JP2013029860A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device reduced in display performance change resulting from temperature and humidity changes.SOLUTION: The liquid crystal display device includes: a pair of opposite substrates at least one of which has an electrode; a liquid crystal layer arranged between the pair of substrates and controlled in orientation; a liquid crystal cell (10) in which an electric field is generated by the electrode, the electric field having a parallel component with respect to a substrate having the electrode; and a pair of polarization plates (PLa and PLb) arranged with the liquid crystal cell (10) between them. At least one (PLa and/or PLb) of the pair of polarization plates has polarizers (12a and 12b) and a thermoplastic resin film containing a lactone-ring-containing polymer satisfying the expressions (I) and (II): (I) 0≤|Re(630)|≤10 and |Rth(630)|≤25, and (II) |Re(400)-Re(700)|≤10 and |Rth(400)-Rth(700)|≤35.

Description

  The present invention relates to a liquid crystal display device, and more particularly to an in-plane switching mode liquid crystal display device that performs display by applying a horizontal electric field to nematic liquid crystal aligned in the horizontal direction.

A liquid crystal display device using a so-called in-plane switching (IPS) mode in which a lateral electric field is applied to liquid crystal has been proposed. In recent years, liquid crystal display devices have been developed for TV applications, and accordingly, screen brightness has been greatly improved. For this reason, a slight light leakage in the diagonally oblique incident direction during black display, which has not been considered as a problem in the IPS mode, has become apparent as a cause of a decrease in display quality.
As one means for improving the viewing angle characteristics of color tone and black display, an optical compensation material having birefringence characteristics is disposed between the liquid crystal layer and the polarizing plate, and the protective film of the polarizing plate is provided with the optical compensation. This is also studied in the IPS mode (see, for example, Patent Documents 1 to 8).

Japanese Patent Laid-Open No. 9-80424 Japanese Patent Laid-Open No. 10-54982 JP-A-11-202323 Japanese Patent Laid-Open No. 9-292522 JP 11-133408 A JP-A-11-305217 JP-A-10-307291 JP 2006-227606 A

However, the optical characteristics (particularly Rth) of the retardation film change depending on the temperature even with the proposed method, so that the display performance of the liquid crystal display device changes greatly depending on the observation conditions. There is a problem in that the unevenness of Δnd becomes remarkable. In addition, there are retardation films whose absolute values of optical characteristics (especially Re) increase due to changes in temperature and humidity, and because the absolute value of Re increases, variations in molecular axes that the retardation film inevitably has Has become a cause of lowering the front contrast.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a liquid crystal display device, particularly a horizontal alignment mode liquid crystal display device, in which fluctuations in display performance due to temperature and humidity changes are reduced.
Another object of the present invention is to provide a liquid crystal display device, particularly an IPS mode liquid crystal display device, in which the color shift in the oblique direction caused by the environmental humidity and temperature and the decrease in front contrast are reduced. .

Means for solving the above problems are as follows.
[1] It has a pair of substrates disposed opposite to each other, at least one of which has an electrode, and an alignment-controlled liquid crystal layer disposed between the pair of substrates, and is parallel to the substrate having the electrode by the electrode. A liquid crystal cell in which an electric field having a component is formed, and a pair of polarizing plates disposed across the liquid crystal cell;
At least one of the pair of polarizing plates is a polarizing plate having a polarizer and a thermoplastic resin film containing a lactone ring-containing polymer that satisfies the following formulas (I) and (II). Liquid crystal display device.
(I) 0 ≦ | Re (630) | ≦ 10 and | Rth (630) | ≦ 25
(II) | Re (400) −Re (700) | ≦ 10 and | Rth (400) −Rth (700) | ≦ 35
(In the above formulas (I) and (II), Re (λ) represents the in-plane retardation value (nm) at the wavelength λnm, and Rth (λ) represents the retardation value in the film thickness direction at the wavelength λnm (nm). )
[2] The liquid crystal display device according to [1], wherein among the pair of polarizing plates, a polarizing plate disposed at least on the backlight side is a polarizing plate having the thermoplastic resin film.
[3] The liquid crystal display device according to [1], wherein a polarizing plate disposed on at least a display surface side of the pair of polarizing plates is a polarizing plate having the thermoplastic resin film.
[4] The liquid crystal display device according to [1], wherein both of the pair of polarizing plates are polarizing plates having the thermoplastic resin film.
[5] The Re {T} and Rth {T} (T is a temperature at the time of measurement (° C.)) at a wavelength of 550 nm of the thermoplastic resin film satisfy the following formulas (III) and (IV): The liquid crystal display device according to any one of [1] to [4].
(III) | Re {50} −Re {25} | <5
(IV) | Rth {50} −Rth {25} | <10
[6] Re [H] and Rth [H] (H is a relative humidity (%) at the time of measurement) at a wavelength of 550 nm of the thermoplastic resin film satisfy the following formulas (V) and (VI): The liquid crystal display device according to any one of [1] to [5].
(V) | Re [80] −Re [10] | <5
(VI) | Rth [80] −Rth [10] | <10

  ADVANTAGE OF THE INVENTION According to this invention, the liquid crystal display device with which the fluctuation | variation of the display performance by the temperature / humidity change was reduced, especially the liquid crystal display device of an IPS mode can be provided.

It is a cross-sectional schematic diagram of an example of the liquid crystal display device of this invention.

Hereinafter, the present invention will be described in detail.
In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
First, terms used in this specification will be described.
(Retardation, Re, Rth)
In the present specification, Re (λ) and Rth (λ) represent in-plane retardation (nm) and retardation in the thickness direction (nm) at wavelength λ, respectively. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments).
When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method.
Rth (λ) is Re (λ), with the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotation axis) (if there is no slow axis, any in-plane film The light is incident at a wavelength of λ nm from the inclined direction in steps of 10 degrees from the normal direction to 50 degrees on one side with respect to the film normal direction of the rotation axis of KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumed value of the average refractive index, and the input film thickness value.
In the above case, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, retardation at a tilt angle larger than the tilt angle. The value is calculated by KOBRA 21ADH or WR after changing its sign to negative.
In addition, the retardation value is measured from the two inclined directions, with the slow axis as the tilt axis (rotation axis) (in the absence of the slow axis, the arbitrary direction in the film plane is the rotation axis), Rth can also be calculated from the following formula (X) and formula (XI) based on the value, the assumed value of the average refractive index, and the input film thickness value.

式（XI）
Ｒｔｈ＝｛（ｎｘ＋ｎｙ）／２−ｎｚ｝×ｄ
注記：
上記のＲｅ（θ）は法線方向から角度θ傾斜した方向におけるレターデーション値をあらわす。また、式中、ｎｘは面内における遅相軸方向の屈折率を表し、ｎｙは面内においてｎｘに直交する方向の屈折率を表し、ｎｚはｎｘ及びｎｙに直交する方向の屈折率を表す。ｄは膜厚を表す。

Formula (XI)
Rth = {(nx + ny) / 2−nz} × d
Note:
The above Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction. In the formula, nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction orthogonal to nx in the plane, and nz represents the refractive index in the direction orthogonal to nx and ny. . d represents a film thickness.

In the case where the film to be measured cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film having no so-called optical axis, Rth (λ) is calculated by the following method.
Rth (λ) is from −50 degrees to +50 degrees with respect to the normal direction of the film, with Re (λ) being the in-plane slow axis (determined by KOBRA 21ADH or WR) and the tilt axis (rotating axis). In each of the 10 degree steps, light of wavelength λ nm is incident from the inclined direction and measured at 11 points. Based on the measured retardation value, the assumed average refractive index, and the input film thickness value, KOBRA 21ADH or WR is calculated.
In the above measurement, the assumed value of the average refractive index may be a value in a polymer handbook (John Wiley & Sons, Inc.) or a catalog of various optical films. Those whose average refractive index is not known can be measured with an Abbe refractometer. Examples of the average refractive index values of main optical films are given below:
Cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).
The KOBRA 21ADH or WR calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

In the present invention, the “slow axis” of the retardation film or the like means a direction in which the refractive index is maximized. The “visible light region” means 380 nm to 780 nm. Further, the measurement wavelength of the refractive index is a value at λ = 550 nm in the visible light region unless otherwise specified.
Further, in the present specification, numerical values, numerical ranges, and qualitative expressions (for example, expressions such as “equivalent” and “equal”) indicating optical characteristics of each member such as a retardation film and a liquid crystal layer are liquid crystal. It shall be construed as indicating numerical values, numerical ranges and properties including generally permissible errors for the display device and the members used therefor.

FIG. 1 shows a schematic cross-sectional view of an example of the liquid crystal display device of the present invention. However, the relative relationship of the thickness of each layer in the figure does not reflect the actual relative relationship. In the figure, the upper side is the display surface side and the lower side is the back side (backlight side).
The liquid crystal display device shown in FIG. 1 has an IPS mode liquid crystal cell 10 and a pair of polarizing plates PLa and PLb above and below it. Each polarizing plate PLa and PLb includes polarizers 12a and 12b, and liquid crystal cell-side protective films 14a and 14b and outer protective films 16a and 16b that protect the polarizers 12a and 12b. In this example, at least one of the protective films 14a, 14b, 16a, and 16b is made of a thermoplastic resin film containing a lactone ring-containing polymer that satisfies a predetermined formula. At least one of the liquid crystal cell side protective films 14a and 14b is preferably the thermoplastic resin film, and more preferably both are the thermoplastic resin film. The outer protective films 16a and 16b may be the thermoplastic resin film, or may be other polymer films such as a cellulose acylate film, a polycarbonate film, and a norbornene film.
In this example, by using the thermoplastic resin film as at least one of the protective films 14a, 14b, 16a and 16b, a liquid crystal display device in which fluctuations in display performance due to temperature and humidity changes are reduced.

