KR101597830B1 - Polarizing plate and liquid crystal display device with high contrast - Google Patents

Abstract

The present invention relates to a polarizing plate comprising a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol based resin film, wherein a polarizing film single contrast (S _CR ( ?)) satisfies the following expressions (2) and (3).

&Quot; (1) "

(here,

Is the transmittance (%) of the polarizing film measured in relation to the linearly polarized light of incident wavelength? Nm and the parallel Nicol, and Tc (?) Is the transmittance (%) of the linearly polarized light of incident wavelength? (%) Of the polarizing film measured by the polarizing ultraviolet absorption spectrophotometer, all of which are measured values obtained by polarized ultraviolet visible absorption spectroscopy by a spectrophotometer)

&Quot; (2) "

[(S _CR (550) + S _CR (600))] / 2? 30,000

&Quot; (3) "

3,000? S _CR (450) < 30,000

High contrast polarizer, liquid crystal display, polyvinyl alcohol resin film

Description

TECHNICAL FIELD [0001] The present invention relates to a high contrast polarizing plate and a liquid crystal display,

The present invention relates to a high-contrast liquid crystal display device having clear display and a polarizing plate used therefor.

Polarizing films are widely used in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film. An iodine-based polarizing film using iodine as a dichroic dye or a dye-based polarizing film using a dichromatic direct dye as a dichromatic dye are known. These polarizing films are usually polarized by adhering a transparent protective film such as triacetylcellulose or cycloolefin to an adhesive or the like on one or both sides thereof with an adhesive containing an aqueous solution of polyvinyl alcohol resin.

The polarizing plate is widely used as an optical component for a liquid crystal display device. 2. Description of the Related Art [0002] A liquid crystal display device has been widely used as a display screen for a liquid crystal television, a personal computer monitor, a notebook computer, a mobile phone, and the like. Particularly, mobile phones have been popularized every generation, and their progress is remarkable. Particularly, improvement in display quality is demanded in addition to weight reduction, thinning, and cost reduction. In addition, the liquid crystal television also has a remarkable increase in the rate of diffusion in recent years, and it is required to improve the display quality as well as the cost.

Among such display quality, there is a characteristic called &quot; contrast &

Contrast of the display device = (luminance at back display) / (luminance at black display)

. Here, the luminance is an index of the brightness measured by a commercially available luminance meter or the like. For example, the luminance meter BM-5A sold by TOPCON or the like and the spectroscopic radiation meter SR-UL1 ) And the like. These are designed to match the sensitivity of the human eye by applying a correction called visibility correction. The visibility correction will be described later in detail. The higher the contrast, the clearer the black and white, and the clearer the image is obtained, and is generally used as an index of visibility in this field.

As one of the methods for improving the contrast, there is a method of improving the polarization performance of a polarizing plate which is an essential member of a liquid crystal display device. The term &quot; polarization performance &quot; referred to herein is a numerical value mainly called a simple transmittance and a polarization degree, and is a numerical value defined by the following mathematical expression.

(?) = 0.5 x (Tp (?) + Tc (?))

(?) = 100 × (Tp (?) - Tc (?)) / (Tp (?) + Tc

Here, Tp (?) Is the transmittance (%) of the polarizing film measured in relation to the linearly polarized light of the incident wavelength? Nm and the parallel Nicol, Tc (?) Is the relationship of the linearly polarized light of the incident wavelength? (%) Of the polarizing film measured by a spectrophotometer, which is a measurement value obtained by polarized ultraviolet visible absorption spectroscopy. Further, sensitivity correction called visibility correction is added to the simplex transmittance (?) And the degree of polarization (?) Obtained for each wavelength is called a visibility-corrected single unit transmittance Ty and visibility correction polarity Py. The visibility correction will be described later in detail. Ty and Py can be easily measured with, for example, a spectrophotometer (model number: V7100) manufactured by Nippon Bunko Co.,

Until now, there has been room for improvement of the Py and Ty of the polarizing plate. Therefore, the contrast of the liquid crystal display is improved by improving the polarizing performance of the polarizing plate by Py improvement or the like. However, recently, the polarizing performance of the polarizing plate is almost saturated, It is close to the limit value, so that a great improvement due to the polarization performance can not be expected. In terms of the Ty and Py values measured with V7100, the polarizabilities of Py and Py are about 99.996% and 42.5%, respectively. However, it is practically difficult to stably produce polarizers with higher performance. For example, when the degree of polarization is increased, the transmittance decreases and becomes dark. On the other hand, when the transmittance is increased, the degree of polarization decreases.

However, on the other hand, it is a fact that the demand for the contrast enhancement of the liquid crystal display device is still high, and it is necessary to solve the problem by the new thinking method which is fundamentally deviated from the above improvement method.

DISCLOSURE OF THE INVENTION <

An object of the present invention is to provide a liquid crystal display device having a higher contrast than in the prior art. It is still another object of the present invention to provide a polarizing plate for achieving the same and a method for producing the polarizing plate.

In order to solve the above problems, the inventors of the present invention conducted extensive research based on the principle and the principle of the numerical value of contrast. As a result, the present inventors have found that the above- It is possible to increase the contrast as a liquid crystal display device beyond the present level by defining the characteristic for each wavelength of the polarizing plate after understanding the light emission characteristic of the liquid crystal display device The present inventors have reached the present invention. Specifically, it was realized that it is important to set the emission wavelength characteristic of the backlight and the polarizing plate single contrast (S _CR ) wavelength dependence of the polarizing plate to the present invention. Further, a method for producing a polarizing plate having such characteristics has also been found.

That is, the present invention relates to a polarizing plate comprising a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film, wherein the polarizing film has a contrast (S _CR (lambda)) satisfy the relations of the following equations (2) and (3).

(here,

Is the transmittance (%) of the polarizing film measured in relation to the linearly polarized light of incident wavelength? Nm and the parallel Nicol, and Tc (?) Is the transmittance (%) of the linearly polarized light of incident wavelength? (%) Of the polarizing film measured by the polarizing ultraviolet absorption spectrophotometer, all of which are measured values obtained by polarized ultraviolet visible absorption spectroscopy by a spectrophotometer)

[(S _CR (550) + S _CR (600)) / 2]? 30,000

3,000? S _CR (450) < 30,000

The polarizing plate of the present invention is obtained by laminating a cellulose acetate resin film on one side of the polarizing film through an adhesive layer and a cycloolefin resin film on the other side through an adhesive layer or by laminating a cycloolefin resin film on one side of the polarizing film It is preferable that a cellulose acetate resin film is laminated through an adhesive layer and a self-adhesive protective film which can be peeled off through the adhesive layer is laminated on the other side. Further, it is preferable that the adhesive layer is formed from an aqueous adhesive.

The polarizing plate of the present invention is a polarizing plate used in a liquid crystal display device including a backlight and a liquid crystal cell. In the above liquid crystal display, in the spectrum measured with the liquid crystal cell alone in the backlight, It is preferable that the blue emission peak wavelength (Bmax) and the red emission peak wavelength (Rmax) satisfy the following expression (4).

(Rmax-550) < (550-Bmax)

The present invention also relates to a method for producing a polarizing plate, which comprises laminating a film on both sides of a polarizing film having a water content of 9% or more and heat-treating the film at a temperature of 70 캜 or higher within 40 seconds immediately after lamination.

The present invention also provides a liquid crystal display comprising a backlight, a liquid crystal cell and the polarizing plate, wherein in a spectrum measured with the liquid crystal cell alone in the backlight and the backlight illuminated, the blue emission peak wavelength (Bmax) And a red emission peak wavelength (Rmax) satisfy the following expression (4).

&Quot; (4) &quot;

(Rmax-550) < (550-Bmax)

In the polarizing plate of the present invention, the backlight and the liquid crystal cell (color filter) have the light emission wavelength characteristic even if the visual sensitivity correction degree of polarization Py and the visual sensitivity correction single light transmittance Ty are the same as those of the conventional polarizer, The contrast of the screen of the liquid crystal display device can be remarkably improved as compared with the case of using a conventional polarizing plate.

MODES FOR CARRYING OUT THE INVENTION [

Hereinafter, the present invention will be specifically described.

