KR20130015557A

KR20130015557A - Method for treating protective film for polarizer surface and polarising plate using the same

Info

Publication number: KR20130015557A
Application number: KR1020110077605A
Authority: KR
Inventors: 최윤석; 정경문; 유민근
Original assignee: 동우 화인켐 주식회사
Priority date: 2011-08-04
Filing date: 2011-08-04
Publication date: 2013-02-14

Abstract

PURPOSE: A surface processing method of a polarizer protection film and a polarizing plate using the method are provided to raise the adhesion force and maintain the long time adhesion force, by adhering to the polarizer and maintaining the same or higher optical property. CONSTITUTION: The reaction gas containing the anhydrous maleic acid or the anhydride succinic acid compound is treated with the plasma discharge in at least one side of the polarizer protection film. The anhydrous maleic acid or the anhydride succinic compound is selected. The reaction gas is formed by vaporizing the anhydrous maleic acid or the anhydride succinic acid compound in the insoluble gas.

Description

Surface treatment method of polarizer protective film and polarizing plate using same {METHOD FOR TREATING PROTECTIVE FILM FOR POLARIZER SURFACE AND POLARISING PLATE USING THE SAME}

The present invention relates to a surface treatment method of a polarizer protective film that is excellent in adhesive strength and capable of maintaining long term adhesive strength while maintaining optical properties equivalent to those of the prior art by bonding with a polarizer and a polarizing plate using the same.

2. Description of the Related Art Liquid crystal display devices (LCDs) are used in various applications such as computers, televisions, mobile phones, car navigation systems, and portable information terminals.

Such a liquid crystal display device has a liquid crystal cell composed of a liquid crystal layer, a transparent glass plate including a transparent electrode layer, or a plastic-based plate-like material arranged in a uniform manner in terms of the image forming method; It is indispensable that the polarizing plate is disposed on both surfaces of the liquid crystal cell.

In general, the polarizing plate has a structure in which a polarizer having a dichroic material adsorbed and aligned on a polyvinyl alcohol (PVA) resin film, and a transparent polarizer protective film for protecting the polarizer on at least one side of the polarizer. The polarizer protective film may be a cellulose protective film such as triacetylcellulose (TAC), a cycloolefin protective film, an acrylic protective film, or the like.

The polarizer protective film performs an easy bonding process on the surface to be bonded with the polarizer. The cellulose-based protective film introduces a hydrophilic group through an alkali treatment (saponification treatment), and the cycloolefin-based protective film and the acrylic protective film use a method of activating a surface by performing corona treatment and plasma treatment.

However, the alkali treatment may change the optical characteristics of the polarizing plate due to staining or remaining alkali components, and the corona treatment and the plasma treatment have a low surface treatment effect and a short duration of effect.

The present invention is to provide a surface treatment method of a polarizer protective film by bonding with a polarizer, excellent adhesion and maintaining the adhesion for a long time while maintaining the optical properties equivalent to those of the prior art.

In addition, the present invention is to provide a polarizing plate bonded to a polarizer protective film using the surface treatment method.

The present inventors introduced the compound to the surface of the polarizer protective film using a reaction gas containing a maleic anhydride or succinic anhydride-based compound during plasma discharge treatment, the adhesive was introduced to the surface of the polarizer protective film by an adhesive when bonding the polarizer. It has been found that the maleic anhydride-based or succinic anhydride-based compound is hydrated to improve adhesion to light polarizers compared to the prior art.

Therefore, at least one surface of the polarizer protective film, by using a reaction gas containing a maleic anhydride or succinic anhydride-based compound provides a surface treatment method of a polarizer protective film comprising the step of performing a plasma discharge treatment.

The maleic anhydride or succinic anhydride-based compound may be at least one selected from the group consisting of maleic anhydride, citraconic anhydride, itaconic anhydride, and 2-dodecen-1-yl succinic anhydride.

The reaction gas may be formed by vaporizing a maleic anhydride-based or a succinic anhydride-based compound into an inert gas.

