JP2019048960A - Method for producing multilayer sheet - Google Patents

Abstract

To provide a method for producing a multilayer sheet excellent in interlayer adhesion and also excellent in controllability of layer thickness.SOLUTION: The method for producing a multilayer sheet 35 comprises: a step (1) of applying a thermosetting polyurethane composition 18 onto a first substrate 13; a step (2) of laminating a second substrate 23 on the applied thermosetting polyurethane composition 18 and conveying an obtained laminate 35 including the first substrate 13, the thermosetting polyurethane composition 18 in an uncured state, and the second substrate 23 to pass it through a gap, thereby adjusting the thickness of the thermosetting polyurethane composition 18 in the uncured state; and a step (3) of heating the laminate 35 to subject the thermosetting polyurethane composition 18 to a curing reaction, thereby forming an adhesive layer 18a. At least one of the first substrate 13 and the second substrate 23 is an adhesive film.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method of producing a multilayer sheet. More specifically, the present invention relates to a method for producing a multilayer sheet suitable for producing a laminated optical transparent adhesive sheet.

An optically clear adhesive (OCA) sheet is a transparent adhesive sheet used for laminating optical members. In recent years, the demand for touch panels has been rapidly growing in the fields of smartphones, tablet PCs, portable game machines, car navigation devices, etc. With this, the demand for OCA sheets used to bond touch panels to other optical members Is also increasing. A display device provided with a touch panel generally includes a display panel such as a liquid crystal panel, a transparent member (touch panel main body) having a transparent conductive film made of ITO (indium tin oxide) or the like on the surface, and a cover for protecting the transparent conductive film. It has a structure where optical members, such as a panel, were laminated, and an OCA sheet is used for pasting between optical members.

Since a step is formed between the display panel and the touch panel main body by the end of the bezel which is the housing of the display panel, the OCA sheet used for bonding the display panel to the touch panel main body And covering the steps formed by the thickness of the bezel. For this reason, using a polyurethane excellent in flexibility (step difference followability) as a material of an OCA sheet is examined.

With the development of OCA sheets, the required properties of OCA sheets are becoming more sophisticated, and a method of simultaneously satisfying a plurality of contradictory properties is being sought. On the other hand, although it is conceivable to cope with multilayering of the OCA sheet, a method for producing a good quality multilayer OCA sheet has not been established.

In addition, as a prior art relevant to the manufacturing method of a multilayer sheet, patent documents 1-3 are known, for example. In Patent Document 1, a mixing step of mixing the raw materials in the continuous coating method of the thermosetting polyurethane, in which the raw material of the two-component reaction type thermosetting polyurethane is continuously coated on one side or both sides of the substrate And a raw material supply step of discharging the mixed raw material onto the upper surface of the transport body which travels at a constant speed while inclined downward at an angle of 5 ° or more and 40 ° or less with respect to the horizontal surface; The base material is supplied onto the discharged raw material, and while holding the raw material between the base material and the carrier, the held raw material is pressed by a pressure bonding roll and a receiving plate to make the thickness uniform. A coating process, and a defoaming process of degassing the raw material by pressing the raw material sandwiched between the base material and the carrier with at least a pair of nip rolls after the coating process Of thermosetting polyurethane A continuous coating method is disclosed. In addition, Patent Document 1 discloses that the raw material of the two-component reaction type thermosetting polyurethane is continuously coated on one side or both sides of the base material, and the raw material is mixed in the continuous coating method of the thermosetting polyurethane. A mixing step, a raw material supply step of discharging the mixed raw material while reciprocating in the width direction of the conveying body on the upper surface of the conveying body traveling at a constant speed in a horizontal plane, and discharged on the upper surface of the conveying body A coating process of supplying the base material onto a raw material, holding the raw material between the base material and the carrier, and pressing the held raw material with a pressure bonding roll and a receiving plate to make the thickness uniform And a defoaming step of degassing the raw material by pressing the raw material held between the base material and the carrier with at least a pair of nip rolls after the coating step. Continuous coating of thermosetting polyurethane The method is also disclosed.

Patent Document 2 discloses a first plastic film substrate having a thickness of 10 to 200 μm, a second plastic film substrate having a thickness of 10 to 200 μm, the first plastic film substrate, and the second plastic. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer with a film thickness of 100 to 500 μm sandwiched between film substrates, a projector emitting white light, and a sample obtained by cutting the pressure-sensitive adhesive sheet into squares of 1 m in length and width , And a screen, when arranged at intervals of 0.9 m and 0.3 m respectively in that order, one or less substrate uneven streaks projected on the screen as shadows of 50 cm or more in length and 3 mm or more in width A pressure-sensitive adhesive sheet is disclosed, wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer formed by applying and curing an ultraviolet-curable pressure-sensitive adhesive composition. In addition, Patent Document 2 describes a method for producing the pressure-sensitive adhesive sheet, wherein the step of applying the pressure-sensitive adhesive composition to one surface of the first plastic film substrate, and the step of applying the pressure-sensitive adhesive composition Irradiating the coating film with ultraviolet light to precure the adhesive composition; and laminating the second plastic film substrate on the coating film of the adhesive composition that has been precured. The coating film of the pre-cured adhesive composition is irradiated with ultraviolet light through the first plastic film substrate or the second plastic film substrate to substantially cure the adhesive composition. The method for producing a pressure-sensitive adhesive sheet according to claim 1, further comprising: a main curing step of forming the agent layer, wherein the light amount of the ultraviolet light irradiated in the main curing step is larger than the light amount of the ultraviolet light irradiated in the preliminary curing step. The To have.

In Patent Document 3, a 1 to 30 g / m ² curable adhesive layer is formed on one side of a first polyester film, and a second polyester film is attached to the surface on the curable adhesive layer side by a laminating nip roll. After combining, after passing a plurality of conveyance rolls, it winds up on a sheet winding core, and manufactures a lamination sheet which heat-treats 20 to 60 ° C and 24 to 168 hours in the state wound up on the winding core. And the minimum distance M between the self-discharge static eliminator and the transport roll to the transport roll where the total thickness of the laminated sheet is 100 to 300 μm and the contact angle of the sheet to the transport roll is 60 to 180 ° A method for producing a laminated sheet is disclosed, which is characterized in that it is placed in a peeling area having a length of 80 mm and a shortest distance D to the laminated sheet of 1 to 20 mm. Further, in Patent Document 3, a curable adhesive layer of 1 to 30 g / m ² is formed on one side of a first polyester film, and a second polyester film is laminated on the surface on the side of the curable adhesive layer. After pasting together a plurality of transport rolls, winding on a sheet winding core, and performing heat treatment at 20 to 60 ° C. for 24 to 168 hours in a state of being wound on the winding core It is a manufacturing method, The thickness of a 1st polyester film and / or a 2nd polyester film is 30-150 micrometers, and the contact angle of the sheet to a conveyance roll becomes a conveyance roll which becomes 60-180 degrees. It is special to perform discharge elimination by installing a discharge static eliminator in a peeling area where the shortest distance M to the transport roll is 25 to 80 mm and the shortest distance D to the laminated sheet is 1 to 20 mm. To method for producing a laminated sheet it is also disclosed.

