KR20160038753A - Method of producing optical film, optical film, polarizing plate with optical film and liquid crystal display apparatus - Google Patents

Abstract

The purpose of the present invention is to provide a method for manufacturing an optical film having improved brittleness, sufficient hardness and restrained haze, an optical film manufactured by the method, a polarizing plate having the optical film, and a liquid crystal display apparatus. To this end, dope compositions A and B each containing rubber particles (6), a thermoplastic resin (7), and organic solvent (8) are prepared such that the mass of the rubber particles (6) with respect to that of the thermoplastic resin (7) contained in the composition B is less than the mass of the rubber particles (6) with respect to that of the thermoplastic resin (7) contained in the composition A, and also an amount of the rubber particles contained in the composition A is equal to or greater than 5 mass% and equal to or less than 30 mass% with respect to the mass of the thermoplastic resin, and the amount of the rubber particles contained in the composition B is equal to or greater than 4 mass% and equal to or less than 9 mass% with respect to the mass of the thermoplastic resin. The compositions A and B are applied on a flexible substrate (34) in an order of A-B, B-A, or B-A-B to form a flexible film (1), and the organic solvent (8) equal to or greater than 200 mass% with respect to the mass of entire solid contained in the flexible film (1) is removed from the flexible substrate (34).

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a polarizing plate, and a polarizing plate and a liquid crystal display device using the polarizing plate and the polarizing plate,

The present invention relates to a production method of an optical film that can be used as a protective film of a polarizing plate or the like, an optical film, a polarizing plate comprising the optical film, and a liquid crystal display device.

BACKGROUND ART Liquid crystal display devices are in increasing demand for applications such as liquid crystal televisions and liquid crystal displays for personal computers. Generally, a liquid crystal display device is composed of a liquid crystal cell in which a transparent electrode, a liquid crystal layer, a color filter or the like is sandwiched between glass plates, and two polarizing plates formed on both sides of the liquid crystal cell. The polarizing plate includes a polarizer and at least one polarizing plate protective film Respectively.

Recent advances in technology have accelerated the enlargement of liquid crystal display devices, and the use of liquid crystal display devices has diversified, and their use under various circumstances has been assumed, and it is required to respond to environmental problems. For example, when a liquid crystal display device is used outdoors, deterioration due to moisture absorption of the polarizer becomes a problem. Therefore, for the polarizing plate protective film covering the surface of the polarizer, lowering the moisture permeability is an important issue.

As a low moisture permeable film, a film ((meth) acrylic resin film) formed of a (meth) acrylic resin such as polymethyl methacrylate (PMMA) is known. On the other hand, it is known that acrylic resins generally have poor brittleness. In order to improve the brittleness, rubber particles have been incorporated into resins (Patent Documents 1 to 5, etc.).

In Patent Documents 1, 2 and 3, a single-layer acrylic resin film having acrylic rubber particles in a resin has been proposed, and in Patent Documents 4 and 5, an acrylic resin multilayer film having different filling ratios of acrylic rubber particles has been proposed. Patent Document 3 discloses that by providing acrylic rubber particles on an ellipsoid in the methacrylic resin, it is possible to improve the brittleness of the rubber of the particle diameter.

International Publication No. 2005-105918 Japanese Patent Application Laid-Open No. 2005-314534 Japanese Laid-Open Patent Publication No. 2011-88946 Japanese Laid-Open Patent Publication No. 2010-5944 Japanese Laid-Open Patent Publication No. 2011-31499

When the rubber particles are added to the resin, the brittleness is improved. However, as the addition ratio of the rubber particles increases, the transparency deteriorates and the heat resistance decreases due to plasticization. In optical applications such as polarizing plate protective films, the haze value, which is an index of transparency of the film, is preferably as small as possible, and the glass transition temperature (Tg), which is an index of heat resistance, is preferably as high as possible. The heat resistance of the film is important in terms of long-term reliability as an optical member and in ease of manufacture.

Therefore, it is desired to improve the brittleness while keeping the haze value small, the surface hardness, and the glass transition temperature high.

Patent Document 1 discloses that brittleness can be further improved by containing ellipsoidal rubber particles rather than using generally spherical rubber particles. By making a film containing ellipsoidal rubber particles, It is considered that it becomes possible to make the content ratio of the rubber particles smaller than that of the particles. In the method described in Patent Document 1, a method of stretching a film at an appropriate stretching magnification is exemplified as a method of forming a desired ellipsoidal shape of the rubber particles contained in the film. However, in the stretching step, Therefore, if the stretching process becomes unnecessary, more efficient production of the film can be carried out.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an optical film having improved haze value, surface hardness, balance between glass transition temperature and brittleness, .

It is another object of the present invention to provide a polarizing plate and a liquid crystal display device provided with the above optical film.

The method for producing an optical film is characterized in that the dope composition A and the dope composition B containing the rubber particles, the thermoplastic resin and the organic solvent are mixed so that the mass of the rubber particles with respect to the mass of the thermoplastic resin contained in the dope composition B The content of the rubber particles in the dope composition A is 5 mass% or more and 30 mass% or less with respect to the mass of the thermoplastic resin, and the content of the rubber particles in the dope composition A By mass based on the mass of the thermoplastic resin, so that the content is 4% by mass or more and 9%

A step of simultaneously or sequentially laminating the dope compositions A and B onto the flexible substrate in the order of A-B, B-A or B-A-B to form a flexible film,

And removing the organic solvent of 200 mass% or more with respect to the mass of the total solid content contained in the flexible film on the flexible substrate.

Here, the rubber particles, the thermoplastic resin and the organic solvent contained in the dope composition A and the dope composition B are preferably of the same species, but they are not necessarily the same species. The thermoplastic resin contained in both of the compositions A and B may be a resin of the same species that has a different weight average molecular weight. The rubber particles contained in both of the compositions A and B may have different average particle diameters.

Mass of total solid content contained in the flexible film " is the sum of the solid masses of the rubber particles and the thermoplastic resin, including the dope composition A and the dope composition B contained in the flexible film.

The thermoplastic resin may be an acrylic resin having a weight average molecular weight of 250,000 or more and 2,000,000 or less.

The optical film of the present invention is produced by the production method of the present invention.

Here, the rubber particle is a flat spherical shape obtained by compressing spherical particles in the film thickness direction, and the relation between the diameter a in the film thickness direction when viewed in cross section in the film thickness direction and the diameter b in the direction perpendicular to the film thickness direction Is b / a > 1.1. b / a is more preferably 1.2 or more, and still more preferably 1.4 or more.

The polarizing plate of the present invention comprises a polarizer and an optical film of the present invention on at least one surface of the polarizer.

The liquid crystal display of the present invention has a pair of polarizing plates and a liquid crystal cell sandwiched between a pair of polarizing plates, and at least one of the pair of polarizing plates is the polarizing plate of the present invention.

According to the optical film production method, the dope composition A and the dope composition B containing the rubber particles, the thermoplastic resin and the organic solvent are mixed so that the mass of the rubber particles with respect to the mass of the thermoplastic resin contained in the dope composition B The content of the rubber particles in the dope composition A is 5 mass% or more and 30 mass% or less with respect to the mass of the thermoplastic resin, and the content of the rubber in the dope composition A is less than the mass of the rubber particle in relation to the mass of the thermoplastic resin And the content of the particles is 4 mass% or more and 9 mass% or less with respect to the mass of the thermoplastic resin, and the dope compositions A and B are simultaneously or sequentially fused on the flexible substrate in the order of AB, BA or BAB A flexible film is formed, and in a state in which the surface direction of the flexible film is fixed on the flexible substrate, the total solid content Since the removal of more than 200% by mass of an organic solvent for the amount, yuyeonmak is reduced in the thickness direction, and at this time, the rubber particles in the thermoplastic resin is a compressed shape in the thickness direction. Since the rubber particles become flatter than the shape in the dope composition, the brittleness can be increased even when the same amount of rubber particles is added as compared with the case where the rubber particles are added to the layer while keeping the original shape, so that the addition amount of the rubber particles can be reduced As a result, it is possible to produce an optical film having good haze and high surface hardness.

