JP7561826B2 - How to cut composite materials - Google Patents

Description

The present invention relates to a method for dividing a composite material in which a resin optical functional layer (e.g., a polarizing film) is laminated on one side of a brittle material layer and a resin protective layer (e.g., a protective film) is laminated on the other side of the brittle material layer. In particular, the present invention relates to a method capable of dividing a composite material without causing cracks on the end surface of the brittle material layer.

In recent years, LCD panels have become thinner and more highly detailed, and in order to add variety to interfaces, LCD panels equipped with on-screen touch sensor functions are now being used in a wide range of fields, from mobile phones to information displays.
Recently, from the viewpoint of reducing thickness and weight, liquid crystal panels having in-cell type liquid crystal cells in which a touch sensor is incorporated into the glass substrate of the liquid crystal cell have appeared.

On the other hand, a film-like glass called thin glass is attracting attention as a front panel to be placed on the outermost surface of a liquid crystal panel. Thin glass can be wound into a roll, so it has the advantage of being applicable to a so-called roll-to-roll manufacturing process, and a glass polarizing film integrated with a polarizing film has been proposed (for example, see Patent Document 1).
Glass polarizing film can be used to produce an LCD panel equipped with a touch sensor function simply by bonding it to an in-cell type LCD cell, making the manufacturing process much simpler than that of conventional LCD panels that use tempered glass as a front panel.

A method described in Patent Document 2 has been proposed as a method for cutting a composite material, such as the above-mentioned glass polarizing film, in which a brittle material layer made of glass or the like and an optically functional layer made of a polarizing film or the like are laminated together, into desired shapes and dimensions depending on the application.
The method described in Patent Document 2 is a method for dividing a composite material by irradiating an optical functional layer (resin layer in Patent Document 2) of the composite material with laser light emitted from a laser light source such as a _CO2 laser light source along a planned dividing line of the composite material to remove the resin that forms the optical functional layer, and then irradiating a brittle material layer with laser light (ultrashort pulse laser light) emitted from an ultrashort pulse laser light source along the planned dividing line of the composite material to remove the brittle material that forms the brittle material layer.
The method described in Patent Document 2 has the advantage that no cracks are generated on the end faces of the brittle material layer after cutting.

Here, as in the above-mentioned glass polarizing film, a composite material in which a brittle material layer formed from glass or the like and an optical function layer formed from a polarizing film or the like are laminated is generally shipped with a protective layer such as a protective film laminated on the side of the cut composite piece opposite the side of the brittle material layer on which the optical function layer is laminated. Since it is time-consuming to perform the process of laminating a protective layer for each cut composite piece, there is a need for a method of cutting a composite material in which an optical function layer is laminated on one side of a brittle material layer and a protective layer is laminated on the other side of the brittle material layer all at once in order to eliminate this time and reduce the number of steps.

However, Patent Document 2 does not propose a method for cutting, in one go, a composite material in which an optical functional layer is laminated on one side of a brittle material layer and a protective layer is laminated on the other side of the brittle material layer.

In addition, Non-Patent Document 1 describes that in processing techniques using ultrashort pulse laser light, the filamentation phenomenon of ultrashort pulse laser light is utilized, and a multi-focus optical system or a Bessel beam optical system is applied to an ultrashort pulse laser light source.

International Publication No. 2013/175767 JP 2019-122966 A

John Lopez et al., "Glass Cutting Using Ultrashort Pulsed Bessel Beams," [online], October 2015, International Congress on Applications of Lasers & Electro-Optics (ICALEO), [Retrieved July 8, 2019], Internet (URL: https://www.researchgate.net/publication/284617626_GLASS_CUTTING_USING_ULTRASHORT_PULSED_BESSEL_BEAMS)

The present invention has been made to solve the problems of the conventional technology as described above, and has an objective of providing a method for dividing a composite material in which a resin optical functional layer is laminated on one side of a brittle material layer and a resin protective layer is laminated on the other side of the brittle material layer, the method being capable of dividing a composite material in which no cracks are generated on the end surface of the brittle material layer.

In order to solve the above problems, the present inventors have considered applying the method described in the above-mentioned Patent Document 2.
Specifically, in a composite material in which a resin optical functional layer is laminated on one side of a brittle material layer and a resin protective layer is laminated on the other side of the brittle material layer, a processed groove (first processed groove) is formed in the optical functional layer along the planned dividing line of the composite material by a laser beam oscillated from a _CO2 laser light source, etc., and a processed groove (second processed groove) is formed in the protective layer along the planned dividing line of the composite material by a laser beam oscillated from a _CO2 laser light source, etc. Then, in order to prevent serious thermal deterioration from occurring on the end face of the optical functional layer after dividing (there is less discolored area due to thermal deterioration), it was thought that it would be sufficient to irradiate the brittle material layer along the planned dividing line of the composite material with a laser beam (ultrashort pulse laser beam) oscillated from an ultrashort pulse laser light source through the second processed groove.

However, when the inventors actually conducted tests on the above method, it was found that if the output of the laser light for forming the second groove is small and the depth of the second groove is too small, when the brittle material layer is irradiated with the ultrashort pulse laser light, a processing mark penetrating the brittle material layer in the thickness direction cannot be formed, and the composite cannot be divided. On the other hand, it was found that if the output of the laser light for forming the second groove is too large, the brittle material layer is thermally damaged, and when the brittle material layer is irradiated with the ultrashort pulse laser light, cracks are generated on the end surface of the brittle material layer starting from the thermally damaged area. It was also found that extremely delicate adjustments are required to set the output of the laser light for forming the second groove to an appropriate value so that processing marks can be formed in the brittle material layer and cracks are not generated on the end surface of the brittle material layer, making automation difficult.

Therefore, the inventors conducted further intensive research and discovered that if the second groove is formed so that its width is equal to or greater than the spot diameter at the irradiating position of the ultrashort pulsed laser light on the brittle material layer, it is possible to cut the composite material without causing cracks on the end surface of the brittle material layer, without requiring delicate adjustment of the output of the laser light to form the second groove, and thus completed the present invention.

The present invention has been completed based on the above-mentioned findings of the present inventors.
That is, in order to solve the above-mentioned problems, the present invention provides a method for dividing a composite material in which a resin optical functional layer is laminated on one surface side of a brittle material layer and a resin protective layer is laminated on the other surface side of the brittle material layer, the method including: a processed groove forming step of irradiating a laser beam oscillated from a first laser light source onto the optical functional layer along a planned dividing line of the composite material to remove the resin that forms the optical functional layer, thereby forming a first processed groove along the planned dividing line, and irradiating a laser beam oscillated from a second laser light source onto the protective layer along the planned dividing line to remove the resin that forms the protective layer, thereby forming a second processed groove along the planned dividing line; and after the processed groove forming step, a laser beam oscillated from an ultrashort pulse laser light source is irradiated onto the brittle material along the planned dividing line from the second processed groove side. and a machining mark forming step of irradiating a material layer with brittle material that forms the brittle material layer to form a machining mark along the planned division line, wherein in the machining groove forming step, the resin that forms the protective layer is removed so that the width of the second machining groove is equal to or greater than the spot diameter at the irradiation position of the brittle material layer with the laser light oscillated from the ultrashort pulse laser light source in the machining mark forming step, and in the machining groove forming step, the irradiation position of the laser light oscillated from the second laser light source on the protective layer is shifted in a direction perpendicular to the planned division line, and the laser light is irradiated to the protective layer along the planned division line at each irradiation position, and then the resin that forms the protective layer between each irradiation position is peeled off to form the second machining groove .

According to the method of the present invention, in the groove forming step, the resin forming the optical functional layer and the resin forming the protective layer are removed to form the first groove and the second groove along the planned division line, and then in the mark forming step, the brittle material forming the brittle material layer is removed from the second groove side to form a mark along the same planned division line. The width of the second groove formed in the groove forming step is formed to be equal to or greater than the spot diameter at the irradiation position of the laser light (ultrashort pulse laser light) oscillated from the ultrashort pulse laser light source in the mark forming step. This makes it possible to divide the brittle material layer without causing cracks on the end face of the brittle material layer, as found by the inventors above.
As in the method of the present invention, by making the width of the second processing groove equal to or greater than the spot diameter at the irradiating position of the ultrashort pulse laser light on the brittle material layer, the energy of the ultrashort pulse laser light is less likely to be consumed in removing the resin that forms the protective layer, and is fully used to remove the brittle material that forms the brittle material layer, so that processing marks can be formed in the brittle material layer and cracks can be prevented from occurring on the end face of the brittle material layer.

In the method according to the present invention, "irradiating the optical functional layer with a laser beam along the planned dividing line of the composite" means irradiating the optical functional layer with a laser beam along the planned dividing line when viewed from the thickness direction of the composite (the stacking direction of the optical functional layer, the brittle material layer, and the protective layer). In the method according to the present invention, "irradiating the protective layer with a laser beam along the planned dividing line" means irradiating the protective layer with a laser beam along the planned dividing line when viewed from the thickness direction of the composite (the stacking direction of the optical functional layer, the brittle material layer, and the protective layer). Furthermore, "irradiating the brittle material layer with a laser beam from the second processing groove side along the planned dividing line" means irradiating the protective layer with a laser beam from the second processing groove side along the planned dividing line when viewed from the thickness direction of the composite (the stacking direction of the optical functional layer, the brittle material layer, and the protective layer).
In the method according to the present invention, "irradiating along the planned dividing line" means irradiating on the planned dividing line, or irradiating a position in the vicinity of the planned dividing line parallel to the planned dividing line.
Furthermore, in the method according to the present invention, the "width of the second groove" means the dimension of the bottom of the second groove in a direction perpendicular to the intended dividing line.

