JP6825654B2 - Manufacturing method of circularly polarizing plate and manufacturing method of optical laminate - Google Patents

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, may be appropriately referred to as an "organic EL display device") may be provided with a circular polarizing plate in order to reduce reflection of external light on the display surface. .. As such a circular polarizing plate, a film in which a linear polarizing element and a quarter wave plate which is a retardation film are combined is generally used. However, most of the conventional 1/4 wave plates can achieve the retardation of about 1/4 wavelength only with light in a specific narrow wavelength range. Therefore, although the circular polarizing plate can reduce the reflection of external light in a specific narrow wavelength range, it is difficult to reduce the reflection of other external light.

On the other hand, a wideband 1/4 wave plate in which a 1/4 wave plate and a 1/2 wave plate are combined has been proposed (see Patent Documents 1 to 6). According to this wideband 1/4 wave plate, retardation of about 1/4 wavelength can be achieved with light in a wide wavelength range, so that a circular polarizing plate capable of reducing reflection of external light in a wide wavelength range can be realized.
Further, there is known a technique of a retardation film in which the slow axis direction of the film is the in-plane direction of the film as in Patent Document 7, and the retardation film exists in an oblique direction that is neither orthogonal nor parallel to the width direction of the film. ..

Japanese Patent No. 4708787 Japanese Unexamined Patent Publication No. 05-100114 Japanese Unexamined Patent Publication No. 2003-114325 Japanese Unexamined Patent Publication No. 10-68816 Japanese Unexamined Patent Publication No. 11-183723 JP-A-11-295526 Japanese Unexamined Patent Publication No. 2012-25167

In a circular polarizing plate that combines a linear polarizer and a wideband 1/4 wave plate, the optical light of the polarization transmission axis of the linear polarizer, the slow axis of the 1/2 wave plate, and the slow axis of the 1/4 wave plate. It is required to adjust the direction of the axes so that these optical axes form a predetermined angle.

However, when the circular polarizing plate is viewed from an inclined direction other than the front direction, the apparent angle formed by the optical axis may deviate from a predetermined angle. Therefore, the conventional circularly polarizing plate can reduce the reflection of external light in the front direction, but may not be able to effectively reduce the reflection of external light in the inclined direction other than the front direction. In particular, since the circular polarizing plate provided with the wideband 1/4 wave plate includes not only the 1/4 wave plate but also the 1/2 wavelength plate, the number of optical axes is larger than that of the conventional circular polarizing plate. Therefore, in the circular polarizing plate provided with the wideband 1/4 wave plate, the apparent deviation of the optical axis is larger than that in the conventional circular polarizing plate not provided with the 1/2 wavelength plate, and the reflection of external light in the tilt direction is caused. It tended to be inferior in its ability to reduce.

The present invention has been devised in view of the above-mentioned problems, and is an optical laminate capable of realizing a long circular polarizing plate capable of effectively reducing reflection of external light in both the front direction and the inclination direction; Provided are a long circular polarizing plate capable of effectively reducing reflection of external light in any of the tilting directions; and an organic electroluminescence display device provided with an antireflection film cut out from the circular polarizing plate. The purpose.

As a result of diligent studies to solve the above problems, the present inventor is an optical laminate provided with a long 1/2 wave plate and a long 1/4 wave plate made of a resin having a positive birefringence value. If an optical laminate in which the directions of the slow axes of the 1/2 wave plate and the 1/4 wave plate and the NZ coefficient of the 1/2 wave plate and the 1/4 wave plate are within a predetermined range is used. The present invention has been completed by finding that a long circular wave plate capable of effectively reducing reflection of external light can be realized in both the front direction and the tilt direction.
That is, the present invention is as follows.

[1] A long 1/2 wave plate and a long 1/4 wave plate made of a resin having a positive birefringence value are provided.
The average orientation angle formed by the slow axis of the 1/2 wave plate with respect to the width direction is 50 ° or more and 90 ° or less.
The NZ coefficient of the 1/2 wave plate is 1.0 to 1.5.
The average orientation angle formed by the slow axis of the 1/4 wave plate with respect to the width direction is 0 ° or more and less than 50 °.
An optical laminate in which the NZ coefficient of the 1/4 wave plate is 1.0 to 1.5.
[2] The optical laminate according to [1], wherein the intersection angle between the slow axis of the 1/2 wave plate and the slow axis of the 1/4 wave plate is 55 ° to 65 °.
[3] The optical laminate according to [1] or [2], wherein the resin having a positive natural birefringence value contains a cyclic olefin polymer.
[4] The optical lamination according to any one of [1] to [3], wherein the 1/2 wave plate and the 1/4 wave plate are stretched films subjected to diagonal stretching at least once. body.
[5] The optical laminate according to [4], wherein the 1/2 wave plate is a sequentially biaxially stretched film that is further longitudinally stretched after the diagonal stretching.
[6] The optical laminate and the long linear polarizing element according to any one of [1] to [5] are subjected to the linear polarizing element, the 1/2 wave plate, and the 1/1 by rolling. A circularly polarizing plate obtained by laminating four wave plates in this order.
A circular polarizing plate in which the angle formed by the polarization transmission axis of the linear polarizer and the slow axis of the 1/2 wave plate is 50 ° or more and less than 90 °.
[7] An organic electroluminescence display device including an antireflection film obtained by cutting out from the circularly polarizing plate according to [6].

According to the present invention, an optical laminate capable of realizing a long circular polarizing plate capable of effectively reducing reflection of external light in both the front direction and the tilt direction; external light in both the front direction and the tilt direction. It is possible to provide a long circular polarizing plate capable of effectively reducing reflection; and an organic electroluminescence display device including an antireflection film cut out from the circular polarizing plate.

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 pre-stretching film. FIG. 3 is a plan view schematically showing an example of a roll stretching machine used for stretching an 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 embodiments and examples shown below, and can be arbitrarily modified and implemented without departing from the scope of claims of the present invention and the equivalent scope thereof.

In the following description, the "long" film means a film having a length of 5 times or more with respect to the width, preferably having a length of 10 times or more, and specifically a roll. A film that has a length that allows it to be rolled 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. 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) unless otherwise specified, and can be calculated by 0.5 + Rth / Re. Here, nx represents the refractive index in the direction perpendicular to the thickness direction of the film (in-plane direction) and in the direction giving the maximum refractive index. ny represents the refractive index in the in-plane direction 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-phase axis of the film represents the in-plane slow-phase axis of the film unless otherwise specified.

In the following description, the orientation angle of a film means the angle formed by the in-plane slow-phase axis of the film with respect to a certain reference direction unless otherwise specified. Further, 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 natural birefringence value means a resin in which the refractive index in the stretching direction is larger than the refractive index in the direction orthogonal to it, unless otherwise specified. Further, a resin having a negative natural birefringence value means a resin in which the refractive index in the stretching direction is smaller than the refractive index in the direction orthogonal to the refractive index, unless otherwise specified. The intrinsic birefringence value can be calculated from the dielectric constant distribution.

In the following description, the term "(meth) acrylic" includes both "acrylic" and "methacryl".

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

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

In the following description, the tilting 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. Points in a range smaller than °.

In the following description, the directions of the elements of "parallel", "vertical" and "orthogonal" include an error within a range that does not impair the effect of the present invention, for example, within a range of ± 5 °, unless otherwise specified. You may be.

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

In the following description, the "polarizing plate", "1/2 wave plate" and "1/4 wave plate" are not only rigid members but also flexible like a resin film, unless otherwise specified. Also includes members having properties.

In the following description, the angles formed by the optical axes (polarization absorption axis, polarization transmission axis, slow phase axis, etc.) of each film in a member including a plurality of films are viewed from the thickness direction unless otherwise specified. 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, on the surface of the 1/4 wave plate 120, the axis 112 on which the slow phase axis 111 of the 1/2 wave plate 110 is projected is shown by a dashed line. Further, in the optical laminate 100 shown in FIG. 1, the width direction of the optical laminate 100, the width direction of the 1/2 wave plate 110, and the width direction of the 1/4 wave plate 120 are the same, so they are indicated by a common reference numeral TD. ..
As shown in FIG. 1, the long optical laminate 100 according to the embodiment of the present invention includes a long 1/2 wave plate 110 made of a resin having a positive intrinsic birefringence value and an intrinsic birefringence value. A long 1/4 wave plate 120 made of a positive resin is provided.

