WO2014061215A1 - Phase difference film, circular polarization plate and organic el display manufactured using phase difference film - Google Patents

Abstract

A phase difference film according to the present invention has an in-plane phase difference (Ro₅₅₀) of 100 to 155nm in a wavelength of 550nm, and the ratio of an in-plane phase difference (Ro₄₅₀) to Ro₅₅₀ in a wavelength of 450nm is 0.72 to 0.95. The ratio of Ro₅₅₀ to an in-plane phase difference (Ro₆₅₀) in a wavelength of 650nm is 0.83 to 0.97. The phase difference film has a slow axis of 10° to 80° with reference to the longitudinal direction, and contains a resin having a positive intrinsic birefringence, an additive that functions to increase retardation and adjust wavelength dispersion, and an additive having a negative intrinsic birefringence.

Description

Retardation film, circularly polarizing plate produced using the retardation film, and organic EL display

The present invention relates to a retardation film, a circularly polarizing plate produced using the retardation film, and an organic EL display.

In recent years, organic electroluminescence elements that emit light by applying a voltage to a light emitting layer provided between electrodes (hereinafter sometimes simply referred to as organic EL elements) have been actively researched and developed. Organic EL elements have excellent characteristics such as luminous efficiency, low voltage drive, light weight, and low cost, so various light sources such as flat illumination, optical fiber light source, liquid crystal display backlight, liquid crystal projector backlight, display, etc. It is used as and has received a great deal of attention.

The organic EL element injects electrons from the cathode and holes from the anode, and recombines them with the light emitting layer, thereby generating visible light emission corresponding to the light emission characteristics of the light emitting layer.

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

On the other hand, a metal electrode is usually used for the cathode. Among metal electrodes, metal materials such as Mg, Mg / Ag, Mg / In, Al, and Li / Al are mainly used from the viewpoint of work function in consideration of electron injection efficiency. These metal materials have high light reflectivity, and in addition to the function as an electrode (cathode), they also have a function of reflecting light emitted from the light emitting layer and increasing the amount of emitted light (light emission luminance). That is, the light emitted in the cathode direction is mirror-reflected on the surface of the metal material that is the cathode, and is extracted as outgoing light from the transparent ITO electrode (anode).

However, in the organic EL element having such a structure, since the cathode has a mirror surface with high light reflectivity, external light reflection is noticeable in a state where no light is emitted. That is, there is a problem that the interior lighting during observation is intense, black color cannot be expressed in a bright place, and the bright room contrast is extremely low for use as a light source for a display.

In order to improve this problem, a method is disclosed in which a circularly polarizing element (hereinafter sometimes simply referred to as a circularly polarizing plate) is used to prevent reflection of external light from a mirror surface (see, for example, Patent Document 1). In the circularly polarizing element described in Patent Document 1, the absorption linear polarizing plate and the quarter retardation film have an absorption axis of the polarizing plate and an in-plane slow axis of the quarter retardation film of 45. It is formed by being laminated so as to intersect at a degree (or 135 degrees).

By using the circularly polarizing element, the linearly polarized light transmitted through the polarizer is completely converted to circularly polarized light by the quarter retardation film and reflected by the above-mentioned metal surface to become reversely rotated circularly polarized light. By passing through the ¼ retardation film, it is converted into linearly polarized light that is orthogonal to the incident light, so that it can be completely blocked by a polarizer. However, while the light source used is light having a wavelength region in the entire visible light region (for example, about 400 nm to 700 nm), it can be exactly ¼ wavelength for a wavelength having a phase difference of the retardation film. However, at other wavelengths, the phase difference may deviate from the quarter wavelength. As a result, it may not function as a quarter retardation film for at least part of the light. That is, for example, when functioning as a ¼ retardation film for green light of 550 nm, it becomes difficult to completely prevent reflection of red light having a longer wavelength or blue light having a shorter wavelength. There is a problem that the phase difference with respect to light is large and the reflected color is blue.

Therefore, in order to prevent reflection with respect to all wavelengths of visible light, an inverse wavelength dispersion characteristic having a phase difference value of substantially λ / 4 in all wavelength regions of the visible light region (the phase difference value becomes longer for longer wavelengths). Large) is desirable. As films exhibiting such reverse wavelength dispersion characteristics, the films described in Patent Documents 2 to 6 are known.

Patent Document 2 and Patent Document 3 disclose a retardation plate adjusted to exhibit reverse wavelength dispersion characteristics by laminating a plurality of stretched films. Since the retardation plate described in Patent Document 2 and Patent Document 3 has a laminated structure, the retardation axis of each stretched film is assembled so as to have a specific arrangement, and further, specific to the polarizer. Since it is necessary to assemble by arrangement, a complicated operation is required, and if the assembling accuracy is not sufficient, the contrast may be lowered due to light leakage of reflected light. Further, since such a retardation plate has a laminated structure, the thickness is increased, resulting in a problem that the thickness of the display is increased.

Therefore, an attempt has been made to produce a single-layer λ / 4 retardation film. For example, Patent Document 4 discloses a single-layer film made of a resin containing a norbornene-based resin and a polymer having negative intrinsic birefringence. Patent Document 5 discloses a single layer film composed of a polymer including a monomer unit having positive intrinsic birefringence and a monomer unit having negative intrinsic birefringence. According to such a technique, by adding a polymer having negative intrinsic birefringence to a resin having positive intrinsic birefringence, it is possible to impart reverse wavelength dispersion characteristics to the phase difference by a single layer configuration. is there. However, when a polymer having a negative intrinsic birefringence is added to a resin having a positive intrinsic birefringence, each component cancels each other by developing a phase difference in a direction perpendicular to the stretching direction. For this reason, the expression of the phase difference is greatly reduced. Therefore, when a phase difference of substantially about λ / 4 is to be imparted, it is necessary to increase the draw ratio, which causes generation of white turbidity (haze). In addition to white turbidity due to stretching, white turbidity due to phase separation at the time of blending raw materials is likely to occur, and there is a problem when the obtained retardation film is used for optical applications such as organic EL displays that require high contrast. There was a case.

In addition, by adding a specific additive having retardation increasing ability and wavelength dispersion adjusting ability to the cellulose ester resin, a technique for expressing a phase difference and imparting reverse wavelength dispersion characteristics to the phase difference has been studied (for example, Patent Document 6). According to such a technique, it is possible to obtain a desired phase difference while keeping the draw ratio relatively small by increasing the retardation expression with an additive. However, if all the phase difference and wavelength dispersion characteristics required by the additive are to be adjusted, it is necessary to add a large amount, which tends to cause white turbidity. Moreover, such an additive expresses a function of improving retardation expression by orienting the long axis direction of the molecule in the stretching direction, but in addition to the retardation expression, the necessary reverse wavelength dispersion characteristic is expressed in a balanced manner. It is difficult to adjust such additives, and in order to obtain sufficient reverse wavelength dispersion characteristics, it is necessary to provide a relatively large molecular structure in the direction perpendicular to the major axis direction of the molecule. As a result, there is a problem that the film becomes cloudy and the contrast of the display is lowered.

Also, when obtaining a circularly polarizing element, it is necessary to adjust the absorption axis of the polarizer and the slow axis of the retardation film to 45 ° as described above. In order to obtain such a circularly polarizing element, a retardation film or a polarizer having a specific size can be obtained by using a retardation film that has been stretched in the width direction or the longitudinal direction to develop a retardation as in the prior art. It is necessary to cut it into a desired size and cut it again to the desired size, which is inefficient, the chips generated at the time of cutting adhere to the film, cause scattering, and cause deterioration in contrast. There is a case. On the other hand, the polarizer and the retardation film are bonded to each other by roll-to-roll by performing a stretching process in the oblique direction to obtain a retardation film having a slow axis in the oblique direction with respect to the longitudinal direction. Therefore, the development of a retardation film having a slow axis in an oblique direction has been studied. However, in order to express the phase difference diagonally, a high-magnification stretching process is inevitably required to orient the slow axis in the diagonal direction, and white turbidity tends to occur. There is a need for technology to control.

Japanese Patent Laid-Open No. 8-321381 JP-A-2-285304 JP 2000-284126 A JP 2001-194527 A International Publication No. 00/26705 JP 2010-254949 A

The present invention has been made in view of such conventional problems, and is excellent in visibility and high in retardation development even when applied to a display such as an organic EL display that requires high contrast. A retardation film having a reverse wavelength dispersion characteristic and capable of providing a phase difference of λ / 4 to broadband light with suppressed white turbidity, a circularly polarizing plate produced using the retardation film, and organic An object is to provide an EL display.

As a result of intensive studies, the present inventors have combined a resin having positive intrinsic birefringence, an additive having retardation increasing ability and wavelength dispersion adjusting ability, and an additive having negative intrinsic birefringence. , Which can suppress the decrease in display contrast due to white turbidity of the film, can exhibit a λ / 4 phase difference substantially without increasing the thickness, and has a wide band with excellent reverse wavelength dispersion characteristics It was found that a retardation film can be obtained.

The retardation film of one aspect of the present invention has an in-plane retardation Ro _{550 at} a wavelength of 550 nm of 100 to 155 nm, and a ratio of the in-plane retardation Ro _{450 at} a wavelength of 450 nm to Ro ₅₅₀ (Ro ₄₅₀ / Ro ₅₅₀ ) The ratio of Ro _{550 to} the in-plane retardation Ro _{650 at} a wavelength of 650 nm (Ro ₅₅₀ / Ro ₆₅₀ ) is 0.83 to 0.97, and is slow with respect to the longitudinal direction. In the retardation film having an angle of 10 to 80 ° in the phase axis, the retardation film has a resin having positive intrinsic birefringence as a main component, and an additive having retardation increasing ability and wavelength dispersion adjusting ability; And an additive having negative intrinsic birefringence.

The objects, features and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.

FIG. 1 is a schematic diagram for explaining the shrinkage ratio in oblique stretching. FIG. 2 is a schematic view showing an example of an oblique stretching apparatus applicable to the production of the retardation film of one embodiment of the present invention. FIG. 3 is a schematic view showing an example of an oblique stretching apparatus applicable to the production of the retardation film of one embodiment of the present invention. FIG. 4 is a schematic explanatory diagram of the configuration of the organic EL display according to the embodiment of the present invention. FIG. 5 is a schematic diagram of a configuration of an organic EL display according to an embodiment of the present invention.

Hereinafter, although the form for implementing this invention is demonstrated in detail, this invention is not limited to this.

<Phase difference film>
The retardation film of the present embodiment (hereinafter sometimes simply referred to as a cellulose acylate film) includes a resin having positive intrinsic birefringence, an additive having retardation increasing ability and wavelength dispersion adjusting ability, and a negative intrinsic And an additive having birefringence, and the slow axis with respect to the longitudinal direction has an angle of 10 to 80 °. As a method for setting the slow axis angle to the longitudinal direction to 10 to 80 ° in this way, there can be mentioned a method of performing oblique stretching described later on the film before stretching. In the present specification, the “retardation film” means an optical film having a specific optical function for imparting a retardation to transmitted light, and has a predetermined light wavelength (usually visible light). In particular, a film having a function of giving an in-plane retardation substantially ¼ of a wavelength to a region) and converting linearly polarized light into circularly polarized light, or converting circularly polarized light into linearly polarized light, It is called “λ / 4 retardation film”.

The λ / 4 retardation film is a broadband λ having a phase difference of approximately ¼ of the wavelength in the visible light wavelength range in order to convert linearly polarized light into almost perfect circularly polarized light in a wide range of visible light wavelengths. A / 4 retardation film is preferable. In the present specification, “a phase difference of approximately ¼ in the wavelength range of visible light” means that in a wavelength range of 400 to 700 nm, a longer wavelength has a reverse wavelength dispersion characteristic that has a larger phase difference value. Say.

The in-plane retardation Ro _λ of the retardation film of the present embodiment is represented by the following formula (i). The value of the phase difference can be calculated by measuring the birefringence at each wavelength in an environment of 23 ° C. and 55% RH using, for example, Axoscan manufactured by Axometrics.

Ro _λ = (nx _λ −ny _λ ) × d (i)
(Wherein λ represents a measurement wavelength, nx and ny are measured in an environment of 23 ° C. and 55% RH, respectively, and nx is the maximum in-plane refractive index (refractive index in the slow axis direction). Ny is the refractive index in the direction perpendicular to the slow axis in the film plane, and d is the thickness (nm) of the film)

Here, the in-plane retardation of the λ / 4 retardation film at a wavelength of 450 nm is Ro ₄₅₀ , the in-plane retardation of the λ / 4 retardation film at a wavelength of 550 nm is Ro _550, and the λ / 4 retardation film at a wavelength of 650 nm. in the case of in-plane retardation of the and _{Ro 650,} lambda / 4 retardation film of the present embodiment _is a _{Ro 550} is 100 ~ 155 _nm, the ratio of _{Ro 450} for _{Ro 550 (Ro 450 / Ro 550} ) is, is 0.72 to _0.95, the ratio of _{Ro 550} for _{Ro 650 (Ro 550 / Ro 650} ) , characterized in that a 0.83 to 0.97.

