JP3260565B2 - Alignment film evaluation apparatus and alignment film evaluation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alignment film evaluation apparatus and an alignment film for judging the alignment of an alignment film widely used in LCDs with high accuracy by measuring anisotropy of light absorption. Regarding the evaluation method.

[0002]

2. Description of the Related Art Alignment films used in LCDs are the most important constituent materials for uniformly aligning liquid crystal molecules, and the alignment films are made of polymer films such as polyimide of several tens nm. After the film is formed on the substrate, the film surface is rubbed with a cloth wound around a roller (rubbing step), whereby the polymer chains on the film surface are molecularly oriented. In the rubbing process, which is a primitive process of rubbing with such a cloth, it is very difficult to control the orientation of the alignment film, and the control largely depends on the experience of the operator, and the quality of the rubbing process is good or bad. Cannot be determined until the final product has become an LCD panel, which is one of the causes of a decrease in the yield in the LCD manufacturing process.

In order to solve this problem, a highly sensitive orientation measurement method capable of judging the orientation of the alignment film immediately after the rubbing process has been desired. Polarized in a direction parallel or perpendicular to the surface into S-polarized light (polarized light oscillating in a direction perpendicular to the plane formed by incident light and reflected light with respect to the alignment film), and transmits infrared light through the alignment film to transmit red light. After measuring the external absorption, the substrate is rotated by 90 degrees in the plane and the measurement is performed again, or the angle of incidence of the light is zero.
If it is close to the degree, the polarization direction is rotated by 90 degrees and measured again as P-polarized light, and the difference in absorption intensity before and after rotation is measured to determine the two-color difference, and the orientation is determined from the intensity of the two-color difference. Several evaluation methods have been proposed.

However, since the size of the LCD is increased and a large substrate from which two or four LCD panels can be obtained is subjected to rubbing processing to improve productivity, it is practically impossible to rotate the substrate. become. In the case of rotating polarized light, the incident angle must be close to 0 degrees, and the incident light and the reflected light are spatially close to each other. Therefore, it is very difficult to design an optical system, and the optical system requires a large space. become,
The optical path length becomes longer, which is one of the causes of a decrease in sensitivity.

[0005]

As described above, the conventional alignment film evaluation apparatus has a problem that the sensitivity is reduced as the size of the substrate is increased. The present invention has been made in view of such a problem, and measures the two-color difference of an alignment film with high sensitivity at a free incident angle without rotating the substrate or the polarization state. It is an object of the present invention to provide an alignment film measuring apparatus and a method for detecting infrared light transmitted through an alignment film, which can evaluate the alignment with high accuracy.

[0006]

According to the present invention, there is provided an alignment film evaluation apparatus, comprising: emission means for emitting infrared light; polarizing means for polarizing the infrared light emitted from the emission means; Splitting means for splitting the infrared light into two light paths, irradiating means for irradiating the alignment film with each of the infrared light split into the two light paths, and detecting the respective infrared light transmitted through the alignment film And a detecting means.

The dividing means can use a mirror chopper. When the alignment film is formed on a predetermined substrate, the detection unit can detect the respective infrared lights reflected by the substrate. The alignment film evaluation method of the present invention emits infrared light, polarizes the infrared light, divides the polarized infrared light into two optical paths, and separates each of the infrared light divided into the two optical paths. Irradiating the alignment film, detecting each of the infrared light transmitted through the alignment film, determining the difference in absorbance of the detected infrared light to evaluate the alignment ability of the alignment film. And

A fourth invention of the present application is the method for evaluating an alignment film according to the second invention of the present application, wherein the alignment film is formed on a predetermined substrate, and the polarized light reflected on the substrate is detected. is there.

Hereinafter, the configuration of the present invention will be described in more detail with reference to FIGS. 1, 2 and 3. First, the alignment film 15 used in the present invention is usually formed on the surface of the transparent electrode 16 formed on the substrate 17, and the glass substrate 17 and the transparent electrode 1 are formed.
The evaluation is performed on the surface of the LCD substrate 8 including the alignment film 6 and the alignment film 15. In such a case, the infrared light irradiated by the irradiation means described later is reflected on the electrode. It is also possible to evaluate an alignment film formed on a substrate for evaluation such as a silicon substrate, and in this case, the infrared light passes through the substrate.

The LCD substrate 8 has an optical stage 8 which can be translated in XYZ directions and adjusted in tilt angle in XY directions.
By setting it up, the angle of the infrared light from the emission means described later can be adjusted.