The 1/2 wave plate 110 is a long optical member having a predetermined in-plane retardation. The 1/2 wave plate 110 has a slow phase parallel to the in-plane direction of the 1/2 wave plate 110 in a direction forming a predetermined average orientation angle θh with respect to the width direction TD of the 1/2 wave plate 110. It has a shaft 111.

Further, the quarter wave plate 120 is a long optical member having a predetermined in-plane retardation. The 1/4 wave plate 120 has a slow phase parallel to the in-plane direction of the 1/4 wave plate 120 in a direction forming a predetermined average orientation angle θq with respect to the width direction TD of the 1/4 wave plate 120. It has a shaft 121.

The optical laminate 100 having such a structure is a wideband 1/4 wave plate capable of imparting in-plane retardation of approximately 1/4 wavelength of the wavelength of light to light in a wide wavelength range transmitted through the optical laminate 100. Can function as. Then, by combining such an optical laminate 100 with a linear polarizer, a circular polarizing plate capable of absorbing one of right-handed circularly polarized light and left-handed circularly polarized light and transmitting the remaining light over a wide wavelength range is realized. it can.

[2.1 / 2 wave plate]
The in-plane retardation of the 1/2 wave plate is usually 240 nm or more and usually 300 nm or less. When the 1/2 wave plate has such an in-plane retardation, it is possible to realize an optical laminate capable of functioning as a wideband 1/4 wave plate by combining the 1/2 wave plate and the 1/4 wave plate. Further, by combining this optical laminate with a linear polarizing element, it is possible to realize a circular polarizing plate capable of suppressing reflection of light in a wide wavelength range in both the front direction and the tilt direction. Above all, in order to particularly effectively reduce the reflection of external light in the tilt direction, the in-plane retardation of the 1/2 wavelength plate is preferably 250 nm or more, preferably 280 nm or less, and more preferably 265 nm or less. is there.

The NZ coefficient of the 1/2 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. It is .30 or less. The fact that the NZ coefficient of the 1/2 wave plate is close to 1.0 as described above indicates that the optical uniaxiality of the 1/2 wave plate is high. Here, the optical uniaxiality indicates a property capable of exhibiting optical characteristics similar to those of a stretched film stretched in one direction. The circularly polarizing plate obtained by using the optical laminate provided with the 1/2 wavelength plate having such high uniaxiality can more effectively reduce the reflection of external light in the tilt direction. Further, the 1/2 wavelength wave plate having such an NZ coefficient can be easily manufactured.

The wavelength dispersion of the 1/2 wavelength plate may have wavelength dispersion characteristics such as forward wavelength dispersion characteristics, flat wavelength dispersion characteristics, and reverse wavelength dispersion characteristics. The forward wavelength dispersion characteristic means a wavelength dispersion characteristic in which the retardation increases as the wavelength becomes shorter. Further, the inverse 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 1/2 wave plate with respect to the width direction of the 1/2 wave plate is usually 50 ° or more, preferably 55 ° or more, more preferably 60 ° or more, and is usually 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 1/2 wave plate within the above range, it is possible to realize an optical laminate capable of functioning as a wideband 1/4 wave plate by combining the 1/2 wave plate and the 1/4 wave plate. Further, by combining this optical laminate with a linear polarizing element, it is possible to realize a circular polarizing plate capable of suppressing reflection of light in a wide wavelength range in both the front direction and the tilt direction.

The average orientation angle of the film is measured using a polarizing microscope (“BX51” manufactured by Olympus Corporation) at intervals of 50 mm in the width direction of the film, and the in-plane slow axis is measured, and the direction of the slow axis and the width of the film are measured. The average value of the angles formed with the direction (orientation angle) can be obtained and measured as the average orientation angle.

The 1/2 wave plate is a member made of a resin having a positive natural birefringence value, and is usually a film made of the above resin. A resin having a positive intrinsic birefringence value contains 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 sulfide such as polyphenylene sulfide; polyvinyl alcohol; polycarbonate; polyarylate; cellulose ester polymer and polyethersulfone. Polysulfone; polyallyl sulfone; polyvinyl chloride; cyclic olefin polymer such as norbornene polymer; rod-shaped liquid crystal polymer and the like. One of these polymers may be used alone, or two or more of these polymers may be used in combination at any ratio. Further, the polymer may be a homopolymer or a copolymer. Among these, a cyclic olefin polymer is preferable because it is excellent in mechanical properties, heat resistance, transparency, low hygroscopicity, dimensional stability and light weight.

A cyclic olefin polymer is a polymer in which the structural unit of the polymer has an alicyclic structure. The cyclic olefin polymer is a polymer having an alicyclic structure in the main chain, a polymer having an alicyclic structure in the side chain, a polymer having an alicyclic structure in the main chain and the side chain, and two of these. It can be a mixture of any of the above ratios. Of these, a polymer having an alicyclic structure in the main chain is preferable from the viewpoint of mechanical strength and heat resistance.

Examples of the alicyclic structure include a saturated alicyclic hydrocarbon (cycloalkane) structure and an unsaturated alicyclic hydrocarbon (cycloalkene, cycloalkyne) structure. Among them, a cycloalkane structure and a cycloalkene structure are preferable from the viewpoint of mechanical strength and heat resistance, 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 20 or less, per one alicyclic structure. Is 15 or less. When the number of carbon atoms constituting the alicyclic structure is in 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 units having an alicyclic structure in the cyclic olefin polymer is in this range, the transparency and heat resistance are good.

Among the cyclic olefin polymers, cycloolefin polymers are preferable. The cycloolefin polymer is a polymer having a structure obtained by polymerizing a cycloolefin monomer. Further, the cycloolefin monomer is a compound having a ring structure formed by 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, crosslinked rings, and polycycles combining these. Of these, a polycyclic cycloolefin monomer is preferable from the viewpoint of highly balancing the characteristics such as the dielectric property and heat resistance of the obtained polymer.

Among the above cycloolefin polymers, preferred examples include norbornene-based polymers, monocyclic cyclic olefin-based polymers, cyclic conjugated diene-based polymers, and hydrides thereof. Among these, the norbornene-based polymer is particularly suitable because it has 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 ring-opening polymers of monomers having a norbornene structure include a ring-opening copolymer of one type of monomer having a norbornene structure and ring-opening of two or more types 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 copolymerizable therewith. Further, as an example of the addition polymer of the monomer having a norbornene structure, the addition homopolymer of one kind of monomer having a norbornene structure and the addition copolymer of two or more kinds of monomers having a norbornene structure , And an addition copolymer of a monomer having a norbornene structure and another monomer copolymerizable therewith. Among these, a hydride of a monomeric ring-opening polymer having a norbornene structure is particularly suitable from the viewpoints of moldability, heat resistance, low hygroscopicity, dimensional stability, light weight and the like.

Examples of monomers having a norbornene structure are bicyclo [2.2.1] hept-2-ene (trivial name: norbornene), tricyclo [4.3.0.1 ^2,5 ] deca-3,7. -Diene (trivial name: dicyclopentadiene), 7,8-benzotricyclo [4.3.0.1 ^2,5 ] deca-3-ene (trivial name: metanotetrahydrofluorene), tetracyclo [4.4. 0.1 ^{2, 5} . ^17,10 ] Dodeca-3-ene (trivial name: tetracyclododecene), and derivatives of these compounds (for example, those having a substituent on the ring) can be mentioned. Here, examples of the substituent include an alkyl group, an alkylene group, and a polar group. Further, these substituents may be the same or different from each other, and a plurality of these substituents may be bonded to the ring. As the monomer having a norbornene structure, one type may be used alone, or two or more types may be used in combination at an arbitrary ratio.

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

Examples of monomers that can be ring-opened and copolymerizable with a monomer having a norbornene structure include monocyclic olefins such as cyclohexene, cycloheptene, and cyclooctene and their derivatives; cyclic conjugated diene such as cyclohexene, cycloheptadiene, and The derivative is mentioned. As the monomer having a norbornene structure and the monomer capable of ring-opening copolymerization, one type may be used alone, or two or more types may be used in combination at an arbitrary ratio.

