TWI552862B - A method of manufacturing a polarizer - Google Patents

Description

Method for manufacturing polarizing plate

The present invention relates to a method of producing a polarizing plate used as a liquid crystal display member.

The liquid crystal panel constituting the core of the liquid crystal display device is configured by disposing a polarizing plate on both surfaces of the liquid crystal cell. In general, the polarizing plate has a structure in which a protective film made of a transparent resin is bonded to the surface of one side of the polarizing film made of a polyvinyl alcohol-based resin via an adhesive. The surface of the other side of the polarizing film is also bonded to the other side of the polarizing film via a bonding agent. The transparent resin film on the side is the same as the protective film on the opposite side, and has a function of protecting only the polarizing film. In the case of a so-called retardation film, in addition to the protective function, a phase difference in the in-plane and/or thickness direction is imparted for the purpose of optical compensation of the liquid crystal cell and compensation of the viewing angle. In the present specification, the protective film and the retardation film which are bonded to each other via the adhesive on the polarizing film are referred to as "optical films". The adhesive for bonding the optical film to the polarizing film is generally liquid, and an adhesive force is expressed between the polarizing film and the optical film by the curing reaction of the liquid adhesive.

In recent years, the price of a liquid crystal display device represented by a television has been drastically lowered, and the demand for a component that constitutes a component thereof has become increasingly strong. On the other hand, the demand for quality has been further enhanced. In this trend, the type of the optical film used for the production of the polarizing plate is limited to the water-based adhesive of a specific resin such as a cellulose resin, and the active energy rich in the applicable optical film. The line curing type adhesive is changed. For example In JP-A-2004-245925, a polarizing film using an active energy ray-curable adhesive is bonded to an optical film.

The active energy ray-curable adhesive is prepared in a liquid form, and is applied to a coating machine directly coated with the liquid adhesive on the coated object, or in a groove formed on the surface to carry a liquid adhesive. This is transferred to a gravure roll on the surface of the object to be coated, and is applied in advance to the bonding surface of the optical film to the polarizing film. Then, a polarizing film is superposed on the adhesive-coated surface, and an active energy ray such as an ultraviolet ray or an electron beam is irradiated to cure the adhesive, thereby exhibiting an adhesive force. A method in which such an active energy ray-curable adhesive is used is a very effective method for many optical films.

As a method of producing a polarizing plate using the active energy ray-curable adhesive, a method of forming a laminate by superposing a protective film on both surfaces of a polarizing film via an adhesive is disclosed, for example, in Japanese Laid-Open Patent Publication No. 2009-134190 The body is irradiated with an active energy ray while adhering to the outer surface of the convex curved surface formed in an arc shape along the conveying direction of the laminated body. According to this method, the reverse curl and the wave curl which are easily generated on the obtained polarizing plate can be suppressed, so that a polarizing plate having good performance can be manufactured.

In the method of producing a polarizing plate by irradiating ultraviolet rays to cure the ultraviolet curable adhesive, the lamp of the ultraviolet irradiation device is deteriorated by long-term use, and even if the same electric power is applied, the ultraviolet illuminance of the ultraviolet ray is gradually lowered. In this case, the ultraviolet ray is gradually lowered. The curing of the curing type adhesive is insufficient, as a polarizing plate Performance may be insufficient. Further, if it is still used for a long period of time, the lamp or the filter or the reflection plate attached to the ultraviolet irradiation device, the glass disposed on the front surface, etc. may be contaminated due to the installation environment of the ultraviolet irradiation device or the structural problem of the device. In this case, in the ultraviolet light to be irradiated, for example, the transmittance of light having a wavelength of 400 nm or less is reduced, and the illuminance is lowered, so that the curing of the ultraviolet curable adhesive is also considered to be insufficient. When the curing of the ultraviolet curable adhesive is insufficient, there is a problem that the adhesive strength is insufficient, and the polarizing film causes discoloration or the like in the durability test, which adversely affects the performance as a polarizing plate. A method of manufacturing a polarizing plate in which an ultraviolet curable adhesive is appropriately managed by ultraviolet illuminance.

The illuminance of the ultraviolet ray to be irradiated is generally measured using an ultraviolet sensor device such as GaN or AlGaN called a power monitor. However, the power monitor has a problem that the measurement accuracy of the illuminance is relatively low for the following reasons, that is, 1) the detection wavelength of the ultraviolet sensor device is limited to a specific wavelength region, and the measurement sensitivity (sensitivity of light absorption per wavelength) is Each wavelength is different; 2) Due to the problem of heat resistance, the illuminance of the irradiated ultraviolet light cannot be directly measured, and the illuminance of the illuminating light is indirectly measured by measuring the reflected light of the irradiated ultraviolet light. Due to this problem, the power monitor is applied to the production of a polarizing plate using an ultraviolet curing type adhesive, and it is difficult to accurately detect the ultraviolet curing type adhesive which has a significant influence on the curing degree of the ultraviolet curing type adhesive. A decrease in the irradiance of the wavelength region required for activation of the polymerization initiator. Therefore, it is desirable to develop a radiation illuminance reduction that can accurately detect the specific wavelength region, and The polarizing plate can be manufactured while maintaining the required spectral illuminance.

Therefore, an object of the present invention is to provide a method for producing a polarizing plate by bonding an optical film to a polarizing film via an ultraviolet curable adhesive and curing the ultraviolet curable adhesive by ultraviolet irradiation. Accurately detecting the irradiance of ultraviolet ray illuminance, especially the wavelength region required for the activation of the polymerization initiator, by properly controlling it, it is possible to produce a discoloration of the polarizing film even under severe conditions of high temperature and humidity. A polarizing plate that is difficult to produce and has high durability.

The present invention provides a method for producing a polarizing plate, which is a method of producing a polarizing plate by bonding an optical film made of a thermoplastic resin to a polarizing film made of a polyvinyl alcohol-based resin via an ultraviolet-curable adhesive containing a polymerization initiator. It has the following steps (A), (B), (C), (D) and (E).

(A) a coating step of applying the ultraviolet curable adhesive described above to the bonding surface of the optical film to the polarizing film; and (B) a bonding step for applying the ultraviolet curable adhesive to the coating step (C) a curing step in which a layered body in which an optical film is bonded to a polarizing film via an ultraviolet curing type adhesive is irradiated with ultraviolet rays from an ultraviolet irradiation device to thereby form an ultraviolet curing type adhesive (D) a measuring step of measuring a spectroscopic illuminance of the ultraviolet ray irradiated in the curing step using a spectrometer, and measuring a specific absorption wavelength region including an absorption peak wavelength of the polymerization initiator, for example, the absorption Ultraviolet light splitting in the wavelength range from -40 nm to +40 nm at the peak wavelength The integral value of the irradiance illuminance; and (E) the control step, the ultraviolet ray irradiation device is controlled according to the integral value Y of the set illuminating illuminance and the integral value X of the obtained illuminating illuminance.

The method for producing a polarizing plate of the present invention preferably comprises the following step (E).

(E) a control step, when the ratio of the absolute value of the difference between the integral value X of the spectral illuminance obtained by the measurement step and the integrated value Y of the set spectral illuminance is greater than or equal to a specific value, for example, When it is 5% or more, the output of the above ultraviolet irradiation device is controlled.

