WO2013137058A1

WO2013137058A1 - Λ/4 phase-shifted film and organic electroluminescent image display device

Info

Publication number: WO2013137058A1
Application number: PCT/JP2013/055949
Authority: WO
Inventors: 理英子れん; 幸仁中澤; 範江谷原; 賢治三島; 翠木暮; 田代　耕二
Original assignee: コニカミノルタ株式会社
Priority date: 2012-03-12
Filing date: 2013-03-05
Publication date: 2013-09-19
Also published as: JP5601433B2; KR20140107693A; JPWO2013137058A1; KR101498440B1

Abstract

The present invention addresses the problem of providing: a λ/4 phase-shifted film with a broad zone in which phase differences are reduced in the thickness direction has a high capacity for expressing phase differences, and is provided with inverse wavelength dispersion characteristics in a thin film; and an organic electroluminescent image display device equipped with said λ/4 phase-shifted film, having excellent image display performance. This λ/4 phase-shifted film is characterized in that the phase difference (Rt) (550) in the thickness direction at a wavelength of 550 nm is 150 nm or less, as measured in an environment at 23°C and a relative humidity of 55%. The λ/4 phase-shifted film is further characterized in that: the wavelength dispersion characteristics of an in-plane phase difference (Ro) is within the ranges of 0.72 ≤ Ro(450)/Ro(550) ≤ 0.96 and 0.83 ≤ Ro(550)/Ro(650) ≤ 0.98 as a first condition; the in-plane refractive index is 1.000 ≤ n_y(280)/n_x(280) ≤ 3.500 as a second condition; and 1.05 ≤ Δn_y(400)/Δn_x(400) ≤ 2.15 as a third condition.

Description

λ / 4 retardation film and organic electroluminescence image display device

The present invention relates to a λ / 4 retardation film and an organic electroluminescence image display device including the same.

In recent years, an organic electroluminescent element (hereinafter also referred to as an organic EL element) that emits light by providing a light emitting layer between opposed electrodes and applying a voltage to the electrode has been developed for flat illumination, light sources for optical fibers, and liquid crystal displays. Research and development are actively conducted as various light sources such as backlights, backlights for liquid crystal projectors, display devices, and image display devices. The organic EL element is an element that has attracted much attention in recent years because it exhibits excellent characteristics in terms of light emission efficiency, low voltage driving, light weight, and low cost, particularly in the above-mentioned fields of use.

An organic EL device injects electrons from the cathode and holes from the anode when voltage is applied, and recombines them in the light-emitting layer, thereby generating visible light emission corresponding to the light-emitting characteristics of the light-emitting layer. It is.

Among the transparent conductive materials, indium tin oxide (hereinafter abbreviated as ITO) is used for the anode because it has the highest electrical conductivity, a relatively large work function, and high hole injection efficiency. , Mainly used.

On the other hand, a metal electrode is usually used for the cathode, but considering the electron injection efficiency, from the viewpoint of work function, mainly Mg, Mg / Ag, Mg / In, Al, Li / Al, etc. The metal material is used.

These metal materials have high light reflectivity, and in addition to the function as an electrode (cathode), they also have a function of reflecting light emitted from the light emitting layer and increasing the amount of emitted light (light emission luminance). That is, the light emitted in the cathode direction is mirror-reflected on the surface of the metal material that is the cathode, and is extracted as emitted light from the transparent ITO electrode (anode).

However, in the organic EL element having such a structure, since the cathode has a mirror-like structure having a strong light reflectivity, the reflection of external light becomes noticeable when no light is emitted.

That is, the reflection of the room lighting during observation becomes intense, black color cannot be expressed in the bright place, and there is a problem that the bright room contrast is extremely low when used as a light source for a display device.

In order to improve these problems, a method of using a circularly polarizing element for preventing reflection of external light from a mirror surface is disclosed (for example, see Patent Document 1). The circularly polarizing element described in Patent Document 1 is formed by laminating an absorption linear polarizing plate and a quarter retardation film so that their optical axes intersect at 45 degrees or 135 degrees. Yes.

Here, when the quarter retardation film is formed of, for example, a single stretched film, the refractive index of the stretched film is different from wavelength to wavelength, and the retardation is relative to a certain wavelength. Although it can be just a quarter wavelength, the phase difference is shifted from the quarter wavelength at other wavelengths, and as a result, it does not function as a quarter retardation film.

That is, for example, when functioning as a ¼ retardation film for green light of 550 nm, it is difficult to completely prevent reflection of red light having a longer wavelength or blue light having a shorter wavelength. In particular, there is a problem that the phase difference for blue light is large and the reflected color becomes bluish.

In order to prevent reflection in the entire wavelength region of visible light, it has reverse wavelength dispersibility having a phase difference value of λ / 4 in the entire wavelength region (the longer the wavelength, the larger the phase difference value). Necessary.

In Patent Document 2, a retardation film having a vertically aligned liquid crystal layer on a cellulose acylate film stretched obliquely has a λ / 4 retardation in a wide wavelength range, and the retardation film is provided. In addition, it is disclosed that the organic EL display device is improved in color variation due to external light reflection.

However, in the method disclosed in Patent Document 2, since a vertical alignment liquid crystal layer is provided after producing a retardation film, the process is complicated, and further improvement is desired from the viewpoint of ease of manufacture. . Further, the organic EL display device provided with the retardation film has a problem that bleeding occurs in an image and a high-definition image cannot be obtained. The problem is that light that enters the retardation film from the light emitting layer is reflected at the interface between the retardation film and the adjacent layer, and is also diffusely reflected by the additives that are phase-separated in the retardation film, resulting in image blurring. It is estimated that this is the cause.

Patent Document 3 and Patent Document 4 disclose a retardation plate composed of a single layer having a reverse wavelength dispersion having a retardation value of λ / 4 in the entire wavelength region by containing a compound having a specific structure. ing. However, these disclosed methods have low actual retardation, and the layer thickness must be increased in order to realize the λ / 4 phase difference. In addition, there is a problem that the light extraction efficiency deteriorates as the transmittance decreases.

Patent Document 5 discloses a retardation plate in which the retardation and reverse wavelength dispersion characteristics are further improved by containing a specific compound. However, since the retardation in the thickness direction is high, the retardation plate is viewed obliquely. Further, there is a problem that the phase difference deviates by more than λ / 4 and the visibility deteriorates. In recent image display devices that require a large screen, the demand for oblique visibility is also very high, and the method described in Patent Document 5 is not sufficient, and the development of rapid improvement means is required. ing.

Japanese Patent Laid-Open No. 8-321381 International Patent No. 2009/25170 JP 2008-6602 A JP 2011-75924 A JP 2010-254949 A

The present invention has been made in view of the above problems, and its solution is a high-performance phase difference, an excellent reverse wavelength dispersion characteristic in a thin film, and a wideband with a reduced phase difference in the thickness direction. It is to provide a λ / 4 retardation film and an organic electroluminescence image display device comprising the same and excellent in image display performance (front and oblique visibility).

As a result of intensive studies in view of the above problems, the present inventor has found that the above-mentioned problems can be achieved by the following means, and as soon as the present invention has been achieved.

1. In-plane position measured in an environment of 23 ° C. and 55% relative humidity with a retardation Rt (550) in the thickness direction at a wavelength of 550 nm of 150 nm or less measured in an environment of 1.23 ° C. and 55% relative humidity. A λ / 4 retardation film, wherein the wavelength dispersion characteristic of the phase difference Ro satisfies the following condition 1 and the in-plane refractive index satisfies the following

conditions

2 and 3 simultaneously.

Condition 1
0.72 ≦ Ro (450) / Ro (550) ≦ 0.96
And 0.83 ≦ Ro (550) / Ro (650) ≦ 0.98
[In the formula, Ro (450) is an in-plane phase difference at a wavelength of 450 nm, Ro (550) is an in-plane phase difference at a wavelength of 550 nm, and Ro (650) is an in-plane phase difference at a wavelength of 650 nm. ]
Condition 2
_{_{1.000 ≦ n y (280) /}} n x (280) ≦ 3.500
[Where n _y (280) represents the refractive index in the fast axis direction at a wavelength of 280 nm, and n _x (280) represents the refractive index in the slow axis direction at a wavelength of 280 nm. ]
Condition 3
1.05 ≦ Δn _y (400) / Δn _x (400) ≦ 2.15
Wherein, [Delta] n _y (400) is the slope of the fast-axis refractive index at a wavelength of 400nm near represented by _{_{Δn y (400) = (n}} y (410) -n y (400)) . n _y (410) is the refractive index in the fast axis direction at a wavelength of 410 nm, and n _y (400) is the refractive index in the fast axis direction at a wavelength of 400 nm. Δn _x (400) is a refractive index gradient in the slow axis direction in the vicinity of a wavelength of 400 nm, and is represented by Δn _x (400) = (n _x (410) −n _x (400)). n _x (410) is a refractive index in the slow axis direction at a wavelength of _410nm, n x (400) is the refractive index in the slow axis direction at a wavelength of 400 nm. ]
2. The film is produced through a stretching / shrinking process in which the film is stretched in the slow axis direction and contracted in the fast axis direction, and the ratio of the shrinkage ratio in the fast axis direction to the stretch ratio in the slow axis direction (shrinkage ratio / stretch ratio) is The λ / 4 retardation film as described in item 1 above, which falls within a range of 0.05 to 0.70.

3. 3. The λ / 4 retardation film according to

item

1 or 2, wherein the slow axis direction is oriented within an angle range of 30 to 60 ° with respect to the transport direction.

4. 4. The λ / 4 retardation film according to any one of items 1 to 3, wherein the film thickness is in the range of 30 to 80 μm.

5. It comprises a circularly polarizing plate having the λ / 4 retardation film according to any one of items 1 to 4 and an organic electroluminescence element, and has a screen size of 20 inches or more. Organic electroluminescence image display device.

That is, in the λ / 4 retardation film of the present invention, the refractive index n _y (280) in the fast axis direction in the ultraviolet region 280 nm is set equal to or higher than the refractive index n _x (280) in the slow axis direction. Accordingly, it was found that the inclination of the forward wavelength dispersion of the refractive index n _y in the fast axis direction in a range of 400 ~ 700 nm in the visible light region becomes steep, it is effective in expressing the targeted effects of the present invention Is.

In the inventions described in

Patent Documents

3 and 4 described above, the reason why a sufficient retardation cannot be expressed is that the main chain direction of the compound constituting the retardation film is a matrix resin. It was presumed to be caused by the fact that it did not coincide with the main chain direction.

As shown in FIG. 1A, when the film is stretched, the main chain 1 of the matrix resin (for example, a cellulose ester resin or the like) is substantially oriented in the stretching direction 2, whereas the low molecular weight having the side chain 5 used as an additive. In the compound 3, the average direction 6 of the main chain 4 and the side chain 5 is oriented in the stretching direction 2. As a result, since the main chain 4 and the side chain 5 constituting the compound 3 and the main chain 1 and the side chain of the matrix resin are displaced in the orientation direction, a sufficient retardation effect is not exhibited. Further, when a highly oriented compound having no side chain as disclosed in Patent Document 5 is used in combination, the thickness direction retardation Rt becomes high.

As a result of intensive studies on the above problems, the present inventors, as shown in FIG. 1B, set the orientation of the compound 3 deviated from the main chain 1 of the matrix resin in the direction perpendicular to the stretching direction in the stretching step ( The direction of orientation of the main chain 4 of the compound 3 is rotated 8 by applying a contraction treatment for shrinking 7 in the direction of the phase advance axis), whereby the orientation direction of the main axis 4 of the compound 3 is changed to the orientation direction of the main chain 1 of the matrix resin. The adjustment means which can be adjusted to is found.

As a specific means of this adjustment method, the ratio between the draw ratio and the shrinkage ratio is an important factor, and a method in which the shrinkage ratio / stretch ratio is in the range of 0.05 to 0.70 is preferable. However, the shrinkage ratio / stretch ratio is more preferably in the range of 0.10 to 0.30.

Therefore, according to the conditions defined in claim 2, as shown in FIG. 1A, the main axis 4 of the compound 3 can be aligned with the main chain 1 of the matrix resin, and the side chain 5 of the compound 3 is also in the fast axis direction of the film. The refractive index ny280 in the fast axis direction in the ultraviolet region 280 nm can be increased by incorporating a high refractive index molecule in the side chain 5 of this compound 3, and as a result, ny forward wavelength dispersion in the visible light region The slope of can be made steep.

