JP7359124B2 - Manufacturing method of fuel cell separator - Google Patents

Description

The present invention relates to a method for manufacturing a fuel cell separator and a fuel cell separator.

A fuel cell has a stack structure in which a predetermined number of single cells are stacked to generate an electromotive force through a reaction between fuel gas (hydrogen) and oxidant gas (oxygen). A single cell includes a membrane electrode assembly including an anode and a cathode electrode layer (a catalyst layer and a gas diffusion layer) on both sides of an electrolyte membrane, and separators arranged on both sides of the membrane electrode assembly.

A fuel cell separator has a function of electrically connecting single cells in series and a function of a partition wall that blocks fuel gas, oxidizing gas, and cooling water from each other.

Various studies are being conducted on such fuel cell separators.

For example, Patent Document 1 describes an amorphous carbon layer forming step of forming an amorphous carbon layer on a metal substrate using a physical vapor deposition method or a chemical vapor deposition method, and a method that is the same as or different from the physical vapor deposition method or the chemical vapor deposition method. A method for producing a fuel cell separator, comprising: forming a conductive part on the amorphous carbon layer using physical vapor deposition in the amorphous carbon layer forming step and the conductive part forming step. The method is a filterless arc ion plating method, in which the amorphous carbon layer is formed using the filterless arc ion plating method, and a graphite part as the conductive part is formed, and the amorphous carbon layer and the A method for manufacturing a fuel cell separator is disclosed, wherein a bias voltage applied to the metal substrate when forming the graphite portion is in the range of -1000V to -150V.

Patent Document 2 discloses that an intermediate layer is formed on a metal base layer, a conductive carbon layer is formed on the intermediate layer by a sputtering method or an ion plating method, and the metal base layer, the intermediate layer, and the conductive carbon layer are formed on the intermediate layer by a sputtering method or an ion plating method. a metal base layer forming a laminate of carbon layers and molding the laminate by pressing; an intermediate layer formed on the metal base layer; and a conductive layer located on the intermediate layer. A method for manufacturing a fuel cell separator made of a conductive member having a conductive carbon layer containing carbon, the fuel cell separator comprising a conductive member having an exposed intermediate layer in a part of the conductive carbon layer. Disclosed.

JP2008-204876A Japanese Patent Application Publication No. 2010-129464

In general, one surface of a fuel cell separator is formed with a reaction gas flow path for flowing a reaction gas into the single cell, and the other surface is formed with a cooling medium flow path for flowing a cooling medium into the single cell. is formed. In addition, a reaction gas manifold opening that functions as an inlet and an outlet of a reaction gas, and a coolant manifold opening that functions as an inlet and an outlet of a coolant flow path are formed in the peripheral edge of the fuel cell separator. Furthermore, seal members are provided around the reaction gas flow path, the cooling medium flow path, the reaction gas manifold opening, and the cooling medium manifold opening, as appropriate, to suppress leakage of the respective fluids.

Fuel cell separators need to be bonded to other members such as resin sheets and gaskets that serve as sealing members to suppress the leakage of reactant gases such as H ₂ and O ₂ and fluids such as cooling water that is a cooling medium. Therefore, the adhesiveness and sealing reliability between the fuel cell separator and other members, such as adhesives used for adhesion to sealing members, are important factors in the characteristics of the fuel cell separator.

Furthermore, the power generating body holding portions of the fuel cell separator that sandwich the power generating body are required to have low contact resistance in order to conduct electricity generated by the power generating body, and to have corrosion resistance.

Therefore, in order to impart the above characteristics to the fuel cell separator, the range including the power generating body clamping part that clamps the power generating body in the fuel cell separator is masked outside the range, and physical vapor deposition (Physical Vapor Deposition) is applied. PVD) to form a carbon layer/titanium layer. Corrosion resistance in the fuel cell separator is ensured by the titanium layer, and low contact resistance in the fuel cell separator is ensured by the carbon layer.

However, in the conventional technology, although the characteristics of each layer (carbon layer/titanium layer) are mentioned, the film thickness distribution conditions and film formation conditions of each layer are specified in order to make products with excellent productivity. However, the design and manufacturing conditions for a fuel cell separator that can be manufactured at low cost while retaining excellent properties have not been clarified.

Therefore, the present invention has sufficient corrosion resistance in the entire separator, low contact resistance in the power generating body holding part, and improved adhesion with the sealing member in the sealing member arrangement part (i.e., An object of the present invention is to provide a method for manufacturing a fuel cell separator at low cost.

(corrosion resistance)
Excellent corrosion resistance is required in the central part of the power generating body clamping portion of the fuel cell separator that clamps the power generating body, so a titanium layer having a certain thickness is required. On the other hand, in order to ensure the corrosion resistance of the entire part, it is preferable to form a titanium layer having a certain thickness at the ends of the power generating body clamping part, although not as thick as the central part of the power generating body clamping part. . However, forming a titanium layer having a thickness comparable to that of the central portion of the power generating body holding portion at the end portions of the power generating body holding portion leads to an increase in cost. Therefore, in a fuel cell separator, by setting the thickness of the titanium layer for the central part of the power generating body clamping part and the end part of the power generating body clamping part, it is possible to provide just enough corrosion resistance according to the requirements of each part. be able to.

