KR102192967B1 - Solution film forming method - Google Patents

Abstract

It provides a solution film forming method that prevents the occurrence of streaks extending in the longitudinal direction of the film.
The first dope 41 and the second dope 42 make a three-layered film. Particles 14 are included in the second dope 42. The fine particles 14 are surface-coated with trimethylsilyl groups as hydrophobic groups. The surface coverage of the fine particles 14 is at least 0.012. The first dope 41 and the second dope 42 are covalently rolled from the flexible die 65 and peeled off the belt 62, dried by the tenter 35 and the roller drying device 36 to form a film 10. do.

Description

Solution film formation method {SOLUTION FILM FORMING METHOD}

The present invention relates to a solution film forming method.

Polymer films are widely used as films for various optical applications, such as a polarizing plate protective film and a retardation film, and in recent years, there is a strong request for thinning. A typical example of such an optical polymer film is a cellulose acylate film. Cellulose acylate films used for optical purposes are mainly produced by a solution film forming method. In the solution film forming method for producing a long cellulose acylate film, as is well known, a cellulose acylate solution in which cellulose acylate is dissolved in a solvent is continuously flowed out from a casting die as a running flexible support. Thereby, a cellulose acylate film is obtained by peeling as a film from the flexible support and drying the flexible film formed on the flexible support.

The cellulose acylate solution usually contains fine particles as a mat agent. The matting agent is for enhancing the scratch resistance and sliding properties of the film, and preventing sticking of the films when wound in a roll shape. Therefore, in the case of manufacturing a single-layered film, a mat agent was added to the cellulose acylate solution forming the film, and in the case of manufacturing a multilayered film, the cellulose acylate solution forming the outer layer serving as the film surface. Contains. As the fine particles used as a mat agent, silica (silicon dioxide) fine particles are generally used.

When a cellulose acylate solution containing fine particles of silica is used, the silica aggregates, and the aggregates entering the film may scatter or reflect light. Therefore, in order to suppress such agglomeration of silica, for example, Japanese Patent Laid-Open Publication No. 2006-070240 includes cellulose acylate, additives, solvent, and silica in which the surface is hydrophobized, and the degree of hydrophobicity of silica is methanol wettability ( A cellulose acylate solution with a methanol wettability (MW) value of 20% or less is proposed.

In addition, in order to suppress haze to a low level despite containing silica and to increase the contrast when mounted on a liquid crystal display device, Japanese Patent Laid-Open Publication No. 2007-017626 discloses the following optical film. This optical film includes a layer composed of an organic compound and a layer containing silica and having a content of an organic compound having a molecular weight of 1000 or less of 30% by mass or less of the silica content, and the MW of silica satisfies 0≤MW≤80. do. In addition, despite containing silica, in order to lower haze and black luminance, Japanese Patent Laid-Open Publication No. 2006-265382 discloses that a silica having an MW range of 80 <MW ≤ 100 is used as silica to be included in the cellulose acylate solution. In addition, it is described to use a cellulose acylate solution in which coarse particles of 5 µm or more are not present with respect to silica.

As the film becomes thinner, it is necessary to increase the amount of silica in order to exhibit a sufficient function as a mat agent. Incidentally, if the amount of silica is increased, scratches of streaks extending in the longitudinal direction of the film will be observed on the film surface of the obtained film. The scratches of this streak are large in the amount of silica even when the silica or cellulose acylate solution described in Japanese Patent Laid-Open No. 2006-070240, Japanese Patent Laid-Open No. 2007-017626, and Japanese Patent Laid-Open No. 2006-265382 is used. If you do, it will occur.

Accordingly, an object of the present invention is to provide a solution film forming method that prevents scratches extending in the longitudinal direction of the film from occurring on the film surface by the use of silica.

The solution film forming method of the present invention includes a casting step (A step) and a peeling drying step (B step). In step A, the polymer solution in which the polymer is dissolved in a solvent is continuously flowed out from the casting die onto the flexible support on which the polymer is continuously running, thereby forming a casting film on the flexible support. The polymer solution contains fine particles of silica. The surface of the fine particles is coated with a hydrophobic group at a surface coverage of at least 0.012. In step B, the cast film is peeled off from the cast member and dried.

