JP2016136171A - Optical film, circularly polarizing plate, and organic electroluminescence display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film which, when used with a circularly polarizing plate, generates retardation of substantially λ/4 on light in a wide band of visible light wavelengths, suppresses variation in optical performance due to variation in degree of substitution of a phenyl carbamoyl group or benzoyl group, and functions also as a polarizing plate protection film, and to provide a circularly polarizing plate and an organic EL display device.SOLUTION: An optical film of the present invention is made of a cellulose ester (C) prepared by mixing a cellulose ester (A) and a cellulose ester (B) having a phenyl carbamoyl group or benzoyl group introduced as some of substitution groups belonging to a glucose skeleton of the cellulose ester (A), where a substitution degree of the phenyl carbamoyl group or benzoyl group is within a range of 0.05-0.6 per glucose skeleton unit of the cellulose ester (C). The optical film satisfies conditions listed as (a) through (e).SELECTED DRAWING: Figure 5

Description

  The present invention relates to an optical film, a circularly polarizing plate, and an organic electroluminescence display device. In particular, when used in a circularly polarizing plate used as a light reflection preventing member in an organic electroluminescence display device, a phase difference of λ / 4 can be substantially imparted to a wide band of visible light. Furthermore, optical performance fluctuation due to humidity fluctuation is suppressed, an optical film having a function as a polarizing plate protective film, a circularly polarizing plate provided with the optical film, and an organic material provided with the circularly polarizing plate as a light reflection preventing member The present invention relates to an electroluminescence display device.

  In recent years, with respect to liquid crystal display devices that are widely used as general display devices, there has been a growing demand for display performance and durability, and it is required to obtain good contrast and color tone balance in a display image with a wide viewing angle. ing. In response to these requirements, liquid crystal panels such as a VA (Vertical Alignment) method, an OCB (Optical Compensated Bend) method, and an IPS (In-Plane Switching) method have been developed as a display format of a liquid crystal display device. Excellent display performance is achieved in a wide viewing angle with respect to the TN (Twist Nematic) liquid crystal system.

  On the other hand, recently, the demand for power saving has increased, and the demand for viewing angle and display performance has further increased, and organic electroluminescence (hereinafter abbreviated as organic EL) is used as a new type of display device. A display device, that is, an organic EL display device has attracted attention as a new display device.

  In the organic EL display device, the light source itself can be driven ON / OFF independently for each pixel, and the power consumption is smaller than that of the liquid crystal display device in which the backlight is always on during image display. Further, in order to control the transmission and non-transmission of light for each pixel during image display, the organic EL display device has a light source itself as opposed to a liquid crystal display device in which a liquid crystal cell and a polarizing plate provided on both sides thereof are essential. Since an image can be formed by turning ON / OFF, a configuration such as a liquid crystal display device is not required, a very high front contrast can be obtained, and a display device with excellent viewing angle characteristics can be obtained. Is expected to be. In particular, the use of organic EL elements that emit light of B, G, and R colors eliminates the need for color filters that are essential in liquid crystal display devices, and therefore, organic EL display devices can provide higher contrast. As expected.

  On the other hand, in an organic EL display device, in order to efficiently extract light from the light emitting layer to the viewing side, a metal material having high light reflectivity is used as the electrode layer constituting the cathode, or a metal plate is separately used as a light reflecting member. In general, a light reflection member having a mirror surface is provided on the surface opposite to the light extraction surface.

  However, unlike the liquid crystal display device, the organic EL display device does not include a polarizing plate arranged in crossed Nicols, so external light is reflected on the light extraction member for light extraction, and reflection is not caused. There is a problem that the contrast is greatly lowered in an environment with high illuminance.

  In order to solve such a problem, for example, a method of using a circularly polarizing element for preventing reflection of external light on 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 ° or 135 °. Yes.

  However, with a conventional phase difference plate, for monochromatic light, it is possible to adjust to a phase difference of λ / 4 or λ / 2 of the light wavelength, but there is a combination of light rays in the visible light range. For white light which is a wave, there is a problem that a distribution occurs in the polarization state at each wavelength and the light is converted into colored polarized light. This originates in the material which comprises a phase difference plate having wavelength dispersion about a phase difference.

  In order to solve such a problem, various studies have been made on a broadband retardation plate capable of giving a uniform phase difference to light in a wide wavelength range. For example, a λ / 4 plate with a birefringent light phase difference of λ / 4 and a λ / 2 plate with a birefringent light phase difference of λ / 2 are bonded together with their optical axes crossing each other. A phase difference plate is disclosed (for example, see Patent Document 2).

  However, in order to produce the proposed retardation plate, a complicated process of adjusting the optical direction (optical axis and slow axis) of the two polymer films is required, and a plurality of films As a result, the advantage of the organic EL display device that it is possible to reduce the thickness of the organic EL display device is impaired. Therefore, the development of a broadband λ / 4 phase difference plate with a single layer configuration that does not require lamination is required. It has been demanded.

  As in the case of the liquid crystal display device, the absorption linear polarizing plate used for the circular polarizing plate is generally made of a polyvinyl alcohol resin (hereinafter abbreviated as PVA) on which a dichroic dye is adsorbed. A polarizer obtained by stretching at a high magnification is used, and such a polarizer film is very easily affected by the external environment, and a protective film is essential together with the polarizer film. As a protective film for a polarizer, a polarizing plate protective film using a cellulose resin such as a cellulose ester having excellent adhesiveness with PVA used as a polarizer and having an excellent total light transmittance is widely used. . Accordingly, the polarizing plate is in a form in which both sides of the polarizer are sandwiched between the polarizing plate protective films, but in order to obtain a circularly polarizing plate, it is necessary to further laminate a λ / 4 retardation film.

  However, when the λ / 4 retardation film is laminated on the polarizing plate protective film, the slight retardation property of the polarizing plate protective film causes a deviation from the desired optical property λ / 4 phase difference. As the number of members increases, it also causes the film to become thicker. Therefore, there is a demand for the development of an optical film that also functions as a broadband λ / 4 plate while serving as a polarizing plate protective film.

  As a technique for obtaining a broadband λ / 4 retardation film with a single layer structure, a polymer monomer unit having positive refractive index anisotropy and a monomer unit having negative birefringence are copolymerized. A method of forming a λ / 4 retardation film by uniaxial stretching using a molecular film is disclosed (for example, see Patent Document 3). Since this uniaxially stretched polymer film has reverse dispersion of wavelength dispersion, it is possible to produce a broadband λ / 4 plate with a single retardation film. However, there is a problem in adhesiveness to a polarizer required as a polarizing plate protective film and a problem that the total light transmittance cannot be obtained sufficiently.

  Further, as an optical film for a liquid crystal display device, an optical film having an optical compensation function and a polarizing plate protective film has been studied. As such a film, an optical film in which a desired retardation is imparted to a cellulose ester film has been studied. For example, as a VA retardation film, an in-plane retardation Ro is about 50 nm, and the thickness direction position is about 30 nm. An optical film is disclosed in which a retardation film having a retardation Rth of about 130 nm is produced using a cellulose ester resin (see, for example, Patent Document 4).

  However, the cellulose ester resin has a relatively high retardation development by lowering the degree of substitution, while the wavelength dispersion characteristic tends to weaken the reverse wavelength dispersibility. When the degree of substitution is increased, the reverse wavelength dispersibility increases. However, it has a characteristic that the retardation development property is lowered. Therefore, in order to obtain a single-layered broadband λ / 4 plate, there is a problem that the film thickness must be increased.

  As another method, a technique for improving retardation development and wavelength dispersion by adding various additives such as a retardation increasing agent and a wavelength dispersion adjusting agent to the cellulose ester resin has been studied. However, when an additive is added in a large amount, the film film quality is lowered, and there is a problem that durability and transparency are deteriorated, and improvement has been demanded.

Then, the technique which improves the wavelength dispersion characteristic of a cellulose-ester resin film by introduce | transducing a specific aromatic ester group into a cellulose-ester resin is examined (for example, refer patent document 5). According to the method proposed in Patent Document 5, it is said that the wavelength dispersion characteristic can be freely controlled without reducing the retardation development property of the cellulose ester resin film.
In addition, it is said that large stretching is required to develop a large phase difference by the same means, and in particular, it is possible to improve the problem that phase difference unevenness in the vicinity of a foreign substance is likely to occur (see, for example, Patent Document 6). .)

  In addition, as a retardation film in which a substituent is introduced into cellulose ester, by controlling the retardation (Rth) in the thickness direction to near zero (within a range of −10 to 10 nm), as an IPS phase retardation film In addition, it is disclosed to use a material in which a phenyl carbamate group is introduced into a cellulose ester resin (see, for example, Patent Document 7).

As a result of a detailed study of the technical content proposed in Patent Document 5, the present inventor has adjusted the phase difference of the cellulose ester resin as described in Patent Documents 5 and 7 by adjusting the substituent. In addition, when a broadband λ / 4 retardation film is manufactured by adjusting the wavelength dispersion characteristics of the retardation, and this is used as a circularly polarizing plate for an organic EL display device, the substitution degree of the phenylcarbamoyl group or benzoyl group changes. It has been found that there is a problem that the color tone and reflection of the display image are likely to fluctuate.
Moreover, it became clear that the said problem becomes easy to generate | occur | produce similarly among organic electroluminescent display apparatuses, and it became clear that an immediate improvement is required.

Japanese Patent Laid-Open No. 8-322138 JP-A-10-68816 International Publication No. 00/26705 JP 2007-47537 A JP 2008-95026 A JP 2013-210561 A Japanese Patent No. 5448145

  The present invention has been made in view of the above-mentioned problems and situations, and its solution is a wide band in visible light when used for a circularly polarizing plate used as a light reflection preventing member in an organic electroluminescence display device. A phase difference of λ / 4 can be substantially imparted to light, and further, fluctuations in optical performance due to variations in the degree of substitution of the phenylcarbamoyl group or benzoyl group are suppressed, and a function as a polarizing plate protective film And an organic electroluminescence display device including the optical polarizing film, the circularly polarizing plate including the optical film, and the circularly polarizing plate as a light reflection preventing member.

  As a result of examining the cause of the above-mentioned problems in order to solve the above-mentioned problems according to the present invention, the degree of substitution of the phenylcarbamoyl group or benzoyl group is within the range of 0.05 to 0.6 per glucose skeleton unit of the cellulose ester. Yes, and by satisfying the specified requirements, the change in the degree of substitution of the phenylcarbamoyl group or benzoyl group effectively suppresses fluctuations in the retardation due mainly to changes in the orientation of the phenylcarbamoyl group or benzoyl group It is possible to provide an optical film that can substantially give a phase difference of λ / 4 to light in a wide band in visible light, and further has a function as a polarizing plate protective film. As a result, the present invention has been achieved.

That is, the said subject which concerns on this invention is solved by the following means.
1. Cellulose ester (A) prepared by mixing cellulose ester (A) and cellulose ester (B) having a phenylcarbamoyl group or benzoyl group introduced as part of the substituent of the glucose skeleton of cellulose ester (A) ( C),
The degree of substitution of the phenylcarbamoyl group or the benzoyl group is in the range of 0.05 to 0.6 per glucose skeleton unit of the cellulose ester (C), and
An optical film characterized by satisfying the following requirements (a) to (e).
(A) The retardation value Ro (550) in the film plane measured at a light wavelength of 550 nm in an environment of a temperature of 23 ° C. and a humidity of 55% RH is in the range of 120 to 160 nm.
(B) The ratio value Ro (450) / Ro (550) of the in-plane retardation values Ro (450) and Ro (550) measured at light wavelengths of 450 nm and 550 nm, respectively, is 0.8-0. It is in the range of 9.
(C) The Ro (450) / Ro (550) value described in (b) satisfies the following formula.
| Ro (450) / Ro (550) max−Ro (450) / Ro (550) min | ≦ 0.02
(D) The substituent other than the phenylcarbamoyl group or the benzoyl group is any one of an acetyl group, a propionyl group, and a butyryl group.
(E) The total degree of substitution per glucose skeleton unit of the cellulose ester (C) is in the range of 2.35 to 2.75.

  2. Item 1 is characterized in that the cellulose ester (B) is contained within a range of 20 to 50% by mass with respect to the total amount of the cellulose ester (A) and the cellulose ester (B). The optical film as described.

  3. The first or second item, wherein the polyester having both ends sealed with an aromatic group is contained within a range of 1 to 15% by mass with respect to 100% by mass of the cellulose ester (C). An optical film according to item.

4). By extending in an oblique direction with respect to the long direction, the slow axis is in the range of 40 to 50 ° with respect to the long direction,
The shrinkage rate defined by the following formula is in the range of 10 to 30%. The optical film according to any one of items 1 to 3,
Shrinkage rate (%) = (1-sin (π−θ)) × 100
(In the above formula, θ represents the angle of the stretching direction with respect to the longitudinal direction.)

  5. A circularly polarizing plate formed by cutting a long roll on which the optical film according to any one of Items 1 to 4 and a long polarizer are bonded.

  6). An organic electroluminescence display device comprising the circularly polarizing plate according to item 5.

When used in a circularly polarizing plate used as an antireflection member in an organic electroluminescence display device by the above means of the present invention, a phase difference of λ / 4 is substantially obtained for a wide band of visible light. Furthermore, the optical film having a function as a polarizing plate protective film in which fluctuations in optical performance (coloring performance, reflection characteristics) due to change in the degree of substitution of the phenylcarbamoyl group or benzoyl group are suppressed, and the optical A circularly polarizing plate provided with a film and an organic electroluminescence display device provided with the circularly polarizing plate as a light reflection preventing member can be provided.
The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.

