JPH09113412A - Method and apparatus for inspection of orientation of organic thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the molecular orientation of an organic thin film by a method wherein light formed by condensing a beam of parallel light through a lens is made incident on a sample, its reflected light is passed again through the lens and the spatial distribution of the intensity of the reflected light is measured as a beam of parallel light. SOLUTION: Radiant light from a monochromatic light source 1 is magnified by a condensing lens 2 so as to be changed into a beam of parallel light, and the light is changed, by a slit 3, into a shape whose cross section is linear. In addition, radiant light from the slit 3 is passed through a polarizer 4, linearly polarized light is formed, and the light is set in such a way that it advances to the periphery from the center of a condensing lens 5. When vibration faces of the transmitted light of the polarizer 4 are parallel in the length direction of the slit 3, P-polarized light is incident on a sample 10, and, when they are vertical, S-polarized light is incident on the sample 10. Reflected light form the sample 10 is passed again through the lens 5 so as to become a beam of parallel light, and the light changes its direction by a reflecting mirror 6 so as to be incident on a slit 7. After the light has been magnified by a magnifier 8, the intensity of the light is measured by a one-dimensional detector 9. An angle of incidence on the sample 10 is known on the basis of the position of reflected light detected by the detector 9. In order to measure the anisotropy of the intensity of the reflected light, the slit 3 which comprises an opening part 11 is used, and the sample 10 is turned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the orientation of small molecules in an organic thin film.
The present invention relates to a method and an apparatus for evaluating the molecular orientation of an organic thin film for controlling the orientation of liquid crystal molecules in a liquid crystal display device.

[0002]

2. Description of the Related Art The orientation of molecules in an organic thin film has a great effect on the function of a device using the same. In particular, in an organic thin film used to give initial alignment to liquid crystal molecules in a liquid crystal display device, it is known that there is a close relationship between the alignment of the organic thin film molecules and the alignment of the liquid crystal molecules ( For example, reference ⁽¹⁾ (Ishihara et al., “Liquid Crystals”, Vol. 4, No. 6, p. 669,
1989)), the greater the degree of molecular orientation of the organic thin film, the greater the alignment regulating force of the liquid crystal molecules. For this reason, quantitative measurement of the molecular orientation of the organic thin film is important for evaluating the function of the device.

[0003] In the conventional evaluation method of an organic thin film, a method of observing the state of a molecule from molecular vibration, such as infrared absorption spectroscopy and Raman scattering spectroscopy, is mainly used. The knowledge about the degree of molecular orientation and the orientation direction in the thin film is evaluated by measuring the optical anisotropy of the thin film caused by the molecular orientation by measuring the dichroic ratio using the polarization of light (for example, see Japanese Unexamined Patent Application Publication No. -1608
No. 62).

In addition to vibrational spectroscopy, optical anisotropy is evaluated by optical rotation of light transmitted through a sample (see, for example, JP-A-6-102512).

Further, a method has been proposed in which linearly polarized light whose polarization direction is horizontal or perpendicular to the film surface is incident on the film surface, and the in-plane refractive index anisotropy of the film caused by molecular orientation is observed from the difference in reflected light intensity. (For example, Japanese Patent Application Laid-Open No. 4-95
No. 845).

[0006] In addition to the above, as a conventional evaluation method of an organic thin film, a two-dimensional measurement of the shape of the thin film surface using an atomic force microscope or a scanning tunnel microscope has been performed (for example, see Reference ^{(2)). )} (Isono et al., Japan Society for the Promotion of Science, 142 Committee a committee a committee, a special study group sample, 34 pp., 1994) reference).

[0007]

The method based on vibrational spectroscopy using light such as infrared absorption is used to measure a liquid crystal display device having a transparent electrode film formed on a glass substrate and a liquid crystal alignment film formed thereon. In addition, the influence of the glass substrate and the transparent electrode film cannot be avoided. In particular, since infrared rays having a wave number lower than 1500 cm ^-1 do not pass through glass, it is difficult to measure an absorption spectrum.

