阅读说明：本技术 一种高透光率高偏振度的偏光片的制备方法 (Preparation method of polaroid with high light transmittance and high polarization degree ) 是由 吴福胜 唐成宏 吴云柱 向学毅 李世琴 刘密密 于 2021-09-28 设计创作，主要内容包括：本发明公开了一种高透光率高偏振度的偏光片的制备方法,是将PVA光学薄膜水洗与膨润、染色、清洗、单轴延伸、清洗与补色后进行干燥形成偏光膜,偏光膜的两侧再各贴合保护层制得偏光片,在水洗与膨润过程中进行横向拉伸,将PVA膜出膨润槽的横向膨润度控制在120％-160％。本发明的方法能够明显提升碘离子进入PVA膜中的速度,解决在提高透光率的情况下偏振度下降的问题,所获得的偏光片具有透光率高、偏振度高的优点,可以应用于OLED等显示领域。(The invention discloses a preparation method of a polaroid with high light transmittance and high polarization degree, which comprises the steps of washing and swelling a PVA optical film, dyeing, cleaning, extending along a single axis, cleaning and complementing colors, drying to form a polarizing film, respectively attaching protective layers to two sides of the polarizing film to prepare the polaroid, and stretching transversely in the washing and swelling processes to control the transverse swelling degree of the PVA film out of a swelling tank to be 120-160%. The method provided by the invention can obviously improve the speed of iodine ions entering the PVA film, solves the problem of polarization degree reduction under the condition of improving the light transmittance, and the obtained polarizer has the advantages of high light transmittance and high polarization degree, and can be applied to the display fields of OLED and the like.)

1. A preparation method of a polaroid with high light transmittance and high polarization degree is characterized by comprising the following steps: and carrying out moderate transverse stretching in the steps of washing and swelling the PVA optical film in the polaroid production process.

2. A method for preparing a polarizer with high transmittance and high degree of polarization according to claim 1, wherein: and controlling the transverse swelling degree of the PVA optical film after washing and swelling to be not less than 120%.

3. A method for preparing a polarizer with high transmittance and high degree of polarization according to claim 2, wherein: the transverse swelling degree of the PVA optical film after washing and swelling is controlled to be 120-160%.

4. A method for preparing a polarizer having high transmittance and high degree of polarization according to claim 1, 2 or 3, wherein: the tension of the transverse stretching is controlled to be 10-80N, and the time is controlled to be 10-300 s.

5. A method for preparing a polarizer with high transmittance and high degree of polarization according to claim 4, wherein: the tension of the transverse stretching is controlled to be 20-50N, the time is controlled to be 20-120 s, and the transverse swelling degree of the PVA optical film after water washing and swelling is controlled to be 130-150%.

Technical Field

The invention belongs to the technical field of optical components, and particularly relates to a preparation method of a polaroid.

Background

Organic Light Emitting Displays (OLEDs) are now the standard of mobile phone screens of flagships of various large manufacturers, and the OLED screens can control colors at a pixel level, so that color accuracy is nearly perfect, the quality requirements on required polarizers are higher, the polarizers are required to be thinner, monomer light transmittance is high, and polarization degree is high.

The existing method for producing the polaroid mainly comprises the steps of washing a PVA optical film, swelling, dyeing, extending in a single axis, curing by boric acid to form a polarizing film, and respectively attaching protective layers to two sides of the polarizing film to obtain the polaroid. The ideal polarizer is that the higher the monomer transmittance is, the better the monomer transmittance is, and the higher the polarization degree is, the better, but the monomer transmittance and the polarization degree are contradictory, and the monomer transmittance is high, and the polarization degree can be reduced. Therefore, it is of great significance to research the preparation method of the polarizer with high monomer transmittance and high polarization degree.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a preparation method of a polarizer with high light transmittance and high polarization degree, and aims to obtain a polarizer with high monomer light transmittance and high polarization degree.

