JPWO2014087593A1 - Retardation film, circularly polarizing plate, and image display device - Google Patents

Abstract

One aspect of the present invention is a first cellulose acylate resin satisfying 2 ≦ X (degree of substitution of acetyl group) + Y (degree of substitution of acyl group other than acetyl group) ≦ 3 and 0 ≦ Y ≦ 1.5, A retardation film comprising a second cellulose acylate resin satisfying 2.4 ≦ X + Y ≦ 2.7 and 0.7 ≦ Y ≦ 1, and the resin constituting the retardation film has a weight average molecular weight, 190,000 to 300,000, and a value obtained by dividing the weight average molecular weight by the number average molecular weight is 2.4 to 3.3, and the weight average molecular weight of the first and second cellulose acylate resins is The retardation film is characterized in that the absolute value of the difference is 50,000 or more and 120,000 or less, and the angle formed by the in-plane slow axis and the width direction is 40 to 50 °.

Description

  The present invention relates to a retardation film, a circularly polarizing plate, and an image display device.

  An organic electroluminescence element (organic EL element) is a light source for a flat illumination device, a light source for an optical fiber, a backlight for a liquid crystal display device, a liquid crystal projector device from the viewpoints of high luminous efficiency, low voltage drive, light weight, and low cost. The use as a light source such as a backlight for a display and a light source of an organic EL display device (OLED) has been widely studied.

  In an organic EL element, a light emitting layer is provided between electrodes, and when a voltage is applied between the electrodes, electrons are injected from the cathode into the light emitting layer, and holes from the anode are injected into the light emitting layer. The light emitting layer emits light by the energy generated by the bonding.

  In addition, the organic EL element has an anode made of indium tin oxide (ITO) because of its high electrical conductivity, relatively high work function, and high hole injection efficiency among transparent conductive materials. , Mainly used. Moreover, a metal electrode is usually used for the cathode. As the metal electrode, Mg, Mg / Ag, Mg / In, Al, Li / Al, etc. are mainly used from the viewpoint of work function in consideration of electron injection efficiency. These metal electrodes have a high light reflectivity, and in addition to the function as an electrode (cathode), they also have a function of reflecting the light emitted from the light emitting layer and increasing the amount of emitted light (light emission luminance). That is, not only the light emitted in the anode direction but also the light emitted in the cathode direction is mirror-reflected on the surface of the metal electrode, which is the cathode, and is extracted as the emitted light from the transparent ITO electrode (anode). The amount of light (emission luminance) can be increased.

  However, since the organic EL element has a mirror surface with a strong light reflectivity, external light is likely to be reflected when light is not emitted. For this reason, in an apparatus using an organic EL element as a light source, for example, an organic EL display device (OLED) or the like, reflection of indoor lighting or the like occurs, it is difficult to express black in a bright place, and the contrast is lowered. There was a problem.

  On the other hand, optical films having various functions are used in apparatuses using organic EL elements as light sources. As an optical film used in an apparatus using an organic EL element as a light source, as described above, since the organic EL element is likely to reflect outside light in a state where it does not emit light, in order to prevent this reflection, polarized light is used. Examples of the retardation film that can be used to form a circularly polarizing plate having antireflection properties by bonding to a child. Examples of the retardation film for exhibiting such antireflection properties include a λ / 4 retardation film whose retardation is about ¼ of the measurement wavelength λ.

  Moreover, as such a retardation film, it is possible to use a cellulose acylate film as described in Patent Document 1, for example.

  As a retardation film, for example, when used for an organic EL display device or the like, unlike an optical pickup device or the like that irradiates only light of a specific wavelength, the phase difference is 1 / wavelength of light over the entire visible light wavelength range. It is required to be about 4. Therefore, the phase difference imparted to the long wavelength light is larger than the phase difference imparted to the short wavelength light. It is required to do. As such a retardation film, for example, a λ / 4 retardation film having an in-plane retardation value Ro (550) at a wavelength of 550 nm of approximately 120 to 160 nm is preferable.

  In addition, the retardation film is required not only to have a phase difference of about ¼ of the wavelength of light in the entire visible light wavelength range, but also to reduce the thickness of the film in order to satisfy the requirements for downsizing the apparatus. Yes.

JP 2008-63531 A

  An object of the present invention is to provide a retardation film having an in-plane retardation value Ro that can realize a λ / 4 retardation film and having sufficiently high transparency. Moreover, it aims at providing the circularly-polarizing plate and image display apparatus provided with the said retardation film.

  One aspect of the present invention is a long retardation film containing a cellulose acylate resin, wherein the cellulose acylate resin satisfies the following formulas (1) and (2): A resin and a second cellulose acylate resin satisfying the following formula (3) and the following formula (4), and the resin constituting the retardation film has a weight average molecular weight of 190,000 to 300,000. And the value obtained by dividing the weight average molecular weight by the number average molecular weight is 2.4 to 3.3, and is the weight average molecular weight of the first cellulose acylate resin and the second cellulose acylate resin. The absolute value of the difference is 50,000 or more and 120,000 or less, and the angle formed by the in-plane slow axis of the retardation film and the width direction of the retardation film is 40 to 50 °. Special It is the phase difference film to be.

2 ≦ X + Y ≦ 3 (1)
0 ≤ Y ≤ 1.5 (2)
2 ≦ X + Y ≦ 2.5 (3)
0 ≤ Y ≤ 1 (4)
Here, in said formula (1)-(4), X shows the substitution degree of the acetyl group of the said cellulose acylate resin, Y shows the substitution degree of acyl groups other than an acetyl group of the said cellulose acylate resin. Indicates.

  Another aspect of the present invention is a circularly polarizing plate provided with the retardation film.

  Another aspect of the present invention is an image display device including the retardation film.

  The objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description and attached 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 a rail pattern of an oblique stretching machine that can be applied to manufacture of a retardation film according to an embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a method for producing a retardation film according to an embodiment of the present invention (an example in which the film is drawn from a long film original fabric roll and then obliquely stretched). FIG. 4 is a schematic view showing a method for producing a retardation film according to an embodiment of the present invention (an example in which a long film original is continuously stretched obliquely without being wound up). FIG. 5 is a schematic diagram showing an example of the configuration of the organic EL display device according to the embodiment of the present invention.

  According to the study by the present inventors, even when a cellulose acylate film as described in Patent Document 1 is stretched, it is thin and has a phase difference of 1 wavelength with respect to light in the entire visible light wavelength range. It was difficult to sufficiently realize the ratio of about / 4. Actually, if it is intended to realize λ / 4 as described above, for example, it may be as thick as 70 μm or more, and in the first place, the in-plane retardation value Ro may not be ensured. There was also a risk of breaking during stretching.

  The present invention has been made in view of such circumstances, and even in a sufficiently thin cellulose acylate film, the in-plane retardation value Ro is a value that can realize a λ / 4 retardation film, An object is to provide a retardation film having sufficiently high transparency. Moreover, it aims at providing the circularly-polarizing plate and image display apparatus provided with the said retardation film.

  Hereinafter, although embodiment of this invention is described, this invention is not limited to these.

<Phase difference film>
The retardation film according to the embodiment of the present invention is a long retardation film containing a cellulose acylate resin. The cellulose acylate resin satisfies the above formula (1) and the above formula (2), and the second cellulose acylate satisfies the above formula (3) and the above formula (4). Resin. The resin constituting the retardation film has a weight average molecular weight of 190,000 to 300,000, and a value obtained by dividing the weight average molecular weight by the number average molecular weight is 2.4 to 3.3. is there. The difference in weight average molecular weight between the first cellulose acylate resin and the second cellulose acylate resin is 50,000 or more and 120,000 or less. Furthermore, the angle which the said retardation film makes with the in-plane slow axis and the width direction of the said retardation film is 40-50 degrees.

  Even if such a retardation film is a sufficiently thin cellulose acylate film, the in-plane retardation value Ro is a value that can realize a λ / 4 retardation film, for example, an in-plane retardation value at a wavelength of 550 nm. Ro (550) is about 120 to 160 nm. Moreover, such a retardation film has sufficiently high transparency. Therefore, even if the cellulose acylate film is sufficiently thin, a λ / 4 retardation film having a retardation of about ¼ of the wavelength with respect to light in a wide range of visible light wavelengths can be obtained. In this specification, “retardation film” refers to a film having a function of converting linearly polarized light having a specific wavelength into circularly polarized light or converting circularly polarized light into linearly polarized light. A “retardation film” refers to a film having an in-plane retardation of the film of about ¼ with respect to a predetermined wavelength of light (usually in the visible light region).

