CN102282485A - Method for manufacturing polarizing plate - Google Patents

Abstract

A method of manufacturing a polarizing plate containing both a laser high-absorptivity film and a low-absorptivity film, in which only the peeled film layer attached to the surface of the substrate is left and the strip-shaped polarizing plate is cut. A method of manufacturing a polarizing plate in which the upper surface of the protective film layer is cut by laser to the layer before the layer made of the laser low-absorption film, and then the layer made of the laser low-absorption film and the adhesive layer are cut by a cutting machine. There is no detachment between the polarizing protective film layer and the surface protective film layer of the polarizing plate, and there is no contamination of the cut surface due to overflow of the adhesive, and a polarizing plate having excellent adhesion to the substrate is obtained.

Description

Manufacturing method of polarizing plate

technical field

The present invention relates to a method for producing a polarizing plate used in an image display device such as a liquid crystal display device, and a polarizing plate cut by the method. Specifically, it relates to a method for producing a polarizing plate including both a layer of a film having a high absorption rate for laser light and a layer of a film having a low absorption rate, and a polarizing plate cut by the method.

Background technique

Since liquid crystal display devices started to be used in desktop computers, electronic clocks, etc., their applications have continued to rapidly expand in recent years. In other words, from mobile devices such as mobile phones to large TVs, liquid crystal display devices are used regardless of their screen size. In addition, in addition to liquid crystal display devices, organic electroluminescence (Organic Electro-Luminescence) display devices are also showing an increasing trend centering on the use of mobile devices. Therefore, the demand for polarizing plates used in these image display devices is also increasing, and they are required to have properties that can be adapted to various uses.

The polarizing plate generally widely used in the above-mentioned image display device is that the dichroic pigment is adsorbed and oriented on both sides of the polarizing layer 1 of the polyvinyl alcohol resin film, through a liquid adhesive layer, and triacetate fiber The plain film is a representative polarizing protective film made by stacking layers. In this state, or if necessary, add a circular or elliptical polarizing plate and retardation plate with optical properties, anti-reflection and anti-glare materials, a light diffusion plate, and a reflective plate through an adhesive layer. In the state of other functions, it is pasted on image display elements such as liquid crystal elements and organic EL display elements to form an image display device. In addition, for the structure of the polarizing plate, a film can also be pasted on the image display element. In order to prevent scratches and pollution on the surface of the polarizing protective film layer or the surface of the additional functional film layer, the bonding surface of the polarizing protective film layer with the image display element The surface on one side or the surface of the additional functional film layer is pasted with a peeling film layer through an adhesive layer, and a surface protection film layer can be pasted through an adhesive on the other side of the polarizing protective film layer.

The layer configuration of the above conventionally used polarizing plate is shown in FIG. 4 . That is to say, it is shown in Fig. 4 that polarizing plate 12 is made of surface protective film layer 4, adhesive layer 3, polarizing protective film layer 2, polarizing layer 1, polarizing protective film layer 2a, additional functional film layer 5, bonding Agent layer 6, release film layer 7 constitute. In such a configuration, the additional functional film layer is an optional layer and is not an essential layer.

In addition, in recent years, in image display devices for mobile devices such as mobile phones, the entire module has become thinner and slimmer in terms of design and portability. Therefore, the polarizing plate as the material of the image display device is also required to be lighter and thinner. As shown in FIG. 1, in the structure of the conventional polarizing plate shown in FIG. There is no polarizing plate, so there is no polarizing protective film layer 2a, and it is proposed to use such a polarizing plate.

That is to say, the band-shaped polarizing plate shown in Fig. 1 consists of a surface protective film layer 4, an adhesive layer 3, a polarizing protective film layer 2, a polarizing layer 1, an additional function film layer 5, an adhesive layer 6, a peeling film Formed by film layer 7. Cycloolefin polymer films are well known as such function-added films.

A polarizing plate is usually provided in a roll with a tape-shaped film extending longitudinally. The method of pasting the polarizing plate on an image display element such as a liquid crystal substrate is cut in advance according to the size of an image display element such as a liquid crystal substrate, and then attached The polarizer sheets are pasted on the image display element one by one. With this method, when bonding polarizer sheets to image display elements, it is difficult to shorten the process time because it is necessary to transfer the polarizer sheets one by one and peel off the release film from the polarizer sheets before bonding. . In addition, the polarizer sheet is usually cut from a roll-shaped polarizing film, which is easy to curl, and it is inconvenient to work when transferring or conveying. Furthermore, when the image display device is an LCD, the polarizing plate must be tilted so that the transmission axis of the polarizing plate is offset by 45° relative to the longitudinal or lateral direction of the LCD screen, so it is necessary to place the roll-shaped strip-shaped polarizing plate in advance relative to the roll. The drum is cut longitudinally at 45°, so that a large part near both ends of the drum cannot be used. In particular, as the size of the LCD screen increases, a large-sized polarizing plate needs to be used, and a reduction in the utilization rate of the polarizing plate is a problem. In addition, polarizers that cannot be laminated are difficult to recycle because their cut sides are made of multiple materials, resulting in an increase in waste.

