Patent Application
20250031283
This application is based upon and claims the benefit of priority from Japanese patent application No. 2023-116528, filed on Jul. 18, 2023, the disclosure of which is incorporated herein in its entirety by reference.
The present disclosure relates to a windshield for vehicle and a manufacturing method thereof.
A laminated glass in which a plurality of glass plates are bonded together or a tempered glass is suitably used for a window glass for vehicle such as an automotive. Typically, a glass plate used as a material for a windshield for vehicle has a light-shielding layer formed in its peripheral region, and is processed into a shape having a curved surface by thermoforming.
Additionally, in a window glass for vehicle, a windshield for vehicle is known that includes: a conductor that includes an electric function portion or is connected to an electric function portion; and feeding members such as a harness and a cable. Examples of the electric function portion include an electric heating wire, an electric heating layer, an antenna, a light control layer, a light emitting element, and combinations thereof.
For example, in a windshield, an electric heating wire or an electric heating layer may be formed at the lower end portion and side end portion of the windshield in order to melt frost, snow, ice, etc. adhering to the wipers and to prevent the wipers from freezing.
Additionally, on the inner surface of the windshield, optical apparatuses may be installed that include optical devices such as ADAS (advanced driver assistance systems) cameras, LiDAR (light detection and ranging), a radar and optical sensors that acquire information in front of the vehicle, and a housing called a bracket etc. that houses these, for autonomous driving and collision accident prevention. In such a configuration, an electric heating wire or an electric heating layer may be formed on the glass portion in front of the optical devices to prevent fogging and frost, in order to improve the sensing accuracy by the optical apparatuses.
The conductor can be formed, for example, by coating and firing a silver-containing paste containing silver powder and glass frit. Firing of the silver-containing paste can be implemented simultaneously with thermoforming of the glass plate.
In this specification, a glass plate having a conductor is referred to as a “glass plate with a conductor.”
Conventionally, a conductor and a feeding member are joined using solder. The conductor may preferably include a feeding portion for feeding electricity to an electric function portion.
Conventionally, for example, a terminal is fixed to the head end portion of a feeding member such as a wire harness, and this terminal is joined to a conductor (preferably a feeding portion included in the conductor) using solder. There are two types of solder: leaded solder and lead-free solder. In recent years, there has been concern about the impacts of lead on the environment, and legal restrictions on leaded solder are becoming more widespread, so high-quality production techniques using lead-free solder are required.
In order to join the conductor and the solder sufficiently, it is necessary to form an alloy layer containing an alloy of one or more metal elements contained in the conductor and a plurality of metal elements contained in the solder at the joining interface between the conductor and the solder. To do this, it is necessary to heat the solder to its melting point or above.
When the above-mentioned solder joining is implemented on a glass plate with a conductor, the glass plate and solder are subjected to local high-temperature heating and temperature drop from high temperature to normal temperature. When the temperature drops, a difference in thermal expansion coefficient between the glass plate and the solder causes a difference in the amount of thermal contraction between the glass plate and the solder, and causes strain between the glass plate and the solder, causing stress (specifically, tensile stress) to be generated in the glass plate with the conductor. The stress may remain after the temperature drop. This residual stress may cause cracks to occur in the glass plate with the conductor after manufacturing of the window glass.
Typically, the melting point of lead-free solder is higher than that of leaded solder, and is, for example, about 220° C., so it is necessary to implement solder joining at a higher temperature (for example, about 300° C.). Therefore, when lead-free solder is used, a larger thermal load is applied to the glass plate with the conductor in terms of temperature and time, and larger stress is generated. In addition, since lead-free solder does not contain lead, which has a low elastic modulus, it has a higher elastic modulus and is less likely to deform than leaded solder, so it is difficult to alleviate stress generated by temperature change. For these reasons, the problem of residual stress after joining and the resulting cracking after manufacturing can occur, especially when lead-free solder is used.
If the breaking strength of the glass plate after terminal attachment is low, cracks may occur when external force is applied to the glass plate. In particular, when a terminal is joined to a feeding portion formed on a light-shielding layer using lead-free solder, the breaking strength of the glass plate after terminal attachment tends to decrease. It is preferable that the conductor be designed so that it is difficult to be seen by people outside the vehicle while the breaking strength of the glass plate after terminal attachment can be increased in solder joining using lead-free solder.
In this specification, “breaking strength before or after terminal attachment” is the load at the time of breakage when a load is applied to the glass before or after terminal attachment, and can be measured through the method described in [Example] section below.
Japanese Unexamined Patent Application Publication No. 2021-18932 discloses
The glass plate module can further include solder (preferably lead-free solder) placed on the feeding portion, and a terminal fixed to the feeding portion with the solder interposed therebetween (claims 23 and 25).
Japanese Unexamined Patent Application Publication No. 2021-18932 states that making a thickness of the feeding portion smaller than that of the heating wire allows reducing tensile stress generated in the glass plate and preventing cracks in the glass plate and the feeding portion (paragraph 0108).
Japanese Unexamined Patent Application Publication No. 2021-18932 also describes a method for: devising a method for printing conductive prints; and making a thickness of the feeding portion smaller than that of the heating wire in a printing process of a conductive print (paragraphs 0117 and 0118).
International Patent Publication No. WO 2006/132319 discloses
In addition, International Patent Publication No. WO 2006/132319 does not describe lead-free solder, but states that according to the above aspect, the joining strength can be improved when a terminal is joined to a conductive film with solder interposed therebetween (paragraph 0015).
International Patent Publication No. WO 2006/132319 also discloses a method for manufacturing a glass article, including: printing a paste on one main surface of a glass plate, the paste being made by adding an organic medium to the silver paste, the organic medium accounting for 1 to 5% by mass of the total mass of a silver paste, the silver paste having a main component of silver; and forming a conductive film by firing the resultant, and joining a terminal onto the conductive film (claim 3).
International Patent Publication No. WO 2006/132319 also discloses a method for manufacturing a conductive film, including: a first step of printing a paste containing silver particles and glass frit on a glass plate; a second step of subjecting the paste to drying processing involving heating; and a third step of heating the glass plate subjected to the drying processing to fire the conductive film (claim 4).
However, Japanese Unexamined Patent Application Publication No. 2021-18932 and International Patent Publication No. WO 2006/132319 does not describe and suggest: an aspect in which at least the surface of the terminal joint portion has a compressive stress portion; and a preferable stress value of the compressive stress portion.
The present disclosure has been made in view of the above circumstances, and an object thereof is to provide: a windshield for vehicle that includes a portion in which a conductor and a terminal are joined using lead-free solder, and that can increase breaking strength after terminal attachment; and a manufacturing method thereof.
The present disclosure provides the following windshield for vehicle and a manufacturing method thereof: [1] to [15].
In the windshield for vehicle of the present disclosure, at least the surface of the terminal joint portion has a compressive stress portion.
According to the present disclosure, it is possible to provide: a windshield for vehicle that includes a portion in which a conductor and a terminal are joined using lead-free solder, and that can increase the breaking strength after terminal attachment; and a manufacturing method thereof.
The above and other objects, features and advantages of the present disclosure will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present disclosure.
Generally, thin film structures are referred to as “films”, “sheets”, etc. depending on the thickness. In this specification, these are not clearly distinguished. Therefore, the term “film” as used herein may include “sheet”.
In this specification, a shape having an additional “substantially” means a partially changed shape, such as a chamfered shape with the corners rounded, a shape with a part of the shape missing, or a shape with a small shape added to the shape.
In this specification, unless otherwise specified, a “surface of a glass plate” refers to the main surface with a large area, excluding the sides (also referred to as side surfaces) of the glass plate.
In this specification, unless otherwise specified, “up and down”, “left and right”, “vertical and horizontal”, and “inside and outside” means “up and down”, “left and right”, “vertical and horizontal”, and “inside and outside” with the windshield for vehicle being fitted into a vehicle (actual usage condition).
In this specification, “lead-free solder” is solder that does not substantially contain lead, and the lead content in lead-free solder is 500 ppm or less.
In this specification, unless otherwise specified, lead-free solder “substantially does not contain any metal element other than lead” means that the content of the metal element is 1000 ppm or less.
In this specification, unless otherwise specified, the symbol “-” (or “to”) indicating a numerical range is used to mean that the numerical values written before and after the symbol are included as the lower limit and upper limit.
Embodiments of the present disclosure will be described below.
The present disclosure relates to a windshield for vehicle including a laminated glass in which a plurality of glass plates are bonded together with an intermediate film interposed therebetween, and a method for manufacturing the windshield for vehicle.
In this specification, unless otherwise specified, “glass plate” refers to un-tempered glass.
The type of the glass plate that is a material of the laminated glass is not particularly limited, and examples thereof include soda lime glass, borosilicate glass, aluminosilicate glass, lithium silicate glass, quartz glass, sapphire glass, and alkali-free glass.
The thickness of the laminated glass is not particularly limited, and is preferably 2 to 6 mm for use as a windshield for vehicle.
When the laminated glass consists of two glass plates, the thickness of the glass plate on the vehicle inner side and the thickness of the glass plate on vehicle outer side may be identical or non-identical. The thickness of the glass plate on the vehicle inner side is preferably 0.3 to 2.3 mm. When the thickness of the glass plate on the vehicle inner side is 0.3 mm or more, handling properties are good, and when the thickness is 2.3 mm or less, the mass is not too large. The thickness of the glass plate on the vehicle outer side is preferably 1.0 to 3.0 mm. When the thickness of the glass plate on vehicle outer side is 1.0 mm or more, the strength such as tolerance to stone chips is sufficient, and when the thickness is 3.0 mm or less, the mass of the laminated glass is not too large, which is preferable in terms of vehicle fuel efficiency. It is preferable that the thickness of the glass plate on the vehicle outer side and the thickness of the glass plate on the vehicle inner side are both 1.8 mm or less so that both the weight reduction and sound insulation properties of the laminated glass can be achieved.
