WO2013147312A1

WO2013147312A1 - Method for manufacturing optical member equipped with adhesive

Info

Publication number: WO2013147312A1
Application number: PCT/JP2013/060139
Authority: WO
Inventors: 柱烈張; 眞求李
Original assignee: 住友化学株式会社
Priority date: 2012-03-28
Filing date: 2013-03-27
Publication date: 2013-10-03
Also published as: KR101738741B1; JP5903978B2; CN104204875A; CN104204875B; JP2013205545A; KR20140146608A; TWI569048B; TW201346355A

Abstract

In the present invention, an optical member (25) equipped with an adhesive is manufactured by peeling a first peeling film (2) from an adhesive sheet (5) that is a laminate of the first peeling film (2), an adhesive layer (1), and a second peeling film (3) and affixing the exposed adhesive layer (1) to an optical member (20). The peeling forces used between the peeling films and the adhesive layer (1) both exceed 0.02 N/25 mm and are both less than 0.15 N/25 mm, with a mutual difference of less than 0.01 N/25 mm. At peel point P, the first peeling film (2) is made to advance straight ahead without bending, the second peeling film (3) and the adhesive layer (1) are carried in a direction different from the direction of advance of the first peeling film (2) so that no pressing force will be added from the opposite side of the adhesive layer, and the first peeling film (2) is peeled off.

Description

Method for producing optical member with adhesive

The present invention relates to a method for producing an optical member with an adhesive which is suitably used for producing a liquid crystal panel or a liquid crystal display device. Specifically, the present invention relates to a method for producing an optical member with an adhesive by peeling off one release film from an adhesive sheet provided with release films on both sides of the adhesive layer and sticking the adhesive layer to an optical member. .

In general, a liquid crystal panel constituting a liquid crystal display device has a configuration in which an optical member such as a polarizing plate or a retardation film is bonded to a liquid crystal cell via an adhesive layer. The optical member for bonding to the liquid crystal cell is produced as an optical member with an adhesive having a structure in which an adhesive layer is formed on the bonding surface to the liquid crystal cell and the surface is temporarily protected with a release film. Is common.
Such an optical member with an adhesive peels off one release film from an adhesive sheet provided with a peelable film (release film) on both sides of the adhesive layer, and attaches the adhesive layer to the optical member. Often manufactured by a method. That is, the adhesive sheet is provided with a release film on the front and back of the adhesive layer, respectively, and has a structure like a double-sided adhesive tape used for general stationery or work, but a general double-sided adhesive tape is While the pressure-sensitive adhesive layer and the release film correspond to one sheet: one sheet, the pressure-sensitive adhesive sheet is different in that a release film is provided on both surfaces of the pressure-sensitive adhesive layer. An optical member provided with a pressure-sensitive adhesive layer manufactured by a method in which one release film is peeled off from the pressure-sensitive adhesive sheet and the pressure-sensitive adhesive surface exposed thereby is bonded to the surface of the optical member, that is, an optical member with a pressure-sensitive adhesive Are stored or distributed in this state. Then, immediately before being bonded to the liquid crystal cell, the release film temporarily protecting the adhesive surface is peeled off, and the exposed adhesive surface is bonded to the liquid crystal cell. The pressure-sensitive adhesive here is sometimes referred to as a pressure-sensitive adhesive, and the release film is sometimes referred to as a separator or a separate film.
If the peeling force from the adhesive layer of the release film that is applied to both sides of the adhesive sheet is the same, pulling both release films outward will cause the part with the adhesive layer to be attached to one release film. The other part of the pressure-sensitive adhesive layer is often peeled off along with the other release film. This phenomenon is also commonly referred to as “crying farewell”, and when crying farewell occurs, a uniform pressure-sensitive adhesive layer cannot be formed on the optical member.
Therefore, conventionally, as a pressure-sensitive adhesive sheet, a release film that exhibits a relatively small release force (also referred to as “light release film”) and a release film that exhibits a relatively large release force (“heavy release”). The film is also referred to as “film”) on both sides of the pressure-sensitive adhesive layer. The release film is produced by applying a release agent such as silicone oil to a film made of a transparent resin such as polyethylene terephthalate. And various release films designed so that the peeling force with respect to a certain adhesive layer differs by changing the composition and / or processing method of a mold release agent are marketed.
Examples of prior art documents that disclose a method using a pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer on a release film in order to form a pressure-sensitive adhesive layer on an optical member are listed below. JP-A-2003-177241 (Patent Document 1) discloses an adhesive sheet for attaching an adhesive layer to an optical member such as a polarizing plate (referred to as “liquid crystal display member” in this document). Discloses "adhesive transfer tape"). In this document, it is proposed that the pressure-sensitive adhesive layer is composed of two or more layers having different adhesive forces, and the pressure-sensitive adhesive layer is sandwiched between two release films. And it is also disclosed that a difference is given to the peeling force of the two release films with respect to the pressure-sensitive adhesive layer so that the ratio between the two is within a certain range.
In JP 2004-10647 A (Patent Document 2), in the pressure-sensitive adhesive sheet with a release film provided with a release film on both sides of the pressure-sensitive adhesive layer, at least one of the release films is composed of a polyolefin film, It is disclosed that the difference in peel force between the release film and the pressure-sensitive adhesive layer is 0.1 N / 25 mm or more. In JP-A-2004-196939 (Patent Document 3), in a pressure-sensitive adhesive sheet with a release film which is provided with a release film on both sides of the same pressure-sensitive adhesive layer, a portion having no pressure-sensitive adhesive layer of 1 to 50 mm at both ends in the width direction While providing, it is disclosed that the difference of the peeling force with respect to the adhesive layer of a peeling film of both surfaces will be 10 mN / 25 mm or more, ie, 0.01 N / 25 mm or more. Japanese Patent Application Laid-Open No. 2005-15489 (Patent Document 4) discloses a release film in which a pressure-sensitive adhesive layer is provided on one side of a release film to form a roll, and the pressure-sensitive adhesive layer contacts the other side of the release film. In the adhesive sheet with adhesive, the surface roughness of both surfaces in contact with the pressure-sensitive adhesive layer of the release film is set to 0.1 μm or less, and the difference in peeling force with respect to the pressure-sensitive adhesive layer on both sides of the release film is 10 mN / 25 mm or more, that is, 0 It is disclosed that it is set to 0.01 N / 25 mm or more.
Furthermore, International Publication No. 2010/038697 (Patent Document 5) discloses a conveyance turning roll on an adhesive sheet in which a light release film is laminated on one side of an adhesive layer and a heavy release film is laminated on the other side. Is applied to peel off the light release film while changing the transport direction of the light release film and / or the transport direction of the laminate of the pressure-sensitive adhesive layer and the heavy release film after peeling.
As in the above-mentioned Patent Document 4, the method of providing only one release film and providing a difference in the peel force with respect to the pressure-sensitive adhesive layer on both sides has a difference in peel force depending on the type of pressure-sensitive adhesive. It is necessary to change the mold release treatment applied to both sides of the release film every time, and to design the release force corresponding to the adhesive. Therefore, since the method of using only one release film increases the cost significantly, it is not industrially adopted, and two release films as disclosed in Patent Documents 1 to 3 and 5 are used. A method in which a pressure-sensitive adhesive layer is sandwiched therebetween to give a difference in the peeling force of each release film with respect to the pressure-sensitive adhesive layer has become the mainstream.
Under such circumstances, as described above, various release films designed to have different release forces for the pressure-sensitive adhesive layer by changing the composition and / or processing method of the release agent are commercially available. And, from these, those showing the peel strength suitable for the target pressure-sensitive adhesive layer are selected as a light release film and a heavy release film, and they are attached to both sides of the pressure-sensitive adhesive layer. Has been produced. However, in this case, it is necessary to select a light release film and a heavy release film exhibiting an appropriate release force from among a number of release films, so the design management of the pressure-sensitive adhesive sheet becomes complicated and the cost is still high. It was.
On the other hand, if the release force of the light release film is too small in order to keep the difference in the release force of the light release film and the adhesive layer of the heavy release film or the ratio of both within a certain range, the light release film becomes an adhesive. There is a case in which a defect called tunneling in which streaks or bubbles accompanying partial peeling are observed between the light release film and the pressure-sensitive adhesive layer is sometimes raised from the layer. Also, if the release force of the heavy release film is too large, the heavy release film will be difficult to peel off, and the heavy release film will not peel off at the stage of peeling off the heavy release film from the optical member with adhesive and pasting it to the liquid crystal cell. In extreme cases, the LCD panel production line could be stopped.

