JP5335303B2 - Method for producing optical resin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit gel formation in an extruder and to hardly occur distribution of thick film in the film produced while forming a film by fusion method using a cyclic olefin resin. <P>SOLUTION: The process comprises: a melting step to heat and melt a cyclic olefin thermoplastic resin by a twin screw extruder 22, a feeding step to extrude the heat molten resin from a single screw extruder 23 and feed to a molding die 24, and a molding step to form a film by spouting the molten resin in film shape from the molding die 24 to a cooling drum 26 and then cooling. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for producing an optical resin film and an optical film, and in particular, a method for producing an optical resin film using a cyclic olefin resin having a quality suitable for a liquid crystal display device, and an optical obtained by the production method. It is related with the film.

  Films produced from cyclic olefin-based resins (hereinafter also referred to as “cyclic polyolefin films”) are attracting attention as films that can improve the hygroscopicity and moisture permeability of cellulose triacetate films, and are based on melt film formation methods and solution film formation methods. A film manufacturing method has attracted attention. In addition, the cyclic polyolefin film has high optical properties and further changes in optical properties due to temperature changes, and a liquid crystal display device such as a retardation film (hereinafter also referred to as “retardation film”). Development as an optical film is being carried out.

  In particular, the melt casting method has the advantage of not using a solvent compared to the solution casting method, and there is a demand for producing a high-quality cyclic olefin-based resin film that can be used for optics by the melt casting method. Yes.

  Film production by the melt film-forming method is produced by heating and melting a resin with an extruder, discharging the molten resin into a film form from a molding die, cooling it on a cooling drum, and peeling it.

  However, in melt film formation of cyclic olefin-based resins, a large amount of gel is generated due to oxidation (thermal deterioration) and shearing force of the resin during melt extrusion, and optical properties are deteriorated by remaining on the produced film. Since it appears as a foreign matter failure, the generation of this gel was a problem in producing an optical film.

From this, in order to reduce gel, the examination which gives the additive etc. which suppress oxidation is made | formed (refer patent document 1-patent document 3). Further, studies have also been made from the extrusion conditions of an extruder in melt film formation, and twin-screw extrusion is performed by melt-kneading at a shear rate of 30 (sec ⁻¹ ) or more using a meshing-type twin-screw extruder. It has also been attempted to reduce the generation of gel by crushing the gel generated in the machine with a shearing force (see Patent Document 4).

A first extruder that dissolves the raw thermoplastic resin; and a second extruder that has a plasticizer supply section and supplies and kneads the plasticizer to the molten resin supplied from the first extruder. Attempts have also been made to reduce foreign matters remaining in the produced film by providing a filter in between and supplying an inert gas to the second extruder (see Patent Document 5).
JP 2007-160720 A JP-A-7-145213 Japanese Patent Laid-Open No. 9-104061 JP 2006-142715 A JP 2000-56130 A

  However, the method of applying an additive for suppressing oxidation described in Patent Documents 1 to 3 does not have sufficient effect of suppressing gel.

  Further, in the method of Patent Document 4 examined from the extrusion conditions, the gel suppression effect was not sufficient, and when a twin screw extruder was used, the quantitative stable supply to the forming die was likely to be lowered. There is a problem that a film thickness distribution tends to occur in the formed film.

  Moreover, although the method of patent document 5 can suppress the gel generation | occurrence | production by oxidation (thermal deterioration) to some extent, the gel generation | occurrence | production by the shear force peculiar to an extruder is not solved essentially.

  The present invention has been made in view of such circumstances, and suppresses the generation of gel in an extruder and forms a film when a film is formed by a melt film forming method using a cyclic olefin resin. It is an object of the present invention to provide a method for producing an optical resin film capable of producing a high-quality optical film and an optical film produced by the production method, because the film thickness distribution of the produced film is less likely to occur. To do.

According to a first aspect of the present invention, in order to achieve the above object, a melting step in which a cyclic olefin-based thermoplastic resin is heated and melted by a twin screw extruder, and the heated and melted molten resin is extruded from a single screw extruder. Supply step to the forming die, and a forming step of forming the film by discharging the molten resin from the forming die into a film and cooling it, and the barrel wall surface and the screw flight of the twin screw extruder The maximum shear rate generated in the part is in the range of 15 to 800 (s ⁻¹ ), the resin temperature at the outlet of the twin screw extruder is T1 (° C.), and the resin temperature at the outlet of the single screw extruder is T2. When the temperature is (° C.), a method for producing an optical resin film is provided, which satisfies 200 ° C. ≦ T1 <T2 .

  According to claim 1, in the melt film-forming method, a twin screw extruder having a self-wiping effect and a large kneading effect is used as an extruder for heating and melting a cyclic olefin-based thermoplastic resin. To do. And, as an extruder for supplying molten resin to the molding die, a high-shearing but single-screw extruder that has better extrusion stability than a twin-screw extruder is used, and the role of the twin-screw and single-screw extruder The assignment was made clear. As a result, the resin can be melted while remarkably suppressing gel generation during melting in the twin screw extruder, and the molten resin can be quantitatively and stably supplied to the molding die in the single screw extruder.

  That is, the generation of the gel is caused by the shearing force applied when the resin is melted in the extruder, but the molten resin once melted is resistant to the shearing force and has the property that the gel is not easily generated. is there. From this fact, if a twin screw extruder is used as an extruder for heating and melting the resin, the resin can be effectively melted while remarkably suppressing gel generation even under low shear conditions. . However, the twin screw extruder cannot secure the extrusion stability, and if the molten resin is supplied directly from the twin screw extruder to the forming die, a film thickness distribution tends to occur in the produced resin film. Therefore, in the present invention, a single screw extruder is interposed between the twin screw extruder and the forming die, and the molten resin melted by the twin screw extruder is once sent to the single screw extruder, and the single screw extrusion is performed. The machine was fed to the forming die. Thereby, since generation | occurrence | production of the gel in an extruder is suppressed and the film thickness distribution of the formed film is hard to generate | occur | produce, a high quality optical film can be manufactured.

  When supplying the molding resin directly from the twin screw extruder to the molding die as in the past, the resin temperature at the outlet of the twin screw extruder is used to quantitatively and stably supply the molten resin to the molding die. It is necessary to raise the temperature to a resin temperature at which the resin can be stably extruded, and the resin is easily oxidized (thermally deteriorated) to form a gel.

On the other hand, according to claim 1 of the present invention, the two roles of melting the resin and stably supplying the molten resin to the molding die are divided between the twin screw extruder and the single screw extruder. Thus, the resin temperature at the exit of the twin screw extruder can be lowered as compared with a case where the resin temperature is directly supplied from the twin screw extruder to the forming die. Thereby, it can suppress further that resin oxidizes (thermal deterioration) and gelatinizes. In addition, when T2 is less than 200 ° C., the viscosity becomes too high due to insufficient melting of the cyclic olefin-based resin, and the extrusion becomes impossible.

A second aspect of the present invention is characterized in that, in the first aspect, an outlet pressure of the twin screw extruder is 0.1 MPa to 5.5 MPa.

  The outlet pressure of the twin screw extruder for melting the resin was 0.1 MPa to 5.5 MPa, which was lower than that of the conventional extruder. As described above, the gel generated in the extruder includes a gel generated when the resins are cross-linked by shearing the resin (shear cross-linking), and a cross-linked (oxidative cross-link) when the resin is oxidized (thermal deterioration). It is known that there is a gel that occurs. In particular, the extrusion conditions for suppressing shear cross-linking during resin melting are important, and the upper limit of the outlet pressure of the twin-screw extruder that serves to melt is suppressed to a low pressure of 5.5 MPa, so that the resin filling rate inside the screw can be reduced. It can be kept low and resin passage through high shear sites such as between flight barrel walls can be suppressed. Thereby, since the shear force which resin receives in a twin screw extruder becomes small, generation | occurrence | production of a shear bridge | crosslinking can be made small and the gel generation | occurrence | production at the time of resin melting can be suppressed more effectively. 0.1 MPa shown as the lower limit of the outlet pressure is a limit that allows stable supply to the single screw extruder.

  In addition, it is preferable to use a twin screw extruder as a meshing different direction rotation type screw because the shearing force applied to the resin at the meshing portion between the screws can be further reduced.

A third aspect is characterized in that, in the first or second aspect , an outlet pressure of the single screw extruder is in a range of 4 MPa to 20 MPa, and a pressure fluctuation is within ± 0.1 MPa.

According to the third aspect of the present invention , as the extrusion condition of the single screw extruder, the outlet pressure is in the range of 4 MPa to 20 MPa and the pressure fluctuation is within ± 0.1 MPa. The molten resin thus obtained can be quantitatively and stably supplied to the molding die. Further, even if the outlet pressure in the single screw extruder is increased, the resin is already melted in the twin screw extruder, so that gel is hardly generated. Here, the pressure fluctuation of ± 0.1 MPa means that, for example, when the outlet pressure is set to a predetermined value satisfying a range of 4 MPa to 20 MPa, the pressure fluctuation is within ± 0.1 MPa with respect to the predetermined value. To do.

According to a fourth aspect of the present invention, in any one of the first to third aspects, a radical trapping agent or an antioxidant is added at an inlet of the twin screw extruder shaft.

According to the fourth aspect , the gel generated by the oxidative crosslinking can be reduced by adding the radical trapping agent or the antioxidant at the inlet of the twin screw extruder.

In a fifth aspect of the present invention, in any one of the first to fourth aspects, an inert gas is allowed to flow from the inlet of the twin screw extruder and the inlet of the single screw extruder, so that the atmospheric oxygen concentration at the inlet portion is 100 ppm or less. It is characterized by doing so.

  By allowing an inert gas to flow from the twin-screw and single-screw extruder inlets so that the atmospheric oxygen concentration at the inlet part is 100 ppm or less, it is possible to further reduce the gel generated by the oxidative crosslinking.

  According to the present invention, when a film is formed by a melt film forming method using a cyclic olefin resin, the generation of gel in an extruder is suppressed, and the film thickness distribution of the formed film is also generated. Since it is difficult, a high quality optical film can be manufactured.

  Hereinafter, preferred embodiments of an optical resin film production method and an optical film produced by the production method according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram showing an example of a production apparatus for carrying out the method for producing an optical resin film of the present invention.

  As shown in FIG. 1, the manufacturing apparatus 10 mainly includes a film forming process unit 14 that manufactures the resin film 12 before stretching, and a longitudinal stretching process unit 16 that longitudinally stretches the resin film 12 manufactured in the film forming process unit 14. The horizontal stretching process section 18 that performs lateral stretching and the winding process section 20 that winds the stretched resin film 12 are configured.

  In the film forming process section 14, the cyclic olefin resin melted by the twin screw extruder 22 is extruded to the single screw extruder 23, and the molten resin melt is extruded from the single screw extruder 23 to the forming die 24. The And it discharges in the shape of a film from the shaping | molding die | dye 24, is cast on the rotating cooling drum 26, is rapidly cooled and solidified, and the resin film 12 is obtained. After the resin film 12 is peeled off from the cooling drum 26, the resin film 12 is sequentially sent to the longitudinal stretching process section 16 and the lateral stretching process section 18 to be stretched, and is wound up in a roll shape by the winding process section 20. Thereby, the stretched resin film 12 as a retardation film is manufactured. Hereinafter, details of each process part will be described.

  FIG. 2 shows the configuration of the twin screw extruder 22 of the film forming process section 14, and FIG. 3 shows the configuration of the single screw extruder 23.

  As shown in FIG. 2, the twin screw extruder 22 includes two screws 38 and 38 in a cylinder 32, and the two screw shafts 34 and 34 have different rotational directions. Yes. Each screw 38 is configured by attaching a screw flight portion 36 to a screw shaft 34, is rotatably supported, and is rotationally driven by a motor (not shown). In the present invention, the groove depth of the twin screw is constant from the inlet to the outlet as shown in FIG. That is, the thickness of the screw shaft 34 is the same from the inlet to the outlet, and the groove depth from the surface of the screw shaft 34 to the tip of the screw flight part 36 is constant from the inlet to the outlet. Thereby, the shearing of the resin in the twin screw extruder 22 is suppressed. Further, a mixing element may be added near the exit of the twin screw. The twin screw extruder 22 may be one in which two screw shafts 34 and 34 are arranged in parallel, or one in which the two screw shafts 34 and 34 are inclined. May be.

  A jacket (not shown) is attached to the outer peripheral portion of the cylinder 32 so that the temperature can be controlled to a desired temperature. This temperature control is controlled so that the resin temperature does not exceed 240 ° C. due to shear heat generation.

  A hopper is provided in the supply port 40 of the cylinder 32 via a quantitative supply device (feeder) (not shown), and a cyclic olefin-based resin is supplied from the hopper and supplied into the cylinder 32 through the quantitative supply device.

  The cyclic olefin-based resin is supplied into the cylinder 32 via the supply port 40 of the twin screw extruder 22 and melted. In this case, the outlet pressure of the twin screw extruder 22 is 0.1 MPa to 5.5 MPa, preferably 0.1 MPa to 4.0 MPa, and more preferably 0.5 MPa to 1.0 MPa. By setting the outlet pressure in the above range, the pressure applied to the molten resin in the twin screw extruder 22 can be suppressed, so that the amount of gel generated by shear crosslinking generated in the screw can be suppressed. Further, even if the pressure is too low, the density of the resin becomes low, so that the resin cannot be stably extruded. Therefore, the pressure is lowered within a range where extrusion is possible, specifically, 0.1 MPa or more.