(Low contact resistance, adhesion and seal reliability)
Since low contact resistance is required for the power generating body clamping portion of the fuel cell separator that clamps the power generating body, a carbon layer having a certain thickness is required. On the other hand, it is assumed that there is a carbon layer with a film thickness similar to that of the power generating body clamping part in the sealing member installation part, which is provided on the outer periphery of the power generating body clamping part and in which a sealing member for sealing the power generating body clamping part is disposed. , the adhesiveness with the sealing member and the sealing reliability will deteriorate. Therefore, in a fuel cell separator, by setting the thickness of the carbon layer for each of the power generating body holding part and the sealing member installation part, low contact resistance, adhesion, and seal reliability can be achieved in accordance with the requirements of each part. It can be given without shortage.

When using the arc ion plating method as PVD to form a carbon layer, a carbon layer with low contact resistance is deposited on the power generating body sandwiching part, and on the other hand, the carbon layer is deposited on the parts other than the power generating body sandwiching part, especially the seal. In order to avoid forming a carbon layer as much as possible on the member placement part, it is necessary to install a masking member at a certain distance from the metal base material in an area other than the area that will become the power generating body clamping part. In the arc ion plating method, a carbon layer with low contact resistance can be formed by lowering the bias voltage. Therefore, in order to form a carbon layer with low contact resistance on the power generating body sandwiching portion, the bias voltage may be lowered. However, although the masking member is installed in the area other than the area that will become the power generating body clamping part, the masking member is installed with a certain distance from the metal base material as described above, so the carbon The carbon layer also wraps around the surface of the metal base material under the member and is formed as a carbon layer. When the bias voltage is lowered, the amount of carbon that wraps around onto the metal base material under the mask increases, and the protrusion of the carbon layer also increases, resulting in the formation of a carbon layer in areas other than the power generating body sandwiching portion. As mentioned above, forming a carbon layer on the sealing member installation part leads to a decrease in adhesion with the sealing member and sealing reliability, so the sealing member installation area where the carbon layer formed by wraparound is thin. In order to form this, it is necessary to add a carbon layer removal step and to make the fuel cell separator larger, which increases the size of the parts, which is unfavorable in terms of mounting efficiency and cost. In other words, in order to form an appropriate carbon layer thickness for each of the power generating body holding part and the sealing member disposed part in the fuel cell separator, it is necessary to appropriately set the bias voltage in the arc ion plating method.

As a result of studying various means for solving the above-mentioned problems, the present inventors have discovered a power generating body clamping part that clamps the power generating body, and a seal that is provided on the outer periphery of the power generating body clamping part and seals the power generating body clamping part. A method for manufacturing a fuel cell separator having a sealing member disposing portion in which a member is disposed, wherein a gap is provided between the metal base material and the region other than the region that becomes the power generating body clamping portion. A masking member is arranged, and a titanium layer having a film thickness in a specific range is formed under a bias voltage in a specific range using an unbalanced magnetron sputtering method in the area that will become the power generating body holding part, and then, By forming a carbon layer with a specific range of film thickness under a specific range of bias voltage using the filterless arc ion plating method in the area that will become the power generating body sandwiching part where the titanium layer is formed, the separator is formed. It is possible to manufacture at a low cost a fuel cell separator that has sufficient corrosion resistance throughout, low contact resistance at the power generating body clamping part, and improved adhesiveness with the sealing member at the sealing member installation part. They discovered what they could do and completed the present invention.

That is, the gist of the present invention is as follows.
(1) For a fuel cell having a power generating body clamping part that clamps a power generating body, and a sealing member arrangement part provided on the outer periphery of the power generating body clamping part and arranging a sealing member for sealing the power generating body clamping part. A method for manufacturing a separator, the method comprising:
a step of preparing a metal substrate;
arranging a masking member with a gap between the metal base material and the metal base material in an area other than the area that will become the power generating body holding part;
A process of forming a titanium layer by depositing titanium on the surface of a metal base material,
Titanium film formation is carried out using an unbalanced magnetron sputtering method under a bias voltage of -50 V or less until the film thickness of the titanium layer at the end of the region that will become the power generator sandwiching part becomes 76 nm or more. process and
A process of forming a carbon layer by depositing carbon on a titanium layer of a metal base material,
A carbon film is formed using a filterless arc ion plating method under a bias voltage of -450V to -250V to form a carbon layer at the end of the area that will become the power generator clamping part of the area where the sealing member is provided. A method for producing a fuel cell separator, the method comprising: carrying out the step such that the film thickness of the separator is 5 nm or less.
(2) The method according to (1), wherein the titanium film is formed using an unbalanced magnetron sputtering method under a bias voltage of -350V or higher.
(3) The method according to (1) or (2), wherein the metal base material is stainless steel.
(4) For a fuel cell having a power generating body clamping part that clamps a power generating body, and a sealing member arrangement part provided on the outer periphery of the power generating body clamping part and arranging a sealing member for sealing the power generating body clamping part. A separator,
It has a metal base material, a titanium layer formed on the surface of the metal base material, and a carbon layer formed on the titanium layer,
The thickness of the titanium layer at the end of the power generating body clamping part is 76 nm or more and 0.38 times or more the thickness of the titanium layer at the central part of the power generating body clamping part,
A separator for a fuel cell, wherein the thickness of the carbon layer at the end of the seal member disposed portion on the side of the power generating body clamping portion is 5 nm or less.

