JP2008268419A - Manufacturing method of retardation film, retardation film, polarizing plate, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a thin and wide retardation film which has a stable retardation value in a width direction, the retardation film manufactured by using the same manufacturing method, a polarizer using the retardation film, and a liquid crystal display device using the polarizer. <P>SOLUTION: The manufacturing method of the retardation film for manufacturing the thin retardation film by a solution casting manufacturing device is characterized in that: the retardation film has a thickness of 20 to 80 μm and a width of 1,500 to 2,500 mm, and while primary drawing is carried out in a first drawing stage wherein the remaining amount of a solvent of a web is 50 to 250 mass%, secondary drawing is carried out in a second drawing stage wherein the remaining amount of the solvent of the web is 5 to 10 mass%, the primary drawing rate of the primary drawing is 10 to 40% in a TD direction and the secondary drawing rate of the secondary drawing is 1 to 10% in the TD direction, and the primary drawing rate of the primary drawing is 80 to 100% of the sum total of the primary drawing rate and secondary drawing rate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a retardation film, a retardation film, a polarizing plate, and a liquid crystal display device.

  Liquid crystal display devices are widely used as display devices for liquid crystal TVs, personal computers, and the like because they can be directly connected to an IC circuit with low voltage and low power consumption, and can be particularly thin. The liquid crystal display device has a basic configuration in which, for example, polarizing plates are provided on both sides of a liquid crystal cell.

  In such a liquid crystal display device, from the viewpoint of contrast or the like, a conventional liquid crystal display device using a twisted nematic (TN) with a twist angle of 90 degrees and a super twisted nematic (STN) with a twist angle of 160 degrees or more are used. Liquid crystal display devices have been developed. Recently, however, a vertical alignment (vertical alignment, VA for short) type liquid crystal display device disclosed in, for example, Japanese Patent Laid-Open No. 2-176625 has been developed. The VA type liquid crystal display device uses a so-called vertical alignment mode liquid crystal cell to display black firmly as black, has high contrast, and has a relatively wide viewing angle compared to TN and STN type. have.

  However, as the liquid crystal screen becomes larger as in a large TV, there is a growing demand for further widening the viewing angle, and a retardation film has been used for widening the viewing angle. Therefore, with the expansion of the liquid crystal screen, it is increasingly important to widen the retardation film. However, when a retardation film having a width of 1000 mm to 2500 mm and a thickness of 20 μm to 80 μm is produced by the solution casting method, after peeling from the endless support, shrinkage occurs due to the influence of the residual solvent. As the shift of the slow axis is not uniform, there is a problem that it is difficult to obtain uniform retardation values.

  When producing a retardation film by the solution casting method, studies have been made on the uniformity of the retardation value. For example, when a cellulose ester film is produced by a solution casting method, an apparatus having a first tenter and a second tenter is used, and after peeling the web from the endless support, the stretch ratio in the width direction is included in the web. A technique for stabilizing the retardation value by changing the first tenter and the second tenter in accordance with the amount of the residual solvent is disclosed (for example, see Patent Document 1).

  However, the technique described in Patent Document 1 produces a thin film / wide retardation film having a thickness of 20 μm to 80 μm and a width of 1500 mm to 2500 mm because the amount of residual solvent when stretching with the first tenter is low. If there is a risk of breaking.

  When producing a cellulose ester film by the solution casting method, using a tenter divided into tenters, the web is peeled from the endless support, and then the residual solvent amount and temperature at the edge and center of the web A technique is disclosed in which the retardation value is stabilized by stretching in the transverse direction by changing (see, for example, Patent Document 2).

  However, in the technique described in Patent Document 2, since the amount of residual solvent when stretching in the first zone of the tenter is low, a thin film / wide retardation film having a thickness of 20 μm to 80 μm and a width of 1500 mm to 2500 mm is used. When manufacturing, there is a risk of breakage.

From such a situation, a method for producing a thin film / wide retardation film having a stable retardation value in the width direction, a retardation film produced by this production method, a polarizing plate using this retardation film, and this polarization Development of a liquid crystal display device using a plate is desired.
JP 2002-31245 A JP 2002-296422 A

The present invention has been made in view of the above situation, and its purpose is to produce a thin film / wide retardation film having a stable retardation value in the width direction, a retardation film produced by this production method, A polarizing plate using a retardation film and a liquid crystal display device using the polarizing plate are provided.

  The above object of the present invention has been achieved by the following constitution.

  1. A dope prepared by dissolving a raw material resin in a solvent is cast on an endless belt support from a die to form a web, and after peeling the web from the endless belt support, at least a stretching step, and drying In the method for producing a retardation film, wherein a thin film retardation film is produced by a solution casting production apparatus having a step and a winding step, the retardation film has a thickness of 20 μm to 80 μm and a width of 1500 mm to 2500 mm. The stretching step includes a first stretching step and a second stretching step. In the first stretching step, the second solvent is primarily stretched when the residual solvent amount of the web is 50% by mass or more and 250% by mass or less. In the stretching step, the residual solvent amount of the web is secondarily stretched at 5% by mass or more and 10% by mass or less, and the primary stretching rate of the primary stretching is 10% to 40% in the TD direction. Next stretching The ratio is 1% to 10% in the TD direction, and the primary stretch ratio is 80% to 100% of the sum of the primary stretch ratio and the secondary stretch ratio. Method.

  2. The stretching time in the first stretching step is 1% / second to 8% / second, and the stretching time in the second stretching step is 0.1% / second to 1% / second. A method for producing a retardation film as described in 1. above.

  3. A retardation film produced by the method for producing a retardation film according to any one of 1 and 2.

  4). A polarizing plate, wherein the polarizing plate is disposed on at least one surface of the polarizer so that the slow axis of the retardation film described in 3 is perpendicular or parallel to the transmission axis of the polarizer.

  5. 5. A liquid crystal display device using the polarizing plate described in 4 above.

  Method for producing thin film / wide retardation film having stable retardation value in width direction, retardation film produced by this production method, polarizing plate using this retardation film, and liquid crystal display using this polarizing plate An apparatus can be provided, and it has become possible to manufacture a high-quality retardation film that can be used for a liquid crystal screen like a large TV.

  Embodiments of the present invention will be described with reference to FIGS. 1 to 3, but the present invention is not limited thereto.

  FIG. 1 is a schematic view of a production apparatus for producing a retardation film by a solution casting film forming method. FIG. 1 (a) shows a production process including a casting process, a first tenter transporting process, a second tenter transporting process, a drying process, and a winding process used in order to manufacture a retardation film by a solution casting film forming method. It is the schematic of an apparatus. FIG. 1B shows a casting step, a first drying step, a first tenter conveying step, a second tenter conveying step, a second drying step, which are used for producing a retardation film by a solution casting film forming method. It is the schematic of the manufacturing apparatus which has a winding-up process sequentially. FIG. 1C shows a casting process, a first drying process, a first tenter transporting process, a second drying process, a second tenter transporting process, which are used to manufacture a retardation film by a solution casting film forming method. It is the schematic of the manufacturing apparatus which has a 3rd drying process and a winding-up process one by one. The present invention was produced by a method for producing a thin film / wide retardation film having a stable retardation value in the width direction in a solution casting production apparatus as shown in FIGS. 1 (a) to 1 (c), and this production method. The present invention relates to a retardation film, a polarizing plate using the retardation film, and a liquid crystal display device using the polarizing plate.

  The manufacturing apparatus shown in FIG. In the figure, reference numeral 1a denotes an apparatus for producing a retardation film by a solution casting film forming method. The manufacturing apparatus 1 a includes a solution casting film forming process 101, a first stretching process 102, a second stretching process 103, a drying process 104, and a winding process 105. The solution casting film forming step 101 includes a mirror-like metal casting belt (hereinafter referred to as a belt) 101a, a die 101b, and a heating device 101c as an endless support. The belt 101a is composed of an endless support that travels endlessly. The dice 101b is disposed to cast the dope 2 in which a resin for forming a retardation film is dissolved in a solvent onto the belt 101a. The heating device 101c is disposed to remove the solvent so that the dope 2 cast on the belt 101a can be peeled from the belt 101a.

  The heating device 101c includes a drying box 101c1, a heating air supply pipe 101d1 disposed on the upper side of the drying box 101c1, a heating air supply pipe 101d2 disposed on the lower side, and an exhaust pipe 101d3. Although the heating device 101c shown in this figure shows the case where heating air is used, the heating means is not particularly limited. In addition, for example, a method of heating the dope contact surface of the belt with an infrared heater, the back surface of the belt There are a method in which warm air is blown onto the belt and heated from the back side, a method in which warm water or heating oil is brought into contact with the back side of the belt and heated. The time from casting to peeling varies depending on the film thickness of the cellulose ester film to be produced and the solvent used, but it takes 0.5 minutes in consideration of peelability from the belt, film-forming efficiency, process length, etc. A range of ˜5 minutes is preferred.

  As the endless support to be used, a mirror-finished surface is preferable, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used. The casting width can be 1 to 4 m. The surface temperature of the endless support in the solution casting film forming step is set to −50 ° C. to a temperature at which the solvent boils and does not foam. A higher temperature is preferable because the web can be dried faster, but if the temperature is too high, the web may foam or the flatness may deteriorate. A preferable endless support temperature is appropriately determined at 0 to 100 ° C, and more preferably 5 to 30 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent. The method for controlling the temperature of the endless support is not particularly limited, and 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 endless support becomes constant is short. When using warm air, considering the temperature drop of the web due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there may be cases where wind at a temperature higher than the target temperature is used while preventing foaming. . In particular, it is preferable to perform drying efficiently by changing the temperature of the support and the temperature of the drying air during the period from casting to peeling.

