CN114761228A

CN114761228A - Optical laminate and method for producing same

Info

Publication number: CN114761228A
Application number: CN202080084725.7A
Authority: CN
Inventors: 伊藤涉; 宝田翔; 野中崇弘; 小川美优
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2019-12-06
Filing date: 2020-11-06
Publication date: 2022-07-15
Also published as: WO2021111801A1; JP2021091117A; KR20220108805A; TW202129380A

Abstract

The optical laminate comprises an adherend bonded to both main surfaces of a pressure-sensitive adhesive layer (21). The adherend to be adhered to one surface of the pressure-sensitive adhesive layer (21) may be a polarizing plate, or may further include an image display unit such as an organic EL unit. The optical laminate is cut out from the mother substrate to obtain chips. In the chip of the optical laminate, the physical properties of the end face of the pressure-sensitive adhesive layer (21) measured by nanoindentation are within a predetermined range. The adhesive constituting the adhesive layer (21) may have photocurability.

Description

Optical laminate and method for producing same

Technical Field

The present invention relates to an optical laminate having an adherend bonded thereto via a pressure-sensitive adhesive layer, and a method for producing the same.

Background

In display devices such as liquid crystal displays and organic EL displays, and input devices for displays such as touch panels, a transparent adhesive sheet is used for attaching an optical member. In addition, a transparent adhesive sheet is also used when a cover window (cover window) formed of a transparent resin plate, a glass plate, or the like is disposed on the visible side surface of the image display device.

A colored layer for decoration and shading is printed on a frame portion covering a window, and a printing step difference of about 10 to several tens of micrometers is generated on the printed portion of the colored layer. As described in patent document 1, in the attachment of an optical member having a printed step, a thick and flexible adhesive sheet is used in order to prevent bubbles from entering a printed step portion and stress concentration.

In recent years, organic EL panels using a substrate (flexible substrate) that can be bent such as a resin film have been put to practical use, and foldable displays that can be folded have also been put to practical use. In the foldable display, since the bending is repeated at the same portion, deformation occurs at the bent portion and its periphery. Patent document 2 proposes the following: in order to prevent the device from being broken due to the concentration of strain at the bent portion, the adhesive sheet for bonding the optical members together is softened to alleviate the stress strain.

A transparent pressure-sensitive adhesive sheet for attaching an optical member is generally provided in the form of a pressure-sensitive adhesive sheet with a release film having both surfaces temporarily attached with release films, and is cut into a predetermined size according to the shape, size, and the like of an adherend. For example, in the attachment of the components of the image display device, an adhesive sheet cut into pieces having a size approximately equal to the screen size is used. As described in patent documents 1 and 3, the transparent adhesive sheet may be cut into individual pieces in a state of being attached to an optical member such as a polarizing plate in advance.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2014-115468

Patent document 2: japanese patent laid-open publication No. 2018-45213

Patent document 3: japanese patent laid-open publication No. 2019-179211

Disclosure of Invention

Problems to be solved by the invention

When an adhesive having a large thickness or a soft adhesive is used, the adhesive exposed at the end face of a product (chip) cut into individual pieces having a predetermined size easily overflows from the end face of the chip, and may cause foreign matter to adhere to the end face or cause contamination of the surroundings. Further, when a plurality of chips are stored in a stacked state, the adhesive sheets are likely to stick to each other due to the adhesive overflowing from the end faces, and it is sometimes difficult to pick up the adhesive sheets 1 by one.

In order to suppress a problem caused by the adhesive overflowing from the end face, patent document 1 proposes the following: the end face of the pressure-sensitive adhesive layer is cut and processed so as to be located inside the end face (cut face) of the release film. The screen shape of the image display device is generally rectangular, but in an instrument panel of an automobile, a smart watch, or the like, the screen shape is a shape other than rectangular (irregular shape). In addition, with the advent of the borderless (bezel-less) mobile devices such as smartphones, irregular screen shapes having cutouts in the outer peripheral portions thereof are adopted for the arrangement of cameras and sensors.

In order to produce an image display device having an irregular screen, it is necessary to process each optical member into an irregular shape. In addition, since accurate alignment is required when the members are bonded, productivity and yield may be reduced. Therefore, the following solutions are proposed: the adhesive sheet is cut into irregular shapes in a state where a plurality of optical members such as organic EL units and polarizing plates are adhered in advance.

When the chip is cut out in a state where a plurality of optical members are stacked as described above, the positions of the end faces of the optical members and the release film are aligned with the position of the end face of the adhesive sheet, and it is difficult to process the optical members and the release film so that the end face of the adhesive layer is positioned inside the laminate.

In view of the above, an object of the present invention is to provide an optical laminate in which adhesion and blocking of foreign matter due to an adhesive exposed to an end face are less likely to occur even when the end face of an adhesive layer is aligned with the end faces of an optical member and a release film.

Means for solving the problems

The optical laminate includes a first adherend and a second adherend that are adhered to both principal surfaces of the first pressure-sensitive adhesive layer. The thickness of the first adhesive layer may be 30 μm or more. Examples of the adherend include optical films such as polarizing plates, image display units, cover windows, and release films. The optical laminate may have a polarizing plate in contact with the first adhesive layer, and an image display unit such as an organic EL unit may be further bonded to the polarizing plate.

The end face of the first adhesive layer preferably has a load curve with a minimum load of-0.2 μ N or more and an unload curve displacement of 8 μm or less, as measured by nanoindentation. The gel fraction of the adhesive in the in-plane center portion of the first adhesive layer is preferably 25% or more.

The first pressure-sensitive adhesive layer may have different physical properties at the center portion in the plane and at the end face. For example, the minimum load of the load curve of the in-plane central portion of the first adhesive layer measured by nano-indentation may be 0.3 times or less the minimum load of the load curve of the end face. The displacement amount of the unloading curve of the first adhesive layer in the central portion in the plane measured by nano indentation may be 0.5 times or less the displacement amount of the unloading curve of the end face.

The first adhesive layer may include an ultraviolet absorber. The adhesive constituting the first adhesive layer may have photocurability.

The photocurable adhesive may further include a monomer or oligomer having a photocurable functional group in addition to the base polymer. In addition, a compound having a photocurable functional group may be bonded to the base polymer. The photocurable adhesive may include a photopolymerization initiator. The gel fraction of the photocurable adhesive after photocuring is preferably 70% or more. The gel fraction of the photocurable adhesive after photocuring is preferably 1.2 times or more the gel fraction before photocuring.

The mother substrate is cut into a predetermined size, thereby obtaining a monolithic optical stack (chip). Dicing of chips from the mother substrate may also be performed by irradiating ultraviolet laser light. The optical stack is preferably: when the first adhesive layer is cut by an ultraviolet laser, the minimum load of the load curve of the adhesive on the cut surface is 0.3 times or less of that before the cutting, the displacement of the unload curve of the adhesive on the cut surface is 0.5 times or less of that before the cutting, and the indentation modulus of the adhesive on the cut surface is 1.5 to 10 times of that before the cutting.

ADVANTAGEOUS EFFECTS OF INVENTION

The optical laminate of the present invention is less likely to cause adhesion and blocking of foreign matter due to an adhesive agent exposed to the end face, even when the adhesive agent layer is exposed to the end face of a chip cut out from a large-area mother substrate, and is excellent in workability.

Drawings

Fig. 1 is a cross-sectional view of an optical stack according to an embodiment.

Figure 2 is a cross-sectional view of an optical stack according to one embodiment.

Figure 3 is a cross-sectional view of an optical stack according to one embodiment.

Figure 4 is a cross-sectional view of an optical stack according to one embodiment.

Figure 5 is a cross-sectional view of an optical stack according to one embodiment.

Fig. 6 is an example of a load-displacement curve of the pressure-sensitive adhesive sheet based on nanoindentation.

Detailed Description

[ example of lamination constitution of optical laminate ]

The optical laminate of the present invention is a laminate in which an adherend is bonded to each of a first main surface and a second main surface of a transparent pressure-sensitive adhesive sheet. The adherend may be fixedly laminated on the pressure-sensitive adhesive layer, or may be attached (temporarily attached) so as to be detachable.

Fig. 1 is a cross-sectional view of an optical stack 101 according to an embodiment. The optical laminate 101 is a release film-attached pressure-sensitive adhesive sheet in which release

films

41 and 43 are temporarily attached to the first main surface and the second main surface of the pressure-sensitive adhesive layer 21, respectively.

The optical laminate 102 shown in fig. 2 is a polarizing plate with an adhesive in which an adhesive layer 21 is laminated on the first main surface of the optical film 10. The optical laminate 102 is formed by peeling the release film 43 from the optical laminate 101 shown in fig. 1 and attaching the optical film 10 to the exposed second main surface of the pressure-sensitive adhesive layer 21.

