WO2013035273A1 - Method for producing acrylic resin-containing film, acrylic resin-containing film, polarizing plate, and liquid crystal display device - Google Patents

Abstract

Provided is a method for producing an acrylic resin-containing film by solution casting whereby a dope composition is cast onto a substrate, allowed to dry, and then peeled from the substrate. The method for producing an acrylic resin-containing film comprises a dope preparation step for preparing a dope composition by stirring and dissolving an acrylic resin, cellulose ester resin, and an additive in an organic solvent inside a dissolution cell to form a dope composition and adding water such that the water content is brought to 0.8 to 2.0 mass% in terms of the total amount of dope composition. The additive is a polymer compound having a hydrogen bond component, and is added in an amount between 1 to 10 mass% per total amount of organic solvent. By means of the method for producing an acrylic resin-containing film, and the like, there is good adhesion between the dry film and the polarizer, and productivity is high.

Description

Method for producing acrylic resin-containing film, acrylic resin-containing film, polarizing plate, and liquid crystal display device

The present invention relates to a method for producing an acrylic resin-containing film, an acrylic resin-containing film produced by the production method, a polarizing plate using the same, and a liquid crystal display device.

In recent years, the development of thinner and lighter information devices equipped with liquid crystal display devices such as LCD TVs, notebook computers, car navigation systems, and mobile phones has been increasingly advanced. Accordingly, there is an increasing demand for a thinner protective film for polarizing plates used in liquid crystal display devices.

In general, a polarizing plate uses a transparent protective film bonded to both sides of a polarizer by a so-called aqueous adhesive in which a polyvinyl alcohol-based material is dissolved in water, and the transparent protective film has high moisture permeability. Triacetyl cellulose or the like is used.

However, since the above-mentioned polarizing plate has a large dimensional change in a high-temperature and high-humidity environment, it is reported that a film containing an acrylic resin having a low moisture permeability is used as a transparent protective film (patent) Reference 1). When such a transparent protective film with low moisture permeability is bonded to a polarizer with a water-based adhesive, there is a problem that adhesion is poor.

On the other hand, Patent Document 2 reports a technique in which a polarizing plate using an electron beam curable adhesive as an adhesive for bonding a polarizer and a transparent protective film has good adhesiveness. However, when such a curable adhesive is used, there is a problem that the curing shrinkage of the adhesive occurs with time, and conversely the productivity is poor.

International Publication No. 2009/90900 JP 2008-170717 A

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for producing an acrylic resin-containing film having good adhesion to a polarizer and high productivity. Furthermore, it aims at providing the acrylic resin containing film produced by this manufacturing method, a polarizing plate using the same, and a liquid crystal display device.

As a result of intensive studies by the present inventors in order to achieve the above object, in the so-called solution casting method in which the dope composition is cast on the support and then peeled off from the support, the dope composition is hydrophilic. By adding a polymer compound having a high hydrogen bonding component as an additive and adding water so as to have a specific water content, the adhesion to the polarizer is good, and the support is soiled. It has been found that an acrylic resin-containing film can be produced, and the present invention has been completed.

That is, the method for producing an acrylic resin-containing film according to one aspect of the present invention is an acrylic resin film-formed by a solution casting film-forming method in which the dope composition is cast on a support and then the dope composition is dried and peeled off. A method for producing a containing film, comprising dissolving an acrylic resin, a cellulose ester resin, and an additive in an organic solvent that dissolves the acrylic resin and the cellulose ester resin while stirring to form a dope composition, containing water A dope preparation step of preparing a dope composition by post-adding water so that the rate is 0.8 to 2.0% by mass with respect to the total amount of the dope composition, and the additive has a high hydrogen bond component. It is a molecular compound and is characterized by being contained in an amount of 1 to 10% by mass relative to the total amount of the organic solvent.

The objects, features and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.

FIG. 1 is a view showing a mechanism in a dope film in the solution casting film forming method of the present invention. FIG. 2 is a schematic diagram showing a dope preparation step, a casting step, and a drying step of the solution casting film forming method.

Hereinafter, embodiments according to the present invention will be described, but the present invention is not limited thereto.

The method for producing an acrylic resin-containing film according to the present embodiment is an acrylic resin-containing film formed by a solution casting film-forming method in which the dope composition is cast on a support and then the dope composition is dried and peeled off. A method for producing a dope composition by dissolving an acrylic resin, a cellulose ester resin and an additive in an organic solvent in which the acrylic resin and the cellulose ester resin are dissolved in a dissolving kettle while stirring, and having a moisture content of the dope A dope preparation step of preparing a dope composition by post-adding water so as to be 0.8 to 2.0% by mass with respect to the total amount of the composition, wherein the additive is a polymer compound having a hydrogen bonding component. And 1 to 10% by mass based on the total amount of the organic solvent.

Hereinafter, the present invention will be described in detail.

[Method for producing acrylic resin film]
In the method for producing an acrylic resin-containing film of the present invention, the dope composition is cast on a support, heated to remove a part of the solvent, then peeled off from the support, and the peeled film is dried. A so-called solution casting film forming method is used.

(Organic solvent)
It is preferable that the organic solvent which forms the dope composition in the manufacturing method of the acrylic resin containing film of this invention is an organic solvent which has mainly the good solvent with respect to an acrylic resin and a cellulose-ester resin. As the organic solvent, in particular, methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms are preferably used. These simultaneously dissolve acrylic resin, cellulose ester resin, and other additives.

The ratio of methylene chloride to aliphatic alcohol (MA represented by formula (i) described later) is 15 to 30, preferably 20 to 25. If MA is less than 15, the peel force may increase, and the dryness may deteriorate, resulting in poor productivity. If it is greater than 30, haze may increase.

When the aliphatic alcohol in the above range is contained in the dope composition, the drying efficiency is good in the evaporation step described later. In addition, a large number of voids are formed at the locations where the aliphatic alcohol to be evaporated exists in the film, and the film can be made thin. As a result, a film having better adhesion with the polarizer can be produced.

The dope composition of the present invention contains methylene chloride and a solvent containing a linear or branched aliphatic alcohol having 1 to 4 carbon atoms in a solid content of acrylic resin, cellulose ester resin, and acrylic fine particles. It is preferable to dissolve 15 to 45% by mass.

Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Among these, ethanol is most preferable from the viewpoints of the stability of the dope, the boiling point being relatively low, and good drying properties.

Hereinafter, a preferable method for forming the acrylic resin-containing film of the present invention will be described.

1) Dope preparation step The dope preparation step of the present invention is a step of dissolving an acrylic resin, a cellulose ester resin, and an additive in an organic solvent mainly composed of a good solvent for the acrylic resin and the cellulose ester resin while stirring. including.

In addition, the dope preparation step of the present invention includes a step of adding water later so that the water content is 0.8 to 2.0 mass% with respect to the total amount of the dope. This is because in the drying step described later, the polymer compound is dried while adhering to water molecules due to its hydration property in the dope composition.

