JP2002258048A - Optical element, surface light source unit and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop an optical element for forming a surface light source apparatus where deterioration in performance owing to tight adhesion to an adjacent member and a damage in form hardly occur, which is excellent in handling workability and which emits a light with excellent directivity in front, and also forming a liquid crystal display device which is excellent in luminance. SOLUTION: The optical element consists of the laminated body of circular polarizing separation boards A and B (1 and 2) consisting of cholesteric liquid crystal layers (11-13 and 21-23) with a Grandjean structure, the board A selectively reflects the same circular polarization light at right and left within a wavelength range being >=200 nm, the reflection light comprises the wavelength range being 520-580 cm, the left and right of the circular polarization light are inverted, which is selectively reflected against the board B, and an end at the short wavelength side of the selection reflected wavelength range is positioned in 550-580 nm wavelength area. The optical element is arranged on the sidelight type or a right-down type surface light source with a triple wavelength tube as a light source in the surface light source unit. Then the liquid crystal display device consists of the surface light source unit and the optical element. Thus, a light within a specified wavelength range which transmits the proceeding circular polarizing separation board is selectively reflected against the succeeding circular polarizing separation board and shielded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lyo-filter type optical element capable of forming a surface light source device which emits light with good front directivity and a liquid crystal display device having excellent brightness.

[0002]

2. Description of the Related Art Conventionally, a prism sheet has been known as an optical element capable of improving the frontal directivity of divergent light from a surface light source such as a sidelight type light guide plate so as to improve the frontal luminance (Japanese Patent Laid-Open No. 10-1998). 68804, JP-A-10-82
902). The prism sheet is an array of mountain-shaped prisms arranged on a transparent base material. The prism sheet refracts oblique light through the prisms to increase the directivity of the surface light source toward the front (vertical) direction. . There is also known a method in which two or more prism sheets are superimposed so that the array directions of the prisms intersect and light diverging in multiple directions is collected in the front direction. However, the prism sheet has a problem that the prism form is easily damaged due to contact or the like, and the scratches cause the generation of bright spots and dark spots. There was a point. Further, when the prism sheet is brought into close contact with an adjacent member such as a film at the time of practical use, there is a problem that the prism function is deteriorated and the performance is liable to be deteriorated.

On the other hand, as a means for increasing the luminance of a liquid crystal display device or the like, there has been known a system in which an optical element comprising a cholesteric liquid crystal layer having a Grand Jean structure and a quarter-wave plate is arranged on a surface light source. . This system utilizes the property of separating the incident natural light shown by the cholesteric liquid crystal layer into left and right circularly polarized light as reflected light and transmitted light, and converts the outgoing light from the surface light source into circularly polarized light through a quarter-wave plate. By supplying linearly polarized light to the polarizing plate, absorption loss by the polarizing plate is suppressed and luminance is improved.
Therefore, it does not contribute to the improvement of the directivity of the divergent light by the surface light source. Also known is a type that separates not a right and left circularly polarized light but a linearly polarized light whose vibration plane is orthogonal (manufactured by 3M, DBEF, etc.). is not.

[0004]

The present invention relates to a surface light source device which emits light with good front directivity and a liquid crystal display device which is excellent in brightness, in which the performance is less likely to be deteriorated due to the close contact with an adjacent member and the shape is not easily damaged, and the handling efficiency is excellent. It is an object of the present invention to develop an optical element capable of forming the optical element.

[0005]

The present invention comprises a laminate having at least circularly polarized light separating plates A and B each composed of one or more cholesteric liquid crystal layers having a Grand Jean structure,
The circularly polarized light separating plate A selectively reflects circularly polarized light of the same left and right in the wavelength range of 200 nm or more, and reflects 520 to 5
In addition to the wavelength range of 80 nm, the circularly polarized light separating plate B has a circularly polarized light selectively reflected from the circularly polarized light separating plate A, and the left and right sides of the circularly polarized light are reversed.
An object of the present invention is to provide an optical element characterized by being located in a wavelength range of 50 to 580 nm.