In the case where the polymer is cellulose acylate, the above solution film formation method is particularly effective.

It is preferable that at least part of the hydrophobic group is a trimethylsilyl group.

It is preferable that the solution film formation method further includes a dissolution step (C step), a dispersion step (D step), an addition step (E step), and a filtration step (F step). In step C, a part of the polymer is dissolved in a part of the solvent to make the raw material dopable. In step D, fine particles are dispersed in the remainder of the polymer and the remainder of the solvent to obtain a fine particle dispersion. In Step E, a fine particle dispersion is added to the raw material dope. In step F, the liquid obtained in step E is filtered to obtain a polymer solution.

The fine particles are preferably obtained by heating silica having a hydroxyl group and Si(CH ₃ ) ₃ -NH-Si(CH ₃ ) ₃ at a temperature in the range of 100°C to 400°C in the presence of water.

According to the present invention, even if silica is used, scratches extending in the longitudinal direction of the film are prevented from occurring on the film surface.

The above objects and advantages will be readily understood by those skilled in the art by reading a detailed description of a preferred embodiment with reference to the accompanying drawings.
1 is a cross-sectional view of a film.
Fig. 2 is an explanatory diagram illustrating the surface coating of fine particles with a trimethylsilyl group.
3 is an explanatory diagram for explaining the surface coating of fine particles with a dimethylsilanol group.
4 is a schematic diagram of a solution film forming facility.

A film obtained by an embodiment of the present invention will be described with reference to FIG. 1. The film 10 shown in FIG. 1 includes a film body 12 and a surface layer 13 disposed on both surfaces of the film body 12. Although the boundary between the film main body 12 and the surface layer 13 is not observed, in FIG. 1, these boundaries are shown for convenience of explanation.

The film body 12 is composed of cellulose acylate and an additive. A pair of surface layers 13 are composed of the same components. Specifically, one surface layer 13 and the other surface layer 13 are made of cellulose acylate, fine particles 14, and an additive, and the ratios of the fine particles 14 and the additive are the same. The additive is a plasticizer, an ultraviolet absorber, a retardation control agent that controls retardation of the film 10, and the like. The fine particles 14 function as a so-called mat agent that improves the scratch resistance and slip properties of the film 10 or prevents sticking of the films 10 to each other. The fine particles 14 are provided to protrude from the film surface 10a, thereby giving the film surface 10a a certain roughness to form minute irregularities. Even if the films 10 overlap with each other due to this irregularity, they do not stick to each other, the sliding of the films 10 is ensured, and a constant scratch resistance is expressed. The fine particles 14 are silica (silicon dioxide, SiO ₂ ) that is coated on the surface with a hydrophobic group and takes the form of secondary particles. Details of the fine particles 14 will be described later using other drawings.

The cellulose acylate of the film main body 12 and each surface layer 13 is made into TAC. However, each cellulose acylate of the film main body 12 and the surface layer 13 is not limited to these. For example, the cellulose acylate of the film main body 12 may be used as DAC, and the cellulose acylate of the surface layer 13 may be used as TAC. Moreover, in this embodiment, although each polymer component of the film main body 12 and the surface layer 13 is made into cellulose acylate, it may be a polymer that can be formed into a film by a solution film forming method. Other polymers include, for example, cyclic polyolefins, acrylics, polyethylene terephthalate (PET), and the like.

In this embodiment, although both surface layers 13 are made into the same structure with each other, it is not limited to this aspect. For example, when both surface layers 13 are formed of the same component and formed of a plurality of components, the ratios of the components may be different from each other. In addition, only one of the surface layers 13 may contain fine particles.