  In addition, the λ / 4 retardation film obtains almost perfect circularly polarized light in the visible light wavelength range, so that the broadband λ / 4 phase difference has a phase difference of approximately ¼ of the wavelength in the visible light wavelength range. A film is preferred. In the present specification, “a phase difference of approximately ¼ in the wavelength range of visible light” means having a reverse wavelength dispersion characteristic in which the phase difference value is larger for longer wavelengths in the wavelength range of 400 to 700 nm. Say.

  In addition, it is generally considered that an optical film such as a retardation film preferably has a smaller variation in resin component, molecular weight, etc. in order to make the properties uniform. In this respect, in order to obtain a retardation film having a retardation of about 1/4 with respect to light in a wide range of visible light wavelengths, it is necessary to impart an appropriate retardation by stretching the resin film. . That is, the in-plane retardation value Ro is preferably a value that can realize a λ / 4 retardation film, for example, the in-plane retardation value Ro (550) at a wavelength of 550 nm is preferably about 120 to 160 nm. For this reason, in the present embodiment, as described above, the cellulose acylate resin includes the first cellulose ester resin and the second cellulose ester resin, and the weight average of the resin constituting the retardation film. When the value obtained by dividing the molecular weight or the weight average molecular weight by the number average molecular weight is in the above range, it is considered that an in-plane retardation value Ro suitable for obtaining a λ / 4 retardation film can be realized. Details will be described later.

  In addition, as described above, the cellulose acylate resin includes the first cellulose acylate resin that satisfies the above formula (1) and the above formula (2), and the first cellulose acylate resin that satisfies the above formula (3) and the above formula (4). 2 cellulose acylate resins. Further, the cellulose acylate resin may contain other resins as long as these two kinds of cellulose acylate resins are contained. In addition, the resin which combined 1st cellulose acylate resin and 2nd cellulose acylate resin satisfy | fills said Formula (1) and said Formula (2). This is clear because the above formulas (3) and (4) are narrower than the above formulas (1) and (2). Moreover, it is preferable that resin which combined 1st cellulose acylate resin and 2nd cellulose acylate resin satisfy | fills following formula (5).

0 ≤ X ≤ 2.5 (5)
Here, in said formula (5), X shows the substitution degree of the acetyl group of the said cellulose acylate resin similarly to said formula (1)-(4).

  The resin constituting the retardation film has a weight average molecular weight of 190,000 to 300,000, preferably 200,000 to 280,000, and 210,000 to 270,000. Is more preferable. If the weight average molecular weight is within such a range, the in-plane retardation value Ro can be made suitable and the breakage can be suppressed by adjusting the following dispersibility value. Therefore, a λ / 4 retardation film is obtained that is sufficiently thin and has a phase difference of about ¼ of the wavelength for light in a wide range of visible light wavelengths.

  In addition, the resin constituting the retardation film has a value obtained by dividing the weight average molecular weight by the number average molecular weight is 2.4 to 3.3, and preferably 2.4 to 2.9. More preferably, it is 5-2.7. The value obtained by dividing the weight average molecular weight by the number average molecular weight indicates dispersibility, which is the spread of the molecular weight distribution of the resin, and the smaller the value, the narrower the molecular weight distribution. For example, if this value is 1, it is monodispersed and has a single molecular weight. If the value indicating such dispersibility is within the above range, the in-plane retardation value Ro can be made suitable, and breakage can be suppressed. This means that if the dispersibility value is as described above, a resin having a relatively low molecular weight and a resin having a relatively high molecular weight are mixed. A resin having a relatively low molecular weight can suppress breakage that may occur due to stretching or the like, but has a tendency to hardly exhibit a phase difference. On the other hand, a resin having a relatively high molecular weight tends to exhibit a phase difference, but tends not to sufficiently suppress breakage that may occur due to stretching or the like. Therefore, the weight average molecular weight is within the above range, the first cellulose acylate resin and the second cellulose acylate resin satisfying the above relationship are included, and the value indicating dispersibility is as described above. By setting the value, it is considered that the in-plane retardation value Ro can be made suitable and the breakage can be suppressed. Therefore, even if it is a sufficiently thin cellulose acylate film, the in-plane retardation value Ro is a value that can realize a λ / 4 retardation film, for example, the in-plane retardation value Ro (550) at a wavelength of 550 nm is 120. A retardation film of about ~ 160 nm is obtained. That is, even if the cellulose acylate film is sufficiently thin, a λ / 4 retardation film having a retardation of about ¼ of the wavelength with respect to light in a wide range of visible light wavelengths can be obtained.

  The retardation film has a weight average molecular weight difference Δa between the first cellulose acylate resin and the second cellulose acylate resin of 50,000 to 120,000, and 70,000 to 120, 000 is preferable, and 90,000 to 115,000 is more preferable. If Δa is within the above range, a resin having a relatively low molecular weight and a resin having a relatively high molecular weight are mixed. From this, as described above, the in-plane retardation value Ro is a value that can realize a λ / 4 retardation film, for example, the in-plane retardation value Ro (550) at a wavelength of 550 nm is about 120 to 160 nm. A retardation film is obtained.

  Further, the retardation film preferably has an angle θ formed by the in-plane slow axis and the width direction thereof, that is, an orientation angle θ of 40 ° or more and 50 ° or less, and 41 ° or more and 48 °. More preferably, it is 43 degrees or more and 47 degrees or less. When the orientation angle θ is in the above range, the film is unwound from the roll body and has a retardation film having a slow axis in an oblique direction with respect to the longitudinal direction, and the transmission film unwound from the roll body and parallel to the longitudinal direction. A circularly polarizing plate can be easily produced by laminating a polarizer film having an axis with a roll-to-roll so that the longitudinal directions thereof are overlapped with each other. Thereby, there is little cut loss of a film and it is advantageous on production.

  In addition, the retardation film satisfies the above formula (1) and the above formula (2), and the second cellulose acylate resin satisfies the above formula (3) and the above formula (4). The resin film is unwound from a raw film made of a roll of a long resin film containing a core member rolled into a core member, and the resin film is obtained by stretching the unwound resin film. Is preferred. When the retardation film is obtained by such off-line stretching, the dried resin film can be appropriately stretched. Therefore, the in-plane retardation value Ro is suitable as a value for realizing a λ / 4 retardation film, and a retardation film having a small thickness can be obtained. Such stretching is preferably oblique stretching. By doing so, a retardation film having an orientation angle θ within the above range can be easily obtained.

  The retardation film preferably has an in-plane retardation value Ro (550) at a wavelength of 550 nm of 120 to 160 nm, and preferably 130 to 150 nm. When Ro (550) is within the above range, λ / 4 can be suitably realized.

  The retardation film preferably has an in-plane retardation value of 130 to 150 nm at a wavelength of 550 nm of the retardation film, and a thickness of the retardation film of 20 to 60 μm. When the thickness of the retardation film is large, the in-plane retardation value can be easily obtained, but if the retardation film according to the present embodiment, the retardation film can be thinned, and an apparatus for applying it, For example, a retardation film capable of realizing λ / 4 with the above-described thickness that can contribute to downsizing of the image display device can be obtained. Further, the thinner the retardation film, the better, but it is considered that the limit is substantially about 20 μm. From this, the suitable range of the thickness of a retardation film is 20-60 micrometers.

  The retardation film preferably has a thickness direction retardation value Rth (550) at a wavelength of 550 nm of 50 nm to 250 nm.

  The retardation film has an in-plane retardation value Ro (450) at a wavelength of 450 nm, an in-plane retardation value Ro (550) at a wavelength of 550 nm, and an in-plane retardation value Ro (650) at a wavelength of 650 nm. It is preferable that the following formula (i) and the following formula (ii) are satisfied.

0.72 ≦ Ro (450) / Ro (550) ≦ 0.93 (i)
0.83 ≦ Ro (550) / Ro (650) ≦ 0.97 (ii)
When Ro (450), Ro (550), and Ro (650) are within the above ranges, a phase difference of λ / 4 can be imparted to light in a wider wavelength region. Therefore, it can function more preferably as a λ / 4 retardation film. In addition, when this retardation film is applied to an image display device such as an organic EL display device, light leakage or the like when displaying black can be reduced. Specifically, when the above formula (1) is satisfied, blue reproducibility is high. Further, when the above formula (2) is satisfied, red reproducibility is high.