According to another aspect of the present invention, there is provided a surface light source device wherein the optical element is arranged on a sidelight type or direct type surface light source using a fluorescent lamp comprising a three-wavelength tube as a light source. A liquid crystal display device characterized by using the optical element of (1).

[0007]

According to the present invention, the above-mentioned selective reflection wavelength of the cholesteric liquid crystal layer is utilized by utilizing the characteristic of the cholesteric liquid crystal layer in which the wavelength range of selective reflection shifts to the shorter wavelength side in relation to cos θ according to the incident angle θ. Front direction (incident angle 0 degree) based on the combination of A and B of the circularly polarized light separating plate whose range is controlled
In the case, light in a predetermined wavelength range is transmitted, and the light is equal to or more than a predetermined value.
In particular, when incident at an incident angle θ of 20 degrees or more, a light-shielding effect is produced, and only light having excellent directivity in the direction in which the front and the incident angle are within a certain value is transmitted, and other light is selectively reflected and substantially reflected. The light can be blocked lightly.

Therefore, light is emitted with good front directivity by combining an optical element exhibiting a light-shielding effect with respect to the incident light having the incident angle θ of not less than a predetermined value and a surface light source which emits light at a wavelength at which the light-shielding effect is produced. A surface light source device can be formed, and a liquid crystal display device having excellent luminance can be formed using the surface light source device. In addition, the optical element according to the present invention does not cause a decrease in performance even when it is brought into close contact with an adjacent member, and does not have a form in which damage such as a projection is likely to occur.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical element according to the present invention comprises a laminate having at least A and B circularly polarized light separating plates each having one or more cholesteric liquid crystal layers having a Grand Jean structure. An example is shown in FIG. 1 is a circularly polarized light separating plate A, 2 is a circularly polarized light separating plate B, 11, 12, 13, 2
Reference numerals 1, 22, and 23 are cholesteric liquid crystal layers. Also,
3 is an adhesive layer, 4 is a 1/4 wavelength plate, and 5 is a dichroic polarizing plate.

The circularly polarized light separating plate A is formed so as to selectively reflect circularly polarized light of the same left and right in a wavelength range of 200 nm or more, and to include the reflected light in a wavelength range of 520 to 580 nm. Further, the circularly polarized light separating plate B is such that the circularly polarized light selectively reflected from the circularly polarized light separating plate A is reversed in the right and left directions, and the short wavelength end of the selective reflection wavelength range is located in the wavelength range of 550 to 580 nm. It is formed in.

The cholesteric liquid crystal layer having a Grand Jean structure used for forming the circularly polarized light separating plates A and B is as follows.
There is no particular limitation, and an appropriate material having the above-described characteristics can be used. The cholesteric liquid crystal layer may be a single layer material or a combination of those having different helical pitches of the Granjan structure, and therefore different selective reflection wavelength ranges.
It may have an arrangement structure in which layers or three or more layers are overlapped. The wavelength range of selective reflection can be expanded by such superimposition.

That is, a cholesteric liquid crystal layer having a Grand Jean structure has a formula: λ =
Circularly polarized light calculated by n · P · cos θ is selectively reflected by Bragg reflection and other light is transmitted (where λ is the center wavelength of the reflected light, and n is the average refractive index of cholesteric liquid crystal molecules (n = (Ne + no) / 2), where θ is the angle of incidence of light). The left and right sides of the reflected circularly polarized light are determined by the left and right sides of the helical direction in the cholesteric liquid crystal layer having a Grand Jean structure. The selective reflection wavelength range △ λ is formed near the center wavelength λ based on the formula: △ λ = △ n △ P ・ cosco by the refractive index difference △ n of the liquid crystal.