Ro ₅₅₀ may be 100 to 155 nm, preferably 125 to 150 nm. When Ro ₅₅₀ exceeds the range of 100 to 155 nm, the phase difference at a wavelength of 550 nm does not become a quarter wavelength. When a circularly polarizing plate is produced using such a film and applied to, for example, an organic EL display In some cases, the reflection of room lighting becomes large, and black color cannot be expressed in bright places.

The ratio of _{Ro 450} for _{Ro 550 (Ro 450 / Ro 550} ) may be any from 0.72 to 0.95, preferably 0.80 to 0.92, more preferably from 0.84 to 0.90 It is. When Ro ₄₅₀ / Ro ₅₅₀ exceeds the range of 0.72 to 0.95, the phase difference does not show an appropriate reverse wavelength dispersion characteristic. For example, when a circularly polarizing plate is manufactured, hue change or hue variation due to humidity environment is not observed. There is a tendency to wake up.

The ratio of _{Ro 550} for _{Ro 650 (Ro 550 / Ro 650} ) may be any from 0.83 to 0.97, preferably 0.85 to 0.94, more preferably 0.87 to 0.92 It is. When Ro ₅₅₀ / Ro ₆₅₀ exceeds the range of 0.83 to 0.97, the phase difference does not show an appropriate inverse wavelength dispersion characteristic. For example, when a circularly polarizing plate is produced, hue change due to hue change or humidity environment There is a tendency to wake up.

Moreover, out of the in-plane phase difference at a wavelength of 550 nm, Ro ₅₅₀ , the in-plane phase difference derived from a resin having positive intrinsic birefringence is derived from an additive having Rc ₅₅₀ and retardation increasing ability and wavelength dispersion adjusting ability. in the case of in-plane retardation _{Ra 550,} an in-plane retardation derived from the additive having a negative intrinsic birefringence and _{Rb 550 (however, Ro 550 = Rc 550 + Ra} 550 + Rb 550), Ra 550 against _{Ro 550} The ratio (Ra ₅₅₀ / Ro ₅₅₀ ) is preferably 0.10 to 1.0, more preferably 0.20 to 0.80, and still more preferably 0.30 to 0.60. . In this _case, greater than the ratio _{(Rc 550 / Ro} 550) are 0 _{Rc 550,} it is preferable that the ratio of _{Rb 550 (Rb 550 / Ro 550} ) is less than _0, Rc 550 _{/ Ro 550} is 0.20 to 0 It is more preferable that Rb ₅₅₀ / Ro ₅₅₀ is −0.30 or more and less than 0, Rc ₅₅₀ / Ro ₅₅₀ is 0.30 to 0.80, and Rb ₅₅₀ / Ro ₅₅₀ is −0. More preferably, it is 10 or more and less than 0. _Further, it is preferable that Ra 550 _{+ Rc 550} exceeds 1.00.

That is, when Rc ₅₅₀ exceeds 0, a resin having positive intrinsic birefringence exhibits a retardation development property at a wavelength of 550 nm. If an additive having a retardation increasing ability and a wavelength dispersion adjusting ability in which the ratio of Ra _{550 to} Ro ₅₅₀ falls within the above range is added to this, it is sufficient even if not added so much that the transparency of the film is deteriorated. Phase difference expression can be imparted. In this state, if an additive having negative intrinsic birefringence with Rb ₅₅₀ of less than 0 is blended, the reverse wavelength dispersion characteristic is further imparted while adjusting by reducing the retardation development property, and the appropriate level is obtained. A retardation film having retardation development and reverse wavelength dispersion characteristics can be obtained.

In general, the in-plane retardation (for example, Ro ₅₅₀ ) can be increased by increasing the film thickness d of the film. However, when the film thickness is increased, there is a problem that the thickness of an image display device such as an organic EL display is increased, or the transmittance is lowered to reduce the light extraction efficiency. However, according to the retardation film of the present embodiment, containing a resin having positive intrinsic birefringence, an additive having retardation increasing ability and wavelength dispersion adjusting ability, and an additive having negative intrinsic birefringence Thus, even when the film thickness is reduced as will be described later, excellent retardation and reverse wavelength dispersion characteristics can be exhibited.

Next, components of the retardation film of the present embodiment will be described.

The retardation film is composed of a resin component (a thermoplastic resin such as a resin having a positive intrinsic birefringence) as a main component, an additive component (an additive having retardation increasing ability and wavelength dispersion adjusting ability, and a negative intrinsic property). Component other than the resin component, such as an additive having birefringence). A resin having positive intrinsic birefringence, an additive having retardation increasing ability and wavelength dispersion adjusting ability, and an additive having negative intrinsic birefringence each have different retardation development and wavelength dispersion characteristics. By using these three kinds of components in combination, a retardation film having high retardation development and reverse wavelength dispersion characteristics and high transparency can be produced.

<Resin having positive intrinsic birefringence>
The retardation film contains a resin having positive intrinsic birefringence as a main component. In the present specification, the “main component” refers to a component contained in the thermoplastic resin component constituting the retardation film by 55% by mass or more. In addition, the “resin having positive intrinsic birefringence” generally refers to a resin having a characteristic that the refractive index increases with respect to the molecular orientation direction. It means a property capable of expressing a phase difference that increases the refractive index in the direction.

The resin having positive intrinsic birefringence is not particularly limited, but it has high retardation development in addition to positive intrinsic birefringence, does not deteriorate reverse wavelength dispersibility, and is easy to form a thin film by oblique stretching. Esters are preferred. In the present specification, the “thermoplastic resin” refers to a resin that has the characteristics that it becomes soft when heated and can be molded into a desired shape.

(Cellulose ester)
The cellulose ester applicable to the present embodiment is not particularly limited, and examples thereof include carboxylic acid esters having about 2 to 22 carbon atoms and aromatic carboxylic acid esters, and particularly lower fatty acid esters having 6 or less carbon atoms. Can be adopted. More specifically, cellulose acylates such as cellulose acetate, cellulose diacetate, cellulose acetate propionate, and cellulose acetate butyrate can be given. The cellulose acylate may be acylated with one kind of acyl group or may be acylated with two or more kinds of acyl groups. Among these, a mixed fatty acid ester of cellulose is preferable from the viewpoint of providing a high retardation and easily forming a thin film by oblique stretching and from easily avoiding a failure such as breakage during stretching.

The acyl substitution degree of cellulose acylate is preferably 1.50 to 2.55, more preferably 1.70 to 2.50, and further preferably 2.00 to 2.45. When the acyl substitution degree of cellulose acylate is less than 1.50, the retardation development property is high, but the wavelength dispersion characteristic of the retardation tends to be almost flat. Moreover, at the time of film production to be described later, the dope viscosity increases and the film surface quality tends to deteriorate, or the internal haze tends to increase due to an increase in stretching tension. On the other hand, when the acyl substitution degree exceeds 2.55, the retardation development property is lowered, but the chromatic dispersion characteristic of the retardation tends to be more reverse dispersion (shows the reverse chromatic dispersion characteristic). In the present specification, “acyl substitution degree” means an average acyl substitution degree, and the average acyl substitution degree is esterified among the three hydroxy groups (hydroxyl groups) of each anhydroglucose constituting cellulose. The average value of the number of hydroxy groups is 0 to 3.0.

The acyl group may be an aliphatic group or an aromatic group and is not particularly limited. Acyl groups include, for example, acetyl, propionyl, butanoyl, heptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, isobutanoyl Group, tert-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like.

Specific cellulose acylates include propionate groups, butyrate groups, or phthalyl groups in addition to acetyl groups such as cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate propionate butyrate or cellulose acetate phthalate. The mixed fatty acid ester of cellulose is mentioned. The butyryl group that forms butyrate may be linear or branched. Among these, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate are preferably used.

Cellulose acylate has an average degree of substitution of acyl groups having 3 or more carbon atoms out of all acyl groups contained in cellulose acylate from the viewpoint of improving hydrophobicity and enhancing the effect of improving wavelength dispersion humidity fluctuation. It is preferably 5 to 2.5.

The acyl group having 3 or more carbon atoms is not particularly limited. For example, propionyl group, butyryl group, heptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group , Octadecanoyl group, isobutanoyl group, t-butanoyl group, cyclohexanoyl group, oleoyl group, benzoyl group, naphthoyl group and cinnamoyl group.

In addition, the part which is not substituted by the said acyl group among cellulose acylates exists normally as a hydroxyl group. Such cellulose acylate can be synthesized by a known method. Further, the substitution degree of the acyl group can be determined according to the provisions of ASTM-D817-96 (testing method for cellulose acylate, etc.).

The number average molecular weight (Mn) of the cellulose acylate is preferably 30,000 to 300,000, and preferably 50,000 to 200,000 from the viewpoint of increasing the mechanical strength of the obtained λ / 4 retardation film. More preferably. The ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn) of the cellulose acylate is preferably 1.4 to 3.0.

The weight average molecular weight (Mw) and the number average molecular weight (Mn) of cellulose acylate can be measured using gel permeation chromatography (GPC), respectively. An example of specific measurement conditions is shown below.
(Measurement condition)
Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three columns manufactured by Showa Denko KK)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: A standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) and a calibration curve with 13 samples having a Mw in the range of 500 to 1000000 is used. Thirteen samples are used at approximately equal intervals.

The cellulose that is a raw material of cellulose acylate is not particularly limited, and cotton linter, wood pulp, kenaf, and the like can be used. Moreover, the cellulose ester obtained from these can be mixed and used for each arbitrary ratio.

The cellulose acylate of this embodiment can be produced by a known method. In general, cellulose is mixed with raw material cellulose, a predetermined organic acid (such as acetic acid), acid anhydride (such as acetic anhydride), and a catalyst (such as sulfuric acid) to esterify (acetylate) cellulose, The reaction proceeds until the ester (acetylation) is formed. In the triester (acetylation), the three hydroxy groups (hydroxyl groups) of the glucose unit are substituted with acetyl groups of organic acids. Next, cellulose acylate having a desired degree of acetyl group substitution is synthesized by hydrolyzing the cellulose triester. Thereafter, cellulose acylate can be obtained through steps such as filtration, precipitation, washing with water, dehydration, and drying. Specifically, it can be synthesized with reference to, for example, the method described in JP-A-10-45804.

(Other thermoplastic resins)
The retardation film of the present embodiment may contain a thermoplastic resin other than the resin having the positive intrinsic birefringence described above.

Examples of other thermoplastic resins include polyethylene (PE), high density polyethylene, medium density polyethylene, low density polyethylene, polypropylene (PP), polyvinyl chloride (PVC), polyvinylidene chloride, polystyrene (PS), and polyacetic acid. Vinyl (PVAc), polytetrafluoroethylene (PTFE), acrylonitrile butadiene styrene resin (ABS resin), AS resin, acrylic resin (PMMA), or the like can be used. When strength and resistance to breakage are particularly required, for example, polyamide (PA), nylon, polyacetal (POM), polycarbonate (PC), modified polyphenylene ether (m-PPE, modified PPE, PPO), poly Butylene terephthalate (PBT), polyethylene terephthalate (PET), glass fiber reinforced polyethylene terephthalate (GF-PET), cyclic polyolefin (COP), and the like can be used. Furthermore, when high heat distortion temperature and durability that can be used for a long time are required, polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polysulfone, polyethersulfone, amorphous polyarylate, liquid crystal polymer, Polyetheretherketone, thermoplastic polyimide (PI), polyamideimide (PAI) and the like can be used. These can be used in combination with different types and molecular weights depending on the application.

<Additives with retardation increasing ability and wavelength dispersion adjusting ability>
The retardation film contains an additive having retardation increasing ability and wavelength dispersion adjusting ability (hereinafter sometimes simply referred to as retardation adjusting agent). Such a compound can impart the property of increasing the retardation development property to the above-described resin having positive intrinsic birefringence, and can also impart the property of enhancing the reverse wavelength dispersion property.

As an additive having retardation increasing ability and wavelength dispersion adjusting ability, when added, the retardation can be increased by 3 nm or more per 1% additive when compared with the case where it is not added to the retardation film, and is the ratio of _{Ro 550} for _Ro 450 _{/ Ro 550} or plane retardation _{Ro 650} at a wavelength of 650 nm, the ratio of in-plane retardation _{Ro 450} at a wavelength of 450nm for the wavelength dispersion _{(Ro 550} per additive 1% added Ro ₅₅₀ / Ro ₆₅₀ ) is lowered by 0.005 or more, that is, there is no particular limitation as long as reverse wavelength dispersion characteristics can be imparted. As such an additive, for example, including a group bonded by a linking group having a linking site in at least three places and linked via the linking group and the two linking sites, a wavelength of 200 nm or more and less than 280 nm Branched with respect to the chemical structure portion X by a chemical structure portion X (main chain) having a maximum absorption wavelength in the region and a group bonded via at least one linking site among the other linking sites of the linking group Examples thereof include a compound having a chemical structure portion Y (side chain) having the above structure, wherein the chemical structure portion Y has a maximum absorption wavelength in a wavelength region of 280 to 380 nm. By using such a compound, the retardation film can impart high retardation development and reverse wavelength dispersion characteristics satisfactorily.

