JP2006299058A - Manufacturing method of cellulose resin film and cellulose resin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose resin film that very hardly suffers from sticking troubles or foreign matter troubles and is therefore excellent as a member of a large-screen liquid crystal display device by suppressing generation of fine particle aggregates turning into foreign matter in a film in a preparation step of a dope containing fine particles. <P>SOLUTION: In the manufacturing method of the cellulose resin film, the cellulose resin has a molecular weight of 200,000-1,000,000 by the static light scattering method and a rotational radius of 50-100 nm by the static light scattering method, and the fine particles are added in a step for dissolving the cellulose resin in a solvent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a cellulose resin film in which a cellulose resin solution containing fine particles dispersed therein is formed by a solution casting method.

  In recent years, notebook computers have been developed to be thinner and lighter, larger screens, and higher definition. Along with this, there is an increasing demand for thinner, wider and higher quality protective films for liquid crystal polarizing plates. In general, a cellulose resin film is widely used as a protective film for a polarizing plate. Cellulose resin films are usually wound around a core to form a film original, which is stored and transported.

  With the recent enlargement of the screen, there is a demand for a film film having a wide film width and a long winding length. When the film width is wide and the winding length is long, the storage stability of the film becomes a problem. For example, a cracking failure in which the films are in close contact with each other and the film is deformed, or a convex failure in which a foreign object is deformed in a convex shape as if a foreign object is sandwiched between the films is likely to occur. In particular, when the width of the original fabric is increased to 1.4 m or more, the effect of knurling provided on both sides is reduced, and the storage stability of the original fabric is likely to deteriorate.

  In order to prevent these, Patent Document 1 proposes a method of adding fine particles. However, with these methods, there is a problem in that foreign substances in the cellulose resin film increase when the addition amount is increased. With the recent increase in image quality, the level of film foreign matter requirements has become stricter, and even small foreign matters that have not been considered a problem have come to be regarded as problems. As a result of our study, foreign matter that appears to be about 50 μm visually is analyzed using an electron microscope, etc., and the core of the foreign matter is about several μm in size, and the periphery of the foreign matter is raised. Then I found that it looked big. It has also been found that most of the core foreign matter is an aggregate of fine particles. For this reason, it has been difficult to satisfy both the characteristics of increasing the amount of addition of fine particles to improve slipperiness and removing only agglomerates of fine particles of several μm or more to reduce foreign matter failure.

  In addition, a method of dispersing a matting agent in a solvent and adding it to a solution containing a resin to produce a fine particle additive solution and adding this to the main dope in-line has been disclosed. When the fine particle addition liquid is filtered with a fine filter, the aggregates of the fine particles are further aggregated with the filter, and the filter is clogged and the filtration pressure increases rapidly. Moreover, in this method, fine particle aggregation occurred due to the impact generated when the fine particle additive solution was added in-line to the main dope, and this could not be removed.

  The method of dispersing the fine particles and the ultraviolet absorber together and adding them to the main dope pot (for example, see Patent Document 2) has a problem that the mixing ratio of the fine particles and the ultraviolet absorber cannot be easily changed. In addition, there is a problem that the dispersion state of the fine particles is poor when the resin and the ultraviolet absorber are dispersed together with the fine particles. Further, since no investigation has been made on the filter medium filtering the main dope, it has been difficult to remove only the aggregates of several μm or more of fine particles.

As a method for removing foreign substances in the dope, multistage filtration is performed in the dope filtration step, and the pore diameter of the filter medium is gradually reduced (for example, see Patent Document 3), or the same pore diameter filter medium is serially connected in the dope filtration process. In the arrangement method (for example, refer to Patent Document 4), foreign substances in the resin can be removed. However, when smaller particles are contained, there is a problem that the filter medium is quickly clogged and the productivity is inferior.
JP 2001-114907 A JP-A-7-11055 JP 2004-105865 A JP 2004-1113897 A

  Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to generate fine particle aggregates that become foreign matters on the film in the production process of a cellulose resin film containing fine particles dispersed therein. It is an object of the present invention to provide a cellulose resin film which is excellent as a member of a large-screen liquid crystal display device and has no foreign matter failure. Moreover, even when a cellulose resin solution containing dispersed fine particles is filtered, a filtration method for a resin solution is provided that has a sufficiently long filtration life and excellent productivity while capturing fine particle aggregates and undissolved resin particles. There is to do.

  The above object of the present invention can be achieved by the following means.

The method for producing a cellulose resin film according to claim 1 is a method for producing a cellulose resin film in which a cellulose resin solution containing dispersed fine particles is formed by a solution casting method.
(I) a step of preparing a cellulose resin solution having a molecular weight of 200,000 to 1,000,000 and a radius of rotation of 50 to 100 nm in a solution state measured by a static light scattering method;
(Ii) filtering the cellulose resin solution;
(Iii) A cellulose resin solution containing fine particles dispersed therein and having a molecular weight of 200,000 to 1,000,000 and a radius of rotation of 50 to 100 nm in a solution state measured by a static light scattering method (hereinafter referred to as in-line) Filtering the additive liquid),
(Vi) adding the in-line additive solution filtered in the step (iii) to the cellulose resin solution filtered in the step (ii) in-line;
(V) a step of casting the cellulose resin solution to which the in-line additive solution has been added on a support;
It is characterized by including.

  The method for producing a cellulose resin film according to claim 2 is the method for producing a cellulose resin film according to claim 1, wherein the fine particles are silicon dioxide, and the content thereof is 0.02 mass% or more and 0.1 mass%. It is characterized by the following.