The windshield for vehicle may have a curved shape such that the windshield is convex to the vehicle outer side when the windshield is attached to the vehicle. When the windshield for vehicle is a laminated glass, the glass plate on the vehicle inner side and the glass plate on the vehicle outer side may both have a curved shape such that they are convex to the vehicle outer side. The windshield for vehicle may have a single curved shape that is curved in only one direction, either the left-right direction or the up-down direction, or the windshield may have a multi-curved shape that is curved in the left-right direction and the up-down direction. The curvature radius of the windshield for vehicle may be between 2000 and 11000 mm. The windshield for vehicle may have the curvature radius in the left-right direction and that in the up-down direction that are identical or non-identical. Gravity forming, press forming, roller forming, etc. are used for bending and forming the windshield for vehicle.
The laminated glass may have a functional film having functions such as water repellency, low reflectivity, low radioactivity, ultraviolet shielding, infrared shielding, and coloring on at least a part of region of surface.
The laminated glass may have a functional film having functions such as low reflectivity, low radioactivity, ultraviolet shielding, infrared shielding, and coloring in at least a part of the region of the inside. At least a part of region of the intermediate film of the laminated glass may have functions such as ultraviolet shielding, infrared shielding, and coloring.
The intermediate film of laminated glass may be a single layer film or a laminated film.
The laminated glass may have a light-shielding layer on a predetermined region of the surface. The light-shielding layer can be formed by a known method, for example, by applying a ceramic paste containing a black pigment and glass frit to a predetermined region on the surface of a glass plate, which is a material for laminated glass, and firing the ceramic paste. The thickness of the light-shielding layer is not particularly limited, and is, for example, 5 to 20 μm. The light-shielding layer can be formed in the peripheral region of any surface of the laminated glass. The light-shielding layer can be formed, for example, in the peripheral region of the interior surface of the glass plate on the vehicle inner side and/or the glass plate on the vehicle outer side.
In the present disclosure, a laminated glass includes a glass plate with a terminal that has: a glass plate; a conductor that is formed on one surface of the glass plate, is made of a material containing silver and glass frit, and has a terminal joint portion to which a terminal is joined; and a terminal joined onto the terminal joint portion of the conductor with lead-free solder interposed therebetween.
In this specification, the “terminal joint portion” of the conductor refers to a portion of the conductor immediately underneath the lead-free solder.
The conductor may be formed directly on the surface of the glass plate in contact with the glass plate, or may be formed on any component formed on the surface of the glass plate.
The conductor may be formed on the glass plate with the terminal on the intermediate film side, or may be formed on the glass plate with the terminal on the side opposite to the intermediate film side.
The glass plate with the terminal can have a light-shielding layer between the glass plate and the terminal joint portion of the conductor. In this case, the conductor can be formed on the light-shielding layer formed on the glass plate.
The conductor having a terminal joint portion is formed through a method for applying a silver-containing paste containing silver powder and glass frit onto a glass plate and firing the paste. The thickness of the conductor is not particularly limited, and is, for example, 5 to 20 μm, preferably 5 to 10 μm.
The silver-containing paste contains silver powder and glass frit, and can further contain a vehicle and additives as necessary.
Silver powder includes particles containing silver and/or a silver alloy. The content of silver powder in the silver-containing paste is preferably 65 to 85% by mass, more preferably 75 to 85% by mass, particularly preferably 80 to 85% by mass. If the content of the silver powder is within this range, the specific resistance of the conductor can be easily adjusted within a suitable range.
The average particle diameter of the silver powder is preferably 0.1 to 10 μm, more preferably 0.1 to 7 μm. If the average particle diameter of the silver powder is within this range, the specific resistance of the conductor can be easily adjusted within a suitable range.
In this specification, unless otherwise specified, the “average particle diameter of silver powder” refers to the average particle diameter (D50) measured with a laser scattering particle size distribution analyzer.
Examples of the glass frit include Bi2O3—B2O3—SiO2-based glass frit and B2O3—SiO2-based glass frit. The content of glass frit in the silver-containing paste is preferably 2 to 10% by mass, more preferably 3 to 8% by mass. If the glass frit content is 2% by mass or more, the conductor can be easily sintered, and if the content is 10% by mass or less, the specific resistance of the conductor can be easily adjusted within a suitable range.
Examples of the vehicle include resin solutions in which binder resins such as ethyl cellulose resins, acrylic resins, and alkyd resins are dissolved in solvents such as a-terpineol, butyl carbitol acetate, and ethyl carbitol acetate. The content of vehicle in the silver-containing paste is preferably 10 to 45% by mass, more preferably 15 to 25% by mass.
Examples of the additive include resistance adjusters such as Ni, Al, Sn, Pt, and Pd; colorants such as V, Mn, Fe, Co, Mo, and compounds thereof. The content of additives in the silver-containing paste (in the case of a plurality of types of additives, the total amount) is preferably 2% by mass or less, more preferably 1% by mass or less.
The electrical conductor can include or be electrically connected to an electric function portion.
Examples of the electric function portion include one or more electric heating wires, an electric heating layer, an antenna, a light control layer, a light emitting element, and a combination thereof. Examples of the light emitting element include an LED (light emitting diode) and an OLED (organic light emitting diode).
The one or more electric heating wires or an electric heating layer make it possible to remove fog, frost, snow, ice, etc. and prevent them from adhering. The one or more electric heating wires or an electric heating layer can be used, for example, to prevent wipers from freezing, and to improve sensing accuracy by optical apparatuses including optical devices such as cameras and radars.
The electric function portion can be manufactured by a known method.
The conductor can include a feeding portion for feeding electricity to the electric function portion, and the feeding portion can include a terminal joint portion. The feeding portion can include a pair of feeding electrodes (also referred to as a pair of busbars), and each feeding electrode can include a terminal joint portion.
For example, one feeding electrode is a positive electrode and is connected to a power source or a signal source provided in the vehicle with the feeding member interposed therebetween, and the other feeding electrode is a negative electrode and is connected to the vehicle body (ground) with the feeding member interposed therebetween. Note that the feeding electrode for the positive electrode may be single or plural, and the feeding electrode for the negative electrode may be single or plural.
When the conductor is connected to an electric function portion, the conductor and the electric function portion may be formed on the same glass surface or on different glass surfaces.
A feeding member including a round-wire-shaped or foil-shaped conducting wire can be fixed to the terminal. The term “conducting wire” as used herein includes a covered conducting wire in which one or more conducting wires are covered with an insulating material. As the feeding member, a covered conducting wire is preferable.
Examples of the specific form of the feeding member include a harness and a cable. Examples of the round-wire-shaped conducting wire include a wire harness. Examples of the foil-shaped conducting wire include a flat harness and a flexible printed circuit board.
The feeding member has a conductor-exposed portion, and a terminal is fixed to this conductor-exposed portion. The material of the conductor-exposed portion is not particularly limited, and examples thereof include Cu, Al, Ag, Au, Ti, Sn, Zn, alloys thereof, and combinations thereof. The conductor-exposed portion may be formed by plating the surface of the main metal with another metal. The conductor-exposed portion may have a thin oxide film on the surface.
Lead-free solder is solder that contains little or no lead, and any known solder can be used. Examples of lead-free solder include SnAg-based solder containing Sn and Ag; SnAgCu (SAC)-based solder containing Sn, Ag, and Cu; SnZnBi-based solder containing Sn, Zn, and Bi; SnCu-based solder containing Sn and Cu; SnZnAl-based solder containing Sn, Zn, and Al; In-based solder containing In.
From the viewpoint of environmental resistance, lead-free solders is preferably, for example, SnAg-based lead-free solder containing Sn and Ag, and substantially free of Sb, Cu and In; or SnAgCu (SAC)-based lead-free solder containing Sn, Ag, and Cu, and substantially free of Sb and In.
The melting point of lead-free solder such as SnAg-based and SnAgCu-based solder is higher than that of leaded solder, and is for example, about 220° C. In using lead-free solder such as SnAg-based and SnAgCu-based solder, the solder joint temperature is, for example, about 300° C. The present disclosure is particularly effective in using lead-free solders such as SnAg-based and SnAgCu-based solders having high melting points.
Hereinafter, preferred aspects of SnAg-based and SnAgCu-based lead-free solders will be described.
The content of Sn in SnAg-based and SnAgCu-based lead-free solder is not particularly limited, and is preferably 95% by mass or more, more preferably 95 to 98.5% by mass, particularly preferably 96 to 98% by mass. If the Sn content is 95% by mass or more (Ag content is 5% by mass or less), the melting point of the lead-free solder can be relatively low, so the solder joint temperature can be relatively low, and the temperature rise of the glass plate can be relatively small. This can reduce residual stress generated in the glass plate and cracking of the glass plate due to the residual stress.
Generally, if Sn-based lead-free solder that does not contain Ag is used, the Sn in the lead-free solder and the Ag in the conductor are highly compatible, so so-called “silver dissolving” is likely to occur in which Ag in the terminal joint portion of the conductor dissolves into the Sn-containing lead-free solder. In this case, the terminal joint portion may be discolored due to deterioration in quality, thinning, etc., resulting in poor appearance.
