JP5636200B2 - Method for producing cellulose triacetate film - Google Patents

Description

The present invention relates to a method for producing a cellulose triacetate film, and more particularly to a method for producing a cellulose triacetate film used as an optical compensation film.

  The cellulose acylate film is used as an optical compensation film such as a retardation film that converts elliptically polarized light after passing through the liquid crystal layer into a state close to linearly polarized light by matching with the retardation of the liquid crystal layer in the liquid crystal display. . Such an optical compensation film may be used as a protective film for a polarizing film in a polarizing plate.

  As known in the art, there are a melt film forming method and a solution film forming method as methods for producing a polymer film. Cellulose acylate films are mainly produced by a solution film forming method. This is because the optical compensation film is required to have excellent optical properties, and the cellulose acylate film having optical properties superior to those obtained by solution casting can be produced.

Among the optical properties, there is retardation, and the retardation of the film includes in-plane retardation Re and thickness direction retardation Rth. Re is retardation in a direction perpendicular to the thickness direction of the film, that is, in a direction along the film surface, and is obtained by the following formula (1). Rth is retardation in the thickness direction of the film, and is obtained from the following formula (2). When light is incident on a film exhibiting birefringence, there are a slow axis and a fast axis. In the following formulas (1) and (2), nx is the refractive index in the slow axis direction in the film plane. , Ny is the refractive index in the fast axis direction, nz is the refractive index in the film thickness direction, and d is the film thickness (nm).
Re = (nx−ny) × d (1)
Rth = {(nx + ny) / 2−nz} × d (2)

  In the use of an optical compensation film, Rth is increasingly regarded as an optical characteristic. For example, various films having different Rth are desired so that the optical compensation film can be selected based on Rth according to the optical properties of other films used together with the optical compensation film and the type of liquid crystal compound.

  However, there is a problem that Rth is difficult to control among optical characteristics. For example, when manufacturing a long film, Re can be controlled by a stretching process in the transport direction and the width direction by applying a tension, but Rth cannot be controlled by adjusting the tension in such a stretching process. It cannot be raised. Even if Rth can be increased by adjusting the tension in the stretching process, Re also fluctuates with the tension adjustment, so that the desired Re does not appear.

  Therefore, a method for increasing Rth by incorporating a compound having a predetermined structure into a film as a retardation increasing agent has been proposed (see, for example, Patent Document 1). Moreover, when cellulose acetate is limited to cellulose acetate, Rth can be increased to some extent by increasing the degree of acetylation (see, for example, Patent Document 2). Furthermore, as a method of developing a high Rth, a method of forming a film having a crystallinity in a predetermined range of 0.9 to 1.8 by heating the film to a predetermined temperature has been proposed (see Patent Document 3). ). In the method of Patent Document 3, the film is stretched by 10% or more in the casting direction or the width direction in the solution casting process.

JP 2003-344655 A JP 2007-072390 A JP 2007-084553 A

  However, if a conventional retardation increasing agent as proposed in Patent Document 1 is used, Re and Rth change together, which is not suitable when Rth is to be controlled selectively. In addition, there is a problem that the Rth increasing agent is deposited on the film in the drying step in solution casting or the like, or vaporizes and adheres to the apparatus and hardens. Furthermore, such a retardation increasing agent is expensive and may cause phase separation between the cellulose acylate and the additive in the dope. Such phase separation causes unevenness of optical properties in the film. Therefore, it is preferable to suppress the amount of the conventional retardation increasing agent as much as possible.

  The degree of acetylation is a factor that is limited to cellulose acylate in which the acyl group is an acetyl group. For this reason, the method of Patent Document 2 cannot control Rth for cellulose acylate having an acyl group different from the acetyl group. Furthermore, for cellulose acetate, although there is a certain degree of correlation between the degree of acetylation and Rth, even if the cellulose acylates have the same degree of acetylation, the films obtained from each have different Rths. Is often expressed. Therefore, Rth cannot be controlled only by the degree of acetylation.

  On the other hand, control of the value of Re has hitherto been important and may be used as an index for classification of film products. The stretching ratio in the stretching process in the solution film forming process is a factor that greatly affects Re, and Re changes when the stretching ratio is changed. In the stretching step, the film is heated to raise the temperature, and this temperature is a factor that greatly affects Re. As described above, in order to control Rth in addition to Re by these factors in spite of the fact that the draw ratio and the film temperature are set in order to express the desired Re in the drawing process, Setting conditions is extremely difficult. Therefore, according to the method of Patent Document 3, although the Rth can be increased, the more film types to be manufactured, the more difficult it is to find the conditions in the stretching process according to each type.

Then, this invention aims at providing the method of suppressing the raise of Re by suppressing the usage-amount of the retardation increasing agent used until now, and manufacturing the cellulose triacetate film by which Rth was controlled selectively. .

In order to solve the above problems, a method for producing a cellulose triacetate film according to the present invention includes a cellulose triacetate and a polyester diol, wherein a substituent in which hydrogen of a hydroxy group in mannan or glucomannan is substituted with another atomic group. the solid components are added at least 1% relative to the weight of the cellulose triacetate, the preparation step of preparing a solution by dissolving in a solvent, the solution was cast supporting lifting body, as a wet film containing the solvent A casting step of peeling from the support, and a drying step of drying the wet film to obtain a cellulose triacetate film, during which the solvent content decreases from 100% by mass to 4% by mass. the wet film was heated so that the temperature in the range of 70 ° C. or higher 0.99 ° C. or less, poly Ester diol, and adipic acid, and is configured as a feature that it has produced from ethylene glycol or propylene glycol.