The optical laminate 103 shown in fig. 3 is a polarizing plate with adhesive on both sides, in which a first adhesive layer 21 is laminated on a first main surface of the optical film 10, and a second adhesive layer 22 is laminated on a second main surface of the optical film 10. The optical laminate 103 is formed by laminating the second pressure-sensitive adhesive layer 22 on the second main surface of the optical film 10 of the optical laminate 102 shown in fig. 2. The first pressure-sensitive adhesive layer 21 may be laminated after the second pressure-sensitive adhesive layer 22 is laminated on the second main surface of the optical film 10, or the first pressure-sensitive adhesive layer 21 and the second pressure-sensitive adhesive layer 22 may be simultaneously laminated on both main surfaces of the optical film 10.

The optical laminate 104 shown in fig. 4 is an image display panel including the optical film 10 on the surface of the image display unit 70. The optical laminate 104 is formed by peeling the release film 42 from the optical laminate 103 shown in fig. 3 and attaching the image display unit 70 to the exposed second pressure-sensitive adhesive layer 22.

The optical laminate 105 shown in fig. 5 is an image display panel including a cover window 80 on the surface of a polarizing plate. The optical laminate 105 is formed by peeling the release film 41 from the optical laminate 104 shown in fig. 4 and attaching the cover window 80 to the first main surface of the exposed first pressure-sensitive adhesive layer 21.

The optical laminate may be obtained by laminating an adherend on the front and back surfaces of the pressure-sensitive adhesive layer 21, and the lamination configuration is not limited to the above configuration. As shown in fig. 3, the optical laminate may further include another pressure-sensitive adhesive layer 22 on the adherend (optical film 10) bonded to the pressure-sensitive adhesive layer 21, may further bond the adherend (image display unit 70) on the pressure-sensitive adhesive layer 22 as shown in fig. 4, or may further bond the adherend (cover window 80) on the first pressure-sensitive adhesive layer 21 as shown in fig. 5. Another adherend may be further laminated on the adherend attached to the first pressure-sensitive adhesive layer 21 via another pressure-sensitive adhesive layer.

[ Properties of optical laminate chips ]

These optical laminates are generally formed into a large-sized mother substrate, and then cut into individual products (chips) having a predetermined size. In this method, since a plurality of sheet products can be obtained from the mother substrate, productivity can be improved. In a die cut out from an optical laminate having adherends bonded to both surfaces of a pressure-sensitive adhesive sheet, the positions of the end surface of the adherend bonded to the pressure-sensitive adhesive and the end surface of the pressure-sensitive adhesive layer are aligned, and the pressure-sensitive adhesive layer is exposed at the end surface of the laminate.

In the optical laminate of the present invention, the end face of the pressure-sensitive adhesive layer 21 has predetermined properties. The characteristics of the end face of the adhesive layer can be evaluated by nano indentation. The nanoindentation method is a method of: the indenter of the nanoindenter was pressed (loaded) into the sample to a predetermined depth, and then the indenter was lifted (unloaded) until the indenter was separated from the sample, and the mechanical properties of the sample surface were analyzed from the relationship between the displacement and the load at that time (load-displacement curve).

Fig. 6 is an example of a load-variation curve of the adhesive sheet measured at a constant load/unload speed. When the indenter is brought close to the sample, a negative load (a force that pulls the indenter toward the sample) acts on the indenter when the indenter contacts the sample (point a). The load w at this time is the minimum load of the load curve. The minimum load w of the load curve is a force with which the pressure-sensitive adhesive layer is drawn into an adherend such as an adherend or a foreign substance (a force with which the pressure-sensitive adhesive adheres to the adherend, adhesion), and reflects the surface tension, wettability, and the like of the pressure-sensitive adhesive. The smaller the minimum load w of the load curve (the larger the absolute value of w), the greater the wettability of the pressure-sensitive adhesive, and adhesion is likely to occur when the pressure-sensitive adhesive is in contact with an adherend.

The indenter is pushed in at a constant load speed until a predetermined depth p is reached (point B). The load q at this time is the maximum load of the load curve, and a larger load q means a harder adhesive.

After the ram is pressed in to the depth p, the ram is lifted up at a certain unloading speed. The test force is reduced in a state where the force for lifting the indenter and the force (adhesive force) of the adhesive for holding the indenter are balanced, and if the two are out of balance, the unload curve shows a minimum value (point C). The load u at this time is the minimum load of the unloading curve, and the absolute value of the load u becomes larger as the adhesive force is higher.

When the indenter is lifted up, the indenter starts to peel off from the adhesive, and when the indenter is completely peeled off from the adhesive, the load reaches 0 (point D). The absolute value d of the displacement amount at this time is the displacement amount of the unloading curve. The adhesive is susceptible to local deformation, and the greater the stringing due to shrinkage or necking, the greater the displacement d of the unloading curve becomes.

The load-displacement curve of the end face of the pressure-sensitive adhesive layer of the optical laminate was measured using a conventional-thermal indenter (an indenter having a Conical shape with a curved tip) having a radius of curvature of 10 μm at the tip under conditions of a load speed/unload speed of 1000 nN/sec and an indentation depth of 3000 nm.

The minimum load w of the load curve of the end face of the pressure-sensitive adhesive layer 21 is preferably-0.2 μ N or more. The minimum load w of the load curve is more preferably-0.15. mu.N or more, still more preferably-0.1. mu.N or more, and particularly preferably-0.07. mu.N or more. As W is larger (smaller in absolute value of W) and closer to 0, the end face of the pressure-sensitive adhesive layer is less sticky, and adhesion due to attachment of foreign matter and contact between the chip end faces tends to be suppressed.

The displacement d of the unloading curve of the end face of the adhesive layer 21 is preferably 8 μm or less. The displacement amount of the unloading curve is preferably 7 μm or less, more preferably 6 μm or less, and still more preferably 5 μm or less. As d is as small as 0, the adhesive layer is less likely to deform at the end face of the adhesive layer, and the flow of the adhesive tends to cause overflow from the end face, thereby suppressing sticking between chips when a plurality of chips are stacked.

From the viewpoint of suppressing the flow of the adhesive at the end faces, the indentation modulus at the end faces of the adhesive layer 21 is preferably 0.3MPa or more, more preferably 0.35MPa or more, and even more preferably 0.4MPa or more.

As described above, in the optical laminate chip in which the pressure-sensitive adhesive layer 21 is exposed at the end face, the absolute value of the minimum load w of the load curve and the displacement amount d of the unload curve are preferably small at the end face of the pressure-sensitive adhesive layer 21 from the viewpoint of suppressing adhesion of foreign substances and blocking between chips due to the end face of the pressure-sensitive adhesive layer.

On the other hand, wettability and viscosity of the pressure-sensitive adhesive are important characteristics for adhesively holding an adherend, and pressure-sensitive adhesive sheets having a small absolute value of the minimum load w of the load curve and the displacement d of the unload curve may have poor adhesive holding force for the adherend. Therefore, the adhesive layer 21 preferably has the above-described characteristics at the end surface, and the absolute value of the minimum load w of the load curve and the displacement d of the unload curve are preferably larger in the center portion of the chip in the plane than in the end surface. In other words, the adhesive layer 21 preferably has a small absolute value of the minimum load w of the load curve and a small displacement d of the unload curve in the local area of the end face (and its vicinity). By locally reducing the sum d of the absolute values of w at the end faces, it is possible to reduce the adhesion and blocking of foreign matter caused by the end faces of the exposed pressure-sensitive adhesive layer while maintaining the adhesive properties to the adherend.

In the chip of the optical laminate, the minimum load w of the load curve is preferably-0.2 μ N or less, more preferably-0.25 μ N or less, at the in-plane central portion of the pressure-sensitive adhesive layer 21. The displacement amount d of the unload curve in the in-plane center portion of the pressure-sensitive adhesive layer 21 is preferably 10 μm or more, more preferably 12 μm or more, and still more preferably 14 μm or more.

The minimum load w of the load curve at the end face of the pressure-sensitive adhesive layer 21 is preferably 0.3 times or less, more preferably 0.2 times or less, and still more preferably 0.1 times or less the minimum load of the load curve at the in-plane center portion. The displacement amount d of the relief curve of the end face of the adhesive layer 21 is preferably 0.5 times or less, more preferably 0.4 times or less, and still more preferably 0.3 times or less the displacement amount of the relief curve of the in-plane center portion. The indentation modulus of the end face of the adhesive layer 21 is preferably 1.5 to 10 times, more preferably 2 to 8 times, and even more preferably 2.5 to 7 times that of the indentation modulus of the center portion in the plane.