The inventors of the present invention synthesized a cellulose ester resin having a substituent adjusted as described in Patent Document 5 described above, and formed the resin to adjust the phase difference and the wavelength dispersion characteristics of the phase difference. A broadband λ / 4 retardation film was produced.
And when using this retardation film as a circularly-polarizing plate for organic electroluminescent display apparatuses, the cause was examined earnestly about the problem that the color tone and reflection of a display image are easy to fluctuate.

  In the configuration as described in Patent Document 5, when the in-plane retardation is adjusted to be λ / 4 and the wavelength dispersion characteristic is reverse wavelength dispersion, the cellulose ester resin has a large surface. Two functions are ensured: a phase difference adjustment function that develops an internal phase difference, and a wavelength dispersion adjustment function that provides reverse wavelength dispersion. As a result, even when the degree of substitution of the phenylcarbamoyl group or benzoyl group varies slightly, it is presumed that the phase difference fluctuation and the wavelength dispersion fluctuation occur synergistically.

  The variation in the wavelength dispersion of the retardation due to the slight variation in the degree of substitution of the phenylcarbamoyl group or benzoyl group of the optical film and the variation in the retardation development property include the phenylcarbamoyl group substituted with the cellulose ester resin, or It is presumed that the occurrence of the change in the orientation of the benzoyl group is likely to occur. Furthermore, since the organic EL display device has a very high contrast and high image performance as described above, even a slight phase difference fluctuation or wavelength dispersion fluctuation that cannot be recognized by a liquid crystal display device can recognize color and reflection fluctuations. It is in an environment where it is easy to be done.

  For the above reason, when trying to obtain a λ / 4 film used for a circularly polarizing plate of an organic EL display device, when the technique disclosed in Patent Document 5 is adopted, the above problem is very obvious. It is thought that it becomes easy to become.

  As a result of further detailed studies, the present inventors have found that cellulose ester (A) and cellulose into which phenylcarbamoyl group or benzoyl group is introduced as a part of the substituent of the glucose skeleton of cellulose ester (A) are included. Cellulose ester (C) prepared by mixing with ester (B), wherein the degree of substitution of the phenylcarbamoyl group or benzoyl group is 0.05 to 0. 0 per glucose skeleton unit of cellulose ester (C). 6 within the range, and by adjusting the wavelength dispersion of the retardation to be in a desired range, as described above, mainly the phenylcarbamoyl group or the benzoyl group can be obtained without reducing the retardation expression. It is possible to effectively suppress the fluctuation of the phase difference that occurs due to the change in the orientation. As a result, it is possible to obtain an optical film that exhibits an in-plane retardation of λ / 4 in a wide band, and even when this optical film is provided in an organic EL display device, variations in color and reflection during display are possible. Has been found to be sufficiently suppressed.

Schematic diagram explaining shrinkage ratio in oblique stretching Schematic which showed an example of the rail pattern of the diagonal stretch apparatus applicable to the manufacturing method of (lambda) / 4 phase difference film of this invention Schematic which shows an example (example which extends | stretches diagonally after extending | stretching from a long film original fabric roll) which concerns on embodiment of this invention. Schematic which shows an example (example which extends continuously diagonally, without winding up a long film original fabric) concerning the manufacturing method which concerns on embodiment of this invention Schematic sectional view showing an example of the configuration of the organic electroluminescence display device of the present invention

The optical film of the present invention is a mixture of cellulose ester (A) and cellulose ester (B) into which phenylcarbamoyl group or benzoyl group is introduced as part of the substituent of the glucose skeleton of cellulose ester (A). Cellulose ester (C) prepared in the above, wherein the degree of substitution of the phenylcarbamoyl group or the benzoyl group is in the range of 0.05 to 0.6 per glucose skeleton unit of the cellulose ester (C), and ,
The above requirements (a) to (e) are satisfied. This feature is a technical feature common to or corresponding to each of claims 1 to 6.
In the present invention, the retardation value Ro (550) in the film plane measured at a light wavelength of 550 nm in an environment of a temperature of 23 ° C. and a humidity of 55% RH is in the range of 120 to 160 nm. The change in reflection performance can be suppressed.

  Further, in the present invention, the ratio value Ro (450) / Ro (550) of the retardation value Ro (450) and Ro (550) in the film plane measured at the light wavelengths of 450 nm and 550 nm, respectively, is 0.00. Since it exists in the range of 8-0.9, the color change of the organic electroluminescent display apparatus under external light can be suppressed.

  Furthermore, by making | Ro (450) / Ro (550) max−Ro (450) / Ro (550) min | 0.02 or less, fluctuations in the film plane can be suppressed, and the above Ro Due to the synergistic effect with the (450) / Ro (550) value, it is possible to suppress the color change of the organic EL display device under the external light.

  Further, since the substituent other than the phenylcarbamoyl group or the benzoyl group is any one of an acetyl group, a propionyl group, and a butyryl group, it is preferable in that the retardation development property is not lowered and the film thickness can be reduced.

  Furthermore, since the total substitution degree per glucose skeleton unit of the cellulose ester (C) is in the range of 2.35 to 2.75, the retardation development property is not lowered, the film thickness can be reduced, Since there is little fluctuation of the phase difference value due to the influence, it is preferable in that the change in color is small.

  Moreover, in this invention, it is that the said cellulose ester (B) contains in the range of 20-50 mass% with respect to the total amount of the said cellulose ester (A) and the said cellulose ester (B). preferable. This dilution can reduce variation in the degree of substitution of the phenylcarbamoyl group or benzoyl group, and suppress changes in optical performance (black color performance, reflection characteristics) caused by variations in the orientation of the phenylcarbamoyl group or benzoyl group. It is preferable from the viewpoint that can be performed.

  In the present invention, the polyester having both ends sealed with an aromatic group is contained in a range of 1 to 15% by mass with respect to 100% by mass of the cellulose ester (C). The (450) / Ro (550) value and the phase difference fluctuation are small, and this is preferable in that the influence of moisture is reduced.

  Further, in the present invention, by stretching in an oblique direction with respect to the longitudinal direction, the angle with respect to the longitudinal direction is within the range of 40 to 50 °, and the slow axis is defined by the above formula. When the organic EL display device is provided, it is preferable that the shrinkage rate is within a range of 10 to 30% in terms of sufficiently suppressing color and reflection fluctuations during display.

The optical film of the present invention can be suitably used for a circularly polarizing plate.
The circularly polarizing plate of the present invention can be suitably used for an organic electroluminescence display device.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, "-" shown in this invention is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

  Hereinafter, each of the optical film, the circularly polarizing plate, and the organic electroluminescence display device of the present invention will be described.

<Optical film>
The optical film of the present invention is a mixture of cellulose ester (A) and cellulose ester (B) into which phenylcarbamoyl group or benzoyl group is introduced as part of the substituent of the glucose skeleton of cellulose ester (A). Cellulose ester (C) prepared in the above, wherein the degree of substitution of the phenylcarbamoyl group or the benzoyl group is in the range of 0.05 to 0.6 per glucose skeleton unit of the cellulose ester (C), and ,
The following requirements (a) to (e) are satisfied.
(A) The retardation value Ro (550) in the film plane measured at a light wavelength of 550 nm in an environment of a temperature of 23 ° C. and a humidity of 55% RH is in the range of 120 to 160 nm.
(B) The ratio value Ro (450) / Ro (550) of the in-plane retardation values Ro (450) and Ro (550) measured at light wavelengths of 450 nm and 550 nm, respectively, is 0.8-0. It is in the range of 9.
(C) The Ro (450) / Ro (550) value described in (b) satisfies the following formula.
| Ro (450) / Ro (550) max−Ro (450) / Ro (550) min | ≦ 0.02
(D) The substituent other than the phenylcarbamoyl group or the benzoyl group is any one of an acetyl group, a propionyl group, and a butyryl group.
(E) The total degree of substitution per glucose skeleton unit of the cellulose ester (C) is in the range of 2.35 to 2.75.

  The optical film of the present invention preferably has an angle with a slow axis in the range of 40 to 50 ° with respect to the longitudinal direction. As a method for setting the angle of the slow axis with respect to the longitudinal direction in the range of 40 to 50 ° in this way, for example, a method of performing oblique stretching described later on the film before stretching is formed. Can do.

  Moreover, in the optical film of this invention, it is an elongate film and it is preferable that the thickness exists in the range of 20-80 micrometers.

  In the present invention, the “optical film” refers to a film having an optical function of imparting a desired phase difference to transmitted light. As the optical function, for example, linearly polarized light having a specific wavelength is used. Examples include a function of converting to elliptically polarized light or circularly polarized light, or a function of converting elliptically polarized light or circularly polarized light into linearly polarized light. In particular, the “λ / 4 retardation film” means an optical film having a characteristic that the in-plane retardation of the film is about 1/4 with respect to a predetermined wavelength of light (usually in the visible light region). Say.

[Characteristics of optical film]
In order to obtain circularly polarized light in the visible light wavelength range, the optical film of the present invention is preferably a broadband λ / 4 retardation film having a phase difference of approximately ¼ of the wavelength in the visible light wavelength range. .

  The in-plane retardation Ro (λ) and the retardation Rth (λ) in the film thickness direction of the optical film of the present invention are represented by the following formula (i). Note that λ represents a wavelength (nm) for measuring each phase difference. The value of the phase difference used in the present invention can be calculated, for example, by measuring the birefringence at each wavelength in an environment of 23 ° C. and 55% RH using an Axoscan manufactured by Axometrics.

Formula (i)
_{Ro (λ) = (n x} -n y) × d
Rth (λ) = [(n _x + n _y ) / 2−n _z ] × d
In the above formula (i), lambda represents an optical wavelength (nm) used in the _measurement, n x, _{n y,} and _{n z} are respectively measured in an environment RH Temperature 23 ° C. · humidity 55%, _{n x} represents the maximum in-plane refractive index (refractive index in a slow axis direction) of the film, n _y represents a refractive index in a direction perpendicular to the slow axis in the film plane, n _z perpendicular to the film plane Represents the refractive index in the thickness direction, and d represents the thickness (nm) of the film.

  Here, when the in-plane retardation of the optical film at the light wavelength λ (nm) is Ro (λ), in the optical film of the present invention, the in-plane retardation value Ro (550) measured at the light wavelength of 550 nm. Is in the range of 120 to 160 nm (the above requirement (a)). Preferably it exists in the range of 130-155 nm, More preferably, it exists in the range of 135-150 nm. In the optical film of the present invention, when Ro (550) is in the range of 120 to 160 nm, the phase difference at a wavelength of 550 nm is approximately ¼ wavelength, and a circularly polarizing plate is formed using an optical film having such characteristics. For example, by providing the organic EL display device with this circularly polarizing plate, reflection of indoor lighting can be prevented, and black display characteristics in a bright place environment can be improved.

  Further, in the optical film of the present invention, Ro (450) / Ro (550) which is a ratio value of retardation value Ro (450) and Ro (550) in the film plane, which is an indicator of wavelength dispersion characteristics, is obtained. In the range of 0.8 to 0.9 (the above requirement (b)). Preferably it exists in the range of 0.80-0.87, More preferably, it exists in the range of 0.80-0.85. When Ro (450) / Ro (550) is in the range of 0.8 to 0.9, the retardation exhibits an appropriate reverse wavelength dispersion characteristic, and when a long circularly polarizing plate is produced, An antireflection effect can be obtained for a wide band of light.

  Furthermore, in the optical film of the present invention, the Ro (450) / Ro (550) value is | Ro (450) / Ro (550) max−Ro (450) / Ro (550) min | ≦ 0.02. It is characterized by the above (requirement (c) above). Preferably, it is 0.01 or less. If the value is 0.02 or less, the fluctuation in the film plane can be suppressed, and the color of the organic EL display device under the external light due to the synergistic effect with the Ro (450) / Ro (550) value. Taste change can be suppressed.

  On the other hand, the phase difference Rth (λ) in the film thickness direction is preferably in the range of 20 to 200 nm, more preferably in the range of 20 to 150 nm, with the phase difference Rth (550) measured at an optical wavelength of 550 nm. Preferably, it is in the range of 20-100 nm. If Rth (550) is in the range of 20 to 200 nm, it is possible to prevent a change in hue when viewed obliquely on a large screen. For this reason, in order to make the retardation Rth in the film thickness direction into a preferable range, it is also preferable to laminate a uniaxial positive C retardation film.

  The optical film of the present invention may be mounted on a liquid crystal display device. For example, it may be mounted on a reflective liquid crystal display device within the phase difference range (Ro (550)) of the present invention. Further, even when the retardation range (Ro (550)) is set to a region smaller than 120 to 160 nm and used as an optical compensation film for liquid crystal display devices such as VA mode and IPS mode, it has good performance.

[Positive C retardation film]
The positive C retardation film satisfies the relationship Nz> Nx≈Ny, and the optical axis is in the Nz direction. There is no particular limitation as long as it is made of a composition containing a thermoplastic resin having optical transparency required as a retardation film.
For example, what consists of a thermoplastic resin composition containing a styrene resin and an acrylic resin is mentioned, It is preferable that it consists of a thermoplastic resin composition which contains these resins as a main component.
The composition constituting the positive C retardation film is preferably a thermoplastic resin composition containing only these styrene resin and acrylic resin as the resin material, and particularly preferably a thermoplastic resin composition comprising these resins. .
Styrenic resins and acrylic resins have high transparency and negative intrinsic birefringence.
These resins can be formed into a film by a known method such as injection molding, sheet molding, blow molding, injection blow molding, inflation molding, extrusion molding or cast molding. Furthermore, it can be uniaxially or biaxially stretched by a known method such as roll stretching, tenter stretching, or tubular stretching, if necessary.
Therefore, a positive C retardation film can be produced by a relatively easy process without using a special technique.
The intrinsic birefringence means a property that the refractive index changes when stress is applied. A material having negative intrinsic birefringence is a material having a refractive index in the direction perpendicular to the direction of stress. Therefore, a positive C retardation film can be produced by a normal stretching process.