If a lead-free solder containing Sn and Ag is used, the Sn in the lead-free solder has already formed a compound with Ag, making it possible to prevent dissolution of Ag in the terminal joint portion of the conductor into the lead-free solder, and to prevent discoloration of the terminal joint portion and resulting poor appearance.
The content of Ag in the lead-free solder is preferably 1.5 to 5% by mass, more preferably 2 to 4% by mass. The Ag content of 1.5% by mass or more makes it possible to effectively prevent dissolution of Ag in the terminal joint portion of the conductor into the lead-free solder and to obtain sufficient joining strength. The Ag content of 5% by mass or less can make the material cost of the lead-free solder low and can make the melting point of the lead-free solder relatively low.
The lead-free solder may contain Cu as a metal element other than Sn and Ag. The content of Cu in the lead-free solder is not particularly limited, and is preferably 1% by mass or less, more preferably 0.5% by mass or less.
Examples of the composition of SnAg-based lead-free solder include Sn: 98% by mass, and Ag: 2% by mass. Examples of the composition of SnAgCu-based lead-free solder include Sn: 96.5% by mass, Ag: 3.0% by mass, and Cu: 0.5% by mass.
From the viewpoint of reducing thermal stress on the glass plate in terminal attachment, In-based lead-free solder containing In, which is low melting point solder, is also preferred.
Examples of In-based lead-free solder include:
The present disclosure provides: a windshield for vehicle that includes a portion in which the conductor and the terminal are joined using lead-free solder, and that can have a higher breaking strength after terminal attachment; and a method for manufacturing the windshield.
As explained in the BACKGROUND section, generally when solder joining is implemented on a glass plate with a conductor, the glass plate with the conductor is subjected to local high-temperature heating and temperature drop from high temperature to normal temperature, and stress may remain after temperature drop. This residual stress may cause cracks to occur in the glass plate with the conductor after manufacturing of the window glass.
Generally, the melting point of lead-free solder is higher than that of leaded solder, so when lead-free solder is used, a larger stress is generated in the glass plate with the conductor. In addition, since lead-free solder does not contain lead, which has a low elastic modulus, lead-free solder has a higher elastic modulus and is less likely to deform than leaded solder, so it is difficult to alleviate the generated stress. For these reasons, the problem of residual stress after joining and the resulting cracking after manufacturing can occur, especially when lead-free solder is used.
If the breaking strength of the glass plate after terminal attachment is low, glass cracking may occur when external force is applied to the glass plate. In particular, when a terminal is joined to a feeding portion formed on a light-shielding layer using lead-free solder, the breaking strength of the glass plate after terminal attachment tends to decrease.
According to the study of the present inventor, the following has been found.
The linear expansion coefficient (CTE) of the glass plate is, for example, about 90×10−7/° C.
The linear expansion coefficient (CTE) of the light-shielding layer formed, as necessary, between the glass plate and the terminal joint portion is, for example, about 70 to 80×10−7/° C. Typically, the linear expansion coefficient (CTE) of a light-shielding layer is smaller than the linear expansion coefficient (CTE) of a glass plate. Therefore, the stress remaining in the light-shielding layer is compressive stress in a glass plate with a conductor, which is obtained after forming a ceramic paste layer and a silver-containing paste layer on a glass plate, firing them at high temperature, and cooling down the resultant to normal temperature.
The linear expansion coefficient (CTE) of the conductor including the terminal joint portion is, for example, about 180×10−7/° C. Typically, the linear expansion coefficient (CTE) of a conductor including a terminal joint portion is larger than the linear expansion coefficient (CTE) of the glass plate. Therefore, the stress remaining in the conductor including the terminal joint portion has tensile stress in a glass plate with a conductor, which is obtained after forming a ceramic paste layer and a silver-containing paste layer on a glass plate, firing them at high temperature, and cooling down the resultant to normal temperature.
Plastically deforming at least the surface of the terminal joint portion can make at least the surface of the terminal joint portion into a compressive stress portion where compressive stress is applied. It is thought that: the surface or surface layer is plastically deformed and stretched, but the deep portion returns to its original shape due to elastic deformation, thereby causing compressive stress to be applied to at least the surface of the conductor.
Examples of a method for plastically deforming at least the surface of the terminal joint portion include surface polishing.
According to the study of the present inventor, it has been found that: if tensile stress is applied to the terminal joint portion, the breaking strength of the glass plate after terminal attachment tends to decrease; and if compressive stress is applied to the terminal joint portion, the breaking strength of the glass plate after terminal attachment can be improved.
The surface layer of the conductor can have a depth range of about 3 to 5 μm from the outermost surface of the conductor, for example.
The relationship between the linear expansion coefficient (CTE) of each material causes the conductor to be pulled by the joined solder in solder joining. It is thought that: if the conductor has compressive stress, the conductor is prevented from being pulled by the joined solder, and the residual tensile stress is reduced in the glass plate with the terminal obtained after solder joining, resulting in an improved breaking strength of the glass plate with the terminal.
If the thickness of the conductor is about 5 to 20 μm, the entire terminal joint portion of the conductor can be made into a compressive stress portion by a method of surface polishing or the like.
Note that Japanese Unexamined Patent Application Publication No. 2021-18932 and International Patent Publication No. WO 2006/132319 cited in the BACKGROUND section does not describe or suggest: an aspect in which at least the surface of a terminal joint portion has a compressive stress portion; and a preferable stress value of the compressive stress portion.
The windshield for vehicle of the present disclosure
In the windshield for vehicle of the present disclosure,
In the windshield for vehicle of the present disclosure, at least the surface of the terminal joint portion has a compressive stress portion to which compressive stress is applied.
According to the present disclosure, it is possible to provide a windshield for vehicle that includes a portion where a conductor and a terminal are joined using lead-free solder and can have a higher breaking strength after terminal attachment.
The stress value of the conductor can be measured by a sin2ψ method using a micro-area X-ray residual stress measurement system. The diffraction angle 2θ is measured while changing the angle ψ between the sample surface normal and the lattice surface normal. The relationship between the stress value σ, the angle ψ between the sample surface normal and the lattice surface normal, and the diffraction angle 2θ is expressed by the following expression.
The data of (x, y)=(sin2ψ, 2θ) is plotted, and the slope of the obtained approximate straight line is determined as data of Δ(2θ)/Δ(sin2ψ). By multiplying this data of Δ(2θ)/Δ(sin2ψ) by a stress constant K determined by the material, the stress value σ can be determined. Note that, regarding the sign of the stress value, a minus sign represents compressive stress, and a plus sign represents tensile stress.
In this specification, unless otherwise specified, the “stress value of the conductor” is a stress value measured by the sin2ψ method using a micro-area X-ray residual stress measurement system, and is determined by the method described in the [Examples] section below.
The stress value of the compressive stress portion just needs to be a negative value, and is preferably −20 MPa or less. The upper limit is more preferably −25 MPa, particularly preferably −30 MPa. The lower limit is not particularly limited, and is, for example, −50 MPa or −45 MPa.
As described above, one method for plastically deforming at least the surface of the terminal joint portion is surface polishing.
In the windshield for vehicle of the present disclosure, the conductor can have a polished portion with a polished surface in a region including the terminal joint portion, and the polished portion can be a compressive stress portion at least on its surface. The conductor can have a non-polished portion in which the surface is not polished in a region that does not include the terminal joint portion.
The polished portion can have a smaller porosity than the non-polished portion in which the surface is not polished. The porosity of the polished portion is preferably small, preferably 10% or less, more preferably 8% or less, particularly preferably 7% or less, particularly preferably 3% or less. The lower limit of the porosity of the polished portion is, for example, 0.5%.
The porosity of the non-polished portion is larger than that of the polished portion, and may be more than 10% or less than 10% and is, for example, 15 to 16%.
The porosity can be measured by a method described in the [Examples] section below.
According to the study conducted by the present inventors, it was found that a conductor containing silver and glass frit has many voids (vacancies) in the conductor in an unpolished state. It is thought that voids (vacancies) in the conductor become a stress concentration source, leading to a decrease in breaking strength after terminal attachment.
In addition, according to the study conducted by the present inventors, it was found that when a conductor containing silver and glass frit is in an unpolished state, a large amount of components of the glass frit is present on the surface of the conductor. In particular, it has been found that when a conductor is formed on a light-shielding layer, more components of the glass frit are present on the surface of the conductor. It is presumed that these are because in firing of the material for forming the conductor and the material for forming the light-shielding layer used as necessary, a part of components of the glass frit contained in these materials move to the surface side.
In general, the wettability of lead-free solder to components of the glass frit is low. It is thought that: when a large amount of components of the glass frit is present on the surface of the conductor, the joining strength of the lead-free solder to the conductor decreases, making it difficult to form a well-shaped solder fillet, which decreases the breaking strength after terminal attachment.
According to the study conducted by the present inventors, it has been found that polishing the surface of the conductor can reduce voids (vacancies) in the conductor that can become the stress concentration source. It is presumed that polishing the surface of the conductor reduces the depth of the voids present on the surface, and further the stretched silver fills voids present on the surface and surface layer of the conductor.
It was also found that polishing the surface of the conductor can reduce the amount of components of the glass frit present on the surface of the conductor. It is presumed that polishing the surface of the conductor removes components of the glass frit that are present in large quantities on the surface. The amount of components of the glass frit present on the surface of the conductor can be reduced, making it possible to improve the wettability of lead-free solder to a conductor, to improve the joining strength of lead-free solder to a conductor, and to form a well-shaped solder fillet.
The method for polishing the surface of the region including the terminal joint portion of the conductor allows applying compressive stress to at least the surface of the terminal joint portion of the conductor, reducing the porosity of the terminal joint portion and the amount of components of the glass frit on the surface of the terminal joint portion, and effectively increasing the breaking strength after terminal attachment.
