JP6048349B2 - Method for producing retardation film - Google Patents

Description

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

  In recent years, the diversification of display devices (displays) has progressed, and the demand for optical films constituting the display has also diversified. For example, when the optical film is used for a 3D display, a touch panel, a flexible display, or an organic EL display, it is required to be thinner and have durability.

  As an optical film for improving the visibility of a display, a λ / 4 retardation film has attracted attention. The λ / 4 retardation film has a phase difference of ¼ of the wavelength (λ) in the wide wavelength range of the visible light range, that is, has reverse wavelength dispersion characteristics. Such a λ / 4 retardation film can be made into a polarizing plate, thereby preventing, for example, reflection of external light in an organic EL display and improving bright place contrast and black reproducibility.

  Patent Document 1 discloses a λ / 4 retardation plate produced by laminating films in order to achieve both the retardation development property and the reverse wavelength dispersion characteristic in a wide band. However, such a λ / 4 retardation plate is a thick film and has a problem that it is difficult to adjust the axis. Therefore, in recent years, there has been proposed a λ / 4 retardation film that uses an additive and has a chromatic dispersion characteristic of a single layer and reverse wavelength dispersion (Patent Document 2).

JP-A-10-68816 JP 2012-103651 A

  When the λ / 4 retardation film containing the additive described in Patent Document 2 is used for, for example, a flexible display, it has been found that the display quality regarding color reproducibility deteriorates due to long-term use.

  By the way, in order to produce a single-layer and thin-film λ / 4 retardation film, it is necessary to stretch the original film after the film formation in an oblique direction. Diagonal stretching is high-temperature and high-magnification stretching, and is usually performed using a film raw film that has been wound up and dried after film formation. Therefore, the load applied to the film at the time of stretching becomes larger than the case of stretching the raw film of the film in which the organic solvent is highly dissolved without being wound up after film formation, for example. It was found that the retardation film produced by applying a load during such stretching is likely to deteriorate the display quality during long-term use as described above. Further, it has been found that such deterioration of display quality during long-term use occurs regardless of whether it is good or bad even when the optical properties of the retardation film after production are observed.

  The present invention has been made in view of the above-described conventional problems. In a method for producing a retardation film that unwinds an original film wound after film formation and performs oblique stretching, the display is less likely to deteriorate display quality. Providing a method for producing a retardation film capable of producing the same, providing a circularly polarizing plate using the retardation film, and using the retardation film and the circularly polarizing plate, bending resistance, black reproduction An object of the present invention is to provide an organic EL display having good properties and reflection performance.

  As a result, the present inventors controlled the amount of change in internal haze before and after stretching when producing a retardation film by unwinding the film original film wound up after film formation and performing oblique stretching. The present invention was completed by paying attention to the point that deterioration of the display quality can be suppressed.

That is, the method for producing a retardation film according to one aspect of the present invention includes a step of unwinding a film original film wound after film formation and stretching in an oblique direction, and in the step of stretching in the oblique direction, The change in internal haze before and after stretching is 0.07% or less per 40 μm film thickness, the slow axis with respect to the longitudinal direction of the obtained retardation film is 10 ° or more and 80 ° or less, and the in-plane retardation at a wavelength of 550 nm. The original film is made so that Ro ₅₅₀ is 100 nm or more and 160 nm or less, and the ratio of in-plane retardation Ro ₄₅₀ at a wavelength of 450 nm to Ro ₅₅₀ (Ro ₄₅₀ / Ro ₅₅₀ ) is 0.8 or more and less than 1.0. It is characterized by stretching.

  According to the method for producing a retardation film of the present invention, in a display produced using the obtained retardation film, display quality deterioration is suppressed. Further, according to the method for producing a retardation film of the present invention, the obtained retardation film has excellent reverse wavelength dispersion characteristics and substantially exhibits a retardation of λ / 4 in a wide band. Therefore, it is used for an organic EL display, for example. It can use suitably for the circularly-polarizing plate obtained.

  The said structure WHEREIN: The said phase difference film is favorably provided with a reverse wavelength dispersion characteristic by including the compound which has a negative intrinsic birefringence.

（一般式（１）において、Ａ_１およびＡ_２は、各々アルキル基、シクロアルキル基、芳香族炭化水素環または芳香族複素環を表し、Ｌ_１、Ｌ_２、Ｌ_３およびＬ_４は、各々単結合または２価の連結基を表し、Ｗ_１およびＷ_２は、各々芳香族複素環または脂肪族複素環を表し、Ｂは、芳香族炭化水素環、脂肪族炭化水素環、芳香族複素環または脂肪族複素環を表す。ｎは、０〜５の整数を表す。ｎが２以上のとき、複数のＬ_３、Ｌ_４およびＷ_２は同じであっても異なっていてもよい） The said structure WHEREIN: The said retardation film has the advantage that the humidity fluctuation | variation of retardation can be suppressed by including the compound represented by the following General formula (1).

(In General Formula (1), A ₁ and A ₂ each represent an alkyl group, a cycloalkyl group, an aromatic hydrocarbon ring or an aromatic heterocyclic ring, and L ₁ , L ₂ , L ₃ and L ₄ are each Represents a single bond or a divalent linking group, W ₁ and W ₂ each represent an aromatic heterocycle or an aliphatic heterocycle, and B represents an aromatic hydrocarbon ring, an aliphatic hydrocarbon ring, an aromatic heterocycle Or n represents an integer of 0 to 5. When n is 2 or more, a plurality of L ₃ , L ₄ and W ₂ may be the same or different.

  The said structure WHEREIN: The said retardation film is easy to show favorable retardation expression by containing a cellulose-ester resin composition.

  The said structure WHEREIN: The said retardation film is easy to show favorable retardation expression by containing a cellulose ether resin composition.

The said structure WHEREIN: In the process extended | stretched in the said diagonal direction, it is preferable to have the process of satisfy | filling at least any two conditions among the following conditions AC.
Condition A: The traveling speed of the gripping tool that grips both ends of the film during oblique stretching is 0.1 to 2 m / min. Condition B: The stretching temperature is 30 ° C. to 60 ° C. higher than the Tg of the retardation film. A certain condition C: the cooling temperature after stretching is Tg to Tg-30 ° C. of the retardation film.

Thus, a change in the internal haze, the slow _axis, a phase difference film is easily obtained which satisfies a range of _{Ro 550} and _Ro 450 _{/ Ro 550.} Therefore, in the display produced using the obtained retardation film, deterioration of display quality is satisfactorily suppressed.

  In addition, a retardation film according to one aspect of the present invention is produced by the above-described retardation film manufacturing method, has excellent reverse wavelength dispersion characteristics, and substantially exhibits a retardation of λ / 4 in a wide band. Therefore, such a retardation film can be suitably used for a circularly polarizing plate used for an organic EL display, for example. Moreover, in the display produced using such a retardation film, deterioration of display quality is suppressed.

  In addition, since the circularly polarizing plate according to one aspect of the present invention has the retardation film and the polarizer, the deterioration of display quality is suppressed, and the organic EL display has excellent bending resistance, black reproducibility, and reflection performance. Can be used.

  Furthermore, since the organic EL display according to one aspect of the present invention uses the retardation film or the circularly polarizing plate, deterioration of display quality is suppressed, and bending resistance, black reproducibility, and reflection performance are excellent.

  According to the present invention, there is provided a method for producing a retardation film capable of producing a display in which display quality is hardly deteriorated in a method for producing a retardation film by unwinding an original film wound after film formation and performing oblique stretching. Providing a circularly polarizing plate using the retardation film, and providing an organic EL display having good bending resistance, black reproducibility and reflection performance using the retardation film and circularly polarizing plate can do.

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

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

<Method for producing retardation film>
The method for producing a retardation film of the present embodiment includes a step (an oblique stretching step) of unwinding a film original film wound after film formation and stretching it in an oblique direction. That is, in the present embodiment, the oblique stretching process is not performed continuously with the film forming process (film forming process), but is wound once without being stretched after the film forming process, or the film is formed. After the process, for example, the original film that has been stretched by about 0.5 to 50% and then wound up is unwound again and subjected to an oblique stretching process. Further, the oblique stretching may be stretched at a high temperature and high magnification as compared with the case of normal transverse stretching or longitudinal stretching. For this reason, when such stretching is performed, the load applied to the film during stretching tends to be larger than in the case of stretching a film raw material in which an organic solvent is highly dissolved without being wound after film formation. The method for producing a retardation film of the present embodiment provides a retardation film that can produce a display that is unlikely to deteriorate in display quality even when such oblique stretching is performed. Hereinafter, the diagonal stretch process which is a characteristic part among the manufacturing methods of the retardation film of this embodiment is demonstrated in detail.

  In the present specification, the “retardation film” means an optical film having a specific optical function for imparting a retardation to the transmitted light, and substantially with respect to a predetermined wavelength of light. In particular, a film having a function of giving an in-plane retardation of ¼ wavelength and converting linearly polarized light into circularly polarized light or converting circularly polarized light into linearly polarized light is particularly “λ / 4 retardation film”. That's it. The λ / 4 retardation film is a broadband λ having a phase difference of approximately ¼ of the wavelength in the visible light wavelength range in order to convert linearly polarized light into almost perfect circularly polarized light in a wide range of visible light wavelengths. A / 4 retardation film is preferable. In the present specification, “a phase difference of approximately ¼ in the wavelength range of visible light” means having an inverse wavelength dispersion characteristic in which the phase difference value increases in the longer wavelength range in the wavelength range of 400 nm to 700 nm. Say.

