Patent Description:
There is known an injection molded article that has protrusions with different inner diameters on its substrate, and that is formed by injection molding involving separating the plurality of protrusions from a mold.

When injection molding a plastic product having a relatively thin base (plate thickness) part that is connected to a gate of a mold, and a protrusion (such as a boss and a rib) or an uneven thickness part, a sink mark is formed, for example, on the surface of a portion where the thickness of the product greatly varies. A sink mark is caused by the following reason. A molten thermoplastic shrinks while being cooled and solidified in a mold. In this process, a portion with a greater thickness than the neighboring portion is cooled more slowly, and therefore solidifies and shrinks after the neighboring portion solidifies. In particular, the core-side portion in the fixed mold defining the product visible portion of a plastic product is generally flat and more quickly cooled than the cavity-side portion in the movable mold having complicated structures such as a boss and a rib. Therefore, the core-side portion in the fixed mold is separated from the mold earlier than the cavity-side portion in the movable mold including the project invisible portion, and causes post-shrinkage, which is likely to result in a sink mark.

A sink mark is a recessed depression on the surface of a product. Sink marks not only reduce the visual quality of the product and lower the value, but also prevent uniform painting and impair the appearance. This may increase the repair cost.

To solve this problem, there is disclosed a technique that controls the location of sink marks such that sink marks are formed on the invisible surface. This is achieved by performing injection molding using a mold configured such that the mold surface on the product visible surface side that would cause sink marks has a higher adhesion force to resin than the mold surface on the invisible surface side (see, for example, PTL <NUM>).

The product visible surface of a component of a micro fluid chip is required to prevent leakage of liquid and achieve the accuracy in height of a flow channel for fluid when an optical component is joined thereto. This is because the flow channel is formed by joining the optical component thereto.

However, according to the technique disclosed in PTL <NUM>, since roughening is applied to the entire region of the product visible surface where sink marks would be formed, roughening is applied even to the region requiring accuracy in specularity that affects the height of the flow channel and leakage of liquid. That is, according to the technique disclosed in PTL <NUM>, there are variations in the surface properties of the product visible surface, which results in leakage of liquid and variations in the height of the flow channel.

An object of the present invention is to provide an injection molded article that can prevent leakage of liquid and achieve the required accuracy in height of a flow channel.

In order to achieve the above-described object, an invention is set out in independent product claim <NUM> and further embodiments are set out in the dependent claims.

According to the present invention, it is possible to achieve the required accuracy in height of the flow channel.

A test chip <NUM> according to the present embodiment is a chip (micro fluid chip) used for test, analysis, and so on of a biological material based on an antigen-antibody reaction. As illustrated in <FIG>, the test chip <NUM> includes a test chip substrate <NUM>, a first protrusion <NUM>, and a second protrusion <NUM>.

The test chip substrate <NUM> is made of a resin. The requirements for the resin are high formability (transformability and releasability), high transparency, and low self-fluorescence with respect to the ultraviolet ray and visible ray. The test chip substrate <NUM> has a flow channel <NUM> through which liquid or the like injected by a non-illustrated liquid feeder flows.

As illustrated in <FIG>, the test chip substrate <NUM> includes a first substrate (base) 12a as a thin plate-shaped member, a flow channel seal (not illustrated), and a second substrate 12b (optical component such as a prism). The flow channel <NUM> is formed in a region defined by the first substrate 12a and the second substrate 12b attached together with a flow channel seal. The first substrate 12a and the second substrate 12b of the test chip substrate <NUM> are manufactured by a method such as injection molding, press molding, and machine processing. At least one of the first substrate 12a and the second substrate 12b may be microfabricated.

The first substrate 12a has a gate GA. The gate GA serves as an inlet when injecting a resin material into the mold. The gate GA has a bridging function for filling the cavity with the resin material injected through a sprue.