The chips of the optical laminate were cut at the center in the plane so that the adhesive did not change in properties, and the indenter was brought into contact with the cut surface, whereby nanoindentation measurement of the adhesive at the center in the plane of the adhesive layer 21 of the optical laminate was performed. Alternatively, the adherend may be peeled off from the pressure-sensitive adhesive layer, and the pressure head may be brought into contact with the main surface of the pressure-sensitive adhesive layer to perform the measurement.

In order to reduce the absolute value of the minimum load w of the load curve of the end face and the displacement amount d of the unload curve while maintaining the adhesion characteristics of the in-plane central portion of the adhesive layer 21, for example, the adhesive in the end face and the vicinity thereof may be locally modified. For example, the adhesive can be modified by locally heating the end face of the chip. When the adhesive constituting the adhesive layer 21 is curable, the end face is irradiated with an active energy ray such as an electron beam or an ultraviolet ray to selectively cure the adhesive at the end face and the vicinity thereof. In addition, when the chip is cut out from the mother substrate, the adhesive on the cut surface can be modified. For example, when the adhesive constituting the adhesive layer 21 is photocurable, if dicing is performed by ultraviolet laser light, the laser light irradiation region at the dicing surface (end surface of the chip) and the vicinity thereof can be partially photocured.

[ Components of optical layered body ]

As described above, the components constituting the optical laminate are the optical member bonded to the pressure-sensitive adhesive layer 21 or the optical member further bonded via another pressure-sensitive adhesive, and specific examples thereof include an optical film, an image display unit, a cover window, and the like.

< image display Unit >

In the optical layered body 104 shown in fig. 4, the image display unit 70 is a top emission type organic EL unit, and a metal electrode 73, an organic light emitting layer 75, and a transparent electrode 77 are provided in this order on a substrate 71. A sealing material 79 is laminated on the transparent electrode 77. Although not shown, the sealing material 79 is preferably provided so as to cover the

electrodes

73 and 77 and the side surfaces of the organic light-emitting layer 75.

As the substrate 71, a glass substrate or a plastic substrate is used. In the top emission type organic EL unit, the substrate 71 does not need to be transparent, and a highly heat-resistant film such as a polyimide film can be used as the substrate 71. When a polyimide film is used as the substrate 71, ultraviolet absorption by polyimide is large, and therefore, the laminate can be cut by irradiating the laminate 104 with an ultraviolet laser beam from the substrate 71 side. Even if the material other than polyimide is used, the dicing process can be easily performed by the ultraviolet laser by using a resin material having high ultraviolet absorptivity such as polyethylene naphthalate (PEN) or a material containing an ultraviolet absorber as the material of the substrate 71.

The organic light-emitting layer 75 may include an electron transport layer, a hole transport layer, and the like, in addition to an organic layer that functions as a light-emitting layer. The transparent electrode 77 is a metal oxide layer or a metal thin film, which transmits light from the organic light emitting layer 75. A back plate (not shown) may be provided on the back surface side of the substrate 71 for the purpose of protecting and reinforcing the substrate.

The organic EL unit may be a bottom emission type in which a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially stacked on a substrate. In the bottom emission type organic EL unit, a transparent substrate is used, and the substrate is disposed on the visible side (the second adhesive layer 22 side). The image display unit is not limited to the organic EL unit, and may be a liquid crystal unit, an electrophoretic display unit (electronic paper), or the like. A touch panel sensor (not shown) may be disposed on the visible side surface of the image display unit 70.

< optical film >

The optical film 10 disposed on the visible-side surface of the organic EL unit 70 may be a polarizing plate. The polarizing plate includes a polarizer 11, and

transparent films

13 and 15 as polarizer protective films are laminated on both surfaces of the polarizer 11. The polarizer protective film on one or both sides of the polarizer may be omitted, and an adhesive layer may be directly provided on the polarizer 11.

Examples of the polarizer 11 include polarizers obtained by uniaxially stretching a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or an ethylene-vinyl acetate copolymer partially saponified film, while adsorbing a dichroic material such as iodine or a dichroic dye; and polyene-based oriented films such as dehydrated polyvinyl alcohol and desalted polyvinyl chloride.

As the polarizer 11, a thin polarizer having a thickness of 10 μm or less may be used. Examples of the thin polarizer include polarizers described in Japanese patent laid-open Nos. 51-069644, 2000-338329, WO2010/100917, 4691205, and 4751481. The thin polarizer is obtained by a manufacturing method including, for example, the steps of: stretching the polyvinyl alcohol resin layer and the stretching resin base material in a state of being laminated; and a step of dyeing with a dichroic material such as iodine.

As the

transparent films

13 and 15, transparent resin films such as cellulose-based resins, cyclic polyolefin-based resins, acrylic resins, phenylmaleimide-based resins, and polycarbonate-based resins are preferably used. When the

transparent films

13 and 15 are provided on both surfaces of the polarizer 11, the

transparent films

13 and 15 may be formed of the same resin material or different resin materials.

The optical film 10 may be provided with an optical functional film laminated on one or both surfaces of the polarizer 11 via an appropriate adhesive layer or pressure-sensitive adhesive layer, as necessary. Examples of the optical functional film include a retardation plate, a viewing angle expanding film, a viewing angle restricting (privacy) film, and a brightness enhancing film. The optical film 10 may include a touch panel sensor as an optical functional film. The

transparent films

13 and 15 in contact with the polarizer may function as a polarizer protective film and an optical functional film. The

transparent films

13 and 15 can also function as electrode substrate films of the touch panel sensor.

The metal electrode 73 of the organic EL unit 70 is light-reflective. Therefore, when external light enters the organic EL unit, the light is reflected by the metal electrode 73, and the reflected light looks like a mirror surface when viewed from the outside. By disposing the circularly polarizing plate as the optical film 10 on the visible-side surface of the organic EL unit 70, the reflected light from the metal electrode 73 can be prevented from being re-emitted to the outside, and the visibility and design of the screen of the display device can be improved.

The circularly polarizing plate has a retardation film on the surface of the polarizer 11 on the organic EL unit 70 side. The transparent film 15 disposed adjacent to the polarizer 11 may be a retardation film. The retardation film has a retardation of λ/4, and when the angle formed by the slow axis direction of the retardation film and the absorption axis direction of the polarizer 11 is 45 °, the laminate of the polarizer and the retardation film functions as a circular polarizing plate for suppressing re-emission of the reflected light at the metal electrode 73. The retardation film constituting the circularly polarizing plate may be a laminate of 2 or more layers. For example, a broadband circular polarizing plate that functions as a circular polarizing plate in a broadband of visible light can be obtained by laminating a polarizer, a λ/2 plate, and a λ/4 plate so that their optical axes form a predetermined angle.

< covering Window >

As the cover window 80, a transparent plate having appropriate mechanical strength and thickness may be used. As such a transparent plate, a transparent resin plate such as an acrylic resin, a polycarbonate resin, or a transparent polyimide resin, a glass plate, or the like can be used. The thickness of the cover window 80 is, for example, about 20 to 2000 μm. In the flexible device, a transparent resin film is preferably used as the cover window 80, and the thickness thereof is preferably 20 to 500 μm, more preferably 30 to 300 μm, and further preferably 50 to 200 μm. As the cover window 80, a thin glass substrate that can be bent can be used.

The cover window 80 may be integrated with the touch panel sensor. An antireflection layer, a hard coat layer, or the like may be provided on the visible side surface of the cover window 80.

< mold release film >

As the

release films

41, 42, and 43 to be temporarily attached to the pressure-sensitive adhesive layers 21 and 22, release films having a release layer on the surface of a film base are preferably used. Examples of the material of the release layer include silicone release agents, fluorine release agents, long-chain alkyl release agents, fatty acid amide release agents, and the like. A silicone release agent is preferable in terms of compatibility between adhesiveness and releasability with respect to an acrylic pressure-sensitive adhesive.

The film base material of the release film is preferably a transparent resin film. Examples of the resin material include polyester resins such as polyethylene terephthalate and polyethylene naphthalate; examples of the resin include an acetate resin, a polyether sulfone resin, a polycarbonate resin, a polyamide resin, a polyimide resin, a polyolefin resin, a (meth) acrylic resin, a polyvinyl chloride resin, a polyvinylidene chloride resin, a polystyrene resin, a polyvinyl alcohol resin, a polyarylate resin, and a polyphenylene sulfide resin. Among these, polyester resins such as polyethylene terephthalate (PET) are particularly preferable. The thickness of the release film is preferably 10 to 200 μm, more preferably 25 to 150 μm.