[Cellulose ester (C)]
The cellulose ester constituting the optical film of the present invention includes a cellulose ester (B) and a cellulose ester (B) into which a phenylcarbamoyl group or a benzoyl group is introduced as a part of the substituent of the glucose skeleton of the cellulose ester (A). The cellulose ester (C) prepared by mixing the cellulose skeleton (C), and the first requirement for the substituent of the glucose skeleton of the cellulose ester (C) is that the degree of substitution of the phenylcarbamoyl group or benzoyl group is the cellulose ester ( It is in the range of 0.05 to 0.6 per glucose skeleton unit of C).
The degree of substitution here refers to the cellulose ester (A) before the phenylcarbamoyl group and benzoyl group are introduced in the mixed cellulose ester (C) after mixing the cellulose ester (A) and the cellulose ester (B). It means the average value of the total number of phenylcarbamoyl groups and benzoyl groups at the 2nd, 3rd and 6th positions in the glucose skeleton unit.

  The second requirement of the substituent that the glucose skeleton of the cellulose ester (C) according to the present invention has is that the substituent other than the phenylcarbamoyl group or the benzoyl group is either an acetyl group, a propionyl group, or a butyryl group.

  Examples of preferable substituents other than the phenylcarbamoyl group or benzoyl group include phenylbenzoate, 4-methylbenzoate, 4-thiomethylbenzoate, 4-methoxybenzoate, 4-heptylbenzoate, 2,4,5-trimethyl Methoxybenzoate, 2,4,5-trimethylbenzoate, 3,4,5-trimethoxybenzoate and 1-naphthoate, phenylcarbamate, biphenylcarbamate, 4-methylphenylcarbamate, 4-thiomethylphenylcarbamate, 4-methoxycarbamate, Examples include 4-heptyl carbamate, 2,4,5-trimethoxy carbamate, 2,4,5-trimethyl carbamate, 3,4,5-trimethoxy carbamate, and 1-naphthyl carbamate.

The third requirement for the substituent of the glucose skeleton of the cellulose ester (C) according to the present invention is that the total degree of substitution per glucose skeleton unit of the cellulose ester (C) is in the range of 2.35 to 2.75. It is. More preferably, it is in the range of 2.55 to 2.75 because deterioration of the polarizing plate due to moisture is suppressed.
That is, the cellulose ester (C) according to the present invention is a phenyl ester in which part of the hydroxy groups at the 2nd, 3rd and 6th positions of the glucose skeleton (β-glucose ring) of the cellulose ester is a phenylcarbamoyl group or a benzoyl group. Cellulose ester (B) having carbamoyl group or benzoyl group, and cellulose ester (A) before phenylcarbamoyl group or benzoyl group is introduced into cellulose ester (B) having phenylcarbamoyl group or benzoyl group, It is a mixed one.

Furthermore, the detail of the cellulose ester (C) which concerns on this invention is demonstrated.
The glucose skeleton of the cellulose ester (C) according to the present invention is a cellulose ester having a glucose skeleton unit represented by the following general formula (1).

In the general formula (1), R ² is a group located at the 2-position of the glucose skeleton, R ³ is a group located at the 3-position of the glucose skeleton, and R ⁶ is a group located at the 6-position of the glucose skeleton. It is.
R ² , R ³ and R ⁶ are not particularly limited as long as the above-described requirements are satisfied, and each represents a hydrogen atom or a substituent. Note that the glucose skeleton in the present invention is intended to refer to a portion except for R ^2, R ³ and R ⁶ in the general formula (1).

The cellulose ester (C) according to the present invention preferably has a weight average molecular weight Mw in the range of 50,000 to 500,000, more preferably in the range of 100,000 to 300,000, and still more preferably in the range of 150,000 to 250,000. It is.
The weight average molecular weight Mw and the number average molecular weight Mn of the cellulose ester (C) can be measured using gel permeation chromatography (GPC), respectively.

  The cellulose ester (C) according to the present invention can be produced by referring to a known method, for example, a method described in “Encyclopedia of Cellulose” pages 131 to 164 (Asakura Shoten, 2000).

In the present invention, the degree of substitution of the substituent of the glucose skeleton is determined using ¹ H-NMR or the method described in Cellulose Communication 6, 73-79 (1999) and Chality 12 (9), 670-674. It can be determined by ¹³ C-NMR.

[Mixing ratio of cellulose ester (A) and cellulose ester (B)]
The introduction of a phenylcarbamoyl group or benzoyl group into a cellulose ester has a large ability to reduce wavelength dispersion and retardation, but has a problem that the ability per unit substituent is large and the wavelength dispersion value and retardation value tend to vary. It has occurred.
In order to solve this problem, the cellulose ester (B) into which the phenylcarbamoyl group or benzoyl group is introduced is mixed with the cellulose ester (A) before the introduction of the phenylcarbamoyl group or benzoyl group. We considered reducing it.
As a result of the examination, it was confirmed that the dispersion of the wavelength dispersion value and the retardation value was decreased by increasing the mixing ratio of the cellulose ester (A). Further, it has been found that there is a region where the variation decreases with respect to the mixing ratio.

  As a preferable mixing ratio of the variation, the cellulose ester (B) is contained in the range of 20 to 50% by mass with respect to the total amount of the cellulose ester (A) and the cellulose ester (B). is there.

On the other hand, when the mixing ratio is compared with the chromatic dispersion value / phase difference value, there is a region where the chromatic dispersion value decreases and the retardation expression value does not decrease, and the ratio is 20 to 50% by mass in the same manner as the above ratio. It was found to be within the range.
When the mixing ratio of the cellulose ester (B) is 50% by mass or less with respect to the total amount of the cellulose ester (A) and the cellulose ester (B), the chromatic dispersion value is 50%. There is no decrease in the expression level.
Thereby, the dispersion of wavelength dispersion can be reduced to half or less, and an equivalent phase difference can be expressed. That is, the dispersion of the chromatic dispersion value can be reduced while maintaining the same film thickness. On the other hand, when the mixing ratio is less than 20% by mass, the dispersion of the chromatic dispersion value and the retardation value is sufficiently small, the decrease of the retardation value is small, and a desired film thickness can be obtained. The value is high, and the color change and reflection performance of the organic EL display device deteriorate.
Although the reason why such a region exists is not known, it is considered that when the cellulose ester (B) is mixed with the cellulose ester (A), the steric hindrance is relaxed, the orientation is improved, and the phase difference is expressed. ing.
Cellulose ester in which unsubstituted benzene and trimethyl-substituted benzene were substituted at the same ratio was prepared, and the orientation coefficient was measured. Unsubstituted benzene> trimethyl-substituted benzene. As a result, it was difficult to orient and support the above phenomenon.

[Optical film additives]
The optical film of the present invention can contain various additives for the purpose of imparting various functions.

Additives that can be applied to the present invention are not particularly limited, and are, for example, ultraviolet absorbers, plasticizers, deterioration inhibitors, matting agents, retardation increasing agents, and chromatic dispersion improvement within the range that does not impair the object effects of the present invention. An agent or the like can be used.
Below, the typical additive applicable to the optical film of this invention is shown.

(UV absorber)
The optical film of the present invention can contain an ultraviolet absorber.

  Examples of ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like, but less benzotriazole compounds. Compounds are preferred. In addition, ultraviolet absorbers described in JP-A-10-182621 and JP-A-8-337574 and polymer ultraviolet absorbers described in JP-A-6-148430 are also preferably used. When the optical film of the present invention is used as a protective film for a polarizing plate in addition to a retardation film, the ultraviolet absorber has an ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of a polarizer and an organic EL device. In view of the display property of the organic EL element, it is preferable that the organic EL element has a characteristic that absorbs less visible light having a wavelength of 400 nm or more.

  Benzotriazole-based UV absorbers useful in the present invention include, for example, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-t -Butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-t-butyl Phenyl) -5-chlorobenzotriazole, 2- [2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl] benzotriazole, 2,2 -Methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (2'-hydroxy-3) -T-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, octyl-3 -[3-t-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-t-butyl-4-hydroxy-5- ( A mixture of 5-chloro-2H-benzotriazol-2-yl) phenyl] propionate can be mentioned, but is not limited thereto.

  Further, as a commercial product, “TINUVIN 109”, “TINUVIN 171”, “TINUVIN 326”, “TINUVIN 328” (above, trade name, manufactured by BASF Japan Ltd.) are preferable. Can be used.

  It is preferable that the addition amount of a ultraviolet absorber exists in the range of 0.1-5.0 mass% with respect to a cellulose ester (C), and it exists in the range of 0.5-5.0 mass%. Further preferred.

(Plasticizer)
In general, the cellulose ester film is less flexible than the cellulose acetate, and when the film is subjected to bending stress or shear stress, the film is likely to be cracked. Moreover, when processing as an optical film, a crack is easy to enter into a cutting part and it is easy to generate | occur | produce chips. The generated chips contaminated the optical film and caused optical defects. In order to improve these problems, the optical film can contain a plasticizer.

  Specific examples of the plasticizer include phthalic acid esters, trimellitic acid esters, aliphatic dibasic acid esters, orthophosphoric acid esters, acetic acid esters, polyester epoxidized esters, ricinoleic acid esters. , Polyolefin, and polyethylene glycol compounds.

  The plasticizer that can be used in the optical film of the present invention is preferably selected from a compound having a normal temperature, normal pressure, liquid, and a boiling point of 200 ° C. or higher. Specific examples of the compound name include aliphatic dibasic acid ester type, phthalic acid ester type, and polyolefin type.

  The addition amount of the plasticizer is preferably in the range of 0.5 to 40.0% by mass, and in the range of 1.0 to 30.0% by mass with respect to the cellulose ester (C). Is more preferable, and it is particularly preferable to be within the range of 3.0 to 20.0 mass%. When the added amount of the plasticizer is 0.5% by mass or more, the plasticizing effect is sufficient and the processability is improved. Further, when the content is 40% by mass or less, separation and elution of the plasticizer can be suppressed when it is aged for a long time, and optical unevenness, contamination to other parts, and the like can be more reliably suppressed.

(Polycondensation ester (polyester) of aliphatic dicarboxylic acid and aliphatic diol)
The optical film of the present invention preferably contains a polyester having both ends sealed with an aromatic group. Specifically, it is preferable to contain a polycondensation ester obtained by polycondensation of an aliphatic dicarboxylic acid and an aliphatic diol as described below.

  As a polycondensation ester, the polycondensation ester represented by the following general formula (D1) or (D2) is preferable.

General formula (D1)
B _1- (GA-) _m GB ₁
(In the formula, B ₁ represents a monocarboxylic acid, G represents a divalent alcohol, A represents a dibasic acid, and m represents a repeating number of 1 or more and 20 or less.)

General formula (D2)
B _2- (A-G-) _n A-B ₂
(In the formula, B ₂ represents a monoalcohol, G represents a divalent alcohol, A represents a dibasic acid, and n represents a repeating number of 1 or more and 20 or less.)

In the general formulas (D1) and (D2), B ₁ represents a monocarboxylic acid component, B ₂ represents a monoalcohol component, G represents a divalent alcohol component, A represents a dibasic acid component, and Represents that it was synthesized. B ₁ and B ₂ each preferably have 1 to 12 carbon atoms, and G and A each preferably have 2 to 12 carbon atoms. G and A are preferably composed of aliphatic groups, and B ₁ and B ₂ preferably include an aromatic ring. m and n represent the number of repetitions.

The monocarboxylic acids represented by B _1, may be a known aromatic ring monocarboxylic acids.
Examples of preferred monocarboxylic acids include, but are not limited to: For example, benzoic acid, toluic acid, 3,5-dimethylbenzoic acid, 2,6-dimethylbenzoic acid, 2,4,6-trimethylbenzoic acid, anisic acid, 3,5-dimethoxybenzoic acid, 2,4,6- Although trimethoxybenzoic acid etc. are mentioned, Of these, benzoic acid or toluic acid is preferable, and benzoic acid is particularly preferable.

The monoalcohol component represented by B ₂ is not particularly limited, and known alcohols can be used. For example, aliphatic saturated alcohols or aliphatic unsaturated alcohols having a straight chain or side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C12.

Examples of the divalent alcohol component represented by G include, but are not limited to, the following. For example, ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, , 6-hexanediol, 1,5-pentylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, etc., among which ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1 , 2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,6-hexanediol, diethylene glycol and triethylene glycol are preferable, and 1,3-propylene glycol, 1,4- Ji glycol, 1,6-hexanediol, diethylene glycol is preferably used.
As the polycondensation ester contained in the optical film of the present invention, the divalent alcohol component represented by G is preferably an aliphatic diol.

As the dibasic acid (dicarboxylic acid) component represented by A, for example, an aliphatic dibasic acid and an alicyclic dibasic acid are preferable, and as the aliphatic dibasic acid, for example, malonic acid, succinic acid, glutar Acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecane dicarboxylic acid, dodecane dicarboxylic acid, etc. Things can be used. That is, two or more dibasic acids may be used in combination.
As the polycondensation ester contained in the optical film of the present invention, the dibasic acid represented by A may be an aliphatic dicarboxylic acid or an aromatic dicarboxylic acid, but is an aliphatic dicarboxylic acid. It is preferable.

  The polycondensation ester contained in the optical film of the present invention may be a compound represented by the above general formula (D1) or a compound represented by the general formula (D2). A compound represented by the general formula (D1) that is not sealed with a monocarboxylic acid is preferable.

  m and n represent the number of repetitions and are preferably 1 or more and less than 50, and more preferably 1 or more and less than 20.

  The number average molecular weight of the preferred polycondensation ester in the high temperature and high stretch ratio is in the range of 1000 to 10,000. If the number average molecular weight is 1000 or more, breakage is unlikely to occur at high temperature and high magnification stretching, and if it is 10,000 or less, whitening due to phase separation is difficult to increase.