  In the retardation film, Ro (450) / Ro (550) is preferably 0.72 or more and 0.93 or less, and preferably 0.79 or more and 0.89 or less, as described above. More preferably, it is 0.81 or more and 0.87 or less. Further, Ro (550) / Ro (650) is preferably 0.83 or more and 0.97 or less, more preferably 0.84 or more and 0.93 or less, as described above, and 0.85. More preferably, it is 0.93 or less.

  Ro (λ) is the in-plane retardation value Ro at a wavelength λ under the condition of 23 ° C. and 55% RH, and Rth (λ) is the wavelength λ under the condition of 23 ° C. and 55% RH. The thickness direction retardation value Rth. For example, Ro (550) is an in-plane retardation value Ro at a wavelength of 550 nm under the condition of 23 ° C. and 55% RH.

  Moreover, Ro and Rth in an optical film (retardation film) are respectively defined by the following formulas.

Formula 1: Ro = (nx−ny) × d (nm)
Formula 2: Rth = {(nx + ny) / 2−nz} × d (nm)
(In formulas 1 and 2, nx represents the refractive index in the slow axis direction x where the refractive index is maximum in the in-plane direction of the optical film, and ny is the slow axis direction in the in-plane direction of the optical film. (The refractive index in the direction y orthogonal to x is represented, nz represents the refractive index in the thickness direction z of an optical film, and d (nm) represents the thickness of an optical film.)

  Ro and Rth can be measured using an automatic birefringence meter. Examples of the automatic birefringence system include AxoScan manufactured by Axometrics, KOBRA-21ADH manufactured by Oji Scientific Instruments, and the like. Specifically, it can be measured by the following method.

  1) Condition the optical film (retardation film) at 23 ° C. and 55% RH. The average refractive index of the optical film after humidity adjustment at 450 nm, 550 nm, and 650 nm is measured using an Abbe refractometer and a spectral light source. Moreover, the thickness of an optical film is measured using a film thickness meter.

  2) In-plane phase difference Ro (450), Ro (550) or light when light having a measurement wavelength of 450 nm, 550 nm, or 650 nm is incident on the optical film after humidity adjustment in parallel with the normal line of the film surface Ro (650) is measured with an AxoScan manufactured by Axometrics.

  3) Using AxoScan made by Axometrics, the wavelength measured from the angle of φ (incident angle (φ)) with respect to the normal to the surface of the optical film with the slow axis in the plane of the optical film as the tilt axis (rotation axis) The phase difference R (φ) when light of 450 nm, 550 nm, or 650 nm is incident is measured. The phase difference R (φ) can be measured at 6 points every 10 ° within a range of φ from 0 ° to 50 °. The in-plane slow axis of the optical film can be confirmed with AxoScan manufactured by Axometrics.

4) From R ₀ and R (φ) measured at each wavelength (λ) and the above-described average refractive index and film thickness, nx, ny and nz are calculated by AxoScan manufactured by Axometrics. Then, based on the above formula, thickness direction retardations Rth (450), Rth (550) or Rth (650) at the measurement wavelengths of 450 nm, 550 nm or 650 nm are respectively calculated.

  Furthermore, Ro (450) / Ro (550) can be calculated from the obtained Ro (450) and Ro (550). Then, Ro (550) / Ro (650) can be calculated from the obtained Ro (550) and Ro (650).

  Next, the components of the retardation film according to this embodiment will be described.

  The resin constituting the retardation film may contain other resins as long as the first cellulose acylate resin and the second cellulose acylate resin satisfying the above relationship are included. . The other resin may be a cellulose acylate resin or a resin other than the cellulose acylate resin.

(Cellulose acylate resin)
Moreover, the cellulose acylate resin used in the present embodiment is not particularly limited as long as it satisfies the above-described relationship. Cellulose acylate resin is a compound obtained by esterifying cellulose and carboxylic acid. That is, the cellulose acylate resin is a compound obtained by dehydrating and condensing a cellulose hydroxyl group and a carboxyl group of a carboxylic acid to form an acyl group. Moreover, although carboxylic acid is not specifically limited, C2-C22 aliphatic carboxylic acid, C2-C22 aromatic carboxylic acid, etc. are mentioned. Among these, lower fatty acids having 6 or less carbon atoms are preferable. Moreover, although carboxylic acid may be used independently, you may use it in combination of 2 or more type.

  The acyl group of the cellulose acylate resin is not particularly limited, and may be linear or branched. Moreover, the acyl group may have a cyclic structure and may have other substituents. When the total acyl substitution degree of the cellulose acylate resin is constant, the birefringence tends to decrease as the carbon number of the acyl group increases. For this reason, it is preferable that it is 2-6 from viewpoints of transparency etc., as for carbon number of an acyl group, it is more preferable that it is 2-4, and it is further more preferable that it is 2-3. Specific examples of the acyl group include an acetyl group, a propionyl group, a butanoyl group, a heptanoyl group, a hexanoyl group, an octanoyl group, a decanoyl group, a dodecanoyl group, a tridecanoyl group, a tetradecanoyl group, a hexadecanoyl group, an octadecanoyl group, and an octadecanoyl group. Examples include decanoyl group, isobutanoyl group, tert-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, and cinnamoyl group.

  Specific examples of the cellulose acylate resin include mixed fatty acid esters such as cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate propionate butyrate, and cellulose acetate phthalate in addition to cellulose acetate such as triacetyl cellulose. Etc. Among these, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and the like are preferable. The butyryl group that can be contained in the cellulose acylate resin may be linear or branched.

  The substitution degree of the acyl group of the cellulose acylate resin preferably satisfies the above relationship. In addition, the substitution degree of the acyl group of the cellulose acylate resin can be measured by a method specified in ASTM-D817-96.

The number average molecular weight (Mn) of the cellulose acylate resin is preferably in the range of 6 × 10 ^{4 to} 3 × 10 ⁵ from the viewpoint of increasing the mechanical strength of the obtained film, and is preferably 7 × 10 ⁴ to 7 × 10 ⁴ . A range of 2 × 10 ⁵ is more preferable.

  The molecular weight such as weight average molecular weight (Mw) and number average molecular weight (Mn) of the cellulose acylate resin is measured using gel permeation chromatography (GPC). The measurement conditions are as follows.

Solvent: methylene chloride;
Column: Three Shodex K806, K805, K803G (made by Showa Denko KK) are connected and used;
Column temperature: 25 ° C .;
Sample concentration: 0.1% by mass;
Detector: RI Model 504 (manufactured by GL Sciences);
Pump: L6000 (manufactured by Hitachi, Ltd.);
Flow rate: 1 ml / min Calibration curve: Standard polystyrene STK standard Polystyrene (manufactured by Tosoh Corporation), a calibration curve with 13 samples in the range of Mw = 100000 to 500 is used. Thirteen samples are used at approximately equal intervals.

  Moreover, it is preferable that content of the residual sulfuric acid in the said cellulose acylate resin is the range of 0.1-45 mass ppm in conversion of a sulfur element, and the range of 1-30 mass ppm is more preferable. Sulfuric acid is considered to remain in the film in a salt state. If the content of residual sulfuric acid exceeds 45 ppm by mass, the film tends to break when it is hot-stretched or when it is cut (slit) after heat-stretching. The residual sulfuric acid content can be measured by a method prescribed in ASTM D817-96.

  The content of the free acid in the cellulose acylate resin is preferably 1 to 500 ppm by mass, more preferably 1 to 100 ppm by mass, and further preferably 1 to 70 ppm by mass. When the content of the free acid is in the above range, it is difficult to break when the film is hot stretched or slitted after the hot stretch, as described above. The content of free acid can be measured by the method prescribed in ASTM D817-96.

  The cellulose acylate resin may contain a trace amount of a metal component. It is considered that the trace amount of the metal component is derived from water used in the cellulose acylate resin synthesis process. Like these metal components, the content of components that can become insoluble nuclei is preferably as small as possible. In particular, metal ions such as iron, calcium, and magnesium may form a salt with a resin decomposition product or the like that may contain an organic acidic group to form an insoluble material. In addition, the calcium (Ca) component easily forms a coordination compound (that is, a complex) with an acidic component such as a carboxylic acid or a sulfonic acid, and many ligands. Insoluble starch, turbidity) may be formed.