Based on the fact that the present invention employs a pressure-sensitive adhesive sheet in which release films are provided on both sides of the pressure-sensitive adhesive layer, the two release films used therein are virtually the same, and both pressure-sensitive adhesives are used. If there is no need to make a difference in the peel force to the layer, it is considered that the design management of the pressure-sensitive adhesive sheet can be facilitated and the cost can be reduced. Even in this state, one peeling film can be removed from the pressure-sensitive adhesive layer without causing so-called tearing. As a result of repeated research from the viewpoint of whether or not it can be peeled off, the present invention has been completed.
Therefore, the object of the present invention is to use a pressure-sensitive adhesive sheet provided with release films on both sides of the pressure-sensitive adhesive layer, without depending on the peeling force of each release film, and without causing so-called crying easily. An object of the present invention is to provide a method for producing an optical member with an adhesive by peeling the release film from the pressure-sensitive adhesive layer, and bonding the pressure-sensitive adhesive layer exposed after peeling off the release film to the optical member.
That is, according to this invention, the peeling process which peels off the 1st peeling film from the adhesive sheet in which the 1st peeling film, the adhesive layer, and the 2nd peeling film are laminated | stacked in this order and exposes an adhesive layer And manufacturing the optical member with the adhesive in which the optical member, the adhesive layer and the second release film are laminated in this order through the bonding step of bonding the adhesive layer exposed in the peeling step to the optical member. The peeling force between the first release film and the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet and the peel force between the second release film and the pressure-sensitive adhesive layer are each 0.3 m / When tested at a peel rate of minutes, both are above 0.02 N / 25 mm and below 0.15 N / 25 mm, and the difference between the two peel forces is less than 0.01 N / 25 mm, The process is the first At the peeling point where the release film is peeled off from the adhesive layer, the first release film is moved straight so as not to bend, and the second release film is subjected to a pressing force from the opposite side of the surface to which the adhesive layer is attached. There is provided a method in which the first release film is transported in a direction different from the linear direction of the first release film together with the adhesive layer, and the first release film is released from the adhesive layer.
In this method, the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet can be a general transparent pressure-sensitive adhesive layer or a so-called light diffusion pressure-sensitive adhesive layer containing a light diffusion agent. In particular, when both sides of the light diffusing adhesive layer are sandwiched between release films that do not have much difference in peel force, pulling each release film to the outside tends to cause so-called crying. If the method of the invention is adopted, the first release film can be peeled off from the pressure-sensitive adhesive layer without causing crying separation, so that it can be used effectively even when a light diffusion pressure-sensitive adhesive layer is bonded to an optical member. it can. In these methods, a typical example of the optical member to which the pressure-sensitive adhesive layer is bonded is a polarizing plate.
The optical member with the pressure-sensitive adhesive produced by these methods peels off the second release film existing on the pressure-sensitive adhesive layer, and pastes the pressure-sensitive adhesive layer exposed thereby to the liquid crystal cell, thereby producing a liquid crystal panel. It can be.
In the method of the present invention, a difference is practically provided in the peeling force between the first release film and the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet and in the peeling force between the second release film and the pressure-sensitive adhesive layer. In a state where there is no state, that is, the first release film and the second release film may be substantially the same, the first release film is peeled off from the adhesive layer at the release point. The film is moved straight so as not to bend, and the second release film is different from the straight direction of the first release film so that no pressing force is applied from the opposite side of the surface on which the adhesive layer is adhered. It is transported in the direction.
Thus, the pressure-sensitive adhesive layer is naturally peeled off from the first release film without depending on the release force from the pressure-sensitive adhesive layer of the first release film and the second release film, and the second release film. At the same time, it is transferred in the conveying direction. For this reason, the so-called crying separation that the adhesive layer partially remains on the first release film is less likely to occur. Thus, since the pressure-sensitive adhesive layer is naturally peeled off from the first release film, there is no need to select a combination of the first release film and the second release film in relation to the pressure-sensitive adhesive layer, The design management of the adhesive sheet becomes easy. And since the pressure-sensitive adhesive layer peeled off from the first release film and left on the second release film is in a good state with no defects, the exposed pressure-sensitive adhesive layer is bonded to the next layer. By adhering to the optical member in the process, it is possible to produce an optical film with a good quality adhesive without a defect in the pressure sensitive adhesive layer.
Therefore, according to this method, the production cost of the optical member with adhesive and the liquid crystal panel can be reduced.

FIG. 1 is a cross-sectional view schematically showing a layer structure of each member until an optical member with an adhesive is obtained.
FIG. 2 is a side view schematically showing an arrangement example of apparatuses when the pressure-sensitive adhesive sheet is produced in a continuous line.
FIG. 3 is a side view schematically showing an arrangement example of apparatuses when an optical member with an adhesive is manufactured in a continuous line.
FIG. 4 is a side view schematically showing some examples in which the peeling process does not satisfy the requirements defined in the present invention and thus easily causes tearing.
FIG. 5 is a cross-sectional view schematically showing a state in which the peeling force of a release film in an example described later is measured.
FIG. 6 is a cross-sectional view schematically showing a state of a high-speed peel test in Examples described later.
FIG. 7 is a cross-sectional view schematically showing a state of a hand peeling test in Examples described later.

Embodiments of the present invention will be described in detail with reference to the accompanying drawings as appropriate. FIG. 1 is a schematic cross-sectional view showing the layer structure of each member until an optical member with an adhesive is obtained by the method of the present invention.
Referring to FIG. 1, in the method of the present invention, first, as shown in FIG. 1A, a first release film 2, an adhesive layer 1, and a second release film 3 are laminated in this order. An agent sheet 5 is prepared. Next, the first release film 2 is peeled off from the pressure-sensitive adhesive sheet 5, and as shown in the same (B), a laminate of the second release film 3 and the pressure-sensitive adhesive layer 1, which is a pressure-sensitive adhesive layer Let 1 be the pressure-sensitive adhesive sheet 10 before bonding exposed. Separately, an optical member 20 shown in FIG. And the adhesive layer 1 exposed with the adhesive sheet 10 before bonding of the (B) is bonded to the optical member 20 of the same (C), and as shown in the same (D), the optical member 20, The optical member 25 with an adhesive in which the adhesive layer 1 and the second release film 3 are laminated in this order is manufactured. FIG. 1 shows an example in which the optical member 20 is a polarizing plate in which transparent

protective films

16 and 17 are bonded to both surfaces of a polarizing film 15. In addition, the optical member can be a retardation film or the like, and the method of the present invention can be applied to various members generally having optical characteristics and provided with an adhesive layer.
The process until the first release film 2 is peeled from the pressure-sensitive adhesive sheet 5 shown in FIG. 1A to obtain the pre-bonding pressure-sensitive adhesive sheet 10 shown in FIG. It corresponds to. Moreover, the process until it bonds the adhesive sheet 10 before bonding shown to the same (B) to the optical member 20 shown to the same (C), and obtains the optical member 25 with an adhesive shown to the same (D) is this book. This corresponds to the bonding step in the invention.
In this invention, as the adhesive sheet 5 shown to FIG. 1 (A), the peeling force between the 1st peeling film 2 and the adhesive layer 1, and between the 2nd peeling film 3 and the adhesive layer 1 are used. The peeling force of each is in the range of more than 0.02 N / 25 mm and less than 0.15 N / 25 mm, and the difference between the two peeling forces is less than 0.01 N / 25 mm. The peeling force here is a value when tested at a peeling speed of 0.3 m / min.
A specific peeling force test method is as shown in the examples with reference to FIG. That is, one release film side (the second release film 3 side in FIG. 5) of the adhesive sheet cut to a width of 25 mm is attached to a glass plate via a double-sided adhesive tape, and in this state, the adhesive sheet is attached to the glass plate. Grasp one end of the unbonded release film (first release film 2 in FIG. 5) in the length direction (direction perpendicular to one side of 25 mm in width) and hold the release film (first release film 2 in FIG. 5). ) Is peeled off in the 180 degree direction (in the direction along the film surface) at a peeling speed of 0.3 m / min, whereby the peeled release film (first release film 2 in FIG. 5) is peeled from the adhesive layer. Seeking power. The laminate that has the adhesive remaining after peeling off one release film is attached to the other release film, and then peeled off from the double-sided adhesive tape that was used to attach to the glass plate first, then the adhesive layer side Is attached to the glass plate, and in this state, one end in the length direction of the release film (second release film 3 in FIG. 5) on the opposite side of the glass plate is grasped, and the gripped release film (second in FIG. 5) The release film 3) is peeled off in the direction of 180 degrees (folded and along the film surface) at a release speed of 0.3 m / min, whereby the pressure-sensitive adhesive layer of the gripped release film (second release film 3 in FIG. 5) Find peel strength from.
When the peeling force between the first release film 2 and the pressure-sensitive adhesive layer 1 and / or the peeling force between the second release film 3 and the pressure-sensitive adhesive layer 1 are reduced to 0.02 N / 25 mm or less, Such inconvenience is likely to occur. That is, the

