JPH0616140B2 - Liquid crystal light modulator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid crystal light modulator, and more particularly to a transmissive liquid crystal display or liquid crystal light modulator utilizing alignment control of liquid crystal molecules.

[Prior Art] Conventionally, a technology of combining a diffraction grating and a liquid crystal is known for a few different purposes.

For example, it is known that a groove having periodic regularity is formed on the surface of a substrate and a liquid crystal is disposed on the groove, which shows the alignment ability of the liquid crystal. However, since this is not specifically intended to function as a diffraction grating, it does not pose a problem of optical difference, particularly difference of refractive index, etc. in an extremely shallow groove.

Next, form a minute grid of materials with different reflection characteristics,
It is known to combine with a liquid crystal by utilizing the polarization function of this grating. Again, the thickness of the grid itself is not particularly emphasized.

Further, there is known a phase diffraction grating in which a grating is formed by a transparent member and a liquid crystal is arranged in a groove between the gratings. For example, Japanese Patent Publication No. 53-3928 and U.S. Pat. No. 4,251,137 disclose a display element and a variable color-reducing filter element. However, the former element disclosed in Japanese Patent Publication No. 53-3928 is only for the purpose of showing a decorative effect, and a display element for displaying a character or an image, a light flux transmission,
It was not satisfactory as an optical modulator for blocking.

Further, the latter variable color filter element disclosed in U.S. Pat.No. 4,251,137 changes the director of a liquid crystal arranged between diffraction gratings by an electric field so that the light transmitted through the cell at a certain angle is absorbed by the grating and the liquid crystal. It utilizes that the difference in the refractive index between the two changes and the diffraction effect changes. However, this element has firstly a technical difficulty in manufacturing, and secondly, it has a drawback that the operation characteristic is bad.

That is, even if a relatively large Δn is used in a practically usable liquid crystal, in order to obtain a sufficient diffraction effect, it is necessary to form a grating having a large groove depth with respect to the grating pitch. In particular, it is optically effective to form a grating having a depth equivalent to a pitch of 3 μm or less, but the processing technology for a grating of such a size currently requires the latest technology for semiconductor devices and is easy to implement. Difficult to create.

Next, as a functional problem, the liquid crystal entered in such a deep groove is not only subjected to the surface restraint force from the upper and lower surfaces of the substrate but also strongly restrained from the left and right wall surfaces of the groove by the lattice. Is. This means that the long axes of the liquid crystal molecules are stably aligned in the groove direction, but on the contrary, they have a large resistance force when they are changed to different alignment states by an external force. This means that the initial orientation is not easily broken by the external force, that is, the electric field applied in the cell, and it is suggested that it is difficult to obtain the steep voltage transmittance characteristics required for the time division characteristics.

Further, conventionally, when a DC voltage is applied to a liquid crystal cell and the threshold voltage is exceeded, “Williams domain (Williams domai
n) ”occurs and the electric field strength is increased, the width of this domain becomes
Alternatively, it is known that the pitch becomes smaller and a diffraction grating can be obtained. For example, Sofa, et al "Optical Computing with Variable Grating Mode Liquid Crystal Device" Proceeding SP I E, 2nd
Volume 18, Page 81, 1980 (SOFFER, et al: "Optical compu
ting with variable grating mode liquid crysutal de
vices ”Proc. SPIE, 1980, 218, P.81).

In the diffraction grating thus formed, the grating pitch changes as the voltage changes, and the spectral characteristics of the diffracted light change accordingly. However, this diffraction grating is disadvantageous for maintaining a constant diffraction condition and for time-division driving in which a bias voltage is applied.

[Problems to be Solved by the Invention] An object of the present invention is to provide a novel liquid crystal light modulating group that solves the above-mentioned conventional drawbacks.

Further, it is an object of the present invention to provide a liquid crystal light modulator having high productivity and high reliability.

Further, the liquid crystal light modulator according to the present invention can obtain a high time-division property and at the same time enable a manufacturing process of a light modulator with a large area display.