Such a compound is dissolved in a solvent and has at least two maximum absorption wavelengths in the ultraviolet absorption region. The maximum absorption wavelength λmax _x on the shorter wavelength side is a spectral absorption characteristic belonging to the main chain X. Yes, it has a maximum absorption wavelength in a wavelength region of 200 nm or more and less than 280 nm, and the longer wavelength side maximum absorption wavelength λmax _y is a spectral absorption characteristic belonging to the side chain Y. The long wavelength maximum absorption wavelength λmax _y attributed to the side chain Y is in the wavelength range of 280 to 380 nm.

The aspect ratio of the compound is preferably less than 1.70, more preferably 1.01 or more and less than 1.70. When the aspect ratio is less than 1.70, it becomes anisotropic with respect to the thermoplastic resin, and it is easy to obtain the effect of increasing the reverse wavelength dispersibility, and it is easy to achieve the retardation development necessary for the retardation film. In this specification, “aspect ratio” uses Winmostar MOPAC AM1 (MOP6W70) (Senda, “Development of Molecular Computation Support System Winmostar”, Idemitsu Technical Report, 49, 1, 106-111 (2006)). The molecular length / molecular width. The “molecular length” is the maximum interatomic distance in a compound plus the van der Waals radii of two atoms at both ends. "Means a value obtained by adding the van der Waals radii of two atoms at both ends to the maximum distance between atoms when each atom is projected onto a plane perpendicular to the molecular long axis.

As a more specific example of such a compound, a compound represented by the following general formula (A) can be exemplified.

（式中、Ｌ_１およびＬ_２は各々独立に単結合または２価の連結基であり、Ｒ_１、Ｒ_２およびＲ_３は各々独立に置換基を表し、ｎは０から２までの整数を表し、ＷａおよびＷｂはそれぞれ水素原子または置換基を表し、（Ｉ）ＷａおよびＷｂが互いに結合して環を形成してもよく、（ＩＩ）ＷａおよびＷｂの少なくとも一つが環構造を有してもよく、または（ＩＩＩ）ＷａおよびＷｂの少なくとも一つがアルケニル基またはアルキニル基であってもよい）

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

L ₁ and L ₂ are preferably O, COO, and OCO.

Specific examples of R ₁ , R ₂ and R ₃ include halogen atoms (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl groups (methyl group, ethyl group, n-propyl group, isopropyl group, tert- Butyl group, n-octyl group, 2-ethylhexyl group, etc.), cycloalkyl group (cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), alkenyl group (vinyl group, allyl group, etc.), cycloalkenyl group ( 2-cyclopenten-1-yl, 2-cyclohexen-1-yl group, etc.), alkynyl group (ethynyl group, propargyl group etc.), aryl group (phenyl group, p-tolyl group, naphthyl group etc.), heterocyclic group ( 2-furyl group, 2-thienyl group, 2-pyrimidinyl group, 2-benzothiazolyl group, etc.), cyano group, hydroxy group, nitro group Carboxy group, alkoxy group (methoxy group, ethoxy group, isopropoxy group, tert-butoxy group, n-octyloxy group, 2-methoxyethoxy group, etc.), aryloxy group (phenoxy group, 2-methylphenoxy group, 4 -Tert-butylphenoxy group, 3-nitrophenoxy group, 2-tetradecanoylaminophenoxy group, etc.), acyloxy group (formyloxy group, acetyloxy group, pivaloyloxy group, stearoyloxy group, benzoyloxy group, p-methoxyphenyl) Carbonyloxy group, etc.), amino group (amino group, methylamino group, dimethylamino group, anilino group, N-methyl-anilino group, diphenylamino group, etc.), acylamino group (formylamino group, acetylamino group, pivaloylamino group, Lauroylamino group, Nzoylamino group, etc.), alkyl and arylsulfonylamino groups (methylsulfonylamino group, butylsulfonylamino group, phenylsulfonylamino group, 2,3,5-trichlorophenylsulfonylamino group, p-methylphenylsulfonylamino group, etc.), mercapto Group, alkylthio group (methylthio group, ethylthio group, n-hexadecylthio group, etc.), arylthio group (phenylthio group, p-chlorophenylthio group, m-methoxyphenylthio group, etc.), sulfamoyl group (N-ethylsulfamoyl group, N- (3-dodecyloxypropyl) sulfamoyl group, N, N-dimethylsulfamoyl group, N-acetylsulfamoyl group, N-benzoylsulfamoyl group, N- (N'-phenylcarbamoyl) sulfamoyl group, etc. ) Fo group, acyl group (acetyl group, pivaloylbenzoyl group, etc.), carbamoyl group (carbamoyl group, N-methylcarbamoyl group, N, N-dimethylcarbamoyl group, N, N-di-n-octylcarbamoyl group, N -(Methylsulfonyl) carbamoyl group and the like.

R ₁ and R ₂ are preferably a substituted or unsubstituted benzene ring or a substituted or unsubstituted cyclohexane ring, more preferably a substituted benzene ring or a substituted cyclohexane ring, and a 4-position substituent. A benzene ring is particularly preferable in that the main chain of the compound of the general formula (A) can be oriented in the slow axis direction of the retardation film to increase the slow axis direction refractive index nx.

Wa and Wb include a halogen atom (eg, fluorine atom, chlorine atom, bromine atom, iodine atom), alkyl group (eg, methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n -Octyl group, 2-ethylhexyl group, etc.), cycloalkyl group (for example, cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), alkenyl group (for example, vinyl group, allyl group, etc.), cycloalkenyl group (for example) For example, 2-cyclopenten-1-yl, 2-cyclohexen-1-yl group, etc.), alkynyl group (eg, ethynyl group, propargyl group, etc.), aryl group (eg, phenyl group, p-tolyl group, naphthyl group, etc.) ), A heterocyclic group (for example, 2-furyl group, 2-thienyl group, 2-pyrimidini) Group, 2-benzothiazolyl group, etc.), cyano group, hydroxy group, nitro group, carboxyl group, alkoxy group (for example, methoxy group, ethoxy group, isopropoxy group, tert-butoxy group, n-octyloxy group, 2-methoxy group) Ethoxy group etc.), aryloxy group (eg phenoxy group, 2-methylphenoxy group, 4-tert-butylphenoxy group, 3-nitrophenoxy group, 2-tetradecanoylaminophenoxy group etc.), acyloxy group (eg Formyloxy group, acetyloxy group, pivaloyloxy group, stearoyloxy group, benzoyloxy group, p-methoxyphenylcarbonyloxy group, etc.), amino group (for example, amino group, methylamino group, dimethylamino group, anilino group, N- Methyl-anilino group, diphenyl Amino groups, etc.), acylamino groups (eg, formylamino group, acetylamino group, pivaloylamino group, lauroylamino group, benzoylamino group, etc.), alkyl and arylsulfonylamino groups (eg, methylsulfonylamino group, butylsulfonylamino group, Phenylsulfonylamino group, 2,3,5-trichlorophenylsulfonylamino group, p-methylphenylsulfonylamino group, etc.), mercapto group, alkylthio group (eg, methylthio group, ethylthio group, n-hexadecylthio group, etc.), arylthio group (Eg, phenylthio group, p-chlorophenylthio group, m-methoxyphenylthio group, etc.), sulfamoyl group (eg, N-ethylsulfamoyl group, N- (3-dodecyloxypropyl) sulfamoyl group) N, N-dimethylsulfamoyl group, N-acetylsulfamoyl group, N-benzoylsulfamoyl group, N- (N′phenylcarbamoyl) sulfamoyl group, etc.), sulfo group, acyl group (for example, acetyl group) Pivaloylbenzoyl group, etc.), carbamoyl group (for example, carbamoyl group, N-methylcarbamoyl group, N, N-dimethylcarbamoyl group, N, N-di-n-octylcarbamoyl group, N- (methylsulfonyl) carbamoyl group) Etc.).

The above substituent may be further substituted with the above substituent.

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

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

Further, when either one of Wa and Wb is a hydrogen atom and the other has a ring-setting group, for example, the following structures can be mentioned.

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

Specific examples (I-1 to I-9) of the compound (A) are listed below, but the compounds that can be used in the present embodiment are not limited by the following specific examples.

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

The content of the compound in the retardation film is preferably in the range of 0.01 to 30% by mass, more preferably in the range of 1.0 to 20% by mass, and still more preferably 1.0. Within the range of ˜10% by mass. When the content of the compound is in the range of 0.01 to 30% by mass, the desired retardation development property is easily obtained without impairing transparency. When the addition amount is within this range, sufficient retardation can be obtained, but the reverse wavelength dispersion characteristic is not sufficient, or the transparency may be lowered when the reverse wavelength dispersion is set to a desired value. Therefore, the present embodiment is characterized in that an additive having negative intrinsic birefringence, which will be described later, is added to adjust the reverse wavelength dispersion characteristic.

<Additives with negative intrinsic birefringence>
The retardation film contains an additive having negative intrinsic birefringence. In the present embodiment, by adding an additive having a negative intrinsic birefringence, the reverse wavelength dispersion characteristic is further imparted while appropriately adjusting the phase difference. In the present specification, “additive having negative intrinsic birefringence” means that when added to the film, the refractive index increases in the direction perpendicular to the stretching direction when compared with the case where it is not added. It refers to an additive having the property of exhibiting a proper phase difference or the property of weakening the expression of a retardation in the stretching direction.

The additive having negative intrinsic birefringence is not particularly limited, and examples thereof include polyester polymers, styrene polymers, acrylic polymers, and copolymers thereof. Among these, an aliphatic polyester polymer, a styrene maleic acid polymer, and an acrylic polymer are preferable from the viewpoint of imparting good reverse wavelength dispersion characteristics while suppressing deterioration of retardation development. Or 2 or more types can be mixed and used.

The number average molecular weight (Mn) of the additive having negative intrinsic birefringence is preferably 700 to 8000, more preferably 700 to 5000, and still more preferably 1000 to 5000.

The content of the additive having negative intrinsic birefringence in the λ / 4 retardation film is preferably in the range of 0.01 to 30% by mass, more preferably in the range of 1 to 20% by mass. More preferably, it is in the range of 1 to 10% by mass. By setting the content of the additive having negative intrinsic birefringence to 0.01 to 30% by mass, a λ / 4 retardation film having low internal haze and high transparency can be obtained. In addition, it fully imparts reverse wavelength dispersion characteristics while adjusting the phase difference obtained by blending a resin having positive intrinsic birefringence and an additive having retardation increasing ability and wavelength dispersion adjusting ability. Can do.

(Polyester polymer)
The polyester polymer is obtained by reacting an aliphatic dicarboxylic acid having 2 to 20 carbon atoms with at least one diol selected from an aliphatic diol having 2 to 12 carbon atoms and an alkyl ether diol having 4 to 20 carbon atoms. Although both of the ends of the reaction product may be obtained as the reaction product, a product obtained by further reacting a monocarboxylic acid, a monoalcohol, or a phenol to perform so-called end-capping can be mentioned. By this end capping, free carboxylic acids are not contained, so that storage stability and the like can be improved. The dicarboxylic acid used in the polyester polymer is preferably an aliphatic dicarboxylic acid residue having 4 to 20 carbon atoms or an aromatic dicarboxylic acid residue having 8 to 20 carbon atoms.

Examples of the aliphatic dicarboxylic acid having 2 to 20 carbon atoms include oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. And acids and 1,4-cyclohexanedicarboxylic acid. Among these, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, and 1,4-cyclohexanedicarboxylic acid are preferable, and succinic acid, glutaric acid, and adipic acid are more preferable.

Examples of the diol include aliphatic diols having 2 to 20 carbon atoms and alkyl ether diols having 4 to 20 carbon atoms.

Examples of the aliphatic diol having 2 to 20 carbon atoms include alkyl diols and alicyclic diols such as ethane diol, 1,2-propanediol, 1,3-propanediol, 1,2-butane. Diol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol) ), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3 -Methyl-1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl 1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like. Or it can be used as a mixture of two or more. Among these, ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4- Preferred are butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, ethanediol, 2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4 -More preferred are cyclohexanediol and 1,4-cyclohexanedimethanol.

Examples of the alkyl ether diol having 4 to 20 carbon atoms include polytetramethylene ether glycol, polyethylene ether glycol, polypropylene ether glycol, and combinations thereof. The average degree of polymerization of these alkyl ether diols is not particularly limited, but is, for example, 2 to 20, preferably 2 to 10, more preferably 2 to 5, and further preferably 2 to 4. Examples of such alkyl ether diols include Carbowax resin, Pluronics resin, and Niax resin.

Polyester polymers are effective against aging at high temperature and high humidity by protecting the terminal with a hydrophobic functional group. From the viewpoint of delaying hydrolysis of the ester group, the terminal is an alkyl group or an aromatic group. It is preferable to be sealed with. Further, it is preferable to protect the polyester additive with a monoalcohol residue or a monocarboxylic acid residue so that both ends of the polyester additive do not become a carboxylic acid or an OH group. In this case, the monoalcohol is preferably a substituted or unsubstituted monoalcohol having 1 to 30 carbon atoms, such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, isopentanol, hexanol, isohexanol, cyclohexyl alcohol. , Octanol, isooctanol, 2-ethylhexyl alcohol, nonyl alcohol, isononyl alcohol, tert-nonyl alcohol, decanol, dodecanol, dodecahexanol, aliphatic alcohols such as dodecaoctanol, allyl alcohol, oleyl alcohol, benzyl alcohol, 3-phenyl Examples thereof include substituted alcohols such as propanol.

