JP5411489B2 - Film, film manufacturing method, polarizing plate, optical compensation film, antireflection film, and liquid crystal display device - Google Patents

Description

  The present invention relates to a method for producing a film. The present invention also relates to a film produced by the production method, a polarizing plate having the film, an optical compensation film, an antireflection film, and a liquid crystal display device.

  In recent years, various films have been developed with the rise of the liquid crystal display market. For example, Patent Documents 1 to 3 disclose tilted retardation films. In such a retardation film for a liquid crystal display device, it is required to process the obtained film and a polarizer with a roll-to-roll to reduce the production cost. Further, in order to realize a wide viewing angle in a transmissive liquid crystal display device such as TN, OCB, or ECB, it is desired that the slow axis and the tilt direction of the retardation film to be used are orthogonal. When the tilt direction is in the direction perpendicular to the slow axis of the retardation film, tilted liquid crystal molecules in the liquid crystal cell can be optically compensated. On the other hand, when it has a slow axis in the direction orthogonal to the tilt direction of the retardation film, it has a viewing angle compensation function of the polarizing plate, and light leakage of the polarizing plate when viewed from an oblique direction can be reduced.

  In response to such a demand, for example, Patent Document 1 discloses that a positive birefringent resin film obtained by solution casting is passed between two rolls having different peripheral speeds, whereby a shearing force is applied to the film. And a method for producing a film having an inclined optical axis is described. In this document, the obtained film is further stretched in the film width direction (hereinafter also referred to as TD direction or transverse direction), so that the slow axis is the TD direction and the tilt direction is the film longitudinal direction (hereinafter referred to as MD). Is also referred to as a direction or a longitudinal direction). However, in the method of forming a film by applying a shearing force to the positive birefringent resin film after film formation described in the document, the management of the peripheral speed difference between the two rolls and the peripheral speed difference accuracy It was difficult to maintain, and there was a problem in the uniformity of the shearing force that could be applied. Therefore, the obtained film has a problem in uniformity of optical properties. Moreover, this document did not suggest applying a method of forming a film by applying a shearing force to the melt.

On the other hand, an example in which a method of forming a film by applying a shearing force is applied to a melt is known. For example, in Patent Documents 2 and 3, an inclined type in which uniformity of optical properties is improved by sandwiching a melt using two rolls of a rubber roll and a metal roll that may have different peripheral speeds and applying a shearing force. A method for obtaining a retardation film is disclosed.
However, the films produced by the methods described in these documents have the same slow axis and tilt orientation. Therefore, a liquid crystal display device incorporating a polarizing plate in which a film obtained by these methods and a polarizer are directly bonded by roll-to-roll has a narrow viewing angle, and improvement is desired. Thus, in order to obtain a film in which the slow axis and the tilt direction are orthogonal when the method of forming a film by applying shear force to the melt described in Patent Documents 2 and 3 is used. In fact, after forming a film by applying a shearing force to the melt, it is necessary to perform a transverse stretching step using an expensive transverse stretching apparatus.

Thus, a method for producing a film having good viewing angle compensation ability and good optical property uniformity at a low cost when processed with a polarizer and a roll-to-roll has not been known. Is the actual situation.
JP-A-6-222213 JP 2003-25414 A JP 2007-38646 A

Therefore, as a result of intensive studies to solve the above problems, the present inventors have surprisingly found that when a negative birefringent resin is used in the method of forming a film by applying a shearing force, the slow axis of the film is the film width. It has been found that it is possible to obtain a film that is oriented in the direction and whose tilt orientation is in the film transport direction. Such knowledge has not been known or anticipated.
Conventionally, such a film could not be produced unless it was subjected to a transverse stretching process using an expensive transverse stretching apparatus (for example, a tenter). Therefore, a negative birefringent resin was used to provide a shearing force. It was expected that the production cost of a film having a tilted retardation structure could be greatly reduced if the optical properties of the film formed were good.

  However, when the negative birefringent resin is used in the method of forming a film by simply applying a shearing force, the film is formed by applying a shearing force using a positive birefringent resin. As a result, the uniformity of optical characteristics tends to deteriorate, which proves to be a problem. Furthermore, it was found that there is a problem that a scale-like surface failure occurs with respect to the surface state of the obtained film. These are also problems that occur in the same way when a film is formed by applying a shearing force to a melt using the melt described in Patent Documents 2 and 3, and the negative compound exemplified in these documents. The above problem was not solved even when a study was made using a refractive resin. Also, there is no suggestion in these documents that there is a problem with optical characteristics peculiar to the use of negative birefringent resins, nor how to improve the problem when using negative birefringent resins. It was.

  The present invention has been made in consideration of the above problems, and a first object of the present invention is to use a thermoplastic resin exhibiting negative birefringence, to form a tilted phase difference structure, and to vary optical characteristics. It is an object to provide a film having a small and improved scale-like surface failure and a method for producing the same. The second object of the present invention is to provide a polarizing plate, an optical compensation film, an antireflection film and a liquid crystal display device using the film.

  As a result of intensive studies to solve the above problems, the present inventor has conventionally used a commercially available resin having a negative birefringence that is commercially available at a low cost, and has a glass transition temperature of about 80 ° C. I found that there are many. Therefore, using a thermoplastic resin exhibiting negative birefringence having a glass transition temperature (hereinafter also referred to as Tg) of 100 ° C. or higher, while controlling the temperature of the composition containing the resin within a specific temperature range. When the composition containing the resin is passed between the clamping devices, it is surprising that surface defects including scale-like unevenness are improved, and the uniformity of optical properties is also improved. all right. That is, the inventors have found that the following production method and a film produced by the method can solve the above problems, and have completed the present invention described below.

[1] A composition containing a thermoplastic resin exhibiting negative birefringence is continuously sandwiched by passing between a first sandwiching surface and a second sandwiching surface constituting the sandwiching device to form a film. A method for producing a film including a pressing step for molding, wherein Tg of the thermoplastic resin is 100 ° C. or more, and immediately before passing between a first pressing surface and a second pressing surface constituting the pressing device. A method for producing a film, wherein the temperature of the composition is controlled to (Tg + 20 ° C.) to Tg + 120 ° C. (where Tg represents the glass transition temperature of the thermoplastic resin).
[2] The difference between the temperature Ts at which the thermoplastic resin has a zero shear viscosity of 3000 Pa · s and the glass transition temperature Tg of the thermoplastic resin is 160 ° C. or less. Film manufacturing method.
[3] The film according to [1] or [2], wherein the thermoplastic resin is at least one selected from an acrylic resin, a styrene resin, a cyclic olefin resin, and a maleimide resin. Manufacturing method.
[4] The pressing step includes a step of melt-extruding a composition containing a thermoplastic resin exhibiting negative birefringence, and the melt-extruded composition includes the first pressing surface and the second pressing surface. The method for producing a film according to any one of [1] to [3], wherein the film is continuously pressed and formed into a film shape.
[5] The moving speed of the first clamping surface of the clamping device is made faster than the moving speed of the second clamping surface, and the first clamping surface and the second clamping surface of the clamping device defined by the following formula (I) are used. The method for producing a film according to any one of [1] to [4], wherein the moving speed ratio of the pressing surface is controlled to 0.600 to 0.999.
Moving speed ratio = moving speed of the second clamping surface / moving speed of the first clamping surface Formula (I)
[6] The method for producing a film according to any one of [1] to [5], wherein the narrow pressure device is two rolls.
[7] The method for producing a film according to any one of [1] to [6], wherein in the narrow pressure step, the composition is clamped at a pressure of 0.5 to 500 MPa.
[8] A film containing a thermoplastic resin exhibiting negative intrinsic birefringence and satisfying the following conditions (I) to (III).
(I) Retardation Re [+ 40 °] at a wavelength of 550 nm measured from a direction tilted 40 ° toward the tilt direction with respect to the normal in a plane including the film tilt azimuth and the film normal, and the normal On the other hand, the retardation Re [−40 °] measured from a direction inclined by 40 ° to the opposite side of the tilt direction is different.
(II) The glass transition temperature is 100 ° C. or higher.
(III) The variation in retardation Re [0 °] at a wavelength of 550 nm measured from the normal direction in a plane including the film tilt direction and the film normal is 20 nm or less.
[9] As described in [8], the Re [40 °] and the Re [−40 °] satisfy 10 nm ≦ | Re [+ 40 °] −Re [−40 °] | ≦ 300 nm. the film.
[10] The film according to [8] or [9], wherein the slow axis in the film plane and the film tilt direction are perpendicular to each other.
[11] The film according to any one of [8] to [10], wherein Re [0 °] satisfies 0 nm ≦ | Re [0 °] | ≦ 300 nm.
[12] The film according to any one of [8] to [11], wherein a difference between a temperature Ts at which the zero shear viscosity is 3000 Pa · s and a glass transition temperature Tg is 160 ° C. or less.
[13] A film produced by the method for producing a film according to any one of [1] to [7].
[14] A polarizing plate using a polarizer and the film described in any one of [8] to [13].
[15] An optical compensation film using the film according to any one of [8] to [13].
[16] An antireflection film using the film according to any one of [8] to [13].
[17] A liquid crystal display device using the film according to any one of [8] to [13].

  According to the present invention, a film having a tilted phase difference structure using a thermoplastic resin exhibiting negative birefringence, small variation in optical characteristics, and improved scaly surface failure, and a method for producing the same are provided. can do. Further, such a film has a slow axis and a tilt direction orthogonal to each other, can be processed with a polarizer and a roll-to-roll, and can provide sufficient optical compensation when used in a liquid crystal display device and a method for producing the same. Can be provided. Specifically, since the film having the above optical characteristics has a slow axis and a tilt direction orthogonal to each other, sufficient optical compensation can be realized when used in a TN mode, ECB mode, or OCB mode liquid crystal display. For example, in a TN mode liquid crystal display, since the viewing angle is narrow, an optical compensation film (for example, WV film (Fuji Film)) provided with an optical compensation layer made of a liquid crystal composition that realizes optical compensation is usually polarized. When the film of the present invention is used, an optical compensation having an optical compensation layer made of a conventional liquid crystal composition can be used without using an optical compensation layer made of a liquid crystal composition. Viewing angle compensation can be performed more easily than those using a film. Further, the method for producing a film of the present invention can omit the transverse stretching step, and can provide the film of the present invention at a low production cost.

  Hereinafter, the present invention will be described in more detail. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

[the film]
The film of the present invention contains a thermoplastic resin exhibiting negative intrinsic birefringence and satisfies the following conditions (I) to (III).
(I) Retardation Re [+ 40 °] at a wavelength of 550 nm measured from a direction tilted 40 ° toward the tilt direction with respect to the normal in a plane including the film tilt azimuth and the film normal, and the normal On the other hand, the retardation Re [−40 °] measured from a direction inclined by 40 ° to the opposite side of the tilt direction is different.
(II) The glass transition temperature is 100 ° C. or higher.
(III) The variation in retardation Re [0 °] at a wavelength of 550 nm measured from the normal direction in a plane including the film tilt direction and the film normal is 20 nm or less.
Hereinafter, the film of the present invention will be described in detail.

  In this specification, the “direction inclined by θ ° from the film normal” is defined as a direction inclined by θ ° from the normal direction to the inclination direction. That is, the normal direction of the film surface is a direction with an inclination angle of 0 °, and an arbitrary direction within the film surface is a direction with an inclination angle of 90 °.

(Retardation Re)
The film of the present invention has different Re [+ 40 °] and Re [−40 °]. That is, when | Re [+ 40 °] −Re [−40 °] | is measured in the tilt direction, it is a feature of the film of the present invention that a phase difference of 0 nm or more is expressed. By having such a tilt structure, the viewing angle compensation ability when used in a liquid crystal display device is improved.

In the film of the present invention, Re [40 °] and Re [−40 °]
10 nm ≦ | Re [+ 40 °] −Re [−40 °] | ≦ 300 nm
Preferably satisfying
60 nm ≦ | Re [+ 40 °] −Re [−40 °] | ≦ 250 nm
It is more preferable to satisfy.

In the film of the present invention, Re [0 °] is 0 nm ≦ | Re [0 °] | ≦ 300 nm
Preferably satisfying
30 nm ≦ | Re [+ 40 °] −Re [−40 °] | ≦ 250 nm
More preferably,
60 nm ≦ | Re [+ 40 °] −Re [−40 °] | ≦ 200 nm
It is more preferable to satisfy.

  The film of the present invention has a Re [0 °] variation of 20 nm or less. The variation in Re [0 °] appears as display unevenness when used in a liquid crystal display device, so the smaller the variation, the better. The variation in Re [0 °] is preferably 5 nm or less, and more preferably 3 nm or less.

The variation in Re [0 °] can be measured by the following method. A sample of 30 cm × 30 cm is sampled in the slow axis direction of the film and the direction perpendicular thereto, and Re [0 °] is measured. Sampling is performed on any 10 samples, and the difference between the maximum value and the minimum value of Re [0 °] between those samples is divided by the average value of each 10 samples of Re [0 °] and expressed as a percentage Is a variation in Re [0 °].
In the present application, the variation was measured using a total of 10 samples sampled as 5 samples in the width direction of the film, the center of the film, and 5 samples in the longitudinal direction.

  Similarly, the variation in the angle of the slow axis also causes display unevenness. Therefore, the variation is preferably as small as possible, specifically within ± 1 °, preferably within ± 0.5 °. It is more preferable that the angle is within ± 0.25 °. The variation of the slow axis is also measured in the same manner as the variation of Re [0 °].

  A film having variations of | Re [+ 40 °] −Re [−40 °] |, Re [0 °], and Re [0 °] in the above preferable range can be produced by the production method of the present invention described later. In addition, when the optical film having the preferable optical characteristics is used for optical compensation of a liquid crystal display such as a TN mode, an ECB mode, and an OCB mode, it contributes to an improvement in viewing angle characteristics and achieves a wide viewing angle. be able to.

