JP3189288B2 - Cleaning method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning electronic parts, optical parts and mechanical parts.

[0002]

2. Description of the Related Art Conventionally, as a method for cleaning a substrate, ultrasonic cleaning using Freon 113, trichloroethylene (hereinafter referred to as tricrene), trichloroethane (the same triethane), or methylene chloride (the same salt as methyl) is used. .

Since chlorofluorocarbon 113 is an ozone-depleting substance, immediate replacement is required. Also, use of trichlene, triethane or salt methoxide is highly likely to be a carcinogenic substance, and is extremely dangerous when leaked. Although many alternative cleaning agents have been developed, there are many problems such as high cost, and satisfactory cleaning properties cannot be secured as compared with the above-mentioned solvents, and replacement of the above-mentioned solvents is not easy.

[0004]

The prior art has problems such as environmental destruction, danger to the human body, an increase in cost, and a decrease in cleaning quality.

Accordingly, the present invention is to solve such a problem, and an object of the present invention is to provide a cleaning method for realizing high cleaning quality at a low cost by using a cleaning agent which has no danger to the environment and the human body. To provide.

[0006]

According to the present invention, there is provided a method for cleaning a substrate to which at least one of a monomer, an oligomer and a polymer is adhered, the method comprising at least a step of performing shower cleaning using an aqueous solution, and at least a surfactant. A step of immersing in a solution, a step of performing ultrasonic cleaning using an aqueous solution containing at least a surfactant and having a dissolved gas concentration of 7 ppm or more, and immersing in a solution containing at least an organic solvent freely mixed with water. It is characterized by having a step of performing ultrasonic cleaning or immersion / jet cleaning, a step of drying by centrifugation, hot air or pure water pulling up.

[0007] Regarding the shower cleaning step, this step is a step for more simply removing dirt having a relatively low adhesion to the substrate.

As for the surfactant, any of a cationic surfactant, an anionic surfactant, an amphoteric surfactant and a nonionic surfactant can be used. Particularly, a good result is obtained for a nonionic surfactant. Show.

Although it is necessary to use a high concentration for the immersion, the ultrasonic cleaning may be a very low concentration. The liquid temperature is desirably as high as possible. However, the nonionic surfactant is most preferably just below the cloud point, and other solutions are desirably 80 degrees Celsius or less in view of damage to the substrate to be cleaned and work environment.

As a method for maintaining the concentration of the dissolved gas at a certain value or more, there are a method of directly feeding gas into a liquid, a method of using a semi-permeable membrane, and a method of forcibly sending gas by a vortex pump. The method using a vortex pump is particularly excellent in terms of the structure of the washing machine. The dissolved gas concentration needs to be higher than the level at which fine bubbles can be seen when ultrasonic waves are applied. For example, when air is dissolved in water at room temperature, the dissolved oxygen concentration needs to be 7 ppm or higher.

For the ultrasonic wave, there are various selection ranges depending on the type of dirt and the type of the substrate.
40 kHz is good, and a high frequency of 100 kHz or more seems to be effective for fine dirt of several tens of microns or less.

As the organic solvent which can be freely mixed with water, lower alcohols, ketones, cellosolves, glycols and the like are used. In particular, N-methyl-2-pyrrolidone has a high dissolving power and is a dirt which cannot be completely removed in the previous step. Even if there is, it dissolves and drops, so it is effective as a finish cleaning.
An organic solvent that is not freely mixed with water has many problems such as the inability to use water in the subsequent rinsing step, and is not so preferable. However, it is used if it can be easily dispersed in water using a surfactant.

In the drying step, a pure water pull-up drying method is preferable in the case of a substrate having a smooth shape and particularly fragile, and a centrifugal drying method is preferable in the case of a substrate having a smooth shape and resistant to cracking and a small size. A conventional drying method using hot air can also be used. Steam drying using Freon 113, isopropyl alcohol, or the like can also be used, but is not preferred because it has many problems such as environmental problems and safety.

