KR20100039807A - Polarizing plate and liquid crystal display device with high contrast - Google Patents

Abstract

PURPOSE: A polarizing plate and a liquid crystal display device with high contrast are provided to improve contrast by applying a polarizer to a liquid crystal display having an emitting wavelength property. CONSTITUTION: A polarizer comprises a polarizing film. The polarizing film is formed by absorbing and growing a polyvinyl alcohol resin film with two color pigments. The cellulose acetate series region film is laminated on one side of the polarizing film through an adhesive film. A cycloolefin-based resin film is laminated on the other side of polarizing film through an adhesive film.

Description

POLARIZING PLATE AND LIQUID CRYSTAL DISPLAY DEVICE WITH HIGH CONTRAST}

The present invention relates to a high contrast liquid crystal display device with clear display and a polarizing plate used therein.

As the polarizing film, a polyvinyl alcohol-based resin film obtained by adsorbing and aligning a dichroic dye is widely used. And the iodine type polarizing film which uses iodine as a dichroic dye, the dye type polarizing film which uses a dichroic direct dye as a dichroic dye, etc. are known. These polarizing films bond a transparent protective film, such as triacetyl cellulose and a cycloolefin, to a polarizing plate normally through the adhesive agent containing the aqueous solution of polyvinyl alcohol-type resin on one or both surfaces.

Polarizing plates are widely used as optical components for liquid crystal display devices. BACKGROUND ART The liquid crystal display device is expanding its market to display screens for liquid crystal televisions, monitors for personal computers, notebook computers, mobile phones, and the like. In particular, mobile telephones are spreading for generations, and their progress is remarkable. In particular, there is a demand for weight reduction, thinning, and cost reduction, as well as improvement in display quality. In addition, the diffusion rate of liquid crystal televisions has increased significantly these days, and this is also required to reduce the cost and to improve the display quality.

Among these display qualities, there is a property called contrast, which is

Contrast of display device = (luminance at white display) / (luminance at black display)

The value defined by. Here, luminance is an index of brightness measured with a commercially available luminance meter, for example, a color luminance meter (BM-5A) sold by TOPCON, etc., or a spectroradiometer (SR-UL1). ) Can be measured with These values are designed to match the sensitivity of the human eye by applying a correction called visibility correction. Vision correction is described in detail later. When the contrast is high, black and white becomes clear and a more clear image is obtained, and thus it is generally used as an index of visibility in this field.

As one of the methods for improving this contrast, there exists a method of improving the polarization performance of the polarizing plate which is an essential member of a liquid crystal display device. The polarization performance here is a numerical value called mainly transmittance and polarization degree, and is a numerical value defined by the following formula.

Single transmittance (λ) = 0.5 × (Tp (λ) + Tc (λ))

Polarization degree λ = 100 × (Tp (λ) -Tc (λ)) / (Tp (λ) + Tc (λ))

Here, Tp (λ) is the transmittance (%) of the polarizing film measured in the relationship between linearly polarized light of incident wavelength λ nm and parallel nicol, and Tc (λ) is a relationship between linearly polarized light and orthogonal nicotine of incident wavelength λ nm It is the transmittance | permeability (%) of the polarizing film measured by, and are all measured values obtained by the polarization ultraviolet visible absorption spectrum measurement by a spectrophotometer. Moreover, what added sensitivity correction called visibility correction to the single transmittance (lambda) and polarization degree (lambda) calculated | required for each wavelength is called visibility correction single transmittance (Ty) and visibility correction polarization degree (Py). Vision correction is described in detail later. Ty and Py can be measured easily, for example by the spectrophotometer (model number: V7100) made from Nippon Bunko Corporation.

Until now, there has been room for improvement of Py and Ty of the polarizing plate, but the contrast of the liquid crystal display device has been improved by improving the polarization performance of the polarizing plate by Py improvement or the like. Since it is also close to the limit value, a significant improvement due to polarization performance is not desired. In terms of Ty and Py values measured by V7100, the polarization performance of the best class of polarizing plates in recent years is Py = 99.996% and Ty = 42.5%, but it is practically difficult to stably manufacture a polarizing plate having a higher performance than this. For example, when the polarization degree is increased, the transmittance is lowered, and when the contrast is increased, the polarization degree is lowered.

However, on the other hand, the demand for improving the contrast of the liquid crystal display device is still only high, and it can be said that there is a need for a solution by a new way of thinking which is fundamentally dismissed from the above-described improvement methods.

<Start of invention>

An object of the present invention is to provide a liquid crystal display device having a higher contrast than conventionally. Moreover, it aims at providing the polarizing plate for achieving it, and providing the method of manufacturing this polarizing plate.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, as a result of earnestly examining back to the principle and principle of numerical value of a contrast, the visibility correction unit transmittance | permeability, visibility correction polarization degree, etc. which are the indicators based on evaluation in the polarizer single piece as before, etc. By realizing the reason why higher contrast can not be achieved by the above-mentioned way of thinking, understanding the light emission characteristics of the liquid crystal display device, and then defining the characteristics for each wavelength of the polarizing plate, the contrast as a liquid crystal display device can be increased. The groundbreaking method was found and the present invention was reached. Specifically, the inventors realized that the light emission wavelength characteristics of the backlight and the polarization film elemental contrast (S _CR ) wavelength dependence of the polarizing plate were important in any particular relationship, and the present invention was reached. Moreover, it also succeeded in finding the method for manufacturing the polarizing plate which has such a characteristic.

That is, this invention is a polarizing plate containing the polarizing film in which a dichroic dye is adsorbed-oriented to a polyvinyl alcohol-type resin film, Comprising: The polarizing film single-piece contrast (S) in each wavelength defined by following formula (1) of the said polarizing film. _CR (λ)) satisfies the relationship of the following expressions (2) and (3).

(here,

Where Tp (λ) is the transmittance (%) of the polarizing film measured in the relationship between the linearly polarized light of the incident wavelength λ nm and the parallel Nicols, and Tc (λ) is the relationship between the linearly polarized light of the incident wavelength λ nm and the orthogonal nicols. Is the transmittance (%) of the polarizing film measured in the above, and all are measured values obtained by polarized ultraviolet visible absorption spectrum measurement by a spectrophotometer.)

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

3,000≤S _CR 450 <30,000

The polarizing plate of this invention laminated | stacked the cellulose acetate resin film on one side of the said polarizing film through the adhesive bond layer, and the cycloolefin resin film was laminated | stacked on the other side through the adhesive bond layer, or on one side of the said polarizing film It is preferable that the self-adhesive protective film which can peel a cellulose acetate type resin film through the adhesive bond layer on the other side through an adhesive layer is preferable. In addition, the adhesive layer is preferably formed from an aqueous adhesive.

In addition, 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, the liquid crystal display device in the spectrum measured in the state in which the backlight is turned on with only the liquid crystal cell in the backlight, It is preferable that the blue peak emission wavelength Bmax and the red peak emission wavelength Rmax satisfy the following expression (4).

(Rmax-550) <(550-Bmax)

Moreover, this invention relates also to the manufacturing method of the polarizing plate which laminates a film on both surfaces of the polarizing film with a moisture content of 9% or more, and heat-processes at the temperature of 70 degreeC or more within 40 second immediately after lamination | stacking as a manufacturing method of the said polarizing plate.

In addition, the present invention is a liquid crystal display device comprising a backlight, a liquid crystal cell and the polarizing plate, the blue light emission peak wavelength (Bmax) in the spectrum measured in the state in which the backlight is turned on with only the liquid crystal cell in the backlight; And a red light emission peak wavelength Rmax satisfies the following expression (4).

<Equation 4>

(Rmax-550) <(550-Bmax)

The polarizing plate of the present invention is a liquid crystal display device in which the backlight and the liquid crystal cell (color filter) have light emission wavelength characteristics even if the visibility correction polarization degree Py and the visibility correction unit transmittance Ty in the polarizing plate are the same as those of the conventional polarizing plate. When used in, the contrast of the liquid crystal display screen can be significantly improved than in the case of using a conventional polarizing plate.

<Mode 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 passes through a color filter of a liquid crystal cell is irradiated, strength and weakness exist for each wavelength. This strength is determined by the emission spectrum from the backlight and the design of the color filter.

