type polarizing element, and the linearly polarized light transmitted through the linearly polarized light separating plate 11 as shown by an arrow in FIG. The absorption type polarizing plate 21 is arranged so that the polarization direction and the transmission axis have a parallel relationship.

On the other hand, when the reflection type polarizing plate is a circularly polarized light separating plate, a circularly polarizing plate composed of a quarter-wave plate and an absorbing type polarizing plate is used for the absorbing type polarizing element. As described above, the circularly polarizing plate 22 is disposed so that the circularly polarized light transmitted from the circularly polarized light separating plate 12 has the same rotation direction as the circularly polarized light. As described above, the transmitted light, such as illumination light, through the absorption type polarizing element is efficiently transmitted through the reflection type polarizing plate, and the object of the present invention is achieved.

On the other hand, the optical member is formed by disposing a 1/4 wavelength plate or an absorption type polarizing plate and a 1/4 wavelength plate on the absorption type polarizing element side of the polarizing member. Incidentally, the optical member illustrated in FIG. 3 is formed by disposing the quarter-wave plate 3 on the absorption type polarizing plate side of the polarizing member including the linearly polarized light separating plate 11 and the absorption type polarizing plate 21.

The optical member shown in FIG. 4 has an absorption type polarizing plate 4 and a quarter-wave plate 3 arranged sequentially on the absorption type polarizing plate 21 side of the polarizing member. Are arranged such that the transmission axis of the transmitted polarized light by the absorption type polarizing element is transmitted, that is, the transmission axis is parallel to the upper absorption type polarizing plate 21.

On the other hand, the optical member illustrated in FIG. 5 is a polarizing member (circular polarizing plate side) of a polarizing member in which a circularly polarized light separating plate 12, a quarter-wave plate 23, and an absorbing polarizing plate 24 are sequentially arranged. 22
Side) and a 波長 wavelength plate 3 arranged on the (side) side. The optical member illustrated in FIG. 6 is an absorption type polarizing plate 2 of the polarizing member.
4, an absorption type polarizing plate 4 and a 波長 wavelength plate 3 are sequentially arranged. The absorption type polarizing plate 4 has an axial relationship of transmitting transmission polarized light by the absorption type polarizing element, that is, an upper absorption type polarization plate. The plate 24 and the transmission axis are arranged in a parallel relationship.

As described above, when the light transmitted through the optical member is reflected by the illuminating device 5 and the like on the lower surface as shown by the arrow, it returns to the optical member as return light and reaches the absorption type polarizing plates 4, 21, and 24. In addition, the polarization direction of the light is cut off in accordance with the absorption axis of the absorption type polarizing plate.
The light transmitted through the four-wavelength plate 3 or the absorption type polarizing plate 4 efficiently transmits through the polarizing member, and the object of the present invention is achieved.

In the above, as the reflection type polarizing plate, an appropriate one showing a characteristic of reflecting linearly polarized light in a predetermined polarization direction or circularly polarized light in a predetermined direction when natural light is incident and transmitting other light can be used. . Incidentally, as an example, a linearly polarized light having a characteristic of transmitting linearly polarized light in a predetermined polarization direction and reflecting other light, such as a multilayer thin film of a dielectric or a multilayered laminate of thin films having different refractive index anisotropy. A circle that reflects one of the left and right circularly polarized light and transmits the other light, such as a separator, a cholesteric liquid crystal layer, especially an alignment film of a cholesteric liquid crystal polymer, or a film having the alignment liquid crystal layer supported on a film substrate. And a polarization separation plate.

The circularly polarized light separating plate has an arrangement structure in which two or three or more cholesteric liquid crystal layers are overlapped in a combination having different reflection wavelengths, and reflects and transmits circularly polarized light in a wide wavelength range such as a visible light region. May be indicated.

As the absorption-type polarizing plate, an appropriate polarizing plate that transmits linearly polarized light in a predetermined polarization direction and absorbs other light can be used, and the type thereof is not particularly limited. By the way, as an example, iodine and / or a dichroic dye is adsorbed on a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, and an ethylene / vinyl acetate copolymer-based partially saponified film. Examples of the polarizing film include a stretched film, a film obtained by dehydrating polyvinyl alcohol and a film obtained by dehydrochlorinating polyvinyl chloride, and a film obtained by orienting a polyene.

The polarizing plate may be provided with a transparent protective layer on one or both sides of the polarizing film for the purpose of protection such as improvement of water resistance or reinforcement. For the formation of the transparent protective layer, a polymer excellent in transparency, mechanical strength, heat stability, moisture shielding property and the like is preferably used.

