JP2009244914A - Method of manufacturing polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a fitted retardation plate not have large change in optical property even when a polarizing plate is placed under a high temperature and a dry condition. <P>SOLUTION: The polarizing plate is manufactured through the steps of: forming a cellulose acylate film from a cellulose acylate solution prepared by dissolving cellulose acylate in a solvent containing 0.003 to 0.1% by mass of water; subjecting the formed cellulose acylate film to a heat treatment for 0.5 to 200 hours at a temperature of 50 to 150°C and at a relative humidity of 0 to 10%; stretching the heat-treated cellulose acylate film at a longitudinal/lateral stretching ratio of 0.3 to 2; and stacking the retardation plate formed of the stretched cellulose acylate film, a first transparent protective film (the retardation plate may serve as the protective film), a moisture-proof layer, a linear polarizing film, and a second transparent protective film. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polarizing plate including a retardation plate having a linear polarizing film disposed between two transparent protective films and further having optical anisotropy. In particular, the present invention relates to a polarizing plate for applications in which accurate optical anisotropy (retardation value) is required for a retardation plate, such as a circularly polarizing plate.

A linear polarizing film is disposed between two transparent protective films, and a polarizing plate including a retardation plate having optical anisotropy is used in various optical fields.
When the retardation plate is a λ / 4 plate and the retardation plate and the linear polarizing film are arranged so that the slow axis of the retardation plate and the transmission axis of the linear polarizing film are at an angle of 45 °, The polarizing plate functions as a circularly polarizing plate. In the use of a circularly polarizing plate, the optical property (retardation value) of a retardation plate that functions as a λ / 4 plate is very important.
Even though the conventional λ / 4 plate is called a λ / 4 plate, most of them achieve λ / 4 only at a specific wavelength.

  Patent Documents 1 and 2 disclose a retardation plate in which a birefringent film having a large retardation and a birefringent film having a small retardation are laminated so that their optical axes are orthogonal to each other. If the retardation difference between the two films is λ / 4 over the entire visible light region, the retardation plate theoretically functions as a λ / 4 plate over the entire visible light region.

In Patent Document 3, a polymer film having a wavelength of λ / 4 at a specific wavelength and a polymer film made of the same material and having a wavelength of λ / 2 are laminated to form a λ / 4 in a wide wavelength region. A phase difference plate that can obtain the above is disclosed.
Patent Document 4 also discloses a retardation plate that can achieve λ / 4 in a wide wavelength region by laminating two polymer films.
As the polymer film, a stretched film of a synthetic polymer such as polycarbonate is used. Since the polymer film is used by superimposing two sheets, it has a drawback that the thickness is increased and a laminating process is required, so that the cost is likely to increase. Further, the retardation value at each wavelength greatly deviated from the target value (1/4 of each wavelength), and the deviation at a high wavelength region was particularly remarkable.

Patent Document 5 discloses a broadband λ / 4 plate using a single polymer film. Specifically, cellulose acetate having a degree of acetylation of 2.5 to 2.8 is used as the polymer. However, with cellulose acetate alone, the optical anisotropy (birefringence index) tends to be insufficient, and in order to obtain the necessary retardation value for the λ / 4 plate, it is necessary to increase the film thickness.
Patent Document 6 discloses a broadband λ / 4 plate made of a single cellulose ester film containing an aromatic compound having a plurality of aromatic rings as a retardation increasing agent. By using a retardation increasing agent, high optical anisotropy (birefringence) can be obtained, and a wide band λ / 4 can be realized even with a single thin cellulose ester film.

JP-A-5-27118 Japanese Patent Laid-Open No. 5-27119 Japanese Patent Laid-Open No. 10-68816 JP-A-10-90521 JP 2000-137116 A International Publication No. 00/65384 Pamphlet

When the present inventor examined the λ / 4 plate described in Patent Document 6, it was found that the retardation value greatly changes under conditions of drying (low humidity) at a high temperature (about 60 ° C.). In many cases, a λ / 4 plate or a circularly polarizing plate is attached to an image display device that is subjected to severe conditions in summer, such as a liquid crystal display device mounted on an automobile.
An object of the present invention is to provide a polarizing plate in which the optical properties of the attached retardation plate do not change greatly even when placed under dry conditions at high temperatures.

The object of the present invention has been achieved by the following (1) to (3).
(1) A step of forming a cellulose acylate film from a cellulose acylate solution in which cellulose acylate is dissolved in a solvent containing 0.003 to 0.1% by mass of water; A step of heat-treating for 0.5 to 200 hours under conditions of 150 to 150 ° C. and a relative humidity of 0 to 10%; a step of stretching the heat-treated cellulose acylate film under a condition that a longitudinal / lateral stretch ratio is 0.3 to 2; And a retardation film made of a stretched cellulose acylate film, a first transparent protective film, a linearly polarizing film, a second transparent protective film, and a moisture-proof layer, the retardation film, the first transparent protective film, the linearly polarizing film, and The cellulose acylate is laminated or stretched in the order of the second transparent protective film so that a moisture-proof layer exists between the retardation film and the linearly polarizing film. The first transparent protective film and a retardation plate consisting of a film, the moisture-proof layer, the linear polarization film and method for manufacturing a polarizing plate, characterized by producing a polarizing plate by the process of the second transparent protective film laminated in this order.

(2) From the retardation value of the retardation plate measured by adjusting the temperature of the produced polarizing plate under the conditions of a temperature of 25 ° C. and a relative humidity of 60% and measuring at a wavelength of 550 nm, the polarizing plate was further heated to a temperature of 60 ° C. and a relative humidity. The method for producing a polarizing plate according to (1), wherein the retardation value of the retardation plate measured at a wavelength of 550 nm after being stored for 3 hours under the condition of 10% is less than 15 nm.
(3) From the retardation value of the retardation plate measured at a wavelength of 550 nm after storing the produced polarizing plate under conditions of a temperature of 60 ° C. and a relative humidity of 10% for 3 hours, the polarizing plate was further heated to a temperature of 60 ° C. and a relative humidity of 10 The method for producing a polarizing plate according to (1), wherein the retardation value of the retardation plate measured at a wavelength of 550 nm after being stored for 47 hours under the condition of% is less than 15 nm.

The present invention can be implemented in the following modes.
(4) The moisture permeability of the entire structure excluding the retardation plate from the polarizing plate is less than 5 g / m ² · day.
(5) The moisture-proof layer has a water vapor transmission coefficient of 10 ^{−12 to} 10 ⁻⁷ (cm ³ / cm · sec · cmHg).
(6) The moisture-proof layer contains 1 to 50% by mass of tabular grains having an average major axis of 0.3 to 20 μm and an average aspect ratio of 20 to 10,000, and the tabular grains are dispersed in the binder. .

(7) A temperature of 25 ° C. and a relative humidity from the two-color ratio of the stretching vibration of the carbonyl group obtained by adjusting the temperature of the cellulose acylate film under conditions of a temperature of 25 ° C. and a relative humidity of 60% and obtained by the polarization infrared method. The amount of reduction of the carbonyl group stretching vibration to the two-color ratio obtained by adjusting the temperature and humidity under the condition of 10% by the polarization infrared method is less than 0.8.
(8) The cellulose acylate film is stretched 1.1 to 2 times under the condition of a moisture content of 2 to 10%.
(9) The cellulose acylate film is adjusted to a moisture content of 2 to 10% by water treatment, and before the water treatment, the cellulose acylate film is heated for 3 seconds to 30 at a temperature of 50 to 150 ° C. and a relative humidity of 0 to 30%. It is heat-dried for minutes.

(10) From the retardation value of the retardation plate measured at a wavelength of 550 nm after storing the polarizing plate at a temperature of 60 ° C. and a relative humidity of 10% for 47 hours, the polarizing plate was further measured at a temperature of 25 ° C. and a relative humidity of 60%. The change in retardation value of the retardation plate measured at a wavelength of 550 nm after being stored for 24 hours under the conditions is less than 15 nm.
(11) The retardation plate is made of a cellulose acylate film that is stretched in multiple stages under the condition that the wrap angle between the nip roll and the film is less than 30 °.
(12) From the retardation value of the retardation plate measured at a wavelength of 550 nm after storing the polarizing plate at a temperature of 25 ° C. and a relative humidity of 60% for 24 hours, the polarizing plate was further subjected to a condition of a temperature of 25 ° C. and a relative humidity of 60%. The retardation value of the retardation plate measured at 550 nm after storage for 216 hours was less than 15 nm.

(13) The retardation value (Re550) of the retardation plate measured at a wavelength of 550 nm is 100 nm <Re550 <330 nm, and the retardation values of the retardation plate measured at wavelengths of 450 nm, 550 nm, and 650 nm (Re450, Re550, Re650). However, 0.5 <Re450 / Re550 <0.98 and 1.01 <Re650 / Re550 <1.35 are satisfied, respectively.
(14) The refractive index nx in the slow axis direction in the plane of the retardation plate, the refractive index ny in the direction perpendicular to the slow axis in the plane of the retardation plate, and the refractive index nz in the thickness direction of the retardation plate, 1.1 <(nx−nz) / (nx−ny) <3 is satisfied.

(15) An image display device in which the polarizing plate produced in (1) is attached to the display surface.
(16) A reflective liquid crystal display device in which the polarizing plate produced in (1) is attached to the display surface.

(17) An organic EL device in which the polarizing plate produced in (1) is attached to the display surface.
(18) A touch panel in which the polarizing plate manufactured in (1) is attached to the display surface.

  A polarizing plate having a small retardation change of the retardation plate even under high temperature drying can be obtained.

It is a chart which shows the change of the retardation value of the phase difference plate corresponding to the test storage conditions about a polarizing plate and time passage.

[Basic configuration of polarizing plate]
The polarizing plate according to the present invention has the following basic configuration (A) or (B).
When the polarizing plate is incorporated in the image display device, the lower side (retardation plate side) is the inner side (image display surface side), and the upper side (second transparent protective film side) is the outer side (viewing side). In general, an adhesive layer is provided between the retardation plate and the image display surface.

────────────────────────────────────
(A) (B)
────────────────────────────────────
Second transparent protective film Second transparent protective film
Linear polarizing film Linear polarizing film First transparent protective film First transparent protective film and retardation plate
Phase plate ─────────────────────────────────────

[Change in retardation value of retardation plate]
As a result of studying the retardation value change of the retardation plate under the use (or storage) conditions of the polarizing plate, the present inventors have found the use (or storage) conditions of the polarizing plate in which the retardation value of the retardation plate is likely to fluctuate. did.
In the present invention, the polarizing plate is improved so that the retardation value of the retardation film does not substantially change even under such conditions.

FIG. 1 is a chart showing experimental storage conditions for a polarizing plate and changes in retardation value of a retardation plate corresponding to the passage of time. In addition, the retardation value (relative change) shown in FIG. 1 is a result of the sample number 12 in an Example.
As shown in FIG. 1, first, the retardation value of the retardation plate is measured at a wavelength of 550 nm after the temperature of the polarizing plate is adjusted at a temperature of 25 ° C. and a relative humidity of 60% (first measurement). ).
The time required for temperature control and humidity varies depending on the storage conditions of the previous polarizing plate. That is, if the polarizing plate is stored under conditions close to a temperature of 25 ° C. and a relative humidity of 60% before the temperature and humidity control, the temperature and humidity control process is completed in a short time. On the other hand, if the polarizing plate is stored under greatly different conditions, it is necessary to carry out the temperature and humidity control treatment for a long time.
Specifically, the temperature of the polarizing plate is adjusted until the retardation value does not substantially vary (for example, the variation is less than ± 1 nm / hour). In general (or when the storage conditions of the polarizing plate are unknown), it is desirable to control the temperature for 24 hours.
After adjusting the temperature and humidity, the retardation plate is peeled off from the polarizing plate, and the retardation value is measured at a wavelength of 550 nm using an automatic birefringence meter (KOBRA-21ADH / PR: manufactured by Oji Scientific Instruments).

Secondly, after the temperature-controlled and humidity-controlled polarizing plate is further stored for 3 hours under conditions of a temperature of 60 ° C. and a relative humidity of 10%, the retardation value of the retardation plate is measured at a wavelength of 550 nm (second measurement). .
After storage for 3 hours, the retardation plate is peeled off from the polarizing plate, and the retardation value is measured at a wavelength of 550 nm using an automatic birefringence meter (KOBRA-21ADH / PR: manufactured by Oji Scientific Instruments).
In the first aspect of the present invention, the change in the retardation value in the second measurement is less than 15 nm from the retardation value in the first measurement (first process of the present invention). The change in retardation value is preferably less than 12 nm, and more preferably less than 10 nm. In the result of sample number 12 shown in FIG. 1, the change in retardation value is 8 nm.
The retardation change in the first process is caused by the structural change of the retardation plate by eliminating the distortion generated in the manufacture of the retardation plate after the manufacture. Similar to the result of the sample number 12 shown in FIG. 1, the retardation value generally decreases in the first process (first measured value> second measured value).
Even after the second measurement, it is preferable to continue the storage of the polarizing plate and the measurement of the retardation plate.

Third, preferably, a polarizing plate stored for 3 hours under conditions of a temperature of 60 ° C. and a relative humidity of 10% is further subjected to 47 hours (temperature of 60 ° C. and relative humidity) under the same conditions (temperature of 60 ° C. and relative humidity of 10%). At 10%, the retardation value of the retardation plate is measured at a wavelength of 550 nm (third measurement).
After storage for 47 hours, the retardation plate is peeled from the polarizing plate, and the retardation value is measured at a wavelength of 550 nm using an automatic birefringence meter (KOBRA-21ADH / PR: manufactured by Oji Scientific Instruments).
In the first aspect of the present invention, it is preferable that the change in the retardation value in the third measurement is less than 15 nm from the retardation value in the second measurement (second process of the present invention). The change in retardation value is more preferably less than 12 nm, and even more preferably less than 10 nm. In the result of sample number 12 shown in FIG. 1, the change in retardation value is 5 nm.
The retardation change in the second process occurs when the moisture contained in the retardation plate is reduced by drying. The change in the second process is slower than in the first process, and storage for a long time (47 hours) is required. Similar to the result of the sample number 12 shown in FIG. 1, the retardation value generally increases in the second process (second measured value <third measured value).
Even after the third measurement, it is preferable to continue the storage of the polarizing plate and the measurement of the retardation plate.
In the second aspect of the present invention, the first measurement and the second measurement are omitted, the temperature is adjusted under the conditions of a temperature of 60 ° C. and a relative humidity of 10%, and the retardation of the retardation plate at a wavelength of 550 nm. The value is measured (third measurement). The time required for temperature control and humidity control is the same as in the first measurement.

