KR100545581B1 - A method for bonding plastic substrates at a low temperature using a X-ray irradiation - Google Patents

Abstract

The present invention comprises the steps of (a) lowering the glass transition temperature by irradiating X-rays or ultraviolet rays to the surface of the plastic to be bonded for a certain time; And (b) thermally bonding the surface of the joined object irradiated with X-rays or ultraviolet rays. According to the thermal bonding method of the present invention, the bonding can be performed at a lower temperature than the conventional thermal bonding temperature, it can be performed without changing the microstructure.

Thermal bonding, microstructure, microchannels, glass transition temperature, X-rays, ultraviolet

Description

A method for bonding plastic substrates at a low temperature using a X-ray irradiation}

1 and 2 are views showing a conventional high temperature thermal bonding process.

3 is a view showing a process of irradiating a plastic member with X-rays generated from an emission accelerator.

4 is a diagram schematically showing a plastic member to which X-rays are irradiated.

5 is a diagram showing an X-ray irradiation amount according to the thickness of the plastic member.

6 is a view showing a change in the glass transition temperature according to the X-ray irradiation amount.

7 is a view schematically illustrating a process of arranging X-rays of two plastic members facing the irradiated surface and applying thermal compression.

8 is a view showing a cross section of a plastic member joined body bonded by the method of the present invention.

The present invention relates to a thermal bonding method of a plastic member having a low glass transition temperature by irradiation with X-rays or ultraviolet rays.

With the miniaturization of analytical devices, research and development of micro devices that can process and analyze many samples and reagents in small units are being conducted. Such microanalytical devices include, for example, biochips, lab-on-a-chips and micro-total analysis systems (micro-TAS). These tiny devices contain multiple channels or microstructures so that all the processes required for analysis can be performed on one small chip. The microchannels or structures must include a space for forming a flow because the sample and the reagent flows into the fluid. For this reason, the plastic member including two or several microstructures should be bonded to each other to make a structure capable of flowing a sample and a reagent.

Furthermore, when the microstructures and the microchannel surfaces are not useful for the samples and reagents due to the characteristics of various reagents and samples, plastic members that can be converted into useful surfaces through surface treatment are frequently used. In addition, the plastic member has intimate surface characteristics in the flow of living things (cells, proteins, DNA, etc.). Such plastic-based structures can be mass-produced by hot embossing or injection molding, which can improve economics when considering the commercialization of biochips, lab-on-a-chips, and micro-TAS.

In such an ultra-small device, the formation of the microchannel is generally made by joining two members. 1 is a view showing a process of thermally bonding two conventional plastic members. The method most frequently used for joining conventional plastic members has been a thermal bonding method. Since the conventional thermal bonding method bonds at a temperature 111 higher than the glass transition temperature of the plastic member, structural damage 112 may be caused to the internal microstructure. In addition, when a high conjugation temperature includes a specific sample or reagent therein, there is a disadvantage in that the quality may be altered 113 depending on the sensitivity of the sample or reagent to the temperature.

On the other hand, there are cases where an adhesive material 115 is used between two members for bonding. 2 is a view illustrating a bonding process using a bonding material. However, according to the above method, the bonding material fills or remains inside the microstructure or the microchannel, so that the bonding material may act as the foreign matter 116 on a portion (microchannel, microstructure) other than the bonding surface. This foreign matter 116 may lose its function as a microchannel.

Therefore, the joining method for forming the microchannels requires proper surface treatment only on the joining surface so that the two members are joined cleanly without addition of other materials. Therefore, the inventors of the present invention, if the surface to be bonded properly and bonded the two members at a low temperature, the method of the two members can improve the bonding force while minimizing damage to the microstructure or the micro-channel formed between the two members Intensive research has led to the completion of the present invention.

Accordingly, an object of the present invention is to provide a bonding method capable of minimizing damage to a microstructure or a microchannel by enabling low-temperature bonding without using a bonding material that can act as a foreign material.

The present invention comprises the steps of (a) lowering the glass transition temperature by irradiating X-rays or ultraviolet rays to the surface of the plastic to be bonded for a certain time; And (b) thermally bonding the surface of the joined object irradiated with X-rays or ultraviolet rays.

It is preferable to determine the X-ray irradiation amount in the step (a) of the present invention from the following formula (I).

식(I)

Formula (I)

는 유리전이온도의 점근값(asymptotic value)이고, K는 고분자 특성 상수이고, M₀는 단분자량이고, M_W0는 초기 분자량이고, D(h)는 X-선 조사량이다. Where Tg is the glass transition temperature,

Is an asymptotic value of glass transition temperature, K is a polymer characteristic constant, M ₀ is a monomolecular weight, M _W0 is an initial molecular weight, and D (h) is an X-ray irradiation amount.