  Further, the maximum shear stress σ generated in the barrel wall surface 44 and the screw flight part 36 of the twin screw extruder 22 in FIG. 2 is preferably 10 kPa or more and 1000 kPa or less, and more preferably 20 kPa or more and 400 kPa or less. By setting the maximum shear stress σ in the above range, the amount of gel generated by shear crosslinking can be suppressed.

  The shear stress σ can be obtained from the following formulas (1) and (2).

Formula (1): γ = π · D · N / 60h
Formula (2): σ = γ × η = (π · D · N / 60h) × η
(Σ: shear stress [Pa], γ: shear rate [s ⁻¹ ], η: viscosity [Pas], D: screw diameter [mm], N: screw speed [rpm], h: flight clearance [mm] )
Temperature T ₀ of the resin just prior to charging into the twin screw extruder 22, when the glass transition point of the resin was Tg, the range of T ₀ is be less than greater Tg ° C. than (Tg-80) ℃ preferably More preferably, it is larger than (Tg-30) ° C. and smaller than Tg ° C., more preferably (Tg−5) ° C. larger than Tg ° C. The temperature fluctuation range is preferably within ± 5 ° C. By setting the temperature T ₀ of the immediately preceding resin within the above range, the viscosity of the molten resin is lowered, so that the frictional force applied between the molten resins during kneading and melting in the screw can be suppressed, and the generation of gel is prevented. Can be suppressed. Further, by suppressing the temperature fluctuation range inside the screw, the temperature is uniformly applied and the frictional force is equally applied inside the screw, so that the generation of gel can be suppressed.

  On the other hand, if the extrusion temperature at the outlet of the twin screw extruder 22 is too low below 200 ° C., extrusion cannot be performed due to insufficient melting. Therefore, when the resin temperature at the outlet of the twin screw extruder 22 is T1 (° C.) and the resin temperature at the outlet of the single screw extruder 23 is T2 (° C.), it is preferable that 200 ° <T1 <T2 is satisfied. .

  Further, it is preferable to knead and melt while flowing an inert gas into the cylinder 32 from the inlet of the twin screw extruder 22. In this case, it is preferable to allow the inert gas to flow so that the oxygen concentration environment at the inlet is 100 ppm or less. By kneading and melting an inert gas such as nitrogen into the twin screw extruder 22, the amount of gel generated by oxidative crosslinking inside the screw can be suppressed. Similarly, by venting the inside of the twin screw extruder 22, oxygen inside the screw can be exhausted, so that generation of gel due to oxidative crosslinking can be prevented. In the present invention, the resin inlet portion refers to the supply portion A, and the resin outlet portion refers to the metering portion C.

  By melting the cyclic olefin resin using the twin screw extruder 22 in which the extrusion conditions are set as described above, the amount of gel generated due to shearing or oxidation (thermal degradation) during resin melting is remarkably suppressed. can do. Then, the molten resin melted by the twin screw extruder 22 is extruded to the single screw extruder 23. Although FIG. 1 shows that the outlet of the twin screw extruder 22 and the inlet of the single screw extruder 23 are directly connected by piping, a gear pump and a buffer tank (not shown) may be arranged in the middle of the piping. Good.

  Next, the single screw extruder 23 will be described with reference to FIG.

  As shown in FIG. 3, a single screw 52 is provided in the cylinder 50. The single screw 52 is configured by attaching a screw flight portion 56 to a screw shaft 54, is rotatably supported, and is rotationally driven by a motor (not shown). A jacket (not shown) is attached to the outer peripheral portion of the cylinder 50 so that the temperature can be controlled to a desired temperature.

  The inside of the cylinder 50 is classified into each section like the twin screw extruder 22. That is, in order from the supply port 58 side, a supply unit (region indicated by A) for quantitatively transporting the cyclic olefin resin supplied from the supply port 58 and a compression unit (region indicated by B) for kneading and compressing the cyclic olefin resin. ) And a metering unit (region indicated by C) that measures the discharge amount while conveying the kneaded and compressed cyclic olefin-based resin to the discharge port 60. However, in the present invention, the cyclic olefin-based resin is already melted by the twin screw extruder 22, the molten resin is supplied to the single screw extruder 23, and the molten resin is supplied from the single screw extruder 23 to the molding die 24. Stable supply. Accordingly, the measuring unit C is particularly important as a function of the single screw extruder 23. Therefore, as the single screw extruder 23 used in the present invention, one having only the supply unit A or the metering unit C (without the compression unit B) can be used, but the existing single screw extruder is used as it is. You can also The resin inlet portion refers to the supply portion A, and the resin outlet portion refers to the measuring portion C.

  The outlet pressure of the single screw extruder 23 is preferably in a high pressure range of 4 MPa to 20 MPa, and the pressure fluctuation is preferably within ± 0.1 MPa. Thereby, the molten resin melted by the twin screw extruder 22 and extruded to the single screw extruder 23 can be quantitatively and stably supplied from the single screw extruder 23 to the forming die 24. Further, even if the outlet pressure in the single screw extruder 23 is set to a high pressure within the above range, the resin is already melted in the twin screw extruder 22, and thus gel is hardly generated. However, the average residence time of the molten resin in the cylinder 50 of the single screw extruder 23 is preferably set within 5 minutes. This is supplied to the single screw extruder 23 in the form of a molten resin, so that gel is hardly generated, but if the average residence time exceeds 5 minutes, there is a concern about thermal deterioration of the resin in the cylinder 50. In addition to the gel, there is a possibility that foreign matter may be generated due to resin kogation or the like. The average residence time of the resin in the cylinder 50 is preferably within 5 minutes, more preferably within 3 minutes, and even more preferably within 2 minutes. Further, the lower limit of the resin residence time is preferably as short as possible so long as stable supply to the molding die 24 is possible, but it is usually preferably 20 seconds or longer.

  Further, it is preferable to provide a gear pump (not shown) for controlling the discharge amount and a foreign matter removing filter (not shown) downstream of the single screw extruder 23. In the present invention, the generation of the gel is suppressed by combining the twin screw extruder 22 and the single screw extruder 23 and sharing the role, but even when the gel is generated, it is removed by the foreign matter removing filter. be able to. Moreover, it becomes easy to adjust the outlet pressure of the single screw extruder 23 to a desired value by adjusting the amount of the gear pump for controlling the discharge amount.

  And the molten resin sent to the shaping | molding die 24 from the single screw extruder 23 is extruded from the shaping | molding die 24 to a film form, is cast on the cooling drum 26, is cooled and solidified, and the resin film 12 is formed into a film. The molten polymer temperature when extruded from the molding die 24 is preferably Tg + 100 ° C. or higher and Tg + 130 ° C. or lower in order to prevent thermal deterioration and coloring. Furthermore, it is preferable that the molding die 24 has its slit formed in a range between a vertical direction and a direction inclined at 45 ° with respect to the rotation direction of the cooling drum 26.

  As described above, in the melt film forming method, the twin screw extruder 22 is used as an extruder for heating and melting the cyclic olefin-based thermoplastic resin, and the extruder for supplying the molten resin to the molding die 24 is used. By using the single screw extruder 23 and clarifying the role sharing between the twin screw and single screw extruders 22 and 23, gel generation during resin melting can be remarkably suppressed, and the molten resin is molded into a molding die. 24 can be quantitatively and stably supplied. As a result, the cyclic olefin resin film 12 produced by the production method of the present invention has a haze of 3% or less and a yellowness index (YI value) of 10 or less when made into a 10% cyclohexane solution. Has a value.

Here, the haze value is an index indicating the amount of gel, and it means that the larger the haze, the more gel is present. The haze value is preferably 3% or less, and preferably 1% or less.
Accordingly, when an optical film is manufactured by carrying out the manufacturing method of the present invention, for example, a uniform optical film, for example, a retardation film, having significantly less gel and no film thickness distribution can be obtained.

  Moreover, the resin film 12 manufactured by this invention is very excellent in terms of heat resistance. That is, in this embodiment, since the resin is melted by the twin screw extruder 22 having a large kneading effect, the amount of the plasticizer or Re developing agent added can be minimized. Therefore, it is possible to prevent the glass transition temperature from being lowered and the heat resistance from being lowered by the plasticizer or the Re developing agent, and the deformation rate of the resin film 12 after the production can be kept low. Thereby, the deformation ratio of the resin film 12 (deformation ratio when left for 24 hours in an environment of 60 ° C. × 90%) can be set to 0.3% or less, preferably 0.1% or less in both length and width. .

  Next, the longitudinal stretching process section 16 for longitudinal stretching and the lateral stretching process section 18 for lateral stretching of the resin film 12 formed in the film forming process section 14 will be described. In the present embodiment, the case where the unstretched resin film 12 formed in the film forming process section 14 is longitudinally and laterally stretched to form a retardation film will be described.

  However, the unstretched resin film 12 produced in the film forming process section 14 can also be used as a protective film application for a liquid crystal display device, or a coating film for alignment film or liquid crystal is applied to form a retardation film. It can also be used as a base film for manufacturing, or can be used as a base film for manufacturing an antireflection film by applying an antireflection coating solution.

  The stretching of the resin film 12 is performed in order to orient the molecules in the resin film 12 and develop in-plane retardation (Re) and thickness direction retardation (Rth).

  As shown in FIG. 1, the resin film 12 is first longitudinally stretched in the longitudinal direction by the longitudinal stretching step 16. In the longitudinal stretching process section 16, after the resin film 12 is preheated, the resin film 12 is heated and wound around two nip rolls 28 and 30. The exit-side nip roll 30 transports the resin film 12 at a transport speed faster than the entrance-side nip roll 28, and thereby the resin film 12 is stretched in the longitudinal direction.

  The preheating temperature in the longitudinal stretching process section 16 is preferably Tg-40 ° C or higher and Tg + 60 ° C or lower, more preferably Tg-20 ° C or higher and Tg + 40 ° C or lower, and further preferably Tg or higher and Tg + 30 ° C or lower. Further, the stretching temperature of the longitudinal stretching step 16 is preferably Tg or more and Tg + 60 ° C. or less, more preferably Tg + 2 ° C. or more and Tg + 40 ° C. or less, and further preferably Tg + 5 ° C. or more and Tg + 30 ° C. or less. The draw ratio in the machine direction is preferably 1.0 to 2.5 times, more preferably 1.1 to 2 times.

  The resin film 12 that has been longitudinally stretched is sent to the lateral stretching step 18 and is laterally stretched in the width direction. For example, a tenter can be suitably used in the lateral stretching step section 18. The tenter grips both ends of the resin film 12 in the width direction with clips, and stretches in the lateral direction. By this transverse stretching, the retardation Rth can be further increased.

  The transverse stretching is preferably carried out using a tenter, and the preferred stretching temperature is preferably Tg or higher and Tg + 60 ° C. or lower, more preferably Tg + 2 ° C. or higher, Tg + 40 ° C. or lower, more preferably Tg + 4 ° C. or higher, Tg + 30 ° C. or lower. . The draw ratio is preferably 1.0 to 2.5 times, more preferably 1.1 to 2.0 times. It is also preferable to relax in the longitudinal direction, the lateral direction, or both after the transverse stretching. Thereby, the distribution of the slow axis in the width direction can be reduced.

  By such stretching, Re is 0 nm to 500 nm, more preferably 10 nm to 400 nm, more preferably 15 nm to 300 nm, and Rth is 0 nm to 500 nm, more preferably 50 nm to 400 nm, and further preferably 70 nm. It is 350 nm or less.

  Of these, those satisfying Re ≦ Rth are more preferable, and those satisfying Re × 2 ≦ Rth are more preferable. In order to realize such a high Rth and low Re, it is preferable to stretch the film that has been longitudinally stretched as described above in the transverse (width) direction. In other words, the difference in orientation between the vertical direction and the horizontal direction becomes the difference in retardation (Re) in the plane, but by stretching in the horizontal direction, which is the orthogonal direction in addition to the vertical direction, the difference in vertical and horizontal orientation is reduced. The surface orientation (Re) can be reduced by reducing the size. On the other hand, since the area magnification increases by stretching in addition to the length, the orientation in the thickness direction increases as the thickness decreases, and Rth can be increased.

  Furthermore, it is preferable that the variation of Re and Rth depending on the location in the width direction and the longitudinal direction is 5% or less, more preferably 4% or less, and still more preferably 3% or less.

The stretched resin film 12 is wound up in a roll shape in the winding process section 20 of FIG. At that time, the winding tension of the resin film 12 is preferably 0.02 kg / mm ² or less. By setting the winding tension in such a range, the stretched resin film 12 can be wound without causing a retardation distribution.

  Next, a resin film suitable for the present invention, a method for forming the resin film 12 before stretching, and a method for forming the resin film will be described.

(Optical film material)
<Cyclic olefin resin>
A cyclic olefin resin is used as the material of the optical resin film of the present invention. The cyclic olefin resin is preferably polymerized from a norbornene compound. This polymerization can be carried out by either ring-opening polymerization or addition polymerization, but addition polymerization is more preferable among cyclic olefin resins.