(Oblique stretching process)
The oblique stretching step is a step of stretching the formed film (film original fabric) in a direction oblique to the width direction. In the method for producing a retardation film of the present embodiment, the original film is slanted so that the change in the internal haze of the original film before and after stretching is 0.07% or less, preferably 0.03% or less per 40 μm film thickness. Stretch. Even if the optical properties of the manufactured optical film, which is considered to be directly related to the display quality, are controlled to a certain value, the deterioration of the display quality at the time of long-term use is not sufficiently improved and has not been paid attention in the past. It is based on the new knowledge of the present inventors that the deterioration of the display quality is improved as a result only by controlling the change of the internal haze in the stretching process.

  In the present specification, “per film thickness of 40 μm” means that 40 μm is adopted as the unit film thickness. That is, for example, when the film thickness of the original film before stretching is 80 μm, the value obtained by multiplying the measured value by 0.5 is adopted as the internal haze value per 40 μm of the original film. .

  The internal haze can be measured, for example, by the method described in JP2009-286931A. Under the present circumstances, it can measure according to JIS-K7136, using NDH2000 by Nippon Denshoku Industries Co., Ltd. as a measuring instrument with one film.

Moreover, in the manufacturing method of the retardation film of this embodiment, the slow axis with respect to the longitudinal direction of the obtained retardation film is 10 ° or more and 80 ° or less, and the in-plane retardation Ro _{550 at} a wavelength of 550 nm is 100 nm or more and 160 nm. The raw film is obliquely stretched so that the ratio of the in-plane retardation Ro ₄₅₀ at a wavelength of 450 nm to Ro ₅₅₀ (Ro ₄₅₀ / Ro ₅₅₀ ) is 0.8 or more and less than 1.0.

  In addition, in this specification, the angle with respect to the width direction of a film is an angle in a film plane. The slow axis in the film plane usually appears in the stretching direction or in a direction perpendicular to the stretching direction. Therefore, in the method for producing a retardation film of the present embodiment, a retardation film having such a slow axis is produced by stretching at an angle of 10 ° to 80 ° with respect to the stretching direction of the film. .

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

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

Ro ₅₅₀ may be 100 nm or more and 160 nm or less, and preferably 120 nm or more and 150 nm or less. When Ro ₅₅₀ exceeds the range of 100 nm or more and 160 nm or less, the phase difference at a wavelength of 550 nm does not become a quarter wavelength, and a circularly polarizing plate is produced using such a film and applied to, for example, an organic EL display In addition, the reflection of indoor lighting becomes large, and black may not be expressed in a bright place.

The ratio of _{Ro 450} for _{Ro 550 (Ro 450 / Ro 550} ) may be less than 0.8 or more 1.0, preferably 0.81 or more 0.92 or less. When Ro ₄₅₀ / Ro ₅₅₀ exceeds the range of 0.8 or more and less than 1.0, the obtained retardation film does not exhibit an appropriate reverse wavelength dispersion characteristic. For example, when a circularly polarizing plate is produced, hue change or humidity environment Tends to cause hue fluctuations.

In general, the in-plane retardation (for example, Ro ₅₅₀ ) can be increased by increasing the film thickness d of the film. However, when the film thickness is increased, there is a problem that the thickness of an image display device such as an organic EL display is increased, or the transmittance is lowered to reduce the light extraction efficiency. However, according to the method for producing a retardation film of the present embodiment, even when the film thickness is reduced as will be described later by appropriately adjusting the resin composition and the additive, excellent retardation expression is achieved. A retardation film is prepared.

The retardation film satisfying the range of change in internal haze, slow axis, Ro ₅₅₀ and Ro ₄₅₀ / Ro ₅₅₀ includes, for example, predetermined constituents (resin composition and additive) based on predetermined stretching conditions. It can be obtained by obliquely stretching the original film. Hereinafter, stretching conditions and components for obtaining a retardation film satisfying the ranges of the change in internal haze, the slow axis, Ro ₅₅₀ and Ro ₄₅₀ / Ro ₅₅₀ will be described.

[About stretching conditions]
The retardation film satisfying the ranges of the change in internal haze, slow axis, Ro ₅₅₀ and Ro ₄₅₀ / Ro ₅₅₀ is, for example, a temperature during oblique stretching when the original film is obliquely stretched using an oblique stretching apparatus. The film can be produced by adjusting stretching conditions such as (stretching temperature), total stretching ratio, traveling speed of a gripping tool that grips and conveys both ends of the original film, and cooling conditions for the film after stretching. In the manufacturing method of this embodiment, it is preferable to have the process of satisfy | filling at least any two conditions among the following conditions AC. By satisfying at least two of the conditions A to C, it is easy to obtain a retardation film satisfying the range of the change in internal haze, the slow axis, Ro _550, and Ro ₄₅₀ / Ro ₅₅₀ .
Condition A: The traveling speed of the gripping tool that grips both ends of the film during oblique stretching is 0.1 to 2 m / min. Condition B: The stretching temperature is 30 ° C. to 60 ° C. higher than the Tg of the retardation film. A certain condition C: the cooling temperature after stretching is Tg to Tg-30 ° C. of the retardation film.

(Condition A: Traveling speed of gripping tool)
The traveling speed of the gripping tool is preferably 0.1 m / min or more and 2.0 m / min or less, and more preferably 0.1 m / min or more and 1 m / min or less. By making the traveling speed of the gripping tool in such a range, the original film before stretching is easily heated to the stretching temperature, and even when stretched to have the total stretching ratio, Crystallization of the resin composition constituting the film is prevented, and changes in the internal haze of the film before and after stretching are easily suppressed.

(Condition B: Stretching temperature)
The stretching temperature can be adjusted by providing a heating device (not shown) for heating the conveyed film original in the oblique stretching device. By this heating device, the unrolled film original is heated to such an extent that it can be stretched obliquely. At this time, the film original is preferably heated to a temperature range 30 ° C. to 60 ° C. higher than the Tg of the retardation film (substantially the Tg of the resin composition constituting the film original). More preferably, the film is heated to a temperature range 35 ° C. to 55 ° C. higher than the Tg of the film.

(Condition C: Condition for cooling the stretched film)
A heat setting zone (including a cooling zone) can be provided on the downstream side in the conveying direction of the oblique stretching apparatus. By this heat setting zone, the retardation film stretched obliquely can be cooled immediately after stretching. It does not specifically limit as cooling temperature, For example, it can be Tg-Tg-30 degreeC of a retardation film, Preferably it is Tg-5 degreeC-Tg-30 degreeC, More preferably, it can be Tg-10 degreeC-Tg-25 degreeC. .

(About total draw ratio)
In the present embodiment, the total draw ratio is defined as follows. That is, the retardation film in the present embodiment is produced by a stretching process including oblique stretching after forming a film original and winding it, and then winding it again. In that case, let A be an arbitrary unit length in the width direction of the original film before stretching. The unit length is stretched to a length of A × α in the direction of the slow axis in the retardation film after the oblique stretching process by the stretching process in the film forming process of the film original film and the film forming process of the retardation film. The total draw ratio is expressed as α times. For example, when the unit length in the width direction of the original film before stretching is 10 cm, the slow axis direction of the obliquely stretched film is obtained by the stretching process in the film forming process of the film original film and the film forming process of the retardation film. When the film is stretched to 15 cm, the total stretch ratio is 1.5 times. In the production process of the original film, when the stretching process is not performed, the total stretching ratio is equal to the stretching ratio in the slow axis direction of the retardation film with respect to the width direction of the unrolled film. In the production method of the present embodiment, the film is preferably stretched so that the total stretching ratio is 1.5 times or more and 3.0 times or less, and may be stretched so that it is 1.7 times or more and 2.5 times or less. More preferred.

Method for producing a retardation film of the present embodiment, by adopting the above stretching conditions, to produce a retardation film which satisfies a range of the change in the internal haze, the slow axis, Ro ₅₅₀ and Ro _{450 /} Ro ₅₅₀ be able to. The retardation film after stretching is wound around a winding core after cooling.

  In addition, the other conditions of the diagonal stretch process in the manufacturing method of the phase difference film of this embodiment, and another process (for example, film forming process) are not specifically limited. Hereinafter, the other conditions of the oblique stretching process and the film forming process which is another process will be described.

(Other conditions for oblique stretching process)
In this embodiment, the film raw material wound up through the film forming process mentioned later is unwound, and it uses for the diagonal stretch process. The stretching method in the oblique stretching process is not particularly limited. For example, a method in which a circumferential speed difference is applied to a plurality of rollers, and a longitudinal stretching is performed using 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 the clips and pins in the advancing direction and extending in the vertical direction, a method of extending the image in the horizontal direction and extending in the horizontal direction, or a method of extending both the vertical and horizontal directions and extending in both the vertical and horizontal directions, alone or in combination. Can be adopted. That is, the film may be stretched in the transverse direction, longitudinally, or in both directions with respect to the film forming direction, and when stretched in both directions, simultaneous stretching or sequential stretching may be used. May be. In the case of the so-called tenter method, driving the clip portion by the linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

  Next, a specific method for producing a retardation film will be described with reference to the drawings. In the following example, a case where a cellulose ester resin composition is included as a resin composition will be described as an example.