Patent No. 4316757 specification JP, 2014-172920, A JP, 2012-116046, A

The present inventors did not exist immediately after lamination at the interface between the base material and the OCA sheet, for example, when the laminate obtained by bonding the base materials together with the OCA sheet of polyurethane is stored at high temperature, etc. It has been found that air bubbles generated in the air, that is, delayed bubbles (delay bubbles) may occur. According to the study of the present inventors, it is effective to improve the cohesion of the OCA sheet in order to prevent the generation of delayed bubbles, but this is contrary to the improvement of the flexibility of the OCA sheet.

Thus, in an OCA sheet requiring a plurality of characteristics, solutions for satisfying each performance may conflict with each other. Therefore, the present inventors examined a method of manufacturing a sheet having a multilayer structure (multilayer sheet) in order to obtain an OCA sheet simultaneously satisfying a plurality of properties.

The following method is mentioned as a manufacturing method of a multilayer sheet. First, a coating solution of a first pressure-sensitive adhesive containing a solvent is coated on a substrate film by a coater, dried in a drying oven, and a first release film is laminated at the drying oven outlet. The laminate including the film, the first adhesive and the first release film is wound up once. Subsequently, a coating solution of a second adhesive containing a solvent is coated on the second release film by a coater, dried in a drying oven, and a laminate is laminated at the outlet of the drying oven to form a multilayer sheet. Get

In this manufacturing method, since the coating solution contains a solvent, the drying of the drying furnace has two purposes of removing the solvent and crosslinking. Since crosslinking is completed in a drying oven before lamination, crosslinking between the adhesives does not occur even if the first adhesive and the second adhesive are laminated. In addition, a base film may be interposed between the first pressure-sensitive adhesive and the second pressure-sensitive adhesive. For this reason, the multilayer sheet obtained by this manufacturing method has weak interlayer adhesion and there is a possibility that delamination may occur.

On the other hand, when another adhesive is directly coated on the coated adhesive, it is applied first by the influence of the solvent contained in the coating liquid of the adhesive. The pressure-sensitive adhesive may swell or dissolve to cause surface roughness or thickness unevenness.

In addition, in patent document 1, the multilayer sheet which has a base material in the center is manufactured (refer FIG. 1 and 2). Also, since it is multi-layered before crosslinking (hardening), it is cast from the first mixing head, and even if the thickness is made uniform by the first pressure bonding roll or the nip roll, it is cast from the second mixing head, It becomes a problem that the film thickness of each layer before crosslinking (hardening) deviates from the target by passing through the pressure bonding roll or the nip roll 2.

The present invention is made in view of the above-mentioned present situation, and an object of the present invention is to provide a manufacturing method of a multilayer sheet which is excellent in adhesion between layers and also in controllability of layer thickness.

The process for producing a multilayer sheet of the present invention comprises the step (1) of applying a thermosetting polyurethane composition on a first substrate, and a second group on the applied thermosetting polyurethane composition. Materials, and the obtained first base material, the thermosetting polyurethane composition in an uncured state, and the second base material are transported to pass through a gap to carry out an uncured state. Step (2) of adjusting the thickness of the thermosetting polyurethane composition in a state, and forming the pressure-sensitive adhesive layer by curing the thermosetting polyurethane composition by heating the laminate 3), and at least one of the first base and the second base is an adhesive film.

The thermosetting polyurethane composition is preferably a solventless thermosetting polyurethane composition.

The laminate is preferably heated in the step (3) without being bent after passing through the gap in the step (2).

The pressure-sensitive adhesive film is preferably an acrylic pressure-sensitive adhesive film.

It is preferable that the said process (1) coats the said thermosetting polyurethane composition on the said adhesive film, peeling the said release film from the laminated film of the said adhesive film and a release film.

In the step (2), the pressure-sensitive adhesive film is attached onto the coated thermosetting polyurethane composition while peeling the release film from the pressure-sensitive adhesive film and the laminated film of the release film. Is preferred.

ADVANTAGE OF THE INVENTION According to this invention, while being excellent in the adhesiveness of an interlayer, the manufacturing method of the multilayer sheet excellent also in the controllability of the thickness of a layer can be provided.

It is a schematic diagram for demonstrating an example of the manufacturing method of the multilayer sheet of this invention. FIG. 1 is a cross-sectional view schematically showing a configuration of a multilayer optical transparent pressure-sensitive adhesive sheet produced in Example 1. It is the figure which showed the lamination method of the acrylic adhesive sheet in the comparative example 1, and a polyurethane adhesive sheet. It is a schematic diagram for demonstrating the evaluation method of the adhesive force of the optical transparent adhesive sheet of an Example and a comparative example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the contents of the following embodiments, and the following embodiments are appropriately modified without departing from the scope of the present invention. It is possible.

FIG. 1 is a schematic view for explaining an example of the method for producing a multilayer sheet of the present invention. As shown in FIG. 1, steps (1), (2) and (3) of the present invention can be carried out continuously. In that case, the first base material 13 is sequentially drawn out from the roll (raw fabric) 11 in which the band-like first base material 13 is wound, and the processing unit of step (1), the processing unit of step (2), and step After passing through the processing unit (3), it may be divided into a desired size. Similarly, the steps (2) and (3) may be carried out while conveying the second base material 23 in a band-like state, and then divided into desired sizes.

In the step (1) of the present invention, the thermosetting polyurethane composition 18 is applied onto the first substrate 13. Subsequently, in the step (2) of the present invention, the second base material 23 is laminated on the coated thermosetting polyurethane composition 18. As a result, a laminate including the first base material 13, the thermosetting polyurethane composition 18 in the uncured state and the second base material 23 is obtained.

One of the first base material 13 and the second base material 23 constitutes the surface layer of the multilayer sheet 35, and the other constitutes the back surface layer of the multilayer sheet 35. The material, thickness and use are not particularly limited except that at least one of them is an adhesive film, but a resin film is suitably used. When at least one of the first substrate 13 and the second substrate 23 is an adhesive film, the multilayer sheet 35 manufactured is used as an adhesive sheet capable of being attached to an adherend. The first substrate 13 and the second substrate 23 may be the same substrate or different substrates. When both the first substrate 13 and the second substrate 23 are pressure-sensitive adhesive films, two adherends can be bonded by the multilayer sheet 35 manufactured.

Examples of applications of the first base material 13 and the second base material 23 include optical films such as an antireflective film, an antiglare film, and an ultraviolet ray cut film, and protective films such as a scratch resistant film, and optical transparency. An adhesive (OCA) film etc. are mentioned. In addition, since this invention manufactures the multilayer sheet 35 excellent in the adhesiveness of an interlayer, as a main use of the 1st base material 13 and the 2nd base material 23, it becomes easily removable. The release film designed in is not included. In the multilayer sheet 35 manufactured, the first base 13 and the second base 23 are bonded and integrated with the pressure-sensitive adhesive layer obtained by curing the thermosetting polyurethane composition 18.