< first adhesive layer >

The first adhesive layer 21 is an adhesive layer in which an adhesive is formed in a layered state. In the optical laminate shown in fig. 2 to 5, the first pressure-sensitive adhesive layer 21 is disposed on the visible side of the optical film 10 and used for bonding the optical film 10 to a transparent member such as the cover window 80.

The adhesive layer 21 is preferably transparent and has a small absorption of visible light. The total light transmittance of the adhesive layer 21 is preferably 85% or more, more preferably 90% or more. The haze of the pressure-sensitive adhesive layer 21 is preferably 2% or less, and more preferably 1% or less. The total light transmittance and haze were measured using a haze meter and in accordance with JIS K7136.

As the adhesive constituting the adhesive layer 21, an adhesive containing a polymer such as an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyvinyl ether, a vinyl acetate/vinyl chloride copolymer, a modified polyolefin, an epoxy-based, a fluorine-based, or a rubber-based polymer as a base polymer can be appropriately selected and used.

An acrylic pressure-sensitive adhesive containing an acrylic polymer as a base polymer is preferably used as the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 21, because it is excellent in optical transparency, exhibits appropriate wettability, adhesive properties such as cohesion and adhesiveness, and is also excellent in weather resistance, heat resistance, and the like. In the acrylic adhesive, the content of the acrylic base polymer with respect to the total solid content of the adhesive composition is preferably 50% by weight or more, more preferably 70% by weight or more, and still more preferably 80% by weight or more.

As the acrylic base polymer, a polymer having a monomer unit of an alkyl (meth) acrylate as a main skeleton is suitably used. In the present specification, "(meth) acrylic acid" means acrylic acid and/or methacrylic acid.

As the alkyl (meth) acrylate, an alkyl (meth) acrylate having an alkyl group with 1 to 20 carbon atoms is preferably used. The alkyl group in the alkyl (meth) acrylate may have a branch. The content of the alkyl (meth) acrylate is preferably 40% by weight or more, more preferably 50% by weight or more, and further preferably 60% by weight or more, based on the total amount of the monomer components constituting the base polymer. The acrylic base polymer may be a copolymer of a plurality of alkyl (meth) acrylates. The arrangement of the constituent monomer units may be random or block.

The acrylic base polymer may contain, as a copolymerization component, an acrylic monomer unit having a crosslinkable functional group. When the base polymer has a crosslinkable functional group, the gel fraction of the binder can be easily increased by thermal crosslinking, photocuring, or the like of the base polymer. Examples of the acrylic monomer having a crosslinkable functional group include a hydroxyl group-containing monomer and a carboxyl group-containing monomer. Among these, the copolymerization component of the base polymer preferably contains a hydroxyl group-containing monomer. When the base polymer contains a hydroxyl group-containing monomer as a monomer unit, the crosslinking properties by an isocyanate crosslinking agent or the like tend to be improved, and the cloudiness of the adhesive under a high-temperature and high-humidity environment tends to be suppressed, whereby the adhesive having high transparency can be obtained.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, and (4-hydroxymethyl) cyclohexylmethyl (meth) acrylate.

The content of the hydroxyl group-containing monomer is preferably 0.1 to 50% by weight, more preferably 1 to 40% by weight, and still more preferably 3 to 30% by weight, based on the total amount of the monomer components constituting the base polymer.

Among the acrylic base polymers, preferred are: the hydroxyl group-containing monomer unit may contain a highly polar monomer unit such as a nitrogen-containing monomer. By containing a high-polarity monomer such as a nitrogen-containing monomer in addition to the hydroxyl group-containing monomer, the pressure-sensitive adhesive has high adhesiveness and holding power, and white turbidity in a high-temperature and high-humidity environment is suppressed.

Examples of the nitrogen-containing monomer include vinyl monomers such as N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, (meth) acryloylmorpholine, N-vinylcarboxylic acid amides, and N-vinylcaprolactam; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile. Among them, N-vinylpyrrolidone and (meth) acryloylmorpholine are preferably used.

The content of the nitrogen-containing monomer is preferably 0.1 to 50% by weight, more preferably 1 to 40% by weight, and still more preferably 3 to 30% by weight, based on the total amount of the monomer components constituting the base polymer.

The acrylic polymer may be formed by polymerizing a monomer component containing a polyfunctional monomer component. The polyfunctional monomer is a monomer having at least two polymerizable functional groups having an unsaturated double bond such as a (meth) acryloyl group or a vinyl group. The polyfunctional monomer may have 3 or more polymerizable functional groups in 1 molecule.

The base polymer can be prepared by a known polymerization method such as solution polymerization, UV polymerization, bulk polymerization, and emulsion polymerization. From the viewpoints of transparency, water resistance, cost, and the like of the adhesive, solution polymerization or UV polymerization is preferable. As a solvent for solution polymerization, ethyl acetate, toluene, and the like are generally used. In the preparation of the base polymer, a polymerization initiator such as a photopolymerization initiator or a thermal polymerization initiator can be used depending on the kind of polymerization reaction. In order to adjust the molecular weight of the base polymer, a chain transfer agent may be used.

The weight average molecular weight of the base polymer is preferably 20 to 100 ten thousand, more preferably 25 to 80 ten thousand, from the viewpoint of providing the pressure-sensitive adhesive with appropriate adhesive holding power and flexibility. The molecular weight of the base polymer refers to the molecular weight of the polymer before the introduction of the crosslinked structure.

The base polymer may have a crosslinked structure. By introducing a crosslinked structure into the base polymer, the cohesive force of the pressure-sensitive adhesive is improved, and the adhesiveness to an adherend is improved. The formation of the crosslinked structure is carried out, for example, by adding a crosslinking agent after the polymerization of the base polymer. As the crosslinking agent, a commonly used crosslinking agent such as an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an oxazoline-based crosslinking agent, an aziridine-based crosslinking agent, a carbodiimide-based crosslinking agent, a metal chelate-based crosslinking agent, or the like can be used. The content of the crosslinking agent is usually in the range of 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, and more preferably 0.07 to 2.5 parts by weight, based on 100 parts by weight of the acrylic base polymer. The larger the amount of the crosslinking agent added, the larger the gel fraction of the adhesive tends to become.

The adhesive constituting the adhesive layer 21 may have photocurability. For example, if a photocurable adhesive is used for attaching an adherend (for example, a cover window) having a print step caused by decorative printing or the like, the adhesive before photocuring can have step following properties by attaching it in a soft state, and the adhesive can be photocured by irradiating ultraviolet rays or the like after attachment, thereby improving the adhesion reliability. Further, if the adhesive has photocurability, when the optical laminate is cut by laser irradiation to cut out chips, the cut surface (end surface of the chip) and its vicinity can be partially photocured, and the absolute value of the minimum load w of the load curve of the end surface and the displacement d of the unload curve can be reduced while maintaining the adhesion characteristics of the in-plane central portion of the adhesive layer 21.

The photocurable adhesive preferably contains a photocurable compound (monomer or oligomer having a photopolymerizable functional group) in addition to the base polymer, for example. The base polymer may be provided with photocurability by introducing a photopolymerizable functional group.

The photocurable compound preferably contains a polyfunctional polymerizable compound having 2 or more polymerizable functional groups in 1 molecule. Examples of the polyfunctional polymerizable compound include a compound having 2 or more ethylenically unsaturated groups in 1 molecule; and compounds having 1C ═ C bond and polymerizable functional groups such as epoxy group, aziridinyl group, oxazoline group, hydrazine group, and hydroxymethyl group. Among them, it is preferable that: a compound having 2 or more ethylenically unsaturated groups in 1 molecule like a polyfunctional (meth) acrylate. Specific examples of the polyfunctional polymerizable compound include polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, bisphenol a ethylene oxide-modified di (meth) acrylate, bisphenol a propylene oxide-modified di (meth) acrylate, alkanediol di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, ethoxylated isocyanuric acid triacrylate, pentaerythritol tri (meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate, dipentaerythritol poly (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and mixtures thereof, Neopentyl glycol di (meth) acrylate, glycerol di (meth) acrylate, urethane (meth) acrylate, epoxy (meth) acrylate, butadiene (meth) acrylate, isoprene (meth) acrylate, and the like.

The amount of the photocurable compound to be used varies depending on the molecular weight, the number of functional groups, and the like, and is preferably 0.3 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the base polymer. As the addition amount of the photocurable compound increases, the adhesive on the cut surface is more easily cured by laser irradiation, and the absolute value of the minimum load w of the load curve on the end surface and the displacement amount d of the unload curve tend to decrease.