In a typical liquid crystal display device, when light emitted from a backlight through a color filter of a liquid crystal cell is irradiated, the light is not the same at all wavelengths and there is a weakness at each wavelength. This intensity is determined by the emission spectrum from the backlight and the design of the color filter.

The backlight is determined depending on the type and the shape of the luminescence spectrum, and the shape of the backlight differs depending on the type thereof. For example, there are a cold cathode fluorescent lamp (CCFL) type having an emission spectrum as shown in FIG. 1, and a light emitting diode (LED) having an emission spectrum as shown in FIG. 2 . The spectral shape is also somewhat characteristic in that the principle of light emission is different from each other.

On the other hand, since the design of the color filter of the liquid crystal cell is important for the color production of the display device, there is a difference in design among the respective companies. Usually, it is often composed of three colors of red (R), green (G), and blue (B).

It should be noted that Rmax, Gmax, and Bmax, which are the peak wavelengths of the three colors of R, G, and B, can not necessarily be designed with equal intervals in the spectrum produced by the combination of the backlight and the liquid crystal cell (color filter) . This is a problem of color production as a display device, and is derived from the wavelength characteristics of the backlight and the color filter. For example, in the case of a cellular phone using a white LED, it is preferable that Bmax is about 450 nm, Gmax is about 550 nm, and Rmax is about 600 nm in view of color production and characteristics of backlight.

The definition of Rmax (emission peak wavelength of red), Gmax (emission peak wavelength of green) and Bmax (emission peak wavelength of blue) will be described. However, LED backlight type, such as mobile phones, But a CCFL type backlight as shown in a large liquid crystal television or the like may be composed of a plurality of fine peaks of one color as shown in Fig. Bmax is a peak at which the integral area becomes the maximum among the emission peaks whose peak positions are between 380 and 500 nm. The peak position can be determined by performing a fitting method such as appropriate normal distribution approximation, as needed, without counting a fine jump or the like such as noise. Gmax can be selected in the same manner in that the peak position is in the range of 500 to 570 nm and the peak position is in the range of 570 to 700 nm.

Here, the mind-sight correction thinking method is introduced. The sensitivity of the human eye is usually the highest at 550 nm wavelength, and the worse the sensitivity of the light at a wavelength away from it. Considering this is the concept of the visibility correction, and the correction spectrum of the right-and-left symmetric normal distribution type as shown in Fig. 3 is multiplied to the actual spectrum to calculate the visibility correction luminance. The peak of this calibration curve is at a position of 550 nm, which means that the light of this wavelength has the highest luminance and the sensitivity of the human eye. On the other hand, the wavelength is farther away from 550 nm. For example, when the visibility correction ratio at 550 nm is set to 1.0, only a ratio of 0.04 or less is obtained at 450 nm, that is, light having a wavelength of 450 nm at the same light emission amount is measured at a luminance of 1/25 of light at 550 nm .

Taking these into consideration, the backlight again shows a gap of about 100 nm between Bmax at 550 nm, but only about 50 nm between Rmax and 550 nm. That is, the following equation (4) is satisfied.

&Quot; (4) &quot;

(Rmax-550) < (550-Bmax)

This means that when the numerical value is measured as the luminance, the blue light is measured to be rather weak compared to the red light. Conversely, the red peak has a considerably higher contribution to luminance than the blue peak.

This tendency is particularly remarkable in the case of a mobile use such as a cellular phone or a PDA in which a white LED or the like is used for a back light because the peak of the long wavelength side can be restricted in principle . However, even in a large-sized TV designed with a CCFL or the like, satisfying the expression (4) is often preferable from the viewpoint of color production and the like, and is in the same tendency.

The present invention provides a polarizing plate for use in a liquid crystal display device having a backlight as described above, in which the wavelength dependence is taken into consideration, whereby the contrast of a display device can be dramatically improved without improving Ty or Py of the polarizing plate will be.

This indicates that the polarizing plate applied to such a display device also has a different importance for each wavelength. In the case of combining with the backlight described above, it is more efficient that the polarizing performance of the red region is emphasized.

The polarizing plate in the present state tends to pursue the polarization performance in the form of care for the entire wavelength range of visible light, if any. Particularly, the visibility-corrected single-unit transmittance and the visibility-correcting polarization degree, which were indicators of the conventional polarization performance, are values to which visibility correction is applied, as the name suggests. This visibility correction is, in other words, the curve itself of FIG. In this index, even in a polarizing plate having a spectrum of a quadrature transmittance (Tp ()) as shown in Fig. 4 (having a relatively uniform orthogonal transmittance at all wavelengths of B, G and R) Even in a polarizing plate having a spectrum of a quadrature transmittance (Tp ()) as shown (the transmittance at a wavelength of G and R is low and the transmittance at a wavelength of B is high), sensitivity decreases symmetrically around 550 nm Therefore, when the visibility correction is applied, the same value is obtained in both cases.

However, when the characteristics of the backlight and the color filter as described above are considered, it can be said that the polarizing plate of the type shown in Fig. 5 is more preferable because the red wavelength region contributes to the luminance.

Considering increasing the visibility correction polarization degree, it is necessary to improve the polarization degree as a whole in the whole wavelength region. Therefore, it is quite difficult for a reality approaching the theoretical limit value. However, from the type of FIG. 4 to the type of FIG. 5, If there is a change of viewpoint, there is room for improvement, and this can be a big solution.

6 and 7 are graphs showing the contrast (S _CR (?)) Of a polarizing film defined by the above-described formula (1) for a polarizing film having a spectrum of the orthogonal transmittance Tc (?) As shown in Figs. Graph. Since the contrast (S _CR (?)) Of the polarizing film is a ratio of the maximum value to the minimum value of the transmittance of the natural light in a state in which two polarizing plates are superimposed on each other than an index obtained by orthogonal transmittance or polarization degree, Is considered to be close to the superiority of contrast.

(A method of measuring the contrast of a single polarizing film)

Hereinafter, a method of measuring the contrast (S _CR (?)) Of a single polarizing film will be described.

<Measuring device>

A spectrophotometer is used as a measuring device for Tp (?) And Tc (?). In order to more accurately evaluate the Tc (?) Value, it is necessary to use a spectrophotometer capable of measuring up to a higher absorbance region. In the present invention, it is necessary to use an apparatus capable of measuring an absorbance of about 7 to 8. As such a spectrophotometer, a spectrophotometer (model number: V7100) manufactured by Nippon Bunko Co., Ltd. and the like can be mentioned.

As a method for introducing linearly polarized light, a method using a polarizing prism made of calcite or the like is generally known. In the present invention, the extinction ratio of the polarizing prism is set to 10 ^-5 or less.

<Measurement sample>

In many cases, the polarizing plate is provided with a transparent protective film bonded to one side or both sides of a polarizing film. However, when the transparent protective film has a retardation property and its slow axis is bonded so as not to be parallel to and orthogonal to the absorption axis of the polarizing film, Linearly polarized light becomes elliptically polarized by the retardation property of the transparent protective film, and Tp (?) And Tc (?) Can not be measured accurately. When evaluating such a polarizing plate, it is necessary to measure the polarizing plate by separating the transparent protective film from the polarizing plate. In the case where the transparent protective film has substantially no retardation property or the transparent protective film has retardation properties and the slow axis thereof is bonded so as to be parallel or orthogonal to the absorption axis of the polarizing film, Tp (?) And Tc (?) Can be accurately measured even if they are not separated from each other.

<Measurement>

(Parallel transmittance: Tp (?)) Measured in the relationship of linearly polarized light and parallel Nicol, and in the relation of orthogonal Nicole using the spectrophotometer, linearly polarized light (wavelength? Nm) A transmittance (orthogonal transmittance: Tc ()) is measured at each wavelength. Further, S _CR (?) Is obtained from the measured Tp (?) And Tc (?) According to the above formula (1).

(Characteristics of polarizing film)

The characteristics of the polarizing plate used in the liquid crystal display of the present invention are required to be a polarizing plate in which the contrast (S _CR (?)) Of the polarizing film of each wavelength defined by the formula (1) satisfies the following formula .

&Quot; (2) &quot;

[(S _CR (550) + S _CR (600)) / 2]? 30,000

In this case, the contrast of the display device is improved when [( _{CR CR} (550) + SC _CR (600) / 2] in the above-described formula (2) is 30,000 or more, preferably 40000 or more. Conversely, when the number is less than 30,000, the contrast of the display device is not obtained. S _CR (550) and S _CR (600) is preferably not less than each alone, 30,000, more preferably not less than 40,000.

