TWI437286B - Manufacturing method of polarizing film - Google Patents

Description

Method for manufacturing polarizing film

The present invention relates to a method of producing a polarizing film.

The polarizing film can be obtained by uniaxially stretching a polarizing lens base material such as polyvinyl alcohol, dyeing with iodine or a dichroic dye, or stretching after dyeing, and further crosslinking with a boron compound to obtain a polarizing lens. After applying the water-based adhesive on both sides or one side of the mirror, a protective film such as a triacetyl cellulose film is adhered to obtain a water-based adhesive to dry the water.

In Japanese Patent Publication No. 2005-84505, for example, paragraph 0045, etc., the temperature at the time of moisture as a dry aqueous binder is adjusted to 60 °C.

As a result of investigations by the present inventors, it has been found that when a polarizing film obtained by drying at 60 ° C in the above preferred temperature range is cut, a plurality of minute cracks are formed on the cut end. The microscopic crack shrinks and swells due to a temperature change or the like, and the polarizing film is broken as a starting point. Further, it has been found that the warpage of the polarizing film is large and it is difficult to adhere to a liquid crystal cell or the like.

An object of the present invention is to provide a method for producing a polarizing film which suppresses minute cracks and warpage on a cut end side when cutting a polarizing film.

The present invention relates to a method for producing a polarizing film, which is a method for producing a polarizing film having a step of adhering a polarizing lens to a protective film by an aqueous binder and a drying step of drying the adhesive obtained in the above-mentioned pasting step, Characterized in that the drying step has 70 seconds after the end of the pasting step The first step of drying the above-mentioned adhesive product under the condition that the temperature range is 40 ° C or lower, and the second drying step of drying the pre-dried product obtained in the first drying step is completely dried in a temperature range of 20 to 60 ° C.

According to the manufacturing method of the present invention, the micro cracks generated at the cutting edge and the warpage of the polarizing film are remarkably suppressed when the obtained polarizing film is cut. Further, a polarizing film in which a surface uneven pattern called orange peel is not seen can be obtained.

The polarizing film obtained by the manufacturing method of the present invention has less warpage, and the concave-convex pattern of the polarizing film is suppressed. Therefore, the transparent base material, the optical compensation film, and the reflective polarized light can be further adhered to the polarizing film by an adhesive. Separation film, retardation film, film with anti-glare function, film with surface anti-reflection treatment, reflective film with reflective function on the surface, transflective film, and the like.

Hereinafter, the manufacturing method of the present invention will be described in detail.

The first half of the present invention is a step of adhering a polarizer to a protective film by an aqueous adhesive (hereinafter sometimes referred to as an adhesive step). The polarizer used in the pasting step refers to adsorption orientation on a resin polarizing substrate made of a polyvinyl alcohol resin, a polyvinyl acetate resin, an ethylene/vinyl acetate (EVA) resin, a polyamide resin, or a polyester resin. A dichroic dye or iodine polarizer.

Here, the polyvinyl alcohol-based resin contains a partially or completely saponified polyvinyl alcohol of a polyvinyl acetate; a vinyl acetate such as a saponified EVA resin and another copolymerizable monomer (for example, an olefin such as ethylene or propylene, butene) Acid or unsaturated carboxylic acid such as acrylic acid, methacrylic acid or maleic acid, unsaturated sulfonate a saponified product of a copolymer of an acid, a vinyl ether or the like; a polyvinyl formal or a polyvinyl acetal modified with polyvinyl alcohol by acetaldehyde. As the polarizer base material, a polyvinyl alcohol-based resin film, in particular, a film of polyvinyl alcohol itself is preferably used from the viewpoint of the adsorptivity and orientation of the dye.

The material which is adsorbed and oriented on the base material of the resin polarizer is preferably iodine from the viewpoint of optical performance, and is preferably a dichroic dye from the viewpoint of durability such as light resistance, heat resistance, and moist heat resistance. In the case of a dichroic dye, a polarizer for a blue channel, a green channel, or a red channel of a projection type liquid crystal display device can be separately produced by using a dye having a different wavelength dependency.