FIG. 1 is a view showing a mechanism in a dope film cast and dried by the solution casting film-forming method of the present invention. In FIG. 1, 31 indicates a metal support, F indicates a film (dope composition), W indicates a water molecule, and V indicates an additive.

FIG. 1A shows the dope composition cast on the metal support 31. The dope composition contains post-added water molecules W and additive V in a deposited state. The dope composition is heated on the metal support 31 in a solvent evaporation step to be described later, and the solvent is evaporated to form a dope film.

As shown in FIG. 1B, at the time of this solvent evaporation, the water molecules W move in the film to the side opposite to the metal support 31 side together with the added additive V.

The film in which both the organic solvent and the water (water molecule W) added after the evaporation were finally evaporated is a film in which the molecules of additive V are biased to one side as shown in FIG. Become. The unevenness of the additive V molecules improves the adhesion of the film after production. At the same time, since the additive V on the metal support 31 side is reduced, the additive V and the like are not contaminated on the metal support 31 after peeling.

The additive must be a polymer compound having a hydrogen bonding component. That is, the polymer compound needs to have a high affinity for water. The content of the additive is 1 to 10% by mass, preferably 2 to 8% by mass, based on the total amount of the organic solvent.

When the content of the additive is less than 1% by mass relative to the total amount of the organic solvent, the adhesion of the film after production is deteriorated. On the other hand, if it is larger than 10% by mass, the water and the polymer compound deposited on each other during the drying step do not move to the adhesion side of the film, and belt contamination occurs when the dope composition is peeled off.

If the water content is less than 0.8% by mass, the adhesion of the film after production deteriorates, and if it is more than 2.0% by mass, the water and the polymer compound that are efficiently adhered to each other during the drying process are adhered to the film. Since it does not move to the side, belt contamination occurs.

For dissolution of acrylic resin and cellulose ester resin, a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, a method carried out under pressure above the boiling point of the main solvent, JP-A-9-95544 and JP-A-9- Various dissolution methods can be used such as a method performed by a cooling dissolution method as described in JP-A-95557 or JP-A-9-95538, a method performed at high pressure as described in JP-A No. 11-21379, In particular, a method of pressurizing at a temperature equal to or higher than the boiling point of the main solvent is preferable.

It is preferable that a total of 15 to 45% by mass of the acrylic resin in the dope, the cellulose ester resin, and the acrylic fine particles is contained. Three types of acrylic resin in the dope, cellulose ester resin, and acrylic fine particles are dissolved and dispersed by adding additives to the dope during or after dissolution, then filtered through a filter medium, defoamed, and sent It is sent to the next process by a pump.

Filtration is preferably performed using a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml. In this method, the aggregate remaining when the fine particles are dispersed or the aggregate generated when the main dope is added is obtained by using a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml. Can only be removed. In the main dope, the concentration of fine particles is sufficiently thin as compared with the additive solution, so that aggregates do not stick together at the time of filtration and a sudden increase in filtration pressure does not occur.

FIG. 2 is a diagram schematically showing a dope preparation step, a casting step, and a drying step of a solution casting film forming method preferable for the present invention.

The large aggregates are removed from the acrylic fine particle charging pot 41 by the filter 44 and fed to the stock pot 42. Thereafter, the acrylic fine particle additive solution is added from the stock kettle 42 to the main dope dissolving kettle 1. Thereafter, the main dope solution is filtered by the main filter 3, and an ultraviolet absorbent additive solution is added inline to the main dope solution 16.

In FIG. 2, 2, 5, 11, 14, and 43 indicate liquid feed pumps, 6, 12, and 15 indicate filters, 4, and 13 indicate stock tanks, 8, and 16 indicate conduits, and 10 indicates An ultraviolet absorber charging pot is shown, 20 is a junction tube, 21 is a mixer, 30 is a die, 31 is a metal support, 32 is a web, 33 is a peeling position, 34 Denotes a tenter device, 35 denotes a roll drying device, 37 denotes a take-up roll, and 41 denotes a fine particle charging pot.

In many cases, the main dope may contain about 10 to 50% by weight of recycled material. Since the return material contains acrylic fine particles, it is preferable to control the addition amount of the acrylic fine particle addition liquid in accordance with the addition amount of the return material. A return material is a finely pulverized acrylic resin-containing film, which is generated when an acrylic resin-containing film is formed, with both sides of the film cut off, or with acrylic resin specs out due to scratches, etc. Film stock is used.

In addition, a pellet obtained by kneading acrylic resin and acrylic fine particles in advance can be preferably used.

2) Casting process In the casting process, an endless metal support 31, such as a stainless steel belt, or a rotation, which feeds the dope to a pressure die 30 through a liquid feed pump (for example, a pressurized metering gear pump) and transfers it indefinitely. This is a step of casting a dope from a pressure die slit to a casting position on a metal support 31 such as a metal drum.

As the die, a pressure die that can adjust the slit shape of the die part and easily make the film thickness uniform is preferable. The pressure die includes a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked. Or it is also preferable to obtain the film of a laminated structure by the co-casting method which casts several dope simultaneously.

3) Solvent evaporation step In the solvent evaporation step, the web (the dope is cast on the casting support, and the formed dope film is called "web") is heated on the casting support, It is a process of evaporating.

To evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. High efficiency and preferable. A method of combining them is also preferably used. The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or heat by means such as infrared rays.

Depending on the film thickness at the time of casting, the web is preferably peeled from the support in the range of 30 to 240 seconds from the viewpoint of productivity, surface quality, peelability and the like. More preferably, the web is peeled from the support in the range of 60 to 180 seconds.

4) Peeling process A peeling process is a process of peeling the web which the solvent evaporated on the metal support body in a peeling position. The peeled web is sent to the next process.

The temperature at the peeling position on the metal support is preferably 10 to 40 ° C., more preferably 11 to 30 ° C.

The residual solvent amount at the time of peeling of the web on the metal support at the time of peeling is 20 to 50% by weight depending on the strength of the drying conditions, the length of the metal support, etc., and 30 to 40%. It is preferable that it is mass%. In the case of peeling when the residual solvent amount is more than 50% by mass, if the web is too soft, the flatness at the time of peeling tends to be impaired, and slippage and vertical stripes due to peeling tension tend to occur. Moreover, when it peels at the time of less than 20 mass%, it tears from an edge part by excessive drying.

The residual solvent concentration (%) of the web is defined by the following formula (i).
Formula (i): Residual solvent concentration (%) = (mass of cast film−mass of dry film) / mass of dry film × 100 (%)

In addition, the heat treatment for measuring the residual solvent amount represents performing heat treatment at 115 ° C. for 1 hour.

