JP2016212171A - Optical laminate, circularly polarizing plate and organic electroluminescence display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical laminate which can give a long circularly polarizing plate capable of effectively reducing reflection of external light in both a frontal direction and an oblique direction.SOLUTION: The optical laminate includes a long half-wave plate 110 and a long quarter-wave plate 120, both comprising a resin having a positive intrinsic birefringence value. In the optical laminate, an average orientation angle of a slow axis 111 of the half-wave plate 110 with respect to a width direction is 50° or more and 90° or less; an NZ coefficient of the half-wave plate 110 is 1.0 to 1.5; an average orientation angle of the slow axis 121 of the quarter-wave plate 120 with respect to the width direction is 0° or more and less than 50°; and an NZ coefficient of the quarter-wave plate 120 is 1.0 to 1.5.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical laminate, and a circularly polarizing plate and an organic electroluminescence display device including the optical laminate.

  An image display device such as an organic electroluminescence display device (hereinafter sometimes referred to as “organic EL display device” as appropriate) may be provided with a circularly polarizing plate in order to reduce reflection of external light on the display surface. . As such a circularly polarizing plate, a film in which a linear polarizer and a quarter-wave plate that is a retardation film are combined is generally used. However, most of the conventional quarter wavelength plates can achieve a retardation of about a quarter wavelength only with light in a specific narrow wavelength range. Therefore, although reflection of outside light in a specific narrow wavelength range can be reduced by the circularly polarizing plate, it is difficult to reduce reflection of other outside light.

On the other hand, a broadband quarter-wave plate combining a quarter-wave plate and a half-wave plate has been proposed (see Patent Documents 1 to 6). According to this wide-band quarter-wave plate, since retardation of about ¼ wavelength can be achieved with light in a wide wavelength range, a circularly polarizing plate that can reduce reflection of external light in a wide wavelength range can be realized.
Further, a retardation film technique is known in which the slow axis direction as in Patent Document 7 is the in-plane direction of the film and exists in an oblique direction that is neither orthogonal nor parallel to the width direction of the film. .

Japanese Patent No. 4708787 Japanese Patent Laid-Open No. 05-100114 JP 2003-114325 A JP-A-10-68816 JP-A-11-183723 Japanese Patent Laid-Open No. 11-295526 JP2012-25167A

  In a circularly polarizing plate that combines a linear polarizer and a broadband quarter-wave plate, the polarization transmission axis of the linear polarizer, the slow axis of the half-wave plate, and the slow axis of the quarter-wave plate It is required to adjust the directions of the axes so that these optical axes form a predetermined angle.

  However, when the circularly polarizing plate is viewed from an inclination direction other than the front direction, the apparent angle formed by the optical axis may deviate from a predetermined angle. For this reason, the conventional circularly polarizing plate can reduce the reflection of external light in the front direction, but cannot effectively reduce the reflection of external light in an inclination direction other than the front direction. In particular, a circularly polarizing plate having a broadband quarter-wave plate has not only a quarter-wave plate but also a half-wave plate, so the number of optical axes is larger than that of a conventional circularly polarizing plate. For this reason, in the circularly polarizing plate having the broadband quarter-wave plate, the apparent optical axis shift is larger than that of the conventional circularly polarizing plate not having the half-wave plate, and the reflection of external light in the tilt direction is reduced. There was a tendency to be inferior to the ability to reduce.

  The present invention was devised in view of the above-described problems, and is an optical laminate that can realize a long circularly polarizing plate that can effectively reduce reflection of external light in both the front direction and the tilt direction; To provide a long circularly polarizing plate capable of effectively reducing reflection of external light in any of the tilt directions; and an organic electroluminescence display device including an antireflection film cut out from the circularly polarizing plate. Objective.

As a result of intensive studies to solve the above problems, the present inventor has found an optical laminate including a long half-wave plate and a long quarter-wave plate made of a resin having a positive intrinsic birefringence value. If the optical laminate is used, the direction of the slow axis of the half-wave plate and quarter-wave plate and the NZ coefficient of the half-wave plate and quarter-wave plate are within a predetermined range. The inventors have found that a long circularly polarizing plate capable of effectively reducing reflection of external light in both the front direction and the tilt direction can be realized, and the present invention has been completed.
That is, the present invention is as follows.

[1] A long half-wave plate and a long quarter-wave plate made of a resin having a positive intrinsic birefringence value,
The average orientation angle formed by the slow axis of the half-wave plate with respect to the width direction is 50 ° or more and 90 ° or less,
The NZ coefficient of the half-wave plate is 1.0 to 1.5,
The average orientation angle formed by the slow axis of the quarter-wave plate with respect to the width direction is 0 ° or more and less than 50 °,
The optical laminated body whose NZ coefficient of the said 1/4 wavelength plate is 1.0-1.5.
[2] The optical laminated body according to [1], wherein an angle of intersection between the slow axis of the half-wave plate and the slow axis of the quarter-wave plate is 55 ° to 65 °.
[3] The optical laminate according to [1] or [2], wherein the resin having a positive intrinsic birefringence value includes a cyclic olefin polymer.
[4] The optical laminate according to any one of [1] to [3], wherein the half-wave plate and the quarter-wave plate are stretched films that have been subjected to at least one oblique stretch. body.
[5] The optical laminated body according to [4], wherein the half-wave plate is a sequential biaxially stretched film that is further subjected to longitudinal stretching after the oblique stretching.
[6] The optical laminate according to any one of [1] to [5] and the long linear polarizer are rolled, and the linear polarizer, the half-wave plate, and the 1 / It is a circularly polarizing plate obtained by laminating so that the four wavelength plates are in this order,
A circularly polarizing plate, wherein an angle formed between a polarization transmission axis of the linear polarizer and a slow axis of the half-wave plate is 50 ° or more and less than 90 °.
[7] An organic electroluminescence display device comprising an antireflection film cut out from the circularly polarizing plate according to [6].

  According to the present invention, an optical laminated body capable of realizing a long circularly polarizing plate that can effectively reduce reflection of external light in both the front direction and the tilt direction; A long circularly polarizing plate that can effectively reduce reflection; and an organic electroluminescence display device that includes an antireflection film cut out from the circularly polarizing plate can be provided.

FIG. 1 is an exploded perspective view schematically showing a long optical laminate according to an embodiment of the present invention. FIG. 2 is a plan view schematically showing an example of a tenter stretching machine used for stretching a film before stretching. FIG. 3 is a plan view schematically showing an example of a roll stretching machine used for stretching the intermediate film.

  Hereinafter, the present invention will be described in detail with reference to embodiments and examples. However, the present invention is not limited to the following embodiments and exemplifications, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof.

  In the following description, the “long” film means a film having a length of 5 times or more, preferably 10 times or more, and specifically a roll. A film having such a length that it can be wound up and stored or transported.

  In the following description, the in-plane retardation Re of the film is a value represented by Re = (nx−ny) × d unless otherwise specified. Further, the retardation Rth in the thickness direction of the film is a value represented by Rth = {(nx + ny) / 2−nz} × d unless otherwise specified. Further, the NZ coefficient of the film is a value represented by (nx−nz) / (nx−ny) and can be calculated by 0.5 + Rth / Re unless otherwise specified. Here, nx represents a refractive index in a direction (in-plane direction) perpendicular to the thickness direction of the film and giving the maximum refractive index. ny represents the refractive index in the in-plane direction and orthogonal to the nx direction. nz represents the refractive index in the thickness direction. d represents the thickness of the film. The measurement wavelength is 590 nm unless otherwise specified.

  In the following description, the slow axis of the film represents the slow axis in the plane of the film unless otherwise specified.

  In the following description, the orientation angle of a film means an angle formed by an in-plane slow axis of the film with respect to a certain reference direction unless otherwise specified. In the following description, the orientation angle of a long film represents the orientation angle formed by the slow axis with respect to the width direction of the film unless otherwise specified.

  In the following description, a resin having a positive intrinsic birefringence value means a resin in which the refractive index in the stretching direction is larger than the refractive index in the direction perpendicular thereto unless otherwise specified. Further, a resin having a negative intrinsic birefringence value means a resin whose refractive index in the stretching direction is smaller than the refractive index in the direction perpendicular thereto unless otherwise specified. The intrinsic birefringence value can be calculated from the dielectric constant distribution.

  In the following description, the term “(meth) acryl” includes both “acryl” and “methacryl”.

  In the following description, the oblique direction of a long film indicates an in-plane direction of the film, unless otherwise specified, and a direction that is neither parallel nor perpendicular to the width direction of the film.

  In the following description, unless otherwise specified, the front direction of a film means the normal direction of the main surface of the film, specifically, the direction of the polar angle 0 ° and the azimuth angle 0 ° of the main surface. Point to.

  In the following description, unless otherwise specified, the inclination direction of a film means a direction that is neither parallel nor perpendicular to the main surface of the film, and specifically, the polar angle of the main surface is larger than 0 ° and 90 °. Point in a direction smaller than °.

  In the following description, the directions of the elements “parallel”, “vertical”, and “orthogonal” include errors within a range that does not impair the effects of the present invention, for example, ± 5 °, unless otherwise specified. You may go out.

  In the following description, the longitudinal direction of a long film is usually parallel to the film conveyance direction in the production line.

  In the following description, “polarizing plate”, “1/2 wavelength plate”, and “¼ wavelength plate” are not only rigid members but also flexible, such as resin films, unless otherwise specified. The member which has property is also included.

  In the following description, the angles formed by the optical axes (polarization absorption axis, polarization transmission axis, slow axis, etc.) of each film in a member having a plurality of films are viewed from the thickness direction unless otherwise noted. Represents the angle of time.

