JP4137074B2 - Cellulose acylate solution and method for producing the same - Google Patents

Description

  The present invention relates to a cellulose acylate solution and a method for producing the same, and more particularly to a cellulose acylate solution that is a raw material for a film used in a polarizing plate, a liquid crystal display device, and the like, and a method for producing the same.

  Cellulose acylate films are used for applications such as photographic films and animation films, but have properties such as transparency, moderate moisture permeability, mechanical strength, dimensional stability and low dependency on humidity and temperature. Therefore, it is widely used in the optical field and the like. In recent years, the demand for a polarizing plate protective film in this application has been remarkably increased due to an increase in demand for liquid crystal displays and higher performance and larger screens. Since the liquid crystal display has recently been improved in definition, the cellulose acylate film used in the liquid crystal display has been required to have improved smoothness and reduced foreign substances.

  Such a cellulose acylate film is often produced by a solution casting method, and according to this casting method, a film having extremely high smoothness can be obtained. However, due to its high smoothness, film surfaces may adhere to each other when winding with a winding core after film formation. When this is used as a product, when the film is unwound, excessive stress is applied to the adhesive surfaces by peeling off the adhered film surfaces, and the film is deformed in a bumpy shape. This deformation significantly reduces the function as a polarizing plate protective film or the like.

  In order to prevent this adhesion, it is necessary to give the film surface an appropriate roughness, and therefore fine particles called matting agent are contained. Adhesion can be prevented by mixing an appropriate amount of matting agent, and failure such as deformation can be suppressed.

  As the matting agent, various metal oxides, metal salts, organic substances, polymer compounds, and the like are used, and these always include coarse particles formed by aggregation. If fine particles are mixed into the film in the presence of coarse particles, foreign matter will fail, and if filtration is applied to prevent this, the filter holes will be immediately closed and stable. Continuous production becomes impossible. Therefore, these fine particles are rarely used as they are, and are generally used after being subjected to a dispersion treatment by some method to achieve further atomization.

Some of these fine particles have a large number of hydroxyl groups on the surface and exhibit hydrophilicity. Such fine particles are likely to agglomerate in a dope using a hydrophobic solvent. For example, fine particles of silicon dioxide (SiO ² ) are representative of this phenomenon. In order to prevent this, a proposal has been made to suppress aggregation in the dope by using fine particles having a methyl group on the surface (see, for example, Patent Document 1). This is a hydrophobic treatment by methylation. In addition, a proposal has been made to suppress aggregation in the dope by using fine particles having an alkyl group having 2 to 20 carbon atoms on the surface (see, for example, Patent Document 2). This is a hydrophobic treatment by alkylation.

  By the way, the solution casting method is a method in which cellulose acylate and various additives are made into a cellulose acylate solution called a dope with a solvent, and then this dope is cast from a casting die to a support, and has self-supporting properties. By the way, it peels off and obtains a film through a drying process. The support is a drum or a band that continuously rotates.

  In the state in which the cellulose acylate and additives are simply dissolved in a solvent, the prepared dope often contains many impurities and gel-like substances (hereinafter referred to as foreign substances) without being dissolved. When the film is cast in this state, these foreign substances are mixed in the film, causing a surface failure of the film, and the commercial value may be reduced or the product may not be used. Therefore, it is common to carry out filtration once or more before casting.

  Various filters are used depending on the properties of the dope and its required characteristics, and filter cloths, filter papers, metal meshes, metal fibers, non-woven fabrics, etc. are common. In addition, in cellulose acylate dope, which is considered to be used for extremely strict standards against foreign substances such as liquid crystal displays, etc., multiple filtration devices using these filters are installed in series. Often improves the properties of the dope obtained as a filtrate.

By the way, the mechanism of filtration can be explained as follows. That is, the filter of the filtration device is a material or a structure having an extremely narrow flow path (hereinafter referred to as a filter hole), and when the dope passes through the filter hole, It is removed here without being able to pass through. In addition, in the inside of a filtration apparatus, one side in which the filtration target object before filtering through a filter exists is called a primary side, and the other in which the filtrate after filtering exists is called a secondary side. In addition, depending on the filter, the shape of the filter hole is not uniform, and is complicatedly bent or branched. Sometimes it is physically trapped at the branch point and trapped. As described above, the dope is obtained as a filtrate that has been cleaned by removing foreign substances.
Japanese Patent Laid-Open No. 7-11055 (page 2-4, FIG. 2) JP 2001-2799 A

  However, the above-described hydrophobization treatment of the surface of fine particles such as silicon dioxide cannot completely suppress the agglomeration phenomenon over time, and is insufficient in suitability for use in a high-definition liquid crystal display.

