WO2010146910A1

WO2010146910A1 - Long gradient phase difference film, method for manufacturing long gradient phase difference film, polarizing plate, and liquid crystal display device

Info

Publication number: WO2010146910A1
Application number: PCT/JP2010/055675
Authority: WO
Inventors: 博紀梅田; 勝己前島; 真治稲垣; 賢治三島; 健司岡田; 秀人木村; 里誌森井; 翠木暮; 範江谷原
Original assignee: コニカミノルタオプト株式会社
Priority date: 2009-06-19
Filing date: 2010-03-30
Publication date: 2010-12-23

Abstract

Disclosed are a long gradient phase difference film having a high degree of uniformity and a versatile method for manufacturing such a long gradient phase difference film. The long gradient phase difference film is characterized in that the angle (β) formed by the surface of a refractive index ellipsoid and the film surface is 7 to 85°, the in-plane phase difference (Ro') of the refractive index ellipsoid is 10 to 90 nm, the thickness phase difference (Rt') is 70 to 300 nm, Rt'>Ro', the standard deviation of the in-plane phase difference Ro of the film, the phase difference R40 from the slant angle 40° of the film, β, and the angle θ formed by the in-plane slow axis of the film and the length direction thereof are 2 nm or less, 2 nm or less, 2° or less, and 2° or less, respectively.

Description

Long inclined retardation film, method for producing long inclined retardation film, polarizing plate and liquid crystal display device

The present invention relates to a retardation film used for liquid crystal display and the like.

When a general-purpose biaxial retardation film is used for a TN type liquid crystal display device (LCD), the vertical viewing angle is not sufficiently widened, and it has been necessary to improve it as a monitor for a personal computer or the like.

On the other hand, in Patent Document 1, the polycarbonate film is sheared by a metal roll or a metal belt, and the upper and lower visual fields are obtained by using a retardation film that develops an inclined retardation by tilting the optical axis in the film thickness direction. It is shown that the corners widen.

For cellulose ester films, polyimide films and the like, production of retardation films having an optical axis inclined in the same manner has been attempted (

Patent Documents

2, 3, and 4), and it has been shown that the viewing angle is similarly improved.

In Patent Document 5, a technique using a thermoplastic norbornene resin (a type of polycycloolefin film) instead of a polycarbonate, polyester, or cellulose ester film in which the uniformity of retardation is unstable due to a large intrinsic birefringence. It is disclosed.

TN LCDs using retardation films produced by these manufacturing methods have the effect of improving the upper and lower viewing angles that are lacking when biaxial retardation films are used. Is a problem.

The cause of non-uniformity is considered to be due to the non-uniformity of how the metal roller or metal belt hits the film itself in the shearing process.

In the metal roller method that performs shearing processing in a short time, the contact time between the film and the metal roller is very short, but the tilt orientation processing must be performed within that time, and the processing method itself is uneven. It is an easy method.

Also, in order to increase the width and increase the production speed, it is necessary to increase the pressure during the treatment, which is a method of increasing the burden on the equipment. Even when a metal belt is used, if the production speed is increased, it is necessary to increase the pressure at the time of processing, and the same problem occurs.

On the other hand, there is known an optical compensation film in which liquid crystal molecules are applied on the surface of a base material and tilted or hybrid-oriented (Patent Document 6). Although there is some improvement in black display unevenness by using this optical compensation film, there are problems such as complicated manufacturing processes, coating failures and orientation defects, and poor yield. It cannot be called a certain manufacturing method.

On the other hand,

Patent Documents

3 and 7 disclose an optical compensation film in which a heat-shrinkable film is provided on the front and back of a light-transmitting film, and the contraction force is transmitted using the difference in shrinkage rate to control the phase difference. Since these contract in one direction when the base material is contracted, the base material is stretched in a state where one end of the base material is fixed (fixed end stretching method).

In this method, the uniformity of the tilt angle and the orientation angle was improved to some extent as compared to the metal roller method, but the contraction control in the width direction was not performed to make the tilt angle and tilt direction constant. As a result, the inclination angle and the orientation angle in the width direction, in particular, the uniformity of the orientation angle was insufficient.

In recent years, with the increase in brightness and contrast of liquid crystal display devices, retardation films used in TN type LCDs have been strongly required to have uniform orientation angles in the width direction.

JP 2003-25414 A JP 2003-315557 A JP-A-9-33908 JP 2005-17328 A JP 2007-38646 A JP 2009-98662 A JP-A-9-318815

An object of the present invention is to provide a long-graded retardation film having high uniformity and a versatile production method for the long-graded retardation film.

The object of the present invention was achieved by the following means.

1. The rising angle β of the refractive index ellipsoid from the film surface in the plane including the longitudinal direction of the film and the thickness direction of the film is 7 to 85 °, and the in-plane retardation (Ro ′) of the refractive index ellipsoid is 10 90 nm, thickness retardation (Rt ′) 70 to 300 nm, Rt ′> Ro ′, in-plane retardation Ro of film, retardation R40, β from film tilt angle 40 °, and in-plane retardation of film A long-graded retardation film characterized in that the standard deviation in the longitudinal direction of the angle θ formed by the phase axis and the longitudinal direction is within 2 nm, within 2 nm, within 2 ° and within 2 °, respectively.

2. 2. The long inclined retardation film as described in 1 above, wherein the in-plane slow axis of the film and the longitudinal direction are perpendicular to each other.

3. In the method for producing a long inclined retardation film having an oblique retardation, a temperature gradient is provided in the longitudinal direction in the inclined orientation zone for imparting the oblique retardation, and the temperature gradient is 20 in the case of a temperature rise. A method for producing a long inclined retardation film, wherein the temperature is from -20 ° C / second to 500 ° C / second, and in the case of descending, from -20 ° C / second to -500 ° C / second.

4. When the elastic modulus (εA) of one surface of the film and the elastic modulus (εB) of the other surface before applying the oblique phase difference are εA <εB, 0.001 <εA / εB <0. 9. The method for producing a long inclined retardation film as described in 3 above, which is .9.

5. 5. The method for producing a long inclined retardation film as described in 3 or 4 above, wherein the retardation development property of the film before applying the oblique retardation is 0.3 nm / μm to 20 nm / μm.

6. The above 3 to 5, wherein in the tilted orientation zone, the rate of dimensional change in the longitudinal direction of the film and the direction perpendicular thereto is within 5% before and after the tilted orientation treatment. Manufacturing method of long slanted phase difference film.

7. A polarizing plate comprising the long inclined retardation film as described in 1 or 2 above.

8. 3. A liquid crystal display device comprising the long inclined retardation film as described in 1 or 2 above.

According to the present invention, it was possible to obtain a highly uniform long inclined retardation film and a versatile production method for the long inclined retardation film.

It is a schematic diagram of a TN type liquid crystal display device of the present invention. It is the schematic which shows an example of the TN type | mold liquid crystal display device of E mode of this invention. It is the schematic which shows an example of the TN type | mold liquid crystal display device of O mode of this invention. It is the schematic of the whole inclination orientation processing apparatus of this invention. It is one of the preferable examples of the inclined orientation zone of this invention. It is one of the preferable examples of the inclined orientation zone of this invention. It is one of the preferable examples of the inclined orientation zone of this invention. It is a related figure of the optical axis and production direction of the film of this invention. It is a perspective view of the inclination retardation film and refractive index ellipsoid of this invention. It is sectional drawing of the refractive index ellipsoid of this invention.

<Long inclined retardation film of the present invention>
The long inclined retardation film of the present invention has a rising angle β of the refractive index ellipsoid from the film surface in a plane including the long direction of the film and the thickness direction of the film of 7 to 85 °, and the refractive index ellipsoid The in-plane retardation (Ro ′) of the film is 10 to 90 nm, the thickness retardation (Rt ′) is 70 to 300 nm, and Rt ′> Ro ′. From the in-plane retardation Ro of the film, the tilt angle of the film is 40 degrees. The standard deviations in the longitudinal direction of the phase difference R40, β and the angle θ between the in-plane slow axis of the film and the longitudinal direction are within 2 nm, within 2 nm, within 2 ° and within 2 °, respectively. And

And when this characteristic long elongate phase difference film of the present invention is subjected to the tilt orientation treatment, the tilt orientation treatment (hereinafter also referred to as the tilt orientation treatment) is performed in a state where the hardness of one surface of the film is different from that of the other surface. ) And manufactured. Hardness can be represented by an elastic modulus at the time of processing.

In order to satisfy the tilt alignment treatment of the present invention, it is necessary to develop birefringence, which effectively exhibits the phase difference developability with respect to the stress applied to the film in the temperature range where the tilt alignment treatment is performed. In addition, the absolute value of the phase difference needs to be a desired value.

In addition to the tension in the longitudinal direction of the film, the gradient orientation treatment of the present invention is characterized by changing the hardness of the film in the longitudinal direction, and the means is a temperature gradient in the longitudinal direction of the film. It is effective to have an area for attaching.

Furthermore, it is preferable to keep the width by suppressing the dimensional change in the width direction of the film in the tilt orientation treatment of the film.

The present invention adjusts the hardness of the front and back of the film, applies tension in the longitudinal direction, imparts a high temperature gradient in the longitudinal direction, and maintains the width in the lateral direction, thereby exhibiting birefringence. This makes it possible to tilt the film axis stably and efficiently.

Details of the present invention will be described below.
<Rising angle β and orientation angle θ of the refractive index ellipsoid from the film surface in the plane including the long direction of the tilted retardation film and the thickness direction of the film>
In the present invention, β is 7 ° to 85 °, preferably 15 ° to 45 °.

Also, the in-plane slow axis and the longitudinal direction of the film may or may not be orthogonal. In addition, orthogonal here means that it is substantially orthogonal which is true orthogonal +/- 5 degree.