Therefore, by using the cholesteric liquid crystal layer in which the left and right helical directions in the Grandian structure are the same, the left and right of the circularly polarized light reflected can be unified, and the cholesteric liquid crystal layer in which the left and right helical directions are opposite to each other can be used. By using this, the left and right of the reflected circularly polarized light can be reversed. Further, by combining cholesteric liquid crystal layers having different wavelength ranges of selective reflection as described above, the wavelength range of selective reflection can be expanded. When the cholesteric liquid crystal layers having different helical pitches are superimposed, there is no particular limitation on the order of superimposition based on the magnitude of the helical pitch, and any superimposition order can be adopted, and the superimposition method is not particularly limited. In general, it is often advantageous to superimpose the helical pitches in the order of magnitude, from the viewpoint of improving the light use efficiency and, consequently, the luminance.

The cholesteric liquid crystal layer having a Grand Jean structure can be obtained in a cell form in which a low molecular liquid crystal is sandwiched between cell substrates. Those that have been used are preferably used. A cholesteric liquid crystal layer such as a film
For example, a film made of a liquid crystal polymer, a layer of a liquid crystal polymer that is oriented on a transparent substrate with a liquid crystal polymer that is oriented through a rubbing treatment or the like via a rubbing treatment, or a low-molecular liquid crystal that is oriented on a transparent substrate with an oriented film via an orientation film. And the like provided with an ultraviolet curing layer.

The material for forming the transparent substrate is not particularly limited, but generally a polymer is used. Examples of the polymer include cellulosic polymers such as cellulose diacetate and cellulose triacetate; polyester polymers such as polyethylene terephthalate and polyethylene naphthalate; acrylic polymers such as polycarbonate polymers and polymethyl methacrylate; polystyrene and acrylonitrile / styrene. Styrene polymers such as copolymers, polyethylene and polypropylene, polyolefins having a cyclo or norbornene structure, olefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, and amide polymers such as nylon and aromatic polyamides. can give.

Further, imide polymers, sulfone polymers, polyether sulfone polymers, polyether ether ketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, Oxymethylene-based polymers, epoxy-based polymers and blends of the above-mentioned polymers, and polyester-based, acrylic-based, urethane-based and amide-based, silicone-based and epoxy-based polymers and the like that are cured by heat or ultraviolet irradiation, etc., are also the transparent base Can be used to form In particular, a transparent substrate having excellent isotropy or low birefringence, such as a cellulose film, is preferably used.

In the above, the superposed layer of the cholesteric liquid crystal layer is formed by an appropriate method such as an overcoating method, a method of fusing a separately formed product, and a method of separately bonding a formed product via a transparent adhesive layer such as an adhesive layer. be able to. For a material exhibiting selective reflectivity in a large wavelength range such as the circularly polarized light separating plate A, a forming method such as a multi-coating method or a method of fusing a separately formed product is preferable from the viewpoint of thinning. On the other hand, as for the superposition of the cholesteric liquid crystal layer in which the left and right of the circularly polarized light selectively reflected, such as the lamination of the circularly polarized light separating plate A and B, a separately formed product is preferably interposed via a transparent adhesive layer.

The circularly polarized light separating plate A, which can be preferably used from the viewpoint of improving the brightness and the like, selectively reflects circularly polarized light having the same right and left in a wavelength range of 200 nm or more and at least including a wavelength range of 440 to 610 nm. . In particular, a circularly polarized light separating plate A showing selective reflection in the entire wavelength range of visible light can be preferably used.

The circularly-polarized light separating plate B which can be preferably used from the viewpoint of improving the brightness and the like includes one having the end on the short wavelength side of the selective reflection wavelength range located in the wavelength range of 550 to 580 nm. In this case, two or three or more cholesteric liquid crystal layers are overlapped in a combination in which a wavelength difference occurs. In particular, the short wavelength end of the selective reflection wavelength range is 440 to 4
A circularly polarized light separating plate B in which three types of cholesteric liquid crystal layers located in the wavelength ranges of 70 nm, 550 to 580 nm and 610 to 650 nm are preferably used.