In addition, in the method according to the present invention, the types of the first laser light source and the second laser light source used in the processing groove forming process are not particularly limited as long as they can remove the resin with the oscillating laser light. However, it is preferable to use a _CO2 laser light source or a CO laser light source that oscillates a laser light with a wavelength in the infrared range, since it is possible to increase the relative moving speed (processing speed) of the laser light with respect to the composite material. The first laser light source and the second laser light source may be the same type or different types. In addition, the first laser light source and the second laser light source do not necessarily need to be prepared separately, and the first laser light source can also be used as the second laser light source.
When the first laser light source and the second laser light source are prepared separately, the first laser light source is arranged on the optical functional layer side, and the second laser light source is arranged on the protective layer side, and the first laser light source is used to form the first groove in the optical functional layer, and the second laser light source is used to form the second groove in the protective layer. Also, the second laser light source may be used to form the second groove in the protective layer, and the first laser light source may be used to form the first groove in the optical functional layer. Furthermore, the first laser light source and the second laser light source may be used to simultaneously form the first groove and the second groove.
In addition, when the first laser light source is also used as the second laser light source, the first laser light source (second laser light source) can be arranged on the side facing either the optical functional layer or the protective layer, and the first laser light source (second laser light source) can be used to form a first processing groove in the optical functional layer (or form a second processing groove in the protective layer), and then the composite material can be inverted so that the first laser light source (second laser light source) faces the other of the optical functional layer and the protective layer, and the first laser light source (second laser light source) can be used to form a second processing groove in the protective layer (or form the first processing groove in the optical functional layer).

Furthermore, in the method according to the present invention, the processing marks formed in the processing mark forming step can be exemplified by perforated through holes along the planned dividing line as described in Patent Document 2. In this case, the composite material can be divided by applying an external force along the planned dividing line after the processing mark forming step. Examples of the method of applying an external force to the composite material include mechanical breaking (mountain folding), heating the area near the planned dividing line with infrared laser light, applying vibration with an ultrasonic roller, and suction and lifting with a suction cup. When the method of applying an external force to the composite material involves heating the area near the planned dividing line with infrared laser light, the thermal stress generated in the brittle material layer causes a crack to develop along the planned dividing line so as to connect the perforated through holes, and the brittle material layer is divided (cut). In addition, if resin residue remains at the bottom of the first processing groove, after applying an external force as described above to divide the brittle material layer, for example, a mechanical external force may be further applied to the optical function layer to divide the composite material. Even if further external mechanical force is applied to the optical function layer and therefore the brittle material layer, no cracks will occur at the end faces of the brittle material layer because the brittle material layer has already been divided at this point.
In the method according to the present invention, the processing marks formed in the processing mark forming step are not necessarily limited to perforated through holes. In the processing mark forming step, if the relative movement speed between the laser light oscillated from the ultrashort pulse laser light source and the brittle material layer along the planned dividing line is set to be small, or the repetition frequency of the pulse oscillation of the ultrashort pulse laser light source is set to be large, a through hole (long hole) integrally connected along the planned dividing line is formed as the processing mark. In this case, the brittle material layer can be divided without applying an external force along the planned dividing line after the processing mark forming step. However, if a resin residue remains at the bottom of the first processing groove, for example, after dividing the brittle material layer, a mechanical external force may be applied to the optical function layer to divide the composite material.

In the method according to the present invention, in order to make the width of the second processed groove formed in the processed groove forming step equal to or larger than the spot diameter at the irradiation position of the brittle material layer with the laser light (ultrashort pulse laser light) oscillated from the ultrashort pulse laser light source in the processed mark forming step, for example, it is possible to shift the irradiation position of the laser light oscillated from the second laser light source in a direction perpendicular to the planned division line, irradiate the protective layer with the laser light at each irradiation position, and then peel off the resin forming the protective layer present between each irradiation position. If the dimension of the part where this resin is peeled off (the dimension in the direction perpendicular to the planned division line) is equal to or larger than the spot diameter at the irradiation position of the brittle material layer with the ultrashort pulse laser light, the width of the second processed groove can be equal to or larger than the spot diameter at the irradiation position of the brittle material layer with the ultrashort pulse laser light.
Therefore, in the present invention , in the processing groove formation process, the irradiation position of the laser light emitted from the second laser light source onto the protective layer is shifted in a direction perpendicular to the planned division line, and the laser light is irradiated onto the protective layer along the planned division line at each irradiation position, and then the resin forming the protective layer that is present between each of the irradiation positions is peeled off, thereby forming the second processing groove.

According to the above method (hereinafter, appropriately referred to as the "peeling method"), for example, in the groove forming step, the laser light emitted from the second laser light source is irradiated at positions at equal distances in a direction perpendicular to the planned division line based on the planned division line, and the resin forming the protective layer present therebetween is peeled off. As a result, after forming the second groove with the planned division line as the center in the width direction, if the ultrashort pulse laser light is irradiated on the planned division line, the irradiation position of the laser light oscillated from the second laser light source and the irradiation position of the ultrashort pulse laser light will be shifted by 1/2 of the width of the second groove.
Therefore, even if the output of the laser light emitted from the second laser light source is set to a certain level during the processing groove formation process, and the resin forming the protective layer is removed to expose the surface of the brittle material layer and cause some thermal damage, it is difficult for the ultrashort pulse laser light to be irradiated to the same location, and therefore cracks are unlikely to occur on the end surface of the brittle material layer.
The resin forming the protective layer between the irradiation positions can be peeled off by using a known peeling device as appropriate.

The method for making the width of the second groove formed in the groove forming step equal to or larger than the spot diameter of the ultrashort pulsed laser light at the irradiated position on the brittle material layer is not limited to the peeling method used in the present invention .
For example, in the processing groove forming process, the irradiation position of the laser light emitted from the second laser light source onto the protective layer may be sequentially shifted in a direction perpendicular to the planned division line, and the laser light may be irradiated onto the protective layer along the planned division line at each irradiation position to form the second processing groove (hereinafter referred to as the "offset method" as appropriate).
By setting the range for shifting the irradiation position of the laser light emitted from the second laser light source (the range in the direction perpendicular to the planned division line) to be greater than or equal to the spot diameter at the irradiating position of the ultrashort pulsed laser light on the brittle material layer, the width of the second processing groove can be made greater than or equal to the spot diameter at the irradiating position of the ultrashort pulsed laser light on the brittle material layer.

In the present invention, the spot diameter of the ultrashort pulse laser light at the irradiated position on the brittle material layer is set to, for example, 100 μm.
Therefore, in the processing groove forming process, it is preferable to remove the resin forming the protective layer so that the width of the second processing groove is 100 μm or more, and it is more preferable to remove the resin forming the protective layer so that the width of the second processing groove is 150 μm or more.
When the spot diameter at the irradiation position of the brittle material layer with the ultrashort pulse laser light is 100 μm, the spot diameter on the surface of the brittle material layer on the optical function layer side is condensed to, for example, 1.2 μm. When the spot diameter at the irradiation position of the ultrashort pulse laser light with the brittle material layer is 100 μm, the spot diameter at the position corresponding to the surface of the protective layer (the surface opposite to the surface on the brittle material layer side) is, for example, 154 μm.

Preferably, the protective layer comprises a base layer and an adhesive layer arranged on the brittle material layer side, and in the processing groove forming process, the resin forming the protective layer is removed so that a portion of the adhesive layer in the thickness direction remains.

According to the above-mentioned preferred method, in the groove forming process, the resin forming the protective layer is removed so that a portion of the adhesive layer in the thickness direction remains, so that the brittle material layer is less susceptible to thermal damage and cracks are even less likely to occur at the end faces of the brittle material layer.

The adhesive that forms the adhesive layer that the protective layer has can be, for example, an acrylic adhesive. However, in order to prevent the generation of fumes when forming the second processing groove in the protective layer in the processing groove formation process, it is preferable to use a urethane adhesive that is less likely to generate fumes.
That is, preferably, the protective layer includes a base layer and a urethane-based pressure-sensitive adhesive layer disposed on the brittle material layer side.

According to the above-mentioned preferred method, it is possible to prevent the generation of fumes from the adhesive layer of the protective layer in the machining groove formation process. The above-mentioned preferred method is particularly effective when the above-mentioned offset method is applied in the machining groove formation process. That is, when the offset method is applied, compared to when the peeling method is applied, there are more points on the protective layer where the laser light emitted from the second laser light source is irradiated, and therefore fumes are more likely to be generated from the adhesive layer of the protective layer. Therefore, the above-mentioned preferred method capable of preventing the generation of fumes is particularly effective when the offset method is applied.

The method according to the present invention is suitable for use, for example, when the brittle material layer includes glass and the optically functional layer includes a polarizing film.

According to the present invention, a composite material having a resin optical functional layer laminated on one side of a brittle material layer and a resin protective layer laminated on the other side of the brittle material layer can be divided without causing cracks on the end surface of the brittle material layer.

1 is a cross-sectional view showing a schematic configuration of a composite material to which a cutting method according to an embodiment of the present invention is applied. FIG. 2 is an explanatory diagram for explaining a schematic outline of a procedure of a method for dividing a composite material according to one embodiment of the present invention. 1A to 1C are cross-sectional views for explaining an outline of a peeling method in a processed groove forming step. 1 is a plan view for explaining the outline of the procedure of the peeling method and the machining mark forming process in the machining groove forming process when dividing a composite material into four rectangular composite material pieces. FIG. 1A to 1C are cross-sectional views for explaining a schematic outline of the procedure of an offset method in a processed groove forming process. 1 is a plan view for explaining the outline of the offset method and the machining mark forming process in the machining groove forming process when cutting a composite material into four rectangular composite material pieces. FIG. As an example, an example of the results when a peeling method is applied in the groove forming process will be shown. As an example, an example of test conditions and test results when the offset method is applied in the machined groove forming process will be described.