The present invention provides a low-cost fuel cell separator that has sufficient corrosion resistance in the entire separator, low contact resistance in the power generating body clamping part, and improved adhesiveness with the sealing member in the sealing member installation part. A method of manufacturing is provided.

FIG. 2 is a schematic diagram of a press separator made of SUS304 used in Examples and Comparative Examples. FIG. 2 is a schematic diagram of a mask jig used in Examples and Comparative Examples. FIG. 3 is a schematic diagram showing a state in which press separator products made of SUS304 in Examples and Comparative Examples are attached to a mask jig. 4 is a schematic diagram of the A-A' cross section in the schematic diagram of FIG. 3. FIG. It is a figure which shows typically the test piece cut-out position of the separator for fuel cells in an Example and a comparative example. 6 is a diagram schematically showing changes in the thickness of the titanium layer and the thickness of the carbon layer in the B-B' cross section in the schematic diagram of FIG. 5. FIG. The bias voltage in titanium film formation and the ratio of the thickness of the titanium layer at the end of the power generating body holding part (t(Ti2)) to the thickness of the titanium layer at the center part of the power generating body holding part (t(Ti1)) ( 2 is a graph showing the relationship between t(Ti2)/t(Ti1)) and the amount of iron elution. Bias voltage in carbon film formation, contact resistance, and carbon layer thickness at the boundary between the middle part and the sealing member arrangement part where the carbon layer is thickest in the sealing member arrangement part (t (C2)) It is a graph showing the relationship between

Preferred embodiments of the present invention will be described in detail below.
In this specification, features of the present invention will be explained with reference to the drawings as appropriate. In the drawings, the dimensions and shapes of various parts are exaggerated for clarity and do not accurately depict actual dimensions and shapes. Therefore, the technical scope of the present invention is not limited to the dimensions and shapes of the parts shown in these drawings. The method for producing a fuel cell separator and the fuel cell separator of the present invention are not limited to the following embodiments, and modifications and improvements that can be made by those skilled in the art are possible without departing from the gist of the present invention. It can be implemented in various forms.

The present invention provides a fuel cell having a power generating body clamping part that clamps a power generating body, and a seal member disposing part provided on the outer periphery of the power generating body clamping part and arranging a seal member for sealing the power generating body clamping part. A method for manufacturing a separator for use in a metal substrate, comprising the steps of preparing a metal base material, and arranging a masking member with a gap between the metal base material and the region of the metal base material other than the region that will become the power generating body clamping part. A process of forming a titanium layer by depositing titanium on the surface of a metal base material, in which the titanium film is deposited on the power generator sandwiching part under a bias voltage in a specific range using an unbalanced magnetron sputtering method. The second step is to form a carbon layer by depositing carbon on the titanium layer of the metal base material, and the second step is to form a carbon layer by depositing carbon on the titanium layer of the metal base material. The film is formed using a filterless arc ion plating method under a bias voltage within a specific range, so that the carbon film thickness at the end of the area where the seal member is placed is on the side of the area where the power generator is held. The present invention relates to a method for manufacturing a fuel cell separator, including steps carried out in a manner that is consistent with the above range, and a fuel cell separator that can be manufactured by such a manufacturing method.

Below, details of the method for manufacturing a fuel cell separator of the present invention will be explained step by step.

<Step 1: Step of preparing metal base material>
First, a metal base material to be used as a material for a fuel cell separator is prepared.

As the metal base material, any metal base material known in the art can be used, including, but not limited to, metal base materials (including alloys) such as stainless steel (SUS: an alloy of iron, chromium, and nickel). A rectangular plate can be used. The metal base material of the separator is preferably a substantially rectangular plate made of stainless steel, for example SUS304.

By selecting a metal base material as the material for the fuel cell separator, a titanium layer and a carbon layer can be formed on the metal base material by PVD as described below, and by selecting stainless steel as the metal base material, The cost of manufacturing separators can be reduced.

As the metal base material, it is preferable to use a metal base material that has been pressed in advance into the shape of the final fuel cell separator.

By using a pre-pressed metal base material as the metal base material, a fuel cell separator can be obtained without further pressing after the titanium layer and carbon layer are formed.

<Step 2: Step of arranging the masking member in an area other than the area that will become the power generating body holding part in the metal base material with a gap between the metal base material and the metal base material>
Subsequently, a masking member is placed on the metal base material prepared in step 1.

The masking member is arranged in a region other than the region serving as the power generating body holding portion, with a gap provided between the masking member and the metal base material.