  The IPS mode liquid crystal cell 10 is not particularly limited as long as an electric field having a component parallel to the substrate having the electrode is formed by the electrode formed in the cell. A normal IPS mode liquid crystal cell can be used. The angle formed by the electric field direction with respect to the surface of the cell substrate is preferably 20 degrees or less, more preferably 10 degrees or less, that is, substantially parallel. Further, the electrodes may be formed separately on the upper and lower substrates or only on one substrate. Alternatively, the electrode may have a two-layer structure with an insulating layer interposed. Of the two-layered electrodes, the lowermost electrode may be an unpatterned electrode or a linear electrode. The upper layer electrode is preferably linear, but may be mesh, spiral, or dot as long as the electric field from the lower electrode can pass through, and a floating electrode having a neutral potential may be further added. The insulating layer may be either an inorganic material such as SiO or nitride film, or an organic material such as acrylic or epoxy.

  As the liquid crystal material used in the liquid crystal cell, nematic liquid crystal having a positive dielectric anisotropy Δε is used. The thickness (gap) of the liquid crystal layer can be controlled by polymer beads. A similar gap can be obtained with glass bead fiber and resin columnar spacers. In an IPS mode liquid crystal cell, the product Δn · d of the thickness d (μm) of the liquid crystal layer and the refractive index anisotropy Δn is usually about 0.2 to 1.2 μm, which meets the demand for thinning. Therefore, it can also be set to about 0.2 to 0.5 μm.

Hereinafter, materials used for various members usable in the liquid crystal display device of the present invention, manufacturing methods thereof, and the like will be described in detail.
[Thermoplastic resin film containing a lactone ring-containing polymer]
In the present invention, a polarizing plate having a thermoplastic resin film containing a lactone ring-containing polymer that satisfies the following formulas (I) and (II) is used. The thermoplastic resin film is preferably a protective film for a polarizer, and more preferably a protective film disposed on the liquid crystal cell side.
(I) 0 ≦ | Re (630) | ≦ 10 and | Rth (630) | ≦ 25
(II) | Re (400) −Re (700) | ≦ 10 and | Rth (400) −Rth (700) | ≦ 35
By compensating the IPS mode liquid crystal cell with the phase difference region satisfying the above formulas (I) and (II), it is possible to reduce coloring (color shift) generated in an oblique direction during black display. The present inventor has found that a thermoplastic resin film containing a predetermined lactone ring-containing polymer can satisfy the above-mentioned conditions, and depends on changes in temperature and humidity by using this for optical compensation of an IPS mode liquid crystal cell. The fluctuation of the optical characteristics is reduced, that is, the fluctuation of the optical compensation ability is reduced. In general, a birefringent polymer film is adjusted so that molecules are aligned in one direction by stretching or the like, but there is inevitably variation in the direction of molecular axes, and there is an axial shift. In particular, when the absolute value of Re increases due to environmental temperature and humidity, this axial shift becomes noticeable and phase difference unevenness occurs, which causes a decrease in front contrast (light leakage occurs in the front during black display, etc.). It is a factor. In the present invention, by using a thermoplastic resin film having a small absolute value of Re using a lactone ring-containing polymer, the absolute value of Re is brought close to 0, and fluctuations in optical properties due to changes in the temperature and humidity environment are reduced. The variation in the molecular axis direction that the retardation polymer film inevitably has is suppressed from becoming obvious. The thermoplastic resin film containing a lactone ring-containing polymer can achieve | Re (630) | of 5 nm or less and | Rth (630) | of 15 nm or less. In order to make optical compensation of the IPS mode liquid crystal cell more ideal, | Re (400) −Re (700) | is 5 nm or less, and | Rth (400) −Rth (700) | is 10 nm or less. This optical property can be achieved by a thermoplastic resin film containing a lactone ring-containing polymer.

Further, it is preferable that Re and Rth of the thermoplastic resin film do not vary depending on the temperature. It is preferable that Re {T} and Rth {T} (T is a temperature at the time of measurement (° C.)) at a wavelength of 550 nm of the thermoplastic resin film satisfy the following formulas (III) and (IV). It is more preferable that (III) ′ and (IV) ′ are satisfied.
(III) | Re {50} -Re {25} | <5
(IV) | Rth {50} -Rth {25} | <10
(III) ′ | Re {50} −Re {25} | <3
(IV) ′ | Rth {50} −Rth {25} | <5
In addition, when measuring Re {T} and Rth {T}, it shall measure after leaving a film to stand at the temperature T degreeC for 1 hour at least.

Moreover, it is preferable that Re and Rth of the thermoplastic resin film do not vary depending on humidity. It is preferable that Re [H] and Rth [H] (H is a relative humidity (%) at the time of measurement) at a wavelength of 550 nm of the thermoplastic resin film satisfy the following formulas (V) and (VI). More preferably, the formulas (V) ′ and (VI) ′ are satisfied.
(V) | Re [80] −Re [10] | <5
(VI) | Rth [80] −Rth [10] | <10
(V) ′ | Re [80] −Re [10] | <3
(VI) ′ | Rth [80] −Rth [10] | <5
In addition, when measuring Re [H] and Rth [H], it shall measure after leaving a film to stand at the humidity H for at least 1 hour.

  The lactone ring-containing polymer that is the main component of the thermoplastic resin film is preferably a polymer having a repeating unit represented by the following formula (1).

In the formula, R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms; the organic residue may contain an oxygen atom.

  The content ratio of the lactone ring structure represented by the formula (1) in the structure of the lactone ring-containing polymer is preferably 5 to 90% by mass, more preferably 10 to 70% by mass, and still more preferably 10 to 60%. It is 10 mass%, Most preferably, it is 10-50 mass%. When the content of the lactone ring structure is less than 5% by mass, the heat resistance, solvent resistance, and surface hardness of the obtained polymer may be lowered. On the contrary, when the content of the lactone ring structure exceeds 90% by mass, the moldability of the obtained polymer may be deteriorated.

  The lactone ring-containing polymer may be a copolymer having a structure other than the lactone ring structure represented by the above formula (1). The structure other than the lactone ring structure represented by the formula (1) is not particularly limited. For example, a (meth) acrylic acid ester, a hydroxyl group-containing monomer, an unsaturated carboxylic acid, A structural unit (repeating structural unit) derived from at least one monomer selected from the group consisting of monomers represented by the following formula (2) is preferred.

In the formula, R ⁴ represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, an —OAc group, a —CN group, a —CO—R ⁵ group, or —CO. —O—R ⁶ group is represented, Ac represents an acetyl group, R ⁵ and R ⁶ represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms.

  The content ratio of the structure other than the lactone ring structure represented by the above formula (1) in the structure of the lactone ring-containing polymer is a polymer structural unit (repeated structure) formed by polymerizing (meth) acrylic acid ester. Unit) is preferably 10 to 95% by mass, more preferably 10 to 90% by mass, still more preferably 40 to 90% by mass, particularly preferably 50 to 90% by mass, and polymerizes a hydroxyl group-containing monomer. In the case of the polymer structural unit (repeating structural unit) formed in this manner, it is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, further preferably 0 to 15% by mass, and particularly preferably 0 to 10% by mass. It is. In the case of a polymer structural unit (repeating structural unit) formed by polymerizing an unsaturated carboxylic acid, it is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, and still more preferably 0 to 15% by mass. Especially preferably, it is 0-10 mass%. Furthermore, in the case of a polymer structural unit (repeating structural unit) formed by polymerizing the monomer represented by the above formula (2), preferably 0 to 30% by mass, more preferably 0 to 20% by mass, More preferably, it is 0-15 mass%, Most preferably, it is 0-10 mass%.

  The method for producing the lactone ring-containing polymer is not particularly limited. For example, after the polymer (a) having a hydroxyl group and an ester group in the molecular chain is obtained by a polymerization step, the obtained heavy polymer is obtained. It can be obtained by carrying out a lactone cyclization condensation step for introducing a lactone ring structure into the polymer by heat-treating the compound (a).

In the polymerization step, for example, a polymer having a hydroxyl group and an ester group in the molecular chain can be obtained by performing a polymerization reaction of a monomer component containing a monomer represented by the following formula (3). .

In the formula, R ⁵ and R ⁶ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms.

  Examples of the monomer represented by the above formula (3) include methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, 2- ( Hydroxymethyl) n-butyl acrylate, 2- (hydroxymethyl) acrylate t-butyl and the like. These monomers may be used alone or in combination of two or more. Among these monomers, 2- (hydroxymethyl) methyl acrylate and 2- (hydroxymethyl) ethyl acrylate are preferable, and since the effect of improving heat resistance is high, methyl 2- (hydroxymethyl) acrylate Is particularly preferred.