The optical characteristic value can be measured by the following method.
In the present invention, Re [0 °], Re [+ 40 °] and Re [−40 °] of the film are measured using KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments Co., Ltd.). , The phase difference at an inclination angle of 0 °, the phase difference at an inclination angle of 40 degrees, and the phase difference at an inclination angle of −40 degrees were measured.
Here, the inclination direction was determined by the following method.
(1) The slow axis direction in the film plane is 0 °, the fast axis direction in the film plane is 90 °, and the temporary tilt direction is set in increments of 0.1 ° between 0 ° and 90 °.
(2) Re [+ 40 °] and Re [−40 °] are measured in a plane including each provisional tilt direction and the film normal to obtain | Re [+ 40 °] −Re [−40 °] |.
(3) The direction in which | Re [+ 40 °] −Re [−40 °] | is maximized is determined as the tilt direction.
The measurement wavelength is 550 nm. Note that a film made of a general thermoplastic resin by a melt film forming method has a value of | Re [+ 40 °] −Re [−40 °] | ≈0 nm regardless of the orientation.

  In the film of the present invention, the slow axis in the film plane and the film tilt direction are preferably orthogonal. The tilt azimuth represents an azimuth in which | Re [+ 40 °] −Re [−40 °] | Further, “the slow axis and the tilt direction are orthogonal” means that the angle formed by the slow axis and the tilt direction is approximately 90 °. When the slow axis in the film plane is perpendicular to the film tilt direction, a polarizing plate with good viewing angle compensation can be obtained by directly processing with a polarizer and a roll-to-roll without going through a transverse stretching step. .

(Scale irregularity)
The film of the present invention is characterized by markedly less scaly unevenness. The scale-like unevenness means a scale-shaped unevenness of about 3 mm × 3 mm on the surface of the film or a tortoise shell-like unevenness, and the film in which such scale-like unevenness is generated has irregularities on the surface, and diffusely reflects light. Therefore, it becomes a significant problem when incorporated into a liquid crystal display device as a film for optical applications. Such scaly unevenness is caused when a negative birefringent thermoplastic resin is used in a method of forming a film by applying a shearing force, and it has not been publicly known that scaly unevenness occurs.

(Glass-transition temperature)
The film of the present invention has a glass transition temperature of 100 ° C. or higher. The glass transition temperature of the film of the present invention is preferably 100 to 200 ° C, more preferably 110 to 175 ° C, and particularly preferably 110 to 150 ° C. Thus, when the glass transition temperature of the film of the present invention is 100 ° C. or higher, scaly unevenness hardly occurs.
The glass transition temperature of the film of the present invention is measured by adding the film of the present invention to a measurement pan using a scanning differential calorimeter (DSC), and in a nitrogen stream, the glass transition temperature is 30 ° C. to 300 ° C. at 10 ° C./min. After raising the temperature to 1 ° C (1st-run), it was cooled to 30 ° C at -10 ° C / min, and again raised from 30 ° C to 300 ° C at 10 ° C / min (2nd-run). The temperature at which the baseline starts to deviate from the low temperature side in 2nd-run can be obtained as the glass transition temperature (Tg).

(Zero shear viscosity)
In the film of the present invention, the difference between the temperature Ts at which the zero shear viscosity is 3000 Pa · s and the glass transition temperature Tg is preferably 160 ° C. or less from the viewpoint of reducing scaly unevenness.
The temperature Ts at which the zero shear viscosity is 3000 Pa · s can be obtained by the following method.
Using a rheometer (Anton Paar MCR301), the resin is melted at a temperature at which the sample can be set (usually Tg + 100 ° C. to 150 ° C.), and the sample is set in a measuring machine. While cooling the sample at a temperature of 5 ° C./min from the temperature at which the sample was set, the viscosity at a shear rate of 0.001 sec ⁻¹ is measured, and the temperature at which 3000 Pa · s is obtained is read as Ts.

  The film thickness of the film of the present invention is preferably 100 μm or less. When used for a liquid crystal display or the like, it is preferably 80 μm or less, more preferably 60 μm or less, and particularly preferably 40 μm or less from the viewpoint of thinning. In the film manufacturing method of the present invention, such a thin film can be produced, which is one of the differences from the prior art.

[Film Production Method]
In the method for producing a film of the present invention, a composition containing a thermoplastic resin exhibiting negative birefringence is continuously passed between a first clamping surface and a second clamping surface constituting a clamping device. A method for producing a film, comprising a pinching step of pinching and forming into a film, wherein the thermoplastic resin has a Tg of 100 ° C. or higher, and a first pinching surface and a second pinching surface constituting the pinching device The temperature of the composition immediately before passing through is controlled from (Tg + 20 ° C.) to Tg + 120 ° C. It is a feature of the present invention that the composition containing a thermoplastic resin exhibiting a specific negative birefringence is pressed under a specific temperature condition, which is different from the conventional method. In addition, the temperature of the composition containing the thermoplastic resin exhibiting negative birefringence when passing between the first clamping surface and the second clamping surface constituting the clamping device is specifically the resin Represents the temperature of the composition at a position of 5 cm immediately above the point where the pressure is sandwiched between the first pressure surface and the second pressure surface.

  Although not bound by any theory, in the film manufacturing method of the present invention, the temperature of the composition when passing between the first and second clamping surfaces constituting the clamping device, and the clamping surface Due to the small temperature difference from the temperature, the composition containing a thermoplastic resin exhibiting negative birefringence is pressed so as not to be rapidly cooled, and the film is formed to form a scale-like surface failure (scale-like unevenness). Can be suppressed, and uneven optical characteristics of the film can be suppressed.

  When such a thermoplastic resin exhibiting negative birefringence is used, a composition containing a thermoplastic resin exhibiting negative birefringence in the method of forming a film by applying a shearing force as in the configuration of the present invention In the past, it has been very difficult to prevent an object from being rapidly cooled. Specifically, in the field of forming a film by applying a shearing force, the temperature of the pressing surface of the pressing device is about Tg of the resin to be used from the viewpoint of suppressing a film failure (so-called peeling dan) at the time of peeling. The following conditions were almost essential. On the other hand, in the field of a method for forming a film by applying a shearing force, when applying a shear stress to a composition containing a thermoplastic resin, it is also necessary to make the composition moderately elastic by setting it to a somewhat high temperature. . Under these circumstances, most of the inexpensive negative birefringent resins that are widely used have a very low glass transition temperature. Therefore, the negative birefringent resin is applied with shear force to form a film. In order to obtain a film having a tilted phase difference structure by film formation by the method described above, the film was inevitably quenched. Such rapid cooling is performed by applying shear force to a melt that has been used in recent years, as it is possible to improve the uniformity of optical properties as compared with the method of forming a film by applying shear force by solution casting. The method becomes even more prominent. Unlike the method of forming a film by applying a shearing force in solution casting using a large amount of a solvent, the method of forming a film by applying a shearing force to the melt is extruded for uniform extrusion of the melt. It is necessary to reduce the viscosity of the resin at that time (in this case, no shear stress is applied, so the zero shear viscosity is taken into consideration). Since the zero shear viscosity of the resin decreases with temperature, the method of forming a film by applying a shearing force to the melt gives a shearing force in solution film formation when a negative birefringent resin is used. It was supposed to cool more rapidly than the method of film formation. In addition, it has not been known that the cause of the variation in optical characteristics and the occurrence of scaly unevenness is such rapid cooling.

  In the production method of the present invention, the temperature difference between the temperature of the composition containing the thermoplastic resin when passing between the first clamping surface and the second clamping surface constituting the clamping device and the temperature of the clamping surface is It was found that this is the cause of variations in optical properties and unevenness in scales. Moreover, the above-described temperature difference that causes rapid cooling can be solved by using a thermoplastic resin exhibiting negative birefringence having a glass transition temperature equal to or higher than a specific temperature.

  Hereinafter, the film production method of the present invention (hereinafter also referred to as the production method of the present invention) will be described in detail.

(Composition containing a thermoplastic resin exhibiting negative birefringence)
The thermoplastic resin used in the production method of the present invention exhibits negative birefringence. The thermoplastic resin exhibiting negative birefringence is a direction in which the refractive index of light in the alignment direction is orthogonal to the alignment direction when light is incident on a layer formed with molecules having a uniaxial alignment. It means a resin that is smaller than the refractive index of light. It is one of the characteristics of the present invention to use such a thermoplastic resin exhibiting negative birefringence, and the slow axis of the film is directed in the TD direction and the tilt direction is in the MD direction without transverse stretching. An oriented film can be obtained.
The thermoplastic resin exhibiting negative birefringence used in the present invention has the above optical characteristics and has a glass transition temperature of 100 ° C. or higher. The glass transition temperature of the thermoplastic resin exhibiting negative birefringence is preferably 100 to 200 ° C, more preferably 110 to 175 ° C, and particularly preferably 110 to 150 ° C.
In addition, the glass transition temperature of the thermoplastic resin which shows negative birefringence is calculated | required similarly to the method of calculating | requiring the glass transition temperature of the film of this invention.

The thermoplastic resin showing negative birefringence used in the production method of the present invention has a difference between the temperature Ts at which the zero shear viscosity is 3000 Pa · s and the glass transition temperature Tg of the thermoplastic resin at 160 ° C. or less. The temperature of the composition containing the thermoplastic resin when passing between the clamping devices and the temperature of the clamping surface (requiring about Tg or less is necessary from the viewpoint of suppressing the peeling dan) Is preferable from the viewpoint of reducing the temperature difference from the above, preventing the composition from being rapidly cooled, and suppressing the occurrence of scaly unevenness. If the temperature of the composition containing the thermoplastic resin is high until the zero shear viscosity becomes 3000 Pa · s or less, the viscosity of the composition is low, and a method of forming a film by applying a uniform shear force is performed. Enough.
The temperature Ts at which the zero shear viscosity of the thermoplastic resin exhibiting negative birefringence exhibits 3000 Pa · s is obtained in the same manner as the method for obtaining the temperature Ts at which the zero shear viscosity of the film of the present invention exhibits 3000 Pa · s. .

  The thermoplastic resin exhibiting negative birefringence used in the production method of the present invention is not particularly limited as long as these conditions are satisfied. However, when the film of the present invention is produced using a melt extrusion method, melt extrusion is performed. It is preferable to use a material having good moldability. From this viewpoint, light is incident on a cyclic olefin resin (however, a positive birefringent resin, that is, a layer in which molecules are uniaxially oriented). When the refractive index of light in the alignment direction is larger than the refractive index of light in the direction orthogonal to the alignment direction), cellulose acylate resin (however, it is a positive birefringent resin) Except), maleimide co-resin, polystyrenes, acrylic resins, styrene resins such as polystyrene, polyacrylonitrile resins, and polyvinyl acetal resins are preferably selected.

  The thermoplastic resin used in the production method of the present invention may contain one kind of the resin, or may contain two or more kinds of the resins different from each other. In addition, one type of resin having negative birefringence may be used alone, or two or more types may be used in combination when two or more types are blended to exhibit negative birefringence. Good. When the negative birefringent resin is a polymer blend consisting of a resin that is a single negative birefringent resin and a resin that is a single positive birefringent resin, it is a single negative birefringent resin. The blending ratio of the resin to the resin that is a single positive birefringent resin varies depending on the magnitude of the absolute value of both intrinsic birefringence values, the manifestation of birefringence at the molding temperature, and the like. The polymer blend may contain other components in addition to the resin that is a negative birefringent resin alone and the resin that is a positive birefringent resin alone. The component is not particularly limited as long as the effects of the present invention are not impaired, and can be appropriately selected depending on the purpose. The compatibilizing agent can be suitably used in the case where phase separation does not occur during blending, and by using the compatibilizing agent, a resin that is a single negative birefringent resin and a single The mixed state with the resin which is a positive birefringent resin can be improved.

  The film of the present invention preferably contains 30% by mass to 100% by mass, more preferably 40% by mass to 100% by mass of the resin, which is a negative birefringent resin alone, with respect to the entire film. It is especially preferable that it is 100 mass%. Moreover, it is preferable that the ratio of the resin which is the negative birefringent resin independently to the whole resin contained in the film of this invention is 30 mass%-100 mass%, and is 40 mass%-100 mass%. More preferably, it is particularly preferably 100% by mass.

  The thermoplastic resin used in the production method of the present invention preferably contains at least one selected from acrylic resins, styrene resins, and maleimide resins, and more preferably acrylic resins or styrene resins. .

By using a negative birefringent resin such as an acrylic resin or a styrene resin, the film of the present invention in which the slow axis and the tilt direction are orthogonal to each other can be obtained. For example, when the styrenic resin is produced by applying a shear deformation with two rolls to form a film by applying a shear force, the fast axis is directed to the tilt direction and the two rolls are arranged in parallel with the die exit. In the case of a general method, the tilt direction is the same as the film longitudinal direction.
On the other hand, using a cellulose acylate-based resin, a cyclic olefin-based resin, a polycarbonate-based resin, or the like that exhibits positive intrinsic birefringence, a shear deformation is applied by two rolls to form a film by applying a shear force. When the method is performed, when the slow axis faces the tilt direction, for example, when two rolls are arranged parallel to the die exit, the tilt direction is the same as the film longitudinal direction.

  When the film of the present invention is applied to a liquid crystal display device as a viewing angle compensation film, the negative intrinsic birefringence resin is appropriately selected in consideration of the characteristics of the liquid crystal display device and the convenience of polarizing plate processing. Can be used.