[1. Overview of optical laminate]
FIG. 1 is an exploded perspective view schematically showing an optical laminate 100 according to an embodiment of the present invention. In FIG. 1, the axis 112 on which the slow axis 111 of the half-wave plate 110 is projected is indicated by a one-dot chain line on the surface of the quarter-wave plate 120. Moreover, in the optical laminated body 100 shown in FIG. 1, since the width direction of the optical laminated body 100, the width direction of the 1/2 wavelength plate 110, and the width direction of the 1/4 wavelength plate 120 correspond, it shows with common code | symbol TD. .
As shown in FIG. 1, a long optical laminate 100 according to an embodiment of the present invention includes a long half-wave plate 110 made of a resin having a positive intrinsic birefringence value, and an intrinsic birefringence value. Is provided with a long quarter-wave plate 120 made of a positive resin.

  The half-wave plate 110 is a long optical member having a predetermined in-plane retardation. The half-wave plate 110 is a slow phase parallel to the in-plane direction of the half-wave plate 110 in a direction that forms a predetermined average orientation angle θh with respect to the width direction TD of the half-wave plate 110. It has an axis 111.

  The quarter-wave plate 120 is a long optical member having a predetermined in-plane retardation. The quarter-wave plate 120 is a slow phase parallel to the in-plane direction of the quarter-wave plate 120 in a direction that forms a predetermined average orientation angle θq with respect to the width direction TD of the quarter-wave plate 120. It has a shaft 121.

  The optical laminated body 100 having such a structure is a wide-band quarter-wave plate capable of giving in-plane retardation of approximately ¼ wavelength of light of light in a wide wavelength range transmitted through the optical laminated body 100. Can function as. In addition, by combining such an optical laminate 100 with a linear polarizer, a circularly polarizing plate capable of absorbing one of right circularly polarized light and left circularly polarized light and transmitting the remaining light in a wide wavelength range is realized. it can.

[2.1 / 2 wave plate]
The in-plane retardation of the half-wave plate is usually 240 nm or more and usually 300 nm or less. When the half-wave plate has such in-plane retardation, an optical laminate that can function as a broadband quarter-wave plate can be realized by combining the half-wave plate and the quarter-wave plate. Furthermore, by combining this optical layered body with a linear polarizer, a circularly polarizing plate capable of suppressing reflection of light in a wide wavelength range in both the front direction and the tilt direction can be realized. Among them, in order to reduce the reflection of external light in the tilt direction particularly effectively, the in-plane retardation of the half-wave plate is preferably 250 nm or more, preferably 280 nm or less, more preferably 265 nm or less. is there.

  The NZ coefficient of the half-wave plate is usually 1.00 or more, preferably 1.05 or more, more preferably 1.10 or more, and usually 1.50 or less, preferably 1.40 or less, more preferably 1. .30 or less. The fact that the NZ coefficient of the half-wave plate is close to 1.0 as described above indicates that the optical uniaxial property of the half-wave plate is high. Here, the optical uniaxial property indicates a property capable of expressing optical properties close to a stretched film stretched in one direction. Thus, the circularly-polarizing plate obtained using an optical laminated body provided with a half-wave plate having high uniaxiality can more effectively reduce reflection of external light in the tilt direction. Further, the half-wave plate having such an NZ coefficient can be easily manufactured.

  The chromatic dispersion of the half-wave plate can have chromatic dispersion characteristics such as forward chromatic dispersion characteristics, flat chromatic dispersion characteristics, and reverse chromatic dispersion characteristics. The forward wavelength dispersion characteristic means a wavelength dispersion characteristic in which retardation increases as the wavelength becomes shorter. Further, the reverse wavelength dispersion characteristic means a wavelength dispersion characteristic in which the retardation becomes smaller as the wavelength becomes shorter. Further, the flat wavelength dispersion characteristic means a wavelength dispersion characteristic in which the retardation does not change regardless of the wavelength.

  The average orientation angle θh formed by the slow axis of the half-wave plate with respect to the width direction of the half-wave plate is usually 50 ° or more, preferably 55 ° or more, more preferably 60 ° or more. It is 90 ° or less, preferably 85 ° or less, more preferably 80 ° or less (see FIG. 1). By keeping the average orientation angle θh of the half-wave plate within the above range, an optical laminate that can function as a broadband quarter-wave plate can be realized by combining the half-wave plate and the quarter-wave plate. Furthermore, by combining this optical layered body with a linear polarizer, a circularly polarizing plate capable of suppressing reflection of light in a wide wavelength range in both the front direction and the tilt direction can be realized.

  The average orientation angle of the film is measured using a polarizing microscope (OLYMPUS "BX51") at an interval of 50 mm in the width direction of the film, the in-plane slow axis is measured, and the slow axis direction and the film width are measured. An average value of angles (orientation angles) formed with the direction can be obtained and measured as an average orientation angle.

  The half-wave plate is a member made of a resin having a positive intrinsic birefringence value, and is usually a film made of the resin. The resin having a positive intrinsic birefringence value includes a polymer having a positive intrinsic birefringence value. Examples of this polymer include polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyarylene sulfides such as polyphenylene sulfide; polyvinyl alcohol; polycarbonate; polyarylate; cellulose ester polymer; Polysulfone; polyallyl sulfone; polyvinyl chloride; cyclic olefin polymer such as norbornene polymer; rod-like liquid crystal polymer. These polymers may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. The polymer may be a homopolymer or a copolymer. Among these, a cyclic olefin polymer is preferable because of excellent mechanical properties, heat resistance, transparency, low hygroscopicity, dimensional stability, and lightness.

  The cyclic olefin polymer is a polymer in which the structural unit of the polymer has an alicyclic structure. The cyclic olefin polymer includes a polymer having an alicyclic structure in a main chain, a polymer having an alicyclic structure in a side chain, a polymer having an alicyclic structure in a main chain and a side chain, and these 2 It can be set as a mixture of the above arbitrary ratios. Among these, from the viewpoint of mechanical strength and heat resistance, a polymer having an alicyclic structure in the main chain is preferable.

  Examples of the alicyclic structure include a saturated alicyclic hydrocarbon (cycloalkane) structure and an unsaturated alicyclic hydrocarbon (cycloalkene, cycloalkyne) structure. Among these, from the viewpoint of mechanical strength and heat resistance, a cycloalkane structure and a cycloalkene structure are preferable, and a cycloalkane structure is particularly preferable.

  The number of carbon atoms constituting the alicyclic structure is preferably 4 or more, more preferably 5 or more, preferably 30 or less, more preferably 20 or less, particularly preferably per alicyclic structure. Is 15 or less. When the number of carbon atoms constituting the alicyclic structure is within this range, the mechanical strength, heat resistance and moldability of the resin are highly balanced.

  In the cyclic olefin polymer, the proportion of the structural unit having an alicyclic structure is preferably 55% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight or more. When the ratio of the structural unit having an alicyclic structure in the cyclic olefin polymer is within this range, transparency and heat resistance are improved.

  Of the cyclic olefin polymers, cycloolefin polymers are preferred. A cycloolefin polymer is a polymer having a structure obtained by polymerizing a cycloolefin monomer. The cycloolefin monomer is a compound having a ring structure formed of carbon atoms and having a polymerizable carbon-carbon double bond in the ring structure. Examples of the polymerizable carbon-carbon double bond include a carbon-carbon double bond capable of polymerization such as ring-opening polymerization. Examples of the ring structure of the cycloolefin monomer include monocycles, polycycles, condensed polycycles, bridged rings, and polycycles obtained by combining these. Among these, a polycyclic cycloolefin monomer is preferable from the viewpoint of highly balancing the dielectric properties and heat resistance of the resulting polymer.

  Among the above cycloolefin polymers, preferred are norbornene polymers, monocyclic olefin polymers, cyclic conjugated diene polymers, hydrides thereof, and the like. Among these, norbornene-based polymers are particularly suitable because of good moldability.

  Examples of the norbornene-based polymer include a ring-opening polymer of a monomer having a norbornene structure and a hydride thereof; an addition polymer of a monomer having a norbornene structure and a hydride thereof. Examples of a ring-opening polymer of a monomer having a norbornene structure include a ring-opening homopolymer of one kind of monomer having a norbornene structure and a ring-opening of two or more kinds of monomers having a norbornene structure. Examples thereof include a copolymer and a ring-opening copolymer with a monomer having a norbornene structure and another monomer that can be copolymerized therewith. Furthermore, examples of the addition polymer of a monomer having a norbornene structure include an addition homopolymer of one kind of monomer having a norbornene structure and an addition copolymer of two or more kinds of monomers having a norbornene structure. And addition copolymers with monomers having a norbornene structure and other monomers copolymerizable therewith. Among these, a hydride of a ring-opening polymer of a monomer having a norbornene structure is particularly suitable from the viewpoints of moldability, heat resistance, low moisture absorption, dimensional stability, lightness, and the like.

Examples of the monomer having a norbornene structure include bicyclo [2.2.1] hept-2-ene (common name: norbornene), tricyclo [4.3.0.1 ^2,5 ] deca-3,7. -Diene (common name: dicyclopentadiene), 7,8-benzotricyclo [4.3.0.1 ^2,5 ] dec-3-ene (common name: methanotetrahydrofluorene), tetracyclo [4.4. 0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene (common name: tetracyclododecene) and derivatives of these compounds (for example, those having a substituent in the ring). Here, examples of the substituent include an alkyl group, an alkylene group, and a polar group. Moreover, these substituents may be the same or different, and a plurality thereof may be bonded to the ring. One type of monomer having a norbornene structure may be used alone, or two or more types may be used in combination at any ratio.

  Examples of the polar group include heteroatoms and atomic groups having heteroatoms. Examples of the hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, and a halogen atom. Specific examples of polar groups include carboxyl groups, carbonyloxycarbonyl groups, epoxy groups, hydroxyl groups, oxy groups, ester groups, silanol groups, silyl groups, amino groups, amide groups, imide groups, nitrile groups, and sulfonic acid groups. Is mentioned.

  Examples of monomers capable of ring-opening copolymerization with monomers having a norbornene structure include monocyclic olefins such as cyclohexene, cycloheptene, and cyclooctene and derivatives thereof; cyclic conjugated dienes such as cyclohexadiene and cycloheptadiene; And derivatives thereof. As the monomer having a norbornene structure and a monomer capable of ring-opening copolymerization, one kind may be used alone, or two or more kinds may be used in combination at any ratio.

