WO2015037553A1 - 偏光フィルム - Google Patents
偏光フィルム Download PDFInfo
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- WO2015037553A1 WO2015037553A1 PCT/JP2014/073640 JP2014073640W WO2015037553A1 WO 2015037553 A1 WO2015037553 A1 WO 2015037553A1 JP 2014073640 W JP2014073640 W JP 2014073640W WO 2015037553 A1 WO2015037553 A1 WO 2015037553A1
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- polarizing film
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
- G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
- G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
Definitions
- the present invention relates to a thin polarizing film with little leakage of blue light in a crossed Nicol state and a method for manufacturing the same.
- a polarizing plate having a light transmission and shielding function is a basic component of a liquid crystal display (LCD) together with a liquid crystal that changes a polarization state of light.
- LCD liquid crystal display
- Many polarizing plates have a structure in which a protective film such as a cellulose triacetate (TAC) film is bonded to the surface of a polarizing film.
- TAC cellulose triacetate
- a polarizing film constituting the polarizing plate a polyvinyl alcohol film (hereinafter referred to as “polyvinyl alcohol”).
- a polarizing film can be obtained by uniaxially stretching a PVA film preliminarily containing an iodine pigment, adsorbing an iodine pigment simultaneously with uniaxial stretching of a PVA film, or adsorbing an iodine pigment after uniaxially stretching a PVA film. Or manufactured.
- LCDs are used in a wide range of devices such as small devices such as calculators and wrist watches, notebook computers, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, in-vehicle navigation systems, mobile phones, and measuring devices used indoors and outdoors.
- small devices such as calculators and wrist watches
- notebook computers liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, in-vehicle navigation systems, mobile phones, and measuring devices used indoors and outdoors.
- LCDs liquid crystal monitors
- liquid crystal color projectors liquid crystal televisions
- in-vehicle navigation systems mobile phones
- mobile phones and measuring devices used indoors and outdoors.
- thinner polarizing plates such as small notebook personal computers and mobile phones.
- thermoplastic resin film is stretched, dyed and dried after being stretched, dyed and dried on a thermoplastic resin film, and then stretched as necessary.
- a method of peeling and removing a film layer is known (see Patent Documents 1 and 2, etc.).
- an object of the present invention is to provide a thin polarizing film with little leakage of blue light in a crossed Nicol state and a method for manufacturing the same.
- the inventors of the present invention have a temperature of a dyeing bath containing an iodine-based dye used when a polarizing film is produced by dyeing and stretching a thin PVA film.
- a temperature of a dyeing bath containing an iodine-based dye used when a polarizing film is produced by dyeing and stretching a thin PVA film In the crossed Nicol state, each measurement result in the thickness direction central part and the surface vicinity of the film obtained by Raman spectroscopic measurement of the cross section satisfies a specific relationship by setting the immersion time in the dyeing bath to a specific range
- the present inventors have found that an unprecedented thin polarizing film with less blue light leakage can be easily obtained, and have further studied based on the knowledge to complete the present invention.
- the present invention [1] A polarizing film having a thickness of 25 ⁇ m or less in which an iodine-based dye is adsorbed on a matrix containing PVA, the absorbance (A) at a wavelength of 480 nm and the absorbance (B) at a wavelength of 700 nm in a crossed Nicol state
- the ratio (A / B) of the polarizing film is 1.42 or more (hereinafter, this may be referred to as “polarizing film (1)”);
- the ratio of the signal intensity at -1 signal intensity at (Int 310) and 210 cm -1 (Int 210) to (Int 310 / Int 210) is L, with respect to the thickness in the interior in the thickness direction from one surface of the film signal intensity at 310 cm -1 in the 10% penetration portion Te ratio of the signal intensity at (Int 310) and 210cm -1 (Int 210) to (Int 310 / Int 210) is M, from the other surface of the film signal intensity at 310 cm -1 in the 10% penetration portion relative to the thickness in the interior in the thickness direction Int 310) with the signal intensity at 210 cm -1 (the ratio of Int 210) (Int 310 / Int 210) to when the N (provided that M ⁇ N), 2 ⁇ L / (M + N) is 0 .91 or less, a polarizing film (hereinafter, this may be referred to as “polarizing film (2)”); [3] The polarizing film according to the above [2], wherein the ratio
- a method for producing a polarizing film comprising a step of dyeing and stretching a PVA film having a thickness of 50 ⁇ m or less, wherein the dyeing is performed by immersing the PVA film in a dyeing bath containing an iodine-based dye.
- the manufacturing method in which the temperature is 25 ° C. or less and the immersion time is 1.5 minutes or less About.
- a thin polarizing film with less blue light leakage in a crossed Nicol state is provided.
- the manufacturing method of the polarizing film which can manufacture the said polarizing film easily is provided.
- an iodine dye is adsorbed on a matrix containing PVA.