Examples of the method for introducing a photopolymerizable functional group into the base polymer include a method in which a compound having a functional group capable of bonding to a functional group (e.g., a hydroxyl group or a carboxyl group) of the base polymer and a radical polymerizable functional group is mixed with the base polymer.

The photocurable adhesive preferably further contains a photopolymerization initiator in addition to the photocurable compound and/or the polymer having a photopolymerizable functional group introduced therein. Examples of the photopolymerization initiator include benzoin ether type photopolymerization initiators, acetophenone type photopolymerization initiators, α -ketol type photopolymerization initiators, aromatic sulfonyl chloride type photopolymerization initiators, photoactive oxime type photopolymerization initiators, benzoin type photopolymerization initiators, benzil type photopolymerization initiators, benzophenone type photopolymerization initiators, ketal type photopolymerization initiators, thioxanthone type photopolymerization initiators, and acylphosphine oxide type photopolymerization initiators. The amount of the photopolymerization initiator added is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, based on 100 parts by weight of the base polymer.

The adhesive may contain additives such as a silane coupling agent, a tackifier, a plasticizer, a softener, an anti-deterioration agent, a filler, a colorant, an antioxidant, a surfactant, and an antistatic agent, in addition to the above-exemplified components.

The adhesive may contain an ultraviolet absorber. If the pressure-sensitive adhesive layer 21 has ultraviolet absorptivity, the pressure-sensitive adhesive layer 21 absorbs the energy of the laser beam when the optical laminate is cut by irradiation with an ultraviolet laser beam, and therefore, there is a tendency that the cutting processability of the optical laminate is improved, defects such as processing defects and peeling of an adherend are suppressed. The light transmittance at a wavelength of 355nm of the first adhesive layer 21 may be 80% or less or 75% or less. The content of the ultraviolet absorber in the adhesive layer 21 is, for example, about 0.01 to 10 wt%.

Examples of the ultraviolet absorber include benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, triazine-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, and the like. From the viewpoint of easily obtaining an acrylic pressure-sensitive adhesive sheet having high ultraviolet absorptivity, excellent compatibility with an acrylic polymer, and high transparency, preferred are a triazine-based ultraviolet absorber and a benzotriazole-based ultraviolet absorber, and among them, preferred are a triazine-based ultraviolet absorber containing a hydroxyl group and a benzotriazole-based ultraviolet absorber having 1 benzotriazole skeleton in 1 molecule.

The adhesive layer is formed by applying the adhesive composition in a layer form onto a substrate, and drying the solvent and crosslinking/curing the base polymer as needed. The thickness of the pressure-sensitive adhesive layer 21 is not particularly limited, but is usually about 5 to 1000 μm. When the pressure-sensitive adhesive layer 21 is required to have step following properties and stress relaxation properties, the thickness of the pressure-sensitive adhesive layer 21 is preferably 30 μm or more. The thickness of the adhesive layer 21 may be 40 μm or more or 50 μm or more. In view of weight reduction and thickness reduction of the display device, easiness of forming the pressure-sensitive adhesive layer, workability, and the like, the thickness of the pressure-sensitive adhesive layer 21 is preferably 500 μm or less, more preferably 300 μm or less, and still more preferably 250 μm or less.

From the viewpoint of flexibility, the storage modulus G' at 25 ℃ of the pressure-sensitive adhesive layer 21 is preferably 0.35MPa or less, more preferably 0.30MPa or less, and still more preferably 0.20MPa or less. On the other hand, if the pressure-sensitive adhesive layer 21 is too soft, foreign matters may adhere to the adhesive exposed at the end face, or the chips may be stuck together. Therefore, the storage modulus G' at 25 ℃ of the first pressure-sensitive adhesive layer 21 is preferably 0.01MPa or more, and more preferably 0.02MPa or more. The first pressure-sensitive adhesive layer 21 may have a storage modulus G' at 25 ℃ of 0.03MPa or more, 0.05MPa or more, or 0.1MPa or more.

The gel fraction of the adhesive layer 21 is preferably 25% or more. If the gel fraction is too low, foreign matter may adhere to the adhesive exposed at the end face, or the chip may be stuck. As will be described in detail later, the larger the gel fraction of the adhesive layer 21, the smaller the absolute value of the minimum load w of the load curve and the displacement amount d of the unload curve of the cut surface (end surface) by laser processing tend to be. The gel fraction of the pressure-sensitive adhesive layer 21 is preferably 30% or more, more preferably 35% or more, further preferably 40% or more, and may be 45% or more.

The gel fraction of the binder can be determined as an insoluble component with respect to a solvent such as ethyl acetate, and specifically, as a weight fraction (unit: weight%) of an insoluble component after the binder is immersed in ethyl acetate at 23 ℃ for 7 days with respect to a sample before the immersion. In general, the gel fraction of a polymer is equivalent to the degree of crosslinking, and the more crosslinking moieties in a polymer, the greater the gel fraction becomes. The gel fraction (the amount of the introduced crosslinked structure) can be adjusted to a desired range by the method of introducing the crosslinked structure, the kind and amount of the crosslinking agent, and the like.

When the adhesive is photocurable, the gel fraction of the adhesive layer 21 after photocuring is preferably 70% or more. The gel fraction of the pressure-sensitive adhesive layer 21 after photocuring is preferably 1.2 times or more, and may be 1.3 times or more, 1.4 times or more, or 1.5 times or more, the gel fraction before photocuring.

< second adhesive layer >

The second adhesive layer 22 is an adhesive layer in which an adhesive is formed in a layered state. In the optical laminate shown in fig. 3 to 5, the second pressure-sensitive adhesive layer 22 is used for bonding the optical film 10 to the image display unit 70.

The second adhesive layer is preferably transparent and has a low absorption of visible light. The total light transmittance of the adhesive layer 22 is preferably 85% or more, more preferably 90% or more. The haze of the pressure-sensitive adhesive layer 22 is preferably 2% or less, and more preferably 1% or less.

The adhesive constituting the adhesive layer 22 is not particularly limited, and adhesives having various polymers as base polymers can be appropriately selected and used. As described above, the adhesive constituting the second adhesive layer 22 is preferably an acrylic adhesive containing an acrylic polymer as a base polymer.

The thickness of the adhesive layer 22 is not particularly limited. The second adhesive layer 22 is not required to have the same thickness and flexibility as those of the first adhesive layer 21. The thickness of the adhesive layer 22 is, for example, about 3 to 50 μm, and may be 5 to 35 μm or 10 to 25 μm. The storage modulus G' of the pressure-sensitive adhesive layer 22 at 25 ℃ is, for example, about 0.02 to 5 MPa. The adhesive layer 22 is thinner than the adhesive layer 22, and is less likely to cause adhesion and blocking of foreign matter due to the adhesive exposed at the end face. Therefore, the adhesive property of the second adhesive layer end face of the second adhesive layer is not particularly limited.

[ dicing of optical laminate ]

The mother substrate of the optical laminate is formed by laminating the components of the optical laminate via the adhesive layer. The lamination may be either a roll-to-roll method or a batch method. A combination of roll-to-roll and batch methods may also be used. For example, the pressure-sensitive adhesive layers 21 and 21 (and the release films 41 and 42) may be laminated on both sides of the optical film 10 by a roll-to-roll method to produce a polarizing plate with a pressure-sensitive adhesive on both sides, and after the polarizing plate is cut into a sheet shape, the pressure-sensitive adhesive layer 22 of the polarizing plate with a pressure-sensitive adhesive on both sides may be attached to the image display unit 70 formed into a sheet shape. The lamination of the image display units may also be implemented using a roll-to-roll method.

The optical laminate chip is obtained by cutting out a single piece product having a predetermined size from a mother substrate of the optical laminate. The shape of the chip is not particularly limited, and may be a rectangle, a polygon, a rounded polygon, a circle, or the like, or may be a shape having a notch (cut) on the outer periphery.

As described above, since the chip of the optical laminate exhibits predetermined physical properties in the nanoindentation measurement of the end face of the pressure-sensitive adhesive layer 21, adhesion and blocking of foreign substances to the end face of the chip are less likely to occur, and the chip has excellent handleability.

The method for cutting the optical laminate is not particularly limited, and examples thereof include: a method of punching with a thomson knife or the like; a method using a cutter such as a circular cutter or a dish cutter; a method using a laser, water pressure, or the like. The laser-based cutting is preferable in that the adhesive on the cut surface and the vicinity thereof can be partially cured. When the adhesive layer 21 is formed of a photocurable adhesive, the absolute value of the minimum load w of the load curve of the end face and the displacement amount d of the unload curve can be reduced by photocuring the end face of the adhesive layer 21 while cutting the optical laminate with an ultraviolet laser.