1 is a schematic view showing one embodiment of a production line of a polarizing plate protective film.
2 is a schematic view for explaining a method for producing an optical film according to an embodiment of the present invention.
3 is a schematic view showing a configuration of a liquid crystal display device according to an embodiment of the present invention.
4 is a cross-sectional view in the thickness direction showing the configuration of the polarizing plate of one embodiment related to the present invention.
5 is a graph showing a preferable range of the rubber particle addition amount.

Hereinafter, the present invention will be described in detail.

The constituent elements described below are described based on representative embodiments and concrete examples, but the present invention is not limited to such embodiments.

[Production method of optical film]

The method for producing an optical film of the present invention is characterized in that the dope composition A containing the rubber particles, the thermoplastic resin and the organic solvent and the dope composition B are mixed so that the mass of the rubber particle with respect to the mass of the thermoplastic resin contained in the dope composition B is larger than the mass of the dope composition A The content of the rubber particles in the dope composition A is 5 mass% or more and 30 mass% or less with respect to the mass of the thermoplastic resin, and the content of the rubber particles in the dope composition A Wherein the content of the rubber particles is 4 mass% or more and 9 mass% or less with respect to the mass of the thermoplastic resin; and a step of mixing the dope compositions A and B in the order of AB, BA or BAB simultaneously or sequentially Forming a flexible film on the flexible substrate; and a step of forming a flexible film on the flexible substrate in such a manner that 200 mass% of the total solid content contained in the flexible film Of a step of removing the organic solvent. This production method is a film production method by the solution softening method.

As described above, the method for producing an optical film of the present invention includes at least a step of preparing a dope composition, a step of forming a flexible film, and a step of removing a solvent.

After the solvent removal step, the flexible film from which the solvent has been removed is peeled off from the flexible substrate to obtain a film. After the peeling step, if necessary, the peeled film is further dried to remove residual solvent (volatile matter) The drying step may be performed.

Hereinafter, each process will be described.

Fig. 1 is a schematic view showing one embodiment of a production line of a polarizing plate protective film, in which these steps can be carried out continuously. However, the film production line used in the production method of the present invention is not limited to those shown in Fig. Further, in the production line of this film, a certain amount of the organic solvent is removed from the flexible film, and the film is peeled off from the flexible substrate to obtain a film "magnetic support film" having self-supporting property. Further, The optical film in the present invention includes a magnetic support film and a film obtained after the peeling process.

The film production line 20 shown in Fig. 1 is provided with the stock tanks 21A and 21B, the filtration devices 30A and 30B, the flexible die 31, the flexible substrate 34 spread over the rotating rollers 32 and 33, Dryer 35 and the like. Further, an edge cutting device 40, a drying chamber 41, a cooling chamber 42, a winding chamber 43, and the like are disposed.

The stock tanks 21A and 21B are equipped with agitators 61A and 61B which are rotated by motors 60A and 60B. The stock tanks 21A and 21B are connected to the flexible die 31 via the pumps 62A and 62B and the filtration devices 30A and 30B.

The width of the flexible die 31 is preferably 1.1 to 2.0 times the width of the film to be a final product.

On the lower side of the flexible die 31, a flexible substrate 34 made of a metal support spread over the rotating rollers 32 and 33 is formed. The rotating rollers 32 and 33 are rotated by a driving device (not shown), and the flexible substrate 34 travels with this rotation.

It is preferable that the heating medium circulating device 63 is mounted on the rotating rollers 32 and 33 in order to set the surface temperature of the flexible substrate 34 to a predetermined value. It is preferable that the flexible substrate 34 can adjust its surface temperature to -20 ° C to 40 ° C.

The width of the flexible substrate 34 is preferably 1.1 to 2.0 times the flexible width of the flexible film 1. It is preferable that the length is 20 m to 200 m, the film thickness is 0.5 mm to 2.5 mm, and the surface roughness is polished to 0.05 m or less. The flexible substrate 34 is preferably made of stainless steel, and more preferably made of austenitic stainless steel (made of SUS316) so as to have sufficient corrosion resistance and strength. It is preferable that the film thickness irregularity of the entirety of the flexible substrate 34 is 0.5% or less.

The flexible die 31, the flexible substrate 34, and the like are accommodated in the flexible chamber 64. The flexible chamber 64 is provided with a temperature control unit 65 for maintaining the internal temperature at a predetermined value and a condenser (condenser) 66 for condensing and recovering the volatilized organic solvent. A recovery device 67 for recovering the condensed and liquefied organic solvent is formed outside the flexible chamber 64. It is preferable that a decompression chamber 68 for controlling the pressure of the back side of the flexible bead formed from the flexible die 31 to the flexible substrate 34 is disposed, and this is also used in the present embodiment.

Vents 70, 71, 72, and 73 are formed near the circumferential surface of the flexible substrate 34 to evaporate the solvent in the flexible film 1.

A blower 81 is provided in the transferring section 80 and the debris of the side end portion (referred to as the edge) of the cut film 3 is cut into small pieces in the edge cutting device 40 downstream of the tenter dryer 35 The crusher 90 is connected.

In the drying chamber 41, a plurality of rollers 91 are provided, and an adsorption recovery device 92 for adsorbing and recovering solvent gas generated by evaporation is mounted. A forced static electricity removing device (static electricity removing device) (a static electricity removing device) for adjusting the voltage of the film 3 to a predetermined range (for example, -3 kV to +3 kV) is provided downstream of the cooling chamber 42 93 are formed. Further, in this embodiment, a knurling imparting roller 94 for appropriately knurling knurling is formed at both edges of the film 3 downstream of the forced static electricity removing device 93. [ A winding roller 95 for winding the film 3 and a press roller 96 for controlling the tension at the time of winding the film 3 are provided in the winding chamber 43.

Next, an example of a method for manufacturing the film 3 using the above-described film production line (referred to as a band production apparatus) 20 will be described below.

(1) Dope preparation process

The dope-preparing step is a step of dissolving a resin and an additive in an organic solvent mainly composed of a good solvent for a thermoplastic resin while stirring in a dissolving furnace and adding rubber particles to form a dope, or a step of mixing the additive solution with a resin solution , And further adding rubber particles to form a dope. The dope preparation is carried out in a separate preparation device separate from the band production device, and the prepared dope composition is injected into the stock tank of the band production device.

The details of the material of the dope composition will be described later.

Here, the dope composition A and the dope composition B are prepared so that the mass of the rubber particle with respect to the mass of the thermoplastic resin contained in the dope composition B becomes smaller than the mass of the rubber particle with respect to the mass of the thermoplastic resin contained in the dope composition A . The mass of the rubber particles to the thermoplastic resin contained in the dope composition B is preferably 1% by mass or less, more preferably 2% by mass or more, more preferably 2% by mass or more, It will be smaller.

The content of the rubber particles in the dope composition A is 5 mass% or more and 30 mass% or less with respect to the mass of the thermoplastic resin, and the content of the rubber particles in the dope composition B is 4 mass% Or more and 9 mass% or less. The content of the rubber particles in the dope composition A is 7 mass% or more and 15 mass% or less with respect to the mass of the thermoplastic resin, and the content of the rubber particles in the dope composition B is 4 mass% or more By mass or less.

1, the dope composition 22A being stirred in the stock tank 21A is the above-described dope composition A and the dope composition 22B stirred in the stock tank 21B is the dope composition B.

The dope composition 22A and the dope composition 22B are preferably prepared at a temperature of 0 ° C or higher (room temperature or high temperature). The dope compositions 22A and 22B can be prepared by using a method and apparatus for preparing dope in an ordinary solvent casting method.

The dissolution of the thermoplastic resin may be carried out at normal pressure, a method of carrying out the polymerization at a boiling point or less of the main solvent, a method of carrying out pressurization at a boiling point or more of the main solvent, JP-A 9-95544, JP 9-95544 -95557 or the cooling dissolution method as disclosed in Japanese Patent Application Laid-Open No. 9-95538, and the method of carrying out at a high pressure as disclosed in Japanese Patent Application Laid-Open No. 11-21379 Can be used. From the viewpoint of the dissolution efficiency, a method of stirring under heating, particularly under pressure, at a temperature not lower than the boiling point of the main solvent at atmospheric pressure, and at a temperature not boiling the solvent is preferred.

The temperature at the time of heating is usually 40 占 폚 or higher, preferably 60 to 200 占 폚, and more preferably 80 to 110 占 폚.

