CN-116324538-B - Retardation film and method for producing same

Abstract

A retardation film comprising an A layer having a slow axis and a B layer having a slow axis at an angle of 85 DEG to 90 DEG to the slow axis of the A layer, wherein the A layer is formed of a resin A having positive intrinsic birefringence, the B layer is formed of a resin B having negative intrinsic birefringence, the resin B comprises a polyester, a polycarbonate or a polyester carbonate containing a fluorene skeleton, the in-plane retardation of the A layer and the in-plane retardation of the B layer satisfy a specific relationship, the in-plane retardation Re (450) and Re (550) of the retardation film at a wavelength of 450nm and at a wavelength of 550nm satisfy a specific relationship, and the ratio T A /T B of the thickness T A of the A layer to the thickness T B of the B layer is 30/70 to 65/35.

Inventors

• Kumuma kazumoto
• ODA YOSHIYA
• Karita Yasuhiro

Assignees

• 日本瑞翁株式会社
• 大阪燃气化学有限公司

Dates

Publication Date

20260505

Application Date

20210831

Priority Date

20200930

Claims (20)

1. 1. A retardation film comprising one or more layers A having a slow axis and one or more layers B having a slow axis at an angle of 85 DEG to 90 DEG to the slow axis of the layers A, The a layer is formed of a resin a having positive intrinsic birefringence, The B layer is formed of a resin B having negative intrinsic birefringence, The resin A comprises at least one polymer of a polymer containing an alicyclic structure and a polymer containing an isosorbide skeleton and containing no aromatic ring, The resin B contains at least one polymer selected from polyester, polycarbonate and polyester carbonate, The polymer contained in the resin B contains a fluorene skeleton, The in-plane retardation Re (a 450) of the entire a layer at a wavelength of 450nm, the in-plane retardation Re (a 550) of the entire a layer at a wavelength of 550nm, the in-plane retardation Re (B450) of the entire B layer at a wavelength of 450nm, and the in-plane retardation Re (B550) of the entire B layer at a wavelength of 550nm satisfy the following formula (i): , An in-plane retardation Re (450) of the retardation film at a wavelength of 450nm and an in-plane retardation Re (550) of the retardation film at a wavelength of 550nm satisfy the following formula (ii): , The ratio T A /T B of the thickness T A of the whole layer A to the thickness T B of the whole layer B is 30/70-65/35.
2. 2. The retardation film as claimed in claim 1, wherein in-plane retardation Re (B450) and Re (B550) of the B layer as a whole satisfy the following formula (iii): 。
3. 3. the retardation film as claimed in claim 1 or 2, wherein the polymer contained in the resin B contains a structural unit having a fluorene-9, 9-diyl group.
4. 4. The retardation film as claimed in claim 3, wherein the structural unit having a fluorene-9, 9-diyl group comprises a fluorene dicarboxylic acid unit represented by the following formula (1) and/or a fluorene diol unit represented by the following formula (2), wherein the formula (1) is: Wherein R 1 represents a substituent, k represents an integer of 0 to 8, X 1a and X 1b each independently represent a divalent hydrocarbon group which may have a substituent, The formula (2) is: Wherein R 2 represents a substituent, m represents an integer of 0 to 8, X 2a and X 2b each independently represent a divalent hydrocarbon group which may have a substituent, A 1a and A 1b each independently represent a linear or branched alkylene group, and n1 and n2 represent integers of 0 or more.
5. 5. The retardation film as claimed in claim 4, wherein the fluorene diol unit comprises a diol unit represented by the following formula (2A), the formula (2A) being: Wherein Z 1a and Z 1b each independently represent an aromatic hydrocarbon ring, R 3a and R 3b each independently represent a substituent, p1 and p2 each independently represent an integer of 0 or more, and R 2 、m、A 1a and A 1b , n1 and n2 are each the same as those of the above formula (2).
6. 6. The retardation film according to claim 5, wherein among the diol units represented by the formula (2A), Z 1a and Z 1b are C 6-12 aromatic hydrocarbon rings, R 3a and R 3b are C 1-4 alkyl groups or C 6-10 aryl groups, p1 and p2 are integers of 0 to 2, A 1a and A 1b are straight-chain or branched C 2-4 alkylene groups, and n1 and n2 are integers of 0 to 2.
7. 7. The retardation film according to claim 4, wherein, in the fluorene dicarboxylic acid unit represented by formula (1), X 1a and X 1b are linear or branched C 2-4 alkylene groups.
8. 8. The retardation film as claimed in claim 1 or 2, wherein the polymer contained in the resin B further comprises an alkylene glycol unit represented by the following formula (3), the formula (3) being: Wherein A 2 represents a linear or branched alkylene group, and q represents an integer of 1 or more.
9. 9. The retardation film according to claim 8, wherein in the alkylene glycol unit represented by formula (3), A 2 is a linear or branched C 2-4 alkylene group, and q is an integer of 1 to 4.
10. 10. The retardation film according to claim 1 or 2, wherein in-plane retardation Re (450) and Re (550) of the retardation film satisfy the following formula (iv): 。
11. 11. The retardation film as claimed in claim 1 or 2, wherein the glass transition temperature TgA of the resin a is 100 ℃ or more and 160 ℃ or less, The glass transition temperature TgB of the resin B is 100-160 ℃.
12. 12. The phase difference film according to claim 1 or 2, wherein a difference |tga-tgb| between the glass transition temperature TgA of the resin a and the glass transition temperature TgB of the resin B is 15 ℃ or less.
13. 13. The retardation film as claimed in claim 1 or 2, wherein the thickness of the retardation film is 90 μm or less.
14. 14. The retardation film as claimed in claim 1 or 2, wherein the thickness of the retardation film is 70 μm or less.
15. 15. A method for producing a retardation film according to any one of claims 1 to 14, comprising: A step of preparing a multilayer film having a layer formed of a resin A having positive intrinsic birefringence and a layer formed of a resin B having negative intrinsic birefringence, and And stretching the multilayer film.
16. 16. The method for producing a retardation film as claimed in claim 15, wherein the step of preparing the multilayer film comprises a step of melt-extruding the resin a and the resin B.
17. 17. The method for producing a retardation film according to claim 15 or 16, wherein the step of stretching the multilayer film comprises a step of stretching at a stretching temperature of "Tg (h) -10 ℃ or higher and" Tg (h) +20 ℃ or lower, wherein Tg (h) represents a temperature of the higher one of the glass transition temperature TgA of the resin a and the glass transition temperature TgB of the resin B.
18. 18. The method for producing a retardation film as claimed in claim 15 or 16, wherein the step of stretching the multilayer film comprises a step of stretching at a stretching ratio of 1.5 times or more and 5.0 times or less.
19. 19. The method for producing a retardation film as claimed in claim 15 or 16, wherein the step of stretching the multilayer film comprises a step of stretching the multilayer film in an oblique direction.
20. 20. A polarizing plate comprising the retardation film according to any one of claims 1 to 14 and a linear polarizer.