Fourth, preferably, a polarizing plate stored for 47 hours at a temperature of 60 ° C. and a relative humidity of 10% is further stored for 24 hours at a temperature of 25 ° C. and a relative humidity of 60%, and then a retardation plate at a wavelength of 550 nm. The retardation value is measured (fourth measurement).
After storage for 24 hours, the retardation plate is peeled off from the polarizing plate, and the retardation value is measured at a wavelength of 550 nm using an automatic birefringence meter (KOBRA-21ADH / PR: manufactured by Oji Scientific Instruments).
In the first aspect of the present invention, it is preferable that the change in the retardation value in the fourth measurement is less than 15 nm from the retardation value in the third measurement (third process of the present invention). The change in retardation value is more preferably less than 12 nm, and even more preferably less than 10 nm. In the result of sample number 12 shown in FIG. 1, the change in retardation value is 4 nm.
In the second aspect of the present invention, the change in retardation value in the fourth measurement is less than 15 nm from the retardation value in the third measurement (third process of the present invention). The change in retardation value is preferably less than 12 nm, and more preferably less than 10 nm.
It is presumed that the retardation change in the third process is caused by the change in the molecular arrangement in the retardation plate accompanying the temperature change (cooling). Similar to the result of the sample number 12 shown in FIG. 1, the retardation value generally increases in the third process (third measurement value <fourth measurement value).
Even after the fourth measurement, it is preferable to continue the preservation of the polarizing plate and the measurement of the retardation plate.

Fifth, preferably, a polarizing plate stored for 24 hours under the conditions of a temperature of 25 ° C. and a relative humidity of 60% is further subjected to 216 hours (temperature of 25 ° C. and relative humidity of 60%) under the same conditions (temperature of 25 ° C. and relative humidity of 60%). At 60%, the retardation value of the retardation plate is measured at a wavelength of 550 nm (5th measurement).
After storage for 216 hours, the retardation plate is peeled off from the polarizing plate, and the retardation value is measured at a wavelength of 550 nm using an automatic birefringence meter (KOBRA-21ADH / PR: manufactured by Oji Scientific Instruments).
In both the first and second aspects of the present invention, it is preferable that the change in retardation value in the fifth measurement is less than 15 nm from the retardation value in the fourth measurement (fourth process of the present invention). The change in retardation value is more preferably less than 12 nm, and even more preferably less than 10 nm. In the result of sample number 12 shown in FIG. 1, the change in retardation value is 5 nm.
The retardation change in the fourth process occurs when the retardation plate absorbs moisture. Similar to the result of the sample number 12 shown in FIG. 1, the retardation value generally decreases in the fourth process (fourth measurement value> fifth measurement value).

[Means for realizing the first to fourth processes]
In order for the retardation value change in the first step to satisfy the conditions of the present invention, the retardation plate was heat-treated at a temperature of 50 to 150 ° C. and a relative humidity of 0 to 70% for 0.5 to 200 hours. It preferably consists of a polymer film.
The heating temperature is more preferably 70 to 140 ° C, further preferably 90 to 120 ° C. The relative humidity is more preferably 0 to 50%, and further preferably 0 to 30%. The heating time is more preferably 1 to 100 hours, and further preferably 3 to 50 hours. The structure of the polymer film can be relaxed by the heat treatment, and the difference between the first measurement value and the second measurement value can be reduced.
It is preferable that the heat amount (relaxation heat amount) of the endothermic peak near the glass transition temperature (Tg) of the polymer film is 0.1 to 2.0 J / g by the heat treatment. The endothermic peak near Tg means a peak existing in the range of Tg-10 ° C to Tg + 50 ° C. The amount of heat at the endothermic peak near Tg is preferably 0.3 to 1.8 J / g, and more preferably 0.5 to 1.6 J / g. Unless heat treatment is performed, generally no endothermic peak appears in the polymer film (0 J / g).

In order for the retardation value change in the second process to satisfy the conditions of the present invention, it is preferable to suppress the moisture permeation amount of the entire structure excluding the retardation plate from the polarizing plate to less than 5 g / m ² · day. The moisture permeability is preferably 0.01 to 4 g / m ² · day, and more preferably 0.05 to 3 g / m ² · day.
The low moisture permeability can be achieved by providing a moisture-proof layer on the polarizing plate. The moisture vapor transmission coefficient of the moisture-proof layer is preferably 1 × 10 ^{−12 to} 1 × 10 ⁻⁷ (cm ³ / cm · sec · cmHg), and 5 × 10 ^{−11 to} 5 × 10 ⁻⁸ (cm ³ / cm · sec · cmHg), more preferably 1 × 10 ^{−10 to} 1 × 10 ⁻⁸ (cm ³ / cm · sec · cmHg).
The moisture-proof layer is a layer containing 1 to 50% by mass of tabular grains having an average major axis of 0.3 to 20 μm and an average aspect ratio of 20 to 10,000, and the tabular grains are dispersed in the binder. It is preferable. The average aspect ratio (ratio of surface area diameter to thickness converted to a circle) is preferably 100 to 50,000, and more preferably 200 to 10,000.

When the phase difference plate is made of cellulose acylate film, the cellulose acylate film was conditioned and conditioned under conditions of a temperature of 25 ° C. and a relative humidity of 60% in order to satisfy the second process. The amount of reduction from the two-color ratio of the stretching vibration of the carbonyl group to the two-color ratio of the stretching vibration of the carbonyl group determined by the polarization infrared method after adjusting the temperature under conditions of a temperature of 25 ° C. and a relative humidity of 10%, It is preferable to suppress to less than 0.8. The amount of decrease is preferably less than 0.7, and more preferably less than 0.6. In the cellulose acylate film stretched by a usual method, the amount of decrease is generally 1.2 or more. Therefore, in order to suppress the decrease, it is necessary to stretch the cellulose acylate film under special conditions.
Specifically, the cellulose acylate film is preferably stretched 1.1 to 2 times under the condition of a moisture content of 2 to 10%. The water content is more preferably 2.5 to 8%, and further preferably 3 to 6%.
By stretching in a water-containing state, a change in retardation with respect to humidity can be reduced. That is, molecules oriented by stretching develop retardation, but the molecular orientation varies with changes in humidity. It is presumed that the molecular orientation change can be suppressed to a small extent by stretching in a state containing moisture in advance.
The moisture content is adjusted by moisture treatment of the cellulose acylate film. Prior to the water-containing treatment, the cellulose acylate film is preferably heat-dried for 3 seconds to 30 minutes under conditions of a temperature of 50 to 150 ° C. and a relative humidity of 0 to 30%. The heating temperature is more preferably 60 to 120 ° C, further preferably 70 to 110 ° C. The relative humidity is more preferably 0 to 25%, further preferably 0 to 20%. The heating time is more preferably 5 seconds to 10 minutes, and further preferably 10 seconds to 3 minutes.

In order for the retardation value change in the third step to satisfy the conditions of the present invention, the retardation plate is formed from a polymer solution in which a polymer is dissolved in a solvent containing 0.003 to 0.1% by mass of water. It is preferable to consist of the formed polymer film.
A small amount of water contained in the polymer solution seems to reduce the temperature change of the retardation. That is, a small amount of water in the film formation forms hydrogen bonds between the polymer molecules. In that state, since heat is applied in the drying process, crystallization is easier. It is presumed that this crystal suppresses the change of the molecule due to the temperature change, and the retardation change can be suppressed small.
Therefore, even if moisture enters after film formation, the effect is small, and it is necessary that a very small amount of moisture be present before drying in casting.
As the solvent containing a very small amount of water, it is optimal to use a recovered solvent. The recovered solvent is obtained by recovering the solvent volatilized in the step of drying the cast film from the drying zone and fractionating it. When collecting in the drying process, a small amount of outside air is also taken in, and a minute amount of moisture is mixed in the outside air. Therefore, the recovered solvent generally contains 0.01 to 0.1% by mass of water. The total amount of the recovered solvent is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more.

In order for the retardation value change in the third step to satisfy the conditions of the present invention, the retardation plate may be composed of a polymer film stretched under a condition where the longitudinal / lateral stretching ratio is 0.3 to 2. preferable. That is, when the ratio between the distance between the stretched spans and the film width (aspect ratio) is reduced, the change in retardation due to temperature can be suppressed.
When the width of the polymer film before stretching is W and the distance between stretching is L, the aspect ratio L / W is preferably 0.3 ≦ L / W ≦ 2. More preferably, 0.3 ≦ L / W ≦ 1.5, and further preferably 0.3 ≦ L / W ≦ 1. Ordinary stretching is generally carried out with an aspect ratio L / W exceeding 2. With a high aspect ratio in normal stretching, retardation is easily developed because molecules are highly aligned in the stretching direction during stretching. However, since the entanglement in the orthogonal (width) direction is reduced, the molecules are likely to move, and retardation changes due to temperature are likely to occur. That is, at a high aspect ratio, the stretch span is long, and neck-in occurs between them, so that molecules are excessively arranged in the longitudinal direction. Therefore, it is effective to reduce the aspect ratio in order to suppress the change in retardation due to temperature. Neck-in is unlikely to occur at low aspect ratios. That is, at a low aspect ratio, the same effect as that obtained by blocking the film to be necked in by applying stress in the lateral direction is obtained, and molecules are arranged in the lateral direction. As a result, at low aspect ratios, it is presumed that the molecules are entangled vertically and horizontally, and the structure is stable against temperature changes.
The draw ratio of the polymer film is preferably 1.1 to 2 times, more preferably 1.2 to 1.8 times, and still more preferably 1.3 to 1.7 times.

When the film is stretched at a low aspect ratio, the NZ value = (nx−nz) / (nx−ny) can be adjusted to a low value. Specifically, the NZ value is preferably 1.1 to 3, more preferably 1.3 to 2.5, and still more preferably 1.5 to 2. In the NZ value, nx is the refractive index in the in-plane slow axis direction, ny is the refractive index in the direction perpendicular to the in-plane slow axis, and nz is the refractive index in the thickness direction. The NZ value corresponds to an index indicating plane orientation. In the stretching with a low aspect ratio, since the stress in the transverse direction that suppresses the neck-in is applied as described above, the same effect as in the case of stretching in the longitudinal and lateral directions can be obtained. Therefore, the plane orientation is more likely to proceed, and the NZ value is small. In normal high aspect ratio stretching, the NZ value generally exceeds 4.
The stretching with a low aspect ratio requires a large stress for stretching and tends to cause scratches. Stretching is generally performed by changing the peripheral speed of two or more pairs of nip rolls. When the wrap angle of the nip roll is large and the contact area between the film and the roll is large, scratches are more likely to occur. For this reason, the wrap angle is preferably less than 30 °, more preferably less than 20 °, and even more preferably less than 30 °.

In order for the retardation value change in the fourth step to satisfy the conditions of the present invention, it is preferable to suppress the moisture permeation amount of the entire structure excluding the retardation plate from the polarizing plate to less than 5 g / m ² · day. The moisture permeability is preferably 0.01 to 4 g / m ² · day, and more preferably 0.05 to 3 g / m ² · day.
The low moisture permeability can be achieved by providing a moisture-proof layer on the polarizing plate. The details of the moisture-proof layer are the same as those described for the second process.

[Polymer film]
The retardation plate, the first transparent protective film, the first transparent protective film / retardation plate, and the second transparent protective film are made of a polymer film. The polymer film used for the phase difference plate or the first transparent protective film / phase difference plate has optical anisotropy. The polymer film used for the first transparent protective film or the second transparent protective film does not require optical anisotropy (it is preferably optically isotropic).
Except for the viewpoint of optical anisotropy, the polymer films that can be preferably used for the phase difference plate, the first transparent protective film, the first transparent protective film / phase difference plate, and the second transparent protective film are substantially the same.

The polymer film preferably has a light transmittance of 80% or more.
The polymer used for the polymer film is preferably cellulose acylate.
The cellulose acylate is preferably a lower fatty acid ester of cellulose. Lower fatty acid means a fatty acid having 6 or less carbon atoms. The number of carbon atoms is preferably 2 (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). Cellulose acetate is particularly preferred. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used.
The cellulose acetate preferably has an acetylation degree of 55.0 to 62.5%. The acetylation degree is more preferably 57.0 to 62.0%, and most preferably 58.5 to 61.5%.
The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation follows the measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like).

The viscosity average degree of polymerization (DP) of the polymer used for the polymer film is preferably 250 or more, and more preferably 290 or more.
The polymer used for the polymer film preferably has a narrow molecular weight distribution of Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) by gel permeation chromatography. The specific value of Mw / Mn is preferably 1.0 to 1.7, more preferably 1.3 to 1.65, and most preferably 1.4 to 1.6. preferable.

It is preferable to produce a polymer film by a solvent casting method. In the solvent cast method, a film is produced using a solution (dope) in which a polymer is dissolved in an organic solvent.
The organic solvent is a solvent selected from ethers having 2 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 2 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 6 carbon atoms. It is preferable to contain.
The ether, ketone and ester may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, —O—, —CO— and —COO—) can also be used as the organic solvent.
The organic solvent may have other functional groups such as alcoholic hydroxyl. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.

Examples of the ether having 3 to 12 carbon atoms include dimethyl ether, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole.
Examples of the ketone having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone.
Examples of the ester having 2 to 12 carbon atoms include methyl formate, ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate.
Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. In the halogenated hydrocarbon, the ratio of the hydrogen atom of the hydrocarbon substituted with the halogen atom is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, and more preferably 35 to 65 mol%. % Is more preferable, and 40 to 60 mol% is most preferable. Methylene chloride is a representative halogenated hydrocarbon.
Two or more organic solvents may be mixed and used.

A recovery solvent is preferably used as the organic solvent. The organic solvent preferably contains 30% by mass or more of the recovered solvent, more preferably 40% by mass or more, and further preferably 50% by mass or more. The solvent can be concentrated and recovered by passing the return air of hot air used for drying in each step of the casting film forming step (casting step to substrate, and subsequent drying step) through a condenser.
The recovered solvent can be used after being separated into each component using a fractionation tower. Alternatively, after the composition of the recovered solvent is quantified by gas chromatography, the insufficient component may be added and used. Unlike the fresh solvent, the recovered solvent is characterized in that a small amount of water accompanying the mixing of outside air is always added.

A polymer solution can be prepared by a general method. The general method means that the treatment is performed at a temperature of 0 ° C. or higher (room temperature or high temperature). The solution can be prepared using a dope preparation method and apparatus in a normal solvent cast method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly methylene chloride) as the organic solvent.
The amount of the polymer is adjusted so that it is contained in an amount of 10 to 40% by mass in the resulting solution. The amount of polymer is more preferably 10 to 30% by mass. Arbitrary additives described later may be added to the organic solvent (main solvent).

  The solution can be prepared by stirring the polymer and the organic solvent at room temperature (0 to 40 ° C.). High concentration solutions may be stirred under pressure and heating conditions. Specifically, the polymer and the organic solvent are put in a pressure vessel and sealed, and stirred while heating to a temperature not lower than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil. The heating temperature is usually 40 ° C. or higher, preferably 60 to 200 ° C., more preferably 80 to 110 ° C.

Each component may be coarsely mixed in advance and then placed in a container. Moreover, you may put into a container sequentially. The container needs to be configured so that it can be stirred. The container can be pressurized by injecting an inert gas such as nitrogen gas. Moreover, you may utilize the raise of the vapor pressure of the solvent by heating. Or after sealing a container, you may add each component under pressure.
When heating, it is preferable to heat from the outside of the container. For example, a jacket type heating device can be used. The entire container can also be heated by providing a plate heater outside the container and piping to circulate the liquid.
It is preferable to provide a stirring blade inside the container and stir using this. The stirring blade preferably has a length that reaches the vicinity of the wall of the container. A scraping blade is preferably provided at the end of the stirring blade in order to renew the liquid film on the vessel wall.
Instruments such as a pressure gauge and a thermometer may be installed in the container. Each component is dissolved in a solvent in the container. The prepared dope is taken out of the container after cooling, or taken out and then cooled using a heat exchanger or the like.

