JP6728575B2 - Joining method - Google Patents

Description

The present invention relates to a method for joining resin surfaces.

Generally, a resin laminated body formed by joining a plurality of resin base materials is widely used for various purposes in various fields.
For example, the microfluidic device made of a resin laminate has been utilized and spread due to the recent progress in fine processing technology and the development and spread of plastic molding processing technology.
A microfluidic device is a means (chemical system) for miniaturizing and integrating various chemical processes such as mixing, reaction, extraction, and separation of target fluids such as human body fluids. Therefore, for example, it is also called a micro mixer (mixing device), a micro reactor (chemical reaction device), a micro TAS (lab-on-a-chip), or the like.

Such a microfluidic device is composed of a microchannel chip that forms a reaction field for mixing and reacting fluids in a minute flow channel space. In a microfluidic device, fluids are mixed and reacted in a micro space that is a reaction field. Therefore, for example, a reaction that was performed in a “cm” space in an ordinary apparatus is performed in a “100 μm” space. Therefore, the size of the reaction field becomes about 1/100, and there is an advantage that the reaction efficiency is high.
Specifically, in the microfluidic device, the molecular diffusion time (proportional to the square of the diffusion distance) is about 1/10,000, and the chemical reaction rate is significantly increased.
Therefore, for example, it is possible to complete a heavy metal contamination inspection of tap water, which normally takes about 3 to 4 hours, in about 50 seconds.

Further, in such a microfluidic device, the amount of the fluid used for the reaction and the like becomes minute, so that the amount of the sample/waste liquid is greatly reduced. Specifically, the volume of the fluid (proportional to the cube of the size) can be set to about 1/1,000,000 of the conventional one, and the amount of the sample/waste liquid can be reduced to the nanoliter order. ..
As a result, for example, in the case of a heavy metal contamination inspection of tap water, the target fluid (water) amount can be reduced from about 1 kg to about 1 μg in a normal inspection device, that is, up to about one billionth.
In recent years, such a microfluidic device has been configured by a resin laminated body in which a plurality of resin base materials are joined.

Here, when a plurality of resin base materials are laminated and bonded to each other, a so-called heat seal method in which the base materials to be bonded are heated to a glass transition point or higher or a melting point or higher to be softened and heat-sealed Is common. However, in the case of the microfluidic device having the minute/narrow channel space as described above, such a joining method by heat sealing causes a problem that the channel space is deformed.
FIG. 13 is an explanatory view schematically showing a manufacturing process in the case where two resin base materials constituting the microfluidic device are heat-sealed, and (a) shows two resin base materials constituting the microfluidic device. The step of laminating, (b) shows the step of heating and pressurizing the two laminated resin base materials to a glass transition point or higher or a melting point or higher to bond them.

As shown in the figure, two resin base materials forming the microfluidic device 100, specifically, the substrate 101 on which the microchannel 103 is formed, and the lid member (cover body) 102 laminated on the upper surface of the substrate 101 are First, they are laminated at predetermined positions (see FIG. 13(a)), and then, in a laminated state, both base materials 101 and 102 are heated to a temperature not lower than the glass transition point or not lower than the melting point, under the heating temperature environment. Is pressurized with.
By heating above the glass transition point or above the melting point, the resin base materials 101, 102 are softened and the molecules come close to each other, and the two base materials are joined by the Van der Waals force.

However, in such a joining method by heat fusion/heat sealing, since the resin base material heated to a glass transition point or higher or a melting point or higher softens/melts, as shown in FIG. The space forming 103 is deformed, the flow path space is narrowed, or the cross-sectional shape of the flow path is deformed to impede the flow of fluid, and in the worst case, the flow path is blocked. ..
Therefore, regarding such a method for manufacturing a resin-made microfluidic device, as a method for preventing deformation of the flow path space due to heating and joining, for example, a technique disclosed in Patent Document 1 has been proposed.

The technique proposed in Patent Document 1 irradiates the bonding surface of a resin base material forming a microfluidic device with vacuum ultraviolet light for a certain period of time or more to hydrogen bond the bonding surface of the resin base material with a high oxidizing power. To improve wettability.
According to Patent Document 1, it is possible to perform thermocompression bonding at a temperature lower than the plastic deformation temperature (for example, ambient temperature 70° C. to 90° C.) by increasing the wettability of the bonding surface of the resin base material.