- a polarizing film can be obtained by stretching a PVA film containing an iodine pigment in advance, adsorbing an iodine pigment simultaneously with the stretching of the PVA film, or forming a matrix by stretching the PVA film. It can be manufactured by adsorbing.
- the polarizing film of the present invention has a thickness of 25 ⁇ m or less.
- the thickness of the polarizing film is preferably 23 ⁇ m or less, more preferably 20 ⁇ m or less, still more preferably 10 ⁇ m or less, and particularly preferably 5 ⁇ m or less.
- the thickness of a polarizing film is 1 micrometer or more (in one example, 2.5 micrometers or more), for example.
- the ratio (A / B) of the absorbance (A) at a wavelength of 480 nm and the absorbance (B) at a wavelength of 700 nm in a crossed Nicol state is 1.42 or more. It is.
- the ratio (A / B) is 1.42 or more, a polarizing film with less blue light leakage is obtained. From such a viewpoint, the ratio (A / B) is preferably 1.43 or more, and more preferably 1.44 or more.
- the ratio (A / B) is preferably 2 or less, and is 1.8 or less. More preferably, it is more preferably 1.6 or less.
- said light absorbency (A) and light absorbency (B) can be calculated
- the ratio (Int 310 / Int 210 ) to the signal intensity (Int 210 ) at 210 cm ⁇ 1 is L, and 310 cm ⁇ 1 in the portion that enters 10% of the thickness in the thickness direction from one side of the film.
- the ratio (Int 310 / Int 210 ) of the signal intensity (Int 310 ) at 210 cm ⁇ 1 and the signal intensity (Int 210 ) at 210 cm ⁇ 1 is M, and the thickness from the other surface of the film is 10 inward with respect to the thickness.
- Raman spectrophotometry may be performed with a Raman spectrophotometer using a sample obtained by slicing the target polarizing film in the thickness direction.
- a laser Raman spectrometer such as a microscopic laser Raman spectrometer “LabRAM ARAMIS VIS”
- the measurement target portion of the sample may be irradiated with laser light having a wavelength of 532 nm to perform Raman spectroscopy.
- the ratio (Int 310 / Int 210 ) is calculated.
- specific measurement methods or conditions for obtaining the ratio (Int 310 / Int 210 ) in each part of the film those described later in the examples can be employed.
- the portion is the polarizing film.
- the ratio (Int 310 / Int 210 ) in each part of the film is considered to depend on the ratio of the amount of I 5 ⁇ to the amount of I 3 ⁇ in that part. It is done.
- the polarizing film (2) has the above 2 ⁇ L / (M + N) of 0.91 or less.
- 2 ⁇ L / (M + N) is 0.91 or less, a polarizing film with little leakage of blue light in the crossed Nicol state is obtained.
- 2 ⁇ L / (M + N) is preferably 0.88 or less, and more preferably 0.85 or less.
- 2 ⁇ L / (M + N) is preferably 0.01 or more, more preferably 0.1 or more, and 0.5 or more. More preferably.
- the polarizing film (2) has a ratio (A / B) of the absorbance (A) at a wavelength of 480 nm and the absorbance (B) at a wavelength of 700 nm in a crossed Nicol state of 1.42.
- it is preferably 1.43 or more, and more preferably 1.44 or more.
- the ratio (A / B) is preferably 2 or less, and is 1.8 or less. More preferably, it is more preferably 1.6 or less.
- vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate, isopropenyl acetate Or what is obtained by saponifying the polyvinyl ester obtained by superposing
- vinyl esters vinyl acetate is preferable from the viewpoints of ease of production of PVA, availability, cost, and the like.
- the above-mentioned polyvinyl ester may be obtained using only one or two or more kinds of vinyl esters as a monomer. It may be a copolymer of two or more kinds of vinyl esters and other monomers copolymerizable therewith.
- Examples of the other monomer copolymerizable with the vinyl ester include ⁇ -olefins having 2 to 30 carbon atoms such as ethylene, propylene, 1-butene, and isobutene; (meth) acrylic acid or a salt thereof; (Meth) methyl acrylate, (meth) ethyl acrylate, (meth) acrylate n-propyl, (meth) acrylate i-propyl, (meth) acrylate n-butyl, (meth) acrylate i-butyl, ( (Meth) acrylic acid esters such as t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate; (meth) acrylamide, N-methyl ( (Meth) acrylamide, N-ethyl (meth) acrylamide, N,
- Vinyl ether vinyl cyanide such as (meth) acrylonitrile
- vinyl halide such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride
- Allyl compounds such as allyl acetate and allyl chloride; maleic acid or its salts, esters or acid anhydrides; itaconic acid or its salts, esters or acid anhydrides
- vinylsilyl compounds such as vinyltrimethoxysilane; unsaturated sulfonic acids be able to.
- Said polyvinyl ester can have a structural unit derived from 1 type, or 2 or more types of an above described other monomer.
- the proportion of structural units derived from the other monomers described above in the polyvinyl ester is preferably 15 mol% or less based on the number of moles of all structural units constituting the polyvinyl ester, and is preferably 10 mol%. Hereinafter, it may be 5 mol% or less.