[0008] The conventional observation of molecular orientation of a liquid crystal alignment film by infrared spectroscopy has focused on the peak at 1240 cm ^-1 (for example, see Reference ⁽³⁾ (Sawa et al., “Japanese Journal of Applied Physics” ^). (Japan
ese Journal of Applied Physics) ", Volume 33, Volume 6
273, 1994)), it is not possible to inspect the alignment film of the liquid crystal display element currently used.

In the measurement of birefringence, it is usually difficult to measure the birefringence of the alignment film itself because the glass substrate itself has birefringence anisotropy due to strain. Therefore, the conventionally known method cannot accurately evaluate the alignment state of the molecules in the alignment film.

In addition to this, the birefringence phase difference φ and the birefringence index Δ
The following equation (1) has a relationship among n, film thickness d, and light wavelength λ.

Φ = 2π (Δn) d / λ (1)

The above equation (1) shows that the quantity obtained from the measurement of the birefringence phase difference φ is the product of the film thickness d and the birefringence index Δn generated by the molecular orientation.

It is known that a rubbed polyimide film, which is widely used as an alignment film in a liquid crystal display element, does not align molecules of the entire film but aligns near the surface (for example, the above-mentioned document). ⁽³⁾ (Sawa et al., “Japanese Journal of Applied Physics (Japan
ese Journal of Applied Physics) ", Volume 33, Volume 6
273, 1994)), so that the molecular orientation cannot be quantitatively known unless the thickness of the oriented portion can be measured.

From the dependence of the intensity of the reflected light from the film on the polarization state of the incident light and the direction of incidence on the film (the direction of the incident light relative to the orientation direction of the molecules), the in-plane refractive index anisotropy is determined. The method of determining the orientation by measuring the
Although it is proposed in Japanese Patent Application Laid-Open No. 95845, it is impossible to measure the molecular orientation itself of the film because the film thickness of the oriented portion cannot be measured as in the birefringence phase difference measurement.

Further, as a technical difficulty in performing the measurement, there is an effect of anisotropy of a surface shape. That is, a polyimide film widely used as a liquid crystal alignment film is:
Rubbing gives the molecules in the film a molecular orientation,
It is known that a fine groove running in the rubbing direction is formed by this rubbing treatment (for example, the above-mentioned literature ⁽²⁾
(Isono et al., Japan Society for the Promotion of Science, 142 Committee A Committee A Subcommittee, Special Study Group Sample, p. 34, 1994) and many other reports.

Due to the presence of the groove, a difference occurs in the amount of light scattered in directions other than the regular reflection direction, which affects the intensity of reflected light. For example, Japanese Patent Application Laid-Open No. 4-95845 (Example 3) describes the evaluation result of the state of the alignment film from the measurement of reflected light intensity having a polarization component perpendicular to the polarization direction of incident light. The amount of the reflected light component to be detected depends on the thickness of the unoriented portion in the film and also on the surface condition (roughness), and cannot be said to be an amount that directly reflects the molecular orientation.

Further, in the observation with an atomic force microscope, only the surface shape such as the roughness of the sample surface is measured, and there is no example in which an organic thin film is observed at an atomic level resolution.

In the case of a liquid crystal alignment film, it has already been reported that the surface shape observed by these methods has no direct relationship with the molecular orientation in the film which affects the alignment state of the liquid crystal (see, for example, the above-mentioned literature ^{). 2)} (Isono et al., Japan Society for the Promotion of Science, 14
2 Committee A Committee A subcommittee, special study group sample, page 34,
(1994).

Further, it is known that a film obtained by treating a rubbed surface with an organic solvent such as acetone has a force for regulating the alignment of liquid crystal molecules, but loses the streaky structure of the surface generated by the rubbing. Thus, surface morphology observation does not provide direct information on the liquid crystal alignment regulating force of the film.

