Retardation film, polarizing plate and liquid crystal display

Patent metadata

Field	Value
Publication number	US-9581728-B2
Application number	US-201314649101-A
Country	US
Kind code	B2
Filing date	Nov 13, 2013
Priority date	Dec 13, 2012
Publication date	Feb 28, 2017
Grant date	Feb 28, 2017

Abstract

The retardation film contains a cellulose ester, has a film thickness of 15 to less than 40 μm, has a film thickness variation both in the widthwise direction and lengthwise direction of 0 to 4 μm, and satisfies an Rt humidity fluctuation of 1% to 12%:

(a difference of retardation Rt (590) values in the thickness direction represented by the following formula (ii) measured at a wavelength of 590 nm after the film has been left to stand for 5 hours in each of a 23° C., 20% relative humidity environment and a 23° C., 80% relative humidity environment)/( Rt (590) value measured after the film has been left to stand for 5 hours in a 23° C., 55% relative humidity environment)×100

Rt (590)={( n x +n y )/2− n z }×d   Formula (ii)

wherein n x : a refractive index in the slow axis direction in the film plane, n y : a refractive index in the direction perpendicular to the slow axis in the film plane, n z : a refractive index in the thickness direction of the film, and d: a film thickness.

First claim

The invention claimed is:

1. A retardation film comprising a cellulose ester as the primary component, which has a film thickness of 15 μm or more and less than 40 μm, has a film thickness variation both in the widthwise direction and lengthwise direction of 0 to 4 μm, and satisfies an Rt humidity fluctuation represented by the formula (1) described below of 1.0% or more and less than 4.0%:
Rt humidity fluctuation (Δ Rt value, difference of retardation Rt (590) values in the thickness direction represented by the following formula (ii) measured at a wavelength of 590 nm after the film has been left to stand for 5 hours in each of a 23° C., 20% relative humidity environment and a 23° C., 80% relative humidity environment)/( Rt (590) value measured after the film has been left to stand for 5 hours in a 23° C., 55% relative humidity environment)×100  Formula (1)

Rt (590)={( n x +n y )/2 −n z }×d   Formula (ii)

wherein n x represents a refractive index in the slow axis direction in the film plane, n y represents a refractive index in the direction perpendicular to the slow axis in the film plane, n z represents a refractive index in the thickness direction of the film, and d represents a film thickness (nm), respectively, and wherein the retardation film further comprises at least one retardation increasing agent including a compound expressed by a general formula (1):

wherein X 1 represents an oxygen atom or a sulfur atom,
Y 1 represents an oxygen atom, a sulfur atom, or a nitrogen atom,
Z 1 represents an oxygen atom, a nitrogen atom or a sulfur atom,
R 11 , R 21 and R 31 each represent a substituent,
k 1 represents an integer from 1 to 5,
m 1 represents an integer from 0 to 4,
n 1 represents an integer from 0 to 4, and
a dashed line represents a single bond (—) or a double bond (═).

2. The retardation film comprising a cellulose ester as the primary component according to claim 1 , wherein the total substitution degree of the cellulose ester is 2.1 to 2.5.

3. The retardation film comprising a cellulose ester as the primary component according to claim 1 , which comprises at least one plasticizer selected from the group consisting of sugar ester compounds, polyester compounds and acrylic compounds.

4. The retardation film comprising a cellulose ester as the primary component according to claim 1 , wherein the total substitution degree of the cellulose ester is 2.15 to 2.35.

5. A polarizing plate, comprising retardation film according to claim 1 is adhered to a polarizer with an active energy ray curable adhesive agent.

6. A vertical alignment type liquid crystal display comprising the polarizing plate according to claim 5 on at least one surface of a liquid crystal cell.

7. The retardation film comprising a cellulose ester as the primary component according to claim 1 , wherein the compound expressed by the general formula (1) is a compound expressed by a general formula (2):

wherein X 2 represents an oxygen atom or a sulfur atom,
Y 2 represents an oxygen atom, a sulfur atom, or a nitrogen atom,
Z 2 represents an oxygen atom, a nitrogen atom or a sulfur atom,
R 12 and R 22 each represent a substituent,
k 2 represents an integer from 1 to 5,
m 2 represents an integer from 0 to 4, and
a dashed line represents a single bond (—) or a double bond (═).

8. The retardation film comprising a cellulose ester as the primary component according to claim 1 , wherein the compound expressed by the general formula (1) is a compound expressed by a general formula (3):

wherein R 13 and R 23 each represent a substituent, k 3 represents an integer from 1 to 5, and m 3 represents an integer from 0 to 4.

9. The retardation film comprising a cellulose ester as the primary component according to claim 1 , wherein the compound expressed by a general formula (1) is a compound expressed by a general formula (4):

wherein R 14 represents a substituent, and k 4 represents an integer from 1 to 5.

Assignees

• Konica Minolta Inc

Inventors

• Kaneko Yuki
• Takimoto Masataka
• Nanjiyou Takashi
• Takagi Takahiro
• Shimane Yuta
• Nishimura Masumi

Classifications

• C08K5/357

  Six-membered rings · CPC title

• G02F1/13363

  Birefringent elements, e.g. for optical compensation · CPC title

• C08L33/066

  containing -OH groups · CPC title

• G02F1/133528

  Polarisers · CPC title

• C08K5/15

  Heterocyclic compounds having oxygen in the ring · CPC title