The present invention has been made in an effort to achieve the above object. The existing method for producing the polaroid mainly comprises the steps of washing and swelling a PVA optical film, dyeing (iodine solution is usually used as a dyeing solution), cleaning, performing uniaxial extension, cleaning and color compensation to form a polarizing film, drying, and then respectively attaching protective layers to two sides to obtain the polaroid, wherein the key steps are dyeing and stretching treatment of the PVA optical film. As shown in the attached drawings: FIG. 1 shows a state of a PVA optical film after swelling; FIG. 2 is a dyed PVA film, which has iodine adsorbed thereon; FIG. 3 shows a stretched PVA film, in which iodine is aligned in the direction of the PVA molecular chain to form a polarizing film.

In order to obtain a polarizer with a high degree of polarization, the total stretching ratio of the PVA optical film is preferably as high as possible, and generally 5 or more times, with respect to the original length. In the actual production process, in order to ensure that the plasticizer in the PVA film is completely washed out and the crystal region in the PVA film is completely destroyed, certain washing and swelling time is required. In order to ensure that the film does not have the conditions of wrinkles, stripes and the like in the production process, the PVA films in all the working procedures are in a 'tight' state, namely the PVA films in all the working procedures are extended to a certain extent. PVA membrane is when washing the swell, can the water absorption inflation, length and width all can the grow, but because the existence of tensile effect, can take place the shrink in the width direction, if the shrink is too big, the PVA molecular chain of subregion is arranged along tensile direction, in the dyeing link, it is difficult in the iodide ion gets into the PVA membrane, this will cause the polarization degree to descend, and if want the polarization degree to promote just need improve the concentration of the iodine in the dye vat, this luminousness that just causes the polaroid descends.

Further intensive research finds that the transverse swelling degree of the PVA optical film after being washed and swelled is controlled to be more than 120%, the speed of iodine ions entering the PVA film can be obviously improved, the problem of reduction of the polarization degree or reduction of the light transmittance can be greatly reduced, and the obtained polarizer has the advantages of high light transmittance and high polarization degree. The transverse swelling degree is the ratio of the film width to the initial film width, and because the film needs to be tightened in the water washing swelling link, the film has an extending effect in the working procedure, so that the transverse swelling degree at the swelling outlet is lower than 120%.

In view of the above, the present invention provides a method for preparing a polarizer with high transmittance and high polarization degree, which comprises the steps of performing moderate transverse stretching during the washing and swelling processes of a PVA optical film, then sequentially performing dyeing, cleaning, uniaxial extension, cleaning, color compensation and drying on the PVA optical film to form a polarizing film, and then respectively attaching transparent protective layers to two sides of the polarizing film to obtain the polarizer.

As the key of the invention, the transverse swelling degree of the PVA optical film after washing and swelling is controlled to be not less than 120 percent, and the specific method comprises the following steps: washing and swelling the PVA optical film in process water at the temperature of 20-40 ℃ for 30-600 s, and stretching the PVA optical film in the transverse direction moderately in the process.

Preferably, the tension of the transverse stretching is controlled to be 10-80N, the time is controlled to be 10-300 s, and finally, the transverse swelling degree of the PVA optical film after water washing and swelling is controlled to be 120-160%. The transverse swelling degree after washing and swelling is measured according to the following method: measuring the original film width L₀Width after washing and swellingDegree L₁(L) degree of swelling in the transverse direction₁/L₀)×100％。

More preferably, the tension of the transverse stretching is controlled to be 20-50N, the time is controlled to be 20-120 s, and the transverse swelling degree is controlled to be 130-150%. The transverse swelling degree is too large, the PVA molecular chain is too much stretched in the transverse direction, the subsequent longitudinal stretching orientation is not facilitated, and the polarization degree of the film is reduced.

As a follow-up of the invention, the high-transmittance high-polarization-degree polarizer is prepared according to the following method:

1. washing and swelling the PVA optical film in process water at the temperature of 20-40 ℃ for 30-600 s, and stretching the PVA optical film in the transverse direction moderately in the process.

