KR20230168975A - Retardation-layer-equipped polarizing plate - Google Patents

Abstract

The present invention provides a polarizing plate with a phase difference layer having a reverse dispersion characteristic, and a polarizing plate with a phase difference layer capable of suppressing the occurrence of appearance defects in a high temperature and high humidity environment. A polarizing plate with a phase difference layer according to an embodiment of the present invention comprises a polarizer; and a phase difference layer containing a cellulose-based resin and an ester-based resin in this order. Re(450)/Re(550) of the phase difference layer is 0 to 1, Re(550) of the phase difference layer is 100 nm to 200 nm, and the angle formed by the absorption axis direction of the polarizer and the slow axis direction of the phase difference layer is 40° to 50°, or 130° to 140°. A nanophase separation structure is formed in the phase difference layer.

Description

Polarizer with retardation layer {RETARDATION-LAYER-EQUIPPED POLARIZING PLATE}

The present invention relates to a polarizing plate with a retardation layer.

Various optical laminates combining a polarizer and an optical compensation film are generally used in image display devices to compensate for optical properties suitable for the intended use. As such an optical laminate, for example, a polarizing plate with a retardation layer has been proposed that includes a polarizer, a retardation layer that is a λ/4 plate, and a retardation layer formed of a modified polyester carbonate resin in this order (e.g., patent (see Document 1). In recent years, the usage environment of image display devices has become more diverse, and durability in high-temperature and high-humidity environments is sometimes required. With regard to durability under such a high-temperature, high-humidity environment, there remains room for improvement in the polarizing plate with a retardation layer described in Patent Document 1, and in the polarizing plate with a retardation layer described in Patent Document 1, cracks, peeling, etc. of the retardation layer are observed, especially in a high-temperature, high-humidity environment. There is a risk of appearance defects.

Japanese Patent Publication No. 2022-013705

The present invention was made to solve the above-described conventional problems, and its main object is to provide a polarizing plate with a retardation layer having an inverse dispersion characteristic, which can suppress the occurrence of appearance defects in a high-temperature, high-humidity environment. The aim is to provide a polarizer with a phase contrast layer.

[1] A polarizing plate with a retardation layer according to an embodiment of the present invention includes a polarizer; A retardation layer containing a cellulose resin and an ester resin is provided in this order. Re(450)/Re(550) of the phase contrast layer is 0 to 1, and Re(550) of the phase contrast layer is 100 nm to 200 nm. The angle formed between the absorption axis direction of the polarizer and the slow axis direction of the phase difference layer is 40° to 50° or 130° to 140°. In the phase contrast layer, a nanophase separation structure is formed.

[2] One embodiment is the polarizing plate with a retardation layer according to the above item [1], in which the cellulose resin has a structural unit represented by the following formula (1).

(In formula (1), each of R ₁ to R ₃ represents a hydrogen atom or a substituent having 1 to 12 carbon atoms _. )

[3] One embodiment is the phase difference according to item [1] or [2], wherein the ester resin has a structural unit represented by the following formula (2) and a structural unit represented by the following formula (3). It is a layer attached polarizer.

(In equation (2), R ₄ is Represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms; R _5a is the carbon number Represents one type selected from 1 to 12 alkyl groups, nitro groups, bromo groups, iodine groups, cyano groups, chloro groups, sulfonic acid groups, carboxylic acid groups _, fluoro groups, or thiol groups; R _5b represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms; R ₆ is a hydrogen atom, nitro group, bromo group, iodine group, cyano group, chloro group, sulfonic acid group, carboxylic acid group, fluoro group, phenyl group, thiol group, amide group, amino group, hydroxy group, or alkoxy group having 1 to 12 carbon atoms. , or a species selected from an alkyl group having 1 to 12 carbon atoms.)

(In formula (3), R ₇ is a 5-membered ring heterocyclic residue or a 6-membered ring heterocyclic residue containing at least one nitrogen atom or oxygen atom as a heteroatom (the 5-membered ring heterocyclic residue and the 6-membered ring heterocyclic residue are It may form other cyclic structures and condensed ring structures.)

[4] One embodiment is the polarizing plate with a retardation layer according to the above item [3], in which the ester resin further has a structural unit represented by the following formula (4).

(In formula (4), R ₈ and R ₉ each represent one type selected from a hydrogen atom, a straight-chain alkyl group with 1 to 12 carbon atoms, a branched alkyl group with 3 to 12 carbon atoms, or a cyclic alkyl group with 3 to 6 carbon atoms. .)

[5] One embodiment is the above-mentioned items [1] to 50% by mass, wherein the content ratio of the cellulose-based resin exceeds 50% by mass when the total of the cellulose-based resin and the ester-based resin is 100% by mass. It is a polarizing plate with a retardation layer according to any one of [4].

[6] In one embodiment, the retardation layer is a stretched film obtained by stretching a resin film containing a cellulose resin and an ester resin, and the number of MITs in the direction perpendicular to the stretching direction of the stretched film is 300. The polarizing plate with a retardation layer according to any one of the above [1] to [5].

According to the embodiment of the present invention, it is possible to realize a polarizing plate with a retardation layer provided with a retardation layer having inverse dispersion characteristics, and in which the occurrence of appearance defects in a high temperature and high humidity environment is suppressed.

1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention.

Hereinafter, representative embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

(Definition of terms and symbols)

The definitions of terms and symbols in this specification are as follows.

(1) Refractive index (nx, ny, nz)

'nx' is the refractive index in the direction where the in-plane refractive index is maximum (i.e., slow axis direction), 'ny' is the refractive index in the direction orthogonal to the slow axis in the plane (i.e., fast axis direction), and 'nz' is It is the refractive index in the thickness direction.

(2) In-plane phase difference (Re)

'Re(λ)' is the in-plane phase difference measured with light with a wavelength of λnm at 23°C. For example, 'Re(550)' is the in-plane retardation measured with light with a wavelength of 550 nm at 23°C. Re(λ) can be obtained by the formula: Re(λ)=(nx-ny)×d when the thickness of the layer (film) is d(nm).

(3) angle

When referring to an angle in this specification, unless otherwise specified, the angle includes angles in both clockwise and counterclockwise directions.

(4) In-plane birefringence (Δn)

'Δn(λ)' is the in-plane birefringence measured with light of wavelength λnm at 23°C. For example, 'Δn(550)' is the in-plane birefringence measured with light with a wavelength of 550 nm at 23°C. In-plane birefringence (Δn) can be obtained from the formula: Δn=nx-ny.

(5) Phase difference in the thickness direction (Rth)

'Rth(λ)' is the phase difference in the thickness direction measured with light with a wavelength of λnm at 23°C. For example, 'Rth(550)' is the phase difference in the thickness direction measured with light with a wavelength of 550 nm at 23°C. Rth(λ) can be obtained by the formula: Rth(λ)=(nx-nz)×d when the thickness of the layer (film) is d(nm).

(6) Nz coefficient

The Nz coefficient can be obtained by Nz=Rth/Re.

A. Overall composition of polarizer with phase contrast layer

1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention. The polarizing plate 100 with a retardation layer in the illustrated example includes a polarizing plate 10 including a polarizer 11; A retardation layer 20 containing a cellulose resin and an ester resin is provided in this order. Re(450)/Re(550) of the phase difference layer 20 is 0 to 1, for example 0.60 to 0.99, for example 0.70 to 0.95, and for example 0.70 to 0.90. Re(550) of the phase contrast layer 20 is 100 nm to 200 nm, for example, 120 nm to 160 nm, and for example, 130 nm to 150 nm. The phase difference layer 20 typically functions as a λ/4 plate. The angle formed by the absorption axis direction of the polarizer 11 and the slow axis direction of the retardation layer 20 is 40° to 50°, preferably 42° to 48°, more preferably 44° to 46°, even more preferably It is about 45°; or 130° to 140°, preferably 132° to 138°, more preferably 134° to 136°, and even more preferably about 135°. In the phase contrast layer 20, a nanophase separation structure is formed. As will be described in detail later, cellulose resins have a relatively low glass transition temperature (Tg), and ester resins have a relatively high Tg.

According to one embodiment of the present invention, the phase difference layer 20 has an inverse dispersion characteristic (wavelength dependence of inverse dispersion in which the phase difference value increases depending on the wavelength of the measurement light) in which Re (450) / Re (550) is in the above range. It contains a cellulose resin with a relatively low Tg and an ester resin with a relatively high Tg. Therefore, the residual stress reduction effect by the cellulose resin and the shrinkage reduction effect by the ester resin can be provided to the retardation layer 20 in a balanced manner. Since the nanophase separation structure is formed in the phase difference layer 20, rapid shrinkage of the phase difference layer 20 can be suppressed under a high temperature and high humidity environment (e.g., 110° C. and 85% RH (relative humidity)). This can prevent cracks from occurring in the retardation layer 20 and/or peeling of the retardation layer 20 from the polarizer 11. As a result, occurrence of appearance defects of the polarizing plate 100 with a retardation layer under a high-temperature, high-humidity environment can be suppressed. In addition, if a nano phase separation structure is formed in the phase difference layer 20, the function as a reverse dispersion phase difference layer can be stably secured.

In this specification, 'nanophase separation structure' refers to a structure in which two components with different electron densities are phase separated into a domain size of the nano order (typically at the level of several tens of nm). The cellulose resin and ester resin may have a sea-island structure or a co-continuous structure. Means for confirming the nanophase separation structure include, for example, transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), and small-angle X-ray scattering (SAXS), preferably using a phase contrast layer ( TEM observation of the cross section of 20). TEM observation is described in detail in the Examples. When a nanophase separation structure is formed in the retardation layer 20, two types of domains with different electron densities can be confirmed in TEM observation of the cross section of the retardation layer 20, and the size (maximum length) of all domains is It can be confirmed that it is less than 100 nm.