Substituents are preferably applied more than 2% relative to the weight of cellulose triacetate. When the refractive index in the slow axis direction in the film plane of the cellulose acylate film is nx, the refractive index in the fast axis direction is ny, the refractive index in the film thickness direction is nz, and the film thickness is d (nm) In addition, the amount of the substitution product in the cellulose acylate solution is preferably adjusted according to the thickness direction retardation Rth obtained by {(nx + ny) / 2-nz} × d of the film to be produced. It is preferable to obtain in advance a relationship between the thickness direction retardation Rth when the drying step is performed under a certain condition and the amount of the substitution product, and to determine the amount of the substitution product in the dope based on the obtained relationship.

The atomic group includes an acetyl group, a propionyl group, a butyryl group, a 2-ethylhexyl group, a methyl group, an ethyl group, a hydroxyethyl group, a carboxymethyl group, a sulfone group, a nitro group, an amino group, an N-azetyl group, and 8 carbon atoms. It is preferably at least any one of 30 or less long-chain fatty acid ester groups.

Ri by the acetylation of cellulose to mannan or glucomannan is added, and cellulose triacetate location recombinants is contained a predetermined amount, it is preferable to make a solution by dissolving the triacetate in Solvent.

According to the present invention, it is possible to easily produce a cellulose triacetate film in which Rth is suppressed by suppressing the amount of the retardation increasing agent that has been used so far, and Rth is selectively controlled.

It is the schematic of the solution casting apparatus which implemented this invention. It is explanatory drawing of the 1st aspect which produces the solid component of dope. It is a graph which shows the relationship between the ratio CS (unit; mass%) of the substituted body with respect to a cellulose acylate, and Rth (unit; nm) of a film. It is a graph which shows the relationship between the solvent content rate (unit; mass%) at the time of reaching | attaining predetermined temperature of a wet film, and Rth (unit: nm) of the film obtained by hold | maintaining predetermined temperature for 1 minute after reaching predetermined temperature. is there. It is the schematic of a clip tenter. It is sectional drawing which follows the VI-VI line of FIG. It is explanatory drawing of the 2nd aspect which produces the solid component of dope. It is a graph which shows the relationship between the ratio CP (unit; mass%) of the polymer with respect to a cellulose, and Rth (unit; nm) of a film.

  The solution casting apparatus 10 in FIG. 1 manufactures a film 22 from the dope 11. The dope 11 is obtained by dissolving cellulose acylate in a solvent. The solution casting apparatus 10 includes a casting device 15 that forms a wet film 12 from a dope 11, a pin tenter 16 that holds each side of the wet film 12 with pins (not shown), and dries the wet film 12, and a wet film. 12 is held by a clip 67 (see FIG. 5), a clip tenter 20 that stretches the wet film 12 in the width direction, a drying chamber 25 that further dries the wet film 12 into a film 22, and cools the film 22 A cooling chamber 26 and a winding device 27 for winding the film 22 in a roll shape are provided in order from the upstream side.

  A cutting device for cutting each deformed side portion of the wet film 12 may be provided between the casting device 15 and the pin tenter 16. Further, an excision device is arranged between the pin tenter 16 and the clip tenter 20 or downstream of the clip tenter 20 to excise each side portion where the pin tenter 16 retains the pin, or to remove the clip tenter 20. You may cut out each side part with the grip mark of a clip.

  The casting apparatus 15 peels off a drum 30 as a casting support, a casting die 31 that flows out the dope 11 toward the circumferential surface of the drum 30, and a casting film 32 that is formed on the circumferential surface of the drum 30. A take-off roller 35 that supports the wet film 12 is provided in a chamber 36 that partitions the external space.

  The drum 30 has a drive unit (not shown), and the drive unit rotates around a shaft 30a provided at the center of a circular cross section in the circumferential direction indicated by an arrow A1. When the dope 11 flows out of the casting die 31 toward the peripheral surface of the rotating drum 30, a casting film 32 is formed on the peripheral surface of the drum 30. A bead made of the dope 11 is formed from the casting die 31 to the drum 30. A chamber (not shown) that decompresses the upstream area of the bead by sucking air is provided upstream of the bead in the rotation direction A1 of the drum 30.

  The temperature of the peripheral surface of the drum 30 is controlled by a temperature controller 37. A flow path through which the heat transfer medium flows is formed inside the drum 30, and the temperature controller 37 adjusts the temperature of the heat transfer medium and circulates the heat transfer medium between the drum 30. For example, in the case of so-called cooling casting in which the casting film 32 is solidified (gelled) by cooling, the temperature controller 37 cools the heat transfer medium and sends the cooled heat transfer medium to the drum 30. By continuously performing this feeding, the heat transfer medium goes around the flow path inside the drum 30 and returns to the temperature controller 37.

  The casting support is not limited to the drum 30. For example, in place of the drum 30, an endless band stretched around the backup roller pair may be used. When an endless band is used as a casting support, the temperature of the band is adjusted through the backup roller by passing a heat transfer medium through each backup roller. In the case of so-called dry casting in which the cast film is dried and solidified, a band is often used instead of the drum 30.

  The stripping roller 35 is disposed so that the longitudinal direction is parallel to the longitudinal direction of the drum 30. The wet film 12 is pulled in the transport direction Z1, and the wet film 12 is supported by the peeling roller 35 on the peripheral surface, whereby the casting film 32 is peeled off from the drum 30 at a predetermined position. In the case of cooling casting, the casting film 32 is peeled off from the drum 30 when the solvent content of the casting film 32 is approximately 200 to 300% by mass. In the case of dry casting, it is performed when the solvent content of the casting film 32 is approximately 15 to 50% by mass.

