KR20150082874A - Preparing method for thin polarizer, thin polarizer and polarizing plate comprising the same - Google Patents

Abstract

The present invention relates to a method for preparing a thin polarizer, a thin polarizer and a polarizing plate manufactured using the same. The method comprises the steps of: forming laminations which are laminated with a poly-vinyl alcohol series film in at least one side of non-stretched base material film; and stretching the laminations to make the thickness of the poly-vinyl alcohol series film to be 10 μm or less, and the difference of the moisture contents of the non-stretched base material film and the poly-vinyl alcohol series film to be 9% or less.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin polarizer and a polarizer using the thin polarizer,

More particularly, the present invention relates to a method of manufacturing a thin polarizer having a thin thickness of 10 탆 or less, a thin polarizer manufactured using the same, and a polarizer .

A polarizer used in a polarizing plate is an optical element for converting natural light or arbitrary polarized light into polarized light in a specific direction, and is widely used in a display device such as a liquid crystal display element and an organic light emitting element (OLED). At present, as a polarizer used in the display device, a polyvinyl alcohol polarizing film in which molecular chains containing an iodine compound or a dichroic dye are oriented in a certain direction is generally used.

The polyvinyl alcohol polarizing film is produced by dying iodine or a dichroic dye to a polyvinyl alcohol film and then stretching the film in a predetermined direction and crosslinking. In this case, the stretching process may be carried out in the same manner as an aqueous solution of boric acid or an aqueous solution of iodine Wet stretching performed in a solution or dry stretching conducted in the atmosphere, and the stretching magnification is generally 5 times or more. However, in such a conventional manufacturing process, it is required that the thickness of the polyvinyl alcohol-based film before stretching exceeds 60 탆 in order to perform stretching without occurrence of breakage. When the thickness of the polyvinyl alcohol-based film before stretching is 60 탆 or less, the degree of swelling of the polyvinyl alcohol-based film is increased, and due to the thin thickness, the modulus of action per unit area in the stretching process becomes large.

On the other hand, according to recent tendency of thinning of display devices, polarizer is also required to have a thinner thickness. However, when a polyvinyl alcohol film having a thickness of more than 60 mu m is used as in the prior art, there is a limit in reducing the thickness of the polarizer.

Accordingly, studies have been made to produce a polarizer with a thin thickness while stretching is performed without occurrence of breakage. In this connection, a hydrophilic polymer layer is coated on a base film, or a base material film forming material and a hydrophilic polymer layer forming material A method of producing a thin polarizer using a laminate prepared by co-extruding a polarizer is proposed.

However, in the above-mentioned production method, when the base film and the polyvinyl alcohol-based film are easily peeled off, or the base film and the polyvinyl alcohol-based film are broken or wrinkled, or curling may occur in the produced polarizer, There is a problem that stability is poor.

More specifically, in the case of a polyolefin-based film or a polyethylene terephthalate-based film conventionally used as a base film, due to a difference in physical properties from a polyvinyl alcohol-based film, the ends of the film are curled or wrinkled at the time of stretching, The characteristics were often poor, which made it difficult to elongate at a high magnification.

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a method of manufacturing a thin polarizer having high optical properties and capable of high-magnification elongation and remarkably reducing rupture, end curling, .

According to one embodiment, the present invention provides a method for producing a laminated body, comprising: forming a laminate in which a polyvinyl alcohol-based film is laminated on at least one side of an unstretched substrate film; And stretching the laminate so that the thickness of the polyvinyl alcohol-based film is not more than 10 占 퐉, wherein a difference in wettability between the unstretched base film and the polyvinyl alcohol-based film is 9% or less to provide.

At this time, the unstretched substrate film is preferably a polyamide-based film.

The unstretched base film preferably has a moisture absorption rate of 0.5% to 8.0% or a glass transition temperature (Tg) of 50 ° C to 110 ° C.

On the other hand, the step of stretching the laminate may be carried out by wet stretching, and the wet stretching may be carried out in an aqueous solution of boric acid.

The stretching of the laminate may be performed by dry stretching. In the dry stretching, the glass transition temperature of the polyvinyl alcohol-based film may be in the range of (Tg-20) ° C to (Tg + 60 ) ° C at a draw magnification of 5 to 15 times.

On the other hand, in the production method of the present invention, it is preferable to further include a step of dying the dichroic dye into the laminate.

In this case, the method may further include a step of applying an aqueous solution containing an iodide compound onto the laminate after the step of dying, and then coloring the laminate.

On the other hand, it is preferable to further include a step of drying the drawn laminate after the step of stretching the laminate.

The method may further include separating the polyvinyl alcohol-based film from the base film after the step of stretching the laminate.

In another aspect, the present invention provides a thin polarizer produced by the above production method and a polarizing plate comprising the same.

At this time, it is preferable that the polarizer produced by the above-mentioned production method has a thickness of 10 μm or less, a simple transmittance of 40% to 45%, and a polarization degree of 99.9% or more.

According to the present invention, it is possible to produce a thin polarizer having a thickness of 10 mu m or less, which is excellent in optical characteristics, by a stable process.