However, even if the film is shrunk in a state containing a compound having no side chain as described in Patent Document 5, the above effect is not exhibited. This is presumed to be because the orientation of the compound having no side chain shifts from the main chain of the matrix resin.

In the λ / 4 retardation film of the present invention, when controlling the orientation of the compound by stretching and shrinking, the matrix resin is stretched obliquely while shrinking, for example, simultaneously controlling the slow axis of the cellulose acetate resin. Therefore, the effect of the present invention can be further expressed.

In the λ / 4 retardation film of the present invention according to claim 4, when the film thickness of the λ / 4 retardation film is set within the range specified above, in particular, when the organic electroluminescence image display device is provided. The display performance in color display can be further improved by thinning the film.

In the organic electroluminescence image display device according to claim 5, comprising a circularly polarizing plate having the λ / 4 retardation film of the present invention and an organic electroluminescence element, and having a screen size of 20 inches or more, An organic electroluminescence image display device excellent in image display performance such as front and oblique visibility can be realized.

By the above means of the present invention, a wide-band λ / 4 retardation film having high retardation development, a thin film with reverse wavelength dispersion characteristics and a reduced retardation in the thickness direction, and image display performance ( It is possible to provide an organic electroluminescence image display device excellent in visibility in front and oblique directions.

Schematic explaining an example of the state of alignment between matrix resin and compound (comparative example) Schematic explaining an example of the method of the present invention for adjusting the orientation of the matrix resin and the compound by the contraction means The schematic diagram explaining the shrinkage ratio in diagonal stretch. Schematic which showed an example of the rail pattern of the diagonal stretcher applicable to the manufacturing method of (lambda) / 4 phase difference film of this invention Schematic which shows the example of extending | stretching diagonally, after extending from a long film original fabric roll in an example of the manufacturing method which concerns on embodiment of this invention. Schematic which shows the other example extended | stretched diagonally, after paying out from a long film original fabric roll in an example of the manufacturing method which concerns on embodiment of this invention. Schematic which shows the other example extended | stretched diagonally, after paying out from a long film original fabric roll in an example of the manufacturing method which concerns on embodiment of this invention. Schematic which shows the example of extending continuously diagonally, without winding up a long film original fabric in an example of the manufacturing method which concerns on embodiment of this invention. Schematic which shows the other example extended continuously diagonally, without winding up a long film original fabric in an example of the manufacturing method which concerns on embodiment of this invention. Schematic sectional view showing an example of the configuration of the organic electroluminescence image display device of the present invention

In the λ / 4 retardation film of the present invention, the thickness direction retardation Rt (550) at a wavelength of 550 nm is 150 nm or less, and the wavelength dispersion characteristic of the in-plane retardation Ro is 0.72 ≦ Ro (condition 1). 450) / Ro (550) ≦ 0.96 and 0.83 ≦ Ro (550) / Ro (650) ≦ 0.98. As condition 2, the in-plane refractive index is 1.000 ≦ n. _y (280) / n _x (280) ≦ 3.500, and as Condition 3, 1.05 ≦ Δn _y (400) / Δn _x (400) ≦ 2.15 Thus, it is possible to realize a broadband λ / 4 retardation film having high retardation development, a thin film with reverse wavelength dispersion characteristics, and a reduced retardation in the thickness direction. This feature is a technical feature common to the inventions according to claims 1 to 5.

Note that Ro (450) is an in-plane phase difference at a wavelength of 450 nm, Ro (550) is an in-plane phase difference at a wavelength of 550 nm, and Ro (650) is an in-plane phase difference at a wavelength of 650 nm. N _y (280) is the refractive index in the fast axis direction at a wavelength of 280 nm, and n _x (280) is the refractive index in the slow axis direction at a wavelength of 280 nm. Further, the [Delta] n _y (400) is the slope of the fast-axis refractive index at a wavelength of 400nm near represented by _{_{Δn y (400) = (n}} y (410) -n y (400)). n _y (410) is the refractive index in the fast axis direction at a wavelength of 410 nm, and n _y (400) is the refractive index in the fast axis direction at a wavelength of 400 nm. Δn _x (400) is a refractive index gradient in the slow axis direction in the vicinity of a wavelength of 400 nm, and is represented by Δn _x (400) = (n _x (410) −n _x (400)). n _x (410) is a refractive index in the slow axis direction at a wavelength of _410nm, n x (400) is the refractive index in the slow axis direction at a wavelength of 400 nm.

In the λ / 4 retardation film of the present invention, the means for realizing the range defined by the above conditions 1 to 3 is not particularly limited. However, the stretching conditions (for example, stretching temperature (° C.), stretch ratio ( %), Bending angle in oblique stretching (°), shrinkage rate (%), shrinkage rate / ratio of stretch ratio, etc.), film thickness, or types and additions of optical performance modifiers represented by general formula (A) By appropriately adjusting the amount, Ro (450) / Ro (550), Ro (550) / Ro (650), which are chromatic dispersion characteristics, and an in-plane refractive index ratio n _y (280) / n _x in the ultraviolet region. Each characteristic value of (280) and inverse wavelength dispersion Δn _y (400) / Δn _x (400) can be adjusted to a desired range.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In the following description, “˜” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

<< λ / 4 retardation film >>
The λ / 4 retardation film of the present invention refers to a film having a function of converting linearly polarized light having a specific wavelength into circularly polarized light or converting circularly polarized light into linearly polarized light. The λ / 4 retardation film has an in-plane retardation value Ro of about ¼ with respect to a predetermined wavelength of light (usually in the visible light region).

In the λ / 4 retardation film of the present invention, Ro (550) measured at a wavelength of 550 nm is preferably in the range of 120 to 180 nm, more preferably in the range of 120 to 160 nm, and 130 to 150 nm. It is particularly preferable that it is within the range.

Since the λ / 4 retardation film of the present invention obtains almost perfect circularly polarized light in the visible light wavelength range, a retardation plate having a phase difference of approximately ¼ of the wavelength in the visible light wavelength range ( A broadband λ / 4 retardation film which is a film) is preferable.

In the present invention, “a phase difference of approximately ¼ in the wavelength range of visible light” means an inverse wavelength dispersion characteristic having a larger phase difference value as the wavelength is longer in the wavelength range of 400 to 700 nm.

In the λ / 4 retardation film of the present invention, the in-plane retardation value Ro is represented by the following formula (i), and Ro (measured at a wavelength of 450 nm with respect to the in-plane retardation value Ro (550) measured at a wavelength of 550 nm). 450) (Ro (450) / Ro (550)) is in the range of 0.72 to 0.96, but is in the range of 0.75 to 0.92. Preferably, it is in the range of 0.78 to 0.88.

The ratio of the in-plane retardation value Ro (550) measured at a wavelength of 550 nm to the in-plane retardation value Ro (650) measured at a wavelength of 650 nm (Ro (550) / Ro (650)) is 0.83 to Although it is within the range of 0.98, the balance with the Ro (450) / Ro (550) is important, and Ro (450) / Ro (550) is 0.72 to 0.96. Ro (550) / Ro (650) is preferably in the range of 0.87 to 0.98, and Ro (450) / Ro (550) is in the range of 0.75 to 0. In the range of .92, Ro (550) / Ro (650) is preferably in the range of 0.88 to 0.96, and Ro (450) / Ro (550) is preferably 0.78 to 0.98. If it is in the range of 0.88, Ro (55 ) / Ro (650) is more preferably in the range of 0.90 to 0.94.

Formula (i)
Ro = (n _x −n _y ) × d
Rt = [(n _x + _ny ) / 2−n _z ] × d
In the above formula _{_{(i), n x, n}} y and _{n z} are, 23 ° C., respectively, were measured in an environment of 55% RH, the refractive index at a wavelength of 450 nm, 550 nm, or 650 nm, the surface of the _{n x} the film a maximum refractive index of the inner (refractive index in a slow axis direction), n _y is a refractive index in a direction perpendicular to the slow axis in the film plane, n _z is the vertical thickness direction in the film plane Where d is the film thickness (nm).

In order to increase the in-plane retardation value Ro (550), it is a simple means to increase the film thickness d, but it is economical, the thickness of the image display device is increased, and the light extraction efficiency is decreased due to the decrease in transmittance. From the viewpoint of

In the λ / 4 retardation film of the present invention, the film thickness d is generally in the range of 20 to 100 μm, preferably in the range of 30 to 80 μm, and preferably in the range of 30 to 65 μm. It is particularly preferable from the viewpoint of further manifesting the effects of the invention.

In the present invention, the in-plane retardation value Ro can be calculated by measuring the birefringence at each wavelength in an environment of 23 ° C. and 55% RH using an Axoscan manufactured by Axometers. it can.

A circularly polarizing plate is obtained by laminating so that the angle between the slow axis of the λ / 4 retardation film and the transmission axis of the polarizer described later is substantially 45 °.

In the present invention, “substantially 45 °” means within a range of 40 to 50 °. The angle between the in-plane slow axis of the λ / 4 retardation film of the present invention and the transmission axis of the polarizer is more preferably in the range of 41 to 49 °, and in the range of 42 to 48 °. More preferably, it is more preferably in the range of 43 to 47 °, and most preferably in the range of 44 to 46 °.

(Optical performance modifier)
In the λ / 4 retardation film of the present invention, a compound represented by the following general formula (A) is used as an optical performance modifier as one of means for achieving the above-mentioned conditions 1 to 3 defined in the present invention. Is preferred.

By using the compound represented by the following general formula (A), the refractive index nx in the slow axis direction can be increased, and the fast axis direction refractive index ny in the ultraviolet region can be increased to increase the fast axis. The forward wavelength dispersion slope of the directional refractive index ny can be made steep.

In the general formula (A), L ₁ and L ₂ each independently represent a single bond or a divalent linking group. R ₁ , R ₂ and R ₃ each independently represent a substituent. n represents an integer of 0 to 2. Wa and Wb each represent a hydrogen atom or a substituent, (I) Wa and Wb may be bonded to each other to form a ring, and (II) at least one of Wa and Wb may have a ring structure Or (III) at least one of Wa and Wb may be an alkenyl group or an alkynyl group.

In the general formula (A), L ₁ and L ₂ each independently represent a single bond or a divalent linking group, and L ₁ and L ₂ are preferably O, COO, and OCO.

R ₁ , R ₂ and R ₃ each independently represent a substituent. Specific examples of the substituent represented by R ₁ , R ₂ and R ₃ include a halogen atom (eg, fluorine atom, chlorine atom, bromine atom, iodine atom), an alkyl group (eg, methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group, etc.), cycloalkyl group (for example, cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), alkenyl group ( For example, vinyl group, allyl group, etc.), cycloalkenyl group (eg, 2-cyclopenten-1-yl, 2-cyclohexen-1-yl group, etc.), alkynyl group (eg, ethynyl group, propargyl group, etc.), aryl group (Eg, phenyl group, p-tolyl group, naphthyl group, etc.), heterocyclic group (eg, 2-furyl group, 2-thienyl group, 2 -Pyrimidinyl group, 2-benzothiazolyl group, etc.), cyano group, hydroxy group, nitro group, carboxy group, alkoxy group (for example, methoxy group, ethoxy group, isopropoxy group, tert-butoxy group, n-octyloxy group, 2 -Methoxyethoxy group), aryloxy group (eg, phenoxy group, 2-methylphenoxy group, 4-tert-butylphenoxy group, 3-nitrophenoxy group, 2-tetradecanoylaminophenoxy group, etc.), acyloxy group ( For example, formyloxy group, acetyloxy group, pivaloyloxy group, stearoyloxy group, benzoyloxy group, p-methoxyphenylcarbonyloxy group, etc.), amino group (for example, amino group, methylamino group, dimethylamino group, anilino group, N-methyl-anilino group, diphe ), Acylamino groups (for example, formylamino group, acetylamino group, pivaloylamino group, lauroylamino group, benzoylamino group, etc.), alkyl and arylsulfonylamino groups (for example, methylsulfonylamino group, butylsulfonylamino group, Phenylsulfonylamino group, 2,3,5-trichlorophenylsulfonylamino group, p-methylphenylsulfonylamino group, etc.), mercapto group, alkylthio group (eg, methylthio group, ethylthio group, n-hexadecylthio group, etc.), arylthio group (Eg, phenylthio group, p-chlorophenylthio group, m-methoxyphenylthio group, etc.), sulfamoyl group (eg, N-ethylsulfamoyl group, N- (3-dodecyloxypropyl) sulfamoyl group, N, N Dimethylsulfamoyl group, N-acetylsulfamoyl group, N-benzoylsulfamoyl group, N- (N'-phenylcarbamoyl) sulfamoyl group, etc.), sulfo group, acyl group (for example, acetyl group, pivaloyl) Benzoyl group, etc.), carbamoyl group (carbamoyl group, N-methylcarbamoyl group, N, N-dimethylcarbamoyl group, N, N-di-n-octylcarbamoyl group, N- (methylsulfonyl) carbamoyl group, etc.) .

