JP3525543B2 - Manufacturing method of polarizing plate - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a polarizing plate.

[0002]

2. Description of the Related Art In recent years, the demand for polarizing plates has increased remarkably as the field of use of liquid crystal display devices such as notebook type word processors, personal computers, and liquid crystal televisions has expanded and the area has increased. Along with this, the requirements for the optical performance of polarizing plates have become more stringent, and in notebook type word processors, personal computers, and LCD TVs that use liquid crystal display devices, in order to make the display screen brighter and easier to see, it is more transparent and has a higher degree of polarization. Polarizing plates are required.

[0003]

As a polarizing plate using a film made of polyvinyl alcohol as a polarizer, for example, an iodine type polarizing plate is known, but it cannot be said that the performance is still satisfactory. Furthermore, development of a polarizing plate with improved optical performance is required.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have pasted an acetyl cellulose film on a polyvinyl alcohol polarizing film in which iodine is adsorbed and oriented, This is temperature 40
3 to 5 in an atmosphere of ~ 90 ° C and humidity of 50 to 95% RH
The inventors have found that a polarizing plate excellent in transmittance and polarization degree can be produced by performing high temperature humidification treatment for 00 hours, and have reached the present invention.

That is, according to the present invention, a polarizing plate obtained by adsorbing and orienting iodine on a polyvinyl alcohol film and adhering acetyl cellulose film on both surfaces of the film is used at a temperature of 40 to 90 ° C. and a humidity of 50 to 95% RH. A method of manufacturing a polarizing plate, characterized by performing a humidification treatment in an atmosphere for 3 to 500 hours.

The present invention will be described in detail below. The polyvinyl alcohol-based film is not particularly limited, and a polyvinyl alcohol-based film that is commonly used for a polarizer can be used. For example, polyvinyl alcohol film, polyvinyl formal film,
Examples thereof include polyvinyl acetal film and poly (ethylene-vinyl acetate) copolymer film.

The thickness of the polyvinyl alcohol film is not particularly limited, and may be, for example, 50 to 150 μm.
The thing of about m is used. The polymerization degree of polyvinyl alcohol is, for example, about 1000 to 10000, and preferably about 1700 to 5000 is used. The saponification degree is, for example, about 80 to 100 mol%, preferably about 98 to 100 mol%.

The method of adsorbing and orienting iodine is not particularly limited, and a known method can be used.
For example, there is a method of adsorbing and orienting iodine on a uniaxially stretched polyvinyl alcohol film. The method for uniaxially stretching the polyvinyl alcohol film is not particularly limited, but a dry stretching method is preferable. Then, the glass transition temperature of the polyvinyl alcohol-based film to 160 ° C.
Then, it is preferable to stretch the film about 4 to 7 times.

As a method for adsorbing and orienting iodine on a uniaxially stretched polyvinyl alcohol film, for example, a uniaxially stretched polyvinyl alcohol film is used.
A method of immersing in an aqueous solution of iodine and potassium iodide can be mentioned. The amount of iodine and potassium iodide is, for example, 1 part of water.
About 0.01 to 0.5 parts by weight of iodine with respect to 00 parts by weight,
The potassium iodide is about 0.5 to 10 parts by weight.

After the iodine is adsorbed and oriented, it is preferably treated with a boric acid-containing aqueous solution. The treatment method is not particularly limited, but a method of immersing in a boric acid-containing aqueous solution is preferable. The amount of boric acid is not particularly limited. For example, boric acid is about 2 to 15 parts by weight with respect to 100 parts by weight of water, and preferably boric acid is about 7 to 10 parts by weight with respect to 100 parts by weight of water. The boric acid-containing aqueous solution preferably contains potassium iodide, and the amount thereof is, for example,
It is about 2 to 20 parts by weight with respect to 100 parts by weight of water,
More preferably, it is about 5 to 15 parts by weight.

An acetylcellulose film is laminated on both sides of the film in which iodine is adsorbed and oriented. Examples of the acetyl cellulose-based film include a triacetyl cellulose film and a diacetyl cellulose film. Although the thickness of the acetyl cellulose-based film is not particularly limited, for example, a film having a thickness of about 50 to 200 μm is used, and for example, a triacetyl cellulose film manufactured by Fuji Photo Film Co., Ltd.
0) can be mentioned.

The film to which the acetyl cellulose film is laminated has a temperature of about 40 to 90 ° C. and a humidity of about 50.
~ 95% RH for about 3 to 500 hours, preferably at a temperature of about 60 to 80 ° C and a humidity of about 60 to 90% RH.
Is humidified for about 6 to 200 hours in the atmosphere. For the treatment, for example, a constant temperature and constant humidity machine can be used.

[0013]

According to the present invention, it is possible to manufacture a polarizing plate having excellent transmittance and polarization degree.

[0014]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited to these. The evaluation method is as follows.

The transmittance T was calculated by Equation 1 from the spectral transmittance τ (λ) obtained every 10 nm in the wavelength region of 400 to 700 nm. In the formula, P (λ) is standard light (C light source)
, Y (λ) is a color matching function based on the 2-degree visual field X, Y, Z system. Spectral transmittance τ (λ) is Shimadzu UV220
It was measured using a 0 spectrophotometer.

[0016]

[Formula 1]

The transmissivity in the case where two polarizing plates are stacked so that the respective polarizers have the same orientation direction is the parallel transmittance Tp, and the two polarizing plates are orthogonal to each other in the orientation direction. The degree of polarization P was calculated by Equation 2 with the transmittance in the case of overlapping as described above set as the orthogonal transmittance Tc.