In order to solve these problems, in recent years, a polarizing plate bonding device (for example, Japanese Patent JP2005-37416-A) has been disclosed that corresponds to a substrate to bond a polarizing plate. The strip-shaped film is cut along the vertical direction corresponding to the length of the substrate, leaving the above-mentioned peeling film layer. This device is equipped with a cutting method for cutting the longitudinal direction perpendicular to the above-mentioned strip-shaped polarizing plate and the above-mentioned adhesive layer, and a method for separating the above-mentioned release film layer from the film sheet cut out by the above-mentioned cutting. The front side end surface of the incoming substrate is parallel to the cut surface of the above-mentioned film, and the laminating surface of the above-mentioned film from which the peeling film layer has been separated is bonded to the corresponding position of the substrate.

Through this method, the polarizing plate can be continuously and automatically pasted on the image display element, the cut polarizing plate does not need to be transferred, and the peeling film layer is not cut, so it is a fast lamination without wasting the polarizing plate. The method of severing slices. Therefore, with this method, only the cutting of the polarizing plate with the peeled film layer left (hereinafter sometimes referred to as half-cut) is a necessary condition for cutting the strip-shaped polarizing plate. Known in this cutting method is to use a push-cut type cutting machine or a wheel type cutting machine, and a blade, a rotating shaft for driving the blade, and a bottom dead center position adjustment member for adjusting the bottom dead point position of the blade are provided. However, for different cutting machines, if the blade angle is sharp, the cutting surface will be perfect, and the blade life of the cutting machine will be short. On the other hand, after the blade angle becomes obtuse, the adhesive and adhesive will overflow on the cutting surface. Then there may be problems such as contamination of the laminated product. In addition, there will be differences in varying degrees depending on the angle of the cutting edge of the cutting machine used. In the case of using a cutting machine, there are the following disadvantages. The detachment of the surface protective film layer on the polarizing protective film layer of the polarizing plate, the decrease of moisture resistance, etc. affect the physical properties of the polarizing plate.

In the conventional method of cutting strip polarizers in advance according to the size of image display elements such as liquid crystal substrates, and attaching polarizer sheets one by one to image display elements, the above-mentioned problems caused by the cutting method due to the cutting edge are The overflow of adhesives and adhesives, and even the detachment of the surface protective film layer on the photoprotective film layer, to solve these problems, after cutting, the cutting end of the polarizing layer can be pre-processed to remove these shortcomings, so that it can be pasted combined on the image display element. However, in the above-mentioned half-cut method, it is difficult to pre-process the cut surface in a continuous operation after cutting, so a cutting method without defects is required.

On the other hand, there is also known a method of cutting a striped polarizing plate using a laser. For example, it is described in Japanese Patent JP2008-284572-A that the cutting of a strip-shaped polarizing plate is realized by laser irradiation. Specifically, a pair of triacetyl cellulose (TAC) film layers are pasted on both sides of the polyvinyl alcohol resin (PVC) film layer, and the TAC film layer on one side is provided with a polyethylene terephthalate layer through an acrylic adhesive layer. A separator made of ethylene glycol formate (PET), and a surface protective film layer made of PET film is provided on the other side of the TAC film layer through an acrylic adhesive layer, and the strip-shaped polarizing plate formed in this way can be cut by laser irradiation .

In Japanese Patent JP2008-284572-A, the strip polarizing plate to be cut is a film with a higher average absorption rate of laser light in the excitation wavelength range of laser light irradiated by PVA film, TAC film, PET film, etc. (hereinafter referred to as "Laser high absorption film"), for example, a film with an average absorption rate higher than 2%. The laminated polarizing plate made of the laser high absorption rate film, according to the traditional method shown in Japanese Patent JP2008-284572-A, has no deformation on the cutting surface of the polarizing plate, and achieves a good cutting effect.