release films

2 and 3 and the pressure-sensitive adhesive layer 1 cause delamination (delamination), and the so-called tunneling phenomenon in which the

release films

2 and 3 are lifted from the pressure-sensitive adhesive layer 1 easily occurs. In addition, in order to reduce the peeling force, it is necessary to apply a large amount of release agent. When the release agent contains silicone oil, the result of applying a lot of release agent containing the silicone oil is that When the pressure-sensitive adhesive sheet is rolled into a roll, the release agent applied to one release film is secondarily transferred to the surface of the other release film (so-called back transfer). May also occur.
On the other hand, when the peeling force between the first release film 2 and the pressure-sensitive adhesive layer 1 and / or the peeling force between the second release film 3 and the pressure-sensitive adhesive layer 1 are increased to 0.15 N / 25 mm or more, The following inconveniences are likely to occur. That is, one of the release films is peeled off from the adhesive sheet, and the adhesive-attached optical member in which the release film is bonded to the adhesive layer obtained by attaching to the optical member is attached to the liquid crystal cell on the liquid crystal panel production line. When bonding, a release tape is adhered to the surface of the release film, the opposite optical member is sucked with an adsorption plate, and in this state, the release tape is pulled up to peel off the release film, and the adhesive layer is attached to the liquid crystal cell. When pasting, if the peel strength of the release film from the adhesive layer is too large, the adhesive force of the release tape to the release film will decrease quickly, and the replacement cycle of the release tape will be accelerated, resulting in the production cost of the liquid crystal panel. Easy to connect. Moreover, if the peeling force from the adhesive layer of the release film is too large, the release film cannot be peeled off from the adhesive layer even if the release tape is pulled, and the liquid crystal panel production line may be stopped. .
Moreover, as above-mentioned, the difference of the peeling force from the adhesive layer 1 of the 1st peeling film 2 and the peeling force from the adhesive layer 1 of the 2nd peeling film 3 is as small as less than 0.01 N / 25mm. To do. The state in which there is no difference between the two peeling forces, that is, the first release film and the second release film may be substantially the same. In this case, since the first release film 2 and the second release film 3 manufactured under the same conditions can be used, the manufacturing process can be shortened and the manufacturing cost can be reduced. In this specification, the peeling force between the first release film 2 and the pressure-sensitive adhesive layer 1 is simply referred to as “the peeling force of the first release film 2”, the second release film 3 and the pressure-sensitive adhesive layer 1. May be referred to simply as “peeling force of the second release film 3”, respectively.
[Adhesive sheet and method for producing the same]
First, a method for producing an adhesive sheet on a continuous line will be described with reference to FIG. FIG. 2 is a schematic side view showing an arrangement example of apparatuses when the pressure-sensitive adhesive sheet is produced in a continuous line. In the illustrated example, a pressure-sensitive adhesive layer is formed on the surface of the second release film 3, the first release film 2 is bonded to the surface of the pressure-sensitive adhesive layer, and a pressure-sensitive adhesive sheet 5 is manufactured and wound up. The roll 35 is wound around. Explaining in order, the second release film 3 wound around the feeding roll 30 is fed from there, and the pressure-sensitive adhesive composition supplied from the coating machine 31 is applied to the release treatment surface. . The applied pressure-sensitive adhesive composition is dried by a dryer 32 to become a pressure-sensitive adhesive layer, and a laminate 10 of the second release film 3 and the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer of the laminate 10 of the second release film 3 and the pressure-sensitive adhesive layer that is fed from the first release film 2 wound around another supply roll 33 and fed from the dryer 32. It is laminated | stacked on the surface by the mold release process surface, and is bonded by the bonding pressure of the bonding roll 34. FIG. The obtained pressure-sensitive adhesive sheet 5 is wound around a winding roll 35 and stored. In FIG. 2, the curved arrow means the rotation direction of the roll.
As described above, the pressure-sensitive adhesive sheet 5 generally has a coating process for coating the second release film 3 with the pressure-sensitive adhesive composition, a drying process for drying the pressure-sensitive adhesive composition to form a pressure-sensitive adhesive layer, and It is manufactured through a bonding step in which the first release film is bonded to the pressure-sensitive adhesive layer. The laminate 10 of the second release film 3 and the pressure-sensitive adhesive layer obtained through the coating process and the drying process is an intermediate for producing a pressure-sensitive adhesive sheet.
In addition, as explained in the section of the background art, in the conventional pressure-sensitive adhesive sheet applied to the optical member, as the release film to be bonded to both surfaces, a film having a different peeling force with respect to the pressure-sensitive adhesive layer was often used. . In this case, the heavy release film having a relatively large release force is used as the second release film 3 in FIG. 2, an adhesive layer is provided on the release treatment surface, and the light release film having a relatively low release force is shown in FIG. The release treatment surface of the light release film (first release film) 2 is bonded to the pressure-sensitive adhesive layer provided on the heavy release film (second release film) 3. It was manufactured by doing.
In the present invention, as explained above, it is necessary to provide a substantial difference between the peeling force of the first release film 2 on the pressure-sensitive adhesive layer and the peel strength of the second release film 3 on the pressure-sensitive adhesive layer. There is no. Therefore, in FIG. 2, for convenience, the pressure-sensitive adhesive composition is applied to the release treatment surface of the second release film 3 in the coating process, and the first pressure-sensitive adhesive layer is then peeled off in the subsequent bonding process. Although drawn so that the release treatment surfaces of the film 2 are bonded together, the first release film 2 and the second release film 3 may be reversed. On the other hand, the pressure-sensitive adhesive sheet 5 used in the present invention is, as shown in FIG. 1, between two