  Inside the casting apparatus 15, a condenser (condenser) is provided that condenses the solvent evaporated from each of the dope 11, the casting film 32, and the wet film 12. The solvent liquefied by the condenser is guided to a recovery device arranged outside the chamber 36 and recovered by the recovery device. In addition, illustration of a condenser and a collection | recovery apparatus is abbreviate | omitted.

  The wet film 12 is guided from the casting device 15 to the pin tenter 16 by the roller 40. The pin tenter 16 has a pin plate (not shown) for penetrating and holding a plurality of pins on the side of the wet film 12, and this pin plate travels on a predetermined track. The wet film 12 is conveyed by the travel of the pin plate. A duct (not shown) through which dry air flows out is provided above the transport path of the wet film 12. A slit-like air outlet that is long in the width direction of the wet film 12 is formed in the lower part of the duct, and when the dry air is discharged from the air outlet, the transported wet film 12 is gradually dried. . The pin tenter 12 is preferably dried so that the solvent content of the wet film 12 is in the range of 4% by mass to 100% by mass. The solvent content in the present specification is determined by {(XY) / Y} × 100, where X is the mass of the wet film 12 and Y is the mass after the wet film 12 is dried. This is a so-called dry weight standard value.

  In this embodiment, the wet film 12 is dried by the pin tenter 16 and then guided to the clip tenter 20. However, in the case of dry casting, the pin tenter 16 need not be used. That is, in the case of dry casting, the wet film 12 from the casting device 15 may be guided to the clip tenter 20 without providing the pin tenter 16. The configuration and operation of the clip tenter 20 will be described later with reference to another drawing.

  The drying chamber 25 includes a plurality of rollers 41 that support the wet film 12 on the peripheral surface. Among these rollers 41, there is a driving roller that rotates in the circumferential direction, and the wet film 12 is conveyed by the rotation of the driving roller. The drying chamber 25 is supplied with heated dry air. The wet film 12 is dried by passing through the drying chamber 25. The cooling chamber 26 is supplied with dry air at approximately room temperature. By passing through the cooling chamber 26, the obtained film 22 is cooled. The film 22 whose temperature has been lowered is guided from the cooling chamber 26 to the winding device 27 and wound around the core 42.

  The dope 11 is a cellulose acylate solution in which cellulose acylate is dissolved in a solvent. The dope 11 includes a substitution product having a predetermined structure in addition to cellulose acylate as a solid component to be the film 22. Rth is controlled by adjusting the amount of the substitution product having the predetermined structure.

  The predetermined structure is a so-called substitution product having a structure in which a hydrogen of a hydroxy group (—OH) is substituted with another atomic group in a polymer obtained by polymerizing a sugar with a glycosidic bond. In addition, in a polymer in which sugar is polymerized by a glycosidic bond, when there is a carboxyl group or an aldehyde group, the predetermined structure is a so-called substituted product having a structure in which a hydroxy group (—OH) is substituted with another atomic group. It is. It is sufficient that this substitution product has the above structure in the dope 11, and it does not matter whether the substitution product has undergone both processes of sugar polymerization and hydrogen substitution of the hydroxy group. Moreover, the said polymer should just have a repeating structure of a basic unit, and any of an oligomer and a polymer may be sufficient as it. Therefore, the substitution product may be either an oligomer or a polymer. The glycosidic bond may be either an α-glucoside bond or a β-glucoside bond.

  By using the substitution product having the predetermined structure as a solid component of the dope 11 and raising the temperature of the wet film 12 as described later, the Rth of the cellulose acylate film is increased without using a conventionally used retardation increasing agent. Can be made. This substitution product does not deposit on the film 22. Moreover, since this substitution body does not vaporize from the wet film 12 and the film 22 in the solution casting process, the solution casting apparatus 10 is not contaminated. These effects are because the conventional retardation increasing agent is a monomer, whereas the substituted product is an oligomer or a polymer.

  This substitution product can be used in combination with a conventional retardation increasing agent. Thereby, the usage-amount of the conventional retardation raising agent can be restrained very much lower than the conventional usage-amount. As a result, each contamination of the film and solution casting equipment by the conventional retardation raising agent is reduced.

  Even if the substitution product having the predetermined structure is included in the dope 11, the dope 11 does not cause phase separation between the oil phase and the aqueous phase. Accordingly, it is possible to produce a film 22 having no unevenness in optical characteristics such as Re and Rth.

  Further, when the cellulose acylate is cellulose triacetate (TAC), crystallization occurs in the solution film forming process. By using the substitution product having the above structure, crystallization of TAC can be promoted. Accordingly, an increase in Rth due to the improvement in crystallinity becomes more certain, and when the wet film 12 is heated for crystallization, the heating time is shortened to prevent the deterioration of TAC more reliably. be able to.

  Further, in the case of cooling casting, gelation of the casting film 32 is promoted by using the above-mentioned replacement body. Therefore, there is also an effect that the manufacturing efficiency in cooling casting can be further increased.

  The sugar skeleton polymerized by glycosidic bonds is more preferably cyclic. However, this predetermined structure is a structure different from cellulose acylate.

  The sugar is a monosaccharide and may be either aldose or ketose. The sugar may be any of triose (3 carbon atoms), tetrose (4 carbon atoms), pentose (5 carbon atoms), hexose (6 carbon atoms), etc. Some hexoses are preferable, and those having a cyclic skeleton as described above are more preferable. This is because the unit structure excluding the acyl group of cellulose acylate is the closest structure compared to other sugars. The closer to the unit structure of cellulose acylate, the greater the effect of improving Rth.