[0014]

According to the present invention, first, shower cleaning is performed.
This step is a step for more simply removing dirt having a relatively low adhesion to the substrate. By this process,
Deterioration of the solution containing at least the surfactant in the next tank can be minimized. Next, the substrate is immersed in a solution containing at least a surfactant. By immersing the substrate first, the surfactant enters the interface between the substrate and the dirt, thereby reducing the adhesive force between the substrate and the dirt. Can be. Furthermore, the dirt is peeled off from the substrate by ultrasonic cleaning.At this time, by keeping the concentration of the dissolved gas at a level higher than that at which fine bubbles appear in the liquid, the dirt is wrapped in the bubbles and the substrate becomes faster. Peel from the surface. Up to this point, most of the stains have been peeled off from the substrate, but if any of the stains adhere more strongly, they are dissolved in the next organic solvent that is freely mixed with water. Since organic solvents are expensive, it is necessary to remove dirt as much as possible in the previous steps. For these reasons, the cleaning time can be reduced, and the cost can be reduced.

[0015]

【Example】

(Examples 1 to 9) Next, a cleaning method according to Examples 1 to 9 of the present invention will be described.

First, a plastic flat lens having a diameter of 65 mm and a thickness of 3.6 mm produced by polymerization using diethylene glycol bis (allyl carbonate) as a main raw material was used as a substrate to be cleaned.

Soil is a raw material monomer / oligomer / polymer that adheres to the substrate when the substrate is manufactured.

The shower was performed with 20 liters of city water per minute. Surfactants in the immersion liquid are nonionic (Johnson
Alkaline cleaner M-6000) with a concentration of 10%
And The same cleaning agent as the immersion liquid was used for the ultrasonic cleaning liquid, and the concentration was 1%. The ultrasonic wave has a frequency of 28 kHz,
500W output (Shitada Rika Model ET
50S-7) was used. The dissolved gas concentration in the cleaning solution was measured using a dissolved oxygen meter (Horiba Seisakusho DO-8F) and a DO electrode (Horiba Seisakusho 5410), replacing the dissolved oxygen concentration with the dissolved oxygen concentration. Table 1 shows the dissolved oxygen concentration and the type of the organic solvent used.

[0019]

[Table 1]

Drying is performed by heating the substrate to a depth of 3 mm from hot pure water at 60 degrees Celsius.
After being pulled up at / Sec, it was dried with warm air.

For cleaning evaluation, the number of dust particles having a diameter of 0.2 μm or more was measured using a visual inspection and a surface foreign matter defect device (Hitachi, GI-1100) by a laser light scattering method.
Table 2 shows the results.

[0022]

[Table 2]

As shown in Table 2, in the cleaning methods according to Examples 1 to 9, as long as the dissolved oxygen concentration is 7 ppm or more, the cleaning results are good regardless of the type of the organic solvent. On the other hand, in Comparative Examples 1 to 6, sufficient cleanliness was not obtained.

Further, as shown in Comparative Example 6, even when the washing step with an organic solvent was omitted, sufficient cleanliness was not obtained.

(Examples 10 to 18) Next, Examples 10 to 18 in which the surfactant was changed from Examples 1 to 9 were used.
Will be described.

The only difference between the cleaning methods of Examples 1 to 9 is the type of the immersion liquid and the ultrasonic cleaning liquid, and other conditions are the same as in Example 1. Table 3 shows the types of surfactants used in the immersion / ultrasonic liquid.

[0027]

[Table 3]

The drying and evaluation methods are the same as in Examples 1 to 9. Table 4 shows the evaluation results.

[0029]

[Table 4]

As shown in Table 4, in the cleaning methods according to Examples 10 to 18, the cleaning results are good regardless of the type of the surfactant.

(Embodiments 19 to 24) Next, a description will be given of a cleaning method according to Embodiments 19 to 24 in which the types of the cleaning substrate and the stain are changed.

The six types of substrates and dirt shown in Table 5 were cleaned by the cleaning method of Example 1.

[0033]

[Table 5]

The drying and evaluation methods are the same as in Examples 1 to 9. Table 6 shows the evaluation results.