However, in the method shown in JP2008-284572-A, in addition to the laser high absorption rate film, it also includes cycloolefin polymer film, polypropylene film, methyl methacrylate film, etc. A film with a low average absorption rate of laser light (hereinafter sometimes referred to as "low laser absorption rate film"), for example, when the strip polarizer of the layer composed of a film with an average absorption rate of 2% or less is cut, if the laser beam The output power of the laser is small, and the layer composed of the laser high absorption film in the strip polarizer can be cut, but the layer composed of the laser low absorption film cannot be cut. On the other hand, if the output power of the laser light is high, both the layer composed of the film with high laser absorption rate and the layer composed of film with low laser absorption rate in the strip polarizing plate can be cut. However, in this case, the end of the cut polarizing plate is melted due to excessive heating of the layer made of the laser high absorption rate film (see FIG. 6 ). A polarizing plate whose cross-sectional shape is deformed has a lowered cross-sectional quality. Furthermore, such a reduction in cross-sectional quality causes various problems. For example, when a polarizing plate is bonded to a glass substrate, high adhesiveness is required. However, there are problems such as generation of air bubbles on the bonding surface with the glass substrate due to unevenness of the cut surface of the polarizing plate.

In addition, for a strip polarizing plate containing a layer composed of a film with a low laser absorptivity, increase the output power of the laser, and when the layer composed of a film with a low laser absorptivity is cut, the The release layer of the laser is usually composed of a high laser absorption rate film, which causes the release film layer to be cut before the laser low absorption rate film is melted and cut. Therefore, it is considered difficult to apply the laser method to the so-called half-cut cutting method in which only the peeled layer is left and all other film layers constituting the polarizing plate are cut.

For this reason, the present inventors have found that a strip-shaped polarizing plate including a layer composed of a laser high absorption film and a layer composed of a laser low absorption film, and a peeling layer composed of a laser high absorption film can be cut. It is required that only the peeling film layer is left and the other film layers and adhesive layers constituting the polarizing plate are all cut off. After cutting, there is no substantial detachment between the polarizing protective film layer and the surface protective film layer constituting the polarizing plate. Adhesives and adhesives are not spilled on the surface, and the blade of the cutting machine has a long life, and only the peeling film is accurately left, while other film layers and adhesive layers constituting the polarizing plate are cut off. In order to find this A method for manufacturing a polarizing plate has been carefully examined, and the present invention has been completed.

Contents of the invention

The present invention contains the following contents.

[1] A method of manufacturing a strip-shaped polarizing plate, comprising: laminating a polarizing protective film layer composed of a laser high absorption rate film on one side of a polarizing layer composed of a polyvinyl alcohol resin film; The surface opposite to the polarizing layer is laminated with a surface protection film layer composed of a laser high absorptivity film via an adhesive layer, and a layer composed of a laser low absorptivity film is laminated on the other side of the polarizing layer via an adhesive layer. A strip-shaped polarizing plate formed by laminating a peeling film layer composed of a high-laser laser-absorbing film on the surface opposite to the polarizing layer of the layer composed of a low-laser low-absorptivity film through an adhesive layer, for the strip-shaped polarizing plate, Only the release film is left and the other constituent layers of the polarizing plate are cut, and the laser is used to cut from the surface protection film layer to the layer before the layer consisting of the laser low absorption rate film layer, and then the cutting machine is used to cut the layer composed of the laser low absorption rate film layer. layer and adhesive layer.

[2] The method described in [1], wherein the low laser absorption rate film is a film with an average laser absorption rate of 2% or less, and the laser high absorption rate film is a film with an average laser absorption rate exceeding 2%.

[3] The method described in [2], wherein the laser light low absorption rate film is a film having an average laser light absorption rate of 1% or less.

[4] The method described in [1] to [3], wherein a polarizing protective film layer composed of a film with high laser absorption rate is included between the polarizing layer and the layer composed of film with low laser absorption rate.

[5] The method described in any one of [1] to [4], wherein the laser low absorption rate film is a cycloolefin polymer film, a polypropylene film, or a methyl methacrylate film.

[6] The method described in any one of [1] to [5], wherein the laser is a carbon dioxide laser.

[7] A polarizing plate manufactured by the method described in any one of [1] to [6].

According to the polarizing plate manufacturing method of the present invention, only the peeling film is left when cutting the strip-shaped polarizing plate, that is, the half-cut method is adopted. After the polarizing plate is cut, the surface protective film layer on the polarizing protective film layer constituting the polarizing plate does not substantially detach from the cut surface of the polarizing plate, and there is no overflow of the adhesive on the cut surface, and the peeling film is accurately left The surface protection film layer, polarizing layer, and laser low-absorption film layer are cut, because they are used together with the laser and have the effect of prolonging the life of the cutting machine blade used in cutting.