The backlight is determined to have the shape of the emission spectrum according to the type, and its shape is different depending on the type thereof. For example, there is a Cold Cathode Fluorescent Lamp (CCFL) type having an emission spectrum as shown in FIG. 1, or a Light Emitting Diode (LED) having an emission spectrum as shown in FIG. . Since the principle of light emission differs, the spectral shape becomes characteristic to some extent.

On the other hand, since the design of the color filter of the liquid crystal cell is important for manufacturing the color of the display device, there is a difference in design for each company. Usually, it consists of three colors, red (R), green (G), and blue (B).

It should be noted that in the spectrum produced by the combination of the backlight and the liquid crystal cell (color filter), Rmax, Gmax, and Bmax, which are the peak wavelengths of three colors of R, G, and B, cannot be designed at equal intervals. . This is a problem of color production as a display device, and originates in the wavelength characteristic of a backlight and a color filter. For example, in the case of a mobile phone using a white LED or the like, considering the viewpoint of color production and the characteristics of the backlight, it is preferable that Bmax is about 450 nm, Gmax is about 550 nm, and Rmax is about 600 nm.

Although the definitions of Rmax (red emission peak wavelength), Gmax (green emission peak wavelength), and Bmax (blue emission peak wavelength) are stated, LED backlight types such as mobile phones have peaks as shown in FIG. Although it is clear and very easy to understand, some CCFL type backlights seen by a large size liquid crystal television etc. are comprised by several peak with one color as shown in FIG. Bmax is the peak at which the integrated area becomes the maximum among the luminescence peaks in which the peak position is between 380 and 500 nm. Fine jumps, such as noise, are not counted as peaks, and a peak position can be determined by performing a fitting method such as an appropriate normal distribution approximation as necessary. Gmax can be selected in the same manner in that the peak position is in the range of 500 to 570 nm, and Rmax is in the range of 570 to 700 nm.

Here, a mindset of visibility correction is introduced. The sensitivity of the human eye is usually the highest at a wavelength of 550 nm, and the light at a wavelength away from it is worsened. Taking this into consideration is the concept of visibility correction, which calculates the visibility correction luminance by multiplying the actual spectrum by a right-left symmetrically distributed correction curve as shown in FIG. 3. The peak of this correction curve is at the position of 550 nm, which means that the light of this wavelength is the most sensitive to the luminance meter or the human eye. On the contrary, the sensitivity is lower as the wavelength is separated from 550 nm. For example, when the visibility correction factor at 550 nm is 1.0, the ratio is only 0.04 or less at 450 nm. That is, even at the same emission amount, light having a wavelength of 450 nm is measured with only 1/25 of the luminance of 550 nm. Will not be.

In view of these, the back light shows that the interval between 550 nm and Bmax is about 100 nm, while the interval between 550 nm and Rmax is only about 50 nm. That is, it is in the relationship of following formula (4).

<Equation 4>

(Rmax-550) <(550-Bmax)

This means that when measuring numerical values as luminance, the blue light is measured relatively weakly compared to the red light. In other words, the red peak has a considerably higher contribution to luminance than the blue peak.

This tendency tends to constrain the peak on the long wavelength side, especially in mobile applications such as cellular phones or PDAs that use white LEDs for backlighting, so that the relationship of Equation 4 is more significant. . However, also in a large TV designed for CCFL or the like, satisfying the expression (4) is often preferable in terms of color production and the like, and tends to be the same.

According to the present invention, in the polarizing plate applied to the liquid crystal display device having the above-mentioned backlight, by designing in consideration of the wavelength dependence, the contrast of the display device can be remarkably improved without improving Ty or Py of the polarizing plate. will be.

This indicates that the degree of importance for each wavelength is different also in the polarizing plate applied to such a display device. When combined with the above-mentioned backlight, it is efficient to give priority to the polarization performance of the red region.

Whatever the polarizing plate of the present state, it tends to pursue polarizing performance in the form which cares for the whole wavelength range of visible light. In particular, the visibility correction single transmittance and the visibility correction polarization degree, which are indices of the conventional polarization performance, are numerical values to which visibility correction is applied, as the name implies. This visibility correction is, in other words, the curve itself of FIG. 3. In this index, for example, even a polarizing plate having a spectrum of orthogonal transmittance (Tp (λ)) as shown in Fig. 4 (having a relatively uniform orthogonal transmittance at all wavelengths of B, G, and R), Even a polarizing plate having a spectrum of orthogonal transmittance (Tp (λ)) (low transmittance at the wavelengths of G and R and high transmittance at the wavelength of B) is insensitive to symmetry around 550 nm. Therefore, when the visibility correction is applied, both of them become the same value.

However, when considering the characteristics of the backlight and the color filter as mentioned above, it can be said that a polarizing plate of the type shown in Fig. 5 is more preferable since the red wavelength region has a large contribution to luminance.

In order to improve the visibility correction polarization degree, it is necessary to improve the polarization degree as a whole in the entire wavelength range, which is quite difficult in reality that is approaching the theoretical limit, but the directionality of improvement from the type of FIG. 4 to the type of FIG. If you change your view point, there is room for improvement, which can be a big solution.

6 and 7 show the polarization film elemental contrast (S _CR (λ)) defined by Equation (1) for polarizing films having a spectrum of orthogonal transmittance Tc (λ) as shown in FIGS. 4 and 5, respectively. It is a graph. Polarizing films groups contrast (S _CR (λ)) is orthogonal transmittance and polarization due also be as an indicator of all, a polarizing plate 2 ratio of the maximum value to the minimum value of the transmittance of the natural light of sheets superposed state or the like, than the actual liquid crystal display device of the This is considered to be close to the superiority of contrast.

(Measurement method of polarizing film unity contrast)

Hereinafter, it describes about the measuring method of polarizing film single-piece contrast (S _CR ((lambda))).

<Measurement device>

A spectrophotometer is used as a measuring apparatus of Tp ((lambda)) and Tc ((lambda)). In order to more accurately evaluate the Tc (λ) value, it is necessary to use a spectrophotometer that can measure up to a higher absorbance region, and in the present invention, it is necessary to use an apparatus capable of measuring absorbances of about 7 to 8. As such a spectrophotometer, the spectrophotometer (model number: V7100) made from Nippon Bunko Corporation etc. is mentioned.

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

<Measurement sample>

In many cases, a transparent protective film is bonded to one or both surfaces of the polarizing film, but the transparent protective film has a phase difference characteristic, and when the slow axis is bonded so as not to be parallel or perpendicular to the absorption axis of the polarizing film, The linearly polarized light to become becomes elliptical polarization by the phase difference characteristic of a transparent protective film, and it becomes impossible to measure the said Tp ((lambda)) and Tc ((lambda)) correctly. When evaluating such a polarizing plate, it is necessary to isolate a transparent protective film from a polarizing plate and to measure it. In the case where the transparent protective film does not have substantially retardation characteristics or the transparent protective film has retardation characteristics, and the slow axis thereof is bonded so as to be parallel or orthogonal to the absorption axis of the polarizing film, the transparent protective film is separated from the polarizing plate. Even if there is no deviation, the Tp (λ) and Tc (λ) can be measured accurately.

<Measurement>

Using the spectrophotometer, linearly polarized light (wavelength λ nm) was incident on a polarizing film, and measured by the relationship between the transmittance (parallel transmittance: Tp (λ)) and orthogonal nicotine measured in the relationship between linearly polarized light and parallel Nicole. One transmittance (orthogonal transmittance: Tc (λ)) is measured at each wavelength, respectively. From the measured Tp (λ) and Tc (λ), S _CR (λ) is obtained according to the above equation (1).

(Characteristics of Polarizing Film)

Characteristics of the polarizer used in the present liquid crystal display according to the invention the device is necessary that the polarizer satisfies a respective wavelength polarizing film Groups contrast relationship (S _CR (λ)) that Equation (2) of which is defined by the equation (1) .

<Equation 2>

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

[(S _CR (550) + S _CR (600)) / 2] in Equation 2 described above is 30000 or more, preferably 40000 or more, and the contrast of the display device is improved. On the contrary, in the case of less than 30000, there is a problem in that contrast of the display device cannot be obtained. The S _CR 550 and the S _CR 600 are each alone, preferably 30,000 or more, and more preferably 40000 or more.