  A ring-opening polymer of a monomer having a norbornene structure can be produced, for example, by polymerizing or copolymerizing a monomer in the presence of a ring-opening polymerization catalyst.

  Examples of monomers that can be addition copolymerized with a monomer having a norbornene structure include α-olefins having 2 to 20 carbon atoms such as ethylene, propylene, and 1-butene, and derivatives thereof; cyclobutene, cyclopentene, and cyclohexene. And non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, and the like. Among these, α-olefin is preferable and ethylene is more preferable. Moreover, the monomer which can carry out addition copolymerization with the monomer which has a norbornene structure may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  An addition polymer of a monomer having a norbornene structure can be produced, for example, by polymerizing or copolymerizing a monomer in the presence of an addition polymerization catalyst.

  The hydrogenated product of the above-described ring-opening polymer and addition polymer is, for example, carbon in the presence of a hydrogenation catalyst containing a transition metal such as nickel or palladium in a solution of these ring-opening polymer or addition polymer. -Carbon unsaturated bonds can be produced by hydrogenation, preferably 90% or more.

Among norbornene-based polymers, as structural units, X: bicyclo [3.3.0] octane-2,4-diyl-ethylene structure and Y: tricyclo [4.3.0.1 ^2,5 ] decane- Having a 9,9-diyl-ethylene structure, the amount of these structural units being 90% by weight or more based on the total structural units of the norbornene polymer, and the ratio of X and Y It is preferable that the ratio is 100: 0 to 40:60 by weight ratio of X: Y. By using such a polymer, a half-wave plate containing the norbornene-based polymer can be made long-term without dimensional change and excellent in optical property stability.

  Examples of the monocyclic olefin polymer include addition polymers of cyclic olefin monomers having a single ring such as cyclohexene, cycloheptene, cyclooctene and the like.

  Examples of cyclic conjugated diene polymers include polymers obtained by cyclization of addition polymers of conjugated diene monomers such as 1,3-butadiene, isoprene and chloroprene; cyclic conjugates such as cyclopentadiene and cyclohexadiene Mention may be made of 1,2- or 1,4-addition polymers of diene monomers; and their hydrides.

  The weight average molecular weight (Mw) of the polymer contained in the resin having a positive intrinsic birefringence value is preferably 10,000 or more, more preferably 15,000 or more, particularly preferably 20,000 or more, preferably 100 50,000 or less, more preferably 80,000 or less, particularly preferably 50,000 or less. When the weight average molecular weight is in such a range, the mechanical strength and molding processability of the resin are highly balanced and suitable. Here, the weight average molecular weight is calculated by polyisoprene or polystyrene measured by gel permeation chromatography using cyclohexane as a solvent (however, toluene may be used when the sample does not dissolve in cyclohexane). The weight average molecular weight of

  The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the polymer contained in the resin having a positive intrinsic birefringence value is preferably 1.2 or more, more preferably 1.5 or more, particularly preferably. Is 1.8 or more, preferably 3.5 or less, more preferably 3.0 or less, and particularly preferably 2.7 or less. By making molecular weight distribution more than the lower limit of the said range, productivity of a polymer can be improved and manufacturing cost can be suppressed. Moreover, since the quantity of a low molecular component becomes small by making it into an upper limit or less, relaxation at the time of high temperature exposure can be suppressed and stability of a half-wave plate can be improved.

  The proportion of the polymer in the resin having a positive intrinsic birefringence value is preferably 50% to 100% by weight, more preferably 70% to 100% by weight, and particularly preferably 90% to 100% by weight. By setting the ratio of the polymer in the above range, the half-wave plate can obtain sufficient heat resistance and transparency.

  The resin having a positive intrinsic birefringence value may contain a compounding agent in addition to the polymer. Examples of compounding agents include colorants such as pigments and dyes; plasticizers; fluorescent brighteners; dispersants; thermal stabilizers; light stabilizers; ultraviolet absorbers; antistatic agents; Examples include activators. These components may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The glass transition temperature Tg of the resin having a positive intrinsic birefringence value is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, particularly preferably 120 ° C. or higher, preferably 190 ° C. or lower, more preferably 180 ° C. or lower, Especially preferably, it is 170 degrees C or less. By setting the glass transition temperature of the resin having a positive intrinsic birefringence value to be equal to or higher than the lower limit of the above range, the durability of the half-wave plate in a high temperature environment can be enhanced. In addition, the stretching process can be easily performed by setting the upper limit value or less.

The resin having a positive intrinsic birefringence value has an absolute value of photoelastic coefficient of preferably 10 × 10 ⁻¹² Pa ⁻¹ or less, more preferably 7 × 10 ⁻¹² Pa ⁻¹ or less, and particularly preferably 4 × 10 ^{− 12} Pa ⁻¹ or less. Thereby, the variation of the retardation of a half-wave plate can be made small. Here, the photoelastic coefficient C is a value represented by C = Δn / σ, where birefringence is Δn and stress is σ.

  The total light transmittance of the half-wave plate is preferably 80% or more. The light transmittance can be measured using a spectrophotometer (manufactured by JASCO Corporation, UV-visible near-infrared spectrophotometer “V-570”) in accordance with JIS K0115.

  The haze of the half-wave plate is preferably 5% or less, more preferably 3% or less, particularly preferably 1% or less, and ideally 0%. Here, according to JIS K7361-1997, haze can measure five places using the Nippon Denshoku Industries Co., Ltd. "turbidimeter NDH-300A", and can employ | adopt the average value calculated | required from it.

The amount of the volatile component contained in the half-wave plate is preferably 0.1% by weight or less, more preferably 0.05% by weight or less, still more preferably 0.02% by weight or less, and ideally zero. It is. By reducing the amount of volatile components, the dimensional stability of the half-wave plate can be improved, and the change over time in optical properties such as retardation can be reduced.
Here, the volatile component is a substance having a molecular weight of 200 or less contained in a trace amount in the film, and examples thereof include a residual monomer and a solvent. The amount of volatile components can be quantified by dissolving the film in chloroform and analyzing it by gas chromatography as the sum of the substances having a molecular weight of 200 or less contained in the film.

The saturated water absorption of the half-wave plate is preferably 0.03% by weight or less, more preferably 0.02% by weight or less, particularly preferably 0.01% by weight or less, and ideally zero. When the saturated water absorption rate of the half-wave plate is in the above range, changes with time in optical characteristics such as in-plane retardation can be reduced.
Here, the saturated water absorption is a value expressed as a percentage of the increased mass of the film specimen immersed in water at 23 ° C. for 24 hours with respect to the mass of the film specimen before immersion.

  The thickness of the half-wave plate is preferably 10 μm or more, more preferably 15 μm or more, further preferably 30 μm or more, preferably 100 μm or less, more preferably 80 μm or less, and further preferably 60 μm or less. Thereby, the mechanical strength of the half-wave plate can be increased.

  The manufacturing method of a half-wave plate is arbitrary. The half-wave plate may be manufactured as a stretched film by a manufacturing method including, for example, subjecting a long unstretched film made of resin to one or more oblique stretches. Here, “oblique stretching” refers to stretching a long film in an oblique direction. According to the manufacturing method including oblique stretching, the half-wave plate can be easily manufactured.

  Further, the half-wave plate is preferably manufactured as a sequential biaxially stretched film by a manufacturing method including further longitudinal stretching after the oblique stretching. Here, “longitudinal stretching” represents stretching a long film in the longitudinal direction.

  Hereinafter, an example of a preferable manufacturing method of the half-wave plate will be described. The half-wave plate manufacturing method according to this example includes (a) a first step of preparing a long unstretched film made of a resin having a positive intrinsic birefringence value, and (b) a long unstretched film. A second step of obtaining a long intermediate film, and (c) a third step of obtaining a long half-wave plate by freely uniaxially stretching the intermediate film in the longitudinal direction. Including.

  (A) In the first step, a long pre-stretch film made of a resin having a positive intrinsic birefringence value is prepared. The film before stretching can be produced by, for example, a melt molding method or a solution casting method. More specific examples of the melt molding method include an extrusion molding method, a press molding method, an inflation molding method, an injection molding method, a blow molding method, and a stretch molding method. Among these methods, in order to obtain a half-wave plate excellent in mechanical strength, surface accuracy, etc., an extrusion molding method, an inflation molding method or a press molding method is preferable. The extrusion method is particularly preferred from the viewpoint of production.

  (A) After preparing a long unstretched film in the first step, (b) performing a second step of stretching the long unstretched film in an oblique direction to obtain an intermediate film. In the second step, stretching is usually performed using a tenter stretching machine while continuously transporting the film before stretching in the longitudinal direction.

FIG. 2 is a plan view schematically showing an example of a tenter stretching machine 200 used for stretching a film before stretching.
As shown in FIG. 2, the tenter stretching machine 200 shown in this example stretches the pre-stretching film 20 fed from the feeding roll 10 in the oblique direction in a heating environment by an oven (not shown) while being transported horizontally. It is a device for.

  The tenter stretching machine 200 is provided on both sides of the film conveyance path to guide the grippers 210R and 210L, and a plurality of grippers 210R and 210L that can grip both ends 21 and 22 of the unstretched film 20, respectively. A pair of guide rails 220R and 220L.

  The grippers 210R and 210L are provided so as to travel along the guide rails 220R and 220L. In addition, the grippers 210R and 210L are provided so as to be able to travel at a constant speed with a certain distance from the front and rear grippers 210R and 210L. Further, the grippers 210R and 210L grip both end portions 21 and 22 in the width direction of the unstretched film 20 that are sequentially supplied to the tenter stretching machine 200 at the inlet portion 230 of the tenter stretching machine 200. It is provided so that it can be opened at the outlet 240.