Further, evaluation of minute portions of the alignment film using a reflection type polarizing microscope has been attempted (see "Alignment Film Observation Microscope", EPIPOL-5D, manufactured by Nikon Corporation). In this method, linearly polarized light is incident on a sample almost perpendicularly, and the in-plane portion of the intensity of the reflected light having a component perpendicular to the polarization component of the incident light is observed. In order to observe a minute area, incident light is condensed using a lens, and reflected light is enlarged through the lens to form an image. The optical anisotropy of the film can be observed to some extent by changing the direction of the sample with respect to the polarization direction of the incident light, but quantitative observation is difficult. Furthermore, since the light is incident on the sample almost perpendicularly, the distortion of the glass substrate greatly affects the polarization state of the reflected light, so that it is more difficult to observe the molecular orientation of the film itself.

On the other hand, the molecular orientation can be measured by observing the anisotropy of the polarization state of the reflected light. However, the polarization state of the reflected light depends not only on the molecular orientation of the sample, but also on the wavelength of the incident light and the angle of incidence on the sample. For this reason, if the incident light is narrowed using a lens in order to measure a minute area, an accurate measurement cannot be performed due to the spread of the incident angle to the sample.

As described above, there is no method for measuring the molecular orientation at the minute part of the liquid crystal alignment film at present.

Accordingly, the present invention has been made in view of the above-mentioned problems, and has been made by measuring the polarization and incident angle dependence of the reflected light intensity of a liquid crystal polymer alignment film used for a liquid crystal display device. It is an object of the present invention to provide a method and an apparatus capable of evaluating the film quality of a film.

[0024]

In order to achieve the above object, the present invention provides a method for measuring the molecular orientation of an organic thin film by measuring the incident angle of reflected light intensity and the directional anisotropy of a sample depending on polarization. And measuring the spatial distribution of the intensity of the reflected light, which is formed by converging parallel light rays with a lens, is incident on the sample, reflects off the sample, passes through the lens again, and is converted into a parallel light ray. And a method for measuring the molecular orientation of a minute portion.

According to a second aspect of the present invention, there is provided a method for measuring the molecular orientation of an organic thin film by measuring the incident angle of the reflected light intensity and the directional anisotropy of the sample, which is dependent on the polarization. Using the incident light obtained by converging the parallel light beams by the lens, measuring the spatial distribution of the intensity of the respective reflected lights that have passed through the lens and turned into parallel light beams again, and performing orientation measurement. Provided is a method for measuring molecular orientation.

Further, the present invention is an apparatus for measuring the molecular orientation of an organic thin film by measuring the direction anisotropy of a sample, which is dependent on the incident angle and the polarization of the reflected light intensity. Characterized in that the orientation measurement is performed by measuring at least the spatial distribution of the intensity of the reflected light, which is reflected by the sample and then passes through the lens and becomes a parallel ray again after being reflected by the sample. The present invention provides an apparatus for measuring the molecular orientation of a part.

The present invention is a device for measuring the molecular orientation of a liquid crystal alignment film by measuring the incident angle of reflected light intensity and the directional anisotropy of a sample depending on the polarization, and the parallel light rays whose incidence planes are orthogonal to each other. Is provided with a lens for condensing light into incident light to the sample, and after measuring the orientation distribution by measuring the spatial distribution of the intensity of each reflected light that is reflected by the sample and then passes through the lens again to become parallel rays. There is provided a molecular orientation measuring device for a minute portion, which is characterized by performing

[0028]

The anisotropy of the refractive index caused by the molecular orientation cannot be distinguished from the anisotropy of the surface roughness by the conventional measurement of the reflected light intensity anisotropy. Can not know.

On the other hand, the measurement of the anisotropy depending on the incident angle according to the present invention can measure the anisotropy of the surface roughness and the refractive index anisotropy caused by the molecular orientation. This causes a reduction in the amount of reflected light to be measured because the surface roughness causes irregular reflection, and the effect is greater as the angle of incidence increases.