As shown in the figure, the optical element is provided with a quarter-wave plate 4 on one side outside the circularly polarized light separating plate via an adhesive layer 3 if necessary.
Further, the dichroic polarizing plate 5 can be put to practical use in a form in which a dichroic polarizing plate 5 is bonded to the outside of the quarter-wave plate via the adhesive layer 3. In addition, an adhesive layer is provided on the side having the dichroic polarizing plate through an adhesive layer.
A practical form in which a layer or two or more layers of retardation plates are bonded together can also be used. Such integration with a quarter-wave plate, a dichroic polarizing plate, or the like can further improve the handling workability and can simplify the assembling process of the surface light source device, the liquid crystal display device, and the like.

The purpose of the quarter wavelength plate is to convert circularly polarized light transmitted through the circularly polarized light separating plate into linearly polarized light. Therefore, the quarter-wave plate is arranged outside the circularly polarized light separating plate,
The arrangement position may be on either side of the circularly polarized light separating plate A or B. The side of the circularly polarized light separating plate A (1) is preferred as shown in the figure from the viewpoint of improving the brightness and the directivity of the front. Examples of the quarter-wave plate include birefringent films composed of stretched films of various polymers, oriented films of liquid crystal polymers such as discotic and nematic, and those in which the oriented liquid crystal layer is supported on a transparent substrate. Appropriate conventional ones can be used.

The polymer forming the birefringent film may be any suitable polymer such as those exemplified for the transparent substrate described above. Above all, a polymer having excellent crystallinity, such as a polyester-based polymer or polyetheretherketone, can be preferably used. The stretched film may be processed by an appropriate method such as uniaxial or biaxial. Further, a birefringent film in which the refractive index in the thickness direction of the film is controlled by a method of applying a contraction force and / or a stretching force while adhering to the heat-shrinkable film may be used. One more
The 波長 wavelength plate may have an expanded wavelength range that functions as a 波長 wavelength plate, for example, a layer obtained by laminating phase difference plates having different phase differences with their optical axes crossing each other.

On the other hand, lamination of dichroic polarizing plates is intended to obtain linearly polarized light for achieving a liquid crystal display or the like. 1
By supplying the linearly polarized light through the 波長 wavelength plate so that the vibrating surface thereof matches the transmission axis of the dichroic polarizing plate as much as possible, absorption loss can be prevented and the luminance can be further increased. . Therefore, the dichroic polarizing plate is disposed outside the quarter-wave plate 4 as shown in FIG.

As the dichroic polarizing plate, an appropriate one that transmits linearly polarized light having a predetermined polarization axis and absorbs other light can be used, and the type thereof is not particularly limited. Above all, those having excellent polarization degree and transmittance are preferable. In general, a polarizing film or a dichroic polarizing plate having one or both surfaces protected by a transparent protective layer is used. Incidentally, examples of the polarizing film include adsorption of iodine and / or a dichroic dye 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. And a stretching treatment.

The transparent protective layer provided on one side or both sides of the polarizing film, if necessary, can be formed of the polymer exemplified for the above transparent substrate. Above all, a transparent protective layer made of a polymer having excellent transparency, mechanical strength, heat stability, moisture shielding property and the like is preferable. 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.

On the other hand, the retardation plate, which is provided as necessary on the side where the dichroic polarizing plate is disposed, has an object of compensating for a phase difference due to birefringence of the liquid crystal cell and improving display quality. I do. In general, such a retardation plate for optical compensation is preferably disposed so as to be located between the dichroic polarizing plate and the liquid crystal cell from the viewpoint of improving display quality. As the retardation plate for optical compensation, a retardation plate having an appropriate retardation made of a birefringent film or an oriented liquid crystal layer according to the above-mentioned quarter wavelength plate is used, and the optical characteristics such as retardation are controlled. It may be a laminate of two or more retardation layers for the purpose. The retardation plate may be a half-wave plate or the like for expanding the wavelength range that functions as the above-described quarter-wave plate.