The peeling tension when peeling the metal support from the film is usually preferably 196 to 245 N / m. However, when wrinkles are likely to occur during peeling, peeling with a tension of 190 N / m or less is preferable. It is preferable to peel at a minimum tension of ˜166.6 N / m, in particular, a minimum tension of ˜137.2 N / m, and most preferable to peel at a minimum tension of ˜100 N / m.

In the present invention, the temperature at the peeling position on the metal support is preferably −50 to 40 ° C., more preferably 10 to 40 ° C., and most preferably 15 to 30 ° C.

5) Drying and stretching step After peeling, using a drying device 35 that alternately conveys the web through a plurality of rolls arranged in the drying device, and / or a tenter device 34 that clips and conveys both ends of the web with a clip. , Dry the web.

Drying is generally performed by blowing hot air on both sides of the web, but there is also a method of heating by applying microwaves instead of wind. Too rapid drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of the residual solvent. Throughout, drying is generally performed at 40-250 ° C. In particular, drying at 40 to 160 ° C. is preferable.

When using a tenter device, it is preferable to use a device that can independently control the film gripping length (distance from the start of gripping to the end of gripping) left and right by the left and right gripping means of the tenter device. In the stretching process, it is also preferable to intentionally create compartments having different temperatures in order to improve planarity. It is also preferable to provide a neutral zone between different temperature zones so that the zones do not interfere with each other.

The stretching operation may be performed in multiple stages, and it is also preferable to perform biaxial stretching in the casting direction and the width direction. When biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise. In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible. That is, for example, the following stretching steps are possible.

-Stretch in the casting direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction-Stretch in the width direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction

In addition, simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension. The preferred draw ratio of simultaneous biaxial stretching can be in the range of 1.01 to 1.5 times in both the width direction and the longitudinal direction.

The amount of residual solvent of the web when stretching is preferably 20 to 100% by mass at the start of stretching, and both ends of the web are held by a tenter device until the residual solvent amount of the web is 10% by mass or less. However, it is preferable to carry out drying, and more preferably 5% by mass or less.

When drying, the drying temperature is preferably 30 to 150 ° C, more preferably 50 to 120 ° C, and most preferably 70 to 100 ° C.

In the stretching step, it is preferable that the temperature distribution in the width direction of the atmosphere is small from the viewpoint of improving the uniformity of the film, and the temperature distribution in the width direction in the stretching step is preferably within ± 5 ° C, and within ± 2 ° C. Is more preferable, and within ± 1 ° C. is most preferable.

6) Winding process The winding process is a process in which the amount of the residual solvent in the web is sufficiently reduced and then wound by the winder 37 as an acrylic resin-containing film. Preferably, a film having good dimensional stability can be obtained by setting the amount of residual solvent at the time of winding to 0.4% by mass or less.

As a winding method, a generally used method may be adopted, and a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, or the like may be properly used.

The acrylic resin-containing film of the present invention is preferably a long film, specifically, a film having a thickness of about 100 to 5000 m is preferable, and is usually in the form of a roll. The film width is preferably 1.3 to 4 m, more preferably 1.4 to 2 m.

The film thickness of the acrylic resin-containing film of the present invention is not particularly limited, but when used for a polarizing plate protective film described later, it is preferably 10 to 60 μm, and more preferably 20 to 40 μm.

[Acrylic resin-containing film]
The acrylic resin containing film of this invention is manufactured by the said manufacturing method.

Further, it is preferable that the acrylic resin-containing film of the present invention does not show breakage such as breakage, that is, does not cause ductile breakage even when a large stress is applied to bend the film in two. The ductile fracture in the present invention is caused by a stress that is greater than the strength of a certain material, and is defined as a fracture accompanied by significant elongation or drawing of the material before the final fracture. The fracture surface is characterized by numerous indentations called dimples.

The demand for the brittleness of optical films is increasing from the viewpoint of reworkability and productivity as optical films become larger and thinner with the recent increase in liquid crystal display devices, and the above ductile fracture does not occur. Is required. The acrylic resin-containing film in which ductile fracture does not occur can be obtained by appropriately selecting the material configuration such as the acrylic resin used, cellulose ester, and other additives.

The acrylic resin-containing film of the present invention has a tension softening point of 105 when considering use in a high-temperature environment such as a device having a high haze and a high temperature such as a projector or a vehicle-mounted display device. The temperature is preferably ˜145 ° C., more preferably 110 to 140 ° C.

As a specific method for measuring the tension softening point temperature of an acrylic resin-containing film, for example, using a Tensilon tester (ORIENTEC, RTC-1225A), the acrylic resin-containing film is 120 mm (length) × 10 mm (width). The temperature is increased at a rate of temperature increase of 30 ° C./min while pulling at a tension of 10 N, and the temperature at the time of 9 N is measured three times, and the average value can be obtained.

In the acrylic resin-containing film of the present invention, the glass transition temperature (Tg) is preferably 110 ° C. or higher, more preferably 120 ° C. or higher, and particularly preferably 150 ° C. or higher.

The glass transition temperature referred to here is an intermediate value determined according to JIS K7121 (1987) by using a differential scanning calorimeter (DSC-7 manufactured by Perkin Elmer Co.) at a heating rate of 20 ° C./min. It refers to the point glass transition temperature (Tmg).

The acrylic resin-containing film of the present invention has 1/10 cm square or less, more preferably 0.5 / 10 cm square or less, particularly preferably 0.1 / 10 cm square, having a film surface diameter of 5 μm or more. It is as follows.

Here, the defect is a void in the film (foaming defect) generated due to the rapid evaporation of the solvent in the drying process of the solution casting, a foreign matter in the film forming stock solution, or a foreign matter mixed in the film forming. This refers to foreign matter (foreign matter defect) in the film. The diameter of the defect indicates the diameter when the defect is circular, and when the defect is not circular, the range of the defect is determined by observing with a microscope according to the following method, and the maximum diameter (diameter of circumscribed circle) is determined.

The range of the defect is the size of the shadow when the defect is observed with the transmitted light of the differential interference microscope when the defect is a bubble or a foreign object. When the defect is a change in the surface shape, such as transfer of a roll flaw or an abrasion, the size is confirmed by observing the defect with the reflected light of a differential interference microscope.

In addition, when observing with reflected light, if the size of the defect is not clear, aluminum or platinum is vapor-deposited on the surface for observation.

In order to obtain a film having excellent quality expressed by such a defect frequency with high productivity, it is necessary to filter the polymer solution with high precision immediately before casting, to increase the cleanliness around the casting machine, It is effective to set drying conditions after rolling stepwise and to dry efficiently while suppressing foaming.

When the number of defects is more than 1/10 cm square, for example, when a tension is applied to the film during processing in a later process, the film breaks with the defect as a starting point, and the productivity may be significantly reduced. Moreover, when the diameter of a defect becomes 5 micrometers or more, it can confirm visually by polarizing plate observation etc., and when used as an optical member, a bright spot may arise.

In addition, even when it cannot be visually confirmed, when a hard coat layer or the like is formed on the film, the coating agent may not be formed uniformly, which may result in a defect (missing coating).