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

Examples of monomers that can be additionally 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. Cycloolefins and derivatives thereof; and non-conjugated diene such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene. Among these, α-olefins are preferable, and ethylene is more preferable. Further, as the monomer having a norbornene structure and the monomer capable of addition copolymerization, one type may be used alone, or two or more types may be used in combination at an arbitrary ratio.

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

The above-mentioned hydrogenated compounds of the ring-opening polymer and the addition polymer are, for example, carbon in the solution of the ring-opening polymer and the addition polymer in the presence of a hydrogenation catalyst containing a transition metal such as nickel and palladium. -A carbon unsaturated bond can be produced, preferably by hydrogenating 90% or more.

Among the 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 ] decan- It has a 7,9-diyl-ethylene structure, and the amount of these structural units is 90% by weight or more based on the total structural units of the norbornene-based polymer, and the ratio of X and the ratio of Y It is preferable that the ratio is 100: 0 to 40:60 in terms of the weight ratio of X: Y. By using such a polymer, the 1/2 wavelength plate containing the norbornene-based polymer can be made to have no dimensional change in a long period of time and have excellent stability of optical characteristics.

Examples of the monocyclic cyclic olefin polymer include an addition polymer of a cyclic olefin monomer having a monocycle such as cyclohexene, cycloheptene, and cyclooctene.

Examples of cyclic conjugated diene-based polymers are polymers obtained by cyclization reaction of addition polymers of conjugated diene-based monomers such as 1,3-butadiene, isoprene, and chloroprene; cyclic conjugates such as cyclopentadiene and cyclohexadiene. 1,2- or 1,4-additional polymers of diene-based monomers; and hydrides thereof can be mentioned.

The weight average molecular weight (Mw) of the polymer contained in the resin having a positive birefringence value is preferably 10,000 or more, more preferably 15,000 or more, particularly preferably 20,000 or more, and preferably 100. It is 000 or less, more preferably 80,000 or less, and particularly preferably 50,000 or less. When the weight average molecular weight is in such a range, the mechanical strength and moldability of the resin are highly balanced and suitable. Here, the weight average molecular weight is converted to polyisoprene or polystyrene as measured by gel permeation chromatography using cyclohexane as a solvent (however, toluene may be used if the sample does not dissolve in cyclohexane). 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 birefringence value is preferably 1.2 or more, more preferably 1.5 or more, and 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 setting the molecular weight distribution to the lower limit of the above range or more, the productivity of the polymer can be increased and the production cost can be suppressed. Further, when the value is set to the upper limit or less, the amount of the low molecular weight component becomes small, so that the relaxation at the time of high temperature exposure can be suppressed and the stability of the 1/2 wave plate can be improved.

The proportion of the polymer in the resin having a positive natural birefringence value is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, and particularly preferably 90% by weight to 100% by weight. By setting the proportion of the polymer in the above range, the 1/2 wavelength plate can obtain sufficient heat resistance and transparency.

The resin having a positive natural birefringence value may contain a compounding agent in addition to the above-mentioned polymer. Examples of compounding agents include colorants such as pigments and dyes; plasticizers; optical brighteners; dispersants; heat stabilizers; light stabilizers; UV absorbers; antistatic agents; antioxidants; fine particles; surfactants. Activators and the like can be mentioned. One of these components may be used alone, or two or more of these components may be used in combination at any ratio.

The glass transition temperature Tg of the resin having a positive natural 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 ° C. or lower. By setting the glass transition temperature of a resin having a positive birefringence value to be equal to or higher than the lower limit of the above range, the durability of the 1/2 wave plate in a high temperature environment can be improved. Further, by setting the value to the upper limit or less, the stretching treatment can be easily performed.

A resin having a positive birefringence value has an absolute 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 ^{−. It is 12} Pa ^-1 or less. As a result, the variation in the retardation of the 1/2 wavelength plate can be reduced. Here, the photoelastic coefficient C is a value represented by C = Δn / σ, where Δn is the birefringence and σ is the stress.

The total light transmittance of the 1/2 wave plate is preferably 80% or more. The light transmittance can be measured using a spectrophotometer (manufactured by JASCO Corporation, ultraviolet-visible near-infrared spectrophotometer "V-570") in accordance with JIS K0115.

The haze of the 1/2 wave plate is preferably 5% or less, more preferably 3% or less, particularly preferably 1% or less, and ideally 0%. Here, the haze can be measured at five points using a "turbidity meter NDH-300A" manufactured by Nippon Denshoku Kogyo Co., Ltd. in accordance with JIS K7361-1997, and the average value obtained from the measurements can be adopted.

The amount of the volatile component contained in the 1/2 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. Is. By reducing the amount of the volatile component, the dimensional stability of the 1/2 wave plate can be improved, and the change with time of optical characteristics 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 the volatile component can be quantified by dissolving the film in chloroform and analyzing it by gas chromatography as the total amount of substances having a molecular weight of 200 or less contained in the film.

The saturated water absorption of the 1/2 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 1/2 wave plate is within the above range, it is possible to reduce the change over time in optical characteristics such as in-plane retardation.
Here, the saturated water absorption rate is a value expressed as a percentage of the mass of the increased mass of the test piece of the film after being immersed in water at 23 ° C. for 24 hours with respect to the mass of the test piece of the film before immersion.

The thickness of the 1/2 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, still more preferably 60 μm or less. Thereby, the mechanical strength of the 1/2 wave plate can be increased.

The method for manufacturing the 1/2 wave plate is arbitrary. The 1/2 wave plate may be produced as a stretched film by, for example, a manufacturing method including applying diagonal stretching of a long pre-stretched film made of resin one or more times. Here, "diagonal stretching" means stretching a long film in an oblique direction. According to the manufacturing method including diagonal stretching, the 1/2 wavelength plate can be easily manufactured.

Further, it is preferable that the 1/2 wavelength plate is manufactured as a sequentially biaxially stretched film by a manufacturing method including further longitudinal stretching after the diagonal stretching. Here, "longitudinal stretching" means stretching a long film in the longitudinal direction.

Hereinafter, an example of a preferable manufacturing method of the 1/2 wavelength plate will be described. The method for producing the 1/2 wavelength plate according to this example includes (a) a first step of preparing a long pre-stretched film made of a resin having a positive unique birefringence value, and (b) a long pre-stretched film. The second step of obtaining a long intermediate film by stretching the intermediate film in an oblique direction, and (c) the third step of freely uniaxially stretching the intermediate film in the longitudinal direction to obtain a long 1/2 wavelength plate. Including.

(A) In the first step, a long unstretched film made of a resin having a positive natural birefringence value is prepared. The pre-stretched film can be produced, for example, by 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, an extrusion molding method, an inflation molding method or a press molding method is preferable in order to obtain a 1/2 wave plate having excellent mechanical strength, surface accuracy, etc. Among these methods, the 1/2 wave plate can be efficiently and easily obtained. The extrusion molding method is particularly preferable from the viewpoint of manufacturing.

After (a) preparing a long pre-stretched film in the first step, (b) performing a second step of stretching the long pre-stretched film in an oblique direction to obtain an intermediate film. In the second step, usually, the film before stretching is continuously conveyed in the longitudinal direction, and the film is stretched using a tenter stretching machine.

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

The tenter stretching machine 200 is provided on both sides of a film transport path to guide a plurality of grippers 210R and 210L capable of gripping both ends 21 and 22 of the pre-stretched film 20, respectively, and the grippers 210R and 210L. The pair of guide rails 220R and 220L are provided.

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

The guide rails 220R and 220L have an asymmetrical shape 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 becomes wider 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 pre-stretching film 20 to the left. The shape is set so that 20 can be conveyed, and the moving distance of one gripper 210R is longer than the moving distance of the other gripper 210L. Here, the traveling direction of a long film means the moving direction of the midpoint in the width direction of the film unless otherwise specified. Further, "right" and "left" indicate directions when observing from upstream to downstream in the transport direction unless otherwise specified.