release films

2 and 3 having a difference in peel strength with respect to the pressure-sensitive adhesive layer 1 of less than 0.01 N / 25 mm. As long as the adhesive layer 1 is sandwiched, one of the two release films is the first release film 2 and the other is the second release film 3. The method of the invention may be applied.
The pressure-sensitive adhesive composition can be applied by a known method, for example, a die coater, a gravure roll coater, a comma coater, or the like. After the application of the pressure-sensitive adhesive composition, the pressure-sensitive adhesive layer is formed by passing through a drying furnace 32 as shown in FIG. The thickness of the pressure-sensitive adhesive layer is usually about 1 to 100 μm.
The first release film 2 and the second release film 3 are generally composed of a resin film that has been subjected to a release treatment. Examples of the resin constituting the release film include polyester resins such as polyethylene naphthalate, polyethylene isophthalate, and polybutylene terephthalate, polyolefin resins, polyamide resins, cellulose resins, polycarbonate resins, and polyphenylene sulfide. Resins, polyvinyl chloride resins, polyvinylidene chloride resins, various liquid crystalline polymers, various biodegradable resins, and the like can be used. Among these, polyethylene terephthalate or polyethylene naphthalate is preferable from the viewpoint of heat resistance and ease of subsequent release treatment, and polyethylene terephthalate is most practical in view of cost. Of course, if desired, two or more kinds of resins may be used in combination.
The above resin may be unstretched or uniaxially or biaxially stretched. Of these, a uniaxial or biaxially stretched film having a maximum strain of the orientation main axis of 10 degrees or less is preferable. As the release film, a single film may be used, or a laminated film in which a plurality of single films are laminated may be used. The thickness of the release film can be, for example, about 5 to 200 μm.
The mold release treatment applied to the surface of the release film can be performed by a method of applying a mold release agent to the film surface. Any release agent can be used, but a silicone release agent having excellent release characteristics is particularly preferable. Examples of silicone release agents include addition-reactive silicone release agents that cure at relatively low temperatures, acrylic silicone release agents that do not apply heat, and UV-curable epoxy group-containing silicone release agents. Can be used. The peeling force can be adjusted by the thickness of the release agent, the presence or absence of the oligomer added to the release agent, and the amount thereof.
The coating amount of the release agent is 0.01-3 g / m ² It is preferable to set the degree. The coating amount of the release agent is 0.01 g / m ² If it is less than 1, the peeling force of the release film increases, but the release performance is insufficient and the release film is difficult to peel from the pressure-sensitive adhesive layer. On the other hand, the coating amount of the release agent is 3 g / m. ² If it exceeds, the release force will be reduced, but when the release film that has been subjected to the release treatment is rolled into a roll, the release agent on the coated surface will be the other side that has not been released. It becomes easy to cause so-called blocking that adheres to the back surface and solidifies.
[Adhesive]
The pressure-sensitive adhesive layer 1 constituting the pressure-sensitive adhesive sheet 5 shown in FIG. 1 is a pressure-sensitive adhesive whose base polymer is an acrylic polymer, a silicone polymer, a polyester polymer, a polyurethane polymer, a polyether polymer, or the like. It can be formed using the composition. Among these, from the viewpoints of transparency, wettability, cohesive strength, durability including weather resistance and heat resistance, an acrylic pressure-sensitive adhesive based on an acrylic polymer (acrylic resin) is preferably used. .
The acrylic resin constituting the acrylic pressure-sensitive adhesive is generally composed of a structural unit derived from (meth) acrylic acid ester as a main component, such as a heterocyclic group including a free carboxyl group, a hydroxyl group, an amino group, and an epoxy ring. An acrylic copolymer having a structural unit derived from an unsaturated monomer having a crosslinkable polar functional group is useful. The unsaturated monomer having a polar functional group is also preferably a (meth) acrylic acid compound. The acrylic resin constituting the acrylic pressure-sensitive adhesive preferably has a glass transition temperature of 20 ° C. or lower, more preferably 0 ° C. or lower. Moreover, the thing whose weight average molecular weight of standard polystyrene conversion by a gel permeation chromatography (GPC) is 100,000 or more is preferable.
Usually, a crosslinking agent is mix | blended with the adhesive composition which has an acrylic resin as a main component. The crosslinking agent is a compound having at least two functional groups in the molecule that can react with polar functional groups constituting the acrylic resin to form a crosslinked structure. Specific examples include isocyanate compounds, epoxy compounds, metal chelate compounds, and aziridine compounds.
In order to improve the adhesiveness between the pressure-sensitive adhesive layer and the liquid crystal cell glass, the pressure-sensitive adhesive composition containing an acrylic resin as a main component preferably contains a silane compound also called a silane coupling agent. Prior to blending the crosslinking agent, a silane compound may be blended in the pressure-sensitive adhesive composition.
Moreover, an ionic compound can also be contained in an adhesive composition. Thereby, antistatic property is imparted to the pressure-sensitive adhesive layer 1. As the ionic compound, for example, a compound having an imidazolium cation, a pyridinium cation, an ammonium cation, or the like can be used.
The pressure-sensitive adhesive layer can contain a light diffusing agent, whereby light diffusibility can be imparted to the pressure-sensitive adhesive layer itself. The pressure-sensitive adhesive sheet containing a light-diffusing agent sandwiched between two release films is particularly prone to crying when one of the release films is peeled off. The method of the present invention is effective when manufacturing an attached optical member. The light diffusing agent is generally organic or inorganic fine particles, and the shape thereof is preferably spherical.
Organic fine particles are generally made of resin (polymer compound). Examples of resins that can be used as light diffusing agents include polyolefin resins such as polystyrene, polyethylene and polypropylene, acrylic resins such as polymethacrylate resins and polyacrylate resins. There are resin, silicone resin, benzoguanamine resin, melamine resin and the like. Of course, these resins may be copolymers obtained from two or more types of monomers. Furthermore, resin fine particles having a crosslinked structure can also be used effectively as a light diffusing agent. On the other hand, examples of inorganic fine particles that can serve as a light diffusing agent include silica fine particles, titanium oxide fine particles, and aluminum oxide fine particles. In consideration of the dispersibility to the acrylic resin constituting the pressure-sensitive adhesive composition, the coating properties of the pressure-sensitive adhesive composition, the optical properties of the resulting pressure-sensitive adhesive layer, etc., the light diffusing agent may be a silicone resin or an acrylic resin (usually Fine particles comprising a methyl methacrylate resin) are preferred.
When a light diffusing agent is blended to impart light diffusibility, the light diffusing agent is 0.01 or more and 0.07 or less, more preferably 0.01 or more, between the acrylic resin constituting the pressure-sensitive adhesive composition. It preferably has a refractive index difference of 0.04 or less. When the difference in refractive index between the two is less than 0.01, a desired light diffusibility is not imparted to the resulting pressure-sensitive adhesive layer, and as a result, it becomes close to a transparent pressure-sensitive adhesive. On the other hand, if the difference in refractive index between the two becomes too large, light diffusibility is strongly developed, so that white luminance when the liquid crystal display device is viewed from the front is lowered.
Among the components described above, components other than the light diffusing agent are mixed in a state dissolved in an organic solvent. When blending a light diffusing agent, it can be prepared by dispersing the light diffusing agent in the mixed solution. The pressure-sensitive adhesive composition is, for example, an acrylic resin dissolved in an organic solvent such as toluene or ethyl acetate, and a necessary component among a crosslinking agent, a silane compound, an ionic compound and a light diffusing agent, and further blended as desired. The following components are dissolved or dispersed to prepare a solution having a solid content concentration of about 10 to 40% by weight.
The pressure-sensitive adhesive composition (solution) may further contain a crosslinking catalyst, a weathering stabilizer, a tackifier, a plasticizer, a softening agent, a dye, a pigment, and the like. When a crosslinking catalyst is blended with the crosslinking agent in the pressure-sensitive adhesive composition, the pressure-sensitive adhesive layer 1 can be prepared by aging in a short time. For this reason, in the obtained optical member with an adhesive or a liquid crystal display device using the same, floating or peeling occurs between the adhesive layer 1 and the optical member, or foaming occurs in the adhesive layer 1. Can be suppressed, and reworkability can be further improved. Examples of the crosslinking catalyst include amine compounds such as hexamethylenediamine, ethylenediamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethylenetetramine, isophoronediamine, trimethylenediamine, polyamino resin, and melamine resin. . When an amine compound is added to the adhesive as a crosslinking catalyst, an isocyanate compound is suitable as the crosslinking agent.
[Method for producing optical member with adhesive]
FIG. 3 is a schematic side view showing an arrangement example of apparatuses when an optical member with an adhesive is produced in a continuous line. The example of illustration peels off the 1st peeling film 2 from the adhesive sheet 5, and the adhesive layer 1 of the adhesive sheet 10 before bonding which is the laminated body of the 2nd peeling film 3 and the adhesive layer 1 obtained is obtained. The optical member 25 with adhesive is bonded to the surface of the optical member 20, and the optical member 25 with pressure-sensitive adhesive thus obtained is wound up by a winding roll 42. In FIG. 3, the straight arrow means the film conveyance direction, and the curved arrow means the roll rotation direction. The manufacturing method of the optical member 25 with an adhesive according to the present invention will be described with reference to FIG.
The pressure-sensitive adhesive sheet 5 wound around the feeding roll 36 is fed out therefrom. And between the upstream tension roll 37 and the downstream tension roll 38, tension is applied to the first release film 2 constituting the pressure-sensitive adhesive sheet 5, and the first release film 2 is moved straight so as not to bend. Thus, at a certain point (peeling point P) between the straight sections L, the second peelable film 3 is the pressure-sensitive adhesive layer 1 and the laminated body of both, that is, the pressure-sensitive adhesive sheet 10 before being bonded to the optical member. Thus, the first release film 2 is conveyed in a direction different from the straight direction. At this time, a pressing force is not applied to the second release film 3 from the side opposite to the surface where the pressure-sensitive adhesive layer 1 is adhered.