Further, the method of the other aspect of the present invention provides a method of producing a polarizing plate having the following steps (A), (B), (C), (D), and (E).

(A) step of applying an ultraviolet curable adhesive containing a polymerization initiator to an optical film made of a thermoplastic resin; and (B), superposing a polyvinyl alcohol resin on the surface of the ultraviolet curable adhesive coated on the optical film The polarizing film is prepared, and the optical film is pressed against the polarizing film to obtain a laminate in which the polarizing film and the optical film are bonded via the ultraviolet curing type adhesive; and (C), the laminated body is irradiated with ultraviolet rays by the ultraviolet irradiation device. And curing the ultraviolet curable adhesive; (D), measuring the spectral irradiance of the irradiated ultraviolet light using a spectrometer, and determining a specific absorption wavelength region including the absorption peak wavelength of the polymerization initiator, for example, from An integral value of the illuminating illuminance in a wavelength region where the wavelength of the peak wavelength is 40 nm to a wavelength larger than the wavelength of the absorption peak by 40 nm; and (E), according to the integral value Y of the illuminance of the split radiant Obtain The integral value X of the split radiance illuminance controls the ultraviolet ray irradiation device.

The manufacturing method of the other aspect of the invention preferably comprises the following step (E).

In the step (E), the ratio of the absolute value of the difference between the integral value X of the spectral illuminance obtained and the integrated value Y of the set spectroscopy illuminance is greater than a specific value of the integrated value Y of the set illuminating illuminance In the case of, for example, 5% or more, the ultraviolet irradiation device is controlled.

According to the present invention, when an optical film is bonded to a polarizing film via an ultraviolet curable adhesive, and the ultraviolet curable adhesive is cured by ultraviolet irradiation to produce a polarizing plate, the ultraviolet curable type is accurately measured using a spectrometer. The integrated value of the spectral illuminance in the specific absorption wavelength region of the absorption peak wavelength of the polymerization initiator contained in the subsequent agent, and the output of the ultraviolet irradiation device is controlled according to the result to prevent the curing of the ultraviolet curing adhesive from being insufficient. Therefore, it is possible to provide a polarizing plate having excellent adhesion strength and having high durability against discoloration of the polarizing film even under severe conditions of high temperature and high humidity.

In the present embodiment, a polarizing plate is produced by laminating an optical film made of a thermoplastic resin to a polarizing film made of a polyvinyl alcohol-based resin via an ultraviolet curable adhesive (hereinafter simply referred to as an adhesive). The optical film may be attached only to one side of the polarizing film or may be attached to both surfaces of the polarizing film. When the optical film is bonded to both surfaces of the polarizing film, the method of the present invention can be applied to the bonding of one of the optical films, and the method of the present embodiment can be applied to the bonding of the two optical films. law.

[Polarizing film]

The polarizing film is made of a polyvinyl alcohol-based resin, and is a film which transmits light having a vibration surface of a certain direction among light incident on the film and absorbs light having a vibration surface orthogonal thereto, typically The dichroic dye is adsorbed and aligned on the polyvinyl alcohol-based resin. The polyvinyl alcohol-based resin constituting the polarizing film is obtained by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate-based resin which is a raw material of the polyvinyl alcohol-based resin may be a copolymer of vinyl acetate and other monomers copolymerizable therewith, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate. . The polarizing film can be produced by subjecting the film made of the polyvinyl alcohol-based resin to uniaxial stretching, dyeing with a dichroic dye, and boric acid crosslinking treatment after dyeing. As the dichroic dye, an organic dye of iodine or dichroic is used. The uniaxial stretching may be carried out before the dyeing with the dichroic dye, or simultaneously with the dyeing with the dichroic dye, or after the dyeing with the dichroic dye, for example, in the boric acid crosslinking treatment. The polarizing film made of a polyvinyl alcohol-based resin which is produced and adsorbed and aligned with a dichroic dye is one of the raw materials of the polarizing plate.

[Optical film]

A polarizing plate was produced by laminating an optical film made of a thermoplastic resin on the polarizing film. Preferably, the optical film has a refractive index measured by D rays at a temperature of 20 ° C in the range of 1.4 to 1.7. The refractive index of the optical film is measured in accordance with JIS K 0062: 1992 "Measurement Method of Refractive Index of Chemicals". When the optical film has a refractive index in this range, the display characteristics of the produced polarizing plate when it is assembled to a liquid crystal panel are excellent. For the same reason, optical film comparison Good refractive index is in the range of 1.45~1.67. The haze value of the optical film is in the range of about 0.001 to 3%, which improves the contrast of the obtained polarizing plate, and in particular, when the liquid crystal panel is assembled and black-displayed, there is a possibility that the brightness is lowered, and the like. Preferably. The haze value is measured by (diffusion transmittance / total light transmittance) × 100 (%), and is measured in accordance with JIS K 7136: 2000 "Method for determining the haze of plastic-transparent material".

Examples of the thermoplastic resin constituting the optical film include the following materials, and the refractive index measured by D rays at a temperature of 20 ° C is shown as n _D (20 ° C).

Cycloolefin resin [n _D (20 ° C) = 1.51 to 1.54], crystalline polyolefin resin [n _D (20 ° C) = 1.46 to 1.50], polyester resin [n _D (20 ° C) = 1.57~1.66], polycarbonate resin [n _D (20 ° C) = 1.57~1.59], acrylic resin [n _D (20 ° C) = 1.49~1.51], triacetyl cellulose resin [ n _D (20 ° C) = 1.48 before and after] and so on.

The cycloolefin-based resin is a polymer mainly composed of a norbornene-like cycloolefin-based monomer, and includes a resin obtained by hydrogenating a ring-opening polymer of a cycloolefin-based monomer; and a cyclic olefin It is a monomer and a chain olefin monomer having a carbon number of 2 to 10 such as ethylene and propylene, and/or an addition polymer of a vinyl aromatic monomer such as styrene.

The crystalline polyolefin resin is a polymer having a chain olefin monomer having 2 to 10 carbon atoms as a main constituent unit, and includes a homopolymer of a chain olefin monomer; and two or more kinds thereof are used. A binary or ternary copolymer of a chain olefin monomer. Specifically, it includes polyethylene resin and polypropylene. A resin, an ethylene-propylene copolymer, a homopolymer of 4-methyl-1-pentene, or a copolymer of 4-methyl-1-pentene and ethylene or propylene.

The polyester-based resin includes an aliphatic polyester-based resin in addition to an aromatic polyester-based resin such as polyethylene terephthalate or polyethylene naphthalate. The polycarbonate resin is typically obtained by reacting bisphenol A with phosgene and having a carbonate-bonded-O-CO-O- polymer in the main chain. The acrylic resin is typically a polymer mainly composed of methyl methacrylate, and includes methyl methacrylate and other methacrylates and/or acrylates in addition to the homopolymer of methyl methacrylate. Copolymer and the like. The triacetate cellulose resin is an acetate of cellulose.