Further, the guide rails 220R and 220L have an endless continuous track so that the grippers 210R and 210L can orbit a predetermined track. Therefore, 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 portion 240 of the tenter stretching machine 200 can be sequentially returned to the inlet portion 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 pre-stretched film 20 is fed out from the feeding roll 10, and the pre-stretched 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 at its inlet portion 230 by the grippers 210R and 210L. The pre-stretched film 20 gripped at both ends 21 and 22 is conveyed 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 pre-stretching film 20 is bent to the left. Therefore, the distance of the track that one gripper 210R travels while gripping the pre-stretched film 20 is longer than the distance of the track that the other gripper 210L travels while gripping the pre-stretched film 20. Therefore, the set of grippers 210R and 210L that were opposed to the traveling direction of the pre-stretching film 20 at the inlet portion 230 of the tenter stretching machine 200 are on the left side at the outlet portion 240 of the tenter stretching machine 200. Since the gripper 210L precedes the gripper 210R on the right side, the pre-stretching film 20 is stretched in an oblique direction to obtain a long intermediate film 30 (broken lines L _D1 , L _D2 and FIG. 2 in FIG. 2). See L _D3 ). The obtained intermediate film 30 is released from the grippers 210R and 210L at the outlet portion 240 of the tenter stretching machine 200, is wound up, and is 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, and more preferably 3.0 times or less. (B) The refractive index in the stretching direction can be increased by setting the stretching ratio B1 in the second step to be equal to or higher than the lower limit of the above range. Further, by setting the value to the upper limit or less, the slow-phase axial direction of the 1/2 wavelength 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 natural birefringence value. Further, in the tenter stretching machine 200, (b) the stretching temperature T1 in the second step means the temperature in the stretching zone 250 of the tenter stretching machine 200. (B) By setting the stretching temperature T1 in the second step to 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 characteristics 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 phase axis. (B) In the second step, since stretching is performed in the oblique direction, the slow axis of the intermediate film 30 is expressed in the oblique direction of the intermediate film 30. Specifically, the intermediate film 30 usually has a slow phase axis in the range of 5 ° to 85 ° with respect to the width direction thereof.

The specific direction of the slow-phase axis of the intermediate film 30 is preferably set according to the direction of the slow-phase axis of the 1/2 wavelength plate to be manufactured. Normally, the angle formed by the slow axis of the 1/2 wave plate obtained in 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 1/2 wavelength plate with respect to the width direction.

Since the slow-phase axis of the intermediate film 30 is expressed by stretching the pre-stretched film 20 in an oblique direction, the specific direction of the slow-phase axis of the intermediate film 30 is described in the second step (b) described above. It can be adjusted according to the stretching conditions in. 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 unstretched film 20 from the feeding roll 10 and the winding direction D30 of the intermediate film 30. .. Here, the feeding direction D20 of the pre-stretched film 20 indicates the advancing direction of the pre-stretching film 20 fed from the feeding roll 10. Further, the winding direction D30 of the intermediate film 30 indicates the traveling direction of the intermediate film 30 wound as the roll 40.

(B) After the second step, (c) the intermediate film 30 is freely uniaxially stretched in the longitudinal direction to obtain a long 1/2 wavelength plate. Here, free uniaxial stretching means stretching in a certain direction without applying a binding force in a direction other than the stretching direction. Therefore, the free uniaxial stretching of the intermediate film 30 in the longitudinal direction shown in this example means stretching in the longitudinal direction 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 a device for stretching the intermediate film 30 unwound 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 capable of transporting the intermediate film 30 in the longitudinal direction in order from the upstream in the transport direction. Here, the rotation speed of the downstream roll 320 is set to be faster than the rotation 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 unwound 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 to obtain the 1/2 wavelength plate 50. In the stretching by the roll stretching machine 300, both ends 31 and 32 in the width direction of the intermediate film 30 are not restrained. Therefore, normally, the width of the intermediate film 30 shrinks with stretching in the longitudinal direction, so that a 1/2 wavelength plate 50 having a width smaller than that of the intermediate film 30 can be obtained. In this example, the 1/2 wavelength plate 50 is obtained as a biaxially stretched film stretched in two directions, a longitudinal direction and an oblique direction.
After that, the 1/2 wavelength plate 50 is wound up and collected as a roll 60 after both ends thereof are trimmed as needed.

The draw ratio B2 in the (c) third step is preferably smaller than the draw ratio B1 in the (b) second step. This makes it possible to stretch the 1/2 wavelength plate 50 having a slow axis in the oblique direction while suppressing the occurrence of wrinkles. In this way, by combining the diagonal stretching and the free uniaxial stretching in the longitudinal direction in this order and the stretching ratio of B1> B2, the conventional diagonal uniaxial stretching film with respect to the width direction A 1/2 wave plate 50 having a slower axis in a larger angular direction can be easily manufactured.

At this time, by increasing the draw ratio B2, the optical uniaxiality of the 1/2 wavelength plate 50 can be enhanced. In the 1/2 wave plate 50 obtained by stretching a resin having a positive birefringence, the higher the uniaxiality, the closer the NZ coefficient tends to be to 1.0. Since the 1/2 wavelength plate 50 having high uniaxiality has an NZ coefficient close to 1.0, the circular polarizing plate obtained by using the optical laminate provided with this 1/2 wavelength 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, and preferably 2.0 times or less. , More preferably 1.8 times or less, and particularly preferably 1.6 times or less. (C) By setting the stretching ratio B2 in the third step to be equal to or higher than the lower limit of the above range, wrinkles of the 1/2 wavelength plate 50 can be suppressed. Further, by setting the value to the upper limit or less, the direction of the slow phase 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 higher, particularly preferably "T1-18 ° C" or higher, based on (b) the stretching temperature T1 in the second step. Is "T1-16 ° C." or higher, preferably lower than "T1 + 5 ° C.", more preferably "T1 + 4 ° C." or lower, and particularly preferably "T1 + 3 ° C." or lower. (C) By setting the stretching temperature T2 in the third step within the above range, the in-plane retardation of the 1/2 wavelength plate 50 can be effectively adjusted.

The method for manufacturing the 1/2 wavelength plate shown in the above example may be further modified.
For example, the method for manufacturing a 1/2 wave plate may further include any step other than (a) first step, (b) second step and (c) third step. Examples of such a step include a step of providing a protective layer on the surface of the 1/2 wavelength plate.
Further, for example, as the pre-stretching film, a film obtained by stretching the pre-stretching film in any direction may be used. As described above, as the method (b) of stretching the pre-stretching film before being subjected to the second step, for example, a roll method, a float method, a longitudinal stretching method, a transverse stretching method using a tenter stretching machine, or the like can be used.
Further, in the above-mentioned example, the intermediate film 30 was wound into a roll 40, and the intermediate film 30 was 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 winding up.

[3.1 / 4 wave plate]
The in-plane retardation of the 1/4 wave plate is usually 110 nm or more and usually 154 nm or less. When the 1/4 wave plate has such an in-plane retardation, it is possible to realize an optical laminate capable of functioning as a wideband 1/4 wave plate by combining the 1/2 wave plate and the 1/4 wave plate. Further, by combining this optical laminate with a linear polarizing element, it is possible to realize a circular polarizing plate capable of suppressing reflection of light in a wide wavelength range in both the front direction and the tilt direction. Above all, in order to particularly effectively reduce the reflection of external light in the tilt direction, the in-plane retardation of the 1/4 wave plate is preferably 118 nm or more, preferably 138 nm or less, and more preferably 128 nm or less. is there.

The NZ coefficient of the 1/4 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. It is .30 or less. The fact that the NZ coefficient of the 1/4 wave plate is close to 1.0 as described above indicates that the optical uniaxiality of the 1/4 wave plate is high. The circularly polarizing plate obtained by using the optical laminate provided with the 1/4 wave plate having such high uniaxiality can effectively reduce the reflection of external light in the tilt direction. Further, a quarter wave plate having such an NZ coefficient can be easily manufactured.

The wavelength dispersion of the 1/4 wavelength plate may have wavelength dispersion characteristics such as forward wavelength dispersion characteristics, flat wavelength dispersion characteristics, and reverse wavelength dispersion characteristics.

The average orientation angle θq formed by the slow axis of the 1/4 wave plate with respect to the width direction of the 1/4 wave plate is usually 0 ° or more, preferably 5 ° or more, more preferably 10 ° or more, and is usually 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 1/4 wave plate within the above range, it is possible to realize an optical laminate capable of functioning as a wideband 1/4 wave plate by combining the 1/2 wave plate and the 1/4 wave plate. Further, by combining this optical laminate with a linear polarizing element, it is possible to realize a circular polarizing plate capable of suppressing reflection of light in a wide wavelength range in both the front direction and the tilt direction.