The first base material 13 and the second base material 23 may be composed of a single layer, or may be composed of two or more layers. Each of the first substrate 13 and the second substrate 23 shown in FIG. 1 is a laminated film of the pressure-sensitive adhesive film and the release film (support) 12 in the state of the rolls (raw sheet) 11 and 21. However, when the release film 12 is provided on the side in contact with the thermosetting polyurethane composition 18, the release film 12 is peeled off in advance before coming into contact with the thermosetting polyurethane composition 18. That is, when the first base material 13 is a laminated film of an adhesive film and a release film 12, the step (1) peels the release film 12 from the laminated film of the adhesive film and the release film 12. Preferably, the thermosetting polyurethane composition 18 is coated on the pressure-sensitive adhesive film. When the second substrate 23 is a laminated film of an adhesive film and a release film 12, the step (2) peels the release film 12 from the laminated film of the adhesive film and the release film 12. Preferably, the adhesive film is laminated on the applied thermosetting polyurethane composition 18. For example, a PET film is used as the release film 12. By providing the release film 12, the fouling of the adhesive surface of the adhesive film can be prevented.

It does not specifically limit as a material of an adhesive film, For example, the hardened | cured material (polyurethane) of an acrylic resin and a thermosetting polyurethane composition is mentioned, An acrylic resin is especially preferable. Pressure-sensitive adhesives (acrylic pressure-sensitive adhesives) made of acrylic resin are widely and generally used, and according to various applications, adjusting the adhesion from strong adhesion to slight adhesion, and specific characteristics such as cohesion and environmental resistance It is possible to improve the adhesive strength and to have the function of improving the adhesive strength by post-crosslinking with ultraviolet light. Moreover, since acrylic resin can be formed into a thin film (300 μm or less) by solvent coating, cost performance is extremely high. The thickness of the pressure-sensitive adhesive film formed of an acrylic pressure-sensitive adhesive is preferably 300 μm or less from the viewpoint of solvent coating, and preferably 1 μm or more which can be formed by gravure coating. A general method for producing acrylic adhesive is solvent coating, so the solvent is volatilized in a drying oven, but if it is intended to have a thickness of more than 300 μm, there is a risk that bubbles may be generated during coating and drying. is there. The thickness of the pressure-sensitive adhesive film composed of an acrylic pressure-sensitive adhesive is more preferably 50 μm or less, still more preferably 30 μm or less. A thin film of 50 μm or less can be formed by solvent coating using a comma coater or the like.

Even if the thermosetting polyurethane composition used as the raw material of the first base material 13 and / or the second base material 23 has the same composition as the thermosetting polyurethane composition 18 applied in the step (1) The composition may be different or different, but different characteristics of the first substrate 12, the pressure-sensitive adhesive layer and the second substrate 23 included in the multilayer sheet 35 manufactured by making the both compositions different Can be granted. Thereby, for example, when manufacturing a multilayer sheet 35 for an optical transparent adhesive (OCA) film, there is a contradiction such as flexibility required for step followability and cohesion improvement important for delay bubble measures. It is possible to make the performance compatible in one multilayer sheet.

The thermosetting polyurethane composition 18 applied at a process (1) will not be specifically limited if it produces | generates a polyurethane by heating. The optical transparent adhesive sheet made of polyurethane is flexible, stretches well and is very hard to break when a tensile stress is applied. For this reason, it is possible to peel off without adhesive residue. In addition, since the optical transparent adhesive sheet made of polyurethane is flexible and can be thickened, it can be made excellent in impact resistance. Furthermore, the optical transparent adhesive sheet made of polyurethane has a high dielectric constant and can obtain a high capacitance, so it is suitably used for bonding of a capacitive touch panel.

It is preferable that the thermosetting polyurethane composition 18 applied at a process (1) does not contain a solvent substantially. That is, the thermosetting polyurethane composition 18 is preferably a solventless thermosetting polyurethane composition. Here, the “solvent” is a component that dissolves other components in the thermosetting polyurethane composition 18 such as a polyol component, a polyisocyanate component, and a urethane prepolymer, and is a product after the curing reaction. It means a component not contained in the agent layer. Moreover, "having substantially no solvent" means that the content of the solvent in the thermosetting polyurethane composition 18 is less than 5% by mass. In the present invention, the thermosetting polyurethane composition 18 more preferably contains no solvent. As the polyol component and the polyisocyanate component, those which are liquid at normal temperature (23 ° C.) are known. By mixing the polyol component and the polyisocyanate, a liquid or gel thermosetting polyurethane composition can be obtained without using a solvent. Other optional components such as tackifiers, catalysts, etc. can be added to either the polyol component and the polyisocyanate component, and are preferably added to the polyol component. The components contained in the thermosetting polyurethane composition 18 will be described in detail later.

By using the solvent-free thermosetting polyurethane composition 18, the volume reduction associated with the removal of the solvent does not occur, so that the pressure-sensitive adhesive layer obtained by curing the thermosetting polyurethane composition 18 can be formed thick. it can. In addition, if the solventless thermosetting polyurethane composition 18 is used, it is not necessary to remove the solvent, the thermosetting polyurethane composition 18 in the uncured state of the first substrate 13 and the second substrate 23 is obtained. Even if it is heated while holding n, generation of air bubbles can be prevented. From the above, it is possible to manufacture a multilayer sheet 35 which is excellent in the adhesion between the pressure-sensitive adhesive layer and the first base 13 and the second base 23 and is also excellent in controllability of the thickness of the layer. In addition, being excellent in the controllability of the thickness of a layer means that the thickness of a layer is uniform in the surface of the multilayer sheet 35 (a dispersion | variation is small), and thickness of each layer is aimed at thickness. It means that it can be matched with high accuracy. In addition, when the solventless thermosetting polyurethane composition 18 is used, there is no risk of the substrate being corroded by the solvent, so there is no need to select the material of the substrate according to the type of the solvent, An acrylic adhesive film or the like can be used as the base 13 and the second base 23.

The coating method of the thermosetting polyurethane composition 18 on the first substrate 13 is not particularly limited, and a conventionally known coating method can be used. The thermosetting polyurethane composition 18 is preferably coated uniformly on the first substrate 13, but since the film thickness is adjusted in the step (2) described later, it is desirable at the time of coating The thickness may not be adjusted, and as shown in FIG. 1, as a coating method, even if the thermosetting polyurethane composition 18 is dropped onto the first substrate 13 from the casting machine Good. Moreover, from a viewpoint of suppressing reaction, it is preferable to prepare separately for a polyol component and a polyisocyanate component, and to coat immediately after mixing. The thermosetting polyurethane composition 18 may be at normal temperature at the time of coating or may be cooled.

The method of laminating the second base material 23 on the thermosetting polyurethane composition 18 is not particularly limited, and a conventionally known laminating method can be used. In the present invention, since the second base material 23 is laminated on the thermosetting polyurethane composition 18 in the low viscosity state before curing reaction, air bubbles or the like at the interface between the pressure-sensitive adhesive layer and the second base material 23 Contamination of foreign matter can be easily prevented.