2. The PVA film treated in step 1 is immersed in a solution containing a dichroic substance to be dyed. Aiming at the iodine polaroid taking iodine as a dichromatic substance, the solution in the dyeing tank is KI and I₂And boric acid, wherein the KI concentration is 1-3 wt%, and I₂The concentration is 0.01-0.5 wt%, the concentration of boric acid is 0.5-3 wt%, the solution temperature is 20-50 ℃, and the dyeing time is 50-300 s.

3. After dyeing, washing is performed to prevent or reduce transfer of the dichroic substance to a subsequent process, and the washing liquid is an aqueous solution containing a crosslinking agent. Usually an aqueous solution of boric acid, the concentration of boric acid is 0.5-3 wt%, the temperature in the cleaning process is usually 20-40 ℃, and the cleaning time is 10-200 s.

4. After the cleaning, the PVA optical film is uniaxially stretched, and in the actual production process, the PVA film is initially stretched to an original length, and the total stretching ratio is 4 to 8 times (preferably 5 to 6 times). The stretching liquid is an aqueous solution of boric acid and KI, the concentration of the boric acid is 0.5-3 wt%, and the concentration of the KI is 1-3 wt%.

5. After stretching, cleaning and color complementing are needed, the cleaning is consistent with the cleaning procedure in the step 3, the color complementing is color tone adjustment of the polaroid, the color complementing liquid is an aqueous solution of boric acid and KI, the concentration of the boric acid is 0.5-3 wt%, the concentration of the KI is 3-8 wt%, and the color complementing time is 10-100 s.

6. And drying the PVA film after color compensation by using an air blower at the drying temperature of 30-60 ℃ for 10-100 s.

7. After drying, respectively attaching transparent protective layers to two sides of the obtained polarizing film to obtain the polarizer, wherein the protective layers are generally cellulose triacetate films (TAC films), and the operation and treatment methods are conventional methods in the field, and refer to CN110172315A and CN108957616A, which are not described in detail herein.

Compared with the prior art, the invention has the beneficial effects that:

on the premise of basically not changing the existing polarizer manufacturing process, the PVA film is properly transversely stretched in the water washing and swelling links, the transverse swelling degree of the PVA film out of the swelling groove is controlled to be 120-160%, the speed of iodine ions entering the PVA film can be obviously increased, the problem of polarization degree reduction under the condition of improving the light transmittance can be solved, and the product quality is improved; the polaroid obtained by the method has the advantages of high light transmittance and high polarization degree, and can be applied to the display fields of OLED and the like.

Drawings

FIG. 1 shows the state of a PVA optical film after swelling in the production of a polarizer;

FIG. 2 shows a dyed PVA film in the production of a polarizer;

FIG. 3 shows a stretched PVA film in the production of a polarizer.

Detailed Description

In order to further explain the present invention, the following examples of the present invention are described in detail, which are implemented on the premise of the technical solution of the present invention, and the detailed embodiments and specific operation procedures are given, but the scope of the present invention is not limited to the following examples.

Example 1

The polarizer is prepared according to the following steps:

the PVA optical film was washed and swollen in 30 ℃ process water for 180 seconds, and in the washing and swelling step, a force of 30N was applied in the direction perpendicular to the production line, i.e., in the transverse direction, to stretch it in the transverse direction for 120 seconds.

The PVA film treated in the step 1 contains 2wt percent of KI and I₂Concentration ofDyeing for 60s in a dyeing solution with the concentration of 0.2 wt%, the concentration of boric acid of 1 wt% and the solution temperature of 32 ℃; then washing the mixture for 50s in a solution with boric acid concentration of 1 wt% and temperature of 32 ℃; then, the film is stretched in a stretching liquid with KI concentration of 2 wt%, boric acid concentration of 1 wt% and temperature of 40 ℃ to 5.5 times of the original film length; after stretching, the obtained product is put into a solution with boric acid concentration of 1 wt% and temperature of 32 ℃ for cleaning for 20s, and color is supplemented for 30s in a color supplementing liquid with boric acid concentration of 1 wt% and KI concentration of 5 wt%; and (5) drying after the color compensation is finished, and drying in hot air at 40 ℃ for 80s to obtain the polarizing film. And then, attaching the treated TAC film according to a conventional process to obtain a polarizer sample, and measuring the light transmittance and the polarization degree of the polarizer.