The standard deviations of β and θ are within 2 ° and 2 °, respectively. The standard deviations of β and θ were calculated as follows.
<Calculation method of standard deviation of β>
<Calculation method of β>
Measurement wavelength: 632 nm, measurement spot diameter: 100 μm or less, measurement pitch: 0.5 mm, phase difference in increments of 5 ° is measured at a tilt angle of −40 to 40 °. At that time, take the data measured with the tilt angle of -40 ~ 40 ° around the film's longitudinal direction and the data measured with the width direction as the center of rotation, and the tilt angle (horizontal axis) Draw a graph plotting the phase difference (vertical axis) against.

Among them, in the graph that is not symmetrical about 0 ° (the graph measured with the width direction as the center of rotation), the tilt angle value at which the phase difference takes the extreme value is read, and the angle is β To do.

As an apparatus for measuring the phase difference at a tilt angle of −40 to 40 ° in this way, for example, a micro-region birefringence measuring apparatus manufactured by Mizoji Optical Industry Co., Ltd., KOBRA-21ADH manufactured by Oji Scientific Instruments, A commercially available retardation (birefringence) measuring device such as AxoScan manufactured by Axometrics may be used.

The standard deviation σ [°] of β calculated as described above at 500 points in the longitudinal direction (MD direction) at the same position as the width direction (TD direction) is defined as the standard deviation of β.

As a phase difference measuring apparatus that can be used for calculating the standard deviation σ [°] of β as described above, for example, a micro-region birefringence measuring apparatus manufactured by Mizoji Optical Co., Ltd. can be cited.

<Ro 'and Rt' of refractive index ellipsoid>
The in-plane retardation value (Ro ′) and thickness direction retardation value (Rt ′) of the refractive index ellipsoid of the present invention are Rt ′> Ro ′, 10 ≦ Ro ′ ≦ 90 nm and 70 ≦ Rt ′ ≦ 300 nm. More preferably, 20 ≦ Ro ′ ≦ 80 nm and 100 ≦ Rt ′ ≦ 200 nm.

The phase difference values Ro ′ and Rt ′ can be obtained by the following formula.

Ro ′ = (nx′−ny ′) × d
Rt ′ = ((nx ′ + ny ′) / 2−nz ′) × d
d is the thickness (nm) of the film.

X ′ is a direction axis with the maximum refractive index in a plane perpendicular to z ′ of the refractive index ellipsoid, and nx ′ is a refractive index in the x ′ direction.

Y ′ is a directional axis having a minimum refractive index in a plane perpendicular to z ′ of the refractive index ellipsoid, and ny ′ is a refractive index in the y ′ direction.

Z ′ is the thickness direction axis of the refractive index ellipsoid, and nz ′ is the refractive index in the z direction.

<Calculation method of Ro 'of refractive index ellipsoid>
The phase difference is measured at an inclination angle of −40 to 40 ° at the measurement point. At that time, data obtained by measuring the width direction as the rotation center of measurement is taken, and a graph in which the phase difference (vertical axis) is plotted against the tilt angle (horizontal axis) is drawn.

In the graph, the phase difference value at the inclination angle β taking the extreme value is read, and the phase difference value is defined as Ro ′ of the refractive index ellipsoid.

<Calculation method of Rt ′ of refractive index ellipsoid>
In the graph that is not symmetric about the 0 ° center (measured with the width direction as the rotation center) used for the calculation of β and Ro ′, the phase difference value of β + 40 ° or β−40 ° is expressed as a refractive index ellipse. It is defined as R40 ′ of the body.

Among the values of Ro ′, R40 ′, film thickness d (nm), average refractive index of film, and plane perpendicular to the z ′ direction of the refractive index ellipsoid by commercially available calculation software “N-Calc”, The refractive index (nx) in the direction (x ′) in which the refractive index is maximum, the direction (y ′) in which the refractive index is minimum among the planes orthogonal to the z ′ direction of the refractive index ellipsoid, and the thickness direction (z ′) ', Ny', nz '). From the obtained values of nx ′, ny ′, and nz ′, the thickness direction retardation value Rt ′ of the refractive index ellipsoid was calculated according to the above formula.
<Ro, Rt, θ, R40 of tilted retardation film>
The in-plane retardation value (Ro) and thickness direction retardation value (Rt) of the inclined retardation film of the present invention are 10 ≦ Ro ≦ 180 nm and 70 ≦ Rt ≦ 300 nm.

The phase difference values Ro and Rt can be obtained by the following equations.

Ro = (nx−ny) × d
Rt = ((nx + ny) / 2−nz) × d
d is the thickness (nm) of the film.

X is a direction axis (in-plane slow axis) where the refractive index is maximum in the film plane, and nx is a refractive index in the x direction.

Y is a direction axis (in-plane fast axis) in which the refractive index is minimum in the film plane, and ny is a refractive index in the y direction.

Z is the thickness direction axis of the film, and nz is the refractive index in the z direction.

Θ indicates how many times the in-plane slow axis of the film is deviated from this reference line with respect to the transport direction of the long film. The angle was defined clockwise from the reference line.

R40 is a graph symmetric about 0 ° (of the longitudinal direction as the center of rotation) of the two graphs of the center of rotation and the width direction drawn in the calculation of β. In the measured tilt angle vs. phase difference value graph), the phase difference value at a tilt angle of 40 ° is shown.

These standard deviations were measured at a measurement wavelength of 632 nm, a measurement spot diameter of 100 μm or less, a measurement pitch of 0.5 mm, and 500 points in the longitudinal direction (MD direction) at the same position as the width direction (TD direction). The standard deviation σ [°] was calculated by measuring Ro, R40, and θ of the film as described above. This is defined as the standard deviation of Ro of the film, the standard deviation of R40, and the standard deviation of θ.

The above-mentioned retardation value can be measured using a commercially available automatic birefringence meter. Examples thereof include a micro-region birefringence measuring apparatus manufactured by Mizoji Optical Industry Co., Ltd., KOBRA-21ADH manufactured by Oji Scientific Instruments, and AxoScan manufactured by Axometrics. The standard deviation can be measured using an automatic birefringence meter at a measurement wavelength of 632 nm and a measurement spot diameter of 100 μm or less in an environment of 23 ° C. and 55% RH. For example, a micro-region birefringence measuring apparatus manufactured by Mizoji Optical Co., Ltd. can be used.

In the long inclined retardation film of the present invention, the standard deviations of Ro and R40 in the long direction are both within 2 nm. By setting the standard deviations of Ro, R40, β, and θ within the above ranges, it is possible to improve non-uniformity of light leakage (also referred to as screen unevenness or contrast unevenness) that occurs during black display of a liquid crystal display device. . Further, the non-uniformity of θ directly leads to a decrease in front contrast.
<Adjustment of elastic modulus of front and back of retardation film>
The retardation film of the present invention is characterized in that it has a difference in hardness between the front and back surfaces, specifically, a modulus of elasticity during the tilt alignment treatment. As specific means, a method of laminating films having different elastic moduli, a method of creating a temperature difference between the front and back of the film during the tilt orientation treatment, and a method of adjusting the residual solvent amount when the film is cast by solution casting Etc.

In the present invention, the elastic modulus εA of one surface of the long inclined retardation film and the elastic modulus εB of the other surface have a relationship of εA <εB and 0.001 <εA / εB <0.9. It is preferable that there is. Furthermore, 0.001 <εA / εB <0.7 is preferable.

As a method of laminating films having different elastic moduli, a method of laminating layers with different resins, additives, etc. can be selected. Lamination methods include co-casting, co-extrusion, double casting, bonding, etc. This method can be used.

Also, a good solvent can be applied to dissolve the film surface and bonded, or the remaining solvent state at the time of film formation of the optical film can be bonded. Moreover, the coating liquid containing resin and an additive can also be coated on the single side | surface or both surfaces of the already formed film.

When using these means, the adhesive layer at the interface between the films is preferably as thin as possible. For example, any of the adhesive layers formed by the above means is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less.

In the present invention, when the difference in elastic modulus between the front and back surfaces necessary for the tilt orientation treatment is provided by lamination, the difference in elastic modulus can be substantially provided by utilizing the difference in glass transition temperature. In that case, it is preferable to laminate two or more layers having a glass transition temperature difference of 5 ° C. or more, preferably 20 ° C. or more and 150 ° C. or less.

When the elastic modulus difference between the front and back surfaces is given by lamination, one layer may or may not be peeled after the inclined alignment treatment of the present invention. In the case of not peeling, it is preferable to laminate a colorless and transparent one whose optical value is adjusted.

For the glass transition point, the DSC method (JIS C 6481) was used to raise the temperature of the test piece from room temperature at a rate of 20 ° C./minute, the calorific value was measured with a differential scanning calorimeter, and the endothermic curve obtained as a result. Two extension lines are drawn on the (exothermic curve), and Tg is obtained from the intersection of the 1/2 straight line between the extension lines and the endothermic curve.

In the case of carrying out with a single film, it is possible to employ a method based on a temperature difference between the front and back of the film during the tilted orientation treatment, and a method of adjusting the amount of residual solvent when the film is cast. A temperature difference can be made by applying winds with different temperatures on the front and back of the film or bringing rolls with different temperatures into contact with each other. The temperature difference between the front and back of the film is preferably in the range of 20 to 150 ° C.

In the case of the solution casting film forming method, in addition to the method of changing the residual solvent amount by changing the drying speed of the front and back of the film, use the method of changing the plasticizer content in the thickness direction by controlling the drying speed You can also.

The residual solvent amount difference between the front and back of the film is preferably in the range of 1 to 150% by mass. As means for controlling the difference in residual solvent amount, there are means for changing the temperature and air volume of the drying air on the front and back, or laminating components having different solvent amounts.

In addition, a coating solution containing a resin and an additive can be coated on one side or both sides of a film that has already been formed, or a plurality of solutions containing resins and additives with different amounts of solvent can be used for double casting or co-casting. There is also means for laminating by a casting film forming method.

The amount of residual solvent on the front and back sides is the same as the amount of residual solvent in each single layer in the case of a laminate, and the drying conditions for each condition in the front and back sides are fixed to the respective conditions. And measure the amount of residual solvent.