By converting a row of the type polarizing plate having the S _CR (λ) characteristic as shown in FIG. 7 from the polarizing plate having the S _CR (λ) characteristic as shown in FIG. 6, S _CR at 550 nm or 600 nm is But the S _CR at around 450 nm is lowered in the opposite direction,

[(S _CR (550) + S _CR (600)) / 2] > S _{CR 450}

. This is, for example, in the case of the adsorbed iodine oriented polarizing film, the ratio of the absorption of the high wavelength side increases by by the high temperature and high humidity processing to be described below, increasing the proportion of in the polarizing film, iodine I _5, and accordingly I ₃ The absorption at the lower wavelength side is decreased. In addition, there is a phenomenon that the degree of orientation of iodine itself is somewhat raised by the high temperature and high humidity treatment, and there is also an increase in the overall S _CR .

As described above, even when the contrast of a single polarizing film at a wavelength in the B (blue) region is lowered, application to an LED backlight or a color filter with little contribution of blue is not a serious problem considering visibility correction. The contrast of a single polarizing film at wavelengths of red (G), green (G), and blue (G) is given priority, thereby improving the contrast of the liquid crystal display screen.

This is in pursuit of the contrast characteristic of a display device at a point of view completely different from the viewpoint of Ty or Py required for a conventional polarizer. In the development of a polarizer in which the polarization performance is near the theoretical limit, It can be said that it is a solution of contrast enhancement.

(Production method of polarizing plate)

The polarizing plate of the present invention can be manufactured, for example, as follows, but is not limited thereto.

(1) Polarizing Film Manufacturing Process

The polyvinyl alcohol resin constituting the polarizing film is usually obtained by saponifying a polyvinyl acetate resin. The saponification degree of the polyvinyl alcohol-based resin is usually 85 mol% or more, preferably 90 mol% or more, and more preferably 99 to 100 mol%. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate and other monomers copolymerizable therewith, such as ethylene-vinyl acetate copolymer. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and the like. The degree of polymerization of the polyvinyl alcohol-based resin is usually in the range of 1,000 to 10,000, preferably in the range of 1,500 to 5,000.

These polyvinyl alcohol resins may be modified, and for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral and the like modified with aldehydes may be used. Normally, an unoriented film of a polyvinyl alcohol based resin film having a thickness of 20 to 100 占 퐉, preferably 30 to 80 占 퐉 is used as a starting material for polarizing film production. The width of the film is industrially practically 1500 to 4000 mm. The thickness of the polarizing film obtained by uniaxially drawing the unstretched film in the order of swelling treatment, dyeing treatment, boric acid treatment and water washing treatment in the order of boric acid treatment and finally drying is 5 to 50 μm.

As a polarizing film producing method, there are roughly two manufacturing methods. The first method is a method in which a polyvinyl alcohol resin film is uniaxially stretched in air or an inert gas and then subjected to solution treatment in the order of a swelling treatment step, a dyeing treatment step, a boric acid treatment step and a water washing treatment step, to be. The second method is a method in which an unstretched polyvinyl alcohol based resin film is subjected to a solution treatment in the order of a swelling treatment step, a dyeing treatment step, a boric acid treatment step and a water washing treatment step in the form of an aqueous solution and subjected to wet treatment in a boric acid treatment step and / Followed by uniaxial stretching and finally drying.

In both methods, uniaxial stretching may be performed in one step or in two or more steps. For the stretching method, a known method may be employed. For example, a roll-to-roll stretching method in which a main speed difference is applied between two nip rolls for transporting a film, for example, a roll stretching method as described in Japanese Patent No. 2731813, And a tenter stretching method. Basically, the order of the steps is the same as described above, but there are no restrictions on the number of treatment baths and treatment conditions. In addition, the steps not described in the first and second methods may be added for other purposes. Examples of such a process include an immersion treatment (iodide treatment) with an iodide aqueous solution not containing boric acid after the treatment with boric acid, an immersion treatment (zinc treatment) with an aqueous solution containing zinc chloride or the like not containing boric acid, and the like have.

The swelling treatment step is carried out for the purpose of removing foreign substances on the surface of the film, removing the plasticizer in the film, imparting the dyeability in a subsequent step, plasticizing the film, and the like. The treatment conditions are determined within a range in which these objects can be achieved and within a range in which problems such as extreme dissolution of the base film and loss of transparency do not occur. When the film stretched in advance in the gas is swelled, the film is immersed in an aqueous solution of, for example, 20 to 70 占 폚, preferably 30 to 60 占 폚. The immersion time of the film is 30 to 300 seconds, preferably 60 to 240 seconds. When the unstretched original film is swollen from the beginning, the film is immersed in an aqueous solution of, for example, 10 to 50 ° C, preferably 20 to 40 ° C. The immersion time of the film is 30 to 300 seconds, preferably 60 to 240 seconds.

In the swelling process, the film tends to swell in the width direction and wrinkles are likely to enter the film. Therefore, a known widening width of the wiping roll (expander roll), spiral roll, crown roll, cross guide, bend bar and tenter clip It is preferable to carry the film while grasping the film with the apparatus. For the purpose of stabilizing the film transportation in the bath, the water stream in the swelling bath is controlled by an underwater shower, or an EPC (Edge Position Control) device is used to detect the end of the film to prevent meandering of the film Device) can be used in combination. In this process, since the film swells and expands even in the transport direction of the film, it is preferable to take measures such as controlling the speed of the transport roll before and after the process tank in order to eliminate the looseness of the film in the transport direction. In addition to the pure water, the swelling treatment bath to be used may be a mixture of boric acid (described in JP-A No. 10-153709), chloride (described in JP-A No. 06-281816), inorganic acid, Aqueous solutions in which water-soluble organic solvents, alcohols and the like are added in the range of 0.01 to 0.1% by weight can also be used.

The dyeing treatment process using the dichroic dye is performed for the purpose of adsorbing and orienting the dichroic dye to the film. The treatment conditions are determined within a range in which these objects can be achieved and within a range that does not cause problems such as dissolution and loss of transparency at the extremities of the base film. When iodine is used as the dichroism dye, it is preferable to use iodine at a concentration of 0.003 to 0.2 / 0.1 to 10/100 in a weight ratio of iodine / potassium iodide / water at a temperature of, for example, 10 to 45 ° C, Is immersed in an aqueous solution for 30 to 600 seconds, preferably 60 to 300 seconds. Instead of potassium iodide, other iodides, such as zinc iodide, may be used. Other iodides may also be used in combination with potassium iodide. Further, compounds other than iodide, for example, boric acid, zinc chloride, cobalt chloride, and the like may be coexistent. When boric acid is added, it is distinguished from the following boric acid treatment in that it contains iodine. If it contains 0.003 part by weight or more of iodine relative to 100 parts by weight of water, it can be regarded as a dyeing bath.

When a water-soluble dichroic dye is used as the dichroic dye, an aqueous solution having a dichroic dye / water concentration of 0.001 to 0.1 / 100 in a weight ratio of 20 to 80 ° C, preferably 30 to 70 ° C, Is used for 30 to 600 seconds, preferably 60 to 300 seconds. The aqueous solution of the dichroic dye to be used may contain a dyeing aid or the like, for example, an inorganic salt such as sodium sulfate, a surfactant, or the like. The dichroic dye may be used singly or two or more dichroic dyes may be used in combination.

As described above, the film may be stretched in a dyeing bath. Stretching is performed by a method such that the nip rolls before and after the dyeing bath have a major speed difference. In addition, as in the swelling process, a widening roll (expander roll), a spiral roll, a crown roll, a cross guide, a bent bar, and the like may be provided in a dyeing bath and / or a bath door.

The boric acid treatment is carried out by immersing a polyvinyl alcohol-based resin film dyed with a dichroic dye in an aqueous solution containing boric acid in an amount of 1 to 10 parts by weight per 100 parts by weight of water. When the dichroic dye is iodine, iodide is preferably contained in an amount of 1 to 30 parts by weight. Examples of the iodide include potassium iodide and zinc iodide. In addition, compounds other than iodide, for example, zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like may be coexistent.