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 Increases, but S _CR near 450 nm is reversely lowered,

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

Becomes a relationship. This is, for example, in the case of the polarizing film in which the iodine is adsorbed and orientated, by the high temperature and high humidity treatment described later, the ratio of I ₅ in the iodine in the polarizing film increases, so that the absorption on the high wavelength side increases, and thus the ratio of I ₃ . This decreases the absorption on the low wavelength side. Moreover, there exists a phenomenon that the orientation degree of iodine itself raises somewhat by high temperature, high humidity process, and the raise of overall _SCR by this also appears.

As described above, even when the polarization film alone contrast in the wavelength of the B (blue) region is lowered, when applied to an LED backlight or a color filter having a small blue contribution, the visibility correction is not so much a problem. The priority of the polarizing film single-piece | contrast in the wavelength of (red) and G (green) area becomes what improves the contrast of a liquid crystal display screen.

This is to pursue the contrast characteristic of the display device at a point completely different from the viewpoint of Ty or Py, which has been required for a polarizer in the past, and at present, in the development of a polarizer with polarization performance near the theoretical limit, high display device It can be said to be a solution to contrast.

(Production method of polarizing plate)

Although the polarizing plate of this invention can be produced as follows, for example, it is not limited to this.

(1) polarizing film manufacturing process

Polyvinyl alcohol-type resin which comprises a polarizing film is obtained by saponifying a polyvinyl acetate type resin normally. The saponification degree of polyvinyl alcohol-type resin is 85 mol% or more normally, Preferably it is 90 mol% or more, More preferably, it is 99-100 mol%. As polyvinyl acetate type resin, the copolymer of vinyl acetate and the other monomer copolymerizable with this besides the polyvinyl acetate which is a homopolymer of vinyl acetate, for example, an ethylene-vinyl acetate copolymer, etc. are mentioned. As another monomer copolymerizable with vinyl acetate, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, etc. are mentioned, for example. The degree of polymerization of the polyvinyl alcohol-based resin is usually in the range of 1000 to 10000, preferably in the range of 1500 to 5000.

These polyvinyl alcohol-based resins may be modified. For example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral and the like modified with aldehydes may also be used. Usually, as a starting material of polarizing film manufacture, the unstretched film of the polyvinyl alcohol-type resin film whose thickness is 20-100 micrometers, Preferably 30-80 micrometers is used. Industrially, the width of the film is practically 1500 to 4000 mm. The unstretched film is treated in the order of swelling treatment, dyeing treatment, boric acid treatment, water washing treatment, uniaxial stretching in the process up to boric acid treatment, and finally, the thickness of the polarizing film obtained by drying is, for example, 5 to 50. μm.

As a manufacturing method of a polarizing film, there are two manufacturing methods largely divided. The first method is a method in which a polyvinyl alcohol-based resin film is uniaxially stretched in air or an inert gas, followed by 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, and finally drying. to be. The second method is a solution treatment of the unstretched polyvinyl alcohol-based resin film in an aqueous solution in the order of swelling treatment step, dyeing treatment step, boric acid treatment step and water washing treatment step, and wetted in the boric acid treatment step and / or the preceding step. It is a method of performing uniaxial stretching and finally drying.

In either method, uniaxial stretching may be performed by one process, and may be performed by two or more processes. A stretching method can employ | adopt a well-known method, For example, the roll-to-roll extending | stretching which adds a circumferential speed difference between two nip rolls conveying a film, and performs extending | stretching, for example, the hot roll stretching method as described in patent 2731813, Tenter drawing method and the like. In addition, although the order of a process is basically the same as the above-mentioned, there is no restriction | limiting in the number of process baths, process conditions, etc. In addition, a process not described in the first and second methods may be added for other purposes. Examples of such a step include immersion treatment (iodide treatment) with an aqueous solution of iodide not containing boric acid, or immersion treatment (zinc treatment) with an aqueous solution containing zinc chloride or the like that does not contain boric acid after boric acid treatment. have.

The swelling treatment step is performed for the purpose of removing foreign substances on the surface of the film, removing the plasticizer in the film, imparting dichroism in a subsequent step, plasticizing the film, and the like. Treatment conditions are determined within the range in which these objects can be achieved, and in the range in which problems such as extreme dissolution of the base film, loss of transparency, and the like do not occur. When swelling the film previously stretched in gas, it is performed by immersing a film in 20-70 degreeC, Preferably it is 30-60 degreeC aqueous solution. Immersion time of a film is 30 to 300 second, Preferably it is 60 to 240 second. When swelling an unstretched raw film from the beginning, it is performed by immersing a film in 10-50 degreeC, preferably 20-40 degreeC aqueous solution, for example. Immersion time of a film is 30 to 300 second, Preferably it is 60 to 240 second.

In the swelling process, problems such as swelling of the film in the width direction and wrinkles in the film are likely to occur. Therefore, known widening such as widening rolls (expander rolls), spiral rolls, crown rolls, cross guiders, bend bars, tenter clips, etc. It is preferable to convey a film, while crimping a film with an apparatus. In order to stabilize the conveyance of the film in the bath, the water flow in the swelling bath is controlled by an underwater shower, or an EPC (Edge Position Control) device: which detects the end of the film to prevent meandering of the film. It is also useful to use together). In this process, since a film swells and expands also in the conveyance direction of a film, in order to remove the looseness of the film of a conveyance direction, it is preferable to devise means, such as controlling the speed of the conveyance roll before and behind a processing tank. In addition to the pure water, the swelling treatment bath to be used is boric acid (described in JP-A-10-153709), chloride (described in JP-A 06-281816), inorganic acid, inorganic salt, The aqueous solution which added water-soluble organic solvent, alcohol, etc. in 0.01 to 0.1 weight% range can also be used.

The dyeing treatment step by the dichroic dye is carried out for the purpose of adsorbing and orienting the dichroic dye to the film. The treatment conditions are determined within the range in which these objects can be achieved, and in the range in which problems such as dissolution, loss of transparency, and the like, which are extremes of the base film, do not occur. In the case of using iodine as a dichroic dye, for example, at a temperature ratio of 10 to 45 ° C, preferably 20 to 35 ° C, the concentration of iodine / potassium iodide / water = 0.003 to 0.2 / 0.1 to 10/100 Using an aqueous solution, the immersion treatment is performed for 30 to 600 seconds, preferably 60 to 300 seconds. Instead of potassium iodide, other iodides such as zinc iodide may be used. Moreover, another iodide can also be used together with potassium iodide. Moreover, compounds other than iodide, for example, boric acid, zinc chloride, cobalt chloride, etc. can also coexist. When boric acid is added, it is distinguished from the following boric acid treatment in the point which contains iodine. It can be regarded as a dye bath as long as it contains at least 0.003 parts of iodine with respect to 100 parts by weight of water.

In the case of using a water-soluble dichroic dye as a dichroic dye, for example, an aqueous solution having a dichroic dye / water concentration of 0.01 to 0.1 / 100 by weight under a temperature condition of 20 to 80 ° C., preferably 30 to 70 ° C. 30-600 seconds, Preferably it is 60-300 second immersion process. The aqueous solution of the dichroic dye to be used may contain dyeing assistants, etc., for example, may contain inorganic salts, such as sodium sulfate, surfactant, etc. The dichroic dyes may be used alone or in combination of two or more dichroic dyes.

As described above, the film may be stretched in a dye bath. Stretching is performed by, for example, giving a peripheral speed difference to the nip rolls before and after the dyeing tank. In addition, similarly to the swelling treatment step, a widening roll (expander roll), a spiral roll, a crown roll, a cross guider, a bend bar, or the like may be installed in the dye bath and / or at the bath entrance.

Boric acid treatment is performed by immersing the polyvinyl alcohol-type resin film dyed by the dichroic dye in the aqueous solution containing 1-10 weight part of boric acid with respect to 100 weight part of water. When a dichroic dye is iodine, it is preferable to contain 1-30 weight part of iodides. Examples of iodide include potassium iodide, zinc iodide, and the like. Moreover, compounds other than iodide, for example, zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate, etc. can also coexist.

