JP3728686B2 - Method for manufacturing liquid holder made of organic polymer material - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to a liquid holder. This liquid holder can be suitably used as a clinical diagnostic tool that holds a test liquid accurately and quantitatively when measuring components in blood or urine.
[0002]
[Prior art]
The wettability of the liquid with respect to the surface of the organic polymer material depends on the surface properties. Therefore, the surface of the organic polymer material is modified by means of plasma treatment, corona discharge treatment, ultraviolet treatment, etc. so that the organic polymer material has wettability suitable for each application such as analysis, adhesion, painting, and printing. Quality is done. For example, since adhesives, paints, printing inks, and the like are mostly water-based, the surface is modified to be hydrophilic as a pretreatment such as adhesion, painting, and printing.
[0003]
The surface-modified polymer material is not always used immediately but may be stored for use. Therefore, the degree of hydrophilicity of the modified surface needs to be stable over time. In particular, when used as an analytical tool, this stability is important because the degree of hydrophilicity affects the analytical accuracy.
[0004]
Further, the operation of attaching the liquid to the surface of the organic polymer material is not limited to once. For example, when an organic polymer material is to be bonded, painted, or printed, the liquid is often applied multiple times, and even when used as a test piece or analytical tool, the liquid is once applied to adhere to the surface thoroughly. Further liquid may be added to the surface where the liquid is dripped or poured. In addition, after the liquid adheres, an external force may be unexpectedly applied to the organic polymer material during transportation. In such a case, in order to maintain the homogeneity of the product to be bonded, painted, printed, etc., or to improve the analysis accuracy by the analytical tool, the surface of the organic polymer material is added to the amount of liquid added. It is preferable to modify the liquid so that the amount of liquid retained per certain area is constant regardless of the amount of external force.
[0005]
As a method for evaluating the degree of surface modification, a static contact angle is generally measured. The static contact angle becomes smaller as the reforming process proceeds, and the value often remains constant from a certain condition even if the process is continued. Therefore, the range where the static contact angle is constant is estimated to be a state where the surface property is stable, and the treatment conditions at that time are optimized for surface modification.
[0006]
[Problems to be solved by the invention]
However, in a manufacturing method of a structure obtained using wettability such as a thin film made of a retained liquid, or an analytical method using wettability such as a color reaction with a reagent or quantification of a test solution component Even if an organic polymer material whose surface was modified under the condition that the static contact angle was constant, the results varied. This depends not only on the difference in the degree of modification of each organic polymer material but also on the fact that the degree of hydrophilicity changes with time after modification.
[0007]
On the other hand, the inventors have used a dynamic contact angle rather than a static contact angle as a criterion for evaluating whether or not the surface has been modified so that the amount of liquid retained per certain area is constant. It was found that (advance contact angle / retreat contact angle) is appropriate.
[0008]
Therefore, a first object of the present invention is to provide a liquid holder made of an organic polymer whose hydrophilicity of the modified surface is stable over time. The second object is to provide a liquid holder made of an organic polymer that is excellent in the quantitativeness of the liquid to be held.
[0009]
[Means for Solving the Problems]
In order to achieve the object, the manufacturing method of the liquid holder of the present invention comprises:
In the method of modifying the surface of the organic polymer material to hydrophilicity by electromagnetic wave irradiation,
A function in which the advancing contact angle on the surface of the material is θa, the receding contact angle is θr, the electromagnetic wave irradiation amount is i, the difference between the advancing contact angle and the receding contact angle (θa−θr) is the vertical axis, and i is the horizontal axis. When drawing a graph,
When the specific dose at which (θa−θr) is a minimum value is i ₀ , and the specific dose when the function graph first changes from a steep slope to a gentle slope in a range larger than i ₀ is i _V. ,
It is characterized in that the electromagnetic wave is irradiated by i in the range of absolute value | i _V −i ₀ | with i ₀ as the center.