一般式（１）において、ｎは、０又は１の整数を示し、Ｚは、式：−ＣＨ＝ＣＨ−で表される基、又は、式：−ＣＨ２ＣＨ２−で表される基を示し、Ｒ¹、Ｒ²、Ｒ³、Ｒ⁴は、同一でも又は異なっていてもよく、それぞれ、水素原子；ハロゲン原子；酸素原子、窒素原子、イオウ原子及びケイ素原子からなる群から選択される少なくとも１種の連結基を有していてもよい置換若しくは非置換の炭素原子数１〜３０の炭化水素基；及び極性基からなる群から選択される原子若しくは基を示し、波線ｐ、ｑは、ｅｎｄｏ又はｅｘｏの立体配置を示し、波線ｒは、ｅｎｄｏ又はｅｘｏの立体配置を示す。
前記環状オレフィン系樹脂は、開環重合および付加重合のいずれの重合方法によって得られる樹脂であってもよいが、開環重合によって得られる樹脂であることが好ましい。
また、前記環状オレフィン系樹脂は、ノルボルネン系重合体であることが好ましく、開環系ノルボルネン系重合体であることも好ましい。
前記環状オレフィン系樹脂が側鎖に少なくとも１つの芳香環構造を有する環状オレフィン樹脂である場合、該芳香環構造は単数または複数の置換基を有していてもよく、置換基を複数有する場合は置換基どうしが互いに結合してさらに環構造を形成していてもよい。また、側鎖の立体構造についても特に制限はなく、前記芳香環構造がエキソ型で結合していても、エンド型で結合していてもよい。
また，前記スピロ型環状オレフィン樹脂としては，例えば、下記一般式（２）で表される単位構造を含む樹脂を挙げることができる。

一般式（２）中、ａは０〜６、ｂは０〜６、ｃは０又は１であって、ａ＋ｂ＋ｃ＝２〜８の条件を満たす整数を示し、Ｘは、一構造単位中に複数存在する場合は同一でも異なっていてもよく、メチレン基（−ＣＨ₂−）、カルボニル基（＞ＣＯ）、エステル基（−ＣＯＯ−）、オキシ基（−Ｏ−）及び炭素数１〜５のアルキルイミノ基（＞ＮＲ⁵、Ｒ⁵は炭素数１〜５のアルキル基）からなる群から選択される少なくとも一つの基を示し、Ｙは下記構造式（２）、（３）又は（４）：

で表される環を示し、ｍは１０〜１０００００の整数を示す。
前記環構造は単数または複数の置換基を有していてもよく、置換基を複数有する場合は置換基どうしが互いに結合してさらに環構造を形成していてもよく、特に置換基どうしが互いに結合して芳香環構造を形成していてもよい。前記官能基としては、酸素原子を含む官能基（例えばカルボニル基、エステル基、オキシ基など）を有することも好ましい。また、側鎖の立体構造についても特に制限はない。 The cyclic olefin-based resin that is a thermoplastic resin exhibiting negative birefringence that can be used in the present invention includes, for example, a cyclic olefin resin having at least one aromatic ring structure in the side chain, and at least one ring structure in the side chain. The spiro-type cyclic olefin resin and the like are not particularly limited as long as the effects of the present invention are not impaired. For example, Japanese Patent Application Laid-Open Nos. 2003-292639, 2006-189474, and 2008-52119 are disclosed. The known cyclic olefin-based thermoplastic resins described in 1) can be used.
As cyclic olefin resin which has an aromatic ring structure, resin containing the unit structure represented by following General formula (1) can be mentioned, for example.

In the general formula (1), n represents an integer of 0 or 1, Z represents a group represented by the formula: —CH═CH—, or a group represented by the formula: —CH 2 CH 2 —, R ¹ , R ² , R ³ and R ⁴ may be the same or different and are each at least one selected from the group consisting of a hydrogen atom; a halogen atom; an oxygen atom, a nitrogen atom, a sulfur atom and a silicon atom. A substituted or unsubstituted hydrocarbon group having 1 to 30 carbon atoms which may have a linking group; and an atom or group selected from the group consisting of polar groups, and wavy lines p and q are endo or The exo configuration is shown, and the wavy line r indicates the endo or exo configuration.
The cyclic olefin-based resin may be a resin obtained by any polymerization method of ring-opening polymerization and addition polymerization, but is preferably a resin obtained by ring-opening polymerization.
The cyclic olefin resin is preferably a norbornene polymer, and is preferably a ring-opening norbornene polymer.
When the cyclic olefin resin is a cyclic olefin resin having at least one aromatic ring structure in the side chain, the aromatic ring structure may have one or a plurality of substituents, and when it has a plurality of substituents The substituents may be bonded to each other to form a ring structure. Further, the three-dimensional structure of the side chain is not particularly limited, and the aromatic ring structure may be bonded in an exo form or in an end form.
Examples of the spiro-type cyclic olefin resin include a resin including a unit structure represented by the following general formula (2).

In the general formula (2), a is 0 to 6, b is 0 to 6, c is 0 or 1, and represents an integer satisfying the condition of a + b + c = 2 to 8, and X is a plurality in one structural unit. When present, they may be the same or different, and include a methylene group (—CH ₂ —), a carbonyl group (> CO), an ester group (—COO—), an oxy group (—O—) and a C 1-5 carbon atom. At least one group selected from the group consisting of alkylimino groups (> NR ⁵ and R ⁵ are alkyl groups having 1 to ⁵ carbon atoms), and Y represents the following structural formula (2), (3) or (4) :

And m represents an integer of 10 to 100,000.
The ring structure may have one or a plurality of substituents. When there are a plurality of substituents, the substituents may be bonded to each other to form a ring structure. It may combine to form an aromatic ring structure. The functional group preferably has a functional group containing an oxygen atom (for example, a carbonyl group, an ester group, an oxy group, etc.). Moreover, there is no restriction | limiting in particular also about the three-dimensional structure of a side chain.

The styrenic resin that can be used in the present invention refers to a resin obtained by polymerizing styrene and derivatives thereof as a main component, and copolymers of other resins, and is not particularly limited as long as the effects of the present invention are not impaired. A known styrene-based thermoplastic resin can be used, and a copolymer resin that can improve birefringence, film strength, and heat resistance is particularly preferable.
Examples of the copolymer resin include styrene-acrylonitrile resins, styrene-acrylic resins, styrene-maleic anhydride resins, and multi-component (binary, ternary, etc.) copolymer polymers thereof. Among these, styrene-acrylic resins and styrene-maleic anhydride resins are preferable from the viewpoints of heat resistance and film strength.
In the styrene-maleic anhydride resin, the mass composition ratio of styrene and maleic anhydride is preferably styrene: maleic anhydride = 95: 5 to 50:50, and styrene: maleic anhydride = 90: 10. More preferably, it is ˜70: 30. In order to adjust the intrinsic birefringence, hydrogenation of a styrene resin can be preferably used.
Examples of the styrene-maleic anhydride resin include “Daylark D332” manufactured by Nova Chemical Co., Ltd.
As the styrene-acrylic resin, “Delpet 980N” manufactured by Asahi Kasei Chemical Co., Ltd., which will be described later, can be used.

The acrylic resin that can be used in the present invention refers to a resin obtained by polymerizing acrylic acid, methacrylic acid and derivatives thereof as main components, and further derivatives thereof, as long as the effects of the present invention are not impaired. It does not specifically limit, A well-known methacrylic acid type thermoplastic resin etc. can be used.
Examples of the resin obtained by polymerizing acrylic acid, methacrylic acid and derivatives thereof include a resin obtained by polymerizing one having a structure represented by the following general formula (3).

前記一般式（３）中、Ｒ¹¹およびＲ¹²は、それぞれ独立に、水素原子または炭素数１〜２０の有機残基を示す。有機残基とは、具体的には、炭素数１〜２０の直鎖状、分枝鎖状、もしくは環状のアルキル基を示す。

In the general formula (3), R ¹¹ and R ¹² each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue specifically represents a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms.

Specific examples of resins obtained by polymerizing the acrylic acid, methacrylic acid and derivatives thereof include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and (meth) acrylic. N-butyl acid, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxy (meth) acrylate Propyl, 2,3,4,5,6-pentahydroxyexyl (meth) acrylate and 2,3,4,5-tetrahydroxypentyl (meth) acrylate are preferred, and in terms of excellent thermal stability (meta ) Methyl acrylate (hereinafter also referred to as MMA) is more preferable. Among these, only 1 type may be used and 2 or more types may be used together. Further, among these, it may be a single polymer, a copolymer of two or more, or a copolymer of other resins, but from the viewpoint of increasing the glass transition temperature, Particularly preferred is a copolymer with a resin.
Among the acrylic copolymer resins, those containing 30 mol% or more of MMA units (monomer) in all monomers constituting the resin are preferable. In addition to MMA, lactone ring units, maleic anhydride units, glutaric anhydrides More preferably, at least one unit of units is included, and for example, the following can be used.

(1) Acrylic resin containing a lactone ring unit JP 2007-297615 A, JP 2007-63541 A, JP 2007-70607 A, JP 2007-100044 A, JP 2007-254726 A, JP 2007-254727 A , JP 2007-261265, JP 2007-293272, JP 2007-297619, JP 2007-316366, JP 2008-9378, and JP 2008-76764. Can be used. Among these, the resin described in JP-A-2008-9378 is more preferable.
(2) Acrylic resin containing maleic anhydride unit JP 2007-113109 A, JP 2003-292714 A, JP 6-279546 A, JP 2007-51233 A (described here), JP JP-A-2001-270905, JP-A-2002-167694, JP-A-2000-302988, JP-A-2007-111110, JP-A-2007-11565 can be used. Among these, the one described in JP-A-2007-113109 is more preferable. A commercially available maleic acid-modified MAS resin (for example, Delpet 980N manufactured by Asahi Kasei Chemicals Corporation) can also be preferably used.
(3) Acrylic resin containing glutaric anhydride unit JP-A-2006-241263, JP-A-2004-70290, JP-A-2004-70296, JP-A-2004-126546, JP-A-2004-163924, JP-A-2004 -291302, JP-A-2004-292812, JP-A-2005-314534, JP-A-2005-326613, JP-A-2005-331728, JP-A-2006-131898, JP-A-2006-134882, JP-A-2006- 206881, JP 2006-241197, JP 2006-283013, JP 2007-118266, JP 2007-176982, JP 2007-178504, JP 2007-197703, JP 2008-74818. No., International Publication WO2005 / 105 Those described in each publication such as 918 can be used. Among these, those described in JP-A-2008-74918 are more preferable.
The glass transition temperature (Tg) of these resins is preferably 106 ° C to 170 ° C, more preferably 110 ° C to 160 ° C, still more preferably 115 ° C to 150 ° C.

The maleimide-based resin that can be used in the present invention refers to a resin obtained by polymerizing maleimide and a derivative thereof as a main component, and a derivative thereof, and is not particularly limited unless the effects of the present invention are impaired. A well-known maleimide type thermoplastic resin etc. can be used.
Examples of the resin obtained by polymerizing maleimide and derivatives thereof include a resin containing a unit structure represented by the following general formula (4).

In the general formula (4), R ²¹ represents a hydrogen atom, a heterocyclic group formed of an aromatic ring or a non-aromatic ring, or a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms.

R ^{22 to} R ²⁹ each independently represent a hydrogen atom, a halogen atom, an oxygen atom, a nitrogen atom, a sulfur atom or a silicon atom, or a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, Alternatively, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms is preferable, and a hydrogen atom is more preferable.
s and t each independently represent an integer of 0 to 5, preferably 0 to 2, and more preferably 0.

Although the specific example of the unit structure of the maleimide-type resin represented by the said General formula (4) is given, this invention is not limited to these.

As specific examples of the maleimide resin, R is phenyl group, naphthyl group, halogen element, carboxylic acid, carboxylic ester, hydroxyl group, cyano group, nitro group, linear alkyl having 1 to 8 carbon atoms. Group, preferably having a phenyl group or a naphthyl group substituted by a branched alkyl group having 1 to 8 carbon atoms, and N-phenylmaleimide, N- (2-methylphenyl) maleimide and the like are excellent in terms of thermal stability. More preferred. Among these, only 1 type may be used and 2 or more types may be used together. Further, among these, it may be a single polymer, a copolymer of two or more, or a copolymer of other resins, but from the viewpoint of increasing the glass transition temperature, It may be a copolymer with a resin.
Among the maleimide resins, those containing 30 mol% or more of maleimide and its derivative units are preferable in all monomers constituting the resin, and more preferably a homopolymer of maleimide and its derivative units.

  When the thermoplastic resin exhibiting negative birefringence is a copolymer, it may be a random copolymer or a block copolymer.

(Additive)
The composition containing a thermoplastic resin exhibiting negative birefringence and used in the production method of the present invention may contain a material other than the thermoplastic resin exhibiting negative birefringence. One or more of the thermoplastic resins exhibiting the birefringence of the main component (meaning the material having the highest content ratio among all the materials in the composition, in an embodiment containing two or more of the resins, It is preferable that the total content ratio of the other materials is higher than the content ratios of the other materials. Examples of materials other than the thermoplastic resin exhibiting negative birefringence include various additives. Examples thereof include stabilizers, ultraviolet absorbers, light stabilizers, plasticizers, fine particles, and optics. Conditioner is included.

Stabilizer:
The composition containing a thermoplastic resin exhibiting negative birefringence and used in the production method of the present invention may contain at least one stabilizer. The stabilizer is preferably added before or when the thermoplastic resin is heated and melted. The stabilizer has effects such as preventing oxidation of the film constituting material, capturing an acid generated by decomposition, and suppressing or inhibiting a decomposition reaction caused by radical species caused by light or heat. Stabilizers are useful for suppressing the occurrence of alterations such as coloring and molecular weight reduction and the generation of volatile components due to various decomposition reactions including unresolved decomposition reactions. Even at the melting temperature for forming a resin film, the stabilizer itself is required to function without being decomposed. Typical examples of stabilizers include phenol-based stabilizers, phosphorous acid-based stabilizers (phosphite-based), thioether-based stabilizers, amine-based stabilizers, epoxy-based stabilizers, and lactone-based stabilizers. Stabilizers, amine stabilizers, metal deactivators (tin stabilizers) and the like are included. These are described in JP-A-3-199201, JP-A-5-1907073, JP-A-5-194789, JP-A-5-271471, JP-A-6-107854, and the like. Then, it is preferable to use at least one or more of a phenol-based or phosphorous acid-based stabilizer. Among phenolic stabilizers, it is particularly preferable to add a phenolic stabilizer having a molecular weight of 500 or more. Preferable phenolic stabilizers include hindered phenolic stabilizers.

  These materials are readily available as commercial products and are sold by the following manufacturers. From Ciba Specialty Chemicals, Irganox 1076, Irganox 1010, Irganox 3113, Irganox 245, Irganox 1135, Irganox 1330, Irganox 259, Irganox 565, Irganx 565, Irganx 565, Ir35x10 Moreover, it can obtain from Asahi Denka Kogyo Co., Ltd. as ADK STAB AO-50, ADK STAB AO-60, ADK STAB AO-20, ADK STAB AO-70, and ADK STAB AO-80. Furthermore, from Sumitomo Chemical Co., Ltd., it can obtain as Sumilizer BP-76, Sumilizer BP-101, Sumilizer GA-80. In addition, it is also possible to obtain as Sinox 326M and Sinox 336B from Sipro Kasei Co., Ltd.

  Moreover, as said phosphorous acid type stabilizer, the compound as described in [0023]-[0039] of Unexamined-Japanese-Patent No. 2004-182979 can be used more preferably. Specific examples of the phosphite ester stabilizer include JP-A-51-70316, JP-A-10-306175, JP-A-57-78431, JP-A-54-157159, Examples thereof include compounds described in Japanese Utility Model Laid-Open No. 55-13765. Furthermore, as other stabilizers, the materials described in detail on pages 17 to 22 of the Japan Institute of Invention Disclosure Bulletin (Public Technical No. 2001-1745, issued March 15, 2001, Japan Society of Invention) are preferably used. be able to.