Below, we will explain a method for dividing a composite material according to one embodiment of the present invention, with appropriate reference to the attached drawings.

<Composition of composite material>
First, the configuration of a composite material to which the cutting method according to this embodiment is applied will be described.
FIG. 1 is a cross-sectional view showing a schematic configuration of a composite material to which a cutting method according to the present embodiment is applied.
It should be noted that Fig. 1 is shown for reference purposes only, and that the dimensions, scale, and shapes of the components and other elements shown in the figure may differ from the actual ones. The same applies to the other figures.
1, the composite material 10 has a laminated configuration of a brittle material layer 1, a resin-made optical function layer 2 laminated on one surface side (the lower side in the example shown in FIG. 1) of the brittle material layer 1, and a resin-made protective layer 3 laminated on the other surface side (the upper side in the example shown in FIG. 1) of the brittle material layer 1. The protective layer 3 includes a base layer 3a and a pressure-sensitive adhesive layer 3b disposed on the brittle material layer 1 side.
The cutting method according to this embodiment is a method for cutting the composite material 10 in the thickness direction (the lamination direction of the optical function layer 2, the brittle material layer 1, and the protective layer 3, the vertical direction in FIG. 1, the Z direction).

The brittle material layer 1, the optical functional layer 2, and the protective layer 3 are laminated by any suitable method. For example, the brittle material layer 1, the optical functional layer 2, and the protective layer 3 can be laminated by a so-called roll-to-roll method. For example, the long brittle material layer 1 and the main body of the long optical functional layer 2 (for example, a polarizing film, an adhesive, and a release film constituting the optical functional layer 2, in order from the top in FIG. 1. However, in FIG. 1, the polarizing film, the adhesive, and the release film are omitted) are conveyed in the longitudinal direction, and the brittle material layer 1 and the optical functional layer 2 (the main body of the optical functional layer 2 and the adhesive) are laminated by aligning the longitudinal directions of the layers and bonding them together via an adhesive (not shown). Next, the long laminate of the brittle material layer 1 and the optical functional layer 2 and the base layer 3a of the long protective layer 3 are transported in the longitudinal direction, and are bonded to each other via the adhesive layer 3b so that their longitudinal directions are aligned, thereby laminating the brittle material layer 1, the optical functional layer 2, and the protective layer 3. However, the brittle material layer 1 and the main body of the optical functional layer 2 may be cut into a predetermined shape, and then laminated via an adhesive. Also, the laminate of the brittle material layer 1 and the optical functional layer 2 and the base layer 3a of the protective layer 3 may be cut into a predetermined shape, and then laminated via the adhesive layer 3b.

Examples of the brittle material forming the brittle material layer 1 include glass and single crystal or polycrystalline silicon. Preferably, glass is used.
Glass can be classified according to composition, for example, soda-lime glass, borate glass, aluminosilicate glass, quartz glass, and sapphire glass. Glass can be classified according to alkali content, for example, non-alkali glass and low-alkali glass. The content of alkali metal components (e.g., _Na2O , _K2O , _Li2O ) in glass is preferably 15% by weight or less, more preferably 10% by weight or less.

The thickness of the brittle material layer 1 is preferably 150 μm or less, more preferably 120 μm or less, and even more preferably 100 μm or less. On the other hand, the thickness of the brittle material layer 1 is preferably 30 μm or more, and more preferably 80 μm or more. If the thickness of the brittle material layer 1 is in this range, it becomes possible to laminate it with the optical function layer 2 by roll-to-roll.

When the brittle material forming the brittle material layer 1 is glass, the light transmittance of the brittle material layer 1 at a wavelength of 550 nm is preferably 85% or more. When the brittle material forming the brittle material layer 1 is glass, the refractive index of the brittle material layer 1 at a wavelength of 550 nm is preferably 1.4 to 1.65. When the brittle material forming the brittle material layer 1 is glass, the density of the brittle material layer 1 is preferably 2.3 g/cm ³ to 3.0 g/cm ³ , and more preferably 2.3 g/cm ³ to 2.7 g/cm ³ .

When the brittle material forming the brittle material layer 1 is glass, a commercially available glass plate may be used as is as the brittle material layer 1, or a commercially available glass plate may be polished to the desired thickness and used. Examples of commercially available glass plates include "7059", "1737" and "EAGLE2000" manufactured by Corning Incorporated, "AN100" manufactured by Asahi Glass Co., Ltd., "NA-35" manufactured by NH Techno Glass Co., Ltd., "OA-10G" manufactured by Nippon Electric Glass Co., Ltd., and "D263" or "AF45" manufactured by Schott.

Examples of the main body of the optical functional layer 2 include a single layer film formed from a plastic material such as polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), acrylic resins such as polymethyl methacrylate (PMMA), cyclic olefin polymer (COP), cyclic olefin copolymer (COC), polycarbonate (PC), urethane resin, polyvinyl alcohol (PVA), polyimide (PI), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polystyrene (PS), triacetyl cellulose (TAC), polyethylene naphthalate (PEN), ethylene-vinyl acetate (EVA), polyamide (PA), silicone resin, epoxy resin, liquid crystal polymer, and various resin foams, or a laminate film consisting of multiple layers.

When the main body of the optical functional layer 2 is a laminated film composed of a plurality of layers, various pressure-sensitive adhesives such as acrylic pressure-sensitive adhesives, urethane pressure-sensitive adhesives, and silicone pressure-sensitive adhesives, or adhesives may be interposed between the layers.
Furthermore, a conductive inorganic film such as indium tin oxide (ITO), Ag, Au, or Cu may be formed on the surface of the main body of the optical function layer 2 .
The cutting method according to this embodiment is particularly suitable for use when the main body of the optical functional layer 2 is a polarizing film, a retardation film, or the like used in a display.
The thickness of the main body of the optical functional layer 2 is preferably 20 to 500 μm, and more preferably 50 to 300 μm.

In this embodiment, as described above, the main body of the optical functional layer 2 is a laminated film in which a polarizing film, an adhesive, and a release film are laminated in this order from the top in FIG. 1. The main body of the optical functional layer 2 is laminated with the brittle material layer 1 via an adhesive (not shown). In this embodiment, the combination of the main body of the optical functional layer 2 (polarizing film, adhesive, and release film) and the adhesive is referred to as the optical functional layer 2.

The polarizing film constituting the main body of the optical functional layer 2 has a polarizer and a protective film arranged on at least one side of the polarizer. The thickness of the polarizer is not particularly limited, and an appropriate thickness can be adopted depending on the purpose. The thickness of the polarizer is typically about 1 to 80 μm. In one embodiment, the thickness of the polarizer is preferably 30 μm or less. The polarizer is an iodine-based polarizer. More specifically, the polarizer can be composed of a polyvinyl alcohol-based resin film containing iodine.

Examples of methods for producing a polarizer constituting the above polarizing film include the following methods 1 and 2.
(1) Method 1: A method in which a polyvinyl alcohol-based resin film is stretched and dyed alone.
(2) Method 2: A method in which a laminate (i) having a resin substrate and a polyvinyl alcohol-based resin layer is stretched and dyed.
Method 1 is a well-known and commonly used method in the art, and therefore a detailed description thereof will be omitted.
Method 2 preferably includes a step of stretching and dyeing a laminate (i) having a resin substrate and a polyvinyl alcohol-based resin layer formed on one side of the resin substrate to prepare a polarizer on the resin substrate. The laminate (i) can be formed by applying a coating liquid containing a polyvinyl alcohol-based resin onto a resin substrate and drying the coating liquid. The laminate (i) may also be formed by transferring a polyvinyl alcohol-based resin film onto the resin substrate. Details of Method 2 are described in, for example, JP 2012-73580 A, which is incorporated herein by reference.

The protective film constituting the polarizing film is disposed on one or both sides of the polarizer. As the protective film, a triacetyl cellulose-based film, an acrylic-based film, a cycloolefin-based film, a polyethylene terephthalate-based film, etc. can also be used. The polarizing film may further include a retardation film as appropriate. The retardation film may have any appropriate optical properties and/or mechanical properties depending on the purpose.

The release film constituting the main body of the optical functional layer 2 has the role of protecting the adhesive layer constituting the main body of the optical functional layer 2 until the composite material 10 is put to practical use. Examples of materials constituting the release film include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films, porous materials such as paper, cloth, and nonwoven fabrics, and appropriate thin materials such as nets, foam sheets, metal foils, and laminates of these, but plastic films are preferably used because of their excellent surface smoothness.

For example, a polyester-based adhesive, a polyurethane-based adhesive, a polyvinyl alcohol-based adhesive, or an epoxy-based adhesive can be used as the adhesive constituting the optical functional layer 2. In particular, it is preferable to use an epoxy-based adhesive since good adhesion can be obtained.
When the adhesive is a thermosetting adhesive, it can be heated to cure (solidify) and thus exhibit peel resistance. When the adhesive is a light-curing adhesive such as an ultraviolet-curing adhesive, it can be irradiated with ultraviolet light or other light and thus exhibit peel resistance. Furthermore, when the adhesive is a moisture-curing adhesive, it can be cured by reacting with moisture in the atmosphere and thus exhibit peel resistance even when left alone.
As the adhesive, for example, a commercially available adhesive may be used, or an adhesive solution (or dispersion) may be prepared by dissolving or dispersing various curable resins in a solvent.
The thickness of the adhesive is preferably 10 μm or less, more preferably 1 to 10 μm, further preferably 1 to 8 μm, and particularly preferably 1 to 6 μm.