[0010]
The shape of the droplet attached to a certain area on the surface of a certain material does not change due to external factors such as the addition of liquid or the addition of external force, as shown in Fig. 1 (a). This is when the target contact angles (advance angle θa and receding angle θr) are equal, that is, θa−θr = 0 (hereinafter, “θa−θr” is referred to as contact angle hysteresis). In other words, when θa−θr is large as shown in FIG. 1B, the range of contact angles that the liquid can form on this surface is wide, so that the droplets adhering to the same area are in FIG. 2A. It becomes larger as in (b) or smaller as in (b). FIG. 2 shows droplets obtained by gently dropping a predetermined amount of liquid little by little onto the surface of a certain material. At first, even when a liquid is further dropped in the state of (b), the contact area between the liquid and the solid is the same and the contact angle only changes (swells). The swollen state is (a).
[0011]
The inventors examined changes in the contact angle hysteresis with respect to the progress of the surface treatment for various organic polymer materials, and found that most of the materials have the following characteristics in common. First, as the surface treatment starts, the contact angle hysteresis once suddenly rises to reach the maximum value, then suddenly drops to take the local minimum value, gradually increases to return to the value before the surface treatment, and then the surface treatment proceeds. Regardless, it will be constant.
[0012]
Therefore, in the present invention, as described above, the surface modification is performed under the condition that the contact angle hysteresis is a minimum value that is the closest value to 0, and the shape of the droplets adhering to the surface of the material also varies depending on external factors. It was difficult.
[0013]
Furthermore, the newly obtained knowledge is that the storage period of the modified organic polymer is also included in the external factor. That is, the static contact angle of the surface modified under the condition that the contact angle hysteresis becomes a minimum value does not change with time. Rather, this change over time is considered to have the most influence on the above-mentioned variation due to the fact that the degree of hydrophilicity of the surface modified to be hydrophilic under certain conditions changes during the storage period. The inventors consider this phenomenon as follows.
[0014]
When the surface of an organic polymer material is irradiated with electromagnetic waves such as ultraviolet rays, molecular chains are partially broken at the extreme surface, and oxygen is supplied from the atmosphere to generate hydrophilic groups such as hydroxyl groups, carbonyl groups, and carboxyl groups. Sex groups are introduced. A segment of a molecule generated by breaking a molecular chain is easy to move, and the hydrophilic group at the tip thereof is easy to move. This is the cause of contact angle hysteresis. On the other hand, since the amount of oxygen supplied from the inside of the pole surface is small, the energy of electromagnetic waves is mainly spent for crosslinking of molecular chains. Since the cross-linked molecular chain is fixed three-dimensionally, the hydrophilic group is also difficult to move. As described above, it is not clear why the contact angle hysteresis suddenly rises with the start of the surface treatment, but it is in this process that it suddenly falls thereafter.
[0015]
When the electromagnetic wave continues to be irradiated, the uncrosslinked pole surface peels off and disappears as a gas. Here, the newly appearing surface is a cross-linked one in which molecular chain movement is difficult. Therefore, the contact angle hysteresis is small and the static contact angle is also constant for a long time. It is at this time that the contact angle hysteresis becomes the minimum value as described above.
[0016]
When the electromagnetic wave is further irradiated, the crosslinked molecular chain is cut and a hydrophilic group is introduced. However, since the molecular segments are cross-linked, the rate of cleavage and introduction is slower than in the initial stage. It is in this process that the contact angle hysteresis beyond the minimum value gradually increases with the irradiation time.
Therefore, according to the present invention, the amount of liquid retained mainly depends only on the contact area between the material to be retained and the liquid, and the amount of liquid retained is constant as long as the contact area is constant.