The in-plane birefringence Δn(550) of the retardation layer 20 is, for example, 0.0020 or more, preferably 0.0030 or more, more preferably 0.0040 or more, and for example, 0.0070 or less, preferably 0.0060 or less, and more preferably 0.0055 or less.

The Nz coefficient of the phase difference layer 20 is, for example, 0.9 or more and 3 or less, and preferably 1.0 or more and 1.5 or less.

In one embodiment, the content ratio of the cellulose resin typically exceeds 50 mass%, preferably 60 mass% or more, when the total of the cellulose resin and the ester resin is 100 mass%. Preferably it is 70% by mass or more. When the content ratio of the cellulose resin is more than the above lower limit, the cellulose resin and the ester resin can stably form a nanophase separation structure. Additionally, the upper limit of the content of cellulose resin is typically 90% by mass or less.

In one embodiment, the retardation layer 20 is a stretched film obtained by stretching a resin film containing a cellulose resin and an ester resin. Although described in detail later, a stretched film (retardation film) is typically prepared by uniaxially stretching a resin film containing a cellulose resin and an ester resin in a predetermined direction. In such a retardation film, a nanophase separation structure is formed as described above. A polarizing plate with a retardation layer provided with a retardation film alone and a retardation film (retardation layer) has excellent flexibility in the stretching direction and in the direction orthogonal to the stretching direction.

In particular, the retardation film having a nanophase separation structure is significantly superior in bendability in the direction perpendicular to the stretching direction compared to the retardation film (e.g., stretched resin film, liquid crystal polymer film) without the nanophase separation structure, A polarizing plate with a retardation layer provided with a retardation film (retardation layer) having a nanophase separation structure also shows the same tendency.

The number of MITs of the retardation film in the stretching direction is, for example, 800 times or more, preferably 1,000 times or more, more preferably 1,500 times or more, and for example, 2,500 times or less. Additionally, the number of MITs can be measured based on JIS P 8115 (the same applies hereinafter).

The number of MITs of the retardation film in the direction orthogonal to the stretching direction is, for example, 400 times or more, preferably 500 times or more, more preferably 600 times or more, further preferably 1000 times or more, especially preferably 1300 times or more. and, for example, 2000 times or less.

The number of MITs of the polarizing plate 100 with a retardation layer in the stretching direction is, for example, 300 times or more, preferably 500 times or more, more preferably 600 times or more, and for example, 1000 times or less.

The number of MITs of the polarizing plate 100 with a retardation layer in the direction perpendicular to the stretching direction is, for example, 300 times or more, preferably 400 times or more, more preferably 450 times or more, further preferably 500 times or more, especially preferably Typically, it is 550 times or more, for example, it is 900 times or less.

In one embodiment, the retardation layer 20 is attached to the polarizer 10 via an adhesive layer 30. In the illustrated example, the retardation layer 20 is attached to the polarizer 11 through the adhesive layer 30. Additionally, the adhesive layer 30 may be formed directly on the polarizer 11, or, when the polarizing plate 10 is provided with a protective layer on the side of the polarizer 11 opposite to the viewing side, it may be formed on the protective layer. The adhesive layer 30 may be an adhesive layer or an adhesive layer. The adhesive layer 30 is preferably an adhesive layer. When the adhesive layer 30 is an adhesive layer, examples of the adhesive constituting the adhesive layer include (meth)acrylic adhesives. Additionally, ‘(meth)acrylic type’ refers to acrylic type and/or methacrylic type. The thickness of the adhesive layer is, for example, 3.5 μm or more and 35 μm or less.

When the adhesive layer 30 is an adhesive layer, examples of the adhesive constituting the adhesive layer include a thermosetting adhesive and an ultraviolet curing adhesive, and more preferably a (meth)acrylic ultraviolet curing adhesive. Additionally, ‘(meth)acrylic type’ refers to acrylic type and/or methacrylic type. The thickness of the adhesive layer is, for example, 0.4 μm or more and 3.0 μm or less.

In one embodiment, the polarizing plate 100 with a retardation layer further includes an adhesive layer 40 provided on the opposite side of the retardation layer 20 from the polarizer 11. Accordingly, the polarizing plate 100 with a retardation layer can be attached to an image display cell described later. Examples of the adhesive constituting the adhesive layer 40 include (meth)acrylic adhesive. The thickness of the adhesive layer 40 is, for example, 3.5 μm or more and 35 μm or less.

In addition, it is preferable that the release liner 50 is temporarily attached to the surface of the adhesive layer 40 until the polarizing plate 100 with a retardation layer is put into use. By temporarily attaching the release liner, the adhesive layer is protected and roll formation becomes possible.

The polarizing plate with a retardation layer may be sheet-like or elongated. In this specification, 'elongate shape' means an elongated shape with a sufficiently long length relative to the width, and includes, for example, an elongated shape with a length of 10 or more times the width, preferably 20 times or more. A long polarizing plate with a retardation layer can be wound into a roll.

Hereinafter, each member constituting the polarizing plate 100 with a retardation layer will be described.

B. Polarizer

B-1. polarizer

As the polarizer 11, any suitable polarizer can be employed. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

Specific examples of polarizers composed of a single-layer resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA)-based films, partially formalized PVA-based films, and ethylene-vinyl acetate copolymer-based partially saponified films, with iodine or dichroic (II) Examples include those that have been dyed and stretched with dichroic substances such as dyes, and polyene-based oriented films such as dehydrated PVA products and dehydrochloric acid-treated polyvinyl chloride products. Preferably, a polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching is used because it has excellent optical properties.

The dyeing with iodine is performed, for example, by immersing the PVA-based film in an aqueous iodine solution. The draw ratio of the uniaxial stretching is preferably 3 times or more and 7 times or less. Stretching may be performed after dyeing treatment or may be performed while dyeing. Additionally, it may be dyed after stretching. If necessary, the PVA-based film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, etc. For example, by immersing the PVA-based film in water and washing it before dyeing, not only can contamination and anti-blocking agents on the surface of the PVA-based film be removed, but also the PVA-based film can be swelled to prevent uneven dyeing.

Specific examples of the polarizer obtained using the laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a laminate of a resin substrate and a PVA-based resin layer applied to the resin substrate. A polarizer obtained by using a laminated body can be mentioned. A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer formed by applying to the resin substrate, for example, applies a PVA-based resin solution to a resin substrate, dries it, and forms a PVA-based resin layer on the resin substrate. Obtaining a laminate of a base material and a PVA-based resin layer; It can be produced by stretching and dyeing the laminate and using the PVA-based resin layer as a polarizer. In one embodiment of the present invention, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is preferably formed on one side of the resin substrate. Stretching typically involves immersing the laminate in an aqueous boric acid solution and stretching it. Additionally, stretching may further include air stretching the laminate at a high temperature (eg, 95°C or higher) before stretching in an aqueous boric acid solution, if necessary. Furthermore, in one embodiment of the present invention, the laminate is preferably subjected to dry shrinkage treatment to shrink the laminate by 2% or more in the width direction by heating while conveying in the longitudinal direction. Typically, the manufacturing method of this embodiment includes performing aerial auxiliary stretching treatment, dyeing treatment, underwater stretching treatment, and dry shrink treatment on the laminate in this order. By introducing auxiliary stretching, even when applying PVA on a thermoplastic resin, it becomes possible to increase the crystallinity of PVA and achieve high optical properties. Moreover, by simultaneously increasing the orientation of PVA in advance, problems such as a decrease in orientation or dissolution of PVA when immersed in water in the subsequent dyeing process or stretching process can be prevented, making it possible to achieve high optical properties. It becomes. Additionally, when the PVA-based resin layer is immersed in a liquid, the disruption of the orientation of polyvinyl alcohol molecules and the decrease in orientation can be suppressed compared to the case where the PVA-based resin layer does not contain a halide. Thereby, the optical properties of the polarizer obtained through a treatment process performed by immersing the laminate in a liquid, such as dyeing treatment and underwater stretching treatment, can be improved. Additionally, optical properties can be improved by shrinking the laminate in the width direction through dry shrinkage treatment. The obtained resin substrate/polarizer laminate may be used as is (i.e., the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled from the resin substrate/polarizer laminate and applied to the peeled surface for the purpose. Any appropriate protective layer may be laminated and used. Details of the manufacturing method of such a polarizer are described in, for example, Japanese Patent Laid-Open No. 2012-73580 and Japanese Patent No. 6470455. These publications are hereby incorporated by reference in their entirety.

The thickness of the polarizer is, for example, 1 μm or more and 80 μm or less, preferably 1 μm or more and 15 μm or less, more preferably 1 μm or more and 12 μm or less, further preferably 3 μm or more and 12 μm or less, especially preferably 3 μm or more. It is ㎛ or more and 8㎛ or less. If the thickness of the polarizer is within this range, curling during heating can be well suppressed, and good external appearance durability during heating can be obtained.

The polarizer preferably exhibits absorption dichroism at any wavelength from 380 nm to 780 nm. The single transmittance of the polarizer is, for example, 41.5% or more and 46.0% or less, preferably 43.0% or more and 46.0% or less, and more preferably 44.5% or more and 46.0% or less. The polarization degree of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more.

B-2. protective layer

The polarizing plate 10 may further include a protective layer. A protective layer is provided on at least one side of the polarizer. In the illustrated example, the polarizing plate 10 is provided with a protective layer 12 provided on the surface of the polarizer 11 on the viewing side.