Residual solvent amount is defined as follows.

Residual solvent amount (% by mass) = {(MN) / N} × 100
Here, M is the mass at the time of starting the inclined alignment treatment of the web, and N is the mass when the mass M is dried at 110 ° C. for 3 hours.

The elastic modulus adjusted by the above method can be measured by the following method. In addition, the elasticity modulus in this invention means a tensile elasticity modulus.
1) Method of laminating films having different elastic moduli The glass transition temperatures of the single-layer film for each of the first and second layers are measured to obtain Tg1 and Tg2 (Tg1> Tg2). The sample is allowed to stand for 24 hours or more under the conditions of 23 ° C. and 50 ± 5% RH, and then cut into 10 mm width × 200 mm length so that the longitudinal direction of the film (running direction = longitudinal direction) becomes the longitudinal direction. Each sample is set at a king pressure of 0.25 MPa and a distance between marked lines of 50 ± 10 mm, and pulled at a set temperature T2 ° C. of the tilted orientation zone at a pulling speed of 50 ± 10 mm / min.

The tangent line of the obtained SS curve with strain of 1% to 1.5% is extrapolated, and the slope is defined as the elastic modulus.
2) Method of providing temperature difference between film front and back The elastic modulus of the raw film at the temperature applied to the front surface and the temperature applied to the back surface is measured by the same method as in 1).
3) Method of changing the amount of residual solvent by changing the drying speed of the front and back of the film Sample 1 is prepared by drying both surfaces of the film under the drying conditions from the film surface side. Next, a sample 2 is produced by drying both surfaces of the film under the drying conditions from the film back side. The Tg1 and Tg2 of each of the samples 1 and 2 (Tg1> Tg2) are measured by DSC. The elastic modulus of each film is calculated in the same manner as in 1) at the temperature T2 ° C. of the tilted orientation zone.
<Phase difference of the raw film>
In the present invention, the film immediately before the tilt alignment treatment is called a raw film.

The retardation of the original film of the present invention is, for example, an optical film satisfying 0 ≦ Ro ≦ 100 nm and 0 ≦ Rt ≦ 180 nm, and the refractive index ellipsoid of the retardation plate is obtained by applying the tilt alignment treatment of the present invention. A retardation film inclined with respect to the film surface of the retardation plate can be obtained.

As a material capable of realizing the retardation film of the present invention, all transparent films that can be used for optical applications can be used, and cellulose ester films, polycarbonate films, polysulfone films, polyethersulfone films, and polyacrylate films can be used. A film selected from a polycycloolefin film, a polyimide film, an acrylic film, and a polyethylene film is preferable. Furthermore, you may improve retardation development with an additive.

For example, by adding the retardation increasing agent described in JP-A No. 2000-1111914, JP-A No. 2002-62430, JP-A No. 2005-99191, JP-A No. 2008-64941, the retardation development property can be improved. Can do. Or it is also possible to give high phase difference expression property by making process temperature low within a predetermined range. Furthermore, the phase difference can be controlled by the post-stretching temperature. In this case, the phase difference can be increased by lowering the temperature.
<Phase difference expression>
The retardation expression of the present invention refers to the degree of retardation that can be expressed with a thickness per 1 μm of the retardation film, and is in the range of 0.3 to 20 nm / μm, and 0.5 to 5 nm / μm is preferable.

The expression of the retardation can be achieved by applying a force (for example, simple film formation, stretching treatment, conveyance tension, etc.) to the material forming the raw film to form an inclined retardation film.

The retardation development can be measured by the following method.

When the raw film is a laminated film, each single-layer film is prepared.

Measure each Tg by DSC, determine the film with the lower Tg, and call it Film A. In an environment of 23 ° C. and 55% RH, the film A is allowed to stand for 24 hours, and Ro at a measurement wavelength of 590 nm is measured as Ro (1). Further, the film thickness is measured and set to d (1).

Using a tensile tester (TG-2KN, manufactured by Minebea Co., Ltd.), each of the above samples was set at a chucking pressure of 0.25 MPa and a distance between marked lines: 50 ± 10 mm. Then, the film is stretched at a stretching speed of 50 ± 10 mm / min in the longitudinal direction at a stretching ratio of 1.4, and the film thicknesses d (2) and Ro (2) are measured for the sample.

In addition, what added the absolute value of the dimensional change rate of the direction orthogonal to the direction of extending | stretching the dimensional change rate of a film direction and a film center part is defined as an actual draw ratio, and an actual draw ratio will be 1.4 times. Adjust as follows.

Then, phase difference expression = Ro (2) / d (2) −Ro (1) / d (1).

Moreover, when an original film is a laminated body, what added together the retardation expression of each single layer is made into the retardation expression of an original film.
<Inclined orientation treatment>
The tilted retardation film of the present invention can be produced by subjecting the original film to a tilt orientation treatment.

The inclined orientation processing apparatus has a preheating zone, an inclined orientation zone, and a cooling zone as basic zones (processes), and is provided with at least two pairs of nip rolls sandwiching these three zones. Applying tension in the direction.

In the present invention, it is possible to obtain the long inclined retardation film of the present invention simply by passing the preheating zone, the inclined orientation zone, and the cooling zone while applying tension in the long direction and maintaining the width direction dimension. It is possible to do.

The preheating zone of the present invention is a zone for preheating the raw film, and is a zone for heating the temperature of the film to a set temperature T2 ° C. or less of the inclined alignment zone. In the preheating zone, the maximum temperature in the preheating zone is adjusted near the exit of the zone. The maximum temperature varies depending on the material of the original film that is inclined and oriented, but is preferably (Tg2 + 30) ° C. or lower of the original film. The preheating zone preferably passes in 0.5 to 10 seconds.

The inclined orientation zone of the present invention is a zone for actually orienting the original film. By providing the temperature gradient of the present invention in this zone, the refractive index ellipsoid of the raw film can be inclined.

The inclined alignment zone is preferably passed for 0.01 to 10 seconds, more preferably 0.5 to 10 seconds.

The cooling zone of the present invention is for fixing the tilted orientation state in the tilted orientation zone and controlling the tension of the film. The temperature in the cooling zone is T2-5 ° C. or lower, more preferably Tg2 ° C. or lower, when the set temperature of the tilted alignment treatment zone is T2 ° C.

In the present invention, the temperature gradient in the tilted alignment zone is as defined below.
1) In the case of temperature increase: non-contact type radiation at a position 50 cm from the end point of the preheating zone, every 50 cm from the start point to the end point of the inclined alignment treatment zone, and every 50 cm from the start point to the end point of the cooling zone Install a thermometer and measure the surface temperature on both sides of the film.

∙ Set the film setting temperature at the end of the preheating zone to T1 ° C. Further, the film setting temperature in the inclined alignment treatment zone is T2 ° C., and the time from T1 ° C. to T2 ° C. is t1 seconds. Then, (T2−T1) / t1 [° C./second] is a temperature gradient in the case of a temperature rise. T1 and T2 are temperatures set appropriately from Tg1 and Tg2.

Here, the film set temperature refers to a film surface temperature set in advance so as to be the temperature. The film surface temperature is the surface temperature of the lower elastic modulus.
2) In the case of temperature drop: The film set temperature at the end point of the inclined orientation treatment zone is the same as T2. The film set temperature in the cooling zone is T3 ° C., and the time from T2 to T3 ° C. is t2 seconds. Then, (T3−T2) / t2 [° C./second] is a temperature gradient in the case of a temperature drop.

(T3-T1) ° C is defined as the temperature difference between the entry side and the exit side.

The temperature gradient of the present invention is characterized by being 20 ° C./second to 500 ° C./second in the case of a temperature rise, and −20 ° C./second to −500 ° C./second in the case of a fall. Preferably, the temperature is 20 ° C./second to 250 ° C./second in the case of temperature rise. More preferably, it is 20 ° C./second to 100 ° C./second. In the case of a temperature drop, it is −20 ° C./second to −250 ° C./second. More preferably, it is −20 ° C./second to −100 ° C./second.

In the inclined orientation processing apparatus of the present invention, it is preferable to apply tension in the longitudinal direction (MD direction) and regulate the width in the lateral direction (TD direction).

In the manufacturing apparatus of the present invention, there is means for partitioning between adjacent zones using a wind shield, and the wind shield may be partitioned leaving a gap. Moreover, it is also preferable to nip and partition with a roll. As a means for partitioning adjacent zones, a preferred form is a form of partitioning with a wind shield plate, but it is possible to partition using both a wind shield plate and a roll, or partition with a roll alone.

The temperature can be controlled by installing a thermometer (for example, a non-contact thermometer) that can display and measure online in each partitioned zone.

The heating / cooling method for each zone includes a method for changing the temperature and volume of the wind, and a method using a heat roll and a cooling roll. In the present invention, a known method can be used.

The method using the wind can produce an optically uniform film because the film surface is not deteriorated compared to the case of using a roll, and the black display unevenness when the panel is formed can be further reduced. .

(Longitudinal tension)
In order to perform the tilt alignment treatment of the present invention, it is necessary to apply a tension in the MD direction. However, if the tension is excessively increased, the film is stretched in the long direction and the tilt angle becomes small. Therefore, it is preferable to adjust the transport tension so that the dimensional change in the longitudinal direction is within 5% (0.95 to 1.05 times) before entering the inclined orientation processing apparatus and after leaving. .

As means for controlling tension, two or more pairs of nip rolls are provided near the inlet of the preheating zone and the outlet of the cooling zone so as to sandwich the preheating zone, the inclined orientation zone, and the cooling zone (see FIGS. 4 and 7). There is. It is also preferable to provide a spare nip roll in the preheating zone (see FIG. 5). Tension can be applied while transporting with a tenter. Alternatively, the tension can be controlled by compressing with a pair of nip rolls. In that case, the roll is preferably made of rubber.

There is also means for applying tension to the film by utilizing the shrinkage and expansion of the film used in the present invention. In that case, as long as it is a means for easily performing displacement in the longitudinal direction, tension in the longitudinal direction may be applied by a tenter.