A solution can also be prepared by a cooling dissolution method. In the cooling dissolution method, the polymer can be dissolved in an organic solvent that is difficult to dissolve by a normal dissolution method. In addition, even if it is a solvent which can melt | dissolve a polymer with a normal melt | dissolution method, there exists an effect that a uniform solution can be obtained rapidly according to a cooling melt | dissolution method.
In the cooling dissolution method, first, a polymer is gradually added to an organic solvent with stirring at room temperature.
The amount of the polymer is preferably adjusted so as to be 10 to 40% by mass in the mixture, and more preferably 10 to 30% by mass. Furthermore, you may add the arbitrary additive mentioned later in a mixture.

The mixture is then cooled to -100 to -10 ° C (preferably -80 to -10 ° C, more preferably -50 to -20 ° C, most preferably -50 to -30 ° C). The cooling can be performed, for example, in a dry ice / methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). Upon cooling in this way, the mixture of polymer and organic solvent solidifies.
The cooling rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The faster the cooling rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The cooling rate is a value obtained by dividing the difference between the temperature at the start of cooling and the final cooling temperature by the time from the start of cooling to the final cooling temperature.

Further, when this is heated to 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C., most preferably 0 to 50 ° C.), the polymer dissolves in the organic solvent. The temperature can be raised by simply leaving it at room temperature or in a warm bath.
The heating rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The higher the heating rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The heating rate is the value obtained by dividing the difference between the temperature at the start of heating and the final heating temperature by the time from the start of heating until the final heating temperature is reached. is there.

A uniform solution is obtained as described above. If the dissolution is insufficient, the cooling and heating operations may be repeated. Whether or not the dissolution is sufficient can be determined by merely observing the appearance of the solution with the naked eye.
In the cooling dissolution method, it is desirable to use a sealed container in order to avoid moisture mixing due to condensation during cooling. In the cooling and heating operation, when the pressure is applied during cooling and the pressure is reduced during heating, the dissolution time can be shortened. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container.

A polymer film is produced from the prepared polymer solution (dope) by a solvent cast method.
The dope is cast on a drum or band, and the solvent is evaporated to form a film. It is preferable to adjust the concentration of the dope before casting so that the solid content is 10 to 40% (preferably 18 to 35%). The surface of the drum or band is preferably finished in a mirror state. The casting and drying methods in the solvent casting method are described in U.S. Pat. No. 736892, JP-B Nos. 45-4554, 49-5614, JP-A-60-176834, No. 60-203430, and No. 62-1115035.

The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less. After casting, it is preferable to dry it by applying air for 2 seconds or more. The obtained film can be peeled off from the drum or band, and further dried by high-temperature air whose temperature is successively changed from 100 to 160 ° C. to evaporate the residual solvent. The above method is described in Japanese Patent Publication No. 5-17844. According to this method, it is possible to shorten the time from casting to stripping. In order to carry out this method, it is necessary for the dope to gel at the surface temperature of the drum or band during casting.
The amount of residual solvent at the time of stripping is preferably 10 to 45% by mass or less. The stripped film is passed through a drying zone at 100 to 160 ° C. over 10 minutes to 2 hours to make the residual volatile content 2% by mass or less. Both ends of the film are trimmed, knurled and wound.
In the latter half of the drying process, it is also preferable to curl the film by spraying steam or solvent vapor.

A film can also be formed by co-casting two or more layers using a plurality of polymer solutions (dope). The plurality of polymer solutions may have the same composition.
A method of producing a film while casting a plurality of polymer solutions from a plurality of casting openings provided at intervals in the direction of travel of the support and laminating them (Japanese Patent Laid-Open Nos. 61-158414 and 1) No. 122419 and 11-198285). A method for forming a film by casting a polymer solution from two casting ports (Japanese Patent Publication Nos. 60-27562, 61-94724, 61-94725, 61-104413, 61) -158413 and JP-A-6-134933). A polymer film casting method (described in JP-A-56-162617) in which a flow of a high-viscosity polymer solution is wrapped with a low-viscosity polymer solution and the high- and low-viscosity polymer solutions are simultaneously extruded may be employed.

A method for producing a film by peeling off the film formed on the support by the first casting port using the two casting ports and performing the second casting on the side in contact with the support surface. (Described in Japanese Patent Publication No. 44-20235) can also be employed.
The polymer solution can be cast simultaneously with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, a UV absorbing layer, a linearly polarizing film, and a moisture proof layer).
Single layer casting may extrude a highly concentrated and highly viscous polymer solution to obtain a constant film thickness. A polymer solution having a high concentration and a high viscosity often has a problem that the stability is poor, solid matter is generated, a failure occurs, and the flatness is poor. As a solution to this problem, a plurality of polymer solutions may be cast from the casting port. By extruding a plurality of high-viscosity solutions simultaneously onto the support, the planarity is improved and an excellent planar film can be produced. Further, by using a concentrated polymer solution, it is possible to reduce the drying load and increase the production efficiency of the film.

A plasticizer can be added to the polymer film in order to improve mechanical properties or increase the drying speed. As the plasticizer, phosphoric acid ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethyl hexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Phthalate plasticizers (DMP, DEP, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred.
The addition amount of the plasticizer is preferably 0.1 to 25% by mass, more preferably 1 to 20% by mass, and most preferably 3 to 15% by mass of the amount of the polymer.

  A degradation inhibitor (eg, antioxidant, peroxide decomposer, radical inhibitor, metal deactivator, acid scavenger, amine) may be added to the polymer film. The deterioration preventing agents are described in JP-A-3-199201, JP-A-5-190773, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854. The addition amount of the deterioration preventing agent is preferably 0.01 to 1% by mass of the solution (dope) to be prepared, and more preferably 0.01 to 0.2% by mass. When the addition amount is less than 0.01% by mass, the effect of the deterioration preventing agent is hardly recognized. When the added amount exceeds 1% by mass, bleeding-out (bleeding) of the deterioration preventing agent to the film surface may be observed. Particularly preferred degradation inhibitors are butylated hydroxytoluene (BHT) and tribenzylamine (TBA).

A surface treatment may be applied to the polymer film. Specifically, corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment, or ultraviolet irradiation treatment is performed. From the viewpoint of maintaining the flatness of the film, it is preferable that the temperature of the polymer film in the surface treatment is not more than the glass transition temperature (Tg).
When making a polymer film function as a transparent protective film of a polarizing plate, it is preferable to implement an acid treatment or an alkali treatment from an adhesive viewpoint with a polarizing film, and an alkali treatment is further more preferable. When the polymer is cellulose acylate, the alkali treatment functions as an alkali saponification treatment.

The alkali treatment is preferably performed in a cycle in which the film surface is immersed in an alkali solution, neutralized with an acidic solution, washed with water and dried.
The alkali is preferably an alkali metal hydroxide, more preferably potassium hydroxide or sodium hydroxide. The solvent of the solution is preferably water or an organic solvent. The organic solvent is preferably a lower alcohol. More preferably, the lower alcohol is an alcohol or glycol having 1 to 5 carbon atoms. Examples of lower alcohols include ethanol, propanol, isopropanol, butanol, ethylene glycol, propylene glycol. Isopropanol and propylene glycol are preferred. Two or more kinds of solvents may be mixed and used. Examples of the mixed solvent include isopropanol / propylene glycol / water (volume ratio: 70/15/15), isopropanol / water (volume ratio: 85/15) and isopropanol / propylene glycol (volume ratio: 85/15). It is.

The specified concentration of the solution is preferably 0.1 to 3.0N, and more preferably 0.5 to 2.0N. The alkaline solution temperature is preferably in the range of room temperature to 90 ° C, more preferably 40 ° C to 70 ° C. A surfactant may be added to the alkaline solution.
The polymer film can be subjected to alkali treatment by being immersed in an alkali solution. The alkaline solution may be applied to the polymer film (bar coating, curtain coating).

In order to improve adhesion between a polymer film and a layer provided thereon (eg, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, a UV absorbing layer, a linearly polarizing film, a moisture proof layer), an undercoat layer ( JP-A-7-333433) may be provided. The thickness of the undercoat layer is preferably from 0.1 to 2 μm, and more preferably from 0.2 to 1 μm.
The polymer film may be provided with a matte layer in order to improve handling at the time of production. The mat layer may be provided on both sides of the polymer film. The mat layer generally contains a mat agent and a polymer. Matting agents and polymers are described in JP-A-10-44327.

[Phase difference plate]
The optically isotropic polymer film can be used as the first transparent protective film or the second transparent protective film, but the polymer film used for the phase difference plate or the first transparent protective film / phase difference plate needs optical anisotropy. It is.
The optical anisotropy of the retardation plate is determined according to the use of the polarizing plate. However, the present invention is particularly effective in applications such as a circularly polarizing plate that requires strict optical anisotropy. In the use of a circularly polarizing plate, the retardation plate functions as a λ / 4 plate.

The retardation value (Re550) measured at a wavelength of 550 nm is 100 nm <Re550 <330 nm, and the retardation values (Re450, Re550, Re650) measured at wavelengths of 450 nm, 550 nm, and 650 nm are 0.5 respectively. It is preferable that <Re450 / Re550 <0.98 and 1.01 <Re650 / Re550 <1.35 are satisfied.
Re550 preferably satisfies 110 nm <Re550 <250 nm, and more preferably satisfies 120 nm <Re550 <200 nm.

The retardation value (Re) is calculated according to the following formula.
Retardation value (Re) = (nx−ny) × d
In the formula, nx is the refractive index in the slow axis direction in the plane of the polymer film (maximum refractive index in the plane), ny is the refractive index in the direction perpendicular to the slow axis, and d is the thickness ( nm).

In the retardation plate, the refractive index nx in the in-plane slow axis direction, the refractive index ny in the direction perpendicular to the in-plane slow axis, and the refractive index nz in the thickness direction are 1.1 <(nx−nz) / It is preferable to satisfy (nx−ny) <3. The value of (nx−nz) / (nx−ny) may be referred to as an NZ value. The NZ value more preferably satisfies 1.3 <NZ <2.5, and most preferably satisfies 1.5 <NZ <2.
The NZ value means the index of the plane orientation of molecules in the retardation plate. A film having a large NZ value has a large plane orientation.
The polymer film having optical anisotropy used for the phase difference plate can be produced by using a retardation increasing agent and performing a stretching treatment.

As the retardation increasing agent, it is preferable to use a compound having at least two aromatic rings. Aromatic rings include aromatic heterocycles in addition to aromatic hydrocarbon rings.
The retardation increasing agent is preferably used in the range of 0.01 to 10 parts by mass, more preferably 0.1 to 8 parts by mass, and more preferably 0.1 to 6 parts by mass with respect to 100 parts by mass of the polymer. Most preferably, it is used in the range of parts by mass. Two or more types of retardation increasing agents may be used in combination.
The retardation increasing agent preferably has a maximum absorption wavelength in the wavelength region of 230 to 360 nm. The retardation increasing agent preferably has substantially no absorption in the visible region.

The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring).
The aromatic heterocycle is generally an unsaturated heterocycle. The heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the greatest number of double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring.
The aromatic ring is preferably a benzene ring, furan ring, thiophene ring, pyrrole ring, oxazole ring, thiazole ring, imidazole ring, triazole ring, pyridine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring.
The number of aromatic rings is preferably 2 to 20, more preferably 2 to 12, and most preferably 2 to 6.

  The bonding relationship of a plurality of aromatic rings can be classified into (a) when forming a condensed ring, (b) when directly connecting with a single bond, and (c) when connecting via a linking group (for aromatic rings). , Spiro bonds cannot be formed). In the case of having three or more aromatic rings, a plurality of bonding relationships may be combined.

Examples of the condensed ring (a condensed ring of two or more aromatic rings) include an indene ring, a naphthalene ring, an azulene ring, a fluorene ring, a phenanthrene ring, an anthracene ring, an acenaphthylene ring, a biphenylene ring, a naphthacene ring, Pyrene ring, indole ring, isoindole ring, benzofuran ring, benzothiophene ring, indolizine ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring, purine ring, indazole ring, chromene ring, quinoline ring, isoquinoline Ring, quinolidine ring, quinazoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, pteridine ring, carbazole ring, acridine ring, phenanthridine ring, xanthene ring, phenazine ring, phenothiazine ring, phenoxathiin ring, phenoxazine ring and thiant It includes emissions ring. Naphthalene ring, azulene ring, indole ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring and quinoline ring are preferred.
The single bond (b) is preferably a bond between carbon atoms of two aromatic rings. Two aromatic rings may be bonded with two or more single bonds to form an aliphatic ring or a non-aromatic heterocyclic ring between the two aromatic rings.
The linking group in (c) is also preferably bonded to carbon atoms of two aromatic rings. The linking group is preferably an alkylene group, an alkenylene group, an alkynylene group, —CO—, —O—, —NH—, —S—, or a combination thereof. Examples of linking groups composed of combinations are shown below. In addition, the relationship between the left and right in the following examples of the linking group may be reversed.

c1: -CO-O-
c2: —CO—NH—
c3: -alkylene-O-
c4: —NH—CO—NH—
c5: —NH—CO—O—
c6: —O—CO—O—
c7: -O-alkylene-O-
c8: -CO-alkenylene-
c9: -CO-alkenylene-NH-
c10: -CO-alkenylene-O-
c11: -alkylene-CO-O-alkylene-O-CO-alkylene-
c12: -O-alkylene-CO-O-alkylene-O-CO-alkylene-O-
c13: -O-CO-alkylene-CO-O-
c14: -NH-CO-alkenylene-
c15: -O-CO-alkenylene-

The aromatic ring and the linking group may have a substituent.
Examples of the substituent include halogen atom (F, Cl, Br, I), hydroxyl, carboxyl, cyano, amino, nitro, sulfo, carbamoyl, sulfamoyl, ureido, alkyl group, alkenyl group, alkynyl group, aliphatic acyl group , Aliphatic acyloxy group, alkoxy group, alkoxycarbonyl group, alkoxycarbonylamino group, alkylthio group, alkylsulfonyl group, aliphatic amide group, aliphatic sulfonamido group, aliphatic substituted amino group, aliphatic substituted carbamoyl group, aliphatic Substituted sulfamoyl groups, aliphatic substituted ureido groups and non-aromatic heterocyclic groups are included.

The alkyl group preferably has 1 to 8 carbon atoms. A chain alkyl group is preferable to a cyclic alkyl group, and a linear alkyl group is particularly preferable. The alkyl group may further have a substituent (eg, hydroxy, carboxy, alkoxy group, alkyl-substituted amino group). Examples of alkyl groups (including substituted alkyl groups) include methyl, ethyl, n-butyl, n-hexyl, 2-hydroxyethyl, 4-carboxybutyl, 2-methoxyethyl and 2-diethylaminoethyl.
The alkenyl group preferably has 2 to 8 carbon atoms. A chain alkenyl group is preferable to a cyclic alkenyl group, and a linear alkenyl group is particularly preferable. The alkenyl group may further have a substituent. Examples of alkenyl groups include vinyl, allyl and 1-hexenyl.
The alkynyl group preferably has 2 to 8 carbon atoms. A chain alkynyl group is preferable to a cyclic alkynyl group, and a linear alkynyl group is particularly preferable. The alkynyl group may further have a substituent. Examples of alkynyl groups include ethynyl, 1-butynyl and 1-hexynyl.

