JPH0989721A - Method for measuring birefringence of polycarbonate resin - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To improve reproducibility of measured values in measuring birefringence of a polycarbonate resin. Birefringence of a polycarbonate resin is easily affected by temperature and humidity in terms of its physical properties, and therefore the entire birefringence measuring device 1 installed on a measuring table 2 is covered by a hood 3.
By surrounding with, the short-term changes in the measurement environment due to temperature fluctuations of 2 to 3 ° C and humidity fluctuations of 2 to 3% due to the flow of air in the measurement chamber are eliminated, and the measurement environment inside the hood 3 is always kept constant. Below, a stable reading is obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for measuring birefringence of a polycarbonate resin, and more particularly to a method for measuring birefringence of a polycarbonate resin molded as an optical disk substrate.

[0002]

2. Description of the Related Art In recent years, the recording capacity of optical disks used as data recording media for computers has been remarkably increased. The substrate of this optical disc is generally manufactured by cooling and solidifying a polycarbonate resin in a mold by an injection compression molding method, and then taking it out. Therefore, the resin orientation and heat during the cooling process of the resin in the mold are Due to the stress, birefringence occurs inside thereof. Since the birefringence of the substrate has a great influence on the recording / reproducing performance of an optical disc as a recording medium, it is necessary to make an accurate evaluation in manufacturing.

Since the polycarbonate resin is highly water-absorbent, it is considered that physical microscopic dimensional changes and chemical changes always occur on the surface of the substrate, and the birefringence is measured in a measurement environment such as temperature and humidity. It is easily affected. For this reason, various optical disc standards require that the measurement environment be
A temperature of 21 to 25 ° C and humidity of 45 to 55% are specified.
Measurement and evaluation are performed within this range.

[0004]

However, according to such a conventional measuring method, even though the standard of the measuring environment is satisfied, the measured value is repeatedly measured with the accuracy of the measuring device. There is a problem in that there may be variations as described above. For this reason, the reliability of the measured value becomes low, and it is extremely inconvenient to compare and evaluate the birefringence between different optical disk substrates.

As a result of various experiments related to this cause, although the room where the measurement is performed satisfies the standard of the measurement environment by controlling the temperature and humidity, there is a short-term periodic fluctuation in the room environment, 2-3 ° C temperature fluctuation and 2
It was found that a humidity fluctuation of ˜3% occurred. Also,
Since the air flow in the room is also large, it is considered that the measured value of the birefringence of the polycarbonate resin will greatly change due to the properties of the polycarbonate resin described above.

In the future, it is certain that the recording medium of the optical disk will be required to have higher density recording, and at the same time, it is necessary to improve the reliability as the recording medium. Therefore, the technique for accurately measuring the birefringence and improving the reliability of the measured value is particularly important. In view of such conventional problems, the present invention provides a method for measuring the birefringence of a polycarbonate resin, in which the environmental conditions for measuring the birefringence of the polycarbonate resin are adjusted and a reproducible and accurate measurement value can be obtained. With the goal.

[0007]

Therefore, in the invention according to claim 1, there is provided a method for measuring birefringence of a polycarbonate resin, which is a polycarbonate resin which is an object to be measured during a predetermined period before the measurement and during the measurement. It is characterized in that the birefringence is measured under the condition that the fluctuation range of the temperature and the humidity of the environment in which is kept as small as possible.

Thus, the birefringence can be measured in a constant measurement environment. In the invention according to claim 2, the temperature is in the range of 21 to 25 ° C, and the fluctuation range is 0.
The temperature is within 6 ° C., the humidity is within the range of 45 to 55%, and the fluctuation range is within 0.6%. As a result, the birefringence can be measured in an environment where accurate measurement values can be obtained.

Further, in the invention according to claim 3, the birefringence measuring device is surrounded by a hood so as to prevent the influence of the air flow in the room, and the measurement environment is controlled separately and independently from the change in the surrounding environment. It is characterized by doing. As a result, a constant measurement environment can be maintained at all times. The invention according to claim 4 is characterized in that the polycarbonate resin, which is the object of the measurement, is held without being stressed during a predetermined period before the measurement and during the measurement.

As a result, the change in birefringence value due to stress can be suppressed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The inventor of the present invention has arrived at the present invention as a result of earnestly researching a method for improving the reliability of a change in birefringence measurement value of a polycarbonate resin depending on the measurement environment. That is, the present invention provides a method for measuring the birefringence of a polycarbonate resin, in which a change in temperature and humidity, which is a measurement environment, is controlled and measured within a predetermined range.