As the glass frit for the conductor and the light-shielding layer, any known one can be used. As the metal element, those containing Na, Al, Si, P, Zn, Ba, Bi, etc. can be used. Typically, the glass frit for the conductor and the light-shielding layer contains a relatively large amount of Bi, so the proportion of components of the glass frit on the surface of the conductor can be determined by using the Bi/Ag mass ratio as a measure. The Bi/Ag mass ratio indicates that it increases with the increase in the proportion of the components of the glass frit.
The Bi/Ag mass ratio can be measured by energy dispersive X-ray (EDX) analysis or the like.
Note that when the conductor is formed on the light-shielding layer, as described above, a part of components of the glass frit contained in the material for forming the light-shielding layer may move into the conductor in the manufacturing process. Therefore, components of the glass frit contained in the conductor before the step of plastically deforming at least the surface of the terminal joint portion by surface polishing, etc. may contain a part of the components of the glass frit contained in the material for forming the light-shielding layer.
One measure of the surface polishing level is the rate of the arithmetic mean surface roughness (Ra) after polishing with respect to that before polishing. When the conductor includes a non-polished portion, this parameter is synonymous with the rate of the arithmetic mean surface roughness (Ra) of the polished portion with respect to that of the non-polished portion.
The rate of the arithmetic mean surface roughness (Ra) after polishing with respect to that before polishing (=the rate of the arithmetic mean surface roughness (Ra) of the polished portion with respect to that of the non-polished portion) is not particularly limited, and is preferably 5 to 80%, more preferably 5 to 50%, particularly preferably 5 to 20%, because the rates can effectively increase the breaking strength after terminal attachment.
The surface roughness (Ra) can be measured by a method described in the [Examples] section below.
Another indicator of the surface polishing level is a reduction rate of the film thickness after polishing with respect to that before polishing. When the conductor includes a non-polished portion, this parameter is synonymous with a reduction rate of the film thickness of the polished portion with respect to that of the non-polished portion.
The reduction rate of the film thickness after polishing (the reduction rate of the film thickness of the polished portion with respect to that of the non-polished portion) is not particularly limited, and is preferably 4 to 40%, more preferably 4 to 20%, particularly preferably 4 to 10%, because the rates can effectively increase the breaking strength after terminal attachment.
The reduction rate of the film thickness can be measured by a method described in [Examples] section below.
The method for manufacturing the windshield for vehicle of the present disclosure described above is not particularly limited.
The method for manufacturing a windshield for vehicle of the present disclosure may include, for example,
In step (S5), the method for manufacturing a windshield for vehicle according to the present disclosure allows applying compressive stress to at least the surface of the terminal joint portion of the conductor, and increasing the breaking strength after terminal attachment. The stress value of the terminal joint portion of the conductor after step (S5) just needs to be a negative value, preferably −20 MPa or less. The upper limit is more preferably −25 MPa, particularly preferably −30 MPa. The lower limit is not particularly limited, and is, for example, −50 MPa or −45 MPa.
The step (S5) can be a step of polishing the surface of the region including the terminal joint portion of the conductor. The method for polishing the surface of the region including the terminal joint portion of the conductor allows applying compressive stress to at least the surface of the terminal joint portion of the conductor, reducing the porosity of the terminal joint portion and the amount of components of the glass frit on the surface of the terminal joint portion, and effectively increasing the breaking strength after terminal attachment.
Surface polishing of the conductor can be implemented by a known method, and may be a manual method or an electric-powered method. The manual methods include a method for rubbing the surface of the conductor using a polishing member such as a metal fiber and a polishing eraser. The electric-powered methods include a method for polishing the surface of the conductor using an electric-powered cutting tool (also referred to as a hand grinder).
Examples of metal fibers include steel wool. Metal fibers come in several grit numbers depending on the average fiber diameter. In the method using metal fibers, adjustment is performed in the grit number and amount of the metal fiber to be used, the force in rubbing, the number of times of rubbing, and the duration of rubbing, thereby making it possible to adjust the plastic deformation level of at least the surface, the stress value after polishing, the surface roughness, etc. in the polished portion of the conductor.
Polishing erasers contain an abrasive (also referred to as abrasive grains) such as alumina and silica, and rubber, and are commercially available under the names of sand erasers, rust erasers, and the like. There are several grit numbers depending on the average particle diameter of the abrasive (abrasive grains) contained. Adjustment is performed in the grit number of the polishing eraser, the force in rubbing, the number of times of rubbing, and the duration of rubbing, thereby making it possible to adjust the plastic deformation level of at least the surface, the stress value after polishing, the surface roughness, etc. in the polished portion of the conductor.
Examples of commercially available electric-powered cutting tools (hand grinders) include “Leutor (registered trademark)” manufactured by Nihon Seimitsu Kikai Kosaku Co., Ltd. Electric-powered cutting tools can each be used with a tip tool for polishing being attached. As the tip tool, an angle tool is preferable from the viewpoint of workability. Examples of the angle tools include: angle tools each consisting of a combination of a rubber pad that has a polishing disc mounting surface and is attached to an electric-powered cutting tool, and a polishing disc that is attached to the rubber pad; and ceramic angle tools (also referred to as ceramic angle grindstones) that contain ceramic as an abrasive (abrasive grains), a binder, and an elastic body. There are two types of polishing discs: discs containing an abrasive (abrasive grains) and discs containing no abrasive, and when a disc containing no abrasive is used, it is necessary to use an abrasive together. Examples of the polishing disc include a sandpaper disc, a felt disc containing no abrasive, a felt disc containing an abrasive, a nonwoven fabric disc made of nylon and containing an abrasive (also referred to as a cushion disc). Discs and ceramic angle tools containing an abrasive come in several grit numbers depending on the average particle diameter of the abrasive (abrasive grains).
Adjustment is performed in the type and grit number of the tip tool used, the rotational speed, the polishing time, and the like, thereby making it possible to adjust the plastic deformation level of at least the surface, the stress value after polishing, the surface roughness, etc. in the polished portion of the conductor.
In general, if the material is the same, as the grit number decreases, the average size of the abrasive (abrasive grains) contained increases, so that the polishing capacity tends to increase. In any polishing method, the polishing conditions are adjusted so that the polishing capacity is not too large not to damage the glass plate and the light-shielding layer provided as necessary.
In an aspect in which a glass plate with a terminal has a light-shielding layer between the glass plate and the terminal joint portion of the conductor, the method can include a step (S1), before step (S2), of applying a ceramic paste containing a black pigment and glass frit, which are materials for the light-shielding layer, on a glass plate, which is the material for the glass plate with the terminal. In this case, in step (S3), the material for the light-shielding layer can be fired to form the light-shielding layer.
In the laminated glass, it is possible that: the glass plate with the terminal has an exposed portion that is not covered by the glass plate facing the glass plate with the terminal with the intermediate film interposed therebetween; the conductor is formed on the intermediate film side of the glass plate with the terminal; and the terminal joint portion of the conductor is formed in the exposed portion of the glass plate with the terminal.
In this aspect, there can be a step (S4) of bonding a plurality of glass plates together with an intermediate film interposed therebetween, between the step (S3) and the step (S5).
In the laminated glass, the conductor can be formed on the side opposite to the intermediate film side of the glass plate with the terminal.
Also in this aspect, there can be a step (S4) of bonding a plurality of glass plates together with an intermediate film interposed therebetween, between the step (S3) and the step (S5).
A structure of a windshield for vehicle according to a first embodiment of the present disclosure will be described with reference to drawings.
The planar shape of the windshield for vehicle 1 can be designed as appropriate, and examples of the shapes include a shape in which a substantially trapezoidal-shaped plate in a plan view is curved as a whole, as shown in
As shown in
In this embodiment, the laminated glass 10 includes: a glass plate with a terminal 11X that includes: an outer glass plate 11; a conductor 20 that is formed on the vehicle inner surface (surface on the intermediate film 12 side) S2 of the outer glass plate 11, is made of a material containing silver and glass frit, and has a terminal joint portion 20T to which the terminal 102 is joined; and a terminal 102 joined onto the terminal joint portion 20T of the conductor 20 with lead-free solder 101 interposed therebetween. The laminated glass may be made by bonding three or more glass plates together.
As shown in
As shown in
In this embodiment, as shown in
In this embodiment, the conductor 20 has a function of melting frost, snow, ice, etc. adhering to the wipers and of preventing the wipers from freezing. In
As shown in
As shown in
As shown in
The terminal joint portion 20T of the conductor 20 is a portion immediately underneath the lead-free solder 101. In the figure, the region where the terminal joint portion 20T is formed is the region sandwiched between two broken lines T1 and T2. Note that the position of the terminal joint portion 20T of the conductor 20 is not clearly determined from the beginning. The terminal joint portion 20T is the portion immediately underneath the lead-free solder 101 after the terminal 102 is joined to the feeding electrode 20B with the lead-free solder 101 interposed therebetween.
The feeding member 103 is preferably a round-wire-shaped or foil-shaped conducting wire, more preferably a round-wire-shaped or foil-shaped covered conducting wire. The covered conducting wire is preferably a wire harnesses, a flat harnesses, or the like.
The feeding member 103 has a head end portion having a conductor-exposed portion to which the terminal 102 is fixed.