The test chip substrate <NUM> is formed by joining the first substrate 12a and the second substrate 12b. When the first substrate 12a and the second substrate 12b are joined, the flow channel <NUM> is formed therebetween. The substrates may be joined by a welding method that joins resin-made substrates by heating them using a heat plate, hot air, a heating roller, ultrasonic wave, vibration, laser, double-sided seal, or the like, a bonding method that joins resin-made substrates using adhesive or solution, a method that joins resin-made substrates utilizing their own adhesiveness, or a method that joins substrates by applying surface treatment such as plasma treatment to resin-made substrates. In this manner, the test chip <NUM> having the flow channel <NUM> therein is manufactured.

The flow channel <NUM> includes a reaction channel <NUM> extending in a predetermined direction (direction along an upper surface 12c of the test chip substrate <NUM> in <FIG>) inside the test chip substrate <NUM>, a communication channel <NUM> for communication between the reaction channel <NUM> and the first protrusion <NUM>, and a communication channel <NUM> for communication between the reaction channel <NUM> and the second protrusion <NUM>.

The following describes how the flow channel <NUM> is formed. A groove for a flow channel (a part corresponding to the reaction channel <NUM> in <FIG>) is formed in the second substrate 12b. Then, the first substrate 12a serving as a cover is joined to the second substrate 12b having the flow channel groove, in a manner such that the flow channel groove faces inward. In this way, the flow channel <NUM> is formed. Alternatively, the flow channel i i may be formed by joining the first substrate 12a and the second substrate 12b, in a manner such that a double-sided seal having the flow channel <NUM> is interposed therebetween.

The plate thickness of the second substrate 12b having the flow channel groove is preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>. The plate thickness of the first substrate 12a serving as a lid (cover) for the flow channel groove is preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>, taking into account the formability.

The test chip substrate <NUM> is made of a low-cost, disposable resin, specifically a thermoplastic resin. Preferred examples of thermoplastic resins are polycarbonate, polymethylmethacrylate, polystyrene, polyacrylonitrile, polyvinyl chloride, polyethylene terephthalate, nylon <NUM>, nylon <NUM>, polyvinyl acetate, polyvinylidene chloride, polypropylene, polypropylene, polyisoprene, polyethylene, polydimethylsiloxane, and cyclic polyolefin. Particularly preferred examples are polymethylmethacrylate and cyclic polyolefin.

The first protrusion <NUM> is integrally formed on the upper surface of the test chip substrate <NUM> (first substrate 12a). The first protrusion <NUM> has an inner diameter portion <NUM>, and serves as a reagent mixer and a reagent reactor for mixing and reacting a reagent in the inner diameter portion <NUM>. Techniques for mixing and reacting a reagent are well known in the art, and will not be described herein. The inner diameter portion <NUM> communicates with the communication channel <NUM> of the flow channel <NUM>.

The second protrusion <NUM> is integrally formed on the upper surface of the test chip substrate <NUM>, but in a region different from the region where the first protrusion <NUM> is formed. The second protrusion <NUM> has an inner diameter portion <NUM>. The inner diameter portion <NUM> communicates with the communication channel <NUM> of the flow channel <NUM>.

The first protrusion <NUM> and the second protrusion <NUM> respectively have holes 13a and 14a each extending through the first substrate 12a. The holes 13a and 14a in the respective protrusions (first protrusion <NUM> and second protrusion <NUM>) are connected through another component (second substrate 12b) to form the flow channel <NUM>.

Each of the first protrusion <NUM> and the second protrusion <NUM> is formed to have a thickness greater than a plate thickness of the first substrate 12a. In the present embodiment, the thickness of the thickest portion of the protrusions is two or more times greater than the plate thickness of the first substrate 12a.

As illustrated in <FIG>, the thickest portion of the protrusions is the center of a sphere BA that is the largest imaginary sphere located inside the injection molded article (inside the first protrusion <NUM> in the present embodiment) and tangent to the wall surface thereof. The thickest portion of the protrusion can be calculated with, for example, the maximum ball algorithm used in 3D shape analysis software.