Example 2

The polarizer is prepared according to the following steps:

the PVA optical film was washed and swollen in 30 ℃ process water for 180 seconds, and in the washing and swelling step, a force of 5N was applied in the direction perpendicular to the production line, i.e., in the transverse direction, to stretch it in the transverse direction for 120 seconds.

The PVA film treated in the step 1 contains 2wt percent of KI and I₂Dyeing for 60s in a dyeing solution with the concentration of 0.2 wt%, the concentration of boric acid of 1 wt% and the solution temperature of 32 ℃; then washing the mixture for 50s in a solution with boric acid concentration of 1 wt% and temperature of 32 ℃; then, the film is stretched in a stretching liquid with KI concentration of 2 wt%, boric acid concentration of 1 wt% and temperature of 40 ℃ to 5.5 times of the original film length; after stretching, the obtained product is put into a solution with boric acid concentration of 1 wt% and temperature of 32 ℃ for cleaning for 20s, and color is supplemented for 30s in a color supplementing liquid with boric acid concentration of 1 wt% and KI concentration of 5 wt%; and (5) drying after the color compensation is finished, and drying in hot air at 40 ℃ for 80s to obtain the polarizing film. And then, attaching the treated TAC film according to a conventional process to obtain a polarizer sample, and measuring the light transmittance and the polarization degree of the polarizer.

Example 3

The PVA optical film was washed and swollen in 30 ℃ process water for 180 seconds, and in the washing and swelling step, a force of 100N was applied in the direction perpendicular to the production line, i.e., in the transverse direction, to stretch it in the transverse direction for 120 seconds.

The PVA treated by the step 1 is treatedThe film contained KI at a concentration of 2 wt%, I₂Dyeing for 60s in a dyeing solution with the concentration of 0.2 wt%, the concentration of boric acid of 1 wt% and the solution temperature of 32 ℃; then washing the mixture for 50s in a solution with boric acid concentration of 1 wt% and temperature of 32 ℃; then, the film is stretched in a stretching liquid with KI concentration of 2 wt%, boric acid concentration of 1 wt% and temperature of 40 ℃ to 5.5 times of the original film length; after stretching, the obtained product is put into a solution with boric acid concentration of 1 wt% and temperature of 32 ℃ for cleaning for 20s, and color is supplemented for 30s in a color supplementing liquid with boric acid concentration of 1 wt% and KI concentration of 5 wt%; and (5) drying after the color compensation is finished, and drying in hot air at 40 ℃ for 80s to obtain the polarizing film. And then, attaching the treated TAC film according to a conventional process to obtain a polarizer sample, and measuring the light transmittance and the polarization degree of the polarizer.

Example 4

The PVA optical film was washed and swollen in 30 ℃ process water for 180 seconds, and in the washing and swelling step, a force of 30N was applied in the direction perpendicular to the production line, i.e., in the transverse direction, to stretch the film in the transverse direction for 10 seconds.

The PVA film treated in the step 1 contains 2wt percent of KI and I₂Dyeing for 60s in a dyeing solution with the concentration of 0.2 wt%, the concentration of boric acid of 1 wt% and the solution temperature of 32 ℃; then washing the mixture for 50s in a solution with boric acid concentration of 1 wt% and temperature of 32 ℃; then, the film is stretched in a stretching liquid with KI concentration of 2 wt%, boric acid concentration of 1 wt% and temperature of 40 ℃ to 5.5 times of the original film length; after stretching, the obtained product is put into a solution with boric acid concentration of 1 wt% and temperature of 32 ℃ for cleaning for 20s, and color is supplemented for 30s in a color supplementing liquid with boric acid concentration of 1 wt% and KI concentration of 5 wt%; and (5) drying after the color compensation is finished, and drying in hot air at 40 ℃ for 80s to obtain the polarizing film. And then, attaching the treated TAC film according to a conventional process to obtain a polarizer sample, and measuring the light transmittance and the polarization degree of the polarizer.