The aliphatic acyl group preferably has 1 to 10 carbon atoms. Examples of the aliphatic acyl group include acetyl, propanoyl and butanoyl.
The aliphatic acyloxy group preferably has 1 to 10 carbon atoms. Examples of the aliphatic acyloxy group include acetoxy.
The number of carbon atoms of the alkoxy group is preferably 1 to 8. The alkoxy group may further have a substituent (eg, alkoxy group). Examples of alkoxy groups (including substituted alkoxy groups) include methoxy, ethoxy, butoxy and methoxyethoxy.
The alkoxycarbonyl group preferably has 2 to 10 carbon atoms. Examples of the alkoxycarbonyl group include methoxycarbonyl and ethoxycarbonyl.
The number of carbon atoms of the alkoxycarbonylamino group is preferably 2 to 10. Examples of the alkoxycarbonylamino group include methoxycarbonylamino and ethoxycarbonylamino.

The alkylthio group preferably has 1 to 12 carbon atoms. Examples of the alkylthio group include methylthio, ethylthio and octylthio.
The alkylsulfonyl group preferably has 1 to 8 carbon atoms. Examples of the alkylsulfonyl group include methanesulfonyl and ethanesulfonyl.
The aliphatic amide group preferably has 1 to 10 carbon atoms. Examples of the aliphatic amide group include acetamide.
The aliphatic sulfonamide group preferably has 1 to 8 carbon atoms. Examples of the aliphatic sulfonamido group include methanesulfonamido, butanesulfonamido and n-octanesulfonamido.
The number of carbon atoms of the aliphatic substituted amino group is preferably 1 to 10. Examples of the aliphatic substituted amino group include dimethylamino, diethylamino and 2-carboxyethylamino.
The aliphatic substituted carbamoyl group preferably has 2 to 10 carbon atoms. Examples of the aliphatic substituted carbamoyl group include methylcarbamoyl and diethylcarbamoyl.
The aliphatic substituted sulfamoyl group preferably has 1 to 8 carbon atoms. Examples of the aliphatic substituted sulfamoyl group include methylsulfamoyl and diethylsulfamoyl.
The number of carbon atoms in the aliphatic substituted ureido group is preferably 2 to 10. Examples of the aliphatic substituted ureido group include methylureido.
Examples of non-aromatic heterocyclic groups include piperidino and morpholino.

A rod-like compound in which a plurality of aromatic rings are linearly linked (having a linear molecular structure) by the linking group (c) is particularly preferred. The linear molecular structure means that the molecular structure of the rod-like compound is linear in the most thermodynamically stable structure. The most thermodynamically stable structure can be obtained by crystal structure analysis or molecular orbital calculation. For example, molecular orbital calculation can be performed using molecular orbital calculation software (eg, WinMOPAC2000, manufactured by Fujitsu Limited) to determine the molecular structure that minimizes the heat of formation of the compound. The molecular structure being linear means that the angle of the molecular structure is 140 degrees or more in the thermodynamically most stable structure obtained by calculation as described above.
The rod-like aromatic compound preferably exhibits liquid crystallinity. More preferably, the rod-like aromatic compound exhibits liquid crystallinity upon heating (has thermotropic liquid crystallinity). The liquid crystal phase is preferably a nematic phase or a smectic phase.

The rod-like aromatic compound is preferably represented by the following formula (I).
(I) Ar ¹ -L ¹ -Ar ²
In formula (I), Ar ¹ and Ar ² are each independently an aromatic group.
The aromatic group has the above-described aromatic hydrocarbon ring or aromatic heterocycle as an aromatic ring. The substituent of the aromatic group is the same as the substituent of the aromatic ring described above.

In the formula (I), L ¹ is a divalent linking group selected from the group consisting of an alkylene group, an alkenylene group, an alkynylene group, a divalent saturated heterocyclic group, —O—, —CO—, and combinations thereof. is there.
The alkylene group may have a cyclic structure. As the cyclic alkylene group, cyclohexylene is preferable, and 1,4-cyclohexylene is particularly preferable. As the chain alkylene group, a linear alkylene group is more preferable than a branched alkylene group.
The alkylene group preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, still more preferably 1 to 10 carbon atoms, still more preferably 1 to 8 carbon atoms. 6 is most preferred.

The alkenylene group and the alkynylene group preferably have a chain structure rather than a cyclic structure, and more preferably have a linear structure rather than a branched chain structure.
The alkenylene group and the alkynylene group preferably have 2 to 10 carbon atoms, more preferably 2 to 8, more preferably 2 to 6, still more preferably 2 to 4. Most preferred is 2 (vinylene or ethynylene).
The divalent saturated heterocyclic group preferably has a 3- to 9-membered heterocyclic ring. The hetero atom of the hetero ring is preferably an oxygen atom, a nitrogen atom, a boron atom, a sulfur atom, a silicon atom, a phosphorus atom or a germanium atom. Examples of saturated heterocycles include piperidine ring, piperazine ring, morpholine ring, pyrrolidine ring, imidazolidine ring, tetrahydrofuran ring, tetrahydropyran ring, 1,3-dioxane ring, 1,4-dioxane ring, tetrahydrothiophene ring, 1 , 3-thiazolidine ring, 1,3-oxazolidine ring, 1,3-dioxolane ring, 1,3-dithiolane ring and 1,3,2-dioxaborolane. Particularly preferred divalent saturated heterocyclic groups are piperazine-1,4-diylene, 1,3-dioxane-2,5-diylene and 1,3,2-dioxaborolane-2,5-diylene.

The example of the bivalent coupling group which consists of a combination is shown.
L-1: —O—CO-alkylene group —CO—O—
L-2: -CO-O-alkylene group -O-CO-
L-3: —O—CO—alkenylene group —CO—O—
L-4: -CO-O-alkenylene group -O-CO-
L-5: -O-CO-alkynylene group -CO-O-
L-6: -CO-O-alkynylene group -O-CO-
L-7: -O-CO-divalent saturated heterocyclic group -CO-O-
L-8: -CO-O-divalent saturated heterocyclic group -O-CO-

In the molecular structure of the formula (I), the angle formed by Ar ¹ and Ar ² across L ¹ is preferably 140 degrees or more.

The rod-like aromatic compound is more preferably represented by the following formula (II).
(II) Ar ¹ -L ² -XL ³ -Ar ²
In the formula (II), Ar ¹ and Ar ² are each independently an aromatic group.
The aromatic group has the above-described aromatic hydrocarbon ring and aromatic heterocycle as an aromatic ring. The substituent of the aromatic group is the same as the substituent of the aromatic ring described above.

In the formula (II), L ² and L ³ are each independently a divalent linking group selected from the group consisting of an alkylene group, —O—, —CO—, and combinations thereof.
The alkylene group preferably has a chain structure rather than a cyclic structure, and more preferably has a linear structure rather than a branched chain structure.
The alkylene group preferably has 1 to 10 carbon atoms, more preferably 1 to 8, more preferably 1 to 6, still more preferably 1 to 4, and still more preferably 1 or Most preferred is 2 (methylene or ethylene).
L ² and L ³ are particularly preferably —O—CO— or —CO—O—.

In the formula (II), X is 1,4-cyclohexylene, vinylene or ethynylene.
Examples of the rod-like aromatic compound represented by the formula (I) are shown below.

  Specific examples (1) to (34), (41), (42), (46), (47), (52), (53) are two asymmetric carbons at the 1st and 4th positions of the cyclohexane ring. Has atoms. However, the specific examples (1), (4) to (34), (41), (42), (46), (47), (52), (53) have a symmetric meso type molecular structure. Therefore, there is no optical isomer (optical activity) and only geometric isomers (trans and cis forms) exist. The trans type (1-trans) and cis type (1-cis) of specific example (1) are shown below.

As described above, it is preferable that the rod-shaped aromatic compound used as the retardation increasing agent has a linear molecular structure. Therefore, the trans type is preferable to the cis type.
Specific examples (2) and (3) have optical isomers (a total of four isomers) in addition to geometric isomers. As for geometric isomers, the trans type is similarly preferable to the cis type. The optical isomer is not particularly superior or inferior, and may be D, L, or a racemate.
In specific examples (43) to (45), the central vinylene bond includes a trans type and a cis type. For the same reason as above, the trans type is preferable to the cis type.
The retardation increasing agent may be used by mixing two or more kinds of compounds.

In order to adjust the optical anisotropy of the polymer film, it is preferable to carry out a stretching treatment. The polymer film is stretched in at least one direction. In the present invention, it is preferable to stretch at a low aspect ratio.
Stretching is performed using two or more pairs of nip rolls. By adjusting the line speed of the nip roll on the outlet side (generally increasing it), the length and width can be adjusted. The gap between the nip rolls is preferably such that the aspect ratio L / W (ratio of the width of the polymer film before stretching W to the distance L between the nip rolls) is 0.5 ≦ L / W ≦ 2, and 0.7 ≦ L / W ≦ 1.8 is more preferable, and 0.9 ≦ L / W ≦ 1.6 is further more preferable. In general, the aspect ratio in the normal stretching process is a value exceeding 3.
The stretching is performed using nip rolls of 2 pairs or more, more preferably 2 pairs or more and 8 pairs or less, and further preferably 2 pairs or more and 6 pairs or less. Stretching with two pairs of nip rolls is one-stage stretching, and when three or more pairs of nip rolls are used, multi-stage stretching is performed. Two or more stages of stretching are preferred. In stretching with a low aspect ratio, it is easy to break when trying to stretch in one step, and it is preferable to stretch in multiple steps little by little.
The width of the nip roll is preferably 1.01 to 1.5 times the film width before stretching, more preferably 1.03 to 1.4 times, and even more preferably 1.05 to 1.3 times.

The wrap angle between the nip roll and the film used for stretching is preferably less than 30 °, more preferably less than 20 °, and even more preferably less than 10 °.
In the case of multistage stretching, it is preferable that at least one pair of nip rolls has the above wrap angle. More preferably, all nip rolls used have the wrap angle described above.
The nip force is preferably 50 to 800 kg, more preferably 100 to 600 kg, and further preferably 150 to 400 kg per 1 m of the width of the nip roll.
The time required for the stretching treatment is preferably 1 to 30 seconds, more preferably 2 to 25 seconds, and further preferably 3 to 20 seconds.
In order to improve the uniformity in the width direction, the temperature at both ends is preferably stretched under a temperature condition that is 1 ° C. to 30 ° C. higher than the center portion.
The temperature distribution can be realized by using a divided heat source installed along the width direction. Specifically, the end portion may be heated using a radiant heat source (for example, an IR heater), or a plurality of divided blowing ports may be provided to increase the blowing temperature at the end portion.

Specific stretching treatment conditions can be classified into dry stretching and hydrous stretching.
Dry stretching is a general stretching method performed in a dry atmosphere while heating.
The heating temperature is preferably 100 to 160 ° C, more preferably 110 to 150 ° C, and most preferably 120 to 145 ° C.
The draw ratio is preferably 1.1 to 1.7 times, more preferably 1.2 to 1.6 times, and most preferably 1.3 to 1.5 times.
The dry stretching is preferably performed using two or more pairs of nip rolls under the condition that the outlet side speed is larger than the inlet side feeding speed. The number of nip rolls is more preferably 2 to 8 pairs, and most preferably 2 to 6 pairs.
Heating is preferably performed in a casing that has been heated to a certain temperature. The stretching in the casing can reduce the change in optical characteristics in the width direction, compared with a method using a general heating means (a heating roll or a radiant heat source).

In the hydrous stretching, the polymer film is stretched with water. In the hydrous stretching, smoother stretching can be performed due to the plasticizing effect of moisture. Therefore, water-containing stretching is preferable to dry stretching.
Before the water-containing stretching, a treatment for pre-hydrating the polymer film is performed. Prior to that, it is preferable to carry out a drying heat treatment in which the film is heated to 50 to 150 ° C. in a dry state with a relative humidity of 0 to 30%. The heating temperature is more preferably 60 to 120 ° C, further preferably 70 to 110 ° C. The relative humidity is more preferably 0 to 25%, further preferably 0 to 20%. The heating time is preferably 3 seconds to 30 minutes, more preferably 5 seconds to 10 minutes, and even more preferably 10 seconds to 3 minutes. As the heating means, a heat roll, hot air, or a radiant heat source (eg, IR heater) can be used.

The water content of the polymer film before stretching is preferably 2 to 10% by mass, more preferably 2.5 to 8% by mass, and most preferably 3 to 6% by mass.
In order to include water in the polymer film, the polymer film is immersed in water or the polymer film is exposed to water vapor.
When immersed in water, the water temperature is preferably 60 to 100 ° C, more preferably 70 to 100 ° C, and most preferably 80 to 100 ° C. The immersion time is preferably 0.1 to 20 minutes, more preferably 0.2 to 10 minutes, and most preferably 0.5 to 5 minutes. The polymer film can contain water by being conveyed between rolls installed in the water tank.

  When exposed to water vapor, the treatment temperature is preferably 60 to 150 ° C, more preferably 70 to 140 ° C, and further preferably 75 to 130 ° C. The relative humidity in the treatment is preferably 70 to 100%, more preferably 80 to 100%, and most preferably 85 to 100%. The treatment time is preferably 0.1 to 20 minutes, more preferably 0.2 to 10 minutes, and most preferably 0.5 to 5 minutes. It is possible to expose to water vapor by installing a roll in a room filled with water vapor and transporting the polymer film.

Water (or water vapor) may contain components other than water. Examples of other components include organic solvents, plasticizers and surfactants. The organic solvent is preferably a water-miscible liquid having 1 to 10 carbon atoms. It is preferable that 60% by mass or more of water and all other components is water, more preferably 80% by mass or more is water, and most preferably pure water.
You may implement combining the method to immerse in water, and the method to expose to water vapor | steam. It is particularly preferred to carry out the method of exposing to water vapor alone.

The draw ratio in the hydrous drawing is preferably 1.1 to 2 times, more preferably 1.2 to 1.8 times, and most preferably 1.3 to 1.7 times.
The temperature of the water-containing stretching is preferably 50 to 100 ° C, more preferably 60 to 95 ° C, and most preferably 70 to 95 ° C. The relative humidity in the hydrous stretching is preferably 60 to 100%, more preferably 70 to 100%, and most preferably 80 to 95%. The stretching treatment under a condition where the relative humidity is high may be performed in a high humidity atmosphere or while being immersed in water. It is preferable to carry out in a high humidity atmosphere.
Stretching in a high humidity atmosphere can be performed by installing two or more pairs of nip rolls in a humidity-controlled casing and increasing the linear velocity of the nip roll on the outlet side. Stretching in water can be carried out by installing two or more pairs of nip rolls in a heated water tank and increasing the linear velocity of the nip roll on the outlet side.