  The method for producing a cellulose resin film according to claim 3 is the method for producing a cellulose resin film according to claim 1 or 2, wherein the cellulose resin is cellulose triacetate.

  The cellulose resin film according to claim 4 is produced by the method for producing a cellulose resin film according to any one of claims 1 to 3.

  The cellulose resin film according to claim 5 is a cellulose resin film according to claim 4, wherein a distribution index obtained from a Rosin-Rammler distribution in a particle size distribution of fine particles contained in the cellulose resin film is 1.5 or more and 2.2. It is characterized by the following.

  According to the present invention, it is possible to suppress the generation of fine particle aggregates that become foreign matters on the cellulose resin film, greatly reduce cracking failure and foreign matter failure, and filter fine particles aggregates and resin undissolved matters while capturing them. It was possible to provide a method for producing a cellulose resin film that has an effect of having a sufficiently long life and excellent productivity.

  In addition, the coefficient of dynamic friction is small, and the cracking failure and foreign matter failure that occur during film winding are greatly reduced, and a high-quality film can be provided.

  Hereinafter, the present invention will be specifically described.

A method for producing a cellulose resin film containing dispersed fine particles according to the present invention,
(I) a step of preparing a cellulose resin solution having a molecular weight of 200,000 to 1,000,000 and a radius of rotation of 50 to 100 nm in a solution state measured by a static light scattering method;
(Ii) filtering the cellulose resin solution;
(Iii) A cellulose resin solution containing fine particles dispersed therein and having a molecular weight of 200,000 to 1,000,000 and a radius of rotation of 50 to 100 nm in a solution state measured by a static light scattering method (hereinafter referred to as in-line) Filtering the additive liquid),
(Vi) adding the in-line additive solution filtered in the step (iii) to the cellulose resin solution filtered in the step (ii) in-line;
(V) a step of casting the cellulose resin solution to which the in-line additive solution has been added on a support;
It is characterized by including.

  Here, the “solution casting method” refers to a method for producing a film by casting a dope in which a cellulose resin is dissolved on a support, followed by a drying step.

  The “fine particles” referred to here are fine particles as a matting agent for imparting slipperiness to the film surface, and the average primary particle size is preferably 5 nm to 100 nm, more preferably 10 nm. ~ 50 nm. The average primary particle diameter is measured by observing fine particles with a transmission electron microscope and measuring the particle diameter from the photograph.

  The flow sheet of the manufacturing line of one Embodiment of the manufacturing method of the cellulose resin film of this invention is shown in FIG.

  In the main dope charging pot 1, a cellulose resin is dissolved while mixing a predetermined amount of a cellulose resin and a solvent for dissolving the cellulose resin, a plasticizer, a flame retardant, and the like to prepare a dope. In the fine particle dispersion diluent tank 12, a fine particle dispersion in which fine particles are dispersed in advance and a dilution solvent are mixed to prepare a fine particle dispersion dilution. In the in-line additive solution vessel 6, the dilute solution and the ultraviolet absorber are mixed and dissolved in the dope prepared in the main dope charging vessel 1, and the fine particle dispersion diluted solution passed through the fine particle dispersed diluent filter 14 is placed therein. An in-line additive solution is prepared by quantitative mixing.

  The dope prepared in the main dope charging pot 1 passes through the main filter 4 and the dope filter 5 as a filtration step through the dope stationary pot 3 by the dope feed pump 2. Next, a required amount of the inline additive solution is added from the inline addition vessel 6 to the dope via the inline additive solution feed filter 7 by the inline addition solution feed pump 9. Thereafter, the dope and the in-line additive solution are sufficiently mixed by the static mixer 10, and this mixed solution is uniformly cast (casting step) from the casting die 11 onto the stainless steel band support 101 as a film forming step. A part of the solvent evaporates (casting process) on the stainless steel band support 101 to form a film and is peeled off by the peeling roll 102, and then passes through the tenter / drying device 104 and the roll transport / drying device 105. (Film drying step) The film is wound around the film winding device 106. In this way, a cellulose resin film is produced.

  Examples of the cellulose ester according to the present invention include cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, and cellulose acetate propionate. In the case of cellulose triacetate, cellulose triacetate having a polymerization degree of 250 to 400 and a bound acetic acid amount of 54 to 62.5% is particularly preferable, and a base strength having a bound acetic acid amount of 58 to 62.5% is strong and more preferable. As the cellulose triacetate, either cellulose triacetate synthesized from cotton linter or cellulose triacetate synthesized from wood pulp can be used alone or in combination.

  It is preferable to use a large amount of cellulose triacetate synthesized from a cotton linter that has good releasability from a belt or a drum because of high productivity efficiency. Since the ratio of cellulose triacetate synthesized from cotton linter is 60% by mass or more and the effect of releasability becomes remarkable, 60% by mass or more is preferable, more preferably 85% by mass or more, and further, it can be used alone. Most preferred.

  In the present invention, a molecular weight of 200 to 1,000,000 and a radius of rotation of 50 to 100 nm are preferable when measured by a static light scattering method of cellulose resin. When the molecular weight is less than 200,000 or when the radius of rotation is less than 50 nm, the dispersion of the fine particles becomes too good when the fine particles are mixed, and the addition amount of the fine particles must be increased to obtain the desired film slipperiness. The film transparency deteriorates and is not preferable as a film for liquid crystal. When the molecular weight exceeds 1,000,000 or the radius of rotation exceeds 100 nm, when mixed with fine particles, aggregation of the fine particles is promoted, and foreign matter defects are frequently generated due to the generation of coarse particles.