The film is formed by a solvent casting method or a melt extrusion method using the thermoplastic resins, and can be used as the optical film of the present embodiment. Further, it is also possible to use uniaxial or biaxial stretching after film formation as the optical film used in the present embodiment. Before the optical film is attached to the polarizing film, the bonding surface may be subjected to an easy subsequent treatment such as saponification treatment, corona treatment, plasma treatment, primer treatment or anchor coating treatment. Further, various treatment layers such as a hard coat layer, an antireflection layer or an antiglare layer may be provided on the surface of the optical film opposite to the bonding surface of the polarizing film.

The optical film preferably has a thickness of usually about 5 to 200 μm. If the optical film is too thin, handling property is insufficient, and there is a high possibility that cracks or wrinkles are generated in the polarizing plate manufacturing line. On the other hand, if it is too thick, the obtained polarizing plate becomes thick and the weight also becomes large, and the commercial property is impaired. For these reasons, a preferred thickness is 10 to 120 μm, and preferably 10 to 85 μm.

[UV Curing Adhesive]

When the optical film is bonded to the above polarizing film, first, an ultraviolet curable adhesive is applied to the bonding surface of the optical film to the polarizing film. The thickness of the subsequent agent is usually in the range of 0.5 to 5 μm. If the thickness is less than 0.5 μm, the subsequent strength is uneven. On the other hand, when the thickness exceeds 5 μm, not only the manufacturing cost increases, but also the color tone of the polarizing plate may be affected by the type of the adhesive. If it is thicker in this range, for example, 3.5 μm or more, especially 4 μm or more, even if there is some variation in the thickness, defects such as bubbles are hard to occur, but on the other hand, such thickening brings about The increase in cost is therefore preferred to be thinner in the range possible. For these reasons, the UV curable adhesive preferably has a thickness of from 1 to 4 μm, more preferably from 1.5 to 3.5 μm.

The ultraviolet curable adhesive can be used in the form of a liquid coating, and various adhesives used in the production of a polarizing plate from the prior art can be used, but from the viewpoints of weather resistance and polymerizability, etc. A compound which is preferably a cationically polymerizable compound, for example, an epoxy compound, and more specifically, an epoxy compound having no aromatic ring in the molecule as one of ultraviolet curable components, as described in Japanese Laid-Open Patent Publication No. 2004-245925 UV curable adhesive. The epoxy compound can be obtained by, for example, hydrogenating an aromatic polyhydroxy compound which is a raw material of an aromatic epoxy compound, which is a representative example of bisphenol A diglycidyl ether, and etherification of glycidol. a hydrogenated epoxy compound; an alicyclic epoxy compound having at least one epoxy group bonded to an aliphatic ring in the molecule; and an aliphatic epoxy represented by a glycidyl ether of an aliphatic polyhydroxy compound Compounds, etc.

In the ultraviolet curing type of adhesive, in addition to the epoxy compound as a representative example In addition to the cationically polymerizable compound, a polymerization initiator is prepared, and in particular, a photocationic polymerization initiator for causing a cationically polymerizable compound to start polymerization by a cationic active species or a Lewis acid by irradiation with ultraviolet rays is prepared. Further, a thermal cationic polymerization initiator which initiates polymerization by heating may be formulated, or various additives such as a photosensitizer may be formulated.

When the optical film is bonded to both surfaces of the polarizing film, the ultraviolet curable adhesives suitable for the respective optical films may be the same or different, but from the viewpoint of productivity, it is preferable to obtain a suitable adhesive force, preferably. Both surfaces are set to the same adhesive.

[Method of Manufacturing Polarizing Plate]

In the present embodiment, a polarizing plate is produced by laminating an optical film made of a thermoplastic resin to a polarizing film made of a polyvinyl alcohol-based resin described above via an ultraviolet curable adhesive.

At this time, each of the following steps (A), (B), (C), (D), and (E) is performed.

(A) a coating step of applying the ultraviolet curable adhesive described above to the bonding surface of the optical film to the polarizing film; and (B) a bonding step for applying the ultraviolet curable adhesive to the coating step (C) a curing step in which a layered body in which an optical film is bonded via an ultraviolet curing type adhesive on a polarizing film is irradiated with ultraviolet rays from an ultraviolet irradiation device, thereby curing the ultraviolet curing type adhesive (D) a measuring step of measuring a spectroscopic illuminance of the ultraviolet ray irradiated by the curing step using a spectrometer, and based on the measuring, the radiance of the ultraviolet ray in a specific absorption wavelength region including the absorption peak wavelength of the polymerization initiator The integral value of the illuminance; and (E) the control step, the ratio of the absolute value of the difference between the integral value X of the spectroscopic illuminance and the integral value Y of the set spectroscopic illuminance obtained in the above measuring step with respect to the above Y When it is more than a specific value, for example, when it is 5% or more, the output of the said ultraviolet-ray irradiation apparatus is control.

Fig. 1 is a side view schematically showing an arrangement example of a manufacturing apparatus which is preferably applied to the present invention, and Fig. 2 is a block diagram showing an example of the relationship between the steps of the present invention. Hereinafter, a method of manufacturing a polarizing plate will be described in detail with reference to the drawings.

The manufacturing apparatus shown in FIG. 1 is configured such that the polarizing film 1 is continuously conveyed, and the first optical film 2 is bonded to one surface thereof, and the second optical film 3 is bonded to the other surface to produce polarized light. The plate 4 is taken up on the take-up roll 30. As shown in the figure, the optical film is typically bonded to both surfaces of the polarizing film 1, but the form in which the optical film is bonded only to the surface on one side of the polarizing film 1 is of course included in the present embodiment. The form of this case is removed from the description below with respect to another optical film, so that those skilled in the art can easily understand the extent to which it can be carried out.

On the surface of the first optical film 2 to which the polarizing film 1 is bonded, the first coater 10 is coated with the ultraviolet curable adhesive, and on the other hand, the second optical film 3 is bonded to the polarizing film 1. The adhesive is also applied by the second coater 12. The adhesive coating surface of each of the first optical film 2 and the second optical film 3 after the application of the ultraviolet curing type adhesive is superposed on both surfaces of the polarizing film 1, and is sandwiched by the nip rollers 20 and 21 to be thick. The direction is pressurized, and then the ultraviolet light from the ultraviolet irradiation device 16 is irradiated to cure the adhesive, and then the roll is passed. The obtained nip rollers 22, 23 are taken up and the obtained polarizing plate 4 is taken up on the take-up roll 30. Here, the manufacturing apparatus shown in FIG. 1 is provided with a spectroscopic illuminometer 17 composed of a spectrometer between the ultraviolet irradiation device 16 and the film to be conveyed, which can be used to make ultraviolet rays on the line on the manufacturing line of the polarizing plate. While the curable adhesive is cured and the ultraviolet ray is irradiated from the ultraviolet ray irradiation device, the illuminating illuminance of the ultraviolet ray irradiated to the laminated body in which the optical film is bonded to the polarizing film via the ultraviolet curable adhesive is measured. Then, based on the measurement of the spectroscopy illuminance from the spectroscopic illuminometer 17, the integrated illuminating illuminance value of the spectroscopy in the specific absorption wavelength region including the absorption peak wavelength of the polymerization initiator contained in the ultraviolet curable adhesive is measured.