  Examples of the addition polymerization include those described in Japanese Patent No. 3517471, Japanese Patent No. 3559360, Japanese Patent No. 3867178, Japanese Patent No. 3817721, Japanese Patent No. 3907908, Japanese Patent No. 3945598, Japanese Translation of PCT International Publication No. 2005-527696, Japanese Patent Laid-Open No. 2006-28993, and WO 2006-004376. Particularly preferred is that described in Japanese Patent No. 3517471.

  Examples of the ring-opening polymerization include those described in WO98-14499, Japanese Patent 30605532, Japanese Patent 3220478, Japanese Patent 3273046, Japanese Patent 3404027, Japanese Patent 3428176, Japanese Patent 3687231, Japanese Patent 3873934, and Japanese Patent 3912159. Of these, those described in WO98-14499 and Japanese Patent No. 30605532 are preferable.

<Additives>
In these optical resin films, 0 to 20% by mass of alkylphthalylalkyl glycolates, phosphate esters, carboxylic acid esters, and polyhydric alcohols can be added as plasticizers. Phosphite stabilizers (for example, tris (4-methoxy-3,5-diphenyl) phosphite, tris (nonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite) as a stabilizer, Phenolic stabilizers (eg, 2,6-di-t-butyl-4-methylphenol, 2,2-methylenebis (4-ethyl-6-t-butylphenol), 2,5-di-t-butylhydroquinone, Pentaerythrityltetrakis [.3- (3,5-di-tert-butyl-4-hydroxyphenyl) propiolate, 4,4-thiobis- (6-tert-butyl-3-methylphenol), 1,1, -Bis (4-hydroxyphenyl) cyclohexane, octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propiolate] An epoxy compound and a thioether compound can be added in an amount of 0 to 3% by mass, and an inorganic fine particle such as silica, titania, zirconia, alumina, calcium carbonate, or clay, and an organic fine particle such as crosslinked acrylic or crosslinked styrene can be added in an amount of 0 to 1000 ppm. Moreover, ultraviolet absorbers (for example, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2, -methylenebis [4- (1,1,3,3-tetramethylbutyl) -6-[(2H -Benzotriazol-2-yl) phenol]]), an infrared absorber and a retardation modifier are also preferably added.

(Deposition of optical resin film)
<Melt film forming method>
B) Pelletization The resin and additives are preferably mixed and pelletized prior to melt film formation.

  In pelletization, the resin and additives are dried, melted at 150 ° C. to 300 ° C. using a twin-screw kneading extruder (provided separately from the twin-screw extruder 22), and then extruded into noodles in the air. Alternatively, it can be produced by solidifying in water and cutting. Further, pelletization may be performed by an underwater cutting method or the like that is cut while being directly extruded from a die after being melted by an extruder.

  The twin-screw kneading extruder uses a meshing different direction rotating twin-screw extruder. The number of revolutions of the extruder is preferably 10 rpm to 1000 rpm, more preferably 20 rpm to 700 rpm. The extrusion residence time is 10 seconds or more and 10 minutes or less, more preferably 20 seconds to 5 minutes or less.

Preferably, the pellet size is such is preferably 10mm ³ ~1000mm ^3, more preferably 30 mm ³ 500 mm ^3.

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

  The dried pellets are supplied into the cylinder 32 via the supply port of the twin screw extruder 22 and are kneaded and melted. The ratio of the cylinder length to the cylinder inner diameter (L / D) is preferably 20 to 70, and the cylinder inner diameter is preferably 30 mm to 150 mm. L / D is the ratio of the cylinder length (L) to the cylinder inner diameter (D) in FIG.

The molten resin heated and melted by the twin screw extruder 22 is extruded and supplied to the single screw extruder 23 and quantitatively and stably supplied to the forming die 24 via the single screw extruder 23. When the resin temperature at the outlet of the twin screw extruder 22 is T1 (° C.) and the resin temperature at the outlet of the single screw extruder 23 is T2 (° C.), it is preferable that 200 ° <T1 <T2 is satisfied. When the temperature in the single screw extruder 23 exceeds 230 ° C., a cooler (not shown) can be provided between the single screw extruder 23 and the forming die 24. Further, in order to prevent the molten resin due to residual oxygen from being oxidized and generating a gel, the cylinders of the twin screw extruder 22 and the single screw extruder 23 are in an inert (nitrogen or the like) air flow or an extruder with a vent. It is also preferable to carry out the process while evacuating using a vacuum.

C) Filtration It is preferable to provide a filtration device in which a breaker plate type filtration or a leaf type disk filter is incorporated between the single screw extruder 23 and the molding die 24 in order to filter foreign substances such as gel in the molten resin. Filtration may be performed in one stage or multistage filtration. The filtration accuracy is preferably 15 μm to 3 μm, and more preferably 10 μm to 3 μm. It is desirable to use stainless steel as the filter medium. As the configuration of the filter medium, a knitted wire, a sintered metal fiber or metal powder (sintered filter medium) can be used, and among them, a sintered filter medium is preferable.

D) Gear pump It is preferable to provide a gear pump between the single screw extruder 23 and the forming die 24 in order to reduce the fluctuation of the discharge amount and improve the thickness accuracy. As a result, the resin pressure fluctuation range in the die can be within ± 1%. In order to improve the quantitative supply performance by the gear pump, a method of controlling the pressure before the gear pump to be constant by changing the number of rotations of the screw can also be used. Also. It is also preferable to provide another gear pump between the twin screw extruder 22 and the single screw extruder 23.

E) Molding die It is melted by the twin screw extruder 22 configured as described above and supplied to the molding die 24 by the single screw extruder 23. Further, the molten resin is continuously sent to the molding die 24 through a filter and a gear pump as necessary. The molding die 24 may be any of a T die, a fish tail die, and a hanger coat die. It is also preferable to insert a static mixer immediately before the molding die in order to increase the uniformity of the resin temperature. The clearance of the T-die exit portion is generally 1.0 to 10 times the film thickness, preferably 1.2 to 5 times.

  It is preferable that the thickness of the molding die 24 can be adjusted at intervals of 5 to 50 mm. An automatic thickness adjustment die that calculates downstream film thickness and thickness deviation and feeds back the results to the thickness adjustment of the forming die 24 is also effective. In addition to the single layer film forming apparatus, it is also possible to manufacture using a multilayer film forming apparatus.

  In this way, the residence time from when the resin enters the twin screw extruder 22 and the single screw extruder 23 through the supply port to exit from the molding die 24 is preferably 3 minutes to 40 minutes, more preferably 4 minutes to 30 minutes.

F) Cast The molten resin (melt) extruded from the forming die 24 into a film is cooled and solidified on a cooling drum 26 (also referred to as a casting drum) to obtain a film. At this time, it is preferable to shield between the forming die 24 and the cooling drum 26 to suppress the influence of wind.

  When the melt contacts the cooling drum 26, it is preferable to increase the adhesion between the casting drum and the melt using an electrostatic application method, an air knife method, an air chamber method, a vacuum nozzle method, a touch roll method, etc. Is preferred. Such an adhesion improving method may be performed on the entire surface of the melt or may be performed on a part thereof.

  The touch roll method is a method in which a touch roll is provided in contact with the cooling drum 26 to shape the film surface. At this time, the touch roll is preferably not elastic and usually elastic. Thereby, it can suppress that a surface unevenness | corrugation makes below the range of this invention ease by an excessive surface pressure. For this purpose, it is necessary to make the outer cylinder thickness of the touch roll thinner than that of a normal touch roll, and the thickness Z of the outer cylinder is preferably 0.05 mm to 7.0 mm, more preferably 0.2 mm. It is -5.0 mm, More preferably, it is 0.3 mm -3.5 mm. The touch roll may be installed on a metal shaft and a heat medium (fluid) may be passed between them. An elastic layer is provided between the outer cylinder and the metal shaft, and the heat medium (fluid) is filled between the outer cylinders. Can be mentioned. A weaker pressing with a touch roll is preferable because Rth can be reduced more, but if it is too small, the surface roughness of the present invention cannot be achieved. On the other hand, if it is too large, the surface roughness decreases but Rth tends to increase. For this reason, the surface pressure of the touch roll is preferably 0.1 MPa to 5 MPa, more preferably 0.2 MPa to 3 MPa, and still more preferably 0.3 MPa to 2 MPa. Here, the surface pressure is a value obtained by dividing the force pressing the touch roll by the contact area between the optical resin film and the touch roll.

  The temperature of the touch roll is preferably set to 60 ° C to 160 ° C, more preferably 70 ° C to 150 ° C, and still more preferably 80 ° C to 140 ° C. Such temperature control can be achieved by passing a temperature-controlled liquid or gas through these rolls. Thus, what has a temperature control mechanism inside is more preferable.

  The material of the touch roll is preferably a metal, more preferably stainless steel, and the surface is preferably plated. On the other hand, a rubber roll or a metal roll lined with rubber is not preferable because the rubber surface has irregularities and the optical resin film having the surface irregularities cannot be formed.

  The surface of the touch roll and casting roll has an arithmetic average height Ra of 100 nm or less, preferably 50 nm or less, and more preferably 25 nm or less. For example, JP-A-11-314263, JP-A-2002-36332, JP-A-11-235747, WO97 / 28950, JP-A-2004-216717, JP-A-2003-145609 are touch rolls. Can be used.

  More preferably, a plurality of forming drums (rolls) are used for slow cooling (of which the touch roll is disposed so as to touch the first forming drum on the most upstream side (closer to the die)). In general, it is relatively common to use three cooling drums, but this is not a limitation. The diameter of the drum is preferably 100 mm to 1500 mm, more preferably 150 mm to 1000 mm. The interval between the multiple drums is preferably 0.3 mm to 300 mm between the surfaces, more preferably 1 mm to 100 mm, and even more preferably 3 mm to 30 mm. The cooling drum is preferably 60 ° C to 160 ° C, more preferably 70 ° C to 150 ° C, still more preferably 80 ° C to 140 ° C.

  Then, it peels off from the shaping | molding die 24, winds up after passing through a nip roll. The winding speed is preferably 10 m / min to 100 m / min, more preferably 15 m / min to 80 m / min, still more preferably 20 m / min to 70 m / min.

The film forming width is preferably 0.7 m to 3 m, and more preferably 1 m to 2 m. The thickness after film formation (unstretched) is preferably 30 μm to 300 μm, more preferably 40 μm to 250 μm, and still more preferably 60 μm to 200 μm.
G) Trimming, thickening, winding After the film is formed in this way, it is also preferable to trim both ends. The portion cut off by trimming may be crushed and used again as a raw material.

  Further, it is also preferable to perform a thickness increasing process (knurling process) on one or both ends. The height of the unevenness due to the thickness increasing process is preferably 1 μm to 50 μm, more preferably 3 μm to 20 μm. Thickening processing may be convex on both sides or convex on one side. The width of the thickness increasing process is preferably 1 mm to 50 mm, more preferably 3 mm to 30 mm. Extrusion can be performed at room temperature to 300 ° C.

  It is also preferable to attach a laminated film on one side or both sides before winding. The thickness of the laminated film is preferably 5 μm to 100 μm, more preferably 10 μm to 50 μm. The material is not particularly limited, such as polyethylene, polyester, and polypropylene. A preferable winding tension is 2 kg / m width to 50 kg / m width, more preferably 5 kg / m width to 30 kg / m width.

(Stretching)
The melt-formed resin film is preferably subjected to longitudinal stretching and lateral stretching, and may further be combined with shrinkage treatment. Of these, preferred are those in which transverse stretching is carried out after longitudinal stretching, or a combination of transverse stretching and longitudinal shrinkage treatment, the former being suitable for developing high Rth and the latter being suitable for developing low Rth. When the transverse stretching and the longitudinal shrinkage treatment are performed in combination, the longitudinal shrinkage may be performed during the transverse stretching, may be performed after the transverse stretching, or may be performed both. Further, longitudinal stretching may be combined before or after this lateral stretching or both.

[Longitudinal stretching]
Longitudinal stretching may be performed alone or in combination with lateral stretching. The longitudinal stretching may be performed either before or after the lateral stretching, but is more preferably performed before the lateral stretching. In addition, the longitudinal stretching may be performed in one stage or may be performed in multiple stages.

  Longitudinal stretching can be achieved by installing two pairs of nip rolls and heating the gap between them so that the peripheral speed of the nip roll on the outlet side is higher than the peripheral speed of the nip roll on the inlet side. Under the present circumstances, the expression of the retardation of the thickness direction can be changed by changing the space | interval (L) between nip rolls, and the film width (W) before extending | stretching. When L / W exceeds 2 and is 50 or less (long span stretching), Rth can be reduced, and when L / W is 0.01 or more and 0.3 or less (short span stretching), Rth can be increased. In the present invention, any of a long span stretching, a short span stretching, and a region between them (intermediate stretching = L / W is more than 0.3 and 2 or less) may be used. Short span stretching is preferred. Further, when aiming at high Rth, it is more preferable to use short span stretching, and when aiming at low Rth, it is distinguished from long span stretching.

  The preferred stretching temperature for these longitudinal stretching is (Tg-10) to (Tg + 50) ° C, more preferably (Tg-5) to (Tg + 40) ° C, and still more preferably (Tg) to (Tg + 30) ° C. A preferable draw ratio is 2% to 200%, more preferably 4% to 150%, and still more preferably 6% to 100%.