The boric acid treatment is carried out for cross-linking water resistance and color adjustment (to prevent blue light). When boric acid treatment is performed for water resistance by crosslinking, a crosslinking agent such as glyoxal or glutaraldehyde may be used in addition to boric acid or boric acid, if necessary. Further, the boric acid treatment for water resistance may be referred to as a water resistance treatment, a cross-link treatment, an immobilization treatment or the like. The boric acid treatment for color adjustment may also be referred to as a complementary coloring treatment or a re-dyeing treatment.

This boric acid treatment is carried out by suitably changing the concentration of boric acid and iodide and the temperature of the treatment bath, depending on the purpose. The boric acid treatment for moisture resistance and the boric acid treatment for color adjustment are not particularly distinguished, but can be carried out under the following conditions. When the original film is subjected to swelling treatment, dyeing treatment or boric acid treatment, when the boric acid treatment is aimed at water resistance by crosslinking, 3 to 10 parts by weight of boric acid and 1 to 20 parts by weight of boric acid, Is usually carried out at a temperature of 50 to 70 占 폚, preferably 55 to 65 占 폚, by using a boric acid treatment bath containing a part by weight. The immersion time is from 90 to 300 seconds. Further, in the case of performing dyeing treatment or boric acid treatment on the stretched film in advance, the temperature of the boric acid treatment bath is usually 50 to 85 占 폚, preferably 55 to 80 占 폚.

After the boric acid treatment for moisture resistance, the boric acid treatment for color adjustment may be performed. For example, when the dichroic dye is iodine, a boric acid treatment bath containing 1 to 5 parts by weight of boric acid and 3 to 30 parts by weight of iodide is used for 100 parts by weight of water, Lt; RTI ID = 0.0 &gt; 45 C. &lt; / RTI &gt; The immersion time is usually 3 to 300 seconds, preferably 10 to 240 seconds. The subsequent treatment of boric acid for color adjustment is usually carried out at a lower boric acid concentration, higher iodide concentration, and lower temperature, as compared to the boric acid treatment for water resistance.

These boric acid treatments may include a plurality of steps, and are often performed in a step of 2 to 5 in many cases. In this case, the aqueous solution composition and temperature of each boric acid treatment tank to be used may be the same or different within the above-mentioned range. The boric acid treatment for the water resistance and the boric acid treatment for the color adjustment may be carried out by a plurality of steps, respectively.

Also in the boric acid treatment step, stretching of the film can be carried out in the same manner as in the dyeing treatment step. The final integral stretch magnification is 4 to 7 times, preferably 4.5 to 6.5 times. The integral stretch magnification here means the length of the original film in the lengthwise direction of the film after the stretching process has been completed, and for example, the portion of 1 m in the original film is the stretched film 5 m, then the cumulative magnification factor at that time is five times.

After the boric acid treatment, the water washing treatment is carried out. The water washing treatment is carried out by immersing the polyvinyl alcohol resin film treated with boric acid for water resistance and / or color adjustment in water, spraying water as a shower, or using immersion and spray in combination. The temperature of water in the water washing treatment is usually 2 to 40 占 폚, and the immersion time is 2 to 120 seconds.

Here, in each of the steps after the stretching treatment, tension control may be performed so that the tension of the film is substantially constant. Specifically, when the drawing is finished in the dyeing treatment step, the tension control is performed in the subsequent boric acid treatment step and the water washing step. When stretching is completed in all the steps of the dyeing treatment process, the tension control is performed in the subsequent steps including the dyeing treatment step and the boric acid treatment step. In the case where the boric acid treatment step includes a plurality of boric acid treatment steps, the film is stretched in the boric acid treatment step from the first or second stage to the next boric acid treatment step in the stretching treatment step, The tension is controlled in each step from the boric acid treatment step in which the stretching treatment is performed to the next boric acid treatment step in the water washing step in which the film is stretched in the boric acid treatment step from the first stage to the third stage, However, industrially, the film is stretched in the boric acid treatment process from the first stage to the second stage from the first stage to the second stage, and tension control is performed in each step from the boric acid treatment step in which the stretching step is performed to the next boric acid treatment step to the water washing step Is more preferable. Further, in the case where the iodide treatment or the zinc treatment is carried out after the boric acid treatment, the tension control can be performed also for these steps.

A nip roll for controlling the tension, and a rubber roll, a polishing roll made of stainless steel, a sponge rubber roll, or the like can be used as the guide roll for controlling the transport direction of the film. The rubber roll includes NBR and the like, and its hardness is preferably 60 to 90 degrees, more preferably 70 to 80 degrees in JIS Shore C scale measured by the test method of JIS K6301. As the polishing rolls made of stainless steel, SUS304, SUS316 and the like are included. In order to equalize the film thickness, the surface roughness of the abrasive roll is preferably about 0.2 to 1.0 (expressed as an average interval S of the roughness curve of JIS B 0601 S is preferable. As the sponge rubber roll, the hardness of the sponge is 20 to 60 degrees, more preferably 25 to 50 degrees, a density of 0.4 to 0.6 g / m &lt; 3 &gt; and a density of 0.42 to 0.57 g / Cm &lt; 3 &gt;.

The tension in each step from the swelling treatment to the water washing treatment may be the same or may be different. The tension on the film in the tension control is not particularly limited and is preferably 150 to 2000 N / m per unit width Is appropriately set within the range of 600 to 1500 N / m. If the tensile strength is less than 150 N / m, wrinkles and the like easily occur on the film. On the other hand, if the tensile force exceeds 2000 N / m, there arises a problem such as breakage of the film and increase in water retention due to abrasion of bearings. The tension per unit width is calculated from the film width near the entrance of the process and the tension value of the tension detector. In addition, when tension control is performed, there is a case where it is inevitably slightly elongated or contracted, but in the present invention, this is not included in the stretching process.

Drying treatment is performed at the end of the polarizing film producing process. It is preferable that the drying treatment is carried out at a large number of steps by slightly changing the tension. However, the drying treatment is usually carried out in two to three steps due to constraints on equipment and the like. It is preferable that the tension in the previous step is set in the range of 600 to 1500 N / m and the tension in the subsequent step is set in the range of 250 to 1200 N / m. If the tensile force is too large, the breakage of the film is increased, and if it is too small, the occurrence of wrinkles is increased. It is also preferable to set the drying temperature in the previous step to 30 to 90 ° C and the drying temperature in the subsequent step to 40 to 100 ° C. If the temperature is too high, the film will be broken more and the optical characteristics will be lowered, and if the temperature is too low, the stripes will be increased. The drying treatment temperature may be, for example, 60 to 600 seconds, and the drying time in each step may be the same or different. If the time is too long, it is not preferable from the viewpoint of productivity. If the time is too short, drying becomes insufficient, which is not preferable.

Thus, the polyvinyl alcohol-based resin film is subjected to uniaxial stretching, dyeing treatment with a dichroic dye, and boric acid treatment to obtain a polarizing film. The thickness of the polarizing film is usually in the range of 5 to 40 mu m.

(2) a method of imparting a property satisfying equations (2) and (3) to a polarizing film

The polarizing plate of the present invention has such a characteristic that the polarizing film used is represented by the following formula (2). A polarizing film having this property is obtained by keeping the polarizing film under a specific environment. That is, it is necessary to keep the polarizing film in a state of high temperature and high humidity at least in a state in which shrinkage of the polarizing film in the flow direction (absorption axis direction) is suppressed.

&Quot; (2) &quot;

[(S _CR (550) + S _CR (600))] / 2]? 30,000

In the state where the shrinkage of the polarizing film is not suppressed, the polarizing film produced by uniaxially stretching shrinks to lose its polarization performance. In a state in which shrinkage of the polarizing film is suppressed, a method of holding the polarizing film in a high-temperature and high-humidity vessel while maintaining a tension on the polarizing film, a method of laminating films on both surfaces of a polarizing film having a high moisture content, And the like. The tension in the former is 15 x 10 ⁴ N / m 2 to 1500 x 10 ⁴ N / m 2, more preferably 150 x 10 ⁴ N / m 2 to 1200 x 10 ⁴ N / m 2. Below 15 x 10 ⁴ N / m 2, the polarization performance tends to be lost, and at 1500 x 10 ⁴ N / m 2 or more, it is easy to break.