As illustrated in <FIG>, when a thickness value of the thickest portion of the protrusions (in the present embodiment, the thickest portion of the first protrusion <NUM>) is defined as <NUM>%, a processed region processed to have a surface roughness greater (by several nanometers to several tens of nanometers in Ra) than the surface roughness of a mirror surface region E2 including a region between the holes 13a and 14a on the first substrate 12a is formed in a projected region E1 (that is, a region where a perpendicular line is drawn from a region having a thickness value of <NUM> to <NUM>% to the first substrate 12a) where a region having a thickness value of <NUM> to <NUM>% is projected on the first substrate 12a. In the present embodiment, the surface roughness of the processed region is <NUM> to <NUM> in Ra (arithmetic average roughness).

The injection molded article of the present invention is the test chip <NUM> excluding the second substrate 12b that is an optical component.

As illustrated in <FIG>, when the area of a smallest circle C1 containing the projected region E1 is defined as <NUM>%, the injection molded article of the present invention is obtained from a mold roughened (for example, sandblasted) to make the surface roughness greater than the surface roughness of the mirror surface region E2, in an area of a circle (= processed region E3) that is within the smallest circle C1 and is <NUM> to <NUM>% of the area of the smallest circle C1. In the present embodiment, for purposes of explanation, the projected region E1 is circular, and the projected region E1 and the smallest circle C1 exactly coincide. However, the present invention is not limited thereto. That is, the projected region E1 is not always circular, and hence the projected region E1 and the smallest circle Cl do not always coincide. Also, the processed region E3 is not always circular, and may have any shape as long as its area is in the range of <NUM> to <NUM>% of the area of the smallest circle C1.

The injection molded article of the present invention is obtained by injection molding a molten resin into a mold that is processed such that the mirror surface region E2 and the projected region E1 are located close to each other. Specifically, as illustrated in <FIG>, the mirror surface region E2 is included in a region E4 (a region adjacent to the projected region E1) where a region having a thickness value of <NUM> to <NUM>% is projected on the first substrate 12a. That is, the mirror surface E2 is located close to the projected region E1 where sink marks are likely to be formed. Although it is necessary to prevent formation of sink marks, roughening cannot be applied to the mirror surface region E2 because flatness and specularity are required there. Accordingly, in the present embodiment, roughening is applied to the region close to the mirror surface region E2. That is, according to the present invention, even when the region (projected region E1) where sink marks are likely to be formed and the region (mirror surface region E2) requiring flatness and specularity are close to each other, formation of sink marks on the visible surface of the first substrate 12a is prevented.

The test chip <NUM> is produced through a predetermined process by using an injection molding machine (injection mold <NUM>). Hereafter, the injection molding process using the injection mold <NUM> will be described with reference to <FIG> and <FIG>. <FIG> is a schematic diagram illustrating a so-called "mold clamping step" for forming a cavity by clamping two molds (movable mold <NUM> and fixed mold <NUM>). <FIG> is a schematic diagram illustrating a so-called "ejection step" for removing an injection molded article <NUM> from the injection mold <NUM>.

As illustrated in <FIG>, the injection mold <NUM> includes the movable mold <NUM> with a recess (cavity) <NUM> in the shape of the injection molded article <NUM>, the fixed mold <NUM> against which the movable mold <NUM> is pressed so as to close the recess <NUM>, an ejector pin <NUM> that pushes the injection molded article <NUM> outward (in the direction of the arrow X in <FIG>), an ejector member <NUM>, core pins <NUM> each defining the internal shape of a protrusion, and a cylinder unit <NUM> that supplies a resin material (not illustrated) as the material of the injection molded article <NUM> to the cavity.

The injection molding process includes a mold clamping step, an injection step, a pressure holding step, a cooling step, a mold opening step, and an ejection step. Injection molding is performed in this order. As illustrated in <FIG>, in the mold clamping step, the movable mold <NUM> and the fixed mold <NUM> are clamped together to close the recess <NUM> formed in the movable mold <NUM>, thereby forming a cavity. Then, a resin material (molten resin) is injected from a resin material supply furnace <NUM> to fill the cavity therewith (injection step). The resin material flows through a sprue SP (unwanted portion of the injection molded article <NUM>) and the gate GA, and is filled in the cavity. When filled in the cavity of the mold, the resin material is cooled and shrinks in the mold. Since the shrinkage causes a change in the volume, this shrinkage action results in a dimensional change of a molded article, a shape transfer failure, and the like. To prevent these issues, the volume of resin reduced due to the shrinkage is compensated for by applying a holding pressure on the molding machine side (pressure holding step). Then, the resin material is cooled in the mold until its temperature decreases to a level at which it can be extracted from the mold (cooling step).