  The belt 101a is held by the holding roll 101a1 and the holding roll 101a2, and rotates and moves between the holding roll 101a1 and the holding roll 101a2 (in the direction of the arrow in the drawing) as the holding roll rotates. Reference numeral 3 denotes a peeling point at which the solvent is removed from the dope cast on the belt 101a to a state where it can be peeled and the solidified web is peeled off. The temperature at the peeling point is preferably -50 ° C to 40 ° C, more preferably 10 ° C to 40 ° C, and most preferably 15 ° C to 30 ° C. 4 shows the conveyance roll provided in the peeling point. 5 shows the peeled web. When the web 5 is peeled from the belt, the web is stretched in the longitudinal direction by the peeling tension and the subsequent conveying tension. Therefore, in the present invention, when peeling the web from the belt, the peeling and conveying tensions are lowered as much as possible. Preferably it is done. Specifically, for example, it is effective to set it to 50 N / m to 170 N / m. At that time, it is preferable to apply a cold air of 20 ° C. or less to fix the web rapidly in order to enhance the effect of the present invention.

  In the case of the manufacturing apparatus shown in this figure, the web 5 peeled at the peeling point is sent to the first stretching step 102 of the next step. The amount of residual solvent contained in the web 5 when it is sent to the first stretching step 102 is 50% by mass or more and 250% by mass or less. When the amount of residual solvent is less than 50% by mass, the retardation required when the web is broken and the target primary stretch ratio is not obtained when the target primary stretch ratio is obtained in the stretching step. Since a value cannot be obtained, it is not preferable. When the residual solvent amount exceeds 250% by mass, peeling from the belt becomes difficult and stable production cannot be maintained, which is not preferable.

  The first stretching step 102 includes an outer box 102a having a dry air intake port 102b and a discharge port 102c, and a uniaxial stretching device 102d placed in the outer box 102a. Although the case where heated air is used is shown as the solvent removal means in the first stretching step 102, the solvent removal means is not particularly limited, and other examples include infrared rays. The dry air intake port 102b and the discharge port 102c may be reversed. The drying temperature varies depending on the amount of residual solvent of the web when entering the first stretching step 102, but consideration is given to condensation on the surface of the web as the solvent evaporates, adjustment of the residual solvent amount, stretching ratio, foaming of the solvent, etc. In addition, it may be determined by appropriately selecting depending on the amount of residual solvent in the range of 30 ° C. to 180 ° C., it may be dried at a constant temperature, or may be divided into several stages of temperature.

  The total length of the first stretching step 102 can be appropriately determined in consideration of the residual solvent amount at the start of stretching, the primary stretching ratio, the residual solvent amount at the end of stretching, the stretching time, and the like.

  The primary stretching ratio in the first stretching step 102 is 10% to 40% in the TD direction. The TD direction refers to the Transverse Direction direction, which is a direction perpendicular to the web conveyance direction (a direction parallel to the roll).

  When the primary stretching ratio is less than 10%, the expression of the retardation value Ro in the in-plane direction is low due to insufficient stretching ratio, and the ratio between the retardation value Ro in the in-plane direction and the retardation value Rt in the thickness direction. Since Rt / Ro is 7 or more, it is not preferable. A primary stretching ratio exceeding 40% is not preferable because excessive stretching causes breakage of the film and an increase in haze.

  The ratio of the primary stretching ratio in the first stretching step 102 is 80% to 100% of the total of the primary stretching ratio in the first stretching step 102 and the secondary stretching ratio in the second stretching step 103. If it is less than 80%, the second stretch ratio becomes excessive, which is not preferable because the film breaks, the haze rises, the expression of the retardation value Rt in the thickness direction is improved, and Rt may exceed 200 nm.

  The stretching time in the first stretching step 102 is preferably 1 to 10 seconds in consideration of the primary stretching ratio, stretching unevenness and the like.

  The second stretching step 103 includes an outer box 103a having a dry air intake port 103b and a discharge port 103c, and a uniaxial stretching device 103d placed in the outer box 103a. Although the case where heated air is used is shown as the solvent removal means in the second stretching step 103, the solvent removal means is not particularly limited, and other examples include infrared rays. The dry air intake port 103b and the discharge port 103c may be reversed. The drying temperature varies depending on the residual solvent amount of the web when entering the stretching process, but it takes into account condensation on the surface of the web accompanying evaporation of the solvent, adjustment of the residual solvent amount, stretching ratio, foaming of the solvent, etc. The temperature may be appropriately selected and determined depending on the amount of residual solvent in the range of from ° C to 180 ° C, and may be dried at a constant temperature or may be divided into several stages of temperature.

  The residual solvent amount of the web when entering the second stretching step 103 is 5% by mass or more and 10% by mass or less. When the amount is less than 5% by mass, the stretchability of the web is lost, and the risk of web breakage is increased. When it exceeds 10% by mass, the in-plane direction retardation value Ro and the thickness direction retardation value Rt are deteriorated, the in-plane direction retardation value Ro, and the thickness direction retardation value Rt This is not preferable because the ratio Rt / Ro is 7 or more.

  The secondary stretching ratio in the second stretching step 103 is 1% to 10% in the TD direction. When the secondary stretching ratio is less than 1%, the hot air does not hit uniformly due to the slackness of the web, resulting in a film having a large film thickness and optical value deviation. When the secondary stretching ratio exceeds 10%, excessive stretching is not preferable because the film breaks, the haze rises, and the retardation value Rt in the thickness direction is improved and Rt exceeds 200 nm.

  The stretching time in the second stretching step 103 is preferably 1 second to 10 seconds in consideration of the secondary stretching ratio, stretching unevenness and the like.

  The total of the primary stretching ratio in the first stretching step 102 and the secondary stretching ratio in the second stretching step 103 is preferably 11% to 50% in consideration of web breakage, haze increase, and the like. The relationship between the primary stretching ratio of 102 and the secondary stretching ratio of the second stretching process 103 has a primary stretching ratio of the first stretching process 102> and a secondary stretching ratio of the second stretching process 103.

  The total length of the second stretching step 103 can be appropriately determined in consideration of the residual solvent amount at the start of stretching, the secondary stretching ratio, the residual solvent amount at the end of stretching, the stretching time, and the like.

  The tenter used in the uniaxial stretching apparatus 102d of the first stretching process 102 and the uniaxial stretching apparatus 103d of the second stretching process 103 is not particularly limited, and examples thereof include a clip tenter and a pin tenter, which are selected and used as necessary. It is possible.

  The drying process 104 includes a drying box 104a having a drying air intake port 104b and a discharge port 104c, an upper conveyance roll 104d that conveys the web 5, and a lower conveyance roll 104e. The upper conveyance roll 104d and the lower conveyance roll 104e are a set of upper and lower, and are configured by a plurality of sets. Reference numeral 104 f denotes a transport roll for transporting the web 5 coming out of the second stretching process 103 to the drying process 104. The number of transport rolls disposed in the drying step 104 varies depending on the drying conditions, the method, the length of the retardation film to be manufactured, and the like, and is set as appropriate. The upper conveyance roll 104d and the lower conveyance roll 104e are free rotation rolls that are not rotationally driven by a drive source. In addition, between the drying process and the winding process, a transport roll that freely rotates is not used. Usually, one to several transport drive rolls (roll driven to rotate by a drive source) are installed. Need. Basically, the purpose of the transport drive roll is to transport the retardation film by its drive, so the transport of the retardation film and the rotation of the drive roll are performed by nip or suction (air suction). With a synchronization mechanism.

  In the drying step 104, heated air, infrared rays, etc. alone or heated air and infrared drying may be used in combination. It is preferable to use heated air in terms of simplicity. This figure shows the case where heated air is used. The drying temperature varies depending on the residual solvent amount of the cellulose ester film when entering the drying process, but considering the drying time, shrinkage unevenness, stability of the expansion / contraction amount, etc., depending on the residual solvent amount in the range of 30 ° C to 180 ° C It may be selected and determined, and may be dried at a constant temperature, or may be divided into three to four stages of temperature and may be divided into several stages of temperature.

  The residual solvent amount of the retardation film after the drying treatment in the drying step 104 is preferably 0.1% by mass to 0.001% by mass in consideration of the load of the drying step, the dimensional stability expansion / contraction ratio during storage, and the like.

  The total length of the drying step 104 can be appropriately determined in consideration of the residual solvent amount, the conveyance speed, the drying time, and the like.

  The winding process 105 includes a winding device (not shown), and winds the retardation film that has been dried to a necessary length to the winding core. Reference numeral 105a denotes a roll-like retardation film wound around a winding core. The temperature at the time of winding is preferably cooled to room temperature in order to prevent scratches and loosening due to shrinkage after winding. The winder to be used may be a commonly used winder, and can be wound by a winding method such as a constant tension method, a constant torque method, a taper tension method, or a program tension control method with a constant internal stress.

  The manufacturing apparatus shown in FIG. In the figure, reference numeral 1b denotes an apparatus for producing a retardation film by a solution casting film forming method. The production apparatus 1b includes a solution casting film forming step 101, a first drying step 106, a first stretching step 102, a second stretching step 103, a second drying step 107, and a winding recovery step 105. ing. The difference from the retardation film manufacturing apparatus shown in FIG. 1A is that the web 5 peeled from the belt is once dried in the first drying step 106 before being stretched in the first stretching step 102. . Other steps are the same as those of the manufacturing apparatus shown in FIG.

  The first drying step 106 includes a drying box 106a having a drying air intake port 106b and a discharge port 106c, an upper conveyance roll 106d that conveys the web 5, and a lower conveyance roll 106e. The upper transporting roll 106d and the lower transporting roll 106e are a set of upper and lower, and are composed of a plurality of sets. It is possible to adjust the amount of solvent contained in the web 5 before entering the first stretching step 102 in the first drying step 106. After the solvent amount is adjusted in the first drying step 106, the residual solvent amount contained in the web 5 when sent to the first stretching step 102 is the same as that shown in FIG.

  In the 1st drying process 106, you may use heating air, infrared rays alone, or heating air and infrared drying together as a drying means. It is preferable to use heated air in terms of simplicity. The drying conditions vary depending on the residual solvent amount of the web when entering the first drying step 106 and the solvent used, but it is difficult to uniquely determine, but the residual solvent amount when entering the first stretching step 102 It is necessary to select and determine the temperature, time, etc. as appropriate. The total length of the first drying step 106 can be appropriately determined in consideration of the residual solvent amount, the conveyance speed, the drying time, and the like.

  In the first stretching step 102 shown in the figure, the draw ratio (%) applied in the TD direction of the web 5 and the ratio of the primary stretching ratio and the stretching time are the same as those in the first stretching step shown in FIG. Is the same. The residual solvent amount of the web when the first stretching step 102 is completed and sent to the second stretching step 103 is the same as that in the first stretching step shown in FIG.