The maleic anhydride-based or succinic anhydride-based compound may be contained in the reaction gas in an amount of 1 to 5% by volume.

The present invention also provides a polarizing plate in which a polarizer is bonded to a plasma discharge treatment surface of the surface-treated polarizer protective film.

The polarizer protective film may be bonded to the polarizer by an aqueous adhesive.

The present invention can improve adhesion by bonding with a polarizer while maintaining optical characteristics equivalent to those of the prior art.

In addition, the present invention can provide a polarizing plate that is provided with excellent adhesion due to the improved adhesive force can be maintained for a long time (excellent durability reliability).

In addition, the present invention is a continuous and simple surface treatment method of the polarizing plate protective film.

Hereinafter, the present invention will be described in detail.

The surface treatment method of the polarizer protective film according to the present invention includes a plasma discharge treatment of a reaction gas containing maleic anhydride or succinic anhydride-based compound on at least one surface of the polarizer protective film.

When the plasma discharge treatment is performed by the above method, a maleic anhydride-based or succinic anhydride-based compound is introduced onto the surface of the polarizer-protective film. The maleic anhydride-based or succinic anhydride-based compound introduced on the surface of the polarizer protective film is hydrated by an adhesive when bonding the polarizer and the polarizer protective film to form a hydroxyl group (-OH). The polarizer protective film surface is a polar group such as a hydroxyl group (-OH) formed by hydration to form a bond with the polyvinyl alcohol constituting the polarizer is excellent in adhesive strength, it is possible to maintain the adhesion for a long time to improve the durability of the polarizing plate.

The maleic anhydride-based or succinic anhydride-based compound is specifically maleic anhydride, citraconic anhydride, itaconic anhydride and 2-dodecen-1-yl succinic anhydride ((2 -dodecen-1-yl) may be one or more selected from the group consisting of succinic anhydride).

The maleic anhydride-based or succinic anhydride-based compound may be contained in the reaction gas in an amount of 1 to 5% by volume. If the content is less than 1 vol%, the amount of the maleic anhydride-based or succinic anhydride-based compound to be incorporated into the protective film is insufficient to improve the adhesion. If the content is more than 5 vol%, the maleic anhydride- The adhesiveness may be lowered by the system compound.

The maleic anhydride-based or succinic anhydride-based compound is vaporized in a heatable vaporizer and used in a plasma discharge treatment apparatus together with an inert gas. The plasma discharge apparatus is generally used in the art, and its configuration is not particularly limited.

As the inert gas, a gas used for transferring the maleic anhydride-based or succinic anhydride-based compound may be used. Specifically, nitrogen, argon, helium, or the like can be used.

The vaporizer temperature is preferably 110 ° C or less, preferably 50 to 100 ° C, in consideration of the flash point of the maleic anhydride-based or succinic anhydride-based compound.

The flow rate of the reaction gas introduced into the plasma discharge treatment is controlled by the temperature of the vaporizer and the flow rate of the inert gas.

In addition, the voltage to be applied for generating the plasma is not particularly limited, and may be in the range of usually 1 to 10 kV.

Also, the operating frequency of the power supply is not particularly limited, and may be in the range of 1 kHz to 150 MHz, or more, and may be in the stronger GHz range. However, considering the influence of heat of the plasma-treated protective film, it is preferably 1 to 500 kHz.

Further, the inter-electrode distance of the plasma apparatus is determined in consideration of the pressure and concentration of the base gas, the thickness of the solid dielectric, the magnitude of the applied voltage, and the like. When the distance between the electrodes is short, a stable discharge plasma tends to be obtained, but it is generally preferably 0.5 to 50 mm. When the distance between the electrodes is less than 0.5 mm, the concentration of the reaction gas in the base gas varies greatly between the electrodes, the activation treatment tends to be uneven, and the thickness of the object to be provided between the electrodes becomes limited. In addition, when the interelectrode distance exceeds 50 mm, it is difficult to generate a uniform discharge plasma.