The pressure-sensitive adhesive sheet 5 fed out from the feed-out roll 36 has the first release film 2 and the pressure-sensitive adhesive film 2 as shown in the enlarged sectional view A in FIG. The adhesive layer 1 and the second release film 3 are laminated in this order, from which only the first release film 2 moves straight in the direction of the downstream tension roll 38 and is peeled off from the adhesive layer 1. It is. The peeled first release film 2 passes through the downstream tension roll 38 and is then taken up by the take-up roll 39. On the other hand, the pre-bonding pressure-sensitive adhesive sheet 10, which is a laminate of the second peelable film 3 and the pressure-sensitive adhesive layer 1 after peeling off the first peelable film 2, has another pressure roll 40 on the pressure-sensitive adhesive layer 1 side. Is laminated on the optical member 20 that is fed out, and is bonded by the bonding roll 41 to obtain an optical member 25 with an adhesive. The obtained optical member 25 with pressure-sensitive adhesive is wound around a winding roll 42.
In FIG. 3, the process of peeling the 1st peeling film 2 from the adhesive sheet 5 is equivalent to the peeling process said by this invention, and the 2nd peeling film 3 and adhesion after peeling the 1st peeling film 2 The process of bonding the adhesive sheet 10 before bonding which is the laminated body of the agent layer 1 to the optical member 20 with the bonding roll 41 corresponds to the bonding process referred to in the present invention.
<Peeling process>
In the peeling process, as described above, the tension is applied to the first peeling film 2 between the upstream tension roll 37 and the downstream tension roll 38, and the first peeling film 2 is straightened so as not to bend. The The tension at this time can be applied by a method of giving a difference in peripheral speed between the feeding roll 36 and the winding roll 39 or a method of changing the film transport direction using the tension roll as a support. In order to give a difference in peripheral speed, tension is applied to the first release film 2 by making the peripheral speed of the winding roll 39 faster than the peripheral speed of the feeding roll 36. Also, when changing the transport direction of the film with the tension roll, for example, as shown in FIG. 3, if the transport direction of the first release film 2 is largely changed using the downstream tension roll 38 as a support, Tension is applied to the downstream tension roll 38.
The magnitude | size of the tension | tensile_strength provided to the 1st peeling film 2 should just be relatively larger than the peeling force between the 2nd peeling film 3 and the adhesive layer 1. FIG. When the tension applied to the first release film 2 is greater than the release force between the second release film 3 and the pressure-sensitive adhesive layer 1, the direction is different from the transport direction (tension direction) of the first release film 2. In addition, when the second release film 3 is peeled off so that no pressing force is applied, the pressure-sensitive adhesive layer 1 remains on the first release film 2 so that so-called tearing is less likely to occur.
The speed at which the second release film 3 is peeled off varies depending on productivity, workability, surface activation treatment applied to the pressure-sensitive adhesive layer 1 and the optical member 20 described later, and 3 to 50 m / min. It is preferable to set the degree.
The peeling process is performed in the straight section L shown in FIG. 3, but the peeling point P at which the first release film 2 is peeled off from the pressure-sensitive adhesive layer 1 is due to changes in manufacturing conditions such as fluctuations in tension within the range of the direct feed section L. Moving. For example, when the separation point P is provided with sensors for detecting the separation point on the upstream side and the downstream side of the separation point in the straight section L, and the separation surface is detected by these sensors, the feeding roll 36 and the winding roll 39 are provided. The tension applied to the first release film 2 is appropriately adjusted by adjusting the peripheral speed of the belt or by adjusting the distance between the upstream tension roll 37 and the downstream tension roll 38, and the peeling point P is set between the sensors. Can be held. The sensor to be used can be appropriately selected from known sensors such as an ultrasonic sensor and an optical sensor as long as it can detect the peeling point. The tension applied to keep the first release film 2 conveyed in the straight direction can be measured and controlled by a known tension controller.
FIG. 4 is a side view schematically showing some examples in which the above-described peeling process does not satisfy the requirements defined in the present invention, and thus easily causes tearing, and enlarges the straight section L and its peripheral portion in FIG. As shown. The straight arrow in FIG. 4 shows the conveyance direction of a film. FIG. 4A shows a configuration of a production line in which tension is applied to the second release film 3 so that the second release film 3 moves straight, and the first release film 2 is peeled off without applying a pressing force. In this embodiment, unlike the method defined in the present invention, the tension is applied to the second release film 3, so that the attachment of the pressure-sensitive adhesive layer 1 occurs in the first release film 2. FIG. 4B shows a configuration of a production line in which the film is peeled off under the same stress applied to the first release film 2 and the second release film 3. In this form, since there is no difference in the tension applied to the first release film 2 and the second release film 3, the adhesive layer 1 tears apart. FIG. 4C shows a production line in which the second release film 3 and the pressure-sensitive adhesive layer 1 are peeled off using a support, that is, the second release film 3 is peeled off by applying a pressing force. It is a configuration. In this form, since tension is also applied to the second release film 3 by the support, tearing occurs in the pressure-sensitive adhesive layer 1. Thus, in the peeling form which does not satisfy the requirements prescribed | regulated by this invention, there exists a tendency for the adhesive layer 1 to accompany the 1st peeling film 2, or for the adhesive layer 1 to raise | generate a tearing-up easily.
As described above, the method for producing an optical member with an adhesive according to the present invention applies a tension larger than the peeling force of the second release film 3 to the first release film 2, and conveys the first release film 2. The second release film 3 is peeled off so that a pressing force is not applied in a direction different from the direction. According to this method, when a release film having a release force defined in the present invention is used, tearing occurs regardless of the magnitude relationship between the release force of the first release film 2 and the release force of the second release film 3. The 1st peeling film 2 can be peeled from the adhesive sheet 5 without this. At this time, since the same peel force can be used for the first release film 2 and the second release film 3, it is not necessary to set the peel force within a predetermined range as in the prior art. Thereby, there is no need to select a release film or a pressure-sensitive adhesive layer so that the peeling force is within a predetermined range, design management is facilitated, and the manufacturing cost of the pressure-sensitive adhesive sheet 5 and the optical member with the pressure-sensitive adhesive is reduced. be able to.
<Bonding process>
In the bonding step, the optical member 20 is bonded to the surface of the pressure-sensitive adhesive layer 1 in the pressure-sensitive adhesive sheet 10 before bonding, which is a laminate of the second release film 3 and the pressure-sensitive adhesive layer 1 that has passed through the peeling step. The pasting process will be described with reference to FIG. The pressure-sensitive adhesive sheet 10 before bonding is a continuous bonding process, and the pressure-sensitive adhesive layer 1 side is laminated on the surface of the optical member 20 fed from the feeding roll 40, and the bonding pressure is applied by the bonding roll 41. And paste. Thereby, the optical member 25 with an adhesive by which the adhesive layer 1 and the 2nd peeling film 3 were laminated | stacked on the optical member 20 in this order can be manufactured. The produced polarizing plate 25 with the pressure-sensitive adhesive is wound around the winding roll 42 and stored.
In order to increase the adhesive force between the pressure-sensitive adhesive layer 1 and the optical member 20, it is preferable to subject the adhesive surface of the pressure-sensitive adhesive layer 1 and / or the optical member 20 to corona discharge treatment. The corona discharge treatment is a treatment that activates the surface of the resin film or the pressure-sensitive adhesive layer that is discharged by applying a high voltage between the electrodes. The output of the corona discharge treatment is preferably set to about 200 to 1,000 W. When the output of the corona discharge treatment is 200 W or more, the effect of this treatment becomes remarkable, and the adhesive force between the pressure-sensitive adhesive layer 1 and the transparent resin film 17 is improved. Moreover, generation | occurrence | production of the dust which is easy to produce by this process is suppressed as the output of a corona discharge process is 1,000 W or less. The effect of the corona discharge treatment varies depending on the type of electrode, electrode interval, voltage, temperature, etc., but it is preferable to set the moving speed of the object to be processed to about 3 to 50 m / min.
[Optical member]
As described above, the optical member provided with the pressure-sensitive adhesive layer in the present invention has optical characteristics, and typical examples thereof include a polarizing plate and a retardation film. In particular, a polarizing plate is preferably used.
A polarizing plate is an optical member having a function of emitting polarized light with respect to incident light such as natural light. The polarizing plate absorbs linearly polarized light having a vibration surface in a certain direction and reflects linearly polarized light having a vibration surface in a certain direction, and reflects linearly polarized light having a vibration surface in a certain direction. There are a polarization separating plate showing the property of transmitting linearly polarized light having a vibration plane orthogonal to the polarizing plate, an elliptically polarizing plate in which a polarizing plate and a retardation film are laminated. Among these, a linear polarizing plate is representative. Hereinafter, the linearly polarizing plate will be specifically described. Hereinafter, the linearly polarizing plate is simply referred to as a polarizing plate.
The polarizing plate has a structure in which the first transparent protective film 16 and the second transparent protective film 17 are bonded to both surfaces of the polarizing film 15, respectively, as shown in the schematic cross-sectional view of FIG. There are many.
The polarizing film 15 can be composed of a uniaxially stretched polyvinyl alcohol resin film in which a dichroic dye such as iodine or a dichroic dye is adsorbed and oriented. Such a polarizing film is generally produced by subjecting a polyvinyl alcohol resin film to uniaxial stretching, dyeing with a dichroic dye, and boric acid treatment. The thickness of the polarizing film 15 can be set to about 2 to 40 μm, for example.
A saponified polyvinyl acetate resin can be used as the polyvinyl alcohol resin. The polyvinyl acetate resin can be a copolymer of vinyl acetate, which is a homopolymer of vinyl acetate, or a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.
As for the polarizing film 15, the transparent