The dope composition 22A and the dope composition 22B are always homogenized by the rotation of the agitators 61A and 61B, respectively. To the dope compositions 22A and 22B, additives such as a retardation developing agent, a plasticizer, and an ultraviolet absorber may be mixed at the time of stirring.

(2) Flexible process

The fusing step is a step of forming the flexible film 1 by softening the above-described dope compositions 22A and 22B on the flexible substrate 34. [ The dope compositions 22A and 22B are delivered to the filtration devices 30A and 30B by pumps (for example, pressurized metering gear pumps) 62A and 62B, And is flexible on the flexible substrate 34.

Flexible beads are formed from the flexible die 31 to the flexible substrate 34 and the flexible film 1 is formed on the flexible substrate 34. [ The temperature of the dope compositions 22A and 22B at the time of softening is preferably -10 ° C to 57 ° C.

The flexible film 1 moves as the flexible substrate 34 moves. As the flexible die 31, it is preferable to use a pressure die which can adjust the slit shape of the nipping portion and make the film thickness uniform. The pressure die includes a coat hanger die and a T die, all of which are preferably used.

The dope composition 22A and the dope composition 22B are applied in this order from the side of the flexible substrate 34 to the dope compositions 22A and 22B or in the order of the dope compositions 22B and 22A , Or the dope compositions 22B, 22A, and 22B are formed in this order by a covalent bonding method in this order.

At this time, in order to form the flexible film 1 having a laminated structure, any of the simultaneous laminated shared lamination and the sequential lamination shared lamination may be employed. When carrying out the simultaneous lamination sharing process, a flexible die equipped with a feed block may be used, or a multi-manifold type flexible die may be used.

(3) Organic solvent removal process

Next, the flexible film 1 is continuously conveyed to the point where the air outlets 70 to 73 are disposed. The dry wind is blown toward the flexible film 1 from the blowing openings 70 to 73 so that at least 200 mass% or more of the solvent contained in the flexible film 1 in the flexible film 1 is evaporated ). At the time of transporting the flexible film 1, it is preferable to heat the flexible substrate 34 supporting the flexible film 1 to promote evaporation of the organic solvent.

The volatilization amount of the organic solvent is more preferably 250 mass% or more, and more preferably 350 mass% or more, with respect to the mass of the total solid content in the flexible film (1). Incidentally, of course, the dope composition initially prepared contains an organic solvent which evaporates as described above.

As a method of evaporating the solvent, there are a method of blowing wind on the surface of the flexible film and / or a method of heating the flexible substrate as described above. As a method of heating the flexible substrate, A method in which heat is transferred from the front and rear sides by radiant heat, and the like. However, the method of transferring the liquid on the back surface is preferable because the drying efficiency is good. It is also preferable to combine them. In the case of carrying out the liquid heat transfer from the back side of the flexible substrate, it is preferable to heat the liquid at a boiling point or lower of the main solvent of the organic solvent or the organic solvent having the lowest boiling point.

2 is a diagram schematically showing the change of the flexible film in a part of the production line of the optical film. 2 is a flexible film 1 immediately after being softened from a flexible die, and the right drawing shows the magnetic supporting film 2 after the organic solvent removing step. In each drawing, the top view is a cross-sectional view and the bottom view is a top view.

The dope composition 22B, the dope composition 22A, and the dope composition 22B, which contain the rubber particles 6, the thermoplastic resin 7 and the organic solvent 8, respectively, from the side of the flexible substrate 34, A flexible film 1 is formed. At this time, the rubber particles 6 contained in the dope compositions 22A and 22B have the same spherical shape as that in the dope composition. The thickness of each layer of the dope composition layer 22A (hereinafter referred to as A layer) and the layer comprising the dope composition 22B (hereinafter referred to as B layer) can be suitably set. For example, 40 占 퐉 to 800 占 퐉 and the thickness of the B layer is preferably 2 占 퐉 to 150 占 퐉.

The flexible film may be a two-layered flexible film in which the A layer and the B layer are stacked one by one. Even in the case of a two-layer structure or a three-layer structure, the thickness of the B layer is preferably in the range of about 4 to 40% of the total thickness of the flexible film 1. The B layer is more preferably about 10 to 25% of the total thickness. In the case of the three-layer structure, the B layer is allocated on both sides of the A layer in the above-mentioned preferable proportion of the dope composition. Layer structure in which the B layer is disposed at the same thickness with the A layer interposed therebetween from the viewpoint of suppressing the curl at the time of manufacturing.

The organic solvent 8 of 200 mass% or more with respect to the mass of the total solid content contained in the flexible film 1 in the solvent in the flexible film 1 is removed in a state where the flexible film 1 is fixed on the flexible substrate 34, As shown in the cross-sectional view of the right side view of Fig. 2, the flexible film 1 is a wet film containing a residual organic solvent to a certain extent and becomes a magnetic supporting film 2 having self-supporting property. At this time, along with the reduction of the thickness of the flexible film, a compressive force acts on the rubber particles in the thickness direction, and the rubber particles are flattened by squeezing in the thickness direction. In addition, the larger the evaporation amount of the organic solvent 8, the higher the flatness of the rubber particles and the better the embrittlement.

As shown in the plan view of each step in Fig. 2, spherical rubber particles 6 are flattened from above the flexible film (magnetic supporting film), and spherical particles 6A ). When spherical rubber particles 6 are added to the dope composition, the diameters (in this case, the short diameter) a in the film thickness direction of the spherical spherical particles 6A and the diameters in the direction perpendicular to the film thickness direction ) b, it is preferable that the flatness satisfies b / a > 1.1. More preferably, b / a is 1.2 or more, and more preferably 1.4 or more. By setting the removal amount of the organic solvent to 200 mass% or more with respect to the mass of the total solid content in the flexible film 1, b / a > 1.1 can be achieved.

The flatness b / a > 1.1 of the rubber particles may be satisfactory in the optical film at the time of the completion of the production. In the tentering process, after drying in a state in which the width direction and the transport direction of the self- The flatness may be satisfied.

Since the time required to remove a desired amount of solvent from the flexible film on the flexible substrate differs depending on the strength of the drying condition and the length of the flexible substrate, the relationship between the drying time of the dope composition and the solvent removal amount is examined in advance, It is preferable to set the time to a desired amount of solvent removal.

The removal amount of the organic solvent from the flexible film on the flexible substrate is defined by the following formula.

Amount of organic solvent removed (mass%) = Amount of organic solvent (mass%) at the time of preparing the dope composition - Amount of organic solvent (mass%) contained in the flexible film after peeling from the flexible substrate,

(Mass%) = [organic solvent (mass) / total solid component (mass)]] × 100

(Mass%) contained in the flexible film after peeling from the flexible substrate = [(M - N) / N] 100

Here, M is the mass of the sample cut from the flexible film at the time of peeling the flexible film from the flexible substrate to a size of 50 mm x 50 mm, and N is the mass after the sample having the mass M is dried at 140 DEG C for 2 hours . N is a state in which almost all the organic solvent is evaporated and can be regarded as the mass of the total solid content in the flexible film.

In addition to the thermoplastic resin and the rubber particles, the total solid component includes the additive materials described later.

(4) Peeling process

The peeling step is a step of evaporating a predetermined amount of the organic solvent from the flexible film 1 and then peeling off the flexible substrate 34 to obtain a film. The flexible film 1 is supported by the peeling roller 75 as the magnetic supporting film 2 at the stage where the film becomes a film having a self-supporting property (self supporting film) as a result of evaporation of a certain degree of solvent, 34). Further, the peeled magnetic support film 2 is transferred to the next step. If the amount of the organic solvent in the flexible film (self-supporting film) at the time of peeling is too large, the film is not peeled off. On the contrary, if the film is excessively dried on the flexible substrate and peeled off, part of the film is peeled off during transportation.

The separation of the flexible film 1 (the magnetic support film 2) from the flexible substrate is carried out in a range of 5 to 150 mass% with respect to the mass of the total solid content in the film in the amount of the organic solvent (residual solvent amount) , More preferably in the range of 10 to 140 mass%.

(5) drying step (heat treatment step), stretching step

The peeled magnetic support film 2 is conveyed to a tenter dryer (35) by a conveying section (80) in which a plurality of rollers are formed. In the transfer unit 80, the drying of the magnetic supporting film 2 is advanced by blowing the drying air of the desired temperature from the blower 81. At this time, the temperature of the drying wind is preferably 20 ° C to 250 ° C.

