JPH06172791A - Detergent for precision optical element - Google Patents

Abstract

PURPOSE:To obtain a detergent which is excellent in detergency, not offensive to a precision optical element and decreased in the amount of waste water to be dispored of. CONSTITUTION:This detergent comprises 3-20wt.% nonionic surfactant of a cloud point of 20-95 deg.C and the balance of water and has a pH of 6-8. When the cloud point is in the range of 20-95 deg.C, the separation of the water from the surfactant can be performed by decantation, and the amount of waste water to be disporsed of can be decreased. When the pH is in the range of 6-8, the detergent is not offensive to a precision optical element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning agent for precision optical elements, which has properties of low irritation and good wastewater treatment properties and is suitable for cleaning precision optical elements.

[0002]

2. Description of the Related Art Precision optical elements such as lenses and prisms are used in optical microscopes, semiconductor steppers, lasers and the like. A mixed solvent of a halogen-based solvent and an alcohol-based solvent is often used for cleaning these precision optical elements. This is because this mixed solvent has a cleaning ability and has little influence on the base material of the precision optical element. However, the use of this detergent tends to be regulated because of environmental problems such as ozone depletion, and a commercially available alkali-added detergent is used as a substitute. However,
Even with such an alkali-containing cleaning agent, a cleaning agent that can substitute for it is being investigated because it has erosion to the base material and irritation to the human body.

As an alternative cleaning agent, JP-A-58-58
No. 104625 discloses a foaming surfactant composition containing an alkyl glycoside and an anionic surfactant, and JP-A No. 62-74999 discloses an alkyl glycoside, an anionic surfactant and a fatty acid alkanol. Detergents containing amides having excellent foaming power and detergency are described. These cleaning agents are removed from the optical element by removing them by rinsing with water after cleaning, and are one type of so-called water-based cleaning agents.

[0004]

The rinse liquid obtained by rinsing the above-mentioned water-based cleaning agent with water using a sardine contains a large amount of the surfactant and dirt components because the cleaning agent is brought in from the cleaning tank. is doing. Therefore, it is confirmed that a large amount of the surfactant is present when the concentration of the surfactant in the water tank which is the rinse step immediately after the cleaning is measured after cleaning the optical element. Such a rinse solution has a BOD value, C
Since the OD value is high, it cannot be directly discarded as industrial waste water and must be treated as industrial waste, which is troublesome and costly. In order to reduce the amount of waste liquid sent to industrial waste treatment, it is possible to reduce the waste liquid by distillation or separate the waste liquid by decantation, but distillation requires a lot of time and large-scale equipment. However, the anionic surfactant used as the cleaning agent has a problem that it is not suitable for decantation.

The present invention has been made in view of the above-mentioned problems of the prior art. While maintaining the same cleaning ability as in the prior art, the precision optical element is not eroded and the amount of waste rinse liquid is reduced. An object of the present invention is to provide a cleaning agent for precision optical elements, which enables reduction.

[0006]

The cleaning agent of the present invention comprises a nonionic surfactant having a cloud point of 20 to 95 ° C.
~ 20% by weight, balance water, pH 6-8
Is characterized in that. Here, as the nonionic surfactant, a linear secondary alcohol to which 7 to 12 mol of ethylene oxide is added can be used.

In the above structure, the nonionic surfactant is used in the amount of 3
~ 20 wt% keeps the detergency and pH 6 ~
By setting 8, the precision optical element is not eroded, and the cloud point is 20 to
By setting the temperature to 95 ° C., decantation for separating water and the nonionic surfactant in the rinse liquid after washing becomes possible.

In the detergent of the present invention, when the cloud point is 20 ° C. or lower, the surfactant component and water are separated at room temperature,
While the cleaning ability is lost, if the temperature is 95 ° C. or higher, it is difficult to keep the heat after heating and decantation becomes difficult.
On the other hand, it has been confirmed that a cleaning agent using a nonionic surfactant has the highest cleaning ability at a temperature close to the cloud point. Therefore, in the present invention, the cloud point of the nonionic surfactant is 20 to 95 ° C,
When considering decantation temperature and cleaning temperature,
The cloud point in the range of 40 to 60 ° C. is particularly good.

The content of such a nonionic surfactant is 3
When the amount is less than 10% by weight, the solubilizing power of oily stains is small, the cleaning ability is low, and the life of the liquid is shortened, which is not suitable as a cleaning agent. On the other hand, when the content is 20% by weight or more, the viscosity of the cleaning liquid becomes excessively large, and it becomes difficult to clean the precision optical element having a depression or the like in detail.

By setting the pH of the nonionic surfactant to 6 to 8, it is possible to maximize the erosiveness of the precision optical element made of glass, plastic or the like which is easily eroded by alkali or acid. .