Description of drawings

[FIG. 1] A cross-sectional schematic view of an example of the layer configuration of a lightweight strip-shaped polarizing plate applied to the present invention.

[ Fig. 2 ] A schematic cross-sectional view of an example of layer configuration of a striped polarizing plate applied to the present invention.

[Fig. 3] A cross-sectional model diagram of two-step cutting in the present invention.

[FIG. 4] A cross-sectional schematic view of an example of the layer configuration of a polarizing plate to which a conventional method is applied.

[ Fig. 5 ] A micrograph of a cut surface of a polarizing plate obtained in Example 1 cut by the method of the present invention.

[FIG. 6] A micrograph of a cut surface of a polarizing plate cut using only a fixed circular knife.

[ FIG. 7 ] A microscope photograph of a fixed circular knife after cutting the polarizing plate used in Comparative Example 1. [ FIG.

[ FIG. 8 ] A microscope photograph of a fixed circular knife after cutting the polarizing plate used in Comparative Example 1. [ FIG.

Detailed ways

Hereinafter, the present invention will be described in detail with appropriate reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view showing an example of the layer configuration of a light-weight striped polarizing plate applicable to the present invention. The strip-shaped polarizing plate in Fig. 1 is laminated according to the following order: one side of the polarizing layer 1 is pasted with a polarizing protective film layer 2 and the pair of polarizing layers of the polarizing protective film layer 2 through an adhesive layer (not shown in the figure). The side (upper side) is pasted with a surface protection film layer 4 through the adhesive layer 3, and on the other side of the polarizing layer 1 through the adhesive layer (not shown in the figure) is pasted with a polarizing protection function and a phase difference energy by laser low absorption A layer 5, an adhesive layer 6, and a release film layer 7 are composed of a rate film.

The strip-shaped polarizing plate in the implementation of the present invention is usually provided in the form of a roll along the longitudinally extending strip-shaped film. The strip-shaped polarizing plate is cut in advance according to the size of the image display element, and after only the peeling film layer 7 is left, The peeling film layer was peeled off from the polarizing plate, and the polarizing plate sheets were laminated one by one on the image display element. Therefore, as a method of cutting the polarizing plate from the tape-shaped film according to the size of the desired image display element leaving only the release film layer, first, in the case of the tape-shaped polarizing plate shown in FIG. 1 , the uppermost surface protection Layer 4, Adhesive Layer 3, Polarizing Protective Film Layer 2, Polarizing Layer 1, and Adhesive Layer (not shown in the figure) are cut by laser, and then Layer 5, which is made of a film with a low laser absorption rate, and the adhesive layer 6 Cut off with a cutting machine, or in the case of a strip-shaped polarizing plate as shown in Figure 2, the uppermost surface protective film layer 4, adhesive layer 3, polarizing protective film layer 2, polarizing layer 1, polarizing protective film layer 2a. After the adhesive layer (not shown in the figure) is cut with a laser, the layer 5 and the adhesive layer 6 made of a film with a low laser absorption rate are cut with a cutter.

The polarizing layer 1 used in the present invention is a film capable of filtering linearly polarized light from incident natural light, and a polarizing film in which dichroic pigments are adsorbed and oriented by a polyvinyl alcohol resin film can be used. The average laser absorption rate of the film is greater than 2%, for example, about 6%. The polyvinyl alcohol resin constituting the polarizing layer 1 can be obtained from saponified polyvinyl acetate resin. As the polyvinyl acetate resin, besides polyvinyl acetate, which is a single polymer of vinyl acetate, there are also examples of copolymers formed with vinyl acetate and other monomers that can be copolymerized therewith. Examples of other monomers to be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having amino groups. The saponification degree of polyvinyl alcohol resin is about 85-100 mol% normally, Preferably it is 98 mol% or more. This polyvinyl alcohol resin can also be further modified, for example, polyvinyl formal and polyvinyl acetal modified with aldehydes can also be used. In addition, the overlapping degree of the polyvinyl alcohol resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

A film made of such a polyvinyl alcohol resin is used as an original reflection film of the first polarizing layer. The film forming method of polyvinyl alcohol resin is not specifically limited, What is necessary is just to form a film using a well-known method. The thickness of the primary reflection film made of polyvinyl alcohol resin is not particularly limited, and is, for example, about 1 to 150 μm. In consideration of easiness of stretching, the film thickness is preferably 10 μm or more.