  As a method of controlling the molecular weight and the radius of rotation of the present invention, there is a method of controlling by the solubility of the cellulose resin. When the solubility of the cellulose resin is improved, the molecular weight decreases and the radius of rotation also decreases. As a method for improving the solubility, the type of the solvent or the composition of the mixed solvent is changed. For example, in the solution casting film forming method, a method in which a dope cast on a metal support is initially dried, peeled off from the support, and further dried. In order to improve releasability from the support, cellulose is used. Add a poor solvent to the resin. As the poor solvent for the cellulose resin, an alcohol solvent is often used. Increasing the proportion of this poor solvent increases the molecular weight and the radius of rotation. Conversely, when the ratio of the poor solvent is lowered, the molecular weight is lowered and the rotation radius is also reduced. However, when the ratio of the poor solvent is excessively lowered, the peelability from the metal support is deteriorated. It is also possible to reverse the behavior of molecular weight and rotational radius by changing the type of solvent.

  A dynamic light scattering photometer (DLS-7000 series) manufactured by Otsuka Electronics Co., Ltd. can be used as an apparatus for measuring molecular weight and rotational radius by the static scattering method. In addition, the dope used for the measurement is measured after separately preparing a cellulose resin dissolved in a solvent used for the dope without adding fine particles and filtering the solution with a filter (a membrane filter having a pore diameter of 0.2 μm).

  The molecular weight and the radius of rotation by the static scattering method are, for example, a sampled dope (in a state in which fine particles are not added) having the same composition as the solvent used for the dope and a solid content concentration of 1% by mass, 2% by mass, The solution was diluted to 3% by mass and 4% by mass, and each solution was measured at 20 °, 30 °, 40 °, 60 °, 90 °, 120 °, and 150 ° at the above dynamic light scattering photometer DLS-7000 manufactured by Otsuka Electronics. And can be determined by the Zim plot method. The refractive index of the solvent necessary for the analysis is obtained from an Abbe refractometer, and the refractive index concentration gradient (dn / dc) is measured with DRM-1021 manufactured by Otsuka Electronics.

  Examples of the solvent for the cellulose resin according to the present invention include lower alcohols such as methanol, ethanol, n-propyl alcohol, iso-propyl alcohol and n-butanol, lower aliphatic hydrocarbon chlorides such as cyclohexanedioxane and methylene chloride. Things can be used. As the solvent ratio, for example, 70 to 95% by mass of methylene chloride and 5 to 30% by mass of other solvents are preferable. The concentration of the cellulose resin is preferably 10 to 50% by mass.

  The fine particles according to the present invention are used as a matting agent in a cellulose resin film. The kind of fine particles may be an inorganic compound or an organic compound. Examples of the inorganic compound include fine particles of silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, tin oxide, and the like. In this, it is preferable that it is a compound containing a silicon atom, and especially a silicon dioxide fine particle is preferable. As the silicon dioxide fine particles, for example, Aerosil 200, 200V, 300, R972, R972V, R974, R976, R976S, R202, R812, R805, OX50, TT600, RY50, RX50, NY50, NAX50, NA50H, NA50Y manufactured by Aerosil Co., Ltd. , NX90, RY200S, RY200, RX200, R8200, RA200H, RA200HS, NA200Y, R816, R104, RY300, RX300, R106 and the like. AEROSIL 200V and R972V are preferable in terms of controlling dispersibility and particle size.

  The fine particles have different primary particle sizes, particle sizes after being dispersed in a solvent, and particle sizes in the film. Among these, the particle size of the fine particles in the final film affects the cracking failure during storage of the original film, the convex failure due to the generation of foreign matter, and the haze. Therefore, it is important to control the particle size of the fine particles in the film.

  In the present invention, the average secondary particle size of the fine particles in the film must finally be 100 nm to 500 nm. Preferably, they are 150 nm-400 nm, More preferably, they are 200 nm-350 nm. The average secondary particle size in the film can be confirmed by taking and observing a cross-sectional photograph. If the particle diameter exceeds 500 nm, haze deterioration or the like may be observed, or it may cause a failure in a wound state as a foreign matter. Moreover, when it is smaller than 100 nm, sufficient effect of improving the winding property is not seen, and particularly when the film thickness of the cellulose resin film is 20 to 65 μm, it is remarkable.

  The haze of the film can be measured, for example, according to ASTM-D1003-52. The haze is preferably 0 to 0.6%, more preferably 0 to 0.4%, and still more preferably 0.1 to 0.2%.

  In the present invention, it is preferable to add 0.02 to 0.1% by mass of the fine particles in the film state from the viewpoint of cracking failure or convex failure due to generation of foreign matter during storage of the film raw material, and haze. . More preferably, it is 0.04-0.08 mass%.

For the dispersion of the fine particles, a composition in which the fine particles and the solvent are mixed can be processed with a high-pressure dispersion apparatus. The high-pressure dispersion apparatus used for dispersion can be a high-pressure dispersion apparatus that creates special conditions such as high shear and high pressure by passing a composition in which fine particles and a solvent are mixed at high speed through a narrow tube. It is preferable that the maximum pressure condition inside the apparatus is 980 N / cm ² or more in a thin tube having a tube diameter of 1 to 2000 μm, for example, by processing with a high-pressure dispersion apparatus. More preferably, it is 1960 N / cm ² or more. At that time, it is preferable that the maximum reaching speed reaches 100 m / sec or more, and the heat transfer speed reaches 418 kJ / hr or more.