The acrylic resin-containing film of the present invention preferably has a breaking elongation in at least one direction of 10% or more, and more preferably 20% or more in the measurement based on JIS-K7127-1999.

The upper limit of the elongation at break is not particularly limited, but is practically about 250%. In order to increase the elongation at break, it is effective to suppress defects in the film caused by foreign matter and foaming.

The acrylic resin-containing film of the present invention preferably has a total light transmittance of 90% or more, more preferably 93% or more. Moreover, as a realistic upper limit, it is about 99%. In order to achieve excellent transparency expressed by such total light transmittance, it is necessary not to introduce additives and copolymerization components that absorb visible light, or to remove foreign substances in the polymer by high-precision filtration. It is effective to reduce the diffusion and absorption of light inside the film.

Also, reduce the surface roughness of the film surface by reducing the surface roughness of the film contact part (cooling roll, calender roll, drum, belt, coating substrate in solution casting, transport roll, etc.) during film formation. It is also effective to reduce the diffusion and reflection of light on the film surface by reducing the refractive index of the acrylic resin.

The acrylic resin-containing film of the present invention preferably has a haze value (turbidity) of 1.0% or less, which is one of the indices indicating transparency, and has points of brightness and contrast when incorporated in a liquid crystal display device. And more preferably 0.5% or less.

In order to achieve such a haze value, it is effective to remove foreign substances in the polymer by high-precision filtration and reduce the diffusion of light inside the film.

When using acrylic particles, it is also effective to reduce the difference in refractive index between the acrylic resin and the acrylic particles.

In addition, since the surface roughness also affects the haze value as surface haze, the particle size and addition amount of acrylic particles may be suppressed within the above range, or the surface roughness of the film contact portion during film formation may be reduced. It is valid.

The total light transmittance and haze value of the acrylic resin-containing film are values measured according to JIS-K7361-1-1997 and JIS-K7136-2000.

The acrylic resin-containing film of the present invention can be preferably used as an optical acrylic resin-containing film as long as it satisfies the physical properties as described above, but is excellent in workability and heat resistance by having the following composition. Film can be obtained.

In the acrylic resin-containing film of the present invention, the acrylic resin and the cellulose ester resin are preferably contained in a mass ratio of 95: 5 to 30:70, and more preferably 50% by mass or more of the acrylic resin.

The acrylic resin-containing film of the present invention may contain a resin other than acrylic resin and cellulose ester resin.

The total mass of the acrylic resin and the cellulose ester resin is 55 to 100% by mass, preferably 60 to 99% by mass of the acrylic resin-containing film.

Hereinafter, the components of the present invention will be described in detail.

<acrylic resin>
The acrylic resin used in the present invention is not particularly limited, but is preferably composed of 50 to 99% by mass of methyl methacrylate units and 1 to 50% by mass of other monomer units copolymerizable therewith.

Other monomers that can be copolymerized include alkyl methacrylates having 2 to 18 carbon atoms in the alkyl group, alkyl acrylates having 1 to 18 carbon atoms in the alkyl group, acrylic acid, and methacrylic acid. Saturated acids, maleic acids, fumaric acids, divalent carboxylic acids containing unsaturated groups such as itaconic acid, aromatic vinyl compounds such as styrene, α-methylstyrene, and nucleus-substituted styrene, α, β- such as acrylonitrile, methacrylonitrile, etc. Examples thereof include unsaturated nitrile, maleic anhydride, maleimide, N-substituted maleimide, and glutaric anhydride, and these can be used alone or in combination of two or more.

Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used.

The acrylic resin used in the acrylic resin-containing film of the present invention preferably has a weight average molecular weight (Mw) of 80,000 to 1,000,000 from the viewpoint of mechanical strength as a film and fluidity when producing the film. With this molecular weight, both heat resistance and brittleness can be achieved.

The weight average molecular weight of a resin such as an acrylic resin according to the present invention can be measured by gel permeation chromatography. The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 2,800,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

The production method of the acrylic resin in the present invention is not particularly limited, and any known method such as suspension polymerization, emulsion polymerization, bulk polymerization, or solution polymerization may be used. Here, as the polymerization initiator, normal peroxide-based and azo-based polymerization initiators can be used, and redox-based polymerization initiators can also be used. The polymerization temperature may be 30 to 100 ° C. for suspension or emulsion polymerization, and 80 to 160 ° C. for bulk or solution polymerization. Furthermore, in order to control the reduced viscosity of the produced copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent.

Commercially available acrylic resins can be used as the acrylic resin of the present invention. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dynal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Electric Chemical Co., Ltd.), etc. are used. be able to.

<Cellulose ester resin>
The cellulose ester resin used in the present invention may be substituted with either an aliphatic acyl group or an aromatic acyl group, but is preferably substituted with an acetyl group.

When the cellulose ester resin of the present invention is an ester with an aliphatic acyl group, the aliphatic acyl group has 2 to 20 carbon atoms, specifically acetyl, propionyl, butyryl, isobutyryl, valeryl, pivaloyl, hexanoyl, Octanoyl, lauroyl, stearoyl and the like.

In the present invention, the aliphatic acyl group is meant to include those further having a substituent. When the aromatic ring is a benzene ring in the above-described aromatic acyl group, the substituent of the benzene ring Are exemplified.

When the cellulose ester resin is an ester with an aromatic acyl group, the number of substituents X substituted on the aromatic ring is 0 or 1 to 5, preferably 1 to 3, particularly preferably 1 Or two.

Further, when the number of substituents substituted on the aromatic ring is 2 or more, they may be the same or different from each other, but they may be linked together to form a condensed polycyclic compound (for example, naphthalene, indene, indane, phenanthrene, quinoline). , Isoquinoline, chromene, chroman, phthalazine, acridine, indole, indoline, etc.).

As the structure used in the cellulose resin of the present invention, the cellulose ester resin has a structure having a structure selected from at least one of a substituted or unsubstituted aliphatic acyl group and a substituted or unsubstituted aromatic acyl group. Used, these may be single or mixed acid esters of cellulose.

The substitution degree of the cellulose ester resin according to the present invention is such that the total substitution degree (T) of the acyl group is 2.00 to 2.99, and the substitution degree (ac) of the acetyl group is 0.10 to 1.89. More preferably, the acyl group substitution degree (r) other than the acetyl group is 2.00 to 2.89. The acyl group other than the acetyl group preferably has 3 to 7 carbon atoms from the viewpoint of compatibility with the film composition.

The cellulose ester resin of the present invention has an acyl group having 2 to 7 carbon atoms as a substituent, that is, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate. It is preferably at least one selected from benzoate and cellulose benzoate.

Among these, particularly preferable cellulose ester resins are cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.

More preferably, the mixed fatty acid is a lower fatty acid ester of cellulose acetate propionate or cellulose acetate butyrate having an acyl group having 2 to 4 carbon atoms as a substituent.

