WO2013136977A1

WO2013136977A1 - Λ/4 phase difference film and method for producing same, circularly polarizing plate, and organic electroluminescent display device

Info

Publication number: WO2013136977A1
Application number: PCT/JP2013/055037
Authority: WO
Inventors: 範江谷原; 田代　耕二; 理英子れん; 幸仁中澤; 賢治三島; 翠木暮
Original assignee: コニカミノルタ株式会社
Priority date: 2012-03-12
Filing date: 2013-02-27
Publication date: 2013-09-19
Also published as: KR101662920B1; KR20140121446A; JPWO2013136977A1

Abstract

The present invention addresses the problem of providing: a λ/4 phase difference film exhibiting excellent phase-difference-inducing properties, suitability as a thin-film, and reverse-wavelength-dispersion properties, having a low haze level, and also exhibiting excellent light resistance and coloration resistance; a method for producing the same; a circularly polarizing plate; and an organic EL display device. This λ/4 phase difference film contains a thermoplastic resin and a compound (I), and has: a principal chain linked to the linking group of the compound (I) via two link sites thereof, and having maximum absorption at 200-280nm; and a side chain bonding to one or more of the other link sites of the linking group, and branching from a chemical structure section (X; principal chain). The λ/4 phase difference film is characterized by satisfying (a) and (b), and in that the wavelength-dispersion properties satisfy (c) and (d). (a) Side chain having maximum-absorption wavelength of 280-380nm. (b) 25.0≥ΣABS_y/ΣABS_x≥1.01. (c) Ro(450)/Ro(550)=0.72-0.96. (d) Ro(550)/Ro(650)=0.83-0.98.

Description

λ / 4 retardation film and manufacturing method thereof, circularly polarizing plate, and organic electroluminescence display device

The present invention relates to a λ / 4 retardation film, a method for producing the same, a circularly polarizing plate provided with a λ / 4 retardation film, and an organic electroluminescence display device.

In recent years, a self-luminous display device such as an organic electroluminescence display device has attracted attention as a new display device. The self-luminous display device has a room for suppressing power consumption compared with a liquid crystal display device whose backlight is always lit, and in addition, a light source corresponding to each color such as an organic electroluminescence display device is lit. In the self-luminous display device, it is not necessary to install a color filter that causes a reduction in contrast, so that the contrast can be further increased. However, in the organic electroluminescence display device, a reflector such as an aluminum plate is provided on the back side of the display in order to increase the light extraction efficiency. Therefore, the external light incident on the display is reflected by the reflector and the image is reflected. There is a problem of lowering the contrast.

In order to improve these problems, a method of using a circularly polarizing plate provided with a λ / 4 retardation film is known for the purpose of preventing reflection of external light on the mirror surface.

The λ / 4 retardation film has characteristics capable of converting linearly polarized light into circularly polarized light and elliptically polarized light, or converting circularly polarized light and elliptically polarized light into linearly polarized light. Such a λ / 4 retardation film Are widely used in various optical applications such as image display devices and optical pickup devices.

It is ideal that the λ / 4 retardation film used in the organic electroluminescence display device substantially gives a retardation of λ / 4 with respect to a wide wavelength range of visible light. It is required that the phase difference imparted to the light has a negative wavelength dispersion (reverse wavelength dispersion) greater than the phase difference imparted to the short wavelength light. However, at present, it is a film that gives a phase difference of ¼ wavelength and exhibits sufficient negative wavelength dispersion (reverse wavelength dispersion), and has a phase difference of λ / 4 for light in a wide wavelength region. It was difficult to obtain a film capable of imparting.

For example, Japanese Patent Laid-Open No. 8-321381 discloses a method of using a circularly polarizing element for preventing external light reflection on a mirror surface. The circularly polarizing element described in the above patent document is formed by laminating an absorption linear polarizing plate and a λ / 4 retardation film so that their optical axes intersect at 45 degrees or 135 degrees. Yes.

Here, when the λ / 4 retardation film is formed of, for example, a single stretched film, the refractive index of the stretched film is different from wavelength to wavelength. Although it can be exactly ¼ wavelength, the phase difference is shifted from the λ / 4 wavelength at other wavelengths, so that it does not function as a λ / 4 retardation film.

That is, for example, when functioning as a λ / 4 retardation film for 550 nm green light, it is difficult to completely prevent reflection of red light having a longer wavelength or blue light having a shorter wavelength. In particular, there is a problem that the phase difference for blue light is large and the reflected color becomes bluish.

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

In response to the above problems, various methods for controlling the phase difference and the wavelength dispersion of the λ / 4 retardation film have been studied in order to satisfy the physical properties in a wide band.

For example, Japanese Patent Laid-Open No. 2-285304 describes a method of laminating uniaxially stretched films having different Abbe numbers, and Japanese Patent No. 0734211 discloses a λ / 2 retardation film using a liquid crystal coating film. A method of laminating a λ / 4 retardation film is disclosed. Japanese Patent Laid-Open No. 2001-194527 discloses a method of blending a polymer having positive and negative intrinsic birefringence, and Japanese Patent No. 345779 discloses a method of copolymerizing a material having positive and negative intrinsic birefringence. Each method for forming a film is disclosed.

On the other hand, in recent years, thinning of display devices has further progressed, and it has been eagerly desired to obtain a broadband λ / 4 characteristic with a thin film and a single-layer film for a λ / 4 retardation film. It has been difficult to sufficiently respond to such a request with the above technique.

As another technique, a method for producing an optical compensation film for a liquid crystal display device by adding a compound having a retardation increasing function to a cellulose ester film having a retardation exhibiting reverse wavelength dispersibility and performing a stretching treatment is known. Yes. However, since the cellulose ester resin is generally a highly isotropic substance, the retardation development property is low, and in order to achieve the retardation necessary for λ / 4, the addition of a compound capable of increasing retardation It was necessary to increase the amount. In that case, in the conventional compound having the retardation increasing ability, the increasing ability and the chromatic dispersion adjusting ability come together, the chromatic dispersion becomes the forward chromatic dispersion, and the chromatic dispersion required for λ / 4 could not be satisfied. is the current situation.

In order to solve the above problem, Patent Document 1 discloses that a retardation film in which a vertically aligned liquid crystal layer is provided on an obliquely stretched cellulose ester film has a λ / 4 retardation in a wide wavelength range. It is disclosed that the provided organic EL display device improves the color variation due to reflection of external light.

However, in the method disclosed in Patent Document 1, since a vertically aligned liquid crystal layer is provided after producing a retardation film, the process is complicated, and further improvement has been desired from the viewpoint of manufacturability. . In addition, the organic EL display device provided with the retardation film has a problem that the image has bleeding and a high-definition image cannot be obtained. This problem is that light that enters the retardation film from the light emitting layer is reflected at the interface between the retardation film and the adjacent layer, and is further diffusely reflected by the additives separated in the retardation film, resulting in image blurring. Is presumed to be the cause.

Patent Document 2 and Patent Document 3 disclose a retardation plate composed of a reverse wavelength dispersive single layer having a retardation value of λ / 4 in the entire wavelength region by containing a compound having a specific structure. ing. However, in the method disclosed above, the actual retardation development is low, and in order to realize the λ / 4 retardation, it is necessary to increase the film thickness. In addition, there is a problem that the light extraction efficiency deteriorates as the transmittance decreases.

Patent Document 4 discloses a retardation plate in which the retardation and reverse wavelength dispersion characteristics are further improved by containing a specific compound. However, since the retardation in the thickness direction is high, the retardation plate is viewed obliquely. Further, there is a problem that the phase difference deviates by more than λ / 4 and the visibility deteriorates.

Further, in Patent Document 5, as a retardation control agent, a low-molecular compound in which the magnitude of the dipole moment in the direction orthogonal to the molecular major axis direction is larger than the magnitude of the dipole moment in the direction parallel to the molecular major axis direction. Including optical films have been proposed. However, the retardation control agent described in Patent Document 5 has low retardation, particularly in-plane retardation, and the film thickness must be increased in order to obtain a desired retardation. Have a problem.

As described above, the retardation development property and the reverse wavelength dispersion property are in a trade-off relationship, and the λ / 4 retardation film has a high retardation development property in a wide wavelength region and exhibits a sufficient reverse wavelength dispersion property. The development of is eagerly desired.