  The phosphite stabilizer is useful to have a high molecular weight in order to maintain stability at high temperature, has a molecular weight of 500 or more, more preferably a molecular weight of 550 or more, and particularly a molecular weight of 600 or more. Is preferred. Furthermore, at least one substituent is preferably an aromatic ester group. The phosphite ester stabilizer is preferably a triester, and is desirably free of impurities such as phosphoric acid, monoester and diester. When these impurities are present, the content is preferably 5% by mass or less, more preferably 3% by mass or less, and particularly 2% by mass or less. These include compounds described in [0023] to [0039] of JP-A No. 2004-182979, JP-A-51-70316, JP-A-10-306175, JP-A-57. The compounds described in JP-A-78431, JP-A-54-157159, and JP-A-55-13765 can also be mentioned. Preferable specific examples of the phosphite ester stabilizer include the following compounds, but the phosphite ester stabilizer that can be used in the present invention is not limited thereto.

  These are commercially available from Asahi Denka Kogyo Co., Ltd. as ADK STAB 1178, 2112, PEP-8, PEP-24G, PEP-36G, HP-10, and Sandostab P-EPQ from Clariant. Is possible. Furthermore, a stabilizer having phenol and phosphite in the same molecule is also preferably used. These compounds are further described in detail in JP-A-10-273494. Examples of the compounds are included in the examples of the stabilizer, but are not limited thereto. As a typical commercial product, Sumitizer GP is available from Sumitomo Chemical Co., Ltd. These are commercially available from Sumitomo Chemical Co., Ltd. as Sumilizer TPL, TPM, TPS, TDP. Also available from Asahi Denka Kogyo Co., Ltd. as ADK STAB AO-412S.

  The stabilizers can be used alone or in combination of two or more, and the blending amount thereof is appropriately selected within a range not impairing the object of the present invention. Preferably, the addition amount of the stabilizer is preferably 0.001 to 5% by mass, more preferably 0.005 to 3% by mass, and still more preferably 0.01 to 0% with respect to the mass of the thermoplastic resin. 0.8% by mass.

UV absorber:
The composition containing a thermoplastic resin exhibiting negative birefringence used in the production method of the present invention may contain one or more ultraviolet absorbers. From the viewpoint of preventing deterioration, the ultraviolet absorbent is preferably excellent in the ability to absorb ultraviolet light having a wavelength of 380 nm or less and has little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of transparency. Examples include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. Particularly preferred ultraviolet absorbers are benzotriazole compounds and benzophenone compounds. Among these, a benzotriazole-based compound is preferable because unnecessary coloring with respect to the cellulose mixed ester is small. These are disclosed in JP-A-60-235852, JP-A-3-199201, 5-1907073, 5-194789, 5-271471, 6-107854, 6-118233, 6 -148430, 7-11056, 7-11055, 7-11056, 8-29619, 8-239509, and JP-A-2000-204173.
The addition amount of the ultraviolet absorber is preferably 0.01 to 2% by mass of the thermoplastic resin, and more preferably 0.01 to 1.5% by mass.

Light stabilizer:
The composition containing a thermoplastic resin exhibiting negative birefringence and used in the production method of the present invention may contain one or more light stabilizers. Light stabilizers include hindered amine light stabilizer (HALS) compounds, more specifically, US Pat. No. 4,619,956, columns 5-11 and US Pat. No. 4,839. 2,405, 2,2,6,6-tetraalkylpiperidine compounds, or their acid addition salts or complexes of them with metal compounds. These are commercially available from Asahi Denka as ADK STAB LA-57, LA-52, LA-67, LA-62, LA-77, and TINUVIN 765, 144 from Ciba Specialty Chemicals. .

  These hindered amine light stabilizers can be used alone or in combination of two or more. These hindered amine light stabilizers may of course be used in combination with additives such as plasticizers, stabilizers, UV absorbers, etc., or may be introduced into a part of the molecular structure of these additives. Good. The blending amount is determined within a range not impairing the effects of the present invention, and is generally about 0.01 to 20 parts by mass, preferably 0.02 to 15 parts per 100 parts by mass of the thermoplastic resin. About mass parts, and particularly preferably about 0.05 to 10 mass parts. The light stabilizing agent may be added at any stage of preparing the melt of the thermoplastic resin composition, for example, at the end of the melt preparation process.

Plasticizer:
The composition containing a thermoplastic resin exhibiting negative birefringence and used in the production method of the present invention may contain a plasticizer. The addition of a plasticizer is preferable from the viewpoint of film modification such as improvement of mechanical properties, imparting flexibility, imparting water absorption resistance, and reducing moisture permeability. In addition, when the film of the present invention is produced by a melt film-forming method, for the purpose of lowering the melting temperature of the film constituting material by adding a plasticizer rather than the glass transition temperature of the thermoplastic resin used, or without addition Will be added for the purpose of lowering the viscosity at the same heating temperature than the other thermoplastic resins. For the film of the present invention, for example, a plasticizer selected from phosphoric acid ester derivatives and carboxylic acid ester derivatives is preferably used. Further, a polymer obtained by polymerizing an ethylenically unsaturated monomer having a weight average molecular weight of 500 to 10,000 described in JP-A-2003-12859, an acrylic polymer, an acrylic polymer having an aromatic ring in the side chain, or a cyclohexyl group An acrylic polymer or the like having in the side chain is also preferably used.

Fine particles:
The composition containing a thermoplastic resin exhibiting negative birefringence and used in the production method of the present invention may contain fine particles. Examples of the fine particles include fine particles of inorganic compounds and fine particles of organic compounds, and any of them may be used. The average primary particle size of the fine particles contained in the thermoplastic resin in the present invention is preferably 5 nm to 3 μm, more preferably 5 nm to 2.5 μm, more preferably 10 nm to 2.0 μm from the viewpoint of keeping haze low. More preferably. Here, the average primary particle size of the fine particles is determined by observing the thermoplastic resin with a transmission electron microscope (magnification of 500,000 to 1,000,000 times) and determining the average value of the primary particle sizes of 100 particles. The addition amount of the fine particles is preferably 0.005 to 1.0% by mass with respect to the thermoplastic resin, more preferably 0.01 to 0.8% by mass, and further preferably 0.02 to 0%. 4% by mass.

Optical adjusting agent:
The composition containing a thermoplastic resin exhibiting negative birefringence and used in the production method of the present invention may contain an optical adjusting agent. Examples of the optical adjusting agent include a retardation adjusting agent, for example, those described in JP-A Nos. 2001-166144, 2003-344655, 2003-248117, and 2003-66230. Can be used. By adding an optical adjusting agent, in-plane retardation (Re) and thickness direction retardation (Rth) can be controlled. A preferable addition amount is 0 to 10% by mass, more preferably 0 to 8% by mass, and further preferably 0 to 6% by mass.

(Supply of thermoplastic resin composition)
In the production method of the present invention, a composition containing a thermoplastic resin exhibiting negative birefringence (sometimes referred to as a “thermoplastic resin composition”) and the first sandwiching surface and the second sandwiching sheet constituting the sandwiching device. Including a pressing step of passing between the pressing surfaces and continuously pressing to form a film. In the pressing step, a composition containing a thermoplastic resin exhibiting negative birefringence is melt-extruded. A process may or may not be included.
In the case of not performing melt extrusion, for example, a thermoplastic resin composition and a solvent are cast on a support, and the thermoplastic resin composition is formed into a film by solution casting, which is subjected to the pressing step to provide a shearing force. You may perform the method of providing and forming a film.
The production method of the present invention includes a step of melt-extruding a composition containing a thermoplastic resin exhibiting negative birefringence in the pinching step, and the melt-extruded composition includes the first pinching surface and the It is preferable from the viewpoint of suppressing variation in Re [0 °] of the film obtained by passing between the second pressing surfaces and continuously pressing to form a film. The supply means for supplying a composition containing a thermoplastic resin exhibiting negative birefringence is not particularly limited, but for example, melt extrusion from a die is preferable.

When performing the method of forming a film by applying a shearing force to the melt, it is preferable to pelletize the thermoplastic resin composition before melt extrusion. Commercially available thermoplastic resins (for example, Delpet 980N, DayLark D332, etc.) may be pelletized, but the following method can be used when they are not pelletized.
The thermoplastic resin composition is dried, melted at 150 ° C. to 300 ° C. using a twin-screw kneading extruder, and then extruded into noodles, and solidified in air or water and cut. Further, after melting by an extruder, it can be pelletized by an underwater cutting method in which it is cut while being directly extruded from a die into water. Extruders used for pelletization include single screw extruders, non-meshing different direction rotating twin screw extruders, meshing different direction rotating twin screw extruders, and meshing same direction rotating twin screw extruders. Etc. can be used. The number of revolutions of the extruder is preferably 10 rpm to 1000 rpm, more preferably 20 rpm to 700 rpm. The extrusion residence time is 10 seconds to 10 minutes, more preferably 20 seconds to 5 minutes.
No particular limitation is imposed on the size of the pellets is generally about 10mm ³ ~1000mm ^3, more preferably about 30 mm ³ 500 mm ^3.

  It is preferred to reduce the moisture in the pellets prior to melt extrusion. A preferable drying temperature is 40 to 200 ° C, more preferably 60 to 150 ° C. Thereby, the moisture content is preferably 1.0% by mass or less, and more preferably 0.1% by mass or less. Drying may be performed in air, nitrogen, or vacuum.

  In the case where a film is formed by applying a shearing force to the melt, it is preferable to feed the dried pellets into the cylinder via the supply port of the extruder, and knead and melt. The inside of the cylinder is composed of, for example, a supply unit, a compression unit, and a measurement unit in order from the supply port side. The screw compression ratio of the extruder is preferably 1.5 to 4.5, the ratio of the cylinder length to the cylinder inner diameter (L / D) is preferably 20 to 70, and the cylinder inner diameter is preferably 30 mm to 150 mm. The extrusion temperature of the die (hereinafter also referred to as the discharge temperature) is determined according to the melting temperature of the thermoplastic resin, but generally it is preferably about 190 to 300 ° C. Furthermore, in order to prevent the molten resin from being oxidized by residual oxygen, it is also preferable to carry out the inside of the extruder in an inert (nitrogen or the like) air flow or while evacuating using an extruder with a vent.

  It is preferable to provide a filtration apparatus incorporating a breaker plate type filtration or a leaf type disk filter for filtering foreign matter in the thermoplastic resin composition. Filtration may be performed in one stage or may be performed in multistage filtration. The filtration accuracy is preferably 15 μm to 3 μm, more preferably 10 μm to 3 μm. It is desirable to use stainless steel as the filter medium. As the configuration of the filter medium, a knitted wire, a sintered metal fiber or metal powder (sintered filter medium) can be used, and among them, a sintered filter medium is preferable.

  In order to reduce the fluctuation of the discharge amount and improve the thickness accuracy, it is preferable to provide a gear pump between the extruder and the die. Thereby, the resin pressure fluctuation width in the die can be within ± 1%. In order to improve the quantitative supply performance by the gear pump, a method of controlling the pressure before the gear pump to be constant by changing the number of rotations of the screw can also be used.

  The molten resin is melted by the extruder configured as described above, and the molten resin is continuously fed to the die via a filter and a gear pump as necessary. The die may be any of a T die, a fish tail die, and a hanger coat die. It is also preferable to insert a static mixer immediately before the die to increase the uniformity of the resin temperature.

The clearance of the die exit portion (hereinafter also referred to as lip gap) is generally 1.0 to 30 times, preferably 5.0 to 20 times the film thickness. It is preferably 0.1 to 30 mm, more preferably 0.2 to 20 mm, and particularly preferably 0.3 to 15 mm.
In the production method of the present invention, when a die is used as the supply means when supplying the thermoplastic resin composition between the clamping devices, the radius of curvature of the tip of the die lip is not particularly limited, and a known die can be used. .

It is preferable that the die can be adjusted in thickness at intervals of 5 to 50 mm. An automatic thickness adjustment die that calculates downstream film thickness and thickness deviation and feeds back the results to die thickness adjustment is also effective.
In addition to the single layer film forming apparatus, it is also possible to manufacture using a multilayer film forming apparatus.
Thus, the residence time from when the resin enters the extruder through the supply port until it exits from the die is preferably 3 to 40 minutes, more preferably 4 to 30 minutes.

<Clamping process>
Next, the thermoplastic resin composition is passed between the first clamping surface and the second clamping surface constituting the clamping device and continuously pressed to form a film, preferably cooled and solidified to form a film. Get. At this time, from the viewpoint of stabilization of productivity, one of the first clamping surface and the second clamping surface is peeled off from the melt first, and then the melt is peeled off from the other surface. preferable.

(Clamping temperature)
In the production method of the present invention, the temperature of the thermoplastic resin composition (hereinafter also referred to as the clamping temperature) when the thermoplastic resin composition is supplied to the clamping apparatus is (Tg + 20 ° C.) to Tg + 120 ° C. When the clamping temperature is Tg + 20 ° C. or higher, the viscosity of the thermoplastic resin composition becomes sufficiently low, so that the moldability can be improved and variations in the optical properties of the resulting film, in particular, variations in Re [0 °] are suppressed. Can do. On the other hand, if the clamping temperature is Tg + 120 ° C. or less, the temperature difference from the clamping surface of the clamping device can be made sufficiently small, and the variation in Re [0 °] and the scale-like unevenness of the resulting film can be significantly improved. it can. The clamping temperature is preferably Tg + 20 to Tg + 120 ° C., more preferably Tg + 30 to Tg + 100 ° C., and particularly preferably Tg + 50 to Tg + 100 ° C.
When the thermoplastic resin composition is supplied from the die to the clamping device, the clamping pressure temperature is different from the so-called discharge temperature (the resin temperature at the supply means outlet, for example, the resin temperature at the die outlet), and the clamping pressure temperature is the discharge temperature. About 20-100 ° C. below. The discharge temperature of the present invention is preferably equal to or higher than a temperature Ts at which the viscosity of the resin exhibits 3000 Pa · s, more preferably Ts to Ts + 80 ° C., and further preferably Ts to Ts + 50 ° C. For example, when a film is formed by applying a shearing force to the melt, the discharge temperature from the outlet of the supply means is controlled within the above range, and the temperature of the air gap and the distance of the air gap to be described later are controlled. The clamping temperature can be achieved.