The polarizing layer 1 passes through the process of uniaxially stretching such a polyvinyl alcohol resin film, the process of dyeing the polyvinyl alcohol resin with a dichroic dye to adsorb the dichroic dye, and the process of absorbing the dichroic dye The polyvinyl alcohol resin film is produced by the process of treating the boric acid aqueous solution and the water washing process after the boric acid aqueous solution treatment. As the dichroic dye, iodine and a dichroic organic dye can be used.

The polarizing protective film layers 2 and 2a used in the present invention are composed of films with high laser absorptivity, the average absorptivity of laser light is usually greater than 2%, and can be composed of suitable transparent films. Among them, a film made of a resin excellent in transparency, uniformity of optical properties, mechanical strength, thermal stability, and the like is preferably used. Other examples include cellulose resin films such as cellulose triacetate or cellulose diacetate, polyethylene terephthalate or polyethylene isophthalate, and polybutylene terephthalate. polyester resin film, polycarbonate resin film, polyethersulfone resin film, polysulfone resin film, polyimide resin film, etc. The transparent protective film layers 2 and 2a are laminated on the polarizing layer 1 through an adhesive layer, and a well-known adhesive in this field can be used. The known adhesive has an average value of the laser light within the excitation wavelength range of the irradiated laser light. The absorption rate is high, usually greater than 2%.

Examples of such adhesives include water-soluble adhesives, organic solvent adhesives, hot-melt adhesives, and non-solvent adhesives. More specifically, water-soluble adhesives, such as polyvinyl alcohol resin aqueous solution, water-based two-component polyurethane latex adhesive, etc.; organic solvent-based adhesives, such as two-component polyurethane adhesive, etc.; non-solvent Adhesives, such as one-component polyurethane adhesives, etc. When a cellulose acetate film that has been hydrophilized by saponification treatment or the like to the polarized light is used as a polarized light protection film, it is preferable to use a polyvinyl alcohol type resin aqueous solution as an adhesive. In the polyvinyl alcohol type resin used as an adhesive, in addition to the vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, a single polymer of vinyl acetate, it can also be vinyl acetate and other monomers that can be polymerized with it. A vinyl alcohol-type copolymer obtained by saponification of a copolymer formed from a body, or even a modified polyvinyl alcohol polymer in which a part of the hydroxyl groups of the above-mentioned polymer is modified. In the adhesive, polyaldehydes, water-soluble epoxy compounds, melamine compounds, etc. can also be used as additives.

The polarizing plate in the present invention uses a laser light low absorption rate film as a constituent layer material of the polarizing plate. The average absorptivity of the laser light in the excitation wavelength range of the irradiated laser light is usually 2% or less, preferably 1% or less. In this specification, [average absorptance (%) of laser light in the excitation wavelength range of irradiated laser light] can be measured by the conventionally known ATR (Attenuated total reflection) method. In this [ATR method], an absorption spectrum on the surface of the measurement object is obtained by irradiating the measurement object with light (laser light) having an arbitrary wavelength and measuring the total reflected light on the surface of the measurement object. Within the excitation wavelength range of the irradiated laser, the absorptivity of light containing any wavelength is measured by the ATR method. According to the average value of the calculated absorptivity, the above-mentioned [average absorptivity of the laser in the excitation wavelength range of the irradiated laser ( %)].

Examples of low laser absorption rate films include poly(methyl)acrylate or poly(ethyl)acrylate-like acrylic resin films and polyolefin-type resin films; norbornene-like cyclic olefins as monomers The cyclic olefin-type resin film, more specifically, cyclic olefin polymer (COP) film, polypropylene (PP) film, polymethyl methacrylate (PMMA) film etc. are mentioned. Due to the requirements of polarizers, these films have the function of phase difference film, and also have excellent functions of preventing water absorption and moisture resistance. Just like the strip polarizer shown in Figure 1, polarizing protective films such as TAC can also be used instead. .

In addition, the polarizing plate in the present invention can also add film layers with additional functions such as retardation film layer, viewing angle expansion film layer, anti-reflection film layer, anti-glare film layer, reflective film layer, etc., corresponding to its purpose, It can be added to any layer in the layer composed of surface protection film layer and laser low absorption rate film layer. These additional functional film layers are composed of laser high absorption rate film. In addition, one or more layers can be used.