  Examples of the high-pressure dispersion apparatus include an ultrahigh-pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation or a nanomizer manufactured by Nanomizer, and other examples include a Manton Gorin type high-pressure dispersion apparatus such as a homogenizer manufactured by Izumi Food Machinery. .

  The fine particle is dispersed in a solvent containing 25 to 100% by weight of a water-soluble solvent, and then diluted by adding a non-water-soluble organic solvent 0.5 to 1.5 times with respect to the water-soluble solvent and diluting. Can be used as A dilute solution in which the fine particles are dispersed in a dissolving step of dissolving the cellulose resin in a solvent can be added and used as a dope. The dope is cast on a support and dried to form a cellulose resin film.

  As the water-soluble solvent, lower alcohols are mainly used. Preferred examples of lower alcohols include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like.

  The water-insoluble solvent is not particularly limited, but it is preferable to use a solvent used when forming a cellulose resin film, and those having a solubility in water of 30% by mass or less are used, such as methylene chloride, chloroform, and methyl acetate. It is done.

  The fine particles are dispersed in the solvent at a concentration of 1 to 30% by mass. Dispersing at a concentration higher than this is not preferable because the viscosity increases rapidly. The concentration of fine particles in the dispersion is preferably 5 to 25% by mass, more preferably 10 to 20% by mass.

  In the present invention, a plasticizer may be added. Although it does not specifically limit as a plasticizer which can be used by this invention, In a phosphate ester type | system | group, a triphenyl phosphate, a tricresyl phosphate, a cresyl diphenyl phosphate, an octyl diphenyl phosphate, a diphenyl biphenyl phosphate, a trioctyl phosphate, a tributyl phosphate In the phthalate ester system, diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, etc., in the glycolate system, triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl Use phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate alone or in combination It is preferred.

  If necessary, two or more plasticizers may be used in combination. In this case, the use ratio of the phosphate ester plasticizer is 50% or less, which hardly causes hydrolysis of the cellulose resin film and is durable. It is preferable because of its excellent properties.

  It is more preferable that the ratio of the phosphate ester plasticizer is small, and it is particularly preferable to use only a phthalate ester or glycolate ester plasticizer.

  In the cellulose resin film of the present invention, it is preferable to use an ultraviolet absorber, and the ultraviolet absorber is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the liquid crystal and has good liquid crystal display properties. Those having as little absorption of visible light as possible with a wavelength of 400 nm or more are preferably used.

  In the present invention, in particular, the transmittance at a wavelength of 370 nm needs to be 10% or less, preferably 5% or less, more preferably 2% or less.

  Examples of commonly used compounds include, but are not limited to, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like.

  In this invention, it is preferable to use 1 or more types of these ultraviolet absorbers, and you may contain 2 or more types of different ultraviolet absorbers.

  The ultraviolet absorber preferably used in the present invention is a benzotriazole ultraviolet absorber, a benzophenone ultraviolet absorber, or the like. An embodiment in which a benzotriazole-based ultraviolet absorber with less unnecessary coloring is added to the cellulose resin film is particularly preferable.

  The ultraviolet absorber may be added to the dope after dissolving the ultraviolet absorber in an organic solvent such as alcohol, methylene chloride, dioxolane, or directly into the dope composition. For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and the cellulose resin to be dispersed and then added to the dope.

  The amount of the ultraviolet absorber used in the present invention is 0.1% by mass to 2.5% by mass, preferably 0.5% by mass to 2.0% by mass, and more preferably 0.8% by mass with respect to the cellulose resin. It is mass%-2.0 mass%. When the amount of the ultraviolet absorber used is more than 2.5% by mass, the transparency tends to deteriorate, which is not preferable.

  The process for producing the cellulose resin film in the present invention is not particularly limited, and may be a method generally used in the art. For example, U.S. Pat. Nos. 2,492,978, 2,739,070, 2 739,069, 2,492,977, 2,336,310, 2,367,603, 2,607,704, British Patents 64,071, 735,892 The methods described in JP-B-45-9074, JP-A-49-4554, JP-A-49-5614, JP-A-60-27562, JP-A-61-39890, and JP-A-62-4208 can be referred to.

In the present invention, it is preferable to add the fine particles to the dope in the following order.
B) Disperse the fine particles in the solvent in advance.
(B) The dispersion is filtered for at least one step.
(C) Then, the dope is mixed and stirred with the diluted solution.
D) Thereafter, the filtration is performed again for at least one step.
After that, add in-line to the dope.

  By doing in this way, generation | occurrence | production of the foreign material in a film can be suppressed. In addition, the fine particles may remain in powder form and may be mixed and stirred with a solution in which the above-mentioned dope is diluted. However, it is preferable to disperse in a solvent in advance from the viewpoint of dispersibility. Moreover, it is preferable from a viewpoint of the dispersibility of microparticles | fine-particles to prepare the solution mixed with microparticles | fine-particles by diluting dope and making a solid content concentration low.

  Additives such as a plasticizer and an ultraviolet absorber may be mixed with a solvent in advance and dissolved or dispersed, and then added to the solvent before dissolving the cellulose resin, or may be added to the dope after dissolving the cellulose resin.