Incidentally, examples of the above-mentioned polymer include cellulosic polymers such as cellulose diacetate and cellulose triacetate, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, polyether sulfone and polycarbonate, polyamide and polyimide, polyolefin and acrylic resin. Examples of the resin include a thermosetting resin such as an acrylic resin, a urethane resin, an acrylic urethane resin, an epoxy resin, and a silicone resin, or an ultraviolet curing resin. The transparent protective layer can be formed by an appropriate method such as a method of applying a polymer liquid or an adhesive lamination method of a film.

In the above, an appropriate quarter-wave plate can be used in combination with an absorption-type polarizer to form a circular polarizer. One that functions as a quarter-wave plate in a wide wavelength range such as a visible light region is, for example, a wavelength 55 nm.
A retardation layer functioning as a quarter-wave plate for monochromatic light such as light of 0 nm and a retardation layer exhibiting other retardation characteristics, for example, 1
It can be obtained by a method of superimposing a retardation layer functioning as a / 2 wavelength plate or the like. Therefore, the quarter-wave plate is 1
It may be composed of a layer or two or more retardation layers.

The quarter-wave plate or the retardation layer is made of, for example, a birefringent film composed of a stretched film of various polymers, an alignment film of a liquid crystal polymer such as discotic or nematic, and an alignment liquid crystal layer thereof. It can be obtained as one supported on a film substrate.

The polymer forming the birefringent film is, for example, an olefin polymer such as polyethylene, polypropylene, or polyolefin having a norbornene structure; an acrylic polymer such as polyester polymer, polymethyl methacrylate; a cellulose polymer; a polyamide; Appropriate materials such as polyimide, polysulfone, polyethersulfone, polyetheretherketone, polyphenylene sulfide, polyvinyl alcohol, polyvinyl chloride, polyvinyl butyrate, polycarbonate, polystyrene, polyarylate, and polyoxymethylene may be used.

The stretched film may be processed by an appropriate method such as uniaxial or biaxial. The stretched film may be subjected to a shrinking force and / or a stretching force while being bonded to the heat shrinkable film. May be a birefringent film in which the refractive index in the thickness direction is controlled. In addition, the above-mentioned circularly polarizing plate,
It may be made of, for example, a liquid crystal alignment film without using a quarter-wave plate.

Examples of the 1/4 wavelength plate and the absorption type polarizing plate used for forming the optical member include those exemplified above.

In the polarizing member or optical member according to the present invention, a reflective polarizing plate such as a linear polarizing plate or a circular polarizing plate, an absorbing polarizing element such as an absorbing polarizing plate or a circular polarizing plate, a 1/4 wavelength plate or an absorbing member. All or a part of each forming layer such as a mold polarizing plate may be simply placed, but it is appropriate to use an adhesive or the like from the viewpoint of preventing misalignment of the axial relationship and preventing foreign matter from entering the interlayer. It is preferable that the adhesive is fixed by a method.

As the above-mentioned adhesive, for example, an appropriate adhesive such as an acrylic polymer, a silicone-based polymer, an appropriate polymer such as polyester, polyurethane, polyether or synthetic rubber as a base polymer or the like can be used. Above all, it is excellent in optical transparency like acrylic adhesive, shows moderate wettability, cohesiveness and adhesive properties such as adhesiveness, excellent in weather resistance and heat resistance, etc., under heating and humidifying conditions Those which do not cause a peeling problem such as floating or peeling can be preferably used.

Examples of the acrylic pressure-sensitive adhesive include 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, and a butyl group; Based on an acrylic polymer having a weight average molecular weight of 100,000 or more, obtained by copolymerizing an acrylic monomer comprising an improving component such as hydroxyethyl (meth) acrylate in a combination having a glass transition temperature of 0 ° C. or lower. Examples thereof include polymers, but are not limited thereto.

The attachment of the adhesive layer to the reflective polarizing plate or the like may be performed, for example, by directly applying an adhesive liquid by an appropriate developing method such as a casting method or a coating method, or by applying an adhesive layer on a separator according to the above. Can be performed by an appropriate method such as a method of forming and transferring the same. In that case, the pressure-sensitive adhesive layer can be provided on one or both surfaces of a reflective polarizing plate or the like, and the provided pressure-sensitive adhesive layer may be a superposed layer of a different composition or type. When an adhesive layer is provided on both surfaces, an adhesive layer having a different composition or type on the front and back of a reflective polarizing plate or the like may be used.