International Publication No. 2009/25170 JP 2008-6602 A JP 2011-75924 A JP 2010-254949 A JP 2007-249180 A

The present invention has been made in view of the above problems, and its solution is high retardation development in a wide wavelength region, excellent reverse wavelength dispersion characteristics in a thin film, low haze and high transparency, A λ / 4 retardation film excellent in light resistance and coloring resistance, a method for producing the same, a circularly polarizing plate using the same, and an organic electroluminescence display device including the circularly polarizing plate and excellent in color stability Is to provide.

As a result of diligent investigation in view of the above problems, the present inventor has obtained a λ / containing a thermoplastic resin and a compound (I) bonded with a linking group having a linking site at least at three positions as a phase difference adjusting agent. In the four phase difference film, the compound (I) includes a linking group and a group linked via the two linking sites, and has a chemical structure moiety X (having a maximum absorption wavelength in a wavelength region of 200 nm or more and less than 280 nm) A main chain) and a chemical structure moiety Y (a structure branched from the chemical structure moiety X (main chain) by a group bonded via at least one of the other linking sites of the linking group. A) chemical structural moiety Y (side chain) of the compound (I) has a maximum absorption wavelength in the wavelength range of 280 to 380 nm, and b) chemical structural moiety X (main chain) Total absorption intensity and total absorption intensity of chemical structure part Y (side chain) And the ratio of Ro (450) / Ro (550) and the value of Ro (550) / Ro (650) are set to a specific range as chromatic dispersion characteristics. The λ / 4 retardation film has high retardation development in a wide wavelength region, excellent reverse wavelength dispersion characteristics in a thin film, low haze, high transparency, light resistance, and excellent coloring resistance. It has been found that a phase difference film can be realized and has reached the present invention.

That is, the above problem of the present invention is solved by the following means.

1. A λ / 4 retardation film containing a thermoplastic resin and a compound (I) bonded with a linking group having a linking site at least at three positions, the linking group in the compound (I) and the two positions A chemical structure moiety X (main chain) having a maximum absorption wavelength in a wavelength region of 200 nm or more and less than 280 nm, and at least one of the other linking sites of the linking group. A group bonded through two linking sites, having a chemical structure portion Y (side chain) having a structure branched from the chemical structure portion X (main chain), wherein the compound (I) comprises the following (a) and (Lambda) / 4 phase difference film characterized by satisfy | filling simultaneously the conditions prescribed | regulated by (b), and satisfy | filling the following chromatic dispersion characteristics (c) and (d) simultaneously.

(A) The chemical structure portion Y (side chain) has a maximum absorption wavelength in a wavelength range of 280 to 380 nm. (B) 25.0 ≧ ΣABS _y / ΣABS _x ≧ 1.01
(C) DSP1; Ro (450) / Ro (550) = 0.72 to 0.96
(D) DSP2; Ro (550) / Ro (650) = 0.83 to 0.98
[In the formula, ΣABS _x represents the total absorption intensity of the chemical structure portion X (main chain) of the compound (I), and ΣABS _y represents the total absorption intensity of the chemical structure portion Y (side chain) of the compound (I). To express. DSP1 and DSP2 each represent the wavelength dispersion characteristic of a λ / 4 retardation film, Ro (450) is an in-plane retardation value for light having a wavelength of 450 nm, and Ro (550) is an in-plane retardation for light having a wavelength of 550 nm. Ro (650) is an in-plane retardation value for light having a wavelength of 650 nm. In addition, each in-plane retardation value is the value measured in the environment of 23 degreeC and 55% RH. ]
2. The λ / 4 retardation film according to item 1, wherein the compound (I) is a compound represented by the following general formula (A).

[Wherein, L ₁ and L ₂ each independently represent a single bond or a divalent linking group. R ₁ , R ₂ and R ₃ each independently represent a substituent. n represents an integer of 0 to 2. Wa and Wb each represent a hydrogen atom or a substituent; (I) Wa and Wb are bonded to each other to form a ring; (II) at least one of Wa and Wb has a ring structure; or (III) Wa and Wb At least one of Wb is an alkenyl group or an alkynyl group. ]
3. The aspect ratio of the compound (I) is less than 1.70, The λ / 4 retardation film according to item 1 or 2,

4. The λ / 4 retardation film according to any one of Items 1 to 3, wherein the thermoplastic resin is a cellulose ester.

5. It is produced by stretching in the slow axis direction and shrinking in the fast axis direction, and the ratio of the shrinkage ratio in the fast axis direction to the stretch ratio in the slow axis direction (shrinkage ratio / stretch ratio) is 0.05. The λ / 4 retardation film according to any one of Items 1 to 4, wherein the λ / 4 retardation film is in a range of ˜0.70.

6. The λ / 4 retardation film according to any one of items 1 to 4, wherein the slow axis direction is oriented within an angle range of 30 to 60 ° with respect to the transport direction. .

7. The first to second aspects, wherein the film feeding direction and the film take-off direction are obliquely crossed, and the slow axis is within an angle range of 30 to 60 ° with respect to the film take-up direction. The λ / 4 retardation film according to any one of items 4 to 4.

8. A method for producing a λ / 4 retardation film for producing the λ / 4 retardation film according to any one of items 1 to 4, wherein the film is stretched in a slow axis direction and is advanced in a fast axis direction. The ratio of the shrinkage ratio in the fast axis direction to the stretch ratio in the fast axis direction (shrinkage ratio / stretch ratio) is in the range of 0.05 to 0.70 through the stretching shrinkage step of shrinking into A method for producing a λ / 4 retardation film, wherein the film is produced by stretching the film.

9. A method for producing a λ / 4 retardation film, which produces the λ / 4 retardation film according to any one of items 1 to 4, wherein a slow axis direction is 30 to A method for producing a λ / 4 retardation film, which is produced under the condition of orientation within an angle range of 60 °.

10. A method for producing a λ / 4 retardation film for producing the λ / 4 retardation film according to any one of items 1 to 4, wherein the film feeding direction and the film take-up in the stretching step A method for producing a λ / 4 retardation film, characterized in that the film is produced under the condition that the direction is oblique and the slow axis is provided within an angle range of 30 to 60 ° with respect to the film take-off direction.

11. A circularly polarizing plate comprising the λ / 4 retardation film according to any one of items 1 to 7 and a polarizer.

12. An organic electroluminescence display device comprising the circularly polarizing plate according to item 11 and an organic electroluminescence element.

It is presumed that the above problem could be solved by the configuration defined in the present invention for the following reason.

In order to solve the above problems, the present inventors have studied a wide range of compounds having various structures by paying attention to the main chain structure of a phase difference adjusting agent that is excellent in retardation increasing effect. The wavelength dispersion characteristics were insufficient. Furthermore, as a result of investigations by changing the types and combinations of substituents constituting the side chain moiety, the compound having a specific absorption peak in the absorption intensity ratio between the main chain structure and the side chain structure is in a specific condition. However, it discovered that it was excellent in the wavelength dispersion characteristic and phase difference expression.

In addition, by producing a film containing such a compound by a specific stretching method and stretching conditions, a λ / 4 retardation film having both retardation and wavelength dispersion characteristics could be obtained.

By the above means of the present invention, λ / 4 position having high retardation development in a wide wavelength region, excellent reverse wavelength dispersion characteristics in a thin film, low haze, high transparency, excellent light resistance and coloring resistance A phase difference film, a method for producing the same, a circularly polarizing plate using the same, and an organic electroluminescence display device having the circularly polarizing plate and having excellent color stability can be provided.

Schematic diagram illustrating the shrinkage ratio in the stretching / shrinking process of stretching in the slow axis direction and contracting in the fast axis direction The schematic diagram which shows an example of the extending | stretching apparatus with which the feed direction of a film applicable to this invention and the take-up direction of a film correspond. The schematic diagram which shows another example of the extending | stretching apparatus with which the feed direction of a film applicable to this invention and the take-up direction of a film correspond. The schematic diagram which shows an example of the extending | stretching apparatus with which the feed direction of a film applicable to this invention and the take-up direction of a film crossed diagonally It is a schematic sectional drawing which shows an example of a structure of the organic electroluminescent element applicable to this invention.