In addition, in the present invention, the term "plastic" means a material which is made from an organic compound having a large molecular weight and is usually in a solid state, but fluidized and freely molded by the action of heat or pressure in the meantime. The plastics include, for example, polyethylene, polypropylene, polymethylmethacrylate (PMMA), polyvinylchloride (PC), polystyrene, and the like. The thermal bonding is preferably performed at a temperature of 8 to 15 ℃ higher than the glass transition temperature. When the thermal bonding at a temperature lower than the glass transition temperature, the bonding is not made completely, when the thermal bonding at a higher temperature, bubbles are generated.

Hereinafter, an example of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited thereto.

3 is a view showing a process of irradiating a plastic member with X-rays generated from an emission accelerator. In FIG. 3, the high energy content X-ray 121 is emitted from the radiation accelerator 120 and irradiated to the plastic member 122. The plastic member 123 irradiated to the high energy X-ray has a different X-ray dose from the member surface 124 to the member bottom surface 125. 4 schematically shows a plastic member to which X-rays are irradiated, where a large amount of X-rays are irradiated from the plastic member surface 124, and a relatively small amount of X-rays is irradiated from the plastic member bottom surface 125. do. 5 is a diagram showing an X-ray irradiation amount according to the thickness of this plastic member.

X-rays irradiated in this way serve to reduce the molecular weight by causing the polymer chain inside the plastic member to break. When the molecular weight decreases, the glass transition temperature of the plastic member is lowered. 6 is a view showing a change in the glass transition temperature according to the X-ray irradiation amount. While the glass transition temperature at the surface 124 of the plastic member having a large amount of X-ray irradiation is greatly decreased, the glass transition temperature at the bottom surface 125 of the member is almost unchanged. Therefore, the difference in the glass transition temperature at the surface 124 and the bottom surface 125 of the plastic member is increased, thereby performing thermal bonding in correspondence to the plastic member surface 124, thereby reducing the heat to other parts with less influence. You can join.

In addition, since the glass transition temperature is reduced by the irradiation of X-rays, the temperature at which thermal bonding is performed is also lowered. In this case, the X-ray dose may vary depending on the desired glass transition temperature, preferably X-ray dose (D (h)) and glass transition temperature (Tg) This can be determined through the correlation of.

식(I)

Formula (I)

는 유리전이온도의 점근값(asymptotic value)이고, K는 고분자 특성 상수이고, M₀는 단분자량이고, M_W0는 초기 분자량이고, D(h)는 X-선 조사량이다. 상기 식(I)에 따라 원하는 유리전이온도 감소에 맞도록 X-선 조사량을 계산할 수 있다. 이와 같이 결정된 X-선 조사량을 플라스틱 부재(예를 들면, 두께가 1.2mm인 PMMA 재질)에 X-선을 조사하여 접합을 위한 플라스틱 부재를 제조할 수 있다. Where Tg is the glass transition temperature,

Is an asymptotic value of glass transition temperature, K is a polymer characteristic constant, M ₀ is a monomolecular weight, M _W0 is an initial molecular weight, and D (h) is an X-ray irradiation amount. According to Equation (I), it is possible to calculate the X-ray dose to suit the desired glass transition temperature decrease. The X-ray irradiation amount thus determined may be irradiated with X-rays on a plastic member (eg, a PMMA material having a thickness of 1.2 mm) to prepare a plastic member for bonding.

The plastic member irradiated with X-rays obtained as described above is put in a device capable of hot pressing and heated, and then joined at a constant pressure. 7 is a view schematically illustrating a process of arranging X-rays of two plastic members facing the irradiated surface and applying thermal compression. As shown in Fig. 7, it can be bonded by applying a thermal compression 126 to the surface of the plastic member 123 irradiated with X-rays and whose internal configuration has been changed. In this case, when the plastic member is polymethacrylate (PMMA) having a thickness of 1.2 mm, the original glass transition temperature is 105 ° C., but the glass transition temperature is lowered by, for example, about 25 ° C. by X-ray irradiation. And at a temperature of about 92 ° C. By this process, thermal bonding is possible even at a temperature of about 30 ° C. to 40 ° C. lower than 120 ° C. to 130 ° C., which is a normal thermal bonding temperature. In addition, as shown in Figure 6, the glass transition temperature is lower from the surface and has the original glass transition temperature toward the bottom surface. Therefore, when the surface having a low glass transition temperature is bonded, the microstructure 127 inside the glass having a relatively high glass transition temperature has no large damage, and thus bonding is possible without deteriorating the function of the internal structure. The microstructures include microchannels and microchambers that are frequently used in microfluidic systems.