In the latter case, shrinkage of the polarizing film is suppressed by laminating a film such as a transparent protective film described later on both sides of the polarizing film. Further, in this method, since the polarizing film is placed under high temperature and high humidity only by heating the laminated polarizing plate, there is no need to provide a high-temperature and high-humidity bath when the polarizing film is kept in a high temperature and high humidity environment.

A high temperature and high humidity environment refers to an environment at a temperature of 40 ° C to 90 ° C and a humidity of 50% to 95% RH, more preferably a temperature of 60 ° C to 80 ° C and a humidity of 60% to 90% RH. When the temperature is less than 40 DEG C or when the humidity is less than 50% RH, the temperature and humidity are insufficient, and it becomes difficult to obtain the characteristics described in the formula (3). When the temperature exceeds 90 占 폚, the polarizing film is deteriorated and is likely to be partially and partially visible in a blue color. When the humidity is higher than 95% RH, condensation tends to occur.

The time of exposure in a high temperature and high humidity environment is 10 seconds to 1200 seconds, more preferably 20 seconds to 600 seconds. If the time is short, a sufficient processing effect can not be obtained. If it is too long, the polarizing film is deteriorated and it is liable to be partially and partially visible in a blue color.

In a method of laminating a film on both sides of a polarizing film and imparting high temperature in a state where the polarizing film is highly moisture, it is difficult to quantify the temperature and humidity environment in which the polarizing film is exposed. Therefore, Conditions. This temperature is 70 DEG C or higher, preferably 75 DEG C or higher, and usually 100 DEG C or lower, preferably 90 DEG C or lower. If the temperature is too low, a sufficient treatment effect can not be obtained, whereas if the temperature is too high, the polarizing film deteriorates and it is liable to be partially and partially visible in a blue color.

This treatment imparts a high temperature within 40 seconds, preferably within 30 seconds, and more preferably within 20 seconds from immediately after bonding. If the time taken to impart a high temperature is long, the water content of the polarizing film is lowered, and it becomes difficult to obtain a treatment effect.

The time for applying the high temperature after bonding is 10 seconds to 1200 seconds, more preferably 20 seconds to 600 seconds. If the time is short, a sufficient processing effect can not be obtained. If it is too long, the polarizing film is deteriorated and it is liable to be partially and partially visible in a blue color.

The polarizing film having a high water content is a polarizing film having a moisture content of 9% or more, preferably 10% or more. If it is lower than 9%, it is difficult to obtain a treatment effect even if a film is laminated on both sides of the polarizing film to give a high temperature. If the moisture content is too high, wrinkles or the like may occur when a film is laminated on both sides of the polarizing film, which is not preferable. The upper limit of the moisture content is usually 20% or less, and more preferably 15% or less.

The moisture content of the polarizing film was determined by the following equation based on the value measured with an infrared ray moisture meter IM-3SCV MODEL-1900 (L) manufactured by Fuji Work Co., Ltd.

Moisture content = (1/28) * (1.2145 * measured value -941.662)

This equation is a relational expression obtained in that the value of the water content coefficient of the polarizing film having a different water content and the water content obtained from the change in the water content before and after the heat treatment at 105 ° C for one hour are almost linear.

The polarizing film having a moisture content within the preferable range described above can be obtained, for example, by controlling the drying temperature and the drying time of the polarizing film, and the polarizing film having a low water content can be obtained by lowering the temperature of the drying furnace and / And the polarizing film having a high water content can be obtained by increasing the temperature of the drying furnace and / or lengthening the drying time.

In the present invention, in order to obtain the performance of the formula (3), as a method of laminating a film on both surfaces of a polarizing film to give a high temperature in a state of high water content of the polarizing film, a combination of the above temperature, It is important.

After drying, it may also be cured at room temperature or slightly above that, for example, at a temperature of about 20 to 50 DEG C for about 12 to 600 hours. The temperature at the time of curing is generally set lower than the temperature employed at the time of drying.

(3) lamination of a film such as a transparent protective film to a polarizing film

As a method for laminating a film such as a transparent protective film on both sides of a polarizing film, a film is laminated directly or through an adhesive layer. When a film is laminated only on one side of the polarizing film, even if a high temperature is applied thereafter, the polarizing film is difficult to keep under a high humidity environment, which is not preferable.

The lamination of the films can be achieved by sequentially joining the polarizing film and the film in a side-by-side manner or using a roll or the like. It is preferable to perform simultaneous bonding on both sides in terms of production efficiency. The bonding temperature is usually in the range of about 15 to 30 占 폚. In the case of laminating through the adhesive layer, for example, a method in which an adhesive is uniformly applied to the surface of a polarizing film and / or a transparent protective film, and the other film is overlaid on the coated surface, . Usually, the adhesive is applied after its preparation at a temperature of 15 to 40 占 폚.

As the adhesive through the adhesive, a water-soluble adhesive, an organic solvent adhesive, a hot melt adhesive, a solventless adhesive and the like can be used. As the water-soluble adhesive, there may be mentioned, for example, a polyvinyl alcohol-based resin aqueous solution, a water-based liquid-type emulsion adhesive and the like. Examples of the organic solvent-based adhesive include a liquid type urethane- A urethane-based adhesive, and an epoxy-based adhesive.

In the case of using a polyvinyl alcohol-based resin aqueous solution, the polyvinyl alcohol-based resin used as an adhesive may be a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate which is a homopolymer of vinyl acetate, vinyl acetate and other monomers copolymerizable therewith , A modified polyvinyl alcohol polymer obtained by partially modifying a hydroxyl group of these copolymers, and the like. The adhesive may include polyvalent aldehyde, a water-soluble epoxy compound, a melamine compound, a zirconia compound, a zinc compound or the like as an additive. When such a water-based adhesive is used, the adhesive layer obtained therefrom usually has a thickness of 1 μm or less, and even if a cross section is observed with an ordinary optical microscope, its adhesive layer is practically not observed.

As the adhesive, a photo-curable adhesive may be used. As the photo-curable adhesive, for example, a radical polymerization initiator and / or a cationic polymerization initiator may be added to an epoxy resin, an acrylic resin, an octacene resin, a urethane resin or a polyvinyl alcohol resin. Among them, it is preferable to add a cationic polymerization initiator to a mixture of an alicyclic epoxy resin and an epoxy resin having no alicyclic structure.

When a polarizing film and a film to be bonded thereto are bonded using a photo-curable adhesive, the photo-curable adhesive is cured by irradiating an active energy ray after bonding. A light source of an active energy ray is not particularly limited, but an active energy ray having a light emission distribution at a wavelength of 400 nm or less is preferable. Specifically, a low energy mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, Mercury lamp, metal halide lamp and the like are preferably used. The light irradiation intensity to the photo-curable adhesive is appropriately determined depending on the composition of the photo-curable adhesive and is not particularly limited, but it is preferable that the irradiation intensity in the wavelength range effective for activation of the polymerization initiator is 0.1 to 6000 mW / cm &lt; 3 & . When the irradiation intensity is not less than 0.1 mW / cm 2, the reaction time does not become too long, and when the irradiation intensity is 6000 mW / cm 2 or less, the heat radiated from the light source and the yellowing of the epoxy resin due to heat generation upon curing of the photo- There is little fear of generating deterioration. The light irradiation time to the photo-curable adhesive is not particularly limited, as it is controlled for each photo-curable adhesive to be cured, but it is set so that the integrated light quantity indicated as the product of the irradiation intensity and the irradiation time is 10 to 10000 mJ / desirable. When the total amount of light to the photo-curable adhesive is 10 mJ / cm 2 or more, the active species originating from the polymerization initiator can sufficiently be generated and the curing reaction can be more surely proceeded. In the case of 10000 mJ / cm 2 or less, , And good productivity can be maintained. The thickness of the adhesive layer after irradiation with active energy rays is usually about 0.001 to 5 μm, preferably 0.01 μm or more, more preferably 2 μm or less, further preferably 1 μm or less.

When the photo-curable adhesive is cured by irradiation of an active energy ray, it is preferable to perform curing under the condition that all functions of the polarizing plate such as the degree of polarization, transmittance and hue of the polarizing film are not deteriorated.

When a film is laminated on both sides of a polarizing film, when the film is laminated through an adhesive layer, the film is preferably a transparent protective film.

