Protective film of polarizer, polarizer and method for producing it, and liquid crystal display device

A polarizer produced by the method for producing a polarizer comprising alkali-saponifying a protective film to a polarizer containing a cellulose acylate and an organic acid having an octanol/water partition coefficient of at least 3.0 and satisfying one of the following requirements:

• (1):
• The surface of the film has a pH of from 3.0 to 4.5;
• or
• (2):
• The surface of the film has a pH of more than 4.5 and at most 6.0, and
• wherein the film has a moisture permeability of at least 2800 g/m2 ·day,
• and including washing the alkali-saponified protective film to a polarizer with water, and laminating the washed protective film to a polarizer on at least one surface of a polarizing element,
• the protective film to a polarizer comprising an organic acid represented by the following formula (1), wherein the ratio of the organic acid to the cellulose acylate is from 0.01 to 10% by mass:
• X-L-(R1)n Formula (1)
• wherein:
• X represents an acid group wherein the acid dissociation constant is 5.5 or less;
• L represents a single bond, or a di- or more valent linking group;
• R1 represents an alkyl group having from 6 to 30 carbon atoms, an alkenyl group having from 6 to 30 carbon atoms, an alkynyl group having from 6 to 30 carbon atoms, an aryl group having from 6 to 30 carbon atoms or a from 6 to 30 membered heterocyclic group, and each group may have a substituent;
• n represents 1 when L is a single bond, or represents the number expressed by:
• (the valent number of L)-1
• when L is a di- or more valent linking group.

A polarizer comprising a polarizing element and at least one sheet of a protective film to a polarizer containing a cellulose acylate and an organic acid having an octanol/water partition coefficient of at least 3.0 and satisfying one of the following requirements:

• (1):
• The surface of the film has a pH of from 3.0 to 4.5;
• or
• (2):
• The surface of the film has a pH of more than 4.5 and at most 6.0, and
• wherein the film has a moisture permeability of at least 2800 g/m2 ·day,
• the protective film to a polarizer comprising an organic acid represented by the following formula (1), wherein the ratio of the organic acid to the cellulose acylate is from 0.01 to 10% by mass:
• X-L-(R1)n Formula (1)
• wherein:
• X represents an acid group wherein the acid dissociation constant is 5.5 or less;
• L represents a single bond, or a di- or more valent linking group;
• R1 represents an alkyl group having from 6 to 30 carbon atoms, an alkenyl group having from 6 to 30 carbon atoms, an alkynyl group having from 6 to 30 carbon atoms, an aryl group having from 6 to 30 carbon atoms or a from 6 to 30 membered heterocyclic group, and each group may have a substituent;
• n represents 1 when L is a single bond, or represents the number expressed by:
• (the valent number of L)-1
• when L is a di- or more valent linking group.

A liquid crystal display device comprising at least one sheet of a protective film to a polarizer containing a cellulose acylate and an organic acid having an octanol/water partition coefficient of at least 3.0 and satisfying one of the following requirements:

• (1):
• The surface of the film has a pH of from 3.0 to 4.5;
• or
• (2):
• The surface of the film has a pH of more than 4.5 and at most 6.0, and
• wherein the film has a moisture permeability of at least 2800 g/m2 ·day,
• the protective film to a polarizer comprising an organic acid represented by the following formula (1), wherein the ratio of the organic acid to the cellulose acylate is from 0.01 to 10% by mass:
• X-L-(R1)n Formula (1)
• wherein:
• X represents an acid group wherein the acid dissociation constant is 5.5 or less;
• L represents a single bond, or a di- or more valent linking group;
• R1 represents an alkyl group having from 6 to 30 carbon atoms, an alkenyl group having from 6 to 30 carbon atoms, an alkynyl group having from 6 to 30 carbon atoms, an aryl group having from 6 to 30 carbon atoms or a from 6 to 30 membered heterocyclic group, and each group may have a substituent;
• n represents 1 when L is a single bond, or represents the number expressed by:
• (the valent number of L)-1
• when L is a di- or more valent linking group.