  In the preparation of the dope, the type of the pressure vessel is not particularly limited as long as it can withstand a predetermined pressure and can be heated and stirred under pressure. In addition to the pressure vessel, other instruments such as a pressure gauge and a thermometer are appropriately disposed. The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or by increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy. The heating temperature with the addition of the solvent is preferably a temperature that is not lower than the boiling point of the solvent used and does not boil, and is preferably set in the range of 60 ° C. or higher and 80 to 110 ° C., for example. The pressure is determined so that the solvent does not boil at the set temperature. After dissolution, remove from the container while cooling, or extract from the container with a pump or the like and cool with a heat exchanger or the like, and then pass through at least one filtration step from the viewpoint of suppressing foreign matter, and then use this for film formation Is preferred. Although the cooling temperature at this time may be cooled to room temperature, it is more preferable to cool to a temperature 5 to 10 ° C. lower than the boiling point and perform casting at that temperature because the dope viscosity can be reduced.

  In the film forming process of the present invention, a dope containing dispersed fine particles is cast on a support (casting process), heated to remove a part of the solvent (drying process on the support), and then supported. The film peeled from the body is dried (film drying step) to obtain a cellulose resin film.

  As the support in the casting process, a support in which a belt-like or drum-like stainless steel is mirror-finished is used. The temperature of the support in the casting process can be cast in a general temperature range of 0 ° C. to a temperature lower than the boiling point of the solvent, but the dope is gelled by casting on a support at 5 ° C. to 30 ° C. In order to increase the peeling limit time, it is preferable to cast on a support at 5 to 15 ° C. The peeling limit time is the time during which the cast dope is on the support at the limit of the casting speed at which a transparent and flat film can be continuously obtained. A shorter peeling limit time is preferable because of excellent productivity.

  In the drying process on the support, the dope is cast and gelled, and the time from casting to peeling is defined as 100%, and the dope temperature is set to 40 ° C. to 70 ° C. within 30% from the casting. By promoting the evaporation of the solvent, it can be peeled off from the support as soon as possible, and the peel strength is further increased, and it is more preferable that the dope temperature be 55 ° C. to 70 ° C. within 30%. . This temperature is preferably maintained at 20% or more, more preferably 40% or more.

  Drying on the support is preferably peeled from the support with a residual solvent amount of 60% to 150% because the peel strength from the support is reduced, and more preferably 80 to 120%. The dope temperature at the time of peeling is preferably 0 ° C. to 30 ° C., because the base strength at the time of peeling can be increased and the base breakage at the time of peeling can be prevented, and 5 ° C. to 20 ° C. is more preferable.

  The amount of residual solvent in the film is represented by the following formula.

Residual solvent amount (mass%) = residual volatile matter mass / heat-treated film mass × 100
The residual volatile matter mass is a value obtained by subtracting the film mass after the heat treatment from the film mass before the heat treatment when the film is heat treated at 115 ° C. for 1 hour.

  In the film drying step, the film peeled off from the support is further dried, and the residual solvent amount is 3% by mass or less, preferably 1% by mass or less, more preferably 0.5% by mass or less. It is preferable for obtaining a good film. In the film drying process, generally, a roll suspension system, a pin tenter system, or a clip tenter system is used for drying while transporting the film. For the liquid crystal display member, it is preferable to dry while maintaining the width by a tenter method in order to improve the dimensional stability. In particular, maintaining the width where the amount of residual solvent is large immediately after peeling from the support exhibits a greater effect of improving dimensional stability. In particular, in the drying process after peeling from the support, the film tends to shrink in the width direction due to evaporation of the solvent, and thus shrinkage increases as the film is dried at a higher temperature. In order to improve the flatness of the finished film, it is preferable to dry while suppressing the shrinkage as much as possible. From this point, for example, a method of drying the whole drying process or a part of the process as shown in Japanese Patent Application Laid-Open No. 62-46625 while holding the both ends of the web with a width in the width direction (tenter method) ) Is preferred.

  The means for drying the film is not particularly limited, and is generally performed with hot air, infrared rays, a heating roll, microwaves, or the like. It is preferable to carry out with hot air in terms of simplicity. The drying temperature is preferably in the range of 40 ° C. to 150 ° C. and divided into 3 to 5 stages, and it is preferable to increase the temperature step by step, and it is more preferable to carry out in the range of 80 ° C. to 140 ° C. in order to improve the dimensional stability. .

  These steps from casting to post-drying may be performed in an air atmosphere or an inert gas atmosphere such as nitrogen gas.

  It goes without saying that the dry atmosphere is carried out in consideration of the explosion limit concentration of the solvent.

  The winding machine relating to the production of the cellulose resin film of the present invention may be a commonly used winding method such as a constant tension method, a constant torque method, a taper tension method, a program tension control method with a constant internal stress. Can be rolled up.

  The thickness of the cellulose resin film according to the present invention is generally used in a thickness of 20 to 200 μm, but 20 to 65 μm is required in order to reduce the thickness and weight of the polarizing plate used in the liquid crystal display device. More preferably, it is 30-60 micrometers, More preferably, it is 35-50 micrometers. If it is thinner than this, the stiffness of the film will decrease, so it will be easy to cause problems due to wrinkles on the polarizing plate making process, and if it is thicker than this, it will contribute to the thinning of the polarizing plate. Less is.

  In order to stabilize the winding property, a so-called knurling process may be performed in which unevenness is imparted to both ends in the width direction of the cellulose resin film to make the ends bulky.