An embodiment of the present invention will be described below with reference to the drawings by taking as an example the case of measuring the birefringence of an optical disk substrate made of a polycarbonate resin. FIG. 1 is a schematic configuration diagram of a birefringence measuring apparatus used in the method for measuring birefringence of a polycarbonate resin of the present invention. A birefringence measuring device 1 is installed on a measuring table 2, and the whole is surrounded by a hood 3.

When the measurement room is a clean room, an air flow (downflow) in the direction of arrow A occurs around the room. Although the clean room is always controlled so that both the temperature and the humidity therein are constant, when the air around the birefringence measuring apparatus 1 and the optical disk to be measured is constantly changing due to this downflow, As described above, a short-term change in measurement environment occurs due to temperature fluctuation of 2 to 3 ° C. and humidity fluctuation of 2 to 3%. Even if the measurement room is not a clean room, there is air flow in the room,
Since the change in temperature and humidity is larger than that in a clean room, similar effects occur.

By blocking the air flow with the hood 3, the measurement environment in the hood 3 can be kept constant and stable measurement values can be obtained. The programmable controller 4, which controls the measuring device 1 and processes the obtained data,
It is a heat source itself, and considering the influence of the attached cooling fan on the air flow, it is installed outside the hood 3 and connected to the birefringence measuring device 1 via the data transfer cable 5. It should be set to.

FIG. 2 is a perspective view of the entire hood 3. The hood 3 has a structure in which the four side surfaces and the upper surface of a metal frame 6 are covered with vinyl sheets 7. A fastener 8 is vertically attached to the front vinyl sheet so that a measurer can move in and out for putting in and out a measured object and operating the birefringence measuring apparatus 1. The specific measurement is performed by the following procedure. (1) Hold the optical disk substrate so that no external stress is applied. This is because the stress from the outside has a great influence on the birefringence of the substrate, and therefore it is preferable to keep the stress-free state for a predetermined time before the measurement. At this time, if the disk rack 9 as shown in FIG. 3 is used, it becomes easy to hold the optical disk substrate 10 without applying stress. (2) In the state of (1), leave it in the hood 3 placed in the measurement room for at least 10 minutes. At this time, it is desirable that the environment inside the measurement room is a normal environment with a temperature of 24 ° C. and a humidity of about 50%, and the same each time. (3) After that, measurement is performed by the birefringence measuring device 1 placed in the same environment. (4) The above (1) to (3) are repeated for each measurement.

The method for measuring the birefringence of a polycarbonate resin of the present invention is a polycarbonate resin such as a CD substrate such as CD-AUDIO or CD-ROM, a magneto-optical disc substrate, a phase change type optical disc substrate, a write-once type optical disc substrate, a mini disc substrate or the like. Can be applied to all optical disk substrates molded by the injection molding method. The present invention can also be applied to each optical disc medium in which a film is formed on the optical disc substrate by a sputtering method, a vapor deposition method, or the like.

In the method for measuring the birefringence of a polycarbonate resin of the present invention, basically, it is sufficient to sufficiently control the environmental conditions in the room in order to suppress the change due to the measurement environment, but as described above, The hood 3 that blocks the air flow in the room is provided around the optical disk substrate and the birefringence measuring device 1 that are the objects of measurement, the optical disk substrate to be measured is held there for a predetermined time or longer, and further measurement is performed in that environment. It is simpler and more reliable.

The measuring environment may be further stabilized by enclosing the measuring device with a completely sealed object such as a glove box.

[0019]

EXAMPLE An example of the present invention will be described below in more detail. (Example) In order to stabilize the thermal property and water absorption of the optical disk substrate manufactured by the injection molding method, the disk rack of FIG. 3 is used so as not to apply stress to the substrate,
It was left in a clean room for 3 days or more. Immediately before the measurement, after leaving it in the hood 3 placed in a clean room for 10 minutes or more, the birefringence value at the same point on the sample substrate is measured by the birefringence measuring apparatus 1 (Admon Science Co., Ltd.). Made by a disk birefringence automatic measuring device)
It was measured at minute intervals. At the same time, the temperature, humidity and wind force around the birefringence measuring device were also measured.