In the hydrous stretching, it is preferable to dry after the stretching.
The drying temperature is preferably 40 to 150 ° C, more preferably 50 to 130 ° C, and most preferably 60 to 120 ° C.
The drying time is preferably 10 seconds to 20 minutes, more preferably 20 seconds to 10 minutes, and most preferably 30 seconds to 7 minutes.
The water content of the polymer film after drying is preferably less than 2%.

The polymer film before stretching preferably has a thickness of 50 to 300 μm, more preferably 60 to 280 μm, and most preferably 70 to 250 μm.
The polymer film before being stretched preferably has a width of 60 cm to 3 m, more preferably 70 cm to 2.5 m, and most preferably 80 cm to 2 m.
The stretched polymer film preferably has a thickness of 40 to 250 μm, more preferably 50 to 230 μm, and most preferably 60 to 200 μm.
The polymer film after stretching preferably has a haze value of 0 to 2%, more preferably 0 to 1.5%, and most preferably 0 to 1%.

The polymer film used for the phase difference plate is preferably further subjected to a heat treatment.
The heating temperature is preferably 50 to 150 ° C, more preferably 70 to 140 ° C, and most preferably 90 to 120 ° C.
The heating time is preferably 0.5 to 200 hours, more preferably 1 to 100 hours, and most preferably 3 to 50 hours.
The heat treatment can be carried out by conveying the polymer film in the heating zone. The polymer film is preferably conveyed using a roll. Heating with a roll tends to cause a temperature difference between the film surface and the inside. The temperature difference causes a reduction in surface condition (generation of wrinkles). In order to eliminate the temperature difference, it is preferable to heat from the inside of the roll using a hollow core, or to heat while slowly rotating the roll.
It is preferable to cause structural relaxation in the polymer film by heat treatment, and as a result, an endothermic peak appears at a temperature near the glass transition temperature (Tg) of the polymer. The endothermic peak is preferably 0.1 to 2.0 J / g, more preferably 0.3 to 1.8 J / g, and most preferably 0.5 to 1.6 J / g. . When structural relaxation is caused in the polymer film and the endothermic peak is increased, the change in optical anisotropy (retardation value) accompanying a change in temperature can be reduced.
In addition, when providing a moisture-proof layer (below) in a polarizing plate (the polymer film), it is preferable to heat-process, after providing a moisture-proof layer in a polymer film.

[Dampproof layer]
It is preferable to suppress the moisture permeation amount of the entire structure excluding the retardation plate from the polarizing plate to less than 5 g / m ² · day. The moisture permeability is preferably 0.01 to 4 g / m ² · day, and more preferably 0.05 to 3 g / m ² · day.
In order to realize a low moisture permeability, it is preferable to provide a moisture-proof layer on the polarizing plate.
In the polarizing plate having the basic structure (A), it is common to provide an adhesive layer between the retardation plate and the first transparent protective film for the convenience of the production process. That is, the polarizing plate (A) generally has a structure of a first transparent protective film to a second transparent protective film, and is bonded to the retardation plate with an adhesive.
For the above reasons, when a single moisture-proof layer is provided on the polarizing plate of the basic configuration (A), it is preferable to employ any one of the following (A1) to (A5).

────────────────────────────────────
(A1) (A2) (A3) (A4) (A5)
────────────────────────────────────
Second protective film Second protective film Second protective film Second protective film Moisture-proof layer Linear polarizing film Linear polarizing film Linear polarizing film Moisture-proof layer Second protective film First protective film First protective film Moisture-proof layer Linear protective film Linear polarizing film Adhesive Adhesive layer Moisture-proof layer 1st protective film 1st protective film 1st protective film Moisture-proof layer Adhesive layer Adhesive layer Adhesive layer Adhesive layer Retardation plate Retardation plate Retardation plate Retardation plate Retardation plate───── ───────────────────────────────

  When a single moisture-proof layer is provided on the polarizing plate of the basic configuration (B), it is preferable to employ any one of the following (B1) to (B3).

────────────────────────────────────
(B1) (B2) (B3)
────────────────────────────────────
Second protective film Second protective film Moisture-proof layer Linear polarizing film Moisture-proof layer Second protective film Moisture-proof layer Linear polarizing film Linear polarizing film First protective film and phase difference plate First protective film and phase difference plate First protective film and phase difference Board ────────────────────────────────────

  As shown in the above (A1) to (A5) and (B1) to (B3), the moisture-proof layer is composed of the retardation film (A1), the first transparent protective film (A2, A3), and the first transparent protective film. It can be provided on the phase difference plate (B1) or the second transparent protective film (A4, A5, B2, B3). The retardation film and the transparent protective film are generally polymer films, and the moisture-proof layer can be formed on the polymer film.

Two or more moisture-proof layers may be provided on the polarizing plate. If it is difficult to achieve the low moisture permeability (less than 5 g / m ² · day) with a single moisture-proof layer, a moisture-proof layer is further added. Two or more moisture barrier layers may be provided in the same position. When two or more moisture-proof layers are provided at different positions, a plurality of aspects (A1) to (A5) or aspects (B1) to (B3) may be combined. A moisture-proof layer can also be provided below the phase difference plate (image display surface side).
However, in general, the low moisture permeation amount can be realized only by providing one moisture barrier layer.

The moisture vapor transmission coefficient of the moisture-proof layer is preferably 1 × 10 ^{−12 to} 1 × 10 ⁻⁷ (cm ³ / cm · sec · cmHg).
The moisture-proof layer can be formed from an organic material or an inorganic material. An organic material and an inorganic material may be combined.

The organic material is preferably a polymer. The water vapor transmission coefficient of the polymer is preferably 10 ^{−12 to} 10 ⁻⁷ (cm ³ / cm / s · cmHg).
The moisture-proof layer is provided in order to realize the low moisture permeability. The moisture permeability is proportional to the water vapor transmission coefficient and inversely proportional to the thickness. Therefore, the moisture permeability (g / m ² · day) can be calculated from the water vapor transmission coefficient (cm ³ / cm · sec · cmHg) and the thickness (μm) by the following formula.
Moisture permeability = 10 ¹⁰ × water vapor permeability coefficient / thickness

Examples of polymers that can be used in the moisture barrier are given below along with the water vapor transmission coefficient (cm ³ / cm · sec · cmHg) and the thickness required to achieve a low moisture permeability of less than 1 g / m ² · day.

────────────────────────────────────
Polymer Water vapor transmission coefficient Required thickness ----------------------
# 1 ethylene / vinyl alcohol copolymer 6 × 10 ⁻¹⁰ 6 μm
# 2 Vinyl acetate / ethylene copolymer 8 × 10 ⁻¹⁰ 8 μm
# 3 Polyvinyl alcohol 9 × 10 ⁻¹⁰ 9 μm
# 4 Polyvinylidene chloride 1 × 10 ⁻⁹ 10 μm
# 5 Polyvinyl fluoride 1 × 10 ⁻⁹ 10 μm
# 6 High density polyethylene 1 × 10 ⁻⁹ 10 μm
# 7 Hydrochloric acid rubber 1 × 10 ⁻⁹ 10 μm
# 8 Vinylidene chloride / acrylic acid copolymer 1 × 10 ⁻⁹ 10 μm
# 9 Vinyl chloride / acrylonitrile copolymer 2 × 10 ⁻⁹ 20 μm
# 10 Polyethylene naphthalate 5 × 10 ⁻⁹ 50 μm
# 11 Polypropylene 6 × 10 ⁻⁹ 60 μm
# 12 Butadiene / acrylonitrile copolymer 8 × 10 ⁻⁹ 80 μm
# 13 Tetrafluoroethylene / ethylene copolymer 1 × 10 ⁻⁸ 100 μm
# 14 Low density polyethylene 1 × 10 ⁻⁸ 100 μm
# 15 Polyamide (MX nylon) 2 × 10 ⁻⁸ 200 μm
# 16 ethylene / propylene copolymer 4 × 10 ⁻⁸ 400 μm
# 17 Polypropylene 6 × 10 ⁻⁹ 60 μm
# 18 Polyhexamethylene adipamide 8 × 10 ⁻⁸ 800 μm
────────────────────────────────────
(Ii) Polyhexamethylene adipamide: 6,6-nylon

The moisture-proof layer made of a polymer can be provided by coating.
The moisture-proof layer made of a polymer can enhance the moisture-proof function by crystallizing the polymer. In order to crystallize the polymer, it is preferable to heat-treat the coating solution containing the polymer (solution, dispersion, emulsion) after coating and drying.
The heat treatment temperature is preferably 100 to 200 ° C., more preferably 120 to 180 ° C., and most preferably 140 to 170 ° C. The heat treatment time is preferably 0.5 to 60 minutes, more preferably 1 to 20 minutes, and more preferably 2 to 10 Minutes are most preferred.

The moisture-proof layer can also be composed of an inorganic material.
If the moisture-proof layer is composed of only an inorganic material that does not transmit water vapor at all, such as a glass plate, a low water vapor transmission coefficient can be easily achieved. However, since a layer composed only of an inorganic material is generally brittle and thick, it is not suitable as a constituent layer of a polarizing plate attached to an image display device. Therefore, it is preferable to form the moisture-proof layer by combining an inorganic material and an organic material.
When a moisture-proof layer is formed by combining an inorganic material and an organic material, a low moisture permeability coefficient can be easily achieved while being a flexible layer. When an inorganic material and an organic material are combined, the moisture permeability coefficient can be reduced to about 1/100 compared to the case where the organic material is used alone.

When combining an inorganic material and an organic material, it is preferable to use the above-mentioned polymer having a low water vapor transmission coefficient as the organic material and to make it function as a binder for the inorganic material.
The inorganic material is preferably an oxide. Examples of inorganic materials include silicon dioxide, alumina, talc, mica, diatomaceous earth, titanium oxide, teniolite, montmorillonite, saponite, hectorite and zirconium phosphate.
The shape of the inorganic material is preferably layered. As the layered inorganic material, mica and talc are preferable.

  Both natural mica and synthetic mica are preferably used. Examples of natural mica include muscovite (aspect ratio: 25), soda mica (aspect ratio: 50), phlogopite (aspect ratio: 105), biotite (aspect ratio: 215) and scale mica (aspect ratio: 525). ) Is included. Examples of synthetic mica include fluorine phlogopite (aspect ratio: 825), potassium tetrasilicon mica (aspect ratio: 950), Na tetralithic mica (aspect ratio: 3000), Na or Li teniolite (aspect ratio: 10,000). ), Montmorillonite Na or Li hectorite (aspect ratio: 30,000). Fluorophlogopite and Potassium tetrasilicon mica are classified as non-swellable mica, and other synthetic mica is classified as swellable mica. Synthetic smectite (aspect ratio: 80,000) can also be used as the layered inorganic compound. Synthetic mica is preferred, and fluorine-based swellable mica is particularly preferred.

The aspect ratio of the inorganic layered compound is preferably 200 to 100,000, more preferably 100 to 50,000, and most preferably 200 to 10,000. The aspect ratio is the ratio of the thickness to the major axis of the particles.
The average major axis of the inorganic layered compound is preferably 0.3 to 20 μm, more preferably 0.5 to 10 μm, and most preferably 1 to 5 μm. The average thickness of the inorganic layered compound is preferably less than 0.1 μm, more preferably less than 0.05 μm, and most preferably less than 0.01 μm.

When the inorganic material and the organic material are used in combination, the amount of the inorganic material is preferably 1 to 50% by mass, more preferably 3 to 40% by mass, based on the amount of the organic material. Most preferred is 30 to 30% by mass.
A moisture-proof layer combining an inorganic material and an organic material can be formed by a solution dispersion method or a melt dispersion method.

In the solution dispersion method, the moisture-proof layer is formed by the following procedures (1) to (5).
(1) An organic material is dissolved or emulsified in a solvent to prepare a solution or latex. The concentration of the solution or latex is preferably 0.3 to 30% by mass, more preferably 0.5 to 20% by mass, and most preferably 1 to 10% by mass. The solvent is preferably a polar solvent considering the dispersibility of the inorganic compound. The polar solvent is preferably water, alcohol or a mixture thereof.
(2) Disperse the inorganic material in water, alcohol or a mixture thereof.
(3) The inorganic material dispersion is slowly dropped into the organic material solution or latex and stirred.
(4) The obtained coating solution is applied to a polymer film (retardation plate, first transparent protective film, first transparent protective film / retardation plate or second transparent protective film).
(5) Dry the coating layer.

In the melt dispersion method, the moisture-proof layer is formed by the following procedures (1) to (3).
(1) The organic material is heated and melted.
(2) The inorganic material is added to the molten organic material and stirred. It is preferable to use a kneader for the stirring.
(3) The polymer constituting the polymer film (retardation plate, first transparent protective film, first transparent protective film / retardation plate or second transparent protective film) and the above mixture are coextruded, and the polymer film A moisture-proof layer is formed at the same time.
Alternatively, the film formed by extrusion only with the above mixture is bonded onto the polymer film via an adhesive layer to form a moisture-proof layer.

The solution dispersion method is preferable to the melt dispersion method.
The moisture-proof layer in which the inorganic material is dispersed in the polymer (organic material) can enhance the moisture-proof function by crystallizing the polymer. In order to crystallize the polymer, it is preferable to heat-treat after forming the moisture-proof layer.
The heat treatment temperature is preferably 100 to 200 ° C, more preferably 120 to 180 ° C, and most preferably 140 to 170 ° C.
The heat treatment time is preferably 0.5 to 60 minutes, more preferably 1 to 20 minutes, and most preferably 2 to 10 minutes.

Combinations of organic and inorganic materials are shown below along with the water vapor transmission coefficient (cm ³ / cm · sec · cmHg) and the thickness required to achieve a low moisture permeability of less than 1 g / m ² · day.