Japanese Patent No. 4992433

However, in the method described in Patent Document 1, it is necessary to irradiate vacuum ultraviolet rays for a certain period of time, such as 2 minutes or 5 minutes, in order to impart high wettability to the bonding surface of the resin base material.
Therefore, not only the process time becomes long, but also the ultraviolet irradiation for a long time causes a problem that the bonding surface of the resin base material becomes rough. It is considered that this roughening may reduce the mechanical strength of the resin base material or the transparency of the resin when it is transparent.

The present invention has been proposed in order to solve the problems of the conventional techniques as described above, by flattening and softening the bonding surface of the resin base material, the resin base material to be bonded, glass transition It is an object of the present invention to provide a joining method suitable for manufacturing a microfluidic device made of resin, for example, which can be securely and firmly joined at a temperature below the point or above the melting point and at a lower temperature.

To achieve the above object, the joining method of the present invention is a method of joining resin surfaces to each other, and a step of flattening and softening the joining surface of the base material by performing high-energy irradiation. A step of joining the base material by heating and/or pressurizing the joint surface after contacting the joint surface, wherein the base material is made of a thermoplastic resin, which constitutes a microfluidic device, in the step of performing energy irradiation, the bonding surface of the base material, the range of irradiation time 2-10 seconds, by irradiating argon plasma, the surface roughness of the bonding surface of the pre Kimoto material, arithmetic average roughness Ra≦10 nm , and the bonding surfaces of the base materials are bonded to each other at a temperature not higher than the glass transition point of the thermoplastic resin and not higher than 70° C.

According to the present invention, by flattening and softening the bonding surface of the resin base material, the resin base material to be bonded can be bonded at a temperature lower than the glass transition point or higher than the melting point and lower in temperature.
This makes it possible to provide a joining method suitable for manufacturing a microfluidic device made of resin, for example.

FIG. 3A is a perspective view schematically showing a microfluidic device manufactured by a bonding method according to an embodiment of the present invention, in which (a) is a substrate having microchannels engraved and a lid member bonded to the upper surface thereof. FIG. 2B shows a state in which the cover member is disassembled, and FIG. It is explanatory drawing which shows typically the manufacturing process of the microfluidic device by the joining method which concerns on one Embodiment of this invention, (a) shows argon plasma irradiation to the joining surface of two resin base materials which comprise a microfluidic device. The step of flattening and softening the joint surface by performing (b) is a step of stacking two resin base materials having the joint surface flattened and softened, and then joining the two resin base materials by heating and pressing. The process is shown. (A) is a graph showing the relationship between the bonding strength (bonding energy) of two resin base materials bonded by the bonding method according to one embodiment of the present invention and the irradiation time of argon plasma, and (b) is ( It is explanatory drawing which shows typically the measuring method of the binding energy shown to a). (A) shows the relationship between the bonding strength (bonding energy) of two resin base materials bonded by the bonding method according to one embodiment of the present invention, the irradiation time of argon plasma, and the surface roughness (Ra) of the bonding surface. It is a graph which shows, and (b) is explanatory drawing which shows typically the difference of surface roughness (Ra) with irradiation time. (A) shows the relationship between the bonding strength (bonding energy) of two resin base materials bonded by the bonding method according to one embodiment of the present invention, the irradiation time of argon plasma, and the Young's modulus (GPa) of the bonding surface. It is a graph and (b) is explanatory drawing which shows the measuring method of the Young's modulus shown to (a) typically. It is sectional drawing of the joining part which shows typically the packaging container manufactured by the joining method which concerns on one Embodiment of this invention, (a) is a conventional packaging container, (b) is one embodiment of this invention. The packaging container is shown. 6 is a graph showing the relationship between the bonding strength (bonding energy) of two resin base materials bonded by the bonding method according to the embodiment of the present invention and the irradiation time of oxygen plasma. It is a graph which shows the joint strength (bonding energy) of two resin base materials joined by the joining method which concerns on one Embodiment of this invention, the irradiation time of oxygen plasma, and the surface roughness (Ra) of a joint surface. It is a graph which shows the joint strength (bonding energy) of two resin base materials joined by the method which concerns on one Embodiment of this invention, the irradiation time of oxygen plasma, and the Young's modulus (E) of a joint surface. It is a graph which shows the joint strength (bonding energy) of two resin base materials joined by the method which concerns on one Embodiment of this invention, and the irradiation time of a vacuum ultraviolet ray. It is a graph which shows the bond strength (bonding energy) of two resin base materials joined by the method which concerns on one Embodiment of this invention, the irradiation time of a vacuum ultraviolet ray, and the surface roughness (Ra) of a joint surface. 6 is a graph showing the relationship between the bonding strength (bonding energy) of two resin base materials bonded by the method according to the embodiment of the present invention, the irradiation time of vacuum ultraviolet rays, and the Young's modulus (E) of the bonding surface. It is explanatory drawing which shows the manufacturing process in the conventional joining method typically, (a) is the process of laminating|stacking the two resin base materials which comprise a microfluidic device, (b) is the two laminating resin base materials. The process of joining by heating and pressurizing is shown.