In the step (2) of the present invention, the thickness of the uncured thermosetting polyurethane composition 18 is adjusted by conveying the laminate and passing through the gap. The method of forming the gap is not particularly limited, and as shown in FIG. 1, the gap formed between the pair of rollers 25 and 26 may be used. The roller used to form the gap may utilize the one installed to laminate the second substrate on the thermosetting polyurethane composition, or it may be an independently provided roller. Good. By passing the gap in this step, the thickness of the laminate is regulated to coincide with the size of the gap in the direction perpendicular to the transport surface of the laminate. That is, the thickness of the uncured thermosetting polyurethane composition 18 decreases to a predetermined thickness. In particular, when a solventless thermosetting polyurethane composition is used, the final thickness of the multilayer sheet 35 is determined in this step.

In the step (3) of the present invention, the laminate is heated to cure the thermosetting polyurethane composition 18, thereby forming a pressure-sensitive adhesive layer. The heating method is not particularly limited, and as shown in FIG. 1, the strip-like laminate may pass through the crosslinking furnace 31 in a fixed time. The heating conditions are preferably conditions under which the curing (crosslinking) of the thermosetting polyurethane composition 18 proceeds, for example, at 60 to 120 ° C. for 10 minutes. By curing the thermosetting polyurethane composition 18 sandwiched between the first base material 13 and the second base material 23 in this step to form an adhesive layer, the first base material 13, the adhesive layer and The multilayer sheet 35 which is excellent in the adhesiveness of the second base material 23 and in which the delamination is prevented is completed.

In addition, after passing a gap | interval in a process (2), it is preferable that a laminated body is heated in a process (3), without being bend | folded. As a result, it is possible to prevent the reduction in the adhesion between layers and the controllability of the thickness of the layer.

It is preferable that the multilayer sheet 35 manufactured by this invention is used as an optical transparent adhesive sheet. The optically transparent pressure-sensitive adhesive sheet preferably has a haze of 0.5% or less and a total light transmittance of 90% or more. The haze is measured by the method according to JIS K 7136, and the total light transmittance is measured by the method according to JIS K 7361-1.

It is preferable that the thickness of an optical transparent adhesive sheet is 50-3000 micrometers. When the thickness is less than 50 μm, when one surface of the optically transparent pressure-sensitive adhesive sheet is attached to the surface of the adherend, the optically transparent pressure-sensitive adhesive sheet covers irregularities or steps present on the surface of the adherend In some cases, the other surface of the optically transparent pressure-sensitive adhesive sheet can not be attached to the surface of another adherend with sufficient adhesion. In addition, the thicker the optical transparent adhesive sheet, the larger the amount of moisture absorption, and thus delayed bubbles due to the absorption of moisture by the optical transparent adhesive sheet are more likely to occur. However, if the thickness is 3000 μm or less, this can be sufficiently suppressed. The preferable lower limit of the thickness of the optical transparent pressure-sensitive adhesive sheet is 100 μm, the more preferable lower limit is 250 μm, and the preferable upper limit is 2000 μm. Moreover, it is preferable that an optical transparent adhesive sheet has thickness 3 times or more with respect to the height of the unevenness | corrugation or level | step difference which exists in the sticking surface of a to-be-adhered body.

When the adherend is a display panel, the display panel is accommodated in a bezel (a housing of the display panel) having an opening on the display surface side, and the thickness of the bezel is at the outer edge of the opening of the bezel There is a step corresponding to The optical transparent adhesive sheet to be attached to cover the display surface side of the display panel and the bezel is required to be thicker than the bezel in order to cover the steps formed by the thickness of the bezel, for example, a thickness of 700 μm or more It is preferable to have.

The multilayer sheet 35 manufactured according to the present invention preferably has a three-layer structure without including a release film, and more preferably, the first base 13 and the second base 23 are made of acrylic resin. The pressure-sensitive adhesive layer is a multilayer sheet made of polyurethane. The first base material 13 and the second base material 23 constituting the surface layer of the multilayer sheet 35 are made of an acrylic resin having a high degree of freedom in designing adhesive force, so that the first base material 13 and the second base material 23 are suitable according to the type of adherend Adhesiveness can be obtained. In addition, since the pressure-sensitive adhesive layer constituting the central layer of the multilayer sheet 35 is made of polyurethane, hardness (flexibility) can be selected between super soft and high hardness depending on the type of adherend, and Since the film can be formed without a solvent, the film thickness can be selected from a thin film of about 100 μm to an ultra thick film of about 5 mm. That is, by using a three-layer structure of acrylic resin / polyurethane / acrylic resin, for example, a thick and soft strong adhesive tape can be manufactured.

The components contained in the thermosetting polyurethane composition 18 to be applied in the step (1) will be described in detail below.
The thermosetting polyurethane composition preferably contains a polyol component and a polyisocyanate component, and a polyurethane can be obtained by reacting the polyol component and the polyisocyanate component. It is preferable that this polyurethane is not acrylic-modified, and it is preferable that the main chain does not contain a site derived from an acrylic ester, a methacrylic ester or the like. When the thermosetting polyurethane is acrylic-modified, it becomes hydrophobic, and therefore, aggregation of water tends to occur under high temperature and high humidity. The aggregation of the water may cause whitening, foaming and the like, which may impair the optical properties. Therefore, by setting the polyurethane to be non-acrylic modified, it is possible to prevent the deterioration of the optical characteristics due to whitening, foaming and the like under high temperature and high humidity. In the polyurethane, the total amount of the monomer unit derived from the polyol component and the monomer unit derived from the polyisocyanate component is preferably 80 mol% or more of the monomer units constituting the entire polyurethane. More preferably, it consists only of a monomer unit derived from a polyol component and a monomer unit derived from a polyisocyanate component.

[Polyol component]
The polyol component is not particularly limited, and examples thereof include polyether polyol, polycaprolactone polyol, polycarbonate polyol, polyester polyol and the like. These may be used alone or in combination of two or more.

Examples of the polyether polyols include polyethylene glycol, polypropylene glycol, polypropylene triol, polypropylene tetraol, polytetramethylene glycol, polytetramethylene triol, polyalkylene glycols such as copolymers thereof, and side chains introduced into these. And derivatives having a branched structure introduced, modified products, and mixtures of these.

Examples of the polycaprolactone polyol include polycaproate glycol, polycaprolactone triol, polycaprolactone tetraol, derivatives into which side chains are introduced or branched structures introduced into them, modified products, and mixtures of these, etc. It can be mentioned.

As said polycarbonate polyol, the reaction material of dialkyl carbonate and diol is mentioned, for example.

Examples of the dialkyl carbonate include dialkyl carbonates such as dimethyl carbonate and diethyl carbonate; diaryl carbonates such as diphenyl carbonate; and alkylene carbonates such as ethylene carbonate. These may be used alone or in combination of two or more.