In the present invention, as the adhesive used for the adhesive layers 3 and 6 constituting the polarizing plate, known adhesives in this field can be used. The average absorptivity of the laser light in the excitation wavelength range of the irradiated laser light of this known adhesive is relatively high, usually greater than 2%. For example, adhesives containing base polymers such as acrylics, rubbers, polyurethanes, silicones may be used. In addition, an energy ray-curable adhesive, a thermosetting adhesive, or the like may be used. Among them, an adhesive having an acrylic resin as a base polymer having excellent transparency, weather resistance, heat resistance, etc. is preferable.

The acrylic resin is not particularly limited, but preferably used are butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, Ester-like (meth)acrylate-type base polymers and copolymerization-type base polymers containing two or more of these (meth)acrylates. More preferably, polar monomers are copolymerized in these base polymers. Examples of polar monomers include (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (meth)acrylamide, 2-N,N-di Methylaminoethyl (meth)acrylate, epoxy (meth)acrylate-like monomers containing carboxyl, hydroxyl, amine, amino and epoxy groups.

As an acrylic adhesive, it can be used alone or in combination with a common crosslinking agent. As the cross-linking agent, enumerate can contain divalent or polyvalent metal ion, form carboxylate metal salt between it and carboxyl; Or contain polyamine compound, form amide bond between carboxyl; Or contain polyepoxide and A polyol compound, which forms an ester bond with a carboxyl group; or a compound containing a polyisocyanate compound, which forms an amide bond with a carboxyl group, and the like. Among them, polyisocyanate compounds are widely used as organic crosslinking agents.

Energy ray-curable adhesives have the property of being hardened after being irradiated with energy rays such as ultraviolet rays or electron rays. Before the energy ray is irradiated, they adhere tightly to the covered body such as a film, and can be cured by energy ray irradiation. its stickiness. In addition, in the present invention, when a curable adhesive is used for the adhesive layer, it means that the adhesive layer is a layer formed of a cured product of the curable adhesive. As the energy ray-curable adhesive, it is preferable to use an ultraviolet-curable adhesive. An energy ray-curable adhesive generally contains an acrylic adhesive and an energy ray polymerizable compound as main components. It is usually combined with a crosslinking agent, and if necessary, it can also be used in combination with a photopolymerization initiator or a photosensitizer.

In the adhesive composition used to form the adhesive layer, in addition to the above-mentioned base polymer and crosslinking agent, it is also possible to adjust the adhesive force, cohesion, viscosity, elastic modulus, Glass transition temperature, etc., can also be combined with some appropriate additives, such as natural or synthetic resins, adhesive resins, anti-oxidants, dyes, pigments, defoamers, corrosive agents, photopolymerization initiators, etc. Even fine particles can be added to form an adhesive layer exhibiting light scattering properties. In addition, an antioxidant, an ultraviolet absorber, or the like may be blended in the adhesive layer. The ultraviolet absorber includes a benzophenone compound, a salicylate compound, a benzotriazole compound, a cyanoacrylate compound, a nickel complex salt compound, and the like.

The peeling film layer 7 constituting the polarizing plate in the present invention is a peeling material made of a film with a high laser absorption rate, and is composed of a film with an average laser light absorption rate greater than 2% in the excitation wavelength range of the irradiated laser light. As a usual release material using an optical film, for example, a polyester film, a polyethylene terephthalate film, and the like can be used.

In addition, the substrate 8 of the display device bonded to the polarizing plate after the peeling film layer 7 is peeled is a flat member such as a glass substrate or a synthetic resin substrate applied in display devices such as a liquid crystal display device and a plasma display device. A substrate on which components such as a liquid crystal cell and electrodes are formed is prepared. The shape of the substrate generally uses a shape such as a square or a rectangle.

The laser device used for cutting the strip-shaped polarizing plate in the present invention may be a conventionally known infrared laser such as carbon dioxide laser, YAG laser, UV laser or the like. However, it is recommended to use a carbon dioxide laser in order to reduce cracks or defects in the cut surface and to facilitate the work.

The speed of laser cutting is affected by the thickness of the strip-shaped polarizing plate to be cut. If the thickness of the polarizing plate is in the range of 70-500 μm, the speed is more than 1 m/min, preferably 5-60 m/min. If the cutting speed is less than 1 m/min, productivity tends to be poor. In addition, the output of the infrared laser is determined by factors such as the thickness of the polarized light and the desired cutting speed, but generally a range of 10W to 40W is used. The wavelength of the laser light used in the present invention, because the object to be cut in the present invention is only one side of the polarized light, and it is a polarizing plate containing a low-absorptivity film-forming layer for irradiating laser light, it is a particularly thin strip-shaped polarizing plate. The recommended laser wavelength is that used at a thickness of 9.4 μm. When cutting with such a laser wavelength, the cut end surface should be more beautiful than cutting with a laser wavelength of 10.6 μm.