The protective layer is formed from any suitable film that can be used as a protective layer for a polarizer. Specific examples of materials that become the main component of the film include cellulose-based resins such as triacetylcellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, Transparent resins such as polysulfone-based, polystyrene-based, polynorbornene-based, polyolefin-based, (meth)acrylic-based, and acetate-based resins can be mentioned. In addition, thermosetting resins or ultraviolet curing resins such as (meth)acrylic, urethane, (meth)acrylic urethane, epoxy, silicone, etc. may also be included. In addition, for example, glassy polymers such as siloxane polymers can also be mentioned. Additionally, the polymer film described in Japanese Patent Application Laid-Open No. 2001-343529 (WO01/37007) can also be used.

When the polarizing plate 10 is provided with a protective layer located on the outermost surface of the image display device described later, the protective layer may be subjected to surface treatment such as hard coat treatment, anti-reflection treatment, anti-sticking treatment, and anti-glare treatment as necessary. may be implemented.

The thickness of the protective layer is typically 5 mm or less, preferably 1 mm or less, more preferably 1 μm or more and 500 μm or less, and further preferably 5 μm or more and 150 μm or less. In addition, when surface treatment is performed, the thickness of the protective layer is a thickness including the thickness of the surface treatment layer.

C. Phase contrast layer

The phase contrast layer 20 typically exhibits refractive index characteristics of nx>ny≥nz. 'ny=nz' includes not only the case where ny and nz are completely the same, but also the case where ny and nz are substantially the same. The retardation layer 20 with refractive index characteristics of nx>ny=nz may be referred to as a 'positive A plate' or the like. The retardation layer 20 having a refractive index characteristic of nx>ny>nz may be referred to as a “negative B plate” or the like.

The thickness of the retardation layer 20 is, for example, 10 μm or more, preferably 20 μm or more, for example, 80 μm or less, preferably 60 μm or less. The thickness of the retardation layer 20 can be appropriately adjusted arbitrarily depending on the use of the polarizing plate with a retardation layer, and is not limited to the above range. The thickness of the retardation layer 20 may be, for example, 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less. If the thickness of the retardation layer is below the above upper limit, the flexibility of the polarizing plate with a retardation layer can be further improved, and the number of MITs of the polarizing plate with a retardation layer can be improved. In this case, the lower limit of the thickness of the retardation layer is typically 5 μm or more.

The retardation layer 20 contains cellulose-based resin and ester-based resin as described above. Cellulose resin exhibits positive birefringence. Ester-based resins exhibit negative birefringence. Here, 'exhibiting positive birefringence' means that when a polymer is oriented by stretching or the like, the refractive index in the direction perpendicular to the stretching direction becomes relatively small. In other words, it means that the refractive index in the stretching direction increases. 'Exhibiting negative birefringence' means that when a polymer is oriented by stretching, etc., the refractive index in the stretching direction becomes relatively small. In other words, it means that the refractive index in the direction orthogonal to the stretching direction increases.

C-1. Cellulose-based resin

Cellulose resin is typically a polymer in which β-glucose units are polymerized in a linear form, and has structural units shown in the following formula (1).

(In formula (1), R ₁ to R ₃ each represent a hydrogen atom or a substituent having 1 to 12 carbon atoms _. )

Substituents having 1 to 12 carbon atoms represented by R ₁ to R ₃ in the formula (1), for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, decanyl group, dodeca. Alkyl groups such as nyl group, isobutyl group, and t-butyl group; Cycloalkyl groups such as cyclohexyl groups; Aryl groups such as phenyl group and naphthyl group; Aralkyl groups such as benzyl group; Acyl groups such as acetyl group and propionyl group; Cyanoalkyl groups such as cyanoethyl group; Aminoalkyl groups such as aminoethyl group; Hydroxyalkyl groups such as 2-hydroxyethyl group and 3-hydroxypropyl group can be mentioned.

In formula (1), R ₁ ~R ₃ are They may be the same or different from each other.

As each of R ₁ to R ₃ in the formula (1), preferably a hydrogen atom and an alkyl group having 1 to 12 carbon atoms, more preferably a hydrogen atom and an alkyl group having 1 to 4 carbon atoms, More preferably, a hydrogen atom and an ethyl group are mentioned.

The degree of substitution (hereinafter referred to as DS) of the cellulose resin is typically 1.5 or more and 2.95 or less, and preferably 1.8 or more and 2.8 or less. DS is the ratio at which hydroxyl groups are substituted in the cellulose resin, and in the case of 100% substitution, DS is 3. DS can be calculated from the peak area of gas chromatography, as described in the Japanese Pharmacopoeia, 17th edition.

The number average molecular weight (Mn) of the cellulose resin in terms of standard polystyrene is, for example, 1 × 10 ³ or more and 1 × 10 ⁶ or less, preferably 5 × 10 ³ or more and 2 × 10 ⁵ or less. Mn of the cellulose resin can be calculated from the elution curve measured by gel permeation chromatography (GPC). If the Mn of the cellulose resin is in the above range, the mechanical properties and/or molding processability of the phase difference layer can be improved.

The glass transition temperature (Tg) of the cellulose resin is, for example, 140°C or lower, preferably 135°C or lower, for example, 120°C or higher, preferably 125°C or higher. The glass transition temperature (Tg) of a cellulose resin can be measured using a thermal analysis device such as DSC (Differential Scanning Calorimetry).

Specific examples of cellulose resin include alkyl cellulose such as methyl cellulose, ethyl cellulose, and propyl cellulose; Hydroxyalkyl cellulose such as hydroxyethyl cellulose and hydroxypropyl cellulose; Aralkyl cellulose such as benzyl cellulose; Cyanoalkyl cellulose such as cyanoethyl cellulose; carboxyalkyl cellulose such as carboxymethyl cellulose and carboxyethyl cellulose; Carboxyalkyl alkyl cellulose such as carboxymethyl methyl cellulose and carboxymethyl ethyl cellulose; Aminoalkyl cellulose such as aminoethylcellulose can be mentioned. Cellulose-based resins can be used individually or in combination.

Among cellulose resins, alkyl cellulose is preferred, and ethyl cellulose is more preferred.

C-2. Ester-based resin

Ester resin typically has a structural unit shown in the following formula (2) and a structural unit shown in the following formula (3).

(In equation (2), R ₄ is Represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms; R _5a is the carbon number 1 to 12 alkyl group, nitro group, bromo group, iodine group, cyano group, chloro group, sulfonic acid group, carboxylic acid group, Represents one type selected from a fluoro group or a thiol group; R _5b represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms; R ₆ is a hydrogen atom, nitro group, bromo group, iodine group, cyano group, chloro group, sulfonic acid group, carboxylic acid group, fluoro group, phenyl group, thiol group, amide group, amino group, hydroxy group, or alkoxy group having 1 to 12 carbon atoms. , or a species selected from an alkyl group having 1 to 12 carbon atoms.)

(In formula (3), R ₇ is a 5-membered ring heterocyclic residue or a 6-membered ring heterocyclic residue containing at least one nitrogen atom or oxygen atom as a heteroatom (the 5-membered ring heterocyclic residue and the 6-membered ring heterocyclic residue are It may form other cyclic structures and condensed ring structures.)

The structural unit shown in the above formula (2) is a cinnamic acid ester residue unit. In equation (2) above, Examples of the alkyl group having 1 to 12 carbon atoms represented by R ₄ include methyl, ethyl, isopropyl, n-propyl, n-butyl, s-butyl, t-butyl, isobutyl, and ethylhexyl. I can hear it. In equation (2) above, Among R ₄ , alkyl groups having 1 to 4 carbon atoms are preferred, and ethyl groups and isobutyl groups are more preferred.

Among R _5a in the formula (2), alkyl groups and cyano groups having 1 to 12 carbon atoms are preferred, and alkyl groups and cyano groups having 1 to 4 carbon atoms are more preferred. Cyano group can be mentioned.

Among R _5b in the formula (2), a hydrogen atom and an alkyl group having 1 to 4 carbon atoms are preferred.

R ₆ in formula (2) is Only one may be bonded to the benzene ring, or two or more may be bonded to the benzene ring. Among R ₆ in the above formula (2), a carboxylic acid group and a hydroxy group are preferred.

Specific examples of the structural units (cinnamic acid ester residue units) shown in the above formula (2) include α-cyano-4-hydroxycinnamic acid methyl residue units, α-cyano-2-hydroxycinnamic acid ethyl residue units, α-cyano-3-hydroxycinnamate ethyl residue unit, α-cyano-4-hydroxycinnamate ethyl residue unit, α-cyano-4-hydroxycinnamic acid n-propyl residue unit, α-cyano No-4-hydroxycinnamic acid isopropyl residue unit, α-cyano-4-hydroxycinnamic acid n-butyl residue unit, α-cyano-4-hydroxycinnamic acid isobutyl residue unit, α-cyano α-cyano-hydroxycinnamic acid ester residue units such as s-butyl -4-hydroxycinnamic acid residue units and α-cyano-2,4-dihydroxycinnamic acid methyl residue units; α-cyano-4-carboxycinnamate methyl residue unit, α-cyano-4-carboxycinnamate ethyl residue unit, α-cyano-2,3-dicarboxycinnamate methyl residue unit, α-cyano- α-cyano-carboxycinnamic acid ester residue units such as 2,3-dicarboxycinnamate ethyl residue units; α-Cyano-carboxy-hydroxycinnamic acids, such as methyl α-cyano-2-carboxy-3-hydroxycinnamate residue units and ethyl α-cyano-2-carboxy-3-hydroxycinnamate residue units. ester residue unit; 3-alkyl-3, such as 3-methyl-3-(hydroxyphenyl)-propa-2-methyl enoate residue unit, 3-ethyl-3-(hydroxyphenyl)-propa-2-ethyl enoate residue unit, etc. -(hydroxyphenyl)-propa-2-enoic acid ester residue unit; 3-alkyl-3-(, such as 3-methyl-3-(carboxyphenyl)-propa-2-methyl enoate residue unit, 3-ethyl-3-(carboxyphenyl)-propa-2-ethyl enoate residue unit, etc. carboxyphenyl)-propa-2-enoic acid ester residue unit; 2-Cyano-3-methyl-3-(hydroxyphenyl)-propa-2-enoic acid Methyl residue unit, 2-cyano-3-ethyl-3-(hydroxyphenyl)-propa-2-enoic acid 2-cyano-3-alkyl-3-(hydroxyphenyl)-propa-2-enoic acid ester residue units such as ethyl residue units; 2-cyano-3-methyl-3-(carboxyphenyl)-propa-2-enoate methyl residue unit, 2-cyano-3-ethyl-3-(carboxyphenyl)-propa-2-enoate ethyl residue 2-cyano-3-alkyl-3-(carboxyphenyl)-propa-2-enoic acid ester residue units such as the unit.

