Process for producing cellulose acylate film

A process for producing a cellulose acylate film, the process comprising:

• a step of preparing a cellulose acylate solution containing a cellulose acylate, a functional additive, a first organic solvent, and a second organic solvent, the solubilities of the functional additive in the first organic solvent and the second organic solvent being different;
• a step of casting the cellulose acylate solution on a band or a drum;
• and
• a step of drying the cast cellulose acylate solution so as to remove the organic solvents therefrom;
• wherein
• the solvent composition of mixed organic solvent in the cast cellulose acylate solution changes during the drying step, and
• when S1(25) (solids weight concentration of the functional additive) is the solubility of the functional additive at 25° C. in the mixed organic solvent having a solvent composition where the proportion by weight of the first organic solvent, in which the solubility of the functional additive is the lowest, is the highest in the mixed organic solvent, and S0(25) (solids weight concentration of the functional additive) is the solubility of the functional additive at 25° C. in the mixed organic solvent of the solvent composition in the step of preparing the cellulose acylate solution, then for the cellulose acylate solution that is cast,
• 0≦S0(25)−S1(25)<12.5 or
• S1(25)/S0(25)≧0.5.

A process for producing a cellulose acylate film, the process comprising:

• a step of preparing a cellulose acylate solution containing a cellulose acylate, a functional additive, a first organic solvent, and a second organic solvent, the solubilities of the functional additive in the first organic solvent and the second organic solvent being different;
• a step of casting the cellulose acylate solution on a band or a drum;
• and
• a step of drying the cast cellulose acylate solution so as to remove the organic solvents therefrom;
• wherein
• the solvent composition of mixed organic solvent in the cast cellulose acylate solution changes during the drying step, and
• when S1(20) (solids weight concentration of the functional additive) is the solubility of the functional additive at 20° C. in the mixed organic solvent having a solvent composition where the proportion by weight of the first organic solvent, in which the solubility of the functional additive is the lowest, is the highest in the mixed organic solvent, and S0(20) (solids weight concentration of the functional additive) is the solubility of the functional additive at 20° C. in the mixed organic solvent of the solvent composition in the step of preparing the cellulose acylate solution, then for the cellulose acylate solution that is cast,
• 0≦S0(20)−S1(20)<12.5 or
• S1(20)/S0(20)≧0.5.

A process for producing a cellulose acylate film, the process comprising:

• a step of preparing a cellulose acylate solution containing a cellulose acylate, a functional additive, a first organic solvent, and a second organic solvent, the solubilities of the functional additive in the first organic solvent and the second organic solvent being different;
• a step of casting the cellulose acylate solution on a band or a drum;
• and
• a step of drying the cast cellulose acylate solution so as to remove the organic solvents therefrom;
• wherein
• the solvent composition of the mixed organic solvent in the cast cellulose acylate solution changes during the drying step, and
• when S1(35) (solids weight concentration of the functional additive) is the solubility of the functional additive at 35° C. in the mixed organic solvent having a solvent composition where the proportion by weight of the first organic solvent, in which the solubility of the functional additive is the lowest, is the highest in the mixed organic solvent, and S0(35) (solids weight concentration of the functional additive) is the solubility of the functional additive at 35° C. in the mixed organic solvent of the solvent composition in the step of preparing the cellulose acylate solution, then for the cellulose acylate solution that is cast,
• 0≦S0(35)−S1(35)<12.5 or
• S1(35)/S0(35)≧0.5.

A process for producing a cellulose acylate film, the process comprising:

• a step of preparing a cellulose acylate solution containing a cellulose acylate (a), an additive (b) selected from the group consisting of a plasticizer, a retardation control agent, a degradation inhibitor, and a UV absorbing agent, and an organic solvent or a mixed organic solvent (c);
• a step of casting the cellulose acylate solution on a band or a drum;
• and
• a step of drying the cast cellulose acylate solution so as to remove the organic solvent therefrom;
• wherein for the cellulose acylate solution that is cast, the heat of solution ΔH0 of the additive (b) in the organic solvent or mixed organic solvent (c) is larger than the heat of solution ΔHs thereof in a solution in which only the cellulose acylate (a) is dissolved, and ΔH0−ΔHs is 0.3 kcal/mol or more.

A process for producing a cellulose acylate film, the process comprising:

• a step of preparing a cellulose acylate solution containing a cellulose acylate (a), an additive (b′) selected from the group consisting of a retardation control agent, a degradation inhibitor, and a UV absorbing agent, a plasticizer (b1), and an organic solvent or a mixed organic solvent (c);
• a step of casting the cellulose acylate solution on a band or a drum;
• and
• a step of drying the cast cellulose acylate solution so as to remove the organic solvent therefrom;
• wherein
• for the cellulose acylate solution that is cast, the heat of solution ΔH0 of the additive (b′) in the organic solvent or mixed organic solvent (c) is larger than the heat of solution ΔHs thereof in a solution in which the plasticizer (b1) alone is dissolved, and ΔH0−ΔHs is 0.3 kcal/mol or more.

A process for producing a cellulose acylate film, the process comprising:

• a step of preparing a cellulose acylate solution containing a cellulose acylate (a), an additive (b′) selected from the group consisting of a retardation control agent, a degradation inhibitor, and a UV absorbing agent, a plasticizer (b1), and an organic solvent or a mixed organic solvent (c);
• a step of casting the cellulose acylate solution on a band or a drum;
• and
• a step of drying the cast cellulose acylate solution so as to remove the organic solvent therefrom;
• wherein
• for the cellulose acylate solution that is cast, the heat of solution ΔH0 of the additive (b′) in the organic solvent or mixed organic solvent (c) is larger than the heat of solution ΔHs thereof in a solution in which the cellulose acylate (a) and the plasticizer (b1) are dissolved, and ΔH0−ΔHs is 0.3 kcal/mol or more.