  The polycondensation of the polycondensed ester is performed by a conventional method. For example, heat melting and shrinkage by direct reaction of the above dibasic acid and glycol, polycondensation esterification reaction or transesterification reaction of the above dibasic acid or alkyl esters thereof such as methyl ester of dibasic acid and glycols. Polycondensed esters having a weight average molecular weight of not so large can be synthesized by either a conventional method or a dehydrohalogenation reaction of an acid chloride of these acids with a glycol, but synthesized by direct reaction. It is preferable.

The polycondensation ester having a high distribution on the low molecular weight side has a very good compatibility with the cellulose ester, and after forming the film, the moisture permeability is small, and an optical film (λ / 4 retardation film) that is rich in transparency is used. Can be obtained.
A conventional method can be used as a method for adjusting the molecular weight without particular limitation. For example, although depending on the polymerization conditions, when a method of blocking the molecular ends with a monovalent acid or monovalent alcohol is used, the molecular weight is adjusted by adjusting the addition amount of these monovalent raw material compounds. be able to. In this case, it is preferable from the viewpoint of the stability of the polymer to adjust the addition amount of the monovalent acid. For example, acetic acid, propionic acid, butyric acid and the like can be mentioned, but it is preferable to select one that does not distill out of the system during the polycondensation reaction, but easily distills out when stopped and removed from the reaction system.
For this purpose, a plurality of compounds may be mixed and used. In the case of a direct reaction, the weight average molecular weight can also be adjusted by measuring the timing for stopping the reaction based on the amount of water produced during the reaction. In addition, the molecular weight can be adjusted by biasing the number of moles of glycol or dibasic acid to be charged, and the molecular weight can be adjusted by controlling the reaction temperature.

The polycondensation ester (polyester) is preferably contained in an amount of 1 to 40% by mass with respect to 100% by mass of the cellulose ester. In the general formula (D1) or (D2), B ₁ and B ₂ each have 1 to 12 carbon atoms, and G and A each have 2 to 12 carbon atoms. It is preferably included in an amount, particularly preferably 1 to 15% by mass, and most preferably 1 to 15% by mass.
Examples of compounds (additive compounds E-1 to E-45) are shown in Table 1 below, but are not limited thereto.

(Degradation inhibitor)
The optical film of the present invention may contain a deterioration inhibitor such as an antioxidant, a peroxide decomposer, a radical polymerization inhibitor, a metal deactivator, an acid scavenger, and amines.

  The deterioration inhibitor is described in, for example, JP-A-3-199201, JP-A-5-97073, JP-A-5-194789, JP-A-5-271471, JP-A-6-107854.

  The amount of the deterioration inhibitor added is a cellulose solution (dope) used for the production of an optical film from the viewpoint of suppressing the bleed-out of the deterioration inhibitor to the film surface because of the effect of the addition of the deterioration inhibitor. Is preferably in the range of 0.01 to 1% by mass, and more preferably in the range of 0.01 to 0.2% by mass.

  Examples of particularly preferred deterioration inhibitors include butylated hydroxytoluene (abbreviation: BHT) and tribenzylamine (abbreviation: TBA).

(Matting agent fine particles)
The optical film of the present invention can contain fine particles as a matting agent.
The matting agent fine particles include, for example, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, silica A magnesium acid, a calcium phosphate, etc. can be mentioned. Among these matting agent fine particles, those containing silicon are preferable in terms of low turbidity (haze), and silicon dioxide is particularly preferable.
The fine particles of silicon dioxide preferably have a primary average particle size in the range of 1 to 20 nm and an apparent specific gravity of 70 g / liter or more. The primary average particle size is more preferably in the range of 5 to 16 nm from the viewpoint of reducing the haze of the optical film. The apparent specific gravity is more preferably in the range of 90 to 200 g / liter, and particularly preferably in the range of 100 to 200 g / liter. A larger apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

  These fine particles usually form secondary particles having an average particle size in the range of 0.05 to 2.0 μm. These secondary particles exist as an aggregate of primary particles in the optical film, and form irregularities of 0.05 to 2.0 μm on the optical film surface. The secondary average particle size is preferably in the range of 0.05 to 1.0 μm, more preferably in the range of 0.1 to 0.7 μm, and in the range of 0.1 to 0.4 μm. It is particularly preferred. The primary particle size and the secondary particle size were determined by observing fine particles in the optical film with a scanning electron microscope and determining the diameter of a circle circumscribing the particles as the particle size. Also, 200 particles are observed at different locations, and the average value is taken as the average particle size.

  As the fine particles of silicon dioxide, for example, commercially available products such as Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above, Nippon Aerosil Co., Ltd., trade name) may be used. it can. Zirconium oxide fine particles are commercially available, for example, as Aerosil R976 and R811 (above, trade name, manufactured by Nippon Aerosil Co., Ltd.) and can be used.

  Among these, Aerosil 200V and Aerosil R972V are fine particles of silicon dioxide having a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g / liter or more, and the friction coefficient is maintained while keeping the haze of the optical film low. This is particularly preferable because the effect of lowering is great.

  The matting agent fine particles are preferably prepared by the following method and applied to an optical film. That is, a matting agent fine particle dispersion in which a solvent and matting agent fine particles are stirred and mixed is prepared in advance, and this matting agent fine particle dispersion is added to various additive solutions prepared separately with a cellulose ester concentration of less than 5% by mass. After stirring and dissolving, a method of further mixing with the main cellulose ester (C) dope solution is preferable.

  Since the surface of the matting agent fine particles is hydrophobized, when an additive having hydrophobicity is added, the additive is adsorbed on the surface of the matting agent fine particles, and the aggregate of the additive is formed using this as a core. Likely to happen. Therefore, by mixing the hydrophilic additive in advance with the matting agent fine particle dispersion and then mixing the hydrophobic additive, aggregation of the additive on the matting agent surface can be suppressed, and the haze can be suppressed. It is preferable because an optical film with low light leakage in black display when incorporated in a liquid crystal display device can be produced.

  It is preferable to use an in-line mixer for mixing the matting agent fine particle dispersant and the additive solution and mixing the cellulose ester dope liquid. Although the present invention is not limited to these methods, the concentration of silicon dioxide when the silicon dioxide fine particles are mixed and dispersed with a solvent or the like is preferably in the range of 5 to 30% by mass, and 10 to 25% by mass. It is more preferable that it is within the range, and it is particularly preferable that it be within the range of 15 to 20% by mass. A higher dispersion concentration is preferable because turbidity with respect to the same amount of addition is reduced, and generation of haze and aggregates can be suppressed. The addition amount of the matting agent in the final cellulose ester dope solution is preferably in the range of 0.001 to 1.0% by mass, and in the range of 0.005 to 0.5% by mass. Is more preferable, and it is particularly preferable to be within the range of 0.01 to 0.1% by mass.

<< Production of Optical Film Having Cellulose Ester (C) >>
The method for producing the optical film of the present invention is not particularly limited, and examples thereof include a solution casting method and a melt casting method, but a method of producing by the solution casting method is preferable.

[Solution casting method]
The optical film of the present invention is preferably manufactured by a solution casting method. The solution casting method is a method for producing an optical film using a solution (dope) obtained by dissolving cellulose ester (C) in an organic solvent. The solution casting method includes a step of preparing a dope by heating and dissolving cellulose ester (C) satisfying the characteristics specified in the present invention and various additives in an organic solvent, and the prepared dope is a belt-shaped or drum-shaped metal. The step of casting on a support, the step of drying the cast dope as a web, the step of peeling from the metal support, the step of stretching or shrinking the peeled web, the step of further drying, the step of winding up the finished film Etc. are included.

(Process for preparing dope)
The organic solvent used for the preparation of the dope includes ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and 1 to 6 carbon atoms. The halogenated hydrocarbons are preferably selected from the following.

  Ethers, ketones and esters may have a cyclic structure. A compound having two or more functional groups of ethers, ketones and esters (that is, —O—, —CO— and —COO—) can also be used as the organic solvent. The organic solvent may have other functional groups such as alcoholic hydroxy groups. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms is preferably within the range of the above-mentioned preferable number of carbon atoms of the solvent having any functional group.

  Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole, phenetole and the like.

  Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone, and methylcyclohexanone.

  Examples of esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, pentyl acetate and the like.

  Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol, 2-butoxyethanol and the like.

  The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogen atoms in the halogenated hydrocarbon substituted with halogen is preferably in the range of 25 to 75 mol%, more preferably in the range of 30 to 70 mol%, and more preferably 35 to 65 mol%. More preferably, it is in the range of mol%, and particularly preferably in the range of 40 to 60 mol%. Methylene chloride is a representative halogenated hydrocarbon.

  For the preparation of the dope, it is preferable to use a mixed solvent of methylene chloride and alcohols, and the ratio of alcohols to methylene chloride is preferably in the range of 1 to 50% by mass, and 5 to 40% by mass. It is preferably within the range, and particularly preferably within the range of 8 to 30% by mass. As the alcohol, methanol, ethanol and n-butanol are preferable, and two or more kinds of alcohols may be mixed and used.

  The dope can be prepared by a general method under a temperature of 0 ° C. or higher (room temperature or high temperature). The dope can be prepared using a dope preparation method and apparatus in a normal solvent cast method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly, methylene chloride) as the organic solvent.

  The concentration of the cellulose ester (C) in the dope is preferably in the range of 5 to 40% by mass, and more preferably in the range of 10 to 30% by mass. Various additives described above may be added to the organic solvent (main solvent).

  The dope can be prepared by stirring the cellulose ester (C) and the organic solvent at room temperature (0 to 40 ° C.). The high concentration solution may be stirred under pressure and heating conditions. Specifically, the cellulose ester (C) and the organic solvent are put in a pressure vessel and sealed, and stirred while heating to a temperature not lower than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil.

  The heating temperature is usually 40 ° C or higher, preferably in the range of 60 to 200 ° C, more preferably in the range of 80 to 110 ° C.

  Each component may be mixed roughly beforehand and then charged into the container. Moreover, you may put into a container sequentially. The container needs to have a mechanism capable of stirring. An inert gas such as nitrogen gas can be injected to pressurize the container. Moreover, you may pressurize using the raise of the vapor pressure of the solvent by heating. Or after sealing a container, you may add each component under pressure.

  When heating, the method of heating from the outer peripheral part of a container is preferable. For example, a jacket type heating device can be used. The entire container can also be heated by providing a plate heater outside the container, or by piping and circulating a heated liquid in the pipe.

  It is preferable to provide a stirring blade inside the container and use this to stir. The stirring blade preferably has a length that reaches the vicinity of the wall of the container. A scraping blade is preferably provided at the end of the stirring blade in order to renew the liquid film on the vessel wall.

  Instruments such as a pressure gauge and a thermometer may be installed in the container. Each component is dissolved in a solvent in a container. The prepared dope is taken out of the container after cooling, or is taken out and then cooled using a heat exchanger or the like.

  A solution can also be prepared by a cooling dissolution method. In the cooling dissolution method, the cellulose ester (C) can be dissolved in an organic solvent that is difficult to dissolve by a normal dissolution method. In addition, even if it is a solvent which can melt | dissolve a cellulose ester (C) with a normal melt | dissolution method, there exists an effect by which a rapid and uniform solution is obtained by applying a cooling melt | dissolution method.

  In the cooling dissolution method, first, the cellulose ester (C) is gradually added to an organic solvent at room temperature while stirring. The amount of the cellulose ester (C) is preferably adjusted so as to be contained in the mixture in the range of 5 to 40% by mass. The amount of the cellulose ester (C) is more preferably in the range of 10 to 30% by mass. Furthermore, the above-mentioned optional additives may be added to the mixture.

  Next, the mixture is cooled within a range of −100 to −10 ° C. (preferably −80 to −10 ° C., more preferably −50 to −20 ° C., particularly preferably −50 to −30 ° C.). The cooling can be performed, for example, in a dry ice / methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). By cooling, the mixture of the cellulose ester (C) and the organic solvent is solidified.

  The cooling rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and particularly preferably 12 ° C./min or more. The faster the cooling rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The cooling rate is a value obtained by dividing the difference between the temperature at the start of cooling and the final cooling temperature by the time from the start of cooling to the final cooling temperature.

  Furthermore, when this is heated within the range of 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C., and still more preferably 0 to 50 ° C.), cellulose ester (C) in the organic solvent. Dissolves. The temperature may be increased by simply leaving it at room temperature or in a warm bath.

  The heating rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and even more preferably 12 ° C./min or more. The higher the heating rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The heating rate is the value obtained by dividing the difference between the temperature at the start of heating and the final heating temperature by the time from the start of heating until the final heating temperature is reached. is there.

  A uniform solution is obtained as described above. If the dissolution is insufficient, the cooling and heating operations may be repeated. Whether or not the dissolution is sufficient can be determined by merely observing the appearance of the solution with the naked eye.

  In the cooling dissolution method, it is preferable to use an airtight container in order to avoid moisture mixing due to condensation during cooling. In the cooling and heating operation, when the pressure is applied during cooling and the pressure is reduced during heating, the dissolution time can be shortened. In order to perform pressurization and pressure reduction, it is preferable to use a pressure-resistant container.

(Process for casting dope, process for drying web)
The dope prepared as described above is cast on a drum or a band, and the solvent is evaporated to form a film. It is preferable to adjust the concentration of the dope before casting so that the solid content is in the range of 18 to 35%. The surface of the drum or band is preferably finished in a mirror state. The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less.

  Regarding the method of drying the cast dope as a web, U.S. Pat. No. 2,607,704, No. 2739069 and No. 2739070, British Patent Nos. 640731 and No. 736892, and Japanese Patent Publication No. 45-4554, No. 49-5614, JP-A-60-176834, JP-A-60-203430, and JP-A-62-115035. Drying on the drum or band can be performed by blowing an inert gas such as air or nitrogen to the cast film.