The λ / 4 retardation film of the present invention is a λ / 4 retardation film containing a thermoplastic resin and a compound (I) bonded with a linking group having a linking site at least at three positions, and the compound A chemical structure moiety X (main chain) having a maximum absorption wavelength in a wavelength region of 200 nm or more and less than 280 nm, which includes the linking group in (I) and a group linked via the two linking sites; Among the other linking sites of the group, a group bonded via at least one linking site, and having a chemical structure portion Y (side) having a shorter molecular length than the chemical structure portion X (main chain, hereinafter also referred to as main chain X) The compound (I) satisfies the conditions specified in the above (a) and (b) at the same time, and the wavelength dispersion characteristics satisfy the above (c) and (d) at the same time. It is characterized by the fact that it exhibits phase difference in a wide wavelength range. A λ / 4 retardation film that is high, has a thin film with excellent reverse wavelength dispersion characteristics, low haze, high transparency, and excellent light resistance and coloring resistance can be realized. This feature is a technical feature common to the inventions according to claims 1 to 12.

The chemical structure part X (main chain) and the chemical structure part Y (side chain) in the compound (I) according to the present invention are defined as follows.

That is, in the molecular structure of the compound (I) bonded with a linking group having a linking site at least at three positions, the linking group and a group linked via the two linking sites are included, and the molecular structure is 200 nm or more and less than 280 nm. A chemical structure portion having a maximum absorption wavelength in the wavelength region is defined as a chemical structure portion X (main chain). In many cases, the chemical structure portion X (main chain) is a chemical structure portion constituted by an interatomic distance between atoms having the longest linear distance. Further, the chemical structure portion Y (side chain) is a group that is bonded to at least one linking site among the other linking sites of the linking group and is branched from the chemical structure portion X (main chain). Is defined as a chemical structure portion having a maximum absorption wavelength in the wavelength range of 280 to 380 nm.

As an embodiment of the present invention, it is preferable that the compound (I) is a compound represented by the general formula (A) from the viewpoint that the effect intended by the present invention can be further expressed. Moreover, it is a preferable aspect that the aspect ratio of the said compound (I) is less than 1.70, More preferably, it is the range of 1.01 or more and less than 1.70.

Moreover, it is preferable that the thermoplastic resin is a cellulose ester. Further, the film is produced by stretching in the slow axis direction and shrinking in the fast axis direction, and the ratio of the shrinkage ratio in the fast axis direction to the stretch ratio in the slow axis direction (shrinkage ratio / stretch ratio) is 0. It is preferably within the range of .05 to 0.70. The slow axis direction is preferably oriented within an angle range of 30 to 60 ° with respect to the transport direction. Further, it is preferable that the film feeding direction and the film take-up direction are obliquely crossed and that the slow axis is within an angle range of 30 to 60 ° with respect to the film take-up direction.

The λ / 4 retardation film of the present invention can be produced by a stretching / shrinking process of stretching in the slow axis direction and contracting in the fast axis direction, and then proceeding to the stretch ratio in the slow axis direction. It is produced by stretching under the condition that the ratio of shrinkage ratio in the axial direction (shrinkage ratio / stretching ratio) is in the range of 0.05 to 0.70, and the slow axis direction is 30 to 60 with respect to the conveying direction. The film is manufactured under the condition that the film is oriented within the angle range of °, and the film feeding direction and the film drawing direction in the stretching process are obliquely crossed, and within the angle range of 30 to 60 ° with respect to the film drawing direction. It is preferable to produce them under the condition of providing a slow axis.

The λ / 4 retardation film of the present invention can be suitably included in a circularly polarizing plate and an organic electroluminescence display device.

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

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

In the λ / 4 retardation film of the present invention, Ro (550) measured at a wavelength of 550 nm is preferably in the range of 120 to 180 nm, more preferably in the range of 120 to 160 nm, and 125 to 150 nm. It is particularly preferable that it is within the range.

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

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

In the present invention, the in-plane retardation value Ro is represented by the following formula (i).

Formula (i)
Ro = (n _x −n _y ) × d
Maximum In the above formula (i), _{n x} and _{n y} is, 23 ° C., respectively, were measured under the environment of 55% RH, the refractive index at a wavelength of 450 nm, 550 nm, or 650 nm, _{n x} is the plane of the film the refractive index of the (refractive index in a slow axis direction), n _y is a refractive index in a direction perpendicular to the slow axis in the film plane, d is the film thickness (nm).

In the λ / 4 retardation film of the present invention, the ratio of Ro (450) measured at a wavelength of 450 nm to the in-plane retardation value Ro (550) measured at a wavelength of 550 nm (as defined in the above item (c)) ( DSP1; Ro (450) / Ro (550)) is in the range of 0.72 to 0.96, preferably in the range of 0.75 to 0.92. More preferably, it is within the range of 78 to 0.88.

Further, as defined in the above item (d), the ratio of the in-plane retardation value Ro (550) measured at a wavelength of 550 nm to the in-plane retardation value Ro (650) measured at a wavelength of 650 nm (DSP2; Ro (550) ) / Ro (650)) is in the range of 0.83 to 0.98, but the balance with the value of Ro (450) / Ro (550) is important. When the value of (450) / Ro (550) is in the range of 0.72 to 0.96, the value of Ro (550) / Ro (650) is in the range of 0.87 to 0.98. Preferably, when the value of Ro (450) / Ro (550) is in the range of 0.75 to 0.92, the value of Ro (550) / Ro (650) is 0.88 to 0.00. Preferably within the range of 96, Ro (450) / R If the value of (550) is in the range of from 0.78 to 0.88, the value of Ro (550) / Ro (650) is more preferably in the range of 0.90 to 0.94.

In the case of increasing the in-plane retardation value Ro (550), it is a simple means to increase the film thickness d, but light extraction due to a decrease in economic efficiency, an increase in the thickness of the image display device, and a decrease in transmittance. It is not preferable from the viewpoint of efficiency reduction.

In the λ / 4 retardation film of the present invention, the film thickness d is generally within the range of 30 to 150 μm, preferably within the range of 40 to 100 μm, and preferably within the range of 50 to 75 μm. It is particularly preferable from the viewpoint of further manifesting the effects of the invention.

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

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

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

[Phase difference adjusting agent: Compound (I)]
In the λ / 4 retardation film of the present invention, the compound (I) according to the present invention is a compound bonded with a linking group having a linking site in at least three places, and the linking group and the two linking sites. A chemical structure moiety X (main chain) having a maximum absorption wavelength in a wavelength region of 200 nm or more and less than 280 nm, and at least one linking site among the other linking sites of the linking group. And a chemical structure portion Y (side chain) having a structure branched from the chemical structure portion X (main chain), and the conditions specified in the following (a) and (b): It is characterized by satisfying at the same time.

As the first condition,
(A) The chemical structure part Y (side chain) part constituting the compound (I) has a maximum absorption wavelength in a wavelength range of 280 to 380 nm.

The compound (I) having a main chain and a side chain according to the present invention has at least two maximum absorption wavelengths in the ultraviolet absorption region in a state dissolved in a solvent, and the maximum absorption wavelength λmax _x on the shorter wavelength side is Spectral absorption characteristics belonging to the main chain X of the compound (I), having a maximum absorption wavelength in a wavelength range of 200 nm or more and less than 280 nm, and the maximum absorption wavelength λmax _y on the longer wave side is the side chain Y of the compound (I) Spectral absorption characteristics belonging to In the present invention, the maximum absorption wavelength λmax _y on the long wave side belonging to the side chain Y is in the wavelength range of 280 to 380 nm.

The second condition is
(B) The total absorption intensity attributed to the chemical structure part X (main chain) of the compound (I) is ΣABS _x, and the total absorption intensity attributed to the chemical structure part Y (side chain) of the compound (I) is ΣABS _y The value of the absorption intensity ratio (ΣABS _y / ΣABS _x ) between ΣABS _x and ΣABS _y is in the range of 1.01 to 25.0.

ShigumaABS _y total absorption intensity attributed the total absorption intensity attributable to the chemical structure moiety X (main chain) of the present invention to ShigumaABS _x and chemical structure moiety Y (side chain) can be measured according to the following procedure .

Compound (I) according to the present invention is dissolved in tetrahydrofuran (without stabilizer) at a concentration of 10 ⁻⁴ mol / L to prepare a compound (I) solution.

The prepared compound (I) solution is put in a quartz cell (10 mm long square cell), and an ultraviolet-visible infrared spectrophotometer (U-570, manufactured by JASCO Corporation) is used to measure the wavelength range of the compound (I) solution. The absorbance (solution absorption spectrum) in the range of 200 to 380 nm is measured.

