JP2010286573A - Electro-optic element - Google Patents

Abstract

An electro-optical element capable of switching to scatter or transmit light incident obliquely without impairing the transmittance of light incident from the front.
An electro-optical element includes a first substrate having a first electrode on one side, a second substrate having a second electrode on one side, a surface of the first substrate, and a second substrate. And a liquid crystal layer 15 provided between the two surfaces. The liquid crystal layer includes a plurality of first regions 17 in which the orientation of the liquid crystal molecules is likely to change according to the electric field, and a plurality of second regions 16 in which the orientation of the liquid crystal molecules is unlikely to change according to the electric field The boundaries 18 between the plurality of first regions and the plurality of second regions are alternately provided at a constant interval p along a first direction parallel to one surface of the first substrate. The thickness d of the liquid crystal layer is set larger than the interval p.
[Selection] Figure 1

Description

  The present invention relates to an electro-optical element having a function of controlling the state of transmitted light.

  A liquid crystal optical element disclosed in Japanese Patent Application Laid-Open No. 2007-79459 (Patent Document 1) is known as a conventional example of an electro-optical element having a function capable of controlling the state of transmitted light. This liquid crystal optical element has a configuration in which a grating part and a non-grating part are formed in a liquid crystal layer sandwiched between a pair of substrates, and the grating part and the non-grating part are applied by applying a voltage to the liquid crystal layer. Is caused to scatter in the light passing through the liquid crystal layer due to the difference in refractive index, and thereby the light emitted from the liquid crystal layer to the outside is controlled.

  By the way, when observing a landscape, an image, or the like, there is a case where it is desired to control the state viewed from an oblique direction without affecting the state viewed from the front. For example, there is a case where glare is desired to be prevented (antiglare) or a case where it is desired to prevent an image from being viewed from an oblique direction. Since the liquid crystal optical element disclosed in Patent Document 1 described above also scatters light incident from the front, it is not optimal for such a demand.

JP 2007-79459 A

  A specific aspect of the present invention is to provide an electro-optical element capable of switching to scatter or transmit light incident from an oblique direction without impairing the transmittance of light incident from the front. .

  An electro-optic element according to one aspect of the present invention includes a first substrate having a first electrode on one surface side, a second substrate having a second electrode on one surface side, one surface of the first substrate, and the second substrate. A liquid crystal layer provided between the first surface and the second surface. The liquid crystal layer has a plurality of first regions in which the orientation of liquid crystal molecules is likely to change in response to an electric field, and a plurality of second regions in which the orientation of the liquid crystal molecules is unlikely to change in response to an electric field. Boundaries between the plurality of first regions and the plurality of second regions are alternately provided at a constant interval p along a first direction parallel to one surface of the first substrate. The thickness d of the liquid crystal layer is set larger than the interval p.

  In the above electro-optical element, when a voltage is applied to the liquid crystal layer through the first electrode and the second electrode, the change in the direction of the liquid crystal molecules (director) is relatively large in the first region, and in the second region, Since the change of the director is relatively small, the refractive index at the boundary between the two can be changed by turning on and off the voltage. By providing the boundary between the first region and the second region at a constant interval p, and by making the thickness d of the liquid crystal layer larger than the boundary interval p, light incident obliquely to the substrate surface When passing through the boundary between the first region and the second region, the effect of scattering obliquely incident light due to the difference in refractive index at the boundary can be enhanced. On the other hand, regardless of whether the voltage is on or off, light incident at an angle perpendicular to or close to the substrate surface can be passed without causing scattering. Therefore, according to the above electro-optical element, it is possible to switch the light incident from an angle to be scattered or transmitted without impairing the transmittance of the light incident from the front.

  In the above electro-optic element, the refractive index difference at the boundary between the first region and the second region can be continuously changed by increasing or decreasing the voltage applied to the liquid crystal layer. This makes it possible to control the voltage of the degree of scattering with respect to obliquely incident light. Furthermore, although it is an element using liquid crystal, since there is no polarizing plate, there is an advantage that the light utilization efficiency is high and the transmittance is relatively high.

  Such an electro-optical element according to the present invention is used for, for example, a sunshade for preventing glare, a sun visor, a vehicle-mounted sun visor, goggles, and the like, or for peeping prevention in a display unit of a portable device such as a mobile phone. It is suitable for. It is also preferable to apply to a transmissive / reflective display device. By disposing the electro-optic element according to the present invention in front of a transmissive / reflective display device, the voltage to the liquid crystal layer of the electro-optic element is turned off at the time of transmissive display. In this case, a good display can be obtained in any display state by turning on the voltage.