  The retardation film is stretched in the slow axis direction and then stretched and contracted in the fast axis direction, and then the ratio of the shrinkage ratio in the fast axis direction to the stretch ratio in the slow axis direction (shrinkage ratio / stretching). The film can be produced by stretching under the condition that the magnification is in the range of 0.05 to 0.70, preferably 0.10 to 0.30.

  By setting the shrinkage ratio / stretch ratio in the range of 0.05 or more and 0.70 or less, a desired retardation value is expressed using the resin composition described later, and the slope of chromatic dispersion in the visible light region is made steep. And the axial direction can be 10 ° to 80 °.

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

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

FIG. 1 is a schematic diagram for explaining the shrinkage ratio in oblique stretching. In Figure 1, when obliquely stretching the film F in the direction of the reference numerals A2, the film F is shrink M ₂ by being obliquely bent. That is, when the gripping tool that grips the film F proceeds as it is without bending at the bending angle θ, it proceeds by the length M ₁ ′ in a predetermined time. However, in reality, it bends at a bending angle θ and proceeds by M ₁ (where M ₁ = M ₁ ′). At this time, since the gripping tool advances by M ₂ in the film entering direction (direction orthogonal to the stretching direction (TD direction) A1), the film F has a length M ₃ (where M ₃ = M ₁ −M ₂ ).

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

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

  In consideration of the productivity of the circularly polarizing plate, the retardation film of the present embodiment has an orientation angle of 45 ° ± 2 ° with respect to the transport direction, and can be bonded with a polarizing film in a roll-to-roll manner. It is preferable.

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

  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 an oblique stretching apparatus in which the film feeding direction and the film take-up direction applicable to the production of the retardation film of the present embodiment are the same. In addition, the figure shown here is an example, Comprising: The extending | stretching apparatus applicable by this embodiment is not limited to this. 2 (a) and 2 (b), reference numeral 12-2 is a guide roll (on the tenter outlet side), reference numeral 13 is a film stretching direction, reference numeral 14-1 is a film feeding direction, Reference numeral 14-2 indicates the direction in which the film is stretched, and reference numeral 15 indicates a portion where the conveyance speeds of the left and right grippers are different.

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

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

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

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

  FIG. 2B is a schematic view of an oblique stretching apparatus of a system in which a film feeding direction and a film drawing direction applicable to the present embodiment match.

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

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

  In addition, although the extending | stretching apparatus shown by FIG.2 (b) has a location where the distance between left-right rails widens, it does not necessarily need to have a location where the distance between left-right rails widens. Further, in this specification, the pair of left and right grippers traveling at different speeds means that the difference between the travel speeds of the pair of left and right grippers substantially exceeds 1% of the travel speed. That is, the difference between the traveling speeds of the pair of left and right gripping tools is usually 1% or less, preferably 0.5% or less, more preferably 0.1% or less of the traveling speed. This is because if there is a difference in the traveling speed between the left and right sides of the film at the exit of the stretching process, wrinkles and shifts will occur at the exit of the stretching process, so the speed difference between the right and left gripping tools is required to be substantially the same speed. Because.

  The difference in travel speed between the pair of left and right gripping tools is preferably more than 1% of the travel speed and 50% or less, more preferably more than 1% of the travel speed and 30% or less, and more than 1% of the travel speed. 10% or less is more preferable. In general stretching devices, etc., there are speed irregularities that occur in the order of seconds or less depending on the period of the sprocket teeth driving the chain, the frequency of the drive motor, etc. Does not correspond to the speed difference in this embodiment.

  Moreover, in the extending | stretching apparatus shown by Fig.2 (a) and FIG.2 (b), if it has a mechanism in which the traveling speed of a holding | gripping tool changes on the way, a well-known thing can be used.

  As one aspect of the method for producing a retardation film of the present embodiment, the film feeding direction and the film drawing direction in the stretching step are obliquely crossed, and the film drawing direction is 10 ° or more and 80 °. Manufacture under conditions that provide a slow axis within the following angle range.

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

  As shown in FIG. 3, the original film 4 whose direction is controlled by the guide roll 12-1 on the entrance side of the stretching apparatus includes an outer film holding start point 8-1 and an inner film holding start point 8-2. It is gripped by the gripper in position.

  The pair of left and right grippers are transported and stretched at an equal speed with each other in the oblique direction indicated by the outer film gripper track 7-1 and the inner film gripper track 7-2 by the oblique stretching device 6. The gripping is released by the film gripping end point 9-1 and the inner film gripping end point 9-2, and the conveyance is controlled by the guide roll 12-2 on the stretching device outlet side, whereby the obliquely stretched film 5 is formed. The same range as described above can be adopted as the heating temperature of the film during stretching, the traveling speed of the gripping tool, and the total stretching ratio. In the figure, the original film is stretched obliquely at an angle 14 (feeding angle θi) in the film stretching direction 14-2 with respect to the film feeding direction 14-1. In FIG. 3, reference numeral 5 indicates a long stretched film, reference numeral W indicates a film width after oblique stretching, and reference numeral Wo indicates a film width before oblique stretching.

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

  In the oblique stretching apparatus shown in FIG. 3, the traveling direction 14-1 at the entrance of the stretching apparatus of the original film is different from the traveling direction 14-2 at the exit of the stretching apparatus of the film after stretching. The feeding angle θi is an angle formed by the traveling direction 14-1 at the entrance of the stretching apparatus and the traveling direction 14-2 on the exit side of the stretched film.

  More specifically, in the manufacturing method of the present embodiment, it is particularly preferable to perform oblique stretching using the oblique stretching apparatus shown in FIG. This stretching apparatus can heat a film original fabric to an arbitrary temperature at which it can be stretched and obliquely stretch the film. This stretching apparatus includes a heating zone, a pair of rails on the left and right on which a gripping tool for transporting the film travels, and a number of gripping tools that travel on the rails. 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. Further, this oblique stretching apparatus is provided with a heat fixing zone (including a cooling zone) (not shown) on the downstream side in the transport direction. The raw film that is sequentially supplied to the inlet of the stretching device is first gripped at both ends by a gripping tool, guided into the heating zone, stretched in the stretching zone, and then released from the gripping tool at the outlet of the stretching device. Is done. The retardation film released from the gripper is cooled immediately after stretching by passing through the heat setting zone. In addition, the temperature range at the time of cooling can employ | adopt the same range as the above-mentioned range.

  Note that the rail pattern of the stretching apparatus has an asymmetric shape on the left and right, and the rail pattern can be adjusted manually or automatically according to the orientation angle θ, the stretching ratio, and the like given to the long stretched film to be manufactured. In the oblique stretching apparatus used in the manufacturing method of the present embodiment, it is preferable that the position of each rail part and the rail connecting part can be freely set, and the rail pattern can be arbitrarily changed (circle part in FIG. 3 is an example of the connecting part) Is).

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

  The retardation film after stretching is wound around a winding core after cooling. Before being rolled up, the retardation film is slit and trimmed to the width of the product, and knurled (embossed) at both ends to prevent sticking and scratching during winding. Also good. 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.

(Film forming process)
Next, typical solution casting methods and melt casting methods among known film forming methods that can be employed in the method for producing a retardation film of the present embodiment will be described.

(Solution casting method)
The film original fabric of this embodiment can be manufactured by a solution casting method. In the following description, as an example, a method for forming a film original film including a cellulose ester resin composition as a main component will be described. In the solution casting method, a step of preparing a dope by heating and dissolving a cellulose ester resin composition (hereinafter also simply referred to as cellulose ester) and additives (including a compound having negative intrinsic birefringence) in an organic solvent, A step of casting the prepared dope on a belt-like or drum-like metal support, a step of drying the cast dope as a web, a step of peeling from the metal support, a step of stretching or shrinking the peeled web, and The process of drying, the process of winding up the finished film, etc. are included.

(Dope preparation process)
In the dope adjusting step, it is preferable that the cellulose ester in the dope has a high concentration because the drying load after casting on the metal support can be reduced, but if the concentration of the cellulose ester is too high, the load during filtration increases. , Filtration accuracy deteriorates. Therefore, the concentration for achieving both of these is preferably in the range of 10% by mass to 35% by mass, and more preferably in the range of 15% by mass to 25% by mass.

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

  The cast width is preferably in the range of 1 m to 4 m. The surface temperature of the metal support in the casting step is −50 ° C. or higher, and is appropriately set within the temperature range where the solvent does not boil and foam. A higher temperature can increase the drying speed of the web, but if it is too high, the web may foam and flatness may deteriorate. The surface temperature of the metal support is preferably 0 ° C. or higher and 100 ° C. or lower, more preferably 5 ° C. or higher and 30 ° C. or lower. 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, and a method of blowing warm air or cold air or a method of bringing hot water into contact with the back side of the metal support can be employed. The method using hot water is preferable because the heat transfer is efficiently performed, and the time until the temperature of the metal support becomes constant is short. In the method using warm air, considering the decrease in the temperature of the web due to the latent heat of vaporization of the solvent, there are cases where warm air that is higher than the boiling point of the solvent is used and wind that is higher than the target temperature is used while preventing foaming. is there. In particular, it is preferable to perform drying efficiently by changing the temperature of the support and the temperature of the drying air during the period from casting to peeling.