protective films

16 and 17 are bonded on both surfaces, respectively. These transparent

protective films

16 and 17 are, for example, acrylic resins such as methyl methacrylate resins, olefin resins, polyvinyl chloride resins, cellulose resins, styrene resins, acrylonitrile / butadiene / styrene copolymers. Resin, acrylonitrile / styrene copolymer resin, polyvinyl acetate resin, polyvinylidene chloride resin, polyamide resin, polyacetal resin, polycarbonate resin, modified polyphenylene ether resin, polyester resin (for example, polybutylene terephthalate, Polyethylene terephthalate, etc.), polysulfone resin, polyethersulfone resin, polyarylate resin, polyamideimide resin, polyimide resin, epoxy resin, oxetane resin, etc. These transparent resins can contain additives as long as transparency and adhesiveness with the polarizing film 15 are not impaired. The transparent

protective films

16 and 17 can have a thickness of about 5 to 200 μm, preferably 20 to 120 μm.
The transparent protective film bonded to one surface of the polarizing film, in particular, the second transparent protective film 17 on the liquid crystal cell side when the pressure-sensitive adhesive layer 1 is provided to form a liquid crystal panel is stretched and positioned. A phase difference can be given. When employing a film provided with a retardation, that is, a retardation film, a film having an appropriate retardation value may be selected depending on the mode of the liquid crystal cell to which the polarizing plate is applied. For example, for a vertical alignment (VA) mode liquid crystal cell, a polymer film having positive intrinsic birefringence is uniaxially stretched, and the refractive index ellipsoid is n. _x > N _y ≒ n _z A positive A plate having the following relationship, lateral stretching and sequential biaxial stretching are applied, and n _x > N _y > N _z A biaxial film having the relationship _x ≒ n _y > N _z A negative C plate having the following relationship can be used. For a liquid crystal cell in a lateral electric field (In-Plane Switching: IPS) mode, a refractive index ellipsoid is n. _x ≒ n _y ≒ n _z A generally non-oriented film having the following relationship is preferably used. Where n _x Is the refractive index in the in-plane slow axis (x-axis) direction of the film, n _y Is the refractive index in the in-plane fast axis (y-axis: axis perpendicular to the slow axis in the plane), and n _z Is the refractive index in the thickness (z-axis) direction.
For the VA mode liquid crystal cell, a biaxially stretched biaxial retardation film is particularly preferably used as the second transparent protective film 17. When a biaxial retardation film is used, the Nz coefficient that is a measure of the biaxiality is defined by the following equation (1). Further, the in-plane retardation value Re and the thickness direction retardation value Rth when the film thickness is d are defined by the following equations (2) and (3), respectively.
Nz = (n _x -N _z ) / (N _x -N _y (1)
Re = (n _x -N _y ) × d (2)
Rth = [(n _x + N _y ) / 2-n _z ] Xd (3)
Furthermore, from the above equations (1) to (3), the relationship between the Nz coefficient, the in-plane retardation value Re, and the thickness direction retardation value Rth can be expressed by the following equation (4).
Nz = Rth / Re + 0.5 (4)
When a biaxial retardation film is used as the second transparent protective film 17, the in-plane retardation value Re is preferably in the range of 30 to 300 nm, particularly in the range of 50 to 260 nm. The Nz coefficient is preferably in the range of 1.1 to 7, and more preferably in the range of 1.4 to 5. From these ranges, the value of the optical characteristic may be appropriately selected according to the viewing angle characteristic required for the applied liquid crystal display device.
On the other hand, the first transparent protective film 16 on the side far from the liquid crystal cell is subjected to a surface treatment selected from hard coat treatment, antistatic treatment, antireflection treatment, antifouling treatment, antiglare treatment and the like. Functions such as scratch prevention and visibility improvement can be imparted.
The polarizing plate 20 is obtained by bonding the first transparent protective film 16 and the second transparent protective film 17 to the polarizing film 15 described above via an adhesive, respectively. The adhesive used for the bonding is usually made of a transparent resin, and an aqueous adhesive such as an aqueous solution of a polyvinyl alcohol resin can be used, or an ultraviolet curable adhesive that is cured by irradiation with ultraviolet rays is used. You can also The adhesive that forms the adhesive layer provided on both surfaces of the polarizing film 15 may be the same or different.
[Liquid crystal panel and liquid crystal display device]
The optical member with an adhesive produced according to the present invention can be used as a constituent member of a liquid crystal panel. The optical member with pressure-sensitive adhesive (polarizing plate with pressure-sensitive adhesive) 25 shown in (D) of FIG. 1 peels off the second release film 3 therefrom, and the pressure-sensitive adhesive layer 1 exposed thereby is laminated on the liquid crystal cell. It is a liquid crystal panel. The liquid crystal panel is composed of a liquid crystal cell, a front side polarizing plate disposed on the viewing side of the liquid crystal cell, and a back side polarizing plate disposed on the side opposite to the viewing side of the liquid crystal cell. It becomes a member.
The liquid crystal display device includes a liquid crystal panel, a light diffusing plate and a backlight sequentially arranged on the side opposite to the viewing side. In the liquid crystal display device, the liquid crystal panel is disposed so that the back side polarizing plate is on the backlight side. Here, the back side means the backlight side when the liquid crystal panel is mounted on the liquid crystal display device, and the viewing side (front side) is opposite to the backlight when the liquid crystal panel is mounted on the liquid crystal display device. It means the side where the person who sees the display device is present. The pressure-sensitive adhesive-coated polarizing plate produced according to the present invention can be used for the front side polarizing plate 25 or the back side polarizing plate.
A liquid crystal cell is an element that displays an image by electrically controlling a cell in which a liquid crystal material is sealed between glass substrates. As a mode of the liquid crystal cell, a known mode such as a VA mode, an IPS mode, or a liquid crystal driving mode using a blue phase liquid crystal can be employed.
When the adhesive-attached polarizing plate 25 is bonded to the liquid crystal cell, the second release film 3 is peeled off from the adhesive layer 1, and the surface of the adhesive layer 1 exposed thereby is bonded to the surface of the liquid crystal cell. The polarizing plate with an adhesive 25 may be rolled out into a sheet and pasted into a liquid crystal cell by a roll-to-cell method, or stored in a sheet-cut state. It is also possible to paste the paste on the liquid crystal cell by the sheet-to-cell method.
The backlight is a device for supplying display light to the liquid crystal cell. Examples of the backlight include an edge light type and a direct type. The edge-light type backlight is composed of a light guide plate and a light source such as a cold cathode tube or an LED arranged on the side thereof, and light from the light source irradiates the liquid crystal panel through the light guide plate. The direct type backlight is composed of a plurality of light sources arranged on the back side of the liquid crystal panel, and light from the light source irradiates the liquid crystal panel through the light diffusion plate. The type of the backlight can be appropriately selected and used according to the application of the liquid crystal display device.
The light diffusing plate disposed between the liquid crystal panel and the backlight is an optical member having a function of diffusing light from the backlight and supplying uniformed light to the liquid crystal panel. Examples of the light diffusing plate include those obtained by dispersing particles as a light diffusing agent in a thermoplastic resin and imparting light diffusibility, those obtained by forming irregularities on the surface of the thermoplastic resin film and imparting light diffusibility, For example, a coating layer of a resin composition in which particles are dispersed is provided on the surface of a thermoplastic resin film to impart light diffusibility. The light diffusion plate usually has a thickness of about 0.1 to 5 mm.
Between the light diffusing plate and the liquid crystal panel, a brightness enhancement film (such as a reflective polarizing film sold under the name “DBEF” from 3M (Sumitomo 3M Co., Ltd. in Japan)) In addition, a sheet or film exhibiting other optical functionalities such as a light diffusion film different from the light diffusion plate disposed immediately above the backlight may be disposed. A plurality of types or a plurality of sheets or films exhibiting other optical functionalities may be arranged as necessary.