[0017]
The amount of electromagnetic wave irradiation is proportional to the irradiation time when all irradiation conditions other than the irradiation time are constant. Accordingly, the present invention, when the irradiation conditions constant, to replace the dose i in time t, the absolute value around the t ₀ | and characterized by reforming with a t in the range _| t V _-t 0 To do.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
In the case of modification by ultraviolet irradiation, a low-pressure mercury lamp is optimal as the ultraviolet light source. This is because the tube wall temperature of this lamp is as low as about 100 ° C., and high energy short wavelength ultraviolet rays are emitted. The short wavelength ultraviolet rays to be irradiated may have high energy at wavelengths of 185 nm and then 254 nm. The irradiation conditions are usually about time: 1 to 120 minutes, irradiation distance: 0.5 to 8 cm, and illuminance: about 1 to ²⁰ mW / cm ² .
[0021]
The obtained liquid holder is used as a clinical diagnostic tool, for example. In this case, since the liquid holder itself has a quantitative function, there is an advantage that the quantitative operation by the pipette can be omitted. However, the amount of the test solution such as blood or urine that adheres depends not only on the wettability but also on the area of the modified region. Therefore, it is preferable to modify the surface of the material covered with a mask having a predetermined pattern so that only a predetermined region is modified.
[0022]
When the surface is modified by irradiation with electromagnetic waves such as ultraviolet rays, the organic polymer is at least one selected from polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyacrylic amide, polyacrylic ester, and polyvinyl acetate. Is preferred. This is because these are cross-linked by electromagnetic wave irradiation and introduce a hydrophilic group, so that the penetration of the hydrophilic group due to molecular motion is reduced and the hydrophilic group becomes stable. Of these, polystyrene (PS) is particularly preferred because it is easy to process and handle.
[0023]
In the case of PS, the clarity and value of the minimum point of contact angle hysteresis depends on its molecular weight. That is, when PS is subjected to electromagnetic wave treatment, for example, the smaller the molecular weight, the clearer the (θa−θr) minimum point becomes, and the value approaches zero. Conversely, as the molecular weight is smaller, the minimum point of (θa−θr) becomes unclear, and the value also moves away from zero. When the molecular weight is 200,000 or less, the minimum point is not shown. Accordingly, in the case of PS, those having a molecular weight greater than 200,000 are preferable.
[0024]
When the surface area to be modified is a part of the whole surface of the organic polymer material and is surrounded by the boundary line with the surface area that is not modified, the contact area between the liquid and the organic polymer material is Since it is regulated by the boundary line, the contact area can be kept constant. As a result, the quantitative property of the retained liquid can be easily maintained.
[0025]
【Example】
A number of 1 mm thick sheets made of polystyrene (PS) having a molecular weight of 350,000 were prepared. The sheet is ultrasonically washed with 50% ethanol aqueous solution and dried, then set in an ultraviolet irradiation device, a 95 W low-pressure mercury lamp is fixed at a height of 3 cm above the sheet, and ultraviolet rays are applied to the sheet for 0 to 120 minutes. The surface of the PS sheet was modified by irradiating each sheet for a different time in the range of.
[0026]
FIG. 3 shows the relationship between the static contact angle of the modified sheet with pure water and the irradiation time, and FIG. 4 shows the relationship between (θa−θr) and the irradiation time. Moreover, the time-dependent change of a static contact angle when each sheet | seat is put into a silica gel desiccator at 23 degreeC and preserve | saved for 0-5 months is shown in FIG.
[0027]
As shown in FIG. 3, the static contact angle becomes constant when irradiated with ultraviolet rays for a certain period of time, but (θa−θr) takes a minimum value when it is seen in FIG. And the sheet | seat modified | reformed by irradiation time 15 minutes used as this minimum value was the most stable with time so that FIG. 5 might see.
[0028]
FIG. 6 shows a graph obtained by measuring the oxygen / carbon ratio of the surface of the PS sheet with respect to the time of ultraviolet irradiation by X-ray photoelectron analysis (XPS) using the escape angle as a parameter. The escape angle corresponds to the analysis depth from the outermost surface, and the O / C ratio measured at 75 ° is deeper than the O / C ratio measured at the escape angle of 45 °. Indicates. In addition, since oxygen atoms do not exist in the original polystyrene molecule, the larger the O / C ratio, the more hydrophilic groups are introduced. In the initial ultraviolet irradiation, the amount of oxygen introduced into the deep layer is small, but if the irradiation is continued, the depth dependency of the oxygen introduction amount tends to disappear. From this, it can be seen that the position where oxygen is introduced by irradiation gradually moves from the surface to the inside.