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

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

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

  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.

  The original film obtained through the drying step is either wound up without being stretched or stretched by about 0.5 to 50% and then wound up. The conditions at the time of winding are not particularly limited, and for example, winding can be performed with a take-up tension of 200 (N / m). Moreover, when extending | stretching about 0.5 to 50%, it can extend | stretch continuously after drying after a film peeling with a conventionally well-known extending | stretching apparatus, for example.

(Melting method)
The film raw material described above 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 the melt 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 ester, plasticizer, and other additives are fed to an extruder with a feeder, kneaded using a single or twin screw extruder, It can be obtained by extruding into a strand, 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.

  Using a single-screw or twin-screw type extruder, the melting temperature when extruding is in the range of 200 ° C. or higher and 300 ° C. or lower, and removing foreign matter by filtering with a leaf disk type filter or the like. The film is cast from a T die into a film, and 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. Stainless steel fiber sintered filter is made by compressing the stainless steel fiber body in a complicatedly intertwined state, and sintering and integrating the contact points, changing the density depending on the thickness and compression amount of the fiber, Filtration 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 or more and (Tg + 110 ° C.) or less 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 original film obtained as described above passes through the step of contacting the cooling roller, and is then wound up without being stretched, or stretched by about 0.5 to 50%, and then wound once. The conditions described above in the explanation of the solution casting method can be adopted as the conditions at the time of winding and the conditions for stretching about 0.5 to 50%.

[Selection of components]
The retardation film satisfying the range of the change in internal haze, slow axis, Ro ₅₅₀ and Ro ₄₅₀ / Ro ₅₅₀ is selected from, for example, a cellulose ester resin composition or a cellulose ether resin composition as the resin composition, and an additive It can also be prepared by blending a compound having a negative intrinsic birefringence or a plasticizer having an electron donating property.

(Resin composition)
The original film includes a resin composition as a main component. Although it is not particularly limited as the resin composition, since it has a positive intrinsic birefringence, excellent retardation development, reverse wavelength dispersibility is not deteriorated, a film raw fabric that can be easily thinned by oblique stretching is obtained. An ester resin composition and a cellulose ether resin composition are preferred.

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

  The acyl substitution degree of cellulose acylate is preferably 1.50 to 2.95, more preferably 1.70 to 2.90, and further preferably 2.00 to 2.90. When the acyl substitution degree of cellulose acylate is less than 1.50, the retardation development property is high, but the wavelength dispersion characteristic of the retardation tends to be almost flat. Moreover, at the time of film production to be described later, the dope viscosity increases and the film surface quality tends to deteriorate, or the internal haze tends to increase due to an increase in stretching tension. On the other hand, when the acyl substitution degree exceeds 2.95, the retardation development property is lowered, but the chromatic dispersion characteristic of the retardation tends to be more reverse dispersion (shows the reverse chromatic dispersion characteristic). In the present specification, “acyl substitution degree” means an average acyl substitution degree, and the average acyl substitution degree is esterified among the three hydroxy groups (hydroxyl groups) of each anhydroglucose constituting cellulose. It is shown by the average value of the number of hydroxy groups, and takes a value of 0 to 3.0.

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

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

  Cellulose acylate is an average of acyl groups having 3 or more carbon atoms out of all acyl groups contained in cellulose acylate from the viewpoint of improving the hydrophobicity of cellulose acylate and enhancing the effect of improving the wavelength dispersion humidity fluctuation. The degree of substitution is preferably 0.5 to 2.5.

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

  In addition, the part which is not substituted by the said acyl group among cellulose acylates exists normally as a hydroxyl group. Such cellulose acylate can be synthesized by a known method. Moreover, the substitution degree of an acyl group can be calculated | required according to prescription | regulation of ASTM-D817-96 (test methods, such as a cellulose acylate).

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

  The weight average molecular weight (Mw) and the number average molecular weight (Mn) of cellulose acylate can be measured using gel permeation chromatography (GPC), respectively. An example of specific measurement conditions is shown below.

(Measurement condition)
Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three columns manufactured by Showa Denko KK)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: A calibration curve using 13 samples of standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) and having an Mw in the range of 500 to 1000000 is used. Thirteen samples are used at approximately equal intervals.

  The cellulose that is a raw material of the cellulose acylate is not particularly limited, and cotton linter, wood pulp, kenaf and the like can be used. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

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

(Cellulose ether resin composition)
The cellulose ether resin composition (hereinafter also simply referred to as cellulose ether) used in the present embodiment is preferably one in which the hydroxyl group of cellulose is substituted with an alkoxy group having 4 or less carbon atoms. Specifically, the hydroxyl group of cellulose is substituted with one or a plurality of alkoxy groups of methoxy group, ethoxy group, propoxy group, butoxy group. In particular, those in which the hydroxyl group of cellulose is substituted by a single or a plurality of alkoxy groups of methoxy group and ethoxy group are preferred, and ethyl cellulose can be suitably used.

  In this specification, DSet represents the average number of ethoxylations of the three hydroxyl groups present at 2, 3, and 6 positions in the cellulose molecule. When the degree of substitution is 3, all hydroxyl groups Is ethoxylated. The degree of substitution at each position may be equal or may be biased to any position. The degree of ether substitution can be quantified by the method described in ASTM D4794-94.

  If the degree of substitution is less than 2.0, the type of solvent that can be dissolved alone is limited, and the water absorption rate of the film increases and the dimensional stability tends to decrease. In addition, even if the degree of substitution exceeds 2.9, the type of solvent that dissolves is not limited, and the resin itself tends to be expensive. Therefore, the preferable range of DSet is 2.0 or more and 2.8 or less, and more preferably 2.2 or more and 2.6 or less.

  Cellulose ether can be produced by a method known per se. For example, it can be produced by treating cellulose with a strong caustic soda solution to obtain alkali cellulose, which is etherified by reacting it with methyl chloride or ethyl chloride.

  The weight average molecular weight of the cellulose ether is preferably 50,000 to 1,000,000, more preferably 100,000 to 800,000, and further preferably 200,000 to 700,000. When the molecular weight is larger than 1 million, not only the solubility in the solvent is lowered, but also the viscosity of the resulting solution becomes too high, which is not suitable for the solvent casting method, making thermoforming difficult, and the transparency of the film is lowered. Tend to cause such problems. On the other hand, when the molecular weight is smaller than 50,000, the mechanical strength of the resulting film tends to decrease.

(Additive)
The film raw fabric may contain an additive. Although it does not specifically limit as an additive, It is preferable to add the compound which has a negative intrinsic birefringence from a viewpoint which further provides reverse wavelength dispersion characteristics, adjusting the retardation of the phase difference film obtained appropriately. Moreover, it is preferable to add the compound represented by following General formula (1) from a viewpoint of suppressing the humidity fluctuation | variation of a phase difference. In addition, it is preferable to add a plasticizer having an electron donating property from the viewpoint of preventing an increase in internal haze before and after stretching. In the present specification, the “compound having a negative intrinsic birefringence” means that when added to the film, the refractive index increases in the direction perpendicular to the stretching direction when compared with the case where it is not added. It refers to a compound having the property of developing a phase difference or the property of weakening the expression of a phase difference in the stretching direction. In the present specification, the “plasticizer having an electron donating property” refers to a plasticizer having a property of increasing the electron density.

(Compound represented by the general formula (1))

In the general formula (1), A ₁ and A ₂ each represents an alkyl group, a cycloalkyl group, an aromatic hydrocarbon ring, or an aromatic heterocyclic ring. L ₁ , L ₂ , L ₃ and L ₄ each represents a single bond or a divalent linking group. W ₁ and W ₂ each represents an aromatic heterocyclic ring or an aliphatic heterocyclic ring. B represents an aromatic hydrocarbon ring, an aliphatic hydrocarbon ring, an aromatic heterocyclic ring or an aliphatic heterocyclic ring. n represents an integer of 0 to 5. When n is 2 or more, the plurality of L ₃ , L ₄ and W ₂ may be the same or different.

Examples of the alkyl group represented by A ₁ and A ₂ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a tert-butyl group, an n-octyl group, and a 2-ethylhexyl group. Examples of the cycloalkyl group represented by A ₁ and A ₂ include a cyclohexyl group, a cyclopentyl group, a 4-n-dodecylcyclohexyl group, and the like. Examples of the aromatic hydrocarbon ring represented by A ₁ and A ₂ include a benzene ring and a naphthalene ring. Examples of the aromatic heterocycle represented by A ₁ and A ₂ include a furfuran ring, a thiophene ring, a pyrrole ring, a pyrimidine ring, a pyridine ring, a pyrazine ring, a pyridazine ring, an imidazole ring, a triazole ring, an oxazole ring, and a thiazole ring. And an oxadiazole ring.

The alkyl group, cycloalkyl group, aromatic hydrocarbon ring, and aromatic heterocyclic ring represented by A ₁ and A ₂ may each be substituted with an arbitrary substituent.

