JP2007057443A - Method and device for evaluating orientation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for evaluating an orientation film which evaluates the uniformity in the face of the orientation film accurately in a short period of time. <P>SOLUTION: The method and device for evaluating the orientation film comprise processes of: scanning liquid crystal orientation film with linearly polarized conical light while keeping the incident angle to a substrate constant and detecting the reflected light intensity from the orientation film surface occurring in that time; measuring location dependency in the substrate face of the reflected light intensity; and evaluating the uniformity in the face of the orientation film, based on the location dependency of the reflected light intensity. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal alignment film inspection method and inspection apparatus, for example, and more particularly to a method and an evaluation apparatus for evaluating the molecular alignment of a thin film for controlling the alignment of liquid crystal molecules in a liquid crystal display element.

  A liquid crystal element is a display element that utilizes the polarization characteristics of light possessed by a liquid crystal. In a liquid crystal element, liquid crystal is interposed between a pair of substrates, and transmitted light and reflected light are controlled by applying an electric field generated on the substrate to a liquid crystal layer. An alignment film for determining the initial alignment of the liquid crystal layer is formed on the substrate, and a transparent electrode is formed between the substrate and the alignment film. The alignment state of the molecules in the alignment film has a great influence on the liquid crystal element. For this reason, quantitative measurement of the molecular orientation of the alignment film is very important.

  Conventional methods for evaluating alignment films include methods for observing molecular states from molecular vibrations, such as infrared absorption spectroscopy and Raman scattering spectroscopy. These are mainly used for research purposes and are used for molecular-level orientation analysis (for example, non-patent literature: Journal of Organic Molecules and Bioelectronics [M & BE] “Rubbed polyimide films by polarized infrared absorption spectroscopy”). Orientation analysis "Ryuichi Arafune, Kenji Sakamoto, Shigekatsu Shioda, Vol. 9, No. 4, 1998, page 186).

  In addition to vibrational spectroscopy using infrared absorption or the like, for example, the birefringence phase difference of light transmitted through a sample is evaluated (see, for example, JP-A-6-102512).

  There is also a method in which linearly polarized light whose polarization direction is horizontal or perpendicular to the film surface is incident and the in-plane anisotropy caused by molecular orientation is observed from the difference in reflected light intensity and the degree of polarization of the reflected light. It has been proposed (see, for example, Japanese Patent Laid-Open Nos. 4-95845 and 9-90368).

JP-A-6-102512 Japanese Patent Laid-Open No. 4-95845 JP-A-9-90368 Journal of Organic Molecules and Bioelectronics [M & BE] “Orientation Analysis of Rubbed Polyimide Films by Polarized Infrared Absorption Spectroscopy” Ryuichi Arafune, Kenji Sakamoto, Motokashi Ushioda Vol. 9, No. 4, 1998, page 186 Ichiro Serizawa “Surface Anisotropy of Liquid Crystal Alignment Films” Journal of Liquid Crystal Society of Japan “Liquid Crystal” 2003 Vol.

  A method using vibrational spectroscopy using light, such as infrared absorption spectroscopy, is suitable for analysis of an alignment film formed on a silicon substrate. However, when measuring a liquid crystal element in which a transparent electrode film is formed on a glass substrate and a liquid crystal alignment film is provided thereon, there are problems such as the glass substrate and the transparent electrode film absorbing infrared rays. Therefore, it is not suitable for evaluating liquid crystal elements.

  When the birefringence measurement of the alignment film is performed by analyzing the transmitted light, since the birefringence anisotropy is caused by the strain of the glass substrate itself, the measurement of the birefringence of the alignment film itself is greatly affected.

  In this respect, the reflected light generated when the light is incident on the surface of the alignment film is small in the influence of the substrate distortion, and is therefore suitable for evaluating the molecular alignment state of the film (for example, Japanese Patent Laid-Open No. 4-95845). No., and JP-A-9-90368).

  A rotation analyzer method is widely used in which the polarization state of the reflected light is obtained from the dependence of the intensity of light passing through the analyzer on the analyzer angle. However, in this method, in order to measure the light intensity at 360 ° rotation of the analyzer, the measurement time for one point on the sample surface is long, and it is enormous for evaluating the uniformity of molecular orientation over a wide area. There is a problem that time is required. In addition, even when the polarization modulation method is used, when the alignment film is evaluated by the method disclosed in JP-A-9-90368, it is necessary to rotate the alignment film 360 ° while keeping the incident angle constant (Ichiro Serizawa “Liquid Crystal”). Surface Anisotropy of Alignment Films, “Liquid Crystal, Journal of Japanese Liquid Crystal Society 2003, Vol. 7, No. 2) Therefore, the measurement takes a long time. Also, the accuracy of the rotation mechanism is required.

  Accordingly, an object of the present invention is to solve the above-mentioned various problems and provide a method and an apparatus capable of evaluating an alignment film produced on a glass substrate.