The method of producing a thin polarizer of the present invention is a method of producing a thin polarizer by using a substrate film having a moisture absorption rate similar to that of a polyvinyl alcohol film to form a laminate and then performing a stretching process, And problems such as occurrence of edge curling phenomenon or curling of the produced polarizer can be minimized.

Fig. 1 is a conceptual diagram showing a method of measuring curl of a laminate after drying treatment in the examples and the comparative examples. Fig.

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art.

The present inventors have found that when a base film conventionally used, for example, a polyethylene terephthalate film or a polyolefin film, is used after a long period of research, the inventors have found that, due to the difference in moisture content between the film and the polyvinyl alcohol film as a polarizer, The degree of shrinkage of the film and the polyvinyl alcohol-based film is greatly changed, and thus, the breakage of the polarizer or the curling of the end portion occurs. Accordingly, the inventors of the present invention have found that, by forming a laminate using a substrate film having a moisture absorption rate similar to that of a polyvinyl alcohol-based film, breakage and curling can be remarkably reduced during the manufacturing process.

More specifically, a method of producing a thin polarizer according to the present invention comprises: forming a laminate in which a polyvinyl alcohol film is laminated on at least one surface of an unstretched base film; And stretching the laminate so that the thickness of the polyvinyl alcohol-based film is 10 m or less. The difference in wettability between the unstretched base film and the polyvinyl alcohol-based film is 9% or less.

First, the unstretched base film prevents breakage of the polyvinyl alcohol-based film and curling of the end portion in the stretching process, and the difference in moisture permeability with the polyvinyl alcohol-based film laminated on the base film is 9% or less , Preferably not more than 7%, and more preferably not more than 6%. When the difference in moisture content between the base film and the polyvinyl alcohol-based film exceeds 9%, the degree of shrinkage and expansion between the base film and the polyvinyl alcohol-based film during the stretching process or dyeing process of the laminate is significantly different, And the end curling phenomenon occurs, and wrinkles are generated on the surface of the polarizer, thereby deteriorating the quality of the thin polarizer.

More specifically, the laminate is shrunk by heat and expanded by moisture in the wet and dry stretching process. When the film is subjected to a drying process after the dry stretching or after the wet stretching, both the polyvinyl alcohol film and the substrate layer are dried by hot air. At this time, the drying shrinkage is caused to pass through the hot air bath, and after that, the substrate is expanded again by moisture absorption. Such shrinkage and expansion of the film are largely caused by moisture contained in the film itself, and a substrate having a moisture content similar to that of a polyvinyl alcohol-based film is used in order to alleviate the rupture of the polarizer and the curling of the end portion .

In the present invention, each film is stored at 25 ° C and 50% RH for 5 days, and the film is allowed to equilibrate under the above conditions. Then, the weight is measured do. Thereafter, the weight change after drying for 3 days in a convection oven at 80 ° C was measured and expressed as the moisture content. This was measured with an unoriented film, and in general, the moisture content of the substrate itself does not change significantly with elongation.

On the other hand, specific examples of the non-stretched base film include, but are not limited to, a polyurethane film, a polyester film, a polyamide film, an acrylic film, a high density polyethylene film, a low density polyethylene film, A low density polyethylene coextrusion film, a copolymer resin containing ethylene vinyl acetate in high density polyethylene, a polyvinyl alcohol film, a cellulose film and a polyamide film can be used.

However, as described above, it is most preferable to use a polyamide-based film from the viewpoint of satisfying the difference in the wetting ratio with the polyvinyl alcohol-based film. Generally, the moisture content of the polyamide-based film is about 0.5% to 8%.

The unstretched base film preferably has a moisture absorption rate of about 0.5% to about 8%, preferably about 0.5% to about 7.0%, and more preferably about 1.0% to about 7.0%. This is in order to satisfy the moisture content difference as described above because the moisture absorption rate of the polyvinyl alcohol film forming the polarizer is generally about 8% to 13%. When the moisture absorption rate of the base film is more than 8%, the swelling of the polymer is severe, so that it may not be able to sufficiently fulfill its role as a substrate in the post-processing.

Further, the unstretched base film usable in the present invention is particularly preferably a glass transition temperature of about 50 캜 to 110 캜, for example, from 60 캜 to 90 캜. This is because the glass transition temperature of the polyvinyl alcohol-based film is about 70 ° C to 80 ° C, and if the difference in the glass transition temperature between the base film and the polyvinyl alcohol-based film is large during the stretching process, stretching may not be possible. Therefore, it is preferable to select a substrate having a level similar to the glass transition temperature of the polyvinyl alcohol-based film. On the other hand, the glass transition temperature can be measured by a differential scanning calorimeter (DSC). For example, in the case of using a differential scanning calorimeter (DSC), when a sample of about 10 mg is sealed in a special pen and heated at a constant temperature, the endothermic heat and the heat generation amount of the material due to the phase change occur, The transition temperature can be measured.