Examples of the diol include 1,4-butanediol, diethylene glycol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 2-methyl-1, 8-octanediol, 1,9-nonanediol, 1,10-dodecanediol, 2-ethyl-1,6-hexanediol, 3-methyl-1,5-pentanediol, 2,4-dimethyl-1,5 -Pentanediol, neopentyl glycol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 2,2'-bis (4-hydroxycyclohexyl) -propane and the like. These may be used alone or in combination of two or more. As the diol, an aliphatic or alicyclic diol having 4 to 9 carbon atoms is preferable, and, for example, 1,4-butanediol, diethylene glycol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl- 1,5-pentanediol, 2,4-dimethyl-1,5-pentanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 2-methyl-1,8 It is preferable to use -octanediol and 1,9-nonanediol singly or in combination of two or more. As the diol, a copolycarbonate diol consisting of 1,6-hexanediol and 3-methyl-1,5-pentanediol, and a copolycarbonate diol consisting of 1,6-hexanediol and 1,5-pentanediol are also available. preferable.

In addition, as the polycarbonate polyol, for example, polycarbonate glycol, polycarbonate triol, polycarbonate tetraol, derivatives in which a side chain is introduced or a branched structure is introduced thereto, modified products, and a mixture thereof can also be used. it can.

As said polyester polyol, what carried out dehydration condensation of the dicarboxylic acid and the glycol component is mentioned, for example.

Examples of dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid and the like. Be

As the glycol component, for example, ethylene glycol, 1,4-butanediol, diethylene glycol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,5-pentanediol, 1,9-nonanediol, triethylene Aliphatic glycols such as glycols; alicyclic glycols such as 1,4-cyclohexanedimethanol; aromatic diols such as p-xylene diol; polyoxyalkylene glycols such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol Be

The polyester polyol is a polyester having a linear molecular structure when formed by the dicarboxylic acid and glycol components exemplified above, but having a branched molecular structure using a trivalent or higher ester forming component. It may be. The dicarboxylic acid and the glycol component may be reacted at 150 to 300 ° C. at a molar ratio of 1.1 to 1.3.

The number average molecular weight of the polyol component is preferably 300 or more and 5,000 or less. When the number average molecular weight of the polyol component is less than 300, the reaction between the polyol component and the polyisocyanate component is too fast, which makes it difficult to form the polyurethane into a uniform sheet, or the flexibility of the thermosetting polyurethane is May fall and become brittle. When the number average molecular weight of the polyol component exceeds 5000, the viscosity of the polyol component becomes too high, which makes it difficult to form the polyurethane into a uniform sheet, or the polyurethane crystallizes and becomes cloudy. May occur. The number average molecular weight of the polyol component is more preferably 500 or more and 2000 or less.

The polyol component is preferably one having an olefin skeleton, that is, one whose main chain is constituted by a polyolefin or a derivative thereof. Examples of the polyol component having an olefin skeleton include polybutadiene-based polyols such as 1,2-polybutadiene polyol, 1,4-polybutadiene polyol, 1,2-polychloroprene polyol and 1,4-polychloroprene polyol, and polyisoprene Polyols and those having their double bonds saturated with hydrogen or halogen etc. may be mentioned. Further, the polyol component may be a polyol obtained by copolymerizing an olefin compound such as styrene, ethylene, vinyl acetate or acrylic ester with a polybutadiene type polyol or the like or a hydrogenated product thereof. The polyol component may have a linear structure or may have a branched structure. Only one type of polyol component having an olefin skeleton may be used, or two or more types may be used. The polyol component used for the polyurethane preferably contains 80 mol% or more of a polyol component having an olefin skeleton, and more preferably consists only of the polyol component having an olefin skeleton.

Among the known polyol components having an olefin skeleton, for example, a polyolefin polyol (“EPOL (registered trademark)”) obtained by hydrogenating hydroxyl-terminated polyisoprene manufactured by Idemitsu Kosan Co., Ltd., number average molecular weight: 2500), both-end hydroxyl group hydrogenated polybutadiene (“GI-1000”, number average molecular weight: 1500) manufactured by Nippon Soda Co., Ltd., polyhydroxy polyolefin oligomer (“Polytail (registered trademark)”) manufactured by Mitsubishi Chemical Corporation, etc. may be mentioned. .

[Polyisocyanate component]
The polyisocyanate component is not particularly limited, and conventionally known polyisocyanates can be used, and hydrophilic polyisocyanate having a hydrophilic unit (hydrophilic group) and hydrophobic polyisocyanate having no hydrophilic unit Either one or both may be used.

An ethylene oxide unit is suitable as the hydrophilic unit. The action of suppressing whitening due to moisture absorption can be obtained by including the hydrophilic unit. It is preferable that content of the said ethylene oxide unit is 0.1 weight% or more and 20 weight% or less with respect to the whole thermosetting polyurethane composition. If the content is less than 0.1% by weight, whitening may not be sufficiently suppressed. When the content is more than 20% by weight, the compatibility with the low polar olefin-based polyol component, tackifier, plasticizer and the like is reduced, whereby the optical properties such as haze may be reduced. The content of the ethylene oxide unit is more preferably 0.1 to 5% by weight. When the content exceeds 5% by weight, the amount of moisture absorption in the high temperature and high humidity environment may be too large.

Examples of hydrophilic units other than ethylene oxide units include units containing a carboxylic acid group, an alkali metal base of carboxylic acid, a sulfonic acid group, an alkali metal base of sulfonic acid, a hydroxyl group, an amide group, an amino group and the like. More specifically, polyacrylic acid, alkali metal salt of polyacrylic acid, sulfonic acid group-containing copolymer, alkali metal salt of sulfonic acid group-containing copolymer, polyvinyl alcohol, polyacrylamide, carboxymethylcellulose, alkali metal of carboxymethylcellulose Salt, polyvinyl pyrrolidone and the like can be mentioned.

As said hydrophilic polyisocyanate, the modified polyisocyanate obtained by, for example, making aliphatic polyisocyanate and the ether compound which has an ethylene oxide unit react is used suitably. By using the aliphatic polyisocyanate, it is possible to prevent the occurrence of coloration or discoloration of the optically transparent pressure-sensitive adhesive sheet, and to ensure the transparency of the optically transparent pressure-sensitive adhesive sheet for a long time more reliably. In addition, the polyisocyanate component can suppress whitening by the action of the hydrophilic portion (ethylene oxide unit) by forming a modified product in which an ether compound having an ethylene oxide unit is reacted, and the hydrophobic portion (other unit) The compatibility with low polarity tackifiers, plasticizers, etc. can be exhibited by the action of

Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate, tetramethylene diisocyanate, 2-methyl-pentane-1,5-diisocyanate, 3-methyl-pentane-1,5-diisocyanate, lysine diisocyanate, trioxyethylene diisocyanate And isophorone diisocyanate, cyclohexyl diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, norbornane diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated tetramethyl xylene diisocyanate, and modified products thereof. These may be used alone or in combination of two or more. In addition, as a modified body of hexamethylene diisocyanate, what carried out isocyanurate modification, allophanate modification, and / or urethane modification etc. of hexamethylene diisocyanate, etc. are mentioned, for example.

Examples of the ether compounds having ethylene oxide units include ethylene oxide adducts of alcohols, phenols and / or amines, and from the viewpoint of enhancing hydrophilicity, those having three or more ethylene oxide units per molecule It is preferably used.