  Using the prepared cellulose ester (C) solution (dope), two or more layers can be cast to form a film. In this case, it is preferable to adjust the concentration of the dope before casting so that the solid content is in the range of 5 to 40%.

(Process to stretch the web)
The web obtained by drying as described above is peeled off from the drum or band, and the peeled web is stretched.
As described above, the optical film of the present invention is characterized in that the in-plane retardation Ro (550) measured at a light wavelength of 550 nm is in the range of 120 to 160 nm, and the web formed as described above is stretched. By doing so, the in-plane phase difference Ro can be given.

  The stretching method applicable to the present invention is not particularly limited. For example, a method in which a circumferential speed difference is applied to a plurality of rollers and a longitudinal stretching is performed using a circumferential speed difference between the plurality of rollers therebetween. , Both ends of the web are fixed with clips and pins, and the distance between the clips and pins is extended in the longitudinal direction according to the direction of travel. The method of extending | stretching to both directions is employable individually or in combination.

  In other words, the film may be stretched in the transverse direction, in the longitudinal direction, or in both directions, 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 the linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

  As the stretching process, the film is usually stretched in the width direction (TD direction) and contracted in the transport direction (MD direction), but when contracted, 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 can be determined by the transport angle.

FIG. 1 is a schematic diagram for explaining the shrinkage ratio in oblique stretching.
In FIG. 1, when the optical film F is obliquely stretched in the oblique stretching direction 12, the optical film F is contracted to M ₂ by being obliquely bent. That is, when the gripping tool that grips the optical film F advances as it is without bending at the bending angle θ, it should advance by a length M ₁ ′ in a predetermined time. However, in reality, it bends at a bending angle θ and proceeds by M ₁ (where M ₁ = M ₁ ′). At this time, since the gripping tool advances by M ₂ in the film entering direction (direction orthogonal to the stretching direction (TD direction) 11), the optical film F has a length M ₃ (where M ₃ = M ₁ -M ₂₎ the fact that only shrinkage.

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 the shrinkage rate is
Shrinkage rate (%) = (1-sin (π−θ)) × 100
It is represented by
In the present invention, the shrinkage rate is preferably in the range of 10 to 30%.

  In FIG. 1, the optical film F is transported in the transport direction (MD direction) 13 and has a slow axis 14.

  Considering the productivity of the long circular polarizing plate, the optical film of the present invention has an orientation angle of 45 ± 2 ° with respect to the transport direction, and can be bonded with a polarizing film in a roll-to-roll manner. It is preferable.

(Stretching with an oblique stretching device)
Next, the oblique stretching method of stretching in the 45 ° direction will be further described. In the method for producing an optical film of the present invention, it is preferable to use an oblique stretching apparatus as a method for imparting an oblique orientation to the optical film to be stretched.

  As an oblique stretching apparatus applicable to the present invention, the orientation angle of the film can be freely set by changing the rail pattern in various ways, and the orientation axis of the film can be oriented with high accuracy evenly in the left-right direction across the film width direction. It is preferable that the film stretching apparatus can control the film thickness and retardation value with high accuracy.

  FIG. 2 is a schematic view showing an example of a rail pattern of an oblique stretching apparatus applicable to the production of the optical film of the present invention. In addition, FIG. 2 shown here is an example, and the diagonal stretch apparatus applicable in this invention is not limited to this.

  In general, in the oblique stretching apparatus, as shown in FIG. 2, 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. doing. The feeding angle θi can be arbitrarily set to a desired angle within a range of more than 0 ° and less than 90 °. In the present specification, the term “long” refers to a film having a length of at least about 5 times the width of the film, preferably a film having a length of 10 times or more.

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

  At this time, as the left and right gripping tools facing each other at the entrance of the oblique stretching device (position A in the figure) travel on the left and right asymmetric 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 that are opposed to the film feeding direction D1 at the oblique stretching apparatus entrance (the gripping start position by the film gripping tool) A are positions 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. Here, “substantially vertical” indicates that the angle is in a range of 90 ± 1 °.

  The oblique stretching apparatus configured as described above will be described in more detail.

  The oblique stretching apparatus applied to the production of the optical film of the present invention is an apparatus that heats an original film to an arbitrary stretchable temperature and obliquely stretches the film. This oblique stretching apparatus includes a heating zone, a pair of rails on the left and right on which a gripping tool for transporting a film travels, and a number of gripping tools that travel on the rail. Both ends of the film sequentially supplied to the inlet of the oblique stretching apparatus 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 outlet of the oblique stretching apparatus. 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 that has released the grip of the film at the outlet of the oblique stretching apparatus travels outside and is sequentially returned to the inlet.

  Note that the rail pattern of the oblique stretching apparatus has an asymmetric shape on the left and right, and the rail pattern can be adjusted manually or automatically depending on the orientation angle, stretching ratio, etc. given to the long stretched film to be manufactured. It is like that. In the oblique stretching apparatus used in the present invention, it is preferable that the position of each rail portion and the rail connecting portion can be freely set, and the rail pattern can be arbitrarily changed (the ○ portion in FIG. 2 indicates an example of the connecting portion). .)

  In the present invention, the gripping tool of the oblique stretching apparatus travels at a constant speed with a constant distance from the front and rear gripping tools. Although the traveling speed of a holding | gripping tool can be selected suitably, it is 1-100 m / min normally. The difference in travel speed between the pair of left and right grippers is usually 1% or less, preferably 0.5% or less, more preferably 0.1% or less of the travel speed. This is because if there is a difference in the traveling speed between the left and right sides of the film at the exit of the stretching process, wrinkles and shifts occur at the exit of the stretching process, so the speed difference between the left and right gripping tools is required to be substantially the same speed. Because. In general oblique stretching devices, etc., there are speed irregularities that occur in the order of seconds or less depending on the period of the sprocket teeth driving the chain, the frequency of the drive motor, etc. This does not correspond to the speed difference described in the present invention.

  In the oblique stretching apparatus applicable to the present invention, a large bending rate is often required for the rail that regulates the locus of the gripping tool, particularly in a portion where the film is transported obliquely. For the purpose of avoiding interference between gripping tools due to sudden bending or local stress concentration, it is preferable that the trajectory of the gripping tool draws a curve at the bent portion.

  In the present invention, the long film original fabric is gripped in order by the right and left gripping tools at the entrance of the oblique stretching apparatus (position A in the drawing) and travels as the gripping tool travels. The left and right gripping tools facing the direction substantially perpendicular to the film traveling direction (feeding direction D1) at the entrance of the oblique stretching apparatus (position A in the figure) run on a rail that is asymmetrical to the preheating zone. Through a heating zone having a stretching zone and a heat setting zone.

  The preheating zone refers to a section that travels while maintaining a constant interval between the gripping tools that grip both ends at the entrance of the heating zone.

  The stretching zone refers to a section where the gap between the gripping tools gripping both ends starts to reach a predetermined distance. In the stretching zone, 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, there is contraction in the MD direction (fast axis direction) which is a direction perpendicular to the slow axis during bending.

  The heat setting zone refers to a section in which the gripping tools at both ends run in parallel with each other in a period in which the interval between the gripping tools after the stretching zone becomes constant again. You may pass through the area (cooling zone) by which the temperature in a zone is set to below the glass transition temperature Tg of resin which comprises a film, after passing through a heat setting zone. 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 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., the temperature of the cooling zone relative to the glass transition temperature Tg of the resin constituting the film. The temperature is preferably set within the range of Tg-30 ° C to Tg.

  In order to control thickness unevenness in the width direction, a temperature difference may be given in the width direction 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 that sends warm air into the temperature-controlled room to make a difference in the width direction, or a method of controlling heating by arranging heaters in the width direction, etc. 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% with respect to the length of the stretching zone, and the length of the fixed zone. Is usually in the range of 50 to 100%.

  The draw ratio (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 can be reduced. In the stretching zone of the oblique stretching apparatus, it is possible to further improve the thickness unevenness in the width direction by making a difference in the stretching temperature in the width direction. W0 represents the width of the film before stretching, and W represents the width of the film after stretching.

  Examples of the oblique stretching method applicable in the present invention include the stretching methods shown in FIGS. 3A to 3C and FIGS. 4A and 4B in addition to the method shown in FIG. it can.

  FIG. 3 is a schematic view showing an example of a production method applicable to the present invention (an example in which the film is drawn from a long film original fabric roller and then obliquely stretched), and the long film original fabric once wound up in a roll shape. The pattern which extends | stretches and diagonally stretches is shown. FIG. 4 is a schematic view showing an example of another manufacturing method applicable to the present invention (an example of continuous oblique stretching without winding a long film original), and winding the long film original. The pattern which performs a diagonal stretch process continuously, without showing is shown.

  In the configuration shown in FIG. 3, an oblique stretching device 15, a film feeding device 16, a transport direction changing device 17, a winding device 18 and the like are provided. In the configuration shown in FIG. 4, an oblique stretching device 15, a conveyance direction changing device 17, a winding device 18, a peeling / drying process outlet 19, and the like are provided.

FIG. 3 shows a configuration in which the film fed from the film feeding device 16 is obliquely stretched, and FIGS. Are changed respectively. The film feeding device 16 is configured to be able to slide and turn so that the film can be fed at a predetermined angle with respect to the inlet of the oblique stretching device 15. Further, as shown in FIG. 3C, the film feeding device 16 may be configured to be slidable, and may be configured to send the film to the entrance of the oblique stretching device 15 by the transport direction changing device 17.
4 shows a configuration in which the film conveyed from the peeling / drying process outlet 19 is obliquely extended directly. FIGS. 4A and 4B are positions where the conveyance direction changing device 17 is provided. Is a change.
By arranging the film feeding device 16 or the peeling / drying process outlet 19 and the transport direction changing device 17 as described above, the width of the entire manufacturing apparatus can be made narrower, and the film feeding position and angle can be set. Fine control is possible. As a result, it is possible to obtain a long stretched film with small variations in film thickness and optical value. In addition, by making the film feeding device 16 or the peeling / drying process outlet 19 and the transport direction changing device 17 movable, it is possible to effectively prevent the left and right clips from being caught in the film.

  The winding device 18 is arranged so that the film can be pulled at a predetermined angle with respect to the outlet of the oblique stretching device 15, so that the film take-up position and angle can be finely controlled. A long stretched film with small variations can be obtained. Therefore, it is possible to effectively prevent the film from being wrinkled and to improve the winding property of the film, so that the film can be wound up in a long length. In the present invention, the take-up tension T (N / m) of the stretched film is adjusted within a range of 100 N / m <T <300 N / m, preferably 150 N / m <T <250 N / m. .

  Moreover, in the method for producing the optical film of the present invention, a drying step for further drying the film wound as described above, and a winding step for rewinding the film after the drying step may be further performed.

[Melt casting method]
The optical film of the present invention may be produced by a melt casting method in addition to the solution casting method described above. The melt casting method is a molding method in which a composition containing additives such as cellulose ester (C) and a plasticizer is heated and melted to a temperature exhibiting fluidity, and then cast as a melt having fluidity. .

  The molding method for heating and melting can be classified into, for example, a melt extrusion molding method, a press molding method, an inflation method, an injection molding method, a blow molding method, and a stretch molding method. 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. Pelletization can be performed by a known method. For example, dry cellulose ester (C), a plasticizer, and other additives are supplied to an extruder with a feeder and kneaded using a single-screw or twin-screw extruder. It can be obtained by extruding into a strand form from a die, 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 matting agent fine particles and antioxidants are preferably mixed in advance in order to mix uniformly.

  The extruder used for pelletization preferably has a method of suppressing the shearing force and processing at the lowest possible temperature so that the resin can be pelletized so that the resin does not deteriorate (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.

  A film is formed using the pellets obtained as described above. Of course, it is also possible to form the film as it is after it is not formed into pellets, and the raw material powder is put into the feeder as it is, supplied to the extruder, heated and melted.

  Using a single-screw or twin-screw type extruder, the melting temperature when extruding is within the range of 200 to 300 ° C. After removing foreign matter by filtering with a leaf disk type filter or the like, from the T-die 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 or reduced pressure or in an inert gas atmosphere to prevent oxidative decomposition and the like.

  The extrusion flow rate is preferably performed stably by introducing a gear pump or the like. 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 stainless steel fiber bodies are intricately intertwined and compressed, and the contact points are sintered and integrated. The density is changed according to the thickness of the fiber and the amount of compression, and filtration is performed. The accuracy can be adjusted.

  Additives such as plasticizers 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 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 the elastic touch roller having an elastic surface used for such a purpose. 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.

  The film obtained as described above can be subjected to stretching and shrinkage treatment by stretching operation after passing through the step of contacting the cooling roller. As a method of stretching and shrinking, a known roller stretching device, an oblique stretching device or the like as described above can be preferably used. The stretching temperature is usually preferably performed in the temperature range of Tg to Tg + 60 ° C. of the resin constituting the film.

  Prior to winding, the ends may be slit and cut to the product width, and knurled (embossing) may be applied to both ends to prevent sticking and 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 reused.

  The optical film of the present invention can be formed into a circularly polarizing plate by laminating so that the angle between the slow axis 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 optical film of the present invention and the transmission axis of the polarizer is preferably within a range of 41 to 49 °, and within a range of 42 to 48 °. More preferably, it is more preferably in the range of 43 to 47 °, and particularly preferably in the range of 44 to 46 °.

《Circularly polarizing plate》
The circularly polarizing plate of the present invention is produced by cutting a long roll having a long protective film, a long polarizer and a long optical film of the present invention in this order.
Since the circularly polarizing plate of the present invention is produced using the optical film of the present invention, it is applied to an organic EL display device or the like to be described later, so that the specular reflection of the metal electrode of the organic EL element is performed at all wavelengths of visible light. The effect of shielding can be expressed. As a result, reflection during observation can be prevented and black expression can be improved.