In the second stretching step 103, the stretching ratio (%) applied in the TD direction of the web 5 and the ratio of the secondary stretching ratio and the stretching time are the same as those in the second stretching step shown in FIG.
The sum of the primary stretching ratio of the first stretching step 102 and the secondary stretching ratio of the second stretching step 103 is the sum of the primary stretching ratio of the first stretching step 102 and the second stretching step 103 shown in FIG. It is the same as the sum of the secondary stretching ratios.

  The second drying step 107 includes a drying box 107a having a drying air inlet 107b and a discharge port 107c, an upper conveying roll 107d for conveying the web 5, and a lower conveying roll 107e. The upper transport roll 107d and the lower transport roll 107e are a set of upper and lower, and are composed of a plurality of sets. Reference numeral 107 f denotes a transport roll for transporting the web 5 coming out of the second stretching process 103 to the second drying process 107. The number of transport rolls arranged in the second drying step 107 differs depending on the drying conditions, the method, the length of the retardation film to be produced, etc., and is set as appropriate. The upper conveyance roll 107d and the lower conveyance roll 107e are free rotation rolls that are not rotationally driven by a drive source. In addition, between the drying process and the winding process, a transport roll that freely rotates is not used. Usually, one to several transport drive rolls (roll driven to rotate by a drive source) are installed. Need. Basically, the purpose of the transport drive roll is to transport the retardation film by its drive, so the transport of the retardation film and the rotation of the drive roll are performed by nip or suction (air suction). With a synchronization mechanism. The second drying step 107 has the same configuration as the drying step 104 shown in FIG.

  The heating method, heating means, temperature, and drying method in the second drying step 107 are the same as those in the drying step 104 shown in FIG. Moreover, the residual solvent amount of the retardation film after the drying process in the second drying step 107 is the same as that in the drying step 104 shown in FIG. The total length of the second drying step 107 can be appropriately determined in consideration of the residual solvent amount, the conveyance speed, the drying time, and the like.

  As shown in this figure, disposing the first drying step 106 before the first stretching step 102 makes it possible to reduce the load of the solution casting film forming step 101, and the process goes to the first stretching step 102. It is preferable because the residual solvent amount can be accurately adjusted in accordance with the thickness of the web when entering and the primary stretching ratio. Other symbols are synonymous with FIG.

  The manufacturing apparatus shown in FIG. In the figure, reference numeral 1c denotes an apparatus for producing a retardation film by a solution casting film forming method. The manufacturing apparatus 1c includes a solution casting film forming step 101, a first drying step 106, a first stretching step 102, a second drying step 108, a second stretching step 103, a third drying step 109, and a winding. And a recovery step 105. The difference from the retardation film manufacturing apparatus shown in FIG. 1B is that a second drying step 108 is disposed between the first stretching step 102 and the second stretching step 103. Other steps are the same as those of the manufacturing apparatus shown in FIG.

The second drying step 108 includes a drying box 108a having a drying air intake port 108b and a discharge port 108c, an upper conveyance roll 108d that conveys the web 5, and a lower conveyance roll 108e. The upper transport roll 108d and the lower transport roll 108e are a pair of upper and lower, and are composed of a plurality of sets.
It is possible to adjust the amount of solvent contained in the web 5 before entering the second stretching step 103 in the second drying step 108. After the solvent amount is adjusted in the second drying step 108, the residual solvent amount contained in the web 5 when being stretched in the second stretching step 103 is the same as that in the second stretching step 103 shown in FIG. It is. The drying means in the second drying step 108 is the same as that in the first drying step 106. The total length of the second drying step 108 can be appropriately determined in consideration of the residual solvent amount, the conveyance speed, the drying time, and the like.

  The amount of residual solvent of the web 5 when it is stretched in the first stretching step 102 and the second stretching step 103 shown in the figure is the same as that in the first stretching step and the second stretching step shown in FIG. It is. The draw ratio (%) applied in the TD direction of the web 5 in the first drawing step 102 and the second drawing step 103 shown in this figure, the ratio of the draw ratio, and the drawing time are shown in FIG. 1 (a). This is the same as in the process and the second stretching process. The sum of the primary stretching ratio of the first stretching step 102 and the secondary stretching ratio of the second stretching step 103 is the sum of the primary stretching ratio of the first stretching step 102 and the second stretching step 103 shown in FIG. It is the same as the sum of the secondary stretching ratios.

  The third drying step 109 includes a drying box 109a having a drying air intake port 109b and a discharge port 109c, an upper conveyance roll 109d that conveys the web 5, and a lower conveyance roll 109e. The upper transport roll 109d and the lower transport roll 109e are a set of upper and lower, and are composed of a plurality of sets. Reference numeral 109f denotes a transport roll for transporting the web 5 coming out of the second stretching step 103 to the third drying step 109. The number of transport rolls disposed in the third drying step 109 varies depending on the drying conditions, the method, the length of the retardation film to be manufactured, and the like, and is appropriately set. The upper transport roll 109d and the lower transport roll 109e are free rotating rolls that are not rotationally driven by a drive source. In addition, between the drying process and the winding process, a transport roll that freely rotates is not used. Usually, one to several transport drive rolls (roll driven to rotate by a drive source) are installed. Need. Basically, the purpose of the transport drive roll is to transport the retardation film by its drive, so the transport of the retardation film and the rotation of the drive roll are performed by nip or suction (air suction). With a synchronization mechanism. The third drying step 109 has the same configuration as the second drying step 107 shown in FIG.

The heating method, heating means, temperature, and drying method in the third drying step 109 are the same as those in the drying step 104 shown in FIG. Moreover, the residual solvent amount of the retardation film after the drying process in the second drying step 107 is the same as that in the drying step 104 shown in FIG. The third drying step 109 can be used according to the amount of residual solvent in the first drying step 106 to the second stretching step. The total length of the third drying step 109 can be appropriately determined in consideration of the residual solvent amount, the conveyance speed, the drying time, and the like.
Other symbols are synonymous with FIG.
In the present invention, as shown in FIGS. 1A to 1C, a web in which the residual solvent amount before winding in the winding process is 1.5% by mass or less is referred to as a retardation film.

  As shown in this figure, the first drying step 106 is disposed before the first stretching step 102, and the second drying step 108 is disposed before the second stretching step 103. 1) First stretching The drying load in the step 102 can be reduced, and the stretching in the first stretching step 106 can be performed in the high residual solvent region. 2) The film thickness of the web when entering the second stretching step 102, 2 This is preferable because the amount of residual solvent can be accurately adjusted in accordance with the next stretching ratio.

The retardation value Rt in the thickness direction of the retardation film produced by the production apparatus shown in FIGS. 1A to 1C is preferably 0 to 200 nm in consideration of the viewing angle, color, and the like. Further, the ratio (Rt / Ro) between the retardation value Ro in the in-plane direction and the retardation value Rt in the thickness direction is preferably 1 to 7 in consideration of the viewing angle, the tint, and the like.
The retardation value Ro in the in-plane direction and the retardation value Rt in the thickness direction are values measured using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments).

The thickness of the retardation film manufactured by the manufacturing apparatus shown in FIGS. 1A to 1C is 20 μm to 80 μm, and the width is 1500 mm to 2500 mm. A thickness of less than 20 μm is not preferable because curling occurs when a polarizing plate is produced, resulting in poor handling. A thickness exceeding 80 μm is not preferable because the unit cost of the material increases, resulting in an increase in cost. The thickness indicates a value measured by μ-mate manufactured by Sony Corporation.
When the width is less than 1500 mm, it is not preferable because it becomes impossible to handle a liquid crystal screen like a large TV. When the width exceeds 2500 mm, the risk of breakage increases due to its own weight, which is not preferable.

  The haze of the retardation film produced by the production apparatus shown in FIGS. 1A to 1C is preferably 0 to 0.1 in consideration of contrast. The haze is a value measured with a Nippon Denshoku Industries Co., Ltd. haze meter 1001DP type according to the method defined in JIS K6714.

  As for the concentration of the resin for forming the retardation film of the dope 2 used in the production apparatus shown in FIGS. 1A to 1C, the higher the concentration, the lower the drying load after casting on the metal support. However, if the concentration of the resin for forming the retardation film is too high, the load during filtration increases and the filtration accuracy deteriorates. As a density | concentration which makes these compatible, 10-35 mass% is preferable, More preferably, it is 15-25 mass%.

  The value of the residual solvent amount (% by mass) in the present invention is B (retardation film) when the web (retardation film) having a constant size is dried at 115 ° C. for 1 hour, and B before drying. When the mass of the web (retardation film) is A, ((A−B) / B) × 100 = the value obtained by the amount of residual solvent (mass%).

  The primary stretching ratio in the present invention indicates a value obtained by calculation from the following calculation formula.

Primary stretch ratio (%) = (width from center to end of web after primary stretching / width from center to end of web before stretching) × 100
For the width from the center of the web to the end, a value obtained by measuring the width with a C-type JIS grade 1 steel scale is used.

Secondary stretch ratio (%) = (width from center to end of web after secondary stretch / width from center to end of web before stretch) × 100
For the width from the center of the web to the end, a value obtained by measuring the width with a C-type JIS grade 1 steel scale is used. The web before stretching refers to the web before primary stretching.

The following effects can be obtained by producing a retardation film by the method for producing a retardation film by the solution casting production apparatus shown in FIGS.
1. By stretching the web peeled from the belt by dividing it into a region with a high residual solvent amount and a region with a low residual solvent amount, a retardation film having a retardation value stable in the width direction even with a wide and thin film Manufacture is possible.
2. Support for large liquid crystal display devices is now possible.

  FIG. 2 is a schematic view of a polarizing plate produced using the retardation film produced in the present invention.

  In the figure, 6 indicates a polarizing plate. The polarizing plate 6 has a configuration in which a protective film 602 is disposed on one side of a polarizer 601 and a retardation film 603 that also functions as a protective film is disposed on the other side. The retardation film 603 is disposed so that the slow axis of the retardation film is orthogonal or parallel to the transmission axis of the polarizer.