  The content ratio of the monomer represented by the above formula (3) in the monomer component to be subjected to the polymerization step is preferably 5 to 90% by mass, more preferably 10 to 70% by mass, and further preferably 10 to 60%. It is 10 mass%, Most preferably, it is 10-50 mass%. When the content ratio of the monomer represented by the above formula (3) is less than 5% by mass, the heat resistance, solvent resistance and surface hardness of the obtained polymer may be lowered. Conversely, if the content of the monomer represented by the above formula (3) exceeds 90% by mass, gelation may occur in the polymerization step or the lactone cyclization condensation step, and the resulting polymer may be processed. May decrease.

  You may mix | blend monomers other than the monomer represented by the said Formula (3) with the monomer component provided to a superposition | polymerization process. Such a monomer is not particularly limited. For example, a (meth) acrylic acid ester, a hydroxyl group-containing monomer, an unsaturated carboxylic acid, and a single monomer represented by the following formula (2) are used. Examples include masses. These monomers may be used alone or in combination of two or more.

In the formula, R ⁴ represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, an —OAc group, a —CN group, a —CO—R ⁵ group, or —CO. —O—R ⁶ group is represented, Ac represents an acetyl group, R ⁵ and R ⁶ represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms.

  The (meth) acrylic acid ester is not particularly limited as long as it is a (meth) acrylic acid ester other than the monomer represented by the above formula (3). For example, methyl acrylate, acrylic acid Acrylic esters such as ethyl, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, cyclohexyl acrylate, benzyl acrylate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, methacryl And methacrylic acid esters such as isobutyl acid, t-butyl methacrylate, cyclohexyl methacrylate, and benzyl methacrylate. These (meth) acrylic acid esters may be used alone or in combination of two or more. Among these (meth) acrylic acid esters, methyl methacrylate is particularly preferable because the obtained polymer has excellent heat resistance and transparency.

  When (meth) acrylic acid ester other than the monomer represented by the above formula (3) is used, the content ratio in the monomer component to be subjected to the polymerization step is sufficient to exert the effect of the present invention. The content is preferably 10 to 95% by mass, more preferably 10 to 90% by mass, still more preferably 40 to 90% by mass, and particularly preferably 50 to 90% by mass.

  The hydroxyl group-containing monomer is not particularly limited as long as it is a hydroxyl group-containing monomer other than the monomer represented by the above formula (3). For example, α-hydroxymethylstyrene, α- And 2- (hydroxyalkyl) acrylic acid esters such as hydroxyethylstyrene and methyl 2- (hydroxyethyl) acrylate; 2- (hydroxyalkyl) acrylic acids such as 2- (hydroxyethyl) acrylic acid; and the like. These hydroxyl group-containing monomers may be used alone or in combination of two or more.

  In the case of using a hydroxyl group-containing monomer other than the monomer represented by the above formula (3), the content ratio in the monomer component to be subjected to the polymerization step is sufficient to exert the effect of the present invention. Preferably it is 0-30 mass%, More preferably, it is 0-20 mass%, More preferably, it is 0-15 mass%, Most preferably, it is 0-10 mass%.

  Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, crotonic acid, α-substituted acrylic acid, α-substituted methacrylic acid and the like. These unsaturated carboxylic acids may be used alone or in combination of two or more. Among these unsaturated carboxylic acids, acrylic acid and methacrylic acid are particularly preferable because the effects of the present invention are sufficiently exhibited.

  When using an unsaturated carboxylic acid, the content ratio in the monomer component to be subjected to the polymerization step is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, in order to sufficiently exhibit the effects of the present invention. %, More preferably 0 to 15% by mass, particularly preferably 0 to 10% by mass.

  Examples of the monomer represented by the above formula (2) include styrene, α-methylstyrene, vinyl toluene, acrylonitrile, methyl vinyl ketone, ethylene, propylene, and vinyl acetate. These monomers may be used alone or in combination of two or more. Of these monomers, styrene and α-methylstyrene are particularly preferable because the effects of the present invention are sufficiently exhibited.

  When the monomer represented by the above formula (2) is used, the content ratio in the monomer component to be subjected to the polymerization step is preferably 0 to 30% by mass in order to sufficiently exhibit the effects of the present invention. More preferably, it is 0-20 mass%, More preferably, it is 0-15 mass%, Most preferably, it is 0-10 mass%.

  The form of the polymerization reaction for polymerizing the monomer components to obtain a polymer having a hydroxyl group and an ester group in the molecular chain is preferably a polymerization form using a solvent, and solution polymerization is particularly preferred.

  The polymerization temperature and the polymerization time vary depending on the type and ratio of the monomer used. For example, the polymerization temperature is preferably 0 to 150 ° C., the polymerization time is 0.5 to 20 hours, and more Preferably, the polymerization temperature is 80 to 140 ° C. and the polymerization time is 1 to 10 hours.

  In the case of a polymerization form using a solvent, the polymerization solvent is not particularly limited. For example, aromatic hydrocarbon solvents such as toluene, xylene, and ethylbenzene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; tetrahydrofuran And ether solvents such as These solvents may be used alone or in combination of two or more. Moreover, since the residual volatile matter of the lactone ring containing polymer finally obtained will increase when the boiling point of a solvent is too high, the solvent whose boiling point is 50-200 degreeC is preferable.

  During the polymerization reaction, a polymerization initiator may be added as necessary. The polymerization initiator is not particularly limited. For example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxyisopropyl Organic peroxides such as carbonate and t-amylperoxy-2-ethylhexanoate; 2,2′-azobis (isobutyronitrile), 1,1′-azobis (cyclohexanecarbonitrile), 2,2 ′ -Azo compounds such as azobis (2,4-dimethylvaleronitrile); These polymerization initiators may be used alone or in combination of two or more. The amount of the polymerization initiator used is not particularly limited as long as it is appropriately set according to the combination of monomers and reaction conditions.

  When performing the polymerization, it is preferable to control the concentration of the polymer produced in the polymerization reaction mixture to be 50% by mass or less in order to suppress gelation of the reaction solution. Specifically, when the concentration of the polymer formed in the polymerization reaction mixture exceeds 50% by mass, it is preferable that the polymerization solvent is appropriately added to the polymerization reaction mixture and controlled to be 50% by mass or less. . The concentration of the polymer formed in the polymerization reaction mixture is more preferably 45% by mass or less, and further preferably 40% by mass or less. In addition, since productivity will fall when the density | concentration of the polymer produced | generated in the polymerization reaction mixture is too low, the density | concentration of the polymer produced | generated in the polymerization reaction mixture becomes like this. Preferably it is 10 mass% or more, More preferably, it is 20 mass%. That's it.

  The form in which the polymerization solvent is appropriately added to the polymerization reaction mixture is not particularly limited, and for example, the polymerization solvent may be added continuously or the polymerization solvent may be added intermittently. By controlling the concentration of the polymer formed in the polymerization reaction mixture in this way, the gelation of the reaction solution can be more sufficiently suppressed, and in particular, to increase the lactone ring content and improve the heat resistance. Even when the ratio between the hydroxyl group and the ester group in the molecular chain is increased, gelation can be sufficiently suppressed. The polymerization solvent to be added may be, for example, the same type of solvent used during the initial charging of the polymerization reaction or a different type of solvent, but the solvent used during the initial charging of the polymerization reaction. It is preferable to use the same type of solvent. Moreover, the polymerization solvent to be added may be only one kind of single solvent or two or more kinds of mixed solvents.

  The polymerization reaction mixture obtained when the above polymerization step is completed usually contains a solvent in addition to the obtained polymer, but it is necessary to completely remove the solvent and take out the polymer in a solid state. Rather, it is preferably introduced into the subsequent lactone cyclization condensation step in a state containing a solvent. If necessary, after taking out in a solid state, a solvent suitable for the subsequent lactone cyclization condensation step may be added again.

  The polymer obtained in the polymerization step is a polymer (a) having a hydroxyl group and an ester group in the molecular chain, and the weight average molecular weight of the polymer (a) is preferably 1,000 to 2,000,000. 000, more preferably 5,000 to 1,000,000, still more preferably 10,000 to 500,000, particularly preferably 50,000 to 500,000. In addition, a weight average molecular weight is the value calculated | required by polystyrene conversion using gel permeation chromatography. The polymer (a) obtained in the polymerization step is subjected to heat treatment in the subsequent lactone cyclization condensation step, whereby a lactone ring structure is introduced into the polymer to become a lactone ring-containing polymer.

  The reaction for introducing a lactone ring structure into the polymer (a) is a reaction in which a hydroxyl group and an ester group present in the molecular chain of the polymer (a) are cyclized and condensed to form a lactone ring structure by heating. Yes, by the cyclocondensation, alcohol is by-produced. By forming the lactone ring structure in the molecular chain of the polymer (in the main skeleton of the polymer), high heat resistance is imparted. If the reaction rate of the cyclization condensation reaction leading to the lactone ring structure is insufficient, the heat resistance will not be improved sufficiently, or a condensation reaction will occur during the molding due to the heat treatment during molding, and the resulting alcohol will be contained in the molded product. May exist as bubbles or silver streaks.