Description

Retardation film and method for producing same Technical Field The present invention relates to a retardation film and a method for producing the same. Background A phase difference film may be provided in an image display device (patent document 1). Among such retardation films, there are retardation films having a multilayer structure including two or more layers (patent documents 2 to 3). Prior art literature Patent literature Patent document 1, japanese patent laid-open No. 2002-40258; patent document 2, japanese patent application laid-open No. 2017-177342; Patent document 3 Japanese patent application laid-open No. 2018-128568. Disclosure of Invention Problems to be solved by the invention In an image display device, a circularly polarizing plate is sometimes provided to reduce reflection of external light on a display surface. As such a circularly polarizing plate, a film combining a linear polarizer and a retardation film is generally used. However, most of the conventional retardation films have positive wavelength dispersion. Therefore, although the conventional circular polarizer can reduce reflection of external light in a specific narrow wavelength range, it is difficult to reduce reflection of external light other than the specific narrow wavelength range, and thus a sufficiently high reflection suppressing ability may not be obtained. In order to improve the reflection suppressing ability, it is conceivable to provide a retardation film having inverse wavelength dispersion on the circularly polarizing plate. As such a retardation film having inverse wavelength dispersion, there is a film in which a resin having positive intrinsic birefringence and a resin having negative intrinsic birefringence are combined. The retardation film can generally exhibit inverse wavelength dispersion by utilizing the difference between the in-plane retardation exhibited by the resin having positive intrinsic birefringence and the in-plane retardation exhibited by the resin having negative intrinsic birefringence. Specifically, the longer the measurement wavelength is, the larger the difference in-plane retardation is, and thus the inverse wavelength dispersion can be achieved. However, a retardation film obtained by using a resin having positive intrinsic birefringence in combination with a resin having negative intrinsic birefringence tends to be inferior in reworkability as shown below. It is sometimes required that after the phase difference film is first bonded to a certain member, the phase difference film is peeled off and bonded again to the member. The property that the operation of peeling from the member and bonding again can be easily performed is called "reworkability". For example, when a phase difference film is attached to an image display device and then the phase difference film is peeled off from the image display device and reattached again, excellent reworkability is required. However, the reworkability of a conventional retardation film obtained by combining a resin having positive intrinsic birefringence and a resin having negative intrinsic birefringence is poor. Among them, a retardation film having high reflection suppressing ability tends to be significantly deteriorated in reworkability, and it is particularly difficult to achieve both the reflection suppressing ability and reworkability in a thin retardation film. The present invention has been made in view of the above-described problems, and an object thereof is to provide a retardation film having high reflection suppressing ability and excellent reworkability, a method for producing the same, and a polarizing plate and an image display device having the retardation film. Solution for solving the problem The present inventors have conducted intensive studies in order to solve the above-mentioned problems. As a result, the present inventors have found that the above-described problems can be solved in the case where a phase difference film formed by combining an a layer formed of a resin a having positive intrinsic birefringence and a B layer formed of a resin B having negative intrinsic birefringence satisfies specific requirements, and completed the present invention. Namely, the present invention includes the following. [1] A retardation film comprising one or more layers A having a slow axis and one or more layers B having a slow axis at an angle of 85 DEG to 90 DEG to the slow axis of the layer A, The above-mentioned layer a is formed of a resin a having positive intrinsic birefringence, The above-mentioned layer B is formed of a resin B having negative intrinsic birefringence, The resin B contains at least one polymer selected from the group consisting of polyesters, polycarbonates and polyestercarbonates, The above-mentioned polymer contains a fluorene skeleton, The in-plane retardation Re (A450) of the entire A layer at a wavelength of 450nm, the in-plane retardation Re (A550) of the entire A layer at a wavelength of 550nm, t