  The polarizing plate shown in this figure can be manufactured by a general method. The back side of the retardation film 603 of the present invention is preferably bonded to at least one surface of a polarizer 601 produced by alkali saponification treatment and immersed in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. . The retardation film 603 or the protective film 602 may be used on the other surface.

  With respect to the retardation film 603 of the present invention, the protective film 602 used on the other surface is an optically isotropic protective film having an in-plane retardation Ro of 0 to 20 nm and an Rt of -50 to 50 nm. Preferably there is. The protective film preferably has a hard coat layer or an antiglare layer having a thickness of 8 to 20 μm. For example, JP 2003-114333 A, JP 2004-203309 A, 2004-354699 A A polarizing plate protective film having a hard coat layer or an antiglare layer described in JP-A No. 2004-354828 is preferably used. Further, an antireflection layer, an antifouling layer or the like is preferably laminated on the hard coat layer or antiglare layer.

  Alternatively, it is also preferable to use a polarizing plate protective film that also serves as an optical compensation film having an optical anisotropic layer formed by aligning liquid crystal compounds such as discotic liquid crystal, rod-shaped liquid crystal, and cholesteric liquid crystal. For example, the optically anisotropic layer can be formed by the method described in JP-A-2003-98348. By using in combination with the polarizing plate of the present invention, a liquid crystal display device having excellent flatness and a stable viewing angle expansion effect can be obtained.

  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. As the polarizing film, a polyvinyl alcohol aqueous solution is formed and dyed by uniaxially stretching or dyed, or uniaxially stretched after dyeing, and then preferably subjected to a durability treatment with a boron compound. On the surface of the polarizing film, one side of the optical film of the present invention is bonded to form a polarizing plate. It is preferably bonded with an aqueous adhesive mainly composed of completely saponified polyvinyl alcohol or the like. Ethylene-modified polyvinyl alcohol is also preferably used as a polarizer. The film thickness of the polarizer is preferably 5 to 30 μm, particularly 10 to 25 μm.

  FIG. 3 is a schematic exploded configuration diagram of a liquid crystal display device using a polarizing plate produced using the retardation film produced in the present invention.

  In the figure, reference numeral 7 denotes a liquid crystal display device. The liquid crystal display device 7 is configured to have a polarizing plate 7b on one side of the liquid crystal cell 7a and a polarizing plate 7b on one side. The polarizing plate 7b includes a retardation film 7b2 on the liquid crystal cell 7a side of the polarizer 7b1 and a protective film 7b3 on the other side. E represents the transmission axis of the polarizer 7b1, and F represents the slow axis of the retardation film 7b2. The polarizing plate 7c includes a retardation film 7c2 on the liquid crystal cell 7a side of the polarizer 7c1 and a protective film 7c3 on the other side. G represents the transmission axis of the polarizer 7b1, and H represents the slow axis of the retardation film 7b2. The polarizing plate 7b and the polarizing plate 7c are disposed so that their slow axes are orthogonal to each other.

  The liquid crystal display device shown in the figure, which is composed of a polarizing plate using the retardation film of the present invention, is used for developing a higher display quality than a normal polarizing plate. In particular, it is preferably used for a multi-domain liquid crystal display device, more preferably a multi-domain liquid crystal display device with a birefringence mode.

  Multi-domaining is also suitable for improving the symmetry of image display, and various methods have been reported "Okita, Yamauchi: Liquid Crystal, 6 (3), 303 (2002)". The liquid crystal display cell is also shown in “Yamada, Yamahara: Liquid Crystal, 7 (2), 184 (2003)”, but is not limited thereto.

  The polarizing plate of the present invention includes an MVA (Multi-domain Vertical Alignment) mode represented by a vertical alignment mode, in particular, a MVA mode divided into four, a known PVA (Patterned Vertical Alignment) mode and an electrode multi-domained by an electrode arrangement. It can be effectively used in a CPA (Continuous Pinwheel Alignment) mode in which arrangement and chiral ability are fused. Above all, the retardation film of the present invention is preferably used for a vertical alignment mode liquid crystal display device, and particularly preferably for a MVA (Multi-domain Vertical Alignment) mode liquid crystal display device.

  The display quality of the display cell is preferably symmetrical with respect to human observation. Therefore, when the display cell is a liquid crystal display cell, the domains can be multiplied substantially giving priority to the symmetry on the observation side. A known method can be used to divide the domain, and can be determined by taking into account the properties of the known liquid crystal mode by a two-division method, more preferably a four-division method.

  Liquid crystal display devices are being applied to color display and moving image display devices, and the display quality in the present invention is less fatigued and more faithful to display moving images due to improved contrast and resistance to polarizing plates. It becomes.

  In the liquid crystal display device of the present invention, the polarizing plate using the retardation film of the present invention is disposed only on one surface of the liquid crystal cell or on both surfaces. At this time, by using the retardation film of the present invention contained in the polarizing plate so as to be on the liquid crystal cell side, it is possible to contribute to improvement in display quality. Next, the material used for manufacturing the retardation film of the present invention will be described.

(Resin material)
The retardation film of the present invention is preferably manufactured easily, has good adhesion to a polarizer, and is optically transparent. Among them, a resin film is preferable. Transparent means that the visible light transmittance is 60% or more, preferably 80% or more, and particularly preferably 90% or more.

  There is no particular limitation as long as it is a resin that forms a resin film having the above-mentioned properties. For example, cellulose ester-based resins such as cellulose diacetate resin, cellulose triacetate resin, cellulose acetate butyrate resin, and cellulose acetate propionate resin Resins, polyester resins, polycarbonate resins, polyarylate resins, polysulfone (including polyethersulfone) resins, polyester resins such as polyethylene terephthalate resins and polyethylene naphthalate resins, polyethylene resins, polypropylene resins, cellophane, polyvinylidene chloride Resin, polyvinyl alcohol resin, ethylene vinyl alcohol resin, syndiotactic polystyrene resin, polycarbonate resin, cycloolefin resin, polymethyl Pentene resins, polyether ketone resins, polyether ketone imide resin, polyamide resin, fluorine resin, nylon resin, polymethylmethacrylate resin, and acrylic resin. Among these, cellulose ester resins, cycloolefin resins, polycarbonate resins, and polysulfone (including polyethersulfone) resins are preferable. In the present invention, cellulose ester resins, cycloolefin resins, and polycarbonate resins are particularly preferable in production. From the viewpoints of cost, transparency, adhesion and the like, it is preferably used.

  The cellulose ester resin according to the present invention will be described. The cellulose ester resin is preferably cellulose acetate resin, cellulose propionate resin, cellulose butyrate resin, cellulose acetate butyrate resin, or cellulose acetate propionate resin. Among them, cellulose acetate butyrate resin, cellulose acetate phthalate resin, cellulose acetate Propionate resin is preferably used.

  In particular, when the substitution degree of the acetyl group is X and the substitution degree of the propionyl group or butyryl group is Y, a cellulose ester resin having a mixed fatty acid ester of cellulose in which X and Y are in the following ranges is preferably used.

Formula (I) 2.0 ≦ X + Y ≦ 2.6
Formula (II) 0.1 ≦ Y ≦ 1.2
Furthermore, a cellulose acetate propionate (total acyl group substitution degree = X + Y) resin of 2.4 ≦ X + Y ≦ 2.6 and 1.4 ≦ X ≦ 2.3 is preferable. Among them, 2.4 ≦ X + Y ≦ 2.6, 1.7 ≦ X ≦ 2.3, 0.1 ≦ Y ≦ 0.9, cellulose acetate propionate resin, cellulose acetate butyrate (total acyl group substitution degree = X + Y ) Resins are preferred. The portion not substituted with an acyl group usually exists as a hydroxyl group. These cellulose ester resins can be synthesized by a known method. The measuring method of the substitution degree of an acyl group can be measured according to the provisions of ASTM-D817-96.

  When a cellulose ester resin is used as the retardation film of the present invention, the cellulose used as the raw material for the cellulose ester resin is not particularly limited, and examples include cotton linters, wood pulp (derived from coniferous trees and hardwoods), kenaf and the like. I can do it. Moreover, the cellulose ester-type resin obtained from them can be mixed and used in arbitrary ratios, respectively. When the acylating agent is an acid anhydride (acetic anhydride, propionic anhydride, butyric anhydride), these cellulose ester resins use an organic acid such as acetic acid or an organic solvent such as methylene chloride, It can obtain by making it react with a cellulose raw material using such a protic catalyst.

When the acylating agent is acid chloride (CH ₃ COCl, C ₂ H ₅ COCl, C ₃ H ₇ COCl), the reaction is carried out using a basic compound such as an amine as a catalyst. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804. The cellulose ester resin used in the present invention is obtained by mixing and reacting the above acylating agent amounts in accordance with the degree of substitution. In the cellulose ester resin, these acylating agents react with hydroxyl groups of cellulose molecules. To do. Cellulose molecules are composed of many glucose units linked together, and the glucose unit has three hydroxyl groups. The number of acyl groups derived from these three hydroxyl groups is called the degree of substitution (mol%). For example, cellulose triacetate has acetyl groups bonded to all three hydroxyl groups of the glucose unit (actually 2.6 to 3.0).

  As described above, the cellulose ester-based resin used in the present invention may be propionate group or butyrate in addition to acetyl group such as cellulose acetate propionate resin, cellulose acetate butyrate resin, or cellulose acetate propionate butyrate resin. A mixed fatty acid ester of cellulose to which a group is bonded is particularly preferably used. In addition, the cellulose acetate propionate resin containing a propionate group as a substituent is excellent in water resistance and is useful as a film for a liquid crystal image display device.

  The number average molecular weight of the cellulose ester-based resin is preferably 40000 to 200000, and has a high mechanical strength when molded, and an appropriate dope viscosity in the case of a solution casting method, and more preferably 50000 to 150,000. . The weight average molecular weight (Mw) / number average molecular weight (Mn) is preferably in the range of 1.4 to 4.5.