The emission means of the present invention can be used without particular limitation as long as it can emit infrared light having the absorption wavelength of the alignment film. The deflecting means of the present invention polarizes the infrared light emitted by the emitting means into an s-polarized state. For example, an interferometer 3 for dispersing the infrared light, It is obtained by combining the polarizers 4 to be used.

The dividing means of the present invention divides the infrared light into at least two parts. For example, when the mirror chopper 5 is rotated, the wings are irradiated with the polarized infrared light and reflected. It is possible to divide the infrared light into two, that is, the infrared light that has passed through the mirror chopper without being irradiated on the wing.

The detecting means of the present invention is a means for detecting the intensity of infrared light transmitted through the alignment film, and uses an infrared light detector or the like. Further, by adjusting the optical path of the infrared light irradiated from a plurality of directions by the irradiation means using a mirror or the like, the infrared light can be detected by one infrared light detector as shown in the figure. It can be carried out.

In order to evaluate the orientation film in the present invention, the difference in the intensity (or absorbance) of the infrared light irradiated from the plurality of directions detected by the detection means may be obtained. What can perform arithmetic processing may be used.

[0015]

According to the alignment film evaluation apparatus and the alignment film evaluation method of the present invention, it is possible to measure the two-color difference of the alignment film without rotating both the substrate and the polarization state. Enables in-plane measurement.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described below with reference to the drawings. FIG. 1A is a schematic view showing an example of the alignment film measuring device of the present invention. FIG. 1B is a sectional view taken along line A- in FIG.
It is sectional drawing in A '. FIG. 2 is a schematic plan view of a mirror chopper that is a dividing unit according to the present invention. FIG.
FIG. 1 is a schematic configuration diagram showing an example of an alignment film measuring device of the present invention.

The basic structure of the device required for carrying out the present invention is as follows. First, an LCD substrate 8 having a transparent electrode 16 and an alignment film 15 formed on a glass substrate 17 and an LCD substrate can be installed in the XYZ directions. Can be translated to
An optical stage 8 capable of adjusting the tilt angle in the XY directions, a light source 1 for emitting infrared light 2, and an interferometer 3 for dispersing infrared light
A polarizer 4 for converting infrared light into linearly polarized light, a rotating chopper 5 having a mirror surface for transmitting or reflecting infrared light and separating an optical path, and applying the infrared light separated by the chopper to a substrate surface. Mirrors 6 and 7 for incidence, mirrors 11 and 12 for guiding reflected light from the substrate to a rotating chopper 13 formed of a mirror surface, and an infrared light detector 14 for detecting infrared light;
A controller 20 for controlling the rotation of the two choppers, a high-pass filter 18 for transmitting only high-frequency components of the electric signal from the infrared light detector, a low-pass filter 19 for transmitting only low-frequency components, A lock-in amplifier 21 that can selectively select and amplify (phase-sensitive detection) only electrical components synchronized with a modulation frequency due to rotation and an interferometer and an optical stage that control an interferometer and an optical stage to obtain electricity obtained from a lock-in amplifier and a low-pass filter. And a computer 22 for converting the signal into an infrared spectrum and displaying it.

The measurement procedure is performed by the following procedure using the present alignment film measuring apparatus. The infrared light 2 emitted from the light source 1 is transmitted through a spectroscopic interferometer 3 and a polarizer 4 controlled by a computer 22, and then applied to a rotating chopper 5 having wings on a mirror surface. When the wings of the chopper 5 come to the optical path of the infrared light 2, the infrared light 2 is reflected in the vertical direction, is guided to the mirror 7, and is incident on the LCD substrate 9 in a direction parallel to the rubbing direction 10. Will be. If there is no chopper wing in the optical path of the infrared light 2, the infrared light goes straight, is reflected by the mirror 6, and enters the LCD substrate 9 from the direction perpendicular to the rubbing direction 10. That is, chopper 5
, The infrared light 2 is irradiated alternately from two directions parallel and perpendicular to the rubbing direction 10. The polarization state of the infrared light incident on the substrate is set by the polarizer 4 to an s-polarization state parallel to the substrate plane.