The thickness of the adhesive layer such as an adhesive layer can be appropriately determined according to the adhesive strength and the like, and is generally 1 to 500 μm. When the adhesive layer is exposed on the outer surface of the polarizing member or optical member, it is preferable to temporarily cover the surface with a separator or the like until practical use to prevent contamination and the like.

The axial relation in the arrangement of the reflection type polarizing plate and the absorption type polarizing element of the above-mentioned odor polarizing member and optical member should be as parallel as possible, although an axis deviation due to a working error is allowed. Is more preferable from the viewpoint of light transmittance and absorption cutoff of reflected light. When the optical axis of the reflective polarizing plate or the like varies, it is preferable to form a parallel relationship based on the average direction.

The polarizing member and the optical member according to the present invention can be used for various applications such as a transflective, transmissive or reflective liquid crystal display device. In particular, a transflective liquid crystal display device which is required to achieve high contrast by cutting unnecessary reflected light of external light in the reflective display mode and to achieve high luminance by good transmittance of illumination light in the transmissive display mode. It can be preferably used for formation and the like.

In the above, the polarizing member or the optical member according to the present invention is arranged such that when a transflective or transmissive liquid crystal display device is formed, a reflective polarizing plate is disposed between the liquid crystal cell and the illuminating device on the liquid crystal cell side. Is done. On the other hand, when a reflective liquid crystal display device is formed, the reflective liquid crystal display device is disposed on the viewing side of the liquid crystal cell and the reflective polarizing plate is disposed on the viewing side. In this case,
Unnecessary reflected light of external light which is reflected on the surface of the liquid crystal cell or the like and hinders visual recognition of display light is absorbed and cut.

The liquid crystal display device can be formed according to a conventional method except for the above points. Therefore, the liquid crystal cell to be used is arbitrary, and for example, an appropriate type of liquid crystal cell such as an active matrix driving type represented by a thin film transistor type, a simple matrix driving type represented by a twisted nematic type or a super twisted nematic type is used. It can be used to form various liquid crystal display devices. In forming a liquid crystal display device, one or more layers of appropriate components such as a prism array sheet, a lens array sheet, a light diffusing plate, and a backlight can be arranged at appropriate positions.

[0034]

Example 1 Absorption type polarizing plate (EG1425DU, manufactured by Nitto Denko Corporation; transmission) on one surface of a linearly polarized light separating plate (manufactured by 3M, DBEF) so that the polarization direction of the transmitted linearly polarized light is parallel to the transmission axis. Rate 4
4% and a degree of polarization of 99.5%, the same applies hereinafter) via an acrylic pressure-sensitive adhesive layer to obtain a polarizing member.

The above-mentioned polarizing member functions as a transflective polarizer, and the transmitted light exhibits a high degree of polarization depending on the absorptive polarizer to provide a high-contrast display. This is twice as high as that of a simple absorption type semi-transmissive layer having a transmittance of 40%. The same effect as in the case where the conventional light-absorbing layer was provided was also obtained with respect to the prevention of a decrease in contrast in the reflective display mode in the state where the electroluminescent illumination device was provided on the back surface (the same applies hereinafter).

Example 2 A wide-band quarter-wave plate (Nitto Denko, NRF 270 nm and 1 nm) was formed on one surface of a circularly polarized light separating plate made of cholesteric liquid crystal so that the rotation directions of the transmitted circularly polarized light and the circularly polarized light were the same.
A polarizing member was obtained by bonding a 40-nm laminated body (hereinafter the same) and a circularly polarizing plate (hereinafter the same) composed of an absorption-type polarizing plate via an acrylic pressure-sensitive adhesive layer.

The above-mentioned polarizing member has a function as a transflective polarizer, and the transmitted light exhibits a high degree of polarization depending on the absorption type polarizing plate, so that a high-contrast display can be obtained. This is twice as high as that of a simple absorption type semi-transmissive layer having a transmittance of 40%. The same effect as in the case where the conventional light-absorbing layer was provided was also obtained with respect to the prevention of reduction in contrast in the reflective display mode.

Example 3 The absorption type polarizing plate was adjacent to the absorption type polarizing plate side of the polarizing member of Example 1, and the circular polarizing plate was bonded via an acrylic adhesive layer so that the transmission axes became parallel. A member was obtained (FIG. 4).
This optical member maintains the function as a transflective polarizer, and the transmitted light shows a high degree of polarization depending on the absorption type polarizing plate to obtain a high-contrast display. This is twice as high as that of a simple absorption type semi-transmissive layer of 40%.