  The cycloolefin resin according to the present invention will be described. The cycloolefin resin used in the present invention is composed of a polymer resin containing an alicyclic structure. A preferred cycloolefin resin is a resin obtained by polymerizing or copolymerizing a cyclic olefin. Examples of the cyclic olefin include norbornene, dicyclopentadiene, tetracyclododecene, ethyltetracyclododecene, ethylidenetetracyclododecene, tetracyclo [7.4.0.110, 13.02,7] trideca-2,4. Unsaturated hydrocarbons of polycyclic structures such as 6,11-tetraene and derivatives thereof; cyclobutene, cyclopentene, cyclohexene, 3,4-dimethylcyclopentene, 3-methylcyclohexene, 2- (2-methylbutyl) -1-cyclohexene, cyclo Examples thereof include monocyclic unsaturated hydrocarbons such as octene, 3a, 5,6,7a-tetrahydro-4,7-methano-1H-indene, cycloheptene, cyclopentadiene, cyclohexadiene, and derivatives thereof. These cyclic olefins may have a polar group as a substituent. Examples of the polar group include a hydroxyl group, a carboxyl group, an alkoxyl group, an epoxy group, a glycidyl group, an oxycarbonyl group, a carbonyl group, an amino group, an ester group, and a carboxylic acid anhydride group. Or a carboxylic anhydride group is preferred.

  Preferred cycloolefin resins may be those obtained by addition copolymerization of monomers other than cyclic olefins. Addition copolymerizable monomers include ethylene, propylene, 1-butene, 1-pentene, and other ethylene or α-olefins; 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl- Examples include dienes such as 1,4-hexadiene and 1,7-octadiene.

The cyclic olefin is obtained by an addition polymerization reaction or a metathesis ring-opening polymerization reaction. The polymerization is carried out in the presence of a catalyst. Examples of the addition polymerization catalyst include a polymerization catalyst composed of a vanadium compound and an organoaluminum compound. As a catalyst for ring-opening polymerization, a polymerization catalyst comprising a metal halide such as ruthenium, rhodium, palladium, osmium, iridium, platinum, nitrate or acetylacetone compound, and a reducing agent; or titanium, vanadium, zirconium, tungsten, molybdenum And a polymerization catalyst composed of a metal halide such as acetylacetone compound and an organoaluminum compound. The polymerization temperature, pressure and the like are not particularly limited, but the polymerization is usually carried out at a polymerization temperature of -50 ° C to 100 ° C and a polymerization pressure of 0 to 490 N / cm ² .

  The cycloolefin resin according to the present invention is preferably a resin obtained by polymerizing or copolymerizing a cyclic olefin, followed by a hydrogenation reaction to change the unsaturated bond in the molecule to a saturated bond. The hydrogenation reaction is performed by blowing hydrogen in the presence of a known hydrogenation catalyst. Examples of hydrogenation catalysts include cobalt acetate / triethylaluminum, nickel acetylacetonate / triisobutylaluminum, transition metal compounds such as titanocene dichloride / n-butyllithium, zirconocene dichloride / sec-butyllithium, tetrabutoxytitanate / dimethylmagnesium / alkyl. Homogeneous catalyst consisting of a combination of metal compounds; heterogeneous metal catalyst such as nickel, palladium, platinum; nickel / silica, nickel / diatomaceous earth, nickel / alumina, palladium / carbon, palladium / silica, palladium / diatomaceous earth And a heterogeneous solid-supported catalyst in which a metal catalyst such as palladium / alumina is supported on a carrier.

  Or the following norbornene-type resin is also mentioned as a cycloolefin resin. The norbornene-based resin preferably has a norbornene skeleton as a repeating unit. Specific examples thereof include, for example, JP-A-62-252406, JP-A-62-2252407, and JP-A-2-133413. JP, JP 63-145324, JP 63-264626, JP 1-224017, JP 57-8815, JP 5-2108, JP 5-39403. JP-A-5-43663, JP-A-5-43834, JP-A-5-70655, JP-A-5-279554, JP-A-6-206985, JP-A-7-62028, JP-A-8-176411, JP-A-9-241484, JP-A-2001-277430, JP-A-2003-139 No. 50, JP-A No. 2003-14901, JP-A No. 2003-161832, JP-A No. 2003-195268, JP-A No. 2003-111588, JP-A No. 2003-211589, JP-A No. 2003-268187 Gazette, JP-A-2004-133209, JP-A-2004-309799, JP-A-2005-121183, JP-A-2005-164632, JP-A-2006-72309, JP-A-2006-178191, Although what was described in Unexamined-Japanese-Patent No. 2006-215333, Unexamined-Japanese-Patent No. 2006-268065, Unexamined-Japanese-Patent No. 2006-299199 etc. is mentioned, It is not limited to these. Moreover, these may be used individually by 1 type and may use 2 or more types together. Specifically, ZEONEX, ZEONOR manufactured by Nippon Zeon Co., Ltd., Arton manufactured by JSR Corporation, APPEL manufactured by Mitsui Chemicals, Inc. (APL8008T, APL6509T, APL6013T, APL5014DP, APL6015T) and the like are preferably used.

  The molecular weight of the cycloolefin polymer according to the present invention is appropriately selected depending on the purpose of use, but polyisoprene measured by gel permeation chromatography method of cyclohexane solution (toluene solution when the polymer resin does not dissolve). Alternatively, when the weight average molecular weight in terms of polystyrene is usually in the range of 5,000 to 500,000, preferably 8,000 to 200,000, more preferably 10,000 to 100,000, the mechanical strength and molding processability of the molded body are highly balanced. It is preferable.

  Moreover, when a low-volatile antioxidant is blended at a ratio of 0.01 to 5 parts by mass with respect to 100 parts by mass of the cycloolefin polymer, it can effectively prevent the polymer from being decomposed or colored during the molding process. I can do it.

  The polycarbonate resin according to the present invention will be described. There are various types of polycarbonate resins, and aromatic polycarbonates are preferable from the viewpoint of chemical properties and physical properties, and bisphenol A polycarbonates are particularly preferable. Among them, more preferred is a bisphenol A derivative in which a benzene ring, a cyclohexane ring, or an aliphatic hydrocarbon group is introduced into bisphenol A, and these groups are introduced asymmetrically with respect to the central carbon. A polycarbonate having a structure in which the anisotropy in the unit molecule is reduced, obtained by using the obtained derivative is preferable. For example, one in which two methyl groups on the central carbon of bisphenol A are replaced with a benzene ring, and one hydrogen on each benzene ring in bisphenol A is replaced asymmetrically with respect to the central carbon by a methyl group or a phenyl group The polycarbonate resin obtained is preferable. Specifically, 4,4′-dihydroxydiphenylalkane or a halogen-substituted product thereof can be obtained by a phosgene method or a transesterification method. For example, 4,4′-dihydroxydiphenylmethane, 4,4′-dihydroxydiphenylethane 4,4'-dihydroxydiphenylbutane and the like. In addition, for example, polycarbonate resins described in JP-A-2006-215465, JP-A-2006-91836, JP-A-2005-121813, JP-A-2003-167121 and the like can be mentioned. It is done.

  The retardation film made of the polycarbonate resin used in the present invention may be used by mixing with a transparent resin such as a polystyrene resin, a methyl methacrylate resin, or a cellulose acetate resin, or at least one of the cellulose acetate films. A polycarbonate resin may be laminated on the surface.

  The retardation film made of polycarbonate resin used in the present invention has a glass transition point (Tg) of 110 ° C. or higher and a water absorption rate (measured under conditions of 23 ° C. water and 24 hours) of 0.3%. The following should be used: More preferably, Tg is 120 ° C. or higher and water absorption is 0.2% or less.

(Dope)
The solvent used for preparing the dope may be any solvent that can dissolve the resin, and even a solvent that cannot be dissolved alone can be dissolved by mixing with another solvent. Can be used. In general, a mixed solvent composed of a good solvent and a poor solvent is used. In addition, what melt | dissolves resin to be used independently is defined as a good solvent, and what swells or does not melt | dissolve independently is defined as a poor solvent. For example, in the case of a cellulose ester resin, the good solvent and the poor solvent change depending on the acyl group substitution degree of the cellulose ester. 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. In the case of a cellulose ester resin, the 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.

  Since the good solvent and the poor solvent differ depending on the resin to be used, it will be described in the case of a cellulose ester resin. Examples of the good solvent include methylene chloride, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2 , 2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1 , 1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane and the like, but organic halogen compounds such as methylene chloride, Dioxolane derivatives, methyl acetate, ethyl acetate, acetone and the like are mentioned as preferred organic solvents (that is, good solvents). That.

  Examples of the poor solvent include alcohols having 1 to 8 carbon atoms such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol, methyl ethyl ketone, methyl isobutyl ketone, propyl acetate, and monochloro. Examples thereof include benzene, benzene, cyclohexane, tetrahydrofuran, methyl cellosolve, ethylene glycol monomethyl ether, and the like. These poor solvents can be used alone or in combination of two or more.

  Next, a method for preparing a dope using a cellulose ester resin will be described. As a method for dissolving the cellulose ester resin when preparing the dope, 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 equal to or higher than the boiling point of the solvent at normal pressure and that the solvent does not boil under pressure, in order to prevent the formation of massive undissolved materials called gels and mamacos. In addition, a method in which a cellulose ester resin is mixed with a poor solvent and wetted or swollen, and then a good solvent is further added and dissolved is also preferably used.

  The 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 a 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. A preferable 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 resin can be dissolved in a solvent such as methyl acetate.

  Next, this cellulose ester resin solution is filtered using a suitable 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. However, if the absolute filtration accuracy is too small, there is a problem that the filter medium is likely to be clogged. 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 is when two polarizing plates are placed in a crossed Nicol state, a cellulose ester film is placed between them, light is applied from the side of one polarizing plate, and observed from the side of the other polarizing plate. 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, More preferably, it is 50 pieces / m < ² > or less, More preferably, it is 0-10 pieces / cm < ² > or less. 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. A 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 preferred. 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.