  The temperature of the first clamping surface and the second clamping surface is the glass transition of the thermoplastic resin exhibiting the negative birefringence from the viewpoint of eliminating a planar failure (stripping dan) that occurs when the film is stripped. The temperature Tg is preferably set to Tg−70 ° C. to Tg + 20 ° C., more preferably Tg−50 ° C. to Tg + 10 ° C., and further preferably Tg−40 ° C. to Tg + 5 ° C. Since the thermoplastic resin having negative birefringence used in the present invention has a Tg higher than that of a normal negative birefringent resin, the temperature of the first clamping surface and the second clamping surface is substantially increased. Can be set. As a result, the thermoplastic resin composition can be prevented from being rapidly cooled. A known method can be used as the control means.

(Air gap)
In the production method of the present invention, for example, when the thermoplastic resin composition is supplied from a supply means such as a die to the pinching device, the air gap (the distance from the outlet of the supply means to the thermoplastic resin composition landing point of the pinching device). ) Is preferably as close as possible from the viewpoint of heat insulation of the thermoplastic resin composition between the air gaps, specifically, preferably 10 to 300 mm, more preferably 20 to 250 mm, particularly preferably. Is 30-200 mm.

(Line speed)
In the production method of the present invention, the line speed (film forming speed) is preferably 2 m / min or more, more preferably 5 m / min or more, from the viewpoint of heat insulation of the thermoplastic resin composition in the air gap. It is particularly preferably 10 m / min or more. When the line speed is increased, cooling of the thermoplastic resin composition in the air gap can be suppressed, and a more uniform shear deformation is imparted by a clamping device while the temperature of the thermoplastic resin composition is controlled within a preferable range. it can. The line speed represents the speed at which the melt passes between the clamping apparatuses and the film conveyance speed in the conveyance apparatus.

In the production method of the present invention, in the clamping step, the thermoplastic resin composition is preferably clamped at a pressure of 0.5 to 500 MPa, more preferably 0.5 to 300 MPa, and more preferably 5 to 200 MPa. It is particularly preferable to clamp at a pressure of 20 to 200 MPa, more preferably 20 to 200 MPa. By sandwiching the composition with the pressure in this way, an appropriate shearing force can be added to the composition passing between the clamping devices, and the variation in Re [0 °] of the obtained film can be suppressed. it can. In addition, by sandwiching the composition at 20 to 200 MPa, the inclined structure, that is, | Re [40 °] −Re [−40 °] | becomes larger, which is preferable.
The pressure between the clamping devices can be measured by passing a pressure measuring film (such as a prescale manufactured by Fuji Film) between the clamping devices.

In the manufacturing method of the present invention, the moving speed of the first pressing surface of the pressing device is made faster than the moving speed of the second pressing surface, and the first pressing surface of the pressing device defined by the following formula (I) And the moving speed ratio of the second clamping surface is controlled to 0.60 to 0.99, and shear stress is applied when the thermoplastic resin composition passes through the clamping device to produce the film of the present invention. preferable. By setting it in the above range, the inclined structure, that is, | Re [40 °] −Re [−40 °] | The moving speed ratio of the clamping device is preferably 0.75 to 0.98, and more preferably 0.90 to 0.97.
Moving speed ratio = moving speed of the second clamping surface / moving speed of the first clamping surface (I)
The surface from which the thermoplastic resin composition is peeled off first may be the first pressure-clamping surface or the second pressure-clamping surface. Is preferably the first clamping surface (a clamping surface having a high moving speed).

  In the production method of the present invention, the width of the film is not particularly limited, and can be, for example, 200 to 2000 mm.

(Clamping process using two rolls)
Examples of the clamping device having different speeds on the first clamping surface and the second clamping surface include, for example, a combination of two rolls having different peripheral speeds, and rolls having different speeds described in Japanese Patent Application Laid-Open No. 2000-219752. Examples include a combination of touch belts (single-sided belt method), a combination of belts and belts (double-sided belt method), and the like. Among these, it is preferable to use two rolls having different peripheral speeds from each other because the pressure is uniformly applied in the pinching step and the variation in Re [0 °] of the obtained film is easily suppressed within the scope of the present invention.
In addition, in this specification, when it has multiple casting rolls which convey the said thermoplastic resin composition, the casting roll nearest to the most upstream die | dye is also called a chill roll. Hereinafter, the preferable aspect of the manufacturing method of this invention using two rolls is demonstrated.

In the film production method of the present invention, the landing point of the thermoplastic resin composition of the clamping device from the outlet of the supply means is not particularly limited. For example, in the case of melt film formation, the thermoplastic resin composition supplied from the supply means The distance between the landing point of the object and the vertical line passing through the midpoint of the gap at the portion where the touch roll and the cast roll are closest may be zero or may be shifted.
The landing point of the thermoplastic resin composition supplied from the supply means refers to a point where the melt extruded from the die comes into contact (landing) with the touch roll or chill roll for the first time. The midpoint of the gap between the touch roll and the cast roll refers to the midpoint of the touch roll surface and the cast roll surface where the gap between the touch roll and the cast roll is the narrowest.

  The surface of the two rolls (for example, a touch roll or a casting roll) preferably has an arithmetic average height Ra of 100 nm or less, more preferably 50 nm or less, and further preferably 25 nm or less.

  In the production method of the present invention, the width of each of the two rolls is not particularly limited, and can be freely changed and employed according to the width of the film-like melt.

  The preferable range of the roll pressure between the two rolls is the same as the preferable range of the pressure for sandwiching the thermoplastic resin composition between the clamping surfaces of the clamping device in the description of the clamping device.

  In the manufacturing method of the present invention, in order to pressurize the roll pressure in the above range, the cylinder set value is appropriately changed. The cylinder set value varies depending on the resin material used and the material of the two rolls. For example, when the effective width of the film-like melt is 200 mm, it is preferably 3 to 100 KN, and preferably 3 to 50 KN. Is more preferable, and 3 to 25 KN is particularly preferable.

In the production method of the present invention, in order to pressurize the roll pressure in the above range, it is preferable to use a roll having a roll hardness of 45 HS or more. The Shore hardness of the two preferable rolls is preferably 50 HS or more, and more preferably 60 to 90 HS.
The Shore hardness can be determined from the average value of values measured at 5 points in the roll width direction and 5 points in the circumferential direction using the method of JIS Z 2246.

  The material of the two rolls is preferably a metal from the viewpoint of achieving the Shore hardness, more preferably stainless steel, and a roll whose surface is plated is also preferred. Moreover, if the material of two rolls is a metal, since the surface unevenness | corrugation is small and the surface of a film is hard to be damaged, it is preferable. Moreover, when the material of two rolls is metal and is rigid, the pressure between rolls can be made high easily, and it is preferable. On the other hand, a rubber roll or a metal roll lined with rubber can be used without particular limitation, but it is preferable that the roll pressure can be achieved.

  When one of the materials of the two rolls is an elastic roll and the other roll is a rigid metal roll, based on the difference in elastic modulus or the ease of deformation of the roll when passing between the rolls Asymmetric deformation occurs between the pair of roll surfaces, and even when the pair of rolls is rotated at a constant speed, a shearing force can be applied to the film through the contact portion with the roll, and an inclined structure is imparted. be able to. In this case, since the speed management between rolls is easy and processing accuracy can be maintained at a high level, such a configuration may be used as necessary. Further, when the surface of the elastic roll is metal-coated, both rolls have a metal surface, which is preferable because the surface irregularities are small as in the case of the metal roll, and the film surface is hardly damaged. Examples of the roll whose metal surface is coated with the elastic roll surface include a roll provided with a metal belt on the surface of a roll made of silicon rubber, or a roll subjected to metal plating. The metal coat may be a metal thin film such as a plating layer as long as it can prevent the surface from being damaged when the film passes between rolls by utilizing the smooth surface characteristics of the metal layer. Moreover, the diameter of an elastic roll and a metal rigid roll can be determined suitably according to a film width etc., and may be the same or different.

  Note that the roll is “rigid” when the ratio of the rigid material outer cylinder thickness / roll diameter is, for example, about 1/80 or more, for example, when a rigid material is used for a part of the touch roll. Even if it exists, the pinching surface or the touch roll is not necessarily “rigid”. Moreover, the roll being “elastic” means that the ratio of the rigid material outer cylinder thickness / roll diameter is less than about 1/80, including the case where a rigid material is used for a part of the touch roll, for example. Sometimes. That is, a roll in which a layer that does not contain any rigid material such as an elastic layer is formed inside the touch roll will elastically deform as a whole even if a rigid material layer is formed on the surface or inside. Therefore, it is included in the elastic roll. Also, in the case of a roll whose core is rubber and whose surface is a rigid material (a roll having a surface metal ring as an outer cylinder), the metal on the surface is not deformed, but the center of the rotating shaft and the surface metal ring is shifted, Included in elastic roll.

  As for the touch roll, for example, JP-A-11-314263, JP-A-2002-36332, JP-A-11-235747, WO97 / 28950, JP-A-2004-216717, JP The thing of 2003-145609 gazette and JP, 2003-25414, A can be used.

  Furthermore, in the production method of the present invention, by adjusting the peripheral speed ratio of the two rolls through which the thermoplastic resin composition passes, a shear stress is imparted when the thermoplastic resin composition passes through the two rolls, It is preferable to produce the film of the present invention. The preferable range of the peripheral speed ratio of the two rolls is the same as the preferable range of the moving speed ratio of the pressing surface in the description of the pressing device. Here, the peripheral speed ratio of the two rolls means the peripheral speed of the slow roll / the peripheral speed of the fast roll.

  In order to obtain the film of the present invention, whichever speed of the two rolls may be high, when the touch roll is slow, the bank (the surplus of the thermoplastic resin composition supplied is the roll It stays up and the formed stay) is formed. Since the touch roll has a short contact time with the thermoplastic resin composition, the bank formed on the touch roll side cannot be cooled sufficiently, causing peeling dans and causing a surface failure. easy. Therefore, it is preferable that the slow roll is a chill roll (second roll) and the fast roll is a touch roll (first roll).

  Furthermore, in the production method of the present invention, it is preferable to use a roll having a large diameter as each of the two rolls. Specifically, two rolls having a diameter of 350 to 600 nm, more preferably 350 to 500 nm are used. Is preferred. When a roll having a large diameter is used, the contact area between the film-like melt and the roll becomes wide, and the time for shearing becomes longer. Therefore, | Re [40 °] −Re [−40 °] | Moreover, it can be manufactured while suppressing variations in Re [0 °]. In the production method of the present invention, the diameters of the two rolls may be the same or different.

  In the manufacturing method of the present invention, the two rolls may be driven at different peripheral speeds or at a constant speed, but are preferably driven at different peripheral speeds. The two rolls may be driven or driven independently, but in order to suppress variations in Re [0 °], the two rolls are preferably driven independently.

Further, in order to increase | Re [40 °] −Re [−40 °] |, the surface temperatures of the two rolls may be differentiated. A preferable temperature difference is 5 ° C to 80 ° C, more preferably 20 ° C to 80 ° C, and further preferably 20 ° C to 60 ° C.
At that time, the temperature of the two rolls is preferably Tg−70 ° C. to Tg + 20 ° C., more preferably Tg−50 ° C. to Tg + 10 ° C., further preferably Tg−40 ° C. to Tg + 5, using the glass transition temperature Tg of the resin. Set to ° C. Such temperature control can be achieved by passing a temperature-controlled liquid or gas through the touch roll.

In the production method of the present invention, the thermoplastic resin composition supplied from the supply means is kept warm until just before it contacts at least one of the two rolls, thereby reducing the temperature distribution in the width direction. Specifically, the temperature distribution in the width direction is preferably within 5 ° C. In order to reduce the temperature distribution, it is preferable to dispose a member having a heat insulating function or a heat reflecting function in at least a part of the air gap to shield the thermoplastic resin composition from the outside air. Thus, by arranging the heat insulating member in the passage and shielding it from the outside air, it is possible to suppress the influence of the external environment, such as wind, and to suppress the temperature distribution in the width direction of the thermoplastic resin composition. it can. The temperature distribution in the width direction of the thermoplastic resin composition is more preferably within ± 3 ° C., and even more preferably within ± 1 ° C.
The temperature distribution of the thermoplastic resin composition can be measured with a contact thermometer or a non-contact thermometer.

The said shielding member is provided inside the both ends of two rolls, for example, and the width direction side surface of the supply means (for example, die | dye) of a thermoplastic resin composition, and a clearance gap. The shielding plate may be directly fixed to the side surface of the supply means, or may be supported and fixed by a support member. For example, the width of the shielding member is preferably equal to or greater than the width of the side surface of the supply means so that the rising airflow due to the heat radiation of the supply means can be effectively blocked.
The gap between the shielding member and the end portion in the width direction of the thermoplastic resin composition is preferably formed narrowly in order to efficiently shield the rising airflow flowing along the surface of the roll, and the width direction of the thermoplastic resin composition More preferably, it is about 50 mm from the end. The gap between the side surface of the thermoplastic resin composition supply means and the shielding member is not necessarily provided, but may be formed to such an extent that the airflow in the space surrounded by the shielding member can be discharged, for example, 10 mm or less. preferable.
In addition, as the material having a heat insulating function and / or a heat reflecting function, a material excellent in wind insulation and heat retention is preferable. For example, a metal plate such as stainless steel can be preferably used.

  As a method for eliminating variations in Re [0 °], Re [+ 40 °], and Re [−40 °], there is a method of increasing adhesion when the thermoplastic resin composition comes into contact with the casting roll. Specifically, the adhesion can be improved by combining electrostatic application method, air knife method, air chamber method, vacuum nozzle method and the like. Such an adhesion improving method may be carried out on the entire surface of the thermoplastic resin composition or may be carried out partially.

  After film formation in this way, it is preferable to cool the film by using one or more casting rolls in addition to two rolls (for example, a casting roll and a touch roll) through which the thermoplastic resin composition passes. The touch roll is usually arranged so as to touch the first casting roll on the most upstream side (closer to the die). In general, it is relatively common to use three cooling rolls, but this is not a limitation. The distance between the plurality of casting rolls is preferably 0.3 mm to 300 mm, more preferably 1 mm to 100 mm, and still more preferably 3 mm to 30 mm between the surfaces.