A polarizer comprising:

• a polarizing element and two protective films to a polarizer disposed on both sides of the polarizing element,
• wherein the pH of the aqueous solution of the polarizing element, as measured according to the following method (1), is from 4 to 7, and before and after aged at 60° C. and a relative humidity of 95% for 500 hours, the pH change in the aqueous solution of the polarizing element, as measured according to the following method (1), is less than 0.4, and
• wherein at least one protective film to the polarizer contains an organic acid having an octanol/water partition coefficient of at least 3.0,
• Method (1):
• 40 mg of the polarizing element is dipped in 15 ml of pure water and heated at 100° C. for 2 hours, and then the pH of the aqueous solution is measured,
• wherein the organic acid is a compound represented by the following formula (1):
• X-L-(R1)n Formula (1)
• wherein:
• X represents an acid group wherein the acid dissociation constant is 5.5 or less;
• L represents a single bond, or a di- or more valent linking group;
• R1 represents an alkyl group having from 6 to 30 carbon atoms, an alkenyl group having from 6 to 30 carbon atoms, an alkynyl group having from 6 to 30 carbon atoms, an aryl group having from 6 to 30 carbon atoms or a from 6 to 30 membered heterocyclic group, and each group may have a substituent;
• n represents 1 when L is a single bond, or represents the number expressed by:
• (the valent number of L)-1
• when L is a di- or more valent linking group.

A liquid crystal display device comprising:

• at least one of the polarizer, having a polarizing element and two protective films to a polarizer disposed on both sides of the polarizing element,
• wherein the pH of the aqueous solution of the polarizing element, as measured according to the following method (1), is from 4 to 7, and before and after aged at 60° C. and a relative humidity of 95% for 500 hours, the pH change in the aqueous solution of the polarizing element, as measured according to the following method (1), is less than 0.4, and
• wherein at least one protective film to the polarizer contains an organic acid having an octanol/water partition coefficient of at least 3.0,
• Method (1):
• 40 mg of the polarizing element is dipped in 15 ml of pure water and heated at 100° C. for 2 hours, and then the pH of the aqueous solution is measured,
• wherein the organic acid is a compound represented by the following formula (1):
• X-L-(R1)n Formula (1)
• wherein:
• X represents an acid group wherein the acid dissociation constant is 5.5 or less:
• L represents a single bond, or a di- or more valent linking group:
• R1 represents an alkyl group having from 6 to 30 carbon atoms, an alkenyl group having from 6 to 30 carbon atoms, an alkynyl group having from 6 to 30 carbon atoms, an aryl group having from 6 to 30 carbon atoms or a from 6 to 30 membered heterocyclic group, and each group may have a substituent:
• n represents 1 when L is a single bond, or represents the number expressed by:
• (the valent number of L)-1
• when L is a di- or more valent linking group.

A polarizer comprising:

• a polarizing element and at least one protective film to a polarizer and having, between the polarizing element and the protective film to a polarizer, a layer containing an organic acid of the following formula (1) in an amount of from 0.01 to 10 g/m2,
• wherein at least one protective film to the polarizer contains an organic acid having an octanol/water partition coefficient of at least 3.0,
• X-L-(R1)n Formula (1)
• wherein:
• X represents an acid group wherein the acid dissociation constant is 5.5 or less;
• L represents a single bond, or a di- or more valent linking group;
• R1 represents an alkyl group having from 6 to 30 carbon atoms, an alkenyl group having from 6 to 30 carbon atoms, an alkynyl group having from 6 to 30 carbon atoms, an aryl group having from 6 to 30 carbon atoms or a from 6 to 30 membered heterocyclic group, and each group may have a substituent;
• n represents 1 when L is a single bond, or represents the number expressed by:
• (the valent number of L)-1
• when L is a di- or more valent linking group.

A liquid crystal display device comprising:

• at least one of the polarizer having at least one protective film to a polarizer and having, between the polarizing element and the protective film to a polarizer, a layer containing an organic acid of the following formula (1) in an amount of from 0.01 to 10 g/m2,
• wherein at least one protective film to the polarizer contains an organic acid having an octanol/water partition coefficient of at least 3.0,
• X-L-(R1)n Formula (1)
• wherein:
• X represents an acid group wherein the acid dissociation constant is 5.5 or less;
• L represents a single bond, or a di- or more valent linking group;
• R1 represents an alkyl group having from 6 to 30 carbon atoms, an alkenyl group having from 6 to 30 carbon atoms, an alkynyl group having from 6 to 30 carbon atoms, an aryl group having from 6 to 30 carbon atoms or a from 6 to 30 membered heterocyclic group, and each group may have a substituent;
• n represents 1 when L is a single bond, or represents the number expressed by :
• (the valent number of L)-1
• when L is a di- or more valent linking group.