Among the obtained absorption spectra of the solution, the maximum absorption wavelength on the long wavelength side belonging to the chemical structure portion Y (side chain) in the absorption spectrum in the wavelength region of 200 to 380 nm is expressed as λmax _y And the absorbance at λmax _y is determined as the total absorption intensity ΣABS _y attributed to the chemical structure portion Y (side chain). Similarly, the wavelength of the maximum absorption on the short wavelength side belonging to the chemical structure portion X (main chain) is λmax _x, and the absorbance at λmax _x is measured as the total absorption intensity ΣABS _x belonging to the chemical structure portion X (main chain). To do. Next, the value of the absorption intensity ratio (ΣABS _y / ΣABS _x ) is calculated from each obtained measurement value.

The main chain X and the side chain Y of the compound (I) according to the present invention can be defined by measurement by the above-described method. In many compounds (I), a λ / 4 retardation film described later is used. In many cases, the orientation is such that the direction of the slow axis of the compound coincides with the direction of the main chain X of the compound (I).

In the compound (I) according to the present invention, the aspect ratio is preferably less than 1.70, more preferably 1.01 or more and less than 1.70.

With respect to the aspect ratio of the compound (I) in the present invention, Winstar MOPAC AM1 (MOP6W70) (Senda, “Development of molecular computing support system Winmostar”, Idemitsu Technical Report, 49, 1, 106-111 (2006)) is used. This is the calculated value.

In the present invention, the aspect ratio is the molecular length / molecular width, and the molecular length is a value obtained by adding the van der Waals radii of two atoms at both ends to the maximum interatomic distance in the compound, and the molecular width is This is a value obtained by adding the van der Waals radii of two atoms at both ends to the maximum interatomic distance when each atom is projected onto a plane perpendicular to the molecular long axis.

In the present invention, by selecting the compound (I) having an aspect ratio of less than 1.70, it becomes anisotropic to the thermoplastic resin, and the effect of increasing the reverse wavelength dispersibility is easily obtained. The retardation development required for the retardation film can be achieved.

The compound (I) according to the present invention is not particularly limited as long as it simultaneously satisfies the conditions (a) and (b) specified above, but is represented by the following general formula (A) and the condition (a It is preferable that the compound satisfies the conditions specified in (b) and (b) at the same time.

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

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

In the general formula (A), L ₁ and L ₂ each independently represent a single bond or a divalent linking group. Examples of the divalent linking group include an alkylene group, an alkenylene group, an alkynylene group, O, and (C = O), (C═O) —O, NR, S, and (C═O) —NR (R has the same meaning as R ₁ , R _2, and R ₃ described later). L ₁ and L ₂ are preferably O, (C═O) —O, or O (C═O).

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

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

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

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

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

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

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

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

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

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

Specific examples of compound (I) according to the present invention are shown below, but compound (I) that can be used in the present invention is not limited by the following specific examples.

The content of the compound (I) according to the present invention in the λ / 4 retardation film is preferably in the range of 0.01 to 30% by mass, more preferably 1.0 to 20% by mass. Within range.

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

〔Thermoplastic resin〕
The λ / 4 retardation film of the present invention is configured using a thermoplastic resin as a matrix resin. Although there is no restriction | limiting in particular as a thermoplastic resin, Cellulose ester resin (cellulose acetate, cellulose acylate, etc.), a polycarbonate-type resin, and a cycloolefin type resin are preferable, and it is preferable that especially a main component is a cellulose ester resin. The “main component” in the present invention means that 60% by mass or more of the thermoplastic resin component constituting the λ / 4 retardation film is composed of a cellulose ester.

By adopting the above configuration, retardation development is high, and as a result, even when a retardation film having a high retardation is obtained, a thin film can be formed. It has excellent visibility and durability when stored under a long period of time, and excellent saponification suitability.

(Cellulose ester resin)
One of the cellulose ester resins applicable to the present invention is cellulose acetate. The cellulose acetate preferably has an average degree of acetyl group substitution of 2.00 or more, more preferably in the range of 2.00 to 2.95, and further in the range of 2.20 to 2.90. preferable. The average acetyl group average substitution degree here means the average number of esterified (acetylated) hydroxy groups (hydroxyl groups) among the three hydroxy groups (hydroxyl groups) of each anhydroglucose constituting the cellulose. Value, a value in the range of 0 to 3.0.

If the average degree of acetyl group substitution of cellulose acetate is 2.0 or more, it is possible to suppress the occurrence of deterioration in film surface quality due to an increase in dope viscosity and haze increase due to an increase in stretching tension.

In the present invention, the portion not substituted with an acetyl group is usually present as a hydroxy group (hydroxyl group). These can be synthesized by known methods.

The degree of substitution of the acetyl group was determined according to the method prescribed in ASTM-D817-96 (test method for cellulose acetate etc.).

The number average molecular weight (Mn) of the cellulose acetate according to the present invention is preferably in the range of 30,000 to 300,000 because the mechanical strength of the resulting film is strong. Further, it is preferably in the range of 50,000 to 200,000.

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

The weight average molecular weight Mw and number average molecular weight Mn of cellulose acetate can be determined by measurement using gel permeation chromatography (GPC).

The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
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: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 1000,000 to 500, a calibration curve with 13 samples was used. Thirteen samples are used at approximately equal intervals.

The cellulose which is a raw material of the cellulose acetate according to the present invention is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

The cellulose acetate according to the present invention 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 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 acetate having a desired degree of acetyl group substitution can be synthesized by hydrolyzing the triester of cellulose. Thereafter, cellulose acetate can be obtained through steps such as filtration, precipitation, washing with water, dehydration, and drying.

Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

In the λ / 4 retardation film of the present invention, the retardation development property is high, and even if it is a retardation film having a high retardation, it can be made into a thin film, and even if a high retardation is exhibited, the draw ratio Cellulose acylate other than the above-mentioned cellulose acetate can be applied as the cellulose ester resin from the standpoint that the failure can be avoided and failure such as breakage can be avoided, and the total acyl group substitution degree of the cellulose acylate can be reduced. One preferred embodiment is to use a film having an average value of 1.00 or more and 3.00 or less.

In addition, from the viewpoint of improving hydrophobicity while maintaining moisture permeability, the average value of the degree of substitution of acyl groups having 3 or more carbon atoms is preferably in the range of 0.50 to 2.50.

The method for measuring the degree of acyl group substitution defined in the present invention can be carried out in accordance with ASTM D-817-91. The average value of the total acyl group substitution degree is preferably in the range of 1.00 to 3.00, more preferably in the range of 2.00 to 2.90, and particularly preferably 2.40. Within the range of ~ 2.75. Further, the average substitution degree of acyl groups having 3 or more carbon atoms is preferably in the range of 0.50 to 2.50, more preferably in the range of 0.80 to 2.00, Particularly preferably, it is within the range of 1.00 to 1.70.

If the total acyl group substitution degree of cellulose acylate is 1.0 or more, the film is not damaged by the alkali saponification treatment at the time of forming the circularly polarizing plate, and can function as a protective film. The upper limit of the total acyl group substitution degree of cellulose acylate is determined to be 3.0.

When the acyl group substitution degree of 3 or more carbon atoms of cellulose acylate is 0.50 or more, the λ / 4 plate can be imparted with hydrophobicity, and the effect of improving the durability of the light emitting device according to the present invention can be obtained. If it can be obtained and it is 2.50 or less, the adhesiveness with the polarizer becomes good, and the production of the polarizing plate becomes easy.

From the viewpoint of suitability for saponification, the acyl group having 3 or more carbon atoms is preferably a propionyl group.

The number average molecular weight (Mn) of the cellulose acylate is preferably in the range of 30000 to 300000, since the mechanical strength of the resulting film is strong. Further, those within the range of 50,000 to 200,000 are preferably used.

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

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

The cellulose acylate including the cellulose acetate according to the present invention can be obtained by acylating a cellulose raw material. For example, when the acylating agent is an acid anhydride (for example, acetic anhydride, propionic anhydride, butyric anhydride, etc.), an organic acid such as acetic acid or an organic solvent such as methylene chloride is used. Synthesize using a protic catalyst. Further, for example, when the acylating agent is acid chloride (for example, CH ₃ COCl, C ₂ H ₅ COCl, C ₃ H ₇ COCl, etc.), the reaction is carried out using a basic compound such as amine as a catalyst. Done.