  Examples of hexose include glucose (Glc), mannose (Man), galactose (Gal), fructose (Fru), N-acetylglucosamine (GlcNAc), and glucosamine (GlcN).

  When the polymer having a structure in which sugar is polymerized by glycosidic bonds is a polymer, preferred polymers include mannan, glucomannan, guar gum, starch (amylose, amylopectin), glycogen, pectin, xylan, chitin, agarose, etc. There is. However, the polymer is not limited to these. Of these, mannan, glucomannan and starch are particularly preferred. These polymers are very inexpensive and readily available, and replacement of hydrogen in the hydroxy group can be carried out easily and at low cost. Therefore, the obtained substitution product can be obtained very cheaply and easily as compared with the conventional retardation increasing agent.

  Substituents as atomic groups for substituting hydrogen of the hydroxy group of the polymer are acetyl group, propionyl group, butyryl group, 2-ethylhexyl group, methyl group, ethyl group, hydroxyethyl group, carboxymethyl group, sulfone group, A nitro group, an amino group, an N-acetyl group, a carboxyl group containing alkyl and having 8 to 30 carbon atoms, and the like are preferable. The carboxyl group containing alkyl and having 8 to 30 carbon atoms is more preferably a long-chain fatty acid ester group having 8 to 30 carbon atoms. The long chain fatty acid ester group is a group in which a hydroxyl group forms an ester with a fatty acid.

  In the substituted product, not all hydroxy groups may be substituted with the above-mentioned atomic groups. For example, some hydroxy groups may be carboxyl groups or aldehyde groups.

  In the first embodiment, cellulose acylate and a substituted product whose substituent is an acyl group such as an acetyl group are used as solid components of the dope 11. In the case where the acyl group in the cellulose acylate 51 and the acyl group in the substituted body 52 are made the same, the cellulose 55 and the polymer 56 may be acylated 57 together as shown in FIG. That is, the acylation target 54 is a mixture of cellulose 55 and polymer 56. Thereby, the solid component 58 is obtained as a mixture of the cellulose acylate 51 and the substituted body 52.

  Even if it refine | purifies, the said polymer is normally contained in the cellulose obtained from a conifer. This content is higher than cellulose obtained from hardwood or cotton linter. For example, mannan is contained in cellulose obtained from conifers at a content of 1% or more, whereas cellulose obtained from hardwoods is at most about 0.5% and is obtained from cotton linter. It is not contained in cellulose.

  Conventionally, hemicellulose such as mannan contained in cellulose is considered to be undesirably contained in the production of a cellulose acylate film for use as a retardation film or a polarizing plate protective film. Cellulose has been synthesized and purified to remove hemicellulose from cellulose as much as possible. On the other hand, in the present invention, the polymer such as mannan is positively used, and the substitution product obtained from this polymer is used as the solid component of the dope 11. Therefore, the use of cellulose obtained from coniferous trees is more preferable from the viewpoint of cost and the like because the amount of the polymer 56 or the substitution product 52 to be newly added can be reduced.

  In the case of dry casting, cellulose obtained from cotton linter is used rather than using cellulose obtained from softwood or hardwood from the viewpoint of keeping the peeling force of the casting film 32 from the casting support low. Is preferred. Thus, the present invention is effective even when the cellulose obtained from cotton linter is used as a raw material. It is particularly preferable to use cellulose from conifer as a raw material because it has not only an effect of increasing Rth but also an effect that the casting film 32 can be peeled off with a smaller peeling force.

  Line segments L1, L2, and L3 in FIG. 3 are cases where different substitutes 52 are contained in the film 22. As shown in FIG. 3, the Rth (unit: nm) of the film 22 is proportional to the ratio of the substituted body 52 to the cellulose acylate 51 (hereinafter simply referred to as “substitute body ratio”) CS (unit: mass%). There is a relationship. Therefore, the film 22 having a higher Rth is obtained as the substitution product ratio CS increases. Therefore, the substitution product ratio CS corresponding to the target Rth is obtained, and the amount of the substitution product 52 in the dope 11 is adjusted based on the obtained substitution product ratio CS. In this way, the amount of the substitute 52 in the dope 11 is adjusted according to the target Rth.

  As shown by line segments L1, L2, and L3, when the structure of the substitute 52 is different, the value of Rth that is expressed is different even if the substitute ratio CS is the same. Therefore, it is preferable to obtain in advance the relationship between Rth and the substitution product ratio CS for each substitution product 52 to be used. Thereby, the relationship between Rth and the amount of the substitute 52 in the dope 11 is also obtained in advance. For example, the target Rth is Rth (P). Since the substitute that expresses Rth (P) is the substitute 52 of the line segment L1 and the line segment L3, any of these can be used for the solid component 58. In addition, when it is desired to suppress the use amount of the substitute 52, it is preferable to select the substitute 52 of the line segment L1 having a smaller substitute proportion CS. FIG. 3 illustrates CS (P) with respect to the ratio of substitutes CS that expresses Rth (P) when the substitute 52 of the line segment L1 is selected.

  When a polymer is previously contained in cellulose used as a raw material, this raw material is acylated, which corresponds to the difference between the substitution rate CS and the predetermined substitution rate CS (P) in the obtained cellulose acylate. An amount of the substitution product may be added to the obtained cellulose acylate.