The dichromatic dye is a compound described in "Development of a Bichromatic Pigment for Liquid Crystal Display Devices" (Baigen et al., Sumitomo Chemical, 2002-II, pages 23 to 30).

Specifically, a dichroic dye represented by the formula (I) in the form of a free acid, (wherein Me represents a metal atom selected from a copper atom, a nickel atom, a zinc atom and an iron atom. A ¹ represents a phenyl group which may be substituted or a naphthyl group which may be substituted. B ¹ represents a naphthyl group which may be substituted. R ¹ and R ² each independently represent an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a carboxyl group, a sulfinyl group (sulfinyl group), a sulfonylamino group, a sulfoalkylguanamine. Base, amine group, guanamine group, halogen atom or nitro group)

a dichroic dye represented by formula (II) in the form of a free acid, (wherein A ³ and B ³ each independently represent a phenyl group which may be substituted or a naphthyl group which may be substituted, and R ³ and R ⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and a carbon number of 1 to 4. Alkoxy, carboxy, sulfinyl, sulfonylamino, sulfoalkylguanidino, amine, halogen or nitro, m represents 0 or 1.)

a dichroic dye represented by formula (III) in the form of a free acid, Q ¹ -N=N-Q ² -X-Q ³ -N=N-Q ⁴ (III) [wherein, Q ¹ and Q ⁴ are each Independently represents a phenyl group which may be substituted or a naphthyl group which may be substituted, and X represents a divalent residue represented by the formula (III-1) or the formula (III-2). Q ² and Q ³ each independently represent a phenyl group which may be substituted. ]

a dichroic dye represented by formula (IV), Wherein Me represents a metal atom selected from a copper atom, a nickel atom, a zinc atom and an iron atom, and Q ⁵ and Q ⁶ each independently represent a naphthyl group which may be substituted, an oxygen atom bonded to Me and -N=N - The azo group shown is bonded to a position adjacent to each other on the carbon of the benzene ring. Y represents a divalent residue represented by the formula (IV-1) or the formula (IV-2). R ⁵ and R ⁶ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms or a sulfinylene group. ]

And by CI Direct Yellow 12, CI Direct Red 31, CI Direct Red 28, CI Direct Yellow 44, CI Direct Yellow 28, CI Direct Orange 107, CI Direct Red 79, CI Direct Red 2, CI Direct Red 81, CI Direct Orange 26, CI direct orange 39, CI direct red 247 and CI direct yellow 142 are grouped as a dichroic dye represented by the generic name of the dye index.

The dichroic dye may be used in the form of a free acid, or may be used in the form of an amine salt such as an ammonium salt, an ethanolamine salt or an alkylamine salt, and is usually used in the form of an alkali metal salt such as a lithium salt, a sodium salt or a potassium salt.

These dichroic dyes may be used alone or in combination of two or more.

The following method can be exemplified as a method of manufacturing the polarizer. First, a dichroic dye is dissolved in water to a concentration of about 0.0001 to 10% by weight to prepare a dyeing solution. A dye aid may also be used as needed, for example, a method of using 0.1 to 10% by weight of Glauber's salt in the dyeing solution.

The polarizer base material is immersed in the dye liquid thus prepared for dyeing. The dyeing temperature is preferably from 40 to 80 °C. The orientation of the dye is carried out by stretching the polarizing film base material before dyeing or the dyed polarizer base material. As a method of stretching, for example, a wet method or a dry method can be used. The method of stretching, etc.

In order to increase the light transmittance, the degree of polarization, and the light resistance of the polarizer, post-treatment such as boric acid treatment may be performed. The boric acid treatment varies depending on the kind of the polarizer base material used or the kind of the dye used, and a boric acid aqueous solution having a concentration of 1 to 15% by weight, preferably 5 to 10% by weight, is usually used, at 30 to 80 ° C, The polarizing film base material is preferably impregnated in a temperature range of 50 to 80 °C. Further, it may be fixed in parallel in an aqueous solution containing a cationic polymer compound as needed.