When the resin material is sufficiently cooled after a lapse of a predetermined time, the movable mold <NUM> is separated from the fixed mold <NUM> (mold opening step) as illustrated in <FIG>. In this step, the molded article comes with the movable mold <NUM>. Then, by moving the ejector pin <NUM> and the ejector member <NUM> outward, the injection molded article <NUM> is demolded (ejection step). The second substrate 12b is joined to the injection molded article <NUM> to obtain a test chip <NUM>.

In the present embodiment, since the predetermined region (the region corresponding to the processed region of the first substrate 12a) of the surface of the fixed mold <NUM> is roughened (sandblasted), resin is not easily separated from the fixed mold <NUM> during cooling and shrinkage. This prevents formation of sink marks on the visible surface of the injection molded article <NUM> (first substrate 12a).

In the following, Examples <NUM> to <NUM> and Comparative Examples <NUM> to <NUM> of the test chip substrate <NUM> (first substrate 12a) according to the present invention will be described with reference to <FIG>.

A test chip substrate <NUM> of Comparative Example <NUM> is configured such that the plate thickness of a first substrate 12a (base plate thickness) is <NUM>, and the thickness value of the thickest portion of the first substrate 12a is <NUM>. The area of a smallest circle C1 containing a projected region E1 is <NUM>. 4n mm<NUM>; the area of a processed region E3 is 1π mm<NUM>; and the ratio (percentage) of the area of a processed region E3 to the area of the smallest circle C1 is <NUM>%. The surface roughness of the processed region E3 is <NUM> in Ra.

A test chip substrate <NUM> of Comparative Example <NUM> is configured such that the plate thickness of a first substrate 12a (base plate thickness) is <NUM>, and the thickness value of the thickest portion of the first substrate 12a is <NUM>. The area of a smallest circle Cl containing a projected region E1 is <NUM>. 4π mm<NUM>; the area of a processed region E3 is 1π mm<NUM>; and the ratio (percentage) of the area of a processed region E3 to the area of the smallest circle C1 is <NUM>%. The surface roughness of the processed region E3 is <NUM> in Ra.

A test chip substrate <NUM> of Comparative Example <NUM> is configured such that the plate thickness of a first substrate 12a (base plate thickness) is <NUM>, and the thickness value of the thickest portion of the first substrate 12a is <NUM>. The area of a smallest circle Cl containing a projected region E1 is <NUM>. 4π mm<NUM>; the area of a processed region E3 is <NUM>. 5π mm<NUM>; and the ratio (percentage) of the area of a processed region E3 to the area of the smallest circle C1 is <NUM>%. The surface roughness of the processed region E3 is <NUM> in Ra.

A test chip substrate <NUM> of Example <NUM> is configured such that the plate thickness of a first substrate 12a (base plate thickness) is <NUM>, and the thickness value of the thickest portion of the first substrate 12a is <NUM>. The area of a smallest circle C1 containing a projected region E1 is <NUM>. 4π mm<NUM>; the area of a processed region E3 is 1π mm<NUM>; and the ratio (percentage) of the area of a processed region E3 to the area of the smallest circle C1 is <NUM> %. The surface roughness of the processed region E3 is <NUM> in Ra.

A test chip substrate <NUM> of Example <NUM> is configured such that the plate thickness of a first substrate 12a (base plate thickness) is <NUM>, and the thickness value of the thickest portion of the first substrate 12a is <NUM>. The area of a smallest circle C1 containing a projected region E1 is <NUM>. 4π mm<NUM>; the area of a processed region E3 is 1π mm<NUM>; and the ratio (percentage) of the area of a processed region E3 to the area of the sm allest circle C1 is <NUM>%. The surface roughness of the processed region E3 is <NUM> in Ra.