  When obtaining the relationship between Rth and the substitutional substance ratio CS as shown in FIG. 3 for a predetermined substitution product, the conditions in a series of drying steps until the wet film 12 becomes the film 22 are made constant. When the film 22 is manufactured by the solution casting apparatus 10 of FIG. 1, a series of drying processes are the processes in the pin tenter 16, the clip tenter 20, and the drying chamber 25, but the process of peeling off from the drum 30. In addition, it is more preferable to consider the transition between the devices as a drying step. However, among the series of drying steps, only the conditions of the predetermined step in the clip tenter 20 may be made constant to obtain the relationship between Rth and the substitution product ratio CS. This is because, when the replacement body 52 is used, the condition of the predetermined process in the clip tenter 20 has the greatest influence on Rth among the series of drying processes.

  The casting film 32 when a certain amount of the substitute body 52 is included in the dope 11 becomes the film 22 having a high Rth by raising the temperature. However, the increase width of Rth becomes small depending on the temperature rise timing. The solvent content (unit: mass%) on the horizontal axis in FIG. 4 corresponds to the timing at which the wet film 12 is heated to reach a predetermined temperature, that is, when the predetermined temperature is reached. In FIG. 4, the temperature of the wet film 12 that has reached a predetermined temperature at the timing of the solvent content on the horizontal axis is maintained for 1 minute, and the Rth (unit: nm) of the obtained film 22 is the vertical axis.

  When the time for maintaining the predetermined temperature is 1 minute, when the timing at which the wet film 12 is heated to reach the predetermined temperature is greater than 100 mass% and less than 4 mass%, as shown in FIG. On the other hand, Rth remains small. On the other hand, when the timing at which the wet film 12 is heated to reach the predetermined temperature is in the range of 4% by mass or more and 100% by mass or less, Rth greatly increases. When the solvent content is in the range of 4% by mass or more and 100% by mass or less, the wet film 12 corresponds to when the inside of the clip tenter 20 is conveyed. Therefore, when determining the relationship between Rth and the substitution product ratio CS, the temperature of the wet film 12 in the clip tenter 20 in which the solvent content is in the range of 4% by mass to 100% by mass is set to a predetermined temperature. It should be constant.

  As shown in FIG. 4, when the timing at which the wet film 12 is heated to reach a predetermined temperature is in the range of 40% by mass or more and 50% by mass or less, Rth increases particularly significantly. In addition, when the temperature at which the wet film 12 is heated to reach a predetermined temperature is in the range of 20% by mass or more and 40% by mass or less or 50% by mass or more and 70% by mass or less, it is 40% by mass or more and 50% by mass or less. Rth of at least 80% in the case of this range. Therefore, when obtaining the relationship between Rth and the substitution product ratio CS, the temperature of the wet film 12 in the clip tenter 20 having a solvent content in the range of 20 mass% or more and 70 mass% or less is set to a predetermined temperature, and this condition is kept constant. More preferably, the temperature of the wet film 12 having a solvent content in the range of 40% by mass or more and 50% by mass or less is set to a predetermined temperature, and this condition is more preferably constant, and the solvent content is 40% by mass. It is particularly preferable that the temperature of the wet film 12 is a predetermined temperature and this condition is kept constant.

  The predetermined temperature differs depending on the type of cellulose acylate and substituted product. For example, when the cellulose acylate is TAC and the substitution product is mannan acetate, the predetermined temperature is in the range of 90 ° C to 140 ° C. Further, when the cellulose acylate is cellulose diacetate (DAC) and the substitution product is a mixture of xylan acetate and mannan acetate in a mass ratio of 1: 1, the predetermined temperature is in the range of 100 ° C. or more and 150 ° C. or less. is there. In any of the above cases, a more preferable predetermined temperature is in the range of 90 ° C. or higher and 130 ° C. or lower.

  When the cellulose acylate is TAC, TAC has a higher degree of crystallinity than DAC. Therefore, a graph (not shown) in which the vertical axis of FIG. 4 is replaced with the TAC crystallinity has the same shape as FIG. As described above, when TAC is used as cellulose acylate, when the temperature at which the casting film 32 is heated to reach a predetermined temperature is in the range of 4% by mass to 100% by mass, the crystallinity is A big rise. Therefore, when the relationship between Rth and the substitution product ratio CS is obtained, the timing at which the predetermined temperature is reached may be obtained based on the TAC crystallinity.

  As shown in FIG. 5, the clip tenter 20 includes a chamber 60 that surrounds the transport path of the wet film 12 and partitions the transport path and its periphery from the external space. The chamber 60 has a preheating area 61, an extending area 62, a relaxation area 63, and a cooling area 64 in order from the upstream side in the transport direction Z1. However, the chamber 60 does not include a partition member that partitions the areas 61 to 64 so that the areas 61 to 64 are independent spaces. As will be described later, each of the areas 61 to 64 is formed by the travel path of the clip 67 and the dry air flowing out from each of the first to fourth air supply chambers 71a to 71d (see FIG. 6).

  The clip tenter 20 includes a plurality of clips 67 that grip the side portion of the wet film 12, rails 68 and 69 that form a running track of the clip 67, a duct 71 that discharges dry air, and dry air that has a predetermined condition in the duct 71. The air supply part 72 which feeds in. The rails 68 and 69 are installed on both sides of the transport path of the wet film 12.

  The rail 68 and the rail 69 are separated from each other by a predetermined rail width. The rail width is constant at the width W1 in the preheating area 61, gradually increases from the width W1 to the width W2 in the extending area 62 in the direction Z1, and in the relaxation area 63 from the width W2 to the width W3 in the direction Z1. The cooling area 64 has a constant width W3. By setting each rail width in this way, in the preheating area 61, the wet film 12 is conveyed in a state in which the width is regulated so as to maintain a constant width, and in the stretching area 62, the wet film being conveyed. The film 12 is stretched so as to expand in the width direction. In the relaxation area 63, the wet film 12 is transported in a state where the width is restricted while the width is reduced, and in the cooling area 64, the wet film 12 is transported in a state where the width is kept constant.