As the transparent protective film, for example, a cycloolefin resin film, a cellulose acetate resin film, a polyester resin film such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polycarbonate resin film, A resin film, a polypropylene resin film, and the like, which are conventionally widely used in the field.

Examples of the cycloolefin resin include commercially available products such as Topas (manufactured by Ticona), Aton (manufactured by JSR Corporation), ZEONOR (manufactured by Nippon Zeon Co., Ltd.), Zeonex (ZEONEX) (manufactured by Nippon Zeon Co., Ltd.) and APEL (manufactured by Mitsui Chemicals, Inc.) can be preferably used. When the cycloolefin resin is formed into a film, known methods such as solvent casting method and melt extrusion method are suitably used. Further, a preformed cycloolefin such as, for example, Essener (manufactured by Sekisui Chemical Co., Ltd.), SCA40 (manufactured by Sekisui Chemical Co., Ltd.) or Zeonorfilm (manufactured by Optesis) A commercially available product of a film made of a resin can also be used.

The cycloolefin-based resin film may be uniaxially stretched or biaxially stretched. By stretching, an arbitrary retardation value can be imparted to the cycloolefin-based resin film. The stretching is usually performed continuously while winding the film roll, and is stretched in the heating furnace in the direction of the roll, in the direction perpendicular to the direction of the roll, or both. The temperature of the heating furnace is usually in the range of the glass transition temperature +100 deg. C in the vicinity of the glass transition temperature of the cycloolefin resin. The magnification of the stretching is usually 1.1 to 6 times, preferably 1.1 to 3.5 times.

When the cycloolefin-based resin film is stretched, its stretching direction is arbitrary, but it is generally 0 °, 45 °, and 90 ° with respect to the flow direction of the film. The retardation of the film having the stretching direction of 0 ° is in the case of perfect uniaxial, 45 ° and 90 °, and the retardation characteristic of the film often has a slight biaxial property. The characteristics are affected by the viewing angle of the display device, but can be timely selected in accordance with the type of the liquid crystal display device or the type of the composite polarizing plate to which the display device is applied. Frequently, the retardation value is often referred to as? / 4,? / 2 or the like, and is often in the range of 90 to 170 nm when? / 4 and 200 to 300 nm when? / 2.

When the cycloolefin-based resin film is in a roll state, the films tends to adhere to each other and tend to cause blocking. Normally, a protective film is bonded and rolled. Since the cycloolefin-based resin film generally has a low surface activity, it is preferable to perform surface treatment such as plasma treatment, corona treatment, ultraviolet ray irradiation treatment, frame (flame) treatment and saponification treatment on the surface to be bonded with the polarizing film . Among them, a plasma treatment and a corona treatment which can be performed relatively easily are preferable.

Examples of the cellulose acetate resin that can be used for the transparent protective film include partially or completely acetic acid esterified products of cellulose, for example, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate and the like.

Examples of such a cellulose ester resin film include commercially available products such as Fuji Tack TD80 (manufactured by Fuji Film), Fuji Tack TD80UF (manufactured by Fuji Film), Fuji Tack TD80UZ (manufactured by Fuji Film Co., Ltd.) KC8UX2M (manufactured by Konica Minolta Opto) and KC4UY (manufactured by Konica Minolta Opto) can be preferably used.

Acetic acid cellulose-based resin films imparted with retardation characteristics are also preferably used. As commercially available products of the cellulose acetate-based resin films imparted with such retardation properties, WV BZ 438 (manufactured by Fuji Film), KC4FR-1 (Konica Minolta Opto (Manufactured by Nippon Polyurethane Industry Co., Ltd.). Acetic acid cellulose is also referred to as acetylcellulose or cellulose acetate.

When a cellulose based resin film is laminated with a polarizing film by using an aqueous adhesive, the saponification treatment is carried out in order to enhance adhesion with the polarizing film. As the saponification treatment, a method of immersing in an aqueous solution of an alkali such as sodium hydroxide or potassium hydroxide can be adopted.

The surface of the cycloolefin resin film and the cellulose acetate resin film may be subjected to surface treatment such as antiglare treatment, hard coating treatment, antistatic treatment and antireflection treatment depending on the application. In addition, a liquid crystal layer or the like may be formed to improve the viewing angle characteristics.

When the film is laminated on both sides of the polarizing film, it is more preferable that at least one side of the film is a resin film having low moisture permeability. When the moisture permeability is low, the polarizing film tends to be kept under a high humidity environment when laminated and given a high temperature.

The preferable water vapor permeability is 400 g / m &lt; 2 &gt; 24 hours or less, preferably 300 g or less, more preferably 100 g or less, further preferably 50 g or less under the environment of 40 deg.

Since the transparent protective film tends to cause blocking when the films adhere to each other when the transparent protective film is in a roll state, it is usually necessary to carry out roughing processing on the roll end, insert a ribbon into the end portion, or adhere a protective film, Is used.

The thickness of the transparent protective film is preferably small, but if it is too thin, the strength is lowered and the workability is lowered. On the other hand, if it is too thick, there arises a problem that the transparency is lowered or the curing time required after lamination is prolonged. Therefore, the suitable thickness of the transparent protective film is, for example, 5 to 200 占 퐉, preferably 10 to 150 占 퐉, and more preferably 20 to 100 占 퐉.

When the film is directly laminated on both sides of the polarizing film, the film is preferably a peelable protective film. The protective film is peeled off at a stage where it is unnecessary, for example, in the case of forming a pressure-sensitive adhesive layer on the polarizing film side of the polarizing plate.

The peel force between the protective film and the polarizing film is 0.01 to 5 N / 25 mm, preferably 0.01 to 2 N / 25 mm, and more preferably 0.01 to 0.5 N / 25 mm. When the peeling force is less than 0.01 N / 25 mm, the adhesion between the polarizing film and the protective film is small, so that the protective film may partially peel off. When the peeling force exceeds 5 N / 25 mm, it is not preferable because it is difficult to peel the protective film from the polarizing film.

As the material of the protective film, a polyethylene resin, a polypropylene resin, a polystyrene resin, a polyethylene terephthalate resin or the like which can be easily handled and secures a certain degree of transparency can be preferably used. Can be used as a protective film.

Specific examples of such protective films include an E-mask (available from Shin-Etsu Chemical Co., Ltd.) having a pressure-sensitive adhesive layer formed on the surface of a polyethylene resin film, an E-mask having an adhesive layer formed on the surface of a polyethylene terephthalate resin film (Manufactured by Nitto Denko K.K.), and Matsutake (manufactured by Fujimori Kogyo Co., Ltd.) having a pressure-sensitive adhesive layer formed on the surface of a polyethylene terephthalate resin film.

Among them, a self-adhesive protective film having a sticking property to a polarizing film alone can be used easily and more preferably because it does not need to protect the pressure-sensitive adhesive layer on the protective film surface. As a commercial product of a self-adhesive resin film exhibiting a preferable peeling force for the polarizing film, for example, Toretec (manufactured by Toray Co., Ltd.) containing a polyethylene resin can be mentioned.

In addition, the transparent protective film preferably has less defects such as fish eyes. If there is a defect, the shape may be transferred to the polarizing film, resulting in a defect of the polarizing film.

In the polarizing plate produced as described above, an optical film having an optical function other than the polarizing plate may be laminated on the protective film surface or the pressure-sensitive adhesive layer surface thereof. Examples of such an optical film include an optical compensation film coated with a liquid crystalline compound on the surface of a base material, an oriented optical compensation film which transmits polarized light of any kind and reflects polarized light exhibiting a property opposite to that of any polarized light, A retardation film including a cyclic polyolefin resin, a film with an antiglare function having a concavo-convex shape on a surface, a film with a surface antireflection function, a reflection film having a reflection function on the surface, And a transflective film having a transmissive function together. As a commercially available product corresponding to the oriented optical compensation film coated with a liquid crystalline compound on the surface of the base material, WV film (manufactured by Fuji Film), NH film (manufactured by Shin-Nippon Sekiyu Co., Ltd.), NR film (Manufactured by Sekiyu Co., Ltd.). As a commercially available product corresponding to a reflection type polarizing film that transmits polarized light of any kind and reflects polarized light exhibiting a property opposite to that of polarized light, for example, DBEF (manufactured by 3M Company, Sumitomo 3M Co., Ltd. in Japan) (Available from Sumitomo 3M Co., Ltd., Japan), and the like. Examples of commercially available products corresponding to the retardation film containing a cyclic polyolefin resin include commercially available products such as Aton film (manufactured by JSR Corporation), Essen (manufactured by Sekisui Chemical Co., Ltd.), Zeonor film ) Manufactured by Optesis).