Hereinafter, embodiments of a joining method according to the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view schematically showing a microfluidic device 10 manufactured by a bonding method according to an embodiment of the present invention. FIG. 1A is a substrate 11 having a microchannel 13 engraved and an upper surface thereof. The cover member 12 to be joined with the cover member 12 is disassembled, and (b) similarly shows the state where the cover member 12 is joined to the upper surface of the substrate 11.

[Microfluidic device]
As shown in the figure, the microchannel chip constituting the microfluidic device 10 has a microchannel which is a minute channel space having a width of about 100 μm and a depth of about 50 μm on a substrate 11 made of synthetic resin such as plastic. 13 is engraved, and a lid member (cover body) 12 is joined to the upper surface thereof to form a microchannel 13 serving as a reaction field. The size (width/depth), flow channel length, flow channel shape, etc. of the micro flow channel 13 engraved on the substrate 11 depend on the application of the microfluidic device and the type of fluid. It is set arbitrarily.

Here, the synthetic resin material for forming the substrate 11 and the lid member 12 is not particularly limited, and various thermoplastic resins, for example, olefin resins such as polyethylene and polypropylene, and the like, as in known microfluidic devices and the like, A polyester resin typified by polyethylene terephthalate (PET) can be used.
Then, various detection/control elements and the like (not shown) are embedded in the microchannel chip having the above-described fine channel space to form the microfluidic device 10 constituting the chemical system. , For example, a microfluidic device or the like, which is a simple rapid diagnostic kit for influenza.

[Joining method]
In the present embodiment, the microfluidic device 10 as described above is bonded by using the following method.
That is, the joining method according to the present embodiment is a method of joining two resin base materials to manufacture a resin laminated body, in which high energy is applied to the joining surface of at least one resin base material of the two resin base materials. It comprises a step of flattening and softening the joint surface by irradiation, and a step of stacking two resin base materials and then joining the two resin base materials by heating and/or pressurizing them. ..

[High energy irradiation]
Specifically, in the bonding method according to the present embodiment, first, as shown in FIG. 2A, the substrate 11 in which the micro flow path 13 of the microfluidic device 10 is formed, and the lid stacked on the substrate 11 are formed. High-energy irradiation is performed on the surface of the base material that is the bonding surface of each member 12.
By irradiating the surface of the resin substrate with high energy having a large atomic weight, the substrate surface can be modified, and specifically, the substrate surface can be flattened and softened.
By flattening and softening, the contact and adhesion between the surfaces of the base materials are enhanced, and both can be firmly fused and bonded by Van der Waals force even at a lower bonding temperature.

Here, in the present embodiment, as shown in FIG. 2A, high-energy irradiation is performed by irradiating the joining surface of the resin base material with argon plasma.
In argon plasma, Ar ions or Ar radicals, which are the active species of argon, are generated by plasma by introducing argon gas, which has a large atomic weight and is easily turned into plasma, as a raw material gas to perform discharge. The molecules of the resin base material can be cut by causing a strong argon active species to collide with the surface of the resin base material.
As a result, the surface of the resin base material can be modified. Specifically, the base material surface is flattened, and the base material surface is reduced in molecular weight, that is, softened.

By using the flattened and softened (lowered molecular weight) surface as the joining surface, the contact and adhesion between the substrate surfaces are enhanced, and the two are firmly fused even at a lower joining temperature. -It becomes possible to join.
As a result, as shown in FIG. 2B, the resin base material (the substrate 11 and the lid member 12) can be joined even at a temperature below the glass transition point or below the melting point. For example, as shown in FIG. It becomes possible to bond two substrates at a bonding temperature of about 30°C.
Then, the bonding is performed at a temperature not higher than the glass transition point or not higher than the melting point, so that the microchannel 13 formed on the substrate 11 is not deformed, and is preferably used as a method for manufacturing the microfluidic device 10. it can.

Note that, as shown in FIG. 2B, in the present embodiment, since the joining can be performed at the joining temperature of 30° C., at least one of heating and pressurization may be performed. For example, heating is performed. It is also possible to bond the resin base materials by simply pressing without applying pressure, or it is possible to bond the resin base materials without applying pressure by applying only heating.
However, in order to bond the resin base materials to each other more firmly and reliably, it is desirable to heat and pressurize at an appropriate temperature and pressure.