As the terminal 102, a known crimp terminal is preferable. The crimp terminal preferably has: a feeding member joint portion 102A (see
When a wire harness is used as the feeding member 103, the crimp terminal is preferably a crimp terminal including: a feeding member joint portion 102A that caulks and fixes the head end portion (conductor-exposed portion) of the wire harness; and a bridge-shaped portion having solder joint portions 102B at opposing ends, as shown in
As the terminal 102, a terminal made of metal is preferable. The constituent metal of the terminal is not particularly limited, and examples thereof include metals such as Cu, Fe, Cr, Ni, and Zn; alloys containing one or more metal elements such as Cu, Fe, Cr, Ni, and Zn; and combinations thereof. Examples of the alloy include stainless steel (SUS) and brass. The surface of the terminal 102 may be subjected to a surface treatment such as tin plating. At least a part of the terminal 102 may be covered with an insulating material. The thickness of the terminal 102 is not particularly limited, and is preferably 0.4 to 0.8 mm. The terminal 102 made of a single material can be manufactured, for example, by punching a metal plate (pressing processing using a cutting die) to obtain a metal plate of a desired size and then bending this (bending processing).
For example, a terminal 102 (preferably a crimp terminal) is caulked and fixed to the head end portion (conductor-exposed portion) of the feeding member 103, and the terminal 102 is joined to the terminal joint portion 20T in the feeding electrode 20B with lead-free solder 101 interposed therebetween. Note that the head end portion (conductor-exposed portion) of the feeding member 103 and the terminal 102 may be connected by soldering or welding.
In this embodiment, a region including at least the terminal joint portion 20T of the exposed portion 20E of each feeding electrode 20B is a compressive stress portion 20CS, at least the surface of which is subjected to compressive stress.
In this embodiment, at least a region including the terminal joint portion 20T of the exposed portion 20E of each feeding electrode 20B can be entirely a compressive stress portion 20CS.
The compressive stress portion 20CS just needs to have a negative value in a stress value measured by the sin2ψ method using a micro-area X-ray residual stress measurement system, and is preferably −20 MPa or less. The upper limit is more preferably −25 MPa, particularly preferably −30 MPa. The lower limit is not particularly limited, and is, for example, −50 MPa or −45 MPa.
In this embodiment, the exposed portion 20E of each feeding electrode 20B can have a region, including at least the terminal joint portion 20T, that is a polished portion 20P in which the surface is polished. In the example shown in
The porosity of the polished portion 20P of the conductor 20 is preferably 10% or less, more preferably 8% or less, particularly preferably 7% or less, particularly preferably 3% or less. The lower limit of the porosity of the polished portion 20P of the conductor 20 is, for example, 0.5%.
The porosity of the non-polished portion 20NP of the conductor 20 is larger than the porosity of the polished portion 20P, and may be more than 10%, or 10% or less, for example 15 to 16%.
The rate of the arithmetic mean surface roughness (Ra) of the polished portion 20P of the conductor 20 with respect to that of the non-polished portion 20NP is preferably 5 to 80%, more preferably 5 to 50%, particularly preferably 5 to 20% because the breaking strength after terminal attachment can be effectively increased.
The reduction rate of the film thickness of the polished portion 20P of the conductor 20 with respect to that of the non-polished portion 20NP is preferably 4 to 40%, more preferably 4 to 20%, particularly preferably 4 to 10% because the breaking strength after terminal attachment can be effectively increased.
An example of a method for manufacturing a windshield for vehicle according to this embodiment will be described with reference to the drawings.
First, a ceramic paste containing a black pigment and glass frit, which are the materials of the light-shielding layer BL2, is applied, as necessary, to a predetermined region on the vehicle inner surface S2 of the outer glass plate 11 (glass plate on vehicle outer side) as necessary, and the paste is dried to form a ceramic paste layer.
In addition, a ceramic paste containing a black pigment and glass frit, which are the materials of the light-shielding layer BL4, is applied to a predetermined region on the vehicle inner surface S4 of the inner glass plate 13, as necessary, and the paste is dried to form a ceramic paste layer.
The drying conditions for the ceramic paste can be appropriately designed depending on the paste composition, and are preferably 120 to 150° C. for about 5 minutes, for example.
Note that the inner glass plate 13 is processed into a shape having a cut-out portion 13N in advance.
Next, a silver-containing paste containing silver and glass frit, which are the materials of the conductor 20, is applied to directly on the vehicle inner surface S2 of the outer glass plate 11 or to the ceramic paste layer formed on the outer glass plate 11 as necessary, and the paste is dried to form a conductive paste layer. The drying conditions for the silver-containing paste can be appropriately designed depending on the paste composition, and are preferably, for example, 120 to 150° C. for about 5 minutes.
Next, the outer glass plate 11 and the inner glass plate 13 after the above steps are heated simultaneously or individually to a temperature of the softening point or above (for example, 600 to 700° C.), and each glass plate is bent and formed. In this step, the ceramic paste layer and the silver-containing paste layer formed as necessary are fired, and one or more light-shielding layers BL and conductor 20 are formed as necessary. After firing, each glass plate is slowly cooled.
After the above steps, as shown in
Next, as shown in
The constituent resin of the resin film 12F is not particularly limited, and is preferably one or more types of resin selected from the group consisting of polyvinyl butyral (PVB), ethylene vinyl acetate copolymer (EVA), cycloolefin polymer (COP), polyurethane (PU), and ionomer resin, for example. The resin film 12F may contain one or more types of additives other than resin, as necessary. Examples of additives include colorants such as pigments. The resin film 12F may be colorless and transparent, or colored and transparent. The resin film 12F may have a single layer structure or a laminated structure of two or more layers.
The bonding can be implemented by thermocompression bonding. Examples of the thermocompression bonding methods include: a method for placing a temporary laminate obtained by stacking a plurality of members shown in
The thermocompression bonding conditions of temperature, pressure, and time are not particularly limited, and are designed depending on the type and temperature of the resin film 12F. The thermocompression bonding conditions just needs to be conditions such that the resin film 12F is softened, sufficiently pressurized, and the glass plate with the conductor 11Y and the inner glass plate 13, which may have a light-shielding layer BL4, are sufficiently bonded together with the resin interposed therebetween. Thermocompression bonding may be implemented in a plurality of stages by changing the method or conditions.
Note that the constituent resin of the resin film 12F softens and spreads so as to fill the space between the glass plate with the conductor 11Y and the inner glass plate 13, which may have a light-shielding layer BL4.
Next, at least the surface of the region including the terminal joint portion 20T of the conductor 20 is plastically deformed. The step (S5) can be, for example, a step of polishing the surface of the region including the terminal joint portion 20T of the conductor 20.
In this embodiment, in the exposed portion 20E of each feeding electrode 20B, the surface of the region including the terminal joint portion 20T can be polished. The surface of the entire exposed portion 20E may be polished, or the surface of a part of the exposed portion 20E may be polished.
Generally, the stress remaining in the conductor 20 before implementation of step (S5) is a tensile stress, and the stress value of the conductor 20 before implementation of step (S5) is a positive value. Plastically deforming at least the surface of the terminal joint portion 20T by a method such as surface polishing can make at least the surface of the terminal joint portion 20T into a compressive stress portion 20CS to which compressive stress is applied. The stress value of the compressive stress portion 20CS is a negative value, preferably −20 MPa or less.
After this step, as shown in
Note that in the conductor 20, the film thickness of the polished portion 20P becomes thinner than the film thickness of the non-polished portion 20NP due to polishing.
Next, as shown in
Solder joining can be implemented by a known method, preferably a method using a soldering iron or resistance heating.
In using a soldering iron, for example, joining can be implemented as follows.
An appropriate amount (for example, 0.05 to 0.10 g) of lead-free solder is attached to each solder joint portion of the terminal. This terminal is placed on the terminal joint portion in which the surface of the conductor has been polished. In this state, the tip of a soldering iron set at a temperature of the melting point of the lead-free solder or above is pressed against the solder joint portion of the terminal to heat and melt the lead-free solder. Thereafter, the soldering iron is removed from the terminal, and the lead-free solder is solidified by natural cooling.
Before soldering, it is preferable to apply flux to the surface of the unmelted lead-free solder and/or the surface of the solder joint portion of the terminal. The metal oxide film is melted by the action of the flux, and a sufficient joining state can be obtained.
Before solder joining, it is preferable to place an appropriate amount of lead-free solder on the tip of a soldering iron, and heat and melt it. This solder is called preliminary solder and can improve heat conduction in solder joining.
Generally, in order to join a conductor and solder sufficiently, it is necessary to form an alloy layer containing an alloy of one or more metal elements contained in the conductor and a plurality of metal elements contained in the solder at the joining interface between the conductor and the solder. Therefore, solder joining is implemented by heating the solder to its melting point or above.
The melting point of lead-free solder such as SnAg-based and SnAgCu-based solder is, for example, about 220° C., and in this case, the solder joining temperature is preferably, for example, about 300° C.
The terminal 102 is sealed with a resin such as silicone resin by a known method, as necessary.
In the manner described above, the windshield for vehicle 1 of this embodiment is manufactured.
The method for manufacturing a windshield for vehicle 1 according to this embodiment includes: a step (S5) of plastically deforming at least the surface of a region including the terminal joint portion 20T of the conductor 20 by surface polishing or the like; and a step (S6) of joining the terminal 102 onto the terminal joint portion 20T, at least the surface of which has been plastically deformed, with lead-free solder 101 interposed therebetween. In this method, in the step (S5), compressive stress can be applied to at least the surface of the terminal joint portion 20T of the conductor 20, and the breaking strength after terminal attachment can be increased.
The method for polishing the surface of the region including the terminal joint portion 20T of the conductor 20 allows applying compressive stress to at least the surface of the terminal joint portion 20T of the conductor 20, reducing the porosity of the terminal joint portion 20T and the amount of components of the glass frit on the surface of the terminal joint portion 20T, and effectively increasing the breaking strength after terminal attachment.