R ₁ and R ₂ are preferably a substituted or unsubstituted benzene ring or a substituted or unsubstituted cyclohexane ring. More preferably, they are a benzene ring having a substituent and a cyclohexane ring having a substituent, and the benzene ring having a substituent at the 4-position is a compound of the general formula (A) in the slow axis direction of the λ / 4 retardation film. This is particularly preferred from the viewpoint of orienting the main chain and increasing the slow axis direction refractive index nx.

R ₃ is preferably a hydrogen atom, halogen atom, alkyl group, alkenyl group, aryl group, heterocyclic group, hydroxyl group, carboxyl group, alkoxy group, aryloxy group, acyloxy group, cyano group, amino group, More preferably, they are a hydrogen atom, a halogen atom, an alkyl group, a cyano group, and an alkoxy group.

Wa and Wb each independently represent a hydrogen atom or a substituent, and Wa and Wb may be bonded to each other to form a ring, or at least one of Wa and Wb may have a ring structure, or Wa and Wb At least one may be an alkenyl group or an alkynyl group.

Specific examples of the substituent represented by Wa and Wb include halogen atoms (eg, fluorine atom, chlorine atom, bromine atom, iodine atom), alkyl groups (eg, methyl group, ethyl group, n-propyl group, Isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group, etc.), cycloalkyl group (for example, cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), alkenyl group (for example, vinyl group, Allyl group), cycloalkenyl group (eg 2-cyclopenten-1-yl, 2-cyclohexen-1-yl group, etc.), alkynyl group (eg ethynyl group, propargyl group etc.), aryl group (eg phenyl group) , P-tolyl group, naphthyl group, etc.), heterocyclic group (for example, 2-furyl group, 2-thienyl group, 2-pyryl group) Dinyl group, 2-benzothiazolyl group, etc.), cyano group, hydroxyl group, nitro group, carboxyl group, alkoxy group (for example, methoxy group, ethoxy group, isopropoxy group, tert-butoxy group, n-octyloxy group, 2- Methoxyethoxy group), aryloxy group (for example, phenoxy group, 2-methylphenoxy group, 4-tert-butylphenoxy group, 3-nitrophenoxy group, 2-tetradecanoylaminophenoxy group, etc.), acyloxy group (for example, , Formyloxy group, acetyloxy group, pivaloyloxy group, stearoyloxy group, benzoyloxy group, p-methoxyphenylcarbonyloxy group, etc.), amino group (for example, amino group, methylamino group, dimethylamino group, anilino group, N -Methyl-anilino group, diphenyl Amino group, etc.), acylamino group (eg, formylamino group, acetylamino group, pivaloylamino group, lauroylamino group, benzoylamino group, etc.), alkyl and arylsulfonylamino groups (eg, methylsulfonylamino group, butylsulfonylamino group, Phenylsulfonylamino group, 2,3,5-trichlorophenylsulfonylamino group, p-methylphenylsulfonylamino group, etc.), mercapto group, alkylthio group (eg, methylthio group, ethylthio group, n-hexadecylthio group, etc.), arylthio group (Eg, phenylthio group, p-chlorophenylthio group, m-methoxyphenylthio group, etc.), sulfamoyl group (eg, N-ethylsulfamoyl group, N- (3-dodecyloxypropyl) sulfamoyl group, N, N— The Methylsulfamoyl group, N-acetylsulfamoyl group, N-benzoylsulfamoyl group, N- (N′phenylcarbamoyl) sulfamoyl group, etc.), sulfo group, acyl group (for example, acetyl group pivaloylbenzoyl group) ), Carbamoyl groups (eg, carbamoyl group, N-methylcarbamoyl group, N, N-dimethylcarbamoyl group, N, N-di-n-octylcarbamoyl group, N- (methylsulfonyl) carbamoyl group, etc.) Can do.

The above substituents may be further substituted with the above groups.

When Wa and Wb are bonded to each other to form a ring, the following structures may be mentioned.

In the formula, R ₄ , R ₅ and R ₆ each represent a hydrogen atom or a substituent, and examples of the substituent include the same groups as the specific examples of the substituent represented by R ₁ , R ₂ and R ₃ above. be able to.

In addition, when one of Wa and Wb is a hydrogen atom and the other has a ring-setting group, the following structures are exemplified.

In the formula, R _ii and R _iii may include the same groups as the specific examples of the substituents represented by R ₁ , R ₂ and R ₃ , respectively.

In the general formula (A), when Wa and Wb are bonded to each other to form a ring, it is preferably a nitrogen-containing 5-membered ring or a sulfur-containing 5-membered ring, for example, represented by the following general formula (1) A compound can be mentioned.

In the general formula (1), A ₁ and A ₂ each independently represent O, S, NR _X (R _X represents a hydrogen atom or a substituent) or CO. Examples of the substituent represented by R _X has the same meaning as specific examples of substituents represented by the Wa and Wb. R _X is preferably a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group.

In the general formula (1), X is a nonmetallic atom belonging to Groups 14 to 16 after the third period, or a substituent containing a nonmetallic atom belonging to Groups 14 to 16 or a conjugated system after the third period. The λ / 4 retardation film is preferable for increasing the refractive index in the ultraviolet region of the refractive index ny in the fast axis direction.

X is preferably O, S, NRc, or C (Rd) Re. Here, Rc, Rd and Re each represent a substituent, and examples thereof include groups similar to the specific examples of the substituents represented by Wa and Wb.

L

_{_{_{_1, L 2, R 1, R}}} 2, R 3, and n is an _L 1 in the general formula (A), _{_{_{respectively, L 2, R 1, R}}} 2, R 3, and the n synonymous.

Specific examples of the compound represented by the general formula (A) are shown below, but the compound represented by the general formula (A) that can be used in the present invention is not limited by the following specific examples. Absent.

In addition, the synthesis of the compound represented by the general formula (A) can be performed by applying a known synthesis method. Specifically, synthesis may be performed with reference to the methods described in Journal of Chemical Crystallography (1997); 27 (9); 512-526), JP 2010-31223 A, JP 2008-107767 A, and the like. it can.

[Cellulose acylate]
In the λ / 4 retardation film of the present invention, it is preferable to use a thermoplastic resin as the matrix resin, and it is more preferable that the main component is cellulose acylate. The “main component” in the present invention means that 70% by mass or more of the thermoplastic resin component constituting the λ / 4 retardation film is composed of cellulose acylate.

In the cellulose acylate according to the present invention, the average acyl group substitution degree is preferably in the range of 2.0 to 3.0, more preferably in the range of 2.2 to 2.8, and still more preferably. Is in the range of 2.4 to 2.7. The average degree of acyl group substitution here means the average value of the number of esterified hydroxy groups (hydroxyl groups) out of the three hydroxy groups (hydroxyl groups) of each anhydroglucose constituting cellulose. It takes a value in the range of ~ 3.0.

When the average acyl group substitution degree of cellulose acylate is low, the in-plane retardation Ro developability is high, but the Ro wavelength dispersion characteristic becomes almost flat, and conversely, when the average acyl group substitution degree is high, Ro While the expression is reduced, the wavelength dispersion characteristic is more reverse dispersion.

In the present invention, the portion not substituted with an acyl group usually exists as a hydroxy group (hydroxyl group). These cellulose acylates can be synthesized by a known method.

The substitution degree of the acyl group is a value determined according to the method specified in ASTM-D817-96 (testing method for cellulose acylate, etc.).

The number average molecular weight (Mn) of the cellulose acylate according to the present invention is preferably in the range of 30,000 to 300,000 from the viewpoint of increasing the mechanical strength of the obtained λ / 4 retardation film. Furthermore, those in the range of 50,000 to 200,000 are preferably used.

The ratio Mw / Mn of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the cellulose acylate is preferably in the range of 1.4 to 3.0.

The weight average molecular weight Mw and the number average molecular weight Mn of cellulose acylate can be determined by measuring each using gel permeation chromatography (GPC).

An example of specific measurement conditions is shown below.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three columns manufactured by Showa Denko KK)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: A standard polystyrene STK standard polystyrene (manufactured by Tosoh Co., Ltd.) and a calibration curve with 13 samples having a Mw in the range of 1,000,000 to 500 was used. Thirteen samples are used at approximately equal intervals.

For the λ / 4 retardation film of the present invention, a thermoplastic resin other than cellulose acylate may be used.

The term “thermoplastic resin” as used in the present invention refers to a resin that has the characteristics that it becomes soft when heated to the glass transition temperature or melting point and can be molded into the desired shape.

Examples of the thermoplastic resin include polyethylene (PE), high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), polypropylene (PP), polyvinyl chloride (PVC), and polyvinylidene chloride ( PVDC), polystyrene (PS), polyvinyl acetate (PVAc), Teflon (registered trademark) (polytetrafluoroethylene, PTFE), ABS resin (acrylonitrile butadiene styrene copolymer), AS resin (acrylonitrile styrene copolymer), Acrylic resin (PMMA) or the like can be used.

When strength and resistance to breakage are particularly required, for example, polyamide (PA), nylon, polyacetal (POM), polycarbonate (PC), modified polyphenylene ether (m-PPE, modified PPE, PPO), poly Butylene terephthalate (PBT), polyethylene terephthalate (PET), glass fiber reinforced polyethylene terephthalate (GF-PET), cyclic polyolefin (COP), and the like can be used.

Furthermore, when high heat distortion temperature and durability that can be used for a long time are required, polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polysulfone (PSF), polyethersulfone (PES), amorphous Polyarylate, liquid crystal polymer, polyetheretherketone (PEEK), thermoplastic polyimide (PI), polyamideimide (PAI) and the like can be used.

In addition, it is also possible to use two or more types in combination of the types and molecular weights of the thermoplastic resin in accordance with the application of the present invention.

[Other Additives for λ / 4 Retardation Film]
(Organic solvent)
Organic solvents useful for preparing cellulose acylate solution or dope by dissolving cellulose acylate mainly include chlorinated organic solvents and non-chlorinated organic solvents.

Examples of the chlorinated organic solvent include methylene chloride (methylene chloride). However, application of non-chlorine organic solvents has been actively studied from the viewpoint of recent environmental problems. Examples of the non-chlorine organic solvent include methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1, Examples include 1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, and nitroethane.

When these organic solvents are used for cellulose acylate, a dissolution method at normal temperature can be used, but a known dissolution method such as a high-temperature dissolution method, a cooling dissolution method, or a high-pressure dissolution method should be used. However, it is preferable from the viewpoint of reducing insoluble matter. For the cellulose acylate, methylene chloride can be used, but methyl acetate, ethyl acetate, and acetone are preferably used, and among them, methyl acetate is particularly preferable.

In the present invention, an organic solvent having good solubility in the cellulose acylate is referred to as a good solvent, and has a main effect on dissolution, and an organic solvent used in a large amount among them is a main (organic) solvent or It is called the main (organic) solvent.

The dope used for forming the λ / 4 retardation film of the present invention preferably contains an alcohol having 1 to 4 carbon atoms in the range of 1 to 40% by mass in addition to the organic solvent. . These alcohols, after casting the dope on a metal support, start to evaporate the organic solvent, and when the relative proportion of the alcohol component increases, the dope film (web) gels, making the web strong and supporting the metal It can act as a gelling solvent that makes it easy to peel off from the body. When the proportion of these alcohols is low, it also has a role of promoting dissolution of cellulose acylate, a non-chlorine organic solvent.

Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Of these, it is preferable to use ethanol from the viewpoints of excellent dope stability, relatively low boiling point, and good drying properties. These alcohols are categorized as poor solvents because they are not soluble in cellulose acylate alone.

The concentration of cellulose acylate in the dope is preferably in the range of 15 to 30% by mass, and the dope viscosity can be adjusted in the range of 100 to 500 Pa · s to obtain excellent film surface quality. It is preferable from the viewpoint.