  In the above-described electro-optical element, it is also preferable that at least one of the first electrode or the second electrode has a plurality of striped electrode pieces extending in a second direction intersecting the first direction. . Note that either the first electrode or the second electrode may have a plurality of stripe-shaped electrode pieces extending in a second direction intersecting the first direction. In these cases, it is preferable that each of the plurality of electrode pieces is disposed in association with one of the plurality of first regions.

  As a result, a voltage can be selectively applied only to each first region, and light incident obliquely on the electro-optic element can be scattered more efficiently.

  Each of the plurality of electrode pieces has a width in the first direction smaller than the interval p, and both ends in the first direction are disposed inside any one of the plurality of first regions. More preferred. That is, it is more preferable that each electrode piece is included in one first portion in plan view.

  Thereby, it is possible to preferentially collect the electric lines of force generated from each electrode piece in each first region, and it is possible to further enhance the effect of scattering obliquely incident light.

1 is a cross-sectional view schematically illustrating a configuration of an electro-optic element according to a first embodiment. It is a figure for demonstrating an example of the method of forming each hardening part and each non-hardening part in a liquid crystal layer. It is a figure shown about an example of the viewing angle characteristic of the transmittance | permeability of the electro-optical element which concerns on 1st Embodiment. It is sectional drawing which shows typically the structure of the electro-optical element of 2nd Embodiment. It is a typical fragmentary top view for demonstrating the arrangement state of each electrode piece and a hardening part. It is a figure shown about an example of the viewing angle characteristic of the transmittance | permeability of the electro-optical element which concerns on 2nd Embodiment. It is sectional drawing which shows typically the structure of the modification of an electro-optical element.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional view schematically showing the configuration of the electro-optic element of the first embodiment. 1 includes a first substrate 11 having a first electrode 12 on one surface side, a second substrate 13 having a second electrode 14 on one surface side, and one surface of the first substrate 11. And a liquid crystal layer 15 provided between one surface of the second substrate 13. The first electrode 12 and the second electrode 14 are connected to a voltage applying means 20 for applying an arbitrary voltage thereto.

  The first substrate 11 and the second substrate 13 are transparent substrates such as a glass substrate and a plastic substrate, respectively. For the first electrode 12 and the second electrode 14, a transparent conductive film such as an indium tin oxide film (ITO film) is formed by a film forming method such as an evaporation method, an ion plating method, or a sputtering method, and this is appropriately patterned. It is formed by doing. In the present embodiment, the first electrode 12 is formed over substantially the entire surface of the first substrate 11, and the second electrode 14 is formed over the entire surface of the second substrate 13. The first electrode 12 and the second electrode 14 are disposed to face each other with the liquid crystal layer 15 interposed therebetween.

  The liquid crystal layer 15 is formed using, for example, a liquid crystal material having a positive dielectric anisotropy Δε (Δε> 0). Therefore, when a potential difference is applied between the first electrode 12 and the second electrode 14 by the voltage applying means 20, the major axis of the liquid crystal molecules is aligned along the electric field direction. The refractive index anisotropy Δn of the liquid crystal material is, for example, about 0.3. Specifically, the refractive index no for ordinary light is about 1.51, and the refractive index ne for extraordinary light is about 1.81 (Δn = ne−no≈0.3). Although the numerical value here is only an example, the larger the value of the refractive index anisotropy Δn, the better the principle of the electro-optical element 1 of the present embodiment. As shown in the figure, the liquid crystal layer 15 includes a plurality of hardened portions (second regions) 16 that are unlikely to change according to the electric field of the liquid crystal molecules, and a plurality of non-volatile portions in which the directions of the liquid crystal molecules are likely to change according to the electric field. And a hardened portion (first region) 17.

  The plurality of hardened portions 16 and the plurality of non-hardened portions 17 are alternately arranged along a first direction (X direction in the drawing) parallel to one surface of the first substrate. A boundary 18 between each cured portion 16 and each non-cured portion 17 is arranged at a constant interval p. Each curing portion 16 is formed by previously mixing a photocurable monomer into the liquid crystal material constituting the liquid crystal layer 15 and then polymerizing the photocurable monomer by light irradiation. Thereby, a state in which the orientation of the liquid crystal molecules hardly changes even when an electric field is applied can be obtained. Moreover, each non-hardening part 17 is a part which such a polymer hardly exists and a liquid crystal molecule can change freely according to an electric field. In addition, the detail of the formation method of each hardening part 16 is further mentioned later.