Furthermore, as shown in FIG. 1, it is also preferable to use the first film thickness gauge 14 and the second film thickness on the line after the application of the adhesive on the manufacturing line of the polarizing plate and before the polarizing film is bonded to the optical film. The thickness of the ultraviolet curable adhesive applied to the optical film was measured, and based on the measurement result, the coating thickness control mechanism of the coater was controlled in such a manner as to maintain a uniform desired thickness of the adhesive.

In the first coater 10 and the second coater 12, the first optical film 2 and the second optical film 3 are coated with an ultraviolet curable adhesive by the gravure rolls 11 and 13 provided thereon. The guide roller 24 for conveyance is appropriately provided on the surface on one side of the polarizing film 1 or on the surface on the opposite side to the surface on which the adhesive film is applied to each of the first optical film 2 and the second optical film 3. As described above, when the optical film is bonded only to the side of one side of the polarizing film 1, only one of the first optical film 2 and the second optical film 3 shown in FIG. 1 is applied (for example, only the first optical The film 2) is sufficient. The straight arrow in the figure indicates the flow direction of the film, and the curved arrow indicates the rotation of the roller. to.

The polarizing film 1 is usually produced by uniaxially stretching a polyvinyl alcohol-based resin film, dyeing with a dichroic dye, and boric acid cross-linking treatment after being subjected to a polarizing film production step (not shown). It is supplied without being wound up on the roll. Of course, once the film produced in the polarizing film production step is taken up on the roll, it may be taken out by the extractor. On the other hand, the first optical film 2 and the second optical film 3 are taken out from the rolls (not shown) by an extractor. Each film is transported at the same linear velocity, for example, a linear velocity of about 10 to 50 m/min, in the same flow direction. The first optical film 2 and the second optical film 3 are extracted while being subjected to a tension of, for example, about 50 to 1000 N/m in the flow direction.

Then, the coating step (A) described above is performed by the first coater 10 and the second coater 12, and the bonding step (B) is performed by the bonding nip rollers 20, 21 by ultraviolet rays. The irradiation device 16 performs the above-described curing step (C), and the above-described measurement step (D) is performed by the spectroscopic illuminometer 17, and the above control is performed by feeding back the measurement result of the spectroscopic illuminometer 17 to the ultraviolet irradiation device 16. Step (E).

An example of the relationship between the various steps will be described based on the block diagram of FIG. First, after the coating step (A) and the bonding step (B), setting (0) sets the wavelength region of the integration target of the spectroscopic illuminance and sets the integral value of the illuminating illuminance of the ultraviolet spectroscopy ( The integral value of the set spectroscopic illuminance) Y. This setting (0) can of course also be carried out before the bonding step (B) or before the coating step (A). The wavelength region of the integral object of the astigmatism irradiance includes the absorption wavelength of the absorption peak wavelength of the polymerization initiator The area is determined by the polymerization initiator used. The integrated value Y of the astigmatism of the astigmatism radiant is selected from the range of the polarizing plate which is excellent in the durability of the polarizing film and which is difficult to produce discoloration even under the severe conditions of high temperature and high humidity. .

Then, the ultraviolet ray irradiation device 16 irradiates the ultraviolet ray to perform the curing step (C), and the spectroscopic illuminance meter composed of the spectrometer is used to measure the illuminating illuminance of the irradiated ultraviolet ray in the wavelength region set by the setting (0). The integral value (the integral value of the obtained spectral illuminance) X is obtained and output (measurement step (D)). On the other hand, in the control step (E), the integral value X of the obtained astigmatism illuminance is compared with the integrated value Y of the set illuminating illuminance. Then, for example, the absolute value of the difference between the integral value X of the obtained spectral radiance and the integrated value Y of the set spectroscopy illuminance is equal to or greater than a specific threshold value with respect to the integrated value Y of the set illuminating illuminance, for example, 5 In the case of % or more, in order to make the absolute value of the difference between the two smaller, it is preferable to make the absolute value of the difference between the integral value X of the obtained spectral radiance and the integral value Y of the set spectral illuminance, with respect to The integrated value Y of the astigmatism illuminance is set to a specific threshold value, for example, less than 5%, and the electric power input to the ultraviolet ray irradiation device 16 is adjusted to control the output. As described above, there is a case where the illuminance of a specific wavelength region is lowered due to deterioration due to long-term use of the lamp of the ultraviolet ray irradiation device or contamination due to long-term use of a member attached to the ultraviolet ray irradiation device, but also In this case, the integral value X of the obtained astigmatism illuminance is usually lower than the integral value Y of the set spectroscopy illuminance due to the long-term use of the ultraviolet ray irradiation device.

In this case, the absolute value of the difference between the integral value X of the spectral illuminance and the integrated value Y of the set spectroscopy illuminance is 5% or more with respect to the integrated value Y of the set spectroscopy illuminance. The following formula (I) is satisfied, and FIG. 2 shows whether or not the change of the output condition of the ultraviolet irradiation device is determined depending on whether or not the formula is satisfied. Further, the method of comparing the integral value X of the spectral irradiance illuminance obtained in the present embodiment with the integral value Y of the set spectroscopy illuminance is not limited to the method described in the description of FIG. That is, the comparison between the integral value X of the obtained astigmatism illuminance and the integral value Y of the set spectroscopy illuminance may not be the integral value of the illuminance based on the obtained astigmatism illuminance and the integral value of the set illuminating illuminance Y The difference may not be based on absolute value. For example, the ratio of the difference between the integral value X of the obtained astigmatism illuminance and the integrated value Y of the set spectroscopy illuminance to the integrated value Y of the set spectroscopy illuminance may be below a certain threshold or above a certain threshold. For example, a comparison of -5% or less or +5% or more may be performed according to the ratio of the integral value X of the obtained spectral radiance to the integrated value Y of the set spectral illuminance, below a certain threshold or above a certain threshold. For example, comparison is made below 95% or above 105%. The above threshold is not limited to 5% (or -5%, 95%, etc.), and may be a lower value, such as 1% or 3%, or a higher value, such as 7% or 10%. Further, the upper threshold and the lower threshold may be different values (for example, -3% or less or 7% or more).

Hereinafter, the coating step (A), the bonding step (B), the curing step (C), the measuring step (D), and the controlling step (E) constituting the method of the present embodiment will be described in detail.

(A) Coating step

In the coating step (A), an ultraviolet curable adhesive is applied to the bonding surface of the optical films 2 and 3 to the polarizing film 1. Examples of the coater used herein include the use of the gravure rolls 11 and 13 described with reference to Fig. 1 . In the coater using the gravure roll, there are, for example, a direct gravure coater, a closed blade coater, an indirect gravure coater, an anastomotic coater using a gravure roll, and a reverse roll composed of a plurality of rolls. Coating machine, etc. Further, various coaters such as a squeegee blade having a cylindrical squeegee and a coating agent for supplying the adhesive to the coating portion and scraping off by the squeegee may be applied; A die coater that directly supplies an adhesive; a doctor blade that produces a liquid reservoir while applying a blade to scrape off excess liquid. Among these, in consideration of the degree of freedom of film coating or track line, etc., in the coater using the gravure roll, a direct gravure coater, a closed blade coater, an indirect gravure coater, etc. are preferable. Further, in addition to the gravure roll, a die coater using a slit die is also preferred. It is more preferably a closed blade coater since it is easy to cope with the widening of the polarizing plate or the point that the odor of the adhesive supplied by the liquid is hard to be released.