  The guide rails 220R and 220L have asymmetric shapes according to conditions such as the direction of the slow axis of the intermediate film 30 to be manufactured and the draw ratio. The tenter stretching machine 200 shown in this example is provided with a stretching zone 250 in which the distance between the guide rails 220R and 220L increases toward the downstream. In the stretching zone 250, the shape of the guide rails 220R and 220L is such that the grippers 210R and 210L guided by the guide rails 220R and 220L bend the traveling direction of the film 20 before stretching in the left direction. 20 is set in a shape capable of transporting, and the moving distance of one gripper 210R is longer than the moving distance of the other gripper 210L. Here, the traveling direction of the long film means the moving direction of the middle point in the width direction of the film unless otherwise specified. Further, “right” and “left” indicate directions when the conveyance direction is observed from the upstream to the downstream unless otherwise specified.

  The guide rails 220R and 220L have endless continuous tracks so that the grippers 210R and 210L can go around a predetermined track. For this reason, the tenter stretching machine 200 has a structure in which the grippers 210R and 210L, in which the pre-stretching film 20 is opened at the outlet 240 of the tenter stretching machine 200, can be sequentially returned to the inlet 230.

(B) In the second step, stretching of the pre-stretching film 20 using such a tenter stretching machine 200 is performed as follows.
The unstretched film 20 is unwound from the feed roll 10, and the unstretched film 20 is continuously supplied to the tenter stretching machine 200.
The tenter stretching machine 200 sequentially grips both end portions 21 and 22 of the pre-stretching film 20 with grippers 210R and 210L at the entrance 230 thereof. The unstretched film 20 gripped at both ends 21 and 22 is transported as the grippers 210R and 210L travel. As described above, in the tenter stretching machine 200 of this example, the shapes of the guide rails 220R and 220L are set so that the traveling direction of the unstretched film 20 is bent leftward. Therefore, the distance of the track on which one gripper 210R travels while gripping the unstretched film 20 is longer than the distance of the track on which the other gripper 210L travels while gripping the unstretched film 20. Therefore, the pair of grippers 210R and 210L that are opposed to the direction perpendicular to the traveling direction of the pre-stretching film 20 at the entrance 230 of the tenter stretching machine 200 are on the left side at the outlet 240 of the tenter stretching machine 200. Since the gripper 210L precedes the right gripper 210R, the film 20 before stretching is stretched in an oblique direction to obtain a long intermediate film 30 (broken lines L _D1 , L _D2 and FIG. 2). See L _D3 ). The obtained intermediate film 30 is released from the grippers 210 </ b> R and 210 </ b> L at the outlet 240 of the tenter stretching machine 200, wound up, and collected as a roll 40.

  (B) The draw ratio B1 in the second step is preferably 1.1 times or more, more preferably 1.2 times or more, preferably 4.0 times or less, more preferably 3.0 times or less. (B) By setting the draw ratio B1 in the second step to be equal to or higher than the lower limit of the above range, the refractive index in the drawing direction can be increased. Further, by setting the upper limit value or less, the slow axis direction of the half-wave plate can be easily controlled.

  (B) The stretching temperature T1 in the second step is preferably Tg ° C. or higher, more preferably Tg + 2 ° C. or higher, particularly preferably Tg + 5 ° C. or higher, preferably Tg + 40 ° C. or lower, more preferably Tg + 35 ° C. or lower, particularly preferably. Tg + 30 ° C. or lower. Here, Tg refers to the glass transition temperature of a resin having a positive intrinsic birefringence value. In the tenter stretching machine 200, (b) the stretching temperature T1 in the second step refers to the temperature in the stretching zone 250 of the tenter stretching machine 200. (B) By setting the stretching temperature T1 in the second step within the above range, the molecules contained in the pre-stretching film 20 can be reliably oriented, so that the intermediate film 30 having desired optical properties can be easily obtained. be able to.

  (B) The molecules contained in the intermediate film 30 are oriented by being stretched in the second step. Therefore, the intermediate film 30 has a slow axis. (B) In the second step, since stretching is performed in an oblique direction, the slow axis of the intermediate film 30 appears in the oblique direction of the intermediate film 30. Specifically, the intermediate film 30 has a slow axis in the range of usually 5 ° to 85 ° with respect to the width direction.

  The specific direction of the slow axis of the intermediate film 30 is preferably set according to the direction of the slow axis of the half-wave plate to be manufactured. Usually, (c) the angle formed by the slow axis of the half-wave plate obtained by the third step with respect to the width direction is larger than the angle formed by the slow axis of the intermediate film 30 with respect to the width direction. growing. Therefore, the angle formed by the slow axis of the intermediate film 30 with respect to the width direction is preferably smaller than the angle formed by the slow axis of the half-wave plate with respect to the width direction.

  Since the slow axis of the intermediate film 30 is expressed by stretching the pre-stretching film 20 in an oblique direction, the specific direction of the slow axis of the intermediate film 30 is the above-described (b) second step. It can be adjusted according to the stretching conditions. For example, the direction of the slow axis of the intermediate film 30 can be adjusted by adjusting the feeding angle φ formed by the feeding direction D20 of the pre-stretching film 20 from the feeding roll 10 and the winding direction D30 of the intermediate film 30. . Here, the feeding direction D <b> 20 of the pre-stretching film 20 indicates the traveling direction of the pre-stretching film 20 that is fed from the feeding roll 10. The winding direction D30 of the intermediate film 30 indicates the traveling direction of the intermediate film 30 that is wound as the roll 40.

  (B) After the second step, (c) a third step is performed in which the intermediate film 30 is freely uniaxially stretched in the longitudinal direction to obtain a long half-wave plate. Here, free uniaxial stretching refers to stretching in a certain direction and applying no restraining force in directions other than the stretching direction. Therefore, the free uniaxial stretching in the longitudinal direction of the intermediate film 30 shown in this example refers to stretching in the longitudinal direction performed without restraining the end portion in the width direction of the intermediate film 30. (C) Such stretching in the third step is usually performed using a roll stretching machine while continuously transporting the intermediate film 30 in the longitudinal direction.

FIG. 3 is a plan view schematically showing an example of a roll stretching machine 300 used for stretching the intermediate film 30.
As shown in FIG. 3, the roll stretching machine 300 shown in this example is an apparatus for stretching the intermediate film 30 fed from the roll 40 in the longitudinal direction under a heating environment by an oven (not shown).

  The roll stretching machine 300 includes an upstream roll 310 and a downstream roll 320 as nip rolls that can transport the intermediate film 30 in the longitudinal direction in order from the upstream in the transport direction. Here, the rotational speed of the downstream roll 320 is set faster than the rotational speed of the upstream roll 310.

Stretching of the intermediate film 30 using the roll stretching machine 300 is performed as follows.
The intermediate film 30 is fed out from the roll 40, and the intermediate film 30 is continuously supplied to the roll stretching machine 300.
The roll stretching machine 300 conveys the supplied intermediate film 30 in the order of the upstream roll 310 and the downstream roll 320. At this time, since the rotation speed of the downstream roll 320 is faster than the rotation speed of the upstream roll 310, the intermediate film 30 is stretched in the longitudinal direction, and the half-wave plate 50 is obtained. In the stretching by the roll stretching machine 300, both end portions 31 and 32 in the width direction of the intermediate film 30 are not restrained. Therefore, normally, the width of the intermediate film 30 is reduced as the film is stretched in the longitudinal direction, so that the half-wave plate 50 having a smaller width than the intermediate film 30 is obtained. In this example, the half-wave plate 50 is obtained as a biaxially stretched film stretched in two directions, that is, a longitudinal direction and an oblique direction.
Thereafter, the half-wave plate 50 is wound up and collected as a roll 60 after both ends thereof are trimmed as necessary.

  (C) The draw ratio B2 in the third step is preferably smaller than the draw ratio B1 in (b) the second step. Thereby, in the half-wave plate 50 which has a slow axis in an oblique direction, it becomes possible to perform stretching while suppressing the generation of wrinkles. Thus, the conventional diagonal uniaxially stretched film with respect to the width direction can be obtained by combining stretching in the oblique direction and free uniaxial stretching in the longitudinal direction in this order, and setting the stretching ratio to B1> B2. A half-wave plate 50 having a slow axis in a larger angular direction can be easily manufactured.

  At this time, the optical uniaxiality of the half-wave plate 50 can be increased by increasing the draw ratio B2. In the half-wave plate 50 obtained by stretching a resin having positive intrinsic birefringence, the NZ coefficient tends to approach 1.0 as the uniaxiality increases. The uniaxial half-wave plate 50 having a high uniaxiality can make the NZ coefficient close to 1.0, so that the circularly polarizing plate obtained by using the optical laminate including the half-wave plate reflects external light in the tilt direction. Can be effectively reduced.

  (C) The specific draw ratio B2 in the third step is preferably 1.1 times or more, more preferably 1.15 times or more, particularly preferably 1.2 times or more, preferably 2.0 times or less. More preferably, it is 1.8 times or less, and particularly preferably 1.6 times or less. (C) The wrinkles of the half-wave plate 50 can be suppressed by setting the draw ratio B2 in the third step to be equal to or higher than the lower limit of the above range. In addition, by setting the value to the upper limit value or less, the direction of the slow axis can be easily controlled.

  (C) The stretching temperature T2 in the third step is preferably higher than “T1-20 ° C.”, more preferably “T1-18 ° C.” or more, particularly preferably based on the stretching temperature T1 in the (b) second step. Is “T1−16 ° C.” or more, preferably lower than “T1 + 5 ° C.”, more preferably “T1 + 4 ° C.” or less, and particularly preferably “T1 + 3 ° C.” or less. (C) By setting the stretching temperature T2 in the third step within the above range, the in-plane retardation of the half-wave plate 50 can be effectively adjusted.