Further, as can be seen from the average orientation angle θh of the 1/2 wave plate and the average orientation angle θq of the 1/4 wave plate, the slow axis of the 1/2 wave plate and the slow axis of the 1/4 wave plate are Usually intersecting. Here, the intersection angle θd between the slow axis of the 1/2 wave plate and the slow axis of the 1/4 wave plate is preferably 55 ° or more, more preferably 57 ° or more, and particularly preferably 59 ° or more. It 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 1/2 wave plate and the average orientation angle θq of the 1/4 wave plate. By keeping the intersection angle θd within the above range, the circularly polarizing plate obtained by using the optical laminate can effectively suppress the reflection of light.

The 1/4 wave plate is a member made of a resin having a positive natural birefringence value, and is usually a film made of the above resin. As the resin having a positive intrinsic birefringence value for the 1/4 wave plate, a resin selected from the range described as the resin having a positive intrinsic birefringence value for the 1/2 wavelength plate can be arbitrarily used. By applying a resin selected from the range described as a resin having a positive intrinsic birefringence value for the 1/2 wave plate to the 1/4 wave plate, the same as described in the section of the 1/2 wave plate. The advantage can also be obtained with a 1/4 wave plate. Above all, it is preferable that the 1/2 wave plate and the 1/4 wave plate are made of the same resin.

The total light transmittance of the 1/4 wave plate is preferably 80% or more.
The haze of the 1/4 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 1/4 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. Is. By reducing the amount of the volatile component, the dimensional stability of the 1/4 wave plate can be improved, and the change with time of optical characteristics such as retardation can be reduced.

The saturated water absorption of the 1/4 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 1/4 wave plate is within the above range, it is possible to reduce the change over time in optical characteristics such as in-plane retardation.

The thickness of the 1/4 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 setting the thickness of the 1/4 wave plate to the lower limit of the above range or more, the desired retardation can be easily expressed. Further, by setting the value to the upper limit or less, the optical laminate can be thinned.

The method for manufacturing the 1/4 wave plate is arbitrary. The quarter wave plate can be produced as a stretched film by, for example, a manufacturing method including applying diagonal stretching of a long unstretched film made of resin one or more times. According to the manufacturing method including diagonal stretching, a quarter wave plate can be easily manufactured.

Preferred manufacturing methods for the 1/4 wave plate include, for example, (d) a fourth step of preparing a long pre-stretched film made of a resin having a positive intrinsic birefringence value, and (e) a long pre-stretched film. A manufacturing method including a fifth step of obtaining a long 1/4 wave plate by stretching the film in an oblique direction can be mentioned.

(D) In the fourth step, a long unstretched film made of a resin having a positive natural birefringence value is prepared. The pre-stretched film can be produced, for example, by the same method as in the first step (a) in the method for producing a 1/2 wavelength plate. (D) By producing the pre-stretched film in the fourth step by the same method as in (a) first step, the same advantages as in (a) first step can be obtained in (d) fourth step.

(D) After preparing a long pre-stretched film in the fourth step, (e) the fifth step of stretching the long pre-stretched film in an oblique direction to obtain a quarter wave plate is performed. In the fifth step, usually, the film before stretching is continuously conveyed in the longitudinal direction, and the film is stretched using a tenter stretching machine. At this time, as the tenter stretching machine, the same tenter stretching machine as described in the second step (b) in the method for manufacturing the 1/2 wavelength plate can be used. By using the same tenter stretching machine as in (b) second step in (e) fifth step, the same advantages as in (b) second step can be obtained in (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. Further, by setting the value to the upper limit or less, the slow-phase axial direction of the 1/4 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, and particularly preferably Tg + 30. It is below ° C. (E) By setting the stretching temperature in the fifth step within the above range, the molecules contained in the pre-stretching film can be reliably oriented, so that a 1/4 wave plate having desired optical characteristics can be easily obtained. be able to.

The method for manufacturing the quarter wave plate shown in the above example may be further modified. For example, the method for manufacturing a 1/4 wave plate may further include any step other than the (d) fourth step and (e) fifth step. For example, the method for manufacturing a 1/4 wave plate may include a step of trimming both ends of the manufactured 1/4 wave plate. Further, the method for manufacturing the 1/4 wave plate may include the same steps as any step of the method for manufacturing the 1/2 wave plate.

[4. Any layer]
The optical laminate may be combined with a 1/2 wave plate and a 1/4 wave plate to further include any layer. For example, the optical laminate may include a protective film layer to prevent scratches.

Further, the optical laminate may include an adhesive layer containing an adhesive for adhesion between the 1/2 wave plate and the 1/4 wave plate. Adhesives include not only adhesives in the narrow sense that lose their adhesiveness at room temperature due to curing (including hot melt adhesives, UV curable adhesives, EB type curable adhesives, etc.), but also adhesives that do not lose their adhesiveness. Contains agents (pressure sensitive adhesives, etc.).

The adhesive preferably contains a polymer having an affinity for both the resin contained in the 1/2 wave plate and the resin contained in the 1/4 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. Examples thereof include ethylene-based copolymers such as -vinyl acetate copolymers and ethylene-styrene copolymers, and other olefin-based polymers. Further, a modified product obtained by modifying these polymers by oxidation, saponification, chlorination, chlorsulfonate or the like may be used.

[5. Characteristics of optical laminate]
By providing the above-mentioned 1/2 wave plate and 1/4 wave plate in the optical laminate, at least the following advantages can be obtained.
-The optical laminate is provided with an in-plane retardation of approximately 1/4 wavelength of the wavelength of the light transmitted through the optical laminate in the front direction in a wide wavelength range.
-The optical laminate is provided with an in-plane retardation of approximately 1/4 wavelength of the wavelength of the light transmitted through the optical laminate in a wide wavelength range.
-Therefore, the optical laminate can realize a circularly polarizing plate capable of reducing the reflection of light in a wide wavelength range in both the front direction and the tilt direction by combining with the linear polarizing element.

[6. Manufacturing method of optical laminate]
The optical laminate can be manufactured by laminating a long 1/2 wave plate and a long 1/4 wave plate. Usually, the longitudinal direction of the 1/2 wave plate and the longitudinal direction of the 1/4 wave plate are parallel to each other for bonding. From the viewpoint of increasing the production efficiency of the optical laminate, this bonding is preferably performed by roll-to-roll (Roll to Roll).

Laminating with roll-to-roll means that a film is unwound from a roll of a long film, transported, and the process of laminating with another film is performed on a transport line, and a further bonded product obtained. Refers to laminating in the form of a take-up roll. For example, when the 1/2 wave plate and the 1/4 wave plate are bonded together, the 1/2 wave plate is unwound from the roll of the long 1/2 wave plate, transported, and 1 / on the transport line. By performing the step of laminating with the four-wave plate and using the obtained optical laminate as a take-up roll, laminating with a roll-t-roll can be performed. In this case, the 1/4 wave plate can also be unwound from the roll and supplied to the bonding process.

When manufacturing an optical laminate using rolls, unlike the conventional method of laminating a single-wafer 1/2 wave plate and a 1/4 wave plate, a complicated optical axis alignment process is not required. is there. Therefore, efficient production of the optical laminate can be realized.

[7. Circularly polarized light]
A circular polarizing plate can be obtained by laminating the above-mentioned optical laminate with a linear polarizing element. In this circular polarizing plate, the above-mentioned long optical laminate and long linear polarizing element are bonded together so that the linear polarizer, the 1/2 wave plate and the 1/4 wave plate are in this order in the thickness direction. The obtained circular polarizing plate.

The linear polarized light is a long polarizing plate having a polarization transmitting axis and a polarization absorbing axis, absorbs linearly polarized light having a vibration direction parallel to the polarization absorbing axis, and linearly polarized light having a vibration direction parallel to the polarization transmitting axis. Has a function of allowing light to pass through. Here, the vibration direction of linearly polarized light means the vibration direction of an electric field of linearly polarized light.