Here, the closed blade coater is such that the gravure roll abuts against the closed blade that absorbs the liquid paint (adhesive), and the paint (adhesive) in the closed blade is transferred into the groove of the gravure roll. Then, the coating machine is transferred to the optical film 2, 3 as a coated object. Designed for small people, also known as It is a miniature closed knife coater.

When the adhesive is applied using a gravure roll, the thickness of the adhesive layer can be adjusted according to the speed ratio of the gravure roll to the linear velocity. The linear speeds of the optical films 2 and 3 are set to 10 to 50 m/min, and the gravure roll is reversely rotated with respect to the conveying direction of the optical films 2 and 3, so that the circumferential speed of the gravure roll is 10 to 500 m/min. This can adjust the coating thickness of the adhesive to 0.5 to 5 μm. Since the coating thickness at this time is also affected by the void ratio of the surface of the gravure roll, it is preferred to select a gravure roll having a suitable surface void ratio in advance. Further, the manner in which the gravure roll is reversely rotated with respect to the conveyance direction of the optical films 2 and 3 is also referred to as reverse gravure printing.

As described above, it is also preferred to measure the thickness of the ultraviolet curable adhesive applied to the optical film on the line using the first film thickness gauge 14 and the second film thickness gauge 15 before bonding to the polarizing film, and As a result of the measurement, the coating thickness control mechanism of the coater is controlled in such a manner as to maintain a uniform desired thickness of the adhesive. As the film thickness meter, for example, various types of spectral interference type film thickness meters can be used which irradiate light to the applied adhesive agent surface, and split the reflected light obtained as the interference light in a specific wavelength region, according to the obtained The spectral waveform is obtained to determine the film thickness. In the spectral interference type film thickness meter, the thickness of the applied adhesive (about 0.5 to 5 μm) can be directly measured (the first film thickness meter 14 and the second film thickness meter 15 of Fig. 1 are examples). And those who cannot measure directly. In the latter case, a film thickness meter is provided on the upstream side and the downstream side of the coater, the thickness of the optical film itself is measured by the film thickness of the upstream side, and the total thickness of the optical film and the adhesive is measured by the film thickness of the downstream side. The thickness may be determined by the difference between the measured values.

(B) lamination step

After the coating step (A), the bonding step (B) is carried out, that is, the polarizing film 1 is superposed on the respective adhesive application surfaces of the optical films 2 and 3 and pressurized. In the pressurization of this step, a known method can be used, but from the viewpoint of being continuously pressurized while being continuously transferred, as shown in Fig. 1, it is preferably sandwiched by a pair of nip rolls 20, 21. . In this case, it is preferable that the timing at which the optical films 2 and 3 are superposed on the polarizing film 1 is the same as the timing at which the optical films 2 and 3 are pressed against the polarizing film 1 by the pair of nip rolls 20 and 21, even if The difference between the timings of the two is as short as possible. The combination of the pair of nip rolls 20, 21 may be any of a metal roll/metal roll, a metal roll/rubber roll, a rubber roll/rubber roll, or the like. The pressure at the time of pressurization is preferably about 150 to 500 N/cm when sandwiched by a pair of nip rolls 20, 21.

(C) curing step

After the optical films 2 and 3 are bonded to the polarizing film 1, the laminated body in which the optical film is bonded to the polarizing film 1 via the ultraviolet curing type adhesive is irradiated with ultraviolet rays from the ultraviolet irradiation device 16 to form an ultraviolet curing type. The polarizing plate 4 was produced by curing the agent. When the ultraviolet rays are irradiated onto the laminate, the ultraviolet curable adhesive is applied through the optical film 2.

In the example shown in FIG. 1, the laminated body is irradiated with ultraviolet rays, and the laminated nip rollers 20 and 21 and the pre-winding nip rollers 22 and 23 before and after the ultraviolet irradiation device 16 are provided with a laminated body. Performed under tension. However, it is not limited to this, and it is also disclosed by the above-mentioned Japanese Patent Laid-Open Publication No. 2009-134190, which is irradiated with ultraviolet rays by a convex curved surface which is formed in an arc shape along the conveying direction, and is typically supported by the outer peripheral surface of the roller. Preferably. particular When heat is generated by irradiation of ultraviolet rays and there is a possibility of adversely affecting the product, it is preferred that the laminate is irradiated with ultraviolet rays in a state where the laminate is supported by the outer peripheral surface of the roller as in the latter case, and in this case, it is preferable to support the roller of the laminate. Temperature adjustment is possible in the range of about 10 to 60 °C. Further, the ultraviolet irradiation device may be provided in only one irradiation site, but it is effective to provide two or more irradiation directions along the flow direction of the laminate to form an irradiation from a plurality of light sources to effectively increase the amount of accumulated light.

The ultraviolet light source to be used is not particularly limited, and can be used for, for example, 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 lamp, a microwave-excited mercury lamp, a metal halide lamp, etc. having a light-emitting distribution at a wavelength of 400 nm or less. . When an epoxy compound is used as an ultraviolet curable component, it is preferable to use a large number of high pressure mercury lamps having a light of 400 nm or less as an ultraviolet light source in consideration of an absorption wavelength exhibited by a general polymerization initiator. Metal halide lamp.

When the ultraviolet ray is cured by irradiating ultraviolet rays with an epoxy resin as a curable component, the linear velocity of the laminate is not particularly limited, but generally, the coating step (A) or the bonding step is maintained as it is. (B) The speed of the line. In addition, it is preferable to apply a light amount of 100 to 1000 N/m in the longitudinal direction (transport direction) of the laminate, and to integrate the amount of irradiation in the wavelength region effective for activation of the polymerization initiator (irradiation to the laminate) The total energy) is 100 to 1500 mJ/cm ² . When the total amount of light to the adhesive is too small, the curing reaction of the ultraviolet curable adhesive is insufficient, and the sufficient bonding strength is hard to be expressed. On the other hand, if the integrated light amount is too large, the heat radiated from the light source and the polymerization of the adhesive are generated. The heat may cause yellowing of the ultraviolet curable adhesive and deterioration of the polarizing film.

In addition, when the required amount of accumulated light is achieved by one-time ultraviolet irradiation, the film may be heated to a temperature higher than 150 ° C due to heat generation. In this case, deterioration of the polarizing film may occur. In order to avoid this, as described above, it is effective to provide a plurality of ultraviolet irradiation devices along the transport direction of the film, and to irradiate them in fractions.

As a target, there is a case where the irradiation amount of the ultraviolet irradiation device from one place is 600 mJ/cm ² or less in terms of the cumulative light amount, and finally the cumulative light amount of 100 to 1500 mJ/cm ² described above can be obtained.