(Plasticizer)
Although it does not specifically limit as a plasticizer, Phosphate ester plasticizer, phthalate ester plasticizer, trimellitic acid ester plasticizer, pyromellitic acid plasticizer, glycolate plasticizer, citrate plasticizer Polyester plasticizers can be preferably used. Examples of the phosphate ester include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like. Examples of the phthalic acid ester include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, and butyl benzyl phthalate. Examples of trimellitic acid plasticizers include tributyl trimellitate, triphenyl trimellitate, triethyl trimellitate, and the like. Examples of the pyromellitic acid ester plasticizer include tetrabutyl pyromellitate, tetraphenyl pyromellitate, and tetraethyl pyromellitate. Examples of glycolic acid esters include triacetin, tributyrin, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, and butyl phthalyl butyl glycolate. Examples of the citrate plasticizer include triethyl citrate, tri-n-butyl citrate, acetyl triethyl citrate, acetyl tri-n-butyl citrate, and acetyl tri-n- (2-ethylhexyl) citrate. As the polyester plasticizer, a copolymer of a dibasic acid such as an aliphatic dibasic acid, an alicyclic dibasic acid, or an aromatic dibasic acid and a glycol can be used. The aliphatic dibasic acid is not particularly limited, and adipic acid, sebacic acid, phthalic acid, terephthalic acid, 1,4-cyclohexyl dicarboxylic acid and the like can be used.

  As the glycol, ethylene glycol, diethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol and the like can be used. These dibasic acids and glycols may be used alone or in combination of two or more. The molecular weight of the polyester is preferably in the range of 500 to 2000 in terms of weight average molecular weight from the viewpoint of compatibility with the cellulose ester.

  In the present invention, it is particularly preferable to use a plasticizer having a vapor pressure of less than 1333 Pa at 200 ° C., more preferably a compound having a vapor pressure of 666 Pa or less, and more preferably 1 to 133 Pa. The non-volatile plasticizer is not particularly limited, and examples thereof include arylene bis (diaryl phosphate) ester, tricresyl phosphate, trimellitic acid tri (2-ethylhexyl), and the above polyester plasticizer. These plasticizers can be used alone or in combination of two or more.

  In consideration of dimensional stability and processability, the plasticizer can be added in an amount of 1 to 40% by mass, preferably 3 to 20% by mass, based on the cellulose ester resin. More preferably, it is 4 to 15% by mass. If the amount is less than 3% by mass, a smooth cut surface cannot be obtained when slitting or punching, resulting in increased generation of chips.

  It is preferable to add an antioxidant, an ultraviolet absorber or the like to the retardation film of the present invention. As the antioxidant, a hindered phenol compound is preferably used, and 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl). -4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3 5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3 5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- ( , 5-di-t-butyl-4-hydroxyphenyl) propionate, N, N′-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 1,3,5 -Trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate Etc. In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di-t A phosphorus-based processing stabilizer such as -butylphenyl) phosphite may be used in combination. The amount of these compounds added is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm in terms of mass ratio with respect to the cellulose ester.

  In addition, heat stabilizers such as inorganic fine particles such as kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide, and alumina, and alkaline earth metal salts such as calcium and magnesium may be added. Good.

  The retardation film produced by the production method of the present invention can be used for a polarizing plate or a liquid crystal display member because of its high dimensional stability. In this case, the polarizing plate or liquid crystal can be prevented from being deteriorated. Therefore, an ultraviolet absorber is preferably used.

  As the ultraviolet absorber, those excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less and having little absorption of visible light having a wavelength of 400 nm or more are preferably used from the viewpoint of good liquid crystal display properties. Specifically, the transmittance at 380 nm is preferably less than 10%, more preferably less than 5%.

  Specific examples of preferably used ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, triazine compounds, and the like. For example, the ultraviolet absorbers described in JP-A-10-182621 and JP-A-8-337574 are preferably used. Moreover, the polymeric ultraviolet absorbers described in JP-A-6-148430 and JP-A-12-273437 are also preferably used. Or you may add the ultraviolet absorber described in Unexamined-Japanese-Patent No. 10-152568.

  Among these ultraviolet absorbers, benzotriazole ultraviolet absorbers and benzophenone ultraviolet absorbers are preferable ultraviolet absorbers. Although the specific example of a benzotriazole type ultraviolet absorber is given to the following, this invention is not limited to these.

2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3) '-Tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy -3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole, 2,2-methylenebis (4- (1,1,3,3-tetramethyl) Butyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl)- -Chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol (TINUVIN171, manufactured by Ciba Specialty Chemicals), octyl-3- [ 3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5- (5- Chloro-2H-benzotriazol-2-yl) phenyl] propionate (TINUVIN109, manufactured by Ciba Specialty Chemicals)
Although the specific example of a benzophenone series ultraviolet absorber is shown below, this invention is not limited to these. 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis (2-methoxy-4-hydroxy-5-benzoylphenylmethane) It is done.

  The ultraviolet absorber may be added by dissolving the ultraviolet absorber in an organic solvent such as alcohol, methylene chloride, dioxolane and the like, or adding it directly to the dope composition. For an inorganic powder that does not dissolve in an organic solvent, it is preferable to use a dissolver or a sand mill in the organic solvent and the cellulose ester resin to disperse and then add to the dope. The amount of the ultraviolet absorber used is preferably 0.1% by mass to 2.5% by mass in consideration of the effect as an ultraviolet absorber, transparency, and the like. Furthermore, Preferably, it is 0.8 mass%-2.0 mass%.

  In addition, fine particles as a matting agent may be added to the cellulose ester-based resin film in order to prevent the films from sticking to each other or to impart slipperiness to facilitate handling. The fine particles include inorganic compound fine particles and organic compound fine particles. Inorganic compounds include silicon-containing compounds, silicon dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, etc. More preferred is an inorganic compound containing silicon or zirconium oxide, but silicon dioxide is particularly preferably used since the turbidity of the cellulose ester laminated film can be reduced.

  As fine particles of silicon dioxide, for example, AEROSIL-200, 200V, 300, R972, R972V, R974, R976, R976S, R202, R812, R805, OX50, TT600, RY50, RX50, NY50, NAX50, NA50H manufactured by Aerosil Co., Ltd. NA50Y, NX90, RY200S, RY200, RX200, R8200, RA200H, RA200HS, NA200Y, R816, R104, RY300, RX300, R106, and the like. Among these, AEROSIL-200V and R972V are preferable in terms of controlling dispersibility and particle size.

  As the fine particles of zirconium oxide, commercially available products such as Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) can be used.

  As an organic compound, polymers, such as a silicone resin, a fluororesin, and an acrylic resin, are preferable, for example, Among these, a silicone resin is preferably used.

  Among the above-described silicone resins, those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120 and 240 (above Toshiba Silicone Co., Ltd.) ) Etc. can be used.

  The primary average particle size of the fine particles according to the present invention is preferably 20 nm or less, more preferably 5 to 16 nm, and particularly preferably 5 to 12 nm, from the viewpoint of keeping the haze low.

  The apparent specific gravity of the fine particles is preferably 70 g / liter or more, more preferably 90 to 200 g / liter, and particularly preferably 100 to 200 g / liter. Larger apparent specific gravity makes it possible to make a high-concentration dispersion, which improves haze and agglomerates, and is preferable when preparing a dope having a high solid content concentration as in the present invention. Are particularly preferably used.

  Silicon dioxide fine particles having an average primary particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more are, for example, a mixture of vaporized silicon tetrachloride and hydrogen burned in air at 1000 to 1200 ° C. Can be obtained. Further, for example, Aerosil 200V and Aerosil R972V (manufactured by Nippon Aerosil Co., Ltd.) are commercially available, and these can be used.

  The apparent specific gravity was calculated by the following equation by measuring a weight of silicon dioxide fine particles in a graduated cylinder and measuring the weight at that time.

Apparent specific gravity (g / liter) = Mass of silicon dioxide (g) ÷ Volume of silicon dioxide (liter)
Examples of the method for preparing a dispersion of fine particles according to the present invention include the following three types.

<< Preparation Method A >>
After stirring and mixing the solvent and the fine particles, dispersion is performed with a disperser. This is a fine particle dispersion. The fine particle dispersion is added to the dope solution and stirred.

<< Preparation Method B >>
After stirring and mixing the solvent and the fine particles, dispersion is performed with a disperser. This is a fine particle dispersion. Separately, a small amount of cellulose ester is added to the solvent and dissolved by stirring. As the cellulose ester added here, it is particularly preferable to add the solid material of the present invention. The fine particle dispersion is added to this and stirred. This is a fine particle addition solution. The fine particle additive solution is sufficiently mixed with the dope solution using an in-line mixer.

<< Preparation Method C >>
Add a small amount of cellulose ester to the solvent and dissolve with stirring. Fine particles are added to this and dispersed by a disperser. This is a fine particle addition solution. The fine particle additive solution is sufficiently mixed with the dope solution using an in-line mixer.

  Preparation method A is excellent in dispersibility of silicon dioxide fine particles, and preparation method C is excellent in that silicon dioxide fine particles are difficult to re-aggregate. Among them, the preparation method B described above is a preferable preparation method that is excellent in both dispersibility of the silicon dioxide fine particles and that the silicon dioxide fine particles are less likely to reaggregate.

《Distribution method》
The concentration of silicon dioxide when the silicon dioxide fine particles are mixed with a solvent and dispersed is preferably 5 to 30% by mass, more preferably 10 to 25% by mass, and most preferably 15 to 20% by mass. A higher dispersion concentration is preferable because liquid turbidity with respect to the added amount tends to be low, and haze and aggregates are improved.

  The solvent used is preferably lower alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like. Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film forming of a cellulose ester.

  The amount of silicon dioxide fine particles added to cellulose ester is preferably 0.01 to 0.3 parts by mass, more preferably 0.05 to 0.2 parts by mass, and more preferably 0.0 to 0.2 parts by mass with respect to 100 parts by mass of cellulose ester. Most preferred is 08 to 0.12 parts by mass. The larger the added amount, the better the dynamic friction coefficient, and the smaller the added amount, the lower the haze and the fewer agglomerates.