  However, the above “constant” regarding the rail width in the preheating area 61 and the cooling area 64 is not necessarily strict. In other words, in each of the preheating area 61 and the cooling area 64, the rail width may be slightly changed from upstream to downstream so that the width W1 and the width W3 can be said to be substantially constant. Further, the rail width in the relaxation area 63 does not necessarily need to be gradually narrowed from upstream to downstream. For example, in the mitigation area 63, the rail width may be slightly changed from upstream to downstream to an extent that the width W2 is substantially constant.

  The plurality of clips 67 are attached to a chain (not shown) with a predetermined interval. This chain is attached to a rail 68 and a rail 69, respectively, and is movable along the rails 68 and 69. The chain meshes with a turn wheel 73 disposed on the upstream side of the preheating area 61 and a sprocket 74 disposed on the downstream end of the cooling area 64. As the sprocket 74 rotates, the chain runs continuously. As the chain travels, the clip 67 moves along the rails 68 and 69.

  Upstream from the preheating area 61 is provided gripping start means (not shown) for starting gripping of the side of the wet film 12 by the clip 67, and downstream of the cooling area 64, the wet film 12 by the clip 67 is provided. A grip releasing means (not shown) for releasing the side grip is provided. As a result, the wet film 12 is gripped by the clip 67 upstream of the preheating area 61, and the clip 67 moves along the rails 68 and 69 to be conveyed in the Z1 direction, and sequentially passes through the areas 36 to 39. A predetermined process is performed in each of the areas 36 to 39, and the grip is released at the downstream end of the cooling area 64.

  As shown in FIG. 6, the duct 71 is provided above the conveyance path so that the distance between the wet film 12 and the conveyance path is substantially constant. A slit 77 extending in the width direction Z2 of the wet film 12 is formed in the lower portion of the duct 71, and a plurality of slits 77 are provided in the Z1 direction. In addition, a duct (not shown) having the same configuration as the duct 71 may be provided below the transport path so that the distance from the transport path is substantially constant. Formed. In addition, the conveyance direction Z1 and the width direction Z2 shall be orthogonally crossed.

  The inside of the duct 71 is divided into first to fourth air supply chambers 71 a to 71 d by a plurality of partition plates 78. In FIG. 6, the first and second supply chambers 71a and 71b have a plurality of slits 77, and the third and fourth supply chambers 71c and 71d have one slit 77. However, the number of the slits 77 in each of the air supply chambers 71a to 71d is not limited to this. That is, one slit 77 may be provided in the first supply chamber 71a or the second supply chamber 71b, and a plurality of slits 77 may be provided in the third supply chamber 71c or the fourth supply chamber 71d.

  The air supply unit 72 supplies dry air to the first to fourth supply chambers 71 a to 71 d of the duct 71. The air supply unit 72 includes a temperature controller (not shown) that independently controls the temperature of each dry air supplied to the first to fourth supply chambers 71a to 71d. By this temperature controller, the dry air adjusted to a predetermined temperature is supplied to each of the areas 61 to 64 via the first to fourth supply chambers 71a to 71d, respectively.

  Due to the supply of dry air from the second air supply chamber 71b, the wet film 12 is heated to a predetermined temperature in the stretching area 62.

  Further, the wet film 12 before entering the stretching area 62 is heated in advance by the supply of dry air from the first air supply chamber 71a. Due to the heating by the preheating area 61, the stretching in the stretching area 62 is started quickly, and more uniform tension is applied in the width direction Z2 when stretching in the stretching area 62. .

  In the relaxation area 63, in addition to restricting the width by gripping both sides, the stress (residual stress) remaining inside is appropriately relaxed by heating with dry air from the third supply chamber 71c. In this relaxation step, the molecular orientation in the wet film 12 is brought into an intended state.

  In the cooling area 64, the wet film 12 having the desired molecular orientation in the relaxation process is cooled with dry air. This cooling fixes the molecules in the desired orientation. In FIG. 6, illustration of the clip 67, the turn wheel 73, and the sprocket 74 is omitted to avoid complexity.

  In order to express the target Rth in the film 22, the temperature of the wet film 12 is held at a predetermined temperature by the pin tenter 16 or the clip tenter 20. The holding time for holding the temperature of the wet film 12 at the predetermined temperature may be as short as about 1 minute. As described above, since the temperature holding for expressing the target Rth is sufficient for a very short time, fluctuations in Re can be suppressed. Therefore, after determining the conditions in the clip tenter 20 so as to express the desired Re, it is only necessary to hold the temperature for a short time at the above timing for the desired Rth expression. Although it is possible to promote crystallization by setting the wet film 12 in the range of 155 ° C. or more and 200 ° C. or less in the drying chamber 25, in these cases, vaporization of the additive contained in the wet film 12 is performed. In addition, the wet film 12 is easily damaged on the peripheral surface of the roller 41, which is not necessarily preferable.

  In the first embodiment, the solid component 58 is obtained as a mixture of the cellulose acylate 51 and the substituted body 52 by performing the acylation 57 by combining the cellulose 55 and the polymer 56. However, the method of obtaining the solid component 58 may be the following second embodiment. Taking the case where cellulose acylate and a substituent having the same acyl group as the solid component of the dope 11 are used as an example, as shown in FIG. 7, a first acylation 61 for acylating cellulose 55, The second acylation 62 for acylating the polymer 56 is carried out independently. The cellulose acylate 51 obtained by the first acylation 61 and the substitution product 52 obtained by the second acylation 62 can be combined into a solid component 58. This method can be applied in the case of using the substitute 52 in which the substituent is an acyl group different from cellulose acylate.