The method for manufacturing the half-wave plate shown in the above example may be further modified.
For example, the manufacturing method of a half-wave plate may have arbitrary processes other than (a) 1st process, (b) 2nd process, and (c) 3rd process. As such a step, for example, a step of providing a protective layer on the surface of the half-wave plate can be mentioned.
Moreover, for example, a film obtained by stretching the film before stretching in an arbitrary direction may be used as the film before stretching. Thus, (b) As a method of extending | stretching the film before extending | stretching before using for a 2nd process, the horizontal extending | stretching method using a roll system, the float system longitudinal stretch method, a tenter stretching machine, etc. can be used, for example.
Moreover, in the example mentioned above, the intermediate film 30 is wound up into a roll 40, and the intermediate film 30 is unwound from the roll 40 and supplied to the third step, but (b) the intermediate film obtained in the second step. 30 may be supplied to the third step without being wound up.

[3/4 wavelength plate]
The in-plane retardation of the quarter wavelength plate is usually 110 nm or more and usually 154 nm or less. When the quarter-wave plate has such in-plane retardation, an optical laminate that can function as a broadband quarter-wave plate can be realized by combining the half-wave plate and the quarter-wave plate. Furthermore, by combining this optical layered body with a linear polarizer, a circularly polarizing plate capable of suppressing reflection of light in a wide wavelength range in both the front direction and the tilt direction can be realized. Among them, in order to particularly effectively reduce the reflection of external light in the tilt direction, the in-plane retardation of the quarter-wave plate is preferably 118 nm or more, preferably 138 nm or less, more preferably 128 nm or less. is there.

  The NZ coefficient of the quarter wave plate is usually 1.00 or more, preferably 1.05 or more, more preferably 1.10 or more, and usually 1.50 or less, preferably 1.40 or less, more preferably 1. .30 or less. The fact that the NZ coefficient of the quarter-wave plate is close to 1.0 as described above indicates that the optical uniaxial property of the quarter-wave plate is high. Thus, the circularly-polarizing plate obtained using an optical laminated body provided with a quarter wavelength plate having high uniaxiality can effectively reduce reflection of external light in the tilt direction. Moreover, the quarter wavelength plate having such an NZ coefficient can be easily manufactured.

  The chromatic dispersion of the quarter-wave plate can have chromatic dispersion characteristics such as forward chromatic dispersion characteristics, flat chromatic dispersion characteristics, and reverse chromatic dispersion characteristics.

  The average orientation angle θq formed by the slow axis of the quarter-wave plate with respect to the width direction of the quarter-wave plate is usually 0 ° or more, preferably 5 ° or more, more preferably 10 ° or more. It is less than 50 °, preferably 40 ° or less, more preferably 30 ° or less (see FIG. 1). By keeping the average orientation angle θq of the quarter-wave plate within the above range, an optical laminate that can function as a broadband quarter-wave plate can be realized by combining the half-wave plate and the quarter-wave plate. Furthermore, by combining this optical layered body with a linear polarizer, a circularly polarizing plate capable of suppressing reflection of light in a wide wavelength range in both the front direction and the tilt direction can be realized.

  As can be seen from the average orientation angle θh of the half-wave plate and the average orientation angle θq of the quarter-wave plate, the slow axis of the half-wave plate and the slow axis of the quarter-wave plate are: Usually intersect. Here, the crossing angle θd between the slow axis of the half-wave plate and the slow axis of the quarter-wave plate is preferably 55 ° or more, more preferably 57 ° or more, and particularly preferably 59 ° or more. The angle is preferably 65 ° or less, more preferably 63 ° or less, and particularly preferably 61 ° or less (see FIG. 1). The intersection angle θd can be measured as the difference between the average orientation angle θh of the half-wave plate and the average orientation angle θq of the quarter-wave plate. By keeping the intersection angle θd within the above range, the circularly polarizing plate obtained using the optical laminate can effectively suppress the reflection of light.

  The quarter-wave plate is a member made of a resin having a positive intrinsic birefringence value, and is usually a film made of the resin. As the resin having a positive intrinsic birefringence value for the quarter-wave plate, a resin selected from the range described as a resin having a positive intrinsic birefringence value for the half-wave plate can be arbitrarily used. By applying to the quarter-wave plate a resin selected from the range described as having a positive intrinsic birefringence value for the half-wave plate, the same as explained in the section of the half-wave plate Advantages can also be obtained with a quarter wave plate. Especially, it is preferable that a half-wave plate and a quarter-wave plate consist of the same resin.

The total light transmittance of the quarter-wave plate is preferably 80% or more.
The haze of the quarter-wave plate is preferably 5% or less, more preferably 3% or less, particularly preferably 1% or less, and ideally 0%.

  The amount of the volatile component contained in the quarter-wave plate is preferably 0.1% by weight or less, more preferably 0.05% by weight or less, and further preferably 0.02% by weight or less, ideally zero. It is. By reducing the amount of volatile components, the dimensional stability of the quarter-wave plate can be improved, and the change over time in optical characteristics such as retardation can be reduced.

  The saturated water absorption of the quarter-wave plate is preferably 0.03% by weight or less, more preferably 0.02% by weight or less, particularly preferably 0.01% by weight or less, and ideally zero. When the saturated water absorption rate of the quarter-wave plate is in the above range, it is possible to reduce a change with time in optical characteristics such as in-plane retardation.

  The thickness of the quarter-wave plate is preferably 10 μm or more, more preferably 15 μm or more, particularly preferably 20 μm or more, preferably 80 μm or less, more preferably 60 μm or less, and particularly preferably 50 μm or less. By making the thickness of the quarter-wave plate equal to or greater than the lower limit of the above range, desired retardation can be easily expressed. Moreover, the optical laminated body can be thinned by setting it to the upper limit value or less.

  The manufacturing method of a quarter wavelength plate is arbitrary. The quarter-wave plate can be produced as a stretched film by a production method including, for example, subjecting a long pre-stretch film made of resin to one or more oblique stretches. According to the manufacturing method including oblique stretching, a quarter wavelength plate can be easily manufactured.

  As a preferable manufacturing method of the quarter-wave plate, for example, (d) a fourth step of preparing a long unstretched film made of a resin having a positive intrinsic birefringence value, and (e) a long unstretched film And a fifth step of obtaining a long quarter-wave plate by stretching in a diagonal direction.

  (D) In the fourth step, a long unstretched film made of a resin having a positive intrinsic birefringence value is prepared. The film before stretching can be produced, for example, by the same method as in the first step (a) in the method for producing a half-wave plate. (D) By producing a pre-stretch film in the fourth step by the same method as in (a) the first step, the same advantages as in (a) the first step can be obtained in (d) the fourth step.

  (D) After preparing a long unstretched film in the fourth step, (e) performing a fifth step of stretching the long unstretched film in an oblique direction to obtain a quarter wavelength plate. In the fifth step, usually, stretching is performed using a tenter stretching machine while continuously transporting the film before stretching in the longitudinal direction. At this time, as the tenter stretching machine, the same tenter stretching machine as described in the second step (b) in the method for producing a half-wave plate can be used. (E) By using the same tenter stretching machine as in the (b) second step in the fifth step, the same advantages as in the (b) second step can be obtained in the (e) fifth step.

  (E) The draw ratio in the fifth step is preferably 1.1 times or more, more preferably 1.3 times or more, particularly preferably 1.5 times or more, preferably 5.0 times or less, more preferably It is 4.5 times or less, particularly preferably 4.3 times or less. (E) The refractive index in the stretching direction can be increased by setting the stretching ratio in the fifth step to be equal to or higher than the lower limit of the above range. In addition, by setting the upper limit value or less, the slow axis direction of the quarter-wave plate can be easily controlled.

  (E) The stretching temperature in the fifth step is preferably Tg ° C or higher, more preferably Tg + 2 ° C or higher, particularly preferably Tg + 5 ° C or higher, preferably Tg + 40 ° C or lower, more preferably Tg + 35 ° C or lower, particularly preferably Tg + 30. It is below ℃. (E) By making the extending | stretching temperature in a 5th process into the said range, since the molecule | numerator contained in the film before extending | stretching can be orientated reliably, the quarter wavelength plate which has a desired optical characteristic is obtained easily. be able to.

  The manufacturing method of the quarter wavelength plate shown in the above example may be further modified. For example, the manufacturing method of a quarter wavelength plate may have arbitrary processes other than (d) the 4th process and (e) the 5th process. For example, the method for manufacturing a quarter wavelength plate may include a step of trimming both end portions of the manufactured quarter wavelength plate. Moreover, the manufacturing method of a quarter wavelength plate may include the process similar to the arbitrary processes of the manufacturing method of a half wavelength plate.

[4. Any layer]
The optical layered body may further include an arbitrary layer in combination with the ½ wavelength plate and the ¼ wavelength plate. For example, the optical laminate can include a protective film layer for preventing damage.

  Further, the optical layered body may include an adhesive layer containing an adhesive for bonding the half-wave plate and the quarter-wave plate. Adhesives not only lose adhesiveness at room temperature by curing (including hot melt adhesives, UV curable adhesives, EB cured adhesives, etc.) but also adhesives that do not lose their adhesiveness Including pressure sensitive adhesives.

  The adhesive preferably contains a polymer having affinity for both the resin contained in the half-wave plate and the resin contained in the quarter-wave plate. Examples of the polymer contained in the adhesive include ethylene- (meth) acrylic acid ester copolymers such as ethylene- (meth) methyl acrylate copolymer and ethylene- (meth) ethyl acrylate copolymer; ethylene -Ethylene copolymers such as vinyl acetate copolymer and ethylene-styrene copolymer, and other olefin polymers. In addition, modified products obtained by modifying these polymers by oxidation, saponification, chlorination, chlorosulfonation, or the like may be used.

[5. Characteristics of optical laminates]
The optical laminated body can obtain at least the following advantages by including the above-described half-wave plate and quarter-wave plate.
-An optical laminated body can give the in-plane retardation of the wavelength of the light of about 1/4 with respect to the light which permeate | transmits the said optical laminated body in the front direction in a wide wavelength range.
-An optical laminated body can give the in-plane retardation of about 1/4 wavelength of the wavelength of the light to the light which permeate | transmits the said optical laminated body in the inclination direction in a wide wavelength range.
-Therefore, the optical laminated body can implement | achieve the circularly-polarizing plate which can reduce reflection of the light of a wide wavelength range in both a front direction and an inclination direction by combining with a linear polarizer.