Examples of the end-capping alcohol preferably used include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, isopentanol, hexanol, isohexanol, cyclohexyl alcohol, isooctanol, 2-ethylhexyl alcohol, and isononyl alcohol. Oleyl alcohol, benzyl alcohol, particularly methanol, ethanol, propanol, isobutanol, cyclohexyl alcohol, 2-ethylhexyl alcohol, isononyl alcohol, benzyl alcohol.

In the case of sealing with a monocarboxylic acid residue, the monocarboxylic acid used is preferably a substituted or unsubstituted monocarboxylic acid having 1 to 30 carbon atoms. These may be aliphatic monocarboxylic acids or aromatic ring-containing carboxylic acids. Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butanoic acid, caprylic acid, caproic acid, decanoic acid, dodecanoic acid, stearic acid, oleic acid, and examples of aromatic ring-containing monocarboxylic acids include: Benzoic acid, p-tert-butylbenzoic acid, p-tert-amylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, normal propylbenzoic acid, aminobenzoic acid, acetoxybenzoic acid, etc. These may be used alone or in combination of two or more.

The polyester-based polymer is synthesized by a hot melt condensation method by a polyesterification reaction or transesterification reaction between a dicarboxylic acid and a diol and / or a monocarboxylic acid or monoalcohol for end-capping, or an acid of these acids. It can be easily synthesized by any method of interfacial condensation between chloride and glycols. For these polyester-based additives, reference can be made to Koichi Murai's “Additives: Theory and Application” (Koshobo Co., Ltd., first edition published on March 1, 1973). In addition, JP 05-155809 A, JP 05-155810 A, JP 5 197073 A, JP 2006-259494 A, JP 07-330670 A, JP 2006-342227 A, Materials described in Japanese Patent Application Laid-Open No. 2007-003679 can be used.

(Styrene polymer)
Preferred examples of the styrenic polymer include polymers having a structural unit obtained from an aromatic vinyl monomer represented by the general formula.

（式中、Ｒ^１０１～Ｒ^１０４は、各々独立に、水素原子、ハロゲン原子、酸素原子、硫黄原子、窒素原子またはケイ素原子を含む連結基を有していてもよい置換もしくは非置換の炭素原子数１～３０の炭化水素基または極性基を表し、Ｒ^１０４は全て同一の原子または基であっても、それぞれ異なる原子または基であっても、互いに結合して、炭素環または複素環（これらの炭素環、複素環は単環構造でもよく、他の環が縮合した多環構造であってもよい）を形成してもよい）

(Wherein R ¹⁰¹ to R ¹⁰⁴ each independently represents a substituted or unsubstituted carbon atom optionally having a linking group containing a hydrogen atom, a halogen atom, an oxygen atom, a sulfur atom, a nitrogen atom or a silicon atom) R ¹⁰⁴ represents a hydrocarbon group or a polar group having a number of 1 to 30, and R ¹⁰⁴ may be the same atom or group or different atoms or groups, and may be bonded to each other to form a carbocyclic or heterocyclic ring (these The carbocyclic ring and heterocyclic ring may be a monocyclic structure or may be a polycyclic structure in which other rings are condensed).

The aromatic vinyl monomer is not particularly limited. For example, styrene; alkyl-substituted styrenes such as α-methylstyrene, β-methylstyrene, and p-methylstyrene; 4-chlorostyrene, 4-bromostyrene, etc. Halogen-substituted styrenes; hydroxystyrenes such as p-hydroxystyrene, α-methyl-p-hydroxystyrene, 2-methyl-4-hydroxystyrene, 3,4-dihydroxystyrene; vinyl benzyl alcohols; p-methoxystyrene, Alkoxy-substituted styrenes such as p-tert-butoxystyrene and m-tert-butoxystyrene; vinyl benzoic acids such as 3-vinylbenzoic acid and 4-vinylbenzoic acid; methyl-4-vinylbenzoate, ethyl-4-vinylbenzoate Vinyl benzoate esthetics such as 4-vinylbenzyl acetate; 4-acetoxystyrene; amide styrenes such as 2-butylamidostyrene, 4-methylamidostyrene, p-sulfonamidostyrene; 3-aminostyrene, 4-aminostyrene, 2-isopropenyl Aminostyrenes such as aniline and vinylbenzyldimethylamine; nitrostyrenes such as 3-nitrostyrene and 4-nitrostyrene; cyanostyrenes such as 3-cyanostyrene and 4-cyanostyrene; vinylphenylacetonitrile; Examples thereof include aryl styrenes and indenes, and two or more thereof may be used as a copolymerization component. Of these, styrene and α-methylstyrene are preferable because they are easily available industrially and are inexpensive.

(Acrylic polymer)
The acrylic polymer is not particularly limited, and examples thereof include those having a structural unit obtained from an acrylate ester monomer represented by the following general formula.

（式中、Ｒ^１０５～Ｒ^１０８は、各々独立に、水素原子、ハロゲン原子、酸素原子、硫黄原子、窒素原子もしくはケイ素原子を含む連結基を有していてもよい置換もしくは非置換の炭素原子数１～３０の炭化水素基、または極性基を表す）

(Wherein R ¹⁰⁵ to R ¹⁰⁸ each independently represents a substituted or unsubstituted carbon atom which may have a linking group containing a hydrogen atom, a halogen atom, an oxygen atom, a sulfur atom, a nitrogen atom or a silicon atom) Represents a hydrocarbon group of 1 to 30 or a polar group)

Such an acrylate monomer is not particularly limited. For example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s- , Tert-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-) ), Nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic Acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid ( -Methoxyethyl), acrylic acid (2-ethoxyethyl) phenyl acrylate, phenyl methacrylate, acrylic acid (2 or 4-chlorophenyl), methacrylic acid (2 or 4-chlorophenyl), acrylic acid (2 or 3 or 4- Ethoxycarbonylphenyl), methacrylic acid (2 or 3 or 4-ethoxycarbonylphenyl), acrylic acid (o or m or p-tolyl), methacrylic acid (o or m or p-tolyl), benzyl acrylate, benzyl methacrylate Phenethyl acrylate, phenethyl methacrylate, acrylic acid (2-naphthyl), cyclohexyl acrylate, cyclohexyl methacrylate, acrylic acid (4-methylcyclohexyl), methacrylic acid (4-methylcyclohexyl), acrylic acid (4-ethyl) Cyclohexyl), methacrylic acid (4-ethylcyclohexyl) and the like, or those obtained by replacing the above acrylic ester with a methacrylic ester, and two or more thereof may be used as a copolymerization component. Of these, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, tert-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), or those obtained by replacing the acrylate ester with a methacrylate ester are preferred.

The copolymer preferably contains at least one structural unit obtained from the aromatic vinyl monomer and the acrylate monomer.

Further, the structure other than the above constituting the copolymer is not particularly limited, but is preferably one having excellent copolymerizability with the monomer, for example, maleic anhydride, citraconic anhydride, cis-1 Acid anhydrides such as cyclohexene-1,2-dicarboxylic anhydride, 3-methyl-cis-1-cyclohexene-1,2-dicarboxylic anhydride, 4-methyl-cis-1-cyclohexene-1,2-dicarboxylic anhydride Nitrile group-containing radical polymerizable monomers such as acrylonitrile and methacrylonitrile; amide bond-containing radical polymerizable monomers such as acrylamide, methacrylamide and trifluoromethanesulfonylaminoethyl (meth) acrylate; fatty acids such as vinyl acetate Vinyls; chlorine-containing radical polymerizable monomers such as vinyl chloride and vinylidene chloride; , It may be mentioned 3-butadiene, isoprene, conjugated diolefins such as 1,4-dimethyl butadiene. Of these, styrene-acrylic acid copolymers, styrene-maleic anhydride copolymers, and styrene-acrylonitrile copolymers are preferred.

<Other additives>
The retardation film of the present embodiment has a resin having positive intrinsic birefringence as the main component described above, and further has an additive having retardation increasing ability and wavelength dispersion adjusting ability, and an additive having negative intrinsic birefringence. In addition, various additives can be contained as other additives.

(Organic solvent)
In the present embodiment, an organic solvent can be used to dissolve the cellulose acylate to prepare a cellulose acylate solution or a dope. As the organic solvent, a chlorinated organic solvent and a non-chlorinated organic solvent can be mainly used.

Examples of the chlorinated organic solvent include methylene chloride (methylene chloride). Non-chlorine organic solvents include, for example, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoro Ethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, Examples include 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, and nitroethane. From the viewpoint of recent environmental problems, non-chlorine organic solvents are preferably used.

When these organic solvents are used for cellulose acylate, the insoluble matter should be reduced by a known dissolution method such as a dissolution method at room temperature, a high-temperature dissolution method, a cooling dissolution method, or a high-pressure dissolution method. Is preferred. For the cellulose acylate, methylene chloride can be used, but methyl acetate, ethyl acetate, and acetone are preferably used, and among them, methyl acetate is particularly preferable.

In the present specification, an organic solvent having good solubility with respect to the cellulose acylate is referred to as a good solvent, and an organic solvent which exhibits a main effect on dissolution and is used in a large amount among them is referred to as a main (organic) solvent. Or the main (organic) solvent.

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

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

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

Examples of additives that can be added to the dope include plasticizers, ultraviolet absorbers, phosphorus-based flame retardants, matting agents, antioxidants, antistatic agents, anti-degradation agents, peeling aids, surfactants, Examples thereof include dyes and fine particles. In the present embodiment, additives other than the fine particles may be added when preparing the cellulose acylate solution, or may be added when preparing the fine particle dispersion. It is preferable to add a plasticizer, an antioxidant, an ultraviolet absorber, or the like that imparts heat and moisture resistance to the polarizing plate used in the image display device.

(Plasticizer)
In the retardation film of this embodiment, various plasticizers can be used in combination for the purpose of improving the fluidity and flexibility of the composition. Examples of plasticizers include polyhydric alcohol ester plasticizers, glycolate plasticizers, phthalate ester plasticizers, citrate ester plasticizers, fatty acid ester plasticizers, phosphate ester plasticizers, and polyvalent plasticizers. Examples thereof include carboxylic acid ester plasticizers and acrylic plasticizers. It can be applied to a wide range of uses by selecting or using these plasticizers according to the use.

(Sugar ester compound)
In the retardation film of this embodiment, it is preferable to contain a sugar ester compound as a compatibilizer. Examples of the sugar ester compound include sugar ester compounds excluding cellulose ester having 1 to 12 at least one pyranose structure or furanose structure, and all or part of the hydroxy groups of the structure are esterified. it can.

The sugar ester compound is not particularly limited, and examples of the compound (saccharide) having a pyranose structure or furanose structure include glucose, galactose, mannose, fructose, xylose, or arabinose, lactose, sucrose, nystose, 1F-fructosyl varnish. Tose, stachyose, maltitol, lactitol, lactulose, cellobiose, maltose, cellotriose, maltotriose, raffinose, kestose and the like can be mentioned. In addition, gentiobiose, gentiotriose, gentiotetraose, xylotriose, galactosyl sucrose and the like can be mentioned. Among these, compounds having both a pyranose structure and a furanose structure are particularly preferable. Specifically, for example, sucrose, kestose, nystose, 1F-fructosyl nystose, stachyose and the like are preferable, and sucrose is particularly preferable.

The monocarboxylic acid used for esterifying all or part of the hydroxy group of the compound (sugar) having the pyranose structure or furanose structure described above is not particularly limited, and is a known aliphatic monocarboxylic acid or alicyclic group. Monocarboxylic acids, aromatic monocarboxylic acids and the like may be used alone or in combination of two or more.

Preferred aliphatic monocarboxylic acids include, for example, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecyl acid, Saturation of lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, mellicic acid, and laxaric acid Fatty acids: Undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid, unsaturated fatty acids such as octenoic acid, and the like.

Preferred examples of the alicyclic monocarboxylic acid include acetic acid, cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, and derivatives thereof.

Preferred aromatic monocarboxylic acids include, for example, aromatic monocarboxylic acids having an alkyl group or alkoxy group introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, cinnamic acid, benzylic acid, biphenylcarboxylic acid, and naphthalene. Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as carboxylic acid and tetralin carboxylic acid, or derivatives thereof. More specifically, xylyl acid, hemelic acid, mesitylene acid, prenicylic acid, γ-isodryl. Acid, duryl acid, mesitoic acid, α-isoduric acid, cumic acid, α-toluic acid, hydroatropic acid, atropic acid, hydrocinnamic acid, salicylic acid, o-anisic acid, m-anisic acid, p-anisic acid, creosote Acid, o-homosalicylic acid, m-homosalicylic acid, p-homosalicylic acid, o-pyrocate Acid, β-resorcylic acid, vanillic acid, isovanillic acid, veratromic acid, o-veratrumic acid, gallic acid, asaronic acid, mandelic acid, homoanisic acid, homovanillic acid, homoveratrumic acid, o-homoveratric acid, phthalonic acid, p-coumaric Examples include acids. Among these, benzoic acid is particularly preferable.