  Furthermore, the fine particles in the dope flow according to the dope streamline, and when entering the filter from the primary side, the interval between the streamlines is narrowed at the entrance of the hole, so the distance between the fine particles is also narrowed, which causes more aggregation. It will be promoted. This phenomenon has a problem that it cannot be completely prevented even by the above hydrophobization treatment. This is because it is difficult to completely hydrophobize the surface of the fine particles, or, during the above-described dispersion treatment, the portion that was inside the fine particles appears on the surface to form an interface with the solvent. Because.

  Part of the particles formed by aggregation in the filter in this way is trapped in the filter, and when the filtration is continued, the blocking rate of the filter holes increases and the filtration pressure increases. When the pressure rises to a high filtration pressure, some trapped particles may leave the filter and flow downstream (secondary side) at that pressure. There is a problem of being included and reducing the product value.

  The present invention has been made in view of the above problems, and in the process of forming cellulose acylate by a solution casting method, it is possible to prevent the secondary side outflow of foreign matters due to increased filtration pressure of a dope filtration device. A cellulose acylate solution that can be produced and a method for producing the same, specifically, a cellulose acylate solution capable of suppressing aggregation of solid components when passing through a filter of a filtration device, and a method for producing the same. For the purpose.

In the present invention, in order to solve the above problems, in the cellulose acylate solution containing fine particles, the fine particles have a positive charge on the surface, and the primary average particle diameter of the fine particles is 0.001 μm or more and 20 μm or less. It is configured as a feature.

The fine particles is preferably dioxide silicic containing der Rukoto, it is preferable apparent specific gravity of the fine particles is not more than 200 g / l or more 50 g / liter.

The method for producing a cellulose acylate solution of the present invention, the first solution of cellulose acylate is dissolved in a solvent, the particulate organic and average primary particle size of charged positive is 20μm or less than 0.001μm on the surface A dispersion step of dispersing the fine particle additive solution and a mixing step of mixing the fine particle additive with a second solution in which cellulose acylate is dissolved to obtain a cellulose acylate solution. ing.

  The cellulose acylate solution of the present invention and the method for producing the same can prevent foreign substances from flowing out to the secondary side due to increased filtration pressure during filtration in the process of forming a film by the solution casting method, and pass through the filter of the filtration device. Aggregation of solid components during the process can be suppressed.

  A solution casting apparatus embodying the present invention is shown in FIG. The solution casting apparatus 11 includes a stock tank 12, a pump 13, a filtration device 14, a reserve tank 17, a film forming device 18, and a liquid feed path that connects them in series. Further, the film forming apparatus 18 has a die 21, a band 22 as a support, a plurality of rollers 23 for carrying, a drying device 26, and a winding device 27. In the present embodiment, the support is the band 22 that continuously travels by the rotation of the backup roller 28, but a drum or the like may be used as another general support. However, the present invention does not depend on the above solution casting equipment.

  The cellulose acylate solution 31 a in the stock tank 12 is fed by the pump 13, passes through the filtration device 14, and is retained in the reserve tank 17. The cellulose acylate solution 31 a fed from the reserve tank 17 is peeled off as a film 31 b on the band 22 with self-supporting properties, and sent to the drying device 26 while being conveyed by the roller 23. The film 31b is wound by the winding device 27 after being sufficiently dried while being transported by the plurality of rollers 23 in the drying device 26. In the drying device 26, a tenter device (not shown) is separately provided here, and the width of the film 31b may be regulated or stretched for drying. The cellulose acylate solution 31a of the present invention includes a dispersion in which an undissolved material is dispersed, and means that the solid main component before dissolution is cellulose acylate. Yes.

  The cellulose acylate solution 31a is obtained by dissolving or dispersing cellulose acylate and various additives in a solvent. A matting agent is contained as one of various additives, and fine particles are used as the matting agent. The matting agent includes what is generally called an anti-blocking agent or an anti-smudge agent.