[6. Manufacturing method of optical laminate]
The optical laminate can be manufactured by laminating a long half-wave plate and a long quarter-wave plate. Usually, bonding is performed with the longitudinal direction of the half-wave plate and the longitudinal direction of the quarter-wave plate being parallel. This bonding is preferably performed by roll to roll from the viewpoint of increasing the production efficiency of the optical laminate.

  Bonding with a roll roll means that the film is fed out from a roll of a long film, conveyed, and subjected to a bonding process with another film on a conveying line, and further obtained bonded material Is a bonding in an embodiment in which is taken up as a winding roll. For example, when a half-wave plate and a quarter-wave plate are bonded together, the half-wave plate is fed out from a long roll of half-wave plate, transported, and 1 / Bonding with a roll roll can be performed by performing the process of bonding with a 4-wavelength plate and using the obtained optical laminate as a take-up roll. In this case, the quarter wavelength plate can also be fed from the roll and supplied to the bonding process.

  When manufacturing an optical layered body using roll rolls, unlike the conventional method of laminating single-wafer half-wave plates and quarter-wave plates, a complicated optical axis alignment process is not required. is there. Therefore, efficient manufacture of the optical laminate can be realized.

[7. Circular polarizing plate]
A circularly polarizing plate is obtained by laminating the above optical laminate with a linear polarizer. This circularly polarizing plate is formed by laminating the above-described long optical laminate and the long linear polarizer so that the linear polarizer, the half-wave plate and the quarter-wave plate are in this order in the thickness direction. It is the circularly-polarizing plate obtained.

  A linear polarizer is a long polarizing plate having a polarization transmission axis and a polarization absorption axis, absorbs linearly polarized light having a vibration direction parallel to the polarization absorption axis, and has a vibration direction parallel to the polarization transmission axis. It has a function that can transmit. Here, the vibration direction of linearly polarized light means the vibration direction of the electric field of linearly polarized light.

  As a linear polarizer, for example, a film of an appropriate vinyl alcohol polymer such as polyvinyl alcohol or partially formalized polyvinyl alcohol, dyeing treatment with dichroic substances such as iodine and dichroic dye, stretching treatment, crosslinking treatment Or the like can be used in an appropriate order and manner. Usually, in the stretching process for producing a linear polarizer, the film is stretched in the longitudinal direction, so that the obtained linear polarizer has a polarization absorption axis parallel to the longitudinal direction of the linear polarizer and the width of the linear polarizer. A polarization transmission axis parallel to the direction can be developed. This linear polarizer is capable of absorbing linearly polarized light having a vibration direction parallel to the polarization absorption axis, and is particularly preferably excellent in polarization degree. The thickness of the linear polarizer is generally 5 μm to 80 μm, but is not limited thereto.

  The polarization transmission axis of the linear polarizer is preferably parallel to the width direction of the linear polarizer. Thereby, the linear polarizer can have an absorption axis in the width direction of a long circularly polarizing plate including the linear polarizer. In this case, it is possible to manufacture a long circularly polarizing plate by laminating a long linear polarizer and a long optical laminated body with their longitudinal directions parallel to each other. Therefore, a long circularly polarizing plate can be manufactured by laminating a long linear polarizer and a long optical laminate by a roll roll.

  When a long circularly polarizing plate is manufactured by laminating a long linear polarizer and a long broadband quarter-wave plate, conventionally, a linear polarizer, a half-wave plate, and a quarter-wave plate are used. It was difficult to adjust the direction of the optical axis so that each optical axis forms a predetermined angle required for the circularly polarizing plate. Therefore, in the past, a circularly polarizing plate was manufactured by laminating a single-wafer linear polarizer and a single-wafer broadband quarter-wave plate cut out from a long film by adjusting the angle. It took time and cost (production of scraps, etc.) to manufacture In view of such conventional circumstances, it is advantageous in terms of industrial production that the circularly polarizing plate of the present invention can be efficiently manufactured using a roll roll.

  In the circularly polarizing plate, the average angle θph formed by the polarization transmission axis of the linear polarizer and the slow axis of the half-wave plate of the optical laminate is preferably 50 ° or more, more preferably 55 ° or more, particularly preferably. It is 60 ° or more, preferably less than 90 °, more preferably 85 ° or less, and particularly preferably 80 ° or less. Usually, since the polarization transmission axis of a long linear polarizer is parallel to the width direction of the linear polarizer, when the circularly polarizing plate is manufactured by roll rolls, the polarization transmission axis of the linear polarizer and the optical lamination The average angle θph formed by the slow axis of the half-wave plate of the body substantially coincides with the average orientation angle θh of the half-wave plate. Thus, when the circularly polarizing plate is manufactured by roll rolls, the relationship among the average angle θph, the average orientation angle θh, and the average orientation angle θq particularly satisfies θq = 2θph−135 ° = 2θh−135 °. preferable. When this circularly polarizing plate is provided on a surface that can reflect light because the average angle θph formed by the polarization transmission axis of the linear polarizer and the slow axis of the half-wave plate is within the above range. Moreover, reflection of external light can be effectively reduced in both the front direction and the tilt direction. Therefore, this circularly polarizing plate can be used as an antireflection film that can effectively reduce the reflection of external light in a wide wavelength range of the visible region.

The circularly polarizing plate may further include an arbitrary layer in combination with the linear polarizer and the optical laminate. Examples of the optional layer include an adhesive layer for bonding the linear polarizer and the optical laminate; a mat layer for improving the slipperiness of the film; a hard coat layer such as an impact-resistant polymethacrylate resin layer; Antireflection layer; antifouling layer and the like.
In addition, the circularly polarizing plate has zero retardation in the front direction for the purpose of suppressing the retardation change that occurs when observing from the tilt direction of the wave plate, but changes the retardation of the wave plate with the tilt in the tilt direction. An optical compensation layer such as a positive C plate whose retardation changes so as to cancel may be further provided. Here, the positive C plate means a plate satisfying the relationship of nx = ny <nz.

[8. Organic EL display device]
The organic EL display device of the present invention includes an antireflection film obtained by cutting out from the above-described long circularly polarizing plate. The antireflection film is usually provided on the display surface in an organic EL display device. By providing an antireflection film on the display surface of the organic EL display device so that the surface on the linear polarizer side faces the viewing side, light incident from the outside of the device is reflected inside the device and emitted to the outside of the device. As a result, glare of the display surface of the display device can be suppressed. Specifically, only a part of the linearly polarized light from the outside of the apparatus passes through the linear polarizer, and then passes through the half-wave plate and the quarter-wave plate, thereby circularly polarized light. It becomes. Circularly polarized light is reflected by a component (such as a reflective electrode in an organic EL element) that reflects light in the display device, and passes again through a quarter-wave plate and a half-wave plate, thereby entering linearly polarized light. Linearly polarized light having a vibration direction orthogonal to the vibration direction of the light beam, and does not pass through the linear polarizer. Thereby, the function of antireflection is achieved.
When viewing an organic EL display device using polarized sunglasses, the polarization transmission axis of the linear polarizer provided in the organic EL display device is + 45 ° or −45 ° with respect to the polarization transmission axis of the polarized sunglasses. Some can maintain better visibility.

  In particular, in the optical laminated body described above, since the NZ coefficient of the half-wave plate and the NZ coefficient of the quarter-wave plate are within a predetermined range, not only the antireflection function in the front direction but also the antireflection in the oblique direction. It can also have a function.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof. In the following description, “%” and “parts” representing amounts are based on weight unless otherwise specified. In addition, the operations described below were performed in a normal temperature and pressure atmosphere unless otherwise specified.

[Evaluation method]
[Measurement method of average orientation angle]
The average orientation angle formed by the slow axis of the film with respect to the width direction is measured at intervals of 50 mm in the width direction of the film using a polarizing microscope (OLYMPUS "BX51"), and the in-plane slow axis is measured. The average value of the angle (orientation angle) formed by the direction of the slow axis and the width direction of the film was determined, and this was taken as the average orientation angle.

[Measurement method of retardation and NZ coefficient]
In-plane retardation and retardation in the thickness direction were measured at a plurality of points at intervals of 50 mm in the width direction of the film using a phase difference meter (“KOBRA-21ADH” manufactured by Oji Scientific Instruments). The average value of the measured values at these points was calculated, and this average value was used as the in-plane retardation and the thickness direction retardation of the film. At this time, the measurement was performed at a wavelength of 590 nm. Further, the NZ coefficient was calculated from the obtained in-plane retardation and retardation in the thickness direction.

[Visual evaluation method]
A mirror having a planar reflecting surface was prepared. This mirror was placed so that the reflecting surface was horizontal and facing upward. A circularly polarizing plate was attached on the reflecting surface of this mirror so that the polarizing film side would face upward.

Thereafter, the circularly polarizing plate on the mirror was visually observed in a state where the circularly polarizing plate was illuminated with sunlight on a sunny day. Observation of the circularly polarizing plate,
(I) a front direction with a polar angle of 0 ° and an azimuth angle of 0 °;
(Ii) The measurement was carried out in both a polar angle of 45 ° and an inclination direction of an azimuth angle of 0 ° to 360 °.

(I) In the observation in the front direction, it was evaluated whether or not the reflection of sunlight is hardly concerned and the circularly polarizing plate looks black.
Further, (ii) in the observation in the tilt direction, it was evaluated whether or not the reflectance and the tint did not change depending on the azimuth angle.

  The above visual evaluation is performed by 20 observers, and each person ranks the results of all the examples and comparative examples, and the points corresponding to the ranks (1st place 7 points, 2nd place 6 points,...・ The lowest one was given. For each of the examples and comparative examples, the total points scored by each person were arranged in the order of points, and evaluation was performed in the order of A, B, C, D, and E from the upper group within the range of the points.