Generally, when the temperature of the mixed liquid of the nonionic surfactant, oil and water is set to the cloud point of the nonionic surfactant or higher, micelles are formed as the movement of water molecules is activated. Dissolved nonionic surfactant molecules lose their hydratability.
Then, by leaving still at this temperature, the nonionic surfactant and water are separated into two layers. The oil component solubilized in the surfactant accompanying this separation is taken into the surfactant layer. This enables decantation of the mixed liquid into a mixed layer of oil and a nonionic surfactant and a water layer. Therefore, by physically separating the layers, the oil and the surfactant can be taken out from the mixed liquid in which the oil, the surfactant and water are mixed. This action is peculiar to nonionic surfactants, and the above decantation is impossible with anionic, cationic and amphoteric surfactants.

[0012]

EXAMPLE A cleaning agent was prepared by mixing 10% by weight of a secondary alkyl ether having a cloud point of 33 ° C. and adding 7 mol of polyoxyethylene (POE) and 90% by weight of water. This cleaning agent was filled in the first tank, 100 precision optical elements after polishing were immersed as a sample, and ultrasonic waves were applied for 3 minutes at a liquid temperature of 35 ° C. to perform cleaning. On the other hand, the second tank, the third tank, and the fourth tank following the first tank were filled with city water, and the fifth tank was filled with pure water. Then, the liquid temperature of the second, third, and fourth tanks was set to 35 ° C., and the sample washed in the first tank was rinsed while applying ultrasonic waves for 1 minute. In the fifth tank, the liquid temperature was set to 35 ° C., and the sample was immersed and rocked for rinsing, and then pulled up and dried with warm air. When the samples that had undergone the above steps were visually observed, all the samples did not have cleaning residues.

Next, LaSF016, PSK01, SK1
1. Optical glass is made of each material of 1, SF03, FK01, and SF15, ultrasonic waves are applied to the above-mentioned cleaning agent at a liquid temperature of 40 ° C. for 10 minutes, and then the glass is left at room temperature for 2
It was immersed for 4 hours. Visual inspection of the appearance of these optical glasses,
When the weight change and the spectral reflectance were measured, the appearance color was good with no clouding in the interference color, and the weight change was 0.1.
%, The spectral reflectance was 10% or less.

Further, the rinse liquid is taken out from the second tank in which the rinse of 100 samples described above is completed, and the rinse liquid is removed at 80 ° C. for 3 hours.
After standing for a period of time, the layers other than water were removed, and the decantation effect was confirmed by measuring the COD value of the water layer. As a result, the COD value of the water layer after decantation was 400 mg.
/ L, which was smaller than the COD value (3350 mg / l) of the rinse liquid before decantation, and it was found that the oil stain component and the surfactant component were 88% removed. Therefore, the liquid of the water layer after this removal can be used again as a rinse liquid. Further, the amount of the surfactant and the oil stain component separated into the water layer by decantation was 3 vol% of the liquid amount before decantation. Therefore, the amount of industrial waste is reduced by 30 times.

In the above-mentioned embodiment, since the ethylene oxide adduct of linear secondary alcohol is used as the nonionic surfactant, it has good biodegradability and is hypoallergenic to the human body. There are merits. With such a cleaner,
It maintains detergency equivalent to that of conventional cleaning agents, has no corrosiveness, can be decanted, and has a waste liquid treatment amount of 1/30
Can be reduced to

20% by weight of secondary alkyl ether having a cloud point of 33 ° C. and 7 moles of POE and 80% by weight of water, and 3% by weight of secondary alkyl ether of 7 moles of POE and 95% of water. % Was mixed to form a cleaning agent. Further, 5% by weight of a secondary alkyl ether to which 9 mol of POE was added and 95% by weight of water were mixed at a cloud point of 56 ° C. to form a detergent, and a cloud point was 83 ° C. and 12 mol of POE was added. A cleaning agent was prepared by mixing 20% by weight of secondary alkyl ether and 80% by weight of water. When each of these cleaning agents was washed, inspected and decanted in the same manner as described above, the same result was confirmed.

[0017]

As described above, according to the present invention, not only the cleaning power can be maintained, but also the precision optical element is not eroded, and
It is possible to reduce the waste liquid treatment amount of the rinse liquid.

Claims (2)

[Claims] 1. A nonionic surfactant having a cloud point of 20 to 95 ° C. in an amount of 3 to 20% by weight, the balance being water, and a pH of
Is 6-8, The cleaning agent for precision optical elements characterized by the above-mentioned. 2. The cleaning agent for precision optical elements, wherein the nonionic surfactant is a linear secondary alcohol to which 7 to 12 mol of ethylene oxide is added.