The ester resin may contain only one type or two or more types of structural units shown in the above formula (2). Among the structural units shown in the above formula (2), preferably α-cyano-hydroxycinnamic acid ester residue unit, α-cyano-carboxycinnamic acid ester residue unit, 3-alkyl-3-(hydroxy Phenyl)-propa-2-enoic acid ester residue unit and 3-alkyl-3-(carboxyphenyl)-propa-2-enoic acid ester residue unit.

The content ratio of the structural unit of the formula (2) in the ester resin is, for example, 21 mol% or more, for example, 70 mol% or less, preferably 60 mol% or less, and more preferably 49 mol% or less. The content ratio of each structural unit in the ester resin can be measured by, for example, ¹ H-NMR.

Specific examples of the ring structure represented by R ₇ in the above formula (3) include 1-vinylpyrrole residue unit, 2-vinylpyrrole residue unit, 1-vinylindole residue unit, 9-vinylcarbazole residue unit, and 2-vinylquinoline residue. units, 4-vinylquinoline residue units, N-vinylphthalimide residue units, N-vinylsuccinimide residue units, 2-vinylfuran residue units, and 2-vinylbenzofuran residue units, preferably 9. -Vinylcarbazole residue units and N-vinylphthalimide residue units can be mentioned.

The ester resin may contain only one type or two or more types of structural units shown in the above formula (3).

The content ratio of the structural unit of the formula (3) in the ester resin is, for example, 21 mol% or more, preferably 35 mol% or more, for example, 70 mol% or less, preferably 60 mol% or less.

The ester resin preferably has, in addition to the structural units shown in the above (2) and (3), a structural unit shown in the following formula (4).

(In formula (4), R ₈ and R ₉ each represent one type selected from a hydrogen atom, a straight-chain alkyl group with 1 to 12 carbon atoms, a branched alkyl group with 3 to 12 carbon atoms, or a cyclic alkyl group with 3 to 6 carbon atoms. ).

In the above formula (4), linear alkyl groups having 1 to 12 carbon atoms represented by R ₈ and R ₉ include, for example, methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, etc. can be mentioned.

In the formula (4), examples of the branched alkyl group having 3 to 12 carbon atoms represented by R ₈ and R ₉ include isopropyl group, isobutyl group, sec-butyl group, and tert-butyl group.

In the above formula (4), examples of the cyclic alkyl group having 3 to 6 carbon atoms represented by R ₈ and R ₉ include cyclopropyl group, cyclobutyl group, and cyclohexyl group.

In the above formula (4), R ₈ and R ₉ may be the same as each other or may be different from each other.

Among R ₈ in the above formula (4), hydrogen atoms and linear alkyl groups having 1 to 12 carbon atoms are preferred, and hydrogen atoms and methyl groups are more preferred.

Among R ₉ in the above formula (4), a branched alkyl group having 3 to 12 carbon atoms is preferred, and a branched alkyl group having 3 to 8 carbon atoms is more preferred.

The structural unit shown in the above formula (4) is typically an acrylic resin residue unit. Specific examples of the structural units shown in the formula (4) include acrylic acid residue unit, methacrylic acid residue unit, 2-ethylacrylic acid residue unit, 2-propylacrylic acid residue unit, 2-isopropylacrylic acid residue unit, and 2-pentylacrylic acid. residue unit, 2-hexyl acrylic acid residue unit, methyl acrylate residue unit, ethyl acrylate residue unit, n-propyl acrylate residue unit, isopropyl acrylate residue unit, n-butyl acrylate residue unit, isobutyl acrylate residue unit, sec-butyl acrylate residue unit, n-pentyl acrylate residue unit, isopentyl acrylate residue unit, sec-pentyl acrylate residue unit, 3-pentyl acrylate residue unit, neopentyl acrylate residue unit, n-hexyl acrylate residue unit, isohexyl acrylate residue unit, acrylic acid Neohexyl residue unit, methyl methacrylate residue unit, ethyl methacrylate residue unit, n-propyl methacrylate residue unit, isopropyl methacrylate residue unit, n-butyl methacrylate residue unit, isobutyl methacrylate residue unit, sec-butyl methacrylate residue unit, n-pentyl methacrylate residue unit, isopentyl methacrylate residue unit, sec-pentyl methacrylate residue unit, 3-pentyl methacrylate residue unit, methacrylic acid Neopentyl residue unit, n-hexyl methacrylate residue unit, isohexyl methacrylate residue unit, neohexyl methacrylate residue unit, 2-ethyl methyl acrylate residue unit, 2-ethyl acrylate ethyl residue unit, 2-ethyl acrylic acid n-propyl residue units, 2-ethylacrylate isopropyl residue units, 2-ethylacrylate n-butyl residue units, 2-ethylacrylate isobutyl residue units, 2-ethylacrylate sec-butyl residue units, etc. are preferred. Examples include isobutyl acrylate residue units.

The ester resin may contain only one type or two or more types of structural units shown in the formula (4).

The content ratio of the structural unit of the formula (4) in the ester resin is, for example, 0 mol% or more, preferably 1 mol% or more, for example, 30 mol% or less.

The ester resin may contain monomer residue units other than those of formulas (2) to (4). Examples of such monomer residue units include styrene residues such as styrene residues and α-methylstyrene residues; Vinylnaphthalene moiety; Vinyl ester residues such as vinyl acetate residues and vinyl propionate residues; Vinyl ether residues such as methyl vinyl ether residue, ethyl vinyl ether residue, and butyl vinyl ether residue; N-methylmaleimide residue; N-substituted maleimide residues such as N-cyclohexylmaleimide residues and N-phenylmaleimide residues; an acrylonitrile moiety; a methacrylonitrile moiety; fumaric acid ester residue; fumaric acid residues; and olefin residues such as ethylene residues and propylene residues.

The number average molecular weight (Mn) of the ester resin in terms of standard polystyrene is, for example, 1 × 10 ³ or more and 5 × 10 ⁶ or less, preferably 5 × 10 ³ or more and 3 × 10 ⁵ or less. Mn of the ester resin can be calculated from the elution curve measured by gel permeation chromatography (GPC). If the Mn of the ester resin is within the above range, the mechanical properties and/or molding processability of the phase difference layer can be improved.

The glass transition temperature (Tg) of the ester resin is, for example, 220°C or lower, preferably 210°C or lower, for example, 180°C or higher, preferably 190°C or higher. The glass transition temperature (Tg) of an ester resin can be measured using a thermal analysis device such as DSC (Differential Scanning Calorimetry).

Specific examples of such ester resins include α-cyano-2-hydroxycinnamic acid ester-styrene-acrylic acid ester copolymer, α-cyano-2-hydroxycinnamic acid ester-2-vinylnaphthalene-acrylic acid ester copolymer. Polymer, α-cyano-2-hydroxycinnamic acid ester-1-vinylindole-acrylic acid ester copolymer, α-cyano-2-hydroxycinnamic acid ester-9-vinylcarbazole-acrylic acid ester copolymer, α -Cyano-3-hydroxycinnamic acid ester-styrene-acrylic acid ester copolymer, α-cyano-3-hydroxycinnamic acid ester-2-vinylnaphthalene-acrylic acid ester copolymer, α-cyano-3-hydride Roxycinnamic acid ester-1-vinylindole-acrylic acid ester copolymer, α-cyano-3-hydroxycinnamic acid ester-9-vinylcarbazole-acrylic acid ester copolymer, α-cyano-4-hydroxycinnamic acid Ester-styrene-acrylic acid ester copolymer, α-cyano-4-hydroxycinnamic acid ester-2-vinylnaphthalene-acrylic acid ester copolymer, α-cyano-4-hydroxycinnamic acid ester-1-vinylindole- Acrylic acid ester copolymer, α-cyano-4-hydroxycinnamic acid ester-9-vinylcarbazole-acrylic acid ester copolymer, α-cyano-2-hydroxycinnamic acid ester-styrene-methacrylic acid ester copolymer , α-cyano-2-hydroxycinnamic acid ester-2-vinylnaphthalene-methacrylic acid ester copolymer, α-cyano-2-hydroxycinnamic acid ester-1-vinylindole-methacrylic acid ester copolymer , α-cyano-2-hydroxycinnamic acid ester-9-vinylcarbazole-methacrylic acid ester copolymer, α-cyano-3-hydroxycinnamic acid ester-styrene-methacrylic acid ester copolymer, α -Cyano-3-hydroxycinnamic acid ester-2-vinylnaphthalene-methacrylic acid ester copolymer, α-cyano-3-hydroxycinnamic acid ester-1-vinylindole-methacrylic acid ester copolymer, α -Cyano-3-hydroxycinnamic acid ester-9-vinylcarbazole-methacrylic acid ester copolymer, α-cyano-4-hydroxycinnamic acid ester-styrene-methacrylic acid ester copolymer, α-cyano No-4-hydroxycinnamic acid ester-2-vinylnaphthalene-methacrylic acid ester copolymer, α-cyano-4-hydroxycinnamic acid ester-1-vinylindole-methacrylic acid ester copolymer, α-cyano and no-4-hydroxycinnamic acid ester-9-vinylcarbazole-methacrylic acid ester copolymer.