The boric acid treatment is carried out for water resistance by crosslinking, color adjustment (preventing a bluish color, etc.). When boric acid treatment is performed for water resistance by crosslinking, a crosslinking agent such as glyoxal, glutaraldehyde or the like can be used, if necessary, in addition to boric acid or together with boric acid. In addition, the boric acid treatment for water resistance may be called by names, such as a water treatment process, a crosslinking process, and an immobilization process. In addition, the boric acid treatment for color adjustment may be referred to by names such as complementary color treatment, re-dyeing treatment and the like.

This boric acid treatment is performed by suitably changing the concentration of boric acid and iodide, and the temperature of a process bath according to the objective. The boric acid treatment for water resistance and the boric acid treatment for color adjustment are not particularly distinguished, but can be carried out under the following conditions. In the case of swelling treatment, dyeing treatment, boric acid treatment of the raw film, when boric acid treatment is intended for water-resistant by crosslinking, 3 to 10 parts by weight of boric acid and 1 to 20 parts of iodide to 100 parts by weight of water It is usually performed at 50-70 degreeC, Preferably it is 55-65 degreeC using the boric acid treatment bath containing a weight part. Immersion time is 90-300 second. Moreover, when dyeing and boric acid treatment are performed to the film previously stretched, the temperature of a boric acid treatment bath is 50-85 degreeC normally, Preferably it is 55-80 degreeC.

After the boric acid treatment for water resistance, the boric acid treatment for color adjustment may be performed. For example, when the dichroic dye is iodine, for this purpose, usually 10 to 10 parts by using a boric acid treatment bath containing 1 to 5 parts by weight of boric acid and 3 to 30 parts by weight of iodide with respect to 100 parts by weight of water. It is performed at the temperature of 45 degreeC. Immersion time is 3 to 300 second normally, Preferably it is 10 to 240 second. Boric acid treatment for subsequent color adjustment is usually performed at low boric acid concentrations, high iodide concentrations, and low temperatures as compared to boric acid treatments for water resistance.

These boric acid treatments may include a some process and are usually performed by the process of 2-5. 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 water resistance and the boric acid treatment for color adjustment may be performed in a plurality of processes, respectively.

Moreover, also in a boric acid treatment process, you can extend | stretch a film similarly to a dyeing process. The final integrated draw ratio is 4 to 7 times, preferably 4.5 to 6.5 times. The integrated draw ratio referred to here means how long the longitudinal reference length of the master film has become in the film after the completion of all the stretching treatments, and for example, the film that has been 1 m in the master film is the film after the completion of all the stretching treatments. If it is set to 5 m, the integrated draw ratio at that time is 5 times.

After the boric acid treatment, water washing treatment is performed. A water washing process is performed by immersing the polyvinyl alcohol-type resin film processed by boric acid in water for water resistance and / or color adjustment, spraying water as a shower, or using dipping and spraying together. The temperature of water in a water washing process is 2-40 degreeC normally, and immersion time is 2 to 120 second.

Here, in each process after an extending | stretching process, tension control may be performed so that the tension of a film may become substantially constant, respectively. Specifically, when the stretching is finished in the dyeing treatment step, tension control is performed in the subsequent boric acid treatment step and water washing treatment step. When extending | stretching is complete | finished in all the processes of a dyeing process, tension control is performed in the subsequent process including a dyeing process and a boric acid process. When the boric acid treatment step includes a plurality of boric acid treatment steps, the film is stretched in the first or first to second boric acid treatment steps, and each of the following boric acid treatment steps to the water washing step of the boric acid treatment step in which the stretching treatment is performed. The tension control is performed in the step of, or the film is stretched in the boric acid treatment process from the first to the third stage, and the tension control is performed in each of the processes from the boric acid treatment process to the water washing process in the subsequent boric acid treatment process. Although it is preferable, the film is stretched in the boric acid treatment process from the first or the first stage to the second stage, and tension control is carried out in each process from the boric acid treatment process following the stretching process to the washing process in the stretching process. It is more preferable to carry out. In addition, when performing the above-mentioned iodide treatment or zinc treatment after a boric acid treatment, tension control can also be performed about these processes.

As the nip roll for controlling the tension and the guide roll for controlling the conveying direction of the film, a rubber roll, a stainless steel polishing roll, a sponge rubber roll and the like can be used. As a rubber roll, NBR etc. are included, It is preferable that it is 60-90 degree and 70-80 degree on the JIS Shore C scale measured by the test method of JISK6301. Stainless steel polishing rolls include SUS304, SUS316, and the like, and in order to achieve uniform film thickness, the surface roughness thereof is represented by the average interval S of local calculations of the local calculation of the roughness curve of JIS B 0601 (surface roughness), and is about 0.2 to 1.0. It is preferable that it is S. As the sponge rubber roll, the hardness of the sponge is 20 to 60 degrees, 25 to 50 degrees, density is 0.4 to 0.6 g / m 3, and O.42 to O.57 g, respectively, on the JIS Shore C scale measured by the test method of JIS K 6301. / Cm 3 is preferred.

The tension in each step from the swelling treatment to the water washing treatment may be the same or different, and the tension to the film in the tension control is not particularly limited, and is 150 to 2000 N / m per unit width, preferably Preferably it is set suitably in the range of 600-1500 N / m. If tension is less than 150 N / m, wrinkles etc. will arise easily in a film. On the other hand, when the tension exceeds 2000 N / m, problems such as breakage of the film and reduction of life due to wear of the bearing occur. In addition, the tension per unit width is calculated from the film width near the inlet of the process and the tension value of the tension detector. In addition, when tension control is performed, it may inevitably be slightly stretched and contracted, but in the present invention, this is not included in the stretching treatment.

At the end of the polarizing film production process, a drying treatment is performed. The drying treatment is preferably performed in a large number of steps by changing the tension little by little, but is usually performed in two to three steps due to equipment limitations. When performed in two steps, the tension in the previous step is preferably 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. When the tension is too large, the breakage of the film increases, and when too small, the occurrence of wrinkles increases, which is not preferable. Moreover, it is preferable to set the drying temperature of a previous step to the range of 30-90 degreeC, and to set the drying temperature of a next step to the range of 40-100 degreeC. If the temperature is too high, the breakage of the film increases, the optical properties decrease, and if the temperature is too low, streaks increase, which is not preferable. 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 in terms of productivity. If the time is too short, drying becomes insufficient, which is not preferable.

In this way, 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 this polarizing film is in the range of 5-40 micrometers normally.

(2) Method to give the polarizing film the characteristic which satisfy | fills Formulas 2 and 3

The polarizing plate of this invention has the characteristic in which the polarizing film used is represented by following formula (2). The polarizing film which has this characteristic is obtained by maintaining a polarizing film in a specific environment. That is, the state in which shrinkage of at least the flow direction (absorption axis direction) of the polarizing film is suppressed also needs to be maintained under a high temperature and high humidity environment.

<Equation 2>

[(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 uniaxial stretching is greatly contracted to lose polarization performance. The state in which shrinkage of the polarizing film is suppressed is a method of retaining it in a high temperature and high humidity bath while maintaining tension in the polarizing film, laminating the film on both sides of the polarizing film having a high moisture content, and applying a high temperature in a high moisture state of the polarizing film. The method etc. are mentioned. The tension in the former is 15 × 10 ⁴ N / m 2 to 1500 × 10 ⁴ N / m 2, more preferably 150 × 10 ⁴ N / m 2 to 1200 × 10 ⁴ N / m 2. If it is less than 15 * 10 <^4> N / m <2>, it will become easy to lose polarization performance and will break easily at 1500 * 10 <^4> N / m <2> or more.

In the latter case, shrinkage of the polarizing film is suppressed by laminating films such as a transparent protective film described later on both surfaces of the polarizing film. In addition, since the polarizing film is placed under high temperature and high humidity only by heating the laminated polarizing plate, when maintaining the polarizing film in a high temperature and high humidity environment, it is not necessary to provide a high temperature and high humidity bath, and it is simple and preferable.

