Patent Application
20250033346
The present invention relates to a method for separating glass, the method including separating plate-like glass in a layer form by carbonizing only a print layer present between glass and an adhesive layer with laser light.
Due to economic activities of mass consumption and mass disposal, global environmental problems such as global warming and resource depletion have arisen.
Under such circumstances, the Home Appliance Recycling Act has been enforced in Japan since April 2001 in order to construct a resource recycling society. The Home Appliance Recycling Act requires mandatory recycling of used home appliances (air conditioners, televisions, refrigerators, freezers, washing machines, clothes dryers, and the like). Thus, used home appliances are crushed into small pieces in home appliance recycling plants, and then sorted and collected by material types using magnetism, wind, vibration, or the like, and recycled as recycled materials.
In recent years, products using glass instead of a conventional metal plate or resin on the surface of home appliances are increasing because of their high designability. Examples of the products using glass include refrigerators, washing machines, and IH stoves.
However, when considered from the viewpoint of recycling, glass used for a glass door of a glass door refrigerator accounts for 7% to 8% of the weight of the refrigerator body, and it is expected to greatly affect a future home appliance recycling rate. In addition, it is assumed that glass causes problems such as wear of a blade of a crusher in a recycle plant (RP), or contamination of glass debris in a post-process. As of 2022, the problem has not become apparent because the amount is small, but it is conceivable that glass is mixed into recycled materials due to an increase in the amount of glass used as a product. As a result, the recycled material is handled as industrial waste, and there is a concern about a decrease in the recycling rate. Thus, a technique for removing glass is required in the pre-process of crushing the recycled product.
However, it is difficult to easily remove glass from a product. This is because, in the structure in which a design glass is bonded to a base material, the glass and the base material are firmly bonded to each other entirely with an adhesive material, and thus, it is very difficult to separate the glass from the product. In addition, if the glass is separated while being crushed, it is not possible to recycle the separated glass, and thus it is necessary to separate the glass in the form of one sheet of glass.
PTL 1 proposes a method in consideration of the above problem. As a background of the development of this method, a chemical reaction such as softening, melting, foaming, and decomposition is caused to occur by irradiating an object to be separated with laser light in recycling a smartphone, causing a print layer to absorb the laser light and generate heat, and propagating the heat to an adhesive layer. It is a method of separating glass from a product by reducing the adhesive force in these reactions.
A method for separating glass according to one aspect of the present invention is a method for separating glass for separating a plate-like glass from an article including a surface to which the plate-like glass is attached, the method including:
The invention according to PTL 1 is effective in that design printing can be made separable at an adhesive layer using heat generated by laser light.
However, in the method of propagating heat, it is assumed that it takes time to become a separable state in the case of a large product such as a refrigerator, compared with a small product such as a smartphone. In addition, in the structure bonded with an adhesive material, the softened adhesive layer is fixed again to resin or glass with time after the irradiation of laser light, and thus separation becomes eventually impossible. Thus, when considering application to a wide variety of products, it is necessary to reduce the influence of re-fixing by treating only the print layer rather than causing a chemical reaction in the adhesive material.
The present invention has been made to solve the above conventional problems, and an object of the present invention is to provide a method for separating glass, the method including separating glass in a layer form from an article by carbonizing only a print layer with laser light without damaging the adhesive layer in a structure in which glass is bonded to a base material.
Hereinafter, an exemplary embodiment of the present invention will be described in detail below with reference to the drawings.
Irradiation sample 1 illustrated in
Plate-like glass 2 can be made of, for example, soda glass, borosilicate glass, or the like. Plate-like glass 2 may be colorless and transparent, but it may be colored as long as most of laser light 6 can pass therethrough.
Print layer 3 is formed using various printing methods such as offset printing, gravure printing, and screen printing.
The components of print layer 3 are composed of, for example, organic and inorganic compounds, and are deposited, printed, or stuck to glass. However, since it is necessary to finally carbonize, it is necessary to contain a compound containing a carbon atom and an organic substance. The component of the organic coating may be one having an azo group or a polycyclic organic compound such as phthalocyanine or quinone.
The print layer 3 does not transmit laser light 6. Not transmitting laser light 6 means a state in which laser light 6 is absorbed when laser light 6 is emitted.
A vapor deposited metal film may be provided between print layer 3 and plate-like glass 2. In this case, it is necessary to decompose the vapor deposited metal film through laser irradiation and to realize separation in a layer form in print layer 3.
Examples of the adhesive material constituting adhesive layer 4 include an acrylic adhesive material. As the adhesive material, an elastomer-based adhesive material may be used, and in this case, for example, an acrylic elastomer, a urethane-based elastomer, a polyolefin-based elastomer, or a styrene-based elastomer can be exemplified. As the adhesive material, a typical rubber-based adhesive material may also be used. As the adhesive material, not only a single adhesive material but also an adhesive material applied to the surfaces of a base material such as a double-sided tape may be used. Different types of adhesive materials may be mixed as the adhesive material.
Base material 5 is, for example, resin, metal, ceramic, or urethane foam, and it needs to be able to be bonded to adhesive layer 4.
The type of laser light 6 is not particularly limited, and examples thereof include a solid laser such as an Nd: YAG laser, and a short pulse laser such as a nanosecond laser. In particular, when the improvement of the processing speed is taken into consideration, the beam profile is performed with the top hat instead of the Gaussian, whereby the improvement of the processing speed can be realized while suppressing the thermal influence on adhesive layer 4.