  Specifically, the content of the iron (Fe) component in the cellulose acylate resin is preferably 1 mass ppm or less. Moreover, content of the calcium (Ca) component in cellulose acylate resin becomes like this. Preferably it is 60 mass ppm or less, More preferably, it is 0-30 mass ppm. The content of the magnesium (Mg) component in the cellulose acylate resin is preferably 0 to 70 ppm by mass, and particularly preferably 0 to 20 ppm by mass.

  The content of metal components such as iron (Fe) component, calcium (Ca) component, and magnesium (Mg) component is the same as that obtained by subjecting an absolutely dry cellulose acylate resin to microdigest wet decomposition equipment (sulfuric acid decomposition) and alkali melting. After processing, it can be measured using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer).

  The content of residual alkaline earth metal, residual sulfuric acid and residual acid can be adjusted by thoroughly washing the cellulose acylate resin obtained by synthesis.

  The manufacturing method of a cellulose acylate resin will not be specifically limited if a cellulose acylate resin can be manufactured, A well-known manufacturing method is mentioned. Specifically, if an example is given, it can be synthesized with reference to the method described in JP-A-10-45804. Moreover, the cellulose as a raw material of the cellulose acylate resin is not particularly limited, and may be cotton linter, wood pulp, kenaf, and the like. As the cellulose acylate resin, a cellulose acylate resin produced from a single raw material may be used, or two or more cellulose acylate resins of different raw materials may be used in combination.

  Further, as described above, the retardation film may contain a resin other than the cellulose acylate resin. For example, a thermoplastic resin may be contained. The term “thermoplastic resin” as used in the present specification refers to a resin that has the characteristics that it softens when heated to the glass transition temperature or melting point and can be molded into the desired shape.

  Examples of the thermoplastic resin include polyethylene (PE), high density polyethylene, medium density polyethylene, low density polyethylene, polypropylene (PP), polyvinyl chloride (PVC), polyvinylidene chloride, polystyrene (PS), polyvinyl acetate ( PVAc), polytetrafluoroethylene (PTFE), acrylonitrile butadiene styrene resin (ABS resin), AS resin, acrylic resin (PMMA), and the like can be used. When strength and resistance to breakage are particularly required, for example, polyamide (PA), polyacetal (POM), polycarbonate (PC), modified polyphenylene ether (m-PPE, modified PPE, PPO), polybutylene 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, for example, polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polysulfone, polyethersulfone, amorphous polyarylate, liquid crystal A polymer, polyether ether ketone, thermoplastic polyimide (PI), polyamideimide (PAI), or the like can be used. These can be used in combination with types and molecular weights depending on the application.

(Optical performance modifier)
The retardation film preferably contains a compound represented by the following general formula (A) as an optical performance modifier.

一般式（Ａ）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 general formula (A), L ₁ and L ₂ are each independently a single bond or a divalent linking group, R ₁ , R ₂ and R ₃ each independently represent a substituent, and n is from 0 to 2 And Wa and Wb each represent a hydrogen atom or a substituent, and (I) Wa and Wb may be bonded to each other to form a ring. (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 a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl group (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 preferred from the viewpoint that the main chain of the compound of the general formula (A) can be oriented in the slow axis direction of the λ / 4 retardation film to increase the slow axis direction refractive index nx.

  Wa and Wb include halogen atoms (for example, fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl groups (for example, 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, 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-pyrimidinyl group, 2-benzothi Zolyl 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-methoxyethoxy group, etc.) An aryloxy group (for example, phenoxy group, 2-methylphenoxy group, 4-tert-butylphenoxy group, 3-nitrophenoxy group, 2-tetradecanoylaminophenoxy group), acyloxy group (for example, formyloxy group, Acetyloxy group, pivaloyloxy group, stearoyloxy group, benzoyloxy group, p-methoxyphenylcarbonyloxy group, etc.), amino group (for example, amino group, methylamino group, dimethylamino group, anilino group, N-methyl-anilino group) , Diphenylamino group, etc.), acylami Groups (for example, formylamino group, acetylamino group, pivaloylamino group, lauroylamino group, benzoylamino group, etc.), alkyl and arylsulfonylamino groups (for example, methylsulfonylamino group, butylsulfonylamino group, phenylsulfonylamino group, 2 , 3,5-trichlorophenylsulfonylamino group, p-methylphenylsulfonylamino group, etc.), mercapto group, alkylthio group (eg, methylthio group, ethylthio group, n-hexadecylthio group, etc.), arylthio group (eg, phenylthio group, p-chlorophenylthio group, m-methoxyphenylthio group, etc.), sulfamoyl group (for example, 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. can be mentioned.

  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.

式中、Ｒ_４、Ｒ_５、Ｒ_６はそれぞれ水素原子または置換基を表し、置換基としては、上記Ｒ_１、Ｒ_２およびＲ_３で表される置換基の具体例と同様の基を挙げることができる。

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

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

式中、Ａ_１およびＡ_２は各々独立に、Ｏ、Ｓ、ＮＲ_Ｘ（Ｒ_Ｘは水素原子または置換基を表す）またはＣＯを表す。Ｒ_Ｘで表される置換基の例は、上記ＷａおよびＷｂで表される置換基の具体例と同義である。Ｘは第３周期以降で第１４〜１６族の非金属原子、または、第３周期以降で第１４〜１６族の非金属原子または共役系を含む置換基である。Ｘとしては、Ｏ、Ｓ、ＮＲｃ、Ｃ（Ｒｄ）Ｒｅが好ましい。ここでＲｃ、Ｒｄ、Ｒｅは置換基を表し、たとえば、上記ＷａおよびＷｂで表される置換基の具体例と同義である。Ｌ_１、Ｌ_２、Ｒ_１、Ｒ_２、Ｒ_３、ｎは、一般式（Ａ）におけるＬ_１、Ｌ_２、Ｒ_１、Ｒ_２、Ｒ_３、ｎと同義である。

In the formula, each of A ₁ and A ₂ independently represents O, S, NR _X (R _X represents a hydrogen atom or a substituent) or CO. Examples of the substituent represented by R _X has the same meaning as specific examples of substituents represented by the Wa and Wb. X is a non-metallic atom of Group 14 to 16 after the third period, or a substituent containing a non-metallic atom of Group 14 to 16 or a conjugated system after the third period. X is preferably O, S, NRc, or C (Rd) Re. Here, Rc, Rd, and Re represent substituents, and are synonymous with specific examples of the substituents represented by Wa and Wb, for example. _{L 1, L 2, R 1} , R _{2, R} 3, n is _{L 1, L 2, R 1} , same meanings as R _{2, R} 3, n in the general formula (A).

  Specific examples of the compound represented by the general formula (A) are shown below, but the compound represented by the general formula (A) that can be used in the present embodiment is limited by the following specific examples. There is no.

  In addition, the synthesis | combination of the compound represented by general formula (A) will not be specifically limited if said compound can be synthesize | combined, It can carry out by applying a known synthesis method. For example, refer to the methods described in Journal of Chemical Crystallography ((1997); 27 (9); 512-526), JP 2010-31223 A, and JP 2008-107767 A, for example. And can be synthesized.

(Other additives)
The retardation film according to this embodiment can contain various additives in addition to the resin component and the optical performance modifier. For example, a solvent can be used to prepare a cellulose acylate solution or dope by dissolving a cellulose acylate resin. Examples of the solvent include a solvent that can dissolve the cellulose acylate resin. Specific examples include organic solvents such as chlorinated organic solvents and non-chlorinated organic solvents.

  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, nitroethane, and the like. From the viewpoint of recent environmental problems, non-chlorine organic solvents are preferably used.

  When these organic solvents are used for cellulose acylate resin, the insoluble matter is reduced by a known dissolution method such as a dissolution method at normal temperature, a high-temperature dissolution method, a cooling dissolution method, and a high-pressure dissolution method. It is preferable. For the cellulose acylate resin, 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 in the cellulose acylate resin is referred to as a good solvent, and has a main effect on dissolution, and an organic solvent used in a large amount among them is mainly (organic). Solvent or main (organic) solvent.

  The dope used for forming the retardation film according to 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 facilitates peeling from the body, and when the proportion of these alcohols is low, it also has a role of promoting dissolution of the cellulose acylate resin of 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 resin alone.