  In the present invention, the fine particles mixed in the cellulose acylate solution 31a have a positive charge on the surface thereof. As a method for positively charging the surface, a known method can be used as a charging process for various fine particle surfaces. For example, a method of imparting a cationic monomer or the like to the surface molecules of the fine particles can be used. Further, having a positive charge on the surface includes a state having a cationic functional group, such as an amino group, an ammonium group, a phosphonium group, or a pyridinium group, with respect to various functional groups on the surface of the fine particles. It is done. By charging the surface positively in this way, when the cellulose acylate solution 31a is prepared or when it passes through the filter of the filtration device, the aggregation of the fine particles is suppressed, and the cellulose acylate solution and this The properties of the film 31b obtained by film formation are improved.

  The fine particles having a positive charge on the surface include both inorganic compounds and organic compounds. Examples of inorganic compounds include silicon-containing compounds such as silicon dioxide, titanium oxide, zinc oxide, aluminum oxide, barium oxide, and oxidation. Zirconium, strongtium oxide, antimony oxide, tin oxide, tin oxide / antimony, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, etc. are preferred Further, inorganic compounds containing silicon and zirconium oxide are more preferable, but silicon derivatives such as silicon dioxide are particularly preferable in that the turbidity of the cellulose acylate film can be reduced.

  Similarly, the organic compound as fine particles having a positive charge on the surface is preferably a polymer such as a silicone resin, a fluorine resin, and an acrylic resin, and among them, a silicone resin is preferably used. Among silicone resins, those having a three-dimensional network structure are particularly preferable.

  In the present invention, the method of adding these fine particles to the cellulose acylate solution 31a is not limited. For example, fine particles may be contained at the stage of mixing cellulose acylate and solvent, or fine particles may be added after preparing a mixed solution of cellulose acylate and solvent. Furthermore, fine particles may be added and mixed immediately before casting the cellulose acylate solution. For mixing the fine particles, the fine particles themselves may be added, but they are dissolved in advance using a solvent, preferably cellulose acylate as a binder, or used as a stabilized solution or dispersion by dispersing in some cases. It is also preferable.

  More specifically, for example, there are three types as shown below. One is a method in which a solvent and fine particles are stirred and mixed, and then a fine particle dispersion is prepared by a disperser, and this is added to cellulose acylate and stirred. The second method is after stirring and mixing the solvent and fine particles. Then, the dispersion is made into a fine particle dispersion, and a small amount of cellulose acylate is added to the solvent and dissolved by stirring. A fine particle additive liquid obtained by adding the fine particle dispersion and stirring to this is sufficiently mixed with the cellulose acylate additive liquid in a tank or an in-line mixer. In the third method, a small amount of cellulose acylate is added to a solvent and dissolved by stirring. Fine particles are added to the solvent and dispersed by a disperser to obtain a fine particle additive solution. The fine particle additive solution is sufficiently mixed with the cellulose acylate solution in a tank or in-line mixer.

  The primary average particle diameter of the fine particles is preferably 0.001 to 20 μm, more preferably 0.001 to 10 μm, and still more preferably 0.002 from the viewpoint of keeping the haze of the obtained film 31b low. It is 1 μm, and particularly preferably 0.005 to 0.5 μm. Measurement of the primary average particle diameter of the fine particles is obtained as an average particle diameter with a transmission electron microscope. The apparent specific gravity of the fine particles is preferably 30 g / liter or more, more preferably 50 g / liter or more and 200 g / liter or less, and most preferably 50 g / liter or more and 100 g / liter or less.

  The concentration of the fine particles when the fine particles are mixed with a solvent or the like can be appropriately set. However, for example, when silicon dioxide is used as the fine particles, it is preferably 30% by mass or less, and 20% by mass. More preferably, the content is 1% by mass or more and 10% by mass or less. Examples of the solvent used for dispersion include lower alcohols, preferably methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like. Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film formation of a cellulose acylate as a solvent.

  Examples of the disperser used for dispersing fine particles in a cellulose acylate solution or a solvent include a ball mill, a sand mill, and a dyno mill as media dispersers, and an ultrasonic type, centrifugal type, and high pressure as medialess dispersers. Examples include molds. In the high pressure dispersing apparatus, for example, the maximum pressure condition inside the apparatus is preferably 9.8 MPa or more in a thin tube having a tube diameter of 1 to 2000 μm. At that time, it is preferable that the maximum reaching speed reaches 100 m / sec or more and the heat transfer speed reaches 420 kJ / hr or more. Examples of the high-pressure dispersion device include an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation or a nanomizer manufactured by Nanomizer. UHN-01 manufactured by Co., Ltd.