  In addition, the circularly polarizing plate of the present invention preferably has an ultraviolet absorption function. It is preferable that the protective film disposed on the viewing side has an ultraviolet absorbing function because a protective effect against ultraviolet rays can be exerted on both the polarizer and the organic EL element. Furthermore, when the optical film of the present invention disposed on the light emitter side (opposite to the viewing side) of the organic EL element has an ultraviolet absorbing function, the organic EL element is more used when used in an organic EL display device described later. Can be prevented from deteriorating.

Further, the circularly polarizing plate of the present invention uses the optical film of the present invention in which the angle of the slow axis (that is, the orientation angle θ) is adjusted to be “substantially 45 °” with respect to the longitudinal direction, The consistent production line enables the formation of the adhesive layer and the bonding of the polarizer and the optical film of the present invention as a retardation film.
Specifically, after finishing the step of producing a polarizer by stretching a polarizing film, after incorporating the step of laminating the polarizer and the optical film during or after the subsequent drying step, Can be continuously supplied. Furthermore, it can connect with the manufacturing line consistent to the next process by winding in a roll state after bonding of a polarizer and an optical film. Moreover, when bonding a polarizer and an optical film, a protective film can also be supplied simultaneously and it can also bond continuously. From the viewpoint of performance and production efficiency, it is preferable to simultaneously bond the optical film and the protective film to the polarizer. That is, after finishing the step of producing a polarizer by stretching the polarizing film, during or after the subsequent drying step, the protective film and the optical film are bonded to both sides with an adhesive, and wound. It is also possible to obtain a rolled circularly polarizing plate by taking it.

  In the circularly polarizing plate of the present invention, the polarizer is preferably sandwiched between the optical film of the present invention and a protective film, and more preferably a cured layer is laminated on the viewing side of the protective film.

  The circularly polarizing plate can be provided in a liquid crystal display device or an organic EL display device. By applying the circular polarizing plate to an organic EL display device as an example, an effect of shielding the specular reflection of a metal electrode of an organic EL light emitter is exhibited. To do.

[Protective film]
The circularly polarizing plate of the present invention is preferably constituted by sandwiching a polarizer between the optical film of the present invention and a protective film.

As such a protective film, other cellulose ester-containing films are suitably used. For example, a commercially available cellulose ester film can be used. For example, Konica Minoltack KC8UX, KC5UX, KC4UX, KC8UCR3, KC4SR, KC4BR, KC4CR, KC4DR, KC4FR, KC4KR, KC8YY, KC6UY, KC4UY, KC4UE, KC8UE (Made by Konica Minolta, Inc.), Fujitac T40UZ, Fujitac T60UZ, Fujitac T80UZ, Fujitac TD80UL, Fujitac TD60UL, Fujitac TD40UL, Fujitac R02, Fujitac R06 (more preferably Fujifilm)
Although the thickness in particular of a protective film is not restrict | limited, It can be in the range of 10-200 micrometers, Preferably it exists in the range of 10-100 micrometers, More preferably, it exists in the range of 10-70 micrometers.

[Polarizer]
A polarizer is an element that passes only light having a plane of polarization in a certain direction. Examples thereof include a polyvinyl alcohol-based polarizing film. The polyvinyl alcohol polarizing film includes those obtained by dyeing iodine on a polyvinyl alcohol film and those obtained by dyeing a dichroic dye.

  The polarizer can be obtained by uniaxially stretching a polyvinyl alcohol film and then dyeing, or dying a polyvinyl alcohol film and then uniaxially stretching, preferably by further performing a durability treatment with a boron compound. The thickness of the polarizer is preferably in the range of 5 to 30 μm, and more preferably in the range of 5 to 15 μm.

  Examples of the polyvinyl alcohol film include, for example, an ethylene unit content of 1 to 4 mol%, a polymerization degree of 2000 to 4000, and a saponification degree of 99.000 described in JP2003-248123A and JP2003-342322A. 0 to 99.99 mol% of ethylene-modified polyvinyl alcohol is preferably used. Moreover, it is preferable to produce a polarizing plate by the method of Unexamined-Japanese-Patent No. 2011-1000016, patent 4691205, and patent 4804589, and sticking it with the optical film of this invention.

[Photocurable adhesive]
The bonding of the optical film of the present invention and the polarizer is not particularly limited, but can be performed using a completely saponified polyvinyl alcohol adhesive after saponifying the optical film. It can also be bonded using actinic ray curable adhesive, etc., but the photocurable adhesive is used from the viewpoint that the obtained adhesive layer has a high elastic modulus and can easily suppress the deformation of the polarizing plate. Is preferred.

  Preferred examples of the photocurable adhesive include (α) a cationic polymerizable compound, (β) a photo cationic polymerization initiator, and (γ) a wavelength longer than 380 nm, as disclosed in JP2011-08234A. And a photo-curable adhesive composition containing each component of a photosensitizer exhibiting maximum absorption in the light of (δ) and a naphthalene-based photosensitization aid. However, other photocurable adhesives may be used.

[Method of manufacturing circularly polarizing plate]
Hereinafter, an example of the manufacturing method of the circularly-polarizing plate using a photocurable adhesive agent is demonstrated.
The circularly polarizing plate includes (1) a pretreatment step for easily adhering the surface of the optical film to which the polarizer is bonded, and (2) at least one of the adhesive surfaces of the polarizer and the optical film, and An adhesive application step of applying the agent, (3) a bonding step of bonding the polarizer and the optical film through the obtained adhesive layer, and (4) a polarizer and the optical film through the adhesive layer. It can manufacture by the manufacturing method including the hardening process which hardens an adhesive bond layer in the state bonded together. What is necessary is just to implement the pre-processing process of (1) as needed.

(Pretreatment process)
In the pretreatment step, an easy adhesion treatment is performed on the adhesive surface of the optical film with the polarizer. When bonding an optical film to both surfaces of a polarizer, easy adhesion processing is performed on the bonding surface of each optical film with the polarizer. Examples of the easy adhesion treatment include corona treatment and plasma treatment.

(Adhesive application process)
In the adhesive application step, the photocurable adhesive is applied to at least one of the adhesive surfaces of the polarizer and the optical film. When the photocurable adhesive is directly applied to the surface of the polarizer or the optical film, the application method is not particularly limited. For example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Moreover, after casting a photocurable adhesive between a polarizer and an optical film, the method of pressurizing with a roller etc. and spreading uniformly can also be utilized.

(Bonding process)
After apply | coating a photocurable adhesive agent, a bonding process is performed. In the bonding step, for example, when a photocurable adhesive is applied to the surface of the polarizer in the previous adhesive application step, an optical film is superimposed thereon. When a photocurable adhesive is applied to the surface of the optical film in the previous adhesive application process, a polarizer is superimposed thereon. In addition, when a photocurable adhesive is cast between the polarizer and the optical film, the polarizer and the optical film are superposed in that state. In the case where the optical film is bonded to both sides of the polarizer and a photocurable adhesive is used on both sides, the optical film is superposed on both sides of the polarizer via the photocurable adhesive. Normally, both sides of the polarizer are stacked (when the optical film is superimposed on one side of the polarizer, the polarizer side and the optical film side, and when the optical film is superimposed on both sides of the polarizer, Press from the film side) with a roller. As the material of the roller, for example, metal or rubber can be used. The rollers arranged on both sides may be made of the same material or different materials.

(Curing process)
In the curing step, the active energy ray is irradiated to the uncured photocurable adhesive to cure the adhesive layer containing the epoxy compound or the oxetane compound. Thereby, the overlapped polarizer and the optical film are bonded via the photocurable adhesive. When bonding an optical film to the single side | surface of a polarizer, you may irradiate an active energy ray from either a polarizer side or an optical film side. Moreover, when bonding an optical film on both surfaces of a polarizer, an active energy ray is applied from either one of the optical films in a state where the optical film is superimposed on both surfaces of the polarizer via a photocurable adhesive. It is advantageous to irradiate and simultaneously cure the photocurable adhesive on both sides.

  As the active energy ray, for example, visible light, ultraviolet ray, X-ray, electron beam and the like can be used, and since it is easy to handle and has a sufficient curing rate, generally, electron beam or ultraviolet ray is preferably used. It is done.

  Any appropriate condition can be adopted as the irradiation condition of the electron beam as long as it can cure the photo-curable adhesive. For example, in the electron beam irradiation, the acceleration voltage is preferably in the range of 5 to 300 kV, more preferably in the range of 10 to 250 kV. When the acceleration voltage is 5 kV or more, the electron beam reaches the photocurable adhesive and can be sufficiently cured, and when the acceleration voltage is 300 kV or less, the penetrating power through the sample does not become too strong, and the electron Damage to the optical film and the polarizer due to the bounce of the line can be more reliably suppressed. The irradiation dose is in the range of 5 to 100 kGy, more preferably in the range of 10 to 75 kGy. When the irradiation dose is 5 kGy or more, the photocurable adhesive can be sufficiently cured, and when it is 100 kGy or less, the optical film and the polarizer are not damaged, and the mechanical strength is reduced or yellowed. Can be suppressed, and predetermined optical characteristics can be obtained.

Any appropriate condition can be adopted as the irradiation condition of the ultraviolet ray as long as it can cure the photo-curable adhesive. For example, the irradiation amount of ultraviolet rays is preferably in accumulated light amount is within the range of 50~1500mJ / cm ^2, and more preferably in the range of 100 to 500 mJ / cm ^2.

  In the circularly polarizing plate obtained as described above, the thickness of the adhesive layer is not particularly limited, but is usually in the range of 0.01 to 10 μm, preferably in the range of 0.5 to 5 μm. .

<< Organic EL display device >>
The organic EL display device of the present invention is manufactured by including the above-described circularly polarizing plate of the present invention.

  More specifically, the organic EL display device of the present invention includes a circularly polarizing plate using the optical film of the present invention and an organic EL element. Therefore, in the organic EL display device of the present invention, reflection during observation is prevented, and black expression is improved. The screen size of the organic EL display device is not particularly limited, and can be 20 inches or more.

  FIG. 5 is a schematic explanatory diagram of the configuration of the organic EL display device of the present invention. The configuration of the organic EL display device of the present invention is not limited to that shown in FIG.

As shown in FIG. 5, the organic EL display device 200 is configured by laminating a circularly polarizing plate 400 on an organic EL element 300.
The organic EL element 300 includes a metal electrode 102, a TFT 103, an organic light emitting layer 104, a transparent electrode (ITO etc.) 105, an insulating layer 106, a sealing layer 107, and a film 108 (on a transparent substrate 101 made of glass, polyimide, etc. It can be omitted). The thickness of the organic EL element 300 configured in this way is about 1 μm.
Further, the circularly polarizing plate 400 is configured such that the polarizer 110 is sandwiched between the retardation film 109 and the protective film 111 which are the optical films of the present invention described above. Moreover, it is preferable that the hardened layer 112 is laminated on the protective film 111 of the circularly polarizing plate 400. Thereby, it is possible to prevent the surface of the organic EL display device 200 from being scratched and to prevent the circularly polarizing plate 400 from warping. Further, an antireflection layer 113 may be laminated on the cured layer 112 of the circularly polarizing plate 400.

  In general, in an organic EL display device, a metal electrode, an organic light emitting layer, and a transparent electrode are sequentially laminated on a transparent substrate to form an element (organic EL element) that is a light emitter. Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Structures having various combinations such as a laminate of such a light emitting layer and an electron injection layer composed of a perylene derivative or the like, or a laminate of these hole injection layer, light emitting layer and electron injection layer are known.

  In organic EL display devices, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the phosphor material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be predicted from this, the current and the emission intensity show strong nonlinearity with rectification with respect to the applied voltage.

  In an organic EL display device, in order to extract emitted light from the organic light emitting layer, at least one of the electrodes needs to be transparent, and is usually formed of a transparent conductor such as indium tin oxide (ITO). The 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 of the present invention can be applied to an organic EL display device composed of 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 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. Therefore, 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 display device looks like a mirror surface.

  Since a circularly polarizing plate is provided on the surface side (viewing side) of the transparent electrode of such an organic EL display device, the circularly polarizing plate has a function of polarizing light incident from the outside and reflected by the metal electrode. The mirror surface of the metal electrode can be prevented from being visually recognized by the polarization action.

That is, only the linearly polarized light component of the external light incident on the organic EL display device is transmitted by the polarizer, and this linearly polarized light becomes circularly polarized light by the optical film of the present invention.
This circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, reflected by the metal electrode, and again transmitted through the organic thin film, the transparent electrode, and the transparent substrate to become linearly polarized light. And since this linearly polarized light is orthogonal to the polarization direction of a polarizer, it cannot permeate | transmit a circularly-polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.

  EXAMPLES 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 "%" is used in an Example, unless otherwise indicated, "mass%" is represented. Further, the degree of substitution and the number of substituents shown below all represent average values.

[Example 1]
In producing the retardation film containing the cellulose ester (C) of the present invention, the following cellulose ester (A) (cellulose ester A-1 to A-9) and cellulose ester (B) (cellulose ester B-1) ~ B-34) were synthesized.
<Synthesis of cellulose ester (A)>
<< Synthesis of Cellulose Ester A-1 >>
After pretreatment activation by spraying 50 parts by mass of glacial acetic acid to 100 parts by mass of softwood sulfite pulp (α-cellulose content 97.2%, hemicellulose content 1.5 mol%), 470 masses of glacial acetic acid A mixture of 410 parts by mass of acetic anhydride and 8.3 parts by mass of sulfuric acid was added, and esterification was performed by a conventional method. Thereafter, 95 parts by mass of acetic acid and 33 parts by mass of water were added for hydrolysis, and 5.7 parts by mass of calcium acetate was added to neutralize sulfuric acid in the system. As a result, cellulose acetate pentylate (cellulose ester A-1) having an acetyl group substitution degree of 2.4 and a viscosity average polymerization degree of 200 was obtained.
It was 160000 as a result of measuring the weight average molecular weight Mw of the said synthesized cellulose ester A-1 using the gel permeation chromatography (GPC). Specific measurement conditions are 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 calibration curve using 13 samples of standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) and having Mw in the range of 500 to 1000000 was used. Thirteen samples are used at approximately equal intervals.