Here, as the high-energy irradiation performed on the bonding surface of the resin base material in the present embodiment, the above-mentioned argon plasma is preferable, but the high-energy irradiation is not limited thereto.
For example, high energy irradiation other than argon plasma may be irradiation with any one of oxygen plasma, mixed plasma of argon and oxygen, or vacuum ultraviolet light.
These are energy irradiations that easily turn into plasma and have an attack force, and like the case of the above-mentioned argon plasma irradiation, reforming the surface of the resin base material, that is, flattening and softening the base material surface (lowering the molecular weight). ), and can be used instead of argon plasma.
Further, these high energy irradiations may be performed on at least one of the joint surfaces of the two resin base materials to be joined. However, in order to obtain a stronger joint strength, it is desirable to perform high-energy irradiation on each joint surface of the two resin base materials to be joined.

[Binding energy]
Next, the relationship between the irradiation time of high energy such as argon plasma and the bonding strength (bonding energy) of the resin base material to be bonded will be described with reference to FIG.
FIG. 3A is a graph showing the relationship between the bonding strength (bonding energy) of two resin substrates bonded by the bonding method according to the embodiment of the present invention and the irradiation time of argon plasma, and FIG. FIG. 4 is an explanatory view schematically showing the method of measuring the binding energy shown in (a).

As a premise, the bonding strength (bonding energy) of the resin base material in the present embodiment was measured by a method called a crack opening method. As shown in FIG. 3B, two base materials having a plate thickness t are joined and a razor blade having a thickness of 2y is inserted between the two base materials to separate the two resin base materials from each other. L is measured and calculated as the binding energy γ by the following formula 1.
[Formula 1]

First, as shown in FIG. 3A, the resin base material cannot be bonded at a bonding temperature of 30° C. (bonding energy=0 J/m) in the state where high energy is not irradiated at all (irradiation time 0 seconds). ² ).
Next, when high energy is irradiated, the bonding strength of the resin base material increases as the irradiation time increases.
After that, when the irradiation time is 8 to 9 seconds, the binding energy γ exceeds 2.8 J/m ² and becomes the highest, but immediately after that, the irradiation time becomes 10 seconds and the binding energy becomes 0 J/m ² , and thereafter, Even if irradiation is continued, the binding energy becomes 0 J/m ² , and the resin base material cannot be joined at the joining temperature of 30°C.

From the above, in relation to the bonding strength (bonding energy), the irradiation time of the high energy to the bonding surface of the resin substrate is preferably 10 seconds or less, more preferably 2 seconds to 8 seconds, and 5 It can be seen that the range of seconds to 8 seconds is particularly preferred.
That is, the irradiation time of high energy is not necessarily long, and it is important to set the irradiation time in the above-mentioned predetermined range.
In this regard, in Patent Document 1 described above, as a result of irradiating the bonding surface of the resin base material with vacuum ultraviolet rays for a long time such as 2 minutes or 5 minutes, lowering of the bonding temperature is hindered. I can understand it well.

[Surface roughness]
Next, regarding the relationship between the irradiation time of high energy as described above, the bonding strength (bonding energy) of the resin base material to be bonded, and the surface roughness (flatness) of the bonding surface of the resin base material, FIG. Will be described with reference to.
FIG. 4A shows the bonding strength (bonding energy) of two resin substrates bonded by the bonding method according to the embodiment of the present invention, the irradiation time of argon plasma, and the surface roughness (Ra) of the bonding surface. It is a graph which shows a relationship, (b) is explanatory drawing which shows typically the difference of surface roughness (Ra) with irradiation time.

As a premise, the arithmetic mean roughness Ra is used as the surface roughness of the joint surface of the resin base material in the present embodiment.
The arithmetic mean roughness is a mean value obtained by sampling the roughness curve by the reference length 1 in the direction of the mean line, summing the absolute values of the deviations from the mean line of the extracted part to the measurement curve, and It is calculated by the equation (2).
Since the influence of one flaw on the measured value becomes extremely small and a stable result is obtained, this arithmetic mean roughness is adopted as a standard for flattening the joint surface in the present embodiment.
[Formula 2]