  Specific examples of the substituent are not particularly limited, and include, for example, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom), an alkyl group (for example, a methyl group, an ethyl group, an n-propyl group, Isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group, etc.), alkenyl group (for example, vinyl group, allyl group, etc.), alkynyl group (for example, ethynyl group, propargyl group, etc.), cyano group, hydroxy Group, nitro group, carboxy group, alkoxy group (for example, methoxy group, ethoxy group, isopropoxy group, tert-butoxy group, n-octyloxy group, 2-methoxyethoxy group, etc.), acyloxy group (for example, formyloxy group) , Acetyloxy group, pivaloyloxy group, stearoyloxy group, etc.), alkoxy Rubonyl group (for example, methoxycarbonyl group, ethoxycarbonyl group, etc.), aryloxycarbonyl group (for example, phenoxycarbonyl group, etc.), amino group (for example, amino group, methylamino group, dimethylamino group, etc.), acylamino group (for example, , Formylamino group, acetylamino group, pivaloylamino group, lauroylamino group, etc., alkylsulfonylamino group (eg, amethylsulfonylamino group, butylsulfonylamino group, etc.), mercapto group, alkylthio group (eg, methylthio group, ethylthio) Group, n-hexadecylthio group, etc.), sulfamoyl group (for example, N-ethylsulfamoyl group, N- (3-dodecyloxypropyl) sulfamoyl group, N, N-dimethylsulfamoyl group, N-acetylsulfa) Yl group etc.), sulfo group, acyl group (eg acetyl group etc.), carbamoyl group (eg carbamoyl group, N-methylcarbamoyl group, N, N-dimethylcarbamoyl group, N, N-di-n-octylcarbamoyl) Group, N- (methylsulfonyl) carbamoyl group, etc.), aryl group (eg, phenyl group, p-tolyl group, naphthyl group, etc.), heteroaryl group (eg, 2-furyl group, 2-thienyl group, 2-pyrimidinyl) Group, 2-benzothiazolyl group, 2-pyridyl group, etc.).

Specific examples of the linking group represented by L ₁ , L ₂ , L ₃ and L ₄ include an alkylene group, an alkenylene group, an alkynylene group, —O—, — (C═O) —, and — (C═O). -O-, -NR'-, -S-,-(O = S = O)-and-(C = O) -NR'-, wherein R 'is a hydrogen atom or a substituent. Examples thereof include a divalent linking group or a combination thereof.

Examples of the aromatic heterocycle represented by W ₁ and W ₂ include a furan ring, a thiophene ring, a pyrrole ring, a pyrimidine ring, a pyridine ring, a pyrazine ring, a pyridazine ring, an imidazole ring, a triazole ring, an oxazole ring, and a thiazole ring. And an oxadiazole ring. Examples of the aliphatic heterocyclic ring represented by W ₁ and W ₂ include a pyrazole ring, piperidine ring, piperazine ring, pyrrolidine ring, morpholine, thiomorpholine, proline and the like.

The aromatic heterocyclic ring or aliphatic heterocyclic ring represented by W ₁ and W ₂ may be substituted with any substituent. Examples of the substituent that W ₁ and W ₂ can have include the same groups as the substituents that A ₁ and A ₂ can have.

W ₁ and W ₂ are preferably aromatic heterocycles, more preferably nitrogen-containing aromatic heterocycles, and still more preferably nitrogen-containing 5-membered aromatic heterocycles. Particularly preferred are an imidazole ring, a pyrazole ring, a triazole ring, and an oxadiazole ring.

  Examples of the aromatic hydrocarbon ring represented by B include a benzene ring and a naphthalene ring. Examples of the aliphatic hydrocarbon ring represented by B include a cyclohexane ring, a cyclopentane ring, a cycloheptane ring, and a cyclooctane ring. Examples of the aromatic heterocycle represented by B include furan ring, thiophene ring, pyrrole ring, pyrimidine ring, pyridine ring, pyrazine ring, pyridazine ring, imidazole ring, triazole ring, oxazole ring, thiazole ring, oxadiazole. A ring etc. are mentioned. Examples of the aliphatic heterocyclic ring represented by B include a pyrazole ring, piperidine ring, piperazine ring, pyrrolidine ring, morpholine, thiomorpholine, proline and the like.

The aromatic hydrocarbon ring, aliphatic hydrocarbon ring, aromatic heterocycle and aliphatic heterocycle represented by B may each be substituted with an arbitrary substituent. Examples of the substituent that B can have include the same groups as the substituents that A ₁ and A ₂ can have.

  B is preferably an aromatic hydrocarbon ring or an aromatic heterocyclic ring, and more preferably an aromatic hydrocarbon ring.

  The compound represented by the general formula (1) preferably has a structure having a plurality of ring structures including a heterocyclic ring in the major axis direction.

<Example of Compound Represented by General Formula (1)>
Hereinafter, exemplary compounds 1-1 to 1-30 are shown as specific examples of the compound represented by the general formula (1), but the compounds that can be used in the present embodiment are not limited by these exemplified compounds. .

<Synthesis Example of Compound Represented by General Formula (1)>
The compound represented by the general formula (1) can be synthesized by a known method. As an example of the synthesis method, for example, the exemplified compound 1-1 can be synthesized according to the synthesis method shown below with reference to Tetrahedoron Letters, 2005, No. 46, pages 3429-3432.

  That is, after replacing a 1 L 4-head flask with nitrogen, 10.0 g of isophthalonitrile, 31.9 g of benzoylhydrazine, and 150 mL of n-butanol are added. After stirring at room temperature for 30 minutes, 18.9 g of potassium carbonate is added and heated to reflux at 130 ° C. for 3 hours. After allowing to cool, the reaction solution is poured into 200 mL of water, and the solid is filtered off.

  The obtained solid is dissolved in 100 mL of 1 mol / L hydrochloric acid and 100 mL of ethyl acetate, and the organic layer is washed 3 times with 50 mL of saturated brine. The organic layers are combined, and the solvent is distilled off under reduced pressure to obtain 31 g of a crude product. The obtained crude product is purified by silica gel chromatography (eluent: hexane / ethyl acetate = 1/3) and recrystallized from methanol to obtain 20.7 g of Exemplified Compound 1-1 as white crystals ( Yield 73%).

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

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

  The content of the compound having negative intrinsic birefringence in the λ / 4 retardation film is preferably in the range of 0.01 to 30% by mass, more preferably in the range of 1 to 20% by mass. More preferably, it is in the range of 1 to 10% by mass. By setting the content of the compound having negative intrinsic birefringence to 0.01 to 30% by mass, a λ / 4 retardation film having low internal haze and high transparency can be obtained. Moreover, by using together with resin compositions, such as above-mentioned cellulose ester and a cellulose ether, the reverse wavelength dispersion characteristic can fully be provided, adjusting the phase difference expression property of the phase difference film obtained.

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

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

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

  Examples of the alkyl ether diol having 4 to 20 carbon atoms include polytetramethylene ether glycol, polyethylene ether glycol, polypropylene ether glycol, and combinations thereof. Although it does not specifically limit as average polymerization degree of these alkyl ether diol, For example, it is 2-20, Preferably it is 2-10, More preferably, it is 2-5, More preferably, it is 2-4. Examples of such alkyl ether diols include Carbowax resin, Pluronics resin, and Niax resin.

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

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

  Moreover, when sealing with a monocarboxylic acid residue, as a monocarboxylic acid used, a C1-C30 substituted and unsubstituted monocarboxylic acid is preferable. These may be aliphatic monocarboxylic acids or aromatic ring-containing carboxylic acids. Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butanoic acid, caprylic acid, caproic acid, decanoic acid, dodecanoic acid, stearic acid, oleic acid, and examples of aromatic ring-containing monocarboxylic acids include: Benzoic acid, p-tert-butylbenzoic acid, p-tert-amylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, normal propylbenzoic acid, aminobenzoic acid, acetoxybenzoic acid, etc. These may be used alone or in combination of two or more.

  The polyester-based polymer is synthesized by a hot melt condensation method by a polyesterification reaction or transesterification reaction between a dicarboxylic acid and a diol and / or a monocarboxylic acid or monoalcohol for end-capping, or an acid of these acids. It can be easily synthesized by any method of interfacial condensation between chloride and glycols. As for these polyester-based additives, Koichi Murai, “Additives, Theory and Application” (Koshobo Co., Ltd., published on March 1, 1973, first edition, first edition) can be referred to. Also, JP 05-155809 A, JP 05-155810 A, JP 5 197073 A, JP 2006-259494 A, JP 07-330670 A, JP 2006-342227 A, The materials described in JP 2007-003679 A and the like can be used.

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

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

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

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

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

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

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

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

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

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

(Plasticizer with electron donating properties)
It does not specifically limit as a plasticizer which has an electron donating property, What is necessary is just a plasticizer which can improve fluidity | liquidity and a softness | flexibility by adding. Examples of such plasticizers include polyhydric alcohol ester plasticizers, glycolate plasticizers, phthalate ester plasticizers, citrate ester plasticizers, fatty acid ester plasticizers, and phosphate ester plasticizers. , Polycarboxylic acid ester plasticizers, acrylic plasticizers and the like. It can be applied to a wide range of uses by selecting or using these plasticizers according to the use. By including these electron-donating plasticizers, the raw film is crystallized even when a large load is applied in a region having a high draw ratio in the oblique stretching process, for example. Hateful. In addition, a plasticizer having an electron donating property has an intermolecular interaction between the resin composition and the plasticizer even when the resin composition is crystallized and the space between the resin compositions becomes narrow. It is difficult to extrude from between resin compositions. Therefore, an increase in internal haze is suppressed. As a result, a display (for example, a flexible display) including a retardation film obtained by using a film original film including a plasticizer having such an electron donating property is excellent in bending resistance and display quality is hardly deteriorated.