Under a high temperature, high humidity environment, the temperature ranges from 40 ° C to 90 ° C, and the humidity ranges from 50% to 95% RH. When temperature is less than 40 degreeC, or when humidity is less than 50% RH, since temperature-humidity is inadequate, it becomes difficult to acquire the characteristic of Formula (3). When temperature becomes 90 degreeC or more, a polarizing film will deteriorate and it will be easy to see it remarkably partly blue, and it will become easy to condensate when humidity is 95% RH or more.

The exposure time under a high temperature, high humidity environment is 10 seconds to 1200 seconds, more preferably 20 seconds to 600 seconds. If the time is short, a sufficient treatment effect cannot be obtained, and if it is too long, the polarizing film may deteriorate and may appear remarkably partially blue, which is not preferable.

When laminating the film on both sides of the polarizing film and applying high temperature in a state where the moisture of the polarizing film is high, it is difficult to quantify the temperature-humidity environment to which the polarizing film is exposed. Specify the conditions. Such temperature is 70 ° C or higher, preferably 75 ° C or higher, and is usually 100 ° C or lower, preferably 90 ° C or lower. If the temperature is too low, a sufficient treatment effect cannot be obtained. If the temperature is too high, the polarizing film is deteriorated and it becomes easy to appear remarkably partly blue, which is not preferable.

This treatment gives a high temperature within 40 seconds, preferably within 30 seconds, more preferably within 20 seconds from immediately after bonding. If the time before giving high temperature is long, the moisture of a polarizing film will fall and it will become difficult to acquire a processing effect.

The time for applying high temperature after the bonding is 10 seconds to 1200 seconds, more preferably 20 seconds to 600 seconds. If the time is short, a sufficient treatment effect cannot be obtained, and if it is too long, the polarizing film may deteriorate and may appear remarkably partially blue, which is not preferable.

The polarizing film with high moisture content is 9% or more, Preferably it is 10% or more of polarizing film. If it is lower than 9%, even if it laminates a film on both surfaces of a polarizing film and gives high temperature, a processing effect will become difficult to obtain. If the moisture content is too high, wrinkles or the like may occur when the films are laminated on both sides of the polarizing film, which is not preferable. As an upper limit of moisture content, it is 20% or less normally, More preferably, it is 15% or less.

The moisture content of a polarizing film is calculated | required by the following formula based on the value measured by the infrared moisture meter IM-3SCV MODEL-1900 (L) manufactured by Fujiwara Corporation.

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

In addition, this formula is a relational formula obtained from the point that the value of the moisture content coefficient value of the polarizing film from which moisture content differs, and the moisture content obtained from the moisture content change before and after heat processing at 105 degreeC for 1 hour become substantially linear relationship.

The polarizing film which has a moisture content in the above-mentioned preferable range can be obtained, for example by controlling the drying temperature and drying time of a polarizing film, and the low moisture content polarizing film is made by making temperature of a drying furnace low and / or shortening drying time. It is obtained, and a high moisture content polarizing film can be obtained by making temperature of a drying furnace high and / or lengthening drying time.

In the present invention, in order to obtain the performance of Equation 3, a combination of the above-described temperature, time, and moisture content may be used as a method of laminating films on both sides of the polarizing film and applying a high temperature in a high moisture state of the polarizing film. It is important.

After drying, it may also cure for about 12 to 600 hours at room temperature or a temperature slightly higher than it, for example, about 20-50 degreeC. It is common to set the temperature at the time of curing lower than the temperature employ | adopted at the time of drying.

(3) Lamination | stacking on polarizing films of films, such as a transparent protective film

As a method of laminating | stacking films, such as a transparent protective film, on both surfaces of a polarizing film, a film is laminated | stacked directly or through an adhesive bond layer. When the film is laminated only on one side of the polarizing film, it is not preferable because the polarizing film is difficult to be maintained in a high humidity environment even if a high temperature is applied thereafter.

Lamination | stacking of a film can join a polarizing film and a film simultaneously by a cross-section or both surfaces simultaneously using a roll etc. It is preferable to join both surfaces simultaneously from the point of manufacture efficiency. Bonding temperature is the range of about 15-30 degreeC normally. When laminating | stacking through an adhesive bond layer, the method of apply | coating an adhesive uniformly to the surface of a polarizing film and / or a transparent protective film, laminating | stacking the other film on the application | coating surface with a roll, etc., etc. are mentioned, for example. Can be. Usually, an adhesive is apply | coated under the temperature of 15-40 degreeC after its manufacture.

As the adhesive in the case of the adhesive, an aqueous solvent adhesive, an organic solvent adhesive, a hot melt adhesive, a solventless adhesive, or the like can be used. As an aqueous solvent adhesive, For example, polyvinyl alcohol-type resin aqueous solution, an aqueous two-component urethane emulsion adhesive, etc., As an organic solvent adhesive, For example, a two-component urethane adhesive etc., As a solvent-free adhesive, For example, one-component type A urethane type adhesive agent, an epoxy type adhesive agent, etc. are mentioned, respectively.

In the case of using an aqueous polyvinyl alcohol-based resin solution, the polyvinyl alcohol-based resin used as an adhesive may include vinyl acetate and other monomers copolymerizable with vinyl acetate homopolymer, in addition to the vinyl alcohol homopolymer obtained by saponifying a polyvinyl acetate homopolymer of vinyl acetate. And vinyl alcohol-based copolymers obtained by saponifying a copolymer of copolymer, and a modified polyvinyl alcohol-based polymer obtained by partially modifying these hydroxyl groups. Polyvalent aldehyde, a water-soluble epoxy compound, a melamine type compound, a zirconia compound, a zinc compound, etc. may be added to this adhesive agent as an additive. When such an aqueous adhesive is used, the adhesive layer obtained therefrom is usually 1 m or less, and even if the cross section is observed with a normal optical microscope, the adhesive layer thereof is virtually not observed.

As an adhesive agent, a photocurable adhesive agent can also be used. As a photocurable adhesive agent, what added the radical polymerization initiator and / or the cation polymerization initiator to an epoxy resin, an acrylic resin, an octacene resin, a urethane resin, and a polyvinyl alcohol resin is mentioned, for example. Especially, what added the cation polymerization initiator to the mixture of an alicyclic epoxy resin and the epoxy resin which does not have an alicyclic structure is preferable.

When bonding a polarizing film and the film bonded to it using a photocurable adhesive agent, a photocurable adhesive agent is hardened by irradiating an active energy ray after bonding. The light source of the active energy ray is not particularly limited, but an active energy ray having a luminescence distribution at a wavelength of 400 nm or less is preferable, and specifically, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave A mercury lamp, a metal halide lamp, etc. are used preferably here. Although the light irradiation intensity | strength to a photocurable adhesive agent is suitably determined by the composition of this photocurable adhesive agent, although it does not specifically limit, It is preferable that the irradiation intensity of the wavelength range effective for activation of a polymerization initiator is 0.1-6000 mW / cm <3>. . In the case where the irradiation intensity is 0.1 mW / cm 2 or more, the reaction time does not become too long, and in the case of 6000 mW / cm 2 or less, the yellowing of the epoxy resin or the polarization film of the epoxy resin due to heat generated from curing of the photocurable adhesive and the heat radiated from the light source There is little possibility of causing deterioration. Although light irradiation time to a photocurable adhesive agent is controlled for every photocurable adhesive agent to harden | cure, it is not specifically limited, It is set so that accumulated light quantity expressed as a product of said irradiation intensity and irradiation time may be set to 10-10000 mJ / cm <2>. desirable. When accumulated light amount to a photocurable adhesive agent is 10 mJ / cm <2> or more, active species derived from a polymerization initiator are fully generated and hardening reaction can be advanced more reliably, and when it is 10000 mJ / cm <2> or less, irradiation time does not become too long , Good productivity can be maintained. In addition, the thickness of the adhesive bond layer after active energy ray irradiation is about 0.001-5 micrometers normally, Preferably it is 0.01 micrometer or more, Preferably it is 2 micrometers or less, More preferably, it is 1 micrometer or less.

When hardening a photocurable adhesive agent by irradiation of an active energy ray, it is preferable to harden on the conditions which all the functions of a polarizing plate, such as polarization degree, a transmittance | permeability, and a hue of a polarizing film do not fall.