  In the present invention, as a method for producing the cellulose acylate solution 31a, dissolution at ordinary temperature is common, but a cooling dissolution method or a high temperature dissolution method can be applied as necessary.

  In the cooling dissolution method, first, an additive such as cellulose acylate and fine particles are gradually added to a solvent with stirring at a temperature around room temperature of about −10 to 40 ° C. simultaneously or sequentially. In some cases, a solution or dispersion of each component is prepared and then these solutions are mixed. The cooling can be performed, for example, in a dry ice / methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). When cooled in this manner, the mixture of the solid component and the solvent of the cellulose acylate solution 31a is solidified. Furthermore, when this is heated to approximately 0 to 200 ° C., a solution in which each component flows in the solvent is obtained. The temperature may be increased by simply leaving it at room temperature or in a warm bath.

  In the high-temperature dissolution method, first, an additive such as cellulose acylate and fine particles are gradually added to a solvent with stirring at a temperature around room temperature of about −10 to 40 ° C. simultaneously or sequentially. Next, the solvent is heated to 70 to 240 ° C. under a pressure of approximately 0.2 MPa to 30 a. The heating temperature is preferably 80 to 220 ° C. Next, the heated solution or dispersion is cooled below the boiling point of the lowest boiling solvent among the solvents used. In general, this is cooled to −10 to 50 ° C. and returned to normal pressure. Preferably, it cools by apparatus cooling using various refrigerant | coolants, such as cooling water.

  According to the present technology, the cellulose acylate solution 31a having a high concentration and excellent stability can be obtained without relying on the means of concentration. However, in order to make it easier to dissolve, the concentration means is used after dissolving at a low concentration. And may be concentrated. The concentration method is not particularly limited. For example, a low-concentration solution is guided between the cylinder and the rotation trajectory of the outer periphery of the rotating blade rotating in the circumferential direction, and a temperature difference between the solution and the solution. To obtain a high-concentration solution while evaporating the solvent, or by blowing the heated low-concentration solution into the container from the nozzle and flashing the solvent between the nozzle and the inner wall of the container, and evaporating the solvent vapor. Known methods such as a method of extracting from a container and extracting a high-concentration solution from the container bottom are applied.

  Furthermore, in this embodiment, after preparing a cellulose acylate solution, this is filtered, thereby achieving desirable properties and optical performance as a film. For the filtration treatment, filter paper, filter cloth, metal mesh, metal fiber, non-woven fabric or the like can be used as a filter. Moreover, in the cellulose acylate which is used for strict standards for the inclusion of foreign substances, it is preferable to install a plurality of filtration devices in series and improve the properties of the dope by multistage filtration.

  In the present invention, it is preferable to carry out the filtration while adding fine particles. Part of the fine particles is one of the main filtration targets as described above, and when added after the filtration treatment, the significance of filtration for improving the properties of the cellulose acylate solution 31a is diminished.

  The filtration device 14 that performs filtration of the cellulose acylate solution 31a uses a filter having an absolute filtration accuracy of 0.1 to 100 μm, and further uses a filter having an absolute filtration accuracy of 0.5 to 25 μm. preferable. The thickness of the filter is preferably from 0.1 to 10 mm, and more preferably from 0.2 to 2 mm. The filtration pressure during filtration is preferably 2.0 MPa or less, more preferably 1.5 MPa or less, and most preferably 1.0 MPa or less.

  The cellulose acylate solution 31a is preferably filtered with a solution viscosity of 1000 Pa · s or less, more preferably 500 Pa · s or less, still more preferably 100 Pa · s or less, and 50 Pa · s or less. More preferably. As the main material of the filter, conventionally known materials such as glass fibers, cellulose fibers, filter paper, and fluororesins such as tetrafluoroethylene resin can be preferably used, and ceramics, metals and the like are particularly preferably used. The filter shape can be applied to either the surface type or the depth type, but the depth type is more preferable because it is less likely to clog.

  One cellulose acylate solution 31a may be cast as a single-layer solution on the above-mentioned various supports, or at least two cellulose acylate solutions may be prepared and cast to form multiple layers. Also good. When casting a plurality of cellulose acylate solutions, the cellulose acylate solutions may be respectively cast from a plurality of casting openings provided at intervals in the traveling direction of the support, and may be sequentially cast. A method of simultaneously casting the cellulose acylate solution from two casting ports may be used. The casting method is not limited to the above, and other known casting methods may be used.