Next, the polyvinyl alcohol film laminated on at least one surface of the unstretched base film can be used without any particular limitation as long as it contains a polyvinyl alcohol-based resin or a derivative thereof. At this time, derivatives of the polyvinyl alcohol-based resin include, but are not limited to, polyvinylformal resin and polyvinyl acetal resin. Alternatively, the polyvinyl alcohol-based film may be a polyvinyl alcohol-based film that is commercially available in the art for producing polarizers. For example, PE20, PE30, PE60 from Kuraray, M2000, M3000 M6000 and the like may be used.

On the other hand, the polyvinyl alcohol film is not limited to this, but the degree of polymerization is preferably about 1,000 to 10,000, and preferably about 1,500 to 5,000. When the degree of polymerization satisfies the above range, molecular motion is free and can be mixed with iodine or a dichroic dye or the like in a flexible manner.

The polyvinyl alcohol film preferably has a thickness of about 1 to 60 mu m, preferably about 1 to 40 mu m. When the thickness of the polyvinyl alcohol film exceeds 60 탆, it is difficult to realize a thickness of 10 탆 or less even when stretched. When the thickness is less than 1 탆, breakage tends to occur during stretching.

On the other hand, in the present invention, the method of laminating the above-mentioned unstretched base film and polyvinyl alcohol film is not particularly limited. For example, an aqueous solution containing the forming material of a polyvinyl alcohol-based film may be applied to the unstretched base film by a known method such as bar coating, reverse coating, gravure coating, spin coating, screen coating, fountain coating, spray coating , Comma coating, or the like, followed by drying to obtain a laminate.

Further, the laminate of the present invention can be formed by coextrusion of a forming material of a base film and a forming material of a polyvinyl alcohol film, and in this case, a laminate in an integrated state can also be obtained. Specifically, the forming material of the base film and the forming material of the polyvinyl alcohol-based film are injected into a co-extruder generally used in the related art, so that the thickness of the co-extruded base film and the polyvinyl alcohol- Whereby a laminate can be obtained.

Meanwhile, in the present invention, the unstretched base film and the polyvinyl alcohol-based film may be adhered by a weak attraction without a separate medium, and the adhesive force is 2N / 2 cm or less. Preferably, it is about 0.1 to 1 N / 2 cm or so. At this time, the adhesive force is an adhesive force measured when sample films having a width of 2 cm are attached. More specifically, after the polyvinyl alcohol film of the laminate is fixed with a sample holder, a force is applied in a direction perpendicular to the surface direction of the laminate, and the peel force (peel) measured while peeling the polyvinyl alcohol film from the base film (TA-XT Plus) manufactured by Stable Micro Systems Co., Ltd. was used as a measuring device. When the adhesive force satisfies the above range, the base film and the polyvinyl alcohol-based film are not separated during the stretching process, and surface damage during the separation process after stretching can be minimized.

On the other hand, in order to improve the adhesion between the base film and the polyvinyl alcohol-based film, the surface treatment may be performed on one surface or both surfaces of the base film and the polyvinyl alcohol-based film. At this time, the surface treatment can be carried out through various surface treatment methods well known in the art, for example, corona treatment, plasma treatment or surface modification treatment using a strong base aqueous solution such as NaOH or KOH.

Alternatively, the base film and the polyvinyl alcohol-based film may be attached using an adhesive. When the base film and the polyvinyl alcohol film are adhered using an adhesive, the thickness of the adhesive layer is preferably about 20 to 4000 nm. When the thickness of the adhesive layer satisfies the above range, it is advantageous to peel off the polyvinyl alcohol-based film after the stretching and drying process without damage.

On the other hand, the adhesive should have an adhesive force (adhesive force) of 2 N / 2 cm or less, and its material is not particularly limited, and various adhesives known in the art can be used without limitation. For example, the adhesive layer may be formed of an aqueous adhesive or an ultraviolet curable adhesive.

Next, a polyvinyl alcohol film is adhered on the unstretched base film to form a laminate, and then the laminate is stretched. In this case, the stretching conditions are not particularly limited. For example, the stretching can be performed at a stretching magnification of 5 to 15 times at a temperature of 40 to 140 캜, more preferably 5 to 12 times Can be performed at a stretching magnification.

In the stretching step, both wet stretching and dry stretching can be used. In the wet stretching process, the stretching in the transverse direction in the process may be difficult, and the stretching may be more preferable in terms of facilitating the change in the absorption axis direction.

At this time, the wet stretching can be performed at 40 ° C to 70 ° C, preferably at 50 ° C to 65 ° C. Further, it may be carried out at a draw magnification of 5 to 15 times, for example, at a draw magnification of 5 to 9 times or 6 to 8 times. On the other hand, in the case of the conventional method of producing a thin polarizer, it is difficult to perform stretching at a high magnification due to the structure and characteristics of the base film itself, or a difference in wettability with the polyvinyl alcohol film is large. There is a problem that breakage and wrinkling occur. On the other hand, in the case of the present invention, the stability of the process can be improved by controlling the generation of wrinkles of the polyvinyl alcohol-based film.

Preferably, the wet stretching is performed in an aqueous solution of boric acid, and the boric acid concentration of the aqueous solution of boric acid is preferably about 1.0 to 5.0% by weight.