[0035]

[Table 6]

As shown in Table 6, in the cleaning methods according to Examples 19 to 24, the cleaning results were good regardless of the type of the substrate and the type of dirt.

Next, the cleaning property when the shower step and the immersion step are omitted will be described.

(Examples 25 to 27) Example 2 for explaining Comparative Examples 7 to 9 when the shower step was omitted.
The cleaning method according to 5 to 27 will be described.

The cleaning was performed by the cleaning method of Example 1. In Examples 25 to 27, the tenth, twentieth and thirty sheets were cleaned using the same cleaning liquid. Example 28 is the first sheet which was cleaned from Example 1 by omitting the shower step. Similarly, Comparative Examples 7 to 9 are the tenth, twentieth, and thirtieth sheets cleaned from Example 1 by omitting the shower step. In Comparative Example 10, the immersion step was omitted from Example 1.

The drying and evaluation methods are the same as in Examples 1 to 9. Table 7 shows the evaluation results.

[0041]

[Table 7]

As shown in Table 7, in the cleaning method according to Examples 25 to 27, if the shower step was performed, 30
The number of foreign substances on the surface remains at a low level even in the second sheet.
Further, in the cleaning method according to Example 28, even if the shower step is omitted, the cleaning property is not lost as long as it is the first sheet. On the other hand, in the cleaning methods according to Comparative Examples 7 to 9, if the shower step is omitted, satisfactory cleaning properties cannot be obtained already on the tenth sheet.

FIG. 1 shows the number of particles in a liquid in a rinsing tank after N-methyl-2-pyrrolidone in the cleaning method according to Example 1 (with a shower step) and Example 28 (without a shower step). This is a correlation with the number of cleanings. The measurement of particles in the liquid was expressed as the number of particles of 0.3 μm or more in 1 ml using a TD-30 liquid particle counter manufactured by Sigma-Tech.

As shown in FIG. 1, those not subjected to the showering step are clearly inferior in the number of particles in the liquid, similarly to the values measured by the surface foreign matter defect device. For this reason, the presence of the shower step can prevent deterioration of the cleaning liquid.

Further, as shown in Comparative Example 10 in Table 7, the one in which the immersion step was omitted obviously had poor cleaning properties.

[0046]

As described above, according to the present invention, by removing dirt having a weak adhesive force by shower cleaning in advance, deterioration of the cleaning liquid in the next bath and thereafter can be prevented and the liquid life can be extended. Next, immersion is performed in advance before applying ultrasonic waves, and the cleaning time can be reduced by maintaining the concentration of the dissolved gas in the cleaning liquid at a certain value or more. Next, the quality of the cleaned product can be improved by performing final cleaning using an organic solvent that is freely mixed with water. Further, since both washing and drying can be performed without using any solvent such as Freon 113, trichlene, triethane or salt methoxide, the washing step can be performed under conditions that are advantageous for environmental issues. It is an excellent cleaning method from various points as described above.

[Brief description of the drawings]

FIG. 1 is a diagram showing that a showering step in the present invention prevents deterioration of a cleaning liquid.

Claims (4)

(57) [Claims] 1. A method for cleaning a substrate to which at least one of a monomer, an oligomer and a polymer is attached, a step of performing shower cleaning using at least an aqueous solution, a step of immersing at least in a solution containing a surfactant, Includes and the dissolved gas concentration is 7p
Ultrasonic cleaning using an aqueous solution maintained at pm or more, immersion / ultrasonic cleaning or immersion / jet cleaning using a solution containing at least an organic solvent freely mixed with water, centrifugation, hot air or A cleaning method comprising a step of drying by pulling up pure water. 2. The cleaning method according to claim 1, wherein the substrate is a polymer. 3. The cleaning method according to claim 1, wherein the organic solvent is N-methyl-2-pyrrolidone. 4. The cleaning method according to claim 1, wherein the organic solvent is at least one selected from lower alcohols, ketones, cellosolves, and glycols.