  In order to achieve the above object, the alignment film evaluation method according to the present invention scans the alignment film with linearly polarized conical light at a constant incident angle to the substrate, and the above-described alignment film is generated at that time. A step of detecting reflected light intensity from the surface of the alignment film; a step of measuring the location dependence of the reflected light intensity in the substrate surface; and the in-plane uniformity of the orientation film from the reflected light intensity location dependence There are provided an alignment film evaluation method and an alignment film evaluation apparatus characterized by evaluating the property.

  According to the alignment film evaluation method and apparatus according to the present invention, the alignment film can be evaluated in a much shorter time than the conventional method. Moreover, since the movable part is only an XY stage for scanning the entire alignment film, for example, the accuracy is also improved.

  Embodiments of the present invention that are considered suitable (how to carry out the invention) will be briefly described with reference to the drawings, illustrating the operation of the present invention.

  As described in the problem to be solved by the invention, the method based on the polarization analysis of the reflected light is excellent for judging the quality of the alignment film. However, since the incident azimuth angle to the substrate has to be swung over 360 degrees, the measurement takes time. In order to solve this problem, it is provided with a step of incident conical light on the substrate to simultaneously irradiate an incident azimuth angle of 360 degrees, and a step of detecting reflected light over a reflection azimuth of 360 degrees is significantly faster. Without the need to analyze the arrangement of alignment film molecules from the reflected light, and the speed is further increased by simply visualizing the orientation indicating the maximum value of the reflected light intensity and the distribution of the intensity within the substrate surface. .

  The principle and operation of the present invention will be described below. The specific configuration described here is merely an example.

  A schematic diagram of this evaluation method is shown in FIG. A transparent electrode 12 is generally disposed on the glass substrate 13, and an alignment film 11 is further coated thereon. The surface of the alignment film 11 is often subjected to alignment treatment. As the alignment treatment, a treatment for rubbing the alignment film surface called a rubbing method or a treatment for irradiating ultraviolet light called a photo-alignment treatment is generally performed.

  A reflected light detection system from the alignment film will be described. The light emitted from the high-intensity light source 17 passes through the interference filter 20 to be monochromatic light, and is then linearly polarized by the circularly polarizing plate 18. Here, as shown in FIG. 1, the polarization axis is characterized by being radial from the center of the polarizing plate. The light that has passed through the circularly polarizing plate 18 is irradiated on the surface of the alignment film 11 after passing through the annular slit 19. The irradiated light is annular, and the angle of the light irradiated from the light source to the alignment film surface, that is, the incident angle is constant at θ throughout the annular irradiation region.

  Furthermore, the vibration direction of the light irradiated to the alignment film is parallel to the incident surface everywhere. This vibration direction is generally called p-polarized light. If the slit width of the annular slit 19 is sufficiently narrowed, the irradiation area can be narrowed, so that the error due to the increase of the light spreading angle can be reduced.

  Furthermore, since the reflected light from the back surface of the substrate 13 and the reflected light from the front surface have different optical paths, reflection from the back surface can be measured separately. In addition, if the distance between the light source 17 and the substrate is made small, a minute region can be measured. The reflection angle of the reflected light from the alignment film, that is, the angle formed between the reflected light and the substrate normal is also θ.

Therefore, the detector 16 is placed so that the reflected light from the surface of the alignment film 11 can be measured. Further, a linear polarizing plate 15 is disposed between the detector 16 and the alignment film 11. If the linearly polarized light transmission axis of the polarizing plate 15 is parallel to the incident surface, only the component in which the vibration direction of the reflected light is parallel to the incident surface can pass through the polarizing plate. This light is called reflected p-polarized light. If the angle of incidence of the alignment film theta was Brewster angle theta _b, it reflected p-polarized light is zero ideally. Brewster angle theta _b when the effective refractive index of the alignment layer is n _a, a tanθ _{b =} n _a. Since the alignment film is subjected to alignment treatment, anisotropy is generated on the surface of the alignment film.

  For this reason, the refractive index of the alignment film surface also depends on φ when the angle formed by the alignment processing direction and the incident surface is φ. An example of the reflected light intensity dependency is shown in FIG. When both the axis of the polarizing plate for incident light and the axis of the polarizing plate on the reflected light side are parallel to the incident surface, an 8-shaped pattern as shown in FIG.

  In addition, when the polarizing plate on the reflected light side is made vertical, the reflected polarized light becomes s-polarized light. In this case, it becomes a clover-like shape as shown in FIG. This figure-eight pattern or clover-like shape represents good or bad orientation. In the method disclosed in Japanese Patent Laid-Open No. 9-90368, the alignment film is formed by numerical analysis of the φ dependence of the reflected light intensity, assuming that the organic molecules forming the alignment film are rod-shaped. The inclination angle of the organic molecule is obtained. However, it takes several hours to calculate the tilt angle. The reason is that the substrate must be rotated in the φ direction, and the numerical calculation requires repeated calculation for several hours for fitting calculation.