≪Long span stretching≫
The film is stretched as it is stretched. At this time, the film is reduced in thickness and width in order to reduce the volume change. Increasing the nip roll interval facilitates shrinkage in the width direction and suppresses a decrease in thickness (less compression in the thickness direction), suppresses molecular orientation in the film plane and decreases Rth.

  L / W is preferably more than 2 and 50 or less, more preferably 3 to 40, still more preferably 4 to 20. Such long span stretching may be performed in multiple stages with three or more pairs of nip rolls, as long as the longest aspect ratio is within the above range.

  Such long span stretching may be performed by heating the film between two pairs of nip rolls separated by a predetermined distance. The heating method is a heater heating method (infrared heater, halogen heater, panel heater, etc. above or below the film). Or heating by radiant heat) or a zone heating method (heating in a zone in which hot air or the like is blown and adjusted to a predetermined temperature) may be used.

≪Short span drawing≫
Longitudinal stretching (short span stretching) is performed with L / W exceeding 0.01 and less than 0.3, more preferably 0.03 to 0.25, and even more preferably 0.05 to 0.2. As a result, neck-in (stretching along with stretching and shrinkage in a direction perpendicular to the stretching) can be reduced, and the thickness tends to decrease. As a result, the film is compressed in the thickness direction, and the orientation (plane orientation) in the thickness direction advances and Rth tends to increase.

  Short span stretching can be carried out by changing the conveyance speed between two or more pairs of nip rolls, but normal roll arrangement (as shown in the longitudinal stretching step (108) in FIG. 3 of JP-A-2007-152558), the nip rolls are arranged in parallel. Unlike the arrangement, a gap is generated between the rolls, and the L / W cannot be reduced. This can be achieved by arranging two pairs of nip rolls obliquely (shifting the rotation axis of the front and rear nip rolls up and down) (Japanese Patent Laid-Open No. 2006-51804). 1, the nip rolls are arranged so as to be shifted up and down as shown in Fig. 1. However, in this figure, the nip rolls (22, 24) are drawn wide, but this interval is narrowed so that the nip rolls are close to each other. L / W can be reduced with this). Accordingly, since a heater for heating cannot be installed between the nip rolls, it is preferable to raise the temperature of the film by flowing a heating medium in the nip rolls. Further, it is also preferable to provide a preheating roll in which a heating medium is flowed inside before the entrance side nip roll and heat the film before stretching.

[Horizontal stretching]
The transverse stretching can be performed using a tenter. That is, the film is stretched by holding both ends in the width direction with clips and widening the film in the lateral direction. At this time, the stretching temperature can be controlled by sending wind at a desired temperature into the tenter. The stretching temperature is preferably Tg-10 ° C or higher and Tg + 60 ° C or lower, more preferably Tg-5 ° C or higher and Tg + 45 ° C or lower, and further preferably Tg or higher and Tg + 30 ° C or lower. A preferable draw ratio is 10% or more and 250% or less, more preferably 20% or more and 200% or less, and further preferably 30% or more and 150% or less. The draw ratio here is defined by the following formula.

Stretch ratio (%) = 100 × {(Length after stretching) − (Length before stretching)} / (Length before stretching)
By performing preheating before stretching and post-heat treatment after stretching, the Re and Rth distribution after stretching can be reduced, and variations in orientation angles associated with bowing can be reduced. Either pre-heating or post-heating may be performed, but both are more preferable. These preheating and post heat treatment are preferably carried out by holding with a clip, that is, carried out continuously with stretching.

  The post-heat treatment is preferably performed at a temperature lower than the stretching temperature by 1 ° C. or higher and 50 ° C. or lower, more preferably 2 ° C. or higher and 40 ° C. or lower, more preferably 3 ° C. or higher and 30 ° C. or lower. More preferably, it is less than the stretching temperature and less than Tg. The preheating time is preferably 1 second or longer and 10 minutes or shorter, more preferably 5 seconds or longer and 4 minutes or shorter, and even more preferably 10 seconds or longer and 2 minutes or shorter. During the heat setting, it is preferable to keep the width of the tenter substantially constant. Here, “substantially” refers to 0% (the same width as the tenter width after stretching) to −10% (shrinking by 10% from the tenter width after stretching = reduced width) of the tenter width after stretching. If the width is wider than the stretched width, residual strain tends to occur in the film, which is not preferable.

  Preheating is a stretching temperature ± 50 ° C, more preferably a stretching temperature ± 35 ° C, and still more preferably a stretching temperature ± 20 ° C. When the bowing after the post heat treatment is convex in the traveling direction, it is preferably lower than the stretching temperature, and when the bowing is concave in the traveling direction, it is preferably higher than the stretching temperature. The preheating time is preferably 1 second or longer and 10 minutes or shorter, more preferably 5 seconds or longer and 4 minutes or shorter, and even more preferably 10 seconds or longer and 2 minutes or shorter. During preheating, it is preferable to keep the width of the tenter substantially constant. Here, “substantially” refers to ± 10% of the width of the unstretched film. Thus, it is more preferable that the heat setting temperature <the stretching temperature <the preheating temperature.

  Such stretching can reduce variations in Re and Rth in the width direction and longitudinal direction, and deviation of the orientation angle from MD (longitudinal direction) or TD (width direction).

[Shrinkage treatment]
Shrinkage treatment is preferably performed during or after stretching, and more preferably, shrinkage relaxation treatment is performed in the longitudinal (longitudinal) direction during or after transverse stretching. Shrinkage treatment can be achieved by lowering the conveying speed in the longitudinal direction on the downstream side from the upstream side, and the amount of shrinkage is preferably 0.1% to 50%, more preferably 1% to 40%, and even more preferably 5%. More than 35%. The amount of contraction referred to here is expressed by the following equation.
Shrinkage (%) = 100 × {(Length before shrinkage treatment) − (Length after shrinkage treatment)} / (Length before shrinkage treatment)
The shrinkage treatment temperature is preferably (Tg-20) ° C to (Tg + 50) ° C, more preferably (Tg-10) ° C to (Tg + 40) ° C, and even more preferably Tg to (Tg + 30) ° C. The shrinkage treatment time is 1 second or more. 15 minutes or less, more preferably 5 seconds or more and 10 minutes or less, and further preferably 10 seconds or more and 5 minutes or less.

  Although the film is stretched in the stretching direction by stretching, the direction perpendicular to the stretching and the thickness direction decrease in order to match the material balance. As the thickness decreases, the film surface is compressed, the molecules are oriented in the surface, and the surface orientation becomes stronger. As a result, Rth increases. However, by performing vertical contraction, thickness reduction can be suppressed and low Rth can be realized. That is, Rth <Re × 1.5, more preferably Rth <Re can be realized by longitudinal contraction. Furthermore, this longitudinal shrinkage also has an effect of suppressing thermal shrinkage of the stretched film, and the amount of thermal shrinkage at 80 ° C. and 100 hr can be reduced to 0.5% or less, more preferably 0.3% or less.

  Such longitudinal contraction can be achieved by, for example, the following method.

≪Shrinkage treatment during stretching≫
Longitudinal shrinkage during transverse stretching can be achieved by stretching in the width direction while slowing the conveying speed of the clip in the tenter from the inlet side to the outlet side, and can be performed using, for example, a biaxial stretching machine. Specifically, transverse stretching and longitudinal shrinkage can be performed simultaneously. For example, Japanese Patent Application Laid-Open No. 2003-211533, Japanese Patent Application Laid-Open No. 6-210726, Japanese Patent Application Laid-Open No. 6-278204, Japanese Patent Application Laid-Open No. 11-77825, Japanese Patent Application Laid-Open No. 2000-24695, Japanese Patent Application Laid-Open No. 2004-195712, Japanese Patent Application Laid-Open No. 2006-142595, Japanese Patent Application Laid-Open No. 2006-142595, An apparatus described in JP-A-2006-22916 can be used. Specifically, a high-performance thin film device (trade name FITZ) manufactured by Ichikin Kogyo Co., Ltd. can be used. This apparatus can arbitrarily set the draw ratio in the machine direction (longitudinal direction of the film = traveling direction of the film) and the draw ratio in the transverse direction (width direction = the proceeding direction of the film), and further in the machine direction (longitudinal direction). ) Can be arbitrarily set, so that stretching and shrinking can be simultaneously performed under predetermined conditions. In addition, for example, by appropriately combining a rail width control method, a panda graph method, a method for controlling the traveling speed by a linear motor, etc., which are generally known, the stretching ratio in the width direction is controlled, and the film edge portion is A biaxial stretching machine or the like that controls the length in the longitudinal direction by changing the interval between the clipped clips can also be used.

≪Shrinkage treatment after stretching≫
Although the following methods I), II), III) and IV) can be mentioned, preferred methods are II) and IV).

  I) The transport speed of the clip in the tenter is made slower than the transport speed of the clip at the entrance of the stretching section during and / or subsequent to the transverse stretching (tenter stretching).

  Lateral stretching is performed by widening both ends of the film with clips (tenter stretching). In order to promote shrinkage in the direction perpendicular to stretching and thickness shrinkage, the transport speed of the clips in the tenter during and / or after stretching Is slower than the entrance of the drawing section.

  Among these, it is more preferable to perform longitudinal shrinkage after transverse stretching (when transverse stretching and longitudinal shrinkage are performed simultaneously, stretching and stretching occur simultaneously in the surface and residual strain is likely to occur, and uniformity within the surface is also preferred. Is likely to decrease). Such longitudinal shrinkage after transverse stretching can be achieved, for example, by preparing separate tenter rails for transverse stretching and longitudinal shrinkage so that the speed can be controlled independently. By using the ones described in JP-A-6-278204, JP-A-11-77825, JP-A-2004-195712, JP-A-2006-142595, and the like, by contracting vertically (conveying direction), realizable.

  II) After transverse stretching with a tenter, heat treatment is performed while the conveyance speed on the outlet side is slower than that on the inlet side of the heat treatment zone.

  This method can be achieved by inserting the film into a heat treatment zone provided with two or more pairs of nip rolls after lateral stretching (after exiting from the tenter) and increasing the conveyance speed of the nip roll on the inlet side than the nip roll on the outlet side. In this longitudinal shrinkage zone, film shrinkage occurs in both the longitudinal and transverse directions. Therefore, in order to express the longitudinal shrinkage preferentially, the aspect ratio of the heat treatment zone (the value obtained by dividing the zone length by the inlet side film width) is 0. It is preferably 0.01 to 2, more preferably 0.05 to 1.6, and still more preferably 0.1 to 1.3. The heat treatment zone may be heated by providing a heat treatment zone or a heater between the nip rolls, or the nip roll may be heated to heat the resin film. Such vertical contraction that lowers the conveyance speed on the outlet side is completely different from the heat treatment that only weakens the conveyance tension. In other words, the effect of promoting the neck-in as described above does not occur at all only by lowering the transport tension.

  III) Shrink the resin film in the transport direction on the chuck of the tenter.

  The resin film can be contracted in the longitudinal direction by slipping the resin film on the chuck during or after the transverse stretching. That is, if the resin film is slid in the conveyance (longitudinal) direction on the chuck, it can be contracted longitudinally. Such a method is not particularly limited, but can be achieved, for example, by installing a pulley in the conveying direction in the clip portion of the chuck, or by attaching a slipping material (eg, Teflon) to the resin film gripping surface of the clip. Good.

IV) Low-tension conveyance between rolls after transverse stretching After transverse stretching (after tenter), when the film is heat-treated at low tension, it tries to shrink in both the longitudinal and transverse directions. At this time, by conveying the film between the rolls, The shrinkage in the transverse direction can be suppressed by the frictional force between the roll and the film, and the vertical shrinkage can be expressed with priority.

  In order to obtain the frictional force necessary to suppress the lateral shrinkage of the film, the length that the film is wrapped on the roll (W) and the length that the film is not in contact with the roll between the rolls (G) The ratio (W / G) is preferably 0.01 or more and 3 or less, more preferably 0.03 or more and 1 or less, and still more preferably 0.05 or more and 0.5 or less. Exceeding this range is not preferable because the distance between the rolls becomes long and the frictional force decreases, TD contraction occurs, Re decreases, Rth / Re easily increases, and vertical lines tend to appear. On the other hand, if W / G is less than this range, the residual strain generated by stretching is not eliminated and the thermal dimensional change increases, which is not preferable.

  The number of rolls is preferably 2 or more and 100 or less, more preferably 3 or more and 50 or less, and still more preferably 4 or more and 20 or less. The diameter of the preferable roll is preferably 5 cm to 100 cm, more preferably 10 cm to 80 cm, and still more preferably 15 cm to 60 cm.

  Furthermore, in order to sufficiently obtain the frictional force between the roll and the resin film, the surface roughness (Ra) of the resin film is preferably 0.005 μm or more and 0.04 μm or less, more preferably 0.007 μm or more and 0.035 μm or less, Preferably they are 0.009 micrometer or more and 0.030 micrometer or less. A film having such a surface can be achieved by a touch roll film forming method. By sandwiching the film immediately after casting with a roll having a smooth surface from both sides, higher smoothness can be achieved compared to the case where this film is not used, and the above-mentioned surface roughness can be realized.

  The longitudinal shrinkage treatments of the above I) and II) may be performed alone or in combination. The shrinking treatment of II) may be performed online after transverse stretching, or may be performed offline after winding after stretching. Preferred is online processing.