The thickness T10 of the film 10 is 60 μm, the thickness T12 of the film body 12 is 54 μm, and the thickness T13 of the surface layer 13 is 3 μm. However, each thickness is not limited to these, the thickness T10 is within the range of 10 μm or more and 80 μm or less, the thickness T12 is within the range of 9 μm or more and 70 μm or less, and the thickness T13 is 1 μm or more and 10 It may be within the range of µm or less. In particular, in the present invention, when the thickness T13 is in the range of 2 μm or more and 5 μm or less, in particular, an increase in haze is suppressed, and the adhesion between the films 10 in the case of a roll shape is prevented. There is. The thicknesses T10, T12, and T13 can be calculated from the concentration of each solid component of the first dope 41 and the second dope 42 described later and the flow rate to the flexible die.

The film 10 is a first polymer solution (hereinafter referred to as a first dope) forming the film body 12 and a second polymer solution forming the surface layer 13 (hereinafter, referred to as a first dope) by means of a solution film forming facility described later. , Referred to as second dope). The fine particles 14 used as a raw material for the second dope are usually dispersed in a dispersion medium, and the fine particles 14 are used in the state of this dispersion to prepare the second dope. When the silica constituting the fine particles 14 is not surface-coated with a hydrophobic group, as shown in the left explanatory diagram of Fig. 2, generally, it contains a hydroxyl group (-OH). Due to the affinity between the hydroxy groups, fine particles are aggregated in the casting die 65 (see Fig. 4). Therefore, by modifying the hydroxy group with a hydrophobic group, the hydroxy group is made hydrophobic.

The hydrophobic group is a trimethylsilyl group (hereinafter referred to as TMS). By the modification of the hydroxy group by TMS, the surface of the fine particles 14 is in a state where there is no hydroxy group and is covered by TMS, as shown in the right explanatory diagram of FIG. The surface coverage is at least 0.012, that is, 0.012 or more. The surface coverage is preferably within the range of 0.012 or more and 0.12 or less, and more preferably within the range of 0.012 or more and 0.016 or less.

The surface coverage is obtained by dividing the carbon content in the fine particles 14 by a specific surface area. That is, the surface coverage is determined by RC/S when the carbon content of the fine particles 14 is RC and the specific surface area is S. The carbon content (RC) is determined by elemental analysis by a combustion method (for example, a fully automatic elemental analysis device, manufactured by PerkinElmer Japan Co., Ltd.). The specific surface area (S) is measured according to the BET method.

As shown in hydrophobicity of the silica according to the TMS and 2, the silica has a hydroxyl group and _{Si (CH 3) 3 -NH-} Si (CH 3) 3 in the presence of water, in vapor phase, of more than 100 ℃ below 400 ℃ It is carried out by heating to a temperature within the range. However, this reaction is carried out in batch mode. In this way, in the surface coating by TMS, one hydroxy group is modified with three methyl groups, and approximately 100% of the hydroxy groups are removed, resulting in fine particles 14 without silanol groups.

In addition to the fine particles 14 surface-coated by TMS, fine particles 14 surface-coated with a dimethylsilanol group (-Si(CH ₃ ) OH, hereinafter referred to as DMS) may be used. By adjusting the mixing ratio of the fine particles 14 surface-coated by TMS and the fine particles 14 surface-coated by DMS, the surface coverage is adjusted to a predetermined value of 0.012 or more.

The hydrophobicization of silica by DMS is performed by heating silica having a hydroxy group and Si(CH ₃ ) ₂ Cl ₂ in a gas phase in the presence of water to a temperature in the range of 100° C. or more and 400° C. All. However, this reaction is carried out continuously. As described above, in the modification of the hydroxy group by Si(CH ₃ ) ₂ Cl ₂ , since the hydroxy group remains after the modification, the reaction continues without reproducibility as long as the environment satisfies the reaction conditions, reaching a degree of hydrophobicity (equation ratio) of about 50%. From one point onward, the degree of hydrophobicity does not change. Therefore, the reaction may be terminated when the degree of hydrophobicity of about 50% is reached.