In the first embodiment, an aspect has been described in which the conductor 20 includes: an electric function portion including one or more electric heating wires 20L or an electric heating layer; and a feeding portion including a pair of feeding electrodes (a pair of busbars) 20B. The conductor 20 may be configured not to include an electric function portion, and include only a feeding portion that is connected to an electric function portion not included in the conductor 20.
For example, as shown in
For example, on the resin film 12F, one or more metal wires (for example, tungsten wires) are placed as one or more electric heating wires, and as necessary, a pair of metal foils (for example, copper foils) as a pair of feeding electrodes (busbars). Alternatively, on the resin film 12F, a resin film (for example, a polyethylene terephthalate (PET) film) may be placed, on the surface of which one or more electric heating wires and a pair of feeding electrodes are formed.
After the glass plate with the conductor 11Y is bonded with the inner glass plate 13 with the intermediate film 12 interposed therebetween, the electric function portion formed on the resin film 12F is connected to a conductor 20 consisting only of a feeding portion included in the glass plate with the conductor 11Y. The electric function portion formed on the resin film 12F may be connected to the conductor 20 consisting only of the feeding portion included in the glass plate with the conductor 11Y with a feeding portion formed on the resin film 12F interposed therebetween.
Note that the following can be designed as appropriate in the configuration, material, formation method, pattern, and formation region: the conductor 40, which is formed on the resin film 12F and includes an electric function portion and a feeding portion as necessary; and the conductor 20 consisting only of the feeding portion included in the glass plate with the conductor 11Y.
Also in this design modification example, as shown in
The structure of a windshield for vehicle according to a second embodiment of the present disclosure will be described with reference to the drawings.
As shown in
In this embodiment, the laminated glass 50 includes: a glass plate with a terminal 13X that includes: an inner glass plate 13; a conductor 80 that is formed on the vehicle inner surface S4 of the inner glass plate 13 (the surface on the side opposite to the intermediate film 12 side), is made of a material containing silver and glass frit, and has a terminal joint portion 80T to which a terminal 102 is joined; and a terminal 102 joined onto the terminal joint portion 80T of the conductor 80 with lead-free solder 101 interposed therebetween. The laminated glass may be made by bonding three or more glass plates together.
As shown in
As illustrated, the light-transmitting portion TP can be formed in a region relatively close to one end side 50E (in the illustrated example, the upper end side) of the windshield for vehicle 2.
For autonomous driving and prevention of collision accidents, etc., for example, the optical apparatuses can include: optical devices such as ADAS (advanced driver assistance systems) cameras, LiDAR (light detection and ranging), a radar, and optical sensors that acquire information in front of the vehicle; and a housing called a bracket etc. that houses these.
The shapes of the optical apparatus mounting region OP and the light-transmitting portion TP can be appropriately designed depending on the shapes of the optical apparatuses, and examples include a substantially trapezoidal shape and a substantially rectangular shape. The shapes of the optical apparatus mounting region OP and the light-transmitting portion TP may be similar or dissimilar. In the illustrated example, the optical apparatus mounting region OP and the light-transmitting portion TP have a substantially trapezoidal shape.
Similarly to the first embodiment, as shown in
In this embodiment, as shown in
As shown in
In the illustrated example, the formation region of the light-shielding layer BL4 includes: the region of the optical apparatus mounting region OP excluding the light-transmitting portion TP; and the region around the optical apparatus mounting region OP, and includes: a region R41 of a substantially trapezoidal region, the outline of which is formed of one end side 50E (in the illustrated example, the upper end side) and sides B41 to B43 of the laminated glass 50, excluding the light-transmitting portion TP; and a peripheral region R42 of the windshield for vehicle 2.
In the illustrated example, the light-shielding layer BL4 surrounds all four sides of the light-transmitting portion TP. However, the light-shielding layer BL4 just needs to surround at least a part of the light-transmitting portion TP, and, for example, may surround only three sides of the substantially trapezoidal or substantially rectangular light-transmitting portion TP.
The wavelength range of light transmitted by the light-transmitting portion TP is not particularly limited, and includes, for example, the visible light range, the infrared light range, or the visible light range to infrared light range.
As shown in
Note that the planar shape of the formation region of the light-shielding layer BL2 and the planar shape of the formation region of the light-shielding layer BL4 can be designed independently, and the planar shapes of these regions may be identical or non-identical.
As shown in
The conductor 80 is preferably placed within the optical apparatus mounting region OP.
The conductor 80 may be formed on almost the entire surface of the windshield for vehicle 2.
The electric heating wire 80L or the electric heating layer for preventing fogging and frost is provided in the region including the light-transmitting portion TP located in front of the optical devices such as a camera and a radar included in the optical apparatus, thereby making it possible to improve the sensing accuracy of the optical apparatus.
The line pattern and arrangement pattern of the electric heating wires 80L are not particularly limited. For example, as shown in
The wire width of the electric heating wire 80L may change on the way from one feeding electrode to the other feeding electrode. In order to adjust the amount of heat generated by the electric heating wire 80L, the electric heating wire 80L may be arranged in regions other than the light-transmitting portion TP.
As shown in
Similarly to the first embodiment, each of the pair of feeding electrodes (pair of busbars) 80B includes a terminal joint portion 80T, and the terminal 102 is joined onto the terminal joint portion 80T of the conductor 80 with lead-free solder 101 interposed therebetween. A feeding member 103 including a round-wire-shaped or foil-shaped conducting wire is fixed to each terminal 102.
Similarly to the first embodiment, the terminal joint portion 80T of the conductor 80 is a portion immediately underneath the lead-free solder 101. In the figure, the region of the terminal joint portion 80T is a region sandwiched between two broken lines T1 and T2. Note that the position of the terminal joint portion 80T of the conductor 80 is not clearly determined from the beginning. The terminal joint portion 80T is the portion immediately underneath the lead-free solder 101 after the terminal 102 is joined to the feeding electrode 80B with the lead-free solder 101 interposed therebetween.
In this embodiment, the light-shielding layer BL is not formed within the light-transmitting portion TP.
In this embodiment, a region of each feeding electrode 80B including at least the terminal joint portion 80T is a compressive stress portion 80CS, at least the surface of which is subjected to compressive stress.
In this embodiment, the entire region of each feeding electrode 80B including at least the terminal joint portion 80T can be a compressive stress portion 80CS.
In the compressive stress portion 80CS, the stress value measured by the sin2ψ method using a micro-area X-ray residual stress measurement system just needs to be a negative value, and is preferably −20 MPa or less. The upper limit is more preferably −25 MPa, particularly preferably −30 MPa. The lower limit is not particularly limited, and is, for example, −50 MPa or −45 MPa.
In this embodiment, in each feeding electrode 80B, at least the region that includes the terminal joint portion 80T can be a polished portion 80P, the surface of which is polished. In the examples shown in
In the polished portion 80P of the conductor 80, the porosity is preferably 10% or less, more preferably 8% or less, particularly preferably 7% or less, particularly preferably 3% or less. The lower limit of the porosity of the polished portion 80P of the conductor 80 is, for example, 0.5%.
The porosity of the non-polished portion 80NP of the conductor 80 is larger than the porosity of the polished portion 80P, and may be more than 10%, or 10% or less, and is for example 15 to 16%.
The rate of the arithmetic mean surface roughness (Ra) of the polished portion 80P of the conductor 80 with respect to that of the non-polished portion 80NP is preferably 5 to 80%, more preferably 5 to 50%, particularly preferably 5 to 20% because the breaking strength after terminal attachment can be effectively increased.
The film thickness reduction rate of the polished portion 80P of the conductor 80 with respect to that of the non-polished portion 80NP is preferably 4 to 40%, more preferably 4 to 20%, particularly preferably 4 to 10% because the breaking strength after terminal attachment can be effectively increased.
Each step of the method for manufacturing the windshield for vehicle according to this embodiment will be described with reference to the drawings.
First, similarly to the first embodiment, a ceramic paste containing a black pigment and glass frit, which are materials for light-shielding layer BL4, are applied to a predetermined region on the vehicle inner surface S4 of the inner glass plate 13 (glass plate on the vehicle inner side), as necessary, and the paste is dried to form a ceramic paste layer.
In addition, as necessary, a ceramic paste containing a black pigment and glass frit, which are the materials of the light-shielding layer BL2, is applied to a predetermined region on the vehicle inner surface S2 of the outer glass plate 11, and the paste is dried to form a ceramic paste layer.
The drying conditions for the ceramic paste layer are the same as in the first embodiment.
Similarly to the first embodiment, a silver-containing paste containing silver powder and glass frit is applied directly onto the vehicle inner surface S4 of the inner glass plate 13 or onto the ceramic paste layer formed as necessary on the vehicle inner surface S4 of the inner glass plate 13, and the paste is dried to form a silver-containing paste layer. The drying conditions for the conductive paste layer are the same as those in the first embodiment.
Next, similarly to the first embodiment, the outer glass plate 11 and the inner glass plate 13 after the above steps are heated to the temperature of the softening point or above, and each glass plate is bent and formed. In this step, the ceramic paste layer and the silver-containing paste layer formed as necessary are fired, and one or more light-shielding layers BL and conductor 80 are formed as necessary. After firing, each glass plate is slowly cooled. The firing temperature is the same as in the first embodiment.
After the above steps, there are obtained: an outer glass plate 11 that may have a light-shielding layer BL2; and a glass plate with a conductor 13Y that has a light-shielding layer BL4 on one surface S4 of the inner glass plate 13 as necessary, and has a conductor 80 formed directly on the inner glass plate 13 or on the light-shielding layer BL4.