In this embodiment, the base material layer 3a of the protective layer 3 is laminated to the brittle material layer 1 via the adhesive layer 3b. It is also possible to configure the base material layer 3a of the protective layer 3 with a self-adhesive film and laminate it to the brittle material layer 1 without an adhesive layer, but from the viewpoint of protecting the brittle material layer 1, it is preferable to laminate it to the brittle material layer 1 via the adhesive layer 3b as in this embodiment.
As the base layer 3a, a film material having isotropy or close to isotropy is selected from the viewpoint of inspectability and manageability. Examples of the film material include transparent polymers such as polyester resins such as polyethylene terephthalate film, cellulose resins, acetate resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, and acrylic resins. Among these, polyester resins are preferred. As the base layer 3a, a laminate of one or more film materials can be used, and a stretched product of the film can also be used. The thickness of the base layer 3a is preferably 35 μm to 100 μm or less, and more preferably more than 38 μm to 100 μm or less.

The adhesive for forming the adhesive layer 3b can be appropriately selected from adhesives having a base polymer such as a (meth)acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based polymer, or a rubber-based polymer. From the viewpoints of transparency, weather resistance, heat resistance, etc., an acrylic adhesive having an acrylic polymer as a base polymer is preferable. However, as described later, in order to prevent the generation of fumes when forming the second processing groove 31 in the protective layer 3, it is preferable to use a urethane adhesive having a polyurethane as a base polymer as the adhesive for forming the adhesive layer 3b. The thickness (dry film thickness) of the adhesive layer 3b is determined according to the required adhesive strength. It is usually about 1 to 100 μm, preferably 5 to 50 μm.

<Method of cutting composite material>
A method for dividing the composite material 10 having the above configuration will now be described.
The cutting method according to the present embodiment includes a processing groove forming step and a processing mark forming step. The cutting method according to the present embodiment also includes a composite material cutting step as necessary. Each step will be described below in order.

[Groove formation process]
Fig. 2 is an explanatory diagram for explaining the outline of the procedure of the cutting method according to the present embodiment. Fig. 2(a) and (b) are cross-sectional views showing a processed groove forming step of the cutting method according to the present embodiment. Fig. 2(c) is a cross-sectional view showing a processed mark forming step of the cutting method according to the present embodiment. Fig. 2(d) is a cross-sectional view showing a composite material cutting step of the cutting method according to the present embodiment.
2A, in the groove forming process, the laser light L1 emitted from the first laser light source 20 is irradiated onto the optical function layer 2 along the planned dividing line of the composite material 10 to remove the resin forming the optical function layer 2. As a result, a first groove 21 is formed along the planned dividing line.
2, for convenience, a straight line DL extending in the Y direction is shown as the planned division line out of two orthogonal directions (X direction and Y direction) within the plane of the composite material 10 (within the XY two-dimensional plane), but the present invention is not limited to this, and various planned division lines can be set, for example, a planned division line in which a plurality of straight lines DL extending in the X direction and a plurality of straight lines DL extending in the Y direction are set in a grid pattern. Hereinafter, this straight line DL will be referred to as the "planned division line DL".
The planned dividing line DL can be actually drawn on the composite material 10 as a visually recognizable display, or its coordinates can be input in advance to a control device (not shown) that controls the relative positional relationship between the laser light L1 and the composite material 10 on the XY two-dimensional plane. The planned dividing line DL shown in FIG. 2 is a virtual line whose coordinates are input in advance to the control device and is not actually drawn on the composite material 10. The planned dividing line DL is not limited to a straight line, and may be a curved line. By determining the planned dividing line DL according to the application of the composite material 10, the composite material 10 can be divided into any shape and size according to the application.

In this embodiment, the first laser light source 20 is a _CO2 laser light source that oscillates laser light L1 with a wavelength of 9 to 11 μm in the infrared range.
However, the present invention is not limited to this, and it is also possible to use a CO laser light source that oscillates laser light L1 with a wavelength of 5 μm as the first laser light source 20.
Also, a visible light and ultraviolet (UV) pulsed laser light source can be used as the first laser light source 20. Examples of visible light and UV pulsed laser light sources include those emitting laser light L1 with a wavelength of 532 nm, 355 nm, 349 nm, or 266 nm (high-order harmonics of a solid-state laser light source using Nd:YAG, Nd:YLF, or YVO4 as a medium), an excimer laser light source emitting laser light L1 with a wavelength of 351 nm, 248 nm, 222 nm, 193 nm, or 157 nm, and an F2 laser light source emitting laser light L1 with a wavelength of 157 nm.
It is also possible to use a pulsed laser light source having a wavelength of the oscillated laser light L1 outside the ultraviolet range and a pulse width on the order of femtoseconds or picoseconds as the first laser light source 20. If the laser light L1 oscillated from this pulsed laser light source is used, it is possible to induce ablation processing based on a multiphoton absorption process.
Furthermore, as the first laser light source 20, it is also possible to use a semiconductor laser light source or a fiber laser light source that oscillates laser light L1 with a wavelength in the infrared region.

As an example of irradiating the laser light L1 along the planned dividing line of the composite material 10 (scanning the laser light L1), for example, the sheet-shaped composite material 10 is placed on an XY two-axis stage (not shown) and fixed (for example, by suction), and the XY two-axis stage is driven by a control signal from the control device to change the relative position of the composite material 10 on the XY two-dimensional plane with respect to the laser light L1. It is also possible to fix the position of the composite material 10 and change the position of the laser light L1 irradiated to the composite material 10 on the XY two-dimensional plane by deflecting the laser light L1 oscillated from the first laser light source 20 using a galvanometer mirror or polygon mirror driven by a control signal from the control device. Furthermore, it is also possible to use both the scanning of the composite material 10 using the above-mentioned XY two-axis stage and the scanning of the laser light L1 using a galvanometer mirror or the like in combination.

The oscillation form of the first laser light source 20 may be pulse oscillation or continuous oscillation. The spatial intensity distribution of the laser light L1 may be a Gaussian distribution, or may be shaped into a flat-top distribution using a diffractive optical element (not shown) or the like to suppress thermal damage to the brittle material layer 1, which is not the target of removal by the laser light L1. There are no restrictions on the polarization state of the laser light L1, and it may be any of linear polarization, circular polarization, and random polarization.

By irradiating the optical function layer 2 with the laser light L1 along the planned dividing line DL of the composite material 10, a local temperature rise occurs due to infrared light absorption of the resin irradiated with the laser light L1 among the resins forming the optical function layer 2, and the resin is scattered, and the resin is removed from the composite material 10, and a first processing groove 21 is formed in the composite material 10. In order to prevent the scattered resin removed from the composite material 10 from re-adhering to the composite material 10, it is preferable to provide a dust collection mechanism in the vicinity of the planned dividing line DL. In order to prevent the width of the first processing groove 21 from becoming too large, it is preferable to focus the laser light L1 so that the spot diameter at the irradiation position on the optical function layer 2 (the spot diameter on the surface opposite to the surface on the brittle material layer 1 side of the optical function layer 2) is 300 μm or less, and it is more preferable to focus the laser light L1 so that the spot diameter is 200 μm or less.
The spot diameter of the laser light L1 at the irradiation position on the optical function layer 2 is, for example, about 150 μm, and at this time, the spot diameter on the surface of the optical function layer 2 facing the brittle material layer 1 is condensed to, for example, 30 to 40 μm. As a result, the first processed groove 21 is formed with a width (the dimension of the bottom of the first processed groove 21 in the direction perpendicular to the planned division line DL) of 30 to 40 μm.
The width of the first groove 21 is, for example, 100 μm or less, and preferably 50 μm or less.

According to the findings of the present inventors, in the case of a resin removal method based on a local temperature rise caused by infrared light absorption by a resin irradiated with laser light L1, it is possible to roughly estimate the input energy required to form the first processed groove 21 based on the thickness of the optical functional layer 2, regardless of the type of resin or the layer structure of the optical functional layer 2. Specifically, the input energy required to form the first processed groove 21, which is expressed by the following formula (1), can be estimated based on the thickness of the optical functional layer 2 by the following formula (2).
Input energy [mJ/mm]=average power of laser light L1 [mW]/processing speed [mm/sec] (1)
Input energy [mJ/mm]=0.5×thickness of optical function layer 2 [μm] (2)
The input energy to be actually set is preferably set to 20 to 180% of the input energy estimated by the above formula (2), and more preferably set to 50 to 150%. The reason for providing a margin for the input energy estimated in this way is that it is considered that the input energy required to form the first processing groove 21 will differ depending on the light absorptance (light absorptance at the wavelength of the laser light L1) of the resin forming the optical function layer 2 and the thermal properties such as the melting point and decomposition point of the resin. Specifically, for example, a sample of the composite material 10 to which the cutting method according to this embodiment is applied is prepared, and a preliminary test is performed to form the first processing groove 21 in the optical function layer 2 of this sample with a plurality of input energies within the above preferred range, and an appropriate input energy can be determined.