It is preferable that the tenter dryer 35 has a holding member (for example, a clip) for gripping the both side ends of the magnetic supporting film 2 and a zone having a different temperature. In the inside of the tenter dryer 35, the residual solvent is volatilized and further dried while the both side ends of the magnetic support film 2 are grasped and conveyed by the holding members. It is preferable that the inside of the tenter dryer 35 is formed by forming a zone of different temperature and drying while adjusting drying conditions.

The means for drying is generally to blow hot air on both surfaces of the magnetic support film 2, but there is also a means for heating and drying by microwaving instead of wind. The temperature, air volume and time vary depending on the solvent used, and the conditions may be suitably selected depending on the type and combination of the solvent to be used.

The amount of the residual solvent in the film of the magnetic support film 2 in the transfer section 80 and / or the tenter dryer 35 is preferably 3.0 mass% or less, more preferably 1.0 mass% or less, Is preferably 0.5 mass% or less, more preferably 0.3 mass% or less, and particularly preferably 0.2 mass% or less. At this time, it is preferable that the film thickness is 10 to 200 占 퐉, more preferably 10 to 150 占 퐉, more preferably 10 to 100 占 퐉, and even more preferably 10 to 60 占 퐉 .

In the conveying section 80 and / or the tenter dryer 35, the magnetic supporting film 2 is formed in a width direction (transverse direction direction, TD direction) perpendicular to the conveying direction (Machine Direction direction, MD direction) . Although stretching is not required in the process simplification, it is preferable to perform the stretching when it is necessary to obtain a specific film, such as obtaining a better surface. By stretching in the width direction, nonuniformity occurring during drying on the flexible substrate and peeling off from the flexible substrate can be reduced to obtain a good surface in the film plane. The draw ratio in the width direction is preferably 10% or more, more preferably 20% or more, further preferably 30 to 80%, particularly preferably 40 to 60%.

The stretching in the carrying direction can be carried out by causing the magnetic supporting film 2 to be subjected to draw tension in the carrying direction by making the rotational speed of the downstream side roller higher than the rotational speed of the upstream side roller in the transfer portion 80.

The stretching magnification in stretching in the carrying direction is preferably 30 to 80%, particularly preferably 40 to 60%. The stretching magnification (elongation) of the coherent film at the time of stretching can be achieved by the speed difference between the metal support speed and the peeling speed (peeling roll). For example, in the case of using a device having two nip rolls, the film can be preferably stretched in the transport direction (longitudinal direction) by increasing the rotation speed of the exit-side nip roll than the rotation speed of the entrance-side nip roll.

In the case of biaxial stretching, it is preferable to perform the stretching treatment in the order of the transport direction and the width direction.

The term " draw ratio (x) " as used herein means to be obtained by the following formula.

Drawing magnification (times) = length after stretching / length before stretching

Alternatively, after the magnetic support film 2 is first stretched, it is dried in the conveyance unit 80 and / or the tenter dryer 35 May be carried out. However, it is preferable that the film used for stretching is an infiltration film having a residual solvent amount of more than 3% by mass. Therefore, it is preferable to conduct the stretching before or simultaneously with the drying process by the tenter dryer.

However, in the method for producing an optical film of the present invention, it is not necessary to provide the stretching step. If the stretching step is not required, the apparatus configuration can be simplified and the number of steps can be reduced, And easiness of manufacturing can be achieved.

The magnetic support film 2 is dried until the residual solvent amount reaches a predetermined residual solvent amount in the tenter dryer 35, and then is sent to the downstream side as the film 3. Both side edges of the film 3 are cut off at both edges by the edge cutting device 40. The cut side end portion is conveyed to the crusher 90 by a cutter blower (not shown). By the crusher 90, the film side end portion is crushed to become a chip. Since this chip is reused for preparing the dope composition, this method is cost effective. The step of cutting both ends of the film may be omitted, but it is preferable to carry out the step from the above-described fusing step to the above-mentioned step of winding the film.

The film (3) whose both side ends are cut off is conveyed to the drying chamber (41) and further dried. The temperature in the drying chamber 41 is preferably in the range of 50 캜 to 160 캜. In the drying chamber 41, the film 3 is transported while being wound around the rollers 91. Here, the solvent gas generated by the evaporation is adsorbed and recovered by the adsorption recovery device 92. The air from which the solvent component has been removed is again blown into the drying chamber 41 as dry air. It is more preferable that the drying chamber 41 is divided into a plurality of compartments in order to change the drying temperature.

The film (3) is cooled in the cooling chamber (42) to approximately room temperature. Further, a humidity control chamber (not shown) may be provided between the drying chamber 41 and the cooling chamber 42. In the case of providing this humidity control chamber, it is preferable to spray the film 3 with air adjusted to a desired humidity and temperature. This makes it possible to suppress the occurrence of curling of the film (3) or occurrence of winding failure at the time of winding.

Further, in the present invention, it is preferable to form the nulling roller 94 and impart knurling to at least one end of the film 3 by embossing. The width of the knurling is preferably from 3 mm to 50 mm, more preferably from 5 mm to 30 mm, and the height is preferably from 0.5 to 500 占 퐉, and more preferably from 1 to 200 占 퐉. This may be nulling only one side, or nulling both sides.

(6) Coiling

Finally, the film 3 is wound by the winding roller 95 in the winding chamber 43. At this time, it is preferable that the press roller 96 is wound while applying a desired tension. It is more preferable that the tension is gradually changed from the start of winding to the end of winding. The length of the film thus obtained is preferably 100 to 10000 m per roll, more preferably 500 to 7000 m, and still more preferably 1000 to 6000 m. The width of the film is preferably 0.5 to 5.0 m, more preferably 1.0 to 3.0 m, and further preferably 1.0 to 2.5 m.

The optical film can be obtained as described above.

From a flexible die, a decompression chamber, and a flexible substrate made of a metal support, etc., from shared drawing, stripping, drawing, drying, handling, curl and planarity after winding to solvent recovery and film recovery Are described in detail in [0617] and [0889] paragraphs of Japanese Patent Application Laid-Open No. 2005-104148.

In the above, an example of the method of producing the optical film of the present invention is described as an example in which the dope composition is plied onto the metal support in the casting step. However, even when the dope composition is softened on the drum in the casting step, Respectively. In this case, the apparatus and the manufacturing conditions described in JP-A-2013-82192 are preferably used.

Materials constituting the dope composition used in the method for producing an optical film of the present invention will be described.

<< Rubber particles >>

The dope composition of the present invention contains rubber particles in order to improve brittleness and impact resistance. The dope composition preferably contains rubber elastic particles at a ratio of 4 to 30 parts by mass with respect to 100 parts by mass of the polymer, more preferably 4 to 15 parts by mass. When the addition amount is 4 parts by mass or more, a sufficient improvement effect can be obtained with respect to the brittleness and impact resistance, and if it is 30 parts by mass or less, the transparency of the optical film is not impaired.

As the rubber particles, rubber particles composed of an acrylic resin can be preferably used. As the rubber particles, for example, commercially available ones can be used. Specific examples thereof include Metablen W-341 (C2) manufactured by Mitsubishi Rayon Co., Ltd., "Kane Ace (registered trademark)" manufactured by Kanegafuchi Kagaku Kogyo Co., "Paraloid" manufactured by Kagaku Kogyo Co., "Acryloid" manufactured by Rohm and Haas, "Staphyloid" manufactured by Gansu Chemical Industry Co., Ltd. and "Parapet (registered trademark) SA" manufactured by Kuraray Co., These may be used alone or in combination of two or more. These rubber particles are basically spherical, but the shape of the rubber particles in the present invention is not necessarily limited to a spherical shape, but may be an ellipsoid, a rugby fugu, or a round shape. According to the production method of the present invention, the rubber particles are compressed in the film thickness direction in accordance with the volatilization of the solvent, so that the rubber particles become flatter than the shape in the dope composition, , The brittleness can be increased even when the same amount of the rubber particles is added, so that the effect of reducing the amount of rubber particles to be added can be obtained.

The particle size of the rubber elastic particles preferably used in the present invention is not particularly limited, but is preferably 10 nm or more and 10 占 퐉 or less, more preferably 20 nm or more and 1 占 퐉 or less, particularly 50 nm or more, And most preferably 400 nm or less.