  In the lactone cyclization condensation step, a lactone ring structure represented by the above formula (1) is introduced.

  The method for heat-treating the polymer (a) is not particularly limited, and a conventionally known method may be used. For example, you may heat-process the polymerization reaction mixture containing the solvent obtained by the superposition | polymerization process as it is. Or you may heat-process using a ring-closure catalyst as needed in presence of a solvent. Or heat processing can also be performed using the heating furnace and reaction apparatus provided with the vacuum apparatus or devolatilization apparatus for removing a volatile component, the extruder provided with the devolatilization apparatus, etc.

  In carrying out the cyclization condensation reaction, in addition to the polymer (a), another thermoplastic resin may coexist. When performing the cyclization condensation reaction, if necessary, an esterification catalyst or a transesterification catalyst such as p-toluenesulfonic acid generally used as a catalyst for the cyclization condensation reaction may be used. Organic carboxylic acids such as propionic acid, benzoic acid, acrylic acid, and methacrylic acid may be used as a catalyst. Furthermore, as disclosed in, for example, Japanese Patent Application Laid-Open Nos. 61-254608 and 61-261303, basic compounds, organic carboxylates, carbonates, and the like may be used.

  Alternatively, an organophosphorus compound may be used as a catalyst for the cyclization condensation reaction. Examples of the organic phosphoric acid compounds that can be used include alkyl (aryl) phosphonous acids such as methyl phosphonous acid, ethyl phosphonous acid, and phenyl phosphonous acid (however, these are alkyl (aryl) which are tautomers. ) Which may be phosphinic acid) and their monoesters or diesters; dialkyl (aryl) phosphinic acids such as dimethylphosphinic acid, diethylphosphinic acid, diphenylphosphinic acid, phenylmethylphosphinic acid, phenylethylphosphinic acid and their Esters; alkyl (aryl) phosphonic acids such as methylphosphonic acid, ethylphosphonic acid, trifluoromethylphosphonic acid, phenylphosphonic acid and their monoesters or diesters; methylphosphinic acid, ethylphosphinic acid Alkyl (aryl) phosphinic acids such as phenylphosphinic acid and esters thereof; methyl phosphite, ethyl phosphite, phenyl phosphite, dimethyl phosphite, diethyl phosphite, diphenyl phosphite, phosphorus phosphite Phosphorous acid monoester, diester or triester such as trimethyl phosphate, triethyl phosphite, triphenyl phosphite; methyl phosphate, ethyl phosphate, 2-ethylhexyl phosphate, octyl phosphate, isodecyl phosphate, phosphoric acid Lauryl, stearyl phosphate, isostearyl phosphate, phenyl phosphate, dimethyl phosphate, diethyl phosphate, di-2-ethylhexyl phosphate, diisodecyl phosphate, dilauryl phosphate, distearyl phosphate, diisostearyl phosphate, Diphenyl phosphate, trimethyl phosphate, triethyl phosphate Phosphoric acid monoesters, diesters or triesters such as triisodecyl phosphate, trilauryl phosphate, tristearyl phosphate, triisostearyl phosphate, triphenyl phosphate; methylphosphine, ethylphosphine, phenylphosphine, dimethylphosphine, diethylphosphine , Diphenylphosphine, trimethylphosphine, triethylphosphine, triphenylphosphine, etc. mono-, di- or tri-alkyl (aryl) phosphine; methyldichlorophosphine, ethyldichlorophosphine, phenyldichlorophosphine, dimethylchlorophosphine, diethylchlorophosphine, diphenyl Alkyl (aryl) halogen phosphines such as chlorophosphine; methylphosphine oxide, ethylphosphine oxide, oxide Mono-, di- or tri-alkyl (aryl) phosphines such as phenyl phosphine, dimethyl phosphine oxide, diethyl phosphine oxide, diphenyl phosphine oxide, trimethyl phosphine oxide, triethyl phosphine oxide, triphenyl phosphine oxide; tetramethylphosphonium chloride, chloride And halogenated tetraalkyl (aryl) phosphoniums such as tetraethylphosphonium and tetraphenylphosphonium chloride. These organic phosphorus compounds may be used alone or in combination of two or more. Among these organophosphorus compounds, since the catalytic activity is high and the colorability is low, alkyl (aryl) phosphonous acid, phosphorous acid monoester or diester, phosphoric acid monoester or diester, and alkyl (aryl) phosphonic acid Preferably, alkyl (aryl) phosphonous acid, phosphorous acid monoester or diester, phosphoric acid monoester or diester is more preferable, and alkyl (aryl) phosphonous acid, phosphoric acid monoester or diester is particularly preferable.

  Although the usage-amount of the catalyst used in the case of a cyclization condensation reaction is not specifically limited, For example, Preferably it is 0.001-5 mass% with respect to a polymer (a), More preferably, it is 0.00. It is 01-2.5 mass%, More preferably, it is 0.01-1 mass%, Most preferably, it is 0.05-0.5 mass%. When the amount of the catalyst used is less than 0.001% by mass, the reaction rate of the cyclization condensation reaction may not be sufficiently improved. On the other hand, when the amount of the catalyst used exceeds 5% by mass, the obtained polymer may be colored or the polymer may be cross-linked to make melt molding difficult.

  The addition timing of the catalyst is not particularly limited. For example, the catalyst may be added at the beginning of the reaction, may be added during the reaction, or may be added in both of them.

  It is preferable to carry out the cyclization condensation reaction in the presence of a solvent and to use a devolatilization step in combination with the cyclization condensation reaction. In this case, a mode in which the devolatilization step is used throughout the cyclization condensation reaction and a mode in which the devolatilization step is not used over the entire cyclization condensation reaction but only in a part of the process. In the method using the devolatilization step in combination, the alcohol produced as a by-product in the condensation cyclization reaction is forcibly devolatilized and removed, so that the equilibrium of the reaction is advantageous for the production side.

  The devolatilization process means a process of removing volatile components such as solvents and residual monomers and alcohol by-produced by a cyclization condensation reaction leading to a lactone ring structure under reduced pressure heating conditions as necessary. To do. If this removal treatment is insufficient, residual volatile components in the obtained polymer increase, and coloring may occur due to deterioration during molding, and molding defects such as bubbles and silver streaks may occur.

  In the case of using a devolatilization step throughout the cyclization condensation reaction, the apparatus to be used is not particularly limited. For example, in order to more effectively perform the present invention, a devolatilization step and devolatilization are performed. It is preferable to use a devolatilizer comprising a tank and an extruder with a vent, or a devolatilizer and an extruder arranged in series, and a devolatilizer comprising a heat exchanger and a devolatilizer or an extrusion with a vent It is more preferable to use a machine.

  The reaction treatment temperature in the case of using a devolatilizer comprising a heat exchanger and a devolatilizer is preferably 150 to 350 ° C, more preferably 200 to 300 ° C. If the reaction treatment temperature is less than 150 ° C., the cyclization condensation reaction may be insufficient and the residual volatile matter may increase. Conversely, when the reaction treatment temperature exceeds 350 ° C., the obtained polymer may be colored or decomposed.

  The reaction treatment pressure when using a devolatilizer comprising a heat exchanger and a devolatilizer is preferably 931 to 1.33 hPa (700 to 1 mmHg), more preferably 798 to 66.5 hPa (600 to 50 mmHg). . When the reaction treatment pressure exceeds 931 hPa (700 mmHg), volatile components including alcohol may easily remain. Conversely, if the reaction treatment pressure is less than 1.33 hPa (1 mmHg), industrial implementation may be difficult.

  When using an extruder with a vent, one or a plurality of vents may be used, but it is preferable to have a plurality of vents.

  The reaction treatment temperature when using an extruder with a vent is preferably 150 to 350 ° C, more preferably 200 to 300 ° C. If the reaction treatment temperature is less than 150 ° C., the cyclization condensation reaction may be insufficient and the residual volatile matter may increase. Conversely, when the reaction treatment temperature exceeds 350 ° C., the obtained polymer may be colored or decomposed.

  The reaction processing pressure when using an extruder with a vent is preferably 931 to 1.33 hPa (700 to 1 mmHg), more preferably 798 to 13.3 hPa (600 to 10 mmHg). When the reaction treatment pressure exceeds 931 hPa (700 mmHg), volatile components including alcohol may easily remain. Conversely, if the reaction treatment pressure is less than 1.33 hPa (1 mmHg), industrial implementation may be difficult.

  In the case of a form in which a devolatilization step is used throughout the cyclization condensation reaction, the physical properties of the lactone ring-containing polymer obtained may deteriorate under severe heat treatment conditions, as will be described later. It is preferable to carry out by using an extruder with a vent etc. on the conditions as mild as possible.

  In the case where the devolatilization step is used in combination throughout the cyclization condensation reaction, the polymer (a) obtained in the polymerization step is preferably introduced into the cyclization condensation reaction device together with a solvent. Depending on the situation, it may be passed once again through a cyclocondensation reaction apparatus such as a vented extruder.

  You may perform the form used together only in a part of process, without using a devolatilization process over the whole process of cyclization condensation reaction. For example, the apparatus for producing the polymer (a) is further heated, and if necessary, a part of the devolatilization step is used together to advance the cyclization condensation reaction to some extent in advance, followed by the devolatilization step. Is a form in which a cyclization condensation reaction is simultaneously used to complete the reaction.