The ultraviolet laser is not particularly limited as long as it can irradiate a laser beam having a wavelength of 400nm or less, and is preferably a third harmonic wave (wavelength of 355nm) of a YAG laser in terms of high output and excellent workability. The laser power is, for example, about 0.1 to 50W.

The laser beam may be irradiated from any surface of the optical layered body. The constituent member disposed on the laser irradiation surface preferably has laser light absorbability. For example, when the optical laminate 101 shown in fig. 1 is cut with an ultraviolet laser, the

release films

41 and 43 disposed on the laser-irradiated surface are preferably made to have ultraviolet absorbability. When the optical laminate 102 shown in fig. 2 is irradiated with an ultraviolet laser from the optical film 10 side and cut, the transparent film 15 is preferably made to have ultraviolet absorbability. When the optical laminate 104 shown in fig. 4 is irradiated with an ultraviolet laser from the image display unit 70 side and cut, the substrate 71 is preferably made to have ultraviolet absorbability.

In order to impart ultraviolet absorbability to the film or the pressure-sensitive adhesive layer, an ultraviolet absorber may be added to the resin material. Alternatively, a resin material having ultraviolet absorptivity such as a polyimide film or polyethylene naphthalate may be used. For example, in the optical

layered bodies

104 and 105 shown in fig. 4 and 5, if the substrate 71 of the image display unit 70 is a polyimide film, the polyimide film is thermally released and vaporized by irradiation with an ultraviolet laser beam from the image display unit 70 side, and therefore the second pressure-sensitive adhesive layer 22, the optical film 10, the first pressure-sensitive adhesive layer 21, and the release film 41 or the cover window 80 provided above the image display unit 70 are blown away together with the vapor, and a through hole penetrating the optical layered body is formed. The optical laminate is moved relative to the laser light source, thereby forming a scribe line formed by connecting the through holes. By forming dicing lines along the outer periphery of the chip shape, a chip of a predetermined shape is cut out.

Members other than the laser irradiation surface may also have ultraviolet absorbability. For example, if the pressure-sensitive adhesive layer 21 has ultraviolet absorptivity, the pressure-sensitive adhesive layer 21 absorbs ultraviolet laser light, and therefore, even when the pressure-sensitive adhesive layer 21 is thick and flexible, good workability is exhibited. Further, if the pressure-sensitive adhesive layer 21 has ultraviolet absorbability, the release film 41 and the cover window 80 temporarily attached to the pressure-sensitive adhesive layer 21 are also processed with the momentum of heating and vaporization during processing, and therefore peeling of the adherend and mixing of bubbles around the laser-irradiated region can be suppressed.

In the chip of the optical laminate subjected to the dicing process with the laser, the adhesive layer 21 has locally different adhesive behavior in the laser-irradiated region at the end face and the vicinity thereof. The adhesive layer 21 is preferably: in the in-plane center portion, the absolute value of the minimum load w of the load curve and the displacement amount d of the unload curve are large, and in the end face cut by laser irradiation, the absolute value of the minimum load w of the load curve and the displacement amount d of the unload curve are small.

In the cut surface by laser irradiation, plasticization occurs due to molecular breakage. On the other hand, since active species such as radicals are generated by laser irradiation, curing action is also caused by generation of a crosslinked structure between polymer chains. When the gel fraction of the adhesive is small, molecular chains having a low molecular weight are generated in large amounts without being crosslinked due to molecular cleavage, and therefore, the plasticizing effect tends to be large. On the other hand, even if the molecular chain is broken, since the low molecular weight component is not generated as long as the crosslinked structure remains, when the gel fraction (crosslinking degree) of the adhesive is large, the influence of curing by a radical reaction or the like tends to be larger than the plasticizing by the molecular breaking. Therefore, there is a tendency that: the larger the gel fraction of the adhesive layer 21 is, the smaller the absolute value of the minimum load w of the load curve of the laser-machined end face and the displacement amount d of the unload curve become.

When the adhesive has photocurability, photocuring of the adhesive by laser irradiation also affects the characteristics of the cut surface. In particular, when the adhesive layer 21 formed of a photocurable adhesive composition containing a photocurable monomer and a photopolymerization initiator is cut by irradiation with ultraviolet laser light, the adhesive layer 21 is partially photocured in the laser-irradiated region of the end face and the vicinity thereof. Therefore, the absolute value of the minimum load w of the load curve of the laser-machined end face and the displacement d of the unload curve tend to be small.

As described above, in the chip of the optical laminate, the minimum load w of the load curve is preferably-0.2 μ N or less, more preferably-0.25 μ N or less, at the in-plane central portion of the pressure-sensitive adhesive layer 21. The minimum load of the load curve at the end face of the pressure-sensitive adhesive layer 21 is preferably-0.2 μ N or more, more preferably-0.15 μ N or more, still more preferably-0.1 μ N or more, and particularly preferably-0.07 μ N or more. The minimum load of the load curve at the end face of the pressure-sensitive adhesive layer 21 is preferably 0.3 times or less, more preferably 0.2 times or less, and still more preferably 0.1 times or less the minimum load of the load curve at the in-plane center portion. In other words, in the optical laminate (mother substrate) before dicing into chips, it is preferable that: the minimum load of the load curve of the pressure-sensitive adhesive layer 21 is-0.2 μ N or less, and when the dicing process is performed by irradiating ultraviolet laser light, the absolute value of the minimum load of the load curve of the dicing surface becomes 0.3 times or less.

In the chip of the optical laminate, the displacement d of the relief curve in the in-plane center portion of the pressure-sensitive adhesive layer 21 is preferably 10 μm or more, more preferably 12 μm or more, and still more preferably 14 μm or more. The displacement amount of the relief curve at the end face of the pressure-sensitive adhesive layer 21 is preferably 8 μm or less, more preferably 7 μm or less, further preferably 6 μm or less, and particularly preferably 5 μm or less. The displacement amount of the relief curve of the end face of the adhesive layer 21 is preferably 0.5 times or less, more preferably 0.4 times or less, and still more preferably 0.3 times or less the displacement amount of the relief curve of the in-plane center portion. In other words, in the optical laminate (mother substrate) before dicing into chips, it is preferable that: the displacement amount of the relief curve of the adhesive layer 21 is 10 μm or more, and when the cutting is performed by irradiating the ultraviolet laser, the displacement amount of the relief curve of the cut surface becomes 0.5 times or less.

In the chip of the optical laminate, the indentation modulus is preferably 0.05 to 0.3MPa, and more preferably 0.1 to 0.25MPa, in the center portion in the plane of the pressure-sensitive adhesive layer 21. The indentation modulus of the end face of the pressure-sensitive adhesive layer 21 is preferably 0.3MPa or more, more preferably 0.35MPa or more, and still more preferably 0.4MPa or more. The indentation modulus of the end face of the adhesive layer 21 is preferably 1.5 to 10 times, more preferably 2 to 8 times, and still more preferably 2.5 to 7 times the indentation modulus of the center portion in the plane. In other words, in the optical laminate (mother substrate) before dicing into chips, it is preferable that: the adhesive layer 21 has an indentation modulus of 0.05 to 0.3MPa, and when the cutting is performed by irradiating ultraviolet laser, the indentation modulus of the cut surface is 1.5 to 10 times.

As described above, when the gel fraction of the pressure-sensitive adhesive layer 21 is high and the pressure-sensitive adhesive has photocurability, the following tendency is present: as compared with the influence of plasticization due to molecular fracture at the time of laser processing, the influence of solidification becomes large, the absolute value of the minimum load of the load curve and the displacement amount of the unload curve based on the cut surface at the time of laser processing become small, and the indentation modulus becomes large.

[ formation of display device ]

The optical laminate processed into a chip shape may further include other members laminated thereon as necessary. For example, in the chip of the optical laminate 104 shown in fig. 4, the image display device can be formed by peeling off the release film 41 temporarily attached to the pressure-sensitive adhesive layer 21 and attaching an adherend such as the cover window 80.

After the cover window 80 is attached to the first pressure-sensitive adhesive layer 21, a treatment such as heating, pressurization, or depressurization may be performed to remove air bubbles at the attachment interface or in the vicinity of the print step. For the purpose of suppressing bubble Delay (Delay bubble), etc., autoclave treatment may be performed. When the pressure-sensitive adhesive layer 21 is a photocurable pressure-sensitive adhesive, the cover window 80 may be attached to the pressure-sensitive adhesive layer 21, and then the pressure-sensitive adhesive may be photocured. As described above, when the pressure-sensitive adhesive layer 21 is cut with an ultraviolet laser, the pressure-sensitive adhesive on the end face may be partially photo-cured, but the pressure-sensitive adhesive in the other region may be uncured. By photo-curing the pressure-sensitive adhesive layer 21, the adhesion reliability thereof to an adherend such as the cover window 80 can be improved.