- the other monomer described above is a monomer that may promote the water solubility of the obtained PVA, such as (meth) acrylic acid or unsaturated sulfonic acid
- the proportion of structural units derived from these monomers in the polyvinyl ester is 5 mol% or less based on the number of moles of all structural units constituting the polyvinyl ester. It is preferable that it is 3 mol% or less.
- the above PVA may be modified with one or two or more types of graft copolymerizable monomers as long as the effects of the present invention are not impaired.
- the graft copolymerizable monomer include unsaturated carboxylic acids or derivatives thereof; unsaturated sulfonic acids or derivatives thereof; ⁇ -olefins having 2 to 30 carbon atoms, and the like.
- the proportion of structural units derived from the graft copolymerizable monomer in PVA (structural units in the graft modified portion) is preferably 5 mol% or less based on the number of moles of all structural units constituting PVA. .
- the above PVA may have a part of its hydroxyl group cross-linked or not cross-linked. Moreover, said PVA may react with aldehyde compounds, such as acetaldehyde and a butyraldehyde, etc. to form an acetal structure, and the said PVA does not react with these compounds and does not form an acetal structure. May be.
- aldehyde compounds such as acetaldehyde and a butyraldehyde, etc.
- the average degree of polymerization of the PVA is preferably in the range of 1,000 to 9,500.
- the average degree of polymerization is more preferably 1,500 or more, and further preferably 2,000 or more. Moreover, it is more preferable that it is 9,200 or less, and it is further more preferable that it is 6,000 or less.
- the average degree of polymerization is 1,000 or more, the polarizing performance of the polarizing film is improved.
- the productivity of PVA is improved.
- the average degree of polymerization of PVA can be measured according to the description of JIS K6726-1994.
- the degree of saponification of the PVA is preferably 98 mol% or more, more preferably 98.5 mol% or more, and more preferably 99 mol% or more from the viewpoint of the polarizing performance of the polarizing film. preferable.
- the degree of saponification is less than 98 mol%, PVA tends to be eluted during the production process of the polarizing film, and the eluted PVA may adhere to the film and reduce the polarizing performance of the polarizing film.
- the degree of saponification of PVA refers to the total number of moles of structural units (typically vinyl ester units) that can be converted into vinyl alcohol units by saponification and the vinyl alcohol units of PVA. The proportion (mol%) occupied by the number of moles of vinyl alcohol units.
- the degree of saponification can be measured according to the description of JIS K6726-1994.
- the iodine-based dye As the iodine-based dye, I 3 -, and the like - and I 5, examples of these counter cations include alkali metals such as potassium.
- the iodine dye can be obtained, for example, by bringing iodine (I 2 ) into contact with potassium iodide.
- Z X ⁇ log (Y) is 0.19 or less.
- Z is preferably 0.185 or less, and more preferably 0.175 or less.
- Z is preferably 0.15 or more, and more preferably 0.16 or more.
- the alkali metal include sodium and potassium, and potassium is preferable.
- the content can be determined by, for example, ICP-MS measurement.
- the single transmittance of the polarizing film of the present invention is preferably in the range of 40 to 45% from the viewpoint of polarization performance, and the single transmittance is more preferably 41% or more, and 42% or more. More preferably, it is more preferably 44% or less.
- the single transmittance of the polarizing film can be measured by the method described later in Examples.
- the method for producing the polarizing film of the present invention is not particularly limited, and can be produced by dyeing and stretching a PVA film as a raw film, for example, used as a raw film.
- a PVA film is sprayed with a dyeing solution containing iodine dye in a specific amount and concentration; a PVA film used as a raw film is brought into contact with a roll coated with a dyeing solution containing iodine dye; an iodine dye is contained
- a PVA film used as a raw film is brought into contact with an impregnated body obtained by impregnating a porous material such as a sponge with a dyeing solution; and the like. It can be easily manufactured by making a difference in the ratio of the amount of I 5 ⁇ to the amount of 3 ⁇ .
- the bright production method is preferable because the polarizing film of the present invention can be produced more easily.
- the production method of the present invention includes a step of dyeing and stretching a PVA film having a thickness of 50 ⁇ m or less, and the dyeing is performed by immersing the PVA film in a dyeing bath containing iodine-based dye, and the temperature of the dyeing bath is It is 25 degrees C or less, and immersion time is 1.5 minutes or less.
- the production method of the present invention includes a step of dyeing and stretching a PVA film having a thickness of 50 ⁇ m or less.
- the PVA film used may be a single layer, or may be laminated on a base material such as a thermoplastic resin base material as described in Patent Documents 1 and 2, etc. Although a single layer is preferable.
- the PVA film preferably contains a plasticizer from the viewpoint of improving stretchability when it is stretched.
- the plasticizer include polyhydric alcohols such as ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, and trimethylol propane.