Next, similarly to the first embodiment, the outer glass plate 11, which may have the light-shielding layer BL2, and the glass plate with the conductor 13Y are bonded together with the intermediate film 12 interposed therebetween, through a known method. After these steps, a laminated glass 50 shown in
Next, at least the surface of the region including the terminal joint portion 80T of the conductor 80 is plastically deformed. The step (S5) can be, for example, a step of polishing the surface of the region including terminal joint portion 80T of conductor 80. The entire surface of each feeding electrode 80B may be polished, or the surface of a part of each feeding electrode 80B may be polished.
Typically, the stress remaining in the conductor 80 before implementation of step (S5) is a tensile stress, and the stress value of the conductor 80 before implementation of step (S5) is a positive value. Plastically deforming at least the surface of the terminal joint portion 80T by a method such as surface polishing can make at least the surface of the terminal joint portion 80T into a compressive stress portion 80CS to which compressive stress is applied. The stress value of the compressive stress portion 80CS is a negative value, preferably −20 MPa or less.
After this step, as shown in
Note that in the conductor 80, the film thickness of the polished portion 80P becomes thinner than the film thickness of the non-polished portion 80NP due to polishing.
Next, similarly to the first embodiment, as shown in
In the manner described above, the windshield for vehicle 2 of this embodiment is manufactured.
Similarly to the first embodiment, the method for manufacturing a windshield for vehicle 2 according to this embodiment includes: a step (S5) of plastically deforming at least the surface of a region including the terminal joint portion 80T of the conductor 80; and a step (S6) of joining the terminal 102 onto the terminal joint portion 80T, at least the surface of which has been plastically deformed, with lead-free solder 101 interposed therebetween. In this method, in the step (S5), compressive stress can be applied to at least the surface of the terminal joint portion 80T of the conductor 80, and the breaking strength after terminal attachment can be increased.
The method for polishing the surface of the region including the terminal joint portion 80T of the conductor 80 allows applying compressive stress to at least the surface of the terminal joint portion 80T of the conductor 80, reducing the porosity of the terminal joint portion 80T and the amount of components of the glass frit on the surface of the terminal joint portion 80T, and effectively increasing the breaking strength after terminal attachment.
As described above, according to the present disclosure, it is possible to provide: a windshield for vehicle that includes a portion in which a conductor and a terminal are joined using lead-free solder, and that can increase the breaking strength after terminal attachment; and a manufacturing method thereof.
The present disclosure will be described below based on Examples, but the present disclosure is not limited thereto. Examples 12 to 17, 22 to 27, 32 to 35, and 42 to 45 are examples, and Examples 11, 21, 31, and 41 are comparative examples.
The evaluation items and evaluation methods are as follows.
Application, firing, and polishing of a silver-containing paste was implemented on a glass plate that is the same as the glass plate used in each example, under the same conditions as those in each example, so that a glass plate with a conductor for evaluation (glass plate without a light-shielding layer for evaluation 1) was obtained. From this glass plate for evaluation, samples were cut out, each of which had a size that allowed easy observation of the terminal joint portion of the conductor.
The terminal joint portion of each of above samples was immersed in epoxy resin (“Aqra Type 53” manufactured by Sankei Co., Ltd) and cured at normal temperature, thereby embedding the terminal joint portion in the resin.
The terminal joint portion of the resin-embedded sample was cut in the thickness direction using a high-speed diamond wheel saw (“Mecatome T180” manufactured by Presi). The cut surface of the terminal joint portion was polished using an automatic polishing apparatus (“Mecatech 234” manufactured by Presi). Furthermore, as necessary, ion milling processing was performed using “ArBlade 5000” manufactured by Hitachi High-Tech Corporation.
Using a field emission scanning electron microscope (FE-SEM, “Regulus 8220” manufactured by Hitachi High-Tech Corporation), images of three randomly selected locations on the cut surface of the terminal joint portion were acquired at 2500 times magnification under the condition of a voltage of 3 kV. In the conductor in the cross-sectional SEM image, there were confirmed light gray regions each corresponding to a silver-containing region, dark gray regions each corresponding to glass frit-containing region, and black regions each corresponding to a vacancy. Image processing is implemented using commercially available image analysis software (“WinRooF 2018” manufactured by Mitani Corporation), and as the porosity of the conductor, the proportion of the cross-sectional area of the black regions corresponding to the vacancies with respect to the total cross-sectional area of the three regions was determined. The average value of the porosity of a total of three cross-sectional SEM images was determined and defined as data of the porosity (%).
A stylus-type measurement was implemented using a surface roughness meter (“Surfcom NEX 001” manufactured by Tokyo Seimitsu Co., Ltd.) to measure the reduction amount of film thickness of the conductor after polishing with respect to the thickness before polishing. Measurements were implemented a total of four times for each condition, and the average value thereof was defined as data of the reduction amount of film thickness.
The arithmetic mean roughness (Ra) of the conductor before and after polishing were measured using a surface roughness meter (“Surfcom NEX 001” manufactured by Tokyo Seimitsu Co., Ltd.). Measurements were implemented three times in total for each condition, and the average value thereof was defined as data of the arithmetic mean roughness (Ra). Then, the rate (%) of the arithmetic mean surface roughness (Ra) of the conductor after polishing with respect to that of the conductor before polishing was determined.
The stress value of the terminal joint portion of the conductor was measured using a “micro-area X-ray residual stress measurement system AutoMATE II” manufactured by Rigaku Corporation. The following were the measurement method and measurement conditions. Note that the diffraction peak position was determined by the half-value-width midpoint method.
A total of two measurements were implemented for each sample, and the average value thereof was defined as data for the stress value of the terminal joint portion.
(Breaking Strength Before or after Terminal Attachment)
A ring bending test was conducted in accordance with ASTM-C1499-1 using an Autograph (“AGS-X” manufactured by Shimadzu Corporation, maximum load: 5 kN) in an environment at normal temperature (20 to 25° C.).
The glass plate for evaluation 1 or 2 before or after terminal attachment was placed on a support ring with a diameter of 98 mm with the surface on the conductor formation side facing down. A load ring with a diameter of 46 mm was placed on this glass plate for evaluation. The central axis of the support ring, the central axis of the glass plate, and the central axis of the load ring were aligned.
A load was applied around the terminal of the glass plate for evaluation using a load ring. The load was continuously increased so that the amount of displacement of the glass plate was 1 mm/min, and the load at which the glass plate broke was defined as the breaking strength.
For each condition, a total of 5 samples were measured, and the average value thereof was defined as data of the breaking strength before or after terminal attachment.
(Manufacture of Glass Plate with Conductor for Evaluation (Glass Plate for Evaluation 1))
A glass plate with a conductor for evaluation (glass plate without a light-shielding layer for evaluation 1) was manufactured in the same manner as described below [Manufacture of Glass Plate with Light-Shielding Layer and Conductor for Evaluation (Glass Plate for Evaluation 2)], except for directly formed a conductive paste layer on one surface of the glass plate without forming a ceramic paste layer.
(Manufacture of Glass Plate with Light-Shielding Layer and Conductor for Evaluation (Glass Plate for Evaluation 2))
A 100 mm×100 mm square, 2 mm thick, un-tempered glass plate (“VFL” manufactured by AGC) was prepared. A ceramic paste for forming a light-shielding layer containing a black pigment and glass frit was applied onto one surface of this glass plate, and dried to form a ceramic paste layer. The drying conditions were 120° C. for about 10 minutes. A ceramic paste A was used as the ceramic paste.
Next, a silver-containing paste for forming a conductor containing silver powder and glass frit was applied onto the ceramic paste layer, and dried to form a conductive paste layer. The drying conditions were 120° C. for about 10 minutes.
In Examples 11 to 17, a silver-containing paste A was used as the silver-containing paste.
In Examples 21 to 27, a silver-containing paste B was used as the silver-containing paste.
Each of the silver-containing pastes A and B had a vehicle content of 10 to 45% by mass.
Next, the ceramic paste layer and the conductive paste layer were fired. The layers were increased in temperature from normal temperature (20 to 25° C.) to 615° C. at a heating rate of about 180° C./min, fired at 615° C. for 3 minutes, and then naturally cooled to normal temperature (20 to 25° C.) (preliminary firing). The layers were then increased in temperature to 600° C. at a heating rate of about 180° C./min, fired at 600° C. for 3 minutes, and naturally cooled to normal temperature (20 to 25° C.) (main firing). In this way, a light-shielding layer and a conductor were formed.
The planar shape of the light-shielding layer was a square of 52 mm×52 mm, and its center and diagonal were aligned with the center and diagonal of the glass plate. The thickness of the light-shielding layer was about 15 μm.
The planar shape of the conductor was a square of 50 mm×50 mm, and its center and diagonal were aligned with the center and diagonal of the glass plate.
The thickness of the conductor formed using the silver-containing paste A was 8.2 μm.
The thickness of the conductor formed using the silver-containing paste B was 6.2 μm.
As described above, a glass plate with a light-shielding layer and a conductor for evaluation (glass plate for evaluation 2) was manufactured.
In Examples 12 to 17 and Examples 22 to 27, the surface of each of the conductors of the glass plates for evaluation 1 and 2 was polished using a polishing eraser, metal fiber, or an electric-powered cutting tool (hand grinder). The following are the polishing conditions. The physical properties of the conductor were evaluated before and after polishing.