By adopting the above preferred resin compositions and additives, a retardation film satisfying the above-mentioned change in internal haze, slow axis, Ro ₅₅₀ and Ro ₄₅₀ / Ro ₅₅₀ can be produced.

  In addition, the film original fabric may contain other resin compositions and additives in addition to the above resin compositions and additives. Hereinafter, other resin compositions and other additives will be described.

(Other resin composition)
In addition to the cellulose ester resin composition and the cellulose ether resin composition described above, the film raw material is, for example, 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. When strength and resistance to breakage are particularly required, for example, polyamide (PA), nylon, polyacetal (POM), polycarbonate (PC), modified polyphenylene ether (m-PPE, modified PPE, PPO), poly Butylene terephthalate (PBT), polyethylene terephthalate (PET), glass fiber reinforced polyethylene terephthalate (GF-PET), cyclic polyolefin (COP), and the like can be used. Furthermore, when high heat distortion temperature and durability that can be used for a long time are required, polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polysulfone, polyethersulfone, amorphous polyarylate, liquid crystal polymer, Polyetheretherketone, thermoplastic polyimide (PI), polyamideimide (PAI) and the like can be used. These can be used in combination with types and molecular weights depending on the application.

(Other additives)
In addition to the resin composition and additives described above, the film raw material can contain, for example, various additives listed below as other additives.

(Organic solvent)
In this embodiment, an organic solvent can be used in order to prepare the resin solution or dope by dissolving the above resin composition. As the organic solvent, a chlorinated organic solvent and a non-chlorinated organic solvent can be mainly used.

  Examples of the chlorinated organic solvent include methylene chloride (methylene chloride). Non-chlorine organic solvents include, for example, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoro Ethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, Examples include 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, 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, for example, 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, or a high-pressure dissolution method. It is preferable. For the cellulose acylate, methylene chloride can be used, but methyl acetate, ethyl acetate, and acetone are preferably used, and among them, methyl acetate is particularly preferable.

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

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

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

  The dope viscosity is preferably adjusted within the range of 100 to 500 Pa · s from the viewpoint of obtaining excellent film surface quality.

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

(Sugar ester compound)
The film raw material preferably contains a sugar ester compound as a compatibilizer. Examples of the sugar ester compound include ester compounds other than cellulose esters, which have 1 to 12 pyranose structures or furanose structures and all or part of the hydroxy groups in the structure are esterified. be able to.

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

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

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

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

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

  In the present embodiment, from the viewpoint of stabilizing the display quality by suppressing the fluctuation of the retardation value, the sugar ester compound described above is included in the range of 1 to 30% by mass with respect to 100% by mass of the original film. It is preferable that it is contained within the range of 5 to 30% by mass. If it exists in the range of 1-30 mass%, while exhibiting the said outstanding effect, bleed-out etc. may be suppressed.

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

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

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

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

<Phase difference film>
In the retardation film obtained by the above-described method for producing a retardation film, the change in internal haze before and after stretching is 0.07% or less per 40 μm thickness, and the slow axis with respect to the longitudinal direction is 10 ° or more and 80 ° or less. The in-plane retardation Ro ₅₅₀ at a wavelength of 550 nm is 100 nm or more and 160 nm or less, and the ratio of the in-plane retardation Ro ₄₅₀ at a wavelength of 450 nm to Ro ₅₅₀ (Ro ₄₅₀ / Ro ₅₅₀ ) is 0.8 or more and less than 1.0. It is a retardation film. A retardation film having such physical characteristics has excellent reverse wavelength dispersion characteristics and substantially exhibits a λ / 4 retardation in a wide band. Therefore, it can be suitably used for a circularly polarizing plate used for an organic EL display, for example. Moreover, in the display produced using such a retardation film, deterioration of display quality is suppressed.

  Hereinafter, other physical characteristics of the retardation film will be described. In addition, the following physical characteristics are illustrations, and the retardation film of this embodiment is not limited to a film provided with the following physical characteristics.

(Film thickness and width)
The film thickness of the retardation film is not particularly limited, and can be, for example, in the range of 10 μm to 250 μm. As described above, the retardation film contains a resin composition such as a cellulose ester resin composition or a cellulose ether resin composition and an additive, so that the retardation is not increased as in the conventional case. The expression can be increased. For example, the film thickness of the film may be 20 μm or more and 100 μm or less, may be 20 μm or more and 80 μm or less, and may be 20 μm or more and 65 μm or less.

  It does not specifically limit as the width | variety of retardation film, It can be set within the range of 1 m or more and 4 m or less, Preferably it can be set within the range of 1.4 m or more and 4 m or less, More preferably, it is 1.6 m or more and 3 m or less. It can be as follows. By setting the width of the retardation film to 4 m or less, it is possible to ensure conveyance stability.

(Surface roughness)
The arithmetic average roughness of the retardation film surface is not particularly limited and can be about 2.0 nm to 4.0 nm, preferably about 2.5 nm to 3.5 nm.

(Dimensional change rate)
Although the dimensional change rate (%) of the retardation film is not particularly limited, for example, when applied to an organic EL display, unevenness or level is caused by dimensional change due to moisture absorption in the environment atmosphere (for example, high humidity environment) to be used. In order not to cause problems such as a change in phase difference value, a decrease in contrast, and color unevenness, it is preferably less than 0.5%, more preferably less than 0.3%.

(Fault tolerance)
The retardation film preferably has few failures in the film (hereinafter also referred to as defects). Specifically, in the film plane, the defect having a diameter of 5 μm or more is preferably 1 piece / 10 cm square or less, more preferably 0.5 piece / 10 cm square or less, and 0.1 piece / 10 cm square. More preferably, it is as follows. 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, the polymer solution should be filtered with high precision immediately before casting, the degree of cleanness around the casting machine should be increased, It is effective to set drying conditions after rolling stepwise 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 be produced.

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

(Glass transition temperature Tg)
Tg is the average of the temperature at which the baseline originating from the glass transition of the film begins to change and the temperature returning to the baseline again when measured at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC) It can be obtained as a value. It is preferable that Tg of the retardation film of this embodiment is 70 degreeC or more and 250 degrees C or less.

<Circularly polarizing plate>
The retardation film described above 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 °. As used herein, “substantially 45 °” means within a range of 40 to 50 °.

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

  Since the circularly polarizing plate of the present embodiment is produced using the above-described retardation film, it is applied to an organic EL display or the like, which will be described later, so that the specular reflection of the metal electrode of the organic EL element at all wavelengths of visible light. The effect of shielding can be expressed. As a result, reflection during observation can be prevented and black expression can be improved.

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

  Further, the circularly polarizing plate of the present embodiment uses the retardation film in which the angle of the slow axis (that is, the orientation angle θ) is adjusted to be “substantially 45 °” with respect to the longitudinal direction, It is possible to form an adhesive layer and bond the polarizing film and the retardation film plate together by a consistent production line. Specifically, after finishing the process of stretching and producing the polarizing film, a step of laminating the polarizing film and the retardation film can be incorporated during or after the subsequent drying process. In addition, it is possible to connect with a production line that is consistent with the next process by winding in a roll state even after bonding. In addition, when bonding a polarizing film and retardation film, a protective film can also be simultaneously supplied in a roll state and can also be bonded continuously. From the viewpoint of performance and production efficiency, it is preferable to simultaneously bond the retardation film and the protective film to the polarizing film. That is, after finishing the process of stretching and producing the polarizing film, after the subsequent drying process or after the drying process, the protective film and the retardation film are bonded to both sides with an adhesive, respectively, It is also possible to obtain a circularly polarizing plate.

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

  The thickness of the polarizer is not particularly limited, and can be, for example, 3 μm or more and 35 μm or less, preferably 5 μm or more and 25 μm or less. By using a polarizer having such a thickness, the obtained circularly polarizing plate can be thinned.

<Organic EL display>
The organic EL display of this embodiment is produced using the circularly polarizing plate. More specifically, the organic EL display of the present embodiment includes a circularly polarizing plate using the retardation film and an organic EL element. The screen size of the organic EL display is not particularly limited, and can be 20 inches or more.

  FIG. 4 is a schematic diagram of the configuration of the organic EL display of the present embodiment. The configuration of the organic EL display shown in FIG. 4 is an example, and the configuration of the organic EL display of the present embodiment is not limited at all.

  As shown in FIG. 4, a metal electrode 102, a TFT (thin film transistor) 103, an organic light emitting layer 104, a transparent electrode (ITO (indium tin oxide) 105), insulating, etc. in order on a transparent substrate 101 using glass, polyimide, or the like. On the organic EL element B having the layer 106, the sealing layer 107, and the film 108 (optional), the above-described circularly polarizing plate C in which the polarizer 110 is sandwiched between the above-described retardation film 109 and the protective film 111 is provided. The organic EL display A is configured. It is preferable that a hardened layer 112 is laminated on the protective film 111. The hardened layer 112 not only prevents scratches on the surface of the organic EL display but also has an effect of preventing warpage due to the circularly polarizing plate. Further, an antireflection layer 113 may be provided on the cured layer. The thickness of the organic EL element itself is about 1 μm.