(Width direction regulation)
In the tilted orientation zone of the present invention, it is necessary to regulate the width of the film in the width direction, and the degree of change is preferably within 5% (0.95 to 1.05 times the dimensional change). .

In this range, the uniformity of the tilt angle can be improved, and the uniformity can be improved in the tilt direction as well as in the in-plane axial direction. It is presumed that by causing shrinkage in the width direction, there is a place where the contraction stress applied in the width direction is released, so that the uniformity is impaired.

There are tenters and rolls as the width dimension regulating method of the film in the present invention. In the case of regulating the width with a tenter, there is a method of performing desired processing while holding both ends of the obtained raw film with clips and transporting it with a tenter while maintaining the width.

When the width is restricted by a roll, a desired treatment is performed while one or both sides of the film are in contact with the roll. As the material of the roll, metal, rubber, or the like can be used, but it is preferable that the frictional force in the width direction is as large as possible.

(Stretching process)
In the present invention, a stretching step may be provided either before or after the tilt alignment treatment. This stretching step is exclusively for stretching in the TD direction, and is provided to finally adjust the retardation (Ro, Rt) as a retardation film.

The draw ratio is 1.06 to 1.30 times, preferably 1.06 to 1.15 times. The stretching treatment is preferably performed within a range that does not affect the tilt alignment treatment.
<Other optical properties>
1) Haze Haze measures haze according to JIS-K7136 using Nippon Denshoku Co., Ltd. haze meter NDH2000. The smaller the haze, the better the display quality of the liquid crystal display device, particularly the front CR. The haze value of the retardation film of the present invention is not particularly limited, but is preferably 0.1% or less, more preferably 0.05% or less.
2) Wavelength dispersion The Ro [480] / Ro [590] of the tilted retardation film of the present invention is preferably 0.8 to 1.2, more preferably 0.8 to 1.1, and particularly preferably. Is 0.8 to 1.03.

The smaller the value in the above range, the more constant the phase difference value in a wide visible light region. Therefore, when used in a liquid crystal display device, light leakage at a specific wavelength is less likely to occur. The color shift in the oblique direction can be further improved.
3) Other film properties (Ra: surface irregularities)
1 m ² of the film obtained in the above Example was sampled, and the average value of arithmetic average roughness (Ra) on both sides of the film was measured according to the method of JISK7125. That is, using a film surface roughness measuring machine (WYKO-NT1100) manufactured by Veeco, the measurement was performed at a magnification of 20 times on each side of the film at three points, and the average value was determined as Ra (surface roughness). It was.

(curl)
The curl is measured by placing a polarizing plate having a size of 230 mm × 305 mm on a flat table with the surface where the end is lifted down and leaving it in an environment of 25 ° C. and 55% RH for 2 hours or more. The height of the farthest position at the end of the polarizing plate is measured with respect to the surface as the curl amount.

A case where the surface is affixed to the liquid crystal cell is concave (+) curl, and a case where the surface is convex is-(minus) curl. When a separate film and a protective film were attached, the measurement was performed with these films attached.
<Material for forming long inclined retardation film>
As the long inclined retardation film of the present invention, all the transparent films that can be used for the above-mentioned optical applications can be used.

Examples of the cellulose ester film of the present invention include an optical film described in Japanese Patent Application No. 2009-67724, a commercially available cellulose ester film (for example, Konica Minoltack KC8UX, KC4UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC12U KC8UY-HA, KC8UX-RHA, KC8UXW-RHA-C, KC8UXW-RHA-NC, KC4UXW-RHA-NC (manufactured by Konica Minolta Opto Co., Ltd.).

As the commercially available polycycloolefin film, those described in Japanese Patent Application Laid-Open No. 2007-38646 can be used, and trade names “ZEONEX”, “ZEONOR”, manufactured by Nippon Zeon Co., Ltd., manufactured by JSR Corporation. Product name “ARTON”, a product name “TOPAS” manufactured by TICONA Corporation, and a product name “APEL” manufactured by Mitsui Chemicals, Inc.

Examples of commercially available polycarbonate films include Pure Ace, Panlite (manufactured by Teijin Chemicals Ltd.), Elmec (Kaneka Corp.), and the like.

A thermoplastic resin having a substituted imide group or an unsubstituted imide group in the side chain as described in JP-A No. 2001-343529 (WO 01/37007) and JP-A No. 2003-315559, and a side chain Also, a mixture of a substituted phenyl group or a thermoplastic resin having an unsubstituted phenyl group and a nitrile group can be used. Specific examples include a resin composition having an alternating copolymer of isobutene and N-methylenemaleimide and an acrylonitrile / styrene copolymer.

Among these forming materials, a mixture of the above-mentioned thermoplastic resin having a substituted imide group or an unsubstituted imide group in the side chain and a thermoplastic resin having a substituted phenyl group or an unsubstituted phenyl group and a nitrile group in the side chain. Is preferred.

The thickness of the long inclined retardation film of the present invention is not particularly limited, but is, for example, in the range of 5 to 500 μm, preferably in the range of 10 to 200 μm, and particularly preferably in the range of 15 to 150 μm.

(Phase difference, wavelength dispersion adjusting agent)
Specific examples of the retardation and chromatic dispersion adjusting agent preferably used in the present invention include the above-mentioned ascending agents, compounds described in JP-A-2005-99191, JP-A-2008-64941, for example, benzotriazole compounds Benzophenone compounds, triazine compounds, cyanoacrylate compounds, salicylic acid ester compounds, nickel complex compounds, and the compounds described in JP-A No. 2000-11914 and JP-A No. 2002-62430. It is not limited only to the compound.

(Other additives)
The long inclined retardation film of the present invention contains general additives as described in Table 1 of JP-A-2008-64941, for example, an ultraviolet absorber, an antioxidant, and fine particles. be able to.

The raw film of the present invention can also be prepared by a melt film forming method. In that case, the cellulose ester melts at a high temperature at the same time as the thermal decomposition causes a decrease in the molecular weight of the cellulose ester, which may adversely affect the mechanical properties of the resulting optical film. It is necessary to let

In order to lower the melting temperature of the optical film constituting material, it can be achieved by adding a plasticizer having a melting point or glass transition temperature lower than the glass transition temperature of the cellulose ester.

The plasticizer that can be used in the present invention is not particularly limited, but a polyhydric alcohol ester plasticizer is preferable. The polyhydric alcohol ester is composed of an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule.

The polyhydric alcohol used in the polyhydric alcohol ester is represented by the following general formula (1).

Formula (1): R ^1- (OH) _l
In the formula, R ¹ represents a monovalent organic group, l represents a positive integer of 2 or more, and the OH group represents an alcoholic hydroxyl group or a phenolic hydroxyl group.

An example of a preferable polyhydric alcohol is trimethylolpropane. As the monocarboxylic acid used in the polyhydric alcohol ester, a known aromatic monocarboxylic acid can be used, and a preferable aromatic monocarboxylic acid is used. As an example of the acid, benzoic acid is particularly preferable, but the present invention is not limited thereto.

(Antioxidants, thermal degradation inhibitors)
In the present invention, as antioxidants and thermal degradation inhibitors, degradation inhibitors generally known (antioxidants, peroxide decomposition agents, radical inhibitors, metal deactivators, acid scavengers, amines, etc.) Can be used. In particular, lactone, sulfur, phenol, double bond, hindered amine, and phosphorus compounds can be preferably used. The deterioration preventing agents are described in JP-A-3-199201, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854.

As the antioxidant, those having a 2,6-dialkylphenol structure are preferred as the antioxidant, and those commercially available under the trade names Irganox 1076 and Irganox 1010 from Ciba Japan, for example, are preferred.

Examples of the phosphorus compound include those commercially available from Sumitomo Chemical Co., Ltd. under the trade name Sumilizer-GP.

These antioxidants and thermal deterioration inhibitors can obtain a synergistic effect by using several different types of compounds in combination rather than using only one kind.
<Manufacture of the film used as the raw material of the long inclination retardation film of this invention>
Next, as an example of a method for producing a retardation film used in the present invention, a method for producing a film using a cellulose ester film as a raw film will be described.
<Manufacturing method of cellulose ester film of the present invention-raw film forming step>
<Method for producing cellulose ester film>
The cellulose ester film according to the present invention can be preferably used regardless of whether it is a film produced by a solution casting method or a film produced by a melt casting method.

The cellulose ester film of the present invention is prepared by dissolving a cellulose ester and an additive in a solvent to prepare a dope, casting a dope onto an endless metal support that moves infinitely, and casting the dope. It is carried out by a step of drying as a web, a step of peeling from a metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

The process for preparing the dope will be described. The concentration of cellulose ester in the dope is preferably higher because the drying load after casting on the metal support can be reduced. However, if the concentration of cellulose ester is too high, the load during filtration increases and the filtration accuracy is poor. Become. The concentration that achieves both of these is preferably 10 to 35% by mass, and more preferably 15 to 25% by mass.

The solvent used in the dope may be used alone or in combination of two or more, but it is preferable to use a mixture of a good solvent and a poor solvent of cellulose ester in terms of production efficiency, and there are many good solvents. This is preferable from the viewpoint of the solubility of the cellulose ester.

A preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent. With a good solvent and a poor solvent, what dissolve | melts the cellulose ester to be used independently is defined as a good solvent, and what poorly swells or does not melt | dissolve is defined as a poor solvent.

Therefore, depending on the average acetylation degree (acetyl group substitution degree) of the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as the solvent, the cellulose ester acetate ester (acetyl group substitution degree 2.4), cellulose Acetate propionate is a good solvent, and cellulose acetate (acetyl group substitution degree 2.8) is a poor solvent.

The good solvent used in the present invention is not particularly limited, and examples thereof include organic halogen compounds such as methylene chloride, dioxolanes, acetone, methyl acetate, and methyl acetoacetate. Particularly preferred is methylene chloride or methyl acetate.