When laminating | stacking a film through an adhesive bond layer, when laminating | stacking a film on both surfaces of a polarizing film, it is preferable that a film is 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 or polyethylene naphthalate, polybutylene terephthalate, a polycarbonate resin film, or an acryl type The film widely used conventionally in the said field | areas, such as a resin film and a polypropylene resin film, is mentioned.

Cycloolefin resins are suitable commercially available products, such as Topas (manufactured by Ticona), Aton (manufactured by JSR Corporation), Zeonor (manufactured by Nihon Xeon Corporation), Zeonex (ZEONEX) (made by Nippon Xeon Co., Ltd.), Apel (made by Mitsui Chemical Industries, Ltd.), etc. can be used preferably. When forming a cycloolefin resin into a film and forming into a film, well-known methods, such as the solvent casting method and the melt-extrusion method, are used suitably. For example, cycloolefin previously formed into a film, such as esciner (made by Sekisui Kagaku Kogyo Co., Ltd.), SCA40 (made by Sekisui Kagaku Kogyo Co., Ltd.), and Zeonor film (made by Optes Co., Ltd.) The commercial item of the film made of system resin can also be used.

The cycloolefin-based resin film may be uniaxially stretched or biaxially stretched. By extending | stretching, arbitrary phase difference values can be provided to a cycloolefin resin film. Stretching is normally performed continuously while winding a film roll, and it extends | stretches in the advancing direction of a roll, the direction perpendicular | vertical to the advancing direction, or both in a heating furnace. As for the temperature of a heating furnace, the range of glass transition temperature +100 degreeC is employ | adopted normally in the glass transition temperature vicinity of cycloolefin resin. The magnification of stretching is usually 1.1 to 6 times, preferably 1.1 to 3.5 times.

In the case where the cycloolefin resin film is stretched, the stretching direction thereof is arbitrary, but it is generally 0 °, 45 °, or 90 ° with respect to the flow direction of the film. The retardation characteristics of the film having the stretching direction of 0 ° are completely uniaxial, and the retardation characteristics of the films having 45 ° and 90 ° are often weak. Although the characteristic is influenced by the viewing angle of a display apparatus, it can select timely according to the type of liquid crystal display device applied or the type of a composite polarizing plate. The retardation values are commonly referred to as λ / 4, λ / 2, and the like, and are often in the range of 90 to 170 nm for λ / 4 and 200 to 300 nm for λ / 2.

When a cycloolefin resin film exists in a roll state, since it exists in the tendency for film to adhere | attach and to cause blocking, normally, a protective film is bonded and roll winding. Moreover, since cycloolefin resin film generally has low surface activity, it is preferable to perform surface treatment, such as a plasma treatment, a corona treatment, an ultraviolet irradiation treatment, a flame | frame (flame) treatment, and a saponification treatment, to the surface adhere | attached with a polarizing film. . Especially, the plasma process and corona treatment which can be implemented comparatively easily are preferable.

The cellulose acetate-based resin that can be used in the transparent protective film is, for example, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate and the like as a partial or complete acetate ester of cellulose.

As a film of such a cellulose ester-type resin, a suitable commercial item, for example, Fujitak TD80 (manufactured by Fuji Film Co., Ltd.), Fujitak TD80UF (manufactured by Fuji Film Co., Ltd.), Fujitak TD80UZ (manufactured by Fujifilm Co., Ltd.), KC8UX2M (made by Konica Minolta Opto Co., Ltd.), KC4UY (made by Konica Minolta Opto Co., Ltd.), etc. can be used preferably.

Moreover, the cellulose acetate type resin film which provided retardation characteristic is also used preferably, As a commercial item of the cellulose acetate type resin film provided with such retardation characteristic, WV BZ 438 (made by Fujifilm Co., Ltd.), KC4FR-1 (Konica Minolta Opto) Co., Ltd.) etc. are mentioned. The cellulose acetate is also called acetyl cellulose or cellulose acetate.

When a cellulose resin film is laminated | stacked especially with a polarizing film using an aqueous adhesive agent, in order to improve adhesiveness with a polarizing film, saponification process is given. As a saponification process, the method of immersing in aqueous solution of alkalis, such as sodium hydroxide and potassium hydroxide, can be employ | adopted.

Surface treatments such as an antiglare treatment, a hard coating treatment, an antistatic treatment, an antireflection treatment and the like may be applied to the surfaces of the cycloolefin resin film and the cellulose acetate resin film, depending on the application. In addition, a liquid crystal layer or the like may be formed in order to improve the viewing angle characteristic.

When laminating | stacking a film on both surfaces of a polarizing film, it is more preferable that a film makes at least one surface into a resin film with low water vapor transmission rate. When the moisture permeability is low, the polarizing film is easily maintained in a high humidity environment when laminating and imparting high temperature.

Preferable water vapor transmission rate is 400 (g / m <2> * 24 hours) or less in 40 degreeC 90% RH environment, Preferably it is 300g or less, More preferably, it is 100g or less, More preferably, it is 50g or less.

When the transparent protective film is in a roll state, the films tend to adhere to each other and easily cause blocking, and therefore, usually, the uneven processing is performed at the roll end, the ribbon is inserted at the end, or the protective film is bonded or roll wound. One is used.

Although it is preferable that the thickness of a transparent protective film is thin, when too thin, intensity | strength will fall and workability will be inferior. On the other hand, when too thick, problems, such as transparency fall or the curing time required after lamination | stacking may arise. Therefore, a suitable thickness of a transparent protective film is 5-200 micrometers, for example, Preferably it is 10-150 micrometers, More preferably, it is 20-100 micrometers.

When laminating | stacking a film directly on both surfaces of a polarizing film, it is preferable that a film is a protective film which can be peeled off. A protective film is peeled off at the stage which a need disappeared, for example, when forming an adhesive layer in the polarizing film surface of a polarizing plate.

The peeling force between a protective film and a polarizing film is 0.01-5 N / 25 mm, Preferably it is 0.01-2 N / 25 mm, More preferably, it is 0.01-0.5 N / 25 mm. When the peeling force is less than 0.01 N / 25 mm, since the adhesive force between the polarizing film and the protective film is small, partial peeling of the protective film may occur. Moreover, when peeling force exceeds 5 N / 25 mm, since peeling of a protective film from a polarizing film becomes difficult, it is not preferable.

As a material of a protective film, polyethylene resin, polypropylene resin, polystyrene resin, polyethylene terephthalate resin, etc. which are easy to handle and ensure some transparency can be used preferably, These 1 type, or 2 or more types Can be used as a protective film.

Specifically as such a protective film, Sanitec (Sale by Sangen Co., Ltd.) in which the adhesive layer is formed in the polyethylene resin film surface, E-mask in which the adhesive layer is formed in the polyethylene terephthalate resin film surface ( Commercial products, such as Nitto Denko Co., Ltd.) and masstack (The Fujimori Kogyo Co., Ltd. product) in which the adhesive layer is formed in the polyethylene terephthalate resin film surface, are mentioned.

Especially, the self-adhesive protective film which has adhesiveness with respect to a polarizing film by itself is simple in the point which does not need to protect the adhesive layer on the protective film surface, and can be used more preferably. As a commercial item of the self-adhesive resin film which shows a preferable peeling force with respect to the said polarizing film, Torretec (made by Toray Corporation) etc. containing a polyethylene resin is mentioned, for example.

Moreover, it is preferable that the transparent protective film has few defects, such as a fish eye. If there is a defect, the shape is transferred to the polarizing film, and it may become a defect of the polarizing film.