8 is a view showing a cross section of a plastic member joined body bonded by the method of the present invention. As shown in Fig. 8, the bonding surface 128 is so faint that it is almost invisible to the eye. This indicates that the joining of the two members is well done. In addition, the tensile strength was measured and found to have a tensile strength of about 0.96 MPa. This tensile strength is determined as the strength that can prevent the leakage of the internal fluid when configuring the biochip, lab-on-a-chip, and micro-total analysis system (Micro-Total Analysis system).

Hereinafter, the present invention will be described in detail through examples. However, these examples are for illustrative purposes only and the scope of the present invention is not limited to these examples.

Example

Example 1 Irradiation of X-Rays to Plastic Members

X-rays (energy level 140-150mA) were irradiated for 9-18 minutes using a radiation accelerator (LIGA beam line of Pohang accelerator) on the surface of a 1.2 mm thick PMMA member. X-ray irradiation time is calculated by setting the amount to reduce the glass transition temperature by about 25 ℃ according to formula (I).

The PMMA member obtained by X-ray irradiation predicted and calculated the change of X-ray irradiation amount and glass transition temperature according to the thickness.

As a result, the changes in X-ray dose and glass transition temperature according to the thickness of the PMMA member were as shown in FIGS. 5 and 6. As shown in Figures 5 and 6, it can be seen that the X-ray irradiation dose decreases with thickness, while the glass transition temperature increases with thickness.

Example 2 Thermal Bonding of X-Ray Irradiated PMMA Members

The X-ray irradiated PMMA member (25 mm x 25 mm x 1.2 mm) obtained in Example 1 was thermally bonded using a hot embossing apparatus. The high temperature embossing device is a device capable of applying heat and pressure and cooling. Thermal bonding was performed by placing the PMMA member irradiated to the X-ray on the upper and lower plates of the apparatus and then at a temperature of about 92 ° C. and a minimum pressure of 3-4 MPa (compression rate of 10 μm / s) for about 2 minutes. Then, it cooled to 80 degreeC and thermally bonded.

After thermal bonding, the bonded cross section of the bonded body was obtained and the state of the bonded surface was observed through a scanning electron microscope. As a result, as shown in Fig. 8, the joining surface 128 was very faint, indicating that the joining was well done. In addition, the tensile strength of the bonding surface was measured according to the tensile test method (pulling the bonded member using an MTS device, the tensile strength until the bond is dropped), the tensile strength of about 0.96MPa Appeared.

Example 3: Confirmation of Proper Heat Junction Temperature

As in Example 1, the PMMA member was irradiated with X-ray to lower the glass transition temperature, thereby producing a PMMA member having four kinds of glass transition temperatures. Each member was thermally bonded as in Example 2 by varying the temperature.

The results are shown in Table 1 below. Table 1 shows the proper bonding temperature and the temperature at which bubbles are generated for each PMMA member.

Table 1. Proper Junction Temperature and Bubble Generation Temperature

Glass transition temperature (Tg) (℃) Proper temperature (temperature difference) (℃) Bubble generation temperature (temperature difference) (℃) 75 90 (15) 98 (23) 80 92 (12) 100 (20) 85 95 (10) 105 (20) 95 103 (8) 113 (18)

As shown in Table 1, it was confirmed that thermal bonding was performed well at a temperature of about 8-15 ° C. higher than the glass transition temperature. When the temperature is lower than the proper temperature, the bonding is not completed, and when the temperature is higher, bubbles are generated.

In the embodiment of the present invention mainly illustrates the method of lowering the glass transition temperature of the plastic material by irradiating X-rays. However, it will be readily understood by those skilled in the art that the glass transition temperature can be lowered in the same way even when irradiated with ultraviolet rays.

According to the thermal bonding method of the present invention, the bonding can be performed at a lower temperature than the conventional thermal bonding temperature, it can be performed without changing the microstructure.

Claims (4)

(a) lowering the glass transition temperature by irradiating a predetermined amount of X-rays on the surface of the plastic member to be bonded; And (b) thermally bonding the surface of the joined object irradiated with X-rays. The method of claim 1, wherein the X-ray dosage in step (a) is determined from the following formula:

Formula (I) Where Tg is the glass transition temperature,

Is an asymptotic value of glass transition temperature, K is a polymer characteristic constant, M ₀ is a monomolecular weight, M _W0 is an initial molecular weight, and D (h) is an X-ray irradiation amount. The method of claim 1 wherein the plastic material is PMMA, PC, polystyrene or PDMS. The method of claim 1, wherein the thermal bonding is carried out at a temperature of 8 to 15 ℃ higher than the glass transition temperature.

Images