  As the disperser, a normal disperser can be used. Dispersers can be broadly divided into media dispersers and medialess dispersers. For dispersing silicon dioxide fine particles, a medialess disperser is preferred because of its low haze. Examples of the media disperser include a ball mill, a sand mill, and a dyno mill. Examples of the medialess disperser include an ultrasonic type, a centrifugal type, and a high pressure type. In the present invention, a high pressure disperser is preferable. The high pressure dispersion device is a device that creates special conditions such as high shear and high pressure by passing a composition in which fine particles and a solvent are mixed at high speed through a narrow tube. When processing with a high-pressure dispersion apparatus, for example, the maximum pressure condition inside the apparatus is preferably 9.807 MPa or more in a thin tube having a tube diameter of 1 to 2000 μm. More preferably, it is 19.613 MPa or more. Further, at that time, those having a maximum reaching speed of 100 m / second or more and those having a heat transfer speed of 420 kJ / hour or more are preferable.

  The high-pressure dispersing apparatus as described above includes an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation or a nanomizer manufactured by Nanomizer, and other manton gorin type high-pressure dispersing apparatuses such as homogenizer manufactured by Izumi Food Machinery, Examples include UHN-01 manufactured by Wako Co., Ltd.

  These fine particles may be uniformly distributed in the thickness direction of the film, but it is more preferable that they are mainly distributed so as to exist mainly in the vicinity of the surface. It is preferable to add fine particles mainly to the dope arranged on the surface layer side using a dope of a seed or more because a film having high slip properties and low haze can be obtained. It is preferable to add fine particles mainly to two dopes on the surface layer side using three kinds of dopes.

  Moreover, the optical film which has preferable impedance can also be obtained by adding the substance which has electroconductivity to the film of this invention. Although it does not specifically limit as an electroconductive substance, The antistatic agent etc. which have compatibility with an ionic electroconductive substance, electroconductive fine particles, or a cellulose ester can be used.

  Here, the ion conductive substance is a substance that shows electric conductivity and contains ions that are carriers for carrying electricity, and examples thereof include ionic polymer compounds.

  Examples of the ionic polymer compound include anionic polymer compounds such as those described in JP-B-49-23828, JP-A-49-23827, and JP-A-47-28937, such as JP-B-55-734, JP-A-50- An ionene type polymer having a dissociating group in the main chain, as shown in Japanese Patent No. 54672, Japanese Patent Publication Nos. 59-14735, 57-18175, 57-18176, 57-56059, etc. No. 13223, No. 57-15376, No. Sho 53-45231, No. 55-145578, No. 55-65950, No. 55-67746, No. 57-11342, No. 57-19735, No. Sho-58- No. 56858, JP-A 61-27853, and 62-9346, a cationic pender having a cationic dissociation group in the side chain It can be mentioned door type polymers, and the like.

Examples of the conductive fine particles include conductive metal oxides. As an example of the metal oxide, ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , MgO, BaO, MoO ₂ , V ₂ O ₅ , or a composite oxide thereof is preferable. In particular, ZnO, TiO ₂ and SnO ₂ are preferred. Examples of containing different atoms include, for example, addition of Al, In, etc. to ZnO, addition of Nb, Ta, etc. to TiO ₂ , and addition of Sb, Nb, halogen elements, etc. to SnO ₂ . Addition is effective. The amount of these different atoms added is preferably in the range of 0.01 to 25 mol%, particularly preferably in the range of 0.1 to 15 mol%.

Further, the volume resistivity of these conductive metal oxide powders is 10 ⁷ Ωcm or less, particularly 10 ⁵ Ωcm or less, the primary particle diameter is 10 nm or more and 0.2 μm or less, and the major structure has a long diameter. It is preferable that a powder having a specific structure of 30 nm or more and 6 μm or less contains 0.01% or more and 20% or less in volume fraction in at least a part of the region of the film.

  It is particularly preferable to contain an ionene conductive polymer described in JP-A-9-203810 or a quaternary ammonium cation conductive polymer having intermolecular crosslinking.

  The characteristic of the cross-linked cationic conductive polymer is the dispersible granular polymer obtained, and it can have a high concentration and high density of the cationic component in the particles, so it has not only excellent conductivity. No deterioration of conductivity was observed even under low relative humidity, and although the particles were well dispersed in the dispersed state, the adhesion of the particles was good in the film-forming process after coating, so the film strength was also low. It is strong and has excellent adhesion to other substances such as substrates, and has excellent chemical resistance.

  The dispersible granular polymer, which is a crosslinked cationic conductive polymer, generally has a particle size range of about 0.01 μm to 0.3 μm, preferably a particle size of 0.05 μm to 0.15 μm. As used herein, the term “dispersible particulate polymer” is a polymer that appears as a clear or slightly turbid solution by visual observation but appears as a granular dispersion under an electron microscope.

  The addition of the antistatic agent or matting agent is preferably included in the surface layer portion (portion of 10 μm from the surface) of the optical film, and the antistatic agent and / or matting agent is added to the surface of the film by a method such as co-casting. It is preferable to contain. Specifically, a dope A containing a conductive material and / or a matting agent and a dope B substantially not containing these are used, and the dope B is cast so that the dope A is present on at least one side of the dope B. It is preferable.

  If necessary, an antistatic agent, a flame retardant, a lubricant, an oil agent, a matting agent, and other additives may be added.

  The retardation film manufactured by the manufacturing method of this invention can be used for the polarizing plate used for a liquid crystal display, and a liquid crystal display device.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
Using the manufacturing apparatus shown in FIG. 1B, the dope shown below is cast on a belt having a length of 100 m at a temperature of 35 ° C., and the web is peeled off at the peeling point of the belt (from casting to peeling). 1.5 minutes), the thickness of the retardation film, the width, the residual solvent amount in the first stretching step, the residual solvent amount in the second stretching step, the primary stretching ratio in the first stretching step, the second The ratio of the secondary stretching ratio in the stretching process to the total of the primary stretching ratio and the secondary stretching ratio of the primary stretching ratio was changed as shown in Tables 1 and 2 for stretching. Thereafter, a retardation film having a thickness of 3000 m was prepared by drying in the drying process and rolled in the winding process. 101-151.

The belt used was a 2500 mm wide stainless steel with a mirror finished surface. When the web was peeled from the belt, cold air of 10 ° C. was blown. The peel tension at the time of peeling the web from the belt varied in accordance with the width of the final retardation film. Moreover, the conveyance tension in each process from the peeling point to the winding process also changed corresponding to the width of the retardation film finally finished.
In the first drying step, the second drying step, the first stretching step, and the second stretching step, heated air is used as the solvent removing means, and the residual solvent amount of the retardation film at the time when the second drying step is finished is set to 0. It was made to become 001 mass%. The first drying step was 100 m long, and the second drying step was 1000 m long. The first stretching step and the second stretching step were 40 m in total length. A clip tenter was used as a uniaxial stretching apparatus for the first stretching step and the second stretching step.

The residual solvent amount of the web before entering the first stretching step was adjusted by adjusting the temperature and air volume of the heating air in the first drying step. The residual solvent amount of the web before entering the second stretching step was adjusted by adjusting the temperature and air volume of the heating air in the first stretching step.
The value of the residual solvent amount (% by mass) is 10 cm × 5 cm in web (retardation film) when the web (retardation film) is dried for 1 hour at 115 ° C. When the mass of the retardation film is A, it is a value obtained by ((A−B) / B) × 100 = residual solvent amount (mass%). The change in the residual solvent amount of the web immediately after peeling was adjusted by changing the heating temperature in the solution casting film forming step.

  The stretch ratio in the first stretching step indicates a value obtained by calculation from the following calculation formula.

Primary stretch ratio (%) = (width from center to end of web after primary stretching / width from center to end of web before stretching) × 100
For the width from the center of the web to the end, a value obtained by measuring the width with a C-type JIS grade 1 steel scale is used.

Secondary stretch ratio (%) = (width from center to end of web after secondary stretch / width from center to end of web before stretch) × 100
For the width from the center of the web to the end, a value obtained by measuring the width with a C-type JIS grade 1 steel scale is used. The web before stretching refers to the web before primary stretching.

  Thickness of the retardation film is an average value obtained by using 1 μm from the end of winding using μ-mate manufactured by Sony Corporation, measuring 20 points at 100 cm intervals in the width direction, and 10 points at 10 cm intervals in the length direction. Indicates.

  The total length of the first stretching step was 40 m, and the primary stretching time was 4% / second. The total length of the second stretching step was 40 m, and the secondary stretching time was 1% / second.

<Preparation of fine particle dispersion>
11 parts by mass of silicon dioxide fine particles (trade name: AEROSIL-R972V (manufactured by Nippon Aerosil Co., Ltd.))
(Average primary particle diameter 16 nm, apparent specific gravity 90 g / liter)
89 parts by mass of ethanol or more was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<Fine particle additive solution>
The following cellulose ester resin was added to a dissolution tank containing methylene chloride and heated to completely dissolve, and this was then added to Azumi Filter Paper No. Azumi Filter Paper No. Filtered using 244. While finely stirring the filtered cellulose ester solution, the fine particle dispersion was slowly added thereto. 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.

Methylene chloride 99 parts by mass Cellulose acetate propionate (acetyl group substitution degree 1.5, propionyl group substitution degree 1.0, total acyl group substitution degree 2.5) 4 parts by mass Fine particle dispersion 11 parts by mass <Preparation of main dope >
A main dope having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. The cellulose ester resin was added to a pressurized dissolution tank containing a solvent while stirring. This was heated and stirred to completely dissolve, and a plasticizer and an ultraviolet absorber were further added and dissolved. This was designated as Azumi Filter Paper No. The main dope was prepared by filtration using 244.

  The main dope was added so as to be 100 parts by mass and 5 parts by mass of the fine particle additive solution, and sufficiently mixed with an in-line mixer (Toray static in-tube mixer Hi-Mixer, SWJ) to obtain a dope.

<Composition of main dope>
Methylene chloride 390 parts by mass Ethanol 80 parts by mass Cellulose acetate propionate (acetyl group substitution degree 1.5, propionyl group substitution degree 1.0, total acyl group substitution degree 2.5) 100 parts by mass Plasticizer: Aromatic terminal ester Sample No. 4 5 parts by mass Plasticizer: Trimethylolpropane tribenzoate 5.5 parts by mass UV absorber: Tinuvin 109 (manufactured by Ciba Specialty Chemicals)
1 part by mass UV absorber: Tinuvin 171 (manufactured by Ciba Specialty Chemicals)
1 part by mass

Evaluation The produced sample No. The in-plane retardation value Ro and the thickness direction retardation value Rt were measured by the methods shown below for 101 to 151, and the results are shown in Tables 3 and 4. The in-plane retardation value Ro and the thickness direction retardation value Rt were evaluated by obtaining a lateral deviation from the measured values.