The portion not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by known methods.

Incidentally, the substitution degree of the acetyl group and the substitution degree of other acyl groups were determined by the method prescribed in ASTM-D817-96.

If the weight average molecular weight (Mw) of the cellulose ester resin of the present invention is 75,000 or more, the object of the present invention can be achieved even if the weight average molecular weight (Mw) is about 1,000,000. Preferably, 100,000 to 240,000 is more preferable.

<Additive>
The acrylic resin-containing film obtained by the production method of the present invention contains an additive. The additive is a polymer compound having a hydrogen bonding component, and is a copolymer of vinyl pyrrolidone and vinyl acetate, or a copolymer of vinyl acetate and maleic anhydride. It is preferable in terms of compatibility.

When this additive is used, as described above, when the dope composition is dried while water and the additive are deposited in the dope composition, the additive molecules are mixed with the water molecules at the time of solvent evaporation. Move to one side. Accordingly, the adhesion molecules of the manufactured film are improved by the unevenly distributed additive molecules, the amount of the additive on the belt support side is reduced, and the contamination of the additive and the like does not occur on the belt after peeling.

<Acrylic particles>
In the present invention, the acrylic resin-containing film may contain acrylic particles.

The acrylic particles can be present in the state of particles in the acrylic resin and cellulose ester resin and the acrylic resin-containing film (also referred to as incompatible state).

The acrylic particles are obtained by, for example, collecting a predetermined amount of the prepared acrylic resin-containing film, dissolving in a solvent, stirring, and sufficiently dissolving and dispersing the PTFE film having a pore diameter less than the average particle diameter of the acrylic particles. It is preferable that the insoluble matter is filtered using a membrane filter, and the weight of the insoluble matter collected is acrylic particles that are 90% by mass or more of the acrylic particles added to the acrylic resin-containing film.

The acrylic particles used in the present invention are not particularly limited, but are preferably acrylic particles having a layer structure of two or more layers, and particularly preferably the following multilayer structure acrylic granular composite.

The multilayer structure acrylic granular composite is formed by laminating an innermost hard layer polymer, a cross-linked soft layer polymer exhibiting rubber elasticity, and an outermost hard layer polymer from the center to the outer periphery. It refers to a particulate acrylic polymer having a structure.

Preferred embodiments of the multilayer structure acrylic granular composite used in the acrylic resin composition of the present invention include the following.

(A) Monomer comprising 80 to 98.9% by weight of methyl methacrylate, 1 to 20% by weight of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group, and 0.01 to 0.3% by weight of polyfunctional grafting agent An innermost hard layer polymer obtained by polymerizing a body mixture, and (b) 75-98.5% by mass of an alkyl acrylate having 4 to 8 carbon atoms in the presence of the innermost hard layer polymer. A crosslinked soft layer polymer obtained by polymerizing a monomer mixture composed of 0.01 to 5% by mass of a polyfunctional crosslinking agent and 0.5 to 5% by mass of a polyfunctional grafting agent; In the presence of a polymer comprising an inner hard layer and a crosslinked soft layer, a monomer mixture comprising 80 to 99% by weight of methyl methacrylate and 1 to 20% by weight of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group is prepared. Outermost obtained by polymerization The obtained three-layer structure polymer has a three-layer structure composed of a hard layer polymer and 5 to 40% by mass of the innermost hard layer polymer (a), the crosslinked soft layer polymer (b) 30 to 60% by mass and outermost hard layer polymer (c) 20 to 50% by mass, having an insoluble part when fractionated with acetone, and the degree of swelling of methyl ethyl ketone in the insoluble part being 1.5 to 4.0 Acrylic granular composite.

As disclosed in Japanese Patent Publication No. 60-17406 or Japanese Patent Publication No. 3-39095, the multilayer structure acrylic granular composite not only defines the composition and particle diameter of each layer, but also includes a multilayer structure acrylic system. By setting the tensile modulus of the granular composite and the degree of swelling of methyl ethyl ketone in the acetone-insoluble portion within a specific range, it is possible to realize a further sufficient balance between impact resistance and stress whitening resistance.

Here, the innermost hard layer polymer (a) constituting the multilayer structure acrylic granular composite is 80 to 98.9% by mass of methyl methacrylate and 1 to 20 mass of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group. % And a monomer mixture consisting of 0.01 to 0.3% by mass of a polyfunctional grafting agent is preferred.

Here, examples of the alkyl acrylate having 1 to 8 carbon atoms in the alkyl group include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like. And n-butyl acrylate are preferably used.

The ratio of the alkyl acrylate unit in the innermost hard layer polymer (a) is 1 to 20% by mass. When the unit is less than 1% by mass, the thermal decomposability of the polymer is increased. On the other hand, when the unit exceeds 20% by mass, the glass transition temperature of the innermost hard layer polymer (a) is decreased, resulting in three layers. Since the impact resistance imparting effect of the structural acrylic granular composite is lowered, neither is preferable.

Examples of the polyfunctional grafting agent include polyfunctional monomers having different polymerizable functional groups, such as allyl esters of acrylic acid, methacrylic acid, maleic acid, and fumaric acid, and allyl methacrylate is preferably used. . The polyfunctional grafting agent is used to chemically bond the innermost hard layer polymer and the cross-linked soft layer polymer, and the ratio used during the innermost hard layer polymerization is 0.01 to 0.3% by mass. is there.

The crosslinked soft layer polymer (b) constituting the acrylic granular composite is an alkyl acrylate having from 9 to 8 carbon atoms having an alkyl group of 1 to 8 in the presence of the innermost hard layer polymer (a). What is obtained by polymerizing a monomer mixture consisting of 10% by mass, 0.01 to 5% by mass of a multifunctional crosslinking agent and 0.5 to 5% by mass of a multifunctional grafting agent is preferred.

Here, n-butyl acrylate or 2-ethylhexyl acrylate is preferably used as the alkyl acrylate having 4 to 8 carbon atoms in the alkyl group.

In addition to these polymerizable monomers, it is possible to copolymerize 25% by mass or less of other monofunctional monomers capable of copolymerization.

Examples of other monofunctional monomers that can be copolymerized include styrene and substituted styrene derivatives. As the ratio of the alkyl acrylate having 4 to 8 carbon atoms in the alkyl group and styrene increases, the glass transition temperature of the crosslinked soft layer polymer (b) decreases as the former increases, that is, it can be softened.

On the other hand, from the viewpoint of the transparency of the resin assembly, the refractive index of the soft layer polymer (b) at room temperature is set to the innermost hard layer polymer (a), the outermost hard layer polymer (c), and the hard heat. It is more advantageous to make it closer to the plastic acrylic resin, and the ratio between the two is selected in consideration of these.

For example, in applications where the coating layer thickness is small, it is not always necessary to copolymerize styrene.