Examples of additives that can be added to the dope include plasticizers, ultraviolet absorbers, antioxidants, deterioration inhibitors, peeling aids, surfactants, dyes, and fine particles. In the present invention, additives other than fine particles may be added when preparing the cellulose acylate solution, or may be added when preparing the fine particle dispersion. It is preferable to add a plasticizer, an antioxidant, an ultraviolet absorber, or the like that imparts heat and moisture resistance to the polarizing plate used in the image display device.

(Plasticizer)
The λ / 4 retardation film of the present invention preferably contains a plasticizer. In particular, the λ / 4 retardation film of the present invention preferably contains a polyester plasticizer having a number average molecular weight (Mn) in the range of 1000 to 10,000.

The specific structure of the polyester plasticizer is not particularly limited, and a polyester plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be used.

Examples of the polyester plasticizer include a polyester plasticizer represented by the following general formula (a).

Formula (a)
B- (GA) _n -GB
In the general formula (a), B represents a benzene monocarboxylic acid group or an aliphatic monocarboxylic acid group, and G represents an alkylene glycol group having 2 to 12 carbon atoms, an aryl glycol group having 6 to 12 carbon atoms, or 4 carbon atoms. Represents an oxyalkylene glycol group having ˜12, A represents an alkylene dicarboxylic acid group having 4 to 12 carbon atoms or an aryl dicarboxylic acid group having 6 to 12 carbon atoms, and n represents an integer of 1 or more.

The polyester plasticizer represented by the general formula (a) is obtained by the same reaction as a normal polyester plasticizer.

Examples of the benzene monocarboxylic acid component of the polyester plasticizer include benzoic acid, paratertiary butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, normal propylbenzoic acid, and aminobenzoic acid. , Acetoxybenzoic acid and the like, each of which can be used alone or as a mixture of two or more.

The aliphatic monocarboxylic acid component of the polyester plasticizer is preferably an aliphatic monocarboxylic acid having 3 or less carbon atoms, more preferably acetic acid, propionic acid or butanoic acid, and most preferably acetic acid. When the number of carbon atoms of the monocarboxylic acids used at both ends of the polycondensed ester is 3 or less, the heat loss of the compound does not increase, and no surface failure occurs.

Further, a monocarboxylic acid having a cycloaliphatic having 3 to 8 carbon atoms is preferred, a monocarboxylic acid having a cycloaliphatic having 6 carbons is more preferred, and cyclohexanecarboxylic acid and 4-methyl-cyclohexanecarboxylic acid are most preferred. . When the cycloaliphatic carbon number of the monocarboxylic acid used at both ends of the polycondensed ester is in the range of 3 to 8, the heat loss of the compound does not increase, and it is preferable in that a surface failure does not occur.

Examples of the alkylene glycol component having 2 to 12 carbon atoms of the polyester plasticizer include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, and 1,3-butanediol. 1,2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol) 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3 -Methyl-1,5-pentanediol-1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanedio And 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like. Can be used singly or as a mixture of two or more. Among these, an alkylene glycol having 2 to 12 carbon atoms is particularly preferable in terms of excellent compatibility with cellulose acylate, more preferably an alkylene glycol having 2 to 6 carbon atoms, and further preferably a carbon number. Is an alkylene glycol of 2 to 4.

Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the polyester plasticizer include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. It can be used alone or as a mixture of two or more.

Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the polyester plasticizer include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, and the like. Each of these may be used alone or as a mixture of two or more. Further, examples of the arylene dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, and the like.

The number average molecular weight of the polyester plasticizer preferably used for the λ / 4 retardation film of the present invention is in the range of 200 to 10,000, more preferably in the range of 300 to 3000.

The acid value of the polyester plasticizer is preferably 0.5 mgKOH / g or less, more preferably 0.3 mgKOH / g or less. The hydroxy group value of the polyester plasticizer is preferably 25 mgKOH / g or less, more preferably 15 mgKOH / g or less. In addition, an acid value means the milligram number of potassium hydroxide required in order to neutralize the acid (carboxyl group which exists in a sample) contained in 1g of samples. The acid value is measured according to JIS K0070.

In addition to the polyester plasticizer described above, various conventionally known plasticizers may be applied to the λ / 4 retardation film of the present invention.

Examples of such conventionally known plasticizers include polyhydric alcohol ester plasticizers, glycolate plasticizers, phthalate ester plasticizers, citrate ester plasticizers, fatty acid ester plasticizers, and phosphate esters. Examples thereof include a plasticizer, a polycarboxylic acid ester plasticizer, and an acrylic plasticizer.

(Sugar ester compound)
The λ / 4 retardation film of the present invention includes cellulose having at least one pyranose structure or furanose structure in the range of 1 to 12, and all or part of the hydroxy groups of the structure are esterified. It is preferable to include an ester compound excluding the ester. In the present invention, ester compounds excluding the cellulose ester having such a structure are collectively referred to as “sugar ester compounds”.

Examples of sugar ester compounds include the following, but the present invention is not limited to these.

Examples of the compound (saccharide) having a pyranose structure or furanose structure include glucose, galactose, mannose, fructose, xylose, or arabinose, lactose, sucrose, nystose, 1F-fructosylnystose, stachyose, maltitol, lactitol, lactulose , Cellobiose, maltose, cellotriose, maltotriose, raffinose, and kestose.

Other examples include gentiobiose, gentiotriose, gentiotetraose, xylotriose, and galactosyl sucrose.

Among these compounds, compounds having both a pyranose structure and a furanose structure are particularly preferable. For example, sucrose, kestose, nystose, 1F-fructosyl nystose, stachyose and the like are preferable, and sucrose is more preferable.

The monocarboxylic acid used for esterifying all or part of the hydroxy group of the compound (sugar) having the above-described pyranose structure or furanose structure when preparing the sugar ester compound is not particularly limited and is known. Aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, aromatic monocarboxylic acids, and the like can be used. The carboxylic acid used may be one kind alone or a mixture of two or more kinds.

Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid , Saturated fatty acids such as tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid; Examples thereof include unsaturated fatty acids such as undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid and octenoic acid.

Examples of preferable alicyclic monocarboxylic acids include acetic acid, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof.

Examples of preferred aromatic monocarboxylic acids include aromatic monocarboxylic acids having an alkyl group or alkoxy group introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, cinnamic acid, benzylic acid, biphenylcarboxylic acid, and naphthalene. Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as carboxylic acid and tetralincarboxylic acid, or derivatives thereof. More specifically, xylyl acid, hemelic acid, mesitylene acid, prenylic acid, γ-isodryl Acid, duryl acid, mesitoic acid, α-isoduric acid, cumic acid, α-toluic acid, hydroatropic acid, atropaic acid, hydrocinnamic acid, salicylic acid, o-anisic acid, m-anisic acid, p-anisic acid, creosote Acid, o-homosalicylic acid, m-homosalicylic acid, p-homosalicylic acid, o-pyrocatechuic acid, β Resorcylic acid, vanillic acid, isovanillic acid, veratromic acid, o-veratrumic acid, gallic acid, asaronic acid, mandelic acid, homoanisic acid, homovanillic acid, homoveratormic acid, o-homoveratormic acid, phthalonic acid, p-coumaric acid However, benzoic acid is particularly preferable.

In the λ / 4 retardation film of the present invention, from the viewpoint of stabilizing the display quality by suppressing the fluctuation of the retardation value, the sugar ester compound described above is based on 100% by mass of the λ / 4 retardation film. It is preferably contained within the range of 1 to 30% by mass, and more preferably within the range of 5 to 30% by mass. Within this range, the above-described excellent effects are exhibited, and there is no bleed out and the like.

(UV absorber)
The λ / 4 retardation film of the present invention or the protective film constituting the circularly polarizing plate described later preferably contains an ultraviolet absorber.

Examples of the ultraviolet absorber used include benzotriazole-based, 2-hydroxybenzophenone-based or salicylic acid phenyl ester-based ones. For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3 Triazoles such as 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone And benzophenones.

Of the UV absorbers, UV absorbers with a molecular weight of 400 or more are less likely to volatilize at high boiling points and are difficult to disperse even during high temperature molding, so that light resistance is effectively improved with a relatively small amount of addition. Can do.

Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- ( Benzotriazoles such as 1,1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, Hindered amines such as bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and further 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butyl Bis (1,2,2,6,6-pentamethyl-4-piperidyl) malonate, 1- [2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy Cis] ethyl] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine The hybrid type | system | group which has the structure of a hindered amine is mentioned, These can be used individually or in combination of 2 or more types. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

As these ultraviolet absorbers, commercially available products may be used. For example, TINUBIN 109, TINUVIN 171, TINUVIN 234, TINUVIN 326, TINUVIN 327, TINUVIN 328, TINUVIN 928, etc. manufactured by BASF Japan Ltd. are absorbed. An agent can be preferably used.

(Other additives)
Furthermore, various antioxidants can also be added to the λ / 4 retardation film in order to improve the thermal decomposability and thermal colorability during molding. In addition, an antistatic agent can be added to impart antistatic performance to the λ / 4 retardation film.

<Phosphorus flame retardant>
For the λ / 4 retardation film of the present invention, a flame retardant acrylic resin composition containing a phosphorus flame retardant may be used.

Phosphorus flame retardants applicable to the present invention include red phosphorus, triaryl phosphate ester, diaryl phosphate ester, monoaryl phosphate ester, aryl phosphonate compound, aryl phosphine oxide compound, condensed aryl phosphate ester, halogenated Examples thereof include one or a mixture of two or more selected from alkyl phosphates, halogen-containing condensed phosphates, halogen-containing condensed phosphonates, and halogen-containing phosphites.

Specific examples include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl) Examples thereof include phosphate and tris (tribromoneopentyl) phosphate.

<Matting agent>
In addition, the λ / 4 retardation film of the present invention has, for example, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydration from the viewpoint of improving handling properties. It is preferable to include a matting agent such as inorganic fine particles such as calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate, and a crosslinked polymer. Among these, silicon dioxide is preferably used because it can reduce the haze of the film.

The primary average particle diameter of the fine particles is preferably 20 nm or less, more preferably in the range of 5 to 16 nm, and particularly preferably in the range of 5 to 12 nm.

[Formation method of λ / 4 retardation film]
The λ / 4 retardation film of the present invention can be formed according to a known method. Hereinafter, typical solution casting methods and melt casting methods will be described.

(Solution casting method)
The λ / 4 retardation film of the present invention can be produced by a solution casting method. In the solution casting method, a cellulose acylate which is a thermoplastic resin and additives are dissolved in an organic solvent by heating to prepare a dope, and the prepared dope is placed on a belt-shaped or drum-shaped metal support. Casting process for casting, drying process for drying the cast dope as a web, peeling process for peeling the web from the metal support, stretching process for stretching or shrinking the peeled web, further drying process, winding of the finished film Manufactured through a removal process.

The concentration of cellulose acylate in the dope is preferably higher because the drying load after casting on a metal support can be reduced, but if the concentration of cellulose acylate is too high, the load during filtration increases. Filtration accuracy deteriorates. The concentration that achieves both of these is preferably in the range of 10 to 35% by mass, and more preferably in the range of 15 to 25% by mass. The metal support in the casting (casting) step preferably has a mirror-finished surface, and as the metal support, a stainless steel belt or a drum whose surface is plated with a casting is preferably used.

The cast width is preferably in the range of 1 to 4 m. The surface temperature of the metal support in the casting step is appropriately selected and set within a range from −50 ° C. to a temperature at which the solvent does not boil and foam. A higher temperature is preferable because the web can be dried faster, but if it is too high, the web may foam and flatness may deteriorate.

A preferable support temperature is appropriately determined within a range of 0 to 100 ° C., and a temperature range of 5 to 30 ° C. is more preferable. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent. The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing warm air or cold air, and a method of bringing hot water into contact with the back side of the metal support. The method using hot water is preferable because the heat transfer is performed efficiently, and the time until the temperature of the metal support becomes constant is short.

When using warm air, considering the temperature drop of the web due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there is a case where wind at a temperature higher than the target temperature is used while preventing foaming. is there.

In particular, it is preferable to efficiently dry by changing the temperature of the support and the temperature of the drying air during the period from casting to peeling.

In order for the λ / 4 retardation film to exhibit good flatness, the amount of residual solvent when peeling the web from the metal support is preferably set in the range of 10 to 150% by mass, more preferably 20%. It is in the range of ˜40 mass% or 60 to 130 mass%, particularly preferably in the range of 20 to 30 mass% or 70 to 120 mass%.