C-3. Other additives

The retardation layer 20 may contain additives in any appropriate ratio in addition to the resin components described above. As additives, for example, antioxidants such as hindered phenol-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, lactone-based antioxidants, amine-based antioxidants, hydroxylamine-based antioxidants, vitamin E-based antioxidants, and other antioxidants. ; Hindered amine-based light stabilizer; UV absorbers such as benzotriazole, benzophenone, triazine, and benzoate; Surfactants; Polyelectrolyte; conductive complex; pigment; dyes; antistatic agent; anti-blocking agent; Examples include lubricants.

C-4. Method for manufacturing phase contrast layer

Next, one embodiment of a method for manufacturing a retardation layer will be described.

In one embodiment, a method for producing a retardation layer includes dissolving the cellulose resin and the ester resin in a solvent to prepare a resin solution; A step of coating the resin solution on a substrate; A step of preparing a resin film by heating the coating film on the substrate; A process of stretching the resin film; It includes a process of heat shrinking the resin film in the stretching direction.

First, the cellulose-based resin and the ester-based resin are dissolved in a solvent so that the content ratio of the cellulose-based resin described in section A is obtained.

Examples of the solvent include halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, and dichlorobenzene; Phenols such as phenol and chlorophenol; Aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, mesitylene, and dimethoxybenzene; Ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone (MIBK), cyclohexanone, cyclopentanone (CPN), 2-pyrrolidone, and N-methyl-2-pyrrolidone; Ester solvents such as ethyl acetate and butyl acetate; Alcohol-based solvents such as butanol, t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, and 2-methyl-2,4-pentanediol. ; Amide-based solvents such as dimethylformamide and dimethylacetamide; Nitrile-based solvents such as acetonitrile and butyronitrile; Ether-based solvents such as 1,3-dioxolane, cyclopentyl methyl ether (CPME), propylene glycol methyl ether acetate (PGMEA), diethyl ether, dibutyl ether, and tetrahydrofuran; Carbon disulfide, ethyl cellosolve, butyl cellosolve, and mixed solvents thereof may be included.

Among solvents, mixed solvents are preferred. Combinations of mixed solvents include ester-based solvent/aromatic hydrocarbons, ether-based solvent/aromatic hydrocarbons, ester-based solvent/ether-based solvent, ester-based solvent/alcohol-based solvent, ester-based solvent/ketone-based solvent, and two types of ethers. A solvent-based solvent and two types of ester-based solvents can be mentioned.

The Hansen solubility parameter distance (hereinafter sometimes referred to as HSP distance ^{*cellulose system} ) between the cellulose resin and the solvent is, for example, 12.00 or less, preferably 11.30 or less, and more preferably 11.20 or less. HSP distance ^{*Cellulose type} A If it is below the above upper limit, the stretching orientation in the retardation layer can be improved. The HSP distance ^{*cellulose system} can be calculated, for example, using the following formula (I). Additionally, the lower limit of the HSP distance ^{*cellulose type} is typically 6.0 or more.

Equation (I):

HSP distance ^{*Cellulose system} =[4(δ _d2 -δ _d1 ) ² +(δ _p2 -δ _p1 ) ² +(δ _h2 -δ _h1 ) ² ] ^0.5

(In formula (I), δ _d1 represents the dispersion force energy between molecules of the solvent; δ _d2 is It represents the dispersion force energy between molecules of cellulose resin; _δp1 is represents the energy of dipole interaction between molecules of the solvent; _δp2 is It represents the dipole interaction energy between molecules of cellulose resin; δ _h1 represents the hydrogen bond energy between molecules of the solvent, and δ _h2 represents the hydrogen bond energy between molecules of the cellulose resin.)

The HSP distance (hereinafter sometimes referred to as HSP distance ^{* ester system} ) between the ester resin and the solvent is, for example, 6.5 or less, preferably 6.0 or less, for example, 2.0 or more. The HSP distance ^{* ester system} can be calculated, for example, using the following formula (II).

Equation (II):

HSP distance ^{*ester system} =[4(δ _d3 -δ _d1 ) ² +(δ _p3 -δ _p1 ) ² +(δ _h3 -δ _h1 ) ² ] ^0.5

(In formula (II), δ _d3 is It represents the dispersion force energy between the molecules of the ester resin, and δ _p3 is the dipole between the molecules of the ester resin. represents the interaction energy; δ _h3 is Hydrogen bond energy between molecules of ester resin represents; _δd1 , _δp1 and Each of δ _h1 represents the intermolecular energy of the solvent similar to the above formula (I).)

(HSP distance ^{* cellulose system} - HSP distance ^{* ester system} ) ² is, for example, 60 or less, preferably 55 or less, more preferably 50 or less, further preferably 45 or less, especially preferably 30 or less. (HSP distance ^{* cellulose system} - HSP distance ^{* ester system} ) If ² is less than or equal to the above upper limit, the inverse dispersion of the phase difference layer can be stably secured. (HSP distance ^{*cellulose system} -HSP distance ^{*ester system} ) The lower limit of ² is, for example, 10 or more.

The mixed solvent is more preferably ester solvent/aromatic hydrocarbons, still more preferably ethyl acetate/toluene, and particularly preferably 60% by mass of ethyl acetate/40% by mass of toluene. there is. If the solvent is such a mixed solvent, the cellulose resin and the ester resin can more stably form a nanophase separation structure in the phase difference layer.

The solid content concentration in the resin solution is, for example, 1% by mass or more, preferably 5% by mass or more, and for example, 30% by mass or less, preferably 20% by mass or less.

The resin solution is preferably stirred for a predetermined period of time, then allowed to stand and defoamed.

The stirring time is, for example, 5 minutes or more, preferably 10 minutes or more, for example, 3 hours or less, preferably 1 hour or less. The defoaming time (standing time) is, for example, 30 minutes or more, preferably 1 hour or more, and for example, 5 hours or less, preferably 3 hours or less.

Next, the resin solution is applied onto a base material (typically a resin film). As the coating method, any suitable means may be employed. Examples of the coating method include an applicator. As a result, a coating film of the resin solution is formed on the substrate.

Next, the coating film on the substrate is heated to prepare a resin film. The heating temperature is, for example, 35°C or more and 165°C or less, and the heating time is 1 minute or more and 30 minutes or less. More specifically, this heating process includes a primary heating process (drying process) of heating at 165°C or lower and a secondary heating process (annealing process) of heating at 110°C or higher.

The drying process may be performed in one step or may be performed in multiple steps. The drying process is preferably carried out in multiple stages. When the drying process is carried out in multiple stages, the heating temperature of the first stage drying process is set to, for example, 35°C or more and 65°C or less, preferably 45°C or more and 65°C or less, and the heating time of the first stage drying process is set to: For example, set to 1 minute to 30 minutes, preferably 1 minute to 8 minutes. Thereafter, whenever the number of stages in the drying process increases, the heating temperature is raised, for example, to 10°C to 130°C, and preferably to 10°C to 40°C. The heating time of each stage after the second stage is typically shorter than the heating time of the first stage drying process, and is preferably 20 seconds or more and 20 minutes or less, and more preferably 30 seconds or more and 5 minutes or less. The number of stages in the drying process is preferably 2 or more stages and 4 or less stages, and more preferably 3 stages or less. The maximum temperature in the drying process is, for example, 165°C or lower, preferably 130°C or lower, more preferably 120°C or lower, and even more preferably 115°C or lower.

Thereafter, if necessary, the coating film heated in the drying process is cooled to, for example, 30°C or lower, preferably to room temperature (23°C). Once the dried coating film is cooled, the nanophase-separated structure formed by the drying process can be fixed, and the nanophase-separated structure can be maintained without changing in the next annealing process. Next, the coating film is heated in an annealing process. The heating temperature of the annealing process is typically higher than the maximum temperature of the drying process. The heating temperature of the annealing process is, for example, 110°C or higher, preferably 120°C or higher, more preferably 130°C or higher, for example, 180°C or lower, preferably 165°C or lower, more preferably 150°C or lower, even more preferably Typically, it is below 140℃. The heating time of the annealing process is, for example, 1 minute or more, preferably 5 minutes or more, more preferably 15 minutes or more, and for example, 60 minutes or less, preferably 45 minutes or less.

Thereby, a resin film is formed on the substrate. The thickness of the resin film is, for example, 70 μm or more and 200 μm or less. Next, the resin film is peeled from the substrate.

Next, the resin film is stretched. In one embodiment, the resin film is stretched in the width direction perpendicular to the conveyance direction (fixed end transverse stretching) while being conveyed in the longitudinal direction. The resin film may be stretched in one or two steps or more, and stretching in two steps is particularly preferable. The method of manufacturing a retardation layer by two-step stretching includes a first stretching step of stretching the resin film in the width direction; A manufacturing method including a second stretching process in which the resin film after the first stretching process is stretched in the same direction as the first stretching process can be cited.