The cellulose acylate applicable to the present invention can be produced by a known method. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

The cellulose used as a raw material for the cellulose resin is not particularly limited, and examples thereof include cotton linter, wood pulp (for example, derived from coniferous tree, derived from broadleaf tree), kenaf and the like. Moreover, the cellulose acylate obtained from them can be mixed and used in arbitrary ratios, respectively.

Specific cellulose acylates include cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate propionate butyrate or cellulose acetate phthalate as well as propionate group, butyrate group or phthalyl group. A mixed fatty acid ester of cellulose to which is bound can be used. The butyryl group forming butyrate may be linear or branched.

As the cellulose acylate preferably used in the present invention, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate are particularly preferably used. Of these, cellulose acetate propionate is most preferred.

Also, in order to obtain optical properties that meet the purpose, resins having different degrees of substitution may be mixed and used. The mixing ratio is preferably in the range of 10:90 to 90:10 (mass ratio).

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

As used herein, the term “thermoplastic resin” refers to a resin that has the characteristics that it becomes soft when heated to the glass transition temperature (Tg) or melting point and can be molded into the desired shape.

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

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

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

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

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

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

When these organic solvents are used for cellulose esters, a dissolution method at normal temperature can be used, but a known dissolution method such as a high-temperature dissolution method, a cooling dissolution method, or a high-pressure dissolution method may be used. From the viewpoint of reducing the amount of insoluble matter. Although methylene chloride can be used for the cellulose ester, it is preferable to use methyl acetate, ethyl acetate, or acetone, and among them, methyl acetate is particularly preferable.

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

The dope used for forming the λ / 4 retardation film of the present invention preferably contains an alcohol having 1 to 4 carbon atoms in the range of 1 to 40% by mass in addition to the organic solvent. . These alcohols, after casting the dope on a metal support, start to evaporate the organic solvent, and when the relative proportion of the alcohol component increases, the dope film (web) gels, making the web strong and supporting the metal It can act as a gelling solvent that makes it easy to peel off from the body, and when the proportion of these alcohols is low, it also has a role of promoting dissolution of the cellulose ester of the 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 do not have solubility in cellulose esters by themselves.

The concentration of cellulose ester in the dope is preferably in the range of 15 to 30% by mass, and the dope viscosity is adjusted in the range of 100 to 500 Pa · s, from the viewpoint that excellent film surface quality can be obtained. To preferred.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

(Sugar ester compound)
In the λ / 4 retardation film of the present invention, it is preferable to contain a sugar ester compound as a phase solvent, and as a sugar ester compound. Examples of the sugar ester compound, which is an ester compound excluding cellulose ester, having at least one pyranose structure or furanose structure in the range of 1 to 12 and in which part or all of the hydroxy groups of the structure are esterified be able to.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Next, a specific method for producing the λ / 4 retardation film of the present invention will be described with reference to the drawings.

One of the methods for producing a λ / 4 retardation film of the present invention includes a stretching / shrinking step of stretching in the slow axis direction and shrinking in the fast axis direction, and then proceeding with respect to the stretch ratio in the slow axis direction. It is characterized by being manufactured by stretching under the condition that the ratio of shrinkage ratio in the phase axis direction (shrinkage ratio / stretch ratio) is in the range of 0.05 to 0.70.

In the λ / 4 retardation film of the present invention, in particular, the film is stretched in the direction in which the slow axis is to be generated and contracted in the vertical direction (fast axis direction), and the ratio of the shrinkage rate to the stretching ratio is controlled. Thus, the orientation direction of the main axis X of the compound (I) is controlled so that the main chain X direction of the compound (I) according to the present invention coincides with the main axis direction (stretching direction, slow axis direction) of the cellulose ester. It is preferable to do.

That is, as the ratio of the draw ratio in the slow axis direction (width direction) and the shrinkage ratio in the direction perpendicular to the slow axis direction (fast axis direction), the shrinkage ratio / stretch ratio = 0.05. The preferred embodiment is in the range of ˜0.70, but the most preferred is in the range of 0.10 to 0.30. In this range, the main chain X of the compound (I) is changed to If the side chain Y of the compound (I) is oriented in the film fast axis direction and contains a high refractive index molecule in the side chain, the refractive index in the fast axis direction in the ultraviolet region of 280 nm it is possible to increase the n y _(280), it can be a steep slope of n _y order chromatic dispersion in the visible light region.

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

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

FIG. 1 is a schematic diagram for explaining a shrinkage ratio in oblique stretching in a stretching / shrinking process in which stretching in the slow axis direction and shrinking in the fast axis direction.

In Figure 1, when the oblique stretching 112 cellulose ester film F, the major axis M ₁ in the conveying direction, contracts in M ₂ by oblique bending. At this time, the shrinkage rate (%) is
Shrinkage rate (%) = (M ₁ −M ₂ ) / M ₁ × 100
It is represented by

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

1, 111 is the stretching direction (TD direction), 113 is the transport direction (MD direction), and 114 is the slow axis.

As a method for controlling the orientation of the compound (I), the slow axis of the λ / 4 retardation film is preferably in the range of 30 to 60 ° with respect to the transport direction. It is preferably in the range of ˜50%.

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

(Stretching with an oblique stretching tenter)
Next, the oblique stretching method will be described.

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

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

As one aspect of the method for producing a λ / 4 retardation film of the present invention, the method for producing a λ / 4 retardation film is such that the slow axis direction is oriented within an angle range of 30 to 60 ° with respect to the conveying direction. It manufactures on the conditions to do.

FIG. 2A and FIG. 2B are schematic views showing an example of an oblique stretching apparatus in which a film feeding direction and a film drawing direction applicable to the present invention match.

In FIG. 2A, a pair of left and right grips gripping both ends of the film at the entrance of the tenter run at the same speed on the left and right rails in a zone where the distance between the left and right rails is constant in the initial stage of the tenter, and thereafter In the zone where the distance between the rails is increased, the vehicle travels on the left and right rails at different speeds, and then travels on the left and right rails at a constant speed again in the zone where the distance between the left and right rails is equal.

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

The long original film 4 whose direction is controlled by the guide roller 12-1 on the tenter entrance side 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. The 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 referred to as the high speed side gripping tool) is the same as the right side gripping tool (hereinafter referred to as the low speed side gripping). At a point 11-3 where the left and right rails have finished widening and the left and right rails have finished widening, the high speed side gripping tool is again equal to the low speed side gripping tool. 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 also a schematic view of a diagonally stretched tenter in which the film feeding direction and the film take-up direction applicable to the present invention are the same.

A pair of left and right grips that grip both ends of the film at the entrance of the tenter 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 tenter.

The tenter shown in FIG. 2B is a tenter having a portion where the distance between the left and right rails is widened. A pair of left and right grips grip the film at the tenter 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 release point 9-2 at the tenter outlet, the paired low-speed side clips are positioned at 11-1, so The film held by the holding tool is stretched obliquely.

The tenter shown in FIG. 2B is a tenter having a portion where the distance between the left and right rails is widened, but does not necessarily have a portion where the distance between the left and right rails is widened.

In FIGS. 2A and 2B, the traveling speed of the gripper can be selected as appropriate, but is usually 1 to 100 m / min. In addition, the fact that the pair of left and right film grippers travel at different speeds means that the difference in travel speed between the pair of left and right grippers substantially exceeds 1% of the travel speed.

The difference in travel speed between the pair of left and right gripping tools is preferably in the range of more than 1% and less than 50%, more preferably in the range of more than 1% and less than 30% of the travel speed. More preferably within the range of more than 1% and not more than 10% of the speed.

Further, in the oblique stretching apparatus shown in FIGS. 2A and 2B, a known one can be used as long as it is a tenter having a mechanism that changes the traveling speed of the gripping tool in the middle of the tenter.

In general tenter devices, etc., there are speed irregularities that occur in the order of seconds or less depending on the period of the sprocket teeth that drive the chain, the frequency of the drive motor, etc. This does not correspond to the difference in travel speed referred to in the present invention.

In addition, as one aspect of the method for producing a λ / 4 retardation film of the present invention, the film feeding direction and the film take-up direction in the stretching process are obliquely crossed, and 30 with respect to the film take-up direction. The production is characterized in that the slow axis is provided within an angle range of from 60 ° to 60 °.

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

In FIG. 3, the long film original 4 whose direction is controlled by the guide roller 12-1 on the tenter entrance side is the film at the positions of the outer film holding start point 8-1 and the inner film holding start point 8-2. It is gripped by a gripping tool.