The solution film formation for producing the film 10 is performed, for example, in the solution film formation equipment 30 of FIG. 4. The solution film forming facility 30 is provided with a dope preparation device 31, a flexible device 32, a tenter 35, a roller drying device 36, and a winding device 37 in order from the upstream side. do.

The dope preparation device 31 is for making the first dope 41 and the second dope 42. As described above, the first dope 41 forms the film body 12, and the second dope 42 forms the surface layer 13. The dope preparation device 31 may be installed outside the solution film forming facility 30 rather than inside the solution film forming facility 30. In that case, the made first dope 41 and the second dope 42 are once stored in a storage container or the like. The dope preparation device 31 includes a dissolving section 43, a mixing section 46, a dispersion section 47, and filtering sections 48 and 49.

When the cellulose acylate 52 and the solvent 53 are supplied to the melting section 43, heating and stirring are performed on the mixture thereof. In place of or in addition to heating, cooling may be performed. Thereby, the raw material dope 54 in which the cellulose acylate 52 is dissolved in the solvent 53 is made (dissolution step). When a mixture of a part of the raw material dope 54 and the additive 59 is supplied, the filtering unit 48 filters this to form the first dope 41.

When the cellulose acylate 52, the solvent 53, and the fine particles 14 are supplied to the mixing section 46, a mixing process is performed to stir the mixture thereof. The dispersing unit 47 is disposed downstream of the mixing unit 46, and when a mixture of the cellulose acylate 52, the solvent 53, and the fine particles 14 is supplied from the dispersing unit 47, the mixture is ultrasonicated. Is applied, and dispersion treatment of dispersing the fine particles 14 in the liquid is performed. However, a ball mill may be used instead of the dispersing unit 47 for applying ultrasonic waves. When a mixture of the fine particle dispersion liquid 58 obtained by the dispersing unit 47 and another part of the raw material dope 54 is supplied, the filtering unit 49 filters this to form the second dope 42.

The flexible device 32 is for forming the film 10 from the first dope 41 and the second dope 42. The flexible device 32 includes a belt 62 and a first roller 63 and a second roller 64. The belt 62 is an endless flexible support formed in an annular shape, and is made of SUS. The belt 62 is wound around the circumferential surfaces of the first roller 63 and the second roller 64. At least one of the first roller 63 and the second roller 64 has a driving unit (not shown) and rotates in the circumferential direction by the driving unit. By this rotation, the belt 62 in contact with the circumferential surface circulates and continuously travels in the longitudinal direction.

Above the belt 62 is provided with a flexible die 65 through which the first dope 41 and the second dope 42 flow out. By continuously flowing the first dope 41 and the second dope 42 from the flexible die 65 on the running belt 62, the first dope 41 and the second dope 42 overlap each other. In a state, it is cast on the belt 62, and the cast film 66 is continuously formed (flexible step). However, the first dope 41 comes out from the outlet 65a of the flexible die 65 while being inserted into the second dope 42.

The first roller 63 and the second roller 64 each have a temperature controller (not shown) that controls the peripheral surface temperature. By controlling the temperature of each circumferential surface of the first roller 63 and the second roller 64, the temperature of the flexible film 66 is controlled through the belt 62.

Regarding the first dope 41 and the second dope 42, the so-called bead, from the flexible die 65 to the belt 62, a decompression chamber (not shown) upstream in the traveling direction of the belt 62 ) Is provided. This decompression chamber sucks in the atmosphere of the upstream area of the first dope 41 and the second dope 42 that have flowed out, and decompresses this area.

After hardening the cast film 66 to the extent that it can be conveyed to the tenter 35, it is peeled off from the belt 62 in the state containing the solvent 53. Peeling is performed with a solvent content within a range of 10% by mass or more and 100% by mass or less in the case of a dry flexible method, and a solvent content within the range of 100% by mass or more and 300% by mass or less in the case of a cooling and flexible method. The dry flexible method is a method in which the cast film 66 is hardened mainly by drying, and the cooling flexible method is a method in which the cast film 66 is gelled mainly by cooling to harden it. However, the solvent content rate in this specification is calculated as {(XY)/Y}×100 when the mass of the film 10 in a wet state is X and the mass after drying the film 10 is Y. This is the so-called dry weight standard.