  The concentration of cellulose acylate 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 the additive that can be added to the dope include a plasticizer, an ultraviolet absorber, an antioxidant, a deterioration inhibitor, a peeling aid, a surfactant, a dye, 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.

  In the retardation film according to this embodiment, various plasticizers can be used in combination as an additive for the purpose of improving the fluidity and flexibility of the composition. Examples of plasticizers include phthalate plasticizers, fatty acid ester plasticizers, trimellitic ester plasticizers, phosphate ester plasticizers, polyester plasticizers, sugar ester plasticizers, and epoxy plasticizers. And polyhydric alcohol ester plasticizers. It can be applied to a wide range of uses by selecting or using these plasticizers according to the use.

  Although there is no limitation in particular as an additive, For example, the compound which has an aromatic terminal ester type compound and a triazine ring is preferable. The aromatic terminal ester compound may be either an oligoester type or a polyester type, and the molecular weight is preferably in the range of 100 to 10,000, and preferably in the range of 350 to 3000. An acid value of 1.5 mgKOH / g or less and a hydroxyl value of 25 mgKOH / g or less can be used, more preferably an acid value of 0.5 mgKOH / g or less and a hydroxyl value of 15 mgKOH / g or less. can do.

  Moreover, it is preferable to add 0.5-30 mass parts with respect to 100 mass parts of (lambda) / 4 phase difference films, and add 2.0-15 mass parts of aromatic compounds which have at least 3 aromatic rings. Is more preferable.

  Although an example of the various additives applicable to this embodiment is given below, it is not limited to these.

  The polyhydric alcohol ester preferably used in this embodiment is composed of an ester of a divalent or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule.

  The polyhydric alcohol used in the present embodiment is represented by the following general formula (a).

R _1- (OH) _n (a)
In the general formula (a), R ₁ represents an n-valent organic group, and n represents an integer of 2 or more. The OH group represents an alcoholic or phenolic hydroxy group (hydroxyl group).

  Examples of preferred polyhydric alcohols include, for example, adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol Galactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like. Of these, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  The monocarboxylic acid used in the polyhydric alcohol ester is not particularly limited, and known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, and the like can be used.

  By using an alicyclic monocarboxylic acid or an aromatic monocarboxylic acid for the retardation film according to this embodiment, moisture permeability and retentivity can be improved. Preferred examples of the monocarboxylic acid include the following, but are not limited to these in the present embodiment.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. As carbon number, it is more preferable that it is 1-20, and it is further more preferable that it is C1-C10. Moreover, since compatibility with cellulose acylate can be improved by using acetic acid, it is preferable to use a mixture of acetic acid and another monocarboxylic acid.

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

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

  Preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and aromatics having two or more benzene rings such as biphenylcarboxylic acid, naphthalenecarboxylic acid, and tetralincarboxylic acid. Group monocarboxylic acids, or derivatives thereof. Among these, benzoic acid is particularly preferable.

  Although it does not specifically limit as molecular weight of a polyhydric alcohol ester, It is preferable that it is the range of molecular weight 300-1500, and it is more preferable that it is the range of 350-750. It is preferable that the molecular weight is large to some extent because volatilization is difficult. From the viewpoint of moisture permeability and compatibility with the cellulose acylate resin, a certain small amount is preferable. From these points, the molecular weight is preferably within the above range.

  The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  Although the specific compound of a polyhydric alcohol ester is shown below, the polyhydric alcohol ester which can be used in this embodiment is not limited to these at all.

  In the present embodiment, the compound having a triazine ring is preferably a discotic compound from the viewpoint of developing retardation in a λ / 4 retardation film and reducing water content, and has a molecular weight of 300 to 2,000. It is preferable that In the present embodiment, the boiling point of the discotic compound is preferably 260 ° C. or higher. The boiling point can be measured using a commercially available measuring device (for example, TG / DTA100, manufactured by Seiko Electronics Industry Co., Ltd.).

  Specific examples of the compound having a triazine ring that can be suitably used in the present embodiment are shown below, but the compound having a triazine ring that can be used in the present embodiment is not limited to these.

  The protective film used in the retardation film according to the present embodiment or the circularly polarizing plate described later preferably contains an ultraviolet absorber.

  Examples of the ultraviolet absorber include a benzotriazole ultraviolet absorber, a 2-hydroxybenzophenone ultraviolet absorber, and a salicylic acid phenyl ester ultraviolet absorber. 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 include benzophenones such as -4-methoxybenzophenone.

  In addition, since the ultraviolet absorber with a molecular weight of 400 or more hardly volatilizes at a high boiling point and hardly disperses even at high temperature molding, the 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- ( 1,1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] and the like, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, Hindered amines such as bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and further 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butyl Bis (1,2,2,6,6-pentamethyl-4-piperidyl) malonate, 1- [2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionylo Xyl] ethyl] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine The hybrid type | system | group which has the structure of a hindered amine is mentioned, These can be used individually or in combination of 2 or more types. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3-tetrabutyl) ) -6- (2H-benzotriazol-2-yl) phenol] is preferred. Commercially available products may be used, and 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.

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

  For the retardation film according to the present embodiment, 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.

  Further, the retardation film according to the present embodiment has, for example, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, and hydrated calcium silicate in order to improve handling properties. 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.

(width)
As the retardation film according to this embodiment, a film having a width in the range of 1 to 4 m can be used. Those having a width of 1.4 to 4 m are preferably used, and those having a width of 1.6 to 3 m are preferably used. If the width is 4 m or less, the conveyance stability can be ensured.

(Surface roughness)
The arithmetic average roughness of the retardation film surface according to this embodiment is about 2 to 4 nm, preferably 2.5 to 3.5 nm.

(Dimensional change rate)
When the retardation film according to the present embodiment is applied to, for example, an organic EL display, due to dimensional changes due to moisture absorption under an environmental atmosphere (for example, a high humidity environment), unevenness, change in retardation value, and contrast In order not to cause problems such as reduction 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 according to this embodiment, it is preferable that there are few failures in the film (hereinafter also referred to as defects). 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.

  When the number of defects is greater than 1/10 cm square, for example, when the film is tensioned during processing in a subsequent process, the film may be broken starting from the defects to reduce productivity. 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 according to the present embodiment has a breaking elongation of 10% or more in at least one direction (width direction (TD direction) or conveyance direction (MD direction)) in the measurement based on JIS-K7127-1999. It is preferable that it is 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 according to 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 (λ / 4 retardation film) will be described.

  The retardation film according to this 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 according to this embodiment can be produced by a solution casting method. In the solution casting method, a step of preparing a dope by heating and dissolving cellulose acylate resin and additives in an organic solvent, a step of casting the prepared dope on a belt-shaped or drum-shaped metal support, casting A step of drying the 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.

(Dope preparation process)
In the dope preparation process, the cellulose acylate resin in the dope preferably has a higher concentration because the drying load after casting on the metal support can be reduced, but if the concentration of the cellulose acylate resin is too high, The load increases and the filtration accuracy deteriorates. Therefore, as a density | concentration which makes these compatible, the inside of the range of 10-35 mass% is preferable, and the inside of the range of 15-25 mass% is more preferable.

(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 the 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 a range of 0 to 100 ° C. A temperature range of 5 to 30 ° C. is more preferable. 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 λ / 4 retardation film to exhibit good flatness, the amount of residual solvent when peeling the web from the metal support is preferably set within the range of 10 to 150% by mass, and more preferably 20 It is in the range of -40 mass% or 60-130 mass%, More preferably, it exists in the range of 20-30 mass% or 70-120 mass%.

  In the present specification, the amount of residual solvent is defined by the following formula.

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

(Drying process)
In the drying step, the web is peeled off from the metal support and further dried, and the residual solvent amount is preferably 1.0% by mass or less, and 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 the web is dried while being conveyed by a tenter method is employed.

(Stretching process)
As described above, the λ / 4 retardation film of this embodiment preferably has an in-plane retardation Ro550 measured at a wavelength of 550 nm of 115 to 160 nm, and such retardation is imparted by stretching the film. obtain.

  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.

  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 numeral 112, is the major axis M ₁ in the conveying direction, contracts in M ₂ by oblique bending. At this time, the shrinkage rate (%) is
Shrinkage rate (%) = (M ₁ −M ₂ ) / M ₁ × 100
It is represented by If the bending angle is θ,
M ₂ = M ₁ × sin (π−θ)
And the shrinkage rate is
Shrinkage rate (%) = (1-sin (π−θ)) × 100
It is represented by

  In FIG. 1, reference numeral 111 is a stretching direction (TD direction), reference numeral 113 is a transport direction (MD direction), and reference numeral 114 indicates a slow axis.