The pair of left and right film grippers are transported and stretched at the same speed in the diagonal direction indicated by the outer film gripping means trajectory 7-1 and the inner film gripping means trajectory 7-2 by the oblique stretching tenter 6. The gripping is released by the outer film gripping end point 9-1 and the inner film gripping end point 9-2, and the conveyance is controlled by the guide roller 12-2 on the tenter outlet side, whereby the obliquely stretched film 5 is formed. In the drawing, the long film original is obliquely stretched at an angle (feeding angle θi) in the film stretching direction 14-2 with respect to the film feeding direction 14-1.

In FIG. 3, the traveling speed of the film gripper can be selected as appropriate, but is usually 1 to 100 m / min. The pair of left and right film grippers having the same speed means that the travel speed of the pair of left and right grippers is substantially 1% or less of the travel speed.

In the obliquely stretched tenter used in the present invention, in particular, as shown in FIG. 3, a large bending rate is often required for the rail that regulates the locus of the gripping tool inside the tenter. In order to avoid interference between gripping tools due to sudden bending or local stress concentration, it is desirable that the trajectory of the gripping tool draws an arc at the bent portion.

In the oblique stretching tenter shown in FIGS. 2A and 2B, the traveling direction 14-1 at the tenter entrance of the long film original is different from the traveling direction 14-2 at the tenter exit side of the stretched film. . The feeding angle θi is an angle formed by the traveling direction 14-1 at the tenter entrance and the traveling direction 14-2 on the tenter exit side of the stretched film.

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

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

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

In the embodiment of the present invention, the tenter gripping tool is configured to travel at a constant speed with a constant interval from the front and rear gripping tools.

The traveling speed of the gripping tool can be selected as appropriate, but is usually 1 to 100 m / min. The difference in travel speed between the pair of left and right grippers is usually 1% or less, preferably 0.5% or less, more preferably 0.1% or less of the travel speed. This is because if there is a difference in the traveling speed between the left and right sides of the film at the exit of the stretching process, wrinkles and shifts will occur at the exit of the stretching process, so the speed difference between the right and left gripping tools is required to be substantially the same speed. Because.

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

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

For pelletization, a known method can be applied. For example, dry cellulose ester, plasticizer, and other additives are fed to an extruder with a feeder, kneaded using a single-screw 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. In addition, in order to mix a small amount of additives, such as microparticles | fine-particles and antioxidant, uniformly, the method of mixing in advance is preferable.

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

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

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

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

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

In addition, the film obtained as described above is subjected to stretching and shrinking treatment by the stretching operation after passing through the step of contacting the cooling roller.

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

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

[Characteristics of λ / 4 retardation film]
(Film specification)
The film thickness of the λ / 4 retardation film of the present invention is not particularly limited, but can be used in the range of 10 to 250 μm, preferably in the range of 20 to 100 μm, more preferably in the range of 40 to 80 μm. It is within the range, and particularly preferably within the range of 40 to 65 μm.

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

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

(Dimensional change rate)
When the λ / 4 retardation film of the present invention is provided in the organic electroluminescence display device of the present invention, unevenness and retardation values caused by dimensional changes due to moisture absorption in a high humidity environment, for example, From the viewpoint of suppressing the occurrence of problems such as a change in image quality and a decrease in contrast and color unevenness, the dimensional change rate (%) of the λ / 4 retardation film of the present invention is preferably less than 0.5%. , Preferably less than 0.3%.

(Fault tolerance)
In the λ / 4 retardation film of the present invention, it is preferable that there are few failures in the film (hereinafter also referred to as defects). The failure mentioned here refers to a cavity failure (foaming defect) in the film caused by the rapid evaporation of the solvent in the drying process in film formation by the solution casting method, foreign matter in the film-forming stock solution and production. A foreign matter failure (foreign matter defect) in the film caused by foreign matter mixed in the film.

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

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

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

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

If the number of defects is 1/10 cm square or less, for example, even when tension is applied to the film during processing in the subsequent process, the probability of the film starting to break and the film breaking can be reduced, resulting in high productivity. Can be maintained. Moreover, if the diameter of a fault is 5 micrometers or less, it will not be visually recognized by polarizing plate observation etc., but when it uses as an optical member, a bright spot will not arise.

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

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

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

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

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

In the circularly polarizing plate of the present invention, the polarizer is preferably sandwiched between the λ / 4 retardation film of the present invention and a protective film, and a cured layer is laminated on the viewing side of the protective film. It is more preferable because it has an effect of preventing the polarizing plate from warping.

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

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

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

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

Generally, in an organic EL display device, a metal electrode, an organic light emitting layer, and a transparent electrode are sequentially laminated on a transparent substrate to form 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 or the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Or a structure having various combinations such as a laminate of such a light-emitting layer and an electron injection layer made of a perylene derivative, or a laminate of these hole injection layer, light-emitting layer, and electron injection layer. Are known.

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

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

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

In the organic EL display device having such a configuration, the organic light emitting layer is formed of an extremely thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, the light incident from the surface of the transparent substrate when not emitting light, transmitted through the transparent electrode and the organic light emitting layer, and reflected by the metal electrode is radiated again to the surface side of the transparent substrate. When the display surface of the organic EL display device is observed as a mirror surface.

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

Since the retardation plate and the polarizing plate have a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization action. In particular, if the retardation plate is composed of a ¼ retardation film and the angle formed by the polarization direction of the polarizing plate and the retardation plate is adjusted to π / 4, the mirror surface of the metal electrode can be completely shielded. it can.

That is, the external light incident on the organic EL display device is transmitted only by the linearly polarized light component by the polarizing plate, and this linearly polarized light is generally elliptically polarized light by the phase difference plate. In particular, the phase difference plate has a λ / 4 position. When the angle formed by the polarization direction of the polarizing plate and the retardation plate is π / 4, it is circularly polarized.

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

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

<< Production of λ / 4 retardation film >>
[Production of λ / 4 Retardation Film 1]
(Preparation of fine particle dispersion)
Fine particles (Aerosil R812, primary particle size: about 7 nm, made by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above is stirred and mixed with a dissolver for 50 minutes, and then dispersed using a high-pressure disperser Manton Gorin disperser To prepare a fine particle dispersion.

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

(Preparation of dope 1)
First, methylene chloride and ethanol shown below were added to the pressure dissolution tank. The following cellulose ester having an acetyl group substitution degree of 2.45 was added to a pressurized dissolution tank containing an organic solvent while stirring. This was completely dissolved while being heated and stirred, and this was dissolved in Azumi filter paper No. 1 manufactured by Azumi Filter Paper Co., Ltd. The main dope was prepared by filtration using 244.

Subsequently, the exemplified compound (I-2), the sugar ester compound (benzyl saccharose having an average substitution degree of 7.3) as the compound (I) and the fine particle addition liquid prepared as described above were charged into the main dissolution vessel at the following ratio and sealed. Then, the dope 1 was prepared by dissolving with stirring.

<Composition of dope 1>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose ester (CE-1, acetyl group substitution degree: 2.45, propionyl group substitution degree: 0, weight average molecular weight about 220,000) 100 parts by mass Compound (I): Exemplified compound ( I-2) (λmax _{y of} side chain = 355 nm, ΣABS _y / ΣABS _x = 1.15, aspect ratio (AR) = 1.37)
5 parts by mass Sugar ester compound (benzyl saccharose with an average substitution degree of 7.3)
10 parts by mass Particulate additive liquid 1 2 parts by mass (film formation)
The prepared dope 1 is cast on a stainless steel belt support, and after the solvent is evaporated until the residual solvent amount in the film reaches 75% by mass, the film is peeled at a peeling tension of 130 N / m. Then, it was peeled from the stainless steel belt support.

<Extension process>
Next, the peeled film was stretched according to the stretching method described in FIG. Using a tenter while heating the peeled film at 185 ° C., the film was uniaxially stretched only in the width direction 11 (TD direction) at a stretch ratio of 100%, and then contracted 27% in the transport direction 13 (MD direction). It was. The residual solvent at the start of stretching was 15% by mass.

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

As described above, a roll-like λ / 4 retardation film 1 having a dry film thickness of 60 μm was obtained. The orientation angle of the λ / 4 retardation film 1 was 0 °.

[Production of λ / 4 retardation films 2 to 24]
In the production of the λ / 4 retardation film 1, the type of cellulose ester (acetyl group substitution degree, propionyl group substitution degree), the compound (I) according to the present invention as a phase difference adjusting agent, and the kind and addition amount of the comparative compound. Λ / 4 retardation films 2 to 24 were produced in the same manner except that the stretching conditions (details are described in Table 2) and the film thicknesses were changed to the combinations shown in Table 1, respectively.