[Volatile components during stretching]
In the longitudinal stretching and lateral stretching, the volatile components (solvent, moisture, etc.) are preferably 0.5 wt% or less, more preferably 0.3 wt% or less, and still more preferably 0 wt%, based on the resin. This is because when volatile components are present, shrinkage stress accompanying drying acts and bowing becomes more prominent.

[Film properties after stretching / shrinking]
Thus, it is preferable that the films Re and Rth after the stretching and shrinking treatment satisfy the following formulas (R-1) and (R-2).
Formula (R-1): 0 nm ≦ Re ≦ 300 nm
Formula (R-2): 10 nm ≦ Rth ≦ 300 nm
More preferably, the following formulas (R-3) and (R-4) are satisfied.
Formula (R-3): 20 nm ≦ Re ≦ 200 nm
Formula (R-4): 20 nm ≦ Rth ≦ 200 nm
In this specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at a wavelength λ, respectively. Re (λ) is measured with KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments) by making light of wavelength λnm incident in the normal direction of the film. It can be measured by exchanging it with a manual or a program.

  When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method. Rth (λ) is Re (λ), with the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotating axis) (if there is no slow axis, any in-plane The light is incident at a wavelength of λ nm from the inclined direction in steps of 10 degrees from the normal direction to 50 degrees on one side with respect to the film normal direction of the rotation axis of KOBRA 21ADH or WR calculates based on the measured retardation value, the assumed average refractive index, and the input film thickness value.

  In the above case, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, retardation at a tilt angle larger than the tilt angle. The value is calculated by KOBRA 21ADH or WR after changing the sign to negative. The retardation value is measured from the two inclined directions with the slow axis as the tilt axis (rotation axis) (in the absence of the slow axis, the arbitrary direction in the film plane is the rotation axis). Based on the value, the assumed value of the average refractive index, and the input film thickness value, Rth can also be calculated from the following equations (3) and (4).

--- Formula (3)
Note that Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction. In formula (3), nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction perpendicular to nx in the plane, and nz represents the refractive index in the direction perpendicular to nx and ny. .

Rth = ((nx + ny) / 2−nz) × d −−−- type (4)
In the case where the film to be measured cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film having no so-called optic axis, Rth (λ) can be calculated by the following method. Rth (λ) is from -50 ° to + 50 ° with respect to the normal direction of the film, with Re (λ) as the slow axis (determined by KOBRA 21ADH or WR) in the plane and the tilt axis (rotation axis). Measured at 11 points by making light of wavelength λ nm incident from each tilted direction in 10 degree steps, and based on the measured retardation value, average refractive index assumed value and input film thickness value, KOBRA 21ADH Or WR is calculated.

  In the above measurement, the assumed value of the average refractive index may be the value in the polymer handbook (JOHN WILEY & SONS, INC) and various optical film catalogs. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). By inputting these assumed values of average refractive index and film thickness, KOBRA 21ADH or WR calculates nx, ny, and nz. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

  The angle θ formed by the film forming direction (longitudinal direction) and the slow axis of Re of the film is preferably as close to 0 °, + 90 °, or −90 °. That is, the deflection angle from 0 °, 90 °, and −90 ° is preferably within ± 3 °, more preferably within ± 2 °, and further preferably within ± 1 °. θ may be 0 ° (vertical alignment), 90 °, or −90 ° (horizontal alignment), but more preferably is horizontal alignment. In-plane and longitudinal variations of Re and Rth are preferably 0% to 8%, more preferably 0% to 5%, and still more preferably 0% to 3%.

  The change in Re and Rth before and after aging at 80 ° C. for 200 hours is preferably from 0% to 8%, more preferably from 0% to 6%, and even more preferably from 0% to 4%. The longitudinal (MD) and lateral (TD) dimensional changes before and after 80 ° C. for 200 hours are preferably 0% or more and ± 0.5% or less, more preferably 0% or more and ± 0.3% or less, and still more preferably It is 0% or more and ± 0.1% or less.

  The film thickness after stretching is preferably 15 μm to 200 μm, more preferably 20 μm to 120 μm, and still more preferably 25 μm to 80 μm. The thickness unevenness is preferably 0% to 3% in both the longitudinal direction and the width direction, more preferably 0% to 2%, and still more preferably 0% to 1%.

(Film processing)
The resin film thus obtained may be used alone, or may be used in combination with a polarizing plate, a liquid crystal layer or a layer with a controlled refractive index (low reflection layer), A hard coat layer may be provided for use. These can be achieved by the following steps.

≪Surface treatment≫
By performing the surface treatment, adhesion with each functional layer (for example, the undercoat layer and the back layer) can be improved. For example, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, acid or alkali treatment can be used. Here, the glow discharge treatment includes low-temperature plasma treatment performed under a low pressure gas of 1 × 10 ^{−3 to} 20 Torr (0.13 to 2700 Pa). Further, plasma treatment under atmospheric pressure is also a preferable glow discharge treatment.

  Of these, glow discharge treatment, corona treatment, and flame treatment are preferable, and corona treatment is more preferable.

  It is also preferable to provide an undercoat layer for adhesion to the functional layer. This layer may be coated after the surface treatment or may be coated without the surface treatment. Details of the undercoat layer are described on page 32 of the Japan Society for Invention and Innovation (Public Technical Number 2001-1745, published on March 15, 2001, Japan Institute of Invention). These surface treatment and undercoating processes can be incorporated at the end of the film forming process, can be performed alone, or can be performed in the functional layer application process described later.

≪Function layer grant≫
In the embodiment of the optical resin film of the present invention, the example in which the retardation film is produced by longitudinally stretching and transversely stretching the resin film 12 (base film) formed by the film forming process unit 14 has been described. However, the functional layer described in detail on pages 32 to 45 in the Technical Report of the Japan Society of Invention (Public Technical Number 2001-1745, issued on March 15, 2001, Japan Society of Invention) is applied to the unstretched base film. It can also be combined. Among these, application of a polarizing layer (polarizing plate), application of an optically anisotropic layer (optical compensation layer), and application of an antireflection layer (antireflection film) are preferable.

(Optically anisotropic layer)
The optically anisotropic layer is preferably designed so as to compensate for the liquid crystalline compound in the liquid crystal cell in the black display of the liquid crystal display device. The alignment state of the liquid crystal compound in the liquid crystal cell in black display varies depending on the mode of the liquid crystal display device. The alignment state of the liquid crystal compound in this liquid crystal cell is described in IDW'00, P411 to 414 of FMC7-2, and the like.

  The optically anisotropic layer is formed directly from the liquid crystalline compound on the support or from the liquid crystalline compound via an alignment film. The alignment film preferably has a thickness of 10 μm or less.

  The liquid crystalline compound used for the optically anisotropic layer includes a rod-like liquid crystalline compound and a discotic liquid crystalline compound. The rod-like liquid crystal compound and the discotic liquid crystal compound may be a high-molecular liquid crystal or a low-molecular liquid crystal, and further include those in which the low-molecular liquid crystal is cross-linked and no longer exhibits liquid crystallinity. The optically anisotropic layer can be formed by applying a liquid crystal compound and, if necessary, a coating liquid containing a polymerizable initiator and optional components on the alignment film. A preferred example of the alignment film of the present invention is described in JP-A-8-338913.

[Bar-shaped liquid crystalline compound]
Examples of rod-like liquid crystalline compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used.

  The rod-like liquid crystalline compound includes a metal complex. Moreover, the liquid crystal polymer which contains a rod-shaped liquid crystalline compound in a repeating unit can also be used as a rod-shaped liquid crystalline compound. That is, the rod-like liquid crystalline compound may be bonded to a (liquid crystal) polymer.

  Regarding rod-like liquid crystalline compounds, for example, Quarterly Chemical Review Vol. 22, Liquid Crystal Chemistry (1994), Chapter 4, Chapter 7 and Chapter 11 of the Chemical Society of Japan, and Liquid Crystal Device Handbook, Japan Society for the Promotion of Science, 142nd Committee The one described in Chapter 3 of the edition can be adopted.

  The birefringence of the rod-like liquid crystalline compound is preferably in the range of 0.001 to 0.7.

  The rod-like liquid crystalline compound preferably has a polymerizable group in order to fix its alignment state. The polymerizable group is preferably an unsaturated polymerizable group or an epoxy group, more preferably an unsaturated polymerizable group, and most preferably an ethylenically unsaturated polymerizable group.

[Discotic liquid crystalline compounds]
Examples of discotic liquid crystalline compounds include C.I. Benzene derivatives described in a research report of Destrade et al. (Mol. Cryst. 71, 111 (1981)), C.I. Destrode et al. (Mol. Cryst. 122, 141 (1985), Physics lett, A, 78, 82 (1990)) described in The cyclohexane derivatives described in the research report of Kohne et al. (Angew. Chem. 96, 70 (1984)) and M.M. Lehn et al. (JCS, Chem. Commun., 1794 (1985)), J.C. Azacrown-type and phenylacetylene-type macrocycles described in the research report of Zhang et al. (J. Am. Chem. Soc. 116, 2655 (1994)) are included.

  The discotic liquid crystalline compound also includes a compound having a structure in which a linear alkyl group, an alkoxy group, and a substituted benzoyloxy group are radially substituted as a side chain of the mother nucleus with respect to the mother nucleus at the center of the molecule. The molecule or the assembly of molecules is preferably a compound having rotational symmetry and imparting a certain orientation. The optically anisotropic layer formed from the discotic liquid crystalline compound does not necessarily require that the compound finally contained in the optically anisotropic layer is a discotic liquid crystalline compound. Also included are compounds having a group that reacts with heat or light and, as a result, polymerized or cross-linked by reaction with heat or light, resulting in a high molecular weight and loss of liquid crystallinity. Preferred examples of the discotic liquid crystalline compound are described in JP-A-8-50206. Moreover, about superposition | polymerization of a discotic liquid crystalline compound, Unexamined-Japanese-Patent No. 8-27284 has description.

  In order to fix the discotic liquid crystalline compound by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline compound. However, when the polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain the orientation state in the polymerization reaction. Therefore, a linking group is introduced between the discotic core and the polymerizable group. Therefore, the discotic liquid crystalline compound having a polymerizable group is preferably a compound represented by the following formula (5).

General formula (5)
D (-LQ) _r
(In General Formula (5), D is a discotic core, L is a divalent linking group, Q is a polymerizable group, and r is an integer of 4 to 12.)
An example of the disk-shaped core (D) is shown below. In each of the following examples, LQ (or QL) means a combination of a divalent linking group (L) and polymerizability (Q).

  In the general formula (5), the divalent linking group (L) is selected from the group consisting of an alkylene group, an alkenylene group, an arylene group, —CO—, —NH—, —O—, —S—, and combinations thereof. It is preferable that it is a bivalent coupling group. The divalent linking group (L) is a divalent combination of at least two divalent groups selected from the group consisting of an alkylene group, an arylene group, -CO-, -NH-, -O-, and -S-. More preferably, it is a linking group. The divalent linking group (L) is most preferably a divalent linking group in which at least two divalent groups selected from the group consisting of an alkylene group, an arylene group, -CO- and -O- are combined. . The alkylene group preferably has 1 to 12 carbon atoms. The alkenylene group preferably has 2 to 12 carbon atoms. The number of carbon atoms in the arylene group is preferably 6-10.

Examples of the divalent linking group (L) are shown below. The left side is bonded to the discotic core (D), and the right side is bonded to the polymerizable group (Q). AL represents an alkylene group or an alkenylene group, and AR represents an arylene group. The alkylene group, alkenylene group and arylene group may have a substituent (eg, an alkyl group).
L1: -AL-CO-O-AL-,
L2: -AL-CO-O-AL-O-,
L3: -AL-CO-O-AL-O-AL-,
L4: -AL-CO-O-AL-O-CO-,
L5: -CO-AR-O-AL-,
L6: -CO-AR-O-AL-O-,
L7: -CO-AR-O-AL-O-CO-,
L8: -CO-NH-AL-,
L9: -NH-AL-O-,
L10: -NH-AL-O-CO-,
L11: -O-AL-,
L12: -O-AL-O-,
L13: -O-AL-O-CO-,
L14: -O-AL-O-CO-NH-AL-,
L15: -O-AL-S-AL-,
L16: -O-CO-AL-AR-O-AL-O-CO-,
L17: -O-CO-AR-O-AL-CO-,
L18: -O-CO-AR-O-AL-O-CO-,
L19: -O-CO-AR-O-AL-O-AL-O-CO-,
L20: -O-CO-AR-O-AL-O-AL-O-AL-O-CO-,
L21: -S-AL-,
L22: -S-AL-O-,
L23: -S-AL-O-CO-,
L24: -S-AL-S-AL-,
L25: -S-AR-AL-.

  The polymerizable group (Q) of the general formula (5) is determined according to the type of polymerization reaction. Examples of the polymerizable group (Q) are shown below.

  The polymerizable group (Q) is preferably an unsaturated polymerizable group (Q1, Q2, Q3, Q7, Q8, Q15, Q16, Q17) or an epoxy group (Q6, Q18). More preferably, it is most preferably an ethylenically unsaturated polymerizable group (Q1, Q7, Q8, Q15, Q16, Q17). A specific value of r is determined according to the type of the disk-shaped core (D). In addition, although the combination of several L and Q may differ, it is preferable that it is the same.