[Means for Solving the Problems] That is, according to the present invention, in a liquid crystal optical modulator in which a liquid crystal is sandwiched between two substrates having transparent electrodes, at least one of the liquid crystal light modulator forms a diffraction grating. The surface of the substrate has a homogeneous alignment region and a homeotropic alignment region, one of the homogeneous alignment region and the homeotropic alignment region is formed as a fine alignment region, and the shape of the fine alignment region is the axis of the same direction. The liquid crystal light modulating base is characterized by having a uniaxially symmetric pattern that is symmetrical with respect to.

Hereinafter, the present invention will be described in detail.

The liquid crystal light modulator according to the present invention comprises two types of uniaxially symmetric fine alignment regions having different liquid crystal alignment abilities and arranged on the same substrate surface.

Among the two kinds of different liquid crystal aligning ability, typically one has homeotropic alignment and the other has homogeneous alignment. However, these are combinations of those having two kinds of orientation ability having an arbitrary pretilt angle in the range of 0 ° to 90 °, and are not limited to the above combination of homeotropic / homogeneous orientations.

FIG. 1 is a basic configuration diagram showing an example of a liquid crystal light modulator according to the present invention. FIG. 1 (a) is a partial plan view showing an example of a substrate in which uniaxially symmetric fine alignment regions of a liquid crystal light modulator are arranged. (Abbreviated as region).

For example, 14 is a homogeneous alignment ability region, and 15 is a homeotropic alignment ability region. FIG. 1 (b) is a cross-sectional view of a liquid crystal cell in which a substrate having a surface subjected to such an alignment treatment and another substrate having a homogeneous alignment are opposed to each other, and a liquid crystal is sandwiched between the substrates. FIG. 1 (a) shows a sectional cell of the substrate taken along the line AA '.

11 and 11 'are transparent substrates such as glass, 13 and 13' are transparent electrodes,
Reference numerals 14 and 14 'are the homogeneous orientation ability area, and 15 is the homeotropic orientation ability area.

FIG. 1 (C) is a sectional view taken along the line CC 'of FIG. 1 (b).
The cross-sectional structure cell of the substrate of FIG. 16, 1
6 ', 16 "are liquid crystal molecules. The directions of the directors of liquid crystal molecules are shown by drawing them in a slender shape, and those close to a circle are perpendicular to the paper surface and their intermediate states are shown by intermediate lengths.

The homeotropic alignment function regions 15 of FIG. 1 (a) are symmetrical with respect to the axis of the BB 'line and are arranged at the pitch P with the adjacent pattern. This pattern is asymmetric with respect to the axis of line AA 'and has a directivity toward line BB'. The repeating unit of this uniaxially symmetric pattern is indicated by. Counter substrate 1
Although 1'is shown as a treated surface showing a homogeneous alignment ability, it can also be homeotropic.

In the cell cross-sectional configuration diagram of FIG. 1 (b), the molecules show an arrangement close to the vertical direction in the vicinity of the 15 homeotropic orientation ability regions, and in the other homogeneous orientation ability regions, the orientation state is horizontal. Since the nematic liquid crystal molecules are aligned in the same direction due to the interaction between adjacent molecules, even if there are finely different alignment-treated surfaces, they are discontinuously arranged along the shape of these surfaces. It does not change, and continuously takes a slightly different orientation direction for each molecule.

Therefore, in the alignment treatment as shown in FIG. 1 (a), firstly, the molecules are easily arranged in the direction of the axis of symmetry, and secondly, the pretilt angle is arranged in the direction in which the area of the homeotropic alignment ability region is widened. FIG. 1 (C) schematically shows a state in which the pretilt angle, which is the average tilt of the molecule, becomes θ by the processing pattern of FIG. 1 (a).

In Fig. 1 (b), when the liquid crystal molecules are arranged in this way, the linearly polarized light perpendicular to the paper surface is at the pitch P as a diffraction grating, the refractive index anisotropy Δn of the liquid crystal, and the liquid crystal molecules at this time. Diffraction occurs with the optical thickness that is determined by the distribution of the arrangement of as a parameter.

When sufficient voltage in the example of FIG. 1 is applied to the transparent electrodes 13, 13 ', N _p liquid crystal having a positive dielectric anisotropy to be used shows a vertical alignment to the substrate in the cell the entire surface, uniform transparent state Becomes

Therefore, in this example, the liquid crystal light modulator has diffraction that occurs in the initial state where no voltage is applied, and the diffraction is extinguished by applying the voltage.