Polarizer protective film is generally used in the art, specifically, polyester-based films such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, polybutylene terephthalate; Cellulose films such as diacetyl cellulose and triacetyl cellulose; Polycarbonate film; Acrylic films such as polymethyl (meth) acrylate and polyethyl (meth) acrylate; Styrene films such as polystyrene and acrylonitrile-styrene copolymers; Polycarbonate film; Vinyl chloride film; Amide type films such as nylon and aromatic polyamide; Imide film; Polyether sulfone-based film; Sulfone based films; Polyether ether ketone film; Sulfided polyphenylene-based films; Vinyl alcohol film; Vinylidene chloride-based film; Polyoxymethylene film; Epoxy type film etc. are mentioned.

The protective film may be one containing an appropriate one or more additives. As an additive, a ultraviolet absorber, antioxidant, a lubricant, a plasticizer, a mold release agent, a coloring agent, a flame retardant, a nucleating agent, an antistatic agent, a pigment, a coloring agent, etc. are mentioned, for example.

In addition, the thickness of a protective film is 20-200 micrometers normally.

The surface of the polarizer protective film plasma-treated by the above method has a water contact angle of 10 to 50 ° range.

The polarizing plate of the present invention includes the plasma discharge treated polarizer protective film. Specifically, the adhesive layer is bonded to one surface of the polarizer and the plasma discharge treatment surface of the surface-treated polarizer protective film.

The polarizer is a dichroic dye adsorbed on the stretched polyvinyl alcohol-based film.

The polyvinyl alcohol-based resin constituting the polarizer can be obtained by saponifying a polyvinyl acetate-based resin. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Other monomers copolymerizable with vinyl acetate include acrylamide monomers having an unsaturated carboxylic acid type, an unsaturated sulfonic acid type, an olefin type, a vinyl ether type, and an ammonium group. The polyvinyl alcohol resin may be modified, for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. Saponification degree of polyvinyl alcohol-type resin is 85-100 mol% normally, Preferably it is 98 mol% or more. In addition, the degree of polymerization of the polyvinyl alcohol-based resin is usually 1,000 to 10,000, preferably 1,500 to 5,000.

Such a polyvinyl alcohol-based resin film is used as the original film of the polarizer. The film forming method of the polyvinyl alcohol resin is not particularly limited, and a known method can be used. The thickness of the original film is not particularly limited, and may be, for example, 10 to 150 mu m.

A polarizer is normally manufactured through the process of uniaxially stretching a polyvinyl alcohol-type film as described above, a process of dyeing with a dichroic dye and adsorbing, a process of treating with an aqueous solution of boric acid, and washing with water and drying.

The process of uniaxially stretching the polyvinyl alcohol-based film may be performed before dyeing, may be simultaneously performed with dyeing, or may be performed after dyeing. When uniaxial stretching is performed after dyeing, it may be performed before boric acid treatment or may be performed during boric acid treatment. Of course, it is also possible to perform uniaxial stretching in these multiple steps. For uniaxial stretching, rolls or heat rolls with different circumferential speeds can be used. In addition, uniaxial stretching may be dry stretching extending | stretching in air | atmosphere, and wet extending | stretching extending | stretching in the state swollen with a solvent may be sufficient as it. The draw ratio is usually 3 to 8 times.

As a process of dyeing a stretched polyvinyl alcohol-type film with a dichroic dye, the method of immersing a polyvinyl alcohol-type film in the aqueous solution containing a dichroic dye can be used, for example. As a dichroic dye, iodine or a dichroic dye is used. In addition, the polyvinyl alcohol-based film is preferably swelled by dipping in water before dyeing.

When using iodine as a dichroic dye, the method of immersing and dyeing a polyvinyl alcohol-type film in the dyeing aqueous solution containing iodine and potassium iodide can be used normally. Usually, the content of iodine in an aqueous solution for dyeing is 0.01 to 1 part by weight with respect to 100 parts by weight of water (distilled water), and the content of potassium iodide is 0.5 to 20 parts by weight with respect to 100 parts by weight of water. The temperature of the aqueous solution for dyeing is usually 20 to 40 ° C., and the immersion time (dyeing time) is usually 20 to 1,800 seconds.