2(b), in the groove forming step, the protective layer 3 is irradiated with laser light L2 emitted from a second laser light source 30 along the planned dividing line of the composite material 10 to remove the resin forming the protective layer 3. This forms a second groove 31 (see FIG. 2(c)) along the planned dividing line. In this embodiment, a peeling method or an offset method is used to form the second groove 31, the specific details of which will be described later.
In this embodiment, the second processed groove 31 is formed after the first processed groove 21 is formed, but the present invention is not limited to this, and it is also possible to form the first processed groove 21 after forming the second processed groove 31. In addition, as shown in Fig. 2, when the first laser light source 20 and the second laser light source 30 are prepared separately, it is also possible to form the first processed groove 21 and the second processed groove 31 at the same time.

In this embodiment, the second laser light source 30 uses a _CO2 laser light source of the same type as the first laser light source 20. However, the present invention is not limited to this, and other laser light sources such as a CO2 laser light source can be used, as described above for the first laser light source 20. The second laser light source 30 may be the same type as the first laser light source 20, or may be a different type. As a mode in which the laser light L2 is irradiated along the planned division line DL (a mode in which the laser light L2 is relatively scanned), a mode using an XY two-axis stage, a galvanometer mirror, or the like can be adopted, as described above for the laser light L1.
The laser light L2 is focused so that the spot diameter at the irradiation position on the protective layer 3 (the spot diameter on the surface of the protective layer 3 opposite to the surface on the brittle material layer 1 side) is, for example, 120 to 130 μm. As a result, a groove having a width of 20 to 30 μm at the bottom is formed.

The second machining groove 31 is formed so that its width W (see FIG. 2(c)) is greater than or equal to the spot diameter D (see FIG. 2(c)) at the irradiation position of the laser light L3 emitted from the ultrashort pulse laser light source 40 on the brittle material layer 1 in the machining mark formation process described below.
Specifically, the width W of the second groove 31 in this embodiment is preferably 100 μm or more, and more preferably 150 μm or more. The upper limit of the width W of the second groove 31 is, for example, 1000 μm or less, preferably 500 μm or less, and more preferably 300 μm or less.
As described above, the width W of the second groove 31 is preferably 100 μm or more, and is preferably greater than the width of the first groove 21, which is preferably 100 μm or less.

In the example shown in Figure 2, a first laser light source 20 is arranged on the side facing the optical functional layer 2, and a second laser light source 30 separate from the first laser light source 20 is arranged on the side facing the protective layer 3, but the present invention is not limited to this, and it is also possible for the first laser light source 20 to also serve as the second laser light source 30.
When the first laser light source 20 is also used as the second laser light source 30, for example, as shown in Figure 2 (a), the first laser light source 20 (second laser light source 30) is arranged on the side facing the optical functional layer 2, and a first processing groove 21 is formed in the optical functional layer 2 using the first laser light source 20 (second laser light source 30). After that, the composite material 10 is inverted upside down using a known inversion mechanism so that the first laser light source 20 (second laser light source 30) faces the protective layer 3, and a second processing groove 31 is formed in the protective layer 3 using the first laser light source 20 (second laser light source 30). Alternatively, as shown in FIG. 2(b), a first laser light source 20 (second laser light source 30) is disposed on the side facing the protective layer 3, and a second machining groove 31 is formed in the protective layer 3 using the first laser light source 20 (second laser light source 30). After that, the composite material 10 is inverted upside down using a known inversion mechanism so that the first laser light source 20 (second laser light source 30) faces the optical functional layer 2, and the first machining groove 21 is formed in the optical functional layer 2 using the first laser light source 20 (second laser light source 30).

In addition, in the processed groove forming step, as a preferred embodiment, it is also possible to remove the resin forming the optical functional layer 2 so that a part of the optical functional layer 2 in the thickness direction remains as a residue. In addition, in the present embodiment, as a preferred embodiment, the resin forming the protective layer 3 is removed so that a part of the pressure-sensitive adhesive layer 3b of the protective layer 3 in the thickness direction remains as a residue. The thickness of the residue is preferably 1 to 30 μm, and more preferably 1 to 10 μm, for both the optical functional layer 2 and the protective layer 3.
In this way, by removing the resin so that a residue remains, the thermal damage to the brittle material layer 1 is reduced compared to the case where the resin forming the optical functional layer 2 and the protective layer 3 along the planned division line DL is completely removed, and the edge surface of the brittle material layer 1 is less likely to crack, which has the advantage.

[Processing mark formation process]
As shown in Figure 2 (c), in the machining mark formation process, after the machining groove formation process, laser light (ultrashort pulse laser light) L3 oscillated (pulsed) from an ultrashort pulse laser light source 40 is irradiated to the brittle material layer 1 along the planned division line DL from the second machining groove 31 side to remove the brittle material that forms the brittle material layer 1, thereby forming a machining mark 11 along the planned division line DL.
As a manner in which the laser light L3 is irradiated along the planned division line DL (a manner in which the laser light L3 is scanned relatively), the same manner as the manner in which the laser light L1 described above is irradiated along the planned division line DL can be adopted, so detailed explanation will be omitted here.

The brittle material forming the brittle material layer 1 is removed by utilizing the filamentation phenomenon of the laser light L3 emitted from the ultrashort pulse laser light source 40, or by applying a multi-focus optical system (not shown) or a Bessel beam optical system (not shown) to the ultrashort pulse laser light source 40.
In addition, the use of the filamentation phenomenon of ultrashort pulsed laser light and the application of a multi-focus optical system or a Bessel beam optical system to an ultrashort pulsed laser light source are described in Non-Patent Document 1. In addition, Trumpf of Germany sells products related to glass processing in which a multi-focus optical system is applied to an ultrashort pulsed laser light source. As described above, the use of the filamentation phenomenon of ultrashort pulsed laser light and the application of a multi-focus optical system or a Bessel beam optical system to an ultrashort pulsed laser light source are publicly known, and therefore detailed description thereof will be omitted here.

The processing marks 11 formed in the processing mark forming step of this embodiment are perforated through holes along the planned dividing line DL as described in Patent Document 2, for example. The pitch of the through holes along the planned dividing line DL is determined by the repetition frequency of the pulse oscillation and the relative moving speed (processing speed) of the laser light L3 with respect to the composite material 10. In order to perform the composite material dividing step described later simply and stably, the pitch of the through holes is preferably set to 10 μm or less. More preferably, it is set to 5 μm or less. The diameter of the through holes is often 5 μm or less.
However, the processing marks 11 are not limited to perforated through holes along the planned division line DL. If the relative movement speed along the planned division line DL between the laser light L3 oscillated from the ultrashort pulse laser light source 40 and the brittle material layer 1 is set to be low, or the repetition frequency of the pulse oscillation of the ultrashort pulse laser light source 40 is set to be high, a through hole (long hole) that is integrally connected along the planned division line DL is formed as the processing marks 11.

The wavelength of the laser light L3 emitted from the ultrashort pulse laser light source 40 is preferably 500 nm to 2500 nm, which shows high light transmittance when the brittle material forming the brittle material layer 1 is glass. In order to effectively induce a nonlinear optical phenomenon (multiphoton absorption), the pulse width of the laser light L3 is preferably 100 picoseconds or less, and more preferably 50 picoseconds or less. The oscillation form of the laser light L3 may be single pulse oscillation or burst mode multi-pulse oscillation.
As shown in FIG. 2(c), the spot diameter D at the irradiating position of the laser light L3 on the brittle material layer 1 is, for example, 100 μm, and as described above, the width W of the second processing groove 31 is greater than or equal to this spot diameter D.

The method may further include a cleaning step of removing the resin residue forming the protective layer 3 by applying various wet or dry cleaning methods to the second processed groove 31 formed in the processed groove forming step before the processed mark forming step. If the resin residue forming the protective layer 3 is removed in the cleaning step, even if the laser light L3 oscillated from the ultrashort pulse laser light source 40 is irradiated to the brittle material layer 1 from the second processed groove 31 side in the processed mark forming step, the laser light L3 is not affected by the resin residue, and a more appropriate processed mark 11 can be formed in the brittle material layer 1.

[Composite material cutting process]
As shown in Fig. 2(d), in the composite material dividing step, after the processing mark forming step, an external force is applied along the planned dividing line DL to divide the composite material 10. In the example shown in Fig. 2(d), the composite material 10 is divided into composite material pieces 10a and 10b.
The composite dividing step is particularly necessary when the processing marks 11 formed in the processing mark forming step are perforated through holes along the planned dividing line DL, or when the resin forming the optical function layer 2 is removed so that a part of the optical function layer 2 in the thickness direction remains as a residue (residue remains at the bottom of the first processing groove 21). When the processing marks 11 are through holes (long holes) integrally connected along the planned dividing line DL and no residue remains at the bottom of the first processing groove 21, the composite material 10 can be divided at the same time as the processing mark forming step is performed, and therefore the composite dividing step is not necessarily required.
Examples of methods for applying an external force to the composite material 10 include mechanical breaking (mountain folding), heating the area near the intended cutting line DL with infrared laser light, applying vibration with an ultrasonic roller, and suction and lifting with a suction cup.

Below, we will explain in order the peeling method and offset method used to form the second groove 31 in the groove formation process of the dividing method of this embodiment.