Measurement of in-plane retardation value Ro and thickness direction retardation value Rt Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), the film was allowed to stand for 24 hours in an environment of 23 ° C. and 55% RH. In the same environment, the retardation of the film is measured at a wavelength of 589 nm, and the lateral deviation of the in-plane retardation value Ro, the thickness direction retardation value Rt, and the thickness direction retardation value Rt is obtained. The width deviation indicates the difference between the maximum value and the minimum value measured by measuring 20 phase difference values Rt in the thickness direction.
The Ro width deviation can be made 2 nm or less because display unevenness occurs when the polarizing plate is processed.
Since the display unevenness occurs when the polarizing plate is processed, the Rt width deviation can be 5 nm or less.

  In Tables 3 and 4, Sample No. 107 could not be produced because it was broken due to poor peeling. Sample No. No. 108 was broken because the residual solvent amount was low, and could not be produced. Sample No. In 121, the film was slackened, and the deviation of the film thickness and the optical value increased, making it impossible to produce a product. Sample No. Since it exceeded 10% which is the critical stretching ratio in the 128 low residual dissolution region, it broke and Ro and Rt could not be measured. Sample No. 129 showed good results in the Ro width deviation and the Rt width deviation, but since the haze degree was inferior, commercialization was impossible. Sample No. No. 135 was ruptured frequently due to the thin film limit film thickness, and thus ruptured and Ro and Rt could not be measured. Sample No. No. 142 showed good results in the Ro width deviation and the Rt width deviation, but because it was difficult to form a polarizing plate with a thick film, it was not possible to make a product. Sample No. No. 143 showed good results in the Ro width deviation and the Rt width deviation. However, since the width was narrow and it was not possible to cope with a large-scale product, it was impossible to commercialize the product. Sample No. 151 showed good results in the Ro width deviation and the Rt width deviation. However, since the width was wide and it was difficult to stabilize the film thickness, commercialization was impossible. In the present invention, the Ro width deviation was 2 nm or less and the Rt width deviation was 5 nm or less, and the effectiveness of the present invention was confirmed.

Example 2
Using the manufacturing apparatus shown in FIG. 1B, the dope shown below is cast on a belt having a length of 100 m at a temperature of 35 ° C., and the web is peeled off at the peeling point of the belt (from casting to peeling). 1.5 minutes), and the primary stretching time in the TD direction in the first stretching step and the secondary stretching time in the TD direction in the second stretching step are changed as shown in Table 5 for stretching. did. Thereafter, the film was dried in a drying process, and in a winding process, a retardation film having a thickness of 40 μm and a width of 2000 mm was produced in a thickness of 3000 m. 201-213.

The thickness of the dope on the belt was 80 μm, and the casting width was 2300 mm. The belt used was a 2500 mm wide stainless steel with a mirror finished surface. When the web was peeled from the belt, cold air of 10 ° C. was blown. The peeling tension when peeling the web from the belt was 200 N / m. The conveyance tension from the first drying step to the second drying step was 200 N / m, and in the winding process, the retardation film was wound and collected at 150 N / m.
The amount of residual solvent when performing primary stretching in the first stretching step was 60% by mass. The amount of residual solvent when performing secondary stretching in the second stretching step was 7% by mass.
In the first drying step, the second drying step, the first stretching step, and the second stretching step, heated air is used as the solvent removing means, and the residual solvent amount of the retardation film at the time when the second drying step is finished is set to 0. It was made to become 001 mass%. The first drying step was 100 m long, and the second drying step was 1000 m long. The first stretching step and the second stretching step were 40 m in total length. A clip tenter was used as a uniaxial stretching apparatus for the first stretching step and the second stretching step.

  The residual solvent amount of the web before entering the first stretching step was adjusted by adjusting the temperature and air volume of the heating air in the first drying step. The residual solvent amount of the web before entering the second stretching step was adjusted by adjusting the temperature and air volume of the heating air in the first stretching step.

The width of the web when entering the first stretching step was 2000 mm. The primary stretching ratio in the first stretching step was 25%. The secondary stretching ratio in the second stretching step was 5%.
The primary stretching ratio, the secondary stretching ratio, the residual solvent amount, and the thickness of the retardation film are values measured by the same method as in Example 1.

  The total length of the first stretching step was 40 m, and the total length of the second stretching step was 40 m.

<Fine particle dispersion>
The same fine particle dispersion as in Example 1 was prepared.

<Fine particle additive solution>
The same fine particle additive solution as in Example 1 was prepared.

<Main dope>
A main dope having the same composition as in Example 1 was prepared in the same manner as in Example 1.

Evaluation The produced sample No. In Table 201, the same method in-plane retardation value Ro and thickness direction retardation value Rt as in Example 1 were measured, and the results are shown in Table 6. The in-plane retardation value Ro and the thickness direction retardation value Rt were evaluated by obtaining a lateral deviation from the measured values.

  In the present invention, the Ro width deviation was 2 nm or less and the Rt width deviation was 5 nm or less, and the effectiveness of the present invention was confirmed.

Example 3
Production of liquid crystal display device (Production of polarizing plate)
A polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a polarizer.

  Subsequently, each retardation film sample No. 1 produced in the polarizer and Example 1 according to the following steps 1 to 5 was used. 101 to 152 and Konica Minolta Tack KC8UX-RHA (manufactured by Konica Minolta Opto Co., Ltd.) were bonded as a protective film on the back side to produce a polarizing plate. 3-1 to 3-51.

  Step 1: Soaked in a 1 mol / L sodium hydroxide solution at 50 ° C. for 60 seconds, then washed with water and dried to obtain a saponified cellulose ester film bonded to the polarizer.

  Process 2: The said polarizer was immersed in the polyvinyl alcohol adhesive tank of 2 mass% of solid content for 1-2 seconds.

  Step 3: Lightly wipe off excess adhesive adhering to the polarizer in Step 2 and place it on the cellulose ester film treated in Step 1 so that the anti-reflection layer of KC8UX-RHA is on the outside Laminated and placed.

Step 4: The retardation film, the polarizing film, and the cellulose ester film sample laminated in Step 3 were bonded at a pressure of 20 to 30 N / cm ² and a conveyance speed of about 2 m / min.

  Step 5: The polarizer, cellulose ester film, and each sample No. prepared in Step 4 in a dryer at 80 ° C. The sample bonded with 101 to 140 was dried for 2 minutes to prepare a polarizing plate.

  Thereafter, the polarizing plate of a commercially available liquid crystal TV (Sharp Aquos 32AD5) was peeled off, and the produced sample No. 101-151 were each bonded to the glass surface of a liquid crystal cell. At that time, the polarizing plate is bonded so that the surface of the retardation film is on the liquid crystal cell side and the absorption axis is oriented in the same direction as the previously bonded polarizing plate. A display device was manufactured and 301 to 351.

Evaluation The liquid crystal display device No. As a result of evaluating the front contrast by the following method after turning on the backlight of the liquid crystal TV display device of the manufactured liquid crystal display device in the environment of 301 to 351 at 23 ° C. and 55% RH and leaving it for 30 minutes. Are shown in Tables 7 and 8.

Evaluation Method of Front Contrast For measurement, EZ-Contrast 160D manufactured by ELDIM was used to measure front luminance from the normal direction of white display and black display on a liquid crystal TV, and the ratio was defined as front contrast. The higher the value, the better the contrast.

  Front contrast = brightness of white display measured from normal direction of display device / brightness of black display measured from normal direction of display device

  Sample No. A polarizing plate could not be formed due to the thick film of the retardation film 342 used. The effectiveness of the present invention was confirmed.

It is the schematic of the manufacturing apparatus which manufactures the phase difference film by a solution casting film forming method. It is a schematic diagram of the polarizing plate produced using the phase difference film manufactured by this invention. It is a model exploded block diagram of the liquid crystal display device using the polarizing plate produced using the retardation film manufactured by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b, 1c Manufacturing apparatus 101 Solution casting film forming process 101a Mirror surface metal casting belt 101b Dice 101c Heating apparatus 102 1st extending process 102d, 103d Uniaxial stretching apparatus 103 2nd extending process 104 Drying process 105 Winding process 105a , 603, 7b2, 7c2 retardation film 106 first drying step 107, 108 second drying step 109 third drying step 2 dope 5 web 6, 7b, 7c polarizing plate 601, 7b1 polarizer 602, 7b3 protective film 7 liquid crystal display Device 7a Liquid crystal cell

Claims (5)

A dope obtained by dissolving a raw material resin in a solvent is cast on an endless belt support from a die to form a web, and after peeling the web from the endless belt support, at least a stretching step, and drying In the method for producing a retardation film, a thin film retardation film is produced by a solution casting production apparatus having a step and a winding step.
The retardation film has a thickness of 20 μm to 80 μm, a width of 1500 mm to 2500 mm,
The stretching step has a first stretching step and a second stretching step,
In the first stretching step, the residual solvent amount of the web is primarily stretched at 50% by mass or more and 250% by mass or less,
In the second stretching step, the residual solvent amount of the web is secondarily stretched at 5% by mass or more and 10% by mass or less,
The primary stretching ratio of the primary stretching is 10% to 40% in the TD direction,
The secondary stretching ratio of the secondary stretching is 1% to 10% in the TD direction,
And the said primary stretch rate is 80 to 100% of the sum total of the said primary stretch rate and the said secondary stretch rate, The manufacturing method of the phase difference film characterized by the above-mentioned. The stretching time in the first stretching step is 1% / second to 8% / second, and the stretching time in the second stretching step is 0.1% / second to 1% / second. A method for producing the retardation film according to 1. A retardation film manufactured by the method for manufacturing a retardation film according to claim 1. A polarizing plate, wherein the retardation film according to claim 3 is disposed on at least one surface of the polarizer so that the slow axis of the retardation film is orthogonal or parallel to the transmission axis of the polarizer. A liquid crystal display device using the polarizing plate according to claim 4.

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