  In the form of using the devolatilization step throughout the cyclization condensation reaction described above, for example, when the polymer (a) is heat-treated at a high temperature of about 250 ° C. or higher using a twin-screw extruder. Depending on the thermal history, partial decomposition or the like may occur before the cyclization condensation reaction occurs, and the physical properties of the resulting lactone ring-containing polymer may deteriorate. Therefore, if the cyclization condensation reaction is allowed to proceed to some extent before the cyclization condensation reaction using the devolatilization process at the same time, the latter reaction conditions can be relaxed, and the physical properties of the resulting lactone ring-containing polymer deteriorated. Is preferable. As a particularly preferred form, for example, a form in which the devolatilization step is started after a lapse of time from the start of the cyclization condensation reaction, that is, a hydroxyl group and an ester present in the molecular chain of the polymer (a) obtained in the polymerization step A mode in which a group is preliminarily subjected to a cyclization condensation reaction to increase the cyclization condensation reaction rate to some extent and then a cyclization condensation reaction using a devolatilization step simultaneously is performed. Specifically, for example, a cyclization condensation reaction is allowed to proceed to a certain reaction rate in the presence of a solvent in advance using a kettle reactor, and then a reactor equipped with a devolatilizer, for example, heat exchange Preferred is a mode in which the cyclization condensation reaction is completed with a devolatilizer comprising a vessel and a devolatilization tank, an extruder with a vent, or the like. In particular, in the case of this form, it is more preferable that a catalyst for the cyclization condensation reaction is present.

  As described above, the hydroxyl group and ester group present in the molecular chain of the polymer (a) obtained in the polymerization step are preliminarily subjected to a cyclization condensation reaction to increase the cyclization condensation reaction rate to some extent. The method of carrying out the cyclization condensation reaction simultaneously using the volatilization process is a preferred form in obtaining the lactone ring-containing polymer in the present invention. With this form, a lactone ring-containing polymer having a higher glass transition temperature, a higher cyclization condensation reaction rate, and excellent heat resistance can be obtained. In this case, as a measure of the cyclization condensation reaction rate, for example, the mass reduction rate in the range of 150 to 300 ° C. in the dynamic TG measurement shown in the examples is preferably 2% or less, more preferably 1.5% or less. More preferably, it is 1% or less.

  The reactor that can be employed in the cyclization condensation reaction performed in advance before the cyclization condensation reaction using the devolatilization process at the same time is not particularly limited. For example, an autoclave, a kettle reactor, a heat exchanger And a devolatilizer comprising a devolatilization tank, and a vented extruder suitable for a cyclization condensation reaction using a devolatilization step at the same time can also be used. Of these reactors, an autoclave and a kettle reactor are particularly preferable. However, even when a reactor such as an extruder with a vent is used, the autoclave or kettle can be adjusted by adjusting the temperature conditions, barrel conditions, screw shape, screw operating conditions, etc. It is possible to carry out the cyclization condensation reaction in the same state as the reaction state in the type reactor.

  In the case of the cyclization condensation reaction carried out in advance before the cyclization condensation reaction using the devolatilization step at the same time, for example, a mixture containing the polymer (a) and the solvent obtained in the polymerization step is used as (i) a catalyst. And (ii) a method of performing a heat reaction without a catalyst, a method of performing the above (i) or (ii) under pressure, and the like.

  The “mixture containing the polymer (a) and the solvent” introduced into the cyclization condensation reaction in the lactone cyclization condensation step refers to the polymerization reaction mixture obtained in the polymerization step itself or once the solvent is removed. It means a mixture obtained by re-adding a solvent suitable for the cyclization condensation reaction later.

  The solvent that can be re-added in the cyclization condensation reaction that is carried out in advance before the cyclization condensation reaction using the devolatilization step at the same time is not particularly limited. For example, aromatic carbonization such as toluene, xylene, ethylbenzene, etc. Hydrogens; ketones such as methyl ethyl ketone and methyl isobutyl ketone; chloroform, dimethyl sulfoxide, tetrahydrofuran; and the like. These solvents may be used alone or in combination of two or more. It is preferable to use the same type of solvent as that used in the polymerization step.

  Examples of the catalyst to be added in the method (i) include commonly used esterification catalysts such as p-toluenesulfonic acid or transesterification catalysts, basic compounds, organic carboxylates, and carbonates. In the invention, it is preferable to use the aforementioned organophosphorus compound. The addition timing of the catalyst is not particularly limited. For example, the catalyst may be added at the beginning of the reaction, may be added during the reaction, or may be added in both of them. The addition amount of the catalyst is not particularly limited, but for example, is preferably 0.001 to 5% by mass, more preferably 0.01 to 2.5% by mass with respect to the mass of the polymer (a). More preferably, it is 0.01-1 mass%, Most preferably, it is 0.05-0.5 mass%. Although the heating temperature and heating time of method (i) are not particularly limited, for example, the heating temperature is preferably room temperature to 180 ° C., more preferably 50 to 150 ° C., and the heating time is preferably 1 to 20 hours, more preferably 2 to 10 hours. If the heating temperature is less than room temperature or the heating time is less than 1 hour, the cyclization condensation reaction rate may be lowered. Conversely, if the heating temperature exceeds 180 ° C. or the heating time exceeds 20 hours, the resin may be colored or decomposed.

  In the method (ii), for example, the polymerization reaction mixture obtained in the polymerization step may be heated as it is using a pressure-resistant kettle reactor or the like. Although the heating temperature and heating time of method (ii) are not particularly limited, for example, the heating temperature is preferably 100 to 180 ° C, more preferably 100 to 150 ° C, and the heating time is preferably 1 to 20 hours, more preferably 2 to 10 hours. When the heating temperature is less than 100 ° C. or the heating time is less than 1 hour, the cyclization condensation reaction rate may be lowered. Conversely, if the heating temperature exceeds 180 ° C. or the heating time exceeds 20 hours, the resin may be colored or decomposed.

  In any method, there is no problem even under pressure depending on conditions.

  In the case of the cyclization condensation reaction performed in advance before the cyclization condensation reaction using the devolatilization step at the same time, there is no problem even if part of the solvent volatilizes spontaneously during the reaction.

  The mass reduction rate within the range of 150 to 300 ° C. in the dynamic TG measurement at the end of the cyclization condensation reaction performed in advance before the cyclization condensation reaction simultaneously used in combination with the devolatilization step, that is, immediately before the start of the devolatilization step is Preferably it is 2% or less, More preferably, it is 1.5% or less, More preferably, it is 1% or less. When the mass reduction rate exceeds 2%, the cyclization condensation reaction rate does not rise to a sufficiently high level even if the cyclization condensation reaction is performed simultaneously with the devolatilization step, and the physical properties of the resulting lactone ring-containing polymer. May deteriorate. In addition, when performing said cyclization condensation reaction, in addition to a polymer (a), you may coexist other thermoplastic resins.

  The hydroxyl group and ester group present in the molecular chain of the polymer (a) obtained in the polymerization step are preliminarily subjected to a cyclization condensation reaction to increase the cyclization condensation reaction rate to some extent. In the case of the form in which the cyclized condensation reaction is performed, the polymer obtained by the cyclized condensation reaction performed in advance (the polymer in which at least a part of the hydroxyl group and the ester group present in the molecular chain is subjected to the cyclized condensation reaction) and the solvent May be introduced into the cyclization condensation reaction using the devolatilization step at the same time, and if necessary, the polymer (at least a part of the hydroxyl group and ester group present in the molecular chain is cyclized and condensed). You may introduce | transduce into the cyclocondensation reaction which used the devolatilization process together, after passing through other processes, such as adding a solvent again after isolating the polymer which reacted.

  The devolatilization step is not limited to being completed at the same time as the cyclization condensation reaction, and may be completed after a lapse of time from the completion of the cyclization condensation reaction.

  The weight average molecular weight of the lactone ring-containing polymer is preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, still more preferably 10,000 to 500,000, particularly preferably. 50,000 to 500,000. In addition, a weight average molecular weight is the value calculated | required by polystyrene conversion using gel permeation chromatography.

  The lactone ring-containing polymer preferably has a mass reduction rate in the range of 150 to 300 ° C. in dynamic TG measurement of 1% or less, more preferably 0.5% or less, and still more preferably 0.3% or less.

  Since the lactone ring-containing polymer has a high cyclization condensation reaction rate, it is possible to avoid the disadvantage that bubbles and silver streaks enter the molded product after molding. Furthermore, since the lactone ring structure is sufficiently introduced into the polymer due to the high cyclization condensation reaction rate, the obtained lactone ring-containing polymer has sufficiently high heat resistance.

  The lactone ring-containing polymer has a coloring degree (YI) of preferably 6 or less, more preferably 3 or less, still more preferably 2 or less, and particularly preferably 1 or less when a chloroform solution having a concentration of 15% by mass is used. . If the degree of coloring (YI) exceeds 6, transparency may be impaired by coloring, and it may not be used for the intended purpose.