The polarizing plate manufactured as mentioned above can also laminate | stack the optical film which has optical functions other than a polarizing plate in the protective film surface or the adhesive layer surface. As an example of such an optical film, the liquid crystal compound is apply | coated to the base material surface, the reflective polarizing film which transmits the oriented optical compensation film, some kind of polarized light, and reflects the polarized light which shows the opposite property, Polycar A retardation film containing a carbonate resin, a retardation film containing a cyclic polyolefin resin, an antiglare function film having an uneven shape on the surface, a film with an antireflection function, a reflection film having a reflection function on the surface, and a reflection function The semi-transmissive reflective film etc. which have a transmissive function are mentioned. As a commercial item which a liquid crystalline compound is apply | coated to the base material surface, and is aligned, the WV film (Fuji Film Co., Ltd. product), NH film (Shin Nippon Sekiyu Co., Ltd. product), NR film (Shin Nippon) Saki Oil Co., Ltd.) etc. are mentioned. As a commercial item which corresponds to the reflective polarizing film which permeate | transmits some kind of polarized light and reflects the polarized light which shows the opposite property, it is DBEF (made by 3M Corporation, Sumitomo Three M Co., Ltd. in Japan), for example. Available), APF (manufactured by 3M Corporation, available from Sumitomo 3M Co., Ltd. in Japan), and the like. Moreover, as a commercial item corresponded to the retardation film containing cyclic polyolefin type resin, an aton film (made by JSR Corporation), Essina (made by Sekisui Kagaku Kogyo Co., Ltd.), a zenor film ((Note) ) Optes manufacture) etc. are mentioned.

When providing such another optical film in the protective film side of the said polarizing plate, both are laminated | stacked normally through an adhesive. Although the same thing as what was demonstrated above can be used as an adhesive in this case, storage elastic modulus may not be very large. In addition, when providing another optical film in the adhesive layer side of the said polarizing plate, an optical film is adhere | attached by the adhesive layer. In this case, it is usual to provide an adhesive layer for bonding to a liquid crystal cell on the outside of the optical film.

The polarizing plate with a pressure-sensitive adhesive layer produced by the production method of the present invention usually has a form of a large roll material or sheet material, and is cut by a cutting tool having a sharp edge in order to obtain a polarizing plate having a desired shape and transmission axis ( Chip cut). For this reason, in the polarizing plate chip obtained by cutting | disconnecting, the state by which the polarizing film was exposed at the outer peripheral edge part arises.

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

(Bonding to liquid crystal cell of polarizing plate)

The polarizing plate manufactured by the manufacturing method as described above is bonded to the liquid crystal cell of a liquid crystal display device via an adhesive layer.

Such a pressure-sensitive adhesive layer is generally used using a variety of pressure-sensitive adhesives, such as acrylic, rubber, urethane, silicone, polyvinyl ether, etc. which have conventionally been used for bonding a liquid crystal cell and a polarizing plate. Moreover, an energy-beam hardening type and a thermosetting adhesive can also be used, Among these, the acrylic adhesive which used the acrylic resin excellent in transparency, weather resistance, heat resistance, etc. as a base polymer is preferable.

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

The acrylic pressure-sensitive adhesive is not particularly limited, but (meth) acrylic acid ester base polymers such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate and 2-ethylhexyl (meth) acrylate, and these ( The copolymer base polymer which used 2 or more types of meth) acrylic acid ester etc. is used preferably. In addition, polar monomers are copolymerized in these base polymers. As a polar monomer, it is (meth) acrylic acid, 2-hydroxypropyl (meth) acrylic acid, hydroxyethyl (meth) acrylate, (meth) acrylamide, N, N- dimethylaminoethyl (meth) acrylate, glyco The monomer which has functional groups, such as a carboxyl group, a hydroxyl group, an amide group, an amine group, and an epoxy group, such as a cyl (meth) acrylate, is mentioned.

Although these acrylic adhesives can be used alone or of course, a crosslinking agent is usually used in combination. As a crosslinking agent, it is a divalent or polyvalent metal salt which forms a carboxylic acid metal salt between a carboxyl group, As a polyamine compound, forms an amide bond between a carboxyl group, As a polyepoxy compound or a polyol compound, it is a carboxyl group Forming an ester bond between and a polyisocyanate compound, forming an amide bond between a carboxyl group, etc. are illustrated. Especially, a polyisocyanate compound is used widely as an organic type crosslinking agent.

The energy ray-curable pressure-sensitive adhesive has a property of being cured by irradiation with energy rays such as ultraviolet rays or electron beams, and has adhesiveness even before energy ray irradiation, adheres to adherends such as films, and cures by irradiation with energy rays to adjust adhesion. It is an adhesive having the property of being able to. It is preferable to use an ultraviolet curable adhesive especially as an energy-ray-curable adhesive. The energy ray-curable pressure sensitive adhesive generally contains an acrylic pressure sensitive adhesive and an energy ray polymerizable compound as main components. Usually, a crosslinking agent is mix | blended further, and also a photoinitiator and a photosensitizer can also be mix | blended as needed.

In addition to the base polymer and crosslinking agent mentioned above as an adhesive composition, in order to adjust the adhesive force, cohesion force, viscosity, elasticity modulus, glass transition temperature, etc. of an adhesive as needed, For example, resin which is a natural product or a compound, tackifying resin, antioxidant And suitable additives such as ultraviolet absorbers, dyes, pigments, antifoaming agents, corrosion inhibitors, and photopolymerization initiators. Moreover, it can also be set as the adhesive layer which contains microparticles | fine-particles and shows light scattering property.

It is preferable that the thickness of an adhesive layer is 1-40 micrometers, but in order to obtain the thin polarizing plate which is the objective of this invention, it is preferable to apply it thinly in the range which does not impair workability and durability characteristics, maintains good workability, and also polarizer More preferably, it is 3-25 micrometers at the point which suppresses the dimensional change of. If the pressure-sensitive adhesive layer is too thin, the adhesiveness is lowered, and if it is too thick, problems such as sticking out of the adhesiveness tend to occur.

As mentioned above, it is preferable that all the storage elastic modulus in the temperature range of 23-80 degreeC is 0.15-1 MPa as the adhesive formed directly on the polarizing film surface. The pressure-sensitive adhesive used in a normal image display device or an optical film for the use thereof has a storage elastic modulus of only about 0.1 MPa, and in comparison thereto, a preferred storage elastic modulus of 0.15 to 1 MPa of the pressure-sensitive adhesive used in the present invention has a high value. do. In addition, a storage elastic modulus can be measured using a commercially available viscoelasticity measuring apparatus, for example, a DYNAMIC ANALYZER RDA II (made by REOMETRIC).

Moreover, in the manufacturing method of the polarizing plate of this invention, it does not specifically limit as a method of forming an adhesive layer in a polarizing film, The solution containing each component containing said base polymer including said base polymer is apply | coated to the other surface of a polarizing film. After drying and forming an adhesive layer, the separator by which the mold release process, such as a silicone type, is performed may be laminated | stacked, or after forming an adhesive layer on a separator, you may transfer and laminate | stack on a polarizing film. In addition, when forming an adhesive layer in a polarizing film, you may perform an adhesion process, for example corona treatment, etc. to at least one of a polarizing film and an adhesive layer as needed. In addition, the surface of the formed adhesive layer is normally protected by the separator film which performed the mold release process, and a separator film is peeled off before bonding this polarizing plate etc. to a liquid crystal cell or another optical film.

<Examples>

Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these examples.

Example 1

(Production of Polarizing Film)

After uniaxially stretching the polyvinyl alcohol film having a thickness of about 5 times with a mean polymerization degree of about 2400 and a saponification degree of 99.9 mol% or more by about 5 times in a dry manner and maintaining it in a tension state, it was immersed in pure water at 60 ° C. for 1 minute, and then iodine The weight ratio of / potassium iodide / water was immersed in an aqueous solution of 0.1 / 5/100 for 60 seconds at 28 ° C. Thereafter, the weight ratio of potassium iodide / boric acid / water was immersed in an aqueous solution of 10.5 / 7.5 / 100 for 300 seconds at 72 ° C. Subsequently, the resultant was washed with pure water at 10 ° C. for 5 seconds, and then dried at 60 ° C. for 75 seconds and then at 75 ° C. for 30 seconds in a state maintained at a tension of 400 N to obtain a polarizing film having an iodine adsorbed orientation having a moisture content of 10.9%. .

(Production of adhesive)

Separately, 3 parts by weight of a carboxyl group-modified polyvinyl alcohol (Kurare foam KL318 (manufactured by Kuraray)) and a water-soluble polyamide epoxy resin (Sumirez resin 650 (manufactured by Sumika Chemtex)) in 100 parts by weight of water ( 1.5 parts by weight of an aqueous solution having a solid content concentration of 30% was dissolved to prepare an aqueous adhesive (A) containing polyvinyl alcohol-based resin as a main component, and 2 parts by weight of a carboxyl-modified polyvinyl alcohol and a water-soluble polyamide epoxy resin, respectively. And 1.0 weight part of adhesives (B) were adjusted.