In the retardation film of the present embodiment, the sugar ester compound described above is 1 to 30% by mass with respect to 100% by mass of the retardation film from the viewpoint of stabilizing the display quality by suppressing the fluctuation of the retardation value. It is preferably contained within the range, and more preferably contained within the range of 5 to 30% by mass. When the content of the sugar ester compound is in the range of 1 to 30% by mass, the above-described excellent effects can be achieved and bleeding out and the like can be suppressed.

(UV absorber)
The protective film used in the retardation film of the present embodiment or the circularly polarizing plate described later preferably contains an ultraviolet absorber.

Examples of UV absorbers include benzotriazole UV absorbers, 2-hydroxybenzophenone UV absorbers, and salicylic acid phenyl ester UV absorbers. Specifically, for example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, Triazoles such as 2- (3,5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy Examples thereof include benzophenones such as -4-methoxybenzophenone.

It should be noted that an ultraviolet absorber having a molecular weight of 400 or more is less likely to volatilize at a high boiling point and is difficult to disperse even during high temperature molding, and therefore weather resistance can be effectively improved with a relatively small amount of addition.

Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- ( Benzotriazoles such as 1,1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, Hindered amines such as bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butyl Bis (1,2,2,6,6-pentamethyl-4-piperidyl) malonate, 1- [2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl Oxy] ethyl] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine and the like with hindered phenol The hybrid type | system | group which has the structure of a hindered amine is mentioned, These can be used individually or in combination of 2 or more types. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3-tetrabutyl) ) -6- (2H-benzotriazol-2-yl) phenol] is preferred. Commercially available products may be used. For example, TINUVIN such as TINUVIN 109, TINUVIN 171, TINUVIN 234, TINUVIN 326, TINUVIN 327, TINUVIN 328, and TINUVIN 928 manufactured by BASF Japan Ltd. can be preferably used.

(Phosphorus flame retardant)
For the retardation film, a flame retardant acrylic resin composition containing a phosphorus flame retardant may be used. Phosphorus flame retardants include red phosphorus, triaryl phosphate ester, diaryl phosphate ester, monoaryl phosphate ester, aryl phosphonate compound, aryl phosphine oxide compound, condensed aryl phosphate ester, halogenated alkyl phosphate ester, Examples thereof include one or a mixture of two or more selected from halogen-condensed phosphoric acid esters, halogen-containing condensed phosphonic acid esters, halogen-containing phosphorous acid esters, and the like. Specifically, for example, triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl) Examples thereof include phosphate and tris (tribromoneopentyl) phosphate.

(Matting agent)
Further, the retardation film of this embodiment has, for example, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, It is preferable to contain a matting agent such as inorganic fine particles such as aluminum silicate, magnesium silicate and calcium phosphate, and a crosslinked polymer. Among these, silicon dioxide is preferably used because it can reduce the haze of the film.

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

(Other)
Furthermore, various antioxidants can also be added to the retardation film in order to improve the thermal decomposability and thermal colorability during molding. It is also possible to add an antistatic agent to impart antistatic performance to the retardation film.

<Physical properties of retardation film>
(Film thickness and width)
The film thickness of the retardation film of the present embodiment is not particularly limited, and can be in the range of 10 to 250 μm. As described above, the retardation film contains a resin having positive intrinsic birefringence, an additive having retardation increasing ability and wavelength dispersion adjusting ability, and an additive having negative intrinsic birefringence. Even if the film thickness is not increased as in the prior art, the phase difference can be enhanced. The retardation film may have a film thickness of, for example, 20 to 100 μm, a thinner thickness of 20 to 80 μm, and a thinner thickness of 20 to 65 μm, and can exhibit sufficiently excellent retardation development and reverse wavelength dispersion characteristics.

The retardation film of the present embodiment can be used in the range of 1 to 4 m in width, preferably in the range of 1.4 to 4 m, more preferably in the range of 1.6 to 3 m. be able to. If the width is 4 m or less, the conveyance stability can be ensured.

(Surface roughness)
The arithmetic average roughness of the surface of the retardation film of the present embodiment is about 2.0 to 4.0 nm, preferably 2.5 to 3.5 nm.

(Dimensional change rate)
When the retardation film of the present embodiment is applied to, for example, an organic EL display, unevenness, a change in retardation value, and a decrease in contrast due to a dimensional change due to moisture absorption under an environmental atmosphere (for example, a high humidity environment) to be used. In order to prevent problems such as color unevenness and color unevenness, the dimensional change rate (%) is preferably less than 0.5%, and more preferably less than 0.3%.

(Fault tolerance)
In the retardation film of this embodiment, it is preferable that there are few failures (hereinafter also referred to as defects) in the film. Specifically, the defects having a diameter of 5 μm or more in the film surface are preferably 1 piece / 10 cm square or less, more preferably 0.5 pieces / 10 cm square or less, and 0.1 pieces / 10 cm square or less. More preferably. In the present specification, the “defect” refers to a void in the film (foaming defect) generated due to rapid evaporation of the solvent in the drying step in film formation by the solution casting method described later, film formation This refers to foreign matter (foreign matter defect) in the film due to foreign matter in the stock solution or foreign matter mixed during film formation. The diameter of the defect indicates the diameter when the defect is circular, and when the defect is not circular, the range of the defect is determined by observing with a microscope according to the following method, and the maximum diameter (diameter of circumscribed circle) is determined. . When the defect is a bubble or a foreign object, the defect range is measured by the size of the shadow when the defect is observed with the transmitted light of the differential interference microscope. Further, when the defect is accompanied by a change in the surface shape such as transfer of a roller flaw or an abrasion, the size is confirmed by observing the defect with reflected light of a differential interference microscope. In addition, when observing with reflected light, if the size of the defect is unclear, aluminum or platinum is deposited on the surface for observation. In order to obtain a film with excellent quality expressed by the defect frequency with good productivity, it is necessary to filter the polymer solution with high precision immediately before casting, to increase the cleanliness around the casting machine, It is effective to set the subsequent drying conditions in stages, and to dry efficiently while suppressing foaming.

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

(Elongation at break)
The retardation film of the present embodiment has a breaking elongation of at least 10% in at least one direction (the width direction (TD direction) or the conveyance direction (MD direction)) in the measurement based on JIS-K7127-1999. It is preferably 20% or more. The upper limit of the elongation at break is not particularly limited, and is practically about 250%. In order to increase the elongation at break, it is effective to suppress defects in the film caused by foreign matter and foaming.

(Total light transmittance)
The retardation film of this embodiment preferably has a total light transmittance of 90% or more, and more preferably 93% or more. The upper limit of the total light transmittance is not particularly limited, and is practically about 99%. In order to achieve the excellent transparency expressed by the total light transmittance, it is necessary not to introduce additives and copolymerization components that absorb visible light, or to remove foreign substances in the polymer by high-precision filtration. It is effective to reduce the diffusion and absorption of light inside the film. Also, reduce the surface roughness of the film surface by reducing the surface roughness of the film contact area (cooling roller, calender roller, drum, belt, coating substrate in solution casting, transport roller, etc.) during film formation. It is effective to reduce the diffusion and reflection of light on the film surface.

<Method for producing retardation film>
Next, a method for producing the above retardation film will be described.

The retardation film of the present embodiment can be formed according to a known method. Hereinafter, typical solution casting methods and melt casting methods will be described.

(Solution casting method)
The retardation film of this embodiment can be produced by a solution casting method. In the solution casting method, thermoplastic resins such as cellulose acylate (resin having positive intrinsic birefringence) and additives (additives having retardation increasing ability and wavelength dispersion adjusting ability and negative intrinsic birefringence) A step of preparing a dope by heating and dissolving an additive in an organic solvent, a step of casting the prepared dope on a belt-shaped or drum-shaped metal support, a step of drying the cast dope as a web, A step of peeling from the metal support, a step of stretching or shrinking the peeled web, a step of drying, a step of winding up the finished film, and the like are included.

(Dope preparation process)
In the dope adjusting step, the cellulose acylate in the dope is preferably high in concentration because the drying load after casting on the metal support can be reduced, but if the concentration of cellulose acylate is too high, the load during filtration is high. It increases and the filtration accuracy deteriorates. For this reason, the concentration at which these are compatible is preferably in the range of 10 to 35% by mass, more preferably in the range of 15 to 25% by mass.

(Casting process)
In the casting (casting) step, the metal support used preferably has a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used.

The cast width is preferably in the range of 1 to 4 m. The surface temperature of the metal support in the casting step is appropriately selected and set within a range of −50 ° C. to a temperature at which the solvent boils and does not foam. A higher temperature is preferable because the web can be dried faster, but if it is too high, the web may foam and flatness may deteriorate. A preferable support temperature is appropriately determined within the range of 0 to 100 ° C. A temperature range of 5 to 30 ° C. is more preferred. In addition, the web can be gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent. The method for controlling the temperature of the metal support is not particularly limited, but there are a method of blowing warm air or cold air, and a method of bringing hot water into contact with the back side of the metal support. The method using hot water is preferable because the heat transfer is performed efficiently, and the time until the temperature of the metal support becomes constant is short. When using warm air, considering the temperature drop of the web due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there is a case where wind at a temperature higher than the target temperature is used while preventing foaming. is there. In particular, it is preferable to perform drying efficiently by changing the temperature of the support and the temperature of the drying air during the period from casting to peeling.

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

In the present specification, the amount of residual solvent is defined by the following formula.
Residual solvent amount (% by mass) = {(MN) / N} × 100
Where M is the mass of the sample taken at any time during or after the web or film is produced, and N is the sample taken at any time during or after the web or film is produced at 115 ° C. (Mass after heating for 1 hour)

(Drying process)
In the drying step, the web is peeled off from the metal support and further dried, so that the residual solvent amount is preferably 1.0% by mass or less, more preferably 0 to 0.01% by mass.

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

(Stretching process)
As described above, the in-plane retardation Ro ₅₅₀ measured at a wavelength of 550 nm is preferably 100 to 155 nm in the retardation film of this embodiment, and such retardation can be imparted by stretching the film.

The stretching method is not particularly limited, for example, a method in which a circumferential speed difference is provided to a plurality of rollers, and a longitudinal stretching is performed using the roller circumferential speed difference therebetween, and both ends of the web are fixed with clips or pins. A method of extending the distance between pins in the traveling direction and extending in the vertical direction, a method of expanding in the horizontal direction and extending in the horizontal direction, or a method of extending the vertical and horizontal directions simultaneously and extending in both the vertical and horizontal directions may be employed alone or in combination. it can. That is, the film may be stretched in the transverse direction, longitudinally, or in both directions with respect to the film forming direction, and when stretched in both directions, simultaneous stretching or sequential stretching may be used. May be. In the case of the so-called tenter method, driving the clip portion by the linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

Next, a specific method for producing a retardation film will be described with reference to the drawings.

The retardation film is stretched in the slow axis direction and then stretched and contracted in the fast axis direction, and then the ratio of the shrinkage ratio in the fast axis direction to the stretch ratio in the slow axis direction (shrinkage ratio / stretching). The film can be produced by stretching under the condition that the magnification is in the range of 0.05 to 0.70.

In the retardation film, in particular, the film is stretched in the direction in which the slow axis is desired to be generated, is contracted in the vertical direction (the fast axis direction), and the ratio of the shrinkage rate with respect to the stretching ratio is controlled. Retardation increasing ability and chromatic dispersion adjusting ability so that the main chain direction of the additive having chromatic dispersion adjusting ability matches the principal axis direction (stretching direction, slow axis direction) of the resin having positive intrinsic birefringence. It is preferable to control the orientation direction of the main axis of the additive having. Similarly, for an additive having negative intrinsic birefringence, the orientation direction of the main chain of the additive is controlled so that the main chain direction of the additive coincides with the direction perpendicular to the main axis direction of the resin. It is desirable.

That is, as the ratio of the draw ratio in the slow axis direction (width direction) and the shrinkage ratio in the direction perpendicular to the slow axis direction (fast axis direction), the shrinkage ratio / stretch ratio is 0.05. Is preferably in the range of ˜0.70, and more preferably in the range of 0.10 to 0.30. By setting the shrinkage ratio / stretch ratio in the range of 0.05 to 0.70, the main chain of the additive having the retardation increasing ability and the wavelength dispersion adjusting ability is changed to the main chain of the resin having positive intrinsic birefringence. If the side chain of the additive having retardation increasing ability and wavelength dispersion adjusting ability is also oriented in the film fast axis direction and a high refractive index molecule is contained in the side chain, the process proceeds in the ultraviolet region of 280 nm. it is possible to increase the axis direction of the refractive index n _{y (280),} it can be a steep slope of n _y wavelength dispersion in the visible light region. Similarly, for an additive having negative intrinsic birefringence, the main chain of the additive can be aligned in the direction perpendicular to the main chain of the resin, and the slope of chromatic dispersion in the visible light region can be made steep.