In order to improve the adhesion, plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, saponification treatment, or the like may be performed on the bonding surface of the polarizer. Specific examples of the saponification treatment include a method of immersing a polarizer in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

Examples of the aqueous binder used in the pasting step include an aqueous binder containing polyvinyl alcohol as a main component, an aqueous binder mainly comprising a modified polyvinyl alcohol, and an aqueous emulsion of an amine ester. An aqueous binder such as an adhesive for a main agent or a vinyl acetate-based aqueous binder. Among them, an aqueous binder mainly comprising a modified polyvinyl alcohol as a main component is preferred. Here, as the modified polyvinyl alcohol, for example, polyvinyl alcohol having an ethyl oxime group obtained by reacting acetylacetic acid or the like with polyvinyl alcohol may be mentioned. The modified polyvinyl alcohol is sold under the names "Gohsefimer (registered trademark of Nippon Synthetic Chemical Industry Co., Ltd.)" and "Kuraray K Polymer (trade name, manufactured by Kuraray)".

The water-based adhesive with polyvinyl alcohol as the main agent, the water-based adhesive with modified polyvinyl alcohol as the main agent, and the adhesive with the amine ester-based aqueous latex as the main agent are Refers to the polymerization of a water-soluble crosslinking agent such as boric acid, borax, glyoxal, zirconium nitrate, melamine, oxalic acid, chitin, chitosan, metal salt, alcohol solvent, hydrophilic epoxy resin, etc. The product of the reaction. It is preferred to use a water-soluble crosslinking agent to have a tendency to improve durability.

The water-based adhesive may further contain an acrylic resin-based adhesive, an acrylic resin-based adhesive, an amine-ester resin-based adhesive, a cyanoacrylate-based adhesive, and an organic fluorene-based organic hydrazine. It is a self-adhesive resin such as a non-aqueous adhesive such as a binder or a modified organic bismuth-based adhesive containing polypropylene oxide as a main component, a polypropylene resin, a polyethylene resin, or a propylene-based elastomer resin.

The viscosity of the adhesive is preferably lower, 23 ° C. The viscosity at 55% RH is 12mPa. s (12cP) or less, preferably 1mPa. s (1cP) to 11mPa. s (11cP). The viscosity is 12mPa. When it is s or less, it is preferable to suppress the phenomenon of the uneven pattern called orange peel due to the uneven thickness of the adhesive layer during coating. As a method of adjusting the viscosity, a method of lowering the concentration of the binder or a method of changing the grade of the binder may be mentioned. An example of controlling the viscosity by the concentration of the binder in the aqueous solution, for example, when the Gohsefimer (registered trademark of Nippon Synthetic Chemical Industry Co., Ltd.) Z200 which is a polyvinyl alcohol-based resin is dissolved in water, the aqueous solution containing 1.5% by weight of Z200 is contained. The viscosity is about 2.5mPa. s (2.5cP), about 2.0m%, about 3mPa. s (3cP), about 3.0mPa when it is 3.0% by weight. s (6cP). These viscosities were all measured at 20 ° C using a vibrating viscosity system SV-10 (manufactured by A & D). In addition, as long as the viscosity is changed by changing the grade of the adhesive, a polyvinyl alcohol-based resin different from the above can be obtained by Kuraray, and contains 3% by weight. The aqueous solution of PVA117H is at 23 ° C. The viscosity at 55% RH is about 12mPa. s (12cP) water-based adhesive. Thus, the viscosity can be adjusted by appropriately adjusting the viscosity or grade of the adhesive.