<< Thermoplastic Resin >>

Regardless of the type of the resin to be added, the effect of improving the brittleness due to the addition of the rubber particles can be obtained. As the resin of the resin composition of the present invention, a resin suitable for film production by the solution casting method do.

As such a resin, a cellulose ester resin, an acrylic resin, a polycarbonate resin, or a cycloolefin resin is preferably exemplified.

Among them, an acrylic resin is most preferably used in the present invention because it is excellent in transparency and low moisture permeability.

In the present invention, the resin to be used may be only one type of resin, but may be a resin obtained by blending plural kinds of resins. In addition to the above-mentioned preferable resin, the resin of the additive component may be contained within a range not hindering the effect of the present invention.

The acrylic resin preferably contains a structural unit derived from methyl methacrylate, and may or may not contain a structural unit derived from an alkyl (meth) acrylate other than methyl methacrylate.

In the acrylic resin, the content ratio of the structural units derived from methyl methacrylate is preferably 95% by mass or more, more preferably 97% by mass or more, and more preferably 100% by mass or more, in view of sufficiently exhibiting the effects of the present invention including heat resistance. More preferably, it is in mass%.

Examples of the alkyl (meth) acrylates other than methyl methacrylate include acrylic acid esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, cyclohexyl acrylate, Alkyl acrylate preferably having 1 to 18 carbon atoms in the alkyl group); Methacrylic acid esters such as ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate and the like An alkyl methacrylate in which the alkyl group has 2 to 18 carbon atoms); These may be used alone or in combination of two or more.

Methyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate and the like are preferable, and methyl acrylate and n-butyl acrylate are particularly preferably used from the viewpoints of thermal decomposition resistance and fluidity of the copolymer .

The acrylic resin used in the present invention may contain a structural unit other than those described above. Examples of such structural units include unsaturated carboxylic acid containing an unsaturated group such as an?,? - unsaturated acid such as acrylic acid and methacrylic acid, maleic acid, fumaric acid and itaconic acid, aromatic vinyls such as styrene and? Compounds,?,? -Unsaturated nitriles such as acrylonitrile and methacrylonitrile, maleic anhydride, maleimide, N-substituted maleimide and glutaric anhydride. These constituent units may be introduced singly into the acrylic resin, or may be introduced into the acrylic resin in combination of two or more.

When an acrylic resin is used as the resin, examples of the resin that may be contained as an additive component include olefinic thermoplastic resins such as polyethylene, polypropylene, ethylene-propylene copolymer and poly (4-methyl-1-pentene); Halogen-based thermoplastic resins such as vinyl chloride and vinyl chloride resin; Acrylic thermoplastic resins such as methyl polymethacrylate; Styrene-based thermoplastic resins such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, and acrylonitrile-butadiene-styrene block copolymer; Polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; Polyamides such as nylon 6, nylon 66 and nylon 610; Polyacetal; Polycarbonate; Polyphenylene oxide; Polyphenylene sulfide; Polyether ether ketone; Polysulfone; Polyethersulfone; Polyoxybenzylene; Polyamideimide; Polybutadiene rubber, rubber polymers such as ABS resin and ASA resin in which an acrylic rubber is blended, and the like. When a resin other than the acrylic resin is added to the acrylic resin composition, the added resin may be in a compatible state or may be mixed without dissolution.

The acrylic resin preferred in the resin composition of the present invention is commercially available and can be obtained by a synthetic method using known emulsion polymerization, solution polymerization, bulk polymerization, suspension polymerization and the like. Among these polymerization methods, emulsion polymerization and suspension polymerization are preferred. In the case of the suspension polymerization, as the initiator, those used for ordinary suspension polymerization can be used, and examples thereof include organic peroxides and azo compounds. As the suspension stabilizer, known ones which are commonly used can be used, and examples thereof include organic colloidal polymer materials, inorganic colloidal polymer materials, inorganic fine particles, and combinations of these with surfactants.

(Weight average molecular weight of acrylic resin)

In the case of using an acrylic resin as the resin, the weight average molecular weight of the acrylic resin is not particularly limited, but in order to fully exhibit the effect of the present invention, the weight average molecular weight of the acrylic resin is preferably 250,000 to 2,000,000, More preferably from 1 million to 2 million, and even more preferably from 1 million to 2 million. The acrylic resin having such a weight average molecular weight range is larger than the weight average molecular weight of the acrylic resin used in the production of a molten film and is suitable for producing a solution film.

When the weight average molecular weight (Mw) of the acrylic resin is 250,000 or more, the amount of the organic solvent at the time of preparing the dope can be sufficiently increased. The weight average molecular weight (Mw) of the acrylic resin is preferably 2,000,000 or less in view of the polymerization process.

In the present invention, the "weight average molecular weight (Mw)" is a weight average molecular weight measured by gel permeation chromatography under the following conditions.

Solvent tetrahydrofuran

Device name TOSOH HLC-8220GPC

Three columns of TOSOH TSKgel Super ㎐ M-H (4.6 mm x 15 cm) were connected

           use.

Column temperature 25 ° C

Sample concentration 0.1 mass%

Flow rate 0.35 ml / min

Calibration curve TSK standard polystyrene manufactured by TOSOH Mw = 2800000 ~ 1050

           Using a calibration curve with 7 samples of.

The content of the solid content (sum of the resin, rubber particles, and additives to be added as required) in the dope composition is preferably 10% by mass or more and 40% by mass or less based on 100% by mass of the total mass of the dope composition , More preferably 10 mass% or more and 30 mass% or less, still more preferably 15 mass% or more and 25 mass% or less. With such a content, it is possible to obtain a dope composition having a desired viscosity, which can obtain a film having a desired film thickness with a desired film thickness unevenness suppressed in its surface shape in the production of a solution film. When an acrylic resin is used as the resin, when the content of the solid content is set at 22 mass% or less, film separation from the support can be facilitated by using an alcohol described later as a solvent.

Hereinafter, embodiments of the dope composition are exemplified in the case of an acrylic resin composition using an acrylic resin excellent in transparency and low moisture permeability as a resin, but the resin of the resin composition is limited to an acrylic resin no.

<< Organic solvent >>

The solvent used in the dope composition is not particularly limited so long as it dissolves the rubber particles and the thermoplastic resin. However, it is preferable that the solvent is a solvent in which additives and the like to be added as needed are dispersed or dissolved well.

The amount of the organic solvent in the dope composition depends on the weight average molecular weight of the thermoplastic resin. In order to form a flexible film, the viscosity of the dope composition is preferably 1 to 100 Pa s, , More preferably from 20 to 80 Pa s. The amount of the organic solvent in the dope composition is required to be small as the thermoplastic resin is a low-molecular-weight material and as high as possible to become a polymer. In the present invention, it is necessary to remove at least 200% by mass of the total solid content of the organic solvent in the flexible film. Therefore, it is necessary that the dope composition contains the organic solvent.

For example, in the case of using an acrylic resin having a weight average molecular weight of 250,000 to 2,000,000, it is preferable to use an organic solvent in an amount of about 210 to 900% by mass with respect to the mass of all solids in the film.

When the thermoplastic resin is an acrylic resin, any of chlorine-based solvents containing chlorine-based organic solvents as the main solvent and non-chlorine-based solvents containing no chlorine-based organic solvent may be used as the organic solvent. Two or more kinds of organic solvents may be mixed and used. Here, the main solvent is the solvent having the largest weight ratio among the solvents contained in the dope composition.

When the thermoplastic resin is an acrylic resin, a chlorinated organic solvent is preferably used as the main solvent. In the present invention, the kind of the chlorinated organic solvent is not particularly limited so long as the acrylic resin and the additive contained in the acrylic resin composition can be dissolved and formed into a flexible film. These chlorinated organic solvents are preferably dichloromethane and chloroform. In particular, dichloromethane is preferred.

In addition, it is not particularly problematic to mix an organic solvent other than the chlorinated organic solvent. In this case, it is necessary to use at least 50 mass% of dichloromethane in the total amount of the organic solvent. Other organic solvents used in combination with the chlorinated organic solvent in the present invention are described below. That is, preferred examples of the other organic solvent include a solvent selected from esters, ketones, ethers, alcohols and hydrocarbons having 3 to 12 carbon atoms. The esters, ketones, ethers and alcohols may have a cyclic structure. A compound having at least two functional groups (that is, -COO-, -CO- and -O-) of ester, ketone and ether can be used as a solvent. For example, a compound having two or more functional groups such as an alcoholic hydroxyl group do. In the case of a solvent having two or more kinds of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.

Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, and pentyl acetate. Examples of the ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone. Examples of the ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole, . Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

The alcohol to be used in combination with the chlorine-based organic solvent may be a linear chain, a branched chain or a cyclic hydrocarbon. Of these, a saturated aliphatic hydrocarbon is preferred. The hydroxyl group of the alcohol may be any of the first to third classes. Examples of alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol. As the alcohol, a fluorinated alcohol is also used. For example, 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol, and the like. The hydrocarbon may be linear, branched or cyclic. Any of aromatic hydrocarbons and aliphatic hydrocarbons may be used. The aliphatic hydrocarbons may be saturated or unsaturated. Examples of hydrocarbons include cyclohexane, hexane, benzene, toluene and xylene.

As the other solvent, for example, the solvent described in JP-A-2007-140497 can be used.

The solvent includes a mixed solvent of (I) methylene chloride and (II) an alcohol having 1 to 4 carbon atoms, and the mass ratio (I: II) of (I) and (II) in the mixed solvent is 90: 50:50 is preferred. (I: II) is more preferably 90:10 to 60:40, further preferably 90:10 to 70:30, and particularly preferably 90:10 to 75:25. (I: II) within such a range, the effect of facilitating the peeling of the magnetic support film from the flexible substrate can be obtained. The term "self-supporting film" means a film in which the organic solvent is removed until it becomes self-supporting to such an extent that the flexible film formed by film-forming the dope composition on the support can be peeled off from the flexible substrate.

Methanol, ethanol and isopropanol are preferably used as the alcohol (C) having 1 to 4 carbon atoms in the (II) mixed solvent, more preferably methanol and ethanol, and most preferably methanol alone.

In the production method of the present invention, one or more plasticizers, ultraviolet absorbers, antioxidants, brittleness improvers, optical agents and the like are added as additives to the dope compositions A and B within the range not hindering the effects of the present invention .

The plasticizer has a function of improving the fluidity and flexibility of the dope composition. The antioxidant is preferably a compound that prevents oxidation of the resin composition of the present invention. Particularly, a vinyl group-containing phenol-based antioxidant capable of capturing an alkyl radical generated at the beginning of the autoxidation of the resin is preferable, and for example, SUMILIZER GM, SUMILIZER GS manufactured by Sumitomo Chemical Co., Ltd. can be exemplified. The antioxidant may have an action mechanism for capturing or decomposing peroxide radicals generated in the mid to late stages of autoxidation of the resin, and the effect can be expected by adding an antioxidant suitable for each.

Hereinafter, the optical film produced by the method for producing an optical film of the present invention will be described. The constituent materials thereof are as described above.

In the optical film, the thickness ratio of the layer derived from the layer A and the layer derived from the layer B may be larger, but it is preferable that the thickness ratio of the layer derived from the layer B is smaller than the layer derived from the layer A from the viewpoint of brittleness.

The total thickness of the optical film is preferably 15 to 80 占 퐉, and more preferably 25 to 60 占 퐉. Among them, from the viewpoint of hardness, the layer derived from the layer B preferably has a thickness of at least 1 mu m, more preferably at least 2 mu m. The B-layer-derived layer is preferably 15 탆 or less from the viewpoint of balance between hardness and brittleness.

In the case of a three-layer structure, the thicknesses of the layers derived from the B layer may be the same or different. It is preferable that the layer has a three-layer structure in which the layer derived from the layer B is disposed at the same thickness with the layer derived from the layer A interposed therebetween, since there is no need to discriminate between the front and the back.

The optical film (2) is formed by dispersing rubber particles (6) in a thermoplastic resin (7). If the thermoplastic resin of the dope composition A and the thermoplastic resin of the dope composition A are the same as each other, the lamination interface of the dope composition A and the dope composition B is not discriminated and becomes a substantially uniform resin film. However, the density of the flat rubber particles 6 is smaller at the surface side, and the density is larger at the inner side than at the surface side. The shape of the rubber particles added to the dope compositions A and B is crushed in the film thickness direction in the film.

Specifically, when spherical rubber particles 6 are used in the preparation of the dope composition, the rubber particles in the film after production have a diameter a in the film thickness direction (here, a short diameter) a and a direction perpendicular to the film thickness direction (In this case, the long diameter) b, a flattened flat shape satisfying b / a &gt; 1.1 and being squashed in the film thickness direction.

The rubber particles added in the dope composition are flattened by the reduction of the film thickness due to the volatilization of the solvent of the flexible film so that the embrittlement is improved as compared with the optical film disposed in the film while retaining the shape of the rubber particles in the dope composition, The surface hardness and the haze are maintained to the same level as that of the rubber particles of the original shape.

In general, an increase in the amount of rubber particles increases the brittleness, but there is a trade-off in that the surface hardness decreases and the haze deteriorates. However, even if the addition amount of the rubber particles is the same, The brittleness can be improved without changing the surface hardness and the haze. In the present invention, it is possible to flatten the rubber particles without passing through a stretching step, and it becomes possible to obtain a preferable optical film having optical properties by a simpler method.

Hereinafter, the application of the optical film of the present invention will be described.

<< Protective Film for Polarizer >>

The optical film of the present invention can be used as the polarizing plate protective film 121 (see Fig. 4 described later).

The polarizing plate protective film 121 may have a layer other than the above-mentioned film of the present invention, may be subjected to surface treatment or may have a functional layer, if necessary, It is preferable that the polarizing plate protective film 121 is provided with the film of the present invention in the outermost layer (layer having an air interface).

The thickness of the polarizing plate protective film 121 is not particularly limited, but is preferably 10 to 80 占 퐉, more preferably 10 to 50 占 퐉, and still more preferably 20 to 50 占 퐉.

In the polarizing plate protective film 121, the lower the total haze value, the better the optical performance. However, considering the selection of raw materials and the handling property of the production control and the roll film, it is preferably not less than 0.01% and not more than 0.6%, more preferably not more than 0.4% desirable. When the total haze value is 0.6% or less, transparency of the film is high, which is effective in improving the contrast ratio and luminance of the liquid crystal display device.

As described above, the haze value of the optical film of the present invention can be achieved because the film has a small haze as an index of transparency, a good heat resistance, and a low moisture permeability.

Next, one embodiment of a polarizing plate and a liquid crystal display device provided with the optical film of the present invention will be described with reference to the drawings. In the drawings of the present specification, the scale of each part is appropriately changed for easy visibility.

<Polarizing plate protective film, polarizing plate, liquid crystal display device>

3 is a schematic diagram showing the configuration of a liquid crystal display device 101 according to an embodiment of the present invention. As shown in the figure, the liquid crystal display device 101 has a pair of polarizing plates (an upper polarizer 110 and a lower polarizer 118) and a liquid crystal cell 102 sandwiched therebetween. The liquid crystal cell 102 Has a liquid crystal layer 115, an electrode substrate 113 on a liquid crystal cell disposed above and below the liquid crystal layer 115, and a liquid crystal cell lower electrode substrate 116.

When the liquid crystal display device 101 is used as a transmission type, the upper polarizer 110 is a front polarizer and the lower polarizer 118 is a rear polarizer. Although not shown, And a color filter is provided between the backlight unit and the liquid crystal layer 115 and the front-side polarizing plate 110 on the lower side of the polarizing plate 118. In Fig. 3, reference numerals 112 and 119 denote directions of absorption axes of the respective polarizing plates that are substantially perpendicular to each other, and reference numerals 114 and 117 denote orientation control directions of the electrode substrates.

In the liquid crystal display device 101, at least one pair of polarizers 110 and 118 is a polarizer of the present invention comprising the polarizer and the polarizer protective film of the present invention on at least one surface of the polarizer.

4 is a cross-sectional view in the thickness direction showing the configuration of the upper polarizer 110. Fig. As shown in the figure, the upper polarizer 110 includes a polarizer protective film 121 made of the optical film 3 of the present invention on one side of the polarizer 120. A polarizing plate protective film 122 is provided on the other surface of the polarizer 120 which is the liquid crystal cell side and an optically anisotropic layer 123 is provided on the liquid crystal cell side. The lower polarizing plate 118 has a structure in which the upper polarizing plate 110 and the layers are stacked upside down.