(D) Measurement steps

In the measuring step, the spectroscopic illuminometer 17 is used to measure the illuminating illuminance of the ultraviolet ray irradiated in the curing step (C), and based on this, the specific absorption wavelength region including the absorption peak wavelength of the polymerization initiator is determined. The integral value X of the illuminance of the ultraviolet ray. The spectroradiometer 17 is a spectroradiometer that can split the wavelength of ultraviolet light by a spectrometer in a wavelength range of 220 to 800 nm, and measure the illuminance of the split spectroscopy of each wavelength. The splitting can be performed by a diffraction grating, a chirp, or the like. The measurement of the spectroscopic illuminance using a spectroradiometer composed of a spectrometer is advantageous in that: 1) the spectroscopic illuminance can be measured across a wide wavelength region, and since the measurement sensitivity of each wavelength is the same, even if it is used In the case where the type of the polymerization initiator of the ultraviolet curing type adhesive is changed, the spectroradiometer does not need to be changed; 2) the spectroscopic illuminance of the irradiated ultraviolet light can be directly measured, and because each wavelength is The measurement sensitivity is the same, so it is possible to accurately measure the ultraviolet radiation of the specific absorption wavelength region. The integral value of the illuminance.

The wavelength region to be integrated with the illuminating illuminance of the spectroscopic radiance may be any wavelength region as long as it is an absorption wavelength region including the absorption peak wavelength of the polymerization initiator, but the light in the wavelength region having a low absorbance contributes to the curing reaction. Small, it is preferred to integrate the spectroscopic illuminance in the wavelength range of -40 nm to +40 nm of the absorption peak wavelength of the polymerization initiator, more preferably -30 nm at the absorption peak wavelength of the polymerization initiator. The integration of the spectroscopic illuminance is performed in the wavelength region of ~+30 nm. Furthermore, in the above description, the wavelength range of -40 nm to +40 nm (as the wavelength region A) of the absorption peak wavelength of the polymerization initiator may be 40 nm smaller than the absorption peak wavelength of the polymerization initiator. The wavelength is in a wavelength region of a wavelength 40 nm larger than the above absorption peak wavelength. Further, when the wavelength region to which the illuminating illuminance is integrated is, for example, in the wavelength region A, the wavelength region to be integrated as the astigmatism illuminance is not limited to the wavelength region A, and is included in the wavelength region A. Any wavelength region including the above absorption peak wavelength.

Furthermore, in the case of the integral value X of the astigmatism illuminance obtained, the number of times of measurement may be one, and it may be obtained from the measurement of the illuminance of the astigmatism of the first time, but for example, if the number of measurements is one, it is expected When the deviation is large, the number of measurement of the spectral illuminance can be made a plurality of times, and the integrated value X of the obtained spectral illuminance can be obtained by performing a Fourier transform or the like to reduce the deviation processing using the measured values.

(E) Control step

In the present embodiment, according to the above-described measurement step (D) The control step (E) of controlling the output of the ultraviolet irradiation device 16 in the curing step (C) is set. In other words, the integral value of the astigmatism illuminance obtained in the above-described measurement step (D) is deteriorated due to long-term use of the lamp of the ultraviolet ray irradiation device, or the member attached to the ultraviolet ray irradiation device is contaminated by long-term use. Slowly lower the tendency. Moreover, the illuminance of the ultraviolet ray from the lamp is generally stable in a few tens of minutes since the ultraviolet ray is irradiated, but it is also slowly lowered due to the change of the lamp environment due to the heating of the lamp or the like. The situation. This decrease in irradiance results in an offset from the integral value of the expected spectroscopic illuminance (the integral value Y of the set spectroscopic illuminance). Further, in particular, in the initial stage of ultraviolet irradiation, the voltage of the ultraviolet irradiation device is unstable, and the integral value X of the spectral irradiance obtained is higher or lower than the integral value of the desired spectral illuminance (the integral value Y of the set spectroscopy illuminance). . In order to correct the offset, in the measuring step (D), the output of the ultraviolet irradiation device 16 is controlled based on the integral value X of the obtained spectral illuminance.

For example, when the absolute value of the difference between the integral value Y of the set spectral irradiance and the integral value X of the obtained spectroscopy illuminance is 5% or more with respect to the integrated illuminance of the set spectroscopy illuminance, the difference between the two is made As the absolute value becomes smaller, it is preferable to make the absolute value of the difference between the integrated value Y of the set spectral irradiance and the integral value X of the obtained spectral illuminance, and the integral value Y of the illuminating illuminance with respect to the set is lower than 5 %, the electric power input to the ultraviolet irradiation device 16 is adjusted in such a manner that its output is increased or decreased. More specifically, when the integral value X of the astigmatism illuminance obtained is larger than the integral value Y of the set spectroscopy illuminance, the integral value of the obtained astigmatism illuminance is reduced. The ultraviolet irradiation device 16 is controlled in such a manner that the integral value X of the astigmatism illuminance is smaller than the integral value Y of the set spectroscopy illuminance, and the ultraviolet ray irradiation device 16 is controlled in such a manner as to increase the integral value of the astigmatic illuminance. This control can be done using a computer or manually.

The integral value Y of the set spectroscopic illuminance is as described above, and it is preliminarily verified that the adhesive can be cured well, and a polarizing plate having high durability in which the polarizing film is hard to be decolored can be obtained even under severe conditions of high temperature and high humidity. The range is selected, usually in the range of 50~6000 mW/cm ² . Within this range, the higher the integrated value of the spectral illuminance, the easier it is to produce a polarizing plate having good performance even if the linear velocity is high. When the integrated value Y of the set spectroscopic illuminance is less than 50 mW/cm ² , in order to satisfy the above-described integrated light amount, there is a need to increase the amount of the ultraviolet irradiation device (to extend the line, etc.) or to increase the number of the ultraviolet irradiation devices. That is, since the cumulative amount of ultraviolet light is determined by the management of the productivity speed and the illuminance of the ultraviolet ray, it is also important to achieve the above-described preferred integrated light amount by setting the integral value Y of the set spectroscopy illuminance within the above range.

In the polarizing plate manufactured as described above, the curing reaction of the ultraviolet curable adhesive is sufficiently performed, the reaction amount thereof is also stable, and therefore, the bonding strength is good, and the polarizing film is hard to be decolored under the severe conditions of high temperature and high humidity, and is used as a product. The quality stability is also excellent.

[Examples]

The present invention will be more specifically illustrated by the following examples and comparative examples, but the invention is not limited by the examples.

Figure 3 is a schematic view showing the use of the following examples and comparative examples. Side view of the configuration. The arrangement shown in FIG. 3 differs from the first embodiment described above in only one point, and the same reference numerals as in FIG. 1 are attached to portions other than the difference points. Therefore, a detailed description of the parts will be described with reference to FIG.

3 is a difference from FIG. 1 : (1) When the laminated body after the first optical film 2 and the second optical film 3 are bonded to both surfaces of the polarizing film 1 is irradiated with ultraviolet rays, the laminated body is made The second optical film 3 side is in close contact with the outer peripheral surface of the irradiation winding roller 26, and the laminated body is sandwiched by the ultraviolet irradiation device 16 disposed on the opposite side of the winding roller 26, and the first optical film 2 is laminated to the laminated body. The side is exposed to ultraviolet light.