When stretching is performed in the aqueous boric acid solution as described above, the fracture occurrence rate of the polyvinyl alcohol-based film is lowered due to crosslinking of boric acid, thereby increasing the process stability and controlling the generation of wrinkles of the polyvinyl alcohol-based film that is likely to occur during the wet process . In addition, there is an advantage that drawing can be performed even at a low temperature compared with dry drawing.

In general, the polarizer manufacturing process is performed by washing, swelling, dying, washing, stretching, complementing, drying and the like. In the present invention, it is preferable that the washing and drawing process is performed in an aqueous solution of boric acid. More preferably, the boric acid concentration in the washing step may be about 0.1 to 2.5% by weight, preferably about 0.5 to 2.0% by weight, and in the case of the stretching step, the boric acid concentration is about 1.0 to 5.0% by weight, 4.5% by weight.

The stretching may be performed by dry stretching, and the dry stretching may be performed at a temperature of (Tg-20) ° C to (Tg + 60) ° C, where Tg is a glass transition temperature of the polyvinyl alcohol- , And more preferably at a temperature of (Tg + 10) DEG C to (Tg + 40) DEG C. For example, in general, the glass transition temperature of the polyvinyl alcohol-based film is about 70 ° C to 80 ° C, and the dry drawing can be performed at a temperature of 60 ° C to 140 ° C. When the stretching temperature is lower than 60 ° C, the polyvinyl alcohol film is hardly stretched. Since the temperature is higher than 140 ° C at which the crystallization of the substrate occurs, the stretching temperature of the substrate is not suitable.

Further, the stretching step may be performed at a draw magnification of 5 to 15 times, for example, at a draw magnification of 5 to 12 times. If the stretching magnification exceeds the above range, breakage may occur at the time of stretching. If the stretching ratio is less than the above range, the degree of orientation of the polymer decreases and the degree of polarization of the polarizer produced may be lowered.

Similarly to the above-described wet stretching, in the case of the present invention, unlike a conventional polyolefin film or polyethylene terephthalate film, the moisture content is close to that of the polyvinyl alcohol film, and the shrinkage degree of the film Do. Accordingly, there is an advantage that the wrinkle and breakage of the polyvinyl alcohol-based film are suppressed, the problem of damaging the film is solved, and the appearance property can be excellently given.

More specifically, the dry stretching can be usually performed by performing uniaxial stretching. This uniaxial stretching can be carried out with respect to the longitudinal direction (MD) of the laminate, or with respect to the transverse direction (TD) of the laminate. Also, longitudinal (MD) shrinkage may be caused by simultaneous biaxial stretching of the laminate in the transverse direction (TD). On the other hand, the transverse (TD) stretching method of the laminate is, for example, a fixed one uniaxial stretching method in which one end is fixed through a tenter, and the longitudinal (MD) stretching Examples of the method include an inter-roll stretching method, a compression stretching method, and a free-end uniaxial stretching method. On the other hand, the stretching treatment may be carried out in multiple stages, or by biaxial stretching, warp stretching, or the like.

On the other hand, the laminate is stretched in the stretching step. At this time, the width in the direction perpendicular to the stretching direction of the laminate is reduced by about 35% to 65% after stretching based on the stretching step And the thickness of the laminate may be reduced by 20% to 50% after the step of stretching based on the pre-stretching step. In this case, in the stretching step and the drying step after the stretching step, the base film and the polyvinyl alcohol-based film show similar stretching behavior and width shrinkage behavior, so that the orientation of the polyvinyl alcohol-iodine complex can be increased, It is possible to manufacture a thin polarizer having optical performance. Particularly, when the base film and the polyvinyl alcohol-based film have similar moisture absorption rates, the stretching behavior and the shrinking behavior between the two films become similar, and more excellent effects can be obtained.

The above wet stretching and dry stretching is preferably performed so that the thickness of the polyvinyl alcohol film is 10 탆 or less, for example, 1 탆 to 8 탆 or 2 탆 to 7 탆 . The present invention is for producing a thin polarizer, and the thickness of the polyvinyl alcohol film is 10 mu m or less, whereby a thin polarizer can be produced.

Meanwhile, the thin polarizer manufacturing method of the present invention may further include the step of dying the dichroic dye into the laminate. At this time, the dyeing step may be performed before, simultaneously or after the stretching, but it is preferably performed after stretching in that the dichroic substance is favorably oriented on the polyvinyl alcohol-based film during dry stretching.

The dyeing step is carried out by adsorbing and orienting a dichroic dye on the formed laminate. On the other hand, the dichroic dye is not particularly limited as long as it is used in the art in the production of a polarizer, and for example, iodine or an organic dye can be used. Examples of the organic dyes include red BR, red LR, red R, pink LB, rubin BL, Borde GS, sky blue LG, lemon yellow, blue BR, blue 2R, navy RY, green LG, violet LB, violet B , Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, , Direct First Orange S, First Black, and the like can be used.

On the other hand, in the case of the present invention, iodine is more preferably used as the dichroic dye, and iodine and iodide are preferably used together. In this case, the efficiency of the dyeing can be further improved.