  Further, it is preferable to trim both ends of the processed film. The portion cut off by trimming may be crushed and used again as a raw material. Further, it is also preferable to perform a thickness increasing process (knurling process) on one or both ends. The height of the unevenness due to the thickness increasing process is preferably 1 μm to 50 μm, more preferably 3 μm to 20 μm. Thickening processing may be convex on both sides or convex on one side. The width of the thickness increasing process is preferably 1 mm to 50 mm, more preferably 3 mm to 30 mm. Extrusion can be performed at room temperature to 300 ° C.

  It is also preferable to attach a lami film on one side or both sides before winding. The thickness of the laminated film is preferably 5 μm to 100 μm, more preferably 10 μm to 50 μm. The material is not particularly limited, such as polyethylene, polyester, and polypropylene.

  The winding tension is preferably 2 kg / m width to 50 kg / width, more preferably 5 kg / m width to 30 kg / width.

  The film thickness of the film obtained by the production method of the present invention when unstretched is preferably 100 μm or less. When used for a liquid crystal display or the like, from the viewpoint of thinning, it is more preferably 80 μm or less, particularly preferably 60 μm or less, and particularly preferably 40 μm or less.

<Stretching and relaxation treatment>
Furthermore, after film formation by the above method, stretching and / or relaxation treatment may be performed. For example, each process can be implemented by the following combinations (a) to (g).
(A) transverse stretching (b) transverse stretching → relaxation treatment (c) longitudinal stretching (d) longitudinal stretching → relaxation treatment (e) longitudinal (transverse) stretching → lateral (longitudinal) stretching (f) longitudinal (transverse) stretching → lateral (Longitudinal) stretching → relaxation treatment (g) Transverse stretching → relaxation treatment → longitudinal stretching → relaxation treatment Among these, the steps (a) to (d) are particularly preferable.

The transverse stretching can be performed using a tenter. That is, the film is stretched by holding both ends in the width direction with clips and widening the film in the lateral direction. At this time, the stretching temperature can be controlled by sending wind at a desired temperature into the tenter. The stretching temperature is preferably Tg-10 ° C to Tg + 60 ° C, more preferably Tg-5 ° C to Tg + 45 ° C, and further preferably Tg-10 ° C to Tg + 20 ° C or less. Moreover, a preferable lateral stretch ratio is 1.2 to 3.0 times, more preferably 1.2 to 2.5 times, and still more preferably 1.2 to 2.0 times.
By performing preheating before stretching and heat setting after stretching, the Re and Rth distribution after stretching can be reduced, and the variation in orientation angle associated with bowing can be reduced. Either preheating or heat setting may be performed, but both are more preferable. These preheating and heat setting are preferably performed by holding with a clip, that is, preferably performed continuously with stretching.
Preheating can be performed at a temperature about 1 ° C to 50 ° C higher than the stretching temperature, preferably 2 ° C to 40 ° C or less, more preferably 3 ° C to 30 ° C. The preheating time is preferably 1 second to 10 minutes, more preferably 5 seconds to 4 minutes, and even more preferably 10 seconds to 2 minutes. During preheating, it is preferable to keep the width of the tenter substantially constant. Here, “substantially” refers to ± 10% of the width of the unstretched film.
The heat setting can be performed at a temperature lower by 1 ° C. to 50 ° C. than the stretching temperature, more preferably 2 ° C. to 40 ° C., further preferably 3 ° C. to 30 ° C. More preferably, it is less than the stretching temperature and less than Tg. The preheating time is preferably 1 second to 10 minutes, more preferably 5 seconds to 4 minutes, and even more preferably 10 seconds to 2 minutes. During the heat setting, it is preferable to keep the width of the tenter substantially constant. Here, “substantially” refers to 0% (the same width as the tenter width after stretching) to −10% (shrinking by 10% from the tenter width after stretching = reduced width) of the tenter width after stretching. If the width is wider than the stretched width, residual strain tends to occur in the film, which is not preferable.

Longitudinal stretching can be achieved by making the peripheral speed on the outlet side faster than the peripheral speed on the inlet side while heating between two pairs of rolls. Under the present circumstances, the expression of the retardation of the thickness direction can be changed by changing the space | interval (L) between and the film width (W) before extending | stretching. When L / W (referred to as aspect ratio) is 2 to 50 or less (long span stretching), it is easy to produce a film having a small Rth, and when L / W is 0.01 to 0.3 (short span), a film having a large Rth is used. Can be created. In this embodiment, any of long span stretching, short span stretching, and a region between them (intermediate stretching = L / W exceeds 0.3 and 2 or less) may be used. Span stretching and short span stretching are preferred. Further, when aiming at high Rth, it is more preferable to use short span stretching, and when aiming at low Rth, it is distinguished from long span stretching.
The stretching temperature is preferably Tg-10 ° C to Tg + 60 ° C, more preferably Tg-5 ° C to Tg + 45 ° C, and further preferably Tg-10 ° C to Tg + 20 ° C or less. Moreover, a preferable longitudinal draw ratio is 1.2 to 3.0 times, more preferably 1.2 to 2.5 times, and still more preferably 1.2 to 2.0 times.

Furthermore, dimensional stability can be improved by performing relaxation treatment after these stretching. Thermal relaxation is preferably performed either after film formation, after longitudinal stretching, or after lateral stretching, or both. The relaxation treatment may be performed online continuously after stretching, or may be performed offline after winding after stretching.
Thermal relaxation is (Tg-30) ° C to (Tg + 30) ° C, more preferably (Tg-30) ° C to (Tg + 20) ° C, and more preferably (Tg-15) ° C to (Tg + 10) ° C for 1 second to 10 minutes. More preferably 5 seconds to 4 minutes, still more preferably 10 seconds to 2 minutes, 0.1 kg / m to 20 kg / m, more preferably 1 kg / m to 16 kg / m, still more preferably 2 kg / m to 12 kg / m. It is preferable to carry out while conveying with tension.

[Polarizer]
The polarizing plate of the present invention can be obtained by laminating at least a polarizer (hereinafter also referred to as a polarizing film) on the film of the present invention. Hereinafter, the polarizing plate of the present invention will be described. Examples of the polarizing plate of the present invention include a polarizing plate formed on the surface of a polarizing film for the purpose of two functions of a protective film and viewing angle compensation, and a composite polarizing plate laminated on a protective film such as TAC. Can be mentioned.

  If the polarizing plate of this invention uses the film and polarizer of this invention, there will be no restriction | limiting in particular in a structure. For example, when the polarizing plate of the present invention is composed of a polarizer and two polarizing plate protective films (transparent polymer films) that protect both sides of the polarizer, the film of the present invention may be used as at least one polarizing plate protective film. it can. Moreover, the polarizing plate of this invention may have an adhesive layer for sticking with another member in the at least one surface. Moreover, in the polarizing plate of this invention, if the surface of the film of this invention is an uneven | corrugated structure, it will have an anti-glare (anti-glare) function. Further, the polarizing plate of the present invention has an antireflection film of the present invention in which an antireflection layer (low refractive index layer) is further laminated on the surface of the film of the present invention, and further optical anisotropy on the surface of the film of the present invention. It is also preferable to use the optical compensation film of the present invention in which layers are laminated.

  In general, a liquid crystal display device includes four polarizing plate protective films because a liquid crystal cell is provided between two polarizing plates. The film of the present invention may be used for any of the four polarizing plate protective films, but the film of the present invention is particularly advantageous as a protective film disposed between a liquid crystal cell and a polarizing plate in a liquid crystal display device. Can be used.

  The polarizing plate of the present invention more preferably has a configuration in which a cellulose acylate film, a polarizer and a film of the present invention are laminated in this order. Moreover, the structure which the cellulose acylate film, the polarizer, the film of this invention, and the adhesive layer are laminated | stacked in this order is also more preferable.

(Optical film)
The film of the present invention is used for the optical film of the polarizing plate of the present invention. The film can be surface treated. Examples of the surface treatment method include methods such as corona discharge, glow discharge, UV irradiation, and flame treatment.

(Cellulose acylate film)
As the cellulose acylate film of the polarizing plate of the present invention, a known cellulose acylate film for a polarizing plate is used. For example, a known triacetyl cellulose (TAC) film (for example, Fujitac T-60 manufactured by Fuji Film Co., Ltd.) can be preferably used. The lurose acylate film may be surface treated. Examples of the surface treatment method include saponification treatment.

(Polarizer)
As the polarizer, for example, a film obtained by immersing and stretching a polyvinyl alcohol film in an iodine solution can be used.

  As the polarizer used in the present invention, any appropriate one can be selected as long as the object of the present invention can be achieved. Examples of the polarizer include a uniaxially stretched film obtained by adsorbing a dichroic substance such as iodine or a dichroic dye on a hydrophilic polymer film, a dehydrated polyvinyl alcohol product or a dehydrochlorinated polyvinyl chloride product. And polyene-based oriented films. Examples of the hydrophilic polymer film include a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, and an ethylene / vinyl acetate copolymer partially saponified film. In the present invention, a polarizer in which iodine is adsorbed on a polyvinyl alcohol film is preferable.

  The polarizer preferably further contains at least one of potassium and boron. When the polarizer contains potassium and boron, a polarizer (polarizing plate) having a composite elastic modulus (Er) in a preferable range and having a high degree of polarization can be obtained. For production of a polarizer containing at least one of potassium and boron, for example, a film which is a material for forming a polarizer may be immersed in a solution of at least one of potassium and boron. The solution may also serve as a solution containing iodine.

  Any appropriate molding method can be adopted as a method for obtaining the polyvinyl alcohol film. A conventionally known method can be applied as the molding method. Moreover, a commercially available film can be used as it is for the polyvinyl alcohol film. Examples of commercially available polyvinyl alcohol films include the product name “Kuraray Vinylon Film” manufactured by Kuraray Co., Ltd., the product name “Tosero Vinylon Film” manufactured by Tosero Co., Ltd., and the product manufactured by Nippon Synthetic Chemical Industry Co., Ltd. Names include “Nippon Vinylon Film”.

  Regarding an example of a method for producing a polarizer, for example, a polymer film (raw film) mainly composed of a polyvinyl alcohol resin is immersed in a swelling bath containing pure water and a dyeing bath containing an aqueous iodine solution. Swelling treatment and dyeing treatment are performed while applying tension in the film longitudinal direction with different rolls. Next, the film subjected to the swelling treatment and the dyeing treatment is immersed in a crosslinking bath containing potassium iodide, and is subjected to crosslinking treatment and final stretching treatment while tension is applied in the longitudinal direction of the film with rolls having different speed ratios. Is given. The film subjected to crosslinking treatment is immersed in a washing bath containing pure water by a roll and subjected to a washing treatment. The film subjected to the water washing treatment is dried and wound up after adjusting the moisture content. Thus, the polarizer can be obtained by stretching the original film, for example, 5 to 7 times the original length.

  The polarizer may be subjected to any surface modification treatment in order to improve the adhesion with the adhesive. Examples of the surface modification treatment include corona treatment, plasma treatment, glow discharge treatment, flame treatment, ozone treatment, UV ozone treatment, and ultraviolet treatment. These treatments may be used alone or in combination of two or more.

(Adhesive layer)
The polarizing plate of the present invention may have an adhesive layer as at least one of the outermost layers (such a polarizing plate may be referred to as an adhesive polarizing plate). As a particularly preferred embodiment, a pressure-sensitive adhesive layer for adhering to another member such as another optical film or a liquid crystal cell can be provided on the side of the optical film where the polarizer is not adhered.

(Production method of polarizing plate)
The manufacturing method of the polarizing plate of this invention is demonstrated.
The polarizing plate of the present invention can be produced by bonding one side of the film of the present invention (a surface-treated surface in the case of surface treatment) to at least one side of the polarizer using an adhesive. When the cellulose acylate film, the polarizer, and the film of the present invention are bonded together in this order, the polarizing plate of the present invention can be produced by laminating the polarizer and other films using an adhesive on both sides of the polarizer. . In the manufacturing method of the polarizing plate of this invention, it is preferable that the film of this invention is directly bonded with the polarizer.

  As the adhesive, a known polarizing plate production adhesive can be used. Moreover, the aspect which has an adhesive bond layer between the said polarizer and each film is also preferable. Specific examples of the adhesive include an aqueous solution of polyvinyl alcohol or polyvinyl acetal (eg, polyvinyl butyral) and a latex of a vinyl-based polymer (eg, polybutyl acrylate). A particularly preferred adhesive is an aqueous solution of fully saponified polyvinyl alcohol. The polyvinyl alcohol-based adhesive preferably contains a polyvinyl alcohol-based resin and a crosslinking agent.

  The manufacturing method of the polarizing plate of this invention is not limited to said method, Another method can also be used. For example, JP 2000-171635, JP 2003-215563, JP 2004-70296, JP 2005-189437, JP 2006-199788, JP 2006-215463, JP 2006-227090. JP, 2006-243216, JP 2006-243681, JP 2006-259313, JP 2006-276574, JP 2006-316181, JP 2007-10756, JP 2007-128025, Use methods described in JP 2007-140092, JP 2007-171943, JP 2007-197703, JP 2007-316366, JP 2007-334307, JP 2008-20891, etc. it can. Among these, the methods described in JP2007-316366A and JP2008-20891A are more preferable.

  It is preferable that a protective film is also attached to the other surface of the polarizing film, and the protective film may be the film of the present invention. Moreover, the various films conventionally used as a protective film of a polarizing plate, such as a cellulose acylate film and a cyclic polyolefin polymer film, can be used.

  The polarizing plate of the present invention thus obtained is preferably used in a liquid crystal display device, and may be provided on either the viewing side or the backlight side of the liquid crystal cell, or on both sides. Not. Specific examples of the image display device to which the polarizing plate of the present invention can be applied include a self-luminous display device such as an electroluminescence (EL) display, a plasma display (PD), and a field emission display (FED: Field Emission Display). Can be mentioned. The liquid crystal display device is applied to a transmissive liquid crystal display device, a reflective liquid crystal display device, and the like.

[Liquid Crystal Display]
The film and polarizing plate of the present invention can be used for liquid crystal display devices of various modes. Preferably, it can be used for TN (Twisted Nematic), OCB (Optically Compensatory Bend), ECB (Electrically Controlled Birefringence) mode liquid crystal display devices, and more preferably for TN and ECB mode liquid crystal displays.