Examples

The present invention will be described in more detail below by way of examples and comparative examples, but the present invention is not limited to these examples.

[ production of adhesive sheet ]

Production example 1

(preparation of base Polymer)

In a reaction vessel, while 139 parts by weight of ethyl acetate was charged, 64 parts by weight of Butyl Acrylate (BA), 6 parts by weight of cyclohexyl acrylate (CHA), 10 parts by weight of isostearyl acrylate (ISA), 5 parts by weight of N-vinylpyrrolidone (NVP), 15 parts by weight of 4-hydroxybutyl acrylate (4HBA), and 0.2 part by weight of Azobisisobutyronitrile (AIBN) as a thermal polymerization initiator were charged, and the mixture was stirred at 23 ℃ for 1 hour under a nitrogen atmosphere to replace nitrogen. Thereafter, the reaction mixture was reacted at 65 ℃ for 5 hours and then at 70 ℃ for 2 hours to prepare an acrylic base polymer solution. The weight average molecular weight of the resulting polymer was 45 ten thousand.

(preparation of adhesive composition and preparation of adhesive sheet)

To a solution of the base polymer, 0.27 part by weight of trimethylolpropane xylylene diisocyanate ("TAKENATE D110N" manufactured by Mitsui chemical corporation) as an isocyanate-based crosslinking agent, 2.5 parts by weight of polypropylene glycol (#400) diacrylate ("APG 400" manufactured by Ningmura chemical industry Co., Ltd.) as a polyfunctional acrylate, 2.2 parts by weight of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate ("KAYARAD DPHA" manufactured by Nippon chemical corporation), 0.22 part by weight of Ominirad 184 "manufactured by IRM Resins as a photopolymerization initiator, and 0.33 part by weight of KBM-403" manufactured by shin-Etsu chemical industry Co., Ltd.) as a silane coupling agent were added and uniformly mixed to prepare an adhesive composition (solution). The adhesive composition was applied to the release-treated surface of a separator having a thickness of 75 μm so that the thickness after drying became 150 μm, and the mixture was dried at 130 ℃ for 3 minutes to remove the solvent, and then the release-treated surface of another separator was superimposed on the adhesive layer, thereby obtaining an adhesive sheet a having separators temporarily attached to both surfaces thereof.

Production example 2

(preparation of base Polymer)

In the reaction vessel, 139 parts by weight of ethyl acetate was charged, and at the same time, a monomer component of BA: 60 parts by weight, CHA: 6 parts by weight, ISA: 1 part by weight, NVP: 18 parts by weight and 4 HBA: 15 parts by weight, and AIBN as a thermal polymerization initiator: 0.2 part by weight, and stirred at 23 ℃ for 1 hour under a nitrogen atmosphere, followed by nitrogen substitution. Thereafter, the reaction mixture was reacted at 65 ℃ for 5 hours and then at 70 ℃ for 2 hours to prepare an acrylic polymer solution. The weight average molecular weight of the resulting polymer was 30 ten thousand.

(preparation of adhesive composition and preparation of adhesive sheet)

To a solution of the base polymer, 0.27 part by weight of "TAKENATE D110N" as an isocyanate-based crosslinking agent, 1 part by weight of "APG 400" and 2.2 parts by weight of "KAYARAD DPHA" as multifunctional acrylates, "omniirad 651" 0.22 part by weight of IRM Resins as a photopolymerization initiator, "Tinuvin 384-2" 0.02 part by weight of BASF as an ultraviolet absorber, and "KBM-403" 0.33 part by weight of shin-Etsu chemical company as a silane coupling agent were added, and uniformly mixed to prepare an adhesive composition (solution). Using this adhesive composition, an adhesive sheet B having a thickness of 150 μm was produced in the same manner as in production example 1.

< preparation example 3>

In the preparation of the adhesive composition, the amount of the isocyanate-based crosslinking agent (TAKENATE D110N) was changed to 0.05 parts by weight, the amount of "APG 400" was changed to 3 parts by weight, and the amount of "KAYARAD DPHA" was changed to 1 part by weight. Except for this, a pressure-sensitive adhesive sheet C having a thickness of 150 μm was produced in the same manner as in production example 2.

Production example 4

In the preparation of the adhesive composition, the amount of the isocyanate-based crosslinking agent (TAKENATE D110N) was changed to 0.08 parts by weight, and the polyfunctional acrylate and the photopolymerization initiator were not added. Except for this, a psa sheet D with a thickness of 150 μm was produced in the same manner as in production example 2.

< production example 5>

97 parts by weight of Butyl Acrylate (BA) and 3 parts by weight of Acrylic Acid (AA) were polymerized in the presence of a thermal polymerization initiator (AIBN) using ethyl acetate as a solvent to obtain a polymer solution having a weight average molecular weight (Mw) of 110 ten thousand. To this solution, 0.8 parts by weight of trimethylolpropane toluene diisocyanate ("CORONATE L" manufactured by tokyo corporation) as an isocyanate crosslinking agent and 0.1 parts by weight of a silane coupling agent ("KBM-403" manufactured by shin-Etsu chemical corporation) were added and mixed uniformly with respect to 100 parts by weight of the polymer to prepare an adhesive composition (solution). The composition was applied to the release-treated surface of a separator having a thickness of 38 μm so that the thickness after drying became 20 μm, and after drying at 100 ℃ for 3 minutes to remove the solvent, the release-treated surface of another separator was superimposed on the pressure-sensitive adhesive layer, and heated at 50 ℃ for 48 hours to perform a crosslinking treatment, thereby obtaining a pressure-sensitive adhesive sheet P having a thickness of 30 μm with separators temporarily attached to both surfaces thereof.

[ production of laminate A ]

An adhesive sheet a was attached to one surface (hard coat layer) of a polarizing plate having a thickness of about 75 μm using a roll laminator, and an adhesive sheet P was attached to the other surface, to obtain a long polarizing plate with adhesive on both sides. As the polarizing plate, a polarizing plate was used in which a cellulose triacetate film (32 μm) having a hard coat layer was attached to one surface of a polarizer made of a stretched polyvinyl alcohol film having a thickness of 12 μm and impregnated with iodine, and a cellulose triacetate film (31 μm) having a retardation layer applied thereto was attached to the other surface of the polarizer.

The release film on the surface of the pressure-sensitive adhesive sheet P was peeled off, and a polyimide film (KAPTON EN100 manufactured by du pont, donnay) having a thickness of 25 μm was bonded to the surface of the pressure-sensitive adhesive sheet P by roll-to-roll to obtain a laminate of polyimide film (25 μm)/pressure-sensitive adhesive sheet P (30 μm)/polarizing plate (75 μm)/pressure-sensitive adhesive sheet a (150 μm))/separator (75 μm).

[ production of laminates B to D ]

In the same manner as in the production of the laminate a except that the adhesive sheets B to D were used instead of the adhesive sheet a, an optical laminate was produced in which a polyimide film was adhered to one surface of a polarizing plate via an adhesive sheet P having a thickness of 30 μm, and an adhesive sheet having a thickness of 150 μm was provided on the other surface of the polarizing plate, and a release film was temporarily adhered thereto.

[ dicing of optical laminate ]

The optical laminate was cut into a rounded rectangle of 40mm × 60mm (radius of curvature of corner portion: 7mm) by two methods.

< cutting by cutter >

The optical laminate was punched out using a thomson knife.

< cutting by ultraviolet laser >

The optical laminate was cut out by irradiating the polyimide film side with a YAG third harmonic ultraviolet laser (wavelength: 355nm, frequency: 40Hz, output: 0.4W) while moving at a scanning speed of 10 mm/sec.

[ evaluation ]

< gel fraction of adhesive >

About 1g of the adhesive was collected from the adhesive sheets A to D, wrapped with a porous polytetrafluoroethylene film (NTF-1122, manufactured by Rindong electrician Co., Ltd.) cut into a size of 100mm X100 mm and having a pore diameter of 0.2 μm, and the wrapping opening was tied with a kite string. The weight (B) of the adhesive sample was calculated by subtracting the total weight (A) of the porous polytetrafluoroethylene film and the kite string measured in advance from the weight of the sample. The adhesive sample wrapped with the porous polytetrafluoroethylene membrane was immersed in about 50mL of ethyl acetate at 23 ℃ for 7 days to elute the sol component of the adhesive out of the porous polytetrafluoroethylene membrane. After the impregnation, the adhesive coated with the porous polytetrafluoroethylene film was taken out, dried at 130 ℃ for 2 hours, and naturally cooled for about 20 minutes, and then the dry weight (C) was measured. The gel fraction of the adhesive is calculated by the following formula.