- One or more of the agents can be included. Among these, glycerin is preferable from the viewpoint of the effect of improving stretchability.
- the content of the plasticizer in the PVA film is preferably in the range of 1 to 20 parts by mass with respect to 100 parts by mass of PVA contained therein. When the content is 1 part by mass or more, the stretchability of the PVA film can be further improved. On the other hand, when the content is 20 parts by mass or less, it is possible to prevent the PVA film from becoming too flexible and handling properties from being lowered.
- the content of the plasticizer in the PVA film is more preferably 2 parts by mass or more with respect to 100 parts by mass of PVA, further preferably 4 parts by mass or more, particularly preferably 5 parts by mass or more, The amount is more preferably 15 parts by mass or less, and further preferably 12 parts by mass or less.
- the PVA film may further contain components such as an antioxidant, an antifreezing agent, a pH adjuster, a hiding agent, a coloring inhibitor, an oil agent, and a surfactant as necessary.
- the content of PVA in the PVA film is preferably in the range of 50 to 99% by mass in view of ease of preparation of the desired polarizing film, and the content is preferably 75% by mass or more. More preferably, it is more preferably 80% by mass or more, particularly preferably 85% by mass or more, more preferably 98% by mass or less, further preferably 96% by mass or less, 95 It is particularly preferable that the content is not more than mass%.
- the PVA film used in the production method of the present invention has a thickness of 50 ⁇ m or less.
- the thickness of the PVA film is preferably 40 ⁇ m or less, more preferably 20 ⁇ m or less, and still more preferably 10 ⁇ m or less.
- the thickness of the PVA film is, for example, 2 ⁇ m or more (in the example, 5 ⁇ m or more).
- the shape of the PVA film is not particularly limited, but is preferably a long PVA film because it can be used continuously when manufacturing a polarizing film.
- the length of the long PVA film (length in the long direction) is not particularly limited, and can be set as appropriate according to the use of the polarizing film to be produced. For example, the length is in the range of 5 to 20,000 m. It can be.
- the width of the PVA film is not particularly limited and can be set as appropriate according to the application of the polarizing film to be produced.
- the PVA film has been increasing in screen size for liquid crystal televisions and liquid crystal monitors. If the width is set to 0.5 m or more, more preferably 1.0 m or more, it is suitable for these applications.
- the width of the PVA film is 7 m or less. Is preferred.
- the production method of the present invention includes a step of dyeing a PVA film (dyeing step) and a step of drawing (stretching step).
- the production method includes a swelling step and a crosslinking step in addition to the dyeing step and the drawing step. Further, a fixing process, a washing process, a drying process and the like may be further included as necessary. The order of each process may be changed as needed, each process may be performed twice or more, and different processes may be performed simultaneously.
- the PVA film is first subjected to a swelling process, then subjected to a dyeing process, further subjected to a crosslinking process if necessary, and then subjected to a stretching process, and further to a fixing treatment process as necessary. And / or a method of subjecting to a washing step and subjecting to a drying step.
- the swelling step can be performed by immersing the PVA film in water.
- the temperature of the water when immersed in water is preferably within a range of 20 to 40 ° C., more preferably 22 ° C. or higher, further preferably 25 ° C. or higher.
- the temperature is more preferably 38 ° C. or lower, and further preferably 35 ° C. or lower.
- the time for immersion in water is preferably within a range of 0.1 to 5 minutes, and more preferably within a range of 0.5 to 3 minutes. By making it within the range of 0.1 to 5 minutes, the PVA film can be efficiently swollen.
- the water at the time of immersing in water is not limited to pure water, The aqueous solution in which various components melt
- the dyeing is performed by immersing the PVA film in a dyeing bath containing an iodine-based dye, wherein the temperature of the dyeing bath is 25 ° C. or less and the immersion time is 1.5 minutes or less. It is necessary to be.
- the temperature of the dyeing bath is preferably 23 ° C. or less, more preferably 21 ° C. or less, further preferably 18 ° C. or less, 15 ° C. or less, and further 10 ° C. or less.
- the target polarizing film can be obtained more efficiently by lowering the temperature of the dyeing bath.
- the temperature of the dyeing bath is preferably 3 ° C. or higher, and more preferably 5 ° C. or higher.
- the immersion time is preferably 1.3 minutes or less, more preferably 1.1 minutes or less, 0.8 minutes or less, 0.5 minutes or less, and further 0.3 minutes.
- the immersion time is preferably 0.05 minutes or more, and more preferably 0.1 minutes or more.
- a representative example of the dyeing bath is that obtained by mixing iodine (I 2 ) and potassium iodide with water. By mixing the iodine and potassium iodide and water, I 3 - and I 5 - such can generate iodine dye.
- the concentration of iodine and potassium iodide in the dyeing bath is not particularly limited, but the iodine concentration is within a range of 0.01 to 2% by mass as a ratio of the mass of iodine used to the mass of the resulting dyeing bath.