(Manufacture of Polarizing Plate)

On one side of the obtained polarizing film, a 40 μm-thick film (KC4UY, manufactured by Konica Minolta Opto Co., Ltd.) containing saponification-treated triacetyltyl cellulose was further used on the other side of the adhesive (A). The retardation film (Zeonor film ZD14-141158-A1340 (made by Optes), thickness: 32 micrometers) made from the norbornene-type resin to which the surface was previously corona-treated was nip-rolled using the said adhesive (B) It bonded by. After 5 seconds had elapsed from the bonding at room temperature while maintaining the tension of the bonded product at 430 N / m, drying was performed for 11 seconds at 60 ° C., 141 seconds at 80 ° C., and 93 seconds at 70 ° C. sequentially to obtain a polarizing plate.

[Example 2]

(Production of Polarizing Film)

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

(Manufacture of Polarizing Plate)

4 seconds after joining at room temperature, maintaining the tension of the joined body at 430 N / m, except that the drying was continuously performed for 9 seconds at 60 ° C, 113 seconds at 80 ° C, and 75 seconds at 70 ° C in that order. In the same manner as in 1, a polarizing plate was obtained.

Example 3

(Production of Polarizing Film)

A polarizing film having a moisture content of 13.9% was obtained in the same manner as in Example 1, except drying at 40 ° C for 60 seconds and 25 ° C at 50 ° C.

(Manufacture of Polarizing Plate)

After 4 seconds have elapsed from the joining at room temperature while maintaining the tension of the joining at 430 N / m, the drying is continued for 9 seconds at 60 ° C, 39 seconds at 90 ° C, 74 seconds at 80 ° C and 75 seconds at 70 ° C in that order. A polarizing plate was obtained in the same manner as in Example 1 except that the reaction was carried out.

Comparative Example 1

(Production of Polarizing Film)

Except having dried for 106 second at 90 degreeC, it carried out similarly to Example 1, and obtained the polarizing film of 8.7% of moisture content.

(Manufacture of Polarizing Plate)

After 4 seconds have elapsed from the joining at room temperature while maintaining the tension of the joining at 430 N / m, the drying is continued for 10 seconds at 50 ° C, 43 seconds at 65 ° C, 83 seconds at 80 ° C, and 84 seconds at 70 ° C. A polarizing plate was obtained in the same manner as in Example 1 except that the reaction was carried out.

Comparative Example 2

(Production of Polarizing Film)

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

(Manufacture of Polarizing Plate)

Example 4 After elapse of 4 seconds from the joining at room temperature while maintaining the tension of the joining at 430 N / m, except that the drying was sequentially performed at 50 ° C. for 10 seconds, at 65 ° C. for 43 seconds, and at 80 ° C. for 167 seconds. In the same manner as in 1, a polarizing plate was obtained.

Comparative Example 3

(Production of Polarizing Film)

Except having dried for 106 second at 90 degreeC, it carried out similarly to Example 1, and obtained the polarizing film of 8.7% of moisture content.

(Manufacture of Polarizing Plate)

After 4 seconds have elapsed from the joining at room temperature while maintaining the tension of the joining at 430 N / m, the drying is continued for 10 seconds at 50 ° C, 43 seconds at 70 ° C, 83 seconds at 80 ° C, and 84 seconds at 90 ° C. A polarizing plate was obtained in the same manner as in Example 1 except that the reaction was carried out.

[Measurement of S _CR of Each Polarizing Plate]

About the polarizing plate samples obtained by the said Examples 1-3 and Comparative Examples 1-3, the Nippon Bunko Co., Ltd. product was manufactured by peeling retardation film and the triacetyl cellulose film which does not have retardation characteristic substantially in the state bonded together. The S _CR of each polarizing plate at wavelength 450 nm, 550 nm, and 600 nm was measured with the spectrophotometer (model number: V7100). The results are shown in Table 2.

(Contrast Evaluation of Liquid Crystal Display)

Table 1 shows the results of determining the Bmax and Rmax by measuring the emission spectrum of a mobile phone module (state without a polarizing plate) including a white LED backlight and a VA type liquid crystal cell. Bmax and Rmax of the mobile phone module satisfy the above expression (4). The polarizing plates produced in Examples 1-3 and Comparative Example 1 were bonded to both surfaces of the liquid crystal cell of this module, and the contrast of the liquid crystal screen of the liquid crystal display device (mobile phone) which combined this module was measured by Topcon Co., Ltd. It was measured by a radiometer (SR-UL1). The results are shown in Table 2. Although very good contrast ratio was obtained for the liquid crystal display device using the polarizing plates of Examples 1-3, the liquid crystal display device using the polarizing plate of a comparative example obtained only a low contrast ratio compared with an Example.

The polarizing plate of the present invention has a liquid crystal display device having light emission wavelength characteristics of a backlight and a liquid crystal cell (color filter) even if the visibility correction polarization degree Py and the visibility correction unit transmittance Ty in the polarizing plate are the same as those of the conventional polarizing plate. When used for, the contrast of the screen of the liquid crystal display device can be significantly improved than in the case of using a conventional polarizing plate.

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

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

3 is a graph showing an example of a visibility correction curve.

It is a graph which shows the orthogonal transmittance spectrum of the polarizing film used for the conventional polarizing plate.

It is a graph which shows the orthogonal transmittance spectrum of the polarizing film used for the polarizing plate of this invention.

It is a graph which shows the contrast of the polarizing film single body of the same polarizing film as FIG.

It is a graph which shows the contrast of the polarizing film single body of the same polarizing film as FIG.

Claims (7)

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 alone contrast (S _CR (λ)) at a wavelength λ nm defined by Equation 1 below. A polarizing plate characterized by satisfying the relationship of the following formula (2) and (3). <Equation 1>

(here,

Where Tp (λ) is the transmittance (%) of the polarizing film measured in the relationship between the linearly polarized light of the incident wavelength λ nm and the parallel Nicols, and Tc (λ) is the relationship between the linearly polarized light of the incident wavelength λ nm and the orthogonal nicols. Is the transmittance (%) of the polarizing film measured in the above, and all are measured values obtained by polarized ultraviolet visible absorption spectrum measurement by a spectrophotometer.) <Equation 2> [(S _CR (550) + S _CR (600)) / 2] ≥30,000 <Equation 3> 3,000≤S _CR 450 <30,000 The polarizing plate of Claim 1 which laminated | stacked the cellulose acetate type resin film on one side of the said polarizing film through an adhesive bond layer, and laminated the cycloolefin resin film on the other side via an adhesive bond layer. The polarizing plate of Claim 1 which laminated | stacked the cellulose acetate type resin film on one surface of the said polarizing film through the adhesive bond layer, and laminated | stacked the self-adhesive protective film which can peel on the other surface. The polarizing plate according to claim 2 or 3, wherein the adhesive layer is formed from an aqueous adhesive. The polarizing plate of claim 1, wherein the liquid crystal display includes a liquid crystal cell including a backlight and a liquid crystal cell, wherein the liquid crystal display is blue in a spectrum measured in a state where only a liquid crystal cell is placed in the backlight and the backlight is turned on. A polarizing plate in which the emission peak wavelength Bmax and the red emission peak wavelength Rmax satisfy the following expression (4). <Equation 4> (Rmax-550) <(550-Bmax) The manufacturing method of the polarizing plate in any one of Claims 2-4 which laminates a film on both surfaces of a polarizing film with a moisture content of 9% or more, and heat-processes at the temperature of 70 degreeC or more within 40 second immediately after lamination. It is a liquid crystal display device containing a backlight, a liquid crystal cell, and the polarizing plate of Claim 1, In the spectrum measured with only the liquid crystal cell in the backlight and the backlight is turned on, the blue emission peak wavelength Bmax and the red emission peak wavelength Rmax satisfy Equation 4 below. Liquid crystal display. <Equation 4> (Rmax-550) <(550-Bmax)

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