  In order to obtain the φ dependence of the reflected light intensity as shown in FIG. 2 at high speed, a plurality of polarizing plates and detectors may be arranged at regular intervals as shown in FIG. In this way, there is no need to rotate the substrate in the φ direction. In FIG. 1, only three sets are illustrated for the sake of easy viewing, but it is better as the number increases. For example, when 16 pieces are arranged, information at intervals of 22.5 degrees is obtained for φ. The measurement values from the 16 detectors can be automatically measured by sending them to a personal computer via an analog / digital converter.

  In addition, what the liquid crystal display manufacturer demands is that it does not want the inclination angle of the organic molecules constituting the alignment film, but wants to know the degree of uniformity of the entire alignment film in a short time. . Therefore, focusing on the fact that the φ dependence of the reflected light intensity in FIG. 2 represents the degree of anisotropy without obtaining the tilt angle of the organic molecules constituting the alignment film, The degree of uniformity of the entire alignment film is evaluated from the characteristics of the φ dependence graph.

  That is, it can be understood that the orientation process direction of the figure 8 pattern as shown in FIG. 2A is the direction of the dotted line in FIG. 2A from the axis of the figure 8 pattern. If the glass substrate is placed on a stage that can move in the XY directions, it is a great feature that the orientation state of the entire glass substrate can be easily measured.

  For example, when the alignment film is evaluated by the method of Japanese Patent Laid-Open No. 9-90368, the substrate must be rotated 360 degrees for each measurement point, but in the case of this measurement method, the reflected light intensity is not rotated. Since it is possible to take the φ dependence, it is only necessary to move in the XY directions when viewing the uniformity of the orientation of the entire substrate surface. Further, when the uniformity of the entire surface of the substrate surface of the maximum value of reflected light in FIG. 2A is observed, it is only necessary to move in the XY directions.

  A first embodiment of the present invention will be described with reference to the drawings.

  With the above-described form and procedure, a two-dimensional distribution regarding the uniformity of the alignment film can be obtained. FIG. 3 shows an in-plane distribution of arrows indicating the orientation treatment direction shown in FIG. It can be viewed in the same way as the wind direction map used for weather. That is, the direction of the arrow is the alignment direction of the alignment film molecules, and the length of the arrow represents the maximum value of the reflected light intensity. In the example of FIG. 3, the alignment abnormality occurs in a streak pattern at the center of the substrate. Here, it can be seen that since the alignment treatment was not sufficiently performed, the alignment direction is out of place and the illegality is small. Further, since the abnormal distribution of streaks appears parallel to the substrate, it may be caused by contamination during cleaning or transportation of the substrate. As described above, the detection of the in-plane orientation abnormality provides a clue for investigating the cause. Such a measurement can be realized simply by adding a stage that can move in the XY directions to the measurement system of FIG.

  A second embodiment of the present invention will be described with reference to the drawings.

  Further, in order to speed up the measurement, if the measurement system of FIG. 1 is set as one unit and eight units are arranged in a straight line, only the X-direction moving stage is required to create an orientation in-plane distribution map as shown in FIG. In other words, an in-plane distribution map as shown in FIG. 3 can be created using only the X-direction moving stage by the same operation as the image reading scanner for personal computers.

  The present invention is not limited to the first and second embodiments, and the specific configuration of each component can be designed as appropriate.

It is a composition conceptual diagram of the measuring device of the present invention. It is a measurement result by the present invention. It is an example of the in-plane distribution measurement result of the orientation processing direction by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Alignment film 12 Transparent electrode 13 Glass plate 14 Light irradiation area | region on alignment film 15 Linearly polarized light plate 16 Detector 17 Light source 18 Circularly polarizing plate 19 Annular slit 20 Interference filter

Claims (4)

  A method for evaluating the alignment film on the substrate having an alignment film formed on one surface of a transparent substrate, wherein linearly polarized conical light is incident on the substrate. Scanning with a constant angle, detecting the reflected light intensity from the surface of the alignment film generated at that time, measuring the location dependence of the reflected light intensity in the substrate surface, and the reflection An evaluation method of an alignment film, wherein the in-plane uniformity of the alignment film is evaluated from light intensity location dependency.   2. The alignment film evaluation method according to claim 1, further comprising means for scanning the alignment film in the X and Y directions with respect to the light source, and measuring in-plane uniformity of the molecular alignment state of the alignment film.   An apparatus for evaluating the alignment film on the substrate having an alignment film formed on one surface of a transparent substrate, wherein linearly polarized conical light is incident on the substrate on the alignment film of the substrate A linearly polarized light scanning mechanism for scanning with a constant angle, a reflected light intensity detecting mechanism for detecting reflected light intensity from the alignment film surface generated during the scanning, and a location of the reflected light intensity in the substrate surface An alignment film evaluation apparatus configured to evaluate the in-plane uniformity of the alignment film from the location dependency measurement mechanism for measuring dependency and the reflected light intensity location dependency. 4. The apparatus according to claim 3, further comprising means for scanning and moving the alignment film in the X and Y directions with respect to the light source, and having a function of measuring in-plane uniformity of the molecular alignment state of the alignment film. Evaluation apparatus for alignment films.

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