Here, the power generating body holding part is a substantially rectangular part for holding the power generating body located in the center of the fuel cell separator, and the sealing member arrangement part is a part for holding the power generating body in the fuel cell separator. This is a part provided on the outer periphery of the part, and a sealing member for sealing the power generating body clamping part is disposed.

Further, an intermediate portion exists between the power generating body holding portion and the sealing member disposed portion provided on the outer periphery of the power generating body holding portion. The intermediate portion is a portion formed in the titanium layer and carbon layer formation steps (steps 3 and 4) described below due to the presence of a gap between the metal base material and the masking member. The shortest distance between the power generating body clamping part and the sealing member arrangement part in the intermediate part is not limited, but is preferably shorter, and is usually 6 mm or less, preferably 3 mm or less. The size of the fuel cell separator can be reduced by setting the shortest distance between the power generating body holding part and the sealing member arrangement part in the intermediate part within the above range.

Therefore, the region that becomes the power generating body clamping part is a region for clamping a substantially rectangular power generating body smaller than the metal base material located in the center of the approximately rectangular plate-shaped metal base material, and the power generating body clamping part The area other than the area is the outer circumferential area of the area that will be the power generating body holding part, that is, the area that is the sum of the area that will be the intermediate part and the area that will be the sealing member placement part.

The masking member is a plate having the same shape as a fuel cell separator, and is hollow in an area that will become a power generating body holding part on which a titanium layer and a carbon layer are formed. The masking member is preferably made of the same metal as the fuel cell separator, for example, SUS304. Since the masking member is made of the same material as the separator, the separator and masking, which have reached a temperature of several hundred degrees Celsius or more during PVD, have the same coefficient of linear expansion, making it possible to make the positional deviation during targeted film formation relatively small. I can do it.

The gap between the metal base material and the masking member is provided horizontally so that the metal base material and the masking member maintain a constant distance, and the size of the gap, that is, the distance between the metal base material and the masking member is preferably shorter, but is not limited, and is usually 1 mm or less, preferably 0.2 mm to 0.5 mm. Note that when a pre-pressed metal base material is used as the metal base material, since the metal base material has an uneven shape, the size of the gap can be changed depending on the uneven shape; The distance can be set so that the shortest distance between the metal base material and the masking member falls within the above range.

During film formation in the titanium layer and carbon layer formation steps (steps 3 and 4) described below, plasma collides with the metal base material, causing the temperature of the metal base material to rise and the metal base material to expand. . At this time, the masking member also expands. As the temperature of the metal base material increases, the amount of expansion increases, so if there is no gap or the gap is too small, the metal base material may be deformed during processing. Therefore, by providing a gap between the metal base material and the masking member, deformation of the metal base material in steps 3 and 4 can be suppressed.

Further, by setting the distance between the metal base material and the masking member within the above range, an intermediate part is formed, and furthermore, the shortest distance between the power generating body clamping part and the sealing member installation part in the middle part is set within the above range. It becomes easier to adjust.

<Step 3: Step of forming a titanium layer by depositing titanium on the surface of the metal base material>
Subsequently, in step 2, a titanium layer is formed by depositing titanium on the surface of the metal base material whose area other than the area that will become the power generator holding part is masked by a masking member.

The titanium film is formed using unbalanced magnetron sputtering (UBMS), which is a type of PVD.

The unbalanced magnetron sputtering (UBMS) method is a sputtering method that strengthens plasma irradiation to the substrate by intentionally making the magnetic field of the sputtering cathode unbalanced, making it possible to form dense thin films. .

For unbalanced magnetron sputtering, conditions other than the bias voltage conditions described below, such as the initial degree of vacuum in the device chamber, cleaning conditions for the surface of the metal substrate (for example, conditions for argon bombardment treatment), plasma Conditions known in the technical field (for example, see International Publication No. 2015/068776) can be used for the generation gas conditions, film formation time, film formation temperature, and the like. Note that the longer the film formation time, the thicker the film becomes, so a desired film thickness can be obtained by adjusting the film formation time.

In addition, the film thickness of the titanium layer in the present invention means the average value of three measurement points in cross-sectional observation in a SEM or TEM image of a target portion.

The bias voltage in the unbalanced magnetron sputtering method is -50V or less, preferably -350V to -50V, more preferably -250V to -50V. In the unbalanced magnetron sputtering method, a glow discharge is generated between a target (i.e., titanium) as a cathode and a metal base material as an anode, and an inert gas plasma, For example, when Ar plasma is formed, the positively ionized Ar ions in the Ar plasma repel the target atoms, accelerate the target atoms, and form a film on the surface of the metal base material, so the metal base material has a negative bias voltage. (negative) voltage is applied. Furthermore, in this specification, when expressing the level of negative bias voltage, a bias voltage closer to 0V is expressed as "higher bias voltage."