The amount of residual solvent as used in the present invention is defined by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
In the formula, M is the mass of a sample collected at any time during or after production of the web or film, and N is the mass after heating M at 115 ° C. for 1 hour.

Further, in the drying step of the λ / 4 retardation film, the web is peeled off from the metal support, and further dried, so that the residual solvent amount is preferably 1.0% by mass or less, more preferably 0 to 0.00. The range is 01% by mass.

In the film drying process, a roller drying method, for example, a method in which webs are alternately passed through a number of upper and lower rollers and a method in which the web is dried while being conveyed by a tenter method is employed.

<Extension process>
In the λ / 4 retardation film of the present invention, the in-plane retardation Ro550 measured at a wavelength of 550 nm is preferably in the range of 120 to 180 nm. The retardation can be imparted by film stretching. Hereinafter, the λ / 4 retardation film of the present invention may be referred to as a cellulose acylate film.

There is no particular limitation on the stretching method. For example, a method in which a difference in peripheral speed is applied to a plurality of rollers, and the rollers are stretched in the longitudinal direction using the difference in peripheral speed between the rollers, and both ends of the web are fixed with clips and pins, and the interval between the clips and pins is increased in the traveling direction. And a method of stretching in the vertical direction, a method of stretching in the horizontal direction and stretching in the horizontal direction, a method of stretching in the vertical and horizontal directions and stretching in both the vertical and horizontal directions, and the like. Of course, these methods may be used in combination. That is, the film may be stretched in the transverse direction, longitudinally, or in both directions with respect to the film forming direction, and when stretched in both directions, simultaneous stretching or sequential stretching may be used. May be. In the case of the so-called tenter method, driving the clip portion by a linear drive method is preferable from the viewpoint that smooth stretching can be performed and the risk of breakage and the like can be reduced.

In the λ / 4 retardation film of the present invention, in particular, the film is stretched in the direction in which the slow axis is to be generated and contracted in the vertical direction (fast axis direction), and the ratio of the shrinkage rate to the stretching ratio is controlled. Thus, as explained in FIG. 1B, the principal axis direction of the compound represented by the general formula (A) suitably used in the present invention is matched with the principal axis direction (stretching direction) of the cellulose acylate. It is preferable to control the orientation direction of the main axis of the compound represented by the general formula (A).

That is, as the ratio of the draw ratio in the slow axis direction (width direction) and the shrinkage ratio in the direction perpendicular to the slow axis direction (fast axis direction), the shrinkage ratio / stretch ratio = 0.05. The preferred embodiment is in the range of ˜0.70, but the most preferred is in the range of 0.10 to 0.30. In this range, the main axis of the compound represented by the general formula (A) is If it can be matched with the main chain of the matrix resin, the side chain of the compound represented by the general formula (A) is also oriented in the film fast axis direction, and the side chain contains a high refractive index molecule, the ultraviolet region it is possible to increase the refractive index of the fast axis direction in the 280 nm n _{y (280),} can be a steep slope of the forward wavelength dispersion of n _y in the visible light region.

In the stretching step according to the present invention, a method of starting shrinkage after stretching within 30 to 70% of the total stretching step is preferable.

The stretching process usually involves stretching in the width direction (TD direction) and contracting in the transport direction (MD direction), but when contracting, it is easy to match the main chain direction when transported in an oblique direction. In addition, the phase difference effect is even greater. The shrinkage rate is determined by the transport angle.

FIG. 2 is a schematic diagram for explaining the shrinkage ratio in oblique stretching.

In FIG. 2, when the cellulose acylate film F is obliquely stretched 12, the major axis M _1, which is the transport direction, contracts to M ₂ by being obliquely bent. At this time, the shrinkage rate (%) is
Shrinkage rate (%) = (M ₁ −M ₂ ) / M ₁ × 100
It is represented by

If the bending angle is θ,
M ₂ = M ₁ × sin (π−θ)
And therefore
Shrinkage rate (%) = (1−sin (π−θ)) × 100
It is represented by

In FIG. 2, 11 is a stretching direction (TD direction), 13 is a transport direction (MD direction), and 14 is a slow axis.

As a method of controlling the orientation of the compound represented by the general formula (A), the slow axis of the λ / 4 retardation film is preferably within a range of 30 to 60 ° with respect to the transport direction. The shrinkage ratio is preferably in the range of 10 to 50%.

In consideration of the productivity of the circularly polarizing plate, the λ / 4 retardation film of the present invention has an orientation angle of 45 ° ± 2 ° with respect to the conveying direction, and can be bonded roll-to-roll with a polarizing film. Most preferred.

(Stretching with an oblique stretching tenter)
Next, the oblique stretching method of stretching in the 45 ° direction will be further described.

In the method for producing a λ / 4 retardation film of the present invention, it is preferable to use an obliquely stretched tenter as a method for imparting an oblique orientation to the cellulose acylate film to be stretched.

As an obliquely stretched tenter that can be applied to the present invention, the orientation angle of the film can be set freely by changing the rail pattern in various ways, and the film orientation axis can be set to the left and right in the film width direction with high accuracy. It is preferable that the film stretching apparatus be capable of being oriented to the film and controlling the film thickness and retardation with high accuracy.

FIG. 3 is a schematic view showing an example of a rail pattern of an oblique stretching machine applicable to the production of the λ / 4 retardation film of the present invention. In addition, the figure shown here is an example, Comprising: This invention is not limited to this.

Generally, in the oblique stretching apparatus, the feeding direction D1 of the long film original is different from the winding direction D2 of the stretched film after stretching, and forms a feeding angle θi.

The feeding angle θi can be arbitrarily set to a desired angle in the range of more than 0 ° and less than 90 °.

The long film original is gripped by the right and left grippers (tenters) at the entrance of the oblique stretching machine (position A in the figure), and travels as the grippers travel. The left and right gripping tools are at the entrance of the oblique stretching machine (position A in the figure), and the left and right gripping tools Ci and Co facing the direction substantially perpendicular to the film traveling direction (feeding direction D1) are It runs on the asymmetric rails Ri and Ro, and releases the film gripped by the tenter at the position at the end of stretching (position B in the figure).

At this time, as the left and right gripping tools opposed at the entrance of the oblique stretching machine (position A in the figure) travel on the asymmetrical rails Ri and Ro, the gripping tool Ci traveling on the Ri side becomes the Ro side. The positional relationship is advancing with respect to the gripping tool Co traveling.

That is, the gripping tools Ci and Co, which are opposed to the film stretching direction D1 at the entrance of the oblique stretching machine (the gripping start position by the film gripping tool) A, are positioned at the end of the film stretching. In the state of B, the straight line connecting the grippers Ci and Co is inclined by an angle θL with respect to a direction substantially perpendicular to the film winding direction D2.

According to the above method, the original film is stretched obliquely in the direction of θL. Here, “substantially vertical” indicates that it is within a range of 90 ± 1 °.

More specifically, in the method for producing a λ / 4 retardation film of the present invention, it is preferable to perform oblique stretching using the above-described tenter capable of oblique stretching.

This tenter is an apparatus that heats an original film of the film to an arbitrary temperature at which it can be stretched and stretches it obliquely. This tenter includes a heating zone, a pair of rails on the left and right on which a gripping tool for transporting the film travels, and a number of gripping tools that travel on the rails. Both ends of the film sequentially supplied to the entrance portion of the tenter are gripped by a gripping tool, the film is guided into the heating zone, and the film is released from the gripping tool at the exit portion of the tenter. The film released from the gripping tool is wound around the core. Each of the pair of rails has an endless continuous track, and the gripping tool which has released the grip of the film at the exit portion of the tenter travels outside and is sequentially returned to the entrance portion.

In addition, the rail pattern of the tenter has an asymmetric shape on the left and right, and the rail pattern can be adjusted manually or automatically according to the orientation angle θ, stretch ratio, etc. given to the long stretched film to be manufactured. ing. In the oblique stretching machine used in the manufacturing method according to the λ / 4 retardation film of the present invention, it is preferable that the position of each rail part and the rail connecting part can be freely set and the rail pattern can be arbitrarily changed. In addition, the “◯” part shown in FIG. 3 is an example of the connecting part.

In the embodiment of the present invention, the gripping tool of the tenter travels at a constant speed while maintaining a constant distance from the front and rear gripping tools.

The traveling speed of the gripping tool can be selected as appropriate, but is usually in the range of 1 to 100 m / min. The difference between the traveling speeds of the pair of left and right grippers is usually 1% or less of the traveling speed, preferably 0.5% or less, more preferably 0.1% or less. This is because if there is a difference in the conveyance speed between the left and right of the film at the exit of the stretching process, wrinkles and deviations will occur at the exit of the stretching process, so the speed difference between the left and right gripping tools may be substantially the same speed. Desired. In general tenter devices, etc., there are speed irregularities that occur in the order of seconds or less depending on the period of the sprocket teeth that drive the chain, the frequency of the drive motor, etc. This does not correspond to the speed difference described in the embodiment of the invention.

In the oblique stretching machine used in the manufacturing method according to the embodiment of the present invention, a rail that regulates the trajectory of the gripping tool is often required to have a high bending rate, particularly in a portion where the film is transported obliquely. In order to avoid interference between gripping tools due to sudden bending or local stress concentration, it is desirable that the trajectory of the gripping tool draws a curve at the bent portion.

In the embodiment of the present invention, the long film original is sequentially gripped by the right and left grippers at the entrance of the oblique stretching machine (position A in the drawing), and is conveyed along with the travel of the grippers. The left and right gripping tools facing the direction substantially perpendicular to the film traveling direction D1 at the entrance of the oblique stretching machine (position A in the figure) run on a rail that is asymmetrical to the preheating zone and the stretching zone. Through a heating zone having a heat setting zone.

The preheating zone refers to a section where the distance between the gripping tools gripping both ends is kept constant at the heating zone entrance.

The stretching zone refers to the interval until the gap between the gripping tools that grips both ends starts to reach a predetermined interval.

At this time, the oblique stretching as described above is performed, but the stretching may be performed in the longitudinal direction or the transverse direction before and after the oblique stretching as necessary.

In the case of oblique stretching, at the time of bending, there is contraction in the MD direction (fast axis direction) which is a direction perpendicular to the slow axis.

In the λ / 4 retardation film of the present invention, an optical adjusting agent deviated from the main chain of the cellulose acylate that is the matrix resin (for example, the general formula (A)) by performing a shrinkage treatment following the stretching treatment. The orientation of the optical adjusting agent is rotated by shrinking the orientation of the compound represented by the compound)) in the direction perpendicular to the stretching direction (the fast axis direction), and the main axis of the optical adjusting agent compound is cellulose which is a matrix resin. Match to the main chain of the acylate. As a result, the refractive index ny280 in the fast axis direction in the ultraviolet region 280 nm can be increased, and the slope of the ny forward wavelength dispersion in the visible light region can be made steep.

The heat setting zone refers to the section in which the gripping tools at both ends run parallel to each other during the period when the spacing between the gripping tools after the stretching zone becomes constant again.

After passing through the heat setting zone, it may pass through a section (cooling zone) where the temperature in the zone is set to the glass transition temperature Tg ° C. or lower of the thermoplastic resin constituting the film.

At this time, in consideration of shrinkage of the film due to cooling, a rail pattern that narrows the gap between the opposing grippers in advance may be used.

The temperature of each zone is the glass transition temperature Tg of the thermoplastic resin, the temperature of the preheating zone is within the range of Tg to Tg + 30 ° C, the temperature of the stretching zone is within the range of Tg to Tg + 30 ° C, and the temperature of the cooling zone is It is preferable to set within the range of Tg-30 to Tg ° C.

In order to control the thickness unevenness in the width direction, a temperature difference in the width direction may be applied in the stretching zone. In order to create a temperature difference in the width direction in the stretching zone, a method of adjusting the opening degree of the nozzle for sending warm air into the temperature-controlled room so as to make a difference in the width direction, or controlling the heating by arranging the heaters in the width direction is known. Can be used. The length of the preheating zone, the stretching zone, the shrinking zone and the cooling zone can be appropriately selected. The length of the preheating zone is usually within a range of 100 to 150% of the length of the stretching zone, and the length of the fixed zone Is usually set within a range of 50 to 100%.