Examples of the iodide compound include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide and titanium iodide. Of these, potassium iodide is particularly preferable. In this case, the weight ratio of iodine and iodide compound is preferably in the range of 1: 4 to 1:20, more preferably in the range of 1: 5 to 1:15, in the range of 1: 7 to 1:12 Is particularly preferable. When the weight ratio of iodine and iodide compound satisfies the above range, the optical characteristics of the polarizer produced are more excellent.

In the present invention, although not limited thereto, the step of dying may include a method of immersing the laminate in an aqueous solution containing the dichroic dye or a method of applying an aqueous solution containing a dichroic dye and coating have.

On the other hand, in the aqueous solution containing the dichroic dye, the concentration of the dichroic dye is preferably 4 to 20 wt%, more preferably 5 to 15 wt%, and particularly preferably 7 to 12 wt% . If the concentration of the dichroic dye is less than 4% by weight, the efficiency of the dyeing is lowered and the polarization efficiency may be lowered. If the concentration exceeds 20% by weight, the dye may be overbased to decrease the transmittance. At this time, an organic solvent compatible with water may be further added to the aqueous solution.

More specifically, the coating method may be a coating method widely known in the art such as a coating method, a roll coating method, a spin coating method, a printing method, and a blade coating method. More specifically, in a coating method well known in the art, coating is carried out while applying heat to the laminate at 30 DEG C to 80 DEG C, more preferably 40 DEG C to 70 DEG C, particularly preferably 45 DEG C to 65 DEG C, Can be performed. In this case, the heat of the temperature range is transferred to the laminate, so that swelling of the polyvinyl alcohol can easily occur, and as a result, the efficiency of the dyeing can be increased. On the other hand, when the coating is carried out at a temperature of less than 30 캜, when the thickness of the polyvinyl alcohol-based film after stretching is about 4 탆 or more, the polarization efficiency of the polarizer produced is poor, When the coating is carried out under the temperature condition of < RTI ID = 0.0 > 100 C, < / RTI > the excessively high heat is applied.

On the other hand, in the above-mentioned coating method, a method of applying heat in the temperature range to the laminate is not particularly limited. For example, a hot air nozzle or the like may be separately installed in the coating process to apply heat to the laminate, or heat may be applied to the laminate using a heating roll. Among them, it is particularly preferable to apply heat to the laminate by using a heating roll. When heated by a hot air nozzle, a change in the concentration of the dye may be caused by hot air, and due to the flow of hot air, the appearance of the film may be poor and nonuniformity may be caused. However, This is because such a problem does not occur.

On the other hand, the method using the heating roll is not particularly limited as long as it can apply the heat of the temperature range to the stretched laminate in the coating process. For example, in a general coating process, a coating process may be carried out using a heating roll heated to the above-mentioned temperature range, or a heating guide roll heated to the above temperature range may be added to the rear end in a general coating process So that the efficiency of the dyeing can be increased. On the other hand, the method of heating the roll is not particularly limited, and can be heated by methods well known in the art.

On the other hand, in the case of performing the coating process using a heating roll heated to the above-mentioned temperature range in the general coating process as described above, heat transfer to the stretched laminate is carried out by heating the polyvinyl alcohol- It is more preferable to carry out through the opposite surface of the substrate. This is because when the heating roll is in contact with the surface of the polyvinyl alcohol-based film to transmit heat, there is a possibility that the problem of appearance defects of the produced polarizer may be caused.

Meanwhile, the thin polarizer manufacturing method of the present invention may further include a step of crosslinking to fix the dichroic dye adsorbed and oriented on the polyvinyl alcohol-based film after the dyeing step. The crosslinking step may be performed by immersing, coating or coating the laminate using an aqueous solution containing a crosslinking agent.

At this time, conventionally known materials may be used as the crosslinking agent to be used. Boron compounds such as boric acid and sodium borate, and glyoxal or glutaraldehyde. These compounds may be used alone or in combination. Among them, boric acid is particularly preferably used.

On the other hand, in the aqueous solution containing the crosslinking agent, the concentration of the crosslinking agent is preferably 0.5 to 5% by weight, more preferably 0.6 to 4% by weight, and particularly preferably 1 to 3% by weight. If the concentration of the cross-linking agent is less than 0.5% by weight, the amount of the cross-linking agent can be easily dissolved in water because of the small amount of cross-linking. This is because the crosslinking agent may precipitate on the surface of the film to cause surface contamination.

On the other hand, an iodide compound may be further added to the aqueous solution containing the crosslinking agent. Examples of such iodine compounds include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide and titanium iodide. Of these, potassium iodide desirable.

In the meantime, in order to prevent the color change of the dichroic dye adsorbed and oriented on the laminate after the step of dying the laminate, the method of producing a thin polarizer of the present invention is a method of preparing a polyvinyl alcohol film with an aqueous solution containing iodide compound Step < / RTI > The step of complementing in the present invention may also be carried out by a method of immersion or coating, as in the above-mentioned dyeing step.

On the other hand, the concentration of the iodide compound in the aqueous solution containing the iodide compound is preferably 1 to 10% by weight, more preferably 3 to 8% by weight, and 4 to 6% by weight Particularly preferred. When the concentration of the iodide compound is less than 1% by weight, the effect is insufficient and the polyvinyl alcohol film is bluish due to the color change of the dichroic dye. When the concentration of the iodide compound exceeds 10% by weight, The concentration is too high to cause the polyvinyl alcohol film to become reddish.