Examples of the protective film include an acetyl cellulose film such as a triacetyl cellulose (TAC) film, a polyester resin film such as a polyethylene terephthalate (PET) film, and an olefin such as a cyclic cycloolefin film. A resin film, a polycarbonate resin film, a polyetheretherketone resin film, a polyfluorene resin film, or the like.

As the TAC film, there are "Fujitac (registered trademark of Fujifilm Co., Ltd.) TD80", "Fujitac (registered trademark of Fujifilm Co., Ltd.) TD80UF", "Fujitac (registered trademark of Fujifilm Co., Ltd.) TD80UZ", "Fujitac (registered trademark of Fujifilm Co., Ltd.) TD40UZ", "KC8UX2", "KC8UY", "KC4UY" sold by Konica Minolta Opt.

As a cyclic cycloolefin film, for example, ZEONOR is sold as a registered trademark of Zeon, Japan, and is sold as a registered trademark of Arton by JSR.

Among them, from the viewpoint of optical properties, a TAC film or a cyclic cycloolefin film is preferable, and a TAC film having high hydrophilicity is particularly preferable.

The thickness of the protective film is usually 10 to 90 μm, particularly preferably 10 to 45 μm. When the thickness is 90 μm or less, since the removal of the moisture of the adhesive is rapidly performed, it is preferably 10 μm or more, and the strength of the polarizing film can be ensured, which is preferable.

As the moisture permeability of the protective film, 40 ° C. The moisture permeability of 90% RH is 100 [g/(24 h.m ² )] or more, preferably 400 [g/(24 h.m ² )] or more. When the moisture permeability is 100 [g/(24 h.m ² )] or more, the moisture in the binder is quickly removed by the protective film, which is preferable.

In order to improve the adhesion on the adhesion surface of the protective film, plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, saponification treatment, or the like may be performed in the same manner as the polarizing surface.

When the method of attaching the polarizer and the protective film is described with reference to Fig. 1, a specific example of the application of an aqueous binder (not shown) on both surfaces or one surface of the polarizer (4) is used, and two surfaces are used from both sides. A method in which a mirror roll (2, sometimes referred to as a nip roll) is adhered to a protective film (3).

By adjusting the thickness of the aqueous adhesive layer by contact with the nip rolls, the surface of the polarizing film can be made smooth.

The thickness of the adhesive layer obtained as a water-based adhesive is usually 10 nm to 25 μm.

An adhesive in which a polarizing film and a protective film are adhered by an adhesive layer is supplied to the drying step. The present invention is characterized in that the drying step has a drying step 1 of drying the adhesive article under the conditions of a temperature range of 40 ° C or less, preferably 20 ° C or more and 40 ° C or less within 70 seconds after the end of the pasting step, and at 20 The second drying step of the predried product obtained in the above drying step 1 is completely dried under the conditions of a temperature range of 60 °C.

Specifically, when the first step of the drying step is "within 70 seconds after the end of the pasting step", the time (P) at which the nip roll of the pasting step is stopped is used as a starting point, and the adhesive is dried by a broken line. The adhesive is dried in an environment of 40 ° C or less between 70 seconds in the machine.

In general, since the adhesive material is dried as it advances inside the dryer, the temperature of the hot air in the dryer after 70 seconds from the start of P can be adjusted to 40 ° C or lower, and ventilated and dried.

Preferably, in the first step of drying, the adhesive is pressed by a mirror roll different from the nip roll to which the bonding is performed. Referring to Fig. 1, even if the two mirror rollers (pushing rolls 2, P) pass over the first mirror roll (the right end roll of 1), it is preferable that the adhesive arrives within 70 seconds, particularly preferably at 70 seconds. Cross the location Q of the three mirror rollers (1). In the first step of drying, by pressing the adhesive with a mirror roll, the thickness unevenness of the adhesive layer can be corrected, and the unevenness on the surface of the polarizing film can be smoothed.

