Description

Method to determine properties of a coating on a transparent film, method for manufacturing a capacitor film and device to determine properties of a coating on a transparent film

The invention concerns method to determine properties of a coating on a transparent film, a method for manufacturing a capacitor film and a device to determine properties of a

coating on a transparent film for a better confirmability.

For a better control of final product quality, it is

important to know the exact properties of a product during the production process. Especially in the sector of thin film production in which a layer of a compound is coated on a thin substrate, it is important to measure thickness and element ratios of the coated layers just in time with the production process .

It is the purpose of this invention to create a fast and

reliable method to determine properties of a coating on a transparent film. It can be a further task to provide a non destructive method to determine the ratios of several

elements in a multilayer coated film on a thin substrate

during a production process. It is another objection to

provide a device for performing the above-mentioned method.

The invention as disclosed in independent claim 1 or the

method in the independent claim 16 offers a solution to this problem. The dependent claims to claim 1 can lead to a

preferable solution. The other objection is solved by the subject matter of claim 15. The invention relates to a first method. It is a method to determine properties of a coating on a transparent film for a capacitor. The method uses a structure comprising a light source, a sensor and a central process unit. The method includes the following steps to determine properties of a coating on a transparent film: Moving the transparent film with the coating on a path which passes between the light source and the sensor, Illuminating the coating on the transparent film by the light source, Detecting the intensity of the transmitted light from the light source by the sensor, and calculating the properties of the coating on the

transparent film based on the measured intensity of

transmitted light by the process unit.

Therein the coating can be comprise a metal or consist of metal. Nevertheless the invention is not limited to such a metallization.

Such a structure used in this invention can allow a

determination of properties during a production process, since the path can be a part of a production line.

Furthermore no comparison with reference data may be needed, since all results are calculated. Therefore the calculation may save a lot of time and accelerates the process of

determination .

In a possible embodiment of the invention, the light source emits light of multiple wavelengths of the electromagnetic spectrum which is used to illuminate the coating on the transparent film. Therein the wavelength of the emitted light can be in a range from 10 nm to 10 ym. A further limitation of the range to the optical spectra is possible. The optical spectra can be defined by light with multiple wavelengths in the range from 380 nm to 780 nm. The use of light of multiple wavelengths allows to determine not only the thickness of the coating but other properties also, for example the content of a certain element in the coating.

In a further embodiment of the invention the method comprises a step of performing a sweep in the frequency of the emitted light. The sweep can be proceeded for frequencies that relate to every wavelength of a range of wavelengths provided by the light source, or partly sub-ranges of those.

The sweep of frequencies can be used to determine one or more optimal wavelengths of light. The optimal wavelength can be defined by the behaviour of an attenuation coefficient of a material of interest in the coating. In a more specific way an optimal wavelength can be defined as that one at which the attenuation coefficient becomes maximal for the material of interest in the coating. Furthermore, it can be part of the definition of an optimal wavelength that attenuation

coefficients of materials differs from each other and the difference is maximal at this wavelength, in a case of several materials of interest.

In one embodiment of the invention, the sensor can be

configured to detect light from the light source in the range of emitted wavelengths by the light source. The sensor can be configured to detect the intensity of the light reaching the detector. It can be possible that only a part of the range of emitted wavelengths by the light source can be detected by the sensor, due to its characteristics. It can be possible that at least all optimal wavelengths are detectable for the sensor. The sensor can be implemented as a photo diode or a line camera. The measurement of light intensities of multiple wavelengths can improve the accuracy of the results,

particularly in a case of a multilayer coating.

In another embodiment the method is characterised in that the coating on the transparent film comprises more than one layer. Each layer of the coating on the transparent film can comprise one or more materials. The method can be

characterised in that the thickness of each layer is

calculated by the central process unit as a property of the coating on the transparent film. Furthermore, it can be possible to calculate the content of each material by the central process unit as a property of the coating on the transparent film.

All or at least one calculation by the central process unit can base on the Beer's law. Beer's law describes the

dependency of a light absorbance A by transmitting the light through a material with a specific material attenuation coefficient e, a certain concentration C, and a length 1 of the path of the transmitted light. The dependency of the light absorbance is described to: A= -C-1

A possible embodiment of the invention can comprise a metal as a material of interest. In a more specific variation of the coating the material of interest can comprise at least one element out of Al, Zn, Cu, or Mg. It is also possible that the transparent film comprises a polymer.

In one embodiment of the invention the method is proceeded in a vacuum. Therein the maximal pressure of the vacuum can be in a range from 10 ^L -2 mbar to 10 ^L -6 mbar, e.g. a vacuum with a pressure of at least 10 ^A -4mbar. In a further embodiment of the invention, the first step of moving the transparent film with the coating is realized by unwinding the transparent film from a first roll and

simultaneous up winding the transparent film on a second roll. Therein the path of the moving transparent film between the two rolls can be partly lead between the light source and the sensor. Furthermore it can be possible that the method to determine properties of a coating on a transparent film is part of a production line. Therein it can be possible to log the calculated data in real time or use the data to regulate any production procedures.

Furthermore, the invention relates to a second method. This is a method for manufacturing a capacitor film. The method uses a structure comprising a light source, a sensor, and a central process unit. The method for manufacturing a

capacitor comprises the followed steps: Coating of metal on a transparent film, moving the coating on the transparent film on a path which passes between the light source and the sensor, illuminating the coating on the transparent film by the light source, detection of the intensity of the

transmitted light from the light source by the sensor, calculation of properties of the coating on the transparent film based on the measured intensity of transmitted light by the central process unit, adapting the coating process of the first step based on the calculated properties from the step bevor .