[0018]

[Formula 2]

Example 1 A polyvinyl alcohol film (Kuraray Co., Ltd .: Kuraray Vinylon # 7500) was uniaxially stretched at a stretching temperature of 110 ° C. at a stretching ratio of 5.0 to obtain a polarizing substrate. The polarizing substrate was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.075 / 5/100 for 60 seconds while maintaining the tension state during stretching. Next, it was immersed for 300 seconds in a boric acid-containing aqueous solution at 65 ° C. in which the weight ratio of potassium iodide / boric acid / water was 6 / 7.5 / 100. This was washed with pure water and dried. A triacetyl cellulose film (Fuji TAC-UV80: manufactured by Fuji Photo Film Co., Ltd.) was attached to both surfaces of the dried film using a polyvinyl alcohol-based adhesive. The polarizing plate thus obtained had a transmittance and a degree of polarization of 40.0% and 100.0%, respectively. The polarizing plate was humidified for 200 hours in an atmosphere of a temperature of 60 ° C. and a humidity of 90% RH, and then its optical characteristics were measured. The transmittance was 43.8% and the polarization degree was 99.8%.

Example 2 A polarizing plate was prepared in the same manner as in Example 1. The polarizing plate was humidified for 6 hours in an atmosphere of a temperature of 80 ° C. and a humidity of 90% RH, and then its optical characteristics were measured. Transmittance is 44.4
%, And the polarization degree was 99.7%.

Example 3 A polyvinyl alcohol film (manufactured by Kuraray Co., Ltd., polymerization degree: 2400) was drawn at a drawing temperature of 110 ° C. and a draw ratio of 5.0.
It was uniaxially stretched twice to obtain a polarizing substrate. While keeping the polarizing substrate in a tension state, it was immersed for 60 seconds in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.075 / 5/100. Next, it was immersed for 300 seconds in a boric acid-containing aqueous solution at 68 ° C. in which the weight ratio of potassium iodide / boric acid / water was 6 / 7.5 / 100. This was washed with pure water and dried. Using a polyvinyl alcohol adhesive on both sides of the dried film, a triacetyl cellulose film (Fuji TA
C-UV80: manufactured by Fuji Photo Film Co., Ltd. was attached. The transmittance and the degree of polarization of the polarizing plate thus obtained were 43.1% and 99.9%, respectively. The polarizing plate was humidified for 40 hours in an atmosphere of a temperature of 60 ° C. and a humidity of 90% RH, and then its optical characteristics were measured. The transmittance was 43.8% and the polarization degree was 99.8%.

Example 4 A polarizing plate was prepared in the same manner as in Example 3. This polarizing plate was humidified for 7 hours in an atmosphere of a temperature of 70 ° C. and a humidity of 90% RH, and then the optical characteristics were measured. Transmittance is 43.8
%, And the polarization degree was 99.8%.

Example 5 A polyvinyl alcohol film (manufactured by Kuraray Co., Ltd., polymerization degree: 4000) was stretched at a stretching temperature of 110 ° C. and a stretching ratio of 4.5.
It was uniaxially stretched twice to obtain a polarizing substrate. The polarizing substrate was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.075 / 5/100 for 60 seconds while maintaining a tension state. Next, it was immersed for 300 seconds in a boric acid-containing aqueous solution at 70 ° C. in which the weight ratio of potassium iodide / boric acid / water was 6 / 7.5 / 100. This was washed with pure water and dried. Using a polyvinyl alcohol adhesive on both sides of the dried film, a triacetyl cellulose film (Fuji TA
C-UV80: manufactured by Fuji Photo Film Co., Ltd. was attached. The transmittance and the polarization degree of the thus obtained polarizing plate were 43.7% and 99.9%, respectively. Set this polarizing plate to a temperature of 6
After humidifying for 120 hours in an atmosphere of 0 ° C. and humidity of 90% RH, the optical characteristics were measured. The transmittance was 44.0% and the polarization degree was 99.9%.

Comparative Example 1 A polarizing plate was prepared in the same manner as in Example 1. This polarizing plate was humidified in an atmosphere of a temperature of 95 ° C. and a humidity of 98% RH for 6 hours, and then its optical characteristics were measured. Transmittance is 59.0
%, And the polarization degree was 52.6%.

[0025]

[Table 1]

Continuation of the front page (56) Reference JP-A-5-119216 (JP, A) JP-A-2-253204 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 5 / 30

Claims (4)

(57) [Claims] 1. A polarizing plate in which iodine is adsorbed and oriented on a polyvinyl alcohol-based film, and then an acetyl cellulose-based film is attached to both surfaces of the film , the temperature is set to 40 to 90.
3 to 500 hours in an atmosphere of ℃ and humidity of 50 to 95% RH
Method for producing a polarizing plate, characterized in that during humidification process. 2. The polyvinyl alcohol film has a degree of polymerization of 1,000 to 10,000 and a degree of saponification of 80 to 1.
00 Method person according claim 1 mole%. 3. A polyvinyl alcohol film is adsorbed and oriented iodine and then was immersed in the aqueous solution containing boric acid, methods who claim 1 wherein the bonding acetylcellulose-based film on both surfaces of the film. 4. A temperature of 60 to 80 ° C. and a humidity of 60 to 90%
Method person of claim 1 to 6 to 200 hours hot humidification in an atmosphere of RH.