────────────────────────────────────
Polymer Inorganic material Addition amount Water vapor permeability coefficient Necessary thickness ----------------------
# 1 Swellable mica 3% by mass 3 × 10 ⁻¹⁰ 3 μm
# 1 Swellable mica 10% by mass 6 × 10 ⁻¹¹ 0.6 μm
# 1 Swellable mica 20% by mass 6 × 10 ⁻¹² 0.06 μm
# 1 Montmorillonite 15% by mass 5 × 10 ⁻¹¹ 0.5 μm
# 1 Smectite 7% by mass 2 × 10 ⁻¹⁰ 2 μm
────────────────────────────────────
(Ii) # 1: Ethylene / vinyl alcohol copolymer

────────────────────────────────────
Polymer Inorganic material Addition amount Water vapor permeability coefficient Necessary thickness ----------------------
# 2 Swellable mica 3% by mass 4 × 10 ⁻¹⁰ 4 μm
# 2 Swellable mica 10% by mass 8 × 10 ⁻¹¹ 0.8 μm
# 2 Swellable mica 20% by mass 8 × 10 ⁻¹² 0.08 μm
# 2 Montmorillonite 15% by mass 7 × 10 ⁻¹¹ 0.7 μm
# 2 Smectite 7% by mass 2 × 10 ⁻¹⁰ 2 μm
────────────────────────────────────
(Ii) # 2: Vinyl acetate / ethylene copolymer

────────────────────────────────────
Polymer Inorganic material Addition amount Water vapor permeability coefficient Necessary thickness ----------------------
# 3 Swellable mica 3% by mass 2 × 10 ⁻¹⁰ 2 μm
# 3 Swellable mica 10% by mass 4 × 10 ⁻¹¹ 0.4 μm
# 3 Swellable mica 20% by mass 3 × 10 ⁻¹² 0.03 μm
# 3 Montmorillonite 15% by mass 6 × 10 ⁻¹¹ 0.6 μm
# 3 Smectite 7% by mass 1 × 10 ⁻¹⁰ 1 μm
────────────────────────────────────
(Ii) # 3: Polyvinyl alcohol

────────────────────────────────────
Polymer Inorganic material Addition amount Water vapor permeability coefficient Necessary thickness ----------------------
# 4 Swellable mica 3% by mass 2 × 10 ⁻⁹ 20 μm
# 4 Swellable mica 10% by mass 3 × 10 ⁻¹⁰ 3 μm
# 4 Swellable mica 20% by mass 4 × 10 ⁻¹¹ 0.4 μm
# 4 Montmorillonite 15% by mass 3 × 10 ⁻¹⁰ 3 μm
# 4 Smectite 7% by mass 9 × 10 ⁻¹⁰ 9 μm
────────────────────────────────────
(Ii) # 4: Polyvinylidene chloride

────────────────────────────────────
Polymer Inorganic material Addition amount Water vapor permeability coefficient Necessary thickness ----------------------
# 16 Swellable mica 3% by mass 2 × 10 ⁻⁸ 200 μm
# 16 Swellable mica 10% by mass 4 × 10 ⁻⁹ 40 μm
# 16 Swellable mica 20% by mass 3 × 10 ⁻¹⁰ 3 μm
# 16 Montmorillonite 15% by mass 3 × 10 ⁻⁹ 30 μm
# 16 Smectite 7% by mass 1 × 10 ⁻⁸ 100 μm
────────────────────────────────────
(Ii) # 16: Ethylene / propylene copolymer

The thickness of the moisture-proof layer is determined according to the moisture-proof function (water vapor transmission coefficient) of the organic material, inorganic material, or combination thereof used as described above. In general, the thickness of the moisture-proof layer is preferably 1 to 50 μm (1 μm or more and less than 50 μm), more preferably 1.2 to 35 μm, and most preferably 1.5 to 10 μm. In the case of providing a plurality of moisture-proof layers, it means the total thickness.
When laminating a plurality of moisture-proof layers, it is preferable to laminate them in the order of a moisture-proof layer containing an organic material and an inorganic material and a moisture-proof layer consisting only of an organic material from the polymer film side. In the moisture-proof layer containing an organic material and an inorganic material, irregularities are generated on the surface by the inorganic material, and the surface haze tends to increase. If a moisture-proof layer made of only an organic material is provided thereon, surface irregularities can be relaxed and haze can be reduced.
The refractive indexes of the plurality of moisture-proof layers are preferably close to each other. For this purpose, it is preferable to use the same organic material for the plurality of moisture-proof layers.

The moisture-proof layer can also be formed by depositing an inorganic material on the polymer film. As the inorganic material, silica, alumina, ITO (indium / tin oxide), alkaline earth metal fluoride (described in JP-A-8-224955) and magnesium oxide are preferable. Two or more kinds of inorganic materials may be used in combination.
As a specific vapor deposition means, a vacuum vapor deposition method, a sputtering method or an ion plating method can be employed. Vacuum deposition is preferred. Two or more deposited layers may be formed.
The thickness of the vapor-deposited moisture-proof layer is preferably 10 to 1000 nm (10 nm or more and less than 1000 nm), more preferably 20 to 800 nm, and most preferably 30 to 500 nm.

[Linear polarizing film]
Examples of the linear polarizing film include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. The iodine-based polarizing film and the dye-based polarizing film are generally produced using a polyvinyl alcohol film.
After impregnating the polyvinyl alcohol film in an iodine-containing aqueous solution, the iodine-based linearly polarizing film can be produced by stretching 2 to 7 times or less at 25 to 100 ° C.
Stretching may be performed at right angles to the width direction of the polyvinyl alcohol film. The stretching in the orthogonal direction is described in JP-A-7-333425, JP-A-9-274108, JP-A-2000-141926, JP-A-2000-147251, and JP-A-2001-290026.

The polyvinyl alcohol film can also be stretched obliquely in the 45 ° direction.
Stretching in an oblique direction can be carried out by attaching a tenter in the width direction of the film. Diagonal stretching can be realized by changing the length of the left and right tenter clips. Specifically, a tenter bent in a “<” shape is used and stretched by utilizing the difference between the left and right circumferences.
The inclination angle of the orientation axis in the stretched film can be controlled and adjusted by the ratio of the tenter outlet (holding release point) width W and the stroke difference | L1-L2 | In order to obtain an orientation angle close to 45 °, 0.9W <| L1-L2 | <1.1W is preferable, and 0.97W <| L1-L2 | <1.03W is more preferable. .
The length from the tenter holding start point at one end to the holding release point (L1), the length from the holding start point to the holding release point at the other end (L2), and the width (W) between the holding release points However, it is preferable that the relationship | L2-L1 |> 0.4W is satisfied. It is also preferable to reduce the volatile content rate while shrinking after stretching in a state where the volatile content rate is 5% or more.
Regarding the oblique stretching method, the description of US Patent Publication No. 2002-8840A1 can be referred to.

The relationship between the slow axis of the retardation plate and the transmission axis of the linear polarizing film is determined according to the application of the polarizing plate. When the polarizing plate is used as a circularly polarizing plate, the slow axis of the λ / 4 plate (retardation plate) and the transmission axis of the linear polarizing film are arranged to be substantially 45 °. Substantially 45 ° means within a range of 45 ° ± 5 °. The angle between the slow axis and the transmission axis is preferably within the range of 45 ° ± 4 °, more preferably within the range of 45 ° ± 3 °, even more preferably within the range of 45 ° ± 2 °, and 45 ° ± 1. The range of ° is most preferable.
When a roll-shaped linearly polarizing film having a transmission axis of substantially 45 ° with respect to the longitudinal direction is used, a circularly polarizing plate can be produced simply by bonding it with a roll-shaped retardation plate and roll-to-roll.

[Image display device]
A polarizing plate (especially a circularly polarizing plate) can be used for various image display devices. The image display device includes a liquid crystal display device, a touch panel, and an organic EL element. A touch panel is described in JP-A-5-127822. Organic EL elements are described in JP-A-11-305729, JP-A-11-307250, and JP-A-2000-267097.
The polarizing plate according to the present invention is advantageously used in a liquid crystal display device. Liquid crystal display devices can be classified into a reflective type, a transflective type, and a transmissive type. The polarizing plate according to the present invention can be preferably used for a reflective or transflective liquid crystal display device. A reflective liquid crystal display device is particularly preferable.

The reflective liquid crystal display device includes, in order from the bottom, a lower substrate, a reflective electrode, a lower alignment film, a liquid crystal layer, an upper alignment film, a transparent electrode, an upper substrate, and a polarizing plate.
The lower substrate and the reflective electrode constitute a reflective plate. The lower alignment film to the upper alignment film constitute a liquid crystal cell. The polarizing plate is configured according to the present invention. It is preferable that the retardation plate functions as a λ / 4 plate and the polarizing plate functions as a circularly polarizing plate.
In the case of color display, a color filter layer is further provided. The color filter layer is preferably provided between the reflective electrode and the lower alignment film, or between the upper alignment film and the transparent electrode.
A reflective plate may be attached separately using a transparent electrode instead of the reflective electrode. As the reflection plate used in combination with the transparent electrode, a metal plate is preferable. If the surface of the reflecting plate is smooth, only the regular reflection component is reflected and the viewing angle may be narrowed. Therefore, it is preferable to introduce an uneven structure (described in Japanese Patent No. 275620) on the surface of the reflector. When the surface of the reflecting plate is flat (instead of introducing a concavo-convex structure on the surface), a light diffusion film may be attached to one side (cell side or outside) of the polarizing film.

The liquid crystal cell includes TN (Twisted Nematic) type, STN (Supper Twisted Nematic) type or HAN (Hybrid Aligned Nematic) type, VA (Vertically Alignment) type, ECB type (Electrically Controlled Birefringence), OCB type (Optically Compensatory Bend), A CPA (Continuous Pinwheel Alignment) type is preferable.
The twist angle of the TN liquid crystal cell is preferably 40 to 100 °, more preferably 50 to 90 °, and most preferably 60 to 80 °. The product (Δnd) of the refractive index anisotropy (Δn) of the liquid crystal layer and the thickness (d) of the liquid crystal layer is preferably 0.1 to 0.5 μm, preferably 0.2 to 0.4 μm. More preferably it is.
The twist angle of the STN type liquid crystal cell is preferably 180 to 360 °, and more preferably 220 to 270 °. The product (Δnd) of the refractive index anisotropy (Δn) of the liquid crystal layer and the thickness (d) of the liquid crystal layer is preferably 0.3 to 1.2 μm, and preferably 0.5 to 1.0 μm. More preferably it is.
In the HAN type liquid crystal cell, it is preferable that the liquid crystal is aligned substantially vertically on one substrate and the pretilt angle on the other substrate is 0 to 45 °. The product (Δnd) of the refractive index anisotropy (Δn) of the liquid crystal layer and the thickness (d) of the liquid crystal layer is preferably 0.1 to 1.0 μm, preferably 0.3 to 0.8 μm. More preferably it is. The substrate on the side on which the liquid crystal is vertically aligned may be a reflector side substrate or a transparent electrode side substrate.

In a VA mode liquid crystal cell, rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied. The VA mode liquid crystal cell includes (1) a narrowly defined VA mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied, and substantially horizontally when a voltage is applied (Japanese Patent Laid-Open No. Hei 2-). 176625 and Japanese Examined Patent Publication No. 7-69536), and (2) a liquid crystal cell in which the VA mode is multi-domained for widening the viewing angle. Specifically, MVA (described in SID97, Digest of tech. Papers (Preliminary Collection) 28 (1997) 845, SID99, Digest of tech. Papers (Preliminary Collection) 30 (1999) 206 and JP-A-11-258605. , SURVAIVAL (Monthly Display, Vol. 6, No. 3 (1999) 14), PVA (Asia Display 98, Proc. Of the 18th Inter. Display res. Conf. (Preliminary Collection) (1998) 383), Para- A (announced at LCD / PDP International '99), DDVA (SID98, Digest of tech. Papers (Preliminary Collection) 29 (1998) 838), EOC (SID98, Digest of tech. Papers (Preliminary Collection) 29 (1998) 319), PSHA (SID98, Digest of tech. Papers (Preliminary Collection) 29 (1998) 1081), RFFMH (A Sia Display 98, Proc. of the 18th Inter. Display res. Conf. (Preliminary Collection) (1998) 375), HMD (SID98, Digest of tech. Papers (Preliminary Collection) 29 (1998) 702). In addition, (3) a mode (n-ASM mode) liquid crystal cell (IWD'98, Proc. Of the 5th Inter) in which rod-like liquid crystalline molecules are substantially vertically aligned when no voltage is applied and twisted multi-domain alignment is applied when a voltage is applied. Display Workshop. (Proceedings) (1998) 143))) is also included.
The OCB mode uses an alignment mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned in a substantially opposite direction (symmetrically) between the upper part and the lower part of the liquid crystal cell. As a result, it has a self-optical compensation capability. The OCB mode liquid crystal cell is described in US Pat. Nos. 4,583,825 and 5,410,422.
The ECB mode is characterized in that liquid crystals are aligned horizontally, and details are described in JP-A-5-203946.

The reflective liquid crystal display device can be used in a normally white mode that is bright when the applied voltage is low and dark when the applied voltage is high, or in a normally black mode that is dark when the applied voltage is low and bright when the applied voltage is high. . Normally white mode is preferred.
The touch panel is described in JP-A-5-127822 and JP-A-2002-048913.

[Example 1]
(Measurement method of water vapor transmission coefficient)
The two containers separated by the sample film are evacuated and water vapor with a relative humidity of 92% is introduced on the primary side. The amount of water vapor that has passed through the film and has come out to the secondary side is measured at 25 ° C. using a vacuum gauge. This is measured over time, and a transmission curve is prepared by taking the secondary water vapor pressure (cmHg) on the vertical axis and time (seconds) on the horizontal axis. The water vapor transmission coefficient is determined from the slope of the straight line portion of this permeation curve according to the following formula.
Water vapor transmission coefficient (cm ³ (STP) · cm ⁻¹ · sec ⁻¹ · cmHg ⁻¹ ) = (Δp / Δt) × (V / 760) × (l / p · a)
Δp / Δt: slope of the linear part of the transmission curve V: volume on the secondary side (cm ³ )
l: Film thickness (cm)
p: Primary water pressure (cmHg)
a: Film thickness (cm)

(Measurement method of moisture permeability)
A stainless steel cylinder having an outer diameter of 82 mm and a height of 15 mm, and a container having a hole with a diameter of 6 cm on one side is prepared.
Weigh 20 g of desiccant (anhydrous calcium chloride) and place in a container.
A double-sided tape is affixed around the hole of the container (so as not to block the hole), and a sample film having a diameter of 82 mm is affixed thereon.
Wrap Mylar adhesive tape around the outer periphery of the sample film 5mm and attach it to the stainless steel container.
This is weighed using a precision balance. This value is defined as W (0) (g). All the operations so far are performed at a temperature of 25 ° C. and a relative humidity of 10%.
This is transferred to an environment with a temperature of 25 ° C. and a relative humidity of 60% and left to stand.
After 24 hours, the basis weight is measured in an environment of a temperature of 25 ° C. and a relative humidity of 60%. Let this mass be W (1) g. The moisture permeability is obtained from the following formula.
Moisture permeability (g / m ² · day) = 354 × (W (1) −W (0))

(Measurement method of Re450, Re550 and Re650)
After adjusting the sample film to a temperature of 25 ° C. and a relative humidity of 60% for 3 hours or more, using an automatic birefringence meter (KOBRA-21ADH / PR: manufactured by Oji Scientific Instruments), the temperature is 25 ° C. and the relative humidity is 60%. , The retardation values at wavelengths of 450 nm, 550 nm and 650 nm are measured from the direction perpendicular to the surface of the sample film to obtain values of Re450, Re550 and Re650.

(Measurement method of NZ value)
Using an ellipsometer (KOBRA-21ADH / PR, manufactured by Oji Scientific Instruments), the refractive index nx in the slow axis direction, the refractive index ny in the direction perpendicular to the in-plane slow axis, and the refractive index nz in the thickness direction Ask for. Then, the value of (nx−nz) / (nx−ny) is calculated as the NZ value.