In addition, the invention relates to a device to determine properties of a coating on a transparent film. The device comprises a light source which is configured to illuminate the coating on the transparent film, a sensor which is configured to detect the transmitted light intensity through the coating on the transparent film, a central process unit which is configured to calculate the properties of the coating on the transparent film based on the measured

intensity of transmitted light which is depending on the wavelength of the light.

The invention of the method for manufacturing a capacitor or the invention of the device to determine properties of a coating on a transparent film can be combined with any embodiments of the first method of the invention. In

specific, any possible feature of the method to determine properties of a coating on a transparent film (1) for a capacitor can be a feature of the method for manufacturing a capacitor too.

In the following, the invention and preferred embodiments of the invention are discussed with respect to the figures.

In the figures:

Figure 1 shows a schematic overview of the device or

structure of the subject matter.

Figure 2 is a sectional view perpendicular to the path of the film to illustrate the function of the present invention in a schematic way.

In Figure 1 a schematic overview of a structure is shown. The structure is used to determine properties of a coating 1 on a transparent film 7 and comprises a light source 2, a sensor 3 and a central process unit 4. Between the light source 2 and the senor 3 a path 10 is defined. On this path 10 the coating 1 on the transparent film 7 is lead from a first roll 8 to a second roll 9.

Therein the coating 1 can be comprise a metal or consist of metal. In this case the coating 1 would represent a

metallization on the transparent film 7. Nevertheless, the invention is not limited to such a metallization.

The light of the light source 2 can comprise multiple wave lengths and is directed on the coating 1 on the transparent film 7 to illuminate the same. The wavelength of the light can be in a range from 10 nm to 10 ym. In one embodiment the wavelength of the light can be in the optical spectra. The optical spectra can be defined as a range from 380 nm to 780 nm. Related to the multiple wavelengths emitted by the light source 2, the sensor 3 is chosen to detect light in the complete range or in parts out of the range of wavelengths of emitted light by the light source 2. The sensor is a photo diode or a line scan camera.

The transmitted light 5 is detected by the sensor 3 after transition through the coating 1 on the transparent film 7. The intensity of the transmitted light 5 is detected for each wavelength emitted by the light source. The sensor 3 is connected to the central process unit 4. The central process unit 4 calculates properties of the coating 1 on the

transparent film 7, based on the detected intensity of transmitted light 5. Those properties can be thickness or composition of a coated layer 6 of the coating 1 on the transparent film 7. The results of the calculation can be logged as data for quality control in a subsequent process 41. Furthermore, in the subsequent process 41, the calculated results can be used for a dynamic adapting of a coating process of a transparent film 7, in order to achieve the coating 1 on the transparent film 7. Thereby the amount of a specific component of the coating or the amount of the coating to a layer 6 on the transparent film 7 can be adapted to a reference input variable.

Figure 2 is a sectional view of the schematic view of a part of the coating 1 on the transparent film 7, the light source 2 and the sensor 3. The direction of view is perpendicular to a surface normal of the coating 1 on the transparent film 7 and perpendicular to the path 10. There, the coating 1 on the transparent film 7 is shown on the path 10 which leads through between the light source 2 and the sensor 3.

The coating 1 on the transparent film 7 is illuminated by the light source 2. The light source 2 emits multiple wavelengths as described above. The coating 1 on the transparent film 7 can consist of a transparent film 7 coated with several layers 6 with different compounds. In one aspect the

transparent film 7 is a polymer film. By passing through a layer 6 the intensity of light gets reduced, depending on the layer thickness, the content of a specific material in the layer 6 and the wavelength dependent attenuation coefficient of this material, according to Beer's law.

Each layer 6 can comprise different kinds of elements. Those elements can be metals. For example, each layer 6 can

comprise one or more elements out of Al, Zn, Cu, Ag, or Mg. The transparent film 7 may reduce the intensity of the transmitted light 5, too. The light source and the sensor are arranged in a way, that the transmitted light can reach the sensor 3 and be detected by the sensor 3. The sensor 3 detects the transmitted light 5. In one embodiment of the invention, the sensor 3 detects the intensity of the

transmitted light 5 in dependency of the wavelength of the light .

The information about the detected light intensity can be send to the central process unit 4. The central process unit 4 can use the information to calculate properties of the coating 1 on the transparent film 7. The calculation of the properties base on Beer's law. The calculation on the basis of Beer' s law allows to determine a closed set of equations and therefore no need to compare with pre-existing spectrum or data is given.

To minimize errors in the calculations, it is an advantage to find an optimal wavelength of light for each used material of interest. This optimal wavelength is characterized by the wavelength dependent attenuation coefficient of the used material of interest. The wavelength should be chosen in a way that the attenuation coefficient becomes maximal.

Furthermore the wavelength should be chosen in a way that the difference of between different attenuation coefficients of different materials becomes maximal for the given wavelength. That increases the precision of relative composition

measurement as an example. Such an optimal wavelength can be determined by an initial frequency sweep of the light.

According to the absorbance equation of Beer's Law:

A=e · C · 1

Therein A relates to a light absorbance which is direct proportional to a material attenuation coefficient e, a material concentration C and a length of the light path 1 trough the material.

In the case of metal coatings, the amount of material can be expressed by the product C-l. As the material attenuation coefficient is a property of each material for a particular wavelength, it is possible to determine the metal quantity of the coating by measuring the light absorbance. In case of several metals, the light absorbance shall be measured at several wavelengths to create a system of equations in which the number of equations n will be the same or higher than the number of metals to measure and wavelengths of the

measurement :

\ _n = _gn ^iri etall . ø metall

List of Reference Signs

1 coating

2 light source

3 sensor

4 process unit

41 subsequent process

5 transmitted light

6 layer ( s )

7 transparent film

8 first roll

9 second roll

10 path of the film