By forming a titanium film by unbalanced magnetron sputtering on the surface of the metal base material with the masking member masking the area other than the region that will become the power generator clamping part, titanium is removed in the center of the region that will become the power generator clamping part. The film thickness of the layer and the thickness of the titanium layer at the end of the region that will become the power generating body clamping part have different values, and the film thickness of the titanium layer at the end of the region that will become the power generating body clamping part is thinner. . The reason why the thickness of the titanium layer at the edge of the area that will become the power generating body clamping part is thinner than that of the titanium layer at the center of the area that will become the power generating body clamping part is due to the growth from the target to the metal base material. Reasons include that the end of the masking member casts a shadow when forming a film, and that the end of the masking member is sharp and is therefore affected by the magnetic field. Note that the end of the region that becomes the power generating body clamping part is the end of the region that becomes the power generating body clamping part, that is, the boundary between the region that becomes the power generating body clamping part and the middle part, and This is the area where the titanium layer is the thinnest in the area that will become the sandwiching part. Approximately 3 mm from the edge of the area that will become the power generating body clamping part to the center of the area that will become the power generating body clamping part (this value depends on the bias voltage in the unbalanced magnetron sputtering method, and the higher the bias voltage, the shorter the distance. The thickness of the titanium layer gradually increases until it reaches approximately 3 mm at the bias voltage of the present invention.In other words, the thickness of the titanium layer has a gradient (transition), and the thickness of the titanium layer gradually increases. The central part of the power generating body clamping part, which is the inner region from the end of the power generating body clamping part to the center of the power generating body clamping part in the region that becomes the power generating body clamping part, This is the area where the titanium layer is the thickest in the area that will become the body holding part.

The unbalanced magnetron sputtering method is performed until the thickness of the titanium layer at the end of the region that will become the power generating body sandwiching portion becomes 76 nm or more.

By setting the bias voltage in the unbalanced magnetron sputtering method to the above range, the thickness of the titanium layer at the end of the region that will become the power generation body sandwiching portion will be changed to the thickness of the titanium layer at the center of the region that will be the power generation body sandwiching portion. (thickness of the titanium layer at the end of the region that will become the power generating body clamping part/thickness of the titanium layer at the center of the region that will become the power generating body clamping part) can be adjusted to 0.38 or more. In addition, by performing the unbalanced magnetron sputtering method until the thickness of the titanium layer at the end of the region that will become the power generating body clamping part, that is, the thinnest part in the region that will become the power generating body clamping part, falls within the above range. , the corrosion resistance of the entire fuel cell separator can be improved. Note that the corrosion resistance can be confirmed by an iron elution test or the like.

Furthermore, by setting the bias voltage in the unbalanced magnetron sputtering method to the above range and performing the unbalanced magnetron sputtering method until the film thickness of the titanium layer at the end of the region that becomes the power generating body sandwiching part falls within the above range, The thickness of the titanium layer at the center of the region that will become the power generating body clamping portion can be adjusted to usually 200 nm or more, preferably 200 nm to 500 nm. Corrosion resistance of the fuel cell separator is ensured by adjusting the thickness of the titanium layer in the central part of the region that will become the power generating body clamping part to be within the above range.

In addition, in the unbalanced magnetron sputtering method, a titanium layer is also formed on the surface of the metal base material under the masking member, that is, the area that will be the intermediate part and the area where the sealing member is provided, due to the wraparound of the plasma. . The thickness of the titanium layer changes depending on the amount of plasma wraparound, and the thickness of the titanium layer is such that the region that is the intermediate portion is greater than the region that is the sealing member disposed portion. The thickness of the titanium layer in the region serving as the intermediate portion and the region serving as the sealing member placement portion is not limited because it does not affect the corrosion resistance of the separator.

<Step 4: Step of forming a carbon layer by depositing carbon on the titanium layer of the metal base material>
Subsequently, in step 3, a titanium layer is formed on the surface of the metal base material with the masking member masking the area other than the area that will become the power generator clamping part. Carbon is formed into a film on the titanium layer of the metal base material to form a carbon layer. form.

The carbon film is formed using filterless arc ion plating (AIP), which is a type of PVD.

Here, the filterless arc ion plating method uses ionized substances (targets are evaporated and ionized, hereinafter referred to as ionized evaporated substances) generated by arc discharge generated between the target constituting the anode and the cathode. ) is accelerated by applying a bias voltage to the metal base material, and an ionized evaporated substance is formed into a film on the metal base material.

Regarding the filterless arc ion plating method, conditions other than the bias voltage conditions described below, such as the initial degree of vacuum in the device chamber, cleaning conditions for the surface of the metal substrate (for example, conditions for argon bombardment treatment), Conditions known in the technical field (for example, see Patent Document 1) can be used for the plasma generation gas conditions, film formation time, film formation temperature, and the like. Note that the longer the film formation time, the thicker the film becomes, so a desired film thickness can be obtained by adjusting the film formation time.

In addition, the film thickness of the carbon layer in the present invention means the average value of three measurement points obtained from the cross-sectional observation results in the SEM or TEM image of the target portion.

The bias voltage in the filterless arc ion plating method is -450V to -250V, preferably -350V to -250V. In addition, in the filterless arc ion plating method, a titanium layer is formed by accelerating the positively ionized evaporated material, similar to the principle of applying a negative voltage as a bias voltage in the unbalanced magnetron sputtering method. In order to form a film on the surface of the metal base material, a negative voltage is applied to the metal base material.