[Optical compensation film]
The film of the present invention can be preferably used as a film for optical applications, and can be particularly preferably used as an optical compensation film.

(Laminated film)
Furthermore, it can also be set as a laminated | multilayer film by providing a well-known optically anisotropic layer to the film of this invention, and can also be used for an optical compensation film use as a laminated | multilayer film.

[Antireflection film]
The antireflection film of the present invention is obtained by providing an antireflection layer on the film of the present invention. The antireflection film generally includes a low refractive index layer which is also an antifouling layer, and at least one layer having a refractive index higher than that of the low refractive index layer (a high refractive index layer and a medium refractive index in the present specification). Layer) on a (transparent) support.

Colloidal metal by multilayer deposition of transparent thin films of inorganic compounds (metal oxides, etc.) with different refractive indexes by chemical vapor deposition (CVD) method, physical vapor deposition (PVD) method, sol-gel method of metal compounds such as metal alkoxides Examples include a method of forming a thin film by post-processing (ultraviolet irradiation: JP-A-9-157855, plasma processing: JP-A-2002-327310) after forming an oxide particle film.
On the other hand, various antireflection films formed by laminating thin films in which inorganic particles are dispersed in a matrix have been proposed as antireflection films with high productivity.
The antireflection film which consists of the antireflection layer which provided the anti-glare property which the antireflection film by application | coating as mentioned above provided the surface of the uppermost layer with the shape of a fine unevenness | corrugation is also mentioned.
The film of the present invention can be applied to any of the above methods, but the coating method (coating type) is particularly preferable.

(Layer structure)
(Transparent) The antireflection film comprising a layer structure of at least a middle refractive index layer, a high refractive index layer, and a low refractive index layer (outermost layer) on the support has a refractive index satisfying the following relationship: Designed.
The refractive index of the high refractive index layer> The refractive index of the medium refractive index layer> The refractive index of the transparent support> The refractive index of the low refractive index layer Further, a hard coat layer is provided between the transparent support and the medium refractive index layer. May be. Furthermore, it may consist of a medium refractive index hard coat layer, a high refractive index layer and a low refractive index layer.
Examples thereof include JP-A-8-122504, JP-A-8-110401, JP-A-10-300902, JP-A-2002-243906, JP-A-2000-11706, and the like.

  Other functions may be imparted to each layer, for example, an antifouling low refractive index layer or an antistatic high refractive index layer (eg, JP-A-10-206603, JP-A-2002). -243906 publication etc.) etc. are mentioned.

  The haze of the antireflection film is preferably 5% or less, more preferably 3% or less. Further, the strength of the film is preferably H or more, more preferably 2H or more, and most preferably 3H or more in a pencil hardness test according to JIS K5400.

(High refractive index layer and medium refractive index layer)
The layer having a high refractive index of the antireflection film is composed of a curable film containing at least an inorganic compound ultrafine particle having a high refractive index having an average particle size of 100 nm or less and a matrix binder.
Examples of the high refractive index inorganic compound fine particles include inorganic compounds having a refractive index of 1.65 or more, preferably those having a refractive index of 1.9 or more. Examples thereof include oxides such as Ti, Zn, Sb, Sn, Zr, Ce, Ta, La, and In, and composite oxides containing these metal atoms.
In order to obtain such ultrafine particles, the surface of the particles is treated with a surface treatment agent (for example, silane coupling agents, etc .: JP-A-11-295503, JP-A-11-153703, JP-A-2000-9908). No., anionic compound or organometallic coupling agent: Japanese Patent Laid-Open No. 2001-310432, etc., core-shell structure with high refractive index particles as a core (Japanese Patent Laid-Open No. 2001-166104, etc.), specific dispersant Combined use (for example, Unexamined-Japanese-Patent No. 11-153703, patent number US62081058B1, Unexamined-Japanese-Patent No. 2002-27776069 etc.) etc. are mentioned.
Examples of the material forming the matrix include conventionally known thermoplastic resins and curable resin films.
Further, it is selected from a polyfunctional compound-containing composition containing at least two radically polymerizable and / or cationically polymerizable groups, an organometallic compound containing a hydrolyzable group, and a partial condensate composition thereof. At least one composition is preferred. Examples thereof include compounds described in JP-A Nos. 2000-47004, 2001-315242, 2001-31871, and 2001-296401.
A curable film obtained from a colloidal metal oxide obtained from a hydrolyzed condensate of metal alkoxide and a metal alkoxide composition is also preferred. For example, it describes in Unexamined-Japanese-Patent No. 2001-293818.
The refractive index of the high refractive index layer is generally 1.70 to 2.20. The thickness of the high refractive index layer is preferably 5 nm to 10 μm, and more preferably 10 nm to 1 μm.
The refractive index of the middle refractive index layer is adjusted to be a value between the refractive index of the low refractive index layer and the refractive index of the high refractive index layer. The refractive index of the middle refractive index layer is preferably 1.50 to 1.70.

(Low refractive index layer)
The low refractive index layer is formed by sequentially laminating on the high refractive index layer. The refractive index of the low refractive index layer is 1.20 to 1.55. Preferably it is 1.30-1.50.
It is preferable to construct as the outermost layer having scratch resistance and antifouling property. As means for greatly improving the scratch resistance, imparting slipperiness to the surface is effective, and conventionally known thin film layer means such as introduction of silicone or introduction of fluorine can be applied.
The refractive index of the fluorine-containing compound is preferably 1.35 to 1.50. More preferably, it is 1.36-1.47. The fluorine-containing compound is preferably a compound containing a crosslinkable or polymerizable functional group containing fluorine atoms in the range of 35 to 80% by mass.
For example, paragraph numbers [0018] to [0026] of Japanese Patent Application Laid-Open No. 9-222503, paragraph numbers [0019] to [0030] of Japanese Patent Application Laid-Open No. 11-38202, and paragraph numbers of Japanese Patent Application Laid-Open No. 2001-40284. [0027] to [0028], JP-A 2000-284102, and the like.
The silicone compound is a compound having a polysiloxane structure, preferably containing a curable functional group or a polymerizable functional group in the polymer chain and having a crosslinked structure in the film. Examples thereof include reactive silicone (eg, Silaplane, manufactured by Chisso Corporation), polysiloxane containing silanol groups at both ends (Japanese Patent Laid-Open No. 11-258403, etc.), and the like.

The crosslinking or polymerization reaction of the fluorine-containing and / or siloxane polymer having a crosslinking or polymerizable group is carried out at the same time or after the coating composition for forming the outermost layer containing a polymerization initiator, a sensitizer, etc. It is preferable to carry out by light irradiation or heating.
Also preferred is a sol-gel cured film in which an organometallic compound such as a silane coupling agent and a specific fluorine-containing hydrocarbon group-containing silane coupling agent are cured by a condensation reaction in the presence of a catalyst.

  For example, a polyfluoroalkyl group-containing silane compound or a partially hydrolyzed condensate thereof (Japanese Patent Laid-Open Nos. 58-142958, 58-147483, 58-147484, Japanese Patent Laid-Open Nos. 9-157582, 11) -106704), silyl compounds containing a poly "perfluoroalkyl ether" group which is a fluorine-containing long chain group (Japanese Patent Application Laid-Open Nos. 2000-117902, 2001-48590, 2002) 53804), and the like.

The low refractive index layer has an average primary particle diameter of 1 to 150 nm such as a filler (for example, silicon dioxide (silica), fluorine-containing particles (magnesium fluoride, calcium fluoride, barium fluoride)) as an additive other than the above. Low refractive index inorganic compounds, organic fine particles described in paragraphs [0020] to [0038] of JP-A-11-3820, etc.), silane coupling agents, slip agents, surfactants, and the like can be contained.
When the low refractive index layer is located below the outermost layer, the low refractive index layer may be formed by a vapor phase method (vacuum deposition method, sputtering method, ion plating method, plasma CVD method, etc.). The coating method is preferable because it can be manufactured at a low cost.
The film thickness of the low refractive index layer is preferably 30 to 200 nm, more preferably 50 to 150 nm, and most preferably 60 to 120 nm.

(Hard coat layer)
The hard coat layer is provided on the surface of the transparent support in order to impart physical strength to the antireflection film. In particular, it is preferably provided between the transparent support and the high refractive index layer.
The hard coat layer is preferably formed by a crosslinking reaction or a polymerization reaction of a light and / or heat curable compound.
The curable functional group is preferably a photopolymerizable functional group, and the hydrolyzable functional group-containing organometallic compound is preferably an organic alkoxysilyl compound.
Specific examples of these compounds are the same as those exemplified for the high refractive index layer.
Specific examples of the constituent composition of the hard coat layer include those described in JP-A Nos. 2002-144913, 2000-9908, and WO 00/46617.
The high refractive index layer can also serve as a hard coat layer. In such a case, it is preferable to form fine particles dispersed in the hard coat layer using the method described for the high refractive index layer.

The hard coat layer can also serve as an antiglare layer (described later) provided with particles having an average particle size of 0.2 to 10 μm to provide an antiglare function (antiglare function).
The film thickness of the hard coat layer can be appropriately designed depending on the application. The film thickness of the hard coat layer is preferably 0.2 to 10 μm, more preferably 0.5 to 7 μm.
The strength of the hard coat layer is preferably H or higher, more preferably 2H or higher, and most preferably 3H or higher in a pencil hardness test according to JIS K5400. Further, in the Taber test according to JIS K5400, the smaller the wear amount of the test piece before and after the test, the better.

(Forward scattering layer)
The forward scattering layer is provided in order to give a viewing angle improvement effect when the viewing angle is inclined in the vertical and horizontal directions when applied to a liquid crystal display device. By dispersing fine particles having different refractive indexes in the hard coat layer, it can also serve as a hard coat function.
For example, Japanese Patent Laid-Open No. 11-38208 specifying a forward scattering coefficient, Japanese Patent Laid-Open No. 2000-199809 having a relative refractive index of a transparent resin and fine particles in a specific range, and Japanese Patent Laid-Open No. 2002 specifying a haze value of 40% or more. -107512 gazette etc. are mentioned.

(Other layers)
In addition to the above layers, a primer layer, an antistatic layer, an undercoat layer, a protective layer, and the like may be provided.

(Production method of antireflection film)
Each layer of the antireflection film is formed by a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating, a micro gravure method or an extrusion coating method (US Pat. No. 2,681,294). It can be formed by coating.

  The antireflection film may have an antiglare function that scatters external light. The antiglare function is obtained by forming irregularities on the surface of the antireflection film. When the antireflection film has an antiglare function, the haze of the antireflection film is preferably 3 to 30%, more preferably 5 to 20%, and most preferably 7 to 20%.

  As a method for forming irregularities on the surface of the antireflection film, any method can be applied as long as these surface shapes can be sufficiently maintained. For example, a method of forming irregularities on the film surface using fine particles in the low refractive index layer (for example, JP 2000-271878 A), a lower layer of the low refractive index layer (high refractive index layer, medium refractive index layer) Alternatively, a small amount (0.1 to 50% by mass) of relatively large particles (particle size 0.05 to 2 μm) is added to the hard coat layer to form a surface uneven film, and these shapes are maintained thereon. A method of providing a low refractive index layer (for example, JP 2000-281410 A, JP 2000-95893 A, JP 2001-100004 A, 2001-281407, etc.), an uppermost layer (antifouling layer) A method of physically transferring the uneven shape onto the surface after coating (for example, as an embossing method, Japanese Patent Laid-Open Nos. 63-278839, 11-183710, 2000-275401) It includes equal forth) and the like.

  The present invention will be described more specifically with reference to the following examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

[Production Example 1] Production of acrylic resin pellets As acrylic resins, pellets of "Delpet 980N" manufactured by Asahi Kasei Chemicals Corporation, which is a styrene-acrylic copolymer, were used. “Delpet 980N” indicates negative intrinsic birefringence. Further, Table 1 below shows the glass transition temperature Tg and the temperature Ts at which the zero shear viscosity becomes 3000 Pa · s.

[Production Example 2] Production of acrylic resin pellets As acrylic resins, pellets of "Delpet 80N" manufactured by Asahi Kasei Chemicals Co., Ltd., which is a styrene-acrylic copolymer, were used. “Delpet 80N” indicates negative intrinsic birefringence. Further, Table 1 below shows the glass transition temperature Tg and the temperature Ts at which the zero shear viscosity becomes 3000 Pa · s.

[Production Example 3] Production of Styrenic Resin Pellets As styrene-maleic anhydride resin, pellets of "Daylark D332" manufactured by Nova Chemical Co. were used. “Daylark D332” indicates negative intrinsic birefringence. Further, Table 1 below shows the glass transition temperature Tg and the temperature Ts at which the zero shear viscosity becomes 3000 Pa · s.

[Production Example 4] Production of cyclic olefin pellets As a cyclic olefin resin, HpE described in Example 5 of JP-A-2008-52119 was synthesized and used according to Reference Synthesis Example 3. The obtained cyclic olefin resin exhibits negative intrinsic birefringence. Further, Table 1 below shows the glass transition temperature Tg and the temperature Ts at which the zero shear viscosity becomes 3000 Pa · s.

[Production Example 5] Production of methyl methacrylate-styrene copolymer resin pellets As a methyl methacrylate-styrene copolymer resin, Estyrene MS600 (trade name, methyl methacrylate / styrene = 6) manufactured by Nippon Steel Chemical Co., Ltd. / 4 copolymer resin) pellets. “Estyrene MS600” exhibits negative intrinsic birefringence. Further, Table 1 below shows the glass transition temperature Tg and the temperature Ts at which the zero shear viscosity becomes 3000 Pa · s.

[Production Example 6] Production of polystyrene resin pellets Polystyrene resin pellets (GPPS) were used. The resin exhibits a negative intrinsic birefringence. Further, Table 1 below shows the glass transition temperature Tg and the temperature Ts at which the zero shear viscosity becomes 3000 Pa · s.