During peeling, the film 10 is supported by a peeling roller (hereinafter referred to as a peeling roller) 70, and a peeling position at which the flexible film 66 is peeled off from the belt 62 is kept constant. When the belt 62 circulates and returns from the peeling position to the flexible position where the first and second dope 41 and 42 are flexible, the new first dope 41 and the second dope 42 are flexible again.

An air supply duct (not shown) may be provided so as to face the flexible surface of the belt 62 on which the flexible film 66 is formed. This air supply duct discharges gas and advances drying of the flexible film 66 passing therethrough.

The flexible film 66, that is, the film 10 peeled off by the peeling roller 70 is guided by the tenter 35. The tenter 35 proceeds to dry the film 10 while supporting each side portion of the film 10 with the support member 71. As the support member 71 of the tenter 35, at least one of a clip and a pin is used. Clips hold the film 10, and pins penetrate the film 10 in the thickness direction, thereby supporting the film 10, respectively.

The tenter 35 extends the width of the film 10 by applying tension in the width direction while supporting the film 10 by the support member 71 and conveying it in the longitudinal direction. The tenter 35 is provided with a duct 72 for supplying the dry gas by flowing it in the vicinity of the film 10. While the film 10 is conveyed, drying is performed by the drying gas from the duct 72, and the width can be changed at a predetermined timing by the support member 71.

The roller drying apparatus 36 is for drying the film 10 being conveyed. The roller drying apparatus 36 includes a plurality of rollers 73 arranged in a plurality in the conveyance direction of the film 10, an air conditioner (not shown), and a chamber (not shown). Among the plurality of rollers 73, there is a drive roller that rotates in the circumferential direction, and the film 10 is conveyed downstream by the rotation of the drive roller. The air conditioner sucks the atmosphere inside the chamber, adjusts the humidity or temperature of the sucked gas, and then sends the gas back into the chamber. Thus, the temperature and humidity inside the chamber are kept constant. The take-up device 37 winds up the film 10 supplied from the roller drying device 36 in a roll shape. However, a cooling chamber (not shown) may be provided between the roller drying device 36 and the winding device 37. This cooling chamber cools the film 10 passing through the inside to room temperature before winding up.

The solution film forming equipment 30 is an example of the embodiment of the present invention, and may be another solution film forming equipment. For example, instead of the belt 62, a drum (not shown) rotating in the circumferential direction may be used as the flexible support. In the case of the cooling flexible method, a drum is often used as a flexible support. Further, a tenter (not shown) having the same configuration as the tenter 35 may be provided between the tenter 35 and the roller drying device 36.

The operation of the above configuration will be described. When the cellulose acylate 52 and the solvent 53 are sent to the melting section 43, they become the raw material dope 54 by heating or stirring. Before a part of the raw material dope 54 is guided to the filter unit 48, the additive 59 is added, and the first dope 41 is filtered by the filter unit 48 in a mixed state with the additive 59. It becomes (first filtration step).

Further, the fine particles 14 are surface-coated with a surface coverage of at least 0.012 by hydrophobizing silica of secondary particles by TMS. When the fine particles 14, cellulose acylate 52, and solvent 53 are guided to the mixing unit 46, they are mixed by the mixing unit 46 (mixing step), and the dispersing unit from the mixing unit 46 It is sent to (47). The fine particles 14 in the mixture have a certain degree of dispersion by the dispersion unit 47, and a fine particle dispersion liquid 58 is obtained (dispersion step). The particulate dispersion 58 is added to another part of the raw material dope 54 (addition gas step), guided to the filtration unit 49, and filtered by the filtration unit 49 to become the second dope 42 ( 2nd filtration step).