This state can be replaced if the film is not completely transparent and has absorption. Even in the case where the film has absorption, if the incident angle increases, the optical path of the reflected light in the film becomes longer, so that the influence increases. That is, the surface roughness anisotropy is apparently observed as absorption anisotropy, and is observed separately from the refractive index anisotropy depending on the molecular orientation.

In the method of observing the molecular orientation of the liquid crystal alignment film by observing the polarization state anisotropy of the reflected light, the incident angle distribution of the light on the sample becomes large when the light is condensed by a lens or the like. In addition, the refractive index cannot be accurately obtained from the polarization analysis, and the molecular orientation of the minute portion cannot be quantitatively measured.

On the other hand, in the measurement of the dependence of the intensity of the reflected light on the incident angle, it is not necessary to make a parallel ray having a fixed incident angle incident on the sample. Light can be made incident, so that the optical properties of the minute portion can be measured.

In the present invention, preferably, the incident light is condensed using a lens so as to be focused on the sample surface.
The incident angle of light that has passed through the periphery of the lens is large, and the light that has passed near the center has a smaller incident angle. Therefore, the change of the incident angle can be performed at the same time in the observation of a minute portion by light collection.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram for explaining the configuration of an apparatus according to one embodiment of the present invention.

Referring to FIG. 1, light emitted from monochromatic light source 1 is expanded by condenser lens 2 to be a parallel light beam, and slit 3 has a substantially linear cross-sectional shape. Further, the light emitted from the slit 3 passes through the polarizer 4 to be linearly polarized, and enters one side of the condenser lens 5. At this time, the longitudinal direction of the light is set so as to extend from the center of the condenser lens 5 to the periphery.

If the vibration plane of the light passing through the polarizer 4 is parallel to the longitudinal direction of the slit 3, the p-polarized light
And if perpendicular, s-polarized light will be incident on the sample 10.

Further, the light is transferred to the sample 1 by the condenser lens 5.
Focus on surface 0. At this time, the light incident on the surface of the sample 10 has a larger incident angle as it passes through the periphery of the condensing lens 5 and has a smaller angle at the center. The optical path from the monochromatic light source 1 to the sample 10 is shown by a dashed line in FIG.

Then, the light reflected from the surface of the sample 10 passes through the condenser lens 5 used for condensing the incident light again to be made into a parallel light, and after being turned by the reflecting mirror 6, the slit 7 is turned. Incident on.

Further, after being magnified by the magnifying lens 8, the intensity of light is measured by the one-dimensional detector 9.

In FIG. 1, the angle of incidence of the reflected light entering the upper side of the one-dimensional detector 9 is smaller than that of the reflected light coming below the one-dimensional detector 9. As described above, the angle of incidence on the sample 10 can be determined from the position of the reflected light detected by the one-dimensional detector 9.

Although the reflecting mirror 6 is arranged at the position shown in FIG. 1 for the sake of space of the optical element and the measurement is performed, it is not always necessary for the measurement (for example, the one-dimensional detector 9 may be used). The reflecting mirror 6 is not necessary when it is disposed above the condenser lens 5), and the position and the number of the reflecting mirror 6 vary depending on the situation.

The measurement of the anisotropy of the reflected light intensity is performed by rotating the sample 10 using the slit 3 shown in FIG. 1 having an opening having a shape as shown in FIG. 2A.

However, when the sample 10 is rotated in order to observe the anisotropy of the minute portion on the surface of the sample 10, the observation position needs to exactly coincide with the center of rotation. It takes time to adjust the position of the device.

Therefore, the opening of the slit 3 is changed as shown in FIG.
As shown in (2), two lights whose longitudinal directions are orthogonal to each other are incident on the sample. In this case, if the light emitted from the first opening 12 of the slit shown in FIG. 2B is p-polarized, the light emitted from the second opening 13 becomes s-polarized light, and the first opening 12 becomes s-polarized. In the case of polarized light, the second opening 13 becomes p-polarized light.