Each material such as a cholesteric liquid crystal layer, a circularly polarized light separating plate, a quarter-wave plate, a dichroic polarizing plate, and a phase difference plate, which form an optical element, is simply superposed. However, it is preferable that they are laminated and integrated via a transparent adhesive layer such as an adhesive layer in order to stabilize the quality by preventing displacement of the optical axis and improve the efficiency of assembling the liquid crystal display device. Incidentally, in the illustrated example, the circularly polarized light separating plates A and B (1 and 2), the 、 wavelength plate 4 and the dichroic polarizing plate 5 are bonded and integrated via the adhesive layer 3 respectively.

The adhesive layer is formed by using an appropriate adhesive substance such as an adhesive having a base polymer of an appropriate polymer such as an acrylic polymer, a silicone polymer, polyester, polyurethane, polyether or synthetic rubber. be able to. Among them, those which are excellent in optical transparency, weather resistance, heat resistance and the like and are hardly caused to float or peel off under the influence of heat or humidity, such as acrylic adhesives, can be preferably used.

Incidentally, examples of the acrylic pressure-sensitive adhesive include those having 20 or more carbon atoms such as a methyl group, an ethyl group and a butyl group.
A combination of an alkyl ester of (meth) acrylic acid having the following alkyl group and an acrylic monomer composed of an improving component such as (meth) acrylic acid or hydroxyethyl (meth) acrylate having a glass transition temperature of 0 ° C. or lower. And an acrylic polymer having a weight average molecular weight of 100,000 or more as a base polymer. However, the present invention is not limited thereto.

The adhesive layer is formed by applying an adhesive substance to a material for forming a circularly polarized light separating plate or the like by an appropriate method such as a rolling method using a calender roll method or a coating method using a doctor blade method or a gravure roll coater method. It can be carried out by an appropriate method such as a method of attaching, or a method of forming an adhesive layer on a separator according to the method and transferring it to a forming material such as a circularly polarized light separating plate.

The pressure-sensitive adhesive layer may be formed as a light diffusion type by a method of including transparent particles therein. The transparent particles include, for example, silica and alumina,
Titania or zirconia, tin oxide or indium oxide, cadmium oxide or antimony oxide or the like, inorganic particles that may be conductive, organic particles of a cross-linked or uncross-linked polymer or the like suitable one kind or such. Two or more types can be used.

On the outer surface of the optical element, if necessary, an adhesive layer for the purpose of adhering to another member such as a liquid crystal cell can be provided. If the adhesive layer is exposed on the surface, the surface may be temporarily covered with a separator or the like for the purpose of protection such as contamination prevention until practical use. Further, when the material for forming the optical element is exposed on the surface, the exposed surface can be adhered and covered with a surface protection film to protect it from scratches and the like.

The separator and the surface protective film are
At the practical stage of the optical element, the optical element is peeled off and removed, and in that case, static electricity or dust adhesion may occur. Therefore, an antistatic-treated separator or surface protective film can be used as necessary. Similarly, an optical element which has been subjected to an antistatic treatment by an appropriate method such as a method in which an antistatic layer is positioned between layers or a surface of a material for forming an optical element can be used.

The optical element can be used for various applications, and can be preferably used particularly for forming a surface light source device for improving front directivity and a liquid crystal display device for improving luminance. The surface light source device can be formed by, for example, a method in which an optical element is arranged on a surface light source such as a sidelight type or a direct type using a fluorescent lamp formed of a three-wavelength tube as a light source. Further, the liquid crystal display device can be formed by, for example, a method in which an appropriate liquid crystal cell is disposed above the optical element in the above-mentioned surface light source device via a polarizing plate or the like as necessary. In this case, when the optical element has a quarter-wave plate or the like, the optical element is arranged such that the side of the circularly polarized light separating plate not having the same is the surface light source side.