  Here, in the electro-optic element 1 of the present embodiment, the thickness d of the liquid crystal layer 15 is set to be larger than the arrangement interval (pitch) p of the boundary 18 between the cured portion 16 and the non-cured portion 17 described above (d). > P). For example, in the present embodiment, the interval p between the boundary 18 between the hardened portion 16 and the non-hardened portion 17 is set to 20 μm. More specifically, in this embodiment, the width of each cured portion 16 and each non-cured portion 17 in the X direction is set to 20 μm, and the adjacent cured portions 16 and non-cured portions 17 are substantially free of gaps. They are arranged in stripes. In the present embodiment, the thickness d of the liquid crystal layer 15 is set to 30 μm, which is 1.5 times the interval p (20 μm) described above. In addition, the numerical value of the space | interval p and the thickness d is an example, and as long as the relationship of d> p is satisfy | filled, it is not limited to these numerical values.

  In addition, although illustration is abbreviate | omitted, the process (orientation process) for aligning the liquid crystal molecule | numerator of the liquid-crystal layer 15 in a fixed direction is made | formed on one surface of each of the 1st board | substrate 11 and the 2nd board | substrate 13. . A typical example of the alignment treatment includes forming an alignment film made of an organic polymer film such as a polyimide resin and performing a rubbing treatment thereon. Here, the rubbing process is performed between the first substrate 11 and the second substrate 13 so as to be in an anti-parallel state. In addition, a sealing material is provided on the periphery of the first substrate 11 and the second substrate 13 so as to surround the liquid crystal layer 15 (not shown).

  The electro-optic element 1 of the present embodiment has such a configuration, and next, an example of a method of forming each cured portion 16 and each non-cured portion 17 in the liquid crystal layer 15 will be described in detail with reference to FIG. To do.

  The liquid crystal layer 15 is formed by injecting a liquid crystal material into the gap between the first substrate 11 and the second substrate 13. At this time, in this embodiment, a photocurable monomer (a monomer exhibiting liquid crystallinity in the monomer state) is added in advance to the liquid crystal material. For example, a UV curable liquid crystal capable of polymerizing a monomer by irradiating ultraviolet rays (UV) is added at a weight ratio in the range of 1 to 15 wt% with respect to the liquid crystal material. As an example, the addition amount can be a weight ratio of 4 wt%.

  Next, a photomask 30 (a metal mask using a metal film or an emulsion mask) in which the light shielding portions 31 and the transmission portions 32 are alternately arranged is used to form the liquid crystal layer 15 via the first substrate 11 or the second substrate 13. Irradiate light (ultraviolet rays in this example). As the photomask 30, a striped photomask is used in which light-shielding portions 31 having a predetermined width (20 μm in this example) and transmission portions 32 having a predetermined width (20 μm in this example) are alternately arranged. As a result, each non-cured portion 17 is formed in a region corresponding to the light shielding portion 31, and each cured portion 16 is formed in a region corresponding to the transmissive portion 32.

The photomask 30 is preferably arranged so that the stripe pattern is parallel to the rubbing direction of the rubbing process described above. Further, it is desirable that the irradiated light (ultraviolet light) is as close as possible to parallel light. This is because the boundary between each cured portion 16 and each non-cured portion 17 obtained after the light irradiation can be made perpendicular to or close to the substrate surface. For such exposure, for example, an exposure machine used in a photolithography process or the like, or a light irradiation apparatus for performing photo-alignment, which is one of apparatuses used for manufacturing a liquid crystal display device, is suitable. In this embodiment, an apparatus with an illuminance of 80 mW / cm ² is used.

Here, it is preferable to perform so-called intermittent exposure at the time of ultraviolet irradiation. For example, light irradiation for 5 seconds and non-irradiation for 25 seconds can be alternately repeated 6 times with the photomask 30 placed, and then light irradiation for 30 seconds can be performed. In this case, the total irradiation time of ultraviolet rays is 60 seconds, and the irradiation amount is 4.8 J / cm ² . Although the conditions for intermittent exposure are not limited to those described here, intermittent exposure combining a short exposure of several seconds and a non-irradiation waiting time is performed prior to a relatively long exposure (main exposure). Thereby, the monomer contained in each non-hardened part 17 moves to the adjacent hardened part 16 during the waiting time, and finally the monomer remaining in each non-hardened part 17 can be reduced. Thereby, the reliability of the electro-optical element 1 can be further improved.