First, as shown in FIG. 4(a), the arithmetic mean roughness Ra of the joint surface is about 10 nm in the state where no high energy is applied (irradiation time 0 seconds) (FIG. 4(b)). This is the flatness of the joint surface of the resin base material at room temperature/normal state.
Next, when high energy is irradiated, first, as the irradiation time becomes longer, the arithmetic mean roughness of the joint surface of the resin base material becomes smaller, and the irradiation time becomes smaller until about 8 seconds, and therefore, It can be seen that the joint surface is being flattened. For example, Ra is 10 nm or less when the irradiation time is 2 seconds, about 5 nm when the irradiation time is 5 seconds, and about 3 nm when the irradiation time is 8 seconds.
When the irradiation time is around 8 seconds, the arithmetic mean roughness becomes the minimum, but immediately after that, Ra becomes 60 nm at the irradiation time of 10 seconds, and thereafter, the value of Ra becomes larger as the irradiation time becomes longer. At the time of 20 seconds, Ra exceeds 70 nm (see the right diagram of FIG. 4B).

From the above, in relation to the surface roughness (flatness) of the joint surface, the irradiation time of high energy to the joint surface of the resin base material is preferably 8 seconds or less, and preferably in the range of 2 seconds to 8 seconds. Is more preferable, and the range of 5 seconds to 7 seconds is particularly preferable.
If this is understood from the surface roughness of the bonding surface, as described above, Ra rapidly changes (increases) to 60 nm immediately after reaching the minimum value (about 3 nm) from 10 nm or less. It can be seen that it is preferable to control the irradiation time of high energy so that the arithmetic average roughness Ra of the surface becomes Ra≦10 nm.

That is, as in the case of the relationship with the bonding strength (bonding energy) described above, the relationship with the surface roughness of the bonding surface does not mean that the irradiation time of the high energy is long, and the predetermined range as described above is used. It is desirable to adopt the irradiation time.
In this respect also, in Patent Document 1 described above, as a result of irradiating the bonding surface of the resin base material with vacuum ultraviolet rays for a long time such as 2 minutes or 5 minutes, lowering of the bonding temperature is hindered. I can understand it well.

[Young's modulus]
Next, with reference to FIG. 5, regarding the relationship between the irradiation time of high energy as described above, the bonding strength (bonding energy) of the resin base material to be bonded, and the Young's modulus (softening degree) of the bonding surface of the resin base material, I will explain.
FIG. 5A shows the relationship between the bonding strength (bonding energy) of two resin substrates bonded by the bonding method according to the embodiment of the present invention, the irradiation time of argon plasma, and the Young's modulus (E) of the bonding surface. And (b) is an explanatory view schematically showing the method of measuring the Young's modulus shown in (a).

As a premise, the Young's modulus (softening degree) of the joint surface of the resin base material in the present embodiment is a proportional constant of strain and stress in the coaxial direction. Strain = ε, stress = σ, Young's modulus = E is It is calculated by the equation 3 below. In the present embodiment, as shown in FIG. 5B, a probe having a radius of curvature of R400 nm at the tip is brought into vertical contact with the bonding surface of the resin base material and pressed to a depth of 50 nm. I am measuring.
[Formula 3]

First, as shown in FIG. 5A, the Young's modulus E of the bonding surface is about 3.3 GPa in the state where high energy is not applied at all (irradiation time is 0 seconds). It is the degree of softening of the joint surface at room temperature/normal state.
When high energy is irradiated, first, as the irradiation time becomes longer, the Young's modulus of the joint surface of the resin base material also becomes smaller, and the Young's modulus becomes smaller until the irradiation time is in the vicinity of 5 seconds. It can be seen that the molecular weight is being changed. For example, when the irradiation time is 2 seconds, E becomes about 1.7 GPa, and when the irradiation time is 5 seconds, it becomes smaller at about 1.6 GPa.
The Young's modulus became the minimum when the irradiation time was around 5 seconds, but immediately after that, the Young's modulus started to rise and reached 2.0 GPa at the irradiation time of 10 seconds. It can be seen that there is no change and there is no further change in softening (lowering of molecular weight).

From the above, in relation to the Young's modulus (softening degree) of the joint surface, the irradiation time of high energy to the joint surface of the resin base material is preferably 8 seconds or less, and more preferably in the range of 2 seconds to 8 seconds. It is understood that the range of 2 seconds to 5 seconds is preferable and the range of 2 seconds to 5 seconds is particularly preferable.
That is, as in the case of the relationship between the bonding strength (bonding energy) and the surface roughness (flattening) of the bonding surface described above, the irradiation time of high energy is also determined from the relationship with the Young's modulus (softening degree) of the bonding surface. It is not desirable that the length is long, and it is desirable to adopt the irradiation time within the predetermined range as described above.
Also in this respect, in Patent Document 1 described above, as a result of irradiating the bonding surface of the resin base material with vacuum ultraviolet light for a long time such as 2 minutes or 5 minutes, lowering of the bonding temperature is hindered. You can understand it well.