Further, as the spectroscopic illuminometer 17, a UV-curable lamp monitoring system manufactured by Otsuka Electronics Co., Ltd. was used. The spectroradiometer is split using the spectrometer previously described, and the spectroscopic illuminance at each wavelength is measured. Then, the spectroscopic illuminance of the ultraviolet ray irradiated from the ultraviolet ray irradiation device 16 is measured at the predetermined measurement interval in advance, and the illuminance of the spectroscopy radiance of each wavelength in the predetermined wavelength region is integrated and used as The integral value X of the astigmatism illuminance obtained is obtained.

[Example 1] (0) Materials used for the experiment

In this example, as the first optical film 2, a biaxial alignment retardation film "ZEONOR" made of a cycloolefin resin having a thickness of 60 μm and a width of 1490 mm is obtained from [Japan ZEON (share)] . As the second optical film 3, a propylene-based resin film having a thickness of 75 μm and a width of 1490 mm and supplied from a roll was used. The above propylene resin film is obtained by a uniaxial extruder for a propylene resin (melting point = 164 ° C) to achieve an extrusion temperature of 275 ° C. The mixture was melt-kneaded in the form of a film, extruded from a T-die, and cooled and solidified by a cooling roll set at 20 ° C, and then both ends were removed by a cutting blade. The adhesive for the polarizing film 1 and the first optical film 2, and the adhesive for the polarizing film 1 and the second optical film 3, both containing an epoxy compound and a photopolymerization initiator (absorption peak) An epoxy-based ultraviolet curable adhesive having a wavelength of 290 nm and substantially no solvent.

(A) Coating step

The polarizing film 1 having a thickness of 25 μm with iodine adsorbed by polyvinyl alcohol, the above-mentioned cycloolefin-based resin film as the first optical film 2, and the above-mentioned propylene-based resin film as the second optical film 3 are respectively 15 m. The line speed of /min is supplied in the same way as the flow direction. The above-mentioned ring is applied to the surface of the cycloolefin-based resin film 2 to which the polarizing film 1 is bonded, using a first coater 10 having a gravure roll 11 ["Micro-closed blade" manufactured by Fuji Machinery Co., Ltd.] Oxygen-based UV-curable adhesive. In addition, the second coater 12 having the gravure roll 13 (the "micro-closed scraper" manufactured by Fuji Machinery Co., Ltd.) is also applied to the surface of the propylene resin film 3 to which the polarizing film 1 is bonded. The above epoxy-based ultraviolet curable adhesive is used.

The gravure rolls 11 and 13 provided in the coaters 10 and 12 are rotated in the reverse direction with respect to the conveyance direction of the film. Further, on the side of the cycloolefin-based resin film 2, the first coater 10 had a gravure roll 11 having a rotation peripheral speed of 21 m/min, and the adhesive was applied to the optical film at a thickness of about 2.6 μm. The second coater 12 on the side of the propylene resin film 3 was set so that the gravure roll 13 had a peripheral speed of 19.5 m/min, and the adhesive was applied to the film at a thickness of about 3.0 μm.

(B) lamination step

The cycloolefin-based resin film 2 and the propylene-based resin film 3 coated with the adhesive agent have their respective adhesive-coated surfaces superposed on the polarizing film 1, and are bonded to the nip rolls 20 and 21 at a line of 240 N/cm. Pressure clamping.

(C) curing step, (D) measuring step and control step (E)

The laminated body of the cycloolefin-based resin film 2 / the polarizing film 1 / the propylene-based resin film 3 after passing through the nip rolls 20 and 21 is made to have the propylene-based resin film 3 side and the irradiation winding roll 26 set to 20 ° C When the outer peripheral surface is in close contact with each other and a tension of 600 N/m is applied in the longitudinal direction (transport direction), the conveyance is performed at the same linear velocity of 15 m/min as before the bonding. The layered body wound around the irradiation winding roller 26 is irradiated with ultraviolet rays from the cycloolefin-based resin film 2 side by the ultraviolet irradiation device 16 (curing step (C)). At this time, the spectroscopic illuminometer 17 composed of the spectrometer is used to measure the integrated value of the illuminating illuminance of the ultraviolet ray, and the ultraviolet ray is irradiated (measurement step (D)), and the spectroscopic illuminometer 17 composed of the spectrometer is set to The spectral illuminance of the wavelength region of -30 nm to +40 nm across the absorption peak wavelength of 290 nm across the polymerization initiator contained in the above ultraviolet curable adhesive is integrated. In the above-mentioned curing step (C), the device manufactured by GS Yuasa is used as the ultraviolet irradiation device 16, and the "EHAN1700NAL high-pressure mercury lamp" which is equipped as an ultraviolet lamp is provided for each lamp. The ultraviolet ray is irradiated in such a manner that the integrated value of the astigmatism illuminance in the above-mentioned wavelength region is 55 mW/cm ² (the integrated value of the set spectroscopy illuminance Y = 55 mW/cm ² ). The cumulative amount of ultraviolet light 2 lamps is 77 mJ/cm ^{2 in total} . In this way, the adhesive layer is cured, and the polarizing plate 4 in which the cycloolefin-based resin film 2 is bonded to the single surface of the polarizing film 1 and the propylene-based resin film 3 is bonded to the other surface is formed and wound up on the take-up roll 30. on.

In the above-described measurement step (D), the measurement condition of the spectroscopic illuminance of the spectroradiometer 17 is set in advance to the number of measurement times of one measurement, the measurement interval of 3 seconds, and the measurement time of 25 milliseconds, and the above-mentioned wavelength region is measured. The instantaneous value of the integrated value of the astigmatism illuminance is outputted approximately every one minute, and this instantaneous value is used as the integral value X of the obtained astigmatic illuminance.

Then, in the control step (E), when the integral value X of the astigmatism illuminance obtained above is reduced by 5% or more compared with the integral value of the set spectroscopy illuminance Y=55 mW/cm ² , that is, (YX) At 2.75 mW/cm ² , the ultraviolet irradiation device 16 is controlled to perform output adjustment so that the output is increased by 5 W per lamp. The average value of the integral value X of the spectroscopic illuminance obtained when the operation is performed for 300 minutes is the offset of the integral value Y of the spectroscopic illuminance from the set (that is, the average value of YX) / Y (%) is called "spectral illuminance" The offset of the integral value is shown in Table 1.

[Comparative Example 1]

In the first embodiment, the control step (E) is not provided, that is, even if the integral value X of the spectroscopic illuminance obtained in the measuring step (D) is reduced by 5% or more compared with the integral value Y of the set spectroscopic illuminance, The polarizing plate is also produced by controlling the output of the ultraviolet irradiation device 16 without performing ultraviolet irradiation. The "offset of the integrated value of the spectral illuminance" at the time of the 300-minute operation is shown in Table 1.