The resin film is preferably preheated before stretching. The preheating temperature varies in relation to the Tg of the material included in the resin film, and is set with an eye on the Tg of the material with the lowest Tg: (Tg1). (Tg1) is, for example, Tg of cellulose resin. The preheating temperature is, for example, (Tg1) -20°C or higher, preferably (Tg1) -10°C or higher, for example, (Tg1) +50°C or lower, preferably (Tg1) +40°C or lower.

The stretching temperature is the same as the preheating temperature, for example, (Tg1) -20°C or higher, preferably (Tg1) -10°C or higher, such as (Tg1)+50°C or lower, preferably (Tg1)+40°C or lower. am.

The stretching speed is, for example, 1 mm/sec or more, preferably 2 mm/sec or more, for example, 200 mm/sec or less, preferably 100 mm/sec or less. The stretch ratio (when the resin film is stretched in two steps, the product of the stretch ratio of the first stretching process and the stretching ratio of the second stretching process) is, for example, 2.0 times or more, preferably 2.5 times or more, for example, 8.0 times or less. , preferably 7.5 times or less.

Next, the stretched resin film is heat-shrinked in the stretching direction. The heat shrinkage temperature is also set in relation to (Tg1) like the preheating and stretching temperatures, for example, (Tg1) -20°C or higher, preferably (Tg1) -15°C or higher, for example (Tg1) +45°C or lower, preferably (Tg1)+35℃ or less. The heat shrinkage temperature is more preferably equal to or lower than the stretching temperature. The shrinkage rate is typically between 1% and 5%.

As described above, the phase difference layer 20 is manufactured.

D. Image display device

The polarizing plate with a retardation layer described in items A to C above can be applied to an image display device. Accordingly, one embodiment of the present invention also includes an image display device using such a polarizing plate with a retardation layer. Representative examples of image display devices include liquid crystal display devices and organic EL display devices. An image display device according to an embodiment of the present invention includes an image display cell and the polarizing plate with a retardation layer described in the above items A to C. Typically, an image display device includes an image display panel including image display cells, and the polarizing plate with a retardation layer disposed on a viewer side of the image display panel. Additionally, an image display device may be referred to as an optical display device, an image display panel may be referred to as an optical display panel, and an image display cell may be referred to as an optical display cell.

[Example]

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The measurement method for each characteristic is as follows.

(1) Measurement of phase difference value

The phase difference value of the phase difference layer used in the examples and comparative examples was automatically measured using Axoscan (manufactured by Axometrics). The measurement wavelength was 450 nm or 550 nm, and the measurement temperature was 23°C.

(2) Observation of nanophase separation structure

The vicinity of the center of the thickness direction of the retardation film used in the examples and comparative examples (specifically, an area ±20% from the center of the thickness direction of the retardation film when the thickness of the retardation film is set to 100%) was sampled, and heavy metals were sampled. Using an ultra-thin sectioning method including dyeing, the cross-section of the retardation film was observed by TEM (HT7820, manufactured by Hitachi Corporation) (cross-sectional TEM observation).

It was evaluated visually from the analyzed photos and based on the following criteria.

○: The size (maximum length) of all domains is less than 100 nm.

△: Domains less than 100 nm and domains longer than 100 nm are mixed.

×: The size (maximum length) of all domains is 100 nm or more.

(3) HAST (High Accelerated Stress Test) test

The polarizing plate with a retardation layer obtained in the examples and comparative examples was affixed to a glass plate with an adhesive layer to prepare a sample. Next, the sample was put into a pressurized humidifying oven and kept for 36 hours under conditions of 110°C/85% RH, and then the appearance was visually evaluated based on the following criteria.

○: No cracking and/or peeling.

×: Cracks and/or peeling are present.

(4) MIT exam

The MIT test was performed on each of the retardation films used in the examples and comparative examples, and the polarizing plate with a retardation layer obtained in the examples and comparative examples. The MIT test was conducted in accordance with JIS P 8115. Specifically, each of the retardation film and the polarizing plate with a retardation layer was cut to 15 cm in length and 1.5 cm in width so that the stretching direction was the width direction (TD direction) and the direction perpendicular to the stretching direction was the longitudinal direction (MD direction). It was used as a measurement sample. The measurement sample was mounted on an MIT fold fatigue tester BE-202 type (manufactured by Tester Sangyo Co., Ltd.) (load 1.0 kgf, clamp R: 0.38 mm), and in each of the width direction (TD direction) and longitudinal direction (MD direction), Repeated bending was performed at a test speed of 90 cpm and a bending angle of 90°, and the number of bendings when the measurement sample broke was taken as the test value. The test values were evaluated based on the following criteria.

○: In the polarizing plate with a retardation layer, the test value in the TD direction is 500 or more, and the test value in the MD direction is 300 or more.

×: In the polarizing plate with a retardation layer, the test value in the TD direction is less than 500 times and/or the test value in the MD direction is less than 300 times.

<<Manufacturing Example 1; Synthesis of ester resin A (9-vinylcarbazole/α-cyano-4-hydroxycinnamic acid isobutyl/isobutyl acrylate) showing negative birefringence>>

In a 50 mL glass ampoule, 12.20 g of 9-vinylcarbazole, 7.74 g of isobutyl α-cyano-4-hydroxycinnamate, 4.05 g of isobutyl acrylate, and 2,5-dimethyl-2,5-di as a polymerization initiator. 0.453 g of (2-ethylhexanoyl peroxy)hexane and 36.00 g of methyl ethyl ketone were added, nitrogen substitution and decompression were repeated, and then sealing was performed under reduced pressure. Radical polymerization was performed by placing this ampoule in a constant temperature bath at 54°C and maintaining it for 24 hours. After completion of the polymerization reaction, the polymer was taken out from the ampoule, 100 g of tetrahydrofuran was added, and this polymer solution was added dropwise to 800 g of methanol/water mixed solvent (mass ratio 80/20) to precipitate. After filtration, 110 g of the filtrate was added. It was washed five times with a methanol/water mixed solvent (mass ratio 90/10) and filtered. By vacuum drying the obtained resin at 80°C for 10 hours, 22.3 g of cinnamic acid ester copolymer showing negative birefringence was obtained. The number average molecular weight of the obtained polymer is 50,000, and the ratio of residue units is 50 mol% of 9-vinylcarbazole residue units, 25 mol% of α-cyano-4-hydroxycinnamic acid isobutyl residue units, and isobutyl acrylate residue units. It was 25 mol%.

<<Manufacturing Example 2; Synthesis of ester resin B (α-cyano-4-hydroxycinnamate ethyl/9-vinylcarbazole copolymer)>>

In a 50 mL glass ampoule, 5.0 g of ethyl α-cyano-4-hydroxycinnamate, 4.4 g of 9-vinylcarbazole, and 2,5-dimethyl-2,5-di(2-ethyl) as a polymerization initiator. 0.17 g of hexanoylperoxy)hexane and 8.5 g of tetrahydrofuran were added, nitrogen substitution and decompression were repeated, and then sealed under reduced pressure. Radical polymerization was performed by placing this ampoule in a constant temperature bath at 62°C and maintaining it for 48 hours. After completion of the polymerization reaction, the polymer was taken out from the ampoule and dissolved in 25 g of tetrahydrofuran. This polymer solution was added dropwise into 500 mL of methanol to precipitate, and then vacuum-dried at 60°C for 10 hours to obtain 7.7 g of cinnamic acid ester copolymer (ester resin B) showing negative birefringence (yield: 82%). . The number average molecular weight of the obtained cinnamic acid ester copolymer was 22,000, and the ratio of structural units was 58 mol% of 9-vinylcarbazole residue units and 42 mol% of α-cyano-4-hydroxycinnamate ethyl residue units.

<<Preparation Example 3; Production of polarizer>>

As a thermoplastic resin substrate, an amorphous isophthalic copolymerization polyethylene terephthalate film (thickness: 100 μm) with a long shape and a Tg of about 75°C was used, and corona treatment was performed on one side of the resin substrate.

100 parts by mass of PVA-based resin, which is a 9:1 mixture of polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Japan Synthetic Chemical Industry Co., Ltd., brand name “Gosephimer”), contains potassium iodide 13. The added mass was dissolved in water to prepare a PVA aqueous solution (coating solution).

The PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60°C to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate.

The obtained laminate was uniaxially stretched 2.4 times in the machine direction (longitudinal direction) in an oven at 130°C (air auxiliary stretching treatment).

Next, the laminate was immersed in an insolubilization bath (boric acid aqueous solution obtained by mixing 4 parts by mass of boric acid with 100 parts by mass of water) at a liquid temperature of 40°C for 30 seconds (insolubilization treatment).

Next, in a dyeing bath (iodine aqueous solution obtained by mixing iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by mass of water) at a liquid temperature of 30°C, the single transmittance (Ts) of the polarizer finally obtained is the desired value. It was immersed for 60 seconds while adjusting the concentration to achieve this (dyeing treatment).

Next, it was immersed in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by mass of potassium iodide and 5 parts by mass of boric acid with respect to 100 parts by mass of water) at a liquid temperature of 40°C for 30 seconds (crosslinking treatment).

Thereafter, the laminate was immersed in an aqueous solution of boric acid (boric acid concentration: 4% by weight, potassium iodide concentration: 5% by weight) at a liquid temperature of 70°C, while the total stretch ratio was stretched in the longitudinal direction (longitudinal direction) between rolls with different circumferential speeds. Uniaxial stretching was performed to increase the size by 5.5 times (underwater stretching treatment).

Thereafter, the laminate was immersed in a washing bath (aqueous solution obtained by mixing 4 parts by mass of potassium iodide with respect to 100 parts by mass of water) at a liquid temperature of 20°C (washing treatment).

Afterwards, it was dried in an oven maintained at about 90°C and brought into contact with a heating roll made of SUS whose surface temperature was maintained at about 75°C (dry shrink treatment).