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

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 Figure 1, when the oblique stretching the cellulose acylate film F in the direction of reference numerals A2, cellulose acylate film F shrinks to M ₂ by being obliquely bent. That is, when the gripping tool that grips the cellulose acylate film F proceeds 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 has advanced by M ₂ in the film entering direction (direction orthogonal to the stretching direction (TD direction) A1), the cellulose acylate film F has a length M ₃ (however, M ₃ = M ₁ −M ₂ ).

At this time, the shrinkage rate (%) is
Shrinkage rate (%) = (M ₁ −M ₂ ) / M ₁ × 100
Represented by
M ₂ = M ₁ × sin (π−θ)
And the shrinkage rate is
Shrinkage rate (%) = (1−sin (π−θ)) × 100
It is represented by

In FIG. 1, reference symbol A3 is the transport direction (MD direction), and reference symbol A4 indicates the slow axis.

As a method for controlling the orientation of the additive having retardation increasing ability and wavelength dispersion adjusting ability, it is preferable that the slow axis of the retardation film is within a range of 10 to 80 ° with respect to the transport direction, and 30 to The angle is more preferably 60 °, and particularly preferably in the range of 40 to 50 °. The shrinkage at that time is preferably in the range of 10 to 50%.

In consideration of the productivity of the circularly polarizing plate, the retardation film of the present embodiment 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 a retardation film of the present embodiment, it is preferable to use an oblique stretching apparatus as a method for imparting an oblique orientation to a cellulose acylate film to be stretched.

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

FIG. 2 is a schematic diagram showing an example of an oblique stretching apparatus in which a film feeding direction and a film take-up direction that can be applied to the production of the retardation film of the present embodiment coincide with each other. In addition, the figure shown here is an example, Comprising: The extending | stretching apparatus applicable by this embodiment is not limited to this. In FIG. 2, reference numeral 12-2 is a guide roll (on the tenter outlet side), reference numeral 13 is a film stretching direction, reference numeral 14-1 is a film feeding direction, and reference numeral 14-2 is a film stretching. The direction and reference numeral 15 indicate portions where the conveyance speeds of the left and right grippers are different.

As shown in FIG. 2 (a), the pair of left and right grips that grips both ends of the film at the entrance of the stretching device are on the left and right rails in a zone where the distance between the left and right rails is constant in the stretching device at the initial stage. In the zone where the distance between the left and right rails is widened after that, run on the left and right rails at different speeds, and then again on the left and right rails in the zone where the distance between the left and right rails is equal. Run.

For example, as shown in FIG. 2A, a case will be described in which the gripping tool traveling on the left rail is faster than the gripping tool traveling on the right rail.

The long film original 4 whose direction is controlled by the guide roll 12-1 on the entrance side of the stretching apparatus is gripped by the gripping tool at the positions of the outer film gripping start point 8-1 and the inner film gripping start point 8-2. Is done. Thereafter, in a region where the distance between the left and right rails is equal, the pair of left and right grips travel on the rails at a constant speed. Thereafter, at points 10-1 and 10-2 at which the left and right rails start to widen, the traveling speed of the left gripping tool (hereinafter also referred to as the high speed gripping tool) is the same as that of the right gripping tool (hereinafter referred to as the low speed gripping tool). At a point 11-3 where the left and right rails have finished widening and the left and right rails have finished widening, the high speed side gripping tool is again equal to the low speed side gripping speed. The pair of left and right gripping tools starts running again at the same speed. Thereafter, when the low-speed side gripping tool reaches the point 11-1 at which the widening of the left and right rails ends, one of the pair of left and right gripping tools reaches 11-2.

Thereafter, the pair of left and right clips travel on the left and right rails at a constant speed, the left gripper releases the film at the left grip end point 9-2, and then the right gripper at the right grip end point 9-1. The film is released and the oblique stretching is finished.

FIG. 2B is a schematic view of an oblique stretching apparatus of a system in which the film feeding direction applicable to the present embodiment and the film take-up direction coincide with each other.

A pair of left and right grips that grip both ends of the film at the entrance of the stretching apparatus travel on the left and right rails at different speeds in a zone where the distance between the left and right rails is constant in the initial stage of the stretching apparatus.

As shown in FIG. 2B, the stretching device has a portion where the distance between the left and right rails is increased. A pair of left and right grips grip the film at the film grip start points 8-1 and 8-2 at the entrance of the stretching device, and the left and right grips travel on the left and right rails at different speeds. When the high-speed gripper of the pair of left and right grippers reaches the grip end point 9-2 of the stretching device outlet, the paired low-speed gripper is positioned at 11-1, The film gripped by the pair of left and right grippers is stretched obliquely.

In addition, although the extending | stretching apparatus shown by FIG.2 (b) has a location where the distance between left-right rails widens, it does not necessarily need to have a location where the distance between left-right rails widens.

2 (a) and 2 (b), the traveling speed of the gripping tool can be selected as appropriate, but is usually 1 to 100 m / min. Further, in this specification, the pair of left and right grippers traveling at different speeds means that the difference between the travel speeds of the pair of left and right grippers substantially exceeds 1% of the travel speed. That is, the difference between the traveling speeds of the pair of left and right gripping tools is usually 1% or less, preferably 0.5% or less, more preferably 0.1% or less of the traveling 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 will occur at the exit of the stretching process, so the speed difference between the right and left gripping tools is required to be substantially the same speed. Because.

The difference in travel speed between the pair of left and right gripping tools is preferably more than 1% of the travel speed and 50% or less, more preferably more than 1% of the travel speed and 30% or less, and more than 1% of the travel speed. 10% or less is more preferable.

Further, the stretching apparatus shown in FIGS. 2A and 2B may have a known mechanism in which the traveling speed of the gripping tool changes in the middle.

In general stretching equipment, etc., there are speed irregularities that occur on the order of seconds or less depending on the period of the sprocket teeth that drive the chain, the frequency of the drive motor, etc. This does not correspond to the speed difference in the embodiment.

Further, as one aspect of the method for producing a retardation film of the present embodiment, the film feeding direction and the film take-up direction in the stretching step are obliquely crossed, and 10 ° to It is characterized by being manufactured under the condition that a slow axis is provided within an angle range of 80 °.

FIG. 3 is a schematic diagram showing an example of an oblique stretching apparatus in which a film feeding direction and a film take-up direction applicable to the present embodiment are obliquely crossed.

As shown in FIG. 3, the long film original 4 whose direction is controlled by the guide roll 12-1 on the drawing apparatus entrance side has an outer film holding start point 8-1 and an inner film holding start point 8- It is gripped by the gripping tool at position 2.

The pair of left and right grippers are transported and stretched at an equal speed with each other in the oblique direction indicated by the outer film gripper trajectory 7-1 and the inner film gripper trajectory 7-2. The film holding end point 9-1 and the inner film holding end point 9-2 are released, and the conveyance is controlled by the guide roll 12-2 on the outlet side of the drawing apparatus, whereby the obliquely stretched film 5 is formed. In the drawing, the long film original is obliquely stretched at an angle 14 (feeding angle θi) in the film stretching direction 14-2 with respect to the film feeding direction 14-1. In FIG. 3, reference numeral 5 indicates a long stretched film, reference numeral W indicates a film width after oblique stretching, and reference numeral Wo indicates a film width before oblique stretching.

In the oblique stretching apparatus used in the present embodiment, a large bending rate is often required especially for the rail that regulates the locus of the gripping tool inside the stretching apparatus as shown in FIG. In order to avoid interference between gripping tools due to sudden bending or local stress concentration, it is preferable that the bent portion is formed so that the locus of the gripping tool draws an arc.

In the oblique stretching apparatus shown in FIG. 2, the traveling direction 14-1 at the entrance of the stretching device of the long film is different from the traveling direction 14-2 at the exit side of the stretched film. The feeding angle θi is an angle formed between the traveling direction 14-1 at the entrance of the stretching apparatus and the traveling direction 14-2 at the exit side of the stretched film.

More specifically, in the manufacturing method of this embodiment, it is particularly preferable to perform oblique stretching using the oblique stretching apparatus shown in FIG. This stretching apparatus can heat a film original fabric to an arbitrary temperature at which it can be stretched and obliquely stretch the film. This stretching apparatus includes a heating zone, a pair of rails on the left and right on which a gripping tool for transporting the film travels, and a number of gripping tools that travel on the rails. Both ends of the film sequentially supplied to the inlet of the 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 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 which has released the grip of the film at the outlet portion of the stretching apparatus travels outside and is sequentially returned to the inlet portion.

In addition, the rail pattern of the 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 θ, the stretching ratio, etc. given to the long stretched film to be manufactured. In the oblique stretching apparatus used in the manufacturing method of the present embodiment, it is preferable that the position of each rail part and the rail connecting part can be freely set, and the rail pattern can be arbitrarily changed (circle part in FIG. 3 is an example of the connecting part) Is).

In the present embodiment, the gripping tool of the stretching apparatus travels at a constant speed with a constant distance from the front and rear gripping tools.

(Melting method)
The above retardation film may be formed by a melt film forming method. The melt film-forming method is a molding method in which a composition containing an additive such as a resin and a plasticizer is heated and melted to a temperature exhibiting fluidity, and then a melt containing a fluid thermoplastic resin is cast. .

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 in advance and pelletized. Pelletization can be performed by a known method, for example, dry cellulose acylate, plasticizer, and other additives are fed to an extruder with a feeder, and kneaded using a single or twin screw extruder, It can be obtained by extruding into a strand form from a die, cooling with water or air, and cutting.

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

The extruder used for pelletization is preferably an extruder that employs a method of processing at as low a temperature as possible so that pelletization can be performed so that the shear force is suppressed and 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.

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

After the pellets are extruded using a single or twin screw type extruder, the melting temperature is in the range of 200 to 300 ° C. After removing foreign matter by filtering with a leaf disk type filter or the like, T A film is cast from the die, the film is nipped by 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 carried out stably by introducing a gear pump. Further, a stainless fiber sintered filter is preferably used as a filter used for removing foreign substances. A stainless steel fiber sintered filter is a product in which a stainless steel fiber body is intricately intertwined and compressed, and the contact points are sintered and integrated. The 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 during the extrusion. 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 the film from being deformed.

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

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

The above retardation film 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 specification, “substantially 45 °” means within a range of 40 to 50 °.

The angle between the slow axis in the plane of the retardation film and the transmission axis of the polarizer is preferably in the range of 41 to 49 °, and more preferably in the range of 42 to 48 °. , 43 to 47 ° is more preferable, and 44 to 46 ° is particularly preferable.

<Circularly polarizing plate>
The circularly polarizing plate of this embodiment is produced by cutting a long roll having a long protective film, a long polarizer and a long retardation film in this order. Since the circularly polarizing plate of the present embodiment is produced using the above-described retardation film, it is applied to an organic EL display or the like, which will be described later, so that the specular reflection of the metal electrode of the organic EL element 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.

The circularly polarizing plate preferably has an ultraviolet absorption function. It is preferable that the protective film on the viewing side has an ultraviolet absorbing function from the viewpoint that both the polarizer and the organic EL element can exhibit a protective effect against ultraviolet rays. Furthermore, when the retardation film on the light emitter side also has an ultraviolet absorption function, when used in an organic EL display described later, deterioration of the organic EL element can be further suppressed.

Further, the circularly polarizing plate of the present embodiment uses the retardation film 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, It is possible to form an adhesive layer and bond the polarizing film and the retardation film plate together by a consistent production line. Specifically, after finishing the process of stretching and producing the polarizing film, a step of laminating the polarizing film and the retardation film can be incorporated during or after the subsequent drying process. It can be continuously supplied and can be connected in a production line that is consistent with the next process by winding in a roll state even after bonding. In addition, when bonding a polarizing film and retardation film, a protective film can also be simultaneously supplied in a roll state and can also be bonded continuously. From the viewpoint of performance and production efficiency, it is preferable to simultaneously bond the retardation film and the protective film to the polarizing film. That is, after finishing the process of stretching and producing the polarizing film, after the subsequent drying process or after the drying process, the protective film and the retardation film are bonded to both sides with an adhesive, respectively, It is also possible to obtain a circularly polarizing plate.

In the circularly polarizing plate of this embodiment, the polarizer is preferably sandwiched between the retardation film and the protective film, and a cured layer is preferably laminated on the viewing side of the protective film.

<Organic EL display>
The organic EL display (organic EL image display device) of this embodiment is produced using the circularly polarizing plate. More specifically, the organic EL display of the present embodiment includes a circularly polarizing plate using the retardation film and an organic EL element. Therefore, the organic EL display is prevented from being reflected during observation, and the black expression is improved. The screen size of the organic EL display is not particularly limited, and can be 20 inches or more.

FIG. 4 is a schematic explanatory diagram of the configuration of the organic EL display of the present embodiment. The configuration of the organic EL display of this embodiment is not limited to that shown in FIG.