[Embodiment 2]

A biaxially stretched polyethylene terephthalate film having a thickness of 38 μm and a width of 1330 mm is used as the first optical film 2, and has a thickness of 60 μm and a width. A biaxially oriented retardation film "ZEONOR" made of a 1330 mm cycloolefin resin is used as the second optical film 3. As an ultraviolet curable adhesive, an epoxy compound and a photopolymerization initiator are used (absorption peak wavelength = 320 nm) epoxy-based UV-curable adhesive. Then, in the same manner as in Example 1, except for the following points, (A) coating step, (B) bonding step, (C) curing step, (D) measurement step and control step (E) were carried out to prepare a polarizing plate. .

(1) In the curing step (C), the integral value of the illuminating illuminance of each of the lamps in the wavelength region shown in the following (2) is 200 mW/cm ² (the total amount of light of the two lamps is 280 mJ/cm ² ) and ultraviolet rays (ie, the integrated value of the set spectroscopic illuminance Y=200 mW/cm ² ); (2) in the measuring step (D), the absorption peak wavelength across the polymerization initiator The spectral irradiance of the wavelength range of -30 nm to +30 nm at 320 nm is integrated, so that the spectroscopic illuminometer 17 is set; and (3) the integrated value of the astigmatism of the spectroscopic radiance obtained in the control step (E) When X is reduced by 5% or more compared with the integral value Y of the set split illuminance, that is, (YX) At 10 mW/cm ² , the ultraviolet irradiation device 16 is controlled to perform an output adjustment in which the output is increased by 5 W per 1 lamp.

The "offset of the integrated value of the spectral illuminance" at the time of the 300-minute operation is shown in Table 1.

[Comparative Example 2]

In the second embodiment, the control step (E) is not provided, that is, even if the integral value X of the spectroscopic illuminance obtained in the measuring step (D) is reduced by 5% or more compared with the integrated value Y of the set spectroscopic illuminance, Also does not control the ultraviolet irradiation device The output of 16 was irradiated with ultraviolet rays to prepare a polarizing plate. The "offset of the integrated value of the spectral illuminance" at the time of the 300-minute operation is shown in Table 1.

[Density evaluation test of polarizing plate]

At any position of the obtained polarizing plate, it is cut into a strip shape of 80 mm (flow direction) × whole width, and the strip is cut into a width of 300 to 400 mm, and the plurality of small pieces thus obtained are taken as one For the sample, the small pieces were suspended in a constant temperature/humidifier adjusted to 60 ° C × 90% RH in a state of not contacting each other for 500 hours. Light was transmitted through the light box, and the light leakage was evaluated by visual comparison with a polarizing plate not placed in the thermostat/humidifier. The decolorization evaluation test was performed on four samples cut at any position of the polarizing plate, and the case where no light leakage occurred in all of the four samples was set to "OK", and one or more samples of the four samples were used. When the light leakage occurred, it was set to "NG", and the results are shown in the column of "Decolorization Evaluation Results" in Table 1. The numerical values in the brackets of the column indicate the number of samples in the four samples that cause light leakage.

As shown in Table 1, in Comparative Examples 1 and 2 in which the control step (E) was not provided, the integral value of the ultraviolet spectroscopy illuminance was greatly reduced, and accordingly, the obtained polarizing plate was decolored in a severe environment, and accordingly, When the control step (E) is set and the integral value X of the astigmatism illuminance obtained in the specific wavelength region is reduced by 5% or more compared with the integrated value Y of the set spectroscopy illuminance, the embodiment 1 and the ultraviolet ray irradiation output are changed. In the case of 2, the variation of the integral value X of the integrated illuminance of the astigmatism illuminance (the offset of the integrated value of the astigmatism illuminance) is suppressed to be less than 5%, compared with the integral value Y of the set illuminance of the astigmatism. A polarizing plate that does not discolor in harsh environments.

1‧‧‧ polarizing film

2‧‧‧First optical film

3‧‧‧Second optical film

4‧‧‧Polar plate

10‧‧‧First coater

11‧‧‧ gravure roll

12‧‧‧Second coating machine

13‧‧‧ gravure roll

14‧‧‧First film thickness gauge

15‧‧‧Second film thickness gauge

16‧‧‧UV irradiation device

17‧‧‧Splitting illuminance meter

20, 21‧‧‧ nip rollers for lamination

22, 23‧‧‧ Rolling front nip rollers

24‧‧‧guide roller

26‧‧‧Ring winding roller

30‧‧‧Winding roller

Fig. 1 is a schematic side view showing an arrangement example of a manufacturing apparatus to which the present invention is applied.

Figure 2 is a block diagram showing one of the relationships between the steps of the present invention.

Fig. 3 is a schematic side view showing the configuration of a manufacturing apparatus used in the embodiment.

1‧‧‧ polarizing film

2‧‧‧First optical film

3‧‧‧Second optical film

4‧‧‧Polar plate

10‧‧‧First coater

11‧‧‧ gravure roll

12‧‧‧Second coating machine

13‧‧‧ gravure roll

14‧‧‧First film thickness gauge

15‧‧‧Second film thickness gauge

16‧‧‧UV irradiation device

17‧‧‧Splitting illuminance meter

20, 21‧‧‧ nip rollers for lamination

22, 23‧‧‧ Rolling front nip rollers

24‧‧‧guide roller

30‧‧‧Winding roller

Claims (4)

A method for producing a polarizing plate, which is a method for producing a polarizing plate, and comprising the steps of: (A) applying an ultraviolet curing type adhesive containing a polymerization initiator to an optical film made of a thermoplastic resin; (B) a polarizing film made of a polyvinyl alcohol resin is applied onto the ultraviolet curable adhesive coated surface of the optical film, and the optical film is pressed against the polarizing film to obtain the polarizing film and the optical film are cured by the ultraviolet curing type. (C) irradiating the laminated body with ultraviolet rays to cure the ultraviolet curable adhesive from the ultraviolet irradiation device; (D) measuring the spectral illuminance of the ultraviolet rays irradiated by the spectrometer using a spectrometer, and obtaining the above-mentioned An integral value of the above-mentioned spectroscopic illuminance in a specific absorption wavelength region of the absorption peak wavelength of the polymerization initiator; and (E) an integral value of the spectroscopic illuminance according to the set spectroscopic illuminance and the integral value of the spectroscopic illuminance obtained above X controls the above ultraviolet irradiation device. The method of manufacturing the polarizing plate of claim 1, wherein the absolute value of the difference between the integral value X of the spectral radiance illuminance obtained above and the integrated value Y of the set spectroscopy illuminance is integrated with respect to the set illuminating illuminance When the ratio of the value Y is a specific value or more, the ultraviolet irradiation device is controlled. The method for manufacturing a polarizing plate according to claim 1, wherein the product of the integrated value X of the spectral radiance obtained as described above and the illuminance of the spectral radiance set above is obtained. When the ratio of the absolute value of the difference of the scores Y to the integral value Y of the spectroscopic illuminance set as described above is 5% or more, the ultraviolet irradiation device is controlled. The method for producing a polarizing plate according to any one of claims 1 to 3, wherein the specific absorption wavelength region is a wavelength from a wavelength 40 nm smaller than the absorption peak wavelength to a wavelength 40 nm larger than the absorption peak wavelength. within the area.