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

  In an organic EL display, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the fluorescent material. It emits light on the principle that it emits light when the excited fluorescent material returns to the ground state. The mechanism of recombination is the same as that of a general diode, and current and light emission intensity show strong nonlinearity with rectification with respect to applied voltage.

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

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

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

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

  Since the retardation film and the polarizing plate have a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization 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 is transmitted only through the linearly polarized light component by the polarizing plate, and this linearly polarized light is generally elliptically polarized by the retardation plate. In particular, the retardation film is a λ / 4 retardation film. Moreover, when the angle formed by the polarization direction of the polarizing plate and the retardation film is π / 4, circular polarization is obtained.

  This circularly polarized light is transmitted through the transparent substrate, 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 in 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. Therefore, according to the organic EL display of this embodiment, external light reflection is suppressed and the bright place contrast and black reproducibility are excellent.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, it shall represent "mass part" or "mass%".

Example 1
<Production of retardation film original fabric>
(Preparation of fine particle dispersion)
Fine particles (Aerosil R812 manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed using a Manton Gorin disperser to prepare a fine particle dispersion.

(Preparation of fine particle additive solution)
50 parts by mass of methylene chloride was placed in the dissolution tank, and 50 parts by mass of the fine particle dispersion prepared above was slowly added while sufficiently stirring the methylene chloride. Further, the particles were dispersed by an attritor so that the secondary particles had a particle size of about 0.01 to 1.0 μm. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.

(Preparation of dope)
First, methylene chloride and ethanol shown below were added to the pressure dissolution tank. A cellulose acylate resin composition A having an acetyl group substitution degree of 1.5 and a propionyl group substitution degree of 0.9 was charged into 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 additive a, additive b and the fine particle additive solution prepared as described below were charged into the main dissolution vessel at the following ratio, sealed, and dissolved with stirring to prepare a dope solution.

<Dope composition>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose acylate resin composition A 100 parts by mass Additive a 6 parts by mass Additive b 3 parts by mass Particulate additive solution 2 parts by mass

(Additive a)

(Additive b)

(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 original film was peeled from above. The peeled film original was wound up into a roll with a take-up tension of 200 (N / m).

(Oblique stretching process)
Next, the film original film is unwound, both ends of the film original film are gripped by a gripper, and heated to a temperature 50 ° C. higher than the Tg (163 ° C.) of the film original film, as shown in FIG. Using a stretching device, the film is stretched in an oblique direction so that the slow axis is 45 ° with the film longitudinal direction so that the stretch ratio is 2.0 times, and then 10 ° C. higher than the Tg of the original film. The film was dried (cooled) for 5 minutes at a high temperature to prepare a retardation film having a slow axis in the direction of 45 ° with respect to the longitudinal direction. The traveling speed of the gripping tool during oblique stretching was set to 0.1 m / min. Under these stretching conditions, the total stretching ratio was 2.0 times.

(Example 2)
In the oblique stretching step, using a gripping tool having a running speed of 0.1 m / min, the film is heated to a temperature higher by 50 ° C. than the Tg of the original film, and then obliquely stretched, and then 10 ° C. lower than the Tg of the original film. A retardation film was produced in the same manner as in Example 1 except that the film was dried for 5 minutes. Under these stretching conditions, the total stretching ratio was 2.0 times.

Example 3
Using the retardation film original fabric (Tg: 120 ° C) shown below, and using a gripping tool with a running speed of 3 m / min in the oblique stretching step, heat it to a temperature 50 ° C higher than the Tg of the film original fabric. A retardation film was produced in the same manner as in Example 1 except that the film was obliquely stretched and then dried for 5 minutes at a temperature 10 ° C. lower than the Tg of the original film. Under these stretching conditions, the total stretching ratio was 2.0 times.

<Production of retardation film original fabric>
A fine particle additive solution was prepared in the same manner as in Example 1.

(Preparation of dope)
First, the following methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose ether resin composition B having a benzoyl group substitution degree of 0.6 and an ethyl group substitution degree of 2.3 was charged into 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 additive a, the additive c shown below, and the fine particle additive solution prepared above were charged into the main dissolution vessel in the following ratio, sealed, and then dissolved with stirring to prepare a dope solution.

<Dope composition>
Methylene chloride 340 parts by weight Ethanol 64 parts by weight Cellulose acylate resin composition B 100 parts by weight Additive a 6 parts by weight Additive c 3 parts by weight Particulate additive liquid 1 part by weight

(Additive c) Compound 1-1 represented by formula (1)

(Film formation)
The prepared dope is cast on a stainless steel belt support, the solvent is evaporated until the residual solvent amount in the film reaches 75% by mass, and then the film is applied from the stainless steel belt support with a peeling tension of 130 N / m. The original fabric was peeled off. The peeled film original was wound up into a roll with a take-up tension of 200 (N / m).

Example 4
A retardation film was produced by stretching in the same manner as in Example 2 except that the film original fabric produced in Example 3 was used.

(Example 5)
Using the retardation film original fabric (Tg: 135 ° C.) shown below, and using a gripping tool at a traveling speed of 0.1 m / min in the oblique stretching step, the temperature is 50 ° C. higher than the Tg of the film original fabric. A retardation film was produced in the same manner as in Example 1 except that it was heated and obliquely stretched, and then dried for 5 minutes at a temperature 10 ° C. higher than the Tg of the original film. Under these stretching conditions, the total stretching ratio was 2.0 times.

<Production of retardation film original fabric>
A fine particle additive solution was prepared in the same manner as in Example 1.

(Preparation of dope)
First, the following methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose ether resin composition C having an ethyl group substitution degree of 2.3 was charged into 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. Subsequently, additive d (compound having a negative intrinsic birefringence, a copolymer of methyl methacrylate and 2-hydroxyethyl methacrylate, number average molecular weight Mn: 4000), additive e shown below and the above-mentioned preparation The fine particle addition solution was charged into the main dissolution vessel at the following ratio, sealed, and then dissolved with stirring to prepare a dope solution.

<Dope composition>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose acylate resin composition C 100 parts by mass Additive d 15 parts by mass Additive e 3 parts by mass Fine particle additive solution 2 parts by mass

(Additive e)

(Film formation)
The prepared dope is cast on a stainless steel belt support, the solvent is evaporated until the residual solvent amount in the film reaches 75% by mass, and then the film is applied from the stainless steel belt support with a peeling tension of 130 N / m. The original fabric was peeled off. The peeled film original was wound up into a roll with a take-up tension of 200 (N / m).

(Example 6)
A retardation film was produced by stretching in the same manner as in Example 2, except that the film original fabric produced in Example 5 was used.

(Example 7)
A retardation film was produced in the same manner as in Example 1 except that the retardation film original fabric (Tg: 170 ° C.) shown below was used.

<Production of retardation film original fabric>
A fine particle additive solution was prepared in the same manner as in Example 1.

(Preparation of dope)
First, the following methylene chloride and ethanol were added to the pressure dissolution tank. A cellulose acylate resin composition D having an acetyl group substitution degree of 2.89 was charged into 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. Subsequently, the additive a, the additive c, and the fine particle additive solution prepared above were charged in the main dissolution vessel in the following ratio, sealed, and then dissolved with stirring to prepare a dope solution.

<Dope composition>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose acylate resin composition B 100 parts by mass Additive a 6 parts by mass Additive c 1 part by mass Particulate additive solution 2 parts by mass

(Film formation)
The prepared dope is cast on a stainless steel belt support, the solvent is evaporated until the residual solvent amount in the film reaches 75% by mass, and then the film is applied from the stainless steel belt support with a peeling tension of 130 N / m. The original fabric was peeled off. The peeled film original was wound up into a roll with a take-up tension of 200 (N / m).

(Example 8)
A retardation film was produced by stretching in the same manner as in Example 2 except that the film original fabric produced in Example 7 was used.

(Comparative Example 1)
After exfoliating the original film by the same method as in Example 1, the film was drawn 1.25 times in the TD direction at a drawing temperature 15 ° C. higher than the Tg of the original film, and the take-up tension was 200 (N / m). The film was rolled up into a roll. Next, in the oblique stretching step, using a gripping tool having a running speed of 3 m / min, the film is heated to a temperature 20 ° C. higher than the Tg of the original film and is stretched obliquely so that the stretching ratio is 1.7 times. A retardation film was produced in the same manner as in Example 1 except that the film was dried for 5 minutes at a temperature 10 ° C. higher than the Tg of the original film. Under these stretching conditions, the total stretching ratio was 2.12 times.

(Comparative Example 2)
A film original fabric was produced in the same manner as in Example 1. The produced film original is heated at a temperature 20 ° C. higher than the Tg of the film original by using a gripping tool having a running speed of 0.1 m / min in the oblique stretching step, and the draw ratio becomes 2.0 times. A retardation film was produced in the same manner as in Example 1 except that the film was obliquely stretched and then dried for 5 minutes at a temperature 10 ° C. higher than the Tg of the original film. Under these stretching conditions, the total stretching ratio was 2.0 times.

(Comparative Example 3)
A retardation film was produced by stretching in the same manner as in Comparative Example 1 except that the film original fabric produced in Example 3 was used.