The poor solvent used in the present invention is not particularly limited, but for example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone and the like are preferably used. The dope preferably contains 0.01 to 2% by mass of water.

Also, the solvent used for dissolving the cellulose ester is used by collecting the solvent removed from the film by drying in the film-forming process and reusing it.

The recovery solvent may contain trace amounts of additives added to the cellulose ester, such as plasticizers, UV absorbers, polymers, monomer components, etc., but these are preferably reused even if they are included. Can be purified and reused if necessary.

As a method for dissolving the cellulose ester when preparing the dope described above, a general method can be used. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure.

It is preferable to stir and dissolve while heating at a temperature that is higher than the boiling point of the solvent at normal pressure and does not boil under pressure, in order to prevent the formation of massive undissolved material called gel or mamako.

In addition, a method in which a cellulose ester is mixed with a poor solvent and wetted or swollen, and then a good solvent is added and dissolved is also preferably used.

Pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or a method of increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

The heating temperature with the addition of the solvent is preferably higher from the viewpoint of the solubility of the cellulose ester, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates.

The preferred heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and still more preferably 70 ° C to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

Alternatively, a cooling dissolution method is also preferably used, whereby the cellulose ester can be dissolved in a solvent such as methyl acetate.

Next, the cellulose ester solution is filtered using an appropriate filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like, but there is a problem that the filter medium is likely to be clogged if the absolute filtration accuracy is too small.

For this reason, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium with 0.001 to 0.008 mm is more preferable, and a filter medium with 0.003 to 0.006 mm is still more preferable.

There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel do not drop off fibers. preferable.

It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material cellulose ester by filtration.

Bright spot foreign matter means that when two polarizing plates are placed in a crossed Nicol state, an optical film or the like is placed between them, light is applied from one polarizing plate side, and observation is performed from the other polarizing plate side. It is a point (foreign matter) where light from the opposite side appears to leak, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less.

More preferably, it is 100 pieces / cm ² or less, still more preferably 50 pieces / m ² or less, still more preferably 0 to 10 pieces / cm ² . Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

The dope can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The increase in the difference (referred to as differential pressure) is small and preferable.

The preferred temperature is 45 to 120 ° C, more preferably 45 to 70 ° C, and still more preferably 45 to 55 ° C.

A smaller filtration pressure is preferable. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and further preferably 1.0 MPa or less.

Here, the dope casting will be described.

The metal support in the casting process is preferably a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used as the metal support.

The cast width can be 1 ~ 4m. The surface temperature of the metal support in the casting step is −50 ° C. to less than the boiling point of the solvent, and a higher temperature is preferable because the web drying speed can be increased. May deteriorate.

The preferred support temperature is 0 to 55 ° C, more preferably 25 to 50 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent.

The method for controlling the temperature of the metal support is not particularly limited, but there are a method of blowing hot air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When warm air is used, wind at a temperature higher than the target temperature may be used.

In order for the cellulose ester film to exhibit good flatness, the amount of residual solvent when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. Particularly preferred is 20 to 30% by mass or 70 to 120% by mass.

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

Residual solvent amount (% by mass) = {(MN) / N} × 100
Note that M is the mass of a sample collected during or after the production of the web or film, and N is the mass after heating M at 114 ° C. for 1 hour.

Further, in the drying step of the cellulose ester film, the web is peeled off from the metal support, and further dried, and the residual solvent amount is preferably 1% by mass or less, more preferably 0.1% by mass or less, Particularly preferred is 0 to 0.01% by mass or less.

In the film drying process, generally, a roll drying method (a method in which webs are alternately passed through a plurality of rolls arranged above and below) and a method in which the web is dried while being conveyed by a tenter method are employed.

In order to produce a cellulose ester film as a raw material of the present invention, it is particularly preferable to stretch in the width direction (lateral direction) by a tenter method in which both ends of the web are held with clips or the like. Peeling is preferably performed at a peeling tension of 300 N / m or less.

The means for drying the web is not particularly limited, and can be generally performed with hot air, infrared rays, a heating roll, microwave, or the like, but is preferably performed with hot air in terms of simplicity.

It is preferable that the drying temperature in the web drying process is increased stepwise from 40 to 200 ° C.

The film thickness of the cellulose ester film is not particularly limited, but 10 to 500 μm is used. The film thickness is particularly preferably 10 to 200 μm. More preferably, it is 15 to 150 μm.

The cellulose ester film used as the raw material of the present invention has a width of 1 to 4 m. In particular, those having a width of 1.4 to 4 m are preferably used. If it exceeds 4 m, conveyance becomes difficult.

Here, as an example, the method for producing a cellulose ester film has been described. However, for each of the other polycarbonate film, polysulfone film, polyethersulfone film, polyacrylate film, polycycloolefin film, and polyimide film, an optimum film forming method is selected. Thus, a film can be formed.

(Multiple film bonding method)
The raw film for producing the retardation film of the present invention may be a laminate of a plurality of films, and the laminate may be bonded using a substrate-less adhesive film.

(Application and lamination of multiple optical layers)
The raw film for producing the retardation film of the present invention may be a laminate of a plurality of optical layers, and there is a method of applying a coating solution for the optical layer to a support film. As a method of coating the coating solution, spin coating method, roll coating method, printing method, dip pulling method, die coating method, casting method, bar coating method, blade coating method, spray coating method, gravure coating method, reverse coating method Ink jet method or extrusion coating method.

Alternatively, the film may be saponified and then bonded using polyvinyl alcohol. Moreover, a good solvent may be apply | coated and the film surface may be dissolved and bonded, and you may bond in the residual solvent state at the time of film forming of retardation film.

When using these bonding means, the adhesive layer at the interface between the films is preferably as thin as possible. For example, any of the adhesive layers formed by the above means is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. Further, as described in paragraph (0246) of JP2009-25604A, the adhesive layer can be applied without saponification treatment by atmospheric pressure plasma treatment.

(Dimension change method in the long direction)
You may change the dimension of the elongate direction of the formed raw film by the tension | tensile_strength by a roll or a tenter. Further, it may be changed by contraction and expansion of the retardation film itself.

At that time, the dimensional change rate in the longitudinal direction and the dimensional change rate in the width direction are preferably in the range of 95 to 105%, respectively.
<Other functional layers>
The long inclined retardation film of the present invention can be provided with a back coat layer, a hard coat layer and an antireflection layer as described in JP-A Nos. 10-319536 and 2007-159330, if necessary. .
<Polarizing plate>
The retardation film of the present invention can be used for a polarizing plate having a polarizing plate protective film, and a liquid crystal display device of the present invention using the same.

The polarizing plate of the present invention is characterized by being a polarizing plate bonded to at least one surface of a polarizer using the transparent film of the present invention as a polarizing plate protective film. The liquid crystal display device of the present invention is characterized in that the polarizing plate according to the present invention is bonded to at least one liquid crystal cell surface via an adhesive layer.

The polarizing plate of the present invention can be produced by a general method.

A polarizer, which is a main component of a polarizing plate, is an element that allows only light of a plane of polarization in a certain direction to pass. A typical polarizer currently known is a polyvinyl alcohol-based polarizing film, which is polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed.

The polarizer is formed by forming a polyvinyl alcohol aqueous solution into a film and dyeing the film by uniaxial stretching or dyeing or uniaxially stretching, and then performing a durability treatment with a boron compound. The film thickness of the polarizer is preferably 5 to 30 μm, particularly preferably 10 to 20 μm.

Further, the ethylene unit content described in JP-A-2003-248123, JP-A-2003-342322, etc. is 1 to 4 mol%, the degree of polymerization is 2000 to 4000, and the degree of saponification is 99.0 to 99.99 mol%. Ethylene-modified polyvinyl alcohol is also preferably used.

Among them, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73 ° C. is preferably used.

Specifically, for example, a PVA adhesive is preferable from the viewpoint of the stability of the adhesive treatment. These adhesives and pressure-sensitive adhesives may be applied to the surface of the polarizer or the transparent protective layer as they are, for example, or a layer such as a tape or sheet composed of the adhesive or pressure-sensitive adhesive is disposed on the surface. May be. For example, when prepared as an aqueous solution, other additives and catalysts such as acids may be blended as necessary. In the aqueous solution, for example, other additives and a catalyst such as an acid can be blended as necessary. Among these, as the adhesive, a PVA adhesive is preferable from the viewpoint of excellent adhesiveness with a PVA film.

In the cellulose ester film, the polarizer side is preferably bonded to at least one surface of a polarizer produced by alkali saponification treatment and immersed in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution.

The polarizing plate of the present invention is characterized in that it is a polarizing plate bonded to at least one surface of a polarizer using the long inclined retardation film of the present invention as a polarizing plate protective film.

The cellulose ester film may be used on the other surface, or another polarizing plate protective film may be bonded. For example, commercially available cellulose ester films (for example, Konica Minoltac KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC8UX-RHA-KC8UX-RHA-KC8UX-RHA-KC8UX KC4UXW-RHA-NC, manufactured by Konica Minolta Opto Co., Ltd.) is also preferably used.

When laminating the retardation film of the present invention and a polarizer, if the retardation axis of the retardation film is in the TD direction, the retardation axis of the retardation film and the transmission axis of the polarizer are overlapped within ± 3 °. It is preferable to arrange them within a range of ± 2 °.

In addition to the antiglare layer or the clear hard coat layer, the polarizing plate protective film used on the surface side of the display device preferably has an antireflection layer, an antistatic layer, an antifouling layer, and a backcoat layer.
<Configuration of liquid crystal display device>
By using the long inclined retardation film of the present invention for a TN liquid crystal display device, various TN liquid crystal display devices of the present invention having excellent visibility can be produced.

With the TN liquid crystal display device according to the present invention, it is possible to reduce coloration during black display due to light leakage and to obtain a liquid crystal display device with excellent visibility such as front contrast.