The first dope 41 and the second dope are continuously guided to the flexible die 65 and are continuously discharged from the outlet 65a. If the surface coverage of the fine particles 14 is less than 0.012, the fine particles are likely to adhere to the outlet 65a, but the fine particles 14 of this embodiment are surface coated with a surface coverage of at least 0.012, so that the flexible die 65 At the outlet 65a of, adhesion in an agglomerated state is suppressed. For this reason, in the flow of the second dope 42 coming out of the outlet 65a with the flow of the first dope 41 interposed therebetween, streaks due to the particulate mass adhering to the outlet 65a do not occur. For this reason, a line extending in the longitudinal direction does not occur even on the film surface of the flexible film 66. The flexible film 66 is subjected to a peeling and drying step by the peeling roller 70, the tenter 35, and the roller drying device 36. The peeling drying step includes a peeling step with a peeling roller 70 and a drying step with a tenter 35 and a roller drying device 36. The flexible film 66 formed on the running belt 62 is peeled off from the belt 62 in a state containing the solvent 53 after having self-supporting properties, thereby forming the film 10 (peel step). The film 10 is sent to the tenter 35 and passes through the atmosphere of the dry gas supplied from the duct 72 in a state whose width is regulated by the support member 71. Thereby, the film 10 is dried. The film 10 exiting the tenter 35 is guided to a roller drying device 36, and is dried while passing through the inside of a chamber (not shown) of the roller drying device 36 (drying step). The dried film 10 is guided to a take-up device 37 and is wound in a roll shape. Since no lines extending in the longitudinal direction are generated on the film surface of the flexible film 66, the film 10 obtained from the flexible film 66 also has no lines extending in the longitudinal direction.

There is a relationship between the mass ratio of the fine particles 14 to the cellulose acylate 52 in the second dope 42 and the generation of streaks extending in the longitudinal direction in the film 10. About this relationship, it shows in Table 1. The data in Table 1 are the cellulose acylate in the second dope 42 for each of the cases of using silica surface-coated by DMS and silica surface-coated by TMS as the fine particles 14. It is obtained by changing the mass ratio of the fine particles 14 to (52). The evaluation of the string is performed according to the method and standard described in Examples described later.

[Table 1]

In the second dope 42, when the fine particles 14 are DMS, the mass ratio of the fine particles 14 to the cellulose acylate 52 is 0.050% or less, and the evaluation of the string is a pass level. When the fine particles 14 are TMS, even if the mass ratio of the fine particles 14 to the cellulose acylate 52 is 1.000%, the evaluation of Joule is a pass level. As described above, when the fine particles 14 are TMS, the mass ratio of the fine particles 14 to the cellulose acylate 52 is 1.000% or less, and the evaluation of the string is maintained at a pass level.

In this embodiment, the film 10 having a three-layer multilayer structure is produced, but the present invention is effective also for a film having a single-layer structure. Moreover, in this embodiment, although the film 10 of the three-layer structure which consists of the film main body 12 and the pair of surface layers 13 is manufactured, the film obtained by this invention is not limited to this. For example, it may be made into 4 or more layers by interlayer casting or coating. However, in the case of manufacturing a single-layered film, similarly, when the fine particles 14 are DMS, the mass ratio of the fine particles 14 to the cellulose acylate 52 is 0.050% or less, and the evaluation of Joule is at a pass level. to be. When the fine particles 14 are TMS, the mass ratio of the fine particles 14 to the cellulose acylate 52 is 1.000% or less, and the evaluation of Joule is a pass level.

Hereinafter, examples of the present invention and comparative examples for the present invention are given.

[Example]

[Example 1] to [Example 3]

Three types of fine particles 14 having different surface coverage ratios were made. The surface coverage of each fine particle 14 is shown in the "surface coverage" column of Table 2. As the fine particles 14, there are two types, consisting of only silica surface-coated by TMS, and a mixture of silica surface-coated by DMS and silica surface-coated by TMS. Therefore, the mixing ratio of the silica surface-coated by DMS and the silica surface-coated by TMS is shown in the “DMS:TMS” column of Table 2.