  When the ratio of the knurling height (a: μm) to the film thickness (d: μm) X (%) = (a / d) × 100, the range of X = 1 to 25% stabilizes the winding property. Good for. Preferably, it is 1 to 15%, more preferably 1 to 10%. From this range, if the knurling height ratio is large, the winding shape is likely to be deformed, and if the ratio is small, the winding property is deteriorated, which is not preferable.

  It is preferable that there are few foreign substances contained in the cellulose resin film according to the present invention. Foreign materials include foreign materials that are recognized in the polarization crossed Nicol state, and foreign materials due to aggregates of fine particles protruding on the film surface.

  The foreign substance recognized in the polarization crossed Nicol state refers to that measured by placing two polarizing plates in a direct (crossed Nicol) state and placing a cellulose resin film between them. In the polarization crossed Nicol state, such a foreign substance is observed by shining only the part of the foreign substance in the dark field, so that the size and number can be easily identified.

  In the production method according to the present invention, in order to obtain a cellulose resin film with few foreign matters, fine particles are dispersed in a solution in which cellulose resin is dissolved in advance, and the dispersion is passed through at least one filtration step. This can be achieved by adding in-line to the resin solution that has passed at least one step and forming a film by the solution casting method. In this case, it is preferable to use a filter paper having a drainage time of 20 sec or more as a kind of filter paper, and form a film by filtering at a filtration pressure of 1.6 MPa or less. More preferably, a filter paper of 30 sec or more is used and the filtration pressure is 1.2 MPa or less, and still more preferably, a filter paper of 40 sec or more is used and the filtration pressure is 1 MPa or less. Moreover, it is more preferable to use two or more of the above filter papers. The filtration pressure can be controlled by appropriately selecting the filtration flow rate and the filtration area.

  Foreign matter due to fine particle aggregation can be reduced by improving the dispersion state of the fine particles in the film. In the present invention, the particle size of the fine particles in the film is measured, and the distribution index obtained from the rosin lambler distribution calculated from the particle size distribution is reduced to 1.5 to 2.2 while reducing foreign matter on the surface, The slipperiness effect due to the fine particles can be maintained. If it is less than 1.5, the number of foreign matters increases, and as a result, the coefficient of friction of the film decreases too much, and winding disturbance occurs in the winding process, which is not preferable. If it is 2.2 or more, the coefficient of friction becomes high, film deformation occurs in the film winding process, and the deformation remains when the polarizing plate is processed.

  The particle size of the fine particles used to determine the Rosin-Rammler distribution can be determined from the particle size distribution of 1000 or more fine particles by observing a tomographic photograph of the film with a transmission electron microscope at a magnification of 5000 times. As the particle size at this time, the equivalent circle diameter is used, and particles having an equivalent circle diameter of less than 50 nm are not counted.

  In order to make the distribution index obtained from the Rosin-Lambler distribution within the above range, a resin having a molecular weight of 200 to 1,000,000 and a radius of rotation of 50 to 100 nm obtained by a static light scattering method of a cellulose resin solution is used and contains fine particles. This can be achieved by filtration of the cellulose resin solution. It can also be adjusted by a combination of filter filter pore size, filter arrangement, filter material, and the like. Moreover, it can adjust also by the addition timing which adds the surface treatment of microparticles, and microparticles | fine-particles to a cellulose resin melt | dissolution process.

Example 1
FIG. 1 shows a flow sheet of the cellulose resin film production apparatus used in Example 1.
<Preparation of each solution>
(Dope)
100 parts by weight of cellulose ester (cellulose triacetate synthesized from linter cotton)
(Mn = 116000, Mw = 360000, Mw / Mn = 3.1)
Triphenyl phosphate 9.5 parts by weight Ethylphthalylethyl glycolate 2.2 parts by weight Methylene chloride 440 parts by weight Ethanol 40 parts by weight The above is put into the main dope charging vessel 1, heated and stirred, and completely dissolved. And it filtered using the main filter 4 (Azumi filter paper Co., Ltd. product: Azumi filter paper No. 24), and prepared dope. Thereafter, the dope was further filtered with a dope filter 5 (manufactured by Nippon Seisen Co., Ltd .: Finemet NF).
(Silicon dioxide dispersion)
Aerosil 200V (manufactured by Nippon Aerosil Co., Ltd.) 2 parts by mass (average diameter of primary particles 12 nm, apparent specific gravity 0.1)
18 parts by mass or more of ethanol was stirred and mixed with a dissolver for 30 minutes, and then dispersed with Manton Gorin. The liquid turbidity after dispersion was 100 ppm. To this silicon dioxide dispersion, 18 parts by mass of methylene chloride was added while stirring, and the mixture was stirred and mixed for 30 minutes with a dissolver to prepare a silicon dioxide dispersion dilution. The obtained silicon dioxide dispersion dilution was filtered with a fine particle dispersion dilution filter 14 (Advantech Toyo Co., Ltd .: polypropylene wind cartridge filter TCW-PPS-1N) in FIG.
(In-line additive solution)
Methylene chloride 100 parts by weight Dope solution 34 parts by weight Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 5 parts by weight Tinuvin 171 (manufactured by Ciba Specialty Chemicals) 5 parts by weight Tinuvin 326 (manufactured by Ciba Specialty Chemicals) 3 Part by mass The above was put into the in-line additive solution kettle 6, heated, and completely dissolved while stirring.

  To this was added 20 parts by mass of a silicon dioxide dispersion diluted solution while stirring, and further stirred for 60 minutes, and then an in-line additive solution circulating filter 7 (Advantech Toyo Co., Ltd .: polypropylene wind cartridge filter TCW-PPS-1N). To prepare an in-line additive solution.