The draw ratio R (W / W0) in the drawing step is preferably in the range of 1.3 to 3.0, more preferably in the range of 1.5 to 2.8. When the draw ratio is within this range, the thickness unevenness in the width direction is preferably reduced. In the stretching zone of the oblique stretching tenter, if the stretching temperature is made different in the width direction, the thickness unevenness in the width direction can be further improved. W0 represents the width of the film before stretching, and W represents the width of the film after stretching.

As the oblique stretching method applicable to the present invention, in addition to the method shown in FIG. 3, the stretching methods shown in FIGS. 4A to 4C, 5A and 5B can be exemplified.

4A to 4C are schematic views showing an example of the manufacturing method according to the embodiment of the present invention (an example in which the film is unwound from a long film roll and then obliquely stretched). It shows a pattern in which the original film is drawn out and obliquely stretched.

5A and 5B are schematic views illustrating an example of a manufacturing method according to an embodiment of the present invention (an example in which a long film original fabric is continuously stretched obliquely without winding up). The pattern which performs a diagonal stretch process continuously, without winding up is shown.

In each figure, a film feeding device 16, a transport direction changing device 17, a winding device 18, and a film forming device 19 are shown.

The film unwinding device 16 is slidable and pivotable so that the film can be fed at a predetermined angle with respect to the obliquely stretched tenter entrance, or the film unwinding device 16 is slidable and the transport direction is changed. It is preferable that the film can be sent out to the entrance of the obliquely stretched tenter by the device 17. By configuring the film feeding device 16 and the conveyance direction changing device 17 in such a configuration, the width of the entire manufacturing apparatus can be further reduced, and the film feeding position and angle can be finely controlled. This makes it possible to obtain a long stretched film with small variations in film thickness and optical characteristic values. Further, by making the film feeding device 16 and the conveyance direction changing device 17 movable, it is possible to effectively prevent the left and right clips from being caught in the film.

By forming the winding device 18 so that the film can be pulled at a predetermined angle with respect to the outlet of the obliquely stretched tenter, it is possible to finely control the film take-up position and angle, and variations in film thickness and optical characteristic values. It becomes possible to obtain a long stretched film having a small diameter. Therefore, it is possible to effectively prevent wrinkling of the film and improve the winding property of the film, so that the film can be wound as a long roll. In this embodiment, the take-up tension T (N / m) of the stretched film can be adjusted within a range of 100 N / m <T <300 N / m, preferably 150 N / m <T <250 N / m. preferable.

(Melting method)
The λ / 4 retardation film of the present invention may be formed by a melt film forming method. In the melt film forming method, a composition containing an additive such as a resin and a plasticizer is heated and melted to a temperature exhibiting fluidity, and then a melt containing a fluid thermoplastic resin is cast to form a film. Is the method.

More specifically, the heating and melting molding method can be classified into a melt extrusion molding method, a press molding method, an inflation method, an injection molding method, a blow molding method, a stretch molding method, and the like. Among these molding methods, the melt extrusion method is preferable from the viewpoint of mechanical strength and surface accuracy. The plurality of raw materials used in the melt extrusion method are usually preferably kneaded and pelletized in advance.

A known method can be applied to pelletization, for example, dry cellulose acylate, plasticizer, and other additives are fed to an extruder with a feeder, and kneaded using a single or twin screw extruder, Pellets can be obtained by extrusion from a die into strands, water cooling or air cooling, and cutting.

The additives may be mixed before being supplied to the extruder, or may be supplied by individual feeders. A small amount of additives such as fine particles and antioxidants are preferably mixed in advance in order to mix uniformly.

The extruder used for pelletization is preferably a method in which pelletization is possible and processing is performed at as low a temperature as possible so that the shearing force is suppressed and the resin does not deteriorate (for example, molecular weight reduction, coloring, gel formation, etc.). For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

Film formation is performed using the pellets obtained as described above. Of course, the raw material powder can be put into a feeder as it is, supplied to an extruder, heated and melted, and then directly formed into a film without being pelletized.

The pellets are extruded using a single or twin screw type extruder and the melting temperature is within the range of 200 to 300 ° C. After removing foreign matter by filtering with a leaf disk type filter etc., the T die Then, the film is cast into a film, and the film is nipped with a cooling roller and an elastic touch roller, and solidified on the cooling roller.

When introducing into the extruder from the supply hopper, it is preferable to carry out under vacuum, reduced pressure, or inert gas atmosphere to prevent decomposition due to oxidation.

The extrusion flow rate is preferably carried out stably by introducing a gear pump. Further, a stainless fiber sintered filter is preferably used as a filter used for removing foreign substances. A stainless steel fiber sintered filter is a product in which a stainless steel fiber body is intricately intertwined and compressed, and the contact points are sintered and integrated. The accuracy can be adjusted.

Each additive such as plasticizer and fine particles may be mixed with the resin in advance, or may be kneaded in the middle of the extruder. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer.

The film temperature on the elastic touch roller side when the film is nipped between the cooling roller and the elastic touch roller is preferably in the range of Tg to Tg + 110 ° C. of the film. A known elastic touch roller can be used as an elastic touch roller having an elastic body on the surface for such purposes. The elastic touch roller is also called a pinching rotary body, and a commercially available one can also be used.

When peeling the film from the cooling roller, it is preferable to control the tension to prevent deformation of the film.

In addition, the film obtained as described above is subjected to a stretching and shrinking treatment by the same stretching method as described in the solution casting method after passing through the step of contacting the cooling roller.

As a method of stretching and shrinking, a known roller stretching machine or tenter as described above can be preferably used. The stretching temperature is usually preferably in the temperature range of Tg to Tg + 60 ° C. of the resin constituting the film.

Before winding, the end may be slit and cut to the product width, and knurled (embossed) may be applied to both ends to prevent sticking or scratching during winding. The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing. In addition, since the film has deform | transformed and cannot use as a product normally, the holding | grip part of the clip of both ends of a film is cut out, and the cut waste material is reused.

[Characteristics of λ / 4 retardation film]
(Film specification)
The film thickness of the λ / 4 retardation film of the present invention is not particularly limited, but can be used in the range of 10 to 250 μm, preferably in the range of 20 to 100 μm, more preferably 30 to 80 μm. And particularly preferably in the range of 30 to 65 μm.

The λ / 4 retardation film of the present invention may have a width in the range of 1 to 4 m. Furthermore, those having a width of 1.4 to 4 m are preferably used, and particularly preferably 1.6 to 3 m. If it is 4 m or less as a width | variety, conveyance stability can be ensured.

(Surface roughness)
The arithmetic average roughness Ra on the surface of the λ / 4 retardation film of the present invention is generally in the range of 2.0 to 4.0 nm, preferably in the range of 2.5 to 3.5 nm.

(Dimensional change rate)
When the λ / 4 retardation film of the present invention is provided in the organic EL image display device of the present invention, due to dimensional changes due to moisture absorption in a high-humidity environment, for example, unevenness and retardation values In order not to cause a problem such as a change or a decrease in contrast or color unevenness, the dimensional change rate (%) of the λ / 4 retardation film of the present invention is preferably less than 0.5%. Preferably it is less than 3%.

(Fault tolerance)
In the λ / 4 retardation film of the present invention, it is preferable that there are few failures in the film (hereinafter, also referred to as defects), and the defects referred to here are those of the solvent in the drying step in film formation by the solution casting method. It refers to a void in a film (foaming defect) generated due to rapid evaporation, a foreign matter failure (foreign matter defect) in the film due to a foreign matter in the film-forming stock solution or a foreign matter mixed in the film.

Specifically, it is preferable that a defect having a diameter of 5 μm or more is 1 piece / 10 cm square or less in the film plane. More preferably, it is 0.5 piece / 10 cm square or less, and particularly preferably 0.1 piece / 10 cm square or less.

The diameter of the above defect indicates the diameter when the defect is circular, and when the defect is not circular, the range of the defect is determined by observing with a microscope according to the following method, and the maximum diameter (diameter of circumscribed circle) is determined.

¡When the defect is a bubble or a foreign object, the defect range is measured by the size of the shadow when the defect is observed with the transmitted light of the differential interference microscope. In addition, when the defect is accompanied by a change in surface shape such as transfer of a roller scratch or an abrasion, the size is confirmed by observing the defect with reflected light of a differential interference microscope.

In addition, when observing with reflected light, if the size of the defect is not clear, aluminum or platinum is vapor-deposited on the surface for observation. In order to obtain a film having excellent quality expressed by such a defect frequency with high productivity, it is necessary to filter the polymer solution with high precision immediately before casting, to increase the cleanliness around the casting machine, It is effective to set drying conditions after rolling stepwise and to dry efficiently while suppressing foaming.

When the number of defects is larger than 1/10 cm square, for example, when the film is tensioned during processing in a later process, the film may be broken starting from the defects and productivity may be reduced. Moreover, when the diameter of a defect becomes 5 micrometers or more, it can confirm visually by polarizing plate observation etc., and when used as an optical member, a bright spot may arise.

(Elongation at break)
Further, the λ / 4 retardation film of the present invention preferably has a breaking elongation of at least 10% or more in at least one direction (TD direction or MD direction) in the measurement based on JIS-K7127-1999, Preferably it is 20% or more.

The upper limit of the elongation at break is not particularly limited, but is practically about 250%. In order to increase the elongation at break, it is effective to suppress the occurrence of defects in the film due to foreign matter and foaming by the above method.

(Total light transmittance)
The λ / 4 retardation film of the present invention preferably has a total light transmittance of 90% or more, more preferably 93% or more. Moreover, as a realistic upper limit, it is about 99%. In order to achieve excellent transparency expressed by such total light transmittance, it is necessary not to introduce an additive or copolymer component that absorbs visible light, or to remove foreign substances in the polymer by high-precision filtration. It is an effective means to reduce the diffusion and absorption of light inside the film. Also, reduce the surface roughness of the film surface at the time of film formation (cooling roller, calendar roller, drum, belt, coating substrate in the film forming process by the solution casting method, transport roller, etc.) A method of reducing the diffusion and reflection of light on the film surface by reducing the roughness is effective.

《Circularly polarizing plate》
The circularly polarizing plate according to the present invention is produced by cutting a long roll having a long protective film, a long polarizer and a long λ / 4 retardation film of the present invention in this order, The long λ / 4 retardation film satisfies the conditions defined in claim 1, and by applying the circularly polarizing plate according to the present invention to an organic EL image display device, An effect of shielding the specular reflection in the metal electrode of the organic EL light-emitting body is exhibited.

In addition, when the λ / 4 retardation film of the present invention is obliquely stretched so that the angle of the slow axis (that is, the orientation angle θ) is “substantially 45 °” with respect to the longitudinal direction, The direction of the maximum elastic modulus is also “substantially 45 °” with respect to the longitudinal direction. In such a case, the circularly polarizing plate tends to bend in an oblique direction.

For the above-mentioned problem, the circularly polarizing plate according to the present invention preferably has a configuration in which the polarizer is sandwiched between the λ / 4 retardation film of the present invention and a protective film, and a cured layer is laminated on the viewing side of the protective film. By this, it is preferable from a viewpoint which can express the effect which prevents the curvature of a circularly-polarizing plate.

Further, in the organic EL image display device of the present invention, it is preferable that the circularly polarizing plate according to the present invention has an ultraviolet absorption function in order to prevent deterioration due to ultraviolet rays. If the protective film on the viewing side has an ultraviolet absorbing function, both the polarizer and the organic EL element are preferable from the viewpoint of exhibiting the protective effect against ultraviolet rays, but the λ / 4 retardation film on the light emitter side also has an ultraviolet absorbing function. It is preferable that deterioration of the organic EL element can be further suppressed.

《Organic electroluminescence image display device》
The organic electroluminescence image display device of the present invention comprises a circularly polarizing plate having the λ / 4 retardation film of the present invention and an organic electroluminescence element, and has a screen size of 20 inches or more.

FIG. 6 shows an example of the configuration of the organic EL image display device of the present invention, but the present invention is not limited to this.

Organic having a metal electrode 102, a TFT 103, an organic functional layer unit 104, a transparent electrode (ITO, etc.) 105, an insulating layer 106, a sealing layer 107, and a film 108 (optional) on a substrate 101 made of glass, polyimide, or the like. On the EL element B, the circularly polarizing plate C according to the present invention in which the polarizer 110 is sandwiched between the λ / 4 retardation film 109 and the protective film 111 of the present invention is provided to constitute the organic EL image display device A. A cured layer 112 is preferably laminated on the protective film 111. The hardened layer 112 not only prevents scratches on the surface of the organic EL image display device A but also has an effect of preventing warpage due to the circularly polarizing plate. Further, an antireflection layer 113 may be provided on the cured layer. The thickness of the organic EL element B itself is about 1 μm.