As the linear polarizer, for example, a film of an appropriate vinyl alcohol-based polymer such as polyvinyl alcohol or partially formalized polyvinyl alcohol is dyed, stretched, or crosslinked with a dichroic substance such as iodine or a dichroic dye. It is possible to use a product obtained by performing appropriate treatments such as, etc. in an appropriate order and method. Normally, in the stretching process for producing a linear polarizer, the film is stretched in the longitudinal direction. Therefore, in the obtained linear polarizer, the polarization absorbing axis parallel to the longitudinal direction of the linear polarizer and the width of the linear polarizer are obtained. A polarization transmission axis parallel to the direction can be developed. This linearly polarized light can absorb linearly polarized light having a vibration direction parallel to the polarization absorption axis, and is particularly preferably one having an excellent degree of polarization. The thickness of the linear polarizer is generally, but is not limited to, 5 μm to 80 μm.

The polarization transmission axis of the linear polarizer is preferably parallel to the width direction of the linear polarizer. As a result, the linearly polarized light beam may have an absorption axis in the width direction of the long circular polarizing plate provided with the linearly polarized light. In this case, a long circular polarizing plate can be manufactured by laminating a long linear polarizing element and a long optical laminate with their longitudinal directions parallel to each other. Therefore, it is possible to manufacture a long circular polarizing plate by laminating a long linear polarizing element and a long optical laminate by rolls.

When manufacturing a long circular polarizing plate by laminating a long linear polarizing element and a long wideband 1/4 wave plate, conventionally, a linear polarizer, a 1/2 wave plate and a 1/4 wave plate have been used. It has been difficult to adjust the direction of the optical axes of the above so that each optical axis forms a predetermined angle required for the circularly polarizing plate. Therefore, conventionally, a circular polarizing plate has been manufactured by laminating a single-wafer linear polarizing element cut out from a long film by adjusting the angle and a single-wafer broadband 1/4 wave plate. It took time and cost (generation of scraps, etc.) to manufacture the polarized wave. In view of such conventional circumstances, it is advantageous in industrial production that the circularly polarizing plate of the present invention can be efficiently manufactured by using rolls.

In the circular polarizing plate, the average angle θph formed by the polarization transmission axis of the linear polarizing element and the slow axis of the 1/2 wave plate of the optical laminate is preferably 50 ° or more, more preferably 55 ° or more, and particularly preferably 55 ° or more. It is 60 ° or more, preferably less than 90 °, more preferably 85 ° or less, and particularly preferably 80 ° or less. Normally, the polarization transmission axis of a long linear polarizer is parallel to the width direction of the linear polarizer. Therefore, when a circular polarizing plate is manufactured by rolls, it is optically laminated with the polarization transmission axis of the linear polarizer. The average angle θph formed by the slow axis of the 1/2 wave plate of the body substantially coincides with the average orientation angle θh of the 1/2 wave plate. When the circular polarizing plate is manufactured by rolls in this way, the relationship between the average angle θph, the average orientation angle θh, and the average orientation angle θq particularly satisfies θq = 2θph-135 ° = 2θh-135 °. preferable. When the average angle θph formed by the polarization transmission axis of the linear polarizer and the slow axis of the 1/2 wave plate is within the above range, this circular polarizing plate is provided on a surface capable of reflecting light. In addition, the reflection of external light can be effectively reduced in both the front direction and the inclined direction. Therefore, this circularly polarizing plate can be used as an antireflection film capable of effectively reducing the reflection of external light in a wide wavelength range in the visible region.

The circularly polarizing plate may further include an arbitrary layer in combination with a linear polarizing element and an optical laminate. As an arbitrary layer, for example, an adhesive layer for adhering a linear polarizing element and an optical laminate; a matte layer for improving the slipperiness of a film; a hard coat layer such as an impact-resistant polymethacrylate resin layer; Anti-reflection layer; antifouling layer and the like can be mentioned.
In addition, the circular 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 the retardation change of the wave plate is caused by the tilt in the tilt direction. An additional optical compensation layer, such as a positive C plate, whose retardation changes to cancel out may be further provided. Here, the positive C plate means a plate that satisfies 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-mentioned long circular polarizing plate. The antireflection film is usually provided on a 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, the 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 on the display surface of the display device can be suppressed. Specifically, the light incident from the outside of the device is circularly polarized by passing only a part of the linearly polarized light through the linearly polarized light and then passing through the 1/2 wave plate and the 1/4 wave plate. It becomes. The circularly polarized light is reflected by a component that reflects light in the display device (a reflective electrode in the organic EL element, etc.), and is passed through the 1/4 wave plate and the 1/2 wave plate again to enter the linearly polarized light. It becomes linearly polarized light having a vibration direction orthogonal to the vibration direction of, and does not pass through the linear polarizer. As a result, the antireflection function is achieved.
When visually recognizing the 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. One can maintain good visibility.

In particular, in the above-mentioned optical laminate, since the NZ coefficient of the 1/2 wave plate and the NZ coefficient of the 1/4 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 examples shown below, and can be arbitrarily modified and implemented without departing from the scope of claims of the present invention and the equivalent scope thereof. In the following description, "%" and "part" representing quantities are based on weight unless otherwise specified. Further, the operations described below were performed in the air at normal temperature and pressure unless otherwise specified.

[Evaluation method]
[Measuring 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 (“BX51” manufactured by Olympus Corporation), and the slow axis in the plane is measured. , The average value of the angles (orientation angles) formed by the direction of the slow axis and the width direction of the film was obtained, and this was taken as the average orientation angle.

[Measurement method of retardation and NZ coefficient]
Using a phase difference meter (“KOBRA-21ADH” manufactured by Oji Measurement Co., Ltd.), in-plane retardation and thickness direction retardation were measured at a plurality of points at intervals of 50 mm in the width direction of the film. 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. In addition, the NZ coefficient was calculated from the obtained in-plane retardation and the thickness direction retardation.

[Visual evaluation method]
A mirror having a flat reflecting surface was prepared. The mirror was placed so that the reflecting surface was horizontal and facing upward. A circular polarizing plate was attached on the reflective surface of the mirror so that the polarizing film side was facing upward.

Then, the circular polarizing plate on the mirror was visually observed in a state where the circular polarizing plate was illuminated with sunlight on a sunny day. Observation of the circular polarizing plate
(I) In the front direction with a polar angle of 0 ° and an azimuth of 0 °,
(Ii) This was performed in both the polar angle of 45 ° and the inclination direction of the azimuth angle of 0 ° to 360 °.

(I) In the observation in the front direction, it was evaluated whether or not the circular polarizing plate looked black with almost no concern about the reflection of sunlight.
In addition, (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 was performed by 20 observers, and each person ranked the results of all the examples and comparative examples, and the points corresponding to the rankings (1st place 7 points, 2nd place 6 points, ...・ The lowest 1 point) was given. The total points scored by each person for each example and comparative example were arranged in the order of points, and evaluated in the order of A, B, C, D and E from the top group in the range of points.

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

In the model for simulation, a structure was set in which a circular polarizing plate was attached to the reflecting surface of a mirror having a flat reflecting surface so as to be in contact with the mirror on the 1/4 wave plate side. Therefore, in this model, a structure in which a polarizing film, a 1/2 wave plate, a 1/4 wave plate, and a mirror are provided in this order is set in the thickness direction.

Then, in the above model, the reflectance when the circular polarizing plate was irradiated with light from the D65 light source was calculated in the (i) front direction and (ii) tilt direction of the circular polarizing plate. Here, (i) in the front direction, the reflectances in the directions of the polar angle 0 ° and the azimuth angle 0 ° were calculated. Further, in the (ii) tilt direction, at a polar angle of 45 °, calculations are performed in azimuth angles of 5 ° each in the range of azimuth angles of 0 ° to 360 °, and the average of the calculated values is the modeled circular polarizing plate. It was adopted as the reflectance in the tilt direction of. 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]
Pellets of thermoplastic norbornene resin (manufactured by Nippon Zeon Co., Ltd., glass transition temperature Tg = 126 ° C.) were dried at 100 ° C. for 5 hours. The dried pellets were fed to the extruder, melted in the extruder and fed to the T-die through a polymer pipe and 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 unstretched base material (A) having a thickness of 70 μm and a width of 1350 mm. The pre-stretched base material (A) was wound up while being bonded to a masking film (“FF1025” manufactured by Treteger) for protection, and recovered as a roll.