On the other hand, when using a dichroic organic dye as a dichroic dye, the method of immersing and dyeing a polyvinyl alcohol-type film in the aqueous dyeing solution containing a water-soluble dichroic organic dye can be used normally. The content of the dichroic organic dye in the aqueous solution for dyeing is usually 1 × 10 ^-4 to 10 parts by weight, preferably 1 × 10 ^-3 to 1 part by weight based on 100 parts by weight of water. The dyeing aqueous solution may further contain an inorganic salt such as sodium sulfate as a dyeing aid. The temperature of the aqueous solution for dyeing is usually 20 to 80 ° C, and the immersion time (dyeing time) is usually 10 to 1,800 seconds.

The process of boric acid treating the dyed polyvinyl alcohol-based film may be performed by immersing in an aqueous solution containing boric acid. The content of boric acid in an aqueous solution containing boric acid is usually 2 to 15 parts by weight, preferably 5 to 12 parts by weight based on 100 parts by weight of water. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide, and the content thereof is usually 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight with respect to 100 parts by weight of water. The temperature of the boric acid-containing aqueous solution is usually 50 ° C or higher, preferably 50 to 85 ° C, more preferably 60 to 80 ° C, and the immersion time is usually 60 to 1,200 seconds, preferably 150 to 600 seconds, more preferably. Preferably it is 200 to 400 seconds.

After the boric acid treatment, the polyvinyl alcohol-based film is usually washed with water and dried. Washing treatment can be performed by immersing the boric acid-treated polyvinyl alcohol-based film in water. The temperature of water at the time of water washing process is 5-40 degreeC normally, and immersion time is 1-120 second normally. A polarizer can be obtained by drying after washing with water. The drying treatment can usually be carried out using a hot air dryer or a far infrared heater. The drying treatment temperature is usually 30 to 100 ° C, preferably 50 to 80 ° C, and the drying time is usually 60 to 600 seconds, preferably 120 to 600 seconds.

The thickness of the polarizer produced as described above is 5 to 40㎛.

The adhesive layer is preferably an aqueous adhesive layer obtained by dissolving or dispersing the adhesive composition in water. More preferably, it is preferable to contain a polyvinyl alcohol-based adhesive (PVA-based adhesive) in a range similar to that of the polarizer component.

The PVA-based resin as the main component of the PVA-based adhesive is a partially saponified PVA resin; Fully saponified PVA resin; A modified PVA resin such as a carboxyl group modified PVA resin, an acetoacetyl group modified PVA resin, a methylol modified vinyl PVA resin, and an amino group modified PVA resin.

Further, the PVA adhesive preferably further comprises a curing component such as glyoxal or a water-soluble epoxy resin or a crosslinking agent in order to increase the adhesive strength. The water-soluble epoxy resin may be a polyamide epoxy resin.

The content of the component is not particularly limited as long as it can perform its role as an adhesive in a range generally used in the art.

The bonding method may be a conventional method in the art, for example, using a casting method, a meyer bar coating method, a gravure coating method, a die coating method, a dip coating method, a spray coating method, or the like on the bonding surface of the polarizer or the protective film. After apply | coating an adhesive composition, the method of joining these is mentioned. The flexographic method is a method in which the polarizer or the protective film is moved in the vertical direction, the horizontal direction, or the inclined direction between the two, while applying the adhesive composition to the joint surface. After applying the adhesive composition, a polarizer or a protective film is put on a nip roll or the like and bonded.