  The lactone ring-containing polymer has a 5% mass reduction temperature in thermal mass spectrometry (TG) of preferably 330 ° C. or higher, more preferably 350 ° C. or higher, and still more preferably 360 ° C. or higher. The 5% mass reduction temperature in thermal mass spectrometry (TG) is an index of thermal stability, and if it is less than 330 ° C., sufficient thermal stability may not be exhibited.

  The lactone ring-containing polymer has a glass transition temperature (Tg) of preferably 115 ° C. or higher, more preferably 125 ° C. or higher, still more preferably 130 ° C. or higher, and particularly preferably 140 ° C. or higher.

  The total amount of residual volatile components contained in the lactone ring-containing polymer is preferably 1,500 ppm or less, more preferably 1,000 ppm or less. If the total amount of residual volatile components exceeds 1,500 ppm, it may be colored due to alteration during molding, foaming, or molding defects such as silver streak.

  The lactone ring-containing polymer has a total light transmittance of 85% or more, more preferably 88% or more, and still more preferably measured by a method based on ASTM-D-1003 for a molded product obtained by injection molding. 90% or more. The total light transmittance is an index of transparency, and if it is less than 85%, the transparency is lowered and it may not be used for the intended purpose.

  The thermoplastic resin film used in the present invention contains a lactone ring-containing polymer as a main component. Specifically, the content thereof is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, and further Preferably it is 70-100 mass%, Most preferably, it is 80-100 mass%. When the content of the lactone ring-containing polymer in the thermoplastic resin film is less than 50% by mass, the effects of the present invention may not be sufficiently exhibited.

  The thermoplastic resin film may contain a polymer other than the lactone ring-containing polymer (hereinafter sometimes referred to as “other polymer”) as another component. Examples of other polymers include olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, poly (4-methyl-1-pentene); halogens such as vinyl chloride, vinylidene chloride, and chlorinated vinyl resins. Acrylic polymers such as polymethyl methacrylate; Styrene polymers such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene block copolymer Polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; polyamides such as nylon 6, nylon 66 and nylon 610; polyacetal; polycarbonate; polyphenylene oxide; Sulfides; polyetheretherketone; polysulfones; polyethersulfones; polyoxyethylene benzylidene alkylene; polyamideimide; polybutadiene rubber, rubber-like polymer such as ABS resin or ASA resin containing an acrylic rubber; and the like.

  The content of the other polymer in the thermoplastic resin film is preferably 0 to 50% by mass, more preferably 0 to 40% by mass, further preferably 0 to 30% by mass, and particularly preferably 0 to 20% by mass. is there.

  The thermoplastic resin film may contain various additives. Examples of additives include antioxidants such as hindered phenols, phosphorus, and sulfur; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fibers and carbon fibers; phenyls UV absorbers such as salicylate, (2,2′-hydroxy-5-methylphenyl) benzotriazole, 2-hydroxybenzophenone; near infrared absorbers; tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide, etc. Flame retardants; Antistatic agents such as anionic, cationic and nonionic surfactants; Colorants such as inorganic pigments, organic pigments and dyes; Organic fillers and inorganic fillers; Resin modifiers; Organic fillers and inorganic fillers Agents, plasticizers, lubricants, antistatic agents, flame retardants, and the like.

  The content of the additive in the thermoplastic resin film is preferably 0 to 5% by mass, more preferably 0 to 2% by mass, and still more preferably 0 to 0.5% by mass.

  The method for producing the thermoplastic resin film is not particularly limited. For example, the lactone ring-containing polymer and other polymers and additives are sufficiently mixed by a conventionally known mixing method. It can be manufactured by forming a film from the thermoplastic resin composition in advance. Alternatively, the lactone ring-containing polymer and other polymers and additives may be made into separate solutions and mixed to form a uniform mixed solution, and then formed into a film.

  First, in order to produce a thermoplastic resin composition, for example, the above film raw material is pre-blended with a conventionally known mixer such as an omni mixer, and then the obtained mixture is extrusion kneaded. In this case, the mixer used for extrusion kneading is not particularly limited. For example, a conventionally known mixer such as an extruder such as a single screw extruder or a twin screw extruder or a pressure kneader may be used. it can.

  Examples of the film forming method include conventionally known film forming methods such as a solution casting method (solution casting method), a melt extrusion method, a calendar method, and a compression molding method. Among these film forming methods, the solution casting method (solution casting method) and the melt extrusion method are preferable.

  Examples of the solvent used in the solution casting method (solution casting method) include aromatic hydrocarbons such as benzene, toluene and xylene; aliphatic hydrocarbons such as cyclohexane and decalin; esters such as ethyl acetate and butyl acetate Ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; alcohols such as methanol, ethanol, isopropanol, butanol, isobutanol, methyl cellosolve, ethyl cellosolve and butyl cellosolve; ethers such as tetrahydrofuran and dioxane; dichloromethane, Halogenated hydrocarbons such as chloroform and carbon tetrachloride; dimethylformamide; dimethyl sulfoxide; These solvents may be used alone or in combination of two or more.

  Examples of the apparatus for performing the solution casting method (solution casting method) include a drum casting machine, a band casting machine, and a spin coater.

  Examples of the melt extrusion method include a T-die method and an inflation method, and the molding temperature at that time is preferably 150 to 350 ° C., more preferably 200 to 300 ° C.

  When forming a film by the T-die method, a roll-shaped film can be obtained by attaching a T-die to the tip of a known single-screw extruder or twin-screw extruder and winding the film extruded into a film. it can. At this time, it is possible to perform uniaxial stretching by appropriately adjusting the temperature of the winding roll and adding stretching in the extrusion direction. Further, simultaneous biaxial stretching, sequential biaxial stretching, and the like can be performed by stretching the film in a direction perpendicular to the extrusion direction.

  The thermoplastic resin film may be an unstretched film or a stretched film. In the case of a stretched film, either a uniaxially stretched film or a biaxially stretched film may be used. In the case of a biaxially stretched film, either a simultaneous biaxially stretched film or a sequential biaxially stretched film may be used. In the case of biaxial stretching, the mechanical strength is improved and the film performance is improved. The thermoplastic resin film containing a lactone ring-containing polymer as a main component can suppress an increase in retardation even when stretched by mixing other thermoplastic resins, and retains optical isotropy. be able to.

  The stretching temperature is preferably in the vicinity of the glass transition temperature of the thermoplastic resin composition that is the film raw material, and specifically, preferably (glass transition temperature-30 ° C) to (glass transition temperature + 100 ° C), more preferably. Is within the range of (glass transition temperature−20 ° C.) to (glass transition temperature + 80 ° C.). If the stretching temperature is less than (glass transition temperature-30 ° C.), a sufficient stretching ratio may not be obtained. Conversely, when the stretching temperature exceeds (glass transition temperature + 100 ° C.), the resin composition may flow, and stable stretching may not be performed.

  The draw ratio defined by the area ratio is preferably in the range of 1.1 to 25 times, more preferably 1.3 to 10 times. If the draw ratio is less than 1.1 times, the toughness accompanying the drawing may not be improved. On the other hand, when the draw ratio exceeds 25 times, the effect of increasing the draw ratio may not be recognized.

  The stretching speed is unidirectional, preferably 10 to 20,000% / min, more preferably 100 to 10,000% / min. When the stretching speed is less than 10% / min, it takes time to obtain a sufficient stretching ratio, and the production cost may increase. On the contrary, when the stretching speed exceeds 20,000% / min, the stretched film may be broken.

  In addition, in order to stabilize the optical isotropy and mechanical characteristics of the thermoplastic resin film, heat treatment (annealing) or the like can be performed after the stretching treatment. The conditions for the heat treatment may be appropriately selected similarly to the conditions for the heat treatment performed on a conventionally known stretched film, and are not particularly limited.

  The thermoplastic resin film preferably has a thickness of 5 to 200 μm, more preferably 10 to 100 μm. When the thickness is less than 5 μm, not only the strength of the film is lowered, but also when the durability test of the polarizing plate is conducted, the crimp may be increased. On the other hand, when the thickness exceeds 200 μm, not only the transparency of the film is lowered, but also the moisture permeability becomes small, and when a water-based adhesive is used, the drying speed of the solvent water may be slow. .

  The thermoplastic resin film has a surface wetting tension of preferably 40 mN / m or more, more preferably 50 mN / m or more, and even more preferably 55 mN / m or more. When the surface wetting tension is at least 40 mN / m or more, the adhesive strength between the thermoplastic resin film and another layer such as a polarizer is further improved. In order to adjust the surface wetting tension, for example, corona discharge treatment, plasma treatment, ozone spraying, ultraviolet irradiation, flame treatment, chemical treatment, and other conventionally known surface treatments can be performed.

  The thermoplastic resin film may contain various additives. For example, a retardation adjusting agent that reduces in-plane retardation and / or thickness direction retardation of the film may be added. An optical property can be made into a desired range by adding a retardation adjusting agent and performing a stretching treatment as desired.

(Easily adhesive layer)
In this invention, in order to improve the adhesiveness with the polarizer of the said thermoplastic resin film, it is preferable to form an easily bonding layer on the surface of the said thermoplastic resin film. The easy-adhesion layer comprises a polyurethane resin composition (a composition containing a polyurethane resin and / or a precursor that gives a polyurethane resin after reaction) and / or a resin composition containing an amino group-containing polymer (hereinafter, both “easily” It is preferably formed from “adhesive layer coating composition”. It is formed by preparing the composition as a coating liquid, applying the composition to at least one surface of the thermoplastic resin film, and drying / curing or drying.