The polarizing plate protective film 122 on the liquid crystal cell side may also adopt the optical film of the present invention.

The polarizing plate 110 is formed by applying an alkali treatment to the polarizing plate protective films 121 and 122 and applying a completely saponified polyvinyl alcohol aqueous solution to both surfaces of the polarizer 120 produced by immersing and stretching the polyvinyl alcohol film in an iodine solution There is a method of attaching them. Instead of the alkali treatment, an easy adhesion treatment as described in JP-A-6-94915 and JP-A-6-118232 may be carried out. The surface treatment described above may be carried out.

Examples of the adhesive used for bonding the polarizing plate protective film treated surface and the polarizer include a polyvinyl alcohol-based adhesive such as polyvinyl alcohol and polyvinyl butyral, a vinyl-based latex such as butyl acrylate, .

The polarizing plate protective films 121 and 122 and the polarizer 120 may be laminated by other adhesives or pressure-sensitive adhesives or may be laminated directly on the sheet without interposing an adhesive or a pressure-sensitive adhesive.

Since the polarizing plate 110 is provided with the optical film of the present invention and the liquid crystal display device 101 is provided with the polarizing plate, it can be manufactured by a manufacturing process that does not require a stretching process, It is possible to do.

<Optical Compensation Film>

The optical film of the present invention can be used in various applications besides the polarizing plate protective film as described above. For example, in the liquid crystal display device described above, it can be preferably used as an optical compensation film. The optical compensation film generally refers to an optical material which is used in a liquid crystal display device and compensates for a retardation, and is in agreement with a retardation plate, an optical compensation sheet, and the like. The optical compensation film has birefringence and is used for the purpose of eliminating the coloring of the display screen of the liquid crystal display device or improving the viewing angle characteristic.

The optical film of the present invention may be an optical compensation film itself, or may be used as a support for an optical compensation film, and an optically anisotropic layer may be formed thereon. The optically anisotropic layer is not limited to the optical performance and the driving method of the liquid crystal cell of the liquid crystal display device in which the optical film of the present invention is used, and any optically anisotropic layer required as the optical compensation film can be used in combination. The optically anisotropic layer to be used in combination may be a composition containing a liquid crystalline compound or a thermoplastic film having birefringence.

Example

Hereinafter, the present invention will be described in detail based on examples. The materials, amounts and ratios, operations, and the like shown in the following examples can be appropriately changed as long as they do not deviate from the purpose of the present invention. Therefore, the present invention is not limited to the following examples.

[Example 1]

The optical film of Example 1 was produced by the following production method.

(Dope preparation step)

Dope Composition A and Dope Composition B are prepared.

As the Dope Composition A, rubber particles were prepared by mixing 100 parts by mass of the rubber particles (mass parts) in the A layer shown in Table 1, 100 parts by mass of the acrylic resin having the molecular weights (weight average molecular weight) shown in Table 1, and 0.1 parts by mass of SUMILIZER GS manufactured by Sumitomo Chemical Co., , 383 parts by mass of dichloromethane and 57 parts by mass of methanol were put into a mixing tank and stirred while heating to dissolve the respective components.

Likewise, rubber particles were obtained in the same manner as in D-1 except that the rubber particles were added in an amount (parts by mass) of the rubber particles in the B layer shown in Table 1, 100 parts by mass of acrylic resin having a molecular weight shown in Table 1, 0.1 part by mass of SUMILIZER GS manufactured by Sumitomo Chemical Co., 383 parts by mass of dichloromethane, and 57 parts by mass of methanol were charged into a mixing tank and stirred while heating to dissolve the respective components.

Here, Carnece M-210 manufactured by Kaneka was used as the rubber particles.

&Lt; Preparation of acrylic resin &

The molecular weight of the acrylic resin in Table 1 is the weight average molecular weight.

An acrylic resin having a weight average molecular weight of 1.3 million and an MMA ratio of 100% was synthesized and used in the following manner.

300 g of ion-exchanged water and 0.6 g of polyvinyl alcohol (saponification degree: 80%, degree of polymerization: 1700) were added to a 1-liter three-necked flask equipped with a mechanical stirrer, a thermometer and a cooling tube to stir the polyvinyl alcohol completely , 100 g of methyl methacrylate and 0.15 g of benzoyl peroxide were added, and the mixture was reacted at 85 DEG C for 6 hours. The resulting suspension was filtered and washed with a filter cloth made of nylon, and the filtrate was dried at 50 占 폚 overnight to obtain a target polymer (92.0 g) as a beads.

An acrylic resin having a weight average molecular weight of 45,000 and an MMA ratio of 100% was synthesized and used in the same manner as in the synthesis of an acrylic resin having a weight average molecular weight of 1,300,000 except that the addition amount of benzoyl peroxide was changed to 0.41 g.

An acrylic resin having a weight average molecular weight of 100,000 and an MMA ratio of 100% was synthesized and used in the same manner as in the synthesis of an acrylic resin having a weight average molecular weight of 1,100,000 except that the addition amount of benzoyl peroxide was changed to 1.83 g.

(Flexible process)

Using the film production line as shown in Fig. 1, the prepared dope compositions A and B were laminated on a stainless steel endless band (flexible substrate) with a width of 2000 mm from the flexible die, and the laminate of the dope composition B, the dope composition A and the dope composition B So that a flexible film consisting of three layers of BAB was formed.

(Solvent removal step)

On the flexible substrate, the solvent removal amount (mass%) of the organic solvent shown in Table 1 was removed with respect to the mass of the total solid content contained in the coherent film. The solvent removal amount is determined by examining the relationship between the drying time and the solvent removal amount for the flexible film produced in the same step in advance and drying the same at the drying time to obtain the solvent removal amount shown in the table.

(Peeling drying step)

At the point when the solvent removal amount was removed, the flexible film was peeled from the flexible substrate as a film having self-supporting property.

And was conveyed without being actively stretched by a tenter, and was dried at 140 占 폚.

A film having a thickness of 40 占 퐉 was produced by the above process.

(Observation of shape of rubber particles)

In the film produced as described above, the rubber particles had a flat-spherical shape with a long diameter / short diameter of 1.4 in the film thickness direction cross section.

The shape of the rubber particles was observed by cutting the obtained film into a size of 3 mm x 6 mm, cutting the cut sample using a microtome, taking a picture at a magnification of 100,000 times with a transmission electron microscope, 100 particles are randomly selected, and the diameters a in the film thickness direction and the diameters b perpendicular to the film thickness direction are calculated, and the arithmetic average value is obtained. From the average diameters in the film thickness direction and the diameters in the vertical direction of the average Long diameter / short diameter (here, the film thickness direction diameter is a short diameter and the vertical direction diameter is a long diameter).

[Example 2]

In the preparation process of the dope composition of Example 1, the addition amount of the rubber particles in the dope compositions A and B was changed as shown in Table 1, and the weight average molecular weight of the acrylic resin was set at 45,000, An optical film of Example 2 was prepared in the same manner as in Example 1 except that the solvent removal amount in the solvent removal step was changed.

[Example 3]

An optical film of Example 3 was prepared in the same manner as in Example 1 except that the solvent removal amount in the solvent removal step before peeling was different as shown in Table 1.

[Example 4]

The addition amount of the rubber particles in the dope compositions A and B was changed in the process of preparing the dope composition of Example 1 as shown in Table 1 and the dope compositions A and B prepared in the softening step were applied to the flexible substrate side Except that a flexible film composed of two layers of AB was formed so as to be in the form of a laminated layer in the order of the dope composition A and the dope composition B in this order and the solvent removal amount in the solvent removal step before separation was changed. The optical film of Example 4 was produced by the same method.

[Example 5]

The optical film of Example 5 was prepared in the same manner as in Example 1 except that the film was stretched 1.5 times in the width direction by a tenter.

[Comparative Example 1]

As Comparative Example 1, an optical film was produced using a melt film production.

The same rubber particles as those used in Example 1 were used, but the addition amounts shown in Table 1 were used. In addition, since the production of a molten film, an organic solvent is not used and there is no step of removing an organic solvent.

More specifically, a pellet of a thermoplastic polymer obtained by bulk polymerization of a monomer consisting of 97.8% of methyl methacrylate and 2.2% of methyl acrylate was used.