- the concentration of potassium iodide is preferably in the range of 0.02 to 0.5% by mass, and the concentration of potassium iodide is the amount of potassium iodide used relative to the mass of iodine used.
- the mass ratio is preferably in the range of 10 to 200 times by mass, and more preferably in the range of 15 to 150 times by mass.
- the dyeing bath may contain a boron compound such as borate such as boric acid and borax.
- the crosslinking step is preferably performed after the dyeing step and before the stretching step.
- the crosslinking step can be performed by immersing the PVA film in an aqueous solution containing a crosslinking agent as a crosslinking bath.
- a crosslinking agent one or more of boron compounds such as boric acid and borate such as borax can be used.
- the concentration of the crosslinking agent in the crosslinking bath is preferably in the range of 1 to 15% by mass, more preferably 2% by mass or more, more preferably 7% by mass or less, and 6% by mass or less. More preferably. Sufficient stretchability can be maintained when the concentration of the crosslinking agent is in the range of 1 to 15% by mass.
- the crosslinking bath may contain an auxiliary agent such as potassium iodide.
- the temperature of the crosslinking bath is preferably in the range of 20 to 50 ° C., particularly preferably in the range of 25 to 40 ° C. By setting the temperature within the range of 20 to 50 ° C., crosslinking can be performed efficiently.
- the wet stretching method is preferable from the viewpoint of the uniformity of the thickness in the width direction of the obtained polarizing film, and it is more preferable to stretch in a boric acid aqueous solution.
- the concentration of boric acid in the boric acid aqueous solution is preferably in the range of 0.5 to 6.0 mass%, more preferably 1.0 mass% or more, and 1.5 mass% More preferably, it is more preferably 5.0% by mass or less, and further preferably 4.0% by mass or less.
- the boric acid concentration is in the range of 0.5 to 6.0% by mass, a polarizing film having excellent thickness uniformity in the width direction can be obtained.
- the aqueous solution containing the boron compound may contain potassium iodide, and its concentration is preferably in the range of 0.01 to 10% by mass.
- concentration of potassium iodide is in the range of 0.01 to 10% by mass, a polarizing film with better polarizing performance can be obtained.
- the temperature at which the PVA film is stretched is preferably in the range of 5 to 90 ° C., more preferably 10 ° C. or more, and more preferably 80 ° C. or less. More preferably, it is not higher than ° C.
- a polarizing film having excellent thickness uniformity in the width direction can be obtained.
- the stretching ratio at the time of stretching the PVA film is preferably 4 times or more, more preferably 5 times or more, and further preferably 6 times or more.
- the upper limit of the draw ratio of the PVA film is not particularly limited, but is preferably 8 times or less. Stretching of the PVA film may be performed at one time or divided into a plurality of times, but when performed in a plurality of times, the total stretching ratio obtained by multiplying the stretching ratio of each stretching is within the above range. I just need it.
- the draw ratio in this specification is based on the length of the PVA film before extending
- the stretching of the PVA film is preferably uniaxial stretching from the viewpoint of the performance of the obtained polarizing film.
- Uniaxial stretching in the longitudinal direction is preferred. Uniaxial stretching in the longitudinal direction can be performed by changing the peripheral speed between the rolls using a stretching apparatus including a plurality of rolls parallel to each other. On the other hand, lateral uniaxial stretching can be performed using a tenter type stretching machine.
- the fixing treatment step is mainly performed in order to strengthen the adsorption of the iodine-based pigment to the PVA film.
- the fixing treatment step can be performed by immersing the PVA film before stretching, during stretching or after stretching in a fixing treatment bath.
- a fixing treatment bath an aqueous solution containing one or more of boron compounds such as boric acid such as boric acid and borax can be used.
- the concentration of the boron compound in the aqueous solution containing the boron compound used as the fixing treatment bath is generally within the range of 0.1 to 15% by mass, and particularly preferably within the range of 1 to 10% by mass.
- the concentration of the iodine-based dye can be further strengthened.
- the temperature of the fixing treatment bath is preferably in the range of 10 to 60 ° C, particularly preferably in the range of 15 to 40 ° C. By setting the temperature within the range of 10 to 60 ° C., it is possible to further strengthen the adsorption of the iodine dye.
- the cleaning process is often performed to remove unnecessary chemicals and foreign matters on the film surface and to adjust the optical performance of the finally obtained polarizing film.
- the cleaning step can be performed by immersing the PVA film in a cleaning bath or by spraying a cleaning liquid on the PVA film. Water can be used as the washing bath or the washing liquid, and potassium iodide may be contained therein.
- the drying conditions in the drying step are not particularly limited, but it is preferable to perform the drying at a temperature within the range of 30 to 150 ° C, particularly within the range of 50 to 130 ° C.
- a polarizing film excellent in dimensional stability can be easily obtained by drying at a temperature in the range of 30 to 150 ° C.
- the polarizing film is usually used as a polarizing plate by attaching a protective film on both sides or one side.