The second step of drying is a step of completely drying the predried product obtained in the above drying step 1 under the conditions of a temperature range of 20 to 60 °C. Here, the complete drying means that the water content per 1 m ^{2 of the} polarizing film is adjusted to 2 g/m ² to 15 g/m ² .

The moisture content per square meter is for a polarizing film having an adhesive layer and a protective film adhered on both sides of the polarizing mirror, and is cut into a polarizing film (W ₀ ) having a size of 5 cm × 5 cm in a 120 ° C air vent dryer until The polarizing film reached a constant weight, and the weight (W ₁ ) and the value of (W _{0 -} W ₁ ) × 400 of the reduced polarizing film were determined.

In the second step of drying, drying is carried out in an environment adjusted to 20 to 60 ° C, preferably 40 to 50 ° C. When the temperature is 60° C. or lower, the warpage of the obtained polarizing film tends to decrease, which is preferable. When the temperature is 20° C. or more, the uneven pattern on the surface of the obtained polarizing film tends to be lowered, which is preferable.

In order to adjust the temperature range to 20 to 60 ° C, hot air adjusted to 60 ° C or less can be introduced into a dryer for drying.

The drying time as the second step of drying is usually about 180 to 1200 seconds when hot air adjusted to 60 ° C is introduced into the dryer.

It is preferred to set the heating temperature of the second step of drying to be higher than the first drying step. The reason for the highest temperature of the step is that the uneven pattern on the surface of the obtained polarizing film tends to decrease.

(Example)

The embodiment is shown below. In the examples, "%" and "parts" indicating the content or amount are weight standards.

The viscosity in the example is a value measured using a vibrating viscometer ((stock) A & D SV-10) at 23 ° C, 55% RH.

The moisture permeability is a value measured according to the cup method described in JIS Z0208.

(Example 1) <Production Example of Polarizing Mirror>

The polyvinyl alcohol film having an average polymerization degree of about 2400, a saponification degree of 99.9 mol% or more, and a thickness of 75 μm was uniaxially stretched five times in a dry state, and further kept in a state of tension, and directly immersed in pure water at 60 ° C for 1 minute, at 28 ° C. The solution was immersed in an aqueous solution of iodine/potassium iodide/water in a weight ratio of 0.05/5/100 for 60 seconds. Thereafter, it was immersed in an aqueous solution of potassium iodide/boric acid/water in a weight ratio of 8.5/8.5/100 at 72 ° C for 300 seconds. Subsequently, it was washed with pure water at 26 ° C for 20 seconds, and then dried at 90 ° C to adsorb iodine adsorption to PVA to obtain a polarizer.

<Production Example of Polarizing Film>

<Paste step> A solution A containing 0.35 parts by weight of zinc chloride and a specially modified PVA additionally mixed with 3 parts by weight of an aqueous solution of modified polyvinyl alcohol (Specially Modified PVA Z200 manufactured by Synthetic Chemical Industry Co., Ltd.) were prepared. Z200) 3 parts by weight, 0.28 parts by weight of glyoxal, and 3 parts by weight of solution B of polyvinyl alcohol (PVA117H manufactured by Kuraray Co., Ltd.) as a viscosity modifier The solutions A and B were combined to form an adhesive. The viscosity within 60 seconds after mixing solutions A and B is 8mPa. s (8cP).

Using the apparatus of Fig. 1, a mixture of solutions A and B is applied to one side (upper surface) of the polarizer, and a protective film is adhered thereto, and two mirror rollers (pressure) are used on the remaining single side (lower side) of the polarizer. The feeding roller) has a self-adhesive polyethylene film adhered to the surface (adhesive surface to the polarizer).

This protective film was coated with an acrylic resin-coated film on a non-adhesive surface of a polarizer mirrored with a TAC film (TD40UZ manufactured by Fujifilm Co., Ltd., thickness: 40 μm). The TAC film is 40 ° C. The moisture permeability of 90% RH is 450 [g/(24 h.m ² )].