Further, the effect of preventing a decrease in contrast in the reflection display mode was obtained more than that of the conventional light-absorbing layer, and was comparable to that of the conventional light-absorbing layer. The light transmittance was slightly lower than 38% when the absorption type polarizing plate was arranged in parallel Nicols.

Example 4 An optical member was obtained by bonding a broadband 波長 wavelength plate to the absorption type polarizing plate side of the polarizing member of Example 1 via an acrylic adhesive layer (FIG. 3). This optical member maintains the function as a semi-transmissive reflective polarizer, has excellent light transmittance and excellent thinness as compared with the above-described circular polarizer, and transmits transmitted light as an absorption polarizer. , A high-contrast display is obtained, and the light use efficiency of transmitted light is twice as high as that of a simple absorption type semi-transmissive layer having a transmittance of 40%. Further, the effect of preventing a decrease in contrast in the reflective display mode was obtained more than that of the conventional light-absorbing layer, and was comparable to that of the conventional light-absorbing layer.

Example 5 An optical member was obtained by bonding a circularly polarizing plate via an acrylic adhesive layer so that the absorbing type polarizing plates were adjacent to the circularly polarizing plate side of the polarizing member of Example 2 (FIG. 6). . This optical member maintains the function as a transflective polarizer, and the transmitted light shows a high degree of polarization depending on the absorption type polarizing plate to obtain a high-contrast display. 40%
This is twice as high as that of the simple absorption type semi-transmissive layer.

Further, the effect of preventing a decrease in contrast in the reflective display mode was obtained more than that of the conventional light-absorbing layer, and was comparable to that of the conventional light-absorbing layer. The light transmittance was slightly lower than 38% when the absorption type polarizing plate was arranged in parallel Nicols.

Example 6 An optical member was obtained by bonding a broadband quarter-wave plate to the circularly polarizing plate side of the polarizing member of Example 2 via an acrylic adhesive layer (FIG. 5). This optical member maintains the function as a semi-transmissive reflective polarizer, has excellent light transmittance and excellent thinness as compared with the above-described circular polarizer, and transmits transmitted light as an absorption polarizer. And a high contrast display is obtained, and the light utilization efficiency of the transmitted light is 40%.
%, Which is twice as high as that of a simple absorption type semi-transmissive layer. Also, regarding the prevention of a decrease in contrast in the reflective display mode, an effect higher than that of the conventional light-absorbing layer is obtained,
An effect comparable to that of the conventional complete light absorbing layer was obtained.

Comparative Example A polarizing member was obtained in the same manner as in Example 2 except that a light absorbing layer having a transmittance of 40% and an absorptance of 60% was provided instead of the circularly polarizing plate.
Although this polarizing member exhibited a function as a transflective polarizer, the contrast in black display in the reflective display mode was significantly reduced by unnecessary reflected light, and the display quality was unsatisfactory.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view of another example of a polarizing member.

FIG. 3 is a cross-sectional view of an example of an optical member.

FIG. 4 is a cross-sectional view of another example of an optical member.

FIG. 5 is a sectional view of still another optical member example.

FIG. 6 is a sectional view of still another optical member example.

[Explanation of symbols]

 1: Reflective polarizing plate 11: Linear polarizing separating plate 12: Circular polarizing separating plate 2: Absorbing polarizing element 21: Absorbing polarizing plate 22: Circular polarizing plate 23: 1/4 wavelength plate 24: Absorbing polarizing plate 3: Quarter-wave plate 4: Absorption polarizing plate 5: Illumination device

Claims (3)

[Claims] An absorptive polarizing element is disposed on one side of a reflective polarizing plate for separating incident natural light into reflected light and transmitted light composed of polarized light so as to transmit the polarized light composed of the transmitted light. Polarizing member. 2. The method according to claim 1, wherein the reflection-type polarizing plate comprises a linearly-polarized light separating plate or a circularly-polarized light separating plate, and the absorption-type polarizing element has a transmission axis parallel to transmitted light of linearly polarized light. A polarizing member comprising an arranged absorbing polarizing plate or a quarter-wave plate and an absorbing polarizing plate arranged so that the rotation direction of the circularly polarized light becomes the same as the transmitted light of the circularly polarized light. 3. A polarizing member according to claim 1, wherein a quarter-wave plate or an absorptive polarizing plate and a quarter-wave plate are arranged on the side of the absorptive polarizing element. An optical member characterized by having an axial relationship of transmitting polarized light transmitted by an absorption type polarizing element.