(Comparative Example 4)
In the oblique stretching process using the film original fabric produced in Example 3, using a gripping tool having a running speed of 3 m / min, the film was heated to a temperature higher by 50 ° C. than the Tg of the film original fabric, and the draw ratio was 2.0. A retardation film was produced in the same manner as in Example 1 except that the film was obliquely stretched so as to be doubled and then dried for 5 minutes at a temperature 10 ° C. higher than the Tg of the original film. Under these stretching conditions, the total stretching ratio was 2.0 times.

(Comparative Example 5)
A retardation film was produced by stretching in the same manner as in Comparative Example 1 except that the film original fabric produced in Example 5 was used.

(Comparative Example 6)
A retardation film was produced by stretching in the same manner as in Comparative Example 2 except that the film original fabric produced in Example 5 was used.

(Comparative Example 7)
A retardation film was produced by stretching in the same manner as in Comparative Example 1 except that the film original fabric produced in Example 7 was used.

(Comparative Example 8)
A retardation film was produced by stretching in the same manner as in Comparative Example 2 except that the film original fabric produced in Example 7 was used.

<Measurement of each characteristic value of film>
(Slow axis, Ro ₅₅₀ , Ro ₄₅₀ / Ro ₅₅₀ )
About the retardation film produced in the said Examples 1-8 and Comparative Examples 1-8, in 23 degreeC and 55% RH environment, Axometrics Axoscan made the in-plane direction in the wavelength of 450 nm and 550 nm. Retardation Ro ₄₅₀ and Ro ₅₅₀ were measured to calculate Ro ₄₅₀ / Ro ₅₅₀ . Also about the slow axis, it measured using Axoscan made from Axometrics. The results are shown in Table 1.

(Glass transition temperature Tg)
Tg is the temperature at which the baseline derived from the glass transition of the film begins to change when measured with a differential scanning calorimeter (DSC) Q2000 manufactured by TA Instruments at a rate of temperature increase of 5 ° C / min. It calculated | required as an average value with the temperature which returns to a line.

<Production of 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.

  Then, according to the following processes 1-5, a polarizer, each retardation film produced in Examples 1-8 or Comparative Examples 1-8, and the protective film mentioned later on the back side are match | combined with a longitudinal direction. In this way, the circularly polarizing plates were produced by laminating by roll-to-roll.

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

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

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

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

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

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

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

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

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

(Internal haze)
When producing each of the above retardation films, the internal haze of the original film before and after oblique stretching was measured according to the following method.

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

      (Haze 2)-(Haze 1) = (Internal haze value of original film before stretching)

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

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

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

  Glycerin: Deer special grade (purity> 99.0%) manufactured by Kanto Chemical Co., Inc., refractive index 1.47

  By the same method, the internal haze of the original film (retardation film) after oblique stretching was measured. The obtained measured values of the internal haze before and after stretching were converted per 40 μm film thickness, and the difference was calculated. The results are shown in Table 1.

(Flexibility)
A retardation film having a sample size of 100 mm × 50 mm is allowed to stand for 48 hours in an environment of 23 ° C. and 50% RH, and then tested for bending resistance according to the JIS K 5600-5-1: 1999 cylindrical mandrel method (type 1 test). The test was carried out in the longitudinal direction of the test piece with a diameter of 10 mm, a bending time of 2 seconds, and a 23 ° C. and 50% environment using an apparatus. The results are shown in Table 1.

(Black color)
First, the produced organic EL display was stored at 50 ° C. and 85% RH for 48 hours. Thereafter, it was stored at 23 ° C. and 55% for 48 hours. This cycle was repeated three times. Thereafter, a black image was displayed on the organic EL display under conditions where the illuminance was 1000 Lx at a position 5 cm higher than the outermost surface of each organic EL display in a normal humidity environment of 23 ° C. and 55% RH. Next, the front position of each organic EL display (0 ° with respect to the surface normal) and the color of the black image from an oblique angle of 40 ° with respect to the surface normal are observed and evaluated by 10 general monitors. Evaluation was made according to criteria. The results are shown in Table 1. In addition, if it was more than (triangle | delta), it was judged that it was practically possible as a black color.

(Evaluation criteria)
A: Nine or more monitors determined that the displayed image was black.
○: 7 to 8 monitors determined that the displayed image was black.
Δ: 5 to 6 monitors determined that the displayed image was black.
X: The number of monitors judged to be black in the displayed image was 4 or less.

(Reflective)
In the production of the organic EL display device, an organic EL display device for evaluation was produced in the same manner except that red, blue, and green lines were given to the viewing side surface with magic ink at the stage of producing the organic EL cell. did. About the organic EL display which has the produced red, blue, and green line | wire, the illumination intensity in the position 5cm higher than the outermost surface of each organic EL display apparatus will be 1000Lx in the normal humidity environment of 23 degreeC and 55% RH Thus, the visibility (reflection performance) of the lines of the magic ink attached to the organic EL display device was evaluated by 10 general monitors according to the following criteria. The results are shown in Table 1. If Δ or more, the reflection performance was judged to be practical. The reflection performance here refers to reflection in the organic EL cell that enters the inside of the circularly polarizing plate, not reflection on the surface of the circularly polarizing plate.

(Evaluation criteria)
A: Nine or more monitors judged that no magic ink line was visible.
○: 7 to 8 monitors determined that no color of the magic ink line was visible.
Δ: Five to six monitors determined that no two magic ink lines were visible.
X: The number of monitors judged that two lines of magic ink were not visible was 4 or less.

  As shown in Table 1, the retardation film of the present invention has a small change in internal haze, and the organic EL display using a circularly polarizing plate produced using the obtained retardation film has excellent bending resistance, and It was found that the color and black display characteristics were excellent in visibility.

  According to the present invention, in a method for producing a retardation film in which a film original film wound after film formation is unwound and obliquely stretched, a retardation film capable of producing a display that hardly deteriorates display quality is obtained. Therefore, for example, the present invention can be suitably used in the field of displays that require flexibility and display quality such as flexible displays.

101 Transparent substrate 102 Metal electrode 103 TFT
DESCRIPTION OF SYMBOLS 104 Organic light emitting layer 105 Transparent electrode 106 Insulating layer 107 Sealing layer 108 Film 109 (lambda) / 4 phase difference film 110 Polarizer 111 Protective film 112 Hardened layer 113 Antireflection layer 1a Transparent substrate 2a Metal electrode 3a, 3aR, 3aG, 3aB Light emission Layer 4 Original film 4a Transparent electrode 5 Long stretched film 5a Insulating film 6 Diagonal stretcher 6a Adhesive layer 7a Polarizing plate protective film (λ / 4 retardation film)
7-1, 7-2 Trajectory 8a Polarizer 8-1, 8-2 Holding start point 9a Polarizing plate protective film 9-1, 9-2 Holding end point 10a Polarizing plate 10-1, 10-2 Point of starting widening 11a Organic EL elements 11-1 and 11-3 Points at which widening ends 11-2 Points at which one of the pair of left and right grips reaches 12-1 Guide roll 12-2 Guide roll (on the tenter outlet side) 13 Stretching of film Direction 14 Angle of film stretching direction with respect to film feeding direction (θi)
14-1 Film Feeding Direction 14-2 Film Stretching Direction 15 Parts with Different Feeding Speeds between Left and Right Grip Tools A Organic EL Display A1, A2 Stretching Direction A3 Transporting Direction A4 Slow Axis B Organic EL Element C Circular Polarizer Wo Width of film before stretching W Width of film after stretching θi Feeding angle

Claims (5)

Unwinding the original film that has been wound up after film formation, and has a step of stretching in an oblique direction,
In the step of stretching in the oblique direction,
A process that satisfies the following conditions B and C :
Condition B: Stretching temperature is a temperature higher by 50 ° C. to 60 ° C. than Tg of the retardation film. Condition C: Cooling temperature after stretching is Tg to Tg-30 ° C. of the retardation film. The change in haze is 0.07% or less per 40 μm film thickness,
The obtained retardation film has a slow axis with respect to the longitudinal direction of 10 ° or more and 80 ° or less, an in-plane retardation Ro ₅₅₀ at a wavelength of 550 nm of 100 nm or more and 160 nm or less, and an in-plane retardation at a wavelength of 450 nm with respect to Ro ₅₅₀ . as the ratio of _{Ro 450 (Ro 450 / Ro 550} ) is less than 0.8 to 1.0, method for producing a retardation film, which comprises stretching the raw film.   The said retardation film is a manufacturing method of the retardation film of Claim 1 containing the compound which has a negative intrinsic birefringence. The said retardation film is a manufacturing method of the retardation film of Claim 1 or 2 containing the compound represented by the following general formula (1).

(In General Formula (1), A ₁ and A ₂ each represent an alkyl group, a cycloalkyl group, an aromatic hydrocarbon ring or an aromatic heterocyclic ring, and L ₁ , L ₂ , L ₃ and L ₄ are each Represents a single bond or a divalent linking group, W ₁ and W ₂ each represent an aromatic heterocycle or an aliphatic heterocycle, and B represents an aromatic hydrocarbon ring, an aliphatic hydrocarbon ring, an aromatic heterocycle Or n represents an integer of 0 to 5. When n is 2 or more, a plurality of L ₃ , L ₄ and W ₂ may be the same or different.   The said retardation film is a manufacturing method of the retardation film of any one of Claims 1-3 containing a cellulose-ester resin composition.   The said retardation film is a manufacturing method of the retardation film of any one of Claims 1-3 containing a cellulose ether resin composition.

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