(Measurement method of infrared dichroic ratio by polarization infrared method)
The sample film is conditioned for 2 hours or more at a temperature of 25 ° C., a relative humidity of 60%, a temperature of 25 ° C., and a relative humidity of 10%.
Under the same atmosphere, a sample film is sandwiched between both sides of an ATR crystal plate (KRS-5, incident angle 60 degrees, 5 cm × 1 cm).
Set in the infrared spectrometer from the incident light side in the order of the polarizer and ATR measuring instrument, and integrate and measure 200 times each at a polarization angle of 90 degrees (polarized light perpendicular to the film surface) and 0 degrees (polarized light parallel to the film surface). To do.
The absorbance of the peak due to the stretching vibration of the acetyl group (peak appearing at 1700 cm-1 to 1800 cm-1) is measured. That is, the difference between the light absorption part at the highest part of the peak and the background on both sides of the peak is obtained.
The absorbance of 90-degree polarized light is A (90 °), the absorbance of 0-degree polarized light is A (0 °), and B = A (90 °) / A (0 °) is the infrared dichroic ratio. A value when the humidity is adjusted at a temperature of 25 ° C. and a relative humidity of 60% (B (relative humidity 60%)) and a value when the humidity is adjusted at a temperature of 25 ° C. and a relative humidity of 10% (B (relative humidity 10%) )), And B (relative humidity 60%)-B (relative humidity 10%) is defined as the amount of decrease in the two-color ratio of the stretching vibration of the carbonyl group.

(Measurement method of relaxation heat)
About 20 mg of the film is sampled, weighed precisely, and put in an aluminum pan.
Measurement is performed by DSC (scanning differential thermal analyzer) while increasing the temperature from 30 ° C. to 250 ° C. at a rate of 20 ° C./min.
At Tg, the baseline moves discontinuously, but the amount of heat of the endothermic peak that appears across this point is determined. That is, a point where an endothermic peak rises from the low-temperature side baseline with respect to Tg and a point where the endothermic peak merges with the high-temperature side base line are connected, and the endothermic amount is obtained from the area of the peak formed thereon. The value obtained by dividing this by the mass of the sample film is taken as the amount of relaxation heat.

(Aspect ratio measurement method)
An inorganic compound sample is dispersed on a smooth substrate (glass plate, metal plate), and a conductive material (gold, silver, carbon) is deposited thereon. This is observed using a scanning electron microscope (S-900, manufactured by Hitachi, Ltd.).
Observation is made from the front (directly above) the substrate, 50 inorganic compound particles are photographed, and the surface area is measured. The diameter of a circle having the same area is determined as D. Let the average value of these 50 points be Da.
The substrate is rotated 90 degrees, 50 cross sections of the inorganic compound are photographed from the side, and the short side is defined as a thickness T. Let the average value of these 50 points be Ta.
Let Da / Ta be the aspect ratio of this inorganic compound.

(Method of measuring moisture content)
Measured by the Karl Fischer method as follows.
(1) Two samples of 0.9 m × 4.5 cm are weighed. If the sample is wet, wipe away any moisture on the surface. Immediately after sampling, place it in a glass bottle with a stopper and carry it to the moisture meter, and measure within 3 minutes after sampling.
(2) Using a vaporizer (VA-05 type, manufactured by Mitsubishi Chemical Corporation), the water in the sample is volatilized at 150 ° C. and introduced into a moisture meter. Measurement is performed using a Karl Fischer moisture meter (CA-03 type, manufactured by Mitsubishi Chemical Corporation).
(3) Moisture content (%) = 0.1 × (W / F) is calculated assuming that the moisture content (μg) indicated by the moisture meter is W and the weighed sample amount is F (mg).

(Method of acetyl substitution degree)
It is measured from 13C-NMR spectrum by the method described in Polymer Journal (Polymer Journal vol. 17.1065-1069 (1985)).

1. 1. Production of retardation plate with moisture-proof layer 1-1. Production of Retardation Plate (1) Composition A cellulose acetate dope (high concentration solution) having the following composition was produced. The retardation increasing agent is the following compound.

────────────────────────────────────
Methylene chloride (MC) dope composition ─────────────────────────────────────
Cellulose acetate (degree of acetylation is listed in Table 1) 100 parts by weight Triphenyl phosphate 10.0 parts by weight Biphenyl diphenyl phosphate 5.0 parts by weight Methylene chloride 565.6 parts by weight Methanol 49.2 parts by weight Retardation increasing agent Listed in Table 1 Silica fine particles (particle size: 20 nm) 0.05 parts by mass ───────────────────────────────── ───

────────────────────────────────────
Methyl acetate (MA) dope composition ────────────────────────────────────
Cellulose acetate (degree of acetylation is listed in Table 1) 118 parts by weight Triphenyl phosphate 9.19 parts by weight Biphenyl diphenyl phosphate 4.60 parts by weight Tribenzylamine 2.36 parts by weight Methyl acetate 530 parts by weight Ethanol 99.4 parts by weight Part Butanol 33.1 parts by mass Retardation increasing agent listed in Table 1 Silica fine particles (particle size: 20 nm) 0.05 parts by mass ───────────────────── ───────────────

(2) Dissolution The MC system was dissolved using a room temperature dissolution method, and the MA system was dissolved using a cooling dissolution method to prepare a dope. In any method, 20% by mass of cellulose acetate collected from the film-forming scraps described later was added. All of these cellulose acetates were dried at 120 ° C. for 2 hours or more so that the water content was 1% by mass or less.

(2a) Room temperature dissolution method The above compound was gradually added to a solvent while stirring well, and allowed to swell for 3 hours at room temperature (25 ° C). The resulting swollen mixture was dissolved in a mixing tank with a reflux condenser at 50 ° C. with stirring.

(2b) Cooling / dissolving method The above compound was gradually added to the solvent while stirring well, and allowed to swell for 3 hours at room temperature (25 ° C.). The obtained swollen mixture was slowly stirred at −8 ° C./min to −30 ° C., then cooled to the temperature shown in Table 1, and after 6 hours, the temperature was raised at + 8 ° C./min. At the stage where the sol-solation progressed to some extent, stirring of the contents was started. The dope was obtained by heating to 50 ° C.

(3) Film formation The film was selected from the following two methods and listed in Table 1. In either method, after film-forming and before winding, trimming 15 cm at both ends, and knurling (thickening processing) with a height of 50 μm and a width of 1 cm at both ends, unstretched with a width of 1.5 m and a length of 3000 m A cellulose acetate film was obtained. In addition, a cellulose acetate is isolated from the cellulose acetate film waste (film formation waste) trimmed here, is mixed as a dope raw material as mentioned above, and is reused.

(3a) Single-layer film formation The solution (dope) obtained by the above method is filtered through a filter paper (No. 244 manufactured by Azumi Filter Paper Co., Ltd.) and a filter cloth manufactured by Nell, and then sent to a pressure die with a quantitative gear pump. Liquid was cast using a band casting machine having an effective length of 6 m so that the final film thickness after drying and stretching was as shown in Table 2. The band temperature was 0 ° C. When it is blown for 2 seconds to dry and the volatile content in the film reaches 50% by weight, the film is peeled off from the band, and further 3 minutes at 100 ° C, 5 minutes at 130 ° C, and 5 minutes at 160 ° C. The film was shrunk freely without being fixed, and dried stepwise to evaporate the remaining solvent to 1% by mass or less, and then wound up.

(3b) Multilayer casting Using a three-layer co-casting die, the dope having the above composition from the inner layer, and the dope diluted by increasing the amount of solvent to 10% on both sides are simultaneously ejected onto the metal support to form a multilayer casting. Thereafter, the cast film was peeled off from the support and dried to produce a three-layer cellulose acetate film laminate (inner layer thickness: each surface layer thickness = 8: 1) of the present invention. After drying at 70 ° C. for 3 minutes and at 130 ° C. for 5 minutes, the film was peeled off from the glass plate and dried stepwise at 160 ° C. for 30 minutes to evaporate the solvent to 1% by mass or less. I took it.

(4) Stretching Stretched under the conditions described in Table 1 to obtain a retardation plate.
The water content before stretching was selected from a dipping method or a water vapor method. The former was immersed in warm water at 90 ° C., and the latter was exposed to water vapor at 120 ° C. to obtain the moisture content described in Table 1. Prior to the hydrous treatment, it was dried and heat-treated under the conditions shown in Table 1.
Stretching was performed in the longitudinal (MD) direction using nip rolls, and the magnifications are listed in Table 1. In the case of single-stage stretching, two pairs of nip rolls were used, and in the case of multi-stage stretching, three or more pairs of nip rolls arranged in tandem were used continuously. In the case of multi-stage stretching, the total draw ratio is a product of the respective draw ratios. In addition, the aspect ratio of the stretching in each stage (distance between center axes of nip rolls / width of original fabric before stretching) is shown in Table 1. The wrap angles listed in Table 1 were adjusted so that all nip rolls were the same.
The stretching time (stretching time required from the start to the end of stretching) was 20 seconds. In the case of multi-stage stretching, the stretching time is from the start of the first stage to the end of the final stage.
The stretching temperature was adjusted so that the temperature at both ends was 20 ° C. higher than the central portion.
The stretched film was trimmed by 3 cm at both ends and then wound up. In this way, a stretched film having a width of 1.3 m and a length of 3000 m was obtained.
The optical properties of the obtained retardation plate were evaluated by the methods described above. The results are listed in Table 2. The scratches shown in Table 2 were expressed as a value converted per unit area by observing 10 cm square of reflected light on the film surface under a 100 W tungsten lamp, counting the number of star-like bright spots.

1-2. Formation of moisture-proof layer The moisture-proof layer shown in Table 3 was provided on the retardation plate or transparent protective film by coating as shown in Table 4.
The moisture permeation amount of the moisture-proof layer was determined by coating the substrate (polyvinylidene fluoride film) with poor adhesion and then peeling off and measuring the moisture permeation amount by the above method.
Further, before applying the moisture-proof layer, one of the following methods was selected (described in Table 4) to saponify the surface of the retardation plate or transparent protective film.

(Ii) Coating method The coating was applied to one side of a retardation plate or transparent protective film with a # 3 bar at 60 ° C, washed with water after 30 seconds, and dried at 60 ° C.
The saponification solution used was a 1.5 N concentration solution in which potassium hydroxide was dissolved in isopropanol / propylene glycol / water (volume ratio: 70/15/15).

(B) Immersion method The phase difference plate or transparent protective film was immersed in a 1N aqueous solution of sodium hydroxide at 40 ° C for 3 minutes, washed with water, and dried at 60 ° C for 3 minutes.

1-3. Heat treatment The retardation plate provided with the moisture-proof layer was heat-treated at the temperature and time described in Table 1 (relative humidity: 10 to 20%). After the moisture barrier layers on the front and back sides were shaved off with a razor, DSC measurement was performed by the above-described method, the relaxation heat quantity was measured, and the results shown in Table 2 were obtained.

2. Preparation of circularly polarizing plate A retardation plate, a linearly polarizing film, and a moisture-proof layer described in Table 3 were laminated in the order described in Table 4 to prepare a circularly polarizing plate. For the moisture-proof layer provided on the transparent protective film, the cellulose triacetate film used for the transparent protective film was saponified by a method selected from the following methods, and provided thereon by coating.

(A) Coating method The coating was applied to one side of a retardation plate at # 3 bar at 60 ° C., washed with water after 30 seconds, and dried at 60 ° C.
The saponification solution used was a 1.5 N concentration solution in which potassium hydroxide was dissolved in isopropanol / propylene glycol / water (volume ratio: 70/15/15).

(B) Immersion method After immersing in a 1N aqueous solution of sodium hydroxide at 40 ° C. for 3 minutes, it was washed with water and dried at 60 ° C. for 3 minutes.

The linear polarizing film was laminated so that the transmission axis (absorption axis) of the linear polarizing film and the slow axis (stretching axis) of the phase difference plate were 45 degrees. These laminations were carried out with the retardation plate as it was (full width without slitting) after adjusting the humidity to a temperature of 25 ° C. and a relative humidity of 60%.
When the optical properties of the obtained circularly polarizing plate were examined, the retardation value hardly changed in a wide wavelength region (450 to 590 nm) during and after 60 ° C., and almost perfect circularly polarized light was observed. Has been achieved.

The linear polarizing film was manufactured by the following method.
(1) Polyvinyl alcohol casting Polyvinyl alcohol (PVA) having an average polymerization degree of 4000 and a saponification degree of 99.8 mol% was dissolved in water to obtain a 4.0% aqueous solution. This solution was cast and dried, peeled off from the band, and an unstretched polyvinyl alcohol film was obtained.
(2) Iodine impregnation An unstretched polyvinyl alcohol film was immersed in an aqueous solution of 2.0 g / liter of iodine and 4.0 g / liter of potassium iodide at 25 ° C. for 240 seconds, and further at 25 ° C. in an aqueous solution of boric acid 10 g / liter. For 60 seconds, and then in a water washing tank at 20 ° C. for 10 seconds.

(3) Stretching The iodine-impregnated film was stretched 5.3 times at 80 ° C. without being dried. At this time, those stretched in parallel to the longitudinal direction of the original fabric (unstretched polyvinyl alcohol film) are described as “parallel” stretching, and those stretched at 45 degrees in the longitudinal direction of the original fabric are referred to as “oblique” stretching. . Parallel stretching was accomplished by using a pair of nip rolls and rotating the outlet nip roll at a high speed. Diagonal stretching was performed by using a tenter bent in a "<" shape at 45 degrees, stretching 5.3 times up to the bent portion, and then stretching in the oblique direction by carrying it while keeping it parallel. At this time, the speeds of the left and right tenter clips were the same.
After stretching, the film was dried at 80 ° C. for 5 minutes to obtain a long linear polarizing film. All of these had a width of 1290 mm and a thickness of 20 μm.

(4) Attaching the transparent protective film Two transparent protective films (Fujitac, Fuji Photo Film Co., Ltd.) using a linear polarizing film as an adhesive with a 3% by weight aqueous solution of polyvinyl alcohol (PVA-117H, manufactured by Kuraray Co., Ltd.). )), And a transparent protective film was attached. The retardation (Re550) of the transparent protective film is 3.0 nm. The surface of the transparent protective film in contact with the linearly polarizing film was previously saponified by the above immersion method.

Lamination of the retardation plate, the linear polarizing film, the transparent protective film, and the moisture-proof layer was performed with the retardation plate as it was (full width without slitting) after adjusting the humidity to a temperature of 25 ° C. and a relative humidity of 60%.
The retardation at a wavelength of 550 nm was measured at a temperature of 25 ° C. and a relative humidity of 60% (first measurement), and this was designated as Re (0).
This was put in an air thermostat having a temperature of 60 ° C. and a relative humidity of 10%, taken out in a temperature of 25 ° C. and a relative humidity of 60% after 3 hours, and allowed to stand for 30 minutes, and then measured for retardation at a wavelength of 550 nm in this environment. (Second measurement). This is Re (1). A value obtained by subtracting Re (1) from Re (0) is a change in retardation for 3 hours at a temperature of 60 ° C. and a relative humidity of 10%, which corresponds to the first process described above. In Table 4, “60 ° C. 3 hr” is shown.