When these other optical films are provided on the side of the protective film of the above-mentioned polarizing plate, they are usually laminated through the pressure-sensitive adhesive. As the pressure-sensitive adhesive in this case, the same materials as described above can be used, but the storage elastic modulus may not be so large. When another optical film is provided on the pressure-sensitive adhesive layer side of the polarizing plate, the optical film is bonded by the pressure-sensitive adhesive layer. In this case, a pressure-sensitive adhesive layer for bonding to the liquid crystal cell is usually provided outside the optical film.

In general, a polarizing plate having a pressure-sensitive adhesive layer formed by the production method of the present invention has a form of a large-sized roll material or sheet material. In order to obtain a polarizing plate having a desired shape and a transmission axis, a polarizing plate Chip cut). Therefore, the polarizing plate obtained by cutting has a state in which the polarizing film is exposed to the outside at the outer circumferential end.

When a polarizing plate in this state is subjected to a durability test such as, for example, a heat shock test, compared with a polarizing plate which is generally used, that is, a polarizing plate in which both surfaces of a polarizing film are protected with a cellulose resin film or the like, There is a tendency to occur. In order to avoid such a problem, it is preferable that the polarizing plate chip obtained in the present invention is continuously cut on the outer peripheral end face by the fly-cut method or the like.

(Bonding of the polarizing plate to the liquid crystal cell)

The polarizing plate produced by the above-described manufacturing method is bonded to the liquid crystal cell of the liquid crystal display device through the pressure-sensitive adhesive layer.

Such a pressure-sensitive adhesive layer is generally formed by using various pressure-sensitive adhesives conventionally used for bonding liquid crystal cells and polarizing plates, for example, pressure-sensitive adhesives such as acrylic, rubber, urethane, silicone, and polyvinyl ether. Further, an energy ray curable or heat curable pressure sensitive adhesive may be used, and among these, an acrylic pressure sensitive adhesive having an acrylic resin excellent in transparency, weather resistance, heat resistance and the like as a base polymer is preferable.

When the pressure-sensitive adhesive layer is formed directly on the surface of the polarizing film, the pressure-sensitive adhesive layer preferably has a storage elastic modulus of 0.15 to 1 MPa in a temperature range of 23 to 80 캜, and in other cases, it may not have such a high elastic modulus.

The acrylic pressure-sensitive adhesive is not particularly limited, but a (meth) acrylic acid ester base polymer such as (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate or 2-ethylhexyl Methacrylic acid esters and the like are preferably used. Polar monomers are also copolymerized in these base polymers. Examples of polar monomers include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N, N-dimethylaminoethyl And monomers having a functional group such as a carboxyl group, a hydroxyl group, an amide group, an amine group, and an epoxy group, such as a syndile (meth) acrylate.

These acrylic pressure-sensitive adhesives can be used alone, of course, but usually a crosslinking agent is used in combination. Examples of the crosslinking agent include a divalent or polyvalent metal salt which forms a carboxylic acid metal salt with a carboxyl group, a polyamine compound which forms an amide bond with a carboxyl group, a polyepoxy compound and a polyol compound, To form an ester bond, and as the polyisocyanate compound, an amide bond with a carboxyl group is exemplified. Among them, polyisocyanate compounds are widely used as organic crosslinking agents.

The energy ray curable pressure sensitive adhesive has a property of being cured upon irradiation with an energy ray such as ultraviolet ray or electron ray and has adhesion even before energy ray irradiation and is adhered to an adherend such as a film and cured by irradiation of an energy ray, Is a pressure-sensitive adhesive having a property of being able to do. As the energy radiation curable pressure sensitive adhesive, an ultraviolet curable pressure sensitive adhesive is preferably used. The energy radiation curable pressure sensitive adhesive generally comprises an acrylic pressure sensitive adhesive and an energy ray polymerizable compound as a main component. Usually, a crosslinking agent is further blended, and if necessary, a photopolymerization initiator and a photosensitizer may be blended.

In order to adjust the adhesive force, cohesive force, viscosity, elastic modulus, glass transition temperature and the like of the pressure-sensitive adhesive in addition to the above-mentioned base polymer and crosslinking agent as the pressure-sensitive adhesive composition, for example, resins such as natural or synthetic resins, , An ultraviolet absorber, a dye, a pigment, a defoaming agent, a corrosion inhibitor, and a photopolymerization initiator. It is also possible to add a fine particle to obtain a pressure-sensitive adhesive layer exhibiting light scattering properties.

The thickness of the pressure-sensitive adhesive layer is preferably from 1 to 40 占 퐉. However, in order to obtain a thin polarizing plate for the purpose of the present invention, it is preferable to apply a thin layer within a range that does not impair workability and durability, More preferably 3 to 25 占 퐉 in view of suppressing the dimensional change of the substrate. If the pressure-sensitive adhesive layer is too thin, the adhesiveness is deteriorated. If the pressure-sensitive adhesive layer is too thick, the pressure-sensitive adhesive property tends to be pushed out.

As described above, the pressure-sensitive adhesive directly formed on the surface of the polarizing film preferably has a storage elastic modulus in a temperature range of 23 to 80 캜 of 0.15 to 1 MPa. The pressure-sensitive adhesive used in a conventional image display apparatus or an optical film for its use has a storage elastic modulus of only about 0.1 MPa and a preferable storage elastic modulus of 0.15 to 1 MPa of the pressure-sensitive adhesive used in the present invention has a high value do. The storage elastic modulus can be measured using a commercially available viscoelasticity measuring device such as a DYNAMIC ANALYZER RDA II (manufactured by REOMETRIC Co., Ltd.).

In the method for producing a polarizing plate of the present invention, the method of forming the pressure-sensitive adhesive layer on the polarizing film is not particularly limited, and a solution containing each component including the base polymer described above is applied to the other side of the polarizing film The pressure sensitive adhesive layer may be formed by laminating a separator to which a releasing treatment such as a silicone treatment has been applied. Alternatively, a pressure sensitive adhesive layer may be formed on the separator and transferred to a polarizing film to be laminated. Further, when the pressure-sensitive adhesive layer is formed on the polarizing film, at least one of the polarizing film and the pressure-sensitive adhesive layer may be subjected to adhesion treatment, for example, corona treatment or the like, if necessary. Further, the surface of the formed pressure-sensitive adhesive layer is usually protected by a separator film subjected to a releasing treatment, and the separator film is peeled off before bonding the polarizing plate to a liquid crystal cell or another optical film.

<Examples>

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

[Example 1]

(Production of polarizing film)

A polyvinyl alcohol film having an average degree of polymerization of about 2400 and a degree of saponification of 99.9 mol% or more and having a thickness of 75 탆 was uniaxially stretched by about 5 times in a dry state and immersed in pure water at 60 캜 for one minute while being kept in a stretched state, / Potassium iodide / water at a weight ratio of 0.1 / 5/100 at 28 ° C for 60 seconds. Thereafter, the mixture was immersed in an aqueous solution of potassium iodide / boric acid / water at a weight ratio of 10.5 / 7.5 / 100 at 72 ° C for 300 seconds. Subsequently, the film was washed with pure water at 10 DEG C for 5 seconds, dried at 60 DEG C for 75 seconds and then at 75 DEG C for 30 seconds while maintaining the tensile strength of 400 N, to obtain a polarizing film in which iodine adsorption orientation with a moisture content of 10.9% .

(Preparation of adhesive)

Separately, 100 parts by weight of water was mixed with 3 parts by weight of a carboxyl group-modified polyvinyl alcohol (Kurarapoval KL318 (manufactured by Kuraray Co., Ltd.)) and a water-soluble polyamide epoxy resin (Sumirez Resin 650 (A) having a polyvinyl alcohol-based resin as a main component were prepared by dissolving 1.5 parts by weight of a water-soluble polyamide epoxy resin and 2 parts by weight of a carboxyl group-modified polyvinyl alcohol and a water-soluble polyamide epoxy resin And 1.0 part by weight of an adhesive (B).