  Next, an example of the viewing angle characteristic of the transmittance of the electro-optical element 1 according to the present embodiment will be described with reference to FIG. In addition, the manufacturing conditions of the electro-optic element 1 used for the measurement of the viewing angle characteristics are in accordance with the conditions exemplified in the above description.

  In FIG. 3, the viewing angle characteristics in the state where the voltage is applied between the first electrode 12 and the second electrode 14 using the voltage applying means 20 (voltage ON) and in the state where no voltage is applied (voltage OFF) are shown. It is shown. As shown in FIG. 3, it can be seen that the transmittance with respect to the incident angle of the incident light (in other words, the viewing angle, that is, the viewing angle) is changed by the ON / OFF of the voltage. It can be seen that when the voltage is OFF, it is almost transparent when viewed from any direction, and when the voltage is ON, the transmittance is lower as the viewing angle is inclined, and the incident light is scattered. The viewing angle characteristics shown in FIG. 3 are obtained when the distance p between the boundaries 18 between the cured portions 16 and the non-cured portions 17 is 20 μm and the thickness (cell thickness) d of the liquid crystal layer 15 is 30 μm, that is, the ratio d between the two. / P is about 1.5. In this case, it can be seen that the transmittance at a viewing angle of 50 ° is about ½ of the front. Theoretically, as the cell thickness d becomes larger than the interval p (that is, as the ratio d / p becomes larger), the viewing angle when viewed from an oblique direction becomes lower, or the viewing angle at which the transmittance becomes about 1/2 of the front. Is considered to be smaller. Therefore, it can be understood that the ratio d / p may be appropriately changed in accordance with the performance required as a product.

(Second Embodiment)
In the above-described embodiment, the voltage is applied uniformly over the entire cured portion 16 and the non-cured portion 17 of the liquid crystal layer 15. May be. The embodiment in this case will be described below.

  FIG. 4 is a cross-sectional view schematically showing the configuration of the electro-optic element of the second embodiment. The electro-optical element 1a according to this embodiment shown in FIG. 1 basically has the same configuration as the electro-optical element 1 according to the first embodiment described above. About the component which is common to both, detailed description is abbreviate | omitted after attaching | subjecting the same code | symbol.

  As shown in the figure, the electro-optic element 1a of the present embodiment is composed of a plurality of striped electrode pieces 12a extending in a second direction (direction intersecting the paper surface) intersecting the first direction (X direction shown). The first electrode and a second electrode composed of a plurality of stripe-shaped electrode pieces 14a extending in a second direction that intersects the first direction as well. A voltage applying means 20 for applying an arbitrary voltage is connected to each electrode piece 12a as the first electrode and each electrode piece 14a as the second electrode. In the illustrated example, a common wiring is connected to each electrode piece 12a and each electrode piece 14a. However, a separate wiring can be provided and a voltage can be individually applied to each electrode piece 12a and 14a. You may do it.

  FIG. 5 is a schematic partial plan view for explaining an arrangement state of each electrode piece and the cured portion. As shown in the figure, each electrode piece 12 a is arranged in association with one of the non-cured portions 17. The same applies to each electrode piece 14a. More specifically, each electrode piece 12a, 14a in the present embodiment is formed such that the width x1 in the first direction (X direction) is smaller than the interval p of the boundary 18 described above, and the electrode pieces 12a, 14a Both ends in the first direction are disposed inside the corresponding non-cured portions 17. Specifically, in the electro-optical element 1a of the present embodiment, the interval p between the boundaries 18 between the cured portion 16 and the non-cured portion 17 is set to 5 μm, and the width x1 of each electrode piece 12a, 14a is set to 4 μm. The distance between the electrode pieces is set to 6 μm. The thickness d of the liquid crystal layer 15 is set to 20 μm.