Similar effects can be obtained by changing the liquid crystal used to a negative dielectric anisotropic liquid crystal (N _n liquid crystal) with respect to this basic structure. In addition, by changing the shape change of the repeating unit with respect to the pitch and directionality of the pattern, changing the cell gap, the liquid crystal used and its additives, etc., the liquid crystal that was initially uniformly aligned exhibits diffraction when a voltage is applied. You can also get the state one.

Next, FIGS. 2 (a), (b), and (c) are not limited to the pattern shown in FIG. 1 (a), and the arrangement of the uniaxially symmetric pattern having directionality and other arrangement methods It is explanatory drawing which shows an example.

Next, as an example of different liquid crystal alignment ability used in the present invention, a polymer film is used for horizontal alignment treatment, and examples thereof include polyimide, polyamide, polyester, polycarbonate, polystyrene, polyvinyl chloride, polyvinyl alcohol and the like.

As the vertical alignment treatment, a surfactant having a fluorinated carbon chain (Daikin FS 150), a silicic acid ester having a fluorinated carbon chain (Daikin FS 116), a quaternary ammonium salt surfactant (DMOAP), lecithin, hexa Decylamine and the like.

In addition, inorganic coatings such as SiO ₂ and Ti can be used depending on the surface condition and the liquid crystal used.
O ₂ , Zr ₂ O ₃ , In ₂ O ₃ , silicon nitride, etc. are available. The metal coating is also a material close to this class.

The formation of different alignment capabilities is not particularly limited, but a method of patterning one alignment film on the other alignment film is used, and a photolithographic method or printing can be applied.

Regarding the cell formation of the present invention, the technique used in general TN display can be applied, but the uniaxial symmetric pattern having the directionality of the present invention is characterized in that it is difficult to form a reverse tilt by providing a pretilt angle in a certain direction. have. A substrate as shown in FIG. 1 (a) can also be used as the opposing substrate, but in this case, it is necessary to align the upper and lower substrates.
In practice, it is preferable that the upper and lower substrates are not required to be aligned in order to obtain the required diffraction. Therefore, it is preferable to construct the cell by combining the upper and lower substrates in an arrangement in which the pretilt angles face each other.

[Operation] In the liquid crystal light modulator of the present invention, since at least one substrate is formed by arranging two or more kinds of fine alignment regions having different liquid crystal alignment capabilities in the same substrate surface, the arrangement-dependent It is presumed that the liquid crystal molecules can be given a pretilt angle rising from a certain direction because a diffraction pitch can be obtained by the property and the alignment function region has a directional uniaxial symmetry pattern.

[Examples] Hereinafter, the present invention will be described more specifically with reference to Examples.

Example 1 A transparent conductive film 300 to 500 Å containing In ₂ O ₃ as a main component was laminated on a blue glass surface having a thickness of 1.1 mm, a vertical length of 300 mm, and a width of 300 mm, and a polyimide layer of 300 to 800 Å was sequentially laminated thereon. Photoresist AZ-1350J (made by Spree) or OFP on the substrate
A positive type resist such as R-77 (manufactured by Tokyo Ohka Co., Ltd.) is spin-coated, heated at 80 ° C for 10 minutes, and then the pattern shown in Fig. 1 (a) has a pitch of 8 µm and a stripe width of 7.2 µm maximum.
m, minimum 0.8 μm, repeating unit: 10 μm, exposed, baked, developed with a predetermined developer, dried, and then dip-coated with FS-116, 0.5 wt% diflon solution, 100
It was dried at 0 ° C for 20 minutes.

After that, the remaining photoresist portion is dissolved and removed together with FS-116 by using a stripping solution such as acetone or MEK, and further at 150 ° C to
It was heated at 200 ° C. for 1 hour and baked.

Using this substrate and a substrate treated with only polyimide, the polyimide substrate is rubbed and arranged so that the pre-tilt angles are aligned, and a space member is provided so that the gap becomes 3 μm, and they are arranged opposite to each other, and Hoffmann-La Roche is inside. A nematic liquid crystal RO-TN403 was introduced and the periphery was sealed to produce a cell.