(Peeling method)
3A to 3D are cross-sectional views for explaining the outline of the peeling method in the groove forming process. The peeling method is carried out in the order of Fig. 3A, Fig. 3B, and Fig. 3C. Fig. 3C is an enlarged view of the area surrounded by the dashed line C in Fig. 3B.
As shown in Figures 3(a) and 3(b), in the peeling method, the irradiation position of the laser light L2 emitted from the second laser light source 30 on the protective layer 3 is shifted in a direction perpendicular to the planned division line DL (X direction in the example shown in Figure 3), and the laser light L2 is irradiated to the protective layer 3 along the planned division line DL at each irradiation position (position A1 shown in Figure 3(a) and position A2 shown in Figure 3(b). Specifically, in this embodiment, the laser light L2 emitted from the second laser light source 30 is irradiated to positions A1 and A2 that are equidistant in a direction (X direction) perpendicular to the planned division line DL based on the planned division line DL. As a result, processing grooves 31a and 31b are formed at each irradiation position A1 and A2. The distance between the processed grooves 31a, 31b in the X direction (the distance between the irradiation positions A1, A2) is set to be equal to or greater than the spot diameter D (see FIG. 2(c)) at the irradiation position of the ultrashort pulsed laser light L3 on the brittle material layer 1 in the processed mark formation process.
As described above, in the present embodiment, as a preferred aspect, the resin forming the protective layer 3 is removed by irradiating the protective layer 3 with the laser light L2 so that a part of the pressure-sensitive adhesive layer 3b of the protective layer 3 in the thickness direction remains as a residue (see FIG. 3(c)). As described above, the thickness T of the residue is preferably 1 to 30 μm, and more preferably 1 to 10 μm.

Next, as shown in Fig. 3(d), in the peeling method, the resin forming the protective layer 3 present between the irradiation positions A1 and A2 is peeled off to form the second processed groove 31. The resin can be peeled off by appropriately using a known peeling device. As described above, since the separation distance between the processed grooves 31a and 31b is equal to or larger than the spot diameter D of the ultrashort pulsed laser light L3, the width W (see Fig. 2(c)) of the second processed groove 31 is also equal to or larger than the spot diameter D of the ultrashort pulsed laser light L3.
In addition, when the resin forming the protective layer 3 between each of the irradiation positions A1, A2 is peeled off by the peeling method, as can be seen from Figure 3 (c) or (d) , a part of the adhesive layer 3b in the thickness direction will remain as a residue in the vicinity of each of the irradiation positions A1, A2, but in other parts, the entire protective layer 3 including the adhesive layer 3b will peel off, and it is expected that the surface of the brittle material layer 1 will be exposed.

According to the peeling method described above, when the ultrashort pulse laser light L3 is irradiated onto the planned division line DL (see Figure 2 (c)), the irradiation positions A1, A2 of the laser light L2 emitted from the second laser light source 30 and the irradiation position of the ultrashort pulse laser light L3 will be shifted by 1/2 of the width W of the second processing groove 31.
Therefore, even if the output of the laser light L2 emitted from the second laser light source 30 is set to a certain level during the processing groove formation process, and the resin forming the protective layer 3 is removed to expose the surface of the brittle material layer 1 and cause some thermal damage, it is difficult for the ultrashort pulse laser light L3 to be irradiated to the same location, and therefore cracks are unlikely to occur on the end surface of the brittle material layer 1.

4 is a plan view for explaining the outline of the peeling method and the processing mark forming step in the processing groove forming step when dividing the composite material 10 into four rectangular composite material pieces. Figures 4(a) to 4(c) show the outline of the peeling method, and Figure 4(d) shows the outline of the processing mark forming step. In Figure 4, the second laser light source 30 and the ultrashort pulse laser light source 40 are shown in perspective for convenience.
As shown in Fig. 4(a), in the peeling method, the irradiation position of the laser light L2 emitted from the second laser light source 30 on the protective layer 3 is shifted in a direction perpendicular to the planned division line DL, and the laser light L2 is irradiated to the protective layer 3 along the planned division line DL at each irradiation position. Specifically, in the example shown in Fig. 4(a), the laser light L2 is irradiated to a position (position shown by a solid line) shifted inward by 1/2 of the width W (see Fig. 2(c)) of the second processing groove 31 from the planned division line DL. The parts indicated by the symbols 31a and 31b in Fig. 4(a) correspond to the processing grooves 31a and 31b shown in Fig. 3.

Next, in the peeling method, the resin forming the protective layer 3 between each irradiation position is peeled off to form the second processing groove 31. Figure 4(b) shows the resin forming the peeled protective layer 3, and Figure 4(c) shows the composite material 10 after peeling. In the example shown in Figure 4(b), not only is the resin forming the protective layer 3 between each irradiation position (the resin present in the cross-shaped region in Figure 4(b)) peeled off, but also the resin forming the protective layer 3 located outside the irradiation positions is peeled off at the same time.

Next, as shown in FIG. 4D, in the processing mark forming step, the planned division line DL is irradiated with ultrashort pulse laser light L3 oscillated from an ultrashort pulse laser light source 40.
This (or by further performing a composite cutting process) allows the composite to be cut into four rectangular pieces.

(Offset method)
5A to 5D are cross-sectional views for explaining the outline of the offset method in the groove forming process. The offset method is carried out in the order of FIG.
As shown in Fig. 5(a) to (c), in the offset method, the irradiation position of the laser light L2 emitted from the second laser light source 30 on the protective layer 3 is sequentially shifted in a direction perpendicular to the planned division line DL (X direction in the example shown in Fig. 5), and the laser light L2 is irradiated to the protective layer 3 along the planned division line DL at each irradiation position (position B1 shown in Fig. 5(a), position B2 shown in Fig. 5(b), and position B3 shown in Fig. 5(c). Specifically, in this embodiment, the laser light L2 emitted from the second laser light source 30 is sequentially shifted at a predetermined pitch (for example, a pitch of about 30 μm, which is the same size as the spot diameter of the laser light L2) from position B1 to position B3, which are equidistant in a direction perpendicular to the planned division line DL based on the planned division line DL (X direction), and is irradiated to each position. As a result, the width of the processed groove 31c formed at each irradiation position is sequentially increased, and finally, as shown in Fig. 5(d), the second processed groove 31 is formed. By setting the range for shifting the irradiation position of the laser light L2 (the distance between irradiation positions B1, B3) to be greater than or equal to the spot diameter D (see Figure 2(c)) at the irradiation position of the ultrashort pulse laser light L3 on the brittle material layer 1 in the processing mark formation process, the width W (see Figure 2(c)) of the second processing groove 31 can be made greater than or equal to the spot diameter D of the ultrashort pulse laser light L3.

In addition, in a preferred embodiment of the offset method, the protective layer 3 is irradiated with the laser light L2 to remove the resin forming the protective layer 3 so that a part of the adhesive layer 3b of the protective layer 3 in the thickness direction remains as a residue. In particular, when the offset method is applied, the protective layer 3 is irradiated with the laser light L2 oscillated from the second laser light source 30 at more locations than when the peeling method is applied, so that the brittle material layer 1 is more susceptible to thermal damage. Therefore, leaving a part of the adhesive layer 3b in the thickness direction as a residue is particularly effective when the offset method is applied.
Furthermore, when the offset method is applied, compared to when the peeling method is applied, there are more locations on the protective layer 3 that are irradiated with the laser light L2 oscillated from the second laser light source 30, and this makes it easier for fumes to be generated from the adhesive layer 3b of the protective layer 3. Therefore, when the offset method is applied, in order to prevent the generation of fumes, it is preferable that the adhesive layer 3b be a urethane-based adhesive layer.

6 is a plan view for explaining the outline of the offset method and the machining mark forming step in the machining groove forming step when dividing the composite material 10 into four rectangular composite material pieces. Fig. 6(a) shows the outline of the offset method, and Fig. 6(b) shows the outline of the machining mark forming step. In Fig. 6, the second laser light source 30 and the ultrashort pulse laser light source 40 are shown in perspective for convenience.
As shown in Fig. 6(a), in the offset method, the irradiation position of the laser light L2 emitted from the second laser light source 30 on the protective layer 3 is sequentially shifted in a direction perpendicular to the planned division line DL, and the laser light L2 is irradiated to the protective layer 3 along the planned division line DL at each irradiation position. Specifically, in the example shown in Fig. 6(a), the laser light L2 is irradiated to a range of positions (positions shown by solid lines) shifted inward and outward by 1/2 of the width W (see Fig. 2(c)) of the second processed groove 31 from the planned division line DL, so that the width of the processed groove 31c formed at each irradiation position is sequentially increased. As a result, the second processed groove 31 (the area not hatched with diagonal lines in Fig. 6(b)) is formed as shown in Fig. 6(b).

Next, as shown in FIG. 6B, in the processing mark forming step, the planned division line DL is irradiated with ultrashort pulsed laser light L3 oscillated from an ultrashort pulsed laser light source 40.
This (or by further performing a composite cutting process) allows the composite to be cut into four rectangular pieces.

According to the above-described dividing method of the present embodiment, in the cutting groove forming process, the resin forming the optical functional layer 2 and the resin forming the protective layer 3 are removed to form the first cutting groove 21 and the second cutting groove 31 along the planned dividing line DL, and then in the cutting mark forming process, the brittle material forming the brittle material layer 1 is removed from the second cutting groove 31 side to form the cutting mark 11 along the same planned dividing line DL. The second cutting groove 31 formed in the cutting groove forming process is formed so that its width W is equal to or greater than the spot diameter D at the irradiation position of the brittle material layer 1 with the laser light (ultrashort pulse laser light) L3 oscillated from the ultrashort pulse laser light source 40 in the cutting mark forming process, so that the brittle material layer 1 can be divided without causing cracks on the end surface of the brittle material layer 1.

Hereinafter, an example of the results of a test performed to cut the composite material 10 using the cutting method according to this embodiment (Examples 1 to 5) and the cutting methods according to comparative examples (Comparative Examples 1 and 2) will be described.
Fig. 7 shows an example of main test conditions and test results when the peeling method is applied in the groove forming process as an embodiment. Fig. 8 shows an example of main test conditions and test results when the offset method is applied in the groove forming process as an embodiment.