By depositing a carbon film by filterless arc ion plating on the surface of the metal base material on which a titanium layer is formed, with the masking member masking the area other than the area that will become the power generating body clamping part, the power generating body can be clamped. The thickness of the carbon layer at the center of the area that will become the power generating body clamping part is different from the thickness of the carbon layer at the edge of the area that will become the power generating body clamping part. The thickness of the layer becomes thinner. The reason why the thickness of the carbon layer at the ends of the region that will become the power generating body clamping portion is thinner than the thickness of the carbon layer at the center of the region that will become the power generating body clamping portion is due to the transition from the target to the metal base material. Reasons include the fact that the end of the masking member casts a shadow when forming a film, and that the end of the masking member is sharp and is therefore affected by the magnetic field. Note that the end of the region that becomes the power generating body clamping part is the end of the region that becomes the power generating body clamping part, that is, the boundary between the region that becomes the power generating body clamping part and the middle part, and This is the part where the thickness of the carbon layer is the thinnest in the region that becomes the sandwiching part. Approximately 3 mm from the edge of the area that will become the power generation body clamping part toward the center of the area that will become the power generation body clamping part (this value depends on the bias voltage in the filterless arc ion plating method, and the higher the bias voltage, the more The thickness of the carbon layer gradually increases until it reaches approximately 3 mm at the bias voltage of the present invention. In other words, the thickness of the carbon layer is inclined, and In the area where the power generating body is held, the central part of the power generating body held part, which is the area about 3 mm inside from the end of the area that becomes the power generating body held part toward the center of the area that becomes the power generating body held part, is This is the region where the carbon layer is thickest.

Furthermore, in the filterless arc ion plating method, due to the wraparound of the plasma, carbon is also deposited on the titanium layer of the metal base material below the masking member, that is, on the titanium layer in the intermediate region and the region where the sealing member is disposed. A layer is deposited. The thickness of the carbon layer changes depending on the amount of plasma wraparound, and the thickness of the carbon layer is such that the region that is the intermediate portion is greater than the region where the seal member is provided.

In the filterless arc ion plating method, the film thickness of the carbon layer in the region where the seal member is disposed is determined, particularly at the end of the region where the seal member is disposed on the side of the region where the power generating body is held, that is, the seal member. This is carried out so that the thickness of the carbon layer at the boundary between the region to be the disposed portion and the region to be the intermediate portion is 5 nm or less, preferably 3 nm or less. Note that the thinner the thickness of the carbon layer in the region where the seal member is provided, the better, so no lower limit is set.

By setting the bias voltage in the filterless arc ion plating method to the above range, the balance of the thickness of the carbon layer in the area where the power generating body is held and the area where the sealing member is placed can be adjusted appropriately, and power generation can be achieved. It is possible to ensure low contact resistance in the region serving as the body-clamping portion and good adhesiveness between the sealing member disposed portion and the sealing member. Furthermore, by setting the bias voltage in the filterless arc ion plating method to the above range, it is possible to form a denser carbon layer with low contact resistance, ensuring lower contact resistance at the power generating body sandwiching part. be able to. The crystallinity of the carbon layer can be measured, for example, by Raman spectroscopy, X-ray diffraction, or the like.

The thickness of the carbon layer at the center of the region that will become the power generating body clamping portion is not limited, but is usually 75 nm or more. By setting the thickness of the carbon layer at the central portion of the region that will become the power generating body holding portion within the above range, low contact resistance of the separator can be ensured.

In the method for manufacturing a fuel cell separator of the present invention, steps 1 to 4 can be performed continuously, and in this case, the masking member is not changed between steps 1 to 4.

The fuel cell separator of the present invention, which can be obtained by the method for manufacturing a fuel cell separator of the present invention described above, includes a power generating body holding part that holds a power generating body, and a power generating body holding part provided on the outer periphery of the power generating body holding part, A fuel cell separator comprising: a sealing member disposed portion for disposing a sealing member for sealing a power generating body clamping portion; a metal base material; a titanium layer formed on the surface of the metal base material; a carbon layer formed on a titanium layer, the thickness of the titanium layer at the end of the power generating body holding part is 76 nm or more, and the thickness of the titanium layer at the center part of the power generating body holding part is 0. .38 times or more, and the thickness of the carbon layer at the end of the seal member disposed portion on the side of the power generating body holding portion is 5 nm or less. The characteristics of the fuel cell separator of the present invention are as described in the method for manufacturing a fuel cell separator of the present invention.

The fuel cell separator in the present invention is a component of a fuel cell (single cell), and is arranged on both sides of a membrane electrode assembly (electrolyte membrane, anode and cathode electrode layers arranged on both sides of the electrolyte membrane). be done.

The fuel cell separator of the present invention is adhered to fuel cell components known in the technical field, such as membrane electrode assemblies, seal members, etc., using an adhesive, to produce a fuel cell.

A fuel cell manufactured using the fuel cell separator of the present invention can be used in various electrochemical devices such as polymer electrolyte fuel cells.

Hereinafter, some examples relating to the present invention will be described, but the present invention is not intended to be limited to what is shown in these examples.