As shown in FIG. 4, 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 are sequentially formed on a transparent substrate 101 using glass, polyimide, or the like. An organic EL display A is configured by providing the above-described circularly polarizing plate C in which the polarizer 110 is sandwiched between the above-described retardation film 109 and the protective film 111 on the organic EL element B having 108 (can be omitted). It is preferable that a hardened layer 112 is laminated on the protective film 111. The hardened layer 112 not only prevents scratches on the surface of the organic EL display but also has an effect of preventing warpage of the circularly polarizing plate. Furthermore, an antireflection layer 113 may be provided on the cured layer. The thickness of the organic EL element itself is about 1 μm.

Generally, in an organic EL display, a metal electrode, an organic light emitting layer, and a transparent electrode are sequentially laminated on a transparent substrate to form a light emitting element (organic EL element). 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, Alternatively, a structure 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 is known. It has been.

In an organic EL display, 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 fluorescent material. It emits light on the principle that it emits light when the excited fluorescent material returns 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, in order to take out light emitted from the organic light emitting layer, at least one of the electrodes needs to be transparent. Usually, a transparent electrode formed of a transparent conductor such as indium tin oxide (ITO) is used. It is preferably used as an anode. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

The circularly polarizing plate having the above-mentioned λ / 4 retardation film can be applied to an organic EL display having a large screen having a screen size of 20 inches or more, that is, a diagonal distance of 50.8 cm or more.

In the organic EL display 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 looks like a mirror surface.

In an organic EL display including an organic EL element having a transparent electrode on the surface side of an organic light emitting layer that emits light by applying a voltage and a metal electrode on the back side of the organic light emitting layer, the surface side (viewing side) of the transparent electrode ), And a retardation plate between the transparent electrode and the polarizing plate.

Since the retardation film and the polarizing plate have a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization action. In particular, if the retardation film is composed of a quarter retardation film and the angle formed by the polarization direction of the polarizing plate and the retardation film is adjusted to π / 4, the mirror surface of the metal electrode can be completely shielded. it can.

That is, the external light incident on the organic EL display is transmitted only through the linearly polarized light component by the polarizing plate, and this linearly polarized light is generally elliptically polarized by the retardation plate. In particular, the retardation film is a λ / 4 retardation film. Moreover, when the angle formed by the polarization direction of the polarizing plate and the retardation film is π / 4, circular polarization is obtained.

This circularly polarized light is transmitted through the transparent substrate, transparent electrode, and organic thin film, reflected by the metal electrode, again transmitted through the organic thin film, transparent electrode, and transparent substrate, and becomes linearly polarized light again on the retardation film. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.

The technical characteristics of the above retardation film, the circularly polarizing plate produced using the retardation film and the organic EL display are summarized below.

That is, the retardation film of one aspect of the present invention has an in-plane retardation Ro _{550 at} a wavelength of 550 nm of 100 to 155 nm, and a ratio of the in-plane retardation Ro _{450 at} a wavelength of 450 nm to Ro ₅₅₀ (Ro ₄₅₀ / Ro ₅₅₀ ). Is 0.72 to 0.95, and the ratio of Ro _{550 to} the in-plane retardation Ro _{650 at} a wavelength of 650 nm (Ro ₅₅₀ / Ro ₆₅₀ ) is 0.83 to 0.97, and is in the longitudinal direction. In addition, in a retardation film having a slow axis of 10 to 80 °, the retardation film has a resin having positive intrinsic birefringence as a main component, and has addition of retardation increasing ability and wavelength dispersion adjusting ability And an additive having negative intrinsic birefringence.

Since the present invention has such a configuration, a circularly polarizing plate used for a display requiring high contrast, such as an organic EL display, as a λ / 4 retardation film that substantially exhibits a λ / 4 retardation in a wide band. Can be suitably used. In addition, since the retardation film of the present invention has an angle of 10 to 80 ° with respect to the longitudinal direction, the retardation film can be bonded to the polarizing film by roll-to-roll, and undergoes a complicated assembly process. And can be used when producing a circularly polarizing plate. Further, in the retardation film of the present invention, the in-plane retardation Ro ₅₅₀ is expressed by a retardation which is expressed by a resin having positive intrinsic birefringence, and an additive having retardation increasing ability and wavelength dispersion adjusting ability. Achieved as the sum of phase differences. Therefore, since a necessary in-plane retardation can be obtained without excessively depending on the retardation increasing ability of the additive, it is possible to suppress the additive amount of the additive and suppress the occurrence of cloudiness.

In addition, the retardation film of the present invention increases the reverse wavelength dispersion characteristics by adding an additive having negative intrinsic birefringence to a resin having positive intrinsic birefringence, and also has retardation increasing ability and wavelength dispersion adjusting ability. Also, an additive having the above is configured to supplement the reverse wavelength dispersion characteristics. With such a configuration, the additive having negative intrinsic birefringence and the additive having retardation increasing ability and wavelength dispersion adjusting ability can obtain the necessary reverse wavelength dispersion characteristics. It is not necessary to adjust the wavelength dispersion characteristics with an additive alone having a wavelength dispersion adjusting ability. Therefore, it is easy to adjust the additive, and it is possible to select the additive by giving priority to the compatibility with the resin as the base material. Moreover, each addition amount can be suppressed and the cloudiness of a film can also be suppressed. In addition, when the wavelength dispersion characteristic is adjusted by the resin having positive intrinsic birefringence and the additive having negative intrinsic birefringence, the retardation expression is lowered, but it is lowered by the additive having negative intrinsic birefringence. Since the retardation developing property can be supplemented by an additive having retardation increasing ability and wavelength dispersion adjusting ability, a necessary retardation can be achieved without excessively increasing the draw ratio.

Furthermore, the retardation film of the present invention is excellent in visibility even when applied to a display such as an organic EL display that requires high contrast, has high retardation expression, has excellent reverse wavelength dispersion characteristics, and , Cloudiness is suppressed.

In the above structure, the resin having positive intrinsic birefringence is preferably a cellulose ester having an acyl substitution degree of 1.5 to 2.55.

The retardation film of the present invention can impart a high retardation expression without deteriorating the reverse wavelength dispersion characteristics by using a cellulose ester resin having an acyl substitution degree within the above range. The load can be reduced and the transparency of the retardation film can be further increased.

In the above configuration, the additive having the retardation increasing ability and the wavelength dispersion adjusting ability is preferably a compound defined by the following general formula (A).

（式中、Ｌ_１およびＬ_２は各々独立に単結合または２価の連結基であり、Ｒ_１、Ｒ_２およびＲ_３は各々独立に置換基を表し、ｎは０から２までの整数を表し、ＷａおよびＷｂはそれぞれ水素原子または置換基を表し、（Ｉ）ＷａおよびＷｂが互いに結合して環を形成してもよく、（ＩＩ）ＷａおよびＷｂの少なくとも一つが環構造を有してもよく、または（ＩＩＩ）ＷａおよびＷｂの少なくとも一つがアルケニル基またはアルキニル基であってもよい）

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

In the retardation film of the present invention, by using the compound represented by the general formula (A), high retardation expression can be imparted to the film, and good reverse wavelength dispersion characteristics can be imparted.

In the above structure, it is preferable that the additive having negative intrinsic birefringence contains at least one selected from the group consisting of an aliphatic polyester polymer, an acrylic polymer, and a styrene maleic acid polymer.

The retardation film of the present invention can impart good reverse wavelength dispersion characteristics while adjusting the retardation expression by using the above compound as an additive having negative intrinsic birefringence.

The circularly polarizing plate according to one aspect of the present invention includes the retardation film and a polarizer.

Since the circularly polarizing plate of the present invention is produced using the above retardation film, the effect of shielding the specular reflection of the metal electrode of the organic EL element at all wavelengths of visible light when applied to an organic EL display or the like. Can be expressed. As a result, reflection during observation can be prevented and black expression can be improved.

Further, in the organic EL display according to one aspect of the present invention, the circularly polarizing plate is arranged on the viewing side.

In the organic EL display of the present invention, since the circularly polarizing plate is disposed on the viewer side, reflection during observation can be prevented and black expression can be improved.

According to the present invention, even when applied to a display that requires high contrast such as an organic EL display, it has excellent visibility, high retardation development, excellent reverse wavelength dispersion characteristics, and suppresses white turbidity. It is possible to provide a retardation film capable of imparting a retardation of substantially λ / 4 to the obtained broadband light, a circularly polarizing plate produced using the retardation film, and an organic EL display.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, it will represent "mass part" or "mass%" unless there is particular notice.

(Example 1)
<Production of retardation film>
(Preparation of fine particle dispersion)
Fine particles (Aerosil R812 manufactured by Nippon Aerosil Co., Ltd.) 11 parts by mass Ethanol 89 parts by mass 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)
50 parts by mass of methylene 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 methylene chloride. Further, the particles were dispersed by an attritor so that the secondary particles had a particle size of about 0.01 to 1.0 μm. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.

(Preparation of dope)
First, the following methylene chloride and ethanol were added to the pressure dissolution tank. Resin CE-1 (cellulose acylate) having positive intrinsic birefringence having an acetyl group substitution degree of 1.52 and a total substitution degree of 1.52 was added to a pressure dissolution tank containing an organic solvent while stirring. . This was heated and stirred to dissolve completely, and this was dissolved in Azumi Filter Paper No. The main dope was prepared by filtration using 244. Next, as an additive having retardation increasing ability and wavelength dispersion adjusting ability, additive A-1 having the structure shown below, additive B-1 having negative intrinsic birefringence (succinic acid / propylene glycol terminal hydroxyl group, number Average molecular weight Mn: 400), sugar ester compound (benzyl saccharose with an average substitution degree of 7.3) and the fine particle addition liquid prepared above were put into the main dissolution vessel in the following ratio, sealed, and dissolved with stirring. A dope solution was prepared.

<Dope composition>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass CE-1 100 parts by mass A-1 3.5 parts by mass (3% by mass with respect to the film mass)
B-1 14 parts by mass (12% by mass with respect to the film mass)
5 parts by mass of a sugar ester compound (benzyl saccharose with an average substitution degree of 7.3) 2 parts by mass of a fine particle additive solution

(Additive having retardation increasing ability and wavelength dispersion adjusting ability: A-1)

(Film formation)
The dope prepared as described above was cast on a stainless steel belt support, and after the solvent was evaporated until the amount of residual solvent in the film reached 75% by mass, the peel tension was 130 N / m on the stainless steel belt support. The film was peeled off.

While the peeled film is heated at 185 ° C., the stretching / shrinkage ratio shown in Table 1 is set so that the slow axis forms 45 ° with the film longitudinal direction using the stretching apparatus shown in FIG. The film was stretched in an oblique direction to prepare a retardation film having a slow axis in a direction of 43 ° with respect to the longitudinal direction.

(Examples 2 to 24 and Comparative Examples 1 to 3, 5)
The resin having positive intrinsic birefringence, the additive having retardation increasing ability and wavelength dispersion adjusting ability, the additive having negative intrinsic birefringence, the slow axis angle and the film thickness were used under the conditions shown in Table 1. A retardation film was produced in the same manner as the retardation film of Example 1 except that the change was made.

(Comparative Example 4)
A retardation film was produced in the same manner as in Example 1 described in JP 2012-37899 A.

In addition to the additives described above, additives A-2 to A-8 having retardation increasing ability and wavelength dispersion adjusting ability used in Examples 2 to 24 and Comparative Examples 1 to 5, addition having negative intrinsic birefringence Agents B-2 to B-6 are shown below.

(Additive having retardation increasing ability and wavelength dispersion adjusting ability: A-2)

(Additive having retardation increasing ability and wavelength dispersion adjusting ability: A-3)

(Additive having retardation increasing ability and wavelength dispersion adjusting ability: A-4)

(Additive having retardation increasing ability and wavelength dispersion adjusting ability: A-5)

(Additive having retardation increasing ability and wavelength dispersion adjusting ability: A-6)

(Additive having retardation increasing ability and wavelength dispersion adjusting ability: A-7)

(Additive having retardation increasing ability and wavelength dispersion adjusting ability: A-8)

(Additive having negative intrinsic birefringence: B-2)
Succinic acid / ethylene glycol terminal hydroxyl group, number average molecular weight Mn: 1000

(Additive having negative intrinsic birefringence: B-3)
Adipic acid / ethylene glycol terminal acetyl ester residue, number average molecular weight Mn: 1000

(Additive having negative intrinsic birefringence: B-4)
Copolymer of methyl methacrylate and acryloylmorpholine, number average molecular weight Mn: 7000

(Additive having negative intrinsic birefringence: B-5)
Copolymer of methyl methacrylate and 2-hydroxyethyl methacrylate, number average molecular weight Mn: 4000

(Additive having negative intrinsic birefringence: B-6)
Styrene maleic acid copolymer (manufactured by Elf Atchem: SMA1000P), number average molecular weight Mn: 2000

<Measurement of each characteristic value of film>
The retardation films produced in Examples 1 to 24 and Comparative Examples 1 to 5 were in-plane at wavelengths of 450 nm, 550 nm, and 650 nm using Axoscan made by Axometrics under an environment of 23 ° C. and 55% RH. Directional retardation Ro ₄₅₀ , Ro ₅₅₀ and Ro ₆₅₀ were measured, and Ro ₄₅₀ / Ro ₅₅₀ and Ro ₅₅₀ / Ro _{650 were} calculated. The orientation angle was also measured using an Axoscan manufactured by Axometrics.