From the above, when joining the resin base material forming the substrate 11 and the lid member 12 of the microfluidic device 10, the irradiation time when high energy irradiation such as argon plasma is applied to the bonding surface of the resin base material is: The relationship with the bonding strength of the base material is 2 seconds to 10 seconds, the relationship with the surface roughness (flatness) of the bonding surface is 2 seconds to 8 seconds, and the relationship with the Young's modulus (softening degree) of the bonding surface. Therefore, it is preferable to set it in the range of 2 seconds to 5 seconds.
Therefore, the irradiation time of the high energy of the bonding surface of the resin base material is particularly preferably in the range of 2 seconds to 5 seconds, and in this range, the surface roughness (flatness) Ra≦10 nm of the bonding surface of the resin base material, The Young's modulus (softening degree) of the joint surface may be E≦3.0.

[Packing container]
Although the embodiment of the joining method according to the present invention has been described above by taking the microfluidic device 10 as an example, the joining method according to the present invention is not limited to the microfluidic device.
For example, the packaging container manufactured by the joining method according to the present invention can be applied to packaging containers for so-called retort pouches and pouches for food such as curry and stew.

Generally, a packaging container called a retort pouch is formed by stacking airtight and light-shielding resin base materials to form a container, filling the container with food and sealing the container, and then sterilizing with a retort (pressurized heating). It has excellent storability and storability, and is easy to cook and dispose of. Therefore, it is widely used for curry, stew, porridge, hamburger, pasta sauce, and other ingredients. There is.
Further, the pouch is used not only for foods but also as a simple packaging container in various fields such as detergents, seasonings and alcoholic beverages.

The resin base material that constitutes such a retort pouch is not a single resin material, but a plurality of resins or metals, so-called multi-layers, are laminated to form a resin base material.
For example, a two-layer structure having a stretched nylon film as an outer layer and a polyolefin film such as low density polyethylene or polypropylene as an inner layer, a two-layer structure having a stretched polyester film as an outer layer and a polyolefin film as an inner layer, or such inner/outer layers There is a three-layered film in which a metal foil such as aluminum is laminated between the films.

FIG. 6 is a cross-sectional view of a joint part schematically showing a packaging container manufactured by the joining method according to one embodiment of the present invention, (a) is a conventional packaging container, and (b) is one of the present invention. 1 illustrates a packaging container according to an embodiment.
FIG. 1A shows a conventional retort pouch in which the ends of two resin base materials 101a and 102a are heated and pressure-bonded to form a packaging container 100a.
The resin base materials 101a and 102a constituting the packaging container 100a are multi-layers each composed of a plurality of layers, and specifically, the PET layer, the aluminum layer, and the PP layer are arranged from the container exterior side. It has a structure in which three layers are laminated.

In the conventional packaging container 100a having such a configuration, the two resin base materials 101a and 102a are laminated, and the end portions of the outer circumference of the container are heated and pressed, so that the PP layers located on the inner surface side of the container Will be melted and joined.
Here, the layer structure as shown in FIG. 6 is that the PET layer is arranged as the outer layer because the PET resin has excellent strength, flexibility, durability, etc. This is because the suitability is also excellent.
On the other hand, the reason why the PP layer is arranged as the inner layer is that the PP resins have excellent heat sealability and can be reliably joined by heat fusion.

However, the PP layer located in the inner layer of the container has a high sorption property of the PP resin, so that the dye, taste, and aroma of the contents (for example, curry) filled in the retort pouch are sorbed. There was a problem.
For this reason, the contents to be filled in the conventional retort pouch are premised on that they are sorbed in the inner PP layer. For example, in the case of curry, curry with a stronger color and flavor than the original one is filled. Then, after being sorbed by the PP layer, what was cooked to have the original color, taste and aroma of curry was filled.
Therefore, when the conventional retort pouch is filled with the one cooked as a normal dish, the sorption effect of the PP layer makes the curry odorless, tasteless and odorless in which the color, taste and aroma are light. Will end up.