  In casting for forming a multilayer, the plurality of cellulose acylate solutions may be the same solution or different solutions. In addition, when casting so as to have three or more layers, the fine particles may be added to at least the outermost layer in terms of its function, so it is preferable that the fine particles be cast in a solution for forming the outermost layer. . When forming three or more layers, fine particles may be added to any other layer other than the outermost layer, or may be contained in all layers. In order to give each of the plurality of cellulose acylate layers functions such as specific optical characteristics, a cellulose acylate solution corresponding to the function may be extruded from each casting port. Further, together with the obtained cellulose acylate solution, other functional layers such as an adhesive layer, a dye layer, an antistatic layer, an ultraviolet absorbing layer, and a polarizing film layer can be cast simultaneously or sequentially.

  In the present invention, the solvent preferably used as the main solvent of the cellulose acylate solution 31a is selected from esters having 3 to 12 carbon atoms, ketones, ethers, and halogenated hydrocarbons having 1 to 7 carbon atoms. Organic solvents are preferred. The ester, ketone and ether may have a cyclic structure. Furthermore, compounds having two or more functional groups of esters, ketones and ethers (that is, —O—, —CO— and —COO—) can also be used as the main solvent. Such other functional groups may be included. In the case of the main solvent having two or more kinds of functional groups, the number of carbon atoms is preferably within the specified range of the compound having any one of the functional groups.

  Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate.

  Examples of ketones having 3 to 12 carbon atoms as the main solvent include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone and methylcyclohexanone.

  Examples of the ether having 3 to 12 carbon atoms as the main solvent include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. it can. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol, and 2-butoxyethanol. Furthermore, examples of the halogenated hydrocarbon include dichloromethane and dichloromethylene.

  Furthermore, in the present invention, alcohols can be used in combination as a solvent. The alcohol is preferably a monoalcohol or dialcohol having 1 to 8 carbon atoms, more preferably methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol. , 2-methyl-2-butanol, and cyclohexanol. These may be mixed alone with the main solvent, or may be mixed with the main solvent as a mixture of two or more. The weight ratio of the alcohol to the total solvent amount is preferably 2% by weight to 40% by weight, more preferably 3% by weight to 30% by weight, and more preferably 5% by weight to 20% by weight. Most preferably.

  The cellulose acylate film 31b obtained from the cellulose acylate solution of the present invention includes a film stretched using a tenter device or the like. The cellulose acylate film 31b is stretched mainly to increase the in-plane retardation value of the film, and is performed at room temperature or under heating conditions. It may be. The heating temperature at the time of stretching is preferably not higher than the glass transition temperature of cellulose acylate. The film 31b can be stretched by a treatment during drying, and is particularly effective when a solvent remains. For example, the film 31b is stretched when the speed of the transport roller 23 is adjusted so that the winding speed of the film 31b is higher than the peeling speed of the film 31b. The film 31b can also be stretched by transporting it while being held by a tenter device and gradually increasing the holding width of the film 31b by the tenter device. In addition, after the film 31b is dried, it can be stretched using a stretching machine such as a long stretching machine.

  The thickness of the cellulose acylate film 31b obtained by the present invention varies depending on the purpose of use and is not limited. The thickness of the film 31b is adjusted by adjusting the solid content in the cellulose acylate solution 31a, the slit gap at the tip of the die 21, the extrusion pressure from the die 21, the traveling speed of the band 22, and the cellulose acylate solution 31a from the die 21. This can be carried out by adjusting the discharge flow rate and the like.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated concretely, this invention is not limited to this.

[Experiment 1]
A dispersion having the following composition was finely dispersed with an attritor so that the volume average particle diameter was 0.5 μm to obtain a fine particle dispersion. The volume average particle size was measured with a particle size distribution measuring apparatus LA920 manufactured by Horiba. The silicon dioxide fine particles described below have a positive charge on the surface.
・ Silicon dioxide fine particles 2.00% by weight
(Aerosil RA200HS, manufactured by Nippon Aerosil Co., Ltd.)
・ Cellulose triacetate (acetylation degree 61.0%) 2.00% by weight
Triphenyl phosphate (TPP) 0.16% by weight
・ Biphenyldiphenyl phosphate 0.08% by weight
・ Dichloromethane 88.10% by weight
・ Methyl alcohol 7.66% by weight