  In the hybrid alignment, the angle between the major axis (disk surface) of the discotic liquid crystalline compound and the surface of the support, that is, the inclination angle is in the direction of the depth of the optically anisotropic layer (that is, perpendicular to the transparent support). And it increases or decreases as the distance from the plane of the polarizing film increases. The angle preferably increases with increasing distance. Further, the change in the tilt angle can be continuous increase, continuous decrease, intermittent increase, intermittent decrease, change including continuous increase and continuous decrease, or intermittent change including increase and decrease. . The intermittent change includes a region where the inclination angle does not change in the middle of the thickness direction. Even if a region where the angle does not change is included, it may be increased or decreased as a whole. However, it is preferred that the tilt angle changes continuously.

  The average direction of the major axis (disk surface) of the discotic liquid crystalline compound (average of the major axis direction of each molecule) is generally selected by selecting the discotic liquid crystalline compound or the material of the alignment film, or selecting the rubbing treatment method. By doing so, it can be adjusted. The major axis (disk surface) direction of the discotic liquid crystalline compound on the surface side (air side) is generally adjusted by selecting the type of additive used together with the discotic liquid crystalline compound or the discotic liquid crystalline compound. be able to.

  Examples of the additive used together with the discotic liquid crystalline compound include a plasticizer, a surfactant, a polymerizable monomer and a polymer. The degree of change in the orientation direction of the major axis can also be adjusted by selecting liquid crystalline molecules and additives as described above.

  The plasticizer, surfactant and polymerizable monomer used together with the discotic liquid crystalline compound are compatible with the discotic liquid crystalline compound, and can change the tilt angle of the discotic liquid crystalline compound or change the orientation. It is preferable not to inhibit. Among the additive components, addition of a polymerizable monomer (eg, a compound having a vinyl group, a vinyloxy group, an acryloyl group and a methacryloyl group) is preferable. The amount of the compound added is generally in the range of 1 to 50% by mass and preferably in the range of 5 to 30% by mass with respect to the discotic liquid crystalline compound. In addition, when a monomer having 4 or more polymerizable reactive functional groups is mixed and used, adhesion between the alignment film and the optically anisotropic layer can be improved.

The optically anisotropic layer may contain a polymer together with the discotic liquid crystalline compound. The polymer preferably has a certain degree of compatibility with the discotic liquid crystalline compound and can change the tilt angle of the discotic liquid crystalline compound. A cellulose ester can be mentioned as an example of a polymer. Preferable examples of the cellulose ester include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose and cellulose acetate butyrate. The addition amount of the polymer is preferably in the range of 0.1 to 10% by mass with respect to the discotic liquid crystalline compound so as not to inhibit the orientation of the discotic liquid crystalline compound, and 0.1 to 8% by mass. More preferably, it is in the range of 0.1 to 5% by mass. The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline compound is preferably 70 to 300 ° C, more preferably 70 to 170 ° C.
[Fixing the alignment state of liquid crystalline molecules]
The aligned liquid crystal molecules can be fixed while maintaining the alignment state. The immobilization is preferably performed by a polymerization reaction. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. A photopolymerization reaction is preferred.

  Examples of photopolymerization initiators include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ethers (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin compounds ( U.S. Pat. No. 2,722,512), a polynuclear quinone compound (described in U.S. Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (described in U.S. Pat. No. 3,549,367), acridine and Phenazine compounds (described in JP-A-60-105667 and US Pat. No. 4,239,850) and oxadiazole compounds (described in US Pat. No. 4,221,970) are included.

  The amount of the photopolymerization initiator used is preferably in the range of 0.01 to 20% by mass, more preferably in the range of 0.5 to 5% by mass, based on the solid content of the coating solution.

  It is preferable to use ultraviolet rays for light irradiation for polymerization of liquid crystalline molecules.

The irradiation energy ^is preferably in the range of ^{20mJ / cm 2 ~50J / cm 2} , more preferably in the range of ^{20mJ / cm 2 ~5000mJ / cm 2} , a range of 100mJ / cm ² ~800mJ / cm 2 More preferably. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions.

  A protective layer may be provided on the optically anisotropic layer.

  The optically anisotropic layer is prepared by preparing a coating solution containing at least one of the liquid crystalline compounds and, optionally, an additive such as a polymerizable initiator and a fluorine-based polymer, and applying the coating solution to the alignment film surface. It can be formed by drying.

  Examples of the fluorine-based compound include conventionally known compounds. Specific examples include the fluorine-based compounds described in paragraphs [0028] to [0056] of JP-A-2001-330725. It is done.

  As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane, tetrachloroethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.

  When producing an optical compensation film with high uniformity, the surface tension of the coating solution is preferably 25 mN / m or less, and more preferably 22 mN / m or less.

  The coating liquid can be applied by a known method (eg, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).

[Polarizer]
(Polarizing film)
The polarizing film that can be used in the polarizing plate of the present invention is preferably a coating type polarizing film typified by Optiva, or a polarizing film comprising a binder and iodine or a dichroic dye.

  Iodine and dichroic dye in the polarizing film exhibit deflection performance by being oriented in the binder. It is preferable that the iodine and the dichroic dye are aligned along the binder molecule, or the dichroic dye is aligned in one direction by self-assembly such as liquid crystal.

  A general-purpose polarizer can be prepared, for example, by immersing a stretched polymer in a solution of iodine or dichroic dye in a bath and allowing the iodine or dichroic dye to penetrate into the binder. it can.

  In general-purpose polarizing films, iodine or dichroic dye is distributed about 4 μm (about 8 μm on both sides) from the polymer surface, and a thickness of at least 10 μm is necessary to obtain sufficient polarization performance. The penetrability can be controlled by the solution concentration of iodine or dichroic dye, the temperature of the bath, and the immersion time.

  As described above, the lower limit of the binder thickness is preferably 10 μm. On the other hand, the upper limit of the thickness is not particularly limited, but the thinner the better, from the viewpoint of the light leakage phenomenon that occurs when the polarizing plate is used in a liquid crystal display device. Currently, it is preferably a general-purpose polarizing plate (about 30 μm) or less, preferably 25 μm or less, and more preferably 20 μm or less. When it is 20 μm or less, the light leakage phenomenon is not observed in a 17-inch liquid crystal display device.

  The binder of the polarizing film may be cross-linked. As the crosslinked binder, a polymer that can be crosslinked per se can be used. A polarizing film can be formed by reacting a polymer having a functional group or a binder obtained by introducing a functional group into a polymer between the binders by light, heat, or pH change.

  Moreover, you may introduce | transduce a crosslinked structure into a polymer with a crosslinking agent. It can be formed by cross-linking between binders by introducing a bonding group derived from the cross-linking agent between binders using a cross-linking agent which is a compound having high reaction activity.

  Crosslinking is generally carried out by applying a coating solution containing a polymer or a mixture of a polymer and a crosslinking agent on a transparent support and then heating. Since it is only necessary to ensure durability at the stage of the final product, the cross-linking treatment may be performed at any stage until the final polarizing plate is obtained.

  As the binder for the polarizing film, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used. Examples of polymers include polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, polystyrene, gelatin, polyvinyl alcohol, modified polyvinyl alcohol, poly (N-methylolacrylamide), polyvinyltoluene, chlorosulfonated polyethylene, nitrocellulose, chlorinated Polyolefin (eg, polyvinyl chloride), polyester, polyimide, polyvinyl acetate, polyethylene, carboxymethylcellulose, polypropylene, polycarbonate and copolymers thereof (eg, acrylic acid / methacrylic acid polymer, styrene / maleimide polymer, styrene / vinyl) Toluene polymer, vinyl acetate / vinyl chloride polymer, ethylene / vinyl acetate polymer). Water-soluble polymers (eg, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol and modified polyvinyl alcohol) are preferred, gelatin, polyvinyl alcohol and modified polyvinyl alcohol are more preferred, and polyvinyl alcohol and modified polyvinyl alcohol are most preferred. .

  The saponification degree of polyvinyl alcohol and modified polyvinyl alcohol is preferably 70 to 100%, more preferably 80 to 100%, and most preferably 95 to 100%. As for the polymerization degree of polyvinyl alcohol, 100-5000 are preferable.

Modified polyvinyl alcohol is obtained by introducing a modifying group into polyvinyl alcohol by copolymerization modification, chain transfer modification or block polymerization modification. In the copolymerization modification, —COONa, —Si (OH) ₃ , N (CH ₃ ) ₃ .Cl, C ₉ H ₁₉ COO—, —SO ₃ Na, —C ₁₂ H ₂₅ may be introduced as a modifying group. it can. In chain transfer modification,
COONa, _-SH, may be introduced _-SC 12 _{H 25.} The degree of polymerization of the modified polyvinyl alcohol is preferably 100 to 3000. The modified polyvinyl alcohol is described in JP-A-8-338913, JP-A-9-152509 and JP-A-9-316127.

  Unmodified polyvinyl alcohol and alkylthio-modified polyvinyl alcohol having a saponification degree of 85 to 95% are particularly preferable.

  Two or more kinds of polyvinyl alcohol and modified polyvinyl alcohol may be used in combination.

  When a large amount of the crosslinking agent for the binder is added, the heat and humidity resistance of the polarizing film can be improved. However, when 50 mass% or more of a crosslinking agent is added to the binder, the orientation of iodine or the dichroic dye is lowered. 0.1-20 mass% is preferable with respect to a binder, and, as for the addition amount of a crosslinking agent, 0.5-15 mass% is more preferable.

  The binder contains some crosslinking agent that has not reacted even after the crosslinking reaction has been completed. However, the amount of the remaining crosslinking agent is preferably 1.0% by mass or less in the binder, and more preferably 0.5% by mass or less. When the crosslinking agent is contained in the binder layer in an amount exceeding 1.0% by mass, there may be a problem in durability. That is, when a polarizing film having a large amount of residual crosslinking agent is incorporated in a liquid crystal display device and used for a long time or left in a high-temperature and high-humidity atmosphere for a long time, the degree of polarization may decrease.

  The crosslinking agent is described in US Reissue Patent 23297. Boron compounds (eg, boric acid, borax) can also be used as a crosslinking agent.

  As the dichroic dye, an azo dye, stilbene dye, pyrazolone dye, triphenylmethane dye, quinoline dye, oxazine dye, thiazine dye or anthraquinone dye is used. The dichroic dye is preferably water-soluble. The dichroic dye preferably has a hydrophilic substituent (eg, sulfo, amino, hydroxyl).

  Examples of dichroic dyes include C.I. I. Direct Yellow 12, C.I. I. Direct Orange 39, C.I. I. Direct Orange 72, C.I. I. Direct Red 39, C.I. I. Direct Red 79, C.I. I. Direct Red 81, C.I. I. Direct Red 83, C.I. I. Direct Red 89, C.I. I. Direct Violet 48, C.I. I. Direct Blue 67, C.I. I. Direct Blue 90, C.I. I. Direct Green 59, C.I. I. Acid Red 37 is included. As for the dichroic dyes, those described in JP-A-1-161202, 1-172906, 1-172907, 1-183602, 1-248105, 1-265205, 7-261024 are used. There are descriptions in each publication. The dichroic dye is used as a free acid or an alkali metal salt, ammonium salt or amine salt. By blending two or more kinds of dichroic dyes, polarizing films having various hues can be produced. A polarizing film using a compound (pigment) that exhibits a black color when the polarization axes are orthogonal to each other, or a polarizing film or a polarizing plate in which various dichroic molecules are blended so as to exhibit a black color, have both a single-plate transmittance and a polarizability. It is excellent and preferable.

  In order to increase the contrast ratio of the liquid crystal display device, the transmittance of the polarizing plate is preferably higher and the degree of polarization is preferably higher. The transmittance of the polarizing plate is preferably in the range of 30 to 50%, more preferably in the range of 35 to 50%, and in the range of 40 to 50% in the light having a wavelength of 550 nm (of the polarizing plate). Most preferably, the maximum value of the single plate transmittance is 50%. The degree of polarization is preferably in the range of 90 to 100%, more preferably in the range of 95 to 100%, and most preferably in the range of 99 to 100% in light having a wavelength of 550 nm.

  It is also possible to arrange the polarizing film and the optically anisotropic layer, or the polarizing film and the alignment film via an adhesive. As the adhesive, a polyvinyl alcohol resin (including a modified polyvinyl alcohol with an acetoacetyl group, a sulfonic acid group, a carboxyl group, or an oxyalkylene group) or an aqueous boron compound solution can be used. Of these, polyvinyl alcohol resins are preferred. The thickness of the adhesive layer is preferably in the range of 0.01 to 10 μm after drying, and particularly preferably in the range of 0.05 to 5 μm.

(Manufacture of polarizing plates)
From the viewpoint of yield, the polarizing film is stretched at an angle of 10 to 80 degrees with respect to the longitudinal direction (MD direction) of the polarizing film (stretching method) or rubbed (rubbing method). It is preferable to dye with a dichroic dye. The tilt angle is preferably stretched so as to match the angle formed between the transmission axis of the two polarizing plates bonded to both sides of the liquid crystal cell constituting the LCD and the vertical or horizontal direction of the liquid crystal cell.