Generally, the organic EL image display apparatus A forms an element (organic EL element) which is a light emitting body in which a metal electrode 102, an organic functional layer unit 104, and a transparent electrode 105 are sequentially laminated on a transparent substrate 101. Here, the organic functional layer unit 104 is a laminate of various organic thin films, for example, a hole injection layer made of a triphenylamine derivative or the like and an organic light emitting layer made of a fluorescent organic solid such as anthracene. Various combinations such as a laminate, or a laminate of an electron injection layer composed of such a light emitting layer and a perylene derivative, or a laminate of these hole injection layer, organic light emitting layer, and electron injection layer, etc. A configuration with this is known.

In an organic EL image display device, holes and electrons are injected into an organic light emitting layer by applying a voltage to a transparent electrode and a metal electrode, and energy generated by recombination of these holes and electrons is converted into phosphor or phosphorus. When the photoluminescent substance is excited and the excited fluorescent substance or phosphorescent substance returns to the ground state, the fluorescent substance emits fluorescence or phosphorescence within the organic light emitting layer or at the interface of the organic light emitting layer. The mechanism of recombination of holes and electrons in the middle is the same as that of ordinary diodes. As can be expected from this, current and emission intensity show strong nonlinearity with rectification against the applied voltage. .

In order to extract light emitted from the organic light emitting layer in an organic EL image display device, it is a requirement that at least one of the electrodes must be transparent, and it is usually formed of a transparent conductor such as indium tin oxide (ITO). A transparent electrode is preferably used as the anode. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

The circularly polarizing plate having the λ / 4 retardation film of the present invention is characterized by being applied to an EL image display device having a large screen having a screen size of 20 inches or more, that is, a diagonal distance of 50.8 cm or more.

In the organic EL image display device having such a configuration, the organic light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, light that is incident from the surface of the transparent substrate at the time of non-light emission, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode is again emitted to the surface side of the transparent substrate. The display surface of the organic EL image display device looks like a mirror surface.

In an organic EL image display device including an organic EL element having a transparent electrode on the surface side of an organic functional layer unit that emits light by applying a voltage and a metal electrode on the back side of the organic functional layer unit, the surface of the transparent electrode While providing a polarizing plate on the side (viewing side), a retardation plate can be provided between the transparent electrode and the polarizing plate.

Since the retardation plate and the polarizing plate have a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization action. In the organic EL image display device of the present invention, the retardation plate is composed of the λ / 4 retardation film of the present invention, and the angle formed by the polarization direction of the polarizing plate and the retardation plate is adjusted to π / 4. Thus, the mirror surface of the metal electrode can be completely shielded.

That is, the external light incident on the organic EL image display device transmits only the linearly polarized light component by the polarizing plate, and this linearly polarized light is generally elliptically polarized light by the phase difference plate, but in the present invention, the phase difference plate is The λ / 4 retardation film of the present invention is circularly polarized when the angle formed by the polarization direction of the polarizing plate and the λ / 4 retardation film as the retardation plate is π / 4.

In the circularly polarized light according to the present invention, the transparent substrate, the transparent electrode and the organic functional layer are transmitted, reflected by the metal electrode, and again transmitted through the organic functional layer, the transparent electrode and the transparent substrate, and the λ / 4 retardation film It becomes linearly polarized light again. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, in the circularly polarized light according to the present invention, the mirror surface of the metal electrode can be completely shielded.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<< Production of λ / 4 retardation film >>
[Production of λ / 4 Retardation Film 101: Comparative Example]
In a nitrogen atmosphere, 500 parts of dehydrated cyclohexane were mixed with 1.2 parts of 1-hexene, 0.15 parts of dibutyl ether and 0.30 parts of triisobutylaluminum in a reactor at room temperature. While maintaining at 45 ° C., 20 parts of tricyclo [4.3.12,5] deca-3,7-diene (dicyclopentadiene, hereinafter abbreviated as DCP), 1,4-methano-1, 140 parts of 4,4a, 9a-tetrahydrofluorene (hereinafter abbreviated as MTF) and 8-methyl-tetracyclo [4.4.0.12,5.17,10] -dodec-3-ene (hereinafter A norbornene monomer mixture consisting of 40 parts of MTD (abbreviated as MTD) and 40 parts of tungsten hexachloride (0.7% toluene solution) were continuously added over 2 hours for polymerization. To this polymerization solution, 1.06 part of butyl glycidyl ether and 0.52 part of isopropyl alcohol were added to inactivate the polymerization catalyst, and the polymerization reaction was stopped.

Next, 270 parts of cyclohexane was added to 100 parts of the reaction solution containing the obtained ring-opening polymer, and 5 parts of a nickel-alumina catalyst (manufactured by JGC Chemical Co., Ltd.) was added as a hydrogenation catalyst. The mixture was heated to 200 ° C. while being pressurized to 5 MPa and stirred, and then reacted for 4 hours to obtain a reaction solution containing 20% by mass of a hydrogenated polymer of a DCP / MTF / MTD ring-opening polymer. After removing the hydrogenation catalyst by filtration, a soft polymer (manufactured by Kuraray Co., Ltd .; Septon 2002) and an antioxidant (manufactured by BASF Japan Co., Ltd .; Irganox 1010) were added to the resulting solution per 100 parts of the soft polymer. 0.1 part was added and dissolved.

Next, the solvent cyclohexane and other volatile components are removed from the solution using a cylindrical concentration dryer (manufactured by Hitachi, Ltd.), and the hydrogenated polymer is extruded in a strand form from an extruder in a molten state and cooled. It was then pelletized and collected. When the copolymerization ratio of each norbornene monomer in the polymer was calculated from the composition of residual norbornenes in the solution after polymerization (by gas chromatography), DCP / MTF / MTD = 10/70/20, It was equal to the composition of the addition conditions. The ring-opened polymer hydrogenated product had a weight average molecular weight (Mw) of 31,000, a molecular weight distribution (Mw / Mn) of 2.5, a hydrogenation rate of 99.9%, and a Tg of 134 ° C.

The pellets of the hydrogenated ring-opening polymer prepared as described above were dried at 70 ° C. for 2 hours using a hot air dryer in which air was circulated to remove moisture. Next, the pellets were melt extruded using a short shaft extruder having a coat hanger type T die (manufactured by Mitsubishi Heavy Industries, Ltd .: screw diameter 90 mm, T die lip material is tungsten carbide, peel strength 44N from molten resin). A cycloolefin polymer film having a thickness of 100 μm was produced by molding. In the extrusion molding, an unstretched film having a length of 1400 mm was obtained in a clean room of class 10,000 or less under molding conditions of a molten resin temperature of 240 ° C. and a T die temperature of 240 ° C. The unstretched film was wound up on a roll.

The norbornene-based unstretched film obtained above is stretched according to the following conditions using the rail pattern of the oblique stretching apparatus shown in FIG. 3 to obtain a λ / 4 retardation film 101 which is a stretched film. It was.

In the stretching apparatus shown in FIG. 3, the angle θi formed by the film feeding direction and the winding direction was set to 49 degrees.

First, near the front of the heating zone, both ends of the unstretched film sent from the film feeding device were gripped by the first clip Ci (rail IN side) and the second clip Co (rail OUT side). When gripping the unstretched film, the unstretched film was gripped by moving the clip levers of the first clip and the second clip with the clip closer. When gripping a clip, both ends of the film are simultaneously gripped by the first clip Ci and the second clip Co, and a line connecting the gripping positions at both ends is parallel to an axis parallel to the lateral direction of the film. Was gripped.

Next, the gripped unstretched film is heated by passing through the preheating zone, the stretching zone, and the heat setting zone in the heating zone by the first clip and the second clip, and stretched in the width direction to stretch the stretched film. Got.

The moving speed of the film during heating and stretching was 20 m / min. The temperature of the preheating zone was 160 ° C, the temperature of the stretching zone was 140 ° C, and the temperature of the heat setting zone was 120 ° C. Further, the stretching ratio of the film before and after stretching (the value defined by the ratio of the magnification W / Wo when the distance Wo between the clip ends gripped at the tenter inlet A becomes the distance W at the tenter outlet B) is 120%. (1.2 times), and the stretched film had a thickness of 60 μm and a width of 3080 mm. The produced retardation film was shrunk by 25% in the longitudinal direction.

Finally, both ends of the obtained stretched film were subjected to trimming treatment to obtain a λ / 4 retardation film 101 with a final film width of 2160 mm.

[Production of λ / 4 Retardation Film 102]
(Preparation of fine particle dispersion 1)
Fine particles (Aerosil R812, primary particle size: about 7 nm, manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above is stirred and mixed with a dissolver for 50 minutes, and then dispersed using a Manton Gorin disperser to obtain a fine particle dispersion 1 was prepared.

(Preparation of fine particle additive solution 1)
50 parts by mass of methylene chloride was placed in the dissolution tank, and 50 parts by mass of the fine particle dispersion 1 prepared above was slowly added while sufficiently stirring the methylene chloride. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution 1.

(Preparation of dope)
First, methylene chloride and ethanol shown below were added as an organic solvent to the pressure dissolution tank. The following cellulose acetate having an acetyl group substitution degree of 1.90 was added to a pressurized dissolution tank containing an organic solvent while stirring. After complete dissolution with heating and stirring, Azumi Filter Paper No. 1 manufactured by Azumi Filter Paper Co., Ltd. was used. The main dope was prepared by filtration using 244.

Next, in the main dissolution vessel containing the main dope prepared above, the exemplified compound (221), the sugar ester compound (benzyl saccharose having an average substitution degree of 7.3) as the compound represented by the general formula (A) and the above preparation The fine particle addition liquid 1 was added at the following ratio, sealed, and then dissolved with stirring to prepare a dope.

<Dope composition>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose acetate (acetyl group substitution degree 2.85, weight average molecular weight about 180,000) 100 parts by mass Compound represented by general formula (A): Exemplified compound (221) 4 parts by mass Sugar Ester compound (benzyl saccharose with an average substitution degree of 7.3) 5 parts by mass Fine particle additive solution 1 2 parts by mass (film formation)
The prepared dope is cast on a stainless steel belt support, the solvent is evaporated until the residual solvent amount in the film reaches 75% by mass, and then the stainless steel belt support with a peeling tension of 130 N / m. The film was peeled from above.

<Extension process>
The peeled original film 102 was uniaxially stretched at a stretch ratio of 120% only in the width direction (TD direction) using a tenter while heating at 180 ° C., and then 6% in the transport direction (MD direction). Shrink. The residual solvent at the start of stretching was 15% by mass.

Next, drying was completed while the drying zone was conveyed through a number of rollers. The drying temperature was 130 ° C. and the transport tension was 100 N / m.

As described above, a roll-like λ / 4 retardation film 102 having a dry film thickness of 60 μm was obtained. Note that the orientation angle of the λ / 4 retardation film 102 was 0 °.

[Production of λ / 4 Retardation Film 103]
In the raw film produced with the λ / 4 retardation film 102, the dry film thickness was similarly obtained except that the draw ratio in the width direction was 1.0% and the conveyance tension was adjusted so as not to shrink in the conveyance direction. Produced a roll-shaped original film 103 having a thickness of 125 μm.

<Extension process>
Using the oblique stretching apparatus having the configuration shown in FIG. 3, this raw film 103 is stretched at a temperature of 180 ° C., a stretching ratio of 120%, a bending angle θi = 70 °, and a shrinkage rate (MD direction) = 6%. The film was stretched under the condition of an orientation angle of 60 ° to obtain a roll-like λ / 4 retardation film 103 having a film thickness of 60 μm.

[Production of λ / 4

Retardation Films

104, 105, 111 and 112]
In the production of the λ / 4 retardation film 102, the film thickness (μm), stretching temperature (° C.), stretching ratio (%), shrinkage ratio (%), shrinkage ratio / stretching ratio under the condition that the bending angle is 0 °. The λ / 4

retardation films

104, 105, 111, and 112 were similarly manufactured according to the same stretching process used in the production of the λ / 4 retardation film 102 except that the ratio was changed to the conditions described in Table 1. Was made.