<< Synthesis of Cellulose Esters A-2 to A-4 and A-9 >>
In the synthesis of the cellulose ester A-1, in addition to acetic anhydride, propionic anhydride and butyric anhydride were used, and the amount and reaction conditions were changed as appropriate to obtain the substitution degree shown in Table 2. Similarly, cellulose esters A-2 to A-4 and A-9 were obtained.
Moreover, the weight average molecular weight Mw of each cellulose ester was calculated | required by the method similar to the said cellulose ester A-1.

<< Synthesis of Cellulose Ester A-5 >>
After pretreatment activation by spraying 50 parts by mass of glacial acetic acid to 100 parts by mass of softwood sulfite pulp (α-cellulose content 96.8%, hemicellulose content 1.5 mol%), 470 parts by mass of glacial acetic acid Then, a mixture of 265 parts by mass of acetic anhydride, 153 parts by mass of valeric anhydride and 8.3 parts by mass of sulfuric acid was added, and esterification was performed by a conventional method. Thereafter, 95 parts by mass of acetic acid and 33 parts by mass of water were added for hydrolysis, and 5.7 parts by mass of calcium acetate was added to neutralize sulfuric acid in the system. As a result, cellulose acetate pentylate (cellulose ester A-5) having an acetyl group substitution degree of 1.55, a pentyl group substitution degree of 0.90, and a viscosity average polymerization degree of 180 was obtained.
It was 18000 as a result of measuring the weight average molecular weight Mw of the said cellulose ester A-5 by the method similar to the said cellulose ester A-1.

<< Synthesis of Cellulose Esters A-6 to A-8 >>
In the synthesis of the cellulose ester A-5, propionic anhydride and butyric anhydride were used in place of acetic anhydride and valeric anhydride, and the amounts and reaction conditions were appropriately changed so that the substitution degree shown in Table 2 was obtained. In the same manner as above, cellulose esters A-6 to A-8 were obtained.
Moreover, the weight average molecular weight Mw of each cellulose ester was calculated | required by the method similar to the said cellulose ester A-1.
The phase difference values Ro (550) and Ro (450) / Ro (550) shown in Table 2 were measured and determined according to the method described later.

<Synthesis of cellulose ester (B)>
<< Synthesis of Cellulose Ester B-3 >>
A 3 L three-necked flask equipped with a mechanical stirrer, thermometer, condenser, and dropping funnel was added to cellulose acetate having a degree of acetyl group substitution of 2.4 ("CA-394-60s" manufactured by Eastman Chemical, weight average molecular weight Mw: 160000) ), 250 mL of pyridine, and 3000 mL of acetone were added, and the mixture was stirred at room temperature. To this, 26.7 g of benzoyl chloride was slowly dropped and added, followed by further stirring at 50 ° C. for 8 hours. After the reaction, the reaction solution was allowed to cool to room temperature, and the reaction solution was poured into 20 L of methanol with vigorous stirring, whereby a white solid was precipitated. The white solid was separated by suction filtration and washed with a large amount of methanol three times. The obtained white solid was dried at 60 ° C. overnight and then vacuum dried at 90 ° C. for 6 hours to obtain the target cellulose ester B-3.

About the substitution degree of the substituent which the glucose skeleton of the said cellulose ester B-3 synthesize | combined, according to the method of Cellulose Communication 6,73-79 (1999) and Chrality 12 (9), 670-674, ¹ H As a result of measuring by -NMR and ¹³ C-NMR and obtaining the average value, the degree of substitution of the benzoyl group, which is a substituent having an aromatic ring, is 0.60, and the degree of substitution of the acetyl group is 2.40. Yes, the total degree of substitution was 3.00.

  It was 166000 as a result of measuring the weight average molecular weight Mw of the said synthesized cellulose ester B-3 using gel permeation chromatography (GPC). Specific measurement conditions are 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 calibration curve using 13 samples of standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) and having Mw in the range of 500 to 1000000 was used. Thirteen samples are used at approximately equal intervals.

<< Synthesis of Cellulose Ester B-23 >>
Cellulose acetate propionate with an acetyl group substitution degree of 1.55 and a propionyl group substitution degree of 0.90 (manufactured by Eastman Chemical Co., Ltd., weight) (Average molecular weight Mw: 170000) 250 g, N methylpyrrolidone (114 mL), and acetone (3000 mL) were added, and the mixture was stirred at room temperature. 10.0 g of phenyl isocyanate was slowly added dropwise thereto and added, and the mixture was further stirred at 50 ° C. for 8 hours. After the reaction, the mixture was allowed to cool to room temperature, and the reaction solution was poured into 10 L of methanol with vigorous stirring, whereby a white solid was precipitated. The white solid was separated by suction filtration and washed with a large amount of methanol three times. The obtained white solid was dried at 60 ° C. overnight and then vacuum dried at 90 ° C. for 6 hours to obtain the target cellulose ester B-23.

As a result of obtaining the degree of substitution of the substituent of the glucose skeleton of cellulose ester B-23 by the same method as in the case of cellulose ester B-3, the degree of substitution of the phenylcarbamoyl group, which is a substituent having an aromatic ring, is The substitution degree of the acetyl group was 1.55, the substitution degree of the propionyl group was 0.90, and the total substitution degree was 2.70.
Moreover, it was 172000 as a result of calculating | requiring the weight average molecular weight Mw of the cellulose ester B-23 by the method similar to the said cellulose ester B-3.

<< Synthesis of Cellulose Esters B-1, B-2, B-4 to B-22, B-24 to B-34 >>
In the synthesis of the cellulose ester B-3, the type and amount of the raw material cellulose ester, other reaction conditions, etc. were changed as appropriate to obtain the substitution degree shown in Tables 3 and 4 in the same manner. Cellulose esters B-1, B-2, B-4 to B-22, and B-24 to B-34 were obtained.
Moreover, the weight average molecular weight Mw of each cellulose ester was calculated | required by the method similar to the said cellulose ester B-3.
In addition, the dispersion | variation (variation) of phase difference value Ro (550) of Table 3 and Table 4, Ro (450) / Ro (550), and Ro (450) / Ro (550) was measured according to the method mentioned later. Asked.

<Preparation of retardation film containing cellulose ester (C)>
It is a combination of the cellulose ester (A) and the cellulose ester (B) described in Table 5 below, and is mixed at the mixing ratio of the cellulose ester (B) described in Table 5. Further, the additive described in Table 5 The compound was added to prepare retardation films C1 to C24 containing cellulose ester (C) (C-1 to C-24).
The mixing ratio shown in Table 5 is the ratio (mass%) of cellulose ester (B) to the total amount of cellulose ester (A) and cellulose ester (B) (cellulose ester (B) / cellulose ester ( A) + cellulose ester (B)).

<< Production of Retardation Film C1 >>
(Preparation of fine particle dispersion)
Fine particles (Aerosil R812 manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed using a Manton Gorin disperser to prepare a fine particle dispersion.

(Preparation of fine particle additive solution 1)
50 parts by mass of dimethyl chloride was placed in the dissolution tank, and 50 parts by mass of the fine particle dispersion prepared above was slowly added while sufficiently stirring the dimethyl 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, the following dimethyl chloride and ethanol were added to the pressure dissolution tank. Cellulose ester A-2, the synthesized cellulose ester B-23, and the following additive compound were added to a pressure dissolution tank containing an organic solvent while stirring. This was completely dissolved with heating and stirring. Subsequently, after adding the fine particle addition liquid 1, Azumi filter paper No. 1 manufactured by Azumi Filter Paper Co., Ltd. was used. The dope was prepared by filtration using 244.

<Dope composition>
Dimethyl chloride 340 parts by mass Ethanol 64 parts by mass Cellulose ester B-23 20 parts by mass Cellulose ester A-2 80 parts by mass Additive compound (polyester) E-1 10 parts by mass Fine particle additive liquid 1 2 parts by mass

(Film formation)
The prepared dope was cast on a stainless steel belt support, and then the film was peeled from the stainless steel belt support.
The peeled raw film was uniaxially stretched only in the width direction (TD direction) using a tenter while heating, and the conveyance tension was adjusted so as not to shrink in the conveyance direction (MD direction).
Next, drying was terminated while the drying zone was conveyed through many rollers, and a roll-shaped raw film was produced. The stretch ratio of the film was 10%, and the thickness was approximately 100 μm.

(Stretching process)
Using the oblique stretching apparatus having the configuration shown in FIG. 2, this raw film is stretched in an oblique direction so that the optical slow axis of the film is 45 ° with respect to the transport direction. A phase difference film C1 (optical film of the present invention) was produced.

  The stretching conditions were an oblique stretching rate of 100% and a shrinkage rate of 20%.

<< Production of Retardation Films C2 to C24 >>
In the production of the retardation film C1, in place of the cellulose esters B-23, A-2 and the additive compound E-1, cellulose esters (A), (B) and additive compounds as shown in Table 5 respectively. And retardation films C2 to C24 were produced in the same manner except that the mixing ratio of the cellulose ester (B) shown in Table 5 was used.

<Production of organic EL display device>
<< Production of Circular Polarizing Plates C1 to C24 >>
A 120 μm-thick polyvinyl alcohol film was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution composed 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. composed of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a polarizer.
Bonding is performed using an ultraviolet curable adhesive so that the slow axis of each of the produced retardation films C1 to C24 and the absorption axis of the polarizer are 45 °, and a protective film is provided on the back side of the polarizer. (Konica Minolta Tack KC4UY, thickness 40 μm, manufactured by Konica Minolta Co., Ltd.) was bonded together with water paste to prepare circularly polarizing plates C1 to C24.

<< Production of Organic EL Display Devices C1 to C24 >>
According to the method described in the example of JP 2010-20925 A using a 3 mm-thick 50 inch (127 cm) non-alkali glass, it was described in FIG. 8 of JP 2010-20925 A An organic EL cell having a configuration was produced.
After apply | coating an adhesive agent on the surface of the retardation film of each produced said circularly-polarizing plate C1-C24, organic EL display apparatus C1-C24 was produced by bonding on the visual recognition side of an organic EL cell.

<Evaluation>
<< Evaluation of retardation films C1 to C24 >>
The following evaluation was performed about the produced retardation film. The evaluation results are shown in Table 6.
(1) In-plane retardation value (Ro (550))
The in-plane retardation value (Ro (550)) of the retardation film obtained above is a surface defined by the following formula (1) at an optical wavelength of 550 nm in an environment of a temperature of 23 ° C. and a humidity of 55% RH. The phase difference value (Ro) was measured using Axoscan manufactured by Axometrics.
Specifically, under the environment of 23 ℃ · 55% RH The film performs refractive index measurement of three-dimensional in the light wavelength of 550 nm, after the average value of the refractive index _{n x, n y, n z} , The in-plane retardation value Ro was calculated according to the following formula.
Equation _{(1): Ro = (n} x -n y) × d
In the formula (1), n _x represents a refractive index in the direction x in which the refractive index in the plane direction becomes maximum retardation films. n _y, in-plane direction of the retardation film, the refractive index in the direction y perpendicular to the direction x. n _z represents the refractive index in the thickness direction z of the retardation film. d represents the thickness (nm) of the film.

(2) Ro (450) / Ro (550) (chromatic dispersion value)
The chromatic dispersion value (DSP) of the retardation film obtained above is the same as the in-plane retardation value (Ro) at an optical wavelength of 450 nm and 550 nm in an environment of a temperature of 23 ° C. and a humidity of 55% RH. Measurement was performed using an Axoscan manufactured by the company, and Ro (450) was determined as an in-plane retardation value at a light wavelength of 450 nm, and Ro (550) was determined according to the following equation as an in-plane retardation value at 550 nm.
Formula (2): DSP = Ro (450) / Ro (550)

(3) Dispersion (variation) of Ro (450) / Ro (550)
The variation (variation) of Ro (450) / Ro (550) is 13 points at intervals of 10 cm in the width direction, 5 points at intervals of 500 mm in the length direction, and Ro at each wavelength (450 nm, 550 nm) at a total of 65 points. Was measured. The value of Ro (450) / Ro (550) is calculated from the measured Ro value, and | Ro (450) / Ro (550) max−Ro (450) / Ro is calculated from the difference between the maximum value and the minimum value. (550) min | was determined.

(4) Haze With respect to the retardation film obtained above, a haze meter (NDH2000 type, Nippon Denshoku Co., Ltd.) was prepared according to JIS K-7136 for one sample that was conditioned for 24 hours in an air conditioning room at a temperature of 23 ° C. and a humidity of 55% RH. Haze was measured using Kogyo Co., Ltd.