  A normal inclination angle is 45 degrees. Recently, however, devices that are not necessarily 45 degrees have been developed in transmissive, reflective, and transflective LCDs, and it is preferable that the stretching direction can be arbitrarily adjusted in accordance with the design of the LCD.

  In the stretching method, the stretching ratio is preferably 2.5 to 30.0 times, and more preferably 3.0 to 10.0 times. Stretching can be performed by dry stretching in air. Moreover, you may implement wet extending | stretching in the state immersed in water. The stretch ratio of dry stretching is preferably 2.5 to 5.0 times, and the stretch ratio of wet stretching is preferably 3.0 to 10.0 times. The stretching step may be performed in several steps including oblique stretching. By dividing into several times, it is possible to stretch more uniformly even at high magnification. Before the oblique stretching, a slight stretching (a degree to prevent shrinkage in the width direction) may be performed horizontally or vertically. Note that. The stretching ratio here is expressed by the ratio (L ′ / L) of the length (L) before stretching and the length (L ′) after stretching, with a mark on the film before stretching. The

  Stretching can be performed by performing tenter stretching in biaxial stretching in different steps. The biaxial stretching is the same as the stretching method performed in normal film formation. In biaxial stretching, stretching is performed at different speeds on the left and right, so that the thickness of the binder film before stretching needs to be different on the left and right. In casting film formation, the flow rate of the binder solution can be differentiated between the left and right sides by tapering the die.

  As described above, a binder film that is obliquely stretched by 10 to 80 degrees with respect to the MD direction of the polarizing film is produced.

  In the rubbing method, a rubbing treatment method widely adopted as a liquid crystal alignment treatment process of LCD can be applied. That is, orientation is obtained by rubbing the surface of the film in a certain direction using paper, gauze, felt, rubber, nylon, or polyester fiber. In general, it is carried out by rubbing several times using a cloth in which fibers having a uniform length and thickness are planted on average. It is preferable to carry out using a rubbing roll in which the roundness, cylindricity, and deflection (eccentricity) of the roll itself are all 30 μm or less. The film wrap angle on the rubbing roll is preferably 0.1 to 90 degrees. However, as described in JP-A-8-160430, a stable rubbing treatment can be obtained by winding 360 degrees or more.

  When rubbing a long film, the film is preferably transported at a speed of 1 to 100 m / min in a constant tension state by a transport device. The rubbing roll is preferably rotatable in the horizontal direction with respect to the film traveling direction for setting an arbitrary rubbing angle. It is preferable to select an appropriate rubbing angle in the range of 0 to 60 degrees. When used in a liquid crystal display device, 40 to 50 degrees is preferable. 45 degrees is particularly preferable.

[Liquid Crystal Display]
The optical film manufactured by the method for manufacturing an optical resin film of the present invention can be used in various modes of liquid crystal display devices. Hereinafter, preferred forms of the optically anisotropic layer in each liquid crystal mode will be described.

(TN mode liquid crystal display)
The TN mode liquid crystal cell is most frequently used as a color TFT liquid crystal display device, and is described in many documents.

  The alignment state in the liquid crystal cell in the TN mode black display is an alignment state in which a rod-like liquid crystalline molecule rises at the center of the cell and the rod-like liquid crystalline compound lies in the vicinity of the cell substrate.

  The rod-like liquid crystalline compound in the center of the cell is compensated with a discotic liquid crystalline compound of the homeotropic orientation (horizontal orientation in which the disk surface is lying) or a (transparent) support, and the rod-like liquid crystalline property in the vicinity of the cell substrate The compound can be compensated with a discotic liquid crystalline compound having a hybrid alignment (an alignment in which the inclination of the major axis changes with the distance from the polarizing film).

  In addition, the rod-like liquid crystalline compound at the center of the cell is compensated with a rod-like liquid crystalline compound having a homogeneous orientation (horizontal orientation in which the major axis lies) or a (transparent) support, and the rod-like liquid crystalline property in the vicinity of the cell substrate is compensated. The compound can be compensated with a discotic liquid crystalline compound having a hybrid alignment.

  The homeotropic alignment liquid crystal compound is aligned in a state where the angle between the average alignment direction of the major axis of the liquid crystal compound and the plane of the polarizing film is 85 to 95 degrees.

  The liquid crystal compound of homogeneous alignment is aligned with the angle between the average alignment direction of the major axis of the liquid crystal compound and the plane of the polarizing film being less than 5 degrees.

  In the hybrid alignment liquid crystalline compound, the angle between the long axis average alignment direction of the liquid crystalline compound and the plane of the polarizing film is preferably 15 degrees or more, and more preferably 15 degrees to 85 degrees.

  Optically anisotropic layer in which support or discotic liquid crystalline compound is homeotropically oriented, optically anisotropic layer in which rod-like liquid crystalline compound is homogeneously oriented, and further homeotropically oriented discotic liquid crystalline compound And an optically anisotropic layer made of a mixture of rod-like liquid crystalline compounds that are homogeneously oriented have an Rth retardation value of 40 nm to 200 nm, and an Re retardation value of 0 to 70 nm.

  Regarding the discotic liquid crystal compound layer having homeotropic alignment (horizontal alignment) and the rod-like liquid crystal compound layer having homogeneous alignment (horizontal alignment), Japanese Patent Laid-Open Nos. 12-304931 and 12-304932 describe them. Have been described. The discotic liquid crystal compound layer having a hybrid orientation is described in JP-A-8-50206.

(OCB mode liquid crystal display)
The OCB mode liquid crystal cell is a bend alignment mode liquid crystal cell in which a rod-like liquid crystal compound is aligned in a substantially opposite direction (symmetrically) between an upper portion and a lower portion of the liquid crystal cell. Liquid crystal display devices using a bend alignment mode liquid crystal cell are disclosed in US Pat. Nos. 4,583,825 and 5,410,422. Since the rod-like liquid crystal compounds are symmetrically aligned at the upper and lower portions of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function. Therefore, this liquid crystal mode is called an OCB (Optically Compensatory Bend) liquid crystal mode.

  Similarly to the TN mode, the liquid crystal cell in the OCB mode is in a black display, and the alignment state in the liquid crystal cell is such that the rod-like liquid crystal compound rises at the center of the cell and the rod-like liquid crystal compound lies in the vicinity of the cell substrate. .

  Since the TN mode and the liquid crystal orientation are the same in black display, the preferred mode is the same as that for the TN mode. However, since the OCB mode has a larger range in which the liquid crystal compound has risen at the center of the cell than the TN mode, an optically anisotropic layer in which the discotic liquid crystal compound is homeotropically aligned or a rod-like liquid crystal It is necessary to slightly adjust the retardation value of the optically anisotropic layer in which the functional compound is homogeneously oriented. Specifically, the optically anisotropic layer in which the discotic liquid crystalline compound on the support is homeotropically oriented, or the optically anisotropic layer in which the rod-like liquid crystalline compound is homogeneously oriented has an Rth retardation value. Is preferably 150 nm to 500 nm, and the Re retardation value is preferably 20 to 70 nm.

(VA mode liquid crystal display device)
In the VA mode liquid crystal cell, the rod-like liquid crystalline compound is aligned substantially vertically when no voltage is applied.

  The VA mode liquid crystal cell includes (1) a narrowly defined VA mode liquid crystal cell in which a rod-like liquid crystal compound is aligned substantially vertically when no voltage is applied, and is substantially horizontally aligned when a voltage is applied (Japanese Patent Laid-Open No. 2). 176625 (in Japanese Patent Publication No. 176625), and (2) a liquid crystal cell (SID97, Digest of tech. Papers (Proceedings) 28 (1997) 845 in which the VA mode is converted into a multi-domain (in MVA mode) for widening the viewing angle ), (3) A liquid crystal cell in a mode (n-ASM mode) in which a rod-like liquid crystalline compound is substantially vertically aligned when no voltage is applied and twisted multi-domain alignment is applied when a voltage is applied (Preliminary Collection 58-59 of the Japan Liquid Crystal Society) (1998)) and (4) SURVAVAL mode liquid crystal cells (announced at LCD International 98).

  In the black display of the VA mode liquid crystal display device, most of the rod-like liquid crystalline compounds in the liquid crystal cell are in a standing state, so that the optically anisotropic layer in which the discotic liquid crystalline compounds are homeotropically aligned, Alternatively, the liquid crystalline compound is compensated by an optically anisotropic layer in which the rod-like liquid crystalline compound is homogeneously oriented, and separately, the rod-like liquid crystalline compound is homogeneously oriented, and the average orientation direction of the major axis of the rod-like liquid crystalline compound and the polarizing film It is preferable to compensate the viewing angle dependency of the polarizing plate with an optically anisotropic layer having an angle with respect to the transmission axis direction of less than 5 degrees.

  The optically anisotropic layer in which the support or the discotic liquid crystalline compound is homeotropically oriented, or the optically anisotropic layer in which the rod-like liquid crystalline compound is homogeneously oriented has an Rth retardation value of 150 nm to 500 nm. The Re retardation value is preferably 20 to 70 nm.

(Other liquid crystal display devices)
The ECB mode and STN mode liquid crystal display devices can be optically compensated in the same way as described above.

(C) Application of an antireflection layer (antireflection film)
An antireflection layer may be provided on the optical resin film of the present invention. The antireflection film generally has a low refractive index layer which is also an antifouling layer, and at least one layer having a higher refractive index than that of the low refractive index layer (ie, a high refractive index layer and a medium refractive index layer) on a transparent substrate. It is provided and formed.

  Colloidal metal by multilayer deposition of transparent thin films of inorganic compounds (metal oxides, etc.) with different refractive indexes by chemical vapor deposition (CVD) method, physical vapor deposition (PVD) method, sol-gel method of metal compounds such as metal alkoxides Examples include a method of forming a thin film by post-processing (ultraviolet irradiation: JP-A-9-157855, plasma processing: JP-A-2002-327310) after forming an oxide particle film.

  On the other hand, various antireflection films formed by laminating thin films in which inorganic particles are dispersed in a matrix have been proposed as antireflection films with high productivity.

  The antireflection film which consists of the antireflection layer which provided the anti-glare property which the antireflection film by application | coating as mentioned above provided the surface of the uppermost layer with the shape of a fine unevenness | corrugation is also mentioned.

  The optical resin film of the present invention can be applied to any of the above methods, but a coating method (coating type) is particularly preferable.

(C-1) Layer structure of coating type antireflection film An antireflection film comprising a layer structure of at least a medium refractive index layer, a high refractive index layer, and a low refractive index layer (outermost layer) on the substrate has the following relationship: It is designed to have a refractive index that satisfies

The refractive index of the high refractive index layer> The refractive index of the medium refractive index layer> The refractive index of the transparent support> The refractive index of the low refractive index layer Further, a hard coat layer is provided between the transparent support and the medium refractive index layer. May be. Furthermore, it may consist of a medium refractive index hard coat layer, a high refractive index layer and a low refractive index layer.

  Examples thereof include JP-A-8-122504, JP-A-8-110401, JP-A-10-300902, JP-A-2002-243906, JP-A-2000-11706, and the like.

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

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

(C-2) High refractive index layer and medium refractive index layer The layer having a high refractive index of the antireflection film is a curable film containing at least inorganic compound ultrafine particles having a high refractive index with an average particle size of 100 nm or less and a matrix binder. Consists of.

  Examples of the high refractive index inorganic compound fine particles include inorganic compounds having a refractive index of 1.65 or more, preferably those having a refractive index of 1.9 or more. Examples thereof include oxides such as Ti, Zn, Sb, Sn, Zr, Ce, Ta, La, and In, and composite oxides containing these metal atoms.

  In order to obtain such ultrafine particles, the surface of the particles is treated with a surface treatment agent (for example, silane coupling agents, etc .: JP-A-11-295503, JP-A-11-153703, JP-A-2000-9908). No., anionic compound or organometallic coupling agent: Japanese Patent Laid-Open No. 2001-310432, etc., core-shell structure with high refractive index particles as a core (: Japanese Patent Laid-Open No. 2001-166104, etc.), specific dispersion (For example, Japanese Patent Laid-Open No. 11-153703, Japanese Patent No. US6210858B1, Japanese Patent Laid-Open No. 2002-27776069, etc.).

  Examples of the material forming the matrix include conventionally known thermoplastic resins and curable resin films.

  Further, it is selected from a polyfunctional compound-containing composition containing at least two radically polymerizable and / or cationically polymerizable groups, an organometallic compound containing a hydrolyzable group, and a partial condensate composition thereof. At least one composition is preferred. Examples thereof include compounds described in JP-A Nos. 2000-47004, 2001-315242, 2001-31871, and 2001-296401.

  A curable film obtained from a colloidal metal oxide obtained from a hydrolyzed condensate of metal alkoxide and a metal alkoxide composition is also preferred. For example, it describes in Unexamined-Japanese-Patent No. 2001-293818.

  The refractive index of the high refractive index layer is generally 1.70 to 2.20. The thickness of the high refractive index layer is preferably 5 nm to 10 μm, and more preferably 10 nm to 1 μm.

  The refractive index of the middle refractive index layer is adjusted to be a value between the refractive index of the low refractive index layer and the refractive index of the high refractive index layer. The refractive index of the middle refractive index layer is preferably 1.50 to 1.70.

(C-3) Low refractive index layer The low refractive index layer is formed by sequentially laminating on the high refractive index layer. The refractive index of the low refractive index layer is 1.20 to 1.55. Preferably it is 1.30-1.50.