Furthermore, for each retardation film, the solid component was made only cellulose acylate except for the additive having retardation increasing ability and wavelength dispersion adjusting ability, the additive having negative intrinsic birefringence, the plasticizer, and the matting agent. Except for the above, a film was prepared under the same conditions, and the in-plane retardation Rc ₅₅₀ at a wavelength of 550 nm was measured. Similarly, a film is prepared under the same conditions except that the solid component is only an additive having cellulose acylate, retardation increasing ability and wavelength dispersion adjusting ability, and the above-mentioned retardation from in-plane direction retardation at a wavelength of 550 nm By subtracting Rc ₅₅₀ , in-plane retardation Ra ₅₅₀ at a wavelength of 550 nm was calculated. Further, similarly, a film is prepared under the same conditions except that the solid component is only cellulose acylate and an additive having negative intrinsic birefringence, and the Rc ₅₅₀ is subtracted from the in-plane retardation at a wavelength of 550 nm. Thus, retardation Rb ₅₅₀ in the in-plane direction at a wavelength of 550 nm was calculated. Based on _these, to calculate the ratio of _{Ra 550} against _{Ro 550 (Ra 550 / Ro 550} × 100). The film thickness was measured using a commercially available micrometer. Tables 1 and 2 show the film characteristic values obtained as described above.

<Production of circularly polarizing plate>
A polyvinyl alcohol film having a thickness of 120 μm 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.

Next, a polarizer according to the following steps 1 to 5, the respective retardation films produced in Examples 1 to 22 or Comparative Examples 1 and 2, and a protective film (described later) on the back side are rolled so that the longitudinal direction is aligned. -A circularly polarizing plate was prepared by bonding with a toe roll.

Step 1: The retardation film was immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried to saponify the side to be bonded to the polarizer.
Step 2: The polarizer was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.
Step 3: Excess adhesive adhered to the polarizer in Step 2 was gently wiped off and placed on the retardation film treated in Step 1. At that time, a tension of 50 N / m was applied to the retardation film and the polarizer so as not to sag.
Step 4: The retardation film, the polarizer, and the protective film laminated in Step 3 were bonded at a pressure of 20 to 30 N / cm ² and a conveyance speed of about 2 m / min.
Process 5: The sample which bonded the polarizer, retardation film, and protective film which were produced in the process 4 in the 80 degreeC dryer was dried for 2 minutes.

In addition, about each retardation film produced in Examples 23 and 24 and Comparative Examples 4 and 5, the retardation film was cut according to the size of the panel of the image display device at an angle of 45 ° in the longitudinal direction, Thereafter, a circularly polarizing plate was prepared in the same manner.

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

(Preparation of dope)
Cellulose acetate (acetyl group substitution degree 2.88, weight average molecular weight: about 180,000) 90 parts by mass Ester compound 10 parts by mass Tinuvin 928 (manufactured by BASF Japan Ltd.) 2.5 parts by mass Fine particle additive solution 4 parts by mass Methylene chloride 432 parts by mass Ethanol 38 parts by mass

The above is put into a sealed container, heated and stirred to dissolve completely, and Azumi Filter Paper No. No. 24 was used for filtration to prepare a dope solution.

(Film formation)
Next, the belt casting apparatus was used to uniformly cast on a stainless steel band support. With the stainless steel band support, the solvent was evaporated until the residual solvent amount reached 100%, and the stainless steel band support was peeled off. Cellulose ester film web was evaporated at 35 ° C, slitted to 1.65m width, stretched at 160 ° C while applying heat at 160 ° C, 30% in TD direction (film width direction), MD direction draw ratio Was stretched 1%. The residual solvent amount when starting stretching was 20%. Then, after drying for 15 minutes while transporting the inside of a drying device at 120 ° C. with many rollers, slitting to a width of 1.49 m, applying a knurling process with a width of 15 mm and a height of 10 μm at both ends of the film, and winding it around a winding core A protective film was obtained. The residual solvent amount of the protective film was 0.2%, the film thickness was 40 μm, and the number of turns was 3900 m. The orientation angle θ of the protective film was measured using KOBRA-21ADH manufactured by Oji Scientific Instruments, and as a result, it was in the range of 90 ° ± 1 ° with respect to the longitudinal direction of the film.

<Production of organic EL element>
Using an alkali-free glass for 50 inches (127 cm) having a thickness of 3 mm, an organic EL device was produced according to the following method. FIG. 5 is a schematic diagram of the configuration of the organic EL display of the present embodiment.

As shown in FIG. 5, a reflective electrode made of chromium is formed on a transparent glass substrate 1a, ITO is formed on the reflective electrode as a metal electrode 2a (anode), and poly (3,3 is formed on the anode as a hole transport layer. 4-Ethylenedioxythiophene) -polystyrene sulfonate (PEDOT: PSS) was formed by sputtering to a thickness of 80 nm, and then a shadow mask was used on the hole transport layer, as shown in FIG. The light emitting layers 3aR, 3aG, and 3aB were formed to a thickness of 100 nm. As the red light emitting layer 3aR, tris (8-hydroxyquinolinate) aluminum (Alq ₃ ) shown below as a host and a luminescent compound [4- (dicyanomethylene) -2-methyl-6 (p-dimethylaminostyryl) -4H -Pyran] (DCM) were co-evaporated (mass ratio 99: 1) to form a thickness of 100 nm. The green light emitting layer 3aG was formed to a thickness of 100 nm by co-evaporating Alq ₃ as a host and the light emitting compound coumarin 6 (mass ratio 99: 1). As the blue light emitting layer 3aB, BAlq shown below and a light emitting compound Perylene were co-deposited (mass ratio 90:10) as a host and formed to a thickness of 100 nm.

Further, calcium is deposited to a thickness of 4 nm by vacuum deposition as a first cathode having a low work function so that electrons can be efficiently injected onto the light emitting layer, and a second cathode is formed on the first cathode. As described above, aluminum was formed to have a thickness of 2 nm. The aluminum used as the second cathode has a role of preventing the first cathode calcium from being chemically altered when the transparent electrode 4a formed thereon is formed by sputtering. . Thus, an organic light emitting layer was formed. Next, a transparent conductive film was formed on the cathode so as to have a thickness of 80 nm by sputtering. ITO was used as the transparent conductive film. Further, a silicon nitride film was formed on the transparent conductive film by a CVD method so as to have a thickness of 200 nm, thereby forming the insulating film 5a, and the organic EL element 11a was manufactured. 5, reference numeral 6a is an adhesive layer, reference numeral 7a is a polarizing plate protective film (retardation film), reference numeral 8a is a polarizer, reference numeral 9a is a polarizing plate protective film, and reference numeral 10a is a polarizing plate. Show.

<Production of organic EL display>
After applying an adhesive to the surface of the retardation film of each circularly polarizing plate produced as described above, each organic EL display was produced by bonding to the viewing side of the organic EL element.

<Evaluation of retardation film and organic EL display>
The following evaluation was performed about each retardation film and organic electroluminescent display produced as mentioned above.

(Evaluation of scattering resistance)
About each produced said retardation film, the internal haze was measured in accordance with the following method.

First, blank haze 1 (external haze value) of a measuring instrument other than the retardation film was measured. One drop (0.05 ml) of glycerin was dropped on a glass slide that had been washed cleanly, taking care not to enter air bubbles. A cover glass was placed thereon, and glycerin was spread over the entire surface of the cover glass. It set to the haze meter shown below and measured blank haze 1 (external haze value). Next, haze 2 (total haze value) including the retardation film was measured by the following procedure. 0.05 ml of glycerol was dripped on the slide glass. A retardation film to be measured was placed thereon so as not to contain air bubbles. On the phase difference film, 0.05 ml of glycerin was dropped. A cover glass was placed thereon. The laminate (cover glass / glycerin / retardation film / glycerin / slide glass) prepared as described above was set on a haze meter, and haze 2 was measured. The internal haze value was determined from the following formula. The internal haze was measured under an environment of 23 ° C. and 55% RH using a retardation film conditioned for 5 hours or more in an environment of 23 ° C. and 55% RH.

(Haze 2)-(Haze 1) = (Internal haze value of retardation film)

The haze meter, glass, and glycerin used for the above measurement are shown below.

Haze meter: Haze meter (turbidity meter) (model: NDH 2000, manufactured by Nippon Denshoku Co., Ltd.), light source: 5V9W halogen bulb, light receiving part: silicon photocell (with a relative visibility filter), measurement: JIS K- 7136.

Slide glass: MICRO SLIDE GLASS S9213 MATSUNAMI Cover glass: Matsunami cover glass 24 × 50mm (KN33221827)

Glycerin: manufactured by Kanto Chemical Co., Inc. Deer special grade (purity> 99.0%), refractive index 1.47, based on each of the above measured internal hazes, the scattering resistance of each retardation film was determined according to the following criteria. evaluated. The results are shown in Table 2.

(Evaluation criteria)
○: The internal haze value was less than 0.04.
(Triangle | delta): The internal haze value was 0.04 or more and less than 0.06.
X: The internal haze value was 0.06 or more.

(Evaluation of visibility 1: color characteristics)
A BGR color chart image was displayed on the organic EL display under conditions where the illuminance was 1000 Lx at a position 5 cm higher than the outermost surface of the organic EL display in an environment of 23 ° C. and 55% RH. With respect to the displayed BGR color image, the front position of the organic EL display (0 ° with respect to the surface normal) and the visibility from an oblique angle of 40 ° with respect to the surface normal were evaluated according to the following criteria by 10 general monitors. . In the present invention, it was judged practically acceptable if it was Δ or more. The results are shown in Table 2.

A: Nine or more monitors were judged to be good BGR color images.
◯: It was determined that 7 to 8 monitors had good BGR color images.
Δ: It was determined that 5 to 6 monitors were good BGR color images.
X: The number of monitors judged to be good BGR color images was 4 or less.

(Visibility evaluation 2: black display characteristics)
In an environment of 23 ° C. and 55% RH, a black image was displayed on the organic EL display under the condition that the illuminance was 1000 Lx at a position 5 cm higher than the outermost surface of the organic EL display. Next, for the displayed black image, the front position of the organic EL display (0 ° with respect to the surface normal) and the visibility of the black image from an oblique angle of 40 ° with respect to the surface normal are as follows by 10 general monitors: Evaluation was performed according to the criteria. In the present invention, it was judged practically acceptable if it was Δ or more. The results are shown in Table 2.
(Evaluation criteria)
A: Seven or more monitors determined that the displayed image was black.
Δ: Five to six monitors determined that the displayed image was black.
X: The number of monitors judged to be black in the displayed image was 4 or less.

As shown in Tables 1 and 2, the retardation film of the present invention has low internal haze and good transparency. An organic EL display using a circularly polarizing plate produced using this retardation film has a color It was found that it was excellent in visibility such as taste and black display characteristics.

The present invention can be widely used in technical fields such as a retardation film, a circularly polarizing plate produced using the retardation film, and an organic EL display.

Claims (6)

In-plane retardation Ro _{550 at a} wavelength of 550 nm is 100 to 155 nm,
The ratio of the in-plane retardation Ro ₄₅₀ at a wavelength of 450 nm to Ro ₅₅₀ (Ro ₄₅₀ / Ro ₅₅₀ ) is 0.72 to 0.95,
The ratio of Ro ₅₅₀ to in-plane retardation Ro _{650 at} a wavelength of 650 nm (Ro ₅₅₀ / Ro ₆₅₀ ) is 0.83 to 0.97,
In a retardation film having a slow axis of 10 to 80 ° with respect to the longitudinal direction,
The retardation film contains a resin having positive intrinsic birefringence as a main component, and has an additive having retardation increasing ability and wavelength dispersion adjusting ability, and an additive having negative intrinsic birefringence. the film. The retardation film according to claim 1, wherein the resin having positive intrinsic birefringence is a cellulose ester having an acyl substitution degree of 1.5 to 2.55. The retardation film according to claim 1, wherein the additive having the retardation increasing ability and the wavelength dispersion adjusting ability is a compound defined by the following general formula (A).

(In the formula, L ₁ and L ₂ each independently represent a single bond or a divalent linking group, R ₁ , R ₂ and R ₃ each independently represent a substituent, and n represents an integer of 0 to 2) And Wa and Wb each represent a hydrogen atom or a substituent, (I) Wa and Wb may be bonded to each other to form a ring, and (II) at least one of Wa and Wb has a ring structure Or (III) at least one of Wa and Wb may be an alkenyl group or an alkynyl group) The additive according to any one of claims 1 to 3, wherein the additive having negative intrinsic birefringence contains at least one selected from the group consisting of an aliphatic polyester polymer, an acrylic polymer, and a styrene maleic acid polymer. The retardation film according to item. A circularly polarizing plate comprising the retardation film according to any one of claims 1 to 4 and a polarizer. The organic electroluminescent display which has arrange | positioned the circularly-polarizing plate of Claim 5 in the visual recognition side.

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