After bonding the polarizer and the polarizer protective film may be a drying treatment. The drying treatment is carried out, for example, by spraying hot air, and the drying temperature is appropriately selected in the range of 40 to 100 ° C, preferably 60 to 100 ° C. Drying time may be about 20 to 1,200 seconds. After drying, curing is preferably performed at room temperature or slightly higher, for example, at a temperature of 20 to 50 ° C. for about 12 to 600 hours. The thickness of an adhesive bond layer after drying is 0.001-5 micrometers normally, Preferably it is 0.01 micrometer-2 micrometers, More preferably, it is 0.01-1 micrometer or less. When the thickness of an adhesive bond layer exceeds 5 micrometers, it will be easy to produce the external appearance problem of a polarizing plate.

On the other side of the polarizer, the protective film is bonded to one surface, a surface treatment layer such as a hard coating layer, an antireflection layer, an antiglare layer, an antistatic layer may be further laminated as necessary. Further, an optical functional film may be further laminated by a pressure-sensitive adhesive layer. As the optical functional film, for example, an optical compensation film in which a liquid crystalline compound or a polymer compound thereof is oriented on the surface of a substrate, reflective polarization that transmits polarized light of any kind and reflects polarized light having a property opposite thereto. Separation film, retardation film containing polycarbonate resin, retardation film containing cyclic polyolefin-based resin, anti-glare function film having an uneven shape on the surface, an additional film subjected to the surface anti-reflection treatment, a reflection film having a reflection function on the surface, The semi-transmissive reflective film etc. which have a reflection function and a transmission function together are mentioned.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention. Such variations and modifications are intended to be within the scope of the appended claims.

Example 1

One surface of a triacetyl cellulose-based polarizer protective film having a width of 250 mm × length of 700 mm × thickness of 80 μm was activated on the surface of the film by using a plasma discharge treatment apparatus (PN-APP300TT, Emaye).

During the discharge treatment, the reaction gas was supplied to the plasma electrode part at a flow rate of 10 L / min using 1% by volume of maleic anhydride and 99% by volume of nitrogen. The power source of the plasma generating apparatus was an AC power source having a frequency of 20 Hz, a voltage of 8.5 Hz was applied, the distance between the plasma electrodes was 2 mm, and the discharge treatment rate was 300 mm / sec.

Example 2

The reaction gas was mixed in the same manner as in Example 1 except that 3% by volume of maleic anhydride and 95% by volume of nitrogen were used.

Example 3

In the same manner as in Example 1, 5% by volume of maleic anhydride and 90% by volume of nitrogen were used as a reaction gas.

Example 4

In the same manner as in Example 1, 1% by weight of citric anhydride and 99% by volume of nitrogen were used as a reaction gas.

Example 5

The reaction gas was mixed in the same manner as in Example 1 except that 1 vol% of itaconic anhydride and 99 vol% of nitrogen were mixed.

Example 6

The reaction gas was mixed in the same manner as in Example 1 except that 1 vol% of 2-dodecen-1-yl succinic anhydride and 99 vol% of nitrogen were mixed.

Example 7

In the same manner as in Example 1, a cycloolefin-based polarizer protective film (norbornene-based, Japan Xeon, Zeanoa) was used in place of the triacetyl cellulose-based polarizer protective film.

Example 8

In the same manner as in Example 1, but instead of the triacetyl cellulose polarizer protective film was used an acrylic polarizer protective film (Xeon, I-Film).

Comparative Example 1

In the same manner as in Example 1, but using a reaction gas mixed with 1% by volume of oxygen and 99% by volume of nitrogen.

Comparative Example 2

In the same manner as in Example 1, but using a reaction gas of 1% by volume acrylic acid and 99% by volume nitrogen.

Comparative Example 3

The reaction gas was mixed in the same manner as in Example 1, but using 1% by volume of hydroxyethyl acrylate and 99% by volume of nitrogen.

Experimental Example

One side of the polarizer was placed on the surface where the plasma discharge treatment of the polarizer protective films obtained in the above Examples and Comparative Examples was completed, and the other side was placed on the saponified triacetylcellulose-based film, and bonded using a polyvinyl alcohol adhesive. . The conjugate was dried at a temperature of 60 캜 for 5 minutes to prepare a polarizing plate.