[Example 1]
(Production of film)
Using the resin pellets shown in Table 1 below as a thermoplastic resin exhibiting negative birefringence, drying at Tg-20 ° C. for 2 hours or more, melting at Ts + 10 ° C., and kneading using a single screw kneading extruder Extruded. At this time, a screen filter, a gear pump, and a leaf disk filter were arranged in this order between the extruder and the die, and these were connected by a melt pipe. This was extruded from a die having an extrusion temperature (discharge temperature) Ts + 5 ° C. and a width of 1900 mm and a lip gap of 1 mm.
Thereafter, a melt (molten resin) was extruded between the chill roll and the touch roll. At this time, a cylinder is set on the most upstream side cast cast metal (chill roll) having a width of 2000 mm and a diameter of 400 mm so as to achieve the touch pressure shown in Table 1 below, and an HCr plating with a width of 1700 mm and a diameter of 350 mm. The touched metal touch roll was brought into contact. The touch pressure was measured by sandwiching a prescale for medium pressure (manufactured by Fuji Film Co., Ltd.) between two rolls at a constant circumferential speed (5 m / min) in the absence of melt, and the value was measured at the time of film formation. Pressure was used. Touch rolls and chill rolls having a Shore hardness of 60 HS were used. In addition, the melt was dropped on the central part sandwiched between the cast roll and the touch roll. Using these rolls, the touch roll peripheral speed, the chill roll peripheral speed and the peripheral speed ratio are set to the conditions shown in Table 1 below, and the distance between the die and the melt landing point is set to the distance shown in Table 1 below. The film was formed at the transport speed (chill roll speed) described in Table 1. Further, the temperature of the melt immediately before the pinching, that is, the upper part of the landing point was measured and listed as the pinching temperature in Table 1 below. Note that the discharge temperature and the clamping pressure temperature almost coincided. The temperatures of the touch roll and chill roll were both Tg-5 ° C. The film forming atmosphere was 25 ° C. and 60%.
Then, after trimming both ends (5 cm each of the full width) immediately before winding, thicknessing (knurling) with a width of 10 mm and a height of 20 μm was applied to both ends. The film forming width was 1540 mm and the film was wound up by 450 m. The thickness of the film after film formation was set to the thickness shown in the following Table 1, and the film of Example 1 was produced.

(Characteristics of film)
As characteristics of the obtained film of Example 1, the slow axis direction, tilt direction, Re [0 °], | Re [40 °] -Re [−40 °] |, Ts, Tg measured by the above method. , ΔRe [0 °] are listed in Table 1 below.

(Scale irregularity)
The scaly unevenness of the film of Example 1 was measured by the following method. The obtained results were evaluated based on the following criteria, and the results are shown in Table 1 below.
A film sampled at 20 × 20 cm was sandwiched between polarizing plates arranged in crossed Nicol so that the slow axis of the film was at an angle of 45 ° with the absorption axis of the polarizing plate, and scaly unevenness was visually evaluated.
(Double-circle): When generation | occurrence | production of scaly unevenness is not recognized over the sample film whole surface, but there is no problem practically.
◯: When scaly unevenness is observed in a part of the sample film, but its strength is weak and there is no practical problem.
Δ: Scale-like unevenness is observed on the entire surface of the sample film, but its strength is weak and practically acceptable.
X: When the occurrence of scaly unevenness is observed on the entire surface of the sample film, its strength is strong, and there is a problem in practical use.

[Examples 2, 3 , 5-7, 9-11, Reference Examples 4, 8, Comparative Examples 1-3]
Except having changed resin used and film forming conditions as described in the following Table 1, it carried out similarly to Example 1, and obtained the film of each Example , the reference example, and the comparative example. The characteristics of the films of each Example , Reference Example and Comparative Example are shown in Table 1 below. In Comparative Example 2 in which the tilt direction was not observed, Re [+ 40 °] and Re in a direction inclined by θ ° from the normal direction to the longitudinal direction within the plane including the film normal and the film longitudinal direction. [−40 °] was measured.

From Table 1, in Examples 1-11 which performed the pinching process at the pinching temperature of the range of this invention using the negative thermoplastic resin whose Tg is 100 degreeC or more, all are the inclination phase difference structure. , ΔRe [0 °] was small, and it was found that the scale-like planar failure was improved. On the other hand, in Comparative Example 1, a negative thermoplastic resin having a general glass transition temperature (Tg = 75 ° C.) was used, ΔRe [0 °] was large, optical characteristics varied greatly, and scaly surface faults occurred. There were very many. In Comparative Example 2, the clamping step was performed without any difference in peripheral speed, and there was no tilt orientation, no tilt phase difference structure was measured, and there were very many scale-like surface faults. In Comparative Example 3, a negative thermoplastic resin having a Tg of 82 ° C. was used, but ΔRe [0 °] was large, there was no tilt orientation, and there were very many scaly surface failures.
From the above, it has been found that according to the production method of the present invention, it is possible to produce a film in which a tilted phase difference structure is formed, variation in optical characteristics is small, and scale-like surface failure is improved.
Moreover, from Examples 1 to 11, it was found that the film of the present invention is a film suitable for optical applications, and can be particularly suitably used as an optical compensation film.

<Mounting and evaluation on TN liquid crystal panel>
(Preparation of polarizing plate for TN mode)
A polyvinyl alcohol (PVA) film having a thickness of 80 μm is dyed by immersing in an iodine aqueous solution (30 ° C.) having an iodine concentration of 0.05 mass% and a KI concentration of 3 mass% for 60 seconds, and then boric acid concentration is 4 mass%. The film was longitudinally stretched 5.5 times the original length while immersed in an aqueous solution (55 ° C.) with a KI concentration of 3.5% by mass for 55 seconds, and then dried at 50 ° C. for 4 minutes to obtain a thickness. A 20 μm polarizer was obtained.
Separately, a cellulose acylate film (manufactured by Fuji Film Co., Ltd., Fujitac T60) was immersed and saponified in an aqueous sodium hydroxide solution at 55 ° C. at a concentration of 2.0 mol / L, and then sufficiently washed with water. The sodium oxide was washed away. Then, after being immersed for 1 minute in 35 degreeC dilute sulfuric acid aqueous solution at 0.005 mol / L, it was immersed in water, the dilute sulfuric acid aqueous solution was washed away sufficiently, and it dried at 105 degreeC.
The surface of the unstretched film of Example 1 was subjected to corona discharge treatment, and a polyvinyl alcohol-based adhesive was used, and was directly attached to one side of the polarizer with a roll-to-roll. The saponified Fujitac T60 was attached to the opposite side of the polarizer using a polyvinyl alcohol adhesive to obtain a polarizing plate.

(Production of liquid crystal display device)
A pair of polarizing plates provided in a liquid crystal display device (AQUAS LC-20C1-S, manufactured by Sharp Corporation) using a TN type liquid crystal cell is peeled off, and a polarizing plate produced using the film of each example instead. Were attached to the viewer side and the backlight side one by one through an adhesive so that the film of each example was on the liquid crystal cell side. As a result, it was found that when the film of the example of the present invention was used, the display visibility was good when incorporated in a TN liquid crystal display device.

(Preparation of transflective ECB mode polarizing plate)
<Mounting and evaluation on transflective ECB liquid crystal panel>
A polarizing plate was produced using the produced film of Example 1 and the film of Comparative Example 1. Specifically, first, iodine was adsorbed to a stretched polyvinyl alcohol film to prepare a polarizing film. Using this polarizing film, a Re = 270 nm λ / 2 plate composed of an 80 μm TAC film (manufactured by Fuji Film Co., Ltd.) and a uniaxially stretched norbornene polymer film in the arrangement shown in FIG. 1, Invention 1 Or the film of the comparative example 1 was bonded together. In this manner, two polarizing plates PL1 using the film of Example 1 and two PL2 using the film of Comparative Example 1 were produced.

(Production and evaluation of transflective ECB mode liquid crystal display)
Next, an ECB type transflective liquid crystal display device was manufactured using the polarizing plate. The liquid crystal cell used uses ZLI-1695 (manufactured by Merck) as the liquid crystal material, and the liquid crystal layer thickness is 2.4 μm in the reflective electrode region (reflective display portion) and 4.9 μm in the transmissive electrode region (transmissive display portion). did. The pretilt angle at the substrate interface of the liquid crystal layer was 2 degrees, and Δnd of the liquid crystal cell was about 150 nm for the reflective display portion and about 320 nm for the transmissive display portion.
The two types of polarizing plates prepared above were arranged above and below the liquid crystal cell as shown in FIG. The arrows in the polarizing plates P1 and P2 indicate the respective absorption axes, the arrows in the retardation film indicate the respective slow axes, and the arrows of the ECB cells indicate the rubbing direction of the rubbing treatment applied to the respective facing surfaces. Here, the 12 o'clock direction is 0 ° and the clockwise direction is +.

With respect to the liquid crystal display device LCD1 which is an embodiment of the present invention, a viewing angle with a contrast ratio of 10 or more in monochrome display was obtained. On the other hand, in the LCD 2 using the film of the comparative example, the viewing angle with a contrast ratio of 10 or more was less than 260 ° in any of the upper, lower, left and right directions.
Thus, when the film of the present invention is used, when it is incorporated in a transflective ECB mode liquid crystal display device, a large viewing angle compensation can be performed.

<Mounting and evaluation on IPS liquid crystal panel>
(Preparation of polarizing plate for IPS mode)
A polyvinyl alcohol (PVA) film having a thickness of 80 μm is dyed by immersing in an iodine aqueous solution (30 ° C.) having an iodine concentration of 0.05 mass% and a KI concentration of 3 mass% for 60 seconds, and then boric acid concentration is 4 mass%. The film was longitudinally stretched 5.5 times the original length while immersed in an aqueous solution (55 ° C.) with a KI concentration of 3.5% by mass for 55 seconds, and then dried at 50 ° C. for 4 minutes to obtain a thickness. A 20 μm polarizer was obtained.
Separately, a cellulose acylate film (manufactured by Fuji Film Co., Ltd., Fujitac T60) was immersed and saponified in an aqueous sodium hydroxide solution at 55 ° C. at a concentration of 2.0 mol / L, and then sufficiently washed with water. The sodium oxide was washed away. Then, after being immersed for 1 minute in 35 degreeC dilute sulfuric acid aqueous solution at 0.005 mol / L, it was immersed in water, the dilute sulfuric acid aqueous solution was washed away sufficiently, and it dried at 105 degreeC.
The surface of the unstretched film of Example 7 was subjected to corona discharge treatment, and a polyvinyl alcohol-based adhesive was used, and the film was directly attached to one side of the polarizer using a roll-to-roll. The saponified Fujitac T60 was attached to the opposite side of the polarizer using a polyvinyl alcohol adhesive to obtain a polarizing plate.

(Production of liquid crystal display device)
On one glass substrate, electrodes were arranged so that the distance between adjacent electrodes was 20 μm, and a polyimide film was provided as an alignment film thereon, and a rubbing treatment was performed. A polyimide film was provided on one surface of a separately prepared glass substrate, and a rubbing treatment was performed to obtain an alignment film. Two glass substrates are laminated and bonded so that the alignment films face each other so that the rubbing directions are parallel, and then the refractive index anisotropy (Δn) is 0.0888 and the dielectric anisotropy (Δε) ) Is a positive nematic liquid crystal composition of 4.5, a liquid crystal cell having a cell gap d of 3.5 μm and Δn × d of 311 nm was formed.
Two polarizing plates 1 prepared as described above were prepared and placed one above the other on the liquid crystal layer. At this time, the upper and lower polarizing plates were arranged so that the absorption axes thereof were orthogonal to each other. Moreover, it bonded so that the unstretched film of Example 7 might become a liquid crystal cell side. The liquid crystal layer and the polarizing plate of the IPS type liquid crystal display device (26 type IPS liquid crystal television monitor (26C3500), manufactured by Toshiba Corp.) were peeled off and incorporated to obtain an IPS type liquid crystal display device.
As a result, it was found that when the film of the embodiment of the present invention was used, the symmetry of the light leakage azimuth 4 direction was improved and the display visibility was good when incorporated in an IPS liquid crystal display device.

(Antireflection film for liquid crystal display)
When the optical film of Example 1 was produced as a low reflection film according to Example 47 of the Japan Institute of Invention and Technology (Publication No. 2001-1745) and incorporated in a liquid crystal display device, good optical performance was obtained.

(Anti-reflection film for organic EL)
According to Japanese Patent Laid-Open No. 9-127885, the optical film of Example 1 and a linearly polarizing plate were bonded to each other so that the angle between the slow axis and the absorption axis was 45 degrees to prepare an antireflection film. The antireflection film was incorporated into an organic EL display device, and the antireflection function was confirmed. Furthermore, it confirmed that it had the asymmetric viewing angle performance from the characteristic of the film of this invention.

It is a top view showing the absorption axis of the polarizing plate, the orientation direction of a liquid crystal cell, and the slow axis of a film in the transflective ECB mode liquid crystal display device of the present invention.

Claims (6)

A sandwich comprising a composition containing a thermoplastic resin exhibiting negative birefringence passing between the first sandwiching surface and the second sandwiching surface constituting the sandwiching device, and continuously sandwiched to form a film. A method for producing a film including a pressing step,
Tg of the thermoplastic resin is 100 ° C. or higher,
The temperature of the composition immediately before passing between the first and second clamping surfaces constituting the clamping device is controlled to (Tg + 20 ° C.) to Tg + 120 ° C. (where Tg is the glass transition of the thermoplastic resin) represents the temperature),
The moving speed of the first clamping surface of the clamping device is made faster than the moving speed of the second clamping surface, and the first clamping surface and the second clamping surface of the clamping device defined by the following formula (I) are moved. A method for producing a film in which the speed ratio is controlled to 0.600 to 0.999 .
Moving speed ratio = moving speed of the second clamping surface / moving speed of the first clamping surface Formula (I)   2. The film according to claim 1, wherein a difference between a temperature Ts at which a zero shear viscosity of the thermoplastic resin exhibits 3000 Pa · s and a glass transition temperature Tg of the thermoplastic resin is 160 ° C. or less. Production method.   The method for producing a film according to claim 1 or 2, wherein the thermoplastic resin is at least one selected from an acrylic resin, a styrene resin, a cyclic olefin resin, and a maleimide resin.   The sandwiching step includes a step of melt-extruding a composition containing a thermoplastic resin exhibiting negative birefringence, and the melt-extruded composition is interposed between the first sandwiching surface and the second sandwiching surface. The method for producing a film according to any one of claims 1 to 3, wherein the film is continuously pressed and formed into a film shape. The said narrow pressure apparatus is two rolls, The manufacturing method of the film of any one of Claims 1-4 characterized by the above-mentioned. In the said narrow pressure process, the said composition is clamped by the pressure of 0.5-500 Mpa, The manufacturing method of the film as described in any one of Claims 1-5 characterized by the above-mentioned.

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