[Calculation method of reflectance by simulation]
Using the “LCD Master” manufactured by Shintec Co., Ltd. as the simulation software, the circularly polarizing plates manufactured in each Example and Comparative Example were modeled, and the reflectance was calculated.

  In the simulation model, a structure in which a circularly polarizing plate was attached to the reflecting surface of the mirror having a planar reflecting surface so as to be in contact with the mirror on the quarter wavelength plate side was set. Therefore, in this model, a structure in which a polarizing film, a half-wave plate, a quarter-wave plate, and a mirror are provided in this order in the thickness direction is set.

  And in the said model, the reflectance when light was irradiated to a circularly-polarizing plate from D65 light source was calculated in the (i) front direction and (ii) inclination direction of the said circularly-polarizing plate. Here, (i) In the front direction, the reflectance in the direction of polar angle 0 ° and azimuth angle 0 ° was calculated. (Ii) In the tilt direction, at a polar angle of 45 °, calculation is performed in 5 ° increments in the azimuth angle range from 0 ° to 360 °, and the average of the calculated values is the modeled circularly polarizing plate It was adopted as the reflectance in the tilt direction. In this simulation, the surface reflection component actually generated on the surface of the polarizing film is excluded from the reflectance.

[Production Example 1: Production of base material (A) before stretching]
A pellet of thermoplastic norbornene resin (manufactured by ZEON Corporation, glass transition temperature Tg = 126 ° C.) was dried at 100 ° C. for 5 hours. The dried pellets were fed into an extruder, melted in the extruder, and fed to a T die through a polymer pipe and a polymer filter. Then, the molten resin was extruded from the T die onto a casting drum in the form of a film and cooled to obtain a long base material (A) having a thickness of 70 μm and a width of 1350 mm. This base material (A) before stretching was wound up while being bonded to a masking film ("FF1025" manufactured by Tretegar) for protection and recovered as a roll.

[Production Example 2: Production of base material (B) before stretching]
A long substrate before stretching having a thickness of 70 μm and a width of 1350 mm in the same manner as in Production Example 1 except that “ZEONOR1420R” (glass transition temperature Tg = 137 ° C.) manufactured by Nippon Zeon was used as a thermoplastic norbornene resin pellet. (B) was produced and recovered as a roll.

[Example 1]
[Production of 1-1.1 / 2 wave plate]
The base material (A) before stretching was drawn from the roll of the base material (A) before stretching obtained in Production Example 1, and the masking film was continuously peeled off and supplied to a tenter stretching machine. And the base material (A) before extending | stretching was diagonally stretched with the tenter stretching machine, and the elongate intermediate film was obtained. The stretching conditions for the oblique stretching were a stretching ratio of 1.5 times and a stretching temperature of 140 ° C. The average orientation angle formed by the slow axis of the obtained intermediate film with respect to the width direction was 45 °, and the in-plane retardation was 190 nm.

  The obtained intermediate film was further subjected to free longitudinal uniaxial stretching. During the free longitudinal uniaxial stretching, the stretching direction was the film longitudinal direction, the stretching ratio was 1.42 times, and the stretching temperature was 125 ° C. Thereafter, both ends in the width direction of the stretched intermediate film were trimmed to obtain a long half-wave plate having a width of 1330 mm. The resulting half-wave plate had a slow axis of 75 °, an average orientation angle of 75 °, an NZ coefficient of 1.15, an in-plane retardation of 260 nm, and a thickness of 40 μm. The obtained half-wave plate was wound up while being bonded to a new masking film ("FF1025" manufactured by Tretegar) for protection to obtain a first film roll (I-1).

[Production of 1-2 / 1/4 wave plate]
The base material (A) before stretching was drawn from the roll of the base material (A) before stretching obtained in Production Example 1, and the masking film was continuously peeled off and supplied to a tenter stretching machine. And the base material (A) before extending | stretching was diagonally extended with the tenter extending | stretching machine, and the elongate quarter wavelength plate was obtained. The stretching conditions for the oblique stretching were a stretching ratio of 4.3 times and a stretching temperature of 142 ° C. The obtained 1/4 wavelength plate had an average orientation angle of 15 ° with respect to the width direction of the slow axis, an NZ coefficient of 1.19, an in-plane retardation of 130 nm, and a thickness of 17 μm. The obtained quarter-wave plate was wound up while being bonded to a new masking film ("FF1025" manufactured by Tretegar) for protection to obtain a second film roll (I-2).

[1-3. (Manufacture of optical laminate)
The half-wave plate was pulled out from the first film roll (I-1), and the masking film was continuously peeled off. Well, the 1/4 wavelength plate was pulled out from the second film roll (I-2), and the masking film was continuously peeled off. Then, the half-wave plate and the quarter-wave plate were bonded to each other through an adhesive layer (“CS9621” manufactured by Nitto Denko Corporation) with the longitudinal directions thereof being parallel to each other. As a result, the long optical laminate (I−) was bonded so that the slow axis of the half-wave plate and the slow axis of the quarter-wave plate intersected at 60 ° when viewed from the thickness direction. 3) was obtained.

[1-4. (Manufacture of circularly polarizing plate)
As a long linear polarizer, a polarizing film (“HLC2-5618S” manufactured by Sanritz Corporation, a thickness of 180 μm, a polarizer having a polarization transmission axis in a direction of 0 ° with respect to the width direction) was prepared. One surface of this polarizing film and the surface on the half-wave plate side of the optical laminate (I-3) are parallel to the longitudinal direction of the polarizing film and the longitudinal direction of the optical laminate (I-3). Then, they were bonded together via an adhesive layer (“CS9621” manufactured by Nitto Denko). This obtained the elongate circularly-polarizing plate which has a layer structure of (polarizing film) / (adhesive layer) / (1/2 wavelength plate) / (adhesive layer) / (1/4 wavelength plate). The circularly polarizing plate thus obtained was evaluated by the method described above.

[Example 2]
In the process of producing a half-wave plate, the stretching ratio of the free longitudinal uniaxial stretching of the intermediate film was changed to 1.41 times so that a half-wave plate with an average orientation angle of 72.5 ° was obtained, The temperature was changed to 124 ° C.
Further, in the step of producing a quarter wavelength plate, the stretching direction of the base material (A) before stretching was adjusted so that a quarter wavelength plate having an average orientation angle of 10 ° was obtained.
Except for the above, the same as in Example 1, a long circle in which the slow axis of the half-wave plate and the slow axis of the quarter-wave plate intersect at 62.5 ° when viewed in the thickness direction. A polarizing plate was produced. The circularly polarizing plate thus obtained was evaluated by the method described above.

[Example 3]
In the step of producing a half-wave plate, the stretching temperature for oblique stretching of the base material (A) before stretching is changed to 139 ° C. so that a half-wave plate with an average orientation angle of 70.0 ° is obtained, The stretching ratio of free longitudinal uniaxial stretching of the intermediate film was changed to 1.41 times, and the stretching temperature was changed to 123 ° C.
Moreover, in the process of manufacturing a quarter wavelength plate, the stretching direction of the base material (A) before stretching is adjusted so that a quarter wavelength plate having an average orientation angle of 5 ° is obtained, and the stretching ratio is 4.1. The stretching temperature was changed to 141 ° C.
Except for the above, the same as in Example 1, a long circular polarizing plate in which the slow axis of the half-wave plate and the slow axis of the quarter-wave plate intersect at 65 ° when viewed from the thickness direction. Manufactured. The circularly polarizing plate thus obtained was evaluated by the method described above.

[Example 4]
In the process of manufacturing a half-wave plate, the stretching ratio of the oblique stretching of the base material (A) before stretching is changed to 1.36 times so that a half-wave plate having an average orientation angle of 67.5 ° is obtained. Then, the stretching temperature was changed to 136 ° C., and the stretching ratio of free longitudinal uniaxial stretching of the intermediate film was changed to 1.28 times.
Further, in the step of producing a quarter-wave plate, the stretching direction of the base material (A) before stretching is set to that of the base material (A) before stretching so that a quarter-wave plate having an average orientation angle of 0 ° is obtained. The width direction was changed and the draw ratio was changed to 3.4 times.
Except for the above, the same as in Example 1, a long circle in which the slow axis of the half-wave plate and the slow axis of the quarter-wave plate intersect at 67.5 ° when viewed from the thickness direction. A polarizing plate was produced. The circularly polarizing plate thus obtained was evaluated by the method described above.

[Example 5]
[Production of 5-1.1 / 2 wavelength plate]
The base material (B) before stretching was drawn from the roll of the base material (B) before stretching obtained in Production Example 2, the masking film was continuously peeled, and free longitudinal uniaxial stretching was performed. During the free longitudinal uniaxial stretching, the stretching direction was the film longitudinal direction, the stretching ratio was 1.9 times, and the stretching temperature was 136 ° C. Thereafter, both ends in the width direction of the stretched intermediate film were trimmed to obtain a long half-wave plate. The average orientation angle formed by the slow axis of the obtained half-wave plate with respect to the width direction was 90 °, the Nz coefficient was 1.0, and the in-plane retardation was 260 nm. The obtained half-wave plate was wound up with a new masking film ("FF1025" manufactured by Tretegar) for protection to obtain a first film roll (V-1).

[Production of 5-2.1 / 4 wave plate]
The base material (A) before stretching was drawn from the roll of the base material (A) before stretching obtained in Production Example 1, and the masking film was continuously peeled off and supplied to a tenter stretching machine. And the base material (A) before extending | stretching was diagonally extended with the tenter extending | stretching machine, and the elongate quarter wavelength plate was obtained. The stretching conditions for oblique stretching were a stretching ratio of 2.4 times and a stretching temperature of 138 ° C. The average orientation angle formed by the slow axis of the obtained quarter-wave plate with respect to the width direction was 30 °, the Nz coefficient was 1.19, and the in-plane retardation was 130 nm. The obtained quarter-wave plate was wound up while being bonded to a new masking film ("FF1025" manufactured by Treteger) for protection to obtain a second film roll (V-2).