In this way, a polarizer with a thickness of about 5 μm was formed on the resin substrate, and a laminate having a resin substrate/polarizer configuration was obtained.

An HC-TAC film (thickness 20 μm) was bonded to the polarizer surface (surface opposite to the resin substrate) of the obtained laminate as a protective layer. Next, the resin substrate was peeled to obtain a polarizing plate having a protective layer/polarizer configuration.

[Example 1 and 2]

<<Production of phase contrast film>>

Ethylcellulose (manufactured by Dow Chemical Company, ETHOCEL standard 100, number average molecular weight (Mn) = 58,000, weight average molecular weight (Mw) = 180,000, Mw/Mn = 3.2, total degree of substitution (DS) = 2.51 ) and the ester resin A obtained in Production Example 1 were dissolved in a mixed solvent of ethyl acetate/toluene = 60/40 (mass ratio) so that the mass ratio shown in Table 1 was dissolved to obtain a resin solution with a solid content concentration of 16% by mass. got it

Next, the resin solution was stirred with a disper mixer for 30 minutes and left to stand for 2 hours to degas. The degassed resin solution was applied using an applicator onto a polyethylene terephthalate (PET) film (Cosmoshine A4610, manufactured by Toyobo Corporation) so that the wet thickness was approximately 810 μm.

Next, the coating film was dried in an oven in three stages at 65°C/6 minutes, 85°C/1 minute, and 110°C/2 minutes, and then left to stand at room temperature (23°C) for 60 minutes. Afterwards, the dried coating film was again annealed in an oven at 130°C for 60 minutes. As a result, a resin film was formed on the PET film.

Next, the resin film was peeled from the PET film. After preheating the peeled resin film at 165°C/1 minute, it was fixed-end transversely stretched 2.4 times under the conditions of a stretching temperature of 155°C and a stretching speed of 2 mm/sec. Thereafter, the stretched resin film was shrunk by 2% in the width direction at a shrinkage temperature of 155°C to obtain a retardation film with a thickness of 46 μm. The refractive index characteristics of the retardation film showed nx>ny>nz.

The retardation film was used for measurement of the above-described retardation value and observation of the nanophase separation structure. The results are shown in Table 1.

<<Production of polarizer with phase contrast layer>>

Next, the retardation film was affixed to the polarizer of the polarizing plate obtained in Production Example 3 using a (meth)acrylic adhesive. The thickness of the adhesive layer was 5 μm. Bonding was performed so that the angle between the absorption axis direction of the polarizer and the slow axis direction of the retardation film was the value shown in Table 1.

Afterwards, a (meth)acrylic adhesive was applied to the retardation film to form an adhesive layer. The thickness of the adhesive layer was 15 μm.

As a result of the above, a polarizing plate with a retardation layer was obtained. A polarizing plate with a retardation layer was subjected to the HAST test described above. The results are shown in Table 1.

[Example 3]

A polarizing plate with a retardation layer was obtained in the same manner as in Example 1, except that the ester resin A of Production Example 1 was changed to the ester resin B of Production Example 2. Additionally, the retardation film was used for the measurement of the above-mentioned retardation value and observation of the nanophase separation structure, and the polarizing plate with a retardation layer was used for the above-described HAST test. The results are shown in Table 1.

[Example 4]

A polarizing plate with a retardation layer was obtained in the same manner as in Example 1, except that the preheating temperature was changed to 162°C, the stretching temperature was changed to 162°C, and the stretching ratio was changed to 3.0 times. Additionally, the thickness of the retardation film was 36 μm. Additionally, the retardation film was subjected to the above-mentioned retardation value measurement, observation of nanophase separation structure, and MIT test, and the polarizing plate with a retardation layer was subjected to the above-mentioned HAST test and MIT test. The results are shown in Table 2.

[Example 5]

A resin film (before stretching) was prepared in the same manner as in Example 3, except that the wet film thickness of the resin solution was changed to 1050 μm. Next, the resin film was preheated at 162°C/1 minute, then fixed-end transversely stretched 3.4 times at a stretching temperature of 162°C and a stretching speed of 2 mm/sec, and then at 167°C/1 minute. It was preheated and fixed-end transversely stretched 2.1 times under the conditions of a stretching temperature of 167°C and a stretching speed of 2 mm/sec.

Thereafter, the stretched resin film was shrunk by 2% in the width direction at a shrinkage temperature of 155°C to obtain a retardation film with a thickness of 20 μm. The obtained retardation film was subjected to the above-described retardation value measurement, observation of nanophase separation structure, and MIT test.

Thereafter, in the same manner as in Example 3, a polarizing plate with a retardation layer was prepared. The obtained polarizing plate with a retardation layer was subjected to the above-mentioned HAST test and MIT test. The results are shown in Table 2.

[Comparative Example 1]

A polarizing plate with a retardation layer was obtained in the same manner as in Example 1, except that the retardation film was changed to a retardation film produced as follows. Additionally, the retardation film was subjected to the above-mentioned retardation value measurement, observation of nanophase separation structure, and MIT test, and the polarizing plate with a retardation layer was subjected to the above-mentioned HAST test and MIT test. The results are shown in Table 1 and Table 2.

<<Production of phase contrast film>>

29.60 parts by mass (0.046 mol) of bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane was added to a batch polymerization apparatus comprising two vertical reactors equipped with stirring blades and a reflux condenser controlled at 100°C. ), 29.21 parts by mass (0.200 mol) of isosorbide (ISB), 42.28 parts by mass (0.139 mol) of spiroglycol (SPG), 63.77 parts by mass (0.298 mol) of diphenyl carbonate (DPC), and acetic acid as a catalyst. 1.19×10 ^-2 mass parts (6.78×10 ^-5 mol) of calcium monohydrate were added. After purging the inside of the reactor with reduced pressure nitrogen, heating was performed using a heat exchanger, and stirring was started when the internal temperature reached 100°C. 40 minutes after the start of the temperature increase, the internal temperature reached 220°C, and while controlling to maintain this temperature, pressure reduction was started, and 90 minutes after reaching 220°C, the temperature was adjusted to 13.3 kPa. The phenol vapor produced as a by-product along with the polymerization reaction is guided to a reflux cooler at 100°C, the monomer component contained in a small amount in the phenol vapor is returned to the reactor, and the uncondensed phenol vapor is directed to a condenser at 45°C for recovery. did. After nitrogen was introduced into the first reactor and the pressure was restored to atmospheric pressure, the oligomerized reaction solution in the first reactor was transferred to the second reactor. Next, the temperature increase and pressure reduction in the second reactor were started, and the internal temperature was 240°C and the pressure was 0.2 kPa in 50 minutes. Thereafter, polymerization was allowed to proceed until the predetermined stirring power was reached. When the predetermined power was reached, nitrogen was introduced into the reactor to restore pressure, the resulting polyester carbonate-based resin was extruded into water, and the strands were cut to obtain pellets.

After vacuum drying the obtained polyester carbonate resin (pellet) at 80°C for 5 hours, it was extruded into a single screw extruder (manufactured by Toshiba Machinery Co., Ltd., cylinder set temperature: 250°C), T die (width 200 mm, set temperature: 250°C), A long resin film with a thickness of 130 μm was produced using a film forming apparatus equipped with a chilled roll (set temperature: 120 to 130°C) and a winder. The obtained long resin film was stretched longitudinally at the free end 1.4 times at 140°C to obtain a retardation film with a thickness of 110 μm.

[Comparative Example 2]

A polarizing plate with a retardation layer was obtained in the same manner as in Example 1, except that a retardation film was produced using only ethyl cellulose without using the ester resin A of Production Example 1 as a resin material. Additionally, the retardation film was used for the measurement of the above-mentioned retardation value and observation of the nanophase separation structure, and the polarizing plate with a retardation layer was used for the above-described HAST test. The results are shown in Table 1.

[Comparative Example 3]

A polarizing plate with a retardation layer was obtained in the same manner as in Example 3, except that a retardation film was produced using only the ester resin B of Production Example 2 without using ethylcellulose as a resin material. Additionally, the retardation film was used for the measurement of the above-mentioned retardation value and observation of the nanophase separation structure, and the polarizing plate with a retardation layer was used for the above-described HAST test. The results are shown in Table 1.

[Comparative Example 4]

In a mixed solvent containing ethyl acetate/toluene in a ratio of 6:4, ethylcellulose and the ester resin A obtained in Production Example 1 were dissolved in a mass ratio of 80:20 to obtain a resin solution with a solid content concentration of 16% by mass. .

Next, the resin solution was stirred with a disper mixer for 30 minutes and left to stand for 2 hours to degas. The degassed resin solution was applied using an applicator onto a polyethylene terephthalate (PET) film (Cosmoshine A4610, manufactured by Toyobo Corporation) so that the wet thickness was approximately 810 μm.

Next, the coating film was dried in an oven in four stages under the following conditions: 40°C/4 minutes, 85°C/4 minutes, 135°C/4 minutes, and 155°C/6 minutes to form a resin film with a thickness of 110 μm on the PET film. did.

Next, the resin film was peeled from the PET film. After preheating the peeled resin film at 165°C/1 minute, it was fixed-end transversely stretched 2.4 times under the conditions of a stretching temperature of 155°C and a stretching speed of 2 mm/sec. Thereafter, the stretched resin film was contracted by 2% in the width direction at the same temperature as the stretching temperature (shrinkage temperature of 155°C) to obtain a retardation film with a thickness of 46 μm. This retardation film was used for measurement of the above-mentioned retardation value and observation of the nanophase separation structure. The results are shown in Table 1. In Comparative Example 4, the TEM cross-sectional image obtained from observation of the nanophase-separated structure showed that each phase-separated domain was larger than 100 nm, and that a sufficient phase-separated state was not obtained.