Example 1
[Fabrication of optical functional layer 2]
As a thermoplastic resin substrate, a long amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a glass transition temperature (Tg) of about 75° C. was used, and one side of this resin substrate was subjected to a corona treatment.
On the other hand, a PVA aqueous solution (coating solution) was prepared by adding 13 parts by weight of potassium iodide to 100 parts by weight of a PVA-based resin prepared by mixing polyvinyl alcohol (polymerization degree 4,200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., product name "GOHSEFFIMER") in a ratio of 9:1, and dissolving the mixture in water.
The above-mentioned aqueous PVA solution was applied to the corona-treated surface of the above-mentioned resin substrate and dried at 60° C. to form a PVA-based resin layer having a thickness of 13 μm, thereby producing a laminate.

The laminate produced as described above was uniaxially stretched 2.4 times in the longitudinal direction (machine direction) in an oven at 130° C. (auxiliary in-air stretching treatment).
Next, the laminate after uniaxial stretching was immersed in an insolubilizing bath (a boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (insolubilizing treatment).
Next, the laminate was immersed in a dye bath (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with 100 parts by weight of water) having a liquid temperature of 30° C. for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer would have a desired value (dyeing treatment).
Next, the above laminate was immersed in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (crosslinking treatment).
Next, the laminate was immersed in an aqueous boric acid solution (boric acid concentration: 4 wt %, potassium iodide concentration: 5 wt %) at a liquid temperature of 70° C., and uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds to a total stretch ratio of 5.5 times (underwater stretching treatment).
Next, the laminate was immersed in a cleaning bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20° C. (cleaning treatment).
Finally, the laminate was dried in an oven maintained at about 90° C., while being brought into contact with a stainless steel heated roll having a surface temperature maintained at about 75° C. (drying shrinkage treatment).
In this manner, a polarizer having a thickness of about 5 μm was formed on the resin substrate, and a laminate having a resin substrate/polarizer structure was produced.

Next, an acrylic protective film (thickness: 40 μm) was attached to one surface (the surface opposite to the resin substrate side) of the polarizer constituting the above laminate to prepare a polarizing film. Then, the resin substrate was peeled off from the polarizing film, and a polyethylene terephthalate release film (thickness: 38 μm) was attached to the peeled surface via an acrylic pressure-sensitive adhesive (thickness: 20 μm) to prepare the main body of the optical functional layer 2.
In addition, an epoxy adhesive was prepared as the adhesive by blending 70 parts by weight of Celoxide 2021P (manufactured by Daicel Chemical Industries, Ltd.), 5 parts by weight of EHPE3150, 19 parts by weight of Aron Oxetane OXT-221 (manufactured by Toa Gosei Co., Ltd.), 4 parts by weight of KBM-403 (manufactured by Shin-Etsu Chemical Co., Ltd.), and 2 parts by weight of CPI101A (manufactured by San-Apro Ltd.).
The combination of the main body of the optical function layer 2 and the adhesive constitutes the optical function layer 2 .

[Preparation of Laminate of Brittle Material Layer 1 and Optical Functional Layer 2]
As the brittle material layer 1, a glass film (manufactured by Nippon Electric Glass Co., Ltd., product name "OA-10G", thickness: 100 μm) was prepared.
Next, the brittle material layer 1 and the main body of the optical functional layer 2 were bonded together via the adhesive. At this time, the main body of the optical functional layer 2 was arranged so that the acrylic protective film was on the brittle material layer 1 side. Next, the adhesive was irradiated with ultraviolet light (500 mJ/cm ² ) from a high-pressure mercury lamp to harden the adhesive, thereby producing a laminate of the brittle material layer 1 and the optical functional layer 2. The thickness of the adhesive after hardening was 5 μm.

[Preparation of composite material 10]
Next, as shown in FIG. 7, a surface protection film having an acrylic adhesive layer (manufactured by Nitto Denko Corporation, product name "RP207") was prepared as the protection layer 3.
The base layer 3a of the protective layer 3 is formed from an untreated polyethylene terephthalate film (Diafoil T100 #38, manufactured by Mitsubishi Chemical Polyester Corporation) having a thickness of 38 μm.
The adhesive layer 3b of the protective layer 3 is prepared as follows. First, 100 parts by weight of 2-ethylhexyl acrylate and 4 parts by weight of 2-hydroxyethyl acrylate are copolymerized in ethyl acetate so that the monomer content is 35% to obtain a solution containing an acrylic polymer having a weight average molecular weight of 600,000. Next, 4 parts by weight of an isocyanate-based crosslinking agent (Coronate HX, manufactured by Nippon Polyurethane Industry Co., Ltd.) having an isocyanurate ring is mixed with 100 parts by weight of the acrylic polymer (dry weight) in this solution, and ethyl acetate is further added to prepare an adhesive solution having a solid content concentration of 20%. Finally, this adhesive solution is applied to the substrate layer 3a so that the dry film thickness is 20 μm, and the adhesive layer 3b is formed by drying at 140° C. for 2 minutes.
The protective layer 3 (RP207) includes the base layer 3a and the adhesive layer 3b prepared as described above. The protective layer 3 and the brittle material layer 1 of the laminate of the brittle material layer 1 and the optical function layer 2 were bonded together via the adhesive layer 3b of the protective layer 3 to prepare a composite material 10.

[Groove forming process (forming first groove 21)]
After the composite material 10 produced as described above was separated into sheets, a first processed groove 21 was formed in the optical function layer 2. Specifically, a TLSU series (CO2 laser light source with an oscillation wavelength of 9.4 μm, a pulse oscillation repetition frequency of 12.5 _kHz , and a power of 250 W of the laser light L1) manufactured by Takei Electric Co., Ltd. was used as a laser processing device equipped with an optical system and a control device for controlling the scanning of the first laser light source 20 and the laser light L1, the output of the laser light L1 oscillated from the first laser light source 20 was set to 11.8 W, and the laser light L1 was focused to a spot diameter of 150 μm at the irradiation position on the optical function layer 2 using a focusing lens, and was irradiated to the optical function layer 2 along the planned division lines DL (plural planned division lines set in a lattice pattern) of the composite material 10. The relative movement speed (processing speed) of the laser light L1 with respect to the composite material 10 was set to 400 mm/sec. As a result, the resin forming the optical function layer 2 was removed, and the first processed groove 21 was formed along the planned division lines DL. At this time, the resin was removed so that a part of the resin forming the optical function layer 2 remained as a residue (thickness: 10 to 20 μm) on the bottom of the first processed groove 21 .

[Groove forming process (forming second groove 31)]
Next, the second processed groove 31 was formed in the protective layer 3. Specifically, as in the case of forming the first processed groove 21, a TLSU series (CO2 laser light source with an oscillation wavelength of 9.4 μm, a repetition frequency of pulse oscillation of 12.5 kHz, and a power of 250 W of the laser light L2) manufactured by Takei Electric Co., Ltd. was used as a laser processing device equipped with an _optical system and a control device for controlling the scanning of the second laser light source 30 and the laser light L2, and as shown in FIG. 7, the output of the laser light L2 oscillated from the second laser light source 30 was set to 10.5 W, and the laser light L2 was focused to a spot diameter of 120 to 130 μm at the irradiation position on the protective layer 3 using a focusing lens, and was irradiated to the protective layer 3 along the planned division lines (plural planned division lines set in a lattice pattern) DL of the composite material 10. The relative movement speed (processing speed) of the laser light L2 with respect to the composite material 10 was set to 400 mm/sec. Then, by applying a peeling method, a second processed groove 31 with a width of 200 μm was formed as shown in FIG. 7. When the protective layer 3 was irradiated with the laser light L2, the resin was removed so that no part of the resin forming the protective layer 3 remained as a residue at the irradiated position (thickness: 0 μm) as shown in FIG.

[Processing mark formation process]
After the above-mentioned processing groove forming process, a processing mark forming process was carried out. Specifically, an ultrashort pulse laser light source 40 was used, which had an oscillation wavelength of 1064 nm, a pulse width of 10 picoseconds for the laser light L3, a repetition frequency of pulse oscillation of 50 kHz, and an average power of 10 W. The laser light L3 oscillated from the ultrashort pulse laser light source 40 was irradiated from the second processing groove 31 side to the brittle material layer 1 of the composite material 10 through a multi-focus optical system. The spot diameter D at the irradiation position of the laser light L3 on the brittle material layer 1 was set to 100 μm. When the relative movement speed (processing speed) of the laser light L3 with respect to the composite material 10 was set to 100 mm/sec and the laser light L3 was scanned along the planned division line DL, a perforated through hole (diameter about 1 to 2 μm) with a pitch of 2 μm was formed as the processing mark 11.

[Composite material cutting process]
After the above-mentioned machining mark forming process, the composite material dividing process was carried out. Specifically, as a laser processing device equipped with a _CO2 laser light source and an optical system and a control device for controlling the scanning of the laser light, MLG-9300 (oscillation wavelength 10.6 μm, laser light power 30 W) manufactured by Keyence Corporation was used, the output of the laser light emitted from the laser light source was set to 80% (i.e., output 24 W), and the laser light was focused to a spot diameter of 0.7 mm using a focusing lens (the energy density at this time was 62 W/m ² ), and the brittle material layer 1 was irradiated from the protective layer 3 side along the planned dividing line DL of the composite material 10. At this time, the relative moving speed of the laser light with respect to the composite material 10 was set to 500 mm/sec.
Finally, a mechanical external force was applied to the composite material 10 to break up the resin residue remaining at the bottom of the first groove 21 after the groove formation step, thereby breaking up the composite material 10.