As the polyfunctional grafting agent, those mentioned in the section of the innermost layer hard polymer (a) can be used. The polyfunctional grafting agent used here is used to chemically bond the cross-linked soft layer polymer (b) and the outermost hard layer polymer (c), and the ratio used during the innermost hard layer polymerization is the resistance to resistance. From the viewpoint of impact imparting effect, 0.5 to 5% by mass is preferable.

As the polyfunctional crosslinking agent, generally known crosslinking agents such as divinyl compounds, diallyl compounds, diacrylic compounds, dimethacrylic compounds and the like can be used, but polyethylene glycol diacrylate (molecular weight 200 to 600) is preferably used.

The polyfunctional cross-linking agent used here is used to generate a cross-linked structure during the polymerization of the cross-linked soft layer polymer (b) and to exhibit the effect of imparting impact resistance. However, if the above polyfunctional grafting agent is used during the polymerization of the soft layer, the cross-linking structure of the cross-linked soft layer polymer (b) is generated to some extent, so the polyfunctional cross-linking agent is not an essential component, The proportion of the functional crosslinking agent used during the soft layer polymerization is preferably 0.01 to 5% by mass from the viewpoint of imparting impact resistance.

The outermost hard layer polymer (c) constituting the multi-layered acrylic granular composite is formed of methyl methacrylate 80 to 99 in the presence of the innermost hard layer polymer (a) and the crosslinked soft layer polymer (b). What is obtained by polymerizing a monomer mixture consisting of 1 to 20% by mass of an alkyl acrylate having 1 to 8% by mass and an alkyl group having 1 to 8 carbon atoms is preferred.

Here, as the acrylic alkylate, those described above are used, but methyl acrylate and ethyl acrylate are preferably used. The proportion of the alkyl acrylate unit in the outermost hard layer (c) is preferably 1 to 20% by mass.

Also, when the outermost hard layer polymer (c) is polymerized, an alkyl mercaptan or the like can be used as a chain transfer agent to adjust the molecular weight for the purpose of improving compatibility with the acrylic resin.

In particular, it is preferable to provide the outermost hard layer with a gradient such that the molecular weight gradually decreases from the inside toward the outside in order to improve the balance between elongation and impact resistance. As a specific method, the monomer mixture for forming the outermost hard layer is divided into two or more, and the molecular weight is increased from the inside to the outside by a method of sequentially increasing the amount of chain transfer agent to be added each time. It is possible to make it smaller.

The molecular weight of the polymer formed at this time can also be examined by polymerizing the monomer mixture used at each time under the same conditions and measuring the molecular weight of the obtained polymer.

The particle diameter of the acrylic granular composite which is a multilayer structure polymer preferably used in the present invention is not particularly limited, but is preferably 10 nm or more and 1000 nm or less, and more preferably 20 nm or more and 500 nm or less. More preferably, it is most preferably 50 nm or more and 400 nm or less.

By using fine particles having a large particle size, it is possible to obtain a sufficient effect with a smaller addition amount, which is preferable. However, if there is a large difference in the refractive index with the acrylic resin, the transparency of the film may be impaired. Therefore, it is important to approximate the refractive indexes of both.

In the acrylic granular composite which is a multilayer structure polymer preferably used in the present invention, the mass ratio of the core layer and the shell layer is not particularly limited, but when the entire multilayer structure polymer is 100 parts by mass. Further, the core layer is preferably 50 parts by mass or more and 90 parts by mass or less, and more preferably 60 parts by mass or more and 80 parts by mass or less.

When the ratio of the core layer is less than 50 parts by mass, when the film formed is subjected to processing such as stretching, the particles are deformed to cause a refractive index difference between the resin and the particles, resulting in the transparency of the film. There is a risk of damaging sex.

As an example of a commercial product of such a multilayer structure acrylic granular composite, for example, “Metablen” manufactured by Mitsubishi Rayon Co., Ltd., “Kane Ace” manufactured by Kaneka Co., Ltd., “Paraloid” manufactured by Kureha Chemical Industry Co., Ltd., Examples include “Acryloid” manufactured by Rohm and Haas, “Staffroid” manufactured by Gantz Kasei Co., Ltd., and “Parapet SA” manufactured by Kuraray Co., Ltd., which can be used alone or in combination of two or more.

In addition, specific examples of the acrylic particles that are graft copolymers that are preferably used as the acrylic particles preferably used in the present invention include unsaturated carboxylic acid ester monomers, unsaturated monomers in the presence of a rubbery polymer. A graft copolymer obtained by copolymerizing a monomer mixture comprising a saturated carboxylic acid monomer, an aromatic vinyl monomer, and, if necessary, other vinyl monomers copolymerizable therewith. Can be mentioned.

There is no particular limitation on the rubbery polymer used for the acrylic particles that are the graft copolymer, but diene rubber, acrylic rubber, ethylene rubber, and the like can be used. Specific examples include polybutadiene, styrene-butadiene copolymer, block copolymer of styrene-butadiene, acrylonitrile-butadiene copolymer, butyl acrylate-butadiene copolymer, polyisoprene, butadiene-methyl methacrylate copolymer. , Butyl acrylate-methyl methacrylate copolymer, butadiene-ethyl acrylate copolymer, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-isoprene copolymer, and ethylene-acrylic acid Examples thereof include a methyl copolymer. These rubbery polymers can be used alone or in a mixture of two or more.

Further, it is preferable that the refractive indexes of the acrylic resin and the acrylic particles are close to each other because the transparency of the acrylic resin-containing film of the present invention can be obtained. Specifically, the refractive index difference between the acrylic particles and the acrylic resin is preferably 0.05 or less, more preferably 0.02 or less, and particularly preferably 0.01 or less.

As a method for satisfying such a refractive index condition, a method for adjusting the composition ratio of each monomer unit of the acrylic resin and / or a composition ratio of the rubbery polymer or monomer used for the acrylic particles is prepared. A method etc. can be adopted. According to these methods, the difference in refractive index can be reduced, and an acrylic resin-containing film excellent in transparency can be obtained.

The difference in refractive index referred to here is a solution in which the acrylic resin-containing film of the present invention is sufficiently dissolved in a solvent in which the acrylic resin is soluble to obtain a cloudy solution, which is subjected to an operation such as centrifugation. After separating the soluble part and the insoluble part and purifying the soluble part (acrylic resin) and the insoluble part (acrylic particles), the difference in the measured refractive index (23 ° C., measurement wavelength: 550 nm) is shown.

In the present invention, the method of blending the acrylic particles with the acrylic resin is not particularly limited, and after blending the acrylic resin and other optional components in advance, usually at 200 to 350 ° C. while adding the acrylic particles, uniaxial or biaxial A method of uniformly melt-kneading with a shaft extruder is preferably used.

In addition, a method in which a solution in which acrylic particles are dispersed in advance is added to and mixed with a solution (dope solution) in which an acrylic resin and a cellulose ester resin are dissolved, and a solution in which acrylic particles and other optional additives are dissolved and mixed. A method such as in-line addition can be used.