A test chip substrate <NUM> of Example <NUM> is configured such that the plate thickness of a first substrate 12a (base plate thickness) is <NUM>, and the thickness value of the thickest portion of the first substrate 12a is <NUM>. The area of a smallest circle Cl containing a projected region E1 is <NUM>. 4π mm<NUM>; the area of a processed region E3 is <NUM>. 7π mm<NUM>; and the ratio (percentage) of the area of a processed region E3 to the area of the smallest circle Cl is <NUM>%. The surface roughness of the processed region E3 is <NUM> in Ra.

In the case of the test chip substrate <NUM> of Comparative Example <NUM> configured such that the surface roughness of the processed region E3 is <NUM> in Ra, since the roughness was too low, the resin did not properly stick to the mold. Accordingly, satisfactory results were not obtained.

In the case of the test chip substrate <NUM> of Comparative Example <NUM> configured such that the surface roughness of the processed region E3 is <NUM> in Ra, since the roughness was too high, the resin remained in the mold. Accordingly, satisfactory results were not obtained.

In the case of the test chip substrate <NUM> of Comparative Example <NUM> configured such that the ratio (percentage) of the area of the processed region E3 to the area of the smallest circle C1 is <NUM>%, since the area was too small, the resin did not properly stick to the mold. Accordingly, satisfactory results were not obtained.

Meanwhile, in the case of the test chip substrates <NUM> of Examples <NUM> to <NUM>, satisfactory results were obtained.

It was found from the above that when the test chip substrate <NUM> is configured such that the surface roughness of the processed region E3 is <NUM> to <NUM> in Ra, satisfactory results are obtained. It was also found that when the test chip substrate <NUM> is configured such that the ratio (percentage) of the area of the processed region E3 to the area of the smallest circle Cl is <NUM> to <NUM>%, satisfactory results are obtained.

With any of the configurations of Examples <NUM> to <NUM>, it is possible to prevent formation of sink marks on the visible surface of the first substrate 12a.

Meanwhile, a region where the surface accuracy of the mold is not achieved is formed in a region where the region of the thickest portion is projected on the invisible surface (for example, the side wall of the protrusion) defining the surface other than the visible surface. The region where the surface accuracy of the mold is not achieved is a region where the shape of the mold is not accurately transferred, and is a region where a so-called sink mark is formed. That is, in the present embodiment, formation of sink marks on the visible surface of the first substrate 12a is prevented by guiding sink marks to the invisible surface.

As described above, the injection molded article according to the present embodiment includes: a base (first substrate 12a) as a thin plate-shaped member that is connected to the gate GA of a mold (injection mold <NUM>); and a plurality of protrusions (first protrusion <NUM> and second protrusion <NUM>) each integrally molded on the base and having a thickness greater than a plate thickness of the base. The plurality of protrusions have holes 13a and 14a each extending through the base, and the holes 13a and 14a in the respective protrusions are connected through another component to form a flow channel. When the thickness value of the thickest portion of the protrusions is defined as <NUM>%, the processed region E3 processed to have a surface roughness greater than the surface roughness of the mirror surface region E2 including a region between the holes 13a and 14a on the base is formed in the projected region E1 where a region having a thickness value of <NUM> to <NUM>% is projected on the base. The injection molded article is obtained from the mold processed such that the mirror surface region E2 and the projected region E1 are located close to each other.

Accordingly, according to the injection molded article of the present embodiment, the region of the product visible surface in which sink marks are likely to be formed is processed such that resin is not easily separated, so that formation of sink marks on the product visible surface is prevented. Accordingly, the surface properties of the product visible surface are sufficiently secured. Therefore, it is possible to prevent leakage of liquid, and achieve the required accuracy in height of the flow channel.

According to the injection molded article of the present embodiment, the thickness of the thickest portion is two or more times greater than the plate thickness of the base.

Accordingly, according to the injection molded article of the present embodiment, even when the molded artic has a large thickness, formation of sink marks on the visible surface is prevented. Therefore, it is possible to prevent leakage of liquid, and achieve the required accuracy in height of the flow channel.