<< Evaluation of Organic EL Display Devices C1 to C24 >>
The following evaluation was performed about the produced said organic electroluminescent display apparatus. The evaluation results are shown in Table 6.
(1) Evaluation of black color (normal environment)
Under an environment of a temperature of 23 ° C. and a humidity of 55% RH, a black image was displayed on the organic EL display device under the condition that the illuminance was 1000 Lx at a position 5 cm higher than the outermost surface of each organic EL display device.
The color of the black image from the front position of each organic EL display device (0 ° with respect to the surface normal) and the oblique angle of 40 ° with respect to the surface normal is comparatively observed and The presence or absence of influence was evaluated according to the following criteria by 10 general monitors. In addition, if it was more than (triangle | delta), it was judged that it was practically possible as visibility of the observation position difference of a black hue.
◎: 9 or more monitors determined that the displayed black color was not affected by the observation position. ○: 7 to 8 monitors determined that the displayed black color was not affected by the observation position. △: Five to six monitors determined that the displayed black color was not affected by the observation position. ×: Four or fewer monitors indicated that the displayed black color was not affected by the observation position. Judged

(2) Evaluation of reflection performance (under normal environment)
In the production of the organic EL display device, in the same manner as in the production of the organic EL cell, except that red, blue, and green lines were provided with magic ink on the surface on the viewing side of the organic EL cell. An EL display device was produced.
The produced organic EL display having red, blue, and green lines has an illuminance of 1000 Lx at a position 5 cm higher than the outermost surface of each organic EL display device in a normal humidity environment at a temperature of 23 ° C. and a humidity of 55% RH. Under the conditions, the visibility (reflection performance) of the lines of the magic ink attached to the organic EL display device was evaluated by 10 general monitors according to the following criteria. If Δ or more, the reflection performance was judged to be practical. The reflection performance here refers to reflection in the organic EL cell that enters the inside of the circularly polarizing plate, not reflection on the surface of the circularly polarizing plate.
◎: Nine or more monitors determined that no color of the magic ink line was visible ○: 8-7 monitors determined that no color of the magic ink line was visible △: 5 ~ 6 monitors determined that two of the magic ink lines were not visible ×: Less than four monitors determined that two of the magic ink lines were not visible

As is clear from the results shown in Tables 5 and 6, the organic EL display device of the present invention including the circularly polarizing plate having the retardation film having the structure defined in the present invention is an organic EL display device of a comparative example. On the other hand, it can be seen that the visibility of black color and the reflection performance are excellent due to different observation positions.
That is, an organic EL display having an optical film using a cellulose ester in which the degree of substitution of a substituent having an aromatic ring (benzoyl group or phenylcarbamoyl group) is in the range of 0.05 to 0.6 per glucose skeleton unit The device is excellent in black color visibility and reflection performance. It can be seen that the organic EL display device C6 using the mixed cellulose ester C-6 in which the degree of substitution of the substituent having an aromatic ring is less than 0.05 is inferior in black color visibility.
It can be seen that the organic EL display device C21 using the mixed cellulose ester C-21 in which the substitution degree of the substituent having an aromatic ring is more than 0.6 is inferior in reflection performance.
In addition, organic EL display using mixed cellulose esters C-4, C-5, C-8, C-13, C-20, and C-21 whose Ro (550) value is less than 120 nm and greater than 160 nm It can be seen that the devices C4, C5, C8, C13, C20 and C21 are inferior in reflection performance.
Organic EL display devices C5, C6 using mixed cellulose esters C-5, C-6, and C-17 having Ro (450) / Ro (550) values of less than 0.8 and greater than 0.9, And C-17 shows that the visibility of black color is inferior.
C-5 and C-22 not mixed with the cellulose ester (A) before introducing the phenylcarbamoyl group and benzoyl group are represented by | Ro (450) / Ro (550) max-Ro (450) / Ro (550). ) The value of min | is large, and it can be seen that the black color and the reflection performance are partially disturbed.

[Example 2]
<< Preparation of retardation film C30 >>
(Preparation of fine particle dispersion)
Fine particles (Aerosil R812 manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed using a Manton Gorin disperser to prepare a fine particle dispersion.

(Preparation of fine particle additive solution 1)
50 parts by mass of dimethyl chloride was placed in the dissolution tank, and 50 parts by mass of the fine particle dispersion prepared above was slowly added while sufficiently stirring the dimethyl 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, the following dimethyl chloride and ethanol were added to the pressure dissolution tank. Cellulose ester A-2 and the synthesized cellulose ester B-23 were added to a pressure dissolution tank containing an organic solvent while stirring. This was completely dissolved with heating and stirring. Subsequently, after adding the fine particle addition liquid 1, Azumi filter paper No. 1 manufactured by Azumi Filter Paper Co., Ltd. was used. The dope was prepared by filtration using 244.

<Dope composition>
Dimethyl chloride 340 parts by mass Ethanol 64 parts by mass Cellulose ester B-23 35 parts by mass Cellulose ester A-2 65 parts by mass Fine particle additive liquid 1 2 parts by mass

(Film formation)
The prepared dope was cast on a stainless steel belt support, and then the film was peeled from the stainless steel belt support.

  The peeled raw film was uniaxially stretched only in the width direction (TD direction) using a tenter while heating, and the conveyance tension was adjusted so as not to shrink in the conveyance direction (MD direction).

  Next, drying was terminated while the drying zone was conveyed through many rollers, and a roll-shaped raw film was produced. The stretch ratio of the film was 10%, and the thickness was approximately 100 μm.

(Stretching process)
Using the oblique stretching apparatus having the configuration shown in FIG. 2, this raw film is stretched in an oblique direction so that the optical slow axis of the film is 45 ° with respect to the transport direction. A phase difference film C1 (optical film of the present invention) was produced.

  The stretching conditions were an oblique stretching rate of 100% and a shrinkage rate of 20%.

<< Production of Retardation Films C31 to C34 >>
In the production of the retardation film C30, retardation films C31 to C34 were produced in the same manner except that the additive compound and the addition amount thereof were as shown in Table 7, respectively.

<< Production of Circular Polarizing Plates C30 to C34 >>
Using the produced retardation films C30 to C34, circularly polarizing plates C30 to C34 were produced in the same manner as the circularly polarizing plates C1 to C24 in Example 1.

<< Production of Organic EL Display Devices C30 to C34 >>
Using the produced circularly polarizing plates C30 to C34, organic EL display devices C30 to C34 were produced in the same manner as the production of the organic EL display devices C1 to C24 in Example 1.

<Evaluation>
<< Evaluation of Retardation Films C30 to C34 >>
About the produced retardation film, it carried out similarly to evaluation of the retardation film of Example 1, (1) In-plane retardation value (Ro (550)), (2) Ro (450) / Ro (550) (Chromatic dispersion value), (3) Ro (450) / Ro (550) variation (variation), (4) haze, and the following evaluations were performed. The evaluation results are shown in Table 8.

(5) Moisture permeability Moisture permeability was measured by allowing each retardation film to stand for 24 hours under conditions of a temperature of 40 ° C. and a humidity of 90% RH based on the cup method described in JIS Z 0208.

<< Evaluation of Organic EL Display Devices C30 to C34 >>
For each of the produced organic EL display devices C30 to C34, the evaluation of black color and reflection performance under normal environment and the following evaluation were performed in the same manner as in Example 1. The evaluation results are shown in Table 8.

(1) Humidity stability of black color Organic EL in a low humidity environment with a temperature of 23 ° C. and a humidity of 20% RH under conditions where the illuminance at a position 5 cm higher than the outermost surface of each organic EL display device is 1000 Lx A black image was displayed on the display device. Next, a black image was similarly displayed in a high humidity environment at a temperature of 23 ° C. and a humidity of 80% RH.
Under the above two environments, the front position of each organic EL display device (0 ° with respect to the surface normal) and the color tone of the black image from an oblique angle of 40 ° with respect to the surface normal are compared and observed depending on the humidity. The presence or absence of an influence on the black color was evaluated according to the following criteria by 10 general monitors. In addition, if it was more than (triangle | delta), it was judged that it was practically possible as humidity stability of a black hue.
A: Nine or more monitors have determined that the displayed black color has no humidity effect. ○: Seven to eight monitors have determined that the displayed black color has no humidity effect. Δ: 5 ~ 6 monitors determined that the displayed black color had no humidity effect ×: Less than 4 monitors determined that the displayed black color had no humidity effect

(2) Humidity stability of reflection performance In the production of the organic EL display device, at the stage of producing the organic EL cell, red, blue, and green lines were added to the viewing side surface of the organic EL cell with magic ink. In the same manner, an organic EL display device for evaluation was produced.
Conditions for the organic EL display having the red, blue, and green lines produced to have an illuminance of 1000 Lx at a position 5 cm higher than the outermost surface of each organic EL display device in a low humidity environment at a temperature of 23 ° C. and a humidity of 20% RH. Below, the visibility (reflection performance) of the line of the magic ink attached to the organic EL display device was evaluated. Subsequently, the visibility (reflection performance) of the magic ink line was similarly evaluated by 10 general monitors according to the following criteria under a high humidity environment of 23 ° C. and 80% RH. In addition, if it was more than (triangle | delta), it was judged that it was practically possible as humidity stability of reflective performance. The reflection performance here refers to reflection in the organic EL cell that enters the inside of the circularly polarizing plate, not reflection on the surface of the circularly polarizing plate.
A: Nine or more monitors determined that there was no humidity effect on the visibility of the magic ink line. ○: Seven to eight monitors determined that there was no humidity effect on the visibility of the magic ink line. ~ 6 monitors determined that there was no humidity effect on the visibility of magic ink lines. X: Less than 4 monitors determined that there was no humidity effect on the visibility of magic ink lines.

  As is clear from the results shown in Tables 7 and 8, the organic EL display device of the present invention including the circularly polarizing plate having the retardation film having the structure defined in the present invention is an organic EL display device of a comparative example. On the other hand, it can be seen that the visibility of black color and the reflection performance are excellent due to different observation positions.

That is, the organic EL display devices C33 and C34 using the mixed cellulose esters C-33 and C-34 whose Ro (450) / Ro (550) value exceeds 0.9 have a black color visibility. It turns out that it is inferior.
Moreover, it turns out that the cellulose ester C-30 which does not put an additive compound is a little inferior in the visibility of the black color in a humidity environment.

[Example 3]
<< Production of Retardation Films C25 and C26 >>
In the production of the retardation film C2 of Example 1, retardation films C25 and C26 were produced in the same manner except that the shrinkage rate in the stretching process was changed to the conditions described in Table 9.

<< Production of Retardation Films C27 and C28 >>
In the production of the retardation film C7 of Example 1, retardation films C27 and C28 were produced in the same manner except that the shrinkage rate in the stretching process was changed to the conditions described in Table 9.

<< Production of Circular Polarizing Plates C25-C28 >>
Circular polarizing plates C25 to C28 were prepared in the same manner as the circular polarizing plates C1 to C24 in Example 1 using the prepared retardation films C25 to C28.

<< Production of Organic EL Display Devices C25 to C28 >>
Organic EL display devices C25 to C28 were manufactured in the same manner as the organic EL display devices C1 to C24 in Example 1 using the circular polarizers C25 to C28 manufactured above.

<< Evaluation of Organic EL Display Devices C25 to C28 >>
About each produced said organic EL display apparatus C25-C28, similarly to the said Example 1, the black color and reflection performance evaluation in normal environment were performed. Table 9 shows the evaluation results.

  As is clear from the results shown in Table 9, the organic EL display devices C2, C7, C25 and C27 having an optical film having a shrinkage ratio in the range of 10 to 30% during stretching have a shrinkage ratio of 10 to 30. It can be seen that the visibility of black color and the reflection performance are superior to those of the organic EL display devices C26 and C28 having an optical film not in the range of%.

DESCRIPTION OF SYMBOLS 11 Stretching direction 12 Diagonal stretching direction 13 Conveying direction 14 Slow axis 15 Diagonal stretching device 16 Film feeding device 17 Conveying direction changing device 18 Winding device 19 Peeling / drying process exit 101 Transparent substrate 102 Metal electrode 103 TFT
DESCRIPTION OF SYMBOLS 104 Organic light emitting layer 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 200 Organic EL display device 300 Organic EL element 400 Circularly polarizing plate Ci , Co Grip D1 Feeding direction D2 Winding direction F Optical film Ri, Ro Rail θ Bending angle θi Bending angle (feeding angle)
θL Angle Wo Width of the film before stretching W Width of the film after stretching

Claims (6)

Cellulose ester (A) prepared by mixing cellulose ester (A) and cellulose ester (B) having a phenylcarbamoyl group or benzoyl group introduced as part of the substituent of the glucose skeleton of cellulose ester (A) ( C),
The degree of substitution of the phenylcarbamoyl group or the benzoyl group is in the range of 0.05 to 0.6 per glucose skeleton unit of the cellulose ester (C), and
An optical film characterized by satisfying the following requirements (a) to (e).
(A) The retardation value Ro (550) in the film plane measured at a light wavelength of 550 nm in an environment of a temperature of 23 ° C. and a humidity of 55% RH is in the range of 120 to 160 nm.
(B) The ratio value Ro (450) / Ro (550) of the in-plane retardation values Ro (450) and Ro (550) measured at light wavelengths of 450 nm and 550 nm, respectively, is 0.8-0. It is in the range of 9.
(C) The Ro (450) / Ro (550) value described in (b) satisfies the following formula.
| Ro (450) / Ro (550) max−Ro (450) / Ro (550) min | ≦ 0.02
(D) The substituent other than the phenylcarbamoyl group or the benzoyl group is any one of an acetyl group, a propionyl group, and a butyryl group.
(E) The total degree of substitution per glucose skeleton unit of the cellulose ester (C) is in the range of 2.35 to 2.75.   The cellulose ester (B) is contained within a range of 20 to 50% by mass with respect to the total amount of the cellulose ester (A) and the cellulose ester (B). The optical film as described.   The polyester having both ends sealed with an aromatic group is contained in the range of 1 to 15% by mass with respect to 100% by mass of the cellulose ester (C). 2. The optical film according to 2. By extending in an oblique direction with respect to the long direction, the slow axis is in the range of 40 to 50 ° with respect to the long direction,
The optical film according to any one of claims 1 to 3, wherein a shrinkage rate defined by the following formula is in a range of 10 to 30%.
Shrinkage rate (%) = (1-sin (π−θ)) × 100
(In the above formula, θ represents the angle of the stretching direction with respect to the longitudinal direction.)   A circularly polarizing plate formed by cutting a long roll in which the optical film according to any one of claims 1 to 4 and a long polarizer are bonded.   An organic electroluminescence display device comprising the circularly polarizing plate according to claim 5.

Images