Hereinafter, the present invention will be described in more detail by showing specific experimental examples, but the present invention is not limited to these examples. In the examples, parts and% indicating the amount used or content are based on weight unless otherwise specified.
[Preparation of adhesive sheet]
(A) Release film The following four types of polyethylene terephthalate films subjected to a release treatment were prepared, and each was used as a release film. The films shown below are arranged in the order of the peel force from the pressure-sensitive adhesive layer, with the top having a small peel force and the bottom having a large peel force.
Release film 1: Trade name “MRF” sold by Mitsubishi Plastics, Inc.
Release film 2: Trade name “MRE (MT125)” sold by Mitsubishi Plastics, Inc.
Release film 3: Trade name “MRV (08)” sold by Mitsubishi Plastics, Inc.
Release film 4: Trade name “A71-T1” sold by Teijin Limited.
(B) Preparation of acrylic resin for pressure-sensitive adhesive In a reactor equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer and a stirrer, 169.8 parts of ethyl acetate, 98.6 parts of butyl acrylate, 2-hydroxyethyl acrylate 1 A mixed solution of 0.0 part and 0.4 part of acrylic acid was charged, and the internal temperature was raised to 55 ° C. while substituting the air in the apparatus with nitrogen gas so as not to contain oxygen. Next, a total amount of a solution obtained by dissolving 0.14 part of azobisisobutyronitrile as a polymerization initiator in 5 parts of ethyl acetate was added. Thereafter, the temperature was maintained for 12 hours while maintaining the internal temperature at 54 to 56 ° C., and finally ethyl acetate was added to adjust the concentration of the acrylic resin to 28%. The obtained acrylic resin has a polystyrene-reduced weight average molecular weight Mw of 1.34 million by gel permeation chromatography, a ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn of 1.7, and a refractive index. 1.46.
(C) Preparation of acrylic pressure-sensitive adhesive composition The following were used as an isocyanate-based crosslinking agent, a silane compound, an ionic compound serving as an antistatic agent, and a light diffusing agent to be blended in the pressure-sensitive adhesive composition. Names enclosed in “” are product names.
(Isocyanate-based crosslinking agent)
“Coronate L”: Ethyl acetate solution containing 75% concentration of trimethylolpropane adduct of tolylene diisocyanate, obtained from Nippon Polyurethane Industry Co., Ltd.
(Silane compound)
“KBM-403”: 3-glycidoxypropyltrimethoxysilane, liquid, obtained from Shin-Etsu Chemical Co., Ltd.
(Ionic compounds)
“FC-4400”: tributylmethylammonium bis (trifluoromethanesulfonyl) imide having a structure of the formula (C ₄ H ₉ ) ₃ (CH ₃ ) N ⁺ (CF ₃ SO ₂ ) ₂ N ⁻ , melting point 26 ° C., Sumitomo 3M Obtained from Co., Ltd.
(Light diffusing agent)
“MX-1000”: spherical type acrylic resin fine particles having an average particle diameter of 10 μm and a refractive index of 1.49, obtained from Soken Chemical Co., Ltd.
The above-mentioned isocyanate crosslinking agent, silane compound, ionic compound, and light diffusing agent are added to the ethyl acetate solution of the acrylic resin prepared in (b) above (however, expressed as the solid content in the following) in the following proportions. To prepare an acrylic pressure-sensitive adhesive composition.
(Composition of acrylic pressure-sensitive adhesive composition)
100 parts of (b) acrylic resin (solid content)
Isocyanate-based crosslinking agent 0.16 parts Silane compound 0.5 part Ionic compound 1.0 part Light diffusing agent 35 parts (d) Preparation of adhesive sheet The four types of release films shown in (a) above 1 is used as the first release film 2 and the second release film 3 in the combination shown in FIG. 1, and an adhesive layer formed from the acrylic adhesive composition prepared in (c) above is sandwiched between them. An agent sheet was prepared. The specific operation is as follows. First, the pressure-sensitive adhesive composition is applied to the release-treated surface of the second release film using an applicator so that the thickness after drying is 25 μm, and dried at 90 ° C. for 2 minutes to form a sheet. An adhesive was obtained. Next, the surface (adhesive surface) opposite to the second release film of the sheet-like pressure-sensitive adhesive obtained above was bonded to the release treatment surface of the first release film with a laminator, and then the temperature was 23 ° C. Adhesive sheets A to D were prepared by aging for 10 days at a relative humidity of 65%.
(E) Evaluation of presence / absence of tunneling When producing an adhesive sheet in (d) above, the adhesive layer formed on the second release film was bonded to the release treatment surface of the first release film. Immediately thereafter, the presence or absence of a delamination phenomenon (the presence of streaks or bubbles due to tunneling) between the first release film and the pressure-sensitive adhesive layer was visually observed. The results are shown in the “tunneling” column of Table 1.
(F) Measurement of peeling force of first release film For each pressure-sensitive adhesive sheet prepared in (d) above, the peeling force from the pressure-sensitive adhesive layer of the first release film was measured by the following procedure. First, a test piece having a length of 150 mm and a width of 25 mm was cut from the adhesive sheet using a super cutter. And as shown to FIG. 5 (A), the commercially available double-sided adhesive tape 45 is affixed on the surface of the 2nd peeling film 3, and also the opposite surface of the double-sided adhesive tape 45 is glass substrate 50 [ It was affixed to the product name “EAGLE XG” manufactured by Corning. In this state, using the autograph [product name “AGS-X” manufactured by Shimadzu Corporation], one end in the length direction (one side of 25 mm in width) of the first release film 2 is grasped, and the load range is 5,000 g. At a peeling speed of 0.3 m / min, the film is pulled from the pressure-sensitive adhesive layer 1 by pulling in the direction of 180 degrees (the direction along the film surface in the direction of the curved arrow in the figure), and the peeling force at that time is recorded on a chart. did. Since the data is not stable immediately after the start of measurement and immediately before the end of measurement, 20% of the data after the start of measurement and 20% of the data before the end of the measurement are cut and averaged only from the range of 60% of the middle portion where the data is relatively stable. The value was calculated and this was taken as the peel force. Each pressure-sensitive adhesive sheet A to D was tested, and the results are shown in Table 1.
(G) Measurement of Peeling Force of Second Release Film The second release film / adhesive layer laminate after peeling off the first release film in (f) above was peeled off from the double-sided adhesive tape 45. Next, as shown in FIG. 5B, the pressure-sensitive adhesive layer 1 was attached to the same glass substrate “EAGLE XG” as shown in (f) above using a hand roller. In this state, the same autograph “AGS-X” as shown in (f) above is used to grasp one end in the lengthwise direction of the second release film 3, and the other conditions are the same as in (f) above. The peel force was measured with and the results are shown in Table 1.
(H) Evaluation of Possibility of Unpeeling of Second Release Film Regarding the pressure-sensitive adhesive sheet C in which the peel force of the second release film 3 obtained in (g) above is 0.15 N / 25 mm, from there When the first release film is peeled off, the adhesive layer is attached to the optical member to form an optical member with an adhesive, and when the second release film is peeled off just before being bonded to the liquid crystal cell, the second release film is not peeled off. Therefore, “Yes” is displayed in the column “Possibility of non-peeling of the second release film” in Table 1. The other adhesive sheets A, B, and D were judged that the non-peeling problem is unlikely to occur because the peel strength of the second release film is less than 0.15 N / 25 mm. “None”.