- the protective film include those that are optically transparent and have mechanical strength. Specifically, for example, cellulose triacetate (TAC) film, acetic acid / cellulose butyrate (CAB) film, acrylic film, and polyester film.
- TAC cellulose triacetate
- CAB acetic acid / cellulose butyrate
- acrylic film acrylic film
- polyester film polyester film.
- a film or the like can be used.
- examples of the adhesive for bonding include a PVA adhesive and a urethane adhesive, and a PVA adhesive is preferable.
- the visibility correction of the visible light region of the C light source and 2 ° field of view is performed, and the sample is measured in the length direction.
- the light transmittance when tilted by 45 ° and the light transmittance when tilted by ⁇ 45 ° were measured, and the average value (%) was taken as the single transmittance of the polarizing film.
- the sample to be measured is irradiated with a laser beam having a wavelength of 532 nm on the cross-section to be measured on the cross section produced by the microtome. performed, among the signals observed at that time, because the intensity of the signal at 310cm intensity of the signal at -1 (Int 310) and 210cm -1 (Int 210), the ratio in that portion (Int 310 / Int 210 ) was calculated.
- said measurement object part shall be the part which penetrated 10% with respect to thickness to the thickness direction center part of the polarizing film and the thickness direction of the film from each surface of the polarizing film from the thickness direction center part of the polarizing film.
- the obtained ratios (Int 310 / Int 210) is L, also two ratios obtained from 10 percent penetration portion of the thickness inside from each side of the polarizing film in the thickness direction of the film (Int 310 / For Int 210 ), each value was set to M or N so as to satisfy M ⁇ N, and 2 ⁇ L / (M + N) was calculated using these L, M, and N.
- Example 1 100 parts by mass of PVA (saponified copolymer of vinyl acetate and ethylene, average polymerization degree 2,400, saponification degree 99.4 mol%, ethylene unit content 2.5 mol%), glycerin 10 as plasticizer
- PVA film having a thickness of 30 ⁇ m obtained by casting a film using a film-forming stock solution consisting of 0.1 parts by mass of sodium polyoxyethylene lauryl ether sulfate and water as a surfactant,
- the polarizing film was manufactured by performing a dyeing process, a crosslinking process, a stretching process, a fixing process, and a drying process.
- the amount of the PVA film used is uniaxially stretched (MD) in the length direction (MD) up to twice the original length while immersed in water at a temperature of 30 ° C. for 1 minute.
- MD length direction
- iodine is mixed with water at a concentration of 0.03% by mass and potassium iodide at a concentration of 0.7% by mass up to three times the original length.