  Considering the productivity of the long circularly polarizing plate, the λ / 4 retardation film according to this embodiment has an orientation angle of 45 ° ± 2 ° with respect to the transport direction. Bonding with can be performed, which 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 λ / 4 retardation film according to this embodiment, it is preferable to use an oblique stretching apparatus as a method for imparting an oblique orientation to the 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 view showing an example of a rail pattern of an oblique stretching apparatus applicable to the manufacture of the λ / 4 retardation film according to the present embodiment. In addition, the figure shown here is an example, Comprising: The extending | stretching apparatus applicable by this embodiment is not limited to this.

  In general, in the oblique stretching apparatus, as shown in FIG. 2, the feeding direction D1 of the long film original is different from the winding direction D2 of the stretched film after stretching, and forms a feeding angle θi. doing. The feeding angle θi can be arbitrarily set to a desired angle in the range of more than 0 ° and less than 90 °. In the present specification, the term “long” refers to a film having a length of at least about 5 times the width of the film, preferably a film having a length of 10 times or more.

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

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

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

  According to the above method, the original film is stretched obliquely so that the orientation angle is θL, and a retardation film is obtained. Here, “substantially vertical” indicates that the angle is in a range of 90 ± 1 °.

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

  This stretching apparatus is an apparatus that heats a film raw fabric to an arbitrary temperature at which stretching can be performed and obliquely stretches 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 device has an asymmetric shape on the left and right, and the rail pattern can be adjusted manually or automatically depending on the orientation angle, stretch ratio, etc. given to the long stretched film to be manufactured. It has become. In the oblique stretching apparatus used in the present embodiment, it is preferable that the position of each rail portion and the rail connecting portion can be freely set, and the rail pattern can be arbitrarily changed (the ○ portion in FIG. 2 indicates an example of the connecting portion). )

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

  In the stretching apparatus of this embodiment, a large bending rate is often required for the rail that regulates the trajectory of the gripping tool, particularly where the film is transported obliquely. In order to avoid interference between gripping tools due to sudden bending or local stress concentration, it is preferable that the trajectory of the gripping tool draws a curve at the bent portion.

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

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

  The stretching zone refers to a section where the gap between the gripping tools gripping both ends starts to reach a predetermined distance. In the stretching zone, the oblique stretching as described above is performed, but the stretching may be performed in the longitudinal direction or the transverse direction before and after the oblique stretching as necessary. In the case of oblique stretching, there is contraction in the MD direction (fast axis direction) which is a direction perpendicular to the slow axis during bending.

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

  The heat setting zone refers to a section in which the gripping tools at both ends run in parallel with each other in a period in which the interval between the gripping tools after the stretching zone becomes constant again. You may pass through the area (cooling zone) by which the temperature in a zone is set to below the glass transition temperature Tg of the thermoplastic resin which comprises a film, after passing through a heat setting zone. At this time, in consideration of shrinkage of the film due to cooling, a rail pattern that narrows the gap between the opposing grippers in advance may be used.

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

  In order to control the thickness unevenness in the width direction, a temperature difference may be given in the width direction in the stretching zone. In order to create a temperature difference in the width direction in the stretching zone, a method of adjusting the opening degree of the nozzle for sending warm air into the temperature-controlled room so as to make a difference in the width direction, or controlling the heating by arranging the heaters in the width direction is known. Can be used.

  The length of the preheating zone, the stretching zone, the shrinking zone and the cooling zone can be appropriately selected. The length of the preheating zone is usually within a range of 100 to 150% with respect to the length of the stretching zone, and the length of the fixed zone. Is usually in the range of 50 to 100%.

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

  As an oblique stretching method applicable in the present embodiment, in addition to the method shown in FIG. 2, the stretching methods shown in (a) to (c) of FIG. 3 and (a) and (b) of FIG. Can be mentioned.

  FIG. 3 is a schematic view showing a method for producing a retardation film according to an embodiment of the present invention (an example in which the film is drawn from a long film roll and then obliquely stretched), and is a length once wound into a roll shape. The pattern which draws out the original film and draws it diagonally is shown. FIG. 4 is a schematic diagram illustrating a method for producing a retardation film according to an embodiment of the present invention (an example in which a long film original is continuously stretched obliquely without winding up). The pattern which performs a diagonal stretch process continuously, without winding up is shown.

  3 and 4, reference numeral 15 is an oblique stretching apparatus, reference numeral 16 is a film feeding apparatus, reference numeral 17 is a conveying direction changing apparatus, reference numeral 18 is a winding apparatus, and reference numeral 19 is a film forming apparatus. Yes. In each figure, reference numerals indicating the same components may be omitted.

  The film feeding device 16 is slidable and swivelable or slidable so that the film can be sent out at a predetermined angle with respect to the oblique stretching device inlet. It is preferable to be able to send 3A to 3C show patterns in which the arrangement of the film feeding device 16 and the conveyance direction changing device 17 is changed. FIGS. 4A and 4B show a pattern in which the film formed by the film forming apparatus 19 is directly fed to a stretching apparatus. By adopting such a configuration for the film feeding device 16 and the transport direction changing device 17, the width of the entire manufacturing apparatus can be further reduced, and the film feeding position and angle can be finely controlled. Thus, it becomes possible to obtain a long stretched film with small variations in film thickness and optical value. Further, by making the film feeding device 16 and the transport direction changing device 17 movable, it is possible to effectively prevent the left and right clips from being caught in the film.

  The winding device 18 is arranged so that the film can be pulled at a predetermined angle with respect to the outlet of the oblique stretching device, so that it is possible to finely control the film take-up position and angle, and there are variations in film thickness and optical value. A small elongated stretched film can be obtained. Therefore, the generation of wrinkles in the film can be effectively prevented, and the winding property of the film is improved, so that the film can be wound up in a long length. In this embodiment, the take-up tension T (N / m) of the stretched film can be adjusted within a range of 100 N / m <T <300 N / m, preferably 150 N / m <T <250 N / m. preferable.

(Melting method)
The above-mentioned λ / 4 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 and pelletized in advance. 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 preferably has a method of suppressing the shearing force and processing at the lowest possible temperature so that the resin can be pelletized so that the resin does not deteriorate (molecular weight reduction, coloring, gel formation, etc.). For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

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

  The pellets are extruded using a single-screw or twin-screw type extruder, and the melting temperature during extrusion is within 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 performed stably by introducing a gear pump or the like. Further, a stainless fiber sintered filter is preferably used as a filter used for removing foreign substances. A stainless steel fiber sintered filter is a product in which stainless steel fiber bodies are intricately intertwined and compressed, and the contact points are sintered and integrated. The density is changed according to the thickness of the fiber and the amount of compression, and filtration is performed. The accuracy can be adjusted.

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

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

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

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

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

  The above-mentioned λ / 4 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 in-plane slow axis of the λ / 4 retardation film and the transmission axis of the polarizer is preferably in the range of 41 to 49 °, and in the range of 42 to 48 °. Is more preferable, it is still more preferable to be in the range of 43 to 47 °, and it is particularly preferable to be in the range of 44 to 46 °.

<Circularly polarizing plate>
The circularly polarizing plate (long circular polarizing plate) according to this embodiment is a long roll having a long protective film, a long polarizer and a long λ / 4 retardation film in this order. It is made by cutting. Since the elongate circularly polarizing plate according to the present embodiment is produced using the above-described λ / 4 retardation film, it can be applied to a wide range of visible light wavelengths by applying it to an organic EL display device described later. An effect of shielding the specular reflection of the metal electrode of the EL element can be exhibited. As a result, reflection during observation can be prevented and black expression can be improved.

  The long 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 λ / 4 retardation film on the light emitter side also has an ultraviolet absorbing function, when used in an organic EL display described later, deterioration of the organic EL element can be further suppressed.