The iodine compound may be, for example, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, Among them, potassium iodide is particularly preferable.

In the meantime, the method of the present invention further includes a step of washing the laminate to remove unnecessary residues deposited on the surface of the polyvinyl alcohol-based film, if necessary, after the step of dying the dichroic dye can do. The present invention can be carried out by a method of immersing or applying, if necessary. In this case, the cleaning step is not particularly limited in the order of the drying step to be described later. At this time, water or an iodide compound may be used as the cleaning agent.

On the other hand, in the cleaning step, when water is used as the cleaning agent, it can usually be treated with pure water such as ion-exchanged water or distilled water. When the cleaning agent is an iodide compound, the concentration of the iodide compound in the aqueous solution containing the iodide compound is preferably 1 to 10% by weight, more preferably 3 to 8% by weight, and more preferably 4 to 6% by weight Particularly preferred. Examples of the iodide compound include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide and titanium iodide. Of these, Potassium is preferred.

Meanwhile, the thin polarizer manufacturing method of the present invention may further include a step of drying the laminate after the stretching. In this case, the drying is preferably performed at a temperature of about 20 ° C. to 100 ° C., more preferably about 40 ° C. to 90 ° C., in consideration of the optical characteristics of the polarizer, To about 10 minutes. In the drying step, moisture is removed from the surface and inside of the polyvinyl alcohol to prevent degradation of the properties of the polyvinyl alcohol-based polarizer due to moisture during the production process of the polarizer, and the width shrinkage of the stretched polyvinyl alcohol- Thereby enhancing the polarizability of the polarizer by increasing the orientation of the complex composed of polyvinyl alcohol and iodine. At this time, it is preferable that the drying step is carried out after performing the dyeing, crosslinking, complementary treatment, and the like.

On the other hand, after the stretching or drying of the film laminate as described above, a step of separating the polyvinyl alcohol-based film from the base film may be further included if necessary. That is, in the present invention, the base film may be used as it is as a polarizer protective film, or may not be peeled off. On the other hand, the separating step may be carried out by applying a peeling force to the polyvinyl alcohol-based film or the base film to release both films. At this time, the peeling force is preferably 2 N / 2 cm or less, for example, about 0.1 to 2 N / 2 cm and 0.1 to 1 N / 2 cm.

When the separation step as described above is completed, a polyvinyl alcohol thin film polarizer having a thickness of 10 탆 or less is obtained. When a polyvinyl alcohol film is attached to both sides of a base film, two thin polarizers can be obtained in one step. The polarizer of the present invention produced by the above method has a thickness of 10 μm or less, for example, 1 μm to 10 μm, 3 μm to 10 μm, or 1 μm to 5 μm, , And a degree of polarization of at least 99.0%, at least 99.5%, and more preferably at least 99.9%.

Meanwhile, the present invention provides a polarizer comprising the thin polarizer produced by the above-described method.

The polarizer of the present invention can be formed by laminating a transparent film on one surface or both surfaces of the thin polarizer of the present invention. As the transparent film, various films used as a polarizer protective film or a retardation film in the related art can be used without limitation, and examples thereof include a polyester polymer, a styrene polymer, a cellulose polymer, a polyether sulfone polymer A polymer, a polycarbonate polymer, an acrylic polymer, a polyolefin polymer, a polyamide polymer, a polyimide polymer, a sulfone polymer, a polyether sulfone polymer, a polyether ether ketone polymer, a polyphenylene sulfide polymer, Films comprising at least one member selected from the group consisting of an alcohol polymer, a vinylidene chloride polymer, a vinyl butyral polymer, an arylate polymer, a polyoxymethylene polymer, an epoxy polymer, and a mixture of these polymers may be used .

The method of laminating the polarizer and the transparent film is not particularly limited, and may be performed using an adhesive or a pressure sensitive adhesive well-known in the art. In this case, the adhesive or pressure sensitive adhesive may be appropriately selected in consideration of the material of the transparent film to be used. For example, when TAC is used as the transparent film, an aqueous adhesive such as a polyvinyl alcohol adhesive may be used. When an acrylic film or a COP film is used as the transparent film, a photo-curing or thermosetting adhesive such as an acrylic adhesive or an epoxy adhesive can be used.

In addition, if necessary, the polarizing plate of the present invention may further include an adhesive layer on the thin polarizer of the present invention or the above-mentioned transparent film. The pressure-sensitive adhesive layer may be formed by a known pressure-sensitive adhesive composition such as an acrylic copolymer, an epoxy resin, a polyurethane resin, a silicone resin, a polyether resin, a polyamide resin and a polyvinyl alcohol A resin, and a resin are coated on a polarizer or a transparent film, and then irradiated with light or heat to cure the composition.

More specifically, the polarizing plate of the present invention comprises a polyvinyl alcohol thin polarizer having a thickness of 10 탆 or less, a transparent film attached to at least one side of the polyvinyl alcohol thin polarizer, and a pressure- Layer.