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

The orientation angle was also measured using an Axoscan made by Axometrcs.

The film thickness was measured using a commercially available micrometer.

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

Table 2 shows details of each stretching condition described in abbreviations in Table 1.

In the stretching conditions shown in Table 2, the condition (I) is the stretching method according to claim 4 and claim 7, and is stretched 100% in the slow axis direction and stretched in the fast axis direction by the method shown in FIG. The film shrinks under the condition of 27%, and the ratio of the shrinkage ratio in the fast axis direction to the stretch ratio in the fast axis direction (shrinkage ratio / stretch ratio) is 0.27.

The condition (II) is a stretching method according to claims 6 and 9, wherein the film feeding direction and the film take-off direction are obliquely crossed as shown in FIG. This method has a slow axis at °. In addition, the condition (III) is the stretching method according to claim 5 and claim 8, and the method shown in FIGS. 2A and 2B, the film feeding direction and the film take-up direction are the same, This is a method of obliquely stretching with a speed difference. Condition (IV) is a method in which uniaxial stretching is performed only in the MD direction (film transport direction) by the method described in JP-A-2007-197508 without performing oblique stretching.

The orientation angles shown in Table 2 are displayed with reference to the TD direction (width direction).

<< Production of circularly polarizing plates 101 to 124 >>
A 120 μm-thick polyvinyl alcohol film was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times).

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

The polarizer was bonded to one side of the produced λ / 4 retardation films 101 to 124 using a completely saponified polyvinyl alcohol 5% aqueous solution as an adhesive. At that time, bonding was performed such that the transmission axis of the polarizer and the slow axis of the λ / 4 retardation film were 45 degrees. The following protective film 1 is similarly alkali saponified and bonded to the other surface of the polarizer, and circularly polarizing plates 101 to 124 composed of a λ / 4 retardation film, a polarizer and a protective film are formed. Produced.

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

<Preparation of dope A>
Cellulose ester (acetyl group substitution degree 2.88, weight average molecular weight: about 180,000) 90 parts by mass Ester compound 1 10 parts by mass Tinuvin 928 (manufactured by BASF Japan Ltd.) 2.5 parts by mass Fine particle additive solution 1 (supra) ) 4 parts by mass Methylene chloride 432 parts by mass Ethanol 38 parts by mass The above constituent materials were charged into a sealed container and completely dissolved while being heated and stirred, and Azumi Filter Paper No. Azumi Filter Paper No. 24 and filtered to prepare Dope A.

(Film formation)
Next, the dope A was uniformly cast on a stainless steel band support using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the residual solvent amount reached 100%, and the stainless steel band support was peeled off. The cellulose ester film web was evaporated at 35 ° C., slit to 1.65 m width, and 30% in the TD direction (film width direction) with a tenter while applying heat at 160 ° C. (stretch ratio: 1.30). The draw ratio in the MD direction was 1% (stretch ratio: 1.01). The residual solvent amount at the start of stretching was 20%. After drying for 15 minutes while transporting the inside of a drying device at 120 ° C. with many rollers, slitting to 1.49 m width, applying a knurling process with a width of 15 mm and a height of 10 μm at both ends of the film, and winding it around the core The protective film 1 was obtained. The residual solvent amount of the protective film 1 was 0.2%, the film thickness was 40 μm, and the winding length was 3900 m.

The orientation angle θ of the protective film 1 was measured using KOBRA-21ADH manufactured by Oji Scientific Instruments, and as a result, it was in the range of 90 ° ± 1 ° with respect to the 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 having the structure shown in FIG. 4 was produced according to the following method.

As shown in FIG. 4, a reflective electrode made of chromium was formed by vapor deposition on a glass transparent substrate 1a, and ITO was formed as a metal electrode 2a (anode) by vapor deposition on the formed reflective electrode. Next, poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT: PSS) was formed as a hole transport layer on the anode with a thickness of 80 nm by a sputtering method.

Next, using a shadow mask on the hole transport layer, as shown in FIG. 6, RGB light emitting layers 3aR, 3aG, and 3aB were formed with a layer thickness of 100 nm.

The red light emitting layer 3aR includes tris (8-hydroxyquinolinate) aluminum (Alq ₃ ) as a host compound and [4- (dicyanomethylene) -2-methyl-6 (p-dimethylaminostyryl) -4H-pyran as a light emitting compound. (DCM) were co-evaporated (mass ratio 99: 1) to form a thickness of 100 nm.

The green light emitting layer 3aG was formed to a thickness of 100 nm by co-evaporating Alq ₃ as a host compound and coumarin 6 as a light emitting compound (mass ratio 99: 1).

The blue light emitting layer 3aB was formed to have a thickness of 100 nm by co-evaporation (mass ratio 90:10) of the following BAlq as a host compound and Perylene as a light emitting compound.

Further, as a first cathode having a low work function so that electrons can be efficiently injected, calcium is deposited in a thickness of 4 nm on the light emitting layer by a vacuum deposition method, and a second cathode is formed on the first cathode. Aluminum was formed with a thickness of 2 nm as a cathode. Here, when the transparent electrode 4a (transparent conductive film) formed on the aluminum used as the second cathode is formed by sputtering, the calcium serving as the first cathode is chemically altered. There is a role to prevent this. The organic light emitting layer and each cathode were formed as described above.

Next, a transparent conductive film (transparent electrode) was formed with a thickness of 80 nm on the cathode by sputtering. Here, ITO was used as the transparent conductive film. Furthermore, 200 nm of silicon nitride was formed on the transparent conductive film by a CVD method, whereby the organic EL element 11a was manufactured by using the insulating film 5a.

<< Production of organic EL display device >>
After the adhesive is applied to the surface of the λ / 4 retardation film of each of the circular polarizing plates prepared above, the organic EL display devices 101 to 124 are manufactured by pasting on the viewing side of the organic EL element prepared above. did.

<< Evaluation of λ / 4 retardation film and organic EL display >>
[Evaluation of λ / 4 retardation film]
The following evaluation was performed on the produced λ / 4 retardation film.

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

First, blank haze 1 (external haze value) of a measuring instrument other than the retardation film was measured.

1) One drop (0.05 ml) of glycerin was dropped on a clean glass slide, taking care not to enter air bubbles.

2) A cover glass was placed thereon, and glycerin was spread over the entire surface of the cover glass.

3) Set to the following haze meter and measure blank haze 1 (external haze value).

Then, haze 2 (total haze value) including the retardation film was measured by the following procedure.

4) 0.05 ml of glycerin was dropped on the slide glass.

5) The retardation film to be measured was placed thereon so that no bubbles would enter.

6) 0.05 ml of glycerin was dropped on the retardation film.

7) A cover glass was placed thereon.

8) The laminate produced as described above (from above, cover glass / glycerin / retardation film / glycerin / slide glass) was set on a haze meter, and haze 2 was measured.

9) The internal haze value was obtained from the following formula. (Haze 2) − (Haze 1) = (Internal haze value of retardation film)
The internal haze was measured in a 23 ° C. and 55% RH environment using a retardation film conditioned for 5 hours or more in a 23 ° C. and 55% RH environment.

Moreover, the haze meter, glass, and glycerin used in the above measurement are as follows.

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

Glass slide: MICRO SLIDE GLASS S9213 MATUNAMI
Cover glass: Matsunami cover glass 24 × 50mm (KN33221827)
Glycerin: Kanto Chemical deer special grade (purity> 99.0%), refractive index 1.47
Based on each measured internal haze, the scattering resistance of each retardation film was evaluated according to the following criteria.

◎: Internal haze value is less than 0.015 ○: Internal haze value is 0.015 or more and less than 0.040 Δ: Internal haze value is 0.040 or more and less than 0.060 × : Internal haze value is 0.060 or more (light resistance evaluation)
Each of the prepared retardation films was irradiated with ultraviolet rays continuously for 200 hours with a light resistance tester (eye super UV tester, manufactured by Iwasaki Electric Co., Ltd.) in an environment of 23 ° C. and 55% RH.

Next, the spectral transmittance T ₁ (%) of the retardation film before ultraviolet treatment and the spectral transmittance T ₂ (%) of the retardation film after ultraviolet irradiation were measured for the spectral transmittance at a wavelength of 550 nm, and T ₁ The reduction width ΔT (%) of the transmittance of T ₂ with respect to the film was obtained, and the light resistance was evaluated according to the following criteria.