This cell showed diffraction when no voltage was applied, and almost disappeared at 2.2 V and became a transparent state. Disappearance of diffraction was uniform, and no disturbance due to reverse tilt was observed.

Example 2 With the same material configuration as in Example 1, the pattern pitch 3
When a cell was constructed with a maximum width of 2.4 μm, a minimum width of 0.6 μm, a repeating unit of 4 μm and a cell gap of 1.5 μm, a cell having no diffraction in the initial state and no defects such as microdomains was obtained. When a voltage of 1.8 V was applied to this, strong diffraction was exhibited.

Example 3 Using the two array pattern substrates used in Example 2, a cell having a cell gap of 2 μm was formed so that the pretilt angles faced each other without rubbing, and diffraction was generated in the initial state. When a voltage of 2.3 V was applied to this, the whole was in a uniform transparent state.

[Effects of the Invention] As described above, the liquid crystal light modulator of the present invention has at least one substrate in which fine uniaxially symmetry alignment regions having two different liquid crystal alignment abilities are arranged in the same substrate. Since it is used for the substrate, it has the following excellent effects.

Compared with a conventional diffraction grating formed by a grating, processing becomes easier and productivity is increased.

Only a chemically stable aligning agent can be used without interposing a lattice material or the like, and high reliability can be obtained.

Since the difference in refractive index of the liquid crystal itself is utilized, a sufficiently large Δn value can be utilized, and predetermined optical characteristics can be obtained with a thicker cell thickness than in the past.

The liquid crystal is not sealed between the narrow lattices, only the orientation process of the interface is performed, the threshold voltage of the liquid crystal is low, and the steepness of the optical change with respect to the voltage is large, which is suitable for time-division driving.

Since fine alignment regions are arranged and formed only by surface patterning such as printing, large area treatment and multifaceted production on a single substrate are possible, resulting in high productivity.

The pretilt angle can be set only by forming the lattice pattern, and compared to when rubbing is performed, scratches and dust are less mixed, and cells with good uniformity can be created.

[Brief description of drawings]

FIG. 1 (a) is a partial plan view showing an example of a substrate in which fine alignment processing regions of the liquid crystal light modulator according to the present invention are arranged, and FIG. 1 (b) is a liquid crystal light modulator according to the present invention. A cross-sectional view showing an example, FIG. 1 (c) is a cross-sectional view taken along the line CC ′ of FIG. 1 (b), and FIGS. 2 (a), (b), and (c) are fine alignment treatments arranged on a substrate. It is explanatory drawing which shows the other example of an area | region. 10, 12 …… Substrate 11, 11 ′ …… Transparent substrate 13, 13 ′ …… Transparent electrode 14, 14 ′ …… Homogeneous alignment functional area 15 …… Homeotropic alignment functional area 16,16 ′, 16 ″ …… Liquid crystal Molecule P …… Pitch …… Repeating unit of uniaxially symmetric pattern

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Takayuki Ishii 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Masato Yamanobe 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Kazuya Ishiwata 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-54-5754 (JP, A) JP-A-53-94955 ( JP, A) JP 63-14124 (JP, A)

Claims (4)

[Claims] 1. A liquid crystal light modulator comprising a liquid crystal sandwiched between two substrates having transparent electrodes, wherein at least one of the substrates has a homogeneous alignment region and homeotropic alignment so that the liquid crystal forms a diffraction grating. A uniaxially symmetric pattern having an alignment region, one of the homogeneous alignment region and the homeotropic alignment region being formed as a fine alignment region, and the shape of the fine alignment region being symmetrical with respect to an axis in the same direction. A liquid crystal light modulator characterized in that 2. The liquid crystal light modulator according to claim 1, wherein the fine alignment region is formed by a homeotropic alignment region. 3. The fine orientation region is formed by using a printing method, as claimed in claim 1 or 2.
A liquid crystal light modulator according to the item. 4. The liquid crystal light modulator according to claim 1 or 2, wherein the fine alignment region is formed by using a photolithography method.