In the TN liquid crystal display device according to the present invention, the rubbing axes of the two substrates sandwiching the liquid crystal cell and the absorption axes of the first polarizing plate and the second polarizing plate are arranged orthogonally, and the liquid crystal When the horizontal direction of the liquid crystal cell in the case of the display device is set to 0 °, the absorption axis of the first polarizing plate is 45 + 0.1 to 3 degrees as the counterclockwise angle with respect to the horizontal direction of the liquid crystal cell. Preferably, the second polarizing plate is disposed at an angle in the range, and the absorption axis of the second polarizing plate is disposed at an angle in the range of 135-0.1 to 3 degrees. In the present invention, the TN liquid crystal display device having such an arrangement is referred to as an E mode.

In the TN liquid crystal display device, the rubbing axis of the liquid crystal cell and the absorption axes of the first polarizing plate and the second polarizing plate may be arranged in parallel, which is referred to as an O mode in the present invention. .

In the present invention, an O-mode TN liquid crystal display device is preferable because excellent results are obtained in viewing angle, gradation inversion, color shift, and blur.

Hereinafter, the TN type liquid crystal display device of the present invention will be described with reference to the drawings.

Units such as electrodes, color filters, and backlights are not shown because the figure becomes complicated and optically important parts in the present invention are difficult to see.

The TN type liquid crystal display device of the present invention preferably has the configuration shown in FIG. 1, and includes a first protective film 1, a first polarizer 2, and a first retardation film 3 in this order from the viewing side. 1 polarizing plate 4, twisted nematic liquid crystal cell 5, second retardation film 9 configured in the order of the second retardation film 6, the second polarizer 7, and the second protective film 8 from the liquid crystal cell side. And a backlight unit 10.

2 and 3 are schematic views showing an example of a TN type liquid crystal display device.

FIG. 2A is a schematic diagram showing a liquid crystal monitor, and the horizontal direction of the liquid crystal cell means the long side direction (x) of the monitor in the figure. The absorption axis (y direction) of the first polarizing plate is arranged at an angle in the range of (45 ° + 0.1-3 °) with respect to the x-axis direction (0 °), and the absorption axis (z direction) of the second polarizing plate Is preferably arranged at an angle in the range of (135 ° -0.1 to 3 °) with respect to the x-axis direction (0 °).

FIG. 2B shows the rubbing

axes

25 and 26 of the liquid crystal cell of the TN liquid crystal display device in the E mode, the polarizer absorption axis 23 orthogonal to the rubbing axis, and the position orthogonal to the polarizer absorption axis 23. It is a schematic diagram which shows the relationship of the slow axis 24 of a phase difference film.

FIG. 3B shows the rubbing

axes

25 and 26 of the liquid crystal cell of the TN type liquid crystal display device in the O mode, the polarizer absorption axis 23 parallel to the rubbing axis, and the position orthogonal to the polarizer absorption axis 23. It is a schematic diagram which shows the relationship of the slow axis 24 of a phase difference film.

<Preparation of raw film (cellulose ester film) 101>
<Fine particle dispersion 1>
Fine particles (Aerosil R972V manufactured by Nippon Aerosil Co., Ltd.)
11 parts by mass Ethanol 89 parts by mass The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<Fine particle addition liquid 1>
The fine particle dispersion 1 was slowly added to the dissolution tank containing methylene chloride with sufficient stirring. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution 1.

Methylene chloride 99 parts by mass Fine particle dispersion 1 5 parts by mass A main dope solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose ester A was added to a pressurized dissolution tank containing a solvent while stirring. This is completely dissolved with heating and stirring. This was designated as Azumi Filter Paper No. The dope 1 was prepared by filtering using 244.

<Composition of dope 1>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose ester A (acetyl group substitution degree 1.56, propionyl group substitution degree 0.90, total acyl group substitution degree 2.46) 100 parts by mass Polyester compound 1 * 6.5 parts by mass Part Sucrose octabenzoate (Monopet SB (Daiichi Kogyo Seiyaku Co., Ltd.)) 6.0 parts by weight Fine particle additive 1 1 part by weight <Composition of dope 2>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose ester C (diacetyl cellulose, acetyl group substitution degree 2.41)
100 parts by mass Polyester compound 1 * 6.5 parts by mass Sucrose octabenzoate (Monopet SB (Daiichi Kogyo Seiyaku Co., Ltd.)) 6.0 parts by mass Fine particle additive 1 1 part by mass The dope solution was prepared by dissolving with stirring. The prepared dope was co-cast using an apparatus described in FIG. 1 of JP-A-2007-86254 on an endless stainless steel belt having an infinite traveling length of 2 m.

The temperature of the stainless steel belt was set to 35 ° C. so that the belt surface side had a dope 1 layer and the air side surface had a dope liquid 2 layer.

The solvent was evaporated on the stainless steel belt, and the web was peeled off from the stainless steel belt. The peeled web was cut to 1.5 m width with a slitter, the web was introduced into a tenter dryer, both ends were gripped with clips and dried at 135 ° C. while stretching 1.3 times in the width direction, Drying was completed while alternately transporting a number of rolls arranged vertically in a roll dryer having each drying zone of 125 ° C., and the total film with Dope 1 layer of 80 μm and Dope 2 layer of 40 μm A laminated original film 101 having a thickness of 120 μm and a width of 1500 mm was produced.

The original film 101 had Ro = 0, Rt = 180 nm, and β = 0 °. Further, the Tg of the dope 1 layer is 163 ° C., and the Tg of the dope 2 layer is 200 ° C. In this case, the Tg of the dope 1 layer is Tg 2. The elastic modulus of the layer of dope 1 was 70 MPa and the elastic modulus of the layer of dope 2 was 500 MPa at the temperature of the inclined alignment treatment zone (T2 = 170 ° C.). The elastic modulus ratio εA / εB = 70/500 = 0.14. Moreover, the retardation development property of the raw film at this temperature (170 ° C.) was 1.5 (180 nm / 120 μm) nm / μm.

Polyester compound 1 *

<Inclined orientation treatment>
As shown in FIG. 4, the raw film 101 is applied with a transport tension of 0.75 N / cm in the longitudinal (MD) direction by a pair of nip rolls arranged and arranged before the preheating zone and after the cooling zone. Each zone was passed through.

At that time, a rubber roll having a diameter of 100 mm was installed so that the distance between the centers of the rolls was 250 mm, and the shrinkage in the TD direction (width regulation roll) was regulated.

In addition, a non-contact infrared thermometer was installed on the lower elastic modulus side surface (dope 1 layer) of the raw film, and the film surface temperature change of the lower elastic modulus side surface of the film being transported was observed. .

The atmospheric temperature of each zone was set so that the temperature was as follows, and the raw film was passed. Processing time refers to the total time it takes for a point on the film to leave the preheating zone, the inclined orientation zone, and the cooling zone.

At this time, the film set temperatures in each zone were as follows.
T1 = 124 ° C., T2 = 170 ° C., T3 = 83 ° C., t1 = 0.19 sec, t2 = 0.35 sec Therefore, the temperature gradient at the time of temperature rise is 242 ° C./sec (= (170-124) / 0 19), and the temperature gradient during the temperature drop was −247 ° C./second (= (83−170) /0.35).

The temperature control of each zone was performed by the following method.

Preheating zone: Hot air was blown onto the front and back of the film being transported to preheat. Two rolls and wind shields were installed between the preheating zone and the inclined orientation zone so that the temperature of each zone could be controlled independently.

Inclined orientation zone: The film was passed between two heated rolls in contact. Thereafter, hot air was blown onto the front and back of the film being conveyed.

Two rolls and wind shields were also installed between the inclined orientation zone and the cooling zone so that the temperature of each zone could be controlled independently.

Cooling zone: Immediately after passing through the two rolls, cooling was performed by blowing cold air on the front and back of the film.

The film width when leaving the cooling zone was 2% smaller than the film width just before entering the preheating zone.

Subsequently, the film subjected to the tilt alignment treatment was stretched by 10% (1.10 times) in the TD direction at 160 ° C. using a tenter to obtain the long tilt retardation film 101 of the present invention.

Only the MD tension was changed, and the other conditions were the same as the production of the long inclined retardation film 101, and the long

inclined retardation films

102, 103, and 104 were produced.

As Comparative Example 1, a retardation film described in Example 1 of JP-A-2005-17328 was produced as follows.

The dope 1 was cast on a metal belt, peeled off and dried to prepare an 80 μm film. Subsequently, it extended | stretched by 1.5 times the draw ratio in MD direction using the nip roll. At the time of stretching, the wind blowing temperature on the upper and lower surfaces of the film was adjusted so that the upper surface of the film was 100 ° C. and the lower surface of the film was 30 ° C. In this way, a comparative retardation film 1 was produced.

As Comparative Example 2, a comparative retardation film 2 was produced as follows according to paragraph (0090) of JP-A-2007-38646, Example 1.

First, the cycloolefin polymer was extruded into a film. Subsequently, the extruded film was sandwiched between a 300 mmφ mirror roll having a surface roughness of 0.1S and a metal belt having a thickness of 0.3 mm, and the surface of the film was transferred to a glossy surface. The metal belt (width 700 mm) is held by a rubber-covered roll (the diameter of the roll to be held is 150 mmΦ) and a cooling roll (roll diameter 150 mm), and a commercially available sleeve type transfer roll (manufactured by Chiba Machine Industry) is used. And transcribed. The roll interval at the time of transfer was 0.35 mm, and the transfer pressure was a linear pressure of 25 kgf / cm.

At this time, the peripheral speed of the outer periphery of the mirror roll was set to 8.8 m / min. Moreover, the peripheral speed of the rubber coating roll was controlled at 8.5 m / min. At this time, the temperature of the mirror surface roll was set to 125 ° C. using an oil temperature controller, and the temperature of the rubber coating roll was set to 115 ° C. Then, it peeled from the mirror surface roll and formed the resin film of thickness 100 micrometers.