I. Manufacture of fuel cell separator A fuel cell separator was manufactured according to the following procedure.

1. Step of preparing a metal base material A press separator made of SUS304 was prepared as a metal base material. FIG. 1 shows a schematic diagram of a pressed separator made of SUS304.

2. A step of arranging a masking member with a gap between the metal base material and the area other than the area that will become the power generation body clamping part. A mask jig serving as a masking member was placed with a gap of 0.5 mm between the metal base material and the masking member so that areas other than the area were masked. Figure 2 shows a schematic diagram of the mask jig. FIG. 3 shows a schematic diagram of a separator pressed product made of SUS304 attached to a mask jig. FIG. 4 shows a schematic diagram of the AA' cross section in the schematic diagram of FIG. 3.

3. Step of forming a titanium layer by depositing titanium on the surface of a metal base material The separator press article to which the mask jig prepared in step 2 was attached was introduced into a batch type PVD processing apparatus. Subsequently, the sample chamber was evacuated to 0.1 Pa and heated to 150° C. using a heater. Sputter cleaning was performed for 5 minutes at an Ar flow rate of 120 sccm and a bias voltage of -200V.

A titanium layer was formed by depositing titanium on the surface of a metal substrate using magnetron sputtering (MS), unbalanced magnetron sputtering (UBMS), or filterless arc ion plating (AIP). . The degree of vacuum was adjusted to 0.3 Pa in both methods. Furthermore, in each film-forming method, the processing time was adjusted so that the thickness of the titanium layer at the center of the region serving as the power generating body sandwiching portion was 200 nm.

4. Step of forming a carbon layer by depositing carbon on the titanium layer of a metal base material. Using magnetron sputtering (MS) or filterless arc ion plating (AIP), the titanium layer is formed in step 3. A carbon layer was formed by depositing carbon on the titanium layer of the deposited metal base material. The degree of vacuum was adjusted to 0.3 Pa in both methods. Furthermore, in each film forming method, the processing time was adjusted so that the thickness of the carbon layer at the center of the region that would become the power generating body sandwiching portion was 75 nm.

After completing steps 1 to 4, the sample was taken out of the device, the mask jig was removed, and a fuel cell separator was obtained.

II. Evaluation of fuel cell separator The obtained fuel cell separator was subjected to film thickness measurement of each layer, adhesiveness (sealability) evaluation, contact resistance measurement, and corrosion resistance measurement.

Film thickness measurement: A sample was cut out from a predetermined film thickness measurement position, and the film thickness was measured by cross-sectional observation using SEM or TEM. In the observation section, the average value of the film thicknesses at three locations was adopted as the film thickness.

Adhesiveness (sealability) evaluation: It is known that adhesiveness can be ensured if the thickness of the carbon layer is 5 nm or less, so the middle part where the carbon layer is thickest in the sealing member arrangement part. The thickness of the carbon layer was measured at the boundary between the carbon layer and the seal member disposed portion, and it was confirmed that sealing performance was ensured if the thickness was 5 nm or less.

Contact resistance measurement: A test piece (evaluation area 4 cm x 4 cm) was cut out from the obtained fuel cell separator, and the cut out test piece was subjected to a constant potential test (sulfuric acid (pH 3), 0.9 V vs. A standard hydrogen electrode, 300-hour test) was conducted, and the test piece after the constant potential test was evaluated by measuring the contact resistance with the gas diffusion layer (GDL) using a four-terminal method. FIG. 5 schematically shows the test piece cutting position. It is preferable that the contact resistance is low.

Corrosion resistance measurement: Evaluated by measuring the iron ion concentration in the solution in which the test piece was immersed after a constant potential test in contact resistance measurement. Preferably, the iron ion concentration is low.

III. Evaluation results of fuel cell separators Table 1 shows the results. In Table 1, in the prepared fuel cell separator, the film thickness (t(Ti2)) of the titanium layer at the end of the power generating body clamping part as measured by film thickness measurement is the thickness of the titanium layer at the center of the power generating body clamping part (t(Ti2)). t(Ti1)), and is 0.38 to 0.60 times the middle part and the seal member arrangement part where the thickness of the carbon layer is the thickest in the seal member arrangement part according to the adhesiveness (sealability) evaluation. The thickness of the carbon layer (t(C2)) at the boundary with the carbon layer is 5 nm or less, the contact resistance measured by contact resistance measurement is 6 mΩ・cm ² or less, and the iron ion concentration is 2.0 × 10 ^-10 by corrosion resistance measurement. Examples were those that were mol/cm ² /Hr or less, and those that were out of the range in at least one of the evaluations were considered comparative examples.

The intermediate portion between the power generating body clamping part and the seal member disposed part provided on the outer periphery of the power generating body clamping part was 6 mm.