A base material of a cellulose acylate solution having a solid content concentration of 18.5 wt% is prepared by adding a mixed solvent of 92: 8 in weight ratio of dichloromethane and methyl alcohol to the solid content of the following composition and stirring and dissolving. did. 6.5 parts by weight of the fine particle dispersion was added to 100 parts by weight of the base material. This was stirred and mixed to obtain a cellulose acylate solution 31a, which was filtered with a filter paper (# 63, manufactured by Toyo Filter Paper Co., Ltd.).
・ Cellulose triacetate (acetylation degree 61.0%) 89.3% by weight
Triphenyl phosphate (TPP) 7.1% by weight
Biphenyl diphenyl phosphate 3.6% by weight

The cellulose acylate solution 31 a obtained by the above method was packed in the stock tank 12 as shown in FIG. 1, filtered by the filtration device 14, and then sent to the reserve tank 17. As the filter of the filtration device 14, a metal filter (model number: 06N, nominal pore diameter 10 μm, manufactured by Nippon Seisen) is used. The flow rate of the pump 13 was set so that the filtration pressure in the filtration device would be 0.3 × 10 ⁶ Pa at the start of feeding the cellulose acylate solution.

The cellulose acylate solution 31a was cast on the band 22, dried and peeled off, and further subjected to a drying treatment to obtain a film 31b having a thickness of about 80 μm. 0.1 m ² of the obtained film 31b was sampled and spread on a flat table, and the number of foreign matters was counted visually. Furthermore, the site | part in which a foreign material does not exist, and a foreign material were taken out as a section | slice using a microtome, and each elemental analysis was implemented using the element analyzer (XMA). As a result of elemental analysis of the foreign matter, the foreign matter was classified into a foreign matter having a high silicon content and a foreign matter having a silicon content equal to or less than that of a portion where no foreign matter was present. The results are shown in Table 1, where the former is the number of foreign matters A and the latter is the number of foreign matters B. In Table 1, the cellulose acylate solution 31a sampled when the filtration pressure in the filtration device 14 rises to 0.4 × 10 ⁶ Pa is defined as solution X, and when the pressure rises to 1.0 × 10 ⁶ Pa. When the cellulose acylate solution 31a is the solution Y, in Table 1, the solution X is formed as a sample X, and the solution Y is formed as a sample Y.

[Comparative Experiment 1]
The experiment was performed in the same manner as in Experiment 1 except that the silica dioxide fine particles were Aerosil R972 (manufactured by Nippon Aerosil Co., Ltd.). The results are shown in Table 1 together with Experiment 1.

According to the first embodiment, in the sample X formed with the cellulose acylate solution 31a when the filtration pressure is as low as 0.4 × 10 ⁶ Pa, foreign matter in which a large amount of silicon is detected with respect to the presence or absence of positive charge on the surface of the fine particles There is almost no difference in the number. However, in the sample Y formed with the cellulose acylate solution 31a when the filtration pressure is increased to 1.0 × 10 ⁶ Pa, compared to the sample Y having a positive charge on the surface of the fine particles, there is no silicon-containing foreign matter. The number of has increased. Since the variation factor of sample X and sample Y is only the filtration pressure, it can be seen that the case using a positively charged surface is superior to the case using no surface than the case using no. This is because the use of fine particles having a positive charge on the surface prevents the fine particles from aggregating inside the filter, so that even if the filtration pressure increases, the fine particles do not flow out to the secondary side. it is conceivable that.

It is the schematic of the solution casting apparatus which is embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Solution casting apparatus 14 Filtration apparatus 31a Cellulose acylate solution 31b Cellulose acylate film

Claims (4)

In the cellulose acylate solution containing fine particles,
The microparticle has a positive charge on its surface;
A cellulose acylate solution having a primary average particle size of the fine particles of from 0.001 μm to 20 μm. The fine particles, cellulose acylate solution according to claim 1, wherein dioxide silicic containing der Rukoto. The cellulose acylate solution according to claim 1 or 2, wherein the apparent specific gravity of the fine particles is 50 g / liter or more and 200 g / liter or less . First a solution of cellulose acylate is dissolved in a solvent, and dispersing step of the fine particles are dispersed and particulate additive solution is positive chromatic and an average primary particle diameter of the charged is 20μm or less than 0.001μm to the surface,
A mixing step of mixing the fine particle additive with a second solution in which cellulose acylate is dissolved to form a cellulose acylate solution;
A method for producing a cellulose acylate solution, comprising:

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