Examples of the alcohol include monohydric alcohols, dihydric alcohols (ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,3-butylenediol And peopentyl glycol etc., trihydric alcohols (glycerin, trimethylolpropane etc.). These may be used alone or in combination of two or more.

Examples of the above-mentioned phenols include hydroquinone, bisphenols (bisphenol A, bisphenol F, etc.), and formalin low condensates of phenol compounds (novolak resin, intermediate of resole). These may be used alone or in combination of two or more.

The number of isocyanate groups per molecule of the modified polyisocyanate is preferably 2.0 or more on average. If the number of isocyanate groups is less than 2.0 on average, the decrease in the crosslink density may result in the thermosetting polyurethane composition not sufficiently curing.

The above-mentioned hydrophobic polyisocyanate is not particularly limited, but aliphatic isocyanates are suitably used. For example, hexamethylene diisocyanate (HDI), tetramethylene diisocyanate, 2-methyl-pentane-1,5-diisocyanate, 3-methyl -Pentane-1,5-diisocyanate, lysine diisocyanate, trioxyethylene diisocyanate, isophorone diisocyanate (IPDI), cyclohexyl diisocyanate, 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), norbornane diisocyanate (NBDI), hydrogenated tolylene And isocyanates, hydrogenated xylene diisocyanate, hydrogenated tetramethyl xylene diisocyanate, and modified products thereof. These may be used alone or in combination of two or more.

The compounding ratio of the above-mentioned hydrophilic polyisocyanate and the above-mentioned hydrophobic polyisocyanate is preferably 9: 1 to 1: 9, more preferably 7: 3 to 3 from the viewpoint of achieving both the prevention of whitening and the reduction of moisture absorption. : 7.

The polyurethane composition preferably has an α ratio (mole number of OH group derived from polyol component / mole number of NCO group derived from polyisocyanate component) of 1 or more. If the α ratio is less than 1, the amount of the polyisocyanate component is excessive with respect to the amount of the polyol component, so that the polyurethane becomes hard and secures the flexibility required for the optically transparent adhesive sheet. It becomes difficult. If the flexibility of the optical transparent pressure-sensitive adhesive sheet is low, in particular, when bonding an optical member such as a touch panel, it is not possible to cover the unevenness and the level difference present on the bonding surface. Moreover, there is a possibility that the adhesive force required for the optical transparent adhesive sheet can not be secured. The α ratio more preferably satisfies 1.3 <α <2.0. When the α ratio is 2.0 or more, the thermosetting polyurethane composition may not be cured sufficiently.

[Tackfire]
The thermosetting polyurethane composition may further contain a tackifier (tackifier). A tackifier is an additive that is added to improve adhesion, and is usually an amorphous oligomer with a molecular weight of several hundred to several thousand, and is a thermoplastic resin that is liquid or solid at normal temperature. When the thermosetting polyurethane composition contains a tackifier, the adhesion of the optically transparent pressure-sensitive adhesive sheet formed of the cured product of the thermosetting polyurethane composition can be improved.

The above-mentioned tackifier is not particularly limited, and examples thereof include petroleum resin-based tackifiers, hydrocarbon resin-based tackifiers, rosin-based tackifiers, terpene-based tackifiers and the like. Only one type of these may be contained, or two or more types may be contained.

As the above-mentioned tackifier, a petroleum resin-based tackifier is suitably used since it is excellent in compatibility with the polyol component having the above-mentioned olefin skeleton. Among the above-mentioned petroleum resin-based tackifiers, a hydrogenated petroleum resin obtained by hydrogenating a copolymer of dicyclopentadiene and an aromatic compound is preferably used. Dicyclopentadiene is obtained from the C5 fraction. As said aromatic compound, vinyl aromatic compounds, such as styrene, (alpha)-methylstyrene, vinyl toluene, are mentioned, for example. The ratio of dicyclopentadiene to the vinyl aromatic compound is not particularly limited, but on a weight basis, it is preferable that dicyclopentadiene: vinyl aromatic compound = 70: 30 to 20:80, 60:40 to 40:60. It is more preferable that The preferable softening point of the above-mentioned hydrogenated petroleum resin is 90 to 160 ° C., the preferable vinyl aromatic compound unit content is 35 mass% or less, the preferable bromine number is 0 to 30 g / 100 g, and the preferable number average molecular weight is 500 to 1100. As a well-known thing among said hydrogenated petroleum resins, "Imarb P-100" by Idemitsu Kosan Co., Ltd. is mentioned, for example.

As said tackifier, since it is excellent in compatibility with the polyol component etc. which have the said olefin frame, a hydrocarbon resin type tackifier is used suitably. Among the above-mentioned hydrocarbon resin tackifiers, alicyclic saturated hydrocarbon resins are preferably used. Among the above-mentioned alicyclic saturated hydrocarbon resins, known ones include, for example, "Arcon P-100" manufactured by Arakawa Chemical Industries, Ltd.

It is preferable that content of the said tackifier is 1 weight% or more and 20 weight% or less with respect to a thermosetting polyurethane composition. When the content of the tackifier is less than 1% by weight, the adhesion of the optical transparent adhesive sheet may not be sufficiently improved, and in particular, the adhesion under high temperature and high humidity may be insufficient. . When the content of the tackifier exceeds 20% by weight, the reaction between the polyol component and the polyisocyanate component may be inhibited, and urethane crosslinking may not be sufficiently formed in the polyurethane. As a result, the optical transparent pressure-sensitive adhesive sheet may be dissolved and the shape may change or the tackifier may be precipitated (bleed) under high temperature and high humidity. In addition, if the reaction time between the polyol component and the polyisocyanate component is increased to sufficiently form urethane crosslinking, the productivity is lowered.

[Plasticizer]
The thermosetting polyurethane composition may further contain a plasticizer. By the addition of the plasticizer, the handling property and the level difference followability of the optical transparent adhesive sheet can be improved by lowering the hardness.

The plasticizer is not particularly limited as long as it is a compound used to impart flexibility to a thermoplastic resin, but from the viewpoint of compatibility and weather resistance, it is preferable to include a carboxylic plasticizer. Examples of the carboxylic acid plasticizer include phthalic acid esters such as diundecyl phthalate, dioctyl phthalate, diisononyl phthalate, diisodecyl phthalate, and dibutyl phthalate (phthalic acid plasticizers), and 1,2-cyclohexanedicarboxylic acid. Acid diisononyl ester, adipic acid ester, trimellitic acid ester, maleic acid ester, benzoic acid ester, poly-α-olefin and the like can be mentioned. Only one type of these may be contained, or two or more types may be contained. Among the above-mentioned carboxylic acid plasticizers, for example, “DINCH” manufactured by BASF, “San-sizer DUP” manufactured by Shin Nippon Rika, “Durasyn (registered trademark) 148” manufactured by Iones Oligomers, etc. Can be mentioned.

[catalyst]
The thermosetting polyurethane composition may further contain a catalyst. The catalyst is not particularly limited as long as it is a catalyst used for the urethanation reaction, for example, organic tin compounds such as di-n-butyl tin dilaurate, dimethyl tin dilaurate, dibutyl tin oxide, octane tin, etc .; organic titanium compounds Organic zirconium compounds; carboxylic acid tin salts; carboxylic acid bismuth salts; amine-based catalysts such as triethylenediamine.