  Further, the long circularly polarizing plate according to the present embodiment has the λ / 4 phase difference adjusted so that the angle of the slow axis (that is, the orientation angle θ) is “substantially 45 °” with respect to the longitudinal direction. By using a film, it is possible to form an adhesive layer and bond the polarizing film and the λ / 4 retardation film plate with a consistent production line. Specifically, after finishing the step of producing the polarizing film by stretching, the step of bonding the polarizing film and the λ / 4 retardation film can be incorporated during or after the subsequent drying step, Each 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 after bonding. In addition, when bonding a polarizing film and (lambda) / 4 phase difference 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 a λ / 4 retardation film and a protective film to the polarizing film. That is, after finishing the step of producing the polarizing film by stretching, after the subsequent drying step or after the drying step, the protective film and the λ / 4 retardation film are bonded to both sides with an adhesive, It is also possible to obtain a rolled circularly polarizing plate.

  In the long circularly polarizing plate according to this embodiment, the polarizer is preferably sandwiched between the λ / 4 retardation film and the protective film, and a cured layer is preferably laminated on the viewing side of the protective film. .

<Organic EL display>
An image display device according to the present embodiment, for example, an organic EL display device (organic EL image display device) is manufactured using the long circularly polarizing plate. More specifically, the organic EL display device according to this embodiment includes a long circular polarizing plate using the λ / 4 retardation film and an organic EL element. The screen size of the organic EL display is not particularly limited, and can be 20 inches or more.

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

  As shown in FIG. 5, a metal electrode 2, TFT 3, organic light emitting layer 4, transparent electrode (ITO etc.) 5, insulating layer 6, sealing layer 7, film on a transparent substrate 1 made of glass, polyimide or the like. On the organic EL element B having 8 (can be omitted), the above-described long circularly polarizing plate C having the polarizer 10 sandwiched between the above-described λ / 4 retardation film 9 and the protective film 11 is provided, and an organic EL display device A is configured. The protective film 11 is preferably laminated with a cured layer 12. The hardened layer 12 not only prevents scratches on the surface of the organic EL display device but also has an effect of preventing warpage due to the long circularly polarizing plate. Further, an antireflection layer 13 may be provided on the cured layer. The thickness of the organic EL element itself is about 1 μm.

  In general, in an organic EL display device, a metal electrode, an organic light emitting layer, and a transparent electrode are sequentially laminated on a transparent substrate to form an element (organic EL element) that is a light emitter. Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, 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 device, holes and electrons are injected into an organic light emitting layer by applying a voltage to a transparent electrode and a metal electrode, and 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 device, in order to take out light emitted from the organic light emitting layer, at least one of the electrodes needs to be transparent, and is usually a transparent electrode formed of a transparent conductor such as indium tin oxide (ITO). Is preferably used as the anode. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

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

  In an organic EL display device 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 of the transparent electrode (visible) A polarizing plate can be provided on the side), and a retardation plate can be provided 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 function. 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 device is transmitted only by the linearly polarized light component by the polarizing plate, and this linearly polarized light is generally elliptically polarized light by the phase difference plate. In particular, the retardation film has a λ / 4 phase difference. When the angle between the polarization direction of the polarizing plate and the retardation film is π / 4, the film is circularly polarized.

  This circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, is again transmitted through the organic thin film, the transparent electrode, and the 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.

  As described above, the present specification discloses various modes of technology, of which the main technologies are summarized below.

  One aspect of the present invention is a long retardation film containing a cellulose acylate resin, wherein the cellulose acylate resin satisfies the following formulas (1) and (2): A resin and a second cellulose acylate resin satisfying the following formula (3) and the following formula (4), and the resin constituting the retardation film has a weight average molecular weight of 190,000 to 300,000. And the value obtained by dividing the weight average molecular weight by the number average molecular weight is 2.4 to 3.3, and is the weight average molecular weight of the first cellulose acylate resin and the second cellulose acylate resin. The absolute value of the difference is 50,000 or more and 120,000 or less, and the angle formed by the in-plane slow axis of the retardation film and the width direction of the retardation film is 40 to 50 °. Special It is the phase difference film to be.

2 ≦ X + Y ≦ 3 (1)
0 ≤ Y ≤ 1.5 (2)
2 ≦ X + Y ≦ 2.5 (3)
0 ≤ Y ≤ 1 (4)
Here, in said formula (1)-(4), X shows the substitution degree of the acetyl group of the said cellulose acylate resin, Y shows the substitution degree of acyl groups other than an acetyl group of the said cellulose acylate resin. Indicates.

  According to such a configuration, even with a sufficiently thin cellulose acylate film, the in-plane retardation value Ro is a value that can realize a λ / 4 retardation film, and the retardation is sufficiently high. A film can be provided.

  In addition, the retardation film satisfies the above formula (1) and the above formula (2), and the second cellulose acylate resin satisfies the above formula (3) and the above formula (4). The resin film is unwound from a raw film made of a roll of a long resin film containing a core member rolled into a core member, and the resin film is obtained by stretching the unwound resin film. Is preferred.

  According to such a configuration, the in-plane retardation value Ro is suitable as a value for realizing a λ / 4 retardation film, and a thin retardation film can be obtained.

  In the retardation film, the stretching is preferably oblique stretching.

  According to such a configuration, the in-plane retardation value Ro is suitable as a value for realizing a λ / 4 retardation film, and a thin retardation film can be obtained.

  In the retardation film, it is preferable that an in-plane retardation value of the retardation film at a wavelength of 550 nm is 130 to 150 nm, and a thickness of the retardation film is 20 to 60 μm.

  According to such a configuration, the in-plane retardation value Ro is suitable as a value for realizing a λ / 4 retardation film, and a thin retardation film can be obtained.

  Another aspect of the present invention is a circularly polarizing plate provided with the retardation film.

  According to such a configuration, it is possible to obtain a circularly polarizing plate that is sufficiently thin and can sufficiently exhibit the antireflection ability.

  Another aspect of the present invention is an image display device including the retardation film.

  According to such a configuration, it is possible to obtain an image display device capable of displaying a good image in which external light reflection or the like is sufficiently suppressed.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the examples, “parts” or “%” represents “parts by mass” or “% by mass” unless otherwise specified.

[Cellulose acylate resin]
First, the resin (cellulose acylate resin) used in this example will be described.

  Examples of the cellulose acylate resin include triacetyl cellulose (TAC), cellulose acetate propionate (CAP), and diacetyl having the acyl group substitution degree and molecular weight (number average molecular weight Mn and weight average molecular weight Mw) shown in Table 1. Cellulose (DAC) was used.

[Example 1]
(Preparation of fine particle additive solution)
The fine particle additive solution added to the dope will be described.

  First, 11 parts by mass of fine particles (Aerosil R812 manufactured by Nippon Aerosil Co., Ltd.) and 89 parts by mass of ethanol were stirred and mixed with a dissolver for 50 minutes, and then dispersed using a Manton Gorin disperser to prepare a fine particle dispersion.

  Then, 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, dispersion was performed with an attritor so that the volume average particle diameter was 0.1 μm. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.

(Preparation of dope)
First, methylene chloride and ethanol as organic solvents were added to the pressurized dissolution tank in the amounts shown below. Cellulose acylate resin 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, the compound a having the following structure as the compound represented by the general formula (A), the sugar ester compound (benzyl saccharose having an average substitution degree of 7.3) and the fine particle addition liquid prepared above are mainly dissolved in the following ratios: After putting in a kettle, sealing, and dissolving with stirring, a dope solution was prepared.

<Dope composition>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass TAC1 100 parts by mass CAP2 100 parts by mass Optical performance modifier (compound of general formula (A): Compound a) 3 parts by mass Sugar ester compound (benzyl saccharose having an average substitution degree of 7.3) 5 parts by mass Particulate additive solution 2 parts by mass Compound of general formula (A): Compound a

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

  The peeled film is uniaxially stretched at a stretch ratio of 1% only in the width direction (TD direction) using a stretching apparatus while being heated at 180 ° C., and transport tension so as not to shrink in the transport direction (MD direction). Adjusted. The residual solvent at the start of stretching was 15% by mass.

  Next, drying was completed while the drying zone was conveyed through a number of rollers. The drying temperature was 130 ° C. and the transport tension was 100 N / m. As described above, a resin film original fabric in which a resin film having a dry film thickness of 33 μm was wound into a roll was produced.

(Stretching process)
The resin film is unwound from the resin film original, and the resin film is stretched at a stretching temperature of Tg + 20 ° C., a stretching ratio of 2.0 times, and a bending angle using an oblique stretching apparatus having the configuration shown in FIG. (Drawing angle) θi was 49 °, shrinkage (MD direction) was 25%, and the orientation angle was 45 °. That is, oblique stretching was performed offline. By doing so, a λ / 4 retardation film was produced.