<<Production of polarizer with phase contrast layer>>

Next, the retardation film was affixed to the polarizer of the polarizing plate obtained in Production Example 3 using a (meth)acrylic adhesive. The thickness of the adhesive layer was 5 μm. Bonding was performed so that the angle formed between the absorption axis direction of the polarizer and the slow axis direction of the retardation film was the value shown in Table 1.

Afterwards, a (meth)acrylic adhesive was applied to the retardation film to form an adhesive layer. The thickness of the adhesive layer was 15 μm.

As a result of the above, a polarizing plate with a retardation layer was obtained. A polarizing plate with a retardation layer was subjected to the HAST test described above. The results are shown in Table 1. The polarizing plate with a retardation layer of Comparative Example 4 had cracks after the HAST test.

[Comparative Example 5]

In a mixed solvent containing ethyl acetate/toluene in a ratio of 6:4, ethylcellulose and the ester resin A obtained in Production Example 1 were dissolved in a mass ratio of 80:20 to obtain a resin solution with a solid content concentration of 16% by mass. .

Next, the resin solution was stirred with a disper mixer for 30 minutes and left to stand for 2 hours to degas. The degassed resin solution was applied using an applicator onto a polyethylene terephthalate (PET) film (Cosmoshine A4610, manufactured by Toyobo Corporation) so that the wet thickness was approximately 810 μm.

Next, the coating film was dried in an oven in four stages under the conditions of 40°C/10 minutes, 85°C/4 minutes, 135°C/4 minutes, and 155°C/10 minutes to form a resin film with a thickness of 110 μm on the PET film. did.

Next, the resin film was peeled from the PET film. After preheating the peeled resin film at 165°C/1 minute, it was fixed-end transversely stretched 2.4 times under the conditions of a stretching temperature of 155°C and a stretching speed of 2 mm/sec. Thereafter, the stretched resin film was contracted by 2% in the width direction at the same temperature as the stretching temperature (shrinkage temperature of 155°C) to obtain a retardation film with a thickness of 46 μm. This retardation film was used for measurement of the above-mentioned retardation value and observation of the nanophase separation structure. The results are shown in Table 1. In Comparative Example 5, sufficient characteristics could not be secured as a λ/4 plate. In the TEM cross-sectional image obtained from observation of the nanophase-separated structure, each phase-separated domain was around 100 nm, and domains less than 100 nm and domains exceeding 100 nm were mixed. Therefore, it was found that an appropriate nanophase separation structure was not formed.

<<Production of polarizer with phase contrast layer>>

Next, the retardation film was affixed to the polarizer of the polarizing plate obtained in Production Example 3 using a (meth)acrylic adhesive. The thickness of the adhesive layer was 5 μm. Bonding was performed so that the angle formed between the absorption axis direction of the polarizer and the slow axis direction of the retardation film was the value shown in Table 1.

Afterwards, a (meth)acrylic adhesive was applied to the retardation film to form an adhesive layer. The thickness of the adhesive layer was 15 μm.

As a result of the above, a polarizing plate with a retardation layer was obtained. The polarizing plate with a retardation layer of Comparative Example 5 was not normally subjected to the HAST test because sufficient characteristics as a circularly polarizing plate were not obtained, but was subjected to the above-described HAST test just in case. The results are shown in Table 1. The polarizing plate with a retardation layer of Comparative Example 5 had no problems with the appearance after the HAST test.

[Comparative Example 6]

A polarizing plate with a retardation layer was obtained in the same manner as in Comparative Example 1, except that the film thickness after stretching was different. Additionally, the thickness of the retardation film was 37 μm. Additionally, the retardation film was subjected to the above-mentioned retardation value measurement, observation of nanophase separation structure, and MIT test, and the polarizing plate with a retardation layer was subjected to the above-mentioned HAST test and MIT test. The results are shown in Table 2.

[Comparative Example 7]

<<Production of phase contrast film>>

10 g of a polymerizable liquid crystal exhibiting a nematic liquid crystalline phase (manufactured by BASF, brand name 'Paliocolor LC242', expressed in the formula below), and a photopolymerization initiator for the polymerizable liquid crystal compound (manufactured by BASF, brand name 'Irgacure') 907') was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating solution).

The surface of a polyethylene terephthalate (PET) film (thickness 38 μm) was rubbed using a rubbing cloth to perform orientation treatment. The direction of the orientation treatment was set to be 15° when viewed from the viewer's side with respect to the direction of the absorption axis of the polarizer when bonding to the polarizing plate. The liquid crystal coating liquid was applied to this alignment treated surface using a bar coater, and the liquid crystal compound was aligned by heating and drying at 90°C for 2 minutes. By irradiating light of 1 mJ/cm2 using a metal halide lamp to the liquid crystal layer formed in this way and curing the liquid crystal layer, PET A liquid crystal alignment solidification layer was formed on the film. The liquid crystal alignment solidification layer had a refractive index characteristic of nx>ny=nz. The thickness of the liquid crystal alignment solidification layer was 1 μm, and the in-plane retardation Re (550) was 140 nm. The liquid crystal alignment solidification layer was used as a retardation film, and the retardation film was subjected to measurement of the retardation value, observation of the nanophase separation structure, and MIT testing. The results are shown in Table 2.

<<Production of polarizer with phase contrast layer>>

Next, the retardation film was affixed to the polarizer of the polarizing plate obtained in Production Example 3 using a (meth)acrylic adhesive. The thickness of the adhesive layer was 5 μm. Bonding was performed so that the angle formed between the absorption axis direction of the polarizer and the slow axis direction of the retardation film was 45°.

Afterwards, a (meth)acrylic adhesive was applied to the retardation film to form an adhesive layer. The thickness of the adhesive layer was 15 μm.

As a result of the above, a polarizing plate with a retardation layer was obtained. A polarizing plate with a retardation layer was subjected to the above-mentioned HAST test and MIT test. The results are shown in Table 2.

[Table 1]

[Table 2]

[evaluation]

As is clear from Tables 1 and 2, if the retardation layer contains cellulose resin and ester resin and they constitute a suitable nanophase separation structure, the inverse dispersion characteristics of the retardation layer can be maintained and It can be seen that a polarizing plate with a retardation layer in which appearance defects are suppressed can be realized. In addition, when a nanophase separation structure is formed in the retardation layer (retardation film), the flexibility in the stretching direction (MD direction) and the direction perpendicular to the stretching direction (TD direction) is improved in the retardation film and the polarizing plate with a retardation layer. Know what you can do.

The polarizing plate with a retardation layer according to an embodiment of the present invention can be suitably applied to an image display device (typically a liquid crystal display device or an organic EL display device).

10: Polarizer
11: Polarizer
20: Phase contrast layer
30: Adhesive layer
40: Adhesive layer
50: Release liner
100: Polarizer with phase contrast layer

Claims (6)

With polarizer,
A retardation layer containing a cellulose resin and an ester resin is provided in this order,
Re(450)/Re(550) of the phase difference layer is 0 to 1,
Re(550) of the phase difference layer is 100nm~200nm,
The angle formed between the absorption axis direction of the polarizer and the slow axis direction of the retardation layer is 40° to 50° or 130° to 140°,
A polarizing plate with a retardation layer in which a nanophase separation structure is formed in the retardation layer. According to paragraph 1,
The cellulose-based resin has a structural unit shown in the following formula (1): A polarizing plate with a retardation layer:

(In formula (1), each of R ₁ to R ₃ represents a hydrogen atom or a substituent having 1 to 12 carbon atoms _. ) According to claim 1 or 2,
The ester-based resin has a structural unit represented by the following formula (2) and a structural unit represented by the following formula (3): A polarizing plate with a retardation layer:

(In equation (2), R ₄ is Represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms; R _5a is the carbon number Represents one type selected from 1 to 12 alkyl groups, nitro groups, bromo groups, iodine groups, cyano groups, chloro groups, sulfonic acid groups, carboxylic acid groups _, fluoro groups, or thiol groups; R _5b represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms; R ₆ is a hydrogen atom, nitro group, bromo group, iodine group, cyano group, chloro group, sulfonic acid group, carboxylic acid group, fluoro group, phenyl group, thiol group, amide group, amino group, hydroxy group, or alkoxy group having 1 to 12 carbon atoms. , or represents a species selected from alkyl groups having 1 to 12 carbon atoms)

(In formula (3), R ₇ is a 5-membered ring heterocyclic residue or a 6-membered ring heterocyclic residue containing at least one nitrogen atom or oxygen atom as a heteroatom (the 5-membered ring heterocyclic residue and the 6-membered ring heterocyclic residue are It may form a condensed ring structure with another cyclic structure). According to paragraph 3,
The ester-based resin further has a structural unit represented by the following formula (4): A polarizing plate with a retardation layer:

(In formula (4), R ₈ and R ₉ each represent one type selected from a hydrogen atom, a straight-chain alkyl group with 1 to 12 carbon atoms, a branched alkyl group with 3 to 12 carbon atoms, or a cyclic alkyl group with 3 to 6 carbon atoms. ). According to claim 1 or 2,
A polarizing plate with a phase contrast layer, wherein the content ratio of the cellulose resin exceeds 50% by mass when the total of the cellulose resin and the ester resin is 100% by mass. According to claim 1 or 2,
The retardation layer is a stretched film obtained by stretching a resin film containing a cellulose resin and an ester resin,
A polarizing plate with a retardation layer, wherein the number of MITs in a direction perpendicular to the stretching direction of the stretched film is 300 or more.