  Next, the in-line additive solution is filtered with an in-line additive solution feeding filter 8 (manufactured by Nippon Seisen Co., Ltd .: Finemet NF), and the filtered in-line additive solution 2.5 mass with respect to 100 parts by mass of the filtered dope. The in-line mixer 10 (Toray static type in-tube mixer Hi-Mixer, SWJ) was sufficiently mixed. Next, the belt was cast uniformly on the stainless steel band support 101 at a temperature of 35 ° C. and a width of 1800 mm using a belt casting apparatus. With the stainless steel band support 101, the solvent was evaporated until the residual solvent amount reached 100%, and the stainless steel band support 101 was peeled off. The web of the peeled cellulose resin film was evaporated at 35 ° C., slit to 1650 mm width, and then stretched 1.1 times at 130 ° C. in the TD direction (direction perpendicular to the film transport direction). At this time, the amount of residual solvent when starting stretching with a tenter was 20%. Then, drying is completed while transporting the inside of the drying apparatus 105 at 120 ° C. and 110 ° C. with a number of rolls, slitting to a width of 1400 mm, a knurling process having a width of 15 mm and a height of 10 μm is applied to both ends of the film, and wound around a winding core. To obtain a cellulose resin film. The residual solvent amount of the cellulose resin film was 0.2%, the film thickness was 80 μm, and the winding number was 4000 m.

  Moreover, the following were used as dope for molecular weight and rotation radius measurement by a static light scattering method.

100 parts by weight of cellulose ester (cellulose triacetate synthesized from linter cotton)
(Mn = 116000, Mw = 360000, Mw / Mn = 3.1)
Methylene chloride 440 parts by mass Ethanol 40 parts by mass or more was put into a sealed container, heated, stirred and completely dissolved, and filtered through a membrane filter (material PTFE) having a pore size of 0.2 μm. The dope was diluted, the molecular weight measured by the static light scattering method was 430000, and the rotation radius was 70 nm.
(Example 2)
A cellulose resin film was obtained in the same manner as in Example 1 except that the molecular weight of the cellulose ester of Example 1 was changed to Mn = 135000, Mw = 340000, and Mw / Mn = 2.5.

  Moreover, the following were used as dope for molecular weight and rotation radius measurement by a static light scattering method.

100 parts by weight of cellulose ester (cellulose triacetate synthesized from linter cotton)
(Mn = 135000, Mw = 340000, Mw / Mn = 2.5)
Methylene chloride 440 parts by mass Ethanol 40 parts by mass or more was put into a sealed container, heated, stirred and completely dissolved, and filtered through a membrane filter (material PTFE) having a pore size of 0.2 μm. The dope was diluted, the molecular weight measured by the static light scattering method was 210000, and the rotation radius was 52 nm.
(Example 3)
A cellulose resin film was obtained in the same manner as in Example 1 except that the molecular weight of the cellulose ester of Example 1 was changed to Mn = 100000, Mw = 370000, and Mw / Mn = 3.7.

  Moreover, the following were used as dope for molecular weight and rotation radius measurement by a static light scattering method.

100 parts by weight of cellulose ester (cellulose triacetate synthesized from linter cotton)
(Mn = 100000, Mw = 370000, Mw / Mn = 3.7)
Methylene chloride 440 parts by mass Ethanol 40 parts by mass or more was put into a sealed container, heated, stirred and completely dissolved, and filtered through a membrane filter (material PTFE) having a pore size of 0.2 μm. The dope was diluted, the molecular weight measured by the static light scattering method was 720000, and the rotation radius was 78 nm.
Example 4
The fine particles of Example 1 were changed to Aerosil R972V (manufactured by Nippon Aerosil Co., Ltd.) (average particle size of primary particles 16 nm, apparent specific gravity 90 g / liter), and 40 parts by mass of silicon dioxide dispersion diluted solution was added to the in-line additive solution. In the same manner as in Example 1, a cellulose resin film was obtained.

(Comparative Example 1)
The molecular weight of the cellulose ester of Example 1 was changed to Mn = 155000, Mw = 305000, and Mw / Mn = 2.0, and the inline additive solution of the inline additive vessel 6 was added to the main dope dissolving vessel 1 as shown in FIG. Then, a cellulose resin film was obtained in the same manner as in Example 1 except that it was dissolved by heating together with the cellulose resin.

  Moreover, the following were used as dope for molecular weight and rotation radius measurement by a static light scattering method.

100 parts by weight of cellulose ester (cellulose triacetate synthesized from linter cotton)
(Mn = 155000, Mw = 305000, Mw / Mn = 2.0)
Methylene chloride 440 parts by mass Ethanol 40 parts by mass or more was put into a sealed container, heated, stirred and completely dissolved, and filtered through a membrane filter (material PTFE) having a pore size of 0.2 μm. The dope was diluted, the molecular weight measured by the static light scattering method was 18000, and the rotation radius was 45 nm.
(Comparative Example 2)
The molecular weight of the cellulose ester of Example 1 was changed to Mn = 145000, Mw = 300,000, Mw / Mn = 2.1, and the filtration of the in-line additive liquid circulation filter 7 was omitted. A cellulose resin film was obtained.

  Moreover, the following were used as dope for molecular weight and rotation radius measurement by a static light scattering method.