In the above-mentioned thermosetting polyurethane composition, various additives such as a coloring agent, a stabilizer, an antioxidant, a mildew, a flame retardant and the like are optionally added within the range not to impair the required characteristics of the optical transparent pressure sensitive adhesive sheet. It may be added.

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

Example 1
(1) Production of Acrylic Adhesive Sheet A curing agent (manufactured by Soken Chemical Co., Ltd.) of an acrylic resin (“SK1838” manufactured by Soken Chemical Co., Ltd.) to 0.15% by weight with respect to the entire acrylic resin composition. An epoxy resin "E-AX" was added to prepare an acrylic resin composition. The resulting acrylic resin composition is coated on a release film (PET film whose surface has been subjected to a release treatment) with a comma coater, and then dried in a drying oven at 80 to 120 ° C., and then acrylic resin A release film (PET film whose surface was subjected to release treatment) was superimposed on the coated surface of the resin composition. Finally, aging was carried out at 40 ° C. for 1 week to complete curing, and a 30 μm thick acrylic pressure-sensitive adhesive sheet covered with a release film on both sides was produced.

(2) Preparation of thermosetting polyurethane composition 100 parts by weight of polyolefin polyol ("EPOL (registered trademark)" manufactured by Idemitsu Kosan Co., Ltd.) and tackifier ("Aimab P-100" manufactured by Idemitsu Kosan Co., Ltd.) 3 5 parts by weight of hexamethylene diisocyanate (HDI) -based polyisocyanate ("Coronato 4022" manufactured by Tosoh Corporation) and isophorone diisocyanate (IPDI) -based polyisocyanate (IPDI) so that the α ratio is 1.4 5 parts by weight of "Desmodur I" manufactured by Sumika Bayer Urethane Co., Ltd. and 0.01 parts by weight of a catalyst (dimethyl tin dilaurate) were mixed by stirring to prepare a thermosetting polyurethane composition.

(3) Production of Multilayer Sheet The roll obtained by winding the acrylic pressure-sensitive adhesive sheet provided with the release film on both sides obtained in the above (1) was placed above and below the molding apparatus shown in FIG. An acrylic adhesive provided with a release film on one side while peeling off the release film 12 on the side to be positioned on the upper surface side from the roll 11 installed at the lower side and rolling up on the roll 12A The sheet 13 was fed to the coating unit. In the coating section, the thermosetting polyurethane composition 18 obtained in the above (2) was dropped from the discharge device 16 onto the acrylic pressure-sensitive adhesive sheet 13. Then, the release film 22 on the side to be located on the lower surface side of the laminated portion is peeled off from the roll 21 installed on the upper side, and taken up by the roll 22A, and the acrylic adhesive with the release film provided on one side Agent sheet 23 was fed out to the laminating section. In the laminating section, the thermosetting polyurethane composition 18 in the uncured state is sandwiched between the pair of acrylic pressure-sensitive adhesive sheets 13 and 23 by the pair of rollers 25 and 26, whereby the thermosetting polyurethane composition 18 in the uncured state is over the thermosetting polyurethane composition 18. The laminated body in which the lower surface was laminated by the acrylic adhesive sheet 13 was obtained. Further, the thickness of the thermosetting polyurethane composition 18 is controlled by passing the laminated uncured thermosetting polyurethane composition 18 through the gap formed by the pair of rollers 25 and 26. The Then, while conveying the obtained laminate, it was crosslinked and cured in a crosslinking furnace 31 under conditions of an oven temperature of 70 ° C. and an oven time of 10 minutes, to prepare a multilayer optical transparent adhesive sheet 35. FIG. 2 is a schematic cross-sectional view showing the configuration of the multilayer optical transparent pressure-sensitive adhesive sheet produced in Example 1. As shown in FIG. 2, the multilayer optical transparent adhesive sheet 35 obtained is a release film (thickness 125 μm) 13b / acrylic adhesive sheet (thickness 30 μm) 13a / polyurethane adhesive (thickness 360 μm) 18a / It has a laminated structure of an acrylic adhesive sheet (thickness 30 μm) 23 a / releasing film (thickness 125 μm) 23 b and has transparency usable as a laminated optical transparent adhesive sheet (OCA).

(Comparative example 1)
(1) Production of Acrylic Pressure-Sensitive Adhesive Sheet In the same manner as in Example 1, an acrylic pressure-sensitive adhesive sheet having a thickness of 30 μm and having both surfaces covered with a release film was produced.

(2) Production of polyurethane adhesive sheet The thermosetting polyurethane composition prepared in the same manner as in Example 1 is conveyed while being sandwiched between a release film (PET film whose surface has been subjected to a release treatment on the surface) and conveyed while being furnace It was crosslinked and cured under the conditions of an internal temperature of 70 ° C. and an oven time of 10 minutes to prepare a 340 μm thick polyurethane pressure-sensitive adhesive sheet covered on both sides with a release film.

(3) Production of Multilayer Sheet FIG. 3 is a view showing a method of laminating an acrylic pressure-sensitive adhesive sheet and a polyurethane pressure-sensitive adhesive sheet in Comparative Example 1. As shown in FIG. 3 (a), the roll 11 obtained by winding the acrylic pressure-sensitive adhesive sheet provided with the release film on both sides obtained in the above (1), and obtained on the both sides, in the above (2) The roll 41 which wound up the polyurethane adhesive sheet in which the release film was provided was installed up and down. Then, the release film 12 on the side to be positioned on the upper surface side of the coating unit is peeled off from the roll 11 installed on the upper side, and is taken up on the roll 12A, and the acrylic having the release film provided on one side The pressure-sensitive adhesive sheet 13 is drawn out, and the release film 42 on the upper side of the coated portion is peeled off from the roll 41 disposed below and taken up on the roll 42A while the release film is formed on one side. The polyurethane pressure-sensitive adhesive sheet 43 provided is fed, and the acrylic pressure-sensitive adhesive sheet 13 and the polyurethane pressure-sensitive adhesive sheet 43 are bonded together by a laminating roll (roll temperature 23 ° C.) consisting of a rubber roll 51 and a metal roll 52. A laminated sheet 55 of an acrylic pressure-sensitive adhesive sheet and a polyurethane pressure-sensitive adhesive sheet covered with a film was obtained. Next, as shown in FIG. 3 (b), a roll 21 obtained by winding the acrylic pressure-sensitive adhesive sheet provided with the release film on both sides obtained in the above (1) is shown in FIG. 3 (a). The rolls 55A of the laminated sheet 55 were placed up and down. Then, the release film 22 on the side to be positioned on the upper surface side of the coating section is peeled off from the roll 21 disposed below, and taken up on the roll 22A, and the acrylic having the release film provided on one side The pressure-sensitive adhesive sheet 23 is drawn out, and the release film 56 on the upper side of the laminating unit is peeled off from the roll 55A installed on the upper side, and the release film is peeled off on one side while rolling up on the roll 56A. The provided laminate sheet 53 is fed out, and the acrylic adhesive sheet 23 is bonded to the surface of the laminated sheet 53 on the polyurethane adhesive sheet 43 side with a laminate roll (roll temperature 23 ° C.) consisting of a rubber roll 51 and a metal roll 52 It wound up and it obtained roll 65A of a multilayer sheet. The resulting multilayer sheet is a release film (thickness 125 μm) 13 b / acrylic adhesive sheet (thickness 30 μm) 13 a / polyurethane adhesive (thickness 340 μm) 18 a / acrylic adhesive sheet (thickness 30 μm) 23 a / release It had a laminated structure of a mold film (thickness 125 μm) 23 b and had transparency usable as a laminated optical transparent adhesive sheet (OCA).