For example, the polarizing plate of the present invention comprises a polyvinyl alcohol thin polarizer having a thickness of 10 탆 or less, a transparent film adhered to one surface of the polyvinyl alcohol thin polarizer, and a pressure-sensitive adhesive layer formed on the other surface of the polyvinyl alcohol polarizer Layer.

If necessary, a primer layer or an adhesive layer may be further provided between the adhesive layer and the polyvinyl alcohol thin polarizer and / or between the adhesive layer and the transparent film to increase the adhesion.

Hereinafter, the present invention will be described in more detail with reference to specific examples.

Example

Example 1

A polyvinyl alcohol aqueous solution was prepared by dissolving a polyvinyl alcohol-based film (NH-26, Tg = 80 deg. C, moisture content = 11%) in water. The polyvinyl alcohol-based aqueous solution was coated on a polyamide film (MGC, Lexter, Tg = 66 캜, Tm = 215 캜, 150 탆, humidity = 4.0%) and dried to prepare polyvinyl alcohol To prepare a laminate having a coating film.

The laminate was dry-drawn at a stretching magnification of 5 times in the machine direction (MD) by uniaxial free-end drawing at a temperature of 100 캜. The thickness of the polyvinyl alcohol film after stretching was 6.1 占 퐉.

Next, the stretched laminate was immersed in an aqueous solution containing 4% by weight of a dichroic dye (iodine: potassium iodide = 1: 10), followed by a dying treatment. Thereafter, the layered product was immersed in an aqueous solution containing 1% by weight of boric acid and crosslinked. Thereafter, the laminate was immersed in an aqueous solution containing 5% by weight of potassium iodide to perform complementary treatment. Next, the laminate was dried in an oven at 80 캜 for 60 seconds, and after drying, the polyvinyl alcohol film was peeled off from the polymer film.

Example 2

The laminate was obtained in the same manner as in Example 1, except that the laminate was dry-drawn at a draw ratio of 5 times in the transverse direction (TD) by uniaxial free-end drawing at a temperature of 100 ° C Polarizers were prepared. The final thickness of the prepared polarizer was 3.5 탆.

Example 3

The laminate was obtained in the same manner as in Example 1 except that the laminate was dry-drawn at a draw ratio of 5 times in the machine direction (MD) by uniaxial free-end drawing at a temperature of 110 ° C. Polarizers were prepared. The final thickness of the prepared polarizer was 6.5 탆.

Example 4

A polyvinyl alcohol aqueous solution was prepared by dissolving a polyvinyl alcohol-based film (NH-26, Tg = 80 deg. C, moisture content = 11%) in water. The above polyvinyl alcohol aqueous solution was coated on a polyamide film (MGC, MXD6, Tg = 88 ° C, Tm = 234 ° C, 150 탆, humidity = 5.8%) and dried to obtain polyvinyl alcohol To prepare a laminate having a coating film.

The laminate was dry-drawn at a draw ratio of 5 times in the machine direction (MD) by uniaxial free-end drawing at a temperature of 110 ° C. The thickness of the polyvinyl alcohol-based film after stretching was 6.6 mu m.

Example 5

In the same manner as in Example 4 except that the laminate was dry-drawn at a draw ratio of 5 times in the transverse direction (TD) by uniaxial free-end drawing at a temperature of 110 ° C Polarizers were prepared. The final thickness of the prepared polarizer was 3.3 탆.

Example 6

In the same manner as in Example 1 except that the laminate was dry-drawn at a draw ratio of 7 in the machine direction (MD) by uniaxial free-end drawing at a temperature of 100 ° C in Example 4 Polarizers were prepared. The final thickness of the prepared polarizer was 5.4 mu m.

Comparative Example 1

A polyvinyl alcohol aqueous solution was prepared by dissolving a polyvinyl alcohol-based film (NH-26, Tg = 80 deg. C, moisture content = 11%) in water. The polyvinyl alcohol aqueous solution was coated on a polyethylene terephthalate film (Mitsubishi Plastics, SG-007, Tg = 80 캜, 150 탆, humidity = 0.3%) and dried to give a polyvinyl alcohol- To prepare a laminate having a coated film.

The laminate was dry-drawn at a stretching magnification of 5 times in the machine direction (MD) by uniaxial free-end drawing at a temperature of 100 캜. The thickness of the polyvinyl alcohol-based film after stretching was 6.2 占 퐉.

Next, the stretched laminate was immersed in an aqueous solution containing 4% by weight of a dichroic dye (iodine: potassium iodide = 1: 10), followed by a dying treatment. Thereafter, the layered product was immersed in an aqueous solution containing 1% by weight of boric acid and crosslinked. Thereafter, the stretched laminate was immersed in an aqueous solution containing 5% by weight of potassium iodide to perform complementary treatment. Next, the laminate was dried in an oven at 80 캜 for 60 seconds, and after drying, the polyvinyl alcohol film was peeled off from the polymer film.

Comparative Example 2

In the same manner as in Example 1 except that the laminate was dry-drawn at a draw ratio of 5 in the transverse direction (TD) by uniaxial free-end drawing at a temperature of 100 ° C in the above-mentioned Comparative Example 1 Polarizers were prepared. The final thickness of the prepared polarizer was 3.5 탆.