The manufacturing method of the electro-optical element 1 of this embodiment is basically the same as that of the first embodiment described above. About each electrode piece 12a, 14a, after forming a transparent conductive film, pattern formation is carried out by wet etching using iron dioxide or the like or dry etching using methanol or the like. Further, the amount of UV curable liquid crystal added to the liquid crystal material is 10 wt% as an example. In addition, a photomask 30 (see FIG. 2) in which light shielding portions 31 having a width of 5 μm and transmission portions 32 having a width of 5 μm are alternately arranged is used. At the time of light irradiation, the photomask 30 is aligned so that each electrode piece 12a or each electrode piece 14a and each light shielding portion 31 overlap each other. For the exposure, light irradiation for 2 seconds and non-irradiation for 28 seconds are alternately repeated 5 times with the photomask 30 disposed, and then light irradiation for 20 seconds is performed. In this case, the total irradiation time is 30 seconds, and the irradiation amount is 2.4 J / cm ² . These conditions are only examples.

  Next, an example of the viewing angle characteristic of the transmittance of the electro-optical element 1a according to this embodiment will be described with reference to FIG. The manufacturing conditions of the electro-optical element 1a used for the measurement of the viewing angle characteristics are in accordance with the conditions exemplified in the above description.

  In FIG. 6, the viewing angle characteristics in the state where the voltage is applied between the first electrode 12 and the second electrode 14 using the voltage application means 20 (voltage ON) and in the state where no voltage is applied (voltage OFF) are shown. It is shown. As shown in FIG. 6, it can be seen that the transmittance with respect to the incident angle of the incident light (in other words, the viewing angle, that is, the viewing angle) is changed by the ON / OFF of the voltage. It can be seen that when the voltage is OFF, it is almost transparent when viewed from any direction, and when the voltage is ON, the transmittance is lower as the viewing angle is inclined, and the incident light is scattered. From FIG. 6, it can be seen that the transmittance at a viewing angle of 40 ° is about ½ of the front, and the transmittance at a viewing angle of 50 ° is about ３ of the front. Further, it can be seen that there is almost no difference between the front transmittance and the voltage ON / OFF. It can also be seen that an effect of further reducing the transmittance of oblique incident light is obtained as compared with the viewing angle characteristic in the first embodiment (FIG. 3).

  In addition, this invention is not limited to the content of embodiment mentioned above, In the range of the summary of this invention, it can change and implement variously. For example, in the second embodiment described above, a case has been described in which both the first electrode and the second electrode are constituted by a plurality of electrode pieces, but only one of the first electrode and the second electrode is plural. The other electrode piece may be the same as in the case of the first embodiment.

  Further, in each of the above-described embodiments, the configuration in which the boundary between each cured portion 16 and each non-cured portion 17 is substantially orthogonal to each surface of the first substrate 11 and the second substrate 13 has been described. As illustrated in FIG. 7, the boundary 18 between each cured portion 16 and each non-cured portion 17 may be oblique to one surface of the first substrate 11 and the like. In addition, the same code | symbol is used about the component which is common in FIG. 1, etc., and detailed description is abbreviate | omitted about them. The electro-optic element 1b of the modification shown in FIG. 7 can be manufactured by obliquely entering light (such as ultraviolet rays) used for exposure in exposure using a photomask (see FIG. 2). According to this modification, it is possible to realize an electro-optic element having angular characteristics corresponding to the tilt direction of the boundary.

  DESCRIPTION OF SYMBOLS 1, 1a, 1b ... Electro-optical element (liquid crystal optical element), 11 ... 1st board | substrate, 12, 12a ... 1st electrode, 13 ... 2nd board | substrate, 14, 14a ... 2nd electrode, 15 ... Liquid crystal layer, 16 ... Cured portion (second region), 17 ... non-cured portion (first region), 18 ... boundary, 20 ... voltage applying means

Claims (3)

A first substrate having a first electrode on one side;
A second substrate having a second electrode on one side;
A liquid crystal layer provided between one surface of the first substrate and one surface of the second substrate;
With
The liquid crystal layer has a plurality of first regions in which the orientation of the liquid crystal molecules is likely to change according to an electric field, and a plurality of second regions in which the orientation of the liquid crystal molecules is unlikely to change according to the electric field,
The boundaries between the plurality of first regions and the plurality of second regions are alternately provided at a constant interval p along a first direction parallel to one surface of the first substrate,
A thickness d of the liquid crystal layer is set larger than the interval p;
Electro-optic element. At least one of the first electrode or the second electrode has a plurality of striped electrode pieces extending in a second direction intersecting the first direction,
Each of the plurality of electrode pieces is disposed in association with any of the plurality of first regions,
The electro-optical element according to claim 1. Each of the plurality of electrode pieces has a width in the first direction smaller than the interval p, and both ends in the first direction are arranged inside any one of the plurality of first regions.
The electro-optical element according to claim 2.

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