  In the first and second embodiments, the relationship between the substitution product ratio and Rth is obtained in advance, but instead of this aspect, the following third embodiment may be used. In the third embodiment, the relationship between Rth and the ratio of polymer 56 to cellulose 55 (hereinafter referred to as polymer ratio) CP is obtained in advance. Line segments L4, L5, and L6 shown in FIG. 8 are obtained by acylating 57 different polymers 56 together with cellulose 55 and using each solid component 58 thus obtained to produce Rth ( It is a graph of unit; nm). The horizontal axis represents the polymer ratio (unit: mass%). The solid component 58 used in L4 is the same as the solid component 58 used in L1 of FIG. Further, the solid components 58 used in L5 and L6, respectively, are the same as the solid components 58 used in L2 and L3 in FIG.

  As shown in FIG. 8, the Rth of the film 22 and the polymer ratio CP are in a proportional relationship. Furthermore, L4, L5, and L6 have the same relationship as L1, L2, and L3 in FIG. 3, respectively. Thus, the polymer ratio CP and the substituent ratio CS have the same relationship with Rth. Therefore, the polymer ratio CP corresponding to the target Rth (Rth (P) in FIG. 8) is obtained, and the amount of the polymer 56 in the acylation object 54 is adjusted based on the obtained polymer ratio CP (P). By doing so, the amount of the substitute 52 in the dope 11 may be adjusted.

  In the first to third embodiments, all are cases where cellulose acylate and a substitute are used as the solid component 58. However, other materials may be further added to the dope 11. For example, a plasticizer, an ultraviolet absorber, a mat agent and the like can be mentioned.

  The present invention is particularly effective when manufacturing an optical compensation film such as a retardation film that requires a high Rth.

[Experiment 1] to [Experiment 16]
[Preparation of cellulose acylate dope]
The following composition was put into a mixing tank and stirred while heating to dissolve or disperse each component to prepare a dope 11. The prepared dope 11 is 11 types of sample numbers A-1 to A-11 shown in Table 1. In addition, the solvent composition of each dope 11 of A-1 to A-11 is as follows. Each dope 11 of A-1 to A-11 was prepared by adjusting the concentration so that the concentration of the solid component 58 shown in Table 1 was 20% by mass. The solid components 58 shown in Table 1 are cellulose acylate, Re increasing agent, Rth increasing agent, polyester diol, and matting agent in the matting agent dispersion. In addition, in A-1 to A-11, since the Re raising agent is not used, it is described as 0 (zero) in Table 1. In Table 1, “CA” is cellulose acylate, “AA” is adipic acid (C6), “EG” is ethylene glycol (C2), “PG” is 1,2-propyne glycol (C3), respectively. Show.
Methylene chloride (first solvent component) 100 parts by mass Methanol (second solvent component) 19 parts by mass 1-butanol 1 part by mass

[Preparation of matting agent dispersion]
In order to prepare each dope in Table 1, a matting agent dispersion was prepared in advance. The matting agent dispersion in Table 1 was prepared by charging the following composition into a disperser (not shown) and stirring to disperse each component.

Composition of matting agent dispersion ・ Silica particle dispersion (average particle size 16 nm) 10.0 parts by mass “AEROSIL R972” manufactured by Nippon Aerosil Co., Ltd. ・ Methylene chloride 72.8 parts by mass • Methanol 3.9 parts by mass • Butanol 0.5 parts by mass-Cellulose acylate solution 10.3 parts by mass The above-mentioned "cellulose acylate solution" as the composition of the matting agent dispersion is a table used for A-1 to A-11 to be prepared. The same cellulose acylate as each cellulose acylate No. 1 was used. That is, “CA” in Table 1 of each dope of A-1 to A-11 and the cellulose acylate used for the “mat agent dispersion” are the same as each other.

The prescription of the above-mentioned “cellulose acylate solution” as the property of the matting agent dispersion is as follows.
Cellulose acylate 100 parts by mass Methylene chloride (first solvent component) 100 parts by mass Methanol (second solvent component) 19 parts by mass 1-butanol 1 part by mass

  The following compounds were used as Re raising agents.

  A cellulose acylate film was produced using the dope 11 by the solution casting apparatus 10 as follows. The dope 11 was cast from the casting port of the casting die 31 onto the drum 30 cooled to −5 ° C. The casting film 32 is peeled off in a state where the solvent content is approximately 70% by mass, and both end portions in the width direction of the wet film 12 are held by a pin tenter (a pin tenter described in FIG. 3 of JP-A-4-1009). In the state where the temperature of the wet film 12 having a solvent content of 4 to 100% by mass is maintained at the temperature shown in Table 2, the stretching ratio in the transverse direction (direction perpendicular to the conveying direction Z1) is about 3%. In this way, the wet film 12 was dried while maintaining a distance between the pin holding one side end and the pin holding the other side end. Then, it dried further by conveying between the rolls 41 of the drying chamber 25, and produced the film 22 whose thickness is about 60 micrometers.

[Method for evaluating optical properties of cellulose acylate film 22]
The optical properties of the obtained film 22 were evaluated by the following method.