Three types of second dope 42 were made using each fine particle 14, respectively. In each second dope 42, the mass ratio of the fine particles 14 to the cellulose acylate 52 is 0.100%. The first dope 41 does not contain particulates 14. Using the first dope 41 and the second dope 42, three types of films 10 were produced by the solution film forming equipment 30.

Evaluation 1. Evaluation of the line

From each of the obtained films 10, 10 samples of an A4 plate (210 mm x 297 mm) were cut out. Specifically, 5 sheets were cut out along the width direction of the film 10, and 5 sheets were similarly cut out along the width direction at a position 5 m away from the cut position in the length direction of the film 10. Each sample was cut out by aligning the long side of the sample in the longitudinal direction of the film 10. For each sample, the presence or absence of a flaw extending in the longitudinal direction and its degree were evaluated. In the evaluation, the number of lines having a width of 100 μm or more and a length of 5 cm or more generated on the film surface was visually counted, and the average value of the number was calculated. About the average value, the joule was evaluated based on the following criteria. However, A and B are pass levels, and C and D are disqualified levels.

A: 0

B: greater than 0 and less than 0.5

C: greater than 0.5 and less than 1

D: greater than 1

Evaluation 2. Evaluation of coarse particle ratio

In addition, the fine particle dispersion (58) is sampled from the dope preparation device (31), the sample is diluted to 1 to 5% with a solvent, and then the particle size distribution is measured using a particle size distribution analyzer (product name LA920, manufactured by HORIBA). I did. From the obtained particle size distribution, whether or not particles of 10 µm or more are contained, and the peak area of the particles of 10 µm or more in the graph of the particle size distribution is examined, and the ratio (unit; %) of this peak area to the total peak area is coarse It was calculated|required as a particle ratio. This coarse particle ratio was evaluated based on the following criteria. However, A and B are pass levels, and C and D are disqualified levels.

A: 0%

B: greater than 0% and less than 20%

C: greater than 20% and less than 40%

D: greater than 40%

[Table 2]

[Comparative Example 1], [Comparative Example 2]

Two types of fine particles having different surface coverage ratios were made. The surface coverage of each fine particle is shown in the "surface coverage" column of Table 2. As the fine particles, as shown in Table 2, there are two types: one composed of only silica surface-coated by DMS, and a mixture of silica surface-coated by DMS and silica surface-coated by TMS.

Each fine particle was used to make two types of second dope. In each of the second dope, the mass ratio of the fine particles to the cellulose acylate 52 is 0.100%. Using this second dope and the same first dope 41 as in the example, two types of films were produced under the same conditions as in the example.

Using the same method and standard as in the examples, the string and coarse particle ratio were evaluated. The results are shown in Table 2.

Claims (5)

In the solution film forming method for producing a film having a thickness of 10 μm or more and 60 μm or less,
(A) forming a flexible film on the flexible support by continuously flowing a polymer solution in which the polymer is dissolved in a solvent from the flexible die onto the flexible support continuously running; And
(B) step of peeling off the flexible film from the flexible support and drying to obtain the film
And,
The polymer solution contains fine particles of silica, the fine particles are coated with a surface coverage of at least 0.012 by a hydrophobic group,
When at least a part of the hydrophobic group is a trimethylsilyl group, and when a part of the hydrophobic group is a trimethylsilyl group, another hydrophobic group is a dimethylsilyl group. The method of claim 1,
Solution film forming method, characterized in that the polymer is cellulose acylate. delete The method according to claim 1 or 2,
(C) dissolving a part of the polymer in a part of the solvent to form a raw material dopant;
(D) dispersing the fine particles in the remainder of the polymer and the remainder of the solvent to obtain a fine particle dispersion;
(E) adding the fine particle dispersion to the raw material dope; And
(F) a step to obtain the polymer solution by filtering the liquid obtained in step E
Solution film forming method further comprising a. The method according to claim 1 or 2,
The fine particles are obtained by heating silica having a hydroxyl group and Si(CH ₃ ) ₃ -NH-Si(CH ₃ ) ₃ to a temperature in the range of 100°C to 400°C in the presence of water.

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