The spectral transmittance was measured using a spectrophotometer U-3400 (manufactured by Hitachi, Ltd.), and from a spectral transmittance τ (λ) profile obtained every 10 nm in a wavelength region of 350 to 700 nm, a wavelength of 550 nm. The transmittance was determined.

○: The transmittance decrease width ΔT is less than 5%. Δ: The transmittance decrease width ΔT is 5% or more and less than 10%. X: The transmittance decrease width ΔT is 10% or more. Evaluation of coloring characteristics)
Each λ / 4 retardation film was cut as a 30 mm square sample, its absorption spectrum was measured using a spectrophotometer U-3310 manufactured by Hitachi High-Technologies, and tristimulus values X, Y, and Z were calculated. . From these tristimulus values X, Y and Z, a yellow index YI was calculated according to JIS-K7103, specifically, the following equation, and the coloring characteristics were evaluated according to the following criteria.

：: YI is less than 0.8 ○: YI is 0.8 or more and less than 1.0 Δ: YI is 1.0 or more and less than 2.0 ×: YI is 2. 0 or more [Evaluation of organic EL display device]
Each of the organic EL display devices produced above was evaluated as follows.

(Evaluation of visibility 1: color characteristics)
In an environment of 23 ° C. and 55% RH, a BGR color chart image was displayed on the organic EL display device under the condition that the illuminance at the position 5 cm higher than the outermost surface of the organic EL display device was 1000 Lx.

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

A: Nine or more monitors were determined to be good BGR color images. O: Seven to eight monitors were determined to be good BGR color images. Δ: Five to six monitors were good BGR colors. ×: The number of monitors determined to be good BGR color images is 4 or less (Visibility evaluation 1: black display characteristics)
In an environment of 23 ° C. and 55% RH, a black image was displayed on the organic EL display device under the condition that the illuminance at a position 5 cm higher than the outermost surface of the organic EL display device was 1000 Lx.

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

◎: Nine or more monitors determined that the displayed image was black ○: Seven to eight monitors determined that the displayed image was black △: Five to six monitors The displayed image was determined to be black. ×: The number of monitors determined that the displayed image was black was 4 or less. Table 3 shows the results obtained as described above.

As is apparent from the results shown in Table 3, the λ / 4 retardation film of the present invention having the characteristic values defined in the present invention is excellent in transparency, light resistance and coloring resistance. It can be seen that the organic EL display device including the circularly polarizing plate having a film is superior in the image display performance (visibility) of the displayed black image and BGR color image as compared with the comparative example.

The λ / 4 retardation film of the present invention has a high retardation development property in a wide wavelength region, an excellent reverse wavelength dispersion characteristic in a thin film, a low haze, a high transparency, and an excellent light resistance and coloring resistance. It has characteristics and can be suitably used for a circularly polarizing plate and an organic electroluminescence display device.

4 Long film original fabric 5 Stretched film 6 Diagonal stretch tenter 7-1 Trajectory of outer film gripping means 7-2 Trajectory of inner film gripping means 8-1 Outer film grip start point, tenter entrance,
8-2 Inner film grip start point, tenter entrance 9-1 Right film grip end point 9-2 Left film grip end point 10-1, 10-2 Point where rail starts widening 11-3 Widening ends Points 12-1, 12-2 Guide roller 14-1 Film feeding direction 14-2 Film stretching direction θi Bending angle (feeding angle)
111 Stretching direction (TD direction)
112 oblique stretching 113 transport direction 114 slow axis F cellulose acylate film 1a transparent substrate 2a metal electrode 3aR red light emitting layer 3aG green light emitting layer 3aB blue light emitting layer 4a transparent electrode 5a insulating film 6a adhesive layer 7a λ / 4 plate T2

8a Polarizer

9a Protective film 10a Circularly polarizing plate 11a Organic EL element

Claims

A λ / 4 retardation film containing a thermoplastic resin and a compound (I) bonded with a linking group having a linking site at least at three positions, the linking group in the compound (I) and the two positions A chemical structure moiety X (main chain) having a maximum absorption wavelength in a wavelength region of 200 nm or more and less than 280 nm, and at least one of the other linking sites of the linking group. A group bonded via two linking sites, and having a chemical structure portion Y (side chain) branched from the chemical structure portion X (main chain), and the compound (I) has the following (a) A λ / 4 retardation film characterized by satisfying the conditions defined in (b) and (c) and (d) below at the same time.
(A) The chemical structure portion Y (side chain) has a maximum absorption wavelength in a wavelength range of 280 to 380 nm. (B) 25.0 ≧ ΣABS y / ΣABS x ≧ 1.01
(C) DSP1; Ro (450) / Ro (550) = 0.72 to 0.96
(D) DSP2; Ro (550) / Ro (650) = 0.83 to 0.98
[In the formula, ΣABS x represents the total absorption intensity of the chemical structure portion X (main chain) of the compound (I), and ΣABS y represents the total absorption intensity of the chemical structure portion Y (side chain) of the compound (I). To express. DSP1 and DSP2 each represent the wavelength dispersion characteristic of a λ / 4 retardation film, Ro (450) is an in-plane retardation value for light having a wavelength of 450 nm, and Ro (550) is an in-plane retardation for light having a wavelength of 550 nm. Ro (650) is an in-plane retardation value for light having a wavelength of 650 nm. In addition, each in-plane retardation value is the value measured in the environment of 23 degreeC and 55% RH. ]
The λ / 4 retardation film according to claim 1, wherein the compound (I) is a compound represented by the following general formula (A).

[Wherein, L 1 and L 2 each independently represent a single bond or a divalent linking group. R 1 , R 2 and R 3 each independently represent a substituent. n represents an integer of 0 to 2. Wa and Wb each represent a hydrogen atom or a substituent; (I) Wa and Wb are bonded to each other to form a ring; (II) at least one of Wa and Wb has a ring structure; or (III) Wa and Wb At least one of Wb is an alkenyl group or an alkynyl group. ]
The aspect ratio of the compound (I) is less than 1.70, and the λ / 4 retardation film according to claim 1 or 2.
The λ / 4 retardation film according to any one of claims 1 to 3, wherein the thermoplastic resin is a cellulose ester.
It is produced by stretching in the slow axis direction and shrinking in the fast axis direction, and the ratio of the shrinkage ratio in the fast axis direction to the stretch ratio in the slow axis direction (shrinkage ratio / stretch ratio) is 0.05. The λ / 4 retardation film according to any one of claims 1 to 4, wherein the λ / 4 retardation film is in a range of ˜0.70.
The λ / 4 retardation film according to any one of claims 1 to 4, wherein the slow axis direction is oriented within an angle range of 30 to 60 ° with respect to the transport direction. .
The film feed direction and the film take-off direction are obliquely crossed, and the slow axis is in an angle range of 30 to 60 ° with respect to the film take-up direction. The λ / 4 retardation film according to any one of Items 4 to 4.
It is a manufacturing method of (lambda) / 4 phase difference film which manufactures (lambda) / 4 phase difference film as described in any one of Claim 1- Claim 4, Comprising: It extends | stretches to a slow axis direction, A phase fast axis direction The ratio of the shrinkage ratio in the fast axis direction to the stretch ratio in the fast axis direction (shrinkage ratio / stretch ratio) is in the range of 0.05 to 0.70 through the stretching shrinkage step of shrinking into A method for producing a λ / 4 retardation film, wherein the film is produced by stretching the film.
A method for producing a λ / 4 retardation film for producing a λ / 4 retardation film according to any one of claims 1 to 4, wherein a slow axis direction is 30 to A method for producing a λ / 4 retardation film, which is produced under the condition of orientation within an angle range of 60 °.
It is a manufacturing method of (lambda) / 4 phase difference film which manufactures (lambda) / 4 phase difference film as described in any one of Claim 1- Claim 4, Comprising: The feeding direction of a film in a extending process, and film take-up A method for producing a λ / 4 retardation film, characterized in that the film is produced under the condition that the direction is oblique and the slow axis is provided within an angle range of 30 to 60 ° with respect to the film take-off direction.
A circularly polarizing plate comprising the λ / 4 retardation film according to any one of claims 1 to 7 and a polarizer.
An organic electroluminescence display device comprising the circularly polarizing plate according to claim 11 and an organic electroluminescence element.