The pellets and the rubber particles were mixed in the amounts shown in Table 1 in a super mixer and melt-kneaded by a twin-screw extruder to obtain pellets for the A and B layers. Then, each of the pellets was melted by a single-screw extruder to form a laminated body, which was extruded through a T-shaped die having a set temperature of 265 ° C. Subsequently, the resulting film was sandwiched between a pair of metal rolls whose surfaces were smooth, and an optical film having a thickness of 40 탆 was produced.

[Comparative Example 2]

As shown in Table 1, in the same manner as in Example 1, except that an acrylic resin having a weight average molecular weight of 100,000 as a lower molecular weight as compared with the Examples was used and the solvent removal amount in the solvent removal step was changed, An optical film of Example 2 was prepared.

[Comparative Example 3]

As shown in Table 1, an optical film of Comparative Example 3 was produced in the same manner as in Example 2 except that the solvent removal amount in the solvent removal step was reduced.

The following evaluations were made on the above examples and comparative examples.

&Lt; Evaluation of optical film &

The brittleness, surface hardness, haze and heat resistance of each of the obtained optical films of the examples and comparative examples were measured and evaluated by the following methods.

(Brittle)

A width of 15 mm and a width of 15 mm which were allowed to stand at 25 占 폚 and 65% RH for 1 hour or longer using a folding endurance tester (MIT, BE-201 type, A sample film having a length of 80 mm and a thickness of 40 占 퐉 was measured under the condition of a load of 500 g in accordance with JIS P 8115 and evaluated by the number of times until the sample was broken.

A: 600 times or more

B: 200 times or more and less than 600 times

C: Less than 200 times

(Surface hardness)

The surface hardness was evaluated by Knoop hardness.

A sample surface of a "Fisher Scope H100Vp type hardness meter" manufactured by Fisher Instruments Co., Ltd. was used and fixed on a glass substrate by a nuffra indenter in accordance with the method of JIS Z 2251 with a load time of 10 sec, a creep time of 5 sec, The time was 10 sec, and the indentation load was 50 mN. The hardness was calculated from the relationship between the contact area of the indenter and the sample and the maximum load obtained from the indentation depth. In addition, JIS Z 2251 is Japanese Industrial Standard based on ISO4545.

A: 180 N / mm or more

B: 150 N / mm or more and 180 N / mm or less,

C: Less than 150 N / mm

(Hayes)

The haze was measured using a haze meter (NDH2000 manufactured by Nippon Seimei Kogyo Co., Ltd.). The measurement was carried out based on JIS K 7105.

A: less than 0.4%

B: 0.4% or more and less than 0.6%

C: 0.6% or more

(Heat resistance)

The film was conditioned at a temperature of 25 캜 and a relative humidity of 60% for 2 hours or more at a clamping distance of 20 mm with a dynamic viscoelasticity measuring device (Vibron: DVA-225, manufactured by Haitian Instrumentation Control Co., Ltd.) , A temperature raising rate of 2 DEG C / min, a measurement temperature range of 30 DEG C to 250 DEG C, and a frequency of 1 Hz. Then, the glass transition temperature Tg was measured by drawing a straight line 1 in the solid region, drawing a straight line 2 in the glass transition region, and establishing an intersection between the straight line 1 and the straight line 2, and evaluated by the following criteria.

A: 115 ℃ or higher

B: 110 ° C or more and less than 115 ° C

C: less than 110 캜

The evaluation results for Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 1 together with the production conditions.

Regarding Examples 1 to 5, excellent properties as an optical film were obtained with either A or B in any evaluation. On the other hand, in Comparative Example 1 and Comparative Example 3, sufficient brittleness was not obtained, and in Comparative Example 2, the surface of the film surface was bad, the surface haze was high, and the glass transition temperature was low.

In Comparative Example 1, since there was no solvent removal step, the rubber particles were spherical, and sufficient brittleness could not be obtained.

From the comparison between Example 2 and Comparative Example 1, it can be seen that the acrylic resin has a low molecular weight and is poor in brittleness in film production by the melting method. From the comparison of Example 2 and Comparative Example 3, it was found that when the removal amount of the solvent was insufficient, the embrittlement was bad. In Comparative Example 3, the shape of the rubber particles was not sufficiently flat as compared with Example 2, so that the brittleness was not sufficiently improved.

From the comparison of Example 1 and Comparative Example 2, it is clear that when the molecular weight of the acrylic resin is small and the solvent removal amount is small, the haze is large and the heat resistance is low.

Next, optical films of Examples 6 to 11 were prepared in order to investigate the change in the characteristics of the optical film due to the change in the amount of the rubber particles added to the dope compositions A and B. [

[Examples 6 to 8 and Comparative Examples 4 to 6]

Examples 6 to 8 and Comparative Examples 4 to 6 were prepared in the same manner as in Example 1 except that the amount of rubber particles added to the dope composition A and the dope composition B was changed as shown in Table 2 in Example 1 Respectively.

The brittleness, surface hardness, haze and heat resistance of the optical films of Examples 6 to 11 were measured and evaluated by the following methods. The evaluation results for Examples 6 to 8 and Comparative Examples 4 to 6 are shown in Table 2 together with the production conditions. Table 2 also describes the first embodiment for reference.

The relationship between the addition ratios of the rubber particles of Examples 1, 6 to 8 and Comparative Examples 4 to 6 shown in Table 2 to the dope compositions A and B is shown in Fig. 5, the examples indicated by black circles (.circle-solid.) Are evaluation of A or B in both the brittleness, hardness, haze and heat resistance, and the comparative examples indicated by white circles (?) Are brittleness, hardness, There was an evaluation of at least one of the heat resistance.

5 that the content of the rubber particles in the dope composition A is 5 mass% or more and 30 mass% or less with respect to the mass of the thermoplastic resin, and the content of the rubber particles in the dope composition B is 4 By mass or more and 9% by mass or less.

Next, optical films of Examples 9 to 11 were produced in order to investigate the change in the characteristics of the optical film due to the difference in the film thicknesses of the A layer and the B layer in the flexible process.

[Examples 9 to 11]

Examples 9 to 11 were produced in the same manner as in Example 1 except that the thickness of each layer in the softening step was changed as shown in Table 3 in Example 1. [

Similarly to Examples 9 to 11, the brittleness, surface hardness, haze and heat resistance of the optical film were measured and evaluated by the following methods. The evaluation results for Examples 9 to 11 are shown in Table 3 together with the production conditions. Table 3 also describes the first embodiment for reference.

As shown in Table 3, it was found that when the thickness of the B layer as the outer layer was reduced to 1 占 퐉 as in Example 11, the hardness was lowered. The B layer is preferably at least 2 mu m or more.

Claims (6)

The dope composition A containing the rubber particles, the thermoplastic resin and the organic solvent and the dope composition B are mixed so that the mass of the rubber particle with respect to the mass of the thermoplastic resin contained in the dope composition B is larger than the mass of the thermoplastic resin And the content of the rubber particles in the dope composition A is 5 mass% or more and 30 mass% or less with respect to the mass of the thermoplastic resin, and the content of the rubber particles in the dope composition A The content of the rubber particles is 4 mass% or more and 9 mass% or less with respect to the mass of the thermoplastic resin;
A step of simultaneously or sequentially laminating the dope compositions A and B onto the flexible substrate in the order of AB, BA or BAB to form a flexible film;
And removing at least 200 mass% of the organic solvent with respect to the mass of the total solid content contained in the flexible film on the flexible substrate. The method according to claim 1,
Wherein the thermoplastic resin is an acrylic resin having a weight average molecular weight of 250,000 or more and 2,000,000 or less. An optical film containing the rubber particles produced by the production method according to claim 1 or 2. The method of claim 3,
The rubber particle is a flat spherical shape obtained by compressing spherical particles in the thickness direction and the relationship between the diameter a in the film thickness direction when viewed in the film thickness direction and the diameter b in the direction perpendicular to the film thickness direction is b / a &gt; 1.1. A polarizer,
A polarizing plate comprising the optical film according to claim 4 as a protective film on at least one surface of the polarizer. A pair of polarizing plates,
And a liquid crystal cell sandwiched between the pair of polarizing plates,
Wherein at least one of the pair of polarizing plates is the polarizing plate according to claim 5.

Images