FIG. 4 is a graph showing the change with time of the birefringence measurement value. The vertical axis represents the phase difference (Retardation), and each point in the graph represents the measured value at each measurement. As a result, the fluctuation range of the birefringence measurement value was only 3 nm. FIG. 5 is a graph showing changes over time in temperature and humidity. The fluctuation range of temperature and humidity is 0.5 ℃,
It was 0.4%.

Throughout the measurement, the wind force was almost zero. (Comparative Example) An optical disk substrate similar to that of the example was prepared, and in order to stabilize the thermal property and water absorption of the substrate, the disk rack of FIG. did. Then, using the birefringence measuring apparatus 1 installed in the clean room without using the hood 3, the birefringence value at the same point of this sample was measured at 2 minute intervals. At the same time, the temperature, humidity and wind force around the birefringence measuring apparatus 1 were also measured.

FIG. 6 is a graph showing the change with time of the birefringence measurement value. As a result, the fluctuation range of the birefringence measurement value is 10 nm.
Met. FIG. 7 is a graph showing changes over time in temperature and humidity. The fluctuation range of temperature and humidity is 1.0 ℃,
It was 2.0%. Wind force is 0.5m / sec during all measurements
Met.

As is clear from the examples and comparative examples,
Compared with the case of measuring in a clean room without using a hood, the stability of the birefringence value of the optical disk substrate measured by the method of the present invention is very good, and it is possible to meet even more strict standards in the future.

[0024]

As described above, according to the invention of claim 1, birefringence is always measured in a constant measurement environment by controlling the fluctuation range of temperature and humidity within a predetermined range. Therefore, there is an effect that a measurement result with good reproducibility can be obtained. This makes it possible to properly evaluate an optical disc having a high recording density and provide an optical disc with high reliability.

According to the second aspect of the present invention, by measuring the birefringence under a limited environment in which the measurement standard of the optical disk is satisfied and an accurate measured value can be obtained, it is possible to obtain a higher birefringence than expected in the future. There is an effect that it is possible to perform highly accurate measurement that can comply with the standard of the standard. Further, according to the invention of claim 3, a simple and inexpensive method of surrounding the birefringence measuring device with a hood can always maintain a constant measurement environment and perform stable measurement. The effect is that you can do it.

According to the invention of claim 4, the object to be measured is held without being stressed for a predetermined period before the measurement and at the time of the measurement, so that the change of the birefringence value due to the stress is suppressed. There is an effect that an accurate measured value with good reproducibility can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a birefringence measuring apparatus used in a method for measuring birefringence of a polycarbonate resin of the present invention.

FIG. 2 is a perspective view showing the entire structure of the hood.

FIG. 3 is a perspective view showing the entire structure of a disk rack.

FIG. 4 is a graph showing a change with time of birefringence measurement values according to the birefringence measurement method of the present invention.

FIG. 5 is a graph showing changes over time in temperature and humidity in the birefringence measurement method according to the present invention.

FIG. 6 is a graph showing a change with time of birefringence measurement values in a conventional measurement environment.

FIG. 7 is a graph showing changes over time in temperature and humidity in a conventional measurement environment.

[Explanation of symbols]

 1 Birefringence measuring device 2 Measuring stand 3 Hood 4 Programmable controller 5 Data transfer cable 6 Metal frame 7 Vinyl sheet 8 Fastener 9 Disc rack 10 Optical disc substrate

Claims (4)

[Claims] 1. A method for measuring the birefringence of a polycarbonate resin, wherein the fluctuation range of the temperature and humidity of the environment in which the polycarbonate resin, which is the object of measurement, is held is minimized throughout a predetermined period before the measurement and during the measurement. A method for measuring birefringence, which comprises measuring birefringence under the conditions described above. 2. The temperature is within the range of 21 to 25 ° C., the fluctuation range is within 0.6 ° C., the humidity is within the range of 45 to 55%, and the fluctuation range is within 0.6%. The birefringence measuring method according to claim 1, which is characterized in that. 3. The birefringence measuring device is surrounded by a hood so as to prevent the influence of the air flow in the room, and the measurement environment is controlled separately from and independent of changes in the surrounding environment. The method for measuring birefringence according to claim 1 or claim 2. 4. The polycarbonate resin, which is an object of the measurement, is held without being stressed during a predetermined period before the measurement and during the measurement. The method for measuring birefringence described in 1.