FIG. 6 schematically shows changes in the thickness of the titanium layer and the thickness of the carbon layer in the BB' cross section in the schematic diagram of FIG.
(Titanium film formation conditions)
Figure 7 shows the bias voltage during titanium film formation, the thickness of the titanium layer at the end of the power generating body clamping part (t(Ti2)), and the thickness of the titanium layer at the center of the power generating body clamping part (t(Ti1)). ) and the relationship between the ratio (t(Ti2)/t(Ti1)) and the amount of iron eluted. From Table 1, FIG. 6, and FIG. 7, it was found that the lower the bias voltage, the smaller the amount of drop in the film thickness (t(Ti2)) of the titanium layer at the end of the power generator sandwiching portion. On the other hand, when the bias voltage becomes higher than -50V, the amount of drop in t(Ti2) suddenly increases and becomes less than 1/3 of the thickness of the titanium layer (t(Ti1)) at the center of the power generator sandwiching part. I understand. In a fuel cell separator with a film thickness obtained under such conditions where the bias voltage is higher than -50V, it was found that the amount of iron eluted increases in corrosion resistance measurements, which results in a decrease in corrosion resistance that has a negative impact on the MEA. I understand. Therefore, it was found that under the titanium film forming conditions, the bias voltage needs to be -50V or less.

Further, although corrosion resistance can be improved by increasing the overall titanium film thickness, the surface treatment time becomes significantly longer, resulting in higher costs. Therefore, the thickness (t(Ti2)) of the titanium layer at the end of the power generating body clamping part is 0.38 to 0.38 times the thickness (t(Ti1)) of the titanium layer at the center of the power generating body clamping part. It was found that 60 times is preferable.

Further, it has been found that although the lower the bias voltage is, the better the characteristics are, but if it is less than -350V, the film formation rate decreases, so it is preferably -350V or more, and more preferably -250V or more.

In addition, when a titanium film is formed by AIP, droplets are generated on the film surface, making it impossible to obtain excellent corrosion resistance. Therefore, it was found that UBMS is preferable as the titanium film forming method.

(Carbon film formation conditions)
Figure 8 shows the bias voltage during carbon film formation, the contact resistance, and the carbon layer thickness (t (C2)). From Table 1, FIG. 6, and FIG. 8, the amount of carbon that wraps under the mask (=film thickness t(C2)) increases as the bias voltage decreases, and when the bias voltage is lower than -450V, t( It was found that C2) was 5 nm or more, and the sealing performance was NG.

On the other hand, it was found that the lower the bias voltage, the better the contact resistance after the constant potential test. In other words, it was found that the lower the bias voltage during film formation of the carbon layer, the more dense the carbon layer with low contact resistance could be formed.

Therefore, it was found that the range in which both adhesion (sealability) and contact resistance can be achieved is -450V to -250V.

Table 2 summarizes the evaluation results for Comparative Examples 1 to 7 and Examples 1 to 6. In Table 2, when the characteristics are good, ◯ is shown, and when the characteristics are bad, it is shown x. Further, Table 3 summarizes preferred film forming methods and bias voltages for titanium film forming conditions and carbon film forming conditions.

Note that it is possible to reduce t(C2) to 5 nm or less by increasing the shortest distance between the power generator holding part and the sealing member installation part in the intermediate part, but the fuel cell separator itself is large. This is not preferable in terms of component cost and component mountability.

In addition, in a separator that requires a smaller amount of iron to be eluted, a thicker titanium layer (t(Ti2)) may be required at the end of the power generating body clamping portion. In that case, it is possible to cope with this by making the mask window slightly larger than the film forming area, that is, the area that will become the power generating body clamping part. The selection of titanium and carbon film forming conditions in that case can also be selected based on the idea of the present invention.

1: Region to be the power generating body clamping part 2: Region to be the sealing member arrangement part 3: Region to be the intermediate part 4: Mask jig 5: Cavity having the same shape as the region to be the power generating body clamping part 6: Separator press product 7: Power generating body holding part 8: Seal member arrangement part 9: Intermediate part 10: Test piece cutting position for contact resistance and corrosion resistance test (evaluation area 4 cm x 4 cm)

Claims (3)

Manufacture of a fuel cell separator having a power generating body clamping part that clamps a power generating body, and a sealing member disposing part provided on the outer periphery of the power generating body clamping part and arranging a sealing member for sealing the power generating body clamping part. A method,
a step of preparing a metal substrate;
arranging a masking member with a gap between the metal base material and the metal base material in an area other than the area that will become the power generating body holding part;
A process of forming a titanium layer by depositing titanium on the surface of a metal base material,
Titanium film formation is carried out using an unbalanced magnetron sputtering method under a bias voltage of -50 V or less until the film thickness of the titanium layer at the end of the region that will become the power generator sandwiching part becomes 76 nm or more. process and
A process of forming a carbon layer by depositing carbon on a titanium layer of a metal base material,
A carbon film is formed using a filterless arc ion plating method under a bias voltage of -450V to -250V to form a carbon layer at the end of the area that will become the power generator clamping part of the area where the sealing member is provided. A method for producing a fuel cell separator, the method comprising: carrying out the step such that the film thickness of the separator is 5 nm or less. The method according to claim 1, wherein the titanium film is deposited using an unbalanced magnetron sputtering method under a bias voltage of -350V or more. The method according to claim 1 or 2, wherein the metal base material is stainless steel.

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