[Production Example 2: Production of Pre-stretched Substrate (B)]
A long unstretched base material having a thickness of 70 μm and a width of 1350 mm in the same manner as in Production Example 1 except that “ZEONOR1420R” manufactured by ZEON Corporation (glass transition temperature Tg = 137 ° C.) was used as the pellets of the thermoplastic norbornene resin. (B) was manufactured and collected as a roll.

[Example 1]
[Manufacturing of 1-1.1/2 wave plate]
The pre-stretching base material (A) was pulled out from the roll of the pre-stretching base material (A) obtained in Production Example 1, and the masking film was continuously peeled off and supplied to the tenter stretching machine. Then, the base material (A) before stretching was obliquely stretched by a tenter stretching machine to obtain a long intermediate film. The stretching conditions for diagonal 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. At the time of this 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. Then, both ends of the stretched intermediate film in the width direction were trimmed to obtain a long 1/2 wave plate having a width of 1330 mm. The average orientation angle formed by the slow axis of the obtained 1/2 wave plate with respect to the width direction was 75 °, the NZ coefficient was 1.15, the in-plane retardation was 260 nm, and the thickness was 40 μm. The obtained 1/2 wavelength plate was wound while being bonded to a new masking film (“FF1025” manufactured by Tretegra) for protection to obtain a first film roll (I-1).

[Manufacturing of 1-2.1 / 4 wave plate]
The pre-stretching base material (A) was pulled out from the roll of the pre-stretching base material (A) obtained in Production Example 1, and the masking film was continuously peeled off and supplied to the tenter stretching machine. Then, the base material (A) before stretching was obliquely stretched by a tenter stretching machine to obtain a long 1/4 wave plate. The stretching conditions for diagonal stretching were a stretching ratio of 4.3 times and a stretching temperature of 142 ° C. The average orientation angle formed by the slow axis of the obtained 1/4 wave plate with respect to the width direction was 15 °, the NZ coefficient was 1.19, the in-plane retardation was 130 nm, and the thickness was 17 μm. The obtained 1/4 wave plate was wound while being bonded to a new masking film (“FF1025” manufactured by Tretegra) for protection to obtain a second film roll (I-2).

[1-3. Manufacture of optical laminate]
The 1/2 wavelength plate was pulled out from the first film roll (I-1), and the masking film was continuously peeled off. Well, the 1/4 wave plate was pulled out from the second film roll (I-2), and the masking film was continuously peeled off. Then, the 1/2 wave plate and the 1/4 wave plate were bonded together via an adhesive layer (“CS9621” manufactured by Nitto Denko) with their longitudinal directions parallel to each other. As a result, a long optical laminate (I-) in which the slow axis of the 1/2 wave plate and the slow axis of the 1/4 wave plate are bonded so as to intersect at 60 ° when viewed from the thickness direction. 3) was obtained.

[1-4. Manufacture of circularly polarizing plates]
As a long linear polarizing element, a polarizing film (“HLC2-5618S” manufactured by Sanritz Co., Ltd., a polarizer having a thickness of 180 μm and a polarization transmitting axis in the direction of 0 ° with respect to the width direction) was prepared. One surface of the polarizing film and the surface of the optical laminate (I-3) on the 1/2 wave plate side are made 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). As a result, a long circular polarizing plate having a layer structure of (polarizing film) / (adhesive layer) / (1/2 wave plate) / (adhesive layer) / (1/4 wave plate) was obtained. The circular polarizing plate thus obtained was evaluated by the method described above.

[Example 2]
In the process of manufacturing the 1/2 wave plate, the stretching ratio of the free longitudinal uniaxial stretching of the intermediate film was changed to 1.41 times so that the 1/2 wave plate having an average orientation angle of 72.5 ° could be obtained. The temperature was changed to 124 ° C.
Further, in the step of manufacturing the 1/4 wave plate, the stretching direction of the pre-stretching base material (A) was adjusted so that the 1/4 wave plate having an average orientation angle of 10 ° could be obtained.
Except for the above items, in the same manner as in Example 1, a long circle in which the slow axis of the 1/2 wave plate and the slow axis of the 1/4 wave plate intersect at 62.5 ° when viewed from the thickness direction. A polarizing plate was manufactured. The circular polarizing plate thus obtained was evaluated by the method described above.

[Example 3]
In the step of manufacturing the 1/2 wave plate, the stretching temperature of the diagonally stretched base material (A) before stretching was changed to 139 ° C. so that the 1/2 wave plate having an average orientation angle of 70.0 ° could be obtained. The stretching ratio of the free longitudinal uniaxial stretching of the intermediate film was changed to 1.41 times, and the stretching temperature was changed to 123 ° C.
Further, in the step of manufacturing the 1/4 wave plate, the stretching direction of the pre-stretching base material (A) is adjusted so that a 1/4 wave plate having an average orientation angle of 5 ° can be obtained, and the stretching ratio is 4.1. The stretching temperature was changed to 141 ° C.
Except for the above items, in the same manner as in Example 1, a long circular polarizing plate in which the slow axis of the 1/2 wave plate and the slow axis of the 1/4 wave plate intersect at 65 ° when viewed from the thickness direction. Manufactured. The circular polarizing plate thus obtained was evaluated by the method described above.

[Example 4]
In the process of manufacturing the 1/2 wave plate, the stretching ratio of the diagonally stretched base material (A) before stretching was changed to 1.36 times so that the 1/2 wave plate having an average orientation angle of 67.5 ° could be obtained. Then, the stretching temperature was changed to 136 ° C., and the stretching ratio of the free longitudinal uniaxial stretching of the intermediate film was changed to 1.28 times.
Further, in the step of manufacturing the 1/4 wave plate, the stretching direction of the pre-stretching base material (A) is set to that of the pre-stretching base material (A) so that a 1/4 wave plate having an average orientation angle of 0 ° can be obtained. The width direction was changed, and the draw ratio was changed to 3.4 times.
Except for the above items, in the same manner as in Example 1, a long circle in which the slow axis of the 1/2 wave plate and the slow axis of the 1/4 wave plate intersect at 67.5 ° when viewed from the thickness direction. A polarizing plate was manufactured. The circular polarizing plate thus obtained was evaluated by the method described above.

[Example 5]
[Manufacturing of 5-1.1 / 2 wave plate]
The pre-stretching base material (B) was pulled out from the roll of the pre-stretching base material (B) obtained in Production Example 2, the masking film was continuously peeled off, and free longitudinal uniaxial stretching was performed. At the time of this 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. Then, both ends of the stretched intermediate film in the width direction were trimmed to obtain a long 1/2 wave plate. The average orientation angle formed by the slow axis of the obtained 1/2 wave plate in the width direction was 90 °, the Nz coefficient was 1.0, and the in-plane retardation was 260 nm. The obtained 1/2 wavelength plate was wound while being bonded to a new masking film (“FF1025” manufactured by Tretegra) for protection to obtain a first film roll (V-1).

[Manufacturing of 5.2.1 / 4 wave plate]
The pre-stretching base material (A) was pulled out from the roll of the pre-stretching base material (A) obtained in Production Example 1, and the masking film was continuously peeled off and supplied to the tenter stretching machine. Then, the base material (A) before stretching was obliquely stretched by a tenter stretching machine to obtain a long 1/4 wave plate. The stretching conditions for diagonal 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 1/4 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 1/4 wave plate was wound 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 1/2 wavelength plate was pulled out from the first film roll (V-1), and the masking film was continuously peeled off. Well, the 1/4 wave plate was pulled out from the second film roll (V-2), and the masking film was continuously peeled off. Then, the 1/2 wave plate and the 1/4 wave plate were bonded together via an adhesive layer (“CS9621” manufactured by Nitto Denko) with their longitudinal directions parallel to each other. As a result, a long optical laminate (V-) in which the slow axis of the 1/2 wave plate and the slow axis of the 1/4 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 plates]
As a long linear polarizing element, a polarizing film (“HLC2-5618S” manufactured by Sanritz Co., Ltd., a polarizer having a thickness of 180 μm and a polarization transmitting axis in the direction of 0 ° with respect to the width direction) was prepared. One surface of the polarizing film and the surface of the optical laminate (I-3) on the 1/2 wave plate side are the polarization transmission axis of the polarizing film and the slow axis of the 1/2 wave plate (V-1). The bonded parts were bonded via an adhesive layer (“CS9621” manufactured by Nitto Denko) so that the two intersect at 75 ° when viewed from the thickness direction, and the bonded portion was cut out. As a result, a single-wafer circular polarizing plate having a layer structure of (polarizing film) / (adhesive layer) / (1/2 wave plate) / (adhesive layer) / (1/4 wave plate) was obtained. The circular polarizing plate thus obtained was evaluated by the method described above.