The wavelength of laser light 6 is preferably more than or equal to 300 nm and less than or equal to 3 μm, and particularly preferably more than or equal to 355 nm and less than or equal to 2 μm. Setting the wavelength of this laser light to the above range of more than or equal to 300 nm and less than or equal to 3 μm makes it possible to achieve carbonization of print layer 3 with an optimum laser output through plate-like glass 2 and to improve the carbonization efficiency and reliability.
The separation method illustrated in
Print layer carbide 7 is formed by carbonizing print layer 3 through irradiation with laser light 6.
It is desirable that separation tool 8 can fix only a surface of plate-like glass 2, and for example, an adsorption pad capable of adsorbing and holding a surface of glass 2 can be used.
Here, an example of a method for separating glass according to the exemplary embodiment will be described with reference to
In the present exemplary embodiment, the method was performed by using a refrigerator glass door as irradiation sample 1.
In step S01, irradiation sample 1 is installed to perform irradiation with laser light 6. In Examples, irradiation sample 1 was a refrigerator glass door. The thickness of print layer 3 is 5 μm to 200 μm. Irradiation sample 1 is installed so as to be perpendicular to laser light 6 at the shortest distance to the surface of plate-like glass 2.
Next, in step S02, laser light 6 is emitted through plate-like glass 2 and applied to print layer 3 of irradiation sample 1. Laser light 6 oscillated at a wavelength of 1064 nm with an output of 200 W and a pulse of 70 nanoseconds to 600 nanoseconds. The refrigerator glass door was irradiated with laser light 6 so that the entire surface of print layer 3 was carbonized. As a scanning method, a laser galvanometer was used to generate line light in accordance with the size of the door glass, and scanning was performed at a scanning speed of 10 m/s to 40 m/s. The focus diameter was 410 μm. The number of times of irradiation with laser light 6 may be one or a plurality of times. The thermal influence on adhesive layer 4 can be suppressed by irradiating the same portion with laser light 6 set to low output and gradually treating print layer 3 when the thickness of print layer 3 is small. This makes it possible to perform separation in irradiation sample 1 having thin print layer 3.
Next, in step S03, glass is separated from irradiation sample 1 treated in step S02. After it is confirmed that print layer 3 is changed to print layer carbide 7, separation tool 8 is installed on a surface of plate-like glass 2. As separation tool 8, an adsorption pad capable of adsorbing and holding a surface of glass 2 was used. That is, the surface of plate-like glass 2 is adsorbed and held by the adsorption pad, then a force is applied to plate-like glass 2 using the adsorption pad in a direction opposite to the direction in which adhesive layer 4 is present, whereby print layer carbide 7 separates in a layer form, and plate-like glass 2 separates from the refrigerator glass door.
This phenomenon is illustrated in
The pulse energy required to carbonize print layer 3 is at least more than or equal to 0.5 J/cm2, but when there is reserve power of the pulse energy with respect to the laser output, it is possible to process an area having a size of more than or equal to a beam diameter while utilizing the influence of thermal diffusion in an energy density region where adhesive layer 4 does not melt.
Here, P is the beam thermal diffusivity, and x is the pulse energy density.
When considered in relation to the pulse energy density required for carbonization based on Formula (1), it was found that the beam thermal diffusivity is 32% at the pulse energy density of 0.5 J/cm2, and the beam thermal diffusivity is 215% at the pulse energy density of 9.0 J/cm2.
In the separation method according to this example, it is necessary to carbonize the entire surface of print layer 3. Adopting the pulse energy density having a high thermal diffusivity makes it possible to increase the treatment area per pulse, and an effect of shortening the treatment time can be expected.
In this manner, according to the method for separating glass according to the exemplary embodiment, the organic component on the entire surface of print layer 3 is carbonized by irradiating print layer 3 with laser light 6, and print layer 3 is separated in a layer form, whereby plate-like glass 2 having print layer 3 bonded to base material 5 with adhesive layer 4 can be separated in a layer form from article 1.
Here, to separate glass 2 where a printing is applied adjacent to adhesive layer 4 without breaking glass 2, it is necessary to inactivate an adhesive component between glass 2 and an article, for example, the adhesive component on an entire surface of a refrigerator door. However, in the structure bonded by adhesive layer 4, after irradiation with laser light 6, softened adhesive layer 4 is fixed again to resin or glass 2 with time, and thus, separation becomes impossible. Thus, considering the application to a wide variety of products, the influence of re-fixing can be reduced by treating only print layer 3.
Thus, by carbonizing only print layer 3 using laser light 6 without damaging adhesive layer 4 present between glass 2 and base material 5, separation of glass 2 in a layer form from base material 5 is realized. That is, plate-like glass 2 can be separated in a layer form from article 1 by irradiating print layer 3 with the laser light 6 through glass 2 to carbonize an organic component on the entire surface of print layer 3 and separating print layer 3 in a layer form.
By appropriately combining any exemplary embodiments or modifications among the various exemplary embodiments or modifications described above, it is possible to achieve the effect possessed by each of them. Combination of exemplary embodiments, combination of examples, or combination of exemplary embodiments and examples are possible, and features in different exemplary embodiments or examples are also possible.
As described above, according to the method for separating glass according to the aspect of the present invention, a plate-like glass having a print layer bonded to a base material with an adhesive layer can be separated in a layer form from the article by irradiating the print layer with laser light to carbonize an organic component on the entire surface of the print layer, and separating the print layer in a layer form.
From the above description, the method for separating glass according to the aspect of the present invention can separate a plate-like glass having a print layer bonded to a base material with adhesive layer 4 at a high speed, and it can be applied to a large-sized product such as a refrigerator or an IH stove in addition to a small product such as a smartphone.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-071802 | Apr 2022 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2023/005271 | Feb 2023 | WO |
| Child | 18911249 | US |