What is cut by such a laser is, as shown in FIG. 3 , the layers constituting the strip polarizing plate from the surface protective film layer to the layer 5 which has a low laser absorption rate. This cutting only leaves the peeling film layer 7, and when the layer 5 and the adhesive layer 6 positions made of the laser low absorptivity film are cut off, because the light absorption capacity of the layer 5 made of the laser low absorptivity film is low, use It is difficult for laser to guarantee the accuracy of cutting (adjustment of cutting depth). In many cases, the release film is also cut, and it is difficult to achieve expectations with half cutting. In addition, even if the half-cut is successful, the peeling layer is peeled off from the polarizer after cutting because the resin melts to form a block, and when it is bonded to the substrate 8, detachment occurs at the bonded part of the substrate and the polarizer, and uniform tight bonding cannot be achieved. .

In the present invention, the layer before the layer 5 made of the laser low absorption rate film is cut with a laser, and then cut with a cutting machine, leaving the peeled film layer 7 . When the cutting machine is completely used to cut off, the surface protection film 4 will be detached or the adhesive will leak, and even the life of the cutting machine will be significantly shortened. However, the method of the present invention can improve these production costs. Compared with only using laser to cut the tape For a polarizing plate formed by lamination of a protective film layer and a peeling film layer with significant differences in laser absorptivity, if only the peeling film layer is to be left, a highly complicated technology is required. The present invention adopts a two-step method, Just solved the above-mentioned existing problem with extremely simple method.

As a cutting machine for cutting the laser low absorption rate film-forming layer 5 and the adhesive layer, cutting machines commonly used in the field of optical films can be used, such as a press cutting type cutting machine, a wheel type cutting machine, and a fixed circular blade and a rotary circular blade. Blades and the like are enumerated. As for these blades, it is recommended to use a blade having a rotation shaft for driving the blade and a bottom dead center position adjusting member for adjusting the bottom dead point position of the blade. In this case, adjusting the position of the bottom dead center to less than 0.5 times the thickness of the release film layer 7 will accurately leave the release film 7 and only the layer 5 made of a laser low absorption rate film and the adhesive layer along the The vertical direction is cut off.

In addition, in the output wavelength range of carbon dioxide laser (9.2 ~ 10.8μm), the average absorptivity of representative films used in polarizing plates was measured, triacetate cellulose film (TAC film): 13%, polyvinyl alcohol resin film (PVA film): 6%, polyethylene terephthalate film (PET film): 8%, cycloolefin polymer film (COP film): 0.3%, polymethyl methacrylate film (PMMA film): 0.8%, polypropylene film (PP film): 0.7%.

The polarizing plate cut into a desired shape according to the method of the present invention described in detail above is bonded to a substrate 8 such as a liquid crystal display after peeling off the release film layer 7 . As shown in Figure 1 or Figure 2, the laminated tape-shaped film is rolled into a cylinder, and the cylindrical film is unfolded in the longitudinal direction. It includes a cutting step of cutting the strip-shaped polarizing plate and the above-mentioned adhesive layer in a direction perpendicular to the longitudinal direction by leaving only the peeling film layer, a separation step of separating the film cut out by the cutting from the peeling film layer, and the above-mentioned In the bonding process where the bonding surface of the film sheet and the release film layer is transported to the substrate and bonded to the substrate, it is recommended to use a polarizing plate bonding device that can continuously bond the polarizing plate on the prepared substrate.

【Example】

The following is a more detailed description of the method of the present invention based on the examples.

[structure of polarizing plate]

As the strip polarizing plate in this embodiment, a polarizing plate substantially having a structure as shown in FIG. 1 is used. That is, the two sides of the polarizing layer 1 composed of a film with a thickness of 25 μm in which iodine is adsorbed and oriented in polyvinyl alcohol are polarized protective film layers 2 composed of a cellulose triacetate film with a thickness of 80 μm. The adhesive layer composed of an aqueous solution of epoxy resin is pasted; then on the top of the polarizing protective film layer 2 composed of triacetate cellulose film, in order to prevent scratches or dust during use and operation for the purpose of protection, pass a 20 μm thick pressure Sensitive acrylic adhesive layer 3, a surface protection film 4 made of polyethylene terephthalate film with a thickness of 40 μm is pasted; A layer 5 (hereinafter sometimes referred to as additional functional layer 5) (trade name: ZEONOR, manufactured by Japan ZEON Co., Ltd.) made of cycloolefin resin film with a thickness of 70 μm is attached to an adhesive composed of an aqueous solution; 25 μm of acrylic pressure-sensitive adhesive layer 6; on it is a release film 7 of polyethylene terephthalate film with a thickness of 38 μm, ready to bond two layers of strip-shaped polarizing plates (size: 1m ×1m).