When two lights are used in this way, the shape of the slit 7 is made to have two openings as shown in FIG. 2B. A two-dimensional detector or a combination of two one-dimensional detectors is used as the reflected light detector 9. In the actual measurement, two one-dimensional detectors were used in combination.

The following samples were measured using this apparatus.

Nissan Chemical's SE731 for polyimide raw material liquid
1 was applied to the surface of 7059 glass manufactured by Corning Co. using a spin coater, and then baked by heating at 200 ° C. for 1 hour. Using this sample as a light source, light of 632.8 nm of a He-Ne laser was used, and two light beams were simultaneously incident on the sample to measure anisotropy. The size of the focal point is about 30 μm.

FIGS. 3 and 4 show the measurement results of the dependency of the reflectance on the incident angle. 3 and 4 are diagrams showing measurement results when a sample before rubbing is measured by simultaneously irradiating light in two directions, and FIGS. 3 and 4 show distributions of reflectance in directions orthogonal to each other. I have. The points in the figure are the measured values,
The solid line shows the calculated value. The solid line in the figure is the theoretical formula (Reference ⁽⁴⁾ (Azam and Basara, “Ellipsometry and Polarized Light” (Azzam & Bashar
a, “Ellipsometry and Polarized light”), North-H
Olland, p. 285, 1987)) is a calculated value of the reflectance obtained when the refractive index and thickness of the polyimide film were obtained.

As a result, the refractive index was 1.60 to 1.61,
The film pressure became 7.8 to 8.2 nm. Since rubbing is not performed, apparent absorption due to roughness of the polyimide surface does not occur, so that the absorption effect is not considered.

The measurement results shown in FIG. 3 and FIG.
It can be seen that the sample surface before the rubbing treatment is in a non-oriented state.

After this measurement, the sample was fed to a buff cloth roller having a diameter of 50 mm at 800 rpm and at a feed rate of 20 mm / s.
After rubbing two times, observation was performed again.

The measurement was performed with one longitudinal direction of the two lights being aligned with the rubbing direction. The measurement results are shown in FIGS. 5 shows a direction parallel to the rubbing direction, and FIG. 6 shows a direction perpendicular to the rubbing direction.

It is clear from FIGS. 5 and 6 that there is a difference in the angle dependence of the reflectance between the two. The solid line in the figure is the reflectance calculated from the refractive index film thickness of the polyimide film, as in the case of FIGS. 3 and 4. This time, we also considered absorption. When the film thickness was fixed at 8 nm and the refractive index and absorption were determined from the measurement, the refractive index was 1.679 in the direction parallel to the rubbing.
˜1.685, which cannot be clearly determined due to small absorption, and was estimated to be about 5 × 10 ⁻⁴ .

On the other hand, in the direction perpendicular to the rubbing, the refractive index was 1.533 to 1.543, and the absorption was 2 × 10 ⁻³ .

As described above, the state in which the polyimide molecules were oriented by rubbing became apparent from the anisotropy of the refractive index. Note that the absorption value is larger in the direction perpendicular to the rubbing than in the case where the absorption is parallel, and the influence of the surface roughness is more remarkable.

[0057]

As described above, according to the present invention,
From the measurement of the incident angle and the polarization dependence of the reflected light intensity, it becomes possible to measure the optical anisotropy such as the refractive index of a minute area that cannot be measured by the polarization analysis of the reflected light so far. This has an effect that measurement can be performed in a microscopic region of orientation.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an opening of a slit according to an embodiment of the present invention. (A) is a figure which shows the slit used at the time of one-way incidence, and (b) is a figure which shows the slit at the time of two-way incidence.

FIG. 3 is a diagram showing a result when a sample before rubbing is measured by simultaneous incidence in two directions according to an embodiment of the present invention.

FIG. 4 is a diagram showing a result when a sample before rubbing is measured by simultaneous incidence in two directions according to an embodiment of the present invention.

FIG. 5 is a diagram showing a result of measurement of a sample after rubbing by simultaneous incidence in two directions according to an embodiment of the present invention (a direction parallel to the rubbing direction).