In the above, when a surface light source using a fluorescent lamp (cold cathode tube) comprising a three-wavelength tube as a light source is used, an optical element which can be preferably used from the viewpoint of obtaining a surface light source device having excellent front directivity is the fluorescent lamp. It has a circularly polarized light separating plate B formed by using a cholesteric liquid crystal layer having an end on the short wavelength side of the selective reflection wavelength range at a position where the wavelength is 10 nm or more than the emission line wavelength shown. Such a circularly polarized light separating plate B using a cholesteric liquid crystal layer whose end on the short wavelength side corresponds to the emission line wavelength of a fluorescent lamp may be one that can correspond to one emission line among three wavelengths, but is preferably used. It can correspond to two or more emission lines, particularly all wavelengths of the emission line.

Therefore, for example, wavelengths of about 440 nm and about 550 nm
In the case of a surface light source using a general-purpose fluorescent lamp composed of a three-wavelength tube showing a bright line at about 610 nm as a light source, the above paragraph [00]
18] and A and B of the circularly polarized light separating plate described in [0019].
Are preferably used.

Further, the bright line having an incident angle of more than 20 degrees is shielded and the bright line having an excellent front directivity at an incident angle of 20 degrees or less is transmitted based on the short-wavelength shift due to the involvement of cos θ. An optical system having a circularly polarized light separating plate B formed by using a cholesteric liquid crystal layer having a wavelength longer than that of each emission line of the light source by 10 nm or more, particularly 15 to 100 nm, particularly 20 to 50 nm, on the short wavelength side of the selective reflection wavelength range. An element is preferably used.

In the above, the light that has been shielded by the optical element and reflected toward the surface light source can be confined via the light reflecting layer. Therefore, in that case, it is preferable to use a surface light source such as a side light type light guide plate capable of providing a light reflection layer without blocking light emission of the surface light source. By providing a light reflection layer on the bottom surface of a light guide plate or the like and confining the light reflected by the light shielding between the optical element and the light reflection layer, the optical path is changed by refraction or diffusion or scattering by a light guide plate or the like interposed therebetween. Light having a small angle of incidence that can be transmitted through the element can be transmitted through the optical element with good directivity to improve the luminance.

In forming a surface light source device or a liquid crystal display device, an optical element is provided with a light emitting surface of a surface light source, a viewing surface of a liquid crystal cell, and / or
It may be simply installed at an appropriate position such as on the back and back, but it is more transparent such as an adhesive layer to prevent the occurrence of curl and undulation when performing performance tests such as sticking with other members and heat resistance. It is preferable to perform an adhesive treatment on a surface light source, a liquid crystal cell, or the like via an adhesive layer. In forming a surface light source device or a liquid crystal display device, one or more appropriate optical layers such as an antiglare layer, an antireflection layer, and a light diffusion layer can be arranged at appropriate positions.

[0040]

EXAMPLE 1 A cholesteric liquid crystal polymer was coated on an 80 μm-thick cellulose triacetate film via a rubbing alignment film.
On top of that, three kinds of cholesteric liquid crystal polymers having different central wavelengths of selective reflection are overcoated, and they are subjected to a Grandian alignment treatment, and a circularly polarized light separating plate A1 having a selective reflection wavelength range of 410 to 680 nm and reflecting left circularly polarized light. I got

On the other hand, the selective reflection wavelength range is 4
60-489 nm, 570-603 nm or 630 nm-67
A circularly polarized light separating plate B1 is formed by using three types of cholesteric liquid crystal layers that reflect right circularly polarized light at 0 nm, and is adhered and laminated with the circularly polarized light separating plate A1 via an acrylic adhesive layer. Phase difference consisting of a stretched polycarbonate film through an acrylic adhesive layer on the outside of the is 140nm
The 1/4 wavelength plate and the dichroic polarizing plate were bonded to obtain an optical element. The dichroic polarizing plate was bonded such that the transmission axis was parallel to the vibration plane of the linearly polarized light via the quarter wavelength plate.