  It is preferable to construct as the outermost layer having scratch resistance and antifouling property. As means for greatly improving the scratch resistance, imparting slipperiness to the surface is effective, and conventionally known thin film layer means such as introduction of silicone or introduction of fluorine can be applied.

  The refractive index of the fluorine-containing compound is preferably 1.35 to 1.50. More preferably, it is 1.36-1.47. The fluorine-containing compound is preferably a compound containing a crosslinkable or polymerizable functional group containing fluorine atoms in the range of 35 to 80% by mass.

  For example, paragraph numbers [0018] to [0026] of Japanese Patent Application Laid-Open No. 9-222503, paragraph numbers [0019] to [0030] of Japanese Patent Application Laid-Open No. 11-38202, and paragraph numbers of Japanese Patent Application Laid-Open No. 2001-40284. [0027] to [0028], JP-A 2000-284102, and the like.

  The silicone compound is a compound having a polysiloxane structure, preferably containing a curable functional group or a polymerizable functional group in the polymer chain and having a crosslinked structure in the film. For example, reactive silicone (eg, Silaplane (manufactured by Chisso Corporation), silanol group-containing polysiloxane (Japanese Patent Laid-Open No. 11-258403, etc.) and the like can be mentioned.

  The crosslinking or polymerization reaction of the fluorine-containing and / or siloxane polymer having a crosslinking or polymerizable group is carried out at the same time or after the coating composition for forming the outermost layer containing a polymerization initiator, a sensitizer, etc. It is preferable to carry out by light irradiation or heating.

  Also preferred is a sol-gel cured film in which an organometallic compound such as a silane coupling agent and a specific fluorine-containing hydrocarbon group-containing silane coupling agent are cured by a condensation reaction in the presence of a catalyst.

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

  The low refractive index layer has an average primary particle diameter of 1 to 150 nm such as a filler (for example, silicon dioxide (silica), fluorine-containing particles (magnesium fluoride, calcium fluoride, barium fluoride)) as an additive other than the above. Low refractive index inorganic compounds, organic fine particles described in paragraphs [0020] to [0038] of JP-A-11-3820, etc.), silane coupling agents, slip agents, surfactants, and the like can be contained.

  When the low refractive index layer is located below the outermost layer, the low refractive index layer may be formed by a vapor phase method (vacuum deposition method, sputtering method, ion plating method, plasma CVD method, etc.). The coating method is preferable because it can be manufactured at a low cost.

  The film thickness of the low refractive index layer is preferably 30 to 200 nm, more preferably 50 to 150 nm, and most preferably 60 to 120 nm.

(C-4) Hard coat layer The hard coat layer is provided on the surface of the transparent support in order to impart physical strength to the antireflection film. In particular, it is preferably provided between the transparent support and the high refractive index layer.

  The hard coat layer is preferably formed by a crosslinking reaction or a polymerization reaction of a light and / or heat curable compound.

  The curable functional group is preferably a photopolymerizable functional group, and the hydrolyzable functional group-containing organometallic compound is preferably an organic alkoxysilyl compound.

  Specific examples of these compounds are the same as those exemplified for the high refractive index layer.

  Specific examples of the constituent composition of the hard coat layer include those described in JP-A Nos. 2002-144913, 2000-9908, and WO 00/46617.

  The high refractive index layer can also serve as a hard coat layer. In such a case, it is preferable to form fine particles dispersed in the hard coat layer using the method described for the high refractive index layer.

  The hard coat layer can also serve as an antiglare layer (described later) provided with particles having an average particle size of 0.2 to 10 μm to provide an antiglare function (antiglare function).

  The film thickness of the hard coat layer can be appropriately designed depending on the application. The film thickness of the hard coat layer is preferably 0.2 to 10 μm, more preferably 0.5 to 7 μm.

  The strength of the hard coat layer is preferably H or higher, more preferably 2H or higher, and most preferably 3H or higher in a pencil hardness test according to JIS K5400. Further, in the Taber test according to JIS K5400, the smaller the wear amount of the test piece before and after the test, the better.

(C-5) Forward scattering layer The forward scattering layer is provided in order to give a viewing angle improvement effect when the viewing angle is inclined in the vertical and horizontal directions when applied to a liquid crystal display device. By dispersing fine particles having different refractive indexes in the hard coat layer, it can also serve as a hard coat function.

  For example, Japanese Patent Laid-Open No. 11-38208 specifying a forward scattering coefficient, Japanese Patent Laid-Open No. 2000-199809 having a relative refractive index of a transparent resin and fine particles in a specific range, and Japanese Patent Laid-Open No. 2002 specifying a haze value of 40% or more. -107512 gazette etc. are mentioned.

(C-6) Other layers In addition to the above layers, a primer layer, an antistatic layer, an undercoat layer, a protective layer, and the like may be provided.

(C-7) Coating method Each layer of the antireflection film is formed by a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating, a micro gravure method or an extrusion coating method (US patent). No. 2,681,294) can be formed by coating.

(C-8) Anti-glare function The antireflection film may have an anti-glare function that scatters external light. The antiglare function is obtained by forming irregularities on the surface of the antireflection film. When the antireflection film has an antiglare function, the haze of the antireflection film is preferably 3 to 30%, more preferably 5 to 20%, and most preferably 7 to 20%.

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

<Measurement method>
The measurement method used in the present invention is described below.
(1) Range of Rth / Re ratio and Rth / Re ratio [1] After slitting 5 cm at both ends of the film, 20 points were sampled at regular intervals over the entire width (3 cm × 3 cm square). At this time, each side of the square was cut out parallel to MD (film forming direction) and TD (width direction).

  [2] After adjusting the sample film to 25 ° C. and 60% relative humidity for 5 hours or more, using an automatic birefringence meter (KOBRA-21ADH: manufactured by Oji Scientific Instruments) at 25 ° C. and 60% relative humidity As described above, the retardation value at a wavelength of 550 nm was measured from the direction inclining by 10 ° from the normal direction to the sample film surface and ± 50 ° from the normal to the film surface.

  [3] In-plane retardation (Re) from the vertical (normal) direction, and retardation (Rth) in the thickness direction were calculated from the measured values in the vertical direction and ± 10 to 40 ° directions.

[4] The average value of the Rth / Re ratio at each of these measurement points was defined as “Re / Rth ratio”. The difference between the maximum value and the minimum value among the 20 Rth / Re ratios was defined as the “Rth / Re ratio range”.
(2) Thermal dimensional change, thermal dimensional change unevenness [1] Sampling is performed at a point obtained by dividing the entire width of the following sample into five equal parts.
B) MD sample: MD15cm x TD5cm
B) TD sample: TD15cm × MD5cm
[2] Each sample is conditioned at 25 ° C. and 60% rh for 3 hours or more, and measured in this environment using a 10 cm-basic pin gauge. This is L1.

  [3] Each sample is allowed to stand at 80 ° C. and dry for 200 hours, then conditioned for 3 hours or more at 25 ° C. and 60% rh, and measured in this environment using a 10 cm base length pin gauge. This is L2.

  [4] The thermal dimensional change at each point (10 points) of MD and TD is measured from the following formula, and this average value is defined as the thermal dimensional change.

Thermal dimensional change (%) = 100 × | L2-L1 | / L1
[5] The difference between the maximum value and the minimum value of the thermal dimensional change (absolute value) among the 10 points was divided by the average value of the 10 thermal dimensional changes, and the thermal dimensional change was uneven.

(3) Surface roughness Ra was measured using a compact laser interferometer (F601, manufactured by Fuji Photo Optical Co., Ltd.).

(4) Glass transition temperature (Tg)
20 mg of the sample was placed in a measurement pan of a scanning differential calorimeter (DSC). This was heated from 30 ° C. to 250 ° C. at 10 ° C./min in a nitrogen stream (1st-run), and then cooled to 30 ° C. at −10 ° C./min. Thereafter, the temperature was raised again from 30 ° C. to 250 ° C. (2nd-run). The glass transition temperature (Tg) was defined as the temperature at which the baseline began to deviate from the low temperature side at 2nd-run.

Next, examples of the present invention will be described.
(Test conditions)
The test uses a pellet of cyclic olefin resin containing 0.1% by mass of a stabilizer (Irganox 1010) as a raw material resin, and passes through a twin screw extruder and a single screw extruder in this order, and supplies them to a molding die. An optical resin film was manufactured by extruding a resin from a molding die.

  As the twin screw extruder, two screw diameters (diameter of screw fried) of 37 mm and L / D54 different direction meshing type were used. The single screw extruder used was a full fried type having a single screw diameter (screw fried diameter) of 50 mm. The conditions of the twin screw extruder and the single screw extruder are as shown in FIG. 4. In FIG. 4, the first screw means an extruder through which resin passes first, and the second screw means second. Means an extruder that passes through. T1out is the resin temperature at the first screw outlet, and T2out is the resin temperature at the second screw outlet.

  Then, the evaluation of the test results is based on the solution haze value obtained by dissolving the manufactured film in cyclohexane and preparing a 10% by mass solution with a haze meter, and the outlet at the second screw (second extruder). The stability of the pressure was evaluated. When the gel is generated, the melt haze value appears to increase, and the melt haze value is preferably 3% or less as an optical use film. In addition, if the outlet pressure at the second screw is not stable, the discharge pressure discharged from the forming die fluctuates and a film thickness distribution occurs in the manufactured film.

(Test results)
As can be seen from FIG. 4, in Examples 1-12, the cyclic olefin-based resin was first heated and melted with a twin screw extruder, then extruded from the single screw extruder and supplied to the forming die. It is as follows and it can be seen that the generation of gel is small.

  On the other hand, in Comparative Example 1 in which a single screw extruder and a single screw extruder are combined, the stability is good, but the solution haze value is 15%, and the gel is remarkably generated (15%). I understand that. Moreover, although the comparative example 2 which combined the twin screw extruder and the twin screw extruder has the solution haze value somewhat lower than the comparative example 1, stability is worsening. Also, Comparative Example 3 using only a single screw extruder and Comparative Example 4 using only a twin screw extruder have a high solution haze value (10%, 5%) and a large amount of gel is generated. I understand.

  Moreover, when paying attention to the resin temperature at the exit of the twin screw extruder in Examples 1 to 12, the resin temperature at the exit of the twin screw extruder is 200 ° C. (Examples 3 to 12). The solution haze value is lower than in Example 1) and 300 ° C. (Example 2).

  Moreover, when paying attention to the outlet pressure of the twin screw extruder in Examples 1 to 12, the solution haze value is 3% or less when the outlet pressure is 10 MPa (Examples 1 to 3), but 4 MPa or less ( Further improvement of the solution haze value was seen in Examples 4-12).

  Further, when focusing on the maximum shear rate of the twin screw extruder in Examples 1 to 12, the solution haze value is 3% or less even when the maximum shear rate is 1500 (Example 12). Further improvements in solution haze values were seen at speeds of 15 (Example 10) and 800 (Example 11).

It is a model diagram which shows the structure of the film manufacturing apparatus used for the manufacturing method of the optical resin film of this invention. It is a conceptual diagram which shows the structure of a twin screw extruder. It is a conceptual diagram which shows the structure of a single screw extruder. It is a table | surface figure which shows the Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Film manufacturing apparatus, 12 ... Resin film, 14 ... Film forming process part, 16 ... Longitudinal stretch process part, 18 ... Lateral stretch process part, 20 ... Winding process part, 22 ... Twin screw extruder, 23 ... Uniaxial Screw extruder, 24 ... Molding die, 26 ... Cooling drum, 32 ... Cylinder, 34 ... Screw shaft, 36 ... Screw flight part, 38 ... Screw, 40 ... Supply port (inlet), 42 ... Discharge port (outlet), 44 ... barrel wall, 50 ... cylinder, 52 ... screw, 54 ... screw shaft, 56 ... screw flight part, 58 ... supply port (inlet), 60 ... discharge port (outlet)

Claims (5)

A melting step in which a cyclic olefin thermoplastic resin is heated and melted by a twin screw extruder;
A supply step of extruding the molten resin melted by heating from a single screw extruder and supplying it to a molding die;
Forming the film by discharging the molten resin from the molding die into a film and cooling it, and
The maximum shear rate generated at the barrel wall surface and screw flight part of the twin screw extruder is in the range of 15 to 800 (s ⁻¹ ),
When the resin temperature at the outlet of the twin screw extruder is T1 (° C.) and the resin temperature at the outlet of the single screw extruder is T2 (° C.), 200 ° C. ≦ T1 <T2 is satisfied. A method for producing an optical resin film. The method for producing an optical resin film according to claim 1 , wherein an outlet pressure of the twin screw extruder is in a range of 0.1 MPa to 5.5 MPa.   The method for producing an optical resin film according to claim 1 or 2, wherein an outlet pressure of the single screw extruder is in a range of 4 MPa to 20 MPa, and a pressure fluctuation is within ± 0.1 MPa. The method for producing an optical resin film according to any one of claims 1 to 3 , wherein a radical trapping agent or an antioxidant is added at an inlet of the twin screw extruder. The biaxially by flowing an inert gas from the inlet of the screw extruder inlet and the single screw extruder, atmospheric oxygen concentration at the inlet portion of the preceding claims, characterized in that set to be a 100ppm or less The manufacturing method of the optical resin film in any one.

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