The physical properties of the prepared polarizing plate were measured by the following method and the results are shown in Table 1.

[How to measure]

1. Adhesion

The polarizer of the prepared polarizer and the polarizer protective film treated by plasma discharge were peeled off by hand, and the degree of peeling and the degree of breakage between them were observed, and evaluated based on the following criteria. At this time, the polarizer and the protective film are not peeled off from each other, and the more excellent the adhesion is.

(Circle): It is broken without peeling.

(Triangle | delta): It hardly peels and some damage is not carried out.

X: It peels and hardly breaks.

2. water contact angle

The water contact angle of the treated surface after the plasma treatment was measured using a contact angle measuring instrument (CAM200, KSV Instruments). At this time, the water contact angle is preferably less than 50 °.

3. Optical characteristics (polarization, transmittance)

The prepared polarizer was cut into a size of 2.5 cm x 2.5 cm, and then the transmittance was measured using an ultraviolet ray spectrophotometer (V-7100, manufactured by JASCO). At this time, the polarization degree is defined by the following equation (1).

(Wherein T ₁ is the parallel transmittance obtained when the pair of polarizers are arranged in parallel with the absorption axis, and T ₂ is the orthogonal transmittance obtained when the pair of polarizers are arranged in the state where the absorption axes are orthogonal) .

4. Durability reliability (long term adhesion)

The durability reliability (long-term adhesive strength maintenance) was predicted by observing the state of peeling in hot water.

The prepared polarizing plate was cut to a size of 2.5 cm × 10 cm, and then immersed in 60 ° C. water for 30 minutes to observe a peeling state. In this case, the smaller the peeling amount is, the more excellent the durability is, and if it is 1000 µm or more, the durability is predicted to be poor.

division Adhesion Water contact angle
(°) Optical characteristic Endurance reliability
(Μm) Polarization degree (%) Transmittance (%) Example 1 ○ 30 42.1 99.991 350 Example 2 ○ 26 42.0 99.992 450 Example 3 ○ 21 42.2 99.991 420 Example 4 ○ 32 42.3 99.992 380 Example 5 ○ 31 42.1 99.991 430 Example 6 ○ 29 42.3 99.990 420 Example 7 ○ 25 42.1 99.991 410 Example 8 ○ 24 42.1 99.992 420 Comparative Example 1 × 40 42.1 99.992 3200 Comparative Example 2 △ 22.5 42.2 99.991 1800 Comparative Example 3 △ 24.8 42.1 99.992 1100

As shown in Table 1, the polarizing plate using the polarizer protective film of Examples 1 to 8 subjected to plasma discharge treatment using a reaction gas containing a maleic anhydride or succinic anhydride-based compound according to the present invention has optical characteristics, adhesive strength and durability in particular. It was confirmed that this is excellent.

On the other hand, the comparative example using the conventional reaction gas was able to confirm the low adhesion and durability.

Claims

Plasma discharge treatment on at least one surface of the polarizer protective film, using a reaction gas containing a maleic anhydride or succinic anhydride-based compound, the surface treatment method of the polarizer protective film.

The method of claim 1, wherein the maleic anhydride or succinic anhydride-based compound of the polarizer protective film is at least one selected from the group consisting of maleic anhydride, citraconic anhydride, itaconic anhydride and 2-dodecen-1-yl succinic anhydride Surface treatment method.

The method of claim 1, wherein the reaction gas is formed by vaporizing a maleic anhydride or succinic anhydride compound in an inert gas.

The method according to claim 3, wherein the maleic anhydride or succinic anhydride compound is contained in the reaction gas at 1 to 5% by volume.

The polarizing plate in which the polarizer was bonded by the plasma discharge process surface of the polarizer protective film surface-treated by the method of any one of Claims 1-4.

The polarizer of claim 5, wherein the polarizer protective film is bonded to the polarizer by an aqueous adhesive.