Comparative Example 3

In the same manner as in Example 1 except that the laminate was dry-drawn at a draw ratio of 6 in the machine direction (MD) by uniaxial free-end drawing at a temperature of 110 ° C in the above Comparative Example 1 Polarizers were prepared. The final thickness of the prepared polarizer was 5.3 탆.

Experimental Example 1

In Examples 1 to 6 and Comparative Examples 1 to 3, the degree of formation of wrinkles and end curls of the polyvinyl alcohol-based film caused by the water content difference between the base film and the polyvinyl alcohol-based film during the stretching process was measured Are shown in Table 1 below. More specifically, the examples and the comparative examples were repeated five times each time, and the number of wrinkles and the number of occurrences of curling of the end portions after stretching was judged by naked eye. X, respectively.

Experimental Example 2

In Examples 1 to 6 and Comparative Examples 1 to 3, the degree of curling of the laminate after stretching and before lamination was measured and is shown in Table 1 below. More specifically, as shown in Fig. 1, the laminate is placed on a horizontal glass substrate with the polarizer facing upward, and the distance H from the top or bottom of the curved portion of the laminate to the end of the laminate is measured using a steel ruler The results are shown in Table 1 below.

Experimental Example 3

The optical characteristics of the polarizers prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were measured with a V-7100 spectrophotometer equipped with an automatic polarizing film analyzer VAP-7070 manufactured by JASCO Corporation and are shown in Table 1 below

division Base film Humidity
(%) Glass transition temperature
(° C) Stretching condition TD Curl
(mm) PVA thickness
(탆) Group Transmittance (%) Polarization degree
(%) Wrinkles and end curl Example 1 PA-based film 4.0 66 100 ℃, 5 times 1 axis MD 19 6.1 42.6 99.99 ○ Example 2 4.0 66 100 占 폚, 5 times 1 axis TD 21 3.5 39.4 99.99 ○ Example 3 4.0 66 110 ℃, 5 times 1 axis MD 19 6.5 42.7 99.99 ○ Example 4 5.8 88 110 ℃, 5 times 1 axis MD 10 6.6 42.8 99.99 ◎ Example 5 5.8 88 110 deg. C, 5 times 1 axis TD 8 3.3 39.6 99.99 ◎ Example 6 5.8 88 100 ℃, 7 times 1 axis MD 7 5.4 42.9 99.99 ◎ Comparative Example 1 PET film 0.3 82 100 ℃, 5 times 1 axis MD 31 6.2 42.7 99.99 × Comparative Example 2 0.3 82 100 占 폚, 5 times 1 axis TD 45 3.5 39.5 99.99 × Comparative Example 3 0.3 82 110 ℃, 6 times 1 axis MD 33 5.3 42.7 99.98 ×

As can be seen from Table 1, when a PET film having a water content difference of 9% or more with a PVA film as in the prior art was used, it was found that curl of the laminate produced was large.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be obvious to those of ordinary skill in the art.

F:
H: distance from the lowest or lowest end of the curved portion of the laminate to the end portion of the laminate

Claims (14)

Forming a laminate in which a polyvinyl alcohol film is laminated on at least one surface of an unstretched base film; And
And stretching the laminate so that the thickness of the polyvinyl alcohol-based film is not more than 10 mu m,
Wherein the difference in moisture content between the unstretched base film and the polyvinyl alcohol-based film is 9% or less.
The method according to claim 1,
Wherein the unstretched base film is a polyamide-based film.
The method according to claim 1,
Wherein the unstretched base film has a moisture content of 0.5% to 8%.
The method according to claim 1,
Wherein the unstretched base film has a glass transition temperature (Tg) of 50 ° C to 110 ° C.
The method according to claim 1,
Wherein the step of stretching the laminate is performed by wet stretching.
6. The method of claim 5,
Wherein the wet stretching is performed in an aqueous boric acid solution.
The method according to claim 1,
Wherein the step of stretching the laminate is performed by dry stretching.
8. The method of claim 7,
Wherein the dry stretching is performed at a stretching magnification of 5 to 15 times at a temperature of (Tg-20) DEG C to (Tg + 60) DEG C, where Tg is the glass transition temperature of the polyvinyl alcohol- ≪ / RTI >
The method according to claim 1,
And dewaxing the dichroic dye to the laminate.
10. The method of claim 9,
Further comprising a step of applying an aqueous solution containing an iodide compound to the laminate after the step of dyeing to thereby complement the thin polarizer.
The method according to claim 1,
Further comprising a step of drying the laminated body after the step of stretching the laminated body.
The method according to claim 1,
Further comprising the step of separating the polyvinyl alcohol-based film from the base film after the step of stretching the laminate.
14. A process for producing a polyurethane foam, which is produced by the process of any one of claims 1 to 12,
A thickness of 10 mu m or less, a single transmittance of 40 to 45%, and a polarization degree of 99.9% or more.
The thin polarizer of claim 13; And
And a protective film on at least one side of the thin polarizer.

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