The film was heated to 125 ° C. in a tenter and stretched 1.04 times in the width direction in the film in-plane direction. Then, it cooled, hold | maintaining this state for 1 minute in 110 degreeC atmosphere, Furthermore, it cooled at room temperature, The comparative phase difference film 2 was obtained by taking out from the inside of a tenter.
<Evaluation>
Ro, R40, β, and θ were measured in an atmosphere of 23 ° C. and 55% RH using a micro-area birefringence measuring apparatus manufactured by Mizoji Optical Co., Ltd. Each standard deviation of the long inclined retardation film 101 was 1.5 nm, 1.8 nm, 1.4 °, and 2 °, respectively.

<Production of polarizing plate>
<Preparation of Polarizing Plate 1>
Using the produced long inclined retardation film 101 and a commercially available cellulose ester film (manufactured by Konica Minolta Tac KC-8UY Konica Minolta Opto Co., Ltd.), a polarizing plate 101 was produced according to the following steps 1 to 5.
Step 1: It was immersed in a 2 mol% sodium hydroxide solution at 50 ° C. for 90 seconds, then washed with water and dried to saponify the side to be bonded to the polarizer.
Step 2: A polarizer was prepared by adsorbing iodine to a stretched polyvinyl alcohol film, and the polarizer was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.
Step 3: Excess adhesive adhered to the polarizer in Step 2 was gently wiped, and this was placed on the long inclined retardation film 101 treated in Step 1 and a commercially available cellulose ester film.
Step 4: The long inclined retardation film 101 laminated in Step 3, the polarizer, and a commercially available cellulose ester film on the back side were bonded at a pressure of 20 to 30 N / cm ² and a conveyance speed of about 2 m / min. Step 5: A sample in which the polarizer prepared in Step 4, the long inclined retardation film and the commercially available cellulose ester film were bonded together was dried in an oven at 80 ° C. for 5 minutes to prepare the polarizing plate 101.

In the same manner,

polarizing plates

102, 103 and 104 and comparative polarizing plates 1 and 2 were produced. In the comparative polarizing plate, an epoxy adhesive was used for bonding with the polarizer.

<Production of liquid crystal display device>
A liquid crystal panel was produced as follows, and the characteristics as a polarizing plate and a liquid crystal display device were evaluated.

The polarizing plates on both sides that had been bonded in advance were peeled off on a 17-inch display SyncMaster 743BM manufactured by Samsunung Co., Ltd., and the prepared polarizing plates 101 to 104 were each bonded to the glass surface of the liquid crystal cell.

At that time, the polarizing plate is bonded so that the long inclined retardation film of the present invention is on the liquid crystal cell side and the absorption axis is directed in the same direction as the previously bonded polarizing plate. The liquid crystal display devices 101 to 104 and the comparative liquid crystal display devices 1 and 2 were manufactured as shown in Table 2, respectively.

(Evaluation of unevenness)
The backlight of the liquid crystal display device produced above was turned on to display black, and after 24 hours, the intensity of occurrence of unevenness was visually evaluated from 40 ° obliquely above the normal direction of the display surface.

Situation evaluation Strong unevenness occurs on the entire screen ×
Weak unevenness occurs on the entire screen △
Weak unevenness occurs on the screen.
No unevenness ◎
Table 2 shows the tilt orientation conditions and characteristics of the long tilt retardation film.

According to the tilt retardation film of the present invention, the occurrence of unevenness in black display is suppressed.
Example 2
The original film 101 is passed through MD tension-adding rolls R1 to R4 (between nip rolls), which are rubber rolls having a diameter of 300 mm provided in the preheating zone (FIG. 5). The roll speed was R1 = R2 <R3 = R4, and R3 was set 1% faster than R1. While passing between the pair of rolls, it was stretched in the 1% MD direction.

Then, the same tilt orientation treatment as 101 of Example 1 was performed to obtain a long tilt retardation film 201. At that time, a rubber roll having a diameter of 100 mm was installed so that the distance between the centers of the rolls was 250 mm, and the shrinkage in the TD direction was regulated.

The film width when leaving the cooling zone was 2% smaller than the film width just before entering the preheating zone. The MD direction contracted by 1%.

The long gradient retardation films 202 and 203 having the MD direction shrinkage of 2% and 3% after the tilt orientation treatment by making the MD direction stretch rate 2% and 3% are produced in the same manner as 201. did.

This sample was evaluated in the same manner as in Example 1. The results are shown in Table 3.

According to the long inclined retardation film of the present invention, the occurrence of unevenness in black display is suppressed.
Example 3
The original film 101 was passed through the tilted orientation zone in a state where a pair of nip rolls were provided at the inlet and outlet of the tilted orientation zone and a transport tension of 0.75 N / cm was applied in the MD direction (FIG. 6). The roll speed is R1 = R2 <R3 = R4, and R3 is set 1% faster than R1.

The film was stretched to 1% MD while passing between the pair of rolls. As the nip roll, a rubber roll having a diameter of 300 mm was used, and a rubber roll having a diameter of 100 mm was installed so that the distance between the centers of the rolls was 250 mm, thereby restricting shrinkage in the TD direction.

The other conditions were the same as 101 in Example 1, and a long inclined retardation film 301 was produced. The MD stretch ratio was adjusted to 2% and 3% to produce long inclined retardation films 302 and 303.

The film width when exiting the cooling zone was 2% smaller than the film width immediately before entering the preheating zone.

This sample was evaluated in the same manner as in Example 1. The results are shown in Table 4.

According to the long inclined retardation film of the present invention, the occurrence of unevenness in black display is suppressed.
Example 4
In the dope 1 for producing the raw film, the dope 3 in which the cellulose ester is changed to F, the dope 4 in which the cellulose ester is changed to G, the dope 5 in which the amount of the polyester-based compound 1 is changed to 9.5 parts by mass, A dope 6 in which the amount of the polyester-based compound 1 was changed to 3.5 parts by mass was prepared, and co-cast with the dope 2 to prepare original films 401 to 404.

The original film was subjected to the same tilt orientation treatment as 101 in Example 1 to produce long tilted retardation films 401 to 404. Table 5 shows the film set temperatures T1 to T3 in the preheating zone, the inclined orientation zone, and the cooling zone. This sample was evaluated in the same manner as in Example 1. The results are shown in Table 5.

According to the long inclined retardation film of the present invention, the occurrence of unevenness in black display is suppressed.
Example 5
Only the dope 2 was cast on a metal belt in the same manner as 101 in Example 1, peeled and dried to obtain a raw film 501 having a film thickness of 120 μm. The raw film 501 had Ro = 0, Rt = 180, and β = 0 °.

This raw fabric film 501 is subjected to an inclined orientation treatment in the same manner as 101 in Example 1 except that the temperature of a rubber roll having a diameter of 100 mm for TD regulation in FIG. A phase difference film 501 was produced. In addition, long inclined retardation films 502 and 503 having been subjected to an inclined alignment treatment with the temperature of the rubber roll being 100 ° C. and 150 ° C. were produced. This sample was evaluated in the same manner as in Example 1. The results are shown in Table 6.

According to the long inclined retardation film of the present invention, the occurrence of unevenness in black display is suppressed.
Example 6
Only dope 2 was cast and peeled onto the metal belt in the same manner as 101 in Example 1, and then the drying temperature was adjusted to 120 ° C on one side and 20 ° C on the other side in the preheating zone. As a result, the amount of residual solvent on one surface is 1% or less (surface with high elastic modulus) and the amount of residual solvent on the other surface (surface with low elastic modulus) is 10%. Under the same conditions, the tilted alignment treatment zone was passed through to produce a long tilted retardation film 601.

The remaining solvent amount on the other surface was 5% (drying temperature 50 ° C.) and 3% (drying temperature 80 ° C.), and long inclined retardation films 602 and 603 were similarly produced.

This sample was evaluated in the same manner as in Example 1. The results are shown in Table 7.

Example 7
A dope 7 in which 1.4 parts by mass of Compound A (retardation adjusting agent) was added to the composition of dope 1 was prepared, cast on a metal belt, peeled off, and dried to prepare an 80 μm film 7.

Compound A

In addition, the cellulose ester of dope 1 was changed to polycarbonate (Pure Ace WR manufactured by Teijin Chemicals Ltd., hereinafter abbreviated as PC. Tg = 150 ° C.), ethanol was removed, and polycycloolefin (manufactured by JSR Corp.). Arton, hereinafter abbreviated as CO. Tg = 167 ° C.) was used to prepare dope 9 excluding ethanol, and film 8 and film 9 were prepared in the same manner as film 7.

Similarly, the dope 2 was cast on a metal belt, peeled off and dried to produce a film 2 having a thickness of 40 μm.

Each of the two films is saponified, and water paste is applied onto the saponified film, bonded to each other, and dried to be a raw film 701 (bonded film of film 7 and film 2), 702 ( Film 8 and film 2 bonding film) and 703 (film 9 and film 2 bonding film) were produced.

The original fabric films 701 to 703 were subjected to a tilt orientation treatment in the same manner as the original fabric film 101 of Example 1 to produce long inclined retardation films 701 to 703.

This sample was evaluated in the same manner as in Example 1. The results are shown in Table 8.

According to the long inclined retardation film of the present invention, the occurrence of unevenness in black display is suppressed.
Example 8
The production conditions of Example 1 in which the long inclined retardation film 101 was produced were the conditions described in Table 11, and long inclined retardation films 801 to 808 were produced. This sample was evaluated in the same manner as in Example 1. The results are shown in Table 9. The original film 101 is used, and the retardation development property is 1.5 nm / μm.

According to the long inclined retardation film of the present invention, the occurrence of unevenness in black display is suppressed.
Example 9
In the manufacturing conditions of Example 1 in which the long inclined retardation film 101 was produced, the partition of each zone was changed to a partition plate as shown in FIG. 7, the manufacturing conditions were as shown in Table 10, and the long inclined phase difference was obtained. Films 901 to 907 were produced. This sample was evaluated in the same manner as in Example 1. The results are shown in Table 10. The original film 101 is used, and the retardation development property is 1.5 nm / μm.