As shown in Table 1, in the adhesive sheet D, tunneling occurred because the peel strength of the first release film 2 was as small as 0.02 N / 25 mm. Moreover, in the adhesive sheet C, since the peeling force of the 2nd peeling film 3 is as large as 0.15N / 25mm, when peeling off the 2nd peeling film just before bonding to a liquid crystal cell, the problem of unpeeling There is a high possibility of waking up.
Next, among the pressure-sensitive adhesive sheets A to D produced above, the pressure-sensitive adhesive sheet A and the pressure-sensitive adhesive sheet A determined that no tunneling occurs in the first release film and no unpeeled problem occurs in the second release film. An experimental example is shown in which a peel test is performed using B and the presence or absence of tearing is evaluated.
[Example 1]
(A) High-speed peeling test A test piece having a length of 500 mm and a width of 25 mm was cut from the pressure-sensitive adhesive sheet A using a super cutter. Then, as shown in FIG. 6 (A), a commercially available double-sided adhesive tape 45 having a thickness of about 0.1 mm is attached to the surface of the first release film 2, and further using a hand roller, The opposite surface of the double-sided pressure-sensitive adhesive tape 45 was attached to a glass substrate 50 (trade name “EAGLE XG” manufactured by Corning). In this state, a peel tester [CHUNG BUK TECHNOLOGY CO. Manufactured product name “SSA-034-SD (Double Type)”, holding one end in the length direction (one side of 25 mm in width) of the second release film 3, setting the load range to 5,000 g, and the release speed. The second release film 3 was peeled off by pulling in the direction of the curved arrow in the figure while changing at three levels of 5 m / min, 10 m / min, and 15 m / min, and the peel force at that time was recorded on a chart. Since the data is not stable immediately after the start of measurement and immediately before the end of measurement, 20% of the data after the start of measurement and 20% of the data before the end of the measurement are cut and averaged only from the range of 60% of the middle portion where the data is relatively stable. The value was calculated and this was taken as the peel force. The results are shown in Table 2. This test is performed by fixing the first release film 2 in the horizontal direction and pulling the second release film 3 in a different direction, and on the opposite side of the adhesive layer of the second release film 3. No special pressing force is applied from the roll. Therefore, relatively, the first release film 2 is made to advance straight so as not to bend, and the second release film 3 is made so that no pressing force is applied from the opposite side of the pressure-sensitive adhesive layer. This corresponds to a state in which the sheet is conveyed in a direction different from the horizontal direction in which is located.
(B) Manual peeling test A test piece having a length of 400 mm and a width of 25 mm was cut from the adhesive sheet A using a super cutter. Then, as shown in FIG. 7 (A), one person holds both ends in the length direction of the first release film 2 with both left and right hands, and pulls it in the direction of two linear arrows facing outward in the figure. With some tension applied in the direction, another person grabbed one end of the second release film 3 and pulled it up in the direction of the curved arrow in the figure to peel off the second release film 3. This test is also performed by fixing the first release film 2 in the horizontal direction and pulling the second release film 3 in a different direction, and opposite to the adhesive layer of the second release film 3. No special pressing force is applied from the side by rolls. Therefore, relatively, the first release film 2 is made to advance straight so as not to bend, and the second release film 3 is made so that no pressing force is applied from the opposite side of the pressure-sensitive adhesive layer. This corresponds to a state in which the sheet is conveyed in a direction different from the horizontal direction in which is located.
(C) Observation of presence / absence of crying After the above (a) high-speed peeling test and (b) hand peeling test were performed, the surface of the first release film 2 was visually observed. Then, according to the amount of the pressure-sensitive adhesive remaining on the surface of the first release film 2, it was divided into the following 4 levels of levels 0 to 3, and the presence or absence of crying was evaluated. Only level 0 corresponds to a state in which the pressure-sensitive adhesive layer 1 has all moved to the second release film 3 without crying. In addition, although the state of level 3 is not said to cry, it is a state in which the adhesive layer 1 remains on the first release film 2 that is not intended. The results are shown in Table 2.
<Level of tearing up>
Level 3: All the pressure-sensitive adhesive remains on the first release film 2.
Level 2: More than 50% and less than 100% of the pressure-sensitive adhesive remains in the first release film 2.
Level 1: More than 0% and 50% or less of the pressure-sensitive adhesive remains in the first release film 2.
Level 0: No adhesive remains on the first release film 2 at all.
[Example 2]
The pressure-sensitive adhesive sheet A was changed to the pressure-sensitive adhesive sheet B, and other tests were performed in the same manner as in Example 1, and the results are summarized in Table 2.
[Comparative Example 1]
(A) High-speed peeling test Like (a) in Example 1, a test piece having a length of 500 mm and a width of 25 mm is cut from the pressure-sensitive adhesive sheet A. As shown in FIG. The second release film 3 side is pasted on the glass substrate 50 through the wire, and the first release film 2 is changed so as to be pulled and peeled in the direction of the curved arrow in the figure, and the others are the same as in (a) of Example 1. The test was conducted. The results are shown in Table 2. This test is performed by fixing the second release film 3 in the horizontal direction and pulling the first release film 2 in a different direction, and on the opposite side of the adhesive layer of the first release film 2. No special pressing force is applied from the roll. Therefore, relatively, the second release film 3 is made to go straight so as not to bend, and the first release film 2 is made so that no pressing force is applied from the opposite side of the pressure-sensitive adhesive layer. This corresponds to a state in which the sheet is conveyed in a direction different from the horizontal direction in which is located. That is, this test corresponds to the state shown in FIG.
(B) Manual peeling test As in (b) of Example 1, a test piece having a length of 400 mm and a width of 25 mm is cut from the pressure-sensitive adhesive sheet A. As shown in FIG. In the state where one person grasps both ends of the film 3 with both left and right hands and pulls it in the direction of two straight arrows facing outward in the drawing, and gives some tension in that direction, the first release film 2 Another person grabbed one end of the film, pulled it up in the direction of the curved arrow in the figure, and peeled off the first release film 2. The results were evaluated according to Example 1 and are shown in Table 2. This test is also performed by fixing the second release film 3 in the horizontal direction and pulling the first release film 2 in a different direction, and opposite to the adhesive layer of the first release film 2. No special pressing force is applied from the side by rolls. Therefore, relatively, the second release film 3 is made to go straight so as not to bend, and the first release film 2 is made so that no pressing force is applied from the opposite side of the pressure-sensitive adhesive layer. This corresponds to a state in which the sheet is conveyed in a direction different from the horizontal direction in which is located.
[Comparative Example 2]
The pressure-sensitive adhesive sheet A was changed to the pressure-sensitive adhesive sheet B, and the others were subjected to the same test as in Comparative Example 1, and the results are summarized in Table 2.
[Comparative Example 3]
(A) High-speed peel test As in (a) of Example 1, a test piece having a length of 500 mm and a width of 25 mm is cut from the pressure-sensitive adhesive sheet A. As shown in FIG. A double-sided adhesive tape 45 having a thickness of about 0.1 mm is attached to only one end in the outer length direction of the first release film 2 (one end having a width of 25 mm), and the opposite side of the double-sided adhesive tape 45 is a glass substrate. Affixed to 50. In this state, the second release film 3 was changed so as to be pulled and peeled in the direction of the curved arrow in the figure, and the other tests were performed in the same manner as in (a) of Example 1, and the results are shown in Table 2. Since this test is performed in a state in which the first release film 2 and the second release film 3 are bent as shown in FIG. 6 (C), the state is close to FIG. 4 (B) described above. It is.
(B) Manual peeling test As in (b) of Example 1, a test piece having a length of 400 mm and a width of 25 mm is cut from the pressure-sensitive adhesive sheet A. As shown in FIG. A test was conducted in which one person grasped the first release film 2 and the second release film 3 at one end with both left and right hands, pulled in the direction of the curved arrow pointing left and right in the figure, and then peeled off both. The results are shown in Table 2.
[Comparative Example 4]
Similarly to (a) of Comparative Example 3, a test piece having a length of 500 mm and a width of 25 mm was cut from the pressure-sensitive adhesive sheet A. As shown in FIG. 6D, the second release film 3 of this test piece was cut. The double-sided pressure-sensitive adhesive tape 45 having a thickness of about 0.1 mm was attached to only one end in the outer length direction (one end having a width of 25 mm) with a width of 25 mm, and the opposite surface of the double-sided adhesive tape 45 was further attached to the glass substrate 50. In this state, the first release film 2 was changed so as to be pulled and peeled in the direction of the curved arrow in the figure, and the other experiments were performed in the same manner as in (a) of Comparative Example 3, and the results are shown in Table 2. Since this test is also performed in a state in which the first release film 2 and the second release film 3 are bent as shown in FIG. 6 (D), the state is close to FIG. 4 (B) described above. It is.
Since the hand peel test corresponding to this example is the same as (b) of Comparative Example 3, only “same as above” is described in the “hand peel test” column of Table 2. This is the same as “Comparative Example 3”.
[Comparative Examples 5 and 6]
The pressure-sensitive adhesive sheet A was changed to pressure-sensitive adhesive sheet B, and the others were the same as in Comparative Examples 3 and 4, and the results are shown in Table 2.

As shown in Table 2, when the release film is peeled off, the first release film 2 is placed in a horizontal state, and the second release film 3 is pulled in a different direction. Is peeled off with the second release film 3, whereas when the second release film 3 is placed in a horizontal state and the first release film is pulled in a different direction, the adhesive layer 1 is all pulled. If it moves to the one peeling film 2 side and is pulled in a state where the first peeling film is bent, crying separation occurs. From these results, the first release film 2 is moved straight so as not to bend, and the second release film 3 is not subjected to a pressing force from the opposite side of the surface to which the adhesive layer 1 is adhered. It can be seen that the pressure-sensitive adhesive layer 1 is peeled off along with the second release film 3 without causing crying separation if transported in a direction different from the straight direction of the one release film 2.

1 …… Adhesive layer,
2 …… First release film,
3. Second release film,
5 …… Adhesive sheet,
10 ... Laminated body of the second release film and the pressure-sensitive adhesive layer (becomes an intermediate for producing a pressure-sensitive adhesive sheet and also serves as a pressure-sensitive adhesive sheet before bonding to an optical member),
15: Polarizing film,
16, 17 ... Transparent protective film,
20: Optical member (polarizing plate),
25 …… Optical member with adhesive,
30, 33, 36, 40...
31 …… Coating machine,
32 …… Dryer,
34, 41 …… bonding roll,
35, 39, 42 ... take-up roll,
37 …… Upstream tension roll,
38 …… Downstream tension roll,
L: Straight section of the first release film,
P …… Peeling point
A: Expanded sectional view of the adhesive sheet,
45 …… Double-sided adhesive tape,
50: Glass substrate.

Claims

In the peeling step, the first peeling film, the pressure-sensitive adhesive layer, and the second peeling film are laminated in this order to peel off the first peeling film to expose the pressure-sensitive adhesive layer, and in the peeling step A method for producing an optical member with an adhesive in which the optical member, the adhesive layer, and the second release film are laminated in this order through a bonding step of bonding the exposed adhesive layer to the optical member. Because
The peel force between the first release film and the pressure-sensitive adhesive layer and the peel force between the second release film and the pressure-sensitive adhesive layer were each tested at a peel speed of 0.3 m / min. When both are in the range of more than 0.02 N / 25 mm and less than 0.15 N / 25 mm, and the difference between the two peel forces is less than 0.01 N / 25 mm,
In the peeling step, at the peeling point where the first release film is peeled off from the pressure-sensitive adhesive layer, the first release film is moved straight so as not to bend, and the pressure-sensitive adhesive layer is pasted on the second release film. The pressure-sensitive adhesive layer is transported in a direction different from the linear direction of the first release film so that no pressing force is applied from the opposite side of the attached surface, and the first release film is the pressure-sensitive adhesive. It is performed so that it may peel from a layer, The manufacturing method of the optical member with an adhesive.
The method for producing an optical member with an adhesive according to claim 1, wherein the adhesive layer contains a light diffusing agent.
The method for producing an optical member with an adhesive according to claim 1 or 2, wherein the optical member is a polarizing plate.