[Example 1]

刀锋角度20°，厚度0.3mm，萩原工业株式会社制)，切断功能附加层5以及粘合剂层6，仅留下剥离膜层7。这样得到的偏光板切断断面的显微镜照片为图5所示。另外，用这种激光(激光波长9.4μm)加固定圆刀的二步切断法对150枚偏光板切断处理后，观察了固定圆刀的刀刃，结果刀刃没有出现卷刃，也没有观察到切断能力的明显下降。For the strip-shaped polarizing plate above, use a carbon dioxide laser with a laser wavelength of 9.4 μm (laser irradiation device: Coherent Co., Ltd., USA) to cut at right angles to the absorption axis of the polarizing plate from the surface protective film layer of the polarizing plate to the functional additional layer 5. Up to the previous layer (surface protection film layer, adhesive layer, polarizing protective film layer, polarizing layer, adhesive layer) (cutting conditions: frequency 20kHz, output power: 59W, speed: 60m/min), and then use a fixed Round Knife (

Blade angle 20°, thickness 0.3 mm, Hagiwara Kogyo Co., Ltd.), cut off the functional additional layer 5 and the adhesive layer 6, leaving only the release film layer 7. A micrograph of the cut section of the polarizing plate thus obtained is shown in FIG. 5 . In addition, after cutting 150 polarizers with the two-step cutting method of laser (laser wavelength 9.4 μm) and fixed circular knife, the blade of the fixed circular knife was observed, and the result was that there was no curling edge on the blade, and no cutting was observed. Significant decline in capacity.

[Comparative example 1]

For the same strip-shaped polarizing plate used in Example 1, only the circular knife used in Example 1 was used, leaving only the peeling film layer 7 on the bonding surface with the substrate to carry out the cutting operation. FIG. 6 shows a micrograph of the cut surface of the polarizing plate cut at the 10th time from the start of the implementation.

As clearly shown in FIG. 6 , when only the fixed circular knife was used to cut the strip-shaped polarizing plate, detachment between the polarizing protective film layer and the surface protective film layer was found at the 10th cutting section. In addition, the sharpness of the round knife was deteriorated in the 10th time, as shown in Figure 7 and Figure 8, a gap was found on the edge of the round knife, and it was difficult to continue to use it.

Symbol Description

1. Polarizing layer 2. Polarizing protective film layer

2a. Polarizing protective film layer 3. Adhesive layer

4. Surface protective film layer 5. Layer composed of laser low absorption rate film

6. Adhesive layer 7. Peeling film layer

8. Substrate

Claims (7)

1. A manufacturing method of a polarizing plate, comprising: on one side of a polarizing layer made of a polyvinyl alcohol resin film, a polarizing protective film layer made of a laser high absorptivity film is laminated; On the opposite side, a surface protection film layer composed of a laser high-absorption film is laminated through an adhesive layer, and a layer composed of a laser low-absorption film is laminated on the other side of the polarizing layer through an adhesive layer. A strip-shaped polarizing plate formed by laminating a peeling film layer composed of a laser high-absorbing film on the surface opposite to the polarizing layer through an adhesive layer, and leaving only the peeling film on the strip-shaped polarizing plate While cutting off the other constituent layers constituting the polarizing plate, The laser is used to cut from the surface protection film layer to the layer before the layer composed of the laser low absorption rate film layer, and then the layer composed of the laser low absorption rate film layer is cut with a cutter. 2 . The method according to claim 1 , wherein the laser low absorption rate film is a film having an average laser absorption rate of 2% or less, and the laser high absorption rate film is a film having an average laser absorption rate exceeding 2%. 3. The method according to claim 2, wherein the laser light low absorption rate film is a film having an average laser light absorption rate of 1% or less. 4. The method according to claim 1 or 2, wherein there is a polarizing protective film made of a laser high absorptivity film between the polarizing layer and the layer made of a laser low absorptivity film. 5. The method according to any one of claims 1 to 4, wherein the laser low absorption rate film is a cycloolefin polymer film, a polypropylene film, or a polymethylmethacrylate film. 6. A method according to any one of claims 1 to 5, wherein the laser is a carbon dioxide laser. 7. A polarizing plate manufactured by the method according to any one of claims 1-6.

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