(Comparative example 2)
Release film 13b / acrylic pressure-sensitive adhesive sheet 13a / polyurethane pressure-sensitive adhesive 18a / acrylic pressure-sensitive adhesive sheet 23a / in the same manner as in Comparative Example 1 except that the high-temperature laminating process was performed with a roll temperature of 80C. A multilayer sheet having a laminated structure of the release film 23b and having transparency that can be used as a laminated optical transparent adhesive sheet (OCA) was produced.

(Evaluation of optical transparent adhesive sheet)
The laminated optical transparent pressure-sensitive adhesive sheets prepared in Examples and Comparative Examples were evaluated by the following method. The results are shown in Table 1 below.

(1) Adhesive Strength The 180 ° peel test was conducted by the following method to measure the adhesive strength (N / 25 mm). FIG. 4: is a schematic diagram for demonstrating the evaluation method of the adhesive force of the optical transparent adhesive sheet of an Example and a comparative example. First, the optical transparent adhesive sheet produced by the Example and the comparative example was cut | judged to length 75 mm * width 25 mm, and it was set as the test piece. After peeling the release film on one side of this test piece, the optical transparent adhesive sheet side is pasted to the slide glass 81 of length 75 mm × width 25 mm, and held for 30 minutes at a pressure of 0.4 MPa. The slide glass 81 was attached. Next, the mold release film on the opposite side to the slide glass 81 is peeled off, and as shown in FIG. 4 (a), a PET sheet having a thickness of 125 μm on the side opposite to the slide glass 81 of the optical transparent adhesive sheet “Melinex (registered trademark) S” 82 manufactured by Teijin DuPont Films, Inc. was laminated. Then, after standing for 12 hours under normal temperature and normal humidity (temperature 23 ° C., humidity 50%), as shown in FIG. 4 (b), the PET sheet 82 is pulled in the direction of 180 °, and the optical speed is 30 mm / min The transparent adhesive sheet 85 was peeled off at the interface with the slide glass 81, and the adhesion of the optical transparent adhesive sheet 85 to the slide glass 81 was measured. The measurement was performed at 23 ° C. and 80 ° C., respectively. Moreover, measurement was performed about two test pieces for each condition, and the average value of the obtained two measured values was made into the measurement result.

In the above-mentioned adhesive strength evaluation, no delamination occurs in the optical transparent adhesive sheet 85, and the optically transparent adhesive sheet 85 cleanly interfacially peeled from the slide glass 81 is evaluated as “o”, and the optical transparent adhesive sheet 85 is evaluated. Delamination occurs, the acrylic adhesive sheet 13a remains on the slide glass 81, and the polyurethane adhesive 18a and the acrylic adhesive sheet 23a remain on the PET sheet 82, or the acrylic adhesive sheet 13a and the polyurethane adhesive The agent 18 a remained on the slide glass 81 and the acrylic adhesive sheet 23 a remained on the PET sheet 82 was evaluated as “x”.

(2) Thickness uniformity The thickness of the optical transparent adhesive sheet produced by the Example and the comparative example was measured by Laser Displacement Gauge ZW-S20 made by OMRON Corporation. The measurement was carried out at intervals of 10 mm in the XY directions on a sample of 30 cm × 30 cm in size. Using the maximum value (MAX), the minimum value (MIN), and the average value (AVE) of the film thickness obtained from the measurement results, the film thickness uniformity was evaluated based on the following equation.
Formula: MAX-MIN / AVE

The lamination type optically transparent adhesive sheet of Example 1 does not generate delamination at the time of measurement of adhesive power also in any of 23 ° C and 80 ° C, and adhesion power higher than a laminated type optical transparent adhesive sheet of comparative example 1 and 2 was gotten. In addition, the laminated optically transparent adhesive sheet of Example 1 was superior in film thickness uniformity to the laminated optically transparent adhesive sheets of Comparative Examples 1 and 2. Furthermore, Example 1 was an excellent method also in that the cost required for processing and time could be shortened because the number of processes is smaller than in Comparative Examples 1 and 2.

11, 12A, 21, 22A, 41, 42A, 56A: rolls 12, 13b, 22, 23b, 42, 56: release film 13: first substrate (acrylic adhesive with release film provided on one side Sheet)
13a, 23a: acrylic adhesive sheet 16: discharge device 18: thermosetting polyurethane composition 18a: polyurethane adhesive 23: second base material (acrylic adhesive sheet provided with a release film on one side)
25, 26: Roller 31: Crosslinking furnace 35: Multilayer sheet (multilayer optical transparent adhesive sheet)
43: polyurethane adhesive sheet 51 provided with release film on one side: rubber roll 52: metal roll 53: laminated sheet 55 provided with release film on one side: laminated sheet 55A of acrylic adhesive sheet and polyurethane adhesive sheet : Roll of laminated sheet 65A: Roll of multilayer sheet 81: Slide glass 82: PET sheet 85: Optical transparent adhesive sheet

Claims (6)

Applying a thermosetting polyurethane composition on a first substrate (1);
A second substrate is laminated on the coated thermosetting polyurethane composition, the obtained first substrate, the thermosetting polyurethane composition in an uncured state, and the second substrate Adjusting the thickness of the thermosetting polyurethane composition in the uncured state by conveying the laminate including the above and passing through the gap, and (2)
And (3) forming a pressure-sensitive adhesive layer by heating the laminate to cure and cure the thermosetting polyurethane composition.
At least one of said 1st base material and said 2nd base material is an adhesive film, The manufacturing method of the multilayer sheet characterized by the above-mentioned. The method for producing a multilayer sheet according to claim 1, wherein the thermosetting polyurethane composition is a solventless thermosetting polyurethane composition. The method according to claim 1 or 2, wherein the laminate is heated in the step (3) without being bent after passing through the gap in the step (2). . The method for producing a multilayer sheet according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive film is an acrylic pressure-sensitive adhesive film. In the step (1), the thermosetting polyurethane composition is coated on the pressure-sensitive adhesive film while peeling the release film from the laminated film of the pressure-sensitive adhesive film and the release film. The manufacturing method of the multilayer sheet in any one of the Claims 1-4 characterized by these. In the step (2), the pressure-sensitive adhesive film is bonded onto the coated thermosetting polyurethane composition while peeling the release film from the laminated film of the pressure-sensitive adhesive film and the release film. The method for producing a multilayer sheet according to any one of claims 1 to 5, characterized in that

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