According to the long inclined retardation film of the present invention, the occurrence of unevenness in black display is suppressed.
Example 10
An optical film was produced by the melt casting method using the following composition.

(Composition 1)
Cellulose ester A 85.5 parts by mass Compound 1 * 12 parts by mass IRGANOX-1010 (manufactured by Ciba Japan Co., Ltd.) 0.5 parts by mass PEP-36 (manufactured by ADEKA Co., Ltd.) 0.1 parts by mass Sumizer-GS ( Sumitomo Chemical Co., Ltd.) 0.3 parts by mass TINUVIN 928 (manufactured by Ciba Japan Co., Ltd.) 1.5 parts by mass Seahoster KEP-30 (manufactured by Nippon Shokubai Co., Ltd.) 0.1 parts by mass (Composition 2)
Cellulose Ester C 85.5 parts by mass Compound 1 * 12 parts by mass IRGANOX-1010 (manufactured by Ciba Japan) 0.5 parts by mass PEP-36 (manufactured by ADEKA) 0.1 parts by mass Sumizer-GS ( Sumitomo Chemical Co., Ltd.) 0.3 parts by mass TINUVIN 928 (manufactured by Ciba Japan Co., Ltd.) 1.5 parts by mass Seahoster KEP-30 (manufactured by Nippon Shokubai Co., Ltd.) 0.1 parts by mass Compound 1 *

Each of the above compositions was dried at 80 ° C. for 6 hours to a moisture content of 200 ppm or less, and further dried with mixing in a vacuum nauter mixer at 80 ° C. and 1 Torr for 3 hours to a moisture content of 50 ppm.

The obtained mixture was melt-mixed at 235 ° C. using a twin-screw extruder and pelletized. At this time, an all screw type screw was used instead of a kneading disk in order to suppress heat generation due to shear during kneading.

Also, evacuation was performed from the vent hole, and volatile components generated during kneading were removed by suction. In addition, between the feeder, hopper, and extruder die supplied to the extruder and the cooling tank, a dry nitrogen gas atmosphere was used to prevent moisture from being absorbed into the resin and to remove oxygen.

Thereafter, using the apparatus described in FIG. 1 of JP-A-2009-96955, a raw film was produced. The first cooling roll and the second cooling roll were made of stainless steel having a diameter of 40 cm, and the surface was hard chrome plated. Further, oil for temperature adjustment (cooling fluid) was circulated inside to control the roll surface temperature to 130 ° C.

The elastic touch roll had a diameter of 20 cm, the inner cylinder and the outer cylinder were made of stainless steel, and the outer cylinder surface was hard chrome plated. The wall thickness of the outer cylinder was 2 mm, and the surface temperature of the elastic touch roll was controlled at 130 ° C. by circulating temperature adjusting oil (cooling fluid) in the space between the inner cylinder and the outer cylinder.

Using the above pellets, melted at 250 ° C. in a nitrogen atmosphere and co-extruded with a coat hanger type two-layer, on the first cooling roll so that the ratio of composition 1 and composition 2 is 2: 1. Extrusion was performed by pressing the melt extruded between the first cooling roll and the elastic touch roll to obtain a laminated original film 1001 having a film thickness of 240 μm. The film thickness was controlled by adjusting the extrusion amount and the take-up speed. The casting width at this time was 1.5 m.

At this time, a T die having a lip clearance of 1.5 mm and an average surface roughness Ra of 0.01 μm was used. Further, an elastic touch roll having a 2 mm thick metal surface was pressed on the first cooling roll at a linear pressure of 10 kg / cm.

The obtained raw film 1001 was subjected to the same inclination treatment as the inclination treatment 101 in Example 1.

Thereafter, the obtained film was stretched 1.5 times in the longitudinal direction at 155 ° C. by a stretching machine utilizing a difference in peripheral speed of the roll. Next, it is introduced into a tenter having a preheating zone, a stretching zone, a holding zone, and a cooling zone (there is also a neutral zone for ensuring thermal insulation between the zones), and is 1. After stretching 6 times, the film was cooled to 30 ° C. while relaxing 2% in the width direction, then released from the clip, and the clip gripping part was cut off to obtain a long inclined retardation film 1001.

The cellulose ester of composition 1 was changed as shown in Table 11 to prepare long inclined retardation films 1002, 1003. This sample was evaluated in the same manner as in Example 1. The results are shown in Table 11.

According to the long inclined retardation film of the present invention, the occurrence of unevenness in black display is suppressed.
Example 11
A solution obtained by diluting 50 parts by mass of the following hard coat layer-forming resin composition 1 on a raw film 501 with a mixed solvent of methyl ethyl ketone / methyl isobutyl ketone = 30/70 (mass ratio) has a pore diameter of 0.4 μm. A hard coat layer coating solution is prepared by filtration through a polypropylene filter, applied using an extrusion coater, dried at 80 ° C. for 1 minute, and then irradiated using an ultraviolet lamp with an illuminance of 100 mW / cm ² and an irradiation dose of 0. The film was cured under the condition of ² J / cm ² to form a hard coat layer having a dry film thickness of 20 μm to produce a raw film 1101.

(Resin composition for forming a hard coat layer 1)
Pentaerythritol triacrylate 20.0 parts by mass Pentaerythritol tetraacrylate 50.0 parts by mass Dipentaerythritol hexaacrylate 30.0 parts by mass Dipentaerythritol pentaacrylate 30.0 parts by mass Irgacure 184 (manufactured by Ciba Japan Co., Ltd.) 2 0.0 parts by mass In addition, raw films 1102 and 1103 in which 2 parts by mass (IG2) of Irgacure 184 (polymerization initiator) (IG3) and 5 parts by mass (IG5) were produced in the same manner. The Tg of the hard coat layer of IG2 is 220 ° C., IG3 is 250 ° C., IG5 is 260 ° C., and the Tg of the opposite surface is 200 ° C. (cellulose ester C), so the opposite surface Tg becomes Tg2.

The original fabric films 1101 to 1103 were subjected to the same tilt alignment treatment as in Example 1 and evaluated. The results are shown in Table 12.

According to the long inclined retardation film of the present invention, the occurrence of unevenness in black display is suppressed.

DESCRIPTION OF SYMBOLS 1 1st protective film 2 1st polarizer 3 1st phase difference film 4 1st polarizing plate 4
DESCRIPTION OF SYMBOLS 5 Twist nematic type liquid crystal cell 6 2nd phase difference film 7 2nd polarizer 8 2nd protective film 9 2nd polarizing plate 10 Backlight unit TN TN type | mold liquid crystal display device a Liquid crystal monitor 11 1st polarizing plate 12 twisted nematic liquid crystal cell 13 second polarizing plate 14 first protective film 15 first polarizer 16 first retardation film 17 substrate 18 liquid crystal 19 substrate 20 second retardation film 21 second polarizer 22 Second protective film 23 Absorption axis 24

Slow axis

25, 26 Rubbing axis A Preheating zone B Inclined orientation zone C Cooling zone 100 MD tension applying roll (R1, R2, R3, R4 nip roll)
DESCRIPTION OF SYMBOLS 101 Width control roll 102 Non-contact thermometer 103,104 TD stretching apparatus 105 Film unwinding apparatus 106 Film winding apparatus 107 Partition plate 108 Partition roll a Width direction axis (TD direction) of inclined retardation film
b Longitudinal axis of tilted retardation film (MD direction)
c Thickness direction axis of tilted retardation film x Direction axis with maximum refractive index in the film plane (in-plane slow axis)
y Direction axis that minimizes the refractive index in the film plane z Film thickness direction axis β Average tilt angle θ Angle formed by the in-plane slow axis of the film and the longitudinal direction x ′ perpendicular to z ′ of the refractive index ellipsoid Direction axis where the refractive index is the largest among the planes to be produced y ′ direction axis where the refractive index is the smallest among the planes orthogonal to z ′ of the refractive index ellipsoid z ′ the thickness direction axis of the refractive index ellipsoid nx ′ x ′ direction Refractive index of ny 'y' direction refractive index nz 'z' direction refractive index

Claims

The rising angle β of the refractive index ellipsoid from the film surface in the plane including the longitudinal direction of the film and the thickness direction of the film is 7 to 85 °, and the in-plane retardation (Ro ′) of the refractive index ellipsoid is 10 90 nm, thickness retardation (Rt ′) 70 to 300 nm, Rt ′> Ro ′, in-plane retardation Ro of film, retardation R40, β from film tilt angle 40 °, and in-plane retardation of film A long inclined retardation film, characterized in that the standard deviation in the longitudinal direction of the angle θ formed by the phase axis and the longitudinal direction is within 2 nm, within 2 nm, within 2 ° and within 2 °, respectively.
The long inclined retardation film according to claim 1, wherein the in-plane slow axis of the film is perpendicular to the longitudinal direction.
In the method for producing a tilted retardation film having a tilted phase difference, the tilted orientation zone for imparting the tilted phase difference has a temperature gradient in the longitudinal direction, and the temperature gradient is 20 ° C. / A method for producing a long inclined retardation film, characterized in that it is from second to 500 ° C./second, and in the case of descending from −20 ° C./second to −500 ° C./second.
When the elastic modulus (εA) of one surface of the film and the elastic modulus (εB) of the other surface before applying the oblique phase difference are εA <εB, 0.001 <εA / εB <0. The manufacturing method of the long inclination retardation film of Claim 3 characterized by the above-mentioned.
5. The method for producing a long inclined retardation film according to claim 3, wherein a retardation development property of the film before applying the oblique retardation is 0.3 nm / μm to 20 nm / μm. .
6. The dimensional change rate in the longitudinal direction of the film and in a direction perpendicular to the film in the inclined orientation zone is within 5% before the inclined alignment treatment and after the inclined alignment treatment, respectively. Manufacturing method of long inclination retardation film.
A polarizing plate comprising the long inclined retardation film according to claim 1.
A liquid crystal display device comprising the long inclined retardation film according to claim 1.