Example 5

The PVA optical film was washed and swollen in 30 ℃ process water for 180 seconds, and in the washing and swelling step, a force of 30N was applied in the direction perpendicular to the production line, i.e., in the transverse direction, to stretch it for 180 seconds in the transverse direction.

The PVA film treated in the step 1 contains 2 wt% of KI,I₂Dyeing for 60s in a dyeing solution with the concentration of 0.2 wt%, the concentration of boric acid of 1 wt% and the solution temperature of 32 ℃; then washing the mixture for 50s in a solution with boric acid concentration of 1 wt% and temperature of 32 ℃; then, the film is stretched in a stretching liquid with KI concentration of 2 wt%, boric acid concentration of 1 wt% and temperature of 40 ℃ to 5.5 times of the original film length; after stretching, the obtained product is put into a solution with boric acid concentration of 1 wt% and temperature of 32 ℃ for cleaning for 20s, and color is supplemented for 30s in a color supplementing liquid with boric acid concentration of 1 wt% and KI concentration of 5 wt%; and (5) drying after the color compensation is finished, and drying in hot air at 40 ℃ for 80s to obtain the polarizing film. And then, attaching the treated TAC film according to a conventional process to obtain a polarizer sample, and measuring the light transmittance and the polarization degree of the polarizer.

Comparative example 1

The PVA optical film is washed and swelled in process water at 30 ℃ for 180s, and transverse stretching operation is not carried out in the washing and swelling process.

The PVA film treated in the step 1 contains 2wt percent of KI and I₂Dyeing for 60s in a dyeing solution with the concentration of 0.2 wt%, the concentration of boric acid of 1 wt% and the solution temperature of 32 ℃; then washing the mixture for 50s in a solution with boric acid concentration of 1 wt% and temperature of 32 ℃; then, the film is stretched in a stretching liquid with KI concentration of 2 wt%, boric acid concentration of 1 wt% and temperature of 40 ℃ to 5.5 times of the original film length; after stretching, the obtained product is put into a solution with boric acid concentration of 1 wt% and temperature of 32 ℃ for cleaning for 20s, and color is supplemented for 30s in a color supplementing liquid with boric acid concentration of 1 wt% and KI concentration of 5 wt%; and (5) drying after the color compensation is finished, and drying in hot air at 40 ℃ for 80s to obtain the polarizing film. And then, attaching the treated TAC film according to a conventional process to obtain a polarizer sample, and measuring the light transmittance and the polarization degree of the polarizer.

In each of the examples and comparative examples, the transverse swelling degree of the PVA optical film after washing and swelling, and the transmittance and the degree of polarization of the polarizer obtained were shown in table 1.

TABLE 1

	Example 1	Example 2	Example 3	Example 4	Example 5	Comparative example 1
							Transverse degree of swelling/%)	135.6	116.9	170.5	117.1	168.8	115.6
Transmittance (a)	43.2	42.0	43.9	42.1	43.8	41.8
							Degree of polarization/%)	99.92	99.93	98.90	99.94	99.05	99.94

The polarizer for high-end OLED generally requires a polarization degree of 99.9% and a transmittance of 42.5% or more, and it can be seen from the table that: the degree of polarization of example 1 was not substantially decreased as compared with the comparative example, but the transmittance reached 43.2%, which was significantly improved as compared with the transmittance of comparative example 1. The tension applied in example 2 is too low, the transverse stretching time in example 4 is too short, the transverse swelling degree of the two is not substantially improved, and the light transmittance is not improved; example 3 is too much applied, example 5 is too long in transverse stretching time, and both are too much in transverse swelling degree, and although the light transmittance is also obviously improved, the polarization degree is only 98.9%, which is not satisfactory for high-end polarizers. Therefore, in the water washing swelling link, proper transverse stretching is carried out, the transverse swelling degree is controlled in a proper range, the light transmittance of the polaroid can be obviously improved, and the polaroid still keeps high polarization degree.

The above description is only exemplary of the present invention and should not be taken as limiting the invention, and any modifications, equivalents, improvements, etc. made within the spirit and principle of the present invention should be included in the scope of the present invention.