<Drying step> After drying, it is dried by hot air. Air drying is performed in a dryer adjusted to a hot air temperature of 37 to 40 ° C within 70 seconds after P (pressure feed roller) (the above is the first drying step), and is also adjusted to 600 seconds after 70 seconds. Air drying was carried out in a dryer of 43 to 47 ° C (drying second step) to obtain a polarizing film having a water content of about 2.1 g/m ² .

The Q in the first figure is the first step of drying. That is, in Example 1, the pressing of the mirror roll was performed three times.

<evaluation> The obtained polarizing film was cut by a vertical drop type cutting machine (SUPPER CUTTER PN1-600 manufactured by Takino Seiki Co., Ltd.), and the occurrence of minute cracks was confirmed by a magnifying glass. As a result, the number of cracks per 200 mm side length was three. Further, when the shape of the surface of the polarizing film is confirmed, irregularities called orange peel do not occur, and the appearance is good.

(Example 2)

The polarized light having a water content of about 3.0 g/m ² was obtained in the same manner as in Example 1 except that the hot air temperature in the first step of drying was 37 to 40 ° C and the hot air temperature in the second drying step was 37 to 40 ° C. membrane.

<evaluation> The number of cracks per 200 mm side length is three. Further, when the shape of the surface of the polarizing film is confirmed, irregularities called orange peel do not occur, and the appearance is good.

(Comparative Example 1)

A polarizing film having a water content of about 2.6 g/m ² was obtained in the same manner as in Example 1 except that the hot air temperature in the first step of drying was 48 to 52 C and the hot air temperature in the second step was 48 to 52 ° C. .

<evaluation> Significant warpage occurred and could not be processed normally with a cutter.

(Comparative Example 2)

The polarized light having a water content of about 2.2 g/m ² was obtained in the same manner as in Example 1 except that the hot air temperature in the first step of drying was 43 to 47 ° C and the hot air temperature in the second drying step was 43 to 47 ° C. membrane.

<evaluation> The number of cracks per 200 mm side length is 18. Further, when the shape of the surface of the polarizing film is confirmed, irregularities called orange peel do not occur, and the appearance is good.

1‧‧‧Mirror roll

2‧‧‧2 mirror rollers (pressure feed rollers)

3‧‧‧Protective film

4‧‧‧ polarizer

5‧‧‧Part of ventilation dryer (schematic diagram)

P‧‧‧Time

Q‧‧‧Location

Figure 1 is an embodiment showing a pasting step and a drying step 1 Schematic diagram.

1‧‧‧Mirror roll

2‧‧‧2 mirror rollers (pressure feed rollers)

3‧‧‧Protective film

4‧‧‧ polarizer

5‧‧‧Part of ventilation dryer (schematic diagram)

P‧‧‧Time

Q‧‧‧Location

Claims (6)

A method for producing a polarizing film, which is a method for producing a polarizing film having a step of adhering a polarizing mirror to a protective film by an aqueous binder and a drying step of drying the adhesive obtained in the pasting step, The drying step has the following steps: (1) drying the adhesive article under the condition that the temperature is within 40 seconds after the end of the pasting step is 40 ° C or less, and (2) at 20 to The second step of drying the predried product obtained in the drying step 1 is completely dried under the conditions of a temperature range of 60 °C. The manufacturing method of claim 1, wherein the temperature range of the drying second step is higher than the highest temperature of the drying first step. The production method of the first aspect of the invention, wherein a protective film having a moisture permeability of 40 [deg.] ‧90% RH of 100 [g/(24 h‧m ² )] or more is used as the protective film. The production method of the first aspect of the invention, wherein a protective film containing an acetaminocellulose-based film is used as the protective film. The production method according to the first aspect of the invention, wherein the aqueous adhesive is an aqueous adhesive having a viscosity of 23 m C ‧5% RH of 12 mPa ‧ or less. The manufacturing method of claim 1, wherein in the drying the first step, the adhesive is brought into contact with the mirror roll at least once.