Gel fraction (%) (100X (C-A)/B

The adhesive sheets A to C were irradiated with a cumulative light amount of about 3000mJ/cm²The gel fraction was also measured with respect to the adhesive obtained by photocuring the composition with ultraviolet rays.

< nanoindentation measurement of end face of adhesive layer >

The laminate of examples and comparative examples was cut at a position 3mm from the end face to prepare a sample for measurement. The sample was fixed on a stage of a nanoindenter system ("TI 950 TriboIndenter" manufactured by hysetron) so that the end face of the laminate became a measurement surface. The test was carried out at a load speed of 1000nN/s up to a depth of 3000nm under an environment of a temperature of 25 ℃ and a relative humidity of 50% by using a Conical-thermal indenter (radius of curvature of the tip: 10 μm), and at an unload speed of 1000 nN/s. And (4) calculating the minimum load, the indentation modulus and the displacement of the unloading curve of the load curve according to the obtained load-displacement curve. The indentation modulus E is calculated from the slope of the unloading curve, the projected contact area a of the indenter, and the circumferential ratio pi using the following equation.

E＝(S√π)/(2√A)

< tackiness on end face >

A PET film having a thickness of 50 μm and not subjected to surface treatment was cut into pieces having a size of 5mm X10 mm, and placed on a horizontal table. The end face (cut face) of the optical laminate was pressed against the surface of the PET film and then lifted upward, and the adhesiveness of the end face was evaluated based on the state of adhesion between the end face of the optical laminate and the PET film in this case according to the following criteria.

Good component: the end face of the optical laminate was not bonded to the PET film, and the optical laminate could be pulled up without resistance

And (delta): when the optical laminate was pulled up, the PET film was not pulled up, but the peel resistance between the end face of the optical laminate and the PET film was felt

X: the end face of the laminate was kept in a state bonded to the PET film, and the PET film was lifted up

< pickup test >

The optical laminate of the single sheet was stacked by 10 sheets so that the surface on the polyimide film side was the lower side. The laminated body is sucked by bringing a suction pad into contact with the upper side (surface on the release film side) of the stacked adhesive sheets, and the laminated body stacked uppermost is lifted up by the suction pad and picked up. It was confirmed whether only 1 optical laminate could be picked up, and the pickup performance was evaluated according to the following criteria.

Good component: only the picked-up 1 laminated body was lifted up

And (delta): the laminate immediately below the picked-up laminate was lifted up, but thereafter, separation occurred, and only 1 sheet could be picked up

X: the 2 or more laminated bodies are lifted up as one body, and cannot be picked up one by one

The gel fractions (before and after photocuring) of the adhesive, the method for dicing the adhesive into chips, and the evaluation results of the adhesive in each of the optical laminates obtained above are shown in table 1.

[ Table 1]

When the chips were cut out by die cutting, laminate a and laminate B had tackiness on the cut surfaces and had poor pickup, but when the chips were cut out by ultraviolet laser processing, the end surfaces had no tackiness and exhibited good pickup. In the laminate a and the laminate B, the laser-processed end face has a larger elastic modulus than the die-cut processed end face, and the absolute value of the minimum load of the load curve and the displacement amount of the unload curve become smaller. From these results, it can be considered that: in the chips of laminate a and laminate B, the end faces are cured by laser processing, and therefore, the stickiness of the end faces of the adhesive layer is reduced.

In the laminate C using the adhesive having a small gel fraction before photocuring, both when the chips were cut out by die cutting and when the chips were cut out by laser processing, tackiness existed on the cut surface, and pickup failure occurred. In addition, the laminate D using a binder having no photocurability also has a problem in pickup properties.

Therefore, the following steps are carried out: the laminate C had an uncured end face even when cut with an ultraviolet laser although the adhesive was photocurable, but when cut with a laser, a decrease in elastic modulus and an increase in the displacement amount (stringiness) of the unload curve were observed, and plasticization occurred. It can be considered that: in the laminate C, since the gel fraction of the binder is small, the influence of molecular breakage (generation of low-molecular-weight components) by laser irradiation becomes a dominant factor, which is a cause of softening of the binder.

In the laminate D, the adhesive does not have photocurability, but when the chips are cut out by laser processing, the displacement amount of the relief curve becomes smaller than that in the case where the chips are cut out by die cutting. From a comparison of laminate C and laminate D, it can be seen that: in order to obtain a laminate with no stickiness on the end faces of the adhesive layer by laser processing, it is important that: not only the adhesive is photocurable, but also the gel fraction of the adhesive is large.

Description of the reference numerals

10 optical film (polarizing plate)

11 polarizing element

13. 15 transparent film

21. 22 adhesive layer

41. 42, 43 Release film

70 image display unit (organic EL unit)

71 base plate (polyimide film)

80 cover window

101. 102, 103, 104, 105 optical laminate

Claims

1. An optical laminate comprising: a first adhesive layer having a first major surface and a second major surface; a first adherend attached to the first main surface of the first pressure-sensitive adhesive layer; and a second adherend attached to the second main surface of the first pressure-sensitive adhesive layer,

The minimum load of a load curve measured by nanoindentation on the end face of the first adhesive layer is-0.2 [ mu ] N or more, and the displacement of an unload curve is 8 [ mu ] m or less.

2. The optical laminate according to claim 1, wherein the gel fraction of the adhesive in the in-plane central portion of the first adhesive layer is 25% or more.

3. The optical laminate according to claim 1 or 2, wherein the minimum load of the load curve of the first adhesive layer in the in-plane central portion measured by nano-indentation is 0.3 times or less the minimum load of the load curve of the end face.

4. The optical laminate according to any one of claims 1 to 3, wherein the first adhesive layer has a displacement amount of an unloading curve in an in-plane central portion as measured by nanoindentation that is 0.5 times or less the displacement amount of an unloading curve of an end face.

5. An optical laminate comprising: a first adhesive layer having a first major surface and a second major surface; a first adherend attached to the first main surface of the first pressure-sensitive adhesive layer; and a second adherend attached to the second main surface of the first pressure-sensitive adhesive layer,

the gel fraction of the first adhesive layer is 25% or more,

When the first adhesive layer is cut using an ultraviolet laser,

the minimum load of the load curve of the adhesive in the cut surface is 0.3 times or less of that before the cutting,

the displacement of the unloading curve of the adhesive in the cutting processing surface is less than 0.5 times of that before cutting processing,

the indentation modulus of the adhesive in the cutting processing surface is 1.5-10 times of that before cutting processing.

6. The optical laminate according to any one of claims 1 to 5, wherein the adhesive constituting the first adhesive layer comprises a base polymer,

the adhesive contains a monomer or oligomer having a photocurable functional group, or a compound having a photocurable functional group is bonded to the base polymer, and the adhesive has photocurability.

7. The optical stack of claim 6, wherein the adhesive further comprises a photopolymerization initiator.

8. The optical laminate according to claim 6 or 7, wherein the gel fraction of the adhesive in the in-plane central portion of the first adhesive layer after photocuring is 70% or more.

9. The optical laminate according to any one of claims 6 to 8, wherein the gel fraction of the adhesive in the in-plane central portion of the first adhesive layer after photocuring is 1.2 times or more the gel fraction before photocuring.

10. The optical stack according to any one of claims 1 to 9, wherein the first adhesive layer comprises an ultraviolet absorber.

11. The optical laminate according to any one of claims 1 to 10, wherein the thickness of the first adhesive layer is 30 μm or more.

12. The optical laminate according to any one of claims 1 to 11, wherein the second adherend has a polarizing plate in contact with the first pressure-sensitive adhesive layer.

13. The optical laminate according to claim 12, wherein the second adherend further comprises an image display unit attached to the polarizing plate via a second adhesive layer.

14. The optical stack of claim 13, wherein the image display unit is an organic EL unit.

15. The optical stack of claim 13 or 14, wherein the image display unit comprises a polyimide film.

16. The optical laminate according to any one of claims 1 to 15, wherein the first adherend is a release film which is detachably attached to the first pressure-sensitive adhesive layer.

17. A method for producing an optical laminate according to any one of claims 1 to 16,

A mother substrate for preparing an optical laminate, the optical laminate comprising: a first pressure-sensitive adhesive layer having a first main surface and a second main surface, a first adherend attached to the first main surface of the first pressure-sensitive adhesive layer, and a second adherend attached to the second main surface of the first pressure-sensitive adhesive layer,

the optical laminate is cut into chips having a size smaller than that of the mother substrate by irradiating the mother substrate with an ultraviolet laser beam and cutting the optical laminate.