In response to such problems, if the inner layer of the container is a PET layer, PET resin has almost no sorption property as compared with PP resin, and the sorption of dyes, tastes, aromas, etc. of the contents as described above No problem occurs.
However, when the PET layer is used as the inner layer of the container, there arises a problem that the packaging container (retort pouch) cannot be formed by heat sealing.
In order to heat-seal/heat-bond the PET resins to each other, it is possible to fuse/bond them at a high temperature of, for example, 260° C. which is a melting point, but in that case, the PET resins are crystallized and, for example, dropped. It becomes a hard and brittle state that breaks, and can no longer function as a retort pouch.
Therefore, no retort pouch in which the PET layer is arranged on the inner layer of the container has been proposed at all.

On the other hand, as described above, according to the bonding method according to the present embodiment, after the bonding surface is modified so as to be flattened/softened, heat sealing is performed, so that the melting point is, for example, 200° C. or less. The resin surfaces can be heat-sealed at the joining temperature.
As a result, as shown in FIG. 6(b), as the base materials 11a and 12a constituting the packaging container 10a, three layers of a PET layer, an aluminum layer and a PET layer are laminated from the container exterior side, respectively. A substrate can be used.
In this case, the joint surface of the PET layer on the inner layer side of the container is irradiated with high energy such as argon plasma shown in FIG. 2 and then heated/pressurized by laminating the base materials 11a and 12a, for example, at 200° C. Both base materials 11a and 12a can be heat-sealed at the joining temperature of.

As a result, the PET layers are bonded together at a low temperature below the melting point, so there is no deterioration such as hardening or weakening due to the high temperature heating of the PET resin as described above, and the pouch is excellent in flexibility and durability. can do.
The pouch having the PET layer disposed on the inner layer side of the container does not have a problem of sorption of the pigment, taste, and aroma of the contents due to the low sorption property of the PET resin, and as a result, a normal pouch. It is possible to realize an ideal retort pouch/pouch in which the color, taste, and scent do not change even if the food cooked as a dish is filled as it is.

As described above, according to the bonding method of the present embodiment, by performing modification for flattening/softening the bonding surface of the resin base material to be bonded, the glass transition point or the melting temperature is lower than the melting temperature, and the temperature is lower. The joining surfaces made of resin can be heat-sealed to each other at the joining temperature.
By such low-temperature bonding, the microfluidic device 10 having a desired channel space can be manufactured, for example, without the fine microchannels 13 formed in the microfluidic device 10 being deformed by high temperature heating. ..

Moreover, it becomes possible to bond polyester resins such as PET resin at low temperature, and for example, it is possible to manufacture a polyester retort pouch having a PET layer in the container inner layer. Further, it may be used for joining packaging materials such as caps, spouts, lid materials, etc., and not only a plurality of base materials but also end portions of the base materials may be joined to form a tubular or bag-shaped packaging container. It is preferable to select the same kind of material for the same resin surface.
Therefore, the present invention can be used as a manufacturing method suitable for, for example, a microfluidic device that constitutes a simple rapid diagnostic kit for influenza and a packaging container (retort pouch) for retort food such as curry.

Examples of the joining method according to the present invention will be described below.
The present invention will be further described with reference to the following examples, but the present invention is not limited to the following examples.

[Example 1]
Polymethylmethacrylate (manufactured by Kuraray, trade name Parapet GF, glass transition point 100° C.) was injection molded with an injection molding machine to produce a plate-shaped substrate and a lid member having outer dimensions of 60 mm×15 mm×1.0 mm.
The substrate surface was washed with 70% ethanol and dried by CDA.
Subsequently, high-energy irradiation is performed by irradiating the surface of the substrate with plasma under the conditions of an argon gas flow rate of 200 SCCM, a microwave frequency of 2.45 GHz, a microwave output of 1.5 kW, and a vacuum degree of 400 Pa in a surface wave plasma device. The surface was flattened and softened. Immediately, the plasma irradiation surface of the base material is placed inside, and the substrate and the lid member are overlapped with each other, and the substrate and the lid member are joined by a heat sealing machine under a joining temperature of 30° C. and a joining pressure of 1.9 MPa for 60 seconds. did.
When the binding energy was measured by the crack opening method, the surface of the base material was flattened and softened by the irradiation of argon plasma as shown in FIGS. 3 to 5, so that the binding energy increased (FIG. 3). reference).

[Example 2]
A sample was prepared in the same manner as in Example 1 except that the high-energy irradiation was performed under the conditions of an oxygen gas flow rate of 200 SCCM, a vacuum degree of 100 Pa, and a bonding temperature of 70° C. in a surface wave plasma device.
As a result, as shown in FIGS. 7 to 9, the surfaces of the substrate and the lid member were flattened and softened, so that the binding energy increased (see FIG. 7).