According to the injection molded article of the present embodiment, the surface roughness of the processed region E3 is <NUM> - <NUM> in Ra.

Accordingly, according to the injection molded article of the present embodiment, the resin on the product visible surface side adheres sufficiently well, so that formation of sink marks on the product visible surface is more reliably prevented.

According to the injection molded article of the present embodiment, when the area of the smallest circle Cl containing the projected region E1 is defined as <NUM>%, the injection molded article is obtained from a mold roughened to make the surface roughness greater than the surface roughness of the mirror surface region E2, in an area that is within the smallest circle C1 and that is <NUM> to <NUM>% of the area of the smallest circle C1.

According to the injection molded article of the present embodiment, a region where a surface accuracy of the mold is not achieved is formed in a region where a region of the thickest portion is projected on an invisible surface defining a surface other than the base.

Accordingly, according to the injection molded article of the present embodiment, sink marks are guided to the invisible surface, so that formation of sink marks on the product visible surface is prevented.

According to the injection molded article of the present embodiment, the mirror surface region E2 is included in a region where a region having a thickness value of <NUM> to <NUM>% is projected on the base.

Accordingly, according to the injection molded article of the present embodiment, even when the region (projected region E1) where sink marks are likely to be formed and the region (mirror surface region E2) requiring flatness and specularity are close to each other, formation of sink marks on the visible surface is prevented. Therefore, it is possible to prevent leakage of liquid, and achieve the required accuracy in height of the flow channel.

Although the present invention has been described in conjunction with the specific embodiment, the present invention is not limited to the above embodiment, and changes and modifications may be made without departing from the scope of the present invention as set out in the appended set of claims.

For example, in the above embodiment, the thickness of the thickest portion of the protrusions is two or more times greater than the plate thickness of the first substrate 12a. However, the present invention is not limited thereto. That is, the thickness of the thickest portion of the protrusions only needs to be greater than the plate thickness of the first substrate 12a. The thickness of the thickest portion of the protrusions may be less than twice the thickness of the first substrate 12a.

In the above embodiment, surface roughening is performed by sandblasting. However, the present invention is not limited thereto. For example, surface roughening is performed by rubbing with sand paper or etching, in place of sandblasting. Alternatively, fine indentations may be formed on the surface by using a processing machine capable of high precision processing so as to have a desired surface roughness (Ra).

Other changes and modifications may also be made to the configuration and operation of the devices included in the test chip without departing from the scope of the present invention as set out in the appended set of claims.

Claim 1:
An injection molded article (<NUM>) that is obtained by injection molding a molten resin into a mold (<NUM>), the injection molded article (<NUM>) comprising:
abase (12a) as a thin plate-shaped member that is connected to a gate (GA) of the mold (<NUM>); and
a plurality of protrusions (<NUM>, <NUM>) each integrally molded on the base (12a) and having a thickness greater than a plate thickness of the base (12a);
wherein the plurality of protrusions (<NUM>, <NUM>) have holes (13a, 14a) each extending through the base (12a), and the holes (13a, 14a) in the respective protrusions (<NUM>, <NUM>) are connected through another component to form a flow channel (<NUM>);
wherein when a thickness value of a thickest portion of the protrusions (<NUM>, <NUM>) is defined as <NUM>%, a processed region (E3) processed to have a surface roughness greater than a surface roughness of a mirror surface region (E2) including a region between the holes (13a, 14a) on the base (12a) is formed in a projected region (E1) where a region having a thickness value of <NUM> to <NUM>% is projected on the base (12a); and
wherein the injection molded article (<NUM>) is obtained from the mold (<NUM>) processed such that the mirror surface region (E2) and the projected region (E1) are located close to each other,
wherein when an area of a smallest circle (C1) containing the projected region (E1) is defined as <NUM>%, the injection molded article (<NUM>) is obtained from the mold (<NUM>) roughened to make a surface roughness greater than the surface roughness of the mirror surface region (E2), in an area (E3) that is within the smallest circle and is <NUM> to <NUM>% of an area of the smallest circle (C1).