(Production of polarizing plate)

On one side of the obtained polarizing film, a film of 40 占 퐉 thick (KC4UY, manufactured by Konica Minolta Opto Co., Ltd.) containing triacetyltylcellulose to which saponification treatment had been applied was applied by using the above adhesive (A) (Zeonor film ZD14-141158-A1340 (manufactured by Optesis), thickness: 32 μm) made of a norbornene resin previously subjected to corona treatment was laminated on the surface of the nip roll . After the lapse of 5 seconds from the bonding at room temperature while maintaining the tensile force of the bonded product at 430 N / m, the polarizer was successively dried at 60 ° C for 11 seconds, at 80 ° C for 141 seconds, and at 70 ° C for 93 seconds successively.

[Example 2]

(Production of polarizing film)

A polarizing film having a water content of 13.9% was obtained in the same manner as in Example 1 except that the film was dried at 40 占 폚 for 60 seconds and at 50 占 폚 for 26 seconds.

(Production of polarizing plate)

Except that the joints were continuously dried at 60 ° C for 9 seconds, at 80 ° C for 113 seconds, and at 70 ° C for 75 seconds, successively after 4 seconds from joining at room temperature while maintaining the tensile strength of the joint at 430 N / m 1, a polarizing plate was obtained.

[Example 3]

(Production of polarizing film)

A polarizing film having a water content of 13.9% was obtained in the same manner as in Example 1 except that the film was dried at 40 캜 for 60 seconds and at 50 캜 for 25 seconds.

(Production of polarizing plate)

After 4 seconds from joining at room temperature while maintaining the tensile strength of the joint at 430 N / m, successively drying at 60 ° C for 9 seconds, at 90 ° C for 39 seconds, at 80 ° C for 74 seconds, and at 70 ° C for 75 seconds , A polarizing plate was obtained in the same manner as in Example 1. &lt; tb &gt; &lt; TABLE &gt;

[Comparative Example 1]

(Production of polarizing film)

A polarizing film having a water content of 8.7% was obtained in the same manner as in Example 1, except that the film was dried at 90 캜 for 106 seconds.

(Production of polarizing plate)

After 4 seconds from joining at room temperature while maintaining the tensile force of the bonded material at 430 N / m, successive drying at 50 ° C for 10 seconds, at 65 ° C for 43 seconds, at 80 ° C for 83 seconds, and at 70 ° C for 84 seconds , A polarizing plate was obtained in the same manner as in Example 1. &lt; tb &gt; &lt; TABLE &gt;

[Comparative Example 2]

(Production of polarizing film)

A polarizing film having a moisture content of 10.6% was obtained in the same manner as in Example 1. [

(Production of polarizing plate)

Except that the joints were continuously dried at 50 ° C for 10 seconds, at 65 ° C for 43 seconds, and at 80 ° C for 167 seconds successively, after 4 seconds from joining at room temperature while maintaining the tensile force of the joint at 430 N / m, 1, a polarizing plate was obtained.

[Comparative Example 3]

(Production of polarizing film)

A polarizing film having a water content of 8.7% was obtained in the same manner as in Example 1, except that the film was dried at 90 캜 for 106 seconds.

(Production of polarizing plate)

After 4 seconds from joining at room temperature while maintaining the tensile strength of the joint at 430 N / m, successive drying at 50 ° C for 10 seconds, at 70 ° C for 43 seconds, at 80 ° C for 83 seconds, and at 90 ° C for 84 seconds , A polarizing plate was obtained in the same manner as in Example 1. &lt; tb &gt; &lt; TABLE &gt;

[Measurement of S _CR of each polarizing plate]

With respect to the polarizing plate samples obtained in Examples 1 to 3 and Comparative Examples 1 to 3, the retardation film was peeled off and the triacetyl cellulose film having substantially no retardation property was peeled from the triacetylcellulose film S _CR of each polarizing plate at wavelengths of 450 nm, 550 nm and 600 nm was measured with a spectrophotometer (model No. V7100). The results are shown in Table 2.

(Evaluation of contrast of liquid crystal display device)

Table 1 shows the results of measuring the emission spectra of Bmax and Rmax by measuring the emission spectrum of a cellular phone module (including no polarizer) containing any white LED backlight and VA type liquid crystal cell. Bmax and Rmax of the cellular phone module satisfies the expression (4). The polarizers produced in Examples 1 to 3 and Comparative Example 1 were bonded to both sides of the liquid crystal cell of this module and the contrast of the liquid crystal screen of the liquid crystal display device (cellular phone) in which these modules were combined was measured by spectroscopy (SR-UL1). The results are shown in Table 2. The liquid crystal display device using the polarizing plates of Examples 1 to 3 had a very good contrast ratio, but the liquid crystal display device using the polarizing plate of the comparative example had only a low contrast ratio as compared with the examples.

The polarizing plate of the present invention is a liquid crystal display device having a backlight and a liquid crystal cell (color filter) having the light emission wavelength characteristics even when the visual sensitivity correction degree Py of the polarizing plate itself or the visual sensitivity correcting single light transmittance Ty is the same as that of the conventional polarizing plate The contrast of the screen of the liquid crystal display device can be significantly improved as compared with the case of using a conventional polarizing plate.

1 is a graph showing an example of a luminescence spectrum measured by placing a color filter on a CCFL type backlight.

2 is a graph showing an example of a light emission spectrum measured by placing a color filter on a backlight of an LED type.

3 is a graph showing an example of a visual sensitivity correction curve.

4 is a graph showing a quadrature transmittance spectrum of a polarizing film used in a conventional polarizing plate.

5 is a graph showing a quadrature transmittance spectrum of a polarizing film used in the polarizing plate of the present invention.

Fig. 6 is a graph showing a single polarizing film contrast of the same polarizing film as Fig.

Fig. 7 is a graph showing a single polarizing film contrast of the same polarizing film as Fig.

Claims (8)

A polarizing plate comprising a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol based resin film, wherein a contrast (S _CR (λ)) of a polarizing film at a wavelength λ nm defined by the following equation (1) Satisfies the following expressions (2) and (3): &quot; (2) &quot; &Quot; (1) &quot;

(here,

Is the transmittance (%) of the polarizing film measured in relation to the linearly polarized light of incident wavelength? Nm and the parallel Nicol, and Tc (?) Is the transmittance (%) of the linearly polarized light of incident wavelength? (%) Of the polarizing film measured by the polarizing ultraviolet absorption spectrophotometer, all of which are measured values obtained by polarized ultraviolet visible absorption spectroscopy by a spectrophotometer) &Quot; (2) &quot; [(S _CR (550) + S _CR (600)) / 2]? 30,000 &Quot; (3) &quot; 3,000? S _CR (450) < 30,000 The polarizing plate according to claim 1, wherein a cellulose acetate resin film is laminated on one side of the polarizing film through an adhesive layer, and a cycloolefin resin film is laminated on the other side through an adhesive layer. The polarizing plate according to claim 1, wherein a cellulose acetate resin film is laminated on one side of the polarizing film through an adhesive layer and a peelable self-adhesive protective film is laminated on the other side. The polarizer according to claim 2, wherein the adhesive layer is formed from an aqueous adhesive. The polarizer according to claim 3, wherein the adhesive layer is formed from an aqueous adhesive. The polarizing plate according to claim 1, wherein the liquid crystal display device is a polarizing plate for use in a liquid crystal display device including a backlight and a liquid crystal cell, wherein the liquid crystal display device has a liquid crystal cell in the backlight, (Bmax) and the emission peak wavelength (Rmax) of red satisfy the following expression (4): &quot; (4) &quot; &Quot; (4) &quot; (Rmax-550) < (550-Bmax) The method of producing a polarizing plate according to any one of claims 2 to 5, wherein a film is laminated on both sides of a polarizing film having a moisture content of 9% or more, and heat treatment is performed at a temperature of 70 캜 or higher within 40 seconds immediately after lamination. A liquid crystal display comprising a backlight, a liquid crystal cell, and a polarizing plate according to claim 1, (Bmax) and a red luminescence peak wavelength (Rmax) satisfy the following expression (4) in a spectrum measured with the liquid crystal cell placed in the backlight and the backlight illuminated: Liquid crystal display device. &Quot; (4) &quot; (Rmax-550) < (550-Bmax)

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