As the polishing eraser, “Sand Eraser for Ink and Ballpoint Pens” manufactured by SEED Co., Ltd. (grit number: #220 equivalent) was used. A polishing eraser was held by the fingers of one hand, and the eraser was moved horizontally from one end of the conductor to the other end with the eraser pressed against the surface of the conductor. This operation was implemented a total of 8 times.
As the metal fiber, steel wool manufactured by Bonstar Co., Ltd. (grit number: #000, fiber center diameter: 14 μm, 1 g) was used.
The steel wool was held by the fingers of one hand, and the steel wool was moved horizontally from one end of the conductor to the other end with the steel wool pressed against the surface of the conductor. This operation was implemented totally 24 times of back-and-forth motion.
As an electric-powered cutting tool (hand grinder), “Leutor (registered trademark)” manufactured by Nihon Seimitsu Kikai Kosaku Co., Ltd. was used. As each tip tool, an angle tool consisting of a combination of a rubber pad and a polishing disc attached to the rubber pad was used. Four types of polishing discs were used: cushion disc #1200, cushion disc #800, cushion disc #400, and cushion disc #240.
In the example in which the silver-containing paste A was used as the silver-containing paste, the rotational speed of the Leutor was 2000 rpm, and the polishing time was 10 seconds.
In the example in which the silver-containing paste B was used as the silver-containing paste, the rotational speed of the Leutor was 2000 rpm, and the polishing time was 5 seconds.
In each example, a brass crimp terminal is joined onto the conductor of each of the glass plates for evaluation 1 and 2 using SnAg-based lead-free solder (Sn: 98% by mass, Ag: 2.0% by mass, melting point: about 220° C.). The brass crimp terminal includes: a tubular feeding member joint portion into which the head end portion (conductor-exposed portion) of the wire harness is inserted; and a bridge-shaped portion having solder joint portions at opposing ends as shown in
The specific method is as follows.
An appropriate amount of lead-free solder was placed on the tip of a soldering iron and heated to melt. This solder is called preliminary solder.
A 0.05 g of lead-free solder chip was attached to each solder joint portion of the terminal. The terminal was placed on the terminal joint portions of the conductor. In this state, the tip of a soldering iron set at 300° C. was pressed against the solder joint portions of the terminal to heat and melt the lead-free solder chip. Thereafter, the soldering iron was removed from the terminal, and the lead-free solder was solidified by natural cooling.
After one hour elapsed from when the terminal was joined onto the conductor with lead-free solder interposed therebetween, the breaking strength of each of the glass plates for evaluation 1 and 2 after terminal attachment was measured.
Tables 1-1 and 1-2 show the main experimental conditions and evaluation results of Examples 11 to 17.
Tables 2-1 and 2-2 show the main experimental conditions and evaluation results of Examples 21 to 27.
Comparison of Example 11 and Example 21 showed that under the same conditions except for the type of silver-containing paste, the conductor obtained using the silver-containing paste A had a smaller surface roughness (Ra) and a larger porosity than the conductor obtained using the silver-containing paste B when they are compared in an unpolished state.
The conductor of Example 11 obtained using the silver-containing paste A has a porosity of 16.0% in the unpolished state, and the porosity was comparable to the porosity of the conductive tracks of Examples 2 and 3 in [Examples] section of International Patent Publication No. WO 2006/132319.
The results of Examples 11 and 21 showed that under the same conditions except for the presence or absence of a light-shielding layer, the glass plate for evaluation 2 (with a light-shielding layer) had a lower breaking strength after terminal attachment than the glass plate for evaluation 1 (without a light-shielding layer) when they are compared in an unpolished state. It is presumed that under conditions with a light-shielding layer, a part of the components of the glass frit contained in the material for forming the light-shielding layer moves to the surface of the conductor in firing the paste, so that more components of the glass frit is present on the surface of the conductor, decreasing the joining strength between the conductor and solder.
Each of Examples 12 to 17 in which the surface of the conductor was polished had a lower porosity, film thickness, and arithmetic mean surface roughness (Ra) of the conductor than Example 11 in which the surface of the conductor was not polished.
Each of Examples 22 to 27 in which the surface of the conductor was polished had a lower porosity, film thickness, and arithmetic mean surface roughness (Ra) of the conductor than Example 21 in which the surface of the conductor was not polished.
Each of Examples 12 to 17 in which the surface of the conductor was polished successfully obtained a lower porosity of the conductor, which was 10% or less, than Example 11 in which the surface of the conductor was not polished. It is presumed that voids in the conductor are filled by polishing.
Examples of measuring porosity are shown in
The two images on the left side of
The two images on the left side of
The two images on the left side of
In the conductor obtained in Example 21 (without polishing, with a light-shielding layer), many large voids were observed both on the surface and in the cross section, whereas in the conductor obtained in Example 22 (with polishing, with a light-shielding layer), it was confirmed that voids disappeared or significantly reduced both on the surface and in the cross section. It is presumed that polishing the surface of the conductor stretches the silver to fill the voids.
Examples 12 to 17, in each of which the surface of the conductor was polished, satisfied the following conditions 1 and 2, and each had an improved breaking strength after terminal attachment relative to Example 11 in both of the glass plate for evaluation 1 (without a light-shielding layer) and the glass plate for evaluation 2 (with a light-shielding layer).
Examples 22 to 27, in each of which the surface of the conductor was polished, satisfied the following conditions 1 and 2, and each had an improved breaking strength after terminal attachment relative to Example 21 in both of the glass plate for evaluation 1 (without a light-shielding layer) and the glass plate for evaluation 2 (with a light-shielding layer).
In Example 31, the glass plate with a light-shielding layer and a conductor for evaluation (glass plate for evaluation 2, conductor (without polishing)/light-shielding layer/glass plate) was manufactured in the same manner as Example 21 except for changing the type of ceramic paste for forming the light-shielding layer.
In Example 32, the glass plate with a light-shielding layer and a conductor for evaluation (glass plate for evaluation 2, conductor (with polishing)/light-shielding layer/glass plate) was manufactured in the same manner as Example 22 except for changing the type of ceramic paste for forming the light-shielding layer.
In each of Examples 33 to 35, the glass plate with a light-shielding layer and a conductor for evaluation (glass plate for evaluation 2, conductor (with polishing)/light-shielding layer/glass plate) was manufactured in the same manner as Example 32 except for changing the grit number of polishing eraser.
In these examples, a ceramic paste B was used as the ceramic paste for forming the light-shielding layer.
The polishing erasers used in each of Examples 32 to 35 are as follows. Example 32: polishing eraser “SK-11” manufactured by Fujiwara Sangyo Co., Ltd. (grit number: #220),
The conductors obtained in each of Examples 31 to 35 were subjected to solder joining in the same manner as in Examples 21 and 22, and the breaking strength of the glass plate for evaluation 2 after terminal attachment was measured. Table 3 shows the main experimental conditions and evaluation results of Examples 31 to 35.
In each of Examples 32 to 35 in which the surface of the conductor was polished, the breaking strength after terminal attachment was improved relative to Example 31 in which the surface of the conductor was not polished.
A glass plate for evaluation with a light-shielding layer and a conductor (glass plate for evaluation 2) was manufactured using a ceramic paste C and the silver-containing paste B in the same method as in Example 21 except for changing the firing conditions. The firing conditions were as follows: increasing the temperature from normal temperature (20 to 25° C.) to 600° C. at a heating rate of 180° C./min; firing at 600° C. for about 4 minutes; and then naturally cooling to normal temperature (20 to 25° C.).
Similarly to Example 21, surface polishing of the conductor was not implemented.
An attempt was made for implementing solder joining on the conductor of the obtained glass plate for evaluation 2 in the same manner as in Example 21. However, the wettability of the lead-free solder to the surface of the conductor on the light-shielding layer formed using the ceramic paste C was ineffective, so that solder joining could not be implemented.
In each of Examples 42 to 45, a glass plate with a light-shielding layer and a conductor for evaluation (glass plate for evaluation 2) was manufactured in the same method as in Example 41.
The surface of the conductor of the obtained glass plate for evaluation 2 was polished using a polishing eraser. A polishing eraser was held by the fingers of one hand, and the eraser was moved horizontally from one end of the conductor to the other end with the eraser pressed against the surface of the conductor. This operation was implemented totally 6 times of back-and-forth motion.
The polishing erasers used in each example are as follows.
Solder joining was implemented on the conductor of the obtained glass plate for evaluation 2 in the same manner as in Example 22. In these examples, surface polishing improved the wettability of lead-free solder on the surface of the conductor on the light-shielding layer formed using the ceramic paste C, and solder jointing was implemented sufficiently. Each breaking strength of the glass plate for evaluation 2 after terminal attachment was measured.
Table 4,
In Example 41, in which the surface of the conductor was not polished, had a stress value of +45 MPa at the terminal joint portion of the conductor. It was confirmed that tensile stress was applied to the terminal joint portion of the unpolished conductor. The breaking strength of the obtained glass plate for evaluation 2 before terminal attachment was measured and found to be 65 MPa.
Examples 42 to 45, in which the surface of the conductor was polished, each had a stress value of −50 to −20 MPa at the terminal joint portion of the conductor after surface polishing. With this, it was confirmed that the terminal joint portion of the conductor after surface polishing became a compressive stress portion, at least the surface of which was subjected to compressive stress. In these examples, the breaking strength after terminal attachment was high and sufficient.
From the disclosure thus described, it will be obvious that the embodiments of the disclosure may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure, and all such modifications as would be obvious to one skilled in the art are intended for inclusion within the scope of the following claims.
The first and second embodiments can be combined as desirable by one of ordinary skill in the art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-116528 | Jul 2023 | JP | national |