[5-3. (Manufacture of optical laminate)
The half-wave plate was pulled out from the first film roll (V-1), and the masking film was continuously peeled off. Well, the 1/4 wavelength plate was pulled out from the second film roll (V-2), and the masking film was continuously peeled off. Then, the half-wave plate and the quarter-wave plate were bonded to each other through an adhesive layer (“CS9621” manufactured by Nitto Denko Corporation) with the longitudinal directions thereof being parallel to each other. Thereby, the long optical laminate (V−) in which the slow axis of the half-wave plate and the slow axis of the quarter-wave plate are bonded so as to intersect at 60 ° when viewed from the thickness direction. 3) was obtained.

[5-4. (Manufacture of circularly polarizing plate)
As a long linear polarizer, a polarizing film (“HLC2-5618S” manufactured by Sanritz Corporation, a thickness of 180 μm, a polarizer having a polarization transmission axis in a direction of 0 ° with respect to the width direction) was prepared. One surface of this polarizing film and the surface on the half-wave plate side of the optical laminate (I-3) are the polarization transmission axis of the polarizing film and the slow axis of the half-wave plate (V-1). Were bonded through an adhesive layer (“CS9621” manufactured by Nitto Denko) so that the two crossed at 75 ° as viewed from the thickness direction, and the bonded portion was cut out. Thus, a single-wafer circularly polarizing plate having a layer configuration of (polarizing film) / (adhesive layer) / (1/2 wavelength plate) / (adhesive layer) / (¼ wavelength plate) was obtained. The circularly polarizing plate thus obtained was evaluated by the method described above.

[Comparative Example 1]
[Production of C1-1.1 / 2 Wave Plate]
The base material (A) before stretching was drawn from the roll of the base material (A) before stretching obtained in Production Example 1, and the masking film was continuously peeled off and supplied to a tenter stretching machine. And the base material (A) before extending | stretching was diagonally extended with the tenter extending | stretching machine, and the elongate 1/2 wavelength plate was obtained. The stretching conditions for the oblique stretching were a stretching ratio of 1.5 times and a stretching temperature of 142 ° C. The average orientation angle formed by the slow axis of the obtained half-wave plate with respect to the width direction was 15 °, the Nz coefficient was 1.19, and the in-plane retardation was 260 nm. The obtained half-wave plate was wound up with a new masking film ("FF1025" manufactured by Tretegar) for protection to obtain a first film roll (CI-1).

[Production of C1-2.1 / 4 Wave Plate]
The base material (A) before stretching was drawn from the roll of the base material (A) before stretching obtained in Production Example 1, and the masking film was continuously peeled off and supplied to a tenter stretching machine. And the base material (A) before extending | stretching was diagonally stretched with the tenter stretching machine, and the elongate intermediate film was obtained. The stretching conditions for the oblique stretching were a stretching ratio of 1.25 times and a stretching temperature of 135 ° C. The average orientation angle formed by the slow axis of the obtained intermediate film with respect to the width direction was 45 °, and the in-plane retardation was 140 nm.

  The obtained intermediate film was further subjected to free longitudinal uniaxial stretching. During the free longitudinal uniaxial stretching, the stretching direction was the film longitudinal direction, the stretching ratio was 1.40 times, and the stretching temperature was 133 ° C. Thereafter, both ends in the width direction of the stretched intermediate film were trimmed to obtain a long quarter-wave plate. The average orientation angle formed by the slow axis of the obtained quarter-wave plate with respect to the width direction was 75 °, the NZ coefficient was 1.15, and the in-plane retardation was 130 nm. The obtained quarter-wave plate was wound up while being bonded to a new masking film ("FF1025" manufactured by Tretegar) for protection to obtain a second film roll (CI-2).

[C1-3. (Manufacture of optical laminate)
The half-wave plate was pulled out from the first film roll (CI-1), and the masking film was continuously peeled off. Well, the 1/4 wavelength plate was pulled out from the second film roll (CI-2), and the masking film was continuously peeled off. Then, the half-wave plate and the quarter-wave plate were bonded to each other through an adhesive layer (“CS9621” manufactured by Nitto Denko Corporation) with the longitudinal directions thereof being parallel to each other. As a result, the long optical laminate (CI−) was bonded so that the slow axis of the half-wave plate and the slow axis of the quarter-wave plate intersected at 60 ° when viewed from the thickness direction. 3) was obtained.

[C1-4. (Manufacture of circularly polarizing plate)
As a long linear polarizer, a polarizing film (“HLC2-5618S” manufactured by Sanritz Corporation, a thickness of 180 μm, a polarizer having a polarization transmission axis in a direction of 0 ° with respect to the width direction) was prepared. One surface of the polarizing film and the surface on the half-wave plate side of the optical laminate (CI-3) are parallel to the longitudinal direction of the polarizing film and the longitudinal direction of the optical laminate (CI-3). Then, they were bonded together via an adhesive layer (“CS9621” manufactured by Nitto Denko). This obtained the elongate circularly-polarizing plate which has a layer structure of (polarizing film) / (adhesive layer) / (1/2 wavelength plate) / (adhesive layer) / (1/4 wavelength plate). The circularly polarizing plate thus obtained was evaluated by the method described above.

[Comparative Example 2]
[Manufacture of C2-1.1 / 4 Wave Plate]
The base material (A) before stretching was drawn from the roll of the base material (A) before stretching obtained in Production Example 1, and the masking film was continuously peeled off and supplied to a tenter stretching machine. And the base material (A) before extending | stretching was diagonally extended with the tenter extending | stretching machine, and the elongate quarter wavelength plate was obtained. The stretching conditions for the oblique stretching were a stretching ratio of 2.36 times and a stretching temperature of 144 ° C. The average orientation angle formed by the slow axis of the obtained quarter-wave plate with respect to the width direction was 45 °, the NZ coefficient was 1.15, and the in-plane retardation was 130 nm. The obtained quarter-wave plate was wound up while being bonded to a new masking film ("FF1025" manufactured by Treteger) for protection to obtain a film roll (CII-1).

[C2-2. (Manufacture of circularly polarizing plate)
The quarter wave plate was pulled out from the film roll (CII-1), and the masking film was continuously peeled off. This 1/4 wavelength plate and a polarizing film as a long linear polarizer ("LLC2-5618S" manufactured by Sanlitz Co., Ltd., a polarizer having a thickness of 180 μm and a polarization transmission axis in a direction of 0 ° with respect to the width direction. ) With the longitudinal direction of the quarter-wave plate and the longitudinal direction of the polarizing film parallel to each other through an adhesive layer (“CS9621” manufactured by Nitto Denko). This obtained the elongate circularly-polarizing plate which has a layer structure of (polarizing film) / (adhesive layer) / (1/4 wavelength plate). The circularly polarizing plate thus obtained was evaluated by the method described above.

[result]
The results of the examples and comparative examples are shown in the table below. In the following table, the meanings of the abbreviations are as follows.
λ / 2: 1/2 wavelength plate.
λ / 4: 1/4 wavelength plate.
Oblique: Diagonal direction.
Horizontal: width direction.
Vertical: Longitudinal direction.
Re: In-plane retardation.
Crossing angle: The angle at which the slow axis of the half-wave plate and the slow axis of the quarter-wave plate intersect.

[Consideration]
As shown in Table 1, in the example, the reflectance can be lowered in both the front direction and the tilt direction. From this, it was confirmed that by using the optical layered body of the present invention, a circularly polarizing plate capable of effectively reducing the reflection of external light in both the front direction and the tilt direction can be realized.

DESCRIPTION OF SYMBOLS 10 Feeding roll 20 Films before extending | stretching 21 and 22 End part of width direction of film before extending | stretching 30 Intermediate | middle film 31 and 32 End part of width direction of intermediate | middle film 40 Roll 50 1/2 wavelength plate 60 Roll 100 Optical laminated body 110 1 / Two-wavelength plate 111 Slow axis of half-wave plate 112 Axis obtained by projecting the slow-axis of half-wave plate on the surface of quarter-wave plate 120 1/4 wavelength plate 121 Slow of quarter-wave plate Phase shaft 200 Tenter stretching machine 210R and 210L Grasping element 220R and 220L Guide rail 230 Inlet part of tenter stretching machine 240 Outlet part of tenter stretching machine 250 Drawing zone 300 Roll stretching machine 310 Upstream roll 320 Downstream roll

Claims (7)

A long half-wave plate and a long quarter-wave plate made of a resin having a positive intrinsic birefringence value,
The average orientation angle formed by the slow axis of the half-wave plate with respect to the width direction is 50 ° or more and 90 ° or less,
The NZ coefficient of the half-wave plate is 1.0 to 1.5,
The average orientation angle formed by the slow axis of the quarter-wave plate with respect to the width direction is 0 ° or more and less than 50 °,
The optical laminated body whose NZ coefficient of the said 1/4 wavelength plate is 1.0-1.5.   The optical laminated body of Claim 1 whose crossing angle of the slow axis of the said 1/2 wavelength plate and the slow axis of the said 1/4 wavelength plate is 55 degrees-65 degrees.   The optical laminate according to claim 1, wherein the resin having a positive intrinsic birefringence value includes a cyclic olefin polymer.   The optical laminate according to any one of claims 1 to 3, wherein the half-wave plate and the quarter-wave plate are stretched films subjected to one or more oblique stretches.   The optical laminate according to claim 4, wherein the half-wave plate is a sequential biaxially stretched film that has been subjected to longitudinal stretching after the oblique stretching. The optical laminated body according to any one of claims 1 to 5 and a long linear polarizer are made up of the linear polarizer, the half-wave plate, and the quarter-wave plate by a roll roll. It is a circularly polarizing plate obtained by laminating to be in order,
A circularly polarizing plate, wherein an average angle formed between a polarization transmission axis of the linear polarizer and a slow axis of the half-wave plate is 50 ° or more and less than 90 °.   An organic electroluminescence display device comprising an antireflection film cut out from the circularly polarizing plate according to claim 6.

Images