[Example 3]
High-energy irradiation was performed using a vacuum ultraviolet ray device (MD Excimer, model MEIRA-M-1-152-H2) with a wavelength of 172 nm, a tube surface illuminance of 78 W/cm ² , an RF output of 600 W, an irradiation distance of 2 mm, and atmospheric conditions. A sample was prepared in the same manner as in Example 1 except for the following.
As a result, as shown in FIGS. 10 to 12, the surfaces of the substrate and the lid member were flattened and softened, so that the binding energy increased (see FIG. 10).

[Comparative Example 1]
A sample was prepared in the same manner as in Example 1 except that the joining temperature was 30° C. and 70° C. without irradiating the surface of the base material with high energy.
As a result, when the substrate and the lid member were taken out from the heat sealing machine, the substrate and the lid member were not joined (bonding energy 0 J/m ² ).

[Example 4]
Aluminum foil (thickness 6 μm) was laminated on the outer layer of stretched polyester (thickness 12 μm), and stretched polyester (thickness 100 μm, melting point 260° C.) was laminated on the inner layer by a dry laminating machine to prepare a base material.
The substrate surface was washed with 70% ethanol and dried by CDA.
Then, the surface of the base material is irradiated with plasma under a condition of an argon gas flow rate of 200 SCCM, a microwave frequency of 2.45 GHz, a microwave output of 1.5 kW and a vacuum degree of 400 Pa by a surface wave plasma device to flatten the surface. Softened.
The base materials were overlapped with the stretched polyester of the inner layer inside and were held for 60 seconds under a condition of a bonding temperature of 200° C. and a bonding pressure of 1.3 MPa with a heat sealing machine to bond the substrates. As a result of measuring the bonding strength by a T-peel test at a tensile speed of 300 mm/min with a tensile tester, the sealing strength was 23 N/15 mm or more.
In addition, a four-side sealed bag (170 mm×130 mm) was prepared, and after curry was filled and sealed, pressure heat sterilization was performed in a retort kettle under a condition of a temperature of 121° C. for 2 hours.
As a result of confirming the sorption of the dye on the inner surface of the seal bag by visual inspection, the stretched polyester in the inner layer was not colored.

[Comparative example 2]
Polypropylene (thickness: 100 μm) was used for the inner layer of the base material of Example 4, and the base materials were bonded by holding for 10 seconds under the conditions of a bonding temperature of 200° C. and a bonding pressure of 1.3 MPa without performing high energy irradiation. A sample was prepared in the same manner as in Example 4 except for the above.
As a result, the seal strength was 23 N/15 mm or more, but the sorption of the dye on the inner surface of the seal bag was confirmed by visual inspection after retort. As a result, the polypropylene in the inner layer was colored yellow.

The bonding method of the present invention has been described above with reference to the preferred embodiments. However, the bonding method according to the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention. It goes without saying that it is possible.

For example, in the above-described embodiment, as an example of the joined body according to the present invention, a microfluidic device that constitutes a diagnostic kit for influenza and a packaging container for food and the like have been described as an example, but with the joining method according to the present invention. What can be joined (manufactured) is not limited to such a microfluidic device or a packaging container.
That is, the invention of the present application is not particularly limited as long as it is a use for which heat bonding is required at a temperature not higher than either the glass transition point or the melting point.

INDUSTRIAL APPLICABILITY The present invention can be suitably used for manufacturing a microfluidic device which constitutes a simple rapid diagnostic kit for influenza and the like, and a resin laminate which constitutes a packaging container for food and the like.

10 microfluidic device 11 substrate 12 lid member (cover body)
13 Micro Channel 10a Packaging Container 11a Base Material 12a Base Material

Claims (2)

A method of joining resin surfaces together,
A step of flattening and softening the joint surface of the base material by irradiating the joint surface with high energy;
A step of joining the substrates by heating and/or pressurizing after bringing the joining surfaces into contact with each other;
Have
The base material is made of a thermoplastic resin that constitutes a microfluidic device,
In the step of performing the high energy irradiation,
By irradiating the bonded surface of the base material with argon plasma in an irradiation time range of 2 to 10 seconds,
The surface roughness of the bonding surface before Kimoto material, the arithmetic mean roughness Ra ≦ 10 nm,
A joining method , wherein the joining surfaces of the base materials are joined together at a temperature not higher than the glass transition point of the thermoplastic resin and not higher than 70°C . The bonding method according to claim 1, wherein the high-energy irradiation is performed on a bonding surface of at least one of the two base materials.