100 parts by weight of cellulose ester (cellulose triacetate synthesized from linter cotton)
(Mn = 145000, Mw = 300000, Mw / Mn = 2.1)
Methylene chloride 440 parts by mass Ethanol 40 parts by mass or more was put into a sealed container, heated, stirred and completely dissolved, and filtered through a membrane filter (material PTFE) having a pore size of 0.2 μm. The dope was diluted, the molecular weight measured by the static light scattering method was 120,000, and the rotation radius was 38 nm.

The evaluation methods of Examples 1 to 4 and Comparative Examples 1 and 2 are as shown below, and the results are shown in Table 1.
(Dynamic friction coefficient)
The dynamic friction coefficient between the film surface and the back surface is cut out so that the front and back surfaces of the film are in contact with each other according to JIS-K-7125 (1987), a 200 g weight is placed, the sample moving speed is 100 mm / min, and the contact area is 80 mm × 200 mm. The weight was pulled horizontally under the following conditions, the average load (F) while the weight was moving was measured, and the dynamic friction coefficient (μ) was determined from the following equation.

Coefficient of dynamic friction = F (N) / Weight of weight (N)
When the coefficient of dynamic friction is 1.00 or more, the film has a lot of cracking failure and is not suitable for practical use.
(Evaluation of film foreign matter)
An online defect inspection machine was installed immediately before the winding part of the belt casting apparatus, and 10 cellulose acetate raw films were inspected, and the average number of foreign matters of 20 μm or more per 100 m ^{2 of} the cellulose acetate film was calculated.
(Particle size of fine particles in the film)
The final film of 2600 m roll was sampled, the particles were observed with a scanning electron microscope (magnification 5000 times), and the diameter of the circle circumscribing the particles was taken as the particle size. In addition, 200 particles were observed at different locations, the particle size distribution was plotted on a Rosin-Rammler diagram, and the slope of the diagram was taken as the distribution index.
(Molecular weight and radius of rotation of cellulose resin in dope)
The molecular weight and the radius of rotation are measured by diluting the sampled dope with the same composition as the solvent used for the dope to a solid content concentration of 1%, 2%, 3%, and 4% by weight. Were measured with a DLS-7000 manufactured by Otsuka Electronics at measurement angles of 20 degrees, 30 degrees, 40 degrees, 60 degrees, 90 degrees, 120 degrees, and 150 degrees, and analyzed by the Zimm plot method. The refractive index of the solvent required for the analysis was obtained from an Abbe refractometer, and the refractive index concentration gradient (dn / dc) was measured with DRM-1021 manufactured by Otsuka Electronics.

  As is clear from the results in Table 1 above, in Examples 1 to 4 of the present invention, it can be seen that the number of foreign matters is very small and the dynamic friction coefficient is small. In addition, according to the cellulose resin films of Examples 1 to 4 of the present invention, the rosin Ramler distribution index of the fine particles in the film is in the range of 1.5 to 2.2. As a result, it becomes possible to meet the demands for thinning, widening and high quality of the protective film for the liquid crystal polarizing plate.

  In contrast, it can be seen that Comparative Example 1 has a large dynamic friction coefficient, and Comparative Example 2 has a large number of foreign matters. In Comparative Examples 1 and 2, it can be seen that the Rosin-Rammler distribution index exceeds the range of 1.5 to 2.2, the number of foreign matters is large, and the dynamic friction coefficient is large.

It is a flow sheet which shows the manufacturing method of the cellulose resin film of this invention. It is a flow sheet which shows the manufacturing method of the cellulose resin film of a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main dope preparation tank 2 Dope liquid feed pump 3 Dope stationary tank 4 Main filter 5 Dope filter 6 Inline additive liquid tank 7 Inline additive liquid circulation filter 8 Inline additive liquid liquid filter 9 Inline additive liquid liquid pump DESCRIPTION OF SYMBOLS 10 In-line mixer 11 Casting die 12 Fine particle dispersion dilution liquid tank 13 Fine particle dispersion dilution liquid circulation pump 14 Fine particle dispersion dilution liquid filter 101 Stainless steel band support 102 Peeling roll 103 Film 104 Tenter / drying device 105 Roll conveyance / drying device 106 Film winding device

Claims (5)

In the method for producing a cellulose resin film in which a cellulose resin solution containing fine particles dispersed therein is formed by a solution casting method,
(I) a step of preparing a cellulose resin solution having a molecular weight of 200,000 to 1,000,000 and a radius of rotation of 50 to 100 nm in a solution state measured by a static light scattering method;
(Ii) filtering the cellulose resin solution;
(Iii) A cellulose resin solution containing fine particles dispersed therein and having a molecular weight of 200,000 to 1,000,000 and a radius of rotation of 50 to 100 nm in a solution state measured by a static light scattering method (hereinafter referred to as in-line) Filtering the additive liquid),
(Vi) adding the in-line additive solution filtered in the step (iii) to the cellulose resin solution filtered in the step (ii) in-line;
(V) a step of casting the cellulose resin solution to which the in-line additive solution has been added on a support;
The manufacturing method of the cellulose resin film characterized by including. The method for producing a cellulose resin film according to claim 1, wherein the fine particles are silicon dioxide, and the content thereof is 0.02 mass% or more and 0.1 mass% or less. The method for producing a cellulose resin film according to claim 1, wherein the cellulose resin is cellulose triacetate. A cellulose resin film produced by the method for producing a cellulose resin film according to claim 1. 5. The cellulose resin film according to claim 4, wherein a distribution index obtained from a rosin Ramler distribution in a particle size distribution of fine particles contained in the cellulose resin film is 1.5 or more and 2.2 or less.

Images