- second-stage stretching is uniaxially stretched in the length direction (MD) (second-stage stretching) and then immersed in a crosslinking bath at a temperature of 32 ° C.
- the original length Is uniaxially stretched in the length direction (MD) up to 3.6 times (third-stage stretching), and further contains boron at a temperature of 57 ° C. containing 2.8% by mass of boric acid and 5% by mass of potassium iodide.
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Abstract
Description
[1]PVAを含むマトリックスにヨウ素系色素が吸着している、厚みが25μm以下の偏光フィルムであって、クロスニコル状態における波長480nmでの吸光度(A)と波長700nmでの吸光度(B)との比率(A/B)が1.42以上である、偏光フィルム(以下、これを「偏光フィルム(1)」と称することがある);
[2]PVAを含むマトリックスにヨウ素系色素が吸着している、厚みが25μm以下の偏光フィルムであって、当該偏光フィルムの断面をラマン分光測定して得られる、フィルムの厚み方向中央部における310cm-1でのシグナル強度(Int310)と210cm-1でのシグナル強度(Int210)との比率(Int310/Int210)をLとし、フィルムの一方の面から厚み方向に内部に厚みに対して10%進入した部分における310cm-1でのシグナル強度(Int310)と210cm-1でのシグナル強度(Int210)との比率(Int310/Int210)をMとし、フィルムの他方の面から厚み方向に内部に厚みに対して10%進入した部分における310cm-1でのシグナル強度(Int310)と210cm-1でのシグナル強度(Int210)との比率(Int310/Int210)をNとした際に(但し、M≦Nである)、2×L/(M+N)が0.91以下である、偏光フィルム(以下、これを「偏光フィルム(2)」と称することがある);
[3]クロスニコル状態における波長480nmでの吸光度(A)と波長700nmでの吸光度(B)との比率(A/B)が1.42以上である、上記[2]の偏光フィルム;
[4]偏光フィルムに含まれるアルカリ金属の含有率をXモル/kgとし、偏光フィルムの厚みをYμmとしたときに、式:Z=X×log(Y)で示されるZが0.19以下である、上記[1]~[3]のいずれか1つの偏光フィルム;
[5]単体透過率が40~45%である、上記[1]~[4]のいずれか1つの偏光フィルム;
[6]厚みが50μm以下のPVAフィルムを染色および延伸する工程を含む、偏光フィルムの製造方法であって、染色はヨウ素系色素を含む染色浴にPVAフィルムを浸漬することにより行われ、染色浴の温度が25℃以下であり、浸漬時間が1.5分以下である、製造方法;
に関する。
(偏光フィルム)
本発明の偏光フィルムは、PVAを含むマトリックスにヨウ素系色素が吸着している。このような偏光フィルムは、ヨウ素系色素を予め含有させたPVAフィルムを延伸したり、PVAフィルムの延伸と同時にヨウ素系色素を吸着させたり、PVAフィルムを延伸してマトリックスを形成した後にヨウ素系色素を吸着させたりするなどして製造することができる。
特に前記した他の単量体が、(メタ)アクリル酸、不飽和スルホン酸などのように、得られるPVAの水溶性を促進する可能性のある単量体である場合には、偏光フィルムの製造過程においてPVAが溶解するのを防止するために、ポリビニルエステルにおけるこれらの単量体に由来する構造単位の割合は、ポリビニルエステルを構成する全構造単位のモル数に基づいて、5モル%以下であることが好ましく、3モル%以下であることがより好ましい。
本発明の偏光フィルムを製造するための方法は特に制限されず、PVAフィルムを原反フィルムとして用いて、これを染色および延伸することにより製造することができ、例えば、原反フィルムとして使用されるPVAフィルムにヨウ素系色素を含む染色液を特定の量および濃度で散布する;ヨウ素系色素を含む染色液を塗布したロールに原反フィルムとして使用されるPVAフィルムを接触させる;ヨウ素系色素を含む染色液をスポンジ等の多孔質体に含浸させた含浸体に原反フィルムとして使用されるPVAフィルムを接触させる;などして、得られる偏光フィルムの厚み方向中央部と表面近傍とのそれぞれにおけるI3 -の存在量に対するI5 -の存在量の割合に差をつけることによって容易に製造することができるが、以下の本発明の製造方法によれば、本発明の偏光フィルムをより容易に製造することができることから好ましい。
なお、偏光フィルムの製造条件などにもよるが、PVAフィルムに含まれる可塑剤は偏光フィルムを製造する際に溶出するなどするため、その全量が偏光フィルムに残存するとは限らない。
偏光フィルムは、通常、その両面または片面に保護膜を貼り合わせて偏光板にして使用される。保護膜としては、光学的に透明でかつ機械的強度を有するものが挙げられ、具体的には例えば、三酢酸セルロース(TAC)フィルム、酢酸・酪酸セルロース(CAB)フィルム、アクリル系フィルム、ポリエステル系フィルムなどを使用することができる。また、貼り合わせのための接着剤としては、PVA系接着剤やウレタン系接着剤などを挙げることができるが、PVA系接着剤が好適である。
なお、以下の実施例、比較例および参考例において採用された、偏光フィルムの吸光度、単体透過率、アルカリ金属の含有率および2×L/(M+N)の各測定ないし算出方法を以下に示す。
以下の実施例、比較例または参考例で得られた偏光フィルムの幅方向(TD)の中央部から、偏光フィルムの長さ方向(MD)に2cmの長方形のサンプルを採取し、積分球付き分光光度計(日本分光株式会社製「V7100」)を用いて、このサンプルを当該分光光度計の偏光板に対してクロスニコル状態に設置し、波長480nmでの吸光度(A)および波長700nmでの吸光度(B)を測定した。次いで、同じサンプルおよび分光光度計を用いてJIS Z 8722(物体色の測定方法)に準拠し、C光源、2°視野の可視光領域の視感度補正を行い、当該サンプルについて、長さ方向に対して45°傾けた場合の光の透過率と-45°傾けた場合の光の透過率を測定して、それらの平均値(%)をその偏光フィルムの単体透過率とした。