  The thickness of the easy-adhesion layer is preferably about 0.01 to 10 μm, more preferably about 0.05 to 3 μm, and still more preferably about 0.1 to 1 μm. It is preferable for the thickness of the easy-adhesion layer to be in the above-mentioned range because the adhesive strength is sufficient, and color loss or discoloration of the polarizing plate hardly occurs in the water resistance or moisture resistance test.

  Regarding the polyurethane resin used for forming the easy-adhesion layer, the composition containing a precursor that gives a polyurethane resin after the reaction, and the amino group-containing polymer, and the method for forming the easy-adhesion layer, Japanese Patent Application Laid-Open No. 2007-127893 The details are described in [0124] to [0175], and such description can be referred to as an explanation of the material and the forming method of the easy-adhesion layer in the present invention.

  In order to adjust the surface wetting tension, for example, corona discharge treatment, plasma treatment, ozone spraying, ultraviolet irradiation, flame is applied to the surface of the thermoplastic resin film or the surface of the easy-adhesion layer formed as desired. Treatment, chemical treatment, and other conventionally known surface treatments may be performed.

(Polarizer)
As the polarizer of the polarizing plate used in the present invention, any of an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film can be used. The iodine polarizing film and the dye polarizing film are generally produced using a polyvinyl alcohol film.

(Second protective film)
The polarizing plate used in the present invention preferably has a second protective film other than the thermoplastic resin film. The second protective film is bonded to the other surface of the polarizer that is not bonded to the thermoplastic resin film. The second protective film may be the thermoplastic resin film, or any other polymer film, cellulose acylate film, polycarbonate film, norbornene-based film, or the like.

(adhesive)
In the production of the polarizing plate of the present invention, an adhesive may be used to bond the thermoplastic resin film or the second protective film and the polarizer. More preferably, it is preferable that the easy-adhesion layer is formed on the surface of the thermoplastic resin film, and the easy-adhesion layer and another layer are bonded using an adhesive. Examples of pressure-sensitive adhesives that can be used include PVA adhesives, polyurethane adhesives, acrylic adhesives, isocyanate adhesives, and the like. These adhesives may be used alone or in combination of two or more. Of these adhesives, polyurethane adhesives and isocyanate adhesives are particularly suitable. The form of the adhesive is not particularly limited, and various forms of adhesives such as solvent-based, water-based, and solvent-free systems can be used, for example.

  Regarding the polyurethane-based adhesive, the isocyanate-based adhesive, the reaction catalyst used in the adhesive, the additive, and the amount of use thereof, there are detailed descriptions in [0174] to [0194] of JP-A-2007-12789. It can be considered as an explanation of the pressure-sensitive adhesive that can be used in the present invention.

(Other functional layers)
The polarizing plate used in the present invention has various functional layers such as antiglare (non-glare) layer, antifouling layer hard coat layer such as photocatalyst layer, antireflection layer, ultraviolet ray shielding layer, heat ray shielding layer, electromagnetic wave shielding layer, gas It may have a barrier layer or the like. The materials used for forming these materials are described in detail in [0060] to [0065] of Japanese Patent Application Laid-Open No. 2006-96960, and the description is referred to as an explanation of the shape material of various functional layers in the present invention. can do.

(Other polarizing plates)
There is no restriction | limiting in particular about the polarizing plate used with the polarizing plate which has the said thermoplastic resin film. Similarly, a polarizing plate having the thermoplastic resin film may be used, or a polarizing plate having only another polymer film, for example, a protective film such as a cellulose acylate film, a polycarbonate film, or a norbornene film may be used. Good. It is preferable that both polarizing plates are the polarizing plates which have the said thermoplastic resin film at the point from which an effect becomes higher. When only one polarizing plate having the thermoplastic resin film is used, it is preferably disposed as a back side polarizing plate (PLb in FIG. 1).

  The liquid crystal display device of the present invention is not limited to the configuration shown in FIG. 1, and may include other members. For example, a color filter may be disposed between the liquid crystal cell and the polarizing film. Further, as will be described later, another optical compensation film can be further disposed between the liquid crystal cell and the polarizing plate. In the case of use as a transmission type, a cold cathode or a hot cathode fluorescent tube, or a backlight having a light emitting diode, a field emission element, or an electroluminescent element as a light source can be disposed on the back surface. In addition, the liquid crystal display device of the present invention may be of a reflective type. In such a case, only one polarizing plate of the present invention may be disposed on the observation side, and the liquid crystal cell back surface or the lower substrate of the liquid crystal cell may be disposed. Install a reflective film on the inner surface. Of course, it is also possible to provide a front light using the light source on the liquid crystal cell observation side.

  The liquid crystal display device of the present invention includes an image direct view type, an image projection type, and a light modulation type. The present invention is particularly effective when applied to an active matrix liquid crystal display device using three-terminal or two-terminal semiconductor elements such as TFT and MIM. Of course, an embodiment applied to a passive matrix liquid crystal display device represented by STN type called time-division driving is also effective.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, the embodiment of this invention is not limited to these.
[Production of IPS mode liquid crystal cell]
On one glass substrate, electrodes were arranged so that the distance between adjacent electrodes was 20 μm, and a polyimide film was provided as an alignment film thereon, and a rubbing treatment was performed. A polyimide film was provided on one surface of a separately prepared glass substrate, and a rubbing treatment was performed to obtain an alignment film. The two glass substrates are stacked and bonded so that the alignment films face each other, the distance between the substrates (gap; d) is 3.9 μm, and the rubbing directions of the two glass substrates are parallel. A nematic liquid crystal composition having a refractive index anisotropy (Δn) of 0.0769 and a dielectric anisotropy (Δε) of 4.5 was enclosed. The value of d · Δn of the liquid crystal layer was 300 nm.

[Production of Polarizing Plates PL1 to PL6]
(Preparation of thermoplastic resin film F1)
A thermoplastic resin film F1 was produced with reference to the production example described in [Example] of JP-A-2006-96960. Specifically, it was produced by the following method.
To a 30 L reaction kettle equipped with a stirrer, temperature sensor, cooling pipe, nitrogen introduction pipe, 9000 g of methyl methacrylate (MMA), 1000 g of methyl 2- (hydroxymethyl) acrylate (MHMA), 10000 g of 4-methyl- 2-Pentanone (methyl isobutyl ketone, MIBK), 5 g of n-dodecyl mercaptan were charged, and the temperature was raised to 105 ° C. while refluxing nitrogen. When refluxed, 5.0 g of tertiary butyl peroxy was used as a polymerization initiator. While adding isopropyl carbonate (manufactured by Akzo Kayaku Co., Ltd., trade name: Kayacaron Bic-7), a solution comprising 10.0 g of tertiary butyl peroxyisopropyl carbonate and 230 g of MIBK was added dropwise over 4 hours, while refluxing. (About 105-120 ° C) Further, aging was performed for 4 hours.

  To the obtained polymer solution, 30 g of stearyl phosphate / distearyl phosphate mixture (manufactured by Sakai Chemicals, trade name: Phoslex A-18) was added and cyclized under reflux (about 90 to 120 ° C.) for 5 hours. A condensation reaction was performed. Subsequently, the polymer solution obtained by the cyclization condensation reaction was subjected to a vent having a barrel temperature of 260 ° C., a rotation speed of 100 rpm, a degree of vacuum of 13.3 to 400 hPa (10 to 300 mmHg), a rear vent number of 1, and a forevent number of 4 It is introduced into a type screw twin screw extruder (φ = 29.75 mm, L / D = 30) at a processing rate of 2.0 kg / hour in terms of resin amount, and cyclization condensation reaction and devolatilization are carried out in the extruder. A transparent pellet (1A) was obtained by extrusion.

  About the obtained pellet (1A), various physical properties were measured by the method of Unexamined-Japanese-Patent No. 2006-96960, and it confirmed that the pellet 1A produced in the Example of Unexamined-Japanese-Patent No. 2006-96960 was manufactured. .

The pellet (1A) obtained in Production Example 1 was melt-extruded from a coat hanger type T die having a width of 150 mm using a twin-screw extruder having a 20 mmφ screw to produce a film F1 having a thickness of about 100 μm. This film F1
Re (630) = 0.6 nm,
Rth (630) =-1.7 nm,
| Re (400) −Re (700) | = 0.1 nm and | Rth (400) −Rth (700) | = 1.0 nm
And the above formulas (I) and (II) were satisfied. Also,
| Re {50} -Re {25} | = 1 nm,
| Rth {50} -Rth {25} | = 2 nm
| Re [80] −Re [10] | = 0 nm and | Rth [80] −Rth [10] | = 0.5 nm
And all of the above formulas (III) to (VI) were satisfied.

(Preparation of ZRF film F2)
A commercially available cellulose acetate film (ZRF80s, manufactured by FUJIFILM Corporation, hereinafter referred to as “ZRF film”) was used as the polymer film F2. Film F2
Re (630) = 1 nm,
Rth (630) = − 7 nm
| Re (400) −Re (700) | = 2 nm and | Rth (400) −Rth (700) | = 15 nm
Met. Also,
| Re {50} -Re {25} | = 3 nm
| Rth {50} -Rth {25} | = 10 nm and | Re [80] -Re [10] | = 0.3 nm
| Rth {80} -Rth {10} | = 16 nm
Met.