[0029]
Next, a portion of about 0.1 μm was scraped off from the surface of the PS sheet irradiated with ultraviolet rays for 5 minutes, 15 minutes and 60 minutes with a cutter blade, and a part thereof was immersed in tetrahydrofuran (THF) at a concentration of 2 mg / ml. As a result, the surface layer of the sheet irradiated only for 5 minutes was completely dissolved, whereas the surface layer of the sheet irradiated for 15 minutes and 60 minutes had a gel-like insoluble portion. Further, when the remaining portion of the scraped surface layer was subjected to differential scanning calorimetry (DSC), as shown in FIG. 7, only the sheet irradiated for 60 minutes was confirmed to have a second transition point on the higher temperature side than the normal glass transition point. It was. From the two results of solubility in THF and DSC, it is clear that a crosslinking phenomenon occurs inside.
[0030]
Furthermore, when the surfaces with irradiation times of 10 minutes and 20 minutes were observed with a scanning electron microscope, molecular segments that were not decomposed appeared to be island-like in the former, but not in the latter.
From the above experimental results, the organic polymer material modified under the condition that (θa−θr) is minimized has the hydrophilic group introduced without breaking the molecular chain on the extreme surface, and the introduced hydrophilic property. Since the sex group is strongly fixed three-dimensionally by cross-linking, it exhibits a stable long-term hydrophilicity. The condition that (θa−θr) is minimized is that the irradiation time is most easily managed when the modifying means is based on ultraviolet irradiation.
[0031]
【The invention's effect】
As described above, the liquid holder of the present invention has a modified surface texture that is stable for a long period of time. Is beneficial.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining contact angle hysteresis (θa−θr);
FIG. 2 is a diagram showing a droplet attached to a solid.
FIG. 3 is a graph showing the results of measuring the relationship between ultraviolet irradiation time and static contact angle using PS having a molecular weight of 350,000.
FIG. 4 is a graph showing the results of measuring the relationship between UV irradiation time and contact angle hysteresis using PS having a molecular weight of 350,000.
FIG. 5 is a graph showing the results of measuring the time-dependent change of the PS static contact angle using the ultraviolet irradiation time as a parameter.
FIG. 6 is a graph showing the results of measuring the relationship between the oxygen / carbon ratio of the surface of PS having a molecular weight of 350,000 and the ultraviolet irradiation time.
FIG. 7 is a differential thermal analysis graph of PS having a molecular weight of 350,000.

Claims (5)

In the method of modifying the surface of the organic polymer material to hydrophilicity by electromagnetic wave irradiation,
A function in which the advancing contact angle on the surface of the material is θa, the receding contact angle is θr, the electromagnetic wave irradiation amount is i, the difference between the advancing contact angle and the receding contact angle (θa−θr) is the vertical axis, and i is the horizontal axis. When drawing a graph,
When the specific dose at which (θa−θr) is a minimum value is i ₀ , and the specific dose when the function graph first changes from a steep slope to a gentle slope in a range larger than i ₀ is i _V. ,
A method of manufacturing a liquid holder, characterized by irradiating an electromagnetic wave by i within a range of an absolute value | i _V −i ₀ | with i ₀ as a center. The method for producing a liquid holder according to claim 1, wherein the electromagnetic waves are ultraviolet rays. Organic polymer, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyacrylic amide, polyacrylic acid esters, liquid according to any of claims 1-2 is at least one selected from among polyvinyl acetate A method for manufacturing a holder. The method for producing a liquid holder according to any one of claims 1 to 3, wherein the organic polymer is polystyrene having a molecular weight exceeding 200,000. Liquid retainer, method of manufacturing a liquid retainer according to any one of claims 1 to 4, which is a clinical diagnosis tool.

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