[Comparative Example 1]
[Manufacturing of C1-1.1 / 2 wave plate]
The pre-stretching base material (A) was pulled out from the roll of the pre-stretching base material (A) obtained in Production Example 1, and the masking film was continuously peeled off and supplied to the tenter stretching machine. Then, the base material (A) before stretching was obliquely stretched by a tenter stretching machine to obtain a long 1/2 wavelength plate. The stretching conditions for diagonal 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 1/2 wave plate in the width direction was 15 °, the Nz coefficient was 1.19, and the in-plane retardation was 260 nm. The obtained 1/2 wavelength plate was wound while being bonded to a new masking film (“FF1025” manufactured by Tretegra) for protection to obtain a first film roll (CI-1).

[Manufacturing of C1.2.1 / 4 wave plate]
The pre-stretching base material (A) was pulled out from the roll of the pre-stretching base material (A) obtained in Production Example 1, and the masking film was continuously peeled off and supplied to the tenter stretching machine. Then, the base material (A) before stretching was obliquely stretched by a tenter stretching machine to obtain a long intermediate film. The stretching conditions for diagonal 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. At the time of this 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. Then, both ends of the stretched intermediate film in the width direction were trimmed to obtain a long 1/4 wave plate. The average orientation angle formed by the slow axis of the obtained 1/4 wave plate in the width direction was 75 °, the NZ coefficient was 1.15, and the in-plane retardation was 130 nm. The obtained 1/4 wave plate was wound while being bonded to a new masking film (“FF1025” manufactured by Tretegra) for protection to obtain a second film roll (CI-2).

[C1-3. Manufacture of optical laminate]
The 1/2 wavelength plate was pulled out from the first film roll (CI-1), and the masking film was continuously peeled off. Well, the 1/4 wave plate was pulled out from the second film roll (CI-2), and the masking film was continuously peeled off. Then, the 1/2 wave plate and the 1/4 wave plate were bonded together via an adhesive layer (“CS9621” manufactured by Nitto Denko) with their longitudinal directions parallel to each other. As a result, a long optical laminate (CI-) in which the slow axis of the 1/2 wave plate and the slow axis of the 1/4 wave plate are bonded so as to intersect at 60 ° when viewed from the thickness direction. 3) was obtained.

[C1-4. Manufacture of circularly polarizing plates]
As a long linear polarizing element, a polarizing film (“HLC2-5618S” manufactured by Sanritz Co., Ltd., a polarizer having a thickness of 180 μm and a polarization transmitting axis in the direction of 0 ° with respect to the width direction) was prepared. One surface of the polarizing film and the surface of the optical laminate (CI-3) on the 1/2 wave plate side are made 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). As a result, a long circular polarizing plate having a layer structure of (polarizing film) / (adhesive layer) / (1/2 wave plate) / (adhesive layer) / (1/4 wave plate) was obtained. The circular polarizing plate thus obtained was evaluated by the method described above.

[Comparative Example 2]
[Manufacturing of C2-1.1 / 4 wave plate]
The pre-stretching base material (A) was pulled out from the roll of the pre-stretching base material (A) obtained in Production Example 1, and the masking film was continuously peeled off and supplied to the tenter stretching machine. Then, the base material (A) before stretching was obliquely stretched by a tenter stretching machine to obtain a long 1/4 wave plate. The stretching conditions for diagonal 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 1/4 wave plate in the width direction was 45 °, the NZ coefficient was 1.15, and the in-plane retardation was 130 nm. The obtained 1/4 wave plate was wound 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 plates]
The 1/4 wave plate was pulled out from the film roll (CII-1), and the masking film was continuously peeled off. This 1/4 wave plate and a polarizing film as a long linear polarizing element (“HLC2-5618S” manufactured by Sanritz Co., Ltd., a polarizer having a thickness of 180 μm and a polarization transmitting axis in the direction of 0 ° with respect to the width direction. ) With the longitudinal direction of the 1/4 wave plate parallel to the longitudinal direction of the polarizing film, and bonded via an adhesive layer (“CS9621” manufactured by Nitto Denko). As a result, a long circular polarizing plate having a layer structure of (polarizing film) / (adhesive layer) / (1/4 wave plate) was obtained. The circular polarizing plate thus obtained was evaluated by the method described above.

[result]
The results of the above Examples and Comparative Examples are shown in the table below. In the table below, the meanings of the abbreviations are as follows.
λ / 2: 1/2 wave plate.
λ / 4: 1/4 wave plate.
Diagonal: Diagonal direction.
Horizontal: Width direction.
Vertical: Longitudinal direction.
Re: In-plane lettering.
Crossing angle: The angle at which the slow axis of the 1/2 wave plate and the slow axis of the 1/4 wave plate intersect.

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

10 Feed roll 20 Pre-stretched film 21 and 22 Width end of pre-stretched film 30 Intermediate film 31 and 32 Width end of intermediate film 40 roll 50 1/2 wave plate 60 roll 100 Optical laminate 110 1 / 2 wave plate 111 1/2 wave plate slow axis 112 1/4 wave plate slow axis projected on the surface of 1/2 wave plate 120 1/4 wave plate 121 1/4 wave plate slow Phase shaft 200 Tenter stretching machine 210R and 210L Grip 220R and 220L Guide rail 230 Tenter stretching machine inlet 240 Tenter stretching machine outlet 250 Stretching zone 300 Roll stretching machine 310 Upstream roll 320 Downstream roll

Claims (3)

A method for manufacturing a circularly polarizing plate containing an optical laminate and a long linear polarizing element.
The optical laminate includes a long 1/2 wave plate and a long 1/4 wave plate made of a resin having a positive birefringence value.
The average orientation angle formed by the slow axis of the 1/2 wave plate with respect to the width direction of the 1/2 wave plate is 50 ° or more and 90 ° or less.
The NZ coefficient of the 1/2 wave plate is 1.0 to 1.5.
The average orientation angle formed by the slow axis of the 1/4 wave plate with respect to the width direction of the 1/4 wave plate is 0 ° or more and less than 50 °.
The NZ coefficient of the 1/4 wave plate is 1.0 to 1.5.
The average angle formed by the polarization transmission axis of the linear polarizer and the slow axis of the 1/2 wave plate is 50 ° or more and less than 90 °.
A step of obtaining the 1/2 wavelength plate by diagonally stretching the first pre-stretching film at a stretching ratio B1 and then performing longitudinal stretching at a stretching ratio B2 smaller than the stretching ratio B1.
A step of diagonally stretching the second pre-stretched film to obtain the 1/4 wave plate.
The step of laminating the 1/2 wave plate and the 1/4 wave plate by rolls to obtain the optical laminate, and the linearly polarized light of the optical laminate and the linear polarizer by rolls. A method for manufacturing a circularly polarizing plate, which comprises a step of laminating the child, the 1/2 wave plate and the 1/4 wave plate in this order. The method for manufacturing a circular polarizing plate according to claim 1, wherein the circular polarizing plate is for an organic electroluminescent display device. A method for manufacturing an optical laminate including a long 1/2 wave plate and a long 1/4 wave plate made of a resin having a positive birefringence value.
The average orientation angle formed by the slow axis of the 1/2 wave plate with respect to the width direction of the 1/2 wave plate is 50 ° or more and 90 ° or less.
The NZ coefficient of the 1/2 wave plate is 1.0 to 1.5.
The average orientation angle formed by the slow axis of the 1/4 wave plate with respect to the width direction of the 1/4 wave plate is 0 ° or more and less than 50 °.
The NZ coefficient of the 1/4 wave plate is 1.0 to 1.5.
A step of obtaining the 1/2 wavelength plate by diagonally stretching the first pre-stretching film at a stretching ratio B1 and then performing longitudinal stretching at a stretching ratio B2 smaller than the stretching ratio B1 .
Optical including a step of diagonally stretching the second pre-stretched film to obtain the 1/4 wave plate, and a step of laminating the 1/2 wave plate and the 1/4 wave plate by rolls. Method for manufacturing a laminate.

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