(Preparation of TAC film F3)
A commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Film Co., Ltd., hereinafter referred to as “TAC film”) was used as the polymer film F3. Film F3
Re (630) = 1 nm,
Rth (630) = 38 nm,
| Re (400) −Re (700) | = 0.8 nm and | Rth (400) −Rth (700) | = 20 nm.

(Polarizing film)
A polarizing film in which iodine was adsorbed on a stretched polyvinyl alcohol film was produced and adopted.

(Preparation of polarizing plate PL1)
While applying an isocyanate-based adhesive on the surface of the thermoplastic resin film F1, applying a PVA-based adhesive on the surface of the TAC film F3, sandwiching the polarizing film between these films, and extruding excess adhesive with a pressure roller Bonded by wet lamination. Then, it heated and dried and the polarizing plate was produced.
(Preparation of polarizing plate PL2)
A PVA adhesive was applied to the surface of the ZRF film F2, a PVA adhesive was applied to the surface of the TAC film F3, a polarizing film was sandwiched between these films, and a polarizing plate was produced in the same manner as described above.
(Preparation of polarizing plate PL3)
A PVA adhesive was applied to each surface of the two TAC films F3, a polarizing film was sandwiched between these films, and a polarizing plate was produced in the same manner as described above.

[Production of IPS mode liquid crystal display device]
A liquid crystal display device having the same configuration as in FIG. 1 was produced. Specifically, it was produced by the following method.
As the display surface side polarizing plate PLa and the back surface side polarizing plate PLb, the liquid crystal display devices LCD1 to LCD6 were respectively prepared by bonding them in the combinations shown in Table 1 above and below the IPS mode liquid crystal cell prepared above. However, about polarizing plate PL1 and PL2, it has arrange | positioned so that a liquid crystal cell side protective film may become the thermoplastic resin film F1 or a ZRF film.

[Evaluation]
The following evaluation was performed for each of the manufactured liquid crystal display devices LCD1 to LCD6.
The degree of color shift observed in an oblique direction during black display after each liquid crystal display device was left at 25 ° C. and 60% humidity for 1 hour and after left at 80 ° C. and 10% humidity for 1 hour. And front (normal direction) black luminance were evaluated. The evaluation criteria are as follows. The results are shown in Table 1 below.
-Color shift ○: No color shift was observed.
Δ: Although there was a slight color shift, it was an acceptable level.
X: Color shift was observed.
・ Front black luminance ○: No light leaks to the front, and CR does not decrease.
Δ: Some light leakage is observed, but CR is hardly lowered.
X: Light leakage to the front is remarkable and CR is lowered.

  The pellet (1A) obtained in Production Example 1 was melt-extruded from a coat hanger type T die having a width of 150 mm using a twin-screw extruder having a 20 mmφ screw, and the thickness, temperature, humidity, stretching at the time of melt extrusion By changing conditions and the like, thermoplastic resin films F10 to F34 having the optical characteristics shown in the following table were produced.

  Triacetylcellulose films F50 to F53 for comparative examples having optical properties shown in the following table were prepared by using triacetylcellulose and changing the thickness, temperature, humidity, stretching conditions, and the like by a known casting method. .

＊１： ｜Ｒｅ（４００）−Ｒｅ（７００）｜
＊２： ｜Ｒｔｈ（４００）−Ｒｔｈ（７００）｜
＊３： ｜Ｒｅ｛５０｝−Ｒｅ｛２５｝｜
＊４： ｜Ｒｔｈ｛５０｝−Ｒｔｈ｛２５｝｜
＊５： ｜Ｒｅ［８０］−Ｒｅ［１０］｜
＊６： ｜Ｒｔｈ［８０］−Ｒｔｈ［１０］｜

* 1: | Re (400) -Re (700) |
* 2: | Rth (400) -Rth (700) |
* 3: | Re {50} -Re {25} |
* 4: | Rth {50} -Rth {25} |
* 5: | Re [80] -Re [10] |
* 6: | Rth [80] -Rth [10] |

Polarizing plates PL10 to PL34 were respectively produced in the same manner as polarizing plate PL1, except that each of the thermoplastic resin films F10 to F34 was used instead of the thermoplastic resin film F1.
Polarizing plates PL50 to PL53 were produced in the same manner as polarizing plate PL2, except that each of the triacetyl cellulose films F50 to F53 was used instead of TAC film F3.

A liquid crystal display device having the same configuration as that in FIG. 1 was prepared using two polarizing plates PL10 to PL34 and two PL50 to Pl53. Specifically, the same polarizing plate is pasted as the display surface side polarizing plate PLa and the back side polarizing plate PLb on the upper and lower sides of the IPS mode liquid crystal cell produced above, respectively, and the liquid crystal display devices L10 to L34 and L50 to L53. Were prepared. However, when arrange | positioning each polarizing plate, it has arrange | positioned so that the liquid crystal cell side protective film may become each of the thermoplastic resin films F10-34 and the cellulose acylate films F50-F53.
Each liquid crystal display device produced was evaluated in the same manner as described above. The evaluation results are shown in the following table.

DESCRIPTION OF SYMBOLS 10 IPS mode liquid crystal cell 12a, 12b Polarizer 14a, 14b Liquid crystal cell side protective film 16a, 16b Outer protective film PLa Display surface side polarizing plate PLb Back side polarizing plate

Claims (8)

At least one of the electrodes has a pair of opposed substrates and an alignment-controlled liquid crystal layer disposed between the pair of substrates, and the electrodes have a component parallel to the substrate having the electrodes. A liquid crystal cell in which an electric field is formed, and a pair of polarizing plates arranged with the liquid crystal cell sandwiched therebetween,
The thickness of the liquid crystal layer is controlled by any of polymer beads, glass bead fibers, and resin-made columnar spacers, and the product Δn · d of the thickness d (μm) of the liquid crystal layer and the refractive index anisotropy Δn. Is 0.2 to 1.2 μm,
At least one of the pair of polarizing plates is a polarizing plate having a polarizer and a thermoplastic resin film containing, as a main component, a lactone ring-containing polymer that satisfies the following formulas (I) and (II):
The lactone ring-containing polymer is at least selected from the group consisting of (meth) acrylic acid esters, hydroxyl group-containing monomers, unsaturated carboxylic acids, and monomers represented by the following formula (2). A liquid crystal display device comprising a structural unit derived from one kind of monomer.
(I) −3 nm ≦ Re (630) ≦ 4 nm and −12 nm ≦ Rth (630) ≦ 6 nm (II) | Re (400) −Re (700) | ≦ 10 and | Rth (400) −Rth (700) | ≦ 35
(In the above formulas (I) and (II), Re (λ) represents the in-plane retardation value (nm) at the wavelength λnm, and Rth (λ) represents the retardation value in the film thickness direction at the wavelength λnm (nm). )

(Wherein R ⁴ represents a hydrogen atom or a methyl group, X represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, an —OAc group, a —CN group, a —CO—R ⁵ group, or — CO—O—R ⁶ group is represented, Ac represents an acetyl group, R ⁵ and R ⁶ represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms.) 2. The liquid crystal display device according to claim 1, wherein among the pair of polarizing plates, a polarizing plate disposed at least on a backlight side is a polarizing plate having the thermoplastic resin film. 3. The liquid crystal display device according to claim 1, wherein among the pair of polarizing plates, a polarizing plate disposed at least on the display surface side is a polarizing plate having the thermoplastic resin film. 4. The liquid crystal display device according to claim 1, wherein both of the pair of polarizing plates are polarizing plates having the thermoplastic resin film. 5. The Re {T} and Rth {T} (T is a temperature at the time of measurement (° C.)) at a wavelength of 550 nm of the thermoplastic resin film satisfy the following formulas (III) and (IV). The liquid crystal display device of any one of -4.
(III) | Re {50} -Re {25} | <5 nm
(IV) | Rth {50} -Rth {25} | <10 nm Re {T} and Rth {T} (T is a temperature at the time of measurement (° C.)) at a wavelength of 550 nm of the thermoplastic resin film are −4 nm ≦ Re {50} −Re {25} ≦ 4 nm and −8 nm ≦ The liquid crystal display device according to claim 5, wherein Rth {50} −Rth {25} ≦ 9 nm is satisfied. Re [H] and Rth [H] (H is a relative humidity (%) at the time of measurement) at a wavelength of 550 nm of the thermoplastic resin film satisfy the following formulas (V) and (VI). The liquid crystal display device according to any one of 1 to 6.
(V) | Re [80] −Re [10] | <5 nm
(VI) | Rth [80] −Rth [10] | <10 nm Re [H] and Rth [H] at a wavelength of 550 nm of the thermoplastic resin film (H is relative humidity (%) during measurement) are −3 nm ≦ Re [80] −Re [10] ≦ 4 nm, and −7 nm. The liquid crystal display device according to claim 7, wherein ≦ Rth [80] −Rth [10] ≦ 9 nm is satisfied.

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