Commercially available acrylic particles can also be used as the acrylic particles of the present invention. For example, Staphyloid AC-3355 (manufactured by Ganz Kasei Co., Ltd.), Delpet SRB215 (manufactured by Asahi Kasei Chemicals Co., Ltd.) and the like can be mentioned.

The acrylic resin-containing film of the present invention preferably contains 0.05 to 45% by mass of acrylic particles based on the total mass of the resin constituting the film.

[Polarizing film]
When the acrylic resin film according to this embodiment is used as a polarizing plate protective film, the thickness of the protective film is preferably 10 to 500 μm. In particular, it is preferably 20 μm or more, and more preferably 35 μm or more. Moreover, 150 micrometers or less, Furthermore 120 micrometers or less are preferable. In particular, it is preferably 25 to 90 μm. If the acrylic resin film is thicker than the above region, the polarizing plate after polarizing plate processing becomes too thick, and the liquid crystal display used for notebook personal computers and mobile electronic devices tends not to be particularly suitable for thin and lightweight purposes. On the other hand, if it is thinner than the above region, the moisture permeability of the film becomes high and the ability to protect the polarizer from humidity tends to decrease.

〔Polarizer〕
A polarizing plate using the acrylic resin film according to this embodiment will be described. The polarizing plate can be produced by a general method. The back side of the acrylic resin film according to the present embodiment is subjected to alkali saponification treatment, and a completely saponified polyvinyl alcohol aqueous solution is applied to at least one surface of a polarizing film prepared by immersing and stretching the treated acrylic resin film in an iodine solution. The method of using and sticking together is preferable. The acrylic resin film may be used on the other surface, or another polarizing plate protective film may be used. The polarizing plate protective film used on the other surface of the acrylic resin film according to this embodiment has an in-plane retardation Ro of 590 nm, an optical compensation film having a phase difference of 20 to 70 nm and Rt of 70 to 400 nm. It is preferable to use (retardation film).

These can be produced, for example, by the methods described in JP-A Nos. 2002-71957 and 2003-170492. Alternatively, it is preferable to use a polarizing plate protective film that also serves as an optical compensation film having an optically anisotropic layer formed by aligning a liquid crystal compound such as a discotic liquid crystal. For example, the optically anisotropic layer can be formed by the method described in JP2003-98348A. Alternatively, a non-oriented film having a retardation Ro of 590 nm at 0 to 5 nm and an Rt of −20 to +20 nm described in JP-A-2003-12859 is also preferably used.

</ RTI> By using in combination with the acrylic resin film according to the present embodiment, a polarizing plate having excellent flatness and a stable viewing angle expansion effect can be obtained.

As a polarizing plate protective film used on the back side, as commercially available cellulose ester films, KC8UX2MW, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC4UEW, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC4FR-1, KC4FR-1, -2, KC8UE, KC4UE (manufactured by Konica Minolta Opto Co., Ltd.) and the like are preferably used.

A polarizing film, which is a main component of a polarizing plate, is an element that transmits only light having a plane of polarization in a certain direction. A typical polarizing film currently known is a polyvinyl alcohol polarizing film, which is a polyvinyl alcohol film. There are ones in which iodine is dyed on a system film and ones in which a dichroic dye is dyed, but it is not limited to this. As the polarizing film, a polyvinyl alcohol aqueous solution is formed and dyed by uniaxially stretching or dyed, or uniaxially stretched after dyeing, and then preferably subjected to a durability treatment with a boron compound. The thickness of the polarizing film is 5 to 30 μm, preferably 8 to 15 μm. On the surface of the polarizing film, one surface of the acrylic resin film according to the present embodiment is bonded to form a polarizing plate. It is preferably bonded with an aqueous adhesive mainly composed of completely saponified polyvinyl alcohol or the like.

(Image display device)
By incorporating a polarizing plate produced using the acrylic resin film according to the present embodiment into a display device, various image display devices with excellent visibility can be produced.

The acrylic resin film according to the present embodiment is incorporated in the polarizing plate, and is a reflective, transmissive, or transflective liquid crystal display device or TN, STN, OCB, HAN, VA (PVA, MVA). , IPS type, OCB type and the like for various drive systems. The acrylic resin film according to the present embodiment is also preferably used for various image display devices such as a plasma display, a field emission display, an organic EL display, an inorganic EL display, and electronic paper.

The production characteristics of the acrylic resin-containing film and technical characteristics of the acrylic resin-containing film, polarizing plate, and liquid crystal display device are summarized below.

The method for producing an acrylic resin-containing film according to one aspect of the present invention includes an acrylic resin-containing film formed by a solution casting film-forming method in which a dope composition is cast on a support and then the dope composition is dried and peeled off. A method for producing a dope composition by dissolving an acrylic resin, a cellulose ester resin and an additive in an organic solvent in which the acrylic resin and the cellulose ester resin are dissolved in a dissolution vessel while stirring, and having a moisture content A dope preparation step of preparing a dope composition by post-adding water so that the total amount of the dope composition is 0.8 to 2.0% by mass, wherein the additive has a hydrogen bonding component; 1 to 10% by mass based on the total amount of the organic solvent.

By providing such a configuration, the present invention can provide a method for producing an acrylic resin-containing film having good adhesion between the dried film and the polarizer and high productivity.

In the method for producing the acrylic resin-containing film, the mass ratio of the acrylic resin to the cellulose resin is preferably 95: 5 to 30:70.

The present invention can provide a film excellent in workability and heat resistance by adopting such a mass ratio.

In the method for producing the acrylic resin-containing film, the additive is preferably a copolymer of vinyl pyrrolidone and vinyl acetate or a copolymer of vinyl acetate and maleic anhydride.

In the present invention, compatibility with the film composition can be improved by using such an additive.

Further, the acrylic resin-containing film according to the present invention is characterized by being produced using the method for producing an acrylic resin-containing film.

Since the acrylic resin-containing film of the present invention is produced by the production method described above, the adhesiveness between the dried film and the polarizer is good, and the productivity is high.

The polarizing plate according to the present invention is characterized in that the acrylic resin-containing film is used on at least one surface.

Since the polarizing plate of the present invention uses the acrylic resin-containing film described above, it has excellent flatness and has a stable viewing angle expansion effect.

The liquid crystal display device according to the present invention is characterized by using the acrylic resin-containing film or the polarizing plate.

Since the liquid crystal display device of the present invention uses the above-mentioned acrylic resin-containing film or polarizing plate, the visibility is excellent.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the examples.