[Production of λ / 4 Retardation Films 106 to 110]
In the production of the λ / 4 retardation film 103, the bending angle θi (°), the orientation angle (°), the film thickness (μm), the stretching temperature (° C), the stretching ratio (%), the shrinkage rate (%), the shrinkage. In the same manner except that the ratio of magnification / stretch ratio was changed to the conditions described in Table 1, using the stretching process (oblique stretching apparatus described in FIG. 3) for producing the λ / 4 retardation film 103, λ / 4 Retardation films 106 to 110 were produced.

[Production of λ / 4 Retardation Film 113]
In the production of the film 121 described in Example 2 of JP 2010-254949 A (see the configuration described in Table 2), the film thickness was changed from 52 μm to 67 μm so that Ro (550) was 140 nm. Except for the above, a λ / 4 retardation film 113 was produced in the same manner.

[Production of λ / 4 Retardation Film 114]
In the production of the film 124 described in Example 2 of JP 2010-254949 A (see the configuration described in Table 2), the film thickness was changed from 52 μm to 67 μm so that Ro (550) was 140 nm. Except for the above, a λ / 4 retardation film 114 was produced in the same manner.

[Measurement of each characteristic value of film]
For each of the λ / 4 retardation films prepared above, retardation Ro in the in-plane direction at wavelengths of 450 nm, 550 nm, and 650 nm using Axoscan manufactured by Axomercs under an environment of 23 ° C. and 55% RH. , Ro (550), Ro (650) and Rt (550) at a wavelength of 550 nm were measured, and Ro (450) / Ro (550) and Ro (550) / Ro (650) were calculated.

The refractive index _{_{n y (280), n x}} (280), Δn y (400), Δn x (400) , using a spectral light source and an Abbe refractometer (1T), 23 ℃, 55 % RH environment Below, the average refractive index of the film sample in wavelength 280nm, 400nm, 410nm was measured.

Further, the orientation angle was also measured using an Axoscan manufactured by Axometrcs.

The film thickness was measured using a commercially available micrometer.

Table 1 shows the film characteristic values obtained as described above.

<< Production of circularly polarizing plates 101 to 114 >>
A 120 μm-thick polyvinyl alcohol film was subjected to uniaxial stretching (temperature: 110 ° C., stretching ratio: 5 times).

This was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. consisting of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. Next, this was washed with water and dried to obtain a polarizer.

The λ / 4 retardation films 101 to 114 produced above were bonded to one side of the polarizer using a completely saponified polyvinyl alcohol 5% aqueous solution as an adhesive. At that time, bonding was performed such that the transmission axis of the polarizer and the slow axis of the λ / 4 retardation film were 45 degrees. The following protective film 1 was similarly subjected to alkali saponification treatment and bonded to the other surface of the polarizer to produce circularly polarizing plates 101 to 114.

[Preparation of Protective Film 1]
(Preparation of ester compound 1)
251 g of 1,2-propylene glycol, 278 g of phthalic anhydride, 91 g of adipic acid, 610 g of benzoic acid, 0.191 g of tetraisopropyl titanate as an esterification catalyst, 2 L equipped with a thermometer, stirrer and slow cooling tube The mixture was charged into a four-necked flask and gradually heated with stirring until it reached 230 ° C. in a nitrogen stream. The ester compound 1 was obtained by carrying out a dehydration condensation reaction for 15 hours, and distilling off unreacted 1,2-propylene glycol under reduced pressure at 200 ° C. after completion of the reaction. The ester compound 1 obtained had an acid value of 0.10 mg KOH / g and a number average molecular weight of 450.

(Preparation of dope)
Cellulose acetate (acetyl group substitution degree 2.88, weight average molecular weight about 180,000) 90 parts by mass Ester compound 1 10 parts by mass Tinuvin 928 (* 1) 2.5 parts by mass Fine particle additive solution 1 (supra) 4 parts by mass Methylene Chloride 432 parts by mass Ethanol 38 parts by mass * 1) Tinuvin 928: 2- (2H-benzotriazol-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol (manufactured by BASF Japan Ltd.) )
The above was put into a sealed container and completely dissolved while heating and stirring, and Azumi Filter Paper No. No. 24 was used for filtration to prepare a dope solution.

(Film formation)
Next, the belt casting apparatus was used to uniformly cast on a stainless steel band support. With the stainless steel band support, the solvent was evaporated until the residual solvent amount reached 100%, and the stainless steel band support was peeled off. Cellulose ester film web was evaporated at 35 ° C, slit to 1.65m width, 30% in TD direction (film width direction) with a tenter while applying heat at 160 ° C, draw ratio in MD direction was Stretched 1%. The residual solvent amount at the start of stretching was 20%. After drying for 15 minutes while transporting the inside of a drying device at 120 ° C. with many rollers, slitting to 1.49 m width, applying a knurling process with a width of 15 mm and a height of 10 μm at both ends of the film, and winding it around the core The protective film 1 was obtained. The residual solvent amount of the protective film 1 was 0.2%, the film thickness was 40 μm, and the number of turns was 3900 m.

The orientation angle θ of the protective film 1 was measured using an automatic birefringence meter KOBRA-21ADH manufactured by Oji Scientific Instruments, and as a result, it was in the range of 90 ° ± 1 ° with respect to the film longitudinal direction.

<< Production of organic EL cell >>
An organic EL cell having a configuration described in FIG. 8 of the publication using a 3 mm-thick 50-inch (127 cm) non-alkali glass in accordance with the method described in Examples of Japanese Patent Application Laid-Open No. 2010-20925. Was made.

<< Production of organic EL image display apparatus >>
After the adhesive was applied to the surface of the λ / 4 retardation film of each circularly polarizing plate produced as described above, organic EL image display devices 101 to 114 were produced by bonding to the viewing side of the organic EL cell.

<< Evaluation of organic EL image display device >>
The following evaluation was performed about each produced said organic EL image display apparatus.

[Evaluation of display performance]
(Visibility evaluation 1: Black display)
In an environment of 23 ° C. and 55% RH, a black image was displayed on the organic EL image display device under the condition that the illuminance was 1000 Lx at a position 5 cm higher than the outermost surface of the organic EL image display device.

Next, with respect to the displayed black image, the front position of the organic EL image display device (0 ° with respect to the surface normal) and the visibility from an oblique angle of 40 ° with respect to the surface normal are performed by 10 general monitors. The black image visibility was evaluated according to the above criteria. In the present invention, it was judged practically acceptable if it was Δ or more.

◎: Nine or more monitors determined that the displayed image was black ○: Seven to eight monitors determined that the displayed image was black △: Five to six monitors , Determined that the displayed image is black ×: The number of monitors determined that the displayed image is black is 4 or less (Visibility evaluation 2: BGR color image)
In an environment of 23 ° C. and 55% RH, a BGR color chart image was displayed on the organic EL image display device under the condition that the illuminance at the position 5 cm higher than the outermost surface of the organic EL image display device was 1000 Lx.

Next, with respect to the displayed BGR color image, the front position of the organic EL image display device (0 ° with respect to the surface normal) and visibility from an oblique angle of 40 ° with respect to the surface normal are performed by 10 general monitors, The visibility of the BGR color image was evaluated according to the following criteria. In the present invention, it was judged practically acceptable if it was Δ or more.

A: Nine or more monitors were determined to be good BGR color images. O: Seven to eight monitors were determined to be good BGR color images. Δ: Five to six monitors were good BGR colors. Table 2 shows the results obtained by the above. The number of monitors determined to be good BGR color images is 4 or less.

As is clear from the results shown in Table 2, the organic EL image display device of the present invention including the circularly polarizing plate having the λ / 4 retardation film of the present invention having each characteristic value defined in the present invention is It can be seen that the image display performance (visibility) of the displayed black image and BGR color image is superior to the comparative example.

Example 2
<< Production of λ / 4 retardation film >>
[Production of λ / 4 retardation films 201 to 207]
In the production of the λ / 4 retardation film 106 described in Example 1, the type and film thickness of the compound represented by the general formula (A) were similarly changed except that the configuration described in Table 3 was used. / 4 Retardation films 201 to 207 were produced.

<< Production of Circular Polarizing Plate, Organic EL Cell, and Organic EL Image Display >>
In the same manner as in the method described in Example 1, using the λ / 4 retardation films 201 to 207 produced above, circularly polarizing plates 201 to 207, organic EL cells 201 to 207, and organic EL image display devices 201 to 207 are used. Was made.

<< Evaluation of organic EL image display device >>
With respect to the organic EL image display devices 201 to 207 manufactured as described above and the organic EL image display device 106 manufactured in Example 1, the image display performance of black display and BGR color image (in the same manner as described in Example 1) ( (Visibility) was evaluated and the obtained results are shown in Table 4.

As is clear from the results shown in Table 4, the organic EL image display device of the present invention comprising the circularly polarizing plate having the λ / 4 retardation film of the present invention having the characteristic values defined in the present invention is It can be seen that the image display performance (visibility) of the black display and the BGR color image is superior to the comparative example.

The λ / 4 retardation film of the present invention is a broadband λ / 4 retardation film having a high retardation development property, a thin film, having reverse wavelength dispersion characteristics, and a reduced retardation in the thickness direction, and organic electroluminescence. It can be suitably used for an image display device.

DESCRIPTION OF SYMBOLS 1 Main chain of matrix resin 2 Stretching direction 4 Compound main chain 5 Compound side chain 11 Stretching method 13 Transport direction 14 Slow axis D1 Feeding direction D2 Winding direction F Cellulose acylate film θi Bending angle (feeding angle)
Ci, Co gripper Ri, Ro Rail Wo Width of film before stretching W Width of film after stretching 16 Film feeding device 17 Transport direction changing device 18 Winding device 19 Film forming device A Organic electroluminescence image display device B Organic Electroluminescence element C Circularly polarizing plate 101 Transparent substrate 102 Metal electrode 103 TFT
104 Organic functional layer unit 105 Transparent electrode 106 Insulating layer 107 Sealing layer 108 Film 109 λ / 4 retardation film 110 Polarizer 111 Protective film 112 Cured layer 113 Antireflection layer

Claims

The thickness direction retardation Rt (550) measured at 23 ° C. and 55% relative humidity is 150 nm or less, and the in-plane retardation Ro measured at 23 ° C. and 55% relative humidity. The λ / 4 retardation film is characterized in that the wavelength dispersion characteristic satisfies the following condition 1 and the in-plane refractive index satisfies the following conditions 2 and 3 simultaneously.
Condition 1
0.72 ≦ Ro (450) / Ro (550) ≦ 0.96
And 0.83 ≦ Ro (550) / Ro (650) ≦ 0.98
[In the formula, Ro (450) is an in-plane phase difference at a wavelength of 450 nm, Ro (550) is an in-plane phase difference at a wavelength of 550 nm, and Ro (650) is an in-plane phase difference at a wavelength of 650 nm. ]
Condition 2
1.000 ≦ n y (280) / n x (280) ≦ 3.500
[Where n y (280) represents the refractive index in the fast axis direction at a wavelength of 280 nm, and n x (280) represents the refractive index in the slow axis direction at a wavelength of 280 nm. ]
Condition 3
1.05 ≦ Δn y (400) / Δn x (400) ≦ 2.15
[The Δn y (400) is the slope of the fast-axis refractive index at a wavelength of 400nm near represented by Δn y (400) = (n y (410) -n y (400)). n y (410) is the refractive index in the fast axis direction at a wavelength of 410 nm, and n y (400) is the refractive index in the fast axis direction at a wavelength of 400 nm. Δn x (400) is a refractive index gradient in the slow axis direction in the vicinity of a wavelength of 400 nm, and is represented by Δn x (400) = (n x (410) −n x (400)). n x (410) is a refractive index in the slow axis direction at a wavelength of 410nm, n x (400) is the refractive index in the slow axis direction at a wavelength of 400 nm. ]
The film is produced through a stretching / shrinking process in which the film is stretched in the slow axis direction and contracted in the fast axis direction, and the ratio of the shrinkage ratio in the fast axis direction to the stretch ratio in the slow axis direction (shrinkage ratio / stretch ratio) is The λ / 4 retardation film according to claim 1, wherein the λ / 4 retardation film is in a range of 0.05 to 0.70.
3. The λ / 4 retardation film according to claim 1, wherein the slow axis direction is oriented within an angle range of 30 to 60 ° with respect to the transport direction.
The λ / 4 retardation film according to any one of claims 1 to 3, wherein the film thickness is in a range of 30 to 80 µm.
It comprises a circularly polarizing plate having the λ / 4 retardation film according to any one of claims 1 to 4 and an organic electroluminescence element, and has a screen size of 20 inches or more. Organic electroluminescence image display device.