[In-plane retardation Re, thickness direction retardation Rth]
From each film 22 obtained, a sample of 30 mm × 40 mm was sampled. The sample was conditioned at 25 ° C. and 60% RH (relative humidity) for 2 hours, and Re (λ) was measured by using an automatic birefringence meter KOBRA 21ADH (manufactured by Oji Scientific Instruments) with light having a wavelength of λ nm as a film normal. Measured by making it incident in the direction. Rth (λ) is the retardation value measured by making light of wavelength λnm incident from the direction inclined by + 40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis. And a retardation value measured in three directions: a retardation value measured by making light of wavelength λ nm incident from a direction inclined by −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis Based on the above, the assumed average refractive index of 1.48 and the thickness were input to the automatic birefringence meter KOBRA 21ADH and calculated.

  In Table 2, “R (nm) increase rate% based on CA alone” and “Rth (nm) increase rate% based on CA alone” indicate polyester diol and matting agent. It was calculated on the basis of Re (nm) and Rth (nm) of cellulose acylate alone contained at a ratio of 1 and containing no Re raising agent or Rth raising agent.

(Film surface)
The surface shape of the obtained film was evaluated by haze measurement. A haze measurement was performed. Each haze is measured by applying liquid paraffin on both sides of a sample of 400 mm x 80 mm and sandwiching it between glass plates, and then using a haze meter (HGM-2DP, Suga Test Instruments) at 25 ° C and 60% relative humidity. Measured according to -6714. Only liquid paraffin with no film sandwiched between them and the measured value of the glass plate were used as blanks. The results were evaluated according to the following criteria and the results are listed in Table 2.
◎: Haze is 1.0 or less ○: Haze is greater than 1.0 and 1.3 or less Δ: Haze is greater than 1.3 and 1.5 or less ×: Haze is 1.5 or more

[Comparative Experiment 1] to [Comparative Experiment 6]
As comparative experiments for the present invention, Comparative Experiments 1 to 6 were performed. First, a dope having sample numbers A-12 and A-13 was prepared in the same manner as in Experiments 1 to 16, using cellulose acylate, other solid components, and a solvent. In addition, the solvent composition of A-12 and A-13 and the density | concentration of a solid component are the same as the solvent composition in Experiment 1-Experiment 16. Each cellulose acylate used in the matting agent dispersion of A-12 and A-13 is the same as “CA” of A-12 and A-13 in Table 1.

  A film was produced in the same manner as in Experiment 1 to Experiment 16 except that the temperature of the wet film 12 having a solvent content of 4 to 100% by mass was maintained at the temperature shown in Comparative Experiment 1 to Comparative Experiment 4 in Table 2. The experiment was conducted except that the dope 11 of A-1 was cast and the temperature of the wet film having a solvent content of 4 to 100% by mass was maintained at the temperature shown in Comparative Experiment 5 and Comparative Experiment 6 in Table 2. Films were produced in the same manner as in 1-16.

  The films obtained in Comparative Experiments 1 to 6 were evaluated in the same manner as in Experiments 1 to 16, respectively. The evaluation results are as shown in Table 2.

  As shown in Table 2, according to the present invention, the increase in Re can be suppressed, Rth can be selectively increased, and the film 22 having a good surface shape can be obtained by adjusting the content of the substitute 52. Could get.

DESCRIPTION OF SYMBOLS 10 Solution casting equipment 11 Dope 15 Casting apparatus 20 Clip tenter 22 Film

Claims (6)

A solid component containing cellulose triacetate and polyester diol, wherein a substituent in which hydrogen of hydroxy group in mannan or glucomannan is substituted with another atomic group is added by 1% or more based on the mass of the cellulose triacetate, A preparation step of preparing a solution by dissolving in a solvent;
A casting step of peeling the solution was cast supporting lifting member, from the support as a wet film containing the solvent,
And drying step to make a cellulose triacetate film by drying the wet film,
The drying step in solvent content is heated so that the temperature of the wet film range of 70 ° C. or higher 0.99 ° C. or less while decreasing a 4 wt% to 100 wt%,
The method for producing a cellulose triacetate film, wherein the polyester diol is produced from adipic acid and ethylene glycol or propylene glycol . 2. The method for producing a cellulose triacetate film according to claim 1, wherein 2% or more of the substitute is added to the mass of the cellulose triacetate. Nx a refractive index in the slow axis direction in the film plane of the cellulose triacetate film, ny a refractive index in the fast axis direction, a refractive index in the thickness direction of the cellulose triacetate film nz, the thickness of the cellulose triacetate film d (nm) And when
The said substituents before Ki溶 solution, manufacturing a film {(nx + ny) / 2 -nz} claim 1 or 2 an amount depending on the thickness direction retardation Rth is characterized in that are adjusted for obtaining at × d The manufacturing method of the cellulose triacetate film of description. A relationship between the thickness direction retardation Rth when the drying step is performed under a certain condition and the amount of the substitution product is obtained in advance, and the amount of the substitution product in the solution is determined based on the obtained relationship. The method for producing a cellulose triacetate film according to claim 3 . The atomic group includes an acetyl group, a propionyl group, a butyryl group, a 2-ethylhexyl group, a methyl group, an ethyl group, a hydroxyethyl group, a carboxymethyl group, a sulfone group, a nitro group, an amino group, an N-azetyl group, and a carbon number. The method for producing a cellulose triacetate film according to any one of claims 1 to 4 , wherein the long-chain fatty acid ester group is 8 or more and 30 or less. The cellulose to which the mannan or the glucomannan is added is acetylated to form a cellulose triacetate containing a predetermined amount of the substitution product, and the cellulose triacetate is dissolved in the solvent to form the solution. Item 6. A method for producing a cellulose triacetate film according to any one of Items 1 to 5 .

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