ICP-MS測定により求めた。なお、いずれの実施例、比較例および参考例においても、測定されたアルカリ金属のうちの99モル%以上はカリウムであった。
以下の実施例、比較例または参考例で得られた偏光フィルムについて、その長さ方向(MD)の任意の位置で、幅方向(TD)における中央部からMD×TD=2mm×10mmの大きさの細片を切り出し、その細片の両面を厚さ100μmのポリエチレンテレフタレートフィルム2枚で挟んでミクロトームに取り付けた。当該細片をポリエチレンテレフタレートフィルムの上から、MDと平行に20μm間隔でスライスし、サイズがMD×TD=2mm×20μmである試料を採取した。
当該試料について、堀場製作所製 顕微レーザラマン分光測定装置「LabRAM ARAMIS VIS」を用いて、ミクロトームによるスライスで生じた断面上の測定対象部分に対して、波長532nmのレーザー光を照射してラマン分光測定を行い、そのときに観測されたシグナルのうち、310cm-1でのシグナルの強度(Int310)と210cm-1でのシグナルの強度(Int210)とから、その部分における比率(Int310/Int210)を算出した。なお上記の測定対象部分は、偏光フィルムの厚み方向中央部、および、偏光フィルムの各面からフィルムの厚み方向に内部に厚みに対して10%進入した部分とし、偏光フィルムの厚み方向中央部より得られた比率(Int310/Int210)をLとし、また、偏光フィルムの各面からフィルムの厚み方向に内部に厚みに対して10%進入した部分より得られた2つの比率(Int310/Int210)について、M≦Nを満たすようにそれぞれの値をMまたはNとし、これらのL、MおよびNを用いて2×L/(M+N)を算出した。
PVA(酢酸ビニルとエチレンとの共重合体のけん化物、平均重合度2,400、けん化度99.4モル%、エチレン単位の含有率2.5モル%)100質量部、可塑剤としてグリセリン10質量部、界面活性剤としてポリオキシエチレンラウリルエーテル硫酸ナトリウム0.1質量部および水からなる製膜原液を用いてキャスト製膜することにより得られた、厚み30μmのPVAフィルムに対して、膨潤工程、染色工程、架橋工程、延伸工程、固定処理工程および乾燥工程を行うことにより偏光フィルムを製造した。
すなわち、上記のPVAフィルムを、温度30℃の水中に1分間浸漬している間に元の長さの2倍まで長さ方向(MD)に一軸延伸(1段目延伸)した後、使用量としてヨウ素を0.03質量%およびヨウ化カリウムを0.7質量%の濃度で水に混合してなる温度20℃の染色浴に1分間浸漬している間に元の長さの3倍まで長さ方向(MD)に一軸延伸(2段目延伸)し、次いでホウ酸を2.5質量%の濃度で含有する温度32℃の架橋浴に2分間浸漬している間に元の長さの3.6倍まで長さ方向(MD)に一軸延伸(3段目延伸)し、さらにホウ酸を2.8質量%およびヨウ化カリウムを5質量%の濃度で含有する温度57℃のホウ酸/ヨウ化カリウム水溶液中に浸漬している間に元の長さの6倍まで長さ方向(MD)に一軸延伸(4段目延伸)し、その後、ホウ酸を1.5質量%およびヨウ化カリウムを5質量%の濃度で含有する温度22℃のヨウ化カリウム水溶液中に5秒間浸漬することによりフィルムを洗浄し、続いて60℃の乾燥機で240秒間乾燥することにより、厚み13μmの偏光フィルムを製造した。
得られた偏光フィルムを用いて、上記した方法により、吸光度、単体透過率、アルカリ金属の含有率および2×L/(M+N)を測定ないし算出した。結果を表1に示した。
PVAフィルムの厚み、染色浴の温度、染色浴への浸漬時間および染色浴の組成を表1に示すように変更したこと以外は、実施例1と同様にして表1に示す厚みを有する偏光フィルムを製造した。
得られた偏光フィルムを用いて、上記した方法により、吸光度、単体透過率、アルカリ金属の含有率および2×L/(M+N)を測定ないし算出した。結果を表1に示した。
Claims (6)
- ポリビニルアルコールを含むマトリックスにヨウ素系色素が吸着している、厚みが25μm以下の偏光フィルムであって、クロスニコル状態における波長480nmでの吸光度(A)と波長700nmでの吸光度(B)との比率(A/B)が1.42以上である、偏光フィルム。
- ポリビニルアルコールを含むマトリックスにヨウ素系色素が吸着している、厚みが25μm以下の偏光フィルムであって、当該偏光フィルムの断面をラマン分光測定して得られる、フィルムの厚み方向中央部における310cm-1でのシグナル強度(Int310)と210cm-1でのシグナル強度(Int210)との比率(Int310/Int210)をLとし、フィルムの一方の面から厚み方向に内部に厚みに対して10%進入した部分における310cm-1でのシグナル強度(Int310)と210cm-1でのシグナル強度(Int210)との比率(Int310/Int210)をMとし、フィルムの他方の面から厚み方向に内部に厚みに対して10%進入した部分における310cm-1でのシグナル強度(Int310)と210cm-1でのシグナル強度(Int210)との比率(Int310/Int210)をNとした際に(但し、M≦Nである)、2×L/(M+N)が0.91以下である、偏光フィルム。
- クロスニコル状態における波長480nmでの吸光度(A)と波長700nmでの吸光度(B)との比率(A/B)が1.42以上である、請求項2に記載の偏光フィルム。
- 偏光フィルムに含まれるアルカリ金属の含有率をXモル/kgとし、偏光フィルムの厚みをYμmとしたときに、式:Z=X×log(Y)で示されるZが0.19以下である、請求項1~3のいずれか1項に記載の偏光フィルム。
- 単体透過率が40~45%である、請求項1~4のいずれか1項に記載の偏光フィルム。
- 厚みが50μm以下のポリビニルアルコールフィルムを染色および延伸する工程を含む、偏光フィルムの製造方法であって、染色はヨウ素系色素を含む染色浴にポリビニルアルコールフィルムを浸漬することにより行われ、染色浴の温度が25℃以下であり、浸漬時間が1.5分以下である、製造方法。
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