[Examples 2 and 4, Comparative Examples 1 to 6]
A retardation film was produced in the same manner as in Example 1 except that the cellulose acylate resin used was changed to that shown in Table 2.

[Example 3]
As the stretching step, a retardation film is produced in the same manner as in Example 1 except that the stretching step is performed as it is without winding the resin film after film formation, instead of the above-described offline stretching. did. That is, a retardation film was produced in the same manner as in Example 1 except that oblique stretching was performed off-line. By doing so, a retardation film was produced.

  In addition, Table 2 below shows the conditions for producing the retardation film according to each example and comparative example.

<Measurement of each characteristic value of film>
(Phase difference value)
About the retardation film produced in the said Examples 1-4 and Comparative Examples 1-6, the phase difference of the in-plane direction in the wavelength of 550 nm is used in 23 degreeC and 55% RH environment using Axoscan by Axometrcs. The value (retardation) Ro (550) was measured. Moreover, when it fractures | ruptures at the time of extending | stretching, it shows as "-" in the following Table 3 as measurement impossible.

(Orientation angle)
The orientation angle (the angle formed by the in-plane slow axis and the width direction) was also measured using an Axoscan manufactured by Axometers. Moreover, when it fractures | ruptures at the time of extending | stretching, it shows as "-" in the following Table 3 as measurement impossible.

(Film thickness)
The film thickness was measured using a photoelectric digital length measuring system (manufactured by Nikon Corporation, MH-15M, counter TC-101, MS-5C).

  When the measured film thickness was 20 μm or more and less than 60 μm, it was evaluated as “◯”, when it was 60 μm or more and less than 70 μm, it was evaluated as “Δ”, and when it was 70 μm or more, it was evaluated as “x”. Moreover, when it fractures | ruptures at the time of extending | stretching, it shows as "-" in the following Table 3 as evaluation impossible.

(Haze)
The haze was measured using a haze meter (NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd.).

  When the measured haze was less than 1, it was evaluated as “◯”, and when it was 1 or more, it was evaluated as “x”. Moreover, when it fractures | ruptures at the time of extending | stretching, it shows as "-" in the following Table 3 as evaluation impossible.

(Possibility of stretching)
When the film was stretched under the above stretching conditions, it was evaluated as “◯” if it did not break, and “x” if it broke.

(Display characteristics)
Display characteristics were evaluated using an organic EL display device using the retardation films prepared in Examples 1 to 4 and Comparative Examples 1 to 6 as follows.

<Production of long circularly polarizing plate>
A 120 μm-thick polyvinyl alcohol film was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a polarizer.

  Subsequently, each said retardation film was bonded on the single side | surface of the said polarizer by making complete saponification type polyvinyl alcohol 5% aqueous solution into an adhesive. In that case, it bonded so that the transmission axis of a polarizer and the slow axis of retardation film might be set to 45 degrees. A protective film to be described later was bonded to the other surface of the polarizer by alkali saponification treatment. By doing so, the elongate circularly-polarizing plate provided with each retardation film was produced, respectively.

<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. The ester compound was obtained by making it dehydrate-condense for 15 hours, and distilling unreacted 1, 2- propylene glycol under reduced pressure at 200 degreeC after completion | finish of reaction. The acid value was 0.10 mg KOH / g, and the number average molecular weight was 450.

(Preparation of fine particle additive solution)
First, 11 parts by mass of fine particles (Aerosil R972V manufactured by Nippon Aerosil Co., Ltd.) and 89 parts by mass of ethanol were stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin. By doing so, a fine particle dispersion was prepared.

  Next, the fine particle dispersion was slowly added to the dissolution tank containing methylene chloride with sufficient stirring. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. The obtained liquid was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. By doing so, the fine particle addition liquid was prepared.

(Preparation of dope)
90 parts by mass of cellulose acetate (acetyl group substitution degree 2.88), 10 parts by mass of the ester compound, 2.5 parts by mass of Tinuvin 928 (manufactured by BASF Japan Ltd.), 4 parts by mass of the fine particle addition liquid, 432 parts by mass of methylene chloride Part and 38 parts by mass of ethanol were put into a sealed container, heated and dissolved while stirring, and Azumi filter paper No. manufactured by Azumi Filter Paper Co., Ltd. 24 was filtered. By doing so, a dope solution was prepared.

(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. The peeled film web was evaporated at 35 ° C, the solvent was evaporated, slit to a width of 1.65m, and 30% in the TD direction (the width direction of the film) with a stretching device while applying heat at 160 ° C. 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 of the protective film was measured using KOBRA-21ADH manufactured by Oji Scientific Instruments Co., Ltd. As a result, it was in the range of 90 ° ± 1 ° with respect to the film longitudinal direction.

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

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

(Evaluation of visibility: black display)
A black image is displayed on the organic EL display device and the screen (image display area) is viewed from the front under an environmental condition in which the fluorescent lamp is uniformly irradiated so that the illuminance at a position 5 cm higher than the outermost surface of the organic EL display device is 1000 Lx. saw. At that time, the following criteria were evaluated.

  If the screen looks black and a color other than black cannot be confirmed, evaluate as “○”, and if the color other than black can be confirmed slightly, evaluate as “△” and the color other than black can be clearly confirmed Was evaluated as “×”.

  The evaluation results are shown in Table 3 above.

  As can be seen from Table 3, the first cellulose acylate resin and the second cellulose acylate resin, which contain two types of cellulose acylate resins, satisfy the above formulas (1) to (4), and constitute the retardation film. The resin obtained by mixing 2 cellulose acylate resins has a weight average molecular weight of 190,000 to 300,000, and a value obtained by dividing the weight average molecular weight by the number average molecular weight is 2.4 to 3.3. The absolute value of the difference in weight average molecular weight between the first cellulose acylate resin and the second cellulose acylate resin is 50,000 or more and 120,000 or less, and the orientation angle is 40-50. When it is ° (Examples 1 to 4), compared with Comparative Examples 1 to 6, the in-plane retardation value Ro is a value that can realize a λ / 4 retardation film, Highly transparent retardation film Rum was obtained. Moreover, in the organic EL display device using the retardation films according to Examples 1 to 4, the image display is better than when the retardation films according to Comparative Examples 1 to 6 are used.

  According to the present invention, even if it is a sufficiently thin cellulose acylate film, the in-plane retardation value Ro is a value capable of realizing a λ / 4 retardation film, and a retardation film having sufficiently high transparency is obtained. Provided. Moreover, the circularly-polarizing plate and image display apparatus provided with the said retardation film are provided.

Claims (6)

A long retardation film containing a cellulose acylate resin,
A first cellulose acylate resin satisfying the following formula (1) and the following formula (2); a second cellulose acylate resin satisfying the following formula (3) and the following formula (4): Including
The resin constituting the retardation film has a weight average molecular weight of 190,000 to 300,000, and a value obtained by dividing the weight average molecular weight by the number average molecular weight is 2.4 to 3.3.
The absolute value of the difference in weight average molecular weight between the first cellulose acylate resin and the second cellulose acylate resin is 50,000 or more and 120,000 or less,
An angle formed by an in-plane slow axis of the retardation film and a width direction of the retardation film is 40 to 50 °.
2 ≦ X + Y ≦ 3 (1)
0 ≤ Y ≤ 1.5 (2)
2 ≦ X + Y ≦ 2.5 (3)
0 ≤ Y ≤ 1 (4)
[In the above formulas (1) to (4), X represents the substitution degree of the acetyl group of the cellulose acylate resin, and Y represents the substitution degree of an acyl group other than the acetyl group of the cellulose acylate resin. . ]   A first cellulose acylate resin that satisfies the above formula (1) and the above formula (2) and a second cellulose acylate resin that satisfies the above formula (3) and the above formula (4). 2. The resin film obtained by unwinding the resin film and stretching the unwound resin film from a raw resin film obtained by rolling a long resin film including the core resin member into a roll shape. The retardation film described in 1.   The retardation film according to claim 2, wherein the stretching is oblique stretching. The retardation film has an in-plane retardation value at a wavelength of 550 nm of 130 to 150 nm,
The thickness of the said retardation film is 20-60 micrometers, The retardation film of any one of Claims 1-3.   A circularly-polarizing plate provided with the phase difference film of any one of Claims 1-4.   An image display apparatus provided with the retardation film of any one of Claims 1-4.

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