FIG. 6 is a diagram showing a result of measurement of a sample after rubbing by simultaneous incidence in two directions according to an embodiment of the present invention (a direction perpendicular to the rubbing direction).

[Explanation of symbols] 1 monochromatic light source 2 condenser lens 3 slit 4 polarizer 5 condenser lens 6 reflecting mirror 7 slit 8 magnifying lens 9 one-dimensional detector 11, 12, 13 slit opening

Claims (10)

[Claims] 1. A method for measuring the molecular orientation of an organic thin film by measuring the direction anisotropy of a sample, which is dependent on the angle of incidence and the polarization of the reflected light intensity, comprising the steps of: And measuring the spatial distribution of the intensity of the reflected light, which is reflected by the sample, is reflected by the sample, passes through the lens again, and is converted into a parallel light beam, and performs orientation measurement. 2. A method for measuring the molecular orientation of an organic thin film by measuring the direction of anisotropy of a sample, which is dependent on the angle of incidence and polarization of reflected light intensity, wherein parallel lenses whose incident surfaces are orthogonal to each other are condensed by a lens. A method for inspecting the orientation of an organic thin film, wherein the orientation measurement is performed by measuring the spatial distribution of the intensity of each of the reflected light that has passed through the lens and turned into parallel rays again using the incident light thus obtained. 3. An apparatus for measuring the molecular orientation of an organic thin film by measuring the direction of anisotropy of a sample, which is dependent on the angle of incidence and the polarization of the reflected light intensity. An alignment test of an organic thin film, wherein the alignment measurement is performed by measuring at least a spatial distribution of the intensity of reflected light, which is reflected by the sample, passes through the lens again, and becomes a parallel ray after being reflected by the sample. apparatus. 4. An apparatus for measuring a molecular orientation of a liquid crystal alignment film by measuring a direction anisotropy of a sample, which is dependent on an incident angle and a polarization of reflected light intensity, and collects parallel light beams whose incident surfaces are orthogonal to each other. A lens for making incident light to the sample, and after measuring the spatial distribution of the intensity of each reflected light, which is reflected by the sample, passes through the lens again, and becomes a parallel light beam, and performs orientation measurement. Characteristic organic thin film orientation inspection equipment. 5. A method for inspecting a liquid crystal alignment film, comprising the step of measuring the molecular alignment of a liquid crystal alignment film formed by forming an organic thin film on a substrate by the method of claim 1 or 2. . 6. An inspection of a liquid crystal alignment film, comprising the alignment inspection device for an organic thin film according to claim 3 or 4, wherein the molecular alignment of a liquid crystal alignment film formed by forming an organic thin film on a substrate is measured. apparatus. 7. A method for measuring the molecular orientation of a minute part by rotating the sample or inputting light whose incident surfaces intersect each other to the sample and measuring the polarization and the incident angle dependence of each reflected light. 2. The method for inspecting the orientation of an organic thin film according to claim 1, wherein: 8. A light source that emits monochromatic light, a first lens that converts light emitted from the light source into parallel rays, and a conversion unit that converts the parallel rays into a predetermined shape on a plane orthogonal to the optical axis. A polarizing means for converting light emitted from the conversion means into linearly polarized light; and a second means for condensing linearly polarized light from the polarizing means on a sample surface and converting reflected light from the sample surface into parallel rays.
An orientation inspection apparatus for an organic thin film, comprising: a lens; and means for detecting a spatial distribution of light intensity of reflected light from the second lens. 9. The organic light emitting device according to claim 8, wherein said converting means for converting said parallel rays into a predetermined shape on a plane orthogonal to the optical axis comprises a slit having a predetermined rectangular opening. Inspection device for thin film. 10. A conversion means for converting the parallel light beam into a predetermined shape on a plane orthogonal to the optical axis has two openings having a predetermined rectangular shape, and the two openings have an extension in the longitudinal direction. 9. The organic thin film orientation inspection apparatus according to claim 8, comprising slits orthogonal to each other.