[Example 1]
<Preparation of acrylic resin-containing film A1>
(Preparation of dope solution for acrylic resin-containing film A1)
BR85 (acrylic resin, manufactured by Mitsubishi Rayon Co., Ltd.) 70 parts by mass Cellulose ester (cellulose acetate propionate acyl group total substitution degree 2.75, acetyl group substitution degree 0.19, propionyl group substitution degree 2.56, Mw = 200000) 30 parts by mass Copolymer of vinylpyrrolidone and vinyl acetate 5 parts by mass Methylene chloride 232.2 parts by mass Ethanol 44.1 parts by mass Water 0.27 parts by mass

In addition, the moisture content was 0.8 mass% with respect to dope whole quantity.

(Formation of acrylic resin-containing film A1)
The produced dope solution was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the residual solvent concentration (residual solvent amount) was 35% by mass, and peeling was performed from the stainless steel band support with a peeling tension of 162 N / m. At this time, the time required from casting to peeling was 100 seconds.

The solvent was evaporated from the peeled acrylic resin web at 35 ° C., slit into 1.6 m width, and then dried at a drying temperature of 135 ° C. while stretching 1.1 times in the width direction with a tenter device. At this time, the residual solvent concentration when starting stretching with a tenter device was 10% by mass.

After stretching with a tenter device, relaxation was performed at 130 ° C for 5 minutes, and then drying was completed while transporting a drying zone at 120 ° C and 130 ° C with many rolls, slitting to a width of 1.5 m, and a width of 10 mm at both ends of the film. A knurling process having a height of 5 μm was performed, and the film was wound around a 6-inch inner diameter core with an initial tension of 220 N / m and a final tension of 110 N / m to obtain an acrylic resin-containing film A1. The draw ratio in the MD direction (casting direction) calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter device was 1.1 times.

The residual solvent concentration of the acrylic resin-containing film A1 described in Table 1 was 0.1% by mass, the film thickness was 60 μm, and the number of turns was 4000 m.

[Examples 2 to 6, Comparative Examples 1 to 4]
Hereinafter, the acrylic resin-containing films A2 to A10 were made in the same manner as the acrylic resin-containing film A1, except that the water content of water, the type of additive, and the amount of additive were changed as shown in Table 1 below. Produced.

<Preparation of polarizing plates H1 to H10>
A 120 μm-thick polyvinyl alcohol film was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a polarizer.

Next, a polarizer, the acrylic resin-containing films A1 to A10, and Konica Minolta Tack KC4UY (cellulose ester film manufactured by Konica Minolta Opto Co., Ltd.) are bonded to the back side in accordance with the following steps 1 to 5, and polarizing plates H1 to H10 Was made.

Step 1: Dipped in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried to obtain an acrylic resin-containing film having a saponified side to be bonded to a polarizer.

Step 2: The polarizer was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.

Step 3: Excess adhesive adhered to the polarizer in Step 2 was gently wiped off, and this was placed on the acrylic resin-containing film treated in Step 1.

Step 4: The acrylic resin-containing film, the polarizer, and the back-side acrylic resin-containing film laminated in Step 3 were bonded at a pressure of 20 to 30 N / cm ² and a conveyance speed of about 2 m / min.

Step 5: A sample obtained by bonding the polarizer, the acrylic resin-containing film, and the Konica Minoltack KC4UY produced in Step 4 in a drier at 80 ° C. is dried for 2 minutes, and each polarizing plate corresponds to the acrylic resin-containing film. H1 to H10 were produced.

Here, using the following evaluation criteria, adhesion evaluation of the polarizing plates H1 to H10 and visual evaluation of white turbidity unevenness were performed.

(Adhesion)
The polarizer of the polarizing plate prepared as described above and the optical film were peeled off by hand, and the adhesiveness was evaluated as follows.

(Double-circle): Material destruction occurs and it does not peel at all.
○: Material destruction occurs, but the area peeled between the sample film and the PVA film is large.
Δ: Some material destruction occurs, but the area peeled between the sample film and the PVA film is large.
X: It peels between a sample film and a PVA film.

(Belt dirt evaluation)
The cloudiness unevenness of the polarizing plate produced as described above was visually observed and evaluated as follows. There were 10 evaluators.

○: No unevenness was recognized by any evaluator.
Δ: The evaluator recognized a slight unevenness, but the product was usable.
X: Although it was faint by five or more evaluators, the nonuniformity was recognized.

As is apparent from Table 1, water was added afterwards so that the water content was 0.8 to 2.0% by mass based on the total amount of the dope, and the additive was contained 1 to 10% by mass based on the total amount of the dope. Examples 1 to 6 were excellent in adhesiveness, and could produce a film with good productivity that hardly adheres to belt dirt.

On the other hand, Comparative Example 1 having a moisture content of less than 0.8% by mass results in poor adhesion, and Comparative Example 2 having a moisture content of more than 2.0% by mass sufficiently adsorbs all the additives to the water molecules. Because of diffusion to the belt side along with the molecules, the belt contamination was poor.

Further, Comparative Example 3 in which no additive was added resulted in particularly poor adhesion.

In Comparative Example 4 in which the additive was excessively blended, all the additives could not be adhered to the water molecules, so the additive molecules could not be unevenly distributed on the opposite side of the belt, and the belt was stained. Was particularly inferior.

DESCRIPTION OF SYMBOLS 1 Melting pot 2, 5, 11, 14, 43 Liquid feed pump 3, 6, 12, 15 Filter 4, 13 Stock tank 8, 16 Pipe | tube 10 Ultraviolet absorber charging pot 20 Merge pipe 21 Mixer 30 Die 31 Metal support Body 32 Web 33 Peeling position 34 Tenter device 35 Roll drying device 37 Winding roll 41 Particle charging tank 42 Stock tank 44 Filter F Film (dope film)
V Additive W Water molecule

Claims (6)

1. After casting the dope composition on a support, the method for producing an acrylic resin-containing film formed by a solution casting film forming method for drying and peeling the dope composition,
   In an organic solvent that dissolves the acrylic resin and the cellulose ester resin, the acrylic resin, the cellulose ester resin and the additive are dissolved in the dissolution vessel while stirring to form a dope composition, and the moisture content is based on the total amount of the dope composition. Having a dope preparation step of preparing a dope composition by post-adding water so as to be 0.8 to 2.0% by mass;
   The method for producing an acrylic resin-containing film, wherein the additive is a polymer compound having a hydrogen bonding component and is contained in an amount of 1 to 10% by mass based on the total amount of the organic solvent.
2. 2. The method for producing an acrylic resin-containing film according to claim 1, wherein a mass ratio of the acrylic resin to the cellulose resin is 95: 5 to 30:70.
3. 3. The method for producing an acrylic resin-containing film according to claim 1, wherein the additive is a copolymer of vinyl pyrrolidone and vinyl acetate, or a copolymer of vinyl acetate and maleic anhydride. .
4. An acrylic resin-containing film produced by using the method for producing an acrylic resin-containing film according to any one of claims 1 to 3.
5. A polarizing plate using the acrylic resin-containing film according to claim 4 on at least one surface.
6. A liquid crystal display device using the acrylic resin-containing film according to claim 4 or the polarizing plate according to claim 5.

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