Place in an air constant temperature bath with a temperature of 60 ° C. and a relative humidity of 10%, and after 50 hours, take out in a temperature of 25 ° C. and a relative humidity of 60%, leave it for 30 minutes, and measure the retardation at a wavelength of 550 nm in this environment. (Third measurement). This is Re (2). A value obtained by subtracting Re (1) from Re (2) is a retardation change from 3 hours to 50 hours at a temperature of 60 ° C. and a relative humidity of 10%, which corresponds to the second process described above. In Table 4, “60 ° C. 3-50 hr” is shown.
After putting it in an air thermostat having a temperature of 60 ° C. and a relative humidity of 10% for 50 hours, it was taken out in a temperature of 25 ° C. and a relative humidity of 60% and allowed to stand for 24 hours, and then retardation measurement at a wavelength of 550 nm was performed in this environment ( Fourth measurement). This is Re (3). The value obtained by subtracting Re (3) from Re (3) is the retardation change from 50 hours at a temperature of 60 ° C. and 10% relative humidity to 24 hours at a temperature of 25 ° C. and 60% relative humidity. It corresponds to. In Table 4, “60 ° C. 50 hr-25 ° C. 60% 24 hr” is shown.

After putting it in an air thermostat having a temperature of 60 ° C. and a relative humidity of 10% for 50 hours, it was taken out in a temperature of 25 ° C. and a relative humidity of 60% and allowed to stand for 240 hours, and then retardation measurement at a wavelength of 550 nm was performed in this environment ( 5th measurement). This is Re (4). The value obtained by subtracting Re (4) from Re (3) is the retardation change after 24 hours to 240 hours at 25 ° C and 60% relative humidity after 50 hours at 60 ° C and 10% relative humidity. This corresponds to the aforementioned fourth process. In Table 4, “25 ° C. 60% 24 hr-240 hr” is shown.
As for these retardation changes, similar values were obtained at the center of the stretched film and the end in the width direction.
Next, a laminate obtained by excluding only the retardation plate from the circularly polarizing plate described in Table 4 was prepared at a temperature of 25 ° C. and a relative humidity of 10%, and the moisture permeability was measured by the above method using this. The results shown in the table were obtained. Thereby, the amount of moisture reaching the retardation plate was determined. The reason why the moisture permeability of Sample No. 22 is smaller than the value obtained by using the above equation (A) from the moisture permeability coefficient and thickness of the moisture barrier layer is due to the moisture resistance of the laminated polarizing plates.

3. Production of Image Display Device (1) Production of TN-type Reflective Liquid Crystal Display Device A glass substrate provided with an ITO transparent electrode and a glass substrate provided with an aluminum reflective electrode formed with fine irregularities were prepared. A polyimide alignment film (SE-7992, manufactured by Nissan Chemical Industries, Ltd.) was formed on each of the electrode sides of the two glass substrates, and a rubbing treatment was performed. The two substrates were stacked with the alignment film facing each other through a 3.4 μm spacer. The orientation of the substrate was adjusted so that the rubbing directions of the two alignment films intersected at an angle of 110 °. Liquid crystal (MLC-6252, manufactured by Merck) was injected into the gap between the substrates to form a liquid crystal layer. In this way, a TN liquid crystal cell (12 inches diagonal) having a twist angle of 70 ° and a value of Δnd of 269 nm was manufactured.
The prepared circularly polarizing plate was conditioned at a temperature of 25 ° C. and a relative humidity of 60% on the side of the glass substrate provided with the ITO transparent electrode, and then pasted from the opposite side of the polarizing layer.
A rectangular wave voltage of 1 kHz was applied to the manufactured reflective liquid crystal display device. As a result of visual evaluation with white display of 1.5 V and black display of 4.5 V, it was confirmed that neutral gray was displayed with no color in both white display and black display.
Next, the contrast ratio of the reflected luminance was measured using a measuring machine (EZcontrast 160D, manufactured by Eldim), and the contrast ratio from the front and the viewing angle at which the contrast ratio was 3 were measured.
In sample numbers 1 to 3, 5 to 10, and 12 to 21, the contrast ratio from the front is immediately after the liquid crystal display device is manufactured, during 60 ° C., and thereafter at a temperature of 25 ° C. and a relative humidity of 60%. The viewing angle at which the contrast ratio was 3 was 130 ° up and down and 130 ° left and right. Further, the same result was obtained at the center and the end in the width direction of the retardation plate.
Sample Nos. 4, 11, and 22 had a contrast ratio of 25 from the front immediately after fabrication, and the viewing angles at which the contrast ratio was 3 were 120 ° vertically and 120 ° horizontally, After that, the contrast ratio from the front is reduced to a maximum of 12 over time at a temperature of 25 ° C. and a relative humidity of 60%, and the viewing angles at which the contrast ratio becomes 10 are both reduced to a maximum of 60 ° up and down and 60 ° to the left and right. Was.

(2) Production of STN type reflective liquid crystal display device A glass plate provided with an ITO transparent electrode and a glass substrate provided with a flat aluminum reflective electrode were prepared. A polyimide alignment film (SE-150, manufactured by Nissan Chemical Industries, Ltd.) was formed on the electrode sides of the two glass substrates, respectively, and a rubbing treatment was performed. The two substrates were stacked with a 6.0 μm spacer so that the alignment films face each other. The orientation of the substrate was adjusted so that the rubbing directions of the two alignment films intersected at an angle of 60 °. Liquid crystal (ZLI-2777, manufactured by Merck & Co., Inc.) was injected into the gap between the substrates to form a liquid crystal layer. In this way, an STN type liquid crystal cell (12 inches diagonal) having a twist angle of 240 ° and a Δnd value of 791 nm was manufactured.
On the side of the glass substrate provided with the ITO transparent electrode, the internal diffusion sheet (IDS, manufactured by Dai Nippon Printing Co., Ltd.) and the circular polarizing plate described above were conditioned at a temperature of 25 ° C. and a relative humidity of 60%. Each of them was pasted through an adhesive so that the polarizing plate was the outermost layer.
A rectangular wave voltage of 55 Hz was applied to the produced reflective liquid crystal display device. As a result of visual evaluation with a black display of 2.0 V and a white display of 2.5 V, it was confirmed that neutral gray was displayed with no color in both the white display and the black display.
Next, the contrast ratio of the reflected luminance was measured using a measuring device (EZcontrast 160D, manufactured by Eldim), and the contrast ratio from the front and the viewing angle at which the contrast ratio was 3 were measured.
In sample numbers 1 to 3, 5 to 10, and 12 to 21, the contrast ratio from the front is high immediately after the liquid crystal display device is manufactured, even during the aging at 60 ° C., and thereafter at the temperature of 25 ° C. and the relative humidity of 60%. The viewing angles at which the contrast ratio was 3 were 130 ° up and down and 130 ° left and right. Further, the same result was obtained at the center and the end in the width direction of the retardation plate.
Sample Nos. 4, 11, and 22 had a contrast ratio of 25 from the front immediately after fabrication, and the viewing angles at which the contrast ratio was 3 were 120 ° vertically and 120 ° horizontally, After this, the contrast ratio from the front is reduced to a maximum of 12 over time at a temperature of 25 ° C. and a relative humidity of 60%, and the viewing angles at which the contrast ratio is 10 are both reduced to a maximum of 60 ° up and down and 60 ° to the left and right. It was.

(3) VA-type liquid crystal display device The VA-type liquid crystal display device is, in order from the bottom, a lower glass substrate, an insulating film, a thin film transistor, a reflector, a lower alignment film, a liquid crystal, an upper alignment film, an ITO transparent electrode, an overcoat layer, It consists of a color filter and an upper glass substrate.
A glass substrate provided with an ITO transparent electrode and a glass substrate provided with an aluminum reflective electrode formed with fine irregularities were prepared. Vertical alignment films (RN783, manufactured by Nissan Chemical Industries, Ltd.) were prepared for the upper alignment film and the lower alignment film, respectively, and subjected to rubbing treatment. Two substrates were stacked with a 1.7 μm spacer so that the alignment films face each other. The orientation of the substrate was adjusted so that the rubbing directions of the two alignment films intersected at an angle of 110 °. A liquid crystal layer having a Δn = 0.08 and Δε = −4 (manufactured by Merck) was injected into the gap between the substrates by a vacuum injection method. In this way, a VA liquid crystal cell having a twist angle of 45 ° and a Δnd value of 135 nm was produced.
From the glass substrate side on the side of the glass substrate provided with the ITO transparent electrode, the retardation plate provided with the moisture proof layer and the commercially available polarizing plate (HLC2-5618HCS, manufactured by Sanlitz Co., Ltd.) in this order via the adhesive And laminated. When the retardation film provided with the moisture-proof layer and the polarizing film were bonded together, they were bonded so that the absorption axis of the polarizing film and the slow axis of the retardation film were 45 °.
In Sample Nos. 1-3, 5-10, and 12-21, the contrast ratio from the front is 25 immediately after the production of the liquid crystal display device, during 60 ° C., and thereafter at a temperature of 25 ° C. and a relative humidity of 60%. The viewing angles at which the contrast ratio was 3 were 120 ° or more vertically and 120 ° or more horizontally. Further, the same result was obtained at the center and the end in the width direction of the retardation plate.
Sample Nos. 4, 11, and 22 had a contrast ratio of 25 from the front immediately after fabrication, and the viewing angles at which the contrast ratio was 3 were 120 ° or more in the vertical direction and 120 ° or more in the horizontal direction. During and after this, at a temperature of 25 ° C. and a relative humidity of 60%, the contrast ratio from the front decreases to a maximum of 12, and the viewing angle at which the contrast ratio becomes 10 is 60 ° at the maximum and 60 ° at the left and right. It was falling.

(4) ECB type liquid crystal display device According to Example 1 of JP-A-11-316378, the second transparent support was a retardation plate provided with the moisture-proof layer. However, when this was bonded to the polarizing film, the polarizing film was bonded so that the absorption axis of the polarizing film and the slow axis of the retardation plate were 45 degrees. Using this, an ECB type liquid crystal display element was produced according to Example 6 of JP-A-11-316378.
In Sample Nos. 1-3, 5-10, and 12-21, the contrast ratio from the front is 25 immediately after the production of the liquid crystal display device, during 60 ° C., and thereafter at a temperature of 25 ° C. and a relative humidity of 60%. The viewing angles at which the contrast ratio was 3 were 120 ° or more vertically and 120 ° or more horizontally. Further, the same result was obtained at the center and the end in the width direction of the retardation plate.
Sample Nos. 4, 11, and 22 had a contrast ratio of 25 from the front immediately after fabrication, and the viewing angles at which the contrast ratio was 3 were 120 ° or more in the vertical direction and 120 ° or more in the horizontal direction. During and after this, at a temperature of 25 ° C. and a relative humidity of 60%, the contrast ratio from the front decreases to a maximum of 12, and the viewing angle at which the contrast ratio becomes 10 is 60 ° at the maximum and 60 ° at the left and right. It was falling.

(5) Mounting on a transflective product The polarizing plate, λ / 2 plate, λ / 4 plate on the upper part of the liquid crystal cell of the liquid crystal display part of Cybershot (manufactured by SONY) is peeled off, and the above moisture-proof layer is formed from the glass substrate side. And a commercially available polarizing plate (HLC2-5618HCS, manufactured by Sanritz Co., Ltd.) were laminated in this order via an adhesive. When the retardation film and the polarizing film were bonded together, the polarizing film was bonded so that the absorption axis of the polarizing film and the slow axis of the retardation film were 45 °.
In sample numbers 1 to 3, 5 to 10, and 12 to 21, the contrast ratio from the front is high immediately after the liquid crystal display device is manufactured, even during the aging at 60 ° C., and thereafter at the temperature of 25 ° C. and the relative humidity of 60%. The viewing angles at which the contrast ratio was 3 were 120 ° or more in the vertical direction and 120 ° or more in the left and right directions. Further, the same result was obtained at the center and the end in the width direction of the retardation plate.
Sample Nos. 4, 11, and 22 had a contrast ratio of 25 from the front immediately after fabrication, and the viewing angles at which the contrast ratio was 3 were 120 ° or more in the vertical direction and 120 ° or more in the horizontal direction. During and after this, the contrast ratio from the front decreases to a maximum of 12 over time at a temperature of 25 ° C. and a relative humidity of 60%. It had fallen to.

(6) Mounting on a reflective liquid crystal display device The reflective liquid crystal display device with a touch panel (Sharp Corp., Zaurus) is used to peel off the touch panel / polarizing plate / retardation plate / polarizing plate and retardation plate of the liquid crystal cell, and the above moisture-proofing It replaced with the phase difference plate which provided the layer, and the commercially available polarizing plate (HLC2-5618HCS, the Sanritz Co., Ltd. product). At this time, the polarizing film was bonded so that the absorption axis of the polarizing film and the slow axis of the retardation plate were 45 °, and were bonded so that the contrast was maximized.
In sample numbers 1 to 3, 5 to 10, and 12 to 21, the contrast ratio from the front is high immediately after the liquid crystal display device is manufactured, even during the aging at 60 ° C., and thereafter at the temperature of 25 ° C. and the relative humidity of 60%. The viewing angles at which the contrast ratio was 3 were 120 ° or more in the vertical direction and 120 ° or more in the left and right directions. Further, the same result was obtained at the center and the end in the width direction of the retardation plate.
Sample Nos. 4, 11, and 22 had a contrast ratio of 25 from the front immediately after fabrication, and the viewing angles at which the contrast ratio was 3 were 120 ° or more in the vertical direction and 120 ° or more in the horizontal direction. During and after this, the contrast ratio from the front decreases to a maximum of 12 over time at a temperature of 25 ° C. and a relative humidity of 60%. It had fallen to.

Claims (3)

  A step of forming a cellulose acylate film from a cellulose acylate solution in which cellulose acylate is dissolved in a solvent containing 0.003 to 0.1% by mass of water; the temperature of the formed cellulose acylate film is 50 to 150 ° C. A step of heat-treating for 0.5 to 200 hours at a relative humidity of 0 to 10%; a step of stretching the heat-treated cellulose acylate film under a condition where the longitudinal / lateral stretch ratio is 0.3 to 2; A retardation plate made of a cellulose acylate film, a first transparent protective film, a linearly polarizing film, a second transparent protective film, and a moisture-proof layer, the retardation film, the first transparent protective film, the linearly polarizing film, and the second transparent film Laminated or stretched cellulose acylate films in the order of the protective film and with a moisture-proof layer between the retardation plate and the linear polarizing film The first transparent protective film and a phase difference plate made of beam, moisture barrier, linear polarizing film and method for manufacturing a polarizing plate, characterized by producing a polarizing plate by the process of the second transparent protective film laminated in this order.   From the retardation value of the retardation plate measured at a wavelength of 550 nm after adjusting the temperature of the produced polarizing plate at a temperature of 25 ° C. and a relative humidity of 60%, the polarizing plate was further heated at a temperature of 60 ° C. and a relative humidity of 10%. The method for producing a polarizing plate according to claim 1, wherein the retardation value of the retardation plate measured at a wavelength of 550 nm after being stored for 3 hours under conditions is less than 15 nm.   The produced polarizing plate was stored for 3 hours at a temperature of 60 ° C. and a relative humidity of 10%, and from the retardation value of the retardation plate measured at a wavelength of 550 nm, the polarizing plate was further subjected to a temperature of 60 ° C. and a relative humidity of 10%. The method for producing a polarizing plate according to claim 1, wherein a change in retardation value of the retardation plate measured at a wavelength of 550 nm after being stored for 47 hours is less than 15 nm.

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