The infrared light 2 radiated to each substrate is L
The light is reflected by the transparent electrode surface 16 while being absorbed by the alignment film 15 of the CD substrate 9, and is guided to the chopper 13 by the mirrors 11 and 12. The structure of the chopper 13 is exactly the same as that of the chopper 5, and the infrared light reflected by the mirror 11 enters the infrared light detector 14 when the chopper wing is not on its optical path. The infrared light 2 reflected by the mirror 12 is reflected when the wings of the chopper 13 are on the optical path and enters the infrared light detector. The phase relationship between the rotation of the wings of the chopper 5 and the chopper 13 is such that when the infrared light travels straight through the chopper 5, the infrared light 2 is reflected by the chopper 13, and conversely, the infrared light 2 is reflected by the chopper 5. Is reflected by the chopper 13, the rotation speed and the phase relationship are controlled by the chopper control system 20 so that the infrared light 2 goes straight. In order to control the infrared light path by the rotation of the chopper 5 and the chopper 13, the infrared light 2 is incident on the infrared light detector 14 in a polarization state parallel to the rubbing direction, and the infrared light 2 is polarized perpendicular to the rubbing direction. The infrared light 2 incident in this state is alternately incident and detected. In other words, when anisotropy (infrared dichroism) occurs in the absorption of polarized infrared light due to the molecular orientation generated in the alignment film 15 by the rubbing, the amount of light incident on the infrared light detector 14 changes, and The electric signal from the external light detector 14 is supplied to the choppers 5 and 13
Is an AC electric field having the same frequency component as the modulation frequency f of the infrared light 2 due to the above. This electric signal is filtered by a high-pass filter 18 that passes f or more, and then demodulated by a lock-in amplifier 21 that uses the modulation frequency f transmitted from the chopper control system 20 as a reference, so that the electric signal is parallel and perpendicular to the rubbing direction 10. An electric signal S corresponding to a change in infrared absorption due to polarized infrared light can be detected and amplified. Further, from an electric signal passing through a low-pass filter 19 through a frequency lower than f, a signal R representing a static optical characteristic of the device is obtained.
Is obtained. These analog signals are AD-converted and Fourier-transformed into spectra in the computer 22, and the former spectrum (S) is divided by the latter spectrum (R) to obtain a two-color difference spectrum (A).
= (S / R)).

XY under the control of the computer 22
The optical stage 8 capable of moving Z in parallel and having a variable tilt angle in the X and Y directions enables evaluation of the alignment film 15 at an arbitrary position within the LCD substrate 9 and automatic optical adjustment.

[0021]

As described above, according to the alignment film evaluation apparatus and the method for detecting the infrared light transmitted through the alignment film of the present invention, the alignment film can be evaluated by a simple operation of only parallel movement of the substrate even for a large substrate. Further, the size of the device can be reduced.

[Brief description of the drawings]

FIG. 1A is a schematic view illustrating an example of an alignment film measuring apparatus according to the present invention. FIG. 2B is a cross-sectional view taken along line AA ′ of FIG.

FIG. 2 is a schematic plan view of a mirror chopper which is a dividing unit according to the present invention.

FIG. 3 is a schematic configuration diagram illustrating an example of an alignment film measuring apparatus according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light source 2 ... Infrared light 3 ... Interferometer 4 ... Polarizer 5 ... Chopper 6 ... Mirror 7 ... Mirror 8 ... Optical stage 9 ... LCD substrate 10 ... Rubbing direction 11 ... Mirror 12 ... Mirror 13 ... Chopper 14 ... Infrared Photodetector 15 ... Orientation film 16 ... Transparent electrode 17 ... Glass substrate 18 ... High pass filter 19 ... Low pass filter 20 ... Chopper control system 21 ... Lock-in amplifier 22 ... Computer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-214232 (JP, A) JP-A-5-173173 (JP, A) JP-A-6-110027 (JP, A) JP-A-4-1992 95845 (JP, A) JP-A-7-151640 (JP, A) JP-A-7-198592 (JP, A) JP-A-64-35419 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1337

Claims (4)

(57) [Claims] [1 claim: a release means for releasing the infrared light, a polarizing means for polarizing the infrared light emitted from said emitting means, dividing means for dividing said infrared light polarized in the second optical path, alignment films evaluated, characterized in that it comprises irradiating means for irradiating a respective infrared light divided into the two light paths to the alignment layer, and detection means for detecting the infrared light of each of said transmitted through the alignment layer apparatus. 2. The alignment film evaluation apparatus according to claim 1, wherein said dividing means is a mirror chopper. 3. The method according to claim 1, wherein the alignment film is formed on a predetermined substrate.
And the detecting means comprises:
2. The method according to claim 1, wherein the infrared light is detected.
Alignment film evaluation device. 4. An infrared light emitting device, wherein said infrared light is polarized.
And splits the polarized infrared light into two optical paths,
Irradiate the alignment film with each infrared light split into
Each of the infrared light transmitted through the alignment film is detected and detected.
Determined the difference in the absorbance of each of the emitted infrared light,
Alignment film evaluation characterized by evaluating the alignment ability of the alignment film
Method.