Example 2 Circularly polarized light separating plate A1 and 1 /
An optical element was obtained according to Example 1, using only the four-wavelength plate and the dichroic polarizing plate.

Example 3 A commercially available prism sheet having an apex angle of 90 ° C. was used as an optical element.

Evaluation Test The emission line wavelength was 438 nm, 545 nm and 610 on the side surface of the light guide plate.
The optical elements obtained in Examples 1 to 3 are mounted on a light-emitting surface of a side light type surface light source, in which a fluorescent lamp including a three-wavelength tube of Then, a surface light source device was formed, and the front luminance on the optical element was examined with a luminance meter (BM7, manufactured by Topcon Corporation). In Example 3, a dichroic polarizing plate was disposed on the prism sheet.

The results are shown in the following table. Example 1 Example 2 Example 3 Front luminance (cd / m ² ) 2209 2050 1603

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment.

[Explanation of symbols]

1: Circularly polarized light separating plate A 2: Circularly polarized light separating plate B 11, 12, 13, 21, 22, 23: Cholesteric liquid crystal layer 3: Adhesive layer 4: Quarter wavelength plate 5: Dichroic polarizing plate

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C09K 3/00 C09K 3/00 U F21Y 103: 00 F21Y 103: 00 F-term (Reference) 2H049 BA02 BA05 BA07 BA25 BA27 BA43 BA47 BB03 BB43 BB49 BB52 BC03 BC04 BC22 2H091 FA08X FA08Z FA11X FA11Z FA42Z KA10 LA02 LA12 LA16

Claims (9)

[The claims] 1. A circularly polarized light separating plate A comprising one or more cholesteric liquid crystal layers having a Grand Jean structure,
A circularly polarized light separating plate A selectively reflects circularly polarized light having the same left and right in a wavelength range of 200 nm or more, and the reflected light includes a wavelength range of 520 to 580 nm. The left and right sides of the circularly polarized light selectively reflected by the separating plate B and the circularly polarized light separating plate A are reversed, and the end on the short wavelength side of the selective reflection wavelength range is 550 to 580 nm.
An optical element characterized by being located in a wavelength range of: 2. The combination according to claim 1, wherein the circularly polarized light separating plate A has a selective reflection wavelength range of at least 440 to 610 nm, and the circularly polarized light separating plate B has a combination in which a wavelength difference occurs between the selective reflection wavelength ranges. An optical element in which layers or three or more cholesteric liquid crystal layers are overlapped. 3. The circularly polarized light separating plate B according to claim 2, wherein the end on the short wavelength side of the selective reflection wavelength range is from 440 to 470 nm.
An optical element using three types of cholesteric liquid crystal layers located in a wavelength range of 50 to 580 nm and 610 to 650 nm. 4. The optical element according to claim 1, wherein a quarter-wave plate is bonded to one of the outer sides of the circularly polarized light separating plate via an adhesive layer. 5. The optical element according to claim 4, wherein a dichroic polarizing plate is bonded to the outside of the quarter-wave plate via an adhesive layer. 6. The optical element according to claim 5, wherein one or two or more retardation plates are adhered to the side having the dichroic polarizing plate via an adhesive layer. 7. A surface light source device wherein the optical element according to claim 1 is arranged on a side light type or direct type surface light source using a fluorescent lamp comprising a three-wavelength tube as a light source. . 8. The cholesteric liquid crystal layer according to claim 7, wherein the circularly polarized light separating plate B uses a cholesteric liquid crystal layer having an end on the short wavelength side of the selective reflection wavelength range at a position at least 10 nm larger than the emission line wavelength of the fluorescent lamp. An optical element. 9. A liquid crystal display device comprising the optical element according to claim 1.