When the end face of the brittle material layer 1 of the composite 10 (composite piece) cut by the cutting method of Example 1 was visually observed, it was found that the brittle material layer 1 was cut without any problems and no cracks were generated, as shown in Figure 7.

Example 2
As shown in Figure 7, when forming the second processing groove 31, the output of the laser light L2 emitted from the second laser light source 30 was set to 8.0 W, and the composite material 10 was divided under the same conditions as in Example 1, except that the resin (adhesive layer 3b) forming the protective layer 3 was removed so that a portion of the resin (adhesive layer 3b) remained as a residue (thickness: 10 μm) at the irradiation position.
When the end face of the brittle material layer 1 of the composite material 10 (composite material piece) cut by the cutting method of Example 2 was visually observed, it was found that the brittle material layer 1 was cut without any problems and no cracks were generated, as shown in Figure 7.

<Comparative Example 1>
When forming the second processed groove 31, the laser light L2 emitted from the second laser light source 30 was irradiated only once on the protective layer 3 on the planned dividing line (plural planned dividing lines set in a lattice pattern) DL of the composite material 10 (the peeling method was not applied), except that the composite material 10 was divided under the same conditions as in Example 1. As shown in Fig. 7, the width of the second processed groove 31 formed in Comparative Example 1 was 30 µm, which was smaller than the spot diameter D (100 µm) at the irradiation position of the laser light L3 oscillated from the ultrashort pulse laser light source 40 on the brittle material layer 1 in the processing mark forming step.
As shown in FIG. 7, in the cutting method according to Comparative Example 1, no processing marks 11 penetrating the brittle material layer 1 were formed, and the composite material 10 could not be cut.

Example 3
A composite material 10 was produced under the same conditions as in Example 1, except for the points (1) to (3) below, and the composite material 10 was cut.
(1) As shown in FIG. 8, a surface protection film having a urethane adhesive layer (manufactured by Nitto Denko Corporation, product name "AW700EC") was prepared as the protection layer 3.
The base material layer 3a of the protective layer 3 is formed from a base material made of polyester resin, "Lumirror S10" (thickness: 38 μm, manufactured by Toray Industries, Inc.).
The adhesive layer 3b of the protective layer 3 is prepared as follows. First, as the polyol, Preminol S3011 (manufactured by Asahi Glass Co., Ltd., Mn=10000), which is a polyol having three OH groups, Sannix GP-3000 (manufactured by Sanyo Chemical Industries Co., Ltd., Mn=3000), which is a polyol having three OH groups, and Sannix GP-1000 (manufactured by Sanyo Chemical Industries Co., Ltd., Mn=1000), which is a polyol having three OH groups, are used. As the polyfunctional isocyanate compound, Coronate HX (manufactured by Nippon Polyurethane Industry Co., Ltd.), which is a polyfunctional alicyclic isocyanate compound, is used. As the catalyst, the product name "Nasem Ferric" manufactured by Nippon Chemical Industries Co., Ltd. is used. As the deterioration inhibitor, Irganox 1010 (manufactured by BASF Co., Ltd.) is used. As the fatty acid ester, isopropyl myristate (manufactured by Kao Corporation, trade name "Exepar IPM", Mn=270) or cetyl 2-ethylhexanoate (manufactured by Nisshin Oillio Group, trade name "Salacos 816T", Mn=368) is used. Then, 1-ethyl-3-methylimidazolium bis(fluoromethanesulfonyl)imide (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name "AS110"), both-end type polyether modified silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KF-6004"), and ethyl acetate as a dilution solvent are added to these and mixed and stirred to prepare a urethane-based adhesive composition. Then, the prepared urethane-based adhesive composition is applied to the above-mentioned base layer 3a with a fountain roll so that the thickness after drying is 10 μm, and the composition is cured and dried under conditions of a drying temperature of 130° C. and a drying time of 30 seconds to form the adhesive layer 3b.
The protective layer 3 (AW700EC) includes the base layer 3a and the adhesive layer 3b prepared as described above. The protective layer 3 and the brittle material layer 1 of the laminate of the brittle material layer 1 and the optical function layer 2, which are the same as those in Example 1, were bonded together through the adhesive layer 3b of the protective layer 3 to prepare a composite material 10.
(2) When forming the second groove 31, the offset method is applied.
(3) As shown in Figure 8, when forming the second processing groove 31, the output of the laser light L2 emitted from the second laser light source 30 was set to 4.3 W, and the resin (adhesive layer 3b) forming the protective layer 3 was removed so that a portion of the resin (thickness: 7.5 μm) remained as a residue at the irradiation position.
When the end face of the brittle material layer 1 of the composite material 10 (composite material piece) cut by the cutting method of Example 3 was visually observed, it was found that the brittle material layer 1 was cut without any problems and no cracks were generated, as shown in Figure 8.

Example 4
As shown in Figure 8, when forming the second processing groove 31, the output of the laser light L2 emitted from the second laser light source 30 was set to 4.9 W, and the composite material 10 was divided under the same conditions as in Example 3, except that the resin (adhesive layer 3b) forming the protective layer 3 was removed so that a portion of the resin (adhesive layer 3b) remained as a residue with a thickness of 2.1 μm at the irradiation position.
When the end face of the brittle material layer 1 of the composite material 10 (composite material piece) cut by the cutting method of Example 4 was visually observed, it was found that the brittle material layer 1 was cut without any problems and no cracks were generated, as shown in Figure 8.

Example 5
As shown in Figure 8, when forming the second processing groove 31, the output of the laser light L2 emitted from the second laser light source 30 was set to 5.1 W, and the composite material 10 was divided under the same conditions as in Example 3, except that the resin was removed so that no part of the resin forming the protective layer 3 remained as residue at the irradiation position (thickness: 0 μm).
When the end face of the brittle material layer 1 of the composite material 10 (composite material piece) cut by the cutting method of Example 5 was visually observed, it was found that the brittle material layer 1 was cut without any problems and no cracks were generated, as shown in Figure 8.

<Comparative Example 2>
When forming the second processed groove 31, the laser light L2 emitted from the second laser light source 30 was irradiated only once on the protective layer 3 on the planned dividing line (plural planned dividing lines set in a lattice pattern) DL of the composite material 10 (the offset method was not applied), except that the composite material 10 was divided under the same conditions as in Example 5. As shown in FIG. 8, the width of the second processed groove 31 formed in Comparative Example 2 was 30 μm, which was smaller than the spot diameter D (100 μm) at the irradiation position of the laser light L3 oscillated from the ultrashort pulse laser light source 40 on the brittle material layer 1 in the processing mark forming step.
As shown in FIG. 8, in the cutting method according to Comparative Example 2, no processing marks 11 penetrating the brittle material layer 1 were formed, and the composite material 10 could not be cut.

REFERENCE SIGNS LIST 1 Brittle material layer 2 Optical functional layer 3 Protective layer 3a Base layer 3b Adhesive layer 10 Composite material 11 Processing marks 20 First laser light source 21 First processed groove 30 Second laser light source 31 Second processed groove 40 Ultrashort pulse laser light source D Spot diameter DL Planned division line L1, L2, L3 Laser light W Width of second processed groove

Claims (6)

A method for dividing a composite material having a brittle material layer on one side of which a resin optical functional layer is laminated, and a resin protective layer on the other side of which the brittle material layer is laminated, comprising the steps of:
a processing groove forming step of irradiating the optical functional layer along a planned dividing line of the composite material with a laser beam emitted from a first laser light source to remove a resin forming the optical functional layer, thereby forming a first processing groove along the planned dividing line, and irradiating the protective layer along the planned dividing line with a laser beam emitted from a second laser light source to remove a resin forming the protective layer, thereby forming a second processing groove along the planned dividing line;
and a processing mark forming step of irradiating the brittle material layer with a laser beam oscillated from an ultrashort pulse laser source along the planned dividing line from the second processing groove side after the processing groove forming step, thereby removing the brittle material forming the brittle material layer, thereby forming a processing mark along the planned dividing line,
removing the resin forming the protective layer so that the width of the second groove is equal to or larger than a spot diameter at a position where the brittle material layer is irradiated with the laser light oscillated from the ultrashort pulse laser light source in the processing mark forming step ;
In the processing groove forming step, the irradiation position of the laser light emitted from the second laser light source onto the protective layer is shifted in a direction perpendicular to the planned division line, and the laser light is irradiated onto the protective layer along the planned division line at each irradiation position, and then the resin forming the protective layer present between each irradiation position is peeled off, thereby forming the second processing groove .
How to separate composite materials. In the groove forming step, the resin forming the protective layer is removed so that the width of the second groove is 100 μm or more.
The method for dividing a composite material according to claim 1 . The protective layer includes a base layer and a pressure-sensitive adhesive layer disposed on the brittle material layer side,
In the processing groove forming step, the resin forming the protective layer is removed so that a part of the pressure-sensitive adhesive layer in the thickness direction remains.
A method for dividing a composite material according to claim 1 or 2 . The protective layer includes a base layer and a urethane-based pressure-sensitive adhesive layer disposed on the brittle material layer side.
A method for dividing a composite material according to any one of claims 1 to 3 . The second laser light source is a _CO2 laser light source;
A method for dividing a composite material according to any one of claims 1 to 4 . The brittle material layer includes glass, and the optical functional layer includes a polarizing film.
A method for dividing a composite material according to any one of claims 1 to 5 .

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